Moving-Mirror Spectroscopy Calibration With Gas-Cell Absorption Signals
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Solution Overview
Problem
Existing spectroscopic apparatuses face challenges in maintaining high measurement precision of the movable mirror's position due to poor parallelism between the light reflecting surfaces, leading to inaccuracies in spectral pattern analysis.
Innovation Solution
A spectroscopic apparatus is designed with a moving mirror having two reflection surfaces and a length measuring optical system using laser light to measure the mirror's position, coupled with a gas cell to compensate for parallelism errors, and a calculation apparatus to correct the mirror's position based on peak wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a movable mirror with two light reflecting surfaces is used to measure the position of the movable mirror, then the measurement precision of the position can be improved, but the parallelism between the two light reflecting surfaces is difficult to maintain, causing length measurement errors
Solution Approach 1:
The patent introduces a reference mirror as an intermediary element. The reference mirror has a single reflection surface that reflects reference light to form an interference pattern. This intermediary reference mirror allows the system to measure the position of the movable mirror using interference fringes without requiring the movable mirror itself to have perfect parallelism between its two reflection surfaces. The reference mirror serves as a stable reference that compensates for the imperfections in the movable mirror's parallelism.
Solution Approach 2:
The patent replaces direct mechanical position measurement with optical interference measurement. Instead of relying on the physical parallelism of the movable mirror surfaces for position measurement, the system uses laser light interference patterns to optically determine the mirror's position. This substitution of mechanical measurement with optical measurement allows position detection without being constrained by the manufacturing precision of the mirror surfaces.
2Measurement precision
If the parallelism between the light reflecting surfaces is increased to reduce length measurement error, then the measurement precision is improved, but the device complexity and difficulty of manufacture increase
Solution Approach 1:
The reference mirror acts as an intermediary that provides a stable optical reference without requiring the movable mirror to achieve perfect parallelism. The reference light reflected from the reference mirror creates interference fringes that encode position information, allowing accurate measurement without demanding high manufacturing precision from the movable mirror surfaces.
Solution Approach 2:
The system creates an optical copy or representation of the position information through interference fringes. Instead of directly measuring position from the movable mirror surfaces, the system captures the position information in the interference pattern formed by reference light. This optical copying allows position measurement to be decoupled from the physical imperfections of the mirror surfaces.
3Ease of manufacture
If the parallelism between the two reflection surfaces is poor, then the device is easier to manufacture, but length measurement error occurs and spectral pattern accuracy decreases
Solution Approach 1:
The reference mirror serves as a mediator that provides a stable reference beam for interference measurement. This reference beam compensates for the poor parallelism in the movable mirror by providing a known reference against which position can be accurately determined through interference fringe analysis, thereby maintaining spectral pattern accuracy despite manufacturing imperfections.
Solution Approach 2:
The patent replaces mechanical position determination (which would be affected by mirror parallelism errors) with optical interference-based position determination. The interference pattern of reference light provides a precise optical measurement system that is insensitive to the mechanical imperfections of the movable mirror surfaces, thereby maintaining accuracy while easing manufacturing 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
The apparatus achieves high-precision spectral pattern generation by correcting for mirror position measurement errors, enhancing the accuracy of spectral analysis.
Implementation Method 1
the beam splitter unit, the movable mirror, and the fixed mirror constitute an interference optical system that measurement target light and laser light enter
Implementation Method 2
The laser light output from the second light source is split by the beam splitter unit. One of the two portions into which the laser light is split is reflected off the movable mirror and returns to the beam splitter unit
Implementation Method 3
a gas cell configured to encapsulate a gas that absorbs light having a predetermined wavelength, and add a light absorption signal to the analysis light when the analysis light enters the gas cell
Data Source
AI summary
A spectroscopic apparatus including an analysis optical system, a length measuring optical system, and a calculation apparatus and performing spectroscopic analysis of a sample, the analysis optical system including a moving mirror having a first reflection surface and a second reflection surface, the moving mirror configured to be translated, a gas cell configured to encapsulate a gas and add a light absorption signal to the analysis light, and a first light receiver configured to receive the analysis light containing a sample derived signal, a first modulation signal, and the light absorption signal, the length measuring optical system including a length measuring optical system configured to acquire a displacement signal corresponding to the position of the moving mirror from laser light reflected off the second reflection surface, the calculation apparatus including a moving mirror position calculator, a light intensity calculator, a Fourier transformer, and a moving mirror position correction section.