Patent ID: 7502153

Claim:
An image display apparatus worn on a head of a user, comprising: a display that operates either in a first state in which the display displays an image with a first light and a second state in which the display displays an image with a second light having a different wavelength from the first light; a first holographic optical element that directs the first light from the display to an eye of the user so that a first virtual image of the image represented by the first light is presented at a first distance from the eye of the user, the first holographic optical element transmitting light from an outside world to the eye of the user; a second holographic optical element that directs the second light from the display to the eye of the user so that a second virtual image of the image represented by the second light is presented at a second distance from the eye of the user, the second holographic optical element transmitting light from the outside world to the eye of the user; a detector that detects an inclination of the user's head; and a controller that switches the display between the first and second states according to the inclination of the user's head detected by the detector to provide one of the first and second virtual images with a corresponding dioptric power.