Asynchronous Readout
Asynchronous Readout
The TM-6705AN has a sophisticated timing control for
async shutter, readout inhibit and partial scan. Progressive
scanning permits a full 484 lines of vertical resolution per single
shutter, as compared with a conventional CCD camera at only
244 lines per shutter. The external VINIT resets the camera.
The VINIT pulse width controls partial scanning lines to vary
the frame rate.
The camera shutter is generated with the ROI (Read Out
Inhibit) leading edge. The image is stored in the CCD while ROI
is low. When ROI goes to high, the image is scanned for the
async readout.
In multiple camera applications for moving objects, all cameras
are activated simultaneously. The readout is controlled as time
sharing for a single image processor. This is done under
continuous lighting conditions. The ROI control is implemented
without async shutter. If a strobe light is used as per conventional
methods, the async “0” shutter is used for photosite integration.
Multiple Shutter
Multiple Shutter
When ROI is applied to the TM-6705AN (pin #11), the readout
is inhibited. During the ROI low, the multiple shutter trigger pulse
can be applied (pin #10) to
capture the multiple dynamic
images in an active frame. This
is similar to the multiple exposure
techniques of still cameras, or to
using multiple strobe lights per
single exposure.
Since the TM-6705AN is a
fast frame rate camera with high
speed electronic shutter, fast
event motion analysis can be
achieved with the VINIT partial
scan control. As ROI control can
be extended to several frame periods, slow speed motion cap-
turing is also possible with normal VGA output.
The minimum duration of the multi-shutter control pulse is 2H
(64 µsec.) and TTL level input. For VGA output format, select
Normal, T and ASY, and supply ROI control pulse. For Partial
scan, select PART, T and ASY, supply pulse width control VINIT,
and ROI. The shutter speed is set by the back panel switch. Since
multi-shutter operates with only async mode, the speed is 1H
(1/32,000 sec.) through 11H (1/2,800 sec.).
Partial Scan Mechanism
Partial Scan Mechanism
The TM-6705AN has a unique structure. Because of the fast
dump structure and two phase vertical shift register of the CCD,
the vertical shift register can be clocked at fast speed while
dumping out unnecessary horizontal lines. When the VINIT pulse
width control is applied, the vertical shift register is clocked at
normal VGA speed (32 µsec per line) during VINIT low. When
VINIT goes high, the clock rate changes to the maximum speed
(2.5 µsec per line). At the same time, the fast dump gate opens
to eliminate unused charges quickly. The fast dump period is
[(488-n) x 2.5µsec.], and stops when all charges are dumped.
For example, if the partial scan is 100 lines, the VINIT must
stay low for [20H (Vblank) + 100H] = 120 x 32 µsec = 3.84
msec. and the fast dump period is (488-100) x 2.5 = 970 µsec.
The VINIT must stay high for at least 960 µsec. before resetting
for the next pulse.
(138 paginas)
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