Tunable-Frequency MEMS Mirror Control for Center Pixel Accuracy
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Solution Overview
Problem
MEMS mirrors in LIDAR systems suffer from pixel inaccuracies and image distortions in the center area due to non-ideal time-spread of measurement points in Raster and Lissajous scanning modes, leading to inefficient scanning patterns.
Innovation Solution
A MEMS mirror arrangement with a superimposed first and second set of electrical signals having tunable frequencies is used to control the 2-axis movement, compensating for non-ideal time-spread by adjusting the angle and direction of reflected light beams, allowing for higher pixel accuracy in the central area of the scanned image.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Raster or Lissajous scanning mode is used with MEMS mirror, then the mirror can systematically cover the scanned area, but the beam movement speed varies causing non-uniform distribution of scanned points with pixel inaccuracies in the center area
Solution Approach 1:
The patent applies dynamics by making the mirror movement pattern adaptable and variable rather than fixed. The mirror is controlled to perform sweeping motions where it can linger in the center area and move quickly along the edges, dynamically adjusting its speed and position to achieve uniform point distribution. This resolves the contradiction by allowing the system to maintain high productivity through systematic coverage while improving measurement precision in the center area through controlled lingering motions.
Solution Approach 2:
The patent changes the motion parameters of the MEMS mirror, specifically the beam movement speed and angular position over time. By varying these parameters to create a non-uniform scanning pattern that compensates for the natural speed variations in Raster/Lissajous modes, the system achieves uniform point distribution. The control signals adjust the mirror's angular velocity and position to ensure adequate sampling in the center area while maintaining overall scanning efficiency.
2Ease of operation
If constant sampling rate is used in Raster scanning, then the scanning process is simple to control, but a larger number of points are scanned near the edges compared to the center resulting in pixel inaccuracies
Solution Approach 1:
The patent changes the sampling rate parameter from constant to variable over time. The control system adjusts the sampling frequency dynamically based on the mirror's position in the scanning pattern, increasing sampling rate when the beam is in the center area and decreasing it at the edges. This resolves the contradiction by maintaining ease of operation through automated control while significantly improving measurement precision through adaptive sampling.
Solution Approach 2:
The patent implements feedback control where the system monitors the mirror position and beam movement speed, then adjusts the sampling rate accordingly. The control signals are generated based on real-time feedback about the scanning state, allowing the system to automatically compensate for speed variations and maintain uniform point distribution. This feedback mechanism resolves the contradiction by keeping the control system relatively simple while achieving high measurement precision.
3Shape
If the mirror moves with highest speed in the center and lowest near edges in Lissajous mode, then the scanning pattern is well-defined, but less points are scanned in the center than near the edges causing image distortion
Solution Approach 1:
The patent applies dynamics by transforming the static, fixed-speed Lissajous pattern into a dynamic scanning pattern where the mirror speed and position are continuously adjusted. The mirror performs sweeping motions that linger in the center area and accelerate along the edges, dynamically adapting to compensate for the natural speed distribution in Lissajous mode. This resolves the contradiction by maintaining a well-defined scanning pattern shape while improving center area sampling through controlled dynamic motion.
Solution Approach 2:
The patent changes the motion parameters of the mirror, specifically varying the angular velocity and position over time to create a modified scanning pattern. The control signals adjust these parameters to ensure the beam spends adequate time in the center area while maintaining the overall Lissajous pattern structure. This resolves the contradiction by preserving the defined scanning pattern shape while correcting the non-uniform point distribution through parameter modulation.
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
The solution provides highly versatile sweep motion control, resulting in improved pixel accuracy and uniform distribution of measurement points across the scanned area, reducing image distortions and enhancing scanning efficiency.
Implementation Method 1
The mirror is configured to reflect an incoming light beam
Implementation Method 2
a first set of actuators connected to the mirror and a second set of actuators connected to the mirror, wherein the first set of actuators and the second set of actuators are configured to move the mirror
Data Source
Figure 1a~1b
Figure 2a~2b
Figure 3a~3c
AI summary
The disclosure describes an arrangement for highly versatile sweep motion control of MEMS mirrors. The disclosed solution allows controlling the 2-axis movement of MEMS mirrors via superimposed first set and second set of electrical signals having tunable frequencies. Mirror motion may be used to compensate for the non-ideal time-spread of measurement points.