On-Axis Collimating Mirror for Spectrometer Aberration Control
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Solution Overview
Problem
Existing imaging spectrometers face issues with aberrations and image distortions due to off-axis reflective components, leading to limited resolution and accuracy, particularly with Czerny-Turner, Ebert, and Offner designs, which hinder the use of two-dimensional detecting elements in high-resolution spectroscopy.
Innovation Solution
An optical collimating system is designed with a curved reflective surface and a folding mirror to function on-axis, eliminating aberrations and allowing for compact and accurate imaging spectrometry by collimating optical radiation and directing it to a dispersive and imaging element, which reduces chromatic and geometrical aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If off-axis reflective components (mirrors) are used in Czerny-Turner, Ebert, and Offner designs, then the spectrometer can be configured to disperse optical radiation, but strong aberrations including coma, astigmatism, field curvature, smile, and Keystone occur, deteriorating image quality and resolution
Solution Approach 1:
The patent inverts the conventional off-axis reflective optical configuration by using on-axis reflective components. Instead of placing mirrors at angles to the optical axis, the invention uses mirrors positioned on the optical axis, fundamentally changing the optical path geometry to eliminate off-axis aberrations while maintaining spectral dispersion capability
Solution Approach 2:
The patent changes the geometric parameters of the optical system by transitioning from off-axis to on-axis mirror positioning. This parameter change fundamentally alters the wavefront propagation path, eliminating the generation of coma, astigmatism, and other off-axis aberrations that plague conventional spectrometer designs
2Manufacturing precision
If refractive optical components are used to collimate optical radiation on-axis, then off-axis aberrations are avoided, but chromatic aberration is introduced, substantially deteriorating spectrometer accuracy
Solution Approach 1:
The patent replaces refractive optical components (lenses) with reflective optical components (mirrors) for the collimation function. This substitution eliminates chromatic aberration because reflection does not disperse light by wavelength, whereas refraction through lenses inherently causes chromatic separation. The mirrors maintain collimation capability without introducing wavelength-dependent focal shifts
Solution Approach 2:
The patent extracts and removes the chromatic aberration problem by eliminating refractive materials from the collimation path. By using purely reflective surfaces, the system removes the mechanism (refraction through dispersive media) that causes chromatic aberration, thereby preserving measurement accuracy across the spectral range
3Volume of moving object
If the detector is placed at the same side as the optical input in Czerny-Turner, Ebert, and Offner designs, then the optical path is compact, but the detector physically hinders the optical input, requiring additional mirrors that increase complexity and cost
Solution Approach 1:
The patent resolves the spatial conflict by changing the dimensional arrangement of the optical path. Instead of using additional mirrors to deflect light in the same plane (adding complexity), the on-axis reflective configuration allows the optical path to fold back on itself more efficiently, enabling the detector to be positioned without blocking the input aperture while maintaining a compact overall footprint
4Device complexity
If zero-deviation dispersive component is used, then the optical path is simplified, but smile and Keystone aberrations occur which are unsymmetrical relative to the optical axis, deteriorating spectrometer accuracy
Solution Approach 1:
The patent addresses the unsymmetrical smile and Keystone aberrations by using symmetrical on-axis reflective geometry. The on-axis mirror configuration creates symmetrical optical paths that naturally counterbalance asymmetrical aberrations, making the overall aberration pattern symmetrical relative to the optical axis and thereby improving measurement 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
The solution significantly reduces aberrations and image distortions, enabling high-resolution spectroscopy with improved accuracy and allowing the use of larger detecting elements, enhancing the overall image quality and resolution of the spectrometer.
Implementation Method 1
a curved reflective surface (114) which reflects the optical radiation (124) back to the folding mirror (100) in a collimated form
Implementation Method 2
A spectrometer is an optical device which receives optical radiation and separates light by wavelengths to produce a spectrum
Data Source
AI summary
Optical radiation from a sample is received by the slit and it is passed through an aperture in a reflective plane of a folding mirror towards a curved reflective surface of a collimating mirror. The slit and the curved reflective surface have a common optical axis. The reflective plane and the curved reflective surface face each other. The optical radiation passed through the folding mirror is collimated by the curved reflective surface. The collimated optical radiation is directed to the reflective plane of the folding mirror by the curved reflective surface. The collimated optical radiation is reflected in a direction other than the common optical axis of the slit and the curved reflective surface by the reflective plane.