Video Projector Zoom/Focus Assembly as Beam Expander

[aaronnoraa]

Both of you are correct, it is never a good idea to do anything that could give cause for concern to anyone involved in the process of taking an airplane from one place and sticking it somewhere else.. and it's also correct that despite living under the approach line for the Renton "let's put it next to this football field, two and a half miles away from another airport and 4 miles away from yet another airport" Airport, I can certainly still use a laser in a horizontal fashion with something or other that will eventually absorb or decoherantize (or incoherantization?) all that sweet, hot steamy $exy sticky photon action before ever leaving my yard without problem...

When giving advise about something that can land a person in prison it's best not to assume.

He said he lives near an airport.

Here are his exact words : I live near an airport so next time I remember when I'm heading out somewhere more accommodating I'll bring it along.

Just admit you gave bad advise and learn something, you can blame the Russians when you're alone, but don't give someone bad advise that could cause them serious trouble on an unfounded assumption.

There are municipal and private airports.

 

[paul1598419]

Aaron, so you are in Renton. I didn't know that. I guess most people who live in the towns along I5 on the way to Seattle just call it Seattle. Unlike the south, the land around here is very mountainous and very hilly. Along the horizontal axis there may be many obstacles between yourself and an airport. It is usually not line of sight unless you live right next to the airport. If it were SeaTac that would be a terrible place to live as it is a busy airport and you'd never get any sleep.

 

[barthchris]

Oops, king of necroposting. Lol!
Im experimenting with the same thing here. Same lens, but a nub03 with gball intact. Finding that without decanning I need another lens such as a g2 to first expand before entering the projector assembly. Lots of glass to pass through but initial bench tests seem promising. Trick will be to find a method of adapting to existing host(early rick trent 9mm diode design with a direct diode fit, no axises 20mm thread adapter. I have several ideas and a retired machinist friend willing to help.


Photo is with a num44 but same setup

 

[barthchris]

Trying not to open a new thread as I want to stay on everyone's good side here.

Im doing the same using a projector lens as a beam expander. Budget engineering and using what I have.

Question is should I first use a 9mm barrel lens before sending it into the BE. I seem to get better results using the raw output.

Ill get some far-field pics tonight. At infinity, I get a nice, enlarged spot. I do notice wings if I try to focus to a smaller spot.

Pictured is my mockup with the projector lens. Also an unpractical but really nice repurposed assemble from an old CRT rear projection TV seems to work really well as a BE

 

[paul1598419]

Do I see a small TV projector lens? They also came in larger sizes. I did a lot of work replacing CRTs in these years ago. Lots of optical grade ethylene glycol. Very viscous.

 

[steve001]

Trying not to open a new thread as I want to stay on everyone's good side here.

Im doing the same using a projector lens as a beam expander. Budget engineering and using what I have.

Question is should I first use a 9mm barrel lens before sending it into the BE. I seem to get better results using the raw output.

Ill get some far-field pics tonight. At infinity, I get a nice, enlarged spot. I do notice wings if I try to focus to a smaller spot.

Pictured is my mockup with the projector lens. Also an unpractical but really nice repurposed assemble from an old CRT rear projection TV seems to work really well as a BEView attachment 66637View attachment 66638View attachment 66639View attachment 66640

Tell me what you think you know about beam expanders.

 

[barthchris]

Do I see a small TV projector lens? They also came in larger sizes. I did a lot of work replacing CRTs in these years ago. Lots of optical grade ethylene glycol. Very viscous.

Yes, but this is the lens after the messy liquid. Lol. Its rear projection not the ones that were projected onto a screen. Learned about the glycol that the hard way, I removed the pictured lens and noticed colored one beneath it. I kept removing screws since it looked like a big solid lens, after removing the last screw and prying with a screwdriver it started leaking. I thought it was mineral oil but glycol makes sense.

Whenever someone who knows me has something they are going to toss they call me first. I turn down lots of stuff but not microwaves or rear projection TVs. Large Fresnel lenses, huge FS mirror, big flyback transformer, etc.


[/QUOTE]

Tell me what you think you know about beam expanders.

Ok, a beam expander does just what its name implies, it expands the collimated beam. Divergence is reduced.

I think I see where this is going. Does the beam need to be collimated(focused to infinity) before its expanded??? I tried that and couldn't get it to work.

I've only been able to try the setup without a 9mm lens for several hundred feet. It seemed divergence was reduced significantly.

Id appreciate any input or criticism into my way of thinking. I only partially grasp optics beyond one simple lens.

 

[aaronnoraa]

[/QUOTE]

Does the beam need to be collimated(focused to infinity) before its expanded??? I tried that and couldn't get it to work.

[/QUOTE]

I'm pretty sure that the adjustable zoom assemblies from projectors also include what amounts to a "collimating" lens in the optics path for the final color summed DMD picture output, probably the first lens or pair of lenses at the input side of the assembly.

I've noticed the same thing, that the laser needs raw diode output to one of these assemblies for the output to land within the focal range that the assembly provides to achieve focus. All pictures I had posted when I started this thread are of raw diode output to assembly.

The AR coating was excellent on my assembly, pulled off an ancient yet originally very very expensive Epson LCD projector.. and since we know that the projector is expected to be outputting all colors (to an extent) you can expect that any projector is going to have wideband AR that will work with just about any laser wavelength, although it is possible that deep reds and violets may not have been part of the spectrum that was expected or possible with the gamut limitations of video projection so those may or may not have acceptable AR performance. All I know is that 462 and 520 had hardly a shadow of light reflecting off the assembly lens.

The downside of this is that when using high power diodes to an expansion assembly, the diode's can window (if it has one, worse if it doesn't) will be exposed to dust in the air and will constantly be vaporizing anything that lands on it's output window, causing build up of carbon and jacking the window all up. Enveloping the diode and projector assembly in an enclosure would eliminate that from happening.

 

[barthchris]

Thank you! Yes, a decanned 525nm so Im trying my best to keep it clean. Been there, done that lol!

I was also worried that a focused output into the BE would damage the optical coating but maybe Im just crazy, IDK....

 

[barthchris]

OK, It appears I was wrong, a lens IS needed before the projector lens assembly. Was able to do some "mid-field" testing this afternoon, about 500' was my line of sight limit. For a proper far-field test I need to get to a wide-open area preferably somewhere with a good flat target such as a barn.

I live in a surprisingly rural area on the Chesapeake Bay about 30 miles SE of Wash DC. No straight roads, lots of trees and a surprisingly hilly topography given its coastal plain geology. Im friendly with my neighbor who owns several hundred acres that would be a perfect spot to test but its kinda awkward to say "hey buddy, can I use your land to test my high power laser".. Lol!

Since the laser is so bright I don't feel comfortable attracting attention by using it in more public areas either. I recently had another neighbor tell me he could clearly see the beam almost five miles away, he thought it was a car dealer sales searchlight or some other event happening in the closest town. This was with the Gball lens still attached! I was shocked to hear that!

With a G2 I still needed a few turns in from infinity to get a nice spot at 500'

Without a lens, before projector lens, I wasn't able to achieve anything resembling a nice well-colluminated spot.

More testing is needed!

 

[aaronnoraa]

OK, It appears I was wrong, a lens IS needed before the projector lens assembly.

Maybe it's just the old LCD projectors that won't need a colli lens on the laser output.. or maybe it's different between manufacturers on whether or not they have that lens in the optic path before the zoom/focus assembly. Either way, thanks for letting us know.