Liquid crystal interferometer

• US 5,600,440 A
• Filed: 07/05/1995
• Issued: 02/04/1997
• Est. Priority Date: 07/05/1995
• Status: Expired due to Fees

• Current Assignee: Navy Department United States of America The As Represented By The Secretary of The Navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Bendall, Charles S.
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): KIM, ROBERT H
• Application Number:
  US08/498,070
• Time in Patent Office: 580 Days
• Field of Search: 356/345, 356/346, 356/361, 359/78
• US Class Current: 356/450
• CPC Class Codes: G01B 2290/40 Non-mechanical variable delay line
• CPC Class Codes: G01B 9/0201 using temporal phase variation
• CPC Class Codes: G01B 9/02027 Two or more interferometric channels or interferometers
• CPC Class Codes: G01J 3/0229 using masks, aperture plates, spatial light modulators or spatial filters, e.g. reflective filters
• CPC Class Codes: G01J 3/4531 Devices without moving parts

Abstract

An interferometer employs liquid crystals to effect optical path length cges in a Michelson-type interferometer. A beam splitter divides a first optical signal into second and third optical signals. The second optical signal is directed through a first array of liquid crystals, and the third optical signal is directed through a second array of liquid crystals. Mirrors reflect the second and third optical signals back through the arrays to the beam splitter which combines them into a fourth optical signal having an interference pattern. A detector array transforms the fourth optical signal into an electrical signal. A processing circuit is used to modulate the indices of refraction of the liquid crystals to effectuate optical path length changes between the second and third optical signals. The data processor may also be employed to transform the electrical signal into digital data which may be analyzed to discern spectral characteristics of the first optical signal that are of interest.

Claims

1. An interferometer, comprising:

a beam splitter for dividing a first optical signal into second and third optical signals;

a first array of liquid crystals through which said second optical signal passes, each said liquid crystal having an index of refraction which may be modulated;

a first mirror for directing said second optical signal array to said beam splitter;

a second array of liquid crystals through which said third optical signal passes, each said liquid crystal having an index of refraction which may be modulated;

a second mirror for directing said third optical signal to said beam splitter where said second and third optical signals are combined to form a fourth optical signal having an interference pattern;

a detector array for transforming said fourth optical signal into an electrical signal; and

first means for transforming said electrical signal into digital data representing said interference pattern and for independently modulating said indices of refraction of said liquid crystals comprising said first and second arrays of liquid crystals.

2. The interferometer of claim 1 wherein said first means transforms said electrical signal into digital data representing said interference pattern.

3. The interferometer of claim 1 wherein said first means includes:

a data processor coupled to receive said electrical signal from said detector array;

a first spatial light modulator driver operably coupled between said data processor and said first array of liquid crystals; and

a second spatial light modulator driver operably coupled between said data processor and said second array of liquid crystals.

4. The interferometer of claim 1 further including a polarizer through which said fourth optical signal is directed.

5. The interferometer of claim 1 further including a third array of liquid crystals through which said second optical signal is directed.

6. The interferometer of claim 1 further including a fourth array of liquid crystals through which said third optical signal is directed.

7. The interferometer of claim 1 wherein each of said liquid crystals of said first array of liquid crystals have substantially the same index of refraction.

8. The interferometer of claim 1 wherein said liquid crystals of said first array of liquid crystals are grouped into multiple sets of said liquid crystals, and all of said liquid crystals comprising any one of said sets have substantially the same index of refraction.

9. The interferometer of claim 1 further including a lens for directing said first optical signal to said beam splitter and for imaging a scene onto said detector array.

10. An interferometer, comprising:

an array of liquid crystals for transforming a first optical signal into a second optical signal having an interference pattern, each said liquid crystal having an index of refraction which may be modulated;

an array detector for transforming said second optical signal into an electrical signal;

lens for focusing said second optical signal onto said array detector; and

first means for independently modulating said indices of refraction of said liquid crystals.

11. The interferometer of claim 10 wherein said first means transforms said electrical signal into data representing said interference pattern.

12. The interferometer of claim 10 wherein said first means includes an array detector.

13. The interferometer of claim 10 wherein said first means includes a data processor.

14. The interferometer of claim 13 wherein said first means includes:

a spatial light modulator driver operably coupled between said data processor and said array of liquid crystals.

15. The interferometer of claim 10 wherein said liquid crystals of said array of liquid crystals are grouped into multiple sets of said liquid crystals, and all of said liquid crystals comprising any one of said sets have substantially the same index of refraction.

16. The interferometer of claim 10 wherein each of said liquid crystals of said array of liquid crystals have substantially the same index of refraction.

17. The interferometer of claim 10 further including a polarizer for polarizing said second optical signal.

18. A method for generating an interference pattern, comprising the steps of:

dividing a first optical signal into second and third optical signals;

directing said second optical signal through a first array of liquid crystals, each of said liquid crystals having an index of refraction;

directing said third optical signal through a second array of liquid crystals, each of said liquid crystals having an index of refraction;

independently modulating said indices of refraction of said liquid crystals comprising said first and second arrays;

combining said second and third optical signals into a fourth optical signal having a waveform characterized by an interference pattern; and

transforming said fourth optical signal into an electrical signal having a waveform representing said interference pattern.

19. The method of claim 18 further including the step of transforming said electrical signal into digital data.

20. The method of claim 18 further including the step of modulating said indices of refraction of said liquid crystals of said first array to be substantially equal.

21. The method of claim 18 further including the step of modulating said indices of refraction of said liquid crystals whereby groups of said liquid crystals of said first array are comprised of liquid crystals having substantially the same index of refraction.

22. The method of claim 18 further including the step of polarizing said fourth optical signal.

23. A method for generating an interference pattern, comprising the steps of:

directing a first optical signal through a first array of liquid crystals to transform said first optical signal into a second optical signal having an interference pattern, each of said liquid crystals having an index of refraction;

independently modulating said indices of refraction of said liquid crystals; and

transforming said second optical signal into an electrical signal having a waveform representing said interference pattern.

24. The method of claim 23 further including the step of transforming said electrical signal into digital data.

25. The method of claim 23 further including the step of modulating said indices of refraction of said liquid crystals of said first array to be substantially equal.

26. The method of claim 23 further including the step of modulating said indices of refraction of said liquid crystals whereby groups of said liquid crystals of said first array are comprised of said liquid crystals each having substantially the same said index of refraction.

27. The method of claim 23 further including the step of polarizing said first optical signal.

28. The method of claim 23 further including the step of polarizing said second optical signal.

29. An interferometer, comprising:

a beam splitter for dividing a first optical signal into second and third optical signals;

first and second groups of liquid crystals configured into a first array for modulating the optical path length of said first optical signal, each said liquid crystal having an index of refraction which may be modulated;

a first mirror for directing said second optical signal array to said beam splitter;

a third group of liquid crystals configured into a second array for modulating the optical path length of said second optical signal, each said liquid crystal having an index of refraction which may be modulated;

a second mirror for directing said third optical signal to said beam splitter where said second and third optical signals are combined to form a fourth optical signal having an interference pattern;

a detector array for transforming said fourth optical signal into an electrical signal; and

first means for transforming said electrical signal into digital data representing said interference pattern, and for modulating said indices of refraction of said liquid crystals comprising said first group to have a first value, and for modulating said indices of refraction of said liquid crystals comprising said second group to have a second value.

30. The interferometer of claim 29 in which said indices of refraction of said liquid crystals comprising said first group have a first value, and said liquid crystals comprising said second group have a second value different from said first value.

31. The interferometer of claim 29 in which said indices of refraction of said liquid crystals comprising said first group and said liquid crystals comprising said second group all have the same value.

32. A method for generating an interference pattern, comprising the steps of:

directing a first optical signal through first and second groups of liquid crystals to transform said first optical signal into a second optical signal having an interference pattern, each of said liquid crystals having an index of refraction;

modulating said indices of refraction of said liquid crystals comprising said first and second groups of liquid crystals; and

transforming said second optical signal into an electrical signal having a waveform representing said interference pattern.

33. The method of claim 32 wherein said indices of refraction of said liquid crystals comprising said first group of liquid crystals each have a first value, and said liquid crystals comprising said second group of liquid crystals each have a second value different from said first value.

34. The method of claim 32 wherein said indices of refraction of said liquid crystals comprising said first group of liquid crystals each have a first value, and said liquid crystals comprising said second group of liquid crystals each have a second value equal to said first value.