Patent ID: 8567683

Claim:
A reader device for recognizing a data carrier capable of transmitting and receiving radio waves to and from the reader device from among a plurality of data carriers respectively installed in a plurality of objects, comprising: an acquisition unit configured to recognize one or more of the plurality of data carriers; a specifying unit that specifies a plurality of first data carriers installed in a predetermined area from among the plurality of data carriers; an outing ID provisional storage unit that stores, when a second data carrier is recognized by the acquisition unit while at least one of the first data carriers is being recognized by the acquisition unit, data carrier identification information for the second data carrier together with a recognition time, which is the time at which the second data carrier is recognized; an outing ID decision unit that identifies, when all of the first data carriers cease to be recognized and the second data carrier remains recognized, the second data carrier as a different type of carrier from the first data carriers, and stores outing data carrier identification information based on the recognition time of the second data carrier; a time acquisition unit that obtains an outing time at which all of the first data carriers cease to be recognized; and a storage unit that stores an outing judgment threshold value for each of the first data carriers, wherein the outing ID decision unit identifies the outing data carrier identification information based on whether a difference between the outing time and the recognition time is equal to or less than the outing judgment threshold value of a most recently recognized first data carrier, and the outing judgment threshold value is updated for each of the first data carriers.