Optical pickup for use with a recording medium

摘要

An optical pickup is provided which includes a light source and an objective lens for converging incident light from the light source onto a recording medium. The objective lens is arranged to be movable in radial and vertical directions of the recording medium. A holographic optical element (HOE) for changing a traveling path of the incident light is positioned along an optical path between the light source and the recording medium, and has first and second diffraction plates which are divided along a first boundary line and have different diffraction patterns. A photodetector has first and second divided plates which are divided along a second boundary line which is perpendicular to the radial and vertical directions of the recording medium. The first and second divided plates receive light passed through the first and second diffraction plates after being reflected from the recording medium. The first boundary line of the HOE is arranged at a predetermined angle with respect to the radial direction of the recording medium, such that the amount of light received by the first and second divided plates is equal to each other when the center of the objective lens is properly located on the optical path, and amount of light received by the first and second divided plates is different from each other when the center of the objective lens is deviated from the optical path.