EP3994496A1

EP3994496A1 - Lidar receiving unit

Info

Publication number: EP3994496A1
Application number: EP20734163.7A
Authority: EP
Inventors: Ralf Beuschel
Original assignee: Ibeo Automotive Systems GmbH
Current assignee: Microvision Inc
Priority date: 2019-07-02
Filing date: 2020-06-19
Publication date: 2022-05-11
Also published as: WO2021001177A1; DE102019209697A1; CN113994229A; US20220252701A1; KR20220016230A; KR102636878B1; JP2022538244A; JP7338904B2; CA3140197A1; IL289491A

Abstract

The invention relates to a LIDAR receiving unit (16) in a focal plane array assembly, comprising a plurality of sensor elements (24) for receiving light pulses of a LIDAR transmitting unit (14), and multiple routing channels (32) for transporting signals from the sensor elements to an edge region (R) of the LIDAR receiving unit, wherein respective multiple sensor elements are arranged in a macrocell (26, 26'), which is assigned to a transmission element (22) of the LIDAR transmitting unit, respective multiple macrocells form a macrocell cluster (32) and respective multiple macrocell clusters are arranged in multiple rows (Z1, Z2, Z3), and the routing channels cross the multiple rows between respective neighbouring macrocell clusters of a row and are designed for transporting the signals in an orthogonal direction relative to the rows. The invention also relates to a LIDAR measuring device (10) for detecting an object (12) in an environment of a vehicle (14).

Description

Lidar receiving unit

The present invention relates to a lidar receiving unit in a focal plane array arrangement. The present invention further relates to a lidar measuring device for detecting an object in the surroundings of a vehicle.

Modern vehicles (cars, vans, trucks, motorcycles, driverless transport systems, etc.) include a variety of systems that provide information to a driver or operator and / or control individual functions of the vehicle partially or fully automatically. The surroundings of the vehicle and, if necessary, other road users are recorded by sensors. Based on the recorded data, a model of the vehicle environment can be generated and changes in this vehicle environment can be reacted to. As a result of the ongoing development in the field of autonomous and semi-autonomous vehicles, the influence and scope of advanced driver assistance systems (ADAS) and autonomously operating transport systems are increasing. The development of ever more precise sensors makes it possible to record the environment and to control individual functions of the vehicle completely or partially without intervention by the driver.

Lidar technology (light detection and ranging) is an important sensor principle for detecting the surroundings. A lidar sensor is based on the emission of light pulses and the detection of the reflected light. A distance to the point of reflection can be calculated using a transit time measurement. A target can be detected by evaluating the reflections received. With regard to the technical implementation of the corresponding sensor, a distinction is made between scanning systems, which mostly function based on micromirrors, and non-scanning systems, in which several transmitting and receiving elements are arranged statically next to one another (especially so-called focal plane array arrangement) .

In this context, WO 2017/081294 A1 describes a method and a device for optical distance measurement. There is a use of a transmission matrix for sending measurement pulses and a receiving matrix for Receiving the measurement pulses disclosed. When the measurement pulses are sent, subsets of the send elements of the send matrix are activated.

One challenge in the field of non-scanning lidar measurement systems is the arrangement of the sensor elements in a receiving array and the routing of the signals from the sensor elements to the edge of the receiving array. On the one hand, the highest possible density of the sensor elements of the array should be achieved. On the other hand, efficient routing of the signals to the edge of the array for further processing should be made possible. In addition, a high resolution and good detection should be guaranteed.

Based on this, the present invention has the task of providing an approach for the efficient reading of an array of sensor elements. In particular, an array is to be implemented in which blind areas are largely avoided. In addition, a high resolution should be achieved.

To achieve this object, the invention relates in a first aspect to a lidar receiving unit in a focal plane array arrangement, with:

a plurality of sensor elements for receiving light pulses from a lidar transmission unit; and

a plurality of routing channels for transporting signals from the sensor elements to an edge area of the lidar receiving unit, wherein

In each case a plurality of sensor elements are arranged in a macro cell which is assigned to a Sen deelement of the lidar transmission unit;

several macro cells each form a macro cell cluster and several macro cell clusters are arranged in several rows; and

the routing channels traverse the multiple rows between adjacent macrocell clusters of a row and are designed to transport the signals in a direction orthogonal to the rows.

In a further aspect, the present invention relates to a lidar measuring device for detecting an object in the surroundings of a vehicle, with:

a lidar receiving unit according to one of the preceding claims; a lidar transmission unit with a plurality of transmission elements for transmitting light pulses; and

a control unit for controlling the lidar transmission unit and for evaluating the signals from the sensor elements in order to detect the object.

Preferred embodiments of the invention are described in the dependent claims. It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination, but also in other combinations or alone, without departing from the scope of the present invention. In particular, the lidar measuring device or the lidar transmitting unit can be designed in accordance with the configurations described for the lidar receiving unit in the dependent claims.

The sensor elements of the lidar receiving unit are designed to receive light pulses from a corresponding lidar transmitting unit. Several sensor elements together form a macro cell. Several macro cells together form a macro cell cluster. The macro cell clusters of the lidar receiver unit are arranged in rows. In order to evaluate the signals that arise when a light pulse is received in a sensor element, they must be transported away from the sensor element via routing channels to an edge area of the lidar receiver unit. According to the invention, the routing channels are arranged essentially orthogonally to the rows. A routing channel runs between two adjacent macro-cell clusters of a row. In particular, the lidar receiving unit is a microchip on which the sensor elements are arranged, and the signals must be routed to an edge area of the chip in which the corresponding evaluation electronics are located.

The arrangement of the routing channels according to the invention results in an efficient transmission of the signals from the sensor elements into the edge area of the lidar receiving unit. It is possible to achieve routing of the signals orthogonally to the rows with a line-by-line layout of the Li dar receiving unit and the lidar transmitting unit or with a line-by-line control of the lidar transmitting unit. In this way, high performance can be ensured in the long range. In the close range there are gaps due to the routing, which means that the resolution solution is reduced. However, the effective spatial resolution is improved since the lidar measuring device works with a constant angular resolution. Efficient routing is achieved. A high resolution can be achieved. The use of a focal plane array arrangement results in a high level of robustness against vibrations. The service life of the lidar measuring device is improved. There are also advantages in terms of manufacturability. A cost-efficient implementation becomes possible.

In a preferred embodiment, two macro cells each form a macro cell cluster. The two macro cells of the macro cell cluster are preferably arranged parallel to the rows. Because a routing channel runs between two adjacent macro cell clusters of a row, the two macro cells of the macro cell cluster can be read from both sides. The result is an efficient readability. An arrangement of the macro cells parallel to the rows results in good contactability.

In a preferred embodiment, the macro cell clusters of a first row are offset from the macro cell clusters of a second row, which is adjacent to the first row. The staggered arrangement (interlace structure) avoids the vertical (orthogonal to the lines) blind areas in which no detections can take place. The result is an improved recognition of objects.

In a preferred embodiment, the routing channels run in channel sections between the rows parallel to the rows. At least in sections, the channels can run parallel to the lines. Nevertheless, the signals are transported out of the array orthogonally to the lines. The channel sections running parallel to the rows are particularly advantageous when the macrocell clusters of two adjacent rows are arranged offset from one another.

In a preferred embodiment, a distance between adjacent macrocell clusters in a row is greater than a distance between adjacent macrocell clusters in adjacent rows. Additionally or alternatively, preprocessing elements for reading out the sensor elements are arranged between adjacent lines. The preprocessing elements preferably include a transistor. The distances are preferably chosen so that the largest possible Density of the sensor elements of the lidar receiver unit results. As many sensor elements as possible should be arranged on a chip. Routing takes place between neighboring macro cell clusters of a row. Pre-processing elements are arranged between the lines, which usually require comparatively less space.

In a preferred embodiment, an integer multiple of a diameter of the sensor elements is different from a distance between centers of the transmission elements of the lidar transmission unit to be assigned. The fact that several sensor elements each receive a light pulse from a transmission element can result in poorer detection due to alignment errors. By appropriately selecting the diameter of the sensor elements or the distance between the centers of the assigned transmission elements, these errors can be balanced or averaged. The errors are leveled out, so to speak, in that at least one macro cell does not completely coincide in its imaging position on the receiving array with the assigned transmitting element. The result is an improved detection of objects in the sense of an improved usability of the sensor data.

In a preferred embodiment, sensor elements with reduced sensitivity are arranged between macro cells of a macro cell cluster. In particular, transmission elements can be used which have a metallization on an opening and thus receive fewer photons. This results in a better delimitation between neighboring macro cells of a macro cell cluster. An improved detection of objects is achieved.

In a preferred embodiment, the lidar receiving unit includes evaluation electronics for reading out the sensor elements line by line. The evaluation electronics are preferably also arranged on the chip. The signals from the sensor elements are evaluated in order to enable object detection.

In a preferred embodiment, a macro cell cluster comprises between 14 and 34 sensor elements. A focal plane array arrangement is understood to mean a configuration of the sensor elements (or the transmission elements) essentially in one plane. A lidar receiving unit is in particular a microchip with the corresponding sensor elements. A lidar transmission unit is also in particular a microchip with the corresponding transmission elements. The receiving and transmitting unit can also be arranged together on a microchip. The sensor elements are arranged on a chip in matrix form. The sensor elements are distributed over a surface of the chip of the lidar receiver unit. A light pulse from a lidar transmission unit is understood to mean, in particular, a pulse of laser light. The surroundings of a vehicle include, in particular, an area around the vehicle that is visible from the vehicle.

The invention is described and explained in more detail below with reference to a few selected exemplary embodiments in conjunction with the accompanying drawings. Show it:

Fig. 1 is a schematic representation of a lidar according to the invention

Measuring device for detecting an object in the vicinity of a vehicle;

2 shows a schematic representation of a lidar transmission unit for emitting light pulses;

3 shows a schematic representation of a lidar according to the invention

Receiving unit; and

4 shows a schematic representation of a macro cell of an inventive

Lidar receiving unit.

In FIG. 1, a lidar measuring device 10 according to the invention for detecting an object 12 in the vicinity of a vehicle 14 is shown schematically. The lidar measuring device 10 is integrated into the vehicle 14 in the exemplary embodiment shown. The object 12 in the vicinity of the vehicle 14 can be, for example, another vehicle or a static object (traffic sign, house, tree, etc.) or another road user (pedestrians, cyclists, etc.). The lidar measuring device 10 is preferably mounted in the area of a bumper of the vehicle 14 and can in particular the surroundings of the vehicle 14 in front of the vehicle evaluate. For example, the lidar measuring device 10 can be integrated into the front bumper.

The lidar measuring device 10 according to the invention comprises a lidar receiving unit 16 and a lidar transmitting unit 18. Furthermore, the lidar measuring device 10 comprises a control unit 20 for controlling the lidar transmitting unit 18 and for evaluating the signals from the sensor elements of the lidar receiving unit 16.

Both the lidar receiving unit 16 and the lidar transmitting unit 18 are preferably designed in a focal plane array configuration. The elements of the respective device are arranged essentially in one plane on a corresponding chip. The chip of the lidar receiving unit or the lidar transmitting unit is arranged in a focal point of a corresponding optical system (transmitting optical system or receiving optical system). In particular, sensor elements of the lidar receiving unit or Sen deelemente of the lidar transmitting unit 18 are arranged in the focal point of the respective receiving or transmitting optics. This optics can be formed, for example, by an optical lens system.

The sensor elements of the lidar receiving unit 16 are preferably designed as SPAD (Single Photon Avalanche Diode). The lidar transmission unit 18 comprises several transmission elements for emitting laser light or laser pulses. The transmission elements are preferably designed as VCSELs (Vertical Cavity Surface Emitting Laser). The transmission elements of the lidar transmission unit 18 are distributed over an area of a transmission chip. The sensor elements of the lidar receiving unit 16 are distributed over an area of the receiving chip.

The transmission chip is assigned a transmission optics, the reception chip is assigned a receiving optics. The optics depict light arriving from a spatial area onto the respective chip. The spatial area corresponds to the visual area of the lidar measuring device 10, which is examined or sensed for objects 12. The spatial area of the lidar receiving unit 16 or the lidar transmitting unit 18 is essentially identical. The transmission optics images a transmission element onto a solid angle that represents a partial area of the spatial area. The transmission element sends out laser light accordingly in this solid angle. The transmission elements jointly cover the entire room area. The receiving optics form a sensor element on a solid angle that represents a sub-area of the spatial area. The number of all sensor elements covers the entire room area. Sending elements and sensor elements that consider the same solid angle map one another and are assigned or assigned to one another accordingly. A laser light from a transmission element is normally always mapped onto the associated sensor element. Favorably, several sensor elements are arranged within the solid angle of a Sendeele element.

To ascertain or detect objects 12 within the spatial area, the lidar measuring device 10 carries out a measuring process. Such a measuring process comprises one or more measuring cycles, depending on the design of the measuring system and its electronics. A TCSPC method (Time Correlated Single Photon Counting method) is preferably used in the control unit 20. Here, individual incoming photons are detected, in particular by a SPAD, and the time at which the sensor element was triggered (detection time) is stored in a memory element. The time of detection is related to a reference time at which the laser light is emitted. The transit time of the laser light can be determined from the difference, from which the distance of the object 12 can be determined.

A sensor element of the lidar receiving unit 16 can be triggered on the one hand by the laser light and on the other hand by ambient radiation. A laser light always arrives at a certain distance from the object 12 at the same time, whereas the ambient radiation always provides the same probability of triggering a sensor element. When a measurement is carried out multiple times, in particular multiple measurement cycles, the triggering of the sensor element add up at the detection time which corresponds to the transit time of the laser light with respect to the distance of the object. In contrast, the triggers from the ambient radiation are evenly distributed over the measurement duration of a measurement cycle. A measurement corresponds to the emission and subsequent detection of the laser light. The data of the individual measurement cycles of a measurement process stored in the memory element enable an evaluation of the multiple detection times in order to infer the distance from the object 12. A sensor element is favorably connected to a TDC (Time to Digital Converter). The TDC stores the time at which the sensor element was triggered in the storage element. Such a storage element can be designed, for example, as a short-term memory or as a long-term memory. For a measurement process, the TDC fills a storage element with the times at which the sensor elements detect the arrival of the photon. This can be represented graphically by means of a histogram based on the data of the memory element. In a histogram, the duration of a measurement cycle is divided into very short time segments (so-called bins). If a sensor element is triggered, the TDC increases the value of a bin by 1. The bin is filled which corresponds to the transit time of the laser pulse, i.e. the difference between the time of detection and the reference time.

The structure of the lidar transmission unit 18 is shown schematically in FIG. 2. The chip comprises several transmission elements 22 which are arranged in an array (matrix). For example, several thousand transmission elements can be used. The transmission elements 22 are activated line by line. For the sake of clarity, only one transmission element 22 is provided with a reference number.

In the exemplary embodiment shown, the lines 0..ny-l each include a large number of transmission elements O..hc-l. For example, 100 lines (ny = 100) and 128 transmission elements per line (nx = 128) can be provided. The line spacing A1 between the lines can be in the range of a few micrometers, for example 40 miti. The element spacing A2 between transmitter elements 22 in the same row can be of a similar order of magnitude.

In Fig. 3, a lidar receiving unit 16 according to the invention is schematically represents Darge. The lidar receiving unit 16 comprises a plurality of sensor elements 24. The sensor elements are each arranged in macro cells 26, 26 ′, with a macro cell 26, 26 ′ comprising those sensor elements 24 which are jointly assigned to a single transmitting element 22 of the lidar transmitting unit. In each case two macro cells 26, 26 ′ are arranged in a macro cell cluster 30. The several macrocell clusters 30 are arranged in several rows Zi, Z ₂ , Z ₃ . Routing channels 32 are arranged between two adjacent macro cell clusters 30, which cross the lines Zi, Z2, Z ₃ and are designed to transport the signals from the sensor elements 24 to an edge region R of the lidar receiving unit 16. In the illustration of FIG. 3, two exemplary spot positions 28, 28 ′ are also marked schematically, which correspond to the positions of assigned transmission elements of the lidar transmission unit in the array of the lidar reception unit 16.

It goes without saying that only a section of the structure of the chip of the lidar receiving unit 16 is shown in FIG. 3 in order to visualize the arrangement of the sensor elements 24, routing channels 32, macro cells 26 and macro cell clusters 30. The chip expands upwards and to the side in the illustration. The number of macro cells preferably corresponds to the number of transmission elements of the lidar transmission unit 18. For the sake of clarity, not all sensor elements 24 or macro cells 26, 26 ′ and macro cell clusters 30 are provided with reference symbols.

As shown, in the exemplary embodiment shown, the routing channels 32 each run between adjacent macro cell clusters 30 and transport the signals in a direction orthogonal to the course of the lines Zi, Z ₂ , Z ₃ . In the exemplary embodiment shown, the routing channels have channel sections 34 which run parallel to the lines in an area between the lines. This makes it possible, please include that the macro cell clusters 30 of a first row are offset from the macro cell clusters 30 of a second row, which is adjacent to the first row. This has the effect that there are no vertical blind areas in the vertical direction. The macro cell clusters 30 are so far net angeord in an interlace structure. The sensor elements or spots of the adjacent line are arranged in the gaps of a line.

As also shown in the illustrated embodiment, a distance A3 between adjacent macro cell clusters 30 of a row is greater than a distance A4 between adjacent macro cell clusters 30 in adjacent (adjacent) rows. The routing channels 32 run within the distance A3 or between the macro cell clusters. Preprocessing elements, preferably transistors, can also be arranged between the rows Zi, Z2, Z ₃ .

In the edge region of the chip of the lidar receiving unit 16, there can be provided evaluation electronics 38 which are designed to read the sensor elements 24 line by line or to further process the signals from the sensor elements. In FIG. 4, a single macro cell cluster 30 is shown schematically. In the exemplary embodiment presented, the macro cell cluster 30 comprises a total of 28 sensor elements 24 or two macro cells 26, 26 '. Between the two macro cells 26, 26 'or on the edge of one or both macro cells 26, 26', two sensor elements with reduced sensitivity 36, 36 'are net angeord in the illustrated embodiment. For example, the sensor elements with reduced sensitivity 36, 36 'can be sensor elements with a metallization on the opening, so that fewer photons can be received. The sensor elements with reduced sensitivity 36, 36 'can also be referred to as aperture SPADs. It goes without saying that a different number of sensor elements with reduced sensitivity can also be used.

In the illustration, two exemplary spot positions 28, 28 'are marked, which represent the positions of transmission elements that are assigned to the macro cells 26, 26'. The fact that an integral multiple of a diameter Ds of the sensor elements differs from a distance DA between centers of assigned transmission elements of the lidar transmission unit, which are located at positions PI and P2, balances out alignment errors. The highest photon density is received in the middle of the spot positions 28, 28 'of the Sen deelemente on the macro cell cluster. In other words, the receiving elements in the middle of the spot position 28, 28 'each receive the highest photon density. Because the spot position 28, 28 'cannot be aligned exactly with respect to the array of the lidar receiver unit, a distance DA which corresponds to a full-line multiple of the distance Ds would result in both spot positions 28, 28' being hit well or badly will. The choice of the distances Ds and DA according to the invention avoids this and leveling the errors in the event of inaccurate alignment is achieved.

The invention has been comprehensively described and explained with reference to the drawings and the description. The description and explanation are to be understood as examples and not restrictive. The invention is not limited to the disclosed embodiments. Other embodiments or variations will become apparent to those skilled in the art after using the present invention and after carefully analyzing the drawings, the disclosure and the following claims. In the claims, the words "comprising" and "having" do not exclude the presence of further elements or steps. The undefined article "a" or "an" does not exclude the presence of a plurality. A single element or a single unit can perform the functions of several of the units mentioned in the patent claims. An element, a unit, an interface, a device and a system can be implemented partially or completely in hardware and / or in software. The mere mention of some measures in several different dependent claims should not be understood to mean that a combination of these measures cannot also be used advantageously. Reference signs in the claims are not to be understood as restrictive.

Reference number

10 Lidar measuring device

12 object

14 vehicle

16 Lidar receiving unit

18 Lidar transmitter unit

20 control unit

22 transmission element

24 sensor element

26 macro cell

28 spot position

30 macro cell clusters

32 routing channel

34 canal section

36, 36 'sensor element with reduced sensitivity

Claims

1. Lidar receiving unit (16) in a focal plane array arrangement, with:

a plurality of sensor elements (24) for receiving light pulses from a lidar transmitting unit (18); and

a plurality of routing channels (32) for transporting signals from the sensor elements to an edge area (R) of the lidar receiving unit, wherein

In each case a plurality of sensor elements are arranged in a macro cell (26, 26 ') which is assigned to a transmission element (22) of the lidar transmission unit;

several macro cells each form a macro cell cluster (30) and several macro cell clusters are arranged in several rows (Zi, Z ₂ , Z ₃ ); and

the routing channels cross the multiple lines between adjacent macro cell clusters of a line and are designed to transport the signals in a direction orthogonal to the lines.

2. Lidar receiving unit (16) according to claim 1, wherein

in each case two macro cells form a macro cell cluster (30); and

the two macro cells of the macro cell cluster are preferably arranged parallel to the rows (Zi, Z2, Z ₃ ).

3. Lidar receiving unit (16) according to one of the preceding claims, wherein the macro cell clusters (30) of a first row (Zi, Z2, Z3) compared to the macro cell clusters of a second row, which is adjacent to the first row, are arranged offset.

4. Lidar receiving unit (16) according to one of the preceding claims, wherein the routing channels (32) in channel sections (34) between the lines (Zi, Z2, Z ₃ ) run parallel to the lines.

5. Lidar receiving unit (16) according to one of the preceding claims, wherein a distance (A ₃ ) between adjacent macro cell clusters (30) of a Zei le (Zi, Z2, Z ₃ ) is greater than a distance (A ₄ ) between neighboring macrocell clusters in neighboring rows; and or preprocessing elements for reading out the sensor elements (24) are arranged between adjacent rows (Zi, Z2, Z3), the preprocessing elements preferably comprising a transistor.

6. Lidar receiving unit (16) according to one of the preceding claims, wherein an integer multiple of a diameter (Ds) of the sensor elements (24) is different from a distance (DA) between centers of the zugeord Neten transmitting elements (22) of the lidar transmitting unit ( 18).

7. Lidar receiving unit (16) according to any one of the preceding claims, wherein between macro cells (26, 26 ') of a macro cell cluster (30) Sensorelemen te (24) are arranged with reduced sensitivity.

8. Lidar receiving unit (16) according to any one of the preceding claims, with evaluation electronics (38) for reading out the sensor elements (24) line by line.

9. Lidar receiving unit (16) according to one of the preceding claims, wherein a macro cell cluster (30) comprises between 14 and 34 sensor elements (24).

10. Lidar measuring device (10) for detecting an object (12) in the surroundings of a vehicle (14), with:

a lidar receiving unit (16) according to one of the preceding claims; a lidar transmission unit (18) with a plurality of transmission elements (22) for emitting light pulses; and

a control unit (20) for controlling the lidar transmission unit and for evaluating the signals from the sensor elements (24) in order to detect the object.