Fast Auto-Focus Control Algorithm Using the VCM Hysteresis Compensation in the Mobile Phone Camera

A practical real-time auto-focus algorithm for a digital camera is presented in this paper, and it improves the reliability and speed of the auto-focus process, especially suitable for a 2 mega-pixel high definition camera. The proposed algorithm divides auto-focusing process into several modes and finds the focus by the different control current in the each mode. Additionally, an adaptive step size searching and a hysteresis compensation of the voice coil motor increased searching speed. The experimental result shows the proposed algorithm is faster auto-focusing than conventional algorithm in the VCM camera system