MEMS Mirror Amplitude Control Circuit for Fast Startup
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Solution Overview
Problem
Conventional MEMS mirrors require a longer initialization period due to constant amplitude drive signals during both initialization and normal operation, which hinders the swift startup of devices like wafer defect scanners and projectors.
Innovation Solution
A control circuit that dynamically adjusts the drive signal amplitude for MEMS mirrors, starting with an upper threshold amplitude and gradually decreasing to a nominal amplitude based on the mirror's opening angle, ensuring the mirror reaches the desired oscillation efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a constant amplitude drive signal is used during initialization and normal operation, then the device structure remains simple, but the initialization period becomes longer
Solution Approach 1:
The drive signal amplitude is made dynamic rather than constant. The control circuit adjusts the amplitude in real-time based on the mirror's current state, transitioning from a high amplitude during initialization to a nominal amplitude during normal operation. This dynamic adjustment reduces the initialization period while maintaining manageable system complexity through state-based control logic.
Solution Approach 2:
The control circuit incorporates feedback from the opening angle determination circuitry to monitor the mirror's current opening angle. This feedback is used to control the amplitude of the drive signal, allowing the system to adapt the drive amplitude based on the mirror's position. The feedback mechanism enables faster initialization by adjusting amplitude according to real-time mirror state without requiring overly complex control architecture.
2Speed
If a high amplitude drive signal is used during initialization, then the mirror reaches desired opening angle faster, but the mirror may not reach the desired opening angle accurately
Solution Approach 1:
The drive signal amplitude is segmented into different levels based on the initialization stage. A high amplitude is used during early initialization to achieve fast startup, while a nominal amplitude is used during normal operation to maintain precision. The opening angle determination circuitry detects when the mirror reaches the desired angle, triggering the transition between amplitude segments. This segmentation allows the system to achieve both fast startup speed and accurate opening angle positioning.
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 initialization period of MEMS mirrors, enabling faster device startup, as demonstrated by reducing the time to reach the desired opening angle from 80 milliseconds to 7 milliseconds.
Implementation Method 1
the MEMS mirror begins an initialization or startup period during which it goes from rest to a oscillating at a resonant frequency
Implementation Method 2
The actuation of mirrors used in MEMS devices, referred to herein as MEMS mirrors, can be via the electromagnetic, electrostatic, piezoelectric, and thermoelectric effects, depending on application
Data Source
AI summary
Disclosed herein is a control circuit for a movable mirror. The control circuit includes driving circuitry configured to drive the movable mirror with a drive signal to effectuate oscillating of the movable mirror, opening angle determination circuitry configured to determine an opening angle of the movable mirror, and amplitude control circuitry. The amplitude control circuitry is configured to a) first cause the driving circuitry to generate the drive signal as having an upper threshold drive amplitude, and b) then later cause the driving circuitry to generate the drive signal as having a nominal drive amplitude, as a function of the opening angle of the movable mirror being equal to a desired opening angle.