Off-axis Refractive Element for Echelle Spectrometer Aberration Correction
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Solution Overview
Problem
Optical imaging errors such as astigmatism, coma, and spherical aberrations limit the imaging quality of spectrometers, causing broadened image points and reduced spectral resolution in echelle spectrometers with internal order separation.
Innovation Solution
A spectrometer arrangement incorporating a first and second dispersing element for spectral separation, collimating optics, camera optics, a two-dimensional detector, and an off-axis section of a rotationally symmetric refractive element between the camera optics and detector, which corrects imaging errors by geometrically separating and focusing individual beams onto the detector.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional camera optics are used to image the spectrum, then the spectrometer structure is simple, but imaging errors (astigmatism, coma, spherical aberration) broaden the image point and reduce spectral resolution
Solution Approach 1:
The camera optics are segmented into two functional parts: a conventional camera optics for basic imaging and a separate aberration correction optics (off-axis section of a rotationally symmetric refractive element) for correcting specific imaging errors. This segmentation allows each component to be optimized for its specific function while maintaining overall system manageability.
Solution Approach 2:
An off-axis section of a rotationally symmetric refractive element is introduced as an intermediary component between the camera optics and the detector. This intermediate element specifically addresses imaging errors without requiring complete redesign of the entire camera optics system, thus improving resolution while limiting complexity increase.
2Area of stationary object
If the image point is broadened in the dispersion direction, then the imaging area is easier to cover, but the spectral resolution is degraded
Solution Approach 1:
The aberration correction optics is designed to convert the harmful effect of broadened image points into a beneficial outcome. By introducing controlled refraction through the off-axis refractive element, the system compensates for astigmatism and other aberrations, effectively narrowing the broadened image points and restoring spectral resolution while maintaining adequate image area coverage.
3Area of stationary object
If the image point is broadened crosswise to the dispersion direction, then the signal-noise ratio is worsened, but the field of view is easier to cover
Solution Approach 1:
The aberration correction optics applies different correction characteristics to different regions of the image field. The off-axis refractive element is specifically designed to address local imaging errors in the cross-dispersion direction without compromising the overall field of view coverage, thereby improving signal-noise ratio while maintaining adequate field of view.
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
Significantly reduces imaging errors across the entire image field, allowing for higher spectral resolution and expanded wavelength range registration with minimal impact on spectral resolving power.
Implementation Method 1
an off-axis section of a rotationally symmetric, refractive element arranged between camera optics and detector
Implementation Method 2
a first dispersing element for spectral separation of radiation in a main dispersion direction
Implementation Method 3
a second dispersing element for spectral separation of radiation in a cross dispersion direction
Data Source
AI summary
The present disclosure resides in a spectrometer arrangement including a first dispersing element for spectral separation of radiation in a main dispersion direction, and a second dispersing element for spectral separation of radiation in a cross-dispersion direction, which is at an angle to the main dispersion direction, so that a two-dimensional spectrum is producible. The spectrometer arrangement also includes a collimating optics, which directs collimated radiation to the first and/or second dispersing element, a camera optics, which images a two-dimensional spectrum in an image plane, a two-dimensional detector for detecting the two-dimensional spectrum in the image plane, and an off-axis section of a rotationally symmetric, refractive element, which is arranged between the camera optics and the detector. The present disclosure resides likewise in an optical module comprising such a spectrometer arrangement.