A variety of systems exist which are useful for projecting images or information, for example, images of the type associated with television displays or information of the type seen at airports to indicate the departure of a plane. Many of these systems employ a device which selectively reflects incident light rays provided by a light source. One such system is disclosed in U.S. Pat. No. 4,680,579, and includes a component often referred to as deformable mirror device. Projection systems which employ a deformable mirror device also include a light source which provides illuminating light to the deformable mirror device (DMD).
The DMD is comprised of a plurality of relatively small mirrors, all of which are contained in a common plane. Each mirror is movable, in response to a signal, between first and second positions, where the respective positions may be identified as "on" or "off". Considering a particular mirror in such a display, if it is in the "on" position, incident illuminating light is then reflected to the viewer. In contrast, if the mirror is in the "off" position, the incident illuminating light is reflected elsewhere and is not visible to the viewer. Thus, by appropriately positioning the mirrors contained in the array, a particular image may be projected to the viewer.
With respect to mirrors which are in the "on" position, light reflected therefrom is often passed through a lens or lens system, of appropriate design, which focuses the reflected light. In addition, the reflected light from a mirror in the "on" position may be transmitted to a screen, whereupon the viewer views the image formed on the mirror array by viewing the screen.
Summarizing the overall construction and operation of projection systems which employ DMDs, it will be appreciated that they comprise a light source, an array of individually adjustable mirrors for selectively reflecting light from the light source, and means for insuring a transmission of the illuminating light from the light source to the DMD, and similarly insuring the appropriate transmission of light reflected from mirrors "on" position, through a lens or in general to the viewer of the projected image.
Systems of the type described above are generally known in the art. Example of such systems are those disclosed in U.S. Pat. Nos. 1,713,213, and 1,984,683 and 3,186,115 and 3,161,726 and 4,680,508. U.S. Pat. No. 4,969,730 is particularly illustrative of such systems.
Considering further the construction and operation of such systems, as noted, such systems generally include means for insuring the transmission of the light from the light source to the DMD, and from the DMD to the viewer. In the prior art, such means generally included mirrors or so called Schlierin devices. Also used in the prior art were so called Dyson Relays. In general, all such devices, i.e Schlierin devices, mirrors and Dyson Relays, resulted in systems having large dimensions and, in addition, often resulted in poor projected images which were characterized by glare or ghost images or both, when the projected image was projected on a screen. One objective of my invention is to provide improved means for transmitting illuminating light from a light source to a selectively reflecting device, such as a DMD, and from the reflecting device to a lens system which, in turn, transmit the light to, for example, a screen.
A further objective of my invention is to provide an improved component for such a system wherein light rays reflected from reflecting elements in the "on" position pass through the component to a receiving lens, but light rays from elements in the "off" position are refracted away from the receiving lens.
Another object of my invention is to provide an overall arrangement of the components of such a system whereby a superior image is obtained.