| The technology research of night-vision imaging and detection in low light condition has always been the focus of national military reconnaissance study. In the low illumination, the fast dynamic detection and recognition of a target is directly related to military forces’ survival ability. Compared with other CCD devices, electron multiplying CCD (EMCCD) has the advantage obviously for its detection sensitivity can reach the standard of military reconnaissance.Based on the electron multiplication CCD devices’requirements of the driving signal and characteristics of the output video signal, this paper will design an EMCCD camera which can work stably, in real time, and with low noise, and is suitable for low light environment.Firstly, the design of analog front-end (AFE) circuit will decide the performance of the EMCCD imaging system.The integrated devices and discrete circuits will all used for the design of analog driver circuit. By adopting a 12 bit analog-to-digital conversion chip with Correlation Double Sampling (CDS) function, the image data of CCD97 output signal can be digitized. Second, considering the characteristics of EMCCD output images, FPGA chip is put in center in designing the system-control and image-processing circuit, with plug-in SDRAM chips added.In this circuit, not only timing generation, data acquisition and data processing can work, but meanwhile four kinds of image processing algorithm:automatic gain control, blind pixel correction, image denoising and image enhancement are embedded in the chip.Third, the design of power supply circuit and signal-output scheme is studied in this paper. In designing the power supply circuit, both DC-DC and LDO are adopted to satisfy the system’s requirements and minimize its power consumption. As to the signal-output scheme, digital video signal is received first, and then is converted into standard PAL and Camera Link format image to be outputted.The debugging results show that the EMCCD camera has the capability of fast real-time imaging, and its output image is clear and stable. With high signal-to-noise ratio, the EMCCD machine can basically meet the demand in the low illumination environment. |
