Apparatus for measuring three-dimensional position of target object

A position measuring apparatus for measuring a three-dimensional position from a reference plane, the position measuring apparatus comprising:

• an image obtaining unit configured to obtain first and second images captured by respective first and second cameras from different viewpoints of the first and second cameras, the first and second images containing a common imaging region;
• a storage unit configured to store:
• a first camera parameter that represents a relationship between a first imaging plane included in the first image and each of first and second common planes based on a camera model;
• and
• a second camera parameter that represents a relationship between a second imaging plane included in the second image and each of the first and second common planes based on the camera model,
• the camera model describing nonlinear map relationships from each of first and second imaging planes to the first and second common planes, the first and second common planes being respectively set to have different positions relative to the reference plane in a depth direction of a world coordinate system;
• a correspondence detector configured to detect, from the respective first and second imaging planes of the first and second images, first and second corresponding points on the respective first and second imaging planes, the first and second corresponding points being estimated to represent a common three-dimensional position;
• a projected-point calculator configured to calculate, based on the first and second camera parameters stored in the storage unit, first to fourth projected points,
• the first projected point representing a projected point of the first corresponding point on the first common plane,
• the second projected point representing a projected point of the first corresponding point on the second common plane,
• the third projected point representing a projected point of the second corresponding point on the first common plane,
• the fourth projected point representing a projected point of the second corresponding point on the second common plane;
• and
• a restored-point calculator configured to calculate:
• a line connecting the first projected point on the first common plane and the second projected point on the second common plane as a first beam;
• a line connecting the third projected point on the first common plane and the fourth projected point on the second common plane as a second beam;
• and
• a point having a minimum square distance relative to each of the first and second beams as a restored point, the restored point representing the three-dimensional position of the first and second corresponding points.