Sharp VL-C780S Serviceanleitung Seite 195

)} WHITE BALANCE CIRCUIT
-1. Outline
1 the white balance section, the video signal processing method is adopted eliminating the conventional
vhite balance sensor exposed outside. Adjustments are all made automatically and the white balance adjust-
1g data of the indoor/outdoor auto offeset are stored in the E2PROM.
. 'he principle of action is described below.
~2. Description of action
Vhen white is imaged outdoors in this condition, the B-Y colour difference signal pin (12) changes into the
ignal with amplitude in the positive direction from the blanking section; the R-Y colour difference compo-
lent into the signal with amplitude in the negative direction (Fig. 6-2 (b)). Consequently, white becomes cyan
| olour.
)n the contrary, when white is imaged under a light source of 3200 K after keeping white balance outdoors
Fig. 6-2 (c)), pin (12) changes into the signal with amplitude in the negative direction from the blanking
ection; pin (15) into the signal with amplitude in the positive direction (Fig. 6-2 (d)).
~
'he system block diagram is shown in Fig. 6-2 (e).
: Outdoor (5000°K)
R-Y
R-Y
3200°K
ave
R-Y —_—_——____+}— B-Y B-Y
R-Y
SY Stone tot
{a) (b)
Keep white
balance
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