3D

I am going to assuime that the scan lines are in the horizontal direction as they usually are (but no always, I have worked on at least one display system that scanned vertically!). So the vertical deflection is the slower one. Yhe vertical rate, horizontal rate and number of lines are all related. The main problems are (a) the video bandwidth (determines, essentially, the total number of pixels displayable in a given time) and the horizontal scan rate. Increasing the vertical rate from 60Hz to 120Hz is fairly easy if you don't mind halving the number of lines. This keeps the horizontal scan rate and the video bandwidth essentially unchanged. So as there are 1024 line 60Hz systems around 30 or more years ago, there couild easily have been 512 line 120Hz units. I wonder about electrostaticeally-deflected CRTs. The main disadvantage is that you gnerally have a much smaller deflection angle than with electromagnetic ones, leading to long CRT (base to sreen) for a given screen size. But driving them fast is considerably easier than driving deflection coils fast. Doesn't help with the video bandwidth, I guess. -tony