Electronic keystone correction for electronic devices with a visual display

• US 6,191,827 B1
• Filed: 12/01/1998
• Issued: 02/20/2001
• Est. Priority Date: 12/01/1998
• Status: Expired due to Term

• Current Assignee: Lone Star Technological Innovations, LLC (TGT Enterprises, LLC)
• Original Assignee: Oplus Technologies Ltd. (Intel Corporation)
• Inventors: Strominger, Avy, Segman, Yosef, Yearim, Gady
• Primary Examiner(s): HSIA, SHERRIE Y
• Application Number:
  US09/201,849
• Time in Patent Office: 812 Days
• Field of Search: H04/N.323, 348/241, 348/252, 348/335, 348/571, 348/572, 348/580, 348/625, 348/628, 348/745, 348/746, 348/747, 348/757, 348/761, 348/806, 348/807, 315/368.13, 315/371, 349/73, 353/69, 358/20, 382/275
• US Class Current: 348/746
• CPC Class Codes: H04N 3/2335 with calculating means

Abstract

A method of electronic Keystone correction for electronic devices having visual displays which exhibit optical distortion on the display screen. The corrective method is based on computation and electronic (physical) manipulation of the pixels of a visual display screen grid, and features the principle steps of: 1) characterization of the size of an input image, 2) determination of the number of generated pixels in the output image, 3) determination of the real position of each pixel in the output image by performing an electronic distortion to the input image opposite to the optical distortion of the input image, 4) interpolation of the output value of all color components of each pixel of the input image, 5) correction of (non-uniform) edge effects at both ends of each line of pixels, 6) transmission of the output corrected image to the electronic display device, individually, pixel by pixel, or as complete set of corrected pixels of the image, and 7) display of the perfected corrected optical image. The method of this invention solves at least two universally known optical distortion problems involving trapezoidal distortion and computerized diagonal line drawing. Moreover, the method of this invention is applicable to real time domain of operation of electronic devices with visual displays.

Claims

1. A method for correcting an optical distortion of an image on a visual display screen, the steps of the method being performed by a data processor, the method comprising the steps of:

(a) receiving an input image featuring pixels;

(b) determining a distortion mode of said input image;

(c) determining a number of said pixels in said input image;

(d) determining a number of horizontal lines of said pixels in each group of said horizontal lines of said pixels in said input image;

(e) determining a number of said groups of said horizontal lines of said pixels in said input image;

(f) determining a number of output pixels of each said horizontal line in a corrected output image;

(g) determining a plurality of positions of said pixels of said input image;

(h) performing an opposite electronic distortion to the optical distortion of said input image, comprising the steps of;

(i) calculating a horizontal position of each of a plurality of first generated said output pixels in grid space of said input image, said horizontal position of each of said plurality of said horizontal positions located between first said input pixel of each said horizontal line and second said input pixel of each said horizontal line in said grid space of said input image, said calculating performed according to said distortion mode of said input image, using a LineCounter; and

(ii) calculating said plurality of said horizontal positions of remaining said output pixels in said grid space of said input image, said calculating performed according to said distortion mode of said input image, using a GroupCounter;

(i) determining said plurality of positions of said output pixels of said opposite electronic distortion to the optical distortion of said input image;

(j) determining a plurality of values of said output pixels of said opposite electronic distortion to the optical distortion of said input image to form said corrected output image;

(k) correcting a plurality of edge effects in said horizontal lines of said plurality of said output pixels of said corrected output image to form a straight diagonal line along each of two sides of said corrected output image;

(l) transmitting said plurality of said output pixels of said corrected output image to a visual display device; and

(m) displaying said corrected output image on the visual display screen.

2. The method of claim 1, wherein the step of determining said plurality of said values of said output pixels of said opposite electronic distortion to the optical distortion of said input image further comprises the step of interpolating said plurality of said values of said input pixels of said opposite electronic distortion to the optical distortion of said input image.

3. The method of claim 2, wherein the step of interpolating said plurality of said values of said input pixels of said opposite electronic distortion to the optical distortion of said input image, further comprises the steps of:

(i) calculating a Keystone output value for each color component of each said pixel in said input image, said calculating comprising the steps of;

(1) evaluating a difference between real said position of each said output pixel and each said real position of each corresponding said input pixel; and

(2) evaluating by a linear combination of said value of each said output pixel from said values of said real positions of neighbors of said input pixels in grid space of said input image, using said difference between said real position of each said output pixel and each said real position of each corresponding said input pixel.

4. The method of claim 1, wherein the step of correcting said plurality of said edge effects in said horizontal lines of said plurality of said output pixels of said corrected output image, further comprises the steps of:

(i) identifying said position and said value of each first generated said output pixel in each said horizontal line of said corrected output image; and

(ii) identifying said position and said value of each last generated said output pixel in each said horizontal line of said corrected output image.

5. The method of claim 1, wherein said distortion mode of said input image is selected from the group consisting of floor mode and ceiling mode, said floor mode featuring said input image narrower at top, said ceiling mode featuring said input image narrower at bottom.

6. The method of claim 1, wherein the step of correcting said plurality of said edge effects in said horizontal lines of said plurality of said output pixels of said corrected output image includes formation of said a straight diagonal line along each of two sides of said display of said corrected output image on the visual display screen.

7. The method of claim 1, wherein step (h), the step of calculating said horizontal position of each of said plurality of first generated said output pixels in grid space of said input image, includes the steps of:

(1) for each said first generated position of said output pixels in grid space of said input image, corresponding said input pixel featuring said floor mode of distortion, each said input pixel is shrunk at the top; and

(2) for each of said first generated position of said output pixels in grid space of said input image, corresponding said input pixel featuring said ceiling mode of distortion, each said input pixel is shrunk at the bottom.

8. The method of claim 1, wherein step (h) the step of calculating said plurality of said horizontal positions of said remaining said output pixels in said grid space of said input image, includes the steps of:

(1) for each said horizontal position of said remaining said output pixels in said grid space of said input image, corresponding said input pixel featuring said floor mode of distortion, each said input pixel is shrunk at the top; and

(2) for each said horizontal position of said remaining said output pixels in said grid space of said input image, corresponding said input pixel featuring said ceiling mode of distortion, each said input pixel is shrunk at the bottom.

9. The method of claim 1, wherein the step of determining said number of said output pixels of each said horizontal line of said opposite electronic distortion to the optical distortion of said input image further comprises the step of calculating said number of said output pixels of each said horizontal line of said opposite electronic distortion to the optical distortion of said input image from said number of said input pixels of said input image by using a GroupCounter, said GroupCounter being a counter of said number of said groups of said horizontal lines of said pixels of said input image, whereby said counting of said GroupCounter is selected from the group consisting of up and down, according to said distortion mode of said input image.

10. The method of claim 9, whereby said GroupCounter features a means for insertion of black pixels at both ends of each said horizontal line of said plurality of said horizontal lines of said output pixels of said corrected output image.

11. The method of claim 1, wherein the step of determining said number of said horizontal lines of said pixels in each said group of said horizontal lines of said pixels in said input image, further comprises the steps of:

(i) evaluating a function of an angle of trapezoidal distortion, said angle of trapezoidal distortion equivalent to a Keystone angle; and

(ii) using said LineCounter, said LineCounter performing iterative counting of said horizontal lines of said pixels of said input image.

12. The method of claim 1, wherein the step of determining said number of said groups of said horizontal lines of said pixels in said input image, further comprises the steps of:

(i) determining said distortion mode of said input image;

(ii) for said distortion mode of said input image being ceiling mode, said ceiling mode featuring said input image narrower at bottom, using said GroupCounter for iterative counting, said GroupCounter being a counter of said number of said groups of said horizontal lines of said pixels of said input image, said GroupCounter is initialized and counts up; and

(iii) for said distortion mode of said input image being floor mode, said floor mode featuring said input image narrower at top, using said GroupCounter for said iterative counting, said GroupCounter is initialized and counts down.

13. The method of claim 1, wherein the step of transmitting said plurality of said output pixels of said corrected output image to said visual display device includes the step of transmitting said output pixels of said corrected output image to said visual display device by a means selected from the group consisting of individually, whereby each said output pixel of said corrected output image is transmitted separately to said visual display device, and collectively, whereby said plurality of said output pixels of said corrected output image are transmitted as a single set to said visual display device.

14. A method of performing an opposite electronic distortion to an optical distortion of an image, the method comprising the steps of:

(a) receiving the image featuring pixels;

(b) determining a distortion mode of the image;

(c) calculating a horizontal position of each of a plurality of first generated output pixels of an output image in grid space of the image, said horizontal position of each of said plurality of said horizontal positions located between first input pixel of each horizontal line and second said input pixel of each said horizontal line in said grid space of the image, said calculating performed according to said distortion mode of the image, using a LineCounter; and

(d) calculating said plurality of said horizontal positions of remaining said output pixels of said output image, said calculating performed according to said distortion mode of the image, using a GroupCounter.

15. The method of claim 14, wherein the step of calculating said plurality of said horizontal positions of said remaining said output pixels in said grid space of the image, said calculating performed according to said distortion mode of the image, said distortion mode selected from the group consisting of floor mode and ceiling mode, said floor mode featuring the image narrower at top, said ceiling mode featuring the image narrower at bottom, further comprises the steps of:

(i) for each said horizontal position of said remaining said output pixels in said grid space of the image, corresponding said pixel of the image featuring said floor mode of distortion, each said pixel of the image is shrunk at the top; and

(ii) for each said horizontal position of said remaining said output pixels in said grid space of the image, corresponding said pixel of the image featuring said ceiling mode of distortion, each pixel of the image is shrunk at the bottom.