Path: utzoo!utgpu!water!watmath!clyde!att!mtunx!rutgers!gatech!ncsuvx!ece-csc!ncrcae!ncr-sd!rb-dc1!severino From: severino@rb-dc1.UUCP (Cunnu the Sardinian) Newsgroups: sci.electronics Subject: Re: CD Player Questions Summary: 3-beam or 1-beam lasers Message-ID: <206@rb-dc1.UUCP> Date: 7 Jun 88 16:46:55 GMT References: <3385@ncrcae.Columbia.NCR.COM> <3608@briar.Philips.Com> Reply-To: severino@rb-dc1.SanDiego.NCR.COM (Cunnu the Sardinian) Distribution: na Organization: Gould CSD, San Diego Lines: 25 In article <3608@briar.Philips.Com> drg@philabs.Philips.Com (Don Gentner) writes: >As far as I know, all CD players have only one laser. In 3-beam players, >the laser beam is split into 3 beam before reflecting off the disc. In single- >beam players, the beam is split after reflecting off the disc. In either >case one signal is used for data and the other two beams are used for >tracking and focus correction. Both systems work, but the single beam system >has the advantage of simpler design and fewer parts to get out of alignment. >I don't know of any advantage of a 3-beam system, except "ad hype" >-- How do you manage to correct the tracking and focusing with 1 laser beam?? It would seem that if you split the laser AFTER it reflects off the disc you are carrying much less critical info for correcting purposes... Andrea Severino, GOULD-CSD (San Diego Division) (619)485-0910 xt. 272 ______________________________________________________________________________ UUCP : {gould|mycroft|ncr-sd|gould9}!rb-dc1!severino UUCP : {noscvax|hp-sdd|sdcsvax|ihnp4}!{gould9|ncr-sd}!rb-dc1!severino ARPA : gould9!rb-dc1!severino@nosc.ARPA BITNET: ihnp4!gould9!rb-dc1!severino@psuvax1.BITNET CSNET : hp-sdd!gould9!rb-dc1!severino@hplabs.CSNET USmail: 15378 Avenue of Science, San Diego CA 92128-3407 USA ------------------------------------------------------------------------------ "Any association with me or my company is purely coincidental"