The Precision Time Protocol (PTP) creates a common time base of all participating cameras in an Ethernet network. This function is particularly useful in industrial multi-camera systems and for moving objects. Based on the time stamp of all images, the common time base can be used to make an exact statement about when an image was exposed in relation to other images or at an intended time. In this way, several images of an object from different perspectives can be precisely assigned to each other in order to more reliably detect any errors that occur.
In addition, PTP allows precise control of multiple cameras to enable their simultaneous triggering.
Precision Time Protocol
GigE Vision Compliance
PTP (Precision Time Protocol) is a protocol according to the IEEE 1588 standard that allows synchronizing multiple GigE Vision devices in a common Ethernet network. PTP IEEE 1588 is part of the GigE Vision standard 2.0. SVS-Vistek cameras with PTP support can be set to PTP mode via GenICam.
One master only
According to the PTP protocol, several devices agree on a master. The other devices in the network communicate as slaves with this master and synchronize their own time base for their timestamp with the time base of the master. The maximum deviation that can be achieved is 10 µs, which enables very precise synchronization of all devices involved.
Special PTP mode
Participating GigE or 10GigE cameras are set to a special PTP mode. As soon as this is set to Slave or Auto, the synchronization of the cameras in the network with the associated master of the subnet begins. The "PTP Status" provides information about whether a camera is operated as a master or as a slave.
Real world time
PTP provides a common time base, but this should not be confused with real time. If a fixed relation to the real world time is to be established, a separate device based on Network Time Protocol (NTP) or Global Positioning System (GPS) must take over the function of the master.
PTP allows synchronous triggering of multiple cameras with a fixed frame rate. It is necessary to know the future time of triggering (ad-hoc event-based triggering is not possible).
Individual events are only supported insofar as they have to be in the future. PTP requires a lead time in order to trigger the cameras via scheduled simultaneous software trigger. A common immediate trigger ("NOW I want to trigger all cameras") is not supported by PTP.