Method and apparatus for optical inspection of a display

• US 20040213449A1
• Filed: 02/02/2004
• Published: 10/28/2004
• Est. Priority Date: 02/03/2003
• Status: Active Grant

• Current Assignee: Photon Dynamics Incorporated (KLA Corporation)
• Original Assignee: Photon Dynamics Incorporated (KLA Corporation)
• Inventors: Hawthorne, Jeffrey, Bukal, Branko, Safaee-Rad, Reza, Crnatovic, Aleksander, Leerentveld, Ray
• Granted Patent: US 7,308,157 B2
• Time in Patent Office: Days
• US Class Current: 382/141
• CPC Class Codes: G06T 2207/30108 Industrial image inspection
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: H04N 17/02 for colour television signals
• CPC Class Codes: H04N 17/04 for receivers

Abstract

A method and apparatus for optically inspecting a display employs sub-pixel accuracy for each primary color to take into account angle of rotation. The method includes capturing images of a display with R×S sensors; determining sets of sensor coordinates mapping to a pixel, determining multiple misalignment angles between the pixel on the display and the R×S sensors, determining multiple x scaling ratios, determining multiple weighting factors associated with R×S sensors in response to the corresponding multiple misalignment angle and the corresponding multiple x and y scaling ratios, determining multiple luminance values for R×S sensors, determining multiple total luminance values in response to the weighting factors and the luminance values, forming scaled images including first and second luminance values, and inspecting the scaled image to identify potential defects of the pixel on the display.

Claims

1. A method for a computer system comprises:

capturing a first and a second image of a pixel on a display at coordinates (m, n) with an array of R×

S sensors in an image sensor;

determining a first and a second set of coordinates on the image sensor that map to coordinates (m,n) on the display for a first and a second group of sub-pixels, respectively, in response to the first and second image, respectively;

determining a first and a second misalignment angle between the pixel on the display and the array of R×

S sensors for the first group and the second group of sub-pixels, respectively;

determining a first and a second x magnification ratio of pixels in the display relative to sensors in the image sensor for the first group and the second group of sub-pixels;

determining a first and a second plurality of weighting factors Wij, where i=1 to R, and j=1 to S, respectively associated with sensors from the array of R×

S sensors in response to the first and second misalignment angle, and the first and the second x magnification ratio, respectively;

determining a first and second plurality of luminance values Lij, where i=1 to R, and j=1 to S, respectively associated with the sensors from the array of R×

S sensors;

determining a first and second luminance value Imn, according to the following relationship;

Imn=Σ

(Wij*Lij) for i=I to R, and j=1 to S, in response to the first and second plurality of weighting factors and the first and second plurality of luminance values, respectively;

forming a first and a second reduced scaled image including a plurality of pixels, wherein a luminance value for a pixel at coordinate (m,n) in the first and the second reduced scaled image is determined in response to the first and the second luminance value Imn, respectively; and

inspecting the first and the second reduced scaled image to identify potential defects of the pixel on the display.

2. The method of claim 1 wherein R=S, and R and S are selected from the group, 5, 6, 7.

3. The method of claim 1 wherein the first and the second plurality of weighting factors Wij, where i=1 to R, and j=1 to S, is also determined in response to the first and second set of coordinates on the image sensor.

4. The method of claim 1 further comprising determining an first and a second y direction magnification ratio of pixels in the display relative to sensors in the image sensor for the first group and the second group of sub-pixels;

5. The method of claim 4 wherein the first and the second plurality of weighting factors Wij, where i=1 to R, and j=1 to S are also determined in response to the first and the second y magnification ratio, respectively.

6. The method of claim 1 wherein the first and second luminance value Imn each have a greater bit-depth resolution than the first and the second plurality of luminance values from the plurality of luminance values Lij.

7. The method of claim 1 wherein the first group of sub-pixels and the second group of sub-pixels are selected, without replacement, from the group:

red sub-pixels, green sub-pixels, and blue sub-pixels.

8. An inspection system comprises:

at least one sensor configured to acquire a first and a second image of a portion of a flat-panel display, wherein at least one array of R×

S sensors are configured to capture a first and a second image of at least one display pixel in the flat-panel display;

a processing unit coupled to at least the one sensor configured to determine a defect in the flat-panel display in response to at least the first and the second image of the portion of the flat-panel display, wherein the processing unit comprises;

a processor configured to instruct the at least one sensor to capture the first image and the second image of the display pixel with the array of R×

S sensors, wherein the processor is configured to determine a first and a second plurality of weighting factors Wij, where i=1 to R, and j=1 to S, respectively associated with sensors from the array of R×

S sensors, for the first image and the second image, wherein the processor is configured to determine a first and a second plurality of luminance values Lij, where i=1 to R, and j=1 to S, respectively associated with the sensors from the array of R×

S sensors in response to the first image and the second of the one display pixel, wherein the processor is configured to determine a first and a second luminance value Imn, in response to Wij and Lij for i=1 to R, and j=1 to S, wherein the processor is configured to determine a first and second scaled-down image including a plurality of pixels, wherein a luminance value associated with the one display pixel in the first and the second scaled-down image is determined in response to the first and the second luminance value Imn, respectively and wherein the processor is configured to inspect the first and second scaled-down image to identify potential defects of the pixel on the display.

9. The inspection system of claim 8 wherein R=S, and R and S are selected from the group:

5, 6, 7.

10. The inspection system of claim 8 wherein the processor is also configured to determine a first and a second vertical offset between the one display pixel relative to the first image and the second image.

11. The inspection system of claim 8 wherein the processor is also configured to determine a first and a second offset angle between the one display pixel relative to the first image and the second image.

12. The inspection system of claim 10 wherein the processor is also configured to determining a first and a second horizontal pitch relative to the one display pixel and to the array of R×

S sensors.

13. The inspection system of claim 11 wherein the processor is also configured to determine a first and second vertical offset between a second display pixel relative to the sensor in response to the first and second offset angle.

14. The inspection system of claim 8 wherein the display comprises a liquid crystal display having pixels comprising red, green and blue sub-pixels.

15. A method for a computer system comprises:

capturing a first image of at least a portion of a display, wherein an image of a first sub-pixel in a display pixel is captured with an array of sensor pixels in an image sensor;

capturing a second image of at least the portion of a display, wherein an image of a second sub-pixel in the display pixel is captured with the array of sensor pixels in the image sensor;

determining a first position and a first orientation of the display with respect to the image sensor in response to the first image;

determining a second position and a second orientation of the display with respect to the image sensor in response to the second image;

for each sensor pixel in the array of sensor pixels, determining a first percentage of overlap of the sensor pixel on top of the display pixel in response to the first position and the first orientation;

for each sensor pixel in the array of sensor pixels, determining a second percentage of overlap of the sensor pixel on top of the display pixel in response to the second position and the second orientation;

for each sensor pixel in the array of sensor pixels, determining a first intensity value in response to the first image of the display pixel;

for each sensor pixel in the array of sensor pixels, determining a second intensity value in response to the second of the display pixel;

determining a first weighted intensity value associated with the display pixel in response to the first percentage of overlap for each sensor pixel and in response to the first intensity value for each sensor pixel;

determining a second weighted intensity value associated with the display pixel in response to the second percentage of overlap for each sensor pixel and in response to the second intensity value for each sensor pixel;

forming a first scaled image in response to the first weighted intensity value;

forming a second scaled image in response to the second weighted intensity value; and

inspecting the first and the second scaled images to determine potential defects in the display.

16. The method of claim 15 further comprising:

processing the first image of the portion of the display to determine defects in the display in response to the potential defects.

17. The method of claim 15 wherein the first position comprises an x and y offset, and wherein the first orientation comprises an angle of rotation.

18. The method of claim 15 wherein inspecting the first and second scaled images further comprises:

normalizing the first and second scaled images to form a first and second normalized image; and

inspecting the first and second normalized image for defects.

19. The method of claim 15 wherein the first sub-pixel and the second sub-pixel are selected without replacement from the group:

red sub-pixel, green sub-pixel, blue sub-pixel.

20. The method of claim 15

wherein the first sub-pixel is a red sub-pixel;

and

wherein capturing the first image of at least the portion of a display also comprises capturing the first image of at least the portion of the display through a red-colored filter.