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Automatic focusing method

An auto-focus and auto-focus technology, applied in the field of visual measurement, can solve problems such as transformation information that is difficult to reflect local details, no public technical documents have been found, and inability to focus accurately, so as to avoid blind reversal, reduce the number of times, and improve robustness sexual effect

Active Publication Date: 2011-05-11
TIANJIN YAAN TECH CO LTD
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  • Claims
  • Application Information

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Problems solved by technology

When the image is close to clear, the details will certainly be richer, but its frequency change is only from low-order high-frequency components to high-order high-frequency components for the whole world. The DCT-based method can only remove zero-frequency components, so non-zero-frequency components energy and did not change anything
The method of global DCT transformation is difficult to reflect the transformation information of local details
After obtaining the image definition criterion, the next step is to realize automatic focusing. The ordinary hill-climbing search algorithm will be interfered by the local extremum of the image definition criterion and cannot focus accurately.
[0004] Through searching, no published technical documents identical to this patent application have been found

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Embodiment Construction

[0034] The present invention will be further described in detail below in conjunction with the accompanying drawings and through specific embodiments. The following embodiments are only descriptive, not restrictive, and cannot limit the protection scope of the present invention.

[0035] An automatic focusing system, comprising the steps of:

[0036] (1) Obtain the image definition criterion:

[0037] a such as figure 1 As shown, the image acquisition module collects video, converts it into a digital video signal through A / D, obtains the image definition criterion through the image processing module, and deduces the focus search strategy to be sent every time. The motor drive module responds to the command to drive the focus motor to move accordingly. The captured video frame size is 720*576. In order to reduce the amount of calculation and effectively replace the global area, the central area selection method (or multi-area selection method) can be used to replace the global...

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Abstract

The invention belongs to the technical field of vision measurement, in particular to an automatic focusing method. In the method, an idea, which comprises that an image definition evaluation function is designed on the basis of improved discrete cosine transformation (DCT) to represent detail information of the image and highlight high frequency energy, and the relative definition is brought in by consideration of a close relation between the definition of the image and the brightness and the gray scale of the image, is provided. Meanwhile, in the method, a scale-variable window selecting scheme is provided on the basis of analyzing the influence from the selection of a focusing window on a focusing result. Experimental results show that the effect of the improved image definition judgment is improved greatly; in the actual application of the method, a partial extreme value of the image definition judgment is hard to avoid, so, by combining return information of a lens, an improved climbing method search strategy of total-range rough adjustment large step length focusing and partial refine adjustment small step length focusing is provided; and in the method, a scheme of starting automatic focusing when a shooting scene is changed or the lens is zoomed is provided.

Description

technical field [0001] The invention belongs to the technical field of visual measurement, and in particular relates to an automatic focusing method. Background technique [0002] With the development of digital imaging technology towards automation and intelligence, the application range of autofocus technology is also expanding, and great progress has been made in automation, high precision, high stability, etc. It has been widely used in cameras, video cameras, Microscopes, scanners and other precision instruments. There are two types of automatic focusing methods: active and passive. The active method mainly refers to calculating the actual focal length by measuring the distance (such as using infrared distance measurement) and using a certain mathematical model; the passive method refers to using the own information of the acquired image To analyze the focus direction, the clearest image can be obtained through repeated adjustment of the focal length, which is usually ...

Claims

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Application Information

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IPC IPC(8): G02B7/36G03B13/36
Inventor 苏伟博
Owner TIANJIN YAAN TECH CO LTD
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