Picture Distortion - NEC FP1355 Service Manual

2.5.1.8

Picture distortion

When the picture distortion is measured, each distortion of the preset timing must be less than
the following values.
<Picture performance inspection items> Inspect the following items for the picture distortion.
No.
1. 4-corner section distortion
Inspect the distortion at the four corners.
• Signal, H character with frame (both normal/reverse)
x
2. 4-edge distortion
When S-character or seagull type high frequency distortion
is visible, check with the following method.
Left/right
distortion
Top/bottom
distortion
Inner distortion
3.
x
Vertical line
measurement method
H line
Per 50mm
Item
• Distortion x:
Distortion in the range of one H
character height.
Judge with the white display G.
(Judge the distortion amount with
a fluorescent material stripe.)
• Distortion x of S-character
distortion, etc.:
Distortion excluding normal pin,
barrel or trapezoid.
Note:There must be no sea-
gull distortion.
x
• Distortion y:
y
High frequency distortion
excluding trapezoid.
• Distortion x:
a. Center line
b. Curve of other vertical line
• Distortion x:
a. Center line
50mm
b. Curve of other vertical
x
X
• Distortion
Scale
Within
n mm Enlarged
V line
Set scale to V line
Judgement reference value
line
x:Curve within
50mm range
2 - 26
Input signal
x 1pitch H character
(=0.3mm) with frame
(both normal/
reverse)
x 0.6mm Crosshatch
* Note pattern
y 1.0mm
a. x 1.0mm
( * )
b. x 1.5mm
(*) Present No. 1
(31.5kHz, 60Hz) is:
a. x 1.5mm
b. x 2.0mm
x
When Fh < 61kHz,
total area : less than 0.9mm.
When Fh 61kHz,
center : less than 0.6mm,
peripheral : less than 0.9mm.