超高分辨率CCD成像系统的设计

Design of ultra-high resolution CCD imaging systems

介绍了基于50Mpixel超高分辨率全帧型CCD芯片KAF50100的成像系统设计方法。该系统采用幕帘式焦平面机械快门对CCD进行曝光控制,CCD输出图像信号在专用模拟前端(AFE)芯片AD9845B中进行处理和模数(A/D)转换后,经现场可编程门阵列(FPGA)缓存和排序,通过低压差分信号(LVDS)接口发送至上位机。系统中所有驱动时序和控制信号均由FPGA产生,上位机通过RS422总线对系统进行命令控制。针对KAF50100四路输出不均匀性问题提出了基于最小二乘法拟合的校正方法。实验验证表明,系统可在KAF50100的最大速度模式下工作,像素读出速度为4×18MHz,最大帧速为1frame/s,电路读出随机噪声为2.76@12bit,动态范围为63.4db。该成像系统设计方法可以充分发挥KAF50100的性能,并且具有良好的通用性和扩展性,可以广泛应用于超高分辨率CCD成像系统的设计中,如可见光水下探测、卫星遥感、天文观测等。

A design method for ultra high resolution image systems based on full frame CCD KAF50100 was proposed, in which a mechanical rolling shutter was adopted to control the exposure. The Analog Front End （AFE） chip AD9845B was used to process and digitize the analog output of KAFS0100 and the digital image signal from the AFE was buffered and arranged in a block ram of Field Programming Gate Arry（FPGA）, then was sent out through a Low Voltage Differential Signaling（LVDS） interface. All the control signals and drive timing signals were generated by the FPGA and the RS422 interface was used to receive command and upload the status of system. The least square method was adopted to correct the non-uniformity from four analog outputs of the CCD sensor. Experiment shows that the CCD sensor KAF50100 can work at a top output speed, its pixel output rate is 4× 18 MHz, and the maximum frame rate, output noise and the dynamic range are 1 frame/s, 2.76@12hit and 63.4 dB, respectively. With better flexibility and extendibility, this design method can be widely used in ultra high resolution imaging fields like visible light underwal：er detection, satel- lite remote sensing and astronomical observation.