Patent ID: 6335809
Filing Date: 2002-01-01
Classification: G02B,G11B

Abstract:
An optical pickup, comprising:a diffraction element for dividing a laser beam from a laser device into a main beam, a +1-order sub-beam and a âˆ’1-order sub-beam; a lens for converging the main beam, the +1-order sub-beam and the âˆ’1-order sub-beam onto a disk; a hologram unit divided into two of a first pattern and a second pattern to respectively diffract the main beam, the +1-order sub-beam, and the âˆ’1-order sub-beam reflected from said disk; and a photodetector including a first portion, a second portion, and a third portion to receive the main beam, the +1-order sub-beam and the âˆ’1-order sub-beam respectively diffracted by said first pattern and said second pattern; wherein said first pattern is made to minimize the spot of the +1-order sub-beam converging onto said first portion based on an optical path length and a wavelength when the +1-order sub-beam is taken as a light source, and said second pattern is made to minimize the spot of the âˆ’1-order sub-beam converging onto said second portion based on an optical path length and a wavelength when the âˆ’1-order sub-beam is taken as a light source.