Design of an infrared monochromatic system with an AOTF as the dispersion element

In this paper, a method on how to design an infrared monochromatic system based on an acousto-optic tunable filter (AOTF) is introduced. Some key problems about optical system (including collimation of incident light beam and working distance-the shortest distance to separate the zero order light and the diffracted light) are researched and solved. The driving circuit for an AOTF based on Direct Digital Synthesis and a Digital Signal Processor is also introduced. The experimental results show a direct proportional relationship between the wave number of diffracted light and the driving frequency. The monochromatic system has a wave number range of 2000-4000 cm(-1) and the spectral half-width is 20 cm(-1).