7
SHUTTER OPERATION OF IMAGE INTENSIFIER
Internal Synchronization (INT) Mode
Internal Synchronization Shutter Timing Chart
Shutter Operation by External Trigger Pulse
TAPPC0084EA
TAPPC0085EA
Of the paramount importance to the CCD's shutter operation is how the operational timing of the shutter is matched
with the synchronization of the CCD. When the shutter is operated in external synchronization (EXT) modes, it is nec-
essary to consider the synchronization with the data transfer time and the readout time of the CCD . (Refer to P11)
Shutter operation on the EIA signal system is described below.
If the shutter mode selection switch of the camera head is set to "INT", the C5909 series executes the matching of shutter operation
with vertical synchronization of the CCD. The shutter timing at this time is shown below.
In this mode, the shutter opens after approximately 1 ms from the beginning (VIDEO READ EDGE) of vertically synchronizing pulses
of even fields in video signals.
In the frame storage mode, an electric charge that has been stored for 1/30 second from the beginning of each vertically synchroniz-
ing pulses is transferred and read out at the beginning of the next frame. Therefore, when the shutter opens concurrent with a vertical
synchronization signal, it follows that two phenomena at the different timing are accummulated as one image each fields. To acquire
an image at the same timing on both fields by frame storage, the shutter must operate in synchronization with a field index signal
(1/30 s), so the internal settings need to be changed. (See "Frame storage and field storage" on page 11.)
In the field storage mode, on the other hand, an electric charge that has been stored in the CCD in the current field (1/60 second) is
transferred and read out at the beginning of the next field. The transfer time of the CCD is approximately 80 µs, and electric charge
transfer commences within approximately 300 µs after the video read edge.
Therefore, if the shutter operates in a state that the shutter time is across that transfer time (80 µs), image data will be separately out-
put in two frames. To prevent this, the shutter operation commences after 1 ms from each video read edge.
External (EXT) Mode
To use EXT mode, set the shutter mode selector to "EXT". In this mode, the shutter operates by supplying a TTL level, positive logic pulse
to pin No. 9 of the 12-pin connector on the rear panel of the camera head. The shutter time is equal to the input pulse width and the shutter
operates at a timing with a delay of less than 100 ns relative to the TTL pulse input. Operating conditions in this mode are shown below.
In the frame storage mode (default setting), an electrical charge stored in the odd-numbered pixels during the periods
1
and
2
is read
out at
B
. An electrical charge stored in the even-numbered pixels during the periods
2
and
3
is read out at
C
. (See page 11.)
It is therefore necessary to set the operational timing of the shutter in such a manner that it operates after 1 ms from the video read
edge. (OUT signal, shown in figure, as a trigger signal.) If the shutter opens within the prohibitive shutter operating range of 1 ms after
the video read edge, its video data is output and divided in two fields. In this situation, the heights of pulses that are output in each field
do not become uniform, thereby causing the screen image to flicker. Care should be taken. In the field storage mode, an electric charge
that has been stored in
1
is output as video data in
A
field, and one that has been stored in
2
is output as video data in
B
field.
Normal Mode
In this mode, the shutter operation of the image intensifier cannot be executed, regardless of whether or not external pulses are input. There-
fore, Hamamatsu ICCD camera units are considered as high-sensitivity CCD TV cameras that provide shutter operation at 1/30 s intervals,
the same read time as that of a CCD camera, in the case of frame storage mode. The shuttering interval in the field storage mode is 1/60 s.
VIDEO
READ EDGE
VIDEO OUT
SHUTTER
TRIGGER TIMING
RANGE
VD OUT
VIDEO
READ EDGE
VIDEO
READ EDGE
EVEN NUMBER
FIELD
ODD NUMBER
FIELD
ODD NUMBER
FIELD
EVEN NUMBER
FIELD
VIDEO
READ EDGE
1 ms
1 ms
1/60 s
D
C
4
3
2
1
B
A
SHUTTER
OPERATING RANGE
PROHIBITED SHUTTER
OPERATING RANGE
1 ms
1 ms
VIDEO
READ EDGE
VIDEO OUT
SHUTTER
TIMING
(FIELD STORAGE)
SHUTTER
TIMING
(FRAME STORAGE)
VIDEO
READ EDGE
VIDEO
READ EDGE
EVEN NUMBER
FIELD
ODD NUMBER
FIELD
EVEN NUMBER
FIELD
SINK
VERTICALLY
SYNCHRONIZING PULSE
1 ms
1 ms
1 ms
SHUTTER TIME (Max. 300 µs*)
1/60 s (16.6 ms)
1/30 s (33.3 ms)
* -06, -07, -08, -09: 100 µs
SHUTTER TIME (Max. 300 µs*)
FIELD
INDEX
High
Low
