Quote:
Originally Posted by
echelon
I'm going to scratch the "clouds" idea completely... it sounds way too
complicated to be safe and compliant, and as a beginner I know I can't do this.
(Thanks Jon! You certainly convinced me that this is extremely unwise.)
Hey, no need to! Cloud scanning is my goal too, but you need some big laser systems for them (multiple watt laser systems) and I don't think I'm experienced enough to handle them. It's just not a good idea to start right off with cloud scanning :)
Quote:
What three lasers (perhaps R, G, B?) would be best to combine to produce
a wide range of output colors in a cost-effective manner? When I do eventually
work outdoors, how powerful will they need to be to shine on a building and
still produce vibrant color? I hesitate to use wattages that are too powerful
for a beginner though. I don't trust myself to be 100% safe until after I've had
experience; I do not want any accidents. I can always upgrade the lasers later.
RGB is how it's mostly done. As for the powers, that depends on the circumstances. 1 W of each colour will be more than enough for a white wall a few tens of metres away in a dark environment, but you might need more when there is ambient lighting involved. Others are more experienced so I'll let them give better suggestions.
Quote:
colouredmirrorball:
I get the sense that heat dissipation is going to be a big problem with some of
these lasers. If I stick with low-power lasers, will this be a non-issue?
When I do scale things up, can I develop a large housing to keep the optics as
far apart as possible to minimize their contributions to total heat? Aside from
a heat sink, do you typically employ fans?
That depends on the lasers theirselves too. Some modules have a cooling system built in and will automatically shut off if the laser becomes too hot. Others require a fan constantly blowing air over them. Some lasers are more than happy if they are just passively cooled when mounted on a big base plate. Most projectors do have fans in them, and that brings the issue of filtering the dust out of the air before it reaches the optics.
Optics generally have no problem with heat, unless you really go crazy with laser power (say, 5-10 W?). If you design a large case you might get away with no fans at all because the heat can be sufficiently dissipated through the case, and you will have room for improvements such as bigger lasers in the future (that might spoil the passively cooled case). But this is of course at the cost of your back, and a big case isn't always better when you don't have a lot of space.
You just have to look at your system, set it up, let it run for some time and touch the laser housings from time to time. If you notice they become too hot, better add some cooling.
Quote:
My knowledge of electrical and mechanical engineering is pretty poor, but do you
think a beginner such as myself could build a laser from the diode, driver,
etc. directly without too much trouble? I've only done extremely basic
soldering work, but as I mentioned before I should be able to get some
assistance from the campus EE department. How hard is it realistically? Would I
be better off getting something already built? (Granted, I _do_ want to learn how
to do this. I just don't want to destroy the equipment on my first go.)
Depends on you I guess. I could do it so there is no reason you wouldn't, but expect to blow a few diodes in the process. It's pretty unevitable but part of the learning curve.
Something you want to look up is ESD. It's the main reason of death of diodes, and you can avoid it with a few basic steps. A Lasorb is a little device that protects the diode from ESD, but it doesn't protect against stupidity. Just a few hints.
Also when you really screw up, don't feel bad because someone has already screwed up more badly (like me... hehe).
Quote:
Misc. questions:
Can the 30K galvos that JohnYayas mentioned reach 1000 points max with minimal
flicker, or do I need higher KPPS? I really want to minimize flicker, maximize
points, and maximize drawing distance, so I'll invest more in the galvos if it helps
and still falls within my budget. I don't want to have to scale down the
image--if anything, I want it to scale up. I may be forced to reduce draw points if
it's absolutely necessary.
1000 points can be achieved with not much flicker, if you reduce your scan angle. You need to experiment (or attend a LEM, it's really recommended!), but you'll find 30k can handle 1000 point frames just fine. There will always be flicker but it's up to your taste if you find it too disturbing or not.
Quote:
Could I get a second laser/xy-galvo/DAC to work synchronously with another set
in order to effectively double the number of points or the scene complexity?
With a clever algorithm, it may do more than double scene complexity since the
vector draw points could be clustered to each galvo, giving them both smaller,
optimal drawing paths. Would aligning and rectifying two separate galvos be
hard? (This setup might be way too expensive to even try. I need to get my feet
wet with the basics anyway.)
PL user masterpj tried that at the most recent DutchLEM. I'd say the technique works, but it's hard to set it up. You need to make sure the images overlap each other perfectly and you need to apply geometric correction.
http://youtu.be/Yyz7I2k6lYM
Quote:
How inefficient is it do draw "solid" figures instead of outlines? I've seen
several videos where lasers are used to "paint" solid surfaces. Perhaps I can
cheat a little bit and draw alternating scanlines that give this illusion.
I don't know what you mean exactly. There are two ways I can think of what you mean: using a raster, or using lenses to quickly expand the beam.
Raster graphics are commonly used and they work similar as a television, only you can tell the different lines apart and you can't have too many detail in them. It's a neat trick for every now and then. You can't make the image too big because a raster is usually rather complex (about 1000 - 1500 points) so the flicker is noticeable. Also you need to optimise blanking. For other graphics you can get away with a poorly blanked line now and then but with rasters each line needs to be blanked accurately, or the effect isn't visible.
The other option is a lens that can quickly alter the divergence of the beam. I think Pangolin developed such a system, but as always with Pangolin, it's not cheap. Also the opinions over the result of the effect are divided. I haven't seen it in person so I can't recommend.
And good luck with your exams! I better start preparing myself for mine as well...
