"Ian Field" wrote in message
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"Arfa Daily" wrote in message
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"Ian Field" wrote in message
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"Arfa Daily" wrote in message
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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