采用外触发方式实现CCD摄像机的全自动调光控制

Full-automatic light adjustment control for CCD camera by external trigger

针对传统的CCD摄像系统自动调光方法在工程使用中存在的不足,提出了一种新的CCD摄像系统的全自动调光方法。该方法采用外触发电子快门和可变光阑相组合的方式进行调光,外触发电子快门调光为主,可变光阑调光为辅。采用外触发方式实现CCD摄像机的电子快门时间调节,由单片机控制电机调节可变光阑的通光口径,以使像面照度适中。由图像目标区域的均值电平获得反馈控制量,从而实现最佳全自动调光。Matlab仿真结果表明,与传统调光方法相比,新型调光方法拍摄的图像更清晰,对比度更高,目标层次也更加明显,对应的直方图分布更宽广且更均匀,功率谱幅值也更高,达到7.5 dB以上,可满足现代CCD摄像系统的最佳全自动调光要求。

In order to improve the automatic light adjustment for traditional CCD camera system in engineering, a new full-automatic light adjustment method for CCD camera system was presented. In this method,light was adjusted by combining external trigger electronic shutter mainly and iris dia- phragm assistantly. For obtaining a moderate image illumination, the electronic shutter time of CCD camera was adjusted by external trigger and the aperture of iris diaphragm was adjusted by motor controlled by single-chip. Feedback control quantity was obtained from the mean level of target region of image, so that the full-automatic light adjustment was implemented. Matlab simulation results show that histogram related to image of new light adjustment system is wide and uniform, and the peak value of its power spectrum is more than 7.5 dB. The image of the new light adjustment system is clean and high-contrast, which shows new system can satisfy requirements of the optimal full-automatic light adjustment for modern CCD camera system.