Substrate inspection apparatus and method

• US 5,754,678 A
• Filed: 05/30/1996
• Issued: 05/19/1998
• Est. Priority Date: 01/17/1996
• Status: Expired due to Fees

• Current Assignee: Photon Dynamics Incorporated (KLA Corporation)
• Original Assignee: Photon Dynamics Incorporated (KLA Corporation)
• Inventors: Hawthorne, Jeffrey A., Setzer, Joseph
• Primary Examiner(s): Boudreau, Leo
• Assistant Examiner(s): MEHTA, BHAVESH M
• Application Number:
  US08/688,265
• Time in Patent Office: 719 Days
• Field of Search: 382/141, 382/145, 382/147-149, 382/151-152, 382/312, 324/770, 345/904, 345/87, 345/103-104, 348/189
• US Class Current: 382/149
• CPC Class Codes: G02F 1/1309 Repairing; Testing
• CPC Class Codes: G06T 2207/30121 CRT, LCD or plasma display
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: H04N 17/04 for receivers
• CPC Class Codes: H04N 5/66 Transforming electric information into light information scanning details H04N3/00
• CPC Class Codes: Y10S 345/904 Display with fail/safe testing feature

Abstract

A method for inspecting a substrate having a plurality of output pixels using an image sensing device having a plurality of input pixels includes the steps of capturing an input image of a plurality of groups of output pixels with a plurality of groups of input pixels, each group of input pixels capturing a group of output pixels, each input pixel in a group of input pixels having a position, inhibiting modulation contributions from input pixels in the input image, forming a plurality of images from the plurality of groups of input pixels in the input image, each image including input pixels from a similar position in each group of input pixels, detecting defects in each of the plurality of images, and determining defects in sub-pixels of the substrate in response to the defects detected in each of the plurality of images.

Claims

1. A method for inspecting a substrate using an image sensing device, the substrate having a plurality of output pixels and the image sensing device having a plurality of input pixels, each of the plurality of output pixels comprising a plurality of sub-pixels, the method comprising the steps of:

capturing an image of at least a portion of the substrate with the image sensing device, the image including an image of a first group of output pixels as a first group image and the image including an image of a second group of output pixels as a second group image, a first group of input pixels of the image sensing device capturing the first group image, and a second group of input pixels of the image sensing device capturing the second group image;

comparing a first intensity value of the first group image, corresponding to a location of a first input pixel within the first group of input pixels, to a first intensity value of the second group image, corresponding to a location of a first input pixel within the second group of input pixels;

comparing a second intensity value of the first group image, corresponding to a location of a second input pixel within the first group of input pixels, to a second intensity value of the second group image, corresponding to a location of a second input pixel within the second group of input pixels; and

determining defects in sub-pixels in the first group of output pixels in response to the comparing steps.

2. The method of claim 1, further comprising the step of:

before the comparing steps, inhibiting modulation from the image.

3. The method of claim 1,

wherein the first group of input pixels is a foursome of input pixels capturing a first foursome image;

wherein the second group of input pixels is a foursome of input pixels capturing a second foursome image;

wherein the step of comparing the first intensity value comprises the step of;

comparing a first intensity value of the first foursome image, corresponding to a location of a first input pixel within the first foursome of input pixels, to a first intensity value of the second foursome image, corresponding to a location of a first input pixel within the second foursome of input pixels; and

wherein the step of comparing the second intensity value comprises the step of;

comparing a second intensity value of the first foursome image, corresponding to a location of a second input pixel within the first foursome of input pixels, to a second intensity value of the second foursome image, corresponding to a location of a second input pixel within the second foursome of input pixels.

4. The method of claim 3, wherein the first foursome of input pixels captures an image of approximately one output pixel.

5. The method of claim 1,

wherein the first group of input pixels is a group of nine input pixels capturing the first group image;

wherein the second group of input pixels is a group of nine input pixels capturing the second group image;

the method further comprising the step of;

comparing a third intensity value of the first group image, corresponding to a location of a third input pixel within the first group of input pixels, to a second intensity value of the second group image, corresponding to a location of a third input pixel within the second group of input pixels.

6. The method of claim 5, wherein the first group of input pixels captures an image of a group of four output pixels.

7. A liquid crystal display substrate inspected according to the method described in claim 1.

8. A method for inspecting a substrate for a liquid crystal display using an image sensing device, the substrate having a plurality of output pixels and the image sensing device having a plurality of input pixels, each of the plurality of output pixels including a plurality of sub-pixels, the method comprising the steps of:

a) capturing an input image of at least a portion of the substrate with the image sensing device, the input image including a first group image comprising an image of a first group of output pixels and the input image including a second group image comprising an image of a second group of output pixels, a first group of input pixels of the image sensing device capturing the first group image, and a second group of input pixels of the image sensing device capturing the second group image, each input pixels in the first and second group of input pixels having respective locations;

b) inhibiting modulation contributions from the input image;

thereafter

c) forming a first subsampled image by sampling a first intensity value of the first group image and a first intensity value of the second group image, the first intensity values corresponding to respective locations of first pixels within the first and the second group of input pixels;

d) forming a second subsampled image by sampling a second intensity value of the first group image and a second intensity value of the second group image, the second intensity values corresponding to respective locations of second pixels within the first and the second group of input pixels;

e) determining defects in sub-pixels in the portion of the substrate in response to variations in the first intensity values in the first subsampled image and to variations in the second intensity values in the second subsampled image.

9. The method of claim 8, wherein the step of inhibiting modulation contributions comprises the steps of:

performing a low-pass filter on the input image to form a background image; and

inhibiting the background image from the input image.

10. The method of claim 8, wherein the step of inhibiting modulation contributions comprises the step of:

performing a high-pass filter on the input image.

11. The method of claim 8, wherein the first group of input pixels is a foursome of input pixels capturing a first foursome image;

wherein the second group of input pixels is a foursome of input pixels capturing a second foursome image;

wherein the step of forming a first subsampled image comprises the step of;

forming a first subsampled image by sampling a first intensity value of the first foursome image and a first intensity value of the second foursome image, the first intensity values corresponding to respective locations of first pixels within the first and the second foursomes of input pixels; and

wherein the step of forming a second subsampled image comprises the step of;

forming a second subsampled image by sampling a second intensity value of the first foursome image and a second intensity value of the second foursome image, the second intensity values corresponding to respective locations of second pixels within the first and the second foursomes of input pixels.

12. The method of claim 11, wherein the first foursome of input pixels captures an image of one output pixel.

13. The method of claim 8, further comprising the steps of:

f) after step e), shifting the image sensing device relative to the substrate; and

g) repeating the steps a)-e).

14. The method of claim 13, wherein step f) occurs in a direction along a row of output pixels in the substrate.

15. The method of claim 13, wherein step f) occurs in a direction along a column of output pixels in the substrate.

16. The method of claim 13, wherein step f) includes shifting the image sensing device approximately one half of a input pixel relative to the substrate.

17. The method of claim 8, wherein the first group of input pixels is a group of nine input pixels capturing the first group image;

wherein the second group of input pixels is a group of nine input pixels capturing the second group image;

the method further comprising the step of;

forming a third subsampled image by sampling a third intensity value of the first group image and a third intensity value of the second group image, the third intensity values corresponding to respective locations of third pixels within the first and the second group of input pixels; and

wherein the step of determining defects in sub-pixels comprises the step of;

determining defects in sub-pixels in the portion of the substrate in response to variations in the first intensity values in the first subsampled image, variations in the second intensity values in the second subsampled image, and variations in the third intensity values in the third subsampled image.

18. The method of claim 17, wherein the first group of input pixels captures an image of a group of approximately four output pixels.

19. A computer system manufactured with a liquid crystal display substrate inspected according to the method described in claim 8.

20. A computer system for inspecting a substrate having a plurality of output pixels, each of the plurality of output pixels comprising a plurality of sub-pixels, the computer system comprising:

an image sensing device having a plurality of input pixels, for capturing an image of at least a portion of the substrate, the image including an image of a first group of output pixels as a first group image and the image including an image of a second group of output pixels as a second group image a first group of input pixels of the image sensing device capturing the first group image, and a second group of input pixels of the image sensing device capturing the second group image;

a comparator coupled to the image sensing device for comparing a first intensity value of the first group image, corresponding to a location of a first input pixel within the first group of input pixels, to a first intensity value of the second group image, corresponding to a location of a first input pixel within the second group of input pixels and for comparing a second intensity value of the first group image, corresponding to a location of a second input pixel within the first group of input pixels, to a second intensity value of the second group image, corresponding to a location of a second input pixel within the second group of input pixels; and

a determiner coupled to the comparator for determining defects in sub-pixels in the first group of output pixels in response to the comparator.

21. A computer system for inspecting a substrate for a liquid crystal display having a plurality of output pixels, each of the plurality of output pixels including a plurality of sub-pixels, the computer system comprising:

an image sensing device having a plurality of input pixels, for capturing an input image of at least a portion of the substrate, the input image including a first group image comprising an image of a first group of output pixels and the input image including a second group image comprising an image of a second group of output pixels a first group of input pixels of the image sensing device capturing the first group image, and a second group of input pixels of the image sensing device capturing the second group image, each input pixel in the first and second group of input pixels having respective locations;

inhibiting means coupled to the image sensing device for inhibiting modulation contributions from the input image;

thereafter

first forming means coupled to the inhibiting means for forming a first subsampled image by sampling a first intensity value of the first group image and a first intensity value of the second group image, the first intensity values corresponding to respective locations of first pixels within the first and the second group of input pixels;

second forming means coupled to the inhibiting means for forming a second subsampled image by sampling a second intensity value of the first group image and a second intensity value of the second group image, the second intensity values corresponding to respective locations of second pixels within the first and the second group of input pixels;

determining means coupled to the first forming means and the second forming means for determining defects in sub-pixels in the portion of the substrate in response to variations in the first intensity values in the first subsampled image and to variations in the second intensity values in the second subsampled image.

22. A computer system including a computer program and an image sensing device, for inspecting a substrate using the image sensing device, the substrate having a plurality output pixels and the image sensing device having a plurality of input pixels, each of the plurality of output pixels having a plurality of sub-pixels, the computer system further comprising:

a computer-readable memory including;

code that directs the image sensing device to capture an image of at least a portion of the substrate with the image sensing device, the image including an image of a first group of output pixels as a first group image and the image including an image of a second group of output pixels as a second group image a first group of input pixels of the image sensing device capturing the first group image, and a second group of input pixels of the image sensing device capturing the second group image;

code that compares a first intensity value of the first group image, corresponding to a location of a first input pixel within the first group of input pixels, to a first intensity value of the second group image, corresponding to a location of a first input pixel within the second group of input pixels;

code that compares a second intensity value of the first group image, corresponding to a location of a second input pixel within the first group of input pixels, to a second intensity value of the second group image, corresponding to a location of a second input pixel within the second group of input pixels; and

code that determines defects in sub-pixels in the first group of output pixels in response to the code that compares the first intensity value and the code that compares the second intensity value.

23. A computer system including a computer program for inspecting a substrate for a liquid crystal display using an image sensing device, the substrate having a plurality of output pixels and the image sensing device having a plurality of input pixels, each of the plurality of output pixels including a plurality of sub-pixels, the computer system further comprising:

a computer-readable memory including;

code that directs an image sensing device to capture an input image of at least a portion of the substrate with the image sensing device, the input image including a first group image comprising an image of a first group of output pixels and the input image including a second group image comprising an image of a second group of output pixels a first group of input pixels of the image sensing device capturing the first group image, and a second group of input pixels of the image sensing device capturing the second group image, each input pixel in the first and second group of input pixels having respective locations;

code that inhibits modulation contributions from the input image;

code that forms a first subsampled image by sampling a first intensity value of the first group image and a first intensity value of the second group image, the first intensity values corresponding to respective locations of first pixels within the first and the second group of input pixels;

code that forms a second subsampled image by sampling a second intensity value of the first group image and a second intensity value of the second group image, the second intensity values corresponding to respective locations of second pixels within the first and the second group of input pixels; and

code that determines defects in sub-pixels in the portion of the substrate in response to variations in the first intensity values in the first subsampled image and to variations in the second intensity values in the second subsampled image.