SVS-Vistek exo174, Manual

Page: 25 / 160

SVS-VISTEK
Feature description 25
Rolling shutter limitations
Due to the principles of rolling shutter, some standard features of SVS-
Vistek cameras are not applicable.
>
External exposure control (expose while trigger signal active) does not
make sense with rolling shutter
>
ROI with rolling shutter
With rolling shutter the whole sensor has to be read out – always.
That means applying ROI will reduce the amount of final data being
transmitted out of the camera (and the framerate might rise, due to
the limited bandwidth of the interface). Nonetheless, the maximum
achievable framerate with applied ROI will be the maximum
framerate of the sensor reading the full sensor area (internal full
sensor speed), please refer to relating sensor specs.
Calculate Framerates
According to the calculation as below, the requested times for scanning
through all lines of the sensor will affect maximum framerate calculation
as well.
In this example, the camera is an exo183 with 3672 lines and 54 dummy
lines. Each line takes 22.2 ms readout time (depending on CameraLink
tap configuration). The camera does have about 300µs exposure time
delay at worst case.
Framerate calculation with exo183CCL with rolling shutter
lines
3672
dummy lines + 54
total lines 3726
readout time 1x3_1Y 22,2 µs * 3726 = 82717,2 µs
exp delay + 300 µs
frame readout time 83017,2 µs
This is minimum time for camera readout with 0s exposure time.
Exposure time has to be added:
frame readout time 83017,2 µs
exposure time 2500 µs
total frame time 85517,2 µs
maximum sensor acquisition time 1/ frame time 11,6 fps
note: readout time 1x2_1Y = 32,63 µs
5.1.3 Exposure
See various exposure and timing modes in chapter: Basic capture modes .
Combine various exposure timings with PWM LED illumination, refer to
sequencer .
Setting Exposure time
Exposure time can be set by width of the external or internal triggers or
programmed by a given value.