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    • 专利摘要:
    1. A method for measuring the distance of environmental targets by transit time measurement of pulses reflected thereon, in particular laser pulses, comprising: emitting a train of pulses (Sk) in which the pulse intervals (ΔTSk) of at least one group (GSm) of successive pulses (Sk) following a known distance pattern (M), as transmission pulse sequence ({Sk}) and accompanying reception of the reflected pulses as a result ({Ek}) of received pulses (Ek) and measuring their pulse intervals (ΔTEk), determining in the received pulse train ({Ek} ), a group (GEm) of received pulses (Ek) whose pulse intervals (ΔTEk) are most similar to the known spacing pattern (M), determining transit times (Tk) between each transmit pulse (Sk) of said transmit pulse group (GSm) and respectively that receive pulse (Ek) of said receive pulse group (GEm), which has therein the same ranking in the group (GEm) as this transmit pulse (Sk) in its group (GSm), and determining Distance measurements (Dk) from the mentioned transit times (Tk).
    公开号:AT515214A4
    申请号:T50828/2013
    申请日:2013-12-16
    公开日:2015-07-15
    发明作者:Peter Dipl Ing Rieger；Andreas Dr Ullrich
    申请人:Riegl Laser Measurement Sys；
    IPC主号:
    专利说明:

    RIEGL Laser Measurement Systems GmbHA-3580 Horn
    The present invention relates to a method for the distance measurement of environmental targets by transit time measurement of pulses reflected therefrom. The pulses may be of any kind, e.g. Light pulses, in particular laser pulses, radio pulses, in particular radar pulses, sound pulses or the like. The invention further relates to a method for laser scanning by directing laser pulses continuously to different Umge¬bungsziele.
    Modern pulse duration rangefinders, such as laser rangefinders or scanners, operate with high pulse power over long distances and / or high pulse repetition rate for rapid creation of a plurality of distance measuring points of the environment. In both cases, the situation may arise that the next pulse is already being transmitted, even before the reflection of the last pulse has been received, so that the incoming receive pulses can no longer be unambiguously assigned to their respective transmit pulse. This is known as "multiple time around" (MTA) or "multiple pulses in theair" problem. The maximum size dmax of the uniquely measurable distance range, the so-called MTA zone, results from the pulse repetition rate PRR and the speed of light c to dmax = c / (2-PRR).
    For example, laser scanners of modern design offer pulse repetition rates of up to 400 kHz, which corresponds to an MTA zone size dmax of approximately 375 m. If this measurement distance is exceeded, the measurement result can not be correctly interpreted due to the unambiguous assignability of the transmit and receive pulses in the rule.
    Figs. 1 and 2 show this situation in detail. From an aircraft-based laser scanner 1, a pulsed laser measuring beam 2 is scanned over an environment U with individual environmental targets (sampling points) Ui, U2 / ..., e.g. line-wise fan-shaped. From time-of-flight measurements on the individual emitted pulses Si, S2,... That are retrieved after the ambient reflection as received pulses Ei, E2 (..., The target distances Di, D2,... To the individual environmental targets Ui, U2,.. become.
    1a and 2a show an exemplary situation both surveying of ambient Ux, U2, which are in the first, the laser scanner 1 nearest MTA zone Z ±: The transmission pulse Ex belonging to the transmission pulse Si is recovered before the next transmission pulse S2 in Time interval τ = 1 / PRR is sent, etc., etc.
    FIGS. 1b and 2b show an exemplary situation when environmental targets U3, U4 are located in the second MTA zone Z2: Here, the receive pulse E3erst belonging to the transmit pulse S3 is received after the next transmit pulse S2 has already been sent out. In order to determine the correct distance D3 of the surrounding target U3 in the zone Z2, it is necessary to assign the reception pulse E3 correctly to the transmission pulse S3; If the receive pulse E3 is erroneously assigned to the immediately preceding transmit pulse S4, a false target distance D3 'results in the wrong MTA zone Zi instead of the correct target range D3 in the correct MTA zone Z2.
    For the correct mutual assignment of the transmission and reception pulses and thus overcoming the MTA zone limits for unique distance measurement results, a variety of methods are known. A first option is to be careful in planning the surveying tasks to ensure that all expected environmental targets in one and the same MTA zone lie in order to make the correct assignment. Naturally, this method can only be used for special measuring tasks and, for example, for highly mobile or large-scale surveying or scanning tasks, e.g. airborne mountain scanning or terrestrial vehicle-based scanning, inappropriate.
    Another group of methods is based on making the individual transmission pulses distinguishable by varying or coding their polarization, amplitude or wavelength in order to allocate the received pulses accordingly. However, these methods are either only for a few "pulses in the air". suitable or require consuming coded pulses, which limits the pulse repetition rate and the measurable distance range and extends the measuring time.
    The object of the invention is to provide a method for removal measurement or scanning, which permits automatic assignment and thus correct measurement of environmental targets in arbitrary MTA zones with a high pulse repetition rate. This object is achieved by a method of the type mentioned in the introduction, which comprises:
    Transmitting a train of pulses in which the pulse intervals of at least one group of successive pulses follow a known spacing pattern as a transmit pulse train and concomitantly receiving the reflected pulses as a train of received pulses and measuring their pulse intervals;
    Determining, in the received pulse train, a group of receive pulses whose pulse intervals are most similar to the known spacing pattern,
    Determining transit times between each transmit pulse of said transmit pulse group and each receive pulse of said receive pulse group having therein the same row in the group as that transmit pulse in its group, and
    Determining distance measurements from said runs.
    It should be mentioned that the variation of the pulse interval and thus the pulse repetition rate (reciprocal value of the pulse spacing) is called "PRR modulation". in the field of radar technology is known per se to "ghost echoes". ("Ghosting") of transmit pulses outside the correct MTA zone identi¬fizieren.
    The present invention uses a novel "time-space" consideration of a PRR-modulated transmit pulse train, wherein the varying pulse intervals in a pulse group of the sequence form a unique spacing pattern that can be recognized in the receive pulse train as a burst group. As a result, an MTA zone-correct assignment of the reception pulses in this group to the transmission pulses of the causative transmission pulse group can be carried out, whereupon precise, individual transit times can be calculated between these transmission and reception pulses assigned to this MTA zone-correct , As a result, highly accurate distance measurement values under automatic MTA zone assignment can be achieved with the complete time resolution of the transmission pulses of the transmission pulse trains.
    The invention is based on the one hand on the knowledge that the "surface roughness". the environment to be measured within a transmit pulse group for the MTA zone assignment is low, i. the pitch pattern of the transmission pulse group is slightly distorted by the environmental reflection of the individual pulses of the group, so that recognition of the pitch pattern in the received signal sequence is possible by means of a pattern similarity search; On the other hand, if the correct received signal group has been assigned to the transmit pulse group, exact transit times between the individual transmit and receive pulses of the groups can be calculated, allowing a very accurate measurement of this surface roughness with individual distance measurement values.
    The MTA assignment according to the invention requires only one groupwise, i. local observation of the transmission and reception signal sequences via only a few pulses in each case and can therefore with comparatively low computational complexity e.g. also be done in real time ("online") directly during the measurement process, as well as the subsequent runtime and Entfer¬ calculation.
    The spacing pattern used can be known in several ways. In a first embodiment, a totally random spacing pattern may be used, for example, by randomly varying the pulse spacings of the successive transmit pulses, which corresponds to PRR modulation with white noise. The concrete pulse intervals occurring in a transmission pulse group can then be recorded directly during transmission, so that the distance pattern for the similarity search in the received signal sequence is known.
    Alternatively, a pre-stored random or pseudo random pattern may be given and the transmitted pulses may be transmitted according to this pitch pattern, whereby the pitch pattern is also known.
    Particularly suitable are spacing patterns based on Pseudo-random sequences, such as an m-sequence or a Barker code, which have advantageous properties for correlation methods for determining the distance pattern-like received signal group.
    As already briefly mentioned, the method of the invention is particularly useful for a repetitive application in the course of a long transmission pulse sequence, which is composed of a multiplicity of successive transmission pulse groups, and is processed locally, in each case transmission pulse group for transmission pulse group. In this case, it is preferred for each transmission pulse group to receive the received signal sequence only up to the next-lying, ie. The individual pulse propagation times are then determined for this pair of adjacent spacing pattern-like transmitted and received signal groups, which are found first in time. The pulse transit times determined in this way - composed over all successive transmit pulse groups - result in a complete sequence of pulse travel times.
    Times and thus distance measured values for the entire transmission pulse sequence, i. for each individual transmit pulse of the same.
    Since in practice an automatic evaluation of an limited number of MTA zones is sufficient, the length of the distance pattern, i. the transmit pulse group are correspondingly limited, which is also favorable if the environmental targets sampled by the transmit pulse sequence lie in different MTA zones. The shorter the transmit and receive pulse groups to be correlated, the faster the method responds to MTA zone change during the transmit pulse train, and the longer the transmit and receive pulse groups to be correlated, the less susceptible to failure the automatic MTA zone allocation. Accordingly, in preferred embodiments of the invention which provide a good compromise between these conflicting requirements, the number of pulses in the transmit pulse group and in the receive pulse group is each 4 to 64, preferably 16 to 32.
    The reception pulse group is preferably determined by correlating the transmission pulse group with a window which slides over the reception pulse sequence with the transmission pulse group length and determining the position of the sliding window which gives the correlation maximum. This can be done, for example, by means of a loop, which is carried out for each transmission pulse group, in which a window position, i.e. a window position, is set in each loop pass. a potential receive signal group, "tried out" with respect to its distance pattern correlation. will be achieved.
    It is particularly advantageous if a hardware-near solution is used for the correlation by using a filter adapted to the known spacing pattern, to which the pulse intervals of the received pulse train are fed as input signal and whose output signal indicates the time of occurrence of the distance pattern-like received signal group thereby directly implemented as a pulse response of a matched filter so that a maximum response of the filter, a "peak", is achieved. at its output indicating the recognition of the distance pattern in the receive signal sequence.
    In this embodiment, it is furthermore particularly advantageous if a further filter adapted to the known spacing pattern is used, to which the pulse spacings of the transmitter pulse train are fed as input signal and whose output signal indicates the time of occurrence of a transmit pulse group, which serves as a time reference for the determination of the transmitter pulse Running times are used between the transmission pulses of a transmission pulse group and the respective reception pulses of the reception pulse group determined for this purpose. On the other hand, the components for generating the transmission pulse sequence with the mentioned spacing patterns on the one hand and those for evaluating the received pulse sequence on the other hand can be decoupled from one another more strongly. The further matched filter extracts the time information about the beginning of a new distance pattern and thus one each new transmit pulse group directly from the transmit pulse train and provides this time information as a reference for the MTA zone-correct transit time measurement of the reception pulses.
    The method of the invention can also be used for multi-target laser scanners, which are capable of generating multiple, one-and-the same transmit pulses, e.g. Foliage of a tree and ground underneath to evaluate reflected multiple receive pulses and thus to provide multiple range readings per transmit pulse. An embodiment of the invention which is suitable for this application is characterized in that the received signal sequence prior to said step of determining the distance pattern-like received signal group is cleaned by multiple receive pulses by taking into account only one received pulse from a plurality of receive pulses occurring within a mean transmit pulse spacing, and the others are left unaccounted for. If desired, run times and distance measurement values for the previously rejected receive pulses can also be subsequently determined, in each case based on the respective originating transmit pulse, i.e., that transmit pulse with respect to which the transit time of a considered receive pulse was determined.
    According to a first aspect of the invention, the method can be used for MTA-correct distance measurement of an environmental target, in that the transmission pulses are continuously directed to the same environmental target.
    According to a second aspect of the invention, the method can also be used for laser scanning in that the pulses of the transmitted pulse sequence are laser pulses and are continuously directed to different environmental targets in order to scan or scan a whole environment point by point. Laser pulses can be caused by rotating mirrors or the like. particularly easy to focus on different goals.
    The invention will be explained in more detail below with reference to embodiments shown in the enclosed drawings. In the drawings shows:
    Fig. 1 schematically shows various reflection situations of a pulsed laser scanning beam on environmental targets located in different MTA zones, according to the prior art;
    FIG. 2 shows exemplary time diagrams of transmit and receive pulses for the reflection situations of FIG. 1 according to prior art; FIG.
    3 shows exemplary timing diagrams of transmit and receive pulses in connection with various steps of the method of the invention;
    4 shows exemplary spacing pattern diagrams of different pulse sequences in the context of the method of the invention;
    5 shows the step of determining individual run times between individual pulses of MTA zone-correctly correlated transmit and receive signal groups according to the method of the invention;
    Fig. 6 is a block diagram of a pitch pattern correlator constructed by means of two matched filters for carrying out the method of the invention; and
    FIG. 7 shows exemplary timing diagrams of the output signals of the two matched filters of FIG. 6. FIG.
    Figures 1 and 2 show the impulse assignment problem of MTA-zone-crossing ranging and have already been discussed. To overcome this problem, the method now described below is used, which is based on a signal-analytical evaluation of a plurality of transmission pulses Si, S2, S3,..., Generally Sk, and reception pulses Ei, E2, E3,..., Generally Ek , based.
    The following process description concretely refers to laser pulses as transmit and receive pulses Sk, Ek. However, it is understood that the transmit and receive pulses Sk, Ekbeliebiger type may be, for example, sound pulses in a sonar, light pulses in a time-of-flight camera (photonic mixing device, PMD), radar pulses in a radar rangefinder or -scanner, electrical impulses in Leitungs¬messgeräten etc. or just laser pulses in a Laserentfernnmessmesser or scanner. Accordingly, the method described herein is generally applicable to any type of pulse transit time measurement method.
    Referring to Figures 3a and 3c, a sequence {Sk} of laser transmit pulses Sk from the laser rangefinder scanner 1 is emitted to the environment U (Figure 1) to detect reflections of the transmit pulses Sk at environmental targets Ui, U2, ..., in general, Ui is to receive a sequence {Ek} of received pulses Ek. From the running time Tk of each ambient-reflected laser pulse, ie the difference between the reception time tEk of the reception pulse Ek and the transmission time tsk of the underlying transmission pulse Sk / can be in a known manner the distance Dk = c-Tk / 2 from the rangefinder or scanner 1 to ver¬ measure environmental target Ui. The transit times Tk and distance measurement values Dk are directly proportional to one another and are therefore used synonymously and interchangeably hereinafter.
    The method described here can be used both for distance measurement, if the transmission pulses Sk are continuously directed to one and the same environmental target Ui, as well as for scanning, if the transmission pulses Sk are continuously directed to different environmental targets Ui, e.g. line by line scanning over the environment U out. In the former case, a multiplicity of distance measurement values Dk of the same and the same environmental target Ui are obtained, which are subsequently - e.g. from outlier values - can be averaged to obtain a final result of the distance D. In the second case, from the plurality of distance measurements Dk and the transmission direction of the transmitted pulses Sk known in the scanner 1, a surface model of the environment U (a "point cloud") can be created, as known to those skilled in the art e.g. in the field of laser scanning.
    The mapping P between transmit pulses Sk and receive pulses Ek shown in FIGS. 3a and 3c is based on the assumption that the environment targets Ui are located in the second MTA zone Z2, see the exemplary environment targets U3 and U4 in FIG shown assignment P is a reception pulse Ek no longer the immediately preceding Sen¬deimpuls but the penultimate transmit pulse assigned. The sampled environmental targets Ui lie in the "correct" corresponding to the assignment P. MTA zone Z2, the distance measurement values Dk calculated on the basis of the shown transit times Tk are correct.
    In general, the MTA zone Zi, Z2, ..., generally Zj, in which the environmental targets Ui are located, is not known. In order to also detect the correct MTA zone location in this case and thereby determine the correct range measurement values Dk, the following procedure is used.
    As shown in Figure 3a, the transmit pulses Skn are not given a constant pulse spacing τ = ΔΤ = 1 / PRR, i. In other words, the pulse repetition rate PRR or the pulse interval ΔΤ is modulated with a signal ("pulse-position-modulated") by the aforementioned variation of the pulse intervals Achieve ATSk.
    The variation of the pulse spacing ATsk from pulse Sk to pulse Sk + i is chosen to be application-specific, for example +/- 1%, +/- 5%, +/- 10% or +/- 50% (or more) about a mean ren (average) transmit pulse distance ΔΤ.
    The modulation signal for achieving the aforementioned pulse spacing variation may be of any type, e.g. a sine-wave signal, triangular signal, sawtooth signal, staircase signal, a data signal with its own information content, or a statistically susceptible signal such as white noise. With such an incident signal, the pulse repetition rate PRRk or the pulse interval ATSk is randomly varied randomly in the manner of a random "phase jitter" of the transmitted pulses Sk. Within certain limits, such a random signal may also be merely pseudo-random, such as an m-sequence or a Barker code.
    FIG. 4a shows an alternative representation of the transmission pulse intervals ATSk of the transmission pulse sequence {Sk} plotted as samples at regular display intervals above the index k, i. in a regular index representation raster k. The amplitude of each sample of the sample sequence of FIG. 4a thus corresponds to a respective pulse spacing ATSk, so that a plurality of consecutive amplitude samples or samples in FIG. 4a is a "spacing pattern"; M several transmit pulses Sk vonFig. 3a play.
    It will be appreciated that the pulse spacings ATSk may also be plotted relative to the average transmit pulse spacing τ = ΔΤ, such that each amplitude sample of the pulse spacing representation of FIG. 4 merely represents the amount of "phase jitter". each transmit pulse Sk relative to an exactly pe¬riodischen Aussendetakt PRR = l / τ reproduces. The distance pattern M can therefore also comprise merely relative pulse distance definitions, based on an average transmission pulse spacing τ = ΔΤ.
    In the example of FIGS. 3 and 4, a pseudorandom spacing pattern M (here: repetitive) after every five transmission pulses Sk of the transmission pulse sequence {Sk} has been selected. The transmit pulse sequence {Sk} can therefore also be viewed as a sequence of transmit pulse groups GSi, GS2,..., Generally GSm, each of which is partially overlapping in the first or last transmit pulse, of transmit pulses Sk between which pulse intervals ATsk corresponding to the distance pattern M are located.
    It is not necessary for each transmit pulse group GSm to have the same spacing pattern M, it could also each have an individual spacing pattern Mm, for example if the pulse intervals ATsk of the transmit pulse sequence {Sk} are modulated with a modulation signal not corresponding to the periodicity of the groups GSm, e.g. with white noise. Preferably, however, the same distance pattern M is used for all groups GSm, which simplifies the method, but limits the number of automatically allocatable MTA zones Zj to the group or pattern length, as explained in more detail below.
    Recognition of the pitch pattern M or Mm of a transmit pulse group GSm in the receive pulse {Ek} can now be performed as follows for automatic MTA zone mapping, i. to find the correct pairing P, can be used.
    4b shows a pulse interval representation of a received pulse sequence {Ek} in reflection of the transmission pulse sequence {Sk} at a target at a constant distance, for example a mirror. As can be seen, the distance pattern M of the transmission pulse groups GSm are found in unmodified form, only offset in time according to the correct MTA zone Z2 or Z2. Pairing P, in the receive pulse train {Ek} again. Those reception pulses Ek, which thus belong to a reception pulse group GEm (Fig. 3c) and show the distance pattern M (or Mm) (Fig. 4b), are accordingly the "correct" ones to the transmission pulses
    Sk of the transmit pulse group GSm to be returned to the received pulse Ek.
    4c shows, instead of the theoretical ideal reflexion case of FIG. 4b, the reflection of the transmission pulse sequence {Sk} at a real environment U at which each transmission pulse is transmitted to another environmental target Ui in e.g. the second MTA zone Z2, however Ditrifft in a different individual distance. As a result, the received pulses Ek each receive a different time offset corresponding to the distance D ± of the respectively met Umge¬bungszieles Ui, which is accordingly to a deviating from the transmission pulse distance pattern MEmpfangssignal distance pattern M ', in the representation of FIG. 4c leads to different amplitude or distance values. By locating that received signal group GEm of received pulses Ek in the received pulse train {Ek}, which corresponds to " the " Abstandmus¬ter M 'shows, now again the belonging to the transmission pulse group GSm receive signal group GEm determined and thus the MTA zone assignment or matching P right be determined.
    Once the distance-pattern-like received signal group GEm has been found in the received signal sequence {Ek} (and thus the correct pairing P), then for each individual transmit pulse Sk the causative transmit pulse group GSm and the respective sequence in the group receiving pulse Ek of the detected receive pulse group GEm the first pulse of the group GSm is assigned to the first pulse of the group G ^ n, the second pulse of the group GSm to the second pulse of the group GEm, etc., etc. in FIG. 5 - an individual propagation time ATk between the transmission time tsk of the respective transmission impulses Sk and the reception time tEk of the received pulse Ek.
    This is illustrated in FIGS. 3c and 5 for one of a plurality of successive transmit and receive pulse groups GSm, GEm. As can be seen, through the group formation and spacing pattern identification in the transmit and receive pulse sequences {Sk}, {Ek}. on the one hand, and the individual time-of-flight calculations Tk of the individual pulses in the groups, on the other hand, are automatically allocated MTA zone-correct, individual pulse transit times Tk and thus distance measurement values Dk for each transmit pulse Sk in time with the transmit pulse sequence {Sk}.
    The finding of the distance-pattern-like receiver signal group Geih for a specific transmit pulse group GSm can be carried out in a wide variety of ways, for example by calculating correlations between potential "candidates". Groups having distance patterns M'i, M'2, ..., generally M'j, (see Fig. 4c), and respectively the transmission pulse distance pattern M, and then selecting the candidate group M'j having the largest degree Similarity to the desired distance pattern M.
    As a measure of similarity between two distance patterns M and M '(or M'j), any measure of difference known in the art can be used, e.g. the standard deviation, the sum of squared differences, etc.
    The length of the pitch pattern M (or M ', M'j), i. the number of pulse intervals ATsk or üTEk (= number of pulses Sk or Ek of a group GSm or GEm minus one), which is used to assign the receive signal groups GEm to the transmit pulse groups Gsm, has an effect on the number of MTA zones Zj, which can be automatically resolved and assigned: the larger the length of the distance pattern M, the more MTA zones Zj can be assigned. However, an excessively long length of the distance pattern M or size of the groups GSm, GEm complicates the detection of MTA zone changes during a transmission pulse sequence {Sk}, so that a compromise is advantageous. In practical applications, 4 to 64, preferably 16 or 32 pulses Sk, Ek per group GSm, Gmi i. Distance pattern M (or M ', M'j) with a length of 3 to 63, preferably 15 to 31 samples.
    FIGS. 6 and 7 show a practical embodiment for real-time or online calculation of correlations between groupwise spacing patterns of the transmit and receive pulse sequences {Sk}, {Ek} with the aid of matched filters ("mat¬ched") , here linear filters 3, 4. From the transmission and reception pulse sequences {Sk} and {Ek} - after corresponding detection of the time of occurrence tSk, tEk of the pulses Sk, Ekdarin - sequences of transmission or reception times {tSk}, {tEk} are formed and from these in turn - by pairwise difference formation, see delay elements 5, 6 and subtractors 7, 8 - distance sequences {ATSk} and {hTEk} generated. The distance sequences {ATsk}, {ATEk} are each fed to a matched filter 3 or 4.
    Each filter 3, 4 has an impulse response h [k] which corresponds to the spacing pattern M impressed into the transmission impulse sequence {Sk} and searched in the reception impulse sequence {Ek}. 7 shows the time characteristic of the signals (samples) at the output of the filters 3, 4: The filter 4 then generates a maximum value YSm in its output signal y (ATSk) when the impressed distance pattern M occurs in the transmission pulse sequence {Sk}. The output signal y (ATEk) of the filter 4 then delivers a maximum value YEm if the maximum correlation (signal matching) occurs between the received distance pattern M 'and the searched spacing pattern M stored in the filter 4 as an impulse response h [k]. From the time or index difference j between two consecutively occurring maximum values YSm and YEm determined, for example, by maximum value finders 9, 10, the pairing P or MTA zone assignment applicable here for the current group GSm or GEm (here the MTA zone Zj = Z2), in order then to be able to calculate the transit time and distance measurement values Tk or Dk for the individual pulses of the groups.
    Fig. 3b shows an optional step of "thinning out" the receive pulse train {Ek} to treat multiple target reflections, e.g. can occur in a multi-target La¬ rangefinder or scanner. In this case, for a transmit pulse Sk, two or more receive pulses Ek, i, Ek, 2, ···, generally Ek, p / are retrieved, for example, because the transmit pulse Sk from an airborne laser scanner passes through a treetop to the bottom and is reflected from both the foliage of the tree and the ground. This results in two temporally close to each other, but usually within a MTA zone Zj lying Ekpangsimpulse Ek, p.
    In order to identify the distance pattern-like reception signal group GEm, in this case, in order to obtain a correspondingly large number of pulses therein for the comparison of the transmission and reception groups GSm / GEm again, the signal sequence {Ek} will soon be used. of a plurality of received pulses Ek, p occurring within an average transmission pulse spacing τ, respectively, only one, in particular the first or last, received pulse Ek, p is taken into account in the received pulse sequence {Ek} and the others remain ignored for the time being, see FIG. 3c. As a result, the multi-target capability of the laser rangefinder or scanner is initially limited to only one (e.g., the first or last) target in an MTA zone Zj to "clean", i.e., "clean". identify the distance pattern M 'in the received signal sequence {Ek} equipped with the correct number of pulses for the pattern comparison and to be able to determine the correct assignment. As soon as the correct zone assignment P has been found between the transmit and receive pulse groups GSm and GEm, the multiple target reflections Ek (P previously left out of consideration can be taken into account again and also for these individual propagation times Tk (P with respect to the previously determined associated transmit pulse Sk and thus individual deletions ¬ungsmesswerte Dk (P be calculated in order to dissolve multiple targets.
    The invention is not limited to the illustrated embodiments, but includes all variants and modifications that fall within the scope of the attached claims.
    权利要求:
    Claims (12)
    [1]
    Claims 1. A method for measuring the range of surrounding targets by measuring the transit time of pulses reflected thereon, in particular laser pulses, comprising: emitting a train of pulses (Sk) in which the pulse spacings (ATsk) of at least one group (GSm) of consecutive pulses (Sk) a known distance pattern (M), as transmission pulse sequence ({Sk}) and accompanying receiving the reflected pulses as a result ({Ek}) of received pulses (Ek) and measuring their pulse intervals (ATEk), determining in the received pulse train ({Ek }), a group (Gsn) of receive pulses (Ek) whose pulse intervals (ATEk) have the greatest similarity to the known distance pattern (M), determining transit times (Tk) between each transmit pulse (Sk) of said transmit pulse group (GSm) and in each case that receiving pulse (Ek) of the said received pulse group (GEm), which has therein the same sequence in the group (GaJ as the said transmission pulse (Sk) in its group ( GSm), and determining range readings (Dk) from said runs (Tk).
    [2]
    2. The method according to claim 1, characterized in that the pulse intervals (ATsk) in said spacing pattern (M) selected at random and during the transmission of the Sendeim¬pulsgruppe (GSm) are drawn on.
    [3]
    3. The method according to claim 1, characterized in that the pulse intervals (ATsk) in said spacing pattern (M) is selected according to a predetermined random or pseudorandom sequence.
    [4]
    Method according to claim 3, characterized in that the pseudorandom sequence is based on an m-sequence or a Barker code.
    [5]
    5. The method according to any one of claims 1 to 4, characterized in that the transmission pulse train (ATsk) is composed of a plurality of successive transmission pulse groups (GSm) each having dem¬ same distance pattern (M) and the steps of determining the received pulse group (GEm), determining the running times (Tk ) and determining the range finding values (Dk) for each transmit pulse group (GSm), wherein for each transmit pulse group (GSm) only the respective nearest receive pulse groups (GEm) are detected in said manner.
    [6]
    6. Method according to one of claims 1 to 5, characterized in that the number of pulses (Sk, Ek) in the transmitting pulse group (GSm) and in the receiving pulse group (GEm) is in each case 4 to 64, preferably 16 to 32.
    [7]
    7. The method according to any one of claims 1 to 6, characterized in that the determination of the received pulse group (GEm) by correlating the transmit pulse group (GSm) with a via the receive pulse train ({Ek}) sliding window (M'j) with the transmission pulse group length and determining that Position (j) of the sliding window (M'j), which gives the correlation maximum (YEm), takes place.
    [8]
    A method according to any one of claims 1 to 7, characterized in that for correlating a filter (4) adapted to the known spacing pattern (M) is used, to which the pulse intervals (ATEk) of the received pulse train ({Ek}) are applied as input signal and whose output signal Y (ATEk) indicates the time of occurrence (YEm) of the distance pattern-like received signal group (GEm).
    [9]
    9. Method according to claim 8, characterized in that a further filter adapted to the known spacing pattern (M) is used, to which the pulse intervals (ATsk) of the transmission pulse sequence ({Sk}) are supplied as input signal and whose output signal Y (ATsk) the Time of occurrence (YSm) of a transmit pulse group (GSm) indicates which is used as a time reference for determining the transit times (Tk) between the transmit pulses (Sk) of a transmit pulse group (GSm) and the respective receive pulses (Ek) of the receive pulse group (GEm) determined therefor.
    [10]
    10. The method according to any one of claims 1 to 9, characterized in that the received signal sequence ({Ek}) before the said step of determining the distance pattern similar to receiving signal group (GEm) is cleaned by multiple receive pulses (Ek, j), in each case by several receive pulses (Ek, j) occurring within an average transmission pulse interval (ΔΤ), only one received pulse (Ek) is taken into account and the others are disregarded.
    [11]
    11. The method according to claim 10, characterized in that after said step of determining the distance pattern-like received signal group (GEm) also run times (Tk, p) and distance measurement values (Dk, p) for the previously unrecognized received pulses with respect to that transmit pulse ( Sk) for which the transit time (Tk) of the respectively considered received pulse (Ek) has been determined.
    [12]
    12. The method according to any one of claims 1 to 10 for La¬serscannen, characterized in that the pulses (Sk) of the transmission pulse sequence ({Sk}) laser pulses and are continuously directed to different environmental targets (Ui).
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    同族专利:
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    EP2889642A1|2015-07-01|
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    DE102019214567A1|2019-09-24|2021-03-25|Zf Friedrichshafen Ag|Method and device for operating a pulsed lidar sensor|
    法律状态:
    优先权:
    申请号 | 申请日 | 专利标题
    ATA50828/2013A|AT515214B1|2013-12-16|2013-12-16|Method for distance measurement|ATA50828/2013A| AT515214B1|2013-12-16|2013-12-16|Method for distance measurement|
    EP14192640.2A| EP2889642B1|2013-12-16|2014-11-11|Method for distance measurement|
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