Proxy Peter

• The most important division of an optical disc drive is an optical path, placed in a pickup head (PUH), frequently consisting of semiconductor laser, a lense for guiding the laser beam, and photodiodes detecting the light reflection from disc's surface.

Double-layered writable broadcasting have: a first polycarbonate layer with a (shallow) groove, a first data layer, a Cassette to CD Recorder semi-reflective layer, a second (spacer) polycarbonate layer with another (deep) groove, and a second data layer. The first groove spiral habitually starts on the inner edge and extends outerwards, while the second groove starts on the outer edge and extends inwards.