
Originally Posted by
mixedgas
30Kpps after some bench tests corresponds to a 2400 Hz small angle bandwidth response at the very small angle in the circle of the test pattern, , and as you open up the scan angle angle that frequency response falls off like mad in a non-linear way.
Wide angle jumps are slow, small angle jumps can be fast. The galvo shaft has inertia, and takes time to respond. It resonances that can cause bending mode failures and bearing failures if the galvo is abused.
There is not a linear relationship between PPS and displayable abstract Cycles per Second, that is dependent on scan angle and the galvo's non-linear frequency response. The galvo is, in simplest terms, a complex low pass filter with several integrals, and with several shaft resonances.
So, say you have an 1000 data point frame, at 30,000 PPS your time for one complete point is 1/30,000 = per point time in seconds, is 3.33 x10-5 seconds..., thus one 1000 point frame is completely scanned every .0333 seconds.
PPS is simply used to tune to the galvo amp to a common response to the standard test frame at a specific angle , so that images from different users are interchangeable.
So 30Kpps means the galvo can be given a point update rate of 30,000 points per second while scanning the ILDA test pattern at 8 degrees.
ILDA rated speed is related to making the feedback and PID loop tuning of different scan system hardware consistent, so artwork is interchangeable. Along the way it became a marketing point, as the first widely used feedback galvo system was 12K PPS, then 20Kpps, then 24Kpps, then 30Kpps, and a few systems have went faster. So for a long time the standards were 12K and 30K, and finally the Asian copies of scanners became less expensive, so most users have a 30K scan set.
Very little of this relates to how an abstract console behaves. In fact, with a console, one has to be careful not to stress the scanners with fast waveforms. You listen to the scanners, monitor their temperature, monitor their current draw, and keep the scan angles small when using a console, as the first thing the clone galvo manufacturers removed from the galvo amps was the "coil temperature calculator" circuit that protected the galvanometer scanners from overheating.
Only two manufacturers of scanners publish a scanner response vs frequency curve table, which is a complex data table that might tell an engineer a few things, but tells an artist basically nothing.
The ILDA test method was a compromise designed by a panel of very bright people to allow laser show companies to interchange images by tuning the hardware to a common response standard. It was NEVER intended to convey the complex response of a galvo scanner. PERIOD.
Steve