Patent ID: 6744720
Filing Date: 2004-06-01
Classification: G11B

Abstract:
An optical element comprising:a first prism having a first refractive index and including a first incidence surface, a first emission surface forming a first angle with the first incidence surface, and a first reflection surface facing the first incidence surface and forming a second angle with the first emission surface; a second prism having a second refractive index and including a second incidence surface in contact with the first emission surface, and a second emission surface facing the second incidence surface; a third prism having the second refractive index and including a third incidence surface in contact with the second emission surface, a first incidence-emission surface forming a fourth angle with the third incidence surface, and a third emission surface forming a fifth angle with the third incidence surface; a film between the second emission surface and the third incidence surface and cooperating with the second emission surface and the third incidence surface to emit the light beam striking the third incidence surface from the second emission surface as a first emitted light beam through the first incidence-emission surface, and to emit a second incident light beam striking the third incidence surface from the first incidence-emission surface as a second emitted light beam through the third emission surface; and wherein the first prism shapes a first incident light beam with a wavelength striking the first incidence surface at an incident angle, and makes the light beam reflected at the first reflection surface parallel to the optical axis of the second prism and strike the second incidence surface, and wherein the first emission surface and the second incidence surface are defined so as to cancel a change of an optical axis caused by a variation of the wavelength of the light beam.