Patent ID: 8576280

Claim:
An image measuring apparatus comprising: a strobe illumination unit that illuminates a measurement target object with light; an image pickup unit that picks up an image of the measurement target object; a movement mechanism that moves the image pickup unit, the measurement target object, or combinations thereof relative to each other; and a control unit that controls the strobe illumination unit, the image pickup unit, and the movement mechanism to measure the measurement target object on the basis of the image picked up by the image pickup unit, the control unit comprising: a focus position detector that detects a focus position of the image pickup unit by controlling the movement mechanism to change a positional relationship between the image pickup unit and the measurement target object along an optical axis of the image pickup unit at a predetermined movement velocity and by controlling the image pickup unit to pick up the image of the measurement target object at a plurality of relative positions, the focus position detector comprising: an illumination controlling section that controls brightness of illumination used for picking up the image of the measurement target object at the image pickup unit by controlling a time period of lighting the strobe illumination unit; a relative position acquiring section that acquires each of the relative positions at the center of the time period of the lighting; and a contrast detecting section that detects contrast of the image picked up by the image pickup unit, wherein, among the relative positions acquired by the relative position acquiring section, the focus position detector selectively detects one relative position that corresponds to an image that maximizes the contrast detected by the contrast detecting section as the focus position.