Scanning Laser Projector Photodiode Feedback for Mirror Angle Control
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Solution Overview
Problem
Existing laser scanning projectors face challenges in reliable mirror opening angle determination and backup power detection systems, leading to increased production time, cost, and potential system failures due to mirror drive electronics and power detector failures.
Innovation Solution
Incorporating photodiodes within the scan area but outside the projection area to provide feedback on laser beam angular position and optical power, utilizing a control circuit for on-the-fly calibration and fault detection, and integrating additional photodiodes as backups for mirror and power detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a power detector is placed within the laser beam path to detect laser beam parameters, then information about spot size, luminosity, color calibration, frequency, and modulation speed can be determined, but the system becomes vulnerable to single-point failures and requires costly redundant circuitry
Solution Approach 1:
The patent combines multiple functions into the photodiode feedback system: it simultaneously measures laser beam power, determines mirror opening angles, and provides fault detection capabilities. By integrating these functions into a single optical path measurement system rather than separate detectors, the patent achieves both precise measurement and inherent redundancy without requiring duplicate circuitry.
Solution Approach 2:
The patent implements a feedback mechanism where photodiodes detect laser beam parameters and provide real-time information to the control system. This feedback enables continuous monitoring of mirror positions and laser power, allowing the system to detect failures and maintain operation through adaptive control rather than requiring redundant detection circuitry.
2Measurement precision
If existing systems perform monitoring of mirror movement to determine opening angles, then feedback can be provided to maintain desired opening angles, but extensive calibration is required which increases production time and cost
Solution Approach 1:
The patent enables the system to perform its own calibration using the laser beam itself as a reference. The photodiodes measure the laser beam position and intensity, and the control system uses these measurements to automatically determine mirror opening angles without requiring external calibration equipment or procedures. This self-calibrating approach eliminates time-consuming manual calibration steps while maintaining measurement precision.
3Reliability
If photodiodes are placed within the scan area but outside the projection area, then feedback on laser beam angular position and optical power can be provided without interfering with the projected image
Solution Approach 1:
The patent positions photodiodes in the angular/spatial dimension of the scan area rather than in the projection plane. By placing detectors at locations where the laser beam passes during scanning but outside the final projection area, the system gains fault detection capability in a different dimensional space, avoiding interference with the projected image while maintaining compact optical module design.
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
Provides accurate and reliable mirror angle control, reduces calibration complexity, detects mirror failures, and ensures continuous operation by compensating for temperature variations and component failures, thereby enhancing system reliability and reducing costs.
Implementation Method 1
utilizing one or more photodiodes within the scan area but outside of the projection area to provide feedback on laser beam angular position and laser beam optical power
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A scanning laser projector (40) includes an optical module (10) and projection engine (41). The optical module includes a laser generator outputting a laser beam, and a movable mirror (20, 24) scanning the laser beam across an exit window defined through the housing in a scanning pattern wider than the exit window such that the laser beam is directed through the exit window in a projection pattern that is smaller than and within the scanning pattern. A first light detector (18a, 18b) is positioned about a periphery of the exit window such that as the movable mirror scans the laser beam in the scan pattern, at a point in the scan pattern where the laser beam is scanned across an interior of the housing and not through the exit window, the laser beam impinges upon the first light detector. The projection engine (41) adjusts driving of the movable mirror based upon output from the first light detector (18a, 18b).