Optics: image projectors – Distortion compensation
Reexamination Certificate
1998-12-17
2001-10-23
Metjahic, Safet (Department: 2858)
Optics: image projectors
Distortion compensation
Reexamination Certificate
active
06305805
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to projection systems for displaying an image on a screen and, more particularly, to systems and methods for correcting image keystoning in a projection system caused by a projection lens of a projector not being centered on the screen.
BACKGROUND OF THE INVENTION
Generally, a display system for displaying an image is divided broadly into direct-view picture display systems represented by CRTs (Cathode Ray Tubes) and projection systems having projectors for displaying an image on a screen (hereinafter referred to as “projectors”). With projectors, an image is magnified via a projection lens and is displayed on a screen. When the projector is not centered or cannot be centered on the screen, i.e., the lens is not at a 90° angle to the center of the screen, the resulting projected image is distorted or skewed. This phenomenon is known in the art as keystoning. With keystoning, an asymmetrical image is projected onto the screen. In other words, the image projected onto the screen has a trapezoidal shape (keystone) as opposed to a rectangular shape.
FIG. 1
illustrates a projector
10
having a projection lens
12
at a 90° angle to the center of a screen
14
resulting in image
16
which is projected in the shape of a rectangle onto screen
14
without keystoning or trapezoidal distortion or skewing as shown in FIG.
2
. As shown in
FIGS. 1 and 2
, a center axis
18
is a line connecting a point
20
lying on the surface plane of screen
14
and a center point
22
of projection lens
12
of projector
10
. Center axis
18
forms an upward/downward projection angle A and a right/left projection angle B with the surface of screen
14
. When projection angles A and B are 90° as shown in
FIGS. 1 and 2
, projector
10
and projection lens
12
are said to be “centered” or at a 90° projection angle to screen
14
. Projection angles A and B are referred to as upward/downward and right/left projection angles, respectively, since center point
22
of projection lens
12
is either below/above point
20
or to the right/left of point
20
, respectively.
Referring now to
FIGS. 3 and 4
wherein reference numerals or letters which are like, similar, or identical to reference numerals or letters used in
FIGS. 1 and 2
indicate like, similar, or identical components or features. Here, upward/downward projection angle A and/or right/left projection angle B are not equal to 90° resulting in image
16
being projected in the shape of a trapezoid onto screen
14
with keystoning.
In U.S. Pat. No. 5,664,858 (incorporated herein by reference), Woo discloses an apparatus and method for pre-compensating an asymmetrical picture in a projection system to correct keystoning when a projection lens of a projector is arranged at an upward or downward projection angle relative to a screen. The apparatus and method disclosed are implemented in a hardware intensive configuration shown in
FIG. 7
therein. With presentation systems utilizing a computer and a software application, such as Power Point (Power Point is a trademark of Microsoft Corporation), to generate and store images and a projector (such as manufactured and sold by Boxlight Corporation or Epson America, Inc.) which interfaces with the computer to project the computer-generated images on a screen, modifing the computer or projector to include the hardware solution proposed by Woo to correct keystoning is not practical. Also, the hardware solution proposed by Woo does not correct keystoning caused by a projection lens of a projector being arranged at projection angles other than an upward/downward projection angle, such as right/left projection angles or a combination of a right/left projection angle and an upward/downward projection angle. What is needed is a software solution for such a presentation system to correct keystoning, without having to center the projector on the screen, to avoid the need to modify the computer's or projector's hardware and to correct keystoning caused by projection angles other than an upward/downward projection angle.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a presentation system comprising at least one processor, memory operably associated with the processor, at least one output port operably associated with the processor and the memory and configured to output an image storable in the memory, a program of instructions configured to be executed by the processor and stored in the memory, the program including instructions configured to correct keystoning of the image output by the output port.
The present invention also provides a method for correcting keystoning of an image projected by a presentation system including at least one processor, memory operably associated with the processor and configured to store the image, and at least one output port operably associated with the processor and the memory and configured to output the image, said method comprising the steps of: maintaining the image in the is memory; and maintaining a program of instructions configured to be executed by the processor and stored in the memory, wherein said program includes instructions to correct keystoning of the image output by the output port by modifying the image stored in memory.
The present invention further provides a computer readable medium tangibly embodying a program of instructions configured to correct keystoning of an image projected by a presentation system including at least one processor, memory operably associated with the processor and configured to store the image, and at least one output port operably associated with the processor and the memory and configured to output the image.
In accordance with one aspect of the present invention, the program includes instructions configured to input a right/left projection angle to correct keystoning of the image caused by, at least in part, the right/left projection angle being greater than or less than 90°.
It is an object of the present invention to provide a software solution for correcting keystoning of an image projected by a projector in a presentation system including a computer interfaced to the projector, without having to center the projector on the screen, to avoid the need to modify the computer's or projector's hardware.
It is another object of the present invention to provide omnidirectional keystone correction, i.e., correcting keystoning of an image when upward/downward and/or right/left projection angles are not 90°.
The present invention provides the advantage of avoiding hardware modification of a presentation system including a projector and a computer and avoiding the need to center the projector on a screen to correct keystoning of an image projected by the projector.
The present invention also provides the advantage of correcting keystoning of an image caused by, at least in part, the right/left projection angle being greater than or less than 90°.
REFERENCES:
patent: 3639034 (1972-02-01), La Russa
patent: 3963337 (1976-06-01), Lundberg
patent: 4004093 (1977-01-01), Oland
patent: 4194216 (1980-03-01), Ohmori
patent: 4210929 (1980-07-01), Takabayashi
patent: 4422153 (1983-12-01), Arai et al.
patent: 5664858 (1997-09-01), Woo
Gateway Inc.
Leroux E P
Metjahic Safet
Suiter & Associates PC
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