Image forming apparatus

An image forming apparatus comprising:

• an image sensor comprising a plurality of pixels at least part of which form a plurality of focus detection pixel pairs, each receiving light rays passing through different pupil areas of an image forming optical system;
• a detection unit configured to detect a defocus amount, based on a phase difference between signals output from the plurality of focus detection pixel pairs in a focusing area;
• a judging unit configured to determine if a subject has a spatial frequency higher than a sampling pitch of the focus detection pixel pairs, based on signals output from pixels other than the focus detection pixel pairs around the plurality of focus detection pixel pairs in the focusing area;
• and
• a control unit configured to cause the detection unit to detect a defocus amount with the image forming optical system driven in a front-focused direction and to detect a defocus amount with the image forming optical system driven in a rear-focused direction, and control to drive the image forming optical system based on the obtained defocus amounts, in a case in which the judging unit determines that the subject has a spatial frequency higher than the sampling pitch.

An image forming apparatus comprising:

• an image sensor comprising a plurality of pixels at least part of which form a plurality of focus detection pixel pairs, each receiving light rays passing through different pupil areas of an image forming optical system;
• a first detection unit configured to detect a defocus amount, based on a phase difference between signals output from the plurality of focus detection pixel pairs in a focusing area;
• a judging unit configured to determine if a subject corresponds to a predetermined pattern, based on signals output from pixels other than the focus detection pixel pairs around the plurality of focus detection pixel pairs in the focusing area;
• a second detection unit configured to detect a contrast evaluation value of signals output from pixels other than the plurality of focus detection pixel pairs in a case in which the judging unit determines that the subject corresponds to the predetermined pattern;
• and
• a focus control unit configured to drive the image forming optical system to be in an in-focus state, based on the defocus amount detected by the first detection unit or the contrast evaluation value detected by the second detection unit.

A focus control method in an image forming apparatus comprising an image sensor comprising a plurality of pixels at least part of which form a plurality of focus detection pixel pairs, each receiving light rays passing through different pupil areas of an image forming optical system,

• a detection step of detecting a defocus amount, based on a phase difference between signals output from the plurality of focus detection pixel pairs in a focusing area;
• a judging step of determining if a subject corresponds to a predetermined pattern;
• and
• a focus control step of driving the image forming optical system to be in an in-focus state, based on the defocus amount detected in the detection step,
• wherein the judging step determines if the subject corresponds to the predetermined pattern, based on the signals output from the pixels other than the focus detection pixel pairs around the plurality of focus detection pixel pairs in the focusing area, and changes the defocus control based on the determination result.

A focus control method in an image forming apparatus comprising an image sensor comprising a plurality of pixels at least part of which form a plurality of focus detection pixel pairs, each receiving light rays passing through different pupil areas of an image forming optical system,

• a first detection step of detecting a defocus amount, based on a phase difference between signals output from the plurality of focus detection pixel pairs in a focusing area;
• a judging step of determining if a subject has a spatial frequency higher than a sampling pitch of the focus detection pixel pairs, based on signals output from pixels other than the focus detection pixel pairs around the plurality of focus detection pixel pairs in the focusing area;
• a second detection step of detecting a defocus amount with the image forming optical system driven in a front-focused direction and detecting a defocus amount with the image forming optical system driven in a rear-focused direction, in a case in which the judging unit determines that the subject has a spatial frequency higher than the sampling pitch in the judging step;
• and
• a control step of controlling the image forming optical system to be driven, based on the defocus amount obtained in the first detection step in a case in which it is determined in the judging step that the subject does not have a spatial frequency higher than a sampling pitch of the focus detection pixel pairs, or based on the defocus amount obtained in the second detection step in a case in which it is determined in the judging step that the subject has a spatial frequency higher than a sampling pitch of the focus detection pixel pairs.

A focus control method in an image forming apparatus comprising an image sensor comprising a plurality of pixels at least part of which form a plurality of focus detection pixel pairs, each receiving light rays passing through different pupil areas of an image forming optical system,

• a first detection step of detecting a defocus amount, based on a phase difference between signals output from the plurality of focus detection pixel pairs in a focusing area;
• a judging step of determining if a subject corresponds to a predetermined pattern, based on signals output from pixels other than the focus detection pixel pairs around the plurality of focus detection pixel pairs in the focusing area;
• a second detection step of detecting a contrast evaluation value of signals output from pixels other than the plurality of focus detection pixel pairs in a case in which it is determined in the judging step that the subject corresponds to the predetermined pattern;
• and
• a focus control step of driving the image forming optical system to be in an in-focus state, based on the defocus amount detected in the first detection step or the contrast evaluation value detected in the second detection step.