Dual-Axis Mirror Resonance Control via Cross-Axis Induced Signal Extraction
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Solution Overview
Problem
Existing mirror devices struggle to reliably drive a scanning mirror in a resonance state due to the difficulty in extracting the counter electromotive force signal, which has a similar frequency and small amplitude compared to the driving signal, making it challenging to control the mirror effectively.
Innovation Solution
A mirror device with dual drive axes, where the mirror is flappable around a first drive axis with a higher resonance frequency and a second drive axis with a lower resonance frequency, includes a signal extracting portion to obtain and amplify the induced signal from the second drive axis, allowing for the generation of a driving signal that maintains the mirror in a resonance state by adjusting the frequency and phase difference between the driving signal and the induced signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the counter electromotive force is detected in a form in which it has been added to the driving signal, then the signal can be obtained from the drive portion, but it is difficult to extract the counter electromotive force component because the frequencies are the same and the amplitude is small
Solution Approach 1:
The patent segments the signal detection process by using two separate drive portions (first and second drive portions) with different resonance frequencies. The counter electromotive force from the first drive portion is detected through the second drive portion, allowing frequency-based signal separation. This segmentation enables the extraction of the counter electromotive force signal by filtering at the specific resonance frequency of the first drive axis, resolving the difficulty of extracting a small signal buried in a larger driving signal at the same frequency.
2Device complexity
If a single drive axis is used for mirror flapping, then the device structure is simple, but it is difficult to reliably drive the mirror in a resonance state due to inability to extract feedback signal
Solution Approach 1:
The patent implements a feedback control mechanism where the counter electromotive force generated by the first drive portion is detected through the second drive portion. The signal extracting portion extracts this counter electromotive force signal, and the signal generating portion uses it to generate a driving signal that maintains the mirror in a resonance state. This feedback loop ensures reliable resonance state control by continuously monitoring and adjusting based on the actual mirror flapping response, overcoming the unreliability of open-loop control in single-axis systems.
Solution Approach 2:
The second drive portion serves multiple functions: it drives the mirror around the second axis and simultaneously acts as a detection mechanism for the counter electromotive force generated by the first drive portion. This multi-functionality allows the system to achieve reliable resonance control without adding separate detection sensors, maintaining relative structural simplicity while enabling feedback control.
3Difficulty of detecting and measuring
If the resonance frequency of the second drive axis is made lower than the first drive axis, then the induced signal can be extracted more easily, but the device requires dual drive axes with different frequency characteristics
Solution Approach 1:
The patent employs dynamic frequency separation where the first drive axis operates at a higher resonance frequency and the second drive axis at a lower resonance frequency. This dynamic frequency differentiation allows the counter electromotive force signal from the first axis to be easily extracted through the second axis by filtering at the specific higher frequency, avoiding signal overlap. The dual-axis configuration with different frequencies creates a natural frequency domain separation that simplifies signal extraction despite the increased structural 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
This configuration enables reliable driving of the mirror in a resonance state, facilitating accurate light irradiation and image acquisition by effectively extracting and utilizing the induced signal for feedback control.
Implementation Method 1
a synthesized signal including an induced signal generated in the second drive portion due to an operation of flapping the mirror around the first drive axis
Data Source
AI summary
Provided is a mirror device including a mirror which is supported to be flappable around a fast axis and supported to be flappable around a slow axis and in which a resonance frequency of flapping thereof with respect to the fast axis is a first value and a resonance frequency of the flapping thereof with respect to the slow axis is a second value lower than the first value; a signal extracting portion configured to obtain from a slow axis coil a synthesized signal including an induced signal generated in the slow axis coil due to an operation of flapping the mirror around the fast axis and configured to extract the induced signal from the synthesized signal; and a signal generating portion configured to generates a driving signal so that the flapping of the mirror with respect to the fast axis is in a resonance state according to the induced signal.