Transmitting device for emitting light

Abstract

A transmitting device (21) for emitting light, at least of one frequency, wherein the transmitting device (21) is configured to emit light into different angular ranges (100, 101) such that the frequency of the light in the respective angular range (100, 101) is time-dependent within a respective frequency range (f a START, f a ENDE , f b START, f b ENDE, f c START, f c ENDE ) is varied (5a, 5b, 5c), with frequencies in different frequency ranges (f a START, f a ENDE , f b START, f b ENDE, f c START, f c ENDE) for different angular ranges (100, 101) at different times (2) do not overlap, wherein a light source (10, 10a, 10b, 10c) and a modulation device (11, 11a, 11b, 11c) for generating the time-dependent variation of frequencies of the light of the light source (10, 10a, 10b, 10c) are arranged, wherein the modulation device has a modulator (11a) for temporal variation of a frequency range and at least one further modulator (11b, 11c) for generating different frequency ranges.

Description

Technical field

[0001] The invention relates to a transmitting device for emitting light of at least one frequency.

[0002] The invention also relates to a receiving device for receiving light.

[0003] The invention further relates to a sensor device, a method for emitting light of at least one frequency, and a method for receiving light of different frequency ranges. State of the art

[0004] Although the present invention is applicable to any transmitting and receiving devices, the present invention is described in connection with light detection and distance systems - LiDAR.

[0005] Known LiDAR systems use narrowband laser beams that are deflected in a specific direction. When the laser beam hits an object, its distance can be determined by measuring the reflection of the laser beam from the object at that angle. For this purpose, a linear frequency ramp, based on the principle of FMCW (frequency modulated continuous wave), is emitted, and the difference frequency between the transmitted and received ramps is determined through coherent reception. The object's distance can then be calculated from this difference frequency. To detect an object within a specific area, the area can be illuminated two-dimensionally. This requires a short measurement time, which, however, typically reduces the range, i.e., the distance at which an object can be detected.The reason for this is that as the distance increases, the signal-to-noise ratio for a given distance depends linearly on the measurement time, and as the measurement time increases, a measurement is no longer possible.

[0006] It is also known to use multiple sensors to detect a specific angular range, with each sensor assigned a separate angular segment of that range. However, this requires a separate transmit and receive path for each segment. Furthermore, multiple reflections from other angular segments can occur. EP 2 177 931 A2, US 2014 / 0 111 808 A1, US 2017 / 0 328 988 A1 and WO 2015 / 120 903 A1 describe related prior art. Disclosure of the invention

[0007] In one embodiment, the invention provides a transmitting device for emitting light of at least one frequency, wherein the transmitting device is configured to emit light into different angular ranges, such that the frequency of the light in the respective angular range is varied time-dependently in a respective frequency range, wherein frequencies in different frequency ranges for different angular ranges do not overlap at different times.

[0008] In a further embodiment, the invention provides a receiving device for receiving light, wherein a separation device for separating frequencies of time-varying different frequency ranges and at least one detector for converting the received light into electrical signals are arranged.

[0009] In a further embodiment, the invention provides a sensor device with a transmitting device according to at least one of claims 1-6 and a receiving device according to one of claims 7-9.

[0010] In a further embodiment, the invention provides a method for emitting light of at least one frequency, wherein the light is emitted into different angular ranges, such that the frequency of the light in the respective angular range is varied time-dependently in a respective frequency range, wherein frequencies in different frequency ranges for different angular ranges do not overlap at different times.

[0011] In a further embodiment, the invention provides a method for receiving light of different frequency ranges, in particular emitted by a method according to claim 11, wherein frequencies of time-varying different frequency ranges are separated and in particular the received light is converted into electrical signals.

[0012] In other words, the transmitting device can emit light into different angular ranges, and a receiving device can receive the reflected light again.

[0013] One advantage is that multiple angular ranges can be illuminated simultaneously without requiring multiple transmitters and / or receivers, i.e., multiple transmission and reception paths. Another advantage is that this allows for a longer measurement time for varying the respective frequency range, thereby improving the signal-to-noise ratio and ultimately increasing the detection range of objects using the sensor device. A further advantage is the increased flexibility, as, for example, multiple horizontal planes can be illuminated simultaneously.

[0014] Further features, advantages and further embodiments of the invention are described below or become apparent therein.

[0015] According to an advantageous embodiment, the transmitting device is configured to vary the frequency linearly over time within the respective angular range, preferably increasing it from a starting frequency to an ending frequency. One of the advantages achieved is that simple temporal variation of the frequency across the entire frequency range is enabled. Furthermore, subsequent evaluation is also simplified, as a clear temporal assignment of the frequencies is made possible.

[0016] According to a further advantageous embodiment, a light source and a modulation device for generating time-dependent variations in the frequencies of the light from the light source are arranged. A simple and reliable modulation of the light from a light source, such as a laser, is possible by means of a modulation device.

[0017] According to a further advantageous development, the modulation device includes a modulator for each of the different frequency ranges. This enables particularly reliable modulation.

[0018] According to a further advantageous embodiment, the modulation device comprises a modulator for temporally varying a frequency range and at least one further modulator for generating different frequency ranges. One of the advantages achieved is that, by separating frequency ranges and their respective temporal variation, a particularly reliable variation of frequencies in different frequency ranges can be provided. For example, a frequency offset between the different ranges can be generated using a phase modulator. Here, the phase is modulated over time, thereby generating a frequency offset. Examples of such modulators are those based on the modulation of the charge carrier density or on electro-optical effects, such as the Pockels effect or the Kerr effect.

[0019] According to a further advantageous development, a separate light source is arranged for each frequency range. In this way, different light sources with different characteristics can be used, which increases the overall flexibility.

[0020] According to a further advantageous embodiment, a separate detector is arranged for each frequency range. This allows for particularly reliable light detection, as the detector can be tuned to the received light of the respective frequency range.

[0021] According to a further advantageous embodiment, the separation device includes a notch filter, in particular in the form of photonic ring oscillators. A notch filter allows received light with different frequency ramps to be reliably separated into light with each of its own frequency ramp.

[0022] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings, and the accompanying description of the figures based on the drawings.

[0023] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0024] Preferred embodiments and configurations of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components or elements. Brief description of the drawings

[0025] This is shown in schematic form Fig. 1 a time-frequency representation of the temporal variation of frequencies according to a first embodiment of the present invention; Fig. 2 a transmitting device according to a second embodiment of the present invention; Fig. 3 a transmitting device according to a third embodiment of the present invention; Fig. 4 a transmitting device according to a fourth embodiment of the present invention; Fig. 5 a transmitting device according to a fifth embodiment of the present invention; Fig. 6 a receiving device according to a sixth embodiment of the present invention; Fig. 7 a receiving device according to a seventh embodiment of the present invention; and Fig. 8 a sensor device according to an eighth embodiment of the present invention. Embodiments of the invention

[0026] Fig. Figure 1 shows a time-frequency representation of the temporal variation of frequencies according to a first embodiment.

[0027] In Fig. Figure 1 shows a time-frequency representation of frequency ramps, where the baseband of the uppermost frequency ramp 6c is indicated by a dashed line. In detail, Figure 1 shows... Fig. Figure 1 shows a time-frequency plot, where frequency 3 is plotted against time 2. Three frequency ramps 5a, 5b, and 5c are visible, each increasing with the same slope over the same time interval. The frequency ramps 5a and 5b differ in their respective starting frequencies by the frequency difference 4a, and the two frequency ramps 5b and 5c differ by the frequency difference 4b. The frequency differences 4a and 4b can be the same or different. The starting frequency f a START the first ramp 5a is in Fig. 1 smallest and the starting frequency f c STARTThe third frequency ramp, 5c, is the largest. Due to the linear increase, the respective final frequency f a,b,c ENDE the respective frequency ramp 5a, 5b, 5c higher than the respective starting frequency f a,b,c START Of course, reverse frequency ramps are also conceivable, or a linearly decreasing frequency ramp. Fig. Figure 1 shows three frequency ramps 5a, 5b, 5c, but any other number of frequency ramps is also possible.

[0028] The generation of frequency ramps 5a, 5b, 5c can be achieved as follows: Light from a light source, for example a laser, is generated using three different phase modulators, thus modulating the three linear frequency ramps 5a, 5b, 5c. The three frequency ramps 5a, 5b, 5c differ in their starting frequencies f. a START , f b START =f a START + Δf1, f c START =f a START+ Δf1 + Δf2, where the offset frequencies 4a, 4b between the different starting frequencies f START , f START + Δf1, f START + Δf1 + Δf2 not necessarily larger than the frequency deviation, i.e. the difference between start and end frequency f a,b,c ENDE - f a,b,c START The respective frequency ramps 5a, 5b, and 5c must be present. During reception, the frequency ramps 5a, 5b, and 5c can be mixed into a respective baseband 6, also known as "dechirping." The modulation is removed, and the frequency ramps 5a, 5b, and 5c are separated. As long as the respective basebands 6 are sufficiently frequency-spaced, especially if the basebands do not overlap, the frequency ramps 5a, 5b, and 5c can also lie at least partially in the same frequency range, in which case frequencies of one frequency range will differ from frequencies of the other frequency range at a given time. Fig. Figure 1 shows only the baseband 6c of the uppermost frequency ramp 5c. In general, other forms of frequency variation are also conceivable, for example, instead of the linear rise of the Fig. 1 a linear increase followed by a linear decrease.

[0029] Fig. Figure 2 shows a transmitting device according to a second utterance of the present invention.

[0030] In Fig. Figure 2 shows a transmitter 21 with three modulators 11 and a light source in the form of a laser 10. The laser 10 emits at a specific frequency f. START Light is modulated by three modulators 11a, 11b, 11c to generate the linear frequency ramps 5a, 5b, 5c. In other words, each modulator 11a, 11b, 11c modulates a frequency ramp 11a, 11b, 11c. Subsequently, the light of the three generated frequency ramps 5a, 5b, 5c is emitted by means of a transmitting optic 12.

[0031] Fig. Figure 3 shows a transmitting device according to a third embodiment of the present invention.

[0032] In Fig. Figure 3 shows a transmitter 21 with a laser 10, a modulator 11a for generating frequency ramps, and two modulators 11b, 11c for generating frequency offsets 4a, 4b. Here, only one modulator 11 is used to generate the frequency ramps 5a, 5b, 5c. The linear frequency ramp for the light from the laser 10, generated by the modulator 11, is then split into three paths 5a, 5b, 5c, with the frequency offset 4a, 4b being shifted in two of the three paths 5b, 5c. This frequency offset 4a, 4b can also be generated using a phase modulator. In this case, the phase is modulated over time, thereby generating a frequency offset 4a, 4b. Such modulators are based, for example, on the modulation of the charge carrier density or on electro-optical effects, such as the Pockels effect or the Kerr effect.

[0033] Fig. Figure 4 shows a transmitting device according to a fourth embodiment of the present invention.

[0034] In Fig. 4 is essentially a transmitting device 21 according to Fig. 2 shown. In contrast to the three modulators 11a, 11b, 11c of the Fig. 2 is the modulator 11 according to Fig. 4 is designed to be broadband, so that it can modulate all three frequency ramps 5a, 5b, 5c onto the light of the laser 10.

[0035] Fig. Figure 5 shows a transmitting device according to a fifth embodiment of the present invention.

[0036] In Fig. 5 is essentially a transmitting device 21 according to Fig. 2 shown. In contrast to the transmitting device 21 according to Fig. 2 are in the transmitting device 21 according to Fig. 5 now three lasers 10a, 10b, 10c arranged, each emitting a light signal with the frequency f START , f' START, f'' STARTThe light is modulated by means of a modulator 11a, 11b, 11c, each assigned to a laser 10a, 10b, 10c, with a frequency ramp 5a, 5b, 5c. The correspondingly modulated light with the frequency ramps 5a, 5b, 5c is then emitted together via the transmitting optics 12.

[0037] The modulated light signals according to Fig. As shown, 1-5 are emitted into space via transmitting optics 12. A separate transmitting optic 12 can be arranged for each modulated light signal, for example, in the form of a micromechanical scanner or an optical phase array or the like, which then emits into a specific angular range so that the different angular ranges of other / additional transmitting optics do not overlap. Alternatively, the transmitting device 21 can be designed such that the different frequency ranges, in particular the mean wavelengths of the different ramps 5a, 5b, 5c, automatically result in emission via a transmitting optic 12 into different angular ranges. The respective light of the three modulated laser beams 10a, 10b, 10c of the Fig. 5 is thus combined and then emitted via the same transmitting optic 12. The different frequencies of the modulated light result in a desired beam deflection into different solid angles. The frequency offset 4a, 4b between the ramps 5a, 5b, 5c is chosen to be sufficiently large, which is why the embodiment of the Fig. 5 is advantageous.

[0038] Fig. Figure 6 shows a receiving device according to a sixth embodiment of the present invention.

[0039] In Fig. Figure 6 shows a receiving device 22 with three detectors 15a, 15b, 15c. Light received by the receiving optics 13 of the receiving device 22 is first separated by a separation device 14 before striking a detector 15a, 15b, 15c. In other words, before mixing, i.e., before converting the optical signal into an electrical signal, the received optical light signal, which comprises several frequency ramps 5a', 5b', 5c', is separated, for example, by notch filters, particularly in the form of photonic ring oscillations. Each frequency ramp 5a', 5b', 5c' is then fed to a respective detector 15a, 15b, 15c.Beforehand, each received frequency ramp 5a', 5b', 5c' is superimposed with the corresponding transmitting ramp 5a, 5b, 5c to ensure coherent reception: More precisely, after the detection of the light with the corresponding frequency ramp 5a', 5b', 5c' by the corresponding detector 15a, 15b, 15c, the superimposed light signal of each frequency ramp 5a', 5b', 5c' with the corresponding transmitting ramp 5a, 5b, 5c is mixed into the respective baseband 6 and can then be evaluated in a known manner according to the FMCW principle.

[0040] Fig. Figure 7 shows a receiving device according to a seventh embodiment of the present invention.

[0041] In Fig. Figure 7 shows a receiving device 22 with a detector 15. Light received by the receiving optics 13 is directed to the detector 15, which may have, for example, one or two photodiodes. Light with one of the received frequency ramps 5a', 5b', 5c' is then superimposed with light of the corresponding transmitted frequency ramp 5a, 5b, 5c. Subsequently, either the entire baseband 6, i.e., all basebands 6a, 6b, 6c with the frequency ramps 5a', 5b', 5c' of the respective transmitted frequency ramps 5a, 5b, 5c, can be sampled, or bandpass filters and / or electrical mixers in the respective baseband 6 can be used to separate the frequency ramps 5a, 5b, 5c. In particular, the frequency difference 4a, 4b of the frequency ramps 5a, 5b, 5c is chosen in relation to the bandwidth of the detector 15 accordingly, so that the detector 15 is designed to receive all ramps 5a, 5b, 5c.

[0042] Fig. Figure 8 shows a sensor device according to an eighth embodiment of the present invention.

[0043] In Fig. Figure 8 shows a sensor device 20 in the form of a LiDAR system. The sensor device 20 comprises a transmitter 21 in the embodiment of Fig. 1 and a receiving device in the embodiment of Fig. 7. The transmitting device 21 emits light with different frequency ramps 5a, 5b into different angular ranges 100, 101. An object 30 located within angular range 100 and within the range of the sensor device reflects the emitted light with frequency ramp 5a. The light reflected from the object 30 with frequency ramp 5a' is then received by the receiving device 22. The sensor device 20 then evaluates the received light and can determine the distance of the object 30 from the sensor device 20.

[0044] In summary, at least one embodiment of the present invention has at least one of the following advantages: • Simultaneous transmission into different angular ranges and reception with only one receiving unit of the reflected light, • simultaneous irradiation of multiple angular ranges, • Increased measurement time per ramp and thus improvement of the signal-to-noise ratio, • greater range, • Parallelization of the LiDAR system is possible, • Higher reliability due to fewer false detections caused by multiple reflections, • simple construction, and • Easy to implement.

[0045] Although the present invention has been described using preferred embodiments, it is not limited to these, but can be modified in many ways.

Claims

[1] Transmitting device (21) for emitting light, at least one frequency, wherein the transmitting device (21) is configured to emit light into different angular ranges (100, 101) such that the frequency of the light in the respective angular range (100, 101) is time-dependent in a respective frequency range (f a START, f a ENDE , f b START, f b ENDE, f c START, f c ENDE ) is varied (5a, 5b, 5c), with frequencies in different frequency ranges (f a START, f a ENDE , f b START, f b ENDE, f c START, f c ENDE) for different angular ranges (100, 101) at different times (2) do not overlap, wherein a light source (10, 10a, 10b, 10c) and a modulation device (11, 11a, 11b, 11c) for generating the time-dependent variation of frequencies of the light of the light source (10, 10a, 10b, 10c) are arranged, wherein the modulation device has a modulator (11a) for temporal variation of a frequency range and at least one further modulator (11b, 11c) for generating different frequency ranges. [2] Transmitting device according to claim 1, wherein it is configured to vary the frequency (3) linearly over time in the respective angular range (100, 101), preferably from a starting frequency (f a START , f b START , f c START ) to a final frequency (f a ENDE ,f b ENDE ,f c ENDE to increase. [3] Transmitting device according to claim 2, wherein the modulation device (11, 11a, 11b, 11c) for each of the different frequency ranges (f a START, f a ENDE ; f b START, f b ENDE ; f c START, f c ENDE ) includes a modulator (11a, 11b, 11c). [4] Transmitting device according to one of claims 1-3, wherein a separate light source (10a, 10b, 10c) for each frequency range (f a START, f a ENDE ; f b START, f b ENDE ; f c START, f c ENDE ) is arranged. [5] Receiving device (22) for receiving light, in particular emitted by a transmitting device (21) according to one of claims 1-4, wherein a separation device (14) for separating frequencies (3) of time-varying different frequency ranges (f a START, f aENDE ; f b START, f b ENDE ; f c S-TART, f c ENDE ) arranged and at least one detector (15, 15a, 15b, 15c) is arranged for converting the received light into electrical signals, wherein the separation device (14) has a notch filter. [6] Receiving device according to claim 5, wherein a separate detector (15a, 15b, 15c) for each frequency range (f a START , f a ENDE ; f b START, f b ENDE ; f c START, f c ENDE ) is arranged. [7] Receiving device according to claim 5 or 6, wherein the notch filter is designed in the form of photonic ring oscillators. [8] Sensor device (20) comprising a transmitting device (21) according to at least one of claims 1-4 and a receiving device (22) according to one of claims 5-7. [9] Method for emitting light of at least one frequency (3), wherein the light is emitted into different angular ranges (100, 101) such that the frequency of the light in the respective angular range (100, 101) varies over time in a respective frequency range (f a START, f a ENDE ; f b START, f b ENDE ; f c START, f c ENDE ) is varied (5a, 5b, 5c), with frequencies (3) in different frequency ranges (f a START, f a ENDE ; f b START, f b ENDE ; f c START, f c ENDE) for different angular ranges (100, 101) at different times (2) do not overlap, wherein the variation of the frequency of the light is carried out by means of a modulator (11a) for temporal variation of a frequency range and at least one further modulator (11b, 11c) for generating different frequency ranges. [10] Method for receiving light of different frequency ranges, in particular emitted by a method according to claim 9, wherein frequencies (3) of time-varying different frequency ranges (f a START, f a ENDE ; f b START, f b ENDE ; f c START, f c ENDE ) are separated (14) and in particular the received light is converted into electrical signals, wherein the frequencies (3) of time-varying different frequency ranges (f a START, f a ENDE ; f bSTART, f b ENDE ; f c START, f c ENDE ) are separated using a notch filter.

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