Patent ID: 8237137

Claim:
A photoelectronic sensor system, comprising a parent station which transmits and receives a monitoring signal and a control signal as parallel signals to a control section, and a plurality of photoelectronic sensors connected to the parent station by a transmission line, wherein each photoelectronic sensor has a child station input/output section, a sensor control section, and a sensor section, the child station input/output section acquires a control signal directed to its own sensor section to perform control output to the sensor section and feeds a monitoring signal to the transmission line as a detection result of the sensor section, the control signal directed to the own sensor section is included in serial transmission signals transmitted through the transmission line, the sensor section includes one pair or plural pairs of a light emitting device and a light receiving device, the sensor control section is disposed between the child station input/output section and the sensor section and comprises an A/D (analog to digital) converter, a microprocessor unit (MPU), a luminance adjusting circuit, a detection driving circuit, and a detecting circuit, the A/D converter converts analog signals signal detected by the sensor section to digital signal data, the luminance adjusting circuit generates a driving clock pulse signal driving the light emitting device in a time divisional manner by the control signal or according to a determination result of the MPU, and the MPU circuit detects a light reception level of the light receiving device, where light reception level data at a non light emission time of the light emitting device is stored as low light amount level data, a difference data is obtained by subtracting the low light amount level data from light reception level data at a light emission time from the light emitting device, presence/absence of a body to be detected is determined based upon a relationship between the difference data and a predetermined threshold, and an intermediate value of the difference data or a value obtained by multiplying the intermediate value by a coefficient is stored as the predetermined threshold.