Can anyone suggest some good quality laser safety googles that I can source in the UK? They need to fit over my prescription glasses.
I am currently building a laser engraver using a NEJE 450nm 30W Continuous Laser Module (7.5w optical).
Regards,
Les
The #1 safety feature is to install interlocks in your system.
True, but I have to look at the laser beam to adjust the focus.
I’m not sure how many active UK visible laser experts we have on the forum, so knowing whether they can be sourced from within the UK vs. ordering from outside might be beyond the particular knowledge of site participants and making people opt out of trying to answer.
Thorlabs has a European site. I know things changed recently 
with respect to what you might have to pay and what shipping times would be like. Here’s their US page for safety glasses. To the best of my knowledge, they are one of several highly-respected outfits.
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=762
J Tech ships internationally but is only US-based, so probably not the best choice for you.
Honeywell certifies to European standards so is in the European market and makes OTG laser goggles, so you should be able to search UK sellers for Honeywell 450nm OTG laser goggles.
Others can chime in with options to search for.
This is one part that I’d be wary of ordering off ebay or amazon though, given the potential cost of being wrong! 
I don’t think your eyes can accurately perceive the point of focus anyway?
You also should have some form of cover over the laser with the correct filtering material in its window.
For adjusting focus, why not use a ramp test? It’s really measuring the effect you want directly, rather than trying to infer from a visual inspection of a highly-attenuated (with goggles that cut out almost all the light) spot.
Thanks for the input guys, I appreciate any advice, but especially safety advice.
I am a complete noob, as this will be my first laser, so please correct me if I am wrong.
I assume that a diode laser has an hourglass shape and there a 2 things that need to be set correctly to get the smallest dot/ best results.
I am very much doubting that the focus will be set perfectly from the factory, so will have to be adjusted and while my crappy old eyes won’t be able to see it it is perfectly tuned, they may be able to tell if it is in the ball park. (Maybe a USB camera or microscope would make it easier and safer)
Once the laser beam is focused then a ramp test would be used to get the correct height.
The focus really sets both the height and the width of the waist of the hourglass shape.
A shorter focus gives a narrower waist but a shorter depth of focus, and is relatively more useful for engraving and worse for cutting. A longer focus gives a wider waist but a longer depth of focus, and is relatively more useful for cutting and worse for engraving.
The ramp test is the measure of focus, because the only thing that matters about focus is what it does to the material. So in the ramp test you care first about optimizing the beam for engraving or cutting. If you are engraving, you want to know the height at which the line is thinnest, and it’s OK if the depth of focus is shallow as long as you are engraving something flat. If you are cutting, you want the depth of focus to support cutting through the entire thickness of the material.
The reason you don’t see much discussion of this for LED lasers is that the entire thickness of material they can cut through is pretty low, even with air assist. So in practice I haven’t heard of people refocusing their LED lasers for cutting, because most of the time people who want to cut are not using LED lasers.
So, do ramp tests for focus, and adjust the focus for the workplane you want.
(I understand that not all LED lasers even have adjustable focus; for those you just use the ramp test to decide where the workplane needs to be.)
I’m not talking you out of high quality laser safety glasses! The blue lasers are super dangerous to your eyes because they will fry your retina without you noticing. (My understanding is that CO2 lasers at least blast your cornea first…) I’m only suggesting that trying to focus by looking at the beam isn’t a good approach.
You should not look directly at the beam for any reason without protection. With or without protection the beam on the surface will be highly diffused and very bright. Your eyes, old or new, will be useless in this regard. If your eyes get exposed they will become even “older” … like blind.
The laser’s DOF at the waist is very small so the only practical way to find the focal point is to measure it with a ramp test. Looking at it with a camera or microscope does not show you the smallest point on the waist of the beam.
You did not tell us anything about how you will adjust focus? Are you setting focus by moving the frame or head up/down?
Once the laser beam is focused then a ramp test would be used to get the correct height
In most systems, the correct height and focus are the same thing? At least in the modules, I have seen the objective lens is not (should not be) adjusted?
There are solid-state lasers with adjustable focal length. It looks like NEJE does have some on the market.
Do you mean “non adjustable” ?
No. There are both fixed and adjustable focal length solid state laser modules. Why would I mean “non adjustable” there?
The great thing about places like this is you learn something new all the time and just when you think you know … you don’t.
I went looking at NEJ laser engravers and now I stand corrected 
.
I would still try it but I don’t know how useful a ramp test would be because you would have to figure out how much to rotate the threaded lens holder to tweak it to hit exactly on the surface. Maybe multiple ramp tries until the smallest point is on the table.
It seems that adjustments for engraving vs cutting will also be a challenge to achieve. At first thought, I would get a selection of various thickness materials to use for engraving vs cutting and put them under the target.
Thanks again for the input.
I do take the safety aspect seriously, which is why I haven’t even tested the laser yet, though I have had it for a few weeks.
The module has a focus wheel on the lens and quite a nice sliding mounting bracket.
Yes but with an adjustable focus lens, surely it is a 2 part job? Adjust the focus for the smallest waist on the hourglass and then get that point in the correct position on the z axis. That is one of the reasons I wanted to add a motor driven z axis.
Anyway I have ordered a cheap digital microscope camera, so I can use it something like this…
I’m in the UK and bought mine from a company called Thorlabs. The have a UK arm but my glasses came from the US. I found them to be good, I spoke with someone to make sure what I was buying was right for my K40. They aren’t cheap but are ce marked and are from a reputable company. What cost can you put on your eyesight? I think mine were £120 ish. The style lg2 should go over your normal glasses. I have those and mine fit.
If you really care about your vision you will install safety interlocks and covers.
There is no way an open beam laser of this power is safe.
Laser Strikes are called accidents because something unexpected happened. The laser was unexpectedly on and a strike occurs when you weren’t wearing protective glasses.
I just cannot imagine myself looking at a laser beam through a microscope. There has to be a safer way.
Thanks for the info, I will take a look at Thorlabs and see if they do anything suitable for a 450nm diode laser.
Well you are looking at the beam on a computer screen, which I guess is no different than looking at a youtube video.
The cheapo (<ÂŁ20) USB microscope arrived yesterday and I am quite surprised at the quality for the price. Now I just need to get the machine built. 
AH! Your talking about a digital microscope. I did not watch the video! Ya I would do that if there was covers on the machine :)!
