Laser Emitter Shutdown Circuit for Fast Eye-Safety Cutoff
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Solution Overview
Problem
Light detection and ranging (LIDAR) systems face challenges in rapidly shutting down laser emission when an optical element becomes damaged or detached, leading to potential eye safety hazards due to the slow response time of software-based controllers.
Innovation Solution
A hardware-level shutdown circuit is implemented, utilizing a photodiode and conductive path to detect unsafe conditions and prevent current flow to the laser emitter, ensuring faster and more reliable shutdown by comparing signals with threshold voltages and filtering laser trigger signals to remove individual pulses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a software-based controller is used to detect and shut down laser emission, then the system can detect unsafe conditions, but the response time is too slow to prevent eye safety hazards
Solution Approach 1:
The patent replaces the software-based control system with a hardware-level shutdown circuit that uses photodiodes, comparators, and logic gates to detect unsafe conditions and trigger immediate laser shutdown. This substitution of software control with hardware circuitry enables instantaneous response to safety hazards, eliminating the delay inherent in software processing and execution.
Solution Approach 2:
The shutdown circuit continuously monitors optical elements through photodiodes before unsafe conditions can cause harm. By maintaining constant hardware-level surveillance and having the shutdown mechanism pre-configured and ready to activate, the system performs safety checks and prepared shutdown actions in advance, ensuring immediate response when damage is detected.
2Speed
If a hardware-level shutdown circuit is implemented, then the shutdown response time is reduced, but the device complexity increases
Solution Approach 1:
The shutdown circuit is divided into distinct functional modules: photodiodes for light detection, comparators for threshold comparison, logic gates for signal processing, and a flip-flop for state maintenance. Each segment performs a specific function, allowing the complex safety system to be constructed from simpler, well-understood components that can be independently optimized and tested.
Solution Approach 2:
The shutdown circuit is designed to work with multiple types of optical elements (lenses, diffusers, protective covers) using the same hardware architecture. The photodiodes and comparators can detect various failure modes including detachment, damage, and contamination, making the circuit universally applicable to different LIDAR configurations without requiring redesign.
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 shutdown circuit effectively and quickly prevents laser light emission when an unsafe condition is detected, enhancing eye safety by reacting faster than software-based systems and ensuring laser radiation levels do not exceed safety thresholds.
Implementation Method 1
a photodiode configured to output a first signal based on light emitted by the laser emitter and reflected from the optical element
Implementation Method 2
a filter for receiving a laser trigger signal for the laser emitter, the filter configured to output a filtered signal in which individual pulses of the laser trigger signal are removed
Data Source
AI summary
A shutdown circuit may include a filter, for receiving a laser trigger signal for a laser emitter, that is configured to output a filtered signal. The shutdown circuit may include a logic gate configured to receive the filtered signal and at least one of a first signal based on a signal from a photodiode or a second signal based on a signal from a conductive path. The shutdown circuit may include a flip-flop configured to receive an output of the logic gate and to output an enablement signal that is based on the output of the logic gate, and a driver circuit for a switch configured to control current flow to the laser emitter. The driver circuit may be configured to receive the enablement signal and the laser trigger signal and to output the laser trigger signal based on whether the enablement signal is a first or a second voltage.