Laser Retroreflection Detection for Eye-Safe Hard Target Sensing
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Solution Overview
Problem
Existing optical systems, such as lidar systems, face challenges in ensuring eye safety for humans when they cannot utilize conventional methods like limiting wavelengths to eye-safe ranges or reducing power levels, especially in applications where these methods are impractical.
Innovation Solution
A hard target detection system for free-space laser systems that includes an optical detector positioned along the laser transmitter path to monitor retroreflections, allowing the system to control the laser into a safe state upon detection of a hard target within the field of view, such as turning off or reducing intensity to eye-safe levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the laser system uses high power levels to improve sensing capability, then the sensing performance is improved, but eye safety is compromised
Solution Approach 1:
The system performs preliminary detection by monitoring retroreflections from potential targets before the laser reaches harmful power levels. The optical detector continuously scans for retroreflected light, and when a target is detected, the system preemptively reduces or shuts off the laser power to prevent eye damage, thus resolving the contradiction between maintaining high power for sensing and ensuring eye safety.
Solution Approach 2:
The system implements a feedback mechanism where the optical detector monitors the retroreflected light from targets and sends signals back to the laser control system. Based on this feedback, the laser power is dynamically adjusted - maintaining high power when no targets are present (good sensing performance) and reducing power when targets are detected (ensuring eye safety), thus resolving the technical contradiction.
2Illumination intensity
If the laser system increases beam intensity to improve detection range, then the detection capability is improved, but the risk of eye damage increases
Solution Approach 1:
The laser beam intensity is made dynamic rather than static. The system continuously adjusts the beam intensity based on real-time detection of retroreflections. When no hard targets are detected, the system operates at high intensity for maximum detection range. When retroreflections indicate a hard target is present, the system dynamically reduces intensity to eye-safe levels, thus resolving the contradiction between detection range and eye safety.
3Object-affected harmful factors
If the system uses conventional eye safety methods (wavelength limiting or power reduction), then eye safety is ensured, but sensing performance deteriorates
Solution Approach 1:
The system implements periodic scanning with the optical detector to monitor for retroreflections while the laser operates at high power. This periodic detection allows the system to maintain high sensing performance during normal operation while periodically checking for safety conditions. When a target is detected during this periodic monitoring, the system switches to safety mode, thus resolving the contradiction between maintaining sensing performance and ensuring eye safety.
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
Effectively ensures eye safety by detecting and responding to the presence of humans or hard targets within the laser's field of view, preventing potential eye damage by controlling the laser beam intensity or shutting it off when necessary.
Implementation Method 1
An optical detector is positioned along the laser transmitter path to receive retroreflections of the laser beam
Data Source
Figure 1
Figure 2~3
Figure 4A~4B
AI summary
A system (10) and method for detecting hard targets (32) in a free-space laser system includes a laser (16), an optical detector (24), and electronics (18). The laser (16) is configured to emit a laser beam along an optical path (22) through transmitter optics (20) into a field of view. The optical detector (24) is positioned along a laser transmitter path and configured to receive retroreflections of the laser beam. The electronics (18) are configured to determine if an output of the optical detector (24) is indicative of presence of a hard target (32) within the field of view, and control the laser (16) to a safe state if the output is indicative of presence of the hard target (32).