Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

Red laser diode intensity

Joined
Apr 18, 2012
Messages
18
Points
0
Hi, I'm quite new to lasers and therefore need your help. I want to buy an inexpensive diode that produces a visible beam. I was wondering if a 650nm 100mW diode would provide this?
Kind regards
 





midias

0
Joined
Mar 14, 2010
Messages
631
Points
0
Not very visible at all.

How cheap? How Visible? You can pick up a crap green 30mw that will make a visible beam.
 
Joined
Apr 18, 2012
Messages
18
Points
0
Thanks for your reply. Sorry, I need a red laser for my project. Preferably, I would only want to spend around £10-£15 but if I can't get anything decent for that amount, then I will stick to my current 5mW diode. With regards to visibility, I would like to be able to see the beam fairly well. Not so much in bright light if that helps.
Thanks again
 

Soren

0
Joined
Apr 7, 2012
Messages
68
Points
0
Building a simple 200-250mW red laser with a diode from a broken dvd drive would fall within your price point, (if you scavenged parts) but the beam would still not be visible in a lit room. If you do get a >5mW laser make sure to purchase safety goggles.
 

Hiemal

0
Joined
Dec 27, 2011
Messages
1,443
Points
63
If you want to go for beam visibility definitely go for a green laser. You'll be able to see the beam of even a 5 mW greenie, in a dark room.

As you get brighter the beam starts to become more and more visible in lit conditions.
 
Joined
Apr 18, 2012
Messages
18
Points
0
Hi, Thanks for all your replies. Lase, the laser really does need to be red. I am building a prop replica of a Star Trek Boomerang phaser and the beam is orange. Now as orange LD's are WAY more than my budget, I decided to go for red. Soren, thanks for the advice. I will look into getting a dvd drive and definitely some safety goggles.
One last question. What sort of power would be needed to produce a beam with a red LD in a dark room?
Many thanks again
 
Joined
Apr 18, 2012
Messages
18
Points
0
Midias, that's fantastic. Just what i need, thanks. Can't wait to receive it now. Thank you to all for a pleasant first experience on your forum.
Kind regards
 
Joined
Mar 22, 2011
Messages
791
Points
0
Midias, that's fantastic. Just what i need, thanks. Can't wait to receive it now. Thank you to all for a pleasant first experience on your forum.
Kind regards

I assume it is safe to say you understand how to build a laser? 'Cause you'll need an aixiz module and a driver. If you need any help building it, let me know. I'll offer as much advice as I can.
 
Joined
Apr 21, 2012
Messages
57
Points
0
Protip: If you can (and if it doesn't interfere with the rest of your project), add some smoke into the beampath.

You can get that from fog machines, or you can also buy canned smoke from hardware stores (the sort used to test smoke and fire detectors).

Even a little bit makes a drastic difference in terms of off-axis beam visibility.
 
Joined
Apr 26, 2010
Messages
4,175
Points
83
And if that doesn't work (can't see why not) try getting a lower powered 635nm diode, around the $20+ range though, but much more visibility.
 
Joined
Apr 18, 2012
Messages
18
Points
0
Ah, fretwrecker94, I was aware I might need a driver but wasn't sure how to go about getting one. Am I right in thinking I can build one? Your advice would be greatly appreciated thanks. Oceansoul, strangely enough I was playing around with smoke with my little 5mW LD and it looked great. I might have to have some smoke on standby. Thank you bloompyle for the advice. Will keep that in mind if the new diode doesn't work.
Thanks again
 
Joined
Mar 22, 2011
Messages
791
Points
0
There is no "might" about it. You absolutely, definitely, undeniably need one :)

Here's just about the simplest one you can build

Laser driver - It can be done

O, the everlasting relevance of that page.

If you need any help building it, PM me and I can give you as much advice as I can.

*additional info edit*
Regarding your 5mW red plus smoke, if you are going to use a smoke machine to expose the beam, you can use a much lower power diode. You just have to keep the area filled with smoke. A good fog machine will do this easily. For safety's sake, I think springing the extra cash for a fog machine and using a low power module (5mW-30mW) would work fine. Just remember the goggles. And the goggles look really cool, so you don't need to worry about ruining the Geek Chic
 
Last edited:
Joined
Apr 18, 2012
Messages
18
Points
0
Thanks for the link. I will take a look at that shortly. I would prefer not to have to depend on smoke to see the beam but if all else fails then I will stick with my 5mW LD and get a fog machine. I will definitely be getting goggles, I think they look cool no mater what. Plus they save your eyesight I anything goes wrong. Thanks for your offer of help as well. I will message you if (more likely, when!) I need help.
Thanks again
 
Last edited:
Joined
Apr 21, 2012
Messages
57
Points
0
You don't need a driver if you don't want the magic smoke to remain in your laser diode for more than, say, a few seconds.

All electronic devices are imbued with a small quantity of magic smoke at the factory. That's what makes them tick. Let the smoke out, and the stop working. :)

The LM317 CC driver that Fretwrecker94 linked is one of the easiest things you could build. If you're game, you can even build the whole assembly onto the back of a diode. It's not something I'd really want to try, but it has been done before.

On the other hand, if you don't want to fiddle around soldering bits and bobs to stripboard, might I recommend these nice, dirt cheap linear drivers from AixiZ.

They do 80-500mA full range and to set the current you just need to tweak the pot while watching the current readout. They're incredibly easy to use.

If someone hasn't already suggested you a diode, I'd recommend this thing. 20mW of 635 at the manufacturer's recommended current and voltage.

$17 isn't overly expensive either (for a single-mode 635nm diode).

The really awesome thing about 635nm is that beam visibility is at least on par with 445nm. It's not quite 532nm-visible, but it's a major improvement over 658nm. Most of the guys over at the 'lexicon use a ratio of 1:1 between 532:635 when they're shooting for a nice white (with additional blue, of course).

If you're in a dark (or even semi-dark) room, 15-20mW of 635nm should be more than easily visible.

The other thing to take into account is the angle from which the observers will view the beam. A beam is significantly less visible when viewed transversely (that's a word?) than if one were, say, looking down it. Try it for yourself. Stand behind your laser and look down the beam. Then try moving yourself around relative to the beam and watch how the visibility changes.

Now, speaking of darkness, there's several things you can do to make the beam more visible without turning up the power.

If the venue has dimmable lights, use them. You've said it's a prop, so I'm assuming it'd be for some sort of production or whatnot.

And of course, use some sort of particulate in the air. And I say particulate because I don't necessarily mean it has to be fog. If that's the case, using a fogger (fog machine) would be entirely inappropriate unless you could fog up the entire room and let it disperse slowly. Because foggers aren't exactly known for a nice, even production rate. They fart a dense cloud of smoke for a little while and then stop. So one moment you'd have a room with nearly nothing in the air, and the next, nobody can see a thing.

Foggers don't exactly have the best hangtime either; you're looking at around 10 or so minutes in a small room and less than 5 in an air-conditioned room. If you do it right, fog can be very discreet, yet bring out a beam like nothing else. If you do it wrong, you'll have everyone choking one minute and nothing left the next.

And if it is a production, sudden bursts of fog may or may not be appropriate (cue disappearing stage). If you have a budget of some sort, I'd recommend going out to your local music store or sound/vision/lighting store and hiring a hazer. They work like this. Not a lot of fog, but a steady trickle of it instead. Great for filling up rooms slowly (and keeping them filled). Just about nobody notices them (which is always nice). You also don't get the sudden disruptive BLAAAAAAAAAAARP of glycerine vapour leaving a nozzle at high pressure.

Over here on the other side of the pond I can get one out for around $80 a night (and these are high-quality Martin units).

I'm guessing you have a fog machine. Canned smoke isn't exactly a viable option for a large-scale rig (for a desktop optics table, it'd be fine, but for anything bigger, don't even think about it). Canned smoke has no hangtime, the propellant is flammable, and often it smells nasty as well.

Now, if you can't get a hazer, but have to use a fog machine instead, you can always see if your machine has an 'idle' or 'standby' mode. Normally when they're idling, they let out a gentle trickle of fog or a very small burst every few seconds. Send this through a fan, and you have an instant hazer. It's far from ideal, but it'd be much better than using a fog machine in burst mode.

A 1kW fogger on continuous burst can do horrible things in a 24sqm room. #LFMF.

But still -- your best option would be a 635nm diode and a fogger. (Relatively) inert (not eye-safe, of course, but much safer to handle than a 658nm DVD burner build) , relatively easy to build too. Worst case scenario it'd be a little too bright in conjunction with the fog, in which case you could back off on the diode current or the fog density.

Anyway -- I hope all of that made some sense. I did a tour of duty ( :/ ) as a lighting tech a while back and hopefully what I've dumped into this post is of some help to you.

Questions? Give me a buzz. I don't bite; I promise. :p
 
Last edited:




Top