红外光斑中心检测在红外自动验光仪、红外测距仪等光学测量和检测仪器中是一项关键技术,检测算法的精度、速度直接影响光学测量的精度及速度.目前的检测处理系统多是基于PC机的,存在着实时性、稳定性问题.在总结各种检测算法的基础上,基于重心法使用FPGA实现了低信噪比红外光斑中心的实时检测.在实验电路中,先使用视频解码芯片SAA7113将模拟CCD视频信号转化为CCIR656格式数字信号;再在FPGA内部使用流水线结构进行直方图计算,计算阈值,二值化图像,五次二值图像收缩,五次二值图像膨胀处理以去除噪声,然后计算重心坐标.实验电路对红外自动验光仪中产生的视网膜反射红外光斑PAL制式视频图像信号能在1/25 s完成一幅图像的检测.而普通PC完成同一过程需要1 s左右.文章介绍了基于FPGA实现方案.

The infrared spot detection is the key technique used in optical measurement and detection instruments, such as infrared automation optometry, infrared range finder. The precision and speed of the detection algorithm affect those of the optical measurement system directly. The detection system is currently based on PC, with the question of real-time and stability. There is a way to realize realtime detec-tion for low SNR infrared spot using FPGA based on gravity model. In test circuit, firstly,analog CCD video signal is converted to CCIR656 digital video signal using the video decoder chip SAA7113; secondly, in FPGA, a streamline structure is used for histogram calculating, binary image, five times eroding and five times dilating for filtering noise, then the coordinate of centre of cavity is calculated. The test circuit can finish the spot detection in one image in 1/25 s for PAL infrared spots video signal from infrared automation optometry, which was generated by retina reflecting. It requires about 1 s for finishing the above process for one normal PC. The scheme based on FPGA is presented.