MEMS Micro-Mirror Array for Active Pushbroom Imaging
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Solution Overview
Problem
Conventional active imaging systems face limitations in power consumption, weight, and complexity due to mechanical beamsteering, and liquid crystal waveguide (LCWG) devices are restricted to steering narrow wavelength bands, requiring multiple devices for different wavelengths and lacking wavefront manipulation capabilities.
Innovation Solution
The use of a Micro-Electro-Mechanical System (MEMS) Micro-mirror Array (MMA) with tip, tilt, and piston actuation for directing and focusing illumination, enabling rapid imaging scans with reduced weight, size, and power consumption, while accommodating multiple wavelengths and providing wavefront correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If mechanical beamsteering optics (gimbals) are used to reduce power consumption and enable selective aiming, then power consumption is reduced, but the system complexity, weight, and cost increase due to mechanical elements and motion compensating elements
Solution Approach 1:
The patent replaces mechanical beamsteering optics (gimbals) with a non-mechanical beamsteering device, specifically a liquid crystal waveguide (LCWG), which uses electro-optic effects to steer the laser beam without moving parts. This substitution eliminates the need for motion compensating elements and reduces system complexity while maintaining selective aiming capability and low power consumption.
2Device complexity
If liquid crystal waveguide (LCWG) is used for non-mechanical beamsteering, then system complexity is reduced, but the device can only steer a very narrow band of wavelengths requiring multiple devices for different wavelengths
Solution Approach 1:
The patent addresses the wavelength limitation of LCWG by integrating it with a diffuser that performs wavelength-dependent spatial filtering. This combination allows a single LCWG device to effectively handle multiple wavelengths by diffracting different wavelength components to different spatial locations, where they are subsequently filtered and recombined, enabling multi-wavelength operation without requiring multiple separate LCWG devices.
3Illumination intensity
If continuous illumination of the entire scene is provided for high-contrast imaging, then image quality is improved, but power consumption increases significantly
Solution Approach 1:
The patent applies local quality by using the LCWG to steer the laser beam and illuminate only specific regions of interest within the scene rather than continuously illuminating the entire scene. The diffuser further enhances this by directing different wavelength components to different spatial locations, allowing selective illumination of different areas simultaneously. This localized illumination approach maintains high image quality in regions of interest while dramatically reducing overall power consumption.
4Ease of operation
If mechanical gimbals are used for beamsteering, then selective aiming is enabled, but the scan speed is limited by the capability of the mechanical elements
Solution Approach 1:
The patent replaces mechanical gimbals with a liquid crystal waveguide that uses electro-optic phase modulation to steer the laser beam. This non-mechanical approach enables much faster beamsteering speeds because the LCWG can change beam direction electronically without the inertia and mechanical limitations of gimbal systems. The system maintains selective aiming capability while achieving rapid scanning speeds suitable for dynamic imaging applications.
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
The MEMS MMA system allows for efficient, rapid imaging scans across a wide field-of-view, reduces diffraction, and compensates for atmospheric distortions, achieving multi-spectral illumination and higher power output with reduced system complexity and cost.
Implementation Method 1
a MEMS MMA positioned along the transmit path to receive the electromagnetic radiation from the optical source and configured to form and scan the electromagnetic radiation in an optical beam
Implementation Method 2
reduces diffraction
Implementation Method 3
compensates for atmospheric distortions
Data Source
AI summary
An active imaging system uses a MEMS Micro-Mirror Array to form and scan an optical beam over a first portion of scene within a first edge region of the field-of-view of the optical receiver in the direction of motion of the imaging system. In addition to tip and tilt control of the mirrors, the MMA may have piston control which can be used to minimize diffraction losses when focusing and scanning the beam, provide wavefront correction or to compensate for path length variations. The MMA may be partitioned into segments to independently form and scan a plurality of optical beams, which may be used to scan the first or different portions of the scene. The different segments may be provided with reflective coatings at different wavelengths to provide for multi-spectral imaging. The different segments may be used to combine multiple optical sources to increase power or provide multi-spectral illumination.