Laser Interferometer Feedback for Temperature-Stable Demodulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing laser interferometers face challenges in maintaining demodulation accuracy due to temperature fluctuations, which affect the modulation signal generated by quartz crystal resonators, leading to a decrease in signal-to-noise ratio.
Innovation Solution
A laser interferometer design incorporating a frequency-shifter type optical modulator with a quartz crystal AT resonator and a diffraction grating on the vibrator, coupled with a signal generation and correction processing unit to stabilize the modulation signal and improve demodulation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a quartz crystal resonator is used to generate a modulation signal by frequency shifting laser light, then the laser interferometer can measure vibration velocity, but the modulation signal changes with temperature fluctuations, causing a decrease in demodulation accuracy
Solution Approach 1:
The patent implements a feedback mechanism where the actual modulation signal is monitored and compared with a reference, and the drive signal to the quartz crystal resonator is adjusted based on the detected deviation. This closed-loop control compensates for temperature-induced frequency drift, maintaining signal stability and demodulation accuracy despite environmental variations.
Solution Approach 2:
The patent dynamically adjusts the drive signal parameters (frequency and/or amplitude) to the quartz crystal resonator based on detected temperature variations or signal deviations. By changing the operating parameters in response to environmental conditions, the system maintains optimal modulation signal quality and demodulation accuracy across varying temperatures.
2Measurement precision
If a quartz crystal resonator is used for frequency shifting, then the interferometer can operate, but the device size and power consumption increase
Solution Approach 1:
The patent employs partial frequency shifting or modulation only when necessary for accurate vibration velocity measurement, rather than continuous full-power operation of the quartz crystal resonator. By applying modulation selectively or at reduced power levels when full performance is not required, the system maintains measurement capability while reducing overall power consumption.
3Measurement precision
If temperature compensation mechanisms are added to stabilize the modulation signal, then demodulation accuracy is maintained, but the device complexity increases
Solution Approach 1:
The patent implements a self-compensating mechanism where the system automatically detects and corrects its own temperature-induced deviations without requiring external intervention or complex additional hardware. The feedback loop uses the system's own output signals to generate correction signals, enabling self-regulation and maintaining accuracy while minimizing added complexity.
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 design stabilizes the modulation signal, enhancing demodulation accuracy and reducing the size and power consumption of the interferometer, while maintaining high precision in measuring vibration velocity.
Implementation Method 1
a laser vibrometer (laser interferometer) that irradiates an object with laser light and measures a vibration velocity based on scattered laser light subjected to a Doppler shift
Implementation Method 2
a Doppler signal included in the scattered laser light is extracted by using optical heterodyne interferometry
Implementation Method 3
a photodetector configured to receive the laser light including a sample signal superimposed thereon due to reflection by an object and the laser light including the modulation signal, and output a light receiving signal
Data Source
AI summary
A laser interferometer includes a laser light source that emits laser light, an optical modulator which superimposes a modulation signal on the laser light using a vibrator driven by a drive signal, a photodetector that receives the laser light including a sample signal and the laser light including the modulation signal, and outputs a light receiving signal, an oscillator that generates a reference signal, an amplifier that outputs the drive signal from the reference signal, and a processor that extracts a frequency modulation component from the light receiving signal and the reference signal, outputs a preprocessing signal including the frequency modulation component, demodulates the sample signal from the preprocessing signal and the reference signal, outputs a correction signal based on an output signal depending on driving of the vibrator, and corrects the drive signal and the reference signal based on the correction signal.