Cheating with low angle galvos ?

SO I have been reading a bunch of postings and I keep seeing that a lot of those cheap chinese units that advertise 30k galvos are only rated at very low beam angles.(as low as 8 degrees.)
Most of the members here have ascertained that most of these units operate at more of a 15k speed which is quite fine for beam shows but not for lettering or graphics, usually.
Now I have been wondering if anyone has considered using good quality front sided mirrors and just "folding" the projection a few times back and forth before finally projecting outward to possibly gain a wider angle output projection while keeping the galvos operating at the smaller scale and at the much faster rate ?
I'm not rying to say you can get a HUGE difference in size but I have a few FS mirrors that I picked up from a surplus outfit that could bounce a tight projection (say 1"x1") back a foot or so to another that might just be big enough to be able to bounce the entire image forward again that could cause the projected image to be up to 4 times the original size at the point where it reaches the front of the projector unit. Probably good enough for a smaller venue.
Would the degradation of the beam be the limiting factor for this sort of set up ? (I don't have any confirmation of the quality of my surplus FS mirrors. I don't have any good lasers yet. )
I have another idea in mind that I will have to wait to post under it's own thread later.
I am very interested to see what you might have to say.
Anyone try this out yet ?

I doubt that would be a good idea, you lose a lot of light that way. While a mirror may be 90% reflective, its clear that you would lose almost half the power in only 6 bounces.

The only way to get better reflectivity would be to use dielectric mirrors, but those generally work only 1 specific wavelength and arent practical for mulpile color projection.

Also, just adding a foot or two wouldn't do THAT much good, unless you're trying to project on a wall thats only a few feet away to begin with.

Good though experiment....

I can see the result (besides the mirror bounce losses) the
same as moving the projector further away from the wall it
will display on.... but less expensive/time consuming and
at a higher power than mirrors...


Jerry

I'm not sure I understand.

Thanks Carmangary but the idea isn't to dispute what the galvos can do but the idea of "bouncing" the projections to gain some advantage that might outweigh the disadvantages. Mostly it is a thought experiment as Laserbee states.
I might add that the bouncing need not be limited to a simple flat plane. What if you were to devise a periscope type tube to allow your heavy expensive unit to remain low where the air is cooler and the unit can't fall down while effectively moving the aperature for the beams to a greater height. (And then it could be easily disguised or hidden by other elements leaving an audience puzzled as to how you do your thing...)
Even if you aren't trying to expand the beam in the process perhaps you could still have an adjustable height for variable circumstances.
-Yeah, just sending the coherent beam to the end point and mounting the galvos there would be so much more efficient with less loss but I am just pushing the thought processes to see if it leads someone to think up something out of the ordinary.
I still have another idea in mind myself...I need to look up some more over at photonlexicon.

Anyone got any wild ideas from this ?

Yea instead of using mirrors why not try one of the DLP chips and some electronics.

EDIT, well that is not going to work I just shined a 445 onto the surface of a DLP
chip and the reflection looks like the beam has passed through a diffraction grating, poop...

ShortyInCanada said:

Anyone got any wild ideas from this ?

Click to expand...

How about a single curved mirror that causes the projection to diverge? There are prisms that are designed for that kind of thing, so a mirror should be able to work too. Of course finding such a mirror might prove a challenge.

Flaminpyro said:

Yea instead of using mirrors why not try one of the DLP chips and some electronics.

EDIT, well that is not going to work I just shined a 445 onto the surface of a DLP
chip and the reflection looks like the beam has passed through a diffraction grating, poop...

Click to expand...

Yeah, the DLP micromirror array isn't going to do much for you unless it's powered up with image data.

I'm not sure I understand.

carmangary said:

Why not bounce the beam from the galvos onto a better set of galvos? Probably would be a better/cheaper solution.

Click to expand...

so buying 2 sets of cheaper galvos is better than buying 1 better set? :na:

and how would you even sync them together?

I'm not sure I understand.

Special lenses can be used to widen the scan angle, at the cost of expanding the beam. Pangolin and Audiovisual Imagineering (AVI) sell similar lenses for this purpose. However they are not inexpensive.

My lenses are ripped out of a specialized short throw DMD projector used for a flight simulator. They expand the scan angle 2,5 times for a beam diameter increase of about 1.5 times. I've yet to find a similar setup in commercial short throw lenses, there are some special corrections made to the optics for lasers.

They are not cheap when new, and not something you can easily make.
It is a highly modified "fisheye" lens, with special corrections for wideband color and a nearly parallel output beam.

I'd guess a new one is around 800-2000$.

I found three at auction by accident. Mine are not for sale.

The other trick, besides relay/fold mirrors using 99% reflective dielectric mirrors, is two scan heads in series. That is a industrial/medical technique, not used for laser shows. By the time you rig two 200$ heads in series, you can afford better wide angle heads, not to mention the relay lens train needed to couple two heads.

A valid technique would be to use a fast scan pair with small mirrors, and then a pair of 6850s or G330s or stepper motors to provide a wide range course position or a 360' projector. This is something you would do if you needed to create "Tinkerbell" for a stage production of Peter Pan where Tinkerbell needs to fly. Its been done, and her name was 'Laserbelle", and it was done by the founder of a certain large laser software company. A company in Germany has a 360" projector using a stepper motor fold mirror called HorizantScan. It comes with sticker shock, as the required safety software is not a easy task.


A valid technique is to split your images across multiple heads. Pro software, ie Pangolin or LSX, can support multiple tracks across multiple cards. You will pay for a extra output device to do this. The costs to do so would drive a hobbyist to just buy the better galvos.

4 or 5 head professional projectors were not uncommon when I started 20 years ago.


Steve

Flaminpyro said:

Yea instead of using mirrors why not try one of the DLP chips and some electronics.

EDIT, well that is not going to work I just shined a 445 onto the surface of a DLP
chip and the reflection looks like the beam has passed through a diffraction grating, poop...

Click to expand...

You just have the wrong coupling mechanism. Special prisms are used for that to couple to the DMD, and a field stop in the near field.

Try again! :shhh:

Steve

Now this thread has become very educational !
I don't suppose there is any sort of video available showing any of the 360' equipment or projections is there ? (I'm a visual learner. Gotta see it to understand it properly.)

What sort of manipulation could be expected from that DLP using image data ? Would it be useful for lumia wheel type projecting ? Hmmmm...

And the curved mirror was part of my other idea. Have the laser projector facing my audience (at home, the room is only 14 feet wide) for beam show effects. But mount a curved mirror on the wall/ceiling above their heads and bounce graphical images off it to shine on the floor and walls in front of them.
Because the image is being"drawn" in the smallest arc even the lower speed galvos might be able to do it. The distance across the room (twice) coupled with a curved reflector would be enough expansion and the ability to fill the room with beams in 3 directions (forward, backward, and downward) could really maximize the usage of a single machine.

Personally, the post is in fact the most excellent on this impressive topic.
I harmonize with your conclusions and will keenly look further to your future updates. :beer: