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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: sci.electronics,comp.dsp
Subject: Re: A question about the Nyquist theorm
Message-ID: <18449@milton.u.washington.edu>
Date: 15 Mar 91 05:28:45 GMT
References: <wilf.667759065@rigel.sce.carleton.ca> <1180@aviary.Stars.Reston.Unisys.COM> <504@dcsun21.dataco.UUCP>
Organization: University of Washington, Seattle
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In article <504@dcsun21.dataco.UUCP> mcphail@dcsun18.UUCP (Alex McPhail,DC ) writes:
>In article <1180@aviary.Stars.Reston.Unisys.COM> gaby@Stars.Reston.Unisys.COM (Jim Gaby - UNISYS) writes:
>>>jbuck@galileo.berkeley.edu (Joe Buck) writes:
>>... if the CD had a higher density (say 8 times) the laser can read 
>>it at this resolution (i.e. you could put 8 time the music on one
>>CD).
>
>Actually, this is not true.  You can not increase the density of information
>on a compact disk without changing the technology. 
> ...  If you attempt to compress the
>data using closer seperation, the optical interference patterns will produce
>intolerable noise

	There are no semiconductor lasers available that can do the
readout task at higher resolution, BUT a frequency-doubling or -tripling
scheme can conceivably be employed.  IBM has shown an 80%-efficient
doubler on a semiconductor laser.  If made commercial in a CD or
similar optical disk, such a frequency-doubling would (in theory)
allow a quadrupling of disk capacity.


I am known for my brilliance,                  John Whitmore
 by those who do not know me well.