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Here's a photo of one of our 2x3 LEDs laying against a piece of bright-white Inkjet paper. We've turned down the ambient light so the difference can be easily seen. The front of the LED is on the right side (it's the yellowish colored emitting surface that you see in our main picture). This area of the LED has been "doped" with a color correcting material to bring the wavelength of the light very close to pure white. On the left side is the "shine-through" that is shining out the back of the LED's ceramic case. Notice the bluish cast to this "uncorrected" light. This is more typical of many "white" LEDs. In our applications, we typically paint the LED housing to prevent any "shine through" from occurring. We've found that a coat or two of Poly Scale Night Black does an excellent job of blocking the stray light that is emitted from the sides and back of LEDs. The added benefit is that this is an acrylic and doesn't attack anything nor does it conduct electricity (you can paint over the wires and solder joints without causing a short).
© 2008 Ngineering