MULTI-IMAGING AUTOMATED INSPECTION METHODS AND SYSTEMS FOR WET OPHTHALMIC LENSES

• US 20090303465A1
• Filed: 06/05/2008
• Published: 12/10/2009
• Est. Priority Date: 06/05/2008
• Status: Active Grant

• Current Assignee: Coopervision International Limited (The Cooper Cos., Inc.)
• Original Assignee: Coopervision International Holding Company LP (The Cooper Cos., Inc.)
• Inventors: Clements, Julie Ann, Marsh, Jennifer Susan, Collier, Steven John
• Granted Patent: US 7,990,531 B2
• Time in Patent Office: Days
• US Class Current: 356/124
• CPC Class Codes: G01M 11/0235 by measuring multiple properties of lenses, automatic lens meters
• CPC Class Codes: G01M 11/0242 by measuring geometrical properties or aberrations
• CPC Class Codes: G01M 11/0278 Detecting defects of the object to be tested, e.g. scratches or dust investigating the presence of flaws or contamination on materials by optical means G01N21/88
• CPC Class Codes: G01N 2021/887 the measurements made in two or more directions, angles, positions
• CPC Class Codes: G01N 2021/8887 based on image processing techniques
• CPC Class Codes: G01N 2021/9511 Optical elements other than lenses, e.g. mirrors testing of optical apparatus in G01M11/00
• CPC Class Codes: G01N 2021/9583 Lenses
• CPC Class Codes: G01N 21/958 Inspecting transparent materials or objects, e.g. windscreens for conveyed flat sheet or rod G01N21/896
• CPC Class Codes: G01N 2201/062 LED's

Abstract

A method for inspecting lenses, especially wet contact lenses provided in a volume of liquid inside a container is described. A first image of the lens at a first position in the container is obtained, the lens then being moved to a second position within the container where a second image is obtained. A computer algorithm processes the first and second images to compare features that have moved with the lens to those features that have not moved with the lens whereby lenses are rejected if a feature has moved with the lens but is not a normal feature of the lens.

Claims

1. A method of inspecting an ophthalmic lens for defects, comprising:

providing an ophthalmic lens in a volume of liquid in a cavity of a container;

obtaining a first image of the ophthalmic lens at a first position in the container, the first image comprising the entire lens edge of the ophthalmic lens;

causing the ophthalmic lens to move from the first position in the container to a second position in the container;

obtaining a second image of the ophthalmic lens at the second position, the second image comprising the entire lens edge of the ophthalmic lens;

processing the first image and second image with a computer algorithm to locate features in the images;

generating a first lens edge profile from the first image;

generating a second lens edge profile from the second image;

determining the amount of movement of the lens from the first position to the second position by comparing the first lens edge profile and the second lens edge profile;

comparing the location of corresponding features located in the first and second images to distinguish features that have moved with the lens from features that have not moved with the lens based on the amount of movement of the lens determined by comparing the first and second lens edge profiles;

classifying a feature that has moved with the lens, and is not a normal lens feature, as a lens defect; and

rejecting the lens if the lens includes a pre-determined number of lens defects.

2. The method of claim 1, wherein the features comprise potential lens defects, and the first image and the second image are only compared when a potential lens defect is detected in both images.

3. The method of claim 1, wherein the step of causing the lens to move from the first position to the second position comprises causing movement of the lens relative to the container.

4. The method of claim 1, wherein the step of causing the lens to move from the first position to the second position comprises rotational lens movement or translational lens movement, or both.

5. The method of claim 1, wherein the step of causing the lens to move from the first position to the second position comprises rotating the container, vibrating the container, or both.

6. The method of claim 1, further comprising a step of thresholding the first and second images to locate the features in the images.

7. The method of claim 1, further comprising a step of identifying the lens edge in the first and second images and locating deviations from an expected lens edge shape, the deviations being identified as a potential lens defect.

8. The method of claim 1, wherein the container is in a first location when the first image is obtained and in a second, different location when the second image is obtained.

9. The method of claim 1, wherein the ophthalmic lens comprises an identification mark, and the identification mark is one of the features located in the first and second images.

10. The method of claim 9, wherein the lens comprises at least one additional feature other than the identification mark, and the movement of the additional feature is determined relative to the identification mark.

11. The method of claim 1, wherein the first and second images are obtained using at least one camera.

12. The method of claim 11, wherein the at least one camera includes a complementary metal oxide semiconductor (CMOS) integrated circuit, a charge-coupled device (CCD) array, or both for recording the images.

13. The method of claim 11, wherein the camera is arranged to have a depth of field sufficiently large to acquire an image in which both the lens edge and the lens surface are in focus simultaneously.

14. The method of claim 1, further comprising generating a bright field image of the ophthalmic lens with a light source.

15. The method of claim 14, further comprising producing collimated light from the light source with a collimating lens and directing the collimated light to a camera.

16. The method of claim 15, wherein the producing of the collimated light from the light source includes partially collimating the light with said collimating lens and then using the container, and the liquid in the container to complete collimation of the partially collimated light.

17. The method of claim 1, further comprising mapping the lens edge by calculating the radial distance around the circumference of the lens.

18. The method of claim 1, further comprising classifying a feature that moves by more than a minimum angular shift relative to the ophthalmic lens as a non-lens feature.

19. The method of claim 1, wherein the first and second lens edge profiles are generated using computer software.

20. The method of claim 1, further comprising providing a plurality of containers, each container comprising a single ophthalmic lens, and inspecting the plurality of lenses for defects simultaneously.

21. The method of claim 20, wherein the plurality of containers are provided in a linear arrangement.

22. An automated ophthalmic lens inspection system comprising:

a camera;

a light source;

a carrier capable of moving an ophthalmic lens in a lens container from a first position in the container to a second position, the camera being arranged to receive light from the light source via the lens carrier; and

a processing unit for receiving first and second lens images taken by the camera, the processing unit having a first processing module for detecting features in the images taken by the camera;

a second processing module for ascertaining movement of the lens by comparing a first lens edge profile generated from the first lens image and a second lens edge profile generated from the second lens image; and

a third processing module for comparing the movement of the features detected by the first processing module to the movement of the lens as ascertained by the second processing module.

23. A computer-implemented method for processing images obtained using an automated lens inspection system the method comprising:

loading a software onto a computer, the software comprising;

a first software module for causing the computer to detect features in first lens images and second lens images stored on the computer,

a second software module for causing the computer to ascertain movement of a lens by comparing a first lens edge profile generated from the first lens image and a second lens edge profile generated from the second lens image, and

a third software module for causing the computer to compare the movement of the features detected as a result of execution of the first software module to the movement of the lens as ascertained by the execution of the second software module; and

making a decision based on information obtained from at least one of the first software module the second software module, and the third software module.