Application of two channel interferometric methods for image formation through inhomogeneous media and optical fibers.

We combine the techniques of holography and laser interferometry to deal with the problems of image formation through inhomogeneous media and through optical fibers. An earlier-developed grating interferometer is reviewed and some of its salient properties are described. We utilize its inherent achromatic properties, solving the difficult path balance problem in various ways for different imaging applications. A short pulse of light (in the femtosecond regime) has a spectral width too broad for use with a conventional interferometer. However, the grating interferometer, being perfectly achromatic, can form fringes with polychromatic light just as well as monochromatic light, and is thus ideal for performing interferometry with ultrashort pulsed light. The insertion of an inhomogeneous medium into one channel of a typical interferometer induces propagation path inequality, thus distorting the originally uniform interference fringes. In our technique, the distorted fringe distribution returns to its original uniform distribution, thus leading to imagery of high quality for objects either behind or embedded in inhomogeneous media. Image formation through optical fibers by the application of interferometric methods is analyzed by treating optical fibers as inhomogeneous media. The optical fibers, as in the case of image formation through inhomogeneous media, are put in one channel of the interferometer. The temporal path unbalance arising from the insertion of the optical fibers is corrected by using this newly conceived hybrid interferometer. Since the image formed through the two channel interferometer is obtained by a holographic process, either real time or non-real time, the transmitted image thus has the phase preserved. This phase preservation property of the fiber-transmitted image enables a three dimensional object to be imaged through the fiber as a three dimensional image. Various experimental results for both three dimensional image formation through optical fibers and image formation through inhomogeneous media, such as biological tissue, were used to demonstrate the validity of the techniques.PhDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103045/1/9303706.pdfDescription of 9303706.pdf : Restricted to UM users only