OBJECT SENSOR AND IC CARD READER HAVING THE SAME

摘要

An object sensor includes excitation coils (13c, 13d) and a sensing coil (12) wound on the same axis of a core body (11) and arranged separately from each other. Sensing is performed according to the balance between the excitation coils (13c, 13d) so that impedance including a DC resistance component and the like are cancelled out and the remaining variation amount can be obtained with a preferable linearity and high sensitivity by using the small-size core body (11). An IC card reader uses the object sensor as an entrance sensor arranged at an appropriate position at the upstream side than the read/write position in the IC card insertion direction. By sensing the contact terminal section of the IC card, the card inserted into the device from the card insertion opening is sensed to be valid or not. The IC card reader can perform stable sensing whether an IC card is present regardless of the ambient temperature fluctuation. Moreover, a plurality of entrance sensors for sensing the type of card inserted are arranged at an appropriate position at the upstream side than the read/write position in the card insertion direction. By using a sensing signal from the entrance sensors, control operation is performed. For example, when an unusable card is inserted, shutter means is closed. Thus, this IC card reader can prevent unauthorized use of a card.