Patent ID: 7336878
Filing Date: 2008-02-26
Classification: G02B

Abstract:
1. A planar optical device characterized in that an optical element for changing an optical path and an optical element for selecting an optical path are provided in this order from an incident light introduction side in a direction of a thickness of the optical device, a transparent medium is provided in the optical device, and when an incident light is introduced like a plane into the optical element for changing an optical path, at least a part of the incident light thus introduced is introduced into the optical element for selecting an optical path and the substantially whole incident light thus introduced is reflected through a Total Internal Reflection (TIR) by an interface of layers constituting the optical device, wherein the incident light is totally reflected through the TIR by the interface of layers when the incident light has a greater angle component than a total reflecting critical angle, and wherein the optical element for changing an optical path includes and forward outputs a light having an angle θt to satisfy at least a condition of sin θt>nw/nt, in which nt represents a mean refractive index of the optical element for changing an optical path, nw represents a refractive index of a medium on a forward side of a total reflecting interface in a front part of the optical path, and θt represents an angle of a light advancing in a medium of the optical element for changing an optical path.