Apparatus for measuring distances
First Claim
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1. Apparatus for measuring distances comprising:
- an acoustic signal generator for directing a burst of ultrasonic frequency energy at a distant location;
an acoustic transducer for receiving a reflected burst of acoustic energy from said distant location;
a detector connected to said acoustic transducer, providing an electrical signal proportional to said reflected burst of acoustic energy, said electrical signal having a time varying amplitude envelope function having a main lobe with a centroid, and lower level side lobes;
a threshold generator for generating a threshold signal equal to an amplitude value of said electrical signal main lobe which exceeds the peak amplitude of said side lobes;
a comparator circuit means connected to receive said threshold signal, and a signal from said detector, said comparator providing a signal when said detector signal produces an envelope signal greater than said threshold signal; and
a timing circuit connected to time at a first timing rate a first time interval which begins with the initiation of said burst of ultrasonic energy, and ends when said comparator circuit produces an output signal, and time at a second timing rate, a second interval following said first interval which ends when said comparator output signal indicates said envelope signal is less than said threshold signal, said first and second intervals representing a distance traversed by said burst of ultrasonic energy and a related reflection.
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Abstract
Apparatus for measuring distances comprising circuit for sending an acoustic signal to a distant location, the distance of which is to be measured, circuit for receiving back reflected acoustic energy, and electronic circuit means for eliminating spurious echoes by providing a threshold signal level above the signal level of said spurious echoes, and a timing circuit to time the interval between the transmission of the acoustic signal and receipt of the acoustic signal.
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Citations
15 Claims
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1. Apparatus for measuring distances comprising:
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an acoustic signal generator for directing a burst of ultrasonic frequency energy at a distant location; an acoustic transducer for receiving a reflected burst of acoustic energy from said distant location; a detector connected to said acoustic transducer, providing an electrical signal proportional to said reflected burst of acoustic energy, said electrical signal having a time varying amplitude envelope function having a main lobe with a centroid, and lower level side lobes; a threshold generator for generating a threshold signal equal to an amplitude value of said electrical signal main lobe which exceeds the peak amplitude of said side lobes; a comparator circuit means connected to receive said threshold signal, and a signal from said detector, said comparator providing a signal when said detector signal produces an envelope signal greater than said threshold signal; and a timing circuit connected to time at a first timing rate a first time interval which begins with the initiation of said burst of ultrasonic energy, and ends when said comparator circuit produces an output signal, and time at a second timing rate, a second interval following said first interval which ends when said comparator output signal indicates said envelope signal is less than said threshold signal, said first and second intervals representing a distance traversed by said burst of ultrasonic energy and a related reflection. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 15)
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11. Apparatus for measuring distances comprising:
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(a) an acoustic signal generator for directing a burst of ultrasonic frequency energy at a distant location; (b) an acoustic transducer for receiving a reflected burst of acoustic energy from said distant location and producing an output signal proportional to the amplitude of said reflected burst of acoustic energy; (c) a threshold detection circuit connected to said transducer for generating an output signal when said transducer produces an output signal in excess of pre-established threshold voltage; (d) a timing capacitor; (e) a charging circuit connected to charge said capacitor at a predetermined charging rate, said charge being initiated when said burst is generated by said signal generator, and being concluded when said threshold detection circuit produces an output signal, whereby a voltage potential is stored on said timing capacitor proportional to a measured distance; (f) a discharging circuit connected to discharge said timing capacitor at a fixed discharge rate; (g) logic circuit connected to said discharging circuit for initiating a first interrupt pulse when said capacitor begins to discharge, and a second interrupt pulse when said capacitor discharges to an initial value; (h) a microprocessor connected to receive said first and second interrupts, programmed to measure a time interval represented by first and second interrupt pulses, and convert said time interval into a distance measurement traversed by said burst of acoustic energy; and
,(i) a display connected to said microprocessor for displaying said distance measurement. - View Dependent Claims (12, 13, 14)
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Specification