DEVICE FOR INSPECTING DISPLAY DEVICE AND INSPECTING METHOD THEREOF

• US 20200134802A1
• Filed: 10/28/2019
• Published: 04/30/2020
• Est. Priority Date: 10/30/2018
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: YEUM, Jong-Hoon
• Granted Patent: US 11,164,305 B2
• Time in Patent Office: Days
• CPC Class Codes: G06T 2207/30121 CRT, LCD or plasma display
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: G06T 7/001 using an image reference approach
• CPC Class Codes: G06T 7/50 Depth or shape recovery
• CPC Class Codes: G06T 7/60 Analysis of geometric attributes
• CPC Class Codes: G06T 7/62 of area, perimeter, diameter or volume
• CPC Class Codes: G06T 7/70 Determining position or orientation of objects or cameras camera calibration G06T7/80
• CPC Class Codes: H04N 25/71 Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors

Abstract

A device for inspecting a display device includes a camera to photograph a substrate and generate image information, a pixel value setter to set pixel values corresponding to respective luminances of a plurality of pixels from the image information, and to detect a crack region based on the pixel values, a stress calculator to calculate a critical stress of a crack included in the crack region, and a determiner to check whether the critical stress is equal to or greater than a first threshold value and to determine whether the substrate has defects. The stress calculator calculates a critical stress of the substrate by using fracture toughness, a shape factor, and a crack depth. The shape factor is set to increase as a compressive stress of the substrate increases.

Claims

1. A device for inspecting a display device, the device comprising:

a camera to photograph a substrate and generate image information;

a pixel value setter to set pixel values corresponding to respective luminances of a plurality of pixels from the image information, and to detect a crack region based on the pixel values;

a stress calculator to calculate a critical stress of a crack included in the crack region; and

a determiner to check whether the critical stress is equal to or greater than a first threshold value and to determine whether the substrate has defects,

wherein;

the stress calculator calculates a critical stress of the substrate by using fracture toughness, a shape factor, and a crack depth, and

the shape factor is set to increase as a compressive stress of the substrate increases.

2. The device for inspecting a display device as claimed in claim 1, wherein the shape factor is greater than 1.1 and equal to or less than 1.3.

3. The device for inspecting a display device as claimed in claim 1, wherein when the substrate is a tempered glass substrate, the shape factor is 1.2.

4. The device for inspecting a display device as claimed in claim 1, further comprising an image storage unit for storing the image information.

5. The device for inspecting a display device as claimed in claim 1, wherein the camera includes a CCD camera including a predetermined number of pixels.

6. The device for inspecting a display device as claimed in claim 5, wherein the plurality of pixels for which the pixel value setter sets pixel values corresponds to the predetermined number of pixels included in the camera.

7. The device for inspecting a display device as claimed in claim 1, wherein the pixel value setter sets a first value to a pixel having luminance that is equal to or greater than a reference luminance, sets a second value to a pixel having luminance that is less than the reference luminance, and categorizes a pixel to which the second value is set to be the crack region.

8. The device for inspecting a display device as claimed in claim 7, wherein

the pixel value setter categorizes a length in which pixels having the pixel value of the second value continue in one direction as being a crack length, and categorizes a portion in which pixels having the pixel value of the second value continue on respective sides in the one direction as being a range of a lateral crack, and

the stress calculator determines the crack depth corresponding to at least one of the crack length and the range of a lateral crack.

9. The device for inspecting a display device as claimed in claim 8, wherein the stress calculator determines the crack depth from a lookup table that provides a crack depth corresponding to a crack length and a range of a lateral crack.

10. The device for inspecting a display device as claimed in claim 1, wherein the pixel value setter sets pixel values to the pixels, compares a pixel values for respective lines that are a summation of the pixel values for respective rows or columns of pixels with a reference pixel value, and detects the crack region.

11. A method for inspecting a display device, the method comprising:

photographing a substrate to generate image information;

setting pixel values corresponding to respective luminances of a plurality of pixels in the image information;

detecting a crack region based on the pixel values, and detecting a crack length for the crack region to continue in one direction;

determining a crack depth corresponding to the crack length;

calculating a critical stress of the substrate based on the crack depth; and

checking whether the critical stress is equal to or greater than a first threshold value to determine whether the substrate has defects.

12. The method for inspecting a display device as claimed in claim 11, wherein the critical stress of the substrate is calculated by using fracture toughness, a shape factor, and the crack depth, and

the shape factor increases as a compressive stress of the substrate increases.

13. The method for inspecting a display device as claimed in claim 12, wherein when the substrate is a tempered glass substrate, the shape factor is 1.2.

14. The method for inspecting a display device as claimed in claim 11, further comprising storing the image information.

15. The method for inspecting a display device as claimed in claim 11, wherein the substrate is photographed by a CCD camera including a predetermined number of pixels.

16. The method for inspecting a display device as claimed in claim 15, wherein the plurality of pixels to which the pixel value is set correspond to a plurality of pixels included in the CCD camera.

17. The method for inspecting a display device as claimed in claim 11, wherein a first value is set to a pixel having a luminance that is equal to or greater than a reference luminance, and a second value is set to a pixel having a luminance that is less than the reference luminance to set pixel values corresponding to respective luminances of the pixels.

18. The method for inspecting a display device as claimed in claim 17, wherein a pixel to which the second value is set is detected as the crack region.

19. The method for inspecting a display device as claimed in claim 18, wherein a length in which pixels having pixel values of the second value continue in one direction is categorized to be the crack length.

20. The method for inspecting a display device as claimed in claim 19, further comprising

detecting a portion in which pixels having the pixel value of the second value continue on respective sides in the one direction to be a range of a lateral crack,

wherein the crack depth is determined corresponding to at least one of the crack length and the range of the lateral crack.