Optical Scanning Mirror Resonance for Low-Power Spiral Rotation
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Solution Overview
Problem
Existing optical scanning devices using MEMS mirrors face issues with increased power consumption due to mismatched resonance frequencies between axes, leading to the need for higher driving voltages and wider power consumption ranges, especially when temperature and time cause frequency deviations.
Innovation Solution
An optical scanning device with a mirror portion that can swing around two orthogonal axes, controlled by separate actuators, uses cyclic voltage signals to maintain a spiral rotation operation by setting resonance frequencies and Q values differently for each axis, ensuring fd falls within a specific frequency range relative to fr1 and fr2, and Q1 and Q2, with varying amplitudes and phases over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the resonance frequency and Q value are matched between the first axis and the second axis, then the MEMS mirror can perform spiral rotation operation with low power consumption, but the driving frequency deviates from resonance frequency when temperature or time causes frequency changes, requiring significantly increased driving voltage and power consumption
Solution Approach 1:
The patent applies asymmetry by intentionally setting different Q values for the first and second resonance modes (Q1 ≠ Q2) while maintaining different resonance frequencies (fr1 ≠ fr2). This asymmetric configuration creates a frequency overlap region where the driving frequency can be set to simultaneously excite both resonance modes effectively. When temperature or time causes frequency drift, the system maintains stable spiral rotation operation within this overlap region without requiring significant increases in driving voltage, thereby resolving the contradiction between low power consumption and reliability under varying conditions.
Solution Approach 2:
The patent utilizes parameter changes by establishing a specific relationship between resonance frequencies and Q values that defines a valid driving frequency range: fr2×(1−1/(1.2×Q2))≤fd≤fr1×(1+1/(6×Q1)). This parameter-based approach allows the system to maintain effective spiral rotation operation across a range of driving frequencies, accommodating temperature and time-induced frequency variations without requiring active adjustment of resonance parameters or significant increases in power consumption.
2Reliability
If the driving voltage is significantly increased to maintain spiral rotation operation when resonance frequency changes, then the spiral rotation operation can be maintained, but the power consumption required for driving increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing the asymmetric resonance frequency and Q value relationship and determining the valid driving frequency range before actual operation. This preliminary configuration ensures that when the system operates within the predetermined frequency range (fr2×(1−1/(1.2×Q2))≤fd≤fr1×(1+1/(6×Q1))), it can maintain stable spiral rotation operation even when temperature or time causes frequency drift, without requiring reactive increases in driving voltage or power consumption.
3Adaptability or versatility
If the dynamic range of power consumption is widened to maintain spiral rotation operation in a wide temperature range, then the operation can be maintained across temperatures, but the overall power consumption is increased
Solution Approach 1:
The patent applies dynamics by creating a dynamic frequency overlap region through the asymmetric resonance configuration that naturally adapts to temperature and time-induced frequency variations. The system maintains spiral rotation operation across a wide temperature range by operating within the predetermined driving frequency range (fr2×(1−1/(1.2×Q2))≤fd≤fr1×(1+1/(6×Q1))), which provides inherent frequency tolerance. This dynamic adaptability is achieved without requiring active power consumption adjustments or widening the power consumption dynamic range, thereby resolving the contradiction between temperature range adaptability and overall power consumption.
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 approach reduces power consumption and minimizes fluctuations over time, maintaining efficient operation across varying temperatures and conditions.
Implementation Method 1
a resonance frequency and a resonance Q value of a resonance mode, among resonance modes accompanied by mirror tilt swing around the first axis, closest to a frequency of the cyclic voltage signal are respectively set as fr1 and Q1
Implementation Method 2
a resonance frequency and a resonance Q value of a resonance mode, among resonance modes accompanied by mirror tilt swing around the second axis, closest to the frequency of the cyclic voltage signal are respectively set as fr2 and Q2
Data Source
AI summary
An optical scanning device causes a mirror portion to perform a spiral rotation operation with a first driving signal applied to a first actuator and a second driving signal applied to a second actuator as cyclic voltage signals. In a case where a resonance frequency and a resonance Q value of a resonance mode, among resonance modes accompanied by mirror tilt swing around a first axis, closest to a frequency of the cyclic voltage signal are respectively set as fr1 and Q1, a resonance frequency and a resonance Q value of a resonance mode, among resonance modes accompanied by mirror tilt swing around a second axis, closest to the frequency of the cyclic voltage signal are respectively set as fr2 and Q2, and the frequency of the cyclic voltage signal is fd, a relationship of Q1≠Q2, Fr2<fr1, and fr2×(1−1/(1.2×Q2))≤fd≤fr1×(1+1/(6×Q1)) is satisfied.