***SEE ALSO EIA TEP 105 SERIES***
Introduction
An excited CRT raster is designed to give the impression of acontinuously excited display without any flicker or scan linestructure. High fiequeixj, field refresh rates and closely spacedscan lines obscure from the human observer the way in which eachphosphor particle receives its excitation. These factors alsodetermine how fast the writing speed of the electron beam is acrossa given point on the phosphor screen, and therefore how long adwell time and how large a charge impulse each particle receives. Awriting speed of one cm per microsecond would produce at eachparticle a charge impulse 100 nanoseconds in width (for a one mmbeam spot diameter), a time much shorter than the rise or fall timeof most CRT phosphors. Consequently the product of the beam currenttimes the dwell time over a particle during each impulse may beconsidered to be in effect an instantaneous charge. The phosphor inthis sense is an integrator.
On the opposite extreme are the refresh times betweenconsecutive pulses, or the time consumed in writing one completefield. This is many orders of magnitude larger than the pulse widthdwell times and at least one order of magnitude larger than theluminescent decay time of most phosphors used in CRT displays. Herewe make the reasonable assumption that the phosphor respondsindependently to the separate impulses, with no accumulative effectamong them, so that the charge per single pulse determines thephosphor linearity behavior. For these reasons we characterize theexcitation density in terms of charge dosage per unit area perpulse rather than in terms of the per unit area beam currentdensity.
- Edition:
- A
- Published:
- 06/01/2000
- Number of Pages:
- 9
- File Size:
- 0 files
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