Pupil detection system, gaze detection system, pupil detection method, and pupil detection program

A pupil detection system comprising:

• a non-transitory computer-readable medium comprising at least one memory operable to store program instructions;
• and
• at least one processor operable to access the at least one memory and read and carry out the program instructions, the program instructions including:
• vector calculation instructions to cause the at least one processor to calculate a plurality of candidate vectors by a stereo method based on a first pupil image of a subject which is picked up by a first camera and a second pupil image of the subject which is picked up by a second camera, each of the plurality of candidate vectors connecting a corneal sphere center and a pupil center, the corneal sphere center being an intersection point between an axis passing through the first camera and a corneal reflection point obtained from the first pupil image and an axis passing through the second camera and a corneal reflection point obtained from the second pupil image;
• and
• determination instructions to cause the at least one processor to select, from among the plurality of candidate vectors, a candidate vector satisfying a vector condition in which an angle between the candidate vector and a reference line, which is set based on the pupil center and a lens center of at least one of the first camera and the second camera, is equal to or less than a predetermined threshold, and determine that the pupil is located at the pupil center corresponding to the candidate vector that is selected from the plurality of candidate vectors.