[Tfug] Yet another optics question

[Bexley Hall]

Hi Jeremy,

> >> My question:  do I need to situate the LEDs at the same position
> >> of the filament in the original bulb?  If so, that would suggest
> >> I need to use a single ultrabright LED as trying to locate multiple
> >> LEDs in the same small region would be problematic.
> 
> When you have a high-end / high magnification microscope, the
> illumination is fairly critical (hehe, that's my little inside joke,
> because it's actually Kohler as opposed to critical). But seriously,
> the illumination can impact the resolution and the way the object
> looks pretty severely.
> 
> On the other hand, you are talking about a stereoscope, so the
> resolution is probably crap and the magnification not that high, so it

This will only do 7X to 30X ("infinitely variable").  I have no
idea what constitutes "good resolution" vs. *bad*.  I just want
to see the damn itsy-bitsy components on the circuit boards
so I can verify the integrity of the solder joints, etc.
Years ago, devices were big enough (and my eyes young enough!)
that you could do this with the naked eye.  Now, I suspect even
folks with *good* eyesight would have a tough time examining a
6 mil trace to check for hairline fractures, etc.

> should matter very little as longs as the illumination is enough to
> see what you are looking at comfortably.

That was my thinking on the subject.  I can't imagine why you
would need 20W to light up something the size of your fingernail...
(unless there are losses in the optics, etc.)
 
> The problem with replacing the incandescent bulb with an
> LED is the power supply. You'll need DC with somewhat regulated
> current. I'd be

Not a problem (that's *my* world  :> )

> tempted to buy one of those cheap flashlights that uses LED's and try
> to rig up a DC current source to it so you don't replace batteries
> constantly. But you may just be offloading some of the wasted heat
> from the bulb to the power brick (although probably not quite as much
> waste).

LEDs use considerably less power.  E.g. a 1W LED would be quite
excessive.  Note that LEDs also tend to push their light in 
a hemisphere (or less) -- whereas incandescent bulb throws
light in all directions.

I can put something together -- even a variable *color* light
source if that was important. But, I don't know *mechanically*
if I have to take care in situating it at the same point that
the incandescent filament was located for the optics to
work their magic... :<

(next time you are in Tucson, I need to buy you lunch and
get some "napkin lessons" so I can grok this stuff  :< )