Abstract:
An apparatus, system, and method for a transmissive electromechanical light valve including a gate pivotable between a first position to allow light to pass through a valvelet and a second position to prevent light from passing through the valvelet are disclosed herein. Other embodiments may be described and claimed herein.

Description:
FIELD OF THE INVENTION 
     Embodiments of the invention relate generally to the field of projection systems, and more particularly to a transmissive electromechanical light valve. 
     BACKGROUND OF THE INVENTION 
     Multimedia projection systems have become popular for purposes such as conducting sales demonstrations, business meetings, classroom training, and for use in home theaters. In typical operation, multimedia projection systems receive analog video signals from an input device and convert the video signals to digital information to control one or more digitally driven light valves. Depending on the cost, brightness, and image quality goals of the particular projection systems, the light valves may be of various sizes and resolutions and may be employed in single or multiple display configurations. 
     One type of light valve found in projection systems is a digital micromirror device (DMD). A DMD uses individually controllable mirrors to selectively reflect light either through projection optics or towards a light-absorbing surface, based on image data. Because the DMD operates by selective reflection, the axis of illumination needs to be separated from the axis of projection. 
     This off-axis illumination could add to the expense and/or sacrifice the compactness of the system. Due to the reflective operation of the DMD, the illumination optics must present light to the same face of the DMD that the projection optics receive light from. This requires either complex optics at the DMD face, or it requires the elements of the two optical systems be placed at distances from the DMD sufficient to allow for unfettered presentation/reception of the light. The physical separation of the components of these prior art systems typically make up a significant portion of the total packaging volume of the system, while necessitating additional optical elements, such as relay lenses, to provide proper illumination at downstream components. Additionally, off-axis illumination could result in oblique illumination of the face of the light valve, which could present additional difficulties. 
     Other types of light valves, e.g., liquid crystal display (LCD) light valves, operate by selectively rotating polarized light. The light that is incident upon the LCD light valve must be polarized to one polarization state, which could result in increased complexity and decreased light transmission through the system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which like references indicate similar elements and in which: 
         FIG. 1  is a simplified block diagram of a projection system with a transmissive electromechanical light valve, in accordance with an embodiment of the present invention; 
         FIG. 2  illustrates a side-view of illumination optics, the transmissive electromechanical light valve, and projection optics in accordance with an embodiment of the present invention; 
         FIG. 3  illustrates a top-view of a transmissive electromechanical light valve having gates and electrodes coupled to a substrate, in accordance with an embodiment of the present invention; 
         FIG. 4  illustrates a top-view of a transmissive electromechanical light valve having gates and electrodes coupled to separate substrates, in accordance with another embodiment of the present invention; 
         FIG. 5  illustrates a top-view of a transmissive electromechanical light valve having gates coupled to a substrate and electrodes coupled to spacers disposed between substrates, in accordance with another embodiment of the present invention; 
         FIG. 6  illustrates a top-view of a valvelet of a transmissive electromechanical light valve having two gates, in accordance with another embodiment of the present invention; 
         FIG. 7  illustrates a top-view of a transmissive electromechanical light valve having hinges placed in the center of gates, in accordance with another embodiment of the present invention; and 
         FIG. 8  illustrates a front-view of a transmissive electromechanical light valve in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrative embodiments of the present invention include a transmissive electromechanical light valve and methods practiced thereon. 
     Various aspects of the illustrative embodiments will be described using terms commonly employed by those skilled in the art to convey the substance of their work to others skilled in the art. However, it will be apparent to those skilled in the art that alternate embodiments may be practiced with only some of the described aspects. For purposes of explanation, specific materials and configurations are set forth in order to provide a thorough understanding of the illustrative embodiments. However, it will be apparent to one skilled in the art that alternate embodiments may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the illustrative embodiments. In particular, a wide variety of optical components such as, but not limited to, prisms, mirrors, lenses, and integration elements may be used as appropriate to fold, bend, or modify the illumination for the intended application. Integration of these optical components into illustrated embodiments may not be specifically addressed unless it is necessary to develop relevant discussion of embodiments of the present invention. 
     Further, various operations will be described as multiple discrete operations, in turn, in a manner that is most helpful in understanding the present invention; however, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation. 
     The phrase “in one embodiment” is used repeatedly. The phrase generally does not refer to the same embodiment; however, it may. The terms “comprising,” “having,” and “including” are synonymous, unless the context dictates otherwise. 
       FIG. 1  illustrates a simplified block diagram of a projection system  100  with a transmissive electromechanical light valve  104  in accordance with an embodiment of the present invention. A projection device  108  may include an illumination arrangement  112 , coupled to a controller  116  and optically coupled to the light valve  104  to provide light along an illumination path  120 . The illumination arrangement  112  may provide light with desired characteristics to the light valve  104 . These characteristics could include, but are not limited to, illumination uniformity, angle, color, and brightness. The illumination arrangement  112  may include a light source optically coupled to a series of optics including, for example, illumination lenses, integration devices, filters, and/or light-directing components (e.g., mirrors, prisms, light guides, etc.). 
     In one embodiment the illumination arrangement  112  may include a polychromatic light source such as, but not limited to, an incandescent lamp (e.g., tungsten halogen) or a gaseous discharge lamp (e.g., a metal halide). In other embodiments, monochromatic light sources such as light-emitting diodes, for example, may be used to produce light of a particular color. 
     In various embodiments, the system  100  may also include more than one light valve  104 . For example, a color-specific light valve may be placed in each of a number of primary colored paths and be used to exclusively modulate the light of these paths. In these embodiments, the illumination arrangement  112  may include optics to facilitate the presentation of colored light to the appropriate light valves along the appropriate illumination paths. 
     The controller  116 , which may include both power and logic circuitry, may be adapted to transmit control signals to the light valve  104  based, at least in part, upon input signals received from an input device  122 . The control signals may cause matrix-addressable valvelets to selectively transmit incident light in order to effectuate the rendering of the image conveyed by the input signals. Projection optics  124  may be positioned adjacent to the light valve  104  to project the image rendered at the light valve  104 , conveyed by light rays transmitted along a projection path  128 , onto a screen or other mechanism for viewing. The rendered image may be, for example, image frames of a video. The projection optics  124  may include, but are not limited to, projection lenses, filters, and light-directing components. 
     For the purpose of this description, a still image may be considered as a degenerate or special video where there is only one frame. Accordingly, both still image and video terminologies may be used in the description to follow, and they are not to be construed to limit the embodiments of the present invention to the rendering of one or the other. 
     The input device  122  may include a personal or laptop computer, a digital versatile disk (DVD), a set-top box (STB), a video camera, a video recorder, an integrated television tuner, or any other suitable device to transmit signals, e.g., video signals, to the projection device  108 . In various embodiments, the system  100  may be, for example, a projector or a projection television. 
       FIG. 2  illustrates various components of the illumination arrangement  112  disposed relative to the light valve  104  and projection optics  124 , in accordance with an embodiment of this invention. A light source  204  may generate polychromatic light that is directed towards color filter segments of a color wheel  208 . The color wheel  208  may have color filter segments, e.g., red, green, and blue, as well as other filter segments to provide additional brightness (e.g., white) or desired color balance (e.g., light-purple to correct for the red deficient nature of typical polychromatic light). The color wheel  208  may transmit color sequential light into an integrating device such as an integrating tunnel  212 . In various embodiments, other color-filtering devices may be used. Additionally, other embodiments, e.g., ones employing monochromatic light sources, may not have a color-filtering device. 
     The integrating tunnel  212  may be composed of a solid glass rod that relies on total internal reflection to transfer light through it and to create, at its output end, a substantially uniform illumination field. The integrating tunnel  212  may include a cladding or reflective mirrored sidewalls that may protect internal reflection. The integrating tunnel  212  may have a tapered output end having an aspect ratio that corresponds to an aspect ratio of the light valve  104 . The shaped and integrated light may then be presented to the light valve  104  along an illumination path that is substantially orthogonal to the face of the light valve  104 , in accordance with an embodiment of the present invention. In various embodiments, other integrating devices such as, but not limited to, a hollow integrating tunnel with reflective sidewalls or a flyseye-lens integrator may be used. 
     This orthogonal arrangement of this embodiment may prevent the oblique illumination of the transmissive electromechanical light valve  104 . Additionally, because the illumination arrangement  112  is presenting light to a different face of the light valve  104  than the projection optics  124  are receiving light from, elements from both of these components may be placed closer to the light valve  104 . This may, in turn, facilitate smaller elements being used. For example, in a prior art system, the first element of the projection lens would need a back focal length that was long enough to allow light to be presented to a DMD unobstructed. However, the further that the element is placed from the DMD, the larger the element has to be in order to accept diverging light rays. Unlike the prior art system, the positioning of the projection optics  124  relative to the light valve  104  of the present embodiment is not constrained by the positioning of the elements of the illumination arrangement  112  relative to the light valve  104 . Therefore a smaller, more compact system may be enabled by the use of the transmissive electromechanical light valve  104  of embodiments of this invention. 
       FIG. 3  illustrates valvelets  300  and  304  of a transmissive electromagnetic light valve  308  in accordance with an embodiment of the present invention. The valvelets  300  and  304  may operate to selectively control the passage of light through portions of the light valve  308 . The light valve  308  may have a transparent substrate  312 , which is common to both valvelets  300  and  304 , that has a surface  316  facing illumination optics and a surface  320  facing projection optics. 
     The valvelet  300  may include a transparent electrode  322 , a hinge  324 , and a landing  328  coupled to the surface  320  as shown. The valvelet  300  may also include a gate  332  that is coupled to the hinge  324  in a pivotable relationship. The gate  332  may be made of a conductive material and have a reflective surface. As shown in  FIG. 3 , the gate  332  of the valvelet  300  may be in a closed position such that light transmitted through the substrate  312  (and possibly the electrode  322  as well) at the area of the valvelet  300  may be reflected by the gate  332  back through the substrate  312  and out from the surface  316 . In another embodiment, the gate  332  may have a non-reflective surface to absorb the light. 
     In one embodiment, the gate  332  may be biased to the closed position by a rotational force applied to the gate  332  through the hinge  324 . In other embodiments, the gate  332  may be biased to an open position. 
     Valvelet  304  may include elements similar to those found in valvelet  300  including a transparent electrode  336 , a hinge  340 , a landing  344 , and a gate  348 . As shown, the gate  348  of the valvelet  304  may be in an open position such that light transmitted through the substrate  312  (and possibly the electrode  336  as well) at the area of the valvelet  304  may be emitted out towards projection optics that face the surface  320 . 
     Light that is transmitted through the valvelet  304  may not be completely collimated, with some of the light drifting from one side of the valvelet  304  to the other as it passes through. Light having this lateral drift may be reflected off of the open gate  348  and out towards the projection optics in order to prevent an effective reduction of the aperture ratio caused by the gate  348 . 
     In one embodiment, the valvelet  304  may be operated by applying an electrical charge to the electrode  336  such that a repulsive electromagnetic force exists between the gate  348  and the electrode  336 . This repulsive force may overcome the rotational bias applied by the hinge  340  and cause the gate  348  to rotate around the hinge  340  and away from the electrode  336 . Releasing the charge to the electrode  336  may allow for the rotational force to restore the hinge to the closed position. 
     In one embodiment, the electrodes  322  and  336  may be electrically coupled to an underlying memory circuit. This memory circuit may be capable of independently addressing the electrodes  322  and  336  in a manner to dictate their respective charges. In one embodiment, the electrodes  322  and  336  may be embedded and/or disposed within the substrate  312 . 
     In other embodiments, an electrical charge may be applied to the gate  348  through the hinge  340  and the electrodes  322  and  336  may be part of a conductive plane disposed within the substrate  312 . 
     The landings  328  and  344  may provide a station for proper disposition of the gates  332  and  348 , respectively, while in the closed position. In various embodiments, the landings  328  and  344  may be electrodes with the same potential as the gates  332  and  348  to facilitate the electrical biasing of the gates  332  and  348 . In other embodiments, the landings  328  and  344  may be made of a dielectric material. 
     In one embodiment, a proper closed disposition may hold the gates  332  and  348  apart from the respective electrodes  322  and  336  by a distance. The distance may be large enough to prevent arcing between the two conductors but small enough to allow a sufficient electromagnetic force to effectuate a rotation from the closed position to an open position. 
     Separation between a gate and an electrode may not be needed in an embodiment with electrodes embedded or disposed within a substrate. However, a landing may still be used in these embodiments for other reasons, such as, but not limited to, electrically biasing the gate and/or preventing contact between the gate and the transparent surface which may compromise one or both of the surfaces. 
     The magnitude of the electromagnetic force between a gate and an electrode may determine the rotation of the gate. In one embodiment, the gates may be driven digitally between a fully open and a fully closed position. Grayscale imaging may be provided through pulse width modulation in this digital fashion. In another embodiment, the electromagnetic force may be exerted to partially rotate the gate. This could allow an analog grayscale to be used by only allowing a portion of the light to pass. 
       FIG. 4  illustrates a valvelet  400  of a light valve  404  in accordance with an embodiment of the present invention. The valvelet  400  may have elements similar to comparable elements of valvelets  300  and  304 , including a gate assembly having a hinge  408 , a landing  412 , and a gate  416 . In this embodiment the gate assembly may be coupled to a transparent substrate  420  while a transparent electrode  424  is coupled to another transparent substrate  428 . In this embodiment, an electrical charge may be applied to the electrode  424  such that an attractive electromagnetic force is exerted between the gate  416  and the electrode  424 . Releasing the charge applied to the electrode  424  may allow the restoring force, exerted by the hinge  408 , to transition the gate  416  into the closed position. 
     In this embodiment, the substrate  420  may be separated a distance from the substrate  428  that would provide the gate  416  sufficient clearance to transition between the open and closed positions. Additionally, the distance may be small enough such that an electromagnetic relationship exists between the two conductors. The substrates  420  and  428  may facilitate the encasing of the movable parts of the light valve  404  in order to protect the parts from particulates and other environmental interference. 
       FIG. 5  illustrates valvelets  500  and  504  of light valve  508  in accordance with an embodiment of the present invention. This embodiment may have spacers  512  and  516  coupled between substrates  520  and  524 . Electrodes  528  and  532  and landings  536  and  540  may be respectively coupled to the spacers  512  and  516  as shown. The spacers  512  and  516  may have a reflective surface opposite the surface coupled with the electrodes  528  and  532 . When a gate  544  of the valvelet  504  is in the open position, light striking the reflective surface of the spacer  512  may be reflected. Likewise, light striking the reflective surface of the open gate  544  may also be reflected. By providing for these complementary reflections through the valvelet  504  the cone angle of the illumination may be substantially unchanged throughout transmission. That is, the distribution of angles of the incoming light may be approximately the same as the distribution of the angles of the transmitted light. For similar reasons, gates of other embodiments may have reflective surfaces on both sides. 
     In one embodiment, the spacer  512  may be made of a dielectric material that may facilitate the prevention of interference from the electrode  528  with the gate  544 . 
       FIG. 6  illustrates a top-view of a valvelet  600  of a light valve  604  in accordance with an embodiment of the present invention. The valvelet  600  may include gates  608  and  612  coupled to a substrate  616  by respective hinges  620  and  624 . An electrode  628  is embedded in substrate  632 . In this embodiment, the elements may be similar to like-named elements discussed with reference to earlier embodiments. However, in this embodiment, the transmission of light through the valvelet  600  is modulated by the pair of gates  608  and  612 . The embedded electrode  628  may have a central portion  636  that is overlaid with a dielectric material, which could be a similar material as that found in the remaining substrate  632 . This design could facilitate the attractive electromagnetic force between the gates  608  and  612  and the electrode  628  being greater at the periphery of the valvelet  600  than at the center. This could, in turn, facilitate a full extension of the gates  608  and  612  while in the open position. 
       FIG. 7  illustrates a top-view of valvelets  700  and  704  of a light valve  708  in accordance with an embodiment of the present invention. Valvelets  700  and  704  may include gates  712  and  716  that are coupled to hinges  720  and  724 , respectively. The hinges  720  and  724  may be located approximately at the centerlines of the respective gates  712  and  716 . 
     In this embodiment, the gates  712  and  716  may cooperate with the addressing electrodes  728 ,  732 , and  736  to effectuate an electromagnetic force resulting in the valvelet  700  being in a closed position, and the valvelet  704  being in an open position. One or more substrates (not shown) may be coupled to the valvelets  700  and  704  to provide sufficient structure while allowing the rotation of the gates  712  and  716  through the open and closed positions. 
       FIG. 8  illustrates a front-view of a rectangular array of valvelets  800  of a light valve  804  in accordance with an embodiment of the present invention. The valvelets  800  may be similar to the valvelets  700  and  704  described and discussed above with reference to  FIG. 7 . Additionally, some or all of the valvelets  800  may be interchanged with any of the valvelets discussed and described with reference to earlier embodiments. 
     Referring also to  FIGS. 1-2 , the face of the light valve  804  may be illuminated by illumination arrangement  112 . The valvelets  800  may be individually controlled to allow or prevent the transmission of light through the light valve  804  to effectuate an image pattern conveyed by control signals from the controller  116 . The pattern of transmitted light may then be imaged onto a viewing device through projection optics  124 . 
     Although specific embodiments have been illustrated and described herein for purposes of description of the preferred embodiment, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent implementations calculated to achieve the same purposes may be substituted for the specific embodiment shown and described without departing from the scope of the present invention. Those with skill in the art will readily appreciate that the present invention may be implemented in a very wide variety of embodiments. This application is intended to cover any adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.