Focusing apparatus, image pickup apparatus, focusing method, and storage medium

An image pickup apparatus comprising:

• a focusing apparatus;
• and
• an image sensor,
• wherein the focusing apparatus includes:
• one or more memories storing instructions;
• and
• one or more processors that, upon execution of the instructions, operate to:
• set a first region used for focus detection in a first image formed via a first optical system and a second region used for focus detection in a second image formed via a second optical system,
• perform focusing by moving a lens included in at least one of the first and second optical systems,
• acquire, in a case where a difference between a first defocus amount of the first region and a second defocus amount of the second region is smaller than a first threshold value, a moving amount of the lens based on at least one of the first and second defocus amounts, and
• change sizes of the first and second regions in a case where the difference is greater than the first threshold value.

A focusing method comprising:

• setting a first region used for focus detection in a first image formed via a first optical system and a second region used for focus detection in a second image formed via a second optical system,
• performing focusing by moving a lens included in at least one of the first and second optical systems,
• acquiring, in a case where a difference between a first defocus amount of the first region and a second defocus amount of the second region is smaller than a first threshold value, a moving amount of the lens based on at least one of the first and second defocus amounts, and
• changing sizes of the first and second regions in a case where the difference is greater than the first threshold value.