Abstract: An automatic focusing device for use in camera lens systems comprises lens means such as a zoom lens for forming the image of an object, detecting means for detecting the amount of defocus of the image of the object formed by the lens means from a predetermined plane such as a film surface, memory means for storing at least one value of conversion coefficient and at least one value of correction coefficient which is used in a calculation for correcting the conversion coefficient, calculating means for correcting the conversion coefficient in accordance with the amount of defocus and the correction coefficient and for calculating the driving amount of at least a portion of the lens means on the basis of the corrected conversion coefficient and the amount of defocus, and lens driving means for driving at least a portion of the lens means, e.g., the front lens group of a zoom lens, in accordance with the driving amount calculated by the calculating means.

Abstract: In an apparatus for detecting the in-focus state of a photo-taking lens of a camera, a defocus signal is produced responsive to a light intensity distribution signal and is indicative of deviation between an image of an object to be photographed and a predetermined surface. An information signal is produced indicative of the effectiveness of the defocus signal. A vignetting detection signal is produced indicative of the state of vegnetting by the photo-taking lens. The information signal is compared with a threshold value to determine the effectiveness of the defocus indicated by the defocus signal, and the threshold value is changed in response to the vignetting detection signal. A photo-taking lens may include a memory that stores data indicating an inverse of a value indicative of a distance from a predetermined plane to an exit pupil of the photo-taking lens, and the data stored in the memory may be used for calculating vignetting.