Apparatus and method for determining sparkle

• US 9,411,180 B2
• Filed: 01/20/2012
• Issued: 08/09/2016
• Est. Priority Date: 02/28/2011
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Gollier, Jacques, Hart, Shandon Dee, Piech, Garrett Andrew, West, James Andrew
• Primary Examiner(s): Miller, Daniel
• Application Number:
  US13/354,827
• Publication Number:
  US 20120221264A1
• Time in Patent Office: 1,663 Days
• Field of Search: 65/291.2, 324/760.01, 324/760.02, 345/207, 348/180, 702/81
• US Class Current: 1/1
• CPC Class Codes: G01J 1/18 using comparison with a reference electric value
• CPC Class Codes: G01J 1/4228 arrangements with two or more detectors, e.g. for sensitivity compensation
• CPC Class Codes: G01J 2001/4247 for testing lamps or other light sources
• CPC Class Codes: G02F 1/1309 Repairing; Testing
• CPC Class Codes: G02F 1/133502 Antiglare, refractive index matching layers

Abstract

An apparatus and method for determining and quantifying “sparkle”—the random noise that is generated when a pixelated image is viewed through a roughened surface of a transparent sample. The apparatus includes a pixelated source and an imaging system located in an optical path originating from the pixelated source, wherein a transparent sample may be placed in the optical path between the pixelated source and the optical system. The degree of sparkle is determined by obtaining an integrated image for the pixelated image; and calculating a standard deviation of the integrated pixel power. An objective level of sparkle can be defined by correlating the amount of sparkle provided by the apparatus with visual impressions.

Claims

1. An apparatus for measuring pixel power deviation of a transparent sample, the apparatus comprising:

a pixelated source, the pixelated source comprising a plurality of pixels, wherein each of the plurality of pixels has referenced indices i and j; and

an imaging system optically disposed along an optical path originating from the pixelated source, the imaging system comprising;

an imaging device receiving an image from the pixelated source through the transparent sample, the imaging device being disposed along the optical path; and

an aperture disposed on the optical path between the pixelated source and the imaging device, wherein the aperture has an adjustable collection angle for an image originating from the pixelated source,

wherein the imaging system determines boundaries between adjacent pixels of the plurality of pixels in the image, integrates within the boundaries to obtain an integrated total power for each of the plurality of source pixels in the image, and calculates the pixel power deviation of the transparent sample based on the integrated total powers.

2. The apparatus of claim 1, wherein the transparent sample is disposed in the optical path between the pixelated source and the aperture.

3. The apparatus of claim 2, further comprising at least one lens disposed in the optical path between the pixelated source and the transparent sample, and wherein the at least one lens forms an image of the pixelated source between the transparent sample and the at least one lens along the optical path.

4. The apparatus of claim 3, wherein the transparent sample is separated from the image of the pixelated source by a distance dz.

5. The apparatus of claim 2, wherein the transparent sample comprises a glass.

6. The apparatus of claim 5, wherein the glass is one of an alkali aluminosilicate glass and an alkali aluminoborosilicate glass.

7. The apparatus of claim 1, wherein the imaging device comprises a film camera.

8. The apparatus of claim 1, wherein the pixelated source is one of a LCD display, an OLED display, a DLP projector, and a LCOS projector.

9. The apparatus of claim 1, wherein the imaging device comprises a pixelated sensitive area comprising a second plurality of pixels, wherein each of the second plurality of pixels is referenced with indices m and n.

10. The apparatus of claim 9, wherein the plurality of pixels in the pixelated source forms a source image and the second plurality of pixels forms a second image, and wherein the source image is greater in spatial extent than the second image.

11. A method of determining pixel power deviation for a transparent sample, the method comprising:

acquiring, by an image device of an image display system, an image of the transparent sample combined with a pixelated source, the image comprising a plurality of source pixels;

determining, by the image display system, boundaries between adjacent source pixels in the image;

integrating, by the image display system, within the boundaries to obtain an integrated total power for each of the plurality of source pixels in the image; and

calculating, by the image display system, a dispersion of the integrated total power for each of the plurality of source pixels, wherein the dispersion is the pixel power deviation.

12. The method of claim 11, wherein the dispersion is a standard deviation of the power per source pixel normalized to an average power per source pixel.

13. The method of claim 11, wherein the step of acquiring an image of the transparent sample combined with the pixelated source comprises:

disposing the transparent sample in an optical path between a pixelated source and an imaging system;

transmitting an image from the pixelated source through the transparent sample;

receiving the image in the imaging system, wherein the imaging system generates a second image, the second image corresponding to the image transmitted through the transparent sample.

14. The method of claim 13, wherein the imaging system comprises a film camera.

15. The method of claim 13, wherein the imaging system comprises a pixelated sensitive area comprising a second plurality of pixels.

16. The method of claim 11, wherein the step of determining boundaries between adjacent pixels comprises:

determining a pitch of each pixel in the image of the pixelated source; and

determining a center position (i,j) for each pixel in the image of the pixelated source.

17. The method of claim 11, wherein the step of integrating within the boundaries to obtain the integrated total power for each of the plurality of source pixels comprises:

integrating power over a window centered on a source pixel center position with a window size corresponding to a source pixel pitch; and

calculating an integrated power per source pixel from the integrated power.

18. The method of claim 11, further comprising correlating the pixel power deviation with a visual impression of sparkle.

19. The method of claim 18, wherein correlating the pixel power deviation with the visual impression of sparkle comprises:

visually observing the pixelated image;

estimating the degree of sparkle; and

assigning a visual sparkle rating to the degree of sparkle.

20. The method of claim 11, wherein the pixelated source is one of a LCD display, an OLED display, a DLP projector, and a LCOS projector.

21. The method of claim 11, further comprising:

acquiring a first image of the pixelated source alone, the first image comprising a plurality of source pixels;

determining boundaries between adjacent source pixels in the first image;

integrating within the boundaries to obtain an integrated total power for each source pixel in the first image; and

calculating a dispersion of the integrated power per source pixel, wherein the standard deviation is the pixel power deviation of the first image.

22. The method of claim 21, further comprising obtaining the pixel power deviation of the transparent sample by subtracting the pixel power deviation of the first image from the pixel power deviation of the image of the transparent sample combined with the pixelated source.

23. The method of claim 11, wherein determining boundaries between adjacent source pixels in the image comprises:

determining a pixel pitch of the source pixels;

calculating a Fourier transform of the image;

identifying peaks in the Fourier transform associated with the pixel pitch and the pixel pitch in both horizontal and vertical directions; and

dividing the image into a plurality of sub-images, each of the plurality of sub-images containing a predetermined number of source pixels.

24. The method of claim 23, wherein the step of integrating within the boundaries to obtain an integrated total power for each source pixel in the image comprises:

calculating a vector V1 and local minima of V1, wherein V1 is equal to the sum of all lines in each of the plurality of sub-images;

defining a plurality of sub-matrices;

calculating a total energy power contained in each of the plurality of sub-matrices;

wherein the total energy power for each of the plurality of sub-matrices is stored a vector W 1;

normalizing the vector W1 to a mean value for the plurality of sub-images; and

transferring the vector W1 into a single vector W2, wherein the vector W2 contains all integrated images for all of the sub-images.