> suggestions for 'sanding' LED's to widen beam? Experiences?
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omarawatch |
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My headset has slight left to right limitations as the 'farthest' one from view dims out and the software has trouble seeing it. the LED's I used are NTE3027. I assume they are narrow band so I scuffed/sanded them just a touch and it improved them, but not a LOT.
Does anyone have any particular sanding suggestions? How much? Just lightly all over, or actually sand down the front a fair distance? Flat shapes, pointed shapes?
Any feedback is appreciated!
~Brendan
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Kestrel |
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You need to do some serious sanding/filing and get the lens down flat and close to the semiconductor base.
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omarawatch |
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Your photo is quite clear - does that mean that the dome on the end of all LED's, regardless of brand, is what creates the focal point? So should it be as flat as possible? Or a slight dome? Has everyone else had the same findings as shown in this photo?
I just figured some serious discussion about sanding/filing were in order - I couldn't find any actual discussion of this on the forum. I also, oddly enough, thought that the inside was hollow and should not be heavily sanded as though it was gas filled like a bulb - hahaha! Just say about the metal a bit?
~Brendan
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Kestrel |
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The LED dome is a lens, focusing the light into a narrow beam, to make the beam as wide as possible you need to file the lens down completely flat and as low as possible without hitting the metal part and damaging the delicate semiconductor. The photo was by Deimos, I've filed LEDs down lower than that in the picture without problems.
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Vortex01 |
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OK all good so far but a question about the finnish.
After sanding it down the resin is not clear and shinny what is the best way to pollish the lens?
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BootStrap |
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Vortex01 @ 07/02/2008 - 17h32 a dit: OK all good so far but a question about the finnish.
After sanding it down the resin is not clear and shinny what is the best way to pollish the lens?
Good point! does the finish matter for IR??
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tristan68 |
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AFAIK, there's no need to polish the led.
I didn't polish the led , but just finished the sanding with a very fine sandpaper, so the result was really flat, without any edges, but still unpolished (looking from the top of the led, you couldn't see the led chip inside the plastic case).
cya
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Deimos |
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Just as Tristan said - you';ll probably be better off with unpolished LEDs. The unpolished matte surface will disperse the light so it'll be visible at larger angles (note that IR light is visible in the photo even at extreme angle), and what is more important, the entire surface will appear to glow, giving much larger and easier to spot point on the image seen by camera. If you polished the surface, the camera would still see the LED at big angles, but only the LED itself (the small chip thingie inside the metal cone) would be seen as glowing object. So you can have a 5mm point with unpolished LED VS ~0.1mm point (well, it will appear as bigger on the captured image due to lens flare, but still will be small...) with polished one - guess which one will work better  |
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nvhlvnop |
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I'll add that I filed my LEDs down before I even found this thread. I was also nervous about the unpolished look. However, I was amazed at how far I could turn my head, and the LEDs never dropped out of the frame! I didn't even file them down as much as I see in the pictures here. So in conclusion, leave the flat surface a little rough! It does help to disperse the light.
Has anyone tried a polygon shaped tip? Like multiple flats. Also like the nose shape of the F117 stealth fighter...haha. I assume the beam would be a little weaker, but since the multiple flats would be point in many directions, perhaps the LEDs will have more than 180 degree beam?
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Gnomie |
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From another thread:
tristan68 @ 06/02/2008 - 09h09 a dit: (...)
It's better to sand the leds really flat. But this has to be adapted, based on your personnal experience. (...) IMO, it's better if the surface is still a bit rough, no need to polish it.
Since you'll loose forward brightness, the lateral brightness could become an issue.
If that's the case, your can paint the border of your leds or wrap them in electrical tape, so only the flat top of the led can emit IR.
I have a question about sanding down the LEDs too. My plan is to use an old bicycle lamp to make a 3-point cap thingy. But you'll notice the LEDs are rounded, not flat. Is this a problem?
My plan was to see if I could detach two of the LEDs and solder them onto some wires which I could fasten on the cap. But if the lamps aren't suitable I'll have to think of something else.. |
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tristan68 |
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hello gnomie
Rounded leds have a narrow beam angle. The rounded top acts like a lens, and concentrates the beam.
That's why you have to :
- either sand your led flat
- either buy SFH485P (their case already has a flat top).
cya
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Deimos |
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tristan68 @ 17/02/2008 - 01h14 a dit: hello gnomie
Rounded leds have a narrow beam angle. The rounded top acts like a lens, and concentrates the beam.
Actually, the round top IS a lens put there to focus the beam :P
@Gnomie - If you plan to use this lamp with red LEDs (and from the looks of it, it's probably a rear lamp so it does have red LEDs), take look at this video by urze:
http://video.google.de/videoplay?docid=-5788390454421132360
You can see another cool idea to make LEDs visible from sides in the video - sanding their surface matte, leaving it dome-shaped. I haven't tested it, but it seems to work fine too, and it takes much less effort so that might be the way to go for you.
If you're planning to solder IR LEDs instead of stock red ones - that's ain't going to work since red diodes are driven by much lower current than IR ones. So newly soldered IR LEDs won't even start shining.
You might have a bit more luck if you used a forward bicycle lamp with very bright white LEDs - white ones have similar electrical specifications to IR LEDs, so if a white one glows brightly, IR LED will too.
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