MEMS Mirror Driving with Modulated Pulse Signals
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Solution Overview
Problem
Existing MEMS mirror systems are limited by sinusoidal oscillation at resonance frequency, restricting movement patterns and requiring external optical measurements for calibration and fault detection, which is complex and unsuitable for large arrays.
Innovation Solution
A modulated pulse signal with a pulse frequency higher than the resonance frequency and a modulation frequency lower than the resonance frequency is used to drive the MEMS mirror, allowing for arbitrary movement patterns and electrical measurement of angular velocity and position without external sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the mirror is driven at resonance frequency using pulse trains, then the mirror oscillation amplitude can be maintained with feedback control, but the movement pattern is restricted to sinusoidal oscillation with varying angular velocity
Solution Approach 1:
The patent uses periodic excitation pulses at the resonance frequency to maintain mirror oscillation, while superimposing a modulation signal on these pulses to create composite waveforms. This allows the mirror to follow arbitrary movement patterns (triangular, sawtooth, rectangular) while still benefiting from resonant amplification and feedback control for amplitude stability.
Solution Approach 2:
The patent dynamically adjusts the phase and amplitude of the modulation signal relative to the excitation pulses to control the mirror's movement pattern. By varying the modulation depth and phase, the system can transition between different movement patterns (sinusoidal, triangular, sawtooth, rectangular) while maintaining stable oscillation through feedback control.
2Adaptability or versatility
If the mirror is driven at constant angular velocity using triangular or sawtooth signals below resonance frequency, then arbitrary movement patterns are achieved, but the driving frequency cannot be changed readily and external optical measurement is required
Solution Approach 1:
The patent replaces external optical measurement systems with electrical measurement of the induced voltage in the coil. The induced voltage is proportional to the mirror's angular velocity, providing a direct electrical signal for feedback control without requiring external optical sensors or test screens.
Solution Approach 2:
The patent uses the induced voltage signal from the coil as feedback to control the modulation signal applied to the mirror. This closed-loop control allows precise regulation of the mirror's movement pattern and angular velocity while maintaining electrical measurement capability.
3Measurement precision
If excitation pulses are used to maintain resonant oscillation, then feedback about mirror movement can be obtained through induced current measurement, but the driving frequency is fixed at the resonance frequency
Solution Approach 1:
The patent makes the driving frequency adjustable by allowing the modulation signal frequency to vary independently from the excitation pulse frequency. The modulation frequency can be changed to achieve different movement patterns and scanning rates, while the excitation pulse frequency remains at or near the resonance frequency for efficient driving.
Solution Approach 2:
The patent separates the excitation function (maintaining resonant oscillation) from the movement pattern control function (modulation signal). This segmentation allows independent optimization of both functions: excitation pulses maintain stable oscillation with electrical measurement, while the modulation signal provides flexible frequency and pattern control.
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 flexible movement patterns, real-time calibration and fault detection of individual MEMS mirror systems in arrays, preventing hazards by monitoring mirror movement and compensating for parasitic frequencies.
Implementation Method 1
driving a mirror (2) pivotably mounted around an axis (7) to a frame (8) via at least one elastic connection element (9) by means of a coil (4)
Implementation Method 2
the counter-voltage induced by the movement of the coil (4) in the magnetic field (B) can be measured
Data Source
Figure 1~2
Figure 3a~3b
Figure 4~5
AI summary
The present invention relates to an apparatus (12) for driving and measuring a MEMS mirror system (1), the MEMS mirror system (1) having a mirror (2) pivotable around an axis (7) by a driving coil (4) and exhibiting a resonance frequency (fr), having a pulse generator (13) and a measuring unit (14), each electrically connected to the coil (4); the pulse generator (13) being configured to feed a modulated pulse signal (sp), comprised of pulses (pk) separated by intervals (ik) and having a modulation frequency (fm) different from the resonance frequency (fr), to the coil (4); the measuring unit (14) being configured to measure a value (svk) of a signal (si) output by the coil (4) during an interval (ik) of the modulated pulse signal (sp). In a further aspect of the invention a method is provided for driving and measuring said MEMS mirror system (1).