Beam splitter arrangement for an optoelectronic sensor, optoelectronic sensor with such arrangement and method for beam splitting in an optoelectronic sensor

Abstract

Beam splitter arrangement (10, 40, 50, 62) for an optoelectronic sensor (60), comprising at least one input (20, 74) for coupling first transmit light beams (16, 70) with first transmit light pulses (18, 72) into the beam splitter arrangement (10, 40, 50, 62), at least one beam splitter (12, 12.1, 12.2a, 12.2b) for splitting the first transmit light beams (16, 70) into a plurality of second transmit light beams (22a, 22b, 22n, 76) with second transmit light pulses (24a, 24b, 24n, 78), and a plurality of outputs (28a, 28b, 28n, 82) for coupling out the second transmit light beams (22a, 22b, 22n, 76) from the beam splitter arrangement (10, 40, 50, 62), wherein the number of outputs (28a, 28b, 28n, 82) is greater than the number of inputs (20, 74), characterized in that at least one beam splitter (12, 12.1, 12.2a, 12.2b) optical compression sections (26a, 26b, 26n) are arranged downstream, which compress the second transmitted light pulses (24a, 24b, 24n, 78) such that a second pulse length of the second transmitted light pulses (24a, 24b, 24n, 78) is shorter than a first pulse length of the first transmitted light pulses (18, 72).

Description

[0001] The invention relates to a beam splitter arrangement for an optoelectronic sensor, an optoelectronic sensor with a beam splitter arrangement and a method for beam splitting in an optoelectronic sensor according to the preamble of claims 1, 11 and 13.

[0002] Many optoelectronic sensors operate on the scanning principle, in which a light beam is emitted into the detection area and the light beam reflected by an object is received again, and the received signal is then electronically evaluated. The time of flight of the light is often measured using a well-known phase or pulse method to determine the distance to a scanned object. This method is also called LIDAR (Light Detection and Ranging).

[0003] To expand the measurement range, the scanning beam can be moved, as is done in a laser scanner. A light beam generated by a laser periodically sweeps the monitored area with the aid of a deflection unit. In addition to the measured distance information, the angular position of the deflection unit is used to determine the angular position of the object, thus determining the location of an object in the monitored area in two-dimensional polar coordinates.

[0004] Another option for extending the measurement range is to simultaneously capture multiple measurement points with multiple scanning beams. This can also be combined with a laser scanner, which then captures not just one monitoring plane, but a three-dimensional spatial area across multiple monitoring planes.

[0005] EP 1 927 867 B1 discloses an optoelectronic multi-plane sensor for monitoring a three-dimensional spatial area. The sensor comprises several spaced-apart image sensors. Each image sensor can be assigned a light source, which can be used to determine a distance using a pulse transit time or a phase method. The multi-plane sensor is essentially constructed as a multiplication of individual plane sensors and is therefore relatively bulky.

[0006] In most laser scanners, the scanning movement is achieved by a rotating mirror. However, especially when using multiple scanning beams, it is also known in the prior art to rotate the entire measuring head, including light sources and light receivers, instead, as described, for example, in DE 197 57 849 B4.

[0007] In all of the described cases of multiple scanning, a light source is required that generates multiple light beams with sufficient power and beam quality. However, the existing solutions, which simply duplicate single-beam transmitter modules, are too complex.

[0008] DE 10 2004 014 041 A1 discloses a sensor system for obstacle detection in which a sensor head rotates around its axis. The sensor head contains a laser array with several individual lasers, which are projected onto the surroundings via an optical system.

[0009] To scan an extended surveillance area, the specified devices use either a plurality of light sources or a single light source whose light beam scans the surveillance area by moving the light source itself or with the help of movable optics such as rotating mirrors. The use of multiple light sources generally requires more space for the sensor. Movable optical arrangements can, for example, be susceptible to vibration, which can be disadvantageous for mobile use in vehicles.

[0010] One possibility for beam deflection without moving arrays is the use of so-called "optical phased arrays" (OPAs), as described, for example, in DE 10 2017 222 864 A1 or US 2016 139 266 A1. A German technical term for "optical phased arrays" has not yet been established. In addition to the aforementioned applications for beam deflection or beam steering, optical phased arrays are used, for example, for optical free-space communication applications.

[0011] The principles of phased arrays are familiar from radar technology, in which multiple antennas are controlled at different phase angles. The superposition of the electromagnetic waves from the individual antennas results in a strong directional effect of the overall wave field, which can be pivoted depending on the control of the antennas. In an optical phased array, optical waveguides, through which the transmitted light is guided, are used as antenna feed lines. The antennas are formed by optical radiating elements assigned to the waveguide outputs, with phase-shifting elements connected upstream of each radiating element.

[0012] Phased array technology requires a coherent superposition of the transmitted light emitted by the emitting elements, so the emitting elements require a common light source. The transmitted light emitted by the common light source is typically distributed among the various emitting elements or upstream phase shifters in a beam splitter array. The input of the beam splitter array typically limits the power density of the transmitted light pulses to be coupled in.

[0013] The beam splitter arrangement is typically implemented in the form of integrated optical circuits, for example, as a "silicon-on-insulator" (SOI) structure. Different material systems are used, each with different maximum power densities, which can depend, for example, on the refractive index, mode field diameter, fundamental mode (single-mode waveguide), and band gaps (absorption edge). Light is guided in the transparent region, i.e., away from the absorption edge. However, due to the dimensions of the waveguides and mode field diameters, power densities are achieved even at low transmitted light powers (e.g., 100 mW for a silicon-on-insulator waveguide), which make two-photon absorption or other nonlinear processes relevant.Two-photon absorption is particularly critical here, as it leads to free charge carriers and thus strong linear absorption, resulting in material destruction. The peak power of pulsed transmitted light is critical here, and even long pulse-pause ratios offer no advantage.

[0014] The beam splitter arrangement is typically implemented using "1 to 2" beam splitters cascaded in multiple planes, so that the power density is halved after each plane of the beam splitter arrangement. The problem of maximum power densities is well known, so the prior art proposes amplifying the light power behind or within the beam splitter arrangement using so-called semiconductor optical amplifiers (SOAs). However, these amplifiers are active components, require a power supply, and generate thermal losses. They must have the same gain in all branches of the beam splitter arrangement and strictly maintain the phase relationship between the individual beam components.

[0015] It is known to implement beam splitter arrays in materials with a larger band gap or smaller refractive index differences, and thus larger mode field diameters (for example, by using SiN or Si3N4 structures instead of SOI structures). The subsequent coupling of the beam splitter array outputs to integrated optical circuits based on "silicon-on-insulator" (SOI) structures, which are advantageous for optical phased arrays, is also possible. Disadvantages of such a technical implementation are coupling losses at the coupling point between the beam splitter array and the optical phased array, as well as the use of different material systems.

[0016] Since the power of transmitted light pulses in beam splitters based on silicon-on-insulator structures is limited to 100 mW without additional measures, optical phased arrays have so far only been used in conjunction with continuous wave (CW) light sources. For example, the implementation of an optoelectronic sensor operating according to a direct time-of-flight (dToF) method using optical phased arrays has not been practical due to this power limitation. To utilize the advantages of a dToF method, pulses with peak power are required, which have not been feasible to date due to the power density limitation at the input of a beam splitter arrangement based on silicon-on-insulator structures.

[0017] From JP 2018 185 196 A an optoelectronic sensor is known which has an optical compression path for compressing transmitted light pulses.

[0018] WO 2020 / 109 854 A1 describes a waveguide structure with alternating optical compression and decompression paths for generating a supercontinuum.

[0019] It is therefore an object of the invention to provide an improved beam splitter arrangement, in particular for an optoelectronic sensor.

[0020] This object is achieved by a beam splitter arrangement for an optoelectronic sensor, an optoelectronic sensor with such a beam splitter arrangement and a method for beam splitting in an optoelectronic sensor according to claims 1, 11 and 13.

[0021] The invention is based on the basic idea of ​​reducing the power density of first transmitted light pulses of a first transmitted light beam by controlled pulse broadening in such a way that non-destructive coupling into a beam splitter arrangement is enabled, and of providing a plurality of second transmitted light beams by subsequent pulse compression in and / or after the beam splitter arrangement, wherein a pulse length of the second transmitted light pulses is shorter than the pulse length of the first transmitted light pulses of the first transmitted light beam coupled into the beam splitter arrangement.

[0022] By means of the invention, the input pulse powers and thus also the output pulse powers of a beam splitter arrangement can be significantly increased, in particular when used in an optical phased array.

[0023] The device and method according to the invention are based on the so-called chirped pulse amplification (CPA) process, which is known from laser technology but has not previously been used in connection with beam splitter arrangements for optoelectronic sensors. Chirped pulse amplification is used, for example, to generate ultrashort laser pulses in the femtosecond range. A diffraction- or bandwidth-limited output pulse is first broadened, then amplified, and then compressed again. Pulse broadening is used to reduce the power densities in the amplifying medium.

[0024] The pulse broadening over time occurs through the imposition of a parabolic phase in frequency domain – a naturally occurring process during light propagation in dispersive media, where the refractive index depends on the frequency or wavelength of the light. A distinction is made between the generally weak material dispersion (refractive index of the material) and the geometric or waveguide dispersion (effective index of the waveguide modes) in waveguides, which is generally much more pronounced and can be either positive or negative with respect to the group velocity dispersion (GVD), which is responsible for pulse broadening and / or compression – important for both compression and broadening.Compared to a bandwidth-limited pulse, this pulse broadening is referred to as a chirp (tweeting) of the pulse, as the low-frequency (red) components of the pulse advance while the high-frequency (blue) components are delayed (or vice versa, depending on the sign of the dispersion). By lengthening the pulse, the power density of the pulse is reduced accordingly. By using a medium with the opposite group velocity dispersion, the pulse can be compressed again, thus increasing the power density.

[0025] Based on this, the beam splitter arrangement according to the invention initially has at least one input for coupling a first transmitted light beam with first transmitted light pulses into the beam splitter arrangement and a plurality of outputs for coupling second transmitted light beams with second transmitted light pulses out of the beam splitter arrangement, wherein the number of outputs is greater than the number of inputs. To divide the first transmitted light pulses between the outputs, the beam splitter arrangement has at least one beam splitter with a beam splitter input and a plurality of beam splitter outputs. An optical compression path is arranged downstream of the beam splitter outputs of at least one beam splitter. The optical compression paths compress the second transmitted light pulses such that a pulse length of the second transmitted light pulses is shorter than a pulse length of the coupled, first transmitted light pulses.

[0026] The optical compression sections can preferably be designed as resonant, structured waveguides. By appropriately matching the structure sizes to the wavelength of the transmitted light, the dispersion in the waveguide can be controlled. This allows the group velocity dispersion to be significantly increased, particularly near resonance, so that the length of the optical compression sections required for pulse compression is in the cm or mm range. This allows the optical compression sections to be implemented together with the beam splitters as an integrated optical circuit.

[0027] The structuring of the waveguides of the optical compression path can preferably be periodic and, more preferably, have characteristic periods or spacings in the sub-wavelength range. This suppresses scattering losses, i.e., the coupling of the waveguide mode to radiation modes outside the waveguide. When using purely dielectric materials, propagation in the waveguide can be virtually lossless.

[0028] The resonant, structured waveguides can be designed, for example, as slow-light photonic crystal waveguides, as so-called meta-waveguides with structures in the sub-wavelength range, or as a combination of these waveguide types.

[0029] To split the coupled transmitted light beam into a plurality of outputs of the beam splitter arrangement, several beam splitters can be cascaded in several levels, whereby the outputs of each beam splitter can be connected to the inputs of subsequent beam splitters. When using beam splitters that split an input beam into two output beams, 2 is obtained for n levels. n Outputs. Each level can have optical compression paths arranged downstream of the outputs of the beam splitters of the respective level. In a preferred embodiment, only the last level has optical compression paths arranged downstream of the outputs of the beam splitters of the last level. The beam splitter arrangement can preferably be implemented as an integrated optical circuit.

[0030] In one embodiment of the invention, at least one optical expansion path for broadening the first transmitted light pulses can be arranged upstream of the input of the beam splitter arrangement. This allows transmitted light pulses emitted by a light source whose power density is too high for coupling into the beam splitter arrangement to be initially broadened.

[0031] For pulse broadening, the optical expansion section comprises at least one optical fiber and / or an optical grating and / or a prism. Such optical expansion sections are known, for example, from short-pulse laser technology. The group velocity dispersion of the optical expansion section can be positive or negative; typical factors for pulse broadening are in the range of 10 to 100, which also reduces the power amplitude by a factor of 10 to 100. For pulse compression, the optical compression sections in the beam splitter arrangement have a group velocity dispersion opposite to the group velocity dispersion of the optical expansion section, so that the broadened pulses are compressed again in the beam splitter arrangement or at its end.

[0032] The broadening of the transmitted light pulses can also occur within the light source, for example, by using so-called chirped semiconductor lasers or fiber lasers that incorporate an optical fiber for pulse broadening. Such laser sources emit chirped, i.e., broadened laser pulses, eliminating the need for an optical expansion section upstream of the beam splitter arrangement. The group velocity dispersion of the optical compression sections in the beam splitter arrangement is then matched to the pulse widths and chirp of the emitted transmitted light pulses, allowing the optical compression sections to recompress the transmitted light pulses after beam splitting.

[0033] Phase-shifting elements can be arranged downstream of the outputs of the beam splitter array to influence a phase shift of the transmitted light pulses or the transmitted light beams relative to one another. The beam splitter array then forms an optical phased array with the phase-shifting elements, which can be used to control the propagation direction of a wavefront generated by superimposing the transmitted light beams in a known manner, thus enabling a scanning of a surveillance area. A control unit controls the phase-shifting elements in such a way that they impart the phase shift required for the desired propagation direction of the wavefront to the transmitted light beams.

[0034] The phase-shifting elements are preferably implemented as an integrated optical circuit. Beam splitters, compression sections, and phase-shifting elements are particularly preferably combined in an integrated optical circuit.

[0035] State-of-the-art semiconductor optical amplifiers (SOAs) can be arranged in the beam splitter arrangement or downstream of the beam splitter arrangement. This allows for further amplification of the light power of the split transmitted light pulses.

[0036] The beam splitter arrangement according to the invention can preferably be used in an optoelectronic sensor for detecting objects in a surveillance area. Such a sensor preferably comprises at least one light source for emitting first transmitted light beams with first transmitted light pulses, as well as a beam splitter arrangement according to the invention arranged downstream of the light source. A transmitting optics projects the second transmitted light beams into the surveillance area. A light receiver with upstream receiving optics generates received signals from the light beams remitted by objects in the surveillance area, and a control and evaluation unit is designed to determine a distance to the object using a light propagation time between the emission of the transmitted light beams and the reception of the remitted light beams.

[0037] To detect the light rays remitted by objects in the monitored area, a spatially resolving area detector can be provided, preferably a matrix of photodiodes or APDs (avalanche photodiodes), or an image sensor with correspondingly assigned individual pixels or pixel groups. Another conceivable embodiment provides a SPAD (single-photon avalanche diode) receiver with a plurality of SPADs.

[0038] The control and evaluation unit can be connected to the light source, the beam splitter arrangement, and the detector and is preferably designed, in particular using a known phase or pulse method, to measure the light propagation time between the emission of the light beams and the reception of the remitted light beams, thus determining the distance of an object in the monitoring area. The sensor thus becomes a distance-measuring device. Alternatively, the presence of an object can be detected and output, for example, as a switching signal.

[0039] The outputs of the beam splitter array can be arranged two-dimensionally in a matrix. This allows a two-dimensional monitoring area to be scanned.

[0040] The control unit can control the phase-shifting elements in the beam splitter array depending on the evaluation results of the control and evaluation unit. For example, if the control and evaluation unit detects an object in the surveillance area, the control and evaluation unit can control the phase-shifting elements via the control unit in such a way that the area surrounding the detected object is scanned with increased resolution.

[0041] To suppress stray or extraneous light, the detector can be synchronized with the scanning of the monitored area. For example, only those detector receivers or pixel groups that receive light reflected from the scanned areas of the monitored area can be activated.

[0042] The method according to the invention can be further developed in a similar manner and thereby exhibits similar advantages. Such advantageous features are described by way of example, but not exhaustively, in the subclaims following the independent claims.

[0043] The invention will be explained in more detail below with regard to further features and advantages, using exemplary embodiments and with reference to the accompanying drawings. The figures of the drawing show: Fig. 1 a schematic representation of an embodiment of the invention Fig. 2 a schematic representation of an alternative embodiment of the invention Fig. 3 a schematic representation of an embodiment of the invention with a beam splitter arrangement with cascaded beam splitters Fig. 4 a schematic representation of an embodiment of the invention with a beam splitter arrangement designed as an optical phased array Fig. 5 a schematic representation of an optoelectronic sensor with a beam splitter arrangement according to the invention.

[0044] Fig. Figure 1 shows a schematic representation of an embodiment of the invention with a beam splitter arrangement 10, wherein the beam splitter arrangement 10 has only one beam splitter 12 for the sake of clarity. A light source 14 emits transmitted light, which is coupled into an input 20 of the beam splitter arrangement 10 as a first transmitted light beam 16 with first transmitted light pulses 18 having a first pulse length. The beam splitter 12 splits the first transmitted light beam 16 into two second transmitted light beams 22a, 22b with second transmitted light pulses 24a, 24b. Two optical compression paths 26a, 26b are arranged downstream of the beam splitter 12, which compress the second transmitted light pulses 24a, 24b such that a pulse length of the second transmitted light pulses 24a, 24b is shorter than the pulse length of the first transmitted light pulses 18. The second transmitted light beams 22a, 22b can be coupled out of the beam splitter arrangement 10 via the outputs 28a, 28b of the beam splitter arrangement 10.

[0045] Fig. Figure 2 shows a schematic representation of an alternative embodiment of the invention. In contrast to the Fig. In the embodiment shown in Figure 1, an optical expansion path 28 is arranged upstream of the input 20 of the beam splitter arrangement 10. The transmitted light pulses 30 emitted by the light source 14 cannot be coupled into the beam splitter arrangement 10 due to excessive power density. The transmitted light pulses 32 emitted by the light source 12 are broadened by the optical expansion path 30, thereby reducing their power density. The transmitted light pulses broadened in this way can then be coupled into the input 20 of the beam splitter arrangement 10 as first transmitted light pulses 18 and, as shown in the Fig. 1 shown embodiment can be compressed again after beam splitting to increase the power density.

[0046] Fig. Figure 3 shows a schematic representation of an embodiment of the invention with a beam splitter arrangement 40 with cascaded beam splitters. The beam splitter arrangement 40 has two planes 42.1, 42.2 with beam splitters 12.1, 12.2a, 12.2b, each of which splits an input beam into two output beams. The beam splitter arrangement 40 thus generates four second transmitted light beams 22a, 22n. As in the embodiments illustrated above, a first transmitted light beam 16 with first transmitted light pulses 18 having a first pulse length is coupled into an input 20 of the beam splitter arrangement 40. On the first level 42.1 of the beam splitter arrangement 40, a beam splitter 12.1 splits the first transmitted light beam 16 into two transmitted light beams, which are then split on the second level 42.2 by two further beam splitters 12.2a, 12.2b into four second transmitted light beams 22a, 22n with second transmitted light pulses 24a, 24n. The beam splitters 12.2a, 12.2b of the second level 42.2, four optical compression paths 26a, 26n are arranged downstream, which compress the second transmitted light pulses 24a, 24n of the second transmitted light beams 22a, 22n such that a pulse length of the second transmitted light pulses 24a, 24n is shorter than the pulse length of the first transmitted light pulses 18. The second transmitted light beams 22a, 22n can be coupled out of the beam splitter arrangement 40 via the outputs 28a, 28n of the beam splitter arrangement 40.

[0047] To compress the transmitted light pulses, optical compression paths can also be arranged between the planes 42.1, 42.2 within the beam splitter arrangement, so that a successive pulse compression takes place up to the output of the beam splitter arrangement.

[0048] The limitation to two planes in the illustration of this embodiment is purely exemplary. As indicated by the points between planes 42.1, 42.2, beam splitters 12.2a, 12.2b, optical compression paths 26a, 26n, and the second transmitted light beams 22a, 22n, the beam splitter arrangement can also have more than two planes and generate correspondingly more transmitted light beams. For an optoelectronic sensor for object detection, a beam splitter arrangement can typically have 16-512 outputs.

[0049] Fig. 4 shows a schematic representation of a further embodiment of the invention, wherein in a further development of the Fig. In the embodiment shown in Figure 3, phase-shifting elements 52a, 52n are arranged downstream of the outputs 28a, 28n of the beam splitter arrangement 50. The phase-shifting elements 52a, 52n are controlled via a control unit 54 and are configured to influence phase shifts of the transmitted light beams 22a, 22n relative to one another. Thus, the beam splitter arrangement 50, together with the phase-shifting elements 52a, 52n, forms an optical phased array, with which a propagation direction 56 of a wavefront 58 generated by superimposing the transmitted light beams 22a, 22n can be controlled in a known manner.

[0050] Fig.5 shows a schematic representation of an optoelectronic sensor 60 with a beam splitter arrangement 62 according to the invention. The sensor 60 has a light source 64, for example, a laser diode. The light source 64 emits transmitted light pulses 66, which cannot be directly coupled into the beam splitter arrangement 62 due to their excessive power density. The sensor 60 therefore includes an optical expansion section 68 in which the transmitted light pulses 66 emitted by the light source 64 are broadened, thereby reducing their power density. The thus broadened transmitted light pulses can then be coupled into the input 74 of the beam splitter arrangement 62 as first transmitted light beams 70 with first transmitted light pulses 72. In the beam splitter arrangement 62, the first transmitted light beams 70 are split into a plurality of second transmitted light beams 76 with compressed second transmitted light pulses 78, as in the embodiments described above.Phase-shifting elements 80 for influencing the phase shift of the second transmitted light beams 76 relative to one another are arranged downstream of the outputs 82 of the beam splitter arrangement 62. The second transmitted light beams 76 can be projected into a monitoring area 88 as transmitted light 86 using a transmitting optics 84. The transmitted light reflected by an object 90 in the monitoring area 88 is guided as received light 92 via a receiving optics 94 to a light receiver 96.

[0051] The light receiver 96 is designed as a matrix of a plurality of light receiving elements, preferably as a matrix of photodiodes, APDs (avalanche photo diodes), or SPAD receivers (single-photon avalanche diodes) or also as an image sensor with correspondingly assigned individual pixels or pixel groups.

[0052] The sensor 60 also includes a control and evaluation unit 98, which is connected to the light source 64, the beam splitter arrangement 62, and the light receiver 96. The control and evaluation unit 98 comprises a light source controller 100, a control unit 102 for the phase-shifting elements 80, a time-of-flight measuring unit 104, and an object distance estimation unit 106. These are initially only functional blocks that can also be implemented in the same hardware or in other functional units such as the light source 64, the beam splitter arrangement 62, or the light receiver 96. Via an interface 108, the control and evaluation unit 98 can output measurement data or, conversely, receive control and parameterization instructions.The control and evaluation unit 98 can also be arranged in the form of local evaluation structures on a chip of the light receiver 96 or can interact as a partial implementation with the functions of a central evaluation unit (not shown).

Claims

[1] Beam splitter arrangement (10, 40, 50, 62) for an optoelectronic sensor (60), comprising at least one input (20, 74) for coupling first transmitted light beams (16, 70) with first transmitted light pulses (18, 72) into the beam splitter arrangement (10, 40, 50, 62), at least one beam splitter (12, 12.1, 12.2a, 12.2b) for splitting the first transmitted light beams (16, 70) into a plurality of second transmitted light beams (22a, 22b, 22n, 76) with second transmitted light pulses (24a, 24b, 24n, 78) and a plurality of outputs (28a, 28b, 28n, 82) for coupling out the second transmitted light beams (22a, 22b, 22n, 76) from the beam splitter arrangement (10, 40, 50, 62), wherein the number of outputs (28a, 28b, 28n, 82) is greater than the number of inputs (20, 74), characterized bythat at least one beam splitter (12, 12.1, 12.2a, 12.2b) is followed by optical compression paths (26a, 26b, 26n) which compress the second transmitted light pulses (24a, 24b, 24n, 78) in such a way that a second pulse length of the second transmitted light pulses (24a, 24b, 24n, 78) is shorter than a first pulse length of the first transmitted light pulses (18, 72). [2] Beam splitter arrangement (10, 40, 50, 62) according to claim 1, characterized by that the optical compression paths (26a, 26b, 26n) are designed as resonant, structured waveguides. [3] Beam splitter arrangement (10, 40, 50, 62) according to claim 2, characterized by that the resonant, structured waveguides are slow-light photonic crystal waveguides. [4] Beam splitter arrangement (10, 40, 50, 62) according to one of the preceding claims, characterized by that the beam splitter arrangement (10, 40, 50, 62) has a plurality of cascaded beam splitters (12, 12.1, 12.2a, 12.2b). [5] Beam splitter arrangement (10, 40, 50, 62) according to one of the preceding claims, characterized by that the optical compression sections (26a, 26b, 26n) and the beam splitters (12, 12.1, 12.2a, 12.2b) are combined in an integrated optical circuit. [6] Beam splitter arrangement (10, 62) according to one of the preceding claims, characterized by that at least one optical expansion path (30, 68) for widening transmitted light pulses (32, 66) emitted by a light source (14, 64) is arranged upstream of the at least one input (20) of the beam splitter arrangement (10, 62). [7] Beam splitter arrangement (10, 62) according to claim 6, characterized by that the at least one optical expansion path (30, 68) is designed as an optical fiber and / or optical grating and / or prism. [8] Beam splitter arrangement (50, 62) according to one of the preceding claims, characterized bythat phase-shifting elements (52a, 52n, 80) for influencing phase shifts of the second transmitted light beams (22a, 22n, 76) are arranged downstream of the outputs (28a, 28n, 82) of the beam splitter arrangement (50, 62). [9] Beam splitter arrangement (50, 62) according to claim 8, characterized by that the beam splitters (12.1, 12.2a, 12.2b), compression sections (26a, 26n) and phase-shifting elements (52a, 52n, 80) are combined in an integrated optical circuit. [10] Beam splitter arrangement (10, 40, 50, 62) according to one of the preceding claims, characterized by that at least one beam splitter (12.1, 12.2a, 12.2b) is followed by a semiconductor optical amplifier for amplifying a light power of the second transmitted light pulses (24a, 24b, 24n, 78). [11] Optoelectronic sensor (60) for detecting an object (90) in a surveillance area (88) with at least one light source (64) for emitting transmitted light beams with transmitted light pulses (66), a beam splitter arrangement (62) arranged downstream of the light source (64) for splitting the transmitted light beams into a plurality of second transmitted light beams (76), a transmitting optics (84) for projecting the second transmitted light beams (76) as transmitted light (86) into the surveillance area (88), a light receiver (96) with an upstream receiving optics (94) for generating received signals from light beams (92) remitted by the object and a control and evaluation unit (98) for obtaining information about the object (90) from the received signals, characterized by that the beam splitter arrangement (62) is designed according to one of the preceding claims. [12] Optoelectronic sensor according to claim 11, characterized bythat the control and evaluation unit is designed to determine a distance of the object (90) from the sensor (60) from a light propagation time between the emission of the transmitted light (86) and the reception of the light rays (92) remitted by the object (90). [13] Method for splitting transmitted light beams in an optoelectronic sensor (60), comprising the following steps: - coupling first transmitted light beams (16, 70) with first transmitted light pulses into a beam splitter arrangement (10, 40, 50, 62); - splitting the first transmitted light beams into a plurality of second transmitted light beams (22a, 22b, 22n, 76) with second transmitted light pulses (24a, 24b, 24n, 78), wherein the number of second transmitted light beams (22a, 22b, 22n, 76) is greater than the number of first transmitted light beams (16, 70), characterized by the next step: - Compressing the second transmitted light pulses such that a second pulse length of the second transmitted light pulses (24a, 24b, 24n, 78) is shorter than a first pulse length of the first transmitted light pulses (18, 72). [14] Method according to claim 13 characterized by the next step: - influencing a phase shift of the second transmitted light beams (22a, 22b, 22n, 76) relative to one another.

Images