(Jeff Peterson) wrote in message
i am no expert on this, but i think the selection is to find the ones
with the narrow (and therefore bright) beams. we want braod beams so
would should
buy the cheaper LEDs

I've looked into this a bit and used to work at a company that made
extensive use of LEDs for detection and color sensing. The beam width
is dictated by the lens that is formed on the epoxy encapsulant, take
a look at a wide and narrow beam LED side by side and you can see the
difference.

I think it does make a lot of sense however to use a mix of different
lenses. It would be an intersting excercise to ask Excel's Solver how
many of which variety of LED to use provided with the right economic
and light inputs.

p.s. Congrats to CMU on that oragami folding robot.