Optical Modulator Frequency Down-Conversion for Laser Interferometer Demodulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical modulators used in laser Doppler measurement apparatuses have high resonance frequencies, resulting in high-frequency modulation signals that require costly and complex demodulation circuits to process.
Innovation Solution
An optical modulator system comprising a first and second resonator vibrating at different frequencies, an optical modulator that adds a modulation signal to incident laser light using the first resonator, and a reference signal generator that produces a reference signal with a lower frequency than both resonator frequencies, allowing for down-conversion of the modulation signal for simpler demodulation processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a frequency shifter type optical modulator with a quartz crystal AT resonator is used, then the optical modulator can perform thickness-shear vibration and frequency shifting, but the resonance frequency is high, requiring costly and complex demodulation circuits
Solution Approach 1:
The patent changes the operating frequency parameter of the optical modulator from high frequency (quartz crystal AT resonator) to low frequency (piezoelectric ceramic resonator). This parameter change allows the modulation signal to be processed at a lower frequency by the demodulation circuit, simplifying the circuit requirements and reducing costs while maintaining optical modulation functionality
Solution Approach 2:
The patent replaces the expensive quartz crystal AT resonator with a cheaper piezoelectric ceramic resonator. Although ceramic resonators have shorter operational lifetimes than quartz crystals, they provide sufficient performance for the application while dramatically reducing component cost and simplifying the overall system
2Measurement precision
If a high-frequency modulation signal is used, then the optical modulator can achieve precise frequency shifting, but the demodulation circuit requires high-frequency handling capability, increasing component cost
Solution Approach 1:
The patent changes the frequency parameter of the modulation signal from high frequency to low frequency by using a piezoelectric ceramic resonator instead of a quartz crystal AT resonator. This parameter change maintains the precision of frequency shifting while allowing the demodulation circuit to operate at a lower frequency, reducing component cost and simplifying manufacturing
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 proposed solution reduces the frequency of signals processed in the demodulation circuit, simplifying circuit specifications and reducing electronic component costs while maintaining measurement accuracy.
Implementation Method 1
a first resonator configured to vibrate at a first frequency
Implementation Method 2
an optical modulator configured to add, using the first resonator, the modulation signal to incident laser light
Implementation Method 3
a second resonator configured to vibrate at a second frequency different from the first frequency
Implementation Method 4
a reference signal generator configured to generate, using the first signal and the second signal, the reference signal having a frequency lower than both the first frequency and the second frequency
Implementation Method 5
an optical modulator configured to add, using the first resonator, the modulation signal to incident laser light
Data Source
AI summary
An optical modulator coupled to a demodulation circuit for demodulating, from a laser light reception signal including a sample signal and a modulation signal, the sample signal based on a reference signal, the optical modulator including: a first resonator; a second resonator; an optical modulator configured to add, using the first resonator, the modulation signal to incident laser light; a first signal oscillator configured to generate, using the first resonator as source oscillation, a first signal having a first frequency; a second signal oscillator configured to generate, using the second resonator as source oscillation, a second signal having a second frequency; and a reference signal generator configured to generate the reference signal having a frequency lower than both the first frequency and the second frequency.