Ultrasonic wave distance detection system

• US 4,451,909 A
• Filed: 12/11/1981
• Issued: 05/29/1984
• Est. Priority Date: 12/18/1980
• Status: Expired due to Term

• Current Assignee: Nippon Soken, Inc.
• Original Assignee: Nippon Soken, Inc.
• Inventors: Akita, Shigeyuki, Kodera, Masao
• Primary Examiner(s): Farley, Richard A.
• Application Number:
  US06/329,826
• Time in Patent Office: 900 Days
• Field of Search: 367/900, 367/99, 343/5 SM, 73/900
• US Class Current: 367/99
• CPC Class Codes: G01S 15/14 wherein a voltage or current pulse is initiated and terminated in accordance respectively with the pulse transmission and echo reception
• CPC Class Codes: Y10S 367/90 Sonar time varied gain control systems
• CPC Class Codes: Y10S 73/90 Automatic gain control

Abstract

In an ultrasonic wave distance detection system, an ultrasonic wave pulse radiated into the selected area is reflected on an object. Said reflected ultrasonic wave pulse is partly received by an ultrasonic wave transducer. The received signal is supplied to a variable gain amplifier, noise components are removed from the amplified signal through a band pass filter, the noise removed signal is detected by an envelope detector, the detected signal is compared with a predetermined level by a comparator, and the output of the comparator is applied to a flip-flop circuit.

As the gain of the variable gain amplifier is set to be a lower level only at the beginning of the ultrasonic wave pulse to minimize the amplification of unnecessary signals without reducing the detection efficiency, a signal can be surely obtained which has a pulse width corresponding to the distance between the system and the object and thus the distance can be detected or measured.

Claims

1. An ultrasonic wave distance detection system comprising:

ultrasonic wave transducer means for sending and receiving ultrasonic wave pulses;

oscillator means for generating carrier waves of a carrier frequency available for said ultrasonic wave pulses;

first pulse generator means for generating transmit/receive switching signals;

second pulse generator means for generating gain control signals of a selected pulse width in synchronization with said transmit/receive switching signal;

variable gain amplifier means comprising an operational amplifier having an inverted input terminal and an output terminal, an analog switch coupled to said inverted input terminal and responsive to said gain control signal, a series circuit including a capacitor and an input resistor connected with said inverted input terminal, and a feedback resistor connected between said inverted input terminal and said output terminal of the operational amplifier, said variable gain amplifier means for controlling the gain of signals applied to said amplifier means in accordance with said gain control signal; and

transmit/receive switching circuit means for effecting selective changeover between said transducer means, oscillator means, first pulse generator means and amplifier means in response to the switching signal; and

detecting circuit means for detecting the presence of an obstacle according to the output of said amplifier means;

wherein the gain of said variable gain amplifier means is decreased at the beginning of reception of the ultrasonic wave pulses.

4. An ultrasonic wave distance detection system as set forth in claim 1, 2 or 3 wherein said detection circuit means comprises:

an envelope detection circuit means for envelope-detecting the output of said amplifier means;

a comparator for comparing an output signal of said envelope detection circuit with a predetermined level; and

a flip-flop circuit which receives the switching signal and an output signal from said comparator to generate a pulse signal of a time duration corresponding to the distance between said system and said obstacle.

2. An ultrasonic wave distance detection system comprising:

ultrasonic wave transducer means for sending and receiving ultrasonic wave pulses;

oscillator means for generating carrier waves of a carrier frequency available for said ultrasonic wave pulses;

first pulse generator means for generating transmit/receive switching signals;

second pulse generator means for generating gain control signals of a selected pulse width in synchronization with said transmit/receive switching signal;

variable gain amplifier means comprising an operational amplifier having an inverted input terminal and an output terminal, a capacitor connected with said inverted input terminal, a field effect transistor connected between one end of said capacitor and an input terminal and responsive to said gain control signal, and resistors for applying a selected potential to a gate terminal of said field effect transistor, said variable gain amplifier means for controlling the gain of signals applied to said input terminal in accordance with said gain control signal;

transmit/receive switching circuit means for effecting selective changeover between said transducer means, oscillator means, first pulse generator means and amplifier means in response to the switching signal; and

detection circuit means for detecting the presence of an obstacle according to the output of said amplifier means;

wherein the gain of said variable gain amplifier means is decreased at the beginning of reception of the ultrasonic wave pulses.

3. An ultrasonic wave distance detection system comprising:

ultrasonic wave transducer means for sending and receiving ultrasonic wave pulses;

oscillator means for generating carrier waves of a carrier frequency available for said ultrasonic wave pulses;

first pulse generator means for generating transmit/receive switching signals;

second pulse generator means for generating gain control signals of a selected pulse width in synchronization with said transmit/receive switching signal;

variable gain amplifier means comprising an operational amplifier having an inverted input terminal and an output terminal, input resistance means coupled to said inverted input terminal, feedback resistance means connected between said inverted input terminal and said output terminal, and means, responsive to said gain control signals, for varying an impedance of at least one of said input resistance means and said feedback resistance means in accordance with said gain control signal, said variable gain amplifier means for varying the gain of signals applied to said amplifier means in accordance with said gain control signals;

transmit/receive switching circuit means for effecting selective changeover between said transducer means, oscillator means, first pulse generator means and amplifier means in response to the switching signal; and

detection circuit means for detecting the presence of an obstacle according to the output of said amplifier means;

wherein the gain of said variable gain amplifier means is decreased at the beginning of reception of the ultrasonic wave pulses.