Range measuring system

• US 6,314,055 B1
• Filed: 10/16/1998
• Issued: 11/06/2001
• Est. Priority Date: 10/16/1998
• Status: Expired due to Term

• Current Assignee: Thales Visionix Incorporated (Thales SA)
• Original Assignee: Intersense Incorporated
• Inventors: Moore, Russell L., Foxlin, Eric
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US09/173,967
• Time in Patent Office: 1,117 Days
• Field of Search: 367/99, 367/127, 735/97, 738/612.7
• US Class Current: 367/127
• CPC Class Codes: G01S 7/523 Details of pulse systems short-range imaging G01S7/52017; methods or devices for transmitting, conducting or directing sound G10K11/18

Abstract

A system is provided for determining range to a wave energy source. The system includes a transmitter for transmitting a burst of pulses of wave energy in response to a trigger signal. A receiver is provided for determining a time of arrival of the burst and from such determined time of arrival, the range to the wave energy source. The receiver includes: an envelope detector for detecting an envelope of the burst; a network for producing an output in response to an early point on the detected envelope occurring prior to a peak in the detected envelope; a timer, responsive to the trigger signal and the network output for determining the time of arrival of the burst; and a processor, responsive to such determined time of arrival, for determining the range of the wave energy source from the transmitter. The receiver includes a differentiator network for producing an output in response to the nth derivative of the detected envelope, where n is an integer greater than one; and, the timer is responsive to the trigger signal and the differentiator output for determining the time of arrival of the burst. The receiver also includes a means for confirming detection of a valid burst after the detection of the early point and a means to transmit and wherein the previously recorded time of arrival point only if it is followed by a valid burst confirmation.

Claims

1. A system for determining a time of arrival of a waveform having a certain shape including a rising portion and terminating portion, such waveform possibly being attenuated as such waveform passes through a medium, such medium maintaining the shape of the waveform, such system comprising:

a detector for detecting a point corresponding to a zero crossing of the nth derivative (n>

1) of the waveform on the rising portion of the waveform, such point occurring at a fixed time delay after the beginning of the waveform which delay is unaffected by any attenuation of the waveform or by any alteration of the portion of the waveform after the point; and

a timer, responsive to the detected point on the waveform, for determining the time of arrival.

2. A system for determining range between a transmitter and a receiver, such system comprising:

(a) a transmitter for transmitting a burst of wave energy in response to a trigger signal;

(b) a receiver for determining a time of arrival of the burst, and from such determined time of arrival, the distance traversed by the wave burst, such receiver comprising;

(i) an analog envelope detector for detecting an envelope of the burst;

(ii) a network for producing an output in response to a point corresponding to a zero crossing of the nth derivative (n>

1) of the envelope on the detected envelope occurring prior to a peak in the detected envelope such point occurring at a fixed time from the beginning of he burst regardless of any amplitude alteration of the burst; and

(iii) a timer, responsive to the trigger signal and the network output for determining the time of arrival of the burst; and

(c) a processor, for determining the distance from the determined time of arrival.

3. The system recited in claim 2 wherein the receiver includes a burst validation means for confirming reception of the burst and wherein the time of arrival of the point is stored until after such burst confirmation has been detected.

4. The system recited in claim 3 wherein the burst validation means includes a means of measuring the extent of the burst.

6. The system recited in claim 3 wherein the burst validation means includes a burst threshold detector for determining detection by the receiver of a burst with peak amplitude exceeding a predetermined threshold.

5. A system for determining distance traversed by a burst of wave energy, such system comprising:

(a) a transmitter for transmitting a burst of wave energy in response to a trigger signal;

(b) a receiver for determining a time of arrival of the burst, such receiver comprising;

(i) an analog envelope detector for detecting an envelope of the burst; and

(ii) a network for producing an output in response to a zero crossing of the nth derivative of the detected envelope, where n is an integer greater than one.

7. The system recited in claim 5 wherein the first peak of the (n−

1)th derivative of the envelope is detected by detecting the zero-cross immediately following the first peak of the nth derivative.

8. The system recited in claim 5 wherein the burst of wave energy comprises acoustic wave energy.

9. The system recited in claim 5 wherein the distance traversed by the burst corresponds to a round trip distance from the transmitter to a reflecting object and back to the receiver located spatially coincident with the transmitter.

10. A method for determining a time of arrival of a waveform having a certain shape including a rising portion and terminating portion, such waveform possibly being attenuated as such waveform passes through a medium, such medium maintaining the shape of the waveform, such method comprising:

detecting a point corresponding to a zero crossing of the nth derivative (n>

1) of the waveform on the rising portion of the waveform such point occurring at a fixed time delay after the beginning of the waveform which delay is unaffected by any attenuation of the waveform or by any alteration of the portion of the waveform after the point; and

determining the time of arrival from the time of detection of the point on the waveform.

11. A system for determining a time of arrival of an ultrasonic sound burst, comprising:

a microphone for receiving the ultrasonic burst;

an analog envelope detector fed by the microphone for detecting an envelope of the ultrasonic burst received by the microphone;

a differentiator network for producing a signal representative of the nth derivative of the detected envelope, where n is an integer greater than one;

a comparator fed by a threshold signal and the signal produced by the differentiator network.

12. A system for generating a pulse at a time of arrival of a waveform having a certain shape including a rising portion and terminating portion, such waveform possibly being attenuated as such waveform passes through a medium, such medium maintaining the shape of the waveform, such system comprising:

a detector for detecting a point corresponding to a zero crossing of the nth derivative (n>

1) of the waveform on the rising portion of the waveform, such point occurring at a fixed time delay after the beginning of the waveform, such delay being unaffected by any attenuation of he waveform or by any alteration of the portion of the waveform after the point.

13. A system for determining time of arrival of a wave energy source, such system comprising:

(a) a transmitter for transmitting a burst of pulses of wave energy in response to a trigger signal; and

(b) a receiver for determining a time of arrival of the burst, and from such determined time of arrival, the distance traversed by the wave burst, such receiver comprising;

(i) an analog envelope detector for detecting an envelope of the burst;

(ii) a network for producing an output in response to a point on the detected envelope corresponding to a zero crossing of the nth derivative (n>

1) of the detected envelope occurring prior to a peak in the detected envelope; and

(iii) a timer, responsive to the trigger signal and the network output for determining the time of arrival of the burst.

14. A system for determining range to a wave energy source, such system comprising:

(a) a transmitter for transmitting a burst of pulses of wave energy in response to a trigger signal;

(b) a receiver for determining a time of arrival of reflections of such energy by the wave energy source, and from such determined time of arrival, the range to the wave energy source, such receiver comprising;

(i) an analog envelope detector for detecting an envelope of the burst;

(ii) a differentiator network for producing an output in response to the nth derivative of the detected envelope, where n is an integer greater than one.

15. A system for determining a time of arrival of a sound burst, comprising:

a microphone for receiving the sound burst;

an analog envelope detector fed by the microphone for detecting an envelope of the sound burst received by the microphone;

a differentiator network for producing a signal representative of the nth derivative of the detected envelope, where n is an integer greater than one;

a comparator fed by a threshold signal and the signal produced by the differentiator network.

16. A system for determining a time of arrival of a waveform having a certain shape including a rising portion and terminating portion, such waveform possibly being attenuated as such waveform passes through a medium, such medium maintaining the shape of the waveform, such system comprising:

a non-automatically gain controlled receiver, comprising;

a detector for detecting a point on the rising portion of the waveform corresponding to a zero crossing of the nth derivative (n>

1) of the waveform; and

a timer, responsive to the detected point on the waveform, for determining the time of arrival.