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Overview of Electronic Rolling Shutter (ERS) Exposures
Referring to the following graphic:
Each sensor line is exposed for the programmed time integration period.
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Exposures start with Line 1. The sensor design uses a shared line readout circuit. Due to
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this simplified circuitry, only a single line of pixel data can be readout at any given time.
Therefore the line 2 exposure (integration period) is delayed by the required readout time of
line 1.
This delayed line exposure is repeated from the sensor's first line to its last sensor line.
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This sequence allows the common readout circuit to read the data from each row. This
results in an exposure start time delay between the first to last row – thus the name rolling
shutter.
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To avoid motion artifacts the user needs to freeze motion using flash lighting of suitable
length in a dark environment. The flash is triggered at the start of the last line's exposure
and stops at the end of the first line's exposure. The flash must maintain a constant light
output during this period.
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To control the flash device, use the Genie Nano output signal with these feature selections:
outputLineSource=PulseOnStartofExposure, outputLinePulseDelay=flashZoneDelay (delay to
the start of the last line exposure), outputLinePulseDuration=flashZoneDuration (optimal
flash zone time as shown in the graphic below).
The two new features mentioned, flashZoneDelay and flashZoneDuration, automatically
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provide the optimal flash zone time values no matter the exposure duration and any vertical
cropping/offset settings. The user is free to use any delay or duration as required.
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The dark environment illumination ensures minimal exposure (and thus motion artifacts)
during the sensor lines integration time occurring before and after the flash period.
88 • On-Semi Sensor Models
Nano Series GigE Vision Camera
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