Ladar Range Rate Compensation for Moving Target Precision
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Solution Overview
Problem
Ladar systems face challenges in accurately characterizing moving targets due to blurring caused by accumulating photon counts over long periods, which affects signal-to-noise ratio and results in imprecise range and range rate estimates.
Innovation Solution
A method and system for ladar signal processing that involves transmitting laser pulses, detecting return photons with an array detector, forming range histograms, applying a Radon transform, and iteratively adjusting the range rate to sharpen the collapsed histogram peak, thereby improving the precision of range and range rate estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If photon counts are accumulated over a relatively long period of time to improve the signal to noise ratio, then the signal to noise ratio is improved, but blurring occurs in the target characterization
Solution Approach 1:
The patent applies dynamics by making the range histogram dynamic through range rate compensation. Instead of using a static accumulation approach, the system continuously updates the range histogram by compensating for target motion (range rate) between frames. This allows the system to maintain long integration times for improved signal-to-noise ratio while dynamically adjusting for target movement to prevent blurring, thus resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The patent changes the parameter of range rate compensation to resolve the contradiction. By estimating and compensating for range rate (the rate of change of range), the system adjusts the range histogram to account for target motion during the integration period. This parameter change allows long accumulation times for better signal-to-noise ratio while maintaining measurement precision through motion compensation.
2Reliability
If photon counts are accumulated over a relatively long period of time, then the signal to noise ratio is improved, but blurring results in imprecise range and range rate estimates
Solution Approach 1:
The patent implements feedback by using the range rate estimate from the previous frame to compensate for motion in the current frame's range histogram. This feedback loop allows the system to accumulate photons over long periods for improved signal-to-noise ratio while continuously correcting for target motion to maintain precise range and range rate estimates. The feedback mechanism resolves the contradiction by using the motion information itself to correct the blurring it causes.
Solution Approach 2:
The patent applies preliminary action by performing range rate compensation before forming the final range histogram. The system estimates the range rate and uses this information to pre-adjust the range bins in the histogram, preventing motion-induced blurring before it occurs. This preliminary compensation allows long integration times for better signal-to-noise ratio while maintaining estimation precision.
3Device complexity
If a simple range histogram is formed without range rate compensation, then the processing is simpler, but the range estimate is blurred and less accurate for moving targets
Solution Approach 1:
The patent applies segmentation by dividing the range histogram formation process into distinct stages: (1) forming individual range histograms for each frame, (2) estimating range rate from these histograms, and (3) compensating for range rate by shifting range bins before accumulation. This segmentation allows the system to maintain relative simplicity in each individual step while achieving high accuracy through the coordinated sequence of operations, resolving the contradiction between processing complexity and measurement precision.
Solution Approach 2:
The patent introduces another dimension by adding the time dimension to the range histogram analysis. Instead of forming a single static histogram, the system creates a sequence of histograms over time and uses range rate compensation to account for motion in the temporal dimension. This dimensional expansion allows accurate range estimation for moving targets while maintaining manageable processing complexity through efficient algorithms.
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 approach enhances the accuracy of target range and range rate estimation by reducing blurring and improving the signal-to-noise ratio, allowing for sharper peaks in the collapsed histogram and more precise target characterization.
Implementation Method 1
a camera including an array detector, the camera being configured to: detect, for each laser pulse of the sequence of laser pulses, a plurality of ladar return photons from the laser pulse, each detection producing an electrical pulse
Data Source
AI summary
A system and method for forming a range estimate for a target with a laser detection and ranging system. The system includes a laser transmitter and an array detector. The method includes: transmitting a plurality of laser pulses; for each transmitted laser pulse: detecting, with the array detector, a plurality of ladar return photons from the laser pulse, each detection producing an electrical pulse; identifying, for each of the electrical pulses, a time bin of a plurality of time bins corresponding to the laser pulse, within which the electrical pulse was produced; forming a one dimensional range histogram array having, for each of a subset of the plurality of bins, an element with a value equal to the number of electrical pulses produced in the array detector during a time interval corresponding to the bin; and forming an estimated range rate for the target.