Scanning Mirror Synchronization via Low-Pass Filtered Adjustment
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Solution Overview
Problem
In scanning display systems, achieving precise control of the scanning mirror's position and velocity at frequencies other than its natural resonant frequency is challenging, leading to image artifacts due to ringing from harmonic oscillations, especially when shifting the mirror position between frames to maintain synchronization.
Innovation Solution
A low pass filtered adjustment signal is used, with a cutoff frequency based on the lowest resonant frequency of the scanning mirror, to avoid energizing resonant frequencies and reduce ringing, allowing the adjustment signal to be applied before the end of a frame without prolonging the frame rate or reducing image size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the scanning mirror is adjusted between frames to maintain synchronization, then synchronization precision is improved, but resonant vibrations cause image artifacts
Solution Approach 1:
The patent applies preliminary anti-action by using a low-pass filtered adjustment signal that proactively suppresses frequency components near the mirror's resonant frequency before the adjustment is applied. This prevents the resonant vibrations from occurring in the first place, rather than attempting to correct them afterward. The filter is designed with a cutoff frequency that specifically targets and attenuates the problematic resonant frequencies, eliminating image artifacts while maintaining synchronization precision.
Solution Approach 2:
The patent changes the frequency domain parameters of the adjustment signal by applying low-pass filtering. This transforms the signal to remove harmful frequency components while preserving the necessary low-frequency adjustment components. By modifying the spectral content of the adjustment signal, the system achieves precise mirror positioning without exciting resonant modes that cause image artifacts.
2Productivity
If the adjustment signal is applied before the end of a frame, then frame rate is maintained, but resonant oscillations may occur
Solution Approach 1:
The low-pass filter is applied in advance to the adjustment signal, preparing a vibration-free control signal before it is applied to the mirror. This preliminary filtering ensures that when the adjustment signal is applied during the frame, it does not contain frequency components that would excite resonant oscillations, thus maintaining both frame rate and mirror stability.
Solution Approach 2:
The patent transforms the adjustment signal in the frequency domain by applying low-pass filtering, changing its spectral characteristics to eliminate harmful high-frequency components. This parameter change allows the system to apply adjustments rapidly (maintaining frame rate) while the filtered signal ensures stability by excluding resonant frequencies.
3Adaptability or versatility
If the scanning mirror is controlled at frequencies other than resonant frequency, then scanning flexibility is improved, but control precision deteriorates
Solution Approach 1:
The patent applies low-pass filtering to the adjustment signal, which changes the frequency domain parameters by attenuating high-frequency components. This allows the system to operate at non-resonant frequencies with improved precision, as the filter removes frequency components that would otherwise cause control instability and positioning errors.
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 enables fast and precise adjustment of the scanning mirror, minimizing ringing and image artifacts, and maintains synchronization between video data and the scanning mirror system without requiring fine-tuning or re-tuning over the device's lifetime.
Implementation Method 1
combining the control signal with an adjustment signal to adjust the scanning in the second direction, the adjustment signal comprising a low pass filtered signal with a cutoff frequency based on a lowest resonant frequency of the scanning mirror system
Implementation Method 2
achieving precise control of the scanning mirror's position and velocity at frequencies other than its natural resonant frequency is challenging, leading to image artifacts due to ringing from harmonic oscillations
Data Source
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AI summary
Examples are disclosed herein related to controlling a scanning mirror system. One example provides a display device, comprising a light source, a scanning mirror system configured to scan light from the light source in a first direction at a first, higher scan rate, and in a second direction at a second, lower scan rate, and a drive circuit configured to control the scanning mirror system to display video image data by providing a control signal to the scanning mirror system to control scanning in the second direction, and for each video image data frame of at least a subset of video image data frames, combining the control signal with an adjustment signal to adjust the scanning in the second direction, the adjustment signal comprising a low pass filtered signal with a cutoff frequency based on a lowest resonant frequency of the scanning mirror system in the second direction.