Scanning Mirror Oscillation Control for Laser Safety
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Solution Overview
Problem
Conventional scanning image display devices face challenges in preventing laser beam emission due to various failure modes and malfunctions, which can lead to unsafe radiation levels and increased power consumption, as they rely on mechanical spring forces or complex optical systems to control the scanning mirror.
Innovation Solution
A scanning mirror system with a mirror unit, supporter, and oscillation sensor that monitors the mirror's oscillation and laser intensity, using a breaking signal to cause the supporters to oscillate beyond their breaking limit angles when abnormal conditions are detected, ensuring safe operation and preventing excessive laser radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional scanning image display devices use mechanical spring forces or complex optical systems to control the scanning mirror, then the device can operate, but it cannot reliably prevent laser beam emission due to various failure modes and malfunctions
Solution Approach 1:
The patent extracts the safety control function from the complex optical system and mechanical spring forces, implementing it through a dedicated oscillation sensor and control unit that independently monitors mirror oscillation and controls laser emission. This separates the safety monitoring function from the display function, improving reliability without requiring complex optical systems.
Solution Approach 2:
The patent implements feedback control by using an oscillation sensor to continuously monitor the scanning mirror's oscillation state and feeding this information back to the control unit. The control unit then adjusts or stops laser emission based on the monitored oscillation, ensuring safe operation. This feedback mechanism reliably prevents laser beam emission during abnormal conditions.
2Illumination intensity
If the laser output is increased to make the display brighter, then the display brightness improves, but the risk of radiating dangerous laser levels outside the device increases
Solution Approach 1:
The oscillation sensor provides real-time feedback on the scanning mirror's oscillation state to the control unit. When the sensor detects abnormal oscillation or stops in oscillation, the control unit immediately reduces or stops laser emission, preventing dangerous laser radiation even when high brightness is attempted. This feedback mechanism allows the system to maintain brightness during normal operation while automatically preventing harmful radiation during abnormal conditions.
3Object-affected harmful factors
If the scanning mirror oscillation amplitude is reduced to prevent laser radiation, then safety improves, but the image display quality and brightness deteriorate
Solution Approach 1:
The oscillation sensor continuously monitors the scanning mirror's oscillation amplitude and provides feedback to the control unit. During normal operation with sufficient oscillation amplitude, the control unit allows high laser output for bright display. When the sensor detects reduced oscillation amplitude indicating potential malfunction, the control unit automatically reduces or stops laser emission, preventing safety hazards while maintaining display quality during normal operation.
4Reliability
If additional sensors and control mechanisms are added to improve safety monitoring, then the reliability of preventing laser radiation improves, but the device complexity and cost increase
Solution Approach 1:
The oscillation sensor serves multiple functions: it monitors the scanning mirror's oscillation state for safety control, detects abnormal oscillation patterns, and provides feedback for controlling laser emission. By making the sensor multi-functional, the patent improves safety monitoring capability without adding separate dedicated components, thereby limiting the increase in device complexity.
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 effectively prevents excessive laser radiation and reduces power consumption by reliably shutting down the laser beam emission, maintaining safety standards and efficient operation without requiring additional materials or complex optical systems.
Implementation Method 1
a supporter that causes the mirror unit to rotate and oscillate
Implementation Method 2
an oscillation sensor that outputs a monitor signal according to oscillation of the mirror unit
Implementation Method 3
A photodetector detects an intensity of the laser beam
Implementation Method 4
a breaking signal for causing the supporter to oscillate more than a breaking limit angle of the supporter is input
Data Source
AI summary
A scanning mirror includes a mirror unit configured to reflect a laser beam, a supporter configured to cause the mirror unit to rotate and oscillate, and an oscillation sensor configured to output a monitor signal indicating oscillation of the mirror unit. A photodetector detects an intensity of the laser beam. When a value of the monitor signal falls out of a predetermined range of a normal operation and a value of the intensity detected by the photodetector fails to decrease, a breaking signal for causing the supporter to oscillate more than a breaking limit angle of the supporter is input. This scanning mirror and an image projection device using this scanning mirror can display an image at sufficient brightness safely.