DIY reflector paint

Spatial coherence is a big issue. A LED is a diffuse source with light coming from inside a material with n~=3.45, so if you got 100% extraction efficiency you'd have a Lambertian source about 11 times the area. That makes the solid angle/beam diameter tradeoff difficult.

Actually not. I've designed a couple of tactical optical transceivers for the US military, both of which used white LEDs. You get a lot of bang for the buck--much better than the corresponding blue LED dice.

Cheers

Phil Hobbs

Phil Hobbs wrote in news: snipped-for-privacy@electrooptical.net:

Can place at the back of a black tube for stopping the side reads.

Deep voice inflection... (coat it with Vantablack)(Bou! bou!)(oh yeah!)(chic-a-chic-ahhh)

Seems though that lasers (diodes) are far more efficient for data xcvrs.

Dice-a-roni...

Dice... Dice... very nice, so many people in the same deDice!

There were baffles and stuff for that, yeah.

Just shiny black plastic. Shiny black baffles let you ray-trace the reflections and make sure they hit black surfaces three or four times before escaping. That gets you down into the PPMs.

These were intended for handheld use on ships, e.g. the ramp rats talking to the island on an aircraft carrier.

Cheers

Phil Hobbs

I have found a reflector I would try out

Another idea is to place an array of 20 of the LED, that should give me much more combined intensity

COB has been ordered and will try it out next week

Cheers

Klaus

COB = PCB

Damn autocorrect function

Phil Hobbs wrote in news: snipped-for-privacy@electrooptical.net:

A 'new' variant of the shutter windowed shipboard 'signal lamps'.

Hopefully at higher rate and better character set than morse code.

You should check that vantablack stuff out (for applicable uses of course).

snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:

There is a street lamp up in a parking lot that has a VERY bright LED flood lamp on it. During the day I went and looked at it. It is about 14 (two rows of seven) 'pads' of ten LEDs each (2x5). So there

snipped-for-privacy@gmail.com wrote in news:11c282f5-4ab5-48cb-9669- snipped-for-privacy@googlegroups.com:

Chip On Board.

At least it was not a complete morphing. :-)

Vantablack and other designer blacks aren't that useful in the general case, because they scatter light into 2 pi steradians. Even if their reflectance is very low, they aren't generally competitive compared with properly-designed baffles. They're good for cleaning up the general background scatter.

A lot of the time designer blacks get pulled in to fix a design problem.

Cheers

Phil Hobbs

Phil Hobbs wrote in news: snipped-for-privacy@electrooptical.net:

Does the hubble tube have these baffles? I am unaware of the configuration as I thought it was a smooth bore tube.

Anyway, I know that it does not have vantablack coating.

I want a car with several pieces done in it.

It is a forest of vertical carbon nanotubes and it lets light in, but does not let it out.

The one fatal mistake in baffle design is to allow any single-bounce reflection to reach the detector. That is, as you go towards the detector you shrink the baffle diameter so that the earlier stages are out of the FOV of the later ones.

Telescopes are actually an easier case in general, because reflecting the light back out the aperture is just as good as absorbing it.

The exoplanet detection folks are making the running in baffle design these days, but I haven't looked very closely at what they're doing. Soft rather than hard edges, I expect--that reduces the amplitude of the diffraction rings just as windowing reduces leakage in spectral estimation.

Plus or minus, depending on the angle of incidence. It turns out that (if you can stand the outgassing) Edmund's black flocked paper is about as good in the visible as any of the fancy designer blacks.

No use on spacecraft, of course.

Cheers

Phil Hobbs