text:
One-step generation of hybrid micro-optics with high-frequency diffractive structures on infrared materials by ultra-precision side milling
Zhanwen Sun, Suet To, and K. M. Yu
Zhanwen Sun, Suet To,* and K. M. Yu
State Key Laboratory in Ultra-Precision Machining Technology, Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong
*Corresponding author: sandy.to@polyu.edu.hk
Z Sun
S To
K Yu
Zhanwen Sun, Suet To, and K. M. Yu, "One-step generation of hybrid micro-optics with high-frequency diffractive structures on infrared materials by ultra-precision side milling," Opt. Express 26, 28161-28177 (2018)
Development of self-tuned diamond milling system for fabricating infrared micro-optics arrays with enhanced surface uniformity and machining efficiency (OE)
Machining approach of freeform optics on infrared materials via ultra-precision turning (OE)
Active control of residual tool marks for freeform optics functionalization by novel biaxial servo assisted fly cutting (AO)
Freeform surfaces
Microlens arrays
Original Manuscript: August 30, 2018
2. Principle for one-step generation of hybrid micro-optics
3. Optimal toolpath generation for the UPSM
5. Results and discussion
Hybrid micro-optics of infrared (IR) materials are of great advantage in realizing the function integration and minimization of advanced IR optical systems. However, due to the hard-and-brittle nature of IR materials, it is still challenging for both non-mechanical and mechanical technologies to achieve one-step generation of hybrid infrared micro-optics with high form accuracy. In the present study, a flexible method, namely ultra-precision side milling (UPSM), is first introduced to achieve one-step generation of infrared hybrid micro-optics in ductile mode, and the corresponding reflective diffraction characteristics are analyzed. In UPSM, the reflective/refractive primary surface of the hybrid micro-optics is formed via the removal of workpiece material, and the high-frequent secondary diffractive micro/nanostructures are simultaneously generated by the tool residual marks of cutting trajectories. With the consideration of the changing curvature of the primary surface, the optimal toolpath generation strategy is introduced to acquire the desired shapes of the secondary micro/nanostructures, and the selecting criteria of the machining parameters is discussed to avoid the brittle fractures of IR materials. In practice, two types of hybrid micro-optic components, namely hybrid micro-aspheric arrays and sinusoid grid surface with high-frequent secondary unidirectional phase gratings, are successfully fabricated on single-crystal silicon to validate the proposed method. The method adopted in this study is very promising for the deterministic fabrication of hybrid micro-optics on infrared materials.
© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Hybrid micro-optics of infrared (IR) materials has attracted widespread attention for a variety of applications in advanced IR optical systems, due to its unique advantages for function integration and minimization [1–3]. For example, hybrid micro-lens arrays with the imposition of hierarchical nanostructures enable a better antireflective property compared with conventional ones [3]. Hybrid micro-optics constructed by high-frequent secondary nanometric phase gratings generally comprise both reflective/refractive as well as high-frequent diffractive functions, which is helpful for the creation of new optics systems and the improvement of the optics performance [4]. However, most IR materials, such as silicon and germanium, are characterized as hard-and-brittle nature with very low fracture toughness, which imposes great difficulties in the fabrication of infrared optical components with ultra-smooth surfaces and ultra-precision form accuracy for both non-mechanical and mechanical technologies. It is known that once the undeformed chip thickness is beyond a critical value, brittle fractures will vastly generate and severely destroy the finished surfaces of IR materials [5]. This difficult-to-machine nature of IR materials can be more significant in the fabrication of hybrid optics with complicated hierarchical micro/nanostructures. Generally, complex machining technologies that combines multi-step machining processes are required to generate hybrid structures on IR materials, which is very low-efficient and difficult to control form accuracy [6–8].
Various non-mechanical machining methods based on lithographic technologies, such as electron beam lithography, focused ion bean and laser ablation, have been proposed to fabricate diffractive micro/nanostructures on IR materials [9–11]. Although these methods have been demonstrated to be effective for the construction of micro/nanostructures with very high resolution, they are commonly restricted to planar substrates or simple concave/convex surfaces with a large radius of curvature [9]. To obtain the hybrid IR micro-optics with desired shapes, multi-step processes that combines ultra-precision machining and picosecond laser ablation was normally required [3]. In this case, ultra-precision machining methods are applied to generate the refractive/reflective primary surface, which is further processed using the picosecond laser ablation to construct secondary high-frequent diffractive structures. Nevertheless, this hybrid process not only introduce unnecessary machining errors, but also is relatively high-cost and low-efficient. Similarly, etching methods, dominated by laser-assed and chemical etching, are also applied to construct secondary diffractive micro/nanostructures on the processed primary surfaces to form hybrid IR optical components [12–14]. In practical, these methods normally require very expensive facilities, and are difficult to generate complex secondary structures due to the uncontrolled etching direction. Femtosecond laser polymerization is a promising method to form hybrid structures in a flexible way, but this method highly restricts to low efficiency and photocurable polymer materials. Therefore, to achieve one-step generation of hybrid IR freeform micro-optics with high form accuracy as well as low processing time is still challenging for non-mechanical methods.
Ultra-precision diamond cutting technologies, dominated by fast and slow tool servo (FTS/STS), vibration-assisted cutting and diamond milling, are more promising for the deterministic generation of hybrid IR micro-optics with complex shapes, due to their capability of achieving ultra-smooth surface quality as well as ultra-high from accuracy [15–17]. Slow tool servo system upgrades from the diamond turning by applying the servo motion on the spindle. In the machining process, the spindle and the x slide move with a constant speed, and structured surfaces can be generated with the assistance of the oscillations of the z slide. The configuration of fast tool servo (FTS) is similar to that of slow tool servo, but FTS possesses a much higher frequency movement in z direction normally driven by piezoelectric ceramics or voice-coil motor. By means of FTS/STS, freeform surfaces and some simple micro-structures, such as Fresnel lens and micro-sphere lens arrays, have been successfully fabricated on brittle IR materials with high form quality [18,19]. The advantage of FTS/STS is its flexibility for deterministic generation of microstructures with nanometric surface roughness and sub-micrometric form accuracy [20]. However, because of the bandwidth limitation of the servo system, the resolution of the microstructures fabricated using FTS/STS generally ranges in a few hundred micrometers, which highly restrict the highest attainable periodicity of the secondary diffractive micro/nanostructures of hybrid micro-optics. Besides, to avoid brittle fractures, very small machining parameters, i.e. feed rates and depths of cut, are necessarily adopted in FTS/STS of brittle IR materials, which further limit the achievable height variation of the generated hybrid IR surfaces [21].
With the assistance of the high-frequent vibration, much higher resolution of secondary micro/nanostructures can be achieved by ultrasonic vibration-assisted diamond cutting (UVAC) [22,23]. In UVAC, the diamond tool normally vibrates elliptically with a very high frequency in the plane determined by the chip flow direction and the normal cutting direction [22]. For the hybrid micro-grooves generated by UVAC, the micro-dimples constructed by the tool residual marks between two connective elliptical loci serve as the hierarchical structures. In this case, the material is removed in a way similar to plunge cutting, so brittle fractures will easily generate at a higher depth of cut. Especially, this method is only suitable for planer surface, and is hard for UVAC to generate the hybrid structures with a freeform primary surface.
Compared with FTS/STS and UVAC, diamond milling is more convenient to generate functional surfaces with uniform surface quality, because of its process consistency and flexible tool path generation. Diamond milling employs a rotational diamond tool to remove the material. The different clamped styles of the diamond tool lead to different definitions of the milling processes. Diamond milling generally can be classified into diamond face milling and fly cutting. Face milling is characterized as a rotational ball milling tool with its axis perpendicular to the workpiece. Even though face milling is flexible in the generation of freeform surface or micro lens arrays, this method cannot be used to fabricated hybrid structures with high-frequent secondary nanostructures, due to the limitation of size of the gyration radius. Besides, the commercial ball milling tools used in face milling may not be able to be designed with a desired negative rake angle, which is easy to cause brittle fractures in the machining of brittle IR materials [16]. According to zhang et al. [24], fly cutting generally relate to the rotational diamond tool with a large swing radius (over 30 mm). It has been demonstrated that the intermittent cutting process of fly cutting is more beneficial to the ductile machining of IR materials [5]. However, the large swing radius of fly cutting will easily lead to the interference between tool path and the finished surface, thereby highly restricting the curvature radius of the primary surface.
For milling, previous toolpath generation strategies designed for continuous freeform surfaces cannot be directly applied in the fabrication of hybrid optics on infrared materials. The unique scenarios in the fabrication of hybrid structures should be considered, and new and special contents in terms of toolpath generation algorithm for hybrid structures need to be optimized. For example, the size and shape of constructed secondary diffractive nanostructures need to be uniform for hybrid micro-optics, regardless of the curvature changes of the reflective/refractive primary surface. Nevertheless, previous strategies generally neglect the uniformity of tool residual marks, which inevitably induces a non-uniform secondary nanostructure for hybrid optics. Besides, in order to acquire the desired hybrid shapes with high form accuracy on infrared materials, the selecting criteria of the machining parameters, including swing radius and feed rate, is also different from that of ordinary ones.
Overall, it is still challenging for both non-mechanical and mechanical technologies to achieve one-step generation of hybrid infrared micro-optics that is characterized as a complex freeform primary surface with the imposition of high-frequent diffractive secondary micro/nanostructures. In this paper, a novel ultra-precision side milling (UPSM) method first adopted for the fabrication of hybrid micro-optics on IR materials in ductile mode. In UPSM, an insert diamond tool tip is adopted instead of a diamond turning tool or ball milling tool. Fang et al. [25] made a definition on milling that if the diamond tool is close to the axis of rotation, this process is commonly referred to as raster milling. Based on this definition, both the face milling and the proposed UPSM are under the definition of raster milling. Nevertheless, in face milling using a ball milling tool, the tool rotates along an axis perpendicular to the workpiece, while the rotational axis of UPSM is parallel to the machined surface. Due to the unique machining principle of UPSM, the generation mechanism of the hybrid surfaces is introduced, and the optimal tool path generation strategy is detailed considering the compensation of the swing radius and tilting geometry of the diamond tool. Besides, the selecting criteria of the machining parameters is also discussed to ensure the ductile machining of brittle IR materials. In practical, two types of hybrid micro-optic components, namely hybrid micro-aspheric arrays and sinusoid grid surface with high-frequent secondary unidirectional phase gratings, were fabricated on a single-crystal silicon wafer. The acquired surface quality and the characteristics of the diffractive performances are further identified and analyzed in this study.
Hybrid micro-optics are characterized as high-frequent secondary micro/nanostructures superposed on a low-frequent primary surface with arbitrary shapes. In UPSM, the primary surface of the hybrid micro-optics is constructed via the removal of workpiece material, and the high-frequency secondary micro/nanostructures are simultaneously formed by the interference of the diamond tool edge between two neighboring raster cutting trajectories. The machining principle of UPSM for hybrid micro-optics is illustrated in Fig. 1. A diamond tool is fixed on the high-speed spindle with an adjustable swing radius. During the machining process, the rotating spindle horizontally feeds in the x direction, and the diamond tool intermittently cuts into and out of the workpiece surface with a specific depth of cut. In the meantime, the workpiece performs the transitional servo motions in z direction, just like slow tool servo, so as to deterministically generate the desired primary surface. After finishing one profile of cutting, a step motion along the raster direction (y direction) is carried out on the diamond tool, so the whole workpiece can be covered by material removal. In this way, secondary micro/nanostructures with desired shapes are flexibility generated using the tool residual marks through actively controlling the step interpolation in the raster direction.
Fig. 1 Schematic of the machining approach for hybrid surfaces with secondary micro/nanostructures.
The strategy of UPSM for hybrid micro-optics with desired primary surface and secondary micro/nanostructures is shown in Fig. 2. To avoid the interference of the cutting trajectories on the finished surface, the swing radius of the diamond tool should be selected first according to the smallest curvature radius of the desired primary surface. Then, the step interpolation of the raster movement is determined according to the desired shape of the secondary micro/nanostructures. It worth to note that micro/nanostructures with different cross-sectional profiles (including arc-shape, V-shape and rectangle) can be obtained by adopting the diamond tools with different edge shapes. By compensating the swing radius and the geometry tilt of the diamond tool, the toolpath is generated for the desired hybrid surfaces. To avoid brittle fracturs of IR materials, feed rates need to be carefully selected based on the ductile machining model for UPSM. Finally, the machined hybrid micro-optics are characterized by optical surface profiler to evaluate the surface quality and form error. The diffractive experiments are also conducted to evaluate the reflective diffraction characteristics of the generated hybrid surfaces.
Fig. 2 Strategy of UPSM for hybrid micro-optics.
Due to the unique cutting process of UPSM, the following advantages for fabricating hybrid micro-optics on IR materials can be achieved: (i) the primary surface and the secondary micro/nanostructures of the desired micro-optics can be simultaneously generated, without needing complicated machining processes that combines several machining technologies; (ii) deep ductile machining depth on IR materials can be achieved by the intermittent material removal process of UPSM, which increases the achievable azimuthal height variation of IR optical components; (iii) high-frequent diffractive structures with different shapes are flexibly constructed, which is difficult to be achieved by fast and slow tool servo due to the restriction of the feeding bandwidth of the hardware servo system; (iv) the hybrid optical surfaces are generated in a deterministic way, so the form accuracy can be well guaranteed.
The unique machining principle of UPSM leads to a different toolpath determination strategy compared with conventional diamond milling. In UPSM, the swing center point (SCP) needs to be determined as the toolpath according to the shapes of the desired hybrid optical surfaces. To determine the appropriate SCPs for the desired hybrid surfaces, the swing radius and the geometry tilt of the diamond tool should be compensated by the compensation algorithm. Then, the selecting criteria of the machining parameters are detailed to avoid the brittle fracturs of IR materials.
3.1 Compensation and determination of toolpath
In UPSM, the toolpath for the desired hybrid surface is decomposed into the 3-axis transitional servo motions of the milling machine, and hybrid surfaces are generated by the alternative feed and raster motions of the rotational diamond tool. Thus, the projected toolpath of UPSM is a set of parallel lines along feed direction with a constant length (L). Differential approach is adopted to determine the SCPs. The length of the feed motion is uniformly discretized into (Ns + 1) points. As shown in Fig. 3, a coordinate system (oc-xcyczc) is built on the cutter contacting point with the xc-axis and zc-axis are parallel to the feed and raster direction, respectively. For the n-th point of the m-th feed motion cycle, the coordinate of the cutter contacting point Oc(m,n), denoted as (xc(m,n),yc(m,n),zc(m,n)), can be expressed by:
(1){xc(m,n)=nNsLyc(m,n)=mSrzc(m,n)=F(xc(m,n),yc(m,n))
where Sr represents the step distance in the raster direction, and F(x, y) is the expression of the desired primary surface of the hybrid micro-optics. Due to ever-changing topography of the hybrid surface, the rake face of the diamond tool will always be tilted with respect to the depth of cut direction (zc-axis) and raster direction (yc-axis) with the tilting angles θ(m,n)and φ(m,n), respectively. As shown in Fig. 3, Point Pt(m,n) is the corresponding the tool nose center point for Oc(m,n), whose coordinate (xt(m,n),yt(m,n),zt(m,n)) is denoted as:
(2){xt(m,n)=xc(m,n)+Rsinθ(m,n)yt(m,n)=yc(m,n)+Rcosθ(m,n)sinφ(m,n)zt(m,n)=zc(m,n)+Rcosθ(m,n)cosφ(m,n)
where R is the tool nose radius. As shown in Fig. 3, line PK is perpendicular to line KOc and line KG is perpendicular to line GOc. Based on the geometry relation, the corresponding tiling angles α(m,n), θ(m,n) and φ(m,n) can be acquired as follows:
Fig. 3 Geometrical relation between the diamond tool and the workpiece surface.
(3){α(m,n)=−arctan∂F(xc(m,n),yc(m,n))∂xc(m,n)θ(m,n)=arctan∂F(xc(m,n),yc(m,n))∂yc(m,n)φ(m,n)=arctan(cosθ(m,n)tanα(m,n))
Different from fast and slow tool servo, the tool nose center points cannot be directly used as the tool path due to the rotation cutting trajectory for UPSM. In contrast, the coordinate of SCPs, denoted as (xs(m,n),ys(m,n),zs(m,n)), is not determined by the rotational angle of the diamond tool, so SCPs are used as the toolpath for the hybrid surfaces. According to Eqs. (1) and (2), the coordinate of the SCP can be calculated as:
(4){xs(m,n)=xc(m,n)+Rsinθ(m,n)+(Sw−R)sinα(m,n)ys(m,n)=yc(m,n)+Rcosθ(m,n)sinφ(m,n)zs(m,n)=zc(m,n)+Rcosθ(m,n)cosφ(m,n)+(Sw−R)cosα(m,n)
where Sw is the swing radius of the diamond tool. Following the aforementioned steps, the SCPs can be well determined according to the desired primary surface of the hybrid micro-optics.
3.2 Machining parameters
According to the principle of UPSM, three machining parameters, namely swing radius, step distance in raster direction and feed rate, need to be determined before conducting the machining operation. To avoid the interference of the diamond tool, swing radius should be determined first based on the curvature radius of the desired primary surface. For convex primary surface, there is no limit on the swing radius, while for concave surface the swing radius should be less than the minimum curvature radius of the primary surface in feed direction, which is expressed as follows:
(5)Sw<min[|(1+(∂F∂x)2)32∂2F∂x2|]
As learned from the surface generation principle of UPSM, the size of the secondary micro/nanostructures is not only determined by the step distance, but also influenced by the changing curvature of the primary surface. Nevertheless, in the previous toolpath generation strategies, the uniformity of the tool residual marks is generally neglected by employing evenly spaced step distance in the raster direction, which inevitably induces the non-uniform secondary diffractive structures in terms of size with the changing curvature of the primary surface [26]. Thus, an optimized algorithm with the consideration of the changing curvature is required to ensure the uniformity and the form accuracy of the secondary diffractive micro/nanostructures.
The geometrical relation between the height of the secondary micro/nanostructures and the step distance with the consideration of the changing curvature is shown in Fig. 4. To obtain a constant height of the desired secondary micro/nanostructures (h), the step distance for the n-th point of the m-th feed motion cycle (Sr(m,n)) is determined by the corresponding curvature. As the step distance is small in UPSM, the change of curvatures between two neighboring cutting points is regarded as unchanged in the algorithm. As shown in Fig. 4, an angle (γ) exists between the tangent line of the primary surface and the y-axis, the step distance in the raster direction can be calculated based on the geometric relation as:
(6)Sr(m,n)=2cos[|arctan(∂F∂y)|]×h(2R−h)
where h is the height of the desired secondary structures, and R is the tool nose radius which determines the shape and width of the secondary structures. As a result, the height of secondary micro/nanostructures can be well controlled by adopting appropriated step distance calculated by Eq. (6).
Fig. 4 Geometrical relation between the residual tool height and the step distance.
To avoid the brittle fractures and micro-cracks of IR materials in diamond cutting, the undeformed chip thickness needs to remain lower the critical depth of cut (DoC) of the IR material [27–29]. The chips of UPSM are intermittently formed as a result of two consecutive cutting processes, namely the current rotary cutting and the previous rotary cutting. In order to acquire a smooth surface, the maximum chip thickness (hmax) is required to be less than the critical DoC. As shown in Fig. 5, a tilting angle exits between the finished surface and the original surface in feed direction due to the curvature of the primary surface. As the space between two neighboring swing center points is very small in UPSM, the change of the curvature is neglected in the calculation, and the trochoidal cutting trajectory is equivalent to separate circles. The chip thickness of UPSM approaches zero at point a, then increases to the maximum chip thickness at point b. Based on the geometric relation, the coordinates of point b (xb, zb) in the os-xszs system can be calculated by the follow equations:
(7){xb=−fe+Sw2−yb2yb=∂F∂x×xb+Sw−d0cos(|arctan(∂F∂x)|)
where f is the feed rate in µm/r and d0 denotes the depth of cut. After determining the (xb, zb), the maximum chip thickness (hmax) can be obtained by:
Fig. 5 Schematic of UPSM viewed along the y direction.
(8)hmax=Sw−(xb2+yb2)
Equations (7) and (8) are used to calculate the maximum chip thickness (hmax) of UPSM under a specific group of machining parameters, i.e., feed rate and depth of cut. If the calculated hmax is smaller than the critical DoC of silicon, ductile material removal process can be ensured. For a desired hybrid surfaces, the larger the height variation of its primary surface, the deeper depth of cut is required in the machining process. It is well known that the critical depth of cut is determined by the material characteristics [27–29]. As the critical depth of cut is generally calculated based on the empirical formula [21,30], the result is not quite accurate. To acquire the accurate critical DoC of silicon, experiment method is applied by sculpturing silicon for a taper groove with increasing cutting depth in this study. Figure 6 shows the cross-sectional profile of the taper groove in <100> direction. Obvious ductile-brittle transition can be observed with a depth of 148 nm, which is the critical DoC of the silicon wafer [31,32]. Thus, according to the critical DoC of silicon and the height variation of the primary surface, appropriate feed rates can be calculated from Eqs. (7) and (8) to ensure the ductile machining process of UPSM.
Fig. 6 Cross-sectional profile of the taper groove in <100> direction.
Figure 7(a) shows the toolpath for a hybrid sinusoid surface with periodicity of 5 mm and amplitude of about 25 µm. A step distance of 20 µm is adopted in the raster direction. As shown in Fig. 7(a), the toolpath is smooth and characterized by a set of parallel lines in feed direction. Thus, this machining strategy offers an unchanged feed direction with respect to the crystallographic direction of the single-crystal IR materials, such as single-crystal silicon, which effectively avoid the undesired radial-spoke marks generated in fast and slow tool servo [18,33]. Besides, the SCPs is not uniformly distributed in the x-y plane, as shown in Fig. 7(b). This varying distance between two adjacent SCPs in both feed and raster directions is induced by the varying curvature radius of the primary surface, which indicates the effectiveness of the compensation algorithm of the swing radius and the tilt of the diamond tool. More importantly, this unique machining strategy of UPSM makes the generation of the secondary micro/nanostructures only dependent on the geometry and step distance of the diamond tool, instead of the dynamic property of the machining system. As a result, hybrid micro-optics with high-frequent secondary micro/nanostructures can be deterministically generated with one step in a much easier way.
Fig. 7 Schematic of (a) the toolpath and (b) the SCPs in x-y plane.
A five-axis milling machine (Precitech 705G) with two rotational tables and three translational servo slides was applied in UPSM of hybrid micro-optics on IR materials, as shown in Fig. 8. The workpiece glued on a fixture was installed on the parallel rotational table (b-axis). The tilting angle along feed direction can be minimized by carefully turning the rotation angle of the rotary table. After that the titling angle along raster direction is minimized by changing the pressing force on the back of the fixture. After the adjustment, the height variation along both feed and raster direction can be reduced to 1~2 µm with a sampling length of 10 mm. A commercial single-crystal diamond tool is clamped on the end of the spindle in z-axis with an adjustable swing radius. The workpiece material is single-crystal silicon, a typical IR material applied in infrared optics. The Young's elastic modulus is 160 Gpa, and the hardness is 12 Gpa. A three-dimensional non-contact optical measurement system provided by Zygo Corporation was then applied to capture the corresponding micro-topographies with proper magnification. To acquire a large measurement area, a set of small profiles were pitched together using the analysis software of the Zygo profiler.
Fig. 8 Picture of the milling system.
To validate the proposed method, two types of hybrid micro-optic components, namely micro-aspheric arrays and sinusoid grid surface with high-frequent secondary unidirectional phase gratings, were fabricated on a single-crystal silicon wafer. The pitch and height of the desired nano-grooves is 24 µm and 620 nm, respectively. The shape of the secondary unidirectional phase gratings is the same with that of tool edge shape. The primary surface of each micro-aspheric arrays can be expressed by [34]:
(9)z(x,y)=sCR024+41−(1+k)C2R02−sCρ2(x,y)4+41−(1+k)C2ρ2(x,y)
where s is the shape coefficient determining the concave-convex characteristic of the micro-aspheric surface; k determines the conic constant; C represents the curvature; R0 is the radius of the micro-aspheric surface. Ordered nano-microgrooves were superimposed on the primary surface, which serve as the secondary unidirectional phase gratings, the expression of the primary surface of the sinusoid surface is
(10)z(x,y)=Axsin(2πfxx)+Aysin(2πfyy)
where Ax = Ay = 6 µm and fx = fy = 0.2 × 10−3. Two diamond tools with different nose radius were applied for the hybrid micro-aspheric arrays and hybrid sinusoid grid surface, respectively (see Table 1). The adopted diamond tools have a rake angle of −25°, while the clearance angle is 10°. The machining parameters are detailed in Table 2.
Table 1. Structure parameters used for the primary micro-aspheric surface.
View Table | View all tables in this article
Table 2. Machining parameters used for the hybrid micro-aspheric and sinusoid surfaces.
To validate the feasibility of the proposed UPSM, two types of hybrid micro-optics including hybrid micro-aspheric arrays and hybrid sinusoid grid surface with high-frequent unidirectional phase gratings, were fabricated on a single-crystal silicon wafer. The characteristics of the generated hybrid surfaces are discussed in this section, and the corresponding reflective diffraction characteristic is also analyzed.
5.1 Micro-aspheric arrays with nano-gratings
Figure 9 illustrates the characteristics of the generated hybrid micro-aspheric arrays. An overview of the hierarchical surface topographies is shown in Fig. 9(a), which is captured by the stitched optical images with a 5 times amplification. It can be observed that a total of 10 hybrid micro-aspheric lens with secondary parallel nano-grooves are uniformly distributed in two lines. Figure 9(b) further shows an enlarged view of a hybrid micro-aspheric profile, which is captured by a 20 times amplification. As the secondary nano-grooves are formed by the periodic raster movement of the diamond tool, these nano-grooves are unidirectionally distributed with respect to raster direction. As shown in Fig. 9(c), the characteristics of the hybrid micro-aspheric structure can be more clearly observed by the cross-sectional profile in raster direction. It is observed that the cross-sectional profile is characterized as a curved primary surface imposed by a set of high-frequent arc-shaped nanostructures.
Fig. 9 Characteristics of the machined hybrid micro-aspheric arrays, (a) a large area view, (b) for an individual structure and (c) cross-sectional profile.
As shown in Figs. 10(b) and 10(c), through directly subtracting the secondary nano-grooves, the hierarchical surface is further divided into the primary aspheric surface and a nanostructured surface. Moreover, the shapes of the secondary nano-grooves are perfectly in accordance with the edges of the diamond tool, as shown in Fig. 10(d). The mean value of the pitch and the height of the nano-grooves is 24.1 µm and 607.5 nm, respectively. In view of the curvature change of the primary surface, the pitch and height of the desired nano-grooves is 24 µm and 620 nm, respectively. Thus, the generated height and pitch commonly present a good agreement with that of desired nano-grooves, with a slight deviation of 2%. This deviation can be regarded as the form error of the generated hybrid micro-aspheric surfaces, which might jointly result from the material spring back and kinematic error of the machine tool. Besides, the green envelop curve of the secondary nanogrooves that is shown in Fig. 9(c) is in good accordance with the desired primary surface derive from Eq. (9), which strongly validates the feasibility of the UPSM for deterministic generation of IR hybrid micro-optics with high form accuracy.
Fig. 10 3D topographies of (a) generated hierarchical micro-aspheric surface, (b) the filter primary aspheric surface, (c) the extracted secondary nano-grooves and (d) 2D profile in cross-sectional direction after removing the primary profile.
To fulfill the optical application, the maximum allowable form error of an optical element is λ/4 of the transmitted light [35]. As single-crystal silicon is normally used in IR optical area that transmits the light with wavelength ranging from 1.2 µm to 6 µm. As a result, the required form error for a silicon micro-groove needs to be less than 300 nm PV for a 1.2 µm wavelength, in order to avoid the distortion of the gathered profile. The experiment results validate that the height and pitch of the generated secondary diffractive nanostructures present a good agreement with that of desired ones, with a form error about 0.1 µm, which fulfils the requirement of IR application.
Through removing the groove shape from the hybrid micro-aspheric structure in a small area, the corresponding micro-topography can be acquired, as shown in Fig. 11. Very small surface roughness value was obtained at Sa = 2 nm, indicating the ductile material removal without brittle fractures. More importantly, both the acquired 3D surface topographies and the 2D cross-sectional profiles are very smooth, as shown in Fig. 10, which further validate capability of UPSM in ductile machining of IR materials for desired hybrid micro-optics. Obviously, the micro-topography of the micro-grooves is characterized as undesired stripe patterns that is vertical to the feed direction, which should correspond to the tool residual marks. These marks may be caused by the intermittent cutting operation of UPSM. To obscure these marks, large swing radius and small feed rates are possibly adopted.
Fig. 11 Micro-topography of the generated surface.
Generally, researcher use an index named total integrated scattering (TIS) to evaluate the optimal performance of an optical component [18,36]. According to Harvey et al. [36], TIS smaller than 0.01 is acceptable for most optical systems, and TIS can be expressed by
(11)TIS≈(4πδλ)2
where λ is the incident light wavelength and δ denotes the RMS surface roughness Rq. As single-crystal silicon is normally used to transmit the infrared light with wavelength ranging from 1.2 µm to 6 µm, the surface roughness is required to be less than 10 nm Rq. To simplify the calculation, the required Ra is estimated as 0.8 that of Rq, so surface roughness lower than 8 nm Ra is required for the IR optical components made by single-crystal silicon. The surface roughness acquired in the study is 2 nm Sa fulfils the requirement. In the revised manuscript, the assessment of the finished surface quality from the view of optical performance is added and highlighted.
5.2 Sinusoid freeform surface with nano-gratings
To further validate the effectiveness of UPSM, another kind of hybrid micro-optics with much large height variation, namely hybrid sinusoid surface with secondary diffractive phase gratings, is also deigned and machined. The mathematical expression of the primary sinusoid freeform surface is described by Eq. (10). Figure 12(a) illustrates the 3D topography of the generated hybrid sinusoid freeform surface, whose largest height variation is about 25 µm. It is known that due to the hard-and-brittle nature of silicon, it is difficult to fabricate freeform silicon optical components with large height variation, while guaranteeing ultra-smooth surface quality by fast and slow tool servo. As shown in Fig. 13, the microscope image of the generated surface by UPSM is very smooth without brittle fractures. This is majorly attributed to the intermittent cutting process UPSM, in which way very small chip thickness can be generated even under large depth of cut. Thus, UPSM is more superior to generate IR optics with large variation for a variety of shapes.
Fig. 12 (a) 3D topography of the generated hybrid sinusoid freeform surface and its cross-sectional profiles in (b) feed direction and (c) raster direction.
Fig. 13 Microscope image of the generated sinusoid freeform surface in a small zone.
Figures 14(a) and 14(b) compare the 2D profiles of the hybrid sinusoid freeform surface generated by ordinary algorithm and the optimized algorithm, respectively. It is obvious that the secondary nanostructures generated by ordinary algorithm is more non-uniform in height, and a very bumpier envelope line is observed on the top of the secondary nanostructures. This is caused by the change of the curvature in the raster direction. In comparison, the envelop line of the secondary nanostructures generated by the optimized algorithm is much smoother, which is attributed to the consideration of the changing curvature in the calculation of step distance as expressed in Eq. (6).
Fig. 14 2D profiles in cross-sectional direction after removing the primary profile by (a) ordinary algorithm and (b) optimized algorithm.
The major advantage of the proposed UPSM in fabricating hybrid infrared optics is that the primary reflective/refractive surface and the secondary diffractive nanostructures of the hybrid micro-optics can be simultaneously generated, without complicated machining processes. In comparison, for previous methods, multi-step processes that combines ultra-precision machining technologies and non-mechanical methods were normally required to obtain the hybrid IR micro-optics with desired shapes [6,8]. However, this multi-step processes not only introduce unnecessary machining errors, but also is relatively high-cost and low-efficient. More importantly, the form accuracy acquired by etching processes is generally difficult to control. In contrast, it is learned from the experiment results from Fig. 8 and Fig. 12, very high form accuracy and smooth finished surface quality are achieved, which is also validate the superiority of UPSM.
Besides, high-frequent diffractive structures with different shapes are flexibly constructed by UPSM, which is difficult to be achieved by fast and slow tool servo (FTS/STS) due to the restriction of the feeding bandwidth of the hardware servo system. It is known that the periodicity of the secondary structures generated by FTS/STS is in an order of several hundred micrometers [37]. In contrast, the periodicity of the secondary diffractive nanostructures generated by UPSM is about 20 µm, as shown in Fig. 9, which is much less than that of FTS/STS. Especially, as learned from the machining principle of UPSM, an even smaller periodicity can be easily achieved by UPSM regardless of the moving bandwidth limitation of the servo system, as the secondary diffractive micro/nanostructures are constructed by the interference of two neighboring raster cutting operations in UPSM, which is the advantage of UPSM.
Moreover, the unidirectional characteristics of the secondary nano-gratings can be clearly illustrated in Figs. 11(b) and 11(c). Smooth profile without nano-gratings can be observed on the cross-sectional profile in feed direction, while sinusoid profile with imposition of secondary arc-shaped micro/nanogrooves is acquired in the raster direction. This unidirectional property leads to a unique reflective diffraction characteristic. As illustrated in Fig. 15, a set of even-distributed light spots can be acquired from the diffractive light obtained from the hybrid sinusoid freeform surface. In contrast, only a diffractive spot is observed from the diffractive light of the conventional sinusoid surface. This unique optical property may be useful in the optics design for special infrared imaging system and light path correction [38,39]. Further, this hierarchical surface can be designed to be an integrated hybrid IR optical component with both reflective/refractive primary surface and high-frequent secondary diffractive nanostructures [8].
Fig. 15 Reflective diffraction characteristics of the hybrid sinusoid freeform surface.
In the present study, a novel ultra-precision side milling (UPSM) method has been adopted and demonstrated to achieve one-step generation of hybrid micro-optics on infrared (IR) materials with high form accuracy. This approach effectively overcomes the difficulties in fabricating complicated hierarchical structures on hard-and-brittle IR materials with very low defects. Further, based on this machining strategy, both the primary refractive/reflective freeform surface and secondary diffractive nanostructures are formed within one-step operation, which accordingly is more beneficial to reduce the processing time and improve the machining accuracy. The main conclusions can be summarized as follows:
(1) In UPSM, the primary surface of the hybrid micro-optics is formed by the removal of workpiece material, and the high-frequency secondary micro/nanostructures are simultaneously formed by the interference of the diamond tool edge between two neighboring raster cutting operations. Thus, very high-frequent diffractive secondary structures can be conveniently construed by adjusting the step distance in raster direction, without the limitation of the bandwidth of the hardware servo system.
(2) Via the intermittent material removal process of UPSM, very small chip thickness can be realized even under a large depth of cut, which is beneficial to ductile machining of brittle IR materials. This approach provides a guidance to simultaneously fabricate complicated hierarchical structures on brittle IR materials with ultra-precision form accuracy and ultra-smooth surface quality.
(3) Two types of hybrid micro-optic components, namely micro-aspheric arrays and sinusoid grid surface with high-frequent secondary unidirectional phase gratings, are successfully fabricated on single-crystal silicon to validate the proposed method. The generated surfaces present a good agreement with that of desired ones, with a slight deviation of 2%. Smooth surface with a roughness of 2 nm Sa is achieved.
(4) The unidirectional diffractive nanostructures of the generated hybrid micro-optics lead to a set of even-distributed diffractive light spots, while the diffractive light from the conventional sinusoid surface only include a diffractive spot. This unique optical property provides more imaginations in the design of IR optical systems.
Research Committee of the Hong Kong Polytechnic University (Project Code: RUNS); National Natural Science Foundation of China (51675455)
This work was supported partially by the Research Committee of The Hong Kong Polytechnic University (Project Code: RUNS) and the National Natural Science Foundation of China (51675455).
1. S. Liu, J. A. Mulligan, and S. G. Adie, "Volumetric optical coherence microscopy with a high space-bandwidth-time product enabled by hybrid adaptive optics," Biomed. Opt. Express 9(7), 3137–3152 (2018). [CrossRef] [PubMed]
2. Y. Pang, Y. Li, M. Yan, D. Liu, J. Wang, Z. Xu, and S. Qu, "Hybrid metasurfaces for microwave reflection and infrared emission reduction," Opt. Express 26(9), 11950–11958 (2018). [CrossRef] [PubMed]
3. M. Malinauskas, A. Žukauskas, V. Purlys, K. Belazaras, A. Momot, D. Paipulas, R. Gadonas, A. Piskarskas, H. Gilbergs, A. Gaidukevičiūtė, I. Sakellari, M. Farsari, and S. Juodkazis, "Femtosecond laser polymerization of hybrid/integrated micro-optical elements and their characterization," J. Opt. 12(12), 124010 (2010). [CrossRef]
4. D.-H. Ko, J. R. Tumbleston, K. J. Henderson, L. E. Euliss, J. M. DeSimone, R. Lopez, and E. T. Samulski, "Biomimetic microlens array with antireflective "moth-eye" surface," Soft Matter 7(14), 6404–6407 (2011). [CrossRef]
5. Z. Sun, S. To, and S. Zhang, "A novel ductile machining model of single-crystal silicon for freeform surfaces with large azimuthal height variation by ultra-precision fly cutting," Int. J. Mach. Tools Manuf. 135, 1–11 (2018). [CrossRef]
6. Z. Deng, Q. Yang, F. Chen, X. Meng, H. Bian, J. Yong, C. Shan, and X. Hou, "Fabrication of large-area concave microlens array on silicon by femtosecond laser micromachining," Opt. Lett. 40(9), 1928–1931 (2015). [CrossRef] [PubMed]
7. H. Zhang, L. Li, S. Scheiding, A. Gebhardt, S. Risse, R. Eberhardt, A. Tünnermann, D. Yao, and Y. Y. Allen, "Fabrication of three-dimensional functional microstructures on curved substrates using three-dimensional microlens projection," J. Micro Nano-Manuf. 1(3), 031006 (2013). [CrossRef]
8. R. Kleindienst, R. Kampmann, S. Stoebenau, and S. Sinzinger, "Hybrid optical (freeform) components--functionalization of nonplanar optical surfaces by direct picosecond laser ablation," Appl. Opt. 50(19), 3221–3228 (2011). [CrossRef] [PubMed]
9. J. Kim, N. Takama, B. Kim, and H. Fujita, "Optical-softlithographic technology for patterning on curved surfaces," J. Micromech. Microeng. 19(5), 055017 (2009). [CrossRef]
10. Y. Chen, "Nanofabrication by electron beam lithography and its applications: a review," Microelectron. Eng. 135, 57–72 (2015). [CrossRef]
11. C. M. Waits, A. Modafe, and R. Ghodssi, "Investigation of gray-scale technology for large area 3D silicon MEMS structures," J. Micromech. Microeng. 13(2), 170–177 (2002). [CrossRef]
12. J. M. Ramirez, V. Vakarin, J. Frigerio, P. Chaisakul, D. Chrastina, X. Le Roux, A. Ballabio, L. Vivien, G. Isella, and D. Marris-Morini, "Ge-rich graded-index Si 1-xGex waveguides with broadband tight mode confinement and flat anomalous dispersion for nonlinear mid-infrared photonics," Opt. Express 25(6), 6561–6567 (2017). [CrossRef] [PubMed]
13. V. J. Kitsmiller, M. M. Dummer, K. Johnson, G. D. Cole, and T. D. O'Sullivan, "Frequency domain diffuse optical spectroscopy with a near-infrared tunable vertical cavity surface emitting laser," Opt. Express 26(16), 21033–21043 (2018). [CrossRef] [PubMed]
14. H. Zuo, D.-Y. Choi, X. Gai, B. Luther-Davies, and B. Zhang, "CMOS compatible fabrication of micro, nano convex silicon lens arrays by conformal chemical vapor deposition," Opt. Express 25(4), 3069–3076 (2017). [CrossRef] [PubMed]
15. Z. Li, F. Fang, J. Chen, and X. Zhang, "Machining approach of freeform optics on infrared materials via ultra-precision turning," Opt. Express 25(3), 2051–2062 (2017). [CrossRef] [PubMed]
16. B. S. Dutterer, J. L. Lineberger, P. J. Smilie, D. S. Hildebrand, T. A. Harriman, M. A. Davies, T. J. Suleski, and D. A. Lucca, "Diamond milling of an Alvarez lens in germanium," Precis. Eng. 38(2), 398–408 (2014). [CrossRef]
17. J. Zhang, N. Suzuki, Y. Wang, and E. Shamoto, "Fundamental investigation of ultra-precision ductile machining of tungsten carbide by applying elliptical vibration cutting with single crystal diamond," J. Mater. Process. Technol. 214(11), 2644–2659 (2014). [CrossRef]
18. M. Mukaida and J. Yan, "Ductile machining of single-crystal silicon for microlens arrays by ultraprecision diamond turning using a slow tool servo," Int. J. Mach. Tools Manuf. 115, 2–14 (2017). [CrossRef]
19. A. R. A. Manaf, T. Sugiyama, and J. Yan, "Design and fabrication of Si-HDPE hybrid Fresnel lenses for infrared imaging systems," Opt. Express 25(2), 1202–1220 (2017). [CrossRef] [PubMed]
20. Z. Li, F. Fang, X. Zhang, X. Liu, and H. Gao, "Highly efficient machining of non-circular freeform optics using fast tool servo assisted ultra-precision turning," Opt. Express 25(21), 25243–25256 (2017). [CrossRef] [PubMed]
21. S. Goel, X. Luo, A. Agrawal, and R. L. Reuben, "Diamond machining of silicon: a review of advances in molecular dynamics simulation," Int. J. Mach. Tools Manuf. 88, 131–164 (2015). [CrossRef]
22. J. Zhang, J. Zhang, T. Cui, Z. Hao, and A. Al Zahrani, "Sculpturing of single crystal silicon microstructures by elliptical vibration cutting," J. Manuf. Process. 29, 389–398 (2017). [CrossRef]
23. J. Zhang, T. Cui, C. Ge, Y. Sui, and H. Yang, "Review of micro/nano machining by utilizing elliptical vibration cutting," Int. J. Mach. Tools Manuf. 106, 109–126 (2016). [CrossRef]
24. S. Zhang, S. To, Z. Zhu, and G. Zhang, "A review of fly cutting applied to surface generation in ultra-precision machining," Int. J. Mach. Tools Manuf. 103, 13–27 (2016). [CrossRef]
25. F. Fang, X. Zhang, A. Weckenmann, G. Zhang, and C. Evans, "Manufacturing and measurement of freeform optics," CIRP Ann. 62(2), 823–846 (2013). [CrossRef]
26. L. Kong, "Modeling of ultra-precision raster milling and characterization of optical freeform surfaces," (Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, 2010).
27. T. G. Bifano, T. A. Dow, and R. O. Scattergood, "Ductile-regime grinding: a new technology for machining brittle materials," J. Eng. Ind. 113(2), 184–189 (1991). [CrossRef]
28. A. V. Gopal and P. V. Rao, "A new chip-thickness model for performance assessment of silicon carbide grinding," Int. J. Adv. Manuf. Technol. 24(11-12), 816–820 (2004). [CrossRef]
29. Z. Dong and H. Cheng, "Ductile mode grinding of reaction-bonded silicon carbide mirrors," Appl. Opt. 56(26), 7404–7412 (2017). [CrossRef] [PubMed]
30. S. Goel, X. Luo, P. Comley, R. L. Reuben, and A. Cox, "Brittle–ductile transition during diamond turning of single crystal silicon carbide," Int. J. Mach. Tools Manuf. 65, 15–21 (2013). [CrossRef]
31. G. Xiao, S. To, and E. Jelenković, "Effects of non-amorphizing hydrogen ion implantation on anisotropy in micro cutting of silicon," J. Mater. Process. Technol. 225, 439–450 (2015). [CrossRef]
32. J. Yan, T. Asami, H. Harada, and T. Kuriyagawa, "Fundamental investigation of subsurface damage in single crystalline silicon caused by diamond machining," Precis. Eng. 33(4), 378–386 (2009). [CrossRef]
33. M. Wang, W. Wang, and Z. Lu, "Anisotropy of machined surfaces involved in the ultra-precision turning of single-crystal silicon—a simulation and experimental study," Int. J. Adv. Manuf. Technol. 60(5-8), 473–485 (2012). [CrossRef]
34. D. Yu, Y. Wong, and G. Hong, "Ultraprecision machining of micro-structured functional surfaces on brittle materials," J. Micromech. Microeng. 21(9), 095011 (2011). [CrossRef]
35. H. Ottevaere, R. Cox, H.-P. Herzig, T. Miyashita, K. Naessens, M. Taghizadeh, R. Völkel, H. Woo, and H. Thienpont, "Comparing glass and plastic refractive microlenses fabricated with different technologies," J. Opt. A, Pure Appl. Opt. 8(7), S407–S429 (2006). [CrossRef]
36. J. E. Harvey, N. Choi, S. Schroeder, and A. Duparré, "Total integrated scatter from surfaces with arbitrary roughness, correlation widths, and incident angles," Opt. Eng. 51(1), 013402 (2012). [CrossRef]
37. L. Zhu, Z. Li, F. Fang, S. Huang, and X. Zhang, "Review on fast tool servo machining of optical freeform surfaces," Int. J. Adv. Manuf. Technol. 95(5-8), 2071–2092 (2018). [CrossRef]
38. D. Fattal, Z. Peng, T. Tran, S. Vo, M. Fiorentino, J. Brug, and R. G. Beausoleil, "A multi-directional backlight for a wide-angle, glasses-free three-dimensional display," Nature 495(7441), 348–351 (2013). [CrossRef] [PubMed]
39. T. Ando, T. Korenaga, M. A. Suzuki, and J. Tanida, "Diffraction light analysis method for a diffraction grating imaging lens," Appl. Opt. 53(11), 2532–2538 (2014). [CrossRef] [PubMed]
S. Liu, J. A. Mulligan, and S. G. Adie, "Volumetric optical coherence microscopy with a high space-bandwidth-time product enabled by hybrid adaptive optics," Biomed. Opt. Express 9(7), 3137–3152 (2018).
Y. Pang, Y. Li, M. Yan, D. Liu, J. Wang, Z. Xu, and S. Qu, "Hybrid metasurfaces for microwave reflection and infrared emission reduction," Opt. Express 26(9), 11950–11958 (2018).
M. Malinauskas, A. Žukauskas, V. Purlys, K. Belazaras, A. Momot, D. Paipulas, R. Gadonas, A. Piskarskas, H. Gilbergs, A. Gaidukevičiūtė, I. Sakellari, M. Farsari, and S. Juodkazis, "Femtosecond laser polymerization of hybrid/integrated micro-optical elements and their characterization," J. Opt. 12(12), 124010 (2010).
D.-H. Ko, J. R. Tumbleston, K. J. Henderson, L. E. Euliss, J. M. DeSimone, R. Lopez, and E. T. Samulski, "Biomimetic microlens array with antireflective "moth-eye" surface," Soft Matter 7(14), 6404–6407 (2011).
Z. Sun, S. To, and S. Zhang, "A novel ductile machining model of single-crystal silicon for freeform surfaces with large azimuthal height variation by ultra-precision fly cutting," Int. J. Mach. Tools Manuf. 135, 1–11 (2018).
Z. Deng, Q. Yang, F. Chen, X. Meng, H. Bian, J. Yong, C. Shan, and X. Hou, "Fabrication of large-area concave microlens array on silicon by femtosecond laser micromachining," Opt. Lett. 40(9), 1928–1931 (2015).
H. Zhang, L. Li, S. Scheiding, A. Gebhardt, S. Risse, R. Eberhardt, A. Tünnermann, D. Yao, and Y. Y. Allen, "Fabrication of three-dimensional functional microstructures on curved substrates using three-dimensional microlens projection," J. Micro Nano-Manuf. 1(3), 031006 (2013).
R. Kleindienst, R. Kampmann, S. Stoebenau, and S. Sinzinger, "Hybrid optical (freeform) components--functionalization of nonplanar optical surfaces by direct picosecond laser ablation," Appl. Opt. 50(19), 3221–3228 (2011).
J. Kim, N. Takama, B. Kim, and H. Fujita, "Optical-softlithographic technology for patterning on curved surfaces," J. Micromech. Microeng. 19(5), 055017 (2009).
Y. Chen, "Nanofabrication by electron beam lithography and its applications: a review," Microelectron. Eng. 135, 57–72 (2015).
C. M. Waits, A. Modafe, and R. Ghodssi, "Investigation of gray-scale technology for large area 3D silicon MEMS structures," J. Micromech. Microeng. 13(2), 170–177 (2002).
J. M. Ramirez, V. Vakarin, J. Frigerio, P. Chaisakul, D. Chrastina, X. Le Roux, A. Ballabio, L. Vivien, G. Isella, and D. Marris-Morini, "Ge-rich graded-index Si 1-xGex waveguides with broadband tight mode confinement and flat anomalous dispersion for nonlinear mid-infrared photonics," Opt. Express 25(6), 6561–6567 (2017).
V. J. Kitsmiller, M. M. Dummer, K. Johnson, G. D. Cole, and T. D. O'Sullivan, "Frequency domain diffuse optical spectroscopy with a near-infrared tunable vertical cavity surface emitting laser," Opt. Express 26(16), 21033–21043 (2018).
H. Zuo, D.-Y. Choi, X. Gai, B. Luther-Davies, and B. Zhang, "CMOS compatible fabrication of micro, nano convex silicon lens arrays by conformal chemical vapor deposition," Opt. Express 25(4), 3069–3076 (2017).
Z. Li, F. Fang, J. Chen, and X. Zhang, "Machining approach of freeform optics on infrared materials via ultra-precision turning," Opt. Express 25(3), 2051–2062 (2017).
B. S. Dutterer, J. L. Lineberger, P. J. Smilie, D. S. Hildebrand, T. A. Harriman, M. A. Davies, T. J. Suleski, and D. A. Lucca, "Diamond milling of an Alvarez lens in germanium," Precis. Eng. 38(2), 398–408 (2014).
J. Zhang, N. Suzuki, Y. Wang, and E. Shamoto, "Fundamental investigation of ultra-precision ductile machining of tungsten carbide by applying elliptical vibration cutting with single crystal diamond," J. Mater. Process. Technol. 214(11), 2644–2659 (2014).
M. Mukaida and J. Yan, "Ductile machining of single-crystal silicon for microlens arrays by ultraprecision diamond turning using a slow tool servo," Int. J. Mach. Tools Manuf. 115, 2–14 (2017).
A. R. A. Manaf, T. Sugiyama, and J. Yan, "Design and fabrication of Si-HDPE hybrid Fresnel lenses for infrared imaging systems," Opt. Express 25(2), 1202–1220 (2017).
Z. Li, F. Fang, X. Zhang, X. Liu, and H. Gao, "Highly efficient machining of non-circular freeform optics using fast tool servo assisted ultra-precision turning," Opt. Express 25(21), 25243–25256 (2017).
S. Goel, X. Luo, A. Agrawal, and R. L. Reuben, "Diamond machining of silicon: a review of advances in molecular dynamics simulation," Int. J. Mach. Tools Manuf. 88, 131–164 (2015).
J. Zhang, J. Zhang, T. Cui, Z. Hao, and A. Al Zahrani, "Sculpturing of single crystal silicon microstructures by elliptical vibration cutting," J. Manuf. Process. 29, 389–398 (2017).
J. Zhang, T. Cui, C. Ge, Y. Sui, and H. Yang, "Review of micro/nano machining by utilizing elliptical vibration cutting," Int. J. Mach. Tools Manuf. 106, 109–126 (2016).
S. Zhang, S. To, Z. Zhu, and G. Zhang, "A review of fly cutting applied to surface generation in ultra-precision machining," Int. J. Mach. Tools Manuf. 103, 13–27 (2016).
F. Fang, X. Zhang, A. Weckenmann, G. Zhang, and C. Evans, "Manufacturing and measurement of freeform optics," CIRP Ann. 62(2), 823–846 (2013).
L. Kong, "Modeling of ultra-precision raster milling and characterization of optical freeform surfaces," (Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, 2010).
T. G. Bifano, T. A. Dow, and R. O. Scattergood, "Ductile-regime grinding: a new technology for machining brittle materials," J. Eng. Ind. 113(2), 184–189 (1991).
A. V. Gopal and P. V. Rao, "A new chip-thickness model for performance assessment of silicon carbide grinding," Int. J. Adv. Manuf. Technol. 24(11-12), 816–820 (2004).
Z. Dong and H. Cheng, "Ductile mode grinding of reaction-bonded silicon carbide mirrors," Appl. Opt. 56(26), 7404–7412 (2017).
S. Goel, X. Luo, P. Comley, R. L. Reuben, and A. Cox, "Brittle–ductile transition during diamond turning of single crystal silicon carbide," Int. J. Mach. Tools Manuf. 65, 15–21 (2013).
G. Xiao, S. To, and E. Jelenković, "Effects of non-amorphizing hydrogen ion implantation on anisotropy in micro cutting of silicon," J. Mater. Process. Technol. 225, 439–450 (2015).
J. Yan, T. Asami, H. Harada, and T. Kuriyagawa, "Fundamental investigation of subsurface damage in single crystalline silicon caused by diamond machining," Precis. Eng. 33(4), 378–386 (2009).
M. Wang, W. Wang, and Z. Lu, "Anisotropy of machined surfaces involved in the ultra-precision turning of single-crystal silicon—a simulation and experimental study," Int. J. Adv. Manuf. Technol. 60(5-8), 473–485 (2012).
D. Yu, Y. Wong, and G. Hong, "Ultraprecision machining of micro-structured functional surfaces on brittle materials," J. Micromech. Microeng. 21(9), 095011 (2011).
H. Ottevaere, R. Cox, H.-P. Herzig, T. Miyashita, K. Naessens, M. Taghizadeh, R. Völkel, H. Woo, and H. Thienpont, "Comparing glass and plastic refractive microlenses fabricated with different technologies," J. Opt. A, Pure Appl. Opt. 8(7), S407–S429 (2006).
J. E. Harvey, N. Choi, S. Schroeder, and A. Duparré, "Total integrated scatter from surfaces with arbitrary roughness, correlation widths, and incident angles," Opt. Eng. 51(1), 013402 (2012).
L. Zhu, Z. Li, F. Fang, S. Huang, and X. Zhang, "Review on fast tool servo machining of optical freeform surfaces," Int. J. Adv. Manuf. Technol. 95(5-8), 2071–2092 (2018).
D. Fattal, Z. Peng, T. Tran, S. Vo, M. Fiorentino, J. Brug, and R. G. Beausoleil, "A multi-directional backlight for a wide-angle, glasses-free three-dimensional display," Nature 495(7441), 348–351 (2013).
T. Ando, T. Korenaga, M. A. Suzuki, and J. Tanida, "Diffraction light analysis method for a diffraction grating imaging lens," Appl. Opt. 53(11), 2532–2538 (2014).
Adie, S. G.
Agrawal, A.
Al Zahrani, A.
Allen, Y. Y.
Ando, T.
Asami, T.
Ballabio, A.
Beausoleil, R. G.
Belazaras, K.
Bian, H.
Bifano, T. G.
Brug, J.
Chaisakul, P.
Chen, F.
Chen, J.
Cheng, H.
Choi, D.-Y.
Choi, N.
Chrastina, D.
Cole, G. D.
Comley, P.
Cox, A.
Cox, R.
Cui, T.
Davies, M. A.
Deng, Z.
DeSimone, J. M.
Dong, Z.
Dow, T. A.
Dummer, M. M.
Duparré, A.
Dutterer, B. S.
Eberhardt, R.
Euliss, L. E.
Fang, F.
Farsari, M.
Fattal, D.
Fiorentino, M.
Frigerio, J.
Fujita, H.
Gadonas, R.
Gai, X.
Gaidukeviciute, A.
Gao, H.
Ge, C.
Gebhardt, A.
Ghodssi, R.
Gilbergs, H.
Goel, S.
Gopal, A. V.
Hao, Z.
Harada, H.
Harriman, T. A.
Harvey, J. E.
Henderson, K. J.
Herzig, H.-P.
Hildebrand, D. S.
Hong, G.
Hou, X.
Huang, S.
Isella, G.
Jelenkovic, E.
Johnson, K.
Juodkazis, S.
Kampmann, R.
Kim, B.
Kitsmiller, V. J.
Kleindienst, R.
Ko, D.-H.
Korenaga, T.
Kuriyagawa, T.
Le Roux, X.
Li, Z.
Lineberger, J. L.
Liu, D.
Liu, S.
Liu, X.
Lopez, R.
Lu, Z.
Lucca, D. A.
Luo, X.
Luther-Davies, B.
Malinauskas, M.
Manaf, A. R. A.
Marris-Morini, D.
Meng, X.
Miyashita, T.
Modafe, A.
Momot, A.
Mukaida, M.
Mulligan, J. A.
Naessens, K.
O'Sullivan, T. D.
Ottevaere, H.
Paipulas, D.
Pang, Y.
Peng, Z.
Piskarskas, A.
Purlys, V.
Qu, S.
Ramirez, J. M.
Rao, P. V.
Reuben, R. L.
Risse, S.
Sakellari, I.
Samulski, E. T.
Scattergood, R. O.
Scheiding, S.
Schroeder, S.
Shamoto, E.
Shan, C.
Sinzinger, S.
Smilie, P. J.
Stoebenau, S.
Sugiyama, T.
Sui, Y.
Suleski, T. J.
Sun, Z.
Suzuki, M. A.
Suzuki, N.
Taghizadeh, M.
Takama, N.
Tanida, J.
Thienpont, H.
To, S.
Tran, T.
Tumbleston, J. R.
Tünnermann, A.
Vakarin, V.
Vivien, L.
Vo, S.
Völkel, R.
Waits, C. M.
Wang, J.
Wang, M.
Wang, W.
Wang, Y.
Weckenmann, A.
Wong, Y.
Woo, H.
Xiao, G.
Xu, Z.
Yan, J.
Yan, M.
Yang, H.
Yang, Q.
Yao, D.
Yong, J.
Yu, D.
Zhang, B.
Zhang, G.
Zhang, H.
Zhang, J.
Zhu, L.
Zhu, Z.
Žukauskas, A.
Zuo, H.
Biomed. Opt. Express (1)
CIRP Ann. (1)
Int. J. Adv. Manuf. Technol. (3)
Int. J. Mach. Tools Manuf. (6)
J. Eng. Ind. (1)
J. Manuf. Process. (1)
J. Mater. Process. Technol. (2)
J. Micro Nano-Manuf. (1)
J. Micromech. Microeng. (3)
J. Opt. A, Pure Appl. Opt. (1)
Microelectron. Eng. (1)
Opt. Eng. (1)
Precis. Eng. (2)
Soft Matter (1)
Table 1 Structure parameters used for the primary micro-aspheric surface.
Table 2 Machining parameters used for the hybrid micro-aspheric and sinusoid surfaces.
(1) { x c (m,n) = n N s L y c (m,n) =m S r z c (m,n) =F( x c (m,n) , y c (m,n) )
(2) { x t (m,n) = x c (m,n) +Rsin θ (m,n) y t (m,n) = y c (m,n) +Rcos θ (m,n) sin φ (m,n) z t (m,n) = z c (m,n) +Rcos θ (m,n) cos φ (m,n)
(3) { α (m,n) =−arctan ∂F( x c (m,n) , y c (m,n) ) ∂ x c (m,n) θ (m,n) =arctan ∂F( x c (m,n) , y c (m,n) ) ∂ y c (m,n) φ (m,n) =arctan(cos θ (m,n) tan α (m,n) )
(4) { x s (m,n) = x c (m,n) +Rsin θ (m,n) +( S w −R)sin α (m,n) y s (m,n) = y c (m,n) +Rcos θ (m,n) sin φ (m,n) z s (m,n) = z c (m,n) +Rcos θ (m,n) cos φ (m,n) +( S w −R)cos α (m,n)
(5) S w <min[| (1+ ( ∂F ∂x ) 2 ) 3 2 ∂ 2 F ∂ x 2 |]
(6) S r (m,n) =2cos[| arctan( ∂F ∂y ) |]× h(2R−h)
(7) { x b =− f e + S w 2 − y b 2 y b = ∂F ∂x × x b + S w − d 0 cos(| arctan( ∂F ∂x ) |)
(8) h max = S w − ( x b 2 + y b 2 )
(9) z(x,y)= sC R 0 2 4+4 1−(1+k) C 2 R 0 2 − sC ρ 2 (x,y) 4+4 1−(1+k) C 2 ρ 2 (x,y)
(10) z(x,y)= A x sin(2π f x x)+ A y sin(2π f y y)
(11) TIS≈ ( 4πδ λ ) 2
Structure parameters used for the primary micro-aspheric surface.
Shape coefficient s −1
Radius of the array R0 0.223 mm
Conic constant k −0.8
Curvature C 0.2 mm−1
Machining parameters used for the hybrid micro-aspheric and sinusoid surfaces.
Machining parameters
Hybrid micro-aspheric surface
Hybrid sinusoid surface
Swing radius (mm) 5 15.5
Spindle rotation rate (rpm) 7000 4000
Step distance (µm) 24 40
Tool nose radius (mm) 0.12 0.27
Material Single-crystal silicon Single-crystal silicon
Cutting direction <100> <100>
Depth of cut (µm) 3 5
Feed rate (µm/r) 2 4


text:
Q: Asp.net Mvc: access external project Bundles I have a project called WebLibrary, which contains lots of library controls css and js files.
To improve performance, i am compressing and combining all the css files using Bundles:
public class BundleConfig
{
    // For more information on Bundling, visit http://go.microsoft.com/fwlink/?LinkId=254725
    public static void RegisterBundles(BundleCollection bundles)
    {
        BundleTable.EnableOptimizations = true;
        bundles.IgnoreList.Clear();

        bundles.Add(new Bundle("~/bundles/allLibrary8Css", new CssMinify())
            .Include(
                "~/Controls/Common/common.css",
                "~/Controls/ApplicationTopHeader/applicationTopHeader.css",
                "~/Controls/StatusBar/statusBar.css"
                // other files
            ));
    }
}

This generates a compressed and minified random css file (or resource)

However, i want from an external project to reference to this compressed file (or resource), but i can't do it because of the random name it generates:
/bundles/allLibrary8Css?v=VSqWZLr-gqdgDlMqOOg6ULA53tJ-5qFiIBRY6Qe-VHw1
http://library.myApp.com/bundles/allLibrary8Css?v=VSqWZLr-gqdgDlMqOOg6ULA53tJ-5qFiIBRY6Qe-VHw1
Is there any way to prevent the random name created by the bundle so i can reference it properly?

A: Actually, you can, you can safely ignore query string, and everything will be ok, however, then you have problem with cache ...

redpajama_set_name: RedPajamaStackExchange


text:
ASDa Webinar Series on Data Analysis
Webinar series I
Applied Statistics and Data Science Group at UBC Statistics is pleased to announce the launch of the webinar series on Data analysis: Practical application of Linear Mixed Effects Models.
Sign up for the webinar series to learn how to apply linear mixed effects models to appropriately answer your research questions, happening soon on Tuesday/...
Date posted January 17, 2023
Professor Lang Wu appointed as Associate Director representing Alberta/BC/Yukon
Congratulations to our Professor Lang Wu on his role as the Associate Director representing Alberta, British Columbia, and Yukon of the Canadian Statistical Sciences Institute (CANSSI). As an Associate Director, Lang will provide feedback on all aspects of CANSSI operations, help steer CANSSI developments, and adjudicate the smaller budget programs as well as the CANSSI...
Date posted December 14, 2022
Call for nominations for the Department of Statistics Award in Data Science for Academic Year 2022-23
The Department of Statistics is soliciting nominations for the Department of Statistics Award in Data Science, an award to recognize the importance of developing and applying tools to answer important questions through the analysis of data.
This $1,000 award is offered to an undergraduate or graduate student who has demonstrated initiative and creativity in making outstanding contributions in the field of Data Science. The award is made on the recommendation of the Department of...
Free Statistical Consultation: 2022/23
The Statistics Department offers several types of free statistical consultation, via STAT 450/550, SOS and STAT 551 as follows:
STAT 450/550: Term 2 only, open to anyone, via students in STAT 450 mentored by faculty; accepting projects for term 2 2022-23 from now until Dec 15
SOS (Statistical Opportunity for Students): year-round, UBC-V graduate students only, via a team of a senior Statistical consultant and a Statistics graduate...
Date posted November 3, 2022
Professor Jiahua Chen elected as fellow of the prestigious Royal Society of Canada
UBC Statistics Professor Jiahua Chen has been named a new Fellow of the Royal Society of Canada (RSC), Canada's highest academic honour. Founded in 1882, the Royal Society of Canada (RSC) comprises the Academies of Arts, Humanities and Sciences, and The College of New Scholars, Artists and Scientists. It recognizes excellence, advises the government and the larger society, and promotes a culture of knowledge and innovation in Canada and...
Date posted September 13, 2022
Professor Daniel J. McDonald's talk in the Data Science Applied Research and Education Seminar (ARES) series
Data Science Applied Research and Education Seminar (ARES) collaborated between the Department of Statistical Sciences at University of Toronto and CANSSI Ontario is a new speaker series that showcases opportunities in all realms of society for Data Science. And our faculty member Daniel J. McDonald is one of the speakers in the series!
To join...
Welcoming our three new faculty members
UBC Statistics announces the appointment of three new tenured/tenure track faculty – Lucy Gao, Joel Östblom, and Geoff Pleiss.
Lucy began an Assistant Professor position with us on July 1, 2022.
Joel joined us on August 23, 2022 in an Assistant Professor of Teaching position with a primary focus on the Master of Data Science (MDS) program.
And Geoff will begin his role as an Assistant Professor in the...
Date posted August 30, 2022
Recipients of the 2022 Dr. John and Barbara Petkau Scholarship
This year's recipients of the Dr. John and Barbara Petkau Scholarships are Chenyue Qian and Yujie Chen.
Chenyue Qian is a Statistics major with stellar grades in all courses and the recipient of the Faculty of Science International Student Scholarship and the Trek Excellence Scholarship for Continuing Students. In the summer of 2021, he was an intern at the Bank of Ningbo, which helped him...
The Statistics Department offers several types of free statistical consultation, via STAT 551, SOS and STAT 450/550, as follows:
STAT 551: Term 1 only, open to anyone, via students in STAT 551 mentored by faculty; accepting projects for term 1 2022-23 from now until Oct 31
SOS (Statistical Opportunity for Students): year-round, UBC-V graduate students only, via a team of a senior Statistical consultant and a Statistics graduate student...
PhD Student Evan Sidrow receives the 2021 Rick White Award
Congratulation to Evan Sidrow, the recipient of the Rick White Award for the UBC academic year 2021.
Evan has made important contributions to the applied fields of ecology, developing new methods to analyze high frequency biologging data, with a focus on killer whale kinematic data. This work has helped scientists to identify crucial behaviours such as foraging and to understand the differences in health of the Southern and Northern Resident Killer Whales. He is now developing...
Date posted June 6, 2022

redpajama_set_name: RedPajamaCommonCrawl


Great Kerala Style 3 Bedroom Single Floor House Plans Best Of 3 Bedroom 3 Bedroom House Plans In Kerala Single Floor 3d Photo - The image above with the title Great Kerala Style 3 Bedroom Single Floor House Plans Best Of 3 Bedroom 3 Bedroom House Plans In Kerala Single Floor 3d Photo, is part of 3 Bedroom House Plans In Kerala Single Floor 3d picture gallery. Size for this image is 630 × 473, a part of Floor Plans category and tagged with Floor, Kerala, Bedroom, In, Plans published January 29th, 2019 10:58:52 AM by Edgar. Find or search for images related to "Great Kerala Style 3 Bedroom Single Floor House Plans Best Of 3 Bedroom 3 Bedroom House Plans In Kerala Single Floor 3d Photo" in another posts. Back to: 3 Bedroom House Plans In Kerala Single Floor 3d.


Now I may be a day late, but i wasn't going to miss an opportunity to shout about my fur babies on National Pet Day. I feel like the luckiest person alive to be Mum to my cats, Charlie and Rosie (collectively known as The Bobs).
They came into my life two years ago when my impulsive boyfriend visited Hassocks pet shop, which always has about 30 cats wondering around the shop, and found two one-week-old kittens in a box in the back of the shop. He reserved them without a second thought, despite only being in the country a couple of months a year because of work, and so it was my luckiest of lucky days. We went and visited them most weeks until they were old enough to take home.
They have a very privileged existence, living in the countryside with more moles and shrews and voles and pheasants than they could have dreamed of, and have been my most wonderful companions when I've worked from home. They come on walks with me around the fields (much to the confusion of passing dog walkers) and have inspired a few illustrations as well, of course. There is actually quite an exciting project to be announced soon that is all about our adored little night-monsters. Watch this space.
I've grown up with cats my whole life, and I'll particularly never forget Osc, my original studio cat and childhood friend, who we lost two years ago. He was as tame and docile as they come, and a wonderful little cow-coloured life-model.
Animals really are the greatest gift of all and how lucky are we that we get to share our homes them.


text:
Stories from Friday, February 22, 2013
The beauty of it (Local News ~ 02/22/13)
Thursday's storms brought a bit of beauty along with the cold, the wind, and the rain. Most of the area was covered with ice by dusk, but roadways remained clear. Schools in the county were back in session on Friday.
Utility surcharge measure OK'd by Senate panel (State News ~ 02/22/13)
JEFFERSON CITY, Mo. -- Missouri power companies could seek a surcharge for infrastructure projects under a proposal endorsed this past week by a Senate energy committee. Utilities could ask to levy the infrastructure surcharge between formal rate cases before the state Public Service Commission. ...
Authorities continue to investigate Advance death (Local News ~ 02/22/13)
BLOOMFIELD, Mo. -- Authorities continue to investigate a suspicious death in Advance on Wednesday. Stoddard County Sheriff Carl Hefner said at 8:30 a.m. Friday that there was no new information to release regarding the death of 34-year-old Sean Crow...
2013 PAT Strollerthon to include a historical "stroll" of local school campuses (Local News ~ 02/22/13)
The second annual Parents as Teachers 5K and Strollerthon is slated for Saturday, March 23, with a number of changes from last year's event. The PAT Easter Egg Hunt will also be tied in with the event, but this year the Strollerthon will take place around the Dexter School campuses, with maps available for strollers to take note of some of the campus history and even some points of interest from the neighborhoods surrounding the school campuses...
ICE Storm spares county (Local News ~ 02/22/13)
A snowstorm that caused major headaches throughout the midwest Thursday left minimal problems in its wake as of Friday morning. While all area schools dismissed early on Thursday, all within the county are back in session on Friday. Freezing rain covered virtually everything in the county Thursday -- except the roads...
Sean Robert Crow (Obituary ~ 02/22/13)
Sean Robert Crow, son of Bob Crow of Dexter, Mo., and the late Karen Weaver Ritz, was born on July 30, 1978, in Charleston, Mo., and died Feb. 20, 2013, in Advance, Mo., at the age of 34. Sean was a heavy equipment operator, enjoyed riding his motorcycle, a graduate of Bernie High School and a former resident of Stoddard County...
Deborah Hatchell (Obituary ~ 02/22/13)
Deborah Hatchell of Dexter died Feb. 21, 2013, at the age of 57. Funeral arrangements are incomplete at this time. Rainey-Mathis Funeral Home in Bernie is in charge of arrangements.
Dexter District basketball to be webcast live at dailystatesman.com (Local News ~ 02/22/13)
People who aren't able to make it to the Class 4 District 1 basketball tournament in Dexter beginning tonight will have another option. The tournament will be webcast at dailystatesman.com. The first game tips off at 5:30 between the number four seed Kennett Indians (17-9) and the number five seed Dexter Bearcats (7-15)...


text:
Reimagining virtual collaboration for the future of work and learning
By Jared Spataro, Corporate Vice President for Microsoft 365
We've reached an inflection point. As the global response to COVID-19 evolves, communities around the world have moved from an era of "remote everything" into a more hybrid model of work, learning, and life. And as we all scramble to keep up, the future of work and education is being shaped before our eyes. At Microsoft, we've spent the last few months learning from our customers and studying how they use our tools. We've also worked with experts across virtual reality, AI, and productivity research to help understand the future of work. These findings, which are published here, guide us as we design technology to help our customers today and in the future.
Today we're announcing a set of new features in Microsoft Teams that make virtual interactions more natural, more engaging, and ultimately, more human. These features offer three key benefits for people at work and in education. First, they help you feel more connected with your team and reduce meeting fatigue. Second, they make meetings more inclusive and engaging. And third, they help streamline your work and save time. It's all about enabling people everywhere to collaborate, to stay connected, and to discover new ways to be productive from anywhere. Let's dig into the details.
Feel more connected and reduce meeting fatigue
Together mode—At a time when people are conducting more virtual meetings than ever, our research has shown that many of us feel less connected since moving to remote work, and experience more fatigue during video meetings than during in-person collaboration. Together mode is a new meeting experience in Teams that uses AI segmentation technology to digitally place participants in a shared background, making it feel like you're sitting in the same room with everyone else in the meeting or class. Together mode makes meetings more engaging by helping you focus on other people's faces and body language and making it easier to pick up on the non-verbal cues that are so important to human interaction. It's great for meetings in which multiple people will speak, such as brainstorms or roundtable discussions, because it makes it easier for participants to understand who is talking. Together mode with auditorium view is rolling out now and will be generally available in August. And we'll bring more views to Together mode in the future.
Dynamic view—While Together mode offers an extraordinary new meeting experience, it's not intended for every meeting. We believe that traditional video meetings people use every day can also be more engaging and dynamic. A set of enhancements we call dynamic view gives you more control over how you see shared content and other participants in a meeting. Using AI, meetings dynamically optimize shared content and video participants. New controls—including the ability to show shared content and specific participants side-by-side—let you personalize the view to suit your preferences and needs. Dynamic view builds on the meetings enhancements we announced last month, which include large gallery view (rolling out in August), where you can see video of up to 49 people in a meeting simultaneously, and virtual breakout rooms, which allow meeting organizers to split meeting participants into smaller groups for things like brainstorming sessions or workgroup discussions.
Dynamic view
Large gallery view
Video filters—We've all become familiar with video filters used in photography and social media apps, and now we're bringing them to Teams. Before joining a meeting, you can use the filters to subtly adjust lighting levels and soften the focus of the camera to customize your appearance.
Reflect messaging extension—Our research shows that employee well-being is more important to productivity than ever. Creating an emotionally supportive environment is key to keeping people healthy, happy, and focused. The new Reflect messaging extension gives managers, leaders and teachers an easy way to check in with how their team or students are feeling — either in general, or about a specific topic like work-life balance, the status of a project, current events, or a change within the organization. IT administrators will be able to install the Reflect extension from GitHub, and then make it available to employees in their organization in the message extension menu. Once installed, the extension provides suggested check-in questions and the ability to add custom questions that team members can respond to in a poll-like experience. Managers or teachers can also choose to make poll results anonymous. The Reflect messaging extension will be available in the coming weeks.
Make meetings more inclusive, engaging, and effective
Live reactions—Non-verbal cues like smiles and head nods can be difficult to notice in online meetings, making it challenging for presenters to gauge audience reactions and for participants in large meetings to share a sentiment without interrupting the meeting flow. Soon, you will be able to react during a meeting using emojis that will appear to all participants. Live reactions is a shared feature with PowerPoint Live Presentations, which allows audience members to provide instant feedback to the presenter. We are also bringing PowerPoint Live Presentations to Teams in the future, further enabling audience engagement right from Teams.
Chat bubbles—During meetings, chat has become a lively space for conversation and idea-sharing, and offers an option for people to participate in the discussion without having to jump in verbally. But it can be challenging to pay attention to video feeds, presentations, and chats all at the same time. Currently, Teams users need to manually open a chat window to view the chat screen. Soon, however, chats sent during a Teams meeting will surface on the screens of all meeting participants, making the chat more central to the conversation.
Speaker attribution for live captions and transcripts—While Teams already provides live captions as a way to follow along with what is being said in a meeting, soon we will add speaker attribution to captions so that everyone knows who is speaking. Live transcripts, coming later this year, provide another way to follow along with what has been said and who said it. After a meeting, the transcript file is automatically saved in a tab as a part of the meeting.
Note: Remarks made by participants joining from a conference room device will be attributed to the room rather than to the individuals in the room.
Live Captions with speaker attribution
Live transcription with speaker attribution
Interactive meetings for 1,000 participants and overflow—There are times when it's important to bring large groups together for meetings or classes. For more interactive meetings—where attendees can chat, unmute to talk, and turn on their videos for real-time collaboration—Teams meetings are growing to support up to 1,000 participants. When you want to bring more people together to watch a presentation or discussion, Teams can support a view-only meeting experience for up to 20,000 participants.
Microsoft Whiteboard updates—Visual collaboration tools can make meetings and teaching environments more effective and inclusive. Whiteboard in Teams will soon be updated with new features including faster load times, sticky notes, text, and drag and drop capabilities. These features enable team members who don't have access to a touchscreen or Surface Hub to participate in whiteboarding sessions during Teams meetings.
Streamline your work and save time
Tasks app–The Tasks app in Teams, rolling out this month, provides a new unified view of tasks from across Microsoft To Do, Planner, and Outlook. Smart lists like "Assigned to me" bring tasks together across different shared plans, whether you're on desktop, web, or mobile. Add Tasks as a tab in a channel and get your familiar Planner tab experience with the new list view.
Suggested replies—Get your message across with just one tap! Suggested replies in Teams chat uses assistive AI to create short responses based on the context of the previous message. So the next time someone asks you "Do you have time to meet today?" you can respond "I sure do!" without even pulling up your keyboard. This feature will be rolling out this month.
Cortana in Teams—Coming soon to the Teams mobile app, Cortana uses AI and the Microsoft Graph to provide voice assistance in Teams. To stay connected to your team even when you have your hands full, you can ask Cortana to make a call, join a meeting, send chat messages, share files, and more. These voice assistance experiences are delivered using Cortana enterprise-grade services that meet Microsoft 365 privacy, security, and compliance commitments. Cortana will be available in the Teams mobile app on iOS and Android in the coming weeks for Microsoft 365 Enterprise users in the U.S. in English.
Microsoft Teams displays—Organizations need to enable their employees to set up more effective home office spaces while also preparing some to return to the office. To help, we're introducing new Microsoft Teams display, a new category of all-in-one dedicated Teams devices that feature an ambient touchscreen and a hands-free experience powered by Cortana. With natural language, users can ask Cortana to join and present in meetings, dictate replies to a Teams chat, and more. These devices seamlessly integrate with your PC, providing easy access to Teams chat, meetings, calling, calendar, and files. And with a camera shutter and microphone mute switch, your conversations stay private. The Lenovo ThinkSmart View will be the first Microsoft Teams display to market, and Yealink will deliver one of the first devices in this category too. Microsoft Teams displays with Cortana will be available in the U.S. starting later this year.
Touchless meeting experiences—As some people begin to return to their worksites, touchless meeting experiences in shared spaces are more relevant than ever. Today, Teams enables people to join meetings and share content to meeting room devices from their own mobile device or PC. Later this year, we'll enable these capabilities on Surface Hub as well. We're building on these capabilities with a new room remote in the Teams mobile app, which will provide additional meeting controls such as the ability to leave the meeting, mute and unmute the room, adjust audio volume, and turn cameras on and off. Beginning later this year, voice assistance will be enabled for Microsoft Teams Room devices, allowing in-room participants to ask Cortana to join and leave a meeting, add a participant from the address book to a meeting using their name or phone number, and more. We're also introducing the ability to wirelessly cast to any Teams Room, collaboration bar, or Surface Hub device, enabling seamless ad-hoc in-person collaboration for people in a shared space.
Note: Voice commands will launch first for Microsoft 365 Enterprise users in the U.S., in English. Not all Teams Room audio devices will support Cortana voice assistance.
Room remote for Microsoft Teams devices
While the above capabilities are designed for work and school, we aspire to make Teams the platform for work, life, and learning. To that end, we also recently introduced new features in Teams that help you stay connected and organized with family and friends. Learn more about these capabilities, now available in mobile preview, here.
Unless otherwise specified, all of these features will roll out later this year.
And they all reflect our vision for the future of work: where everyone is able to contribute and do their best work; where they can move fluidly between experiences, apps, and devices; where AI lends a helping hand to streamline tasks, provide short cuts, and save you time; and where technology contributes to wellbeing and doesn't detract from it.
From the kickoff call to the project's launch—and all points in-between—Teams is the place where people come together to get work done. Working alongside our customers, we'll continue reimagining the future of work and delivering technologies that put people at the center of every experience.
Tagged under:
Get started with Microsoft 365
Microsoft 365 brings together Office 365, Windows 10, and Enterprise Mobility + Security. It delivers a complete, intelligent, and secure solution to empower people.


text:
Q: Rails assets: reset bootstrap css attributes so they don't conflict with google code's prettifier I'm trying to use Bootstrap and google code prettyfier together but the end result is rather dissapointing. In the Gemfile:
gem 'bootstrap-sass', '~> 2.2.1.1'
gem 'google-code-prettify-rails'

In application.css:
*= require bootstrap
*= require google-code-prettify-rails/prettify

In application.js:
//= require bootstrap$
//= require google-code-prettify-rails/prettify
//= require google-code-prettify-rails/lang-sql

And I run prettyPrint() on load from a .coffee script:
jQuery ->
  prettyPrint()

It all works fine, the ... gets formatted. But alas the CSS that formats it is a mixture of Bootsrap's CSS and the prettyprint theme CSS, which displays ... ugly. Element Inspect shows the style applied coming from Bootstrap:
/* line 8, .../bootstrap-sass-2.2.1.1/vendor/assets/stylesheets/bootstrap/_code.scss */
code,
pre {
  padding: 0 3px 2px;
  font-family: Monaco, Menlo, Consolas, "Courier New", monospace;
  font-size: 12px;
  color: #333333;
  -webkit-border-radius: 3px;
  -moz-border-radius: 3px;
  border-radius: 3px;
}

/* line 17, .../bootstrap-sass-2.2.1.1/vendor/assets/stylesheets/bootstrap/_code.scss */
code {
  padding: 2px 4px;
  color: #d14;
  background-color: #f7f7f9;
  border: 1px solid #e1e1e8;
}

My question is

*

*is there a way to prevent the asset pipeline from including Bootstrap's own _code.scss ?

*if not, how do I reset Bootstrap's applied style?


This post assumes you have some familiarity with PHP. If that is not the case, I'd suggest looking at the php.net tutorial or the w3schools tutorial. SVG is an XML based format, so you may want to learn about XML at w3schools.com. Most modern browsers can display SVG images without trouble. If you are using a version of Internet Explorer prior to IE 9, you will not be able to view SVG. Stop now and download Chrome or Firefox!
Scalable Vector Graphics (SVG) are not like the most common image formats (things like JPEG and GIF) which are Raster Graphics. A raster image contains color information for each individual pixel, making for much larger files. In contrast, SVG files contain only the structural information necessary to recreate an image. For example, a simple circle could be described with only a few words about its position, radius, and color. So one of the benefits of SVG is image files are much smaller than the equivalent JPEG.
The name "Scalable Vector Graphic" implies another benefit: the ability to scale or zoom in without changing the image. For instance, if you blow up a JPEG image of a circle, the edges will become jagged. Anti-aliasing is an imperfect strategy which works only if you aren't changing the size of an object too much. But a circle in SVG is described only by its position and radius, so you can zoom in forever and always see a sharp edge (limited only by the resolution of your computer screen or printer).
SVG files can be created either with a simple text editor, or a graphical editor such as Inkscape. This post will focus on creating images in a text file using the primitive SVG commands. Full documentation of the latest version of SVG can be found at w3.org. Without further ado, let's get to an example.
Here's some code to get you started writing a "Hello World!" Scalable Vector Graphic. It doesn't really spell out "Hello World!" (although SVG can contain text, that's not very exciting). Creating the images above required only slightly more sophistication, and some PHP, but I'll get to that.
<!-- Definitions are for graphical objects that may be used multiple times.
// Writing text to the file requires 'echo' statements in php.
// Remember to escape all of your quotation marks!
echo "<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.0//EN\"
// always between 0 and 255.
// center of the gradient. fx and fy change the focus point.
echo "<radialGradient id=\"basecolor" . $i . "\" cx=\"50%\"
echo "   <stop offset=\"0%\" stop-color=\"rgb(" . $ri . "," .
echo "   <stop offset=\"100%\" stop-color=\"rgb(" . $rf . "," .
echo " <ellipse cx=\"" . $cx . "\" cy=\"" .
$cy . "\" rx=\"" . $rx . "\" ry=\"" . $ry . "\"
So that's only 74 lines of code (I never know whether to count comments as code?) for a lovely little design. One thing I discovered in this process: having a single color theme is far more aethetically pleasing than picking truly random colors. There's a lesson in here that it's always a good idea to play around with what goes inside and outside of your for loops!


text:
Anatomy 11
LungEpithelial CellsMuscle, SmoothMyocytes, Smooth MuscleTracheaMuscle, Smooth, VascularBronchiExtracellular MatrixNasal MucosaNasal CavityEosinophils
Ralstonia pickettii
Diseases 13
AsthmaInflammationBronchial HyperreactivityRespiratory HypersensitivityAirway RemodelingBronchiolitis ObliteransAirway ObstructionNasal ObstructionOtorhinolaryngologic DiseasesHypersensitivityFibrosisPulmonary EosinophiliaEosinophilia
Anti-Asthmatic AgentsOvalbuminCollagen Type VMatrix Metalloproteinase 2Matrix Metalloproteinase 9Matrix MetalloproteinasesTissue Inhibitor of Metalloproteinase-1Matrix Metalloproteinase InhibitorsCalcium ChannelsLeukotriene C4B7 AntigensAllergensAntigens, CD80Receptors, Tumor Necrosis Factor
Lung TransplantationImmunohistochemistryRespiratory TherapyRadioallergosorbent Test
Airway RemodelingCaves
ImmunohistochemistryOtolaryngology
Respiratory Therapy Department, HospitalRespiratory Care UnitsCavesManagement Information Systems
Geographicals 2
CyprusNew Jersey
Role of histamine in airway remodeling of asthmatic guinea pig. (1/267)
To investigate the role of histamine in airway remodeling, 50 healthy guinea pigs were divided into 5 groups: control group: nebulized inhalation of distilled water for 8 weeks; asthma model group: nebulized inhalation of ovalbumin (OVA) for 8 weeks after sensitization; continued asthma model group: nebulized inhalation of OVA for 14 weeks after sensitization; histamine group: nebulized inhalation of OVA for 14 weeks after sensitization and histamine was added in the last 6 weeks; antagonist group: nebulized inhalation of OVA for 14 weeks after sensitization and histamine receptor antagonists were added in the last 6 weeks. For each group, the concentration of histamine, sodium ion (Na(+)), chlorine ion (Cl(-)), arterial partial pressure of oxygen (PaO2), arterial partial pressure of carbon dioxide (PaCO2), pH, actual bicarbonate (AB), standard bicarbonate (SB) in serum, and thickness of airway mucosa, base membrane and smooth muscle were measured and compared with each other. The results showed that: (1) the concentration of histamine in serum and the thickness of airway increased, the following order was, the control group, the asthma model group, the continued asthma model group and histamine group (P<0.01); and the concentration of histamine in serum and the thickness of airway of antagonist group was lower than that of the continued asthma model group (P<0.05, 0.01). (2) PaO2 of the asthma model group was lower than that of the normal control group (P<0.01); PaO2, pH, AB, SB decreased, the following order was, the asthma model group, the continued asthma model group and the histamine group (P<0.01); and PaO2, pH, AB, SB of the antagonist group was higher than that of the continued asthma model group (P<0.01); but for PaCO2, the order was converse (P<0.01); For the concentration of Na(+) and Cl(-) in serum, there was no difference among these groups. It is concluded that: (1) Histamine is one of the mediators in the airway remodeling of asthma. (2) Histamine receptor antagonists may play a role in preventing and treating airway remodeling. (3) There is a negative correlation between the PaO2, pH and the wall thickness of the airway (P<0.01), while a positive correlation between the PaCO2, anion gap (AG) and the wall thickness of the airway (P<0.01). (+info)
Anti-angiogenic activity of carebastine: a plausible mechanism affecting airway remodelling. (2/267)
(+info)
Reticular basement membrane in asthma and COPD: similar thickness, yet different composition. (3/267)
BACKGROUND: Reticular basement membrane (RBM) thickening has been variably associated with asthma and chronic obstructive pulmonary disease (COPD). Even if RBM thickness is similar in both diseases, its composition might still differ. OBJECTIVE: To assess whether RBM thickness and composition differ between asthma and COPD. METHODS: We investigated 24 allergic asthmatics (forced expiratory volume in one second [FEV(1)] 92% predicted), and 17 nonallergic COPD patients (FEV(1) 60% predicted), and for each group a control group of similar age and smoking habits (12 and 10 persons, respectively). Snap-frozen sections of bronchial biopsies were stained with hematoxylin/eosin and for collagen I, III, IV, V, laminin and tenascin. RBM thickening was assessed by digital image analysis. Relative staining intensity of each matrix component was determined. RESULTS: Mean (SD) RBM thickness was not significantly different between asthma and COPD 5.5 (1.3) vs 6.0 (1.8) microm, but significantly larger than in their healthy counterparts, ie, 4.7 (0.9) and 4.8 (1.2) microm, respectively. Collagen I and laminin stained significantly stronger in asthma than in COPD. Tenascin stained stronger in asthma than in healthy controls of similar age, and stronger in COPD controls than in asthma controls (p < 0.05). CONCLUSION: RBM thickening occurs both in asthma and COPD. We provide supportive evidence that its composition differs in asthma and COPD. (+info)
Monitoring sputum eosinophils in mucosal inflammation and remodelling: a pilot study. (4/267)
Effects of vitamin E on mitochondrial dysfunction and asthma features in an experimental allergic murine model. (5/267)
Recovery of airway protective behaviors after spinal cord injury. (6/267)
p70 Ribosomal S6 kinase is required for airway smooth muscle cell size enlargement but not increased contractile protein expression. (7/267)
Arginase: a key enzyme in the pathophysiology of allergic asthma opening novel therapeutic perspectives. (8/267)


Chutney /Chammanthi had been always my favorite,so does my elder son loves it.Whenever I think of mango chutney/ manga chammanthi,the first things that comes to my mind is the long train journeys when we loved carrying the parcels of steamed rice ,chammanthi(chutney),mezhukuparetti(stir fry)& omelettes in wilted banana leaves wrap.The aroma of the wilted banana leaves with the parboiled rice just increases the hunger,and we can devour it so much..My mom always used to say at home they never are fond of cooked rice but during travel they are just the opposite and that was true :-)Coming back to today's recipe of the same flavorful, simple chutney /chammanthi with raw mango.
-Heat a pan and dry roast the chillies first to warm it up(makes easier to grind).Remove on aplate ,keep aside.
-Then add all other ingredients in the same pan except salt and dry roast for 2-3mins.
-Put all the ingredients in a blender with salt,add little water and grind to smooth till all the ingredients are well ground and combined.Hold it in your hand,see if it holds shape then chammanthi/ chutney is ready to serve.
* Check the sourness of mangoes and add accordingly.
* Dry roasting the ingredients is optional,You can directly put it in the blender and grind it too.
Enjoy the yummy chutney with steamed rice,until next time..
Wishing all my US friends & readers,A Very Happy Long Weekend !!!!
Your chutney different from mine a lot n sounds spicy m yumm...I just love it with curd rice n kanji...heavenly combo!!
I have never tried such!
Very delicious and authentic chutney. love the presentation too !!
Love this. Tastes so good with hot rice.
hi julie , a very appetizing way to prepare mango... a perfect ingredient since mangoes are so tasty.
delicious mango chutney dear...loved it !!!!!
Yummy version of chammanthi..luv to have with hot rice.
This is such a refreshing recipe and mango is perfect for this time of year with the warmer temperatures!
Love mango and this recipe sounds perfect!
this chutney is so different than what we make..love the nice little ball of chutney..
dry chamanthi with plain rice is a match made in heaven...Loved this recipe.
And thank u so much dear for your lovely comments!
My all time fav this one is Julie.The season is around and we can enjoy the sour mangoes.Superbly done.