Grating Spectrometer Wavelength Calibration via Rotatable Grating
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Solution Overview
Problem
The accuracy of wavelength calibration in spectrometers with rotatable gratings is limited by the fixed characteristic peaks of calibration light sources and the simplicity of existing physical models, which do not adequately account for detector plane inclination and pixel gaps.
Innovation Solution
A wavelength calibration method that involves rotating the rotatable grating to move characteristic peaks to the detector's central position, determining a functional relationship between grating rotation angle and central wavelength, and using a refined physical model to calculate wavelengths at each pixel, incorporating parameters to optimize for detector geometry and pixel positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple physical model is used for wavelength calibration, then the device complexity is reduced, but the measurement precision deteriorates due to insufficient accuracy in accounting for detector plane inclination and pixel gaps
Solution Approach 1:
The patent introduces multiple parameters (a, b, c) to describe the detector plane inclination and pixel gap characteristics. By changing from a simple model to a complex model with multiple parameters, the wavelength calibration accuracy is improved. The parameters are determined through fitting processes using characteristic peaks of calibration light sources at different grating angles.
2Measurement precision
If the number of characteristic peaks of calibration light sources is increased, then the measurement precision of wavelength calibration is improved, but the device complexity increases due to more complex physical model requirements
Solution Approach 1:
The patent uses multiple characteristic peaks of calibration light sources at different grating angles to determine multiple parameters (a, b, c) of the physical model. By utilizing the dispersion characteristics of the grating and the geometric relationship between grating angle and wavelength, the patent establishes a comprehensive physical model that accurately accounts for detector plane inclination and pixel gaps.
3Measurement precision
If a physical model adapted to different grating angles is established, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The patent establishes a dynamic physical model that adapts to different grating angles. The model incorporates the relationship between grating rotation angle and wavelength, allowing the spectrometer to accurately calibrate wavelength at any grating angle. The physical model dynamically adjusts parameters based on the specific grating angle and detector geometry.
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 method enhances the accuracy of wavelength calibration by adapting to different grating angles and optimizing for detector geometry, thereby improving the precision of spectral measurements.
Implementation Method 1
a spectrum detected on the CCD detector changes as the grating rotates at an angle
Implementation Method 2
composite light is dispersed into bands via a dispersion element (e.g., a rotatable grating)
Implementation Method 3
The wavelength calibration of the spectrometer needs use of calibration light sources, the spectrum emitted by the calibration light sources is line spectrum
Data Source
AI summary
A wavelength calibration method for a grating spectrometer is provided, including: moving a plurality of characteristic peaks of a calibration light source to a central position of a detector of the spectrometer respectively, and determining a functional relationship between a grating rotation angle of the rotatable grating and a central wavelength; and determining parameters γ, f, a, b, c in the following physical model, the physical model being used to calculate a corresponding wavelength at each pixel within an imaging range of the detector when the central wavelength is determined,λ′=sin(Ψ-γ2)+sin(Ψ+γ2+arctan(a(nx)2+b(nx)+cf))10-6·m·Nwherein Ψ is the grating rotation angle corresponding to the central wavelength as determined via the functional relationship, γ is built-in angle of the spectrometer, f is a focal distance of the spectrometer, m is grating diffraction order, N is the number of grating rulings (unit: line/mm), nx is a distance between a corresponding pixel and a central pixel.