GB1379541A - Ultrasonic mobility aids - Google Patents

Abstract

1379541 Ultrasonic ranging ST DUNSTAN'S 20 Dec 1971 [18 Dec 1970] 60284/70 Heading H4D An ultrasonic pulse-echo distance indicating device transmits pulses at a predetermined rate and the echo receiver is arranged to give an output signal in response to an echo pulse only during periods so timed with respect to the transmission instants that the output signals are provided at a rate which varies with the distance of the echo-producing object from the device. In one binaural blind-aid embodiment clock pulses are fed to a logic switching circuit providing two outputs. One output comprises pulses for triggering or gating anoscillator to periodically energize an ultrasonic transmitting transducer; the other output comprises cyclically recurring trains of pulses for opening receiving circuit gates. Echo pulses of the transmitted ultrasonic pulses are received in two channels. In each channel the output of a receiving transducer is amplified, detected and fed via a gate to an earpiece to give for each gated received ultrasonic pulse an audible pulse of amplitude dependent on the range of the echo-producing object. Fig. 3, shows an example of the timing of the gate-opening pulses. When a first ultrasonic pulse is transmitted at time t = 0 a first pulse 17 opens both receiver gates for a 64 mS period whereby any echo-producing object at a range of up to about 32 ft. will be detected and give an audible click from the earpieces. When a second ultrasonic pulse is transmitted the second gating pulse, 19, of 4 mS duration enables objects up to 2 ft. range to be detected. The third gating pulse is of 8 mS duration, and so on. The result is that in each complete train of gating pulses the number of audible clicks produced relating to an object depends on the object range, being higher at shorter ranges. Other gating pulse sequences are envisaged (Fig. 4, not shown). The transmitting transducer may be hand-held to assist directional location of an object and the receiving transducers are mounted such as to preserve intensity and/or time difference relationships in the two receiving channels.