Improving the performance of acousto-optic tunable filters in imaging applications

Abstract

Acousto-optic tunable filters (AOTFs) can be used as spectral filters for the implementation of multispectral imaging systems. However, obtaining quality images is challenging. In this work, we propose several improvements that enable the use of these systems in quantitative spectroscopic imaging applications. The improvements are based on three pillars: 1. a finer spectral bandpass shaping by dynamically optimizing the radio frequency (rf) driving signal, 2. an extensive calibration process, and 3. careful image preprocessing that uses calibration data to correct some well known AOTF issues in imaging applications. A novel multispectral imaging instrument is built using commercial off-the-shelf components. The instrument includes an Isomet (Springfield, New Jersey) AOTF working in the visible and near-infrared range, and a new concept of rf generator based on a high-speed digital-to-analog converter that allows the generation of multiband signals. The ancillary control software performs the main part of the image optimization process: an initial calibration, a dynamic adjustment of the rf driving signal power and exposure time, and finally the radiometric preprocessing of the acquired multispectral images. Finally, some results of the instrument performance are presented that show the achieved spectral and spatial resolution on different imaging scenarios.