A modified control panel used in office machines, which is disposed on an unfoldable upper cover or an automatic document feeder attached on the upper cover without the need of an extra projective portion for disposition of the control panel. The method further moves the lens according to movement data of the human face if the human face is detected, or moves the lens according to movement data of the motion area if the human face is not detected. When any of the extreme values of the alternating current signal is beyond the input range of the AD converter, the alternating current signal is shifted to make both of the peak and bottom values located within the input range of the AD converter. Two channel electrodes of a first transistor are respectively coupled to the second electrode of the first capacitor and the second electrode of the second capacitor.