Patent ID: 8217335

Claim:
An optical modulation-type detection device in which pulsed light is emitted from a light-emitting element toward an object to be detected, light which is reflected from or transmits through the object is received by a light-receiving element, and presence or absence of an object is detected in accordance with a light-reception signal supplied from the light-receiving element, said device comprising: a pulse signal converting section which converts the light-reception signal into a pulse signal, and cuts off a light-reception signal pathway so as to suppress an offset of the pulse signal converting section; and a detection section which detects in accordance with the pulse signal (i) whether or not a first state occurs in which the light-reception signal is present during a period in which the pulsed light is not being emitted and (ii) whether or not a second state occurs in which the light-reception signal is present during a period in which the pulsed light is being emitted, the optical modulation-type detection device having operation modes including: a first operation mode having (i) a first period in which (a) the light-reception signal pathway of the pulse signal converting section is cut off so that the offset of the pulse signal converting section is suppressed and (b) the light-reception signal pathway of the pulse signal converting section is reconnected while a state in which the offset is suppressed is being maintained, at an end of the first period, and (ii) a second period in which whether or not the first state occurs is detected after the first period, and a second operation mode having at least a third period in which whether or not the second state occurs is detected after the first period is not detected in the first operation mode.