LASER-DETECTOR-HOLOGRAM UNIT FOR THIN OPTICAL PICK-UP HEAD OF A CD-PLAYER

A laser-detector-hologram (LDH) unit having the size of 4.8 x 8.2 x 4. 3 mm for use as a thin optical pick-up head of a CD player has been su ccessfully developed, The technology to make the LDH unit thin and sma ll is based upon the following techniques: 1) an efficient optical com bination of a low operating current laser diode and a 45 degrees built -in micromirror which is formed on a Si photodetector substrate, 2) a thin plastic-molded flat package with good thermal dissipation, and 3) a plastic-molded holographic optical element (HOE) as a cap. The pick -up head with the LDH unit has shown good optical performance, which i s sufficient for the application to CD players.