Calibration method, system, device and medium for lidar

Abstract

The application provides a laser radar calibration method, system, device and medium, the laser radar calibration method comprises: configuring a delay chain-based time-to-digital conversion module inside a field programmable gate array; monitoring the time interval between the trigger output signal of the laser radar and the reference trigger signal sent by the field programmable gate array by using the time-to-digital conversion module; based on the monitored time interval, determining whether the actual light-emitting time of the laser radar has changed due to temperature drift, if yes, recalibrating the actual light-emitting time, if not, confirming that there is no temperature drift. The laser radar calibration method of the application can monitor and dynamically correct the temperature drift of the actual light-emitting time of the laser radar in real time, and improve the absolute ranging accuracy in the full-temperature range.

Description

Technical Field

[0001] This application belongs to the field of lidar technology, and relates to a lidar calibration method, and particularly to a lidar calibration method, system, device and medium. Background Technology

[0002] In LiDAR systems, the ranging accuracy and system stability of Time-of-Flight (ToF) measurement technology are core indicators for evaluating their performance. The principle of ToF ranging dictates that any minute timing error will be directly converted into distance deviation; therefore, the timing accuracy of each component is the cornerstone of achieving high-precision measurement. However, in practical engineering applications, changes in ambient temperature and the resulting temperature drift effect become one of the key bottlenecks restricting the stable output of system performance. Temperature drift affects ranging accuracy in multiple dimensions, primarily manifesting in the two core stages of reception and transmission. At the receiver, core photodetectors, such as silicon photomultiplier tubes (SiPMs) or single-photon avalanche diodes (SPADs), are extremely sensitive to temperature. Specifically, the avalanche breakdown voltage of these devices drifts significantly with temperature changes. When the operating voltage fails to adjust dynamically, it will directly lead to fluctuations in the photon detection efficiency (PDE). Instability of the PDE means that the system's response sensitivity to the echo signal changes. This change will randomly affect the judgment of the signal triggering time, ultimately manifesting as jitter in the measurement of the photon arrival time (T1), thus introducing ranging error.

[0003] Meanwhile, the timing link at the transmitting end also faces the severe challenge of temperature drift. The accuracy of the actual laser emission time (T0), which serves as the starting point for timing, directly determines the absolute accuracy of the overall ranging. However, in the transmitting link, the transmission speed of the electrical signals within the laser driver chip changes with temperature, resulting in a non-negligible timing drift between the issuance of the trigger command and the actual output of the laser pulse. This drift at T0 is a direct systematic error that cannot be corrected by algorithms even with powerful backend signal processing capabilities, thus fundamentally affecting the accuracy of the ranging results.

[0004] In recent years, with advancements in semiconductor processes and packaging technologies, the temperature drift characteristics of receiver detectors can be compensated to some extent through pre-shipment calibration and temperature look-up tables (LUTs), thus mitigating their impact. Similarly, the design of transmitter driver chips is constantly iterating to improve the robustness of their internal delays to temperature changes. However, limited by the complexity of the internal thermal gradient of the chip, the nonlinearity of device aging, and the wide operating range of the system across the entire temperature spectrum, existing technologies still struggle to completely eliminate the dynamic drift at time T0 with temperature. Especially in high-precision, long-distance measurement applications, effectively suppressing transmitter timing deviations remains a critical challenge that urgently needs to be addressed in the development of current lidar technology. Summary of the Invention

[0005] This application provides a calibration method, system, device, and medium for lidar, which addresses the problem of dynamic drift of the actual emission time of lidar with temperature in the prior art.

[0006] Firstly, this application provides a calibration method for a lidar. The lidar calibration method includes: configuring a time-to-digital converter (TDD) module based on a delay chain within a field-programmable gate array (FPGA); using the TDD module to monitor the time interval between the lidar's trigger output signal and the reference trigger signal sent by the FPGA; based on the monitored time interval, determining whether the actual emission time of the lidar has changed due to temperature drift; if so, recalibrating the actual emission time; if not, confirming that there is no temperature drift.

[0007] In one implementation of the first aspect, the time-to-digital conversion module includes a multi-level delay module, which is used to delay the trigger output signal of the lidar step by step.

[0008] In one implementation of the first aspect, the step-by-step delay of the trigger output signal of the lidar using the multi-level delay module includes: when receiving the reference trigger signal sent by the field-programmable gate array, saving the transmission state of the trigger output signal of the lidar as a thermometer code; and calculating based on the thermometer code to obtain the time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array.

[0009] In one implementation of the first aspect, the calculation based on the thermometer code to obtain the time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array includes: after passing through a first-level delay unit, the thermometer code is stored as a high level; and the time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array is obtained by conversion based on the number of high levels in the thermometer code.

[0010] In one implementation of the first aspect, determining whether the actual emission time of the lidar has changed due to temperature drift includes: determining whether the monitored time interval is consistent with the pre-calibrated reference value of the lidar; if so, it is confirmed that there is no temperature drift; if not, it is confirmed that the actual emission time has changed due to temperature drift, and the actual emission time is recalibrated.

[0011] In one implementation of the first aspect, recalibrating the actual emission time includes: when it is confirmed that the actual emission time has changed due to temperature drift, restarting the lidar until the monitored time interval stabilizes to the factory-calibrated actual emission time; or subtracting the monitored time interval in real time from the depth calculation of the lidar to compensate for the deviation of the actual emission time caused by temperature drift.

[0012] Secondly, this application provides a calibration system for a lidar. The lidar calibration system includes: a field-programmable gate array (FPGA); a time-to-digital converter (TD-SCDMA) module, disposed within the FPGA, configured to monitor the time interval between the lidar's trigger output signal and a reference trigger signal sent by the FPGA; and based on the monitored time interval, determine whether the actual emission time of the lidar has changed due to temperature drift. If so, the actual emission time is recalibrated; otherwise, it is confirmed that there is no temperature drift.

[0013] In one implementation of the second aspect, the calibration system of the lidar further includes a laser driver chip configured to receive trigger pulse signals and gating signals sent by the field-programmable gate array, so as to drive the laser corresponding to the gating signal to work.

[0014] Thirdly, this application provides an electronic device. The electronic device includes: a memory for storing a computer program; and a processor for executing the computer program stored in the memory to cause the electronic device to perform the calibration method for a lidar as described in any one of the first aspects.

[0015] Fourthly, this application provides a computer-readable storage medium. The computer-readable storage medium stores a computer program that, when executed by a processor, implements the calibration method for the lidar described in any one of the first aspects.

[0016] As described above, the calibration method, system, device, and medium for lidar described in this application have the following beneficial effects:

[0017] The time interval between the trigger output signal of the lidar and the trigger signal of the field-programmable gate array is monitored by the time-to-digital conversion module to determine whether temperature drift occurs. The actual emission time of the lidar with temperature drift is recalibrated, which significantly offsets the influence of temperature on the propagation speed of the drive link signal. This ensures the accuracy and repeatability of the laser emission time, enabling the radar system to maintain the original ranging benchmark in extreme high or low temperature environments, and greatly improves the absolute ranging accuracy across the entire temperature range. Attached Figure Description

[0018] Figure 1 The diagram shown illustrates an application scenario of the lidar calibration method described in this application.

[0019] Figure 2 The diagram shown is a structural schematic of the end-to-cloud interaction scenario described in the embodiments of this application.

[0020] Figure 3 The diagram shown is a flowchart illustrating the calibration method for a lidar as described in an embodiment of this application.

[0021] Figure 4 The diagram shown is a schematic representation of the signal flow of the lidar described in the embodiments of this application.

[0022] Figure 5 The diagram shown is an internal schematic of the time-to-digital conversion module described in an embodiment of this application.

[0023] Figure 6 The diagram shown is a structural schematic of the lidar calibration system described in an embodiment of this application.

[0024] Figure 7 The diagram shown is a structural schematic of the electronic device described in an embodiment of this application. Detailed Implementation

[0025] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0026] It should be noted that in the embodiments of this application, the words "optionally" or "for example" indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "optionally" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the words "optionally" or "for example" is intended to present the relevant concepts in a specific manner.

[0027] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0028] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0029] In the digital signal processing link of a LiDAR system, two independent clock domains are involved. Data interaction between the LiDAR clock domain and the FPGA clock domain is often hampered by metastability issues, which are a key factor affecting the system's timing stability. Taking the trigger output signal from the LiDAR chip as an example, this signal resides in the LiDAR clock domain and needs to be sampled by the FPGA clock for timing synchronization. Since the LiDAR clock frequency is typically higher than the FPGA clock frequency, this constitutes data transfer from a fast clock domain to a slow clock domain, which exacerbates the probability of metastability. Specifically, when the transition edge of the trigger output signal from low to high does not meet the setup or hold time requirements of the FPGA clock, the signal cannot be stably sampled within the current FPGA clock cycle. The FPGA's trigger output signal will be delayed until the next clock cycle, introducing timing uncertainty for a complete clock cycle. Conversely, if the transition edge meets the timing constraints, the FPGA's trigger output signal can respond immediately within the current clock cycle. This difference directly leads to a periodic drift in the actual emission time (T0) of the laser under different temperature conditions. It is worth noting that the transition rate of the signal edge is significantly affected by temperature—lower carrier mobility at high temperatures results in a slower edge, while the opposite is true at low temperatures. This temperature-dependent edge characteristic causes the settling / holding time to change with temperature, resulting in a non-periodic jump in T0 at different operating temperatures. Since T0 is the starting point for time-of-flight measurement, its uncertainty directly translates into ranging error, severely restricting the absolute accuracy and consistency of the system across the entire temperature range, becoming a core timing problem that urgently needs to be solved in the design of high-precision lidar.

[0030] To address at least the aforementioned issues, this application provides a calibration method for a lidar. The lidar calibration method includes: configuring a time-to-digital converter (TDD) module based on a delay chain within a field-programmable gate array (FPGA); using the TDD module to monitor the time interval between the lidar's trigger output signal and the reference trigger signal sent by the FPGA; and based on the monitored time interval, determining whether the actual emission time of the lidar has changed due to temperature drift. If so, the actual emission time is recalibrated; otherwise, it is confirmed that there is no temperature drift.

[0031] In this embodiment, a time-to-digital converter is used to monitor the time interval between the trigger output signal of the lidar and the trigger signal of the field-programmable gate array to determine whether temperature drift occurs. The actual emission time of the lidar that has temperature drift is then recalibrated, which significantly offsets the influence of temperature on the propagation speed of the drive link signal. This ensures the accuracy and repeatability of the laser emission time, enabling the radar system to maintain the original ranging benchmark even in extreme high or low temperature environments, and greatly improves the absolute ranging accuracy across the entire temperature range.

[0032] Figure 1 This diagram illustrates an application scenario of the lidar calibration method described in this application. The lidar calibration device 1 can be used to implement the lidar calibration method provided in this application embodiment, but the application scenarios of the lidar calibration method provided in this application embodiment are not limited to... Figure 1 The calibration device 1 for the lidar is shown. (For example...) Figure 1 As shown, the lidar calibration device 1 includes a lidar device 11, a local processor 12, and a display terminal 13. The lidar calibration method provided in this embodiment can be applied to the local processor 12.

[0033] in, Figure 1 The local processor 12 can be a single local processor, a cluster of multiple local processors, or a cloud computing center, etc., and is not specifically limited here. Although Figure 1 Only one radar device 11, one local processor 12, and one display terminal 13 are shown, but it should be understood that... Figure 1 The examples in this paper are only for understanding this solution. The specific number of local processors 12 and display terminals 13 should be flexibly determined based on the actual situation.

[0034] In some other implementations, the lidar calibration device 1 may not include the display terminal 13, but only a local processor 12 with display function and a lidar device 11. The lidar calibration method provided in this application embodiment can be applied to the local processor 12. The local processor 12 with display function may include a tablet computer, a laptop computer, a PDA, a mobile phone, a personal computer, and a voice interaction device, or it may be a monitoring device, a face recognition device, etc., which are not limited here.

[0035] In some other implementations, the lidar calibration method described in this application can be applied to edge-cloud interaction scenarios. Figure 2 The diagram shown is a structural schematic of the end-to-cloud interaction scenario described in an embodiment of this application. For example... Figure 2As shown, the terminal-cloud interaction system 2 includes a terminal 20 and a cloud server 21. The terminal 20 and the cloud server 21 can communicate with each other, and the communication method is not limited to wired or wireless.

[0036] The terminal 20 can be mobile or fixed. For example, it can be a wireless terminal or a wired terminal. A wireless terminal can refer to a device with wireless transceiver capabilities, which can be deployed indoors, outdoors, and in industrial workshops. The terminal 20 can be a mobile phone, tablet computer, laptop computer, etc., and is not limited thereto. The cloud server 21 can include one or more servers, or one or more processing nodes, or one or more virtual machines running on the server. The cloud server 21 can also be referred to as a server cluster, management platform, data processing center, etc., and is not limited thereto in this embodiment.

[0037] The technical solutions in the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0038] The following embodiments of this application provide a calibration method for lidar, which, for example, can be achieved through... Figure 1 The local processor 12 shown Figure 2 The cloud server 21 shown is used to implement this. Figure 3 The diagram shown is a schematic flowchart of the lidar calibration method described in an embodiment of this application. Figure 3 As shown, the calibration method of the lidar includes steps S11 to S13.

[0039] Step S11: Configure a time-to-digital converter based on a delay chain inside the field-programmable gate array.

[0040] Step S12: Use the time-to-digital converter module to monitor the time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array.

[0041] Step S13: Based on the monitored time interval, determine whether the actual emission time of the lidar has changed due to temperature drift. If so, recalibrate the actual emission time; otherwise, confirm that there is no temperature drift.

[0042] Among some possible implementations, Figure 4 This diagram illustrates the signal flow of the lidar described in an embodiment of this application. Figure 4As shown, both linear and area-array lidar systems are divided into multiple partitions, such as 1×16 or 32×16, to avoid high reflection expansion. When the SPAD chip only supports trigger output signals from 4 or 8 lidar systems, an FPGA (Field-Programmable Gate Array) is needed as the main controller. This FPGA controls the laser emission by selecting or switching the transmission path using the control signal TxSel. Specifically, the FPGA sends a synchronization signal Sync and an input signal Trigin to control the SPAD timing trigger. After receiving the FPGA's input signal Trigin, the SPAD sends a trigger output signal Trigo. The FPGA, upon receiving the Trigo signal, sends a trigger signal TxTrig to drive the laser driver chip, simultaneously sending a strobe signal TxSel to select the laser to be activated. This involves sampling from two clock domains: the SPAD and the FPGA. The SPAD's system clock is different from the FPGA's clock, and the SPAD's system clock is faster than the FPGA's clock, resulting in a problem of a slow clock acquiring a fast clock signal. If the SPAD's trigger output signal Trigo transitions from low to high in time that does not meet the setup and hold time, the signal cannot be sampled in the first sampling cycle of the FPGA clock, and the trigger signal Tx Trig will be generated in the next FPGA clock cycle. Furthermore, since the speed at which the signal transitions from a falling edge to a rising edge is affected by temperature, the actual emission time of the laser may differ by one cycle at different temperatures, leading to varying accuracy in the lidar's calculations. Therefore, a time-to-digital converter (TDD) module based on a delay chain is configured inside the FPGA. This module monitors the time interval between the lidar's trigger output signal and the trigger signal sent by the FPGA. The trigger output signal Trigo is delayed stage by stage by a multi-stage delay module. When the trigger signal Tx Trig arrives, Trigo is sampled into a register and stored as a temperature code. Based on the time interval of the temperature code, it is determined whether the actual emission time of the lidar has changed due to temperature drift. If so, the actual emission time is recalibrated; otherwise, it is confirmed that there is no temperature drift.

[0043] In this embodiment, a time-to-digital converter is used to monitor the time interval between the trigger output signal of the lidar and the trigger signal of the field-programmable gate array to determine whether temperature drift occurs. The actual emission time of the lidar that has temperature drift is then recalibrated, which significantly offsets the influence of temperature on the propagation speed of the drive link signal. This ensures the accuracy and repeatability of the laser emission time, enabling the radar system to maintain the original ranging benchmark even in extreme high or low temperature environments, and greatly improves the absolute ranging accuracy across the entire temperature range.

[0044] In one embodiment of this application, the time-to-digital conversion module includes a multi-level delay module, which is used to delay the trigger output signal of the lidar step by step.

[0045] In some possible implementations, the input of the multi-stage delay module receives the trigger output signal Trigo from the SPAD, which propagates sequentially through the delay chain from the first stage to the Nth stage. At the rising edge of each FPGA clock cycle, the level states of the N delay nodes are simultaneously latched in parallel, resulting in an N-bit thermometer code. Because the Trigo signal's transition edge propagates through the delay chain, the thermometer code exhibits a sequence of consecutive "0"s followed by a sequence of consecutive "1"s. The transition boundary position indicates the precise phase position of the Trigo signal's transition edge within the current FPGA clock cycle.

[0046] In this embodiment, the propagation position of the transition edge of the Trigo signal in the delay chain is digitized, thereby achieving accurate capture of the metastable edge of the SPAD trigger signal and eliminating clock cycle-level uncertainty caused by the failure to meet the cross-clock domain sampling trigger condition.

[0047] In one embodiment of this application, the step-by-step delay of the trigger output signal of the lidar using the multi-level delay module includes: when receiving the reference trigger signal sent by the field-programmable gate array, saving the transmission state of the trigger output signal of the lidar as a thermometer code; and calculating based on the thermometer code to obtain the time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array.

[0048] Among some possible implementations, Figure 5 The diagram shown is an internal schematic of the time-to-digital conversion module described in an embodiment of this application. Figure 5 As shown, the time-to-digital conversion module based on the delay chain is located inside the FPGA. The multi-level delay module consists of several cascaded delay units, each with an equal unit delay time. When the FPGA sends a reference trigger signal, the multi-level delay module immediately starts the step-by-step propagation of the Trigger 0 edge of the input LiDAR trigger output signal. During this propagation process, the multi-level delay module saves the current propagation state of the trigger output signal edge after passing through each delay unit in real time, in the form of the high and low levels of the tap outputs of each delay unit. Since the signal edge propagates unidirectionally step-by-step in the delay chain, the level states of each tap will exhibit a boundary characteristic of consecutive "0"s and consecutive "1"s, forming a set of thermometer codes. Calculations are performed based on the thermometer codes to obtain the time interval between the LiDAR trigger output signal and the reference trigger signal sent by the FPGA.

[0049] In one embodiment of this application, the calculation based on the thermometer code to obtain the time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array includes: after passing through a delay unit, the thermometer code is stored as a high level. The time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array is obtained by converting the number of high levels in the thermometer code.

[0050] In some possible implementations, by detecting the precise boundary position of the transition from "0" to "1" in the thermometer code using decoding logic, the specific number of stages the trigger output signal edge has propagated in the delay chain can be determined. Finally, by multiplying this propagation stage number by the inherent unit delay time of each delay unit, the time interval between the lidar's trigger output signal and the reference trigger signal sent by the FPGA can be accurately calculated.

[0051] In this embodiment, without relying on a high-frequency frequency multiplication clock, the time resolution can be improved to the picosecond level of a single-stage delay unit simply by quantizing the propagation depth of the signal in the delay chain.

[0052] In one embodiment of this application, determining whether the actual emission time of the lidar has changed due to temperature drift includes: determining whether the monitored time interval is consistent with the pre-calibrated reference value of the lidar; if yes, it is confirmed that there is no temperature drift; if no, it is confirmed that the actual emission time has changed due to temperature drift, and the actual emission time is recalibrated.

[0053] In some possible implementations, during the factory calibration phase, a high-precision time-to-digital converter (TDD) measures and records the initial time interval between the actual laser emission moment and the rising edge of the FPGA system clock. This value is stored as a reference calibration value in a non-volatile register within the FPGA. During actual operation of the lidar, the FPGA monitors the actual emission moment corresponding to the current emission pulse in real time and calculates the real-time time interval between this actual emission moment and the rising edge of the current system clock using the TDD. The real-time monitored time interval is compared with the pre-stored reference calibration value. If the two are consistent or less than a preset tolerance threshold, it is confirmed that there is no temperature drift. If the two are inconsistent or greater than or equal to the preset tolerance threshold, it is confirmed that the actual emission moment has changed due to temperature drift, and the actual emission moment is recalibrated.

[0054] In this embodiment, the system can ensure that subsequent flight time measurements are always calculated based on the accurate actual emission time, effectively eliminating the influence of temperature drift on the ranging starting point.

[0055] In one embodiment of this application, recalibrating the actual emission time includes: when it is confirmed that the actual emission time has changed due to temperature drift, restarting the lidar until the monitored time interval stabilizes to the factory-calibrated actual emission time. Alternatively, in the lidar's depth calculation, the monitored time interval is subtracted in real time to compensate for the deviation of the actual emission time caused by temperature drift.

[0056] In some possible implementations, when it is confirmed that the actual emission time has changed due to temperature drift, the lidar is restarted until the monitored time interval stabilizes at the factory-calibrated actual emission time. Specifically, the FPGA records the currently monitored real-time time interval. A reset command is sent to the power management unit of the lidar system to perform a system soft restart. During the restart process, the laser driver chip, SPAD detection chip, and time-to-digital converter module are all reinitialized and loaded with default configuration parameters. After the restart is complete, the FPGA restarts real-time monitoring of the actual emission time of the laser, continuously acquiring the current time interval value and comparing each acquisition result with the previous value. Only when the maximum deviation between N consecutive measurements is less than a preset tolerance threshold, and the stable value returns to the vicinity of the factory calibration, is it confirmed that the system timing link has recovered to a stable state, and recalibration is completed. If, after multiple attempts after restarting, the time interval still cannot stably return to the vicinity of the factory calibration value, the system determines that the temperature drift exceeds the recoverable range, records an error flag, and reports it to the host computer, prompting that factory recalibration is required.

[0057] In this embodiment, the forced recovery of the entire link timing state is achieved through hardware reset, effectively eliminating the impact of cumulative temperature drift on the ranging starting point.

[0058] In other possible implementations, when the FPGA confirms that the actual emission time has changed due to temperature drift, the system does not perform a restart operation. Instead, it subtracts the monitored time interval deviation in real time during the LiDAR's depth calculation to dynamically compensate for the impact of temperature drift on ranging accuracy. Specifically, the FPGA is internally configured with a dynamic offset register to store the time offset of the latest monitored actual emission time relative to the reference calibration value. When the LiDAR performs ranging, the depth calculation unit within the FPGA reads the current offset from the dynamic offset register and performs compensation calculations before converting the original time data into a distance value, outputting the corrected distance value.

[0059] In this embodiment, the temperature drift compensation mechanism does not require interruption of the normal operation of the lidar, and can complete the online calibration of calibration drift in the context of continuous system operation, ensuring the continuity and real-time nature of depth data output.

[0060] Figure 6The diagram shown is a structural schematic of the lidar calibration system described in an embodiment of this application. Figure 6 As shown, the calibration system 100 of the lidar includes a field-programmable gate array 110 and a time-to-digital converter module 120.

[0061] The time-to-digital conversion module 120 is located inside the field-programmable gate array 110 and is configured to monitor the time interval between the trigger output signal of the lidar and the trigger signal sent by the field-programmable gate array 110; and based on the monitored time interval, determine whether the actual emission time of the lidar has changed due to temperature drift. If so, the actual emission time is recalibrated; if not, it is confirmed that there is no temperature drift.

[0062] In some possible implementations, the lidar calibration system 100 is used to eliminate the influence of temperature drift on the ranging starting point, ensuring the accuracy and long-term stability of time-of-flight measurement. The time-to-digital converter module 120 is located inside the field-programmable gate array (FPGA) 110 and implemented through internal logic resources. Its input is connected to the trigger output pin of the SPAD chip, and its reference clock is connected to the internal system clock of the FPGA 110. During system operation, the time-to-digital converter module 120 is configured to monitor the time interval between the trigger output signal output by the SPAD chip and the reference trigger signal sent by the FPGA 110 in real time, and compare it with the pre-calibrated reference value of the lidar. If the monitored time interval is consistent with the pre-calibrated reference value or the difference is less than a preset tolerance threshold, it is confirmed that there is no temperature drift in the current system, and the existing parameters are maintained for continued operation. If they are inconsistent, it is confirmed that the actual emission time of the laser has changed due to temperature drift, and the FPGA 110 recalibrates the actual emission time to correct the error.

[0063] In one embodiment of this application, please refer to... Figure 6 The calibration system 100 of the lidar also includes a laser driver chip 130. The laser driver chip 130 is configured to receive trigger pulse signals and gating signals sent by the field programmable gate array 110, so as to drive the laser corresponding to the gating signal to work.

[0064] In some possible implementations, the laser driver chip 130 receives a trigger pulse signal and a gating signal sent by the field-programmable gate array 110. The gating signal is used to select the target laser channel to be driven in the multi-channel laser array, and the trigger pulse signal is used to trigger the laser driver chip 130 to generate a driving current to drive the laser corresponding to the gating signal to emit a laser pulse. The emission time of this laser pulse is the actual emission time.

[0065] In this embodiment, the lidar calibration system 100 realizes real-time monitoring and dynamic correction of the temperature at the actual emission moment, effectively suppressing the drift of the ranging starting point caused by the change of temperature in the drive link delay, and providing a stable and accurate timing reference for subsequent measurements.

[0066] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, or methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of modules / units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or units may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection of apparatuses or modules or units may be electrical, mechanical, or other forms.

[0067] The modules / units described as separate components may or may not be physically separate. The components shown as modules / units may or may not be physical modules; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules / units can be selected to achieve the objectives of the embodiments of this application, depending on actual needs. For example, the functional modules / units in the various embodiments of this application may be integrated into one processing module, or each module / unit may exist physically separately, or two or more modules / units may be integrated into one module / unit.

[0068] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0069] This application also provides an electronic device. Figure 7 The diagram shown is a structural schematic of the electronic device described in an embodiment of this application. Figure 7 As shown, in this embodiment, the electronic device 700 includes a memory 710 and a processor 720.

[0070] The memory 710 is used to store computer programs; preferably, the memory 710 includes various media that can store program code, such as ROM, RAM, magnetic disk, USB flash drive, memory card or optical disk.

[0071] Specifically, memory 710 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) and / or cache memory. Electronic device 700 may further include other removable / non-removable, volatile / non-volatile computer system storage media. Memory 710 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the embodiments of this application. It is understood that memory 710 may be volatile memory or non-volatile memory, or both. Non-volatile memory may be read-only memory (ROM) or programmable read-only memory (PROM), which serves as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM) and synchronous static random access memory (SSRAM). The memories described in the embodiments of this invention are intended to include, but are not limited to, these and any other suitable categories of memory.

[0072] The processor 720 is connected to the memory 710 and is used to execute the computer program stored in the memory 710 so that the electronic device 700 performs the calibration method of the lidar described in any embodiment of this application.

[0073] Optionally, the processor 720 may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0074] Optionally, the electronic device 700 in this embodiment may further include a display 730. The display 730 is communicatively connected to the memory 710 and the processor 720, and is used to display the relevant graphical user interface (GUI) of the lidar calibration method described in this application embodiment.

[0075] This application also provides a computer-readable storage medium storing a computer program. When executed by a processor, the program implements the lidar calibration method described in any embodiment of this application. Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing a processor. The program can be stored in a computer-readable storage medium, which is a non-transitory medium, such as random access memory, read-only memory, flash memory, hard disk, solid-state drive, magnetic tape, floppy disk, optical disk, and any combination thereof. The storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., digital video disc (DVD)), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0076] As used in this specification, the terms "component," "module," "system," etc., are used to refer to computer-related entities, hardware, firmware, combinations of hardware and software, software, or software in execution. For example, a component can be, but is not limited to, a process running on a processor, a processor, an object, an executable file, an execution thread, a program, and / or a computer. As illustrated, applications running on computing devices and computing devices can both be components. One or more components may reside in a process and / or an execution thread, and components may be located on a single computer and / or distributed among two or more computers. Furthermore, these components can be executed from various computer-readable media on which various data structures are stored. Components can communicate, for example, via local and / or remote processes based on signals having one or more data packets (e.g., data from two components interacting with another component between a local system, a distributed system, and / or a network, such as the Internet interacting with other systems via signals).

[0077] The descriptions of the processes or structures corresponding to the above figures each have their own emphasis. For parts of a process or structure that are not described in detail, please refer to the relevant descriptions of other processes or structures.

[0078] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A calibration method for a lidar, characterized in that, include: Configure a time-to-digital converter module based on a delay chain inside the field-programmable gate array; The time-to-digital converter module is used to monitor the time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array. Based on the monitored time interval, it is determined whether the actual emission time of the lidar has changed due to temperature drift. If so, the actual emission time is recalibrated; otherwise, it is confirmed that there is no temperature drift.

2. The calibration method for a lidar according to claim 1, characterized in that, The time-to-digital conversion module includes a multi-level delay module, which is used to delay the trigger output signal of the lidar step by step.

3. The calibration method for lidar according to claim 2, characterized in that, The step-by-step delay of the trigger output signal of the lidar using the multi-stage delay module includes: When the reference trigger signal sent by the field programmable gate array is received, the transmission status of the trigger output signal of the lidar is saved as a thermometer code; The time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array is obtained by calculation based on the thermometer code.

4. The calibration method for a lidar according to claim 3, characterized in that, The time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array is calculated based on the thermometer code, including: After passing through a first-level delay unit, the thermometer code is stored as a high level; The time interval between the trigger output signal of the lidar and the reference trigger signal sent by the field-programmable gate array is obtained by converting the number of high-level signals in the thermometer code.

5. The calibration method for a lidar according to claim 1, characterized in that, Determining whether the actual emission time of a lidar changes due to temperature drift includes: Determine whether the monitored time interval is consistent with the pre-calibrated reference value of the lidar. If yes, confirm that there is no temperature drift. If no, confirm that the actual emission time has changed due to temperature drift and recalibrate the actual emission time.

6. The calibration method for a lidar according to claim 1, characterized in that, Recalibrating the actual emission time includes: When it is confirmed that the actual emission time has changed due to temperature drift, the lidar is restarted until the monitored time interval stabilizes at the factory-calibrated actual emission time; or In the depth calculation of the lidar, the monitored time interval is subtracted in real time to compensate for the deviation caused by temperature drift at the actual emission time.

7. A calibration system for a lidar, characterized in that, include: Field-programmable gate arrays (FPGAs); The time-to-digital conversion module, located inside the field-programmable gate array (FPGA), is configured to monitor the time interval between the trigger output signal of the lidar and the reference trigger signal sent by the FPGA; and based on the monitored time interval, determine whether the actual emission time of the lidar has changed due to temperature drift. If so, the actual emission time is recalibrated; otherwise, it is confirmed that there is no temperature drift.

8. The calibration system for a lidar according to claim 7, characterized in that, Also includes: The laser driver chip is configured to receive trigger pulse signals and gating signals sent by the field-programmable gate array to drive the laser corresponding to the gating signal to work.

9. An electronic device, characterized in that, The electronic device includes: Memory, used to store computer programs; A processor for executing a computer program stored in the memory to cause the electronic device to perform the calibration method for a lidar as described in any one of claims 1 to 6.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the calibration method for the lidar as described in any one of claims 1 to 6.

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