METHOD FOR OPERATING A SENSOR SYSTEM, SENSOR SYSTEM AND COMPUTER PROGRAM PRODUCT

Abstract

The application relates to a method for operating a sensor system (10) for environmental sensing, comprising: Emitting a first electromagnetic signal (L1) modulated with a first frequency, Receiving the reflected first electromagnetic signal (L1) and determining a first number of first samples (S1.1, S1.2, S1.3, S1.4) of a first received signal (ES1), which depends on the received first electromagnetic signal (L1), Emitting a second electromagnetic signal (L2) modulated with a second frequency, Receiving the reflected second electromagnetic signal (L2) and determining a second number of second samples (S2.1, S2.2) of a second received signal (ES2), which depends on the received second electromagnetic signal (L2). The application further relates to a sensor system for environmental sensing, in particular for a vehicle (20), a vehicle (20) and a computer program product.

Description

Technical area

[0001] The application relates to a sensor system, in particular a lidar system, for environmental detection, particularly for vehicles. The application further relates to a method for operating such a sensor system and a computer program product. background

[0002] Modern vehicles (cars, vans, trucks, motorcycles, etc.) are equipped with a multitude of sensor systems whose data is used to inform the driver and / or provide data to driver assistance systems. These sensor systems record the vehicle's surroundings, including other road users. Based on the recorded data, a model of the vehicle's environment can be created, and changes in this environment can be responded to.

[0003] Sensor systems are constantly being developed for various functions, e.g., for capturing environmental information in the near and far range of vehicles, such as passenger cars or commercial vehicles. Sensor systems can also be used for driver assistance systems, particularly assistance systems for autonomous or semi-autonomous vehicle control. They can be used, in particular, to detect obstacles and / or other road users in the front, rear, or blind spot area of ​​a vehicle. Sensor systems can be based on various sensor principles, such as radar, ultrasound, and optics.

[0004] An important optical sensor system for environmental detection, e.g., of vehicles, is Lidar technology (Lidar, or Light Detection and Ranging). A Lidar system has an optical transmitter and an optical receiver. The transmitter can emit an optical signal in the form of light, which can be continuous or pulsed. The optical transmission signal can also be modulated. In a Lidar system, light in the form of laser beams in the ultraviolet, visible, or infrared range can be used. The receiver can receive the light after it has been reflected from an object in the vicinity of the Lidar system. The received optical signal can be evaluated using the transmitted optical signal, e.g., using a time-of-flight method, and the spatial position and distance of the object from which the reflection occurred can be determined.In this context, reflection or reflected light is understood to mean any light that is thrown back and is intended to include, in particular, light that is thrown back by scattering or absorption-emission.

[0005] To resolve distance ambiguities in lidar systems that work with an indirect time-of-flight (iToF) method, Payne, AD, Jongenelen, APP, Dorrington, AA, Cree, MJ & Carnegie, DA, Multiple frequency range imaging to remove measurement ambiguity, Proceedings of at 9th Conference on Optical 3-D Measurement Techniques, July 1-3, 2009, Vienna, Austria (pp. 139-148) propose to superimpose two modulation frequencies when modulating the transmitted light. Overview

[0006] A method for operating a sensor system for environmental detection comprises: Emitting a first electromagnetic signal modulated with a first frequency, Receiving the reflected first electromagnetic signal and determining a first number of first samples of a first received signal which depends on the received first electromagnetic signal, Emitting a second electromagnetic signal modulated with a second frequency, Receiving the reflected second electromagnetic signal and determining a second number of second samples of a second received signal which depends on the received second electromagnetic signal.

[0007] The method can be used, for example, to operate a lidar system in which the first and second electromagnetic signals each comprise an optical signal. The method can also be used, for example, to operate a radar system in which the first and second electromagnetic signals each comprise a radio signal in the microwave range.

[0008] By applying this method, the measured distances in sensor systems, particularly lidar systems based on an indirect measurement method such as iToF, can be checked for the period of the uniqueness distance and assigned to the correct distance. The uniqueness distance depends on the modulation frequency used. By using electromagnetic signals modulated one after the other at different frequencies, the uniqueness can be determined and the correct distance can be determined. When using a modulation frequency with a uniqueness distance of, for example, 5 m, it is not possible to distinguish with a single measurement whether an object is 1 m, 6 m, 11 m, etc. away. When using another modulation frequency with a different uniqueness distance, the correct distance can then be determined from both measurements.

[0009] By sampling the two received signals differently, the efficiency of the detection can be adjusted. Depending on the purpose of the detection, not all possible samples of the second received signal may be necessary for the intended further processing. If the detection using the second electromagnetic signal is only intended to supplement the detection using the first signal, for example, a small number of samples of the second received signal may be sufficient, depending on the application. This can improve efficiency and / or speed. Energy consumption can also be reduced.

[0010] The transmission, reception, and detection using the first electromagnetic signal may also be referred to as the first recording or first measurement. The transmission, reception, and detection using the second electromagnetic signal may also be referred to as the second recording or second measurement.

[0011] The first received signal, which depends on the received first electromagnetic signal, can, for example, comprise a correlation signal of the first transmitted signal and the first received signal. The sampling of the first received signal is carried out such that a first number of first samples of the first received signal is determined.

[0012] The second received signal, which depends on the received second electromagnetic signal, can, for example, comprise a correlation signal of the second transmitted signal and the second received signal. The sampling of the second received signal is carried out such that a second number of second samples of the second received signal is determined.

[0013] The first frequency differs from the second frequency so that a unique distance to the location of the reflection of the first and second signals can be determined. The first number differs from the second number. This allows the effort required to determine the distance to be flexibly adjusted, which can also reduce the time required for calculation. In particular, the first and second numbers can be selected so that the distance can be determined unambiguously while keeping the effort as low as possible or necessary. This can result in a time- and energy-efficient method for determining uniqueness in sensor systems with indirect measurement methods, e.g., in iToF LiDAR systems.

[0014] The order of sending and receiving the first and second signals can also be reversed. The first signal can be sent and received first, followed by the second signal. The second signal can also be sent and received first, followed by the first signal. The order can be determined, for example, by which order is more efficient to implement. The process of sending and receiving a signal is also referred to as reception.

[0015] The method may further comprise determining a phase shift between the transmitted first electromagnetic signal and the received first electromagnetic signal using the first number of first samples. In indirect measurement methods that determine the distance to the location of the reflection via a phase shift between the transmitted and received signals, the phase shift is thus determined by evaluating the first received signal. The distance to the location of the reflection cannot yet be unambiguously determined from the phase shift between the first transmitted signal and the first received signal.

[0016] The method may further comprise: determining a distance to a location of reflection of the first electromagnetic signal and the second electromagnetic signal using the phase shift and at least one second sample value. The ambiguity of the distance to the location of reflection of the first and second signals can be resolved using the second sample value and the location of the reflection can be determined. Since the second frequency differs from the first frequency, the distance ambiguity for the second signal is different from that for the first signal. For the second received signal, the determination of the phase shift can also optionally be omitted and the number of determined sample values ​​can be fewer than for the first received signal. A few second sample values ​​or just one second sample value can then be sufficient to resolve the ambiguity.

[0017] In one embodiment of the method, the distance is determined using an indirect time-of-flight method, with the at least one second sample being used to resolve a distance ambiguity. This enables a particularly efficient implementation of the resolution of the distance ambiguity. The number of samples, also called sampling points, is adjusted for each recording. This can shorten the time required for a single recording. This is particularly advantageous for applications with high frame rates, e.g., in vehicles. The frame rate refers to the repetition frequency of the recordings.

[0018] In one embodiment of the method, the first frequency is higher than the second frequency. The recording with the first frequency as the modulation frequency can therefore be used, in particular, as a precision measurement, and the recording with the second frequency as the modulation frequency can be used as a validation measurement. The high modulation frequency of the first signal results in a short unambiguous distance. This distance ambiguity can be resolved through validation using the second signal.

[0019] In one embodiment of the method, the first number is greater than the second number. For example, instead of a complete measurement with, for example, 4-16 samples, only 1 to 2 samples can be recorded in the validation measurement to determine the uniqueness period. This allows the measured distances to be quickly checked for the uniqueness period and can thus be validated. This makes it possible for the recording using the second signal with inaccurate precision to require fewer samples, since they are used, for example, only to resolve the distance ambiguity of the high-precision recording.

[0020] In one embodiment of the method, the first electromagnetic signal and the second electromagnetic signal are amplitude-modulated, e.g., using an AMCW (amplitude modulated continuous wave) method. The AMCW method can be used, for example, in lidar systems and / or radar systems. Application to frequency-modulated methods, e.g., FMCW methods, is also possible.

[0021] In one embodiment of the method, the first electromagnetic signal and the second electromagnetic signal are transmitted in pulsed form. The method can also be applied to pulsed first and second signals. The pulsed signals can also be amplitude-modulated.

[0022] In one embodiment of the method, a pixel-related determination of the sample values ​​is provided for the first electromagnetic signal, and a determination of the sample values ​​based on a group of pixels is provided for the second electromagnetic signal. This involves reducing the resolution for the second electromagnetic signal. This embodiment is particularly advantageous for lidar systems with optical pixel arrays as the receiving sensor. This can further accelerate the method, as the time required to read the pixel field can be reduced. If the resolution is reduced by combining, for example, two, four, or more pixels, the exposure time can also be reduced.

[0023] The sensor system for environmental detection, particularly for a vehicle, comprises a transmitting device, a receiving device, and a computing device. The transmitting device is configured to transmit the first electromagnetic signal modulated at the first frequency and the second electromagnetic signal modulated at the second frequency. The receiving device is configured to receive the reflected first electromagnetic signal and the reflected second electromagnetic signal.The computing device is configured to determine the first number of first sample values ​​of the first received signal, wherein the first received signal depends on the received first electromagnetic signal, wherein the computing device is further configured to determine the second number of second sample values ​​of the second received signal, wherein the second received signal depends on the received second electromagnetic signal.

[0024] The sensor system can, in particular, comprise a lidar system that operates with electromagnetic signals in the optical range. The lidar system comprises an optical transmitting device, an optical receiving device, and a computing device. The optical transmitting device is configured to transmit the first optical signal modulated at the first frequency and to transmit the second optical signal modulated at the second frequency. The optical receiving device is configured to receive the reflected first optical signal and to receive the reflected second optical signal.The computing device is configured to determine the first number of first sample values ​​of the first received signal, wherein the first received signal depends on the received first optical signal, wherein the computing device is further configured to determine the second number of second sample values ​​of the second received signal, wherein the second received signal depends on the received second optical signal.

[0025] The optical receiving device can comprise a receiving sensor, which in particular has an array of receiving pixels for receiving the optical signal. Using the receiving pixels, the receiving sensor converts the first and second optical signals into an electrical sensor signal. For this purpose, the respective receiving pixel can comprise, for example, photosensitive elements, e.g., photosensitive semiconductor elements such as photodiodes. In particular, a pixel-based evaluation of the first signal can be provided. In particular, an evaluation based on a group of receiving pixels can be provided for the second signal. This can further reduce the effort required to determine the uniqueness of the distance.

[0026] The computing device can be further configured to determine the phase shift between the transmitted first electromagnetic signal and the received first electromagnetic signal using the first number of first samples. The phase shift depends on the distance to the location of the reflection of the first signal, but has a distance ambiguity.

[0027] The computing device can be further configured to determine the distance to the location of the reflection of the first electromagnetic signal and the second electromagnetic signal using the phase shift and at least one of the second sample values. The second sample values ​​or at least one of the second sample values ​​can thus be used to resolve the distance ambiguity.

[0028] In particular, the computing device of the sensor system can be configured to determine the distance using an indirect time-of-flight method and to use the at least one second sample value to resolve the distance ambiguity.

[0029] A vehicle can incorporate the described sensor system, particularly a lidar system. The efficient resolution of distance ambiguity is particularly advantageous for in-vehicle sensor systems where a high frame rate is important.

[0030] A computer program product includes instructions which, when executed by the sensor system, cause the sensor system to perform the described method. Fiquren list

[0031] In the following, embodiments of this application are further explained and described with reference to the figures. Fig. 1 schematically shows a method for operating a sensor system, Fig. 2 schematically shows a vehicle with a sensor system, Fig. 3 a schematic illustration of a distance ambiguity of an indirect time-of-flight method Fig. 4 schematically shows a first and a second received signal.

[0032] The same reference numerals are used throughout the figures to refer to identical or similar elements. Representations in the figures may not be to scale. Character description

[0033] In Fig. Figure 1 schematically illustrates a method for operating a sensor system 10, in particular a lidar system. The method comprises: A: Emitting a first electromagnetic signal L1 modulated with a first frequency. B: Receiving the reflected first electromagnetic signal L1 and determining a first number of first sample values ​​S1.1, S1.2, S1.3, S1.4 of a first received signal ES1, which depends on the received first electromagnetic signal L1. C: Emitting a second electromagnetic signal L2 modulated with a second frequency. D: Receiving the reflected second electromagnetic signal L2 and determining a second number of second sample values ​​S2.1, S2.2 of a second received signal ES2 which depends on the received second electromagnetic signal L2. E: Determining a phase shift between the transmitted first electromagnetic signal L1 and the received first electromagnetic signal L1 using the first number of first samples S1.1, S1.2, S1.3, S1.4. F: Determining a distance to a location of reflection of the first electromagnetic signal and the second electromagnetic signal using the phase shift and at least one second sample value S2.1, S2.2.

[0034] The sensor system 10 can in particular comprise a lidar system which operates with electromagnetic signals L1, L2 which comprise optical signals.

[0035] In particular, the described method can significantly reduce the measurement time and / or the evaluation effort for resolving the distance ambiguity.

[0036] For this purpose, in embodiments, the distance to the location of the reflection can be determined in two steps by means of two measurements with a first and a second frequency as well as reduced sampling of the second received signal ES2.

[0037] The first signal L1 is modulated with a first frequency. The second signal L2 is modulated with a second frequency, which in exemplary embodiments is lower than the first frequency. The precision of the first measurement with the first signal is thus greater than the precision of the second measurement with the second signal L2.

[0038] The first measurement with the first signal L1 can therefore be performed as a precision measurement with a high first modulation frequency. The resulting first measurement has a short unambiguousness distance. The second measurement with the second signal L2 can be performed as a validation measurement with a lower second modulation frequency, with the second number of samples for the second received signal ES2 being selected to be lower than the first number of samples for the first received signal ES1.

[0039] The determination of the uniqueness period for the first measurement, i.e. its validation, is now carried out using one or two samples S2.1, S2.2 of the second received signal ES2. The second received signal ES2 is therefore sampled with the second number of samples, whereby the second number is smaller than the first number of samples of the first received signal ES1. For the second measurement, therefore, a complete measurement with, for example, 4-16 samples, also called acquisitions, is not performed. For the second measurement, distance calculation can also be omitted; a single sample, i.e. the amplitude value of the second received signal ES2 at the sampling time, can be sufficient. Optionally, two samples of the second received signal ES2 can also be performed for validation.

[0040] The order of the first and second measurements is not rigid. It can also be adjusted, for example, to minimize the number of configuration steps required between measurements, such as those of the transmitting and / or receiving device.

[0041] Fig. 2 schematically shows a vehicle 20, for example a passenger car, with the sensor system 10, e.g., a lidar system. The sensor system 10 is arranged in the front region of the vehicle 20. The surroundings 22 detected by the sensor system 10 are located in front of the vehicle 20 in the direction of travel. An object O is schematically shown in the surroundings 22. The sensor system 10 has a transmitting device 12 for transmitting the first and second electromagnetic signals L1, L2. The transmitting device 12 can be designed as an optical transmitting device and, in particular, have a light source for emitting laser light. The sensor system 10 further has the receiving device 14 for receiving the reflected first and second electromagnetic signals L1, L2. The receiving device 14 can be designed as an optical receiving device, which has a receiving sensor for receiving the first and second optical signals L1, L2.The receiving sensor may have an array of receiving pixels.

[0042] The transmission process in the transmission device 12 and the reception process in the reception device 14 can be monitored and controlled in a computing device 18. The first number of first sample values ​​S1.1, S1.2, S1.3, S1.4 of the first received signal ES1 can also be determined in the computing device 18. The first received signal ES1 can in particular comprise a correlation signal of the transmitted first signal and the received first signal. The second number of second sample values ​​S2.1, S2.2 of the second received signal ES2 can also be determined in the computing device 18. The second received signal ES2 can in particular comprise a correlation signal of the transmitted second signal and the received second signal.

[0043] The first and second sample values ​​can be evaluated in the computing device 18 to perform a detection of the environment 22. For example, the object O can be detected and the distance to the object O can be determined. Optionally, the first and second sample values ​​can also be determined in the receiving device 14.

[0044] In particular, the phase shift between the transmitted first electromagnetic signal L1 and the received first electromagnetic signal L1 can be determined in the computing device 18 using the first number of first sample values ​​S1.1, S1.2, S1.3, S1.4. Furthermore, the distance to the object O at which the reflection of the first electromagnetic signal L1 and the second electromagnetic signal L2 occurred can be determined in the computing device 18 using the phase shift and at least one second sample value S2.1, S2.2. In particular, the distance can be determined using an indirect time-of-flight method, in which the second sample values ​​S2.1, S2.2 or one of the second sample values ​​S2.1, S2.2 is used to resolve the distance ambiguity.

[0045] In the example shown, the surroundings 22 in front of the vehicle 20 can be monitored in the direction of travel. It is also possible to arrange the sensor system 10 in other areas of the vehicle 20, for example, in the rear area and / or in the side areas. It is also possible to arrange multiple sensor systems 10 on the vehicle 20, in particular in corner areas of the vehicle 20.

[0046] With the sensor system 10, stationary or moving objects O, in particular vehicles, persons, animals, plants, obstacles, road surface irregularities, in particular potholes or stones, road markings, traffic signs, open spaces, in particular parking spaces, precipitation or the like, can be detected in the environment 22 and the distance to the objects O can be determined. In the vehicle 20, the environmental information generated by the sensor system 10 can be used to implement autonomous or semi-autonomous driving functions.

[0047] In Fig. Figure 3 shows an example of the sensor system 10 with an object O. Also shown are possible distances O' of the object O, which arise due to the ambiguity of indirect measurement methods.

[0048] For sensor systems 10, especially lidar systems, which use an indirect measurement method with, for example, amplitude or frequency modulation, the measured distances must be checked for the period of the unique distance and assigned accordingly. The unique distance depends on the modulation frequency of the electromagnetic signal L1, L2 used. Fig. 3 shows an example of the object O, which was detected by means of a first electromagnetic signal L1 and a second electromagnetic signal L2 by the sensor system 10. Depending on the modulation frequency, various possible positions O' for the object O result. The higher modulation frequency corresponds to a shorter ambiguity period. Fig. In the example shown in Figure 3, the upper possible positions correspond to the recording with the higher modulation frequency.

[0049] The ambiguity can be resolved by evaluating both measurements. When using amplitude modulation, e.g., the AMCW method, two measurements can be performed with different modulation frequencies and thus different ambiguity limits.

[0050] The first measurement is performed with the first signal at a first frequency that is higher than the second frequency used for the second measurement using the second signal. The described method allows the second measurement to be limited to what is necessary to resolve the ambiguity. A full second measurement with the second signal is not required. This can save time, costs, and / or energy.

[0051] In Fig. Figure 4 schematically illustrates an embodiment of a first and a second received signal ES1, ES2. The respective envelopes of the first and second received signals ES1, ES2 are shown.

[0052] The first received signal ES1 results from the correlation signal of the transmitted first signal L1 and the received first signal L1. The transmitted first signal is a sinusoidally amplitude-modulated electromagnetic signal. The received first signal L1 has the same signal shape with a phase shift due to the distance traveled to the point of reflection and back. The first received signal ES1, as the correlation signal of the two, also has a sinusoidal shape.

[0053] The second received signal ES2 results from the correlation signal of the transmitted second signal L2 and the received second signal L2. The transmitted second signal L2 is a sinusoidally amplitude-modulated electromagnetic signal. The received second signal L2 has the same signal shape with a phase shift due to the distance traveled to the point of reflection and back. The second received signal ES2, as the correlation signal of the two, also has a sinusoidal shape.

[0054] Four sample values ​​S1.1, S1.2, S1.3, and S1.4 are generated by sampling the first received signal ES1. From these sample values, the phase shift between the transmitted first signal L1 and the received first signal L1 can be determined. From the phase shift, the distance to the location of the reflection on the object O can be determined using the described ambiguity.

[0055] To resolve the ambiguity, the two sample values ​​S2.1, S2.2 of the second received signal ES2 are now used.

[0056] For the second received signal ES2, it is not necessary to calculate the phase shift between the transmitted second signal L2 and the received second signal L2. The ambiguous distance to the location of the reflection on the object O can also be omitted. To validate the first measurement, the precision measurement, one or two of the second sample values ​​S2.1, S2.2 are sufficient. This allows the distance calculation to be faster, more efficient, and more energy-efficient, without compromising the precision of the measurement.

[0057] The sinusoidal waveforms are exemplary and do not need to be modulated throughout. Simply generating the amplitudes of the respective received signals ES1, ES2, i.e., the respective sample values ​​S1.1, S1.2, S1.3, S1.4, S2.1, S2.2, at the respective sampling time is sufficient.

[0058] Based on the more accurate, but ambiguous, results of the precision measurement using the first signal L1, together with the known modulation frequencies of the first and second signals L1, L2, the possible amplitude values ​​of the second received signal ES2 at at least one sampling time can be narrowed down. The accuracy of the validation only needs to be within the unambiguousness distance of the precision measurement.

[0059] This significantly reduces the measurement time for the validation measurement, making it possible to achieve a higher frame rate. Further acceleration can be achieved by reducing the image resolution of the validation measurement. In the case of a receiving sensor with a pixel array, the time required to read the pixel array can be reduced. If the resolution is reduced by combining two, four, or more pixels, the measurement / exposure time can also be reduced.

[0060] By reducing the number of samples for the second measurement, the efficiency of the measurement can also be increased, thus saving electrical energy, for example. It is also possible, for example, with pulsed measurements, to reduce the amount of light emitted per measurement. This has a positive impact on eye safety. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] Payne, A.D., Jongenelen, A.P.P., Dorrington, A.A., Cree, M.J. & Carnegie, D.A., Multiple frequency range imaging to remove measurement ambiguity, Proceedings of at 9th Conference on Optical 3-D Measurement Techniques, July 1-3, 2009, Vienna, Austria (pp. 139-148

[0005]

Claims

[1] Method for operating a sensor system (10), in particular a lidar system, for environmental detection, comprising: Emitting a first electromagnetic signal (L1) modulated with a first frequency, Receiving the reflected first electromagnetic signal (L1) and determining a first number of first samples (S1.1, S1.2, S1.3, S1.4) of a first received signal (ES1) which depends on the received first electromagnetic signal (L1), Emitting a second electromagnetic signal (L2) modulated with a second frequency, Receiving the reflected second electromagnetic signal (L2) and determining a second number of second samples (S2.1, S2.2) of a second received signal (ES2) which depends on the received second electromagnetic signal (L2). [2] Method according to claim 1, comprising: Determining a phase shift between the transmitted first electromagnetic signal (L1) and the received first electromagnetic signal (L1) using the first number of first samples (S1.1, S1.2, S1.3, S1.4). [3] Method according to claim 2, comprising: Determining a distance to a location of reflection of the first electromagnetic signal and the second electromagnetic signal using the phase shift and at least one second sample value (S2.1, S2.2). [4] Method according to claim 3, wherein the distance determination is carried out according to an indirect time-of-flight method and the at least one second sample value (S2.1, S2.2) is used to resolve a distance ambiguity. [5] A method according to any one of the preceding claims, wherein the first frequency is greater than the second frequency. [6] A method according to any one of the preceding claims, wherein the first number is greater than the second number. [7] Method according to one of the preceding claims, wherein the first electromagnetic signal (L1) and the second electromagnetic signal (L2) are amplitude modulated. [8] Method according to one of the preceding claims, wherein the first electromagnetic signal (L1) and the second electromagnetic signal (L2) are emitted in pulsed form. [9] Method according to one of the preceding claims, wherein a pixel-related determination of the sample values is provided for the first electromagnetic signal and a determination of the sample values is provided for the second electromagnetic signal in relation to a group of pixels. [10] Sensor system for environmental detection, in particular for a vehicle (20), comprising a transmitting device (12) which is arranged to transmit a first electromagnetic signal (L1) modulated at a first frequency and to transmit a second electromagnetic signal (L2) modulated at a second frequency (L2), a receiving device (14) which is arranged to receive the reflected first electromagnetic signal (L1) and to receive the reflected second electromagnetic signal (L2), and a computing device (18) which is configured to determine a first number of first sample values (S1.1, S1.2, S1.3, S1.4) of a first received signal (ES1), wherein the first received signal (ES1) depends on the received first electromagnetic signal (L1), wherein the computing device (18) is further configured to determine a second number of second sample values (S2.1, S2.2) of a second received signal (ES2), wherein the second received signal (ES2) depends on the received second electromagnetic signal (L2). [11] Sensor system according to claim 10, wherein the computing device (18) is further configured to determine a phase shift between the transmitted first electromagnetic signal (L1) and the received first electromagnetic signal (L1) using the first number of first samples (S1.1, S1.2, S1.3, S1.4), [12] Sensor system according to claim 11, wherein the computing device (18) is further configured to determine a distance to a location of reflection of the first electromagnetic signal (L1) and the second electromagnetic signal (L2) using the phase shift and at least one second sample value (S2.1, S2.2). [13] Sensor system according to claim 12, wherein the computing device (18) is configured to determine the distance according to an indirect time-of-flight method and to use the at least one second sample value (S2.1, S2.2) to resolve a distance ambiguity. [14] Vehicle (20) with a sensor system according to one of claims 10 to 13. [15] A computer program product comprising instructions which, when executed by a sensor system, cause the sensor system to perform a method according to any one of claims 1 to 9.

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