Of Aotf-infrared Spectral Detection Apparatus

As the representation of "non-destructive testing", the infrared spectrometry technology with many merits, such as high efficiency, velocity, low-cost, non-damnification and environment protection, is widely used in petroleum, chemical industry, agriculture, medicinal clinic, biochemistry, etc. There are some actual difficulties to be solved: examinations of indoor gases and analyses of automobile exhaust and waste gases. This paper designed a kind of new infrared spectrometer. The newest acoustic-optic technology is applied in the system and the Acoustic-optic Tunable Filter (AOTF) with the range of spectral wavelength from 2um to 4um (5000cm^-1 -250cm^-1 ) was used as the dispersal element. The infrared spectrometer based on AOTF becomes more and more remarkable, because the system without mechanical movement parts is light, and it is also suitable for locale.This paper summarized the working principles of AOTF, analyzed its performances theoretically and experimentally in detail, and drew several important conclusions to guide the application, as follows: 1. The incidence angle should conform to the momentum principle in order to obtain the best efficiency. 2. The incidence angle must be smaller than the aperture of AOTF.3.Polarizable incidence-light can greatly enhance diffraction efficiency of AOTF. According to the above principles, the optical designs of the launching unit, rays of dispersion, and the acceptable unit were introduced detailedly. The application of single ray-path and double detectors weakened the influence of lamp-house fluctuation and ray-path disturbance, and the correlated detection improved the signal to noise ratio. Standard samples of polystyrene were adopted to correct wavelengths of the infrared spectrometer. The wavelength accuracy of the system is ±0.5 cm^-1 and the stability is 0.8%. The spectrum peaks of benzene and isopropyl alcohol gas collected by AOTF infrared spectrometer were consistent with the results gotten by FTIR, however the resolution should be improved. Furthermore, the preliminary quantitative analysis of isopropyl alcohol gas was made, and the correlation coefficient was 0.9824.The theory study, structural design and experimental analyses of AOTF infrared spectrometer establish the foundations for the exploitation of virulent gas analysis instruments. This work is valuable to improve efficiency in testing and realize the inspection in site. The paper put forward several referenced conclusions, completed a set of experimental instrument and the study achieved the anticipated aim.