![]() ![]() ![]() Once the width of the detector is known you can calculate the focal length of the focusing mirror or lens.Īs mentioned earlier, the spectrometer is imaging the input slit to the detector and we generally want to have the slit as wide as possible to collect as much light through the input slit as possible. Step 5: Calculate focal length of focus lens However, if you require a broad spectral range and/or a high resolution you should aim for a wide detector (typically 1/1” or 25.8 mm). In general, if you need a compact spectrometer you should aim for a short detector (typically 1/4” or 6.4 mm). There is a large range of diode array detectors specifically designed for spectrometers. The purpose of the spectrometer design is to disperse the wavelength range across the width of the detector array L D. These angles can be calculated once the grating groove density G and the total deflection Θ are chosen. The angle of incidence α on the grating and the diffraction angle β for the center wavelength λ c are key parameters in the spectrometer design. The important parameter that you shall use for the design in the next steps is the groove density G. You should choose a grating that has high diffraction efficiency in your wavelength. Most grating vendors have an on-line catalog where you can find one or more grating options to try in your design. The second step is to choose a diffraction grating. For the Czerny Turner a typical value for Θ is around 30° wheras transmission gratings are generally used in the Littrow configuration and –1 st order where α = -β => Θ = 0°. The first step is to choose between the Czerny-Turner or LGL type geometry.
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