Is a DVD laser orange/amber?

Someone tossed an old DVD player in the bins at the flats, so I decided to
investigate its salvage potential, the laser is a proper-job TO18 style
pressed into a block of aluminium - seems a bit extravegant since it was
only a player, not a recorder.

There's some websites out there demonstrating lighting matches & burning
holes through paper with a DVD laser, but I presume they're using a recorder
laser for that much power.

Before I start waving the soldering iron at it - can anyone suggest a
"ball-park figure" for laseing current?

Thanks.

Is a DVD laser orange/amber?

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

"William Sommerwerck" wrote in message
...
Is a DVD laser orange/amber?

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


Someone on ABSE once told me the wavelength, when I looked it up on a chart
it came out as amber-ish or thereabouts.

Apparently the IR long wavelength is the limiting factor for data density on
a CD - I'd expect somewhere more in the general direction of orange than
visible red for DVD, but as yet I've never fired up a DVD or CD laser.

This is the first optical drive laser I've recued that actually had proper
encapsulation.

This article says the DVD wavelength is 650nm, and calls it "red".

http://en.wikipedia.org/wiki/Optical_disc_drive

However, I find that a bit on the short side for red.

"William Sommerwerck" wrote in message
...
This article says the DVD wavelength is 650nm, and calls it "red".

http://en.wikipedia.org/wiki/Optical_disc_drive

However, I find that a bit on the short side for red.


A 'standard' consumer DVD laser is bright red at around 650 nm wavelength. I
have never seen one tending towards amber, or indeed any shade of yellow. A
CD laser is infra red at around 780 nm wavelength. On the other hand, the
laser fitted to a Blu Ray DVD player is just that - blue - and has a much
shorter wavelength at just over 400 nm. The reason for each wavelength
becoming shorter as you go from CD to Blu ray, is that each disc type packs
more data on its playing surface(s) and it does this by using ever smaller
pits and lands. In order to resolve these, shorter and shorter wavelength
lasers are required ...

Arfa

On 1/10/2013 1:41 PM, Ian Field wrote:
Is a DVD laser orange/amber?

Someone tossed an old DVD player in the bins at the flats, so I decided
to investigate its salvage potential, the laser is a proper-job TO18
style pressed into a block of aluminium - seems a bit extravegant since
it was only a player, not a recorder.

There's some websites out there demonstrating lighting matches & burning
holes through paper with a DVD laser, but I presume they're using a
recorder laser for that much power.

Before I start waving the soldering iron at it - can anyone suggest a
"ball-park figure" for laseing current?

Thanks.
Just a quick reminder not to do anything stupid.
Those yellow stickers are on there for a reason.

Reminds me of a sign on the wall at the laser lab....

Caution! Do not look into laser with remaining good eye...

"William Sommer****** is an 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.


.... Phil

"Phil Allison" wrote in message ...
"William Sommer****** is an 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. There's nothing wrong
with using a blue laser to read a CD.

"William Sommerwerck" wrote in message
...
"Phil Allison" wrote in message ...
"William Sommer****** is an 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. There's nothing wrong
with using a blue laser to read a CD.


I don't think that you will find that is true - at least in my experience.
Although the physical optics of the optical block - i.e. the lens etc - may
be common for both formats, there is actually two laser diodes in a DVD
optical block, an IR one for reading CDs, and a visible red for reading
DVDs. In a Blu Ray optical block, there are three laser diodes, IR, vis red
and blue. Often, there are two sets of optics on these as well, which
manifests to the outside world as two lenses. If one short wave laser could
be used to read all three formats, the manufacturers would not waste money
and complexity to have a three-diode block.

You may find this informative

http://repairfaq.cis.upenn.edu/Misc/...e1/optics.html

Arfa

A short wavelength is needed to resolve fine detail. There's nothing
wrong with using a blue laser to read a CD.


I don't think that you will find that is true - at least in my experience.
Although the physical optics of the optical block - i.e. the lens etc - may
be common for both formats, there is actually two laser diodes in a DVD
optical block, an IR one for reading CDs, and a visible red for reading
DVDs. In a Blu Ray optical block, there are three laser diodes, IR, vis red
and blue. Often, there are two sets of optics on these as well, which
manifests to the outside world as two lenses. If one short wave laser could
be used to read all three formats, the manufacturers would not waste money
and complexity to have a three-diode block.

I stand by what I said. There is nothing at all wrong with using a blue laser
to read a CD. I did not say that a single optical block for all formats is
desirable -- now, did I?

The //practical// consideration is that shorter-wavelength lasers are set to
focus closer to the surface of the disk. It's probably simpler to have
multiple blocks, each optimized for the format to be played.

A short wavelength is needed to resolve fine detail. There's nothing
wrong with using a blue laser to read a CD.


I don't think that you will find that is true - at least in my experience.
Although the physical optics of the optical block - i.e. the lens etc - may
be common for both formats, there is actually two laser diodes in a DVD
optical block, an IR one for reading CDs, and a visible red for reading
DVDs. In a Blu Ray optical block, there are three laser diodes, IR, vis red
and blue. Often, there are two sets of optics on these as well, which
manifests to the outside world as two lenses. If one short wave laser could
be used to read all three formats, the manufacturers would not waste money
and complexity to have a three-diode block.

I stand by what I said. There is nothing at all wrong with using a blue laser
to read a CD. I did not say that a single optical block for all formats is
desirable -- now, did I?

The //practical// consideration is that shorter-wavelength lasers are set to
focus closer to the surface of the disk. It's probably simpler to have
multiple blocks, each optimized for the format to be played.

"William Sommerwerck" wrote in message
...
A short wavelength is needed to resolve fine detail. There's nothing
wrong with using a blue laser to read a CD.


I don't think that you will find that is true - at least in my
experience.
Although the physical optics of the optical block - i.e. the lens etc -
may
be common for both formats, there is actually two laser diodes in a DVD
optical block, an IR one for reading CDs, and a visible red for reading
DVDs. In a Blu Ray optical block, there are three laser diodes, IR, vis
red
and blue. Often, there are two sets of optics on these as well, which
manifests to the outside world as two lenses. If one short wave laser
could
be used to read all three formats, the manufacturers would not waste money
and complexity to have a three-diode block.

I stand by what I said. There is nothing at all wrong with using a blue
laser
to read a CD. I did not say that a single optical block for all formats is
desirable -- now, did I?

The //practical// consideration is that shorter-wavelength lasers are set
to
focus closer to the surface of the disk. It's probably simpler to have
multiple blocks, each optimized for the format to be played.


Well, I would have to say that you are going off on one of your word-play
exercises there. I also stand by what I said. I didn't say that you
*couldn't* read a CD or DVD with a blue laser, although I am not
sufficiently versed in the deep nuts and bolts of the technology to know
that for sure. I was actually responding to your contention that there is
"nothing wrong" with using a blue laser. Clearly there is something wrong
with doing so, otherwise in the real commercial world, major manufacturers
like Sony would do it. It's not a case of desirable, or otherwise. It's a
case of cold hard cash.

Arfa

"mike" wrote in message
...
On 1/10/2013 1:41 PM, Ian Field wrote:
Is a DVD laser orange/amber?

Someone tossed an old DVD player in the bins at the flats, so I decided
to investigate its salvage potential, the laser is a proper-job TO18
style pressed into a block of aluminium - seems a bit extravegant since
it was only a player, not a recorder.

There's some websites out there demonstrating lighting matches & burning
holes through paper with a DVD laser, but I presume they're using a
recorder laser for that much power.

Before I start waving the soldering iron at it - can anyone suggest a
"ball-park figure" for laseing current?

Thanks.
Just a quick reminder not to do anything stupid.
Those yellow stickers are on there for a reason.

Reminds me of a sign on the wall at the laser lab....

Caution! Do not look into laser with remaining good eye...


Apparently green lasers are worst - maximum absorbtion by hemoglobin.

On 01/10/2013 06:35 PM, William Sommerwerck wrote:
This article says the DVD wavelength is 650nm, and calls it "red".

http://en.wikipedia.org/wiki/Optical_disc_drive

However, I find that a bit on the short side for red.

650 is a pretty good red. The photopic sensitivity curve rolls off to
about zilch past 700, so there isn't that much redder to be had. Ruby
lasers are about 694 nm, but they're _bright_.

A red HeNe laser is 632.8 nm.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

On 1/11/2013 10:11 AM, Ian Field wrote:


"mike" wrote in message
...
On 1/10/2013 1:41 PM, Ian Field wrote:
Is a DVD laser orange/amber?

Someone tossed an old DVD player in the bins at the flats, so I decided
to investigate its salvage potential, the laser is a proper-job TO18
style pressed into a block of aluminium - seems a bit extravegant since
it was only a player, not a recorder.

There's some websites out there demonstrating lighting matches & burning
holes through paper with a DVD laser, but I presume they're using a
recorder laser for that much power.

Before I start waving the soldering iron at it - can anyone suggest a
"ball-park figure" for laseing current?

Thanks.
Just a quick reminder not to do anything stupid.
Those yellow stickers are on there for a reason.

Reminds me of a sign on the wall at the laser lab....

Caution! Do not look into laser with remaining good eye...


Apparently green lasers are worst - maximum absorbtion by hemoglobin.

I'd argue with that as a practical matter...assuming your intent is to
avoid blindness.
People tend to stare longer at invisible lasers than ones that seem
damagingly bright to them. By the time you perceive the effects of
an invisible laser, it's too late.

"mike" wrote in message
...
On 1/11/2013 10:11 AM, Ian Field wrote:


"mike" wrote in message
...
On 1/10/2013 1:41 PM, Ian Field wrote:
Is a DVD laser orange/amber?

Someone tossed an old DVD player in the bins at the flats, so I decided
to investigate its salvage potential, the laser is a proper-job TO18
style pressed into a block of aluminium - seems a bit extravegant since
it was only a player, not a recorder.

There's some websites out there demonstrating lighting matches &
burning
holes through paper with a DVD laser, but I presume they're using a
recorder laser for that much power.

Before I start waving the soldering iron at it - can anyone suggest a
"ball-park figure" for laseing current?

Thanks.
Just a quick reminder not to do anything stupid.
Those yellow stickers are on there for a reason.

Reminds me of a sign on the wall at the laser lab....

Caution! Do not look into laser with remaining good eye...


Apparently green lasers are worst - maximum absorbtion by hemoglobin.

I'd argue with that as a practical matter...assuming your intent is to
avoid blindness.
People tend to stare longer at invisible lasers than ones that seem
damagingly bright to them. By the time you perceive the effects of
an invisible laser, it's too late.


Challenge someone to observe the dull red glow on an IR laser chip.

"mike" wrote in message ...

On 1/11/2013 10:11 AM, Ian Field wrote:


"mike" wrote in message
...
On 1/10/2013 1:41 PM, Ian Field wrote:
Is a DVD laser orange/amber?

Someone tossed an old DVD player in the bins at the flats, so I decided
to investigate its salvage potential, the laser is a proper-job TO18
style pressed into a block of aluminium - seems a bit extravegant since
it was only a player, not a recorder.

There's some websites out there demonstrating lighting matches & burning
holes through paper with a DVD laser, but I presume they're using a
recorder laser for that much power.

Before I start waving the soldering iron at it - can anyone suggest a
"ball-park figure" for laseing current?

Thanks.
Just a quick reminder not to do anything stupid.
Those yellow stickers are on there for a reason.

Reminds me of a sign on the wall at the laser lab....

Caution! Do not look into laser with remaining good eye...


Apparently green lasers are worst - maximum absorbtion by hemoglobin.

I'd argue with that as a practical matter...assuming your intent is to
avoid blindness.
People tend to stare longer at invisible lasers than ones that seem
damagingly bright to them. By the time you perceive the effects of
an invisible laser, it's too late.




Can you link to any data that shows how many people have been blinded by CD
lasers?

Gareth.

Can you link to any data that shows how many people
have been blinded by CD lasers?

I suspect it's zero. The output of a CD playback laser is only a few
milliwatts, I believe. It would to blind someone with that.

"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

"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 ...

If the pits are indeed a half wavelength deep, then that is the answer to
why all three laser wavelengths are required to read all three formats, and
why the likes of Sony go to all that trouble to integrate three different
laser diodes into one block.

Arfa

"Arfa Daily"
"Phil Allison"


FYI

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

DVD players have both IR and red lasers.


If the pits are indeed a half wavelength deep,

** Slight brain fade: pit depth is of course 1/4 wavelength - so reflected
laser light ( from the bottom of a pit) returns out of phase with incident
light reflected off the adjacent surface and hence causes deep modulation of
the level arriving at the photodiode.

Example: An IR laser used in a CD player has a wavelength of 780nm ** in air
** but in polycarbonate the wavelength is shorter by a factor of 1.6 times
due to the lower speed of light in that material.

So the pits in a pressed into CD are made close to 122nm deep.


..... Phil

** Slight brain fade: pit depth is of course 1/4 wavelength -- so reflected
laser light (from the bottom of a pit) returns out of phase with incident
light reflected off the adjacent surface and hence causes deep modulation
of the level arriving at the photodiode.

I stand corrected.

"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!

On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is loaded.

"mike" wrote in message
...
On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is loaded.


Maybe I'll keep the digital camera to hand just in case.

"Ian Field" wrote in message ...



"mike" wrote in message
...
On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is loaded.


Maybe I'll keep the digital camera to hand just in case.



Maybe I won't ever own a gun.

"Gareth Magennis" wrote in message
...


"Ian Field" wrote in message ...



"mike" wrote in message
...
On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is
loaded.


Maybe I'll keep the digital camera to hand just in case.



Maybe I won't ever own a gun.


Had an air-pistol once - I discovered that the addition of small amounts of
aeromodellers diesel could produce a fairly impressive muzzle flash.

Shortly after - the cops had words about damage in the back gardens & backs
of houses in the next street!

I hadn't actually been aiming there - firing at the garden path, the pellets
made a pretty good ricochet whine.

On Fri, 11 Jan 2013 00:59:01 -0000, "Arfa Daily"
wrote:



"William Sommerwerck" wrote in message
...
This article says the DVD wavelength is 650nm, and calls it "red".

http://en.wikipedia.org/wiki/Optical_disc_drive

However, I find that a bit on the short side for red.


A 'standard' consumer DVD laser is bright red at around 650 nm wavelength. I
have never seen one tending towards amber, or indeed any shade of yellow. A
CD laser is infra red at around 780 nm wavelength. On the other hand, the
laser fitted to a Blu Ray DVD player is just that - blue - and has a much
shorter wavelength at just over 400 nm. The reason for each wavelength
becoming shorter as you go from CD to Blu ray, is that each disc type packs
more data on its playing surface(s) and it does this by using ever smaller
pits and lands. In order to resolve these, shorter and shorter wavelength
lasers are required ...

Arfa
And as demand for greater density increases we will find 'optical'
disc drives using increasingly shorter wavelength lasers - near UV,
extreme UV, X-Ray, Gamma ray...

PlainBill

On 1/12/2013 1:56 PM, Gareth Magennis wrote:


"Ian Field" wrote in message ...



"mike" wrote in message
...
On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is
loaded.


Maybe I'll keep the digital camera to hand just in case.


Just in case of what???


Maybe I won't ever own a gun.

"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.

Arfa

"Ian Field" wrote in message
...


"Gareth Magennis" wrote in message
...


"Ian Field" wrote in message ...



"mike" wrote in message
...
On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is
loaded.


Maybe I'll keep the digital camera to hand just in case.



Maybe I won't ever own a gun.


Had an air-pistol once - I discovered that the addition of small amounts
of aeromodellers diesel could produce a fairly impressive muzzle flash.

Shortly after - the cops had words about damage in the back gardens &
backs of houses in the next street!

I hadn't actually been aiming there - firing at the garden path, the
pellets made a pretty good ricochet whine.

I had a .177 Daisy with one and a half springs in it. Sadly, much to my
parents' embarrassment, the court confiscated it, and fined me £10 after an
'incident' ... :-\

Arfa

On Fri, 11 Jan 2013 08:01:16 -0800, "William Sommerwerck"
wrote:

A short wavelength is needed to resolve fine detail. There's nothing
wrong with using a blue laser to read a CD.


I don't think that you will find that is true - at least in my experience.
Although the physical optics of the optical block - i.e. the lens etc - may
be common for both formats, there is actually two laser diodes in a DVD
optical block, an IR one for reading CDs, and a visible red for reading
DVDs. In a Blu Ray optical block, there are three laser diodes, IR, vis red
and blue. Often, there are two sets of optics on these as well, which
manifests to the outside world as two lenses. If one short wave laser could
be used to read all three formats, the manufacturers would not waste money
and complexity to have a three-diode block.

I stand by what I said. There is nothing at all wrong with using a blue laser
to read a CD. I did not say that a single optical block for all formats is
desirable -- now, did I?

Actually there is. It has to do with the optics works. At nominal
wavelength the phase difference between "pits" and "spaces" is about 1/4
wavelength. If you change the laser wavelength from 700 to 400 there is
no longer an unambiguous flying height solution.

The //practical// consideration is that shorter-wavelength lasers are set to
focus closer to the surface of the disk. It's probably simpler to have
multiple blocks, each optimized for the format to be played.

On Fri, 11 Jan 2013 16:54:11 -0800, "William Sommerwerck"
wrote:

Can you link to any data that shows how many people
have been blinded by CD lasers?

I suspect it's zero. The output of a CD playback laser is only a few
milliwatts, I believe. It would to blind someone with that.

It is less than 1 milliwatt, see class 1 laser. And it still can burn
holes in your retina, albeit slowly.

?-)

"josephkook"


Actually there is. It has to do with the optics works. At nominal
wavelength the phase difference between "pits" and "spaces" is about 1/4
wavelength. If you change the laser wavelength from 700 to 400 there is
no longer an unambiguous flying height solution.


** Care to flesh that last one out a bit ?

A "blue ray" laser would see the pits on a CD reflecting light back
essentially in-phase with the rest of the surface.

The focus height does not come into it.


.... Phil

I suspect it's zero. The output of a CD playback laser is only
a few milliwatts, I believe. It would to blind someone with that.

It is less than 1 milliwatt, see class 1 laser. And it still can burn
holes in your retina, albeit slowly.

Like the guy in "Austin Powers", not running out of the path of a slowly
advancing steam roller.

Way back in 1972, I took photos of the U of MD's laser laboratory. I decided
to take a shot directly into a laser, forgetting that, as the laser beam was
coherent, it would not be strongly dispersed by the matte focusing screen in
my Nikon.

Boy, did I get an eyeful. It apparently created a coagulated "thread" in the
jelly, which took decades to disappear.

"Arfa Daily" wrote in message
...


"Ian Field" wrote in message
...


"Gareth Magennis" wrote in message
...


"Ian Field" wrote in message ...



"mike" wrote in message
...
On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is
loaded.


Maybe I'll keep the digital camera to hand just in case.



Maybe I won't ever own a gun.


Had an air-pistol once - I discovered that the addition of small amounts
of aeromodellers diesel could produce a fairly impressive muzzle flash.

Shortly after - the cops had words about damage in the back gardens &
backs of houses in the next street!

I hadn't actually been aiming there - firing at the garden path, the
pellets made a pretty good ricochet whine.

I had a .177 Daisy with one and a half springs in it. Sadly, much to my
parents' embarrassment, the court confiscated it, and fined me £10 after
an 'incident' ... :-\

Arfa


Mine was a Webley Senior .22 pistol - I blew the breech plate out while
experimenting with more powerful propellants.

My "incident" was an earthenware urn in the next street, it was aboit 2/3
full of soil with some kind of plant growing in it - the pellet made a tiny
entry hole just higher than the soil and a much larger exit hole below the
soil.

The owner seemed almost as impressed as angry!

"mike" wrote in message
...
On 1/12/2013 1:56 PM, Gareth Magennis wrote:


"Ian Field" wrote in message ...



"mike" wrote in message
...
On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is
loaded.


Maybe I'll keep the digital camera to hand just in case.


Just in case of what???

It can see the IR beam that I can't - also handy for checking TV remotes.

"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?

On 1/13/2013 9:41 AM, Ian Field wrote:


"mike" wrote in message
...
On 1/12/2013 1:56 PM, Gareth Magennis wrote:


"Ian Field" wrote in message ...



"mike" wrote in message
...
On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is
loaded.


Maybe I'll keep the digital camera to hand just in case.


Just in case of what???

It can see the IR beam that I can't - also handy for checking TV remotes.

Think about what you just said. You're gonna make a lot of assumptions
and have to point the camera somehow.

Insurance, AKA assuming it's dangerous, is what you use to protect you
against normally safe activities that can go horribly wrong, by accident.

Just in case, AKA carrying a condom in your wallet just in case you
meet a $10 hooker, is an excuse to do stupid unsafe things.

In the specific case of this thread, I wouldn't get too worried about it.
Problem I have is that these threads hang around forever.
Some newbie finds something that looks like a CD laser assembly in
a box of junk and fires it up. "The interweb said it was safe..."

Instead of making a lot of excuses and assumptions about why it's safe,
why not just treat it like it is unsafe and actually BE safe.
Doesn't stop you from playing with it. Just makes it less likely that
you'll hurt yourself.

"mike" wrote in message
...
On 1/13/2013 9:41 AM, Ian Field wrote:


"mike" wrote in message
...
On 1/12/2013 1:56 PM, Gareth Magennis wrote:


"Ian Field" wrote in message ...



"mike" wrote in message
...
On 1/12/2013 10:25 AM, Ian Field wrote:


"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!

Yep, that's the same idea as always behaving as though your gun is
loaded.


Maybe I'll keep the digital camera to hand just in case.


Just in case of what???

It can see the IR beam that I can't - also handy for checking TV remotes.

Think about what you just said. You're gonna make a lot of assumptions
and have to point the camera somehow.

Insurance, AKA assuming it's dangerous, is what you use to protect you
against normally safe activities that can go horribly wrong, by accident.

Just in case, AKA carrying a condom in your wallet just in case you
meet a $10 hooker, is an excuse to do stupid unsafe things.

In the specific case of this thread, I wouldn't get too worried about it.
Problem I have is that these threads hang around forever.
Some newbie finds something that looks like a CD laser assembly in
a box of junk and fires it up. "The interweb said it was safe..."

I never implied it was safe - in fact I highlighted a danger of messing with
a DVD dual unit; that you could be trying to get some visible light and all
the time its pumping out IR.

I can't see the IR - the digital camera can, its easy enough to have the
laser on a non reflective surface and observe the dot through the viewfinder
of a digital camera.

This thread has gathered all the info a newbie needs to play safely with
salvaged DVD lasers - so quit scaremongering and find something sensible to
do.