MEMS Optical Microphone With Variable Waveplate
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional microphones, including optical MEMS microphones, face challenges in achieving high sensitivity and flat frequency response to meet evolving consumer performance requirements.
Innovation Solution
The design incorporates a variable optical waveplate with a birefringent crystal, suspended between a membrane and a waveguide plate, which changes polarization state as the membrane vibrates, allowing for improved acoustic-electrical signal conversion through an optoelectronic module and IC module, enhancing sensitivity and frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional capacitor-based microphone is used, then the structure is simple, but the sensitivity and frequency response are insufficient
Solution Approach 1:
The patent replaces the conventional capacitor-based electrical detection system with an optical detection system. A light source emits light through a waveguide to a membrane, and a photodetector detects light intensity changes caused by membrane vibration. This optical substitution enables higher sensitivity and flat frequency response while maintaining a compact MEMS structure.
Solution Approach 2:
The patent changes the detection parameter from electrical capacitance to optical intensity. By using a photodetector to measure light intensity variations caused by membrane vibration, the system achieves higher measurement precision and broader frequency response compared to conventional electrical capacitance measurement.
2Measurement precision
If the optical path length is increased to improve sensitivity, then the sensitivity improves, but the device size increases
Solution Approach 1:
The patent nests the optical components within the MEMS cavity structure. The light source, waveguide, membrane, and photodetector are integrated in a compact nested arrangement where the optical path is folded within the available space. This allows sufficient optical path length for high sensitivity while maintaining a small overall device footprint.
Solution Approach 2:
The patent utilizes the vertical dimension of the MEMS cavity to accommodate the optical path. Light travels vertically through the waveguide, membrane, and photodetector stack, efficiently using the available headroom in the z-direction to achieve the required optical path length without increasing the lateral footprint of the device.
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 configuration results in a microphone with high sensitivity and flat frequency response, effectively addressing the performance gaps in existing technologies by accurately converting sound signals into electrical signals.
Implementation Method 1
The variable optical waveplate includes a birefringent crystal with different refractive indices in different directions
Implementation Method 2
The photoelectric module converts the intensity and phase signals of the reflected light into electrical signals
Implementation Method 3
When sound waves actuate the membrane of the MEMS module, the membrane slightly vibrates to change the intensity and phase of the light reflected to the optoelectronic module
Data Source
AI summary
An MEMS optical microphone, including: a case, a membrane, a waveguide plate, a variable optical waveplate, an optoelectronic module, and an IC module. The case includes a cavity and a sound inlet. The membrane is suspended in the cavity and closes the sound inlet. The waveguide plate is suspended in the cavity and located at a side of the membrane away from the sound inlet. The optoelectronic module includes an electromagnetic radiation source and a sensing part provided at two opposite sides of the waveguide plate, respectively. The variable optical waveplate is configured to convert an input polarization state of the first light path into an output polarization state, which varies as a moving distance of the variable optical waveplate. The IC module is electrically connected to the membrane and the optoelectronic module. It has advantages such as high sensitivity, flat frequency response, thereby further improving the device performance.