Polarization is a fundamental property of light and a powerful sensing tool that has been applied to many areas. A Mueller matrix is a complete mathematical description of the polarization characteristics of objects that interact with light, and is known as a transfer function of Stokes vectors which characterise the state of polarization of light. Mueller polarimetric imaging measures Mueller matrices over a field of view and thus allows for visualising the polarization characteristics of the objects. It has emerged as a promising technique in recent years for tissue imaging, improving image contrast and providing a unique perspective to reveal additional information that cannot be resolved by other optical imaging modalities. This review introduces the basis of the Stokes-Mueller formulism, interpretation methods of Mueller matrices into fundamental polarization properties, polarization properties of biological tissues, and considerations in the construction of Mueller polarimetric imaging devices for surgical and diagnostic applications, including primary configurations, optimization procedures, calibration methods as well as the instrument polarization properties of several widely-used biomedical optical devices. The paper also reviews recent progress in Mueller polarimetric endoscopes and fibre Mueller polarimeters, followed by the future outlook in applying the technique to surgery and diagnostics. Tissue polarization properties convey morphological, micro-structural and compositional information of tissue with great potential for label free characterization of tissue pathological changes. Recent progress in tissue polarimetric imaging and polarization resolved endoscopy paved the way for translation of polarimetric imaging to surgery and tissue diagnosis.

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Mueller polarimetric imaging for surgical and diagnostic applications: a review

Polarization measurements allow one to enhance the imaging contrast of superficial tissues and obtain new polarization sensitive parameters for better descriptions of the micro- and macro- structural and optical properties of complex tissues. Since the majority of cancers originate in the epithelial layer, probing the morphological and pathological changes in the superficial tissues using an expended parameter set with improved contrast will assist in early clinical detection of cancers. We carry out Mueller matrix imaging on different cancerous tissues to look for cancer specific features. Using proper scattering models and Monte Carlo simulations, we examine the relationship between the microstructures of the samples, which are represented by the parameters of the scattering model and the characteristic features of the Mueller matrix. This study gives new clues on the contrast mechanisms of polarization sensitive measurements for different cancers and may provide new diagnostic techniques for clinical applications.

Mueller matrix polarimetry for differentiating characteristic features of cancerous tissues.

A possible quantitative Mueller matrix transformation technique for anisotropic scattering media/Eine mögliche quantitative Müller-Matrix-Transformations-Technik für anisotrope streuende Medien

We report an experimental implementation of long-range polarimetric imaging through fog over kilometric distance in real field atmospheric conditions. An incoherent polarized light source settled on a telecommunication tower is imaged at a distance of 1.3 km with a snapshot polarimetric camera including a birefringent Wollaston prism, allowing simultaneous acquisition of two images along orthogonal polarization directions. From a large number of acquisitions datasets and under various environmental conditions (clear sky/fog/haze, day/night), we compare the efficiency of using polarized light for source contrast increase with different signal representations (intensity, polarimetric difference, polarimetric contrast, etc.). With the limited-dynamics detector used, a maximum fourfold increase in contrast was demonstrated under bright background illumination using polarimetric difference image.

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Long-range polarimetric imaging through fog

By comparing the spatially resolved unpolarized, polarized reflectance and Mueller matrix elements of skeletal muscle with a scattering medium containing polystyrene microspheres and silk fibers, we demonstrate that the sphere-cylinder scattering model (SCSM) can reproduce the characteristic features of skeletal muscle. Both experiments and polarization sensitive Monte Carlo simulation provide evidences that SCSM may be used to characterize the structural and optical properties of skeletal muscle.

Application of sphere-cylinder scattering model to skeletal muscle.

We demonstrate a linear polarization difference imaging technique which is insensitive to both sample orientation and polarization angle. Various tests show its potential applications in medical diagnosis.

Linear polarization different imaging and its potential applications

The invention discloses a fiber identification method and a method for measuring the fiber content in mixture fabric, wherein, the fiber identification method comprises the following steps: firstly, a rotating linear polarization detection method is used for imaging various standard fiber samples and carrying out data processing so as to extract characteristic parameters Alpha of the standard fiber samples, standard characteristic curves for the characteristic parameters Alpha of the various standard fiber samples are drawn, and the various standard characteristic curves are stored into a standard library; secondly, the rotating linear polarization detection method is used for imaging a fiber sample to be tested and carrying out data processing so as to extract a characteristic parameter of the fiber to be tested, and a characteristic curve to be compared for the characteristic parameter of the fiber to be tested is drawn; thirdly, the characteristic curve to be compared is compared with the various standard characteristic curves in the standard library, to determine whether the characteristic curve to be compared is the same as any of the standard characteristic curves, if so, the fiber sample to be tested is the same as the corresponding fiber of the standard characteristic curve. The method is characterized by speediness, accuracy and intactness.

Qiang Gao

Papers

Linear polarization different imaging and its potential applications

Fiber identification method and measurement method for content of fiber constituent in blended fabric