Passive autofocus device and method

Abstract

The invention discloses a passive automatic focusing apparatus and method. In one embodiment, the apparatus includes a focusing scope determination circuit, a focal length pace determination circuit, and an image information generating circuit. The focusing scope determination circuit is used for comparing the change area scope and preset area of a current scene with a previous scene so as to determine a focusing scope; the focal length pace determination circuit is used for comparing the definition information of the focusing scope with a first preset definition value so as to generate a current space setting value; and the image information generating circuit is used for sequentially generating a plurality of pieces of first pace image information corresponding with the focusing scope when the current space setting value indicates a first pace, and is used for sequentially generating a plurality of pieces of second pace image information corresponding with the focusing scope when the current space setting value indicates a second pace, wherein the first pace is smaller than the second pace. The passive automatic focusing apparatus and method avoid the improperness of the focusing scope.

Description

technical field [0001] The invention relates to an automatic focusing device and method, in particular to a passive automatic focusing device and method. Background technique [0002] The focusing technology adopted by the general image extraction device can be divided into active auto-focus technology and passive auto-focus technology. It is to find the best focus point of the scene to be photographed by analyzing the clarity of the scene image. [0003] In passive focusing technology, Hill Climbing Algorithm is widely used. As the name implies, the Hill Climbing Algorithm will find out the direction of increasing sharpness according to the step change of a focusing mechanism (such as a stepping motor or a voice coil motor). The peak value of the sharpness change curve of a focus area, and the position of the focus mechanism corresponding to the peak value is determined as the best focus point. The above-mentioned focus area is usually the central area of ​​a picture to b...

AI Technical Summary

Problems solved by technology

The above-mentioned focus area is usually the central area of ​​a picture to be shot, and its range is usually fixed. When the range is too large, there is a high probability of including scenes of different depths, so the hill-climbing algorithm may find clear images of uninteresting scenes. When the range is too small, there is a high probability that the scene of interest is not included, so the hill climbing algorithm can only find the sharpness peak of the non-interesting scene within the range, and miss the interesting scene outside the range

In practice, a fixed focus range may be suitable for some scenes, but may be too large or too small for some scenes

As for other passive focusing technologies, there may be similar problems, too slow focusing speed or noise influence.

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