U.S. patent application number 12/086574 was filed with the patent office on 2009-11-05 for system and method for providing uniform brightness in seam portions of tiled images.
Invention is credited to Mark Alan Schultz.
Application Number | 20090273540 12/086574 |
Document ID | / |
Family ID | 38050971 |
Filed Date | 2009-11-05 |
United States Patent
Application |
20090273540 |
Kind Code |
A1 |
Schultz; Mark Alan |
November 5, 2009 |
System and Method for Providing Uniform Brightness in Seam Portions
of Tiled Images
Abstract
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 video image is adjusted
by adjusting pixels of said overlapping portions in accordance with
a modulus determined by the number of overlapping portions defining
the seam.
Inventors: |
Schultz; Mark Alan; (Carmel,
IN) |
Correspondence
Address: |
Thomson Licensing LLC
P.O. Box 5312, Two Independence Way
PRINCETON
NJ
08543-5312
US
|
Family ID: |
38050971 |
Appl. No.: |
12/086574 |
Filed: |
December 18, 2006 |
PCT Filed: |
December 18, 2006 |
PCT NO: |
PCT/US2006/048139 |
371 Date: |
June 16, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60751336 |
Dec 16, 2005 |
|
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Current U.S.
Class: |
345/1.3 ;
348/744 |
Current CPC
Class: |
H04N 9/3147 20130101;
H04N 5/2253 20130101 |
Class at
Publication: |
345/1.3 ;
348/744 |
International
Class: |
G09G 5/00 20060101
G09G005/00 |
Claims
1. A projector system for displaying images on a display screen the
system comprising: An image separator coupled to receive an input
video signal representing an image to be displayed and to provide
separate output video signals corresponding to portions of said
image to projected on said screen; Said image separator adjusting
pixel values of overlapping image portions in accordance with a
modulus (n) of said values where n=the number of projectors
comprising said system.
2. A method for improving dynamic range in seams of tiled image
projected onto a display screen comprising steps of: separating an
input image into at least two image portions, each of said image
portions including at least one image area comprising pixels
corresponding to pixels of the other image portion; for each of
said corresponding pixels dividing pixel brightness value by the
number of corresponding pixels to obtain a divided brightness
value; for each of said corresponding pixel brightness values
determining a modulus n of said value wherein n=the number image
portions; adjusting brightness values of said corresponding pixels
based upon said modulus.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to provisional application
Ser. No. 60/751,336 filed Dec. 16, 2005, incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The invention relates to projection displays, and more
particularly to projection display systems comprising a plurality
of projectors arranged to display tiled images on a display
screen.
BACKGROUND OF THE INVENTION
[0003] The quality of a projected image can be described by
reference to a number of image characteristics. Each characteristic
represents a potential source of distortion in the displayed image.
Brightness and brightness uniformity are important characteristics
of displayed images. Brightness distortion, also referred to as
luminance distortion degrades the quality of a projected image to a
viewer of the image. Most projectors do not project images at a
constant luminance level across the entire display screen.
Therefore, brightness distortion is a common problem in the design
of projector display systems.
[0004] Brightness distortion has many possible sources. A common
source of brightness distortion is due to inherent optical
characteristics of lenses used in projection displays. This non
uniformity is due to the design of the optics within the light
engines of the projectors. Another possible cause for non
uniformity is the projection lamps themselves. Regardless of the
source of the luminance distortion, non-uniformity in luminance
detracts from the displayed image in the eyes of a viewer of the
image.
[0005] The luminance non-uniformity of a projector and its
associated lens can become more pronounced when a plurality of
projectors are employed in combination to display a single image on
a display screen. Such an arrangement of projectors is as "tiling".
Tiling projectors and projector images on a display screen provides
a larger image with higher overall resolution than can be obtained
from a single projector. However, the technique of tiling images
for display has drawbacks. Non-uniformity in luminance is often
much more apparent in a composite image created by multiple
projectors whose individual images are tiled together. This is
particularly a problem in "seam" areas of the displayed image.
Seams are created in those areas where images from a plurality of
projectors overlap each other on the display screen. Brightness non
uniformity in seam areas of a displayed tiled image is distracting
to viewers and degrades the quality of the displayed image.
Therefore, systems and methods for maintaining brightness
uniformity in seam areas of tiled images are needed.
SUMMARY OF THE INVENTION
[0006] The present invention provides systems and methods for
maintaining brightness uniformity in seam areas of tiled
images.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Preferred embodiments of the present invention will be
described below in more detail, with reference to the accompanying
drawings, in which:
[0008] FIG. 1 is a block diagram of an example display system
including two projectors according to an embodiment of the
invention.
[0009] FIG. 2 is a block diagram of an example display system
including four projectors according to an embodiment of the
invention
[0010] FIG. 3 is a flow chart illustrating steps of a method for
smoothing seams in a tiled display according to an embodiment of
the invention.
DETAILED DESCRIPTION
[0011] FIG. 1 illustrates a display system 10 for projecting a
video image 20 onto a display screen 40. System 10 comprises a
plurality of video projectors (160, 260) arranged such that each
projector (160, 260) separately projects first and second portions
(158, 258 respectively) of image 20 onto display screen 40. In the
embodiment illustrated in FIG. 1, projectors 160 and 260 comprise
spatial light modulator (SLM) type projectors. According to one
example embodiment of the invention projectors 160 and 260 comprise
DLP.TM. projectors. DLP is a trademark of Texas Instruments. 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.
[0012] Each separately projected image portion 158, 258 comprises a
corresponding unique image portion (159, 259) respectively of image
20. Each separately projected image portion 158, 258 further
comprises a common image portion (60L and 60R) respectively of
image 20. For example, a first projector 160 projects first portion
158 of image 20 onto screen 40. First portion 158 of image 20
comprises a unique image portion 159, i.e., a portion of image 20
that is not projected by any other projector. First portion 158 of
image 20 also comprises a common portion 60L. Portion 60L is a
duplicate of image portion 60R of image portion 258. Common portion
60L and common portion 60R are projected to overlap each other on
display 40. The overlapping common portions 60L and 60R define a
seam 88 of projected image 20.
[0013] System 10 further comprises a video image separator 90. A
video signal representing video image 20 is provided to video image
separator 90. A processor 95 of image separator 90 separates the
incoming video image signal into video image signal portions 106
and 206. Video image signal portions 106, 206 represent video image
portions 158 and 258 respectively.
[0014] Video image separator further comprises a pixel brightness
adjuster 27. Pixel brightness adjuster 27 examines pixel values
within overlapping image portions (e.g., 60L and 60R) of image
signal portions 106 and 206. Brightness adjuster 27 divides pixel
values corresponding to overlapping pixels of overlapping image
portions 60L and 60R (for example pixel 32 and 22) by the number of
overlapping image portions comprising seam 88. In the system
illustrated in FIG. 1 seam 88 comprises two image overlapping image
portions 60L and 60R. Therefore pixel brightness adjuster divides
the brightness value for pixel 60L and 60R by two. When projected
onto display 40 the combined brightness of pixels 60L and 60R will
approximate the intended brightness corresponding to pixel 60 of
input image 20.
[0015] However, pixel values are represented by a limited number of
bits. For example pixel values are commonly represented by 8 bits.
Each of the 256 combinations of 8 bits corresponds to a different
brightness level. If a brightness level does is not evenly
divisible by the number of projectors it is not possible to
accurately represent the original brightness value by a combination
of equal lower values. In order to more closely approximate the
original brightness value, pixel adjuster 27 determines the modulus
(n) of the pixel brightness value to be adjusted, where n is the
number of projectors comprising system 100. Pixel brightness
adjuster 27 adjusts the pixel brightness value for each projector
based on the modulus (n) it determines.
[0016] In a two projector system pixel brightness adjuster 27
determines the modulus (2) of pixel brightness values of
overlapping pixels. If the modulus (2) is 0, the original
brightness value is evenly divisible by the number of projectors.
In that case dividing the value by two and assigning equal values
to each overlapping pixel will provide the original brightness
value when the overlapping pixels are displayed.
[0017] If the modulus is 1, one of the overlapping pixels is
assigned the integer portion of the original brightness value
divided by the number of projectors. The other overlapping pixel is
assigned a brightness value equal to the brightness value assigned
to the other plus 1.
[0018] FIG. 2 illustrates a projector system 100 according to an
alternative embodiment of the invention. Projector system 100
comprising four projectors 160, 260, 360 and 460. Incoming video
signal 12 is provided to video image separator 90. Video signal 12
represents an image 20 to be displayed on screen 40. Image
separator 90 comprises a processor 95 and a pixel brightness
adjuster 27. Image separator 90 separates incoming video signal
into video signal portions 81, 82, 83 and 84. Each video signal
portion represents a portion of image 20. Similar to the embodiment
of FIG. 1 each image portion 159, 259, 359 and 459 of image 20
comprises a unique image portion and an overlapping image portion.
Overlapping image portions define seams 55, 66, 77 and 88 of
displayed image 20. In a configuration comprising four projectors
arranged in accordance with FIG. 2, an image area 73 comprises four
overlapping image portions. Accordingly the brightness of a given
pixel, for example pixel 800, in image area 73 will be a
combination of four pixel brightness values, one value supplied by
each video signal portion 81, 82, 83 and 84.
[0019] Pixel adjuster 27 of video separator 90 compensates for
distortions in brightness by dividing the brightness value P of
each pixel in area 72, for example the brightness value of pixel
800, by four (the number of projectors providing a pixel value for
pixel 800). A value of P/4 is assigned to each overlapping pixel.
To avoid loss of dynamic range pixel adjuster 27 also determines
the modulus (n) for pixel brightness values of overlapping pixels,
where n=4. If the modulus (4) of the brightness value is 0 each of
the four overlapping pixel values is assigned a brightness value
equal to the original brightness value divided by 4 (P/4). If
modulus (4) of the brightness value is 1 a binary 1 is added to P/4
for one of the four overlapping pixels. If the modulus (4) of the
brightness value is 2 a binary 1 is added to P/4 for two of the
overlapping pixels. If the modulus 4 of the brightness value is 3 a
binary 1 is added to three of the overlapping pixels. By adjusting
pixel brightness values in accordance with the modulus (n) of the
brightness of overlapping pixels, pixel brightness adjuster
improves the dynamic range in the seams of image 20.
* * * * *