Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application relates to U.S. Applications 12/448,320 filed on Jun. 17, 2009 which published as US 2010-0014008A1; 12/312,998 filed on Jun. 3, 2009 which published as US 2010-0315596A1; 12/448,002 filed on Jun. 3, 2009 which published as US 2010-0026959A1; and 12/448,338 filed on Jun. 17, 2009 which published as US2010-0026910A1. 
     FIELD OF THE INVENTION 
     This application claims the benefit, under 35 U.S.C. §365 of International Application PCT/US2007/009,979, filed 25 Apr. 2007, which was published in accordance with PCT Article 21(2) on 6 Nov. 2008, in English. 
     The invention relates to a digital micromirror device (DMD) projection system. In particular, the invention relates to a high resolution 3D DMD projection system. 
     BACKGROUND OF THE INVENTION 
     With the advent of digital micromirror devices (DMD devices) such as digital light processors (DLPs), there has been a desire to integrate the digital projection technology into cinematic theatres for viewing by the public at large. However, as of yet, DMDs (and DLPs in particular) have not yet progressed in native resolution capability so as to allow an acceptable image for large venues which complies with industry standards for display quality. Particularly, the Society of Motion Picture and Television Engineers (SMPTE) promulgates such standards which are well respected by the various members of the motion picture industry. One such standard applies to the display of Digital Cinema Distribution Masters (DCDMs) (digital packages which contains all of the sound, picture, and data elements needed for a show) in review rooms and theatres. A requirement of the SMPTE standard is that the number of pixels for a projected image must be at least 2048×1080 (2K×1K pixels). The standard further requires that the mesh of pixels (the device structure) must be invisible when viewed from a reference viewing distance. While many DMD/DLP projectors meet the minimum requirement regarding resolution, those same projectors cannot meet the second requirement of the standard because the proper reference viewing distance is small enough to cause visibility of the mesh of pixels. Therefore, current DMD/DLP projectors having 2K×1K resolution which may not be suitable for most commercial theatres where the viewing distance is small, such as an IMAX theatre, and where to prevent the appearance of the pixel mesh from an appropriate viewing distance, a DMD/DLP projector must have a resolution of about 4K×2K (which is not currently commercially available). 
     A projected two dimensional (2D) image may be enhanced with an appearance of depth by converting the projected image into a so-called three dimensional (3D) image. This, is accomplished by optically polarizing the images which are to be viewed by a viewer&#39;s left eye differently than the images which are to be viewed by a viewer&#39;s right eye. The 3D effect is perceived by the viewer when the viewer views the polarized images through the use of polarized filter lenses, commonly configured as ‘3D viewing glasses’ with a polarized filter for use with the left eye of the viewer and a differently polarized filter for use with the right eye of the viewer. When the 3D viewing glasses are used to view the 3D images, the left eye of the viewer sees only the light polarized appropriately for passage through the polarized filter associated with the left eye and the right eye of the viewer sees only the light polarized appropriately for passage through the polarized filter associated with the right eye of the viewer. The above described method of displaying 3D images is known as passive 3D viewing where the projector alternates the left eye information with the right eye information at double the typical frame rate and a screen/filter/polarizing blocker in front of the projector&#39;s lenses alternates the polarization of the projected image in such a way that the image of each eye passes through the corresponding polarizing filter of the pair of passive stereo glasses discussed above. An alternative to passive 3D viewing is active 3D viewing where each viewer wears glasses with LCD light shutters which work in synchronization with the projector so that when the projector displays the left eye image, the right eye shutter of the active stereo eyewear is closed, and vice versa. One problem with current systems for providing 3D images is that the projectionist must attach and configure an external special device to the standard projector, which is a costly and time consuming requirement which also leads to technical failure. Further, when the projectionist again desires to project only a 2D image, the special device must be manually removed or turned off. In addition, having such a device attached to the projector parallel to the projection lens surface introduces a risk that light will reflect back to the imagers from which the light originates, often causing lower picture quality in color productions and undesirable contrast ratio change in black &amp; white productions. While there are many advanced methods of displaying 3D images, room for improvement remains. 
     Referring now to  FIG. 1 , a typical three color prism  100  is shown. Prism  100  is typically used with a three-chip digital micromirror device projector. As shown, a light beam  102  enters prism  100 , and in reaction to known optical coating methods, is selectively reflected or transmitted depending on the wavelength of the light. Further, known total internal reflection techniques, such as providing a small air gap between prism  100  components, may be used to control the reflection of the divided components of light beam  100 . After having been separated into three color components, each light beam  102  color component is directed to and selectively reflected out of prism  100  by a digital micromirror device. Particularly, digital micromirror device  104  reflects a blue color component of light beam  102 , digital micromirror device  106  reflects a green color component of light beam  102 , and digital micromirror device  108  reflects a red color component of light beam  102 . Each digital micromirror device  104 ,  106 ,  108  may be individually controlled in a known manner to produce a combined color image which is projected from prism  100 . 
     It is therefore desirable to develop an improved a projection system capable of displaying high resolution 3D images. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a high resolution 3D projection system having a light source for generating and emitting light, a translucent rotatable drum having differently polarized sections for receiving the light therethrough, a plurality of digital micromirror device imagers configured to receive and reflect the light transmitted through the drum, where a light beam is capable of being passed generally orthogonally through a wall of the drum. 
     The present invention is also directed to a method for projecting 3D images. The method includes the steps of polarizing a source light beam into first and second light beams having different polarizations and alternating polarities relative to one another; rotatably controlling the polarizing step; splitting the first and second polarized light beams into a plurality of separate channels of light that each have respective third and fourth differently polarized light beams; dividing each of the channels of the respective third and fourth light beams into respective sets of differently colored light beams; illuminating respective imagers With the respective sets of differently colored light beams; and illuminating different regions of a display with the respective imagers. The method can further include in the rotatably controlling step, the steps of defining an annular path having an inwardly directed surface, where the radii of the annular path intersects the surface in a substantially perpendicular manner; defining a polarizing position on the annular path; directing the source light beam toward the polarizing position on the annular path; and rotatably controlling movement along the annular path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of a three color prism according to the prior art; 
         FIG. 2  is an oblique schematic illustration of a polarization drum according to the present invention; 
         FIG. 3  is an orthogonal schematic illustration of a high resolution 3D projector according to the present invention; and 
         FIG. 4  is an orthogonal schematic illustration of a high resolution high color control 3D projector according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 2  in the drawings, a polarizing drum according to a first embodiment of the present invention is illustrated. Polarizing drum  200  (or otherwise called a polarization hollow cylinder) is a rotatable drum-like structure formed of translucent materials. Drum  200  is shown as a flat band of material (which can have segments that are curved or flat) located in close proximity to a directional light transmission device (or light pipe)  202  for passing light through drum  200  by directing light generally orthogonal to an interior surface  204  of the drum  200  such that light passes through the translucent material and exits the drum  200  through an exterior surface  206  of the drum  200  (through a wall of the) drum). As shown, the drum  200  is divided into radially alternating clockwise circular polarization sections  208  (or P-polarization sections) and counter-clockwise circular polarization sections  210  (or S-polarization sections). In operation, a 2D image can be converted to a 3D image by transmitting the 2D image through the directional light transmission device  202  and subsequently through the polarization drum  200  while drum  200  is rotated about its central axis. The drum  200  is rotated at a controlled speed so as to appropriately polarize each frame of images as either P-polarization or S-polarization by passing the image through sections  208 ,  210 , respectively. Where the drum  200  is to be used with known single-chip type digital micro-mirror device imagers (which can be referred to as “imagers,” DMD/DLP imagers, micro-mirror arrays or microdisplay devices and can include functional equivalent devices), the drum  200  can be colored so as to eliminate the need for a separate spinning color wheel. Specifically, the translucent drum  200  can be divided into differently colored sections. For example, drum  200  can comprise a blue section  212 , a green section  214 , and a red section  216 . 
     Referring now to  FIG. 3  in the drawings, a high resolution 3D projector according to the present invention is illustrated. Projector  300  comprises a light source  302  having a reflector  304 , a directional light transmission device  306  similar to device  202 , a polarizing drum  308  similar to drum  200 , and relay optics  310 . 
     While it is currently thought that a single DMD/DLP imager having resolution of about 2048×1080 (2K×1K) is insufficient for accurately reproducing an entire frame of motion picture image data onto a display surface, high resolution 3D projection system  300  advantageously utilizes a plurality of DMD/DLP imagers (each having resolution of about 2K×1K) to accomplish a total projected image resolution of about 4K×2K, a result acceptable by SMPTE standards. To accomplish this, the entire frame of a target display surface  314  is divided into four regions, an upper left region  316 , a lower left region  318 , an upper right region  320 , and a lower right region  322 . Region  316  is to be projected onto by DMD/DLP imager  324 , region  318  is to be projected onto by DMD/DLP imager  326 , region  320  is to be projected onto by DMD/DLP imager  328 , and region  322  is to be projected onto by DMD/DLP imager  330  such that each imager  324 ,  326 ,  328 ,  330  projects only a discrete portion of an entire frame of a motion picture image. In this embodiment, each imager  324 ,  326 ,  328 ,  330  is configured to project a substantially equal area of an entire frame of a motion picture image onto the display surface  314 . However, it will be appreciated that in alternative embodiments, the imagers can be configured to project unequal portions of a motion picture image while still providing a high resolution display. 
     In operation, light source  302  emits white or full spectrum light beam  312 . An elliptical reflector  304  can then be employed to guide the light into directional light transmission device  306 . The light is then directed into the polarizing drum  308  as polarizing drum  308  rotates about its central axis and the relay optics  310 . Since each DMD/DLP imager  324 ,  326 ,  328 , and  330  must be supplied with light, the light exiting relay optics  310  is separated into four separate beams or channels of light (ideally identical in intensity and color) through the use of light beam splitting prisms. A first light beam splitting prism  332  splits the original light beam  334  into two new light beams  336  and  338 . Light beam  336  is directed from prism  332  into a second light beam splitting prism  340 , resulting in light beams  342  and  344 . Light beam  338  is directed from prism  332  into a third light beam splitting prism  346 , resulting in light beams  348  and  350 . Each of light beams  342 ,  344 ,  348 , and  350  are directed into and delivered through optical fibers  352  to total internal reflection lenses (TIR lenses)  354  associated with DMD/DLP imagers  324 ,  326 ,  328 , and  330 , respectively, such that each imager  324 ,  326 ,  328 , and  330  receives a single beam of light. TIR lenses are suitable for receiving light, directing the received light to a DMD/DLP imager, and finally outputting the light according to an image signal of the DMD/DLP imager. However, it will be appreciated that in an alternative embodiment, the TIR lenses can be replaced by field lenses. TIR lenses  354  are oriented to direct their output into an arrangement of reflective prisms  356  and optical blocks  358  so as to forward the four light beams  342 ,  344 ,  348 , and  350  (or channels of light) (as altered by DMD/DLP imagers  324 ,  326 ,  328 , and  330 , respectively) into a projection optics system  360 . Projection optics system  360  ultimately directs the light beams  342 ,  344 ,  348 , and  350  onto regions  316 ,  318 ,  320 , and  322 , respectively, of the entire frame of the target display surface  314 . The input signals sent from display controllers of DMD/DLP imagers  324 ,  326 ,  328 , and  330  to the mirrors of the respective DMD/DLP imagers comprise only the data necessary to create the desired image to be projected onto the associated regions of display surface  314 . Further, the received beams of light are manipulated by imagers  324 ,  326 ,  328 , and  330  to carry motion picture image data corresponding to only a discrete portion of an entire motion picture image frame. It will be appreciated that in other embodiments of the present invention, more or fewer DLP imagers can be incorporated to achieve a higher or lower overall film screen resolution, respectively. 
     The 3D image is perceived by a viewer of the projected image when the viewer wears polarized filter glasses (not shown) which allow only one of the clockwise and counter-clockwise circular polarized (or alternatively, one of the P and S polarized) portions of light through the glasses to each eye of the viewer. The projector should present approximately twice the number of frames per second in 3D mode as opposed to a normal 2D mode since each eye will only see every other frame. Alternatively, the projector can be used as a 2D projector by projecting image data containing only frames to be viewed by both eyes of the viewer simultaneously and by the viewer not wearing polarized filter glasses. Alternatively, the drum  308  can be configured for automated and/or automatic removal of the drum  308  from the light path, resulting in an increase in the output brightness (by as much as a factor of two). Where the colored drum is removed from the light path, a spinning primary color wheel should be introduced into the light path. A single spinning primary color wheel or functional equivalent (for example, the drum  200  shown in  FIG. 2  in place of drum  308  in  FIG. 3 ) can be introduced before the original light beam is split, or a plurality of spinning primary color wheels or functional equivalents (not shown) can be associated, one each, with the imagers  324 ,  326 ,  328 , and  330 . In the case where a plurality of spinning primary color wheels or equivalents are employed, color wheels or equivalents can be placed before the TIR lenses  354 . 
     Referring now to  FIG. 4  in the drawings, a high resolution high color control 3D projection system according to a second embodiment of the present invention is illustrated. High resolution 3D projection system  400  is similar to system  300  in many ways including the fact that it advantageously utilizes a plurality of DMD/DLP imagers (each having resolution of about 2K×1K) to accomplish a total projected image resolution of about 4K×2K, a result acceptable by SMPTE standards. To accomplish this, the entire frame of a target display surface  414  is divided into four regions, an upper left region  416 , a lower left region  418 , an upper right region  420 , and a lower right region  422 . However, system  400  comprises four three-imager sets  424 ,  426 ,  428 , and  430  each comprising three DMD/DLP imagers  455  instead of four single-imager type imagers (like  324 ,  326 ,  328 , and  330 ). Region  416  is to be projected onto by DMD/DLP imager set  424 , region  418  is to be projected onto by DMD/DLP imager set  426 , region  420  is to be projected onto by DMD/DLP imager set  428 , and region  422  is to be projected onto by DMD/DLP imager set  430 . Since each DMD/DLP imager of the three-DMD/DLP imager sets  424 ,  426 ,  428 ,  430  consistently manipulates a single color (red, green, or blue) there is no need for drum  408  to be colored (as needed in system  300 ). Instead, drum  408  is not colored and passes white or full spectrum light therethrough. 
     In operation, white light or full spectrum light is emitted from a light source  402 . An elliptical reflector  404  can then be employed to guide the light into directional light transmission device  406 . The light is then directed into the polarizing drum  408  as polarizing drum  408  rotates about its central axis and the relay optics  410 . Since each DMD/DLP imager set  424 ,  426 ,  428 , and  430  must be supplied with light, the light exiting the light source  402  is separated into four channels of light (ideally identical in intensity and color) through the use of light beam splitting prisms as was similarly provided in system  300 . A first light beam splitting prism  432  splits the original light beam  434  into two new light beams  436  and  438 . Light beam  436  is directed from prism  432  into a second light beam splitting prism  440 , resulting in light beams  442  and  444 . Light beam  438  is directed from prism  432  into a third light beam splitting prism  446 , resulting in light beams  448  and  450 . Bach of light beams  442 ,  444 ,  448 , and  450  are directed into and delivered through optical fibers  452  to three color prisms  454  (substantially similar to three color prism  100 ) associated with DMD/DLP imager sets  424 ,  426 ,  428 , and  430 , respectively. The three color prisms  454  split the light beams into three primary color light beams (red, green, and blue). Further, three color prisms  454  receive light, direct the received light to DMD/DLP imagers  455 , and finally output the light. However, it will be appreciated that in an alternative embodiment, the total internal reflection lens portion of the three color prisms  454  can be replaced by field lenses. Three color prisms  454  are oriented to direct their output into an arrangement of reflective prisms  456  and optical blocks  458  so as to forward the four light beams  442 ,  444 ,  448 , and  450  (or channels of light) (as altered by DMD/DLP imager sets  424 ,  426 ,  428 , and  430 , respectively) into a projection optics system  460 . Projection optics system  460  ultimately directs the light beams  442 ,  444 ,  448 , and  450  onto regions  416 ,  418 ,  420 , and  422 , respectively, of the entire frame of the target display surface  414 . The input signals sent from display controllers of DMD/DLP imager sets  424 ,  426 ,  428 , and  430  to the mirrors of the respective DMD/DLP imagers comprise only the data necessary to create the desired image to be projected onto the associated regions of display surface  414 . It will be appreciated that in other embodiments of the present invention, more or fewer DLP imagers can be incorporated to achieve a higher or lower overall projected image resolution, respectively. By incorporating DMD/DLP imager sets  424 ,  426 ,  428 , and  430 , so-called rainbow effects are avoided and a higher level of color control is achieved. 
     The foregoing illustrates only some of the possibilities for practicing the invention. Many other embodiments are possible within the scope and spirit of the invention. It is, therefore, intended that the foregoing description be regarded as illustrative rather than limiting, and that the scope of the invention is given by the appended claims together with their full range of equivalents. For example, light beam splitting prism can mean or be substituted with some other functional equivalent beam splitter means and optical fibers can mean or be substituted with some other functional equivalent beam propagating means. 
     In sum, the projector disclosed does directly address and solve industrial problems. They are that current DMD/DLP projectors have 2K×1K resolution which may not be suitable for most commercial theatres (especially at close viewing distances) and that meshing of pixels becomes evident when conventional projectors increase resolution to 4K×2K. The invention provides a single projector with a single light source (having 3D and 2D capability in a single projector) to provide large image resolution (especially for large images) without meshing of pixels.

Technology Category: 3