Distance measuring method and measuring device

Abstract

A method (100) for performing a distance measurement using a single-photon avalanche diode, SPAD, the method comprising the following steps: - emitting (110) a light pulse sequence in the direction of a measurement object using a light source; - measuring (120) the transit time for the light pulses reflected from the measurement object using a SPAD, wherein the SPAD has an adjustable dead time within which the SPAD is not able to detect further photons after detecting a photon; - creating (130) a histogram from the measured runtimes; - determining (140) all peaks within the created histogram whose amplitude exceeds a predetermined threshold; and - Determining (150) the distance of the measuring object based on the determined peaks, whereby - the measurement of the transit time for the light pulses reflected from the measuring object, the execution of n max Single measurements, the dead time of the SPAD during a single measurement n m as tτ(n m ) = t T0 + Δt T (n m ) is defined, t T0 a mean dead time of the SPAD during the measurement of the running time and Δt T (n m ) the dead time difference during the individual measurement n m where the measurement of the running time comprises the following steps: - Carrying out a first single measurement using a first dead time of the SPAD t T1 = t T0 + Δt T1 , where Δt T1 describes the difference between the first dead time and the mean dead time; - Carrying out a second single measurement using a second dead time of the SPAD t T2 = t T0 + Δt T2 ; where Δt T2describes the difference between the second dead time and the mean dead time; where - the second dead time difference Δt T2 one from the first dead time difference Δt T1 has different values.

Description

[0001] The present invention relates to a method for performing a distance measurement using a single-photon avalanche diode as well as a corresponding measuring device and a corresponding measuring system.

[0002] Various optical measuring methods and devices are known from the prior art. DE 10 2020 202 764 A1 describes a light detection device comprising first light detectors arranged at first intervals and configured to convert received light into first signals. Furthermore, the described detection device comprises second light detectors having a first crosstalk rate and configured to convert received light into second signals, wherein the surfaces of the second light detectors are shielded from light.

[0003] US 2022 / 0 120 880 A1 describes a calibration method for a LiDAR system with an analog detection channel comprising an avalanche photodiode. The avalanche photodiode is connected to a receiving optics, with a bias circuit connected to the avalanche photodiode and configured to set a bias target value for the avalanche photodiode.

[0004] DE 10 2014 207 599 A1 describes a method for operating a photodetector. The photodetector has a number of individually activatable avalanche photodiodes per pixel. In an activated state, an avalanche photodiode is configured to provide an electrical pulse when a certain amount of light is received. Following the electrical pulse, the avalanche photodiode is insensitive to light for a regeneration period.

[0005] DE 10 2017 209 643 A1 describes a method for operating a LiDAR system that can be operated in a pulse sequence-coded manner and is designed with a SPAD-based detector element, in which method a dead time of the SPAD-based detector element is detected and, in the transmission range of the LiDAR system, a minimum time interval between transmission pulses of primary light that are to be transmitted directly or immediately consecutively is dimensioned such that it at least approximately corresponds to the dead time.

[0006] Methods for distance measurement using single-photon avalanche diodes (SPADs) are generally known from the prior art. In particular, the so-called "direct time of flight" method (also known as the dToF method or time of flight measurement method) is used for precise distance measurement using a SPAD. In this method, a light signal is emitted from a light source in the direction of a measurement object, and the light reflected by the measurement object is detected by the SPAD. In this method, the time of flight required by the light to propagate to the measurement object and back from the measurement object to the SPAD is determined. For this purpose, the difference between a first time at which a light pulse is emitted and a second time at which the reflected light pulse is detected by the SPAD is determined.Based on this time difference and knowledge of the speed of light, the distance between a measuring device and a measuring object can then be calculated.

[0007] The so-called histogram method has proven effective for evaluating the obtained measurement data. This method creates a histogram with N histogram bins (also called histogram classes), typically with a fixed width, from the determined runtimes. The resulting histogram is then searched for a peak or maximum. The position of the peak is proportional to the distance between the measuring device and the measurement object.

[0008] While the method described above delivers very precise measurement results in many situations, the results are considered to be rather unreliable in some measurement situations. In particular, if the measurement object has a retroreflector or a very high reflectivity and the distance between the measurement object and the light source is relatively small, the methods known from the prior art can fail. If the reflected light intensity is relatively high (particularly if the light source is a laser beam source and light pulses are reflected off a retroreflector), the probability of systematic distortion of the histogram is relatively high. This is due to the fact that the SPAD, which has a dead time during which it cannot detect any further photons after detecting a photon, shows an increased triggering probability immediately after the dead time. For evaluation methods that use multiple peaks orUsing maxima in the histogram will lead to false detections of the second maximum. If the dead time of a SPAD is kept constant, as is the case with state-of-the-art methods, the SPAD leaves the dead time at a fixed point in time and becomes sensitive again. This point in time is identical for each measurement. The probability that the SPAD will be triggered by ambient light immediately after the dead time can be specified as P(ambient). At later points in time, however, the probability of the SPAD being triggered is lower, since the SPAD can only trigger if it has not previously triggered and entered the dead time again. Consequently, the SPAD has an increased probability of being triggered by ambient light immediately after the end of the dead time, which decreases with increasing time. It can be shown that the temporal decrease in the probability of the SPAD being triggered follows a Poisson distribution.In unfavorable conditions, the increased probability of triggering the SPAD can lead to the measuring device, which can be designed as an integrated circuit, for example, producing a false-positive detection.

[0009] Based on the problem described above, it is the object of the present invention to provide a method in which the risk of a false-positive measurement is reduced, thereby increasing measurement reliability.

[0010] To achieve the above-mentioned object, the present invention proposes a method for performing a distance measurement using a single-photon avalanche diode (SPAD), the method comprising the following steps: - Emitting a sequence of light pulses towards a measuring object using a light source; - measuring a travel time for each of the light pulses reflected from the measurement object using a SPAD, wherein the SPAD has an adjustable dead time within which the SPAD is not able to detect further photons after detecting a photon; - Creating a histogram for the measured runtimes; - Determining all peaks within the created histogram whose amplitude exceeds a specified threshold; and - Determine the distance of the measuring object based on the detected peaks, where - the measurement of the transit time for the light pulses reflected from the measuring object, the execution of n max Single measurements, the dead time of the SPAD during a single measurement n m as t T (n m ) = t T0 + Δt T (n m ) is defined, t T0 a mean dead time of the SPAD during the measurement of the running time and Δt T (nm ) the dead time difference during the individual measurement n m where the measurement of the running time comprises the following steps: - Carrying out a first single measurement using a first dead time of the SPAD t T1 = t T0 + Δt T1 , where Δt T1 describes the difference between the first dead time and the mean dead time; - Carrying out a second single measurement using a second dead time t T2 = t T0 + Δt T2 the SPAD; where Δt T2 describes the difference between the second dead time and the mean dead time; where - the second dead time difference Δt T2 to a value different from the first dead time difference Δt T1 different value is set.

[0011] The present invention allows the dead time to be actively varied for at least two measurements, thereby reducing the risk of a false-positive detection occurring at a specific time. Preferably, the number of individual measurements performed during the entire time-of-flight measurement (also referred to as a measurement series, whereby this measurement series provides the measurement data from which the histogram is subsequently created) can be several hundred or several thousand. For each individual measurement, a light pulse is emitted in the direction of the measurement object, and the time of flight of the emitted light pulse is detected. The results of the individual measurements are used to create the aforementioned histogram or a frequency distribution describing the histogram. By varying the dead time within the individual measurements, the probability of a false-positive triggering of the SPAD is distributed across the measurements.This spreads false-positive measurement results across measurements at different time points, reducing histogram distortion after the dead time. This enables a more reliable distance measurement overall, especially in cases where the reflected light intensity is relatively high. In particular, the reliability of the distance measurement is increased in cases where the measurement object has a retroreflector.

[0012] In the method according to the invention, the light pulses can preferably be implemented as laser pulses. Therefore, the light source used can preferably be a laser beam source. As already explained in the introduction, the present method is based on a dToF measurement. Consequently, the distance to the measurement object can be determined according to d=(c⋅T) / 2 where d is the distance traveled by the light, c is the speed of light and T is the travel time.

[0013] According to the method according to the invention, the dead time t T (n m) between the individual measurements can be extended or shortened. The method according to the invention can be implemented in different ways. In particular, the method according to the invention can be computer-implemented. Alternatively, the method according to the invention can be realized in the form of a hardware implementation. Several approaches can be used to actively vary the dead time of the SPAD. For example, the dead time of the SPAD can be varied between the individual measurements by adjusting a bias voltage applied to a quench circuit. Alternatively, a digital quench circuit (also referred to as an active reset circuit) or a control unit can be used to actively set the dead time of the SPAD.

[0014] In the method according to the invention, it can be provided in particular that the threshold value is determined dynamically and as a function of the intensity of the current ambient light.

[0015] In the method according to the invention, it can preferably be provided that the dead time difference Δt T (n m ) for each individual measurement n m is set in such a way that the amount of the dead time difference |Δt T (n m )| for all n m Individual measurements between 0 and t T0 preferably between 0 and 0.7 t T0 , particularly preferably between 0 and 0.5 t T0 and in particular between 0 and 0.3 t T0 Initial studies have shown that particularly good measurement results can be achieved by setting the dead time difference within the ranges specified above. Furthermore, the above-mentioned limitation of the dead time difference ensures that the average dead time of the SPAD is not unnecessarily extended.

[0016] The method according to the invention can also provide that the dead time difference Δt T (nm ) for each individual measurement n m is set randomly or pseudorandomly and values between 0 and Δt T,max By a random distribution of the dead time difference Δt T (n m ) within a series of measurements for each measurement n m This ensures that the increased risk of false-positive SPAD triggering is distributed across individual measurements at different time points. This significantly reduces the overall risk of false-positive detection due to histogram distortion.

[0017] Furthermore, the method according to the invention can provide that the dead time differences Δt T (n m ) for the individual measurements n m between the values 0 and Δt T,max are evenly distributed. This means that the different dead time differences Δt T (n m ), which in the individual measurements n mbe set, occur equally frequently within an overall measurement or are generated with the same probability. This enables a particularly simple implementation of the method according to the invention. For example, a random generator or a pseudo-random generator can be used, which determines the dead time differences Δt T (n m ) for the individual meals n m generated.

[0018] In addition, the method according to the invention can provide that the dead time difference Δt T (n m ) for the individual measurements n m within a total measurement between the values 0 and Δt T,maxare distributed according to an inverse Poisson distribution. As already explained above, the probability of a false-positive measurement after the end of a dead time can be represented using a Poisson distribution. By setting the dead time differences according to an inverse Poisson distribution, the increased probability of a false-positive detection is optimally compensated. This ensures that the probability of the SPAD triggering a false-positive is evenly distributed immediately after the dead time. The previously described peak in the probability of a false-positive detection is optimally compensated by distorting the histogram.

[0019] In addition, the method according to the invention can preferably provide that the histogram has individual bins with a constant width and that the dead time differences Δt T (n m ) for the individual measurements n mare equidistantly distributed, with the distance between adjacent dead time difference values equal to the width of the histogram bins.

[0020] Finally, in the method according to the invention, according to some preferred embodiments, it can be provided that the dead time difference Δt T (n m ) for each individual measurement n mis read from a predefined lookup table (also referred to as a lookup table or LUT). This simplifies the inventive method in that a (pseudo-)random generator is no longer required. Precalculated values for the dead time difference for each individual measurement can be stored in the LUT. While the distance measurement is being carried out, the previously determined value for the dead time difference can then be read from the LUT for each individual measurement. This simplifies the inventive method and provides a particularly efficient method.

[0021] In addition, to solve the problem described above, a method for detecting reflected light pulses by a single-photon avalanche diode (SPAD) is also proposed, which method comprises the following steps: - Detection of light pulses using a SPAD, wherein the SPAD has an adjustable dead time within which the SPAD is unable to detect further photons after detecting a photon; - Measurement of travel times for the individual light pulses; - Creating a histogram for the measured runtimes; - Determining all peaks within the created histogram whose amplitude exceeds a specified threshold; and - Determine the distance of the measuring object based on the detected peaks, where - the measurement of the transit time for the light pulses reflected from the measuring object, the execution of n max Single measurements, the dead time of the SPAD during a single measurement n m as tτ(n m ) = t T0 + Δt T (n m ) is defined, t T0 a mean dead time of the SPAD during the measurement of the running time and Δt T (nm ) the dead time difference during the individual measurement n m where the measurement of the running time comprises the following steps: - Carrying out a first single measurement using a first dead time of the SPAD t T1 = t T0 + Δt T1 , where Δt T1 the difference between the first dead time and the mean dead time; - Carrying out a second single measurement using a second dead time t T2 = t T0 + Δt T2 the SPAD; where Δt T2 describes the difference between the second dead time and the mean dead time; where - the second dead time difference Δt T2 to a value different from the first dead time difference Δt T1 different value is set.

[0022] In addition, to achieve the object described above, a measuring device for measuring a distance to a measurement object is proposed, wherein the measuring device comprises a single-photon avalanche diode (SPAD), a memory unit, a computing unit, and a control unit. In the measuring device according to the invention, it is provided that - the SPAD has an adjustable dead time within which the SPAD is unable to detect incoming photons, and the SPAD is designed to measure the travel times of individual light pulses; - the control unit is designed to actively control the dead time of the SPAD; - the storage unit is designed to store the measured running times; - the computing unit is designed to: - to create a histogram for the measured runtimes; - to identify all peaks within the determined histogram whose amplitude exceeds a specified threshold; and - to determine the distance of the measuring object based on the detected peaks; where - the SPAD is also set up to - a first single measurement using a first dead time t T1 = t T0 + Δt T1 to be carried out, where t T0 a mean dead time and Δt T1 describes the difference between the first dead time and the mean dead time; and - a second single measurement using a second dead time t T2 = t T0 + Δt T2 where Δt T2 describes the difference between the second dead time and the mean dead time; where - the second dead time difference Δt T2 to a value different from the first dead time difference Δt T1 a different value is set.

[0023] The components of the measuring device according to the invention can be designed to carry out the steps described above in connection with the method according to the invention.

[0024] In particular, the measuring device according to the invention can be provided with a multiplexer and a plurality of delay elements connected to the inputs of the multiplexer, wherein the delay elements preferably each have the same delay times, and the multiplexer is configured to receive a dead-time difference input signal and a SPAD reset input signal and, depending on the dead-time difference input signal, to output a time-delayed SPAD reset output signal to the SPAD. This allows for an efficient hardware implementation of the dead-time control.

[0025] In particular, the measuring device according to the invention can be provided with an additional look-up table unit in which several delay values are stored which correspond to the respective individual measurements n m are assigned, wherein the lookup table unit is designed to output a delay value for each individual measurement. The use of the lookup table unit simplifies the measuring device overall, since (pseudo-)random generation of the delay values is no longer necessary.

[0026] It can also be provided in the measuring device according to the invention that all the delay values stored in the lookup table have an amount between 0 and Δt T,max where in particular Δt T,max = t0, preferably Δt T,max = 0.7 · t0, particularly preferably Δt T,max = 0.5 · t0 and in particular Δt T,max = 0.3 · t0.

[0027] Furthermore, in the measuring device according to the invention, it can be provided that the delay values stored in the lookup table are distributed uniformly or according to an inverse Poisson distribution.

[0028] Finally, to solve the problem described above, a system for measuring a distance between a measuring device and a measuring object is proposed, wherein the system - a light source which is designed to emit a sequence of light pulses in the direction of a measuring object, and - a measuring device according to one of the embodiments described above.

[0029] The light source can in particular be designed as a laser beam source.

[0030] The present invention will be explained in more detail below with reference to the figures. Fig. 1 an embodiment of the method according to the invention, Fig. 2 the number of detected events of a SPAD in case of a measurement with constant dead time ( Fig. 2A) and with a variably set dead time ( Fig. 2B), Fig. 3 the triggering of events within several measurements of a SPAD in the case of a measurement with a static dead time ( Fig. 3A) and with a randomly set dead time ( Fig. 3B), Fig. 4 an embodiment of the measuring device according to the invention comprising a control unit and a lookup table, Fig. 5 a first embodiment of the control unit according to the invention, Fig. 6 a second embodiment of the control unit according to the invention, and Fig. 7 the detection of an event for different measurements with a linearly increasing dead time.

[0031] In the Fig. 1 schematically illustrates an embodiment of the method 100 according to the invention. In a first method step 110, a light pulse sequence is emitted in the direction of a measurement object using a light source. The light source can in particular be embodied as a laser beam source designed to generate a plurality of short laser pulses. In a second method step 120, the propagation time for each light pulse reflected from the measurement object is measured using a SPAD. For this purpose, a reflected light pulse is typically detected by the SPAD, and the time of detection is compared with the time of emission of the light pulse by the light source. The difference between the time of detection and the time of emission defines the propagation time of the light pulse. A SPAD typically has a dead time within which it is unable to detect further photons after being triggered.In a third method step 130, a histogram is created from the measured travel times. The histogram has several histogram bins, which preferably have a constant width. Subsequently, in a fourth method step 140, all peaks within the created histogram are determined whose amplitude exceeds a predetermined threshold. This threshold can, in particular, be set dynamically, depending on the intensity of the current ambient light. Typically, the maximum of these peaks describes the travel time that the laser pulses most likely have to travel the distance from the light source to the measurement object and from the measurement object to the SPAD. In a fifth method step 150, the distance of the measurement object is calculated based on the determined maximum of the peaks.For this purpose, the usual approaches are used which are already known from the prior art in order to calculate the distance to the measurement object from the determined travel time and the speed of light. While in the methods known from the prior art the dead time of the SPAD is constant between the individual measurements, in the present invention the dead time of the SPAD is actively varied between the individual measurements. Thus, in the method according to the invention the SPAD has a first dead time within the first individual measurement and a second dead time within the second individual measurement, whereby the second dead time differs from the first dead time. As already explained above, it can be provided within the present invention that the dead time of the SPAD is set to different numerical values according to a random principle for the individual measurements.The dead times can be set according to a uniform distribution or an inverse Poisson distribution. It is also possible to specify the dead times in advance and store them in a lookup table. In this case, the values for the individual dead times can be read from the lookup table during a measurement.

[0032] In the Fig. 2 is the number of detected events of a SPAD in case of a measurement with constant dead time (according to the state of the art, see Fig. 2A) and with a variably set dead time (according to the present invention, see Fig. 2B) is shown schematically.

[0033] As in the Fig. 2A, a light pulse (specifically a reflected laser pulse) is detected at a specific time. After the detection of the light pulse, the SPAD enters the dead time. During this phase, only very few events are detected. Immediately after the dead time, there is a strong increase in the number of events, which decreases over time according to a Poisson distribution. In unfavorable cases, as in the Fig. 2A, this increase can lead to a false-negative detection, namely when the number of detected events exceeds a predefined threshold for detecting a measurement object. In this case, a false-positive detection occurs, the probability of which is highest immediately after the dead time and decreases over time according to a Poisson distribution.

[0034] In the Fig. 2B, however, a measurement according to the present invention is shown schematically. Here, too, it can be seen that a light pulse is detected at a specific time. In the method according to the invention, the SPAD also enters the dead time after detection of a light pulse, in which only a few events are detected. After the dead time, the number of detected events increases. However, since the dead time in the method according to the invention is variably set in the individual measurements, there is no peak of events immediately after the dead time, since the increased risk of triggering the SPAD is distributed over the individual measurements. This Fig. 2A is prevented or at least greatly attenuated. If the distribution of the dead times within the individual measurements is chosen according to an inverse Poisson distribution, the Fig. 2A can be optimally compensated. However, by an equal distribution of the dead time, the increase in the number of events can also be Fig. 2A can be significantly reduced immediately after the dead time, so that the risk of a false-positive measurement can be greatly reduced.

[0035] In the Fig. 3 is the triggering of events within several individual measurements of a SPAD in the case of measurement with a static dead time (according to the state of the art, see Fig. 3A) and with a randomly set dead time (according to the present invention, see Fig. 3B) is shown schematically.

[0036] As in the Fig. As can be seen in Figure 3A, the SPAD exhibits a constant dead time according to the methods known from the state of the art. Therefore, in most measurements, there may be an increased probability of triggering the SPAD by an extraneous light photon immediately after the dead time (also referred to as a parasitic event). This frequent detection leads to the Fig. 2A, which can be falsely attributed to a distance measurement.

[0037] However, in the Fig. 3B that within the scope of the present invention, the dead time varies for the individual measurements. Fig. 3B shows that in most measurements, the SPAD is triggered immediately after the dead time. Relative to the dead time, the false-positive SPAD triggering also occurs statistically at the same time in the present invention. In absolute terms, however, the false-positive events occur at different times in the method according to the invention. This spreads the parasitic events over time, so that (in contrast to the prior art) the peak immediately after the dead time is avoided, as is also the case in the Fig. 2B. This significantly reduces the risk of false-positive detection.

[0038] In the Fig. Figure 4 schematically shows an embodiment of a hardware implementation of the measuring device according to the invention. Measuring devices known from the prior art comprise, in particular, a SPAD, a reset unit, a time-to-digital converter (TDC), a histogram memory, and a data processing unit for peak detection. Compared to the measuring devices known from the prior art, the device shown in Fig. 4, the embodiment of the measuring device according to the invention additionally has the components shown in dashed lines in this figure. In particular, the Fig. 4 additionally comprises a control unit for controlling the dead time of the SPAD. As explained above, various approaches or circuits can be used to adjust the dead time control. Some examples are explained in the following figures. In addition, the Fig. The measuring device shown in Figure 4 has a lookup table in which various dead times for the respective measurements are stored. As explained above, it can preferably be provided that the dead times stored in the lookup table are distributed according to a uniform distribution or a Poisson distribution. The lookup table can be configured to receive the number of the current measurement and, depending on the received number, output the dead time assigned to the current measurement (or alternatively, the dead time difference) to the control unit.

[0039] In the Fig. Figure 5 schematically shows a first embodiment of the control unit according to the invention. In this embodiment, the control unit has a multiplexer and a plurality of delay elements connected to the inputs of the multiplexer. The delay elements are connected in series. A SPAD reset input signal (Reset_in) received at the delay elements is delayed at the delay elements, wherein the delay elements preferably each have the same delay time. In addition, it can be provided that the multiplexer receives an input signal d that defines the specified dead time or the dead time difference for the current measurement. Depending on the input signal d, the multiplexer can adjust the degree of delay and output the input signal with the desired delay at the output (Reset_out).In this way, the dead time of the SPAD can be adjusted depending on a dead time input signal or a dead time difference input signal. It should be noted that the present invention is not limited to the method described in the . Fig. 5 is limited. Alternatively, it can be provided, for example, that various delay elements with different delay times are provided at the inputs of the multiplexer, but are connected in parallel. In this way, each individual delay element provides a delayed signal at the input of the multiplexer. According to this implementation variant, the multiplexer can also output one of its input signals at the output in accordance with the input signal d.

[0040] In the Fig. 6 shows a second embodiment of the control device according to the invention. In addition to the Fig. 5 shown elements has the Fig. The control unit shown in Figure 6 includes a phase detector and a digital-to-analog converter (DAC). Furthermore, the control unit is configured to receive a reference clock signal (Ref_clk) and a calibration signal (Calib_mode). The calibration signal is used to calibrate the delay elements to the reference clock of the TDC between individual measurements. The phase detector is provided to compare the phase delay achieved with the delay elements with the desired phase delay. If a difference between the achieved phase delay and the desired phase delay is detected, the control voltage at the delay elements can be adjusted via the DAC so that the delay time of the delay elements can be regulated accordingly. Preferably, the delay elements can have a delay time equal to one clock period of the TDC.Furthermore, it can preferably be provided that the number of delay elements is equal to the number of delay elements in the TDC. This ensures that the delay time of the delay elements is as large as the width of a histogram bin.

[0041] In the Fig. Figure 7 shows the detection of an event for different individual measurements with a linearly increasing dead time. As can be seen in this figure, the dead time is set to a minimum for the first measurement. For the second measurement, the dead time is increased by the dead time difference Δt. T = T Bin extended, where T Bin the width of a histogram bin. In the third measurement, the dead time difference is again increased by Δt T = T Bin This results in a linear increase in the dead time or the dead time difference across the individual measurements. The dead time for a measurement nm can therefore be used with t T (n m )= t T,min + (n m - 1) · T Bin be specified. This ensures a particularly simple implementation of the present invention. An analytical description of the dead time eliminates the need for a random generator or a lookup table. This allows the present invention to be implemented in a particularly efficient manner. LIST OF REFERENCE SYMBOLS 100 procedures 110 first procedural step 120 second process step 130 third procedural step 140 fourth procedural step 150 fifth procedural step

Claims

[1] A method (100) for performing a distance measurement using a single-photon avalanche diode, SPAD, the method comprising the following steps: - emitting (110) a light pulse sequence in the direction of a measurement object using a light source; - measuring (120) the transit time for the light pulses reflected from the measurement object using a SPAD, wherein the SPAD has an adjustable dead time within which the SPAD is not able to detect further photons after detecting a photon; - creating (130) a histogram from the measured runtimes; - determining (140) all peaks within the created histogram whose amplitude exceeds a predetermined threshold; and - Determining (150) the distance of the measuring object based on the determined peaks, whereby - the measurement of the transit time for the light pulses reflected from the measuring object, the execution of n max Single measurements, the dead time of the SPAD during a single measurement n m as tτ(n m ) = t T0 + Δt T (n m ) is defined, t T0 a mean dead time of the SPAD during the measurement of the running time and Δt T (n m ) the dead time difference during the individual measurement n m where the measurement of the running time comprises the following steps: - Carrying out a first single measurement using a first dead time of the SPAD t T1 = t T0 + Δt T1 , where Δt T1 describes the difference between the first dead time and the mean dead time; - Carrying out a second single measurement using a second dead time of the SPAD t T2 = t T0 + Δt T2 ; where Δt T2describes the difference between the second dead time and the mean dead time; where - the second dead time difference Δt T2 one from the first dead time difference Δt T1 has different values. [2] Method (100) according to claim 1, characterized by that the dead time difference Δt T (n m ) for each individual measurement n m is set in such a way that the amount of the dead time difference |Δt T (n m )| for all n m Individual measurements between 0 and t T0 preferably between 0 and 0.7 t T0 , particularly preferably between 0 and 0.5 t T0 and in particular between 0 and 0.3 t T0 . [3] Method (100) according to claim 1 or 2, characterized by that the dead time difference Δt T (n m ) for each individual measurement n m is set randomly or pseudorandomly and values between 0 and Δt T,maxhas. [4] Method (100) according to claim 3, characterized by that the dead time differences Δt T (n m ) for the individual measurements n m between the values 0 and Δt T,max are evenly distributed. [5] Method (100) according to claim 3, characterized by that the dead time difference Δt T (n m ) for the individual measurements n m between the values 0 and Δt T,max are distributed according to an inverse Poisson distribution. [6] Method (100) according to one of claims 1 to 5, characterized by that the histogram has individual histogram bins with a constant width and that the dead time differences Δt T (n m ) for the individual measurements have equidistant values, whereby the distance between adjacent dead time difference values is identical to the width of the histogram bins. [7] Method (100) according to one of claims 1 to 6, characterized by that dead time difference ΔtT (n m ) for at least some individual measurements or preferably for each individual measurement n m is read from a given lookup table. [8] Measuring device for measuring a distance to a measuring object, comprising a single-photon avalanche diode, SPAD, a storage unit, a computing unit and a control unit, wherein - the SPAD has an adjustable dead time within which the SPAD is unable to detect further incoming photons after detecting a photon, and wherein the SPAD is designed to measure the travel times of received light pulses; - the control unit is designed to actively control the dead time of the SPAD; - the storage unit is designed to store the measured running times; - the computing unit is designed to - to create a histogram for the measured runtimes; - to identify all peaks within the determined histogram whose amplitude exceeds a specified threshold; - to determine the distance of the measuring object based on the detected peaks; - the SPAD is set up to - a first single measurement using a first dead time t T1 = t T0 + Δt T1 to be carried out, where t T0 a mean dead time of the SPAD during the measurement of the running time and Δt T1 describes the difference between the first dead time and the mean dead time; and - a second single measurement using a second dead time t T2 = t T0 + Δt T2 where Δt T2 describes the difference between the second dead time and the mean dead time; where - the second dead time difference Δt T2 one from the first dead time difference Δt T1 has a different value. [9] Measuring device according to claim 8, characterized by , that - the control unit comprises a multiplexer and a plurality of delay elements connected to the inputs of the multiplexer, wherein the delay elements preferably each have the same delay times, and - the multiplexer is configured to receive a dead time difference input signal and a SPAD reset input signal and to output a time-delayed SPAD reset output signal to the SPAD depending on the dead time difference input signal. [10] Measuring device according to claim 8 or 9, characterized by a lookup table unit storing delay values associated with the respective measurements, the lookup table unit being configured to output a delay value for the respective current measurement. [11] Measuring device according to claim 10, characterized bythat all the delay values stored in the lookup table unit have an amount between 0 and Δt T,max where Δt T,max = t T0 , preferably Δt T,max = 0.7 t T0 , particularly preferably Δt T,max = 0.5 - t T0 and especially Δt T,max = 0.3 t T0 . [12] Measuring device according to claim 10 or 11, characterized by that the delay values stored in the lookup table unit are uniformly distributed or distributed according to an inverse Poisson distribution. [13] System for measuring a distance to a measuring object, comprising - a light source configured to emit a sequence of light pulses in the direction of a measuring object, and - a measuring device according to one of claims 8 to 12.

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