Transmitter optics for a scanning LiDAR system, LiDAR system and working device

Abstract

LiDAR system (1) of scanning type for optical detection of a field of view (50) for a work device and / or a vehicle, - with a transmitter optic (60) for generating and emitting primary light (57) into the field of view (50) and - with a receiver optic (30) for receiving secondary light (58) originating from the field of view (50), - wherein the transmitter optics (60) are designed with a light source (65) for generating the primary light (57), - wherein the light source (65) comprises a semiconductor laser (65-1), a solid-state laser (65-2) and a Q-switch (65-3), which are arranged in this order in an output direction for the primary light (57) and configured such that - that in operation the semiconductor laser (65-1) as a continuous-wave pump laser pumps the solid-state laser (65-2) and the pumped solid-state laser (65-2) in optical coupling with the Q-switch (65-3) functions as the primary light source for the output of the primary light (57), - with a stator (100) and a rotor (200) rotatable relative to the stator (100) about a rotational axis (5), and - wherein at least part of the transmitter optics (60), a deflection optics (62) and / or a beam shaping optics (66) or parts thereof, and / or at least part of the receiver optics (30) are incorporated in the rotor (200).

Description

State of the art

[0001] The present invention relates to a transmitter optic for a scanning or sampling LiDAR system for generating and emitting primary light into a field of view, a scanning or sampling LiDAR system for optically detecting a field of view, and a working device and, in particular, a vehicle.

[0002] Document US 2016 / 0294144 A1 discloses a laser system comprising a RE:XAB amplification medium within a resonator. X is selected from Ca, Lu, Yb, Nd, Sm, Eu, Gd, Ga, Tb, Dy, Ho, Er, and RE is selected from Lu, Y, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Pr, Tm, Cr, Ho. The system further comprises a pump source with an optical output directed at the amplification medium.

[0003] US 2012 / 0269214 A1 shows a passively Q-switched laser comprising a pump laser diode, a micro laser resonator with a laser medium and a saturable absorber, a filter and a photodiode.

[0004] Document US 2005 / 0063441 A1 shows a miniaturized laser housing that includes a modified standard semiconductor laser housing which can accommodate a solid-state microchip assembly that is pumped by the diode laser.

[0005] The document “Zhao et al: Spectroscopic characterization and diode-pumped 910 nm laser of Nd:LiluF4 crystal. In: Laser Physics , 2012, 918-921” describes a scientific experiment in which polarized absorption and fluorescence spectra of Nd 3+ LiLuF4-doped single crystals were investigated. Two samples with different dimensions were tested in laser experiments.

[0006] Document WO 2019 / 162004 A1 discloses a transmitting lens unit for a scanning LiDAR system for generating and emitting primary light into a field of view, comprising a light source for generating the primary light, wherein the light source has a semiconductor laser, a solid-state laser and a Q-switch, which are arranged in this order in the direction of propagation of the primary light and are designed such that, in operation, the semiconductor laser pumps the solid-state laser as a pumping continuous-wave laser and the pumped solid-state laser, in optical coupling with the Q-switch, serves as the primary light source for outputting the primary light.

[0007] When using work equipment, vehicles, and other machines and systems, operational assistance systems or sensor arrays for monitoring the operating environment are increasingly being employed. In addition to radar-based or ultrasound-based systems, light-based detection systems are also used, such as so-called LiDAR systems (LiDAR: light detection and ranging).

[0008] In scanning or scanning LiDAR systems, primary light is directed across a field of view after generation. So-called macro scanners are used, which consist of a rotor and a stator. The rotor houses at least some of the optics, sensors, and / or light sources and can be rotated relative to the stator by means of a drive mechanism.

[0009] The problems with conventional arrangements for such LiDAR systems are the comparatively large size, the amount of waste heat generated, and the susceptibility to interference when the radiation intensity used to illuminate a field of view is increased. Disclosure of the invention

[0010] In contrast, the transmitter optics according to the invention for a LiDAR system with the features of claim 1 has the advantage that sufficient radiation intensities can be generated with a comparatively low design effort, high reliability, comparatively small installation space and reduced waste heat generation.According to the invention, this is achieved with the features of claim 1 by providing a transmitter optic for a scanning or sampling LiDAR system for generating and emitting primary light into a field of view, which is equipped with a light source for generating the primary light, wherein the light source comprises a semiconductor laser, a solid-state laser and a Q-switch, which are arranged in this order in an output direction for the primary light and are configured and interconnected in such a way that, during operation, the semiconductor laser acts as a continuous-wave pump laser, pumping the solid-state laser, and the solid-state laser pumped by the solid-state laser functions in optical coupling with the Q-switch as a primary light source for outputting the primary light.

[0011] The dependent claims describe preferred embodiments of the invention.

[0012] In a particularly simple design of the transmitter optics, the Q-switch is configured as a passive optical element, specifically as an optically saturable absorber. Various materials can be used individually or in combination, for example – but not exclusively – made of or containing V:YAG, or Cr. 4+ :YAG and the like, and their combinations.

[0013] A particularly high degree of controllability and regulation of the transmitter optics according to the invention can be achieved if, according to another embodiment, the Q-switch is designed as an active component. This, too, can be realized in various ways, namely by designing the Q-switch as an optoacoustic or acousto-optic modulator and / or as a Pockels cell.

[0014] The underlying solid-state laser, also known as a pumped laser, can be used in various configurations depending on the application.

[0015] With regard to achieving high intensity in the desired spectral range, for example the near infrared, solid-state lasers in monolithic design and / or made of Nd:GDVO4, Nd:YVO4, Nd:KDW or any combination thereof are advantageously suitable.

[0016] It is particularly advantageous if the solid-state laser is configured to emit radiation in a wavelength range of approximately 900 nm to approximately 920 nm, and preferably in a wavelength range of approximately 905 nm to approximately 915 nm. The absorption problem with atmospheric water is significantly reduced in these wavelength ranges because the relevant absorption bands of water are oriented differently in the IR range.

[0017] The underlying semiconductor laser is also preferably adapted to a specific application and can be configured with or as an edge emitter, for example also in connection with a VBG arrangement and / or a VCSEL arrangement.

[0018] According to another advantageous embodiment of the invention, controllability and a correspondingly good adaptation to the respective application can be achieved if, for controlling the operation of the light source, a monitor element for detecting the primary light or a portion thereof is provided on the output side of the light source and / or on the output side of the Q-switch in a beam path of the transmitter optics. The monitor element can be any optical element suitable for detecting the radiation intensity and its temporal profile and generating a representative signal that can be used as the basis for a control or regulation process, particularly in conjunction with a higher-level control unit, a driver, and the like.

[0019] The present invention further relates to a scanning LiDAR system for optically capturing a field of view as such and is particularly designed for a work device and / or for a vehicle and its operation.

[0020] The LiDAR system is designed with a transmitter optics configured according to the invention for generating and emitting primary light into the field of view and with receiver optics for receiving secondary light originating from the field of view.

[0021] An advantageous embodiment of the LiDAR system according to the invention comprises a stator and a rotor rotatable about an axis of rotation relative to the stator. At least part of the transmitter optics, and in particular a deflection optic and / or a beam-shaping optic or parts thereof, and / or at least part of the receiver optics, can be incorporated in the rotor.

[0022] However, with regard to simplifying the construction and / or control and supply of the light-generating components, it is particularly advantageous if, according to another embodiment of the LiDAR system according to the invention, the light source and in particular the semiconductor laser, the solid-state laser and the Q-switch are arranged outside the rotor.

[0023] Alternatively or additionally, it may be provided that at least part of the light source is also located outside the stator.

[0024] For further reduction of installation space and improved thermal decoupling of the components relevant for emitting and receiving the primary and secondary light in connection with the stator and rotor, it is particularly advantageous if the underlying semiconductor laser is arranged outside the stator, with the pumped solid-state laser and the Q-switch inside the stator, and a light guide is provided for optically coupling the radiation of the semiconductor laser into the solid-state laser.

[0025] According to another key aspect of the present invention, a working device and in particular a vehicle with a LiDAR system according to the invention for optically capturing a field of view are also created. Brief description of the characters

[0026] With reference to the attached figures, embodiments of the invention are described in detail. Fig. Figure 1 is a block diagram for the schematic representation of an embodiment of the LiDAR system according to the invention using an embodiment of the control and evaluation unit according to the invention. Fig. 2 and Fig. Figure 3 shows schematic and lateral cross-sectional views of embodiments of transmitter optics according to the invention, which can be used in embodiments of the lidar system according to the invention. Fig. 4 and Fig. Figure 5 shows schematic and lateral cross-sectional views of embodiments of the lidar system according to the invention with rotor and stator using embodiments of the transmitter optics according to the invention. Fig. Figure 6 shows a schematic and lateral cross-sectional view of a further embodiment of the transmitter optics according to the invention for use in a lidar system according to the invention. Fig. 7 and Fig. Figure 8 shows schematic and lateral cross-sectional views of embodiments of the lidar system according to the invention with rotor and stator using embodiments of the transmitter optics according to the invention, in which the primary light or the pump light is generated outside of the rotor and stator and then supplied to the stator via a fiber optic cable. Preferred embodiments of the invention

[0027] The following are, with reference to the Fig. Sections 1 to 8 describe exemplary embodiments of the invention and the technical background in detail. Identical and equivalent elements and components, as well as those acting in the same or equivalent way, are designated by the same reference numerals. Detailed descriptions of the designated elements and components are not provided in every instance where they occur.

[0028] The features and other properties shown can be isolated from one another and combined in any way without leaving the core of the invention.

[0029] Fig. Figure 1 shows a schematic representation of a LiDAR system 1 according to the invention, using an embodiment of the transmitter optics 60 according to the invention, in the form of a block diagram.

[0030] The in Fig. The LiDAR system 1 shown in Figure 1 consists of a control and evaluation unit 40, the optical arrangement 10 underlying the operation of the LiDAR system 1, with a light source 65 as part of a transmitter optic 60 designed according to the invention, and a receiver optic 30 with a detector arrangement 20. The control of the operation of the LiDAR system 1 and the evaluation of the signals received by the LiDAR system 1 can be carried out by the higher-level control and evaluation unit 40, which is designed separately from the optical arrangement 10. However, such a design is not mandatory.

[0031] During operation, the light source 65 is controlled and initiated by the control and evaluation unit 40 via a control line 42 to generate and output primary light 57. The primary light 57 is modulated according to the application by means of a beam shaping optic 66, which may, for example, have a cylindrical lens to achieve line illumination, and then, if necessary, emitted by means of a deflecting optic 62 into a field of view 50 of a scene 53 containing an object 52.

[0032] The preferred line illumination in the field of view 50 is associated with a required high intensity, compared to the lower intensities typically used for point illumination. In this context, the transmitter optics 60 designed according to the invention are particularly advantageous because the required radiation intensities can be provided flexibly and with comparatively simple means.

[0033] The light reflected from the field of view 50 and from the scene 53 and the object 52 is also referred to as secondary light 58 and is captured in the receiver optics 30 by means of a lens 34. It may be further processed by a secondary optics 35 provided in the beam path 31 of the receiver optics 30, which may, for example, also be or have filters, and then transmitted to a detector arrangement 20 with one or more detector elements 22. The detector elements 22 of the detector arrangement 20, in turn, generate signals from the secondary light 58, which are transmitted to the control and evaluation unit 40 by means of a control and measuring line 41.

[0034] The control and evaluation unit 40 according to Fig. 1 can, for example, consist of a higher-level control system 100, which is connected via a bus 101 to a transmitting unit 70, a receiving unit 80 and a correlation unit 90.

[0035] In the Fig. In the embodiment of the lidar system 1 shown in Figure 1, the transmitter optics 60, designed according to the invention, first has a light source 65 in its beam path 61 for generating the primary light 57. To control the generation process for the primary light 57, a monitor element 65-4, for example in the form of a monitor diode as a light detection element, is provided in the beam path 61 of the transmitter optics 60. With this monitor element 65-4, the radiation intensity and its temporal profile can be detected and transmitted as corresponding representative signals via the control / detection line 65-5 and the control line 42 to the higher-level control and evaluation unit 40 or alternatively to a driver 65-9, which will be described later, as described in the Fig. 7 and Fig. 8 is shown, can be traced back.

[0036] According to the invention, the light source 65 itself comprises a semiconductor laser 65-1 as a pump laser, a solid-state laser 65-2 pumped or pumpable by the semiconductor laser 65-1, and a Q-switch 65-3 optically coupled or coupleable with the solid-state laser 65-2. At its ends, the arrangement of solid-state laser 65-2 and Q-switch 65-3 is configured with mirror layers 65-7, which can also be referred to as resonator mirrors or resonator mirror layers, on the light input side and light output side, respectively.

[0037] The Fig. 2 and Fig. Figure 3 shows schematic and lateral cross-sectional views of embodiments of transmitter optics 60 according to the invention, which can be used in embodiments of the lidar system 1 according to the invention.

[0038] The light source 65 shown there, in both embodiments, has in its beam path 61 a semiconductor laser 65-1 as a pump laser, a solid-state laser 65-2 that can be pumped by or is pumped by this laser, and a Q-switch 65-3 optically coupled to the solid-state laser 65-2. The arrangement of the solid-state laser 65-2 and the Q-switch 65-3 has, on the light input side, i.e., on the left side, Fig. 2 and Fig. 3, an input-side mirror layer as the first resonator mirror and on the light-output side, i.e. on the right side in Fig. 2 and Fig. 3, an output-side mirror layer as a second resonator mirror. For beam shaping of the light emitted by the semiconductor laser 65-1 and for adapting it to the entrance side of the arrangement consisting of the solid-state laser 65-2 and Q-switch 65-3, the following is provided in the beam path 61 of the transmitter optics 60. Fig. 2 and Fig. 3 between the semiconductor laser 65-1 and the solid-state laser 65-2 a so-called pump optic 65-6 is formed, which in the simplest case can consist of a single lens.

[0039] In the embodiment according to Fig. 2 In the beam path 61 of the transmitter optics 60, a partially transparent deflecting mirror 65-8 is located on the light output side, with which a part of the primary light 57 is coupled out of the beam path 61 of the transmitter optics 60 and supplied to a monitor element 65-4 for monitoring the intensity of the primary light 57 and its temporal course.

[0040] In the embodiment according to Fig. 3 is located in the beam path 61 on the light output side of the semiconductor laser 65-1 and thus a VBG grating 65-10 is located between semiconductor laser 65-1 and pump optics 65-6.

[0041] In both embodiments of the Fig. 2 and Fig. 3 is located on the light output side, i.e., the Fig. 2 and Fig. 3 on the right side, in the beam path 61 of the transmitter optics 60, a combination of deflection optics 62 and beam shaping optics 66, through which the primary light 57 ultimately illuminates the lidar system 1 for the illumination of the in Fig. 1 of the depicted field of view 50 leaves.

[0042] The Fig. 4 and Fig. Figure 5 shows schematic and lateral cross-sectional views of embodiments of the lidar system 1 according to the invention with rotor 200 and stator 100 using embodiments of the transmitter optics 60 according to the invention.

[0043] The rotor 200 is rotatably arranged relative to the stationary stator 100 by means of a shaft and a rotation 6 about a rotational axis 5. This is intended to allow the primary light 57 to scan the area in the lidar system during operation. Fig. The depicted field of view can cover 50.

[0044] At the in Fig. In the embodiment shown in Figure 4, the transmitter optics 60 are located essentially entirely within the rotor 200 and thus rotate with the lidar system during operation. The transmitter optics 60 according to Fig. 4 has essentially the same structure as the transmitter optics 60 according to Fig. 2 and is located here in the lower part of rotor 200.

[0045] The receiver optics 30, comprising a lens 34 as primary optics and a secondary optic 35, which may, for example, be a filter, is located in the upper region of the rotor 200. A detector arrangement 20 for detecting the secondary light 58 is also schematically depicted.

[0046] The embodiment of the transmitter optics 60 according to Fig. 5 differs from the embodiment of the transmitter optics 60 according to Fig. 4 in that all components related to the light source 65 were transferred from the rotor 200 to the stator 100. In detail, this means that the semiconductor laser 65-1, the pump optics 65-6, the solid-state laser 65-2, the Q-switch 65-3, the partially transparent mirror 65-8, and the monitor element 65-4 are mounted on or in the stator 100.

[0047] The partially transparent deflecting mirror 65-8 directs the majority of the primary light 57 from the beam path 61 through the shaft 7 into the rotor 200, in which a deflecting mirror 65-8' is located, which directs the primary light 57 onto the beam shaping optics 66 and the deflecting optics 62, which in turn direct the primary light 57 into the Fig. 1. Direct the depicted field of view to 50.

[0048] Fig. Figure 6 shows a schematic and lateral cross-sectional view of a further embodiment of the transmitter optics 60 according to the invention for use in a lidar system 1 according to the invention.

[0049] The design of the transmitter optics 60 from Fig. 6 essentially corresponds to the design of the transmitter optics 60 from Fig. 2 - without taking into account a monitor element 65-4 - and with the special feature that the light output-side resonator mirror 65-7 in this embodiment is formed by a planar or convex output coupler mirror, which is provided separately and does not form a terminal coating of the Q-switch.

[0050] The Fig. 7 and Fig. Figure 8 shows schematic and lateral cross-sectional views of embodiments of the lidar system 1 according to the invention with rotor 200 and stator 100 using embodiments of the transmitter optics 60 according to the invention, in which the primary light 57 or the pump light is generated outside of rotor 200 and stator 100 and then supplied to the stator 100 via a light guide 66-2.

[0051] Therefore, in the embodiment according to Fig. 7 The light source 65 with the semiconductor laser 65-1, its driver 65-9, the solid-state laser 65-2 and the Q-switch 65-3 is located completely outside of the stator 100 and rotor 200. In the embodiment shown, the beam shaping optics 66 are Fig. 7 formed by a light-input coupling optic 66-1 for coupling the primary light 57 into a provided light guide 66-2. The light guide 66-2 is designed and configured to guide the primary light 57 received from the light source 65 into the stator 100. For coupling the primary light 57 into the stator 100, a collimation optic 66-3 is provided as a further part of the beam shaping optic 66, which directs the primary light onto the deflecting mirror 65-8'. From there, the primary light 57 passes through the deflection optic 62 into the Fig. 1. Displayed field of view 50.

[0052] At the in Fig. In the embodiment shown in Figure 8, the arrangement of solid-state laser 65-2 and Q-switch 65-3 is relocated from the light source 65 into the stator 100. The light guide 66-2 is used as part of the beam shaping optics 66 to couple the pump light from the semiconductor laser 65-1 into the solid-state laser 65-2 for pumping by means of the coupling optics 65-6, which are also located in the stator 100. In this case, the deflecting mirror 65-8' is partially transparent, so that a portion of the primary light 57 exiting the arrangement of solid-state laser 65-2 and Q-switch 65-3, which is guided through the shaft and reaches the rotor 200, strikes the monitor element 65-4 in the rotor 200 for detection and control.

[0053] These and other features and properties of the present invention are further explained in the following sections:

[0054] The current state of the art in known LiDAR systems differs in the way the field of view is illuminated.

[0055] There are, on the one hand, scanning systems, which only illuminate a small part of the environment or field of view at any given time, and on the other hand, flash systems, which illuminate the entire environment and field of view at one time.

[0056] In scanning LiDAR systems, the field of view (FoV) is illuminated sequentially over time with a point laser beam or a laser line.

[0057] In a flash system, the entire field of view (FoV) is illuminated with a laser flash, and the reflected light is received by a detector array. This typically operates at very low frequencies (e.g., from about 10 Hz to about 100 Hz).

[0058] While solid-state lasers are also an option for pure flash systems, scanning systems are equipped with semiconductor lasers.

[0059] Flash systems with solid-state lasers typically operate at wavelengths above 1000 nm, and especially in the range of 1064 nm to 1550 nm.

[0060] Scanning LiDAR systems – for example, so-called macro scanners – typically use a rotating element that emits, for instance, a vertical laser line into the surrounding area, scanning it. Since only a small area of ​​the field of view is illuminated by a laser pulse, the laser must operate at a high frequency, for example, in the range of approximately 1 kHz to approximately 1000 kHz.

[0061] To achieve ranges of, for example, 200 m and resolutions in the range below 0.15° with line illumination, laser powers close to the kilowatt are required.

[0062] Since a single semiconductor laser cannot provide these power levels (currently available semiconductor lasers achieve power levels of approximately 70 W to approximately 120 W with a pulse duration in the range of approximately 1 ns to approximately 3 ns), a number of semiconductor lasers must be connected in parallel, e.g. with a number of approximately 10 to 15.

[0063] The semiconductor lasers are each connected to a laser driver. The required pulse currents range from approximately 30 A to 60 A. To minimize lead losses, the semiconductor lasers must be positioned very close to the drivers. The closer a laser can be positioned to the driver, the lower the losses caused by lead inductance.

[0064] Electro-optical efficiencies in the range of approximately 5% to 10% are achieved. Systems with 10 to 15 semiconductor lasers and 1000 W transmit power then generate approximately 10 W to 20 W of waste heat. The pitch between laser drivers, which can range from approximately 3 mm to 5 mm, largely determines the size of the transmitting unit in a known LiDAR system.

[0065] The problem with the current state of the art is that semiconductor lasers with laser pulses with a pulse duration in the range of about 1 ns to about 3 ns require a special driver circuit and complex assembly technology to generate such short pulses.

[0066] Furthermore, semiconductor lasers are typically operated at high currents to obtain high power output. However, at high currents, the electro-optical efficiency decreases, and disruptive waste heat is generated. When high power is required, multiple semiconductor lasers are now operated in parallel. Depending on the design, the light then needs to be focused using complex optics. Semiconductor lasers change their wavelengths with temperature. This is particularly problematic in LiDAR systems due to the combination with the sunlight filter, as the wavelength can drift outside the filter's range.

[0067] The shortcomings of the prior art described here can either be avoided or reduced with the invention presented.

[0068] By using the crystal types selected in the invention - e.g. ND:YVO4, ND:GDVO4 and ND:KDW - it is possible to realize a beam source 65 for a LiDAR system 1 with the laser wavelengths 912 nm, 914 nm and 911 nm.

[0069] These wavelengths lie in the preferred range according to the invention of approximately 900 nm to approximately 920 nm, and preferably in the range of approximately 905 nm to approximately 915 nm, and have the advantage that only slight attenuation occurs during transmission and reception due to water absorption, because the IR absorption bands of water are oriented differently. Furthermore, these wavelengths exhibit sufficient sensitivity when using silicon detectors.

[0070] The invention makes it very easy to generate a high repetition rate of laser pulses of the primary light 57. This is particularly necessary when using a single-photon avalanche detector, for example in the sense of a SPAD, in the receiver optics 30 in order to create a TCSPC-based time-of-flight (ToF) system (TCSPC: time-correlated single-photon counting).

[0071] Furthermore, the solid-state laser 65-2 can generate laser pulses in the kilowatt range with pulse durations from approximately 0.5 ns to approximately 2 ns through relatively simple design modifications. Pulse duration and pulse energy are determined by the length of the laser resonator and by the transmittance of the saturable absorber, designated as Q-switch 65-3.

[0072] Due to the compact design of the solid-state laser 5 and 60-2 and the integrated Q-switch 5 and 60-3, e.g. in the version as a saturable absorber and / or with the crystal materials Cr 4+:YAG or V:YAG, a pulsed laser with high laser power, a short laser pulse, a stable wavelength and high repetition rate can be used in a scanning LIDAR system.

[0073] By combining a single semiconductor laser 65-1 in continuous wave or CW operation, the electro-optical efficiency of semiconductor lasers is about 50% in CW and QCW operation, with a solid-state laser with an optical-optical efficiency in the range of about 25% to about 50%, a high electro-optical efficiency in the range of about 12% to about 25% is generated.

[0074] The overall efficiency can therefore be approximately twice as high as with a known scanning LiDAR system. High efficiency is inherently necessary because active cooling is difficult to implement in an automotive LiDAR system.

[0075] The invention almost completely prevents parasitic coupling of electromagnetic fields that arise from the generation of short current pulses at the laser driver 65-9, i.e., in lidar systems with a multitude of semiconductor lasers. The generation of the short laser pulses takes place in the solid-state laser resonator, for example, by means of a saturable absorber as a Q-switch 65-3.

[0076] The laser-active material, e.g., ND:YVO, stores photons, and the saturable absorber, acting as a Q-switch 65-3, activates the laser resonator for a few nanoseconds once a certain beam density is reached. Depending on the length of the resonator and the optical parameters—for example, the mirror reflectivity and the doping of the laser materials—the pulse length can be determined. and pulse energy can be set in lidar system 1.

[0077] Temperature-controlled wavelength stabilization is not required in or on the transmitting laser, i.e., the underlying semiconductor laser 65-1, because the solid-state laser used exhibits very little wavelength change with temperature, for example, with values ​​in the range of less than 0.1 nm per 100 K. This allows the optical filter, for example, as part of the secondary optics 35, in the receive path of the receiver optics 30 to be selected as very narrowband. With a narrowband filter, only a very small amount of stray light—if any at all—is received by the detector array 20 and the detectors 22. Consequently, the range of the LiDAR system 1 can be increased.

[0078] The semiconductor laser 65-1, acting as a pump laser, can be operated in continuous wave (CW) mode with a 360° scanning LiDAR system 1, and in quasi-continuous wave (QCW) mode with, for example, a 180° scanning LiDAR system 1. For instance, a pulse length of approximately 50 ms results for a 180° field of view (FoV) and a frame rate of 10 Hz. Since the semiconductor laser 65-1 can be operated with the driver 65-9 in CW or QCW mode (pulses >10 ms), the lead inductances can be neglected. Complex circuitry, such as low-inductance designs, is not required. Consequently, the underlying laser driver 65-9 is simpler to implement, and power losses are reduced.

[0079] Compared to a lidar system with many semiconductor lasers that produce homogeneous illumination, the preferred lidar system 1 according to the invention requires relatively little effort with regard to the optics used and also has fewer components. Known lidar systems with multiple lasers require complex optical design technology because precise alignment of each laser to the transmitting optics or vice versa is necessary to achieve homogeneous, uniform illumination.

[0080] The transmitter optics 60 according to the invention, and thus the entire transmitter unit, can be realized with a reduced installation volume, since only a single semiconductor laser 65-1 is required as a pump laser, for example with approximately 4 W to approximately 20 W CW power. The solid-state laser 65-2, considered as a transmitting laser, which has an entrance area of ​​approximately 2 mm x 2 mm and a length of approximately 5 mm to approximately 15 mm, requires, in addition to beam shaping, beam shaping optics 66, e.g. with 2 to 3 cylindrical lenses.

[0081] The continuous-wave (CW) operation of the semiconductor laser 65-1 required in the invention does not generate any high-frequency electromagnetic interference. The short optical pulses of approximately 2 ns to approximately 10 ns are generated purely optically and not by short current pulses in the driver 65-9 for the semiconductor laser 65-1. This has a significant advantage over known concepts, as the required evaluation electronics (e.g., ASIC, FPGA, A / D converter, etc.) in the LiDAR system 1 cannot be affected or disrupted by parasitic high-frequency electromagnetic pulses.

[0082] The repetition rate is set using optical CW power at the semiconductor laser 65-1 as a pump laser. This rate is determined by the parameters of the saturable absorber and the pump volume in the crystal. The time-based control loop is set by measuring the actual frequency relative to the target frequency as a system requirement. For measuring the current repetition rate at the solid-state laser 65-2, a monitor diode or, more generally, a monitor element 65-4 is required in the transmission path, i.e., in the beam path 61 of the transmitter optics 60, as described in the following sections. Fig. 1 and Fig. 2 is shown.

[0083] The setup with semiconductor laser 65-1, solid-state laser 65-2 and monitor diode 65-4 can be completely integrated on a rotating rotor 200, as is the case in connection with Fig. 4 is shown.

[0084] Another embodiment of the semiconductor laser 65-1 as a pump laser provides a wavelength-stabilizing VBG grating 65-10, as described in connection with Fig. Figure 3 shows that the VBG grating 5 and 60-10 allow the pump laser 65-1 to operate within a temperature range of, for example, approximately 10°C to approximately 105°C without any significant change in the pump wavelength. This enables the pump laser 65-1 to intercept the solid-state laser 65-2 within its optimal absorption spectrum and operate with optimal optical efficiency. At very low temperatures, in the range of approximately -40°C to approximately +10°C, the system can be brought to this temperature range by heating and does not require active cooling, as is the case with... Fig. 3 is shown.

[0085] Possible alternatives: 1. The solid-state laser 65-2, used as a transmitting laser, is no longer placed on the rotating mirror system and the rotor 200. Since the primary light beam 57 from the solid-state laser has a small diameter of less than 2 mm and a low divergence angle of less than 2°, it becomes possible to guide the beam along the center of the axis of the rotating mirror system and the rotor 200, as described in the following example: Fig. 5 is described. 2. The Q-Switch 65-3, a passive Q-switch (for example, a saturable absorber that switches laser pulses through without control), can be replaced by an active Q-switch. An active Q-switch can precisely adjust the pulse frequency without a control loop, as demonstrated in the arrangement shown in Fig. Figure 6 illustrates this. The active Q-switch can be implemented, for example, by a Q-switch 65-3 in the embodiment of an optoacoustic Q-switch—a so-called AOM or acousto-optic modulator. Depending on the applied acoustic frequency, the AOM either allows the laser beam to pass through the resonator or blocks it. Another embodiment of the active Q-switch is the Pockels cell. The laser crystals used in the invention generate linearly polarized laser light in a preferred direction. A Pockels cell is a birefringent crystal that blocks or transmits linearly polarized light depending on the applied electrical voltage. Since an active Q-switch, such as the Q-switch 65-3, is essentially somewhat larger, this lengthens the resonator of the solid-state laser 65-2. The pulse length of the laser pulse determines the switching behavior and the dimensions of the Pockels cell. 3. The concept according to Fig.5 is characterized in particular by the following advantages: - A smaller housing is sufficient because the laser module, i.e. the light source 65, can be positioned outside the actual arrangement of stator 100 and rotor 200. - There is less heat input in the lidar system 1 because the laser driver 65-9, semiconductor laser 65-1, and solid-state laser 65-2 are separated from each other, are located in a housing, and form a laser module outside the arrangement of stator 100 and rotor 200. The laser module, i.e., the light source 65 as a whole, can be installed in a location with a lower ambient temperature, good heat dissipation, and minimal environmental influences. The Rotor 200 has a smaller footprint and lower mass. Advantages of a smaller Rotor 200 include its reduced sensitivity to external impacts, simpler and more cost-effective bearing design, a smaller and less expensive drive motor, reduced vibration and noise, and lower energy consumption.

Claims

[1] LiDAR system (1) of scanning type for optical detection of a field of view (50) for a work device and / or a vehicle, - with a transmitter optic (60) for generating and emitting primary light (57) into the field of view (50) and - with a receiver optic (30) for receiving secondary light (58) originating from the field of view (50), - wherein the transmitter optics (60) are designed with a light source (65) for generating the primary light (57), - wherein the light source (65) comprises a semiconductor laser (65-1), a solid-state laser (65-2) and a Q-switch (65-3), which are arranged in this order in an output direction for the primary light (57) and configured such that - that in operation the semiconductor laser (65-1) as a continuous-wave pump laser pumps the solid-state laser (65-2) and the pumped solid-state laser (65-2) in optical coupling with the Q-switch (65-3) functions as the primary light source for the output of the primary light (57), - with a stator (100) and a rotor (200) rotatable relative to the stator (100) about a rotational axis (5), and - wherein at least part of the transmitter optics (60), a deflection optics (62) and / or a beam shaping optics (66) or parts thereof, and / or at least part of the receiver optics (30) are incorporated in the rotor (200). [2] LiDAR system (1) according to claim 1, wherein the Q-switch (65-3) is passive, as an optically saturable absorber, made of or with V:YAG and / or made of or with Cr 4+ :YAG trained. [3] LiDAR system (1) according to one of the preceding claims, wherein the Q-switch (65-3) is active, configured as an optoacoustic modulator and / or as a Pockels cell. [4] LiDAR system (1) according to one of the preceding claims, wherein the solid-state laser (65-2) - is set up to emit radiation in a wavelength range of about 900 nm to about 920 nm and preferably in a wavelength range of about 905 nm to about 915 nm, - is monolithically formed and / or - is composed of or consisting of Nd:GDVO4, Nd:YVO4, Nd:KDW or any combination thereof. [5] LiDAR system (1) according to any of the preceding claims, wherein the semiconductor laser (65-1) is configured with or as an edge emitter, VBG arrangement and / or VCSEL arrangement. [6] LiDAR system (1) according to one of the preceding claims, in which, for controlling the operation of the light source (65) in a beam path (61) of the transmitter optics (60), a monitor element (65-4) for detecting the primary light (57) or a part thereof is provided on the output side of the light source (65) and / or on the output side of the Q-switch (65-3). [7] LiDAR system (1) according to any one of the preceding claims, wherein - the light source (65) and / or the semiconductor laser (65-1), the solid-state laser (65-2) and the Q-switch (65-3) are arranged outside the rotor (200) and / or - at least part of the light source (65) is arranged outside the stator (100), in particular with the semiconductor laser (65-1) outside the stator (100), the solid-state laser (65-2) and the Q-switch (65-3) inside the stator (100) and a light guide (66-2) for optically coupling the radiation of the semiconductor laser (65-1) into the solid-state laser (65-2). [8] Working device and in particular vehicle, with a LiDAR system (1) according to one of the preceding claims for optical detection of a field of view (50).

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