Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N9/00—Details of colour television systems
  • H04N9/12—Picture reproducers
  • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
  • H04N9/3141—Constructional details thereof
  • H04N9/3147—Multi-projection systems
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/74—Projection arrangements for image reproduction, e.g. using eidophor
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B37/00—Panoramic or wide-screen photography; Photographing extended surfaces, e.g. for surveying; Photographing internal surfaces, e.g. of pipe
  • G03B37/04—Panoramic or wide-screen photography; Photographing extended surfaces, e.g. for surveying; Photographing internal surfaces, e.g. of pipe with cameras or projectors providing touching or overlapping fields of view
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N5/00—Details of television systems
  • H04N5/44—Receiver circuitry for the reception of television signals according to analogue transmission standards
  • H04N5/57—Control of contrast or brightness
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/22—Telecentric objectives or lens systems

Definitions

• the present invention generally relates to the field of displays, and more particularly relates to multiple projector display systems.
• a difficulty with multiple projector display systems is that the multiple images often do not appear as one single continuous image on the display screen.
• the final display image will either appear as two images placed side-by-side with a gap there-between or, if the images are made to overlap on a single screen, with a bright line there-between.
• it is exceedingly difficult to perfectly match the resultant video images so that no tiling artifact appears among the images. If the images are brought very close together on the same screen, there are typically overlaps at each seam regions.
• the present invention provides method for producing a substantially seamless video image on a display surface.
• the method comprises the steps of separately projecting at least a first and a second video image onto a display surface such that a seam is defined by overlapping portions of said first and second video images. Inside the seam, the brightness of the first video image and the brightness of the second video image are adjusted electronically so as to provide a uniform brightness profile.
• FIG. 1 is a top view of a display system comprising multiple projectors according to an embodiment of the invention.
• FIG. 2 is a front view illustrating projectors of a display device arranged in accordance with an embodiment of the invention.
• FIG. 3 is a graph illustrating the relationship between projected image brightness for pixels from projected images according to an embodiment of the invention.
• Fig. 4 is a graphic illustration of the relationship between projected image brightness for two projected images in the area inside a seam of a system according to an embodiment of the invention.
• Fig. 5 illustrates a representative uniformity curve for a lens of a projector suitable for use in the present invention.
• the quality of a projected image is a function of several characteristics, all of which can suffer distortion in the process of translation from video data to displayed image.
• brightness distortion also referred to as luminance distortion has may possible sources.
• luminance distortion due to the design of the optics within the light engines and/or the lamps themselves, most projectors do not project at a constant luminance level across the entire screen. This non-uniformity in luminance detracts from the displayed image. The luminance non-uniformity of a projector and its associated lens can become more pronounced under certain conditions.
• FIG. 5 illustrates an example of luminance uniformity of a light projected onto a screen 515 by a single projection lens (not shown).
• the graph defines a lens distortion profile for the lens projecting the light onto the screen.
• the projected light is brighter near the center 520 of the screen.
• This center area corresponds to the center of the projecting lens.
• the brightness of projected light drops off from the center of screen 515 toward the outer edges 501 , 502 of the screen. These areas correspond to the outer regions of the projecting lens used to project the light onto the screen 515.
• Each projecting lens has a corresponding brightness uniformity profile.
• each lens profile is measured, or otherwise characterized, and the resulting data stored in a memory accessible to the image processor (for example processor 170 of Fig. 1).
• Figure 1 illustrates a plurality of example projectors 105, 110, 115 and 120 arranged according to an embodiment of the invention.
• An image source 175 provides a video image data representing a video, scene, or other visual image, either moving or still, to be displayed on display 130.
• the image data is typically provided in a variety of conventional television and video formats depending on the particular capabilities of the associated display.
• video image data 180 is provided to a processor 170.
• Video image data 180 includes pixel brightness data for pixels x of the image.
• Processor 170 receives the video image data 180 including the pixel brightness data for pixels x.
• Processor 170 uses tiling techniques, allocates the video image data 180 among the plurality of projectors 105, 110, 115 and 120 such that each projector is enabled to project a discrete image which, when projected onto display 130 and combined with the discrete images from the other projectors, will form a whole image to be displayed on display screen 130. [0017] Therefore, each projector is provided with respective image data181 , 182, 183, 184 for projecting the corresponding discrete image onto display 130.
• Figure 1 illustrates a simplified example.
• Video data 180 is provided to processor 170.
• Image 116 overlaps image 121 so as to define a seam region 117.
• the pixel brightness data corresponding to seam regions 107, 112, 117, is indicated in Fig. 1 as xi, x2, x3 and x4.
• a portion x1 of video data 181 corresponds to a portion of the video image 106 that lies within seam 107, that is, between seam edge 208 and seam edge 209 of seam 107.
• a portion x2 of video data 182 corresponds to of the video image 111 that lies within seam 107, that is, between seam edge 208 and 209 of seam 107.
• the correspondence between video data, video image and seam applies to the remaining projectors and projected images.
• projectors 105, 110, 115 and 120 are of the spatial light modulator (SLM) type.
• SLM spatial light modulator
• DLPTM is a trademark of Texas Instruments.
• display surface 130 is spaced from a plane 131 of the projectors 105, 110, 115 and 120 by about 96".
• Each of projectors 105, 110, 115 and 120 is configured so as to project a corresponding image 106, 111 , 116 and 121 upon display surface 130.
• display surface 130 measures about 120" in width.
• Each of projectors 105, 110, 115 and 120 is configured so as project their corresponding images so as to substantially fit substantially the entire original video image of display surface 130 when projected side by side. Accordingly, images 106, 111 , 116 and 121 overlap thereby defining seams 107, 112, and 117. In this example each seam 107, 112, and 117 measures about 10" in width.
• the light engine for each projector comprises any suitable technology, such as one or more Liquid Crystal Display (LCD) panels, Digital Light Processing (DLP) or Liquid Crystal on Silicon (LCOS). Nonetheless, those skilled in the art will recognize that the present invention may be used, with other projectors, including those using other types of image generation technologies.
• Each projector 205, 210, 215 and 220 includes optical elements to properly prepare the incoming illuminations to illuminate the SLM such as a DMD Tm and project the outgoing image.
• the optical path of such devices typically comprises two segments including an illumination path and a projection path.
• the illumination path starts with a high-reliability, metal halide, short-arc lamp that illuminates the DMDTM .
• the light from the arc lamp passes into a rotating RGB color filter wheel.
• An illumination relay lens magnifies the beam to illuminate the DMD Tm and form a telecentric image at the DMDTM .
• a Total Internal Reflection (TIR) prism enables the incoming light from the lamp to pass onto the DMD T , and back into the projection optics.
• TIR Total Internal Reflection
• the light from the DMD Tm is directed into the pupil of the projection lens (on) or away from the pupil of the projection lens (off).
• a multiple-element projection cell magnifies the image coming off the DMD Tm at the desired MTF, lateral color, and distortion.
• Fig. 2 illustrates an embodiment of image displaying surface 230 having a total image display area measuring about 140" in width.
• the image displaying surface is a display screen having a screen gain of unity.
• the display surface is bordered by a bezel 230 having a width of 2".
• the display surface and bezel are seated in a frame having a width of 3".
• the dimensions given herein represent only one example of a wide variety of possible configurations, display dimensions, frame dimensions etc. for display systems.
• the invention is suitable for implementation in other configurations too numerous to mention but these will be readily apparent to the skilled artisan upon reading the specifications and description of the invention contained herein.
• each of a plurality of projectors for example projectors 105, 110, 115 and 120, illustrated, for example, in Fig. 1 projects, substantially simultaneously, a corresponding image onto image displaying surface 130.
• Each projected image defines a corresponding discrete 205, 210, 215 and 220 upon image displaying screen 230.
• images 205, 210, 215 and 220 substantially fill image displaying surface 230 with a single video image, frame of video, or picture, to be displayed to a viewer.
• the technique of arranging projectors, image portions and image displaying surfaces to display images in this manner is referred to herein as "tiling".
• tiling A drawback of tiling techniques is the resulting visible artifacts in the displayed image that occur in the regions of the seams, that is in the region where an image projected by a first projector, overlaps an image projected by a second projector.
• processor 170 implements the methods according to various embodiments of the invention. As previously described processor 170 receives video signals representing the desired displayed image from image source 175. According to one embodiment of the invention, artifacts due to seams 107, 112 and 117 are corrected in the following manner. For purposes of discussion only projectors 105 and 110 will be discussed. However, the method is the same for the remaining projectors. Processor 170 provides data x1 for projector 105 such that image 106 turns to black at edge 208.
• processor 170 provides data x2 for projector 110 such that image 111 turns to black at edge 209.
• This method is illustrated in more detail in Fig. 3. wherein line 106 represents the brightness of pixels comprising image 106 from edge 208 to edge 209.
• line 111 represents the brightness of pixels of image 111 from edge 208 to edge 209.
• the pixels of Image 106 are at a level brightness at edge. 208, wherein the pixel brightness values begin to decrease until a black value is obtained at edge 209.
• the pixels of image 111 are black at edge 208 and increase to a level of brightness at edge 209.
• processor 170 adjusts the brightness of the portion of image 106 displayed in seam 107 and the brightness of the portion of image 111 displayed in seam 107 in an inverse relationship.
• pixels displayed in a, seam region have a pixel position represented by j.
• Each displayed pixel j in the seam comprises a first pixel X, from the corresponding pixel of the image 106 projected by projector 105, and a second pixel X 2 from the corresponding pixel of the image 111 projected by projector 110.
• For projector 110 for example, brightness of successive projected pixels ⁇ is increased from black at edge 208 to a value Y at edge 209. The value Y corresponds to a uniform brightness for the seam region.
• pixels X 1 f X 2 ,j and Y are expressed, according to one embodiment of the invention, as follows:
• X ⁇ represents a pixel of the image projected by projector 105
• X 2 represents a pixel of the image projected by projector 110
• j is the pixel number in the seamed area of the displayed pixel comprising X ⁇ , X 2
• Overlap represents seam area in number of pixels
• gamma corresponds to the gamma correction for the projector.
• a shadow effect is sometimes observed. This effect is particularly noticeable if a viewer looks at the screen from an oblique angle.
• pixels displayed in a seam region have a pixel position represented by j.
• Each displayed pixel j in the seam comprises a first pixel Xi from the corresponding pixel of the image 106 projected by projector 105, and a second pixel X 2 from the corresponding pixel of the image 111 projected by projector 110.
• brightness of successive projected pixels ⁇ is increased from black at edge 208 to a value Y at edge 209.
• the value Y corresponds to a uniform brightness for the seam region.
• pixels Xi , X 2 , j and Y are, in this embodiment quadratic and is expressed, according to one embodiment of the invention, as follows:
• x11 represents a pixel from said first image portion after processing
• x2 represents a pixel from said second image portion after processing
• j represents the pixel number in the seam region corresponding to the location of overlapping pixels x1 and x2
• overlap is the seaming area in number of pixels
• gamma is related to the gamma correction of the projector.
• pixels x1 and x2 are adjusted based upon the uniformity curve of a correspodning projector.
• An example uniformity curve is illustrated in Fig. 5
• gamma correction is commonly employed to correct for distortion in displayed images due to, for example, inherent non linearities in lens, imagers, displays and other imaging and display system components.
• Gamma correction can substantially reduce the distortion and image artifacts attributable to the properties of the imaging devices and system components themselves.
• projectors 205, 210, 215 and 220 are of a type that includes such gamma correction capabilities.
• a method of reducing tiling artifacts in seam regions relies on adjusting the gamma correction of the projectors in a particular way so as to reduce tiling artifacts.
• a method for reducing artifacts in seams of tiled images comprises the steps of applying a first gamma correction to image portions within the seams and a second gamma correction to image portions displayed outside the seams.
• Non-linearities due to display transfer functions can be corrected by a digital lookup table, referred to as a gamma table.
• the gamma table corrects for the differences in gain in the transfer function.
• gamma values from such a gamma table are adjusted so as to achieve a uniform brightness for the combined images, and, in one embodiment of the invention, further adjusted according to the characteristics of each projector comprising the system.
• the first and second image portions are adjusted based on the uniformity profile of projectors 105 and 110 respectively.
• gamma correction is provided based upon differences in brightness characteristics between seam regions and non-seam regions of the projected image.

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• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Transforming Electric Information Into Light Information (AREA)
• Projection Apparatus (AREA)
• Controls And Circuits For Display Device (AREA)
• Control Of Indicators Other Than Cathode Ray Tubes (AREA)

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• 2004
  • 2004-12-30 EP EP04816032A patent/EP1736002A1/en not_active Withdrawn
  • 2004-12-30 JP JP2006547595A patent/JP4761471B2/ja not_active Expired - Fee Related
  • 2004-12-30 KR KR1020067013103A patent/KR20060117979A/ko not_active Ceased
  • 2004-12-30 US US10/580,811 patent/US7738036B2/en not_active Expired - Fee Related
  • 2004-12-30 WO PCT/US2004/044050 patent/WO2005067288A1/en not_active Ceased
  • 2004-12-30 MX MXPA06007550A patent/MXPA06007550A/es active IP Right Grant

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