Laser Projection Safety Circuit for Power Monitoring
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Solution Overview
Problem
Existing image projection systems using high power lasers and scan mirror drives face safety concerns due to the risk of exceeding regulatory laser power limits, particularly when monitoring systems fail, potentially endangering viewers and bystanders.
Innovation Solution
Incorporating a safety circuit that monitors the output power of lasers and the oscillation of scan mirrors, with redundant safety circuits to deenergize lasers and mirror drives upon detection of malfunctions or excessive power, ensuring compliance with safety standards and enhancing safety features in a compact, portable module.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the output power of each laser is increased to enhance image brightness, then the image brightness is enhanced, but the regulatory safety limits on laser power output are exceeded
Solution Approach 1:
The safety circuit is configured to monitor laser output power before it can exceed regulatory limits. The circuit proactively detects power levels and deenergizes the laser assembly in advance of any potential safety violation, preventing harmful exposure before it occurs.
Solution Approach 2:
The safety circuit continuously monitors the output power of the laser assembly and provides feedback control. When the monitored power exceeds a predetermined threshold, the circuit automatically deenergizes the laser, creating a closed-loop safety mechanism that maintains power within regulatory limits.
2Reliability
If the monitor photodiode fails or becomes electrically disconnected, then the feedback signal is lost and the feedback circuit increases laser output power, but this compromises viewer and bystander safety
Solution Approach 1:
The safety circuit provides a redundant protection layer that operates independently of the feedback circuit. This cushioning safety mechanism ensures that even if the monitor photodiode fails or the feedback circuit malfunctions, the laser power remains controlled and cannot exceed safe levels.
Solution Approach 2:
The safety circuit acts as an intermediary monitoring system that directly monitors laser output power and independently controls the laser assembly's energization state. This intermediary safety layer bypasses the potentially faulty feedback circuit and provides direct, reliable safety control.
3Ease of operation
If the scan angle of each mirror is reduced due to malfunction or stalling, then the drive appears to be working, but the output power intensity exceeds regulatory limits at the smaller angular area
Solution Approach 1:
The safety circuit continuously monitors the actual laser output power and provides feedback control. When power intensity exceeds predetermined safety thresholds - which would occur if scan mirrors stall or reduce scan angles - the circuit automatically deenergizes the laser assembly, preventing intense localized power exposure.
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 power output and ensures safe operation by deenergizing components upon detection of malfunctions or excessive power, maintaining compliance with regulatory limits and enhancing safety in consumer applications.
Implementation Method 1
an energizable laser assembly for generating a laser beam having an output power when energized
Implementation Method 2
an energizable scanner for sweeping the laser beam as a pattern of scan lines on a projection surface
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Red, blue and green lasers respectively emit a plurality of red, blue and green laser beams having respective output powers. The beams are optically focused and collinearly arranged to form a composite beam which is swept by a pair of scan mirrors in a pattern of scan lines on a projection surface, each scan line having a number of pixels. A controller causes selected pixels to be illuminated, and rendered visible, by the composite beam to produce an image. A safety circuit detects a malfunction of at least one of the lasers and the scan mirrors, and deenergizes the at least one of the lasers and the scan mirrors upon detection of the malfunction.