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From: "Adrian M Jansen"
Subject: Re: Detecting colored objects
X-Newsreader: Microsoft Outlook Express 5.00.2919.6600
Date: Thu, 31 Oct 2002 10:04:32 +1000
NNTP-Posting-Date: Thu, 31 Oct 2002 11:02:41 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
But for multiple colors you still need some way of switching the color
target for each color. Seems this would have to be mechanical, and hence
fairly slow. Switching vari-color light sources on and off, and measuring
response can be at electronic speeds.
Adrian Jansen firstname.lastname@example.org
Design Engineer J & K Micro Systems
Microcomputer solutions for industrial control
"Keith Buck" wrote in message
> This problem was literally sorted out years ago, yet no-one seems to have
> heard of the solution. You need a single photomultiplier tube and a lens
> with a white light source also. For every colour that you need to detect,
> you also need a sample of the same colour as a piece of card or painted
> metal. This is arranged to fill the PM tubes field of view. The object to
> detected is then placed in front of the coloured card. If it is identical,
> then it will not be detected as it will be identical to the background.
> however if it is only slightly different in hue or saturation, then the PM
> tube signal will change in one directin or another. You need some support
> electronics for the PM tube and amplifiers etc and a presence detector for
> the object.
> Regards Keith Buck
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