ViewSonic ViewPanel VP140 Service Manual page 4

ViewSonic Corporation
li you want muti-scan and 'ul-scrsen display al tre same 'pat vce Sgn 1GA 40H)
ime. therefore, the video cutout pixals of a personal
=
computer er otner terminal must be converted into LCC
pixels. This is called pixel conversion. {This conversion is
gerevaly called scaing processing.)
TED Pana oz6e78)
Fig. 4 Video Data Scan Image
4-4 Necessity of V.Fine Tuning (Clock)
A clock signa! synchronized with video data is necessary to reproduce an image on tne _CD pane. nis cicck must
be completely ident cal with the video dot clock inside the persona' computer. if the clock signal generate in the
LCD is dferen rom the video cot cicck ore personal computer, the following probiems wil arse
(1) Mach jitter
(2) Serious level cf moire
(3) Screen amplitude :00 large or tco sme!
(4) Image r-nving out of shape (in cese cf large errors)
The personal computer does not cutput 2 § gnal having video dot ciack information, Mult-scan. tnere'cre, aeperds
on the accuracy sf the video dot cick 'rem the syncn-onizing signal suopiled by the cersonal comeuter. It is
extremely difficult. However, to totally elim nate er'ors, (The synchvonizing signa may have the same t"ecuency, but
the outout trig of the video dot c eck may 08 dillerent
Its necessary tneretore, tor tre user '0 make a fine adjustmen: of the clock frequency
This is tne reason why the OSD menu has acjustment items onit
Cause of more
Fig. 5 V. Fine Tuning,
5 Necessity of H.Fine Tuning (Phase}
'As expaned above, cicture wil be abversely atlected if the video dot clock is rat corel
sigral generated in the LCD.
Tris edjustment s also made on the OSO menu,
H+H
ely 'centical wth tne clock
vP140
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