Focus-state detecting device, image sensing apparatus image sensing system and lens unit

Abstract

A focus-state detecting device includes a focus-state detection unit that splits a light beam, which has passed through a removable lens unit, into two light beams and detects a defocus amount based upon a phase difference between two images formed by respective ones of the two light beams; a chromatic aberration information acquisition unit that acquires information relating to chromatic aberration, which corresonds to the wavelength of light, from the lens unit; a storage unit that stores a correction value of chromatic aberration that is based upon the color of the light source; a first photometer that mainly meters a visible-light region in a light beam that has passed through the lens unit; a second photometer that mainly meters a wavelength region longer than visible light in a light beam that has passed through the lens unit; a correction value acquisition unit that acquires a correction value from the storage unit in accordance with a difference between outputs from the first and second photometers; and a correcting unit that corrects the defocus amount, which has been detected by the focus-state detecting unit, in accordance with the information relating to chromatic aberration acquired by the chromatic aberration information acquisition unit and the correction value obtained by the correction value acquisition unit, wherein the information relating to chromatic aberration, which correspond to the wavelength of light, of the lens unit is based upon focal length of the lens unit and distance to the subject.

Dependencies are inferred from the claim text.