Research Of Prism Based Endoscopy Aided Diagnosis System

Nowdays, as a visible medical equipment, the endoscopy was widely used in diagnose of disease as well as surgical treatment. However, the doctors could only see two dimensional image from TV monitor of the traditional endoscopy system. In order to choose a suitable surgical instruments, they should estimate the size of focus just by their experiences. If the doctor got a wrong evaluation, the duration of operation will extend and even more serious, it would lead to medical negligence. Because the problems listed above, we proposed and developed a stereo endoscopy system which was based on prism in this paper. By making use of the prismatic, the system could measure the length of the tissue and focus in hunman body accurately without adding the diameter of endoscope, and help the doctors to diagnose with a high efficiency. The main finished works in this dissertation include:Firstly, two concepts which were named "valid region" and "optimal distance" were defined according to prism based stereovision system. By analyzing this system from the standpoint of camera parameters and prism parameters, we also introduced a methos for analyzing and optimizing the prism based single-lens stereovision system so that the pictures captured by this system are adequate for the application of stereovision.Secondly, a model of geometrical optics which could denote the refraction of prism was proposed. The prism was considered as a single optical system composed of some planes. By analyzing each plane respectively and then combined them together, we derived a transformation matrix which can express the relationship between an object point and its image by the refraction of prism. Our method is based on optical geometry and could be used in multi-ocular prism.Thirdly, a method which could be used for calculating the position of prism was proposed. On the based of second theories, a position estimation method was proposed in order to make up the defects of the exiting method. A mathematical model was introduced which can denote the position of prism with arbitrary faces only by7parameters, then we solved these7parameters by differential evolution.Fourthly, the epipolar geometry and3D reconstructive method of prism based stereovision system was derived by making use of ray tracing, and a3D point could be reconstructed by calculating the midpoint of common perpendicular. The whole algorithmic processes were based on the precise mathematical model and could be used in any prism based stereovision system. Fifthly, we designed and developed a prism based endoscopy aided diagnosis system. The system was composed of hardware and software, which took charge of image acquistion and image processing respectively. Our system could show the images as well as measure the length of the object with the method of human-computer interaction, and could provide a more various information for doctors.Experimentation results proved that the process of our algorithm could acquire an accurate reconstructive results which was enhanced2to6times when compared with the exiting method. This method could extend the application of single-lens stereovision system using prism to a more widely area and could be apply in stereo endoscopy suitably.