Laser Beam Projection System Dynamic Phase Compensation
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Solution Overview
Problem
Coherent imaging systems face challenges in dynamic environments due to relative motion between the sensor and object, which introduces interference features and wavefront errors, requiring high-speed detectors and complex systems to maintain image quality.
Innovation Solution
A coherent imaging system that uses a Doppler sensor to measure and dynamically adjust the reference beam frequency, allowing for coherent imaging with lower bandwidth sensors and adaptive wavefront error correction using a deformable mirror to maintain image quality during dynamic engagements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coherent imaging is performed in dynamic environments with significant relative motion, then image quality degrades due to Doppler shifts and wavefront errors, but using high-speed detectors and complex correction systems increases device complexity and cost
Solution Approach 1:
The system performs preliminary wavefront sensing using the coherent imaging return beam before the high-energy laser beam projection. The measured wavefront errors are used to pre-compensate the outgoing laser beam through a deformable mirror, eliminating the need for complex real-time correction systems during the actual laser engagement.
Solution Approach 2:
The patent uses a separate low-power coherent imaging laser beam as an intermediary to sense atmospheric turbulence and wavefront distortions. This intermediary beam provides measurement data that is then applied to correct the main high-energy laser beam, avoiding the need for complex direct measurement systems on the high-power beam itself.
2Manufacturing precision
If a tightly focused laser beam is directed at a distant object through atmospheric turbulence, then the desired intensity profile at the target is degraded, but increasing beam power does not compensate for wavefront errors
Solution Approach 1:
The system establishes a feedback loop where the coherent imaging system continuously measures wavefront errors in the return beam, and this information is fed back to control the deformable mirror that shapes the outgoing high-energy laser beam. This closed-loop control maintains accurate intensity profiles despite atmospheric turbulence.
Solution Approach 2:
The patent dynamically changes the phase parameters of the outgoing laser beam by adjusting the deformable mirror surface in real-time. This modifies the wavefront of the laser beam to compensate for atmospheric turbulence, maintaining the desired intensity profile at the distant target.
3Device complexity
If relative motion between sensor and object is present, then interference features are introduced to the coherent signal, but using lower bandwidth sensors reduces measurement capability
Solution Approach 1:
The system extracts Doppler shift information from the coherent imaging return beam using a Doppler sensor. This separate extraction of velocity information allows the main imaging sensor to operate at lower bandwidth while still capturing both image and Doppler data, reducing overall system complexity.
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
Enables coherent imaging in dynamic environments with significant relative motion, improving image stability and accuracy by compensating for Doppler shifts and wavefront errors, extending the system's utility to highly dynamic scenarios.
Implementation Method 1
Doppler shift data from the Doppler sensor, corresponding to a longitudinal velocity of the object relative to the imaging system
Implementation Method 2
The difference is applied to a deformable mirror to shape the wavefront of the second projected laser beam for obtaining the optimum or desired intensity profile
Implementation Method 3
Interference between the Doppler-shifted LO illumination and the return illumination facilitates producing an image of the object with the low bandwidth FPA
Data Source
AI summary
An apparatus includes at least one processor configured to determine a wavefront phase profile of return illumination reflected from a remote object, where the wavefront phase profile is based on interference between Doppler-shifted local oscillator (LO) illumination and the return illumination. The at least one processor is also configured to calculate a wavefront error based on a comparison between (i) the determined wavefront phase profile of the return illumination and (ii) a desired wavefront phase profile of a high energy laser (HEL) beam. The at least one processor is further configured to control a deformable mirror to at least partially compensate the HEL beam for the calculated wavefront error.