Event Camera Lidar for Small Target Detection
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Solution Overview
Problem
Lidar systems face range ambiguities and limitations in detection capability due to pulsed laser systems and conventional framing cameras, which hinder accurate detection of small targets and are influenced by solar background noise and system architecture constraints.
Innovation Solution
The implementation of a rotating transmitter and receiver with an event-camera system that uses photon flux changes to calculate target range and angle, employing a bistatic optical arrangement and continuous wave laser for improved detection and reduced noise, allowing for detection of small targets like unmanned aerial systems without radar, day or night, and with reduced background clutter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulsed laser systems are used for Lidar ranging, then distance measurement capability is achieved, but range ambiguities occur making it impossible to determine which pulse is being received
Solution Approach 1:
The patent uses periodic modulation of the continuous wave laser at distinct frequencies for different beams. This periodic action allows the receiver to identify which pulse (or modulation cycle) is being received by detecting the specific frequency signature, thereby eliminating range ambiguities while maintaining continuous illumination for accurate ranging.
2Area of stationary object
If conventional framing cameras are used with rapid scanning, then contiguous coverage is achieved, but exposure times outside the laser signal time window create noise that limits detection capability
Solution Approach 1:
The system uses periodic modulation of the laser at distinct frequencies combined with synchronous detection at the receiver. This allows the receiver to filter out noise by only responding to signals at the expected modulation frequencies, enabling contiguous scan coverage while maintaining high detection capability by rejecting background noise.
3Measurement precision
If low-divergence laser beams are used, then range resolution is improved, but the speed of the second scan is limited reducing productivity
Solution Approach 1:
The patent segments the scanning function into multiple independent beams, each modulated at a distinct frequency. This segmentation allows parallel illumination of multiple spatial regions simultaneously, enabling faster second scan speeds while maintaining the range resolution benefits of low-divergence beams through the use of multiple narrow beams rather than one wide beam.
Solution Approach 2:
The system uses continuous wave lasers instead of pulsed lasers, providing continuous illumination throughout the scan. This continuity of useful action allows for faster scanning speeds since there are no pulse repetition frequency limitations, while range resolution is maintained through the low divergence of the continuous beams and frequency-based signal discrimination.
4Weight of moving object
If rotating transmitter and receiver elements are used, then system size, weight, and cost are reduced, but detection capability must be maintained
Solution Approach 1:
The patent combines the transmitter and receiver into a single rotating assembly that functions as an integrated radar-like system. This merging reduces system size and weight compared to separate stationary Lidar components, while detection accuracy is maintained through the use of frequency-modulated continuous wave illumination and synchronous detection that can accurately measure range and velocity of targets.
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 solution enhances the detection of small targets with improved range and angular resolution, reduces system size, weight, and cost, and increases the second scan rate without sacrificing range or resolution, enabling effective airspace monitoring from moving platforms.
Implementation Method 1
a laser operable to generate laser light 14... transmit the laser light along a first path from the Lidar system to a target... receive at least a portion of the laser light along a second path from the target
Data Source
AI summary
A Lidar system herein includes a transmitter operable to rotate at a first rate, and to transmit laser light along a first path from the Lidar system to a target, and a receiver operable to rotate with the transmitter, and to receive at least a portion of the laser light along a second different path from the target. The system includes an event-camera having a plurality of pixels being triggerable by photon flux changes. A processor calculates a range and an angle to the target using an angular displacement between the second path and the receiver that arises from the first rate of rotation for the transmitter and the receiver and, in part, from event data of at least one of the pixels based on a direction of the first path at a time of a photon flux change and a pixel coordinate of the at least one pixel.