V.V. Shapovalov, B.S. Gurevich, I.A. Kolesov, S.V. Andreyev, A.V. Belyaev

Spectrally selective measurements of intensity of the light transmitted through the biological sample is one of the most common and efficient methods of the biological probes analysis. The basic information which can be obtained by means of this method, is connected with light absorption in the probe at different wavelengths. It is evident that the specific spectral device is required for such measurements performance. Usually a diffraction grating plays part of a selective element in such device. However, it has an important deficiency: light with different wavelengths after grating is localized in different spatial areas, and in order to tune the light wavelength, it is necessary to move the photodetector mechanically. The problem can be avoided if acousto-optic tunable filter (AOTF) is used as a selective element. Light emission diode (LED) looks the optimal light source for the spectral device, although its spectral bandwidth is usually too small in order to provide the device efficient operation. We have proposed the scheme which allows to form the polychrome light beam with tunable spectrum on the basis of the set of LEDs which are located in certain configuration, due to which the light from different LEDs is gathered into the total uniform light beam. It has also been proposed the criterion of the resolving power by light wavelength for the spectral device. According to this criterion, two spectral lines can be considered resolved if the probability of non-recognition of at least one gray scale level in each line is less than certain value given beforehand in accordance with the problem conditions. The light source operating using the proposed principle, meets the demands which are made to the spectral devices intended for biochemical investigations.