Reasearch On Laser Feedback Confocal Tomography Technology Of Biological Tissues

In the case of frequency-shifted feedback, the microchip laser shows very high optical feedback sensitivity. Due to the high sensitivity, the feedback of the microchip laser has a unique advantage in the optical detection of weak signals. Meanwhile, an imaging technology with high resolution as well as greater detection depth compared to the existing optical imaging modalities is needed in the imaging area. It is possible to meet this goal if the high sensitivity of the microchip laser is used in the tomography technology. To this end, Based on the theory of frequency-shifted laser feedback combined with confocal technology, laser feedback confocal tomography technology which is applied in biological tissue is studied in this dissertation.The theoretical model of laser feedback confocal tomography technology is established. Based on the theoretical guidance, a microchip Nd:YVO4 laser feedback confocal tomography system is designed, set up and debugged. The key parameters of the system are optimized referring to the theoretical and experimental studies. And then, A scan imaging program is designed, which can be used for sample scanning, data acquisition and image generation under the setting parameters.Some basic tests including lateral resolution, vertical resolution and stability are taken on the microchip Nd:YVO4 laser feedback confocal tomography system, main performance indicators achieved are as follows:when IR objective lens of NA= 0.42 is employed, the system has a lateral resolution of 1μm, a vertical resolution of 15-20μm, and a longitudinal working range of 20.4mm; the time to get an imaging is 10min to 20min; the detection depth in general scattering samples is a few millimeters.The stability and accuracy of the system were determined by imaging the multilayer glass samples and the foam samples。At last, the system is employed for biological tissue imaging experiments. The results show that the system can present the inner structure of the onion sample in a depth of hundreds of microns, and carry out the three-dimensional positioning of the foreign body in the onion as well. This feature can be extended to the three-dimensional localization of foreign bodies (such as tumors) in tissue. The image processing software of the laser optical feedback tomography system is designed to process the image of the system, which makes the image to obtain more information within the sample.