CPC G01N 21/59 (2013.01) [G01J 3/42 (2013.01); G01N 21/534 (2013.01); G01N 33/0027 (2013.01); G08B 17/10 (2013.01)] | 14 Claims |
1. A receiver comprising:
a divider configured to divide an optical signal transmitted for detecting a detection target on a traveling path over a plurality of paths including a first path and a second path;
a detector configured to detect a received light intensity of the optical signal at a first position of the first path where the received light intensity increases when an optical axis of the optical signal is shifted and at a second position of the second path where the received light intensity decreases when the optical axis is shifted;
a processor; and
a memory storing instructions executable by the processor to:
calculate a received light intensity ratio between the received light intensity at the first position as has been detected and the received light intensity at the second position as has been detected; and
determine presence or absence of an optical axis shift based on a change in the received light intensity ratio over time.
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