Patent ID: 7649808

Claim:
A distance measuring system, comprising: a transmitter that simultaneously emits an infrared radiation and an ultrasonic wave; and a receiver that includes a table showing a relationship between an arrival time, indicative of a period from a detection of receiving the infrared radiation to a detection of receiving the ultrasonic wave, and a required received signal strength of the ultrasonic wave corresponding to the arrival time when the ultrasonic wave is directly received, that compares a received signal strength of the ultrasonic wave with a required received signal strength corresponding to the arrival time retrieved from the table, and that calculates a distance to said transmitter based on the arrival time when the received signal strength of the ultrasonic wave is higher than the required received signal strength corresponding to the arrival time retrieved from the table, said table indicating positive peak reference information showing a relationship between the arrival time of the ultrasonic wave and a required received signal strength corresponding thereto when the ultrasonic wave is directly received in a positive domain, and negative peak reference information showing a relationship between the arrival time of the ultrasonic wave and a required received signal strength corresponding thereto when the ultrasonic wave is directly received in a negative domain.