Laser Direction Finding Under Speckle Illumination
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Solution Overview
Problem
Laser warning systems face significant errors in estimating the direction of a laser source due to non-uniform illumination caused by laser speckle, especially under direct illumination conditions, which affects the accuracy of direction finding.
Innovation Solution
A system comprising a detector array with sensors of unique orientation angles and sizes selected based on the speckle pattern to ensure uniform illumination, including both smaller sensors for speckle conditions and larger sensors for sensitivity in scattered beams, along with amplitude ratio calculation and angle of arrival estimation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large sensors are used to detect laser signals under beam scatter and indirect illumination, then sensitivity is improved, but direction estimation accuracy deteriorates due to laser speckle causing non-uniform illumination
Solution Approach 1:
The patent divides the detection function into two separate sensor arrays: a first array with larger sensors optimized for sensitivity under scattered/indirect illumination, and a second array with smaller sensors optimized for accuracy under direct illumination. This segmentation allows each array to specialize in specific illumination conditions without compromise.
Solution Approach 2:
Different sensor sizes are assigned to different arrays based on local illumination conditions. The first array uses larger sensors for areas experiencing scattered light, while the second array uses smaller sensors for areas experiencing direct laser illumination, matching sensor characteristics to local environmental conditions.
2Measurement precision
If small sensors are used to achieve uniform illumination under laser speckle, then direction estimation accuracy is improved, but detection sensitivity deteriorates in scattered beam conditions
Solution Approach 1:
The detection system is segmented into two specialized arrays: one with small sensors for accurate direction finding under direct illumination, and another with large sensors for sensitive detection under scattered illumination. This eliminates the need to compromise between the two opposing requirements.
Solution Approach 2:
The sensor size parameter is changed between the two arrays to optimize performance for different illumination conditions. The first array uses larger sensor areas for sensitivity, while the second array uses smaller sensor areas for uniform illumination and accurate direction estimation.
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 improves direction estimation accuracy by minimizing the impact of speckle effects and enhancing sensitivity across varying illumination conditions, providing reliable direction finding capabilities.
Implementation Method 1
a detector array comprising multiple sensors configured to detect the amplitude of the received laser signal
Implementation Method 2
laser speckle can cause these systems to generate unacceptably large errors in the estimated direction due to the resulting non-uniform illumination
Data Source
AI summary
Techniques are provided for estimating the direction of a laser source under non-uniform illumination conditions such as laser speckle. An example system may include a detector array comprising sensors configured to detect the amplitude of the received laser signal. The sensors are disposed on the array at unique orientation angles relative to each other. The sensor size is selected based on the speckle pattern of the laser signal such that the sensors are small enough to be uniformly illuminated by the laser signal in the presence of speckle. The system also includes an amplitude ratio calculation circuit configured to calculate ratios of the amplitudes between each of two sensors of one or more pairs of sensors. The system further includes an angle of arrival calculation circuit configured to estimate the direction of the source of the laser signal based on the calculated ratios and the orientation angles of the sensors.