[Scott Riddle]

I am looking to put a 1w 808 nm laser diode on my cnc table to do some simple wood burning and possible light cutting of thin materials. I am looking to use a laser diode off of Ebay. I want to be as safe as possible so I am looking into laser safety glasses as much as possible. For the 808 nm wave length the diode I am looking at puts out I see safety glasses out there from around $35 (ebay again) up to $200+ from commercial sites. My plan is to shield my setup as much as possible but I would still like some way to protect my eyes. I am thinking of getting the $35 glasses from Ebay but I was wondering would brazing or welding glasses provide any protection and/or could they be used. I already have brazing goggles and a welding helmet.
Thoughts?

Scott

[underthetire]

Welding stuff is usually just dark with UV filter. 800nm laser needs 800nm goggles. Why take a chance on the only pair of eyes you have. I wish I could post our laser training video on line. Lots of good info there.

[DaveDoesIT]

It's not a matter of the light being too bright and thus using welding glasses solves the problem. It is a matter of the wavelength physically damaging your eyes.

The glasses are a filter for that specific wavelength group. It will not matter how well you shield the machine, reflections are always a possibility and you will NOT see them until your world starts to dim. That wavelength has the ability to burn the retina, ain't no coming back from that.

If you have $35 eyes then get those. Personally I would be buying from an accredited laser eye-wear protection company. Someone who has a financial liability in selling you the correct glasses.

For CO2 lasers it is an entirely different thing as the IR wavelength is totally filtered out by plain glass and acrylic. So welding glasses are OK just to protect from the brightness.

I have seen cheap pink/red colored "laser" glasses come with a piece of paper saying, "not guaranteed to protect from laser wavelength light." They are your eyes and has been said, you only get one pair.

Dave

[Scott Riddle]

With all of this scare over laser light and damage to your eyes what are other people doing to protect themselves when making and using similar homemade laser burning/etching tables?

Does anyone know of somewhere to purchase safety glasses (for 808nm wave length) from a acredited supplier that stands behind them and dont cost a arm and a leg (ie,$50).

[zax15uk]

Short answer: No.

Many of the Chinese laser vendors sell glasses for around $25 but I wouldn't trust my eyes with them. I value my vision a lot higher than that.

Depending on the power, you could build an enclosure around the laser. Use a webcam or remote video camera to focus the beam - once you know the offset to achieve focus you can set that in the Z-axis and adjust automatically.

Zax.

[Scott Riddle]

That was kind of what I was thinking of doing. I have a old Sony Hi8 camcorder that has a night vision mode that works off of infra red. I am not sure what wave length it will all see but I was thinking to try it. Once I get the Z height figured out for focus then I should be good. I am looking at collimating lenses to focus the beam down to a very small point. Hopefully in the .003-.004" range. I should get pretty good beam density at that point and be able to cut/burn pretty good.

[tdiaz]

Or integrate a beam combiner and use that for alignment.

Then again, that may not be possible, for all I know. I've only worked with C02 so far. Lots more to learn.

[DaveDoesIT]

With all of this scare over laser light and damage to your eyes what are other people doing to protect themselves when making and using similar homemade laser burning/etching tables?

Most of the home built stuff is using CO2 lasers and plain glass or acrylic (Plexiglas) will absorb all that energy. With those you can have a window in the top of the machine and look in with impunity. The bright light will damage your eyes over time but it is not the laser burning them. Welding glasses would be OK to protect for that.

A collimating lens cannot focus. It is used to pack the the light beam into a neat parallel beam. You will need a focusing lens usually called a plano convex, a plano concave or Meniscus lens. It will also have to be made from a material that absorbs little or none of the energy from the laser.

For CO2 lasers that is a Zinc Selenide lens (ZnSe). With 880nm being close to the IR specrtum the ZnSe may be OK. I do not know for sure though.

Interestingly, the lens material has to be the exact opposite of the safety glasses you first asked about. The lens has to pass all of the energy at the laser frequency. The safety glasses has to block it all at that frequency. Both ends of the scale.

Dave

[ImanCarrot]

www.edmundoptics.com will give you all the info you need on safety glasses.

I am trained in laser safety and you do not want to see some of the training videos I've seen about damage to eyes. Don't mess about with your eyes.

[telmnstr]

I found this thread. I'm rebuilding an older laser engraver, and need to build a new box around it. Most of the lasers I've played with were for light show apps (5 watt argon, 150mw argon, 300mw dpss 532nm type stuff).

So commercial laser engravers just use normal plexi glass for the view window?

Any thoughts on a good way to test it?

[bdring]

The normal CO2 lasers sold all over the palce will not "shine" through normal clear materials like glass, plexi and polycarbonate. That is why you can etch them...and why CO2 lenses are so expensive.

An easy verification is to put a piece of thermal fax, or printer paper under the the clear material. That paper marks with a minimum amount of laser power. I have done it with glass and no mark unless the material actually gets hot.

When etched, some materials like glass or granite create an extremely bright spot that can hurt your eyes, like looking at a welding torch tip. You should not look at that even with high quality CO2 glasses.

[ImanCarrot]

As an aside, CO2 lasers will burn the front of your eyes and anything else- was working with one testing a thermal imager when I thought "what's that smell of burning?"-- it was my thumbnail! lol (no kidding).

Alignment lasers like HeNe will actually focus down onto your retina and burn it- done it myself whilst focusing a HeNe onto a microscope objective.Obviously I could't wear safety glasses 'cos I had to see the red dot. Bad mistake, my right eye still can't see straight lines properly.

Dun mess with your mince pies.

[DaveDoesIT]

I'm rebuilding an older laser engraver

snip...

So commercial laser engravers just use normal plexi glass for the view window?

Providing it is a CO2 laser. If it is an Nd:YAG it will eat through Plexi glass in a heartbeat.

The CO2 wavelength is almost totally absorbed by the glass and Plexi glass at a distance.

At the focus point a CO2 will easily cut Plexi glass. I used window glass on the box I made for mine. Be careful of reflections from whatever you are working with under the beam though. Stainless steel has a HIGH reflectivity for the CO2 beam.

Picture 03 is a piece of paper with with some brushed stainless steel at an angle beneath it. The beam was shot through the large hole which I had cut earlier. The small circle was cut by the reflection.

Picture 05 is a piece of paper attached to the underside of the lid and 10" up from the paper with the two holes. The scorch makrs were done when the reflection burned the smaller hole.