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Suggested way to focus UV?

GrahamRounce

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If it's dim through the safety glasses, can't you just make a small fluorescent area on a piece of card (eg. with a highlighter) and shine it at that?

Talking of UV, is it possible to focus the fairly cheap 3-5v modules from eg Aixiz to a 0.1mm dot, with a depth of field of say 3-5mm so that the distance from the target isn't too critical?

Thanks!
 



Arcygenical

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You should have no issues using a lens to focus it to whatever depth you like. (just for god's sake, use a glass one if you're going beyond 30mw or so). If you're going into the higher power ranges, use a lens that's coated for 405nm, they're glass, and around 10$ on amazon. I don't know why you'd want to pinpoint focus a 5$ diode, so I'm not entirely sure how to answer you any better than this!
 

skijohn

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Normal silicate glass blocks actual UV. The terms ultraviolet light and UV refer to a relatively large wavelength range between 400 nm and 100 nm. It falls between violet visible light and x-rays on the electromagnetic spectrum. UV is described as UVA, UVB, UVC, near-ultraviolet, middle ultraviolet, and far-ultraviolet, depending on its wavelength. UVC is completely absorbed by Earth's atmosphere, so it doesn't pose a risk to your health. UV light from the sun and man-made sources are mainly in the UVA and UVB range.
 
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GrahamRounce

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You should have no issues using a lens to focus it to whatever depth you like. (just for god's sake, use a glass one if you're going beyond 30mw or so). If you're going into the higher power ranges, use a lens that's coated for 405nm, they're glass, and around 10$ on amazon. I don't know why you'd want to pinpoint focus a 5$ diode, so I'm not entirely sure how to answer you any better than this!
Thanks. I want to pinpoint focus a UV diode, and the cheaper the better. If it's not possible with those ones, what would you recommend? (Sort by price, low to high! : )
 

Arcygenical

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Thanks. I want to pinpoint focus a UV diode, and the cheaper the better. If it's not possible with those ones, what would you recommend? (Sort by price, low to high! : )
405 is NEAR UV. It will cause most things that would fluoresce under a blacklight, to do so, while still having a visible purple dot. True UV sources, say <400nm are almost invisible to the human eye - which makes them quite neat.

I have a 375nm and 365nm LED (both are 50w) and while I can technically see the purple of the 375, the 365 is all but invisible to me - and my camera. Though it makes my entire house fluoresce. And as always, just because you can't see it, doesn't mean you're not being blinded by it.

AFAIK there's only 1 laser diode that's ~365nm. From some refurb medical application. They're all but impossible to find, expensive as hell, and the optics make it even more challenging.

What are you attempting to do? Sure you need a laser source? If you just want blacklight-esque, go for any 405nm diode, they work quite well. Hell, my 445nm blues will fluoresce "highly reactive" objects (like phosphors - in most laundry detergent - and postIT notes).

I take back what I said: Someone here IS selling a 375nm diode, in the 300$ range. All the warnings about special optics are necessary, but none are hard to find, really. Aliexpress has most of what you need. That's a dangerous laser, though, like IR, it's nigh impossible to focus on/see, You can do serious damage without noticing the damn thing's turned on.
 
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Encap

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Normal silicate glass blocks actual UV. The terms ultraviolet light and UV refer to a relatively large wavelength range between 400 nm and 100 nm. It falls between violet visible light and x-rays on the electromagnetic spectrum. UV is described as UVA, UVB, UVC, near-ultraviolet, middle ultraviolet, and far-ultraviolet, depending on its wavelength. UVC is completely absorbed by Earth's atmosphere, so it doesn't pose a risk to your health. UV light from the sun and man-made sources are mainly in the UVA and UVB range.
Normal silicate glass passes about 75% of UVA 315nm to 400nm . "About 75% of UVA passes through ordinary glass."
See: https://www.thoughtco.com/does-glass-block-uv-light-608316

Thanks. I want to pinpoint focus a UV diode, and the cheaper the better. If it's not possible with those ones, what would you recommend? (Sort by price, low to high! : )
What wavelength and diode are referring to?

UV diodes are expensive --- there may be 1pc of Ushio 375nm still available at a low price 300€ = 363usd ompared to $1,250 elsewhere from an LPF member who ordered 5 if you have any interest.
See: https://laserpointerforums.com/threads/375nm-ushio-200mw-hl37013mg-diode.107917/page-2
 
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GrahamRounce

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I thought I'd mentioned what I'm thinking of, but maybe it was in another thread.

It's simply to draw, using a homemade x-y plotter with a uv laser attached, a printed circuit board layout (that is, the copper bits) onto uv-sensitive board, before etching it in the usual way.
This is as an alternative to shining a uv light through a printed mask, which I've found gives poor results in fine definition areas.

To give an idea, I'd want to be able to put tracks *between* solder pads with 2.54mm (1/10") spacing. So the track would need to be perhaps 0.3mm wide.
I was hoping a uv laser would easily focus down to that. I said 0.1mm to be on the safe side, and to accommodate any blurring.

The mask method, using an array of uv leds about 25mm apart, gave a 40-second exposure time, so I'm guessing that the much more intense laser beam tracing out the tracks could move fairly fast.

Do you think that's doable, without breaking the bank?
Thank-you again,
Graham
 
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Arcygenical

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Are you mounting the diode to a CNC/printer and sending it g-code? otherwise, masks with a proper lens, and a 15$ UV 10w LED might be a lot less hassle (afterall, it's how Intel-Israel does their ULV masking for 30 billion transistors haha, (exactly like that, with a 15$ LED -_-)

But you're correct, the 405nm diodes will do a damn good job with most commercial photoresists.

THIS GUIDE is the one I used, basically, but with much cheaper aliexpress parts. Remember, the intensity of the light at the focus point increases almost early-logarithmically (shush, I know it doesn't quite) when you reduce its radius by half . There are MANY optics in the 3-5$ range that handle 405nm just fine; and it's worked with every dry resist I've ever purchased. Adjust your power output accordingly to accommodate for the increase in intensity at the focal point. Overexposure tends to bleed, and cut out other traces.

I built it years later, when the 150mw diodes were dirt cheap, as well, and threw it on my 3D printer. So, of course, YMMV.
 

GrahamRounce

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Brilliant! Thanks very much.
I haven't put anything together yet. I wanted to check that it wouldn't be a waste of time in the end.

"Are you mounting the diode to a CNC/printer and sending it g-code?"
That's what I was thinking of, yes...
 

Arcygenical

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Brilliant! Thanks very much.
I haven't put anything together yet. I wanted to check that it wouldn't be a waste of time in the end.

"Are you mounting the diode to a CNC/printer and sending it g-code?"
That's what I was thinking of, yes...
Make sure that CNC is perfectly calibrated. I can't get traces smaller than .5mm on mine that can handle more than 35ma without burning out (generic boards/resist, obviously a thicker copper layer would help, I'm buying the <1$ boards for very LV applications). Works well, but it's a slow print, and calibration EVERY damn etch, is a real PITA. Awesome for rapid prototyping, though!
 

GrahamRounce

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Through the side of a bottle would introduce distortion, so vertically down into a test tube, maybe?
 
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GrahamRounce

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Mostly my stuff is digital logic, taking much less than 35mA.

Power tracks would have to be thicker, which would necessitate a rather long and boring repetitive draw. Being able to control the width of the focus, and slow the speed (or raise the power) accordingly would be great, though probably even more beyond my scope.

What recalibration did you have to do? The focus?
 
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hakzaw1

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a heads up--try to avoid double (or triple) posts--just use 'edit' and 'paste' (then dele) to join them..
not a 'hard rule' --- just the way we try to do it here. --(& it looks neater)
if you do not fix it -- a mod may. (insert red face emogi)
hk
 




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