JVC TK-1280E - Page 30

TK-1280E/-1180E/-1281EG
Mi *CHARGE COUPLED DEVICE (CCD) "IMAGER
1 Precautions for handling and replacing CCD imager
CCD is characteristic of many advantages, but it also has
some disadvantages. The following are measures to deal with
these disadvantages.
(1 )CCD imager is a circuit element which is very sensitive to
static electricity.
@ The potential differences caused by the electrostatic charge-
which have been accumulated in the clothing and human
body-sometimes destruct the insulation of the CCD imager.
Therefore, handle the”high-priced”CCD imager with more at-
tention thereto tan to the C-MOS ( Complementary MOS ),
especially during the dry season and in dry places.
@ Maintain the CCD imager in the provided pack or aluminum
foil so that it can be kept at the same potential. Never unpack
its container until the very moment of servicing.
(2 )The CCD imager is easily damaged by dust. Also it suffers
considerable deterioration, when exposed to strong light.
@ When servicing, make sure that the CCD imager is kept free
from such foreign material as dust. Use dry soft cloth or soft
cloth moistured with ethyl aicohol to wipe off the foreign mate-
rial.
© Do not exposed the CCD imager to such Strong light as direct
Sunlight.
(3 )CCD imager is damaged instantly by the following malfunc-
tions. Pay close attention to these malfunctions before servic-
ing
® After removal of CCD, charge may remain at each terminal in
the circuit side for some time. In this situation , when CCD is
inserted to the socket, CCD may be distracted instantaneously
due to the charge. To avoid this, CCD should be inserted with
Passage of some time ( 2 to 3 minutes ) after removal.
4 (No. 6647)
Wi SPECIAL CHARACTERISTICS OF A CCD
The following phenomena can be expected when using the
video camera with the CCD imager; they are not malfunctions.
@ Smear phenomenon
This phenomenon occurs when shooting a very bright object (
such as electronic light, fluorescent lamp, the sun or a strong
reflection ).
Video monitor screen.
Light beit-like line
Very bright object
wl
Due to the interline-transfer organization of the CCD image
sensors ( Refer to "The Interline-transfer Organization of the
CCD Image Sensors” ) , this phenomenon is caused by
electronic charges generated beneath the photosensors by a
fight with a long wavelength, such as an infrared light.
In the shutter mode, as the signal level drops down to 1/20,
the smear level becomes high relatively. However this means
no failure.
® False signal
When vertical stripes or straight lines are shot, they may look
wavy.
@ Biemishes
The photosensor elements generate electronic charges which
ultimately produce horizontal and vertical rows in the CCD im-
age sensor.
Therefore, any malfunctioning photosensor element will even-
tually cause a blemish on the monitor screen.
he interline-transfer organization of CCD image sensors
This CCD video camera module adopts an interline transfer
organization in which precisely aligned photosensors and
vertical shift registers are arrayed interlinearly and horizontal
shift register links up with the vertical shift register, as shown.
Light variations are sensed by the photosensors,which
generate electronic charges proportional to the light intensity.
The generated charges are fed into the vertical shift registers
all at one. The charges are then transferred from the vertical
shift registers to the horizontal shift registers successively and
finally reach the output amplifier to be read out successively.
Vertical
shift
registers
Horizontal shift registers (CCD)