Optical sensor with micro-electro-mechanical system (MEMS) micro-mirror array (MMA) steering of the optical transmit beam

Patent metadata

Field	Value
Publication number	US-11835709-B2
Application number	US-202117171577-A
Country	US
Kind code	B2
Filing date	Feb 9, 2021
Priority date	Feb 9, 2021
Publication date	Dec 5, 2023
Grant date	Dec 5, 2023

Abstract

A beam steering architecture for an optical sensor is based upon a pair of Micro-Electro-Mechanical System (MEMS) Micro-Mirror Arrays (MMAs) and a fold mirror. The MEMS MMAs scan both primary and secondary FOR providing considerable flexibility to scan a scene to provide not only active imaging (to supplement passive imaging) but also simultaneously allowing for other optical functions such as establishing a communications link, providing an optical transmit beam for another detection platform or determining a range to target. A special class of MEMS MMAs that provides a “piston” capability in which the individual mirrors may translate enables a suite of optical functions to “shape” the optical transmit beam.

First claim

We claim:

1. An optical sensor, comprising:
a detector responsive to light in a band of wavelengths;
an optical source that emits an optical transmit beam along an optical axis at a transmission wavelength within the band;
a first steering Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) positioned at an angle to the optical axis to receive and re-direct the optical transmit beam along a first optical path at a first reflection angle, said first steering MEMS MMA comprising at least one mirror responsive to command signals to tip and tilt to scan the optical transmit beam at a scan angle in first and second angular directions about the first reflection angle over a primary transmit field-of-regard (FOR);
a fold mirror positioned to intercept the re-directed optical transmit beam at a range of scan angles within the primary transmit FOR and re-direct the optical transmit beam along a second optical path;
a second steering MEMS MMA positioned to receive and re-direct the optical transmit beam from the fold mirror along a third optical path at a second reflection angle and offset from the first optical path, said second steering MEMS MMA comprising at least one mirror responsive to command signals to tip and tilt to scan the optical transmit beam at a scan angle in said first and second directions about the second reflection angle over a secondary transmit FOR;
a controller configured to issue command signals to said first and second steering MEMS MMAs to scan the optical transmit beam over the primary and secondary transmit FOR;
a receive telescope that receives light within a receive FOR; and
an optical system that couples light from the receive telescope to the detector to image a portion of a scene within the receive FOR.

2. The optical sensor of claim 1 , wherein said first and second steering MEMS MMAs each comprise only a single mirror, said controller is configured to (a) issue command signals to the first steering MEMS MMA to tip and tilt the single mirror to scan the optical transmit beam over the primary transmit FOR and to (b) issue command signals to the first steering MEMS MMA to set the tip and tilt of the single mirror at a specified scan angle within the range of scan angles to re-direct the optical transmit beam off of the fold mirror to the single mirror of the second steering MEMS MMA and to issue command signals to the second steering MEMS MMA to tip and tilt the single mirror to scan the optical transmit beam over the secondary transmit FOR.

3. The optical sensor of claim 1 , wherein said first steering MEMS MMA comprises a single mirror and said second steering MEMS MMA includes a plurality of M mirrors, wherein said range of scan angles includes a specified angle in said first angular direction and a range of angles in said second angular direction, said controller is configured to (a) issue command signals to the first steering MEMS MMA to tip and tilt the single mirror to scan the optical transmit beam over the primary transmit FOR and to (b) issue command signals to the first steering MEMS MMA to set the tip and tilt of the single mirror at the specified angle in the first angular direction to re-direct the optical transmit beam off of the fold mirror and to scan the tip and tilt of the single mirror over the range of angles in the second angular direction to scan the optical transmit beam across the plurality of M mirrors in the second steering MEMS MMA and to issue command signals to the second steering MEMS MMA to tip and tilt the mirror on which the optical transmit beam is incident to scan the optical transmit beam over the secondary transmit FOR, wherein the scan of the single mirror in the first steering MEMS MMA in the second angular direction extends the secondary transmit FOR in the second angular directions.

4. The optical sensor of claim 3 , wherein the plurality of M mirrors in the second steering MEMS MMA are arranged in a row, wherein the range of scan angles further spans a range of angles in the first angular direction, wherein the controller is configured in (b) to issue command signals to the first steering MEMS MMA to tip and tilt the single mirror to scan the optical transmit within the range of angles in the first angular direction to scan the optical transmit beam across the row of M mirrors.

5. The optical sensor of claim 1 , wherein said first steering MEMS MMA comprises a plurality of N mirrors and said second steering MEMS MMA comprises a single mirror, said controller is configured to (a) issue command signals to the first steering MEMS MMA to selectively translate each of the N mirrors to shape the optical transmit beam and to tip and tilt the plurality of N mirrors to scan the shaped optical transmit beam over the primary FOR and to (b) issue command signals to the first steering MEMS MMA to selectively translate each of the N mirrors to shape the optical transmit beam and to set the tip and tilt of each of the N mirrors within the range of scan angles to re-direct the optical transmit beam off of the fold mirror to the single mirror of the second steering MEMS MMA, and to issue command signals to the second steering MEMS MMA to tip and tilt the single mirror to scan the shaped optical transmit beam over the secondary transmit FOR.

6. The optical sensor of claim 5 , wherein the first steering MEMS MMA's N mirrors are selectively translated to shape the optical transmit beam to perform one or more of the following:
adjust a size, divergence or intensity profile of the optical transmit beam;
produce deviations in the wavefront of the optical transmit beam to compensate for atmospheric distortion;
adjust the phase and maintain a zero phase difference across the wavefront of optical transmit beam; and
given a maximum translation of each mirror, form a minimum number of continuous surfaces across the N mirrors at the specified tip and tilt to reduce distortion.

7. The optical sensor of claim 1 , wherein said first and second steering MEMS MMAs include K×L mirrors and P×Q mirrors, respectively, K, L, P and Q are each integers greater than one.

8. The optical sensor of claim 7 , wherein responsive to command signals said first steering MEMS MMAs is partitioned into a plurality of segments, each segment including a plurality of mirrors configured to tip and tilt to scan multiple optical transmit beams at different scan angles over the primary transmit FOR, wherein responsive to command signals said second steering MEMS MMAs is partitioned into a plurality of segments, each segment including a plurality of mirrors configured to tip and tilt to scan multiple optical transmit beams at different scan angles over the secondary transmit FOR.

9. The optical sensor of claim 8 , wherein the mirrors in each segment reflect light at different wavelengths such that the multiple optical transmit beams comprise a plurality of different wavelengths.

10. The optical sensor of claim 7 , wherein the groups of mirrors in the first and second steering MEMS MMA's are selectively translated to shape the optical transmit beam to perform one or more of the following:
adjust a size, divergence or intensity profile of the optical transmit beam;
produce deviations in the wavefront of the optical transmit beam to compensate for atmospheric distortion;
adjust the phase and maintain a zero phase difference across the wavefront of optical transmit beam; and
given a maximum translation of each mirror, form a minimum number of continuous surfaces across the N mirrors at the specified tip and tilt to reduce distortion.

11. The optical sensor of claim 1 , wherein the fold mirror is configured to filter the optical transmit beam based on wavelength or electro-optical (E

Assignees

• Raytheon Co

Inventors

• Uyeno Gerald P
• Gleason Benn H
• Keller Sean D
• Lange Mark K
• Rogala Eric
• Reyna Vanessa
• Shott Craig O
• Leigh Jon E
• Odom Garret A

Classifications

• G02B26/0833 Primary

  the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD (G02B26/0825 takes precedence; micromechanical devices in general B81B) · CPC title

• G01S7/4811

  common to transmitter and receiver · CPC title

• G01S7/4817 Primary

  relating to scanning · CPC title

• G01S17/931

  of land vehicles · CPC title

• G01S17/933

  of aircraft or spacecraft · CPC title