Image pickup system, image pickup apparatus, and program

An image pickup apparatus comprising:

• a phase-difference focus detection unit operable to output a first phase-difference focus detection signal, wherein the first phase-difference focus detection signal corresponds to a plurality of distance-measurement points in the phase-difference focus detection unit;
• an image pickup device operable to output a second phase-difference focus detection signal, wherein the second phase-difference focus detection signal corresponds to a plurality of distance-measurement points of the image pickup device and wherein the plurality of distance-measurement points of the phase-difference focus detection unit are less in number than the plurality of distance-measurement points of the image pickup device;
• an optical device operable to separate a first incident light into a second incident light and a third incident light, wherein the first incident light is transmitted from an interchangeable lens, the second incident light enters the image pickup device, and the third incident light enters the phase-difference focus detection unit;
• and
• a controller operable to select either of the first phase-difference focus detection signal and the second phase-difference focus detection signal on the basis of satisfaction of a predetermined condition and operable to perform focusing.

A non-transitory computer readable medium having stored thereon, a computer program having at least one code section executable by a computer, thereby causing the computer to perform the steps comprising:

• outputting a first phase-difference focus detection signal by a phase-difference focus detection unit, wherein the first phase-difference focus detection signal corresponds to a plurality of distance-measurement points in the phase-difference focus detection unit;
• outputting a second phase-difference focus detection signal by an image pickup device, wherein the second phase-difference focus detection signal corresponds to a plurality of distance-measurement points of the image pickup device and wherein the plurality of distance-measurement points of the phase-difference focus detection unit are less in number than the plurality of distance-measurement points of the image pickup device;
• separating a first incident light into a second incident light and a third incident light by an optical device, wherein the first incident light is transmitted from an interchangeable lens, the second incident light enters the image pickup device, and the third incident light enters the phase-difference focus detection unit;
• selecting either of the first phase-difference focus detection signal and the second phase-difference focus detection signal on the basis of satisfaction of a predetermined condition;
• and
• focusing based on the selection.