Optical Displacement Measurement for Loudspeaker Distortion Control
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Solution Overview
Problem
Traditional loudspeaker systems face distortion issues due to nonlinearities in the electro-mechanical voice coil system and diaphragm, limiting their ability to produce deep bass frequencies, and existing displacement measurement methods accumulate errors, making feed-forward control ineffective.
Innovation Solution
An optical displacement measurement system using an emitter, two detectors, and a lock-in amplifier to remove distortions and noise, allowing for precise measurement of displacement by modulating the optical signal and using bandpass filtering to focus on the reference frequency, thereby improving accuracy and reducing external and inherent noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional velocity and acceleration measurements are integrated to determine displacement, then control techniques can be applied to reduce distortion, but measurement errors accumulate making feed-forward control ineffective
Solution Approach 1:
The patent replaces mechanical/electrical measurement systems (velocity and acceleration sensors with integration) with an optical measurement system. The optical system directly measures displacement by detecting the position of a reflective surface (such as the speaker cone) using light reflection principles, eliminating the need for integration and preventing error accumulation.
Solution Approach 2:
The patent introduces an optical intermediary system consisting of a light source, reflective surface, and optical detector. This intermediary optical path allows direct measurement of displacement without physically contacting the moving parts, avoiding the error accumulation inherent in traditional multi-stage integration methods.
2Measurement precision
If optical measurement system uses emitter and detectors to measure displacement directly, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The optical measurement system is designed to serve multiple functions: it measures displacement directly, provides feedback for control algorithms, and can operate in various loudspeaker configurations. The same basic optical components (emitter, detector, reflective surface) can be applied to different speaker types and measurement scenarios, reducing overall system complexity through standardization.
3Reliability
If feed-forward control is implemented to correct distortions, then distortion reduction is achieved, but requires accurate displacement measurements which traditional methods cannot provide
Solution Approach 1:
The optical measurement system provides preliminary, accurate displacement information before the distortion correction process is applied. By measuring the actual cone position in advance with high precision, the system enables feed-forward control algorithms to pre-compensate for non-linearities, improving overall system performance and distortion reduction effectiveness.
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 provides high-precision displacement measurements, minimizing distortion and noise, allowing for accurate control of loudspeaker systems and extending their frequency range without significant distortion.
Implementation Method 1
detecting reflections of the optical signal from the element, detecting reflections of the optical signal from the raised cover structure
Implementation Method 2
modulating the optical signal and using bandpass filtering to focus on the reference frequency
Implementation Method 3
bandpass filtering the detected reflections from the first and second detectors to remove noise outside a selected frequency range
Data Source
AI summary
Systems and methods for optically measuring displacement of an element include an emitter for emitting an optical signal, a first detector for detecting reflections of the optical signal from the element, a second detector for detecting reflections of the optical signal from a raised cover structure, a processor for receiving the detected reflections from the first and second detectors and removing distortions in the detected reflections from the first detector using the detected reflections from the second detector.