Calibration of an AOTF hyperspectral imager with configurable spectral selectivity

The hyperspectral imager is a kind of camera that can image objects in many narrow spectral bands, and acousto-optic tunable filters (AOTFs) can be used as the optical filtering elements in such instruments. AOTFs have many advantages such as solid-state, small size, good environmental adaptability, programmable, electronically control and so on, which are suitable for space exploration. For instance, AOTFs have been used in Mars and Venus detection. However, more advantages of AOTFs can be utilized in spectral detection, such as random wavelength access and configurable spectral resolution, and more flexible imagers can be expected with these characteristics. As a result, a new hyperspectral imager based on AOTF has been realized. It can not only take images in the spectral range of 460~1100nm with more than one hundred narrow bands, but also allow users to select any set of bands and configure the spectral resolution in a certain range just by computer commands. To do so, a multi-channel RF generation system is developed to drive the AOTF. When multi RF frequencies are applied to the AOTF simultaneously, not only the central wavelength, but also the bandwidth and the passband shape of the selected band, can be controlled by configuring the RF signals. Such capability enhances the flexibility of hyperspectral imaging, but the increased number of configurable variables complicates the course of calibration, so some specific calibration setups and methods are needed. In this paper, the laboratory calibration of the imager is introduced, and some results are presented and analyzed.