400- to 1000-nm imaging spectrometer based on acousto-optic tunable filters

摘要

An imaging spectrometer covering the 400- to 1000-nm band is conceived and developed. The system is based on an acousto-optic tunable filter (AOTF) attached to a high-performance digital camera. The AOTF enables the selection of spectral bands with an rf signal in the range of 70 to 218 MHz. It includes a tele-centric optical system that enhances system efficiency. Additionally, a smart choice of integration time reduces the dependence of the efficiency on the frequency. Calibration includes filter characterization and compensation of crystal nonconstant diffraction efficiency and spatial nonhomogeneity. The system is controlled by a PC application specifically developed for this purpose, providing wide versatility, while enabling transparent and intuitive management to nonexpert users. The spectrometer is validated by estimating the light absorption of leaves and their chlorophyll content.