(OT) Laserjet III laser scanner module

Hi guys, I've got a Laserjet III laser scanner module kicking around in my junkbox, harvested from an utterly screwed LJ3. It has a fibre-optic light pipe on one side, which connects to a photosensor on the motherboard. Does anyone know what the frequency or period of the photocell signal is? That is to say, how long does it take for the scanner to make one complete pass from "horizontal blank" to the right margin -- in other words, the time from the leading edge of one photocell pulse to the next? I'm toying with the idea of repurposing the scanner module for another project (using a BluRay laser diode to print directly onto photographic paper then process using a 3-bath B&W process), and I'd like to figure out (in advance!) what the requirements will be placed on the paper drive system (among other things!) Thanks, -- Phil. philpem at philpem.me.uk http://www.philpem.me.uk/