Patent ID: 7446768

Claim:
An image display apparatus that displays a virtual image on a display screen according to an attitude of a user observing the display screen, the image display apparatus comprising: an attitude sensor that outputs an attitude measurement including an angle of inclination component and an angle of direction component; a conversion unit adapted to convert the attitude measurement from said attitude sensor into an attitude of a user in a reference coordinate system, by using correction information; a display unit adapted to combine a virtual image generated based on the attitude of the user and an image of real space, and display the combined image on the display screen; a calculation unit adapted to calculate the attitude of the user based on a predetermined angle of direction and the angle of inclination component of the attitude measurement and without the angle of direction component of the attitude measurement; an instruction input unit adapted to receive a user's instruction which indicates that the user confirmed that the virtual image and the image of real space are in the correct positional relationship; a calibration unit adapted to calibrate information relating to an angle of direction in the correction information based on the predetermined angle of direction and the angle of direction component of the attitude measurement from said attitude sensor when the user's instruction is received by said user instruction input unit so as to calibrate the attitude sensor; and a mode setting unit adapted to set one of a plurality of modes, the modes including a normal mode and a correction information calculation mode, wherein in the normal mode the virtual image is generated in accordance with the attitude of the user converted by said conversion unit, and wherein in the correction information calculation mode, the virtual image is generated in accordance with the attitude of the user calculated by said calculation unit, and the calibration unit calibrates the information relating to the angle of direction in the correction information so as to calibrate the attitude sensor.