The patent's assignee is
News editors obtained the following quote from the background information supplied by the inventors: "A 3D visual effect may be created by a projector system by operating the projector to deliver left and right images representing different viewpoints to a viewer (observer) who is wearing special 3D viewing eyeglasses. For example, the viewer may wear polarized eyeglasses having polarizing filters (e.g. linearly polarized eyeglasses or circularly polarized eyeglasses). In such case the left and right images are each polarized so that they can be seen by the intended eye but not the other eye when wearing the polarized eyeglasses. In other display technologies, the user may wear spectral filtration eyeglasses to view different left and right images. In such case the projector is operated to provide spectrally filtered light to the viewer so that the left eye is presented with light in a first set of spectral bands (providing a left image) and the right eye is presented with light in a complementary, second set of spectral bands (providing a right image). In each case the human visual system of the viewer combines and interprets the left and right images to perceive a single 3D image having the illusion of depth.
"Some 3D projector systems use a globally controlled polarizer mounted in front of a projector. For example, FIG. 1 shows a front-view projector system 20 having a projector 22 and a reflective screen 24 which reflects the light from projector 22 toward a viewing area in front of screen 24. A polarizer 26 is positioned in the light path between projector 22 and screen 24. Polarizer 26 is controllable to alternate between two opposite polarization states in synchronization with the display of left and right images L, R by the projector. Other 3D projector systems may use an optical element to modulate the polarization of light emitted from a projector so that left and right images are alternately displayed to a viewer.
"In 3D projector systems such as those described above, a design objective is to minimize crosstalk between left and right channels. Crosstalk occurs if one eye sees some residue of the image intended for the other eye. Typically, to minimize crosstalk for 3D projector systems, left and right images are alternately displayed such that the entire screen is made to appear and disappear to each eye of the viewer during each cycle. When a left image is presented to the left eye, a blank screen is presented to the right eye, and vice versa. Flickering and viewer eye fatigue may result if the refresh rate to each eye is below a flicker fusion threshold. 3D viewing is more prone to flickering than 2D viewing because the 3D refresh rate is half of the 2D refresh rate. For example, if a cinema projector is capable of displaying images at a maximum frame rate of 48 fps, then for 3D viewing the frame rate is 24 fps for each eye, which may be below the flicker fusion threshold. The flicker fusion threshold is variable from person to person and also depends on factors such as amount of modulation, intensity, image size (field of view) and brightness.
"FIG. 2 shows the use of a polarizer switching between opposite left and right polarization states P1, P2 for two projector subframe images I1, I2, respectively, to generate different images to the left and right eyes of the viewer. The numbers within each image represent the light intensity. In the illustrated example, the vertical polarizer state P1 directs all the light from image I1 toward the left eye while blocking all light to the right eye. The horizontal polarizer state P2 directs all the light from image I2 toward the right eye while blocking all light to the left eye. The resulting subframe images shown to each of the left and right eyes are L1, R1 for the first subframe and L2, R2 for the second subframe. The human visual system of the viewer combines the light from the two subsequent frames for each eye so that the viewer sees time-integrated left and right eye images LTI, RTI.
"As illustrated by FIG. 2, there is some reduction in the image intensity of time-integrated images LTI, RTI, from target images LTARGET, RTARGET. Also, as can be appreciated by comparing subframe images L1 to L2, and R1 to R2, the large differences in image intensity between subsequent frames for each eye may cause flicker and viewer eye fatigue.
"Patent literature describing technology in the general field of this invention includes:
"US20090040402 'Liquid crystal projector and control method for liquid crystal projector' (
"U.S. Pat. No. 7,190,518 'Systems for and methods of three dimensional viewing' (3ALITY INC; 13 Mar. 2007);
"JP2006301549 'Display method and display device' (EBARA J;
"US20050105610 'Temporal smoothing apparatus and method for synthesizing intermediate image' (
"US20060203339 'Systems for three-dimensional viewing and projection' (3ALITY INC; 14 Sep. 2006);
"U.S. Pat. No. 7,705,935 'Stereoscopic display system' (ECRANS POLAIRES INC; 27 Apr. 2010);
"U.S. Pat. No. 7,646,537 'High-resolution field sequential autostereoscopic display' (
"U.S. Pat. No. 6,111,598 'System and method for producing and displaying spectrally-multiplexed images of 3D imagery for use in flicker-free stereoscopic viewing thereof' (REVEO INC; 29 Aug. 2000);
"U.S. Pat. No. 5,548,427 'Switchable holographic apparatus' (SHARP K K; 20 Aug. 1996);
"US20080303962 'Liquid crystal projector and a method of controlling the same' (
"JP9113862 'Stereoscopic video display device' (
As a supplement to the background information on this patent application, NewsRx correspondents also obtained the inventor's summary information for this patent application: "Aspects of the invention relate to 3D displays. The invention may be embodied in a wide range of ways including: 3D displays (displays may be of any of a variety of types including: televisions, computer displays, media player displays, digital cinema displays, special purpose displays such as virtual reality displays, displays in vehicle simulators, game displays, advertising displays and the like); image processing apparatus for preparing image data for display on a 3D display (the image processing apparatus may be integrated into a display or separate);
"methods for displaying 3D images and/or preparing image data for display on a 3D display; program products comprising non-transitory computer-readable instructions which, when executed by a data processor cause the data processor to implement methods of the invention; and so on.
"According to particular embodiments, a projector system incorporates a locally modulated polarizer which is controllable to produce different polarization states for local regions of projector images. In particular embodiments the polarizer is controllable to direct all of the light for an image to one eye, or a portion of light for an image to both eyes at the same time.
"One aspect of the invention relates to methods and apparatus for producing left and right images which have smaller intensity differences between subsequent frames. This can reduce flickering and viewer eye fatigue.
"Another aspect of the invention relates to methods and apparatus for reducing unwanted crosstalk between left and right eye viewpoints and increasing image contrast and dynamic range.
"Another aspect provides a method for displaying a 3D image. The method comprises receiving left and right image data for the 3D image. The 3D image may comprise a still image or a video frame, for example. The method comprises, from the left and right image data determining first and second subframe images and corresponding first and second eye-control images. The method, in sequence, displays the first and second subframe images and, while displaying each of the subframe images applies the corresponding one of the eye-control images to control a degree to which locations in the subframe image are visible to each of a viewer's eyes.
"Another aspect provides a display comprising an input for receiving 3D image data comprising left and right image data for a 3D image an image processing system and driving circuits. The image processing system is configured to, from the left and right image data determine first and second subframe images and corresponding first and second eye-control images. The driving circuits are configured to, in a first subframe interval, control a spatial light modulator to display the first subframe image and apply the first eye-control image to control a degree to which locations in the first subframe image are visible to each of a viewer's eyes; and, in a second subframe interval, control the spatial light modulator to display the second subframe image and apply the second eye-control image to control a degree to which locations in the second subframe image are visible to each of the viewer's eyes.
"Another aspect provides a method for displaying 3D images. The method comprises receiving left and right image data for a frame; and based on the image data, determining a first projector subframe image for the left image data and a second projector subframe image for the right image data. Based on the first and second projector subframe images the method determines first and second polarizer states such that differences in intensity between resulting left and right subframe images displayed to a viewer are below a threshold level.
"Another aspect provides a display comprising a light source; a first display layer controllable to modulate light emitted by the light source to display an image; and a second display layer incorporating a polarizer controllable to produce different polarization states for local regions of the image.
"Another aspect provides a projector system comprising a projector operable to display projector images; a display screen; and a polarizer mounted in a light path between the projector and the display screen, wherein the polarizer is controllable to produce different polarization states for local regions of the projector images.
"In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1 shows a 3D front-view projector system.
"FIG. 2 shows polarizer states and images for a globally controlled (full frame) polarizer.
"FIG. 3 shows polarizer states and images for a locally modulated polarizer according to one example embodiment.
"FIG. 4 shows polarizer states and images for a locally modulated polarizer according to another example embodiment.
"FIG. 5 shows polarizer states and images for a locally modulated polarizer according to another example embodiment.
"FIGS. 6A and 6B show flowcharts of methods for calculating polarizer states and projector images according to example embodiments.
"FIG. 7 shows a flowchart of a method for calculating polarizer states and projector images according to one example embodiment.
"FIG. 8 shows a flowchart of a method for displaying a 3D image according to an example embodiment.
"FIG. 9 shows a schematic diagram of a display according to an example embodiment."
For additional information on this patent application, see: Atkins, Robin. Method and Apparatus for Flicker Reduction and Contrast Enhancement in 3D Displays. Filed
Keywords for this news article include: Fatigue, Electronics,
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