APPARATUS, METHOD, AND PROGRAM FOR DETECTING ROTATION SPEED INFORMATION, AND APPARATUS, METHOD, AND, PROGRAM FOR DETECTING TIRE HAVING DECREASED PRESSURE

A rotation speed information detection apparatus, including: a wheel sensor for detecting passage of teeth of a gear provided in association with tires of a vehicle; a number-of-teeth calculation means for calculating the number of teeth of the gear passed per a sampling cycle set in advance; and a wheel speed calculation means for regularly calculating rotation speed information of the tire with using the number of teeth calculated. The number-of-teeth calculation means is configured to use a ratio between time information at the point and a remaining time until the time at which the next sampling cycle is started is reached to thereby calculate the number of remaining teeth to calculate the number of teeth passed during the sampling cycle. The wheel speed calculation means is configured to calculate tire rotation speed information based on an interval between neighboring teeth in the gear, the number of teeth passed during the sampling cycle, the number of remaining teeth calculated by the number-of-teeth-calculation means, and the sampling cycle.