feeler: (diy) beam expander?

hello everyone,

theres a thread here about beam expanders in general and details how to built one.
with single lenses being relatively cheap, only the engineering and machining is expensive (timewise and moneywise). is there interest to buy a selfmade universal beamexpander? the prices online are way too high for my taste, up to several hundred dollars, for a beam-expander built for laserpointers!

why at all? a beam expander widens the beam to a larger diameter, while reducing its divergence. a 10x expander, for example, would make a 10mm beam out of your 1mm greenie. the divergence would be a tenth, so it would reach ten times farther!
being adjustable, you can focus the beam too. like having a 10mm beam at the expander, but a tiny focus after 20 meters, possibly still enough to burn stuff after that distance!

so, who would be interested? if it would have adapters to fit all (of our) lasers, for, lets say (total random number) 100$?

not that i could built it, but if enough members show interest, someone may consider doing a small series?

manuel

If you look at the links I put up about the monoculars I got from dx, the cheaper one is perfect for a simple diy expander. I have just been too caught up with school and laziness to get around to making the expander.

It will be about as simple as it gets because the whole thing just screws apart and the lenses are held in place by simple spacers. The first lens has a large diameter which may make getting a short enough FL difficult. If I were to use small beam diameters like with greens and 405-G-1s it could give a decent expansion ratio of near 18x for a slim beam and for <$80 parts cost. Larger beams wouldn't work tho.

I will try to get it together sometime soon to see what I can accomplish with it...I want to try to use an aixiz nut as the threaded receiving part of the expander so it will simply screw onto my own diy lasers. I probably wouldn't sell them but rather just give a tutorial cause most likely it is going to be a piece of cake.

could you make some pics of the parts? diameter of the two lenses and distance between them would be great too! who knows, perhaps there are lenses on surplusshed or similar which would drop in?

manuel

Ok krutz, here are those pics you wanted...enjoy!

The eye piece is disassembled like this...



^there are 2 lenses that just drop into the holder and are separated by a spacer and held in place by the threaded ring(larger black ring) the lenses are ~13mm. Once in the holder it screws into the main housing.

Next the front piece...




^This is just a single lens (~19mm) held in place the same way as the others, it is dropped into the bigger holder and held in place by a threaded ring then the whole thing screws into the main housing, which looks like this when fully assembled...



^The main housing has an adjustable length of 2 1/2 inches-3 1/4 inches. In the middle of the housing is an optic piece (prismatic image rotator?) that just flips images and has no FL(not pictured) The center piece will be removed and discarded because orientation of the beam wont matter.

Tomorrow if I have time I will check out edmund optics and work on getting the correct FL lenses ordered and get this show on the road.

great, thank you for the details and pics!
hmm, a bit small, the 19mm lens. but surely enough for experimenting!
will probably order one too next time i order *there*..

edit:
yes, the "rotator" doesnt seem to focus. still i cant get a clear (upside down) when removing it, need much longer distance between the two lenses in my binocular. it doesnt add "focus" but optical path! being bounced between the prisms, its a few cm longer.. doh!
never saw it that way, that there must be some prisms in every bino!

manuel

what would you people use your expander for? green only? or for red/violet too?
i would like one for all lasers, so "input" must be up to 6mm for red and violet. with 10x expanding, the output beam and -lens would be 60mm though.. for green only, with 2 or 3 mm input, it would be a 20 to 30mm output, obviously.
another idea: however we would build the connection (threads and adapters?), why not do that on both sides? for using it as a beam-diameter-shrinker? sure, it would only reach a few meters, but would instantly burn in that range! no focussing! point it at any match or balloon in the room for destruction!

manuel

I think youvguys need to do a little reading on the optics that go into beam expandefsnfirst. Just choosing random optics from binoculars will not make for an ideal beam expanded. Sure it will expand and collimate the beam, but it will not be ideal.

the opposite, glutton wants to replace the lenses and only use the body..
the body will be the most expensive or difficult part of a diy expander, i think. i was amazed how cheap bare optics are..

manuel

Krutz said:

the opposite, glutton wants to replace the lenses and only use the body..
the body will be the most expensive or difficult part of a diy expander, i think. i was amazed how cheap bare optics are..

manuel

Click to expand...

The body is going to be quite cheap as well as the optics. This monocular only cost $15... do you have a link to a lens shop I can check out?

@LaserBen if you check out the thread this is thread is talking about you will see that there has been a lot of talk about exactly what needs to be done in order to achieve the expanded beam. I did plan on replacing the optics of this monocular with bare lenses and there is a great app that steve001 gave that will show the lens diameters and FLs needed to fit the monocular and achieve an expanded beam.

i just looked at Surplus Shed they have many many lenses, 4 to 12 dollars.
have some aspherics too.

the best candidate i found for the larger, second, "collimating" lens is this one:
PRECISION 55MM DIA, 38.5MM FL PCX ASPHERIC LENS BROADBAND AR CTD - Surplus Shed

55mm diameter, perfect for a 10x expander for thicker diode beams.
short 38.5mm focal length for a short setup
aspheric for less distortion, AR coated for less losses.
Item No: PL1014, Price: $12.00

hell of a deal, the only lens i found which has all of those attributes!
perhaps the focal length is *too* short? needs a real short-focus first lens. 3.85mm, to be exact.. and this really has to be high quality and definitely aspheric, with such a short focal length!
the 405-g1 has a focal length of 2.39mm by the way..

manuel

manuel

Here is a size comparison of a 50mm lens/housing compared to the pocket mini/monocular.

The 55mm lens/housing may be too large for applying it to smaller DIY builds, but I have not calculated the length your set up will be.

yes, its pretty big.. i realized that too when i drew the lens in a sketch. maybe a 10x expander compatible with diode beams is just not practical at all..
but then i use a pretty big host anyway!
thats a nice housing/lens you have there!

manuel

:thanks:

It could be beneficial for things like 405-G-1 and greens where a 20x expansion wouldn't require much over a 20mm lens, but then again using a 405-g-1 to get a thinner beam then expanding it seems kinda circular.

true! but with soo little losses! ;-)

manuel

Krutz said:

aspheric for less distortion

Click to expand...

Doesn't matter for lasers, because the lasers are very narrow frequency range, you do not have the same issues with different focal lengths for white light. You will not notice the difference.

what you are talking about is an achromatic lens, optically glued from two individual elements, to make up for different frequencies being bent differently.
aspherics simply are non-spherical lenses, more and more shaped like a half egg. thats to make a parallel beam really being focused into a single focal point, instead of a focal-area like with normal spherics. this effect is independent from the wavelength (and additional to the above effect).
all our collimating lenses (aixiz, 405-g1, meredith) are aspherics, in fact.

funny, even cheap glass lenses from cheap binoculars are achromats, you can see where its glued together looking from the side.

manuel