JAI RM-2040GE Series, User Manual

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RM/TM-2040GE Series
22 Operation
Figure 13.
Asynchronous Programmable External Trigger
3.5.4 Pulse Width Control Mode
In Pulse Width Control (PWC) Mode, the exposure time is controlled by the external trigger. When an external
trigger is applied, one discharge signal (Vsub) is generated right after the active edge of the trigger. The
exposure starts when the discharge signal is in the off state. The exposure ends following the trigger active off.
Exposure time is controlled by the pulse width of the external trigger. Because the CCD requires some overhead
from trigger-active-off to the transfer gate event, the actual exposure time is equal to:
Exposure Time = Pulse Width +7.45µs
Since one discharge signal (Vsub) is generated right after the active edge of the trigger, it is asynchronous with
LDV, and the discharge signal may happen during an active video transfer period, causing visible reset noise to
show in the current image. To avoid reset noise, the maximum trigger frequency in PWC mode should be less
than 1/ (exposure time + one frame transferring time).
The minimum active period of the external trigger is 5µs. Theoretically, the maximum active period of the
external trigger is unlimited. But, due to the usability of images at 25
o
C it is recommended the active period of
the external trigger be no longer than one second.
Figure 14.
Pulse Width Control Trigger