Research And Implementation Of Multi-Channel Synchronous Image Acquisition Technology

Digital image technology has been in existence for a long time,which is deeply involved in every aspect of people's production and life.The synchronization problem of image acquisition is an important branch of digital image technology.The application of image synchronous acquisition technology is more extensive with the in-depth research and exploration,such as in the fields of image measurement,3D imaging,etc.At present,there are two main research directions of image synchronous acquisition technology: one is to acquire the synchronous image by strictly controlling the synchronization precision of the triggered acquisition signal;the other is to obtain the time information of the image and match the images with similar features by the processing algorithm such as similarity.The first scheme is generally suitable for short-distance synchronous image acquisition.It is because that the delay of the signal in the link is uncertain and the precision is uncontrollable in the long-distance transmission,although the high-precision synchronous trigger signal can be generated by the controller.The second scheme is not limited by the transmission distance,but it is required relatively high performance of the processor to analysis and process a large amount of data.The implementation scheme is complicated because that needs to arrange a specific reference object in the high-precision application scenario.For these problems above,this paper introduces the Precision Time Protocol(PTP)in Ethernet into the multi-channel image synchronization acquisition system to maintain a unified time reference.Synchronous images that satisfy the accuracy requirement are obtained through the timing trigger,and the long-distance transmission of the images is realized by the Ethernet protocol.This article mainly contains the following research contents:Firstly,the significance and development history of multi-channel image synchronous acquisition technology are studied,and the overall architecture and structure division of the system are proposed.It is determined that the PTP technology capable of achieving sub-microsecond synchronization accuracy is adopted in the system by comparing and analyzing the three kinds of time synchronization algorithms commonly used in the network.Secondly,the basic concept and synchronization principle of PTP time synchronization technology are deeply studied.The error sources of time synchronization accuracy are analyzed from three aspects,and the great advantages of by FPGA hardware to obtain time stamps are discussed.Briefly introduce the signal connection and working principle between the FPGA and the peripheral hardware involved in the system to clarify the types and meanings of the signals.Thirdly,the synchronization algorithm module of the master system and the slave system is designed to implement the local clock synchronization(LCS)algorithm of the PTP time synchronization technology by FPGA.Functional simulation of each module is performed by using Modelsim software.The complete LCS algorithm is tested by Chipscope Pro software at the board level,and the result shows that the time synchronization accuracy in distributed systems can reach nanoseconds.Fourthly,modular design and verification method are also adopted to implement the image acquisition and transmission using FPGA device.Customize formats of image messages and control messages to complete information exchange between distributed systems.Fifthly,the LCS algorithm module is cascaded with the image acquisition and transmission module to obtain a synchronous image acquisition system capable of long-distance triggering and transmission.The verification result shows that the synchronization precision of the image can reach millisecond level,and the functions of image transmission and display are normal.