On 25 Aug 2000, at 14:23, Tony Nixon wrote:

> Hi all,
>
> Sorry for the off topic.
>
> Does anyone know if there are light filters available that will only
> pass a certain colour band? Eg. yellow only.
>
>
> --
This will be difficult on a large scale but you could "illuminate"
coloured objects with narrow band light sources (the colour of
interest) and subtract pre and post illumination intensities.
The result is level sensed (digital comparation) and then multiple
sample averaged. This should yield very clean data, but the range is
intended to be only been 5 metres at no more than 5 kph.
I have set up a  mono single line CCD sensor but it should be
possible with a mono camera.

I confess to being stuck on the pattern recognition in the just
described method but I am an optimist.
_____________________________

Lance Allen
Technical Officer
Uni of Auckland
Psych Dept
New Zealand

www.psych.auckland.ac.nz

_____________________________

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