Fast automatic focusing method and camera thereof

Abstract

The invention discloses a method for quickly and automatically focusing in photographing and a photographing device thereof. The method provides a method for controlling the focus search and a method for rapidly focusing in photographing; a photographing device is provided with a focusing window extraction unit; a window signal of an ingested object image is extracted; an acquired signal is output to a focusing value calculation unit; through the extraction and analysis of the frequency characteristic of a specified window image signal and the calculation and analytic judgment, search rapidly enters an acceleration mode 2 from an acceleration mode 1 and rapidly enters a uniform speed region from an acceleration region till a wave crest, namely the focus position is precisely searched; through a focusing motor controller, a focusing motor is driven so as to realize rapid focusing control; and the method and the photographing device effectively reduce the focusing time of the photographing, simultaneously ensure the focusing precision and stability, successfully solve the problem of contradiction between the high-precision focusing and focusing speed of the photographing device and can be applied to various CCD photographing equipment.

Description

technical field [0001] The invention belongs to the field of imaging technology, and relates to a focusing method of an imaging device, in particular to a fast automatic focusing method and an imaging device thereof. Background technique [0002] The traditional automatic focusing method of a camera device is called a "climbing" focal length adjustment method. In mainstream devices with autofocus function, image signals from sensors such as CCD (charge coupled device) are received, and high-pass filter (HPF) or band-pass filter (BFP) is used to extract high-frequency components on the signal unit. Here, high-frequency The component is the focus value. According to the calculated focus value, the moving direction and step length of the focus motor are determined, so as to drive the focus lens to move to the position with the maximum focus value, and complete the automatic adjustment of the focus. figure 1 The focus search process of this method is described. The focus motor...

AI Technical Summary

Problems solved by technology

For example, in the patent of Publication No. CN101034198A, titled "Autofocus Method and Autofocus Device Using It", it is mentioned that the slope of the autofocus value of adjacent points is used to determine the sampling step size, but the size of the focus moving area of ​​the lens is unpredictable , the high-frequency component of the image signal is easily affected by circuit and environmental noise, especially when the defocus is serious. At this time, the slope of adjacent points is irregular, and it is difficult to correctly obtain the sampling step size.

[0005] from figure 1 It is not difficult to know that increasing the sampling step size (reducing the sampling points) can improve the automatic focus speed, but the sparse sampling near the peak will make the focus unstable. On the other hand, high-precision focusing needs to improve the sampling accuracy of the focus value, which is often related to speed is contradictory

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