Characteristics of compact spectrometers with diffraction gratings of different typ

Modern small-sized spectrometers are designed mainly by Czerny – Turner scheme with a flat diffraction grating, and with the goal of the maximum aperture at the expense of resolution — by the scheme with a concave diffraction grating with a flat field. Spectrum registration in such spectrometers is carried out by linear photodiode array. The aim of the work is to inform professionals about the characteristics of the compact spectrometers developed by the authors. These spectrometers use unpackaged linear photodiode arrays for spectrum registration that eliminate the reflection of radiation from the cover glass of the photodiode array and reduce stray-light. The tightness of the spectrometer housing increases their service life. The modification parameters of the spectrometer designed according to Czerny – Turner scheme are given. The main advantage of the spectrometer is the low stray-light inside the device and the same spectral resolution throughout the spectral range. The working aperture in Czerny – Turner scheme is limited by aberrations to 1/6. The scheme with a flat field allows operation with a larger working aperture. Three modifications of the spectrometer are developed according to this scheme (description of their main parameters is given). The results of experimental comparison of the spectrometers with different optical schemes in the light intensity and spectral resolution are presented, along with the examples of their application. Devices designed according to Czerny – Turner scheme are used in atomic emission, atomic absorption spectral analysis, and in spectrophotometry for registration of absorption spectra of condensed media. Luminescence and Raman spectra of minerals are recorded on a flat-field spectrometer. The developed compact spectrometers have an operating spectral range 190 – 1100 nm with the possibility of registering spectral regions from 70 to 1000 nm, the best resolution being 0.1 nm and the stray-light level less than 0.05% with the minimum recorded optical density of more than 3. Flat field spectrometers have an increased aperture due to the large working aperture 1/2.1.

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