Paper thickness detecting apparatus

Abstract

A paper thickness detecting apparatus includes a first sensor and a second sensor in which the electrostatic capacitance changes when a piece of paper such as a bank note or a piece of copying paper is inserted, and a thickness detecting unit for detecting the thickness of the piece of paper from the signals obtained from the respective first sensor and the second sensor, in order to provide a paper thickness detecting apparatus that can reliably detect a foreign object adhered to the paper.

1 . A paper thickness detecting apparatus for detecting a thickness of a piece of paper conveyed through a conveyance path from a change in electrostatic capacitance of a sensor having opposing electrodes, the sensor being arranged such that the conveyance path of the paper passes between the electrodes, the paper thickness detecting apparatus comprising:
 a sensor including a first electrode and a second electrode that are opposed to each other, the sensor being coupled to a first electric current detection circuit for detecting electric current in the first electrode, and being coupled to a second electric current detection circuit for detecting electric current in the second electrode;   a thickness detecting unit configured to alternately obtain a first response signal detected by the first electric current detection circuit and a second response signal detected by the second electric current detection circuit for every certain interval, and to detect a change in the thickness of the paper due to a foreign object from a result of comparing the first response signal with the second response signal.   
     
     
         2 . The paper thickness detecting apparatus according to  claim 1 , wherein
 the first detecting electrode of the sensor and the second detecting electrode of the sensor each comprise a plurality of electrodes.   
     
     
         3 . The paper thickness detecting apparatus according to  claim 1 , wherein
 the thickness detecting unit compares a portion of the first response signal exceeding a predetermined level with a portion of the second response signal exceeding the predetermined level, and determines that a foreign object is adhered to the paper when the portions match each other or approximately match each other as a result of the comparing.   
     
     
         4 . The paper thickness detecting apparatus according to  claim 1 , wherein
 the thickness detecting unit compares a portion of the first response signal exceeding a predetermined level with a portion of the second response signal exceeding the predetermined level, and determines that there is a fold on the paper when the portions do not match each other or do not approximately match each other as a result of the comparing.