Implementations of optical coherence tomography

As part of the OCT project, an existing Ti:Sapphire femtosecond pulse laser has been prepared for future experiments. The mode-locked Ti:Sapphire laser was redesigned substantially using detailed calculations and was eventually made to operate with 71 femtosecond pulses and a 46 nm FWHM bandwidth with a high stability and easy firing up. The coherence length of such a source was found to be about 6.1 μm but it was judged more appropriate to relax the bandwidth constraint for the preliminary interferometer setup and calibration procedure and a commercial semiconductor broadband source from JDSU was chosen instead as an intermediate solution for the first OCT experiments.; A free-space Michelson interferometer was built and aligned with this source, and two computer-controlled linear positioners were employed for the longitudinal scanning of the reference mirror and the lateral scanning of the object. An in-house data acquisition and scanning control program was developed for signal processing. The system was successfully tested using a mirror as the object. The signal-to-noise ratio was measured to be in the 41.3 dB range with a measured coherence length of 32.3 μm. A NA = 0.25 microscope objective was employed to focus the beam onto the sample which lead to a spot size of about 10 μm (the lateral resolution of the system) and an axial scanning depth of 850 μm. Four objects have been scanned and the OCT images have been obtained with this setup.; A novel approach to OCT was proposed and a new experimental setup was built using a white LED as the light source. This source was found to be more stable (both in intensity and spectrum), to have a higher resolution, a much longer lasting time, and to be monitored more easily. (Abstract shortened by UMI.)...