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Old 16th May 2018, 9:04 pm   #28
PaulM
Hexode
 
Join Date: Nov 2006
Location: Near Lincoln, UK.
Posts: 481
Default Re: TV horizontal scanning - why flyback?

Flicker perception depends on many factors, but the primary ones are image brightness (square law), field of view (linear relationship), persistence (complicated response law) and update rate (another complicated response law. . .). In the case of Peano scanning, there is a point where the pattern starts again - the spot comes to the same point - and the time taken to do that is the effective update rate. By the time you get to about 240 Hz 'frame' rate, human perception has as good as lost any sense of flicker. In flight sim, we didn't need to worry about transmission bandwidths, so you could let rip with line and field rates governed only by IG (Image Generator) speed limitations and video bandwidths (often in the hundreds of MHz).

We were never keen on the idea of Peano scanning, but it wasn't much more bizarre than common-place raster calligraphic systems which combined conventional raster scan for about half the frame time with a free address calligraphic (vector scan) overlay. This was used to 'paint' high intensity vector addressed light points (runway lights, cultural lights and other features) over the raster display with all its associated aliasing. Calligraphic lights were precise, bright and moved properly across the display space. Once you have the high power, wide bandwidth deflection amplifiers to do raster-calligraphic, you're half way to be able to do Peano scanning. We never actually tried it, but did think about it.

Cheers,

Paul M
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