david@daisy.UUCP (David Schachter) (04/21/85)
Why is only one side of a compact disk used? Why not use most of both and
use the smallest possible part for the label? Crunch those multi-volume
releases down!
-- David Schachter
[generic disclaimer] {n.f.q}jayj@hpisla.UUCP (Jay Johannes) (04/25/85)
The reason only one side of the compact disk is used is because the laser reads from the bottom of the disk and the image of the 'pit or valley' is reflected off the disk. If both sides were 'reflectable', the laser couldn't read either side. /**********/ Close, but no cigar. True, the laser pickup is on the bottom, but so is the laser. The system is reflective, so it is irrelevent what is on the top of the disc, when reading the bottom. What laser videodiscs do is in fact to bond two single sided discs back to back to make a double sided disc. No reason why they couldnt do the same thing for CDs. I suspect the real reason is 1. They have to put the label someplace. 2. Most releases only require a single side, 3. There is increased tooling costs to make double sided discs. For a long time yield was very low on the video discs. One of the big problems was that concentricity would be out of spec on one side. I guess its hard to bond accurately.
man@bocar.UUCP (M Nevar) (04/25/85)
The reason only one side of the compact disk is used is because the laser reads from the bottom of the disk and the image of the 'pit or valley' is reflected off the disk. If both sides were 'reflectable', the laser couldn't read either side.
kg@amdahl.UUCP (Ken Greer) (04/30/85)
> > The reason only one side of the compact disk is used is because > the laser reads from the bottom of the disk and the image of the > 'pit or valley' is reflected off the disk. If both sides were > 'reflectable', the laser couldn't read either side. Then how come my Laser video disk player reads both sides? I think the real reason is to improve the yield. -- "I'd rather be rolfing" Ken Greer {amdahl,hplabs}!elan!kg
hunter@oakhill.UUCP (Hunter Scales) (05/02/85)
In article <1470@amdahl.UUCP> kg@amdahl.UUCP (Ken Greer) writes: >> >> The reason only one side of the compact disk is used is because >> the laser reads from the bottom of the disk and the image of the >> 'pit or valley' is reflected off the disk. If both sides were >> 'reflectable', the laser couldn't read either side. > >Then how come my Laser video disk player reads both sides? >I think the real reason is to improve the yield. >-- >"I'd rather be rolfing" > >Ken Greer >{amdahl,hplabs}!elan!kg I think it should be possible to manufacture double sided CDs. One way would be to simply attach two CDs back-to-back. I think the reason that CDs are single-sided is that, to play the other side, you would have to turn it over. One of the hassles of LPs that CD were trying to address was their inconvenience. Besides, CDs are long enough for most pop music. Classical music that needs tape length times (like Wagner) couldn't fit on even a double-sided CD. ps I'm sure a double-sided CD player that wouldn't require you to turn the disk could be made, but it wouldn't be cheap. -- Motorola Semiconductor Inc. Hunter Scales Austin, Texas {ihnp4,seismo,ctvax,gatech}!ut-sally!oakhill!hunter (I am responsible for me and my dog and no-one else)
ron@brl-tgr.ARPA (Ron Natalie <ron>) (05/03/85)
> long enough for most pop music. Classical music that needs tape length > times (like Wagner) couldn't fit on even a double-sided CD. > I don't know how your are recording your music, but a 10-1/2 reel on my deck only lasts 70 minutes. -Ron
ark@alice.UUCP (Andrew Koenig) (05/03/85)
The CD format is actually designed to allow two-sided discs to be made. However, at present that would require retooling of a sort that isn't likely to happen until the market becomes more saturated.
jm@tekig.UUCP (Jeff Mizener) (05/11/85)
> > The reason only one side of the compact disk is used is because > the laser reads from the bottom of the disk and the image of the > 'pit or valley' is reflected off the disk. If both sides were > 'reflectable', the laser couldn't read either side. Wrongo Audiophile Breath. (NB: That last sentence doesn't even make sense!!) There is no good reason not to use both sides of a CD for music (or whatever) except for the label. If the CDs were two sided, where would you print the label? The playing surface of current CDs is thin enough that two of them could be sandwiched together in the plastic "envelope" with no noticable increase in disk thickness. It is also possible that different information could be "stamped" on either side with no effect on quality.