The present disclosure relates to optical sensing systems such as a light detection and ranging (LiDAR) system, and more particularly to, an intertwined detector array for the optical sensing system.
Optical sensing systems such as LiDAR systems have been widely used in advanced navigation technologies, such as to aid autonomous driving or to generate high-definition maps. For example, a typical LiDAR system measures the distance to a target by illuminating the target with pulsed laser light beams and measuring the reflected pulses with a sensor such as a photodetector or a photodetector array. Differences in laser light return times, wavelengths, and/or phases can then be used to construct digital three-dimensional (3D) representations of the target. Because using a narrow laser beam as the incident light can map physical features with very high resolution, a LiDAR system is particularly suitable for applications such as sensing in autonomous driving and high-definition map surveys.
The pulsed laser light beams emitted by a LiDAR system are typically directed to multiple directions to scan a 2-dimension pattern (e.g., a field of view (FOV)). For example, a scanner of the LiDAR system may scan a certain scanning range in a first dimension and the LiDAR system may rotate in a second dimension, perpendicular to the first dimension, to cover the FOV. The pulsed laser light beams reflected by an object within the FOV are typically received and detected by a detector array that includes multiple detectors. Each detector within the detector array may be configured to detect emitted light beams within a certain scanning range in the first dimension.
Because of the manufacturing constrains such as the semiconductor processing and fabricating limitations, detectors in the detector array are separated with a significant gap in between. As a result, the light spot formed by the returned light beam may be received by the gap area in between detectors instead of a detector. Accordingly, the optical signal received (e.g., energy of the received photons) can be very weak or entirely missing. As a result, the detecting result of the FOV may show an obvious uneven pattern (e.g., a few dark lines after several lines of normal scanning result) because of the gap. This may significantly reduce the precision and accuracy of the detecting result.
Embodiments of the disclosure provide a receiver of a Light Detection and Ranging (LiDAR) system for detecting optical signals reflected by an object. The receiver includes a detector array configured to detect the optical signals. The detector array includes a plurality of intertwined detectors arranged to each cover a scanning range in a first direction. The scanning range covered by each detector among the plurality of intertwined detectors partially overlaps with the scanning range covered by at least one of its neighboring detectors. The receiver also includes a controller operatively coupled to the detector array, configured to process the optical signals detected by the detector array.
Embodiments of the disclosure also provide a method for detecting optical signals reflected by an object. The method includes detecting a first optical signal by a first pair of neighboring detectors in a detector array. The detector array includes a plurality of intertwined detectors arranged to each cover a scanning range in a first direction. The scanning range covered by each detector among the plurality of intertwined detectors partially overlaps with the scanning range covered by at least one of its neighboring detectors. The method also includes detecting a second optical signal by a second pair of neighboring detectors in the detector array. The method further includes processing, by a controller operatively coupled to the detector array, the first and second optical signals detected by the first and second pairs of detectors.
Embodiments of the disclosure further provide an optical sensing system. The system includes a transmitter configured to emit optical signals steered to scan an object. The system further includes a receiver including a detector array configured to detect the optical signals reflected by the object. The detector array includes a plurality of intertwined detectors arranged to each cover a scanning range in a first direction. The scanning range covered by each detector among the plurality of intertwined detectors partially overlaps with the scanning range covered by at least one of its neighboring detectors. The optical sensing system also includes a controller operatively coupled to the receiver, configured to process the optical signals detected by the detector array.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
Embodiments of the present disclosure provide systems and methods for detecting optical signals reflected by an object using an optical sensing system (e.g., a LiDAR system). For example, the optical sensing system may include a transmitter configured to emit optical beams (e.g., laser beams) steered to scan an object (e.g., scan a field of view (FOV)). The light beams reflected by the object may be received by a receiver including a detector array. The detector array may include a plurality of intertwined detectors arranged to each cover a scanning range in a first direction. The scanning range covered by each detector among the plurality of intertwined detectors partially overlaps with the scanning range covered by at least one its neighboring detector. Detectors within the detector array are separated with a predetermined gap (e.g., determined based on the manufacturing constrains) non-perpendicular to the first direction.
The optical signals (e.g., pulsed laser light beams) emitted by a LiDAR system are typically directed to multiple directions to scan a 2-dimension FOV. For example, the emitted optical signals may be steered by a scanner to scan a certain scanning range in a first dimension (e.g., a range in angular degrees, such as 20 degrees, 40 degrees, etc.) and the LiDAR system may rotate in a second dimension, perpendicular to the first dimension, to cover the FOV. For example, within the scanning range, several hundred lines (e.g., 200 lines, 300 lines, etc.) can be scanned by the scanner in the first dimension. The scanned lines within the scanning range can be determined based on the resolution of the optical sensing system. For example, the higher the resolution is, the larger the number of scanned lines within the scanning range is.
The emitted optical signals may be reflected by an object within the FOV and be received and detected by a detector array. Each of the detectors within the detector array may be configured to cover/receive emitted optical signals within a certain scanning range in the first dimension. For example, if the number of detectors in the detector array is 32, and the scanning range for the transmitter is 20 degree, each detector within the detector array is configured to cover about a 0.625-degree scanning range in the first dimension.
Before being detected by each detector of the detector array, the reflected optical signal may be focused by a lens into an ellipse shape with a major axis in the second dimension. In conventional detector arrays, when the focused optical signal hits the gap between the detectors, a significantly reduced signal intensity may be detected. This may cause uneven scanning pattern in the detecting result.
To reduce the uneven scanning pattern in the detecting result caused by the gap, each of the detectors may be designed such that the covered scanning range of the respective detector overlaps with the scanning range covered by one of its neighboring detector, such that no optical signal is received entirely by the gap area in between the detectors. For one example, a light sensitive area of each detector may be fabricated to have a Z-shape sideway to the first direction and neighboring detectors are arrange in an intertwined fashion. An end arm of the Z-shaped light sensitive area may overlap in scanning range with an end arm of a neighboring detector in the first dimension. Accordingly, the predetermined gap between the detectors may also be in a Z-shape as well (will be disclosed in detail below). As a result, the focused optical signal may always be partially received by a pair of neighboring detectors of the detector array, instead of falling entirely within the gap area. Thus, the uneven scanning pattern in the detecting result caused by the gap can be effectively reduced and the accuracy of the detecting result can be significantly improved.
As illustrated in
Consistent with some embodiments, LiDAR system 102 and sensor 110 may be configured to capture data as vehicle 100 moves along a trajectory. For example, a transmitter of LiDAR system 102 may be configured to scan the surrounding environment. LiDAR system 102 measures distance to a target by illuminating the target with pulsed laser beam and measuring the reflected pulses with a receiver. The laser beam used for LiDAR system 102 may be ultraviolet, visible, or near infrared. In some embodiments of the present disclosure, LiDAR system 102 may capture point clouds including depth information of the objects in the surrounding environment. As vehicle 100 moves along the trajectory, LiDAR system 102 may continuously capture data.
Laser source 206 may be configured to provide a laser beam 207 (also referred to as “native laser beam”) to scanner 210. In some embodiments of the present disclosure, laser source 206 may generate a pulsed laser beam in the ultraviolet, visible, or near infrared wavelength range. In some embodiments of the present disclosure, laser source 206 may include a pulsed laser diode (PLD), a vertical-cavity surface-emitting laser (VCSEL), a fiber laser, etc. For example, a PLD may be a semiconductor device similar to a light-emitting diode (LED) in which the laser beam is created at the diode's junction.
Scanner 210 may be configured to steer a laser beam 209 in the first direction (e.g., along Z axis) to scan an object 212. Scanner 210 may include mirror assembly configured to steer the emitted laser beams in different directions within the scanning range (e.g., a range in angular degrees, such as 20 degrees, 40 degrees, etc.), as illustrated in
In some embodiments, at each time point during the scan, scanner 210 may steer laser beam 209 to object 212 in a direction within a range of scanning angles by rotating the mirror assembly. In some embodiments of the present disclosure, scanner 210 may also include optical components (e.g., lenses, mirrors) that can focus pulsed laser light into a narrow laser beam to increase the scan resolution and the scanning range to scan object 212.
In some embodiments, as will be described below in detail, receiver 204 may include an intertwined detector array for detecting a returned laser beam 211 returned from object 212. Returned laser beam 211 may be in a different direction from laser beam 209. Receiver 204 can collect laser beams returned from object 212 and output electrical signals reflecting the intensity of the returned laser beams. Upon contact, laser light can be reflected by object 212 via backscattering, such as Rayleigh scattering, Mie scattering, Raman scattering, and fluorescence.
As illustrated in
Detector array 216 may include a plurality of intertwined detectors and may be configured to detect returned laser beam 211 returned from object 212. In some embodiments, each detector of detector array 216 may include at least one of a photo detector (PD), an avalanche photodiode (APD) or a single-photon avalanche diode (SPAD). In some embodiments, each detector of detector array 216 may convert the optical signal (e.g., returned laser beam 211) within a certain scanning range in the first direction (e.g., Z axis in
Consistent with the present disclosure, and as will be described in more details below in connection with
LiDAR system 200 may further include one or more controllers, such as a controller 220. Controller 220 may control the operation of transmitter 202 and/or receiver 204 to perform detection/sensing operations. Specifically, controller 220 may control the scanning of transmitter 202 and may control the receiver 204 to receive the optical signals. Controller 220 may also be configured to process the optical signals received accordingly. For example, controller 220 may individually address the optical signals received by each detector of detector array 216 based on electrical signals 218 corresponding to each of the optical signals.
In some embodiments, controller 220 may include components (not shown) such as a communication interface, a processor, a memory, and a storage for performing various control functions. In some embodiments, controller 220 may have different modules in a single device, such as an integrated circuit (IC) chip (implemented as, for example, an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA)), or separate devices with dedicated functions. In some embodiments, the processing module for processing the optical signal received by respective detector of detector array 216 may be disposed on a same microchip with the respective detector. In some other embodiments, the processing module may be disposed on a chip separate from the microchip where the respective detector is disposed on.
In some embodiments, the processor of controller 220 may include any appropriate type of general-purpose or special-purpose microprocessor, digital signal processor, or microcontroller. The memory or storage may be a volatile or non-volatile, magnetic, semiconductor, tape, optical, removable, non-removable, or other type of storage device or tangible (i.e., non-transitory) computer-readable medium including, but not limited to, a ROM, a flash memory, a dynamic RAM, and a static RAM. For example, the memory and/or the storage may be configured to store program(s) that may be executed by the processor to control the operation of scanner 210.
In both
Different from conventional detector array, detector arrays 300A and 300B include a plurality of intertwined detectors arranged to each cover a scanning range (e.g., a range in angular degrees, such as about 0.625 degrees, about 1.25 degrees, etc.) in a first direction (e.g., along Z axis in
In one example, as illustrated in
Different from the conventional detector arrays, the covered scanning rang for detector 303-1 in detector array 300A may partially overlap with the covered scanning rang for a neighboring detector 303-2 in Z axis. In some embodiments, each detector may include a light sensitive area forms a Z-shape sideway to the Z axis. For example, detector 303-1 of detector array 300A may include a light sensitive area 305A-1 in a Z-shape for detecting the returned optical signal (e.g., light spot 301) as shown in
In some embodiments, an end arm 307 of light sensitive area 305A-1 of detector 303-1 may overlap with an end arm 309 of light sensitive area 305A-2 of a neighboring detector 303-2 in Z axis. For example, a lower end of end arm 307 may be lower than an upper end of end arm 309 in Z axis. It is understood that “low”, “up”, “lower”, and “upper” are only for showing the relative spatial relationship. When detector array 300A is disposed upside down the relative spatial relationship can be changed accordingly.
Therefore, a predetermined gap between neighboring detectors 303-1 and 303-2 (e.g., determined based on the fabricating limitations) is non-perpendicular to the Z axis. For example, the gap between neighboring detectors 303A and 303B has a sideway Z-shape as well. As a result, even if light spot 301 partially impinges on the gap area between neighboring detectors 303-1 and 303-2, a majority of light spot 301 may still be detected between light sensitive area 305A-1 of detector 303-1 and light sensitive area 305A-2 of detector 303-1. In some scenarios, light spot 301 may be fully received by the light sensitive area of one detector (e.g., light sensitive area 305A-1 of detector 303-1). In some other cases, light spot 301 may be partially received by light sensitive area 305A-1 of detectors 303-1 and light sensitive area 305A-2 of detector 303-2. In the latter case, although part of light spot 301 may still impinge on the gap area between detectors 303-1 and 303-2, the signal lost in the gap area is insubstantial. This may greatly reduce the uneven pattern in the detecting result caused by the gap and may significantly increase the accuracy of the detecting result generated by detector array 300A.
In some embodiments, the overlap in scanning ranges between the neighboring detectors in detector array 300A of
In some embodiments, the light sensitive area of each detector can also be in an oblique parallelogram-shape, where one side of the parallelogram is parallel to the Z axis and the adjacent side is oblique. For example,
Different from detector array 300A, light sensitive area (e.g., light sensitive areas 305B-1 and 305B-2) of each detector 303 (e.g., detectors 303-3 and 303-4) in detector array 300B can be in a parallelogram-shape. For example, as illustrated in
Therefore, the predetermined gap between neighboring detectors 303-3 and 303-4 is non-perpendicular to the Z axis, and thus would not be in parallel with the major axis of light spot 301. In some scenarios, light spot 301 may be fully received by the light sensitive area of one detector (e.g., light sensitive area 305B-1 of detector 303-3). In some other scenarios, light spot 301 may be partially received by light sensitive areas 305B-1 of detector 303-3 and light sensitive areas 305B-2 of detector 303-4. In the latter case, even if light spot 301 partially impinges on the gap area between neighboring detectors 303-3 and 303-4, a majority of light spot 301 is detected by the light sensitive area of at least one detector. This may greatly reduce the uneven pattern in the detecting result caused by the gap and may significantly increase the accuracy of the detecting result generated by detector array 300B.
In some embodiments, the overlap in scanning ranges between the neighboring detectors in detector array 300B of
It is contemplated that the shape of the light sensitive area of each detector is not limited to the examples disclosed herein. The exemplary shapes disclosed herein are only for illustrative purposes. Any other suitable shapes that can be arranged in an intertwined fashion to make the light sensitive areas of neighboring detectors overlap in scanning range in the first direction, can be used.
After being detected, each of the optical signal detected by detector arrays 300A and/or 300B may be transmitted to controller 220 (e.g., after being converted into electrical signals such as electrical signal 218 in
In step S402, optical signals may be emitted and steered to scan an object by a transmitter (e.g., transmitter 202 in
In step S404, a first optical signal reflected by the object (e.g., returned laser beam 211) is detected by a first pair of neighboring detectors (e.g., neighboring detectors shown in
In step S406, a second optical signal reflected by the object is detected by a second pair of neighboring detectors in the detector array. For example, the second optical signal may be from a scanning range different from the scanning range covered by the first pair of neighboring detectors. In some embodiments, the second optical signal may be focused to a second light spot, e.g., by lens 214, before being detected by the second pair of neighboring detectors. In some embodiments, the second light spot can be detected by both detectors of the second pair of neighboring detectors.
In step S408, the first and second optical signals detected by the detector array can be processed by a controller (e.g., controller 220 as shown in
It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed system and related methods. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed system and related methods.
It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.