UN METODO PARA IDENTIFICAR UN PUNTO Y MODIFICAR LA IMAGEN SOBRE LA PANTALLA DE UNA UNIDAD DE PRESENTACION VISUAL (VDU)

摘要

To indicate a desired point on the screen of a VDU, the VDU is provided with a virtual reference frame in which ultrasonic waves propagate and a hand-held probe (1) with an ultrasonic transducer (2) at its tip. To indicate a desired point, the tip of the probe is pressed against the VDU screen at the desired point as a result of which ultrasonic waves propagate along the screen surface. The ultrasonic wave has a basic frequency, e.g. 100 KHz, and is swept over a range of 10 KHz. Detectors (4) at the corners of the frame respond to the signals they receive, and the relative frequencies thereof indicate the distances from the desired point to the detectors. Thus the desired point may be identified to circuitry for controlling the displayed image.