Article
Rolling and global shutter
A question customers often ask when buying an area scan camera is: what is the difference between a rolling shutter and a global shutter? The answer is that image sensor shutters are either rolling or global. Global shutter sensors are suitable for imaging moving objects. For imaging stationary objects, rolling shutter sensors are a good choice. Rolling shutter sensors are generally cheaper. For the same price, a rolling shutter sensor gives higher resolution than a global shutter sensor. The two figures below show the difference between imaging with rolling and global shutter sensors.
Imaging with a global shutter sensor
As the two images above show, with a rolling shutter the different lines of the sensor array are exposed at different times, whereas with a global shutter all pixels are exposed at exactly the same time.
If your object is moving, a rolling shutter may record it skewed or stretched. This is because the sensor rows are exposed at different times. With a global shutter, all pixels are exposed at the same time and this distortion does not appear. To learn more, read the Rolling shutter article on Wikipedia.
RasaAndishan area scan cameras include both rolling shutter and global shutter types. The RA-ASC-9031 has a rolling shutter. The RA-ASC-0229 has an interlaced CCD sensor and has been discontinued. The RA-ASC-0267, RA-ASC-0134 and RA-ASC-0234 models use a global shutter. The RA-ASC-5000 camera has a pipelined global shutter.
Price also plays a role in this choice. Rolling shutter sensors are generally cheaper. At the same price, they also offer higher resolution than global shutter sensors. So if your object is stationary, a rolling shutter is the more economical choice. If your object is moving, the extra cost of a global shutter is worth it.
When your object is stationary and you need fine detail, the RA-ASC-9031 with its 2.2 µm pixels is a good option. For moving objects and PIV, the RA-ASC-5000 at 60 frames per second is the better choice. See its specifications on the RA-ASC-5000 global shutter camera page.