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From: hp@vmars.tuwien.ac.at (Peter Holzer)
Newsgroups: sci.electronics
Subject: Re: X-Y detection of moving metal ball?
Message-ID: <2404@tuvie.UUCP>
Date: 11 Apr 91 19:11:04 GMT
References: <14815@mcdphx.phx.mcd.mot.com>
Sender: plank@tuvie.UUCP
Lines: 35

hbg6@citek.mcdphx.mot.com writes:

>In article <11206@scolex.sco.COM> deanr@sco.COM (Dean Reece) writes:
>>
>>rlk@telesoft.com (Bob Kitzberger @sation) writes:
>>>5. Video camera mounted above.  Perform pattern recognition for a ball bearing.
>>>   Just kidding!  I know this option is silly.

>It's not silly and it's not really THAT complicated. Take the video signal
>from the camera. A simple circuit will give you horz. and vert. sync
>signals. Attach a counter to the H. Sync that resets to zero on V. Sync.
>Also attach a timer ( counter + timebase ) that is reset by the H. Sync.
>pulse. The last piece is a comparitor watching the video signal, set to
>trigger when the sillouete of the ball is encountered, and enabled by the
		  ^^^^^^^^^ Don't see how you can recognize the
silhouette of a ball with a comparator. You can find the first pixel
that is lighter or darker than a certain threshold that way. If you
want the computer to play labyrinth you would need a black labyrinth
(so that the black holes won't show) and you have to make sure that the
camera sees only the labyrinth (so your comparator doesn't take the
light table for the ball).

I am working on a similar project, and the setup we have now (12MHz AT
with frame grabber card) is much too slow to do serious pattern
recognition in real-time. I can't do much more than find the nearest
dark spot to the last ball position and check if it doesn't exceed a
certain size. If there are lines or holes on the plane it will
eventually find these instead of the ball. I am now looking for signal
processors to get the necessary performance. 

--
|    _  | Peter J. Holzer                       | Think of it   |
| |_|_) | Technical University Vienna           | as evolution  |
| | |   | Dept. for Real-Time Systems           | in action!    |
| __/   | hp@vmars.tuwien.ac.at                 |     Tony Rand |