DVD laser (just out of curiosity).

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.

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

Reply to
William Sommerwerck

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.

Reply to
Ian Field

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

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

Reply to
William Sommerwerck

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...

Reply to
mike

"William Sommerwanker is an Ass"

** Utter bullshit.

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

... Phil

Reply to
Phil Allison

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

Reply to
William Sommerwerck

Apparently green lasers are worst - maximum absorbtion by hemoglobin.

Reply to
Ian Field

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 
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Reply to
Phil Hobbs

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.

Reply to
mike

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

Reply to
Ian Field

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.

Reply to
Gareth Magennis

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.

Reply to
William Sommerwerck

"Arfa Daily" "Phil Allison"

** 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

Reply to
Phil Allison
** 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.

Reply to
William Sommerwerck

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

Reply to
PlainBill

experience.

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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.

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Reply to
josephkk

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

?-)

Reply to
josephkk

"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

Reply to
Phil Allison

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.

Reply to
William Sommerwerck

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