Laser Interferometer Using In-Plane Vibration for Frequency Shift
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Solution Overview
Problem
Existing laser Doppler measurement devices face challenges in efficiently shifting laser light frequency without using a diffraction grating, which increases manufacturing difficulty and cost.
Innovation Solution
A laser interferometer design that utilizes a quartz crystal vibrator with in-plane flexural vibration mode and a side surface irradiated by laser light, eliminating the need for a diffraction grating by ensuring a sufficient inner product for frequency shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a diffraction grating is combined with the quartz crystal AT vibrator to enable frequency shift, then the frequency shift of laser light is achieved, but the manufacturing complexity and cost increase
Solution Approach 1:
The patent extracts and removes the diffraction grating component from the optical modulator system. By using only the quartz crystal AT vibrator with in-plane vibration mode, the system achieves frequency shift capability without the complex diffraction grating structure, thereby reducing manufacturing complexity while maintaining the essential function
Solution Approach 2:
The quartz crystal AT vibrator is designed to perform multiple functions: it serves as both the vibration source for frequency modulation and the sole optical interaction element. By making the vibrator multi-functional, the system eliminates the need for separate diffraction grating components, reducing overall device complexity
2Measurement precision
If a diffraction grating is combined with the quartz crystal AT vibrator to enable frequency shift, then the frequency shift of laser light is achieved, but the cost increases
Solution Approach 1:
The patent extracts and removes the diffraction grating component from the optical modulator system. By using only the quartz crystal AT vibrator with in-plane vibration mode, the system achieves frequency shift capability without the complex diffraction grating structure, thereby reducing manufacturing complexity while maintaining the essential function
Solution Approach 2:
The patent employs a simpler, more cost-effective quartz crystal AT vibrator design without expensive diffraction grating components. This approach uses readily available materials and standard manufacturing processes, reducing overall system cost
3Stability of the object's composition
If the quartz crystal AT vibrator performs thickness-shear vibration, then the vibration occurs, but the inner product with wave number vector difference is substantially zero, preventing efficient frequency shift
Solution Approach 1:
The patent changes the vibration mode parameter of the quartz crystal AT vibrator from thickness-shear vibration to in-plane vibration mode. This parameter change transforms the vibration characteristics so that the vibration vector has a non-zero inner product with the wave number vector difference, enabling efficient frequency shift while maintaining vibration stability
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 reduces manufacturing complexity and cost while maintaining high signal-to-noise ratio and accuracy in measuring displacement and speed, with reduced size and power consumption.
Implementation Method 1
a shift amount of a frequency of the laser light is obtained by using heterodyne interference, and a speed and a displacement of the moving object are obtained based on the shift amount
Implementation Method 2
an object to be measured is irradiated with laser light, and a movement thereof is measured based on scattered laser light subjected to Doppler shift. Specifically, a shift amount of a frequency of the laser light is obtained by using heterodyne interference
Implementation Method 3
The vibration unit vibrates along an in-plane direction of the vibration substrate, the vibration unit includes a side surface intersecting with the in-plane direction, and the side surface is irradiated with the laser light
Implementation Method 4
a shift amount of a frequency of the laser light is obtained by using heterodyne interference
Data Source
AI summary
A laser interferometer includes: a laser light source configured to emit laser light toward an object; an optical modulator including a vibrator configured to modulate the laser light using the vibrator and superimpose a modulation signal on the laser light; a photodetector configured to receive the laser light including a sample signal derived from the object and the modulation signal, and to output a light reception signal; a demodulation circuit configured to demodulate the sample signal from the light reception signal based on a reference signal; and an oscillation circuit configured to operate using the vibrator as a signal source and output the reference signal to the demodulation circuit. The vibrator includes a vibration substrate having a base portion and a vibration unit coupled to the base portion. The vibration unit vibrates along an in-plane direction of the vibration substrate and includes a side surface intersecting with the in-plane direction.