Systems, devices, and methods for remote sensing

Abstract

Provided is a system, device and method for remote sensing of an environment. A lidar for remote sensing of an environment includes a rotating head that rotates relative to a base. The rotating head includes a series of transmit light emitting diodes that emit pulsed laser light into the environment, and a reflector for reflecting light reflected off of the environment, and onto a light receiving sensor. The base is fixed relative to the rotating head. The base includes the light receiving sensor.

Description

SYSTEMS, DEVICES, AND METHODS FOR REMOTE SENSINGTechnical Field

[0001] The following relates generally to remote sensing of an environment, and more particularly to systems, devices, and methods for light detection and ranging.Introduction

[0002] Lidar is a sensor that may be used to guide mobile robots during science and exploration missions. A popular lidar design for mobile robots, be they wheeled or tracked vehicles, bipedal and quadrupedal robots is a conventional puck lidar. The conventional puck lidar is a hockey-puck shaped lidar that rotates a vertical row (e.g., 16) of laser light emitting diodes (LEDs), creating a low-resolution three dimensional (3D) map of the terrain around it.

[0003] Figures 1A to 1 E illustrate a series of robotic exploration vehicles, each having the conventional puck lidar on the top that is being used for mapping and localization. The conventional puck lidars are popular because they are compact, low- cost and only have one moving part, the rotating head. The rotating head of the conventional puck lidar creates a single-axis 360-degree scan. The second (vertical) axis is generated by a row of laser LEDs - each of which fires in sequence.

[0004] Figure 1A illustrates a rover 10 having a track with a puck lidar 12. Figure 1 B illustrates a four-legged robot 20 with a puck lidar 22. Figure 1 C illustrates a rough terrain rover 30 with a puck lidar 32. Figure 1 D illustrates a six-legged robot 40 with a puck lidar 42. Figure 1 E illustrates a quad 50 with a first puck lidar 52 and a second puck lidar 54. The novel systems and devices described herein may be used with the conventional robots 20, 40 and rovers 10, 30, 50.

[0005] The conventional puck lidar may not be suitable for outer space. The conventional puck lidar may use commercial high-speed electronics that do not have a space-flight equivalent. The conventional puck lidar may use adhesives, greases and seals that outgas in the vacuum conditions of space. The conventional puck lidar may rely upon the use of optical receivers prone to fail in radiation environments. The design architecture of conventional puck lidars have all of the electronics spin in the head, anddata is transmitted into, and out of this spinning platform via a series of brushed contacts. The brushed contact interface is problematic in zero gravity, where erosion of the brushes creates conductive debris that can float around and interfere or damage other parts of the circuitry of the conventional puck lidar.

[0006] Conventional lidar designs use a laser and a receiver to measure time of flight to a target, then steer this laser using scanning mirrors. Puck lidars instead use a line of lasers that fire in sequence to scan in the vertical axis, and a spinning motor head to scan in the horizontal axis. Current puck designs build the electronics, including transmit, receive, and processing into the spinning head, then use brushed commutators to get the measurement data out and the power into the spinning head.

[0007] Accordingly, as humanity’s space and lunar ambitions expand, there is a need for an improved system and method for lidars that overcomes at least some of the disadvantages of existing systems and methods.Summary

[0008] Provided is a lidar for remote sensing of an environment. The lidar includes a rotating head that rotates relative to a base. The rotating head includes a series of transmit light emitting diodes that emit pulsed laser light into the environment, and a reflector for reflecting light reflected off of the environment, and onto a light receiving sensor. The base is fixed relative to the rotating head. The base includes the light receiving sensor.

[0009] The rotating head may further include at least one laser diode for transmitting a signal directly onto the light receiving sensor to synchronize a receive time- of-flight timer with a transmit diode sequence.

[0010] The series of transmit laser light emitting diodes may emit pulsed laser light through a transmit lens and into the environment.

[0011] The transmit light emitting diodes may be connected to a transmit laser array circuit board in the rotating head. Each transmit light emitting diodes may fire in sequence.

[0012] The power may be wirelessly applied to the transmit laser array circuit board via inductive power transfer from the base.

[0013] The light sensor may be an avalanche photodiode.

[0014] The pulsed laser light may reflect off of the environment to create incoming light that is received into the rotating head through a receiving lens. The reflected light that is passed through the receiving lens may be reflected off of the reflector.

[0015] The reflector may reflect the incoming light. The receiving lens may focus the incoming light about a central axis of the rotating head.

[0016] The transmit lens may include a first collimating lens and a second collimating lens. The first collimating lens may be a cylindrical fast axis collimator that focuses the pulsed laser light from the plurality of laser diodes in the horizontal direction. The second collimating lens may be a slow axis collimator that vertically focuses the pulsed laser light.

[0017] The transmit lens may include a weak diverging lens that spreads the pulsed laser light in the vertical axis to provide pulsed laser light that has coverage across a field of view.

[0018] The receiving lens may include an F-Theta lens that collects the reflected light and focuses the light onto a flat focal plane.

[0019] The receiving lens may include an array of spherical lenslets that collimates the reflected light and a refocusing lens that re-focuses the reflected light onto the light receiving sensor.

[0020] Provided is a system for remote sensing of an environment. The system includes an exploration vehicle for exploring the environment and a lidar. The lidar includes a rotating head that rotates relative to a base. The rotating head includes a series of transmit light emitting diodes that emit pulsed laser light into the environment, and a reflector for reflecting light reflected off of the environment, and onto a light receiving sensor. The base is fixed on the exploration vehicle. The rotating head rotates relative to the base. The base includes the light receiving sensor.

[0021] The exploration vehicle may be a space rover for exploring a space environment.

[0022] Provided is a method for remote sensing of an environment. The method includes emitting pulsed laser light into the environment from a rotating head, and reflecting light received in the rotating head from the environment onto a light receiving sensor that is in a base that is fixed relative to the rotating head.

[0023] The method may further include transmitting a synchronizing signal from the rotating head directly onto the light receiving sensor, the synchronizing signal for synchronizing the light receiving sensor with the emitted pulsed laser light.

[0024] The method may further include emitting pulsed laser light through a transmit lens in the rotating head.

[0025] The method may further include firing, in sequence, a series of transmit light emitting diodes to generate the pulsed laser light.

[0026] The method may further include wirelessly powering the series of transmit light emitting diodes via inductive power transfer from the base.

[0027] The method may further include focusing the pulsed laser light that is reflected off of the environment about a central axis of the rotating head.

[0028] Other aspects and features will become apparent, to those ordinarily skilled in the art, upon review of the following description of some exemplary embodiments.Brief Description of the Drawings

[0029] The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification. In the drawings:

[0030] Figures 1 A to 1 E are photographs of robots and rovers having conventional puck lidars;

[0031] Figure 2 is a block diagram of a lidar, according to an embodiment;

[0032] Figure 3 is a block diagram of a system for remote sensing of an environment, according to an embodiment;

[0033] Figure 4 is a flowchart of a method for remote sensing of an environment, according to an embodiment;

[0034] Figure 5 is a block diagram of an optical system for transmitting laser light, according to an embodiment; and

[0035] Figure 6 is a block diagram of an optical system for receiving reflected laser light, according to an embodiment.Detailed Description

[0036] Various apparatuses or processes will be described below to provide an example of each claimed embodiment. No embodiment described below limits any claimed embodiment and any claimed embodiment may cover processes or apparatuses that differ from those described below. The claimed embodiments are not limited to apparatuses or processes having all of the features of any one apparatus or process described below or to features common to multiple or all of the apparatuses described below.

[0037] Referring now to Figure 2, provided is a lidar 100 for emitting light and detecting range in an environment, in accordance with an embodiment. The lidar 100 uses light in the form of a pulsed laser to measure time of flight or ranges and determine variable distances from the lidar 100 to objects in the environment. The lidar 100 may be used for autonomous operations.

[0038] The lidar 100 may be a puck shaped lidar. The lidar 100 may be a short- range lidar with 360-degree field of vision. The lidar 100 may localize the lidar 100 within the environment. The lidar 100 may map the environment. The lidar 100 may resolve a three-dimensional map of the environment.

[0039] The lidar 100 includes a rotating head 104 that rotates relative to a base 105. Optical architecture and electronics 102 are located in the base 105 underneath the rotating head 104.

[0040] The rotating head 104 rotates 101 around the central axis 128. The central axis 128 is perpendicular to a rotational interface 107 between the rotating head 104 andthe base 105. Where the central axis 128 is vertical, the rotational interface 107 is horizontal.

[0041] The lidar 100 includes the base 105 that is stationary relative to the rotating head 104. The electronics 102 are in the base 105 that is on the stationary side of the lidar 100. The rotating head 102 is rotated about the central axis 128 by a rotator 130.

[0042] The lidar 100 may be used for rovers deployed in outer-space. The lidar 100 may include space-compatible commutation interfaces. The lidar 100 may have a lower spinning mass than if electronics (especially larger space-rated electronics) were installed in the rotating head 104.

[0043] The lidar 100 includes a series of transmit laser light emitting diodes (LEDs) 106 for emitting pulsed laser light through a transmit lens 108. The transmit LEDs 106 are arranged parallel to the central axis 128. The transmit LEDs 106 are arranged perpendicular to the rotational interface 107. The transmit LEDs 106 emit laser light 110 through the lens 108 and into the surrounding environment (not shown).

[0044] The transmit LEDs 106 fire in sequence to scan in a vertical axis, and a spinning motor (not shown) spins the rotating head 102 to scan in a horizontal axis of the environment.

[0045] The transmit LEDs 106 are connected to a dedicated transmit laser array circuit board (e.g., printed circuit board, PCB) 126 inside the rotating head 104. Each transmit LED 106 fires in sequence where power is applied to the board 126. Power is wirelessly applied to the board 126 via inductive power transfer from the base.

[0046] Inductive power transmission is provided between the base 105 and the rotating head 104. In a variant, the inductive power transmission may be achieved by using the rotation speed of the rotating head 104 to induce current in a wire loop (not shown) within the rotating head 104. This may impact the ability to vary rotation speed of the rotating head 104, according to certain applications. The lidar 100 may include optomechanical assembly and alignment to provide a balanced rotating platform.

[0047] At least one laser diode 132 fires a transmitting signal 134 directly into the receive channel 124 so as to synchronize a receive time-of-flight timer (not shown) withthe transmit diode sequence. The signal 134 is a synchronizing signal that is an internal optical signal, transmitted directly from the optical head into the receiver / sensor 124. The synchronizing signal 134 synchronizes the receiver with the lasers being fired form the optical head, so that when the time-of-flight measurements is performed, the lidar 100 knows when to start the timer in the receiver.

[0048] The laser diode driver and sequencing 126 drives the lasers 106 for accurate time-of-flight measurement. The lasers 106 fire at predictable intervals with low jitter and thermal variation. The lidar 100 includes sequencing the receiver and control logic with the laser firing. One of the laser diodes 132 within the firing sequence fires directly into the receiver 122 so that the transmit sequence start-time is synchronized with the receiver timer.

[0049] The light 110 reflects off of the environment and that incoming light 112 is received into the rotating head 104 through a receiving lens 114. The light 116 that is passed through the receiving lens 114 is reflected off of a reflector 118. The light 120 that is reflected off of the reflector passes onto a receiving lens 122. The receiving lens 122 passes the received light 112 onto a light receiving sensor 124. The light receiving sensor 124 is electrically connected to the electronics 102, which may be on a circuit board.

[0050] The light sensor 124 may be a single avalanche photodiode. The single avalanche photodiode may be more sensitive to the received laser light 120. The avalanche photodiode may provide a longer range for the system. This is in contrast to conventional puck lidars which include a receiver array of photodiodes.

[0051] The light receiving sensor 124 and processing electronics 102 are stationary and are advantageously located underneath the rotating head 104. Further advantages of the lidar 100 are that an optical head 136 is more lightweight, reducing the angular momentum of the sensor 122.

[0052] The reflector 118 reflects the incoming light 112 and the lens 114 focuses the received optical signal 112 about the central axis 128 of the rotating head 104.

[0053] The electronics 102 includes an optical interface 136 that includes the received signal 116 reflected by the reflector 118 about the rotating axis 128 and focusedwith the lens 122 onto the avalanche photodiode 124 on the stationary side 105 of the lidar 100.

[0054] The power, control and time-of-flight circuits of the lidar 100 may be similar to conventional systems. The lidar 100 has novel laser LEDs 106, the laser driver circuit 126, and the x-axis beam-steering with a novel optical head 136. The lidar 100 may be a compact lidar optimized for rover guidance and navigation for science and exploration missions. Other conventional lidar systems may be optimized for long-range sensing and is not suitable for the <300m ranges typically desired for navigation and exploration.

[0055] The electronics inside the rotating head 104 are a series of laser LEDs 106 and their necessary drivers and sequencer on the circuit board 126. Power is supplied to the circuit board 126 via a contactless inductive power transmission. The LEDs 106 fire in sequence, and one LED 132 in each row fires a pulse 134 internally so as to synchronize the laser transmitter timing 126 with that of the receiver timing circuit 124.

[0056] The lidar 100 may achieve a compact lidar design suitable for rover navigation. By way of non-limiting example only, functional and performance estimates are below: The lidar 100 may have a relatively low mass (e.g., 1-10 kg, with a 0.5kg optical head. The volume of the lidar 100 may be in the range of 2U lidar electronics, with 0.5U for the optical head. The power of the lidar 100 may be less than 50 W. The range of the lidar 100 may be 1-250m+, with a range resolution of 0.5-5 cm resolution, and a scan rate of 360 degrees at 1 Hz, and a 5-50khz point measurement rate.

[0057] Figure 2 shows certain aspects of the lidar 100 on either side of the central axis 128. The lidar 100 may include one or more sets of components in the rotating head 104, which are shown as two sets in Figure 2.

[0058] Referring now to Figure 3, provided is a system 200 for remote sensing. The system 200 includes a lidar 202, such as the lidar 100, described with reference to Figure 2. The lidar 202 has a rotating element 204 (e.g., 104 of Figure 2) which rotates relative to a fixed element 206 (e.g., 105 of Figure 2). The lidar 202 is fixed at the fixed element 206 to an exploration vehicle 208. The exploration vehicle 208 explores an environment. The exploration vehicle 208 may be a space rover, a rover, a drone, an automobile, or a robot.

[0059] The lidar 100 may be used for autonomous operations of the exploration vehicle 208.

[0060] The exploration vehicle 208 includes a propulsion system 210, such as rover wheels or drone blades to move the exploration vehicle in the environment. The exploration vehicle 208 includes a power system 212 for driving the propulsion system 210. The exploration vehicle 208 includes a computer system 214 for receiving and processing data from the lidar 202.

[0061] The system 200 may be deployed in the commercial space rover market. The lidar 202 may provide a space-grade lidar that is representative of the terrestrial puck lidars. The system 200 may also be deployed in the terrestrial market.

[0062] The lidar 202 includes puck-like design of lidar wherein the only electrical interface that crosses the rotating element 202 is contactless inductive power transmission, for example from the power system 212 of the exploration vehicle 208. The lidar 202 may provide high-accuracy time-of-flight measurements with space-rated electronics and optical receivers.

[0063] Research and development in lidar based robotic guidance builds on conventional lidars. There may be interoperability advantage to being able to use the novel lidar 100, 202 to guide robotic exploration on the moon and, in particular, underground exploration and science missions within lava tubes. Software algorithms and mission design for terrestrial mobile science and exploration vehicles may rely on conventional puck lidar. There may be advantages to being able to port this conventional development experience to a lunar exploration and science rover.

[0064] The lidar 202 may be a puck-style lidar, and the exploration vehicle 208 may be a lunar rover. The lidar 100 may achieve 360-degree coverage. The lidar 202 may achieve high-speed low resolution scanning required for mapping and localization by a rover.

[0065] The lidar 100, 202 may advantageously overcome issues with conventional puck lidar systems. Conventional puck lidars are not suitable for spaceflight because conventional puck lidars may rely on any one or more of modem high-speed andminiature electronics built into its optical head that do not have spaceflight equivalent, (e.g., closest equivalent radiation tolerant parts may be 2-5x larger); adhesives, greases and rubber seals that may out-gas over the optics when in vacuum; the use of photodiodes that are typically sensitive to radiation effects; and that data transmission to / from the rotating optical head to the stationary mount is performed using brushed contacts. These brushed contacts are problematic in low gravity environments, and are typically restricted to sealed containers which do not contain electronics, since any eroded particles will be conductive.

[0066] Figure 4 illustrates a method 300 for remote sensing of an environment, in accordance with an embodiment. The method 300 uses light in the form of a pulsed laser to measure ranges (variable distances) of the environment. The method 300 may use, for example, the lidar 100, described with reference to Figure 2, or the system 200 described with reference to Figure 3. The method 300 may be used in autonomous operations.

[0067] The method 300 includes emitting 302 pulsed laser light into the environment from a rotating head.

[0068] The method 300 includes reflecting 306 light received in the rotating head from the environment onto a light receiving sensor that is in a base that is fixed relative to the rotating head.

[0069] The method 300 may also include transmitting 304 a signal from the rotating head directly onto the light receiving sensor.

[0070] The emitting 302 pulsed laser light into the environment from a rotating head may include emitting pulsed laser light through a transmit lens in the rotating head.

[0071] The emitting 302 pulsed laser light into the environment from a rotating head firing, in sequence, a series of transmit light emitting diodes to generate the pulsed laser light.

[0072] The method 300 may further include wirelessly powering the series of transmit light emitting diodes via inductive power transfer from the base.

[0073] The method 300 may further include focusing the pulsed laser light that is reflected off of the environment about a central axis of the rotating head.

[0074] Referring now to Figure 5, provided is an optical system 400 for transmitting laser light. The optical system 400 may be used as part of transmit lens 108 of the lidar 100 of Figure 2.

[0075] The optical system 400 includes a plurality of laser diodes 402 that are arranged in a linear array 404. The plurality of laser diodes 402 emit pulsed laser light 406 (e.g., at a wavelength of 905 nm). The pulsed laser light 406 output from the laser diodes 402 may be highly divergent.

[0076] The optical system 400 includes a first collimating lens 408. The optical system 400 includes a second collimating lens 410. The first collimating lens 408 is a cylindrical fast axis collimator that focuses the pulsed laser light 406 from the plurality of laser diodes 402 in the horizontal direction. The second collimating lens 410 is a slow axis collimator (such as a cylindrical lenslet array) that vertically focuses the pulsed laser light 406.

[0077] The spacing of the individual diodes 402 is set such that the output of each diode 406 couples with an individual lens element in the slow axis collimator 410. Individual collimated beams 412 then pass through a weak diverging lens 414 that spreads the beam 412 in the vertical axis to provide pulsed laser light 416 that has coverage across a field of view.

[0078] Referring now to Figure 6, provided is an optical system 500 for receiving reflected light 502a, 502b, 502c. The optical system 400 may be used as part of receiving lens 114 of the lidar 100 of Figure 2.

[0079] The optical system 500 includes a F-Theta lens 504 that collects the reflected light 502a, 502b, 502c from across the field of view. The F-Theta lens 504 focuses this light onto a flat focal plane 506. The F-Theta lens 504 may include a telecentric lens that ensures that central rays from all light bundles 502a, 502b, 502c are perpendicular to the focal plane 506.

[0080] The optical system 500 includes a flat mirror 508 that redirects the laser light 502a, 502b, 502c. The optical system 500 includes an array of spherical lenslets 510 that collimates the light.

[0081] The optical system 500 includes a refocusing lens 512 that re-focuses the reflected light onto a light receiving sensor.514 (e.g., photodiode receiver). Since the light receiving sensor 514 is located below the receiving optics, on the rotation axis (e.g., central axis 128 of Figure 2) of the optical head (e.g., optical head 132 of Figure 2), the flat mirror 508 is located after the F-Theta lens to deflect the beam by 90°. The optical axis of the refocusing lens 512 is aligned with the rotation axis of the rotary mechanics so that the reflected light is always focused onto the stationary light receiving sensor 514, regardless of pointing direction of the optical head while the optical head is spinning.

[0082] While the above description provides examples of one or more apparatus, methods, or systems, it will be appreciated that other apparatus, methods, or systems may be within the scope of the claims as interpreted by one of skill in the art.

Claims

Claims:1 . A lidar for remote sensing of an environment, the lidar comprising: a rotating head that rotates relative to a base, wherein the rotating head includes: a series of transmit light emitting diodes that emit pulsed laser light into the environment; and a reflector for reflecting light reflected off of the environment, and onto a light receiving sensor; and the base that is fixed relative to the rotating head, wherein the base includes the light receiving sensor.

2. The lidar of claim 1 , wherein the rotating head further comprises at least one laser diode for transmitting a signal directly onto the light receiving sensor to synchronize a receive time-of-flight timer with a transmit diode sequence.

3. The lidar of claim 1 , wherein the series of transmit laser light emitting diodes emit pulsed laser light through a transmit lens and into the environment.

4. The lidar of claim 1 , wherein transmit light emitting diodes are connected to a transmit laser array circuit board in the rotating head, and wherein each transmit light emitting diodes fires in sequence.

5. The lidar of claim 4, wherein power is wirelessly applied to the transmit laser array circuit board via inductive power transfer from the base.

6. The lidar of claim 1 , wherein the light sensor is an avalanche photodiode.

7. The lidar of claim 1 , wherein the pulsed laser light reflects off of the environment to create incoming light that is received into the rotating head through a receiving lens, and wherein the reflected light that is passed through the receiving lens is reflected off of the reflector.

8. The lidar of claim 7, wherein the reflector reflects the incoming light, and wherein the receiving lens focuses the incoming light about a central axis of the rotating head.

9. The lidar of claim 3, wherein the transmit lens includes a first collimating lens and a second collimating lens, wherein the first collimating lens is a cylindrical fast axis collimator that focuses the pulsed laser light from the plurality of laser diodes in the horizontal direction, and wherein the second collimating lens is a slow axis collimator that vertically focuses the pulsed laser light.

10. The lidar of claim 9, wherein the transmit lens includes a weak diverging lens that spreads the pulsed laser light in the vertical axis to provide pulsed laser light that has coverage across a field of view.

11. The lidar of claim 7, wherein the receiving lens includes an F-Theta lens that collects the reflected light and focuses the light onto a flat focal plane.

12. The lidar of claim 11 , wherein the receiving lens includes an array of spherical lenslets that collimates the reflected light and a refocusing lens that re-focuses the reflected light onto the light receiving sensor.

13. A system for remote sensing of an environment, the system comprising: an exploration vehicle for exploring the environment; and a lidar comprising:a rotating head that rotates relative to a base, wherein the rotating head includes: a series of transmit light emitting diodes that emit pulsed laser light into the environment; and a reflector for reflecting light reflected off of the environment, and onto a light receiving sensor; and the base that is fixed on the exploration vehicle, wherein the rotating head rotates relative to the base, wherein the base includes the light receiving sensor.

14. The system of claim 13, wherein the exploration vehicle is a space rover for exploring a space environment.

15. A method for remote sensing of an environment, the method comprising: emitting pulsed laser light into the environment from a rotating head; and reflecting light received in the rotating head from the environment onto a light receiving sensor that is in a base that is fixed relative to the rotating head.

16. The method of claim 15 further comprising transmitting a synchronizing signal from the rotating head directly onto the light receiving sensor, the synchronizing signal for synchronizing the light receiving sensor with the emitted pulsed laser light.

17. The method of claim 15 further comprising emitting pulsed laser light through a transmit lens in the rotating head.

18. The method of claim 15 further comprising firing, in sequence, a series of transmit light emitting diodes to generate the pulsed laser light.

19. The method of claim 18 further comprising wirelessly powering the series of transmit light emitting diodes via inductive power transfer from the base.

20. The method of claim 18 further comprising focusing the pulsed laser light that is reflected off of the environment about a central axis of the rotating head.

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