Patent ID: 8072867
Filing Date: 2011-12-06
Classification: G02B,G11B

Abstract:
1. An optical pickup comprising: a laser source for emitting a laser beam to an optical disc; a hologram element provided on an optical axis of the laser beam and having a hologram section provided on a specific area of the hologram element, the hologram section diffracting a return beam reflected by the optical disc; and a photo receptor for receiving the return beam diffracted by the hologram element, wherein the specific area of the hologram element has an x-y plane having a center coordinate point (0, 0), an x-axis that is a first line passing the center coordinate point (0, 0), and a y-axis that is a second line passing the center coordinate point (0, 0) and crossing the first line, and the specific area has a first hologram region, a second hologram region, a third hologram region, a fourth hologram region, a fifth hologram region, and a sixth hologram region on the x-y plane, in which the first hologram region is divided from the second to sixth hologram regions by a first split line that is the first line and a second split line that connects coordinate points (−xa, 0) and (−xb, yb) on the x-y plane, the second hologram region is divided from the first, third, fourth, fifth, and sixth hologram regions by the first and second split lines and a third split line that connects coordinate points (xa, 0) and (xb, yb) on the x-y plane, the third hologram region is divided from the first, second, fourth, fifth, and sixth hologram regions by the first and third split lines on the x-y plane, the fourth hologram region is divided from the first, second, third, fifth, and sixth hologram regions by the first split line and a fourth split line that connects the coordinate point (xa, 0) and a coordinate point (xb, yb) on the x-y plane, the fifth hologram region is divided from the first, second, third, fourth, and sixth hologram regions by the first and fourth split lines and a fifth split line that connects the coordinate point (−xa, 0) and a coordinate point (−xb, −yb) on the x-y plane, and the sixth hologram region is divided from the first, second, third, fourth, and fifth hologram regions by the first and fifth split lines on the x-y plane, in which xa and xb, and −xa and −xb satisfy relations xa<xb and −xb<−xa, respectively, and the second and fifth hologram regions are applied with astigmatism at a first specific angle to the second line and the first, third, fourth, and sixth hologram regions are applied with astigmatism at a second specific angle different from the first specific angle to the second line.