Laser Interferometer Vibration Displacement Measurement
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Solution Overview
Problem
Existing methods for measuring vibration displacement using laser interferometers face limitations in precision due to differences in vibration amplitude between cosine and sine signals, quadrature error angles, and DC components, which hinder achieving picometer-level accuracy and require significant memory storage.
Innovation Solution
The method employs the Heydemann correction method to convert oval-type signals from the light sensor into circle-type signals, allowing for precise calculation of relative angles and phase, thereby improving measurement precision to a few picometers and reducing memory requirements by using a smaller lookup table range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional laser interferometer methods are used for vibration displacement measurement, then measurement can be performed, but precision is limited due to differences in vibration amplitude between cosine and sine signals, quadrature error angles, and DC components
Solution Approach 1:
The patent applies the Heydemann correction method to transform the signal parameters from an oval trajectory (characterized by different amplitudes in cosine and sine components) to a circular trajectory (equal amplitudes). This parameter transformation eliminates the amplitude differences and quadrature errors that limit measurement precision, achieving picometer-level accuracy.
Solution Approach 2:
The patent incorporates feedback mechanisms to correct and realign signal phases and amplitudes in real-time. By continuously monitoring the signal characteristics and applying corrective transformations, the system compensates for DC components and phase errors, maintaining high measurement precision throughout the measurement process.
2Measurement precision
If traditional lookup table methods are used for phase calculation, then measurement can be performed, but significant memory storage is required
Solution Approach 1:
The patent extracts and eliminates the need for large lookup tables by using analytical corrections (Heydemann correction) to compute phase and displacement directly from the transformed signals. This extraction of the computational core allows achieving high precision without requiring the extensive memory storage that traditional lookup table methods demand.
3Productivity
If conventional signal processing is used, then vibration displacement can be measured, but errors from significant digit limitations accumulate
Solution Approach 1:
The patent replaces conventional mechanical signal processing approaches with a mathematical transformation system (Heydemann correction). This substitution eliminates the accumulation of significant digit errors by using exact mathematical relationships in the signal transformation, maintaining both high throughput and picometer-level precision.
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
This approach enhances measurement precision to a few picometers, reduces memory usage by a quarter to a twelfth of traditional methods, and minimizes errors from significant digit limitations, achieving more accurate vibration displacement measurements.
Implementation Method 1
The interferometer (180) measures difference between two beam channels generated by laser beam reflected from the plane mirror (170) and laser beam lit from the laser head (160) passing through the angle prism (140), i.e. interference signal of two laser beams according to relative displacement
Implementation Method 2
overlapping a reference laser beam reflected from a fixed reference side and a laser beam reflected from an object whose vibration displacement is measured
Data Source
AI summary
The present invention is aimed at providing measurement method for vibration displacement using state variation principle which achieves real time implementation through super high-speed DSP or FPGA as well as improves precision as much as picometer level and at the same time saves memory capacity compared to conventional invention.