Rotatable Slit Wheel Spectrometer for Echelle Order Separation
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Solution Overview
Problem
Echelle spectrometers with internal order separation face challenges in achieving high resolution across a large wavelength range while maximizing light throughput and ensuring clean order separation, as the slit height must be adjusted for varying wavelength ranges, leading to inefficient use of detector area and potential intensity centroid shifts during slit changes.
Innovation Solution
A spectrometer arrangement featuring a rotatable slit wheel with falcate openings of varying width and a fixed slit mask, allowing for quick and precise adjustment of slit height, combined with a collimator and dispersive elements like echelle gratings and prisms, to produce a two-dimensional spectrum and adapt dynamically to changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the slit height is increased to maximize light throughput, then the signal-to-noise ratio improves, but the separation between diffraction orders deteriorates
Solution Approach 1:
The patent implements a dynamically adjustable slit height mechanism that allows the slit height to be changed according to the detected wavelength range. This resolves the contradiction by enabling the system to adapt between maximizing light throughput (large slit height) and ensuring clean order separation (smaller slit height) based on real-time spectral conditions, rather than being fixed at a compromise value
Solution Approach 2:
The system changes the slit height parameter dynamically based on the wavelength range being detected. By adjusting this critical parameter according to operating conditions, the system can optimize both light throughput and order separation performance for different spectral regions, resolving the trade-off between these two requirements
2Device complexity
If different wavelength ranges are acquired sequentially with fixed slit height, then the system complexity is reduced, but the light throughput efficiency deteriorates
Solution Approach 1:
The patent introduces dynamic control of slit height that responds to the detected wavelength range. This allows the system to optimize light throughput for each wavelength range without requiring complex mechanical reconfiguration, as the adjustment is integrated into the spectral detection process itself
Solution Approach 2:
The system uses feedback from the spectral detection to automatically adjust the slit height. The detector identifies the wavelength range being measured, and this information feeds back to control the slit height adjustment, optimizing light throughput automatically without manual intervention or complex pre-programming
3Device complexity
If a prism is used as transverse disperser, then the device complexity is reduced, but the order separation performance deteriorates at longer wavelengths
Solution Approach 1:
The patent compensates for the wavelength-dependent limitations of prism-based dispersion by dynamically adjusting the slit height. As the wavelength increases and order separation decreases with the prism, the system adjusts the slit height to maintain optimal separation, effectively compensating for the disperser's inherent limitations without changing the disperser itself
Solution Approach 2:
The system changes the slit height parameter to compensate for the decreasing order separation distance that occurs at longer wavelengths when using a prism. This parameter adjustment maintains effective order separation across the entire spectral range despite the prism's fixed dispersion characteristics
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 high-resolution spectral analysis across a broad wavelength range with improved light throughput and clean order separation, reducing detector area wastage and maintaining intensity centroid stability during slit height adjustments.
Implementation Method 1
gratings having a ladder-like cross-section are used. Illuminating the short facet of the step-like structure with a suitable blaze angle generates a diffraction pattern
Implementation Method 2
If a prism is used as such, the spatial separation of the orders decreases continuously as the wavelength increases
Data Source
AI summary
The present disclosure discloses a spectrometer arrangement including an entrance-slit group including a slit wheel and a slit mask for introducing radiation into and for limiting the optical field of the spectrometer arrangement, a first dispersive element for spectrally decomposing the radiation in a main dispersion direction, and a second dispersive element for spectrally decomposing the radiation in a transverse dispersion direction that forms an angle with the main dispersion direction to yield a two-dimensional spectrum. The slit wheel is mounted rotatably about an axis of rotation and has a falcate opening having a width that changes depending on the angle. The slit mask includes an opening that is longer than a largest width of the falcate opening such that radiation radiates through the falcate opening of the slit wheel and the opening of the slit mask. The present disclosure further includes a corresponding method and an optical component group.