Polarization Difference Imaging Research Articles

烟雾环境下的偏振差成像方法

烟雾环境下的偏振差成像方法

Influence of absorption in linear polarization imaging of melanoma tissues

The contrast mechanism of different polarization imaging techniques for melanoma in mouse skin is studied using both experiments and Monte Carlo simulations. Total intensity, linear polarization difference imaging (DPI), degree of polarization imaging (DOPI) and rotating linear polarization imaging (RLPI) are applied and the relative contrasts of these polarization imaging methods between the normal and cancerous tissues are compared. A two-layer absorption-scattering model is proposed to explain the contrast mechanism of the polarization imaging for melanoma. By taking into account of both scattering of symmetrical and asymmetrical scatterers and absorption of inter-scatterer medium, the two-layer model reproduces the relative contrasts for polarization images observed in experiments. The simulation results also show that, the parameters of polarization imaging change more dramatically with the variation of absorption in the bottom layer than the top layer.

Dragonfly larval polarization sensitivity as a contrast enhancer in turbid water

Dragonfly larval polarization sensitivity as a contrast enhancer in turbid water

Three-dimensional surface reconstruction within noncontact diffuse optical tomography using structured light

A main field in biomedical optics research is diffuse optical tomography, where intensity variations of the transmitted light traversing through tissue are detected. Mathematical models and reconstruction algorithms based on finite element methods and Monte Carlo simulations describe the light transport inside the tissue and determine differences in absorption and scattering coefficients. Precise knowledge of the sample's surface shape and orientation is required to provide boundary conditions for these techniques. We propose an integrated method based on structured light three-dimensional (3-D) scanning that provides detailed surface information of the object, which is usable for volume mesh creation and allows the normalization of the intensity dispersion between surface and camera. The experimental setup is complemented by polarization difference imaging to avoid overlaying byproducts caused by inter-reflections and multiple scattering in semitransparent tissue.

Static polarization-difference interference imaging spectrometer

A static polarization-difference imaging spectrometer is conceptually described and demonstrated through experiment. It consists of a Wollaston prism, a Savart polariscope, a linear analyzer, and a CCD camera. This design improves the existing polarization-difference system by eliminating its moving parts and obtaining the spectral variation of the polarization state, and making the system more compact and robust. After simultaneously acquiring two sequential interference images corresponding to two orthogonal polarization states, the hyperspectral images of the states can be reconstructed, respectively. The use of uniaxial birefringent crystal can widen the detectable spectral region.

Selective polarization imager for contrast enhancements in remote scattering media

Conventional intensity imaging through turbid media suffers from rapid loss of image contrast due to light scattering from particles or random variations of refractive index. This paper features the development of an active imaging, snapshot, system design and postprocessing algorithms that differentiate between radiation that scatters or reflects from remote, obscured objects and the radiation from the scattering media itself through a combination of polarization difference imaging, channel blurring, and Fourier spatial filtering. The produced sensor acquires and processes image data in real time, yielding improved image contrasts by factors of 10 or greater for dense water vapor obscurants.

Sharper focal spot below λ/4 of azimuthally polarized illumination phase-encoded by the binary 0/π phase plate

The intensity distribution in the focal region for the azimuthally polarized beam phase-encoded by the binary 0/π phase plate is calculated on the basis of the vector diffraction theory. With the annular pupil aperture employed, the resolution of the focal spot will be improved remarkably. We demonstrate a sharper focal spot with full width at half maximum (FWHM) of 0.223λ (below λ/4), significantly smaller that of linear, circular and radial polarization beam under the same condition. The focusing phenomena for illumination beam with various polarization status and beam shapes are analyzed explicitly. This analysis could have potential applications in confocal microscopy and two-photo microscopy for polarization difference imaging.

Study of rotational dynamics of receptor-targeted contrast agents in cancerous and normal prostate tissues using time-resolved picosecond emission spectroscopy

We studied the time-resolved polarization-dependent fluorescence spectroscopy of receptor-targeted contrast agents (Cybesin and Cytate) bound with prostate cancer cells in prostate tissue. An analytical model dealing with highly viscous tissue media was developed and used to investigate the rotation times and fluorescence anisotropies of the receptor-targeted contrast agents in prostate tissue. The differences of rotation times and fluorescence anisotropies were observed for Cybesin (Cytate) in cancerous and normal prostate tissues, which reflect changes of the microstructures of cancerous and normal tissues and their different bound affinity with contrast agents. The preferential uptake of Cytate (Cybesin) in cancerous tissue was used to image and distinguish cancerous tissue areas from normal tissue areas. The fluorescence polarization difference imaging technique was used to enhance the image contrast between the cancerous and normal tissue areas. This research may help to introduce a new optical approach and criteria for prostate cancer detection.

Electromagnetic wave beam self - guidance in liquid crystal - semiconductor cell

A theoretical model and numerical results for a new kind of optical waveguide has been presented. The discussed waveguide is optically self-induced during light beam propagation along the boundary between a liquid crystal and a semiconducting polymer in an electrically driven lc cell. Experimental results obtained earlier are briefly reported here, and the theoretical model is discussed. The exploited liquid crystal was of birefringence close to 0.4. The photorefractive polymer was a poly (N-vinyl) carbazole doped with 2, 4, 7-trinitro-fluorenone. Full Text: PDF References H. Knobloch, H. Orendi, M. Buchel, T. Seki, S. Ito, W. Knoll,"Photochromic command surface induced switching of liquid crystal optical waveguide structures", J.Appl. Phys. 77, 481 (1995) [CrossRef] D.N. Christodoulides, R.I. Joseph,"Discrete self-focusing in nonlinear arrays of coupled waveguides", Opt.Lett. 13, 794 (1988) [CrossRef] A. Fratalocchi, G. Assanto, K.A. Brzdąkiewicz, M.A. Karpierz,"Discrete light propagation and self-trapping in liquid crystals", Opt. Expr. 13, 1808 (2005) [CrossRef] G. Assanto, A. Piccardi, A. Alberucci, S. Residori, U. Bortolozza,"Liquid Crystal Light Valves: a versatile platform for Nematicons", Phot. Lett. of Poland 1(4), 151 (2009) F. Sala, M. Karpierz,"Numerical simulation of beam propagation in a layer filled with chiral nematic liquid crystals", Phot. Lett. of Poland 1(4), 163 (2009) A. Spadlo, R. Dabrowski, J. Dziaduszek, S. Urban, E. Scibor, S. Gauza, S.T. Wu,"Liquid crystalline materials with high birefringence", J. Opt. Technol. 72, 659 (2005) [CrossRef] A. Walczak, E. Nowinowski-Kruszelnicki,"Polarization difference imaging system", ECLC Conference, Lisbona 2007 A. Walczak, E. Nowinowski-Kruszelnicki, Liquid Crystal Photonic Workshop, Cambridge 2008 Walczak, E. Nowinowski-Kruszelnicki,"Waveguide couplers induced optically over organic junction", Opt. Eng. 47(3) (2008) [CrossRef] N.V. Kukhtarev, S.F. Lyuksyutov, P. Buchhave, T. Kukhtareva, K. Sayano, P.P. Benerjee,"Self-enhancement of dynamic gratings in photogalvanic crystals", Phys. Rev. A 58, 4051 (1998) [CrossRef]

Linear polarization difference imaging and its potential applications

We demonstrate a novel linear polarization imaging technique and its potential application in dermatology. This technique records a series of images corresponding to different combinations of illumination and detection polarization and calculates intensity differences between orthogonal detection polarizations pixel by pixel. Fitting the polarization difference data to an analytical expression of the incident and detection polarization angles results in two new parameters, G and (phi3)/2. It is shown that G is strongly correlated to the order of alignment of the fibrous structure in the sample, and (phi3)/2 represents the angle of orientation of the fibers. Preliminary clinical testing implies that this method may be applied for medical diagnosis of skin diseases.

Adaptive Polarization Contrast Techniques for Through-Wall Microwave Imaging Applications

In this paper, we describe and utilize polarization contrast techniques of the adaptive polarization difference imaging algorithm and its transient modification for through-wall microwave imaging (TWMI) applications. Originally developed for optical imaging and sensing of polarization information in nature, this algorithm is modified to serve for target detection purposes in a through-wall environment. The proposed techniques exploit the polarization statistics of the observed scene for the detection and identification of changes within the scene and are not only capable of mitigating and substantially removing the wall effects but also useful in detecting motion, when conventional Doppler techniques are not applicable. Applications of the techniques to several TWMI scenarios including both homogeneous and periodic wall cases are presented.

Practical modeling and acquisition of layered facial reflectance

We present a practical method for modeling layered facial reflectance consisting of specular reflectance, single scattering, and shallow and deep subsurface scattering. We estimate parameters of appropriate reflectance models for each of these layers from just 20 photographs recorded in a few seconds from a single viewpoint. We extract spatially-varying specular reflectance and single-scattering parameters from polarization-difference images under spherical and point source illumination. Next, we employ direct-indirect separation to decompose the remaining multiple scattering observed under cross-polarization into shallow and deep scattering components to model the light transport through multiple layers of skin. Finally, we match appropriate diffusion models to the extracted shallow and deep scattering components for different regions on the face. We validate our technique by comparing renderings of subjects to reference photographs recorded from novel viewpoints and under novel illumination conditions.

Polarization Difference Imaging System with LC Filter

Methods of polarization analysis in imaging systems are quite new approach. It allows to remove the polarized light component from recorded images, and is known as Polarization Difference Imaging (PDI). The use of liquid crystals (LC) in PDI was proposed in 2002. Modified LC unit with properly oriented LC layer was proposed by the authors. In this work specific LC filter and set-up for image analysis are presented. The examination of the azimuthal detectivity of PDI system is performed. The method of digital analysis of acquired images and detectivity determination is presented. Obtained results are shown and discussed.

Polarization difference image analysis with LC filter

AbstractImage analysis using polarizing methods allows removing the polarized light component from recorded images. This is known as polarization difference imaging (PDI). The use of liquid crystals (LC) in PDI was proposed in 2002. Modified LC unit with a properly oriented LC layer was proposed by the authors. The main parameters which characterize an imaging system, employing a circular LC filter, were determined and presented in previous papers.In this work, the basics of the circular LC filter construction and theory are presented. Two application configurations of PDI imaging systems are shown. Experimental results of image processing based on object’s polarization properties are discussed.

Rotating orthogonal polarization imaging

Surface reflections often present a problem in the polarization difference imaging of tissue. The technique described involves illumination in a single polarization state and detection in the orthogonal polarization state. Synchronously rotating both the illumination and orthogonal detection states provides an image free from surface reflections that is sensitive to the polarization properties of the underlying tissue. Results on tissue phantoms demonstrate that polarization sensitive measurements of a test target can be made up to a depth of 12 mean free paths within a scattering medium. Preliminary images of bovine tendon are also demonstrated.

WhitebalPR – a New Method for Automatic White Balance

Unlike previous methods, whitebalPR determines the color of illumination by obtaining exact measurements from the photographic scene rather than by estimating it. The new method is based on polarization-difference imaging and discloses new opportunities to measure the color of illumination within digital cameras. It exploits the polarization of light that is specularly reflected at dielectric surfaces.An embodiment is given to integrate whitebalPR into digital cameras.The experimental results demonstrate a very high potential of accuracy and reliability by this approach.

Time-resolved fluorescence polarization anisotropy and optical imaging of Cybesin in cancerous and normal prostate tissues

Time-resolved polarization-dependent fluorescence of Cybesin in solution and in cancerous and normal prostate tissues were measured. The polarization preservation property of Cybesin in tissue was observed. The fluorescence intensity emitted from a Cybesin-stained cancerous tissue area was found to be much stronger than that from a Cybesin-stained normal tissue area indicating that cancerous prostate tissue takes-up more Cybesin than normal tissue. The polarization anisotropy of Cybesin contained in cancerous prostate tissue was found to be larger than that of Cybesin in normal prostate tissue indicating that a larger degree of polarization was preserved in the Cybesin-stained cancerous tissue due to structures. A static anisotropy component from the emission of cell-bonded Cybesin molecules in tissue and a time-dependent anisotropy component from the emission of un-bonded Cybesin molecules were determined and discussed. The static anisotropy value of Cybesin in stained cancerous tissue was found to be much larger than that in stained normal tissue. The fluorescence polarization difference imaging technique based on the polarization preservation of Cybesin was used to enhance the image contrast between cancerous and normal prostate tissue areas.

Adaptive algorithms for two-channel polarization sensing under various polarization statistics with nonuniform distributions

The polarization of light carries much useful information about the environment. Biological studies have shown that some animal species use polarization information for navigation and other purposes. It has been previously shown that a bioinspired polarization-difference imaging (PDI) technique can facilitate detection and feature extraction of targets in scattering media. It has also been established [J. Opt. Soc. Am. A 15, 359 (1998)] that polarization sum and polarization difference are the optimum pair of linear combinations of images taken through two orthogonally oriented linear polarizers of a scene having a uniform distribution of polarization directions. However, in many real environments the scene has a nonuniform distribution of polarization directions. Using principal component analysis of the polarization statistics of the scene, we develop a method to determine the two optimum information channels with unequal weighting coefficients that can be formed as linear combinations of the images of a scene taken through a pair of linear polarizers not constrained to the horizontal and vertical directions of the scene. We determine the optimal orientations of linear polarization filters that enhance separation of a target from the background, where the target is defined as an area with distinct polarization characteristics as compared to the background. Experimental results confirm that in most situations adaptive PDI outperforms conventional PDI with fixed channels.

Polarization-rich continuous wave direct imaging: modeling and visualization

We report a study and comparison of continuous-wave, optical polarization difference imaging (PDI) and polarization modulation imaging (PMI) for imaging through scattering media. The problem is cast in the framework of a theoretical estimation, and the comparison is based on three visualization parameters, namely, the magnitude, the degree, and the orientation of the polarization. We show that PDI is superior in estimating the first two parameters in active imaging under specific conditions, while the PMI is suitable for passive imaging and is the only way to estimate polarization orientation. We also propose new schemes for rendering polarization information as a color image and for applying the newly introduced polarization-orientation imaging for segmentation. Simulation and experimental results verify the theoretical conclusions.

Polarization radio imaging of various objects in the millimeter-wave range

We present methods and results of radio imaging of various technical objects at a frequency of 94 GHz for vertical and horizontal polarizations. We analyze the features of the formation of polarization-difference images in the millimeter-wave range and the typical properties and methods of processing of such images. The influence of experimental conditions (noise level, antenna focusing, and imperfect knowledge of the directional pattern) on the quality of image reconstruction is numerically simulated. To increase the spatial resolution of images, we propose filtering of the spatial spectrum of a reconstructed image, which allows for its a priori statistical characteristics. Possibilities of passive polarization stereo imaging and a method of its realization in the millimeter-wave range are considered.