Patent ID: 8305296

Claim:
A head-mounted type image display device comprising a hexahedron prism, in the hexahedron prism, a first optical surface and a second optical surface opposed to each other are approximately parallel; inner angles θ between each of a third optical surface and a fourth optical surface that are opposed to each other and the first optical surface are equal; and a fifth optical surface and a sixth optical surface opposed to each other are configured to be inclined toward each other and the distance therebetween becomes narrow from the third optical surface to the fourth optical surface, wherein a light beam from an image display element enters through a first partial optical surface, which is a part of the first optical surface, into the hexahedron prism, reflects off the third optical surface first, then off the first optical surface, the second optical surface, the first optical surface and the fourth optical surface, in that order, and exits through a second partial optical surface, which is another part of the first optical surface, in a direction of an eye pupil of a user, thereby projecting an image.