The present invention relates to electronic apparatus for generating data for determining properties of gemstones, such as cut diamonds, as well as methods of and computer programs for determining properties of gemstones using the generated data. In particular, but not exclusively, it relates to electronic apparatus for generating data for determining properties as well as methods of and computer programs for determining properties of gemstones in which a plurality of images of the gemstone are captured for analysis under different lighting conditions.
The beauty of a gemstone, such as a cut diamond, derives from its light handling ability. What attracts the eye is the xe2x80x9cgame of lightxe2x80x9d played by a well-cut diamond as incident light is reflected and refracted off its many facets. Diamonds and other gemstones may be cut according to many different standardised cut patterns such as the standard round brilliant cut, oval, pear, marquise, radiant, princess, heart, emerald cut etc. The most popular cut is the standard round brilliant (SRB) cut as shown in FIG. 1. Diamond cutting and polishing is a highly skilled art and a well-cut diamond, having superior optical performance, will command a significant price premium over a poorly cut diamond having inferior optical performance.
When showing a cut diamond to an untrained observer, one frequently refers to the four C""s of a gemstone, being its carat weight, its clarity, its cut and its colour. Carat weight, clarity and colour can be relatively easily measured objectively and are therefore generally useful. Cut may also be specified or measured in terms of the geometry of the various facets. However, what really matters is the light handling ability of the gemstone and reference is often made to more subjective parameters of a cut diamond, such as its brilliance (the intensity of light returned), scintillation (fast and local fluctuations in the light returned as the diamond moves relative to the lighting conditions), fire (the dispersion of white light into spectral colours) and symmetry (the symmetry of light patterns such as the so-called xe2x80x9chearts and arrowsxe2x80x9d). It can be difficult, particularly for an untrained observer, to make a personal appraisal of these subjective parameters. It can also be difficult to compare the light handling abilities of two diamonds with the same carat weight, clarity and colour, and therefore to appreciate why one is more valuable than the other.
It is recognised that properties such as brilliance, fire and symmetry should be derived, whether by experimental observation or theoretical computer modelling, under a variety of lighting conditions. Moreover, with the property of scintillation it is clearly essential to observe or model the diamond under a variety of lighting conditions. Electronic apparatus for capturing images of gemstones under varying lighting conditions for analysis are known.
International Patent Publication number WO 96/23207 describes a device which captures colour images of a gemstone placed in an analysis chamber and illuminated by a uniform annular light which may be moved along an axis such that the gemstone may be illuminated from a plurality of different angles. The device performs a spectral analysis of the captured images using a tuneable optical band pass filter to determine the colour of the gemstone. Digital images of the gemstone may also be stored, displayed or transmitted over a data network.
The website (www.gemex.com) of GemEx Systems, Inc, a US company, describes a device called the BrillianceScope Analyser which is described as an imaging spectrophotometer. Colour images of a diamond are captured in a controlled lighting environment consisting of six lighting angles, five of which provide reflected light and one of which provides diffuse lighting. These images may then be analysed to generate a report on the diamond. The BrillianceScope Analyser device operates on the same principle as the device described in International Patent Publication number WO 96/23207 referred to above, in that the gemstone is placed in an analysis chamber and illuminated by a uniform annular light which may be moved along an axis such that the gemstone is illuminated from different angles. The images may be analysed by a computer, and the properties of xe2x80x9cwhite lightxe2x80x9d, xe2x80x9ccoloured lightxe2x80x9d and xe2x80x9cscintillationxe2x80x9d for a diamond are determined and displayed on three line chart scales from xe2x80x98lowxe2x80x99, to xe2x80x98mediumxe2x80x99 to xe2x80x98highxe2x80x99. Captured images may also be shown in a repeating sequence in one display area, giving the effect of light movement.
International Patent Publication number WO 99/61890 describes a system for the standardised grading of gemstones. A gemstone is subject to a plurality of incident light sources and images are captured for analysis. Images of the gemstone, such as a SRB cut diamond, may be captured from various viewpoints such as from the pavilion, from the crown and side-on. The gemstone is supported by a rotatable platform which is rotated when images are being captured from a side-on viewpoint to obtain profile and colour images from a variety of rotational positions and to detect internal flaws and inclusions. When capturing images from above and below the gemstone, the platform is moved along an axis from a level position to a down and an up position respectively. The fixed focal length camera is also moved along an axis to focus on the gemstone when the platform is moved between the up, down and level positions. A captured image may be analysed by a processor to obtain colour measurements and measures of the brilliance and scintillation of the gemstone.
One object of the present invention is to provide an electronic apparatus, method and computer program for generating data for improved determination of properties of a gemstone, such as brilliance, scintillation, fire and symmetry.
Another object of the present invention is to provide an electronic apparatus for generating data for determining properties of gemstones which is more compact, lightweight, mechanically simpler, and therefore less expensive to manufacture, than conventional apparatus, making it more suitable for use in retail premises, such as jewellers shops.
Another object of the present invention is to provide an electronic apparatus, method and computer program enabling a observer to more easily compare two diamonds and their properties, in particular the properties of brilliance, scintillation, fire and symmetry.
Another object of the present invention is to provide an electronic apparatus, method and computer program for generating data for determining properties of a cut gemstone which is adapted to and takes into account attributes of the shape and/or symmetry of the cut pattern of a particular gemstone.
Another object of the present invention is to provide an electronic apparatus, method and computer program for generating data for determining properties of a gemstone in which the gemstone is illuminated under more realistic lighting conditions.
Another object of the present invention is to provide an electronic apparatus, method and computer program for measuring the symmetry of a gemstone in terms of the light returned.
According to a first aspect of the present invention there is provided an apparatus for generating data for use in determining a property of a gemstone, such as a cut diamond, the apparatus comprising:
a support structure for supporting a gemstone placed at an observation position, the support structure being arranged such that, if the gemstone has an axis of symmetry, the gemstone is supportable such that the axis of symmetry is parallel to an axis X passing through the observation position;
illumination means arranged to illuminate a gemstone so placed with a spatially varied light pattern;
rotation means arranged to cause relative rotation between the light pattern and the support structure generally about the axis X; and
a camera arranged to capture, at each of a plurality of rotational positions, an image of light returned by the gemstone and to output said images as image data.
By rotating the spatially varied light pattern relative to the supported gemstone about the axis of symmetry of the gemstone, and capturing images at a plurality of rotational positions, the apparatus is particularly adapted to determining properties of cut gemstones having radially symmetric cut patterns, such as SRB cut diamonds. The intensity levels, and colour component proportions, of light returned at any particular spatial region of the gemstone are sensitive to rotational movement. Thus, brilliance, symmetry, fire and scintillation are more easily, accurately and objectively measurable. Furthermore, unlike the prior art referred to above, which are generally mechanically complex, and have laterally moving parts for varying the lighting conditions, the apparatus of the present invention advantageously employs rotationally moving parts for varying the lighting conditions, thus enabling the apparatus to be manufactured in a relatively compact and lightweight form, and relatively inexpensively.
In preferred embodiments, the light pattern comprises at least one relatively light region and at least one relatively dark region, the regions being arranged radially about the axis X. Preferably, the light pattern is generally symmetrical about the axis X. Also preferably, the light pattern has an n-fold symmetry, such as a 4-fold or 8-fold symmetry, where n is a whole number multiple or factor of s, a standardised gemstone cut having an s-fold symmetry.
Thus, the light pattern illuminating the gemstone, corresponds closely to particular gemstone cut patterns, such as the SRB cut, which have a particular shape and a particular arrangement of radially symmetric facets, resulting in the images captured having greater contrast levels between different spatial regions of the gemstone and the intensity levels, and colour component proportions, of light returned at any particular spatial region of the gemstone having greater sensitivity to rotational movement. Thus, brilliance, symmetry, fire and scintillation are more easily, accurately and objectively measurable. Furthermore, the light pattern illuminating the gemstone is a more realistic simulation of the light that would illuminate a gemstone in normal, everyday usexe2x80x94for instance when mounted in an item of jewellery such as a ring. Light is not normally uniform around the axis of symmetry of the diamond and incident only at a narrow range of angles off the axis, as in prior art approaches. Instead, light is normally incident at a wide range of angles off the axis of symmetry of the diamond and not uniform around the axis as in the present invention.
In other preferred embodiments, the illumination means comprises a reflector having a concave surface arranged to reflect light generally towards the gemstone, the concave surface having at least one relatively reflective region and at least one relatively unreflective region, thereby creating said light pattern. Preferably, the reflector is rotatably mounted in said apparatus generally about the axis X, thereby enabling relative rotation between the light pattern and the support structure generally about the axis X. Alternatively, the platform is rotatably mounted in said apparatus generally about the axis X, thereby enabling relative rotation between the light pattern and the support structure generally about the axis X. Preferably, the illumination means comprises an annular light source arranged to emit light towards the concave surface and an annular baffle arranged to prevent direct light reaching the gemstone.
Thus, the apparatus requires only a single stationary light source and a rotatable reflector or rotatable support structure to enable rotation of the light pattern relative to the supported gemstone, resulting in improved mechanical simplicity, as well as reduced size, weight and cost of manufacture.
In a further preferred embodiment, the apparatus comprises a data processing device arranged to determine a property of the gemstone by comparing, using image data corresponding to one or more of said electronic images, the intensity of light at a first and a second image portion, each portion comprising one or more pixels, said first and second image portions corresponding to a first and a second region of the gemstone respectively, said first and second regions being related to each other in accordance with a symmetrical property of a standardised gemstone cut.
Thus, an objective measurement of the symmetry of a gemstone is enabled in terms of the actual light returned from the gemstone and the expected symmetry of the gemstone, such as the 8-fold symmetry of an SRB cut diamond, rather than based on potentially unrealistic or inaccurate models of the geometry of the cut pattern of the gemstone.
In a further preferred embodiment, the apparatus comprises a data processing device arranged to determine a property of the gemstone by comparing, using image data corresponding to two of said electronic images, the intensity of light at one or more pixels of a first image, captured at a first rotational position, with the intensity of light at one or more pixels of a second image, captured at a second rotational position different to said first rotational position, said one or more pixels of the first image corresponding to the same region or regions of the gemstone as said one or more pixels of the second image.
Thus, an improved objective measurement of scintillation is enabled, using data from a plurality of images obtained at different rotational positions of the spatially varied light pattern. With cut gemstones having cut patterns with many radial facets, such as the SRB cut with 32 differently angled facets in the crown and 24 differently angled facets in the pavilion, scintillation may be measured more accurately as, in particular, the intensity levels of returned light have a greater sensitivity to rotational movement of the light pattern relative to the gemstone than to variation of the angle of incidence of the light source.
In a further preferred embodiment, the apparatus comprises a data processing device arranged to determine a property of the gemstone by comparing, using image data corresponding to two of said electronic images, the proportions of colour components at one or more pixels of a first image, captured at a first rotational position, with the proportions of colour components at one or more pixels of a second image, captured at a second rotational position different to said first rotational position, said one or more pixels of the first image corresponding to the same region or regions of the gemstone as said one or more pixels of the second image.
Thus, an improved objective measurement of fire is enabled, using data from a plurality of images obtained at different rotational positions of the spatially varied light pattern. With cut gemstones having cut patterns with many radial facets, such as the SRB cut with 32 differently angled facets in the crown and 24 differently angled facets in the pavilion, fire may be measured more accurately as, in particular, the proportions of colour components of returned light have a greater sensitivity to rotational movement of the light pattern relative to the gemstone than to variation of the angle of incidence of the light source.
According to a second aspect of the present invention there is provided a method of generating data for use in determining a property of a gemstone, such as a cut diamond, the method comprising:
supporting a gemstone at an observation position, such that, if the gemstone has an axis of symmetry, the gemstone is supportable such that the axis of symmetry is parallel to an axis X passing through the observation position;
illuminating the gemstone with a spatially varied light pattern;
causing relative rotation between the light pattern and the gemstone generally about the axis X;
capturing, at each of a plurality of rotational positions, an image of light returned by the gemstone.
According to a third aspect of the present invention, there is provided a method of determining a property of a gemstone by comparing, using image data corresponding to one or more electronic images of the gemstone, the intensity of light at a first and a second image portion, each portion comprising one or more pixels, said first and second image portions corresponding to a first and a second region of the gemstone respectively, said first and second regions being related to each other in accordance with a symmetrical property of a standardized gemstone cut.
According to a fourth aspect of the present invention, there is provided a method of determining a property of a gemstone by comparing, using image data corresponding to two or more electronic images of the gemstone captured under different lighting conditions, the intensity of light at one or more pixels of a first image, captured under a first lighting condition, with the intensity of light at one or more pixels of a second image, captured under second different lighting condition, said one or more pixels of the first image corresponding to the same region or regions of the gemstone as said one or more pixels of the second image.
According to a fifth aspect of the present invention, there is provided a method of determining a property of the gemstone by comparing, using image data corresponding to two or more electronic images of the gemstone captured under different lighting conditions, the proportions, of colour components at one or more pixels of a first image, captured under a first lighting condition, with the proportions of colour components at one or more pixels of a second image, captured under a second different lighting condition, said one or more pixels of the first image corresponding to the same region or regions of the gemstone as said one or more pixels of the second image.
According to a sixth aspect of the present invention, there is provided a computer-implemented method of comparing properties of gemstones, such as cut diamonds, the method comprising:
receiving first image data in respect of a first gemstone and second image data in respect of a second gemstone, said first and second image data each comprising one or more images of said first and second gemstones, respectively;
determining a property of each of said first and second gemstones in dependence on said first and second image data respectively; and
simultaneously displaying one or more images of each of said first and second gemstones together with a representation of the determined property for each of said first and second gemstones.
Thus, an observer, such as a potential purchaser untrained in evaluating properties of gemstones, may compare two gemstones by means of a side by side graphical representation on a computer screen and by means of objectively determined properties, such as brilliance, scintillation, fire and symmetry.
According to a seventh aspect of the present invention, there is provided a apparatus for comparing properties of gemstones, such as cut diamonds, the apparatus comprising:
a support structure for supporting a gemstone placed at an observation position;
illumination means arranged to illuminate a gemstone so placed;
a camera arranged to capture an image of light returned by a gemstone and to output said images as image data; and
a data processing device arranged to:
receive first image data in respect of a first gemstone and second image data in respect of a second gemstone, said first and second image data each comprising one or more images of said first and second gemstones, respectively;
determine a property of each of said first and second gemstones in dependence on said first and second image data respectively; and
simultaneously display one or more images of each of said first and second gemstones together with a representation of the determined property for each of said first and second gemstones.
Due to the compact, lightweight and inexpensive format of the apparatus, the gemstone analysis and comparison may be performed in retail premises, such as in a jeweller shop, with the potential purchaser present.
According to a eighth aspect of the present invention, there is provided an apparatus for generating data for use in determining a property of a gemstone, such as a cut diamond, the apparatus comprising:
a support structure for supporting a gemstone placed at an observation position, the support structure being arranged such that, if the gemstone has an axis of symmetry, the gemstone is supportable such that the axis of symmetry is parallel to an axis X passing through the observation position;
illumination means arranged to illuminate a gemstone so placed with a spatially varied light pattern;
rotation means arranged to cause relative rotation between the light pattern and the support structure;
a camera arranged to capture, at each of a plurality of rotational positions, an image of light returned by the gemstone generally along the axis X and to output said images as image data.
According to a ninth aspect of the present invention, there is provided a apparatus for generating data for use in determining a property of a gemstone, such as a cut diamond, the apparatus comprising:
a support structure for supporting a gemstone placed at an observation position;
illumination means arranged to illuminate a gemstone so placed with a spatially varied light pattern;
rotation means arranged to cause relative rotation between the light pattern and the support structure generally about an axis X passing through the observation position;
a camera arranged to capture, at each of a plurality of rotational positions, an electronic image of light returned by the gemstone generally along the axis X and to output said images as image data
According to a tenth aspect of the present invention, there is provided a apparatus for generating data for use in determining a property of a gemstone, such as a cut diamond, the apparatus comprising:
a support structure for supporting a gemstone placed at an observation position;
illumination means arranged to illuminate a gemstone so placed with a spatially varied light pattern;
rotation means arranged to cause relative rotation between the light pattern and the support structure generally about an axis X passing through the observation position;
a camera arranged to capture, at each of a plurality of rotational positions, an electronic image of light returned by the gemstone and to output said images as image data.
Further aspects and features of the present invention are set out in the appended claims, and further advantages will be apparent from the following description, given by way of example only, in which: