MEMS Mirror Angle Detection Using Support Portion Reflection
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Solution Overview
Problem
Existing irradiation apparatuses face challenges in reliably detecting the rotation angle of a light deflecting mirror, especially when it is stationary, and incur increased costs due to the need for forming through holes in the mirror, which affects the accuracy and efficiency of light reflection and detection.
Innovation Solution
An irradiation apparatus with a first light source, a light deflector including a rotatable light deflecting mirror, a second light source, a light receiver, and an angle detection unit that detects the rotation angle based on the changed reflection direction of the second light, allowing for reliable detection even when the mirror is stationary, and includes a correction unit to prevent displacement of the irradiation range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light emitting unit and light receiving unit are used to detect rotation angle based on light intensity change, then rotation detection is possible, but detection fails when the light deflecting mirror stays still on a slant
Solution Approach 1:
A second light source and light receiver are introduced as intermediary components to detect the rotation angle of the light deflecting mirror. The second light is reflected by the support portion rather than the mirror surface itself, allowing detection to work even when the mirror is stationary on a slant, thus resolving the reliability issue while maintaining measurement precision
2Measurement precision
If a through hole is formed in the light deflecting mirror for light reception, then light receiving condition improves, but the reflected light becomes darker and manufacturing cost increases
Solution Approach 1:
The detection function is extracted from the light deflecting mirror itself by using the support portion as the reflection surface. This eliminates the need to form through holes in the mirror, maintaining manufacturing simplicity and cost-effectiveness while still achieving good light receiving conditions for angle detection
Solution Approach 2:
The support portion serves as an intermediary reflection surface that redirects the second light to the light receiver. This intermediary approach provides adequate light receiving condition without requiring modifications to the light deflecting mirror, thus avoiding the harmful effects of through hole formation
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
Enables reliable detection of the rotation angle of the light deflecting mirror in both axial directions with a simple structure, preventing irradiation range displacement and reducing costs by eliminating the need for through holes, thus enhancing the accuracy and efficiency of light scanning.
Implementation Method 1
a light receiver which receives the second light radiated from the second light source and reflected by the support portion of the light deflector
Data Source
AI summary
In an MEMS projector (10), an image signal processing unit (110) outputs an inspection signal, and an inspection signal processing unit (114) outputs a light emission instruction signal. An inspection light source drive unit (112) outputs a light emission signal, and an inspection light source (13) radiates an inspection light. The inspection light radiated from the inspection light source (13) is reflected at the reflection position RP of a first support portion (22), and then received by a light receiver (14). Then, the light receiver (14) outputs a received light signal. Based on the received light signal, the inspection signal processing unit (114) detects the angle of the light deflecting mirror (20) around the X axial line.