Apparatus and method for projecting laser pattern with reduced speckle noise

• US 5,621,529 A
• Filed: 04/05/1995
• Issued: 04/15/1997
• Est. Priority Date: 04/05/1995
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: Intelligent Automation Systems, Inc. (Azenta, Inc.)
• Inventors: Benayad-Cherif, Faycal E. K., Gordon, Steven J.
• Primary Examiner(s): Gonzalez, Frank
• Assistant Examiner(s): MERLINO, AMANDA H
• Application Number:
  US08/418,142
• Time in Patent Office: 741 Days
• Field of Search: 356/376, 356/371, 356/354, 250/237 G
• US Class Current: 356/604
• CPC Class Codes: G01B 11/00 Measuring arrangements characterised by the use of optical techniques
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G03F 7/70583 Speckle reduction, e.g. coherence control or amplitude/wavefront splitting
• CPC Class Codes: G03F 9/70 for microlithography measuring printed patterns for monitoring overlay G03F7/70633 or focus G03F7/70641; projection system adjustment G03F7/70258; position control G03F7/70775
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light

Abstract

An illuminating apparatus is for use with a visual sensory apparatus, for projecting a light pattern onto a surface to be viewed by the sensory apparatus. The illuminating apparatus comprises: a light source; a patterniser for constraining light emitted from the source to produce on the surface, a light pattern having a light interface, the interface having an extended dimension. The light pattern is caused to move relative to the surface, parallel to the extended dimension of the light interface. The pattern may comprise a plurality of extended straight line interfaces, each interface being parallel to the other interfaces of the plurality. Rather than straight, the plurality may be circular and concentric. Rather than a plurality, the pattern may comprise a single straight line or circular light interface. The motion of the light pattern relative to the surface minimizes any speckle pattern that might arise from optical interference, below the degree of speckle that would be presence if the pattern were not moving. The pattern may be made to move by moving the light source, or a mirror or prism interposed in the optical path from the light source to the surface.

Claims

1. An illuminating apparatus for use with a visual sensory apparatus, for projecting a light pattern onto a surface to be viewed by said sensory apparatus, said surface having a characteristic roughness, said illuminating apparatus comprising:

a. a light source;

b. means for constraining light emitted from said source to produce on said surface, a light pattern having a light interface, said interface having an extended dimension; and

c. means for causing said light pattern to move relative to said surface, parallel to said extended dimension of said light interface.

2. The illuminating apparatus of claim 1, said visual sensory apparatus having a characteristic exposure interval, said means for causing said light pattern to move comprising means for causing a locus of said light pattern to move a sufficient distance relative to the surface during an exposure interval so as to reduce the degree of appearance of any interference speckle, as compared to the degree of appearance of speckle that would arise without relative motion between the light pattern and the surface.

3. The illuminating apparatus of claim 1 said light pattern comprising a plurality of extended straight line interfaces, each interface being parallel to the other interfaces of said plurality.

4. The illuminating apparatus of claim 3, said means for causing said light pattern to move comprising means for moving said light source parallel to said plurality of straight line interfaces.

5. The illuminating apparatus of claim 3, said means for causing said light pattern to move, comprising a moving mirror, located and constrained to move such that light projected onto said mirror is reflected onto said surface and said light pattern moves across said surface parallel to said plurality of parallel straight line interfaces.

6. The illuminating apparatus of claim 3, said means for causing said light pattern to move, comprising a moving prism, located and constrained to move such that light projected onto said prism is transmitted onto said surface and said light pattern moves across said surface parallel to said plurality of parallel straight line interfaces.

7. The illuminating apparatus of claim 1, said light pattern consisting of one interface having as its extended interface dimension a straight line.

8. The illuminating apparatus of claim 3, said light pattern comprising a relatively lighter region sandwiched between two relatively darker regions.

9. The illuminating apparatus of claim 1, said light pattern comprising a plurality of concentric circular light interfaces, each having an axis that is coaxial with the axes of the remaining of said plurality of circular light interfaces.

10. The illuminating apparatus of claim 9, said means for causing said light pattern to move comprising means for rotating said light source around an axis that coincides with said axes of said plurality of concentric light interfaces.

11. The illuminating apparatus of claim 9, said means for causing said light pattern to move, comprising a moving mirror, located and constrained to move such that light projected onto said mirror is reflected onto said surface and said light pattern rotates over said surface around said axes of said plurality of concentric circular light interface.

12. The illuminating apparatus of claim 5, said mirror constrained to rotate around an axis.

13. The illuminating apparatus of claim 5, said mirror constrained to move in a reciprocating pattern around a rest position.

14. The illuminating apparatus of claim 1, said light pattern consisting of one circular light interface.

15. The illuminating apparatus of claim 9, said means for causing said light pattern to move, comprising a moving prism, located and constrained to move such that light projected onto said prism is transmitted onto said surface and said light pattern rotates over said surface around said axes of said plurality of concentric circular light interfaces.

16. An apparatus for registering the configuration of a surface extending over a portion of a viewing field, said surface having a characteristic roughness, said apparatus comprising:

a. means for projecting a light pattern onto said surface, said projection means comprising;

i. a light source;

ii. means for constraining light emitted from said source to produce, on said surface, a light pattern having a plurality of light interfaces spaced from each other, said light interfaces being extended and parallel to each other; and

iii. means for causing said light pattern to move relative to said surface, parallel to the extended dimension of said lighted interfaces; and

b. a visual sensory apparatus that views said projected pattern of light interfaces, said sensory apparatus having a characteristic exposure interval and being located so that said projected pattern is visible to said sensory apparatus.

17. The configuration registering apparatus of claim 16, said light pattern comprising a plurality of extended straight line interfaces, each interface being parallel to the other interfaces of said plurality.

18. The configuration registering apparatus of claim 17, said means for causing said light pattern to move comprising means for moving said light source parallel to said plurality of straight line interfaces.

19. The configuration registering apparatus of claim 17, said means for causing said light pattern to move, comprising a moving mirror, located and constrained to move such that light projected onto said mirror is reflected onto said surface and said light pattern moves across said surface parallel to said plurality of parallel straight line interfaces.

20. The configuration registering apparatus of claim 17, said means for causing said light pattern to move, comprising a moving prism, located and constrained to move such that light projected onto said prism is transmitted onto said surface and said light pattern moves across said surface parallel to said plurality of parallel straight line interfaces.

21. The configuration registering apparatus of claim 16, said light pattern comprising a plurality of concentric circular light interfaces, each having an axis that is coaxial with the axes of the remaining of said plurality of circular light interfaces.

22. The configuration registering apparatus of claim 21, said means for causing said light pattern to move comprising means for rotating said light source around an axis that coincides with said axes of said plurality of concentric light interfaces.

23. The configuration registering apparatus of claim 21, said means for causing said light pattern to move, comprising a moving mirror, located and constrained to move such that light projected onto said mirror is reflected onto said surface and said light pattern rotates over said surface around said axes of said plurality of concentric circular light interface.

24. The configuration registering apparatus of claim 21, said means for causing said light pattern to move, comprising a moving prism, located and constrained to move such that light projected onto said prism is transmitted onto said surface and said light pattern rotates over said surface around said axes of said plurality of concentric circular light interface.

25. A method for projecting a light interface pattern onto a surface having a characteristic roughness, said method comprising:

a. projecting a light interface pattern onto said surface, said pattern comprising a light interface having an extended dimension; and

b. causing said light interface pattern to move, relative to said surface, parallel to said extended dimension.

26. The method of claim 25, said light interface pattern comprising a plurality of light interfaces, each interface having an extended dimension that is parallel to the extended dimension of each of the other interfaces.

27. The method of claim 25, said light interface pattern comprising a plurality of light interfaces, each interface having an extended dimension that is concentric with the extended dimensions of each of the other interfaces.

28. The method of claim 26, said light interface pattern comprising a plurality of parallel, straight line light interfaces.

29. The method of claim 27, said light interface pattern comprising a plurality of concentric, circular light interfaces.

30. The method of claim 25, said step of causing said light interface pattern to move comprising the step of causing said pattern to move through a distance during a characteristic exposure interval of a machine vision apparatus for use with the projecting method such that interference speckle is reduced as compared to the speckle that would arise without motion of the pattern relative to the surface.

31. The method of claim 25, said step of causing said light interface pattern to move comprising the step of moving a light source that generates said light pattern.

32. The method of claim 25, said step of causing said light interface pattern to move comprising the step of projecting said interface pattern onto a moving mirror, and reflecting said pattern from said moving mirror to said surface, such that said light interface pattern moves parallel to said extended dimension.

33. The method of claim 25, said step of causing said light interface pattern to move comprising the step of projecting said interface pattern onto a moving prism, and refracting said pattern from said moving prism to said surface, such that said light interface pattern moves parallel to said extended dimension.