Hyperspectral imaging with a liquid crystal polarization interferometer

Abstract

A novel hyperspectral imaging system has been developed that takes advantage of the tunable path delay between orthogonal polarization states of a liquid crystal variable retarder. The liquid crystal is placed in the optical path of an imaging system and the path delay between the polarization states is varied, causing an interferogram to be generated simultaneously at each pixel. A data set consisting of a series of images is recorded while varying the path delay; Fourier transforming the data set with respect to the path delay yields the hyperspectral data-cube. The concept is demonstrated with a prototype imager consisting of a liquid crystal variable retarder integrated into a commercial 640x480 pixel CMOS camera. The prototype can acquire a full hyperspectral data-cube in 0.4 s, and is sensitive to light over a 400 nm to 1100 nm range with a dispersion-dependent spectral resolution of 450 cm(-1) to 660 cm(-1). Similar to Fourier transform spectroscopy, the imager is spatially and spectrally multiplexed and therefore achieves high optical throughput. Additionally, the common-path nature of the polarization interferometer yields a vibration-insensitive device. Our concept allows for the spectral resolution, imaging speed, and spatial resolution to be traded off in software to optimally address a given application. The simplicity, compactness, potential low cost, and software adaptability of the device may enable a disruptive class of hyperspectral imaging systems with a broad range of applications.

Dynamical optical response of nematic liquid crystal cells through electrically driven Fréedericksz transition: influence of the nematic layer thickness

“…For the following measurements we have, thus, used the thickest, L=180 µm, cell. The findings are of interest for new optical applications, such as the realization of tunable delay lines for ultrashort pulses or the implementation of LC based high-resolution hyperspectral imaging [3,4,6]. For these applications, a scan of the birefringent state is required with a large phase shift.…”

“…Constantly growing applications of liquid crystals (LC) in photonics have recently been extended to novel electro-optical devices relying on their large birefringence. In this framework, electricallyaddressed large cell gap nematics have attracted interests for terahertz phase shifters [1,2], high-resolution hyperspectral imaging [3][4][5], phase and group delay control of ultrashort pulses trains [6], tunable angular shearing in wedge-shaped cells [7] and terahertz vortex beam generators [8]. In such progress, chiral nematics are not in rest with the recent demonstration of sub-picosecond pulse compression [9].…”

Polarimetric performance of a polarization modulator based on liquid crystal variable retarders for wide acceptance angles

“…For this reason, a configuration of doublecell 6 has been selected for the METIS PMP. It consists of two identical antiparallel aligned nematic (APAN) cells stacked together with their LC molecules tilting in opposite directions, which is known to provide a lower angular dependence [7][8][9] and therefore higher incident acceptance angles.…”

Full-Stokes polarization imaging method based on the self-organized grating array in fused silica

“…Therefore it improves the ability of target recognition in the complex background, and also provides valuable information in environmental monitoring, remote sensing, biomedical imaging and military target detection 1 – 6 . After extensive research, several techniques of imaging polarimeter including division-of-time, division-of-amplitude, division-of-aperture, and division-of-focal-plane (DoFP) have been developed in the past decades 7 – 11 . Among them, DoFP polarimeters adopt four independent micropolarimeter on the top of neighboring pixels of the image sensor to measure the four components of a Stokes vector.…”