# US 2018/0321360 A1 · LIDAR Data Acquisition And Control

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- Number: US 2018/0321360 A1
- Document ID: US20180321360A1
- Status: Published application
- Kind: A1
- Application number: 15/974,527
- Filed: 2018-05-08
- Published: 2018-11-08
- Earliest claimed: 2017-05-08
- Assignees: Velodyne Lidar, Inc.
- Applicants: Velodyne Lidar, Inc.
- Inventors: David S. Hall; Raymond Liou; Oren Milgrome; Anand Gopalan; Pravin Kumar Venkatesan
- Web page: https://patentgrep.com/patent/US20180321360A1

## CPC

- G01S 7/4811: {common to transmitter and receiver}
- G01S 7/4865: Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487)
- G01S 7/4876: {by removing unwanted signals (G01S7/495 takes precedence)}
- G01S 17/10: using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32)
- G01S 17/42: Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S17/46)
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

Methods and systems for performing three dimensional LIDAR measurements with an integrated LIDAR measurement device are described herein. In one aspect, a return signal receiver generates a pulse trigger signal that triggers the generation of a pulse of illumination light and data acquisition of a return signal, and also triggers the time of flight calculation by time to digital conversion. In addition, the return signal receiver also estimates the width and peak amplitude of each return pulse, and samples each return pulse waveform individually over a sampling window that includes the peak amplitude of each return pulse waveform. In a further aspect, the time of flight associated with each return pulse is estimated based on a coarse timing estimate and a fine timing estimate. In another aspect, the time of flight is measured from the measured pulse due to internal optical crosstalk and a valid return pulse.

## Claims

### Claim 1

An integrated LIDAR measurement device, comprising:
an illumination source mounted to a printed circuit board;
an illumination driver integrated circuit (IC) mounted to the printed circuit board, the illumination driver IC selectively couples the illumination source to an electrical power source in response to a pulse trigger signal, causing the illumination source to emit a measurement pulse of illumination light;
a photodetector mounted to the printed circuit board, the photodetector configured to detect an amount of return light received by photodetector in response to the measurement pulse of illumination light and generate an output signal indicative of the detected return light;
a return signal receiver IC mounted to the printed circuit board, the return signal receiver IC configured to:
receive the output signal during a duration of a measurement window;
identify one or more return pulses of the detected return light;
determine a time of flight associated with each of the identified return pulses; and
determine one or more properties of a segment of each of the identified return pulses.

### Claim 2 (depends on 1)

The integrated LIDAR measurement system of claim 1, wherein the return signal receiver IC generates the pulse trigger signal in response to a pulse command signal received onto the return signal receiver IC.

### Claim 3 (depends on 1)

The integrated LIDAR measurement device of claim 1, wherein the return signal receiver IC includes a return signal analysis module, wherein the return signal analysis module comprises:
a constant fraction discriminator module having a first input node, a second input node, and an output node, wherein the output signal is received on the first input node, and wherein a hit signal at the output node switches to a different value when the output signal exceeds a threshold voltage value on the second input node.

### Claim 4 (depends on 3)

The integrated LIDAR measurement device of claim 3, wherein the return signal analysis module further comprises:
a coarse timing module having a first input node coupled to the output node of the constant fraction discriminator, a second input node, and an output node, wherein the pulse trigger signal is present on the second input node, and wherein the coarse timing module generates a digital value at the output node indicative of a time elapsed between a transition of the pulse trigger signal and a transition of the hit signal.

### Claim 5 (depends on 4)

The integrated LIDAR measurement device of claim 4, wherein the digital value is a count of a number of transitions of a digital clock signal that occur between the transition of the pulse trigger signal and the transition of the hit signal.

### Claim 6 (depends on 5)

The integrated LIDAR measurement device of claim 5, wherein the return signal analysis module further comprises:
a fine timing module having a first input node, a first output node, and a second output node, wherein the hit signal is present on the first input node, wherein the fine timing module generates a first electrical signal at the first output node indicative of a time difference between the transition of the hit signal and a subsequent transition of the digital clock signal and a second electrical signal at the second output node indicative of a time difference between the transition of the digital hit signal and a subsequent transition of an inverse of the digital clock signal.

### Claim 7 (depends on 5)

The integrated LIDAR measurement device of claim 5, wherein the coarse timing module generates a metastability signal, wherein the metastability signal is the digital clock signal shifted by half of a period of the digital clock signal.

### Claim 8 (depends on 7)

The integrated LIDAR measurement device of claim 7, further comprising:
a time of flight module configured to estimate a value of a time of flight of the measurement pulse of illumination light based at least in part on the digital value indicative of the time elapsed between the transition of the pulse trigger signal and the transition of the hit signal, the time difference between the transition of the hit signal and the subsequent transition of the digital clock signal, the time difference between the transition of the hit signal and the subsequent transition of the inverse of the digital clock signal, and the metastability signal.

### Claim 9 (depends on 3)

The integrated LIDAR measurement device of claim 3, the return signal analysis module further comprising:
a pulse width detection module including:
a first input node, the hit signal present on the first input node,
a second input node, an enable signal present on the second input node, and
an output node, wherein the pulse width detection module generates an electrical signal at the output node that is indicative of a time difference between a transition of the enable signal and a time when an amplitude of the hit signal falls below a threshold value.

### Claim 10 (depends on 3)

The integrated LIDAR measurement device of claim 3, the return signal analysis module further comprising:
a return pulse sample and hold module configured to generate an output signal indicative of a peak amplitude of the output signal after the transition of the hit signal.

### Claim 11 (depends on 10)

The integrated LIDAR measurement device of claim 10, wherein the return pulse sample and hold module is further configured to generate a plurality of output signal values each indicative of the amplitude of the output signal before and after the peak amplitude.

### Claim 12 (depends on 11)

The integrated LIDAR measurement device of claim 11, wherein the number of output signal samples before and after the peak amplitude is programmable.

### Claim 13 (depends on 1)

The integrated LIDAR measurement device of claim 1, wherein a first of the one or more return pulses of the detected return light is due to optical crosstalk between the illumination source and the photodetector, and wherein the time of flight associated with each subsequent return pulse of the one or more return pulses is determined with reference to the first return pulse.

### Claim 14 (depends on 1)

The integrated LIDAR measurement device of claim 1, wherein the duration of the measurement window is approximately a time of flight of light from the LIDAR measurement device to a maximum range of the LIDAR measurement device and back to the LIDAR measurement device.

### Claim 15

A method comprising:
generating a pulse trigger signal in response to a pulse command signal received onto a return signal receiver IC mounted to a printed circuit board;
selectively electrically couple an illumination source to an electrical power source in response to the pulse trigger signal, causing the illumination source to emit a measurement pulse of illumination light;
detecting an amount of return light received by a photodetector in response to the measurement pulse of illumination light, wherein the illumination source and the photodetector are mounted to the printed circuit board;
generating an output signal indicative of the detected return light;
receiving the output signal onto the return signal receiver IC during a duration of a measurement window;
identifying one or more return pulses of the detected return light;
determining a time of flight associated with each of the identified return pulses; and
determining one or more properties of a segment of each of the identified return pulses.

### Claim 16 (depends on 15)

The method of claim 15, further comprising:
generating a hit signal that switches to a different value when the output signal exceeds a threshold voltage value;
generating a digital value indicative of a time elapsed between a transition of the pulse trigger signal and a transition of the hit signal, wherein the digital value is a count of a number of transitions of a digital clock signal that occur between the transition of the pulse trigger signal and the transition of the hit signal.

### Claim 17 (depends on 16)

The method of claim 16, further comprising:
generating a first electrical signal indicative of a time difference between the transition of the hit signal and a subsequent transition of the digital clock signal and a second electrical signal indicative of a time difference between the transition of the digital hit signal and a subsequent transition of an inverse of the digital clock signal; and
generating a metastability signal, wherein the metastability signal is the digital clock signal shifted by half of a period of the digital clock signal.

### Claim 18 (depends on 17)

The method of claim 17, further comprising:
estimating a value of a time of flight of the measurement pulse of illumination light based at least in part on the digital value indicative of the time elapsed between the transition of the pulse trigger signal and the transition of the hit signal, the time difference between the transition of the hit signal and the subsequent transition of the digital clock signal, the time difference between the transition of the hit signal and the subsequent transition of the inverse of the digital clock signal, and the metastability signal.

### Claim 19 (depends on 16)

The method of claim 16, further comprising:
generating an electrical signal indicative of a time difference between a transition of an enable signal and a time when an amplitude of the hit signal falls below a threshold value.

### Claim 20 (depends on 16)

The method of claim 16, further comprising:
generating an output signal indicative of a peak amplitude of the output signal after the transition of the hit signal.

### Claim 21 (depends on 20)

The method of claim 20, further comprising:
generating a plurality of output signal values each indicative of the amplitude of the output signal before and after the peak amplitude, wherein the number of output signal samples before and after the peak amplitude is programmable.

### Claim 22

An integrated LIDAR measurement device, comprising:
an illumination source mounted to a printed circuit board;
an illumination driver integrated circuit (IC) mounted to the printed circuit board, the illumination driver IC selectively couples the illumination source to an electrical power source in response to a pulse trigger signal, causing the illumination source to emit a measurement pulse of illumination light;
a photodetector mounted to the printed circuit board, the photodetector configured to detect a first amount of the measurement pulse of illumination light due to crosstalk between the illumination source and the photodetector and a valid return pulse of light reflected from a location in a surrounding environment illuminated by a second amount of the measurement pulse; and
a return pulse receiver IC mounted to the printed circuit board, the return pulse receiver IC configured to estimate a time between an instance when the first amount of the measurement pulse of illumination light due to crosstalk is detected and an instance when the valid return pulse of light is detected.