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Automatic focusing and locating method

A positioning method and auto-focus technology, applied in focusing devices, televisions, optics, etc., can solve problems such as difficult to accurately determine the search direction, and achieve the effect of accurate focusing and high focusing efficiency

Active Publication Date: 2014-07-23
NAT UNIV OF DEFENSE TECH
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  • Abstract
  • Description
  • Claims
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AI Technical Summary

Problems solved by technology

The diversity of focusing scenes and lighting conditions makes it difficult to accurately determine the search direction by relying on the value of the image sharpness evaluation function in many cases, and it is even more difficult to solve the problem in the case of telephoto

Method used

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  • Automatic focusing and locating method

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Embodiment Construction

[0034] The present invention uses the absolute ambiguity value to determine the search direction, which includes the search direction rapid determination criterion based on the absolute ambiguity value and the current focus position value in a certain situation, and the continuous several absolute ambiguity values. The frame change is used to determine the search direction criteria in normal cases; for the slow change of sharpness value under low contrast, a double sharpness change threshold is used to determine the fine search area, so as to eliminate local peaks and ensure accurate focus on low-contrast scenes Ability; Aiming at the characteristics of small sharpness value fluctuations in the neighborhood around the local peak, while the global peak is steep and the sharpness value will reflect significant continuous changes on both sides of the peak, the number of statistical fluctuations is used to distinguish the local peak from the global peak. In order to further elimina...

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Abstract

The invention discloses an automatic focusing and locating method. The search direction is judged according to an absolute ambiguity value, and the automatic focusing and locating method relates to a search direction rapid judgment rule depending on only one frame of images under the certain condition through the absolute ambiguity value and a current focusing position value and a search direction judgment rule under the common condition according to several frames of continuous changes of the absolute ambiguity value. A dual-acutance change threshold value is adopted for determining a fine search area to eliminate local peak values and guarantee the capacity of long-scale contrast scene accurate focusing. The fluctuation time number is counted to distinguish the local peak values and overall peak values, and interference of the local peak values is eliminated. A multi-window focusing mode is adopted, a focusing target area is comprehensively judged according to the acutance and the ambiguity, and the capacity of initiatively selecting the focusing target area to a certain degree is achieved. The automatic focusing and locating method is high in focusing efficiency and accurate in focusing.

Description

technical field [0001] The invention relates to the technical field of image processing and automatic focus, in particular to an automatic focus positioning method. Background technique [0002] Autofocus is a certain automatic adjustment process that enables the target scene to be accurately and clearly imaged in the imaging system, and is an important basic function of various photoelectric imaging systems. Autofocus methods can be divided into two categories: active focus and passive focus. Active focusing relies on some distance detection method, such as ultrasonic or infrared ranging, to measure the distance between the target scene and the lens, and then focus based on this to obtain an accurate focus position. Active focus can adapt to various lighting situations, especially in low light conditions. The disadvantage of this type of method is that in addition to requiring more cost and power (or battery) consumption, it is also that the focus target area is limited t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04N5/232G03B13/36
Inventor 张政张茂军王炜徐玮熊志辉刘煜
Owner NAT UNIV OF DEFENSE TECH
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