Patent Publication Number: US-2020301118-A1

Title: Light path adjustment mechanism

Description:
BACKGROUND OF THE INVENTION 
     a. Field of the Invention 
     The invention relates generally to an optical mechanism, and more particularly to a light path adjustment mechanism. 
     b. Description of the Related Art 
     Nowadays, various image display technologies are widely used in daily life. In order to increase the resolution and picture quality of an image display device, a light path adjustment mechanism can be used to adjust propagation paths of light in the image display device to shift pixel images and thereby increase addressability. However, the number of components, weight and occupied space of a conventional light path adjustment mechanism is considerably large, and thus the entire mechanism is difficult to be miniaturized. Therefore, it is desirable to provide a simple, reliable, light and compact design of a light path adjustment mechanism. 
     BRIEF SUMMARY OF THE INVENTION 
     According to one aspect of the present disclosure, a light path adjustment mechanism includes a bracket, a light valve, a carrier, a first axis, a second axis and an optical plate member. The light valve has a surface, a surface normal of the surface crosses the bracket to define an intersection closest to the surface of the light valve, and the bracket has an end point furthest from the intersection measured in the direction of the surface normal. A distance between the intersection and the surface measured in the direction of the surface normal is smaller than a distance between the intersection and the end point measured in the direction of the surface normal. The carrier is disposed near the bracket, and the carrier includes an inner frame and an outer frame disposed outside the inner frame. The first axis is connected between the inner frame and the outer frame, and only one side of two sides of the first axis is provided with a first actuator. The second axis is connected between the outer frame and the bracket, and only one side of two sides of the second axis is provided with a second actuator. The optical plate member is disposed on the carrier. 
     According to the above aspect, a part of the light valve is allowed to insert in the opening of the bracket, so that the light path adjustment mechanism can be assembled in a position closer to the prism without being blocked by the light valve or other optical component. This may reduce the overall occupied space and shorten the back focus of optical lenses. 
     According to another aspect of the present disclosure, a light path adjustment mechanism includes a bracket, a carrier, a first pair of flexible members, a second pair of flexible members, an optical plate member and a prism. The carrier is disposed near the bracket, the first pair of flexible members is disposed on the carrier, and the second pair of flexible members is disposed between the carrier and the bracket. Only one side of two sides of the first pair of flexible members is provided with a first actuator, and only one side of two sides of the second pair of flexible members is provided with a second actuator. The optical plate member is disposed on the carrier, and the prism is disposed near the optical plate member. A minimum interval between a surface of the optical plate member and the prism is smaller than 3 mm. 
     According to the above aspect, the light valve may more approach the optical plate member and the prism to reduce the overall occupied space and the back focus of optical lenses. 
     Other objectives, features and advantages of the invention will be further understood from the further technological features disclosed by the embodiments of the invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exploded view of a light path adjustment mechanism according to an embodiment of the invention. 
         FIG. 2  shows a schematic plan view of an assembled light path adjustment mechanism as illustrated in  FIG. 1 . 
         FIG. 3A  shows a schematic diagram of a light path adjustment mechanism in cooperation with other optical components according to an embodiment of the invention. 
         FIG. 3B  shows a schematic diagram illustrating the arrangement of a light valve in relation to a light path adjustment mechanism according to an embodiment of the invention. 
         FIG. 3C  shows a schematic diagram of a light path adjustment mechanism in cooperation with other optical components according to another embodiment of the invention. 
         FIG. 4  shows a schematic diagram illustrating various arrangements of actuators. 
         FIG. 5  shows a waveform diagram of a drive signal for an actuator according to an embodiment of the invention. 
         FIG. 6  shows a schematic diagram illustrating an optical plate member driven by the drive signal shown in  FIG. 5  to lean towards different positions. 
         FIG. 7  shows a time-frequency transform diagram illustrating the corresponding frequency component of the Fourier time series data for an operating optical plate member driven by the drive signal shown in  FIG. 5 . 
         FIG. 8  shows a time-frequency transform diagram illustrating the corresponding frequency component of the Fourier time series data for an operating optical plate member driven by the drive signal shown in  FIG. 9 . 
         FIG. 9  shows a conventional waveform diagram of a drive signal for an actuator. 
         FIG. 10  shows a waveform diagram of a drive signal for an actuator according to another embodiment of the invention. 
         FIG. 11  shows a time-frequency transform diagram illustrating the corresponding frequency component of the Fourier time series data for an operating optical plate member driven by the two signals having an amplitude ratio of 7/6. 
         FIG. 12  shows a schematic diagram of an actuator according to another embodiment of the invention. 
         FIG. 13  shows a schematic diagram of a light path adjustment mechanism used in a projector according to an embodiment of the invention. 
         FIG. 14  shows a schematic diagram of a light path adjustment mechanism used in a projector according to another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description of the preferred embodiments, directional terminology, such as “top,” “bottom,” “front,” “back,” etc., is used with reference to the orientation of the Figure(s) being described. The components of the invention can be positioned in a number of different orientations. As such, the directional terminology is used for purposes of illustration and is in no way limiting. Further, “First,” “Second,” etc, as used herein, are used as labels for nouns that they precede, and do not imply any type of ordering (e.g., spatial, temporal, logical, etc.). 
     The following description relates in general to a light path adjustment mechanism used with an optical system (e.g., a display device or a projector) to modify or change light paths to enhance perceived image resolution, improve picture quality (e.g., eliminating dark regions or blurring image edges), or provide other beneficial effects. Further, it should be understood that the light path adjustment mechanism is not limited to a specific arrangement and location in the optical system. 
       FIG. 1  shows an exploded view of a light path adjustment mechanism according to an embodiment of the invention.  FIG. 2  shows a schematic plan view of an assembled light path adjustment mechanism as illustrated in  FIG. 1 . With reference to  FIG. 1 , the light path adjustment mechanism  100  includes a carrier  110 , a support  120 , a magnet seat  130 , a bracket  140 , a first pair of flexible members  152 , and a second pair of flexible members  154 . The carrier  110  includes an inner frame  112  and an outer frame  114 . In this embodiment, the outer frame  114  is disposed outside the inner frame  112  and connected to the inner frame  112  by the first pair of elastic members  152 , and the inner frame  112  and the outer frame  114  are located at the same height or lie in the same plane. The outer frame  114  of the carrier  110  is connected to the support  120  by the second pair of flexible members  154 . The carrier  110  and the support  120  are disposed on one side of the bracket  140 , and the magnet seat  130  is disposed on another side of the bracket  140 . In this embodiment, the bracket  140  has a first side  142 , a second side opening  144  and a third opening  146  to form a U-shaped profile and define an opening  140   a  that allows for insertion or penetration of other optical component. Further, the light path adjustment mechanism  100  may include an optical plate member  180  and multiple actuators. The optical plate member  180  may be disposed on the carrier  110 . For example, the optical plate member  180  may be disposed on the inner frame  112  of the carrier  110 . The optical plate member  180  is not limited to a specific form or structure, so long as it may change, at least to some extent, the traveling direction of incoming light beams. For example, the optical plate member  180  may be, but is not limited to, a lens or a mirror. In this embodiment, multiple actuators include an actuator  160  and an actuator  170  disposed on different sides of the optical plate member  180 . The actuator  160  may include a coil  162  and a magnet  164 , and the actuator  170  may include a coil  172  and a magnet  174 . The magnets  164  and  174  are fixed on the magnet seat  130 , and the magnet seat  130  is fixed on one side of the bracket  140  to secure the magnets  164  and  174  to the bracket  140 . The coil  162  is fixed on one side of the optical plate member  180 , and the coil  172  is fixed on the coil seat  176 . The coil seat  176  is fixed on the outer frame  114  of the carrier  110  to secure the coil  172  to the outer frame  114  of the carrier  110 . Besides, the carrier  110 , support  120  and magnet seat  130  are connected with or secured to the bracket  140  by fasteners  190  such as screws or pins. In other embodiment, the support  120  may be formed by a part of the bracket  140 . Because the support  120  may be connected to the bracket  140  or formed as a part of the bracket  140 , the outer frame  114  of the carrier  110  can be connected to the bracket  140  by the second pair of flexible members  154 . Further, in one embodiment, a lens mount  192  is provided to lean against a periphery of the optical plate member  180  and thus help to hold the optical plate member  180  in place. 
     As shown in  FIG. 2 , the first pair of elastic members  152  connected between the inner frame  112  and the outer frame  114  define a first axis parallel to, for example, an X-axis direction, and the second pair of elastic members  154  connected between the outer frame  114  and the support  120  (bracket  140 ) define a second axis parallel to, for example, a Y-axis direction. In this embodiment, the actuator  160  and the actuator  170  are disposed on two sides of the optical plate member  180  perpendicular to each other, but the invention is not limited thereto. The actuator  160 , including a coil  162  disposed on the optical plate member  180  and a magnet  164  disposed on the bracket  140  as shown in  FIG. 1 , is energized to generate attractive or repulsive forces that act on one end of the optical plate member  180 , which causes the optical plate member  180  and the inner frame  112  to reciprocally rotate or tilt about the axis of the first pair of flexible members  152  (X-axis direction) as shown in  FIG. 2 . Similarly, the actuator  170 , including a coil  172  disposed on the outer frame  114  and a magnet  174  disposed on the bracket  140  as shown in  FIG. 1 , is energized to generate attractive or repulsive forces that act on one end of the outer frame  114 , which causes the optical plate member  180  and the outer frame  114  to reciprocally rotate or tilt about the axis of the second pair of flexible members  154  (Y-axis direction) as shown in  FIG. 2 . Therefore, the optical plate member  180  may tilt or rotate about two different axes to reach various positions within an angular range to reflect or refract incoming light beams, which may cause a change in the traveling direction and propagation path of incoming light beams. In one embodiment, an image beam that intends to impinge upon the optical plate member  180  is deflected by the optical plate member  180  that rapidly and alternately tilts among four different positions relative to the bracket  140  to form four different pixel images, thereby increasing the perceived image resolution at least by four times. According to the above embodiments, the light path adjustment mechanism may modify or change light paths to enhance image resolution, improve picture quality (e.g., eliminating dark regions or blurring image edges), or provide other beneficial effects. Moreover, at least part of the actuator can be disposed on the carrier to reduce occupied space, weight and component number, and the arrangement in which the actuator is disposed only on a single side of each axis may further reduce occupied space, weight and fabrication costs. 
       FIG. 3A  shows a schematic diagram of a light path adjustment mechanism in cooperation with other optical components according to an embodiment of the invention. As shown in  FIG. 3A , in an optical system  200 , the light path adjustment mechanism  100  may be disposed near a light valve  210  and a prism  220 . The light valve  210  may be a digital micro-mirror device (DMD), a liquid-crystal-on-silicon panel (LCOS panel) or a transmissive type LCD panel. The prism  220  may be, for example, a total-internal-reflection (TIR) prism, a reverse total-internal-reflection (RTIR) prism, or a polarizing beam splitter (PBS) prism. In one embodiment, because an opening  140   a  is formed in one side of the bracket  140 , a part of the light valve  210  is allowed to insert in the opening  140   a , so that the light path adjustment mechanism  100  can be assembled in a position closer to the prism  220  without being blocked by the light valve  210 . This may further reduce the overall occupied space and shorten the back focus of optical lenses.  FIG. 3B  shows a schematic diagram illustrating the arrangement of a light valve in relation to a light path adjustment mechanism according to an embodiment of the invention. Herein, a “surface” of the light valve  210  is defined as a surface of an outermost component (such as a cover glass  212 ) at the light-emitting side. For example, in case the light valve  210  is a digital micro-mirror device, the surface  210   a  of the light valve  210  is a surface of the cover glass  212 . Alternatively, in case the light valve  210  is a liquid-crystal-on-silicon panel, the surface  210   a  of the light valve  210  is a surface of a glass substrate. Further, in case the light valve  210  is a transmissive type LCD panel, the surface  210   a  of the light valve  210  is a surface of a polarizer. As shown in  FIG. 3B , a surface normal N of the surface  210   a  of the light valve  210  may cross the bracket  140  to form multiple intersections, and the intersection P is closest to the surface  210  among the multiple intersections. Further, each point of the bracket  140  may be projected on the surface normal N to form multiple projection points. For example, an end point Q is projected on the surface normal N to form a projection point C. In this embodiment, the projection point C of the end point Q is furthest from the intersection P among all projection points of the bracket  140  on the surface normal N. In other words, the end point Q is, measured in the direction of the surface normal N, furthest from the intersection P. Moreover, in this embodiment, a distance D 1  between the intersection P and the surface  210   a  measured in the direction of the surface normal N is smaller than a distance D 2  between the intersection P and the end point Q measured in the direction of the surface normal N. According to this arrangement, the light valve  210  may more approach the optical plate member  180  and the prism  220  shown in  FIG. 3A  to reduce the overall occupied space and the back focus of optical lenses. In one embodiment, as shown in  FIG. 3A , the optical plate member  180  may be a lens/mirror  180   a , a minimum interval between a surface of the optical plate member  180  (lens/mirror  180   a ) and the prism  220  is smaller than 3 mm, and a minimum interval between a surface of the optical plate member  180  (lens/mirror  180   a ) and a surface  210   a  of the light valve  210  is smaller than 1 mm. Note the U-shaped profile of the bracket  140  provided in the above embodiments is merely for exemplified purposes. The bracket  140  is not limited to a specific shape, as long as a room allows for the insertion of part of the light valve  210  (or other component that may interfere with the light path adjustment mechanism) is provided. In other embodiment, as shown in  FIG. 3C , one end of the bracket  140  near the light valve  210  may extend to form a lug structure  140   c , and the light valve  210  may insert into the opening  140   d  of the lug structure  140   c . Therefore, the light path adjustment mechanism  100  is allowed to more approach the prism  220  due to the opening or extension at the end of the bracket  140  near the light valve  210 , with the opening or extension being capable of providing a room for receiving a part of the light valve  210 . 
     Further, the components of an actuator, such as a magnet and a coil, are not limited to a specific arrangement. For example, as shown in  FIG. 4 , in order to allow the optical plate member  180  to tilt about the first pair of flexible members  152  (X-axis direction), a part  160   a  (a magnet or a coil) of the actuator  160  is disposed on the optical plate member  180  or the inner frame  112  (such as position X 1 ), and other part  160   b  (a coil or a magnet) of the actuator  160  is disposed on the outer frame  114 , the support  120  or the bracket  140  (such as position X 2  or X 3 ). Besides, in order to allow the optical plate member  180  to tilt about the second pair of flexible members  154  (Y-axis direction), a part  170   a  (a magnet or a coil) of the actuator  170  is disposed on the outer frame  114  (such as position Y 1 ), and other part  170   b  (a magnet or a coil) of the actuator  170  is disposed on the optical plate member  180 , inner frame  112 , support  120  or bracket  140  (such as position Y 2  or Y 3 ). 
     In one embodiment, the carrier  110 , the support  120 , the magnet seat  130 , the bracket  140 , the first pair of flexible members  152  and the second pair of flexible members  154  may be all integrally formed as one piece using the same material. Alternatively, two or more than two of them may be integrally formed as one piece and are then combined with the remainder. For example, the carrier  110 , support  120 , bracket  140 , first pair of flexible members  152  and second pair of flexible members  154  may be integrally formed as one piece using the same material and then connected with the magnet seat  130 . Further, in one embodiment, the bracket  140  may be provided with a structure for storing magnets to thus omit the magnet seat  130 . 
       FIG. 5  shows a waveform diagram of a drive signal for an actuator according to an embodiment of the invention. As shown in  FIG. 5 , a drive signal S is in the form of a periodic stepwise square wave and includes, in one period, a lowest potential interval P 1 , a rising time P 2 , a highest potential interval P 3  and a falling time P 4 . In the lowest potential interval P 1 , the optical plate member  180  is tilted to a first position, and, in the highest potential interval P 3 , the optical plate member  180  is tilted to a second position. Further, the transition from the first position to the second position or vice versa is realized during the rising time P 2  or the falling time P 4 . In this embodiment, the lowest potential interval P 1  of the drive signal S has a lowest voltage level SV, the highest potential interval P 3  of the drive signal S has a highest voltage level SP, the lowest voltage level SV is increased to the highest voltage level SP during the rising time P 2 , and the highest voltage level SP is decreased to the lowest voltage level SV during the falling time P 4 . In this embodiment, during the rising time P 2  the voltage level is continuously increased without showing decrease in any time point, but the rising time P 2  includes a flat interval F whose voltage level substantially does not vary over time to therefore form a rising stepwise waveform. During the falling time P 4  the voltage level is continuously decreased without showing increase in any time point, but the falling time P 4  also includes a flat interval F whose voltage level substantially does not vary over time to therefore form a falling stepwise waveform. In this embodiment, the voltage level of the flat interval F is between the voltage level of the highest potential SP and the voltage level of the lowest potential SV. Moreover, a variation in the voltage level (a difference between the maximum and the minimum voltage level) of the flat interval is smaller than 0.1 percent of a difference between the voltage level of the highest potential SP and the voltage level of lowest potential SV. In one embodiment, an absolute value of the slop of the flat interval F is smaller than 1 V/ms. 
       FIG. 6  shows a schematic diagram illustrating an optical plate member driven by the drive signal shown in  FIG. 5  to lean towards different positions. For example, when the drive signal S fed to the actuator  160  is in the lowest potential interval P 1 , the actuator  160  tilts the optical plate member  180  towards a position M, and, when the drive signal S fed to the actuator  160  is in the highest potential interval P 3 , the actuator  160  tilts the optical plate member  180  towards a position L. Further, the transition from the position M to the position L or vice versa is realized during the rising time P 2  or the falling time P 4  of the drive signal S. Therefore, the optical plate member  180  may rotate at an angle θ between the position M and position L, and the value of the angle θ is determined by the amplitudes of the drive signal S in the lowest potential interval P 1  and the highest potential interval P 3 . 
       FIG. 7  shows a time-frequency transform diagram illustrating the corresponding frequency component of the Fourier time series data for an operating optical plate member driven by the drive signal (stepwise waveform in rising/falling time) shown in  FIG. 5 .  FIG. 8  shows a time-frequency transform diagram illustrating the corresponding frequency component of the Fourier time series data for an operating optical plate member driven by the drive signal (sin waveform in rising/falling time) shown in  FIG. 9 . Comparing  FIG. 7  and  FIG. 8  with respect to the portion enclosed by a dashed rectangle, it can be clearly seen using the drive signal shown in  FIG. 5  with a stepwise waveform in rising/falling time may considerably decrease the frequency response in the medium/high frequency band (such as 300-780 Hz) and thus reduce the noise of a rotating optical plate member and achieve more stable and precise controls for rotation angles. In one embodiment, each of the rising time P 2  and the falling time P 4  in one period may be set to be 0.8-1.0 ms to enhance the reduction of frequency response. 
       FIG. 10  shows a waveform diagram of a drive signal for an actuator according to another embodiment of the invention. In this embodiment, two actuators  160  are respectively disposed on two sides of the first pair of flexible members  152  (extending in X-axis direction), and the two actuators  160  are respectively fed two distinct drive signals to tilt the optical plate member  180  about the X-axis. Besides, two actuators  170  are respectively disposed on two sides of the second pair of flexible members  154  (extending in Y-axis direction), and the two actuators  170  are respectively fed two distinct drive signals to tilt the optical plate member  180  about the Y-axis.  FIG. 10  shows the waveforms of two distinct drive signals S 1  and S 2  for a single axis (X-axis or Y-axis). In this embodiment, the signal S 1  has a comparatively smaller amplitude A 1 , the signal S 2  has a comparatively larger amplitude A 2 , and the amplitude ratio A 2 /A 1  is set to satisfy the condition 1&lt;(A 2 /A 1 )≤(7/6) to reduce the frequency response of various frequency bands except for the fundamental frequency, with the reduction effects being enhanced in even-numbered frequency domain multiplication.  FIG. 11  shows a time-frequency transform diagram illustrating the corresponding frequency component of the Fourier time series data for an operating optical plate member driven by the two signals S 1  and S 2  having an amplitude ratio (A 2 /A 1 ) of 7/6. As can be clearly seen in  FIG. 11 , the frequency response of various frequency bands, except for the fundamental frequency, is considerable decreased to reduce the noise of a rotating optical plate member and achieve more stable and precise controls for rotation angles. 
     Note the actuator described in the above embodiments is not limited to a specific structure or operation, as long as sufficient forces can be provided to tilt or rotate the optical plate member. In other embodiment, the carrier  110  may be formed by magnetic substances, and the actuator may be an air coil or an electromagnet. The coil or the electromagnet is energized to generate attractive forces to attract the carrier and force the optical plate member  180  to tile or rotate. In other embodiment, as shown in  FIG. 12 , the actuator may include a piezoelectric element  250  disposed on the carrier  110 . The piezoelectric element  250  may deform and change in shape when an electric field is applied, converting electrical energy into mechanical energy, to cause reciprocate movement of the optical plate member  180 . 
       FIG. 13  shows a schematic diagram of a light path adjustment mechanism used in a projector according to an embodiment of the invention. Referring to  FIG. 13 , a projector  400  includes an illumination system  310 , a light valve  320 , a projection lens  260  and a light path adjustment mechanism  100 . The illumination system  310  has a light source  312  for providing a light beam  314 , and the light valve  320  is disposed in a propagation path of the light beam  314  and converts the light beam  314  into multiple sub images  314   a . Besides, the projection lens  260  is disposed in a propagation path of the sub images  314   a , and the light valve  320  is disposed between the illumination system  310  and the projection lens  260 . Further, the light path adjustment mechanism  100  may be disposed between the light valve  320  and the projection lens  260  or in the projection lens  260 . For example, the light path adjustment mechanism  100  may be disposed between the light valve  320  and a TIR prism  319  or between the TIR prism  319  and the projection lens  260 . The light source  312  may, for example, include a red LED  312 R, a green LED  312 G and a blue LED  312 B. Light from each of the LEDs  312 R,  312 G and  312 B are combined by a light combiner  316  to form the light beam  314 , and the light beam  314  passes a fly-eye lens array  317 , a lens assembly  318  and the TIR Prism  319  in succession. Then, the light beam  314  is reflected by the TIR Prism  319 , directed to the light valve  320 , and converted into multiple sub images  314   a  by the light valve  320 . The sub images  314   a  pass the TIR Prism  319  and are projected on a screen  350  by the projection lens  260 . In this embodiment, when the sub images  314   a  reach the light path adjustment mechanism  100 , the light path adjustment mechanism  100  may reflect the sub images  314   a  and alter the propagation path of the sub images  314   a . Therefore, at a first time point the sub images  314   a  are projected on a first position (not shown) of the screen  350  by the light path adjustment mechanism  100 , at a second time point the sub images  314   a  are projected on a second position (not shown) of the screen  350  by the light path adjustment mechanism  100 , and the second position is away from the first position for a distance in a horizontal direction and/or a vertical direction. In this embodiment, the light path adjustment mechanism  100  is allowed to horizontally and/or vertically shift the position of the sub images  314   a  for a distance to therefore improve horizontally and/or vertically image resolutions. Although the light path adjustment mechanism is described herein as being applied to the projector  400 , in other embodiments, the light path adjustment mechanism can be applied to different optical systems to achieve different effects without limitation. Besides, the arrangement and position of the light path adjustment mechanism in an optical system are not restricted. For example, in other embodiment, the light path adjustment mechanism  100  may be disposed in the projection lens  260  of an optical device  410  as shown in  FIG. 14 . 
     The term “light valve”, which is commonly known in the projector industry, refers to individually-addressed optical units of a spatial light modulator. The spatial light modulator includes multiple individually-addressed optical units arranged as a one-dimensional or a two-dimensional array. Each optical unit can be individually addressed by optical or electrical signals to alter its optical properties through various physical effects (e.g., Pockels effect, Kerr effect, photo-acoustic effect, pagneto-optic effect, self electro-optic effect or photorefractive effect). Therefore, the multiple individually addressed optical units may modify incoming light beams and output image beams. The optical units may be, for example, micro mirrors or liquid crystal cells, and the light valve may be a digital micro-mirror device (DMD), a liquid-crystal-on-silicon panel (LCOS panel) or a transmissive type LCD panel. 
     A projector is an apparatus capable of casting an image on a screen through optical projection. In the projector industry, a variety of different types of projectors, which are distinguished from each other by the type of a light valve, may include a cathode-ray-tube type, a liquid-crystal-display (LCD) type, a digital-light-projector (DLP) type or a liquid-crystal-on-silicon (LCOS) type. An LCD-type projector that uses an LCD as a light valve is a transmissive type projector. A DLP-type projector using digital micro-mirror devices as a light valve and an LCOS-type projector using liquid crystal on silicon as a light valve are reflective type projectors that project images through light reflection. 
     Though the embodiments of the invention have been presented for purposes of illustration and description, they are not intended to be exhaustive or to limit the invention. Accordingly, many modifications and variations without departing from the spirit of the invention or essential characteristics thereof will be apparent to practitioners skilled in this art. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated.