Newsgroups: comp.robotics
Path: brunix!uunet!usc!cs.utexas.edu!utgpu!cunews!dfs
From: dfs@doe.carleton.ca (David F. Skoll)
Subject: Re: What Color is it?
Message-ID: <dfs.700776399@worf>
Sender: news@cunews.carleton.ca (News Administrator)
Organization: Dept. of Electronics, Carleton University
References: <1992Mar16.115043.77@vms.ucc.okstate.edu>
Date: Mon, 16 Mar 1992 20:06:39 GMT
Lines: 27

In <1992Mar16.115043.77@vms.ucc.okstate.edu>
u1906ad@unx.ucc.okstate.edu (11906) writes:

>Has anybody got any thoughts on fairly simple to electronically tell the
>color of a surface such as a piece of wire?  It would seem that the
>ideal device would be a photo cell array which contained a red, blue,
>and green sensative segment like one pixel on a CCD camera.  It should
>be possible to determine the color of a surface by compairing the
>readings of the three cells, a task which should not be difficult for a
>microprocessor-based system.

It depends on how much accuracy you need.  To measure colour
accurately to standard colour references is quite expensive.  You need
to illuminate the object with a special light, compensate for
nonlinearities in the sensor, etc.  There's a company in St. John's,
Newfoundland called "Instrumar" which made an accurate colour-sensing
device for (of all things) inspecting the freshness of cod fish.  It
was quite expensive and needed fairly frequent calibration.  Even
standard colour scanners require fairly expensive lamps which emit
light at known frequencies, and don't degrade too much over time or
with temperature changes.

For a quick-and-dirty colour measurement, your RGB method should work fine.

--
David F. Skoll

