Toroidal Reflector Monochromator Aberration Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional monochromators, such as Czerny-Turner monochromators, suffer from aberrations like coma and spherical aberration, limiting their resolution and requiring complex reorientation of optical elements for different wavelength ranges, making them impractical for use beyond their design wavelength.
Innovation Solution
A monochromator design featuring an off-axis parabolic primary reflector, spherical or toroidal secondary reflectors, and a replaceable diffraction grating, along with a cylindrical lens to reduce astigmatism, allowing for superior wavelength resolution and easier adaptation to different wavelengths without reorienting other optical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If spherical reflectors are used in a Czerny-Turner monochromator, then the device can be manufactured with simpler geometry, but spherical aberration occurs causing rays to be out-of-focus at the detector
Solution Approach 1:
The patent uses toroidal reflectors instead of spherical reflectors. Toroidal surfaces have different curvatures in different directions, which allows them to correct spherical aberration while maintaining the curved reflective geometry needed for compact monochromator design. This resolves the contradiction by improving focus precision without sacrificing manufacturing feasibility.
Solution Approach 2:
The patent applies different surface geometries to different parts of the optical system - specifically using toroidal surfaces for the reflectors which have varying curvature properties in different regions. This local variation in surface quality allows correction of aberrations in specific areas while maintaining overall system simplicity.
2Measurement precision
If the monochromator is designed for optimal performance at a selected design wavelength, then coma aberration is reduced at that wavelength, but coma increases at wavelengths away from the design wavelength
Solution Approach 1:
The toroidal reflectors provide different curvatures in the meridional and sagittal planes, which helps correct coma aberration across a broader wavelength range compared to spherical reflectors. This extends the useful wavelength range while maintaining measurement precision.
Solution Approach 2:
The patent changes the geometric parameters of the reflectors from spherical to toroidal, which fundamentally alters the optical path and aberration characteristics. This parameter change enables the system to maintain acceptable performance over a wider wavelength range.
3Adaptability or versatility
If the angle of the diffraction grating is changed to access different wavelength ranges, then different wavelengths can be measured, but the primary and secondary reflectors must be reoriented and relocated which is difficult and expensive
Solution Approach 1:
The toroidal reflectors are designed to provide aberration correction for multiple wavelength ranges simultaneously. This universal design allows the same optical configuration to serve multiple functions (different wavelength ranges) without requiring reorientation or relocation of the reflectors, reducing device complexity while maintaining versatility.
4Measurement precision
If coma aberration is corrected at the design wavelength through careful alignment, then measurement accuracy is improved at that wavelength, but the system becomes practically limited to that wavelength and surrounding wavelengths
Solution Approach 1:
The toroidal reflectors inherently provide coma correction across a broader wavelength range compared to spherical reflectors. This geometric property allows the system to maintain measurement accuracy over an extended operational wavelength range without requiring complex realignment procedures.
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 design achieves high-resolution dispersion over a wider range of wavelengths with minimal aberrations, simplifying the process of switching between wavelength ranges by replacing the diffraction grating, thereby improving the accuracy and practicality of spectrographic measurements.
Implementation Method 1
The primary reflector 104 collimates the light rays within the beam (reorients the rays into parallel paths focused at infinity)
Implementation Method 2
The grating 102 reflects light at different wavelengths at different angles
Implementation Method 3
All or most of the reflected light is then received by the concave secondary reflector 106, which focuses the light at each wavelength onto some output element
Data Source
Figure 1~2
AI summary
A monochromator for use in a spectrograph admits light from an aperture to a primary reflector (preferably an off-axis parabolic mirror) which collimates the input light with low aberration and directs it to a diffraction grating. The component wavelengths of the input light are then directed to first and second secondary reflectors (preferably spherical or toroidal mirrors), which are chosen to cooperatively focus the component wavelengths in ordered bands across an array detector while each at least substantially cancels the effects of any aberrations introduced by the other. By choosing optical elements which supply the grating with input light with low aberration, and then choosing optical elements which receive the component wavelengths from the grating and which offset any aberrations introduced by the other receiving optical elements, wavelength resolution at the detector can be enhanced.