Capacitive MEMS Mirror Sensing for Amplitude and Direction Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for detecting and regulating the amplitude and direction of oscillations in MEMS mirrors, such as those used in LiDAR systems, face challenges in accuracy and reliability due to ambient parameter variations and the inability to independently detect direction.
Innovation Solution
A device and method utilizing a detection circuit to measure changes in capacitance between electrodes, allowing for the calculation of oscillation amplitude and direction by analyzing time intervals and capacitance derivatives, independent of ambient conditions, and using asymmetries in capacitance profiles to determine direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If capacitance-based detection is used to measure mirror position, then the detection method is simple and integrated, but the measurement precision deteriorates due to ambient parameter variations
Solution Approach 1:
The patent implements feedback by continuously monitoring capacitance changes during oscillation and using this information to regulate the drive voltage. The system measures the actual oscillation amplitude through capacitance variations and adjusts the drive signal accordingly to maintain the desired amplitude, creating a closed-loop control system that compensates for ambient parameter variations.
Solution Approach 2:
The patent changes the operating parameters by using time interval measurements between specific capacitance events (zero crossings and extrema) rather than direct capacitance amplitude measurements. This parameter transformation makes the measurement independent of ambient conditions such as temperature and humidity, while still using the simple capacitance sensing mechanism.
2Loss of information
If capacitance changes are monitored during oscillation, then amplitude information can be obtained, but the ability to independently detect direction is lost
Solution Approach 1:
The patent segments the oscillation cycle into distinct phases by identifying specific events: zero crossings (where capacitance equals a reference value) and extrema (maximum and minimum capacitance points). By analyzing the sequence and timing of these segmented events, the system can independently determine both the amplitude and direction of oscillation without losing directional information.
Solution Approach 2:
The patent performs preliminary identification of zero crossing points and capacitance extrema during the oscillation cycle. By detecting these characteristic points in advance and measuring the time intervals between them, the system extracts both amplitude and direction information from the capacitance signal, preventing loss of directional data while maintaining amplitude measurement capability.
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
Enables accurate detection and regulation of oscillation amplitude and direction, ensuring precise control of the field of view in applications like LiDAR systems, regardless of ambient conditions, and enhances the reliability of MEMS mirror operations.
Implementation Method 1
a change in a capacitance between at least one electrode (20) of the oscillatory body (10) and a stationary electrode (22) takes place during the oscillation of the oscillatory body (10)
Implementation Method 2
the mirror is driven by electrostatic forces that pull the mirror
Data Source
AI summary
A device is provided for detecting and/or regulating an amplitude of an oscillation of an oscillatory body about an oscillation axis, wherein a change in a capacitance between at least one electrode of the oscillatory body and a stationary electrode takes place during the oscillation of the oscillatory body. The device comprises a detection circuit for detecting a signal representing a measure of the change in capacitance; and an evaluation circuit for determining information from the signal, wherein the evaluation circuit is designed to calculate the amplitude of the oscillation of the oscillatory body from the determined information and an ascertained period of the oscillation of the oscillatory body and/or to regulate the amplitude of the oscillation of the oscillatory body using the determined information and the ascertained period of the oscillation of the oscillatory body.