EP3775982A1

EP3775982A1 - Method for carrying out a measurement process

Info

Publication number: EP3775982A1
Application number: EP19716351.2A
Authority: EP
Inventors: Ralf Beuschel; Rainer Kiesel
Original assignee: ZF Friedrichshafen AG; Ibeo Automotive Systems GmbH
Current assignee: Microvision Inc
Priority date: 2018-04-10
Filing date: 2019-04-03
Publication date: 2021-02-17
Also published as: WO2019197243A1; JP2021517966A; US20210026013A1; JP7195335B2; KR20200127245A; CA3094023A1; KR102478719B1; IL277852A; DE102018205376A1; CN112292610A

Abstract

The invention relates to a method for carrying out a measurement process for a LIDAR measurement system, wherein, during the measurement process, a plurality of essentially identical measurement cycles 60, 62, 64 are performed, wherein a new measurement cycle 62 starts only after the end of the previous measurement cycle 60 and a waiting period Δ t ₁, Δ t ₂, the waiting periods Δ t ₁, Δ t ₂ of successive measurement cycles 60, 62 being different from one another. The object 32 which is detected by a sensor element at the shown time is within the measurement period t _meas. An object 66 is also shown. This object 66 is situated outside the fixed maximum measurement range of the LIDAR measurement system. Furthermore, the object 66 has a reflectivity which causes detection by the sensor element in a subsequent measurement cycle. The laser pulse emitted at the start of the first measurement cycle 60 and reflected at the object 66 is now detected in the second measurement cycle 62. A first waiting period Δ t ₁ elapses between the end of the first measurement cycle 60 and the start of the second measurement cycle 62. The laser pulse reflected at the object 66 is thus detected at the time T ₁. A second waiting period Δ t ₂ elapses between the end of the second measurement cycle 62 and the start of the third measurement cycle 64. The first waiting period Δ t ₁ and the second waiting period Δ t ₂ are different. The laser light which is reflected at the object 66 is thus detected at the time T 2. Ghost objects are no longer identified during evaluation of a histogram.

Description

Method for performing a measurement process

The invention relates to a method for controlling sensor elements of a Ll-DAR measuring system.

In WO 2017 081 294 a LIDAR measuring system is described. This is designed statically and comprises a transmitting unit with a plurality of emitter elements and a receiving unit with a plurality of sensor elements. The emitter elements and the sensor elements are formed in a focal plane array configuration and arranged at a focal point of a respective transmission optics and reception optics. With regard to the receiving unit and the transmitting unit, a sensor element and a corresponding emitter element are assigned to a specific solid angle. The sensor element is thus associated with a particular emitter element.

It is an object to provide a method in which a detection of highly reflective objects that are outside the specified measuring range can be prevented.

This object is achieved by the method according to the valid patent claim 1. In the dependent claims advantageous Ausführungsvarian th of the method are described.

Such a method is particularly suitable for LIDAR measuring systems that work according to the TCSPC method, Time Correlated Single Photon Counting. This TCSPC is explained in more detail below and in particular in the description of the figures. In particular, the method is intended for LIDAR measuring systems used in motor vehicles.

A suitable LIDAR measuring system has sensor elements and emitter elements. An emitter element emits laser light and is formed, for example, by a VCSEL, Vertical Cavity Surface Emitting Laser. The emitted La serlicht can be detected by the sensor element, which, for example formed by a SPAD, single photon avalanche diode. The distance of the object from the LI DAR measuring system is determined by the transit time of the laser light or the laser pulse.

The emitter elements are preferably formed on a transmission chip of a transmission unit. The sensor elements are preferably formed on a receiving chip of a receiving unit. The transmitting unit and the receiving unit is accordingly assigned a transmitting optics or a receiving optics. The light emitted by an emitter element is assigned a solid angle by the transmission optics. Likewise, a sensor element via the receiving optics always considered the same solid angle. Accordingly, a sensor element is assigned to an emitter element or both are assigned the same solid angle. The emitted laser light accordingly always hits the same sensor element after reflection in the far field.

The sensor elements and emitter elements are advantageously implemented in a focal plane array configuration, FPA. In this case, the elements of a respective unit are arranged in a plane, for example the sensor elements on a plane of the sensor chip. This level is ordered in the focal plane of the respective optics or the elements are arranged in the focal point of the respective optics.

The FPA configuration allows a static design of the LI DAR measurement system and its transmitter unit and receiver unit so that it does not contain any moving parts. In particular, the LI DAR measuring system is statically arranged on a motor vehicle.

An emitter element is conveniently assigned a plurality of sensor elements, which together form a macrocell of a plurality of sensor elements. The se macrocell or all sensor elements of the macrocell are assigned to an emitter element. This can compensate for imaging effects or aberrations, such as the parallax effect or aberrations of the lens. Measurements are made on the LI DAR measuring system to detect objects and determine their distance. For each emitter element-sensor element pairing, a measurement process is performed.

A measuring process comprises a plurality of measuring cycles. In a measurement cycle, a laser pulse is emitted by the emitter element, which can be detected by a reflection of an object again by one or more sensor elements. The measurement duration is at least so long that the laser pulse can move up to the maximum range of the measurement system and back.

In such a measuring cycle, for example, different measuring ranges are run through. For example, sensor elements or sensor groups can be activated and deactivated at different times in order to achieve optimum detection. The measurement cycles of the measurement process do not have to be identical in their execution. In particular, the different points in time at which sensor elements or sensor groups are activated and deactivated can experience a certain time offset from the measurement cycle to the measurement cycle. The measuring cycles are thus preferably identical in nature and therefore not necessarily identical to one another.

A histogram is the result of a measurement process. A measuring cycle has at least the time it takes for the laser light to travel back to an object at the maximum measuring distance. The histogram divides the measurement duration of a measurement cycle into time segments, which are also called bin. A Bin ent speaks a certain period of time of the entire measurement period.

If a sensor element is triggered by an incoming photon, the bin, which corresponds to the associated transit time of the emission of the laser pulse, is increased by the value 1. The sensor element or the sensor group is read out by a TDC, Time to Digital Converter, and stores the triggering of the sensor element by a photon in the histogram, which is formed for example by a memory element or a short-term memory. This detection is added to the histogram in the bin which corresponds to the time of detection. The sensor element can only detect a photon but does not discriminate whether it originates from a reflected laser pulse or a background radiation. By performing a plurality of measurement cycles per measurement process, the histogram is filled further, the background noise provides a statistically distributed noise floor, but a reflected laser pulse always arrives at the same time. An object thus rises in the histogram as a peak from the noise floor and can thus be evaluated. This is essentially the TCSPC procedure. An evaluation takes place, for example, via the recognition of rising edges or local maxima.

During a measuring process, the measuring cycles can be carried out according to a time scheme which is identical for all successive measuring cycles. In this case, it may happen that highly reflective object, which is outside the maximum measuring distance, reflects the laser pulse of the preceding measuring cycle and this is detected by a sensor element. As a result, in the subsequent measuring cycle an object can be detected which is not within the measuring range. For example, an object is detected at close range even though it is actually at a great distance.

Accordingly, a waiting time is waited after each measurement cycle. Alternatively, the waiting time can also be interpreted as a change in the duration of a measurement cycle who the. This waiting time differs from measuring cycle to measuring cycle. Thereby, the reflected laser pulse of the distant highly reflective object is detected in the fol lowing measuring cycle at another time. Successive waiting periods must therefore differ in their duration. As a result, the highly reflective object is smeared over the measuring cycles in the histogram in width. When evaluating the histogram, the distant object is thus no longer recognized.

Accordingly, a first measuring cycle has a first waiting time, wherein a second measuring cycle has a second waiting time, wherein the first waiting time and the second waiting time differ from each other. Advantageously, the waiting times of the measurement cycles of the measuring procedure differ at least to the extent that a highly reflective object in the histogram is sufficiently smeared.

For example, the waiting time after each measurement changes by one bin. With a number of X measurements, the highly reflective object on the object is distributed over X bins and detected as an increase of the noise floor.

In the following, advantageous embodiments of the method will be explained.

It is suggested that the waiting time be within a predefined time interval.

In order to keep the measuring time as low as possible, the waiting time can be set in advance. Accordingly, the choice of the waiting time can only correspond to a value which is within the time period. For example, with a number of X measurement cycles, this period may be X Bins wide.

In an advantageous embodiment variant, the waiting time of a measuring cycle is chosen randomly.

As a result, a statistical component can be introduced. For example, a linear increase in the waiting time may cause an object to move at just the right speed so that the lubricating effect will be lifted. Advantageously, the random choice is combined with a predefined period of time. As a result, on the one hand, the statistical component can be combined with a short duration of the measuring process.

A waiting time, which has already been used during a measuring process, is expediently consumed for subsequent measuring cycles. Each waiting time is thus only once available. At a predetermined period, each waiting time is used. However, the period of time may also be wider so that more queues are available than needed in a measurement process. By choosing the appropriate period of time, the entire measurement process and its entire measurement duration can be kept as low as possible.

It is further proposed that a waiting period for multiple consumption may be present.

If, for example, each waiting time is duplicated, the width of the time range can be halved. The smearing of the object is still sufficient and the measuring time of the measuring process can be kept low.

In another variant, the waiting times are determined deterministically.

This can be, for example, a selection of waiting times for a measuring cycle, wherein at least some of the waiting times of different measuring cycles differ from one another. In particular, since the deterministic choice is made so that no ghost objects are detected. These predetermined can be selected for example by a modulo counter, which counts the number of the measuring cycle and thereby selects the appropriate value.

For example, short and long waiting times alternate, with the long and short waiting times also differing.

In particular, the waiting times over the entire measurement process can repeat more times, with successive waiting preferably differs. In particular, consecutive waiting times can be identical, provided that this repetition occurs only a few times.

In addition, the method will be explained again in detail with reference to several figures. Show it: 1 shows a LI DAR measuring system in a schematic representation;

FIG. 2 shows a transmission unit and a reception unit of the LIDAR measuring system from FIG. 1 in a front view; FIG.

3 shows a flowchart for a measuring cycle and an associated histogram;

4 shows a graphic representation of a measuring process with several measuring cycles;

Fig. 5 is a graphical representation of another measurement with multiple

Measurement cycles.

In the figure 1, the structure of a LIDAR measuring system 10 is shown schematically. Such a measuring system 10 is true for use on a motor vehicle be. In particular, the measuring system 10 is statically attached to the motor vehicle is arranged and also carried out conveniently even statically. This means that the measuring system 10 as well as its components and components can not perform or execute any Relativbe movement to each other.

The measuring system 10 comprises a LIDAR transmitting unit 12, a LIDAR receiving unit 14, a transmitting optics 16, a receiving optics 18 and an electronics 20.

The transmitting unit 12 forms a transmitting chip 22. This transmitting chip 22 has a plurality of emitter elements 24, which are shown for a clear representation cal tables squares. In contrast, the receiving unit 14 is formed by a receiving chip 26. The receiving chip 26 has a plurality of sensor elements 28. The sensor elements 28 are shown schematically by triangles. However, the actual shape of emitter elements 24 and sensor elements 28 may differ from the schematic illustration. The Emitterele elements 24 are preferably by VCSEL, Vertical Cavity Surface Emitting Laser, educated. The sensor elements 28 are preferably formed by SPAD, single photon avalanche diode.

The transmitting unit 12 and the receiving unit 14 are configured in a FPA configuration, Focal Plane Array. This means that the chip and the associated elements are arranged on one level, in particular a flat level. The respective plane is also arranged in the focal point or the focal plane of a Optikele management 16, 18. Accordingly, the emitter elements 24 are arranged on a plane of the transmitting chip 22 and are located on the measuring system 10 within the focal plane of the transmitting optics 16. The same applies to the sensor elements 28 of the receiving chip 26 with respect to the receiving optics 18th

The transmitting unit 12 is assigned a transmitting optical system 16, the receiving unit 14 is assigned a receiving optical system 18. A laser light emitted by the emitter element 24 or a light incident on a sensor element 28 passes through the respective optical element 16, 18. The transmitting optical system 16 assigns a specific solid angle to each emitter element 24. Likewise, the receiving optics 18 each Sensorele element 28 to a certain solid angle. Since Fig. 1 shows a schematic presen- tation, the solid angle in Fig. 1 is not shown correctly. In particular, the distance from measuring system to object is many times greater than the dimensions of the measuring system itself.

A laser light emitted by the respective emitter element 24 is always emitted by the transmitting optics 16 into the same solid angle. The Sensorele elements 28 consider due to the receiving optics 18 always the same solid angle. Accordingly, a sensor element 28 is always assigned to the same emitter element 24. In particular, a sensor element 28 and an emitter element 24 consider the same solid angle. In this LIDAR measuring system 10, a plurality of sensor elements 28 is assigned to a single emitter element 24. The sensor elements 28, which are assigned to a common emitter element 24, are part of a macrocell 36, wherein the macrocell 36 is assigned to the emitter element 24. An emitter element 28 emits laser light 30 in the form of a laser pulse 30 at the beginning of a measurement cycle. This laser pulse 30 passes through the emission optics 16 and is emitted in the emitter element 24 associated spatial angle. If an object 32 is located within this solid angle, at least a portion of the laser light 30 is reflected thereon. The reflected laser pulse 30, coming from the corre sponding solid angle, is guided by the receiving optics 18 on the associated Senso relement 28 or a macro cell 36 associated sensor elements 28. The sensor elements 28 detect the incoming laser pulse 30, wherein a release of the sensor elements 28 from a TDC 38, Time to Digital Converter, read out and is written in a histogram. With the aid of the time of flight method, the distance of the object 32 to the measuring system 10 can be determined from the transit time of the laser pulse 30. The determination of objects 32 and their distances is advantageously carried out using the TCSPC method, Time Correlated Single Photon Counting. The TCSPC method will be described in more detail below.

The sequence of such a measurement cycle is controlled by the electronics 20, which can read at least the sensor elements 28. The electronics 20 is also connected via a connection 34 with other electronic components of the motor vehicle or connectable, in particular for data exchange. The electronics 20 is shown here as a schematic kit. However, further detailed explanations should not be made. It should be noted that the electronics 20 may be scattered over a plurality of components or assemblies of the measurement system 10. In this case, for example, a part of the electronics 20 at the Empfangsein unit 14 is formed.

In FIG. 2, the transmission chip 22 and the reception chip 26 are shown schematically in a front view. In this case, only a partial section is shown, wherein the wider areas are substantially identical to those shown. The transmission chip 22 has the already described emitter elements 24, which are arranged in a column and row arrangement. However, this row and column arrangement is chosen only as an example. The columns are marked with large Roman numerals, the lines with large Latin letters. The receiving chip 26 has a plurality of sensor elements 28. The number of sensor elements 28 is greater than the number of emitter elements 24. The Sen sorelemente 28 are formed in a row / column arrangement. This row / column arrangement is also chosen by way of example only. The columns are numbered with small Roman numerals, the lines with small Latin letters. However, a row or a column of the receiving chip 26 does not relate to the individual sensor elements 28, but to a macrocell 36 which has a plurality of sensor elements 28. The macrocells 36 are separated from each other by dashed lines for better viewing. The sensor elements 28 of a macrocell 36 are all assigned to a single emitter element 24. The macrocell i, a is assigned to the emitter element I, A, for example. A laser light 30 emitted by a sensor element 24 forms at least part of the sensor elements 28 of the associated macrocell 36.

The sensor elements 28 can advantageously be activated and deactivated individually or at least in groups. As a result, the respectively relevant sensor elements 28 of a macrocell 36 can be activated and the irrelevant deactivated. This makes it possible to compensate for aberrations. Such aberrations may be, for example, static errors, such as aberrations of the optical elements 16, 18 or parallax errors, which will be exemplified in the following section.

Due to the parallax, for example, a emitted laser light 30 is imaged in the near range, ie at a small distance of the object 32 to the sensor elements 28 of the macrocell 36 arranged at the top in FIG. However, if the object is located further away from the measuring system 10, the reflected laser light 30 will strike a lower region of the macrocell 36 and thus the sensor elements 28 lying below. The shift of the incident laser light due to the parallax is particularly dependent on the arrangement of the units and the con structive design of the measuring system 10. The sensor elements 28 of a macrocell 36 are then during a

Measurement cycle activated and deactivated so that unlighted sensor elements are deactivated. Since each active sensor element detects the ambient radiation as a background noise, is kept low by deactivating the unlit sensor elements of the noise reason of a measurement. By way of example, two sensor groups are shown in FIG. 2 on the receiving chip 26.

By way of example, the sensor groups a, ß and g are shown here, which merely serve to explain the method. In principle, the sensor groups can also be chosen differently. The sensor group a comprises a single Sensorele element 28, with which a short-range is to be detected at the beginning of the measurement cycle. The sensor group β comprises a plurality of sensor elements 28 which are active at an average measuring distance. The sensor group g includes some sensor elements 28 which are active in a far-end area. The number of sensor elements 28 of the sensor group β is largest, followed by the sensor group g.

The selection of the sensor elements 28 for the sensor groups a, ß and g is chosen only by way of example and may differ in an application of the Darge presented, as well as the design of the sensor elements 28 and the arrangement relative to the emitter elements 24th

In the near range is normally only a small number of sensor elements 28 ak tively. By way of example, these sensor elements 28 can also differ structurally from the other sensor elements 28 in order to take into account specific requirements for the near range.

The sensor group g is a partial section of the sensor group β, but also has two sensor elements 28, which are exclusive to the sensor group g. For example, the different sensor groups may also completely overlap, ie have a common number of sensor elements 28. However, it is also possible for all the sensor elements 28 of a sensor group to be assigned exclusively to this sensor group. It can also happen that even just a part of the sensor elements 28 for a sensor group is exclusive, the remaining sensor elements 28 are part of several sensor groups.

In the case of a transition from a first measuring range to a second measuring range, for example from the middle range to the far range, only a part of the sensor elements of the previously active sensor group is then deactivated, with part of the sensor elements remaining activated and optionally a further number of sensor elements 28 being activated.

The sensor elements 28 are connected to a TDC 38, Time to Digital Converter, the verbun. This TDC 38 is part of the electronics 20. At the receiving unit for each macro cell 36, a TDC 38 is formed, which is connected to all sensor elements 28 of the macro cell 36. However, this embodiment variant for the TDC 38 is at play.

A trained as SPAD sensor element 28, which is active at the same time, can be triggered by an incoming photon. This trip is read out by the TDC 38. The TDC 38 then enters this detection in a histogram of the measurement process. This histogram will be explained in detail below. On the SPAD, after a detection, the necessary preliminary voltage must first be set up again. Within this time, the SPAD is blind and can not be triggered by incoming photons. This time required for charging is also called dead time. In this regard, it should also be noted that an inactive SPAD requires a certain amount of time to build up the operating voltage.

The emitter elements 24 of the measuring system 10 send out their light pulses in succession, for example in rows or rows. This prevents a row or column of emitter elements 24 from causing the sensor elements 28 of the adjacent row or column of macrocells 36 to be avoided. In particular, only the sensor elements 28 of the macrocells 36 are active, the corresponding elements Emitterele 24 have a laser light 30 emitted. As already mentioned, the TCSPC method is provided for the determination of the distance of the objects. This will be explained with reference to FIG. In the case of the TCSPC, a measuring process is carried out in order to determine any objects and their distance from the measuring system 10. A measurement involves several identical measurement cycles that are repeated identically to provide a histogram.

This histogram is then evaluated to determine any objects and their distance. In this case, FIG. 3 comprises a plurality of subfigures a, b, c, d, e, f, g. Each of the figures has its own Y-axis, but they share a common X-axis, on which the time is plotted. FIGS. 3a to 3f show a single measuring cycle, wherein FIG. 3g shows the result of an entire measuring process. A measuring process starts at time t _start and ends at the _{end of time} .

FIG. 3 a shows the activity of an emitter element 46 during a measurement cycle. The emitter element is activated at time t ₂ and shortly thereafter deactivated at time t _{2 *} , whereby a laser pulse is emitted.

Figures b, c and d show the activity phases of the sensor elements 28 of the Sen sorgruppen a, ß and g within a measuring cycle. The sensor element of the sensor group a is already loaded before the emission of the laser pulse at the time t ₀ and is already active at the time ^. The times ^ and t ₂ may coincide with each other in time or be offset from one another. The sensor group a is thus active at the latest with the emission of the laser pulse 30. This corresponds to the Nahbe rich.

The sensor elements of the sensor group ß are charged shortly before the deactivation of the sensor group a at the time t ₃ and are active at the time t ₄ at which the sensor group a is deactivated. The sensor group β, which covers the central area, remains active for a longer period of time until it is switched off for the transition of the long range. The activity of the sensor elements 28 of the sensor group g is shown in the figure 3d Darge. Since the sensor group g is partially a subgroup of ß, the overlapping sensor elements 28 are left active at the time point t ₇ , whereas the übri gene sensor elements 28 of the sensor group ß are disabled. The remaining sensor elements 28 of the sensor group g are already in advance gela at time t ₆ . The sensor group g also remains active for a long period of time until they are deactivated at time t ₈ . The time t _{8 also} corresponds to the end of the measurement cycle at the time t _end . However, in other embodiments, the end of the measurement cycle need not be identical to deactivating the last active sensor group. The beginning of the measurement cycle 42 is defined by the time t _start and the end of the measurement cycle 44 is defined by the time t _end .

The measurement cycle thus includes the emission of the laser pulse 46, the switching of the sensor groups and the detection of incoming light in the near zone 48, in the central region 50 and in the far region 52.

In the figure 3e an object 32 is shown by way of example, which is located in the central area. The representation corresponds to the reflection surface of the object 32. The laser pulse 30 reflected at the object 32 can be detected by the active sensor elements 28 of the sensor group β at the time t ₅ .

FIG. 3f shows a histogram 54, which represents an exemplary filling of several measuring cycles. The histogram divides the entirety of the measurement cycle into individual time segments. Such a time segment of a histogram 54 is also called bin 56. The TDC 38 filling the histogram 54 reads out the sensor elements 28. Only an active sensor element 28 can pass detection to the TDC 38. If a SPAD is triggered by a photon, the TDC 38 fills the histogram, which is for example represented by a memory, with a digital 1 or a detection 58. The TDC links this detection 58 with the current time and fills the associated time Bin 56 of the histogram 54 with the digital value. Since there is only one single object 32 in the middle area, only one object 32 can be detected. Nevertheless, the histogram is filled with detections 58 over the entire measuring cycle. These detections 58 are generated by the background radiation. The photons of the background rays can trigger the SPADs. The amount of the noise reason generated thereby is thus dependent on the number of active SPADs, ie the number of sensor elements 28 of a sensor group.

It can be seen that in the near range 48 only two bins 56 each filled with a Detekti on 58, wherein a third bin remains empty. This corresponds to the determined background radiation. The number of detections is very low, since only a single SPAD is active.

The sensor group β, which has a multiple of active sensor elements 28, is active in the middle region 50 that follows in time. Accordingly, the detected background radiation is larger, so that a bin is filled on average with three detections NEN 58, partially 4 or 2 detections 58. In the area 32, in which the reflective surface of the object 32 at time t _{5 of} the measuring cycle is, the number of detections 58 is much higher. In this case, seven or eight detections 58 are recorded in the histogram 54.

In the far region 52 there is no object that can be detected. Here, only the background radiation is shown with on average one to two detections 58 per bin. The mean value of the noise floor is correspondingly lower than in the middle area 50, since the number of SPADS is also smaller. However, the mean value of the detections 58 is higher than in the near range 48, since the short range 48 with the sensor group a has only a fraction of the number of sensor elements 28 of the sensor group g.

The histogram shown is, as already mentioned, merely filled by way of example. The number of bins, as well as their fill, can be significantly different for an actual measurement cycle. Normally, no object 32 can yet be detected from a single measurement cycle. Accordingly, in the TCSPC method performed a variety of measuring cycles in succession. Each measurement cycle fills the same histogram. Such a histogram, which has been filled by a plurality of measuring cycles, is shown in FIG. 3g.

The histogram of Figure 3g is also formed by digitally filled bins. For a clearer view, however, the illustration of each bin was omitted in this figure and only a line drawn, which corresponds to the capacity of the bins.

In the near range 48 results in a low noise floor in the central region 50 results in the highest noise floor, since most of the sensor elements are active. In the far region 52, the determined noise floor lies between that of the near zone 48 and that of the far zone 50. In addition, the detection of the laser light 30 reflected by the object 32 can be detected in the middle region 50 in the form of a peak 33. The determined background radiation is distributed statistically evenly, whereby a substantially straight line depending on the number of active Sensorelemen te is provided. However, the object and its reflective surface are always in the same place, and over the sum of the measurement cycles, the peak 33 protrudes above the noise floor.

The peak 33 can now be detected via its maxima or its steeply rising flank as object 32, and the distance of the object 32 can be determined via its position in the histogram.

In the determination of the histogram according to FIG. 3g, the measurement cycle of FIG. 3 was repeated in many identical ways. In particular, all the actions described are always performed at the same times t ₀ to t ₈ .

For an improvement of the detection, the measuring cycles can also be formed merely essentially identical instead of identical. For this purpose, the activation and deactivation of the sensor groups is shifted from measurement cycle to measurement cycle. As a result, the steeply rising and falling flanks in the transition be flattened conditions of the measuring ranges. For the further explanation, however, the drawing of Fig. 3g is more than sufficient.

FIG. 4 shows graphically a measuring process which has a plurality of measuring cycles 60, 62 and 64. With regard to the first measuring cycle 60, the second measuring cycle 62 and the third measuring cycle 64, the respective time axis is shown, which exceeds the measuring duration t _{mess of} a measuring cycle.

Within the measuring time t _mess is the object 32, which is detected at the time Darge presented by the sensor element 28. Through this object 32 the peak 33 is generated in the histogram according to FIG. 3f.

In addition, an object 66 is located. This object 66 is outside the defined maximum measuring range of the LI DAR measuring system 10. Furthermore, the object has a reflectivity, which causes a detection by a sensor element 28 in a subsequent measuring cycle. The laser pulse 30 emitted at the beginning of the first measuring cycle 60 and reflected at the object 66 is now detected in the second measuring cycle 62. The detection in the second measuring cycle it follows at the time T _g .

For the sake of simplicity, the object does not move over the measuring time of the measuring procedure compared to the LI DAR measuring system. In addition, during the measuring process, the next measuring cycle is started immediately at the end of a measuring cycle. As a result, the laser pulse of the second measurement cycle 62 in the third measurement cycle 64 is also detected at the time T _g .

In the histogram, a peak 67 is formed. This peak 67 is detected as a ghost object in a short distance, although the object 66 is actually outside the maximum measuring range.

Such a ghost object can be hidden by the method which is explained with reference to FIG. 5, he. FIG. 5 also shows three measurement cycles 60, 62 and 64 of a plurality of measurement cycles of a measurement process. The objects 32 and 66 behave identically to the method explained in FIG. 4.

Between the end of the first measuring cycle 60 and the beginning of the second measuring cycle 62, a first waiting time awaited. As a result, the laser pulse reflected at the object 66 is detected at the time T ₁ . Between the end of the second measuring cycle 62 and the beginning of the third measuring cycle 64, a second waiting time At _{2 is} awaited. The first waiting time and the second waiting time At ₂ are different here. As a result, the laser light which is reflected on the object 66 is detected at time T ₂ . Likewise, other waiting times differ from each other.

The peak 67 thereby smeared to the smeared peak 68. In a Auswer tion of the histogram no ghost object is detected.

The waiting times can rise linearly, ie be extended from measuring cycle to measuring cycle a certain value. Here, however, it can happen that an object outside the maximum measuring range performs a movement that cancels out the change in the waiting time.

It is therefore proposed that the choice of the waiting time be chosen randomly from measuring cycle to measuring cycle. The probability that an object is currently making such a relative movement with respect to the measuring system is almost zero. In order to keep the measurement time of the measurement still low, a time range can be specified, in which the waiting times are. Such a time range advantageously includes a plurality of bins.

In addition, to effect a uniform smearing, an already used waiting time for subsequent measuring cycles can be used up. This ensures that each waiting time of the time range is used only once or limited often. In addition, the time range can be selected smaller than the number of measurement cycles multiplied by the duration of a bin. In particular, can be this defines very well the shape into which a peak of a ghost object smears.

As an alternative to the random selection of the waiting time, a deterministic choice of the waiting times can also be used. In this case, the waiting times have already been determined in advance and are used for the consecutive measuring cycles. The de terminist choice provides the waiting times so that no ghost objects are detected. For example, the waiting times are also selected within a time range, wherein the waiting times have a minimum distance from each other. In particular, large and small waiting times are alternately ge chooses.

A minimum distance is also conceivable for the statistical distribution in order to optimally distribute the detections of the distant object in the histogram.

Basically, the statements on the statistical choice of waiting times are mutatis mutandis applicable to the deterministic choice of waiting times as well as vice versa.

At the measuring system for the implementation of this method, a Zeitsteuerein unit is formed on the electronics 20. This electronic system controls the timing of the measuring process, in particular the individual measuring cycles as well as the activation of the individual elements of the measuring system. This time control unit has, for example, a timing controller. Accordingly, the time control unit controls the exact adherence to the waiting times between the measuring cycles. Reference LI DAR measuring system

LIDAR transmitting unit

LIDAR receiving unit

transmission optics

receiving optics

electronics

transmitting chip

emitting element

receiving chip

sensor element

Laser light / laser pulse

object

peak

connection

macrocell

TDC

x-axis (time)

Start measuring cycle

End of measuring cycle

Emitting laser pulse

Detection close range

Detection middle area

Detection remote area

histogram

am

detection

first measuring cycle

second measuring cycle

third measuring cycle

object

peak 68 blurred peak a, b, g sensor group

1.11 .... Send chip column

1.11 .... column receiving chip

A, B, ... series transmission chip a, b, ... series reception chip t _start time

t _{the end of} the time

t ₀ time

ti time

t ₂ time

t _{2 *} time

t ₃ time

t ₄ time

t ₅ time

t ₆ time

t ₇ time

t ₈ time

T _g time

Time T ₂ time

Waiting time DG ₂ waiting time

Claims

claims

1. A method for performing a measuring operation for a LI DAR measuring system (10),

- Wherein during the measurement process, a plurality of the same thing

Measuring cycles (60, 62, 64) are performed,

wherein a new measurement cycle (62) begins only after the end of the preceding measurement cycle (60) and a waiting time (At ₁ , At ₂ ),

- Wherein the waiting times (At ₁ , At ₂ ) of successive measuring cycles (60, 62) differ.

2. The method according to claim 1, characterized in that the waiting time

(At ₁ , At ₂ ) lies within a predefined period of time.

3. The method according to claim 1 or 2, characterized in that the waiting time (At ₁ , At ₂ ) of a measuring cycle is chosen randomly.

4. The method according to any one of claims 1 to 3, characterized in that a waiting time (At ₁ , At ₂ ), which has already been used in a measuring operation, is consumed for subsequent measuring cycles.

5. The method according to claim 4, characterized in that a waiting time

(At ₁ , At ₂ ) is available for multiple usage.

6. The method according to claim 1 or 2, characterized in that the waiting time (At ₁ , At ₂ ) of a measuring cycle is chosen deterministically.