Optical Comb Multiwavelength Interferometry Cost Reduction
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Solution Overview
Problem
Existing multiwavelength interferometric displacement measurement methods require expensive, high-stability lasers or lasers with precise wavelength variability to accurately expand measurement ranges, limiting their availability and economic feasibility.
Innovation Solution
A method using an optical comb and a variable wavelength laser to obtain interference measurement values at multiple wavelengths, allowing for interferometric displacement measurement with a synthetic wavelength longer than the individual laser wavelengths, without the need for expensive, stable lasers, by controlling the oscillation wavelength and calculating distance based on phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If expensive, high-stability lasers or lasers with precise wavelength variability are used to expand measurement range by synthetic wavelength, then measurement precision and reliability are improved, but device cost and complexity increase
Solution Approach 1:
The patent replaces expensive, high-stability lasers with inexpensive, less stable lasers. By using a frequency measuring apparatus to accurately measure the wavelengths of these cheap lasers and applying correction based on measured wavelength differences, the system achieves the same measurement precision without requiring costly laser sources.
Solution Approach 2:
The patent substitutes the requirement for mechanically stable lasers with an electronic measurement and correction system. Instead of relying on mechanical/laser stability, the system uses a frequency measuring apparatus to electronically measure wavelengths and a controller to apply mathematical corrections, replacing physical stability requirements with electronic measurement capabilities.
2Length of stationary object
If expensive, high-stability lasers or lasers with precise wavelength variability are used to expand measurement range by synthetic wavelength, then measurement range expansion is achieved, but device cost increases
Solution Approach 1:
The patent uses inexpensive lasers instead of expensive high-stability lasers, achieving the same measurement range expansion capability through electronic measurement and correction of wavelength differences rather than through costly hardware.
Solution Approach 2:
The patent changes the approach from controlling laser physical parameters (stability, wavelength precision) to measuring and correcting wavelength parameters electronically. By measuring the actual wavelengths and using them in corrected synthetic wavelength calculations, the system achieves accurate long-range measurement with cheaper components.
3Measurement precision
If lasers with very high stability or precise wavelength scanning capability are used, then correctness of synthetic wavelength is improved, but availability and ease of manufacture worsen
Solution Approach 1:
The patent replaces rare, specialized high-stability lasers with common, inexpensive lasers that are easily manufactured and widely available. The frequency measuring apparatus and correction algorithm compensate for the lower inherent stability, making the system manufacturable with off-the-shelf components.
Solution Approach 2:
The patent introduces a frequency measuring apparatus as an intermediary between the inexpensive lasers and the measurement system. This intermediary device measures the actual wavelengths and enables the controller to apply corrections, bridging the gap between cheap laser availability and measurement correctness requirements.
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
Enables economical, wide-range interferometric displacement measurement with high accuracy, reducing production costs by utilizing inexpensive lasers with lower stability and simplifying the measurement apparatus.
Implementation Method 1
a method of measuring a distance (displacement) which uses a wavelength of several hundreds of nm as a scale
Implementation Method 2
by using laser beams of plural wavelengths, obtaining interference measurement values that are measured at respective wavelengths
Implementation Method 3
measurement the wavelengths of the laser beams by using an optical comb and one detector on to which the laser beams of the plurality of wavelengths are simultaneously incident
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
When the distance from the body of an interferometer to an object (110) or a displacement is interferometrically measured by using laser beams of a plurality of wavelengths, obtaining interference measurement values that are measured at the respective wavelengths, and expanding a measurement range by a synthetic wavelength that is equivalently longer than the wavelengths of the laser beams from combinations of the wavelengths, the wavelengths of the laser beams are measured by using an optical comb generator (104). An interferometric measurement may be performed while the oscillation wavelength of a variable wavelength laser (101) is measured by using the optical comb, and a feedback control is performed, whereby laser beams of a plurality of predetermined wavelengths are obtained; a variable wavelength laser is caused to oscillate at an arbitrary wavelength to obtain interference measurement values at the plurality of wavelengths, and wavelengths (frequencies) of laser beams at timings when the respective interference measurement values are obtained are measured by the optical comb; or a plurality of lasers (416,417) are used, and wavelengths of laser beams oscillated from the lasers are measured by the optical comb.