Design Of A High-Definition Electronic Endoscope System With USB Interface

The portable electronic endoscope based on USB interface is playing an increasingly important role in the field of modern industrial inspection for its merits as low-cost, easy to operate, plug and play, etc. Currently there are many electronic endoscopes based on USB interface on the market, but their sizes are not small enough and working lengths are not that long, furthermore, the image resolution is not high, the performance cannot meet the actual demand.This paper proposes an imaging acquisition system for electronic endoscope which is composed of a1/6inch CMOS image sensor as the photosensitive element. With LVDS transmission technology, using USB2.0interface control chip as the main control board chip for data acquisition and transmission, the high-definition image data are put into computer and then processed by the PC Applications. Finally, a real-time image acquisition and display system is realized.To achieve the system above, the hardware platform is constructed in this paper, mainly including the miniature camera module design, the performance and the development of CMOS image sensor, LVDS encoding and decoding technology, and the design of CY7C68013interface control chip. To match the processing speed of PC with the output speed of image data from the CMOS image sensor, synchronous mode is adopted respectively in hardware and software design with Slave FIFO to read the image data quickly which in transferred into computer by BULK mode. Simultaneously, the software design of the image acquisition and processing system is described. The image acquisition software contains the USB device drivers for Windows and the firmware for USB2.0interface controller chip. The firmware framework, the configuration of end-point of CY7C68013, and the Slave FIFO transfer mode are emphasized. The image processing software realizes functions of automatic exposure, image zoom, image compression and storage, color adjustment, etc. The image demosaicing method is highlighted. And three kinds of software interface mode are designed for customer. The first is the application software. The second is called direct-show plug-in used for the third-party software, such as Amcap,etc. The last is library functions for secondary development for users.The performance of the electronic endoscope based on USB interface designed by this paper meets practical application requirements. With a140-degree viewing angle of the system’s miniature camera module, the image resolution reaches1280×800.With the adoption of LVDS technology, the working length of the front-end reaches3meters long. The software system which realizes the function of image resolution switching, gain and exposure adjustment and AVI video recording is also designed. This real-time image acquisition and display system can be used for parallel imaging detection when the computer access2～4of such system. And under the condition of full resolution, frame rate is15fps.