一种用于数字成像的自动对焦系统

提出一种用于数字成像的自动对焦系统,它以CMOS为图像传感器,用DSP进行数据处理并控制驱动电路调整镜头的位置,达到准确自动对焦的目的。系统采用对焦深度法实现自动对焦,通过改变镜头的位置获得一系列模糊程度不等的图像,计算每幅图像的清晰度评价值构成对焦评价曲线;采用梯度函数作为评价标准来评价图像的清晰度;采用窗口选择技术控制对焦感兴趣范围,减少了数据处理量;对实验样机的测试表明,系统有较好的自动对焦性能,并解决了百叶窗问题,对透过玻璃窗户的目标仍然能正确对焦。

An auto-focusing system used for digital imaging

An auto-focusing system used for digital imaging is proposed. The system, for the purpose of accurate auto-focusing, make use of CMOS as image sensor, Digital Signal Processor (DSP) for data processing and controlling driving circuit for lens position adjustment. The auto-focusing is achieved by means of Depth From Focus (DFF), through which, a series of images with different fuzzy degrees are obtained through changing lens positions and a focusing evaluation curve is formed through calculating the definition evaluation for each image. The image definition is evaluated through using gradient function as evaluation standard. The interested focusing range is controlled by window selection. This measure reduces the load for data processing. Test for the experimental camera shows that the system has good automatic focusing behavior and can solve the problem of blind window. In this way targets behind glass window can still be focused correctly.