One of the last bits of the slide scanner I needed to make was to make a backlight for the slide scanner. I was thinking about how to make something uniform to light up the slides.

I was thinking about this as I slept and I came up with a design that incorporates the same math as the hollow sphere problem, but in two dimensions instead of three.

I have a solid white top and bottom piece as well as a clear (ish) surround. Around that is a series of 25 LEDs that I’m controlling with an Arduino.

Overall it looks like the lighting is pretty darn even! A tiny bit of dust or stuff isn’t consequential since it’ll be so far out of fucus it doesn’t matter. What does matter is the overall evenness across the field.

I think that it looks pretty good.

I even took a quick test shot with the Canon 5D and after processing it looks really rather nice!  :-D

Ignore the crookedness, that’s just me handholding the camera. The color, even after all those years is still pretty much spot on!