PASSIVE OBJECT DETECTION APPARATUS INCLUDING AMBIENT NOISE COMPENSATION

• US 3,732,536 A
• Filed: 09/18/1970
• Issued: 05/08/1973
• Est. Priority Date: 09/18/1970
• Status: Expired due to Term

• Current Assignee: Larry Wilharm, Vincent E. Larka
• Original Assignee: Larry Wilharm, Vincent E. Larka
• Inventors: Larka, Vincent E., Wilharm, Larry
• Primary Examiner(s): Farley, Richard A.
• Application Number:
  US05/073,316
• Time in Patent Office: 963 Days
• Field of Search: 340/5R,6R,15,16R,258D,261,31R,34
• US Class Current: 367/135
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors
• CPC Class Codes: H04B 11/00 Transmission systems employing sonic, ultrasonic or infrasonic waves
• CPC Class Codes: Y10S 367/901 Noise or unwanted signal reduction in nonseismic receiving system

Abstract

An ambient noise compensating arrangement for use in a passive ultrasonic vehicle detection apparatus carried by a vehicle for compensating for ambient background noise present during the detection of vehicles located in predetermined regions of surveillance rearward of the subject vehicle. Prior to the detection of the presence of a vehicle in one of the regions of surveillance, the prevailing ambient background noise is sensed by a signal-receiving horn member mounted on the subject vehicle and processed by an input signal arrangement coupled to the horn member to produce a noise voltage signal representative of the ambient background noise. The noise voltage signal is applied to a field effect transistor the resistance of which is increased in response to the noise voltage signal by an amount sufficient to essentially fully attenuate the noise voltage signal. When a vehicle subsequently enters the region of surveillance rearward of the subject vehicle, after the aforementioned ambient noise compensation, various signals including ultrasonic signals generated inherently by the vehicle, due to a combination of factors such as engine and body vibrations, and engine and tire noises, are received by the signal-receiving horn member and applied to a piezoelectric crystal transducer provided in the input signal arrangement. The piezoelectric transducer has a predetermined resonant frequency equal to the frequency of particular ultrasonic signals generated inherently by all existing engine-driven road vehicles. The piezoelectric transducer operates in response to the various signals received from the horn member to produce an output voltage which is greatest for ultrasonic signals of the predetermined resonant frequency. The output voltage produced by the piezoelectric transducer is then processed to provide an indication to the operator of the subject vehicle of the presence of the vehicle in the region of surveillance.

Claims

1. In a passive object detection apparatus associated with a first object for detecting and indicating, in the presence of ambient noise signals, the presence of another object in a region of surveillance adjacent to the first object, said another object inherently generating signals, said passive object detection apparatus including signal-receiving means for receiving the ambient noise signals and the signals generated inherently by said object while present in the region of surveillance, signal processing apparatus comprising:

input means adapted to receive from the signal-receiving means the signals received thereby and operative in response to said signals to produce voltage signals representative thereof;

attenuation means adapted to receive the voltage signals produced by the input means and operative in response to signals received thereby to attenuate ambient noise signals by an amount in accordance with the amplitude thereof when said signals have a duration exceeding a predetermined time duration and operative to attenuate subsequent object signals received thereby by only said establishment amount of ambient noise signal attenuation when the subsequent signals have a duration equal to or less than the predetermined ambient noise signal time duration; and

output means coupled to the attenuation means and operative during the operation of said attenuation means to attenuate the ambient noise signals having a duration exceeding the predetermined time duration to produce a first output indication, and operative during the operation of the attenuation Means to attenuate the object signals having a duration equal to or less than the predetermined ambient noise signal time duration by only said amount of ambient noise signal attenuation to produce a second output indication.

2. In a passive object detection apparatus associated with a first object for detecting and indicating, in the presence of ambient noise, the presence of another object in a region of surveillance adjacent to the first object, said another object inherently generating signals of a time duration less than the time duration of the ambient noise, said passive object detection apparatus including signal-receiving means for receiving the ambient noise and the signals generated inherently by said another object while present in the region of surveillance, signal processing apparatus comprising:

input means adapted to receive from the signal-receiving means the ambient noise received thereby and operative in response to said ambient noise to produce a first voltage signal representative thereof;

attenuation means coupled to the input means and including means for discriminating on the basis of time duration, between signals produced by the input means in response to ambient noise and in response to signals generated by an object in the region of surveillance, said attenuation means being adapted to receive a first voltage signal representing ambient noise and being operative in response to the first voltage signal to attenuate the first voltage signal by an amount in accordance with the amplitude thereof;

said input means also receiving from the signal-receiving means signals generated inherently by an object while the object is present in the region of surveillance adjacent to the first object, said input means operating in response to said signals representative of said object to produce a second voltage signal representative thereof;

said attenuation means also receiving the second voltage signal and operating in response thereto to attenuate the second voltage signal by an amount substantially equal to the attenuation of said first voltage signal; and

means for processing the attenuated second voltage signal to provide an indication of the presence of the object in the region of surveillance adjacent to the first object.

3. In a passive object detection apparatus associated with a first object for detecting and indicating, in the presence of ambient noise, the presence of another object in a region of surveillance adjacent to the first object, said another object inherently generating signals of a time duration less than the time duration of the ambient noise, said passive object detection apparatus including signal-receiving means for receiving the ambient noise and the signals generated inherently by said another object while present in the region of surveillance, signal processing apparatus comprising:

input means adapted to receive from the signal-receiving means the ambient noise received thereby and operative in response to said ambient noise to produce a first voltage signal representative thereof;

attenuation means coupled to the input means and including means for discriminating, on the basis of time duration, between signals produced by the input means in response to ambient noise and in response to signals generated by an object in the region of surveillance, said attenuation means being operative in response to the first voltage signal to attenuate the first voltage signal by an amount in accordance with the amplitude thereof; and

means coupled to the attenuation means and operative during the operation of the attenuation means to attenuate the first voltage signal to provide an indication that the attenuation operation is taking place;

said input means also receiving from the signal-receiving means signals generated inherently by an object while the object is present in the region of surveillance adjacent to the first object, said input means operating in response to said signals to produce a Second voltage signal representative thereof;

said attenuation means also receiving the second voltage signal and operating in response thereto to attenuate the second voltage signal by the aforesaid amount of attenuation of said first voltage signal; and

means for processing the attenuated second voltage signal to provide an indication of the presence of the object in the region of surveillance adjacent to the first object.

4. In a passive object detection apparatus associated with a first object for detecting and indicating, in the presence of ambient noise, the presence of another object in a region of surveillance adjacent to the first object, said another object inherently generating signals, said passive object detection apparatus including signal-receiving means for receiving the ambient noise and the signals generated inherently by said object while present in the region of surveillance, signal processing apparatus comprising:

input means adapted to receive from the signal-receiving means the ambient noise received thereby and operative in response to said ambient noise to produce a first voltage signal representative thereof;

attenuation circuit means having an input connection for receiving the first voltage signal, an output connection, and a control connection, said attenuation circuit means having an essentially non-attenuating operating state in the absence of a voltage at the control connection and an attenuating operating state in the presence of a voltage at the control connection, said attenuation circuit means initially operating in the essentially non-attenuating state and applying said first voltage signal at the input connection thereof to the output connection substantially without attenuation;

first circuit means coupled to the output connection of the attenuation circuit means and operative in response to the first voltage signal at the output connection of the attenuation circuit means to produce a first output signal having an amplitude proportional to the amplitude of the first voltage signal;

output circuit means coupled to the first circuit means and adapted to receive the first output signal produced by the first circuit means, said output circuit means being operative in response to the first output signal to process the first output signal to provide an indication of the fact that compensation for the ambient noise has been initiated; and

time delay circuit means coupled between the first circuit means and the control connection of the attenuation circuit means and also receiving the first output signal produced by the first circuit means, said time delay circuit means being operative in response to the first output signal produced by the first circuit means to produce and apply a feedback voltage to the control connection of the attenuation circuit means after a predetermined time delay, said feedback voltage having a value proportional to the amplitude of the first output signal produced by the first circuit means;

said attenuation circuit means being operative in response to the feedback voltage at the control connection thereof to operate in its attenuating operating state and to attenuate the first voltage signal present at its input connection by an amount in accordance with the amplitude of the feedback voltage;

said input means also receiving from the signal-receiving means signal generated inherently by an object while the object is present in the region of surveillance adjacent to the first object, said input means operating in response to said signals to produce a second voltage signal representative thereof;

said attenuation circuit means also receiving the second voltage signal at its input connection and operating in response thereto to attenuate the second voltage signal by the aforesaid amount of attenuation of said first voltage signal;

said first circuit means also receiving the attenuated second voltage signal produced by the attenuation circuit means and operating in respoNse thereto to produce a second output signal having an amplitude proportional to the amplitude of the attenuated second voltage signal;

said output circuit means also receiving the second output signal produced by the first circuit means, said output circuit means operating in response to the second output signal to process the second output signal to provide an indication of the presence of the object in the region of surveillance adjacent to the first object; and

said time delay circuit means also receiving the second output signal produced by the first circuit means and operating in response to the second output signal to produce and apply a feedback voltage to the control connection of the attenuating circuit means after the predetermined time delay, thereby preventing any change in the value of attenuation provided by the attenuation circuit means for a period of time equal to the predetermined time delay and while the object is present in the region of surveillance adjacent to the first object.

5. Apparatus in accordance with claim 4 wherein the first circuit means comprises:

amplifier circuit means adapted to amplify each of the first and second voltage signals produced by the attenuation circuit means by a predetermined quantity thereby to provide amplified first and second voltage signals; and

current switch circuit means coupled to the amplifier circuit means and operative in response to each of the amplified first and second voltage signals to produce corresponding first and second output current signals, each having a value proportional to the amplitude of the corresponding first or second amplified voltage signal.

6. Apparatus in accordance with claim 4 wherein the output circuit means includes:

integrator circuit means operative in response to each of the first and second output signals produced by the first circuit means to develop corresponding first and second progressively increasing output voltages;

threshold detector circuit means coupled to the integrator circuit means and having a predetermined threshold input voltage level associated therewith above which an output signal is produced thereby, the value of said input threshold voltage level being less than the maximum value of output voltage produced by the integrator circuit means, said threshold detector circuit means being operative when the value of the first or second output voltage produced by the integrator circuit means exceeds the predetermined input threshold voltage level associated therewith to produce an output signal; and

means adapted to receive the output signal produced by the threshold detector circuit means and operative in response thereto to provide a sensible output indication.

7. Apparatus in accordance with claim 6 wherein said threshold detector circuit means includes a Schmitt trigger circuit.

8. In a passive object detection apparatus associated with a first object for detecting and indicating, in the presence of ambient noise, the presence of another object in a region of surveillance adjacent to the first object, said another object inherently generating signals, said passive object detection apparatus including signal-receiving means for receiving the ambient noise and the signals generated inherently by said object while present in the region of surveillance, signal processing apparatus comprising:

input means adapted to receive from the signal-receiving means the ambient noise received thereby and operative in response to said ambient noise to produce a first voltage signal representative thereof;

attenuation circuit means having an input connection for receiving the first voltage signal, an output connection, and a control connection, said attenuation circuit means having a non-attenuating operating state in the absence of a voltage at the control connection and an attenuating operating state in the presence of a voltage at the control connection, said attenuation circuit means initially operating in the Essentially non-attenuating state and applying said first voltage signal at the input connection thereof to the output connection substantially without attenuation;

first circuit means coupled to the output connection of the attenuation circuit means and operative in response to the first voltage signal at the output connection of the attenuation circuit means to produce a first output signal having an amplitude proportional to the amplitude of the first voltage signal;

integrator circuit means coupled to the first circuit means and adapted to receive the first output signal produced by the first circuit means and operative in response to the first output signal to develop a progressively increasing output voltage;

threshold detector circuit means coupled to the integrator circuit means and having a predetermined input threshold voltage level associated therewith above which an output signal is produced by the threshold detector circuit means and below which said output signal is terminated, the value of said predetermined input threshold voltage level being less than the maximum value of output voltage and more than the minimum value of output voltage produced by the integrator circuit means, said threshold detector circuit means being operative when the value of the first output voltage of the integrator circuit means exceeds the predetermined threshold voltage level associated therewith to produce a first output signal;

indicator circuit means adapted to receive the output signal produced by the threshold detector circuit means and operative in response thereto to provide a first sensible output indication;

time delay circuit means coupled between the first circuit means and the control connection of the attenuation circuit means and also receiving the first output signal produced by the first circuit means, said time delay circuit means being operative in response to the first output signal produced by the first circuit means to produce and apply a feedback voltage to the control connection of the attenuation circuit means after a predetermined time delay, said feedback voltage having a value proportional to the amplitude of the first output signal produced by the first circuit means;

said attenuation circuit means being operative in response to the feedback voltage at the control connection thereof to operate in its attenuating operating state and to attenuate the first voltage signal present at its input connection by an amount in accordance with the amplitude of the feedback voltage, whereby the first circuit means operates to decrease the amplitude of the first output signal produced thereby and the integrator circuit means operates to reduce the value of the output voltage thereof to a minimum value less than the predetermined input threshold voltage level associated with the threshold detector circuit means, thereby causing the threshold detector circuit means to terminate the first output signal produced thereby and causing the indicator circuit means to terminate the first sensible output indication provided thereby;

said input means also receiving from the signal-receiving means signals generated inherently by an object while the object is present in the region of surveillance adjacent to the first object, said input means operating in response to said signals to produce a second voltage signal representative thereof;

said attenuation circuit means also receiving the second voltage signal at its input connection and operating in response thereto to attenuate the second voltage signal by the aforesaid amount;

said first circuit means also receiving the attenuated second voltage signal produced by the attenuation circuit means and operating in response thereto to produce a second output signal having an amplitude proportional to the amplitude of the attenuated second voltage signal;

said integrator circuit means also receiving the second output signal produced by the first circuit means and operating in respOnse thereto to increase the value of its output voltage toward its maximum value, whereby the predetermined threshold voltage level of the threshold detector circuit means is exceeded and a second output signal is produced by the threshold detector circuit means and a second sensible output indication is provided by the indicator circuit means;

said time delay circuit means also receiving the second output signal produced by the first circuit means, said time delay circuit means producing and applying a feedback voltage to the control connection of the attenuation circuit means after the predetermined time delay thereby preventing any change in in the value of attenuation provided by the attenuation circuit means for a period of time equal to the predetermined time delay and while the object is present in the region of surveillance adjacent to the first object; and

said first circuit means operating to decrease the value of the second output signal produced thereby and said integrator circuit means operating to reduce the value of the output voltage thereof from its last value and below the input threshold voltage level associated with the threshold detector circuit means when the object leaves the region of surveillance within the predetermined time delay of the time delay circuit means, whereby the second output signal produced by the threshold detector circuit means is terminated and the second sensible output indication provided by the indicator circuit means is terminated.

9. Apparatus in accordance with claim 8 further comprising:

means coupled to the integrator circuit means and to the time delay circuit means and operative when the value of the feedback voltage of the time delay circuit means differs from the value of the output voltage of the integrator circuit means by more than a predetermined quantity to adjust the feedback voltage of the time delay circuit means to have a value differing from the value of the output voltage of the integrator circuit means by the predetermined quantity.

10. Apparatus in accordance with claim 8 further comprising:

voltage equalization circuit means coupled to the integrator circuit means, the threshold detector circuit means, and to the time delay circuit means and operative when an output signal produced by the threshold detector circuit means is terminated to adjust the feedback voltage of the time delay circuit means to have a value differing from the value of the output voltage of the integrator circuit means by a predetermined quantity.

11. Apparatus in accordance with claim 8 wherein:

said signal-receiving means includes a horn member having a frustum configuration; and

said region of surveillance has essentially a frustum configuration.

12. Apparatus in accordance with claim 11 wherein:

said another object is a vehicle and the signals inherently generated thereby include ultrasonic signals; and

wherein said input means includes;

an ultrasonic transducer having a predetermined resonant frequency and operable in response to the ultrasonic signals received from the horn member to produce an output voltage which is greatest for ultrasonic signals of the predetermined resonant frequency.

13. Apparatus in accordance with claim 12 wherein said first object is a vehicle.

14. Apparatus in accordance with claim 13 wherein said ultrasonic transducer is a piezoelectric crystal transducer.

15. Apparatus in accordance with claim 8 wherein the attenuation circuit means includes a field effect transistor in series with the input connection and the output connection thereof.

16. Apparatus in accordance with claim 15 wherein:

the first circuit means includes a transistor amplifier circuit and a transistor current switch circuit;

the integrator circuit means includes a capacitance coupled to the transistor current switch circuit for receiving current from the transistor current switch circuit;

the time delay circuit means includes a resistance and a caPacitance coupled to the transistor current switch circuit for receiving current from the current switch circuit; and

the threshold detector circuit means includes a Schmitt trigger circuit coupled to the capacitance included in the integrator circuit means.

17. Apparatus in accordance with claim 16 wherein:

said signal-receiving means includes a horn member having a frustum configuration; and

said region of surveillance has essentially a frustum configuration.

18. Apparatus in accordance with claim 17 wherein:

said another object is a vehicle and the signals inherently generated thereby include ultrasonic signals; and

wherein said input means includes;

an ultrasonic transducer having a predetermined resonant frequency and operable in response to the ultrasonic signals received from the horn member to produce an output voltage which is greatest for ultrasonic signals of the predetermined resonant frequency; and

tuned resonant circuit means connected to the ultrasonic transducer and having a tuned resonant frequency equal to the resonant frequency of the ultrasonic transducer, said tuned circuit means being operable in response to the output voltage produced by the ultrasonic transducer to produce an output signal of a predetermined bandwidth.

19. Apparatus in accordance with claim 18 wherein said first object is a vehicle.

20. Apparatus in accordance with claim 19 wherein said ultrasonic transducer is a piezoelectric crystal transducer.

21. Apparatus for processing signals present in a predetermined region, comprising:

signal-receiving means for receiving signals present in the predetermined region;

input means adapted to receive from the signal-receiving means the signals received thereby and operative in response to said signals to produce voltage signals representative thereof;

attenuation means adapted to receive the voltage signals produced by the input means and operative in response to the signals received thereby to attenuate signals by an amount in accordance with the amplitude thereof when said signals have a duration exceeding a predetermined time duration and operative to attenuate subsequent signals received thereby by only said established amount in accordance with the amplitude thereof when the subsequent signals have a duration equal to or less than the predetermined time duration; and

output means operative during the operation of the attenuation means to attenuate the signals having a duration exceeding the predetermined time duration to produce a first output indication and operative during the operation of the attenuation means to attenuate the signals having a duration equal to or less than the predetermined time duration to produce a second output indication.

22. Apparatus in accordance with claim 21 wherein:

said signal-receiving means includes a horn member having a frustum configuration; and

the predetermined region has essentially a frustum configuration.