Patent ID: 7533989

Claim:
A line-of-sight detection method of a subject using: a first camera for measuring the position of a pupil relative to a coordinate system; a second camera having a light source arranged at a known position in the coordinate system and forming a corneal reflection center to obtain data of a size of vector r from the corneal reflection center to a pupil center and an angle φ of the vector r relative to a coordinate axis of the coordinate system; and a calculation means for calculating the line-of-sight direction for executing steps below based on information from each of the cameras, comprises the stages of: determining a relational formula, including the steps of: obtaining data on a coordinate point O of the position of a pupil of a subject with the first camera by making the subject gaze at a known point G in the coordinate system; obtaining, in the state of the subject, data of the corneal reflection center, a size of vector r from the reflection center to a pupil center P, and an inclination φ of the vector r relative to the coordinate axis with the second camera; calculating an angle θ between a line connecting a reference position of the second camera and the pupil center and a line-of-sight of the subject by the calculation means; and calculating a formula θ=f(r*) showing a relationship between r* related to r and θ based on the measured values and calculated value; and determining a line-of-sight, including the steps of: obtaining data on a coordinate point O′ of the pupil position of the subject with the first camera by making the subject gaze at an unknown point G′ in the coordinate system; obtaining data of the corneal reflection center, a size of vector r′ from the reflection center to the pupil center P, and an inclination φ′ of the vector r′ relative to the coordinate axis with the second camera; and calculating θ=f(r*′) by using the relational formula to obtain the unknown point G′ from the inclination φ′ and θ′.