Summary and Plans for Future Work


The beautiful false-color pictures obtained with the sample of latex spheres clearly show that the apparatus and analysis techniques are working as intended and support the belief that Mueller matrix images provide a reproducible fingerprint of turbid media. This success opens up the possibility of many further more novel investigations of relevant and interesting natural materials. I would like to make matrices for several more concentrations of latex spheres. By establishing a large scope of data, perhaps a mathematical interpretation of the ``rate of change'' in intensity at a given point can be created. I understand how one finds the derivative of a matrix, but I wonder how you could represent the derivative when using images as matrix elements. It is a very intriguing concept, and I am currently quite stumped!

Before the arrival of the latex microspheres, ordinary dairy whole milk was investigated as a scattering substance. However, the images acquired with milk turned out to be very different from those later obtained with the latex microsphere sample. When false coloring was applied, the images were revealed to show a uniform radial decrease in intensity as one moved outwards from the center of the image, with no dipole shapes discernible. I attribute this to the greater concentration of large molecules in the milk as opposed to the less concentrated latex sphere suspension, which was visibly less dense and less viscous. Because there are more molecules per unit volume, the light is likely to scatter many more times to reach a given point than in the latex sphere solution, therefore the polarization is more easily lost, and there are no distinct patterns in the images seen by the camera. In the future, I would like to return to using milk as a scattering substance, diluting whole milk to see the concentration at which the images take some shape. Perhaps the data already acquired recording the connection between concentration and intensity patterns could help predict when the patterns would first become visible. I would also like to then watch how the Mueller matrix for whole milk changes as a function of pH or temperature. As milk becomes acidic, a process that causes a rancid smell and taste, the proteins are no longer held in suspension and fall to the bottom. If a deep enough container is used to hold the sample of milk, the proteins should sink far enough into the medium to no longer effect the scattering of the light, causing a dramatic difference in the final matrix. A study would have to be made of how deep the laser light actually travels in substances before attenuating completely. This could easily be done with increasing depths of a substance by using a laser aimed straight down into the container holding the substance and a photodetector underneath the container to measure the amount of light that passed directly through without scattering.



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