Grating Rotation Angles for Spectrograph Wavelength Accuracy
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Solution Overview
Problem
Current grating scanning spectrographs face challenges in wavelength accuracy due to varying grating rotation angles when the start wavelength changes, leading to inaccurate spectral information.
Innovation Solution
A method and apparatus that determine fixed start and end angles for grating rotation based on preset angle series values, ensuring accurate spectral information collection by overlapping spectral ranges at adjacent angles, regardless of the initial scanning wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the grating rotation angle is calculated based on the start wavelength and end wavelength set by the user, then the spectrograph can scan and collect spectral information across the desired wavelength range, but the wavelength accuracy deteriorates because the grating rotation angle varies with different start wavelengths
Solution Approach 1:
The patent pre-calculates and stores a series of fixed grating rotation angles and their corresponding wavelength ranges before actual spectral measurement. This preliminary action creates a lookup table that maps user-defined wavelength ranges to predetermined grating angles, eliminating the need for real-time angle calculation and ensuring consistent wavelength accuracy regardless of the start wavelength selected by the user.
Solution Approach 2:
The patent transforms the continuous parameter of grating rotation angle into a discrete set of fixed angle values. By changing the angle from a continuously variable parameter to a discrete fixed parameter, the system achieves better wavelength accuracy while maintaining the ability to adapt to different scanning ranges through selective combination of these fixed angles.
2Area of stationary object
If the grating is rotated multiple times to collect spectral information across an ultra-long wavelength width, then the full spectral range can be covered, but the wavelength accuracy deteriorates due to cumulative errors from multiple rotation steps
Solution Approach 1:
The patent pre-establishes a comprehensive mapping between fixed grating rotation angles and their corresponding spectral coverage ranges. This preliminary calibration allows the system to determine the optimal combination of fixed angles needed to cover any desired wavelength range, minimizing the number of rotation steps required and reducing cumulative errors.
Solution Approach 2:
The patent divides the ultra-long wavelength range into multiple segments, each covered by a fixed grating rotation angle. By segmenting the spectral range and assigning each segment to a predetermined angle, the system avoids the cumulative errors associated with continuous multi-step rotation while still achieving complete spectral coverage through splicing of the segmented data.
3Measurement precision
If fixed grating rotation angles are used for spectral scanning, then wavelength accuracy is improved, but the device complexity increases due to the need for preset angle series and splicing operations
Solution Approach 1:
The patent creates a digital copy or lookup table of the relationship between fixed grating rotation angles and their corresponding wavelength ranges. This copied information structure allows the control system to quickly retrieve the appropriate angle settings without complex real-time calculations, reducing control complexity while maintaining the benefits of fixed-angle scanning for improved wavelength accuracy.
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 stabilizes wavelength accuracy by fixing grating rotation angles, ensuring precise spectral information collection across the scanning range without errors from initial wavelength variations.
Implementation Method 1
The grating scanning spectrograph disperses the composite light into a spectral band through the grating
Data Source
AI summary
The present disclosure provides a grating rotation method and apparatus for improving spectrograph wavelength accuracy. The grating rotation method comprises: acquiring a start wavelength and an end wavelength of a scanning range; determining a start angle and an end angle of a grating rotation according to preset grating rotation angle series values, the start wavelength and the end wavelength, wherein a wavelength corresponding to the start angle is smaller than the start wavelength, and a wavelength corresponding to the end angle is larger than the end wavelength; and rotating the grating according to the start angle and the end angle to obtain required spectral information. According to the grating rotation scheme provided by the present disclosure, the problem that the obtained spectral accuracy is inconsistent due to different grating rotation angles can be avoided.