Polarizer-Free AOTF-Based SWIR Hyperspectral Imaging for Biomedical Applications

Abstract

Optical biomedical imaging in short wave infrared (SWIR) range within 0.9–1.7 μm is a rapidly developing technique. For this reason, there is an increasing interest in cost-effective and robust hardware for hyperspectral imaging data acquisition in this range. Tunable-filter-based solutions are of particular interest as they provide image processing flexibility and effectiveness in terms of collected data volume. Acousto-optical tunable filters (AOTFs) provide a unique set of features necessary for high-quality SWIR hyperspectral imaging. In this paper, we discuss a polarizer-free configuration of an imaging AOTF that provides a compact and easy-to-integrate design of the whole imager. We have carried out image quality analysis of this system, assembled it and validated its efficiency through multiple experiments. The developed system can be helpful in many hyperspectral applications including biomedical analyses.

Compact and ultracompact spectral imagers: technology and applications in biomedical imaging

“… 20 To circumvent this shortcoming, imaging in the SWIR wavelengths has been proposed to provide greater penetration depths. 88 By combining compact spectral imagers with other imaging modality, the multimodal system was constructed to provide point-of-care analysis to the patients. 108 , 225 There are several different imaging modalities that pair well with hyperspectral imaging systems.…”

“…However, the disadvantages of filter wheels included speed, size, lack of customization, and small number of bands. An alternative to mechanical filter wheels was electronic tunable filters, which were mainly acoustooptical tunable filters (AOTF), 88 – 90 liquid crystal tunable filters (LCTF), 62 , 63 , 91 – 93 or Fabry–Perot interferometers (FPI). There existed other mechanisms for manufacturing tunable filters, such as surface plasmon coupled tunable filters; 94 however, three types described earlier are still the most popular.…”

“…Both AOTF and LCTF require large external power and large optical pathway, which makes them unsuitable candidates for ultracompact systems 94 . While the size of the filters in AOTF and LCTF themselves is compact and lightweight (often <1 kg), 88 , 89 , 118 , 145 , 146 it is the weight of filter driver that adds up to the weight of these devices. Ishida et al 147 .…”

Review of acousto-optic spectral systems and applications

“…However, this color difference can be almost completely compensated by adjusting the tilt of the output side of the acousto-optic unit to the input side. While, in the collimating scheme, the main aberration is the transverse chromatic aberration, which can be eliminated by choosing a different tilt angle [36,37].…”

Applications of AOTF Spectrometers in In Situ Lunar Measurements

“…Spectrometers and imaging spectrometers using acousto-optic tunable filters have many advantages, such as small size, light weight, absence of moving parts, optional wavelength, high environmental adaptability and high spectral and spatial resolution. [13][14][15] Therefore, it is suitable for the in situ spectral and imaging measurement of extraterrestrial bodies. The Chinese Chang'e Project has implemented three AOTF spectrometers for in situ spectral measurement of the lunar surface: the visible and near-infrared imaging spectrometers (VNIS) onboard Chang'e-3 (2013) [16] and Chang'e-4 (2018) [17] unmanned lunar rovers and the lunar mineralogical spectrometer (LMS) onboard Chang'E-5 (2020) [18].…”