METHOD FOR IMPROVED NEAR AND FAR DETECTION OF A LIDAR RECEIVING UNIT

Description

[0001] The invention relates to a method for improved near and long-range detection of a LIDAR receiving unit for motor vehicles.

[0002] Such LIDAR receiver units are known, for example, for LIDAR measuring systems according to WO 2017 081 294. This LIDAR measuring system comprises a LIDAR transmitter unit and a LIDAR receiver unit. Emitter elements of the LIDAR transmitter unit emit light pulses that pass through a transmitter optics and are reflected by an object. A reflected light pulse is focused via a receiver optics onto sensor elements of the receiver unit so that it can be detected. Based on the propagation time of the light pulse, the distance of the object from the LIDAR measuring system can be determined. Due to various effects, several laser pulses emitted consecutively by the same emitter element can strike at different locations on the receiver unit.This is the case, for example, when switching from a near-field measurement, in which the object is a short distance from the LIDAR measuring system, to a far-field measurement, in which the object is a greater distance from the LIDAR measuring system. Ultimately, this is due to the spatial structure of such a LIDAR measuring system with a receiving unit and transmitting unit in the focal plane array configuration, i.e. the arrangement of the emitter elements and the sensor elements in one plane and an arrangement at the focal point of a respective optics. In the focal plane array configuration, no components are avoided that introduce mobility into the LIDAR measuring system or its components. The spatial displacement of the incoming laser pulse on the receiving unit can impair the detection of the laser light. US 2010 / 0051836 A1 discloses a device for creating a depth image.US 2017 / 0176575 A1 describes a method for measuring the distance to an object.

[0003] It is the object of the present invention to provide a method in which the near and far detection of objects in a LIDAR receiving unit and a LIDAR measuring system is improved.

[0004] The problem is solved by a method according to patent claim 1.

[0005] The method is particularly suitable for a LIDAR receiver unit as described below. The LIDAR receiver unit is typically part of a LIDAR measurement system. The LIDAR measurement system is particularly suitable for a motor vehicle. Ideally, several similar LIDAR measurement systems are installed on a motor vehicle to monitor the entire surroundings of the vehicle.

[0006] The LIDAR measurement system includes, among other components, a LIDAR transmitter unit, a transmitter optics, a LIDAR receiver unit, and a receiver optics. Furthermore, the LIDAR measurement system is advantageously equipped with electronics that, for example, enables an evaluation unit for evaluating the acquired measurement data and can communicate with other systems of a motor vehicle for data transmission. In particular, the LIDAR measurement system has exactly two units: one for the sensor elements and one for the emitter elements.

[0007] According to the invention, the transmitting unit has a plurality of emitter elements for emitting laser pulses, while the receiving unit has a plurality of sensor elements for detecting the laser pulses. The emitter elements are advantageously designed as vertical cavity surface emitting lasers (VCSELs), whereas the sensor elements are preferably designed as single photon avalanche diodes (SPADs).

[0008] The sensor elements typically have a smaller surface area than an emitter element and its laser pulse projected onto the receiver unit. Therefore, multiple sensor elements can be illuminated by a single laser pulse. Furthermore, the incoming laser light can strike different locations on the receiver unit due to various effects. This actual position is described as a shift relative to an optimal reference position, where the laser light strikes the receiver unit under optimal conditions and after being reflected from an object at a great distance. This shift can be sized to one or more sensor elements.

[0009] Therefore, the number of sensor elements on the receiving unit is advantageously greater than the number of emitter elements on the transmitting unit. In particular, several sensor elements are conceptually assigned to one emitter element, with each of the sensor elements potentially capable of receiving a laser pulse from the emitter element.

[0010] The sensor elements of the macrocells are advantageously all of the same type, meaning, for example, that only the same SPADs are used. The same is also advantageous for the emitter elements of the transmitter unit.

[0011] The emitter elements and the sensor elements are advantageously each arranged on a chip on the transmitting unit and the receiving unit, respectively, which are also called emitter chip and sensor chip. Such a chip essentially provides a flat surface. This plane, or the emitter elements and sensor elements arranged thereon, are then arranged on the LIDAR measuring system at a focal point of a respective optics. This arrangement in one plane and at the focal point is also referred to as a focal plane array configuration (FPA). It is particularly advantageous if all emitter elements are formed on the transmitting unit and all sensor elements on the receiving unit. According to the invention, the transmitting unit and the receiving unit are each arranged in a focal plane array configuration.

[0012] The LIDAR measurement system with transmitter and receiver units in FPA configuration is preferably designed to be static. In other words, the components are permanently installed, preventing any relative movement between the LIDAR measurement system and its components. This makes the LIDAR measurement system cost-effective, robust, and compact. In particular, the LIDAR measurement system is also mounted statically on a vehicle.

[0013] According to the invention, the sensor elements are organized into macrocells on the receiving unit. According to the invention, each macrocell has several sensor elements, in particular at least two sensor elements. Advantageously, there can also be many more sensor elements. The number of sensor elements is advantageously between five and forty.

[0014] According to the invention, the macrocells are each assigned to an emitter element of the transmitting unit. This assignment is essentially performed by the optics. An emitter element and a sensor element are each imaged onto a specific solid angle by the associated optics, so that the emitter element and the sensor element view this solid angle. The sensor element that views the same solid angle as an emitter element is assigned to it accordingly. Accordingly, a macrocell is assigned to an emitter element via its sensor elements.

[0015] The emitter elements on the transmitting unit preferably have a planar configuration. The emitter elements are preferably arranged in a matrix structure on the transmitting chip of the transmitting unit, for example, in a column-row format or in a hexagonal pattern. The macrocells are arranged correspondingly in the same spatial configuration on the receiving unit, so that a laser pulse emitted by an emitter element is imaged onto the corresponding macrocell.

[0016] The LIDAR measurement system preferably operates according to the scanning method. Accordingly, a measurement process is first performed for a selection of emitter element-sensor element pairs. The measurement process is then performed for another selection of emitter element-sensor element pairs. For example, a first measurement process is performed for a row or array of emitter elements and their associated sensor elements. The same measurement process is then performed for another row or array. This ensures that sensor elements adjacent to the originally assigned sensor elements are not affected by another measurement process.

[0017] The sensor elements of a macrocell are connected to at least one readout unit at the receiving unit. The readout unit can be implemented, for example, as a time-to-digital converter, also called a TDC. This reads the measured values ​​from the sensor elements and stores them in a memory element, which preferably displays a histogram. A measurement process is preferably carried out according to the TCSPC method (Time Correlated Single Photon Counting).

[0018] A measurement cycle essentially begins with the emission of a light pulse by an emitter element of the transmitting unit and ends with the expiration of the measurement duration. This measurement duration corresponds to the time required for an emitted light pulse to reach the maximum measurement range and back. This light pulse passes through the transmitting optics, which directs the light pulse into the corresponding solid angle. If necessary, the light pulse is reflected by an object and then impinges on a sensor element via the receiving optics.

[0019] For example, the time of arrival of the light pulse is written as a digital value into the histogram of the storage element. Each detected photon is recorded in this histogram. This measurement cycle can be run once or multiple times for a measurement, depending on the configuration of the measurement system and the transmitting and receiving unit. If multiple runs are performed, the described procedure is executed accordingly. In particular, in a measurement process using the TCSPC method, a measurement cycle is performed multiple times, for example, 200 times.

[0020] Using the time-of-flight method, i.e., the travel time of the light pulse, the evaluation unit can determine the distance to the object from the measured values. The measurement distance is ideally around 300 meters, which corresponds to an approximate travel time of the laser pulse of about two microseconds.

[0021] One or more readout elements can be formed on a macrocell. The sensor elements are accordingly connected to the readout element or readout elements. Each sensor element is connected to at least one readout element. It is particularly advantageous for a sensor element to be connected to only a single readout element. Connected means that the readout element can read out a detection from a sensor element and store the detection information in a memory element. A sensor element can only be read out by the readout element when it is active. It is particularly advantageous for the readout element to be connected to all sensor elements of the macrocell. However, this does not preclude the readout element from being connected to further sensor elements of other macrocells, for example sensor elements of macrocells that are inactive during the measuring cycle.

[0022] A macrocell is a construct that is normally not defined by its hardware configuration, but rather by its control and evaluation logic. However, the macrocell can be defined by a specific hardware configuration, i.e., the targeted arrangement and connection of sensor elements and readout elements. The macrocell or its sensor elements advantageously cover an area larger than the area of ​​the emitter element or the projection area of ​​the incoming laser light. This makes it possible to compensate for the aforementioned displacement caused by near- and far-field effects. This displacement results in particular from parallax error. With such a parallax error, the displacement depends on the distance of the object from the measuring system. The macrocell advantageously covers at least a multiple of the projection area of ​​the laser light or the area of ​​an emitter element.

[0023] The sensor elements can be activated and deactivated individually or in groups of several sensor elements. The first variant is particularly preferred. Grouped activation corresponds to the simultaneous activation or deactivation of a plurality of sensor elements, preferably a subgroup of a macrocell. Activation and deactivation in SPAD is achieved, for example, by increasing or decreasing the bias voltage. Deactivated elements cannot detect incoming photons, nor can they be read by the readout element. A photon striking an active sensor element can be read by the readout element.

[0024] The sensor element can be activated and deactivated directly or indirectly. In the former case, for example, a bias voltage is applied to a SPAD, making it active. To deactivate, the bias voltage is reduced below a threshold. With indirect activation or deactivation, the sensor element itself is always active—in the previous example, under bias voltage. Instead, a readout element is deactivated, or storage of the detected photons in a memory is deactivated or prevented.

[0025] During the measurement cycle, at least a portion of the sensor elements are activated at a first point in time. According to the invention, these sensor elements are all part of a macrocell. Accordingly, the activation of at least one sensor element of the macrocell also activates the macrocell. The first point in time is advantageously at the beginning of the measurement cycle, in particular before, simultaneously with, or after the emission of the light pulse by the emitter element.

[0026] When the sensor elements are activated, they can detect photons. Detection can occur, for example, when the emitted and reflected laser light hits the sensor element or when photons from the ambient radiation hit the sensor element. Each active sensor element increases the noise floor that is detected by the sensor elements. By activating only the illuminated sensor elements, the best signal-to-noise ratio can be achieved. However, as the measurement time increases, the position of the incoming laser light changes, meaning that the sensor elements only have a chance to detect the emitted laser light during a specific time period of the measurement cycle.

[0027] Accordingly, at a second time within a measurement cycle, which occurs after the first time, one or more sensor elements are activated and / or one or more sensor elements are deactivated. According to the invention, these are sensor elements of the active macrocell. This ensures that precisely those sensor elements that can detect reflected laser light are active. Furthermore, the inactive sensor elements do not contribute to an increase in the noise floor.

[0028] For example, during a measurement cycle, all sensor elements of the macrocell are activated. During a near-field measurement, the intensity of the reflected laser light is relatively high, so the incoming laser light can be easily detected despite the high noise floor. During the far-field measurement, i.e., at the second time point, some of the sensor elements are deactivated, so that the noise floor decreases and only those sensor elements that can detect the laser light are active.

[0029] In particular, one or more sensor elements can be activated at the second time. Alternatively, one or more sensor elements can be deactivated at the second time. In a further alternative, one or more sensor elements can be activated and one or more other sensor elements can be deactivated at the same time. At the same time, in addition to the identical time, this also includes a temporally close sequence of activation and deactivation of the sensor elements.

[0030] This method can be used in particular in the TCSPC, which carries out a large number of related measuring cycles, as well as in other methods that, for example, only require a single measuring cycle.

[0031] When one measurement cycle expires, the sensor elements and, accordingly, the macrocell are deactivated again. After the required number of measurement cycles, the resulting measurement data is evaluated by an evaluation unit. Objects and their distances are determined based on the travel time of the detected photons.

[0032] The evaluation unit can be designed as a standalone component or be an integrated part of the receiving unit.

[0033] According to the previous statements, one or more sensor elements can also be activated and / or one or more sensor elements can be deactivated at a third or further time point.

[0034] By selectively activating and deactivating sensor elements, an improvement in near and far detection for a LIDAR measuring system or a LIDAR receiving unit is achieved.

[0035] A typical detection range for such a LIDAR measuring system is, for example, 300 meters, with the corresponding pulse travel time to an object 300 meters away and back taking about two microseconds.

[0036] Advantageous variants of the method are explained below.

[0037] It is particularly advantageous if the time interval between the first time and the second time is between 50 and 500 nanoseconds, in particular 200 nanoseconds.

[0038] A time interval of 200 nanoseconds between the time points corresponds approximately to a travel time of 60 meters for the light pulse or a measurement distance of 30 meters. This represents a good ratio for optimizing near-field detection and also maintaining an optimal signal-to-noise ratio for longer measurement distances. A time interval of between 150 and 350 nanoseconds is particularly advantageous.

[0039] Depending on the hardware design of the measuring system, switching between two measuring ranges occurs preferably between 5% and 50% of the specified maximum measuring range.

[0040] According to the invention, with respect to each active macrocell, a potentially incoming laser light causes a displacement at the receiving unit over the duration of the measuring cycle, wherein the respective sensor elements of the macrocell form an active area and are activated and / or deactivated such that the active area follows this displacement.

[0041] As already mentioned, the shift results from the parallax effect. This ensures that at least those sensor elements that are supposedly illuminated by a reflected laser light are active.

[0042] In one example, the supposedly arriving laser spot moves from bottom to top across several rows of sensor elements at the receiving unit. In one variant, all sensor elements can then be active, with a lower, no longer illuminated half being deactivated at the second time. Alternatively, row by row is deactivated successively from bottom to top. It is also conceivable for two rows to be active at any one time, so that successively a row above the active rows is activated and a bottom row of the active rows is deactivated.

[0043] A sensor element does not itself follow the supposed incoming laser spot, but the sensor elements that are active are those at which the laser light would arrive.

[0044] In particular, these active sensor elements form an active region. This active region follows the displacement of the potentially incoming laser light. According to the invention, this active region of each active macrocell is formed by sensor elements of this macrocell.

[0045] A further method for improved near and far detection of a LIDAR receiver unit is proposed according to claim 3. This method also solves the initially stated problem. Advantageous embodiments are described in the dependent claims.

[0046] The basic structure of the LIDAR receiver unit for applying the method is essentially identical to that explained above. The previous explanations can therefore be applied analogously to the method explained below. Differences between the measurement systems or receiver units are explained in more detail below.

[0047] Here, too, the receiver and transmitter units are designed in a focal plane array configuration, with their planes aligned at the focal point of the corresponding optics. Furthermore, a macrocell is assigned to an emitter element, or an emitter element images onto a macrocell of the receiver unit through the corresponding optics.

[0048] The receiving unit has a plurality of sensor elements. The sensor elements are assigned to macrocells, wherein each macrocell has at least two sensor elements. The macrocell is further subdivided into a plurality of readout cells, at least one first readout cell and one second readout cell. The first readout cell has at least one first sensor element and one first readout element, wherein the at least one sensor element is connected to the first readout element. In addition, the second readout cell has at least one second sensor element and one second readout element, wherein the at least one second sensor element is connected to the second readout element. Advantageously, each readout cell has a plurality of sensor elements, wherein the sum of the sensor elements of the readout cell corresponds to the number of sensor elements of the higher-level macrocell.

[0049] If a readout cell contains multiple sensor elements, then preferably each sensor element is connected to a readout element. If necessary, all sensor elements of a readout cell can be connected to the same readout element. If a readout cell contains multiple sensor elements and multiple readout elements, the first sensor elements can each be connected to their own first readout element or in groups with the first readout elements. The same applies to the second readout cell and its second sensor elements and its second readout elements. A sensor element is preferably connected to a readout element, whereby a readout element can also be connected to multiple sensor elements. A readout element can also be connected to multiple sensor elements of different macrocells.

[0050] During the measurement cycle, at least a portion of the readout cells are activated at a first point in time. This can be, for example, a single readout cell, multiple readout cells, if present, or all readout cells of the macrocell. A readout cell is active when a sensor element, the associated readout element, and a memory cell are all active together. This means that when an incoming photon, e.g., from a laser pulse, is detected by the sensor element, the readout element is read out, and the data is stored within the memory element. A readout cell can be controlled, for example, by activating and deactivating the sensor element, as well as by activating and deactivating the readout unit.

[0051] At a second point in time within the measurement cycle, which occurs after the first point in time, a readout cell is activated and / or a readout cell is deactivated. Accordingly, a readout cell can be activated. Alternatively, a readout cell can be deactivated. In a further alternative, a readout cell is activated and another readout cell is deactivated at the same time. Any additional readout cells present remain in their current state.

[0052] The times mentioned here and also the measuring cycle essentially correspond to the above statements regarding the method according to claim 1. The above statements are accordingly applicable.

[0053] For example, a first readout cell and a second readout cell are activated at the first time, while at the second time the first readout cell remains active and the second readout cell is deactivated. This achieves a lower noise floor, which enables better evaluation of the measurement data.

[0054] Only one sensor element or multiple sensor elements can be active per readout cell. However, it is advantageous to have only a portion of the sensor elements in the readout cell active, rather than all of them. At the end of the measurement cycle, the readout unit advantageously fills the memory element, allowing the evaluation unit to subsequently determine the distance to the detected object according to the time-of-flight principle.

[0055] Advantageous embodiments of the method are described below.

[0056] Advantageously, the time interval between the first time point and the second time point is between 150 nanoseconds and 500 nanoseconds, in particular 200 nanoseconds.

[0057] A time interval of 200 nanoseconds corresponds approximately to a travel time of 60 meters for the light pulse. This represents a good ratio for optimal near-field detection and also for maintaining an optimal signal-to-noise ratio at greater distances from the object. A time interval between 150 and 350 nanoseconds is particularly advantageous.

[0058] Depending on the hardware design of the measuring system, switching between two measuring ranges occurs preferably between 5% and 50% of the specified maximum measuring range.

[0059] According to the invention, a potentially incoming laser light causes a displacement at the receiving unit over the duration of the measuring cycle, wherein the readout cells form an active region and are activated and / or deactivated in such a way that the active region follows this displacement.

[0060] As already mentioned, the shift results from the parallax effect. This ensures that at least those readout cells that are supposedly illuminated by a reflected laser light are active.

[0061] In one example, the supposedly arriving laser spot moves from bottom to top across several rows of readout cells at the receiving unit. In one variant, all readout cells can then be active, with a lower, no longer illuminated half being deactivated at the second time. Alternatively, row by row is deactivated successively from bottom to top. It is also conceivable for two rows to be active at any one time, so that successively a row above the active rows is activated and a bottom row of the active rows is deactivated.

[0062] A readout cell does not itself follow the supposed incoming laser spot, but the readout cells that are active are those at which the laser light would arrive.

[0063] In particular, these active readout cells form an active region. This active region follows the displacement of the potentially incoming laser light. According to the invention, this active region of each readout cell is formed by the readout cells of the respective macrocell.

[0064] In addition to the first readout cell and the second readout cell, further cells can also be configured that are deactivated and / or activated in a respective subsequent time period. These can, for example, be deactivated one after the other.

[0065] The problem is also solved by a LIDAR measuring system according to patent claim 5.

[0066] This LIDAR measuring system is suitable for one of the methods according to claims 1 to 4 or for at least one of the methods explained above. Structural designs of such a LIDAR measuring system can be found in the above explanations.

[0067] The measuring system includes, among other things, a receiving unit with sensor elements. The measuring system also advantageously includes a transmitting unit with emitter elements. A control element of the measuring system then controls the emitter elements and the sensor elements.

[0068] In particular, the control element ensures that the individual elements are activated and deactivated at the correct times, so that the measurement process runs synchronously. This is particularly important when a large number of measurement cycles are involved within a measurement process. Such a control element is implemented, for example, by a timing generator, which provides sufficiently accurate time measurement and precisely specifies the times for switching the elements. This ensures that the measurement process remains synchronized even across a large number of measurement cycles, ensuring optimal measurement results. This is particularly advantageous when using the TCSPC method.

[0069] The control element can specify the switching times of the emitter element and sensor elements. Alternatively, the control element can also specify the switching times for readout cells and other elements of the measurement system. In particular, the control element provides a reference time for the histogram.

[0070] The procedures are explained below using several examples. They show: Fig. 1: Schematic representation of a LIDAR measuring system; Fig. 2a, 2b: Schematic representation of a section of a LIDAR receiving unit with sensor elements; Fig. 3: Another variant of a LIDAR receiving unit in a different configuration; Fig. 4: Flow chart of a measuring cycle.

[0071] In the Fig. 1 A schematic representation of a LIDAR measuring system 10 is shown. The LIDAR measuring system 10 has a transmitting unit 12 and a transmitting optics 14, as well as a receiving unit 16 and a receiving optics 18. The transmitting unit 12 and the receiving unit 16 are designed in a focal plane array configuration. This means that the emitter elements 20 of the transmitting unit 12 and the sensor elements 22 of the receiving unit 16 are formed on a flat surface. This flat surface can be formed, for example, by a chip. Furthermore, the units 12 and 16 are arranged in a focal plane or a focal point of the transmitting optics 14 and the receiving optics 16.

[0072] The emitter elements 20 are preferably designed as vertical cavity surface emitting lasers (VCSELs). The sensor elements 22 are advantageously designed as single photon avalanche diodes (SPADs). The advantage of this configuration is that no moving parts are required.

[0073] The transmitting unit 12 and the receiving unit 16 have a plurality of emitter elements 20 and a plurality of sensor elements 22, respectively, which are assigned a respective solid angle by the optics 14 and 18. The transmitting unit and the receiving unit 22 each have emitter elements 20 and sensor elements 22 assigned to one another. Figur 1 Two emitter elements 20 and two sensor elements 22 are shown as examples and clearly. In the exemplary illustration, the transmitting unit 12 has only two emitter elements 20a and 20b and the receiving unit 16 has only two sensor elements 22a and 22b. The number of sensor elements 22 and emitter elements 20 is normally considerably larger in a measuring system 10. Fig. 1 The aim is to explain the parallax effect.

[0074] During a measurement cycle, an emitter element 22 emits laser light, preferably in the form of a laser pulse, which is radiated into a first solid angle 24 via a transmitter optics 14. The laser pulse is then reflected by any object and projected onto the receiver unit 16 via the receiver optics 18. A sensor element 22 also observes a respective solid angle 26 via the optics.

[0075] Exaggerated angles and section ratios are shown here as examples. The first solid angle 24a, into which the emitter element 20a emits its laser light, has a divergence of 10 degrees and is inclined upwards by approximately 20 degrees. The first solid angle 24b, into which the emitter element 20b emits its laser light, has no inclination, but also a divergence of 10 degrees. The same applies to the two sensor elements 22a and 22b, which, via the receiving optics 18, form a second solid angle 26a with the sensor element 22a, which has an upward divergence of approximately 20 degrees with a divergence of 10 degrees, and the sensor element 22b has the solid angle 26b with an inclination of 0 degrees and a divergence of 10 degrees.

[0076] Due to the exaggerated portrayal of the Fig. 1 It is immediately apparent that there is not always an overlap between the solid angles 24 and 26. Nevertheless, the emitter element 20a is assigned to the sensor element 22a and the emitter element 20b to the sensor element 22b. These solid angles essentially overlap completely at large distances. In the close range, which is Fig. 1 As shown, only a slight overlap is shown, and this only occurs in area IV. In this close range, there are various overlap areas between the different solid angles. In a first area I, there is no overlap of the solid angles. In area II, an overlap between the first solid angle 24b and the second solid angle 26a occurs for the first time. If an object is at this distance from the LIDAR measuring system 10, a reflected laser pulse can be detected by the receiving unit.

[0077] The same applies to area III, where there is still an overlap of the two solid angles. The overlap increases in area II and decreases again in area III, being maximum at point 2 and decreasing again towards point 3. An overlap of the solid angles 24b and 26b begins at point 3 in area IV and increases to a maximum overlap at a great distance. In this exaggerated embodiment, the best detection of an object is achieved towards point 2 and the end of area IV, i.e. at a great distance. It can also be seen that the laser light arriving at the receiving unit 16, which is reflected by an object, moves along the sensor elements 22 as the object approaches. The light projected onto the receiving unit 16 always moves towards the transmitter unit 12 as the object approaches. In this case, from the sensor element 22b to the sensor element 22a.In this sense, the distant object A is detected by the sensor element 22b, whereas the object B in the near field is detected by the sensor element 22a.

[0078] In a specific embodiment of such a measuring system 10, considerably more sensor elements 22 are arranged on the receiving unit 16 so that gap-free detection can take place over all areas.

[0079] An emitted and reflected laser pulse is thus detected by a sensor element 22, which is read by a readout element 28, and the resulting measurement data is evaluated by an evaluation unit 30. The time-of-flight principle is applied. The readout unit 28 usually temporarily stores the measurement data in a memory element, from which the evaluation unit 30 receives the measurement data. The evaluated data can then be forwarded to other components of the vehicle.

[0080] In the Fig. 2a A transmitting unit 12 and a receiving unit 16 are shown. These are arranged one above the other for example, but can also be arranged side by side. The illustration shows only a small section of the transmitting unit 12 and the receiving unit 16, as well as their emitter elements and sensor elements. The transmitting unit 12 has the emitter elements 20a and 20b, and the receiving unit 16 has the sensor elements 22a and 22b. The sensor elements 22 are arranged in macrocells 32, which are indicated by the boxes. The logical division for the evaluation unit 30 also corresponds, for example, to the hardware division into macrocells 32.

[0081] The receiving unit 14 has more sensor elements 22 than the transmitting unit 12 has emitter elements 20. This is due, on the one hand, to the parallax effect and, on the other hand, to the imaging behavior of the emitter elements 20 on the receiving unit 16. In particular, the area illuminated by an emitter element 20 is larger than the area of ​​a sensor element 22. A macrocell 32 is defined by the sensor elements 22 arranged in the potential imaging area of ​​the emitter element. The imaging area of ​​the emitter element 20 on the receiving unit 16 is larger than the surface of the emitter element 20 itself. This is due to the effects already explained.

[0082] In this case, each macrocell 32 has its own sensor elements 22a and 22b. Macrocell 32a has the sensor elements 22a, and macrocell 32b has the sensor elements 22b. However, sensor elements can also be assigned to multiple macrocells. This means that macrocells can overlap. A circle 34 is shown as an example, representing a theoretical imaging point of an emitter element 20a and 20b on the associated macrocell 32a and 32b upon reflection from an object at a great distance. A dashed circle 36 is also shown as an example, illustrating imaging behavior in the near field. As already mentioned, the incoming laser light at the receiving unit 14 travels from the far field, starting from the theoretical far-field position, toward the transmitting element 12, since the transmitting unit 12 is arranged above the receiving unit, i.e., upwards.

[0083] The sensor elements in the Fig. 2a Sensor elements 22 are shown partially filled in black, meaning active, or hatched, meaning inactive. Each of the sensor elements 22 can be individually activated and deactivated. In a SPAD, this can be achieved by raising or lowering a bias voltage. The possibility of individual activation and deactivation allows for the precise activation of those sensor elements that are expected to be hit by laser light. This allows, for example, the compensation of imaging errors in the optics.

[0084] The relevant macrocells 32 are activated at the start of a measuring cycle. At the start of the measuring cycle, a subset of the sensor elements is activated, for example. If necessary, all sensor elements of the active macrocell 32 can also be active. A macrocell 32 is active when at least one associated sensor element is active and the measurement data can be read out by a readout element 28. The readout element 28 is in the Fig. 2a und 2b and connected to all sensor elements 22 of the respective macrocell 32.

[0085] To improve near- and far-field detection, the sensor elements 22 are activated and / or deactivated at different times during the measurement cycle, in this case the latter. The sensor elements 22 of a macrocell 32 can thus be divided into first sensor elements 22x and second sensor elements 22y. Third or even additional sensor elements can also be provided if necessary.

[0086] At a first point in time within a measuring cycle, preferably at the beginning of the measuring cycle or shortly thereafter, the first sensor elements 22x and the second sensor elements 22y of the macrocells 32 are activated. Fig. 2a This is indicated by the fill. The active sensor elements 22 are completely filled. These active sensor elements 22 experience the best illumination by reflected laser light. The other partially illuminated sensor elements are deactivated and therefore shown hatched. This allows an optimal signal-to-noise ratio to be achieved, since only illuminated sensor elements can determine meaningful measured values. Unilluminated or poorly illuminated sensor elements 22 primarily detect ambient radiation, i.e., a noise source that degrades the signal-to-noise ratio.

[0087] By activating the first and second sensor elements 22x and 22y, objects can be detected in a close range. Due to the proximity of the object to the LIDAR measurement system 10, a high intensity is also present, which can easily compensate for any increase in the noise floor caused by the use of multiple sensor elements. As the measurement cycle time increases, the first time period ends, after which a second time period begins at the second time point.

[0088] At the second time point during the measurement cycle, the first sensor elements 22x remain active, whereas the second sensor elements 22y are deactivated. This can occur, for example, after a time of approximately 200 nanoseconds. This corresponds to a distance of approximately 30 meters from an object, whereby from this distance, a sufficient long-range overlap of the solid angles 24 and 26 can already be assumed. In other words, the incoming laser pulse moves from the dashed circle 36 toward the circle 34 as the distance from the object increases.

[0089] By deactivating the second sensor elements 22y, which are no longer illuminated, the background noise can be significantly reduced. This also compensates for the lower intensity of the backscattered laser light.

[0090] During the first time period, sensor elements 22x and sensor elements 22y contribute to the measurement, whereas during the second time period, only sensor elements 22x contribute to the measurement. Accordingly, during the first time period, sensor elements 22x and 22y form the active region. During the second time period, the active region then comprises only sensor elements 22x. If additional, for example, third or fourth, sensor elements 22 are used, a correspondingly larger number of points in time is required at which the sensor elements are successively deactivated.

[0091] The sensor elements 22 that are neither sensor elements 22x nor 22y are deactivated, for example, due to calibration. This calibration detects, for example, static imaging errors, such as those caused by tolerances or inaccuracies in the optics used. Such sensor elements can remain inactive throughout the entire measurement cycle.

[0092] In the Fig. 1 A control element 29 is also shown. This control unit coordinates the timing of the measurement cycles and the measurement process. It activates and deactivates the emitter elements 20 and the sensor elements 22 at the correct times. Such a control element 29 is also called a timing generator.

[0093] In the Fig. 4 A corresponding sequence of such a measuring cycle is shown. This is plotted along a time axis 38. The measuring cycle starts with step 40. Simultaneously or shortly after the start of the measuring cycle, the first and second sensor elements are activated at the first time in step 42. After the expiration of the first time period 38a, the second sensor elements are deactivated at the second time in step 44. Upon expiration of the second time period 38b, the measuring cycle 48 ends with the deactivation of the remaining first sensor elements in step 46. Finally, all sensor elements are deactivated in step 46. The deactivation of the second sensor elements 22y from step 44 is shown in the Fig. 2b shown. It can be seen that only the first sensor elements 22x remain active and the sensor elements 22y are deactivated.

[0094] Such a measurement cycle can, for example, be performed only once during a measurement process. In a measurement process according to the TCSPC method, such a measurement cycle is repeated multiple times.

[0095] Another variant is in the Fig. 3 shown. The configuration of the LIDAR measuring system 10 is essentially the same as the configuration of the LIDAR measuring system 10 of the previous embodiment. The above explanations apply accordingly. The differences are explained.

[0096] The macrocells 32 are divided into readout cells 50. A macrocell 32 comprises at least one first readout cell 50a and one readout cell 50b. Each readout cell 50 has its own readout element 28, which is connected to the sensor elements 23 of the readout cell 50. Accordingly, the first sensor elements 23a of the first readout cell 50a are connected to the first readout element 28a, and the second sensor elements 23b of the second readout cell 50b are connected to the second readout element 28b.

[0097] In this embodiment, one readout element 28 is formed per readout cell 50. However, according to other embodiments, additional readout elements 28a and 28b may also be formed in the respective readout cells 50.

[0098] In principle, a readout element 28 of a first readout cell 50a can also be connected to further first sensor elements 23a of other first readout cells 50a. The same applies to the second sensor elements 23b of the second readout cells 50b.

[0099] The timing of the procedure essentially corresponds to that of the Fig. 2a, 2b and 4 and the associated explanations. However, it is not the sensor elements 23 as such that are activated and deactivated, but rather the readout cells 50a and 50b. Accordingly, the readout cells 50a and 50b are active in the first time period, whereas the readout cells 50b are deactivated in the second time period.

[0100] However, this does not necessarily activate or deactivate the sensor elements. The readout cells can also be activated or deactivated. This can be done, for example, by activating or deactivating the readout elements themselves or by specifying time windows within which the readout elements are allowed to write to the memory. This means that a corresponding readout element only reads the measurement data from the sensor elements within the first and / or second time period and stores it in the memory element.

[0101] After completion of a measurement process, the evaluation unit 30 calculates the distance of the object using the first and second sensor elements for the near field and, for the far field, using only the measured values ​​of the first sensor elements 23a of the first readout cell 50a. This also allows for an improved signal-to-noise ratio.

[0102] The Fig. 4 can be transferred in essentially the same way. Only in steps 42, 44, and 46, the activation or deactivation of the sensor element needs to be replaced by the activation or deactivation of the readout cell. Bezugszeichen

[0103] 1 position 2 position 3 position 10 LIDAR measuring system 12 Transmitter unit 14 Transmitter optics 16 Receiver unit 18 Receiver optics 20,a,b Emitter element, VCEL 22,a,b Sensor element, SPAD 23,a,b Sensor element, SPAD 22x First sensor elements 22y Second sensor elements 24 First solid angle 26 Second solid angle 28 Readout element 28a First readout element 28b Second readout element 29 Control element 30 Evaluation unit 32 Macrocell 32a First macrocell 32b Second macrocell 34 Circle 36 Dashed circle 38 Time axis 38a First time period 38b Second time period 40 Step, start measurement cycle 42 Step, activate the first and second sensor elements 44 Step, deactivate the second sensor elements 46 Step, Deactivation of the first sensor elements 48Step, end of measuring cycle 50Readout cell 50aFirst readout cell 50bSecond readout cell IFirst area IISecond area IIIThird area IVFourth area AAbject BObject

Claims

1. Method for improved near and far detection of a LIDAR receiver unit (16), - wherein several emitter elements (20) of a transmitter unit (12) transmit laser pulses, - wherein the receiver unit (16) has several sensor elements (22), - wherein the sensor elements (22) are organized in macrocells (32), - wherein each macrocell (32) has several sensor elements (22), - whereby the sensor elements (22) of the macrocells (32) can be activated and deactivated directly or indirectly, - wherein at a first point in time within a respective measuring cycle with respect to a laser pulse of an emitter element, at least a partial number of the sensor elements (22) of a corresponding macrocell (32) and thus the macrocell (32) is activated - wherein at a second point in time within the measuring cycle, which is after the first point in time, one or several sensor elements of each active macrocell (32) are activated and / or one or several sensor elements of the active macrocell (32) are deactivated characterized in that the transmitter unit (22) and the receiver unit (16) are each arranged in a focal plane array configuration, wherein the macrocells (32) are each assigned to an emitter element (20) of a transmitter unit (12), so that all sensor elements (22) of a macrocell (32) are assigned to the same emitter element (20), wherein, with respect to each active macrocell (32), a potentially incoming laser light performs a displacement at the receiving unit (16) over the duration of the respective measuring cycle, wherein the respective sensor elements (22) of each active macrocell (32) form an active area and are activated and / or deactivated in such a way that the respective active area of the respective macrocell (32) follows this displacement.

2. Method according to claim 1, characterized in that the time interval between the first point in time and the second point in time is between 50 and 500 nanoseconds long, in particular 200 nanoseconds.

3. Method for improved near and far detection on a LIDAR receiver unit (10), - wherein several emitter elements (20) of an transmitter unit (12) transmit laser pulses, - wherein the receiver unit (16) has a plurality of sensor elements (22), - wherein the sensor elements (22) are organized in macrocells (32), - wherein each macrocell (32) has several sensor elements (22), - wherein each macrocell (32) has at least a first readout cell (50a) and a second readout cell (50b), - wherein the first readout cell (50a) has at least a first sensor element (22a) which is connected to a first readout element (28a), and - wherein the second readout cell (50b) has at least one second sensor element (22b) which is connected to a second readout element (28b), - wherein at a first point in time within a respective measuring cycle at each active macrocell (32), at least a partial number of the readout cells is activated, - wherein at a second point in time within the measurement cycle, which is after the first point in time, a readout cell is activated and / or a readout cell is deactivated, - wherein the transmitter unit (22) and the receiver unit (16) are arranged in a focal plane array configuration, - wherein the macrocells (32) are each assigned to an emitter element (20) of a transmitter unit (12), so that all sensor elements (22) of a macrocell (32) are assigned to the same emitter element (20), wherein, with respect to each active macrocell (32), a potentially incoming laser light performs a displacement at the receiving unit (16) over the duration of the respective measuring cycle, wherein the respective readout cells (50) of each active macrocell (32) form a respective active area and are activated and / or deactivated in such a way that the active area of the respective macrocell (32) follows this displacement.

4. Method according to claim 3, characterized in that the time interval between the first point in time and the second point in time is between 50 and 500 nanoseconds long, in particular 200 nanoseconds.

5. LIDAR measuring system (10), comprising a LIDAR transmitting unit (12) with emitter elements (20) and a LIDAR receiving unit (14) with sensor elements (22), as well as a control element (29) for controlling the temporally correct activation and deactivation of sensor elements (22) or readout cells (50) during a measuring process, wherein the LIDAR measuring system (10) is configured for carrying out the method according to claims 1 to 4.