Optical head for information reading and writing to optical disc

摘要

The optical head has an enclosure 14 inside of which is a laser diode 4 that has the output directed through a hologram grating 18. The beam passes through a collimating lens and onto a four-sided prism 28 having a polarising plane. The light is directed onto the surface of the disc. The signals reflected back from the tracks are split by the different interference zones of the hologram grating 18a-d to be received by the photo detectors 8a-d, 6a,b.