Electronic Shutter Operation; Global Shutter (All Cameras Except Aca2500Gm/Gc) - Basler ace acA640-90gm User Manual

Image Acquisition Control
7.7

Electronic Shutter Operation

All ace cameras are equipped with imaging sensors that have an electronic shutter. There are two
types of electronic shutters used in the sensors: global and rolling.
All ace models except the acA2500-14gm/gc use sensors with global shutters. The acA2500-
14gm/gc models use a sensor with a rolling shutter.
The following sections describe the differences between a global shutter and a rolling shutter.
7.7.1 Global Shutter
(All Cameras Except acA2500gm/gc)
All camera models other than the acA2500-14gm/gc are equipped with an electronic global shutter.
On cameras equipped with a global shutter, when frame acquisition is triggered, exposure begins
for all lines in the sensor as shown in Figure 45. Exposure continues for all lines in the sensor until
the programmed exposure time ends (or when the frame start trigger signal ends the exposure time
if the camera is using the trigger width exposure mode). At the end of the exposure time, exposure
ends for all lines in the sensor. Immediately after the end of exposure, pixel data readout begins and
proceeds in a linewise fashion until all pixel data is read out of the sensor.
A main characteristic of a global shutter is that for each frame acquisition, all of the pixels in the
sensor start exposing at the same time and all stop exposing at the same time. This means that
image brightness tends to be more uniform over the entire area of each acquired image, and it helps
to minimize problems with acquiring images of objects in motion.
The cameras can provide an exposure active output signal that will go high when the exposure time
for a frame acquisition begins and will go low when the exposure time ends.
You can determine the readout time for a frame by checking the value of the camera's Readout
Time Abs parameter.
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