Re: Uses for little lenses?

Wildepad wrote: 
For one of my projects, I'm tearing apart 98 old CD-ROM drives (I need
the head-locating mechanisms and a few associated parts).


  First you don't tell us what the project is, then...

Despite the fact that each manufacturer seems to have their own ideas
on how to build them, all of the lenses seem to be the same.

I haven't really checked them out yet, but I assume that they all have
the same focal length. I also assume that it would be fairly short (1
or 2 mm?).

(Most CD drive MFGRs get their laser diodes from the same OEMs, and the available space in a CD drive is limited, so, to a first approximation, yes.)

Anyone have any idea what I might use these for? 

  you want us to tell you what to do with the leftovers!

(The only thing that I've thought of so far is some kind of
"dragonfly's eye", using the photodiodes and hooking it up to a
computer for imaging, but that idea doesn't really appeal to me for a
variety of reasons. I do, though, still have the molds for making golf
balls out of plaster, so a sphere of that size with these lenses on it
is possible, if it would have some neat application.)

New spin on the disco mirror-ball? You'll need a buncha SMT LEDs unless you want an IR disco ball...

So that you have a better idea of the kinds of things I'm capable of
(some of my more ambitious projects):

Purely mechanical: a wood and copper UART (you put pegs into holes,
crank a handle, and it pushes and pulls a six foot dowel while also
turning it. Its companion piece, taking its power from the dowel's
rotation, then raises pegs to match your input.)


  Charles Babbage would be proud ;>)

<snippage>

Hydraulics: a 'jaws of life' type thing small enough that the
operating head could be held in the hand, and the rest could be
strapped to your back. It was powered by a CO2 cartridge.


  For rescuing GI Joes from Tonka trucks? Sorry, couldn't resist.

Most ambitious overall: a tabletop 1/8"x 1/2" cam-operated automatic
lathe driven by a Dremel-type handtool. 

  That sounds like fun. Got plans online?

Miscellaneous extra info:

There is a component directly beneath the lens which I assume is the
photodiode. It would be easy to also salvage (although something of a
bugger to hook up).

Yep, that's a photodiode array; hooking up is pretty much trial and error (pinouts are just about impossible to find IME) unless you have a microscope to lead-trace with, but they're hard to hurt. Remember the laser diode also has a photodiode inside for power management.

The mirrors would be problematic to remove (time consuming and
difficult), but a few of them might be incorporated into a design.

Easy; a little WD-40 or acetone usually loosens whatever it is they stick them in with unless they used a drop of epoxy, then you have to cut the assembly up to get them out in one piece. Ask me how I know. Oh, and the beamsplitters; some drives use dichroic mirrors, some use glued half cubes of glass.

What I assume to be the laser diodes (located at a right angle to the
lens) are nearly impossible to remove.

Unsolder the leads first, then CAREFULLY press out. If you've already cut the assembly up per above you have easy access to the front of the diode.

Somebody (I forget who but I think it was Kevin Aylward in sci.electronics.design) once suggested making up a whole bunch of solar-powered IR laser emitters that followed a visible laser pointer for military use. You drop the emitters at random (they each have limited fields of view/fire but there's lots of them), then paint a target from a safe distance; target gets hot real quick. This uses everything except the locating mechanisms. Wanna build the proof-of-principle?

Since my current projects are most electromechanical or computer
controlled, I'd rather have something a little different. (I'm not
going to start on the Slinky-ator until I can resolve the nagging
doubts at the back of my mind.)


  I still say use a homopolar motor to eliminate cogging.


  Mark L. Fergerson

.

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