JAI TMC-4200GE User Manual download pdf (Page 78)

Page 66

TM-4200GE Hardware

Operation

FIGURE 65. Asynchronous Programmable External Trigger

9.3.5 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 is off 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 +20.6μs

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,

visible reset noise may 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

C it is recommended the active

period of the external trigger be no longer than one second.

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JAI TMC-4200GE User Manual Page 78