MEMS Laser Projection Timing Compensation for Mirror Sensor Delay
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Solution Overview
Problem
Existing laser projection systems suffer from inaccuracies in pixel timing due to temperature-dependent delays in mirror position sensing, which affect the alignment of projected images.
Innovation Solution
A photodetector is integrated to provide an accurate indication of the mirror's actual position, allowing a controller to estimate and compensate for delays in the timing of light source illumination by comparing outputs from both MEMS motion sensors and photodetectors, thereby enhancing pixel alignment accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If MEMS motion sensors are used to sense mirror position, then the system can control scanning modes with high precision, but temperature-dependent delays occur in the sensing signals causing pixel timing inaccuracies
Solution Approach 1:
A photodetector is introduced as an intermediary component to directly detect the mirror's actual position by sensing reflected light. This external optical reference serves as a mediator between the mirror and the control system, providing accurate position information that is independent of the temperature-affected MEMS sensor signals, thereby resolving the timing accuracy issue
Solution Approach 2:
The system implements a feedback mechanism where the photodetector's output is compared with the MEMS sensor output to determine timing delays. This feedback loop continuously monitors the discrepancy between sensed and actual mirror positions and uses this information to compensate for timing errors in pixel projection, maintaining accurate image alignment despite temperature variations
2Manufacturing precision
If the system compensates for timing delays using photodetector comparison, then pixel alignment accuracy improves, but device complexity increases due to additional components
Solution Approach 1:
The photodetector is integrated into the existing light engine structure, serving multiple functions: it acts as a position reference sensor, a timing calibration device, and an optical alignment tool. By making this component multi-functional, the system achieves improved pixel alignment without proportionally increasing overall device complexity
Solution Approach 2:
The patent combines the photodetector with the existing MEMS mirror and light source into an integrated light engine assembly. The photodetector is positioned to utilize the same optical path as the projection system, merging sensing and projection functions into a single compact unit, thereby minimizing 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 system achieves more precise alignment of pixels on the projection surface by compensating for temperature-dependent delays, resulting in improved image quality and accuracy.
Implementation Method 1
an optical sensor or photodiode...which...provides, at at least one time t, an output indication of light reflected from the mirror
Data Source
AI summary
A laser projection system comprising a MEMS structure including a moving mirror and MEMS motion sensor sensing the moving mirror's position; and/or a photodetector which indicates the moving mirror's actual position by providing, at at least one time t, an output indication of light reflected from the mirror at time t which indicates that the moving mirror has reached p at said time t; and/or a controller which, based on the sensor's time-stamps, provides control signals determining illumination of/which illuminates locations of a display surface with illumination reflected off the moving mirror. The location illuminated within the display surface varies as the mirror moves. The controller estimates a delay, in provision of time-stamps for generation of pixels to be displayed on the surface, by comparing outputs of the sensor and photodetector, and, when controlling timing of the light source's illumination, takes into account/compensates for delay as estimated.