Apparatus and method for detecting lens thickness

• US 20060132761A1
• Filed: 12/16/2005
• Published: 06/22/2006
• Est. Priority Date: 12/22/2004
• Status: Active Grant

• Current Assignee: Alcon Incorporated
• Original Assignee: Novartis Ag
• Inventors: Hall, William Jordan
• Granted Patent: US 7,433,027 B2
• Time in Patent Office: Days
• US Class Current: 356/244
• CPC Class Codes: G01M 11/02 Testing optical properties
• CPC Class Codes: G01M 11/0207 Details of measuring devices
• CPC Class Codes: G01M 11/0214 Details of devices holding the object to be tested

Abstract

The present invention relates to a non-contact/non-destructive method and apparatus for measuring the thickness of an ophthalmic lens. The present invention also provides a method for inspecting or measuring the base curve of a lens.

Claims

1. A device for presenting an ophthalmic lens for inspection comprising:

An illumination source in optical connection with;

an imaging system adapted to measure the distance of the lens;

a measurement chamber in optical connection with said illumination source and said imaging system;

a rotating fixture connected to said measurement chamber via an adapter; and

a seat in said measurement chamber adapted to support a sample lens, wherein said seat is rotated by the rotating fixture, and

wherein said device is adapted to measure the thickness of said ophthalmic lens.

2. The device of claim 1, wherein said imaging system further comprises a camera.

3. The device of claim 1, wherein said imaging system further comprises a digital image sensor.

4. The device of claim 3 wherein said digital image sensor is selected from the group consisting of a CCD and a CMOS based imaging technology.

5. The device of claim 1, wherein said imaging system further comprises a telecentric lens.

6. The device of claim 1, wherein said imaging system further comprises a non-telecentric lens.

7. The imaging system of claim 6 where the images have been calibrated to reduce optical errors selected from the group consisting of parallax, distortion, and magnification errors.

8. The device of claim 1, wherein said illumination source is selected from the group consisting of a collimated LED backlight, visible laser with a beam expander, laser diode, and a LED array

9. The device of claim 1, wherein said seat is dome-shaped.

10. The device of claim 1, wherein said seat has a surface selected from the group consisting of multiple radii, aspheric surfaces, and an arbitrary spline-based surface.

11. The device of claim 1, wherein said measurement chamber is adapted to contain a medium.

12. The device of claim 11, wherein said medium is saline.

13. The device of claim 1, wherein said rotating fixture further comprises a seal and a bearing that are connected to said measurement chamber via said adapter.

14. The device of claim 1, further comprising a magnetic coupling that connects said rotating fixture to said measurement chamber.

15. The device of claim 1, further comprising a vacuum line in fluid connection with said seat.

16. The device of claim 1, wherein said measurement chamber has at least one window.

17. The device of claim 1, wherein said seat is made of porous metal.

18. The device of claim 1, wherein said seat is made of a plastic or metal material with a series of drilled holes for creating a vacuum.

19. A method for measuring the thickness of an ophthalmic lens comprising:

Providing an illumination source, and imaging system and a measurement seat;

Taking one set of images comprising the steps of

Taking a first image of said measurement seat

Placing a sample lens on said measurement seat

Taking a second image of said lens on said measurement seat; and

Subtracting the first image from the second image to obtain a thickness measurement.

20. The method of claim 19, further comprising providing a measurement chamber.

21. The method of claim 19, further comprising providing a rotating fixture.

22. The method of claim 19, further comprising taking more than one set of images.

23. The method of claim 19, further comprising transforming said images into numerical data.

24. The method of claim 23, further comprising analyzing said data.

25. The method of claim 23, further comprising archiving said data.

26. A method for measuring the thickness of an ophthalmic lens comprising:

Providing an illumination source, an imaging system, a measurement chamber and a measurement seat;

Calibrating the illumination source, imaging system, measurement chamber, and measurement seat;

Filling the measurement chamber with a medium;

Taking one set of images comprising the steps of

Finding the edge contour of the measurement seat

Taking a first image of said measurement seat

Activating a vacuum pump;

Placing a sample lens on said measurement seat

Finding the edge contour of said sample lens

Taking a second image of said lens on said measurement seat;

Subtracting the first image from the second image to obtain a thickness measurement; and

Converting the thickness measurement to a three-dimensional thickness profile.

27. The method of claim 26 further comprising:

obtaining the front curve geometry of a sample lens, and

offsetting said front curve measurement by said thickness measurement to obtain the base curve surface.

28. A system comprising:

An illumination source in optical connection with an imaging system;

an imaging system adapted to measure the distance to said lens;

a measurement chamber in optical connection with said illumination source and said imaging system;

a rotating fixture connected to said measurement chamber via an adapter; and

a seat in said measurement chamber adapted to support a sample lens, wherein illumination source illuminates said sample lens to allow said imaging system to locate said lens and measure the thickness of said lens.

29.