Optical Pin-Point Microphone Speckle Noise Suppression
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Solution Overview
Problem
Existing sound detection technologies face challenges in identifying specific sound sources amidst background noise, particularly in picking up minute vibrations from non-specular surfaces like human skin, which are degraded by surface roughness and relative motion, leading to sensitivity issues and signal distortion.
Innovation Solution
An optical pin-point microphone system that uses a light source to illuminate the object of interest, employing a detector array to segment and rectify signals, and combines these with acoustic microphone signals to generate a high-fidelity sound with strong background noise suppression, effectively addressing speckle patterns and relative motion effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical beam is used to detect surface vibrations on a rough surface, then the sensitivity to sub-nanometer vibrations is improved, but the surface roughness generates speckles which degrade the detection sensitivity
Solution Approach 1:
The optical detection system segments the rough surface into multiple scattering centers, with each detector element measuring vibrations from a specific spatial region. By dividing the detection area into discrete segments, the system can process speckle patterns from different regions independently and combine them to reconstruct the overall vibration signal, thereby mitigating the degrading effect of speckles on detection sensitivity
Solution Approach 2:
The patent transitions from single-point detection to two-dimensional spatial detection by arranging multiple detector elements in an array. This dimensional expansion allows the system to capture vibration information from multiple spatial locations simultaneously, enabling it to distinguish between speckle pattern variations and actual surface vibrations, thus maintaining high detection sensitivity despite surface roughness
2Adaptability or versatility
If the optical detection scheme tracks and alleviates the effects of relative motion, then the detection capability on moving targets is improved, but the lateral relative motion introduces variations in speckle patterns and axial motion varies the work-point of interferometric setups
Solution Approach 1:
The optical detection system incorporates dynamic tracking capabilities that continuously adjust the optical beam orientation and focus to follow the moving target. The system dynamically compensates for lateral motion by repositioning the beam and for axial motion by adjusting the interferometric work-point, thereby maintaining stable vibration detection on moving targets despite speckle pattern variations
Solution Approach 2:
The system employs feedback mechanisms that monitor target position and motion characteristics in real-time, using this information to adjust optical beam pointing, focus, and interferometric configuration. This closed-loop control enables the system to maintain optimal detection conditions on moving targets, compensating for speckle variations and work-point shifts caused by relative motion
3Reliability
If an ordinary microphone is added to fuse signals from optical pick-up and airborne detection, then the normal airborne sound quality is accomplished, but the device complexity increases
Solution Approach 1:
The patent combines two different detection modalities - optical surface vibration detection and airborne acoustic detection - into a unified hybrid microphone system. By merging the signals from both detection methods through signal processing, the system achieves superior sound quality that leverages the high directional selectivity of optical detection and the natural sound quality of airborne microphones, while the integrated design minimizes the complexity increase
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 system achieves high-fidelity sound detection with significant background noise suppression, capable of picking up sub-nanometer vibrations on rough surfaces with random motion, providing clear acoustic signals even in noisy environments.
Implementation Method 1
a light source for directing a sensing beam for directing to an object of interest so as to be reflected thereby as a reflected signal beam
Implementation Method 2
a detector having multiple detector elements for receiving the reflected signal beam
Implementation Method 3
The optical detection of such vibrations, with typically sub-nanometer amplitudes, on a human skin with multi-micrometer roughness is a challenge addressed in this invention
Data Source
AI summary
A system and method for directional sound sensing directs an optical sensing beam to an object of interest having a rough surface that vibrates acoustically. The light is reflected thereby and scattered as a speckle pattern that includes multiple speckles having a random distribution of phase offsets. A detector array having multiple detector elements receives and detects the speckle pattern and produces signals that are linearly proportional to phase modulation of the speckles. A summer receives signals from at least two of the detector elements that are offset at different phases and sums the received signals to generate a non-vanishing signal representative of an acoustic signal.