Focal length detecting method and focusing device
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United States of America Patent
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Issued Date -
Nov 11, 2004
app pub date -
Feb 9, 2004
filing date -
Feb 10, 2003
priority date (Note) -
Abandoned
status (Latency Note)
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Abstract
The invention enables the accurate measurement of the distance for focusing regardless of blur of the subject image. An image focusing area is defined in the data of a photographed image, and the image focusing area is divided into a plurality of windows. Contrast evaluated values and the position where the maximum value of the evaluated values has been recorded are calculated for each window. A plurality of images are photographed while the optical system 11 is driven to change its focal length. Of the plural image data, the portions corresponding to each window are compared one against another, and a partial focal length is calculated for each respective window. Should the positions at which the respective maximum values of the evaluated values have been recorded differ among the plural image data of a window, it is assumed that the window contains blur. As a result, the reliability of the window is reduced, and the partial focal length of the window is disregarded. Of the partial focal lengths that have been judged to be valid, the shortest or longest distance is used as the focusing position to drive the lens.
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