Small angle optical beam steering using micro-electro-mechanical system (MEMS) micro-mirror arrays (MMAS)

Patent metadata

Field	Value
Publication number	US-11550146-B2
Application number	US-202117152023-A
Country	US
Kind code	B2
Filing date	Jan 19, 2021
Priority date	Jan 19, 2021
Publication date	Jan 10, 2023
Grant date	Jan 10, 2023

Abstract

Small angle optical beam steering is performed using a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) that minimizes diffraction for a specified steering angle, Generally speaking, this is accomplished with a MEMS MMA that exhibits a “piston” capability to translate individual mirrors in addition to the tip and tilt capabilities. Adjacent mirrors can be tipped/tilted to the specified steering angle and then translated by a requisite amount to approximate a continuous surface. For a specified steering angle, the MEMS MMA is partitioned into one or more sections with each section including the maximum number of mirrors that can be grouped together and actuated to approximate a continuous surface given a maximum translation z. As a result, the only edge discontinuities exist between adjacent sections thereby minimizing distortion for a given steering angle.

First claim

We claim:

1. A small angle beam steerer, comprising:
a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) positioned to receive an optical beam, said MEMS MMA comprising a plurality of independently and continuously controllable rigid mirrors responsive to command signals to tip, tilt and piston each mirror in a three-dimensional space, wherein the maximum translation of each said mirror to piston is z; and
a controller responsive to a specified steering angle configured to determine a maximum number of minors that may be grouped together in sections as limited by the maximum translation z to form a continuous surface at specified tip and tilt angles to provide the specified steering angle and to issue command signals to partition the MEMS MMA into the sections and to tip and tilt the mirrors to the same specified tip and tilt angles within and between sections and to translate each mirrors in each section by a requisite amount such that the plurality of mirrors in each section approximate a continuous mirror surface at the same specified tip and tilt angles with edge discontinuities existing only between adjacent sections to steer the optical beam at a specified steering angle.

2. The imaging system of claim 1 , wherein each said mirror rotates about X and Y orthogonal axes, respectively, and translates along a Z axis orthogonal the XY plane to tip, tilt and piston.

3. The imaging system of claim 2 , wherein each said mirror is supported at three vertices of an equilateral triangle, wherein lines defined by three different pairs of said vertices provide three axes at 60 degrees to one another in the XY plane, wherein each said mirror pivots about each said axes to produce tilt, tip and piston in the XYZ space.

4. The imaging system of claim 2 , wherein the controller determines a minimum number of sections N along the Y axis for the specified tip angle and a minimum number of sections M along the X axis for the specified tilt angle.

5. The imaging system of claim 3 , wherein a maximum tip or tilt angle is given by arcsin(z/w) where w is a width of the mirror in the X or Y direction multiplied by the number of mirrors in a section along the X or Y direction.

6. The imaging system of claim 3 , wherein maximum tip and tilt angles for different integer values of N and M are stored in a look-up table (LUT), wherein the controller accesses the LUT to select the minimum integer values for N and M that exceed the specified tip and tilt angles to provide the specified steering angle.

7. The imaging system of claim 1 , wherein the controller determines the maximum number of mirrors that may be grouped together in sections to approximate the continuous surface for specified maximum tip and tilt angles and fixes the partition of the MEMS MMA to that number of sections, wherein the controller tips, tilts and pistons the mirrors for all specified tip and tilt angles less than the specified maximum tip and tilt angles.

8. The imaging system of claim 1 , wherein for each update of the specified steering angle the controller determines specified tip and tilt angles, updates the maximum number of mirrors that may be grouped together sections as limited by the maximum translation z to form a continuous surface at specified tip and tilt angles, updates the partition of the MEMS MMA, and tip, tilts and translates the mirrors to approximate the continuous surface at the specified tip and tilt angles to minimize edge discontinuities for the specified steering angle.

9. The imaging system of claim 7 , wherein max tip and tilt angles for different integer values of N and M are stored in a look-up table (LUT), wherein the controller accesses the LUT to select the minimum integer values for N and M that exceed the specified tip and tilt angles to provide the specified steering angle.

10. The imaging system of claim 1 , wherein the MEMS MMA is responsive to command signals to partition itself into a plurality of segments, each segment including a plurality of mirrors to form and independently steer a plurality of optical beams at specified steering angles, wherein the controller determines the maximum number of mirrors that may be grouped together in sections as limited by the maximum translation z for each said segment to form a continuous surface at specified tip and tilt angles to provide the specified steering angle.

11. The imaging system of claim 10 , wherein the mirrors in each segment reflect light at different wavelengths such that the plurality of optical beams comprise a plurality of different wavelengths.

12. The imaging system of claim 1 , wherein the mirrors of the MEMS MMA tip, tilt and piston, wherein the mirrors are responsive to command signals to translate to shape the beam to perform one or more of the following:
adjust a size, divergence or intensity profile of the beam;
produce deviations in the wavefront of the beam to compensate for atmospheric distortion;
produce deviations in the wavefront of the beam to adjust the phase for path length variations across the beam and maintain a zero phase difference across the beam;
add optical power to focus or defocus the beam; and
partition MMA into a number of sections and approximate a continuous surface across the mirrors at the specified tip and tilt within each section.

13. A small angle beam steerer, comprising:
a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) positioned to receive an optical beam, said MEMS MMA comprising a plurality of independently and continuously controllable rigid mirrors responsive to command signals to partition the MMA into a plurality of segments, each segment including a plurality of mirrors, and to tip, tilt and piston each mirror in a three-dimensional space to form a steer a plurality of optical beams, wherein the maximum translation of each said mirror to piston is z; and
a controller responsive to specified steering angles for the plurality of segments configured to determine a maximum number of mirrors that may be grouped together in sections as limited by the maximum translation z for each segment to form a continuous surface at specified tip and tilt angles to provide the specified steering angle and to issue command signals to partition each segment of the MEMS MMA into the sections and to tip and tilt the mirrors to the same specified tip and tilt angles within and between and to translate each mirror in each section by a requisite amount such that the plurality of mirrors in each section approximate a continuous mirror surface at the same specified tip and tilt angles with edge discontinuities existing only between adjacent sections to steer the optical beam for each segment at a specified steering angle.

14. The imaging system of claim 13 , wherein for each update of the specified steering angle for each segment the controller determines specified tip and tilt angles, updates the maximum number of mirrors that may be grouped together sections as limited by the maximum translation z to form a continuous surface at specified tip and tilt angles, updates the partition of the MEMS MMA, and tip, tilts and translates the mirrors to approximate the continuous surface at the specified tip and tilt angles to minimize edge discontinuities for the specified steering angle for each segment.

15. The imaging system of claim 13 , wherein the mirrors in each segment reflect light at different wavelengths such that the plurality of optical beams comprise a plurality of different wavelengths.

16. A small angle beam steerer, comprising:
a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) positioned to

Assignees

• Raytheon Co

Inventors

• Uyeno Gerald P
• Lange Mark K
• Keller Sean D
• Gleason Benn H
• Barker Zachary D
• Shott Craig O
• Rogala Eric

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