READER AND LIDAR MEASURING DEVICE

Description

[0001] The present invention relates to a readout device for determining a signal propagation time of a light pulse between a lidar transmitter unit and a lidar receiver unit of a lidar measuring device in a focal plane array arrangement. Furthermore, the present invention relates to a method for determining a signal propagation time and a lidar measuring device.

[0002] Modern vehicles (cars, vans, trucks, motorcycles, driverless transport systems, etc.) comprise a multitude of systems that provide information to a driver or operator and / or control individual vehicle functions partially or fully automatically. Sensors record the vehicle's surroundings and, if applicable, other road users. Based on the recorded data, a model of the vehicle's environment can be created and changes in this environment can be responded to. Due to 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 becoming ever greater.The development of increasingly precise sensors makes it possible to detect the environment and control individual functions of the vehicle completely or partially without intervention by the driver.

[0003] An important sensor principle for environmental detection is LIDAR (light detection and ranging) technology. A LIDAR sensor is based on the emission of light pulses and the detection of the reflected light. Using a time-of-flight measurement, the distance to the location of the reflection can be calculated. By evaluating the received reflections, a target can be detected. With regard to the technical implementation of the corresponding sensor, a distinction is made between scanning systems, which usually 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 arrays).

[0004] In this context, WO 2017 / 081294 A1 describes a method and a device for optical distance measurement. It discloses the use of a transmission matrix for transmitting measurement pulses and a reception matrix for receiving the measurement pulses. When the measurement pulses are transmitted, subsets of the transmission elements of the transmission matrix are activated.

[0005] One challenge in detecting objects using such a lidar measuring device in a focal plane array configuration is the limited transmission power. The power emitted by the transmitting elements of the lidar transmitter unit is limited due to the limited chip size and the chip's heating. Increasing the power is associated with increased manufacturing effort and high costs. This results in a limited range and a reduction in the reliability of object detection, especially in the long-range range of the lidar sensor.

[0006] DE 10 2017 223 102 A1 discloses a multipulse lidar system for multidimensional object detection. WO 2019 / 115 148 A1 describes a lidar receiver unit (12) in a focal plane array arrangement comprising a plurality of sensor elements (26) arranged in macrocells (44).

[0007] Based on this, the present invention aims to provide an approach for detecting objects in the field of view of a lidar measuring device. In particular, the range and / or reliability of object detection should be increased while maintaining the same manufacturing effort. The aim is to create a cost-effective and energy-efficient lidar sensor.

[0008] To achieve this object, the invention relates in a first aspect to a readout device for determining a signal propagation time of a light pulse between a lidar transmitting unit and a lidar receiving unit of a lidar measuring device in a focal plane array arrangement according to claim 1.

[0009] In a further aspect, the present invention relates to a lidar measuring device in a focal plane array arrangement for detecting objects in an environment of a vehicle, comprising: a lidar transmitting unit with a plurality of transmitting elements for emitting light pulses and a lidar receiving unit with a plurality of sensor elements for receiving the light pulses, wherein the transmitting elements and the sensor elements are arranged in rows that run parallel to a horizontal plane of the vehicle; and a readout device according to the invention.

[0010] Further aspects of the invention relate to a method designed according to the adaptation device and a computer program product with program code for carrying out the steps of the method when the program code is executed on a computer, as well as a storage medium on which a computer program is stored which, when executed on a computer, effects execution of the method described herein.

[0011] Preferred embodiments of the invention are described in the dependent claims. It is understood that the features mentioned above and those to be explained below can be used not only in the respective combinations specified, but also in other combinations or alone, without departing from the scope of the present invention. In particular, the readout device, the lidar measuring device, as well as the method and the computer program product can be designed according to the embodiments described for the readout device and the lidar measuring device in the dependent claims.

[0012] According to the invention, when combining the detections of the individual sensor elements of a lidar receiving unit, several of which are assigned to a transmitting element of the lidar transmitting unit in a macrocell, a weighting is performed. The weighting is based on a signal-to-noise ratio of the individual sensor element. In particular, sensor elements with a high signal-to-noise ratio are weighted more heavily than other sensor elements. The weighting is selected depending on how much power the individual sensor element receives. The inventive approach corresponds to a maximum-ratio-combining approach, as is known from communications technology for reception with multiple antennas. The maximum-ratio-combining method is applied to a lidar system.The weighting of the signals from the individual sensor elements can be selected, for example, proportional to a root mean square (RMS) of the signal level and / or inversely proportional to a noise component of the signal. The weighting factors are determined individually for each receive path, i.e., for each sensor element.

[0013] Compared to previous approaches, in which all sensor elements assigned to a transmitting element are considered equally, measurement accuracy can be improved. This results in a greater range and greater reliability in object detection. Compared to approaches in which individual sensor elements are completely switched off, the selection of weighting parameters depending on the signal-to-noise ratio of the respective sensor element results in improved detection. Even reception paths with poor reception are used to improve the overall signal. Methods in which active sensor elements are selected may not be optimal in strong ambient light. According to the invention, improved object detection is achieved.

[0014] In one embodiment of the invention, the weighting unit is designed to determine the individual weighting parameters based on a calibration measurement of a spot position on the macrocell, with sensor elements receiving a lower weighting with increasing distance from a center point of the spot position. Sensor elements outside the spot position preferably receive a weighting of 0. A calibration measurement corresponds in particular to a calibration during commissioning and / or during manufacture of the lidar measuring device. Due to manufacturing tolerances and material deviations, a spot position (an imaging position of a transmitting element) on the lidar receiving unit or on the multiple sensor elements of a macrocell varies. This circumstance is usually taken into account by designing the macrocell larger than the spot position.In a calibration survey, a spot position can be measured and the individual weighting parameters can be determined based on this calibration. The individual weighting parameters therefore no longer change during runtime, but are predefined for a lidar measuring device. This results in an efficiently implementable method for determining the individual weighting parameters.

[0015] In a further embodiment of the invention, the weighting unit is designed to determine the individual weighting parameters based on a sequential individual calibration readout of the sensor elements with unchanged signal propagation time, wherein sensor elements with a higher number of detections in the calibration readout receive a higher weighting. Sensor elements with a number of detections in the calibration readout below a threshold value preferably receive a weighting of 0. The calibration readout thus corresponds to activating individual sensor elements one after the other with a constant signal propagation time or spot position. For each sensor element, a separate check is carried out to determine which signal component can be received. This results in an efficiently implementable method for determining the individual weighting parameters before commissioning.

[0016] In a further embodiment of the invention, the weighting unit is designed to determine the individual weighting parameters based on an individual noise parameter of the sensor element, which describes a signal noise of the sensor element. Preferably, the weighting unit is designed to determine the individual noise parameter based on a previous time-of-flight measurement and / or based on a preceding ambient light measurement. The noise is determined separately for each sensor element. This makes it possible to compensate for manufacturing differences. For example, an ambient light measurement can be carried out at regular intervals, assuming that the ambient light is identical for all sensor elements. Depending on the signal of the individual sensor element, an individual influence of the ambient light on the sensor element can then be determined.This provides an efficient way to determine a noise component.

[0017] In a further embodiment of the invention, the weighting unit is configured to determine individual weighting parameters with integer weighting factors, wherein the summation unit is configured to generate the histogram based on a multiple count of detections corresponding to the integer weighting factors. The integer weighting factors are preferably powers of two. This allows for efficient implementation. Integer weighting parameters can enable weighting with comparatively low hardware expenditure. Powers of two are particularly advantageously used. This results in cost-effective implementation.

[0018] In a preferred embodiment, the weighting unit is configured to determine individual weighting parameters with integer counting factors. The summation unit is configured to generate the histogram based exclusively on counting detections that correspond to a multiple of the respective counting factor of the sensor element and to discard the remaining detections. The integer counting factors are preferably powers of two. This also results in efficient implementation of the weighting approach in hardware. Weighting is performed by discarding events from individual sensor elements with a low signal-to-noise ratio. Detections or events from such sensor elements are discarded. The discarding can be implemented using simple counters. This results in efficient implementation and high performance.

[0019] In a further embodiment according to the invention, the weighting unit is designed to generate a partial histogram for each sensor element, wherein the weighting unit is designed to determine the individual weighting parameters based on an evaluation of the partial histograms and the summation unit is designed to generate the histogram based on a summation of the partial histograms weighted with the individual weighting parameters. An individual histogram is generated for each sensor element. The weighting factors can be determined based on the noise level. The partial histograms can be added in a weighted manner, wherein each histogram bin of the partial histogram is added to an overall histogram with a weighting factor. This does, however, result in a comparatively high outlay for calculating the individual histograms.However, it is possible to optimally define the weighting factors for each sensor element after a measurement. This results in the weighting factors being determined at runtime, allowing adaptation to current conditions.

[0020] The respective weighting factor is preferably the same for all detections, especially for all bins, of a sensor element, since it is an individual weighting factor for the corresponding sensor element that affects all detections. No individual weighting parameters are assigned to the individual bins of a partial histogram.

[0021] In a preferred embodiment, the lidar measuring device is configured to perform a time-correlated single photon counting (TCSPC) measuring method. The lidar measuring device is preferably operated based on a TCSPC measuring method. Individual photon events are counted (detections).

[0022] In a preferred embodiment, the lidar measuring device is designed for attachment to a vehicle in an area near the vehicle's bumper. This provides a clear view of objects in front of and behind the vehicle. Good detection of objects in the vehicle's surroundings is achieved.

[0023] A focal plane array arrangement is understood to mean a configuration of the sensor elements (or the transmitting elements) essentially in one plane. A lidar receiving unit is, in particular, a microchip with corresponding sensor elements. A lidar transmitting unit is also, in particular, a microchip with corresponding transmitting elements. The receiving and transmitting units can be arranged together on a microchip. The transmitting and sensor elements are, for example, each arranged on a chip in matrix form and distributed over a surface of the chip. One or more sensor elements are assigned to a transmitting element. A light pulse from a lidar transmitting unit is understood to mean, in particular, a pulse of laser light. A signal propagation time describes, in particular, the time required for a light pulse that is emitted by the lidar transmitting unit and received by the lidar receiving unit after being reflected by an object in the vicinity of the lidar measuring device.A detection describes, in particular, the impact of a photon on a sensor element. A signal propagation time can be determined, in particular, based on a high-point detection in the generated histogram. The environment of a vehicle particularly includes an area in the surroundings of the vehicle that is visible from the vehicle.

[0024] The invention is described and explained in more detail below using selected embodiments in conjunction with the accompanying drawings. They show: Fig. 1 shows a schematic representation of a lidar measuring device according to one aspect of the present invention; Fig. 2 shows a schematic representation of a readout device according to the invention; Fig. 3 shows a schematic representation of a lidar transmitting unit for emitting light pulses; Fig. 4 shows a schematic representation of a macrocell of the lidar receiving unit; and Fig. 5 shows a schematic representation of a method according to the invention.

[0025] In the Fig. 1 1 schematically shows a lidar measuring device 10 according to the invention for detecting an object 12 in the surroundings of a vehicle 14. In the illustrated embodiment, the lidar measuring device 10 is integrated into the vehicle 14. The object 12 in the surroundings of the vehicle 14 can, for example, be another vehicle or a static object (traffic sign, house, tree, etc.) or another road user (pedestrian, cyclist, etc.). The lidar measuring device 10 is preferably mounted in the region of a bumper of the vehicle 14 and can, in particular, evaluate the surroundings of the vehicle 14 in front of the vehicle. For example, the lidar measuring device 10 can be integrated into the front bumper.

[0026] 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 readout device 20 for adjusting a field of view of the lidar measuring device 10.

[0027] Preferably, both the lidar receiving unit 16 and the lidar transmitting unit 18 are configured in a focal plane array configuration. The elements of the respective device are arranged substantially in one plane on a corresponding chip. The chip of the lidar receiving unit or the lidar transmitting unit is arranged at a focal point of a corresponding optical system (transmitting optics or receiving optics). In particular, sensor elements of the lidar receiving unit 16 or transmitting elements of the lidar transmitting unit 18 are arranged at the focal point of the respective receiving or transmitting optics. This optical system can be formed, for example, by an optical lens system.

[0028] The sensor elements of the lidar receiver unit 16 are preferably designed as SPADs (single photon avalanche diodes). The lidar transmitter unit 18 comprises a plurality of transmitter elements for emitting laser light or laser pulses. The transmitter elements are preferably designed as VCSELs (vertical cavity surface emitting lasers). The transmitter elements of the lidar transmitter unit 18 are distributed over a surface of a transmitter chip. The sensor elements of the lidar receiver unit 16 are distributed over a surface of the receiver chip.

[0029] A transmitting optic is assigned to the transmitting chip, and a receiving optic is assigned to the receiving chip. The optics images incoming light from a spatial area onto the respective chip. The spatial area corresponds to the field of view 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 transmitting optics images a transmitting element onto a solid angle that represents a sub-area of ​​the spatial area. The transmitting element emits laser light into this solid angle accordingly. The transmitting elements together cover the entire spatial area. The receiving optics images a sensor element onto a solid angle that represents a sub-area of ​​the spatial area. The number of all sensor elements covers the entire spatial area. Transmitting elements and sensor elements that view the same solid angle image one another and are assigned or assigned to one another accordingly.assigned. A laser beam from a transmitting element normally always projects onto the corresponding sensor element. Advantageously, several sensor elements are arranged within the solid angle of a transmitting element.

[0030] To determine or detect objects 12 within the spatial area, the lidar measuring device 10 performs a measuring process. Such a measuring process comprises one or more measuring cycles, depending on the design of the measuring system and its electronics. Preferably, a TCSPC method (Time Correlated Single Photon Counting method) is used in the readout device 20. Individual incoming photons are detected, in particular by a SPAD, and the time at which the sensor element is triggered (detection time) is stored in a memory element. The detection time is related to a reference time at which the laser light is emitted. The time of flight of the laser light can be determined from the difference, from which the distance to the object 12 can be determined.

[0031] A sensor element of the lidar receiver unit 16 can be triggered by the laser light on the one hand and by ambient radiation on the other. A laser light always arrives at the same time at a certain distance from the object 12, whereas the ambient radiation always provides the same probability of triggering a sensor element. When a measurement is performed multiple times, in particular multiple measurement cycles, the triggering of the sensor element accumulates at the detection time, which corresponds to the travel time of the laser light relative to the distance of the object. In contrast, the triggering by the ambient radiation is distributed evenly 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 measuring cycles of a measuring process stored in the memory element enable an evaluation of the multiple detection times in order to determine the distance of the object 12.

[0032] A sensor element is advantageously connected to a TDC (time-to-digital converter). The TDC stores the time at which the sensor element was triggered in the memory element. Such a memory element can be designed, for example, as a short-term memory or a long-term memory. For a measurement process, the TDC fills a memory element with the times at which the sensor elements detect an incoming photon. This can be represented graphically by a histogram based on the data from the memory element. In a histogram, the duration of a measurement cycle is divided into very short time periods (so-called bins).

[0033] 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 detection time and the reference time.

[0034] In the Fig. 2 A readout device 20 according to the invention for determining a signal propagation time of a light pulse is shown schematically. The readout device 20 comprises an input interface 22, a weighting unit 24, a summation unit 26, a propagation time unit 28, and an output unit 30. The various units and interfaces can be implemented individually or in combination in software and / or hardware. In particular, the units can be implemented in software that is executed on a processor of the lidar measuring device.

[0035] Detections from multiple sensor elements of the lidar receiver unit are received via the input interface 22. In particular, detections from a macrocell with multiple sensor elements are received. A detection can, in particular, correspond to the time of an incoming photon in the sensor element. The detections result, on the one hand, from registered ambient light (noise) and, on the other hand, from reflected light pulses from the lidar transmitter unit on an object.

[0036] In the weighting unit 24, an individual weighting parameter is determined for each individual sensor element. This weighting parameter specifies, in particular, how strongly this sensor element should be considered when generating the histogram for the macrocell or for the measurement. The weighting unit 24 can be configured both to determine the individual weighting parameters at runtime, i.e., during operation of the lidar measuring device, and to determine the weighting parameters once before commissioning.

[0037] Fundamentally, the invention proposes using maximum-ratio combining for multiple sensor elements that are jointly assigned to a transmitting element. The weighting unit 24 is configured to determine the individual weighting parameters, whereby these weighting parameters depend on the signal-to-noise ratio of the individual sensor elements. In particular, a weighting proportional to the root mean square of the signal level and inversely proportional to the noise level can be used. In the weighting unit 24, the weighting factors are determined individually for each receive path, i.e., for each sensor element.

[0038] To determine the weighting parameters, it is possible, on the one hand, to determine the far-field signal strength (root-square) for all sensor elements of the macrocell during a calibration phase. For this purpose, a spot position can be measured during a factory calibration. It is also possible to activate individual sensor elements in order to determine their signal-to-noise ratio one after the other. The noise level depends on the ambient light and can be determined, for example, before a laser pulse is emitted. The sensor elements within the far-field spot positions are summed in a weighted manner. The sensor elements outside the spot positions can be deactivated.

[0039] In the summation unit 26, a histogram is generated with a mapping of the detections to the detection times of the detections. The summation of the sensor elements or the detections of the sensor elements is event-based. Each sensor element generates a binary output signal upon detecting a photon. The time of impact is determined and entered into a histogram. The previously determined individual weighting parameters are taken into account when generating the histogram.

[0040] In particular, it is possible to directly store all detections in a common histogram. The weighting can be based on integer weighting factors. A detection of a sensor element with a high signal-to-noise ratio can, for example, generate an increment of 4 in the corresponding bin of the histogram (weighting factor 4). A detection in a sensor element with a medium signal-to-noise ratio can generate an increment of 2 in the corresponding bin of the histogram (weighting factor 2). A detection in a sensor element with a low signal-to-noise ratio can, for example, generate an increment of 1 in the corresponding bin of the histogram (weighting factor 1). Sensor elements that lie outside the spot position can, for example, be discarded.

[0041] Alternatively, it is possible to weight the rejection of detections from sensor elements with a low signal-to-noise ratio. Discarding individual detections can be achieved using simple counters or based on a counting factor that specifies which detections are to be rejected. For example, a sensor element with a high signal-to-noise ratio can trigger an increment of the corresponding bin of the histogram for each event (counting factor 1). A sensor element with a medium signal-to-noise ratio can, for example, resolve an increment of the corresponding bin of the histogram every second detection (counting factor 2). A sensor element with a low signal-to-noise ratio can, for example, generate an increment of 1 in the corresponding bin of the histogram every fourth event (counting factor 4).

[0042] The use of integer counting factors and weighting factors, especially powers of two, is particularly advantageous in terms of hardware. Using a counting factor is even more efficient, but may result in poorer performance, as detections from sensor elements with high signal-to-noise ratios are discarded and not considered.

[0043] It is also possible to generate the histogram by summing several sub-histograms, each created separately for each sensor element. The contents of the histogram bins can be weighted based on the weighting parameters.

[0044] In the time-of-flight unit 28, a signal propagation time is determined based on the generated histogram. For this purpose, a peak of the histogram can be detected. The peak corresponds to the time of the highest signal strength and thus the location of the reflection of the light pulse from an object.

[0045] The determined signal propagation time is output via the output unit 30. In particular, object localization can then be carried out.

[0046] In the Fig. 3 The structure of the lidar transmitter unit 18 is shown schematically. The chip comprises several transmitter elements 32 arranged in an array (matrix). For example, several thousand transmitter elements can be used. The transmitter elements 32 are preferably controlled line by line. For clarity, only one transmitter element 32 is provided with a reference symbol.

[0047] In the illustrated embodiment, the rows 0..ny-1 each comprise a plurality of transmitting elements 0..nx-1. For example, 100 rows (ny = 100) and 128 transmitting elements per row (nx = 128) can be provided. The row spacing A1 between the rows can be in the range of a few micrometers, for example, 40 µm. The element spacing A2 between transmitting elements 32 in the same row can be of a similar order of magnitude.

[0048] In the Fig. 4 A macrocell 34 with a total of 10 sensor elements 36a - 36j is shown schematically. Also shown schematically is the spot position 38, i.e., the position of a spot corresponding to the transmitting element of the lidar transmitting unit. The spot typically has an at least approximately Gaussian spot profile. In the illustration in the Fig. 4The two concentric circles of spot position 38 indicate how the signal strength decreases outwards within this spot profile. As shown, the center of the spot is in sensor element 36e and thus outside the center of the macrocell 34. Sensor element 36e will therefore have the highest signal component. According to the invention, the individual weighting factors assigned to the transmission elements 36a - 36j determine how strongly these sensor elements are weighted when generating the histogram. In the example shown, it is conceivable that sensor elements 36g and 36j are considered with a weight of 0 and are not included in the determination of the histogram. Sensor element 36e can be weighted four times, sensor elements 36a, 36b and 36c can be weighted twice, and the remaining sensor elements can be weighted once. The representation of the Fig. 4The weightings given above are to be understood as examples. It is understood that other numbers of sensor elements can be arranged in a macrocell and other weightings can be used.

[0049] In the Fig. 5 A method according to the invention is schematically illustrated. The method comprises steps of receiving S10 detections, determining S12 each individual weighting parameter, generating S14 a histogram, determining S16 a signal propagation time, and outputting S18 the signal propagation time. The method can be implemented, for example, in software that is executed on a processor of a lidar measuring device.

[0050] 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 exemplary 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 upon use of the present invention and upon careful analysis of the drawings, the disclosure, and the following claims.

[0051] 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 unit can perform the functions of several of the units recited in the claims. An element, unit, interface, device, and system can be partially or completely implemented in hardware and / or 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 limiting. Reference symbol

[0052] 10Lidar measuring device 12Object 14Vehicle 16Lidar receiving unit 18Lidar transmitting unit 20Readout device 22Input interface 24Weighting unit 26Summation unit 28Runtime unit 30Output unit 32Transmitting element 34Macro cell 36a-36jSensor element 38Spot position

Claims

1. Readout device (20) for determining a signal propagation time of a light pulse between a lidar transmitting unit (18) and a lidar receiving unit (16) of a lidar measuring device (10) in a focal plane array arrangement, with: an input interface (22) for receiving detections of several sensor elements (36a-36j) of the lidar receiving unit, which are arranged in a macrocell (34) assigned to a transmitting element (32) of the lidar transmitting unit; a weighting unit (24) for determining an individual weighting parameter for each of the several sensor elements, wherein the weighting parameter depends on a signal-to-noise ratio of the sensor element; a summation unit (26) for generating a histogram with an assignment of the detections to detection times of the detections, wherein the summation unit is formed for weighting the detections based on the individual weighting parameters; a propagation time unit (28) for determining the signal propagation time based on the generated histogram; and an output unit (30) for outputting the signal propagation time, characterized in that the weighting unit (24) is formed for determining the individual weighting parameters based on a calibration measurement of a spot position (38) on the macrocell (34) and sensor elements (36a-36j) are given a lower weighting with increasing distance from a center point (M) of the spot position; and / or in that the weighting unit (24) is formed for determining the individual weighting parameters based on a sequential individual calibration readout of the sensor elements (36a-36j) with a constant signal propagation time and sensor elements (36a-36j) with a higher number of detections are given a higher weighting in the calibration readout; and / or in that the weighting unit (24) is formed for determining the individual weighting parameters based on an individual noise parameter of the respective sensor element and the individual noise parameter describes a signal noise of the respective sensor element; and / or in that the weighting unit (24) is formed for determining individual weighting parameters with integer weighting factors; and the summation unit (26) is formed for generating the histogram based on a multiple count of detections corresponding to the integer weighting factors; and / or in that the weighting unit (24) is formed for generating a respective partial histogram for each sensor element; and the weighting unit is formed for determining the individual weighting parameters based on an evaluation of the partial histograms; and the summation unit (26) is formed for generating the histogram based on a summation of the partial histograms weighted with the individual weighting parameters.

2. Readout device (20) according to claim 1, wherein the weighting unit (24) is formed for determining individual weighting parameters with integer counting factors; the summation unit (26) is formed for generating the histogram based on an exclusive count of detections corresponding to a multiple of the respective count factor of the sensor element and for discarding the remaining detections.

3. Readout device (20) according to one of the preceding claims, wherein the lidar measuring device (10) is formed for carrying out a Time Correlated Single Photon Counting, TCSPC, measuring method.

4. Lidar measuring device (10) in focal plane array arrangement for detecting objects (12) in an environment of a vehicle (14), with: a lidar transmitting unit (18) with a plurality of transmitting elements (32) for transmitting light pulses and a lidar receiving unit (16) with a plurality of sensing elements (36a-36j) for receiving the light pulses, wherein the transmitting elements and the sensor elements are arranged in lines parallel to a horizontal plane of the vehicle; and a readout device (20) according to one of the preceding claims.

5. Lidar measuring device (10) according to claim 4, wherein the lidar measuring device is formed to be attached to a vehicle (14) in a region of a bumper of the vehicle.

6. Method for determining a signal propagation time of a light pulse between a lidar transmitting unit (18) and a lidar receiving unit (16) of a lidar measuring device (10) in a focal plane array arrangement, with the following steps: receiving (S10) detections of several sensor elements (36a-36j) of the lidar receiving unit, which are arranged in a macrocell (34) assigned to a transmitting element (32) of the lidar transmitting unit; determining (S12) a respective individual weighting parameter for each of the several sensor elements, wherein the weighting parameter depends on a signal-to-noise ratio of the sensor element; generating (S14) a histogram with an assignment of the detections to detection times of the detections, wherein the summation unit is formed for weighting the detections based on the individual weighting parameters; determining (S16) the signal propagation time based on the generated histogram; and outputting (S18) the signal propagation time, characterized in that the individual weighting parameters are determined by means of the weighting unit (24) based on a calibration measurement of a spot position (38) on the macrocell (34); wherein sensor elements (36a-36j) are given a lower weighting with increasing distance from a center point (M) of the spot position; and / or in that the individual weighting parameters are determined by means of the weighting unit (24) based on a sequential individual calibration readout of the sensor elements (36a-36j) while the signal propagation time remains constant; wherein sensor elements (36a-36j) with a higher number of detections are given a higher weighting in the calibration readout; and / or in that the individual weighting parameters are determined by means of the weighting unit (24) based on an individual noise parameter of the respective sensor element and the individual noise parameter describes a signal noise of the respective sensor element; and / or in that the individual weighting parameters are determined by means of the weighting unit (24) with integer weighting factors; wherein the histogram is generated by means of the summation unit (26) based on a multiple count of detections corresponding to the integer weighting factors; and / or in that by means of the weighting unit (24) a partial histogram is determined for each sensor element; and by means of the weighting unit the individual weighting parameters are determined based on an evaluation of the partial histograms; and by means of the summation unit (26) the histogram is generated based on a summation of the partial histograms weighted with the individual weighting parameters.

7. Computer program product with program code for performing the steps of the method according to claim 6, when the program code is executed on a computer of the lidar measuring device according to one of claims 4 or 5.