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MMD > Archives > January 1997 > 1997.01.11 > 08Prev  Next

Re: Fiber Optic Commutator
By Spencer Chase

That commutator idea of Andy LaTorre's sounds like fun. Its just my kind of mix of mechanical and electronic wizardry. It eliminates the need to match photodetectors and eliminates the need to have a lot of channels or electronic multiplexing. I'm adding it to the top of my list of possible reader\scanner designs. I can think of a couple of additional improvements.

Instead of optic fibers being placed at hole centers, use a continuous line of them going from the tracker bar to the ring. This way all formats could be covered with one setup. The read positions could be selected by stepper motor control. Tracking could also be done with the same unit by re-defining the hole positions based on the detected paper edges. The note sheet could just run off the spool without regard to tracking it mechanically. The interface and the software should be quite easy.

Idea #2: Forget the L-shaped fiber optic and mount the detector on the spinning shaft. Use slip rings and maybe mount the preamplifier on the shaft too, to increase signal-to-noise ratio.

Idea #3: Use a fixed speed motor and an encoder or some markers and a clock. Does anyone have any ideas about how slow this method would be?

Spencer Chase

[ Idea #3 would be _very_ fast, probably 10,000 rpm is possible.
[ No special markers are needed, just have a pattern of alternating
[ on/off to identify the margin at one side. (A little paint on the
[ fibers at the "tracker bar"!)
[ The remaining electronics needed closely resembles the hardware
[ which supports a CCD array and sends the data into the computer.
[ -- Robbie

(Message sent Sun 12 Jan 1997, 05:17:36 GMT, from time zone GMT-0800.)

Key Words in Subject:  Commutator, Fiber, Optic

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