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Camera modes of operation 105
Variable line scan rate mode
In variable line scan rate mode, an external trigger signal is provided to the frame
grabber which sends an exposure signal to the camera to initiate line readout.
The time interval between the exposure output pulses determines the line scan
rate. This mode can use internal or external exposure time controls. The time
interval between trigger signals must be greater than the sum of the exposure time
Y and the line transfer time. With external exposure control, the length of the
exposure signal determines the exposure time; without exposure control, the
exposure duration is the reciprocal of the line scan rate. With internal exposure
R control, the exposure time is set from the camera. On cameras that support this
feature, the exposure signal’s pulse width might control the exposure duration.
A 5 The signals used in this mode are an external trigger (line trigger) signal (provided
IN 0 to the frame grabber), a pixel clock and exposure signal (supplied by the frame
grabber to the camera), synchronization signals from camera to frame grabber or
0 from the frame grabber to the camera (if the camera is in slave mode) and a video
PRE19LIMMAY 2 output that can be analog or digital from the camera to the frame grabber.
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