Object detection system

An object detection system in which projectors and optical receivers of a plurality of multiple-optical-axis photoelectric sensors are connected to each other through communication lines to cause detection processes of the respective sensors to sequentially proceed on the basis of communication between the sensors, wherein

• the projector and the optical receiver of each of the multiple-optical-axis photoelectric sensors comprise timers configured to determine timings of operations in their own devices, respectively, one of the devices functioning as a master device,
• the master device comprises a definition information producing unit configured to produce pieces of definition information that determine timings of detection processes in the respective devices including its own device on the basis of relationships between sensors in the system and the number of optical axes of the respective sensors, a definition information transmitting unit configured to transmit the pieces of definition information to the other devices in the system respectively, a timer control unit configured, while recognizing a circulating period of the detection processes in the respective sensors on the basis of a measured time obtained by the timer of its own device and the definition information, to simultaneously transmit commands to require the operations of the timers to be synchronized with each other to the other devices in response to elapse of a time corresponding to a period in which the circulating period proceeds by a predetermined cycle, and a detection control unit configured to determine a timing at which the detection process should be executed on the basis of definition information matched with its own devices to execute the detection process, and
• each of the devices except for the master device comprises a storage unit configured to store the definition information transmitted from the master device, a timer correction unit configured to correct the timer of its own device in response to a command from the master device, and a detection control unit configured to determine a timing at which the detection process should be executed with reference to a time point at which the timer is corrected on the basis of the definition information matched with its own device to execute the detection process.