Does anyone have any reliable brightness/luminosity figures for the older
red
(660nm) and newer green (531nm) laser pointers relative to the sun, at
around
2-5mW power?

I vaguely remember a figure of 10,000x times the brightness of the sun,
staring
directly into the red laser diode beam, but I may be misremembering.

This sign is on my lab wall:

"I.N. Galidakis" <morpheus@olympus.mons> wrote in message
news:1209050181.922712@athprx04...
Does anyone have any reliable brightness/luminosity figures for the
older red
(660nm) and newer green (531nm) laser pointers relative to the sun,
at around
2-5mW power?

I vaguely remember a figure of 10,000x times the brightness of the
sun, staring
directly into the red laser diode beam, but I may be misremembering.

This sign is on my lab wall:

"Do Not Stare Into Laser With Remaining Good Eye!"

Good advice too.

JB
--

Does anyone have any reliable brightness/luminosity figures for the
older red (660nm) and newer green (531nm) laser pointers relative to the
sun, at around 2-5mW power?

I vaguely remember a figure of 10,000x times the brightness of the sun,
staring directly into the red laser diode beam, but I may be
misremembering.

In article <1209050181.922712@athprx04>, I.N. Galidakis wrote:

Does anyone have any reliable brightness/luminosity figures for the
older red (660nm) and newer green (531nm) laser pointers relative to
the sun, at around 2-5mW power?

I vaguely remember a figure of 10,000x times the brightness of the
sun, staring directly into the red laser diode beam, but I may be
misremembering.

For rough ballpark figures:

As for a size of the emitting area of a typical laser diode: Web
searching is pointing me a lot to 1 by 3 micrometers. One specific
one I decided to look at has 1 by 4 micrometers, which I take to mean
an emitting area of 4E-8 square centimeter:

http://www.nvginc.com/D650-5.PDF (US Lasers Inc. D6505I, or NVG Inc.
D650-5, Digi-Key catalog number 38-1007-ND)

That one appears to me intended to produce 5 mW of 650 nm light.

Its beam is typically 5 by 25 degrees. Assuming the beam is
elliptical, it has a solid angle of roughly .04 steradian. 5 mW of
650 nm is .365 lumens. 3.65 lumens into .04 steradian is about 9.1
candela.

9.1 candela divided by 4E-8 square centimeter is about 2.28 E8
candela per square centimeter.

Luminous flux per unit area works out to 9.1 E6 lumens per square
centimeter.

As for the sun: I figure 5780 K blackbody. Luminance is about
1.85 E5 candela per square centimeter. Assuming a piece of solar
surface is nearly enough a lambertian radiator, it produces about 5.8
E5 lumens per square centimeter.

So the above laser diode has a luminance roughly 1200 times that of
the sun, and luminous flux output per unit area of emitting surface
about 15 times that of the sun. These are only *rough ballpark*
figures.

- Don Klipstein (don@misty.com)
--

On Thu, 24 Apr 2008 18:40:30 +0300 I.N. Galidakis
morpheus@olympus.mons> wrote:
JB wrote:

This sign is on my lab wall:

"Do Not Stare Into Laser With Remaining Good Eye!"

Good advice too.

Hehe! I think that's *precisely* the reason we have two eyes. To
still have a good one, after we stare into laser beams.... :-)

Basically, you are given one chance to learn your lesson the hard way.

phil-news-nospam@ipal.ne wrote:
On Thu, 24 Apr 2008 18:40:30 +0300 I.N. Galidakis
morpheus@olympus.mons> wrote:
JB wrote:

This sign is on my lab wall:

"Do Not Stare Into Laser With Remaining Good Eye!"

Good advice too.

Hehe! I think that's *precisely* the reason we have two eyes. To
still have a good one, after we stare into laser beams.... :-)

Basically, you are given one chance to learn your lesson the hard way.

Nah. I wouldn't count lasers as sources for "learning the hard way".
"Learning"
is always associated with PAIN of some sort. Losing your eye to a laser
isn't
likely to hurt very much, unless the laser actually drills a hole on your
retina.

A much faster method would be to be burned by shortwave UV in the eyes
and/or
skin. The pain is unbelievable. Multiply that by 30 and there you have my
experience of "learning the hard way"
--
Agreed that UVB/C is nasty, nasty stuff. But if you want a truly painful

Agreed that UVB/C is nasty, nasty stuff. But if you want a truly
painful lesson which is also a good wake-up experience? Try this:
Testing a 3kW XE/D (compact source xenon lamp) and wondering why it's
not striking, not noticing that the ignitor pulse (>85kV @ 800kHz!)
is taking a shorter way to ground inside the lamphouse. As I'd
stupidly disabled the interlock microswitches so I could poke about
inside while it was still live, I accidently got within ~75mm of the
ignitor 'hot' lead and found the break in the lead insulation the
hard way!. The arc actually came out to meet me across this 75mm
distance in free air. Lovely small pothole burnt in my finger and a
very interesting nervous reaction/trembling/twitching for over 5
hours afterwards too. I couldn't control the hand at all. It had its
own life!
I love the smell of ozone in the morning! (I just don't like the
smell of my burning flesh though).

JB
--

..very rare disease, called
Hindadenitis Suppurativa (to find out more, Google it or look it up
on Wiki).

I.N. Galidakis wrote:
..very rare disease, called
Hindadenitis Suppurativa (to find out more, Google it or look it up
on Wiki).

Messed up the spelling. Should be: "Hidradenitis Suppurativa"

That sounds *really* gruesome. I wouldn't wish that condition on anyone.

Its beam is typically 5 by 25 degrees. Assuming the beam is
elliptical, it has a solid angle of roughly .04 steradian.

In <slrng1293s.dk4.don@manx.misty.com>, I, D. Klipstein wrote in part:

Its beam is typically 5 by 25 degrees. Assuming the beam is
elliptical, it has a solid angle of roughly .04 steradian.

I forgot to multiply by pi/4.

Then again, it is a severe
oversimplification to consider the beam uniform and for all of the
light to be within the stated beam.

- Don Klipstein (don@misty.com)
--