Stereo image projection with high intra-frame contrast

Abstract

A projection system can direct stereo image content to a display surface using an internally located stereo polarization modulator while avoiding intra-frame contrast degradation from using a stereo polarization modulator. In one example, the stereo polarization modulator is positioned between a spatial light modulator device and imaging optics in the projection system. The imaging optics can prevent part of the imaged light scattered by the stereo polarization modulator from being projected by the projection system, while allowing other light to be projected. Doing so can reduce or avoid intra-frame contrast degradation of the projected imaged light that may otherwise occur because of the presence of the stereo polarization modulator. In this or as a separate example, the projection system can include an enclosure between a port window and a projection lens to absorb the portion of the light scattered by the stereo polarization modulator.

What is claimed is: 
     
         1 . A stereo projection system for projecting left-eye images and right-eye images, the stereo projection system comprising;
 a spatial light modulator device configured to modulate incident light to produce image light;   a stereo polarization modulator to alternately encode the image light as imaged light that includes left-eye image light and right-eye image light, the stereo polarization modulator being configured to scatter a portion of the imaged light; and   imaging optics to project images using the left-eye image light and the right-eye image light, the stereo polarization modulator being positioned between the spatial light modulator device and the imaging optics, the imaging optics being configured to prevent the portion of the imaged light scattered by the stereo polarization modulator from being projected by the stereo projection system.   
     
     
         2 . The stereo projection system of  claim 1 , wherein the imaging optics includes an aperture defined by a housing that is configured to prevent the portion of the imaged light scattered by the stereo polarization modulator from being projected by the stereo projection system by angularly filtering the portion of the imaged light scattered by the stereo polarization modulator. 
     
     
         3 . The stereo projection system of  claim 1 , wherein the imaging optics is telecentric optics with an aperture defined by a housing configured to prevent the portion of the imaged light scattered by the stereo polarization modulator from being projected by the stereo projection system. 
     
     
         4 . The stereo projection system of  claim 1 , wherein the imaging optics includes lens elements and is mounted in a housing that has a surface between the lens elements, the surface being configured to prevent the portion of the imaged light scattered by the stereo polarization modulator from being projected by the stereo projection system by trapping the portion of the imaged light between the lens elements. 
     
     
         5 . The stereo projection system of  claim 4 , wherein the surface is configured to trap the portion of the imaged light between the lens elements by absorbing the portion of the imaged light by being coated with a light absorbing material, textured, or configured with baffles. 
     
     
         6 . The stereo projection system of  claim 1 , wherein the stereo polarization modulator is tillable relative to a local optical axis. 
     
     
         7 . The stereo projection system of  claim 1 , wherein the stereo polarization modulator is positionable in an optical path prior to the imaging optics and external to a depth of focus of the imaging optics. 
     
     
         8 . The stereo projection system of  claim 1 , wherein the imaging optics include a projection lens. 
     
     
         9 . The stereo projection system of  claim 8 , wherein the imaging optics further include relay optics configured to provide an intermediate image prior to the projection lens, the projection lens being configured to re-image the intermediate image. 
     
     
         10 . The stereo projection system of  claim 9 , wherein the relay optics include an Offner relay. 
     
     
         11 . The stereo projection system of  claim 1 , wherein the stereo polarization modulator further comprises a polarizing element positionable in an optical path of the image light, the polarizing element being configured to separate image light into light of a first polarization state that is directed towards the stereo polarization modulator and light of a second polarization state that is not directed towards the stereo polarization modulator. 
     
     
         12 . The stereo projection system of  claim 11 , wherein the polarizing element is configured to direct the light of the second polarization state along a second optical path to a second stereo polarization modulator and a second set of imaging optics, wherein the second stereo polarization modulator is positionable in a further optical path relative to a physical aperture stop of the second set of imaging optics. 
     
     
         13 . A method comprising:
 modulating incident light, by a spatial light modulator device, to produce image light;   alternately encoding, by a stereo polarization modulator positioned between the spatial light modulator device and imaging optics, the image light to form imaged light that includes left-eye image light and right-eye image light, a portion of the imaged light being scattered by the stereo polarization modulator; and   projecting, by the imaging optics, images using the left-eye image light and the right-eye image light by preventing the portion of the imaged light scattered by the stereo polarization modulator from being projected.   
     
     
         14 . The method of  claim 13 , wherein the imaging optics includes an aperture defined by a housing that prevents the portion of the imaged light scattered by the stereo polarization modulator from being projected by angularly filtering the portion of the imaged light scattered by the stereo polarization modulator. 
     
     
         15 . The method of  claim 13 , wherein the imaging optics includes telecentric optics with an aperture defined by a housing that prevents the portion of the imaged light scattered by the stereo polarization modulator from being projected. 
     
     
         16 . The method of  claim 13 , wherein the imaging optics includes lens elements and is mounted in a housing that has a surface between the lens elements, wherein the surface prevents the portion of the imaged light scattered by the stereo polarization modulator from being projected by trapping the portion of the imaged light between the lens elements. 
     
     
         17 . The method of  claim 16 , wherein the surface traps the portion of the imaged light between the lens elements by absorbing the portion of the imaged light by being coated with a light absorbing material, textured, or configured with baffles. 
     
     
         18 . The method of  claim 13 , further comprising:
 tilting the stereo polarization modulator relative to a local optical axis.   
     
     
         19 . The method of  claim 13 , wherein the stereo polarization modulator is in an optical path prior to the imaging optics and external to a depth of focus of the imaging optics. 
     
     
         20 . The method of  claim 13 , wherein the imaging optics include a projection lens and relay optics that provide an intermediate image prior to the projection lens, the method further comprising:
 re-imaging, by the projection lens, the intermediate image.   
     
     
         21 . The method of  claim 13 , further comprising:
 separating, by a polarizing element of the stereo polarization modulator positioned in an optical path of the image light, image light into light of a first polarization state that is directed toward the stereo polarization modulator and light of a second polarization state that is not directed toward the stereo polarization modulator.   
     
     
         22 . The method of  claim 21 , further comprising:
 directing, by the polarizing element, the light of the second polarization state along a second optical path to a second stereo polarization modulator and a second set of imaging optics.   
     
     
         23 . A projection system comprising:
 a projection lens to project image light along an image light path towards a port window and to redirect a portion of the image light away from the image light path;   the port window configured to transmit projected image light from the projection lens, the port window having a surface for redirecting a portion of the projected image light; and   an enclosure positioned between the port window and the projection lens to surround the image light path between the port window and the projection lens, the enclosure being configured to absorb the portion of the image light redirected by the projection lens and to absorb the portion of the projected image light redirected by the surface.   
     
     
         24 . The projection system of  claim 23 , further comprising an optical element between the projection lens and the port window, the optical element being configured to redirect part of the projected image light away from the image light path. 
     
     
         25 . The projection system of  claim 24 , wherein the optical element is a stereo polarization modulator. 
     
     
         26 . The projection system of  claim 24 , where the enclosure has an interior surface configured to receive the part of the projected image light from the optical element to be absorbed. 
     
     
         27 . The projection system of  claim 23 , further comprising a stereo polarization modulator positioned internally within the projection system. 
     
     
         28 . The projection system of  claim 23 , wherein the enclosure has interior surfaces configured to absorb light, the interior surfaces having:
 a matte black finish;   a flocked textured finish;   a finish created by a flocking process with black fibers; or   light baffle structures that include a fin, a cone, or a pyramid-like structure.   
     
     
         29 . The projection system of  claim 23 , wherein the enclosure is configured to have an internal positive pressure with respect to pressure external to the enclosure. 
     
     
         30 . The projection system of  claim 23 , wherein the port window has an outer surface having a coating for repelling contaminants. 
     
     
         31 . The projection system of  claim 23 , further comprising:
 a particle transfer roller for contacting a window surface of the port window to remove contaminants from the window surface; or   a nozzle positioned to direct air over the window surface to remove contaminants from the window surface.   
     
     
         32 . The projection system of  claim 31 , wherein the particle transfer roller is configured to transition over the window surface to remove the contaminants. 
     
     
         33 . A method comprising:
 projecting, by a projection lens, image light along an image light path toward a port window and redirecting, by the projection lens, a portion of the image light away from the image light path;   transmitting, by the port window, projected image light from the projection lens and redirecting, by a surface of the port window, a portion of the projected image light; and   absorbing, by an enclosure positioned between the port window and the projection lens to surround the image light path between the port window and the projection lens, the portion of the image light redirected by the projection lens and the portion of the projected image light redirected by the surface.   
     
     
         34 . The method of  claim 33 , further comprising:
 redirecting, by an optical element between the projection lens and the port window, part of the projected image light away from the image light path.   
     
     
         35 . The method of  claim 34 , wherein the optical element is a stereo polarization modulator positioned internally within a projection system. 
     
     
         36 . The method of  claim 34 , further comprising:
 receiving, by an internal surface of the enclosure, the part of the redirected image light from the optical element that is absorbed.   
     
     
         37 . The method of  claim 33 , further comprising:
 creating an internal positive pressure in the enclosure with respect to pressure external to the enclosure.   
     
     
         38 . The method of  claim 33 , further comprising:
 repelling contaminants by a coating on an outer surface of the port window.   
     
     
         39 . The method of  claim 33 , further comprising:
 removing contaminants from a window surface of the port window by a particle transfer roller transitioning over the window surface and contacting the window surface.