A method of spectral resolution improvement was presented based on the double filtering in a single AOTF. A special narrowband hyperspectral imaging system using this single-AOTF double-filtering method was established. The spectral bandwidth of double-filtered spectra was 39% narrower than that of the single-filtered optical signal experimentally. We achieved hyperspectral images of the resolution target with better image resolutions than the single-filtering images because of the improved spectral resolution after the double-filtering process.
As for the common acousto-optic tunable filter (AOTF), the optical wavelength is directly tuned by the frequency of the applied radio frequency (RF) signal. The working wavelength range of the RF controlled AOTF could be limited by the performance of the RF source, especially in the high frequency area. We have proposed a special noncollinear AOTF system, in which the central optical wavelength could be tuned continually by rotating the AOTF, rather than changing its RF. This arrangement is confirmed to be effective to broaden the work wavelength range of a traditional RF based AOTF with the high spectral resolution. Particularly, it is welcomed to the circumstance for the flexible spectral bandwidth. This work has presented not only an original way to tune the wavelength of the filtered optical signal but also a powerful supplement of the RF controlled AOTF. It can lead to a wider applications of a noncollinear AOTF in the field of spectral analysis, hyperspectral imaging, and etc.
Hyperspectral imaging is a technique that integrates multiple spectral bands and image information. Its applications range from improving the accuracy of cancer diagnosis to testing the quality of products. Here, we introduce a double-filtering technique that provides high-resolution diagnostic histological images within minutes. The hyperspectral microscopic imaging system is built based on an acousto-optic tunable filter (AOTF). The optimized system is analyzed from the perspective of spectrum and imaging. The spectral resolution can be improved by 37.08 % to 59.95% in the visible light range. The side lobe is obviously inhibited and the purity of spectrum is improved. Furthermore, the example of hyperspectral microscopic imaging is demonstrated with unstained gastric cancer tissue sections to assess the ability of the system in terms of its spectral performances and image quality. The microscopic imaging results of single filtering optical path system and single crystal double filtering optical path system are compared. In general, the optimized double filtering system achieves excellent performance in bandwidth compression and side lobe suppression, especially the first application of hyperspectral microscopy combined with microscope in the visible light range.
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