Two Material Achromatic Prism for Spectrometer Dispersion
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Solution Overview
Problem
Conventional dispersive elements, such as prisms and diffraction gratings, face challenges in achieving reduced variance of dispersion over a wide wavelength band, leading to distortions and non-linear spectral dispersion, which affects the accuracy of spectroscopic measurements.
Innovation Solution
A spectrometer utilizing a two-material prism system comprising a crystalline crown material and a crystalline flint material, specifically using Potassium Iodide or Cesium Iodide as the flint and Spinel or Aluminum Oxynitride as the crown, configured to disperse light into visible and infrared wavelength bands with approximately equal dispersion across these bands, thereby minimizing variance and achieving a flat dispersion characteristic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-material prism is used for dispersion, then the prism structure is simple, but the dispersion curve shows large variation from linearity causing unacceptable distortion
Solution Approach 1:
The patent applies composite materials by combining two different crystalline materials (crown and flint) with different dispersion characteristics to create a two-material prism. This composite structure allows the prism to achieve flatter, more linear spectral dispersion across a wide wavelength band while maintaining a relatively simple geometric configuration, thereby resolving the contradiction between structural simplicity and dispersion linearity.
2Ease of manufacture
If conventional glass materials are used in two-material achromatic prisms, then material selection is limited by empirical observations, but the dispersion variance across wide wavelength bands remains significant
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional glass materials to crystalline materials with specifically controlled optical parameters. The use of crystalline crown and flint materials with carefully selected refractive indexes and dispersion characteristics enables achievement of flatter dispersion across wide wavelength bands, improving dispersion precision while maintaining manufacturability through established crystal growth techniques.
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 two-material prism system provides improved spectral sampling by maintaining a consistent dispersion across a wide wavelength band, enhancing the accuracy and efficiency of spectroscopic measurements in visible and short-wave infrared ranges.
Implementation Method 1
The dispersion of light is conventionally achieved through a dispersive element, such as a diffraction grating or a prism. Prisms, on the other hand, utilize the transition between materials, such as between air and the solid of the prism, to disperse the incident light.
Implementation Method 2
Prisms, on the other hand, utilize the transition between materials, such as between air and the solid of the prism, to disperse the incident light.
Data Source
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AI summary
A spectrometer comprises a detector array (140) and a prism (60). The prism comprises a first prism element (110) comprising a substantially crystalline crown material, and a second prism element (120) contacting the first prism element, the second prism element comprising a substantially crystalline flint material. The spectrometer further includes optics configured to direct light at least twice through the prism. The prism is configured to disperse light received from the optics at an incident angle therethrough into constituent spectra in visible and infrared wavelength bands that are dispersed from the prism at angles offset from the incident angle. The constituent spectra are directed onto the detector array with approximately equal dispersion across the visible and infrared wavelength bands. Among other things, desirable material selections for the first and second prism elements are also disclosed.