Newsgroups: sci.electronics
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!batcomputer!cornell!uw-beaver!milton!whit
From: whit@milton.u.washington.edu (John Whitmore)
Subject: Re: X-Y detection of moving metal ball?
Message-ID: <1991Apr13.165525.24986@milton.u.washington.edu>
Summary: Remember basic optics!
Organization: University of Washington, Seattle
References: <14815@mcdphx.phx.mcd.mot.com> <2404@tuvie.UUCP>
Date: Sat, 13 Apr 1991 16:55:25 GMT

In article <2404@tuvie.UUCP> hp@vmars.tuwien.ac.at (Peter Holzer) writes:
>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. 
 ...
>>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

	It should be a LOT easier than pattern recognition; remembering
that a convex mirror produces a virtual image, just use a point source
illuminator and put the polished ball in a black environment.  The
image of the light source will be a tiny point inside the ball.
	

	John Whitmore