A method for measuring three-dimensional (3-D) direction images of collagen fibers in biological tissue is presented. Images of the 3-D directions are derived from the measured transmission Mueller matrix images (MMIs), acquired at different incidence angles, by taking advantage of the form birefringence of the collagen fibers. The MMIs are decomposed using the recently developed differential decomposition, which is more suited to biological tissue samples than the common polar decomposition method. Validation of the 3-D direction images was performed by comparing them with images from second-harmonic generation microscopy. The comparison found a good agreement between the two methods. It is envisaged that 3-D directional imaging could become a useful tool for understanding the collagen framework for fibers smaller than the diffraction limit.
The collagen meshwork in articular cartilage of chicken knee is characterized using Mueller matrix imaging and multiphoton microscopy. Direction and degree of dispersion of the collagen fibers in the superficial layer are found using a Fourier transform image-analysis technique of the second-harmonic generated image. Mueller matrix images are used to acquire structural data from the intermediate layer of articular cartilage where the collagen fibers are too small to be resolved by optical microscopy, providing a powerful multimodal measurement technique. Furthermore, we show that Mueller matrix imaging provides more information about the tissue compared to standard polarization microscopy. The combination of these techniques can find use in improved diagnosis of diseases in articular cartilage, improved histopathology, and additional information for accurate biomechanical modeling of cartilage.
A Mueller Matrix Imaging Ellipsometer system is operated in transmission and used to study nematic textures
in colloidal dispersions of synthetic Na-fluorohectorite clay platelets in solution. It is clearly observed that the
anisometric particles organize into phases with strong birefringence, which results in a strong retardance. The
Mueller matrix imaging technique supplies an image of the retardance matrix, even in the presence of other
effects such as light scattering and diattenuation. The spatial variation of the absolute value of the retardance,
the orientation of the fast axis of the retardance, the total diattenuation and the orientation of the diattenuation
are presented. In particular, from knowledge of the anisotropic shape of the particles, the orientation of the
particles within ordered domains, and the density of the particles within the domains are spatially determined.
The experiments are based on adding synthetic clay particles into a solution contained in a thin rectangular glass
container. Upon letting gravitation act on the sample, different phases appear after a few weeks. One phase
contains nematic textures and we are able to determine the ordering and also estimate the density of the
domains/texture within the phase, in addition to estimating the local order within a domain with an image
resolution of 12 μm.
We present the application of a near infra red Mueller matrix imaging ellipsometer to the characterization of
plasmonic polarizers. The samples are prepared by evaporation of Au onto SiO2 ripples. The nanostructured
ripple surface has been produced by ion beam sputtering at an off normal angle of incidence. Au was thereafter
evaporated onto the surface at an grazing angle. As a result, thin lines of nearly connected Au nanoparticles
form along the illuminated side of the ripples, resulting in a large in-plane anisotropy of the structure. Mueller
matrix imaging is used to determine the lateral uniformity of the optical signal in correlation to the real space
topography of the sample, and to determine to what degree the nanoparticles tend to form a connected wire, or
whether there are well separated Au particles. The success of this method in order to produce polarizers, lies
in controlling the process to allow well connected lines of Au particles along the ripples, with a high degree of
homogeneity. Mueller Matrix images of the sample recorded at normal incidence are shown, and the information
that can be extracted from such images is discussed.