WO2022081910A1 - Multi-detector lidar systems and methods for mitigating range aliasing - Google Patents
Multi-detector lidar systems and methods for mitigating range aliasing Download PDFInfo
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/003—Bistatic lidar systems; Multistatic lidar systems
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/88—Lidar systems specially adapted for specific applications
- G01S17/93—Lidar systems specially adapted for specific applications for anti-collision purposes
- G01S17/931—Lidar systems specially adapted for specific applications for anti-collision purposes of land vehicles
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
- G01S7/4816—Constructional features, e.g. arrangements of optical elements of receivers alone
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/4861—Circuits for detection, sampling, integration or read-out
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B60—VEHICLES IN GENERAL
- B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
- B60W2420/00—Indexing codes relating to the type of sensors based on the principle of their operation
- B60W2420/40—Photo, light or radio wave sensitive means, e.g. infrared sensors
- B60W2420/408—Radar; Laser, e.g. lidar
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J1/00—Photometry, e.g. photographic exposure meter
- G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
- G01J1/44—Electric circuits
- G01J2001/4446—Type of detector
- G01J2001/446—Photodiode
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
- G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
- G01S17/06—Systems determining position data of a target
- G01S17/08—Systems determining position data of a target for measuring distance only
- G01S17/10—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves
- G01S17/18—Systems determining position data of a target for measuring distance only using transmission of interrupted, pulse-modulated waves wherein range gates are used
Definitions
- LIDAR systems for example, bistatic LIDAR systems that use a single receiver to detect light emitted by a single emitter
- the emitter used to emit light into the environment and the receiver used to detect return light reflecting from objects in the environment are physically displaced relative to each other.
- Such LIDAR configurations may inherently be associated with parallax problems because the light emitted by the emitter and received by the detector may not travel along parallel paths.
- the emitter and receiver may need to be physically tilted towards each other (as opposed to aligning them at infinity distance).
- this physical tilting may result in a loss of detection capabilities at long ranges from the LIDAR system.
- some LIDAR systems may use a combination of a wide field of view and the aforementioned tilted assembly. This wide field of view, however, may result in another set of problems, including increasing the amount of background light detected by the receiver without increasing the amount of light emitted by the emitter, which may significantly increase the signal to noise ratio of the receiver.
- Range aliasing may arise when multiple light pulses are emitted by an emitter and are traversing the environment at the same time.
- the LIDAR system may have difficulty ascertaining which emitted light pulse the detected return light originated from.
- the emitter emits a first light pulse at a first time and then emits a second light pulse at a second time before return light from the first light pulse is detected by the receiver.
- both the first light pulse and the second light pulse are traversing the environment simultaneously.
- the receiver may detect a return light pulse a short amount of time after the second light pulse is emitted.
- the LIDAR system may have difficulty determining whether the return light is indicative of a short range reflection based on the second light pulse or a long range reflection based on the first light pulse.
- Cross-talk concerns may arise based on a similar scenario, but instead of detecting return light from a first light pulse emitted by the same emitter, the receiver from the LIDAR system may instead detect a second light pulse that originates from an emitter of another LIDAR system. In this scenario, the LIDAR system may mistake the detected second light pulse from the other LIDAR system as return light originating from the first light pulse. Similar to range aliasing, this may cause the LIDAR system to mistakenly believe that a short range object is reflecting light back towards the LIDAR system.
- FIG. 1 depicts an example system, in accordance with one or more example embodiments of the disclosure.
- FIGs. 2A-2B depict an example use case, in accordance with one or more example embodiments of the disclosure.
- FIG. 3 depicts an example use case, in accordance with one or more example embodiments of the disclosure.
- FIGs. 4A-4B depict example circuit configurations, in accordance with one or more example embodiments of the disclosure.
- FIGs. 5 A-5B depict example methods, in accordance with one or more example embodiments of the disclosure.
- FIG. 6 depicts a schematic illustration of an example system architecture, in accordance with one or more example embodiments of the disclosure.
- the LIDAR detectors may be referred to as “receivers,” “photodetectors,” “photodiodes,” or the like herein. Additionally, reference may be made herein to a single “photodetector” or “photodiode,” but the LIDAR systems described herein may also similarly include any number of such detectors). In some instances, the detectors may be photodiodes, which may be diodes that are capable of converting incoming light photons into an electrical signal (for example, an electrical current).
- the detectors may be implemented in a LIDAR system that may emit light into an environment and may subsequently detect any light returning to the LIDAR system (for example, through the emitted light reflecting from an object in the environment) using the detectors.
- the LIDAR system may be implemented in a vehicle (for example, autonomous vehicle, semi-autonomous vehicle, or any other type of vehicle), however the LIDAR system may be implemented in other contexts as well.
- the detectors may also more specifically be Avalanche Photodiodes (APD), which may function in the same manner as a normal photodiode, but may operate with an internal gain as well.
- APD Avalanche Photodiodes
- an APD that receives the same number of incoming photons as a normal photodiode will produce a much greater resulting electrical signal through an “avalanching” of electrons, which allows the APD to be more sensitive to smaller numbers of incoming photons than a normal photodiode.
- An APD may also operate in Geiger Mode, which may significantly increase the internal gain of the APD.
- bistatic LIDAR systems may include emitters and receivers that are physically displaced relative to one another.
- Such LIDAR configurations may inherently be associated with parallax problems because the light emitted by the emitter and received by the detector may not travel along parallel paths.
- the emitter and receiver may need to be physically tilted towards each other (as opposed to aligning them in parallel).
- this physical tilting may result in a loss of detection capabilities at long ranges from the LIDAR system.
- some systems may use a combination of a wide field of view and the aforementioned tilted assembly.
- bistatic LIDAR systems may have difficulty determining the source of certain return light based on range aliasing and/or cross talk problems.
- a LIDAR system may be used that may include multiple photodetectors to detect return light that is based on emitted light from an emitter device (for example, laser diode) of the LIDAR system.
- the photodetectors may be physically orientated (for example, pointed in at different angles) so that their individual fields of view include varying distances from the LIDAR system (for example, as depicted in FIG. 1).
- a first photodetector may be physically oriented so that its detection field of view encompasses a physical space within a short range from the LIDAR system (for example, a range including a distance 0.1m away from the LIDAR system to 0.195m away from the LIDAR system encompassing a field of view of 2.85 degrees).
- a second photodetector may be physically oriented so that its detection field of view covers a physical space just beyond the physical space that the first photodetector covers (for example, a range including a distance 0.19m away from the LIDAR system to 4. Im away from the LIDAR system, also with a field of view of 2.85 degrees).
- third photodetector may be physically oriented so that its detection field of view covers a physical space just beyond the physical space that the second photodetector covers (for example, a range including a distance 4m away from the LIDAR system to an infinite distance away from the LIDAR system with a field of view of 2.85 degrees (these example distances and fields of view are provided as arbitrary examples, and any other ranges and/or fields of view may similarly be applicable).
- the total number of photodetectors included within the LIDAR system may be based on a number of factors. As a first example, the number may be based on a maximum detection range that is desired to be covered by the photodetectors.
- the maximum detection range is a smaller distance from the LIDAR system, then a smaller number of photodetectors may be used, and if the maximum detection range is a larger distance from the LIDAR system, then a larger number of photodetectors may be used (it should be noted that while the term “maximum detection range” is used, this distance could theoretically extend out to infinity).
- the number of photodetectors used may also be based on the size of the fields of view of individual photodetectors being used. A larger number of photodetectors may need to be employed if some or all of the individual photodetectors have a more narrow field of view.
- a smaller number of photodetectors may be employed if some or all of the individual photodetectors have a broader field of view.
- factors that may influence the number of photodetectors used in the LIDAR system, and the number may also depend on any number of additional factors.
- the number of photodetectors used may depend on the amount of overlap in the field of view between the photodetectors. In some instances, the transition between one photodetector’s field of view to another photodetector’s field of view may involve no overlap in the respective fields of view (that is, the end of one photodetector’s field of view may exactly correspond with the beginning of another photodetector’s field of view).
- the photodetectors may be configured in an array such that they are physically spaced apart from one another at equal distances. However, in some embodiments, the photodetector arrays may also be physically spaced apart in unequal intervals.
- a separation that is logarithmically based may be more beneficial to produce equal resolution to minimal range. This may be because using a linearly- spaced detector array with the same FoV may result in ranges that are asymmetrical, with a first detector in the array responsible for a smaller amount of physical space and the last photodetector in the array being responsible for a much larger amount of physical space (for example, 4m to infinity).
- a different spacing model for example, logarithmic spacing as described above
- individual detector ranges may be optimized to be more equalized. This may ensure, for example, that multiple returns from any one area in the environment do not overload the receiver responsible for that area.
- more closely-spaced detectors may be used in the far-field to further reduce the FoV as the distance covered increases and the receiver cone becomes very large, thus making yourself less susceptible to noise in the far-field.
- the photodetectors may be selectively “turned on” and/or “turned off’ (which may similarly be referred to as “activating” or deactivating” a photodetector). “Turning on” a photodetector may refer to providing a bias voltage to the photodetector that satisfies a threshold voltage level. The bias voltage satisfying the threshold voltage level (for example, being at or above the threshold voltage level) may provide sufficient voltage to the photodetector to allow it to produce a level of output current based on light received by the photodetector.
- the output threshold voltage level being used and the corresponding output current being produced may depend on the type of photodetector being used and the desired mode of the operation of the photodetector. For example, if the photodetector is an APD, the threshold voltage level may be set high enough so that the photodetector is capable of avalanching upon receipt of light as described above. Similarly, if it is desired for the APD to operate in Geiger Mode, the threshold voltage level may be set even higher than if the APD were desired to operate outside of the Geiger Mode region of operation. That is, the gain of the photodetector when this higher threshold voltage level is applied may be much larger than if the photodetector were operating as a normal Avalanche Photodiode.
- the threshold bias voltage may be lower.
- the threshold voltage level may be set below a threshold voltage level used to allow the APD to avalanche upon receipt of light. That is, the bias voltage applied to the APD may be set low enough to allow the APD to still produce an output current, but only in a linear mode of operation.
- “turning off’ a photodetector may refer to reducing the bias voltage provided to the photodetector to below the threshold voltage level.
- “turning off’ the photodetector may not necessarily mean that the photodetector is not able to detect return light. That is, the photodetector may still be able to detect return light while the bias voltage is below the threshold voltage level, but the output signal produced by the photodetector may be below a noise floor established for a signal processing portion of the LIDAR system.
- a photodetector may be an Avalanche Photodiode.
- the APD may still produce an output, but the output may be based on a linear mode of operation and the resulting output current may be much lower than if the APD were to avalanche upon receipt of a same number of photons.
- the signal processing portion of the LIDAR system may have a noise floor configured to correspond to an output of the APD in linear mode, so that any outputs from the APD when operating with this reduced bias voltage may effectively be disregarded by the LIDAR system.
- selectively turning on and/or turning off the photodetectors may entail only having some of the photodetectors capable of detecting return light at a given time.
- the timing at which the photodetectors may be turned on and/or turned off may depend on predetermined time intervals.
- these predetermined time intervals may be based on an amount of time that has elapsed since a given light pulse was emitted from the emitter of the LIDAR system.
- a first light pulse being emitted from the emitter may trigger a timing sequence.
- the timing sequence may involve individual photodetectors being turned on when return light corresponding to the emitted light pulse being reflect from an object may be expected to be within a field of view of a particular photodetector.
- a first photodetector may be pointed in a direction such that its field of view may include a range of physical space within a closest distance from the LIDAR system (Rxl as depicted in FIG.l may provide a visual example of this first photodetector’s field of view).
- This first photodetector may be the first photodetector to be turned on for a first time interval during which return light originating from the first light pulse may be expected to have been reflected from objects within the first field of view.
- the field of view of this first photodetector may include a range from 0.19m away from the LIDAR system to 4.1m away from the LIDAR system (again, it should be noted that any specific examples of ranges and/or fields of view of any photodetectors described herein may be arbitrary, and any other ranges and/or fields of view may similarly be applicable) from the LIDAR system. That is, if the emitted light were to be emitted from the LIDAR system and then reflect from an object in the environment within this range from the LIDAR system back towards the first photodetector, then the first photodetector pointing in that direction may be turned on and able to detect the return light.
- a second photodetector may be turned on. Similar to the first time interval, the second time interval may correspond to a period of time during which any return light detected by the second photodetector is expected to have originated from an object in the field of view of the second photodetector. This process may continue with some or all of the remaining photodetectors in the array being turned on after successive time intervals of previous photodetectors in the array have passed. This process may be visualized, for example, in FIG. 2, as described below. Additionally, in some cases, once a time interval associated with a field of view of a particular photodetector has passed, that photodetector may be turned off as well.
- the photodetector associated with the current time interval may be turned on at any given time. This may provide a number of benefits, such as serving to reduce extraneous data received by the other photodetectors during this time and/or reducing the power consumption of the LIDAR system, to name a few examples. In some embodiments, however, some or all of the photodetectors may remain on through multiple time intervals, or may remain on at all times. This may be beneficial because it may allow as much data from the environment to be captured as possible. Additionally, the time intervals may not necessarily need to be the same length of time. For example, a time interval associated with a given photodetector may depend on the size of the field of view of the photodetector.
- a photodetector with a more narrow field of view may be associated with a shorter time interval than a photodetector with a more broad field of view. This situation may arise when photodetectors with varying sizes of field of view are employed. Additionally, in some cases, any other type of time interval may be used to determined when to turn on and/or turn off any of the photodetectors included within the LIDAR system.
- the bias voltage provided to an individual photodetector during a given time interval may not necessarily be fixed. That is, the bias voltage that is provided to the photodetector may vary over time based on a certain function (for example, “function” may refer to a magnitude of bias voltage applied with respect to time. That is, if a plot of the bias voltage applied over time were to be created, the function would be visualized by the plot).
- function may refer to a magnitude of bias voltage applied with respect to time. That is, if a plot of the bias voltage applied over time were to be created, the function would be visualized by the plot).
- the function may not necessarily only involve the threshold voltage level only either being at threshold voltage level or at a value below the threshold voltage value (that is, if the bias voltage applied were plotted as a function, it may not necessarily look like a step function that rises to the threshold voltage level at the beginning of the time interval and drops below the threshold voltage level at the end of the time interval).
- the function may instead be associated with a certain degree of change in the bias voltage throughout the time interval.
- the function may represent a Gaussian function. Using this type of function to dictate the bias voltage being provided, for example, the bias voltage may increase over a first period of time, reach a peak bias voltage, and then may decrease back down to below the threshold voltage level over a second period of time.
- the peak of the example Gaussian function may be maintained throughout the entire predetermined time interval associated with the particular photodetector.
- the upward slope of the Gaussian function may begin at the beginning of the time interval and the peak of the Gaussian function may be reached at a certain amount of time after the beginning of the time interval. This may be desirable if it is desirable for the photodetector to be at its most sensitive to return light at a particular portion of its field of view.
- the upward slope of the example Gaussian function may begin during the time interval of a previous photodetector (and likewise the downward slope may extend into the time interval for a successive photodetector’s time interval).
- the function may be any other function other than a Gaussian function (for example, the function may actually even be a step function in some instances). That is, the bias voltage applied to a given photodetector may vary over time in any other number of ways. Additionally, different photodetectors may be associated with different types of functions. Different photodetectors may also be associated with the same type of function, but certain parameters of the function may vary. For example, the peak of a Gaussian function used for one photodetector may be greater than the peak of a Gaussian function used for a second photodetector. The functions used may also vary for different emitted light pulses from the LIDAR system.
- a first type of function when the LIDAR system emits a first light pulse, a first type of function may be used, but when the LIDAR emits a subsequent light pulse, a second type of function may be used.
- the above examples of how different functions may be used to control the bias voltage applied to a photodetector may merely be exemplary, and any other type(s) of functions may be applied to any combination of photodetectors based on any number of timing considerations.
- the manner in which photodetectors are turned on and/or off may also be dynamic instead of being based on fixed time intervals that are used for successive light pulse emissions from the emitter.
- the time intervals used to determine the bias voltage to be provided to different photodetectors may not consistently iterate in the same manner forever, but may rather change over time.
- the time intervals used for some or all of the photodetectors may change after each successive emitted light pulse by the emitter.
- the time intervals may change after a given number of emitted light pulses are emitted by the emitter.
- the time intervals may also change within a period of time during which a single emitted light pulse may currently be traversing the environment.
- a light pulse may be emitted, a first photodetector may be turned on for a first time interval, and then a second time interval for a second photodetector may be dynamically changed to a different time interval.
- these time interval changes may be based on data that is received from the environment. That is, an closed loop feedback system may be implemented to vary the time intervals (it should be noted that this closed loop feedback system may similarly be used to dynamically adjust the types of functions used to dictate the bias voltage provided to different photodetectors.
- the physical orientation of the photodetectors may also be either fixed and/or dynamically configurable. That is, individual photodetectors may include an actuation mechanism that may allow the direction in which a photodetector is pointed to be dynamically adjusted (and consequentially, the fields of view of the photodetectors may be dynamically adjustable).
- the actuation mechanism may include microelectromechanical systems (MEMS), or any other type of actuation mechanism that may allow a photodetector to adjust the direction in which it points. This dynamic adjustment of the physical orientation of one or more of the photodetectors may be performed for any number of other reasons.
- MEMS microelectromechanical systems
- a first photodetector may be turned on and data may be captured by that first photodetector.
- a direction in which a second photodetector is pointing may then be adjusted based on the data captured by the first photodetector.
- multiple photodetectors may be adjusted to point in the same direction. This may be desirable because this may allow for more data to be captured from a particular portion of the environment than if a single photodetector were used to capture data from that portion of the environment.
- one photodetector may serve as serve as a failsafe for another photodetector (that is, one photodetector may serve to validate the data received by the other photodetector or may serve to capture data from the portion of the environment if the other photodetector is unable to do so for a given period of time).
- This may also be useful if the portion of the environment is determined to be an area of interest and thus it is desirable to obtain as much data from that portion of the environment as possible.
- the circuitry used to capture the data being produced by individual photodetectors within the photodetector array may involve providing individual analog to digital converters (ADCs) for each photodetector.
- ADCs analog to digital converters
- An analog to digital converter may take an analog signal as an input and produce a corresponding digital output.
- the current output by a photodetector may be an analog signal, so the analog to digital converter may take this signal as an input and convert it into a digital form that may be used by a signal processing portion of the LIDAR system.
- a single ADC may be used for multiple of the photodetectors or all of the photodetectors.
- the outputs of the individual photodetectors may be summed and provided as a single output to the ADC.
- the summing may be performed using a summer circuit, which may comprise more than one circuits that are capacitive coupled together, or may also be in the form of an op-amp summer.
- one or more attenuators may be used to attenuate one the outputs of one or more of the photodetectors may be performed as well For example, if all of the detectors are turned on at all times, the attenuators may be used to attenuate outputs of certain detectors at certain times.
- the attenuation may be performed to attenuate the outputs of all of the detectors except one detector.
- the one detector may correspond to a field of view in which it is expected return light from an emitted light pulse would currently be located.
- the attenuators may thus serve to reduce the amount of detector output noise that is provided the ADC and signal processing components 410.
- the attenuators may also be used in other ways as well. For example, all of the outputs of the detectors may be left unattenuated unless it is determined that it is desired to block the output of one or more detectors.
- either of the aforementioned circuitry embodiments may be employed when some or all of the photodetectors remain turned on at all times, instead of being selectively turned on and off during a single light pulse emissions. In some embodiments, however, the circuitry may also be employed when the photodetectors are selectively turned on and/or off as well. For example, in scenarios where a photodetector is selectively turned on as return light based on an emitted light pulse is expected to enter a field of view of the photodetector (that is, only one photodetector is turned on at a time), a single ADC may be employed.
- Range aliasing may be a phenomenon that may occur when a two or more different light pulses emitted by an emitter of the LIDAR system are simultaneously traversing the environment. For example, the emitter of the LIDAR system may emit a light pulse at a first time, and a time at which the light pulse would be expected to return to the LIDAR system from a maximum detection range may elapse. The LIDAR system may then emit a second light pulse.
- the LIDAR system may incorrectly identify the return light pulse as being a short range return of the second light pulse instead of a long range return from the first light pulse.
- This may be problematic because light associated with multiple emitted light pulses from the LIDAR system may exist in the environment during any given time interval. This may result in the shot rate (the rate at which subsequent light pulses may be emitted by the emitter) of the LIDAR system being lowered to reduce the likelihood of numerous light pulses traversing the environment at the same time and resulting in this range aliasing problem.
- a first light pulse may be emitted at a first time.
- the first light pulse may traverse the environment, and successive individual photodetectors may be turned on and/or off at varying time intervals as the first light pulse traverses further away from the emitter.
- the last photodetector may be kept turned on as the first light pulse continues to travel beyond the field of view of the last photodetector.
- a second light pulse may then be emitted by the emitter.
- a short time after the second light pulse is emitted (for example, when it is within the field of view of a first photodetector with a field of view including a closest distance range to the emitter) the last photodetector may detect return light.
- the second light pulse would not have traveled far enough to be detected by the last photodetector as return light, so the detection by the last photodetector is more likely associated with the first light pulse. In this manner, it may be more easily ascertained which light pulse a detected light return may be associated with.
- range aliasing concerns may be mitigated and/or eliminated by the use of multiple photodetectors
- the photodetectors are controlled to be turned on and/or off based on predetermined time intervals as described above, then return light that reflects from an object beyond the maximum detection range of the LIDAR system may never be detected (which may eliminate the possibility for range aliasing).
- the reason for this may be exemplified as follows. In this example, a first light pulse is emitted.
- the photodetectors then proceed through their sequence of turning on and/or off as described above until the final photodetector (the photodetector with the longest distance field of view from the LIDAR system) is turned off (when any expected return light would originate from beyond the maximum detection range). Then a second light pulse is emitted from the LIDAR system. If there were only one photodetector that was always turned on, then return light from the first light pulse may then return and be detected by the photodetector. However, if there are multiple photodetectors and each is only turned on for a given time interval, then it is more likely that return light that is detected by a given photodetector would have originated from the second light pulse.
- the use of the multiple photodetectors may still allow for a determination to be made that the detected return light could potentially originate from the first light pulse. That is, if the return light from the first pulse returns and is detected by one of the turned on photodetectors, but the second light pulse has still not reflected from an object back towards a photodetector, then return light from the light pulse may be detected by a subsequent photodetector that is turned on.
- the LIDAR system may thus be able to determine that at least one of the return light detections was based on range aliasing. If this is the case, the LIDAR system may simply disregard both of these two detected returns.
- mitigating range aliasing as described above may have the added benefit of allowing for a larger number of light pulses being emitted within a time frame than if range aliasing were not mitigating using these systems and methods. This may be because it may not be as concerning to have more light pulses traversing the environment at the same time if it is more likely that the LIDAR system may be able to determine which return light is associated with which emitted light pulse. The ability to emit more light pulses in a given period of time may result in a larger amount of data being able to be collected about the environment at a faster rate.
- the multiple photodetector bistatic LIDAR systems described herein may also have the further benefit of mitigating or eliminating cross talk between different LIDAR systems.
- Cross talk may refer to a scenario that arises when an emitter from a first LIDAR system is pointed towards a second LIDAR system. If the first LIDAR system emits a light pulse, that light pulse may then travel towards the second LIDAR system and be detected by a photodetector of the second LIDAR system. Similar to range aliasing concerns, the second LIDAR system may have difficulty in discerning between its own emitted light pulses and a light pulse originating from another LIDAR system if only one photodetector is used. This cross talk scenario may be mitigated or eliminated in a similar manner in which range aliasing may be mitigated or eliminated.
- the multiple photodetector bistatic LIDAR systems described herein may also have further benefits even beyond mitigating parallax, range aliasing, and/or cross talk concerns.
- the use of the multiple photodetectors may mitigate a scenario where one particular photodetector may become saturated by a bright light. When this is the case, the photodetector may enter a recovery period during which it may not be able to detect any subsequent light. If only one photodetector is used in a LIDAR system, then the LIDAR system may become blind to return light during this recovery period. However, if multiple photodetectors are used, any of the other photodetectors may be used as backups for the photodetector currently in its recovery period.
- FIG. 1 may depict a high-level schematic diagram of an example LIDAR system 101 that may implement the multiple detectors as described herein. A more detailed description of an example LIDAR system may be described with respect to FIG. 6 as well.
- the LIDAR system 101 may include at least one or more emitter devices (for example, emitter device 102a, and/or any number of additional emitter devices) and one or more detector devices (for example, detector device 106a, detector device 106b, detector device 106c, and/or any number of additional detector devices).
- emitter devices for example, emitter device 102a, and/or any number of additional emitter devices
- detector devices for example, detector device 106a, detector device 106b, detector device 106c, and/or any number of additional detector devices.
- the LIDAR system 101 may be incorporated onto a vehicle 101 and may be used at least to provide range determinations for the vehicle 101.
- the vehicle 101 may traverse an environment 108 and may use the LIDAR system 101 to determine the relative distance of various objects (for example, the pedestrian 107a, the stop sign 107b, and/or the second vehicle 107c) in the environment 108 relative to the vehicle 101.
- the one or more detector devices may be configured such that individual detector devices are physically oriented to point in different directions. Consequentially, different detectors may have different corresponding fields of view in the environment 108.
- detector device 106c may be associated with field of view 110
- detector device 106b may be associated with field of view 111
- detector device 106a may be associated with field of view 112.
- a field of view of an individual detector device may cover a particular range of distances from the emitter 102a.
- the field of view 110 of detector device 106c is shown to cover a closest range of distances to the emitter 102a
- field of view 111 of detector device 106b is shown to cover an intermediate range of distances to the emitter 102a
- field of view 112 of detector device 106a is shown to cover a furthest range of distances from the emitter 102a.
- the detector devices may cover a total field of view comprising the field of view 110, the field of view 111, and the field of view 112.
- the figure depicts three detector devices with three associated fields of view the total view of view may similarly be split between any number of detector devices as well.
- one field of view for one photodetector may begin at an exact location where a prior field of view for another photodetector ends, leaving no field of view blind spot between photodetectors.
- the different fields of view may allow the different detector devices to detect return light 120 from the environment 108 that is based on the emitted light 105 from the emitter 102a. Due to the varying range of distances the different fields of view cover, each detector device may be configured to detect objects at varying distances from the vehicle 101.
- the detector device 106c may be configured to detect return light 120 that is reflected from objects a shorter distance away from the vehicle 101 (for example, the vehicle 107c). As is described herein, the detector devices may also be selectively turned on and/or turned off based on time estimates as to when return light 120 would be within the field of view of the individual detector devices.
- FIGs. 2A-2B depicts an example use case 200, in accordance with one or more example embodiments of the disclosure.
- the use case 200 may exemplify a manner in which the one or more detectors may be selectively turned on and/or turned off (as described above) during various time intervals subsequent to a light pulse being emitted from an emitter.
- the use case 200 may depict an emitter 202, which may be the same as emitter 102a described with respect to FIG. 1, as well as any other emitter described herein.
- the use case 200 may also depict one or more detectors, including, for example, a first detector 203, a second detector 204, and a third detector 205, which may be the same as detector device 106a, detector device 106b, and/or detector device 106c, as well as any other detectors described herein.
- Each of the detectors may have an associated field of view.
- the first detector 203 may be associated with field of view 206
- the second detector 204 may be associated with field of view 207
- the third detector 205 may be associated with field of view 208.
- field of view 206 for example, field of view 206, field of view 207, and/or field of view 208 may include varying distance ranges from the emitter 202 (or, more broadly speaking, from the LIDAR system).
- the fields of view may allow for the detectors to detect return light (for example, return light 211, return light 213, and/or return light 215) that is reflected from objects in the environment (for example, a tree 209, a vehicle 214, and/or a house 219).
- field of view 206 associated with the first detector 203 may cover a distance range that may be closest to the emitter 202 (or the LIDAR system)
- field of view 207 associated with the second detector 204 may cover a distance range that is intermediate from the emitter 202 (or the LIDAR system)
- field of view 208 associated with the third detector 205 may cover a distance range that is furthest from the emitter 202 (or the LIDAR system).
- the field of view 206, field of view 207, and field of view 208 may cover a total field of view of the LIDAR system.
- an individual detector with its corresponding field of view may cover a portion of the total field of view of the LIDAR system, and all of the fields of view taken together may cover the desired field of view of the LIDAR system.
- the desired total field of view may correspond to a maximum detection range of the LIDAR system, which may be predefined, or selected based on any number of factors.
- use case 200 may only depict three detectors with three corresponding fields of view, any other number of detectors and associated fields of view may be used to cover a detection range of the LIDAR system.
- the detectors may be the same as the detectors depicted with respect to FIG. 1, as well as any other detectors described herein.
- the emitter 202 and one or more detectors may be a part of an overall LIDAR system, such as a bistatic LIDAR system. That is, the use case 200 may depict a use case being implemented by the LIDAR system depicted in FIG. 1, for example.
- Scene 201 may involve the emitter 202 of the LIDAR system emitting a light pulse 210 into the environment 210.
- Scene 201 may also depict that, subsequent to the light pulse 210 being emitted by the emitter 202, the detector with a field of view 206 that covers a distance range closest to the emitter 202 (the first detector 203) may be turned on.
- This first detector 203 may be turned on for a given first time interval, T 1 .
- the other detectors in the LIDAR system for example, second detector 204 and third detector 205) may be turned off, which may be represented by their fields of view being depicted as dashed lines.
- the first time interval, AT X may correspond to a time interval during which return light reflected from an object in the environment would be expected to be within the field of view 206 of the first detector 203.
- scene 201 may depict a tree 209 that is within the field of view 206, and that reflects return light 211. This return light 211 may then be detected by the first detector 203.
- the tree 209 (and associated return light 211) may be depicted in dashed lines as an example of what return light in the field of view 206 may look like.
- the tree 209 may be considered to not actually exist in the environment so that the light pulse 210 may traverse the environment to further distances from the emitter 202.
- Scene 215 may involve the light pulse 210 continuing to traverse the environment beyond the location of the tree 209 as shown in scene 201.
- Scene 215 may take place during a second time interval, AT 2 •
- the first detector 203 may be turned off and the second detector 204 may be turned on. That is, the second detector 204 may now be the only detector that is currently turned on.
- the second time interval, AT 2 may correspond to a time interval during which return light reflected from an object in the environment would be expected to be within the field of view 207 of the second detector 204.
- the second detector 204 may include a field of view 207 including a distance range that begins starting with the end of the distance range covered by the field of view 206 of the first detector 203. In some cases, although not depicted in the figure, there may also be some overlap between the field of view 207 and/or the field of view 206.
- scene 215 may thus depict a vehicle 214 that is within the field of view 207, and that reflects return light 213. This return light 213 may then be detected by the second detector 204.
- the vehicle 214 (and associated return light 213) may be depicted in dashed lines as an example of what return light in the field of view 207 may look like.
- the vehicle 214 may be considered to not actually exist in the environment so that the light pule 210 may traverse the environment to greater distances as depicted in scene 230 described below.
- the use case may proceed to scene 230.
- Scene 230 may involve the light pulse 210 continuing to traverse the environment beyond the location of the vehicle 214 as shown in scene 215.
- Scene 230 may take place during a third time interval, AT 3 .
- the second detector 204 may be turned off and the third detector 205 may be turned on. That is, the third detector 205 may now be the only detector that is currently turned on.
- the third time interval, AT 3 may correspond to a time interval during which return light reflected from an object in the environment would be expected to be within the field of view 208 of the third detector 205.
- the third detector 205 may include a field of view 208 including a distance range that begins starting with the end of the distance range covered by the field of view 207 of the second detector 204.
- scene 230 may depict a home 217 that is within the field of view 208, and that reflects return light 218. This return light 218 may then be detected by the third detector 205.
- the use case 200 may thus depict a progression of an example of how various detectors may be selectively turned on and/or turned off over time as an emitted light pulse traverses further into the environment 210.
- this use case 200 should not be taken as limiting, and the detectors may be operated in any other manner as may be described herein.
- all of the detectors may be turned on at all times (instead of individual detectors being selectively turned on and/or turned off), more than one detector may be turned on at any given time, and/or any number of detectors may be turned on in any other combination for any other length of times.
- the time intervals during which the various detectors are turned on and/or off may vary.
- the time interval during which one detector is turned on may be shorter and/or longer than the time interval during which another detector is turned on.
- the timing may depend on one or more types of functions used to determine the bias voltage to apply to a given photodetector over time.
- the bias voltage applied to the different photodetectors may be represented as a time-shifted Gaussian function. That is, within a given time interval, the bias voltage applied to the detector 205 may ramp up to a peak bias voltage value, and then ramp back down as the end of the time interval is approached.
- the bias voltage may begin to ramp up for the detector 204 using a similar Gaussian function, and so on.
- fields of view for example, field of view 206, field of view 207, and/or field of view 208 are shown as being fixed in the use case 200, any of these fields of view may also be adjustable. That is, a field of view may be broadened or narrowed, or a direction of a field of view may be altered. The field of view may also be altered in any other manner, such as introducing optical systems that may alter the direction of the field of view. As described herein, the field of view may be altered for any number of reasons, such as to focus multiple detectors towards a similar location within the environment.
- FIG. 3 depicts an example use case 300, in accordance with one or more example embodiments of the disclosure.
- the use case 300 may depict one example of how range aliasing concerns may be mitigated and/or eliminated by the multi-detector systems and methods described herein.
- Use case 300 may depict two parallel timelines.
- Scenes 301 and 310 may comprise one timeline and scenes 320 and 340 may comprise a second, parallel timeline.
- Scenes 301 and 310 may be included to depict how range aliasing issues may arise in single detector LIDAR systems, and scenes 320 and 340 may depict how these issues may be ameliorated by using a multi-detector system as described herein.
- scenes 301 and 310 may depict a LIDAR system that may only include one emitter 302 and one detector 303.
- the detector 303 may be capable of detecting return light with a field of view 304 that may cover up to a maximum detection distance 305.
- scene 301 may depict the emitter 302 emitting a first light pulse 306 into the environment.
- the first light pulse 306 is shown as traversing the environment and eventually moving past the maximum detection distance 305 of the detector 303. That is, the first light pulse 306 in scene 301 may not yet have reflected from an object in the environment as return light and been detected within the field of view 304 of the detector 303. With this being the case, a potential range aliasing problem may arise as depicted in scene 310.
- the emitter 302 is shown as emitting a second light pulse 307 into the environment.
- the first light pulse may finally reflect from an object (for example, tree 308) and return towards the field of view 304 of the detector 303 as return light 309.
- the return light 309 may then be detected by the detector 303 at point 310, which may correspond to a point when the return light 309 first enters the field of view of the detector 303 (which, for exemplification purposes, may take place at a first time).
- the second light pulse may also be currently within the environment at point 311.
- the second light pulse 307 may have only traveled a short distance from the emitter 302 by the time the return light 309 from the first light pulse 306 is detector by the detector 303.
- the back-end signal processing components of the LIDAR system may have difficulty in determining whether the return light that was detected by the detector 303 is a short range detection based on the second light pulse 307, or a long range detection based on the first light pulse 306. This may be because distance determinations based on the emitted light pulses from the emitter 302 may be made based on time of flight (ToF) determinations, for example.
- ToF time of flight
- the LIDAR system may ascertain when a light pulse is emitted, and may then compare the emission time to a time at which return light is detected by the detector determine The resulting difference in time may then be used to determine the distance at which the emitted light was reflected back to the LIDAR system.
- the LIDAR system may not be able to discern between two light pulses at different distances within the field of view 304 of the single detector 303 since both light pulses could theoretically be the source of the return light being detected by the detector 303.
- scene 320 and scene 340 may depict an example manner in which the multi-detector systems described herein may mitigate or eliminate the range aliasing concerns exemplified in scene 301 and scene 310.
- Scene 320 and scene 340 may thus depict a multi-detector system that may include an emitter 302 and one or more detectors (for example, first detector 321, second detector 322, and/or third detector 323, which may be the same as the first detector 203, the second detector 204, and/or the third detector 205, as well as any other detectors described herein).
- a detector may be associated with a field of view covering a particular distance range from the emitter 302.
- the first detector 321 may be shown as being associated with field of view 324 that may include a distance range closest to the emitter 302.
- the second detector 322 may be shown as being associated with field of view 325 that may include a distance range beyond the distance range covered by the field of view 324 of the first detector 321.
- the third detector 323 may be shown as being associated with field of view 326 that may include a distance range beyond the distance range covered by the field of view 325 of the second detector 322.
- the combination of the field of view 324, field of view 325, and field of view 326 may cover the same maximum detection range 305 from the emitter 302.
- scene 320 may begin, similar to scene 301, with the emitter 302 emitting a first light pulse 306 into the environment.
- the first light pulse 306 is shown as traversing the environment and eventually moving past the maximum detection distance 305 of the first detector 321, the second detector 322, and the third detector 323. That is, the first light pulse 306 may not have reflected from an object in the environment and been detected by the first detector 321, the second detector 322, or the third detector 323.
- the emitter 302 may then emit a second light pulse 307.
- the difference between scene 310 with the single detector 303 and the scene 340 with the multiple detectors may be that the multiple detectors may be used to provide more data about detected return light than the single detector 303 may be able to.
- individual detectors may be able to be selectively turned on and/or off as the light pulse traverses the environment.
- the first detector 321, the second detector 322, and the third detector 323 may be selectively turned on and then off as the first light pulse 306 traverses further away from the emitter 302.
- the third detector 323 may be kept on even as the first light pulse 306 travels beyond the maximum detection range 305 of the detectors.
- scene 340 shows the same second light pulse 307 being emitted from the emitter 302 before the first light pulse 306 reflects from an object and is detected by one of the detectors.
- the difference here is that the LIDAR system now has two separate detectors monitoring two different distances from the emitter 302. That is, now both the first detector 321 with a known field of view 324 closer to the emitter 302 and the third detector 323 with a known field of view 326 that is further away from the emitter 302 are turned on.
- third detector 323 may produce an output indicating that it detected return light at the same first time described in scenes 301 and 310.
- this first time may correspond to a time at which return light originating from the second light pulse 307 may be within the field of view 324 of the first detector 321 (thus, the first detector 321 is shown as being on).
- the system is then able to discern that the return light detected by the third detector 323 is associated with the first light pulse 306 instead of the second light pulse 307.
- a LIDAR system may be able to track multiple light pulses traversing the environment simultaneously with reduced concern that range aliasing will cause difficultly in discerning between returns from the multiple emitted light pulses. Something about can double your shot rate (or even more).
- the use case 300 may depict only one example of how a multidetector system may be used to mitigate or eliminate range aliasing concerns.
- range aliasing concerns may be mitigated and/or eliminated by the use of multiple photodetectors, if the photodetectors are controlled to be turned on and/or off based on predetermined time intervals as described above, then return light that reflects from an object beyond the maximum detection range of the LIDAR system may never be detected (which may eliminate the possibility for range aliasing). The reason for this may be exemplified as follows. In this example, a first light pulse is emitted.
- the photodetectors then proceed through their sequence of turning on and/or off as described above until the final photodetector (the photodetector with the longest distance field of view from the LIDAR system) is turned off (when any expected return light would originate from beyond the maximum detection range). Then a second light pulse is emitted from the LIDAR system. If there were only one photodetector that was always turned on, then return light from the first light pulse may then return and be detected by the photodetector. However, if there are multiple photodetectors and each is only turned on for a given time interval, then it is more likely that return light that is detected by a given photodetector would have originated from the second light pulse.
- the use of the multiple photodetectors may still allow for a determination to be made that the detected return light could potentially originate from the first light pulse. That is, if the return light from the first pulse returns and is detected by one of the turned on photodetectors, but the second light pulse has still not reflected from an object back towards a photodetector, then return light from the light pulse may be detected by a subsequent photodetector that is turned on.
- the LIDAR system may thus be able to determine that at least one of the return light detections was based on range aliasing. If this is the case, the LIDAR system may simply disregard both of these two detected returns.
- FIGS. 4A-4B depict example circuit configurations, in accordance with one or more example embodiments of the disclosure.
- the circuit configurations depicted in FIGs. 4A-4B may represent a back-end circuit connected to the outputs of the detectors. This back-end circuit may be used, for example, to pre-process the outputs of the detectors for any signal processing components of the LIDAR system (for example, systems that may make computing determinations based on the data received from the detectors).
- FIG. 4A depicts a first circuit configuration 400.
- individual detectors may be associated with their own individual analog to digital converters (ADCs) (for example, detector 403 may be associated with analog to digital converter 406, detector 404 may be associated with analog to digital converter 407, and detector 405 may be associated with analog to digital converter 408).
- ADC may be used to convert an analog signal to a digital signal. That is, the ADC may be capable of receiving the analog output of a detector as an input and converting that analog signal into a digital signal. This digital signal may then be used by one or more signal processing components 410 of the LIDAR system.
- a detector may be configured to receive one or more photons as an input and provide current as an output. This current output may be in analog form, and the ADC may convert the analog current into a digital current value for use by the one or more signal processing components 410.
- FIG. 4B depicts a second circuit configuration 420. While the first circuit configuration 400 shown in FIG. 4A included multiple ADCs (for example, one ADC for each detector), the second circuit configuration 420 may only include one ADC for all of the detectors (or alternatively may include more than one ADC but multiple detectors may share a single ADC instead of each individual detector being associated with its own ADC). That is, the second circuit configuration 420 may include the outputs of the detectors being provided as inputs to a single ADC. The ADC may then provide a digital output to the one or more signal processing components 410 as was the case in the first circuit configuration 400. However, the second circuit configuration 420 may also include one or more additional components between the detectors and the ADC.
- the first circuit configuration 400 shown in FIG. 4A included multiple ADCs (for example, one ADC for each detector)
- the second circuit configuration 420 may only include one ADC for all of the detectors (or alternatively may include more than one ADC but multiple detectors may share a single ADC instead of
- the one detector may correspond to a field of view in which it is expected return light from an emitted light pulse would currently be located.
- the attenuators may thus serve to reduce the amount of detector output noise that is provided the ADC and signal processing components 410.
- the attenuators may also be used in other ways as well. For example, all of the outputs of the detectors may be left unattenuated unless it is determined that it is desired to block the output of one or more detectors.
- FIGs. 5A-5B illustrate example methods 500A and 500B in accordance with one or more example embodiments of the disclosure.
- the method may include emitting, by a light emitter of a LIDAR system, a first light pulse.
- Block 504a of the method 500A may include activating a first light detector of the LIDAR system at a first time, the first time corresponding a time when return light corresponding to the first light pulse would be within a first field of view of the first light detector.
- Block 506a of the method 500A may include activating a second light detector of the LIDAR system at a second time, the second time corresponding a time when return light corresponding to the first light pulse would be within a second field of view of the second light detector, wherein the first light detector is configured to include the first field of view, the first field of view being associated with a first range from the light emitter, and wherein the second light detector configured to include the second field of view, the second field of view being associated with a second range from the light emitter.
- the method may include emitting, by a light emitter, a first light pulse at a first time.
- Block 504b of the method 500B may include activating a first light detector and a second light detector, wherein a field of view of the first light detector includes a range closer to the light emitter than the field of view of the second light detector.
- Block 506b of the method 500B may include emitting, by the light emitter, a second light pulse at a second time.
- Block 508b of the method 500B may include receiving return light by the second light detector at a third time.
- Block 510 of method 500B may include determining, based on the return light being detected by the second light detector, that the return light is based on the first light pulse.
- the photodetectors may be selectively “turned on” and/or “turned off’ (which may similarly be referred to as “activating” or deactivating” a photodetector). “Turning on” a photodetector may refer to providing a bias voltage to the photodetector that satisfies a threshold voltage level. The bias voltage satisfying the threshold voltage level (for example, being at or above the threshold voltage level) may provide sufficient voltage to the photodetector to allow it to produce a level of output current based on light received by the photodetector.
- the output threshold voltage level being used and the corresponding output current being produced may depend on the type of photodetector being used and the desired mode of the operation of the photodetector. For example, if the photodetector is an APD, the threshold voltage level may be set high enough so that the photodetector is capable of avalanching upon receipt of light as described above. Similarly, if it is desired for the APD to operate in Geiger Mode, the threshold voltage level may be set even higher than if the APD were desired to operate outside of the Geiger Mode region of operation. That is, the gain of the photodetector when this higher threshold voltage level is applied may be much larger than if the photodetector were operating as a normal Avalanche Photodiode.
- the threshold bias voltage may be lower.
- the threshold voltage level may be set below a threshold voltage level used to allow the APD to avalanche upon receipt of light. That is, the bias voltage applied to the APD may be set low enough to allow the APD to still produce an output current, but only in a linear mode of operation.
- “turning off’ a photodetector may refer to reducing the bias voltage provided to the photodetector to below the threshold voltage level.
- “turning off’ the photodetector may not necessarily mean that the photodetector is not able to detect return light. That is, the photodetector may still be able to detect return light while the bias voltage is below the threshold voltage level, but the output signal produced by the photodetector may be below a noise floor established for a signal processing portion of the LIDAR system.
- a photodetector may be an Avalanche Photodiode.
- the APD may still produce an output, but the output may be based on a linear mode of operation and the resulting output current may be much lower than if the APD were to avalanche upon receipt of a same number of photons.
- the signal processing portion of the LIDAR system may have a noise floor configured to correspond to an output of the APD in linear mode, so that any outputs from the APD when operating with this reduced bias voltage may effectively be disregarded by the LIDAR system.
- selectively turning on and/or turning off the photodetectors may entail only having some of the photodetectors capable of detecting return light at a given time.
- FIG. 6 illustrates an example LIDAR system 600, in accordance with one or more embodiments of this disclosure.
- the LIDAR system 600 may be representative of any number of elements described herein, such as the LIDAR system 101 described with respect to FIG. 1, as well as any other LIDAR systems described herein.
- the LIDAR system 600 may include at least an emitter portion 601, a detector portion 605, and a computing portion 613.
- the emitter portion 601 may include at least one or more emitter(s) 602 (for simplicity, reference may be made hereinafter to “an emitter,” but multiple emitters could be equally as applicable) and/or one or more optical element(s) 604.
- An emitter 602 may be a device that is capable of emitting light into the environment. Once the light is in the environment, it may travel towards an object 612. The light may then reflect from the object and return towards the LIDAR system 600 and be detected by the detector portion 605 of the LIDAR system 600 as may be described below.
- the emitter 602 may be a laser diode as described above.
- the emitter 602 may be capable of emitting light in a continuous waveform or as a series of pulses.
- An optical element 604 may be an element that may be used to alter the light emitted from the emitter 602 before it enters the environment.
- the optical element 604 may be a lens, a collimator, or a waveplate.
- the lens may be used to focus the emitter light.
- the collimator may be used to collimate the emitted light. That is, the collimator may be used to reduce the divergence of the emitter light.
- the waveplate may be used to alter the polarization state of the emitted light. Any number or combination of different types of optical elements 604, including optical elements not listed herein, may be used in the LIDAR system 600.
- the detector portion 605 may include at least one or more detector(s) 606 (for simplicity, reference may be made hereinafter to “a detector,” but multiple detectors could be equally as applicable) and/or one or more optical elements 608.
- the detector may be a device that is capable of detecting return light from the environment (for example light that has been emitted by the LIDAR system 600 and reflected by an object 612).
- the detectors may be photodiodes.
- the photodiodes may specifically include Avalanche Photodiodes (APDs), which in some instances may operate in Geiger Mode.
- APDs Avalanche Photodiodes
- any other type of detector may be used, such as light emitting diodes (LED), vertical cavity surface emitting lasers (VCSEL), organic light emitting diodes (OLED), polymer light emitting diodes (PLED), light emitting polymers (LEP), liquid crystal displays (LCD), microelectromechanical systems (MEMS), and/or any other device configured to selectively transmit, reflect, and/or emit light to provide the plurality of emitted light beams and/or pulses.
- the detectors of the array may take various forms.
- the detectors may take the form of photodiodes, avalanche photodiodes (e.g., Geiger mode and/or linear mode avalanche photodiodes), phototransistors, cameras, active pixel sensors (APS), charge coupled devices (CCD), cryogenic detectors, and/or any other sensor of light configured to receive focused light having wavelengths in the wavelength range of the emitted light.
- the functionality of the detector 606 in capturing return light from the environment may serve to allow the LIDAR system 600 to ascertain information about the object 612 in the environment. That is, the LIDAR system 600 may be able to determine information such as the distance of the object from the LIDAR system 600 and the shape and/or size of the object 612, among other information.
- the optical element 608 may be an element that is used to alter the return light traveling towards the detector 606.
- the optical element 608 may be a lens, a waveplate, or filter such as a bandpass filter.
- the lens may be used to focus return light on the detector 606.
- the waveplate may be used to alter the polarization state of the return light.
- the filter may be used to only allow certain wavelengths of light to reach the detector (for example a wavelength of light emitted by the emitter 602). Any number or combination of different types of optical elements 608, including optical elements not listed herein, may be used in the LIDAR system 600.
- the computing portion may include one or more processor(s) 614 and memory 616.
- the processor 614 may execute instructions that are stored in one or more memory devices (referred to as memory 616).
- the instructions can be, for instance, instructions for implementing functionality described as being carried out by one or more modules and systems disclosed above or instructions for implementing one or more of the methods disclosed above.
- the processor(s) 614 can be embodied in, for example, a CPU, multiple CPUs, a GPU, multiple GPUs, a TPU, multiple TPUs, a multi-core processor, a combination thereof, and the like.
- the processor(s) 614 can be arranged in a single processing device.
- the processor(s) 614 can be distributed across two or more processing devices (for example multiple CPUs; multiple GPUs; a combination thereof; or the like).
- a processor can be implemented as a combination of processing circuitry or computing processing units (such as CPUs, GPUs, or a combination of both). Therefore, for the sake of illustration, a processor can refer to a single-core processor; a single processor with software multithread execution capability; a multi-core processor; a multi-core processor with software multithread execution capability; a multi-core processor with hardware multithread technology; a parallel processing (or computing) platform; and parallel computing platforms with distributed shared memory.
- a processor can refer to an integrated circuit (IC), an ASIC, a digital signal processor (DSP), a FPGA, a PLC, a complex programmable logic device (CPLD), a discrete gate or transistor logic, discrete hardware components, or any combination thereof designed or otherwise configured (for example manufactured) to perform the functions described herein.
- the processor(s) 614 can access the memory 616 by means of a communication architecture (for example a system bus).
- the communication architecture may be suitable for the particular arrangement (localized or distributed) and type of the processor(s) 614.
- the communication architecture 606 can include one or many bus architectures, such as a memory bus or a memory controller; a peripheral bus; an accelerated graphics port; a processor or local bus; a combination thereof; or the like.
- such architectures can include an Industry Standard Architecture (ISA) bus, a Micro Channel Architecture (MCA) bus, an Enhanced ISA (EISA) bus, a Video Electronics Standards Association (VESA) local bus, an Accelerated Graphics Port (AGP) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express bus, a Personal Computer Memory Card International Association (PCMCIA) bus, a Universal Serial Bus (USB), and or the like.
- ISA Industry Standard Architecture
- MCA Micro Channel Architecture
- EISA Enhanced ISA
- VESA Video Electronics Standards Association
- AGP Accelerated Graphics Port
- PCI Peripheral Component Interconnect
- PCMCIA Personal Computer Memory Card International Association
- USB Universal Serial Bus
- Memory components or memory devices disclosed herein can be embodied in either volatile memory or non-volatile memory or can include both volatile and nonvolatile memory.
- the memory components or memory devices can be removable or non-removable, and/or internal or external to a computing device or component.
- Examples of various types of non-transitory storage media can include harddisc drives, zip drives, CD-ROMs, digital versatile disks (DVDs) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, flash memory cards or other types of memory cards, cartridges, or any other non- transitory media suitable to retain the desired information and which can be accessed by a computing device.
- non-volatile memory can include read only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM), or flash memory.
- Volatile memory can include random access memory (RAM), which acts as external cache memory.
- RAM is available in many forms such as synchronous RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), Synchlink DRAM (SLDRAM), and direct Rambus RAM (DRRAM).
- SRAM synchronous RAM
- DRAM dynamic RAM
- SDRAM synchronous DRAM
- DDR SDRAM double data rate SDRAM
- ESDRAM enhanced SDRAM
- SLDRAM Synchlink DRAM
- DRRAM direct Rambus RAM
- the disclosed memory devices or memories of the operational or computational environments described herein are intended to include one or more of these and/or any other suitable types of memory.
- the memory 616 also can retain data.
- the multi-detector control modules 620 including computer-executable instructions, code, or the like that responsive to execution by one or more of the processor(s) 614 may perform functions including controlling the one or more detectors as described herein. For example, turning on and/or turning off any of the detectors are described herein. Additionally, the functions may include execution of any other methods and/or processes described herein.
- the LIDAR system 600 may include alternate and/or additional hardware, software, or firmware components beyond those described or depicted without departing from the scope of the disclosure. More particularly, it should be appreciated that software, firmware, or hardware components depicted as forming part of the computing device 600 are merely illustrative and that some components may not be present or additional components may be provided in various embodiments. While various illustrative program modules have been depicted and described as software modules stored in data storage, it should be appreciated that functionality described as being supported by the program modules may be enabled by any combination of hardware, software, and/or firmware. It should further be appreciated that each of the above-mentioned modules may, in various embodiments, represent a logical partitioning of supported functionality.
- This logical partitioning is depicted for ease of explanation of the functionality and may not be representative of the structure of software, hardware, and/or firmware for implementing the functionality. Accordingly, it should be appreciated that functionality described as being provided by a particular module may, in various embodiments, be provided at least in part by one or more other modules. Further, one or more depicted modules may not be present in certain embodiments, while in other embodiments, additional modules not depicted may be present and may support at least a portion of the described functionality and/or additional functionality. Moreover, while certain modules may be depicted and described as sub-modules of another module, in certain embodiments, such modules may be provided as independent modules or as submodules of other modules.
- blocks of the block diagrams and flow diagrams support combinations of means for performing the specified functions, combinations of elements or steps for performing the specified functions, and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flow diagrams, and combinations of blocks in the block diagrams and flow diagrams, may be implemented by special-purpose, hardware-based computer systems that perform the specified functions, elements or steps, or combinations of specialpurpose hardware and computer instructions.
- the terms “environment,” “system,” “unit,” “module,” “architecture,” “interface,” “component,” and the like refer to a computer-related entity or an entity related to an operational apparatus with one or more defined functionalities.
- the terms “environment,” “system,” “module,” “component,” “architecture,” “interface,” and “unit,” can be utilized interchangeably and can be generically referred to functional elements.
- Such entities may be either hardware, a combination of hardware and software, software, or software in execution.
- a module can be embodied in a process running on a processor, a processor, an object, an executable portion of software, a thread of execution, a program, and/or a computing device.
- both a software application executing on a computing device and the computing device can embody a module.
- one or more modules may reside within a process and/or thread of execution.
- a module may be localized on one computing device or distributed between two or more computing devices.
- a module can execute from various computer-readable non-transitory storage media having various data structures stored thereon. Modules can communicate via local and/or remote processes in accordance, for example, with a signal (either analogic or digital) having one or more data packets (for example data from one component interacting with another component in a local system, distributed system, and/or across a network such as a wide area network with other systems via the signal).
- a module can be embodied in or can include an apparatus with a defined functionality provided by mechanical parts operated by electric or electronic circuitry that is controlled by a software application or firmware application executed by a processor.
- a processor can be internal or external to the apparatus and can execute at least part of the software or firmware application.
- a module can be embodied in or can include an apparatus that provides defined functionality through electronic components without mechanical parts.
- the electronic components can include a processor to execute software or firmware that permits or otherwise facilitates, at least in part, the functionality of the electronic components.
- modules can communicate via local and/or remote processes in accordance, for example, with a signal (either analog or digital) having one or more data packets (for example data from one component interacting with another component in a local system, distributed system, and/or across a network such as a wide area network with other systems via the signal).
- modules can communicate or otherwise be coupled via thermal, mechanical, electrical, and/or electromechanical coupling mechanisms (such as conduits, connectors, combinations thereof, or the like).
- An interface can include input/output (I/O) components as well as associated processors, applications, and/or other programming components.
- Conditional language such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain implementations could include, while other implementations do not include, certain features, elements, and/or operations. Thus, such conditional language generally is not intended to imply that features, elements, and/or operations are in any way required for one or more implementations or that one or more implementations necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or operations are included or are to be performed in any particular implementation.
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Abstract
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EP21881130.5A EP4229438A1 (en) | 2020-10-14 | 2021-10-14 | Multi-detector lidar systems and methods for mitigating range aliasing |
KR1020237015271A KR20230085159A (en) | 2020-10-14 | 2021-10-14 | Multi-detector system and method for mitigating range aliasing |
CN202180084273.7A CN116615668A (en) | 2020-10-14 | 2021-10-14 | Multi-detector lidar system and method for mitigating range aliasing |
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US17/070,414 US20220113405A1 (en) | 2020-10-14 | 2020-10-14 | Multi-Detector Lidar Systems and Methods |
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US17/070,414 | 2020-10-14 | ||
US17/070,765 US11822018B2 (en) | 2020-10-14 | 2020-10-14 | Multi-detector LiDAR systems and methods for mitigating range aliasing |
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US20180231645A1 (en) * | 2015-03-26 | 2018-08-16 | Waymo Llc | Multiplexed Multichannel Photodetector |
WO2019005442A1 (en) * | 2017-06-30 | 2019-01-03 | Waymo Llc | Light detection and ranging (lidar) device range aliasing resilience by multiple hypotheses |
US20190317503A1 (en) * | 2016-10-17 | 2019-10-17 | Waymo Llc | Light Detection and Ranging (LIDAR) Device having Multiple Receivers |
JP6729864B2 (en) * | 2015-11-02 | 2020-07-29 | 株式会社デンソーテン | Radar device, signal processing device of radar device, and signal processing method |
US10802122B1 (en) * | 2020-01-15 | 2020-10-13 | Ike Robotics, Inc. | Methods and systems for calibration of multiple lidar devices with non-overlapping fields of view |
-
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- 2021-10-14 WO PCT/US2021/055083 patent/WO2022081910A1/en active Application Filing
- 2021-10-14 KR KR1020237015271A patent/KR20230085159A/en unknown
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Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
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US20180231645A1 (en) * | 2015-03-26 | 2018-08-16 | Waymo Llc | Multiplexed Multichannel Photodetector |
JP6729864B2 (en) * | 2015-11-02 | 2020-07-29 | 株式会社デンソーテン | Radar device, signal processing device of radar device, and signal processing method |
US20190317503A1 (en) * | 2016-10-17 | 2019-10-17 | Waymo Llc | Light Detection and Ranging (LIDAR) Device having Multiple Receivers |
WO2019005442A1 (en) * | 2017-06-30 | 2019-01-03 | Waymo Llc | Light detection and ranging (lidar) device range aliasing resilience by multiple hypotheses |
US10802122B1 (en) * | 2020-01-15 | 2020-10-13 | Ike Robotics, Inc. | Methods and systems for calibration of multiple lidar devices with non-overlapping fields of view |
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