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.