MEMS Lissajous Scan Axis Synchronization for Fast Startup Lock
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Solution Overview
Problem
Lissajous scanning systems face delays in achieving synchronization between scanning axes, particularly during startup, due to the need to align microelectromechanical system (MEMS) mirrors with reference signals, which can be time-consuming and may result in phase errors, especially with narrow resonance curves.
Innovation Solution
A system comprising an oscillator structure, drivers for generating drive signals, a phase error detector, comparator circuit, reference signal generator, and synchronization controller to synchronize the oscillations of two scanning axes by monitoring angular trajectories and triggering reference signals when the phase difference is within a threshold, enabling faster Lissajous lock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the MEMS mirror resonance curve is walked to the targeted working point and the axis is synchronized towards a reference frequency, then synchronization accuracy is improved, but the startup time increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimal frequency points and synchronization parameters in lookup tables before operation. During startup, the system directly retrieves pre-computed synchronization data instead of performing time-consuming real-time frequency walking and phase alignment, thereby achieving fast startup without sacrificing synchronization accuracy.
Solution Approach 2:
The patent replaces the traditional mechanical frequency walking process with a computational approach using lookup tables and digital signal processing. Instead of physically tuning the MEMS mirror frequency through gradual adjustment, the system uses pre-stored frequency data and digital control algorithms to achieve synchronization, significantly reducing startup time while maintaining precision.
2Measurement precision
If large phase errors are compensated for during startup, then synchronization accuracy is improved, but the total startup time is violated
Solution Approach 1:
The patent pre-calculates phase correction values for various initial phase error conditions and stores them in lookup tables. During startup, regardless of the initial phase error magnitude, the system retrieves the appropriate pre-computed correction value and applies it immediately, achieving accurate phase synchronization without the time penalty of gradual compensation.
Solution Approach 2:
The patent changes the control parameter from gradual phase adjustment to direct phase correction using pre-computed values. By storing multiple frequency and phase parameters in lookup tables corresponding to different operating conditions, the system can instantly switch to the correct parameters, achieving fast startup with accurate synchronization even when large initial phase errors exist.
3Adaptability or versatility
If frequency shifts are performed for control and compensation tasks in narrow MEMS resonance curves, then adaptability is improved, but the oscillation stability deteriorates due to collapse risk
Solution Approach 1:
The patent pre-identifies and stores stable frequency operating points within the narrow MEMS resonance curve in lookup tables. These pre-characterized frequency points represent positions where the resonance curve provides adequate stability margins. During operation, the system selects from these pre-validated frequency points rather than performing arbitrary frequency shifts, maintaining adaptability while avoiding instability.
Solution Approach 2:
The patent introduces lookup tables as an intermediary between the control system and the MEMS oscillator. The lookup tables contain pre-computed frequency and phase parameters that mediate between control requirements and physical constraints of the narrow resonance curve, enabling frequency control while maintaining oscillation stability by avoiding direct, potentially destabilizing frequency shifts.
4Measurement precision
If the system waits for Lissajous lock before transmitting light beams, then scanning accuracy is improved, but the operational readiness time increases
Solution Approach 1:
The patent performs preliminary synchronization preparation by pre-calculating and storing the frequency and phase parameters needed for Lissajous lock in lookup tables during system initialization or manufacturing. When the system starts up, it can immediately apply these pre-computed parameters to achieve Lissajous lock rapidly, ensuring both scanning accuracy and fast operational readiness without the traditional waiting period.
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 significantly reduces the time required for the scanning system to achieve synchronization and become operational, allowing for quicker startup and efficient light beam transmission.
Implementation Method 1
two resonant scanning axes which are each driven at constant scanning frequency
Data Source
AI summary
A method of synchronizing a first oscillation about a first axis with a second oscillation about a second axis includes: generating a first position signal that indicates a position of the first oscillation about the first axis; generating a second position signal that indicates a position of the second oscillation about the first axis; determining a phase difference between the first and the second position signals; comparing the phase difference to a threshold value to generate a comparison result; generating a first reference signal having a first frequency and a second reference signal having a second frequency; synchronizing the first oscillation to the first frequency and synchronizing the second oscillation to the second frequency; monitoring the comparison result; and synchronously triggering a start of the first reference signal and the second reference signal responsive to the comparison result indicating that the phase difference is less than the threshold value.