High speed phase based 3D OCT system

Optical coherence tomography (OCT) is a new, non invasive technique for recording crossseetional images of transparent and semi-transparent structures with a resolution of- 10 jrm. Conventional OCT measures and images the intensity distribution of backscattered light within a sample. However, as is known from microscopy, many samples, especially tissues, Show only poor contrast if imaged an an intensity basis. Optical contrasting methods, such as polarization and Phase contrast, can be used to generate new types of improved image contrast. Among the methods of polarization sensitive (PS) OCT and differential Phase contrast (DPC) OCT, these based an direct Phase measurements are especially promising: Phase based PS-OCT can image the distribution of reflectivity, birefringence, and optic axis in a sample simultaneously; DPC-OCT was recently extended to imaging of cell layers. Presently used phase based OCT techniques are rather slow, a cross sectional image is typically recorded in 1-60 sec, too slow for recording 3D data sets in human tissue in vivo, or to image dynamic processes. lt is the purpose of this project to develop new Phase based OCT Systems with muck higher data acquisition speed. A combination of transversal Scanning, acousto optics, and lock-in signal detection shall improve the Speed of Phase based OCT Systems by 1 to 2 orders of magnitude. The goal is to acquire a 113 data sei within 1 sec. The first part of the project is to develop the instruments (in two steps), to optimize their perfonnance, to investigate their properties, limits, and possible trade-offs. In a second phase, the instruments shall be used for imaging in selected medical fields and in materials testing. In medical imaging, focus shall be an diagnostics of the human cornea, where preliminary work has shown that diseases based an stromal disorders zause a considerable change of ihe normal corneal birefringence pattern. Thus, PS-OCT has a great potential for early diagnosis and treatment control in these diseases, onee suffizient imaging speed is available. Other possible medical applications comprise glaucoma diagnostics, caries diagnostics, as well as imaging of cell layers through scattering media by DPC-OCT. Rezent applications to materials science have shown that strain patterns within scattering plastic samples, invisible by other techniques, can be imaged by PS-OCT. High speed PS-OCT shall be used for imaging dynamic processes of stress-strain experiments in these materials. The results can be potentially useful for improvement of fabrication processes of plastic components.