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TFT-LCD
Gate
Frame period
pulse
t1
Vy
Y1
GND
Y2
Y3
Va
X1
Vb
t1 t2 t3
Picture
element
A
Each picture element electrode is controlled by a transistor. To the gate electrodes, the
gate pulse is applied timesharing. VCOM voltage is applied to the common electrodes.
The above figure shows the operation of TFT-LCD. If the gate pulse is not applied to
the gate electrodes, the transistors do not operate even when the potential difference
is given between the common electrodes and source electrodes, and no effect is given
to the liquid crystal. If the gate pulse is applied to Y1, the transistorT1 is in operation
during a priod of t1, and voltage of source electrode of Va is applied to the LCD layer
of picture element A, then electric charges are stored in the picture element of A. After
the period of t1, T1 is turned off, and voltage in the LCD layer of A is held until next
gate pulse comes, but it drops little by little through off leak resistance of TFT and leak
resistance of LCD itself.
BACK LIGHT
The camera unit is equipped with a fluorescent light source to provide the back lighting
for its LCD. The normal service life of the backlight is approximately six years, when the
camera is used for about two hours a day.
The backlight is consumption items, so even under guarantee replace it under charge
basis.
Selective period
Y1
Picture
element A
Y2
Y3
Ym
— 12 —
Source electrode
Gate electrode
T1
T3
T4
T2
X2
X3
X4
X1
TFT array substrate
Common
electrode
V COM
Tn
Xn
Common substrate
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