Distance measurement apparatus and distance measurement method

A distance measurement method which is used by a distance measurement apparatus including:

• an imaging element that includes photoelectric conversion elements arranged in rows and columns, and images an object by performing exposure and readout of electric charges sequentially for each of the rows or each of the columns;
• and
• an optical system that is for forming an image of the object on the imaging element and has an in-focus position that is controllable,
• the distance measurement method comprising:
• (i) controlling the optical system to cause the in-focus position to move at constant speed and (ii) causing the imaging element to image the object sequentially while the in-focus position is being moved at the constant speed, to obtain a plurality of blurred images;
• measuring a distance from a reference position in the optical system to the object using the plurality of blurred images and a point spread function dependent on object distance;
• and
• performing, before or after the measurement of the distance in the measuring, a correction process on the distance for each of the rows or each of the columns according to a movement range of the in-focus position in which the in-focus position is moved during the exposure for the each of the rows or the each of the columns when the plurality of blurred images are obtained.