Patent ID: 8179410

Claim:
A method for adjusting a paper sheet sensor which optically detects a paper sheet using a light emitting element and a light receiving element, the method comprising: in a state where the paper sheet exists between the light emitting element and the light receiving element, gradually increasing an operating current I of the light emitting element; when an output voltage V of the light receiving element reaches a light receiving level Vx during the increase in the operating current I, storing the operating current I at the time as I 1 ; storing, as V 1 , the output voltage V of the light receiving element immediately before the output voltage V of the light receiving element reaches the light receiving level Vx; in a state where the paper sheet does not exist between the light emitting element and the light receiving element, gradually decreasing the operating current I of the light emitting element from the above I 1 ; when the output voltage V of the light receiving element reaches a non-light receiving level Vy during the decrease in the operating current I, storing the operating current I at the time as I 2 ; storing, as V 2 , the output voltage V of the light receiving element immediately before the output voltage V of the light receiving element reaches the non-light receiving level Vy; and setting the operating current I at the time of normal operation of the light emitting element within a range between the above I 1 and I 2 , and setting a reference voltage Vs for paper sheet detection with respect to the output voltage V of the light receiving element within a range between the above V 1 and V 2 .