Patent ID: 7326910
Filing Date: 2008-02-05
Classification: G01V

Abstract:
1. A multiple-optical-axis photoelectric sensor having a light-projection sensor head in which a plurality of projectors are arranged and a light-reception sensor head in which a plurality of photodetectors are arranged, and performing light projecting/receiving operation while sequentially synchronizing light projection/reception periods from one end to the other end of the projectors and the photodetectors arranged in optical axes in predetermined cycles to monitor the presence or absence of invasion of an object to a predetermined area on the basis of detection light, comprising: a disturbance light presence/absence determining device that determines whether disturbance light is incident or not by performing reception light sampling with respect to each of the optical axes in which only a photodetector is activated without activating a projector in at least one of a period immediately after the light projection/reception period and a period immediately before the light projection/reception period in every optical axis; a light incident state determining device that determines an incident state of the disturbance light in the light-reception sensor head, determined by the disturbance light presence/absence determining device; and a cycle changing device that shifts the phase of the following cycle by changing a scheduled next sync timing in accordance with the position of an optical axis in which incidence of the disturbance light is determined by the light incident state determining device.