LIGHT GRID

Description

[0001] The present invention relates to a light grid for detecting objects present in a monitored area.

[0002] A light grid is essentially a combination of several light barriers and is also alternatively referred to as a light curtain, with several designs of light barriers.

[0003] In a one-way light barrier, a light receiver and a light transmitter are positioned on opposite sides of a monitoring area. When the monitoring area is clear, the light emitted by the light transmitter strikes the light receiver and is converted into electrical signals, which are then transmitted to an evaluation unit. If an object enters the monitoring area, the light path between the light receiver and the light transmitter, which runs along a receiving axis, is interrupted. This interruption of the light signal is detected, and a corresponding monitoring signal is then output.

[0004] In a reflective photoelectric sensor, the light receiver and the light transmitter are located on the same side of the monitored area. The emitted light is reflected back towards the light receiver by a reflector located on the opposite side of the monitored area.

[0005] Another type of light barrier is the reflective photoelectric sensor. As with a reflective photoelectric sensor, the light receiver and the light transmitter are located on the same side of the monitored area. Unlike a reflective photoelectric sensor, object detection does not occur by interrupting the light path, but rather by the reflection of the transmitted light by an object present in the monitored area towards the light receiver.

[0006] A light grid consists of multiple light receivers and multiple light emitters, with several spaced-apart receiving axes defined, which usually run parallel to each other in a plane. However, other geometric configurations regarding the arrangement of the receiving axes are also possible, for example, non-parallel arrangements. Typically, the light receivers are combined in a receiver unit and the light emitters in a transmitter unit. All of the light barrier designs described above can also be implemented as light grids or light curtains.

[0007] Compared to a light barrier, a light grid allows for the monitoring of a larger area. Due to the multiple receiving axes of a light grid, the size and / or lateral position of a detected object can also be determined within the resolution determined by the spacing of these axes.

[0008] The receiving axes of a light grid, in conjunction with an evaluation unit and, if applicable, a control unit for activating the light emitters, define respective receiving channels or fields of view. To prevent crosstalk between adjacent receiving channels, sequential activation of the receiving channels can be implemented, so that, for example, at a specific time only one receiving channel or at least only a subset of all receiving channels is active. All other receiving channels, i.e., the associated light receivers or light emitters, are deactivated.

[0009] In conventional light grids, each receiving channel is assigned its own light receiver, so light grids with a large number of receiving channels incur correspondingly high production costs due to the number of light receivers required.

[0010] German patent DE 2008 022 791 C5 describes a light curtain in which several receiving channels share a common light source and a common light receiver. Optical bandpass filters are used to selectively distribute the broadband transmitted light to the different receiving channels according to wavelength. On the receiver side, channel selection is achieved using a tunable optical bandpass filter.

[0011] In the device described in EP 1 811 427 A1 for monitoring a protective field, a marking is illuminated by means of a light transmitter and imaged on a spatially resolved light receiver. Object detection is carried out by comparing a current image with a stored image of the marking, taken when the protective field was free of objects.

[0012] US 2009 / 185164 A1 relates to a device for examining foodstuffs, in which light is shone into an object being examined and the light scattered or reflected by the object is detected by a detector unit. This device is intended to detect foreign bodies such as hair or other residues on or in the object. According to one embodiment, two different objects can be examined simultaneously. For this purpose, two receiving channels are provided, which are deflected towards the common detector unit by means of an arrangement of several deflecting mirrors. The received light passing through the two receiving light paths is detected by two different areas of the receiving light surface of the detector unit, which do not overlap.

[0013] JP 2014 055804 A relates to a device for detecting the presence or absence of objects in a monitored area, similar to a light grid with multiple receiving channels. In the area between receiving lenses or input apertures and a single light receiver, a portion of the individual receiving light paths is deflected.

[0014] EP 1 950 584 A1, EP 1 892 495 A2 and DE 10 2004 038 940 A1 show optoelectronic sensors with deflection elements.

[0015] The object of the invention is to provide a light grating which has reduced costs and manufacturing effort.

[0016] The problem is solved by a light grating with the features of claim 1. Dependent claims are directed to preferred embodiments.

[0017] A light grid according to the invention for detecting objects present in a monitoring area comprises at least one receiving module, wherein the at least one receiving module comprises a spatially resolving light receiver with a light-sensitive receiving surface and at least one deflecting element and has at least two receiving channels, wherein each receiving channel has a respective light entry aperture and a receiving axis passing through the light entry aperture, wherein the receiving surface is divided into at least two non-overlapping sub-areas, wherein each receiving channel is assigned a respective sub-area, and wherein at least a part of the receiving axes passes through the at least one deflecting element.

[0018] The light entry aperture defines, in effect, a viewing area of ​​the associated receiving channel, i.e., a spatial region or solid angle from which received light signals are detected and transmitted towards the light receiver. The term "receiving channel" primarily refers to the optical or optoelectronic components assigned to a given viewing area or receiving axis. In a broader sense, the term "receiving channel" can also extend to a corresponding logic channel, which may be defined in a circuit within an evaluation unit associated with the light grid.

[0019] By using a spatially resolved light receiver, it is possible to provide only a single light receiver for two or more receiving channels. Receiver-side separation of the receiving channels is achieved by directing the received light from the different channels onto different, non-overlapping sub-areas of the receiver's receiving surface, thus achieving the desired channel separation. The term "non-overlapping sub-areas" does not necessarily refer to a physical division, but also to a logical division of the receiving surface, which can be implemented, for example, within an evaluation unit connected to the light receiver. For instance, an image sensor with light-sensitive receiving elements (pixels) arranged in rows and columns can be used, whose image area is divided into so-called non-overlapping ROls (Regions of Interest).In the simplest case, however, the light receiver can also be formed by a two-channel PSD receiver (from English "Position Sensitive Device").

[0020] In each receiving channel, a respective receiving light spot can be generated from the received light signals, which hits the sub-area of ​​the light receiver assigned to this receiving channel.

[0021] The at least one deflecting element serves, in particular, to adapt a desired spacing of the light entry apertures of a receiving module to the spacing of the partial surfaces of the receiving area, which is determined by the geometry of the light receiver. For this purpose, the deflecting element can deflect light signals that propagate along the associated receiving axis and pass through the light entry aperture once or several times.

[0022] In principle, a receiving module can be designed so that all receiving axes or channels pass through the deflection element. However, it is also conceivable that, for example, in a three-channel receiving module, two channels pass through a common deflection element or through two separate deflection elements, and in a third receiving channel the light signals reach the assigned area of ​​the light receiver directly, i.e., without deflection.

[0023] The deflection element(s) of a given receiver module can be designed as separate, channel-separated components or as an integrated component for multiple receiver channels.

[0024] In principle, it is possible for a light grid according to the invention to have only a single receiving module. Advantageously, however, the light grid comprises several, preferably identical, receiving modules, so that a correspondingly large monitoring area can be monitored. In any case, an advantage is that the number of required light receivers is smaller than the number of available receiving channels. This allows for a space-saving arrangement of the light receivers in a common receiver unit. At the same time, the comparatively smaller number of light receivers reduces material and manufacturing costs, resulting in a significant cost advantage.

[0025] A further advantage is that, regardless of the desired grid spacing for the arrangement of the light entry apertures or receiving optics, a universal circuit board can be used on which one or, preferably, several light receivers—i.e., the light receivers of a plurality of receiving modules—can be arranged. Adaptation to a desired grid spacing is then achieved by appropriately dimensioning the deflection elements.

[0026] The light grid according to the invention can be implemented as a one-way light grid, a reflective light grid or as a touch-sensitive light grid, according to the above-described designs of light barriers.

[0027] According to a preferred embodiment, the light entry apertures of two adjacent receiving channels have a base distance that is greater than the distance between the partial areas assigned to these receiving channels. The terms "distance" and "base distance" refer in particular to the respective center-to-center distances of the receiving channels in question. In this embodiment, for example, a deflecting element can first deflect the receiving axis by 90° and, after a certain distance, again by 90° in the opposite direction, so that the receiving axis experiences a specific lateral offset. In this way, the distance between the receiving channels within the assigned receiving module can be reduced to such an extent that the receiving channels of each receiving module are directed onto the common light receiver.

[0028] According to a further advantageous embodiment, the deflecting element is designed as a mirror arrangement, a prism element, or an optical waveguide. In a prism element or optical waveguide configuration, the deflection occurs through internal reflection at the walls of the prism element or the optical waveguide, respectively. The deflecting element can be made, for example, of transparent solid material such as glass or plastic, or it can be a hollow element. To improve the reflection properties, the outer walls can be coated with a reflective material, such as a metal coating. Preferably, however, the deflecting element is designed such that total internal reflection occurs at its walls, thus eliminating the need for an additional, costly coating.In principle, the deflecting element can also be designed as a mirror arrangement with one or more mirror surfaces.

[0029] According to a further advantageous embodiment, the light grid comprises a transmitter for emitting light signals into the monitoring area, wherein the light grid is configured to determine the distance to an object present in the monitoring area based on the time of flight of the light signals emitted by the transmitter, reflected by the object, and detected by the light receiver. This embodiment can also be referred to as a so-called tactile TOF (Time Of Flight) light grid. In this advantageous configuration, the transmitter and the light receivers can be equipped with a control unit or...a combined evaluation and control unit, which can control the transmitting arrangement to emit the light signals, for example in the form of one or more light pulses, and can evaluate the electrical received signals generated by the light receiver on the basis of the detected light signals in order to determine the light travel time between the time of emission of a light signal and its reception and from this to determine the distance to the object.

[0030] Advantageously, the light receiver comprises a SPAD array. Such a SPAD array is an array or a two-dimensional matrix of single-photon avalanche diodes, where SPAD is the abbreviation for "Single Photon Avalanche Diode." These SPAD arrays are particularly suitable for distance measurement based on the time of flight of light. With SPAD arrays, individual return areas (ROls) can typically be defined, whereby only those pixels or diode elements of the SPAD array that are actually illuminated by a particular spot of light are used for evaluation.

[0031] By disregarding or deactivating unilluminated pixels or individual diodes, the signal-to-noise ratio can be reduced. This method of defining ROls can also be used to divide the receiving area into the aforementioned sub-areas.

[0032] According to a further advantageous embodiment, the light entry aperture of a respective receiving channel is defined by at least one aperture, which is provided between a receiving optic arranged upstream of the deflecting element and a light entry surface of the deflecting element and / or between a light exit surface of the deflecting element and the light receiver. The aperture determines at least predominantly the field of view of a respective receiving channel for respective rays of the received light signals and is preferably selected such that crosstalk of received light signals into adjacent receiving channels is avoided, at least for objects whose distance from the light grid lies within the limits of a defined detection range of the light grid, in order to achieve a desired lateral resolution of the light grid. The aforementioned upstream receiving optic is arranged upstream of the deflecting element when viewed in the direction of propagation of the received light signals.

[0033] Each receiving channel can have one or more associated receiving optics. The receiving optics of different receiving channels can preferably be configured as a lens array in which several lenses are formed in a common integrated or monolithic component. By using the same material, or at least materials with similar or identical coefficients of thermal expansion, for the deflecting element and the lens array, temperature-related length changes occur to the same extent. This ensures, for example, that the distance between the receiving optics of a receiving module and the offset of the receiving axes caused by the at least one deflecting element change by the same amount, so that the viewing areas of the individual receiving channels remain constant even under temperature changes, and in particular, the parallel alignment of the receiving channels is maintained even under temperature changes.

[0034] Advantageously, the aperture is arranged in the image plane of the receiving optics. Alternatively or additionally, an aperture can be arranged on a light-entry surface or a light-emission surface of the deflecting element. The aperture can, for example, be applied or generated directly on the light-entry surface or the light-emission surface of the deflecting element. Alternatively, a separate aperture carrier can be provided. Generating the aperture on the deflecting element or on a separate aperture carrier can be achieved, for example, by applying a suitable coating using masks or in the form of a so-called laser-generated aperture, whereby the aperture is generated at the intended location by introducing high-energy laser radiation into the (partially) assembled optical system through energy emission. This method is described, for example, in DE 10 2018 128 669 A1.

[0035] According to the invention, the light-entry surface, light-emission surface, and / or at least one reflection surface of a respective deflecting element are designed with an optically effective geometry. This optically effective geometry also imparts beam-shaping properties to the deflecting element, for example, through a convex or concave curvature of one or more of the aforementioned surfaces. This reduces the number of optical elements that need to be mounted and adjusted, thereby reducing manufacturing effort and potential sources of adjustment errors.

[0036] Advantageously, each deflecting element is designed and arranged such that, by means of its optically effective geometry, an aperture of the associated receiving optics is projected onto the receiving surface. The size of the received light spot on the light receiver thus depends primarily on the size of the receiving optics and the geometry of the beam path downstream of the receiving optics.

[0037] According to a further advantageous embodiment, the light grid comprises at least one circuit board, which has a side facing away from the monitoring area and a side facing the monitoring area, with a light receiver associated with the conductor being arranged on the side facing away from the monitoring area. Thus, the light-sensitive receiving area faces away from the monitoring area. In this case, the deflection element is designed such that each receiving axis is deflected by approximately 180°. The circuit board in question can, for example, be a common circuit board for several light receivers or receiving modules. However, a separate circuit board can also be provided for each receiving module or for each light receiver.

[0038] In principle, even in embodiments where the light-sensitive receiving surface points towards the monitoring area, a common circuit board can be provided for several light receivers or receiving modules.

[0039] According to a further advantageous embodiment, the light grid has several receiving modules which are arranged in such a way that a light entry aperture of one receiving module is provided between two light entry apertures of another receiving module, preferably all light entry apertures of the light grid being arranged along a common axis.

[0040] Such an arrangement can further reduce the occurrence of crosstalk between different receiving channels.

[0041] Advantageous embodiments of the invention are also described in the dependent claims, the description, and the drawings. The claims, the description, and the drawings contain numerous features in combination. It is advantageous for a person skilled in the art to also consider these features individually and combine them into meaningful further combinations.

[0042] The invention is described below by way of example with reference to drawings. The figures are not to be understood as being to scale. They show: Fig. 1 a schematic side view of a light grid according to a first embodiment of the invention; Fig. 2 a schematic top view of a light receiver of the light grid according to Fig. 1Fig. 3 is a schematic side view of a light grid according to a second embodiment according to the invention; Fig. 4 is a schematic side view of a light grid according to a third embodiment according to the invention; Fig. 5 is a schematic side view of a light grid according to an unclaimed fourth embodiment; Fig. 6 is a schematic side view of a light grid according to a fifth embodiment according to the invention; Fig. 7 is a schematic side view of a light grid according to a sixth embodiment according to the invention; and Fig. 8 is a schematic partial top view of a light grid according to a seventh embodiment according to the invention.

[0043] In the following, identical or similar components or elements are referred to by the same reference symbols.

[0044] In Fig. 1A light grid 110 for detecting objects present in a monitoring area 10 is shown according to a first embodiment. A receiving module 12 of the light grid 110 comprises a spatially resolving light receiver 14, two deflection elements 30.1, 30.2, two apertures 36.1, 36.2, two receiving optics 26.1, 26.2 and a common front lens 40.

[0045] On the side of the monitoring area 10 opposite the receiving module 12, a transmitting unit (not shown) can be arranged, which emits transmitting light into the monitoring area, which is detected by the receiving module 12.

[0046] The two receiving optics 26.1, 26.2 are arranged laterally spaced apart from each other with a base distance B and are formed in an integrated component, which can also be referred to as an optical module or lens array.

[0047] The received light propagates along two receiving axes 24.1, 24.2, each passing through the lens centers of the two receiving optics 26.1, 26.2. The received light, focused by the receiving optics 26.1, 26.2, then enters a respective deflecting element 30.1 or 30.2, which is configured as an optical waveguide or prism element. In each deflecting element 30.1, 30.2, a first deflection occurs at a first reflective surface 32, with a deflection angle of slightly more than 90°. Subsequently, a second deflection occurs at a second reflective surface 34, with a reflection angle here of approximately 90°. Both deflections are directed in opposite directions, so that the exit direction from the deflection elements 30.1, 30.2, with respect to the receiving axes 24.1 and 24.2 respectively, is approximately equal to the entry direction of the received light into the deflection elements 30.1, 30.2.The respective first and second reflection surfaces 32, 34 are concavely curved and thus also have beam-shaping properties.

[0048] In the present embodiment, the two deflecting elements 30.1, 30.2 are designed as mirror images of each other and arranged such that the original distance between the receiving axes 24.1, 24.2 is reduced to such an extent that both receiving light beams can be detected by the single light receiver 14. The distance between the receiving axes 24.1, 24.2 is essentially reduced to the center-to-center distance A of the partial surfaces 18.1, 18.2.

[0049] The in Fig. 2The spatially resolved light receiver 14, shown in plan view, has a receiving area 16 which comprises a plurality of light-sensitive receiving elements 17 (e.g., SPAD elements) arranged in rows and columns, which are schematically represented by small squares. In the exemplary embodiment, the receiving area 16 is divided into two sub-areas 18.1, 18.2, with a dashed line marking the boundary between the two sub-areas 18.1, 18.2.

[0050] With the aid of the receiving optics 26.1, 26.2, the transmitted light beams propagating along the receiving axes 24.1, 24.2 are focused in the plane of the receiving surface 16 to form a respective receiving light spot 20.1, 20.2. The received light propagating along the receiving axis 24.1 is focused into the receiving light spot 20.1, while the transmitted light beam propagating along the receiving axis 24.2 is focused into the receiving light spot 20.2. The receiving module 12 is configured and adjusted such that the receiving light spot 20.1 falls completely on the sub-surface 18.1 and the receiving light spot 20.2 falls completely on the sub-surface 18.2. The distance between the receiving light spots 20.1, 20.2 corresponds essentially to the center-to-center distance A of the sub-areas 18.1, 18.2.

[0051] The two receiving axes 24.1, 24.2 together with the sub-areas 18.1, 18.2 form a respective receiving channel, with the receiving optics 26.1, 26.2 and the deflecting elements 30.1, 30.2 arranged as shown in Fig. 1 are assigned to one of these receiving channels.

[0052] In particular, to prevent crosstalk of received light between adjacent channels, the fields of view or "angles of view" of the respective received light beams are limited by means of apertures 36.1, 36.2. Through the interaction of the beam-shaping properties of the deflecting elements 30.1, 30.2 with the entrance pupils of the receiving optics 26.1, 26.2, the size of the received light spots 20.1, 20.2 can be limited such that a certain safety distance remains between the two received light spots 20.1, 20.2, or at least no overlap occurs. As a result, each sub-area 18.1, 18.2 captures only light from its respective assigned receiving channel.

[0053] Fig. 3 Figure 1 shows a light grid 210 according to a second embodiment. The light grid 210 comprises three identical receiving modules 12, which in their design are similar to the receiving module 12 of Fig. 1 The receivers correspond and are arranged along an axis running in the y-direction. For clarity, only the receiver axes 24.1 and 24.2 are shown instead of the transmitting light beams. The spacing of the individual receiver modules 12 in the y-direction is chosen such that all receiver channels or receiver axes 24.1 and 24.2 run at equal intervals from each other within the plane of the drawing. The front panel 40 is designed as a continuous front panel 40 that extends over all six receiver channels.

[0054] According to one modification, all six receiving lenses 26.1, 26.2 can be integrated into a common lens array or optical module (not shown).

[0055] In Fig. 4A light grid 310 according to a third embodiment is shown. The structure of the light grid 310 corresponds in essential aspects to the structure of the light grid 110 of Fig. 1 Therefore, only the essential differences will be described below. Instead of an optical module with the two receiving optics 26.1, 26.2, these are designed as individual elements. In contrast to the embodiment according to Fig. 1 Instead of the two separate deflection elements 30.1, 30.2, an integrated deflection element 30 is provided, which, however, functionally corresponds to the adjacent arrangement of two separate deflection elements 30.1, 30.2. A further difference is that the apertures 36.1, 36.2 are not separate components (as in Fig. 1(shown), but are applied to the respective light entry surfaces of the deflecting element 30, for example in the form of a coating or vapor deposition deposited thereon. Furthermore, the reflective surfaces 32, 34 of the deflecting element 30 have a slightly larger radius of curvature.

[0056] Fig. 5 Figure 410 shows a light grid according to an unclaimed, fourth embodiment, which is essentially the same as the light grid 310 of Fig. 4 corresponds. Unlike Fig. 4The apertures 36.1 and 36.2 are not applied to the light-entry side of the deflecting element 30, but rather to its light-emission side. Here, the apertures 36.1 and 36.2 can be produced directly on the light-emission side, for example, using a processing laser, by focusing the laser so that its focal point lies in the plane of the light-emission side of the deflecting element 30. Furthermore, the reflective surfaces 32 and 34 of the deflecting element 30 of the light grating 410 are not curved but flat and therefore do not have an optically effective geometry.

[0057] In Fig. 6A light grid 510 according to a fifth embodiment is shown. In contrast to the light grids 110 to 410, the receiving surface 16 of the light receiver 14 is located on a side facing away from the monitoring area 10. The light receiver 14 is arranged on a circuit board 42, which has openings 44.1, 44.2 for the received light. To effect the necessary reversal of direction of the received light by an angle of approximately 180°, the deflecting element 30 has a slightly different geometry compared to the deflecting elements 30, 30.1, 30.2 of the light grids 110 to 410. Only the second reflective surfaces 34 are optically effective due to their concave curvature. The first reflective surfaces 32 are flat and therefore not optically effective.

[0058] The advantage of this embodiment is that, for a given installation depth of the receiver module 12, i.e., its extension in the z-direction, a comparatively longer image distance of the received light path can be achieved. A further advantage is that the light receiver 14 is better shielded from interference by the circuit board 42.

[0059] Fig. 7 shows a light grid 610 according to a sixth embodiment, which is similar to the light grid 310 ( Fig. 4). In contrast to the other embodiments, the receiving module 12 of the light grid 610 additionally has a third receiving channel, which is arranged centrally between the first and the second receiving channels. Accordingly, the light receiver 14 has a total of three partial surfaces arranged in series. Unlike the receiving axes 24.1, 24.2, the receiving axis 24.3 of the third receiving channel is not deflected, since there are no corresponding surfaces of the deflecting element 30 in the receiving light path of the third receiving channel, but only a plane-parallel section or an opening. In order to achieve sufficient beam shaping in the third receiving channel even without optically effective surfaces of the deflecting element 30, a further receiving optic 26.4 is provided in addition to the receiving optic 26.3, which is identical in design to the receiving optics 26.1, 26.2. This further receiving optic 26.4 is located between the receiving optic 26.3 and the deflection element 30.

[0060] It is understood that, according to variations not shown, the same applies to light grids 310 to 610 ( Figs. 4 to 7 ) several receiver modules 12 can be provided, which can be arranged in series or in other configurations.

[0061] With reference to Fig. 8 A further light grid 710 is described according to a seventh embodiment. In contrast to the illustrations of the Fig. 1 and 3 to 7 shows Fig. 8A top view of the light grid 710. For simplicity, only the light receivers 14 and the V-shaped deflecting elements 30 of the two receiving modules 12 are shown. The receiving modules 12 are arranged such that the respective light entry surfaces of the deflecting elements 30 (represented by square areas) are distributed along an axis extending in the y-direction, with one arm of each deflecting element 30 projecting between the two arms of the other deflecting element. To achieve this interlocking of the receiving modules 12, the deflecting elements 30 are also slightly tilted relative to each other, so that the light receivers 14 have not only an offset in the y-direction but also an offset in the x-direction.

[0062] All exemplary light grids 110 to 710 can, in principle, be designed as one-way light grids, reflection grids, or tactile light grids. Additionally, the light grids 110 to 710 can include transmitter arrangements that have at least one light transmitter.

[0063] According to a preferred embodiment, the light grids 110 to 710 can be configured as distance-measuring tactile light grids. For this purpose, a SPAD array, for example, can be used as the light receiver 14. Each receiving channel can be assigned a corresponding light transmitter (not shown), with the light transmitters and the light receiver 14 being connected to a common evaluation and control unit. The light transmitters and the receiving module(s) 12 are arranged such that a light pulse emitted by a respective light transmitter is reflected by any object present in the monitored area in the direction of the assigned receiving module 12. The evaluation and control unit is configured to measure the light travel time between the emission of the light pulse and its detection by the light receiver 14 and to determine the distance of the detected object to the light grid from this measurement.

[0064] In principle, a common light transmitter can also be provided for several receiving channels, preferably for all receiving channels of a respective receiving module 12. This allows distance determination to be carried out simultaneously for the several receiving channels.

[0065] Advantageously, individual receiving elements 17 can be deactivated so that only those receiving elements 17 actually illuminated by a receiving light spot 20.1, 20.2 contribute to a detection signal. Deactivating the remaining receiving elements 17 significantly reduces the interference sensitivity of the light receiver 14, which is particularly advantageous for a light receiver designed as a SPAD light receiver. Furthermore, SPAD light receivers 14, in particular, in conjunction with the evaluation and control unit, allow for the circuit-based definition of the sub-areas 18.1, 18.2 within the entire receiving area 16 of the light receiver 14. Reference symbol list

[0066] 110 - 710 Light grid 10 Monitoring area 12 Receiver module 14 Light receiver 16 Receiver area 17 Receiver elements 18.1, 18.2 Partial area 20.1, 20.2 Receiver light spot 24.1 - 24.3 Receiver axis 26.1 - 26.4 Receiver optics 30, 30.1, 30.2 Deflection element 32 First reflective surface 34 Second reflective surface 36.1, 36.2 Aperture 40 Front lens 42 Circuit board 44.1, 44.2 Through-hole A Distance between sub-surfaces B Base distance between light entry apertures X, Y, Z Spatial directions

Claims

1. A light grid (110 - 710) for detecting objects present in a monitored zone (10), said light grid (110 - 710) comprising at least one reception module (12), wherein the at least one reception module (12) comprises a spatially resolving light receiver (14), which has a light-sensitive reception surface (16), and at least one deflection element (30, 30.1, 30.2) and has at least two reception channels, wherein each reception channel has a respective light entry aperture and a reception axis (24.1 - 24.3) extending through the light entry aperture, wherein the reception surface (16) is divided into at least two non-overlapping partial surfaces (18.1, 18.2), wherein each reception channel is assigned a respective partial surface (18.1, 18.2), and wherein at least some of the reception axes (24.1 - 24.3) extend through the at least one deflection element (30, 30.1, 30.2), characterized in that a light entry surface, a light exit surface and / or at least one reflection surface (32, 34) of a respective deflection element (30, 30.1, 30.2) has / have an optically effective geometry having beam-shaping properties.

2. A light grid (110 - 710) according to claim 1, characterized in that the light entry apertures of two adjacent reception channels have a respective base spacing (B) which is greater than the spacing (A) of the partial surfaces (18.1, 18.2) assigned to these reception channels.

3. A light grid (110 - 710) according to claim 1 or 2, characterized in that the deflection element (30, 30.1, 30.2) is configured as a mirror arrangement, as a prism element or as an optical waveguide.

4. A light grid (110 - 710) according to any one of the preceding claims, characterized in that the light grid (110 - 710) comprises a transmission arrangement for transmitting light signals into the monitored zone (10), with the light grid (110 - 710) being configured to determine the distance from an object present in the monitored zone (10) on the basis of the time of flight of the light signals which are transmitted by the transmission arrangement, remitted by an object and detected by the light receiver (14).

5. A light grid (110 - 710) according to claim 4, characterized in that the light receiver (14) comprises a SPAD array (43).

6. A light grid (110 - 710) according to any one of the preceding claims, characterized in that the light entry aperture of a respective reception channel is defined by at least one diaphragm (36.1, 36.2) which is provided between a reception optics (26.1 - 26.4) arranged upstream of the deflection element (30, 30.1, 30.2) and a light entry surface of the deflection element (30, 30.1, 30.2) and / or between a light exit surface of the deflection element (30, 30.1, 30.2) and the light receiver (14).

7. A light grid (110 - 710) according to claim 6, characterized in that the diaphragm (36.1, 36.2) is arranged in the image plane of the reception optics (26.1 - 26.4), and / or in that the diaphragm (36.1, 36.2) is arranged on a light entry surface or a light exit surface of the deflection element (30, 30.1, 30.2).

8. A light grid (110 - 710) according to any one of the preceding claims, characterized in that the light grid (110 - 710) has at least one printed circuit board (42) which has a side facing away from the monitored zone (10) and a side facing the monitored zone (10), wherein a light receiver (14) associated with the printed circuit board (42) is arranged on the side facing away from the monitored zone (10).

9. A light grid (110 - 710) according to any one of the preceding claims, characterized in that the light grid (110 - 710) has a plurality of reception modules (12) which are arranged interlaced such that a light entry aperture of one reception module (12) is provided between two light entry apertures of another reception module (12), wherein preferably all the light entry apertures of the light grid (110 - 710) are arranged along a common axis.