Micromirror Abnormality Detection Using Piezoelectric Signal Fluctuation
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Solution Overview
Problem
Existing methods for detecting abnormal operations in micromirror devices, such as those used in LiDAR and HUD, are unable to do so at high speed due to the need to acquire and evaluate waveforms for one swing period, limiting their effectiveness in identifying dangerous conditions where laser light is continuously emitted to the same position.
Innovation Solution
An optical scanning device and method that utilizes a micromirror device with a piezoelectric element to detect abnormal operations based on temporal fluctuations in an output signal, employing a control device to resonate the mirror at a fixed swing period and a detection device to analyze signal fluctuations within a time interval shorter than 10% of the swing period, using a delay circuit and differential amplification to determine abnormality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If abnormality detection is performed based on current flowing through piezoelectric portion or separate detection piezoelectric portion, then detection coverage includes short circuit abnormalities, but other types of abnormalities cannot be detected
Solution Approach 1:
The piezoelectric element is designed to serve multiple functions: it acts as both the actuator that drives mirror oscillation and the sensor that detects abnormalities through electromotive force generation. This multi-functional design allows the system to detect various types of abnormalities (short circuit, open circuit, mechanical failures) without requiring separate detection components, thereby improving both detection coverage and method applicability.
Solution Approach 2:
The system uses the piezoelectric element's inherent ability to generate electromotive force during oscillation to detect abnormalities. The same component that performs the actuation function also provides the detection function through its electrical characteristics, eliminating the need for external detection systems and enabling versatile abnormality detection across different failure modes.
2Measurement precision
If waveform acquisition and evaluation for one swing period is performed to detect mirror amplitude, then detection accuracy is improved, but abnormal operation cannot be detected at high speed
Solution Approach 1:
The patent extracts only the essential detection information (electromotive force fluctuations) from the piezoelectric element without requiring complete waveform acquisition over a full swing period. By focusing on specific electrical characteristic changes rather than analyzing entire waveforms, the system achieves high-speed abnormality detection while maintaining sufficient detection accuracy.
Solution Approach 2:
Instead of performing complete waveform evaluation for one swing period, the system uses partial action by detecting electromotive force fluctuations that occur during abnormal operations. This partial detection approach enables rapid identification of abnormalities without the time-consuming process of acquiring and analyzing full waveforms, thereby achieving high-speed detection.
3Measurement precision
If phase difference or amplitude detection is performed by acquiring waveform for one swing period, then detection accuracy is improved, but high-speed detection is not achieved
Solution Approach 1:
The patent replaces the mechanical/optical detection approach (waveform acquisition and phase/amplitude analysis) with an electrical detection method. By measuring electromotive force fluctuations from the piezoelectric element, the system directly detects abnormalities without requiring time-consuming waveform acquisition and analysis, thus reducing time loss while maintaining detection accuracy.
Solution Approach 2:
The system continuously monitors the electromotive force output from the piezoelectric element during normal operation. When an abnormality occurs, the pre-existing monitoring system immediately detects the electromotive force fluctuations, enabling rapid response without the delay of acquiring waveforms after abnormality detection is initiated.
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 rapid detection of abnormal mirror operations, preventing dangerous continuous laser emission by identifying deviations in the output signal within a fraction of the swing period, thereby ensuring user safety.
Implementation Method 1
a piezoelectric element that generates and outputs electromotive force by the swinging of the mirror
Data Source
AI summary
An optical scanning device of the present disclosure includes: a micromirror device including a mirror that has a reflecting surface for reflecting light and is swingable around at least one axis, an actuator that allows the mirror to swing, and a piezoelectric element that generates and outputs electromotive force by the swinging of the mirror; a control device configured to control an operation of the actuator; and an abnormality detection device configured to detect an abnormal operation of the mirror based on a temporal fluctuation amount in an output signal from the piezoelectric element.