A novel hemispherical spectro-polarimetric scattering instrument for skin lesion imaging

We present a novel spectro-polarimetric instrument based on hemispherical backscattering for the assessment of superficial skin lesions. The system is capable of capturing polarized light images non-invasively. The effect of the rough skin backscattering is eliminated with the use of out-of-plane illumination. A glass slide with an index matching fluid, commonly used in polarized light imaging, is no longer necessary. The system is composed of sixteen polarized light sources that provide red, green, or blue illumination. The light sources are distributed on a hemispherical shell, and each source produces a collimated beam incident on the center of the hemisphere. A Stokes vector imaging system is mounted on the shell at an oblique angle to the sample normal and consists of a 12-bit scientific camera, two liquid crystal variable retarders, and a fixed polarizer. Stokes vector images of light scattered towards the camera direction are generated for each source. A useful decomposition of the Stokes vector is presented. Examples of images generated by the system are presented.