Acoustic measuring system

• US 5,062,088 A
• Filed: 10/09/1990
• Issued: 10/29/1991
• Est. Priority Date: 10/09/1990
• Status: Expired due to Fees

• Current Assignee: Lundahl Instruments, Inc. (Omron Corporation)
• Original Assignee: Lundahl Instruments, Inc. (Omron Corporation)
• Inventors: Davidson, Amber C., Vandenwijngaert, Ernie
• Primary Examiner(s): Pihulic, Daniel T.
• Application Number:
  US07/594,581
• Time in Patent Office: 385 Days
• Field of Search: 367/2, 367/6, 367/118, 367/127, 367/901, 367/909
• US Class Current: 367/127
• CPC Class Codes: G01S 15/74 Systems using reradiation of acoustic waves, e.g. IFF, i.e. identification of friend or foe
• CPC Class Codes: G01S 15/931 of land vehicles

Abstract

Apparatus for sensing distances between two objects by using multiple pulses from the detector and from the object to be detected by using a transmitter and not using any reflected waves the reliability and the ability to reject clutter is improved. The periods between transmission are accurately controlled so that there is no signal returned until the object to be detected generates such a signal. As a result it is possible to accurately measure the distance between two objects and indeed the system may be used between two objects when both are in motion.

Claims

1. Distance measuring apparatus comprising a first and second ultrasonic device each including transmitting means for emitting an ultrasonic pulse and a receiving means for receiving ultrasonic pulses, a first control means connected to said transmitting and receiving means of said first device to activate each of said transmitting and receiving means at predetermined intervals;

a second control means including timing means integral with said second device and responsive to signals received from said first device to activate the transmitting and receiving means of said second device at predetermined intervals;

means for varying said predetermined time intervals as distance between the devices changes;

means connected to said first device and responsive to reception of ultrasonic signals from said second device to measure the elapsed time from transmission of the pulse from said first device to reception of said pulse from said second device;

means to convert the measured time lapse to a signal indicative of the distance between said devices.

2. An apparatus as claimed in claim 1, wherein said signal indicative of the distance between said devices is compared to a predetermined distance.

3. An apparatus as claimed in claim 1, wherein said control means includes pulsing means for generating ultrasonic pulses.

4. An apparatus as claimed in claim 3, wherein said control means includes timing means for activating and deactivating said second device.

5. An apparatus as claimed in claim 4, wherein said control means also includes means to render inactive the receiving means for a predetermined period of time after said second device transmits an ultrasonic pulse.

6. Method of detecting an object from a vehicle comprising the steps of:

(a) transmitting a first ultrasonic pulse from a first sensor.;

(b) receiving said pulse at a second sensor;

(c) transmitting a second ultrasonic pulse from said second sensor a predetermined time after receiving said first pulse;

(d) receiving said second delayed pulse at said first sensor;

(e) measuring the time lapse including the predetermined delay at said second sensor to determine the distance between sensors;

(f) Changing the predetermined time interval as the distance between sensors reaches predetermined values.