DVD laser (just out of curiosity).

[Phil Allison]

"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

 

[William Sommerwerck]

** 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.

 

[Ian Field]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...

"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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!

 

[mike]

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

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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.

 

[Ian Field]

"mike" <ham789@netzero.net> wrote in message
news:kcsi45$cia$1@dont-email.me...

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


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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.

 

[Gareth Magennis]

"Ian Field" wrote in message news:_pkIs.882$CD3.814@fx04.fr7...



"mike" <ham789@netzero.net> wrote in message
news:kcsi45$cia$1@dont-email.me...

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


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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.

 

[Ian Field]

"Gareth Magennis" <gareth.magennis@ntlworld.com> wrote in message
news:%ZkIs.17465$Pf2.6652@fx30.fr7...

"Ian Field" wrote in message news:_pkIs.882$CD3.814@fx04.fr7...



"mike" <ham789@netzero.net> wrote in message
news:kcsi45$cia$1@dont-email.me...
On 1/12/2013 10:25 AM, Ian Field wrote:


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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"
<arfa.daily@ntlworld.com> wrote:

"William Sommerwerck" <grizzledgeezer@comcast.net> wrote in message
news:kcnj8h$gml$1@dont-email.me...
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

 

[mike]

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

"Ian Field" wrote in message news:_pkIs.882$CD3.814@fx04.fr7...



"mike" <ham789@netzero.net> wrote in message
news:kcsi45$cia$1@dont-email.me...
On 1/12/2013 10:25 AM, Ian Field wrote:


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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.

 

[Arfa Daily]

"Ian Field" <gangprobing.alien@ntlworld.com> wrote in message
news:kUhIs.11$cT.10@fx05.fr7...

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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

 

[Arfa Daily]

"Ian Field" <gangprobing.alien@ntlworld.com> wrote in message
news:2MlIs.4341$K62.3522@fx08.fr7...

"Gareth Magennis" <gareth.magennis@ntlworld.com> wrote in message
news:%ZkIs.17465$Pf2.6652@fx30.fr7...


"Ian Field" wrote in message news:_pkIs.882$CD3.814@fx04.fr7...



"mike" <ham789@netzero.net> wrote in message
news:kcsi45$cia$1@dont-email.me...
On 1/12/2013 10:25 AM, Ian Field wrote:


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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 Ł10 after an
'incident' ... :-\

Arfa

 

[josephkk]

On Fri, 11 Jan 2013 08:01:16 -0800, "William Sommerwerck"
<grizzledgeezer@comcast.net> 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.

 

[josephkk]

On Fri, 11 Jan 2013 16:54:11 -0800, "William Sommerwerck"
<grizzledgeezer@comcast.net> 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.

?-)

 

[Phil Allison]

"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

 

[William Sommerwerck]

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.

 

[Ian Field]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:TUoIs.4833$K62.826@fx08.fr7...

"Ian Field" <gangprobing.alien@ntlworld.com> wrote in message
news:2MlIs.4341$K62.3522@fx08.fr7...


"Gareth Magennis" <gareth.magennis@ntlworld.com> wrote in message
news:%ZkIs.17465$Pf2.6652@fx30.fr7...


"Ian Field" wrote in message news:_pkIs.882$CD3.814@fx04.fr7...



"mike" <ham789@netzero.net> wrote in message
news:kcsi45$cia$1@dont-email.me...
On 1/12/2013 10:25 AM, Ian Field wrote:


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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 Ł10 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!

 

[Ian Field]

"mike" <ham789@netzero.net> wrote in message
news:kcsuul$75d$1@dont-email.me...

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


"Ian Field" wrote in message news:_pkIs.882$CD3.814@fx04.fr7...



"mike" <ham789@netzero.net> wrote in message
news:kcsi45$cia$1@dont-email.me...
On 1/12/2013 10:25 AM, Ian Field wrote:


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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.

 

[Ian Field]

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:ERoIs.4819$Ne.2447@fx27.fr7...

"Ian Field" <gangprobing.alien@ntlworld.com> wrote in message
news:kUhIs.11$cT.10@fx05.fr7...


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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?

 

[mike]

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

"mike" <ham789@netzero.net> wrote in message
news:kcsuul$75d$1@dont-email.me...
On 1/12/2013 1:56 PM, Gareth Magennis wrote:


"Ian Field" wrote in message news:_pkIs.882$CD3.814@fx04.fr7...



"mike" <ham789@netzero.net> wrote in message
news:kcsi45$cia$1@dont-email.me...
On 1/12/2013 10:25 AM, Ian Field wrote:


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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.

 

[Ian Field]

"mike" <ham789@netzero.net> wrote in message
news:kcutrj$rmo$1@dont-email.me...

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


"mike" <ham789@netzero.net> wrote in message
news:kcsuul$75d$1@dont-email.me...
On 1/12/2013 1:56 PM, Gareth Magennis wrote:


"Ian Field" wrote in message news:_pkIs.882$CD3.814@fx04.fr7...



"mike" <ham789@netzero.net> wrote in message
news:kcsi45$cia$1@dont-email.me...
On 1/12/2013 10:25 AM, Ian Field wrote:


"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:JsbIs.896$q_4.804@fx26.fr7...


"Phil Allison" <phil_a@tpg.com.au> wrote in message
news:alc37bFfu6tU1@mid.individual.net...

"William Sommerwanker is a Fucking Ass"

Is a DVD laser orange/amber?

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

Utter bullshit.

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

A short wavelength is needed to resolve fine detail.


** ROTFL !!

What a fucking 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.