Methods for Enhancing the Resolution of AOTF as a NIR Spectroscopy

摘要

AOTF (acoustic-optic tunable filter) has been widely used in spectrum detecting because of its particular advantages. The spectrum resolution is the most important parameter of AOTF spectroscopy. The resolution of AOTF is mainly determined by the purity of diffractive light, the side-lobe and the bandwidth. In this paper the foregoing parameters are analyzed systematically. The following methods are put forward to enhance the resolution. A new theory of equivalent point for the AOTF designing is introduced. The purity of diffractive light can be improved by either optical modulation and electrical demodulation or bipolarization. By altering shape of the acoustic transducer, the side-lobe can be cut down for energy distribution of supersonic passing AOTF has been changed. Fourier self-deconvolution method is adapted to decrease the bandwidth. Highly resolution can be gained with the help of these methods. Compared with usual AOTF system, the performance of enhanced one is greatly improved. The conclusions have been verified by experiments with using higher accurate FT-IR system.