aardvark@nmtsun.nmt.edu (Bill Gallagher) (09/19/88)
I'm looking for a source for Blue LEDs. I recall a discussion last year that proved such a thing exists, but didn't save the address where they could be bought. Now I have a good use for them, and need alot of them. MAIL me the address if you know it, but pointers to reputable, well-stocked supply houses would be appreciated, too. Thanks for your help. -- Bill Gallagher aardvark@nmt.edu NMT Computer Center "What's that watermelon doing here?" Socorro, NM 87801 Drop bomb here--->[34 03'58"N/106 54'12"W]
cep4478@ritcv.UUCP (Christopher E. Piggott) (09/20/88)
I'm pretty sure DigiKey, Inc. sells them -- check 800 information for a good number on them. (1-800-555-1212). I have several, but have no idea where they came from. (They look more purplish than blue to me, as if they were red L.E.D.'s with blue paint mixed into the glass. I have technical reasons to suspect this, also: they are not as grossly enefficient as blue L.E.D.'s should theoretically be). Good luck. Chris
sleat@ardent.UUCP (Michael Sleator) (09/21/88)
In article <862@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: > >I'm pretty sure DigiKey, Inc. sells them -- check 800 information for a good >number on them. (1-800-555-1212). > >I have several, but have no idea where they came from. (They look more >purplish than blue to me, as if they were red L.E.D.'s with blue paint >mixed into the glass. I have technical reasons to suspect this, also: they >are not as grossly enefficient as blue L.E.D.'s should theoretically be). Um, wait a minute... Although not as narrow as a laser diode, LEDs have a reasonably narrow output spectrum. This means that a red LED emits almost all of its energy at the red end of the spectrum. All that blue pigment in the plastic would do is absorb non-blue light. If there were a significant amount of blue light in the original output, then blue pigment would indeed make it look more blueish (shades of Yellow Submarine...), but then the unfiltered LED would look rather magenta-ish, no? Since to my eyes regular red LEDs don't look magenta, I suspect that trying to make a blue LED by throwing away all of the red light from a red LED would be *very* enefficient. (Ever hear of a "DED"?) A quick check with a handy chunk of Lucite acting as a prism doesn't show any significant blue emission from the LEDs on the back of my Sun-3/50. Of course, if you're suggesting a florescent pigment that absorbs red and emits blue, that's another matter. I doubt that's what's going on, though. Michael Sleator Ardent Computer ...!uunet!ardent!sleat
dan@rna.UUCP (Dan Ts'o) (09/21/88)
In article <862@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: >I have several, but have no idea where they came from. (They look more >purplish than blue to me, as if they were red L.E.D.'s with blue paint >mixed into the glass. I have technical reasons to suspect this, also: they >are not as grossly enefficient as blue L.E.D.'s should theoretically be). I'm not sure (therefore I know I shouldn't post this...), but I doubt that your blue LED's could possibly be red LED's with a blue filter. This seems impossible since LED's (which, with red are GaAs? gallium arsenide) are second cousin's to semiconductor lasers, and are very monochromatic. Just try to view a red LED through a green or blue interference filter -- you'll see nothing. Therefore output in the blue region is nil as well. In any case, I also believe that blue LED's are fabricated from silicon nitride. BTW, why should a blue LED necessarily grossly inefficient ? I do believe that blue LED's made from silicon nitride are, but why must a blue LED (regardless of implementation) be inefficient. As far as why your blue LED appears purplish. It probably is psychophysical/physiological, rather than any red output. Just as the extreme shortwavelength end of the rainbow appears violet/purple, the blue LED probably is emitting light at, say 430nm. Your red cones in the retina actually have significant sensitivity in the deep blue region -- more so than your green cones. Thus deep blue appears purplish or actually bluish/red, an anomolous sensation.
dan@rna.UUCP (Dan Ts'o) (09/22/88)
In article <595@ardent.UUCP> sleat@ardent.UUCP (Michael Sleator) writes: >Of course, if you're suggesting a florescent pigment that absorbs red and >emits blue, that's another matter. I doubt that's what's going on, though. Yes, highly unlikely, since fluors absorb a higher energy photon and emit a lower energy photon. Blue is higher energy than red, not vice versa. Maybe its possible to have a fluor absorb two lower energy photons to emit a single higher energy one (absorb two red, output one blue), but then what will happen to the extra photoelectron kicking around ?
ken@hpclkms.HP.COM (Kenneth Sumrall) (09/22/88)
/ hpclkms:sci.electronics / cep4478@ritcv.UUCP (Christopher E. Piggott) / 8:23 am Sep 20, 1988 /
Yes. Blue LED's exists, and are made by Siemen's Optoelectronics. They come
in a stantard T1-3/4 package, and are packaged in CLEAR plastic. The forward
voltage drop is ~4V. When I called Siemen's to ask for a sample, they told
me they cost ~$50.00! They are made from silicon carbide, and emit light
at 420 nm. (I am not sure about the wavelength. This is all from memory.)
If you want to call Seimen's about them, the part number is:
LDB 5410
Good luck getting one.
Kenneth Sumrall
HP California Language Labs
ken%hpclkms@hplabs.hp.com
...!hplabs!hpclkms!kencep4478@ritcv.UUCP (Christopher E. Piggott) (09/23/88)
Hmm ... The reason I thought they would be effecient (since I guess I am the one who started it) is because I read that GREEN LED's are less effecient than red ones are, significantly. (I learned a neat lesson this week - if you're not sure, SHUT UP ... some advice from me to myself). Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of the primary colors (being a combination of blue and yellow)? Why shouldn't it be red, YELLOW, blue? Projection televisions work the same way ... is it possible to emit green, and blue 180 degrees out of phase with the blue component of the green, to cancel out the blue and the green and make yellow? If not, how do you make yellow? Thanks, everyone; sorry about the gum-flapping, I'll know better next time. /Chris
dan@rna.UUCP (Dan Ts'o) (09/23/88)
In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: > >Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >the primary colors (being a combination of blue and yellow)? Why shouldn't >it be red, YELLOW, blue? You are confusing additive colors with subtractive colors. Yes, if you add blue paint to yellow paint, you get green paint. But if you add red light to green light, you get yellow light, not brown paint.
markz@ssc.UUCP (Mark Zenier) (09/23/88)
In article <1138@nmtsun.nmt.edu>, aardvark@nmtsun.nmt.edu (Bill Gallagher) writes: > > I'm looking for a source for Blue LEDs. I recall a discussion > last year that proved such a thing exists, but didn't save the > address where they could be bought. Now I have a good use for > them, and need alot of them. MAIL me the address if you know > it, but pointers to reputable, well-stocked supply houses would > be appreciated, too. Try Panasonic ( I saw one at a trade show about 4 years ago) or Siemans (Or some other German outfit). I think the german version was around $50 and had a reverse breakdown voltage of less than 100 millivolts. Not something you'd want to accidently hook up backwards. Mark Zenier uunet!pilchuck!ssc!markz "He did decide, though, that with more time and a great deal of mental effort, he could probably turn the activity into an acceptable perversion"-Mick Farren
hild@infbs.UUCP (Frank Hildebrandt) (09/23/88)
In article <1138@nmtsun.nmt.edu> aardvark@nmtsun.nmt.edu (Bill Gallagher) writes: >I'm looking for a source for Blue LEDs. ... >..... and need alot of them. ............. I recall that there are two manufacturers of blue LEDs: Siemens and maybe Hitachi. The Siemens' is named LB 5410-H0, it emits blue light at 480 nm and gives 2.5 mcd (milli-candela) at 20 mA. It's 5mm in diameter and the order number is Q68000-A5700. BUT: You won't like to order them. The last time I saw a pricelist they were well above $10 (or even $100 ?), so the LEDs will be more expensive than the remaining parts. Greetings, Frank.
jnh@ece-csc.UUCP (Joseph Nathan Hall) (09/23/88)
In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: >Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >the primary colors (being a combination of blue and yellow)? Why shouldn't >it be red, YELLOW, blue? Well, because then you can't get green. > >Projection televisions work the same way ... is it possible to emit green, >and blue 180 degrees out of phase with the blue component of the green, to >cancel out the blue and the green and make yellow? No. If not, how do you make >yellow? > Red + green. Red + blue = magenta, green + blue = cyan (light blue.) (Really!) Sheesh. -- v v sssss|| joseph hall || 201-1D Hampton Lee Court v v s s || jnh@ece-csc.ncsu.edu (Internet) || Cary, NC 27511 v sss || the opinions expressed herein are not necessarily those of my -----------|| employer, north carolina state university . . . . . . . . . . .
ggs@ulysses.homer.nj.att.com (Griff Smith) (09/23/88)
In article <871@ritcv.UUCP>, cep4478@ritcv.UUCP (Christopher E. Piggott) writes: > > ... (I learned a neat lesson this week - if > you're not sure, SHUT UP ... some advice from me to myself). Strike one. > Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of > the primary colors (being a combination of blue and yellow)? Why shouldn't > it be red, YELLOW, blue? This should be in rec.video or rec.photo. Strike two. You're wrong. Strike three. Red, green and blue are ADDITIVE primaries; combine light sources that radiate the three primaries and get white. Yellow, cyan and magenta are subtractive primaries; cyan subtracts red, magenta subtracts green, yellow subtracts blue. Mix the three subtractive primary dyes and they subtract the three additive primary colors to make black. The sensation of yellow is the result of stimulating the red and green sensitive cells in the retina. A pure yellow light source has this effect because the sensitivity curves for the two cell types overlap strongly in that part of the spectrum. If you bother to look closely at a color television you will see that the red and green phosphors are `on' when the image is yellow. Green can be made by mixing a cyan (blue-green) dye with a yellow (red-green) dye. Cyan subtracts red, yellow subtracts blue; green remains. Please don't bring up two-color primary theories, I know about them. Now, can we get back to the DSP lessons? -- Griff Smith AT&T (Bell Laboratories), Murray Hill Phone: 1-201-582-7736 UUCP: {most AT&T sites}!ulysses!ggs Internet: ggs@ulysses.att.com
hjortsho@cg-atla.UUCP (Erik Hjortshoj) (09/23/88)
In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: > > >Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >the primary colors (being a combination of blue and yellow)? Why shouldn't >it be red, YELLOW, blue? You are confusing the primary PIGMENT colors with primary LIGHT colors. Pigment's primaries are, indeed, red, blue and yeller. If you mix them all together you get black. Light's primaries are red(it's not actualy red but I forget what), green and blue. If you mix them all together you get white. >Projection televisions work the same way ... is it possible to emit green, >and blue 180 degrees out of phase with the blue component of the green, to >cancel out the blue and the green and make yellow? If not, how do you make >yellow? I don't remember, but it IS a mix of the primaries. (red-green maybe) A lot of intro physiscs books have diagrams of the mixes of both pigments and light. An encyclopedia would have it as well. Erik H.
dya@unccvax.UUCP (York David Anthony @ WKTD, Wilmington, NC) (09/23/88)
In article <871@ritcv.UUCP>, cep4478@ritcv.UUCP (Christopher E. Piggott) writes: > Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of > the primary colors (being a combination of blue and yellow)? Why shouldn't > it be red, YELLOW, blue? Actually, you are thinking about pigmented primary colour systems, not optical additive primary colour systems. The RGB primaries represent the maximum span (and define a "triangle" on the CIE colour chart, a 2-d representation of colour space) of reproducible colours. Colours outside the "span" cannot be reproduced. Check out any decent book on physical psychology, Cornsweet's classic text "Visual Perception", or the half-zillion books published on this subject in the 50's w.r.t. colour TV. York David Anthony DataSpan, Inc
syd@dsinc.UUCP (Syd Weinstein) (09/23/88)
In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: >Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >the primary colors (being a combination of blue and yellow)? Why shouldn't >it be red, YELLOW, blue? Its time to explain the color wheel again. The Primary colors are different depending on whether you are talking about light adding up to make colors, or pigments subtracting to make colors. The three primary additive colors are Red, Green and Blue (suprize, RGB monitors) The three subtractive colors are Cyan (a blue-ish green), Magenta (A Red with some purple like tint) and Yellow. In school you learned to mix yellow and blue crayons to make green, the actual primary pigment subtraction (or filtration) is yellow and cyan to make green. If fact, each combination of two of one set of primaries makes one of the other. We call that the color wheel, and if my memory serves me correctly: Red Yellow Magenta Green Blue Cyan Ok, each color is the opposite of the one diagonally across (ie red and cyan, green and magenta, yellow and blue), and each color is made of the two ajacent to it (read and green light makes yellow, magenta and cyan pigment filter white to make blue) How it works subtractively is that Cyan does not let Red through, Magenta does not let Green through and Yellow does not let Blue through thus take white light and filter out the Red and Green and you have blue left. Totally confused? -- ===================================================================== Sydney S. Weinstein, CDP, CCP Datacomp Systems, Inc. Voice: (215) 947-9900 {allegra,bellcore,bpa,vu-vlsi}!dsinc!syd FAX: (215) 938-0235
ins_agh@jhunix.HCF.JHU.EDU (Gary Henry) (09/23/88)
There are electronic clock radios out there with blue digits, so they do exist! (or, at least there is a good trick to make it SEEM like they are blue LEDs!) Gary Henry The Johns Hopkins University ins_agh@jhunix.UUCP
aardvark@nmtsun.nmt.edu (Bill Gallagher) (09/23/88)
In the words of Judge Wapner, "I've heard enough..." I was able to track down a supplier for Blue LEDs. Here is all the vital information you might need. Blue LED, part number Siemens LDB 5410 2.5v, reverse voltage 1.0v, forward current 25 mA Pure-blue, silicon carbide, peak emission @ 480nm $65 each in small quantities Available from Marshall in Phoenix (800) 528-6412 Thanks to those of you who responded. -- Bill Gallagher aardvark@nmt.edu NMT Computer Center "What's that watermelon doing here?" Socorro, NM 87801 Drop bomb here--->[34 03'58"N/106 54'12"W]
fwb@demon.siemens.com (Frederic W. Brehm) (09/24/88)
In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: > >Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >the primary colors (being a combination of blue and yellow)? Why shouldn't >it be red, YELLOW, blue? I thought that red, yellow and blue were the "primary" colors until I took Physics II in high school. Don't believe everything you learned in elementary school. Red, green and blue are the ADDITIVE primary colors. That means that you add different proportions of these three to make all of the different colors. Color CRT screens and the projection TVs add the light from the different phosphors to produce color. The SUBTRACTIVE primaries are cyan (kind of blueish-green), magenta (kind of reddish-purple), and yellow. This means that you subtract different proportions of these three from white light to produce all the different colors. Printing technologies use this method. There is a color wheel which describes the relationships between the additive and subtractive primaries. You can probably find it in a good book on color photography. Fred ---------------------------------------------------------------------------- Frederic W. Brehm phone: (609)-734-3336 Siemens Corporate Research uucp: princeton!siemens!demon!fwb 755 College Road East internet: fwb@demon.siemens.com Princeton, NJ 08540 "From there to here, from here to there, funny things are everywhere." - Dr. Seuss
goehring@cs.purdue.EDU (Scott Goehring) (09/24/88)
In article <7061@jhunix.HCF.JHU.EDU> ins_agh@jhunix.UUCP (Gary Henry) writes: >There are electronic clock radios out there with blue digits, so they >do exist! (or, at least there is a good trick to make it SEEM like >they are blue LEDs!) I have one of those clock-radios. Mine uses a flourescent display, not LEDs. After seeing the prices that some have posted for blue LEDs I don't even want to think about what a blue seven-segment LED display would cost.
larry@kitty.UUCP (Larry Lippman) (09/24/88)
In article <7061@jhunix.HCF.JHU.EDU>, ins_agh@jhunix.HCF.JHU.EDU (Gary Henry) writes: > There are electronic clock radios out there with blue digits, so they > do exist! (or, at least there is a good trick to make it SEEM like > they are blue LEDs!) I suspect that you are looking at a vacuum fluorescent display, most of which emit blue light. <> Larry Lippman @ Recognition Research Corp., Clarence, New York <> UUCP: {allegra|ames|boulder|decvax|rutgers|watmath}!sunybcs!kitty!larry <> VOICE: 716/688-1231 {att|hplabs|mtune|utzoo|uunet}!/ <> FAX: 716/741-9635 {G1,G2,G3 modes} "Have you hugged your cat today?"
henry@utzoo.uucp (Henry Spencer) (09/24/88)
In article <262@rna.UUCP> dan@rna.UUCP (Dan Ts'o) writes: >... But if you add >red light to green light, you get yellow light, not brown paint. Dept of Nitpicking: actually you don't get yellow light, you get light that *looks* yellow to an unaided human eye. A spectrophotometer (or just a prism) will reveal that it really still is red plus green. (I have seen people confused over this, so it seemed worth mentioning.) -- NASA is into artificial | Henry Spencer at U of Toronto Zoology stupidity. - Jerry Pournelle | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
mcdonald@uxe.cso.uiuc.edu (09/25/88)
>Frequency multipliers do exist, though. >One application of their use is to convert the output of a high power >laser; eg: a Nd-YAG laser (IR light); to higher frequency, eg, visible light. >The doubler is grossly inefficient, expensive, and is usable because >the laser gives off lots of watts (large photon flux so multi photon aborption >is more probable). Doublers are not inefficient. 5 mm long potassium titanyl phosphate ( K TiO PO ) crytsals will double 1.064 micron light with typical 4 efficiencies of 60 to 75%. With two in series you can get total 90% efficiency. They are expensive ($2700 for a 5x3x3mm crystal). They do need large powers (say 50 watts to get 60% efficiency). Multiphoton absorption is to be avoided like the plague - if it happens, the crystal EXPLODES! Whoops, $2700 down the drain! These things work on nonlinear index of refraction, not absorption. Doug McDonald
lharris@gpu.utcs.toronto.edu (Leonard Harris) (09/25/88)
Check out Hamilton Avnet - they sell them and I think its fujitsu that manufactures them. sorry - no part numbers. /leonard
jnh@ece-csc.UUCP (Joseph Nathan Hall) (09/26/88)
In article <1988Sep24.051114.15993@utzoo.uucp> henry@utzoo.uucp (Henry Spencer) writes: In article <262@rna.UUCP> dan@rna.UUCP (Dan Ts'o) writes: >... But if you add >red light to green light, you get yellow light, not brown paint. Dept of Nitpicking: actually you don't get yellow light, you get light that *looks* yellow to an unaided human eye. A spectrophotometer (or just a prism) will reveal that it really still is red plus green. (I have seen people confused over this, so it seemed worth mentioning.) Well, now, that depends upon how broad the spectra of the aforementioned red and green sources are, doesn't it? I'm delighted that so many of our audiophiles are opti-philes (or whatever). This is certainly a more exciting topic, anyway, than CD longevity, mercury- filled cables (:-) sorry), Sony Portables and whether or not your car CD player skips ... sheesh! -- v v sssss|| joseph hall || 201-1D Hampton Lee Court v v s s || jnh@ece-csc.ncsu.edu (Internet) || Cary, NC 27511 v sss || the opinions expressed herein are not necessarily those of my -----------|| employer, north carolina state university . . . . . . . . . . .
william@pyr1.cs.ucl.ac.uk (09/26/88)
Blue LEDs : Electrovalue, a (UK?) supplier will sell them for 29 pounds, with a comment to the effect that the price is not a misprint in the catalogue. If you are keen to wait for the currencies to reach near parity, then mail me and I can get some for you! ... Bill ************************************************************************ Bill Witts, CS Dept. * Nel Mezzo del cammin di nostra vita UCL, London, Errrp * mi ritrovai per una selva oscura william@cs.ucl.ac.uk * che la diritta via era smarrita. ************************************************************************
cl@datlog.co.uk (Charles Lambert) (09/26/88)
In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: > >Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >the primary colors (being a combination of blue and yellow)? I just know there'll be a hundred optical physicists leaping to answer that one, so I'll skip over it and ask a corollary. I guess that a yellow LED is really a red and a green LED in the same capsule: correct? -------- Charlie
sukenick@ccnysci.UUCP (George Sukenick) (09/27/88)
>Doublers are not inefficient. [60-90%] [expensive ca. $2700] >They do need large powers (say 50 watts to get 60% efficiency). >Multiphoton absorption is to be avoided like the plague - if it happens, >the crystal EXPLODES! Whoops, $2700 down the drain! >These things work on nonlinear index of refraction, not absorption. Absolutely right! Thanks for the correction. I had said 'absorption' when it should have been about 'virtual levels' and I had forgotten about phase matching (which brings efficiency up) (Its been a while since Yariv and Born & Wolf....) I hope that no one blew up anything on my account :-)
rdp@atexrd.UUCP (Dick Pierce) (09/27/88)
In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: > >Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >the primary colors (being a combination of blue and yellow)? Why shouldn't >it be red, YELLOW, blue? > There are two types of primary colors: additive and subtractive. Those systems (such as TV screens) that create color by adding primaries together use the additive primaries red green and blue. Mixing any two of these together gives you magenta (red+blue), yellow (red+green) and cyan (green+blue), all three mixed together in egaul intensities gives white (or grey). Systems that produce color by subtraction (such as full-color printing or color slides) use the primary colors of magneta, yellow and cyan (sound familiar, eh?). By subtracting two of these primaries from white light, you get red (-(magneta+yellow), green (-(cyan+yellow) and blue (-(cyan+magenta). What this has to do with rec.audio is beyond me, but, what the hell. -- Dick Pierce EPPS, Inc. (617) 276-7317 32 Wiggins Ave. {kodak,ll-xn,sun,genrad}!atexrd!dpierce Bedford, MA. 01730 --
tow@arisia.Xerox.COM (Rob Tow) (09/28/88)
In article <262@rna.UUCP> dan@rna.UUCP (Dan Ts'o) writes: >In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: >> >>Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >>the primary colors (being a combination of blue and yellow)? Why shouldn't >>it be red, YELLOW, blue? > > You are confusing additive colors with subtractive colors. Yes, if >you add blue paint to yellow paint, you get green paint. But if you add >red light to green light, you get yellow light, not brown paint. I am stirred from my dogmatic slumbers, to paraphrase Hume... Wrong. In the "paint" world, adding *cyan* to yellow yields green. Cyan is often confused with blue. In the world of "paint" - subtractive colors, actually - cyan is blue plus green. Adding a really blue paint to a really yellow paint would produce a grey or a black! On a monitor, yellow is made by lighting up the green and red phosphor dots; adding blue then makes white. The entire discussion of color up to this point has been filled with misinformation, with the sole exception of one gentleman who actually quoted sources for cone pigment sensitivity curves. This discussion does not belong in this group. It should be moved elsewhere. The closest match would be comp.graphics - where it gets regularly revived every year or so. A few sources for those who really do wish to explore human color perception and color reproduction (quickly looking at my bookshelf): "The Reproduction of Colour in Photography, Printing, and Television", by Dr. R. W. G. Hunt, Fourth Edition, Fountain Press, England, 1987, ISBN o 86343 088 0. This is perhaps the ultimate reference for color reproduction. Warning: this, and the next book, are rather expensive: on the close order of $100. "Color Science: Concepts and Methods, Quantitative Data and Formulae", Gunter Wyszecki and W. S. Stiles, 2nd Edition, John Wiley and Sons, 1982, ISBN 0-471-02106-7. This is the ultimate deskside reference for psychophics/radiometry/color measurement. "Colour: Why the World Isn't Grey", Hazel Rossotti, Princeton University Press, 1985, ISBN 0-691-08369-X. An entertaining yet informative exploration of color perception and the physics of color. Color perception is not a completely understood area. There are useful engineering models; after all, we find utility in color printing, television, photography, etc. All of these are actually clever illusions which exploit aspects of the human visual system. --- Rob Tow Member Research Staff Electronic Document Lab Xerox PARC 3333 Coyote Hill Drive Palo Alto, CA 94304 (415)-494-4087
etxbrfa@kklm01.ericsson.se (Bjoern Fahller) (09/29/88)
The only problem with blue LEDs is the price. In sweden you can buy blue
LEDs from ELFA AB at SEK 280 each. They're called SLB5410.
some data:
Diameter 5 mm
If 25 mA max
Uf 3.75V typ
intensity 0.6 mcd
angle +- 8 deg
SNAIL: ERICSSON TELECOM Vox humana: (+46) 8 - 719 62 52
Bjoern Fahller Fax machina: (+46) 8 - 740 28 34
KK/ETX/TT/MLG
S-126 25 STOCKHOLM
SWEDENhenry@utzoo.uucp (Henry Spencer) (10/02/88)
In article <870@dlhpedg.co.uk> cl@datlog.co.uk (Charles Lambert) writes: >I guess that a yellow LED is really a red and a green LED in the same capsule: >correct? Nope. It's a different flavor of LED. Red+green LEDs do exist, but they are built for use as multi-color LEDs, with the ability to activate one or the other color. Activating both does give you yellow, but the red+green jobs are more expensive and somewhat of a hassle to drive; using them for single-color applications is not worthwhile. -- The meek can have the Earth; | Henry Spencer at U of Toronto Zoology the rest of us have other plans.|uunet!attcan!utzoo!henry henry@zoo.toronto.edu
hd@kappa.rice.edu (Hubert D.) (10/05/88)
An actual BLUE led (480nm) is available from Siemens. The part number is LDB5410. It has a 16 degree viewing angle and 6.0 mcd luminous intensity @ 20ma. The data book lists their head office at: Optoelectronics Division 19000 Homestead Road Cupertino, CA 95014 (408) 257-7910 I have not used the device, just remembered seeing it in the data book. Hubert Daugherty hd@rice.edu
fwells@wheaton.UUCP (Frank Wells) (10/06/88)
In article <870@dlhpedg.co.uk> cl@datlog.co.uk (Charles Lambert) writes: >In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: >>Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >>the primary colors (being a combination of blue and yellow)? >I just know there'll be a hundred optical physicists leaping to answer that >one, so I'll skip over it and ask a corollary. >I guess that a yellow LED is really a red and a green LED in the same capsule: >correct? Somebody's probably already said it, but the primary PIGMENTS are Red, Yellow, Blue (as opposed to COLORS, tints if you will.). An LED, on the other hand electrically excites the diode material to produce the yellow color. You could have a yellow gun in a monitor, but you'd have trouble getting all the colors right. Hope this helps. Frank Wells
thaler@speedy.cs.wisc.edu (Maurice Thaler) (10/08/88)
The primary additive colors are RED, GREEN, and BLUE. The subtractive primary colors are CYAN, MAGENTA, and YELLOW. Light works differently than pigments. I spent many years as a pro color printer where I spent lots of time mixing light in a color-head enlarger. You need to know color theory to do this right.
wtr@moss.ATT.COM (10/12/88)
In article <795@wheaton.UUCP> fwells@wheaton.UUCP (Frank Wells) writes: >>In article <871@ritcv.UUCP> cep4478@ritcv.UUCP (Christopher E. Piggott) writes: >>>Question: why are R.G.B. monitors Red, GREEN, blue, when GREEN is not one of >>>the primary colors (being a combination of blue and yellow)? >Somebody's probably already said it, but the primary PIGMENTS are Red, >Yellow, Blue (as opposed to COLORS, tints if you will.). >Hope this helps. >Frank Wells Now wait a minute.... :-) In printing (ink), the three pigments used are: yellow, cyan (*not* blue), and magenta (*not* red). there is a pseudo fourth pigment (black), but this is just used because it is a combination of the first three, and much easier to use in everyday printing. In printing, remember that the colors that you see are what is *not* absorbed by the individule pigments. the color green is (are?) the wavelengths that cyan and yellow have in common. likewise blue is the intersection of cyan/magenta and red is the intersection of yellow/magenta. remember that this is a subtractive (is that an adjective :-) effect. green is cyan minus all but the 'yellow' components. light, on the otherhand, is additive. blue *plus* green give you back the cyan. ( a gross generalization at best, but suitable for the moment) if you look at it like red/green/blue are three disjoint sets whose union make up the color 'universe'. then magenta/cyan/yellow are the union of two specific colors. ie |-- red --||-- blue -||- green -| |------ magenta -----| |------- cyan -------| <- yellow --| |-- yellow -> that's why tv/monitors/etc use red/green/blue for the guns, and why printers use cyan/magenta/yellow. critical review welcome, i'll bring the marshmellows ;-) ===================================================================== Bill Rankin Bell Labs, Whippany NJ (201) 386-4154 (cornet 232) email address: ...![ att ulysses allegra ]!moss!wtr ...![ att akgua watmath ]!clyde!wtr =====================================================================