P3D Re: Viewers and white LEDs

[Greg Erker <erker@xxxxxxxxxxxxxx>]

>Tom Deering and I traded Emails recently about using white LEDs in a
>viewer. Since I last wrote to Tom I have had occasion to use white LEDs
>in a design for microscope illumination. I have also had a chance to
>look at some homebrew viewer designs on the internet.

>Anyway, just some thoughts on improving the illumination efficiency of a
>viewer.
>
>Tom Hubin
>thubin@xxxxxxxxx

  Some great ideas there Tom.

  This LED page says that at
least some of the white LEDs
vary in colour with angle:
http://www.misty.com/~don/led.html

"As for shade of white? The ones
I tested seemed like about 6000
to 6500 Kelvin. The color is slightly
different in different directions,
since the chip and the phosphor have
slightly different directional
characteristics."

---

  This sounds bad for a viewer
since the edge would be illuminated
with a different colour than the
center. Unless other white LEDs
are better.  How are the ones you
tried?

Greg E.