Jinx wrote

>Meant to mention that the other main objection to scanning-type lines is
>that this will produce a fast moving dot. As the detectors may come in
>from below or above and at any point at any time, the line needs to be
>omnipresent, particularly as I want to use a carrier frequency. A weak
>beam I can compensate for, a dot that ain't there I can't

provided the scanning movement of the dot of light is 'a lot' faster than the movement of the
detector then some form of integrator on the signal being detected would fix this for you...
for example, if you happened to be detecting the light beam with a phototransistor to vcc and a 1k
pulldown to ground, then by placing a carefully chosen capacitor across the resistor you should be
able to get what you are after - you want the time constant of the capacitor and the pull-down to be
low enough to respond to movement of the detector and high enough to not be too affected by the
scanning.

splitting a beam of light into a fan is going to be a pain and I would not like to bet on your being
able to find a cheap and useable solution.

Regards,
Simon

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