Simultaneous measurement of H2O concentration and effective absorption optical path length under unknown optical path length condition based on a single spectral line

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.

Download Full-text

Stray light characterization with ultrafast time-of-flight imaging

Scientific Reports ◽

10.1038/s41598-021-89324-y ◽

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.

Download Full-text

Measurement of the effective optical path length of diffusing integrating cavities using time-resolved spectroscopy

Applied Optics ◽

10.1364/ao.57.003519 ◽

2018 ◽

Vol 57 (13) ◽

pp. 3519 ◽

Cited By ~ 1

Author(s):

Xue Zhou ◽

Jia Yu ◽

Lin Wang ◽

Zhiguo Zhang

Keyword(s):

Path Length ◽

Optical Path Length ◽

Optical Path ◽

Time Resolved ◽

Time Resolved Spectroscopy ◽

Effective Optical Path Length

Download Full-text

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

Journal of Near Infrared Spectroscopy ◽

10.1255/jnirs.119 ◽

1998 ◽

Vol 6 (1) ◽

pp. 41-46 ◽

Cited By ~ 6

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.

Download Full-text