Abstract:
A baffle and screen arrangement for use in a rear projection display system with multiple imagers with the baffle being positionable with respect to the display screen of the console unit so that the baffle can interfere with at least one of the images produced by the imagers to allow the images to visually merge into a single, contiguous image with no halo effect, overlap, or excessive brightness and gaps. In one embodiment the baffle has an irregular, non-reflective light-absorbing surface to further reduce excessive unwanted image light from hitting the display screen and causing unwanted distortion.

Description:
FIELD OF THE INVENTION 
     The present invention pertains to rear projection systems, and more specifically, to a rear projection console with multiple projectors that uses a baffle arrangement to allow a user to create a visually seamless, sharp image without the use of expensive optics. 
     BACKGROUND OF THE INVENTION 
     The method of using multiple projectors to produce a nearly contiguous image is old in the art. U.S. Pat. No. 4,974,073 (Inova) creates a contiguous image in a forward projecting system using multiple projectors and a signal ramping process to blend the images together. Similarly, movie theaters in previous eras have used multiple techniques, including several projectors projecting at multiple screens to create larger images for viewing audiences with varying degrees of success. The fundamental problems that have arisen in using multiple projectors to create a single image are the difficulty in aligning the projected images in timing, that is, to have the output of one projector matching the output of another frame by frame, and further, the difficulty in aligning the edges of the multiple images with one another in a contiguous fashion, especially with larger viewing surfaces. 
     There have been similar attempts to create a contiguous image on a display screen with rear projection devices such as the one illustrated in U.S. Pat. No. 5,673,145 (Wilson), which shows a multi-panel viewing section. There are gaps in between these panels however. Again, problems arise in trying to arrange contiguity between the panels in either projection frame timing or projection alignment. 
     The present invention, in its typical embodiment, has an oblong screen that can accept two or more projections placed thereupon, while at the same time having no framing system to disrupt the contiguity of multiple projections. Because of the differences in imagers, it is challenging to match video images with no gap and no overlap between the images. In the prior art, when two images arc projected side by side onto a single screen, there will normally be a seam between the two images which the viewer sees as a gap or overlap. While the Inova patent address the problem for front projection screens, the problems in the scope of rear projection screens and especially console screens—a scope in which the screens are made of different materials to project the image through the screen remains a problem. While the device shown in the Inova Patent requires the use of expensive ramp generators and synchronization devices to blend images together. In contrast, the present invention creates a visually seamless, contiguous image on a rear projection screen without the use of expensive digitalization equipment 
     DESCRIPTION OF THE PRIOR ART 
     U.S. Pat. No. 4,974,073 illustrates a seamless video display that uses three forward projecting ramp projectors and a synchronizer to produce a contiguous image. 
     U.S. Pat. No. 5,673,145 illustrates a multiple panel rear projection screen system which utilizes especially narrow perimeter edges on each panel to minimize image loss between panels. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus to create a visually seamless image for a rear projection system. The invention provides a method for merging at least two images into a seamless, contiguous image on a display screen utilizing a baffle arrangement. The baffle which is spaced from the screen sufficiently far so as to interfere and block at least one projected images before the image reaches the display screen to eliminate image overlap on the screen. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a top cut-away view of the display system wherein the baffle is extended the correct distance to create a visually seamless image on a screen; 
     FIG. 2 shows a close-up view of the baffle in FIG. 1; 
     FIG. 3 shows a top cut-away view of the display system wherein the baffle is not extended a sufficient distance to create a seamless image on a screen; 
     FIG. 4 shows a close-up view of the baffle in FIG. 3; 
     FIG. 5 shows a top cut-away view of the display system wherein the baffle is extended too far to create a seamless image on a screen; and 
     FIG. 6 shows a close-up view of the baffle in FIG.  5 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 illustrates a top cut-away view of the rear projection system or display system  10  in operation. A first imager  11  projects an image  11   a  onto the rear of a left side  13  of a display screen  30 . Typically, rear display screens are known in the art and constructed of multiple layers of semi-translucent material to allow sufficiently light to penetrate the screen so the image is viewable from the front. 
     In the embodiment shown in FIG. 1, a portion of the projected image  11   a  is interfered by one side of a baffle  20  before the entirety of beam  11   a  reaches the left side  13  of the display screen  30 . Similarly, a second imager  12  projects an image  12   a  onto the rear of the right side  14  of display screen  30 . Similarly, a portion of the projected image  12   a  is interfered with by the opposite side of baffle  20  before the entirety of the beam  12   a  reaches the right side  14  of the display screen. In FIG. 1, the baffle  20  is spaced sufficiently far from screen  13  and  14  so that the images  11   a  and  12   a  appear on the screen  30  as a single, seamless, contiguous image. That is, the sides of baffle  20  disrupt a portion of at least one of the projected images  11   a  or  12   a  before the projected image reaches it&#39;s respective screen side  13  or  14 . The baffle  20  is made of a non-reflective material so that it absorbs the light of projected images to prevent light from reflecting on the screen and creating “bright” spots. It should be noted that although the image projectors  11  and  12  are shown at the very rear of the interior of the console unit, it is envisioned that they could be configured in many ways inside of the console using mirrors and the like to project a contiguous image onto a screen while keeping the console compact. 
     FIG. 2 illustrates a close-up view of the end of baffle  20  of FIG. 1 located within the display system  10 . In this embodiment the baffle is provided with a smooth non-reflective light absorbing material  20   b . Note that in FIG. 2, the baffle  20  has been spaced sufficiently far from the screen  30  so that the images  11   a  and  12   a  produced by imager  11  and imager  12  unite in a single, visually contiguous image on the display screen  30 . That is, the distance “x” between the edges of the images is zero. It is in this condition that the two images, which would normally interfere in the peripheral region of the images appear as a single visually seamless image. 
     In FIG. 2 the distance of the end of the baffle to the screens  13  and  14  is indicated by “y” with the distance “y” being the proper distance to obtain a visually seamless image on screens  13  and  14 . Note, left ray  21 , which is a portion of the image  11   a , passes baffle  20  at left interference point  11   b  without being absorbed by baffle  20 , and similarly, right ray  22 , which is a portion of the image  12   a , passes baffle  20  at right interference point  12   b  without being absorbed by baffle  20 . When the screen distance between rays  21  and  22 , which is denoted by the alphanumeric character “x,” is equal to zero, the two rays  21  and  22  intersect on the back side of the display screen  13  and  14  at the position L. Generally, if the distance between the rays “x” is less than one eighth of an inch, the two images appears to the eye as a single image. Thus, even thought the images do not match perfectly, to the human eye the images appear as a visually seamless image if the distance “x” is kept small. However, an advantage of the present inventions is that one can precisely match the edges of the two images on the screen. It will be understood that the dimension “x” will also depend on other factors such as the distance of the viewer from the screen. 
     FIG. 2 shows images projected from both sides when the distance “x” equals zero or substantially zero as the images meet at line L. In order to determine the distance “y” that the baffle needs to be positioned from the screen  30  to visually match the images one can measure or determine the angle Ø 2  that the light ray  22  makes with the screen  13 ,  14  and the angle Ø 1  that light ray  21  makes with screen  13 ,  14 . In the embodiment shown the light rays  21  and  22  both impinge at the same angle so that angle Ø 1 =angle Ø 2 . Under these conditions and a baffle of thickness “t” the edges of the two images  11   a  and  12   a  should meet halfway from the edges of the baffle, in other words the junction line L should be a distance “a” from the side of the baffle which is equal to t/2. If one knows the thickness “t” of the baffle one can readily determine the distance “y” the baffle needs to be placed from the screen by solving the equation tangent Ø=y/(t/2), which yields “y”=(t/2) tan Ø. In the event the light rays do not image at the same angle Ø on each side of the baffle one must first determine the position of line L. 
     When the digital imagers are not projecting the light rays  21  and  22  at the same angle Ø one can solve for the distance “a” by knowing each light ray angle and the thickness “t” of the baffle. For example, if the angle of ray  22  impinges on the screen at angle Ø 2  and the angle the ray  21  impinges on the screen at angle Ø 1  then the distance “a” can be determined as follows: tangent Ø 1 =y/a and tangent Ø 2 =y/(t−a). By solving the two equations for “a” we obtain: (a) Tangent Ø 2 =(t−a) tangent Ø 1 . Since we know the angles Ø 1  and Ø 2  as well as the thickness “t” we can solve for the distance “a” where the two images meet. Knowing where the two images meet one can then solve for the distance “y” to determine the spacing of the baffle from the screen in order to produce the visually seamless image on the screens  13  and  14 . 
     To illustrate the elimination of rays that would overlap on screens  13  and  14 , reference should be made to secondary rays  31   a  and  31  which are rays from the imagers which are interfered and absorbed by the sides of the baffle  20 , and therefore never reach the screen. In the embodiment shown in FIG. 2, the baffle  20  has a smooth and regular surface  20   b  although in FIGS. 4 and 6 irregular surfaces are shown to keep unwanted light rays from bouncing to the display screen  30 . Other textures that prevent light reflection onto the display screen could be used. 
     Thus in the present invention one seeking to determine the proper distance of the baffle “y” from the screen to obtain a visually seamless image first determines the position “L” of the intersection or junction line of the two images beneath the baffle  20  by determining the angle at which light rays  21  and  22  impinge on the screens  13  and  14 . For those situations when the images  11   a  and  12   a  are positioned so the light rays  21  and  22  on both sides of the baffle  20  impinge at the same angle Ø the line of image matching occurs at line L which is a halfway distance t/2 from each side of the baffle. Knowing the thickness of the baffle one can solve for “y” according to the formula y=(t/2) tangent Ø. The baffle is then positioned the distance “y” from the screen to produce the visually seamless image. 
     FIG. 3 shows a top, cut-away view of the rear projection system  10  wherein the baffle  20  has not been properly positioned and the images  11   a  and  12   a  overlap upon the display surfaces ( 13  and  14 ). The left and right interference points  11   b  and  12   b , the points closest to the display where images are interfered with but still reach the display, are located farther away from the display screen. As such, the images  11   a  and  12   a  substantially overlap on the display screen ( 13  and  14 ). This overlapping will produce an undesired brighter area on the screen  30  which is distracting to the console user. 
     FIG. 4 shows the console of FIG. 3 in close-up. The left ray  21  and right ray  22  are the image waves from the projector that are respectively interfered with by the baffle  20  at left interference point  11   b  and the right interference point  12   b . In FIG. 4, the baffle  20  is located a distance “y 1 ” too far away from the display ( 13  and  14 ). The result is that the ray  21  and ray  22  cross at an intersection point  23  well above the display, causing there to be a significant image overlap of rays to the left of ray  21  and rays to the right of ray  22  with the width of the overlap image represented by “x 1 ”. This view of the baffle arrangement  20  shows that the baffle  20  has is properly spaced from the screen, and as a result, an overlapping image forms on the display screen  30  thus producing a line between images. To alleviate this condition the baffle  20  needs to be positioned closer to screens  13  and  14 . 
     FIG. 5 shows a top, cut-away view of the display console  10 . In FIG. 5, the baffle  20  has been set too close to the display screen ( 13  and  14 ), and as a result, a non-contiguous image has been formed along the display screen ( 13  and  14 ). FIG. 6 shows the baffle of FIG. 5 in close-up. Rays  21  and  22  are completely interfered with by the baffle  20 , and as such, the image that does form (as represented by phantom rays  41  and  42 ) onto the screen has a significant gap “x 2 ”. This gap will have no images on it whatsoever, so the viewer of the display screen will see that the image is very clearly, non-contiguous. Further, if the baffle gets excessively close to the display screen or actually touches it, baffle  20  will create an unlighted area upon the surface of the display preventing the viewing of a contiguous image. Thus it will be seen that with the present invention, the proper positioning of the end of the baffle from the screen can be used to inexpensively form a visually seamless image. That is, by positioning a baffle sufficiently far from the rear projection screen so as not to block passage of light thereunder one does not leave a dark baffle outline on the screen. Although not in contact with the screen the baffle is sufficiently close so as to block at least a portion of one of the images onto the rear projection screen one can limit the overlap of the image and the second image so that the first image and the second image on the rear projection screen visually appear as a contiguous seamless image. 
     While the description contained herein describes a two imager system, it is envisioned that this invention could be utilized in a display system with two, three, or more imagers and multiple baffles. 
     In the embodiment shown, the end of baffle  20  is positionable with respect to screen  13  and  14 . Typically, the postionable baffle  20  can be positioned by a mechanical means such as a gear drive and motor. On the other hand, if the imagers remain in a fixed position within the display system, the baffle can be fixed in a proper position within the display system.