Laser Interferometer FM Demodulation for Vibration Measurement
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Solution Overview
Problem
Existing laser vibrometers face challenges in accurately demodulating the beat signal when the vibration state of the object does not satisfy a predetermined condition, leading to inaccurate determination of the object's displacement and vibration velocity.
Innovation Solution
A laser interferometer is designed with a light source, an optical modulator using a vibrator to modulate laser light, an optical path switching unit, a reflector with a moving light-reflecting surface, and a photoreceptor to receive interference light, allowing for accurate demodulation of interference signals and measurement of object displacement and velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a demodulation process is performed by splitting the light-receiving signal into two separate arithmetic processes and adding the signals to eliminate unnecessary terms, then the beat signal can be demodulated under certain conditions, but the measurement accuracy deteriorates when the vibration state of the object does not satisfy the predetermined condition
Solution Approach 1:
The patent introduces a frequency modulation (FM) demodulation circuit as an intermediary device to process the light-receiving signal. This FM demodulation circuit serves as a mediator that can handle various vibration states without requiring the signal to be split into two separate arithmetic processes, thereby maintaining measurement accuracy across different vibration conditions while eliminating unnecessary terms through the FM demodulation process itself
2Difficulty of detecting and measuring
If the light-receiving signal is processed through complex arithmetic operations to eliminate unnecessary terms, then the signal processing capability is improved, but the device complexity increases
Solution Approach 1:
The patent replaces complex arithmetic signal processing operations with an FM demodulation circuit that uses frequency modulation principles. Instead of performing multiple separate arithmetic processes and signal additions, the FM demodulation circuit directly extracts the beat signal through frequency demodulation, thereby maintaining signal processing capability while significantly reducing device complexity
Solution Approach 2:
The patent changes the processing approach from arithmetic operations on signal amplitude and phase to frequency-based processing through FM demodulation. By transforming the problem into the frequency domain and using FM demodulation techniques, the system achieves effective signal processing with simpler circuitry, as the FM demodulation naturally eliminates unnecessary terms through its frequency-selective processing
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 laser interferometer effectively demodulates interference signals even under varying vibration conditions, providing accurate measurements of displacement and vibration velocity, thus overcoming the limitations of existing technologies.
Implementation Method 1
first interference light of third laser light generated by reflection of the first laser light on an object to be measured and the second laser light
Implementation Method 2
photoreceptor configured to receive first interference light of third laser light generated by reflection of the first laser light on an object to be measured and the second laser light
Implementation Method 3
optical modulator including a vibrator and configured to use the vibrator to modulate the first laser light into second laser light having a different frequency
Implementation Method 4
reflector including a light-reflecting surface configured to move along the second optical path and reflect the first laser light traveling through the second optical path
Data Source
AI summary
A laser interferometer includes a light source configured to emit first laser light, an optical modulator including a vibrator and configured to modulate, by the vibrator, the first laser light into second laser light having a different frequency, an optical path switching unit disposed in a first optical path through which the first laser light travels and configured to switch a direction of travel of the first laser light between the first optical path and a second optical path different from the first optical path, a reflector including a light-reflecting surface configured to move along the second optical path and reflect the first laser light traveling through the second optical path, and a photoreceptor configured to receive first interference light of the second laser light and third laser light generated by reflection of the first laser light on an object to be measured, and second interference light of the second laser light and fourth laser light generated by reflection of the first laser light on the light-reflecting surface and output a light-receiving signal.