Abstract:
A display system, that includes a light source for providing illumination; a linear array of electromechanical grating devices of at least two individually operable devices receiving the illumination wherein a grating period is oriented at a predetermined angle with respect to an axis of the linear array wherein the angle is large enough to separate diffracted light beams prior to a lens system for projecting light onto a screen; an obstructing element for blocking a discrete number of diffracted light beams from reaching the screen; a scanning element for moving non-obstructed diffracted light beams on the screen; and a controller for providing a data stream to the individually operable devices.

Description:
FIELD OF THE INVENTION 
     This invention relates to a display system with a linear array of electromechanical grating modulators that is scanned in order to generate a two-dimensional image. More particularly, the invention relates to an electromechanical grating display system that has spatially separated diffracted light beams throughout the system. 
     BACKGROUND OF THE INVENTION 
     Electromechanical spatial light modulators with a variety of designs have been used in applications such as display, optical processing, printing, optical data storage and spectroscopy. These modulators produce spatial variations in the phase and/or amplitude of an incident light beam using arrays of individually addressable devices. 
     Spatial phase modulation of an incident beam can be accomplished by arrays of individually addressable deformable mirrors. Such devices can be made by suspending a deformable reflective membrane over a grid of supports, as described U.S. Pat. No. 4,441,791 issued Apr. 10, 1984 to Hornbeck entitled Deformable Mirror Light Modulator. However, because of the membrane and support structure, these particular deformable mirrors are very inefficient. More efficient deformable mirror designs are disclosed in U.S. Pat. No. 5,170,283 issued Dec. 8, 1992 to O&#39;Brien et al. entitled Silicon Spatial Light Modulator, and in U.S. Pat. No. 5,844,711 issued Dec. 1, 1998 to Long, Jr. entitled Tunable Spatial Light Modulator. 
     Another class of electromechanical spatial light modulators has devices with a periodic sequence of reflective elements that form electromechanical phase gratings. In such devices, the incident light beam is selectively reflected or diffracted into a number of light beams of discrete orders. Depending on the application, one or more of these diffracted light beams may be collected and used by the optical system. For many applications, electromechanical phase gratings are preferable to deformable mirrors. Electromechanical phase gratings can be formed in metallized elastomer gels; see U.S. Pat. No. 4,626,920 issued Dec. 2, 1986 to Glenn entitled Solid State Light Modulator Structure, and U.S. Pat. No. 4,857,978 issued Aug. 15, 1989 to Goldburt et al. entitled Solid State Light Modulator Incorporating Metallized Gel and Method of Metallization. The electrodes below the elastomer are patterned so that the application of a voltage deforms the elastomer producing a nearly sinusoidal phase grating. These types of devices have been successfully used in color projection displays; see  Metallized viscoelastic control layers for light-valve projection displays,  by Brinker et al., Displays 16, 1994, pp. 13-20, and  Full-colour diffraction-based optical system for light-valve projection displays,  by Roder et al., Displays 16, 1995, pp. 27-34. 
     An electromechanical phase grating with a much faster response time can be made of suspended micromechanical ribbon elements, as described in U.S. Pat. No. 5,311,360 issued May 10, 1994 to Bloom et al. entitled Method and Apparatus for Modulating a Light Beam. This device, also known as a grating light valve (GLV), can be fabricated with CMOS-like processes on silicon. Improvements in the device were later described by Bloom et al. that included: 1) patterned raised areas beneath the ribbons to minimize contact area to obviate stiction between the ribbons and the substrate, and 2) an alternative device design in which the spacing between ribbons was decreased and alternate ribbons were actuated to produce good contrast; see U.S. Pat. No. 5,459,610 issued Oct. 17, 1995 entitled Deformable Grating Apparatus for Modulating a Light Beam and Including Means for Obviating Stiction between Grating Elements and Underlying Substrate. Bloom et al. also presented a method for fabricating the device; see U.S. Pat. No. 5,677,783 issued Oct. 14, 1997 entitled Method of Making a Deformable Grating Apparatus for Modulating a Light Beam and Including Means for Obviating Stiction Between Grating Elements and Underlying Substrate. Additional improvements in the design and fabrication of the GLV were described in U.S. Pat. No. 5,841,579 issued Nov. 24, 1998 to Bloom et al. entitled Flat Diffraction Grating Light Valve, and in U.S. Pat. No. 5,661,592 issued Aug. 26, 1997 to Bornstein et al. entitled Method of Making and an Apparatus for a Flat Diffraction Grating Light Valve. 
     For display or printing, linear arrays of GLV devices can be used with a scanning Schlieren optical system as described in U.S. Pat. No. 5,982,553 issued Nov. 9, 1999 to Bloom et al. entitled Display Device Incorporating One-Dimensional Grating Light-Valve Array. Alternatively, an interferometric optical system can be used to display an image as disclosed in U.S. Pat. No 6,088,102 issued Jul. 11, 2000 to Manhart entitled Display Apparatus Including Grating Light-Valve Array and Interferometric Optical System. In the scanning Schlieren display system of Bloom et al. &#39;553, the plane of diffraction, which contains the diffracted light beams, is parallel to the axis of the linear GLV array because the grating period is parallel to the axis. This increases the cost and complexity of the display system. Specifically, efficient collection of the primary diffracted light beams requires at least one dimension of the optical elements to be significantly larger than the extent of the linear GLV array. Furthermore, the diffracted and reflected light beams overlap spatially throughout most of the optical system. Separation of diffracted light from reflected light is accomplished in close proximity to a Fourier plane of the Schlieren optical system. However, the Fourier plane is usually also the preferred location of a scanning mirror for producing a two-dimensional image. 
     Recently, a linear array of electromechanical conformal grating devices was disclosed by Kowarz in U.S. Ser. No. 09/491,354 filed Jan. 26, 2000 now U.S. Pat. No. 6,307,663. For this type of device, it is preferable to have the grating period perpendicular to the axis of the linear array. The diffracted light beams are then spatially separated throughout most of the optical system. In U.S. Ser. No. 09/491,354 now U.S. Pat. No. 6,307,663, it was mentioned that a simplified display system is possible to use with a new device. However, no specific description of the display system was given. There is a need therefore for a scanning display system that utilizes a linear array of electromechanical conformal grating devices. Furthermore, there is a need for a system that is simpler and less costly than prior art systems. 
     SUMMARY OF THE INVENTION 
     The need is met according to the present invention by providing a display system that includes a light source for providing illumination; a linear array of electromechanical grating devices of at least two individually operable devices receiving the illumination, wherein a grating period is oriented at a predetermined angle with respect to an axis of the linear array wherein the angle is large enough to separate diffracted light beams prior to a lens system for projecting light onto a screen; an obstructing element for blocking a discrete number of diffracted light beams from reaching the screen; a scanning element for moving non-obstructed diffracted light beams on the screen; and a controller for providing a data stream to the individually operable devices. 
     The present invention has several advantages, including: 1) improvement in contrast by eliminating reflections from projection lens, because of the new flexibility in placing the turning mirror between the linear array and the projection lens; 2) reduction in size of the scanning mirror, because now the scanning mirror can be placed directly at the Fourier plane; 3) increase in design flexibility, because now separation of diffracted orders can take place almost anywhere in the system, not just at the Fourier plane; and 4) reduction in size of lenses and other optical elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective, partially cut-away view of a spatial light modulator with electromechanical conformal grating devices, showing two devices in a linear array; 
     FIG. 2 is a top view of a spatial light modulator with electromechanical conformal grating devices, showing four individually operable devices in a linear array; 
     FIGS. 3 a  and  3   b  are cross-sectional views through line  3 - 3  in FIG. 2, showing the operation of an electromechanical conformal grating device in an unactuated state and an actuated state, respectively; 
     FIGS. 4 a  and 4 b  show the operation of a conventional electromechanical two-level grating device in an unactuated state and an actuated state, respectively; 
     FIG. 5 is a top view of a spatial light modulator with conventional GLV devices, showing five individually operable devices in a linear array with deformable ribbon elements oriented perpendicular to the axis of the array and the grating period oriented parallel to the axis; 
     FIG. 6 is a top view of a spatial light modulator with conventional GLV devices, showing five individually operable devices in a linear array with deformable ribbon elements oriented parallel to the axis of the array and the grating period oriented perpendicular to the axis; 
     FIG. 7 is a schematic illustrating a prior art, line-scanned Schleiren display system that includes a light source, illumination optics, a linear array of conventional GLV devices, a projection lens, a scanning mirror, a controller and a turning mirror located at the Fourier plane of the projection lens; 
     FIG. 8 is a schematic illustrating a line-scanned display system according to the present invention that includes a light source, illumination optics, a linear array of electromechanical conformal grating devices, a projection lens, a scanning mirror, a controller and a turning mirror located between the linear array and the projection lens; 
     FIG. 9 shows a linear array of electromechanical conformal grating devices illuminated by a line of light; 
     FIG. 10 is a view of the projection screen that illustrates the formation of a two-dimensional image by scanning a line image across the screen; 
     FIGS. 11 a - 11   h  are density plots of the light distribution in different planes of a prior art, line-scanned Schleiren display system in which the modulator is a linear array of conventional GLV devices with deformable ribbon elements oriented perpendicular to the axis of the array; 
     FIGS. 12 a - 12   h  are density plots of the light distribution in different planes of a line-scanned display system of the present invention in which the modulator is a linear array of electromechanical conformal grating devices; 
     FIG. 13 is a schematic illustrating an alternate embodiment of the present invention in which the turning mirror is placed between the first projection lens and the scanning mirror, and an intermediate image plane is formed in the system; 
     FIG. 14 is a schematic illustrating an optical subsystem for illumination and diffracted order separation in which the illumination optics, the linear array of electromechanical conformal grating devices, and the turning mirror are combined into a single mechanical structure; 
     FIG. 15 is a schematic illustrating an optical subsystem for illumination and diffracted order separation in which the turning mirror is replaced by a polarization beam splitter, a quarter waveplate and a 0 th  order stop; 
     FIG. 16 is a schematic illustrating a color, line-scanned display system that includes a three-color light source, illumination optics, a color combination cube, three linear arrays of electromechanical conformal grating devices, a projection lens, a scanning mirror and a turning mirror located between the linear arrays and the projection lens; 
     FIG. 17 is a schematic illustrating a color, line-scanned display system with three light sources; 
     FIG. 18 is a schematic illustrating a printer system that includes a light source, illumination optics, a linear array of electromechanical conformal grating devices, an imaging lens, a rotating drum, light sensitive media, a controller and a turning mirror located between the linear array and the projection lens; and 
     FIG. 19 is a schematic illustrating a color printer system with a three-color light source, a color combination cube and three linear arrays of electromechanical conformal grating devices. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The structure and operation of an electromechanical conformal grating device is illustrated in FIGS. 1-3. FIG. 1 shows two side-by-side conformal grating devices  5   a  and  5   b  in an unactuated state. In this embodiment, the devices can be operated by the application of an electrostatic force. The grating devices  5   a  and  5   b  are formed on top of a substrate  10  covered by a bottom conductive layer  12  which acts as an electrode to actuate the devices. The bottom conductive layer  12  is covered by a dielectric protective layer  14  followed by a standoff layer  16  and a spacer layer  18 . On top of the spacer layer  18 , a ribbon layer  20  is formed which is covered by a reflective layer  22 . The reflective layer  22  is also a conductor in order to provide electrodes for the actuation of the conformal grating devices  5   a  and  5   b . The reflective and conductive layer  22  is patterned to provide electrodes to the two conformal grating devices  5   a  and  5   b . The ribbon layer  20  preferably comprises a material with a sufficient tensile stress to provide a large restoring force. Each of the two devices  5   a  and  5   b  has an associated elongated ribbon element  23   a  and  23   b,  respectively, patterned from the reflective and conductive layer  22  and the ribbon layer  20 . The elongated ribbon elements  23   a  and  23   b  are supported by end supports  24   a  and  24   b  formed from the spacer layer  18  and by one or more intermediate supports  27  that are uniformly separated in order to form four equal-width channels  25 . The elongated ribbon elements  23   a  and  23   b  are secured to the end supports and to the intermediate supports  27 . A plurality of square standoffs  29  is patterned at the bottom of the channels  25  from the standoff layer  14 . These standoffs  29  reduce the possibility of the ribbon elements sticking when actuated. 
     A top view of a four-device linear array of conformal grating devices  5   a ,  5   b ,  5   c  and  5   d  is shown in FIG.  2 . The elongated ribbon elements are depicted partially removed over the portion of the diagram below the line  2 — 2  in order to show the underlying structure. For best optical performance and maximum contrast, the intermediate supports  27  must be completely hidden below the elongated ribbon elements  23   a ,  23   b ,  23   c  and  23   d . Therefore, when viewed from the top, the intermediate supports must not be visible in the gaps  28  between the conformal grating devices  5   a - 5   d . Here each of the conformal grating devices has three intermediate supports  27  with four equal-width channels  25 . The center-to-center separation A of the intermediate supports  27  defines the period of the conformal grating devices in the actuated state. The elongated ribbon elements  23   a - 23   d  are mechanically and electrically isolated from one another, allowing independent operation of the four conformal grating devices  5   a - 5   d . The bottom conductive layer  12  of FIG. 1 can be common to all of the devices. 
     FIG. 3 a  is a side view, through line  3 — 3  of FIG. 2, of two channels  25  of the conformal grating device  5   b  (as shown and described in FIG. 1) in the unactuated state. FIG. 3 b  shows the same view of the actuated state. For operation of the device, an attractive electrostatic force is produced by applying a voltage difference between the bottom conductive layer  12  and the conducting layer  22  of the elongated ribbon element  23   b . In the unactuated state (see FIG. 3 a ), with no voltage difference, the ribbon element  23   b  is suspended flat between the supports. In this state, an incident light beam  30  is primarily diffracted into a 0th order light beam  32  in the mirror direction. To obtain the actuated state, a voltage is applied to the conformal grating device  5   b,  which deforms the elongated ribbon element  23   b  and produces a partially conformal grating with period A. FIG. 3 b  shows the device  5   b  (as shown and described in FIG. 1) in the fully actuated state with the elongated ribbon element  23   b  in contact with the standoffs  29 . The height difference between the bottom of element  23   b  and the top of the standoffs  29  is chosen to be approximately ¼ of the wavelength λ of the incident light. The optimum height depends on the specific shape of the actuated device. In the actuated state, the incident light beam  30  is primarily diffracted into the +1st order light beam  35   a  and −1st order light beam  35   b,  with additional light diffracted into the +2nd order  36   a  and −2nd order  36   b.  A small amount of light is diffracted into even higher orders and some is diffracted into the 0th order. One or more of the diffracted beams can be collected and used by the optical system, depending on the application. When the applied voltage is removed, the forces due to the tensile stress and bending restores the ribbon element  23   b  to its original unactuated state. 
     A linear array of conformal grating devices is formed by arranging the devices as illustrated in FIGS. 1-3 with the direction of the grating period Λ (the y direction) perpendicular to the axis of the array (the x direction). For a given incident angle, the planes containing the various diffracted light beams are distinct. These planes all intersect in a line at the linear array. Even with a large linear array consisting, possibly, of several thousand devices illuminated by a narrow line of light, the diffracted light beams become spatially separated over a relatively short distance. This feature simplifies the optical system design and enables feasible designs in which the separation of diffracted light beams can be done spatially without Schlieren optics. 
     A conventional Grating Light Valve (GLV) is shown in FIGS. 4 a  and  4   b.  FIG. 4 a  depicts the ribbon structure of the device in the unactuated state and FIG. 4 b  in the actuated state. For operation of the device, an attractive electrostatic force is produced by a voltage difference between the bottom conductive layer  42  and the reflective and conductive layer  48  atop the ribbon element  46 . In the unactuated state, with no voltage difference, all of the ribbon elements  46  in the GLV device are suspended above the substrate  40  at the same height. In this state, an incident light beam  54  is primarily reflected as from a mirror to form a 0th order diffracted light beam  55 . To obtain the actuated state (see FIG. 4 b ), a voltage is applied to every other ribbon element  46  producing a grating. In the fully actuated state, every other ribbon element  46  is in contact with the protective layer  44 . When the height difference between adjacent ribbons is {fraction (1/14)} of the wavelength of an incident light beam  56 , the light beam is primarily diffracted into a +1st order light beam  57  and a −1st order light beam  58 . One or more of the diffracted beams can be collected and used by an optical system, depending on the application. When the applied voltage is removed, the force due to the tensile stress restores the ribbon elements  46  to their original unactuated state (see FIG. 4 a ). 
     The table below summarizes the key differences between a conformal grating device and a conventional GLV for a single device of each type. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Conformal grating device 
                 Conventional GLV 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 # of moving ribbons 
                 1 
                 3-6 
               
               
                 # of stationary ribbons 
                 none 
                 3-6 
               
               
                 Number of channels 
                 &gt;5 
                 1 
               
               
                 Grating period direction 
                 Parallel to ribbon length 
                 Perpendicular to 
               
               
                   
                   
                 ribbon length 
               
               
                 Grating profile 
                 Smoothly varying 
                 Square (binary) 
               
               
                   
               
             
          
         
       
     
     It should be noted that the parameters above pertain to the preferred forms of each of the devices. 
     In a linear array made from conventional GLV devices, the ribbon elements are usually all arranged parallel to each other. FIG. 5 shows the top view of a portion of such a linear array. In this example, each of 5 devices  45   a ,  45   b ,  45   c ,  45   d  and  45   e  contains 4 movable ribbon elements  46   a  that are electrically connected to each other and 4 stationary ribbon elements  46   b  that are connected to ground. The application of a voltage to a device causes the movable ribbon elements  46   a  belonging to that device to actuate in unison into the channel  50 . The grating period A formed by the actuated ribbons is parallel to the axis of the array and perpendicular to the length of the ribbon elements  46   a  and  46   b . The diffracted light beams then overlap spatially over a relatively long distance. 
     As a comparative example between the two types of linear arrays, let us consider an array of conformal grating devices that is 4 cm long (2000 devices 20 μm wide) illuminated by a 100 μm wide line of light. For devices with a period chosen such that the diffracted orders are angularly separated by 1 rapid separation of diffracted orders occurs because the grating period is perpendicular to the axis of the linear array of conformal grating devices, and is parallel to the length of the ribbon elements. A similar 4 cm linear array of prior art GLV devices with a 4 degree angular separation between diffracted orders would require at least 60 cm for spatial separation, without the use of a Schlieren optical system. This relatively slow order separation occurs because the grating period is parallel to the axis of the linear array of GLV devices. 
     A linear array of GLV devices can also be constructed with the ribbons elements perpendicular to the axis of the array as illustrated in FIG.  6 . Each of the 5 devices  62   a ,  62   b ,  62   c ,  62   d  and  62   e  is individually operable and has its own channel  60   a ,  60   b ,  60   c ,  60   d  and  60   e . For such a GLV array, the grating period Λ is perpendicular to the axis of the array and the diffracted light beams become spatially separated over a relatively short distance. However, this type of GLV array suffers from the existence of significant gaps between devices that cause some pixelation in the display. 
     FIG. 7 shows a GLV-based display system of the prior art that has a Schlieren optical system. The linear array  85  consists of GLV devices of the type shown in FIG.  5 . Light is emitted from a source  70  and passes through a spherical lens  72  and a cylinder lens  74  before hitting a turning mirror  82 . The turning mirror  82  is placed at the Fourier (focal) plane of a projection lens system  75 . Although only a single lens element is shown, in practice, the projection lens system will consist of multiple elements. Light reflected by the turning mirror  82  is focused by the projection lens system  75  into a line illuminating the linear array  85 . A small portion of the illumination that strikes the projection lens system  75  will be reflected. In order to avoid a reduction in the contrast of the display system from such reflections, the projection lens system  75  needs to have very good optical coatings and/or needs to be used off axis. The GLV devices of the linear array  85  are selectively activated by the controller  80  to correspond to a line of pixels. If a particular device of the array is actuated by application of a voltage to the ribbon elements, it diffracts light primarily into +1st order and −1st order light beams. If a particular device is not actuated, it diffracts light primarily into the 0th order light beam. These three primary light beams are collected by the same projection lens  75 , which focuses the three light beams into distinct spots at the Fourier plane. The 0th order light beam hits the turning mirror  82  and is reflected towards the light source  70 . The +1st and −1st order light beams pass above and below the turning mirror  82  and strike a scanning mirror  77  that sweeps the light beams across a screen  90  to form a viewable two-dimensional image. Higher-order light beams also show up as spots in the Fourier plane and can be blocked from reaching the screen  90  by a stop in the Fourier plane (not shown). The controller  80  synchronizes the sweep of the scanning mirror  77  with the actuation of the devices of the linear array  85 . 
     In the prior art display system of FIG. 7, in order to effectively separate the +1st and −1st order light beams from the 0th order light beam, the turning mirror  82  must be placed near the Fourier plane of the projection lens system  75 , i.e., it must be located at approximately the focal distance f from the lens. However, this location is also best for placing the scanning mirror  77  because the +1st and −1st order light beams are tightly focused here, allowing for a reduction in the size and weight of the scanning mirror  77 . 
     FIGS. 8-10 illustrate the preferred embodiment of the present invention. FIG. 8 shows the display system with a turning mirror  82  placed between the linear array  85  and the projection lens system  75 . Light emitted by source  70  is conditioned by a spherical lens  72  and a cylindrical lens  74  before hitting the turning mirror  82  and focusing on the linear array  85 . In this system, the axis of the cylindrical lens is rotated 90 degrees with respect to the cylindrical lens in FIG.  7 . By placing the turning mirror  82  between the linear array  85  and the projection lens system  75 , the contrast-reducing reflections of the prior art system of FIG. 8 are eliminated because the illuminating light beam never passes through the projection lens system  75 . FIG. 9 shows the linear array  85  illuminated by a line of light  88 . In this particular example there are  17  electromechanical conformal grating devices shown. In practice, there would be hundreds or thousands of devices. The controller  80  selects the devices to be actuated based on the desired pixel pattern for a given line of a two-dimensional image. If a particular device is not actuated, it diffracts the incident light beam primarily into the 0th order light beam, which subsequently hits the turning mirror  82  and is reflected towards the source  70 . If the device is actuated, it diffracts the incident light beams primarily into +1st order and −1st order light beams. These two first-order diffracted light beams pass around the turning mirror  82  and are projected on the screen  90  by the projection lens system  75 . Higher-order diffracted light beams can be blocked by the addition of a stop  83 . The scanning mirror  77  sweeps the line image across the screen  90  to form the two-dimensional image. Preferably, the scanning mirror  77  is placed near the Fourier plane of the projection lens system  75 . FIG. 10 is a view facing the screen  90  showing the formation of a two-dimensional image from a series of 1080 sequential line scans. 
     Clearly, there are two kinds of diffracted light beams in this display system: those that are blocked by obstructing elements from reaching the screen  90  and those that pass around obstructing elements to form an image on the screen  90 . In this particular system, the obstructing elements are the turning mirror  82  that blocks the 0th order light beam and the stops  83  that block the ±2nd, ±3rd, ±4th, . . . orders of light. In the subsequent embodiments, similar obstructing elements are used to prevent unwanted diffracted light beams from reaching the screen. However, as is well known to those skilled in the art, other elements may be used for this purpose. For example, the stops  83  can be replaced by tilted mirrors. 
     The linear array  85  is preferably constructed of electromechanical conformal grating devices of the type shown in FIGS. 1-3. It may also be constructed of GLV devices of the type shown in FIG. 6, or of other kinds of electromechanical grating devices. However, in order to place the turning mirror  82  before the projection lens system  75 , the grating period A must be rotated at a sufficiently large angle with respect to the long axis of the linear array  85 . For the electromechanical conformal grating devices of FIGS. 1-3 and the GLV devices of FIG. 6, this angle is 90 degrees. A lesser angle can also be used so long as the diffracted orders become separated before reaching the projection lens system  75 . It is impractical, however, to make this type of display system with no rotation between the grating period and the axis of the linear array  85 . A conventional linear array of GLV devices of the type shown in FIG. 5 can therefore not be used with this kind of system. 
     The significant differences between the display system of the prior art (FIG. 7) and the present display system (FIG. 8) can be understood by examining the propagation of the diffracted light beams throughout the two systems. FIGS. 11 a   14   11   h  show the amplitude of the diffracted light beams along several parallel planes between the linear array  85  and the screen  90  for the prior art system of FIG.  7 . In this modeled example, the lens has a focal length f of 50 mm, the linear array is 1 cm long. D refers to the distance between the linear array  85  to the plane of interest. As the diffracted light beams emerge from the linear array  85 , they begin to spread along the direction of the axis of the linear array as illustrated in FIGS. 11 a - 11   d . The interference between the various diffracted beams causes a rapid variation in the intensity known to those skilled in the art as tilt fringes. At the plane just before the projection lens (see FIG. 11 d ), the diffracted light beams have spread to about twice the length of the linear array. The lens must be large enough to avoid truncating the diffracted light beams to be projected on the screen, which are the −1st and +1st order light beams in this case. After passing through the projection lens system  75 , the beams begin to focus. At a distance of D=90 mm from the linear array  85 , the various diffracted orders are spatially separated. Distinct spots are visible that correspond to the +3rd, +2nd, +1st, 0th, −1st, −2nd and −3rd orders (see FIG. 11 g ). At the Fourier plane (D=100 mm), the turning mirror  82  blocks the 0th order light beam and a stop blocks the +3rd, +2nd, −2nd and −3rd orders. The +1st and −1st order light beams continue towards the screen  90  where they overlap spatially to form the line image. It is important to note that the various order light beams are only spatially separated near the Fourier plane (near D=100 mm). Therefore, only the vicinity of this plane is available for separating the +1st and −1st order light beams from the rest of the diffracted orders. 
     FIGS. 12 a - 12   h  show the amplitude of the diffracted light beams along several parallel planes for the display system of FIG.  8 . In contrast to the prior art display system, as the various diffracted light beams propagate from one plane to the next, they spread out in a direction perpendicular to the axis of the linear array  85 . They become spatially separated a few millimeters from the linear array  85  and remain spatially separated throughout the system, except near the screen  90  and any intermediate image planes. FIG. 12 d  shows the light distribution just before the turning mirror  82  and the stop  83 , which block the unwanted diffracted orders. Only the +1st and −1st order light beams pass through the projection lens system  75 . For better optical efficiency, higher diffracted orders could also be allowed through. FIGS. 12 e - 12   h  show the +1st and −1st order light beams after they have gone through the projection lens system and pass through focus at the Fourier plane (D=100 mm). Near the Fourier plane, the two first order light beams are tightly focused into two spots. Therefore, by placing the scanning mirror  77  here, it can be kept small and light. The +1st and −1st order light beams overlap spatially when they finally reach the screen  90 . 
     An alternate embodiment of the invention is shown in FIG.  13 . The projection lens system now consists of 3 separate lens groups  75   a ,  75   b  and  75   c . The turning mirror  82  is placed between the first lens group  75   a  and the scanning mirror  77  adjacent to the first lens group  75   a . This location for the turning mirror  82  can be beneficial because the diffracted light beams are collimated along one axis in this space. The cylinder lens axis  74  is rotated 90 degrees with respect to the cylinder lens of FIG.  8 . The scanning mirror  77  is preferably placed at the Fourier plane (focal plane) of the first lens group  75   a . The second lens group  75   b  creates an intermediate image  92  of the linear array  85  that can be used to modify the image appearing on the screen  90 . For example, an aperture can be placed in this plane to create a sharp boundary for the image. The third lens group  75   c  projects the intermediate image  92  onto the screen  90 . 
     In order to the improve alignment and stability of the system, some of the optical elements can be combined into a solid structure and/or can be replaced by equivalent components. As an example, FIG. 14 shows the combination of several components of FIG. 8, namely, of the cylinder lens  74 , turning mirror  82 , stop  83  and linear array  85 . The turning mirror  82  may also be replaced by using a polarization beam splitter  96  with a ¼ waveplate  95  and a 0th order stop  97  as in FIG.  15 . 
     The above embodiments can be used either for single color or for color-sequential display systems. For a color-sequential display, the light source  70  produces a plurality of colors that are sequential in time and the controller  80  is synchronized with the light source  70 . For example, if the light source  70  consists of three combined red, green and blue lasers, these are turned on sequentially to produce overlapping red, green and blue images on the screen  90 . The image data sent by the controller  80  to the linear array  85  is synchronized with the turned-on laser color. 
     Color-sequential display systems waste two-thirds of the available light because only one color is used at a time. FIGS. 16 and 17 depict embodiments of the invention that project three colors simultaneously. In FIG. 16, the light source  70  emits red, green and blue. After these three colors hit the turning mirror  82 , they are separated by a color combination cube  100 . Red light illuminates linear array  85   r,  green light linear array  85   g  and blue light linear array  85   b.  The +1st, 0th and −1st order light beams, emerging from the three linear arrays, are combined by the color combination cube  100 . The turning mirror  82  blocks the red, green and blue 0th order light beams after they pass through the cube. The remaining +1st and −1st order light beams are imaged by the projection lens system  75  to form a color image at the screen  90 . Three stops  83   r ,  83   g ,  83   b  block unwanted higher-order diffracted light beams. 
     Alternatively, a color-simultaneous display system can be made with three distinct illumination paths as shown in FIG.  17 . Three separate light sources  70   r ,  70   g ,  70   b,  each with their own illumination optics  72   r ,  72   g ,  72   b ,  74   r ,  74   g ,  74   b , provide light to the three linear arrays  85   r ,  85   g ,  85   b  via three turning mirrors  82   r ,  82   g,    82   b.  The color combination cube  100  now serves only to combine the +1st and −1st order light beams of the three colors. In contrast to the display system of FIG. 17, the color combination cube  100  plays no role in illuminating the device. 
     The embodiments described above can be altered to obtain printing systems. For example, FIG. 18 shows a printer that is fashioned from the building blocks in FIG.  8 . Light emitted by source  70  is conditioned by a spherical lens  72  and a cylindrical lens  74  before hitting the turning mirror  82  and focusing on the linear array  85  of electromechanical conformal grating devices. An imaging lens  105  is used at finite conjugates to create a line image of the linear array  85  on light sensitive media  110 . This line image is formed from the (non-obstructed) diffracted light beams that pass between the turning mirror  82  and the stops  83 . Although a scanning mirror  77  could be used to create a two-dimensional image from the line image, it is usually preferable to use a media transport system to move the light sensitive media  110  with respect to the line image. In FIG. 18, the media transport system has a rotating drum  107 . The motion of the media must be synchronized with the actuation of the electromechanical conformal grating devices of the linear array  85  by the controller  80 . This embodiment can be used for either a monochrome or a color-sequential printer. To obtain a high-speed printer that can print three colors simultaneously on photographic paper, three linear arrays are necessary. FIG. 19 shows an embodiment of a color-simultaneous printer fashioned from the building blocks in FIG. 16 with the following changes: an imaging lens  105  used at finite conjugates replaces the projection lens  75 , light sensitive media  110  replaces the screen  90  and a rotating drum  107  for moving the light sensitive media  110  replaces the scanning mirror  77 . 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
     PARTS LIST 
       5   a  conformal grating device 
       5   b  conformal grating device 
       5   c  conformal grating device 
       5   d  conformal grating device 
       10  substrate 
       12  bottom conductive layer 
       14  protective layer 
       16  standoff layer 
       18  spacer layer 
       20  ribbon layer 
       22  reflective layer 
       23   a  elongated ribbon element 
       23   b  elongated ribbon element 
       23   c  elongated ribbon element 
       23   d  elongated ribbon element 
       24   a  end support 
       24   b  end support 
       25  channel 
       27  intermediate support 
       28  gap 
       29  standoff 
       30  incident light beam 
       32  0th order light beam 
       35   a  +1 st  order light beam 
       35   b  −1 st  order light beam 
       36   a  +2 nd  order light beam 
       36   b  −2 nd  order light beam 
       40  substrate 
       42  bottom conductive layer 
       44  protective layer 
       45   a  GLV device 
       45   b  GLV device 
       45   c  GLV device 
       45   d  GLV device 
       45   e  GLV device 
       46  ribbon element 
       46   a  movable ribbon element 
       46   b  stationary ribbon element 
       48  reflective and conductive layer 
       50  channel 
       54  incident light beam 
       55  0th order light beam 
       56  incident light beam 
       57  +1st order light beam 
       58  −1 st order light beam 
       60   a  channel 
       60   b  channel 
       60   c  channel 
       60   d  channel 
       60   e  channel 
       62   a  GLV device 
       62   b  GLV device 
       62   c  GLV device 
       62   d  GLV device 
       62   e  GLV device 
       70  source 
       70   r  red source 
       70   g  green source 
       70   b  b blue source 
       72  spherical lens 
       72   r  spherical lens 
       72   g  spherical lens 
       72   b  spherical lens 
       74  cylindrical lens 
       74   r  cylindrical lens 
       74   g  cylindrical lens 
       74   b  cylindrical lens 
       75  projection lens system 
       75   a  first lens group 
       75   b  second lens group 
       75   c  third lens group 
       77  scanning mirror 
       80  controller 
       82  turning mirror 
       82   r  turning mirror 
       82   g  turning mirror 
       82   b  turning mirror 
       83  stop 
       83   r  stop 
       83   g  stop 
       83   b  stop 
       85  linear array 
       85   r  linear array 
       85   g  linear array 
       85   b  linear array 
       88  line of light 
       90  screen 
       92  intermediate image 
       95  ¼ waveplate 
       96  polarization beam splitter 
       97  0th order stop 
       100  color combination cube 
       105  imaging lens 
       107  rotating drum 
       110  light sensitive media