Possible hole fix - Drip those holes away!

[Feign]

Attenuating a beam into a fine point is a serious pain. When I worked on beam attenuators I figured out a little trick for making them pretty cheaply that maybe could apply here.

The best method of attenuating a beam so that there is no scatter is to have a series of apertures spaced along the beam and perfectly lined up. In most cases this is a crazy machined assembly that's nearly impossible even at the 10mm beam diameter scale. But if you want a similar effect to the big expensive attenuators, just use a threaded hole with the thread ID the size of the beam you want (provided the material you use isn't at all reflective. I'd recommend a black anodized nut with the tiniest thread you can find.

[Aztecphoenix]

Attenuating a beam into a fine point is a serious pain. When I worked on beam attenuators I figured out a little trick for making them pretty cheaply that maybe could apply here.

The best method of attenuating a beam so that there is no scatter is to have a series of apertures spaced along the beam and perfectly lined up. In most cases this is a crazy machined assembly that's nearly impossible even at the 10mm beam diameter scale. But if you want a similar effect to the big expensive attenuators, just use a threaded hole with the thread ID the size of the beam you want (provided the material you use isn't at all reflective. I'd recommend a black anodized nut with the tiniest thread you can find.

what about using a series of varying aperatures, with the largest nearest the diode? wouldn't this work similarly but reduce the problem of alignment?

[Feign]

what about using a series of varying aperatures, with the largest nearest the diode? wouldn't this work similarly but reduce the problem of alignment?

Well, the problem is that as light passes the edge of the aperture, it gets scattered just slightly. So what you want is it have apertures that only interact with the scattered light. The first aperture reduces the beam width, but the edge scatters some of the light right at the edge of the beam. The next aperture is to block the scattered light, but you want it to not touch the rest of the beam. Of course, some of the scattered light does hit the edge of that aperture and scatters again instead, necessitating a third aperture and so forth...

Of couse, two should be enough for the Peachy, since the first one only scatters about 10% of the light at even at a small scale. The next one of course only scatters 10% of that and so on. Two apertures and you've filtered 99% of the scatter.

[rylangrayston]

Hey Feign
The Graphite worked really well, I didnt have any tap nearly small enough to thread a .3- .5 mm hole, so i just machined a tapered hole that is 1cm deep.

so currently my best setup is some thing like this laser diode-- 3mm-- first aperture--Lens--- 100mm---1cm thick taperd Graphite aperture---->

Id like to get that 100 mm down alot but the light needs space to scatter,
and I think that my first aperture being right up against the lens is probably bad, im going to try giving it a .5 mm gap, and making the first aperture out of graphite too.

any other suggestions, Ill probably try printing with the best thing iv come up with late tomorrow.

[Aztecphoenix]

Ill probably try printing with the best thing iv come up with late tomorrow.

please post a video, it doesn't have to be anything high end like all your other videos, but just something showing the current state of the peachy and how it looks printing, I know I'm not the only one who would like to see this.

[rylangrayston]

Feign Thank you so much for the suggestion ... ive been using a bunch of razor blades stuck to a hollowed out magnet, by sliding the blads up to the beam scatter I can reduce it, but i love the threaded hole idea.... i have a piece of solid graphite ( quite black ) im going to try threading that now.

I have been theorizing exactly the scatter reduction technique you speak of on our white board, good to know with some confidence that multiple apertures is worth trying.

[User_Defined]

Feign Thank you so much for the suggestion ... ive been using a bunch of razor blades stuck to a hollowed out magnet, by sliding the blads up to the beam scatter I can reduce it, but i love the threaded hole idea.... i have a piece of solid graphite ( quite black ) im going to try threading that now.

I have been theorizing exactly the scatter reduction technique you speak of on our white board, good to know with some confidence that multiple apertures is worth trying.

Easy fix for this:

Make some kind of foil holder mechanism that will attach onto the laser diode module. Inside this foil holder will be three discs of aluminum foil (basically like your instructional video, except with three foils within it).

Then perform the same hole making action but pierce through all three foils at once. The only thing is that it would need to be very straight.

You could probably try it easily with some big washers for spacers, with foil folded between them and crumpled on the sides to hold it all together.

For the actual implementation, have the foil holder as part of the peachy frame, and use 4 laser cut plastics before the first foil to line up and guide the hole piercing probe and ensure it being straight. This should keep everything aligned with the laser cut frame and reduce human errors.

Or, make an alignment tool with 4 laser cut plastics for when you need to pierce the triple hole.



- UD

[Aztecphoenix]

you may also try an electro-etching template on some thin steel to make the aperatures, if the template is made properly the only trouble with alignment would be in your frame assembly.

lots of info on electro-etching can be found online, however if there is a sword smith or black smith nearby they may be able to help you get set up.

just remember, the thinner the steel is, the smaller you can make the aperture

@ Feign,
in regards to the apertures, do they have to be an opaque solid with a hole through it or, can it be something like acrylic with a coating of black paint with a speck of unpainted area that the light can pass through? if so then maybe we could silk screen print some apertures.

[Feign]

I like the idea of using solid graphite. And the setup you have is definitely in the right direction. It makes sense to have the second aperture a distance away. Since there is a good dark band between the beam and the first diffracted band, your second aperture doesn't need to be as precisely placed if it's just blocking the band.

I can't remember the formula for the angle of diffraction through a hole, but I do remember that it's dependent on the wavelength, so you've got one of the toughest possible scenarios with this.

Unfortunately, this little revelation adds parts that need machining and I can't for the life of me figure out how you can get it so the end user can calibrate a multi-step attenuator easily, since you have to aim the laser exactly through both of the holes.

[NoctumSolis]

Unfortunately, this little revelation adds parts that need machining and I can't for the life of me figure out how you can get it so the end user can calibrate a multi-step attenuator easily, since you have to aim the laser exactly through both of the holes.

I'm showing my ignorance here, but... wouldn't it just be a matter of extra snap-together parts designed to hold the pre-machined parts in position? If the emitter is mounted to the circuit board then its position, along with all dimensions, are known quantities.

I realise there are plenty of fiddly, moving parts to calibrate, but wouldn't a static attenuator be easy enough to ensure consistent placement for?