3. I want to be
able to chop an X mm wide beam at Y Hz. Why can't I?
Please calculate the speed the disc surface needs to travel
using the following formula:
Speed = X · Y · 0.0072 km/hr (or alternatively
Speed = X · Y · 0.00447 miles/hr)
If the resultant figure is greater than 1193 km/hr (or 741
miles/hr) then you will need to break the sound barrier to reach the required
chopping rate. We can almost reach half this figure with our high speed chopper in the right conditions but it makes rather
a fuss about it.
Please note that the formula does not include the diameter of
the disc. This is due to the limiting factor for the speed of optical choppers
being wind resistance. To a first approximation, the speed at the edge of the
disc is directly related to the wind resistance and is independant of the
diameter of the disc. As an example our 200mm diameter
system will only spin at approximately half the speed of our 102mm diameter system with the same power motor. Hence the
speed at the edge of the disc is the same.
Please also see the following answer if you want to break this