Methods and Apparatus for Facilitating Elimination of Ambient Light from an Image

• US 20100111381A1
• Filed: 11/06/2008
• Published: 05/06/2010
• Est. Priority Date: 11/06/2008
• Status: Active Grant

• Current Assignee: Bausch & Lomb Incorporated (Bausch Health Cos., Inc.)
• Original Assignee: Bausch & Lomb Incorporated (Bausch Health Cos., Inc.)
• Inventors: Zhang, Ning, Allred, Lloyd G., Eagan, Barry T., McBeth, Jeffrey B.
• Granted Patent: US 8,295,635 B2
• Time in Patent Office: Days
• US Class Current: 382/128
• CPC Class Codes: A61B 3/135 Slit-lamp microscopes
• CPC Class Codes: G06T 2207/30041 Eye; Retina; Ophthalmic
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06V 40/19 Sensors therefor

Abstract

An apparatus for facilitating elimination of ambient light from an image of an object, comprising an illumination apparatus adapted to sequentially illuminate the object using multiple lighting arrangements, an image sensor. The apparatus adapted to form on the image sensor (i) a first image of the object using a first illumination arrangement, (ii) a second image of the object using a second illumination arrangement, and (iii) a dark image of the object without illumination. The image sensor is adapted to A) compare an intensity value of a first pixel in the first image to an intensity value of a corresponding, first pixel in the second image to determine a first minimum intensity value, B) determine if the first minimum intensity value is greater than an intensity value of a corresponding, first pixel in the dark image by greater than a predetermined amount; and C) identify an ambient intensity value (a) as the first minimum intensity value, if the first minimum intensity value is not greater than the intensity value of the first pixel in the dark image by greater than the predetermined amount, or (b) as the intensity value of the first pixel in the dark image, if the first minimum intensity value is greater than the intensity value of the first pixel in the dark image by greater than the predetermined amount.

Claims

1. A method of facilitating elimination of ambient light from an image, comprising:

A) obtaining a first image of an object using a first illumination arrangement;

B) obtaining a second image of the object using a second illumination arrangement;

C) obtaining a dark image without illumination;

D) comparing an intensity value of a first pixel in the first image to an intensity value of a corresponding, first pixel in the second image to determine a first minimum intensity value;

E) determining if the first minimum intensity value is greater than an intensity value of a corresponding, first pixel in the dark image by greater than a predetermined amount; and

F) identifying an ambient intensity value (a) as the first minimum intensity value, if the first minimum intensity value is not greater than the intensity value of the first pixel in the dark image by greater than the predetermined amount, or (b) as the intensity value of the first pixel in the dark image, if the first minimum intensity value is greater than the intensity value of the first pixel in the dark image by greater than the predetermined amount.

2. The method of claim 1, wherein the first illumination arrangement is achieved using a first slit arrangement and the second illumination arrangement is achieved using a second slit arrangement.

3. The method of claim 2, wherein the first illumination arrangement and the second illumination arrangement are achieved by selectively illuminating multiple slit projectors.

4. The method of claim 2, wherein the first illumination arrangement and the second illumination arrangement are achieved by selectively positioning one or more slit masks.

5. The method of claim 4, wherein the selective positioning comprises at least one of translation and rotation of the one or more slit masks.

6. The method of claim 1, further comprising subtracting an intensity value equal to the ambient intensity value from one or both of the first pixel in the first image and the first pixel in the second image.

7. The method of claim 1, wherein the first image and the second image constitute two images of a plurality of images of an eye, the method further comprising combining the plurality of images to produce a two-dimensional or a three-dimensional representation of the eye.

8. The method of claim 1, further comprising a step of performing a perspective transform on at least one of the first image and the second image prior to step D).

9. The method of claim 1, further comprising:

G) comparing an intensity value of a second pixel in the first image to an intensity value of a corresponding, second pixel in the second image to determine a second minimum intensity value;

H) determining if the second minimum intensity value is greater than an intensity value of a corresponding, second pixel in the dark image by greater than a second predetermined amount; and

I) identifying an ambient intensity value (a) as the second minimum intensity value, if the second minimum intensity value is not greater than the intensity value of the second pixel in the dark image by greater than the predetermined amount, or (b) as the intensity value of the second pixel in the dark image, if the second minimum intensity value is greater than the intensity value of the second pixel in the dark image by greater than a second predetermined amount.

10. An apparatus for facilitating elimination of ambient light from an image of an object, comprising:

an illumination apparatus adapted to sequentially illuminate the object using a first lighting arrangement and a second lighting arrangement;

an image sensor, the apparatus adapted to form on the image sensor (i) a first image of the object using the first illumination arrangement, (ii) a second image of the object using the second illumination arrangement, and (iii) a dark image of the object without illumination; and

a processor coupled to the image sensor adapted to—

A) compare an intensity value of a first pixel in the first image to an intensity value of a corresponding, first pixel in the second image to determine a first minimum intensity value,

B) determine if the first minimum intensity value is greater than an intensity value of a corresponding, first pixel in the dark image by greater than a predetermined amount; and

C) identify an ambient intensity value (a) as the first minimum intensity value, if the first minimum intensity value is not greater than the intensity value of the first pixel in the dark image by greater than the predetermined amount, or (b) as the intensity value of the first pixel in the dark image, if the first minimum intensity value is greater than the intensity value of the first pixel in the dark image by greater than the predetermined amount.

11. The apparatus of claim 10, wherein the illumination apparatus comprises one or more slit masks configured to achieve the first illumination arrangement and the second illumination arrangement.

12. The apparatus of claim 10, wherein the illumination apparatus comprises a plurality of slit projectors adapted to be selectively illuminated to achieve the first slit arrangement and the second slit arrangement.

13. The apparatus of claim 10, wherein the illumination apparatus comprises one or more slit projectors adapted to be selectively positioned to achieve the first slit arrangement and the second slit arrangement.

14. The apparatus of claim 13, wherein the one or more slit projectors are adapted to be translated to achieve the first slit arrangement and the second slit arrangement.

15. The apparatus of claim 13, wherein the one or more slit projectors are adapted to be rotated to achieve the first slit arrangement and the second slit arrangement.

16. The apparatus of claim 13, wherein the processor is adapted to subtract an intensity value equal to the ambient intensity value from one or both of the first pixel in the first image and the first pixel in the second image.

17. The apparatus of claim 13, wherein the apparatus is adapted to obtain a plurality of images of an eye, the first image and the second image constituting two images of the plurality of images, and wherein the processor is adapted to combine the plurality of images to produce a two-dimensional or a three-dimensional representation of the eye.

18. The apparatus of claim 13, wherein the processor is adapted to perform a perspective transform on at least one of the first image and the second image prior to the comparing of the intensity value of the first pixel in the first image to the intensity value of the corresponding, first pixel in the second image to determine the first minimum intensity value.

19. The apparatus of claim 13, wherein the processor is adapted to—

E) compare an intensity value of a second pixel in the first image to an intensity value of a corresponding, second pixel in the second image to determine a second minimum intensity value,

F) determine if the second minimum intensity value is greater than an intensity value of a corresponding, second pixel in the dark image by greater than a second predetermined amount; and

G) identify an ambient intensity value (a) as the second minimum intensity value, if the second minimum intensity value is not greater than the intensity value of the second pixel in the dark image by greater than the second predetermined amount, or (b) as the intensity value of the second pixel in the dark image, if the second minimum intensity value is greater than the intensity value of the second pixel in the dark image by greater than the second predetermined amount.

20. The apparatus of claim 10, wherein the processor is adapted to interpolate intensity values in the first image prior to comparison of an intensity value of the pixel in the first image to the intensity value of the corresponding, first pixel in the second image to determine the first minimum intensity value

21. The apparatus of claim 20, wherein the image sensor is an interlaced image sensor and the first image and the second image constitute interlaced images.