A new imaging technique which enables near real-time multispectral acquisition of the so-called degree of polarization (DOP) in polarimetry using incoherent white light is described. The experimental setup allows the interactive and dynamic acquisition of DOP for all the possible elliptic polarization states. In such a way, a complete chart of light-matter interaction can be obtained and besides many structure details can be enhanced. Thus, we present the calibration and first images acquired with this system. The particular characteristics of this setup allow it to be the perfect candidate for in vivo as well as ex vivo medical applications.
KEYWORDS: Polarization, Polarimetry, Diagnostics, Calibration, Biomedical optics, CCD cameras, Light scattering, Optical components, Real time imaging, RGB color model
This research proposes a new imaging technique for near real time multispectral acquisition using CCD RGB cameras of
the so called "Degree Of Polarization" (DOP) in polarimetry for future clinical investigation.
The aim of exploiting the DOP as the contrast element is to demonstrate that the elliptical DOP provides more
information characterizing complex medium than the more traditional linear and circular ones. The system considers an
incoherent input white light beam and opportunely calibrated nematic crystals (LCVR), so no mechanical tools are
necessary.
The particular features of the system indicate it to be the perfect candidate for a new imaging system considering in-vivo
(as well as ex-vivo) non invasive superficial diagnostic for medical application as dermatologic diagnostics, since no
type of sample preparation is necessary, i.e. tissue biopsy, radiation or contrast agent injection.
Thus the biomedical application of this method suggests a simple, direct, fast and also easily exploitable future
employment, as a desirable mean for clinical investigation but also for digital recognition in biometrics.
Further new elements to improve the model of light scattering and matter-light interaction will be acquired, in particular
considering a very complete characterization of the system response using latex microspheres suspension to simulate
turbid media with different concentration.
This research proposes a new imaging technique for near real time multispectral acquisition of the so called "Degree Of
Polarization" (DOP) in polarimetry for future clinical investigation.
The aim of exploiting the DOP as the contrast element is to demonstrate that the elliptical DOP provides more
information characterizing complex medium than the more traditional linear and circular ones. The system considers an
incoherent input white light beam and opportunely calibrated nematic crystals, so no mechanical tools are necessary.
The biomedical application of this method suggests a simple, direct, fast and also easily exploitable future employment, as a desirable mean for clinical investigation. Moreover new elements to improve the model of light scattering will be acquired.
It is well known that the interaction between coherent monochromatic radiation and a scattering medium induce
a speckle phenomenon. The direct exposure of a photographic film, without a lens to the transmitted radiation,
gives speckle pattern. The main problem lies in the determination of parameters which can efficiently characterize
this pattern and can be correlated with the optical properties of the medium. In this paper, we present a circular
statistics approach to differentiate media.
In this paper, we present a new approach of the speckle phenomenon. This method is based on the fractal Brownian
motion theory and allows the extraction of three stochastic parameters to characterize the speckle pattern. For the first
time, we present the results of this method applied to the discrimination of the healthy vs. pathologic skin. We also
demonstrate, in case of the scleroderma, than this method is more accurate than the classical frequential approach.
We present a new polarimetric imaging system based on liquid crystal modulators, a spectrally filtered white light source and a CCD camera. The whole Mueller matrix image of the sample is measured in around 5 seconds in transmission mode. The instrument design, together with an original and easy-to-operate calibration procedure
provides a high accuracy (better than 1.5% for the normalized Mueller matrix) over a wide spectral range. The data can be processed with different algorithms. Results on hepatic biopsies with different grades of fibrosis are presented.
In this paper, we propose a new approach of the speckle statistics in
backscattering imagery. Applicate the Brownian motion theory to the
speckle permit us to extract stochastic parameters to characterize it. It seems more powerful than the classical frequential approach to characterize and classify speckle. We present an test application of this method on a human skin.
It is well known that interactions between a coherent monochromatic radiation and a scattering media induce a speckle phenomenon. Spatial and temporal statistics of this speckle allow many applications in laser imaging. The main problem is the characterization of the backscattered media from the speckle pattern in biomedical imagery. In this paper, we present a stochastic approach based on Brownian motion theory in the approximation of the diffusion. Stochastic processes showing statistical scale law are, under some assumptions, called fractional Brownian motion (fBm) which is a generalization of ordinary Brownian motion (Bm) as defined by Mandelbrot and Van Ness. This extension is related to the existence of a long-range statistic dependence in the process. This dependence is quantified by the Hurst exponent H that is a 'scale factor' indicating the persistence (H>0.5), totally random (H=0.5) or the anti-persistence (H<0.5) nature of the process. Variogram analysis is a possible method to estimate the Hurst exponent. We applied this approach by estimation of the mean quadratic spatial difference, or diffusion function, for 2D analysis of speckle image. Hence, spatial speckle is characterize by extracting from diffusion function plot a set of three parameters; the Hurst exponent, the saturation of the variance and the characteristic element size. Applications of this method to characterization of test media are presented. We find that for all test media with different latex micro-ball concentrations (1%, 5% and 10%) the characteristic element size and the saturation of the variance discriminate media while Hurst exponent seems to be constant for all concentrations. This first results permit us to hope in application like skin lesion quantification in dermatology.
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