Methods and systems for measuring an aberated wave front

• US 7,295,292 B1
• Filed: 05/19/2005
• Issued: 11/13/2007
• Est. Priority Date: 05/20/2004
• Status: Active Grant

• Current Assignee: Advanced Technology Applications, LLC, University of Notre DAME Du Lac
• Original Assignee: The University Of Notre Dame
• Inventors: Gordeyev, Stanislav, Cain, Alan, Ng, Terry, Jumper, Eric
• Primary Examiner(s): Toatley, Jr.; Gregory J.
• Assistant Examiner(s): ALLI, IYABO
• Application Number:
  US11/132,312
• Time in Patent Office: 908 Days
• Field of Search: 356/121, 356/124, 356/614, 356/73, 356/27, 73/11.6, 250/201.9, 250/559.32, 250/201, 250/202
• US Class Current: 356/124
• CPC Class Codes: G01J 9/00 Measuring optical phase difference devices or arrangements for controlling the phase of light beams G02F1/01; Determining degree of coherence; Measuring optical wavelength spectrometry G01J3/00
• CPC Class Codes: G01M 11/00 Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
• CPC Class Codes: G01M 9/065 dealing with flow

Abstract

Methods and systems are described for a system for measuring aberrations in a wave front. In the improved system multiple closely-spaced, small-aperture laser beams traverse an aberrating flow that introduces deflections of small-aperture laser beams from which aberrated wavefronts can be constructed. These beams may then be focused on position sensing devices using focusing lenses. The position sensing devices may then detect the positions of these beams and a difference between the detected position and the unaberrated position of the beams detected. This information may then be used to determine information regarding the optical aberrations introduced by the flow that may be used, for example, in improving communications systems and/or laser weapon systems.

Claims

1. A system for obtaining information regarding an optical wave front that passes through a flow resulting in aberrations to the wave front, comprising:

one or more position sensing devices, the one or more position sensing devices capable of detecting a position of a first beam and detecting a position of a second beam;

wherein the first and second beams pass through the flow and the distance between the first and second beams is less than 20 times the diameter of the first beam; and

a processor capable of determining a displacement of the first beam and a displacement of the second beam based on the detected positions of the first and second beam, and determining information regarding the wave front based on the determined displacements.

2. The system of claim 1 further comprising:

a first lens constructed and arranged to refract the first beam;

a second lens constructed and arranged to refract the second beam; and

wherein the processor uses the focal length of at least the first lens to determine the information regarding the wave front.

3. The system of claim 1, wherein the processor is further capable of determining a velocity for the flow based on the detected positions of the first and second beams.

4. The system of claim 3, wherein the processor is further capable of determining the velocity for the flow by calculating a Fourier transform of an angle of deflection for the first beam and by calculating a Fourier transform of an angle of deflection for the second beam;

wherein the angles of deflection are determined from the detected displacements of the first beam and the second beam, respectively.

5. The system of claim 1, further comprising a plurality of mirrors constructed to reflect the first beam a plurality of times in order to lengthen an optical path for the beam.

6. The system of claim 1, further comprising:

a beam director capable of receiving an optical signal having an aperture; and

a first optical narrowing mechanism operable on the optical signal for obtaining a first beam from the optical signal, wherein the first beam has an aperture smaller than the aperture of the optical signal;

a second optical narrowing mechanism operable on the optical signal for obtaining a second beam from the optical signal, wherein the second beam has an aperture smaller than the aperture of the optical signal.

7. The system of claim 1, wherein the system is mounted on an airborne platform.

8. The system of claim 1, wherein the first beam and the second beam each traverse an optical path passing through one or more turbulent flows resulting from air flow passing around a structure.

9. The system of claim 8, wherein the structure is a manmade object.

10. The system of claim 9, wherein the structure is a building.

11. The system of claim 10, wherein the structure is a natural object.

12. The system of claim 11, wherein the structure is a cliff.

13. The system of claim 1, wherein the information regarding the wave front is for use in correcting for aberrations in an optical signal.

14. A system for obtaining information regarding an optical wave front that passes through a flow resulting in aberrations to the wave front, comprising:

one or more lenses constructed and arranged to refract at least two beams, wherein the beams pass through a flow;

one or more position sensing devices, the one or more position sensing devices configured to detect a time history of positions of the beams; and

a processor capable of determining displacements of the beams based on the detected position for the beams, and determining information regarding the wave front based on the determined displacement and the focal length of the lenses.

15. The system of claim 14, wherein the at least two beams includes a first beam and a second beam, and wherein the distance between the first and second beams is less than 20 times the diameter of the first beam.

16. A system for obtaining information regarding an optical wave front that passes through a flow resulting in aberrations to the wave front, comprising:

one or more position sensing devices, the one or more position sensing devices capable of detecting a position of a first beam and detecting a position of a second beam;

wherein the first and second beams pass through the flow; and

a processor capable of determining a displacement of the first beam and a displacement of the second beam based on the determined positions for the first and second beam, determining the angles of deflection for the beams based on the detected displacement of the beams, determining a velocity for the flow based on the detected positions of the first and second beams by taking the Fourier transforms of the angles of deflection for the first and second beams, and determining information regarding the wave front based on the determined displacements and the determined velocity.

17. The system of claim 16, wherein the distance between the first and second beams is less than 20 times the diameter of the first beam.

18. A system for obtaining information regarding an optical wave front that passes through a flow resulting in aberrations to the wave front, comprising:

a plurality of mirrors configured and arranged to reflect two beams a plurality of times in order to lengthen an optical path for the beams;

one or more position sensing devices, the one or more position sensing devices capable of detecting a position of the first beam and detecting a position of a second optical beam;

wherein the first and second optical beams pass through the flow; and

a processor capable of determining a displacement of the first beam and a displacement of the second beam based on the determined positions for the first and second beam, and determining information regarding the wave front based on the determined displacements.

19. The system of claim 18, wherein the distance between the first and second beams is less than 20 times the diameter of the first beam.

20. A system for obtaining information regarding an optical wave front that passes through a flow resulting in aberrations to the wave front, comprising:

a beam director capable of receiving an optical signal having an aperture;

a first optical narrowing mechanism operable on the optical signal for obtaining a first beam from the optical signal, wherein the first beam has an aperture smaller than the aperture of the optical signal;

a second optical narrowing mechanism operable on the optical signal for obtaining a second beam from the optical signal, wherein the second beam has an aperture smaller than the aperture of the optical signal;

one or more position sensing devices, the position sensing devices capable of detecting a position of the first and the second beams; and

a processor capable of determining a displacement of the first and the second beams based on the determined positions for the first and the second beams, and determining information regarding the wave front based on the determined displacements.

21. The system of claim 20, wherein at least one of the optical narrowing mechanisms includes a reflector for obtaining a sub-aperture of the optical signal.

22. The system of claim 21, wherein at least one of the optical narrowing mechanisms includes an iris for obtaining the first and the second beams.

23. The system of claim 20, wherein the distance between the first and second beams is less than 20 times the diameter of the first beam.

24. A system for obtaining information regarding an optical wave front that passes through a flow resulting in aberrations to the wave front, comprising:

a set of one or more position sensing devices, the one or more position sensing devices capable of detecting a position of the first and the second beams; and

a processor capable of determining a displacements of the first and the second beams based on the detected position of the first and the second beams, and determining information regarding the wave front based on the determined displacements; and

wherein the system is mounted on an airborne platform.

25. The system of claim 24, wherein the set of position sensing devices are further capable of detecting a position for the first beam and a second beam and the distance between the first and second beams is less than 20 times the diameter of the first beam.

26. A system for obtaining information regarding an optical wave front that passes through a flow resulting in aberrations to the wave front, comprising:

multiple position sensing devices, the multiple position sensing devices capable of detecting a position of the multiple beams, wherein the beams traverse an optical path passing through one or more turbulent flows resulting from air flow passing around a structure; and

a processor capable of determining the displacements of the multiple beams based on the determined positions for the multiple beams, and determining information regarding the wave front based on the determined displacements.

27. The system of claim 26, wherein the structure is a manmade object.

28. The system of claim 27, wherein the structure is a building.

29. The system of claim 26, wherein the structure is a natural object.

30. The system of claim 29, wherein the structure is a cliff.

31. The system of claim 26 wherein the set of position sensing devices are further capable of detecting the positions for the multiple beams;

and wherein the separations between the multiple beams are less than 20 times the diameter of the first beam.

32. A method for obtaining information regarding an optical wave front that passes through a flow resulting in aberrations to the wave front, comprising:

detecting a position of a first beam, wherein the first beam passes through the flow;

detecting a position of a second beam, wherein the second beam passes through the flow;

wherein the distance between the first and second beams is less than 20 times the diameter of the first beam; and

determining a displacement of the first beam based on the detected position of the first beam;

determining a displacement of the second beam based on the detected position of the second beam; and

correcting a source of the optical wave front based on the determined displacements.

33. A system for obtaining information regarding an optical wave front that passes through a flow resulting in aberrations to the wave front, comprising:

means for detecting a position of a first beam, wherein the first beam passes through the flow;

means for detecting a position of a second beam, wherein the second beam passes through the flow;

wherein the distance between the first and second beams is less than 20 times the diameter of the first beam; and

means for determining a displacement of the first beam based on the detected position of the first beam;

means for determining a displacement of the second beam based on the detected position of the second beam; and

means for determining information regarding the wave front based on the determined displacements.