OPTICAL SENSOR

Description

[0001] The invention relates to an optical sensor.

[0002] Such optical sensors are generally used to detect objects in a monitored area.

[0003] In the simplest embodiment, the optical sensor comprises only a transmitter that emits light beams and a receiver that receives light beams. The optical sensor can be designed as a light sensor, distance sensor, or reflective light barrier, and the like. In these embodiments, the transmitter and receiver are integrated into a common housing. Furthermore, the optical sensor can also be designed as a light barrier. In this case, the transmitter and receiver are housed in separate housings.

[0004] In general, an optical sensor can also have multiple transmitters and / or receivers. A light curtain is an example of such an optical sensor.

[0005] The light curtain typically comprises a row of light-beam emitting transmitters in a first housing at one edge of the monitoring area and a row of light-beam receiving receivers in a second housing at the opposite edge of the monitoring area.

[0006] The optical sensor has an evaluation unit in which an object detection signal is generated based on received signals from the receiver(s). This object detection signal can be, in particular, a binary switching signal whose switching states indicate whether an object is located within the monitored area or not. Alternatively, the object detection signal can be an analog signal, for example, a distance value.

[0007] To ensure reliable object detection, each transmitter and receiver is assigned an optical unit, which includes optical elements such as lenses. These optical units shape the light beams on the transmitting side and focus the light beams on the receiving side onto the respective receiver.

[0008] Despite the use of such optical units, a common problem with these types of optical sensors is that the light beams are not emitted precisely along the optical axis of the transmitter, but rather that sidelobes are present in the beam profile. Furthermore, sidelobes arise from parasitic reflections of portions of the light beams within the housing of the optical sensor. This can impair object detection, meaning that the reliability of object detection is reduced.

[0009] Another disadvantage is that known optical sensors are more complex in design.

[0010] DE 20 2007 010 493 U1 relates to a housing for an optoelectronic sensor arrangement with at least one light transmitter and / or one light receiver, which is designed as a substantially cylindrical hollow profile with a front face, a bottom face, a first side wall and a second side wall and is composed of exactly one first element and one second element. The first element comprises at least the first side wall. The second element comprises at least the second side wall.

[0011] DE 20 2020 100 208 U1 relates to an optoelectronic sensor with at least one transmitting element and at least one receiving element, and at least one tube in front of the transmitting element. The tube has a light-absorbing surface. The light-absorbing surface is formed by a dark thermoplastic elastomer with a matte surface.

[0012] US Patent 6,175,106 B1 describes an optical sensor. This optical sensor is designed in the form of a light grid. The light grid comprises an optical arrangement with a plurality of light-emitting transmitting and receiving elements, a plurality of diffractive / refractive optical elements, and a transparent front cover, in particular a front panel. The diffractive / refractive optical elements are arranged on a single, integrally formed carrier element. The carrier element is formed by the front cover, wherein the diffractive / refractive optical elements are formed directly in the front cover, in particular embossed or cast into it. The transmitting and receiving elements are arranged on a single, integrally formed printed circuit board.

[0013] DE 20 2007 011 016 U1 relates to an optical sensor for detecting objects in a monitored area, comprising at least one transmitter emitting light beams and at least one receiver receiving light beams. The transmitter and / or receiver is each mounted in a one-piece aperture tube, wherein initial parts of the aperture tube form a light trap and further parts are provided for mounting optics and / or forming an aperture.

[0014] US 2021 / 0215804 A1 relates to a sensor with an optical module rotatably mounted on a housing. The optical module comprises a transmitter and receiver mounted in a tube.

[0015] The invention is based on the objective of providing an optical sensor of the type mentioned above, in which the detection reliability is increased with low manufacturing effort.

[0016] To achieve this object, the features of claim 1 are provided. Advantageous embodiments and expedient developments of the invention are described in the dependent claims.

[0017] The invention relates to an optical sensor for detecting objects in a monitoring area, comprising at least one transmitter emitting light beams with an optical axis and at least one receiver, also with an optical axis, configured to receive light beams. Each transmitter and receiver is associated with a tube whose longitudinal axis runs in the direction of the optical axis of the transmitter or receiver. The tube consists of several tube elements that can be joined to the tube transversely to the optical axis. The tube forms at least one element plane in which an optical element is present. The tube has one or more element planes in the form of aperture planes, each containing an aperture, with each aperture being a component of the tube elements. The tube elements are connected via one or more flexible joints.

[0018] The optical sensor according to the invention can generally have only one transmitter and only one receiver, in which case the optical sensor is configured as a light barrier, reflective light barrier, photoelectric sensor, distance sensor, or the like. The optical sensor can also have a multiple arrangement of transmitters and / or receivers. In particular, the optical sensor can be configured as a light curtain.

[0019] The functionality of the optical sensor is generally such that the optical sensor has an evaluation unit in which, depending on the received signals from the receiver(s), an object detection signal is generated which indicates whether an object is present in the monitoring area.

[0020] The optical sensor can generally be designed as a safety sensor. For use in safety technology, it has a fail-safe design, which is achieved, for example, by a two-channel evaluation unit.

[0021] According to the invention, each transmitter and each receiver is assigned a tube, which consists of several tube elements. The transmitting and receiving tubes can be identical, but this is not mandatory.

[0022] A key aspect of the invention is that the tube elements are assembled transversely to the optical unit for mounting the tube, i.e., they are joined and connected together. This assembly is not only easy to perform, but also allows for the simple integration of optical elements into the tube. The optical elements are integrated into the tube in different element planes, which are advantageously oriented perpendicular to the optical axis. The individual tube elements have receiving segments for the optical elements, which can be designed as cavities with undercut structures. The optical elements can be inserted into these receiving segments, and after the tube elements are assembled to form the tube, the receiving segments complete a circumferential recess in which the respective optical element is mounted.

[0023] A further significant advantage is that the number and configuration of the optical elements in the tube can be flexibly specified, allowing the optical properties of the resulting optical unit to be optimized. This also allows for the easy implementation of complex optical sensors. In particular, it makes it possible to eliminate or at least reduce optical interference caused by side lobes of the light beams.

[0024] This ensures a high level of detection reliability in object detection carried out with the optical sensor with little design effort.

[0025] According to an advantageous embodiment, the tube elements of the tube are designed in the form of plastic injection-molded parts.

[0026] Casting the plastic injection-molded parts that form the tube elements is therefore easy to carry out, since the tube elements only extend over a partial angular area of ​​the aforementioned tube and thus do not form closed hollow bodies, but rather open structures in which, in particular, the receiving segments are exposed in the form of undercut structures that define the cavities. The tube elements formed in this way can be efficiently manufactured as plastic injection-molded parts.

[0027] It is particularly advantageous if the tube elements are joined together to form the tube in an overlapping manner.

[0028] This ensures a completely light-tight wall of the tube, which is not reliably guaranteed, for example, with a butt-to-butt connection of the individual tube elements, as narrow gaps may remain between the tube elements due to component tolerances, through which light can break through.

[0029] To form the tube from the tube element, fixing agents are advantageously provided, by means of which tube elements can be connected.

[0030] The fixing agents are particularly useful for forming clip connections.

[0031] This enables simple, tool-free assembly of the tube. The fixing elements are advantageously integrated into the tube element(s) forming the tube, so that they can be manufactured together with the tube elements as injection-molded plastic parts without additional effort.

[0032] Furthermore, each tube advantageously has fastening means for attachment to a surface.

[0033] In particular, the base is formed by a printed circuit board on which the transmitter and / or receiver are arranged.

[0034] Advantageously, the fastening devices are designed as snap-in or clip devices.

[0035] This allows the tube to be attached to the base without the need for tools. Furthermore, the fasteners can be integrated into the plastic injection-molded part(s) forming the tube, eliminating the need for additional manufacturing effort.

[0036] According to the invention, the tube has one or more element planes in the form of aperture planes, in each of which an aperture is present.

[0037] According to the invention, the aperture or each aperture is part of the tube.

[0038] If the tube consists of one or more injection-molded plastic parts, the aperture can be part of these injection-molded plastic parts, which allows the aperture to be manufactured efficiently.

[0039] The functionality of the tube according to the invention can be advantageously further extended by the fact that the inner wall of the tube has light-trapping microstructures.

[0040] This further reduces uncontrolled light reflections on the inner wall of the tube.

[0041] According to a particularly advantageous embodiment, the optical sensor is designed as a light curtain.

[0042] In this case, the light curtain has a series of transmitters, with each transmitter associated with a tube. These tubes form a transmitter-side tube array. The light curtain also has a series of receivers, with each receiver associated with a tube. These tubes form a receiver-side tube array.

[0043] A particularly advantageous feature is that each tube of the transmitting and / or receiving tube arrangement contains a lens arrangement. The lenses of the lens arrangement and adjacent lens arrangements for the transmitting or receiving tube arrangement are connected via flexible bridges.

[0044] This means that the entire lens arrangement for the tubes of all transmitters and receivers can be manufactured in just one production step.

[0045] The invention is explained below with reference to the drawings. They show: Figure 1: Exemplary embodiment of the optical sensor according to the invention in the form of a light curtain. Figure 2: Exemplary embodiment of an optical unit for a receiver of the light curtain according to the invention. Figure 1 . Figure 3: Embodiment of a lens arrangement for a series arrangement of optical units according to Figure 2 Figure 4: Another embodiment of an optical unit for the light curtain according to Figure 1 . a) Sectional view b) Top view Figure 5: Individual view of the tube of the optical unit according to the Figures 4a, 4b .

[0046] Figure 1shows schematically the structure of an embodiment of the optical sensor according to the invention in the form of a light curtain 1 for detecting objects within a surveillance area.

[0047] The light curtain 1 comprises a transmitter unit with a housing 2a containing a series arrangement of transmitters 4 emitting light beams 3 and associated optical units 5. The optical units 5 serve to stretch the light beams 3 emitted by the transmitters 4. The optical units 5 are identically designed.

[0048] Furthermore, the light curtain 1 has a receiver unit with a second housing 2b containing a series arrangement of receivers 6 receiving light beams 3, each of which is preceded by an optical unit 7. The optical units 7 are identically designed and serve to shape and focus the light beams 3 directed to the receivers 6.

[0049] The housings 2a and 2b are arranged at opposite edges of the monitored area such that a receiver 6 is positioned opposite a transmitter 4, forming a transmitter-receiver pair with the transmitter 4, the light beams 3 of the transmitter 4 forming a beam axis. In this case, eight beam axes are provided. Of course, the light curtain 1 can also have a different number of beam axes.

[0050] Alternatively, the light curtain 1 can also be designed as a reflective light curtain. In this case, all transmitters 4 and receivers 6 are arranged in a housing, which is positioned at one edge of the monitored area. A reflector is located at the other end. When the monitored area is clear, the light beams 3 from the transmitters 4 are guided back to their respective receivers 6 via the reflector.

[0051] The transmitters 4 are controlled by a transmitter controller 8. An evaluation unit 9 is assigned to the receivers 6. The beam axes are activated cyclically, one after the other. The evaluation unit 9 controls the receivers 6 and evaluates their received signals to generate an object detection signal in the form of a binary switching signal. The switching states of this signal indicate whether an object is in the monitored area or not. When the monitored area is clear, the light beams 3 of the beam axes reach the receiver 6 of the respective beam axis unimpeded. If an object interferes, at least one beam axis is interrupted. The evaluation unit 9 can have a multi-channel configuration if the light curtain 1 forms a safety sensor.

[0052] Figure 2Figure 1 shows, in a highly schematic form, an embodiment of the receiving optical unit 7. The transmitting optical units 5 have a corresponding, i.e., identical, structure.

[0053] The optical unit 7 has a conical, opaque tube 10 whose longitudinal axis runs along the optical axis A of the receiver 6.

[0054] All receivers 6 of the light curtain 1 are arranged on a printed circuit board 11. All tubes 10 are attached to the printed circuit board (11) by means of fasteners (not shown). The fasteners are formed by snap-fit ​​or clip elements that are integrally formed with the tube 10.

[0055] The tube 10 consists of two tube elements 12a, 12b, which can be joined together along a forming direction B running transversely to the optical unit 7. The tube elements 12a, 12b each consist of a single injection-molded plastic part.

[0056] The tube elements 12a, 12b each extend circumferentially over an angular range of slightly more than 180° and are joined together in an overlapping manner in the forming direction B, so that their edge regions overlap. The tube elements 12a, 12b are fastened to one another with fixing means (not shown). The fixing means are components of the tube elements 12a, 12b and, in this case, are formed in the form of clip connections.

[0057] In the case of tube 10 according to Figure 2 Several element planes perpendicular to the optical axis are provided, in which optical elements are mounted.

[0058] In a first element plane, which forms a lens plane and runs along the upper edge of the tube 10, an aperture 13 is provided, the circular aperture opening 13a of which is arranged symmetrically to the optical axis. This aperture 13 is part of the first tube element 12a, being formed integrally with the tube element 12a. Alternatively, the aperture 13 can also be an insert that can be placed into the tube 10, in which case corresponding receiving segments are provided on the tube elements 12a and 12b.

[0059] Furthermore, two intermediate apertures 14 and 15, each with an aperture opening 14a and 15a, are provided. Intermediate aperture 14 is part of tube element 12b, and intermediate aperture 15 is part of tube element 12a.

[0060] Finally, a field stop 16 with an aperture 16a is provided at the lower edge of the tube 10, facing the receiver 6. The field stop 16 is arranged on the tube element 12b.

[0061] The diameters of the aperture openings 13a, 14a, 15a, 16a of the individual apertures 13, 14, 15, 16 increase from the bottom edge to the top edge, as shown from Figure 2 visible.

[0062] The optical unit 7 according to Figure 2 comprises three lenses 17a-c as additional optical elements. These lenses 17a-c are mounted in element planes forming lens planes in the tube 10. The lenses 17a-c form inserts that are inserted into the tube 10. Receptacle segments are provided on the inner wall of the tube 10 to fix the position of the lenses 17a-c.

[0063] In this case, the lenses 17a-c consist of a plastic injection-molded part. For this purpose, the lenses 17a-c are connected via flexible webs 18a, 18b, which, together with the lenses 17a-c, form the plastic injection-molded part.

[0064] The flexible webs 18a, 18b are advantageously formed in the form of film joints. The flexibility of the webs 18a, 18b can be achieved by material constrictions that are predefined in the plastic injection-molded parts.

[0065] Figure 3 shows a further development of the lens arrangement according to Figure 2. Figure 3 shows a multiple arrangement of lenses 17a-c for tubes 10 of a transmitting or receiving-side array. For each tube 10, a lens arrangement with three lenses 17a-c is provided according to the embodiment according to Figure 2 , which are each connected by webs 18a, 18b. The lens assemblies for adjacent tubes 10 are connected to further flexible webs 19, which are configured to correspond to the webs 18a, 18b. In this way, the lens assemblies for all tubes 10 can be formed from a single plastic injection-molded part. Figure 3shows a lens arrangement for four tubes 10, whereby the number of lens arrangements can of course also be adapted to a different number of tubes 10.

[0066] The Figures 4a, 4b show another example of an optical unit 7. This again has a tube 10 consisting of two tube elements 12a, 12b, which can be joined together in the forming direction B.

[0067] The embodiment according to the Figures 4a, 4b differs from the design of the Figure 2 in that the tube elements 12a, 12b are connected by film joints 20 ( Figure 5 ). The tube elements 12a, 12b with the film joints 20 are formed from a single plastic injection-molded part. Unlike the tube elements 12a, 12b, the film joints 20 are flexible, i.e., bendable, which is achieved by suitable perforations or material constrictions.

[0068] How Figure 5As shown, the tube elements 12a, 12b can be folded together in directions C. For this purpose, the tube elements 12a, 12b are folded according to the embodiment shown. Figure 2 connected to tube 10.

[0069] In the area of ​​the upper edge of the tube 10, in which the film hinges 20 are arranged, the aperture 13 with the aperture opening 13a is again located. In further accordance with the embodiment according to Figure 2 The field stop 16 with aperture 16a is located again at the lower edge of the tube 10.

[0070] The optical unit 7 according to the Figures 4a, 4b The optical element is a lens 17 in a lens plane.

[0071] In addition to the embodiment according to Figure 2 are three of the embodiments of the Figures 4a, 4b Microstructures 21 forming light traps are provided which prevent obliquely incident light from reaching the receiver 6. List of reference symbols

[0072] (1) Light curtain (2a,b) Housing (3) Light beam (4) Transmitter (5) Optical unit (6) Receiver (7) Optical unit (8) Transmitter control (9) Evaluation unit (10) Tube (11) Circuit board (12a,b) Tube element (13) Aperture (13a) Aperture opening (14) Intermediate aperture (14a) Aperture opening (15) Intermediate aperture (15a) Aperture opening (16) Field stop (16a) Aperture opening (17) Lens (17a-c) Lens (18a,b) Bridge (19) Bridge (20) Film hinge (21) Microstructure (A) Optical axis (B) Forming direction

Claims

1. An optical sensor for detecting objects in a monitoring area with at least one transmitter (4) having an optical axis (A) and emitting light beams and with at least one receiver (6) having an optical axis (A), which is designed to receive light beams (3), the transmitter (4) and the receiver (6) each being assigned a tube (10) whose longitudinal axis runs in the direction of the optical axis of the transmitter (4) or receiver (6), the tube (10) consisting of a plurality of tube elements (12a, 12b) which can be joined to the tube (10) transversely to the optical axis, and wherein the tube (10) forms at least one element plane in which an optical element is present, wherein the tube (10) has one or more element planes in the form of aperture planes (14, 15), in each of which an aperture (13) is present and wherein the or each aperture (13) is a component of the tube elements (12a, 12b), characterised in that the tube elements (12a, 12b) of the tube 10 are connected via one or more flexible joints.

2. An optical sensor according to claim 1, characterised in that the tube elements (12a, 12b) of the tube (10) are in the form of injection-moulded plastic parts.

3. An optical sensor according to one of claims 1 or 2, characterised in that fixing means are provided by means of which the tube elements (12a, 12b) can be connected.

4. An optical sensor according to any one of claims 1 to 3, characterised in that the or each tube (10) has fastening means for fastening to a support.

5. An optical sensor according to claim 4, characterised in that the fastening means are designed as latching or clip means.

6. An optical sensor according to one of claims 4 or 5, characterised in that the base is formed by a printed circuit board (11) on which transmitter (4) and / or receiver (6) are arranged.

7. An optical sensor according to one of claims 1 to 6, characterised in that each aperture (13, 16) at least partially encloses an aperture opening.

8. An optical sensor according to one of claims 1 to 7, characterised in that diaphragms (13, 16) in the form of intermediate apertures (14, 15) are present.

9. An optical sensor according to claim 8, characterised in that apertures (13, 16) or intermediate apertures (14, 15) are offset in height.

10. An optical sensor according to claim 9, characterised in that vertically offset apertures (13, 16) or intermediate apertures (14, 15) overlap.

11. An optical sensor according to one of claims 1 to 10, characterised in that the inner wall of the tube (10) has microstructures (21) forming light traps.

12. An optical sensor according to one of claims 1 to 11, characterised in that this is a light curtain (1).

13. An optical sensor according to claim 12, characterised in that the light curtain (1) has a series arrangement of transmitters (4), each transmitter (4) being assigned a tube (10), these tubes (10) forming a tube arrangement on the transmitter side, and in that the light curtain (1) has a series arrangement of receivers (6), each receiver (6) being assigned a tube (10), these tubes (10) forming a tube arrangement on the receiver side.

14. An optical sensor according to one of claims 1 to 13, characterised in that it is a safety sensor.