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Position Sensor 2 D

I am working on a design requiring synchonization of two tool pieces with a variable thickness membrane between them. I want to be able to run a system to get the parts within a few mm, and a laser with enough excess gain to be picked up on a pcb mounted ccd mounted on a sensor on the bottom. When the sensor feeds back the position of the laser dot, the stepper system could microstep into almost dead nuts position using a PID type loop.

Does this make sense? If it does, I am looking for some ideas about suppliers of the CCD sensors.

Reply to
Howhurley
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Let me restate, and tell me if I'm right:

You want to locate your top & bottom tool pieces to within a few mm by other means. Then you're going to shine a laser on the membrane from one side, and pick it up with a CCD imager on the other. You'll use the position of the laser dot on the membrane to align the two tool pieces.

Right?

  1. Why bother? There are inexpensive machine-tool measurement devices that'll get your accuracy down to 25um assuming a good mechanical assembly, which you'll need anyway just to be controllable down to that level. Buy four for X and Y on each side and you're done.

  1. You realize that you'll have to do some serious processing of the CCD image, yes?

  2. You've made sure that your membrane won't distort the laser image to the point where you get a false center?

  1. A LASER? If your membrane doesn't attenuate the light a _lot_ then perhaps you just want an LED and a pinhole?

What sort of CCD output are you looking for? NTSC "TV" format? Whatever comes out of the chip? USB? IEEE-1394?

For a one-off, or just a few, this may be most cost effective to do with a web-cam. For a few more, or if you need custom optics, you may want to buy a few web cams and rip them apart just to see what chips they use.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
Reply to
Tim Wescott

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