Single-Point Detection Architecture via Liquid Crystal Modulation for Hyperspectral Imaging Systems

C Harrison Brodie,Christopher M Collier

doi:10.1109/access.2020.3029550

Abstract

Hyperspectral imaging (HSI) architectures can acquire one-dimension of spatial information and one-dimension of spectral information on a two-dimensional image sensor for an image, such as in the traditional line-scan HSI architecture. However, development of HSI architectures for multiple spatial dimensions is challenging as there is not a third dimension on a two-dimensional image sensor on which to store spectral information. The presented work introduces a snapshot HSI architecture to alleviate this issue. The snapshot HSI architecture incorporates single-point detection via liquid crystal modulation and a single photodiode. Mixing of hyperspectral data is expressed as intermodulation frequency products within the Fourier-domain. Spatial information can be recorded through spatial frequencies and spectral information can be recorded through spectral frequencies. Such modulation is achieved through liquid crystal spatial and spectral arrays of an image beam. The spatial and spectral modulation frequencies form intermodulation frequency products that are recorded on the single photodiode and can be uncovered through Fourier-domain filtering.

Highlights

Digital imaging systems are ubiquitous in everyday life, being deployed for applications in many sectors
The spatial (i = 1, 2, 3, . . . , m) and spectral (j = 1, 2, 3, . . . , n) liquid crystal (LC) pixel arrays are both extended into a second dimension, that is (k = 1, 2, 3, . . . , p) to structure a pair of LC pixel matrices which enable the acquisition of 2D spatial image beams. (Fourier frequency analyses will subsequently reveal information corresponding to these spectral LC pixels.) The image beam can subsequently be focused onto a single photodiode for measurement of the intermodulation frequency products
The fundamental geometry, theoretical operation, and experimental operation have been investigated in this work

Summary

INTRODUCTION

Digital imaging systems are ubiquitous in everyday life, being deployed for applications in many sectors. Hyperspectral imaging architectures exist in a variety of forms: point-scan [12], line-scan [13], and wavelengthscan [14] These HSI architecture categories are defined by the technique used to map the measured image dimensions (i.e., spatial dimensions, Ximage, Yimage, and wavelength, λ) to the physical dimensions of image sensor (i.e., Xsensor, Ysensor) for construction of the hypercube. (Fourier frequency analyses will subsequently reveal information corresponding to these spectral LC pixels.) The image beam can subsequently be focused onto a single photodiode (seen in Fig. 1) for measurement of the intermodulation frequency products (i.e., the sum and difference frequencies). The time-domain output from the single photodiode can undergo Fourier-domain frequency analyses with the amplitude of these intermodulation frequency products describing activity from a specific ith spatial LC pixel and jth spectral LC pixel Under this modulation scheme, the full λ spectra for each Ximage and Yimage spatial position can be revealed. In this way either the lower or upper sidebands contain the entire information needed to construct the spectra for a given spatial LC pixel

EXPERIMENTAL OPERATION

SIMULATION

COMPARISON TO LITERATURE

Findings

CONCLUSION