Spectral-Coding-Based Compressive Single-Pixel NIR Spectroscopy in the Sub-Millisecond Regime.

Paul Gattinger,Ivan Zorin,Christian Rankl,Markus Brandstetter

doi:10.3390/s21165563

Abstract

In this contribution, we present a high-speed, multiplex, grating spectrometer based on a spectral coding approach that is founded on principles of compressive sensing. The spectrometer employs a single-pixel InGaAs detector to measure the signals encoded by an amplitude spatial light modulator (digital micromirror device, DMD). This approach leads to a speed advantage and multiplex sensitivity advantage atypical for standard dispersive systems. Exploiting the 18.2 kHz pattern rate of the DMD, we demonstrated 4.2 ms acquisition times for full spectra with a bandwidth of 450 nm (5250–4300 cm−1; 1.9–2.33 µm). Due to the programmability of the DMD, spectral regions of interest can be chosen freely, thus reducing acquisition times further, down to the sub-millisecond regime. The adjustable resolving power of the system accessed by means of computer simulations is discussed, quantified for different measurement modes, and verified by comparison with a state-of-the-art Fourier-transform infrared spectrometer. We show measurements of characteristic polymer absorption bands in different operation regimes of the spectrometer. The theoretical multiplex advantage of 8 was experimentally verified by comparison of the noise behavior of the spectral coding approach and a standard line-scan approach.

Highlights

Infrared (IR) spectroscopy is a well-established analytical method for non-destructive chemical characterization of materials in all aggregate states
The acquisition speed advantage and multiplexing advantage are inherent either for dispersive or for Fourier transform IR (FTIR) spectrometers, respectively, showing that these properties are contradictory. We address this point by demonstrating a dispersive spectrometer that displays both the multiplex advantage, usually nonspecific for such systems, and the speed advantage by using a spectral coding approach based on the principles of compressive sensing (CS)
The research undertaken in this paper focused on two parallel themes

Summary

Introduction

Infrared (IR) spectroscopy is a well-established analytical method for non-destructive chemical characterization of materials in all aggregate states. During the last two decades new measurement technologies have been developed to overcome these limitations, facilitated by novel laser technology, such as quantum cascade lasers [1,2] and supercontinuum laser sources [3,4]. These laser sources are rather expensive, which limits their range of application and triggers the development of alternative speed- and sensitivity-enhanced measurement approaches. Considering the developments in non-laser spectroscopic instrumentation, three conceptual categories of devices can be distinguished: dispersive systems, filter spectrometers (tunable or discrete filters), and the gold-standard technique of Fourier transform spectrometry [5]. State-of-the-art filter-based systems, such as tunable MEMS-based Fabry–Pérot etalons, represent a cost-efficient alternative

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