Updated 11-08-06
JKL's silicone White Cap filters give you an easy, permanent and inexpensive way to change blue LEDs into any of over 80 shades of white!The filters fit onto any 3mm (T1) or 5mm (T1 3/4) blue LED, and will work with any blue LED with a wavelength ranging from 465nm to 475nm.
Colors range from cool blue to warm white and ivory to lemon yellow! The filters are made in such a way that you can pop them onto a whole bunch of LEDs and the color will be consistent from piece to piece and from order to order (the industry calls this "repeatability").
The filters also diffuse the LED's light, giving an effective viewing angle of 180 degrees, and are designed to be stable for long-term use.
White Cap filters are very easy to use. You simply push them onto the LED's body until you hit bottom. They will never come off by themselves, but they can be removed without damaging the LED if need be.
I was provided with several different colors in the T1 size, and a single T1 3/4 filter. The colors I tried range from a cool sky blue (very neat), to pure white to a true lemon yellow! Several other shades of yellow and yellow-white were also provided, as was a CIE Chromaticity chart with the positions occupied by White Cap filters shown on it.
White Caps installed on Nichia NSPB320BS blue LEDs.
So begs the question: Why?
Simple. In bulk quantities, blue LEDs are considerably less expensive than white ones. Using these filters on blue LEDs gives you a simple and cost-effective means of getting virtually any shade of white you may need for a particular application. Also, white LEDs generally don't match up well. That is, when you buy a bunch of white LEDs, you will find that each one is inevitably a slightly different color from the next. Using JKL's White Caps on blue LEDs gives you consistent color from piece to piece, regardless of the blue LED's original wavelength; provided it falls between 465 and 475nm.
Left: Close-up of White Caps installed on LEDs.
Right: White Caps actually in use, on four blue LEDs.
Photo on right is deliberately underexposed to prevent
blooming (bright areas showing up only as white blotches).
The above photo on the left is a close-up of two LEDs fitted with White Caps.
Notice how they fit snugly, but leave just enough clearance above the LED's base flange that they can be removed without destroying the lamp or the filter.
The picture on the right shows four of the White Cap filters fitted onto four identical blue LEDs (Nichia NSPB320BS) and photographed with the LEDs illuminated. The photo was underexposed by 1.5 stops and the LEDs were driven at only about 5 milliamps.
If I used a normal iris, they would be so bright they'd all just show up as white blobs - which isn't very useful at all, isn't it? This is why they don't look that bright in the picture - but trust me, they work just fine with LEDs driven at normal current in the 20 to 30 milliamp range.
Spectrometer plots of these filters over blue LEDs.
Ocean Optics USB2000 Spectrometer on loan from TWO-CUBED.
TEST NOTES:
Testing of this product depended on the availability of 3mm blue LEDs, which I was not able to locate until just recently. Now that I have hundreds of them, I can finish what I started.
Update 10-14-00 and 11-03-00:
I have found T1 blue LEDs from two different manufacturers, so this show can finally get on the road, including the addition of photographs.
Update 11-04-00:
Filters will work on any blue LED within the specified wavelength range, but best results are obtained when used with Nichia NSPB320BS, an LED with a wide 45° viewing angle. When used with these wide-angle LEDs, the light is very even and consistent on the surface of the treated LED, and as a result, on the surface of whatever you are illuminating with them.
Several visitors have likened White Cap filters to "condoms for LEDs"; and it is easy to see why.
So if anybody submits an order for "a dozen 39-02-W02 LED Condoms" you have nobody to blame but yourselves. Take it with a light heart, and fill the order. :)
PROS:
They really do work
Permanent, but removeable if need be
Diffuses LED light into a wide, even field suitable for backlighting switches and small silkscreened panel graphics
They're nontoxic when swallowed, and flushable too. (but please don't - they're too good for that!)
CONS:
The fact you actually have to take the time to install them onto each individual LED. For an installation with hundreds of LEDs, this could add to assembly time
They do cut down on the LED's overall brightness, but this is to be expected of any optical filtering method of a light source.
JKL 'White Cap' Silicone LED Filters * WWW.JKLLAMPS.COM
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