Acousto-optic imaging spectropolarimetry for remote sensing

Abstract

We review the operating principles of noncollinear acousto-optic tunable filters (AOTF's), emphasizing the use of two orthogonally polarized beams for narrow-band imaging. Spectral characterization and spectral broadening measurements of commercially available AOTF's agree with theoretical predictions and reveal difficulties associated with imaging noncollimated light. An AOTF imaging spectropolarimeter for ground-based astronomy that uses CCD's has been constructed at NASA Goddard Space Flight Center. It uses a TeO(2) noncollinear AOTF and a simple optical relay assembly to produce side-by-side orthogonally polarized spectral images. We summarize the instrument design and initial performance tests. We include sample spectral images acquired at the Goddard Geophysical and Astronomical Observatory.

Recent Advances in Acousto-Optic Instrumentation for Astronomy

“…For that reason, AOTFs for spectropolarimetric imaging are usually designed with parallel optical facets [4,7], as shown in Fig. 2b.…”

AOTF-Based Spectral Imaging for Balloon-Borne Platforms

“…Noncollinear AOTFs are used for numerous applications that require imaging with spectral discrimination, including microscopy, hyperspectral imaging, and spectroscopy. Their design principles have been reviewed in papers extending back several decades (Chang, 1974;Yano & Watanabe, 1976;Smith et al, 1987;Gass & Sambles, 1991;Glenar et al, 1994;Gupta et al, 2002;Georgiev et al, 2002;Zhang et al, 2007). They are made of crystals whose optical properties are altered in the presence of an acoustic wave (e.g.…”

“…Equations (1)-(3) serve as a guide for understanding the tuning relation and spectral resolution Glenar et al (1994)). (a) Broadband, unpolarized incident light is combined with an RF acoustic wave launched into the crystal to produce output light at one specific wavelength and in orthogonal polarizations.…”

High Throughput AOTF Hyperspectral Imager for Randomly Polarized Light

“…The additional spectral information is capable of identifying visually indistinguishable features within a large region of interest (ROI) [2,3]. Therefore, HSI finds applications in many applications, including the food industry [4,5], archeology [6], forensics [7,8], security [9], geology [1], [10][11][12], and medicine [13]. Clinical applications of HSI include retinal vascular inspection [14], early detection of gastric cancer [15], tongue lesion classification [16], and intraoperative tumors residuals detection [17].…”