Foreground region extraction device

A foreground region extraction device, comprising:

• an imaging device that images a three-dimensional space;
• a processor;
• and
• a detector,
• wherein the processor acquires:
• a first image of a first region inside the three-dimensional space, the first region being imaged from a first position at a first time by the imaging device;
• a second image of a second region inside the three-dimensional space, the second region being imaged from a second position at a second time by the imaging device, the second time being different from the first time;
• and
• first distance information including information relating to a plurality of first distances at the first time measured by a length measuring device,
• each of the first distances are a distance between the length measuring device and a position of a plurality of points included in a third region inside the three-dimensional space,
• the first region, the second region, and the third region include a third position inside the three-dimensional space, the third position being different from the first position and the second position,
• the processor calculates a first feature based on the first image, the first feature corresponding to a first projection position of the third position projected onto the first image,
• the processor calculates a second feature based on the second image, the second feature corresponding to a second projection position of the third position projected onto the second image,
• the first projection position is determined based on the first distance information and a relative arrangement of the length measuring device and the imaging device,
• the second projection position is determined based on the first distance information, the relative arrangement of the length measuring device and the imaging device, and a relative arrangement of the first position and the second position, and
• the detector sets the third position to be included in a background region including a moving body moving inside the three-dimensional space when a difference between the first feature and the second feature is larger than a prescribed value, and sets the third position to be included in a foreground region not including the moving body when the difference is not more than the prescribed value.