Image vignetting and shading, Mechanical vignetting, Cos4 vignetting, Sensor shading
All images from lenses suffer from intensity decrease from the centre to
the edge of the image. As this can affect the suitability of a lens for an
application, it is necessary to examine the performance of a lens
concerning this behaviour, which is known as vignetting.
When designing a system, users often focus solely on the technology
required to make the acquisition work. A lot of time is spent diagnosing
why systems have intermittent failures and the answer is often to be
found in a lack of thought in the design of the interfacing hardware.
For machine vision use, CMOS sensors that feature a global shutter
enable sharp images of fast moving objects as all pixels are exposed
at the same time in the same way as progressive scan CCD sensors.
However not all CMOS sensors use Global shutters, some use a