Hello from proud owner of 500mW RGB laser

[hughster]

Hi folks!
I'm new to the forums so hope I'm posting in the right place.
I've recently purchased an 500mW RGB laser to do photography with the interesting time based effects from a linear light source with a line generator.

I've tested the laser with protective glasses and it works. And it's just about the right power for the photography I'm doing.
I'm designing an enclosure with a tripod mount, adjustable line generator, cutoff switch and adjustable mask.
I'm leaving enough space in the enclosure to host an arduino so I can adjust the colour of the laser with PWM.

And of course I'd like to check that the laser is safe - the last thing I want to do is damage anyone's eyesight.
I've read about laser safety and calculating safe distances.

I'm looking forward to getting this project going...

Hugh

[WookieBoy]

Hey Hugh, welcome to the craziness that is laser addiction!

There's plenty of very clever folks on here who can answer most of your questions, but in the meantime, I'll wade in and say hello.

As you're doing photography, it's worth knowing that your laser can fry the ccd in your camera faster than you can blink if you get a direct hit on the lens. So, treat your camera like you would your own eyes and keep the beam from your laser away from them

There's a thread here in the meet and greet section about the next UK LEM and I'd strongly recommend that you come along if you can and join the craziness. You'll learn more there in a weekend than in a year of digging around the forum, if you survive!

In the meantime, welcome, have fun but stay safe

[dnar]

Hi Hugh and welcome!

This thread is worthless without pictures!

[hughster]

Thankyou!
Looks like I've just missed the UK LEM earlier this month and the next one's next April...
I'll put it in my diary

I do worry about frying the camera sensor with direct light - particularly with a wider aperture to suck up more light, and no defocussing or looking away mechanism...

I have a few pictures - and a sketchup model I've been working on - shall I post them here?

Oh go on then...
Here's the laser with the cover taken off, and also a photo of the beam as a line with wobblycam - the colour is way too purple at present...

[WookieBoy]

Ohhh laser pron!

I'm guessing that you bought your laser on eBay and it's of Chinese origin... The big blobs of hot-melt glue are a bit of a tell tale

[dnar]

Yeah... Zero adjustment. The costs come down dramatically without cinematic mounts and quality optics, lasers and scanners....

[hughster]

Great stuff! Thanks for your responses. I was under no illusions that I was purchasing a low cost 'does the job' RGB laser. The other option was to construct my own using red, green and violet laser pointers with a dichroic prism, which was low powered, not quite right and a lot of faff...

My main concern is the infrared content of the green laser - what's the best way of testing that?

It does make black paper smolder, which I think makes sense for 0.5 watts onto a few square mm.

Also will there be heat dissipation issues using a ridged line generator? As it's what's dispersing the beam I need it to be something that's not going to break, or distort or separate in operation, otherwise it's going to go from a 150 degree beam angle to near-to-zero in not much time...

[WookieBoy]

IR may well be quite significant from the green as it looks like dpss source from the photos, but an IR filter should sort that reasonably easily... just mount it at an angle so the reflected IR doesn't bounce straight back down the beam path and fry the source!
I think they're available from a few vendors on here, but I recommend StanWax

The smouldering paper isn't unexpected from 1/2 watt of light at close range... its quite alot of energy dumped in a very small area! However, as long as your lens is of a decent quality, it should be fine. Again, watch the back reflection as alot of diodes REALLY don't like it up em and very few bits of glass/plastic are 100% transmission. Even a few mm of back reflection over time could upset your diodes...

There's plenty more knowledgeable people on here who will hopefully chime in soon with better advice, but in the meantime you could contact StanWax and Rob should be able to help you find your way

[hughster]

OK so I've made some interesting progress.

I designed the enclosure in Sketchup and and created a cut-out template which as you change the model also changes the template.

I built a cardboard prototype which seemed to work fine except for a couple of problems - the disk which rotates the line generator needs to be mounted to something such as a nut, and the tube in which the which the line generater mount sits also needs to be attached with a nut as well - so an extra 6.5 mm was needed (attachment screws needed to be relocated).

So I fired up the laser with the cardboard prototype and found 2 problems: the green laser flickers at below room temperature and needs to wait until it warms up.
I guess that's deal with green lasers?

Second problem - the line generator creates a line that isn't particularly smooth. I don't know if it's been hanging around too much and got scratched but it's inconsistent.
OK so I did stick it on with blu tack, at an angle as recommended, and it's going to be recessed into the end in the final version, but I need something a little better than this!
I did purchase a 3mm line generator rod which proved to be too narrow.

Any ideas for a line generator? It needs to be *fairly* consistent brightness across the length, not too much colour variation (which I know will be tricky wth an RGB laser), and not too noisey, preferably within what the laws of physics will allow

OK so here are some photos:
1) the line showing horizontal banding with the flickering green laser. Also shows vertical banding which is from the line generator.
2) Laser with enclousre. The outer nipple (as the plumber called it) is for adjusting the angle. The inner nipple (trying to contain mirth) will be shortened and sit within the outer.
3) The line with all it;s beautiful fleckliness.
4) The line generator stuck on with blu-tack
5) A photrograph illustrating the kind of desired distortion effect - my desk is normally very tidy... Notice the purple to green colour variation and the interference fringes...
6) Sketchup model with cross section on left and cut-out plan on right.

Next: How many safety features need to be built in? I already have an interlock switch so if the enclousure is removed it won't turn on. I'm considering a key switch so no Tom, Dick or Harry can just switch it on without modifying it, and a connector which can be yanked off in case of emergency. I do have a giant red kill button switch but I think that's definitely overdoing it...

[Draco]

i use a mechanical line generator instead of a glass optic like you are using and the reason for that is i can control the scan rate and the mirror does not to some of the funky stuff that a glass line generator uses, i use either a polygon type mirror on a motor, the other thing i have done is use an older open loop galvanometer (basically a mirror on a spring loaded mech with a electrical coil and a magnet to make it move) and drive that with a small amp and a signal generator, that system can make x and y movements for odd patterns. The reason i use a mecanical scanning system is for liquid smoke effects and have never really liked the glass optic to do a line
The flickering of your green can be your laser warming up, if it does it after 10 mins i would kinda consider that a fault but DPSS lasers generally need a controlled temp to operate at, most have a TEC device mounted to the laser diode and crystal assembly and need some time to be stable
i an curious to how you got the distortion in the one image?