How much power do I need?

[game-genie]

Seriously,

For a image of the size you need, and the distance you need, you are going to need a powerful laser with very low divergence.. Unless you expand the beam ( and loose scanner speed in the process ) your typical Chinese DPSS is not going to cut the cheese..

I would suggest you look at a 8w ( at least ) OPSL, maybe even combine 2 of them, and you are looking at some pretty serious cash now.

Full ACK!

And Im pretty sure the projection will be on a building in a city where something like "night" doesnt exist...

One of these low Mrad lasers... NO actually 2 could do the job!

Best regards
game-genie

Edit: Is it even possible for galvos to run a whole night? I cant imagine these motors running the whole night and living long! Optics which would produce the wanted image would be better (and cheaper). Ive got a cheapo red laser a while ago which had caps with many diffrent logos and texts.

 

[HIMNL9]

Those logos from red ones are generated from cheap diffraction gratings (with a matrix of dots) and are repetitives ..... but i don't think that the OP need something similar (also, obtain from an optic lab a crystal diffractor custom made for your logo, i think is all except cheap )

About galvos, good ones have ball bearing suspensions, so probably they don't suffer to continuous usage ..... cheap ones with bronze rings, maybe yes, after a prolonged working life, like, several weeks in overheated condition) ..... but ball bearings ?

I have seen ball bearings on the heads of HDDs that i have dismantled (basically, they do a similar type of work, alternate moving at fast speed), some of them was used in servers, so, 24/7 work for years at mid-to-high temp, and til now, not found a single one ruined or blocked (and i dismantled so much of them that i literally lost the count )

 

[Things]

Full ACK!

And Im pretty sure the projection will be on a building in a city where something like "night" doesnt exist...

One of these low Mrad lasers... NO actually 2 could do the job!

Best regards
game-genie

Edit: Is it even possible for galvos to run a whole night? I cant imagine these motors running the whole night and living long! Optics which would produce the wanted image would be better (and cheaper). Ive got a cheapo red laser a while ago which had caps with many diffrent logos and texts.

Yes, as long as they are heatsinks, galvo's don't require a duty cycle. Imagine that, having to stop the show every 20 minutes to let your galvo's cool down!

 

[HIMNL9]

Uhm, all the decent galvos that i've seen til now, had a big "tubular" part that fit the ball bearings, and that is held in the holder block (the aluminium block that hold them in position) ..... this is usually a good thermal transfer, and considering that also the holder block is usually very thick and robust, i suppose they are someway heatsinked, especially if the block is fixed on a heavy metal plate ..... but none say that a little fan cannot pointed at the block or fixed over it, too, if needed

No, i think that overheating of galvos, after all, is the last of the problems, in these assemblies

 

[ElektroFreak]

Definitely no duty cycle on galvos. I've used mine for for up to 9 hours at a time. They'll last a very long time.

 

[Cyparagon]

500mW to 1000mW of green should do nicely..

Not in a 200ft image it won't. Are you guys out of your minds?? That's 0.0125mW/sqrft. That's equivalent in brightness to 3-5mW projecting an image on a 5'x5' square. That would be tough to see from 50 feet away. But 500 feet away? On a less than white surface?? with who knows what ambient lighting conditions?? Forget it. You need tens of watts for something THAT big.

The scan angle is also way too large for anything remotely complicated. the angle of 200ft at 200ft is the same as 1m at 1m, so that's 1000mRad, or 1radian which is >57 degrees scan angle.

 

[ElektroFreak]

^Yeah. We kind of established that already in the rest of the posts in this thread... I was definitely incorrect, due to the fact that i didn't take into account all possible variables.

 

[Cyparagon]

Oh, my apologies then. Didn't read everything like I usually do.

 

[casalaserlight]

if need basic laser light, can chat with casa laser light.

 

[Helmholtz Watson]

You need at least 1 gigawatt if you want your lasers to go back in time.

Get it right mate, it's 1.21 "Jigger"watts