wrote in message
oups.com...
I believe a dvd laser can in fact read a cd.. I know a lot of early dvd
players had two lasers to save wear on the more costly dvd laser (and
they do wear out with time), but I thought most modern players used
only a red laser for all media.

It was my understanding that the IR laser in a cd player is just too
"fat" in terms of wavelength to resolve the tin


It's the reverse. Older players which had the red lasers were able to read
factory cd's with a reduced level of efficiency.
They could not read CD-R's because the discs were essentially "invisible" to
the red laser. Some older red-laser players, like Sony's could read CD-RW's
but not CD-R's. Others would not, but that was a firmware issue.
Newer players don't use two separate lasers - they use a special "double"
laser diode, which emits from one side or the other depending on how it's
biased; that is, for an audio cd or CD-R, or a DVD. Ocassionally, one will
malfuction in such a way that DVD's can't be read anymore, but cd's can.

Mark Z.