[Description of differential optical spectropolarimetric imaging system (DOSI) for non-invasive detection of skin tumors].

Background: Most physicians diagnose skin malignancy using theoretical criteria and clinical experience. Apart from dermatoscopy, noninvasive means for skin tumors' diagnosis are highly expensive and are not in daily use. We developed a simple, handy and relatively inexpensive tool for non-invasive diagnosis of skin tumors.

Differential optical spectropolarimetric imaging system assisted by liquid crystal devices for skin imaging.

Skin cancer diagnosis depends not only on histopathological examination but also on visual inspection before and after the excision of suspected lesion. Neoplasm is accompanied with changes in birefringence of collagen, pleomorphicity, and hyperchromatic state of epithelial nuclei. These phenomena can be measured by spectral and polarization changes of light backscattered by the examined tissue.

Skin biomedical optical imaging system using dual-wavelength polarimetric control with liquid crystals.

Spectropolarimetric skin imaging is becoming an attractive technique for early detection of skin cancer. Using two liquid crystal retarders in combination with a dual-band passive spectral filter and two linear polarizers, we demonstrate the spectral and polarimetric imaging of skin tissue in the near infrared. Based on this concept, a compact prototype module has been built and is being used for clinical evaluation.

Tunable optical filter having a large dynamic range.

A novel (to our knowledge) concept for a tunable birefringent filter with a high dynamic range is proposed and demonstrated by using a stack of liquid-crystal retarders having different thicknesses following an arithmetic sequence. Each retarder is between crossed polarizers with its optic axis oriented azimuthally at 45 degrees to the polarizer axis. The tunable filter was fabricated by using nematic liquid crystals demonstrating tunability over a range of 800 nm, covering the visible and the near IR; hence it has a potential for use in biomedical optical imaging applications.

Liquid crystal Lyot tunable filter with extended free spectral range.

Extension of the dynamic range of liquid crystal tunable Lyot filter is demonstrated by incorporating with it a liquid crystal variable retarder as an eliminator for the third and fourth order peaks. The filter is continuously tunable in the range 500 nm to 900 nm with a nominal width in the range 50nm-100nm. Design procedure is described including the exact solution to the LC director profile and the suitability for biomedical optical imaging applications.