OPTICAL PICK UP AND OPTICAL DISC DEVICE

摘要

An optical pickup is provided with a light source (1d) for irradiating an optical disc (4) with light; a lens (3) for focusing the light on the optical disc (4); a photodetector (1c) provided with a plurality of detecting regions (1cf, 1ct) which detect light reflected by a signal plane of the optical disc (4) and convert the detected light into an electric signal; a hologram element (1a) having a hologram region (1b) for guiding the reflected light to the photodetector (1c); and a light blocking plate (2) which blocks at least a part of the light that passes through a region other than the hologram region (1b) in the hologram element (1a). The light blocking plate (2) is provided with a light blocking section (2b) for blocking light and an opening section (2a) which can transmit light. The opening section (2b) exists on a region including the hologram region (1b) on an upper plane of the hologram element (1a), and a center position of the opening section (2b) is shifted from a center position of the hologram region (1b).