INTERFEROMETRIC POLARIZATION CONTROL

• US 20070146723A1
• Filed: 06/20/2006
• Published: 06/28/2007
• Est. Priority Date: 06/20/2005
• Status: Active Grant

• Current Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Chuss, David, Wollack, Edward, Novak, Giles, Moseley, Samuel
• Granted Patent: US 7,412,175 B2
• Time in Patent Office: Days
• US Class Current: 356/491
• CPC Class Codes: G01J 4/00 Measuring polarisation of light
• CPC Class Codes: G01J 4/04 Polarimeters using electric detection means G01J4/02 takes precedence
• CPC Class Codes: G02B 27/286 for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another G02B5/3083 takes precedence; light guide coupling means utilising polarising elements G02B6/34

Abstract

A signal conditioning module provides a polarimeter capability in a photometric system. The module may include multiple variable delay polarization modulators. Each modulator may include an input port, and a first arm formed to include a first reflector and first rooftop mirror arranged in opposed relationship. The first reflector may direct an input radiation signal to the first rooftop mirror. Each modulator also may include an output port and a second arm formed to include a second reflector and second rooftop mirror arranged in opposed relationship. The second reflector can guide a signal from the second rooftop mirror towards the output port to provide an output radiation signal. A beamsplitting grid may be placed between the first reflector and the first rooftop mirror, and also between the second reflector and the second rooftop mirror. A translation apparatus can provide adjustment relative to optical path length vis-a-vis the first arm, the second arm and the grid.

Claims

1. A signal conditioning module configured for insertion into a photometric system to enable the photometric system to operate as a polarimeter, the signal conditioning module comprising:

a plurality of cascaded variable delay polarization modulators, each of the plurality of modulators comprising;

an input port;

a first arm comprising a first reflector and first rooftop mirror arranged in opposed relationship, the first reflector directing an input radiation signal from the input port towards the first rooftop mirror;

an output port;

a second arm comprising a second reflector and second rooftop mirror arranged in opposed relationship, the second reflector guiding a signal from the second rooftop mirror towards the output port to provide an output radiation signal;

a grid placed between the first reflector and the first rooftop mirror, and also placed between the second reflector and the second rooftop mirror; and

translation apparatus for adjustment of relative optical path length vis-a-vis the first arm, the second arm and the grid.

2. The module of claim 1, wherein the module is configured to provide frequency diversity.

3. The module of claim 1, wherein the module comprises two variable delay polarization modulators.

4. The module of claim 1, wherein the first and second reflectors comprise ellipsoidal mirrors.

5. The module of claim 1, wherein the first reflector provides a collimated signal to the first arm.

6. The module of claim 1, wherein the first reflector collimates the input radiation signal to provide a collimated signal to the first arm, and wherein the second reflector focuses the output radiation signal from the second arm into an output waveguide.

7. A millimeter wave receiver comprising:

an input antenna;

a polarization modulation chain coupled to the input antenna and comprising a plurality of cascaded variable-delay polarization modulators each including

an input having a fixed basis of phase introduction;

a translation apparatus providing variable magnitude of phase delay between two orthogonal linear polarizations of an input signal;

a beamsplitter; and

a first arm and a second arm optically coupled to one another via the beamsplitter, each of the first and second arms being formed of opposed reflective elements disposed on opposite sides of the beamsplitter, the opposed reflective elements in each arm including at least one mirror coupled to the translation apparatus such that a first distance separating the beamsplitter from at least one of the opposed reflective elements is variable.

8. The receiver of claim 7, wherein one of each of the opposed reflective elements provides a collimation function.

9. The receiver of claim 7, wherein one of each of the opposed reflective elements is formed as an ellipsoidal mirror and provides a collimation function.

10. The receiver of claim 7, wherein one of each of the opposed reflective elements includes several planar surfaces oriented at right angles in a rooftop configuration and realizing a reflected light path parallel to a path of incident light.

11. The receiver of claim 7, wherein the beamsplitter includes a wire grid.

12. The receiver of claim 7, wherein one of each of the opposed reflective elements is formed as an ellipsoidal mirror and provides a collimation function, another of each of the opposed reflective elements includes several planar surfaces oriented at right angles in a rooftop configuration and realizing a reflected light path parallel to a path of incident light, and wherein the beamsplitter includes a wire grid.

13. The receiver of claim 7, wherein the beamsplitter also functions as a polarizing filter.

14. The receiver of claim 7, wherein the variable-delay polarization modulators are capable of assessing both circular and linear polarization and provide capability for use at multiple wavelengths.

15. A radio telescope comprising:

an antenna;

a receiver coupled to the antenna, the receiver providing a polarizing interferometer function by including a polarization modulation chain coupled to the antenna and comprising a plurality of cascaded variable-delay polarization modulators each including;

a translation apparatus providing variable magnitude of phase delay between two orthogonal linear polarizations of an input signal;

a beamsplitter; and

a first arm and a second arm optically coupled to one another via the beamsplitter, each of the first and second arms being formed of opposed reflective elements disposed on opposite sides of the beamsplitter, the opposed reflective elements in each arm including at least one mirror coupled to the translation apparatus such that a first distance separating the beamsplitter from at least one of the opposed reflective elements is variable.

16. The telescope of claim 15, wherein one of each of the opposed reflective elements provides a collimation function.

17. The telescope of claim 15, wherein one of each of the opposed reflective elements is formed as an ellipsoidal mirror and provides a collimation function.

18. The telescope of claim 15, wherein one of each of the opposed reflective elements includes several planar surfaces oriented at right angles in a rooftop configuration and realizing a reflected light path parallel to a path of incident light.

19. The telescope of claim 15, wherein the first reflector provides a collimated signal to the first arm.

20. The telescope of claim 15, wherein the first reflector collimates the input radiation signal to provide a collimated signal to the first arm, and wherein the second reflector focuses the output radiation signal from the second arm into an output waveguide.

21. A method of characterizing the polarization of a signal comprising:

providing an input antenna;

coupling a polarization modulation chain to the input antenna;

said polarization modulation chain comprising a plurality of cascaded variable-delay polarization modulators each including;

an input having a fixed basis of phase introduction;

a translation apparatus providing variable magnitude of phase delay between two orthogonal linear polarizations of an input signal;

a beamsplitter; and

a first arm and a second arm optically coupled to one another via the beamsplitter, each of the first and second arms being formed of opposed reflective elements disposed on opposite sides of the beamsplitter, the opposed reflective elements in each arm including at least one mirror coupled to the translation apparatus such that a first distance separating the beamsplitter from at least one of the opposed reflective elements is variable;

receiving a signal via the input antenna; and

modulating the signal through the polarization modulation chain to characterize the polarization of the signal.

22. The method of claim 21, wherein one of each of the opposed reflective elements provides a collimation function.

23. The method of claim 21, wherein one of each of the opposed reflective elements is formed as an ellipsoidal mirror and provides a collimation function.

24. The method of claim 21, wherein one of each of the opposed reflective elements includes several planar surfaces oriented at right angles in a rooftop configuration and realizing a reflected light path parallel to a path of incident light.

25. The method of claim 21, wherein the beamsplitter includes a wire grid.

26. The method of claim 21, wherein one of each of the opposed reflective elements is formed as an ellipsoidal mirror and provides a collimation function, another of each of the opposed reflective elements includes several planar surfaces oriented at right angles in a rooftop configuration and realizing a reflected light path parallel to a path of incident light, and wherein the beamsplitter includes a wire grid.

27. The method of claim 21, wherein the beamsplitter also functions as a polarizing filter.

28. The method of claim 21, wherein the variable-delay polarization modulators are capable of assessing both circular and linear polarization and provide capability for use at multiple wavelengths.