Guide To Using A Rolling Shutter Camera; Characteristics - Teledyne G3-GM10-M0641 User Manual

Guide to Using a Rolling Shutter Camera

The Genie Nano C4900 implements the On-Semi AR1820HS rolling shutter sensor to achieve a high
pixel density – low cost solution for a number of imaging implementations.

Characteristics

Rolling shutter sensor cameras have different usage characteristics and thus provide different
application solutions compared to the Nano global shutter models. The following points highlight
those differences:
Simpler Sensor Design Attributes
Rolling shutter cameras have a simpler design with smaller pixels, allowing higher resolutions
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for a given sensor physical area. As an example mobile phones use rolling shutter sensors.
Depending on the imaging requirements, the higher density pixel array may require a higher
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quality lens. Lens specifications define the Resolution and Contrast/Modulation attributes which
must be considered. This commonly used gauge is the Modulation Transfer Function (MTF)
which is extensively covered by lens suppliers to qualify their products. Consider reading
https://www.edmundoptics.com/resources/application-notes/optics/introduction-to-modulation-transfer-function/
an initial start to understanding MTF.
A rolling shutter sensor exposes, samples, and reads out sequentially, as part of the design
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criteria to achieve a higher pixel density via simplified circuitry.
Rolling shutter sensors generate less heat which translates to a lower noise level (SNR).
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Global shutter CMOS sensors require a more complicated circuit architecture, thus limiting the
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pixel density for a given physical size.
Rolling Shutter Trade-offs
When selecting a rolling shutter camera, the user needs to understand that the camera is not
suitable for all machine vision applications. Limitations are such as:
A rolling shutter camera is unsuitable for applications like barcode scanning, machine vision, or
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automated inspection systems, which require the imaging of rapidly moving objects.
• Moving objects are subject to temporal distortions best described as positional errors (shifts)
from the top of an object to its bottom, due to how individual lines are exposed (detailed
below).
• Rolling shutter cameras using Global Reset Release mode (GRR) are not suitable for moving
objects in well-lit environments.
Degree of distortions change as exposure time is increased or decreased.
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Use of a strobe flash with a controlled duration, in a dark imaging environment, is required to
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eliminate positional distortions.
The Internet has many sources and examples of the visual distortions due to Rolling Shutter
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sensors, mostly in reference to using cell phones and consumer cameras. The guidelines that
follow will permit the successful usage of rolling shutter cameras in machine vison applications.
Guide to ERS or GRR Exposure Modes.
The following two pages provide overviews on using either the typical Electronic Rolling Shutter
(ERS) Exposures or Global Reset Release (GRR) Exposures modes. Overall these two exposure
types have similar constraints but need to be understood for a successful application.
Nano Series GigE Vision Camera Genie Nano Specifications
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