Picture Distortion - NEC DPro2070SB 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, etc.:
Distortion excluding normal pin,
barrel or trapezoid.
x
• Distortion y:
y
High frequency distortion
excluding trapezoid.
• Distortion x:
a. Center line
b. Curve of other vertical line
50mm
x
X
• Distortion
Scale
Within
n mm
Enlarged
V line
Set scale to V line
Judgement reference value
a. x 1.0mm
b. x 1.5mm
(*) Preset No.1
(31.5kHz, 60Hz) is:
a. x 1.5mm
b. x 2.0mm
x: Curve within
x 0.9mm
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
( * )