Calibration of solid state laser radar devices

Abstract

According to an embodiment, there is provided a solid-state laser radar device (100) comprising: a laser generator (110); an optical lens device (130) having a focal length (f1) and providing a back focal plane (135); a solid-state sensor array (150) located at the back focal plane (135) of the optical lens device (130) having a first sensor (152a) and a second sensor (152b), the first sensor (152a) and the second sensor (152b) being spaced apart from each other by a first sensor distance (d1); at least one processor (101). The processor (101) is configured to: obtain a measured distance of the target from a pulse time-of-flight measurement using the laser generator (110) and at least one of the first sensor (152a) and the second sensor (152b) in the solid-state sensor array (150); obtain at least one spatial coordinate of the target (140) from the measured distance using a calibration parameter indicative of a ratio of the first sensor distance (d1) to the focal length (f1).

Description

TECHNICAL FIELD

[0001] The present invention relates to a solid-state laser radar device, in particular to a calibration of a solid-state laser radar device. Furthermore, the present invention relates to a method for respectively performing and calibrating a solid-state laser radar device and a corresponding computer program product. BACKGROUND

[0002] Three-dimensional imaging devices can be used to detect spatial coordinates of objects in their field of view. For this purpose, there are currently passive depth sensing devices and active depth sensing devices, the latter also including mechanical scanners and solid-state imaging devices.

[0003] Irrespective of the implementation, imaging devices need to be calibrated to achieve a high level of precision and accuracy. Device models using moving parts usually have more parameters and thus require a more complex calibration process. However, devices with few or no moving parts usually also need to be calibrated by defining a well-defined calibration environment. SUMMARY

[0004] The present summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0005] It is an object of the present invention to provide a solid-state laser radar device and a calibration method thereof. This object can be achieved using the features of the independent claims. Further implementation forms are provided in the dependent claims, the description and the drawings. In particular, it is an object of the present invention to provide a device and a method having an intrinsic calibration functionality, thereby ensuring calibration without the need for a specially set-up three-dimensional calibration environment.

[0006] According to a first aspect, a solid-state lidar device is provided, comprising: a laser generator for generating a pulsed laser beam that can be directed at a target; an optical lens device for collecting the laser beam reflected by the target; a solid-state sensor array; at least one processor. The optical lens device has a focal length and provides a back focal plane, while the solid-state sensor array is located at the back focal plane of the optical lens device for detecting the laser beam. The solid-state sensor array comprises at least a first sensor and a second sensor for detecting the reflected laser beam, wherein the first sensor and the second sensor are spaced apart from each other by a first sensor distance. The at least one processor is configured to obtain a measured distance of the target from a pulsed time-of-flight measurement using the laser generator and at least one of the first sensor and the second sensor of the solid-state sensor array. The at least one processor is further configured to obtain at least one spatial coordinate of the target from the measured distance using a calibration parameter indicative of a ratio of the first sensor distance to the focal length. Using a calibration parameter indicative of the specific ratio enables a simple and efficient calibration of the solid-state lidar device, since no component-specific calibration parameters of the sensor or the optical lens device, respectively, are required. Moreover, it has been found that this can significantly reduce the complexity of the required calibration environment, since the calibration can then be performed without a pre-determined three-dimensional calibration object (e.g. known for its size, shape and position).

[0007] In an implementation form of the first aspect, the first sensor and the second sensor are single-photon avalanche diodes (SPADs) arranged on a common substrate of the solid-state sensor device. This enables a precise positioning of the first sensor and the second sensor even in case of a high sensor density of the solid-state sensor array, thereby providing a high calibration accuracy.

[0008] In a further implementation form of the first aspect, the solid-state sensor array further comprises a third sensor for detecting the reflected laser beam, such that the first sensor, the second sensor and the third sensor are arranged in a one-dimensional arrangement. Thus, the field of view of the solid-state sensor array can be enlarged.

[0009] In a further implementation form of the first aspect, the solid-state sensor array further comprises a third sensor for detecting the reflected laser beam, such that the second sensor and the third sensor define a second sensor distance, which is equal to the first sensor distance. Thus, using equal sensor distances between different sensors can extend the above-described simple and efficient calibration procedure to different types of sensor arrays.

[0010] In a further implementation form of the first aspect, the at least one processor is configured to obtain the at least one spatial coordinate using an optimal value of the calibration parameter. The optimal value is obtained by obtaining a plurality of measured distances to different spatial positions of the target, each measured distance corresponding to a different sensor of the solid-state sensor array, and by calculating the optimal value by fitting a fitting function to a point cloud function comprising temporary spatial coordinates of the different spatial positions of the target, wherein the temporary spatial coordinates are obtained from the plurality of measured distances using temporary values of the calibration parameter, such that the optimal value is the temporary value that optimizes the fitting. This can conveniently optimize the value of the calibration parameter. The optimal value can even be obtained by a single scan of the target. It is not necessary to know the position and size of the target as long as the target has a basic shape corresponding to the fitting function for the scan. This can use the basic shape for intrinsic calibration. In a further implementation form, the fitting function is a linear function that can be represented as a straight line or a plane. This can efficiently calibrate targets that are prevalent in a building environment, e.g. a flat wall.

[0011] In a further implementation form of the first aspect, the at least one spatial coordinate of the target is obtained from the measured distances by modifying the measured distances by at least one additional sensor-specific calibration parameter that indicates an inaccuracy of the measured distances of at least one sensor of the solid-state sensor array. This can efficiently take into account any kind of sensor-specific inaccuracy sources, e.g. measurement errors and / or delays.

[0012] According to a second aspect, there is provided a method comprising causing a solid-state lidar device according to the first aspect or any implementation form thereof to scan a target to obtain an optimal value of a calibration parameter. This can calibrate the solid-state lidar device by one or more scans of the device.

[0013] In a further implementation form of the second aspect, the target comprises a flat surface facing the laser generator, wherein a laser beam is reflected on the flat surface. This can use the flat surface for intrinsic calibration of the solid-state lidar device. It has been found that this can also easily verify the accuracy of the calibration, because any deviation of the calibration parameter from its optimal value can be identified by scanning the solid-state lidar device producing a curved shape when the target is a flat surface.

[0014] In another implementation of the second aspect, the scan is performed using a solid-state sensor array positioned non-parallel to the target. This has been found to improve the robustness of the calibration, as it enables the calibration of a solid-state lidar device according to any one of the first aspects or implementations thereof to provide a single, well-defined optimal value for the calibration parameters rather than two or more distinct local optima.

[0015] According to a third aspect, a method for operating a solid-state lidar device is disclosed. The solid-state lidar device includes: a laser generator for generating a pulsed laser beam that can be directed at a target; an optical lens device for collecting the laser beam reflected from the target; and a solid-state sensor array. The optical lens device has a focal length and provides a back focal plane, while the solid-state sensor array is located on the back focal plane of the optical lens device for detecting the laser beam, wherein the solid-state sensor array includes at least two sensors that are equidistant from each other at a first sensor distance in at least one dimension. The method (e.g., performed by at least one processor configured for this purpose) includes: obtaining a measured distance of the target from a pulse time-of-flight measurement using the laser generator and the sensors in the solid-state sensor array; and obtaining at least one spatial coordinate of the target from the measured distance using a calibration parameter indicating the ratio of the first sensor distance to the focal length. Since it is not necessary to obtain component-specific calibration parameters for the sensors or the optical lens device separately, the solid-state lidar device can be calibrated simply and efficiently using calibration parameters indicating the specific ratio. Furthermore, it has been found that this can significantly reduce the complexity of the required calibration environment, as calibration can then be performed without a pre-determined 3D calibration object (e.g., whose size, shape, and location are known).

[0016] In another implementation of the third aspect, the at least two sensors are single-photon avalanche diodes (SPADs) disposed on a common substrate of the solid-state sensor array. This enables precise positioning of the first and second sensors even with a high sensor density in the solid-state sensor array, thereby providing high calibration accuracy.

[0017] In another implementation of the third aspect, the at least one spatial coordinate is obtained using the optimal value of the calibration parameter. The optimal value is obtained by: obtaining multiple measured distances to different spatial locations of the target, each measuring distance corresponding to a different sensor in the solid-state sensing array; and calculating the optimal value by fitting a fitting function to a point cloud function that includes the temporary spatial coordinates of the different spatial locations of the target, wherein the temporary spatial coordinates are obtained from the multiple measured distances using temporary values ​​of the calibration parameter, such that the optimal value is the temporary value that optimizes the fitting. This allows for convenient optimization of the calibration parameter value. The optimal value can even be obtained by performing a single scan of the target. As long as the target has a basic shape for scanning corresponding to the fitting function, the position and size of the target do not need to be known. Intrinsic calibration can then be performed using the basic shape. In another implementation, the fitting function refers to a linear function that can be represented as a straight line or a plane. This enables efficient calibration of targets commonly found in built environments (e.g., flat walls).

[0018] In another implementation of the third aspect, the at least one spatial coordinate of the target is obtained from the measurement distance by modifying the measurement distance using at least one additional sensor-specific calibration parameter, which indicates inaccuracies in the measurement distance of at least one sensor in the solid-state sensor array. This efficiently accounts for any type of sensor-specific inaccuracy source, such as measurement errors and / or delays.

[0019] According to a fourth aspect, a computer program product is provided, including program code, the computer program product being used to perform a method according to any one of the second aspect, the third aspect, or an implementation thereof.

[0020] According to another aspect, the present invention also relates to a computer-readable medium (e.g., a non-transitory computer-readable medium) and said computer program code, wherein said computer program code is contained in said computer-readable medium, and said computer medium includes one or more of the following groups: read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), flash memory, electrically EPROM (EEPROM), and hard disk drive.

[0021] Many of the accompanying features will become more readily understood, and thus more readily comprehended, with reference to the following detailed description taken in conjunction with the accompanying drawings. Attached Figure Description

[0022] This specification will be better understood by referring to the following detailed embodiments with reference to the accompanying drawings, wherein:

[0023] Figure 1 A schematic representation of a solid-state lidar device for scanning targets according to one embodiment is shown;

[0024] Figure 2 A graphical representation of the mathematical principles for calibrating a solid-state lidar device is shown in one embodiment;

[0025] Figure 3 A flowchart representation of a method for obtaining optimal values ​​of calibration parameters provided in one embodiment is shown;

[0026] Figure 4 This example illustrates two different point cloud functions obtained using two different values ​​of calibration parameters;

[0027] Figure 5 A flowchart characterization of a method for performing a solid-state lidar device is shown in another embodiment.

[0028] In the accompanying drawings, the same reference numerals are used to denote the same parts. Detailed Implementation

[0029] The specific embodiments provided below with reference to the accompanying drawings are intended to illustrate various examples and are not intended to represent the only ways in which the embodiments can be constructed or used. However, the same or equivalent functions and structures can be implemented through different embodiments.

[0030] Figure 1 A schematic representation of a solid-state lidar device 100 (also referred to herein as a "device") for scanning a target 140 according to an embodiment is shown. Hereinafter, "lidar device" may refer to a detection system used to measure the distance to the target 140 by illuminating the target 140 with a laser beam 120 and measuring the reflected laser beam 120' through one or more sensors (152a-152c). The target 140 can then be digitally represented in one, two, or three spatial dimensions using the laser beam return time difference. Hereinafter, "solid-state lidar device" may refer to lidar device 100, wherein the sensor array 150 is a solid-state sensor array 150, and the sensors may be embedded in one or more chips such as silicon chips. The solid-state sensor array 150 can be used for static distance measurement, thus eliminating the need for any mechanical moving parts. Therefore, the solid-state lidar device 100 can be used entirely for static distance measurement, eliminating the need for any mechanical moving parts.

[0031] The device 100 includes a laser generator 110. The laser generator can be used to generate a pulsed laser beam 120 that can be directed towards the target 140. The device 100 may also include a diffuser 112 for diffusing the laser beam 120 from the laser generator 110. The diffuser 112 may include another lens device (…). Figure 1 (Not shown in the image), and may also include a focal length f2. The diffuser 112 may be coupled to the laser generator 110. In some embodiments, the distance between the diffuser 112 and the laser generator 110 may correspond to the focal length f2.

[0032] The device 100 includes an optical lens assembly 130, which can be used to collect the laser beam 120' reflected by the target 140. The optical lens assembly 130 has a focal length f1 and thus provides a back focal plane 135. In some embodiments, the focal length f1 of the optical lens assembly 130 may be the same as the focal length f2 of the diffuser 112. However, according to some other embodiments, the focal length f1 and the focal length f2 may be different.

[0033] The device 100 includes a solid-state sensor array 150 (also referred to herein as an "array") located on the back focal plane 135. The array 150 includes at least two sensors: a first sensor 152a and a second sensor 152b, wherein the first sensor 152a and the second sensor 152b can be used to detect the reflected laser beam 120'. However, for this purpose, the array 150 may also include three or more sensors (e.g., ten or more sensors), and some embodiments may include a very large number of sensors within the practical limits permitted by the solid-state sensor array technology. The array 150 may include a one-dimensional or two-dimensional arrangement of the sensors. Any two sensors arranged in a one-dimensional arrangement (e.g., the first sensor 152a and the second sensor 152b) may be spaced apart from each other by a first sensor distance d1. When the array 150 includes a third sensor 152c for detecting the reflected laser beam 120', the second sensor 152b and the third sensor 152c may define a second sensor distance d2, which may be equal to the first sensor distance d1. In this way, the first sensor 152a, the second sensor 152b, and the third sensor 152c can be positioned at equal distances along a certain line, which can greatly simplify the calibration of the device 100.

[0034] When the one-dimensional arrangement includes three or more sensors (152a-152c), the sensors in the arrangement can therefore be equidistant from each other by the sensor-to-sensor distance between any two adjacent sensors, the sensor-to-sensor distance corresponding to the first sensor distance d1. Therefore, the sensor-to-sensor distance can be constant for any two adjacent sensors along a dimension. When the array 150 includes a two-dimensional arrangement of sensors, the arrangement can have a first sensor-to-sensor distance in the first dimension of the two-dimensional arrangement and a second sensor-to-sensor distance in the second dimension of the two-dimensional arrangement. The first sensor-to-sensor distance can be equal to the second sensor-to-sensor distance, and the second sensor-to-sensor distance can reduce the number of calibration parameters required compared to a two-dimensional arrangement where the first sensor-to-sensor distance is different from the second sensor-to-sensor distance.

[0035] The array 150 may include a substrate configured to support one or more sensors in the array 150, such as the first sensor 152a, the second sensor 152b, and the third sensor 152c. In some embodiments, one or more sensors in the array 150 (e.g., the first sensor 152a and / or the second sensor 152b, optionally including the third sensor 152, or even any one of the plurality of sensors (152a-152c)) are disposed on a common substrate of the array 150. In some embodiments, one or more sensors in the array 150 (e.g., the first sensor 152a and / or the second sensor 152b, optionally including the third sensor 152) may be single-photon avalanche diodes (SPADs) particularly suitable for placement on a common substrate, thereby enabling accurate positioning of the sensors for one-dimensional or two-dimensional arrangement. For example, for multiple SPAD sensors, using a common substrate enables a high-accuracy constant sensor-to-sensor distance.

[0036] The device 100 further includes at least one processor 101 (also referred to herein as a "processor"). The processor 101 is configured to: obtain a measured distance of the target 140 from pulse time-of-flight measurements using the laser generator 110 and at least one sensor in the array 150 (e.g., the first sensor 152a or the second sensor 152b). To operate the laser generator 110, the processor 101 can be coupled to the laser generator 110 via a first link 103 of the device 100, the link including a wired and / or wireless data transmission connection. To obtain the measured distance, the processor 101 can be coupled to the sensor array 150 via a second link 105 of the device 100, the link including a wired and / or wireless data transmission connection.

[0037] In this document, "pulse time-of-flight measurement" can refer to a measurement in which the pulse time of flight of the laser beam (120, 120') is measured, and the pulse travel distance is determined based on the flight time. In this document, "time of flight" can refer to the time from the generation of a pulse at the laser generator 110 to the capture of the pulse at the array 150. The travel distance can be determined by the processor 101. In this document, "measured distance of the target 140" can refer to the distance measured by the sensors (152a-152c) in the array 150 that capture the pulse, wherein the distance represents the distance between the sensor and the target 140. The measured distance can be obtained from the travel distance or the time of flight using any method known to those skilled in the art of time-of-flight measurement. The measured distance can also be determined by the processor 101.

[0038] The processor 101 is further configured to: obtain at least one spatial coordinate of the target 140 from the measured distance. In this document, "spatial coordinate" can refer to a data point representing the spatial location of a single spatial position of the target 140. The at least one spatial coordinate may include two-dimensional or three-dimensional coordinates of the single spatial position of the target 140. The at least one spatial coordinate can be represented in any coordinate system, such as a Cartesian coordinate system.

[0039] The at least one spatial coordinate is obtained using calibration parameters indicating the ratio of the distance d1 of the first sensor to the focal length f1 of the optical lens device 130. Combined with Figure 2 An example is provided.

[0040] For example, the processor 101 may include one or more of various processing devices (e.g., coprocessor, microprocessor, controller, digital signal processor (DSP), processing circuitry with or without an accompanying DSP) or various other processing devices including integrated circuits (e.g., application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), microcontroller unit (MCU), hardware accelerator, dedicated computer chip, etc.).

[0041] The device 100 may also include at least one memory 102 (also referred to herein as "memory"). The processor 101 may be used to execute any process described herein for the processor 101 according to program code included in the memory 102.

[0042] For example, the memory 102 can be used to store computer programs, etc. The memory 102 may include one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination of one or more volatile memory devices and non-volatile memory devices. For example, the memory 102 can be implemented as a magnetic storage device (e.g., hard disk drive, floppy disk, magnetic tape, etc.), an optical-magnetic storage device, and a semiconductor memory (e.g., mask ROM, programmable ROM (PROM), erasable PROM (EPROM), flash memory ROM, random access memory (RAM), etc.).

[0043] The device 100 may also include a transceiver. For example, the transceiver may be used to transmit and / or receive data via 3G, 4G, 5G, LTE or WiFi connections.

[0044] The device 100 may further include Figure 1 Other components and / or parts not shown in the embodiments.

[0045] The functions described herein can be implemented by various components of the device 100. For example, the memory 102 may include program code for performing or causing to perform any of the functions disclosed herein; the processor 101 may be used to perform or cause to perform the functions according to the program code included in the memory 102.

[0046] When the device 100 is used to implement a certain function, one or more components of the device 100 (e.g., the at least one processor 101 and / or the memory 102) can be used to implement that function. Furthermore, when the at least one processor 101 is used to implement some functions, those functions can be implemented using program code included in the memory 102, etc. For example, if the device 100 is used to perform an operation, the at least one memory 102 and the computer program code can be used together with the at least one processor 101 to enable the device 100 to perform that operation.

[0047] Figure 2 A graphical representation of the mathematical principles for calibrating a solid-state lidar device is shown in one embodiment. The principles are applied to a target 140 including a flat surface 141, but can also be applied to targets with other surface shapes (e.g., curved or serrated surfaces).

[0048] As an example of which parameters need to be calibrated for the device 100, the solid-state sensing array 150 is schematically shown relative to the target 140. Importantly, this schematic visualization involves a mathematical transformation of the geometry of the device 100 relative to the target 140, thereby enabling visualization of the effect of the optical lens device 130 by positioning the array 150 between the origin O of the coordinate system and the target 140, such that the vertical distance from the array 150 to the origin O corresponds to the focal length f1 of the optical lens device. This mathematical representation corresponds to a physical arrangement where the array 150 is located on the back focal plane 135 of the optical lens device 130. In this document, as shown, the coordinate system can be a Cartesian coordinate system with its x-axis parallel to the array 150 and its y-axis perpendicular to the array 150. In this document, the origin O of the coordinate system can refer to the optical center of the optical lens device 130.

[0049] The array 150 comprises a one-dimensional arrangement of sensors (152a-152c), which includes at least a first sensor 152a and a second sensor 152b, but optionally also includes a third sensor 152c or even more sensors. In the visualization, each rectangle of the array 150 may correspond to one sensor, thus allowing for a plurality of sensors. The first sensor 152a and the second sensor 152b are spaced apart from each other by a first sensor distance d1. The sensors in the one-dimensional arrangement may be equidistant from each other by a sensor-to-sensor distance equal to the first distance d1. This example also applies when the array 150 comprises a two-dimensional arrangement of sensors, for example, when the two-dimensional arrangement is in a plane parallel to the x-axis and perpendicular to the y-axis.

[0050] The first sensor 152a can be used to obtain a measured distance dB to the target 140. Due to the aforementioned mathematical transformation, the measured distance dB actually corresponds to the length of a visual line OB extending from the origin O to the spatial position B of the target 140. In the actual physical implementation of the device 100, the same measured distance dB can correspond to the actual physical distance between the first sensor 152a and the spatial position B of the target 140. A right triangle OB'B can be defined, with its right angle corresponding to point B', and the line OB' parallel to the y-axis of the coordinate system. If the surface of the target 140 is parallel to the array 150, then for a target with a flat surface 141, point B' will lie on the surface of the target 140. As shown, the surface of the target 140 may not be parallel to the array 150, in which case point B' may not necessarily have any direct physical meaning relative to the target 140. However, in both cases, a reference point is provided because the x-coordinate of point B is xB. A smaller right-side triangle ODE is formed, where points D and E are located at the intersections of array 150 with line OB' and line OB, respectively. The second sensor 152b is located at point D, while the first sensor 152a is located at point E, such that the x-coordinate xE of the first sensor 152a is equal to the distance d1 from the first sensor.

[0051] As a mathematical identity

[0052]

[0053] and

[0054]

[0055] When the length of any line is represented by a combination of two letters at its endpoints, such as OB or OB', combining these two equations yields the y-coordinate of the spatial position B of the target 140:

[0056]

[0057] Where OD = f1, OB = d B In the example shown, x E It equals d1. Furthermore, when the sensor-to-sensor distance is constant (which can be equal to d1), a similar equation holds when point B is located at different spatial positions of the target 140 such that line OB intersects with different sensors. This is when the index i of the different sensors is counted starting from the origin O. E At that time, from index i EStarting with the first adjacent sensor (the first sensor 152a in the diagram) whose index is 1, and incrementing by 1 for each adjacent sensor as we move further away from the origin O. Therefore, x E =i E d1. For negative coordinates, for the third sensor 152c, the index can be a negative value, for example, i E =-1, such as Figure 2 As shown.

[0058] Using index i E The sensor obtains the measured distance d B The y-coordinate of the spatial position of the target 140 can be obtained by the following equation.

[0059]

[0060] Similarly, the x-coordinate of the spatial position of the target 140 can be obtained by the following equation.

[0061]

[0062] The general principles described herein apply to the apparatus as described above. Therefore, the apparatus 100 can be used by the processor 101, etc., based on the measured distance d. B Determine the spatial coordinates of the target 140, for example, the x-coordinate of the spatial position of the target 140. B and y coordinates B Therefore, the index i of the sensor is used. E And the single parameter indicating which sensor was used to obtain the measured distance d. B The information is sufficient:

[0063]

[0064] For example, the coordinates of the spatial position of the target 140 can be obtained from the measured distance using the parameter α through the following equation:

[0065]

[0066] Therefore, this parameter α can be used as a calibration parameter, allowing the device to receive the value of the calibration parameter via a self-calibration process or even manual input, and to use this value to determine any coordinates of the target 140 based on distance measurements from the solid-state sensor array 150. Therefore, it is not necessary to receive separate values ​​for the first sensor distance d1 or the focal length f1 of the optical lens assembly 130. Furthermore, it is not necessary to use separate sensor-specific calibration values ​​for the sensor angles, i.e., to use separate calibration values ​​for the angles of each sensor in the array 150.

[0067] In one embodiment, the measured distance d B The measurement distance d can be indicated B The inaccuracies of the sensor-specific calibration parameters are corrected. These additional sensor-specific calibration parameters can be used to modify the measured distance d through any suitable mathematical relationship (e.g., through addition, subtraction, multiplication, or division). B For example, the measurement distance d of any or all sensors can be modified by the following equation. B

[0068] d B (i E )=d B (i E )+δ(i E ),

[0069] This means that for index i E Any sensor, using the measurement distance d obtained by that sensor B (i E ) through sensor-specific calibration parameter δ(i E (Modifications may be made.) Sensor-specific calibration parameters for two or more sensors may still have equal values. These sensor-specific calibration parameters can be used to compensate for delays in the electronic circuitry of the device 100, which may be due to the placement of the laser generator 110 and / or its optics relative to the solid-state sensing array 150. Furthermore, they can be used to compensate for noise and / or defects in the pulse detection of the laser beam 120'.

[0070] Figure 3 A flowchart characterization of a method 300 for obtaining optimal values ​​of calibration parameters provided in one embodiment is shown. The method 300 can be used to calibrate a solid-state lidar device 100 (e.g., device 100 shown according to any of the examples described herein) to: obtain spatial coordinates from a measured distance using calibration parameters indicating the ratio of a first sensor distance d1 to a focal length f1.

[0071] The method includes causing (310) a solid-state lidar device 100 to scan a target 140 to obtain optimal values ​​for the calibration parameters. Here, "optimal values" may refer to the values ​​of a point cloud function 420 that optimizes the fitting of a fitting function (430, 430') to temporary spatial coordinates including different spatial locations of the target 140. The device 100 may be used with one or more fitting functions (430, 430'), for example, linear functions that can be represented as lines or planes. The effect of using linear functions is that a simplified calibration can then be performed by scanning the target 140, including a flat surface 141 of the laser generator 110 facing the device 100, such that the laser beam 120 from the laser generator 110 is reflected on the flat surface for capture at the solid-state sensing array 150 of the device 100. Thus, detailed knowledge of the shape and / or location of the target 140 is not required, nor is it necessary for the target to have any specific size, shape, or location other than a simple planar interface to be scanned at any distance. If the device is used to use multiple fitting functions (430, 430'), it can also be used to allow the user to select the fitting function (430, 430') for calibration.

[0072] In this document, "point cloud function" can refer to a function corresponding to the representation of target 140. The point cloud function (410, 420) includes the spatial coordinates of different spatial locations of target 140. The point cloud function can be obtained through scanning by the solid-state lidar device 100. Depending on whether the device 100 is correctly calibrated, the point cloud function (410, 420) can visually resemble target 140. For example, the point cloud function (410, 420) can represent a two-dimensional point cloud or a three-dimensional point cloud of spatial coordinates.

[0073] The solid-state lidar device 100 can be used to perform any combination of the following steps to obtain the optimal value of the calibration parameter. The calibration parameter can be initialized (320) to use a temporary value of the calibration parameter. The solid-state lidar device 100 can be used to automatically provide the temporary value. In addition, any constant value of the calibration parameter can also be used. The temporary value of the calibration parameter α can be used to obtain (330) the temporary spatial coordinates of the target 140 based on the scan (e.g., by equation (1)).

[0074] A point cloud function (410, 420) can be formed that includes the temporary spatial coordinates of the target. The point cloud function (410, 420) can include the spatial coordinates of multiple spatial locations of the target 140. A fitting function (430, 430') (e.g., a linear function as described above) can then be fitted (340) to the point cloud function. For this purpose, any suitable fitting method known to those skilled in the art of numerical optimization (e.g., least squares fitting) can be used. A cost function can be calculated to determine the deviation between the point cloud function (410, 420) and the fitting function (430, 430'). This can be achieved when the final deviation has been determined by fitting and optimizing the parameters of the fitting function (430, 430') (e.g., the slope and intercept of a linear function). Using the cost function ensures that the fitted points lie on a straight line upon convergence, even for three-dimensional fitting.

[0075] The optimization can be performed iteratively. To this end, the optimization may involve determining whether the fitting has been completed (360), for example, because the result has converged to the optimal value, or because the fitting process has reached a point where the optimal value cannot be reached. For this purpose, one or more threshold criteria can be used. For example, determining whether the fitting has been completed (360) may include comparing the deviation between the fitted function (430, 430') and the point cloud function (410, 420). If the deviation is less than the threshold, the temporary value of the calibration parameter used to obtain the point cloud function (410, 420) can be used as the optimal value of the calibration parameter (370). If the deviation is large, the temporary value can be changed (380) to obtain new temporary spatial coordinates and a new point cloud function (410, 420). As another example of a stopping condition for the iteration, a no-improvement condition can be used to stop the iteration. For example, the iteration can be stopped if the deviation improvement between two iterations is less than an improvement threshold. For example, the Levenburg-Marquardt algorithm can be used to optimize the calibration parameter.

[0076] For example, when the fitting is complete, the optimal value of the calibration parameter (380) can be obtained as the temporary value of the calibration parameter. To determine the optimal value, it is not necessary to know in advance the distance or size of the scan geometry. This enables scene-independent calibration. Furthermore, this can be used to improve calibration accuracy because any measurement errors or limited measurement accuracy of such known dimensions or distances can be completely avoided. The calibration can utilize a single scan or multiple scans from different distances and / or orientations of the device 100 relative to the target 140. Even so, it is not necessary to know or utilize the actual distances and orientations.

[0077] Such as combination Figure 4As shown, selecting the optimal value of the calibration parameter can be used to provide the correct point cloud function 420, the correctness of which can be easily verified by scanning the calibrated device 100. The robustness of the calibration can be further improved by performing the calibration under the condition that any temporary value and / or the optimal value of the calibration parameter is greater than zero. Such constraints can be included in optimization algorithms used for calibration or for obtaining the optimal value of the calibration parameter. Alternatively or additionally, when the solid-state sensing array 150 is positioned non-parallel to the flat surface 141 of the target 140 for scanning, the calibration can be performed by scanning the target 140 having the flat surface 141 facing the laser generator 110, thereby improving the robustness of the calibration. This has been found to provide a unique scheme for obtaining the optimal value of the calibration parameter, thereby enabling reliable calibration by a single scan.

[0078] When using one or more additional sensor-specific calibration parameters, calibration can be performed in a similar manner as described above. For example, the same algorithm and / or the same cost function can be used. To improve calibration robustness, it has been found that a fixed value (e.g., zero) can be assigned to one of the additional sensor-specific parameters, such as the center sensor in array 150.

[0079] Figure 4 Two distinct point cloud functions (410, 420) obtained using two different values ​​of calibration parameters are illustrated in one embodiment. As described herein, the point cloud functions (410, 420) are obtained by scanning a flat wall using a solid-state LiDAR device 100. The horizontal axis represents a first spatial dimension (e.g., x-dimensional), while the vertical axis represents a second spatial dimension (e.g., y-dimensional). The first point cloud function 410 is obtained by an incorrectly calibrated device 100. Accordingly, the value of the calibration parameter is substantially different from the optimal value optimized using a linear function (430, 430') (in the illustration, the linear fitting function (430, 430') corresponds to a straight line between the first end 430 and the second end 430'). Conversely, the second point cloud function 420 is obtained by a correctly calibrated device 100. In the latter case, the value of the calibration parameter is the optimal value optimized using a linear function. Since the scan from the flat wall provides a curved image represented by the first point cloud function 410, the non-optimal value using the calibration parameter can be immediately observed from the scan performed by the device 100.

[0080] Therefore, as shown in any of the examples disclosed herein, the solid-state lidar device 100 can be used to obtain the spatial coordinates of a target 140 from a measured distance using a parameter α as a calibration parameter, wherein the calibration parameter can be defined as the ratio of the first sensor distance d1 to the focal length f1. When using such a device 100, calibration can be performed to determine the optimal value of the calibration parameter. The device 100 can be used for calibration upon prompting. Therefore, calibration can be performed quickly and on demand, if needed, and can also be performed by an inexperienced user.

[0081] The device 100 can be used to obtain the optimal value of the calibration parameters by acquiring multiple measurement distances to different spatial locations of the target 140. Since the different sensors of the array 150 can provide different measurement distances, a single scan of the device 100 is sufficient to calibrate the device 100, wherein multiple sensors are used to provide a measurement distance corresponding to each sensor.

[0082] Figure 5 A flowchart characterization of a method 500 for performing a solid-state lidar device according to another embodiment is shown. The method 500 can be used to calibrate the solid-state lidar device 100 and / or for scanning via the solid-state lidar device 100. The device 100 can be any of the devices shown in the examples described herein. The method 500 includes: obtaining (510) a measured distance of a target 140 from pulse time-of-flight measurements using the solid-state lidar device 100, particularly the laser generator 110 and sensors (152a-152c) in its solid-state sensing array 150. The method further includes: obtaining (520) at least one spatial coordinate of the target 140 from the measured distance using calibration parameters, which can be calibration parameters shown in any of the examples disclosed herein. According to some embodiments, based on Figure 5 The method 500 shown can be used in accordance with Figure 3 The method 300 shown can also be combined with the method according to Figure 3 The method shown in 300 extracts at least some combinations of features.

[0083] Although the subject matter of the invention has been described in language specific to structural features and / or methodological actions, it should be understood that the subject matter defined in the claims is not necessarily limited to the specific features or actions described above. Rather, the specific features and actions described above are disclosed as embodiments of the claims, and other equivalent features and actions are intended to be included within the scope of the claims.

[0084] The functions described herein may be performed at least in part by one or more computer program product components (e.g., software components). Alternatively or additionally, the functions described herein may be performed at least in part by one or more hardware logic components. For example, but not limited to, exemplary types of hardware logic components that may be used include Field-programmable Gate Arrays (FPGAs), Application-specific Integrated Circuits (ASICs), Application-specific Standard Products (ASSPs), System-on-a-chip Systems (SOCs), Complex Programmable Logic Devices (CPLDs), and Graphics Processing Units (GPUs).

[0085] It should be understood that the above advantages and benefits may relate to one embodiment or several embodiments. The embodiments are not limited to embodiments that solve any or all of the described problems, nor are they limited to embodiments that have any or all of the described advantages and benefits. Furthermore, it should be understood that a reference to "a" item may refer to one or more of these items. The term "and / or" may be used to indicate that one or more associated situations may occur, two or more associated situations may occur, or only one associated situation may occur.

[0086] The operations of the methods described herein can be performed in any suitable order, or simultaneously where appropriate. Additionally, individual blocks can be removed from any of the methods without departing from the purpose and scope of the subject matter described herein. Aspects of any of the above embodiments can be combined with aspects of any other described embodiments to form further embodiments without loss of the desired effects.

[0087] The term “comprising” is used herein to mean including identified methods, blocks or elements, but such blocks or elements do not include an exclusive list, and methods or devices may include additional blocks or elements.

[0088] It should be understood that the above description is provided by way of example only, and various modifications can be made by those skilled in the art. The foregoing specification, embodiments, and data provide a complete description of the structure and application of exemplary embodiments. Although various embodiments have been described above with a degree of specificity or in combination with one or more individual embodiments, those skilled in the art can make numerous modifications to the disclosed embodiments without departing from the spirit or scope of this specification.

Claims

1. A solid-state lidar device (100), characterized in that, include: A laser generator (110) is used to generate a pulsed laser beam (120) that can be directed toward a target (140); An optical lens device (130) is provided for collecting the laser beam (120') reflected by the target (140), the optical lens device (130) having a focal length (f1) and providing a back focal plane (135); A solid-state sensor array (150) is located on the back focal plane (135) of the optical lens device (130). The solid-state sensor array (150) includes at least a first sensor (152a) and a second sensor (152b) for detecting the reflected laser beam (120'). The first sensor (152a) and the second sensor (152b) are spaced apart from each other by a first sensor distance (d1). At least one processor (101) is used for: The measurement distance of the target (140) is obtained from the pulse time-of-flight measurement using the laser generator (110) and at least one of the first sensor (152a) and the second sensor (152b) in the solid-state sensor array (150); At least one spatial coordinate of the target (140) is obtained from the measured distance using a calibration parameter that indicates the ratio of the first sensor distance (d1) to the focal length (f1).

2. The apparatus (100) according to claim 1, characterized in that, The first sensor (152a) and the second sensor (152b) are single-photon avalanche diodes (SPADs), which are disposed on the common substrate of the solid-state sensor array (150).

3. The apparatus (100) according to claim 1 or 2, characterized in that, The solid-state sensor array (150) further includes a third sensor (152c) for detecting the reflected laser beam (120'); the first sensor (152a), the second sensor (152b) and the third sensor (152c) are arranged in a one-dimensional configuration.

4. The apparatus (100) according to claim 1 or 2, characterized in that, The solid-state sensor array (150) further includes a third sensor (152c) for detecting the reflected laser beam (120'); the second sensor (152b) and the third sensor (152c) define a second sensor distance (d2), which is equal to the first sensor distance (d1).

5. The apparatus (100) according to claim 1, characterized in that, The at least one processor (101) is configured to: obtain the at least one spatial coordinate using the optimal value of the calibration parameter, the optimal value being obtained in the following manner: Multiple measurement distances to different spatial locations of the target (140) are obtained, each measurement distance corresponding to a different sensor (152a-152c) in the solid-state sensing array (150); The optimal value is calculated by fitting a fitting function (430, 430') to a point cloud function (420) that includes the temporary spatial coordinates of the different spatial locations of the target (140), wherein the temporary spatial coordinates are obtained from the plurality of measured distances using temporary values ​​of the calibration parameters, such that the optimal value is the temporary value that optimizes the fitting.

6. The apparatus (100) according to claim 5, characterized in that, The fitting function (430, 430') refers to a linear function that can be represented as a straight line or a plane.

7. The apparatus (100) according to any one of claims 1, 2, 5 or 6, characterized in that, The at least one spatial coordinate of the target (140) is obtained from the measurement distance by modifying the measurement distance with at least one additional sensor-specific calibration parameter, the additional sensor-specific calibration parameter indicating the inaccuracy of the measurement distance of at least one sensor (152a-152c) in the solid-state sensor array (150).

8. A calibration method (300) for a solid-state lidar device, characterized in that, include: This enables the solid-state lidar device (100) according to any one of the preceding claims (310) to scan the target (140) to obtain the optimal value of the calibration parameters (370).

9. The method (300) according to claim 8, characterized in that, The target (140) includes a flat surface (141) facing the laser generator (110), wherein the laser beam (120) is reflected on the flat surface (141).

10. The method (300) according to claim 8 or 9, characterized in that, The scan is performed by a solid-state sensor array (150) positioned non-parallel to the target (140).

11. A calibration method (500) for a solid-state lidar device, characterized in that, For operating a solid-state lidar device (100), the solid-state lidar device (100) includes: A laser generator (110) is used to generate a pulsed laser beam (120) that can be directed toward a target (140); An optical lens device (130) is provided for collecting the laser beam (120') reflected by the target (140), the optical lens device having a focal length (f1) and providing a back focal plane (135); A solid-state sensor array (150) is located on the back focal plane (135) of the optical lens device (130) for detecting the laser beam (120'), wherein the solid-state sensor array (150) includes at least two sensors (152a-152c), the at least two sensors being equidistant from each other by a first sensor distance (d1) in at least one dimension; The method (500) includes: Using the laser generator (110) and the sensors (152a-152c) in the solid-state sensor array (150), the measurement distance of the target (140) is obtained (510) from the pulse time-of-flight measurement; Using a calibration parameter that indicates the ratio of the first sensor distance (d1) to the focal length (f1), at least one spatial coordinate of the target (140) is obtained from the measured distance (520).

12. The method (500) according to claim 11, characterized in that, The at least two sensors are single-photon avalanche diodes (SPADs), which are disposed on a common substrate of the solid-state sensing array (150).

13. The method (500) according to claim 11, characterized in that, The at least one spatial coordinate is obtained using the optimal value of the calibration parameter, wherein the optimal value is obtained in the following manner: Multiple measurement distances to different spatial locations of the target (140) are obtained, each measurement distance corresponding to a different sensor (152a-152c) in the solid-state sensing array (150); The optimal value is calculated by fitting a fitting function (430, 430') to a point cloud function (420) that includes the temporary spatial coordinates of the different spatial locations of the target (140), wherein the temporary spatial coordinates are obtained from the plurality of measured distances using temporary values ​​of the calibration parameters, such that the optimal value is the temporary value that optimizes the fitting.

14. The method (500) according to claim 13, characterized in that, The fitting function (430, 430') refers to a linear function that can be represented as a straight line or a plane.

15. The method (500) according to any one of claims 11 to 14, characterized in that, The at least one spatial coordinate of the target (140) is obtained from the measurement distance by modifying the measurement distance with at least one additional sensor-specific calibration parameter, the additional sensor-specific calibration parameter indicating the inaccuracy of the measurement distance of at least one sensor (152a-152c) in the solid-state sensor array (150).

16. A computer program product, characterized in that, Includes program code, which, when the computer program product is executed on a computer, is used to perform the method according to any one of claims 8 to 15.

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