Abstract: A distance measuring system comprising: a transmitter that simultaneously emits an infrared radiation and an ultrasonic wave; and a receiver that include a table showing a relationship between an arrival time, indicative of a period from detection of the received infrared radiation to detection of the received 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 the 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 the distance to the 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.

Abstract: A projector has a transmission time information reception unit for calculating the distances between a transmitter and first and second ultrasonic receivers based on reception times of ultrasonic and infrared pulses transmitted from a transmitter-equipped pointer rod for pointing to positions on a projection surface. The projector also has an image correcting information calculation unit, which, when a test pattern made up of a plurality of reference points including a plurality of points near the corners of the upper and lower edges of the projection surface is projected onto the projection surface, generates a coordinate transformation table to bring the coordinates of the reference points near the upper edge into conformity with the coordinates of corresponding desired corrective points, from the distance information acquired by the transmission time information reception unit through the transmitter-equipped pointer rod and positional information of the desired corrective points.

Abstract: A distance measuring system comprising: a transmitter that simultaneously emits an infrared radiation and an ultrasonic wave; and a receiver that include a table showing a relationship between an arrival time, indicative of a period from detection of the received infrared radiation to detection of the received 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 the 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 the distance to the 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.

Abstract: A projector has a transmission time information reception unit for calculating the distances between a transmitter and first and second ultrasonic receivers based on reception times of ultrasonic and infrared pulses transmitted from a transmitter-equipped pointer rod for pointing to positions on a projection surface. The projector also has an image correcting information calculation unit, which, when a test pattern made up of a plurality of reference points including a plurality of points near the corners of the upper and lower edges of the projection surface is projected onto the projection surface, generates a coordinate transformation table to bring the coordinates of the reference points near the upper edge into conformity with the coordinates of corresponding desired corrective points, from the distance information acquired by the transmission time information reception unit through the transmitter-equipped pointer rod and positional information of the desired corrective points.