Design Of Optical Parameter Measurement System For The Rigid Endoscope

With the developing of minimally invasive surgery, endoscope, a kind of medical assistant appliance, is widespread concerned with their small volume, small incision, and fast recovery after having an operation. Meanwhile, As an optical instrument, the imaging quality of the endoscope has a great influence on the safety, quickness and accuracy of treatment. So the first step to evaluate the quality of imaging is measuring its optical parameter. Nowadays, the measurement method of endoscope applied in national standard usually uses artificial-adjusted devices and eyes to observe results at the same time. So the measurement system has low degree of automation, and the measurement error is big. In order to improve the accuracy of measurement and consistency of t he results, enhance the degree of automation of measuring process, this article provides some new projects of measuring method and system. Then it applies these projects to make a new type of automatic measuring system to measure the angle of field, distor tion, direction angle of view and other optical parameter of rigid endoscope.The new measuring system use LCD replaced traditional test target which is paper-made. The image showed on LCD can be adjusted and controlled, so that it can measure multiple optical parameters by displaying different measuring test target. Using LCD can avoid the process that changing paper test target frequently when measuring different optical parameter. It can increase automation of the system. The LCD is installed on electrical moving platform, which can set working distance accurately. The electrical moving platform is installed on the electrical rotating platform, in order to measure the direction angle of view. There is an optical interface of imaging system after the eye l ens. Then we connect the optical interface and imaging device in order to get the field of view of endoscope in real-time. In the measurement, we can adjust the focusing of the optical interface until getting clear imaging. Finally we link imaging device a nd computer. On the one hand, it makes images of field of view enlarged and displayed on the screen, the images can be observed more easily. On the other hand, it can make images processed by software, and get optical parameter immediately.The method of measuring angle of field of view is that sets a light line moving on the LCD field with constant speed. At the same time, we record the moving process of the light line. Then we can use the method of digital image process to calculate the diameter of the field of view and the angle of view. The disadvantages of this method are that it takes a long time to calculation, and occupy too much storage space. So we use the fringes which consist of bright-dark stripes as the test target to measure angel of field of view to improve this method. The improved method costs less time to measure and process the project, has higher degree of automation and more convenient than before. The method of measuring the distortion of endoscope is using a center symmetric test targe t, which are a set of concentric rings and many lines which pass through the center of circles. Process the images which are from endoscope optical system to get the data of radius of the circle to calculate the distortion of endoscope. Use the data to com pare to the radius of test target, we can get relative distortion. Then we can plot the curve of relative distortion form center to edge of the view. This system can also measure the direction angle of endoscope. This process of measurement is convenient a nd fast.The measuring system of rigid endoscope disribed by this article can measure multiple optical parameters with a higher accuracy, better consistent result and higher-degree automation. It has a bright applying prospect.