Endoscope apparatus and focus control method for endoscope apparatus

An endoscope apparatus comprising:

• an imaging section that includes a phase difference detection element for implementing phase detection autofocus, and acquires a captured image;
• a phase difference calculation section that calculates a phase difference based on a signal output from the phase difference detection element;
• a lens position selection section that selects a focus lens position that is either a near point-side focus lens position or a far point-side focus lens position based on the phase difference, the near point-side focus lens position and the far point-side focus lens position being discrete focus lens positions set in advance;
• a driver section that changes a focus lens position of the imaging section to the focus lens position selected by the lens position selection section;
• and
• a boundary position setting section that sets a boundary position between a near point-side in-focus object plane position that corresponds to the near point-side focus lens position and a far point-side in-focus object plane position that corresponds to the far point-side focus lens position,
• wherein the lens position selection section selects the near point-side focus lens position when the lens position selection section has determined that a position of an object corresponding to the phase difference is closer to the imaging section than the boundary position, and selects the far point-side focus lens position when the lens position selection section has determined that the position of the object corresponding to the phase difference is farther from the imaging section than the boundary position,
• wherein the lens position selection section stores a first phase difference corresponding to the boundary position when the near point-side focus lens position is selected, and a second phase difference corresponding to the boundary position when the far point-side focus lens position is selected, and
• wherein the lens position selection section selects the far point-side focus lens position when the lens position selection section has determined that the phase difference calculated by the phase difference calculation section is larger than the first phase difference in a state in which the near point-side focus lens position is selected, and selects the near point-side focus lens position when the lens position selection section has determined that the phase difference calculated by the phase difference calculation section is smaller than the second phase difference in a state in which the far point-side focus lens position is selected.