DE102018203584A1 - Operating Procedures for a LiDAR System, LiDAR System Control Unit, LiDAR System and Work Device - Google Patents

Abstract

The present invention relates to operating methods for a flash type LiDAR system (1) in which pulses of primary light (57) successively emitted into a field of view (50) for illumination thereof receive secondary light (58) from the field of view (50), and a sampling frequency at which pulses or groups of pulses of the primary light (57) are emitted, a number of pulses of the primary light (57) in a group of pulses and / or one or more a respective pulse of the primary light (57) characterizing pulse parameters are varied over time.

Description

State of the art

The present invention relates to a method of operating a LiDAR system, in particular of the flash type, a control unit for a LiDAR system, a LiDAR system as such, and a working device which is formed with a LiDAR system, in particular a vehicle.

So-called LiDAR systems, which are designed to apply light or infrared radiation to a field of view and to detect and evaluate radiation reflected back from the field of view for analysis of the field of view and for detection of objects contained therein, are increasingly used for detecting the surroundings of working devices and in particular vehicles ,

To reduce crosstalk and interference from other signal sources in pulse-operated LiDAR systems-in particular, in the case of LiDAR systems of the flash type-an elaborate pulse-sequence-coded procedure is used, for example, for operating the respective LiDAR system with a corresponding additional tax expenditure in the Transmitter optics and the receiver optics are used.

Disclosure of the invention

The operating method according to the invention for a LiDAR system with the features of claim 1 has the advantage that reduced with relatively little effort crosstalk and interference from other signal sources and thus improved channel discrimination can be achieved. This is inventively achieved with the features of claim 1, characterized in that an operating method for a LiDAR system is provided, in which (i) successively pulses generated primary light are emitted in a field of view for its illumination, (ii) receive secondary light originating from the field of view and (iii) a sampling frequency at which pulses or groups of pulses of the primary light are emitted, a time period of a number of pulses of the primary light in a group of pulses and / or one or more pulse parameters characterizing a respective pulse of the primary light become. The transmitter-side variation of the sampling rate or sampling frequency, the shape of the groups of emitted pulses of the primary light and / or the shape of the individual pulses of the primary light reduces the probability that the pulses or pulse groups emitted by the LiDAR system under consideration are comparable to pulses or pulse groups a foreign source. Even when detecting signals from a foreign source, they can then be identified with greater probability as extraneous signals and excluded from consideration.

The dependent claims show preferred developments of the invention.

According to an advantageous embodiment of the presented operating method with the sampling frequency, the time interval of pulses or groups of pulses of the primary light and / or the time interval of pulses of the primary light within a group of pulses can be varied over time.

Additionally or alternatively, according to another embodiment of the method according to the invention as a pulse parameter, a pulse width, a pulse shape and / or a pulse time function of a pulse to be emitted of the primary light can be varied over time.

When temporally varying the sampling frequency, the shape of pulse groups, the number of pulses in a pulse group, and / or a pulse parameter characterizing a respective pulse of the primary light, there are many possibilities.

Quite generally, a sampling frequency and / or one or more pulse parameters may be at least partially monotonically or strictly monotonically increasing, at least partially monotone or strictly monotonically decreasing, increasing and / or decreasing according to a linear or quadratic function or a function of higher order, stochastically, be varied on the basis of pseudo-random numbers and / or on the basis of a predetermined read-out table.

Also, any combinations of these approaches are conceivable.

Not under all operating circumstances, a complex temporal variation is required. If, for example, no interfering signals occur or are to be expected, the amount of temporal variation can be significantly reduced. Embodiments are also conceivable in which the temporal variation is at least temporarily eliminated.

To control such a procedure, it is provided in a preferred embodiment of the operating method according to the invention that an occurrence of interfering signals is detected on the receiver side and a sampling frequency and / or one or more pulse parameters of pulses of the primary light in their value depending on the occurrence of receiver-side noise and / or be varied over a corresponding evaluation.

In order to increase the detection quality and / or detection probability on the receiver side, it is provided according to another preferred development of the operating method according to the invention that the receiver side when detecting with respect to a possible temporal variation (i) a sampling frequency, with which pulses or groups of pulses of the primary light emitted (ii) a number of pulses of the primary light in a group of pulses and / or (iii) a pulse parameter characterizing a respective pulse of the primary light are filtered in a signal-matched manner for correlation.

In this case, in particular, that control signal can also be used with which the light source of the transmitter optics or its driver device is controlled.

In accordance with another aspect of the present invention, a control unit for a flash type LiDAR system is also provided. This is adapted to carry out the operating method according to the invention for a Leader system.

Furthermore, the present invention also proposes a flash type LiDAR system as such. This is with a transmitter optics for generating and emitting pulses of primary light in a field of view to its illumination, with a receiver optics for receiving, detecting and evaluating secondary light from the field of view and with a control unit according to the invention for controlling the operation of the transmitter optics and / or the receiver optics educated.

Finally, the present invention also provides a working device which is formed with a LiDAR system according to the invention.

The working device may be a vehicle, for example a motor vehicle. However, it is also conceivable embodiment as a robot or the like.

list of figures

• 1 zeigt in Form eines schematischen Blockdiagramms eine Ausführungsform des erfindungsgemäßen LiDAR-Systems.
• 2 und 3 zeigen in schematischer Form Amplituden-Zeitdiagramme zur Charakterisierung erfindungsgemäß zeitlich variierter Verläufe von Pulsen ausgesandten Primärlichts bei einer senderseitigen Variation der Abtastrate bzw. der Pulszeitfunktion.

Embodiments of the invention will be described in detail with reference to the accompanying drawings.

• 1 shows in the form of a schematic block diagram an embodiment of the LiDAR system according to the invention.
• 2 and 3 show in a schematic form amplitude-time diagrams for the characterization according to the invention temporally varied waveforms of pulses emitted primary light at a transmitter-side variation of the sampling rate or the pulse time function.

Preferred embodiments of the invention

The following are with reference to the 1 to 3 Embodiments of the invention and the technical background described in detail. Identical and equivalent as well as equivalent or equivalent elements and components are designated by the same reference numerals.

Not in every case of their occurrence, the detailed description of the designated elements and components is reproduced.

The illustrated features and other properties can be isolated in any form from each other and combined with each other, without departing from the gist of the invention.

1 shows in the manner of a block diagram schematically an embodiment of the LiDAR system according to the invention 1 ,

This in 1 illustrated and set up for flash operation or pulsed LiDAR system 1 exists next to a control and evaluation unit 40 from the operation of the LiDAR system 1 underlying optical arrangement 10 with a light source unit 65 , for example, with one or more light sources 65 - 1 , a transmitter optics 60 , a receiver optics 30 and a detector assembly 20 , The control of the operation of the LiDAR system 1 and the evaluation of the signals received by the LiDAR system 1 are performed by the control and evaluation unit 40 ,

In operation, by control and instigation by means of the control and evaluation unit 40 via a control line 42 the light source unit 65 for generating and outputting primary light or primary light 57 in the form of pulses or groups of pulses. The primary light 57 is by means of a beam shaping optics 66 modeled according to the application and then by means of a transmitting-side deflection optics 62 in a field of view 50 with an object contained within 52 a scene 53 sent.

In the present invention, the focus is on a pulsed operation of the light source unit 65 and the respective light sources 65 - 1 , for example in the form of pulsed laser sources.

That out of the field of vision 50 and the object 52 reflected light is also called secondary or secondary light 58 designated and in the receiver optics 30 by means of a lens 34 including, where appropriate, an intended secondary optic 35 further treated and then to a detector array 20 with one or more Sensor elements or detector elements 22 transfer. The sensor elements 22 the detector assembly 20 in turn generate the secondary light 58 representing signals by means of a control and measurement line 41 to the control and evaluation unit 40 be transmitted.

The embodiment of the control and evaluation unit 40 according to 1 consists of a higher-level tax system 100 which by means of a bus 101 with a transmitting unit 70 , a receiving unit 80 and a correlation unit 90 connected is.

It can be the tax system 100 and the units 70 . 80 and 90 actually as separate components within the control and evaluation unit 40 be educated.

However, it may be formed a LiDAR system 1, wherein one or more of the components of the control and evaluation 40 combined and integrated, so that the representation according to 1 only the representation of the existing components in principle serves, but the concrete architecture is not necessarily reflected by this and the presentation 1 may differ.

According to the invention, the focus in the operation of the LiDAR system is on the pulse principle, in which the field of view 50 in pulse mode of the light source unit 65 with the light sources 65 - 1 with the primary light 57 illuminated and examined.

In accordance with the invention, in order to increase the detection probability and to avoid false detections, a temporal variation of the sampling rate or sampling frequency of the pulses of the primary light is provided on the transmitter side 57 and / or pulse parameters of the pulses of the primary light 57 carried out, for example, by the control and evaluation unit 40 a corresponding control of the light source unit 65 and in particular the one or more light sources 65 - 1 takes place, optionally via a control of a light source driver, the component of the light source unit 65 can be and is not explicitly shown here.

The 2 and 3 show in schematic form graphs 120 and 130 in the sense of amplitude-time diagrams for characterizing temporally varied courses of the emitted primary light 57 - understood as a transmission signal Tx as a function of time T - in a transmitter-side variation of the sampling rate or the pulse time function according to the invention.

On the respective abscissa 121 . 131 the graph 120 . 130 is the time t as a parameter and on the respective ordinate 122 . 132 the transmit signal amplitude Tx plotted as a function of time t. The results with the tracks 123 . 133 transmitted pulse trains shown.

At the 2 Underlying control in terms of temporal variation according to the invention in one embodiment of the operating method according to the invention for a LiDAR system 1 are individual pulses 57 - 1 generated and in the form of pulse groups 123 - 1 to 123 - 4 with time intervals T1 to T3 emitted, each individual pulse group 123 - 1 to 123 - 4 as a transmission signal of the primary light 57 can be understood.

In the case of the embodiment according to FIG 2 the first two pulse groups 123 - 1 and 123 - 2 of single pulses 57 - 1 educated. The third pulse group 123 - 3 has three identical single pulses 57 - 1 at an identical time interval .DELTA.t3 on.

This is not mandatory, in an alternative embodiment, the time interval between the individual pulses 57 - 1 be varied in a pulse group.

The fourth pulse group 123 - 4 consists of identical single pulses 47 - 1 at a constant time interval Δt4 , This time interval Δt4 can with the previous time interval .DELTA.t3 be identical, but even this is not mandatory.

The pulse groups 123 - 3 to 123 - 4 have time intervals with each other T1 to T3 , which are chosen to be approximately constant here. Alternatively, the time intervals T1 to T3 According to the invention also have different values and can be varied.

The in the lane 123 in the embodiment according to 2 used single pulses 57 - 1 are chosen identical to each other. Here, too, offer variation possibilities according to the invention, namely by different design of the individual pulses 57 - 1 ,

Conceivable variations of the individual pulses are through the track 133 of the graph 130 out 3 illustrated.

Here is the entire transmission signal of the track 133 from a sequence of individual pulses, which consists of a set of different individual pulses 57 - 1 to 57 - 4 are selected. These individual pulses 57 - 1 to 57 - 4 differ from each other exclusively by their respective pulse width t1 to t4 which form a monotonously increasing series in this order, but has an identical amplitude.

These and other features and characteristics of the present invention will be further elucidated with reference to the following statements:

A typical problem with LiDAR systems, but especially with Flash LiDAR approaches, is the crosstalk problem. Identical systems, but even those that have high technological overlaps in wavelength range (bandpass filtering) and time response (eg pulsed TOF method), can influence each other and thus due to mutual glare (eg detector saturation, blooming) to disturbed measurements (eg noisy 3D point clouds). In addition, the readiness of a LiDAR system can be directly attacked by unwanted or malicious external light exposure (jamming).

With the present invention, a higher robustness to the crosstalk problem of identically constructed, mutually influenceable or externally disturbable LiDAR systems is to be achieved by using a variable sampling rate and / or variable pulse characteristics (for example the pulse width, pulse time function). These would typically be easily accomplished by direct control of the emitter, and require no additional circuitry or elements of cryptography as compared to coded illumination techniques (code superposition on the LiDAR sampling behavior).

A key aspect of the invention is the provision of intelligent control or regulation of the sampling rate and / or the pulse shape of a LiDAR system 1, in particular with regard to maximum permissible variability.

In this case, both a higher or lower sampling rate adapted to the current measurement situation can be set or, for example, by a random parameter algorithm or a predetermined sampling frequency / pulse width ramp (frequency / pulse width sweep) of an ego sensor - ie the sensor of a considered LiDAR system 1 - To different sensor different timing can be achieved. The goal here is to minimize over time as an additional degree of freedom the likelihood of a mutual influence of LiDAR systems in the road application (many sensors, often the same wavelengths and operating principles, similar heights, etc.).

• - eine Verringerung oder gar Minimierung der Wahrscheinlichkeit eines Übersprechens baugleicher oder ähnlicher LiDAR-Systeme,
• - eine Variabilität der Abtastrate (z.B. im Bereich etwa 10 Hz bis etwa 30 Hz) und ausgewählter Pulsformparameter, um unterschiedliche Auflösungen der Tiefeninformation oder Belichtungszeiten zu ermöglichen,
• - eine Möglichkeit, in der Tiefe interessante Objekte besonders häufig abzutasten, beispielsweise um deren Existenz oder Maße zu plausibilisieren,
• - Möglichkeiten, besonders gering reflektierende Objekte länger zu beleuchten, um ein höheres Signal-zu-Rauschverhältnis zu erhalten, beispielsweise durch Mittelung vieler von diesem Objekt reflektierter Pulse im Detektor (dabei mittelt sich das Rauschen in der Regel tendenziell zu Null, wogegen sich das Nutzsignal durch die Mittelung aus dem Rauschen stärker erhebt),
• - ein optimierbares zeitliches Systemverhalten hinsichtlich einer aktuell vorliegenden Messsituation und
• - ein vergleichsweise geringer Realisierungsaufwand (keine Codegenerierung, keine Dechiffrierung, keine zusätzlichen Schaltungen, da direkt durch den Lasertreiberansteuerung realisierbar).

Some of the significant advantages of the invention are:

• a reduction or even minimization of the likelihood of crosstalk of identical or similar LiDAR systems,
• a variability of the sampling rate (eg in the range of about 10 Hz to about 30 Hz) and selected pulse shape parameters in order to allow different resolutions of the depth information or exposure times,
• a possibility to scan objects of interest very often, for example to make their existence or dimensions plausible,
• - Possibilities to illuminate particularly low-reflection objects longer in order to obtain a higher signal-to-noise ratio, for example by averaging many of this object reflected pulses in the detector (while the noise tends to average tends to zero, whereas the useful signal by averaging out of the noise),
• an optimizable temporal system behavior with regard to a currently present measurement situation and
• - A relatively low implementation effort (no code generation, no deciphering, no additional circuits, as directly by the laser driver control feasible).

With the help of a controller or a control to the current state of the art time-invariant scanning and lighting of a LiDAR sensor 1 by a time-variant, with regard to minimal crosstalk probability optimized time course of the sampling frequency (see 2 ) and the pulse shape (see 3 ) be replaced. In this case, a controller comprises a fixed specification of the time response, for example, via linear or higher-order functions increasing or decreasing sampling frequencies or pulse shape parameters (eg pulse width or pulse time function). On the other hand, a regulation comprises a back measurement of selected parameters, eg the crosstalk frequency, interpretation of the current measurement situation with regard to the number of object or foreign sensors, the success / failure rate of a measurement ("false positives", "false negatives"), the number of times required in the respective distance Single measurements (histogram formation), the likelihood of small objects at certain distances, the vehicle's own speed or similar parameters for optimizing the LiDAR system time behavior.

This results for the first time in the case of a too frequent disturbance of the ego-sensor, for example, the own sampling rate to make small and amplified random and to use very short pulses, while at low frequency interference higher and more regular sampling rate and longer pulses could be used. The setting of the desired time behavior takes place directly via activation of the laser driver and possibly additionally of the detector module.

For better differentiation of signals in LiDAR systems with in particular identical phase position in the transmission signals, it is possible in CW-based LiDAR systems 1 by varying the phase and / or the waveform and / or by modulating a higher-frequency carrier wave and / or by means of different steep or random waveform-rotated frequency ramps to form a distinction to other CW-based LiDAR systems.

Claims (10)

Operating method for a flash type LiDAR system (1) in which - Successively pulses generated primary light (57) are emitted in a field of view (50) for its illumination, - From the field of view (50) derived secondary light (58) received, detected and evaluated and a sampling frequency at which pulses or groups of pulses of the primary light (57) are emitted, a number of pulses of the primary light (57) in a group of pulses and / or one or more pulse parameters characterizing a respective pulse of the primary light (57) in time be varied. Operating procedure after Claim 1 in which the sampling frequency is used to temporally vary the time interval of pulses or groups of pulses of the primary light (57) and / or the time interval of pulses of the primary light (52) within a group of pulses. Operating method according to one of the preceding claims, in which a pulse width, a pulse shape and / or pulse time function of a pulse to be emitted of the primary light (57) are varied in time as the pulse parameter. Operating method according to one of the preceding claims, wherein a sampling frequency and / or one or more pulse parameters at least partially monotonically or strictly monotonically increasing, at least partially monotonous or strictly monotonically decreasing, increasing and / or decreasing according to a linear or quadratic function or a Higher-order function, stochastic, may be varied in time based on pseudo-random numbers and / or on the basis of a predetermined read-out table. Operating method according to one of the preceding claims, in which - An occurrence of interference signals is detected on the receiver side and - A sampling frequency and / or one or more pulse parameters of pulses of the primary light (57) in their value in dependence on the occurrence of the receiver-side noise signals are varied in time. Method of operation according to one of the preceding claims, in which on the receiver side in detecting a possible temporal variation (i) of a sampling frequency with which pulses or groups of pulses of the primary light (57) are emitted, (ii) a number of pulses of the primary light (57 ) is filtered in a group of pulses and / or (iii) a pulse parameter characterizing a respective pulse of the primary light (57) in a signal-matched manner for correlation. Control unit (40) for a flash type LiDAR system (1) arranged to perform an operation method according to any one of Claims 1 to 6 perform. A flash type LiDAR system (1) comprising: transmitter optics (60) for generating and emitting pulses of primary light (57) into a field of view (50) for illumination thereof; receiver optics (30) for receiving, detecting and evaluating secondary light (58) from the field of view (50) and - a control unit according to Claim 7 for controlling the operation of the transmitter optics (60) and / or the receiver optics (30). Working device, which with a LiDAR system (1) after Claim 8 is trained. Working device after Claim 9 , which is designed as a vehicle.

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