Line-of-sight measurement device, line-of-sight measurement method and line-of-sight measurement program

A line-of-sight measurement method involving a user who gazes mainly in the distance, the user having a left eyeball and a right eyeball, the method comprising:

• calculating with a computing device having a processor optical axes of left and right eyeballs of the user when at least two points at a distance of at least eight meters away are being gazed at by the user;
• calculating with the computing device a discrepancy between the optical axis of the left eyeball and a visual axis of the left eyeball, and calculating a discrepancy between the optical axis of the right eyeball and a visual axis of the right eyeball, under a constraint that visual axes of both left and right eyeballs are parallel when the distance is being gazed at;
• and
• calculating with the computing device a gaze point of said user based on at least one of the discrepancies;
• wherein calculating optical axes comprises acquiring an eyeball image including an image of an eyeball as the user gazes into the distance, and calculating an optical axis which connects a corneal curvature center or an eyeball rotation center and a pupil center of a pupil from said eyeball image.

A line-of-sight measurement device comprising:

• a CPU;
• at least one program storage hardware component in operable communication with the CPU and storing at least a portion of a line-of-sight measurement program, the line-of-sight measurement program upon execution by the CPU performing a method that includes calculating an optical axis of each of a user's left and right eyeballs when the user is gazing at two or more points which are at a distance at least eight meters away from the user, calculating a left discrepancy between the optical axis of the left eyeball and a visual axis of the left eyeball, calculating a right discrepancy between the optical axis of right eyeball and a visual axis of the right eyeball, said calculations occurring under a constraint that visual axes of the left and right eyeballs are parallel when gazing at a distant point, and calculating a gaze point of said user based on at least one discrepancy between an optical axis and visual axis;
• at least two cameras, each camera disposed at a different position, each camera position acquisition of eyeball images of both left and right eyeballs;
• and
• at least two light sources, each light source disposed at a different position so that reflected light source images are separated from each other.