"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...


"Ian Field" wrote in message
...


"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

"Arfa Daily" wrote in message
...


"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...


"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...


"Phil Allison" wrote in message
...

"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.

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.

Now that, I couldn't tell you, I'm afraid. Actual pin numbers or type of the
device tend not to be shown on schematics. Sometimes, the optical block is
shown just as a block, with no indication of what's in it at all. About the
only thing that I can say is that there is usually a photodiode in the
package as well as the laser diode(s). This is used as part of the auto
power control feedback loop. As to whether there are two photodiodes in dual
laser devices, I really don't know. If I get time, I'll have a look on a few
DVD schematics and see if any of them show electrically what the optical
block comprises.

Arfa

"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...


"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...


"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...


"Phil Allison" wrote in message
...

"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.

"tm" wrote in message
...

"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...


"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...


"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...


"Phil Allison" wrote in message
...

"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.

"Arfa Daily" wrote in message
...

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.

Now that, I couldn't tell you, I'm afraid. Actual pin numbers or type of
the device tend not to be shown on schematics. Sometimes, the optical
block is shown just as a block, with no indication of what's in it at all.
About the only thing that I can say is that there is usually a photodiode
in the package as well as the laser diode(s).

Must admit I didn't pay much attention as I tore the flexiprint off the side
of the sled and put the laser in a snuff tin for safe keeping - but I think
it only had 3 leads.

Assuming it has a PD; the 2 lasers would then have to be inverse parallel to
conserve pins?

"Arfa Daily" wrote in message
...

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.

Now that, I couldn't tell you, I'm afraid. Actual pin numbers or type of
the device tend not to be shown on schematics. Sometimes, the optical
block is shown just as a block, with no indication of what's in it at all.
About the only thing that I can say is that there is usually a photodiode
in the package as well as the laser diode(s). This is used as part of the
auto power control feedback loop. As to whether there are two photodiodes
in dual laser devices, I really don't know. If I get time, I'll have a
look on a few DVD schematics and see if any of them show electrically what
the optical block comprises.

Arfa


Had a proper look - it has got 4 pins.

"Ian Field" wrote in message
...


"Arfa Daily" wrote in message
...

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.

Now that, I couldn't tell you, I'm afraid. Actual pin numbers or type of
the device tend not to be shown on schematics. Sometimes, the optical
block is shown just as a block, with no indication of what's in it at
all. About the only thing that I can say is that there is usually a
photodiode in the package as well as the laser diode(s). This is used as
part of the auto power control feedback loop. As to whether there are two
photodiodes in dual laser devices, I really don't know. If I get time,
I'll have a look on a few DVD schematics and see if any of them show
electrically what the optical block comprises.

Arfa


Had a proper look - it has got 4 pins.


I just had a look at a schematic set for a Sony home cinema unit. Although
it only shows the optical block *as* a block, all of the connections to it
are nicely labeled. There is one marked "DVD laser diode", one marked "CD
laser diode", and just one marked "PD", which is the feedback photodiode, so
it looks like just the one is used to monitor both laser diodes. So I would
guess that your four connections are the three as detailed, plus a common
ground.

Arfa