Patent ID: 7800685
Filing Date: 2010-09-21
Classification: G02B,G03B,H04N

Abstract:
1. An auto focus method for a photographic apparatus to adjust a relative distance between an optical system and a sensing unit to make an image surface lie in a depth of field, the photographic apparatus comprising the optical system, the sensing unit capturing an image of a target object through the optical system, a signal processor receiving signals generated by the sensing unit, a driving unit moving the optical system and the sensing unit, and a control unit electronically connected to the signal processor and the driving unit wherein the optical system further comprising at least a focusing lens, the driving unit moves the focusing lens relative to the sensing unit to make the image surface traveling between a micro scene position and a far scene position, and the method comprising (A) moving relatively the optical system and the sensing unit by the driving unit to focus the image surface lying in one of the micro scene position or the far scene position; (B) moving relatively the optical system and the sensing unit at a first speed by the driving unit to adjust the image surface towards another one of the micro scene position and the far scene position, acquiring multiple optical signals by the sensing unit, and converting respectively the optical signals into multiple evaluation values and storing the evaluation values in the control unit with the signal processor; (C) comparing the evaluation values by the control unit to find out a maximum evaluation value, and stopping the driving unit when one of the evaluation values decreases to a coarse tuning beginning value; (D) reversing the driving unit to relatively move the optical system or the sensing unit at a second speed and acquiring continuously the evaluation values until one of the evaluation values increases to a fine tuning beginning value; and (E) moving continuously and relatively the optical system or the sensing unit at a third speed and comparing simultaneously the evaluation values until a substantial maximum evaluation value is acquired, and completing the auto focus;