Endoscopic Imaging System Design Based On NanEye 2D Miniature Image Sensor

Endoscopes are widely used in clinical medical diagnosis and treatment,and are indispensable medical tools for moderr hospitals.However,China's research and development in the field of endoscopy started late,and it still lags behind foreign countries as a whole,and mostly still relies on foreign imports.With the rapid development of medical technology,the use of endoscopes has become more and more popular in clinical practice,and the medical endoscope industry has a very large market prospect.In recent years,the state has vigorously promoted the localization of medical equipment such as endoscopes,which provides a good opportunity for the development of domestic endoscopes.NanEye 2D miniature image sensor is a high-performance CMOS camera chip from Germany.Due to its millimeter scale,it has broad application prospects in medical equipment such as urinary endoscopes.However,due to the monopoly of foreign technology,users are currently unable to independently design and customize endoscopic products based on NanEye 2D camera chips according to their own needs.Research on endoscopic imaging system based on NanEye 2D miniature image sensor is of great significance for breaking the foreign technical blockade,narrowing the gap between domestic and international endoscopes,and promoting the development of medical devices in China.Using Altera's Cyclone IV EP4CE115 FPGA as the core processor and controller of the endoscope system host,this paper designs aind implements a hose eindoscope imaging system based on NanEye 2D miniature image sensor.The main research work and contents are as follows:(1)An oversampling method with dynamic code width adjustment is proposed to recover the asynchronous communication data of NanEye 2D camera and realize the reliable transmission of image data.The NanEye 2D camera chip adopts asynchronous communication mode,and the output signal is in asynchronous serial differential form.Due to the unstable internal serial output clock of the chip,the output sig)nal frequency is jittered between 30MHz-46MHz and the signal width is uncertain.Tlhe receiving end must synchronize and recover the data with an oversampling clock above 380MHz.The oversampling clock frequency is high and difficult to aclhieve by frequency multiplication.The system uses a 200MHz clock to achieve 400MHz oversampling and recovery of the camera asynchronous signal through the double edge sampling module in the FPGA,and extracts the original Bayer format image data.In the process of data oversampling recovery,a dynamic code width threshold adjustment method to ensure the correct rate of signal recovery was designed in this paper.(2)The image decoding and processing algorithms are implemented in Verilog hardware description language,which improves the real-time performance of the image.NanEye 2D camera chip uses Bayer code to compress video data.The Bayer decoding algorithm and white balance algorithm are verified by C language on the host computer,and then are implemented on the FPGA through Verilog hardware description language.The original image data is transmitted and processed internally,which improves the real-time performance of the system.(3)Automatic exposure and automatic gain control algorithms have been proposed to greatly improve image quality.Changes in environmental factors such as external lighting can affect the overall image display of the endoscope in practice.In this paper,a dynamic adjustment algorithm of exposure time and reverse gain register parameters is designed and implemented on the FPGA by Verilog hardware description language,so that the average value of the effective pixel area of each frame is kept within the ideal range,and the system finally reaches a good overall image effect.(4)The HDMI protocol firmware is realized in the FPGA to directly drive the HDMI interface image display,which further reduced the system size and reducing the system cost.The medical device is usually displayed by HDMI interface.The system implements the HDMI video transmission protocol on the FPGA through the Verilog hardware description language,which makes the FPGA able to directly drive the HDMI interface for smooth image display.Finally,the key indicators and complete machine tests were carried out on the system.The test results show that the system can achieve continuous and reliable data acquisition with a bit error rate lower than 0.000004%and a frame loss rate of less than 4 frames per second,and the color is smoothly and stably displayed at a display frame rate of 40Fps-44Fps.The image shows that the overall system power consumption is 1.1 W.This design solves the key problem of data acquisition for asynchronous communication of NanEye 2D miniature image sensor,realizes the expected design goal,and satisfies the basic functional requirements of the endoscope.