OPTOELECTRONIC SENSOR FOR DISTANCE MEASUREMENT

Description

[0001] The present invention relates to an optoelectronic sensor for distance measurement. The sensor comprises a light source configured to convert a transmitted signal into transmitted light and to emit the transmitted light into an environment. The sensor further comprises a light receiver which receives transmitted light reflected from objects in the environment as received light, wherein the light receiver has several, in particular separate, receiving elements for distance measurement.

[0002] Optoelectronic sensors of this type for distance measurement are generally known, and can be used, for example, with the indirect time-of-flight (iTOF) method to determine distances to objects in the environment. From the distances to various objects or to different points on the object, the optoelectronic sensor can then, for example, generate a depth image.

[0003] Such optoelectronic sensors can encounter difficulties in distance measurement when multipath reception occurs, meaning that light from different objects and / or at different distances reaches the same receiving element. This can lead to distance measurement errors, artifacts, and / or ghost images. Furthermore, the sensor's dynamic range can be limited, which can negatively affect depth resolution, especially with high-contrast or very low-contrast objects.

[0004] German patent application DE 10 2020 107450 A1 discloses an optoelectronic sensor according to the preamble of claim 1 and a method for distance measurement using an optoelectronic sensor according to the preamble of claim 13. German patent applications WO 20201021306 A1 and US 20201326563 A1 disclose related sensors and methods.

[0005] It is therefore an object underlying the invention to further develop an optoelectronic sensor of the type mentioned above in such a way that it provides improved measurement results, especially for signals from multipath reception.

[0006] This problem is solved by an optoelectronic sensor according to claim 1.

[0007] The optoelectronic sensor according to the invention is characterized in that the light receiver comprises at least one polarization element which is configured to supply received light with a first polarization to one (first) of the receiving elements and received light with a second polarization, which is different from the first polarization, to another (second) of the receiving elements.

[0008] In other words, different polarizations can be supplied to different receiving elements. The invention is based on the understanding that, particularly in multipath reception, the received light emitted by different objects is usually also polarized differently. By using the polarizing element, a single receiving element can therefore only receive light originating from a single object, whereas received light originating from a different object, which would conventionally have struck the same receiving element, is directed by the polarizing element to a different receiving element.

[0009] For example, if an optoelectronic sensor is used to observe a container of plastic bottles covered with a plastic film, the transmitted light can be reflected back to the optoelectronic sensor from both the plastic film and another wall of a plastic bottle located inside the container. Conventionally, the received light from the plastic film and the received light from the wall of the plastic bottle could then overlap in a receiving element, leading to ambiguous measurement results. However, if it is assumed that the received light from the plastic film is polarized differently than the received light from the plastic bottle, then, according to the invention, the received light from the plastic film is directed to a different receiving element than the received light from the plastic bottle. In this way, the ambiguity of the signal can be resolved.Furthermore, there is the advantage that the two different receiving elements can be evaluated separately, which makes it possible to determine both the distance to the plastic film and to the wall of the plastic bottle.

[0010] In particular, the receiving elements serve to determine the time of flight of light to the object. Preferably, the receiving elements detect a phase difference between the transmitted signal and / or the transmitted light on the one hand and the received light (and optionally a received signal generated from the received light) on the other. Based on the phase difference, the time of flight of light and thus the distance to the object can then be determined. As explained above, distance measurement using phase difference is also referred to as iTOF (intermittent time of flight).

[0011] The receiving elements can each be designed separately from each other, i.e., they can be separate sensors. In particular, the receiving elements can be part of an image sensor, so that a depth image can be determined using the optoelectronic sensor.

[0012] The polarization mentioned herein can refer in particular to a polarization direction (e.g., vertical). However, other polarizations are also possible, for example, circular polarization.

[0013] If the polarizing element directs the first polarization to one (first) of the receiving elements and the second polarization to another, this means that the correspondingly polarized received light is predominantly (for example, more than 50%, more than 80%, or more than 90%) or almost exclusively directed to the corresponding receiving elements. It is understood that a certain amount of stray light cannot be ruled out when receiving elements are arranged side by side.

[0014] Further developments of the invention are specified in the description, the drawings and the dependent claims.

[0015] According to a first embodiment, several of the receiving elements form a group, with at least one of the groups being assigned a separate polarizing element that supplies received light to the receiving elements of the group. For example, the groups can consist of, say, two, three, four, or even more receiving elements. The numbers mentioned can apply to at least one of the groups, preferably to several or all of the groups.

[0016] The polarizing element assigned to a group can then direct differently polarized received light to different receiving elements within that group. For example, received light with a linear polarization of 0° can be directed to the first receiving element in the group, whereas received light with a polarization of 45° is directed to the second receiving element. Received light with polarization directions of 90° and 135° can accordingly be directed to a third and fourth receiving element in the group, respectively. For example, all receiving elements of the light receiver can be assigned to such groups, with each group having a corresponding polarizing element. The assigned polarizing element can, for example, be positioned directly above the receiving elements, so that received light first passes through the polarizing element and then strikes the receiving elements.

[0017] Received light striking a polarizing element is preferably directed predominantly, i.e., at least to, for example, 50%, 80%, or 90%, to the receiving elements of the associated group. The surface of the polarizing element, in particular the area upon which received light can strike, can – in a top view – have the same shape and / or size as the group of receiving elements.

[0018] According to a further embodiment, the at least one polarizing element comprises at least two or three, preferably four, polarizing filters, wherein the different polarizing filters are each transparent to received light of different polarizations, wherein preferably each polarizing filter is assigned to only one receiving element and essentially directs received light only to the assigned receiving element. In particular, the plurality and / or all polarizing elements can also comprise the aforementioned arrangement of polarizing filters. If the polarizing element comprises, for example, two polarizing filters, the polarization direction of the two polarizing filters can differ by 90°. With four filters, the polarization direction can differ by 45° each (in the case of linear polarization). Other polarizations, such as circular polarization, are also possible for the polarizing filters.

[0019] The surface area of ​​each filter within a polarizing element can be the same size and / or shape as the other filters of the same polarizing element. For example, the polarizing filters can be square, so that with four filters, the shape of the polarizing element is again square. It follows that only about a quarter (or a quarter of the surface area) of received light of a given polarization passes through the polarizing filter. With four filters and four receiving elements, for example, the first receiving element can receive horizontally polarized light, the second receiving element can receive light polarized at 45°, the third receiving element can receive vertically polarized light, and the fourth receiving element can receive light polarized at 135°. The term "essentially" used above means that, for example, more than 50%, 80%, or 90% of the received light passes through the filter.whose luminous flux is supplied to the respective assigned receiving element.

[0020] The at least one polarization element comprises a polarization router, which directs received light of different polarizations to different receiving elements. The polarization router can be used in the optoelectronic sensor in combination with polarization filters. Preferably, however, the optoelectronic sensor uses either only polarization filters or only polarization routers. Polarization routers are generally known to those skilled in the art. In particular, the polarization router can be configured to deflect a first polarization in a first direction and a second, different polarization in a second direction, which differs from the first direction. This allows the polarization router to direct different polarizations to different receiving elements.In particular, the polarization router can also be configured to apply a predetermined polarization to essentially only one of the receiving elements (where, as above, this again refers to at least 50%, 80%, or 90% of the received light). The advantage of the polarization router is that virtually all the received light striking it is passed through it. In contrast to polarization filters, there is therefore no light loss.

[0021] According to a further advantageous embodiment, at least one of the receiving elements comprises a lock-in pixel, in particular a 4-tap lock-in pixel. Preferably, the majority of the receiving elements or all of the receiving elements can comprise such a lock-in pixel. The lock-in pixels can also be referred to as iTOF pixels. Lock-in pixels are generally known to those skilled in the art, and the lock-in pixels can in particular comprise various bins or taps in which electrical charges generated by received light are collected. These charges are generated by received light at different times during reception. The bins or taps can also be referred to as reservoirs into which electronically modulated lock-in pixels, controlled by the transmitted signal, conduct electrons generated by the photoelectric effect.

[0022] The lock-in pixel(s) can be controlled by the transmitted signal, i.e., driven by the modulation frequency of the transmitted signal, to direct received light to the various bins or taps. Based on the different signals of the various bins or taps, the received signal can be sampled, allowing the phase and thus the phase difference to the transmitted signal to be determined. This evaluation of the lock-in pixels is therefore an electronic evaluation of the phase and thus an electronic determination of the distance to the object.

[0023] At least one of the receiving elements comprises a routing layer and several receiving pixels. The routing layer is configured to sequentially direct incoming light to different receiving pixels, generating multiple samples in each pixel. Based on these samples, the phase of the receiving light, and thus the phase difference between the transmitted and received light, is determined. In particular, the majority or all of the receiving elements can also comprise a corresponding routing layer and multiple receiving pixels. The use of a routing layer together with the receiving pixels can be used, in particular, as an alternative to lock-in pixels. The routing layer can be located upstream of the receiving pixels in the light path of the received light, but can also be positioned after the received light has passed through the polarizing element.In particular, two, three, or four (or even higher numbers) receiving pixels can be provided per receiving element. Received light arriving at the routing layer is then forwarded sequentially and, in particular, cyclically, for example, in a round-robin fashion, to the receiving pixels. In this way, multiple samples are generated in the receiving pixels, from which the phase of the received light, and thus the phase difference between transmitted and received light, can be determined.

[0024] According to a further embodiment, the routing layer is configured to supply the received light to the various receiving pixels depending on a modulation of the transmitted light and / or the transmitted signal. In particular, the routing layer can be controlled such that, during the duration of a modulation period of the transmitted signal, it supplies received light to each receiving pixel assigned to the respective routing layer only once. The duration for which the routing layer supplies received light to the respective receiving pixel can be identical in each case. In this way, for example, the first receiving pixel is always supplied with the first part of the received light during a modulation period. Thus, the received light can be accumulated in the respective receiving pixel over a multitude of modulation periods in order to obtain the most accurate possible result for the phase of the received light.A particular advantage is that the routing layer can operate at very high frequencies, allowing even phase differences for very high modulation frequencies of the transmitted signal to be resolved. Specifically, the modulation frequency of the transmitted signal is higher than 50 MHz, 100 MHz, 200 MHz, 500 MHz, 1 GHz, or 10 GHz. In these frequency ranges, the modulation contrast can decrease, especially with lock-in pixels, leading to reduced accuracy in distance measurement.

[0025] In particular, the received light can be within a modulation period, i.e., within a time period of 1 Modulationsfrequenz The light is supplied alternately and / or sequentially to the respective receiving pixels of each receiving element, such that within a modulation period each receiving pixel of the receiving elements can receive at least a portion of the received light and convert it into different received signals. The modulation frequency is preferably the modulation frequency of the transmitted light.

[0026] The very fast optical routing, or active steering of the received light by the routing layer, enables the processing of modulation frequencies of, for example, 1 GHz, 5 GHz, 10 GHz and / or more than 10 GHz, compared to lock-in pixels, since the modulation frequency no longer depends on the transport speed of the charge carriers in the semiconductor. Due to the high modulation frequencies, improved depth resolution can be achieved.

[0027] According to another embodiment, the receiving pixels are part of a CMOS image sensor, particularly a conventional one, such as those used in photographic cameras. Specifically, the receiving pixels are not lock-in pixels and / or do not comprise multiple bins or taps. Using such a CMOS image sensor reduces the manufacturing costs of the optoelectronic sensor. Furthermore, such CMOS image sensors are available with high resolution and high sensitivity. The receiving pixels can therefore, for example, comprise a 4T CMOS sensor. However, the use of a CCD sensor or another suitable sensor is also possible. The complex structure of lock-in pixels is avoided by using such image sensors.

[0028] The following section explains further details of the routing layer and receive pixels: In particular, the routing layer comprises a plurality of partitions, each belonging to a receive element, with each partition directing the received light, at least substantially, only to the receive pixels of the receive element belonging to that partition. A partition is, in particular, a delimited and / or independent part of the routing layer. In plan view, the partition can, for example, be square or rectangular. The size of the partition can be at least substantially the size of the receive pixels belonging to it. A partition can be an independent functional unit that can execute the functions of the routing layer independently of the other partitions of the routing layer.A partition can provide the function of focusing the received light and / or directing it to the receiving pixels of the receiving element. Due to its small size, the routing layer partition allows for rapid switching between individual receiving pixels when receiving light. This enables the processing of particularly high modulation frequencies. Furthermore, in the event of a failure and / or malfunction of one partition, the operation of the remaining functional partitions of the routing layer can continue uninterrupted. The number of routing layer partitions is preferably dependent on, and in particular equal to, the number of receiving elements.

[0029] Optionally, the routing layer comprises a first and a second layer, the second layer being configured to deliver the received light sequentially and / or alternately to the receiving pixels of the receiving element. The first and second layers of the routing layer can have different functions, with the first layer receiving the received light and preferably directing it in a focused beam to the second layer, which then delivers the received light sequentially to the receiving pixels of the receiving element, e.g., in a predefined order. Furthermore, the first and second layers of the routing layer can be implemented as a single assembly. For example, the two layers are manufactured as a single assembly. Alternatively, it is also possible for the routing layer to comprise only one layer, which performs all the functions of the first and second layers.

[0030] In particular, the first and / or second layer comprises a plurality of lenses. For example, each partition of the routing layer comprises a lens, and in particular, only one lens. The lenses can, for example, focus and / or selectively deflect the received light. In particular, the lenses can have a concave, convex, and / or other suitable shape, with the lenses preferably being concave.

[0031] Preferably, the first layer is configured to direct the received light onto the second layer, the second layer being electrically controllable to supply the received light sequentially and / or alternately to the receiving pixels of the receiving element. The first layer of the routing layer can direct and / or shape the received light, preferably by means of the aforementioned lenses, and supply the received light to the second layer. The second layer can be electrically controlled, e.g., by means of an electrical control unit (e.g., by the evaluation unit mentioned herein). The evaluation unit can be configured to define a deflection direction of the received light and, in particular, to deflect the received light alternately in two or four different directions.Furthermore, the electrical control can be designed, in particular in the case of more than two receiving pixels per receiving element, to define a sequence in which the receiving pixels of the receiving elements are illuminated with the receiving light.

[0032] The second layer can deflect the received light to individual receiving pixels, for example, using micromirrors and / or prisms, in which the refractive index, and thus the direction of propagation of the received light, is electro-optically altered, and / or other suitable means. In particular, the refractive index can be changed and / or adjusted using a variety of electro-optic effects. For example, phase-change materials, which switch between crystalline and amorphous states, transparent conductive oxides (TCOs), which change the plasma frequency and thus the refractive index by applying a voltage and / or altering the charge carrier density, and / or organic electro-optical materials such as DAST can be used. In general, a wide variety of materials, approaches, and electro-optical effects are known in the field of photonically integrated optics that can be used for the rapid switching of light.The second layer can include the aforementioned means.

[0033] The second layer can further be configured to deflect the received light depending on its polarization. In particular, the second layer can comprise polarization-dependent lenses, metasurfaces, and / or polarization filters. Metasurfaces that control the so-called Pancharatnam-Berry phase and thus enable polarization-dependent beam shaping and deflection of a light beam are known from the literature (e.g., "Multifunctional Metamirror: Polarization Splitting and Focusing", ACS Photonics 2018 5 (5), DOI: 10.1021 / acsphotonics.7b01091 or "Reflective metalens with sub-diffraction-limited and multifunctional focusing", Sci Rep 7, 12632 (2017). DOI: 10.1038 / s41598-017-13004-z). In the first layer, for example, a temporary change in the polarization of the received light can be made in each modulation period.Due to the polarization-dependent deflection of the received light in the second layer, the received light can thus be supplied to different receiving pixels one after the other and / or alternately.

[0034] In particular, the first layer is configured to selectively change the polarization of the received light (i.e., for example, in response to a control signal from the evaluation unit), and the second layer is configured to direct the received light to different receiving pixels of the receiving elements, depending on the polarization of the received light. For example, the emitted transmit light, and thus the received light reflected back by the object in the environment, can have a specific polarization. The first layer of the routing layer can change the polarization of the received light arriving at the first layer. For example, the first layer can convert left-circularly polarized received light to right-circularly polarized received light, or vice versa, for predetermined durations. To change the polarization, the first layer can include an optically active layer and / or any other suitable means.

[0035] In principle, the second layer can be designed to deflect the received light depending on its polarization, amplitude, and / or wavelength. The first layer can then make a corresponding change to the received light.

[0036] The supply of received light to the individual receiving pixels of the receiving elements can thus be adjusted by means of the electrical control and, in particular, adapted to the properties of the received and / or transmitted light. For example, the duration of the supply of received light to a receiving pixel and / or the sequence of the supply of received light can be adapted to the modulation frequency of the transmitted and / or received light, to the number of receiving pixels per receiving element, and / or to the type of receiving pixels.

[0037] Preferably, the routing layer, the first layer, or the second layer may not contain any moving parts. The direction of the received light is then achieved, for example, solely through electro-optical effects and the like.

[0038] According to a further embodiment, the receiving elements are arranged in a flat surface and, in particular, form an image sensor, wherein several polarization elements are arranged, preferably directly, on the flat surface and / or attached and / or fastened. By arranging them as an image sensor, for example, by arranging the receiving elements in uniform rows and columns, a depth image can be generated with the optoelectronic sensor. For example, the receiving elements can be grouped as described above, with a polarization element positioned in front of each group of receiving elements such that the received light first passes through the polarization element and then strikes the receiving elements. In particular, the polarization elements can be attached directly to the receiving elements or arranged in the receiving path in another way upstream of the receiving elements.A receiving optic can be arranged upstream of the polarization elements in the receiving path, which, for example, enables focusing on different distance ranges.

[0039] According to another embodiment, the optoelectronic sensor is configured to generate the transmitted signal as a modulated signal and to modulate the transmitted light (with the frequency of the modulated signal). As already indicated above, the transmitted light can, for example, be amplitude-modulated, which then also results in the received light being amplitude-modulated. The phase of the received light, and thus the phase difference between the transmitted light / signal and the received light / signal, can then be determined by the sampling points, which are generated, for example, by the lock-in pixels or the routing layer with the receiving pixels.

[0040] According to another embodiment, the light source is designed to emit polarized light and / or to change or adjust the polarization of the emitted light. Changing the polarization of the emitted light can be achieved, for example, by using different polarization filters placed in front of the light source. In particular, the polarization filters can be changed and / or rotated to alter the polarization of the emitted light. The polarization can also be modulated, resulting in a time-varying modulation. The advantage of this is that different polarizations can be applied to different areas of an object at different times, so that the ideal polarization for each area can be captured in the final depth image.

[0041] Alternatively or in addition to polarization filters placed in front of the light source, a light source that emits directly polarized light can also be used. For example, the light source can include an edge-emitting laser diode and / or a vertical-cavity surface-emitting laser diode (VCSEL). Variable polarization also allows the emitted light to be adapted to different applications.

[0042] According to a further embodiment, the optoelectronic sensor comprises an evaluation unit to which signals from the receiving elements can be supplied and which is configured, in particular for at least two receiving elements separately, to determine and / or output distance information and / or polarization information from the signals. In particular, the evaluation unit can be electrically coupled to the receiving elements, for example by means of a data connection, in order to receive the signals from the receiving elements. From the signals, the evaluation unit can then determine distance information and / or polarization information. The determined distance and / or polarization information can subsequently be output. Preferably, the determination of the distance information and / or polarization information is carried out separately for at least two of the receiving elements, more preferably for a plurality of the receiving elements or all receiving elements.For each receiving element, a separate distance value can be determined. Furthermore, the polarization with which the received light struck each element can be determined. The polarization of the incident light can also be known in advance (due to the polarizing element used). A depth image can then be generated from the various distance information for different receiving elements, as will be explained in more detail below.

[0043] According to a further embodiment, the evaluation unit is configured to generate a depth image from at least some of the signals from the receiving elements. Preferably, the evaluation unit is configured to select a receiving element from a given group of receiving elements for at least some part of the depth image and to use only the signals from the selected receiving elements for the depth image. By selecting (only) one receiving element from a given group of receiving elements, a selection can be made, for example, based on a specific polarization. Thus, the depth image can then be generated, for example, based only on horizontal or only on vertical polarization. Alternatively or additionally, it is possible to select which polarization should be included in the depth image for at least some or even all groups of receiving elements.For example, image areas can be selected in which a first polarization provides better depth values, while a second, different polarization is used in a second image area.

[0044] According to a further embodiment, the evaluation unit is configured to select the receiving elements based on the signal strength, in particular the received light, of the respective receiving element. In this way, signals / receiving elements that are too strong or too weak (i.e., overdriven or underdriven) can be excluded. Instead, a different receiving element from the group can be selected that is neither overdriven nor underdriven. This allows for the generation of a depth image with a better dynamic range.

[0045] In particular, when creating the depth image, one receiving element can be selected from each group of receiving elements, with the signals of the selected receiving element then being entered into the depth image as a single pixel.

[0046] A further object of the invention is a method for distance measurement using an optoelectronic sensor, wherein a light source converts a transmission signal into transmitted light and emits the transmitted light into an environment, and transmitted light reflected back from objects in the environment is received as received light by a light receiver by means of several, in particular separate, receiving elements. A polarization element directs received light with a first polarization to one of the receiving elements and received light with a second polarization, which differs from the first polarization, to another of the receiving elements, wherein the at least one polarization element comprises a polarization router, which directs received light of different polarizations to different receiving elements.The method according to the invention is characterized in that at least one of the receiving elements comprises a routing layer and several receiving pixels, wherein the routing layer sequentially directs the receiving light incident on the routing layer to different receiving pixels, so that several sample values ​​are generated in the receiving pixels. Based on the sample values, the phase of the receiving light and thus the phase difference between the transmitted light and the received light is determined.

[0047] The above statements regarding the optoelectronic sensor apply accordingly to the method according to the invention, particularly with regard to advantages and preferred embodiments.

[0048] It is understood that all features described herein can be combined with each other, unless explicitly stated otherwise.

[0049] The invention is described below by way of example only, with reference to the drawings. The drawings show: Figure 1 schematically an optoelectronic sensor which emits transmitted light to an object and receives received light from the object; Figure 2 schematically a light receiver of the optoelectronic sensor according to an embodiment not according to the invention; Figure 3 a polarizing element designed as a polarizing filter; Figure 4 a polarization element designed as a polarization router; Figure 5 schematically the light receiver according to an embodiment of the invention, in which the receiving element has a routing layer.

[0050] Fig. 1Figure 10 shows an optoelectronic sensor which emits modulated transmitted light 12 onto an object 14. The object 14 re-emits the transmitted light 12 as received light 16, whereby the received light 16 has a different polarization direction depending on the point of impact of the transmitted light 12 on the object 14.

[0051] In the optoelectronic sensor 10, the transmitting light 12 is generated from a transmitting signal 20 by means of a light transmitter 18 (i.e., a light source). The incoming received light 16 is detected by a light receiver 22, which generates a received signal 24 from the received light 16.

[0052] The transmit signal 20 is generated by an evaluation unit 26, which also receives the received signal 24 and generates a depth image from it.

[0053] In Fig. 2A non-inventive embodiment of the light receiver 22 is shown in more detail. The light receiver 22 comprises a receiving optic 28, shown here in the form of a microlens array. Several polarization elements 30 are arranged below the receiving optic 28. In the exemplary illustration of Fig. 2 Each polarization element 30 comprises four different polarization filters 32, which are also in Fig. 3 are shown.

[0054] Each of the individual polarizing filters 32 is arranged on a square area, so that a single polarizing element 30 again occupies a square area. The four polarizing filters 32 of a polarizing element 30 each have a polarization direction that differs by 45°.

[0055] Below the polarization elements 30 are receiver elements 34. Each polarization element 30 (with four different polarization filters 32 arranged in a square) is assigned four receiver elements 34, one of each individual polarization filter 32. The four receiver elements 34 assigned to a polarization element 30 form a group. The receiver elements 34 can be arranged in the Fig. 2 The example shown is designed as a lock-in pixel.

[0056] The received light 16 reaching the light receiver 22 first passes through the receiving optics 28 and is directed by the receiving optics 28 onto the polarizing elements 30. The individual polarizing filters 32 of the polarizing elements 30 each allow only received light 16 of a specific polarization to pass through and strike the receiving element 34 located below the respective polarizing filter 32. A received signal 24 can then be generated in the receiving element 34, which enables the evaluation unit 26 to determine a phase shift relative to the modulated transmitted light 12, resulting in a depth value for each receiving element 34.

[0057] As an alternative to the one in Fig. 3 The illustrated embodiment of the polarization element 30 with polarization filters 32 shows the Fig. 4 a polarization element 30, which is configured as a polarization router 36. In this case, Fig. 4to recognize that received light 16 incident on the polarization router 36 is deflected in different spatial directions from the polarization router 36 depending on its polarization.

[0058] In Fig. 5 An embodiment of the light receiver 22 according to the invention is shown. According to the embodiment of Fig. 5 The light receiver 22 also comprises a receiving optic 28 in the form of a single lens and polarization elements 30 in the form of polarization routers 36. Depending on the polarization of the received light 16, the polarization routers 36 direct the received light to different receiving elements 34, from which in Fig. 5 six are shown. Each receiving element 34 according to the embodiment of Fig. 5 It comprises a routing layer 38 which cyclically and repeatedly projects the received light 16 onto four receiving pixels in the form of CMOS image sensors 40. Of the four CMOS image sensors 40, in Fig. 4 Only two are shown per receiver element 34.

[0059] The routing layer 38 is controlled by the evaluation unit 26 to cyclically supply the received light 16 depending on the modulation of the transmitted light 12. The evaluation unit 26 then reads the CMOS image sensors 40 to obtain four sampling points from which the phase of the received light 16 can be reconstructed. From this, the phase difference to the transmitted signal 20 or to the transmitted light 12, and thus the distance to the object 14 for each receiving element 34, can be determined.

[0060] From the distances thus obtained, the evaluation unit 26 can generate a depth image which evaluates the same polarization of the received light 16 for all image points or which uses different polarizations of the received light 16 for different areas. Reference symbol list

[0061] 10 electronic sensor 12 transmitting light 14 object 16 receiving light 18 light transmitter 20 transmit signal 22 light receiver 24 receiving signal 26 evaluation unit 28 receiving optics 30 polarizing element 32 polarizing filter 34 receiving element 36 polarizing router 38 routing layer 40 CMOS image sensor

Claims

1. An optoelectronic sensor (10) for distance measurement, comprising: a light source (18) which is configured to convert a transmission signal (20) into transmission light (12) and to transmit the transmission light (12) into an environment; a light receiver (22) which receives transmission light (12) reflected back from objects (14) in the environment as reception light (16), wherein the light receiver (22) has a plurality of reception elements (34) for distance measurement, wherein the light receiver (22) comprises at least one polarization element (30) which is configured to feed reception light (16) with a first polarization to one of the reception elements (34) and reception light (16) with a second polarization, which is different from the first polarization, to another of the reception elements (34), wherein the at least one polarization element (30) comprises a polarization router (36) which feeds reception light (16) of different polarization to different reception elements (34), characterized in that at least one of the reception elements (34) comprises a routing layer (38) and a plurality of reception pixels (40), with the routing layer (38) being configured to feed reception light (16) incident on the routing layer (38) to different ones of the reception pixels (40) successively in time so that a plurality of sampling values are produced in the reception pixels (40), wherein the phase position of the reception light (16), and thus the phase difference between the transmission light (12) and the reception light (16), is determined on the basis of the sampling values.

2. An optoelectronic sensor (10) according to claim 1, wherein a plurality of the reception elements (34) form a group in each case, wherein at least one of the groups is assigned a separate polarization element (30) which feeds reception light (16) to the reception elements (34) of the group.

3. An optoelectronic sensor (10) according to claim 1 or 2, wherein the at least one polarization element (30) comprises at least two, preferably four, polarization filters (32), wherein the different polarization filters (32) are each permeable for reception light (16) of different polarization, wherein preferably each polarization filter (32) is associated with only one reception element (34) and substantially feeds reception light (16) only to the associated reception element (34).

4. An optoelectronic sensor (10) according to any one of the preceding claims, wherein at least one of the reception elements (34) comprises a lock-in pixel, in particular a 4-tap lock-in pixel.

5. An optoelectronic sensor (10) according to any one of the preceding claims, wherein the routing layer (38) is configured to feed the reception light (16) to the different reception pixels (40) in dependence on a modulation of the transmission light (12) and / or transmission signal (20).

6. An optoelectronic sensor (10) according to any one of the preceding claims, wherein the reception pixels (40) are part of a CMOS image sensor.

7. An optoelectronic sensor (10) according to any one of the preceding claims, wherein the reception elements (34) are arranged in a planar surface and in particular form an image sensor, wherein a plurality of polarization elements (30) are arranged or attached, preferably directly, on the planar surface.

8. An optoelectronic sensor (10) according to any one of the preceding claims, wherein the optoelectronic sensor (10) is configured to generate the transmission signal (20) as a modulated signal and to modulate the transmission light (12).

9. An optoelectronic sensor (10) according to any one of the preceding claims, wherein the light source (18) is configured to transmit the transmission light (12) in a polarized manner and / or to change the polarization of the transmission light (12).

10. An optoelectronic sensor (10) according to any one of the preceding claims, wherein the optoelectronic sensor (10) comprises an evaluation unit (26) to which signals of the reception elements (34) can be fed and which is configured, in particular for at least two reception elements (34) separately, to output and / or to determine distance information and / or polarization information from the signals.

11. An optoelectronic sensor (10) according to at least claim 2 and claim 10, wherein the evaluation unit (26) is configured to generate a depth image from at least some of the signals of the reception elements (34), wherein the evaluation unit (26) is preferably configured to make a selection of a reception element (34) from a respective group of reception elements (34) for at least a part of the depth image and to use only the signals of the selected reception elements (34) for the depth image.

12. An optoelectronic sensor (10) according to claim 11, wherein the evaluation unit (26) is configured such that the selection of the reception elements (34) is based on a signal strength of the respective reception element (34).

13. A method for distance measurement by means of an optoelectronic sensor (10), wherein - a light source (18) converts a transmission signal (20) into transmission light (12) and transmits the transmission light (12) into an environment, - transmission light (12) reflected back from objects (14) in the environment is received as reception light (16) by a light receiver (22) by means of a plurality of reception elements (34), and - a polarization element (30) feeds reception light (16) with a first polarization to one of the reception elements (34) and reception light (16) with a second polarization, which is different from the first polarization, to another of the reception elements (34), wherein the at least one polarization element (30) comprises a polarization router (36) which feeds reception light (16) of different polarization to different reception elements (34), characterized in that at least one of the reception elements (34) comprises a routing layer (38) and a plurality of reception pixels (40), wherein the routing layer (38) feeds reception light (16) incident on the routing layer (38) to different ones of the reception pixels (40) successively in time so that a plurality of sampling values are produced in the reception pixels (40), wherein the phase position of the reception light (16), and thus the phase difference between the transmission light (12) and the reception light (16), is determined on the basis of the sampling values.