Autofocus method and autofocus device

Abstract

The invention provides an automatic focusing method and an automatic focusing device. The automatic focusing device includes a lens, a stepping motor, a calculation module and a control module. The autofocus method includes: the control module determines the movement interval L of the stepping motor; the lens acquires an image P1 when the stepping motor is located at the first end point of the two endpoints of L; The image P2 is acquired at the inner point; the lens acquires the image P3 when the stepping motor is located at the second inner point in L; the calculation module calculates the sharpness evaluation values ​​M1, M2 and M3 of P1, P2 and P3; the control module determines that L is greater than the first When a threshold value is reached, determine the new movement interval of the stepper motor according to M1, M2 and M3, and repeat the above steps; when the control module determines that L is less than or equal to the first threshold value, determine the target position of the stepper motor according to M1, M2 and M3 . The technical solution of the present invention can complete auto-focusing faster.

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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