How to tell when a laser is properly focused?

[shumon]

Hello! New here and reasonably new to the hobby.
I am playing around with some LPC826 diodes in a mount with an adjustable plastic lens, but I'm having trouble telling when they are focused how I want them to be / if the lens or diode are a couple degrees off. I'm using my smartphone camera to take an image because I can't see anything through my goggles, but the sensor gets washed out by the light around the focus point to be of any use.
I had a blue diode before that would cause some fluorescence I could see through the goggles that helped me focus it, but red doesn't do that.

How do you guys go about focusing your diodes while wearing your goggles? Any tips would be greatly appreciated.

Thanks!
-shumon

 

[Shmackitup]

A plastic lens will probably melt fairly quickly depending on the power you're putting through it. You should definitely get some glass lenses for anything of power. Multi-mode diodes are focused when you achieve a thin, crisp line if you're just using a single lens solution. You should be able to see it clearly if the goggles you are using are rated for the wavelength you are using.

 

[Alien Laser]

You can place a small piece of 2/4 wood and focus it, Lasers always need to be focused in & out unless you are doing a fix focus you can do it outside and get a perfect dot in far distance

 

[shumon]

A plastic lens will probably melt fairly quickly depending on the power you're putting through it. You should definitely get some glass lenses for anything of power. Multi-mode diodes are focuses when you achieve a thin, crisp line if you're just using a single lens solution. You should be able to see it clearly if the goggles you are using are rated for the wavelength you are using.

I thought the point of the goggles were to completely block out the light? My glasses are at OD7 which is much more than I needed for a 200mW laser but I thought I shouldn't see anything from the laser through them.
Point noted about the plastic lens.

Thanks for the advice!

 

[shumon]

You can place a small piece of 2/4 wood and focus it, Lasers always need to be focused in & out unless you are doing a fix focus you can do it outside and get a perfect dot in far distance

On the wood would I be looking for burn marks? Also, what do you mean by 'focused in & out' and 'fix focus'?

Thank you for the reply!

 

[GSS]

Hello! New here and reasonably new to the hobby.
I am playing around with some LPC826 diodes in a mount with an adjustable plastic lens, but I'm having trouble telling when they are focused how I want them to be / if the lens or diode are a couple degrees off. I'm using my smartphone camera to take an image because I can't see anything through my goggles, but the sensor gets washed out by the light around the focus point to be of any use.
I had a blue diode before that would cause some fluorescence I could see through the goggles that helped me focus it, but red doesn't do that.

How do you guys go about focusing your diodes while wearing your goggles? Any tips would be greatly appreciated.

Thanks!
-shumon

Are you at least seeing some type of spot with the glasses on? Beams aren't really visible but a big maby with a super high power laser and glasses rated at a high 50% VTL.

If you use this LPC826 laser safely with it having no chance of hitting you by a reflection you can look at the beam and spot without using safety glasses. The spot "might" be a little bright at 200mw and your eyes might get a little tired from seeing it but the eye tiredness won't last long at all. It's the green laser spots that really get you tried.
If you do any burning with a laser then glasses are a must.

Some use some type of fog when playing with their lasers to enhance beam/spot.
You can light up some incense which works well also and dim the room lights a little.

Like member "Smackitup" mentioned you should get a glass lens. I'm not sure at what power a plastic lens starts to melt? 200mw or 300mw is probably the plastic lens cut off point.

A laser focuses 2 ways. One way is starting it off with a smaller beam focus from the tip of the laser which then starts to expand and focus the spot down at a wall type of beam stop maby 4 to 5 feet away.

Another way is to turn the lens in?? to which the beam comes out fat from the lens tip and comes to a very thin line maby 3 or 4 inches and then starts to expand after that thin line. That thin beam point is the best focus to burn.


This type of focus is used mostly to burn things or light a match.. Some fog/smoke with the room lights on the dim side really helps to see this.
There are animated pics of the focus setups, googling might help finding it.

Can you post a pic of the spot to see if the lens is melted or dirty?

 

[LumenWorks]

OD7 rated goggles are probably totally blocking the laser light. I have a couple of different rated goggles to work with lasers. OD7 for higher than 3W or so and OD4 for anything less. And of course appropriate goggles for wavelength.

200mW is too bright to look at a beam spot without goggles. OD4 goggles will allow you to see the dot on an object so you can focus it properly without harming your eyes.

 

[Alien Laser]

The LPC826 diode is <200mW is not going to burn anything that quick, very simple to focus post a pic of the laser, fix focus is when you fix the focus in a host and never adjust it again example a pen host.

 

[GSS]

OD7 rated goggles are probably totally blocking the laser light. I have a couple of different rated goggles to work with lasers. OD7 for higher than 3W or so and OD4 for anything less. And of course appropriate goggles for wavelength.

200mW is too bright to look at a beam spot without goggles. OD4 goggles will allow you to see the dot on an object so you can focus it properly without harming your eyes.

I have a pair of Eagle brand glasses at OD6 with a 50% VTL
Using them on the proper WL I can still see a lower power spot. I'm not to sure but I think the VTL makes the difference? and with good quality glasses.

If you use your laser safely and 650 to 660nm red at 200mW or less isn't to bad on the eyes without glasses..
I would never push the issue of not using laser glasses but some spots are meant to be seen..

 

[paul1598419]

I have many lasers below 200 mW and never use goggles to look at the spot as long as it can't give a specular reflection. Wood is best and won't burn at these powers.

 

[GSS]

I have many lasers below 200 mW and never use goggles to look at the spot as long as it can't give a specular reflection. Wood is best and won't burn at these powers.

I was hoping you would chime in Paul.

You have posted before about feeling safe without glasses on 200 mW lasers as long as the conditions are really good.

 

[Encap]

Given that you are new and have little if any experience or knowledge about lasers as you say "what do you mean by focused in & out' and 'fix focus'?" at least be aware of the risk and hazard level of a 200mW laser pointer which can cause eye damage. "fixed" means fixed/not adjustable and "focused in and out" means turn the part that holds the lens adjusting the lens closer or further away from the laser diode--same as focusing anything with a lens.
It's irresponsible not to point out/mention that it is all fun with laser light until an accident happens. Same as with anything else where and accident can cause physical damage of any kind.
It's all fine, well, and good "playtime"until an accident happens and causes ocular damage in less time than the human blink reflex of 0.25 seconds which is how fast it happens making it not possible to correct once an accident is in progress.

see: https://www.lasersafetyfacts.com/3B/ and laser hazard chart here: https://www.lasersafetyfacts.com/resources/FAA---visible-laser-hazard-calcs-for-LSF-v02.png

Best web site and information on all aspects of laser laws and laser pointer safety, see: https://www.laserpointersafety.com/

 

[shumon]

I have no intention of using my laser pointers without safety glasses— it may be easier to focus and not cause eye damage by viewing the spot under good conditions, but as Encap mentioned, all it takes is one accident.
I'll look into picking up a pair of OD4 glasses so I can see a small bit of light from the laser through the glasses, or try increasing the power to my diode since I'm running it below the maximum current it can take to see if it lets me see any light from it through my glasses. Does anyone have information on the lowest amount of laser power that's visible to humans/how powerful a laser has to be to be visible through OD7 goggles?

Thank you all for the helpful advice!

 

[Alien Laser]

I remember testing the diode 300mW & <350mW Max <350mA i try pushing it to 400mW+ and the just dim

 

[atomd]

We sometimes work in lab with 4W average beams (femtosecond lasers) without googles if need we have to. We also like to wear glasses around HeNe if possible. That power doesn't really matter that much. Even 1mW beam can permanently damage your eyesight when collimated and mounted.

I own a set of 5-40mW laser pointers and I already feel uncomfortable playing with it in my room. Too hard to predict random reflections or poor diffusions.

 

[kecked]

What do you want to focus for and on would help answer. If it were me I’d use colored plastic and focus on the plastic. 200 mw when focused should melt say black electrical tape. Measure the hole/ dent with your eye and move the lens when done your done. If you want collimation for distance bounce the laser off some mirrors so it is next to you and move the lens till best size. Watch tech ingredients on YouTube he does this well. Hope that helps.

I guess you could also put a variable polarizer in the beam and attenuate it and measure it directly. Be careful of reflections and you should be fine.