There are ~watt up to ~1kW range output LED sources in the ~400nm wavelength range- one major application being UV polymerization. They're becoming practical in comparison to conventional mercury lamp sources. One supplier is Phoseon.
Overall efficiency seems to be in the 20-25% range (measured from DC input). Water cooling is required for the high power sources.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
If you modulate the LED light and use synchronous detection, you can just use more gain (without getting too badly clobbered by ambient light or noise). That's a cheaper way to go, when one considers (for instance) the unknowns like source aging/dimming. Just be glad you can GET the colors you want in LED form; I'd have been happy to pay kilobucks for a dim blue LED, thirty years ago. We used a mechanical chopper and HeNe-Cd blue laser instead.
I'm already doing that. The numbers I posted are what's required to get a SNR of about 60 dB in a 40-Hz bandwidth around a chopping frequency of a few of kilohertz. Some of the stuff I need to measure exhibits a path loss of 10**-8 (80 dB optical, 160 dB electrical). For a worst-case sample, half a watt of optical power will get me a signal photocurrent of 2 nanoamps, even with f/2 collection optics.
I'm going to need an interference filter per channel anyway. He-cads weren't much fun to maintain, though their main output line at 442 nm is a beautiful colour. (I had one for awhile, many moons ago.)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Ah, I didn't see this earlier because of my filter against Google spam flooding.
Cree and Philips make some good ones.
Philips LXML-PR02-1100
1100 mW minimum @ 700 mA 440 - 460 nm wavelength Vf 3.00 typical Case is 3.17 x 4.61 x 2.10 mm Lens is a silicone hemisphere on one sidePhilips LXZ1-PR01-0600
600 mW typical @ 500mA 440 - 460 nm wavelength Vf 2.90 typical Case is 1.30 x 1.70 x 0.66 mm Naked square emitterCree has high power UV LEDs. I'd quote some Cree part numbers but their catalog is frustrating. Some of the Cree and Philips LEDs have similar enough dimensions that lenses are interchangeable.
There were some very dim blue LEDs available 30 years ago. Mostly used on high end audiophool amplifiers and the like as indicators and just barely visible when lit. ISTR they were Russian silicon carbide based. Not mentioned on Wiki (except as available from 1990's).
Pretty sure they were on some high end kit in the late 70's early 80's.
-- Regards, Martin Brown
I did notice that a couple of places (Ididex, Coherent, among others) make a 577nm diode-pumped laser, but seem to keep it under tight wraps and presumed high expense as a "medical" laser, so it seems unlikely to be suitable.
-- Cats, coffee, chocolate...vices to live by Please don't feed the trolls. Killfile and ignore them so they will go away.
Probably wouldn't work for you, but I experimented some with UV LEDs and fluorescent paints. Fun.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Yeah, I'm fighting a worst-case path loss of 80 dB optical, so I really need a lot of photons. Turns out I can get quite a few just by filtering a 4000K white LED, because 578 nm is pretty near the peak.
You know your LEDs are pathetic when a blue one, driving a phosphor, filtered down to 5 nm wide, is still 100x brighter than yours and has
10x better wall plug efficiency.Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
I've always been impressed that fluorescent tubes are so efficient, when they start with UV photons and then dump them into phosphors.
A "white" LED would be a lot brighter in the yellow, at your wavelength, with a narrower-emission phosphor, but it wouldn't look as good.
-- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
Have you considered using a low pressure sodium vapour lamp for the yellow light?
Lots of problems in that approach,but you do get a lot of light per watt. F rom Wiki
"Another unique property of LPS lamps is that, unlike other lamp types, the y do not decline in lumen output with age. As an example, mercury vapor HID lamps become very dull towards the end of their lives, to the point of bei ng ineffective, while continuing to consume full rated electrical use. LPS lamps, however, do increase energy usage slightly (about 10%) towards their end of life, which is generally around 18,000 hours for modern lamps."
Dan
Thanks. The sodium lines are at 589 nm, which won't work in my application. I really need 578 and 598 nm. If I could do it at 590, there are a ton of bright LEDs there as well.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
just
noise).
unknowns
Cree had blue LEDs (SiC) over 30 years ago, but they had lousy spectral purity and were expensive (>3$ ea. at 1 mW).
?-)
So you need just 10nm either side of it?
How about... erm, hetrodyning what, a CO2 laser with it?
Better yet, a comb generator, and bandpass whatever you like... make an optical Wadley Loop and cover the whole range!
Okay, maybe a *little* crazier than an LED array, certain notches (such as the present problem) aside.
Tim
-- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
The current best guess is either a good white LED or the very greenest among the high-efficiency yellow ones, shining through a 3-5 nm wide interference filter.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Unfortunately both wavelength distances are beyond convenient thermal pulling distance if i understand correctly. Plus, it could be hard to regulate target wavelength well. Maybe a diffraction grating trick would help.
Keep on thimkimg. >?-)
In all this discussion, no one mentioned the possibility of using dye lasers. In principal, it should be possible to use short wavelength LED or diode lasers to pump dye lasers. With gratings or other frequency dispersive methods the dye could be tuned to the desired wavelength. Not having worked much with dye lasers, I have no real clue as to the feasibility of such a scheme.
What little experience I have with dye lasers dates back to before semiconductor pumping was feasible. Ruby lasers or flashtubes were pump sources.
Wit efficient pumping, it may be feasible to incorporate dye into a high quality acrylic or other kind of polymer.
-- Sam Conservatives are against Darwinism but for natural selection. Liberals are for Darwinism but totally against any selection.
This is a technological application--it's an on-line sensor for food quality.
Cheers
Phil Hobbs
t h
Interesting. Is the theory about the spectrum of different object described anywhere?
Would for example an animal have a different spectrum than a human? Does th e bad quality of the food show in a shift of the spectrum? (hope the questi on is not showing too much I haven't a faintest idea about optical theory a part from introductionary course)
Cheers
Klaus
st
ED
Not
mp
igh
ed anywhere?
the bad quality of the food show in a shift of the spectrum? (hope the ques tion is not showing too much I haven't a faintest idea about optical theory apart from introductionary course)
A link describes the different spectrum of normal tissue and fat:
So guess, that is what you are doing, refined using a LED instead of a lase r/strope
Another picture:
A plot of different species of plants with simelar shape, but visible gain difference. But how is the gain calibrated so it's possible to tell the dif ference? (a sensor could be sensible to different angle of attack etc)
Cheers
Klaus
The basic idea is ratiometric multispectral measurement. The basic idea is in Gielen, Robert M A M; De Jong, L.P.; Kerkvliet, Harry M M, "Electrooptical Blood-Spot Detection in Intact Eggs," IEEE Trans. Instrum. Meas., vol.28, no.3, pp.177,183, Sept. 1979.
The parlour trick is seeing the 578 nm haemoglobin absorption peak on a baseline that goes up and down by 3 orders of magnitude in absorption, due to the broad 598-nm protoporphyrin absorption peak. (Protoporphyrin is what makes brown eggs brown.)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
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