# US 7,609,978 B2 · Interferometric polarization control

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- Number: US 7,609,978 B2
- Document ID: US7609978B2
- Status: Granted
- Kind: B2
- Application number: 12/056,964
- Filed: 2008-03-27
- Published: 2008-09-25
- Granted: 2009-10-27
- Earliest claimed: 2005-06-20
- Assignees: The United States of America as represented by the National Aeronautics and Space Administration
- Inventors: Edward J. Wollack; Samuel H. Moseley; Giles A. Novak; David T. Chuss
- Web page: https://patentgrep.com/patent/US7609978B2

## CPC

- G01J 4/00: Measuring polarisation of light
- G01J 4/04: Polarimeters using electric detection means (G01J4/02 takes precedence)
- 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)}
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## 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-à-vis the first arm, the second arm and the grid.

## Claims

### Claim 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-à-vis the first arm, the second arm and the grid.

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 1)

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

### Claim 6 (depends on 1)

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.