Spatial and spectral correction of an acousto-optical imaging spectrometer

Subject of study. This study investigated the spatial-spectral distortions arising from acousto-optic diffraction, which must be considered when constructing an optical system and calibrating an acousto-optical device. Aim of study. This study aimed to perform the spatial and spectral calibration of imaging spectrometers based on acousto-optical tunable filters and to develop a technique for equalizing the transmittance of the acousto-optical tunable filter in the entire working spectral range. Method. To obtain undistorted data, both spectral and spatial inhomogeneities need to be corrected. The calibration procedure consisted of the hardware spectral tuning of the acousto-optical device and software-mathematical correction. The transmission function of the acousto-optical tunable filter is controlled by two parameters: the frequency and power of ultrasound, which, in turn, are determined by the frequency and effective amplitude of the electrical signal. The frequency determines the position of the transmission function, that is, the wavelength of the acousto-optical tunable filter. The amplitude sets the ultrasound power, which determines the intensity of the radiation passing through the acousto-optical tunable filter. Full consideration of the nonuniformity of the transmission coefficient in the entire spectral range is achieved by postprocessing. Main results. A technique for leveling the radiation power by changing the supplied ultrasound power is proposed. The developed software allows the distortions introduced by acousto-optical tunable filters for evaluating visual information to be minimized. The technique was tested on a near-infrared imaging spectrometer with double acousto-optic monochromatization. Practical significance. The presented method enables hardware calibration of hyperspectral devices based on acousto-optical tunable filters and software correction of the displayed results to be performed in real time. The developed method is universal and suitable for other imaging spectrometers based on acousto-optic monochromatization. It will enhance acousto-optic methods both regarding the reliability of the data obtained and the convenience of using such devices.