Image sensor and image capturing apparatus

An image sensor comprising a plurality of image forming pixels which receive light beams passing through an imaging pupil area of an imaging optical system, a plurality of first focus detecting pixels which receive light beams passing through a first pupil area smaller than the imaging pupil area, and a plurality of second focus detecting pixels which receive light beams passing through a second pupil area smaller than the imaging pupil area,

• wherein said plurality of image forming pixels are arrayed in a first direction perpendicular to an optical axis of the imaging optical system,
• said plurality of first focus detecting pixels are arrayed in the first direction so as to shift from said plurality of image forming pixels in a second direction perpendicular to the first direction and a direction of the optical axis,
• said plurality of second focus detecting pixels are arrayed in the first direction so as to shift from said plurality of image forming pixels in the second direction,
• said first focus detecting pixel comprises a first light-shielding layer having a first opening between a lens of said first focus detecting pixel and a photo-electric conversion portion of said first focus detecting pixel,
• said second focus detecting pixel comprises a second light-shielding layer having a second opening located at a position different from a position of the first opening in the first direction between a lens of said second focus detecting pixel and a photo-electric conversion portion of said second focus detecting pixel,
• an average position of a geometric centre of the first opening and a geometric centre of the second opening is eccentric with respect to a geometric centre of a photo-electric conversion portion of said first focus detecting pixel in the first direction,
• eccentricity of a lens of said first focus detecting pixel relative to a center of said pixel differs from eccentricity of a lens of said image forming pixel relative to a center of said pixel in the first direction at the same image height in the first direction,
• eccentricity of a lens of said second focus detecting pixel relative to a center of said pixel differs from eccentricity of a lens of said image forming pixel relative to a center of said pixel in the first direction at the same image height in the first direction, and
• a direction of eccentricity of each of lenses of said first focus detecting pixel and said second focus detecting pixel relative to a center of said pixel in the first direction is opposite to a direction of eccentricity of an average position of a geometric centre of the first opening and a geometric centre of the second opening relative to a center of said pixel.