Can anyone explain in detail the difference between Refresh rate and Flicker rate in a CRT ?
In the context of a CRT vs. flat panel, that is a Cathode Ray (vacuum) Tube, you have to consider the following:
1) Video sync as broken down to Vertical and Horizontal scan rates.
2) Phosphor persistence (the length of time the phosphor coating on the inside of the CRT will glow). "Phosphors are available with persistences ranging from less than one microsecond to several seconds."
These two factors will determine the overall picture quality with regard to time.
Refresh rate would be best explained as vertical frames per second, for NTSC it is 60 fps.
Flicker rate includes the refresh rate plus factoring in the persistence of the phosphor.
Long persistent phosphors were employed in radar screens and O'Scopes as to allow objects to last longer on the screen while shorter persistent phosphors were employed in most consumer TVs to reduce motion blur.
"Flicker occurs on CRTs when they are driven at a low refresh rate, allowing the brightness to drop for time intervals sufficiently long to be noticed by a human eye..."
Refresh rate is the frequency at which an image in a moving picture system is redrawn on screen. In modern video systems, for instance, the screen is redrawn 59.97 times per second. The refresh rate is 59.97. Motion picture projections flash a new image at 48 times per second. Film projectors flash each frame of film twice, which is how you get from 24 frames per second to a 48 image per second refresh rate.
Flicker rate refers to how rapidly images must be presented to in order that a human viewer does not perceive a "flicker" between images. It is a threshold number. Presentations above the "flicker rate" appear continuous while those below the flicker rate appear to flicker on and off.
The actual flicker rate varies with circumstances but the "flicker rate" is historically agreed to be 48 presentations per second, plus or minus. This is why projectors flash each frame twice, turning the 24 frames per second into 48 flashes per second to hide the flicker, and why old films, shot at 16-18fps flicker noticeably on screen.