kbwalker@violet.berkeley.edu (Kevin Baranski-Walker) (12/01/86)
What would it take to hack an audio CD to function as a CD-ROM? All of the literature that I have found hint that this may be possible but stop short of the particulars. Would a three laser drive be neccessary in lieu of a single laser (or preferred)? Many of the CD's are signifigantly in- expensive that even with the addition of an SBC the total cost would still be much less than the commercial CD-ROM drives available.
ben@catnip.UUCP (12/15/86)
In article <1787@jade.BERKELEY.EDU> kbwalker@violet.berkeley.edu(Kevin Baranski-Walker) writes: >What would it take to hack an audio CD to function as a CD-ROM? > >All of the literature that I have found hint that this may be possible but >stop short of the particulars. Would a three laser drive be neccessary in lieu >of a single laser (or preferred)? Many of the CD's are signifigantly in- >expensive that even with the addition of an SBC the total cost would still >be much less than the commercial CD-ROM drives available. I am not familiar with CD ROM drives, but I can tell you that there is no such thing as a three laser audio CD player. What you are probably thinking of is a 'three beam' player. In a three beam player the laser light is split into three beams using a diffraction grating. The main beam is used to read the data, while the two auxiliary beams are aimed half on- half off the pits of the adjacent tracks. Two photodetectors compare the light from the aux beams; when one gets darker than the other, the player knows that the pickup has drifted and makes an appropriate correction. Single beam units have to derive the same information by looking at the at the reflected light from the main beam. I expect that the three beam method would probably be prefered for CD ROMS, since it seems to be more forgiving of damaged disks (particularly eccentric disks) in audio applications. -- Ben Broder {ihnp4,decvax} !hjuxa!catnip!ben {houxm,clyde}/