Quick and automatic focusing method and device for camera

Abstract

The invention relates to the technical field of focusing, and in particular relates to a quick and automatic focusing method and a quick and automatic focusing device for a camera. The quick and automatic focusing method comprises the steps of a focusing value computation step including moving a lens to a plurality of different focusing positions to obtain image data of an object, and computing an estimated focusing value corresponding to each image data under a first high frequency and a focusing judgment value corresponding to each image data under a second high frequency; a direction determination step including computing a change rate between the current focusing judgment value and the previous focusing judgment value, and determining the moving direction of the lens according to the sign of the change rate; a speed determination step including comparing the change rate with a preset focusing change threshold value, and determining the moving speed of the lens according to the comparison result; and repeatedly executing the above steps until the lens moves to the focusing position corresponding to the maximal estimated focusing value. According to the quick and automatic focusing method and device for the camera, the different moving speed is used at different position, the focusing time is effectively reduced, both the focusing speed and accuracy are improved, and very high reliability and practicability are provided.

Description

【Technical field】 [0001] The invention relates to the field of focusing technology, in particular to a method and device for fast automatic focusing of a camera. 【Background technique】 [0002] Due to the wide application of photoelectric image sensors CCD and CMOS in the field of image and video, digital cameras and video cameras can be seen everywhere in engineering applications and daily life. Whether it is a digital camera or a video camera, its main function is to obtain a clear image, that is, to achieve the best clarity of the image by adjusting the position of the lens focusing lens group. Therefore, focusing technology has become the key to imaging products, especially cameras. [0003] At present, the autofocus technology based on digital image processing has gradually replaced the traditional autofocus method based on the principle of distance measurement. The automatic focus technology based on digital image processing uses a certain digital image processing al...

AI Technical Summary

Problems solved by technology

[0004] However, the auto-focus algorithm in the prior art uses a fixed small step size when searching the stroke of the focus motor, which will make the focus speed slow and waste the focus time, and will fall into the problem of oscillation due to local poles, but increase the search speed. Although the step size (reduced sampling points) used in the time can improve the autofocus speed, the sparse sampling near the peak will make the focus accuracy not high

Most of the current autofocus methods and devices are difficult to achieve a balance between speed and accuracy

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