EXHIBIT B 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 1 of 28
(12) United States Patent 

Lenius et al. 

US009368936B1 

US 9,368,936 B1 

Jun. 14, 2016 

(10) Patent No.: 

(45) Date of Patent: 

(54) 

(71) 

(72) 

(73) 

(*) 

(21) 

(22) 

(60) 

(51) 

(52) 

(58) 

LASER DIODE FIRING SYSTEM 

Applicant: Google Inc., Mountain View, CA (US) 

Inventors: Samuel William Lenius, Sunnyvale, CA 

(US); Pierre-yves Droz, Mountain View, 

CA (US) 

Assignee: Google Inc., Mountain View, CA (US) 

Notice: Subject to any disclaimer, the term of this 

patent is extended or adjusted under 35 

U.S.C. 154(b) by 378 days. 

Appl. No.: 14/132,219 

Filed: Dec. 18, 2013 

Related U.S. Application Data 

Provisional application No. 61/884,762, filed on Sep. 

30, 2013. 

Int. Cl. 

G0IC 3/08 (2006.01) 

H0 IS 5/06 (2006.01) 

G0IS 17/32 (2006.01) 

PHOIS 5/062 (2006.01) 

PH05B 33/08 (2006.01) 

G0IJ 1/46 (2006.01) 

U.S. CI. 

CPC H01S 5/06 (2013.01); G0IS 17/32 (2013.01); 

G0IJ 1/46 (2013.01), HOIS 5/062 (2013.01); 

H05B 33/0842 (2013.01); H05B 33/0845 

(2013.01) 

Field of Classification Search 

CPC ... G01J 1/46; H05B 33/0845, H05B 33/0842; 

H01S 5/06; H01S 5/062; G01S 17/06 

USPC ...... 359/4.01 

See application file for complete search history. 

(56) References Cited 

|U.S. PATENT DOCUMENTS 

3,790,277 A 2/1974 Hogan 

4,700,301 A 10/1987 Dyke 

4,709,195 A 11/1987 Hellekson et al. 

5,202,742 A 4/1993 Frank et al. 

6,882,409 B1 4/2005 Evans et al. 

7,089,114 B1 8/2006 Huang 

7,248.342 B1 7/2007 Degnan 

7,255,275 B2 8/2007 Gurevich et al. 

7,969,558 B2 6/2011 Hall 

8,188,794 B2 5/2012 Lautzenhiser 

8,320,423 B2 11/2012 Stern 

9,185,762 B2 * 1 1/2015 Mark ........................ G01J 1/46 

2013/0106468 A1 5/2013 Aso 

2013/0314711 A1 * 1 1/2013 Cantin .................... G01S 17/10 

356/445 

2014/0269799 A1* 9/2014 Ortiz ..................... H01S 5/0428 

372/38.02 

2014/0312233 A1 * 10/2014 Mark ........................ G01J 1/46 

250/341.8 

* cited by examiner 

Primary Examiner – Mark Hellner 

(74) Attorney, Agent, or Firm — McDonnell Boehnen 

Hulbert & Berghoff LLP 

(57) ABSTRACT 

A laser diode firing circuit for a light detection and ranging 

device is disclosed. The firing circuit includes a laser diode 

coupled in series to a transistor, such that current through the 

laser diode is controlled by the transistor. The laser diode is 

configured to emit a pulse of light in response to current 

flowing through the laser diode. The firing circuit includes a 

capacitor that is configured to charge via a charging path that 

includes an inductorand to discharge via a discharge path that 

includes the laser diode. The transistor controlling current 

through the laser diode can be a Gallium nitride field effect 

transistor. 

20 Claims, 11 Drawing Sheets 

y^T 500 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 2 of 28
U.S. Patent 

Vehicle 100 

Propulsion 

System 102 

Jun. 14, 2016 

Sensor System 

104 

Sheet 1 of 11 

Control System 

106 

US 9,368,936 B1 

Peripherals 

108 

Engine / 

Motor 

118 

System 

122 

Global Positioning Steering Unit 

132 

Wireless 

Communicat 

ion System 146 

Energy 

Source 

119 

ment Unit 

124 

Inertial Measure Throttle 

134 

Touch-screen 

148 

Transmiss 

ion 

120 

RADAR Unit 

126 

Brake Unit 

136 

Microphone 

150 

Wheels/Tires 

121 

Laser 

Rangefinder / 

LIDAR Unit 128 

Sensor Fusion 

Algorithm 

138 

Speaker 

152 

Camera 

130 

Computer Vision 

System 

140 

Microphone Navigation / 

Pathing System 

142 

Processor 

113 115 

g 

| Instructions 

Data Storage 

Computer System 

112 

Obstacle 

Avoidance System 

144 

Power Supply 

110 

User Interface 

116 

Figure 1 

 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 3 of 28
U.S. Patent Jun. 14, 2016 Sheet 2 of 11 US 9,368,936 B1 

Back View Top View 

Figure 2 

 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 4 of 28
U.S. Patent Jun. 14, 2016 Sheet 3 of 11 US 9,368,936 B1 

308 

 

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U.S. Patent US 9,368,936 B1 

Z09) 

 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 6 of 28
U.S. Patent Jun. 14, 2016 Sheet 5 of 11 US 9,368,936 B1 

520d 

530 520g 

4tow-> <- AT 

! st-o Atcharge 

T, 

Figure 5B 

 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 7 of 28
9.InõIHOs 3.InÃ¡H GIS 

U.S. Patent US 9,368,936 B1 

 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 8 of 28
U.S. Patent Jun. 14, 2016 Sheet 7 of 11 US 9,368,936 B1 

544 

V, 

542 To 

CIRCUIT 

546 

GATE DRIVER 

548 

 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 9 of 28
U.S. Patent Jun. 14, 2016 Sheet 8 of 11 US 9,368,936 B1 

TURN OFF TRANSISTOR TO THEREBY CAUSE CAPACITOR 

TO CHARGE AND INDUCTOR TO DECREASE STORED 

ENERGY 

! 602 

TURN ON TRANSISTOR TO THEREBY CAUSE CAPACITOR 

TO DISCHARGE, LASER DIODE TO EMIT A PULSE OF 

LIGHT, AND INDUCTOR TO INCREASE STORED ENERGY 

! 604 

END 

Figure 6A 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 10 of 28
U.S. Patent Jun. 14, 2016 Sheet 9 of 11 US 9,368,936 B1 

START 

TURN OFF GaNFET TO THEREBY CAUSE CAPACITOR TO 

CHARGE AND INDUCTOR TO DECREASE STORED ENERGY ay 

TURN ON GaNFET TO THEREBY CAUSE CAPACITOR TO 

DISCHARGE, LASER DIODE TO EMIT A PULSE OF LIGHT, 

AND INDUCTOR TO INCREASE STORED ENERGY 

DETERMINE TRANSMISSION TIME OF THE EMITTED 

LIGHT PULSE 

RECEIVE A REFLECTED LIGHT PULSE DUE TO THE 

EMITTED LIGHT PULSE BEING REFLECTED BY AN 

ENVIRONMENTAL OBJECT 

DETERMINE A RECEPTION TIME OF THE REFLECTED 

LIGHT PULSE 

630 

DETERMINE A DISTANCE TO THE OBJECT BASED ON THE 

–ITRANSMISSION TIME AND RECEPTION TIME “. 

NAVIGATE AN AUTONOMOUS VEHICLE BASED IN PART ON 

THE DETERMINED DISTANCE TO THE OBJECT 

! 634 

END 

2 4 

22 86 

TN 

Ts 

Figure 6B 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 11 of 28
U.S. Patent Jun. 14, 2016 Sheet 10 of 11 US 9,368,936 B1 

640 

INCREASE ENERGY STORED IN INDUCTOR 

TURN OFF GaNFET 

RELEASE ENERGY STORED IN INDUCTOR 

CHARGE CAPACITOR FROM ENERGY RELEASED BY 

INDUCTOR 

REVERSE BLAS DIODE TO HOLD CHARGE ON CAPACITOR 

- - - - - - - - - - - - - - - - - - - 656 

END 

Figure 6C 

 

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U.S. Patent US 9,368,936 B1 

 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 13 of 28
US 9,368,936 B1 

1 

LASER DIODE FIRING SYSTEM 

CROSS-REFERENCE TO RELATED 

APPLICATIONS 

This application claims priority to U.S. Provisional Patent 

Application No. 61/884,762, filed Sep. 30, 2013, which is 

incorporated herein by reference in its entirety and for all 

purposes. 

BACKGROUND 

Unless otherwise indicated herein, the materials described 

in this section are not prior art to the claims in this application 

and are not admitted to be prior art by inclusion in this section. 

Vehicles can be configured to operate in an autonomous 

mode in which the vehicle navigates through an environment 

with little or no input from a driver. Such autonomous 

vehicles can include one or more sensors that are configured 

to detect information about the environment in which the 

vehicle operates. The vehicle and its associated computer 

implemented controller use the detected information to navi 

gate through the environment. For example, if the sensor(s) 

detect that the vehicle is approaching an obstacle, as deter 

mined by the computer-implemented controller, the control 

ler adjusts the vehicle’s directional controls to cause the 

vehicle to navigate around the obstacle. 

One such sensor is a light detection and ranging (LIDAR) 

device. A LIDAR actively estimates distances to environmen 

tal features while scanning through a scene to assemble a 

cloud of point positions indicative of the three-dimensional 

shape of the environmental scene. Individual points are mea 

sured by generating a laser pulse and detecting a returning 

pulse, if any, reflected from an environmental object, and 

determining the distance to the reflective object according to 

the time delay between the emitted pulse and the reception of 

the reflected pulse. The laser, or set of lasers, can be rapidly and repeatedly scanned across a scene to provide continuous 

real-time information on distances to reflective objects in the 

scene. Combining the measured distances and the orientation 

of the laser(s) while measuring each distance allows for asso 

ciating a three-dimensional position with each returning 

pulse. A three-dimensional map of points of reflective fea 

tures is generated based on the returning pulses for the entire 

scanning zone. The three-dimensional point map thereby 

indicates positions of reflective objects in the scanned scene. 

SUMMARY 

A laser diode firing circuit for a light detection and ranging 

(LIDAR) device is disclosed. The firing circuit includes a 

laser diode coupled in series with a transistor, such that cur 

rent through the laser diode is controlled by the transistor. The 

laser diode is configured to emit a pulse of light in response to 

current flowing through the laser diode. A capacitor is con 

nected across the laser diode and the transistor such that the 

capacitor discharges through the laser diode when the tran 

sistor is turned on. The capacitor is charged by a voltage 

source via a charging path that includes a diode and an induc 

tor. The inductor has one terminal coupled to the voltage 

source and another terminal coupled to the anode of the diode, 

and the cathode of the diode is coupled to the capacitor. As a 

result, the capacitoris only charged while the diode is forward 

biased. Upon turning on the transistor, the capacitor dis 

charges through the laser diode and a pulse of light is emitted. 

Once the capacitor discharges to a voltage level sufficient to 

forward bias the diode, current begins flowing through the 

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2 

inductor. The increase in inductor current causes the inductor 

to increase energy stored in its magnetic field, and drives the 

voltage applied to the anode of the diode lower than the 

voltage source. Once the transistor is turned off, the laser 

diode ceases emission, and the current through the inductoris 

directed to recharge the capacitor, which causes the inductor 

current to begin decreasing. The sudden change in current 

through the inductor causes an increase in the voltage applied 

to the anode of the diode. The capacitor is charged until the 

voltage of the capacitor approximately matches the voltage at 

the diode anode, at which point the diode becomes reverse 

biased. Upon reverse biasing the diode, the current through 

the inductor goes to zero and the charging cycle is complete. 

Both the emission and charging operations of the firing circuit 

can thus be controlled by operation of the single transistor. 

Some embodiments of the present disclosure provide an 

apparatus. The apparatus includes a voltage source, an induc 

tor, a diode, a transistor, a light emitting element, and a 

capacitor. The inductor can be coupled to the voltage source. 

The inductor can be configured to store energy in a magnetic 

field. The diode can be coupled to the voltage source via the 

inductor. The transistor can be configured to be turned on and 

turned off by a control signal. The light emitting element can 

be coupled to the transistor. The capacitor can be coupled to a 

charging path and a discharge path. The charging path can 

include the inductor and the diode. The discharge path can 

include the transistor and the light emitting element. The 

capacitor can be configured to charge via the charging path 

such that a voltage across the capacitorincreases from a lower 

voltage level to a higher voltage level responsive to the tran 

sistor being turned off. The inductor can be configured to 

release energy stored in the magnetic field such that a current 

through the inductor decreases from a higher current level to 

a lower current level responsive to the transistor being turned 

off. The capacitor can be configured to discharge through the 

discharge path such that the light emitting element emits a 

pulse of light and the voltage across the capacitor decreases 

from the higher voltage level to the lower voltage level 

responsive to the transistor being turned on. The inductor can 

be configured to store energy in the magnetic field such that 

the current through the inductor increases from the lower 

current level to the higher current level responsive to the 

transistor being turned on. 

Some embodiments of the present disclosure provide a 

method. The method can include turning off a transistor and 

turning on a transistor. The transistor can be coupled to a light emitting element. Both the transistor and the light emitting 

element can be included in a discharge path coupled to a 

capacitor. The capacitor can also be coupled to a charging 

path including a diode and an inductor. The inductor can be 

configured to store energy in a magnetic field. The diode can 

be coupled to a voltage source via the inductor. The capacitor 

can be configured to charge via the charging path such that a 

voltage across the capacitor increases from a lower voltage 

level to a higher voltage level responsive to the transistor 

being turned off. The inductor can be configured to release 

energy stored in the magnetic field such that a current through 

the inductor decreases from a higher current level to a lower 

current level responsive to the transistor being turned off. The 

capacitor can be configured to discharge through the dis 

charge path such that the light emitting element emits a pulse 

of light and the voltage across the capacitor decreases from 

the higher voltage level to the lower voltage level responsive 

to the transistor being turned on. The inductor can be config 

ured to store energy in the magnetic field such that the current 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 14 of 28
US 9,368,936 B1 

3 

through the inductor increases from the lower current level to 

the higher current level responsive to the transistor being 

turned on. 

Some embodiments of the present disclosure provide a 

light detection and ranging (LIDAR) device. The LIDAR 

device can include a light source, a light sensor, and a con 

troller. The light source can include a voltage source, an 

inductor, a diode, a transistor, a light emitting element, and a 

capacitor. The inductor can be coupled to the voltage source. 

The inductor can be configured to store energy in a magnetic 

field. The diode can be coupled to the voltage source via the 

inductor. The transistor can be configured to be turned on and 

turned off by a control signal. The light emitting element can 

be coupled to the transistor. The capacitor can be coupled to a 

charging path and a discharge path. The charging path 

includes the inductor and the diode. The discharge path 

includes the transistor and the light emitting element. The 

capacitor can be configured to charge via the charging path 

such that a voltage across the capacitorincreases from a lower 

voltage level to a higher voltage level responsive to the tran 

sistor being turned off. The inductor can be configured to 

release energy stored in the magnetic field such that a current 

through the inductor decreases from a higher current level to 

a lower current level responsive to the transistor being turned 

off. The capacitor can be configured to discharge through the 

discharge path such that the light emitting element emits a 

pulse of light and the voltage across the capacitor decreases 

from the higher voltage level to the lower voltage level 

responsive to the transistor being turned on. The inductor can 

be configured to store energy in the magnetic field such that 

the current through the inductor increases from the lower 

current level to the higher current level responsive to the 

transistor being turned on. The light sensor can be configured 

to detect a reflected light signal comprising light from the 

emitted light pulse reflected by a reflective object. The con 

troller can be configured to determine a distance to the reflec 

tive object based on the reflected light signal. 

Some embodiments of the present disclosure provide a 

means for controlling a laser diode firing circuit to operate in 

an emission mode and a charging mode using a single tran 

sistor. Embodiments may include means turning off a tran 

sistor and turning on a transistor. The transistor can be 

coupled to a light emitting element. Both the transistor and 

the light emitting element can be included in a discharge path 

coupled to a capacitor. The capacitor can also be coupled to a 

charging path including a diode and an inductor. The inductor 

can be configured to store energy in a magnetic field. The 

diode can be coupled to a voltage source via the inductor. The 

capacitor can be configured to charge via the charging path 

such that a voltage across the capacitorincreases from a lower 

voltage level to a higher voltage level responsive to the tran 

sistor being turned off. The inductor can be configured to 

release energy stored in the magnetic field such that a current 

through the inductor decreases from a higher current level to 

a lower current level responsive to the transistor being turned 

off. The capacitor can be configured to discharge through the 

discharge path such that the light emitting element emits a 

pulse of light and the voltage across the capacitor decreases 

from the higher voltage level to the lower voltage level 

responsive to the transistor being turned on. The inductor can 

be configured to store energy in the magnetic field such that 

the current through the inductor increases from the lower 

current level to the higher current level responsive to the 

transistor being turned on. 

These as well as other aspects, advantages, and alterna 

tives, will become apparent to those of ordinary skill in the art 

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4 

by reading the following detailed description, with reference 

where appropriate to the accompanying drawings. 

BRIEF DESCRIPTION OF THE FIGURES 

FIG. 1 is a functional block diagram depicting aspects of an 

example autonomous vehicle. 

FIG. 2 depicts exterior views of an example autonomous 

vehicle. 

FIG. 3A provides an example depiction of a LIDAR device 

including beam steering optics. 

FIG. 3B symbolically illustrates an example in which a 

LIDAR device scans across an obstacle-filled environmental 

SCèIlê. 

FIG. 3C symbolically illustrates an example point cloud 

corresponding to the obstacle-filled environmental scene of 

FIG. 3B. 

FIG. 4A symbolically illustrates a LIDAR device scanning 

across an example obstacle-filled environmental scene and 

using reflected signals to generate a point cloud. 

FIG. 4B is an example timing diagram of transmitted and 

received pulses for the symbolic illustration of FIG. 4A. 

FIG. 5A is an example laser diode firing circuit. 

FIG. 5B is a timing diagram that shows operation of the 

example laser diode firing circuit of FIG. 5A. 

FIG. 5C shows a current path through the example laser 

diode firing circuit of FIG. 5A during a charging mode. 

FIG. 5D shows a current path through the example laser 

diode firing circuit of FIG. 5A during an emission mode. 

FIG. 5E illustrates an arrangement in which multiple laser 

diode firing circuit are charged via a single inductor. 

FIG. 6A is a flowchart of an example process for operating 

a laser diode firing circuit. 

FIG. 6B is a flowchart of an example process for operating a LIDAR device. 

FIG. 6G is a flowchart of another example process for 

operating a laser diode firing circuit. 

FIG.7 depicts a non-transitory computer-readable medium 

configured according to an example embodiment. 

DETAILED DESCRIPTION 

I. Overview 

Example embodiments relate to an autonomous vehicle, 

such as a driverless automobile, that includes a light detection 

and ranging (LIDAR) sensor for actively detecting reflective 

features in the environment surrounding the vehicle. A con 

troller analyzes information from the LIDAR sensor to iden 

tify the surroundings of the vehicle. The LIDAR sensor 

includes a light source that may include one or more laser 

diodes configured to emit pulses of light that are then directed 

to illuminate the environment surrounding the vehicle. Cir 

cuits forfiring a laser diode and determining a pulse emission 

time from the laser diode are disclosed herein. 

According to some embodiments, a LIDAR device 

includes one or more laser diode firing circuits in which a 

laser diode is connected in series to a transistor such that 

current through the laser diode is controlled by the transistor. 

A capacitoris coupled to a charging path and a discharge path. 

The discharge path includes the laser diode and the transistor 

such that turning on the transistor causes the capacitor to 

discharge through the laser diode, which causes the laser 

diode to emit a pulse of light. 

The capacitor’s charging path includes an inductor and a 

diode. The inductor is configured to store energy in a mag 

netic field, and is connected between a voltage source and the 

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US 9,368,936 B1 

5 

diode. An increasing inductor current charges the inductor by increasing the energy stored in the magnetic field of the 

inductor. The increasing current induces a voltage across the 

inductor, such that a voltage less than the voltage source is 

applied to the diode. A decreasing inductor current discharges 

the inductor by decreasing the energy stored in the magnetic 

field. The decreasing current induces a voltage across the 

inductor, such that the voltage applied to the diode exceeds 

the voltage source. The diode is also connected to the capaci 

tor and is configured to be forward biased when the voltage 

across the capacitor does not exceed the voltage applied to the 

diode by the inductor (to thereby charge the capacitor). The 

diode is also configured to be reverse biased when the voltage 

across the capacitor exceeds the voltage applied to the diode 

by the inductor (to thereby prevent the capacitor from dis 

charging). 

In some embodiments, the firing circuit disclosed herein is 

configured to switch between a charging mode and an emis 

sion mode based on operation of a single transistor. In 

response to turning the transistor off, current through the laser 

diode ceases and emission of a pulse terminates. In response 

to turning off the transistor, if the charging path diode is 

forward biased, the capacitor begins recharging through the 

charging path. As charge accumulates on the capacitor the 

current through the charging path (and the inductor) 

decreases, and the decrease in inductor current causes the 

inductor to release energy stored in its magnetic field. The 

released energy from the inductor causes the voltage applied 

to the capacitor through the diode to exceed the voltage of the 

voltage source, at least transiently. The transient voltage is 

applied to the capacitor through the diode. The capacitor is 

therefore charged according to the transient voltage and then 

holds its charge level when the diode becomes reverse biased. 

Following a charging interval, the voltage charged across the 

capacitor can be greater than the voltage of the voltage source. 

The laser diode can emit light in the visible spectrum, ultraviolet spectrum, infrared spectrum, near infrared spec 

trum, and/or infrared spectrum. In one example, the laser 

diode emits pulses of infrared light with a wavelength of 

about 905 nm. The transistor can be a Gallium nitride field 

effect transistor (FET), for example. 

II. Example Autonomous Vehicle System 

Some aspects of the example methods described herein 

may be carried out in whole or in part by an autonomous 

vehicle or components thereof. However, some example 

methods may also be carried out in whole or in part by a 

system or systems that are remote from an autonomous 

vehicle. For instance, an example method could be carried out 

in part or in full by a server system, which receives informa 

tion from sensors (e.g., raw sensor data and/or information 

derived therefrom) of an autonomous vehicle. Other 

examples are also possible. 

Example systems within the scope of the present disclosure 

will now be described in greater detail. An example system 

may be implemented in, or may take the form of, an automo 

bile. However, an example system may also be implemented 

in or take the form of other vehicles, such as cars, trucks, 

motorcycles, buses, boats, airplanes, helicopters, lawn mow 

ers, earth movers, boats, snowmobiles, aircraft, recreational 

vehicles, amusement park vehicles, farm equipment, con 

struction equipment, trams, golf carts, trains, and trolleys. 

Other vehicles are possible as well. 

FIG. 1 is a functional block diagram illustrating a vehicle 

100 according to an example embodiment. The vehicle 100 is 

configured to operate fully or partially in an autonomous 

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35 

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45 

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55 

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65 

6 

mode, and thus may be referred to as an “autonomous 

vehicle.” For example, a computer system 112 can control the 

vehicle 100 while in an autonomous mode via control instruc 

tions to a control system 106 for the vehicle 100. The com 

puter system 112 can receive information from one or more 

sensor systems 104, and base one or more control processes 

(such as setting a heading so as to avoid a detected obstacle) 

upon the received information in an automated fashion. 

The autonomous vehicle 100 can be fully autonomous or 

partially autonomous. In a partially autonomous vehiclesome 

functions can optionally be manually controlled (e.g., by a 

driver) some or all of the time. Further, a partially autono 

mous vehicle can be configured to switch between a fully manual operation mode and a partially-autonomous and/or a 

fully-autonomous operation mode. 

The vehicle 100 includes a propulsion system 102, a sensor 

system 104, a control system 106, one or more peripherals 

108, a power supply 110, a computer system 112, and a user 

interface 116. The vehicle 100 may include more or fewer 

subsystems and each subsystem can optionally include mul 

tiple components. Further, each of the subsystems and com 

ponents of vehicle 100 can be interconnected and/or in com 

munication. Thus, one or more of the functions of the vehicle 

100 described herein can optionally be divided between addi 

tional functional or physical components, or combined into 

fewer functional or physical components. In some further 

examples, additional functional and/or physical components 

may be added to the examples illustrated by FIG. 1. 

The propulsion system 102 can include components oper 

able to provide powered motion to the vehicle 100. In some 

embodiments the propulsion system 102 includes an engine/ 

motor 118, an energy source 119, a transmission 120, and 

wheels/tires 121. The engine/motor 118 converts energy 

source 119 to mechanical energy. In some embodiments, the 

propulsion system 102 can optionally include one or both of 

engines and/or motors. For example, a gas-electric hybrid 

vehicle can include both a gasoline/diesel engine and an 

electric motor. 

The energy source 119 represents a source of energy, such 

as electrical and/or chemical energy, that may, in full or in 

part, power the engine/motor 118. That is, the engine/motor 

118 can be configured to convert the energy source 119 to 

mechanical energy to operate the transmission. In some 

embodiments, the energy source 119 can include gasoline, diesel, other petroleum-based fuels, propane, other com 

pressed gas-based fuels, ethanol, solar panels, batteries, capacitors, flywheels, regenerative braking systems, and/or 

other sources of electrical power, etc. The energy source 119 

can also provide energy for other systems of the vehicle 100. 

The transmission 120 includes appropriate gears and/or 

mechanical elements suitable to convey the mechanical 

power from the engine/motor 118 to the wheels/tires 121. In 

some embodiments, the transmission 120 includes a gearbox, 

a clutch, a differential, a drive shaft, and/or axle(s), etc. 

The wheels/tires 121 are arranged to stably support the 

vehicle 100 while providing frictional traction with a surface, 

such as a road, upon which the vehicle 100 moves. Accord 

ingly, the wheels/tires 121 are configured and arranged 

according to the nature of the vehicle 100. For example, the 

wheels/tires can be arranged as a unicycle, bicycle, motor 

cycle, tricycle, or car/truck four-wheel format. Other wheel/ 

tire geometries are possible, such as those including six or 

more wheels. Any combination of the wheels/tires 121 of 

vehicle 100 may be operable to rotate differentially with 

respect to other wheels/tires 121. The wheels/tires 121 can 

optionally include at least one wheel that is rigidly attached to 

the transmission 120 and at least one tire coupled to a rim of 

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US 9,368,936 B1 

7 

a corresponding wheel that makes contact with a driving 

surface. The wheels/tires 121 may include any combination 

of metal and rubber, and/or other materials or combination of 

materials. 

The sensor system 104 generally includes one or more 

sensors configured to detect information about the environ 

ment surrounding the vehicle 100. For example, the sensor 

system 104 can include a Global Positioning System (GPS) 

122, an inertial measurement unit (IMU) 124, a RADAR unit 

126, a laser rangefinder/LIDAR unit 128, a camera 130, and/ 

or a microphone 131. The sensor system 104 could also 

include sensors configured to monitor internal systems of the 

vehicle 100 (e.g., O2 monitor, fuel gauge, engine oil tempera 

ture, wheel speed sensors, etc.). One or more of the sensors 

included in sensor system 104 could be configured to be 

actuated separately and/or collectively in order to modify a 

position and/or an orientation of the one or more sensors. 

The GPS 122 is a sensor configured to estimate a geo 

graphic location of the vehicle 100. To this end, GPS 122 can 

include a transceiver operable to provide information regard ing the position of the vehicle 100 with respect to the Earth. 

The IMU 124 can include any combination of sensors (e.g., accelerometers and gyroscopes) configured to sense position 

and orientation changes of the vehicle 100 based on inertial 

acceleration. 

The RADAR unit 126 can represent a system that utilizes 

radio signals to sense objects within the local environment of 

the vehicle 100. In some embodiments, in addition to sensing the objects, the RADAR unit 126 and/or the computer system 

112 can additionally be configured to sense the speed and/or 

heading of the objects. 

Similarly, the laser rangefinder or LIDAR unit 128 can be 

any sensor configured to sense objects in the environment in 

which the vehicle 100 is located using lasers. The laser 

rangefinder/LIDAR unit 128 can include one or more laser 

sources, a laser scanner, and one or more detectors, among other system components. The laser rangefinder/LIDAR unit 

128 can be configured to operate in a coherent (e.g., using 

heterodyne detection) or an incoherent detection mode. 

The camera 130 can include one or more devices config ured to capture a plurality of images of the environment 

surrounding the vehicle 100. The camera 130 can be a still 

camera or a video camera. In some embodiments, the camera 

130 can be mechanically movable such as by rotating and/or 

tilting a platform to which the camera is mounted. As such, a 

control process of vehicle 100 may be implemented to control 

the movement of camera 130. 

The sensor system 104 can also include a microphone 131. 

The microphone 131 can be configured to capture sound from 

the environment surrounding vehicle 100. In some cases, multiple microphones can be arranged as a microphone array, 

or possibly as multiple microphone arrays. 

The control system 106 is configured to control operation 

(s) regulating acceleration of the vehicle 100 and its compo 

ments. To effect acceleration, the control system 106 includes 

a steering unit 132, throttle 134, brake unit 136, a sensor 

fusion algorithm 138, a computer vision system 140, a navi 

gation/pathing system 142, and/or an obstacle avoidance sys 

tem 144, etc. 

The steering unit 132 is operable to adjust the heading of 

vehicle 100. For example, the steering unit can adjust the axis 

(or axes) of one or more of the wheels/tires 121 so as to effect 

turning of the vehicle. The throttle 134 is configured to con 

trol, for instance, the operating speed of the engine/motor 118 

and, in turn, adjust forward acceleration of the vehicle 100 via 

the transmission 120 and wheels/tires 121. The brake unit 136 

decelerates the vehicle 100. The brake unit 136 can use fric 

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tion to slow the wheels/tires 121. In some embodiments, the 

brake unit 136 inductively decelerates the wheels/tires 121 by 

a regenerative braking process to convert kinetic energy of the 

wheels/tires 121 to electric current. 

The sensor fusion algorithm 138 is an algorithm (or a 

computer program product storing an algorithm) configured 

to accept data from the sensor system 104 as an input. The 

data may include, for example, data representing information 

sensed at the sensors of the sensor system 104. The sensor 

fusion algorithm 138 can include, for example, a Kalman 

filter, Bayesian network, etc. The sensor fusion algorithm 138 

provides assessments regarding the environment surrounding 

the vehicle based on the data from sensorsystem 104. In some 

embodiments, the assessments can include evaluations of 

individual objects and/or features in the environment sur 

rounding vehicle 100, evaluations of particular situations, 

and/or evaluations of possible interference between the 

vehicle 100 and features in the environment (e.g., such as 

predicting collisions and/or impacts) based on the particular 

situations. 

The computer vision system 140 can process and analyze images captured by camera 130 to identify objects and/or 

features in the environment surrounding vehicle 100. The 

detected features/objects can include traffic signals, roadway 

boundaries, other vehicles, pedestrians, and/or obstacles, etc. 

The computer vision system 140 can optionally employ an 

object recognition algorithm, a Structure From Motion 

(SFM) algorithm, video tracking, and/or available computer 

vision techniques to effect categorization and/or identifica 

tion of detected features/objects. In some embodiments, the 

computer vision system 140 can be additionally configured to 

map the environment, track perceived objects, estimate the 

speed of objects, etc. 

The navigation and pathing system 142 is configured to 

determine a driving path for the vehicle 100. For example, the 

navigation and pathing system 142 can determine a series of 

speeds and directional headings to effect movement of the 

vehicle along a path that substantially avoids perceived 

obstacles while generally advancing the vehicle along a road 

way-based path leading to an ultimate destination, which can 

be set according to user inputs via the user interface 116, for 

example. The navigation and pathing system 142 can addi 

tionally be configured to update the driving path dynamically 

while the vehicle 100 is in operation on the basis of perceived 

obstacles, traffic patterns, weather/road conditions, etc. In 

some embodiments, the navigation and pathing system 142 

can be configured to incorporate data from the sensor fusion 

algorithm 138, the GPS 122, and one or more predetermined 

maps so as to determine the driving path for vehicle 100. 

The obstacle avoidance system 144 can represent a control 

system configured to identify, evaluate, and avoid or other 

wise negotiate potential obstacles in the environment sur 

rounding the vehicle 100. For example, the obstacle avoid 

ance system 144 can effect changes in the navigation of the 

vehicle by operating one or more subsystems in the control 

system 106 to undertake swerving maneuvers, turning 

maneuvers, braking maneuvers, etc. In some embodiments, 

the obstacle avoidance system 144 is configured to automati 

cally determine feasible (“available”) obstacle avoidance 

maneuvers on the basis of surrounding traffic patterns, road 

conditions, etc. For example, the obstacle avoidance system 

144 can be configured such that a swerving maneuver is not 

undertaken when other sensor systems detect vehicles, con 

struction barriers, other obstacles, etc. in the region adjacent 

the vehicle that would be swerved into. In some embodi 

ments, the obstacle avoidance system 144 can automatically 

select the maneuver that is both available and maximizes 

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safety of occupants of the vehicle. For example, the obstacle 

avoidance system 144 can select an avoidance maneuver pre 

dicted to cause the least amount of acceleration in a passenger 

cabin of the vehicle 100. 

The vehicle 100 also includes peripherals 108 configured 

to allow interaction between the vehicle 100 and external 

sensors, other vehicles, other computer systems, and/or a 

user, such as an occupant of the vehicle 100. For example, the 

peripherals 108 for receiving information from occupants, 

external systems, etc. can include a wireless communication 

system 146, a touchscreen 148, a microphone 150, and/or a 

speaker 152. 

In some embodiments, the peripherals 108 function to 

receive inputs for a user of the vehicle 100 to interact with the 

user interface 116. To this end, the touchscreen 148 can both 

provide information to a user of vehicle 100, and convey 

information from the user indicated via the touchscreen 148 

to the user interface 116. The touchscreen 148 can be config ured to sense both touch positions and touch gestures from a 

user’s finger(or stylus, etc.) via capacitive sensing, resistance 

sensing, optical sensing, a surface acoustic wave process, etc. 

The touchscreen 148 can be capable of sensing finger move 

ment in a direction parallel or planar to the touchscreen sur 

face, in a direction normal to the touchscreen surface, or both, 

and may also be capable of sensing a level of pressure applied 

to the touchscreen surface. An occupant of the vehicle 100 can 

also utilize a voice command interface. For example, the 

microphone 150 can be configured to receive audio (e.g., a 

voice command or other audio input) from a user of the 

vehicle 100. Similarly, the speakers 152 can be configured to 

output audio to the user of the vehicle 100. 

In some embodiments, the peripherals 108 function to 

allow communication between the vehicle 100 and external 

systems, such as devices, sensors, other vehicles, etc. within 

its surrounding environment and/or controllers, servers, etc., 

physically located far from the vehicle that provide useful 

information regarding the vehicle’s surroundings, such as 

traffic information, weather information, etc. For example, 

the wireless communication system 146 can wirelessly com 

municate with one or more devices directly or via a commu 

nication network. The wireless communication system 146 

can optionally use 3G cellular communication, such as 

CDMA, EVDO, GSM/GPRS, and/or 4G cellular communi 

cation, such as WiMAX or LTE. Additionally or alternatively, 

wireless communication system 146 can communicate with a 

wireless local area network (WLAN), for example, using 

WiFi. In some embodiments, wireless communication sys 

tem 146 could communicate directly with a device, for 

example, using an infrared link, Bluetooth, and/or ZigBee. 

The wireless communication system 146 can include one or 

more dedicated short range communication (DSRC) devices 

that can include public and/or private data communications 

between vehicles and/or roadside stations. Other wireless 

protocols for sending and receiving information embedded in 

signals, such as various vehicular communication systems, 

can also be employed by the wireless communication system 

146 within the context of the present disclosure. 

As noted above, the power supply 110 can provide power to 

components of vehicle 100, such as electronics in the periph 

erals 108, computer system 112, sensor system 104, etc. The 

power supply 110 can include a rechargeable lithium-ion or 

lead-acid battery for storing and discharging electrical energy 

to the various powered components, for example. In some 

embodiments, one or more banks of batteries can be config 

ured to provide electrical power. In some embodiments, the 

power supply 110 and energy source 119 can be implemented 

together, as in some all-electric cars. 

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Many or all of the functions of vehicle 100 can be con 

trolled via computer system 112 that receives inputs from the 

sensor system 104, peripherals 108, etc., and communicates 

appropriate control signals to the propulsion system 102, 

control system 106, peripherals, etc. to effect automatic 

operation of the vehicle 100 based on its surroundings. Com 

puter system 112 includes at least one processor 113 (which 

can include at least one microprocessor) that executes instruc 

tions 115 stored in a non-transitory computer readable 

medium, such as the data storage 114. The computer system 

112 may also represent a plurality of computing devices that 

serve to control individual components or subsystems of the 

vehicle 100 in a distributed fashion. 

In some embodiments, data storage 114 contains instruc 

tions 115 (e.g., program logic) executable by the processor 

113 to execute various functions of vehicle 100, including 

those described above in connection with FIG.1. Data storage 

114 may contain additional instructions as well, including 

instructions to transmit data to, receive data from, interact 

with, and/or control one or more of the propulsion system 

102, the sensor system 104, the control system 106, and the 

peripherals 108. 

In addition to the instructions 115, the data storage 114 

may store data such as roadway maps, path information, 

among other information. Such information may be used by vehicle 100 and computer system 112 during operation of the 

vehicle 100 in the autonomous, semi-autonomous, and/or 

manual modes to select available roadways to an ultimate 

destination, interpret information from the sensor system 

104, etc. 

The vehicle 100, and associated computer system 112, 

provides information to and/or receives input from, a user of 

vehicle 100, such as an occupant in a passenger cabin of the 

vehicle 100. The user interface 116 can accordingly include 

one or more input/output devices within the set of peripherals 

108, such as the wireless communication system 146, the 

touchscreen 148, the microphone 150, and/or the speaker 152 

to allow communication between the computer system 112 

and a vehicle occupant. 

The computer system 112 controls the operation of the 

vehicle 100 based on inputs received from various sub 

systems indicating vehicle and/or environmental conditions 

(e.g., propulsion system 102, sensor system 104, and/or con 

trol system 106), as well as inputs from the user interface 116, indicating user preferences. For example, the computer sys 

tem 112 can utilize input from the control system 106 to 

control the steering unit 132 to avoid an obstacle detected by 

the sensorsystem 104 and the obstacle avoidance system 144. 

The computer system 112 can be configured to control many 

aspects of the vehicle 100 and its subsystems. Generally, 

however, provisions are made for manually overriding auto 

mated controller-driven operation, such as in the event of an 

emergency, or merely in response to a user-activated override, 

etc. 

The components of vehicle 100 described herein can be 

configured to work in an interconnected fashion with other 

components within or outside their respective systems. For 

example, the camera 130 can capture a plurality of images 

that represent information about an environment of the 

vehicle 100 while operating in an autonomous mode. The 

environment may include other vehicles, traffic lights, traffic 

signs, road markers, pedestrians, etc. The computer vision 

system 140 can categorize and/or recognize various aspects in 

the environment in concert with the sensor fusion algorithm 138, the computer system 112, etc. based on object recogni 

tion models pre-stored in data storage 114, and/or by other 

techniques. 

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US 9,368,936 B1 

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Although the vehicle 100 is described and shown in FIG. 1 

as having various components of vehicle 100, e.g., wireless 

communication system 146, computer system 112, data stor 

age 114, and user interface 116, integrated into the vehicle 

100, one or more of these components can optionally be 

mounted or associated separately from the vehicle 100. For 

example, data storage 114 can exist, in part or in full, separate 

from the vehicle 100, such as in a cloud-based server, for 

example. Thus, one or more of the functional elements of the 

vehicle 100 can be implemented in the form of device ele 

ments located separately or together. The functional device 

elements that make up vehicle 100 can generally be commu 

nicatively coupled together in a wired and/or wireless fash 1011. 

FIG.2 shows an example vehicle 200 that can include some or all of the functions described in connection with vehicle 

100 in reference to FIG.1. Although vehicle 200 is illustrated 

in FIG. 2 as a four-wheel sedan-type car for illustrative pur 

poses, the present disclosure is not so limited. For instance, 

the vehicle 200 can represent a truck, a van, a semi-trailer 

truck, a motorcycle, a golf cart, an off-road vehicle, or a farm 

vehicle, etc. 

The example vehicle 200 includes a sensor unit 202, a 

wireless communication system 204, a RADAR unit 206, a 

laser rangefinder unit 208, and a camera 210. Furthermore, 

the example vehicle 200 can include any of the components 

described in connection with vehicle 100 of FIG. 1. The 

RADAR unit 206 and/or laser rangefinder unit 208 can 

actively scan the surrounding environment for the presence of 

potential obstacles and can be similar to the RADAR unit 126 

and/or laser rangefinder/LIDAR unit 128 in the vehicle 100. 

The sensor unit 202 is mounted atop the vehicle 200 and 

includes one or more sensors configured to detect information 

about an environment surrounding the vehicle 200, and out 

put indications of the information. For example, sensor unit 

202 can include any combination of cameras, RADARs, 

LIDARs, range finders, and acoustic sensors. The sensor unit 

202 can include one or more movable mounts that could be 

operable to adjust the orientation of one or more sensors in the 

sensor unit 202. In one embodiment, the movable mount 

could include a rotating platform that could scan sensors so as 

to obtain information from each direction around the vehicle 

200. In anotherembodiment, the movable mount of the sensor 

unit 202 could be moveable in a scanning fashion within a 

particular range of angles and/or azimuths. The sensor unit 

202 could be mounted atop the roof of a car, for instance, however other mounting locations are possible. Additionally, 

the sensors of sensor unit 202 could be distributed in different 

locations and need not be collocated in a single location. 

Some possible sensor types and mounting locations include 

RADAR unit 206 and laser rangefinder unit 208. Further 

more, each sensor of sensor unit 202 can be configured to be 

moved or scanned independently of other sensors of sensor 

unit 202. 

In an example configuration, one or more RADAR scan 

ners (e.g., the RADAR unit 206) can be located near the front 

of the vehicle 200, to actively scan the region in front of the 

car 200 for the presence of radio-reflective objects. A 

RADAR scanner can be situated, for example, in a location 

suitable to illuminate a region including a forward-moving 

path of the vehicle 200 without occlusion by other features of 

the vehicle 200. For example, a RADAR scanner can be 

situated to be embedded and/or mounted in or near the front 

bumper, front headlights, cowl, and/or hood, etc. Further 

more, one or more additional RADAR scanning devices can 

be located to actively scan the side and/or rear of the vehicle 

200 for the presence of radio-reflective objects, such as by 

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including such devices in or near the rear bumper, side panels, 

rocker panels, and/or undercarriage, etc. 

The wireless communication system 204 could be located 

on a roof of the vehicle 200 as depicted in FIG. 2. Alterna 

tively, the wireless communication system 204 could be 

located, fully or in part, elsewhere. The wireless communi 

cation system 204 may include wireless transmitters and 

receivers that could be configured to communicate with 

devices external or internal to the vehicle 200. Specifically, 

the wireless communication system 204 could include trans 

ceivers configured to communicate with other vehicles and/or 

computing devices, for instance, in a vehicular communica 

tion system or a roadway station. Examples of such vehicular 

communication systems include dedicated short range com 

munications (DSRC), radio frequency identification (RFID), 

and other proposed communication standards directed 

towards intelligent transport systems. 

The camera 210 can be a photo-sensitive instrument, such 

as a still camera, a video camera, etc., that is configured to 

capture a plurality of images of the environment of the vehicle 

200. To this end, the camera 210 can be configured to detect 

visible light, and can additionally or alternatively be config 

ured to detect light from other portions of the spectrum, such 

as infrared or ultraviolet light. The camera 210 can be a 

two-dimensional detector, and can optionally have a three 

dimensional spatial range of sensitivity. In some embodi 

ments, the camera 210 can include, for example, a range detector configured to generate a two-dimensional image 

indicating distance from the camera 210 to a number of points 

in the environment. To this end, the camera 210 may use one 

or more range detecting techniques. 

For example, the camera 210 can provide range informa 

tion by using a structured light technique in which the vehicle 

200 illuminates an object in the environment with a predeter mined light pattern, such as a grid or checkerboard pattern 

and uses the camera 210 to detect a reflection of the prede termined light pattern from environmental surroundings. 

Based on distortions in the reflected light pattern, the vehicle 

200 can determine the distance to the points on the object. The 

predetermined light pattern may comprise infrared light, or 

radiation at other suitable wavelengths for such measure 

mentS. 

The camera 210 can be mounted inside a front windshield 

of the vehicle 200. Specifically, the camera 210 can be situ 

ated to capture images from a forward-looking view with 

respect to the orientation of the vehicle 200. Other mounting locations and viewing angles of camera 210 can also be used, 

either inside or outside the vehicle 200. 

The camera 210 can have associated optics operable to 

provide an adjustable field of view. Further, the camera 210 

can be mounted to vehicle 200 with a movable mount to vary 

a pointing angle of the camera 210, such as via a pan/tilt 

mechanism. 

III. Example LIDAR Device 

An example light detection and ranging (LIDAR) device 

operates to estimate positions of reflective objects surround 

ing the device by illuminating its surrounding environment 

with pulses of light and measuring the reflected signals. An 

example LIDAR device may include a light source, beam 

steering optics, a light sensor, and a controller. The light 

source may emit pulses of light toward the beam-steering 

optics, which directs the pulses of light across a scanning 

zone. Reflective features in the scanning zone reflect the 

emitted pulses of light and the reflected light signals can be 

detected by the light sensor. The controller can regulate the 

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US 9,368,936 B1 

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operation of the light source and beam-steering optics to scan 

pulses of light across the scanning zone. The controller can 

also be configured to estimate positions of reflective features 

in the scanning zone based on the reflected signals detected by 

the light sensor. For example, the controller can measure the 

time delay between emission of a pulse of light and reception 

of a reflected light signal and determine the distance to the 

reflective feature based on the time of flight of a round trip to 

the reflective feature. In addition, the controller may use the 

orientation of the beam-steering optics at the time the pulse of 

light is emitted to estimate a direction toward the reflective 

feature. The estimated direction and estimated distance can 

then be combined to estimate a three-dimensional position of 

the reflective object relative to the LIDAR device. 

FIG. 3A provides an example depiction of a LIDAR device 

302 including beam steering optics 304. A laser beam 306 is 

directed to the beam steering optics 304. In the example 

illustrated in FIG. 3A, the beam steering optics 304 is a 

rotating angled mirror that directs the laser beam 306 to 

sweep across a scanning zone. The beam steering optics 304 

may include a combination of lenses, mirrors, and/or aper 

tures configured to direct the laser beam to sweep across a 

scanning zone, and are interchangeably described as the rotat 

ing angled mirror 304. The rotating angled mirror 304 rotates 

about an axis substantially parallel, and roughly in line with, 

the initial downward path of the laser beam 306. The rotating 

angled mirror 304 rotates in the direction indicated by the 

reference arrow 308 in FIG. 3A. 

Although rangefinder 302 is depicted as having an approxi 

mately 180 degree range of rotation for the scanning zone of 

the laser beam 306 via the rotating angled mirror 304, this is 

for purposes of example and explanation only. LIDAR 302 

can be configured to have viewing angles (e.g., angular range 

of available orientations during each sweep), including view 

ing angles up to and including 360 degrees. Further, although 

LIDAR 302 is depicted with the single laser beam 306 and a 

single mirror 304, this is for purposes of example and expla 

nation only, LIDAR 302 can include multiple laser beams 

operating simultaneously or sequentially to provide greater 

sampling coverage of the surrounding environment. The 

LIDAR 302 also includes, or works in concert with, addi 

tional optical sensors (e.g., a photo-detector, not shown) con 

figured to detect the reflection of laser beam 306 from fea 

tures/objects in the surrounding environment with sufficient 

temporal sensitivity to determine distances to the reflective 

features. For example, with reference to the vehicle 200 in 

FIG. 2, such optical sensors can optionally be co-located with 

the top-mounted sensors 204 on the autonomous vehicle 200. 

FIG. 3B symbolically illustrates the LIDAR device 302 

scanning across an obstacle-filled environmental scene. The 

example vehicular environment depicted in FIG. 3B includes 

a car 310 and a tree 312. In operation, LIDAR 302 rotates 

according to motion reference arrow 308. While rotating, the 

LIDAR 302 regularly (e.g., periodically) emits laser pulses, 

such as the laser pulse 306. Objects in the surrounding envi 

ronment, such as vehicle 310 and tree 312, reflect the emitted 

pulses and the resulting reflected signals are then received by suitable sensors. Precisely time-stamping the receipt of the 

reflected signals allows for associating each reflected signal 

(if any is received at all) with the most recently emitted laser 

pulse, and measuring the time delay between emission of the 

laser pulse and reception of the reflected light. The time delay 

provides an estimate of the distance to the reflective feature by scaling according to the speed of light in the intervening 

atmosphere. Combining the distance information for each 

reflected signal with the orientation of the LIDAR device 302 

for the respective pulse emission allows for determining a 

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position of the reflective feature in three-dimensions. For 

illustrative purposes, the environmental scene in FIG. 3B is 

described in the two-dimensional x-y plane in connection 

with a single sweep of the LIDAR device 302 that estimates 

positions to a series of points located in the x-y plane. How 

ever, it is noted that a more complete three-dimensional sam 

pling is provided by either adjusting the beam steering optics 

304 to direct the laserbeam 306 up or down from the x-y plane 

on its next sweep of the scene or by providing additional 

lasers and associated beam steering optics dedicated to sam 

pling point locations in planes above and below the x-y plane 

shown in FIG. 3B, or combinations of these techniques. 

FIG. 3C symbolically illustrates a point cloud correspond 

ing to the obstacle-filled environmental scene of FIG. 3B. 

Spatial-point data (represented by stars) are shown from a 

ground-plane (or aerial) perspective. Even though the indi 

vidual points are not equally spatially distributed throughout 

the sampled environment, adjacent sampled points are 

roughly equally angularly spaced with respect to the LIDAR 

device 302. A cluster of points referred to herein as car spatial data 314 corresponds to measured points on the surface of the 

car 310 with a line of sight to the LIDAR device 302. Simi 

larly, a cluster of points referred to herein as tree spatial data 

316 corresponds to measured points on the surface of the tree 

312 visible from the LIDAR device 302. The absence of 

points between the car spatial data 314 and the tree spatial 

data 316 indicates an absence of reflective features along the 

sampled line of sight paths in the plane illustrated. 

Each point in the example point cloud illustrated symboli 

cally in FIG. 3C can be referenced by an azimuth angle p (e.g. 

orientation of the LIDAR device 302 while emitting the pulse corresponding to the point, which is determined by the ori 

entation of the rotating angled mirror 304) and a line-of-sight 

(LOS) distance (e.g., the distance indicated by the time delay between pulse emission and reflected light reception). For 

emitted pulses that do not receive a reflected signal, the LOS 

distance can optionally be set to the maximum distance sen 

sitivity of the LIDAR device 302. The maximum distance 

sensitivity can be determined according to the maximum time 

delay the associated optical sensors wait for a return reflected 

signal following each pulse emission, which can itself be set 

according to the anticipated signal strength of a reflected 

signal at a particular distance given ambient lighting condi 

tions, intensity of the emitted pulse, predicted reflectivity of 

environmental features, etc. In some examples, the maximum 

distance can be approximately 60 meters, 80 meters, 100 

meters, or 150 meters, but other examples are possible for 

particular configurations of the LIDAR device 302 and asso 

ciated optical sensors. 

In some embodiments, the sensor fusion algorithm 138, 

computer vision system 140, and/or computer system 112, 

can interpret the car spatial data 314 alone and/or in combi 

nation with additional sensor-indicated information and/or 

memory-based pattern-matching point clouds and/or base 

line maps of the environment to categorize or identify the 

group of points 314 as corresponding to the car 310. Simi 

larly, the tree spatial data 316 can identified as corresponding 

to the tree 310 in accordance with a suitable object-detection 

technique. As described further herein, some embodiments of 

the present disclosure provide for identifying a region of the 

point cloud for study with enhanced resolution scanning tech 

nique on the basis of the already-sampled spatial-points. 

FIG. 4A symbolically illustrates a LIDAR device 302 scan 

ning across an example obstacle-filled environmental scene. 

The LIDAR device 302 scans the laser beam 306 across the 

environmental scene via its beam steering optics 304 while its 

laser light source pulses, such that successive pulses are emit 

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US 9,368,936 B1 

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ted with an angular separation 01. Successive pulses are emit 

ted periodically with a temporal separation to. For illustrative 

purposes, the angular separation 01 between adjacent, succes 

sively emitted pulses is exaggerated in FIG. 4A to allow 

individual pulses to be represented in the drawing. As a result 

of the rotation of the beam steering optics in the LIDAR 

device 302, temporally separated pulses (e.g., pulses emitted 

at times separated by the time ti) are directed in respective 

angular orientations separated by the amount of rotation of 

the beam steering optics during the interval to, (e.g., the angle 

01). A controller 430 is arranged to receive signals from the 

LIDAR device 302 and/or associated optical sensors to gen 

erate point cloud data 440 indicative of the 3-D positions of 

reflective features in the environmental scene surrounding the 

LIDAR device 302. 

FIG. 4B is a timing diagram of the transmitted and received 

pulses for the exaggerated symbolic illustration of FIG. 4A. 

The timing diagram symbolically illustrates the transmitted 

pulses (labeled on FIG. 4B as “Tx”) and the corresponding 

received pulses (labeled on FIG. 4B as “Rx”). 

An example operation of the LIDAR device 302 is 

described in connection with FIGS. 4A and 4B. At time Ta, a 

first pulse 410a is emitted from the LIDAR device 302 and 

directed along laser beam path 306a via the beam steering 

optics. As shown in FIG. 4A, the beam path 306a is reflected 

from near the front passenger-side region of the car 310, and 

a first reflected signal 420a is detected at optical signals 

associated with the LIDAR device 302 (e.g., via optical sen 

sors included in the sensorsystem 202 mounted on the vehicle 

200 in FIG. 2). The time delay between the emission of pulse 

410a and reception of the reflected signal 420a is indicated by 

time delay ATa. The time delay ATa and the orientation of the 

LIDAR device 302 at time Ta, i.e., the direction of laser beam 

306a, are combined in the controller 430 to map the 3-D 

position of the reflective point on the front passenger-side 

region of the car 310. 

Next, at time Tb, a second pulse 410b is emitted from the 

LIDAR device 302 and directed along laser beam path 306b. 

Time Tb is temporally separated from time Ta by the interval 

time t1, and the direction of the laser beam path 306b is 

angularly separated from the direction of laser beam path 

306a by angular separation 01, due to the change in orienta 

tion of the beam steering optics in the LIDAR device during 

the interval to. The laser pulse 310b is reflected from near the 

rear passenger-side region of the car 310, and a second 

reflected signal 420b is detected with a relative time delay 

ATb from the emission of the second pulse 410b. As illus 

trated in FIG. 4B, the LIDAR device 302 is generally situated 

behind the car 310, and so the reflective point near the rear 

passenger-side region of the car 310 (responsible for the 

reflected signal 420b) is closer to the LIDAR device 302 than 

the reflective point near the front passenger-side region of the 

car 310 (responsible for the reflected signal 420a). As a result, 

the relative time delay ATb is shorter than the relative time 

delay ATa, corresponding to the difference in roundtrip travel 

time at the speed of light between the LIDAR device 302, and 

the respective reflective points at the front and rear of the car. 

Further, the sensors detecting the reflected signals can 

optionally be sensitive to the intensity of the reflected signals. 

For example, the intensity of the reflected signal 420b can be 

perceptibly greater than the intensity of the reflected signal 

420a, as shown symbolically in FIG. 4B. The controller 430 

maps the 3-D position of the reflective point near the rear 

passenger-side of the car 310 according to the time delay 

value ATb and the orientation of the LIDAR device 310 at 

time Tb, i.e., the direction of laser beam 306b. The intensity of 

the reflected signal can also indicate the reflectance of the 

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reflective point, in combination with the distance to the point 

as indicated by the measured time delay. The reflectance of 

the reflective point can be employed by software and/or hard 

ware implemented modules in the controller 430 to charac 

terize the reflective features in the environment. For example, 

traffic indicators such as lane markers, traffic signs, traffic 

signals, navigational signage, etc., can be indicated in part 

based on having a relatively high reflectance value, such as 

associated with a reflective coating applied to traffic and/or 

navigational signage. In some embodiments, identifying a 

relatively high reflectance feature can provide a prompt to 

undertake a further scan of the high reflectance feature with 

one or more sensors, such as those in the sensing system 104. 

Thus, in one example, a reflected signal indicating a high 

reflectance feature can provide a prompt to image the high 

reflectance feature with a camera to allow for identifying the 

high reflectance feature. In some embodiments where the 

high reflectance feature is a traffic sign, the camera image can 

allow for reading the sign via character recognition and/or 

pattern matching, etc. and then optionally adjusting naviga 

tional instructions based on the sign (e.g., a sign indicating a 

construction zone, pedestrian crosswalk, school zone, etc. 

can prompt the autonomous vehicle to reduce speed). 

At time Tc, following the time Tb by the interval t!, a third 

pulse 410c is emitted from the LIDAR device 302. The third 

pulse 410c is directed along a laser beam path 306c, which is 

approximately angularly separated from the beam path 306b 

by the angle 01. The pulse 410c is reflected from a point near 

the middle of the rear bumper region of the car 310, and a 

resulting reflected signal 420c is detected at the LIDAR 

device 302 (or its associated optical sensors). The controller 

430 combines the relative time delay ATc between the emis 

sion of pulse 410c and reception of reflected signal 420c and 

the orientation of the LIDAR device 302 at time Tc, i.e., the 

direction of beam path 306c, to map the 3-D position of the 

reflective point. 

At time Td, following time Tc by the interval ti, a fourth 

pulse 410disemitted from the LIDAR device 302. The fourth 

pulse 410d is directed along a laser beam path 306d, which is 

approximately angularly separated from the beam path 306c 

by the angle 01. The beam path 306d entirely avoids the car 

310, and all other reflective environmental features within a 

maximum distance sensitivity of the LIDAR device 302. As 

discussed above, the maximum distance sensitivity of the 

LIDAR device 302 is determined by the sensitivity of the 

associated optical sensors for detecting reflected signals. The 

maximum relative time delay ATmax corresponds to the 

maximum distance sensitivity of the LIDAR device (i.e., the 

time for light signals to make a round trip of the maximum 

distance). Thus, when the optical sensor associated with the 

LIDAR device 302 does not receive a reflected signal in the 

period ATmax following time Td, the controller 430 deter 

mines that no reflective features are present in the surround 

ing environment along the laser beam path 306d. 

The reflective points on the car 310 corresponding to the 

reflected signals 420a-c form a subset of points included in a 

3-D point cloud map 440 of the environment surrounding the 

LIDAR device 302. In addition, the direction of the laser 

beam 310d is noted in the 3-D point cloud map 440 as being 

absent of reflective features along the line of sight within the 

maximum distance sensitivity of the LIDAR device 302, 

because no reflected signal was received after the duration 

ATmax following the emission of pulse 410d at time Td. The 

points corresponding to laser beam directions 306a-d are 

combined with points spaced throughout the scanning zone 

(e.g., the region scanned by the LIDAR device 302), to create 

a complete 3-D point cloud map, and the results are output as 

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fixed resolution point cloud data 440 for further analysis by object detection systems, pattern recognition systems, com 

puter vision systems, etc. 

IV. Example Laser Diode Firing Circuit 

In order to illuminate a scanning zone with pulses of light, 

a LIDAR device includes one or more light sources that are 

triggered to emit pulses of light. The light sources may 

include light emitting elements such as a laser diode or 

another emissive light source. A laser diode is a semiconduc 

tor device including a p-n junction with an active region in 

which oppositely polarized, energized charge carriers (e.g., 

free electrons and/or holes) recombine while current flows 

through the device across the p-n junction. The recombina 

tion results in emission of light due to a change in energy state 

of the charge carriers. When the active region is heavily populated by such energized pairs (e.g., the active region may 

have a population inversion of energized states), stimulated 

emission across the active region may produce a substantially 

coherent wavefront of light that is then emitted from the laser 

diode. Recombination events, and the resulting light emis 

sion, occur in response to current flowing through the device, 

and so applying a pulse of current to the laser diode results in 

emission of a pulse of light from the laser diode. 

A light pulse with the desired temporal profile can be 

generated by applying a rapidly switched current to a laser 

diode (e.g., a current source that rapidly transitions from near zero current to a current sufficient to cause the laser diode to 

emit light). Circuits configured to convey such currents to 

laser diodes to cause the laser diodes to fire (e.g., emit a pulse 

of light) are referred to herein as laser diode firing circuits. 

One example laser diode firing circuit includes a laser diode 

connected in series with a transistor capable of switching 

large currents over brief transition times. Current through the 

laser diode, and thus emission from the laser diode, can then 

be controlled by operating the transistor. An example circuit 

may switch from near zero current through the laser diode, to 

about 30 amperes, and back to near zero all in a span of about 

1-2 nanoseconds. 

The firing circuits disclosed herein may include a laser 

diode configured to emit a pulse of light with a wavelength in 

the visible spectrum, ultraviolet spectrum, near infrared spec 

trum, and/or infrared spectrum. In one example, the laser 

diode is configured to emit a pulse of light in the infrared 

spectrum with a wavelength of about 905 nanometers. 

FIG. 5A is an example laser diode firing circuit 500. The 

firing circuit 500 includes a capacitor 516 connected to a laser 

diode 518 and a transistor 520. In some examples, the capaci 

tor 516, laser diode 518, and transistor 520 can be connected 

in series. The capacitor 516 is connected to both a charging path (e.g., FIG. 5C) and a discharge path (e.g., FIG. 5D). The 

capacitor 516 has one terminal coupled to a voltage source 

502 (e.g., through inductor 510 and diode 514) and an anode 

of the laser diode 518. The other terminal of the capacitor 516 

can be connected to ground, or to another reference voltage sufficient to allow the capacitor 516 to be charged by the 

voltage source 502, through the charging path. The cathode of 

the laser diode 518 is connected to one terminal of the tran 

sistor 520, which has another terminal connected to ground (which may also connect to the capacitor 516). The transistor 

520 acts as a switch to selectively allow current to flow 

through the laser diode 518 according to a control signal from 

a gate driver 530. 

A discharge diode 522 is coupled across the laser diode 

518. The discharge diode 522 is configured to allow an inter 

nal capacitance of the laser diode 518 to discharge when the 

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transistor 520 is turned off. For example, the discharge diode 

522 may have an anode and a cathode; the anode can be 

connected to the cathode of the laser diode 518; the cathode 

can be connected to the anode of the laser diode 518. As such, 

charge remaining on an internal capacitance of the laser diode 

518 following a firing operation causes the discharge diode 

522 to be forward biased, and the internal capacitance is 

allowed to discharge through the discharge diode 522. Fol 

lowing such discharge, the discharge diode 522 is no longer 

forward biased. 

To initiate firing, the gate driver 530 causes the transistor 

520 to turn on by adjusting the voltage applied to the gate 

terminal 520g, which allows current to flow to the drain 

terminal 520d through the laser diode 518. The capacitor 516 

discharges through a discharge path that includes the laser 

diode 518 and the transistor 520. The discharge current from 

the capacitor 516 causes the laser diode 518 to emit a pulse of 

light. The transistor 520 is turned back off by adjusting the 

voltage applied to the gate terminal 520g via the gate driver 

530. Upon turning off the transistor 520, the laser diode 518 ceases emission. 

The inductor 510 is connected between the voltage source 

502 and the anode of the diode 514. For convenience in the 

description and the drawings a point connecting the inductor 

510 and the anode of the diode 514 is labeled node A512. The 

cathode of the diode 514 is connected to the capacitor 516 and 

also to the anode of the laser diode 518. The capacitor’s 516 

charging path, which couples the capacitor 516 and the volt 

age source 502, includes the inductor 510 and the diode 514. 

During charging, the voltage across the inductor 510 varies in 

accordance with changes in the inductor current, and the 

diode 514 regulates the voltage applied to the capacitor 516 

depending on whether the diode 514 is forward biased or 

reverse biased. The diode 514 is forward biased (and thus 

allows the capacitor 516 to charge) when the voltage at node 

A 512 is greater than the voltage on the capacitor 516. The 

diode 514 is reverse based (and thus prevents the capacitor 

516 from charging) when the voltage at node A 512 is less 

than the voltage on the capacitor 516. Voltage variations at 

node A512 due to changes in current through the inductor 510 

may result in a voltage being applied to the capacitor 516 that 

exceeds the voltage of the voltage source 502. 

For example, the voltage source 502 connected to one side 

of the inductor 510 may have a voltage V1. The voltage on the 

other side of the inductor 510, at node A 512, varies due to 

induced voltage across the inductor 510 as the inductor cur 

rent changes. In particular, during a charging operation to 

recharge the capacitor 516, the current through the inductor 

510 briefly increases and then decreases. As the inductor 

current increases, the voltage at node A512 may decrease to 

a voltage less than V1. As the inductor current changes from 

increasing to decreasing, the voltage at node A 512 may increase to a higher level voltage (e.g., a voltage greater than 

V1), before decreasing. The transient higher level voltage at 

node A512 (e.g., -VI) is applied to the capacitor 516, which 

charges as the voltage at node A 512 decreases due to the 

inductor current continuing to decrease. The capacitor 516 

charges until the voltage on the capacitor 516 approximately 

equal the voltage at node A 512. Upon the voltage at node A 

512 approximately equaling the voltage on the capacitor 516, 

the diode 512 is reverse biased. Upon the diode 514 being 

reverse biased, the current through the inductor 510 goes to 

zero and the voltage across the inductor 510 settles at zero, 

which sets node A to the voltage of the voltage source 502 

(e.g., the voltage VI), but the capacitor 516 may hold a higher 

voltage (e.g., about 2 V1). 

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US 9,368,936 B1 

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The transistor 520 may be a field effect transistor (FET) with a channel region including Gallium nitride (i.e., the 

transistor 520 may be a GaNFET). However, alternative FETs 

may be employed, such as FETs configured to rapidly switch 

large current values, such as transistors with carrier mobility 

(e.g., high electron mobility transistors (HEMTs)). In FIG. 

5A, the transistor 520 is illustrated as a field effect transistor 

(FET); although it is understood the firing circuit 500 may be 

implemented with alternative transistors to selectively switch 

current through the laser diode, such as a bipolar junction 

transistor, etc. Further, while the transistor 520 is illustrated 

as an n-type transistor, a complementary circuit may be 

formed using a p-type transistor. 

FIG. 5B is a timing diagram of a pulse emission operation 

of the example laser diode firing circuit 500 of FIG. 5A. 

Shown in FIG.5B is the gate voltage V., ofthe FET520, the 

drain current Ioran, of the FET 520, the luminosity Loo?e of 

the laser diode 518, the voltage V., of the capacitor 516, the 

voltage.V., at node A512, the current Inly through the inductor 

510, and the light signal received Rx from a reflected portion 

of the emitted pulse. For convenience in the description, the 

time at which an initiating signal is applied to the transistor 

520 and a pulse is emitted is referred to herein and in the 

drawings as the turn on time Toy. Initially, the capacitor 516 is charged to a voltage set in part 

by the voltage source 502. The charge on the capacitor 516 

may exceed the voltage VI of the voltage source 502 due to 

transient variations at node A 512 caused by changes in cur 

rent through the inductor 510. A voltage that exceeds Vi may 

be held on the capacitor 516 after the diode 514 is reverse 

biased to terminate a charging operation. For example, the 

capacitor 516 may be initially charged to a voltage level of 

about 2 V1. At the turn on time Toy, an initiating signal is 

applied to the transistor 520 from the gate driver 530. The 

initiating signal can be a gate voltage Vaan, that transitions 

from a low level to a high level so as turn on the transistor 520. 

The transistor 520 turns on and the drain current Ioran, tran 

sitions from a current near zero to a current sufficient to drive 

the laser diode 518. The laser diode 518 emits a pulse of light, 

as indicated by the luminosity Looe. As the drain current 

I,2,..., flows through the laser diode 518, the capacitor 516 

discharges to source current to the laser diode 518. In some 

examples, during pulse emission, the capacitor 516 and the 

parasitic capacitance of the laser diode 518 can combine to 

form a resonant LC tank circuit, which is heavily damped. Discharging the capacitor 516 thus transfers the electrical 

energy charged on the capacitor 516 to the laser diode 518, 

where energy is consumed by current flowing in the laser 

diode to produce light. Upon completion of a single half 

cycle of the damped LC oscillation, there may be almost no 

energy left to continue to drive current through the laser diode 

518, and remaining voltage, if any, can return to the capacitor 

516 via the diode 522 connected in parallel across the laser 

diode 518. 

In practice then, the energy stored on the capacitor 516 may 

be consumed, and the laser diode 518 may turn off (at time 

Torp), following a single half-cycle of the resonant LC cir 

cuit formed by the capacitor 516 and the parasitic inductance 

of the inductor 518. The pulse duration Atoy may be about 20 

nanoseconds in some examples. In some cases (and as shown 

in FIG. 5B), the laser diode 518 may cease emitting light prior 

to turning off the transistor 520 (e.g., by adjusting the gate voltage Vaale). Although, in some examples, and depending 

on the values of the capacitor 516 and the parasitic inductance 

of the laser diode 518, the pulse duration Atoy may continue 

until the transistor 520 turns off. Thus, in some examples, the 

transistor 520 can be turned off by adjusting the gate voltage 

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Va., to a level sufficient to turn off the transistor 520, which 

terminates current flowing through the laser diode 518. 

The charging cycle is initiated in response to the transistor 

520 firing, which discharges the capacitor 516. Upon the 

capacitor voltage Vc, discharging to a voltage level suffi 

cient to forward bias the diode 514, at time T1, current begins flowing through the inductor 510 (as indicated by In, in FIG. 

5B). In FIG. 5B, time T is shown during the interval Atoy (i.e., before Torp), although in some implementations the 

diode 514 may not begin conducting current until the transis 

tor 520 has turned off (i.e., after Torp). The increase in 

inductor current Inly causes the voltage at node A 512 to 

decrease in proportion to the time derivative of the inductor 

current Ino, because changes in the inductor current In, 

induce a voltage in the inductor 510 that opposes the direction 

of any current change. The voltage at node A512, and thus the 

increasing inductor current Ino, are prevented from changing 

so rapidly as to reverse bias the diode 514. 

For example, starting at time T1, the voltage at node A512 

may decrease to a voltage level less than VI (as indicated by 

V., in FIG. 5B). At time Torp, current ceases flowing through 

the laser diode 518, and the diode 514 connects the inductor 

510 and the capacitor 516, which form a resonant LC tank 

circuit. The current from the inductor 510 charges the capaci 

tor 516, in a sinusoidal oscillatory fashion. At one quarter of 

the oscillation period, the inductor current Ino, reaches a 

maximum, and begins to decrease. At that point, the resonant 

LC circuit divides its stored energy with about half in the 

capacitor 516 and about half in the inductor 510. Continuing 

with the sinusoidal oscillation, current continues to flow to 

the capacitor 516, until the mid-point of the oscillation cycle, 

at time T2, at which point the current reaches zero and the 

capacitor 516 stores substantially all of the energy that had 

been divided between the inductor 510 and the capacitor 516. 

Before the energy stored on the capacitor 516 can transfer 

back to the inductor 510, the diode 514 becomes reverse 

biased, which causes the capacitor 516 to remain charged with approximately twice the supply voltage VI. For 

example, the supply voltage VI may be about 20 volts and the 

voltage stored on the capacitor 516 following charging may 

be about 40 volts. 

The oscillatory LC circuit described herein efficiently 

transfers energy between the inductor 510 and the capacitor 

516 during the recharge interval Atco, logo of the circuit 500, 

but the present disclosure is not limited to the use of resonant 

LC circuits. Generally, the capacitor 516 may be charged to a 

greater value than the supply voltage V1 based on transient 

voltages on the inductor 510 caused by changes in current 

following firing of the circuit 500. Current through the induc 

tor 510 may change from increasing (e.g., between times T1 

and Toro) to decreasing (e.g., following time Toro), and the 

sudden change in current through the inductor 510 can induce 

a rapid increase in voltage at node A512. For example, at time 

Torp, the voltage at node A 512 can go to a voltage greater 

than V1, and may be several times V1. The precise voltage applied to node A 512 depends on the time derivative of the 

inductor current when transitioning from an increasing cur 

rent to a decreasing current, but may be several times the 

voltage of the voltage source 502(e.g., just after Torr, V.1-X 

V1, with X->2). Following the increase in the voltage at node A 512, the 

current through the inductor 510 can continue to decrease as 

the capacitor 516 becomes charged, and the voltage at node A 

512 can therefore decrease. The capacitor 516 may continue 

charging until the diode 514 becomes reverse biased, at time 

T2 in FIG. 5B. While charging, between times Torr, and T2, 

the voltage Vox, across the capacitor 516 increases and the 

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The current paths shown in FIGS. 5C and 5D illustrate two 

operation modes of the firing circuit 500: a charging mode 

(FIG. 5C) and an emission mode (FIG. 5D). In some 

examples, the firing circuit 500 switches between the charg— 

ing mode and the emission mode based solely on whether the 

transistor 520 is turned on or turned off. In the charging mode, 

the transistor 520 is turned off and current flows from the 

voltage source 502 to the capacitor 516 via the charging path 

(e.g., the current path including the inductor 510 and diode 

514) until the diode 514 is reverse biased. In the emission 

mode, the transistor 520 is turned on and current flows from 

the charged capacitor 516 through the laser diode 518 and the 

transistor 520 until the transistor 520 is turned off again. 

FIG. 5E illustrates an arrangement 540 in which multiple 

laser diode firing circuits 550a-n are connected to be charged 

via a single inductor 544. The inductor 544 has one terminal 

connected to a voltage source 542 (labeled V1), and a second 

terminal that connects to the firing circuits 550a-n so as to be 

included in a charging path of the respective firing circuits 

550a-n. Each of the firing circuits 550a-n can be similar to the 

firing circuit 500 described above in connection with FIGS. 

5A-5D. For example, the first firing circuit 550a includes a 

capacitor 558a connected to a laser diode 554a and a transis 

tor 556a. The capacitor 558a, laser diode 554a, and transistor 

556a can be connected in series such that turning on the 

transistor 556a causes the capacitor 558a to discharge 

through the laser diode 554a, which causes the laser diode to 

emit a pulse of light. A discharge diode 560a can be connected 

across the laser diode 554a to discharge the internal capaci 

tance of the laser diode 554a. The first firing circuit 550a also 

includes a diode 552a that connects the firing circuit 550a to 

the inductor 544 and the voltage source 542. The diode 552a 

can function similarly to the diode 514 described above in 

connection with FIGS. 5A-5D. For example, the diode 552a 

can become forward biased and draw current through the 

inductor 544 to charge the capacitor 558a following a firing 

event (and associated discharge of the capacitor 558a). Upon 

the capacitor 558a being recharged, the diode 552a can then 

become reverse biased and thereby cause the capacitor 558a 

to maintain its stored charge. 

The second firing circuit 550b is similarly connected to the 

inductor 544 via a diode 552b and includes a capacitor 558b, 

laser diode 554b, transistor 556b, discharge diode 560b. One 

or more additional firing circuits can also be similarly con 

nected in parallel with the inductor 544 to the “nth” firing 

circuit 550m. In some cases, the arrangement 540 includes 16 

individual laser diode firing circuits 550a-n connected to the 

single inductor 544. 

Similar to the operation of the firing circuit described 

above in connection with FIGS. 5A-5D, the firing circuits 

550a-n are turned on and off by operation of their respective 

transistors 556a-n, which are controlled by the respective 

gate voltages applied by the gate driver 548. For example, the 

gate driver 548 can be used to turn on all of the firing circuits 

550a-n at substantially the same time by setting the gate voltage high (or otherwise manipulating the gate voltage to 

turn the respective transistors on). The discharging capacitors 

558a-n cause current to begin flowing through the inductor 

544. Upon the transistors 556a-n in the firing circuits 550a-n 

being turned back off (by the gate driver 548), the voltage 

across the inductor rises to begin recharging the capacitors 

558a-n in the firing circuits 550a-n until the respective diodes 

552a-n are reverse biased, at which point recharging termi 

nateS. 

Additionally, the firing circuit arrangement 540 shown in 

FIG. 5E also illustrates a snubber circuit 546 connected 

across the inductor 544. The snubber circuit 546 provides an 

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alternative current path during rapid current switching 

through the inductor 544 to regulate and/or smooth the result 

ing variations across the inductor 544. The snubber circuit 

546 may include a resistor and/or capacitor connected in 

parallel across the inductor 544, for example. The snubber 

circuit 546 may additionally or alternatively include one or 

more diodes and/or solid state components configured to limit 

and/or regulate the maximum voltage and/or maximum volt 

age rate across the inductor 544. Thus, the snubber circuit 546 

may operate actively and/or passively to modify transient 

voltage variations across the inductor 544. In some cases, the 

snubber circuit 544 may be used to prevent transient voltage variations from exceeding a predetermined threshold and 

thereby prevent damage to circuit components. While illus 

trated in FIG. 5E, the snubber circuit 544 may (or may not) be 

included in particular implementations of the arrangement 

540 shown in FIG. 5E. Moreover, a snubber circuit may (or 

may not) be included across the charging path inductor in a 

particular implementation of the single firing circuit arrange 

ment described above in connection with FIG. 5A-5D. 

V. Example Operations 

FIGS. 6A through 6C present flowcharts describing pro 

cesses employed separately or in combination in some 

embodiments of the present disclosure. The methods and 

processes described herein are generally described by way of 

example as being carried out by an autonomous vehicle, such 

as the autonomous vehicles 100, 200 described above in 

connection with FIGS. 1 and 2. For example, the processes 

described herein can be carried out by the LIDAR sensor 128 

mounted to an autonomous vehicle in communication with 

the computer system 112, sensor fusion algorithm module 

138, and/or computer vision system 140. 

Furthermore, it is noted that the functionality described in 

connection with the flowcharts described hereincan be imple mented as special-function and/or configured general-func 

tion hardware modules, portions of program code executed 

by a processor (e.g., the processor 113 in the computer system 

112) for achieving specific logical functions, determinations, 

and/or steps described in connection with the flowcharts. 

Where used, program code can be stored on any type of 

computer readable medium (e.g., computer readable storage 

medium or non-transitory media, such as data storage 114 

described above with respect to computer system 112), for 

example, such as a storage device including a disk or hard 

drive. In addition, each block of the flowcharts can represent circuitry that is wired to perform the specific logical functions 

in the process. Unless specifically indicated, functions in the 

flowcharts can be executed out of order from that shown or 

discussed, including substantially concurrent execution of 

separately described functions, or even in reverse order in 

some examples, depending on the functionality involved, so 

long as the overall functionality of the described method is 

maintained. Furthermore, similar combinations of hardware 

and/or software elements can be employed to implement the 

methods described in connection with other flowcharts pro vided in the present disclosure. 

FIG. 6A is a flowchart of an example process 600 for 

operating a laser diode firing circuit. The laser diode firing 

circuit may be the laser diode firing circuit 500 described 

above in connection with FIG. 5. The laser diode firing circuit 

may therefore include a capacitor connected to a charging 

path and a discharge path. The discharge path can include a 

laser diode and a transistor, and the charging path can include 

an inductor and a diode. At block 602, the transistor is turned 

off, which causes the capacitor to charge via the charging 

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path. The current through the charging path can flow through 

the inductor and the diode. As charge builds on the capacitor, 

the current through charging path (and the inductor) 

decreases. The decrease in current through the inductor 

causes the inductor to discharge energy stored in its magnetic 

field. For example, the energy stored in the magnetic field of 

the inductor may transition from a higher energy level to a 

lower energy level in response to the transistor being turned 

off. At block 604, the transistor can be turned on, which 

causes the capacitor to discharge via the discharge path. The 

current through the discharge path can flow through the laser 

diode and the transistor, which causes the laser diode to emit 

a pulse of light. The voltage stored on the capacitor can 

discharge until the diode is forward biased, which causes the 

current through the charging path (and the inductor) to 

increase. The increase in current through the inductor causes 

the inductor to charge energy stored in its magnetic field. For 

example, the energy stored in the magnetic field of the induc 

tormay transition from a lowerenergy level to a higher energy 

level in response to the transistor being turned on. 

In some embodiments, the operation of the transistor in 

blocks 602 and 604 provides for operation of a laser diode 

firing circuit to emit pulses of light and recharge by manipu 

lating only a single transistor. In particular, turning the tran 

sistor on (block 604) can cause the circuit to both emit a pulse of light (by discharging the capacitor through the laser diode) 

and initiate a recharge cycle (by the voltage on the capacitor 

discharging to a level sufficient to forward bias the diode in 

the charging path). The recharge cycle is then terminated in 

response to turning off the transistor (block 602), which 

directs the current conveyed via the charging path to the 

capacitor (rather than through the laser diode). 

FIG. 6B is a flowchart of an example process 620 for 

operating a light detection and ranging (LIDAR) device. The 

LIDAR device includes a light source having a laser diode 

firing circuit similar to the firing circuit 500 described above 

in connection with FIG. 5. For example, the laser diode firing circuit may include a laser diode activated by current through 

a discharge path of a capacitor. A transistor in the discharge pathis configured to control such discharge events by turning 

on and turning off. The capacitoris also connected to a charg 

ing path that includes an inductor and a diode. The transistor 

may be, for example, a Gallium nitride field effect transistor 

(GaNFET). At block 622, the GaNFET is turned off to 

thereby cause the capacitor to charge (via the charging path) 

and the inductor (in the charging path) to decrease its stored 

energy. The inductor can release stored energy as current 

through the inductor decreases. At block 624, the GaNFET is 

turned on to thereby cause the capacitor to discharge (via the 

discharge path), which causes the laser diode to emit a pulse 

of light. The inductor charges to an increased stored energy 

level due to increasing current through the inductor, which 

occurs once the diode is forward biased. At block 626, the 

transmission time of the emitted pulse (e.g., the pulse emis 

sion time) is determined. The pulse emission time may be 

determined based on the time at which the transistor is turned 

on to initiate the discharge current and/or based on the time an 

induced voltage is detected in a conductive feedback loop configured to react to changes in the discharge current path. 

At block 628, a reflected light pulse is received. The reflected 

light pulse can include at least a portion of the light pulse 

emitted in block 624 that is reflected from a reflective object in an environment surrounding the LIDAR device. At block 

630, a reception time of the reflected light pulse is deter 

mined. At block 632, a distance to the reflective object is 

determined based on both the time of reception determined in 

block 630 of the reflected light signal and the transmission 

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time determined in block 624. For example, the distance can 

be determined based on computing the round trip travel time 

to the reflective object from the difference of the reception 

time and emission time, multiplying by the speed of light in 

the surrounding environment and dividing by 2. At block 634, 

the autonomous vehicle is navigated based at least in part on 

the determined distance to the reflective object. In some 

examples, one or more of the control systems 106 of the 

autonomous vehicle 100 described in connection with FIG. 1 

may control the autonomous vehicle to avoid obstacles (e.g., the reflective object), navigate toward a predetermined desti 

nation, etc. 

FIG. 6G is a flowchart of another example process 640 for 

operating a laser diode firing circuit. The laser diode firing 

circuit may be similar to the firing circuit 500 described above 

in connection with FIG. 5. For example, the laser diode firing 

circuit may include a laser diode activated by current through 

a discharge path of a capacitor. A transistor in the discharge 

pathis configured to control such discharge events by turning 

on and turning off. The capacitoris also connected to a charg 

ing path that includes an inductor and a diode. The transistor 

may be, for example, a Gallium nitride field effect transistor 

(GaNFET). At block 642, the GaNFET is turned on. At block 

644, the capacitor discharges through the discharge path. At 

block 646, a pulse of light is emitted from the laser diode due 

to the discharge current. At block 648, energy stored in the 

inductor included in the charging path is increased. For 

example, upon the diode in the charging path becoming for 

ward biased, the current through the inductor can be 

increased, which causes energy to be stored in the magnetic 

field of the inductor. At block 650, the GaNFET is turned off. 

At block 652, energy stored in the inductor is released as the 

inductor current decreases. At block 654, the capacitor is 

charged from energy released by the inductor. For example, 

following turning off the GaNFET, current through the induc 

tor is conveyed to the capacitor via the charging path. The 

inductor current can transition from increasing (while the 

transistor is on) to decreasing (once the transistor is off and 

current no longer flows through the laser diode). The decrease 

in inductor current causes the inductor to release its stored 

energy, and that released energy can be transferred, at least in 

part, to the capacitor. At block 656, the charging path diode 

can become reverse biased, which causes the capacitor to hold 

charge due to the released energy from the inductor. For 

example, while the inductor releases its stored energy, the 

voltage conveyed to the capacitor via the diode can transiently 

exceed the voltage of the voltage source connected to the 

inductor. The capacitor charges until the capacitor voltage approximately equals the voltage applied to the diode, at 

which point the diode is reverse biased. The capacitor holds a 

voltage due in part to the transient voltage while the voltage applied to the diode settles to the voltage of the voltage source 

(e.g., upon the inductor current reaching zero). 

As indicated by the dashed arrow in FIG. 6G, the process 640 can be repeated to cause the firing circuit to repeatedly emit pulses of light, and be recharged immediately following 

each firing event. Moreover, the firing circuit may be operated such that the voltage charged on the capacitor following a 

given firing event is not sufficient to forward bias the diode in 

the charging path. In such an example, the firing circuit is not 

recharged and the firing circuit is re-activated by discharging 

the charge remaining on the capacitor to generate current 

through the laser diode and transistor. If the voltage on the 

capacitor discharges to a level sufficient to forward bias the 

diode in the charging current path following such a second 

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US 9,368,936 B1 

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firing (or third firing, etc.), the firing circuit can then undergo 

the charging mode with the capacitor recharging via the 

charging path. 

FIG. 7 depicts a computer-readable medium configured 

according to an example embodiment. In example embodi 

ments, the example system can include one or more proces 

sors, one or more forms of memory, one or more input 

devices/interfaces, one or more output devices/interfaces, and 

machine-readable instructions that when executed by the one 

or more processors cause the system to carry out the various 

functions, tasks, capabilities, etc., described above, such as 

the processes discussed in connection with FIGS. 6A through 

6C above. 

As noted above, in some embodiments, the disclosed tech 

niques can be implemented by computer program instruc 

tions encoded on a non-transitory computer-readable storage 

media in a machine-readable format, or on other non-transi 

tory media or articles of manufacture (e.g., the instructions 

115 stored on the data storage 114 of the computer system 112 

of vehicle 100). FIG. 7 is a schematic illustrating a conceptual partial view of an example computer program product 700 

that includes a computer program for executing a computer 

process on a computing device, arranged according to at least 

some embodiments presented herein. 

In one embodiment, the example computer program prod 

uct 700 is provided using a signal bearing medium 702. The 

signal bearing medium 702 may include one or more pro 

gramming instructions 704 that, when executed by one or 

more processors may provide functionality or portions of the 

functionality described above with respect to FIGS. 1-6. In 

some examples, the signal bearing medium 702 can be a 

non-transitory computer-readable medium 706, such as, but 

not limited to, a hard disk drive, a Compact Disc (CD), a 

Digital Video Disk (DVD), a digital tape, memory, etc. In 

some implementations, the signal bearing medium 702 can be 

a computer recordable medium 708, such as, but not limited 

to, memory, read/write (R/W) CDs, R/W DVDs, etc. In some 

implementations, the signal bearing medium 702 can be a 

communications medium 710, such as, but not limited to, a 

digital and/or an analog communication medium (e.g., a fiber 

optic cable, a waveguide, a wired communications link, a 

wireless communication link, etc.). Thus, for example, the 

signal bearing medium 702 can be conveyed by a wireless 

form of the communications medium 710. 

The one or more programming instructions 704 can be, for 

example, computer executable and/or logic implemented 

instructions. In some examples, a computing device such as 

the computer system 112 of FIG. 1 is configured to provide 

various operations, functions, or actions in response to the 

programming instructions 704 conveyed to the computer sys 

tem 112 by one or more of the computer readable medium 

706, the computer recordable medium 708, and/or the com 

munications medium 710. 

The non-transitory computer readable medium could also 

be distributed among multiple data storage elements, which 

could be remotely located from each other. The computing 

device that executes some or all of the stored instructions 

could be a vehicle, such as the vehicle 200 illustrated in FIG. 

2. Alternatively, the computing device that executes some or 

all of the stored instructions could be another computing 

device, such as a server. 

While various example aspects and example embodiments 

have been disclosed herein, other aspects and embodiments 

will be apparent to those skilled in the art. The various 

example aspects and example embodiments disclosed herein 

10 

15 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

28 

are for purposes of illustration and are not intended to be 

limiting, with the true scope and spirit being indicated by the 

following claims. 

What is claimed is: 

1. An apparatus, comprising: 

a voltage source; 

an inductor coupled to the voltage source, wherein the 

inductoris configured to store energy in a magnetic field; 

a diode coupled to the voltage source via the inductor; 

a transistor configured to be turned on and turned off by a 

control signal; 

a light emitting element coupled to the transistor; 

a capacitor coupled to a charging path and a discharge path, 

wherein the charging path includes the inductor and the 

diode, and wherein the discharge path includes the tran 

sistor and the light emitting element; 

wherein, responsive to the transistor being turned off, the 

capacitor is configured to charge via the charging path 

such that a voltage across the capacitor increases from a 

lower voltage level to a higher voltage level and the 

inductor is configured to release energy stored in the 

magnetic field such that a current through the inductor 

decreases from a higher current level to a lower current 

level; and 

wherein, responsive to the transistor being turned on, the 

capacitor is configured to discharge through the dis 

charge path such that the light emitting element emits a 

pulse of light and the voltage across the capacitor 

decreases from the higher voltage level to the lower 

voltage level and the inductor is configured to store 

energy in the magnetic field such that the current through 

the inductor increases from the lower current level to the 

higher current level. 

2. The apparatus of claim 1, wherein the lower current level 

is approximately zero. 

3. The apparatus of claim 1, wherein the capacitor is 

charged immediately following emission of a pulse of light 

from the light emitting element. 

4. The apparatus of claim 1, wherein the higher voltage 

level is greater than a voltage of the voltage source, and 

wherein the diode has an anode coupled to the voltage source 

via the inductor and a cathode coupled to the capacitor, such 

that the diode is forward biased when the voltage across the 

capacitor is at the lower voltage level and the diode is reverse 

biased when the voltage across the capacitor is at the higher 

voltage level. 

5. The apparatus of claim 1, wherein the transistor is a 

Gallium nitride field effect transistor (GaNFET). 

6. The apparatus of claim 5, wherein the control signal applies voltage to a gate of the GaNFET to selectively turn the 

GaNFET on and off. 

7. The apparatus of claim 1, wherein the light emitting 

element is a laser diode. 

8. The apparatus of claim 7, further comprising a drain 

diode coupled across the laser diode, wherein the drain diode 

is configured to discharge an internal capacitance of the laser 

diode through the drain diode when the transistor is off. 

9. A method, comprising: 

turning off a transistor, wherein the transistor is coupled to 

a light emitting element, wherein both the transistor and 

the light emitting element are included in a discharge 

path coupled to a capacitor, wherein the capacitoris also 

coupled to a charging path including a diode and an 

inductor, wherein the inductor is configured to store 

energy in a magnetic field, wherein the diode is coupled 

to a voltage source via the inductor, and wherein, 

responsive to the transistor being turned off, the capaci 

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US 9,368,936 B1 

29 

toris configured to charge via the charging path such that 

a voltage across the capacitor increases from a lower 

voltage level to a higher voltage level and the inductoris 

configured to release energy stored in the magnetic field 

such that a current through the inductor decreases from 

a higher current level to a lower current level; and 

turning on the transistor, wherein responsive to the transis 

tor being turned on, the capacitor is configured to dis 

charge through the discharge path such that the light emitting element emits a pulse of light and the voltage 

across the capacitor decreases from the higher voltage 

level to the lower voltage level and the inductor is con 

figured to store energy in the magnetic field such that the 

current through the inductor increases from the lower 

current level to the higher current level. 

10. The method of claim 9, wherein the lower current level 

is approximately zero. 

11. The method of claim 9, wherein the capacitor is 

charged immediately following emission of a pulse of light 

from the light emitting element. 

12. The method of claim 9, wherein the higher voltage level 

is greater than a voltage of the voltage source, and wherein the 

diode has an anode coupled to the voltage source via the 

inductor and a cathode coupled to the capacitor, such that the 

diode is forward biased when the voltage across the capacitor is at the lower voltage level and the diode is reverse biased 

when the voltage across the capacitor is at the higher voltage 

level. 

13. The method of claim 9, wherein the charging of the 

capacitor is carried out in about 500 nanoseconds. 

14. The method of claim 9, wherein the light emitting 

element is a laser diode. 

15. The method of claim 14, further comprising: when the transistor is off, discharging an internal capaci 

tance of the laser diode via a drain diode coupled across 

the laser diode. 

16. The method of claim 9, wherein the transistor com 

prises a Gallium nitride field effect transistor (GaNFET), wherein the GaNFET is turned on and turned off by applying 

a control signal to a gate of the GaNFET. 

17. A light detection and ranging (LIDAR) device compris 

1ng: 

a light source including: 

5 

10 

15 

20 

25 

30 

35 

40 

30 

a voltage source; 

an inductor coupled to the voltage source, wherein the 

inductor is configured to store energy in a magnetic 

field; 

a diode coupled to the voltage source via the inductor; 

a transistor configured to be turned on and turned off by 

a control signal; 

a light emitting element coupled to the transistor; 

a capacitor coupled to a charging path and a discharge 

path, wherein the charging path includes the inductor 

and the diode, and wherein the discharge path 

includes the transistor and the light emitting element; 

wherein, responsive to the transistor being turned off, the capacitor is configured to charge via the charging 

path such that a voltage across the capacitor increases 

from a lower voltage level to a higher voltage level 

and the inductor is configured to release energy stored 

in the magnetic field such that a current through the 

inductor decreases from a higher current level to a 

lower current level; and 

wherein, responsive to the transistor being turned on, the 

capacitor is configured to discharge through the dis 

charge path such that the light emitting element emits 

a pulse of light and the voltage across the capacitor 

decreases from the higher voltage level to the lower 

voltage level and the inductor is configured to store 

energy in the magnetic field such that the current 

through the inductor increases from the lower current 

level to the higher current level; 

a light sensor configured to detect a reflected light signal comprising light from the emitted light pulse reflected 

by a reflective object; and 

a controller configured to determine a distance to the 

reflective object based on the reflected light signal. 

18. The LIDAR device of claim 17, wherein the lower 

current level is approximately zero. 

19. The LIDAR device of claim 17, wherein the capacitor is charged immediately following emission of a pulse of light 

from the light emitting element. 

20. The LIDAR device of claim 17, wherein the transistor 

is a Gallium nitride field effect transistor (GaNFET). 

Case 3:17-cv-00939-WHA Document 1-2 Filed 02/23/17 Page 28 of 28