JAI CV-A11 - Manual (Page 12)

CV-A11
6.7. Frame-delay read out Mode
This mode allows simultaneous capture of multiple camera using a common external trigger
pulse subsequent multiplexed (sequential) readout using a single input frame grabber, as the
user has control over when the image is read out from the CCD sensor. The exposure starts at
the falling edge of the ext. trigger signal, and ends at the rising edge of the ext. trigger signal
(in the same way as Pulse Width Control mode). The captured image is now stored in the CCD
until an ext. VD signal is given to the camera. The effective video signal is output 14H after the
falling edge of WEN signal.
To use this mode:
Set function:
Trigger mode to “Frame Delay Readout” TR=3
HD accumulation HC=0, HC=1
Polarity and other functions
Input: Ext. trigger to pin 5 on 6 pin connector (or 11 on 12 pin connector)
Ext. VD to pin 7 on 12 pin connector.
Ext. HD to pin 6 on 12 pin connector. (If used).
Fig. 19. Frame delay read out
Important notes on using this mode: -
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The readout delay time must not exceed 2 seconds. This is because visible dark current noise
may appear on the video signal due to the long time exposure of the CCD image sensor.
This trigger mode is also supported by a function called “HD Asynchronous Accumulation”,
ACSII command “HC”. This function allows integration to start immediately at the leading
(falling) edge of the Ext. Trig pulse instead of at the next horizontal drive pulse HD. Please
refer to fig. 15 and fig. 16. To enable this function, set HC=1. (Factory default is HC=0). If
the falling edge of the trigger falls inside the HD low pulse, a jitter up to 7.5µsec. can be
expected. The exposure will start up to 7.5µsec. after the falling edge of the trigger.
In HD asynchronous Frame-delay mode avoid the trigger to raise inside the HD low period. It
will cause 1 line image position jitter.
As the start of exposure will be synchronized with the internal H signal, the start of exposure
may be shifted by max 1H. To avoid this shift (jitter), synchronize the camera with an
external HD and make sure that the trigger pulse aligns to the HD signal as shown in Fig. 14.
It is recommended to use a strobe light (e.g. LEDs or Xenon tube), as the CCD must not be
illuminated during readout delay time. The EEN signal can be used to trigger a strobe light
See Fig. 11 for the phase relationship between ext. HD and ext. VD pulses.
Do not input a new trigger before the previous video is read out. (WEN is high).
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