PROBLEM TO BE SOLVED: To perform external calibration between s camera and an object existing outside the field of view without imposing any constraint on the positional relationship among the center of the eyeball, the reference point and the camera center.SOLUTION: On the basis of an image captured by an imaging device, internal parameters of the imaging device, the radius of a corneal sphere obtained by regarding a cornea as a part of as sphere, three-dimensional coordinates of a plurality of reference points of a reference object and two-dimensional coordinates in the image of a primary reflection image of the plurality of reference points on the basis of the cornea included in the image, an image data processing device 1 estimates the position and posture relationship between the reference object located outside the visual field of the imaging device and the imaging device. The image data processing device 1 includes a corneal sphere coordinate estimating section 12 for estimating the center coordinate of the corneal sphere on the basis of the image, the internal parameters and the radius, and an external parameter estimator 13 for estimating an external parameter of the imaging device on the basis of the coordinate system of the reference object on the basis of the internal parameters, the three-dimensional coordinates of the plurality of reference points, the two-dimensional coordinates of the plurality of reference points and the central coordinate.SELECTED DRAWING: Figure 2
