Ultraminiature one-shot Fourier-spectroscopic tomography

Abstract

Abstract. We propose one-shot Fourier-spectroscopic tomography as a method of ultraminiature spectroscopic imaging. The apparatus used in this technique consists solely of a glass slab with a portion of its surface polished at a certain inclination angle-a device we term a relative-inclination phase shifter-simply mounted on an infinite-distance-corrected optical imaging system. For this reason, the system may be ultraminiaturized to sizes on the order of a few tens of millimeters. Moreover, because our technique uses a near-common-path wavefrontdivision phase-shift interferometer and has absolutely no need for a mechanical drive unit, it is highly robust against mechanical vibrations. In addition, because the proposed technique uses Fourier-transform spectroscopy, it offers highly efficient light utilization and an outstanding signal-to-noise ratio compared to devices that incorporate distributed or hyperspectral acousto-optical tunable filters. The interferogram, which is a pattern formed by interference of waves at all wavelengths, reflects the spatial variation in the intensity of the interference depending on the magnitude of the phase shift. We first discuss the design of the phase shifter and the results of tests to validate the principles underlying one-shot Fourier-spectroscopic tomography. We then report the results of one-dimensional spectroscopic imaging using this technique. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

Mid-infrared passive spectroscopic imaging for non-invasive blood glucose sensor (2nd. report): pea-sized (diameter: 6mm, length: 14mm) one-shot passive spectrometer for smartwatch

“…This apparatus has a high temporal resolution because the object ray is given a spatial phase difference with a relative inclined phase shifter. [2] Passive spectroscopy of the living body requires high sensitivity, and thus the numerical aperture (N.A.) is 0.77.…”

Superimposing interferogram method using a multi-slit array to enhance sensitivity and interference definition of spatial-phase-shift interferometers

“…As shown in Fig. 1, using one-shot Fourier spectroscopy [15], which uses one type of spatial-phase-shift interferometer, we tried to extend the width of the aperture area horizontally to increase the amount of incident light. We do not have to consider the height of the field stop because the height is determined by the optical superposition method [16].…”

“…The first is the temporal phase-shift interferometer [4][5][6][7], which registers optical path differences by moving a mirror, as used in the Fourier-transform infrared spectrometer based on the Michelson interferometer. The second is the spatialphase-shift interferometer [8][9][10][11][12][13][14][15], which registers optical path differences using a Wollaston prism to remove the need for moving parts, as used in the static imaging Fourier transform spectrometer. To measure living structures, instruments require not only high sensitivity but also high time resolution because the light from living samples such as tissue containing blood vessels must be registered quantitatively and continuously.…”

Passive one-shot Fourier spectrometer for blood glucose measurements

“…The device is small enough to be installed in wearable devices because it is composed of a lens without a mechanical drive. [4] In this report, we explain the advantages of mid-infrared passive spectroscopy and describe the measurement results of polypropylene using passive one-shot Fourier spectrometer.…”