Method for operating a lidar system and control unit, lidar system and device

Abstract

The invention relates to a method for operating a laser radar system (1), in which method an optical multiple pulse signal (S1; S2) is generated on the transmitter side and transmitted as an optical transmission signal (S) into a field of view (50), the optical multiple pulse signal having a plurality of peaks (P1, P2) which are separated in time and temporally overlapping flanks (F11, F12; F21, F22) of peaks (P1, P2) which directly succeed one another in time. The invention also relates to a corresponding control unit, to a laser radar system (1) of this kind and to a working device, in particular of the vehicle type.

Description

Technical Field

[0001] The present invention relates to an operating method and a control unit for a lidar system, a lidar system of this kind, and a working device having a lidar system and particularly configured as a vehicle. Background Technology

[0002] So-called LiDAR (Light Detection and Ranging) systems are increasingly being used to identify the environment of work equipment, especially vehicles. LiDAR devices are configured to apply light or infrared radiation to a field of view and detect and analyze the radiation reflected back from the field of view in order to analyze the field of view and detect objects contained within it. To improve LiDAR systems and methods, particularly in terms of better signal identification, multi-pulse signals (mehrfachpulssignal) have been introduced to illuminate the field of view to be monitored. Summary of the Invention

[0003] The operating method for a lidar system according to the present invention has the following advantages: the multipulse signal used can be identified more clearly relative to noise, and better spatial resolution can be achieved when monitoring the surrounding environment. This is achieved according to the invention by providing an operating method for a lidar system in which an optical multipulse signal is generated at the transmitter side and transmitted as an optical transmission signal into the field of view, the optical multipulse signal having multiple peaks, particularly time-separated, and temporally overlapping peak edges of peaks that are directly successive to each other in time. According to the invention, using a multipulse signal with temporally overlapping peak edges (particularly with temporally separated peaks) can, on the one hand, make the received signal particularly distinguishable from background noise at the receiver side, and on the other hand, improve spatial resolution.

[0004] Preferred extensions of the invention are shown below.

[0005] Although, in principle, any number of pulses can be generated and used in combination with the multiple pulse signals according to the invention, a particularly simple relationship arises when a double pulse signal having two peaks, especially those separated in time and with overlapping peak edges, is generated and transmitted as a transmission signal according to a preferred embodiment of the operating method according to the invention. .

[0006] Different additional or alternative measures can be envisioned to improve the discernibility of the received signal relative to noise and / or further improve spatial resolution when monitoring the field of view.

[0007] According to a preferred extension of the operating method of the present invention, it is conceivable that the pulse signal that is particularly directly preceding in time, and especially the first pulse signal, is constructed to be relatively narrow, and has a smaller peak width compared to the peak width of the pulse signal that is particularly directly following in time, which is relatively wide and has a larger peak width compared to the peak width of the pulse signal that is particularly directly preceding in time.

[0008] Additionally or alternatively, the peak width of the pulse signal that is particularly directly preceding in time may be in the range of about 1 / 20 to about 1 / 5 of the peak width of the pulse signal that is particularly directly following in time, preferably in the range of about 1 / 10.

[0009] The peak width or pulse width of the earlier pulse or peak can be in the range of 0.5 ns or less. The peak width or pulse width of the later pulse or peak can be in the range of 2 ns or more.

[0010] Here, the corresponding peak width can be understood as the half-value width of the corresponding peak on which it is based (zu Grunde liegenden).

[0011] According to another alternative or additional development of the operating method according to the invention, the earlier pulse signal, especially the first pulse signal, can have a smaller peak height compared to the later pulse signal, especially the second pulse signal.

[0012] Peak heights can be directly sequential in time at a ratio of about 0.9 or less, preferably about 0.8 or less, and even more preferably about 0.6 or less.

[0013] According to another advantageous configuration, the direct succession of pulse signals in the multiple pulse signals according to the invention can have a time interval with respect to the position of the peak: the time interval is in the range of about ten to about twenty times the peak width of the pulse signal that comes first in time or in the first pulse signal, and / or the time interval is in the range of about one to about three times the peak width of the pulse signal that comes second in time or in the second pulse signal, and in the second pulse signal, and in the third pulse signal, and in the fourth pulse signal, and in the fifth pulse signal, and in the sixth pulse signal, and in the seventh ... eighth pulse signal, and in the fifth pulse signal, and in the sixth pulse signal, and in the seventh pulse signal, and in the eighth pulse signal, and in the ninth pulse signal, and in the

[0014] Regarding the timing of the peaks, the time interval between directly successive pulse signals can be within half or the entire pulse width or peak width of the later pulse. Alternatively, the time interval between directly successive pulse signals can be in the range of 2 ns or greater.

[0015] In principle, any light source can be used to generate the multi-pulse signal according to the configuration of the present invention.

[0016] However, if at least one semiconductor laser is used as the light source of the light source unit to generate an optical transmission signal according to another embodiment of the operating method of the present invention, a particularly suitable relationship arises regarding measurement accuracy and repeatability.

[0017] In this context, the use of multiple light sources, particularly semiconductor lasers, is especially advantageous in a particular configuration of the method and the system based on the invention.

[0018] If a single or unique laser device is used as a light source to generate multiple pulses, especially dual pulses, according to one embodiment of the operating method of the present invention, a particularly simple operating relationship emerges.

[0019] In the case of such a single laser device, for example in the sense of a semiconductor laser, oscillation and / or laser resonance can be suppressed at relatively high energy and / or by a relatively high first current pulse in the semiconductor element on which it is based, during the preparatory or first stage of its operation.

[0020] Preferably, this can be achieved, for example, by using an optical absorber and / or by forming a relatively high inversion grad in the laser device on which it is based.

[0021] In the second or main stage of operation of the laser device, the suppression of laser resonance, especially caused by the absorber, is eliminated by applying a second current pulse, and the laser resonance is no longer suppressed.

[0022] Then, prominent and time-defined relaxation oscillations are excited in the laser device, especially by quality switching and / or gain switching, and a first pulse signal that is particularly direct in time and relatively narrow is generated and transmitted.

[0023] Then, after relaxation oscillation, the laser device is started or oscillated by feeding in additional energy and / or by further power supply (Bestromen), and then, in accordance with the timing characteristics of the power supply—that is, especially relative to the timing of the excitation current and / or in the overlap with the falling edge of the first pulse signal—another pulse signal that is wider or relatively wider in time, especially directly following, is generated and transmitted.

[0024] To generate a first pulse signal or a pulse signal that is particularly directly preceding in time and a second pulse signal or a pulse signal that is particularly directly following in time, a single light source, particularly a single laser device, preferably a single semiconductor laser, can be used and operated, for example.

[0025] Instead, the first and second light sources can be used and operated, especially in a time-direct manner, in succession to each other, wherein the light sources used can be configured as laser devices and preferably as semiconductor lasers.

[0026] Different mechanisms can be used to control and operate one or more light sources.

[0027] For example, according to another embodiment of the operating method according to the invention, a driver unit can be used and operated such that the driver unit is configured to realize the timing sequence of excitation of one or two light sources, in particular one or two laser devices or semiconductor lasers, according to pulse signals and their sequence.

[0028] For this purpose, the driver unit may have a first driver and a second driver, which are assigned—in particular one-to-one—to a single light source or two light sources, wherein the drivers are respectively configured as passive oscillating circuits or having passive oscillating circuits and / or configured as current sources or having current sources.

[0029] The present invention also relates to a control unit for a lidar system, the control unit being configured to initiate, implement, terminate, regulate and / or control, embodiments of the operating method according to the present invention within the lidar system on which it is based.

[0030] Furthermore, the present invention relates to a lidar system comprising a transmitter unit and a receiver unit, the transmitter unit being used to generate primary light and transmit it into a field of view to illuminate the field of view, and the receiver unit being used to receive, detect, and analyze secondary light from the field of view.

[0031] The proposed lidar system is configured to be used with and / or controlled or regulated by the method according to the invention.

[0032] For this purpose, the lidar system is advantageously configured with a control unit according to the present invention, which is configured to control the operation of the transmitter unit and / or receiver unit, in particular to initiate, induce, execute, regulate and / or control the generation / transmission of primary light and / or the reception, detection and evaluation of secondary light.

[0033] In an advantageous embodiment of the lidar system according to the invention, the receiver unit has a correlation unit configured to detect transmission patterns or signal patterns in multiple pulse signals on the input side.

[0034] Finally, the present invention also relates to a working device that is configured with a lidar system according to the present invention, and is particularly configured as a vehicle. Attached Figure Description

[0035] The embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0036] Figure 1 An embodiment of a lidar system according to the present invention is schematically illustrated, which can be used in conjunction with the operating method according to the present invention, and

[0037] Figure 2 and 3 The signal form of an embodiment of the multiple pulse signal generated according to the present invention is illustrated in the form of a graph. Detailed Implementation

[0038] The following is for reference. Figures 1 to 3 The embodiments and technical background of the present invention are described in detail below. The same reference numerals denote elements and components with the same or equivalent functions. Detailed descriptions of the represented elements and components are not given again in every case.

[0039] The features and other characteristics shown can be isolated from each other and combined with each other in any form without departing from the core of the invention.

[0040] To illustrate the present invention, Figure 1 The illustration shows an embodiment of a lidar system 1 according to the present invention, which can be used in conjunction with an embodiment of the operating method according to the present invention.

[0041] according to Figure 1 The lidar system 1, combined with its optical device 10, has a transmitter unit 60 and a receiver unit 30, which can also be understood as a transmitter optics device and the receiver unit can also be understood as a receiver optics device.

[0042] The control unit 40 is advantageously constructed such that the transmitter unit 60 and the receiver unit 30 are effectively connected to the control unit via detection and control lines 41 or 42.

[0043] The transmitter unit 60 has a light source unit 65 for generating and transmitting primary light 57, a beamforming optics 66 for beamforming the primary light 57, and a deflection optics 62 for actually transmitting the primary light 57 into a field of view 50 having a scene 53, which may include, for example, an object 52.

[0044] The receiver unit 30 has, for example, a primary optics 34 of the objective lens type and a secondary optics 35 of, for example, a collimator having a receiver side.

[0045] In this regard, it is worth mentioning that conventional commercial LiDAR systems in the automotive field and a large number of conventional development systems are based on the principle of transmitting single pulses at a predetermined solid angle for a short time (e.g., less than about 2 μs), and detecting objects 52 in scene 53 of field of view 50 by secondary light 58 based on the reflection of the transmitted primary light 57.

[0046] Here, the detection occurs through different optical detectors in the detector device 20, such as APD, CCD, SPAD or SiPM, and in particular based on an electrical signal generated by a single pulse.

[0047] The characteristic form of the optical pulse is also reflected in the signal form of the generated electrical signal, more precisely, in the temporal convolution of the optical pulse caused by the spatial displacement (e.g., tilt) of the object 52 to be detected in the scene 53 of the field of view 50. Here, a correlation can be established between the characteristics of the transmitted signal form and the detected signal.

[0048] Typically, optical signals exhibit Gaussian-like or sinistian properties. 2 Characteristics. The cause of this signal form is the current conduction (Stromführung) in the optical signal generation in the transmitter module, which can also be understood as the transmitting unit 60.

[0049] to this end, Figure 2 and Figure 3 The signal form of an embodiment of the multiple pulse signal S generated according to the invention is schematically shown in the form of graphs 120 and 130 and in the form of traces 123 and 133, the multiple pulse signal having a first pulse signal S1 and a second pulse signal S2, i.e. having peaks P1 and P2 respectively, the peaks being surrounded or enclosed by a first rising edge F11 or F21 in time and a second falling edge F12 or F22 in time.

[0050] The variation in current conduction alters the characteristics of the optically transmitted signal S, for example, by generating a Gaussian configuration of the intensity curve over time, i.e., by directly and successively transmitting two different pulse or pulse signals S1 and S2 according to the invention, i.e., exhibiting a bimodal characteristic according to the invention, the bimodal characteristic having a first peak P1 of the first pulse signal S1 and a second peak P2 of the second pulse signal S2, wherein, according to the invention, the pulses or pulse signals are generated and transmitted in a immediately preceding time sequence such that, according to Figure 2 and 3 The diagram shows that the second falling edge F12 of the first pulse signal S1, which is later in time, overlaps with the first rising edge F21 of the second pulse signal S2, which is earlier in time, after the first peak P1.

[0051] By transmitting double pulses over a relatively short period of time, an improved and / or more robust correlation can be generated by implementing a corresponding correlation function to enhance the detection probability, since a double pulse signal with a signal-specific spacing is significantly less likely to be transmitted as a signal S than an interfering signal and / or noise compared to a single pulse signal.

[0052] An embodiment of the pulse generation according to the present invention is characterized in that only one type of beam source or light source 65-1, 65-2 is required in the light source unit 65 if necessary.

[0053] As described above, in a preferred embodiment of the invention, for example in the sense of a semiconductor laser, a single or unique light source 65-1 is particularly sufficient to generate and transmit two pulse signals S1 and S2 as the transmission signal S of a dual-pulse signal.

[0054] The advantages of this invention are that,

[0055] - Better identification of signals in noise at the receiving side;

[0056] - Due to the different pulse widths of the corresponding single pulses S1 and S2, better spatial resolution is achieved on the receiver side.

[0057] The generation of the dual-pulse signal as the transmitted signal S can be based on the concept of an ultrashort time pulse, which is achieved by a combination of a switchable absorber in the underlying semiconductor and / or a diode driver having high current conduction over a short period of time (e.g., in the nanosecond range).

[0058] For example, ultrashort time pulses can be achieved through the relaxation oscillation of a single semiconductor laser 65-1.

[0059] By setting up an absorber, the laser 65-1 on which it is based is prevented from oscillating or oscillating prematurely when powered, and a high degree of reversal is produced.

[0060] The suppression effect of the absorber can be eliminated by the second current pulse, and accompanied by the generation and transmission of a relatively narrow first pulse signal S1, for example by a noticeable and time-limited relaxation oscillation occurring through the gain switch.

[0061] Another variation involves using a relaxation oscillation via a gain switch, with or without an absorber.

[0062] By further powering the relaxed oscillation, the semiconductor laser 65-1 initiates or oscillates the laser, and achieves a longer radiative emission of the relatively long second pulse signal S2—especially corresponding to the time characteristics of the applied current.

[0063] To produce this characteristic, the corresponding drivers 65-3 and 65-4 of the upper driver unit 65-5—for example, need to be used as laser diode drivers—are advantageously configured to have, for example, two separately controllable currents, especially in the sense of a two-stage laser diode driver.

[0064] Drivers 65-3 and 65-4 can be implemented as diode drivers, for example, based on a passive resonant circuit and / or a current source.

[0065] Two drivers, 65-3 and 65-4, can be used to conduct current through diodes in a circuit.

[0066] Therefore, in conjunction with the light source unit 65, Figure 1 An embodiment of a unique light source 65-1 in the form of a semiconductor laser is shown, which is used by a driver unit 65-5 having a first driver 65-3 to generate light as shown in... Figure 2 and Figure 3 The first pulse signal or signal pulse S1 shown has a peak P1, a rising edge F11 and a falling edge F12, and is used to generate a second pulse signal or signal pulse S2 having a peak P2, a rising edge F21 and a falling edge F22.

[0067] Another alternative is the highly accurate timing synchronization of two separate semiconductor lasers 65-1 and 65-2 as light sources, used to generate a double-pulse mode as a double-pulse signal S, which comprises two single pulse signals S1 and S2.

[0068] Figure 1 This illustrates an alternative solution, in which a second semiconductor light source 65-2 is constructed in addition to the first semiconductor light source 65-1, the latter being... Figure 1 The image is shown in dashed lines. In this case, there can be a one-to-one allocation between the drivers 65-3 and 65-4 of the driver unit 65-5 and the light sources 65-1 and 65-2 of the light source unit 65.

[0069] exist Figure 2 and 3 In graphs 120 and 130, time t is plotted on the horizontal axes 121 and 131 in fixed time units, and the relative normalized amplitude ratio I / Imax of intensity I—that is, proportional to the maximum intensity Imax—is plotted on the vertical axes 122 and 132. Traces 123 and 133 show a double-pulse signal as a transmitted signal S generated and constructed according to the invention, which has single pulse signals S1 and S2 overlapping in adjacent lines F12 and F21, having peaks P1 and P2.

[0070] As detailed above, according to the present invention, the pulse widths or peak widths D1 and D2, the pulse interval Dt, and the pulse heights or peaks P1 and P2 are related to each other in corresponding proportions according to the configuration of the present invention.

Claims

1. A method of operation for a laser radar system (1), in which method an optical multiple pulse signal (SI; S2) is generated on the transmitter side and transmitted as an optical transmission signal (S) into a field of view (50), the optical multiple pulse signal having a plurality of peaks (PI, P2) separated in time and temporally overlapping flanks (F11, F12; F21, F22) of peaks (PI, P2) directly consecutive to one another in time, wherein a double pulse signal is generated and transmitted as a transmission signal (S), which double pulse signal has two peaks (PI, P2) separated in time and temporally overlapping flanks (F11, F12; F21, F22), wherein the peak width (Dl) of the temporally preceding pulse signal (SI) in the double pulse signal is smaller compared to the peak width (D2) of the temporally succeeding pulse signal (S2) of the double pulse signal, wherein a second, temporally later falling flank (F12) of the temporally preceding pulse signal (SI) overlaps in time after a first peak (PI) of the temporally preceding pulse signal (SI) with a first, temporally earlier rising flank (F21) of the temporally succeeding pulse signal (S2).

2. The method of operation as claimed in claim 1, in which - the peak width (Dl) of the temporally preceding pulse signal (SI) lies in the range of 1 / 20 to 1 / 5 of the peak width (D2) of the temporally succeeding pulse signal (S2); and / or - the respective peak width (Dl, D2) is the half-value width of the respective peak (PI, P2) on the basis of which it is based.

3. The method of operation as claimed in claim 2, in which - the peak width (Dl) of the temporally preceding pulse signal (SI) lies in the range of 1 / 10 of the peak width (D2) of the temporally succeeding pulse signal (S2).

4. The method of operation as claimed in any of the preceding claims, in which the temporally preceding pulse signal or first pulse signal (SI) compared to the temporally succeeding pulse signal or second pulse signal (S2) - has a smaller peak height (PI) with a ratio of 0.9 or less, and / or - has a time interval with respect to the position of the peaks (PI, P2) which lies in the range of ten to twenty times the peak width (Dl) of the first pulse signal or of the temporally preceding pulse signal (SI) and / or in the range of one to three times the peak width (D2) of the second pulse signal or of the temporally succeeding pulse signal (S2).

5. The method of operation as claimed in claim 4, in which the ratio has a value of 0.8 or less.

6. The method of operation as claimed in claim 5, in which the ratio has a value of 0.6 or less.

7. Method of operation according to any of the preceding claims, in which at least one semiconductor laser is used as a light source (65-1, 65-2) of the light source unit (65) for generating the optical transmission signal (S).

8. Method of operation according to any of the preceding claims, in which, as a basis for the light source (65-1, 65-2), a single laser device is used for generating multiple pulses (S1; S2) or double pulses, (i) first in a preliminary phase or first phase of the operation of the laser device, with a relatively high energy and / or by a relatively high first current pulse in the underlying semiconductor element, suppression of the start-up, oscillation and / or laser resonance, (ii) in a second phase or main phase of the operation of the laser device, (ii-1) elimination of the suppression of the laser resonance by application of a second current pulse, and no longer suppression of the laser resonance, (ii-2) excitation of a pronounced and time-limited relaxation oscillation in the laser device, and generation and transmission of a relatively narrow first pulse signal (S1), (ii-3) after the relaxation oscillation, with the feeding in of additional energy and / or by a further energization, realization of the oscillation of the laser device, and generation and transmission of one further and relatively wide pulse signal (S2) in time overlap with the time of the falling edge (F12) of the first pulse signal (S1) in accordance with the time characteristic of the energization.

9. Method of operation according to claim 8, in which the start-up, oscillation and / or laser resonance is suppressed by using an optical absorber and / or with a high degree of inversion.

10. Method of operation according to claim 8, in which the suppression of the laser resonance caused by the absorber is eliminated.

11. Method of operation according to claim 8, in which the pronounced and time-limited relaxation oscillation is excited in the laser device by a Q-switch and / or a gain switch.

12. Method of operation according to any of the preceding claims, in which, for the generation of a first pulse signal or a temporally preceding pulse signal (S1) and a second pulse signal or a temporally following pulse signal (S2), - a single light source (65-1) is used and operated, - a first light source (65-1) and a second light source (65-2) are used and operated, - using and operating a driver unit (65-5) which is provided for implementing a temporal sequence of the activation of one or both light sources (65-1, 65-2) in accordance with the pulse signals (S1, S2) and their sequence, and / or which has a first driver (65-3) and a second driver (65-4) which are assigned one-to-one to the single light source (65-1) or to the two light sources (65-1, 65-2), wherein, the drivers (65-3, 65-4) are respectively configured as passive oscillation loop or with a passive oscillation loop and / or as current source or with a current source.

13. Method of operation according to claim 12, in which the single light source (65-1) is configured as a single laser device.

14. Method of operation according to claim 13, in which the single laser device is configured as a single semiconductor laser.

15. Method of operation according to claim 12, in which the first light source and the second light source are configured as laser devices.

16. The method of operation as claimed in claim 15, in which the laser device is configured as a semiconductor laser.

17. A control unit (40) for a lidar system and provided for initiating, terminating, conducting, controlling and / or adjusting the method as claimed in any one of claims 1 to 16.

18. A lidar system (1), - the lidar system is configured - with a transmitter unit (60) for generating primary light (57) and sending the primary light into a field of view (50) to illuminate the field of view, - with a receiver unit (30) for receiving, detecting and analyzing secondary light (58) from the field of view (50); - the lidar system is provided to be used and / or controlled or adjusted by the method as claimed in any one of claims 1 to 16 and / or the lidar system has for this purpose a control unit (40) as claimed in claim 17, which is provided for controlling the operation of the transmitter unit (60) and / or the operation of the receiver unit (30).

19. A work device, which is configured with a lidar system (1) as claimed in claim 18 and which is configured as a vehicle.

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