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"Phil Allison" wrote in message
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"William Sommer****** is a ****ing Ass"

Is a DVD laser orange/amber?

It's (supposedly) red. But there would be nothing wrong
using a shorter wavelength.

Utter bull****.

Wavelength is critical to reading the data from a pressed disk.

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a ****ing MORON and NUT CASE.

FYI

the pit depth on pressed disks is half a wavelength in each case.

DVD players have both IR and red lasers.



.... Phil

Indeed, Phil. And as I said in my reply to William, Blu Ray players
have a blue one as well ...

Since I almost never find CD/DVD lasers with any kind of part number,
I pretty much skated over the few assorted datasheets I'd found.

I sort of only half-noticed that some of them are dual lasers.

There is an obvious danger - I could be mucking about with a DVD
laser trying to get some light out of it, unaware that the IR section
is happily lasing away!


All DVD lasers are dual, even though they have a single lens. The
actual laser diode 'pellet' fixed into the optical block, has both
visible red and infra red devices contained within, and firing out of
the same window into the optical block. The power output of these
lasers is generally accepted as being 'eye safe', although I would
still not recommend staring into the lens on the optical axis. The
general advice is to look at the lens from an oblique angle, and this
is considered to be 100% safe. As to seeing whether the CD laser is
burning, they tend to generate enough visible red light to see, if you
shade the lens with your hand. It's clearly visible even in a brightly
lit workshop. The DVD laser burns brightly enough to be able to see
the spot perfectly clearly through the disc.

The DVD player I rescued from the bins was very basic, and certainly
not a recorder - I have no information as to whether or not it could
also play CDs.

Does such thing exist as a single DVD only laser?


Not that I've ever seen. All domestic DVD players play CDs as well. The
initial assumption seems to be that a DVD has been inserted, and it is
the visible red laser that's turned on first. When the player determines
that it is not reading anything that makes sense as being DVD data - and
based on Phil's description of the quarter-wave-deep pits, it's probably
just garbage that is being picked up anyway - then it tries again with
the IR laser turned on. This is why when you put a CD in a DVD player,
it takes that much longer for it start reading the TOC.

Arfa

Thanks. Do the TO18 style cases have standardised pinout? The laser is
pressed into a block of aluminium, I don't want to risk trying to pry it
out, and even if I did - any type number would end up obliterated.

Look he

http://repairfaq.ece.drexel.edu/sam/laserdio.htm#diotoc

Everything you could ever want to know about laser diodes.

Thanks.