new 5mm LED

This is a forum to share experiences and ideas about holography.
Locked
Joe Farina

new 5mm LED

Post by Joe Farina »

Today I received some Light of Victory 5mm warm-white LEDs. The claimed output for these is 27,000mcd, and in truth they do seem very bright. It's surprising to see this much warm-white light from a LED that only needs 20mA. In the picture it shows my meter with a reading of 19.32mA. These small high-flux LEDs are awfully close to being sufficient for lighting 4 X 5 DCG holograms. The distance from the LED to the hologram is about 2 inches (50mm). They cost about 33 cents each.
Attachments
PB160035.JPG
PB160035.JPG (73.77 KiB) Viewed 2926 times
Dutchelm05

new 5mm LED

Post by Dutchelm05 »

Very cool Joe.
I have your LEDs
As soon as this laser here at work ships I will have time to check out the LEDs.
Thanks,
Tony
Dutchelm05

new 5mm LED

Post by Dutchelm05 »

Here are your results
Sorry it was little later than I hoped.

Out of everything your've done which did you conclude is the best?
Tony
Attachments
4.8mm 120' #3 12,000MCD.JPG
4.8mm 120' #3 12,000MCD.JPG (99.75 KiB) Viewed 2890 times
4mm  #4 23000MCD'.JPG
4mm #4 23000MCD'.JPG (100.12 KiB) Viewed 2890 times
8mm 140 #1 210,000MCD'.JPG
8mm 140 #1 210,000MCD'.JPG (99.5 KiB) Viewed 2890 times
#2
#2
8mm 140'.JPG (84.14 KiB) Viewed 2890 times
Joe Farina

new 5mm LED

Post by Joe Farina »

Thanks a lot for running those tests, Tony. This is very helpful to me, and not what I expected. There seems to be good news and bad news. (For others reading this thread, Tony's tests were done with some warm-white LEDs from China that I sent him.)

The bad news is that the blue spike is a lot less than what I was hoping for. Really tiny. When I looked at the spectra with a diffraction grating, it gives the impression that there's a lot more blue than there really is. The "real" tests with the proper equipment shows what it's really like. The only thing which makes this "bad" is if you're illuminating a blue hologram, or a hologram that has blue in it. So if someone is hoping to illuminate a full-color hologram with blue, then I think these warm-white LEDs would be a poor choice. Actually, the first spectra done by Tony with the "regular" white LED (on the "new 8mm and 10mm LEDs" thread) shows a much better distribution for illuminating color holograms, becasue the blue spike is more substantial. If a color hologram was made with 457, 532, and 633nm (and there was minimal shrinkage or expansion) then the "regular" white LED looks more atttractive, since the response at 457 is much better. But there will be a trade-off because the response at 633 will not be so high (as compared to the warm whites). But overall, the regular whites look pretty balanced for the above 3 wavelengths.

But 633 is a sore point because so little power is available there, and that's where the good news comes in for the warm whites. They have much better output in that area. The HeNe is currently a limiting factor in full-color holography (for people like me) and really it's the #1 concern. So if color holograms are made with just 532 and 633 (or the final hologram contains no blue, or marginal amounts of blue) it looks like the warm-whites would be a lot better.

As for my favorite LEDs, I really can't say, becasue my outlook is constantly changing. There are all kinds of LEDs out there, and I'm only familiar with a few.
JohnFP

new 5mm LED

Post by JohnFP »

Hey Joe, are you taking into account the sensitivity of the eye to those wavelengths? From what I understand you may need less green and more blue in relation to the red.
DJ Mathson

new 5mm LED

Post by DJ Mathson »

It would be interesting to see these LED spectrum plots compared to a regular halogen spot plot,
like this one:
http://www.hnuenergy.com/download/LED-V ... isible.jpg
Dutchelm05

new 5mm LED

Post by Dutchelm05 »

Anytime Joe, if there are others you wish me to try I would be happy to try them.
The plot DJ linked to looks pretty much like the ones I took.

I guess the bottom line Joe is how does it look?
As John said it is more about eye sensitivity than the actual spectra. If your were displaying a narrow band blue holo then it could be a problem.

DJ brings up a good point in try hologen, I can see if we have one around here. But going back to John's point, it may be better to see what looks good to you.

Are you worried that in viewing broadband holograms you will get some color biasing?
I would also point out that our brains do some color corection as well. Slip on some pink or yellow glasses and after a few minutes you will see white objects as white.
Also, as you view the hologram at some angle, do they break up (spectrum) sooner than say the sun, hologen etc?

Good work so far,
Tony
Joe Farina

new 5mm LED

Post by Joe Farina »

Personally I think these LEDs are fantastic. With halogen you have to have a separate light source on the wall or ceiling, which is a tremendous pain. With LEDs you can integrate them into the base of the display, and have them work at close range. In my opinion this is far superior to separate lighting or any edge-lighting scheme. That's it in a nutshell.

The color issue is really immaterial if you know what the spectra is, like what you provided. Obviously, if the light source doesn't have a lot of blue, then it won't be good for lighting a narrowband blue hologram, or a color hologram containing blue.

The sensitivity of the eye to different colors is a moot point also. Say you make a hologram, and know what colors it has (by looking at it in sunlight). You need a light source that has those colors, too. The eye is less sensitive to blue, so if you make a blue narrowband hologram and illuminate it with blue, it would look less bright than a yellow narrowband hologram illuminated with yellow.
DJ Mathson

new 5mm LED

Post by DJ Mathson »

Joe Farina wrote:With LEDs you can integrate them into the base of the display, and have them work at close range.
Then you´ll also need to have the reference beam diverging from this close range during the recording of the hologram. Otherwise, you will get a distorted image.
Joe Farina

new 5mm LED

Post by Joe Farina »

A diverging reference beam is no big deal. But with display holograms, some distortion is acceptable. Just look at the photos of the Lasart hologram, which was likely made with a collimated reference beam, and you can see what it looks like with highly diverging LED at close range -- pretty good I'd say.
Locked