Interferometric Displacement Measurement With Dual-Frequency Peaks
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Solution Overview
Problem
Existing phase modulation techniques for interferometric displacement measurement are limited to a small fixed range of measurement distances, require multiple modulators per interferometer, and are complex, large, and costly when measuring multiple displacements over a wide range.
Innovation Solution
An interferometric displacement measurement apparatus using a single light source with a modulated light beam having dual sets of frequency peaks, phase-locked against each other, allows simultaneous measurement of displacements over a wide range without changing modulation frequencies, using a single electro-optic modulator for multiple interferometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single light source with fixed modulation frequency is used, then the apparatus is compact and cost-effective, but it can only measure displacements within a small fixed range of distances
Solution Approach 1:
The patent applies dynamics by making the modulation frequency variable rather than fixed. The system dynamically adjusts the modulation frequency of the electro-optic modulator based on the measurement distance, allowing the same apparatus to adapt to different distance ranges while maintaining a compact single-light-source configuration
Solution Approach 2:
The patent changes the modulation frequency parameter to extend the measurement range. By varying the modulation frequency according to the measurement distance, the system overcomes the limitation of fixed-range measurement while keeping the apparatus structure simple and cost-effective
2Adaptability or versatility
If multiple modulators are used for each interferometer to measure multiple displacements, then the measurement capability is improved, but the device becomes more complex, larger, and more costly
Solution Approach 1:
The patent makes a single electro-optic modulator perform multiple functions by enabling it to measure multiple displacements across different distance ranges through frequency adjustment. This eliminates the need for separate modulators for each interferometer, reducing device complexity while maintaining multi-displacement measurement capability
Solution Approach 2:
The patent merges the functionality of multiple modulators into a single electro-optic modulator. By combining multiple measurement capabilities into one device through frequency modulation, the system reduces the total number of components while achieving the same multi-displacement measurement capability
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 apparatus is cost-effective, compact, and efficient, capable of measuring displacements over a wide range of distances with improved resolution and reduced complexity, suitable for applications in CNC machines, scientific equipment alignment, and geodetic instruments.
Implementation Method 1
an electro-optic modulator arranged to modulate the light output from the light source; wherein the phase modulation voltage is a time dependent function of the first modulation frequency, the second modulation frequency, the first modulation depth and the second modulation depth
Implementation Method 2
the at least one measurement interferometer comprises a photodetector for detecting the interference of the measurement beam with the reference beam
Implementation Method 3
The two or more beams are then superposed at a detector where they exhibit interference. The desired measurement information can then be extracted from the interference intensity measured at a detector
Data Source
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AI summary
An interferometric displacement measurement apparatus (100) includes at least one measurement interferometer (103) for measuring a change in optical path difference between a measurement beam (150) and a reference beam. A light source module (118) is arranged to generate a modulated light beam, having a particular optical spectrum, from which the measurement beam and reference beam are derived. A data acquisition and analysis module (105) can determine a measure representative of the displacement using interference intensity data received from a photodetector (111) which detects the interference of the measurement beam with the reference beam.