Pat.#5216429:		Position measuring system using pseudo-noise signal transmission and reception
INVENTORS:		Nakagawa; Yoshikatsu, Yamato, Japan
		Hasegawa; Takaaki, Kawaguchi, Japan
ASSIGNEES:		Ricoh Company, Ltd., Tokyo, Japan
ISSUED:		June 1 , 1993
FILED:		Apr. 17, 1992
ABSTRACT: A system for measuring a position of an object moving in a limited area includes a transmitter provided on the moving object for periodically transmitting pseudo-noise signals at time intervals in accordance with an intrinsic period assigned to the object, and a plurality of stations located at predetermined coordinates, each of the stations including a receiving part for receiving the signals so that pulse signals whose period is matched with the intrinsic period are output, and a detecting part for detecting correlative pulses from the pulse signals. The system further includes a delay detecting part for detecting a time difference between reception of a first correlative signal by one of the stations and reception of each of the subsequent correlative pulses by the other stations, and a control part for calculating coordinates of the position of the moving object based on the time differences and based on the given coordinates of the stations, so that the calculated coordinates of the position are output.