High-resolution hyperspectral imaging with cascaded liquid crystal cells

• Published in: Optica Vol. 4; no. 4; p. 400
• Main Authors: Jullien, Aurélie, Pascal, Rémy, Bortolozzo, Umberto, Forget, Nicolas, Residori, Stefania
• Format: Journal Article
• Language: English
• Published: Optical Society of America - OSA Publishing 20.04.2017
• Subjects: Physics; Spectroscopy; Fourier transforms; Liquid-crystal devices; OCIS codes: Multispectral and hyperspectral imaging
• ISSN: 2334-2536; 2334-2536
• DOI: 10.1364/OPTICA.4.000400

Hyperspectral imaging collects knowledge about the spectral content enclosed in a given target. For such investigations , fundamental requirements include the ability to extend the spectral range, improve the spectral resolution, and achieve a large field of view together with compactness and robustness. Here we introduce a new method of polarized hyperspectral imaging that makes use of two cascaded liquid crystal cells that we demonstrate to act as a Fourier spectrometer when appropriately driven with a dynamic voltage step. One thick cell (200 μm), electrically addressed, provides a tunable path delay between two polarization directions while a thin static cell is used as a temporal offset. Prior to the imaging, an accurate calibration of the system is performed by broadband spectral interferometry with femtosecond pulses. The calibration procedure allows determining the path delay between the extraordinary and ordinary waves with subfemtosecond accuracy. Thanks to this implementation, 130 cm −1 (6 nm) spectral resolution is demonstrated over a 400-1000 nm spectral range. Furthermore, the device has no moving parts, is compact, inte-grable, and low cost compared to traditional imaging systems relying on Fourier spectrometry. Scalability in size and spectral range can also be considered. Examples of hyperspectral imaging are demonstrated with three representative samples permitting the evaluation of the potential of the technique in terms of its spectral performances, compactness, and robustness.