MEMS Micro-Mirror Array Steering for Active Sensor Scanning
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Solution Overview
Problem
Existing active situational awareness sensors face challenges in achieving size, weight, power, and cost (SWaP-C) efficiency and signal-to-noise ratio (SNR) due to the use of large, expensive lasers and mechanical rotation for scanning, which also results in atmospheric backscatter and limited flexibility in scanning capabilities.
Innovation Solution
A Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) steers a laser spot-beam over a conical mirror, allowing for rapid 360° horizontal scanning with a specified vertical field-of-regard, moving between multiple objects per frame, varying dwell time, and compensating for external factors, without moving parts, using a parabolic mirror and a conical fixed mirror to focus and redirect the beam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single laser is used to generate a collimated spot-beam and a mirror is physically rotated to scan the beam, then the laser power requirement is reduced and atmospheric backscattering is avoided, but mechanical rotation is introduced which increases device complexity and SWaP-C
Solution Approach 1:
The patent replaces the mechanical rotation system with a MEMS micro-mirror array that uses electrostatic actuation to steer the laser beam. Each micro-mirror can be independently controlled to deflect the beam to different angles, eliminating the need for large mechanical rotators while maintaining scanning capability. This substitution of mechanical systems with electro-optical systems directly reduces device complexity and SWaP-C.
Solution Approach 2:
The patent divides a single large mirror into an array of many small micro-mirrors (e.g., 7x7 grid). Each micro-mirror independently controls a portion of the beam, allowing electronic steering of the entire beam profile. This segmentation enables the system to achieve scanning functionality without requiring a single large mechanically rotated mirror, thereby reducing mechanical complexity.
2Device complexity
If flash illumination is used to simultaneously illuminate the entire FOR, then no moving parts are required, but a laser with a lot of power is needed which increases size, weight and cost
Solution Approach 1:
The patent employs a dynamic scanning approach where the MEMS micro-mirror array rapidly switches between different mirror configurations to scan the laser beam across the field of regard. This allows the system to illuminate different portions of the FOR sequentially rather than requiring simultaneous illumination of the entire field, thereby reducing the peak power requirement while maintaining coverage.
Solution Approach 2:
The system uses periodic scanning through the MEMS array to cycle through different beam positions and illumination patterns. By distributing the illumination over time through repeated scanning cycles, the system achieves complete field coverage without requiring the peak power of flash illumination, thus reducing overall laser power requirements.
3Device complexity
If flash illumination is used to simultaneously illuminate the entire FOR, then no moving parts are required, but atmospheric backscatter is produced which reduces the signal-to-noise ratio
Solution Approach 1:
The patent segments the illumination process by using the MEMS micro-mirror array to scan the laser beam across different portions of the field of regard sequentially. This divides the total illumination into many smaller, time-separated illumination events, each illuminating a limited portion of the atmosphere. Consequently, the atmospheric backscatter from each individual illumination event is significantly reduced compared to simultaneous flash illumination of the entire field.
4Speed
If a MEMS MMA is used to steer the spot-beam, then rapid scanning with no moving parts is achieved, but device complexity increases due to the micro-mirror array control system
Solution Approach 1:
The patent replaces complex mechanical scanning systems with a MEMS micro-mirror array that uses electrostatic actuation mechanisms. Each micro-mirror is driven by simple electrostatic forces controlled through standard electronics, avoiding the need for complex mechanical linkages, motors, and gear systems. This substitution achieves rapid scanning capability while keeping the control system relatively simple and integrated.
Solution Approach 2:
The patent integrates the beam steering function directly into the optical path by placing the MEMS micro-mirror array in the laser beam. This merging of the steering mechanism with the optical system eliminates the need for separate mechanical scanning assemblies, reducing overall device complexity while enabling rapid electronic control of beam direction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution reduces SWaP-C, minimizes atmospheric backscatter, and enhances SNR by enabling flexible scanning and real-time adaptation, allowing for efficient object detection and ranging in complex systems without the need for mechanical rotation.
Implementation Method 1
A parabolic mirror with a hole formed at its center is configured to receive the beam of optical radiation and focus it into a spot-beam at a location on a conical shape of a fixed mirror
Implementation Method 2
A fixed mirror having a conical shape is positioned in front of the parabolic mirror... which redirects and focuses the optical radiation into a spot-beam at different locations on the conical shape of the fixed mirror to steer the spot-beam about the optical axis and scan a FOR
Implementation Method 3
A MEMS Micro-Mirror Array (MMA) is positioned between the parabolic mirror and the fixed mirror to receive the beam of optical radiation. The MEMS MMA, responsive to command signals from a controller, tips and tilts one or more mirrors to steer the beam onto different off-axis sections of the parabolic mirror
Data Source
AI summary
An active situational sensor uses a Micro-Electro-Mechanical System (MEMS) Micro-Mirror Array (MMA) to steer an optical beam to different off-axis sections of a parabolic mirror, an “OAP”, to re-direct and focus optical radiation into a spot-beam onto a conical shape of a fixed mirror, which redirects the spot-beam to scan a FOR. The sensor may rapidly scan a 360° horizontal FOR with a specified vertical FOR or any portion thereof, move discretely between multiple specific objects per frame, vary the dwell time on an object or compensate for other external factors to tailor the scan to a particular application or changing conditions in real-time. The MEMS MMA may be configurable to shape the spot-beam to adjust size, focus or intensity profile or to produce deviations in the wavefront of the spot-beam to compensate for path length differences or atmospheric distortion. The MEMS MMA being configurable to produce and independently steer a plurality of spot-beams of the same or different wavelengths.