(OT) Laserjet III laser scanner module

Brent Hilpert hilpert at cs.ubc.ca
Wed Jun 30 01:55:08 CDT 2010


Pete Turnbull wrote:
> 
> On 28/06/2010 22:15, Philip Pemberton wrote:
> > On 28/06/10 20:31, Tony Duell wrote:
> >> I don't know off the top of my head, but it should be farily easy to
> >> measure the speed of rotation of the motor. Each revolution would
> >> generate<n>  beam detect pulses (the output of the photosensor) where<n>
> >> is the number of sides of the polygonal mirror.
> >
> > Well, working backwards from DPI and print speed gives about 3MHz dot
> > clock:
> >
> >   300DPI * 11 inches (paper height) * 3ppm = 9900 lines per minute
> >     (thus, the line rate is 9900Hz, or 9.9kHz)
> >   9900lpm * 300 dots per line = 2.97e6
> >     (thus, the pixel rate is 2.97MHz)
> 
> Am I missing something, or is that too low by a factor of about 8 or 9
> (the number of inches along a line)?  It's somewhere in the region of
> 24MHz, surely.

There would also appear to be a minutes->seconds conversion missing.



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