Deformable Mirror Wavefront Correction for Aero-Optical Distortion
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Solution Overview
Problem
High-speed flight vehicles equipped with EO/IR sensors face significant errors in target location due to aerodynamic and atmospheric effects, such as wavefront distortion caused by temperature and pressure differences, which current software solutions fail to adequately correct, leading to lower quality target state information.
Innovation Solution
A system that uses a pulsed laser, wavefront sensor, and deformable mirror to measure and correct aero-optical and aero-thermal effects on the optical window of the sensor, with separate control algorithms for slow and fast update rates to address aerodynamic and atmospheric effects respectively, and a MEMS MMA for three-dimensional wavefront correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a look up table (LUT) software solution is used to correct aerodynamic effects, then the system cost and weight are kept low, but the target location accuracy deteriorates due to model inaccuracies
Solution Approach 1:
The patent replaces the software-based LUT correction system with a hardware-based wavefront correction system using a deformable mirror. This substitution enables direct measurement and physical correction of wavefront distortions caused by aerodynamic effects, significantly improving target location accuracy while maintaining acceptable system weight.
Solution Approach 2:
The patent introduces a wavefront sensor as an intermediary device between the EO/IR sensor and the target. This intermediary measures the wavefront distortions caused by aerodynamic effects and enables precise correction through the deformable mirror, bridging the gap between the sensor and target to improve location accuracy.
2Device complexity
If no wavefront correction is applied, then the system complexity remains low, but the sensor resolution deteriorates due to wavefront distortion
Solution Approach 1:
The patent replaces the inadequate software-based LUT correction with a hardware-based wavefront correction system using a deformable mirror. This substitution provides active, adaptive correction of wavefront distortions, maintaining high sensor resolution while managing system complexity through integrated design.
3Device complexity
If a single correction system is used for both aerodynamic and atmospheric effects, then the device complexity is reduced, but the correction accuracy deteriorates due to different update rate requirements
Solution Approach 1:
The patent segments the correction system into two independent control loops: a slow loop for aerodynamic effects and a fast loop for atmospheric effects. This segmentation allows each loop to be optimized for its specific update rate requirements, improving overall correction accuracy while managing complexity through modular architecture.
Solution Approach 2:
The patent implements dynamic control with different update rates for different correction loops. The slow control loop operates at lower update rates suitable for aerodynamic effects, while the fast control loop operates at higher update rates for atmospheric effects, allowing the system to adapt to different temporal characteristics of the disturbances.
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 system effectively corrects wavefront distortions, improving the accuracy of target location and reducing aberrations, thereby enhancing the performance of EO/IR sensors on supersonic flight vehicles by directly measuring and compensating for aerodynamic and atmospheric effects in real-time.
Implementation Method 1
A laser is used to emit pulses through the optical window with timing codes referenced to a clock
Implementation Method 2
A wavefront sensor referenced to the clock measures the distortion in the optical path to the target by detecting returning laser pulses
Implementation Method 3
A deformable mirror positioned in the optical path is responsive to command signals to piston orthogonal to the plane of the mirror to correct a wavefront of the received light for the measured aero-optical and aero-thermal effects
Implementation Method 4
Aero-thermal effects are caused by heating of the window/dome and optical system by compression of the air by the flight vehicle operating at high speeds
Implementation Method 5
The heating of the window causes variations in refractive index and distortion of the window shape
Implementation Method 6
caused by compression of air and turbulence around the flight vehicle
Implementation Method 7
Aero-optical effects are caused by fluctuations of refractive index due to temperature and pressure differences in the air around the flight vehicle, which may be caused by compression of air and turbulence around the flight vehicle
Data Source
AI summary
A system and method for measurement and correction of aero-optical and aero-thermal effects to an EO/IR sensor's window/dome on a supersonic flight-vehicle. Range-gating of laser pulses measures and separates aerodynamic and atmospheric effects. Separate control algorithms and control loops at different update rates both simplifies the control algorithms and improves overall performance. The use of a MEMS MMA having tip/tilt/piston capabilities as the deformable mirror to provide wavefront correction enhances overall performance. The corrected laser pulses may also be used to actively illuminate a target to provide both active and passive detection.