MEMS Mirror Deflection Correction via Dual-Region Optical Sensor
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Solution Overview
Problem
Conventional image projection apparatuses using MEMS mirrors face challenges in accurately correcting deflection angles in both horizontal and vertical scanning directions, leading to inaccuracies in the irradiation position of the laser beam due to phase errors and environmental factors like temperature and pressure.
Innovation Solution
An image projection apparatus with a light irradiation device, an optical scan device, and an optical sensor system that includes first and second light receiving regions at different positions along the vertical scanning direction, allowing for the detection and correction of deflection angles in the vertical scanning direction based on the number of times the laser beam is detected by these regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the MEMS mirror is driven at a relatively high resonance frequency to perform horizontal scanning, then the scanning speed is improved, but a phase error is generated between the driving signal and the displacement of the MEMS mirror, causing inaccuracy in the horizontal scanning direction
Solution Approach 1:
The patent uses an optical sensor to detect the actual position of the laser beam and feeds this information back to a control system. The control system then adjusts the driving signal to compensate for the phase error, ensuring that the laser beam is scanned at the correct position despite the high resonance frequency driving
Solution Approach 2:
The patent replaces direct mechanical measurement of the MEMS mirror position with an optical detection system. By using an optical sensor to detect the laser beam position indirectly, the system avoids the limitations of direct mechanical sensing and achieves higher precision in phase error detection and correction
2Measurement precision
If conventional techniques are used to detect and correct phase error in the horizontal scanning direction, then horizontal phase accuracy is improved, but changes in deflection angle in both horizontal and vertical scanning directions due to temperature, pressure, or other effects cannot be corrected
Solution Approach 1:
The patent employs a single optical sensor system that serves multiple functions: it detects phase errors in the horizontal scanning direction, monitors deflection angle changes in both horizontal and vertical directions, and provides data for correcting all these errors. This multi-functional approach enables the system to adapt to various error sources including temperature and pressure effects
Solution Approach 2:
The control system receives feedback from the optical sensor about the actual laser beam position and deflection angle changes, and continuously adjusts the driving signals for both horizontal and vertical scanning to compensate for these changes, maintaining accurate irradiation positions despite environmental variations
3Device complexity
If a single light receiving region is used in the optical sensor, then the device complexity is reduced, but the ability to detect and correct deflection angle changes in the vertical scanning direction is lost
Solution Approach 1:
The optical sensor is segmented into multiple light receiving regions arranged at different positions along the vertical scanning direction. Each region detects the laser beam at a specific vertical position, and by comparing the detection results from different regions, the system can determine deflection angle changes in the vertical scanning direction with high accuracy
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
This solution improves the accuracy of the laser beam's irradiation position by effectively correcting deflection angles in the vertical scanning direction, enhancing the overall precision of the image projection process.
Implementation Method 1
an optical sensor arranged outside the display region, and including a first light receiving region and a second light receiving region that are arranged at different positions along a vertical scanning direction
Data Source
AI summary
An image projection apparatus includes a light irradiation device configured to irradiate a laser beam, an optical scan device configured to deflect the laser beam to make an optical scan, and project an image on a display region, an optical sensor arranged outside the display region, and including a first light receiving region and a second light receiving region that are arranged at different positions along a vertical scanning direction of the optical scan, and a deflection angle controller. The deflection angle controller corrects a deflection angle in the vertical scanning direction of the optical scan device, based on a number of times the laser beam is detected by the first light receiving region and a number of times the laser beam is detected by the second light receiving region.