Retroreflector detection and avoidance in LIDAR devices

Abstract

A light detection and ranging (LIDAR) device includes a light emitter configured to emit light pulses into a field of view and a detector configured to detect light in the field of view. The light emitter emits a first light pulse. The detector detects at least one reflected light pulse indicative of a reflection from a retroreflector during a first measurement period based on a shape of the reflected light pulse, a magnitude of the reflected light pulse, and / or a time interval between two reflected light pulses. In response to detecting the at least one reflected light pulse indicative of a reflection from a retroreflector, the light emitter is deactivated for one or more subsequent measurement periods. Additionally, the LIDAR device may notify one or more other LIDAR devices by sending information indicating that a retroreflector is within the field of view of the light emitter to a computing device.

Description

[0001] This application claims priority to U.S. Patent Application No. 17 / 028,847, filed on September 22, 2020, and U.S. Provisional Patent Application No. 62 / 941,989, filed on November 29, 2019, which are hereby incorporated by reference in their entireties. Background Art

[0002] 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.

[0003] Light detection and ranging (LIDAR) devices can estimate the distance to objects in a given environment. For example, the emitter subsystem of a LIDAR device can emit near-infrared light pulses that can interact with objects in the device's environment. At least a portion of the light pulses can be redirected back to the LIDAR (e.g., due to reflection or scattering) and detected by a detector subsystem. A conventional detector subsystem can include multiple detectors and a corresponding controller that is configured to determine the arrival time of each light pulse with high temporal resolution. The distance between the LIDAR device and a given object can be determined based on the flight time of the corresponding light pulses that interact with the given object. Summary of the Invention

[0004] In a first aspect, a method is provided. The method involves transmitting, by a light emitter of a light detection and ranging (LIDAR) device, a first light pulse into a field of view. The method further involves determining that a detector of the LIDAR device detects, during a first measurement time period, at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object. The detector is configured to detect light from within the field of view. The method further involves, in response to detecting the at least one reflected light pulse indicative of a reflection from the retroreflector or other highly reflective object, deactivating the light emitter during one or more subsequent measurement time periods. The one or more subsequent measurement time periods occur after the first measurement time period.

[0005] In a second aspect, a light detection and ranging (LIDAR) device is provided. The LIDAR device includes a light emitter configured to emit a light pulse into a field of view, a detector configured to detect light from within the field of view, and a controller configured to perform operations. The operations include: (i) controlling the light emitter to emit a first light pulse into the field of view; (ii) determining that the detector detects at least one reflected light pulse indicating a reflection from a retroreflector or other highly reflective object during a first measurement time period; and (iii) in response to detecting the at least one reflected light pulse indicating a reflection from the retroreflector or other highly reflective object, deactivating the light emitter during one or more subsequent measurement time periods. The one or more subsequent measurement time periods occur after the first measurement time period.

[0006] In some embodiments, the operation may further include determining when to reactivate the light emitter. Determining when to reactivate the light emitter may involve determining whether the detector detects additional light pulses indicating reflections from a retroreflector or other highly reflective object during a second measurement period that occurs after the first measurement period. In response to determining that the detector detects additional light pulses indicating reflections from a retroreflector or other highly reflective object during the second measurement period, deactivating the light emitter during a third measurement period that occurs after the second measurement period. In response to determining that the detector does not detect additional light pulses indicating reflections from a retroreflector or other highly reflective object during the second measurement period, reactivating the light emitter during the third measurement period that occurs after the second measurement period.

[0007] In some embodiments, the light emitter emits a first light pulse during a first measurement time period, and determining that the detector detects at least one reflected light pulse indicating a reflection from a retroreflector or other highly reflective object during the first measurement time period includes: determining that the detector detects a reflected light pulse during the first measurement time period; and determining that the reflected light pulse indicates a reflection from a retroreflector or other highly reflective object based at least on a shape of the reflected light pulse.

[0008] In some embodiments, the light emitter is a primary light emitter, the LIDAR device further includes a secondary light emitter, and the primary light emitter emits a first light pulse during a previous measurement period occurring before the first measurement period. The operations further include: controlling the secondary light emitter to emit a secondary light pulse during the first measurement period, wherein the secondary light pulse has a lower intensity than the first light pulse; and controlling the primary light emitter to not emit light during the first measurement period. Furthermore, determining that the detector detected at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object during the first measurement period may include: determining that the detector detected the reflected light pulse during the first measurement period; and determining that the reflected light pulse indicates a reflection from the retroreflector or other highly reflective object based at least on the reflected light pulse having a magnitude exceeding a predetermined threshold.

[0009] In some embodiments, the light emitter is a primary light emitter, the LIDAR device further comprises a secondary light emitter, the primary light emitter emitting a first light pulse during a first measurement time period, and the operation comprises controlling the secondary light emitter to emit a secondary light pulse during the first measurement time period, wherein the first light pulse and the secondary light pulse are separated in time by a predetermined time difference, and wherein the secondary light pulse has a lower intensity than the first light pulse. Furthermore, determining that the detector detected at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object during the first measurement time period comprises: determining that the detector detected the first reflected light pulse at a first time during the first measurement time period and detected the second reflected light pulse at a second time during the first measurement time period; and determining that the first reflected light pulse and the second reflected light pulse indicate a reflection from a retroreflector or other highly reflective object based at least on a time difference between the first time and the second time corresponding to the predetermined time difference.

[0010] In some embodiments, the operations further include sending, from the LIDAR device to the computing device, information indicating that a retroreflector or other highly reflective object was within the field of view of the light emitter and was detected during the first measurement time period.

[0011] In a third aspect, a method for scanning an environment of an autonomous vehicle is provided. The method may include determining portions of the environment that may include retroreflectors. Determining the portions of the environment that may include retroreflectors may include determining, based at least on the shape of the reflected light pulses, that the reflected light pulses indicate reflections from the retroreflectors. The method may also include selectively altering the ability of a LiDAR to scan those portions. Selectively altering the ability of the LiDAR to scan those portions may include selectively preventing the LiDAR from transmitting light to those portions of the environment that may include retroreflectors. Selectively preventing the LiDAR from transmitting light to those portions of the environment that may include retroreflectors may include selectively preventing one or more transmitters from emitting light at specific times. Selectively altering the ability of the LiDAR to scan those portions may alternatively or additionally include emitting secondary light pulses by the same or a secondary light transmitter, wherein the secondary light pulses have a lower intensity than the first light pulses.

[0012] In a fourth aspect, a method for LIDAR-to-LIDAR communication is provided. The method involves receiving, by a computing device, data from a first LIDAR device coupled to a vehicle, wherein the data includes information indicating a location of a retroreflector detected by the first LIDAR device. The method also includes determining, by the computing device, that the location of the retroreflector is within a field of view of a second LIDAR device coupled to the vehicle. The method also includes sending, by the computing device, a message to the second LIDAR device, wherein the message includes information indicating that the retroreflector is within the field of view of the second LIDAR device.

[0013] These and other aspects, advantages and alternatives will become clear to those skilled in the art by reading the following detailed description with appropriate reference to the accompanying drawings. In addition, it should be understood that the descriptions provided in this summary and elsewhere in this document are intended to illustrate the claimed subject matter by way of example and not limitation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a simplified block diagram of a LIDAR device according to an example embodiment.

[0015] Figure 2 A cross-sectional view of a LIDAR device is shown according to example embodiments.

[0016] Figure 3 An example arrangement of fields of view (FOV) for multiple transmission / reception channels of a LIDAR device according to example embodiments is shown.

[0017] Figure 4A A carrier according to an example embodiment is shown.

[0018] Figure 4B A carrier according to an example embodiment is shown.

[0019] Figure 4C A carrier according to an example embodiment is shown.

[0020] Figure 4D A carrier according to an example embodiment is shown.

[0021] Figure 4E A vehicle according to an example embodiment is shown.

[0022] Figure 5 is a flowchart of a method according to an example embodiment.

[0023] Figures 6A-6C A scene is shown of a LIDAR device scanning a portion of its environment where retroreflectors are located, according to an example embodiment. Figure 6A The scene at a first point in time is shown. Figure 6B The scene at a second point in time is shown. Figure 6C The scene at a third point in time is shown.

[0024] Figures 7A-7D is a timing diagram illustrating a scenario of detecting a retroreflector in a field of view of a light emitter of a LIDAR device, responsively deactivating the retroreflector, and then reactivating the retroreflector when the retroreflector is no longer in the field of view of the light emitter, according to example embodiments. Figure 7A is a timing diagram of the first measurement period in this scenario. Figure 7B is a timing diagram of the second measurement period in this scenario. Figure 7Cis a timing diagram of the third measurement period in this scenario. Figure 7D is a timing diagram of the fourth measurement period in this scenario.

[0025] Figures 8A-8D is a timing diagram illustrating a scenario in which a retroreflector is detected in the field of view of a primary light emitter of a LIDAR device, the retroreflector is responsively deactivated, and then reactivated when the retroreflector is no longer in the field of view of the primary light emitter, according to example embodiments. Figure 8A is a timing diagram of the first measurement period in this scenario. Figure 8B is a timing diagram of the second measurement period in this scenario. Figure 8C is a timing diagram of the third measurement period in this scenario. Figure 8D is a timing diagram of the fourth measurement period in this scenario.

[0026] Figures 9A-9D is a timing diagram illustrating a scenario in which a retroreflector is detected in the field of view of a primary light emitter of a LIDAR device, the retroreflector is responsively deactivated, and then reactivated when the retroreflector is no longer in the field of view of the primary light emitter, according to example embodiments. Figure 9A is a timing diagram of the first measurement period in this scenario. Figure 9B is a timing diagram of the second measurement period in this scenario. Figure 9C is a timing diagram of the third measurement period in this scenario. Figure 9D is a timing diagram of the fourth measurement period in this scenario.

[0027] Figure 10 is a block diagram of a system supporting information sharing between LIDAR devices according to an example embodiment.

[0028] Figure 11 is a flowchart of a method according to an example embodiment. DETAILED DESCRIPTION

[0029] Exemplary implementations are described herein. It will be understood that the word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation or feature described herein as "exemplary" or "illustrative" is not necessarily to be construed as preferred or advantageous over other implementations or features. In the drawings, similar symbols generally identify similar components unless the context dictates otherwise. The example implementations described herein are not meant to be limiting. It will be readily understood that aspects of the present disclosure, as generally described herein and shown in the drawings, can be arranged, substituted, combined, separated, and designed in a variety of different configurations.

[0030] I. Overview

[0031] A light detection and ranging (LIDAR) device may include one or more light emitters configured to transmit light pulses into an environment of the LIDAR device and one or more detectors configured to detect returning light pulses corresponding to reflections of the transmitted light pulses by one or more objects in the environment. The time difference between the time the light pulse was emitted and the time the reflection of the light pulse was detected can be used to determine the distance between the LIDAR device and the object reflecting the light pulse. Additionally, the direction to the object can be determined based on the direction in which the light emitter emitted the light pulse. The direction to the object can be characterized, for example, based on an azimuth or yaw angle (e.g., an angle in the horizontal plane) and / or an elevation angle (e.g., an angle relative to the horizontal plane).

[0032] In some implementations, the LIDAR device can emit and detect light pulses in consecutive measurement periods. Each measurement period can include an emission period in which the light emitter emits a light pulse, followed by a detection period in which the detector "listens" for any returning light pulses. In some embodiments, the direction in which the light emitter emits light pulses can change from one measurement period to another (e.g., due to rotation or other movement of the LIDAR device, deflection of a mirror or other beam steering device, or in some other manner). In this way, the LIDAR device can scan a portion of its environment.

[0033] In some implementations, a LIDAR device may include multiple light emitters and multiple detectors. Each light emitter may be configured to emit light pulses in a different direction, and each detector may be configured to detect reflected light pulses from a different direction. The different directions corresponding to the multiple light emitters and detectors may cover a range of azimuth angles and / or elevation angles. In practice, the emitted light pulses from a light emitter may have a beam width that defines the light emitter's field of view. Similarly, each detector may be configured to detect light from a range of directions that define the detector's field of view. The fields of view of the light emitters may overlap or non-overlap, and the fields of view of the detectors may overlap or non-overlap. In some implementations, each light emitter may be paired with a corresponding detector having the same or similar field of view as the light emitter. The light emitters paired with the corresponding detectors may define a transmission / reception channel of the LIDAR device. Thus, a LIDAR device including multiple light emitters and multiple detectors may have multiple transmission / reception channels, each channel having a respective field of view that constitutes a portion of the LIDAR device's overall field of view.

[0034] In general, the intensity of the reflected light pulse detected by the detector depends on various factors, including the intensity of the emitted light pulse, the distance to the object reflecting the light pulse, the angle of incidence relative to the object's surface, the reflectivity of the object's surface, and whether the object's surface reflects light diffusely (e.g., with a Lambertian reflectance pattern) or specularly (such as a mirror). Assuming other factors are equal, more reflective objects generally produce higher-intensity reflected light pulses than less reflective objects. Objects with sufficiently high reflectivity (e.g., greater than 80%, greater than 90%, greater than 95%, or greater than 99%, depending on the application) can be classified as "highly reflective objects," such as "retroreflectors." Furthermore, if the term "reflectivity" is defined as effective Lambertian reflectivity, a "retroreflector" can have a reflectivity greater than 100%. Common examples of retroreflectors include road signs, lane markings, and front, side, and rear reflectors on cars, trucks, bicycles, and other vehicles. In some cases, reflected light pulses from retroreflectors or other highly reflective objects can be so intense that they can cause various problems with the desired operation of the LIDAR device.

[0035] One issue that can be caused by retroreflectors or other highly reflective objects is range aliasing. This problem can arise when a light pulse emitted during a first measurement period reflects from a retroreflector that is far enough away that a reflected light pulse is detected during a second measurement period. When this occurs, it can be difficult to determine whether the reflected light pulse is a reflection of a light pulse emitted during the first measurement period or a reflection of a light pulse emitted during the second measurement period. This, in turn, creates ambiguity in how to determine the distance to the object that generated the reflected light pulse.

[0036] Another problem that can be caused by retroreflectors or other highly reflective objects is crosstalk. As described above, a LIDAR device can include multiple light emitters and multiple detectors arranged to provide multiple transmission / reception channels, where each channel has its own field of view. However, in practice, a small amount of light from one channel may be scattered into another channel. In some cases, this scattering may be the result of incomplete isolation between channels within the LIDAR device. Alternatively or additionally, scattering can occur at the surface of the window, lens, or other optical component of the LIDAR device (e.g., due to scratches, streaks, water droplets, or other defects or debris). Scattering can also occur external to the LIDAR device. For example, fog, rain, and snow can scatter light.

[0037] This scattering can affect the light transmitted from the LIDAR device into the environment of the LIDAR device, and can also affect the light received by the LIDAR device from the environment. With respect to transmitted light, some of the light emitted in the first channel can be scattered into the field of view of a second channel (e.g., an adjacent channel). The stray light generated by this scattering may be reflected by objects in the field of view of the second channel, which can cause the reflected stray light from the objects to be detected by the detector in the second channel. With respect to received light, some of the light reflected by objects in the field of view of the first channel can be scattered into the field of view of the second channel. The stray light generated by this scattering can be detected by the detector in the second channel.

[0038] To address the possibility of light from one channel being scattered into another channel, a threshold value can be used to determine whether to use a detected light pulse for distance determination. In this method, if a detector detects a light pulse that exceeds a threshold value (e.g., the height, integrated area, or other measure of the magnitude of the pulse exceeds the threshold value), the detected light pulse can be considered to be a reflection of a light pulse emitted by the detector's corresponding light emitter and, based on this, can be used for distance determination. On the other hand, if the detector detects a light pulse that does not exceed the threshold value, the light pulse can be considered to be the result of scattered light or noise and, based on this, not used for distance determination.

[0039] However, this threshold approach may be insufficient when a retroreflector or other highly reflective object is within the field of view of a particular channel. When a light emitter in a particular channel transmits a light pulse toward a reflector, the intensity of the reflected light pulse from the retroreflector can be high enough that the reflected light scatters into one or more other channels, causing a detector in one of the other channels to detect a light pulse exceeding the threshold. This, in turn, can lead to false distance determinations. Furthermore, even when the light emitter in a particular channel is turned off, a significant amount of stray light may reach the retroreflector due to scattering of light emitted in other channels. The retroreflector can reflect this stray light, causing the detector in the particular channel to detect a light pulse exceeding the threshold.

[0040] In addition to range aliasing and crosstalk, retroreflectors or other highly reflective objects can cause detector saturation, blooming, and other types of errors in LIDAR devices.

[0041] To mitigate errors that may be caused by retroreflectors or other highly reflective objects, disclosed herein are methods and systems for detecting when a retroreflector or other highly reflective object is in the field of view of a light emitter, for deactivating the light emitter when the retroreflector or other highly reflective object is in the field of view of the light emitter, and for reactivating the light emitter when the retroreflector or other highly reflective object is no longer in the field of view of the light emitter.

[0042] In some examples, a retroreflector or other highly reflective object can be detected based on the characteristic shape of the reflected light pulse. If the detector detects a reflected light pulse indicating a reflection of a retroreflector or other highly reflective object based on the shape of the reflected light pulse during a first measurement time period, the corresponding light emitter of the detector can be deactivated during one or more subsequent measurement time periods. Deactivating the light emitter during one or more subsequent measurement time periods can involve controlling the light emitter so that it does not emit light (e.g., does not illuminate the retroreflector) during the one or more subsequent measurement time periods. Alternatively, deactivating the light emitter during one or more subsequent measurement time periods can involve controlling the light emitter so that the light emitter emits light at a reduced level (e.g., light pulses with reduced pulse energy and / or intensity) during the one or more subsequent measurement time periods. Advantageously, even if the light emitter can still emit some light toward the retroreflector, the reduced light emission level can be low enough so that crosstalk is significantly reduced or eliminated.

[0043] In some examples, a secondary light emitter can be used to detect retroreflectors or other highly reflective objects. The secondary light emitter can emit secondary light pulses having a lower intensity than the light pulses emitted by the primary light emitter used for distance determination. In addition, the secondary light emitter can emit the secondary light pulses into a wide field of view that encompasses the fields of view of the various transmit / receive channels of the LIDAR device. Thus, a detector in any channel can potentially detect a reflected light pulse resulting from a reflection of the secondary light pulse. However, the intensity of the secondary light pulse can be sufficiently low that the detector will typically detect the reflected light pulse (e.g., an above-threshold detection) only if the secondary light pulse is reflected by a retroreflector or other highly reflective object in the detector's field of view.

[0044] In one approach, a secondary light emitter emits a secondary light pulse during a first measurement period, wherein a primary light emitter of a transmit / receive channel does not emit light during the first measurement period. If a detector detects a reflected light pulse having a magnitude (e.g., peak value or integrated area) exceeding a threshold during the first measurement period, the reflected light pulse indicates a reflection from a retroreflector or other highly reflective object. In response, the detector's corresponding primary light emitter can be deactivated during one or more subsequent measurement periods.

[0045] In another method, during a first measurement period, a primary light emitter emits a primary light pulse, and a secondary light emitter emits a secondary light pulse. The primary and secondary light pulses are separated in time by a predetermined time difference. If a corresponding detector of the primary light emitter detects two reflected light pulses separated in time by the predetermined time difference during the first measurement period, the two reflected light pulses indicate a reflection from a reflector or other highly reflective object. In response, the detector's corresponding primary light emitter can be deactivated during one or more subsequent measurement periods.

[0046] When a light emitter is deactivated for one or more subsequent measurement time periods, the light emitter's corresponding detector may continue to detect light during each subsequent measurement time period. If the detector detects a reflected light pulse indicating a reflection from a retroreflector or other highly reflective object during a subsequent measurement time period, the retroreflector is still within the light emitter's field of view. In response, the light emitter remains deactivated. However, if the detector does not detect a reflected light pulse indicating a reflection from a retroreflector or other highly reflective object during a subsequent measurement time period, the retroreflector is no longer within the light emitter's field of view. In response, the light emitter may be reactivated.

[0047] II. Example System

[0048] Figure 1 1 is a simplified block diagram of a LIDAR device 100 according to an example embodiment. As shown, the LIDAR device 100 includes one or more primary light emitters 102, one or more secondary light emitters 104, one or more detectors 106, primary emitter circuitry 108, secondary emitter circuitry 110, detector circuitry 112, one or more primary optical elements 114, one or more secondary optical elements 116, an optical window 118, a housing 120, a rotating platform 122, a fixed platform 124, one or more actuators 126, and a controller 128. In some embodiments, the system 100 may include more, fewer, or different components. Additionally, the components shown may be combined or divided in any number of ways.

[0049] The primary light emitter 102 is configured to emit light, for example, in the form of pulses. Each light pulse can have a duration suitable for determining the distance to an object in the environment. For example, each light pulse can have a duration between 2 nanoseconds and 5 nanoseconds. Other pulse durations are also possible. The light emitted by the primary light emitter 102 can have a narrow range of wavelengths. For example, the primary light emitter 102 can include a laser diode, a laser diode bar, a vertical cavity surface emitting laser (VCSEL), a fiber laser, or other narrowband light source. Alternatively, the primary light emitter 102 can emit light having a wider range of wavelengths. For example, the primary light emitter 102 can include a light emitting diode (LED). Other types of light sources are also possible. The wavelengths emitted by the primary light emitter 102 can be, for example, in the ultraviolet, visible, and / or infrared portions of the electromagnetic spectrum. In an exemplary embodiment, the primary light emitter 102 includes a laser diode that emits light having a wavelength of approximately 905 nanometers.

[0050] In some embodiments, LIDAR device 100 may include only one primary light emitter 102. In other embodiments, LIDAR device 100 may include multiple primary light emitters 102. Each of the multiple primary light emitters 102 may be configured to emit light that illuminates a respective field of view, for example, based on the position of the primary light emitter relative to primary optical element 114. The respective fields of view of primary light emitters 102 may be overlapping or non-overlapping.

[0051] The secondary light emitter 104 is configured to emit light, for example, in the form of pulses. The light pulses emitted by the secondary light emitter 104 can have the same or similar duration as the light pulses emitted by the primary light emitter 102, but can have higher or lower pulse energies. For example, the primary light emitter 102 can emit light pulses with a pulse energy of approximately 76 nJ, while the secondary light emitter 104 can emit light pulses with a pulse energy of approximately 1 μJ. Although the pulse energy can be higher, the intensity of the light from the secondary light emitter 104 can be lower than the intensity of the light from the primary light emitter 102 because the light from the secondary light emitter 104 can be spread over a wider field of view (e.g., by the secondary optical element 116). The wavelength of the light emitted by the secondary light emitter 104 can be the same or similar to the wavelength of the light emitted by the primary light emitter 102. In an example embodiment, both the primary light emitter 102 and the secondary light emitter 104 emit light in the near-infrared range. Similar to the primary light emitter 102, the secondary light emitter 104 may include a narrowband light source (such as a laser diode, a laser diode bar, a VCSEL, or a fiber laser) or a broadband light source (such as an LED).Other types of light sources are also possible.

[0052] In an example embodiment, LIDAR device 100 includes only one secondary light emitter 104. Single secondary light emitter 104 can be configured to emit light that illuminates a field of view that encompasses the respective fields of view of primary light emitters 102. The light from secondary light emitter 104 can have a lower intensity than the light from each of primary light emitters 102 because the light is spread over a wider field of view. In such an embodiment, secondary light emitter 104 can be described as a "flash illuminator" or a "flood illuminator."

[0053] The detector 106 may include any type of light detector arranged to intercept and detect reflections of light emitted by the primary light emitter 102 and the secondary light emitter 104 from the environment back to the LIDAR device 100. Example detectors 106 include photodiodes, avalanche photodiodes (APDs), silicon photomultipliers (SiPMs), single photon avalanche diodes (SPADs), multi-pixel photon counters (MPPCs), phototransistors, active pixel sensors (APSs), charge-coupled devices (CCDs), cryogenic detectors, and / or any other detector capable of detecting light having the wavelengths emitted by the primary light emitter 102 and the secondary light emitter 104.

[0054] In an exemplary embodiment, the detector 106 is paired with the primary light emitter 102 to form multiple transmit / receive channels. In each transmit / receive channel, the primary light emitter is configured to transmit light into a respective field of view, and the detector paired with the primary light emitter is configured to receive and detect light from the same or similar field of view.

[0055] The master emitter circuit 108 includes circuitry capable of selectively activating and deactivating individual master light emitters in the master light emitters 102 during a specific measurement period, for example, under the control of the controller 128. To activate a selected master light emitter during a specific measurement period, the master emitter circuit 108 may include a capacitor (or other energy storage device) that is charged and then discharged so that current flows through the selected master light emitter. The current flowing through the selected master light emitter causes the selected master light emitter to emit a light pulse during the specific measurement period. To deactivate a selected master light emitter during a specific measurement period, the master emitter circuit 108 may not charge the capacitor, or may charge the capacitor and then discharge the capacitor in a manner such that little or no current flows through the selected master light emitter (e.g., the capacitor may be discharged through a current path that does not flow through the selected master light emitter). As a result, the selected master light emitter does not emit a light pulse (or emits a light pulse with reduced intensity or pulse energy) during the specific measurement period.

[0056] Secondary emitter circuit 110 includes circuitry that causes one or more of secondary light emitters 104 to emit light pulses during one or more measurement time periods. In some embodiments, secondary emitter circuit 110 causes secondary light emitters 104 to emit light pulses during dedicated measurement time periods when primary light emitter 102 is not emitting light. Such dedicated measurement time periods can be used to map the location of retroreflectors in an environment based on reflections of light pulses emitted by secondary light emitters 104 detected by detector 106. The dedicated measurement time periods can be followed by one or more standard measurement time periods. During the standard measurement time periods, primary light emitter 102 can be selectively activated to emit light pulses, or deactivated to avoid illuminating retroreflectors, while one or more secondary light emitters 104 are not emitting light.

[0057] In other embodiments, the secondary emitter circuit 110 controls the secondary light emitter 104 to emit a light pulse in each measurement period. For example, during each measurement period, the secondary emitter circuit 110 may cause the secondary light emitter 104 to emit a light pulse a certain period of time (e.g., 50 nanoseconds) after the light pulse is emitted by the primary light emitter 102. Alternatively, the secondary emitter circuit 110 may cause the secondary light emitter 104 to emit a light pulse before or simultaneously with the light pulse emitted by the primary light emitter 102.

[0058] The detector circuit 112 is configured to output a respective signal based on the light detected by each of the detectors 106. For example, the detector circuit 112 may include, for each detector 106, a respective analog-to-digital converter (ADC) configured to sample the output of the detector at different times so as to output a digital value corresponding to the detected light signal (e.g., the current generated by the detected photons) at each time. The sampling rate of the ADC may be selected based on the pulse duration of the transmitted light pulse so as to obtain multiple samples of each reflected pulse. For example, if the transmitted light pulse has a pulse duration of 2 nanoseconds, the ADC may sample the output of the detector every 100 to 500 picoseconds. The digital value determined in this manner may be used to determine the shape of the reflected light pulse detected by the detector as a function of time (e.g., including a rising edge, a peak, and a falling edge).

[0059] The primary optical element 114 may include one or more lenses, mirrors, light guides, apertures, diffusers, and / or other optical elements that direct light emitted by the primary light emitter 102 into the environment of the LIDAR device 100 and direct reflected light from the environment to the detector 106. In an example embodiment, the primary optical element 114 pairs the primary light emitter 102 with the detector 106 to form one or more transmission / reception channels. In such an embodiment, each transmission / reception channel is associated with a respective field of view, and the primary optical element 114 directs light from the primary light emitter of a channel into the channel's specific field of view and directs reflected light from within the channel's specific field of view to the channel's corresponding detector.

[0060] Secondary optical element 116 may include one or more lenses, reflectors, light guides, apertures, diffusers, and / or other optical elements that direct light emitted by secondary light emitter 104 into the environment of LIDAR device 100. In an example embodiment, secondary optical element 116 diffuses light emitted by secondary light emitter 104 into a field of view that encompasses the respective fields of view of primary light emitter 102 and detector 106.

[0061] In some embodiments, LIDAR device 100 is configured to rotate. Figure 1 As shown, the LIDAR device 100 includes a rotating platform 118 that rotates relative to a fixed platform 120 under the control of an actuator 122. The fixed platform 120 can be mounted on a vehicle, for example. The primary light emitter 102, the secondary light emitter 104, the detector 106, the primary emitter circuit 108, the secondary emitter circuit 110, the detector circuit 112, the primary optical element 114, and the secondary optical element 116 can be mounted on or coupled to the rotating platform 118. The actuator 122 can include one or more motors, pneumatic actuators, hydraulic pistons, and / or piezoelectric actuators, and / or any other type of actuator. The actuator 122 can be operated (e.g., by a controller 128) to rotate the rotating platform 118 about a rotation axis. In some embodiments, the rotation axis can be a vertical axis. For example, the LIDAR device 100 can be mounted on a vehicle, and the rotation axis can be substantially perpendicular to the road surface on which the vehicle is operating. In some embodiments, rotating platform 118 can rotate a full 360 degrees at a rate of 3-30 Hz. Other rotation rates are also possible. In other embodiments, rotating platform 118 can rotate less than 360 degrees. For example, rotating platform 118 can rotate back and forth within a certain range of angles. In some embodiments, rotating platform 118 can continuously rotate LIDAR device 100 during multiple measurement time periods. In other embodiments, rotating platform 118 may not provide continuous rotation, but instead may be used to adjust the orientation of LIDAR device 100 at different times (e.g., in response to identifying certain areas of interest in the environment).

[0062] like Figure 1 As shown, LIDAR device 100 includes a housing 124 that encloses primary light emitter 102, secondary light emitter 104, detector 106, primary emitter circuit 108, secondary emitter circuit 110, detector circuit 112, primary optical element 114, and secondary optical element 116. Housing 124 can be coupled to rotating platform 118. In some embodiments, housing 124 can be transparent to light emitted by primary light emitter 102 and secondary light emitter 104. In other embodiments, housing 124 can be opaque but can include an optical window 126 that is transparent to light emitted by primary light emitter 102 and secondary light emitter 104. For example, primary optical element 114 and secondary optical element 116 may be arranged to direct light emitted by primary light emitter 102 and secondary light emitter 104 into the environment of LIDAR device 100 through optical window 126, and may be arranged to direct reflected light from the environment that enters LIDAR device 100 through optical window 126 to detector 106.

[0063] In some embodiments, the primary optical element 114 can define a first optical path from the primary light emitter 102 to the optical window 126, and the secondary optical element 116 can define a second optical path from the secondary light emitter 104 to the optical window 126. The first optical path and the second optical path can be separate. Alternatively, the first optical path and the second optical path can partially overlap.

[0064] The controller 128 may include one or more processors 130 and a data storage device 132. The processor 130 may include one or more general-purpose processors and / or one or more special-purpose processors (e.g., a digital signal processor, etc.). The data storage device 132 may include or may take the form of one or more non-transitory computer-readable storage media that can be read or accessed by the processor 130. The data storage device 132 can include volatile and / or non-volatile storage components, such as electrical, optical, magnetic, organic, or other memory or disk storage devices, which may be fully or partially integrated with at least one of the processors 130. In addition to or in place of the processor 130 and the data storage device 132, the controller 128 may include other types of analog and / or digital circuitry. For example, the controller 128 may include a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

[0065] In some examples, data storage 132 may store program instructions that are executable by processor 130 to cause LIDAR device 100 to perform various operations described herein. For example, controller 128 may control primary light emitter 102 via primary emitter circuit 108 (e.g., activating and deactivating individual light emitters within primary light emitter 102) and may control secondary light emitter 104 via secondary light emitter circuit 110. Controller 128 may also receive data (e.g., ADC values ​​with corresponding timestamps) from detector circuit 112 and analyze the data to detect reflected light pulses and identify reflected light pulses that indicate reflections from retroreflectors. Controller 128 may also control actuator 122 to control the rotation of LIDAR device 100. Controller 128 may also perform other operations. Furthermore, in conjunction with certain operations, controller 128 may communicate with a computing device or other component external to LIDAR device 100. For example, in implementations where the LIDAR device 100 is coupled to an autonomous vehicle, the controller 128 may send data to, and receive instructions from, a computing device that controls the autonomous driving operation of the vehicle.

[0066] Figure 2 2 is a cross-sectional view of a LIDAR device 200 according to an example embodiment. In this example, the LIDAR device 200 is configured to rotate about an axis of rotation in a rotation direction 202 . Figure 2 The cross-sectional view of FIG20 is in a plane perpendicular to the rotation axis. The rotation axis can be a vertical axis, causing rotation in rotation direction 202 to enable LIDAR device 200 to scan a range of azimuth angles in the environment. Alternatively or additionally, LIDAR device 200 can rotate about a horizontal axis to scan a range of elevation angles, or can be configured to scan a portion of the environment in some other manner.

[0067] As shown, LIDAR device 200 includes various optical components enclosed within housing 204 and optical window 206. The optical components of LIDAR device 200 include a plurality of primary light emitters exemplified by primary light emitters 208 and 210, a secondary light emitter 212, and a plurality of detectors exemplified by detectors 218 and 220. In this example, primary light emitter 208 is paired with detector 218 to provide a first transmission / reception channel, and primary light emitter 210 is paired with detector 220 to provide a second transmission / reception channel. Although Figure 2 Two primary light emitters and two detectors are shown, but it should be understood that the LIDAR device 200 can include any number of primary light emitters and detectors to provide any number of transmission / reception channels.

[0068] In this example, LIDAR device 200 includes a telecentric lens assembly 224 comprising a plurality of lenses (exemplified by lenses 226 and 228) mounted in a lens barrel / baffle structure 230 coupled to optical window 206. Telecentric lens assembly 224 is arranged to direct light emitted from primary light emitters 208 and 210 through optical window 206 into the environment of LIDAR device 200 to illuminate fields of view 240 and 242, respectively. Telecentric lens assembly 224 is also arranged to direct reflected light from the environment that enters LIDAR device 200 through optical window 206 from within fields of view 240 and 242 toward detectors 218 and 220, respectively.

[0069] Fields of view 240 and 242 are defined in part by apertures 250 and 252, respectively. Apertures 250 and 252 may be pinhole apertures (e.g., having a diameter between 100 microns and 500 microns) formed in an opaque material (shown as aperture plate 254). For illustrative purposes, Figure 2 Only two apertures are shown. However, it should be understood that aperture plate 254 can include any number of apertures, wherein each aperture defines a corresponding field of view for a corresponding transmission / reception channel including a corresponding primary light emitter and a corresponding detector. The apertures in aperture plate 254 can be arranged in a one-dimensional array, a two-dimensional array, or some other pattern. The various fields of view of the transmission / reception channels can together provide an overall field of view 244 for LIDAR device 200.

[0070] Apertures 250 and 252 are located at the focal plane of telecentric lens assembly 224 between telecentric lens assembly 224 and detectors 218 and 220. With this configuration, light from fields of view 240 and 242 is focused by telecentric lens assembly 224 into apertures 250 and 252, and the focused light is then diverged toward detectors 218 and 220. As shown, detector 218 intercepts diverging light 256 from aperture 250, and detector 220 intercepts diverging light 258 from aperture 252. Advantageously, detectors 218 and 220 can each comprise an array of single-photon detectors that covers an area substantially matching the area illuminated by diverging light 256 and 258, in order to provide single-photon detection with a high dynamic range. For example, detectors 218 and 220 can each comprise a SiPM.

[0071] As shown, light emitted by primary light emitters 208 and 210 is guided by light guides 260 and 262 to apertures 250 and 252, respectively. More specifically, light emitted by primary light emitters 208 and 210 is coupled into input ends of light guides 260 and 262 (e.g., via respective cylindrical lenses), and light guides 260 and 262 guide light from their respective input ends to respective output ends positioned near apertures 250 and 252 by total internal reflection. The output ends of light guides 260 and 262 include reflective angled surfaces that reflect at least a portion of the guided light exiting light guides 260 and 262 toward apertures 250 and 252, respectively. Telecentric lens assembly 224 collimates light emitted from light guides 260 and 262 through apertures 250 and 252 and transmits the collimated light through optical window 206 into fields of view 240 and 242, respectively.

[0072] Secondary light emitter 212 emits light that is collimated by Fresnel lens 260 and then diffused by diffuser 262. The diffused light from diffuser 262 is transmitted through optical window 206 to illuminate a field of view that (beyond a certain distance away from LIDAR device 200) encompasses fields of view 240 and 242 of LIDAR device 200 and an overall field of view 244. Secondary light emitter 212, Fresnel lens 260, and diffuser 262 can be mounted to a coordinate system 264 that is attached to lens barrel / baffle structure 224 and coupled to optical window 206.

[0073] Figure 3 An example arrangement 300 of fields of view (FOVs) of transmission / reception channels of a LIDAR device, such as LIDAR device 100 or LIDAR device 200, is shown. In this example, the FOVs are arranged in a two-dimensional array, with four FOVs arranged horizontally (illustrated by FOVs 302-308) and eight FOVs arranged vertically (illustrated by FOVs 308-322). In other examples, a greater or lesser number of FOVs can be arranged horizontally, and a greater or lesser number of FOVs can be arranged vertically. Additionally, although Figure 3 The FOVs are shown arranged in a two-dimensional array, but the FOVs can be arranged in a one-dimensional array or in some other pattern. Figure 3 In FIG, each FOV is shown as being generally circular. However, in practice, the FOV of a transmission / reception channel can be elliptical, square, rectangular, trapezoidal, or some other shape.

[0074] Figure 3 Also shown is FOV 330, which corresponds to the field of view generated by one or more secondary light emitters such as Figure 1 The secondary light emitter 104 shown in Figure 2As shown in the figure, the FOV 330 of the secondary light emitter covers the FOV of the transmission / reception channel. In addition, although the FOV 330 is in Figure 3 3. Although shown as a rectangle in FIG. 3, FOV 330 may be square, circular, elliptical, trapezoidal, or some other shape.

[0075] Because the light from the secondary light emitter is spread over a wider FOV (e.g., FOV 330) than the FOV of the transmission / reception channels (e.g., FOVs 302-322), the light from the secondary light emitter can have a lower intensity than the light from each primary light emitter. For example, the intensity of the light from the secondary light emitter can be one order of magnitude lower, two orders of magnitude lower, or three or more orders of magnitude lower.

[0076] although Figure 1 and Figure 2 Example configurations of LIDAR devices 100 and 200 are shown, and Figure 3 The resulting example FOV is shown, but it should be understood that other configurations are possible. For example, LIDAR devices 100 and 200 are shown as being capable of rotation. However, non-rotating LIDAR devices are also possible. Furthermore, while LIDAR devices 100 and 200 include one or more secondary light emitters for detecting retroreflectors, some LIDAR devices may include one or more primary light emitters but no secondary light emitters. In such LIDAR devices, reflected light pulses from the primary light emitters can be analyzed to determine whether they have been reflected by a retroreflector.

[0077] Figures 4A-4E A vehicle 400 is shown according to an example embodiment. The vehicle 400 may be a semi-autonomous or fully autonomous vehicle. Figures 4A-4E Vehicle 400 is shown as a car (e.g., a minivan), but it will be understood that vehicle 400 can comprise another type of autonomous vehicle, robot, or drone capable of navigating within its environment using sensors and other information about its environment.

[0078] Vehicle 400 may include one or more sensor systems 402, 404, 406, 408, and 410. In an exemplary embodiment, sensor systems 402, 404, 406, 408, and 410 each include a respective LIDAR device. Additionally, one or more of sensor systems 402, 404, 406, 408, and 410 may include a radar device, a camera, or other sensor. In an exemplary embodiment, sensor system 402 may be coupled to the top of vehicle 400, sensor system 404 may be coupled to the front of vehicle 400, sensor system 406 may be coupled to the rear of vehicle 400, sensor system 408 may be coupled to the right side of vehicle 400, and sensor system 410 may be coupled to the left side of vehicle 400. In other embodiments, one or more sensor systems may be coupled to other parts of the vehicle.

[0079] The LIDAR devices of sensor systems 402, 404, 406, 408, and 410 may be configured to move about an axis (e.g., Figures 4A-4E The vehicle 400 is rotated about the z-axis (shown in FIG) to illuminate at least a portion of the environment surrounding the vehicle 400 with light pulses and detect reflected light pulses. Based on the detection of the reflected light pulses, information about the environment can be determined. The information determined from the reflected light pulses can indicate the distance and direction to one or more objects in the environment surrounding the vehicle 400. For example, this information can be used to generate point cloud information related to physical objects in the environment of the vehicle 400. This information can also be used to determine the reflectivity of objects in the environment, the material composition of objects in the environment, or other information about the environment of the vehicle 400.

[0080] The LIDAR devices of sensor systems 402, 404, 406, 408, and 410 may have different fields of view that may overlap. Figures 4A-4E In the configuration shown, the LIDAR device of sensor system 402 may have a long-range field of view that extends 360 degrees around the vehicle, while the LIDAR devices of sensor systems 404, 406, 408, and 410 may have a shorter-range field of view that covers various directions in front of, behind, to the right, and to the left of vehicle 400. At least a portion of each respective field of view of the LIDAR devices of sensor systems 404, 406, 408, and 410 may overlap with the field of view of the LIDAR device of sensor system 402.

[0081] Information obtained from one or more of sensor systems 402, 404, 406, 408, and 410 can be used to control vehicle 400, such as when vehicle 400 is operating in an autonomous or semi-autonomous driving mode. For example, the information can be used to determine a route (or adjust an existing route), speed, acceleration, vehicle orientation, braking maneuvers, or other driving behaviors or operations of vehicle 400.

[0082] III. Example Method and Timing Diagram

[0083] Described herein are example methods and processes that may be implemented in LIDAR devices 100 and 200. However, the described methods and processes can be implemented in LIDAR devices that are configured differently than LIDAR devices 100 and 200.

[0084] Figure 5 5 is a flow chart of a method 500 according to an example embodiment. For example, the method 500 presents an embodiment of a method that can be used with any of the LIDAR devices 100 and / or the LIDAR devices 200. The method 500 may include one or more operations, functions, or actions as shown in one or more of blocks 502-506.

[0085] In addition, for method 500 and other processes and methods disclosed herein, flow chart illustrates a possible function and operation of the present embodiment. In this regard, each frame can represent a module, segment, a part of a manufacturing or operating process or a part of a program code, which includes one or more instructions for a specific logical function or step in the process that can be executed by a processor. The program code can be stored on any type of computer-readable medium, for example, such as a storage device including a disk or hard drive. The computer-readable medium can include non-transitory computer-readable media, for example, a computer-readable medium that stores data in a short period of time, such as register memory, processor cache and random access memory (RAM). The computer-readable medium can also include non-transitory media, such as secondary or persistent long-term storage devices, such as read-only memory (ROM), optical disc or magnetic disk, compact disc read-only memory (CD-ROM). The computer-readable medium can also be any other volatile or non-volatile storage system. The computer-readable medium can be considered to be, for example, a computer-readable storage medium or a tangible storage device.

[0086] Additionally, for method 500 and other processes and methods disclosed herein, Figure 5 Each block in the diagram may represent circuits that are wired to perform the specific logical functions in the process.

[0087] At block 502, method 500 involves emitting, by a light emitter of a LIDAR device, a first light pulse into a field of view. In some examples, the light emitter can be the only light emitter of the LIDAR device. In other examples, the light emitter can be one of a plurality of light emitters of the LIDAR device, wherein each light emitter is configured to emit light pulses into a respective field of view. In some such examples, the LIDAR device can include one or more primary light emitters (e.g., primary light emitter 102 or primary light emitters 208, 210) and one or more secondary light emitters (e.g., secondary light emitter 104 or secondary light emitter 212). In such examples, the light emitter emitting the first light pulse can be the primary light emitter. The field of view can be any field of view within an environment of the LIDAR device, such as Figure 2 One of the fields of view 240 or 242 shown in Figure 3 One of the fields of view 302-322 shown in .

[0088] In some embodiments, the LIDAR device can be configured to determine the distance to an object in the environment by emitting light pulses and detecting reflected light pulses during consecutive measurement time periods. In such embodiments, a first light pulse can be emitted by the light emitter during one of the consecutive measurement time periods.

[0089] At block 504, method 500 involves determining that a detector of the LIDAR device detects at least one reflected light pulse indicative of a retroreflector or other highly reflective object during a first measurement period, wherein the detector is configured to detect light from within the field of view. The detector can be any detector capable of detecting light, such as Figure 1 The detector 106 shown in Figure 2 Detectors 218 and 220 described in .

[0090] In some embodiments, a first light pulse is emitted by the light emitter during the first measurement time period, and the at least one reflected light pulse detected by the detector is a reflection of the first light pulse.

[0091] In such an embodiment, the reflected light pulse can indicate a reflection from a retroreflector or other highly reflective object based on the shape of the reflected light pulse. For example, a reflected light pulse from a retroreflector can be so intense that it quickly saturates the detector. As a result, the detected signal (e.g., the ADC value as a function of time) can increase to a large peak value (e.g., a peak value corresponding to the saturation value of the detector), but once the detector is saturated and can no longer detect photons, the detected signal can drop very quickly. The resulting pulse has a large peak value but is also very narrow. Therefore, various characteristics of the detected pulse, such as the peak value of the pulse, the width of the pulse, and / or the steepness of the falling edge of the pulse, can indicate a reflection from a retroreflector or other highly reflective object.

[0092] In some embodiments, the at least one reflected light pulse detected by the detector can be a reflection of a secondary light pulse emitted by a secondary light emitter of the LIDAR device during the first measurement time period.

[0093] In such an embodiment, the LIDAR device may include at least one primary light emitter and at least one secondary light emitter, wherein the at least one primary light emitter emits a primary light pulse during a standard measurement period, and the at least one secondary light emitter emits a secondary light pulse during a dedicated measurement period. The light pulses emitted by the at least one secondary light emitter may be spread over a wider field of view than the light pulses emitted by the at least one primary light emitter and may have a lower intensity. The first measurement period may be a dedicated measurement period in which the at least one secondary light emitter emits light to map the position of the retroreflector and the at least one primary light emitter does not emit light. Thus, the first light pulse may be emitted by the primary light emitter during a standard measurement period preceding the first measurement period. In such an embodiment, the reflected light pulse may indicate a reflection from a retroreflector or other highly reflective object based on the magnitude of the reflected light pulse exceeding a predetermined threshold. The magnitude of the reflected light pulse may be determined based on a peak value of the reflected light pulse, an integrated area of ​​the reflected light pulse, or based on some other measurement.

[0094] In some embodiments, the LIDAR device may include multiple secondary light emitters. For example, each primary light emitter may be paired with a corresponding secondary light emitter having the same or similar field of view (e.g., by placing the paired primary and secondary light emitters in close proximity to each other). In each pair, the primary light emitter may emit a primary light pulse, and the secondary light emitter may emit a secondary light pulse at a lower intensity (before or after emitting the primary light pulse) to detect reflectors in the field of view.

[0095] In some embodiments, the at least one reflected light pulse detected by the detector can be two reflected light pulses detected by the detector: a reflection of a first light pulse emitted by the light emitter and a reflection of a secondary light pulse emitted by the secondary light emitter.

[0096] In such an embodiment, the LIDAR device may include at least one primary light emitter and at least one secondary light emitter, and both types of light emitters may emit light pulses during each measurement time period. Thus, a first light pulse may be emitted by the primary light emitter during the first measurement time period, and a secondary light pulse may be emitted by the secondary light emitter during the first measurement time period. The first light pulse and the secondary light pulse may be emitted at different times (e.g., the secondary light pulse may be emitted after the first light pulse), and the two light pulses may be separated in time by a predetermined time difference (e.g., 50 nanoseconds). The two light pulses may also have different intensities and beam widths, with the secondary light pulse being spread over a wider field of view and having a lower intensity than the first light pulse.

[0097] The predetermined time difference can be a fixed time difference that is the same for each measurement period. Alternatively, the predetermined time difference can vary from one measurement period to another. Furthermore, in embodiments where the LIDAR device includes multiple primary light emitters, the predetermined time difference can be the same for all primary light emitters. Alternatively, each primary light emitter can have a different predetermined time difference between the time the primary light emitter emits a primary light pulse and the time the secondary light pulse is emitted.

[0098] A time difference between a first light pulse emitted by a primary light emitter and a secondary light pulse emitted by a secondary light emitter can be used to determine that a reflected light pulse detected by a detector indicates a reflection from a retroreflector or other highly reflective object. For example, the detector can detect a first reflected light pulse at a first time and a second reflected light pulse at a second time. Determination that the two reflected light pulses detected by the detector indicate a reflection from a retroreflector or other highly reflective object can be based on determining that the time difference between the first time and the second time corresponds to a predetermined time difference between the time when the first light pulse was emitted by the primary light emitter and the time when the secondary light pulse was emitted by the secondary light emitter.

[0099] Determining that a reflected light pulse detected by the detector indicates a reflection from a retroreflector or other highly reflective object can also be based on multiple shots.For example, the timing between transmitted light pulses can be varied to resolve ambiguity in detecting retroreflectors.

[0100] Determining whether the first and second reflected light pulses detected by the detector indicate reflection from a retroreflector or other highly reflective object may also consider other characteristics of the first and second reflected light pulses. In some implementations, determining this may involve examining whether the peak values ​​of the first and second reflected light pulses are consistent with the first light pulse emitted by the primary light emitter and the secondary light pulse emitted by the secondary light emitter. For example, if the first light pulse was emitted before the secondary light pulse, the detected first reflected light pulse should have a higher peak value than the detected second reflected light pulse. In some implementations, determining this may involve determining whether one of the reflected light pulses has a shape indicative of reflection from a retroreflector (e.g., a combination of a high peak value with a narrow pulse width and a steep falling edge). In some implementations, determining this may involve determining whether the first and / or second reflected light pulses have a magnitude exceeding a predetermined threshold. For example, the peak value of the first reflected light pulse may be compared to a first threshold indicating that the first light pulse was reflected from a retroreflector, and / or the peak value of the second reflected light pulse may be compared to a second, different threshold indicating that the secondary light pulse was reflected from a retroreflector.

[0101] In a variation of the method, the primary light emitter can emit both the first light pulse and the secondary light pulse (at a lower intensity) separated in time by a predetermined period. Thus, the intensity of the light pulse emitted by the primary light pulse can be controlled rather than using a separate secondary light emitter.

[0102] At block 506, method 500 involves, in response to detecting at least one reflected light pulse indicating a reflection from a retroreflector or other highly reflective object, deactivating a light emitter during one or more subsequent measurement time periods. The one or more subsequent measurement time periods occur after the first measurement time period. In some embodiments, deactivating the light emitter during the one or more subsequent measurement time periods involves controlling the light emitter so that the light emitter does not emit light (e.g., does not illuminate the retroreflector) during the one or more subsequent measurement time periods. Alternatively, deactivating the light emitter during the one or more subsequent measurement time periods can involve controlling the light emitter so that the light emitter emits light at a reduced level (e.g., light pulses with reduced pulse energy and / or intensity) during the one or more subsequent measurement time periods. Advantageously, even though the light emitter can still emit some light toward the retroreflector, the reduced light emission level can be low enough that crosstalk is substantially reduced or eliminated.

[0103] In some embodiments, method 500 further involves determining when to reactivate a deactivated light emitter. Furthermore, determining when to reactivate a deactivated light emitter may involve determining whether the light emitter's corresponding detector detects one or more additional reflected light pulses indicative of a reflection from a retroreflector or other highly reflective object during one or more subsequent measurement time periods. In this regard, even if the light emitter is deactivated during one or more subsequent measurement time periods, the light emitter's corresponding detector may still detect reflected light pulses for at least two possible reasons.

[0104] First, in embodiments where the LIDAR device includes multiple primary light emitters (including deactivated light emitters), stray light from one or more of the other primary light emitters can enter the field of view of the deactivated light emitter and reach the retroreflector. Consequently, a detector configured to detect light within the field of view of the deactivated light emitter can detect reflected light pulses corresponding to stray light from one or more of the other primary light emitters that was reflected by the retroreflector or other highly reflective object.

[0105] Secondly, in embodiments where the LIDAR device includes a secondary light emitter, the secondary light emitter can continue to emit light pulses into a wide field of view that includes the field of view of the deactivated light emitter. Thus, the detector can detect reflected light pulses corresponding to light from the secondary light emitter that is reflected by a retroreflector or other highly reflective object.

[0106] Thus, as a result of stray light reflecting off the retroreflector and / or as a result of light from a secondary light emitter reflecting off the retroreflector, the detector can detect one or more additional reflected light pulses during a second measurement period that occurs after the first measurement period. The second measurement period can occur immediately after the first measurement period or a certain number of measurement periods after the first measurement period. The one or more additional reflected light pulses can be analyzed to determine whether the additional reflected light pulses indicate reflections from the retroreflector.

[0107] In some embodiments, the analysis may involve comparing the magnitude of the additional reflected light pulse (e.g., the peak value or integrated area of ​​the additional reflected light pulse) to a threshold. If the magnitude exceeds the threshold, the additional reflected light pulse may be considered to be the result of a reflection from a retroreflector or other highly reflective object in the field of view of the deactivated light emitter. If the magnitude does not exceed the threshold, the additional reflected light pulse may be considered to be the result of noise or stray light that has not been reflected by the retroreflector or other highly reflective object, thereby indicating that the retroreflector or other highly reflective object is no longer in the field of view of the deactivated light emitter.

[0108] In some embodiments (e.g., in embodiments where the primary and secondary light emitters emit light pulses separated in time by a predetermined time difference), the analysis may involve determining whether two additional reflected light pulses are detected with a time difference corresponding to the predetermined time difference. For example, one of the reflected light pulses may be caused by stray light from light pulses emitted by one or more other primary light emitters reflecting off a retroreflector, and the other reflected light pulse may be caused by light emitted by the secondary light emitter reflecting off a retroreflector or other highly reflective object. If two additional reflected light pulses are detected with a time difference corresponding to the predetermined time difference, the additional reflected light pulses may be considered to be the result of reflections from a retroreflector or other highly reflective object in the field of view of the deactivated light emitter. Failure to detect such additional reflected light pulses may indicate that the retroreflector or other highly reflective object is no longer in the field of view of the deactivated light emitter.

[0109] If the analysis indicates that the one or more additional reflected light pulses detected by the detector during the second measurement time period indicate a reflection from a retroreflector or other highly reflective object, the light emitter may continue to be deactivated for the one or more additional measurement time periods. However, if the analysis indicates that the additional reflected light pulses do not indicate a reflection from a retroreflector or other highly reflective object, the light emitter may be reactivated such that the light emitter emits a second light pulse in a third measurement time period occurring after the second measurement time period.

[0110] Figures 6A-6C An example scenario 600 is shown in which a LIDAR device scans a portion of its environment. The LIDAR device includes multiple transmission / reception channels having a field of view spanning a range of elevation angles and a range of azimuth angles. For illustration purposes, Figures 6A-6C The fields of view of the transmission / reception channels are shown as a grid pattern comprising five different azimuth angles and seven different elevation angles. The field of view of each individual transmission / reception channel is indicated by a circle. However, in practice, the fields of view of the transmission / reception channels may take on some other shape. Additionally, although Figures 6A-6C The fields of view are shown in a grid pattern, but it should be understood that the fields of view of the transmission / reception channels can be arranged differently. In scenario 600, any of the aforementioned techniques can be used to determine when to deactivate a light emitter due to the presence of a retroreflector in the light emitter's field of view, and when to reactivate the light emitter due to the retroreflector no longer being in the light emitter's field of view.

[0111] like Figure 6A6, as would occur when a LIDAR device scans a portion of its environment, the grid pattern of the field of view of the passageway moves in direction 604 toward retroreflector 602. Retroreflector 602 can be, for example, a road sign (e.g., a crosswalk sign), a retroreflective marking on a vehicle, or some other type of retroreflector. Direction 604 can be, for example, a horizontal direction (e.g., parallel to the ground or road surface) based on the rotation of the LIDAR device about a vertical axis.

[0112] exist Figure 6A At the time shown, a portion of retroreflector 602 has just moved into the field of view of channel 606, but is not yet in the field of view of any other channel. The light emitter of channel 606 emits a light pulse toward retroreflector 602, which generates a strong reflected light pulse detected by the detector of channel 606. In addition, one or more adjacent channels (such as channels 608, 610, and / or 612) may detect weak reflected light pulses caused by stray light from the strong reflected light pulse entering the field of view of those channels. If used for distance determination, these weak reflected light pulses may cause inaccuracies. Therefore, it is desirable to detect the presence of retroreflector 602 and control the light emitted in the various transmission / reception channels to avoid illuminating retroreflector 602.

[0113] In scenario 600, any of the techniques described herein may be used (e.g., with or without the assistance of a secondary light emitter) to determine that a strong reflected light pulse detected by a detector in channel 606 is indicative of a reflection from a retroreflector in the field of view of channel 606. In response to this determination, the light emitter in channel 606 is deactivated.

[0114] Figure 6B A later point in time is shown when retroreflector 602 is in the field of view of channel 606 and is also in the field of view of seven other channels. Any of the techniques described herein may be used to detect the presence of retroreflector 602 in the fields of view of these channels and responsively deactivate the light emitters in these channels. Figure 6B , channels with deactivated light emitters are indicated by hatching.

[0115] Figure 6C A later point in time is shown when retroreflector 602 is no longer in the field of view of channel 606. The light emitters in channel 606 have been reactivated, as indicated by channel 606 being shown without shading. In scenario 600, in response to determining that retroreflector 602 is no longer in the field of view of channel 606, the light emitters in channel 606 are reactivated. This determination can be made using any of the techniques described herein. However, retroreflector 602 is in the field of view of other channels. As indicated by shading, the light emitters in these channels have been deactivated.

[0116] Figures 7A-7Dis a timing diagram illustrating scenario 700, in which a retroreflector is detected in the field of view of a light emitter of a LIDAR device, the light emitter is responsively deactivated, and then reactivated when the retroreflector is no longer in the field of view of the light emitter. In scenario 700, the LIDAR device includes multiple transmission / reception channels, each having a respective field of view, into which respective light emitters transmit light pulses, and corresponding detectors configured to detect light from the field of view. For illustrative purposes, three transmission / reception channels (CH1, CH2, and CH3) are depicted in scenario 700. Furthermore, scenario 700 is an example of detecting a retroreflector without using a flood illuminator, flash illuminator, or other type of secondary light emitter.

[0117] Figure 7A A measurement time period T1 is shown, which includes an emission time period followed by a detection time period. Light emitters in CH1, CH2, and CH3 emit light pulses 702, 704, and 706 during the emission time period. In this scenario, light pulses 702-706 are emitted simultaneously or nearly simultaneously. Alternatively, light pulses 702-706 can be emitted at different times within the emission time period.

[0118] The detector in CH1 detects reflected light pulses 708 and 710. The detector in CH2 detects reflected light pulse 712. The detector in CH3 detects reflected light pulse 714. The shapes of reflected light pulses 708-714 are analyzed to determine whether any of these reflected light pulses indicate a reflection from a retroreflector. In this example, reflected light pulse 712 indicates a reflection from a retroreflector based on its shape, specifically, based on the fact that the reflected light pulse is narrow and has a large peak. Therefore, the shape of reflected light pulse 712 indicates that a retroreflector is in the field of view of CH2.

[0119] The shapes of the other reflected pulses do not indicate reflections from a retroreflector and therefore can be used to determine the distance to the object. However, because reflected light pulse 708 is a weak pulse detected simultaneously with retroreflected light pulse 712, it is unclear whether reflected light pulse 708 actually represents a reflection from an object in the field of view of CH1, or whether reflected light pulse 708 represents stray light from a retroreflector that is actually in the field of view of CH2, not CH1.

[0120] Based on the shape of reflected light pulse 712 indicating a retroreflector in CH2's field of view, CH2's light emitter is deactivated for one or more subsequent measurement time periods. Figure 7BA subsequent measurement period T2 is shown. As shown, the light emitters in CH1 and CH3 emit light pulses 720 and 722, but the light emitter in CH2 does not emit light. The detector in CH1 detects a reflected light pulse 724 (which may be similar to reflected light pulse 710), and the detector in CH3 detects a reflected light pulse 726 (which may be similar to reflected light pulse 714). Even though the light emitter in CH2 does not emit light, the detector in CH2 detects a reflected light pulse 728 (e.g., the magnitude of reflected light pulse 728 exceeds a threshold). The detection of reflected light pulse 728 indicates that the retroreflector is still within the field of view of CH2. Specifically, reflected light pulse 728 occurs because stray light from CH1 and / or CH3 reaches the retroreflector and is reflected into the field of view of CH2.

[0121] Figure 7B It is also shown that detector CH1 no longer detects reflected light pulses like the blurred reflected light pulse 708. Thus, in this example, deactivating the light emitter in CH2 so that it does not illuminate the retroreflector effectively prevents CH1 from detecting spurious reflected light pulses.

[0122] The CH2-based detector detects a reflected light pulse while the CH2 light emitter is deactivated, indicating that the retroreflector is still within the retroreflector's field of view, and the CH2 light emitter may remain deactivated for one or more subsequent measurement periods. However, at some point, the retroreflector may no longer be within the CH2 field of view (e.g., because the LIDAR device has scanned past it). In scenario 700, this occurs during measurement period T3, as shown in FIG. Figure 7C shown.

[0123] like Figure 7C As shown, the light emitter in CH1 emits light pulse 730, the light emitter in CH3 emits light pulse 732, but the emitter in CH2 does not emit light. The detector in CH1 detects reflected light pulse 734 (which may be similar to reflected light pulse 724), and the detector in CH3 detects reflected light pulse 736 (which may be similar to reflected light pulse 726). However, the detector in CH2 does not detect a reflected light pulse (e.g., does not detect a reflected light pulse exceeding a threshold). This indicates that the retroreflector is no longer in the field of view of CH2.

[0124] Based on the detector in CH2 not detecting a reflected light pulse during measurement time period T3, the light emitter of CH2 is reactivated to emit light during one or more subsequent measurement time periods. Figure 7DA subsequent measurement period T4 is shown. As shown, the light emitters in CH1, CH2, and CH3 transmit light pulses 740, 742, and 744, respectively, and the detectors in CH1, CH2, and CH3 detect reflected light pulses 746, 748, and 750. In this case, reflected light pulses 746, 748, and 750 do not indicate reflections from the retroreflector and can therefore be used to determine the distance to the object.

[0125] Figures 8A-8D FIG8 is a timing diagram illustrating scenario 800, in which a retroreflector is detected in the field of view of a light emitter of a LIDAR device, the light emitter is responsively deactivated, and then reactivated when the retroreflector is no longer in the field of view of the light emitter. Scenario 800 is similar to scenario 700, except that secondary light emitters are used. Thus, in scenario 800, the LIDAR device includes multiple transmission / reception channels, each having a respective field of view, into which respective primary light emitters transmit primary pulses of light, and corresponding detectors are configured to detect light from the field of view. For illustrative purposes, three transmission / reception channels (CH1, CH2, and CH3) are depicted. In scenario 800, the secondary light emitters also transmit secondary light pulses into a wide field of view encompassing the fields of view of the transmission / reception channels. The secondary light pulses have a much lower intensity than the primary light pulses. As a result, reflections of the secondary light pulses are not expected to be detected as reflected light pulses (e.g., detected above a threshold) unless they are reflected by a retroreflector.

[0126] Figure 8A A measurement time period T1 is shown, which includes an emission time period followed by a detection time period. The primary light emitters in CH1, CH2, and CH3 emit primary light pulses 802, 804, and 806, respectively, during the emission time period. The secondary light emitters emit secondary light pulses 808 during the emission time period. Because the secondary light pulses 808 illuminate the field of view of each channel, the secondary light pulses 808 are shown in CH1, CH2, and CH3. In this example, the primary light pulses 802-806 are emitted simultaneously or nearly simultaneously, and the secondary light pulses 808 are emitted a predetermined time period (e.g., 50 nanoseconds) after the emission of the primary light pulses 802-806. Alternatively, the secondary light pulses 808 may be emitted before the emission of the primary light pulses 802-806, or simultaneously with the emission of the primary light pulses 802-806.

[0127] The detector in CH1 detects reflected light pulses 810 and 812. The detector in CH2 detects reflected light pulses 814 and 816. The detector in CH3 detects reflected light pulse 818. Reflected light pulses 810-818 are then analyzed to determine whether any of the reflected light pulses indicates a reflection from a retroreflector. This analysis can involve determining whether two reflected light pulses occur in the same channel with a time interval corresponding to a predetermined time period between the emission of primary light pulses 802-806 and secondary light pulse 808. In this case, reflected light pulses 814 and 816 in CH2 have such a time interval. Therefore, reflected light pulses 814 and 816 indicate a reflection from a retroreflector in CH2's field of view. This analysis can also consider other factors, such as the shape of the reflected light pulses. In this case, reflected light pulse 814 has a large peak and a narrow width, further indicating a reflection from a retroreflector in CH2's field of view.

[0128] Other reflected light pulses 810, 812, and 818 can be used to determine the distance to the object. However, because reflected light pulse 810 is a weak pulse detected at the same time as the reflected light pulse 814, reflected light pulse 810 may be due to crosstalk caused by a retroreflector in the field of view of CH2 rather than a reflection from an object in the field of view of CH1.

[0129] Based on determining that reflected light pulses 814 and 816 indicate reflections from a retroreflector in the field of view of CH2, the primary light emitter of CH2 is deactivated for one or more subsequent measurement time periods. Figure 8B A subsequent measurement period T2 is shown. During the emission period, the primary light emitters in CH1 and CH3 emit primary light pulses 820 and 822, but the primary light emitter in CH2 does not emit light. During the emission period, the secondary light emitter emits a secondary light pulse 824 into a wide field of view encompassing the fields of view of CH1, CH2, and CH3. During the detection period, the detector in CH1 detects a reflected light pulse 824 (which may be similar to reflected light pulse 812), the detector in CH2 detects weak reflected light pulses 828 and 830, and the detector in CH3 detects a reflected light pulse 832 (which may be similar to reflected light pulse 818).

[0130] Reflected light pulses 826-832 are analyzed to determine whether they indicate a reflection from a retroreflector. As previously described, the analysis can involve determining whether two reflected light pulses occur in the same channel with a time interval corresponding to a predetermined time period between the emission of primary light pulses 820, 822 and secondary light pulse 824. In this case, reflected light pulses 828 and 830 in CH2 have such a time interval. The analysis can also take into account other considerations, such as whether one or both pulses have a magnitude exceeding a threshold.

[0131] Thus, in this example, reflected light pulses 828 and 830 indicate reflections from a retroreflector within the field of view of CH2. Reflected light pulse 828 can be attributed to stray light from a primary light pulse emitted in another channel being reflected by the retroreflector into the field of view of CH2. Reflected light pulse 830 can be attributed to secondary light pulse 824 being reflected by the retroreflector.

[0132] Based on the determination that the retroreflector is still within the field of view of CH2, CH2's primary light emitter may remain deactivated for one or more subsequent measurement time periods. However, at some point, the retroreflector may no longer be within CH2's field of view (e.g., because the LIDAR device has scanned past it). In scenario 800, this occurs during measurement time period T3, as shown in FIG. Figure 8C shown.

[0133] like Figure 8C As shown, the primary light emitter in CH1 emits a primary light pulse 740, the primary light emitter in CH3 emits a primary light pulse 842, but the primary emitter in CH2 does not emit light. The secondary light emitter emits a secondary light pulse 844 into a wide field of view encompassing the fields of view of CH1, CH2, and CH3. During the detection period, the detector in CH1 detects a reflected light pulse 846 (which may be similar to reflected light pulse 826), and the detector in CH3 detects a reflected light pulse 848 (which may be similar to reflected light pulse 848). However, the detector in CH2 does not detect a reflected light pulse (e.g., does not detect a reflected light pulse exceeding a threshold). This indicates that the retroreflector is no longer in the field of view of CH2.

[0134] Based on the detector in CH2 not detecting a reflected light pulse during measurement time period T3, the light emitter of CH2 is reactivated to emit light during one or more subsequent measurement time periods. Figure 8D A subsequent measurement period T4 is shown. As shown, the primary light emitters in CH1, CH2, and CH3 transmit primary light pulses 850, 852, and 854, respectively, and the secondary light emitter transmits secondary light pulse 856. Detectors in CH1, CH2, and CH3 detect reflected light pulses 858, 860, and 862. In this case, reflected light pulses 858, 860, and 862 do not indicate reflections from the retroreflector and can therefore be used to determine the distance to the object.

[0135] In the above scenario 800, the secondary light emitter emits a secondary light pulse during each measurement period to detect retroreflectors. However, in other implementations, the secondary light emitter may emit secondary light pulses only during certain measurement periods. For example, the secondary light emitter may emit secondary light pulses only during dedicated measurement periods when the primary light emitter is not emitting light. The dedicated measurement periods may be interleaved with standard measurement periods in which the primary light emitter emits primary light pulses. For example, the dedicated measurement periods may occur every five measurement periods, every ten measurement periods, every twenty measurement periods, or at some other frequency. Alternatively, the dedicated measurement periods may be dynamically assigned, for example, in response to sensor data or other information indicating that the LIDAR device may scan for retroreflectors. In yet another approach, the dedicated measurement period may be a background measurement period used to determine the background level of ambient light. For example, the background measurement period may occur before the emission period of each measurement period, so that the background level determined during the background measurement period can be used to set a detection threshold used during subsequent measurement periods. Thus, in addition to measuring the background level of ambient light, the background measurement period can be used to detect reflections of secondary light pulses that may be indicative of reflections from retroreflectors or other highly reflective objects.

[0136] A dedicated measurement period can be used to determine when a retroreflector is within the field of view of a channel so that the primary light emitter in that channel can be deactivated responsively. A dedicated measurement period can also be used to determine when a retroreflector is no longer within the field of view of a channel so that the primary light emitter in that channel can be reactivated responsively. Figures 9A-9D is a timing diagram illustrating a scenario 900 in which a dedicated measurement period is used to determine when to deactivate and when to reactivate a primary light emitter.

[0137] Figure 9A A measurement period T1 is shown, which is a dedicated measurement period for detecting whether a retroreflector is within the field of view of any channel (CH1, CH2, and CH3). A secondary light emitter transmits a secondary light pulse 902 into a wide field of view encompassing the fields of view of CH1, CH2, and CH3. The intensity of secondary light pulse 902 is sufficiently low that a reflection of secondary light pulse 902 is detectable (e.g., detected above a threshold) only when it is reflected by a retroreflector. In this case, the detector in CH1 detects reflected light pulse 904, the detector in CH2 detects reflected light pulse 906, and the detector in CH3 does not detect a reflected light pulse. These detections indicate that a retroreflector is present in the fields of view of CH1 and CH2, but not in field of view CH3. In response, the primary light emitters in CH1 and CH2 are deactivated for one or more subsequent measurement periods.

[0138] Figure 9BA subsequent measurement period T2 is shown as a standard measurement period. The primary light emitter in CH3 emits a primary light pulse 910, and the detector in CH3 detects a reflected light pulse 912. The reflected light pulse 912 can be used to determine the distance to the object. The primary light emitters in CH1 and CH2 are deactivated, and the detectors in CH1 and CH2 do not detect any reflected light pulses.

[0139] A subsequent dedicated measurement period may be used to determine whether to reactivate the primary light transmitter in CH1 and / or the primary light transmitter in CH2. Figure 9C A subsequent dedicated measurement time period T3 is shown. As shown, the secondary light emitter transmits a secondary light pulse 920 into a wide field of view encompassing CH1, CH2, and CH3. The intensity of secondary light pulse 920 is sufficiently low that the reflection of secondary light pulse 920 is detectable (e.g., detected above a threshold) only when reflected by a retroreflector. In this case, the detector in CH1 detects reflected light pulse 922, but the detectors in CH2 and CH3 do not detect any reflected light pulses. These detections indicate that the retroreflector is still present in the field of view of CH1, that the retroreflector is no longer in the field of view of CH2, and that the retroreflector is not in the field of view of CH3. In response, the primary light emitter in CH1 is deactivated for one or more subsequent measurement time periods and reactivated in CH2 for one or more subsequent measurement time periods.

[0140] Figure 9D A subsequent standard measurement period T4 is shown. As shown, the primary light emitter in CH2 emits a primary light pulse 930, and the primary light emitter in CH3 emits a primary light pulse 932. The primary light emitter in CH1 is deactivated, and the detector in CH1 does not detect reflected light pulses. The detectors in CH2 and CH3 detect reflected light pulses 934 and 936, respectively, which can be used to determine the distance to the object.

[0141] IV. Example Information Sharing Between LIDAR Devices

[0142] As described above, the LIDAR device may detect that a retroreflector (or other highly reflective object) is within the field of view of a particular light emitter of the LIDAR device during a particular measurement time period and may responsively deactivate the particular light emitter. In some implementations, the LIDAR device may also be configured to share information about the detected retroreflector with one or more other systems (e.g., one or more other LIDAR devices). This information sharing can be particularly beneficial when multiple LIDAR devices with overlapping fields of view are coupled to a vehicle, such as a vehicle. Figures 4A-4EFor example, when a first LIDAR device on a vehicle detects a retroreflector that is also within the field of view of a second LIDAR device on the vehicle, information about the detected retroreflector can be shared with the second LIDAR device, enabling the second LIDAR device to deactivate its light emitter or take other actions to avoid illuminating the retroreflector. The information sharing can occur via a computing device on the vehicle (e.g., a computing device controlling the vehicle in an automated or semi-automated operating mode).

[0143] Figure 10 An example system 1000 for sharing information (e.g., information about detected retroreflectors) between LIDAR devices coupled to a vehicle is shown. In this example, system 1000 includes LIDAR devices 1010, 1020, 1030, 1040, and 1050, and also includes a computing device communicatively coupled to each LIDAR device. For example, Figures 4A-4E As shown, LIDAR devices 1010-1050 can be coupled to a vehicle. Thus, LIDAR device 1010 can be coupled to the top of the vehicle (e.g., as in sensor system 402), and LIDAR devices 1020-1050 can be coupled to the front, back, right, and left sides of the vehicle (e.g., as in sensor systems 404-410). Computing device 1060 can also be coupled to the vehicle. For example, computing device 1060 can be configured to control the vehicle in an autonomous mode, such as controlling the vehicle's speed, acceleration, direction, or other driving behavior.

[0144] The system 1000 can be configured to support one-way or two-way information sharing about retroreflectors. For one-way information sharing, one of the LIDAR devices (e.g., LIDAR device 1010) can be a "source" LIDAR device configured to detect a retroreflector and send information about the detected retroreflector to the computing device 1060, while the other LIDAR devices (e.g., LIDAR devices 1020-1050) can be "receiver" LIDAR devices configured to receive information about the detected retroreflector from the computing device 1060. For example, the source LIDAR device 1010 can detect a retroreflector (e.g., using any of the techniques described herein) and can responsively send information indicating the location of the detected retroreflector to the computing device 1060. Based on this information, the computing device 1060 can identify one or more of the recipient LIDAR devices 1020-1050 as having a field of view that includes the detected retroreflector and can send a message about the detected retroreflector to each of the one or more recipient LIDAR devices. In response to receiving the message, each of the one or more receiving LIDAR devices may deactivate a light transmitter or take other action to avoid illuminating the detected retroreflector.

[0145] This one-way information sharing can be particularly useful when the source LIDAR device has a wide field of view (e.g., 360 degrees around the vehicle) and the receiving LIDAR devices each have a narrower field of view that at least partially overlaps with the field of view of the source LIDAR device. The source LIDAR device can be generally configured to detect objects, or the source LIDAR device can be dedicated to detecting only retroreflectors.

[0146] In some implementations, system 1000 can support bidirectional information sharing about retroreflectors. In such an implementation, a retroreflector can be detected by any one of LIDAR devices 1010-1050, and computing device 1060 can send information about the detected retroreflector to any other LIDAR device that has a detected retroreflector in its field of view.

[0147] Figure 11 is a flow chart illustrating an example method 1100 for sharing information about detected retroreflectors. For purposes of illustration, reference will be made to Figure 10 The method 1100 is described with reference to the system 1000 shown in FIG. However, it should be understood that other configurations can be used.

[0148] As shown in block 1110, method 1100 involves receiving, by a computing device (e.g., computing device 1060), data from a first LIDAR device (e.g., LIDAR device 1010) coupled to a vehicle, wherein the data includes information indicating a location of a retroreflector detected by the first LIDAR device. In some cases, the data can include information indicating the locations of a plurality of retroreflectors detected by the first LIDAR device. The data can also include other information.

[0149] The first LIDAR device can detect the retroreflector using any of the techniques described herein. The information indicating the location of the detected retroreflector can include any information about the location of the retroreflector. For example, the information can indicate that the retroreflector was within the field of view of a particular light emitter among the plurality of light emitters in the first LIDAR device during a particular time period (e.g., a particular measurement time period during which the retroreflector was detected). Based on this information, the computing device can determine the direction in which the retroreflector is located. The information indicating the location of the detected retroreflector can also indicate the distance to the retroreflector (e.g., based on the time difference between the time when the transmitted light pulse was emitted and the time when the reflected light pulse from the retroreflector was detected). Other types of location information are also possible.

[0150] As shown in block 1110, method 1100 further involves determining, by the computing device, that the position of the retroreflector is within the field of view of a second LIDAR device coupled to the vehicle. As shown in block 1120, method 1100 further involves sending, by the computing device, a message to the second LIDAR device, wherein the message includes information indicating that the retroreflector is within the field of view of the second LIDAR device. In some cases, the message may include information indicating that multiple retroreflectors are within the field of view of the second LIDAR device (e.g., when the data from the first LIDAR device includes the positions of multiple retroreflectors).

[0151] In one possible implementation, the computing device can map the position of the retroreflector to a position in the vehicle's world coordinate system. The field of view of each LIDAR device coupled to the vehicle can also be mapped to the vehicle's world coordinate system. The computing device can then identify any LIDAR device (other than the LIDAR device that detected the retroreflector) that has a field of view in the world coordinate system that includes the position of the retroreflector in the world coordinate system. In this way, the computing device can determine that the position of the retroreflector is within the field of view of a second LIDAR device coupled to the vehicle and send a message about the retroreflector to the second LIDAR device. In some cases, the computing device can determine that the position of the retroreflector is within the field of view of multiple LIDAR devices coupled to the vehicle. In this case, the computing device can send a message about the retroreflector to each of the multiple LIDAR devices.

[0152] The information included in the message indicating that the retroreflector is within the field of view of the second LIDAR device can be any information that enables the second LIDAR device to recognize that the retroreflector is within its field of view. In an example embodiment, the second LIDAR device can responsively avoid illuminating the retroreflector. For example, in response to receiving the message, the second LIDAR device can deactivate a light emitter in the second LIDAR device to avoid illuminating the retroreflector.

[0153] In some implementations, the information indicating that the retroreflector is within the field of view of the second LIDAR device can specify the position of the retroreflector. For example, the information can include the relative position of the retroreflector relative to the second LIDAR device. The relative position can be mapped by a computing device from a position in the vehicle's world coordinate system to a position in the coordinate system or reference system of the second LIDAR device. The relative position of the retroreflector can be provided, for example, as a yaw angle of the second LIDAR device and a pitch angle of the second LIDAR device. However, other methods of specifying the position of the retroreflector are also possible.

[0154] The information indicating that the retroreflector is within the field of view of the second LIDAR device can also include other information about the retroreflector, such as whether the retroreflector is moving or static.

[0155] Method 1100 can also include the step of notifying the second LIDAR device when the detector retroreflector is no longer present at the location. For example, when the first LIDAR device reactivates a previously deactivated light emitter in response to a detected retroreflector, the first LIDAR device can notify the computing device, and the computing device can send a second message to the second LIDAR device indicating that the retroreflector is no longer present at the location previously indicated in the first message. However, the second message can indicate that the retroreflector is still within the field of view of the second LIDAR device but at a different relative position. The change in relative position can be the result of movement of the vehicle and / or movement of the retroreflective object.

[0156] V. Conclusion

[0157] The specific arrangements shown in the figures should not be considered as limiting. It should be understood that other implementations may include more or fewer of each element shown in a given figure. In addition, some of the shown elements may be combined or omitted. In addition, exemplary implementations may include elements not shown in the figures. In addition, although various aspects and implementations have been disclosed herein, other aspects and implementations will be clear to those skilled in the art. The various aspects and implementations disclosed herein are for illustrative purposes only and are not restrictive, and the true scope and spirit are indicated by the appended claims. Other implementations may be utilized and other changes may be made without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the various aspects of the present disclosure as generally described herein and shown in the accompanying drawings can be arranged, replaced, combined, separated, and designed in a variety of different configurations.

Claims

1. A method comprising: The light transmitter of the light detection and ranging (LIDAR) device transmits a first light pulse into the field of view. determining that a detector of the LIDAR device detects at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object during a first measurement time period, wherein the detector is configured to detect light from within the field of view; and In response to detecting at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object, the light emitter is deactivated during one or more subsequent measurement time periods, wherein the one or more subsequent measurement time periods occur after the first measurement time period.

2. The method according to claim 1, wherein Deactivating the light emitter during the one or more subsequent measurement time periods comprises: The light emitter is controlled such that the light emitter does not emit light during the one or more subsequent measurement time periods.

3. The method according to claim 1, wherein Deactivating the light emitter during the one or more subsequent measurement time periods comprises: The light emitter is controlled such that it emits light at a reduced level during the one or more measurement time periods.

4. The method according to claim 1, further comprising: Information is sent from the LIDAR device to a computing device indicating that the retroreflector or other highly reflective object was within the field of view of the light emitter and was detected during the first measurement time period.

5. The method according to claim 1, further comprising: Determining when to reactivate the light emitter, wherein determining when to reactivate the light emitter comprises: A determination is made as to whether the detector detects one or more additional reflected light pulses indicative of reflection by a retroreflector or other highly reflective object during the one or more subsequent measurement time periods.

6. The method according to claim 5, wherein: Determining when to reactivate the light emitter further comprises: determining that the detector detects an additional reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object during a second measurement time period, wherein the second measurement time period occurs after the first measurement time period; and In response to the determination, the light emitter is deactivated during a third measurement time period, wherein the third measurement time period occurs after the second measurement time period.

7. The method according to claim 6, wherein: The LIDAR device includes one or more additional light emitters, wherein the additional reflected light pulses indicative of reflections from a retroreflector or other highly reflective object include stray light from the one or more additional light emitters, the stray light being reflected by the retroreflector or other highly reflective object.

8. The method according to claim 6, further comprising: A secondary light pulse having a lower intensity than the first light pulse is emitted, wherein an additional reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object includes light from the secondary light pulse that was reflected by the retroreflector or other highly reflective object.

9. The method according to claim 5, wherein: Determining when to reactivate the light emitter further comprises: determining that the detector detects no additional reflected light pulses indicative of reflections from a retroreflector or other highly reflective object during a second measurement time period, wherein the second measurement time period occurs after the first measurement time period; and In response to the determination, the light emitter is reactivated such that the light emitter emits a second light pulse into the field of view during a third measurement time period, wherein the third measurement time period occurs after the second measurement time period.

10. The method according to claim 1, wherein The light emitter emits the first light pulse during the first measurement time period, wherein determining that the detector detects at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object during the first measurement time period comprises: detecting, by the detector, reflected light pulses during the first measurement period; and It is determined based at least on a shape of the reflected light pulse that the reflected light pulse indicates a reflection by a retroreflector or other highly reflective object.

11. The method according to claim 1, wherein The light emitter emits a first light pulse during a previous measurement time period, wherein the previous measurement time period occurs before the first measurement time period, wherein the light emitter is a primary light emitter of a LIDAR device, wherein the LIDAR device includes a secondary light emitter, wherein the primary light emitter does not emit light during the first measurement time period, the method further comprising emitting, by the secondary light emitter, a secondary light pulse during the first measurement time period, wherein the secondary light pulse has a lower intensity than the first light pulse, wherein determining that the detector detected at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object during the first measurement time period comprises: detecting, by a detector, the reflected light pulse during a first measurement time period; and The determination that the reflected light pulse is indicative of a reflection by a retroreflector or other highly reflective object is based at least on the reflected light pulse having a magnitude exceeding a predetermined threshold.

12. The method according to claim 1, wherein The light emitter is a primary light emitter of the LIDAR device, wherein the LIDAR device includes a secondary light emitter, and wherein the primary light emitter emits the first light pulse during the first measurement time period, the method further comprising: emitting, by the secondary light emitter, a secondary light pulse during the first measurement time period, wherein the secondary light pulse has a lower intensity than the first light pulse, wherein the first light pulse and the secondary light pulse are separated in time by a predetermined time difference, wherein determining that the detector detected at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object during the first measurement time period comprises: detecting, by the detector, a first reflected light pulse at a first time during the first measurement period and a second reflected light pulse at a second time during the first measurement period; and The first and second reflected light pulses are determined to indicate reflections from a retroreflector or other highly reflective object based at least on a time difference between the first and second times corresponding to a predetermined time difference.

13. A light detection and ranging (LIDAR) device, comprising: a light emitter configured to emit light pulses into the field of view; a detector configured to detect light from within the field of view; as well as A controller is configured to perform operations, the operations comprising: controlling the light emitter to emit a first light pulse into the field of view; determining that the detector detected at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object during a first measurement time period; and In response to detecting at least one reflected light pulse indicative of a reflection from a retroreflector or other highly reflective object, the light emitter is deactivated during one or more subsequent measurement time periods, wherein the one or more subsequent measurement time periods occur after the first measurement time period.

14. The LIDAR device according to claim 13, wherein: The operations further include: Determining when to reactivate the light emitter, wherein determining when to reactivate the light emitter comprises: determining whether the detector detects an additional light pulse indicative of a reflection from a retroreflector or other highly reflective object during a second measurement time period; in response to determining that the detector detected additional light pulses indicative of reflections from a retroreflector or other highly reflective object during the second measurement time period, deactivating the light emitter during a third measurement time period; and In response to determining that the detector does not detect additional light pulses indicative of reflections from a retroreflector or other highly reflective object during the second measurement time period, reactivating the light emitter during the third measurement time period, wherein the second measurement time period occurs after the first measurement time period and the third measurement time period occurs after the second measurement time period.

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