Patent ID: 8831420

Claim:
A focus detection device comprising: circuitry including: a phase difference acquisition unit that calculates an amount of deviation between light-reception amount distributions of a pair of light-receiving element groups arranged in a predetermined direction perpendicular to an optical axis direction as a phase difference; a conversion coefficient correction unit that corrects a conversion coefficient, representing a ratio of an amount of focus deviation in the optical axis direction to the phase difference when shapes of the light-reception amount distributions are same, according to a degree of discrepancy between the shapes of the light-reception amount distributions; a defocus amount generation unit that generates the amount of focus deviation as an amount of defocus based on the corrected conversion coefficient and the phase difference; and a discrepancy correction coefficient generation unit that calculates the pair of light-reception amount distributions based on lens aperture information indicating a shape and a position of a pupil in a lens and light-reception sensitivity distribution information indicating a distribution of light-reception sensitivities of the pair of light-receiving element groups, and generates a discrepancy correction coefficient based on the pair of light-reception amount distributions, wherein the conversion coefficient correction unit corrects the conversion coefficient based on the discrepancy correction coefficient which is a proportion of the conversion coefficient to a ratio of the amount of defocus to the phase difference when the shapes of the light-reception amount distributions are not the same.