Rgb spatial filter. One blade pinhole method

[jors]

Thanks!!
Sorry, I'm not versed in optics, maybe it works, there are very talented people here which opinion could be interesting to know.
Anyway, I'll try later when aligning my v2 micro-projector. This spatial Filt. is tested with RGB beam coming out from my 1st projector, so, I'd rather not put my hands inside cause it is adjusted fine

However (and talking about graphics, not beam shows), and IMHO, for me the question is:
Why you need RED that is NOT overlapped with blue & green??

Assuming all beams have very close divergence.... why you want fatter reds on graphics (compared blue/green) or yellows with red around?

[polishedball]

Your correct, I couldn't get a hole just burn mark with 2.2w or 638. My filters are already in this projector so I just wanted to try this method as it was. My next build I had already decided to build it in the rgb path, and now this method will be great to try as well.

you're welcome!! thanks
Mixedgas has very kindly offered to measure pinhole diameter and also the blade thickness with electronic microscope. One drilled blade sample is flying to him (Thanks Steve!!). So hope to get some numbers soon. I think the pinhole is about 50-70µm.
The blade is really thin, I can bend it with just my fingers pressure, also cut it with ordinary scissors.
Attachment 44846
Attachment 44847
Yes, sure that filtering each colour is the way to go, but could be nice to have spatial filter inside micro-projector, and IMHO this RGB filter works when not enough room inside. Also, on drilling with combined rgb beam, we have in just 3sec all colours inside same geometry! (reds clipped).
This 'instant' all-3-beams inside the same geometry is IMO the main advantage with this technique, also we save lenses and setups with a really small footprint. Of course, each colour-divergence is another question. The combined spot is really very accurate and nice quasi-round. Because the temperature is higher in the center beam-core and gradually decreases to the edges, the drilled hole is an exact representation of this, very very close to round.

I think 1-1,5W red is not enough to drill the hole, but this is only an assumption, not tested, so for sure multiple blades/core-shaping Planters' technique is really elegant and suitable for single colour, but also on rgb too with achromatics.
Next step is scanning the pinholed RGB beam, to find for chromatic aberrations, hope not.

[jors]

Thanks Polishedball, ...I drilled @4W, but maybe my blade is also thinner, so lets wait for Steve measurements

[tribble]

Seems there should be some alternative materials that would work well for lower powered units. Maybe some plastics?

[jors]

Sure, maybe....but I have doubts about durability on this materials.
Pinhole edge on plastics, and this again is only an assumption, could suffers from micro-cracks&melts as time goes on; temp air in focus is really high. I think better with multiple blades here, but why not to try? )

What I think is important here, is material should be as hard as possible (but laser capable to drill) also as thin as possible. Thin as possible, because I suppose the pinhole along blade is conic, and when aligning blade we focus one side, so, if material is not thin, we could end with interference rings and so on, cause the output side from conic hole, is not perfectly in-focus.

..but more in depth thinking, I suppose the blade side which is focused and we see on projected FF, is the side which is in focus, and so, this should be ok, that is, the output beam hole is exactly on focus ))

please.. any optics here could correct me?

[planters]

The method has some potential and is an elegant approach to sizing the filter for the beams. I would defiantly stay with metal because you want the pin hole to be an aperture that does not interfere with the beams except at the focus. So, the thinner the material the better. Stainless steel has a very poor thermal conductivity and so will heat up in the beam better than say copper or aluminum.
If I were doing this I would use an achromat for the focusing lens. This will produce a more intense spot (for drilling) and will minimize the differential between the focal positions of the different colors. I would also try a slightly longer "drilling" lens than the operational lens because this will create a slightly larger hole and minimize the light loss at the edges as well as the difractive scattering as the beam grazes the edge of the hole. Even without an EM, I think if you examine a few drilled holes with an inspection microscope, you will see how homogenous and clean the edges are and this might hint at a few adjustments such as thickness and if any post treatment is worth the effort.

[jors]

Thanks Planters,you're right, I can drill stainless steel because of its poor thermal conductivity. And yes, this is with achromats as you suggested in other threads.
As a curiosity, I've tried to drill 'standard' kitchen aluminium foil and although it is much more thinner than blade, I was unable to drill it because its conductivity and reflectance.
I'm very grateful for your instructional videos and threads, great inspiration source!!

[mixedgas]

If you don't mind my asking, can you name the source diode model numbers and diode collimation lenses used? It would be difficult to replicate this without the proper beam sizes.

Steve

[jors]

yes,
Diodes I use:
Nichia 520nm @1W G2 +dave cyl correction optics
9mm 445 @2,4W G2 +dave cyl correction optics
2xOclaro 638 @700mW each (PBS) dave’s 2mm collimators+ cyl correction optics (one set after PBS)

All diodes from DTR, great service!
I tested the spatial filter from the output of my 1st projector. So, the beam comes thru the lens correction, dichros & galvos & window before reach spatial filter setup. The power from the output galvo and window projector is 4W.

[m0f]

I wonder if something like cinefoil would do the trick ? It's black and so would absorb and likely burn at lower power levels, and thicker than kitchen aluminum foil so sturdier once all is done.