Automatic focusing method and device

Abstract

The invention provides an automatic focusing method and device. The method comprises the following steps: moving a focusing motor to a first position according to a set focusing mode, and calculating first definition evaluation values of blocks; moving the focusing motor to a second position, and calculating second definition evaluation values of the blocks; identifying blocks occupied by objects under one object distance in an image in the focusing mode according to change rates of the definition evaluation values of the blocks and a change rate mean value, wherein the objects under one object distance comprise a target object; and setting a definition evaluation value weight of a block where the target object is positioned as an effective weight, setting the definition evaluation value weights of the blocks where other objects are positioned as ineffective weights, and searching for a focusing block to focus. Through adoption of the automatic focusing method and device, a definition evaluation function of a multi-object multi-object-distance image can meet a unimodal property; a network camera can automatically finish switching between a near-object-distance focusing mode and a far-object-distance focusing mode specific to scene features; and target object focusing is realized.

Description

technical field [0001] The invention relates to the technical field of video surveillance, in particular to an automatic focusing method and device. Background technique [0002] According to the basic principle of focusing, the accuracy of automatic focusing of the camera depends on the evaluation function of focus sharpness. The sharpness evaluation function needs to have the following basic characteristics: unimodality, unbiasedness, monotonicity, sensitivity, and sex-to-noise ratio. In a video surveillance scene, if multiple target objects exist at different object distances, the sharpness evaluation value of the entire picture presents figure 1 The trend shown, that is, the sharpness evaluation function may have multiple peaks due to the presence of objects at multiple object distances, does not satisfy unimodality. When the camera is auto-focusing, different focusing results may occur due to the difference in the initial position of the focusing motor, such as figur...

AI Technical Summary

Problems solved by technology

[0004] The present invention provides an automatic focusing method and device to solve the problem that in the prior art, in the scene where multiple objects exist at different object distances, the camera cannot automatically complete the switching between the near object distance and the far object distance focusing mode according to the characteristics of the scene, so as to realize Problems focusing on target objects

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