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US 4,734,571 AGranted
Focus condition detecting device having correlation calculation means and means for determining the range of shifts of image signals
AssigneeMinolta Camera Kabushiki Kaisha
InventorsMasataka Hamada, Tokuji Ishida, Toshihiko Karasaki, Toshio Norita, Nobuyuki Taniguchi
Life of this patent
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Abstract
There is disclosed a focus condition detecting device for a camera. The focus condition detecting device has a preliminary correlation calculation means for calculating correlations between first and second image signals with a relatively low accuracy and a principal correlation calculation means for calculating correlations between first and second image signals with a relatively high accuracy on the basis of data obtained in the preliminary correlation calculation.
Claims11
A focus condition detecting device for a camera having an objective lens for forming an image of an object, comprising:
- optical means for forming first and second object images so that the distance between the first and second object images varies with the focus condition of the object image formed by the objective lens;
- first and second image signal generating means having first and second sensors positioned to receive the first and second object images and adapted to generate first and second image signals corresponding to the light intensity distributions of the first and second object images on the first and second sensors, respectively;
- preliminary correlation calculation means for effecting a preliminary correlation calculation which includes calculation of a plurality of correlation degrees between the first and second image signals with a predetermined lower accuracy by repeated shifting of the first and second image signals relative to one another and determination of a highest correlation degree among the calculated correlation degrees and of the number of the shifts providing the highest correlation degree;
- principal correlation calculation means for effecting a principal correlation calculation which includes calculation of a plurality of correlation degrees between the first and second image signals with a predetermined higher accuracy by repeated shifting of the first and second image signals relative to one another and determination of a highest correlation degree among the calculated correlation degrees and of the number of the shifts providing the highest correlation degree;
- means for determining the range of the shifts for the calculation of the plurality of correlation degrees in the principal correlation calculation in accordance with the number of the shifts determined by the preliminary correlation calculation means;
- and
- means for generating a focus condition detection signal representative of the focus condition of the object image formed by the objective lens, based on the number of the shifts determined by the principal correlation calculation means.
4 more elements
In a camera having an objective lens for forming an image of an object, the improvement comprising:
- means for forming first and second object images that vary with the focus condition of the object image formed by the objective lens;
- first and second image signal generating means having first and second sensors positioned to receive the first and second object images and adapted to generate first and second image signals corresponding to the light intensity distributions of the first and second object images on the first and second sensors, respectively;
- preliminary correlation calculation means for effecting a preliminary correlation calculation which includes calculation of a plurality of correlation degrees between the first and second image signals with a predetermined lower accuracy by repeated shifting of the first and second image signals relative to one another and determination of a highest correlation degree among the calculated correlation degrees and of the number of the shifts providing the highest correlation degree;
- principal correlation calculation means for effecting a principal correlation calculation which includes calculation of a plurality of correlation degrees between the first and second image signals with a predetermined higher accuracy by repeated shifting of the first and second image signals relative to one another and determination of a highest correlation degree among the calculated correlation degrees and of the number of the shifts providing the highest correlation degree;
- means for determining the range of the shifts for the calculation of the plurality of correlation degrees in the principal correlation calculation in accordance with the number of the shifts determined by the preliminary correlation calculation means;
- and
- means for generating a focus condition detection signal representative of the focus condition of the object image formed by the objective lens, based on the number of the shifts determined by the principal correlation calculation means.
4 more elements
Dependencies are inferred from the claim text.