MEMS Light Deflector Phase Difference Amplitude Control
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Solution Overview
Problem
Conventional light deflectors using MEMS mirrors face challenges in accurately measuring deflection angles, especially on the non-resonance side, requiring additional light sources and increasing costs, and struggle with sensitivity issues affecting amplitude detection.
Innovation Solution
A light deflector system with a rotary mirror driven by both resonant and non-resonant axes, utilizing a control unit to generate drive signals and a sensor to detect phase differences, allowing for amplitude calculation and sensitivity correction without needing a separate sensor for non-resonant drive detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a light guide and light receiving element are arranged to detect deflection angle using time difference from reference voltage signal, then the deflection angle can be accurately detected even when sensor sensitivity has lowered, but additional light sources and sensors are required which increases device complexity and cost
Solution Approach 1:
The patent makes the resonant drive signal serve dual purposes: both driving the MEMS mirror and as a reference signal for phase difference-based amplitude detection. This eliminates the need for separate detection light sources and sensors, reducing device complexity while maintaining detection accuracy through phase difference measurement
Solution Approach 2:
The patent combines the drive signal generation and reference signal provision into a single resonant drive signal. By merging these functions, the system avoids needing separate components for driving and reference signaling, thereby simplifying the overall device structure
2Measurement precision
If a sine wave drive waveform on resonance side is used, then the maximum deflection angle can be measured from light detection time, but on non-resonance side the MEMS mirror does not always operate according to drive waveform making accurate measurement difficult
Solution Approach 1:
The patent replaces mechanical/time-based detection methods with phase difference-based electrical signal processing. By using phase difference between drive and detection signals, the system achieves consistent measurement accuracy for both resonant and non-resonant drive modes without being constrained by mechanical operation characteristics
Solution Approach 2:
The patent changes the detection parameter from time-based light detection to phase difference measurement of electrical signals. This parameter change enables the system to accurately measure deflection angles in both resonant and non-resonant conditions by exploiting the phase relationship between drive and detection signals
3Measurement precision
If amplitude of voltage signal is not used for detecting deflection angle, then accurate detection is possible even when sensor sensitivity has lowered, but the configuration becomes more complex requiring additional sensors
Solution Approach 1:
The patent implements feedback by using the phase difference between the drive signal and detection signal to determine amplitude. This feedback mechanism allows the system to accurately detect deflection angle regardless of sensor sensitivity changes, as the phase relationship remains stable even when absolute signal amplitudes vary
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 accurate detection of MEMS mirror amplitude with a simple configuration, reduces costs by eliminating the need for additional sensors, and ensures safe operation by identifying and correcting abnormalities in non-resonant drive signals.
Implementation Method 1
a first axis which resonantly drives the rotary mirror
Data Source
AI summary
A light deflector 130 includes: a control unit 106 configured to generate a resonant drive signal for resonantly driving an MEMS mirror 133, and a non-resonant drive signal for non-resonantly driving the MEMS mirror 133; a resonant sensor 144 configured to detect the resonant drive of the MEMS mirror 133 and generate a resonant sensor signal; and a sensor signal processing unit 103 configured to acquire a phase difference between the resonant drive signal generated by the control unit 106 and the resonant sensor signal, in a case where the MEMS mirror 133 is resonantly driven in a Y-axis direction, also the MEMS mirror 133 is non-resonantly driven in an X-axis direction, and scanning is performed. The control unit 106 calculates an amplitude of the non-resonant drive of the MEMS mirror 133 on the basis of a change in the above phase difference.