Freeform Surface Spectrometer for Astigmatism Correction
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Solution Overview
Problem
Existing spectrometer arrangements face challenges in achieving high spectral resolution while maintaining a large etendue, leading to increased detector size requirements and imaging errors such as astigmatism and coma, which degrade signal-to-noise ratio and limit detection sensitivity.
Innovation Solution
The introduction of freeform surfaces in the beam path, optimized using mathematical expressions or support points, minimizes imaging errors and improves spectral resolution by reducing beam overlapping and optimizing the distribution of orders on the detector, allowing for a more uniform and efficient detection of two-dimensional spectra.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional imaging optics are used in spectrometer arrangements, then the system can register spectral regions, but imaging errors such as astigmatism and coma occur which degrade spectral resolution and detection sensitivity
Solution Approach 1:
The patent applies freeform surfaces with complex curved geometries to optical elements (mirrors or lenses) in the spectrometer arrangement. These freeform surfaces are specifically designed to correct imaging errors such as astigmatism and coma by providing non-spherical curvature that compensates for the aberrations introduced by conventional optical paths, thereby improving spectral resolution without requiring larger detectors
Solution Approach 2:
The patent optimizes various parameters of the freeform surfaces including surface curvature, aspheric coefficients, and positional parameters to minimize imaging errors. By adjusting these parameters during the design phase, the optical system achieves corrected wavefronts that reduce astigmatism and coma, enabling high spectral resolution with compact detector arrays
2Measurement precision
If large spectral regions with high resolution are registered, then detection capability improves, but detector size must be very large increasing system complexity and cost
Solution Approach 1:
The freeform surfaces concentrate and properly focus spectral information onto a compact detector array by correcting beam paths. The curved freeform geometry ensures that spectral orders are properly focused without requiring a large detector area, thus achieving high spectral resolution over large spectral regions with a smaller, more cost-effective detector
Solution Approach 2:
The patent uses freeform surfaces that operate in three-dimensional space to manipulate light paths, effectively packing more spectral information into a smaller detector footprint. By utilizing complex spatial transformations rather than simple planar optics, the system achieves high-resolution spectroscopy of large spectral regions without proportionally increasing detector size
3Measurement precision
If conventional optical elements are used, then the system structure is simpler, but beam overlapping occurs which reduces spectral resolution and detection sensitivity
Solution Approach 1:
The freeform surfaces with precisely engineered curved geometries separate spectral orders and wavelengths by controlling beam paths through non-spherical surfaces. This complex curvature design prevents beam overlapping that occurs with conventional spherical or planar optics, achieving high spectral resolution while maintaining a relatively simple single-element optical design
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 enables a significant reduction in imaging errors, leading to higher spectral resolution and improved detection sensitivity, allowing for smaller detector sizes and more efficient spectral analysis.
Implementation Method 1
gratings with a stepped (echelle is French for staircase) cross section are used. By the step-like structure with a corresponding blaze angle, a diffraction pattern is produced, which concentrates the diffracted intensity in high orders, e.g. fiftieth to one hundredth order
Implementation Method 2
The orders are in the case of echelle spectrometers with internal order separation yet again dispersed transversely to the dispersion direction of the echelle grating, in order to separate the different arising orders
Implementation Method 3
an imaging optics for imaging the radiation entering into the spectrometer arrangement through an entrance slit in an image plane for producing a two-dimensional spectrum
Data Source
AI summary
A spectrometer arrangement with two-dimensional spectrum, comprising a first dispersing element for spectral separation of radiation in a main dispersion direction, an imaging optics for imaging the radiation entering into the spectrometer arrangement through an entrance slit in an image plane for producing a two-dimensional spectrum, and a detector array with a two-dimensional arrangement of a plurality of detector elements in the image plane, wherein a reflector, a refractor, and/or a lens array are arranged in the beam path at a location where the dispersed, monochromatic beams are separated from one another, and the reflector, the refractor, and/or the lens array have a surface in the form of a freeform surface, such that area occupied by selected images of the entrance slit in the case of different wavelengths in the image plane is optimized over a selected spectral region of the two-dimensional spectrum.