Laser beginner need advice about eyes safety

[MarcDorpe]

Hi there,

I have a Briteq 1500 laser.

I'd like to do some testing, using some Laser Software plugged to a laptop.

Due to space restrictions, I will be doing this in the garage, being only a few meters (3-5 m?) away from the laser.

Laser show will directed towards me like the rest of the installation (eg : non laser hardware like disco light and such )

I don't plan to shot any single laser dot (which would probably be very dangerous), only fast animation and a few beams (tons lot of small points scattered around)

Since it's a Class IV laser, eyes safety is a concern.

I'd like to know which google glasses I should buy and wear during the test.
The Briteq is a 1.5W laser, here is the page http://en.briteq-lighting.com/produc...-LASER1500-RGB


Note : during the show laser will be directed a few meters above the audience after being approved by a professional (not me).
What i ask here is for testing the device.

Thanks in advance for your help.

[Draco]

I currently am not aware of any laser glasses for RGB

[Bradfo69]

With your somewhat broken English, I'm going to assume you're not in the US. Where in the world do you reside since that will help people better answer your question or, offer a local solution?

[MarcDorpe]

I currently am not aware of any laser glasses for RGB

So how do professionals test / caliber their lasers ?

Even if it's "only" 1.5 W at full power (when white color is sent) and moving pretty fast (no fixed point) I guess it could cause some retina damage it hits the eyes, even if it only goes there for a few ms (scanning) and from a certain distance (a few meters).

With your somewhat broken English, I'm going to assume you're not in the US. Where in the world do you reside since that will help people better answer your question or, offer a local solution?

Yes, you guessed it.
I live in France.

[buffo]

Hi there,
I have a Briteq 1500 laser.

Welcome to PhotonLexicon! That's a nice looking projector you have there. Out of curiosity, what controller are you using with it?

Since it's a Class IV laser, eyes safety is a concern.

It's refreshing to see this sort of safety awareness in a new laserist. You are wise to be thinking about eye safety. Well done.

I'd like to know which google glasses I should buy and wear during the test.

OK, let's talk a little bit about laser eye safety. Sorry if this gets a bit boring, but it's good information to understand.

The goal of laser safety goggles is to reduce the irradiance (this is a measure of the intensity of the beam; power per unit area) to a level that is considered eye-safe. The Maximum Permissible Exposure (MPE) for a static beam is 2.5 milliwatts per square centimeter. If you are talking about a scanned beam and you make some basic assumptions about the scanners and the geometry of the room (how far you are from the projector, etc), then you can use 10 milliwatts per square centimeter as a good safety level for scanned beams.

Using the method above is the safest way to ensure your exposure is always below the MPE. However, many people take a short cut: they simply say "if I can reduce the beam power to less than 5 mw total, then that brings me into the Class 3A level, for which there is no eye protection required". This is technically true, however in cases where the beam diameter is very small you can still exceed the MPE slightly.

Exceeding the MPE slightly is normally not considered to be a big problem for laserists performing maintenance or calibration, as the MPE has intentionally been set absurdly low. Also, there is no legal rule forcing a laserist to protect his own eyes. (There are rules in place to protect the customer's eyes at a show, however!) Even so, many countries allow audience scanning at much higher irradiance levels than the 10 mw/cm^2 for scanned beams, and laser eye injuries from audience scanning world-wide are incredibly rare. (In fact, outside of the misuse of pulsed lasers, I don't believe there are any documented cases of permanent vision loss from audience scanning.) So the thinking goes,

In any event, the key to understanding how to select the correct set of goggles is that you need to reduce the power (and thus the irradiance) by several orders of magnitude. In your case, the laser projector produces 1.5 watts, or 1500 mw. To reduce the power to less than 5 mw would require a thousand-fold reduction in power (3 orders of magnitude, or 10^-3). If you use the more complete method of calculating the irradiance (power per unit area), you'll see that unless your beam diameter is very small, you are still looking at roughly a thousand-fold reduction in power to get to where you need to be.

Let's assume a 4 mm beam. At 1500 mw, that works out to 3750 mw/cm^2. Remember that the limit for a STATIC beam is 2.5 mw/cm^2. But you said you were going to be working with a scanned beam. That limit is ~ 10 mw/cm^2. So if we reduce the irradiance by a factor of a thousand, that gives us an irradiance of almost 3.75 mw/cm^2. Slightly above the limit for a static beam, but well below the limit for a scanned beam.

So how do we achieve a thousand-fold reduction in power? Easy! We purchase a set of laser safety goggles that have attenuation bands which include the specific wavelengths that our projector produces.

Laser safety goggles are sold with an optical density rating (O.D. rating). The O.D. rating number is equal to how many powers of 10 the goggles will reduce the power. So if you purchase goggles that have an O.D 3 rating, they will reduce the power by 3 orders of magnitude, or 10^-3, at the wavelengths specified.

Fortunately, these goggles are quite reasonably priced. For example, one of the senior members of PhotonLexicon (Stanwax, located in Great Britain) operates a web store that sells O.D. 4 laser safety goggles for around 45 Euros per pair. The goggles will block portions of the red, green, and blue spectrum, while still allowing some other light to pass through so you aren't completely blind when you put them on. And since they are O.D. 4, you have an extra safety margin (extra factor of 10). Here is a link: http://shop.stanwaxlaser.co.uk/laser...ggles-37-p.asp

I currently am not aware of any laser glasses for RGB

There are lots of suppliers for RGB goggles. Typically they have a "hole" in the filter to pass atypical wavelengths that are not normally associated with laser wavelengths. Then too, the human eye is remarkably sensitive even at very low light levels, so even if you made a set of goggles out of neutral density filters (that is, filters that have roughly the same O.D. rating across the entire visible spectrum), you can still see well enough to walk around the room even using O.D 5 lenses.

Recently the price of laser safety goggles has plummeted. 10 years ago you would expect to pay several hundred dollars for a set of goggles that only blocked red, or only blocked green and blue. Now RGB goggles are very common and can usually be purchased for around $50.

So how do professionals test / caliber their lasers ?

The smart ones wear RGB goggles and/or reduce the power output of the projector while they perform any alignment activities.

Sadly, however, I have seen some professionals work on very high power equipment (15 to 20 watts) without any safety goggles at all. These are the sort of people who end up with a laser eye injury sooner or later.

Even if it's "only" 1.5 W at full power (when white color is sent) and moving pretty fast (no fixed point) I guess it could cause some retina damage it hits the eyes, even if it only goes there for a few ms (scanning) and from a certain distance (a few meters).

You are correct. The potential is there for injury even at much lower power levels. However, laser eye injuries are tricky. I have seen people get hit direct in the eye by 5+ watts from an argon laser and suffer no long-term consequences, and I've also known people who have developed a tiny blind spot from a brief exposure to a 1 watt beam that struck from an off-axis angle. The eye is also remarkably adept at healing itself.

And finally, the brain will immediately try to compensate for any loss of vision or blind spot by combining visual information from the other eye, making it difficult to realize you actually have a blind spot. (We all have a blind spot in each eye where the optic nerve attaches to the retina. This blind spot is actually quite large, yet none of us ever notice it unless we are performing a visual experiment that is specifically designed to point it out to us.)

So in the end, you may be exposed and suffer no injury (other than a persistent after-image for a few minutes, and maybe a bad headache), or you may end up with a permanent blind spot that you never notice because your brain hides it so well. If you are ever exposed to a dangerously powerful beam without protective goggles and are worried that you may have injured your eye, you need to go to an ophthalmologist and have him take a look at your retina to be sure.

Yes, you guessed it.
I live in France.

I thought your English was very good. I had no trouble understanding exactly what you were asking. I hope you can understand the replies equally well, but if anything is not clear I will be happy to explain further. Also, I'd like to encourage you to try to attend a Laser Enthusiast's Meeting (LEM) near you in the future. It's a great way to meet other laserists who share your interest, and you can really learn a lot in just a few short days by hanging around with other people (many of whom have been doing this for a long time now). Check in the "Meet and Greet" sub-forum for details on the next LEM near you. (That would probably be one of the "UKLEMs".)

Adam

[Draco]

generally what i see people do is project onto a wall and are never facing the aperture, always view from behind the projector, when distance is needed they just bounce from a large front surface mirror and then onto a projection screen.

The problem is laser glasses are generally made with certain wavelengths in mind, i.e. for a range of infrared or for green, I wear sunglasses or turn the power down but i am never dead on to the aperture, sunglasses will not work with a direct hit or a reflection from a shiny thing, in your case i would just turn the power down, if that's possible, i have no experience with the projector you have, only in home made gear.

in the past i did a test with a static beam and a pair of sunglasses with a camera behind the glasses and hit them with i direct beam from a class 4 laser and the laser literally burned a hole in the tinted layer, plastic lenses, glass ones may not do the same.

But I too am interested in what other people do as my experience is limited

Buffo thanks for the info, i did not know they had glasses for RGB, i had though they would be too dark to do anything useful, the only glasses i have currently are for infrared and have an od of about 7, i sometimes repair DPSS lasers and own a class 4 ir laser too so they get used a lot

[buffo]

Sunglasses should not be considered safe. They are not designed to handle the high power density (irradiance) of a laser beam. Also, their O.D. rating is not nearly high enough. Finally, they are not engineered to have the same O.D. at all wavelengths.

True, some protection is better than none at all, but a typical pair of sunglasses usually measures out at an O.D. level of less than 1. At that point it's only a tiny step above wearing nothing at all, and you are still very likely to be injured. Bottom line: avoid sunglasses and get some appropriate goggles instead.

Adam

[Draco]

yeah when the budget allows i will get a pair, i never knew they existed simply because RGB covers generally the whole spectrum , but now it makes sense. i know a direct hit from a beam would render the sun glasses useless, I dont have a class 4 projector and when i do finish (one of these decades) a real RGB it's still going to be class 3b. getting the RGB will kill 3 birds with one photon. When i show off my IR class 4 i have sets of glasses for every one in the room, i have 4 Trimedyne brand that i got from ebay a while ago, They seem to work very well and have an OD of 7 for 808nm. I should change my avatar from my true form to human wearing the glasses, lol

anyway thank you again Buffo for the link

[MarcDorpe]

@buffo (and also the others): thanks for the information (so much details!) and your help.

Here is a link: http://shop.stanwaxlaser.co.uk/laser...ggles-37-p.asp

Great, small price also. I will probably buy them.

Out of curiosity, what controller are you using with it?

Before it was only plugged to the DMX port and playing default built-in laser animations, synchronized with music.
But we received a FB3 + QuickShow kit recently. That is what i'm going to test soon.

[kecked]

This is not the best way to do rgb but it can work. Get two adjustable moon filters for a telescope. They come as a pair of polarizing filters. When you turn them they block more and more light. Place each one in front of your laser projector at full power and make sure before turning the laser on that there is no chance for a reflection. turn the filter until your power meter reads 2.5mw. do this for both filters. Now make a pair of glasses with side shields and stick these in the place for the lens for each eye. These are no adjusted so the max you can get in your eye is 2.5mw

I think you will find this way to dark to work but will be fine for alignment. For watching shows on the wall you can dial it way forward on the light blockage. ie brighter image. There is also a radiometer that can be used to measure the reflected light. Best thing to do is dial down the laser to as dim as is comfortable and where color is correct. If you do that I really doubt you have to worry about reflected light off a white wall from a 1.5W scanned image.

I would stick to the 2.5mw glasses for beams. Yes people take them in the eye all the time but it is stupid.

LAST: if you wear the polarized filters you will be a source of reflection so make sure everyone in the room has them too!!!