Dynamic measurements of pulse peak value

• US 9,304,154 B1
• Filed: 03/04/2013
• Issued: 04/05/2016
• Est. Priority Date: 03/04/2013
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Droz, Pierre-yves, Levandowski, Anthony
• Primary Examiner(s): Ratcliffe, Luke
• Assistant Examiner(s): Abraham, Samantha K
• Application Number:
  US13/784,329
• Time in Patent Office: 1,128 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G01R 19/04 Measuring peak values or amplitude or envelope of ac or of pulses
• CPC Class Codes: G01R 25/005 Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller, or for passing one of the input signals as output signal

Abstract

Methods and systems are provided for detecting and measuring a peak value of a light pulse. One example method involves (i) receiving an analog signal comprising a pulse, (ii) differentiating the analog signal, using a differentiator, to provide a differentiated signal, (iii) detecting, using a comparator, a zero-crossing in the differentiated signal, (iv) delaying the analog signal by a delay amount, using a signal buffer, to provide a time-delayed analog signal, (v) in response to detecting the zero-crossing, causing a measurement of the time-delayed analog signal to be obtained, (vi) determining a measurement time associated with the measurement, and (vii) outputting the measurement and the measurement time. The methods and systems may be implemented for light detection and ranging (LIDAR) applications. In such applications, the measurement and measurement time may correspond to an object and a distance of the object, respectively, in an environment of a LIDAR device.

Claims

1. A method comprising:

receiving an analog signal comprising a pulse;

directing a first portion of the analog signal to a differentiator and a second portion of the analog signal to a signal buffer;

differentiating the first portion of the analog signal, using the differentiator, to provide a differentiated signal;

detecting, using a comparator, a zero-crossing in the differentiated signal;

delaying the second portion of the analog signal by a delay amount, using the signal buffer, to provide a time-delayed analog signal;

in response to detecting the zero-crossing, causing a measurement of the time-delayed analog signal to be obtained;

determining a measurement time associated with the measurement; and

outputting the measurement and the measurement time.

2. The method of claim 1, wherein the delay amount corresponds to delay associated with the differentiator and the comparator.

3. The method of claim 2, wherein the delay amount is in the range of 3 to 4 nanoseconds.

4. The method of claim 1, wherein detecting, using a comparator, a zero-crossing in the differentiated signal comprises:

providing the differentiated signal to the comparator; and

receiving from the comparator an output indicating a transition from on to off.

5. The method of claim 4, wherein causing a measurement of the time-delayed analog signal to be obtained comprises:

providing to a flip-flop circuit the output of the comparator indicating a transition from on to off; and

receiving from the flip-flop circuit an output that causes an analog-to-digital converter (ADC) to sample the time-delayed analog signal and provide a digital output that corresponds to the measurement.

6. The method of claim 4, wherein determining a measurement time associated with the measurement comprises:

providing to a flip-flop circuit the output of the comparator indicating a transition from on to off; and

receiving from the flip-flop circuit an output that causes a time-to-digital converter (TDC) to provide an output that corresponds to the measurement time.

7. The method of claim 1, wherein the pulse in the analog signal is representative of a light pulse received by a light distance and ranging (LIDAR) device.

8. The method of claim 7, wherein the measurement corresponds to a peak value of the pulse, and wherein the measurement time corresponds to a time that the peak value occurs relative to a reference time.

9. A device comprising:

an input, wherein the input is configured to receive an analog signal comprising a pulse;

a differentiator, wherein the differentiator is configured to differentiate a first portion of the analog signal to provide a differentiated signal;

a comparator, wherein the comparator is configured to detect a zero-crossing in the differentiated signal;

a signal buffer, wherein the signal buffer is configured to delay a second portion of the analog signal by a delay amount to provide a time-delayed analog signal;

an analog-to-digital converter (ADC), wherein the ADC is configured to obtain a measurement of the time-delayed analog signal based on the zero-crossing detected by the comparator; and

a time-to-digital converter (TDC), wherein the TDC is configured to determine a measurement time associated with the measurement.

10. The device of claim 9, further comprising a signal splitter coupled to the input, wherein the signal splitter is configured to direct the first portion of the analog signal to the differentiator and the second portion of the analog signal to the signal buffer.

11. The device of claim 9, wherein the delay amount corresponds to delay associated with the differentiator and the comparator.

12. The device of claim 9, wherein the comparator is configured to provide an output indicating a transition from on to off.

13. The device of claim 12, further comprising a flip-flop circuit, wherein the flip-flop circuit is configured to (i) receive the output of the comparator indicating a transition from on to off, and (ii) provide an output that causes the ADC to sample the time-delayed analog signal and provide a digital output that corresponds to the measurement.

14. The device of claim 12, further comprising a flip-flop circuit, wherein the flip-flop circuit is configured to (i) receive the output of the comparator indicating a transition from on to off, and (ii) provide an output that causes TDC to provide an output that corresponds to the measurement time.

15. A non-transitory computer readable medium having stored thereon instructions executable by a computing device to cause the computing device to perform functions comprising:

receiving a measurement of an analog signal comprising a pulse, wherein a first portion of the analog signal is differentiated, by a differentiator, to provide a differentiated signal and a zero-crossing in the differentiated signal is detected, by a comparator, and a second portion of the analog signal is delayed, by a signal buffer, to provide a time-delayed analog signal and the measurement is a digital output from an analog-to-digital converter (ADC) that samples the time-delayed analog signal based on the zero-crossing detected by the comparator; and

receiving a measurement time associated with the measurement.

16. The computer readable medium of claim 15, wherein the delay amount corresponds to delay associated with the differentiator and the comparator.

17. The computer readable medium of claim 15, wherein the measurement time is a digital output from a time-to-digital converter (TDC).

18. The computer readable medium of claim 15, wherein the pulse in the analog signal is representative of a light pulse received by a light distance and ranging (LIDAR) device.

19. The computer readable medium of claim 18, wherein the measurement corresponds to a peak value of the pulse, and wherein the measurement time corresponds to a time that the peak value occurs relative to a reference time.