A control system for embedded auto-focusing camera modules is proposed for mobile phones and other mobile devices.For the purpose of accurate auto-focusing,the system makes use of an AD5820 as the driver IC for a focusing motor, the OV5642 as an image sensor,and the 68013 microcomputer unit as the data processing and controlling driver IC for lens position adjustment.In auto focusing,the system obtains a series of clear images through controlling a voice coil motor to change lens positions at first,and a focusing evaluation curve is formed through calculating the definition evaluation for each image.Then, the image definition is evaluated by using gradient function as evaluation standard,and the lens position is found by the full search when the image definition comes to the maximum value.According to the experiment,the system can offer the focusing resolutions of 5~10 μm and response time less than 70 ms,which shows that the system has good automatic focusing performance,and can satisfy the requirements of automatic focusing system for the camera module.