Half a croissant, on a plate, with a sign in front of it saying '50c'
h a l f b a k e r y
This is what happens when one confuses "random" with "profound."

idea: add, search, annotate, link, view, overview, recent, by name, random

meta: news, help, about, links, report a problem

account: browse anonymously, or get an account and write.



Laser scanned CD

Hold the disk still, and move the laser beam
  (+2, -1)
(+2, -1)
  [vote for,

In reading the Compact disks (and DVDs, and blu-rays too) the disk moves while the laser beam stays (comparatively) still. At the time the compact disk was introduced, this was the only thing possible from mechanical and optical considerations.

However, the advances in technology have made other arrangements possible. There are advantages to be gained in holding the disk still, and moving the laser beam, by the use of scanning mirrors, to follow the circular data track. Since the mirrors used for deflecting the laser beam do not have to be removed, they can be engineered to move fast. So reading speeds will not be limited by the maximum rotatinal speed of the disk.

The disadvantage is the need for long - throw optics, ie, the laser and the surface of the disk are at a comparatively long distance. This will necessiate higher quality optical components in order to maintain focus across the travel of the beam. But since the disk is being held still there are no rotational components of defocusing as with a rotating disk.

And the track need not be circular any longer - the LSCD drive will need to read the traditionally recorded disks and so will need to scan such disks in the traditional manner. But in making a fresh recording, on a virgin disk, any convoluted non-crossing space-filling pattern can be used. It will be able to record on a scrap of CDR of any shape.

Perhaps this will bring back the ye olden golden years of yore when messages were exchanged in microdots under the postage stamps stuck on to otherwise inocuous letters.

neelandan, Sep 16 2005

Similar? Laser_20Phonograph
[Dub, Sep 16 2005]

DLP - Guided mirror http://www.spgv.com/columns/dlp.html
[Dub, Sep 17 2005]


       While I like the idea of a square CD, I think it is still less sound than having the cheap thing spin.
DrCurry, Sep 16 2005

       Looks redundant with 'fixed CD' above. I'll delete this presently and add the (new) stuff as an annotation there.
neelandan, Sep 16 2005

       In fact my bro wished for this a while ago, I'd forgotten all about it. His version was a scanner in the ceiling which 'located' the disk (very shiny thing on a table), read all of the data into memory (quite do-able AFAICS with some clever optics), and then played the thing from memory. Kinda redundant now coz you just stick it all in a big server under the stairs, I guess.   

       However, I love the idea that you just throw a CD on the table and it just plays. Big stack of buns in Jewel cases from me.   

       He also considered the same unit being able to scan your old vinyl too... I don't know if anyone's done this yet?   

       (Seems to be several HB'd like this though)
Dub, Sep 16 2005

       It would have to spin the laser really fast.
DesertFox, Sep 16 2005

       Erm, mirrors? I saw something somewhere about itsy-bitsy mirrors controlled by even more itsy-bitsy servos (DLP - I'm sure I've seen this ref'd elsewhere on HB too)
Dub, Sep 17 2005

       You beat me to it. I think two mirrors, revolving at a set rate, should fix any problems here.
Worldgineer, Sep 17 2005

       [World] I have a sneaking suspicion that you used a similar link before...
Dub, Sep 17 2005


back: main index

business  computer  culture  fashion  food  halfbakery  home  other  product  public  science  sport  vehicle