Laser Projector Safety Circuit with Dual Feedback Control
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Solution Overview
Problem
Conventional laser projectors and wearable heads-up displays face challenges in ensuring user safety due to potential eye damage from excessive laser power and current consumption, and they often lack aesthetically appealing designs that balance functionality with visual quality.
Innovation Solution
The implementation of a laser projector system with dual safety circuits, including a photodetector and current sensor, that automatically interrupt power to the laser diodes when power or current thresholds are exceeded, combined with a compact design for wearable heads-up displays that integrates a laser projector with a transparent combiner for safe and stylish operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If laser power is increased to improve display brightness and visibility, then visual quality is improved, but eye safety is compromised due to excessive laser exposure
Solution Approach 1:
The patent implements a feedback control system using a photodetector to continuously monitor the actual laser light power and compare it against a predetermined safety threshold. When the monitored power exceeds the threshold, the system automatically adjusts the laser diode current to reduce power output, thereby maintaining display brightness within safe limits and preventing eye damage
Solution Approach 2:
The system establishes a predetermined maximum permissible exposure (MPE) threshold before operation begins. The photodetector and control circuitry are pre-configured to detect and counteract excessive power levels before they can cause harm, proactively preventing eye damage rather than responding after damage occurs
2Power
If laser current is increased to improve laser output power, then display visibility is improved, but device reliability deteriorates due to excessive current consumption
Solution Approach 1:
A current sensor provides real-time feedback on the actual current consumed by the laser diode. The control circuit compares this feedback against a predetermined maximum current threshold and automatically adjusts the drive current to prevent excessive current consumption, thereby maintaining laser output power while preserving device reliability
Solution Approach 2:
The system dynamically adjusts the laser diode operating parameters (current and power) based on real-time monitoring feedback. Rather than operating at a fixed high current level, the system continuously adapts the current to the minimum necessary level to achieve safe and effective display output, reducing stress on components and improving overall device reliability
3Object-affected harmful factors
If safety monitoring circuits are added to prevent eye damage, then eye safety is improved, but device complexity increases
Solution Approach 1:
The patent combines the safety monitoring functions (photodetector, current sensor, threshold comparison, and control) into an integrated control circuit that works seamlessly with the existing laser driver. Rather than adding completely separate safety subsystems, the monitoring and control functions are merged with the operational control architecture, reducing overall system complexity while maintaining comprehensive 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
The solution ensures safe operation by preventing eye damage from excessive laser exposure and provides a compact, aesthetically appealing wearable heads-up display that maintains high visual quality while minimizing the risk of eye injury.
Implementation Method 1
a photodetector responsive to laser light output by the at least one laser diode
Implementation Method 2
a beam splitter positioned and oriented to direct a first portion of laser light from the at least one laser diode along a first optical path towards the photodetector and a second portion of laser light from the at least one laser diode along a second optical path towards an output of the laser projector
Data Source
AI summary
Laser safety systems, devices, and methods for use in laser projectors are described. A laser projector includes any number of laser diodes that each emit laser light, a laser diode power source, a current sensor to detect a magnitude of the electric current output by the power source, a photodetector to detect a power/intensity of the laser light, a beam splitter to direct a first portion of the light towards the photodetector and a second portion of the light towards an output on the projector, and first and second laser safety circuits responsive to signals from the photodetector and the current sensor, respectively. The laser safety circuits selectively electrically couples/uncouples the laser diodes from the power source depending on signals from the photodetector and/or the current sensor. Particular applications of the laser safety systems, devices, and methods in a wearable heads-up display are described.