3D Ladar System for Wide-Area Surveillance
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Solution Overview
Problem
Wide-area surveillance systems face high false alarm rates and low detection probabilities due to the lack of depth information in optical sensors, making it difficult to differentiate anomalous activity from normal activity in large areas.
Innovation Solution
A rapid-update 3D ladar system is employed for wide-area surveillance, utilizing a pulsed laser with a transmitter and receiver comprising Geiger-mode avalanche photodiodes, a scanning system with a polygonal mirror scanner, and a data processing computer that generates 3D point clouds and detects geometric changes to reduce false alarms and detect anomalous activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensors are used for wide-area surveillance, then angular resolution is improved, but depth information is lost making it difficult to differentiate anomalous activity from normal activity
Solution Approach 1:
The patent transitions from 2D optical sensing to 3D ladar sensing by adding the depth dimension through time-of-flight measurements. The ladar system measures range to targets in addition to angular position, creating three-dimensional spatial information that enables differentiation of anomalous activity from normal activity in wide-area surveillance.
2Reliability
If a single-photon 3D ladar system is used for wide-area surveillance, then detection probability is improved, but system complexity increases
Solution Approach 1:
The patent replaces traditional mechanical scanning systems with a polygonal mirror scanner that uses rotational mechanics to achieve rapid scanning. The polygonal mirror with multiple facets enables fast angular modulation without complex electronic beam steering, reducing system complexity while maintaining high detection probability through rapid scene coverage.
Solution Approach 2:
The ladar system integrates multiple functions into a single platform: ranging, imaging, and surveillance detection. The Geiger-mode avalanche photodiode arrays serve both as sensitive photon detectors and as components that can operate in different gating modes to detect various types of targets, reducing the need for separate specialized systems.
3Speed
If rapid-update scanning is implemented to detect moving objects, then detection speed is improved, but false alarm rate increases due to clutter
Solution Approach 1:
The patent implements feedback through the data processing computer that continuously analyzes ladar returns and updates the surveillance display. The system processes range-resolved data to distinguish moving objects from stationary clutter by comparing sequential scans, providing feedback that reduces false alarms while maintaining rapid detection capability.
Solution Approach 2:
The system performs preliminary scanning and data collection before final target identification. The polygonal mirror scanner rapidly accumulates range-resolved data from the entire field of regard, preprocessing the scene information so that when a potential target is detected, the system can quickly confirm or reject it based on already-collected data, reducing false alarms while maintaining speed.
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 achieves low false alarm rates and high detection confidence by providing direct measurement of scene geometry, enabling effective detection of objects moving through empty space with high sensitivity and low false alarms.
Implementation Method 1
The transmitter includes a pulsed laser generating optical pulses for illuminating the scene... The receiver includes a sensor to detect light scattered and reflected from the scene... continuously generates 3D point clouds
Implementation Method 2
The sensor comprises one or more arrays of Geiger-mode avalanche photodiodes... detect light scattered and reflected from the scene
Implementation Method 3
The scanning system includes a polygonal mirror scanner that rotates and scans the FOV across the scene... allows the transmitter and receiver subsystem field-of-view (FOV) to interrogate a field-of-regard (FOR)
Data Source
AI summary
A system for generating a 3D image of a scene includes a transmitter, a receiver, a scanning system and a data processing computer. The transmitter includes a pulsed laser generating optical pulses for illuminating the scene, and the optical pulses have a pulse width of less than 20 nanoseconds and a pulse repetition frequency in the range of 20 kHz to 200 kHz. The receiver includes a sensor to detect light scattered and reflected from the scene, and the sensor comprises one or more arrays of Geiger-mode avalanche photodiodes. The scanning system allows the transmitter and receiver subsystem field-of-view (FOV) to interrogate a field-of-regard (FOR) of at least 30 degrees, with update rates faster than once per 5 seconds, resolution higher than 1 million resolution elements per second, and FOR aspect ratios of 1:10 to 1:1. The data processing computer continuously generates 3D point clouds with latency less than 5 seconds, and generates alarms indicating anomalous activity within the scene.