Investigation of particulate systems using optical pathlength spectroscopy

2000 ◽  
Vol 627 ◽  
Author(s):  
Gabriel Popescu ◽  
Aristide Dogariu
Keyword(s):  
Path Length ◽  
Random Media ◽  
Michelson Interferometer ◽  
Industrial Process ◽  
Optical Path Length ◽  
Industrial Applications ◽  
Optical Path ◽  
Interference Signal ◽  
Optical Length ◽  
Reference Mirror

ABSTRACTIn many industrial applications involving granular media, knowledge about the structural transformations suffered during the industrial process is desirable. Optical techniques are noninvasive, fast, and versatile tools for monitoring such transformations. We have recently introduced optical path-length spectroscopy as a new technique for random media investigation. The principle of the method is to use a partially coherent source in a Michelson interferometer, where the fields from a reference mirror and the sample are combined to obtain an interference signal. When the system under investigation is a multiple-scattering medium, by tuning the optical length of the reference arm, the optical path-length probability density of light backscattered from the sample is obtained. This distribution carries information about the structural details of the medium. In the present paper, we apply the technique of optical path-length spectroscopy to investigate inhomogeneous distributions of particulate dielectrics such as ceramics and powders. The experiments are performed on suspensions of systems with different solid loads, as well as on powders and suspensions of particles with different sizes. We show that the methodology is highly sensitive to changes in volume concentration and particle size and, therefore, it can be successfully used for real-time monitoring. In addition, the technique is fiber optic-based and has all the advantages associated with the inherent versatility.

Development of a MEMS Xylophone Bar Magnetometer Using Optical Interferometry for Detection

1999 ◽  
Vol 605 ◽  
Author(s):  
Joseph Miragliotta ◽  
R. Osiander ◽  
J. L. Champion ◽  
D. A. Oursler ◽  
T.J. Kistenmacher
Keyword(s):  
Magnetic Field ◽  
Path Length ◽  
Dynamic Range ◽  
Michelson Interferometer ◽  
High Sensitivity ◽  
Force Sensor ◽  
Optical Path Length ◽  
Optical Path ◽  
Active Stabilization ◽  
Path Length Difference

AbstractWe report the results of an optical interferometric study, which was designed to measure the magnetic-field induced displacement of a resonating xylophone bar MEMS magnetometer. The MEMS magnetometer is a Lorentz-force sensor, which transduces an alternating current and an orthogonal directed magnetic field into an alternating displacement of the xylophone bar. The Michelson interferometer system includes optics and electronics for active stabilization of the optical path length difference between the reference and sample beams. The active stabilization results in the ability to control or detect pathlength differences as small as ∼ 0.6 ×10−3 Å. With this level of operational sensitivity, the presence of a one nano Tesla magnetic field was found to produce a detectable bar displacement on the order of ∼10−3 Å. In addition to the high sensitivity, the interferometer photodetector displayed linear behavior over six decades of optical path length differences, which corresponded to a magnetic field dynamic range that spanned nano- to milli-Tesla amplitudes.

Nanometer-scale displacement sensing using self-mixing interferometry with a correlation-based signal processing technique

2006 ◽  
Vol 14 (2) ◽  
Author(s):  
J. Hast ◽  
M. Okkonen ◽  
H. Heikkinen ◽  
L. Krehut ◽  
R. Myllylä
Keyword(s):  
Signal Processing ◽  
Phase Difference ◽  
Laser Diode ◽  
Path Length ◽  
Spline Interpolation ◽  
External Cavity ◽  
Optical Path Length ◽  
Optical Path ◽  
Interference Signal ◽  
Length Changes

AbstractA self-mixing interferometer is proposed to measure nanometre-scale optical path length changes in the interferometer’s external cavity. As light source, the developed technique uses a blue emitting GaN laser diode. An external reflector, a silicon mirror, driven by a piezo nanopositioner is used to produce an interference signal which is detected with the monitor photodiode of the laser diode. Changing the optical path length of the external cavity introduces a phase difference to the interference signal. This phase difference is detected using a signal processing algorithm based on Pearson’s correlation coefficient and cubic spline interpolation techniques. The results show that the average deviation between the measured and actual displacements of the silicon mirror is 3.1 nm in the 0–110 nm displacement range. Moreover, the measured displacements follow linearly the actual displacement of the silicon mirror. Finally, the paper considers the effects produced by the temperature and current stability of the laser diode as well as dispersion effects in the external cavity of the interferometer. These reduce the sensor’s measurement accuracy especially in long-term measurements.

scholarly journals Stray light characterization with ultrafast time-of-flight imaging

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
L. Clermont ◽  
W. Uhring ◽  
M. Georges
Keyword(s):  
Path Length ◽  
Imaging System ◽  
Time Of Flight ◽  
Optical Path Length ◽  
Optical Path ◽  
Stray Light ◽  
Laser Source ◽  
Space Telescopes ◽  
Characterization Methods ◽  
Instance Space

AbstractUnderstanding stray light (SL) is a crucial aspect in the development of high-end optical instruments, for instance space telescopes. As it drives image quality, SL must be controlled by design and characterized experimentally. However, conventional SL characterization methods are limited as they do not provide information on its origins. The problem is complex due to the diversity of light interaction processes with surfaces, creating various SL contributors. Therefore, when SL level is higher than expected, it can be difficult to determine how to improve the system. We demonstrate a new approach, ultrafast time-of-flight SL characterization, where a pulsed laser source and a streak camera are used to record individually SL contributors which travel with a specific optical path length. Furthermore, the optical path length offers a means of identification to determine its origin. We demonstrate this method in an imaging system, measuring and identifying individual ghosts and scattering components. We then show how it can be used to reverse-engineer the instrument SL origins.

Non-Traditional Applications of near Infrared Spectroscopy Based on the Optical Characteristic Models for a Biological Material Having Cellular Structure

1998 ◽  
Vol 6 (1) ◽  
pp. 41-46 ◽  
Author(s):  
Satoru Tsuchikawa
Keyword(s):  
Biological Material ◽  
Path Length ◽  
Cellular Structure ◽  
Process Model ◽  
Near Infrared ◽  
Traditional Approach ◽  
Nir Spectroscopy ◽  
Optical Path Length ◽  
Optical Path ◽  
The Mean

Non-destructive measurements, based on near infrared (NIR) spectroscopy, on biological material with a cellular structure like wood require a non-traditional approach. We have developed new concepts to model the optical properties of a sample having cellular structure, for the illumination conditions of the spectrometer available to us. A set of optical models, which consisted of the directional characteristics models, the light-path models and the equivalent surface roughness model was proposed to clarify the behaviour of light propagation in a wood sample. Furthermore, the mean optical path length, which was derived by incorporating the nth power cosine model of radiant intensity into the diffusion process model in consideration of the parallel beam component of incident light, was calculated. By introducing the concept of equivalent sample thickness, compatible with the mean optical path length, into the Kubelka–Munk theory, generalised input/output equations for radiation were constructed. In this non-traditional application of NIR spectroscopy, these optical concepts make it possible to analyse both the physical condition and chemical composition of a biological material with a cellular structure.

Electric-field-induced optical path length change in LiNbO3:MgO crystals: spatial anisotropy analysis

2013 ◽  
Vol 52 (16) ◽  
pp. 3757 ◽  
Author(s):  
Anatoliy S. Andrushchak ◽  
Oleh V. Yurkevych ◽  
Bogdan M. Strychalyuk ◽  
Mykhailo M. Klymash ◽  
Andrzej Rusek ◽  
...  
Keyword(s):  
Electric Field ◽  
Path Length ◽  
Length Change ◽  
Optical Path Length ◽  
Optical Path ◽  
Spatial Anisotropy

Supercritical-fluid cell with device of variable optical path length giving fringe-free terahertz spectra

2000 ◽  
Vol 71 (11) ◽  
pp. 4061 ◽  
Author(s):  
Ken-ichi Saitow ◽  
Keiko Nishikawa ◽  
Hideyuki Ohtake ◽  
Nobuhiko Sarukura ◽  
Hiroshi Miyagi ◽  
...  
Keyword(s):  
Supercritical Fluid ◽  
Path Length ◽  
Optical Path Length ◽  
Optical Path ◽  
Fluid Cell
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