Study On Theory And Experiment Of Optical Coherence Tomography And Broad-Band Light Source

Optical coherence tomography, a novel noninvasive imaging technology to produce high-resolution cross-section image of internal microstructure of living tissue dynamically, has been developed in recent more than ten years. Using broad-band near-infrared laser in the biological detecting window as light source, it can reach a resolution of micrometer. It works in the advantage of the co-function of coherent gate and con-focal structure which selects information carriers—ballistic and lest scattered photons from mass diffusion photons. OCT also has merits of small volume, inexpensive and adaptable to be made in endoscope form. It attracts engineers and scientists of photonics field with challenge and potential of clinical application. This dissertation analyzes theoretical subjects, such as: the way of photon migration and its relationship with deviation and noise of image, which closely concern with imaging quality of OCT. Quantitative or qualitative conclusions are given. The special meaning of function imaging with parameters of circulation and metabolism in the nidi-district to the diagnosis of cancer is accounted by data of anatomy and circulation. A concrete scheme design of parameters detecting and the argument of the possibility of inchoate diagnosis of cancer by double criterions of morphology and circulating dynamics is given. At the aspect of experimental study, an OCT system was setup and bio-samples have been imaged by it. To the problems of synchronization and image-noise induced by the change of scanning velocity appeared in the experiment, solutions are given and good result reached. Experiments of concurrent enhancement of imaging depth and contrast of OCT using hyper-osmotic agents have been done. Using digital image processing method of classification, the cross-section of air and tissue was separated; the contrast and view depth of image is improved. Experiments using 1064nm Na: YAG laser pumping single mode fiber to produce broad band light in the mechanism of co-operation of SRS and other nonlinear process have been done. The main innovative points can be summarized as follows: 1. A new viewpoint is put forward that the speckle of OCT is not the usual amplitude speckle in space domain, but the energy speckle in time domain of energy fluctuate induced by energy matching while the combining of coherent scattering light beams with different phases. 2. A concrete scheme design of inchoate diagnosis of cancer by double criterions of morphology and circulating dynamics is given. Parameters of circulation and metabolism in the nidi-district have special diagnostic meaning. The possibility of this method is expounded. 3. A scheme to attain ultra broad band light in the mechanism of SRS co-operated with other nonlinear process in single mode fiber pumped by high power laser diode is made out. It has been experimentally fulfilled. Open up a new way to produce mini-type medical adaptable OCT light source. 4. The conception of scattering delay is introduced into the theory of image deviation for the first time. The location error corresponding to scattering delay is larger than that induced by the scattering angle. 5. Using hyperosmotic mixture of glycerin and glucose in experiment, the visible depth and contrast of OCT was concurrent enhanced. It is proved that the mixture has higher human sensitivity than using glycerin alone.