Method and apparatus for determining the optical properties of a lens

• US 5,301,004 A
• Filed: 03/13/1992
• Issued: 04/05/1994
• Est. Priority Date: 03/13/1992
• Status: Expired due to Fees

• Current Assignee: Reichert, Inc. (Ametek Incorporated)
• Original Assignee: Leica Incorporated (Danaher Corporation)
• Inventors: Luce, David A., Percival, Christopher J.
• Primary Examiner(s): Rosenberger, Richard A.
• Application Number:
  US07/850,890
• Time in Patent Office: 753 Days
• Field of Search: 356/124, 356/125, 356/127
• US Class Current: 356/125
• CPC Class Codes: G01M 11/0235 by measuring multiple properties of lenses, automatic lens meters

Abstract

Optical properties of a lens, including localized defects, are determined by analyzing the refracted image produced by transmitting a beam of light through an aperture and a lens to be tested. The image is reflected onto a light sensitive detecting surface. Information obtained from the light detecting surface is digitized and sent to an Image Processing Unit which calculates the optical properties of the lens. The aperture may consist of a single shaped opening or alternatively a plurality of concentric, annular rings. Correction lenses may be employed, either permanently or selectively, to alter the refracted beam before the beam intersects the detecting surface.

Claims

1. A device without a moving part for determining optical properties of a lens comprising, means to project a beam of light along a path having an axis, a test plane located on said path, an occluder having a single shaped opening defined by a single border positioned on said path, area detection means responsive to light received from said shaped opening for providing a signal representative of light distribution on said detection means, evaluation means for converting said signal to values representing the optical properties of a lens located at said test plane, and means to report said values.

2. The device according to claim 1, further including a modifying lens between said test plane and said area detection means for adjusting the light distribution on said area detection means.

3. The device according to claim 2, wherein said modifying lens is selectively positionable on said path for adjusting the light distribution on said area detection means.

4. The device according to claim 1, wherein said signal represents the size and shape of light distribution on said detection means.

5. The device according to claim 4, wherein said reporting means reports sphere, cylinder and axis values of a tested lens.

6. The device according to claim 4, wherein said reporting means reports the deviation from a true sphero-cylindrical lens.

7. The device according to claim 1, wherein said signal represents the size, shape and location of light distribution on said detection means.

8. The device according to claim 7, wherein said reporting means reports sphere, cylinder, axis and prism values of a tested lens.

9. The device according to claim 1, wherein said evaluation means includes a central processing unit.

10. The device according to claim 1, wherein said means to project a beam of light along a path includes a light source and a pin hole occluder.

11. The device according to claim 1, wherein said means to project a beam of light along a path includes a collimated light source.

12. The device according to claim 11, wherein said means to project a beam of light along a path includes a laser.

13. The device according to claim 11, wherein said area detection means includes a charge injection device or a charge couple device.

14. The device according to claim 1, wherein said area detection means includes a charge injection device or a charge couple device.

15. The device according to claim 1, wherein said reporting means includes a visual display.

16. The device according to claim 15, wherein said reporting means displays the deviation from a true sphero-cylindrical lens.

17. The device according to claim 1, further including memory means for storing reference information and said signal is representative of the size and shape of light distribution on said detector.

18. The device according to claim 17, wherein said memory means stores information representative of said occluder diameter and the distance between said test plane and said detection means.

19. The device according to claim 18, wherein said memory means stores reference information representative of the size and shape of said beam on said detection means without a lens in said test plane.

20. The device according to claim 18, wherein said memory means stores information representative of the size, shape and location of said beam on said detection means without a lens in said test plane.

21. The device according to claim 20, further including means to automatically determine the size and shape of the beam and store said reference information each time said device is turned on.

22. The device according to claim 18, wherein said memory means stores information representative of the size, shape and intensity of said beam on said detection means without a lens in said test plane.

23. The device according to claim 18, wherein said memory means stores information representative of the size, shape and intensity of said beam on said detection means with a lens in said test plane.

24. The device according to claim 23, wherein said local intensity of said beam on said detection means is used to detect defects in said lens.

25. The device according to claim 1, wherein said shaped opening is in the shape of an ellipse.

26. The device according to claim 1, wherein said single shaped opening is a pinhole aperture.

48. The device according to claim 13, wherein said memory means stores information representative of the size, shape and local intensity of said beam on said detection means with a lens in said test plane.

49. The device according to claim 48, wherein said local intensity of said beam on said detection means is used to detect defects in said lens.

27. An instrument for determining the optical properties of a lens comprising, an illumination source, a path extending from said source, means for projecting a beam of light along said path, a test plane located on said path, area detection means for receiving light from said test plane and producing a first signal representing the size and shape of light distribution on said detection means, means for producing an edge coordinate signal from said first signal utilizing an edge determining algorithm, evaluation means for comparing said edge coordinate signal to a reference signal and converting a difference between said signals to values indicating optical properties of a lens located at said test plane, and means to report said values.

28. The device according to claim 27 further including a modifying lens between said test plane and said area detection means for adjusting the light distribution on said area detection means.

29. The device according to claim 28, wherein said modifying lens is selectively positionable on said path for adjusting the light distribution on said area detection means.

30. The device according to claim 27, wherein said first signal represents the size, shape and location of light distribution on said detection means.

31. The device according to claim 30, wherein said reporting means reports sphere, cylinder, axis and prism values of a tested lens.

32. The device according to claim 27, wherein said evaluation means includes a central processing unit.

33. The device according to claim 27, wherein said means to project a beam of light along a path includes a light source and a pin hole occluder.

34. The device according to claim 27, wherein said means to project a beam of light along a path includes a collimated light source.

35. The device according to claim 34, wherein said means to project a beam of light along a path includes a laser.

36. The device according to claim 27, wherein said area detection means includes a charge injection device or a charge couple device.

37. The device according to claim 27 wherein said signal represents the size and shape of light distribution on said detection means.

38. The device according to claim 37, wherein said reporting means reports the deviation from a true sphero-cylindrical lens.

39. The device according to claim 27, wherein said reporting means includes a visual display.

40. The device according to claim 39, wherein said reporting means displays the deviation from a true sphero-cylindrical lens.

41. The device according to claim 27, wherein said reporting means reports sphere, cylinder and axis values of a tested lens.

42. The device according to claim 27, further including memory means for storing reference information and said signal is representative of the size and shape of light distribution on said detector.

43. The device according to claim 42, wherein said memory means stores information representative of the distance between said test plane and said detection means.

44. The device according to claim 43, wherein said memory means stores reference information representative of the size and shape of said beam on said detection means without a lens in said test plane.

45. The device according to claim 43, wherein said memory means stores information representative of the size, shape and location of said beam on said detection means without a lens in said test plane.

46. The device according to claim 45, further including means to automatically determine the size and shape of the beam and store said reference information each time said device is turned on.

47. The device according to claim 43, wherein said memory means stores information representative of the size, shape and local intensity of said beam on said detection means without a lens in said test plane.

50. The instrument according to claim 27, further comprising an occluder having an aperture positioned on said path.

51. A method of determining optical properties of a lens which comprises,

projecting a collimated beam of light through a test plane onto an occluder having a central shaped opening,

producing a first signal representative of the size and shape of a detector area illuminated by a small bundle of rays passing through said shaped opening,

processing said first signal utilizing an edge determining algorithm to produce an edge coordinate reference signal,

storing said reference signal,

placing a lens to be evaluated at said test plane to refract said beam,

producing a second signal representative of the size and shape of said detector area illuminated by another bundle of rays from said refracted beam passing through said shaped opening,

processing said second signal utilizing an edge determining algorithm to produce an edge coordinate test signal,

comparing said reference and test signals to determine optical properties of said lens, and

reporting said properties.

52. The method according to claim 51, wherein said optical properties are sphere, cylinder and axis values of said lens.

53. A method of determining optical properties of a lens which comprises,

projecting a collimated beam of light first through an occluder having a central shaped opening, then through a test plane,

producing a first signal representative of the size, shape and location of a detector area illuminated by a bundle or rays passing through said shaped opening,

processing said first signal utilizing an edge determining algorithm to produce an edge coordinate reference signal,

storing said reference signal,

placing a lens to be evaluated at said test plane to refract said beam,

producing a second signal representative of the size, shape and location of said detector area illuminated by another bundle of rays from said refracted beam passing through said shaped opening,

processing said second signal utilizing an edge determining algorithm to produce an edge coordinate test signal,

comparing said reference and test signals to determine optical properties of said lens, and

reporting said properties.

54. The method according to claim 53, wherein said optical properties are sphere, cylinder, axis and prism values of said lens.

55. A method of determining the optical properties of a lens which comprises,

A) projecting a beam of light through a test lens to provide a refracted beam of light,

B) illuminating an area detector having a plurality of rows, each row containing a plurality of pixels, with said refracted beam,

C) scanning each row of pixels to produce a digitized signal representative of crude physical parameters representing the size and shape of said illuminated area,

D) processing said digitized signal using an edge determining algorithm to produce a digitized edge coordinate signal,

E) converting said digitized edge coordinate signal into enhanced physical parameters representing the size, shape and location of said illuminated area, and

F) calculating optical properties of said lens using said enhanced physical parameters.

56. The method according to claim 55, wherein said edge determining algorithm includes convolving said digitized signal with an operator described by the equation:

##EQU14## to produce an image zero series of digital signal parameters, convolving said image zero parameters with the following operator;

space="preserve" listing-type="tabular">______________________________________ -1 0 1 -1 0 1 -1 0 1 ______________________________________

to form an image one series of digital signal parameters, convolving said image zero parameters with the following operator;

space="preserve" listing-type="tabular">______________________________________ -1 -1 -1 0 0 0 1 1 1 ______________________________________

to form an image two series of digital signal parameters, calculating an image three series of digital signal parameters using the relationship ##EQU15## where p₃, p₂, and p₁ correspond to digital signals from the pixels of said image three, image two, and image one, respectively, and processing said image three parameters using grey-level skeleton image processing.