Device and method for scanning the distance to an object

Abstract

Device (14) for scanning the distance to an object (12), with a light source (16) which is configured to produce an optical signal with a varying frequency, a distribution matrix (M) designed to distribute the optical signal simultaneously to several optical output waveguides (38), several free-space couplers (40) arranged on a common substrate (46) and configured to couple the optical signals guided in the output waveguides (38) into free space as light beams (L11 to L14; R1 to R4), a deflection optic (44) which is configured to deflect the optical signals emerging from the optical output waveguides (38) in such a way that they are simultaneously emitted in different directions from the device (14), at least one detector (32) configured to detect a superposition of the optical signal generated by the light source (16) with an optical signal reflected by the object (12), an evaluation device (34) which is configured to determine a distance to the object (12) from the superposition detected by the at least one detector (32), characterized by the fact that the device has a beam displacement unit which has an actuator (54; 62) for generating a movement and is configured to temporarily displace the light beams (R1 to R4) emerging from the free-space couplers together before they strike the deflection optics (44).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to a device and a method for scanning the distance to a moving or stationary object based on FMCW LiDAR technology. Such devices can be used, for example, in autonomous vehicles and contain photonic integrated circuits (PICs) that contain no moving parts. 2. Description of the state of the art

[0002] For optical distance measurement, a measuring principle known as FMCW LiDAR is known. In this principle, optical signals with a time-varying frequency (FMCW stands for frequency modulated continuous wave) are directed in different directions at an object to be measured from a measuring device. After being reflected by the object, the signals return to the measuring device and are superimposed with a signal that was not emitted and is therefore referred to as a local oscillator. Due to the light path traveled, the reflected signal has a slightly different frequency than the non-emitting signal. When the two signals are superimposed, a comparatively low-frequency beat frequency is created, which is detected by a detector in the measuring device and used to calculate the distance between the measuring device and the object.If the Doppler shift is also taken into account, the relative velocity between the scanner and the object can also be calculated.

[0003] Measuring devices based on this measuring principle must be extremely robust and reliable if they are to be used in vehicles. This is especially true for autonomous vehicles, as safety in autonomous driving depends crucially on the reliability of generating a three-dimensional image of the environment with sufficiently high resolution.

[0004] Therefore, at least for scanning in horizontal planes, measurement devices that do not require rotating scanning mirrors or other moving components are preferred. In such solutions, such as those described in US 2017 / 0371227 A1 and US 2019 / 0377135 A1, a distribution matrix with several tree-like active or passive splitters distributes the FMCW signals to different free-space couplers. A deflection optic, with the free-space couplers arranged in the focal plane, collimates the optical signals emerging from the free-space couplers and radiates them in different directions.

[0005] To achieve the required high spatial resolution in the horizontal plane, these existing solutions require a large number of free-space couplers to be arranged in a very small space. However, this quickly reaches technological limits. Even if the resolution is achievable, the extremely high integration density leads to high scrap during lithographic production, which adversely affects unit costs.

[0006] From WO 2020 / 202011 A1, a laser image projector is known with an actuator coupled to an objective lens to move it along a movement axis in order to reduce speckle while a laser beam is projected.

[0007] US 2018 / 0180720 A1 discloses a ToF LiDAR system in which a carrier for multiple laser light sources and photodetectors is oscillated relative to a stationary transmitting lens and a stationary receiving lens using a voice coil. This achieves a scanning effect without tilting mirrors or similar devices. SUMMARY OF THE INVENTION

[0008] The object of the invention is to provide a device and a method for scanning measurement of the distance to an object, with which a high spatial resolution can be achieved cost-effectively.

[0009] According to the invention, this object is achieved by a device for scanning measurement of the distance to an object, which device has a light source configured to generate an optical signal with a varying frequency. The device also has a distribution matrix configured to simultaneously distribute the optical signal across a plurality of optical output waveguides. The device further contains a plurality of free-space couplers arranged on a common substrate and configured to couple the optical signals guided in the output waveguides into free space as light beams. Deflection optics of the device are configured to deflect the optical signals emerging from the optical output waveguides such that they are emitted from the device simultaneously in different directions.A detector detects an overlay of the optical signal generated by the light source with an optical signal reflected by the object. The device further comprises an evaluation unit configured to determine a distance to the object from the overlay detected by the at least one detector. According to the invention, the device further comprises a beam shifting unit that has an actuator for generating a movement and is configured to temporarily shift the light beams emerging from the free-space couplers together—preferably in parallel—before they impinge on the deflection optics.

[0010] The invention is based on the consideration that in measuring devices based on the FMCW LiDAR principle, a three-dimensional image of the environment is not obtained instantaneously, but is the result of a scanning process. The three-dimensional image is thus constructed successively, even if several light beams are directed onto the object simultaneously at a given time. This successive image construction makes it possible to superimpose a mechanical movement on the scanning process, which leads to a preferably parallel offset of the light beams emerging from the free-space couplers. An offset of the light beams by an amount predetermined by the movement leads to different emission angles behind the deflection optics. The light beams therefore strike the object at different points before and after the offset.The beam shifting unit can thus be controlled so that points on the object are scanned with a grid density twice that of a measuring device without a beam shifting unit. Such a doubling of resolution could otherwise only be achieved with a corresponding increase in the integration density on the photonic integrated circuit, or at very high cost.

[0011] In one embodiment, the actuator is a translation actuator configured to move the substrate with the free-space couplers arranged thereon. Moving the substrate changes the relative position of the substrate to the deflection optics, resulting in different emission angles. Alternatively, the deflection optics can be moved. However, this is mechanically more complex, since the deflection optics typically weigh more than the photonic integrated circuit with the free-space couplers.

[0012] Preferably, the substrate is moved translationally back and forth along a translation direction that runs perpendicular to an exit direction of the light beams. The free-space couplers are thereby laterally displaced in the focal plane of the deflection optics, which changes the angular spectrum of the emitted light beams accordingly. However, the translational movement can also include a component along the exit direction of the light beams, as disclosed in DE 10 2021 111 949 A1. Thus, not only linear but also circular or elliptical trajectories are possible for the movement of the substrate.

[0013] In principle, it is also conceivable to rotate the substrate. However, compared to a translational movement, this would result in complicated and potentially undesirable angular changes behind the deflection optics.

[0014] The movement of the substrate can be intermittent or continuous. Intermittent movement is defined as a movement in which two or more target positions are approached abruptly, and the substrate briefly comes to a standstill at each of these target positions.

[0015] To avoid the resulting high accelerations, it is often more advantageous to generate continuous movements with the translation actuator. Harmonic oscillations, which can be tuned to the substrate's natural frequency, are particularly advantageous in this context. In particular, the translation actuator can be configured to set the substrate in an oscillating motion along the translation direction at a frequency between 20 Hz and 100 Hz. The oscillation frequency should be tuned to the scanning frequency at which the light beams scan the object.

[0016] The translation actuator can, for example, have a voice coil drive that engages the substrate. Alternatively, the use of piezoelectric actuators is also possible.

[0017] In another embodiment, the beam displacement unit comprises a plane plate transparent to the light beams. The actuator is a rotary actuator configured to move the plane plate between at least two angular positions relative to a rotational axis extending at an angle—preferably of 90°—to an exit direction of the light beams. A plane plate tilted in the beam path of the light beams causes a parallel offset of the light beams that increases with increasing tilt angle. Since the light beams only need to be offset laterally by a small amount to increase resolution, the plane plate can be thin. As a result, the mass to be moved in this embodiment can be smaller than in the embodiment explained above, in which the entire photonic integrated circuit is moved.

[0018] Preferably, the distribution matrix is ​​a switching matrix with multiple optical switches and is configured to selectively distribute the optical signal among the multiple optical output waveguides. In this way, the optical power generated by the light source can be concentrated on a few simultaneously active optical channels. Preferably, a control device is then provided that is configured to synchronize the optical switches of the switching matrix with an offset of the light beams caused by the beam shifting unit. The control device thus coordinates the two available degrees of freedom, namely the selection of the free-space couplers activated via the switching matrix, on the one hand, and the selection of the tilt angle of the plane plate, on the other.

[0019] The distribution matrix can also contain exclusively passive beam splitters, so that the optical signal is distributed simultaneously across all optical output waveguides. In this case, it is advantageous if each output waveguide is assigned an individually controllable optical amplifier. This allows individual channels to be controlled specifically, even with passive beam splitters.

[0020] Preferably, each free-space coupler is configured to couple an optical signal generated by the light source, which was fed to the free-space coupler via an output waveguide connected to the free-space coupler and exited the free-space coupler, back into the same output waveguide as an optical measurement signal after reflection from the object. Alternatively, however, it is also possible to provide separate free-space couplers for receiving the reflected optical signals, which feed the received optical signals to the detector via separate input waveguides.

[0021] Preferably, the free-space couplers are all arranged in a common plane. If scanning is performed in only one direction, the free-space couplers lie on a straight line.

[0022] The light source is typically a laser light source that generates coherent light. This can lead to the formation of speckle patterns on objects with rough surfaces, resulting in no light being received from some scanning points on the surface due to destructive interference.

[0023] To avoid such speckle patterns, the beam shifting unit can be configured to superimpose another movement with smaller amplitudes on the movement. This superimposed movement causes the light beams to move slightly and continuously laterally when they hit the object. While the light beams are directed to other points on the object to increase resolution, the superimposed movements have such a small amplitude that the light beams remain essentially directed at the same object point, but sweep over it in such a way that no neighboring object point in the scan grid is reached. These small movements, which follow predetermined functions or can be (quasi-)random, can ensure that the reflected laser light at least temporarily interferes constructively when it is received by the device.

[0024] With regard to the method, the object posed at the outset is achieved by a method for scanning measurement of the distance to an object, the method comprising the following steps: a) generating an optical signal having a varying frequency; b) distributing the optical signal to several optical output waveguides; c) coupling out the optical signals guided in the output waveguides as light beams into free space by means of free-space couplers arranged on a common substrate; d) deflecting the optical signals emerging from the optical output waveguides so that they are radiated simultaneously in different directions; e) detecting a superposition of the optical signal generated in step a) with an optical signal emitted in step d) and reflected by the object; f) determining the distance to the object from the superposition detected in step e);wherein the light beams emerging from the free-space couplers are temporarily offset together before being deflected in step d).

[0025] The advantages and preferred embodiments explained above with regard to the device apply accordingly to the method.

[0026] In one embodiment, the substrate with the free-space couplers arranged thereon can be moved. In particular, the substrate can be moved back and forth translationally along a translation direction that runs perpendicular to an exit direction of the light beams. In this case, the substrate can be set into an oscillating motion along the translation direction at a frequency between 20 Hz and 100 Hz.

[0027] In another embodiment, the light rays pass through a transparent plane plate that moves between at least two angular positions with respect to a rotation axis.

[0028] In step b), the optical signals from a switching matrix with several optical switches can be selectively distributed to the several optical output waveguides, whereby the optical switches of the switching matrix are synchronized with an offset of the light beams.

[0029] In another embodiment, another movement with smaller amplitudes is superimposed on the movement to avoid speckle patterns. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In the following, exemplary embodiments of the invention are explained in more detail with reference to the drawings. In these drawings: Fig. 1 is a schematic side view of a vehicle approaching an object detected by a measuring device according to the invention; Fig. 2 a plan view of the Fig. 1 measuring device shown; Fig. 3 shows the structure of the measuring device according to an embodiment in a schematic representation; Fig. 4 a graph in which the frequency of the emitted optical signals is plotted over time; Fig. 5 a switching matrix and the deflection optics of the Fig. 3 shown measuring device; Fig. 6a to 6c show an excerpt from the Fig. 3 shows the measuring device in different operating states according to a first embodiment in which a substrate is moved translationally with free-space couplers; Fig. 7a to 7c show an excerpt from the Fig. 3 shown measuring device in different operating states according to a second embodiment in which a plane plate is tilted; Fig. 8 a schematic and Fig. 5 shows a schematic representation of parts of the measuring device according to the second embodiment; Fig. 9 a plan view of the Fig. 1, in which the light beams make small movements to avoid speckle patterns; and Fig. 9 shows a graph in which the x-coordinate of the substrate is plotted against time. DESCRIPTION OF PREFERRED EMBODIMENTS 1. Application example

[0031] The Fig. Figure 1 shows a schematic side view of a vehicle 10 approaching an object 12 which is in the Fig. 1 is a tree. The vehicle 10 has at least one measuring device 14 that uses light beams L11, L21, L31, and L41 to scan the surroundings ahead of the vehicle 10 to obtain distance values. A three-dimensional image of the surroundings is reconstructed from the distance values. Furthermore, the measuring device 14 determines the relative speed to the object 12. This information is particularly important if the object 12 is another vehicle or an animal and is also moving.

[0032] The information about the surroundings ahead of the vehicle 10 determined by the measuring device 14 can be used, for example, to assist the driver of the vehicle 10 in controlling the vehicle by generating warning messages when a collision between the vehicle 10 and the object 12 is imminent. If the vehicle 10 is driving autonomously, the information about the surroundings ahead is required by the control algorithms that control the vehicle 10.

[0033] As in the Fig. 1, the measuring device 14 radiates in a vertical plane (in the Fig. 1 (this is the paper plane) the light rays L11 to L41 are directed in different directions, thereby scanning the surroundings in the vertical direction. At the same time, a scan also takes place in the horizontal direction, as is the case with the Fig. 2 shows a plan view of the measuring device 14. Four light beams L11, L12, L13, and L14 are shown, which are emitted in different directions in a horizontal plane.

[0034] For reasons of clarity, the Fig. 1 and Fig. 2 assumes that only four light beams Ln1 to Ln4 in each of four different planes, ie a total of 16 light beams, are generated by the scanning device 14. Preferably, the measuring device 14 emits many more light beams. For example, k·2 n Light rays, where n is a natural number between 7 and 13 and indicates how many rays are emitted in one of k planes, where k is a natural number between 1 and 16. 2. Measuring device

[0035] Fig. Figure 3 schematically shows the structure of the measuring device 14 according to an embodiment of the invention. The measuring device 14 is designed as a LiDAR system and includes an FMCW light source 16, which, during operation of the measuring device 14, emits measuring light with a varying frequency f chirp generated. As the Fig. 4, varies (“chirps”) the frequency f chirp periodically over time t between a lower frequency f l and a higher frequency f h .

[0036] Each measurement interval with a chirp duration T is divided into two halves of equal length T / 2. During the first interval, the frequency f chirp linear with a constant and positive upchirp rate r chirp , ie df chirp / dt = r chirp During the second interval, the frequency f chirp linear with a constant negative downchirp rate -r chirp , ie df chirp / dt = -r chirp. The frequency of the measuring light can thus be described by a periodic triangular function. However, other functional relationships can also be considered, such as sawtooth functions.

[0037] As from the Fig. As can be seen in Figure 3, the light source 16 is connected to a splitter 22, which splits the measurement light into reference light (local oscillator) and output light. In the illustrated embodiment, the output light is amplified in an optical amplifier 24 and then passes to an optical circulator 26, which guides the amplified measurement light to a deflection unit 28. The optical circulator 26 can, for example, comprise a polarization-sensitive beam splitter that interacts with other polarization-optical elements, as is known per se in the prior art. Instead of the circulator, a 2x2 coupler, for example, can also be used, although this leads to greater light losses.

[0038] The deflection unit 28 directs the output light onto the object 12 - in Fig. 3 is represented by a moving car - along different directions, as described above with reference to the Fig. 1 and Fig. 2. Typically, the optical signal emitted by the deflection unit 28 is at least partially diffusely reflected by the object 12. A small portion of the reflected signal returns to the measuring device 14, where it is coupled back into the deflection unit 28.

[0039] The optical circulator 26 directs the coupled light to a combiner 30, which superimposes the reference light, which was separated from the measurement light by the splitter 22, with the coupled light. Since the frequencies of the superimposed light components differ slightly from one another, a beat signal is generated, which is detected by a detector 32, preferably designed as a symmetrical photodetector. The electrical signals generated by the detector 32 are fed to a computing unit 34, which calculates the distance R to the object and the relative velocity v between the scanning device 14 and the object 12 from the analysis of beat frequencies.

[0040] The Fig. 5 shows parts of the deflection unit 28 in a simplified schematic representation. The deflection unit 28 comprises a switching matrix M in which a plurality of optical switches S11, S21, and S22 are arranged in a tree-like manner. With the aid of the optical switching matrix M, optical signals arriving at an input 36 of the switching matrix M can be successively distributed to a plurality of output waveguides 38. For reasons of clarity, the optical switching matrix M in the illustrated embodiment has only three optical switches, so that a total of four output waveguides 38 can be controlled. In real measuring devices 14, eight or more switching levels can be arranged one behind the other, so that, for example, 256 output waveguides 38 can be selectively connected to the input 36.

[0041] In other embodiments, the switching matrix M is located before the amplifier 24 or between the amplifier 24 and the circulator 26. Alternative embodiments for the integration of switching matrices into the measuring device 14 can be found in the European patent application with the file number EP 20176355.4 and DE 10 2020 110 142 A1.

[0042] The output waveguides 38 terminate in free-space couplers 40, which can couple optical signals carried in the output waveguides 38 into free space. Such couplers are known in the art and can be designed, for example, as grating couplers, which have a widening waveguide region followed by a grating structure. Alternatively, the free-space couplers 40 can be edge couplers, which have a higher coupling efficiency than grating couplers.

[0043] In the Fig. 5 shows that the divergent light beams emerging from the free-space couplers 40 are collimated by a deflection optic 44 and radiated in different directions. The farther a free-space coupler 40 is located from an optical axis 42 of the deflection optic, the greater the angle at which the collimated optical signals are radiated by the deflection optic 44.

[0044] In the illustrated embodiment, the deflection unit 28 also serves to receive the optical signals reflected from the object 12 and to couple them back into the output waveguides 38 via the free-space couplers 40. In other embodiments, the reflected signals can be received by separate free-space couplers 40 and fed to the detector 32 via separate waveguides. 3. Substrate movement

[0045] The Fig. Figure 6a shows a section of the deflection unit 28, also in a schematic representation. Visible is a substrate 46 carrying eight output waveguides 38, each of which terminates in a free-space coupler 40. The free-space couplers are arranged along a line. In the illustrated embodiment, the deflection optics 44 comprises two aspherical lenses L1 and L2.

[0046] A translation actuator 54, which can be designed, for example, as a voice coil drive, engages laterally on the substrate 46. The translation actuator 54 interacts with one or more guides 56 arranged on the opposite side of the substrate 46. The guides 56 ensure that the substrate 46 can only execute lateral translation movements, i.e., directed perpendicular to the optical axis 42. The back-and-forth movements caused by the translation actuator 54 are in the Fig. 6a indicated by a double arrow 58.

[0047] In the Fig. In the switching state of the switching matrix M shown in Figure 6a, light emerges from two free-space couplers 40, which is indicated by two initially diverging light beams R1, R2. As already mentioned above, the deflection optics 44 collimates the light beams R1, R2 so that they exit the deflection optics 44 parallel but inclined with respect to the optical axis 42.

[0048] The Fig. 6b shows the Fig. 6a shows the arrangement in the same switching state, but after a lateral displacement of the substrate 46 by an amount Δx, which was caused by the translation actuator 54. The displacement Δx corresponds to half the pitch between the free-space couplers 40. As a result of this movement, the light beams R1', R2' emerging from the free-space couplers are displaced parallel. Fig. In Figure 6a, the light beams R1, R2 emerging from the free-space couplers before the lateral offset are indicated by dotted lines.

[0049] The offset light rays exit the deflection optics 44 at a different angle, as shown in the Fig. 6b on the right. For light beam R1', the offset means that it exits closer to the optical axis 42, so that the exit angle from the deflection optics 44 becomes smaller. For light beam R2', the situation is reversed (not shown), i.e., the exit angle becomes larger. The lateral offset of the substrate 46 thus creates two additional exit angles that cannot be achieved using the switching matrix M alone.

[0050] The Fig. 6c shows the Fig. 6b, after the substrate has been returned to its position in the Fig. 6a. This corresponds to a movement of the distance -Δx. However, the switching matrix M is now in the next switching state. As can be seen from a comparison of the Fig. 6a and Fig. As can be seen in Figure 6c, in the illustrated embodiment, the switching matrix M is controlled such that the output waveguides 38 are successively switched from one side to the opposite side, with every fourth output waveguide 38 always carrying light. The now emerging light beams R1" and R2" again have different exit angles than the light beams R1, R2, R1', and R2'.

[0051] Through the Fig. 6b, which is effected solely by moving the substrate 46, a virtual additional switching state is created in which the beams R1', R2' are apparently emitted by free-space couplers 40', which are arranged between the beams shown in the Fig. 6a and Fig. 6c. In other words, the movement of the substrate 46 perpendicular to the optical axis 42 results in the apparent availability of twice as many free-space couplers (free-space coupler 40 and free-space coupler 40') as actually present. In this way, the resolution of the measuring device 14 is doubled without having to increase the number of output waveguides 38 and free-space couplers 40. The doubling of the resolution is achieved solely by the slight offset by the distance Δx.

[0052] In the illustrated embodiment, the substrate 46 is moved back and forth intermittently, with the switching state of the switching matrix M being changed with every second movement. However, other schemes are also conceivable, since the order in which the light beams are directed onto the object 12 is generally not important. The only decisive factor is whether all points on the object 12 lying within the scanning grid are scanned within one scan cycle.

[0053] It is therefore also possible, for example, to first switch the free-space couplers 40 one after the other using the switching matrix M and only then to displace the substrate 46 using the translation actuator 54. After this displacement, all free-space couplers 40 are switched through again, but now the Fig. 6b. Such a switching scheme requires fewer movements of the substrate 46 and is therefore advantageous in many cases.

[0054] The translation actuator 54 can also cause the substrate 46 to oscillate harmonically, which is synchronized in the desired manner (i.e., depending on the selected switching scheme) with the optical switches of the switching matrix M. For this purpose, the translation actuator 54 and the switching matrix M are preferably connected to a common control device 59. 4. Tilted plane plate

[0055] The Fig. 7a, Fig. 7b and Fig. 7c show in the Fig. 6a to 6c show a second embodiment in which a parallel offset of the light emitters R1, R2 emerging from the free-space couplers 40 is not caused by a movement of the substrate 46, but by tilting a plane plate 60 that is transparent to the light beams R1, R2 and is arranged between the substrate 46 and the deflection optics 44. If the deflection optics 44 has an intermediate image plane, the plane plate 60 can also be arranged there.

[0056] The plane plate 60 can be tilted about a rotation axis 63 by means of a rotary actuator 62, which is only indicated schematically and which runs at an angle of 90° to an exit direction of the light beams R1, R2 and thus parallel to the optical axis 42.

[0057] The Fig. Figure 7b illustrates how, by tilting the plane plate 60 by a small angle, the beams R1', R2' are offset parallel and thus exit the deflection optics 44 at a different angle. Dotted lines indicate the beam path of the beams R1, R2 for the non-tilted state according to Fig. 7a is shown for comparison. The dot-dash beam path clearly shows that the beams R1', R2' emerging from the tilted plane plate 60 appear to originate from a virtual free-space coupler 40' located between two adjacent free-space couplers 40.

[0058] By tilting the plane plate 60, essentially the same effect is achieved as by the lateral offset of the substrate 46 in the first embodiment. Accordingly, different circuit diagrams are also possible here. In the embodiment according to the Fig. 7a to 7c were based on the same circuit diagram as for the Fig. 6a to 6c. The switching state of the switching matrix M thus changes after every second tilting movement of the plane plate 60.

[0059] The interaction of the switching matrix M and the plane plate 60 is shown again in the schematic Fig. 8. The possible light paths of the emerging light rays R1 to R4 are indicated by solid lines when the plane plate 60 is not tilted. If the plane plate 60 is tilted, the emerging light rays are offset laterally. The tilt angle of the plane plate 60 is Fig. 8, the offset is selected such that the offset is half the lateral spacing of the light beams R1 to R4. In this way, the angular resolution behind the deflection optics 44 is doubled, achieving a uniform angular spectrum. 5. Avoiding speckle patterns

[0060] Due to the coherence of the FMCW light source 16, speckle patterns may form on objects with rough surfaces. Light cannot then be received from some scanning points on the surface due to destructive interference.

[0061] Such speckle patterns can be avoided if the emitted light beams are not directed statically at the desired scanning point during the measurement, but rather perform small movements so that the illuminated light spots move over the respective scanning point on the surface. Fig. 9 shows this in a Fig. 2. The light rays L11 to L14 are not stationary, but rather move across the measuring points of the desired measuring point grid, as indicated by dashed lines.

[0062] Such slightly moving light beams L11 to L14 can be generated if a further movement with a smaller amplitude is superimposed on the above-described movement of the substrate 46 or the plane plate 60. This superimposed movement results in the light beams L11 to L14 moving slightly and continuously laterally upon impinging on the object 12, as is the case with the Fig. 9 illustrated.

[0063] In the graph of the Fig. 10 is an example of the x-coordinate of the substrate 46, which is determined by the translation actuator 54 in the Fig. 6a to 6c, is plotted as a function of time t. It can be seen that the x-coordinate changes intermittently between the values ​​x1 and x2, with the offset Δx being given by x2 - x1. This movement is superimposed with another movement with a significantly smaller maximum amplitude Δx', which serves to avoid speckle patterns. This movement can follow a predetermined function or - as in the Fig. 10 - be (pseudo-)random. Preferably, the relationship |Δx'|≤ 1 / 100 |Δx|, preferably |Δx'| ≤ 1 / 1000 |Δx|, applies to the amplitude Δx' of this superimposed movement.

Claims

[1] Device (14) for scanning measurement of the distance to an object (12), with a light source (16) arranged to generate an optical signal with a varying frequency, a distribution matrix (M) which is designed to distribute the optical signal simultaneously to a plurality of optical output waveguides (38), a plurality of free-space couplers (40) arranged on a common substrate (46) and configured to couple the optical signals guided in the output waveguides (38) into free space as light beams (L11 to L14; R1 to R4), a deflection optic (44) which is designed to deflect the optical signals emerging from the optical output waveguides (38) so that they are emitted simultaneously in different directions from the device (14), at least one detector (32) which is designed to detect a superposition of the optical signal generated by the light source (16) with an optical signal which has been reflected by the object (12), an evaluation device (34) which is designed to determine a distance to the object (12) from the superposition detected by the at least one detector (32), characterized by , that the device comprises a beam displacement unit which comprises an actuator (54; 62) for generating a movement and is designed to temporarily displace the light beams (R1 to R4) emerging from the free-space couplers together before they impinge on the deflection optics (44). [2] Device according to claim 1, characterized by that the actuator is a translation actuator (54) which is designed to move the substrate (46) with the free-space couplers (40) arranged thereon. [3] Device according to claim 2, characterized by that the translation actuator (54) is configured to move the substrate (46) translationally back and forth along a translation direction (x) which is perpendicular to an exit direction (z) of the light rays. [4] Device according to claim 2 or 3, characterized by that the translation actuator (54) is configured to set the substrate (46) into an oscillating movement along the translation direction (x) at a frequency between 20 Hz and 100 Hz. [5] Device according to one of the preceding claims, characterized by that the translation actuator (48) has a voice coil drive (520, 54) which engages the substrate (46). [6] Device according to one of the preceding claims, characterized byin that the beam displacement unit has a plane plate (60) which is transparent to the light beams and in that the actuator is a rotary actuator (62) which is designed to move the plane plate (60) between at least two angular positions with respect to a rotation axis (63) which runs at an angle to an exit direction (z) of the light beams (R1, R2). [7] Device according to one of the preceding claims, characterized by that the distribution matrix is ​​a switching matrix (M) with a plurality of optical switches (S111, S21, S22) and is configured to selectively distribute the optical signal to the plurality of optical output waveguides (38). [8] Device according to claim 7, characterized by a control device (59) which is designed to synchronize the optical switches (S11, S21, S22) of the switching matrix (M) with an offset of the light beams (R1, R2) caused by the beam shifting unit. [9] Device according to one of the preceding claims, characterized by that the free-space couplers (40) are arranged in one plane. [10] Device according to one of the preceding claims, characterized by that the beam shifting unit is configured to superimpose a further movement with smaller amplitudes (Δx') on the movement in order to avoid speckle patterns. [11] Method (14) for scanning measurement of the distance to an object (12), the method comprising the following steps: a) generating an optical signal having a varying frequency; b) distributing the optical signal to a plurality of optical output waveguides (38); c) coupling out the optical signals guided in the output waveguides (38) as light beams into free space by means of free space couplers (40) arranged on a common substrate (46); d) deflecting the optical signals emerging from the optical output waveguides (38) so that they are radiated simultaneously in different directions; e) detecting a superposition of the optical signal generated in step a) with an optical signal emitted in step d) and reflected by the object (12); f) determining the distance to the object (12) from the superposition detected in step e); wherein the method characterized by is that the light beams emerging from the free-space couplers are temporarily offset together before being deflected in step d). [12] Method according to claim 11, characterized by that the substrate (46) with the free-space couplers (40) arranged thereon is moved. [13] Method according to one of claims 11 or 12, characterized bythat the light rays pass through a transparent plane plate (60) which moves between at least two angular positions with respect to an axis of rotation (59) which runs at an angle to an exit direction of the light rays (R1, R2). [14] Method according to one of claims 11 to 13, characterized by that the movement is superimposed with another movement with smaller amplitudes (Δx') to avoid speckle patterns.

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