Patent ID: 8648320

Claim:
A photoelectric sensor, comprising: a light emitting unit and a light receiving unit that are arranged opposite to each other, wherein the photoelectric sensor detects whether there is an object in a space between the light emitting unit and the light receiving unit on the basis of a variation in the intensity of light-signals received by the light receiving unit, the light receiving unit includes first and second light receiving elements and a controller, the first and second light receiving elements are operated in synchronization with a light emission timing signal of the light emitting unit, the controller stores data of the light signals received by the first and second light receiving elements, and the controller converts and calculates a difference between the data of the light signals received by the first and second light receiving elements, the light emitting unit includes: a first light emitting element that is arranged such that light signals are emitted to the first light receiving element without intersecting the object and to the second light receiving element through the object; and a second light emitting element that is arranged such that light signals are emitted to the second light receiving element without intersecting the object and to the first light receiving element through the object, a pair of the first light emitting element and the first light receiving element and a pair of the first light emitting element and the second light receiving element form a first set, a pair of the second light emitting element and the first light receiving element and a pair of the second light emitting element and the second light receiving element form a second set, in the first set, the level of the light signal that is not attenuated by the object and is received by the first light receiving element is compared with the level of the light signal that is attenuated by the object and is received by the second light receiving element so as to detect information indicating whether there is the object, in the second set, the level of the light signal that is attenuated by the object and is received by the first light receiving element is compared with the level of the light signal that is not attenuated by the object and is received by the second light receiving element so as to detect information indicating whether there is the object, and the information obtained from the first set and the information obtained from the second set are checked so as to detect information indicating whether there is the object.