Automatic focusing method and automatic focusing device

Abstract

The invention provides an automatic focusing method and an automatic focusing device. The automatic focusing device comprises a lens, a stepping motor, a calculating module and a control module. The automatic focusing method comprises the steps of determining a movement interval L of the stepping motor; acquiring an image P1 by the lens when the stepping motor is at a first end point between two end points of the L; acquiring an image P2 by the lens when the stepping motor is at a first internal point in the L; acquiring an image P3 by the lens when the stepping motor is at a second internal point in the L; calculating definition evaluation values M1, M2 and M3 of P1, P2 and P3 by the calculating module; when a fact that L is larger than a first threshold is determined by the control module, determining a new movement interval of the stepping motor according to M1, M2 and M3, and repeating the steps above; and when a fact that L is smaller than or equal with the first threshold is determined by the control module, determining the target position of the stepping motor according to the M1, M2 and M3. The automatic focusing method and the automatic focusing device can finish automatic focusing in higher speed.

Description

technical field [0001] The invention relates to the field of image processing. In particular, it relates to an automatic focusing method and an automatic focusing device. Background technique [0002] With the rapid development of digital image and multimedia technology, more and more people pay attention to the automatic focus method based on image processing. The auto-focus method mainly includes the following three aspects: the selection of the focus window, the selection of the focus evaluation function, and the selection of the focus search strategy. The autofocus method is to obtain the sharpness characteristic value of the image according to a certain focusing evaluation function, and control the stepping motor according to the sharpness characteristic value to drive the lens or the image sensor to continuously search for a new position in a certain interval, and then The sharpness characteristic value of the image is reacquired at the new position until the sharpne...

AI Technical Summary

Problems solved by technology

Take the hill-climbing search algorithm with variable step size as an example. When focusing starts, set the focus direction and larger step size, and calculate the focus evaluation function value while acquiring images. When the evaluation value of the latest acquired image is smaller than the evaluation value of the previous image , change the focusing direction; when crossing the peak again, reduce the step size, and finally find the best lens position, which makes the autofocusing speed slower in the traditional self-focusing method

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