Dual burst, wide range sonar system

• US 4,396,268 A
• Filed: 08/26/1981
• Issued: 08/02/1983
• Est. Priority Date: 08/26/1981
• Status: Expired due to Term

• Current Assignee: Polaroid Corporation (PLR IP Holdings LLC)
• Original Assignee: Polaroid Corporation (PLR IP Holdings LLC)
• Inventors: Shenk, Edwin K.
• Primary Examiner(s): Gellner, Michael L.
• Application Number:
  US06/296,508
• Time in Patent Office: 706 Days
• Field of Search: 354/195, 354/198, 352/140
• US Class Current: 396/105
• CPC Class Codes: G01S 15/102 using transmission of pulses having some particular characteristics
• CPC Class Codes: G02B 7/40 using time delay of the reflected waves, e.g. of ultrasonic waves

Abstract

A sonic ranging system providing at least two bursts of sonic energy of unequal duration directed toward a subject with the time interval between the bursts being no less than the round-trip time for the maximum range at which a subject is to be detected by the preceeding burst includes a receiver which is blanked for a time related to the duration of each burst such that the shorter burst is used to detect very close subject distances and the longer burst employed for further distances. Preferably, the range detected by only one of the bursts is automatically utilized, depending upon whether the subject range is greater or less than a given distance.

Claims

1. A sonic rangefinder system comprising transmitting and receiving means for transmitting a burst of sonic energy toward a subject and for receiving an echo therefrom so as to produce a range signal representative of subject distance in accordance with the elapsed time between transmission and reception, said transmitting means including a receiver and blanking means for blanking said receiver in synchronism with transmission of a burst for a blanking period in accordance with at least the duration of said burst, said tramsmitting and receiving means including means for automatically transmitting at least a pair of spaced apart bursts of sonic energy with one of said bursts being a short burst and the other thereof being a long burst, and said blanking means including means for blanking said receiver for a relatively short blanking period during the duration of said short burst and for a relatively long blanking period during the duration of said long burst so that said long burst is applicable to distant subjects whose echo return time is greater than said short blanking period while said short burst is applicable to determine near subject distances, including those whose echo return time is greater than said short blanking period but less than said long blanking period.

2. The system of claim 1 wherein said short and long blanking periods continue for equal duration following termination of their respective bursts.

3. The system of claim 1 wherein said short burst is of lower peak value than said long burst, and said short blanking period continues for a relatively short predetermined time following termination of said short burst while said long blanking period continues for a relatively long predetermined time following said long burst.

4. In a sonic rangefinder system having transmitting and receiving means for transmitting a burst of sonic energy toward a subject and for receiving an echo therefrom so as to produce a range signal representative of subject distance in accordance with the elasped time between transmission and reception, said transmitting means including a receiver and blanking means for blanking said receiver in synchronism with transmission of a burst for a blanking period in accordance with at least the duration of said burst, the improvement wherein said transmitting and receiving means includes means for transmitting at least a pair of spaced apart bursts of sonic energy with one of said bursts being a short burst and the other thereof being a long burst, and said blanking means includes means for blanking said receiver for a relatively short blanking period for transmission of said short burst and for a relatively long blanking period for said long burst so that said short burst is applicable to determine near subject distances while said long burst is applicable to more distant subjects and said system including means for recording a range signal only from transmission of said short burst when the distance to the subject is less than a predetermined distance and only from transmission of said long burst when the distance to the subject is greater than said predetermined distance.

5. The system of claim 4 including means for displaying which burst of said pair produces said recording of a range signal.

6. A sonic rangefinder system comprising:

a transducer for transmitting a burst of sonic energy toward a subject and for producing an output in response to receiving an echo;

means for controlling the operation of the transducer so that it produces at least a pair of spaced apart bursts of different durations;

means including a receiver, responsive to the output of the transducer, for producing a range signal associated with the burst that was echoed from the subject;

control means for blanking the receiver during transmission of the bursts and for a period of time thereafter;

a distance memory; and

logic means for applying the range signal associated with the burst having the shorter duration to the distance memory only if the subject range is less than a predetermined distance and for applying the range signal associated with the burst having the longer duration to the distance memory if the subject range exceeds said preselected distance.

7. The system of claim 6 including a clock-driven range counter, means for resetting the counter each time the transducer transmits a burst so that the contents of the range counter is representative of subject range at the instant of echo reception by the receiver, said logic means being effective to only strobe the range counter into the distance memory in response to reception by the receiver of an echo from the shorter burst after an elapsed time less than a fixed time representative of said predetermined distance or reception of an echo from the longer burst after an elapsed time exceeding said fixed time.

8. The system of claim 6 including an indicator responsive to the logic means for indicating the relationship between subject range and said preselected distance.

9. A camera in combination with the rangefinder of claim 6 wherein the camera includes focusing means responsive to the contents of the distance memory.

10. The system of claim 6 wherein the means for controlling operation of the transducer causes the latter to produce a plurality of pairs of bursts, each pair having bursts of different duration, whereby the distance memory is continuously updated.

11. A movie camera in combination with the system of claim 10 wherein the camera includes focusing means responsive to the contents of the distance memory.

12. In a sonic rangefinder system having transmitting and receiving means for transmitting a burst of sonic energy toward a subject and for receiving an echo therefrom so as to produce a range signal representative of subject distance in accordance with the elapsed time between transmission and reception, the improvement wherein said transmitting and receiving means includes means for transmitting at least a pair of spaced apart bursts of sonic energy with one of said bursts being a short burst and the other thereof being a long burst and means for producing a range signal responsive to the echo from said short burst when the elapsed time for receipt of its echo is less than a given fixed time and for producing a range signal responsive to the echo from said long burst when the time for its echo is greater than said fixed time so that said short burst is applicable to determine near subject distances while said long burst is applicable to more distant subject locations.

13. In a sonic rangefinder system having transmitting and receiving means for transmitting a burst of sonic energy toward a subject and for receiving an echo therefrom so as to produce a range signal representative of subject distance in accordance with the elapsed time between transmission and reception, the improvement wherein said transmitting and receiving means includes means for transmitting at least a pair of spaced apart bursts of sonic energy with one of said bursts being a short burst and the other thereof being a long burst and means for utilizing the echo from said short burst for subject distance when the elapsed time for receipt of its echo is less than a given fixed time and for utilizing the echo from said long burst when the time for its echo is greater than said fixed time so that said short burst is applicable to determine near subject distances while said long burst is applicable to more distant subject locations, said system including means for recording a range signal only from transmission of said short burst when the distance to the subject is less than a predetermined distance and only from transmission of said long burst when the distance to the subject is greater than said predetermined distance.

14. A ranging method for detecting the distance to a subject comprising the steps of:

initiating a relatively short burst of sonic energy directed toward a subject;

enabling a receiver after a short time consistent with said short burst to detect an echo from said subject;

determining the distance to said subject based upon the elapsed time between initiation of said short burst and reception of its echo from said subject when such elapsed time is less than a given elapsed time consistent with a first maximum subject distance;

initiating a relatively long burst of sonic energy directed toward said subject, at least when the elapsed time between initiation of said short burst and return of its echo is greater than said given elapsed time;

enabling said receiver after a long time consistent with said long burst to detect an echo from said subject; and

determining the distance to said subject based upon the elapsed time between initiation of said long burst and reception of its echo at least when its elapsed time is greater than said given elapsed time whereby said short burst is employed for distances up to said first maximum distance and said long burst is employed for distances beyond said first maximum distance.

15. A ranging method for detecting the distance to a subject comprising the steps of:

initiating a relatively short burst of sonic energy directed toward a subject;

enabling a receiver following initiation of said short burst after a first short blanking time at least equal to the duration of said short burst such that the closest subject detectable by said receiver in response to said short burst is defined by the duration of said short blanking time;

determining the distance to said subject based upon the elapsed time between initiation of said short burst and reception of its echo from said subject when such elapsed time is greater than said short blanking time and less than a given elapsed time consistent with a first maximum subject distance;

initiating a relatively long burst of sonic energy directed toward said subject at least when the elapsed time between initiation of said short burst and reception of its echo is greater than said fixed preselected elapsed time;

enabling said receiver following initiation of said long burst at an extended blanking time at least equal to the duration of said long burst such that the closest subject detectable by said long burst is defined by the duration of said extended blanking time; and

determining the distance to said subject based upon the elapsed time between initiation of said long burst and reception of its echo at least when such elapsed time is greater than said given elapsed time consistent with said first maximum subject distance.