Conceiving an easy-to-understand and automated polarimeter: application to a study of collagen

In this paper, the authors describe the design and the experimentation of a polarimeter aimed at characterizing the properties of some scattering materials (e.g., a scattering liquid containing a foreign body, or skin components, such as collagen). The polarimeter presents the advantage of offering an easy understanding of Stokes and Mueller formalism. Thus, it is typically suited for university students in physics (Master´s level), giving them a clear understanding of polarization and birefringence. Another application is possible in schools of engineering, where students may use their design abilities to improve the apparatus performance. Apparatus automation was performed as well, providing easier use for experiment (commodity of use, reproducibility, and possible multiplication of measurements). The apparatus was tested in transillumination and backscattering modes. More generally, measurements can be performed with angles varying from 0° to 150° between the propagation direction and the line from the sensor to the sample material. In addition, the sensor can be either a photodiode (results presented here) or a two-dimensional (2-D) sensor charge-coupled device (CCD) camera. As an application, the apparatus was used to differentiate irradiated and nonirradiated collagen.