Scanning Mirror Control with Position Offset for Resonant Stability
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Solution Overview
Problem
Resonant systems face challenges in maintaining precise control due to component drifts with time, age, and temperature, affecting the stability of feedback control circuits used to excite resonant modes in applications like scanning laser projectors.
Innovation Solution
A drive circuit that combines feedback signals from MEMS devices to phase-lock slow-scan movement to a sync signal and corrects for fast-scan residual by adding position offsets, ensuring consistent raster scan trajectories across frames, thereby maintaining resonant motion on the fast-scan axis and non-resonant motion on the slow-scan axis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback control circuits are used to control resonant systems at peak resonant modes, then the system can maintain resonance at a particular frequency, but component drifts with time, age, and temperature increase design challenges and reduce system reliability
Solution Approach 1:
The system performs preliminary calibration to determine resonant frequencies and Q factors before operation begins. These calibration values are stored and used during normal operation, eliminating the need for complex real-time feedback control circuits and reducing sensitivity to component drifts.
Solution Approach 2:
The patent replaces complex feedback control circuits with a simpler system that uses pre-determined calibration data. Instead of continuously monitoring and adjusting via feedback, the system uses stored resonant frequency and Q factor values to generate drive signals, substituting a mechanical/feedback-based approach with a data-driven approach.
2Measurement precision
If resonant motion is maintained on the fast-scan axis, then scanning precision is improved, but component drifts affect the stability of feedback control circuits
Solution Approach 1:
The system performs preliminary calibration to determine the resonant frequency and Q factor of the fast-scan axis mirror. These calibration values are stored and used to generate drive signals during normal operation, ensuring consistent scanning precision without relying on unstable feedback control circuits.
Solution Approach 2:
The patent creates a model of the resonant system's behavior through calibration measurements. This model (stored resonant frequency and Q factor values) is then used to generate drive signals, copying the ideal resonant response without requiring continuous feedback adjustment.
3Stability of the object's composition
If video buffering is implemented to handle frame rate mismatches, then display stability is improved, but latency increases
Solution Approach 1:
The system dynamically adjusts the slow-scan axis timing based on the actual resonant frequency of the fast-scan axis. By making the slow-scan period a non-integer multiple of the fast-scan period, the system achieves better frame synchronization with reduced buffering requirements and lower latency.
Solution Approach 2:
The patent changes the relationship between slow-scan and fast-scan periods from a fixed integer multiple to a non-integer multiple based on measured resonant frequencies. This parameter adjustment optimizes the synchronization between scan axes, reducing the need for extensive video buffering and minimizing latency.
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 latency and buffering requirements, allowing for accurate video presentation at arbitrary frame rates, matching display frame rates to video frame rates over time and temperature, and minimizing the impact of component drifts on system performance.
Implementation Method 1
a resonant plant is excited to move on a fast-scan axis in response to periodic excitations at a resonant frequency
Data Source
AI summary
A scanning mirror resonates on a first axis and moves on a second axis at a frequency dictated by a sync signal. The period of movement on the second axis is not necessarily an integer multiple of the period of movement on the first axis. A drive circuit excites movement of the mirror. The drive circuit adds a position offset to the signal that excites movement on the second axis. The position offset is capable of causing the resonant movement on the first axis to scan a substantially identical trajectory for at least a portion of each period on the second axis.