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3-5. Projection TV and convergence
The projection TV is CRT which generates one color light
of R.G.B and improved arrange lens Assy to in-line and
appear screen by set screen to the lens focus's appearing
position. At this time, The CRT of R.G.B set as like
follwing figure and active Raster frame is as shown in
below.
G CRT
G lens
B-Raster
In case of G Raster, appeared as not distorted screen as
like original 4:3 screen, but in case of R/B, that became a
trapezoid screen and the center point is distorted. For
this correction in projection TV, set cy to previous Dy and
compensation by flows in cy convergence current which
opposite to the R/B Raster's distortion.
<Figure 1>
R-Raster
G-Raster
<Figure 2>
3-6. Necessity of Dynamic Focus
The CRT panel which used in PJTV is flat completely. So,
the beam distance which scan to each corner and scan to
center from Dy center are very different. In case of usual
TV, correct de-focus by difference of this distance with
DY and focus lens, but in PJTV, little defocus influenced in
screen by extending picture appeared in CRT are said
great.
Improve focus by correct focus voltage of each corner
point with H parabola x V parabola as according to beam
shift distance's difference to D.C voltage.
1
1
SCREEN
- 32 -
DY
DEFLECTION CENTER POINT
CPT panel
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