A method and apparatus for distance measurement of a time-of-flight module

Abstract

The application relates to the technical field of time-of-flight ranging, and discloses a ranging method and device of a time-of-flight module, which comprises the following steps: respectively presetting a first linear relationship between clock-related data of a clock source in the time-of-flight module and an environmental temperature and a second linear relationship between dark counts and the environmental temperature, determining a current temperature value corresponding to current clock-related data according to the first linear relationship, and determining current dark counts corresponding to the current temperature value according to the second linear relationship, so that the current dark counts are removed from photon counts collected by the time-of-flight module to determine the actual distance between the time-of-flight module and a measured object. Therefore, the current dark counts generated by the time-of-flight module under the current clock-related data can be quickly determined through the common influencing factor of the clock-related data and the dark counts, i.e. the environmental temperature, so that the dark counts can be removed during ranging, the influence of the dark counts on the calculation of the actual distance is overcome, and the ranging accuracy of the time-of-flight module is improved.

Description

Technical Field

[0001] This application relates to the field of time-of-flight ranging technology, and in particular to a ranging method and apparatus for a time-of-flight module. Background Technology

[0002] A Time-of-Flight (TOF) module comprises a Vertical Cavity Surface Emitting Laser (VCSEL), a Single Photon Avalanche Diode (SPAD), and a Time-to-Digital Converter (TDC). By calculating the time difference between the emitted light from the VCSEL and the reflected light from the object being measured received by the SPAD, and analyzing the distribution of SPAD photon reception times statistically analyzed by the TDC, the distance between the TOF module and the object being measured can be determined, thereby obtaining the object's depth information. Therefore, TOF modules can be used in technical fields such as measuring the actual distance to an object to achieve single-point focusing in smartphone cameras or obstacle avoidance in robots.

[0003] Besides the avalanche effect of SPADs caused by photons, which leads to TDC (Time-of-Concentration) counting, the thermal effects of various devices in the absence of incident light also contribute to TDC counting. This resulting TDC count is called the dark count, which refers to the average value of the normal SPAD counts in the TOF module when there is no incident light. Therefore, TDC counting typically includes both the dark count and the count during normal photon reception. When the dark count is too large, it can overwhelm the true signal, thus reducing the accuracy of ranging.

[0004] Therefore, accurately eliminating blind counts and improving the ranging accuracy and reliability of time-of-flight modules is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this application is to provide a distance measurement method and apparatus for a time-of-flight module, which proposes dark counting to improve the accuracy of actual distance measurement when measuring the actual distance between the time-of-flight module and the object being measured.

[0006] To address the aforementioned technical problems, this application provides a ranging method for a time-of-flight module, comprising:

[0007] The first linear relationship between clock-related data of the clock source in the preset flight time module and ambient temperature;

[0008] Based on the first linear relationship, determine the current temperature value corresponding to the current clock-related data;

[0009] presetting a second linear relationship between the dark count of the time-of-flight module and the ambient temperature;

[0010] determining a current dark count corresponding to the current temperature value according to the second linear relationship;

[0011] eliminating the current dark count from the photon count collected from the time-of-flight module to determine the actual distance between the time-of-flight module and the measured object.

[0012] Preferably, the presetting a second linear relationship between the dark count of the time-of-flight module and the ambient temperature comprises:

[0013] clearing historical photon counts in the time-of-flight module upon receiving a dark count statistics instruction;

[0014] opening each SPAD in the time-of-flight module in turn, and closing the previous SPAD each time a next SPAD is opened, and performing photon count data collection once after each opening of a SPAD;

[0015] statistically summing photon counts of all the SPADs to obtain a dark count value corresponding to the current ambient temperature;

[0016] storing the current ambient temperature and the corresponding dark count value into a first record table;

[0017] adjusting the current ambient temperature and entering the step of clearing historical photon counts in the time-of-flight module;

[0018] modeling data in the first record table to obtain the second linear relationship.

[0019] Preferably, before the clearing of the historical photon counts in the time-of-flight module, the method further comprises:

[0020] closing all the SPADs;

[0021] performing photon count data collection once;

[0022] Further, after the clearing of the historical photon counts in the time-of-flight module, the method further comprises:

[0023] after a second preset time length, entering the step of opening each SPAD in the time-of-flight module in turn, and closing the previous SPAD each time a next SPAD is opened, and performing photon count data collection once after each opening of a SPAD.

[0024] Preferably, before the step of statistically summing photon counts of all the SPADs to obtain a dark count value corresponding to the current ambient temperature, the method further comprises:

[0025] determining whether each of the SPADs performs a photon counting data collection;

[0026] If yes, entering a step of summing photon counts of all the SPADs to obtain a dark count value corresponding to the current ambient temperature;

[0027] If no, entering a step of opening the next SPAD and closing the previous SPAD.

[0028] Preferably, when the time-of-flight module includes two clock sources, the first linear relationship between clock-related data of the clock source in the preset time-of-flight module and the ambient temperature includes:

[0029] Respectively collecting clock edges of each of the clock sources in a first preset time length to obtain a first clock number and a second clock number;

[0030] Storing a difference between the first clock number and the second clock number and a corresponding relationship with the current ambient temperature in a second record table;

[0031] Adjusting the current ambient temperature and entering the step of respectively collecting clock edges of each of the clock sources in a preset time length to obtain a first clock number and a second clock number;

[0032] Determining the first linear relationship according to the corresponding relationship between each clock number difference and the ambient temperature in the second record table.

[0033] Preferably, when the time-of-flight module includes one clock source, the first linear relationship between clock-related data of the clock source in the preset time-of-flight module and the ambient temperature includes:

[0034] Obtaining a current clock frequency of the clock source;

[0035] Storing a corresponding relationship between the current clock frequency and the current ambient temperature in a second record table;

[0036] Adjusting the current ambient temperature and entering the step of obtaining the current clock frequency of the clock source;

[0037] Determining the first linear relationship according to each of the corresponding relationships in the second record table.

[0038] Preferably, the second linear relationship between the dark count of the preset time-of-flight module and the ambient temperature includes:

[0039] Upon receiving a dark count statistical instruction, clearing historical photon counts in the time-of-flight module;

[0040] opening all SPADs in the time-of-flight module, and performing a photon counting data acquisition after each of the SPADs is opened;

[0041] summing photon counts of all the SPADs to obtain a corresponding dark count value at the current ambient temperature;

[0042] storing the current ambient temperature and the corresponding dark count value into a first record table;

[0043] adjusting the current ambient temperature, and entering the step of clearing the historical photon counts in the time-of-flight module;

[0044] modeling data in the first record table to obtain the second linear relationship.

[0045] Preferably, the preset second linear relationship between the dark count of the time-of-flight module and the ambient temperature comprises:

[0046] receiving a dark count statistic instruction, and clearing the historical photon counts in the time-of-flight module;

[0047] opening the to-be-used SPADs in the time-of-flight module in sequence, and closing a previous to-be-used SPAD when a next to-be-used SPAD is opened, and performing a photon counting data acquisition after each to-be-used SPAD is opened;

[0048] summing photon counts of all the to-be-used SPADs to obtain a corresponding dark count value at the current ambient temperature;

[0049] storing the current ambient temperature and the corresponding dark count value into a first record table;

[0050] adjusting the current ambient temperature, and entering the step of clearing the historical photon counts in the time-of-flight module;

[0051] modeling data in the first record table to obtain the second linear relationship.

[0052] Preferably, the current dark count is removed from the photon counts collected from the time-of-flight module to determine the actual distance between the time-of-flight module and the measured object, and the method comprises:

[0053] obtaining an original histogram of photon counts;

[0054] removing the current dark count from the original histogram to obtain a target histogram;

[0055] performing peak searching on the target histogram to determine the actual distance.

[0056] To solve the above technical problems, the application further provides a distance measuring device of a time-of-flight module, comprising:

[0057] A preset processing module is configured to preset a first linear relationship between clock-related data of a clock source in the time-of-flight module and an ambient temperature, and preset a second linear relationship between dark counts of the time-of-flight module and the ambient temperature.

[0058] A determination module is configured to determine a current temperature value corresponding to the current clock-related data according to the first linear relationship, and determine a current dark count corresponding to the current temperature value according to the second linear relationship.

[0059] A rejection module is configured to reject the current dark count from photon counts collected by the time-of-flight module, so as to determine an actual distance between the time-of-flight module and a measured object.

[0060] The application provides a distance measuring method of a time-of-flight module, comprising: presetting a first linear relationship between clock-related data of a clock source in the time-of-flight module and an ambient temperature, and presetting a second linear relationship between dark counts of the time-of-flight module and the ambient temperature, determining a current temperature value corresponding to the current clock-related data according to the first linear relationship, determining a current dark count corresponding to the current temperature value according to the second linear relationship, and rejecting the current dark count from photon counts collected by the time-of-flight module, so as to determine an actual distance between the time-of-flight module and a measured object.

[0061] Therefore, the application can quickly determine a current temperature value corresponding to current clock-related data according to a common influencing factor, i.e., the ambient temperature, by presetting the relationship between the clock-related data and the ambient temperature, and the relationship between the dark counts and the ambient temperature, and further determine the current dark count generated by the current time-of-flight module at the current temperature value according to the linear relationship between the temperature and the dark counts, so as to reject the dark counts during distance measurement, overcome the influence of the dark counts on the calculation of the actual distance, and further improve the distance measuring accuracy of the time-of-flight module.

[0062] In addition, the application further provides a distance measuring device of a time-of-flight module, which corresponds to the distance measuring method of the time-of-flight module and has the same effect. BRIEF DESCRIPTION OF DRAWINGS

[0063] To more clearly illustrate the embodiments of the application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0064] Figure 1A working principle diagram of a time-of-flight module provided in the application;

[0065] Figure 2 A flowchart of a ranging method of a time-of-flight module provided in the application;

[0066] Figure 3 A linear relationship diagram of dark counts and ambient temperature provided in the application;

[0067] Figure 4 A schematic diagram of a photon counting histogram provided in the application;

[0068] Figure 5 A structural diagram of a ranging device of a time-of-flight module provided in the application. DETAILED DESCRIPTION

[0069] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0070] The core of the application is to provide a ranging method and device of a time-of-flight module, to determine the linear relationship between clock-related data in the time-of-flight module and ambient temperature, and the linear relationship between dark counts and ambient temperature, to determine the dark counts corresponding to the current clock-related data according to the common ambient temperature influencing factor, and to remove the dark counts to improve the accuracy of measuring the actual distance between the time-of-flight module and the measured object.

[0071] In order for those skilled in the art to better understand the application scheme, the application will be further described in detail below with reference to the drawings and specific embodiments.

[0072] The TOF module includes a VCSEL, a SPAD and a TDC. The TOF determines the distance between the module and the measured object by calculating the time difference between the emitted light and the reflected light of the measured object, thereby obtaining the depth information of the measured object. Figure 1 A working principle diagram of a time-of-flight module provided in the application, as shown in Figure 1As shown, the light emitted by the VCSEL hits the measured object, and then the light is reflected into the lens. The SPAD is originally in the Geiger mode. After receiving a single photon, the SPAD undergoes avalanche. At this time, the voltage clamped between the two ends of the diode in the SPAD triggers a drop. After being measured by the voltage measurer, an output pulse signal is generated, which is transmitted to the TDC to trigger the TDC to stop counting. Thus, the TOF module can be used to measure the actual distance from the measured object to realize the single-point focusing of the smartphone camera or the obstacle avoidance of the robot in the technical field.

[0073] In addition to the avalanche of the SPAD caused by the received photons, the thermal effect of each device will also cause the TDC to count when there is no incident light. At this time, the TDC count generated is the dark count, wherein the dark count refers to the average value of the normal count of the SPAD in the TOF module when there is no incident light. Therefore, the TDC count usually includes the dark count and the count when the normal photons are received. When the dark count is too large, the real signal will be submerged, thereby reducing the accuracy of distance measurement.

[0074] In order to solve the above technical problems, eliminate the dark count, and improve the accuracy of measuring the actual distance between the time-of-flight module and the measured object, the embodiments of the present application provide a distance measurement method of a time-of-flight module, a predetermined linear relationship between clock-related data of the time-of-flight module and environmental temperature, and a linear relationship between the dark count and the environmental temperature, so as to quickly determine the current dark count corresponding to the current clock-related data of the time-of-flight module according to the common environmental temperature influencing factor, and then eliminate the dark count to improve the measurement accuracy of the actual distance when determining the actual distance between the current time-of-flight module and the measured object.

[0075] Figure 2 The flowchart of the distance measurement method of the time-of-flight module provided by the embodiments of the present application is shown in Figure 2 The method comprises:

[0076] S10: presetting a first linear relationship between clock-related data of a clock source in the time-of-flight module and environmental temperature;

[0077] S11: determining a current temperature value corresponding to the current clock-related data according to the first linear relationship;

[0078] In specific implementation, the clock source in the time-of-flight module will change due to the influence of the environmental temperature, and there is a certain linear relationship between the two. Therefore, the clock-related data under different environmental temperatures can be obtained by adjusting the environmental temperature, and then the first linear relationship between the clock-related data of the clock source in the time-of-flight module and the environmental temperature is determined. After obtaining the first linear relationship, the current temperature value corresponding to the current clock-related data can be determined according to the first linear relationship.

[0079] Understandably, when there is only one clock source in the time-of-flight module, the correspondence between the clock frequency of the clock source and the ambient temperature is determined, and the first linear relationship is obtained using the least squares method. When there are two clock sources, the difference in clock frequency between the two clock sources is easier to obtain, and the relationship between the clock source and the ambient temperature is easier to determine. Therefore, the number of clocks generated by the two clock sources is obtained separately, and the difference in the number of clocks corresponding to the two clock sources is calculated, thereby determining the first linear relationship between the difference in the number of clocks and the ambient temperature.

[0080] S12: The second linear relationship between the dark count of the preset flight time module and the ambient temperature;

[0081] S13: Determine the current dark count corresponding to the current temperature value based on the second linear relationship;

[0082] In practice, TDC counting typically includes dark counts and counts when receiving photons normally. When the dark count is too large, it can cause the real signal to be overwhelmed, thereby reducing the accuracy of ranging. Therefore, if you want to determine the real distance between the time-of-flight module and the object being measured, you need to remove the dark counts from the TDC count.

[0083] Dark counts vary with ambient temperature; in fact, the relationship between dark counts and ambient temperature can be modeled as linear. If a temperature sensor is included in the time-of-flight module, the dark count generated at the current ambient temperature can be determined based on the sensor's reading and the linear relationship between ambient temperature and dark counts. However, adding a temperature sensor increases material costs, and a sensor malfunction reduces the accuracy of actual distance measurements.

[0084] Therefore, to improve the accuracy of actual distance measurement, the dark count values ​​at different temperatures are obtained by adjusting the ambient temperature beforehand, and a second linear relationship between the dark count and the ambient temperature is obtained using the least squares method. After obtaining the second linear relationship, the dark count value generated at the current ambient temperature can be quickly determined based on the second linear relationship.

[0085] S14: Remove the current dark count from the photon count collected by the time-of-flight module to determine the actual distance between the time-of-flight module and the object being measured.

[0086] Furthermore, after obtaining the first linear relationship between clock-related data and ambient temperature, and the second linear relationship between dark count and ambient temperature through the above steps, when determining the flight time module, the current dark count corresponding to the current clock-related data can be quickly determined directly through the common influencing factor of clock-related data and dark count, namely ambient temperature, thereby eliminating the influence of dark count on determining the actual distance.

[0087] When the dark count is removed, the original histogram of the photon count is obtained first, and the dark count is removed from the original histogram, and then peak searching is performed in a new histogram to determine the actual distance between the time-of-flight module and the measured object.

[0088] The ranging method of the time-of-flight module provided in the embodiments of the present application comprises: presetting a first linear relationship between clock-related data of a clock source in the time-of-flight module and an ambient temperature, and a second linear relationship between dark count of the time-of-flight module and the ambient temperature, respectively, determining a current temperature value corresponding to the current clock-related data according to the first linear relationship, and determining a current dark count corresponding to the current temperature value according to the second linear relationship, so as to remove the current dark count from the photon count collected by the time-of-flight module to determine the actual distance between the time-of-flight module and the measured object. As can be seen, the technical solution provided in the present application determines the relationship between the clock-related data in the time-of-flight module and the ambient temperature, and the relationship between the dark count and the ambient temperature in advance, and according to the common influencing factor, i.e., the ambient temperature, the current temperature value corresponding to the current clock-related data can be quickly determined, and the current dark count of the time-of-flight module at the current temperature value is further determined according to the linear relationship between the temperature and the dark count, so as to remove the dark count during ranging, overcome the influence of the dark count on the calculation of the actual distance, and further improve the ranging accuracy of the time-of-flight module.

[0089] It can be understood that the dark count refers to the average value of the normal count of the SPAD in the TOF module without incident light. Therefore, when determining the linear relationship between the dark count and the ambient temperature, after assembling the lens and the time-of-flight module, the ranging device is subjected to light shielding treatment, i.e., the receiver and the transmitter are subjected to light shielding, specifically, the lens of the transmitter and the receiver is subjected to light shielding treatment.

[0090] Subsequently, when the time-of-flight module receives a dark count statistical instruction, the register is initialized first, and then the historical photon count in the time-of-flight module is cleared. Then, the SPADs in the time-of-flight module are opened one by one, and each time a next SPAD is opened, the previous SPAD is closed, and photon count data collection is performed once after each SPAD is opened, and when all the SPADs are opened once and photon count data collection is performed once, the sum of the photon counts of all the SPADs is counted, and the corresponding relationship between the sum of the photon counts of all the SPADs and the current ambient temperature is obtained, i.e., the corresponding relationship between the sum of the photon counts of all the SPADs and the current ambient temperature.

[0091] Further, the current ambient temperature is adjusted, and after the historical photon count is cleared, all the SPADs are opened once and photon count data collection is performed again. Each time the process is repeated, a corresponding relationship between the ambient temperature and the dark count value is obtained, and recorded in the first record table.

[0092] The second linear relationship can be obtained by modeling the data in the first record table, and it should be noted that the modeling manner of the data in the first record table is not limited in the application. Figure 3 A linear relationship diagram between the dark count and the ambient temperature provided by the embodiment of the application is shown in FIG. 2. Figure 3 After multiple temperature adjustments and dark count statistics are performed, the second linear relationship between the dark count and the ambient temperature can be obtained.

[0093] The ranging method of the time-of-flight module provided by the embodiment of the application opens the SPADs in the time-of-flight module one by one, and closes the previous SPAD when the next SPAD is opened. After each SPAD is opened, the photon counting data acquisition is performed once. Finally, the sum of the photon counts of all the SPADs is counted to obtain the corresponding dark count value at the current ambient temperature, and the linear relationship between the dark count and the ambient temperature can be obtained, which can be used as the basic data for determining the current dark count according to the clock correlation data.

[0094] On the basis of the above embodiment, in order to eliminate all factors that cause inaccuracy, the technical solution provided by the application closes all the SPADs before clearing the historical photon counts in the time-of-flight module, and performs the photon counting data acquisition once.

[0095] Further, after the historical photon counts in the time-of-flight module are cleared, the second preset time length is waited for, and after the second preset time length, the second linear relationship between the dark count and the ambient temperature is obtained by opening the SPADs and performing the photon counting data acquisition.

[0096] The ranging method of the time-of-flight module provided by the embodiment of the application closes all the SPADs before clearing the historical photon counts in the time-of-flight module, and performs the photon counting data acquisition once. At the same time, after the second preset time length is waited for, the sum of the photon counts of the SPADs is counted to determine the linear relationship between the dark count and the ambient temperature, thereby eliminating all factors that affect the statistical dark count and improving the accuracy of measuring the actual distance between the time-of-flight module and the measured object.

[0097] On the basis of the above embodiment, before the sum of the photon counts of all the SPADs is counted to obtain the corresponding dark count value at the current ambient temperature, it is determined whether the photon counting data acquisition is performed once for each SPAD, that is, it is determined whether all the SPADs are opened and the photon counting data acquisition is performed once. If yes, the sum of the photon counts of all the SPADs is counted to obtain the corresponding dark count value at the current ambient temperature. If no, the next SPAD is opened and the photon counting data acquisition is performed once, and the previous SPAD is closed.

[0098] The ranging method of the time-of-flight module provided in the embodiments of the present application determines whether the dark count statistics of each SPAD in the current time-of-flight module are performed through the judgment of whether each SPAD performs a cycle of photon counting data collection, before the corresponding dark count value at the current ambient temperature is obtained by counting the photon counts of all SPADs, so as to further improve the statistical accuracy of the dark count.

[0099] The clock source is one, and the current accurate clock frequency cannot be obtained due to the influence of temperature. In the time-of-flight module, for example, there are two clock sources in the ADS6101 module. In order to more easily obtain the linear relationship between the clock-related data of the clock source in the time-of-flight module and the ambient temperature, if the time-of-flight module includes two clock sources, the first linear relationship between the clock-related data of the clock source in the time-of-flight module and the ambient temperature is preset, the number of clock edges of each clock source in the first preset time length is collected to obtain the first clock number and the second clock number, then the difference between the first clock number and the second clock number is calculated, and the corresponding relationship between each clock number difference and the ambient temperature is stored in the second record table. When the clock source is two, the following operations can be performed: set the target count of the A clock source as c_a, let the A and B clocks start counting from zero, wait until the A clock counts to c_a, and then stop the counting of the B clock, which is recorded as c_b. The difference between the two clocks is more easily obtained, and the relationship between the clock source and the temperature is easily determined.

[0100] Further, the current ambient temperature is adjusted, the corresponding relationship between the clock number difference of the two clock sources and the current ambient temperature is obtained after each adjustment of the ambient temperature, and the first linear relationship between the clock-related data and the ambient temperature is determined according to the corresponding relationship recorded in the second record table. Similarly, the modeling method for determining the first linear relationship between the clock-related data and the ambient temperature is not limited in the present application.

[0101] The ranging method of the time-of-flight module provided in the embodiments of the present application, when the time-of-flight module includes two clock sources, the number of clock edges of each clock source in the first preset time length is collected to obtain the first clock number and the second clock number, the current ambient temperature is adjusted, and the corresponding relationship between the difference between the first clock number and the second clock number and the current ambient temperature is stored in the second record table, and then the first linear relationship is determined according to the corresponding relationship between each clock number difference and the ambient temperature in the second record table, which provides the possibility for determining the dark count according to the current clock-related data of the time-of-flight module.

[0102] Of course, when the time-of-flight module includes a clock source, the current clock frequency of the clock source is directly obtained, and then the corresponding relationship between the current clock frequency and the current ambient temperature is stored in the second record table, the current ambient temperature is continuously adjusted to obtain the clock frequency under different ambient temperatures, and then the first linear relationship between the clock-related data and the ambient temperature is determined according to the corresponding relationship in the second record table.

[0103] The ranging method of the time-of-flight module provided in the embodiments of the present application, when the time-of-flight module includes a clock source, determines the first linear relationship between the clock-related data and the ambient temperature by directly obtaining the current clock frequency of the clock source and the current ambient temperature, which provides the possibility for determining the dark count according to the current clock-related data of the time-of-flight module.

[0104] In specific embodiments, in addition to the way of counting the dark count by sequentially opening each SPAD in the time-of-flight module and performing photon counting data acquisition once after each SPAD is opened, when the dark count counting instruction is received, the historical photon counting in the time-of-flight module can be cleared, all SPADs in the time-of-flight module can be opened, and photon counting data acquisition can be performed once after each SPAD is opened, then the sum of the photon counts of all SPADs is counted to obtain the corresponding dark count value under the current ambient temperature, and then the second linear relationship between the dark count and the ambient temperature is obtained by modeling according to the corresponding relationship between each dark count value and the ambient temperature.

[0105] Of course, in implementation, not all SPADs in the time-of-flight module will be used, therefore, in order to avoid resource waste, when counting the dark count, the dark count can be counted only for the to-be-used SPAD, that is, the to-be-used SPADs in the time-of-flight module are sequentially opened, and each time the next to-be-used SPAD is opened, the previous to-be-used SPAD is closed, and photon counting data acquisition is performed once after each to-be-used SPAD is opened, and the corresponding dark count value under the current ambient temperature is obtained according to the sum of the photon counts of each to-be-used SPAD, and then the second linear relationship between the dark count and the ambient temperature is obtained by modeling according to each corresponding relationship.

[0106] In fact, the present application does not limit the above way of counting the dark count, and the actual business requirements can be selected.

[0107] The ranging method of the time-of-flight module provided in the embodiments of the present application counts the corresponding relationship between the dark count and the current ambient temperature, and models the second linear relationship between the dark count and the ambient temperature, which provides the possibility for determining the dark count according to the current clock-related data of the time-of-flight module.

[0108] In implementation, the current dark count is removed from the photon count collected by the time-of-flight module to determine the actual distance between the time-of-flight module and the measured object, which includes:

[0109] obtaining an original histogram of photon counts;

[0110] removing the current dark count from the original histogram to obtain a target histogram;

[0111] performing peak searching on the target histogram to determine the actual distance.

[0112] Figure 4 A schematic diagram of a photon count histogram provided by an embodiment of the present application is shown in FIG. 1. Figure 4 As shown in FIG. 1, an original histogram of photon counts is first obtained, and a target histogram is obtained by removing the current dark count from the original histogram. Finally, peak searching is performed on the target histogram to determine the actual distance.

[0113] It should be noted that the formula for calculating the signal-to-noise ratio is:

[0114]

[0115] where S is the signal-to-noise ratio, H main is the main peak signal, i.e., the maximum photon area, H amb is the environmental signal, i.e., the average photon area of non-main peak signals.

[0116] It can be understood that the higher the signal-to-noise ratio, the higher the reliability. Therefore, performing peak searching on the target histogram can obtain the actual distance with the highest reliability.

[0117] It should be noted that the formula for calculating the actual distance is:

[0118] d = X K 0.5c

[0119] where d is the actual distance, X is the bin value of the SPAD corresponding to the peak in the histogram, K is the histogram width, and c is the speed of light.

[0120] Thus, after removing the dark count, the actual distance between the time-of-flight module and the measured object can be calculated by the above formula.

[0121] The ranging method of the time-of-flight module provided by the embodiment of the present application removes the current dark count from the photon count collected by the time-of-flight module to determine the actual distance between the time-of-flight module and the measured object. First, an original histogram of photon counts is obtained, and a target histogram is obtained by removing the current dark count from the original histogram. Then, peak searching is performed on the target histogram to determine the actual distance. Thus, by removing the influence of the dark count on the actual distance, the accuracy of the time-of-flight module in measuring the actual distance of the measured object is improved.

[0122] In the above embodiments, the ranging method of the time-of-flight module is described in detail, and the present application also provides a corresponding embodiment of a ranging device of a time-of-flight module. It should be noted that the embodiments of the device part are described from two angles, one is based on the functional module, and the other is based on the hardware structure.

[0123] Figure 5 The structure diagram of a ranging device of a time-of-flight module provided by the embodiments of the present application is shown in FIG. 1, which comprises: Figure 5

[0124] a preset processing module 10, configured to preset a first linear relationship between clock-related data of a clock source in the time-of-flight module and an ambient temperature, and preset a second linear relationship between dark counts of the time-of-flight module and the ambient temperature;

[0125] a determination module 11, configured to determine a current temperature value corresponding to the current clock-related data according to the first linear relationship, and determine a current dark count corresponding to the current temperature value according to the second linear relationship;

[0126] a rejection module 12, configured to reject the current dark count from the photon counts collected by the time-of-flight module, so as to determine the actual distance between the time-of-flight module and the measured object.

[0127] The current dark count is rejected from the photon counts collected by the time-of-flight module, so as to determine the actual distance between the time-of-flight module and the measured object.

[0128] Since the embodiments of the device part correspond to the embodiments of the method part, the embodiments of the device part are described in the description of the embodiments of the method part, which will not be described here.

[0129] ​The ranging device of the time-of-flight module provided in the application comprises: a first linear relationship between clock-related data of a clock source in the time-of-flight module and an ambient temperature, and a second linear relationship between dark counts of the time-of-flight module and the ambient temperature are preset respectively, a current temperature value corresponding to current clock-related data is determined according to the first linear relationship, and a current dark count corresponding to the current temperature value is determined according to the second linear relationship, so that the current dark count is eliminated from photon counts collected from the time-of-flight module to determine an actual distance between the time-of-flight module and a measured object. As can be seen, the technical solution provided in the application determines the relationship between clock-related data in the time-of-flight module and the ambient temperature, and the relationship between dark counts and the ambient temperature in advance, determines the current temperature value corresponding to the current clock-related data according to the common influencing factor, i.e., the ambient temperature, further determines the dark count generated by the current time-of-flight module at the current temperature value according to the linear relationship between the temperature and the dark count, so as to eliminate the dark count during ranging, overcome the influence of the dark count on the calculation of the actual distance, and further improve the ranging accuracy of the time-of-flight module.

[0130] The ranging method and device of the time-of-flight module provided in the application are described in detail above. The embodiments in the specification are described in a progressive manner, and each embodiment mainly describes the difference from other embodiments. The same or similar parts of each embodiment can be understood by referring to each other. For the device disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the related parts can be understood by referring to the method part. It should be pointed out that, for ordinary skilled persons in the technical field, some improvements and modifications can be made to the application without departing from the principles of the application, and these improvements and modifications also fall within the protection scope of the claims of the application.

[0131] It should also be noted that, in the specification, relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or device. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or device including the element.

Claims

1. A method of distance measurement for a time-of-flight module, characterized in that, The method comprises: presetting a first linear relationship between clock-related data of a clock source in a time-of-flight module and an ambient temperature; determining a current temperature value corresponding to current clock-related data according to the first linear relationship; presetting a second linear relationship between dark count of the time-of-flight module and the ambient temperature; determining a current dark count corresponding to the current temperature value according to the second linear relationship; eliminating the current dark count from photon counts collected from the time-of-flight module to determine an actual distance between the time-of-flight module and a measured object; the presetting of the second linear relationship between the dark count of the time-of-flight module and the ambient temperature comprises: when receiving a dark count statistical instruction, clearing historical photon counts in the time-of-flight module; opening each SPAD in the time-of-flight module in turn, and closing a previous SPAD each time a next SPAD is opened, and performing photon count data collection once after each opening of a SPAD; or, opening all SPADs in the time-of-flight module, and performing photon count data collection once after each opening of a SPAD; statistically summing photon counts of all the SPADs to obtain a dark count value corresponding to the current ambient temperature; storing the current ambient temperature and the corresponding dark count value into a first record table; adjusting the current ambient temperature, and entering the step of clearing the historical photon counts in the time-of-flight module; modeling data in the first record table to obtain the second linear relationship; or, when receiving a dark count statistical instruction, clearing historical photon counts in the time-of-flight module; opening each to-be-used SPAD in the time-of-flight module in turn, and closing a previous to-be-used SPAD each time a next to-be-used SPAD is opened, and performing photon count data collection once after each opening of a to-be-used SPAD; statistically summing photon counts of all the to-be-used SPADs to obtain a dark count value corresponding to the current ambient temperature; storing the current ambient temperature and the corresponding dark count value into a first record table; adjusting the current ambient temperature, and entering the step of clearing the historical photon counts in the time-of-flight module; modeling data in the first record table to obtain the second linear relationship.

2. The time-of-flight module ranging method of claim 1, wherein, Before the clearing of the historical photon counts in the time-of-flight module, the method further comprises: closing all the SPADs; performing photon count data collection once; Further, after the clearing of the historical photon counts in the time-of-flight module, the method further comprises: after a second preset time length, entering the step of opening each SPAD in the time-of-flight module in turn, and closing a previous SPAD each time a next SPAD is opened, and performing photon count data collection once after each opening of a SPAD.

3. The time-of-flight module ranging method of claim 2, wherein, Before the statistical summing of the photon counts of all the SPADs to obtain the dark count value corresponding to the current ambient temperature, the method further comprises: judging whether each SPAD has performed photon count data collection once; If yes, entering the step of summing up photon counts of all the SPADs to obtain a dark count value corresponding to the current ambient temperature; If no, entering the step of opening the next SPAD and closing the previous SPAD.

4. The time-of-flight module ranging method of claim 1, wherein, When the time-of-flight module includes two clock sources, the first linear relationship between the clock-related data of the clock source in the preset time-of-flight module and the ambient temperature comprises: Respectively collecting the number of clock edges of each clock source in a first preset time length to obtain a first clock number and a second clock number; Storing the difference between the first clock number and the second clock number and the corresponding relationship with the current ambient temperature in a second record table; Adjusting the current ambient temperature and entering the step of respectively collecting the number of clock edges of each clock source in a preset time length to obtain a first clock number and a second clock number; Determining the first linear relationship according to the corresponding relationship between each clock number difference and the ambient temperature in the second record table.

5. The time-of-flight module ranging method of claim 1, wherein, When the time-of-flight module includes one clock source, the first linear relationship between the clock-related data of the clock source in the preset time-of-flight module and the ambient temperature comprises: Obtaining the current clock frequency of the clock source; Storing the corresponding relationship between the current clock frequency and the current ambient temperature in a second record table; Adjusting the current ambient temperature and entering the step of obtaining the current clock frequency of the clock source; Determining the first linear relationship according to each corresponding relationship in the second record table.

6. The method of claim 1 to 5, wherein The current dark count is removed from the photon count collected from the time-of-flight module to determine the actual distance between the time-of-flight module and the measured object, which comprises: Obtaining an original histogram of photon counts; Removing the current dark count from the original histogram to obtain a target histogram; Performing peak searching on the target histogram to determine the actual distance.

7. A range finding device of a time-of-flight module, characterized in that Comprise: A preset processing module for presetting a first linear relationship between clock-related data of a clock source in a time-of-flight module and an ambient temperature, and presetting a second linear relationship between a dark count of the time-of-flight module and the ambient temperature; A determination module for determining a current temperature value corresponding to the current clock-related data according to the first linear relationship, and determining a current dark count corresponding to the current temperature value according to the second linear relationship; A removal module for removing the current dark count from the photon count collected from the time-of-flight module to determine the actual distance between the time-of-flight module and the measured object; The presetting of the second linear relationship between the dark count of the time-of-flight module and the ambient temperature comprises: Upon receiving a dark count statistical instruction, clearing the historical photon count in the time-of-flight module; Opening each SPAD in the time-of-flight module in turn, and closing the previous SPAD each time a next SPAD is opened, and performing photon count data collection once after each SPAD is opened; or, opening all the SPADs in the time-of-flight module, and performing photon count data collection once after each SPAD is opened; Summing up photon counts of all the SPADs to obtain a corresponding dark count value at the current ambient temperature; Storing the current ambient temperature and the corresponding dark count value into a first record table; Adjusting the current ambient temperature and entering the step of clearing the historical photon counts in the time-of-flight module; Modeling the data in the first record table to obtain the second linear relationship; Or, upon receiving a dark count statistics instruction, clearing the historical photon counts in the time-of-flight module; Opening the SPADs to be used in the time-of-flight module in turn, and each time a next SPAD to be used is opened, a previous SPAD to be used is closed, and photon count data acquisition is performed once after each SPAD to be used is opened; Summing up photon counts of all the SPADs to obtain a corresponding dark count value at the current ambient temperature; Storing the current ambient temperature and the corresponding dark count value into a first record table; Adjusting the current ambient temperature and entering the step of clearing the historical photon counts in the time-of-flight module; Modeling the data in the first record table to obtain the second linear relationship.

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