Hello and inherited laser help

[SamV]

Then it was cool, the smaller beams were from my low power chinese quad beam.

[White-Light]

Err... I think perhaps you meant "what She said"

Heroic is in actual fact an incredibly intelligent young lady

Jem


Edit: .... Whoa Al... Where did your post go

Sorry jem. Took it out as I thought it might be encouraging in the wrong way.

I'll add something back in to show crowd scanning. SamV this is crowd scanning.

This was with a 1 watt laser and seems to have been safely done but with that power, they've obviosuly done something to diverge the beam as the closest people to the scanner are maybe 5 metres (lovely little tech trance night):


http://www.youtube.com/watch?v=CAhZW4SIdlQ

Both my eyes and camera were entirely comfortable with the laser. In fact the only smear on the video can be seen by the brightness of the aperture, not the beams.

Apologies also to heroic for the gender slip.

[heroic]

Then it was cool, the smaller beams were from my low power chinese quad beam.

Ah, okay. The video's a bit confusing. Unless you're going to do the calculations and measurements, it's not safe to scan the crowd with anything over class 3A (and sometimes not even then- if anyone in the crowd might have binoculars or similar you need to be aware of even more risk).

[T0mmm]

lol binoculars i was wondering though, supposing someone had really strong glasses that were hit by a nearly coherent beam, would it affect their retinas more than a non-glasses-clad person or would their eye lens equal this out?

[heroic]

If their glasses were of the correct prescription, they should have equal total focussing power to someone of normal vision.

[Jem]

lol binoculars i was wondering though, supposing someone had really strong glasses that were hit by a nearly coherent beam, would it affect their retinas more than a non-glasses-clad person or would their eye lens equal this out?

The reason a person wears glasses is to give them the same vision as a person who doesn't require a corrective prescription.

Therefore, someone who requires a strong corrective prescription who isn't wearing their glasses would be somewhat protected from a hit with a beam as the beam would be focussed either in front of or behind the retina and not exactly on it.

If you have perfect vision and take a hit with a beam, that's going to get focussed bang on your retina and is going to cause some damage. This also applies to someone who's wearing corrective spectacles.

So, to answer your question... A person with perfect eyesight would suffer exactly the same fate as someone wearing corrective spectacles. However, someone who needs a corrective prescription and isn't wearing their glasses would be protected somewhat.

Bear in mind that this is a simplistic view, the wavelength of laser would play a small part in where the beam was focussed when it was passed through a lens (either internal or external to your eye).

PLEASE, do not try this at home

Jem

[T0mmm]

PLEASE, do not try this at home

Jem

haha don't worry, it was just a thought I thought it'd be the same but was wondering about the coherent line bit of it. but i suppose all light travels in straight lines. Unless you're chuck norris.

[Stoney3K]

If their glasses were of the correct prescription, they should have equal total focussing power to someone of normal vision.

Not if they weren't wearing them at the time. The focal point would miss the retina in that case, which would reduce the power density.

So, to answer your question... A person with perfect eyesight would suffer exactly the same fate as someone wearing corrective spectacles. However, someone who needs a corrective prescription and isn't wearing their glasses would be protected somewhat.

Also, spectacles are generally not AR coated or sometimes less AR coated than quality optics, so the beam will reflect off them and lose some power there. Not much though, in most cases.

[heroic]

It's been at least five years since I bought a pair of glasses that were not AR-coated. Even the plastic ones are AR coated these days, unless you're cheap and *like* not being able to see...

[Jem]

In my opinion *everyone* without exception should wear AR coated lenses. Particularly if they drive at night as this minimizes reflection and glare from tail lights and headlights. Ask for a demo at your local opticians/optometrist/eye doctor. They probably have a demo unit containing LED's that simulate night driving (we do )

There is a stubborness amongst our patients/customers to want to spend the extra bit of money it costs for AR coating. I think a lot of it relates back to the old days when they were difficult to clean. However, with the modern hydrophobic coatings that is a thing of the past.

Here in the UK I would say that around 35% of our paients/customers now would never be without AR coating, and this figure is growing all the time.

Cheers

Jem