OD - A question

atz413 · Jan 5, 2007

I found a site that sells 532nm goggles for $45 (US), but it says the OD is 10 for the goggles. Does that mean I won't be able to see anything? Help!?

Here's the link:

http://www.controloptics.com/product_lasercontrol.htm

Hmm... That may be $45 Canadian... I just wrote to find out how to order, just in case, you know...

timelord · Jan 30, 2007

I'm not sure but i use red sports goggles from Wicked lasers and they are OD5+ and with my 100mw pulsar i can not see the dot at all. I can only see something when i use a lens for burning and the beam is focused to the smallest point.
When this happens the light goes white and very bright and you must control the distance of the focused beam to keep it smoking good.

Hope this was of some help.

Ragnarok · Jan 31, 2007

Man, do I love search engines!

Snipped from

https://www.omegafilters.com/index.php?page=tech_fildes_top

"Transmission can be expressed either as a percentage (e.g., 90%) or decimally (e.g., .90). Optical density is always expressed as the negative logarithm of transmission. Unit conversions are:

OD = -log10 T or T = 10[sup]-OD[/sup] "

What this tells me is that a 532nm filter of OD 10 would transmit 1/10[sup]10[/sup] - 0.00000001% of the light at that wavelength.

That's not much! Those OD10 goggles are probably meant for high power (multi-kilowatt) green pulsed lasers.

There is a handy OD conversion chart linked at the above page which shows the transmittance for fractional OD values up to OD4. Multiplying the transmittance value by your laser power will tell you how many mW (or fractions thereof) will pass through.

https://www.omegafilters.com/index.php?page=tech_con_chart

Example: OD 3 transmits 0.1%, so a filter that is OD3 at 532 will let through 0.1mW from a 100mW laser operating at that wavelength.

[edit]

So what we have in essence is this progression:

OD1 transmits 10%
OD2 transmits 1%
OD3 transmits 0.1%
OD4 transmits 0.01%
OD5 transmits 0.001%
OD6 transmits 0.0001%

Now you can see why people are complaining that they can't see their lasers through certain goggles!

timelord · Jan 31, 2007

That's cleared a few things in my mind and your explanation was very easy to understand too.
So this will be put as a sticky as this is a very relavant and useful post for all of us and newbies too.

Proctor · Feb 1, 2007

OD3-4 is a sweet spot.

I loved my WickedLasers OD3's

timelord · Feb 1, 2007

Proctor said:
OD3-4 is a sweet spot.

I loved my WickedLasers OD3's

Are they the orange goggles??

Proctor · Feb 1, 2007

Timelord said:
[quote author=Proctor link=1168012242/0#4 date=1170333957]OD3-4 is a sweet spot.

I loved my WickedLasers OD3's

Are they the orange goggles??
[/quote]

They were red.

timelord · Feb 2, 2007

I understand that the orange coloured lenses protect against 532nm (Green) & 473nm (Blue)

laser · Feb 6, 2007

im not sure if the color of the lense matters, but most business tend to apply certain color lenses to block out different wavelengths better. ive seen a clear set of goggles that block out red, but i cant seem to find the link anymore.

Justin · Mar 2, 2007

OD is important for your safety, but just as important is VLT (Visible Light Transmission) which is basically your ability to see while you are wearing the goggles. For example, a set of goggles with OD5+ @ 532nm and VLT 40% will transmit only 0.001% of 532nm light, but will also transmit 40% of the total visible spectum. A set of goggles with 30% VLT would be much harder to see out of regardless of the OD. Just something to ask when you are buying goggles!

pseudonomen137 · Mar 3, 2007

Justin said:
OD is important for your safety, but just as important is VLT (Visible Light Transmission) which is basically your ability to see while you are wearing the goggles. For example, a set of goggles with OD5+ @ 532nm and VLT 40% will transmit only 0.001% of 532nm light, but will also transmit 40% of the total visible spectum. A set of goggles with 30% VLT would be much harder to see out of regardless of the OD. Just something to ask when you are buying goggles!

Definitely! A problem with low VLT is not just your personal comfort, but with low VLTs, your pupils dilate to compensate, making you even more vulnerable to laser-related eye damage in the process. The ideal goggles would only block the very narrow band your laser operates at, and pretty much pass everything else, but unfortunately the more you want, the more you pay.

Justin · Mar 7, 2007

I've actually seen a set of 90% VLT goggles with multiband coverage... They are essentially clear and only block very specific wavelengths. Super useful in the lab.

Switch · Dec 11, 2007

Justin said:
I've actually seen a set of 90% VLT goggles with multiband coverage... They are essentially clear and only block very specific wavelengths. Super useful in the lab.

But they still mess with your color perception since they block certain wavelenghts right?

And about the OD10 goggles and the multikilowatt laser, I'm sure it would melt the lense and burn your face before you can get out of the way , anyway

.

Ref · Jan 10, 2008

pseudonomen137 said:
Definitely! A problem with low VLT is not just your personal comfort, but with low VLTs, your pupils dilate to compensate, making you even more vulnerable to laser-related eye damage in the process. The ideal goggles would only block the very narrow band your laser operates at, and pretty much pass everything else, but unfortunately the more you want, the more you pay.

I read somewhere else that this isnt as bad as people think, as because of how colimated a laser is, your pupils dilating would only increase the surface area available for it to enter your eye, not the amount that actually gets in there. Any truth in this?

Amnizu · Jan 21, 2008

Timelord said:
I understand that the orange coloured lenses protect against 532nm (Green) & 473nm (Blue)

Indeed, the 2 pairs I received from Dragonlasers do this at OD3, and I'm not sure of the VLT, but it's pretty high as I have no problem seeing out of them. I could even wear them for non-laser related tasks if I didn't have anything else around.

SMIDSY · Mar 10, 2008

Timelord said:
I'm not sure but i use red sports goggles from Wicked lasers and they are OD5+ and with my 100mw pulsar i can not see the dot at all. I can only see something when i use a lens for burning and the beam is focused to the smallest point.
When this happens the light goes white and very bright and you must control the distance of the focused beam to keep it smoking good.

Hope this was of some help.

My WL red goggles are only OD 2+ and theyre the sport elite ones

OD - A question

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