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MultiCam Boards Documentation > MultiCam Documentation > MultiCam User Guide > General Topics > Line-Scan Inspection Topics > Exposure Issues > Electronic Shutter

Electronic Shutter

The CCD sensor can be temporarily set in a "pixel reset" condition. In this condition, the light has no effect on the sensitive area of the sensor. Any electrical charge that could be contained in the pixels is cleared.

At some instant, the camera leaves the pixel reset condition to enter into the exposure or integration condition. During this time, every pixel builds an electrical charge growing at a rate proportional to the light intensity it receives. The longer the exposure time, the bigger the electrical charge.

Consequently, increasing the exposure time is a mean to increase the light sensitivity of the camera.

The end of the exposure time is marked by a special event usually referred to as the "transfer gate". At this instant, the individual electrical charges built by the pixels are set aside and made ready for transport towards the CCD sensor output.

Simultaneously, the pixels gets emptied of any electrical charge. This sets the pixels in the same state as the pixel reset feature does.

After the transfer gate, the CCD sensor enters the readout period. This takes a fixed amount of time to extract the individual electrical charges set aside at the transfer gate instant. The charges are converted to voltage and serially conveyed outside the CCD sensor. Subsequently, the voltage is converted into digital values, and serially conveyed outside the line-scan camera.

Graphically, the operational sequence can be presented as follows: