Laser Interferometer Demodulation for Stable Phase Synchronization
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Solution Overview
Problem
Existing optical Doppler speedometers face challenges in maintaining accurate phase synchronization due to environmental factors affecting the quartz crystal oscillator, leading to reduced measurement accuracy.
Innovation Solution
A laser interferometer design utilizing a laser light source, optical modulator with a resonator element, and light receiving element, along with a calculation unit that includes preprocessing and demodulation units to extract frequency modulation components and generate orthogonal signals for precise displacement calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a quartz crystal oscillator with an oscillation circuit is used as a reference signal source, then the device size can be reduced, but the phase of the reference signal becomes unstable due to environmental changes affecting capacitor capacitance and parasitic capacitance
Solution Approach 1:
The patent introduces a feedback mechanism where the phase of the reference signal is continuously monitored and adjusted. The oscillation circuit's output phase is fed back to the phase adjustment unit, which modifies the capacitance values in real-time to compensate for environmental variations, thereby maintaining stable phase synchronization between the reference signal and modulation signal.
Solution Approach 2:
The patent dynamically changes the capacitance parameters of the capacitors in the oscillation circuit to compensate for environmental effects. By adjusting the capacitance values in response to temperature and other environmental factors, the system maintains stable oscillation frequency and phase despite external conditions, resolving the contradiction between compact size and phase stability.
2Device complexity
If a quartz crystal oscillator is used for phase synchronization, then the circuit configuration remains simple, but measurement accuracy decreases due to phase misalignment between reference signal and modulation signal
Solution Approach 1:
The patent introduces a phase adjustment unit as an intermediary component between the oscillation circuit and the signal processing chain. This unit acts as a mediator that fine-tunes the phase of the reference signal without significantly increasing overall circuit complexity, enabling accurate phase alignment between the reference signal and modulation signal while maintaining measurement precision.
3Adaptability or versatility
If capacitor capacitance and parasitic capacitance are allowed to change with environment, then the device adapts to environmental conditions, but the phase of the reference signal becomes unstable
Solution Approach 1:
The feedback mechanism continuously monitors the phase drift caused by environmental changes and adjusts the capacitance values accordingly. This closed-loop control allows the system to adapt to environmental conditions while maintaining stable phase, as the capacitance adjustments are made in real-time to counteract environmental effects rather than allowing uncontrolled changes.
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 enhances measurement accuracy by stabilizing phase synchronization and reducing the size and power consumption of the interferometer, enabling precise displacement and vibration speed measurements.
Implementation Method 1
an optical modulator that includes a resonator element and is configured to modulate the first laser light using the resonator element and generate second laser light including a modulation signal
Implementation Method 2
a light receiving element configured to receive the second laser light and third laser light including a sample signal generated by an object to be measured reflecting the first laser light
Implementation Method 3
a preprocessing unit configured to execute a preprocessing of extracting a frequency modulation component from the light reception signal
Data Source
AI summary
A laser interferometer includes a laser light source configured to emit first laser light; an optical modulator that includes a resonator element and is configured to generate second laser light including a modulation signal; a light receiving element configured to receive the second laser light and third laser light including a sample signal; and a calculation unit configured to calculate a displacement of an object to be measured from a light reception signal based on a reference signal, in which the calculation unit includes a preprocessing unit configured to execute a preprocessing of extracting a frequency modulation component from the light reception signal and output a preprocessing signal, a demodulation processing unit configured to mix the preprocessing signal with orthogonal signals to obtain a mixed signal and then execute a demodulation processing of extracting the sample signal from the mixed signal, and an orthogonal signal generation unit configured to generate the orthogonal signals based on a phase of the reference signal and an amplitude of the preprocessing signal.