Patent ID: 8638483
Filing Date: 2014-01-28
Classification: G02B,G02C,H04N

Abstract:
1. An image display device comprising: a display element that displays an image; and an eyepiece optical system that guides image light from the display element to an observer's pupil via a prism; and in parallel with which, guides external light to the observer's pupil via the prism; wherein the eyepiece optical system includes, in the prism, three or more reflection surfaces for bending an optical path of the image light from the display element three or more times; a holographic diffraction optical element is formed on at least one surface of the reflection surfaces; the prism includes: a first reflection surface and a second reflection surface that face each other; and a third reflection surface on which the holographic diffraction optical element is formed; the first reflection surface, the second reflection surface and the third reflection surface each reflect the image light at least one time; the holographic diffraction optical element has optical power; and the image display device meets the following condition formulas (1) and (2): where H: a length of a straight line that connects both ends of an incident region, for the image light, of the reflection surface where the holographic diffraction optical element is formed in a plane that contains a screen-center principal ray;