Method of reducing the visual impact of defects present in a spatial light modulator display

• US 5,504,504 A
• Filed: 07/13/1994
• Issued: 04/02/1996
• Est. Priority Date: 07/13/1994
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Gove, Robert J., Markandey, Vishal
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): CHOW, DOON Y
• Application Number:
  US08/275,057
• Time in Patent Office: 629 Days
• Field of Search: 345/214, 345/87, 345/904, 345/101, 345/138, 345/55, 359/84, 359/86, 359/85, 348/246, 348/247, 348/616, 348/615, 348/607, 382/252
• US Class Current: 345/214
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2330/10 Dealing with defective pixels
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833

Abstract

A method and display system for reducing the visual impact of defects present in an image display. The display includes an array of pixels, each non-defective pixel being selectively operable in response to input data by addressing facilities between an "on" state, whereat light is directed onto a viewing surface, and an "off" state, whereat light is not directed onto the viewing surface. A defect is the result of a defective pixel which does not respond to the input data presented by the addressing facilities, typically by continuously remaining in its "on" or "off" state. Each defective pixel is immediately surrounded by a first ring of compensation pixels adjacent to the central defective pixel. The compensation pixels are immediately surrounded by a second ring of reference pixels spaced from the central defective pixel. The addressing circuit-determined value of at least one compensation pixel in the first ring surrounding the defective pixel is changed to a corrective value, in order to reduce the visual impact of the defect.

Claims

1. A method of reducing the visual impact of defects present in an image display, the display being of the type which includes an array of pixels, each non-defective pixel being selectively operable, in response to input data provided by addressing facilities between an "on" state in which light is directed onto a viewing surface, and an "off" state in which light is not directed onto the viewing surface;

a defect being the result of a defective pixel which continuously remains in the "on" or "off" state regardless of the input data or the operation of the addressing facilities;

each defective pixel being, in effect, a central defective pixel immediately surrounded by a first ring of compensation pixels adjacent to the central defective pixel with the first ring of compensation pixels being immediately surrounded by a second ring of reference pixels spaced from the central defective pixel;

wherein the method comprises;

(a) identifying a defect-producing defective pixel; and

(b) changing the addressing circuit-determined value of at least one compensation pixel in the first ring surrounding the defective pixel to a corrective value given by;

space="preserve" listing-type="equation">C.sub.NEW =C.sub.SINC (D.sub.ACT -D.sub.INT)=D.sub.INT

wherein C_NEW is the intensity value assigned to the compensation pixel, C_SINC is the value of the sinc function evaluated for the compensation pixel, D_ACT is the actual intensity value of the defective pixel, and D_INT is the intended intensity value of the defective pixel.

2. A method as in claim 1, wherein:

step (a) is effected by comparing the actual light directed onto the viewing screen by the defective pixel and the addressing circuit-determined value of the defective pixel.

3. A method as in claim 1, wherein all compensation pixels are assigned the same value.

4. A method as in claim 1, wherein the location of the defective pixels is stored in a memory.

5. A method of reducing the visual impact of defects present in an image display, the display being of the type which includes an array of pixels, each non-defective pixel being selectively operable, in response to input data provided by addressing facilities, between an "on" state in which light is directed onto a viewing surface, and an "off" state in which light is not directed onto the viewing surface;

a defect being the result of a defective pixel which continuously remains in the "on" or "off" state regardless of the input data or the operation of the addressing facilities;

each defective pixel being, in effect, a central defective pixel immediately surrounded by a first ring of compensation pixels adjacent to the central defective pixel with the first ring of compensation pixels being immediately surrounded by a second ring of reference pixels spaced from the central defective pixel;

wherein the method comprises;

(a) identifying a defect-producing defective pixel; and

(b) changing the addressing circuit-determined value of at least one compensation pixel in the first ring surrounding the defective pixel to a corrective value to thereby reduce the visual impact of the defect, the corrective value given by;

space="preserve" listing-type="equation">C.sub.NEW =C.sub.SINC (D.sub.ACT -R.sub.AVG)+D.sub.INT

where C_NEW is the intensity value assigned to the compensation pixel, C_SINC is the value of the sine function evaluated for the compensation pixel, D_ACT is the actual intensity value of the defective pixel, R_AVG is the average value of at least one reference pixel, and D_INT is the desired intensity value of the defective pixel.

6. A method as in claim 5, wherein all compensation pixels are assigned the same value.

7. A method as in claim 5, wherein:

D_INT, the desired intensity value of the defective pixel, is replaced by C_ORG, the original value of the compensation pixel.

8. A method as in claim 5, wherein:

R_AVG the average value of at least one reference pixel and the desired value of the defective pixel.

9. A method as in claim 8, wherein all compensation pixels are assigned the same value.

10. A method as in claim 5, wherein:

step (a) is effected by comparing the actual light directed onto the viewing screen by the defective pixel and the addressing circuit-determined value of the defective pixel.

11. A method as in claim 5, wherein the location of the defective pixels is stored in a memory.

12. A display system comprising:

a modulator comprised of an array of pixels including at least one defective pixel, at least one compensation pixel adjacent to the defective pixel, and at least one reference pixel adjacent to said at least one compensation pixel and spaced apart from said defective pixel, the modulator for receiving a set of image data values corresponding to the array of pixels and for selectively activating the pixels to represent the set of image data values; and

a processor for receiving an image signal and outputting the set of image data values to the modulator, wherein the processor alters the image data value corresponding to the compensation pixels according to the following;

space="preserve" listing-type="equation">C.sub.NEW =C.sub.SINC (D.sub.ACT -D.sub.INT)+D.sub.INT

where C_NEW is the image data value assigned to the compensation pixel, C_SINC is the value of the sinc function evaluated for the compensation pixel, D_ACT is the actual intensity value of the defective pixel, and D_INT is the desired intensity value of the defective pixel.

13. A display system as in claim 12, further comprising a memory containing the locations of the defective pixels, wherein said memory communicates the locations of the defective pixels to the processor.

14. A display system as in claim 12, further comprising a means for defecting the locations of the defective pixels, wherein said means for defecting communicates the locations of the defective pixels to the processor.

15. A display system as in claim 14, wherein the means for defecting the locations of the defective pixels is a camera.

16. A display system as in claim 12, wherein the processor assigns all compensation pixels the same image data value.

17. A display system comprising:

a modulator comprised of an array of pixels including at least one defective pixel, at least one compensation pixel adjacent to the defective pixel, and at least one reference pixel adjacent to said at least one compensation pixel and spaced apart from said defective pixel, the modulator for receiving a set of image data values corresponding to the array of pixels and for selectively activating the pixels to represent the set of image data values; and

a processor for receiving an image signal and outputting the set of image data values to the modulator, wherein the processor alters the image data value corresponding to the compensation pixels according to the following;

space="preserve" listing-type="equation">C.sub.NEW =C.sub.SINC (D.sub.ACT -R.sub.AVG)+D.sub.INT

where C_NEW is the image date value assigned to the compensation pixel, C_SINC is the value of the sinc function evaluated for the compensation pixel, D_ACT is the actual intensity value of the defective pixel, R_AVG is the average value of at least one of the reference pixels, and D_INT is the desired intensity value of the defective pixel.

18. A display system as in claim 17, wherein:

D_INT, the desired intensity value of the defective pixel, is replaced by C_ORG, the original value of the compensation pixel.

19. A display system as in claim 17, wherein:

R_AVG the average value of at least one reference pixel and the desired value of the defective pixel.

20. A display system as in claim 17, further comprising a memory containing the locations of the defective pixels, wherein said memory communicates the locations of the defective pixels to the processor.

21. A display system as in claims 17, further comprising a means for defecting the locations of the defective pixels, wherein said means for defecting communicates the locations of the defective pixels to the processor.

22. A display system as in claim 17, wherein the means for defecting the locations of the defective pixels is a camera.

23. A display system as in claim 17, wherein the processor assigns all compensation pixels the same image data value.