Laser beamsplitter for generating a plurality of parallel beams

• US 5,671,047 A
• Filed: 05/15/1995
• Issued: 09/23/1997
• Est. Priority Date: 05/15/1995
• Status: Expired due to Fees

• Current Assignee: Varian Australia Pty., Ltd. (Agilent Technologies, Inc.)
• Original Assignee: Bio-Rad Laboratories Incorporated
• Inventors: Curbelo, Raul
• Primary Examiner(s): Nelms, David C.
• Assistant Examiner(s): KIM, ROBERT H
• Application Number:
  US08/441,126
• Time in Patent Office: 862 Days
• Field of Search: 356/345, 356/346, 356/358, 359/636, 359/638, 359/639, 359/640
• US Class Current: 356/452
• CPC Class Codes: G02B 27/144 using partially transparent surfaces without spectral selectivity G02B27/147 takes precedence
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces

Abstract

A laser beamsplitter for generating a plurality of parallel beams comprises a first beamsplitter and a second beamsplitter. The first and second beamsplitters are manufactured from glass flats having precisely parallel faces, wherein the front surface is coated with a reflective coating and the back surface is coated with a beamsplitter coating such that an initial laser beam passing through the first beamsplitter at a preferred angle of incidence is split into a first beam and a second beam. The second beamsplitter is positioned relative to the first beamsplitter such that the first beam passes through the second beamsplitter and is split into a third beam and a fourth beam. The parallelism of the output beams are determined by the parallelism of the glass flats, and no manual adjustments need to be made. The second, third, and fourth beams, if shone onto a surface orthogonal to the path of the initial beam, display three points that define a triangle, and preferably an equilateral triangle. The coatings on the surfaces of the first and second beamsplitters are chosen to provide three output beams having substantially the same intensity.

Claims

1. An interferometer comprising

a laser reference source,

a primary beamsplitter,

a fixed mirror,

a movable mirror,

a system for detecting variations in alignment between said fixed mirror and said movable mirror including three detectors located adjacent to a laser beam output field and arranged at the vertices of a triangle,

a laser beamsplitter,

said laser beamsplitter comprising

a first beamsplitter comprising an optical flat having a first partially coated face and a second partially coated face parallel to each other,

a second beamsplitter comprising an optical flat having a third partially coated face and a fourth partially coated face parallel to each other,

said first beamsplitter being positioned such that an incident beam entering said first beamsplitter is split into a first beam and a second beam parallel to each other, and

said second beamsplitter being positioned relative to said first beamsplitter such that at least one of said first beam and said second beam enters said second beam splitter and is split into a third beam and a fourth beam parallel to each other and to said second beam.

2. The interferometer of claim 1 wherein said first partially coated face is coated with a beamsplitting coating and said second partially coated face is coated with a reflective coating.

3. The interferometer of claim 2 wherein said third partially coated face is coated with a beamsplitting coating and said fourth partially coated face is coated with a reflective coating.

4. The interferometer of claim 1 wherein said first beamsplitter and said second beamsplitter are positioned relative to each other and oriented such that at least one of said first and said second beams is positioned in a triangular relationship with said third beam and said fourth beam on an imaginary plane orthogonal to said incident beam.

5. The interferometer of claim 4 wherein said triangular relationship is that of an equilateral triangle such that each beam is equidistant from each other beam.

6. The interferometer of claim 1 wherein said reflective coating on said first face and said third face, and said beamsplitting coating on said second face and said fourth face, are selected such that at least one of said first and said second beams, said third beam, and said fourth beam, are all substantially equal to each other in intensity.

7. The interferometer of claim 1 wherein at least one of said first and said second beams, said third beam and said fourth beam are parallel to said incident beam.

8. The interferometer of claim 1 wherein said first beamsplitter is circular in shape and said second beamsplitter is rectangular in shape.

9. The interferometer of claim 1 wherein said incident beam enters said first beamsplitter at an angle of incidence of fifty degrees and at least said first beam or second beam enters said second beamsplitter at an angle of incidence of fifty degrees.

10. The interferometer of claim 1 wherein said incident beam has a wavelength of 633 nanometers.

11. The interferometer of claim 1 wherein said optical flat of said first beamsplitter and said second beamsplitter has a refractive index between 1.45 and 1.55.

12. The interferometer of claim 1 wherein a thickness of said first beamsplitter and said second beamsplitter is approximately 6 millimeters such that said first beam and said second beam are approximately 5 millimeters apart from each other, and such that said third beam and said fourth beam are approximately 5 millimeters apart from each other.

13. The interferometer of claim 1 wherein said second beamsplitter is positioned approximately 2 centimeters away from said first beamsplitter.

14. A spectrometer comprising

an infrared light source,

a laser reference source,

a primary beamsplitter,

a fixed mirror,

a movable mirror,

a system for detecting variations in alignment between said fixed mirror and said movable mirror including three detectors located adjacent to a laser beam output field and arranged at the vertices of a triangle,

a laser beamsplitter,

said laser beamsplitter comprising

a first beamsplitter comprising an optical flat having a first partially coated face and a second partially coated face parallel to each other,

a second beamsplitter comprising an optical flat having a third partially coated face and a fourth partially coated face parallel to each other,

said first beamsplitter being positioned such that an incident beam entering said first beamsplitter is split into a first beam and a second beam parallel to each other, and

said second beamsplitter being positioned relative to said first beamsplitter such that at least one of said first beam and said second beam enters said second beamsplitter and is split into a third beam and a fourth beam parallel to each other and to said second beam.

15. The spectrometer of claim 14 wherein said first partially coated face is coated with a beamsplitting coating and said second partially coated face is coated with a reflective coating.

16. The spectrometer of claim 15 wherein said third partially coated face is coated with a beamsplitting coating and said fourth partially coated face is coated with a reflective coating.

17. The spectrometer of claim 14 wherein said first beamsplitter and said second beamsplitter are positioned relative to each other and oriented such that at least one of said first and said second beams is positioned in a triangular relationship with said third beam and said fourth beam on an imaginary plane orthogonal to said incident beam.

18. The spectrometer of claim 17 wherein said triangular relationship is that of an equilateral triangle such that each beam is equidistant from each other beam.

19. The spectrometer of claim 14 wherein said reflective coating on said first face and said third face, and said beamsplitting coating on said second face and said fourth face, are selected such that at least one of said first and said second beams, said third beam, and said fourth beam, are all substantially equal to each other in intensity.

20. The spectrometer of claim 14 wherein at least one of said first and said second beams, said third beam and said fourth beam are parallel to said incident beam.

21. The spectrometer of claim 14 wherein said first beamsplitter is circular in shape and said second beamsplitter is rectangular in shape.

22. The spectrometer of claim 14 wherein said incident beam enters said first beamsplitter at an angle of incidence of fifty degrees and at least said first beam or second beam enters said second beamsplitter at an angle of incidence of fifty degrees.

23. The spectrometer of claim 14 wherein said incident beam has a wavelength of 633 nanometers.

24. The spectrometer of claim 14 wherein said optical flat of said first beamsplitter and said second beamsplitter has a refractive index between 1.45 and 1.55.

25. The spectrometer of claim 14 wherein a thickness of said first beamsplitter and said second beamsplitter is approximately 6 millimeters such that said first beam and said second beam are approximately 5 millimeters apart from each other, and such that said third beam and said fourth beam are approximately 5 millimeters apart from each other.

26. The spectrometer of claim 14 wherein said second beamsplitter is positioned approximately 2 centimeters away from said first beamsplitter.

27. An interferometer comprising

a laser reference source,

a primary beamsplitter,

a fixed mirror,

a movable mirror,

a system for detecting variations in alignment between said fixed mirror and said movable mirror including three detectors located adjacent to a laser beam output field and arranged at the vertices of a triangle,

a laser beamsplitter for splitting an incident beam into at least three parallel beams comprising

a first beamsplitter comprising

an optical flat having a first face and a second face parallel to each other,

a first portion of said first face coated with a reflective coating and a second portion of said first face not coated with said reflective coating, said first face positioned such that an incident beam enters said first beamsplitter through said second portion of said first face,

a first portion of said second face coated with a beamsplitting coating and a second portion of said second face not coated with said beamsplitting coating, said second face positioned such that said incident beam is partially transmitted through said first portion of said second face and out of said first beamsplitter as said first beam, and partially reflected back toward said first portion of said first face and then reflected by said first portion of said first face out of said first beamsplitter through said second portion of said second face as said second beam parallel to said first beam,

a second beamsplitter comprising

an optical flat having a third face and a fourth face parallel to each other,

a first portion of said third face coated with a reflective coating and a second portion of said third face not coated with said reflective coating, said third face positioned such that at least one of said first beam and said second beam enters said second beamsplitter through said second portion of said third face,

a first portion of said fourth face coated with a beamsplitting coating and a second portion of said fourth face not coated with said beamsplitting coating, said fourth face positioned such that the beam entering said second beamsplitter is partially transmitted through said first portion of said fourth face and out of said beamsplitter as a third beam, and partially reflected back toward said first portion of said third face and then reflected by said first portion of said third face out of said first beamsplitter through said second portion of said second face as said fourth beam, and

said first beamsplitter and said second beamsplitter positioned relative to each other and oriented such that at least one of said first and said second beams is positioned in a triangular relationship with said third beam and said fourth beam on an imaginary plane orthogonal to said incident beam.

28. The interferometer of claim 27 wherein said first partially coated face is coated with a beamsplitting coating and said second partially coated face is coated with a reflective coating.

29. The interferometer of claim 28 wherein said third partially coated face is coated with a beamsplitting coating and said fourth partially coated face is coated with a reflective coating.

30. The interferometer of claim 27 wherein said first beamsplitter and said second beamsplitter are positioned relative to each other and oriented such that at least one of said first and said second beams is positioned in a triangular relationship with said third beam and said fourth beam on an imaginary plane orthogonal to said incident beam.

31. The interferometer of claim 30 wherein said triangular relationship is that of an equilateral triangle such that each beam is equidistant from each other beam.

32. The interferometer of claim 27 wherein said reflective coating on said first face and said third face, and said beamsplitting coating on said second face and said fourth face, are selected such that at least one of said first and said second beams, said third beam, and said fourth beam, are all substantially equal to each other in intensity.

33. The interferometer of claim 27 wherein at least one of said first and said second beams, said third beam and said fourth beam are parallel to said incident beam.

34. The interferometer of claim 27 wherein said first beamsplitter is circular in shape and said second beamsplitter is rectangular in shape.

35. The interferometer of claim 27 wherein said incident beam enters said first beamsplitter at an angle of incidence of fifty degrees and at least said first beam or second beam enters said second beamsplitter at an angle of incidence of fifty degrees.

36. The interferometer of claim 27 wherein said incident beam has a wavelength of 633 nanometers.

37. The interferometer of claim 27 wherein said optical flat of said first beamsplitter and said second beamsplitter has a refractive index between 1.45 and 1.55.

38. The interferometer of claim 27 wherein a thickness of said first beamsplitter and said second beamsplitter is approximately 6 millimeters such that said first beam and said second beam are approximately 5 millimeters apart from each other, and such that said third beam and said fourth beam are approximately 5 millimeters apart from each other.

39. The interferometer of claim 27 wherein said second beamsplitter is positioned approximately 2 centimeters away from said first beamsplitter.

40. A spectrometer comprising

an infrared light source,

a laser reference source,

a primary beamsplitter,

a fixed mirror,

a movable mirror,

a system for detecting variations in alignment between said fixed mirror and said movable mirror including three detectors located adjacent to a laser beam output field and arranged at the vertices of a triangle,

a laser beamsplitter for splitting an incident beam into at least three parallel beams comprising

a first beamsplitter comprising

an optical flat having a first face and a second face parallel to each other,

a first portion of said first face coated with a reflective coating and a second portion of said first face not coated with said reflective coating, said first face positioned such that an incident beam enters said first beamsplitter through said second portion of said first face,

a first portion of said second face coated with a beamsplitting coating and a second portion of said second face not coated with said beamsplitting coating, said second face positioned such that said incident beam is partially transmitted through said first portion of said second face and out of said first beamsplitter as said first beam, and partially reflected back toward said first portion of said first face and then reflected by said first portion of said first face out of said first beamsplitter through said second portion of said second face as said second beam parallel to said first beam,

a second beamsplitter comprising

an optical flat having a third face and a fourth face parallel to each other,

a first portion of said third face coated with a reflective coating and a second portion of said third face not coated with said reflective coating, said third face positioned such that at least one of said first beam and said second beam enters said second beamsplitter through said second portion of said third face,

a first portion of said fourth face coated with a beamsplitting coating and a second portion of said fourth face not coated with said beamsplitting coating, said fourth face positioned such that the beam entering said second beamsplitter is partially transmitted through said first portion of said fourth face and out of said beamsplitter as a third beam, and partially reflected back toward said first portion of said third face and then reflected by said first portion of said third face out of said first beamsplitter through said second portion of said second face as said fourth beam, and

said first beamsplitter and said second beamsplitter positioned relative to each other and oriented such that at least one of said first and said second beams is positioned in a triangular relationship with said third beam and said fourth beam on an imaginary plane orthogonal to said incident beam.

41. The spectrometer of claim 40 wherein said first partially coated face is coated with a beamsplitting coating and said second partially coated face is coated with a reflective coating.

42. The spectrometer of claim 41 wherein said third partially coated face is coated with a beamsplitting coating and said fourth partially coated face is coated with a reflective coating.

43. The spectrometer of claim 40 wherein said first beamsplitter and said second beamsplitter are positioned relative to each other and oriented such that at least one of said first and said second beams is positioned in a triangular relationship with said third beam and said fourth beam on an imaginary plane orthogonal to said incident beam.

44. The spectrometer of claim 43 wherein said triangular relationship is that of an equilateral triangle such that each beam is equidistant from each other beam.

45. The spectrometer of claim 40 wherein said reflective coating on said first face and said third face, and said beam splitting coating on said second face and said fourth face, are selected such that at least one of said first and said second beams, said third beam, and said fourth beam, are all substantially equal to each other in intensity.

46. The spectrometer of claim 40 wherein at least one of said first and said second beams, said third beam and said fourth beam are parallel to said incident beam.

47. The spectrometer of claim 40 wherein said first beamsplitter is circular in shape and said second beamsplitter is rectangular in shape.

48. The spectrometer of claim 40 whereto said incident beam enters said first beamsplitter at an angle of incidence of fifty degrees and at least said first beam or second beam enters said second beamsplitter at an angle of incidence of fifty degrees.

49. The spectrometer of claim 40 wherein said incident beam has a wavelength of 633 nanometers.

50. The spectrometer of claim 40 wherein said optical flat of said first beamsplitter and said second beamsplitter has a refractive index between 1.45 and 1.55.

51. The spectrometer of claim 40 wherein a thickness of said first beamsplitter and said second beamsplitter is approximately 6 millimeters such that said first beam and said second beam are approximately 5 millimeters apart from each other, and such that said third beam and said fourth beam are approximately 5 millimeters apart from each other.