Patent ID: 7859977
Filing Date: 2010-12-28
Classification: G02B,G11B

Abstract:
1. An optical pick-up apparatus comprising: a plurality of light sources including a first light source for emitting light at a first wavelength and a second light source for emitting light at a second other wavelength; at least one beam combiner for transmitting the light emitted from each light source in the plurality of light sources along a common optical path in a first direction parallel to a first axis; a reflector for redirecting the light transmitted in the first direction in a second direction, the second direction parallel to a second axis substantially perpendicular to the first axis, the reflector including a coating for providing substantially quarter-wave retardation at the first and second wavelengths at a predetermined angle of incidence; an objective lens for focusing the light redirected by the reflector onto an optical disc; and at least one photo-detector for detecting light reflected from the optical disc, wherein the at least one beam combiner and the reflector are disposed along the first axis, wherein the light transmitted in the first direction from the at least one beam combiner includes linearly polarized light having its electric field vector substantially perpendicular to the first axis and at an oblique angle to the second axis, and wherein the coating includes a first plurality of alternating layers of isotropic materials having contrasting refractive indices, a thickness and refractive index of each layer in the first plurality selected such that the coating functions as a C-plate at the first and second wavelengths.