Computer graphics processing and selective visual display system – Computer graphics processing – Attributes
Reexamination Certificate
2000-12-29
2004-08-03
Jankus, Almis R. (Department: 2671)
Computer graphics processing and selective visual display system
Computer graphics processing
Attributes
Reexamination Certificate
active
06771272
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to the field of computer graphics and, more particularly, to high performance graphics systems which generate images for display on one or more display devices, including projection devices.
2. Description of the Related Art
Multiple projection devices may be used to display a single integrated image as shown in FIG.
1
. Each of the projection devices may display a portion of the integrated image. For example, projection devices P
1
and P
2
may target a common display screen SCR, and may generate the left and right portions respectively of an integrated image. The projection devices may use any of a variety of technologies. For example, the projection devices may be based on cathode ray tubes (CRTs), liquid crystal displays (LCDs), digital micro-mirror displays, or liquid crystal on silicon (LCOS) displays, etc.
A computer system CS may be used to drive the multiple projection devices P
1
and P
2
. The computer system CS may provide analog or digital video signals to drive the projection devices P
1
and P
2
. The computer system CS may include a graphics system for the rendering and display of 2D graphics and/or 3D graphics. The graphics system may supply the video signals which drive the projection devices P
1
and P
2
. In addition, the computer system CS may include a monitor device MD, a system unit SU, and input devices such as a keyboard KB and mouse MS. Monitor device MD and projection devices P
1
and P
2
may be referred to generically as display devices.
It is often necessary to overlap the images generated by the two projection devices P
1
and P
2
as shown in
FIG. 2A. A
front view of the two overlapped images as they might appear on the display screen SCR is shown in FIG.
2
B. The left image represented by rectangle ABCD overlaps the right image represented by rectangle EFGH.
FIG. 2C
illustrates a fundamental problem associated with the overlapping of two projected images. The function I
1
represents the distribution of light intensity across the screen SCR due to projection device P
1
. Similarly, function I
2
represents the distribution of light intensity across the screen SCR due to projection device P
2
. In the overlap region (i.e. rectangle EBCH) the intensity functions add. Thus, the intensity in the overlap region may be larger in the non-overlap regions than in the non-overlapped regions of the screen. The increased brightness of the overlap region may be annoying to a viewer of the integrated image AFGD.
The overlap-brightness problem exists when any number of projected images are overlapped. For example,
FIG. 3
illustrates the overlapping of four projected images generated by four projection devices in a “two by two” configuration. One of the projected images is represented by rectangle JLTR. The other three projected images have the same size as rectangle JLTR and are displaced to the three remaining corners M, V and Y. Exactly two of the projected images overlap in regions KLPO, NOSR, STXW and PQUT, and thus, these regions may exhibit a light intensity which is double that of the non-overlap regions JKON, LMQP, RSWV and TUYX. All four projected images overlap in the center region OPST, and thus, the center region may exhibit a light intensity which is four times larger than the intensity of the non-overlap regions.
There currently exist analog systems called “video boxes” which address in some measure the overlap-brightness problem. A video box may couple between computer system CS and projection devices P
1
and P
2
as shown in
FIG. 1
, and may reduce the intensity of the projected images in the overlap region. Thus, the total intensity in the overlap region may be more nearly equal to the intensity of the non-overlap regions after installation of a video box. Although, video boxes provide some measure of correction to the overlap-brightness problem, they may be expensive and may not be easy to configure. Furthermore, their functionality may be limited. Thus, there exists a need for a system and method which could provide an improved blending of the light intensity in the overlap regions. More generally, there exists a need for a system and method which could uniformize the intensity distribution of an integrated image generated by multiple projection devices.
In
FIG. 2C
, the intensity distributions I
1
and I
2
are illustrated as having rectangular profiles. In reality, the intensity distribution of a projected image may be highly non-uniform for a number of different reasons. First, a typical projection device PD radiates light with a non-uniform radiation intensity pattern as shown in FIG.
4
A. The radiation intensity pattern may have a maximum in the on-axis direction, i.e. the direction of central projection ray CPR, and may decrease as a function of the radiation angle RA measured with respect to the central projection ray CPR.
Thus, as shown in
FIG. 4B
, a more realistic screen intensity distribution for a projected image may have a maximum at the point CM where the central projection ray intercepts the screen SCR, and may decrease as a function of horizontal and vertical screen displacements from the central maximum CM. Several level curves of the screen intensity distribution are superimposed on the projected image.
FIG. 4C
illustrates the screen intensity distribution I
D
along a horizontal slice HS of the screen through the central maximum CM.
If the screen material is highly diffusive, the screen intensity distribution I
D
may be relatively independent of the viewing angle and/or position. Diffusivity means that a generic ray R impinging on the screen is scattered with a hemispherical scattering distribution SD. However, if the screen material has high gain, i.e. is more reflective (or transmissive in the rear-projection case), the screen intensity distribution may be highly dependent on the viewer's position with respect to the projector-screen system.
For example,
FIG. 5A
illustrates the screen intensity distributions I
V1
and I
V2
perceived by viewers V
1
and V
2
respectively situated on opposite sides of projection device PD in a front-projection scenario. The screen intensity distribution I
V1
for the first viewer V
1
may attain a maximum value at the point P
1
where the source ray S
1
emanating from the projection device has a reflection ray R
1
which intercepts the viewer V
1
. Thus, the viewer V
1
perceives a “hot spot” on the screen at point P
1
. Similarly, the screen intensity distribution I
V2
for the second viewer V
2
may attain a maximum value at the point P
2
where the source ray S
2
emanating from the projection device has a reflection ray R
2
which intercepts the viewer V
2
. Thus, viewer V
2
perceives a hot spot at point P
2
on the screen SCR.
FIG. 5B
illustrates the screen intensity distributions I
V1
and I
V2
perceived by viewers V
1
and V
2
respectively situated at different positions with respect to a high gain screen in a rear-projection scenario. The screen intensity distribution I
V1
for the first viewer V
1
may attain a maximum value at the point Q
1
where the direct ray D
1
from the projection device to the viewer V
1
intercepts the screen. Similarly, the screen intensity distribution I
V2
for the second viewer V
2
may attain a maximum value at the point Q
2
where the direct ray D
2
from the projection device to the viewer V
2
intercepts the screen.
Multiple projector devices may be used to generate an integrated image on the projection screen SCR. Thus, an observer may observe two or more hot spots on the screen, i.e. the intensity distribution may have two or more local maxima. Thus, there exists a need for a system and method which could correct the hot spots perceived by the observer on screen SCR.
Projection devices generally attempt to project a rectangular array of physical pixels on the projection screen SCR. However, many distortion mechanisms conspire to defeat this desired end. For example, the physical pixel array may exhibit a keystone distortion KST,
Brightwell Mark K.
Hood Jeffrey C.
Jankus Almis R.
Meyertons Hood Kivlin Kowert & Goetzel P.C.
Sun Microsystems Inc.
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