Application of time domain, ultra high resolution optical coherence tomography (UHR-OCT) in evaluation of
microfluidic channels is demonstrated. Presented study was done using experimental UHR-OCT device based on a
Kerr-lens mode locked Ti:sapphire femtosecond laser, a photonic crystal fibre and modified, free-space Michelson
interferometer. To show potential of the technique, microfluidic chip fabricated by VTT Center for Printed
Intelligence (Oulu, Finland) was measured. Ability for full volumetric reconstruction in non-contact manner
enabled complete characterization of closed entity of a microfluidic channel without contamination and harm
for the sample. Measurement, occurring problems, and methods of postprocessing for raw data are described.
Results present completely resolved physical structure of the channel, its spatial dimensions, draft angles and
evaluation of lamination quality.
High-resolving full-field OCT method is considered that provides increased resolution and interferometric data acquisition speed due to high optical magnification and electronic lateral scan provided by video camera. OCT data processing algorithm based on signal squaring with subsequent low-pass filtering is considered. Experimental results obtained when evaluating samples of paper material are presented and discussed.
This paper introduces optical non-contact paper surface characterization based on Low Coherence Interferometry (LCI). Using this technique, the roughness of two different types of fine paper series are measured and the obtained results are compared to those of two air leak methods, PPS and Bendtsen, which are used as reference methods.
Low Coherence Doppler Flowmetry (LCDF) measurement produces a signal, which frequency domain characteristics are
in connection to the speed of the flow. In this study a LCDF measurement data of pulp flow in a capillary was analyzed
with a simple Artificial Neural Network (ANN) method to estimate the flow speed. The accuracy of the method proved
to be good, validation of the method resulted in absolute error of 14 ± 11 percentage units (mean±std) in flow speed
estimation. The results of the study can be utilized in development of industrial pulp flow speed measurement
instruments.
Low Coherence Doppler Flowmetry (LCDF) measurement produces a signal, which frequency domain characteristics
are in connection to the speed of the flow. In this study performances of Artificial Neural Network (ANN) and
Multilinear Regression (MLR) methods in prediction of pulp flow speed from the LCDF measurement data were
compared. In the study the pulp flow speed was estimated distinctly from consecutive frequency bands of the LCDF data
with both methods. The smallest estimation error in flow speed with the ANN method was 20% and with the MLR
method 30%, depending on the selected frequency band. The results indicate the relationship between characteristics of
the LCDF measurement and pulp flow speed includes remarkable number of nonlinear components. The result is in line
with theoretical calculations about the Doppler shifts occurrence in the LCDF data.
The surface microroughness of paper has an important role on its gloss. Unfortunately, commercial glossmeters do not provide information on the local gloss of paper. In this study a low-coherence interferometer was employed for the assessment of the average surface roughness of fine, supercalendered, and Xerox papers by means of recorded topography maps. Furthermore, the local and average gloss were measured by a diffractive-optical-element-based glossmeter. This is the first time that the measurement of the local gloss of paper has been accomplished. The information on both surface roughness and gloss, obtained by the two devices in this study, should help papermakers in their research and development of optimal paper surface quality, which is crucial to optimal ink absorption in printing.
In this paper, optical measurement techniques, which enable non-invasive measurement, are superimposed to glucose sensing in scattering media. Used measurement techniques are Optical Coherence Tomography (OCT), Photoacoustic spectroscopy (PAS) and laser pulse Time-of-Flight (TOF) measurement using a streak camera. In parallel with measurements, a Monte-Carlo (MC) simulation models have been developed. Experimental in vitro measurements were performed using Intralipid fat emulsion as a tissue simulating phantom for OCT and TOF measurements. In PAS measurements, a pork meat was used as a subject but also preliminary in vivo measurements were done. OCT measurement results show that the slope of the OCT signal's envelope changes as a function of glucose content in the scattering media. TOF measurements show that the laser pulse full width of half maximum (FWHM) changes a little as function of glucose content. An agreement with MC-simulations and measurements with Intralipid was also found. Measurement results of PAS technique show that changes in glucose content in the pork meat tissue can be measured. In vivo measurements with a human volunteer show that other factors such as physiological change, blood circulation and body temperature drift may interfere the PA response of glucose.
The Optical Coherence Tomography (OCT) technique proves a subsurface structure investigating along the penetration depth of incident light. The basic principle of this technique is to locate the envelope maximum position of low-coherence interference fringes obtained under the controllable displacement of the reference mirror in interferometer. The obtained OCT image presents a result of convolution of random tissue internal structure presented by a path-length-resolved diffuse reflectance with interferometer response on the ideal change of optical path difference, i.e. with a low-coherence fringe envelope, which has usually known Gaussian form. To increase the OCT image resolution, the deconvolution method can be used. In this paper, the application results of the iterative van Cittert algorithm of deconvolution to the OCT images are presented. Experimental results demonstrate the increase of the envelope peaks after 3 - 5 iterations approximately in 1.5 times with better resolution between them. The tissues tomograms calculated using van Cittert algorithm are presented. Some OCT image details lost in the usual OCT tomograms are visible and more contrast.
Flow velocity of scattering intralipid mixture within the glass capillary is measured using Doppler Optical Coherence Tomography (DOCT) technique. In the DOCT system, interference fringe frequency shift contains information about velocity of mixture. Due to scattering, interference fringe parameters are disturbed and stochastic fringe processing method should be used to evaluate fringe frequency. Interferometric signal frequency and other parameters have been estimated dynamically using discrete nonlinear Kalman filtering method. The stochastic filtering methodology and nonlinear Kalman filtering method are considered with application to experimental DOCT data processing.
In this study, we propose to apply the method optical coherence tomography (OCT) for paper characterization. A PC-controlled experimental measurement system for OCT-imaging of paper is described in detail. A superluminescent diode is used as a light source in a Michelson interferometer. A rapid scanning optical delay line is using a piezo-transducer to modulate the measurement signal for optical heterodyne detection. Amplification, filtering and demodulation are performed by the unit specially designed for this purpose. Experimental measurements include the OCT slice imaging of a paper sample and comparison with a SEM-image. Also some results in surface profilometry are presented briefly. Discussion part gives some ideas of further research that will be carried out in the future.
Peculiarities of light transport in IntralipidTM solutions and the effect of glucose on light scattering properties of the
solution at two different IntralipidTM concentrations were studied with optical coherence tomography (OCT) technique
in vitro. An open air OCT system using a superluminescent light source with center wavelength = 830 nm was used. 5% IntralipidTM
solutions were used to simulate a biological tissue (skin) in our experiment. Glucose concentrations at the
physiologically relevant level were added to IntralipidTM solutions. Increasing IntralipidTM concentration increases the scattering coefficient of the media meanwhile increasing glucose concentration increases the refractive index of the
media and reduces the scattering coefficient of the media. The experimental data were compared to Monte Carlo
simulations. We also made the simulations for 2% IntralipidTM solution. The results indicate that glucose added to 2 and 5% IntralipidTM solutions changes their scattering properties, which is manifested by a decrease in the slope of the OCT signal. This finding shows the ways of using OCT for sensing glucose and monitoring the alterations of its content in
biotissues. Some discrepancies between measurements and simulations were found, which need further investigation.
Interferometers with a low-coherent illumination allow non-contact evaluating random tissues by locating the visibility maxima of interference fringes. The problem is the light scattering by a tissue, it is why interference fringe parameters are randomly varied. Other problem consists in the need to process large amount of data obtained in optical coherence tomography (OCT) systems. We propose to use a stochastic fringe model and Kalman filtering method for noisy low-coherence fringe processing. A fringe signal value is predicted at a next discretization step using full information available before this step and a prediction error is used for dynamic correction of fringe envelope, frequency and phase. The advantages of Kalman filtering method consist in its noise-immunity, high-speed data processing and optimal evaluation of fringe parameters. Specially fabricated random tissues have been measured with a low-coherence interferometer. The obtained data from the tissue internal structure are evaluated using a dynamic stochastic fringe processing algorithm applied to fringe signal samples series. Nonlinear Kalman filtering method was applied to measure scattering liquid velocity profile in the Doppler OCT. The measurement results are in good agreement with the results obtained by the Fourier transform method.
Interferometers with a low-coherent illumination allow non-contact measuring the rough surface relief or multilayer tissues by locating the visibility maxima of interference fringes. The problem is the light scattering by the surface to be evaluated; it is why the interference fringes are often distorted. Other problem consists in the need to process large amount of data obtained in optical coherence tomography (OCT) systems. We propose to use a stochastic fringe model and Kalman filtering method for noisy low-coherent fringe processing. A fringe signal value is predicted at the next discretization step using full information available before this step and the prediction error is used for dynamic correction of fringe envelope and phase. The advantages of Kalman filtering method consist in its noise-immunity, high-speed data processing and optimal evaluation of fringe parameters.
The aim of this study was to measure the velocity and velocity profile of 0.3% Intralipid mixture in a 1.5-mm thick glass capillary using Doppler Optical Coherence Tomography (DOCT). First, while still empty, the dimensions of the capillary were measured. The outer diameter was 1.50 mm ± 0.01 mm while the lumen diameter was 1.01 ± 0.01 mm. Then, having filled the capillary with 0.3% solution, the lumen diameter was measured again. The mean refractive index of the solution was calculated and turned out to be 1.36 ± 0.01 mm. During the next stage, flow measurements were performed at an angle of 88° between the illuminating beam and the velocity vector of the fluid. The velocity profile, based on a set of 10 measurements, was calculated from the DOCT signal using a discrete Fourier transform in 32 sections of the capillary. The maximum velocity, located in the middle part of the capillary, was 0.256 ± 0.035 m/s. The results show that the flow velocity profile of 0.3% Intralipid solution can be obtained from a glass capillary.
Interferometers with a low-coherent illumination allow non-contact evaluating random tissues by locating the visibility maxima of interference fringes. The problem is the light scattering by a tissue, it is why interference fringes are often distorted. Other problem consists in the need to process large amount of data obtained in optical coherence tomography (OCT) imaging systems. We propose to use a stochastic fringe model and Kalman filtering method for noisy low-coherence fringe processing. A fringe signal value is predicted at a next discretization step using full information available before this step and a prediction error is used for dynamic correction of fringe envelope and phase. The advantages of Kalman filtering method consist in its noise-immunity, high-speed data processing and optimal evaluation of fringe parameters. Several specially fabricated wood fiber tissues have been measured with a low-coherence interferometer. The obtained data from the tissue internal structure are evaluated using a dynamic stochastic fringe processing algorithm applied to fringe signal samples series. The statistical approach for characterizing wood fiber tissues of different kinds is proposed.
Optical coherence tomography (OCT) is used mainly for noninvasive cross-sectional imaging in biological systems. In this technique, a lateral scanning low-coherence interferometer is employed to produce a two-dimensional image of an object's internal microstructure. This paper presents an experimental OCT measurement system based on a bulk-type Michelson interferometer illuminated by a superluminescent light source. The system was used to provide a visual image of multilayer plastics. In addition, the research team conducted experiments to measure the thickness of varnish on top of plywood and experimented with paper measurements. The system produced two-dimensional pictures of multilayer plastics, showing that it is applicable to transparent media.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.