The Calibration Methods of Geometric Parameters of Crystal for Mid-Infrared Acousto-Optic Tunable Filter-Based Imaging Systems Design

Abstract

AOTF calibration is a complex topic that has various aspects. As far as geometric calibration is concerned, it includes not only processing errors and fixing errors in the optical system, but also the error of geometric parameters of crystal (GPC). GPC is the preset input in the optical design and optimization of Zemax, which determines the key parameters, including the spatial resolution, the field of view, and aberration. In particular, the compensation of aberration during the optical design requires accurate values of GPC. However, it is currently considered ideal. Therefore, two calibration methods based on the principle of parallel tangent are proposed: (1) the minimum-central wavelength method; (2) the minimum-frequency method. The deviation of the parallel tangent incident angle calibrated by the two methods is 0.03°. As a result, the tuning curve calculated in theory with the calibrated geometric parameters of AOTF is consistent with the tuning curve measured in practice.

Analysis of Phase Mismatch for Mercurous Bromide-Based Non-Collinear AOTF Design in Spectral Imaging Applications

“…For the fixed acoustic angle and frequency, diffracted lights have different central wavelengths, caused by polychromatic light entering from various directions [31], and there are also differences in the spectral bandwidth of the diffracted light. As shown in Figure 3b,c, when the acoustic angle is 5 • and the optical cut angle meets the PTP at 10.1 • , the incident light entering the AOTF normally is diffracted in a central wavelength of 10.6 µm.…”

Angular-Spectral Characteristics of Acousto-Optic Tunable Filters Based on Mercurous Halide Crystals

“…However, when white light is incident, the light outside the angular aperture is also diffracted, with only the central wavelength of diffracted light drifting. This drift can be calibrated both experimentally and theoretically [ 16 ]. A proposal has been made to enhance the throughput of AOTF-based imagers by utilizing a super-angular aperture scheme for AOTF spectral imaging systems [ 17 ].…”