Light grid

Abstract

Light grid (1) for detecting openings in objects (2) within a monitoring area (3), comprising a transmitting unit (4) with light emitters (5) emitting light beams, a receiving unit (6) with light receivers (7) receiving light beams, and a control and evaluation unit (8) in which object detection signals are generated depending on received signals at the outputs of the light receivers (7), wherein an object detection signal is generated by the control and evaluation unit (8) when a beam is interrupted in the monitoring area (4), characterized in that at least one light scattering element (9) is arranged between the object (2) and the receiving unit (6), whereby light penetrating through openings (10) in the object (2) is scattered by the light scattering element (9) and falls onto at least one light receiver (7), wherein blind areas of the light grid, i.e., blind spots between the light receivers,are eliminated, thereby generating an object hole detection signal.

Description

[0001] The present invention relates to a light grid for detecting openings in objects within a surveillance area according to the preamble of claim 1 and to a method for detecting openings in objects within a surveillance area using a light grid according to the preamble of claim 17.

[0002] DE10307770B4 discloses a light grid for hole detection in material webs.

[0003] DE102012101368B4 discloses a light grid for hole detection in material webs, whereby different threshold values ​​can be provided in different areas.

[0004] US Pat. No. 5,798,531 A discloses a pinhole detection system that detects small holes in fast-moving webs of material. An array of LEDs is pulsed by an emitter aligned with an array of photocells positioned to detect the light emitted by the emitter. The receiver sends a signal to a processing unit when light is detected. The pinhole detection system may include an automatic shutter mechanism that automatically adjusts the system to the width of the material being scanned.

[0005] DE 20 2005 003 051 U1 discloses an optoelectronic sensor device, in particular light barriers or light grids, for detecting an object with one or more light transmitters on one side of a monitoring path and one or more light receivers corresponding to the light transmitter on the other side of the monitoring path, wherein the light transmitter(s) emits a light beam with a transmission cone angle into the monitoring path and the light receiver(s) receives the light beam within a reception cone angle, converts it into an electrical quantity and feeds it to an evaluation circuit which emits a detection signal in the event of the presence of an object in the monitoring path, wherein the transmission cone angle of the emitted light beam and / or the reception cone angle of the light receiver can be changed with an attachment lens which can be additionally attached to the light transmitter and / or the light receiver.

[0006] DE 103 35 263 A1 relates to an optical sensor for detecting objects in a surveillance area, comprising a transmitter emitting transmitted light beams, a receiver receiving received light beams, and an evaluation unit in which the received signals at the receiver output are evaluated to generate an object detection signal. A light-scattering film is assigned to the transmitter and / or the receiver to expand the transmitted light beams or the received light beams, respectively.

[0007] WO 2010 / 057553 A1 discloses an optical light scattering unit having a transparent scattering body and having at least one light source, the emitted light of which is coupled into the scattering body and, as it passes through, is scattered by inhomogeneities present in the interior, wherein the inhomogeneities are formed as surface markings and / or subsurface markings introduced into the scattering body by electromagnetic radiation.

[0008] An object of the invention is to provide a light grid to detect small object holes over the entire area along the light grid and to detect fast-moving objects with object holes.

[0009] The object is achieved according to claim 1 by a light grid for detecting openings in objects within a surveillance area, with a transmitting unit with light transmitters emitting light beams, with a receiving unit with light receivers receiving light beams and with a control and evaluation unit in which object detection signals are generated as a function of received signals at the outputs of the light receivers, wherein in the event of a beam interruption in the surveillance area an object detection signal is generated by the control and evaluation unit, wherein at least one light scattering element is arranged between the object and the receiving unit, whereby light which penetrates through openings in the object is scattered by the light scattering element and falls on at least one light receiver, whereby an object hole detection signal is generated.

[0010] The object is further achieved according to claim 17 with a method for detecting openings in objects within a surveillance area with a light grid, with a transmitting unit with light transmitters emitting light beams, with a receiving unit with light receivers receiving light beams and with a control and evaluation unit in which object detection signals are generated as a function of received signals at the outputs of the light receivers, wherein in the event of a beam interruption in the surveillance area an object detection signal is generated by the control and evaluation unit, wherein at least one light scattering element is arranged between the object and the receiving unit, whereby light which penetrates through openings in the object is scattered by the light scattering element and falls on at least one light receiver, whereby an object hole detection signal is generated.

[0011] The transmitting unit and the receiving unit are each arranged in a housing and spaced apart. The object with the holes to be detected is placed between the transmitting unit and the receiving unit.

[0012] The object hole detection signal or object opening detection signal is generated by the control and evaluation unit based on the light received at the light receivers. The object detection signal and the object hole detection signal are generated and reported, for example, by switching elements or an interface.

[0013] According to the invention, a light grid is extended with a light scattering element or a light scattering element in order to be able to detect small object holes or object openings over the entire area along the light grid and to detect fast-moving objects with object holes.

[0014] Blind areas of the light grid, i.e., blind spots between the light receivers or channels, are eliminated by placing the light scattering element between the object to be detected with a hole or opening and the receiving unit. This scatters the transmitted light in different directions after passing through the opening or hole, and a portion of the signal light reaches an active light receiver or receiving element.

[0015] For example, the light emitters and the light receivers are arranged equidistantly, so that the light beams between the light emitter and the light receiver form a resolution of the light grid. Lenses, particularly converging lenses, can also be arranged in front of the light emitters and / or the light receivers for beam shaping.

[0016] In a further development of the invention, the light-scattering element is part of the receiving unit. The light-scattering element is part of the receiving unit, i.e., is arranged on the housing of the receiving unit. For example, the light-scattering element is attached to the outside of the housing of the receiving unit. For example, the light-scattering element is arranged and fixed directly on a front panel of the receiving unit. For example, the light-scattering element is glued to the front panel or attached by means of clips. For example, the light-scattering element can be attached to the receiving unit by means of fastening means, such as fastening screws.

[0017] In a further development of the invention, the light-diffusing element is a diffusing film. The diffusing film is made of plastic, for example. The diffusing film is designed so thin that it is flexible and can be wound onto a roll for installation on the receiving unit. For example, the diffusing film is glued to the windshield.

[0018] In a further development of the invention, the light-scattering element forms a front panel of the receiving unit. The front panel protects the optoelectronic sensor from environmental influences. The light-scattering element is integrally connected to the front panel. The front panel and the light-scattering element form a single unit. This eliminates the need to manufacture any additional components. This allows the receiving unit to be manufactured like a conventional receiving unit.

[0019] In a further development of the invention, the light-scattering element has a microstructure. The microstructure has a geometry that creates the light scattering. The microstructure is reliably defined by a tool. For example, the material of the light-scattering element is a thermoplastic elastomer. For example, the microstructure is embossed into the light-scattering element using a stamp.

[0020] The microstructure can, for example, be structural parts of flatly arranged cones, truncated cones, pyramids, truncated pyramids, truncated cylinders, pins, or similar. The structure or microstructure has, for example, structural parts with a length of 10 µm to 1 mm, in particular 20 µm to 200 µm.

[0021] In a further development of the invention, the microstructure has a stochastic structure. The stochastic structure forms a random microstructure pattern. The stochastic structure is reliably specified, for example, by a tool.

[0022] For example, the material of the light-scattering element is a thermoplastic elastomer. The stochastic microstructure is embossed into the light-scattering element using a stamp.

[0023] The stochastic microstructure can, for example, be structural parts of flatly arranged cones, truncated cones, pyramids, truncated pyramids, truncated cylinders, pins, or similar. The stochastic microstructure has, for example, structural parts with a length of 10 µm to 1 mm, particularly 20 µm to 200 µm.

[0024] In a further development of the invention, the microstructure has a lens structure. The lens structure can be, for example, a microlens structure. In particular, the lens structure is a diverging lens, i.e., concave or biconcave microlens, with a plurality of such lenses arranged flatly on the light-scattering element. The microlenses have, for example, a diameter of 10 µm to 1 mm, in particular of 20 µm to 200 µm.

[0025] In a further development of the invention, the microstructure has a prism structure. The prism structure can, for example, be a microprism structure. A plurality of such microprisms are arranged flatly on the light scattering element. The microprisms have, for example, a side length of 10 µm to 1 mm, in particular of 20 µm to 200 µm.

[0026] In a further development of the invention, the microstructure has a cylindrical lens structure. The cylindrical lens structure can, for example, be a microcylindrical lens structure. A plurality of such microcylindrical lenses are arranged flatly on the light scattering element. The microcylindrical lenses have, for example, a width of 10 µm to 1 mm, in particular of 20 µm to 200 µm.

[0027] In a further development of the invention, the light scattering element has scattering particles in the volume of the scattering light element. The scattering particles can be, for example, micro-bodies that are spatially distributed within the scattering element. For example, the micro-bodies are bodies with any irregular shape, bodies with geometric shapes, and / or bodies with three-dimensional shapes. For example, the scattering particles are microspheres. A large number of such scattering particles are spatially arranged within the light scattering element. The scattering particles have, for example, a width or length of 10 µm to 1 mm, in particular of 20 µm to 200 µm.

[0028] In a further development of the invention, the light scattering element comprises scattering means designed to scatter light only in one direction. This allows the expansion of the scattered light to be limited in only one direction.

[0029] For example, the scattering agent is a cylindrical lens structure. The cylindrical lens structure can be, for example, a microcylindrical lens structure. A plurality of such microcylindrical lenses are arranged flatly on the light scattering element.

[0030] In a further development of the invention, one direction is along the receiving unit. This ensures that light scattering occurs only in the direction along the receiving unit.

[0031] For example, the detection area in the y-direction, a direction parallel to the light grid's extension, is enlarged by the light scattering element. This allows the opening or hole moving in the z-direction to be detected even outside the direct field of view of the light grid. This means that the opening or hole can be detected even if the opening is smaller than the resolution of the light grid. This means that an opening located directly between two light receivers is also detected, or an opening that is not directly in front of a light receiver is detected.

[0032] In a further development of the invention, one direction is perpendicular to the receiving unit. This ensures that light scattering occurs only in the direction perpendicular to the receiving unit.

[0033] For example, the detection area in the z-direction, a direction perpendicular to the light grid's extension, is enlarged by the light scattering element. This allows the opening or hole moving in the z-direction to be detected even outside the direct field of view of the light grid. This means that the activity of an active light receiver can be utilized over a longer period of time.

[0034] For example, the detection range of a light grid without a light scattering element is defined by the aperture of the optics; a typical value here is a lens diameter of, for example, 5 mm. If the light scattering element has a size of, for example, 50 mm in the z-direction, i.e., perpendicular to a longitudinal axis of the light grid housing, the object can travel ten times faster.

[0035] In a further development of the invention, the light scattering element has scattering means which are designed to form a light scattering in two mutually orthogonal directions.

[0036] For example, the detection area is enlarged in the z-direction, in a direction perpendicular to the light grid's extension, and in a direction along the light grid's extension by the light scattering element. This allows the opening or hole moving in the z-direction to be detected even outside the direct field of view of the light grid. This means that the activity of an active light receiver can be utilized over a longer period of time.

[0037] The opening or hole can be detected even if it's smaller than the resolution of the light grid. This means that a hole located directly between two light receivers can be detected, or a hole that's not directly in front of a light receiver can be detected. In a further development of the invention, several light-scattering elements are cascaded one behind the other. This improves the light-scattering effect and allows the light to be scattered more widely over a shorter light path. The cascaded light-scattering elements can be designed in different ways according to the above principles.

[0038] In a further development of the invention, the light scattering element is designed to be remitting and / or reflective. The light changes direction after remission or reflection. This allows the receiving side or the receiving unit to be designed more compactly.

[0039] The invention will be explained below with reference to further advantages and features, using exemplary embodiments, with reference to the accompanying drawings. The figures of the drawing show: Fig. 1 a light grid according to the state of the art; Fig. 2 to 13 each show a light grid according to the invention.

[0040] In the following figures, identical parts are provided with identical reference numerals.

[0041] Fig. 1 shows a prior art light grid 1 for detecting objects 2 within a surveillance area 3, comprising a transmitting unit 4 with light transmitters 5 emitting light beams, a receiving unit 6 with light receivers 7 receiving light beams, and a control and evaluation unit 8 in which object detection signals are generated depending on received signals at the outputs of the light receivers 7. If a beam is interrupted in the surveillance area 3, the object detection signal is generated by the control and evaluation unit 8. The light passing through the opening 10 is not detected by the light receivers of the receiving unit, and the object is thereby detected, and an object detection signal is generated. The opening or hole is not detected.

[0042] Fig. 2 shows a light grid 1 according to the invention for detecting openings in objects 2 within a surveillance area 3, with a transmitting unit 4 with light transmitters 5 emitting light beams, with a receiving unit 6 with light receivers 7 receiving light beams and with a control and evaluation unit 8, in which object detection signals are generated as a function of received signals at the outputs of the light receivers 7, wherein in the event of a beam interruption in the surveillance area 3 the object detection signal is generated by the control and evaluation unit 8, wherein at least one light scattering element 9 is arranged between the object 2 and the receiving unit 6, whereby light which penetrates through openings 10 in the object 2 is scattered by the light scattering element 9 and falls on at least one light receiver 7, whereby an object hole detection signal is generated.

[0043] The transmitting unit 4 and the receiving unit 6 are each arranged in a housing 20 and spaced apart. The object 2 with the openings 10 or holes to be detected is arranged between the transmitting unit 4 and the receiving unit 6.

[0044] The light grid 1 is extended with a light scattering element 9 or a light scattering element in order to be able to detect small object holes or openings 10 in the object 2 over the entire area along the light grid 1 and to detect fast-moving objects 2 with object holes or openings 10.

[0045] Blind areas of the light grid 1, i.e., blind spots between the light receivers 7 or the channels, are eliminated by placing the light scattering element 9 between the object 2 to be detected with the opening 10 or hole and the receiving unit 6. As a result, the transmitted light is scattered in different directions after passing through the opening 10, and a portion of the signal light reaches an active light receiver 7 or receiving element.

[0046] For example, the light transmitters 5 and the light receivers 7 are each arranged equidistantly, so that the light beams between the light transmitter 5 and the light receiver 7 form a resolution of the light grid 1.

[0047] According to Fig. 3, the light-scattering element 9 is part of the receiving unit 6. The light-scattering element 9 is part of the receiving unit 6, i.e., is arranged on the housing 20 of the receiving unit 6. For example, the light-scattering element 9 is attached externally to the housing 20 of the receiving unit 6. For example, the light-scattering element 9 is arranged and fixed directly on a front panel 12 of the receiving unit 6. For example, the light-scattering element 9 is glued to the front panel 12 or fastened by means of clips. For example, the light-scattering element 9 can be attached to the receiving unit 6 by means of fastening means, such as fastening screws. According to Fig. 4, the light-scattering element 9 is a scattering film 11. The scattering film 11 is made of plastic, for example. The scattering film 11 is designed to be so thin that it is flexible and can be wound onto a roll for installation on the receiving unit 6. For example, the scattering film 11 is glued to the windshield 12.

[0048] According to Fig. 5, the light-scattering element 9 forms a front panel 12 of the receiving unit 6. The light-scattering element 9 is integrally connected to the front panel 12. The front panel 12 and the light-scattering element 9 form a single unit. This eliminates the need to manufacture any additional components. The receiving unit 6 can therefore be manufactured like a conventional receiving unit 6.

[0049] According to Fig. 6, the light scattering element 9 has a microstructure 13. The microstructure 13 has a geometry that forms the light scattering.

[0050] The microstructure 13 can, for example, be structural parts of, for example, flatly arranged cones, truncated cones, pyramids, truncated pyramids, truncated cylinders, pins or the like.

[0051] The structure or microstructure 13 has, for example, structural parts with a length of 10 µm to 1 mm, in particular of 20 µm to 200 µm.

[0052] According to Fig. 7, the microstructure 13 has a stochastic structure 14. The stochastic structure 14 forms a random microstructure pattern.

[0053] The stochastic microstructure 14 can, for example, be structural parts of, for example, planarly arranged cones, truncated cones, pyramids, truncated pyramids, truncated cylinders, pins or the like.

[0054] According to Fig. 8, the microstructure 13 has a lens structure 15. The lens structure 15 can be, for example, a microlens structure. In particular, the lens structure 15 comprises diverging lenses, i.e., concave or biconcave microlenses, with a plurality of such lenses arranged flatly on the light-scattering element 9.

[0055] According to Fig. 9, the microstructure 13 has a prism structure 16. The prism structure 16 can, for example, be a microprism structure. A plurality of such microprisms are arranged flatly on the light scattering element 9.

[0056] According to Fig. 10, the microstructure 13 has a cylindrical lens structure 17. The cylindrical lens structure 17 can, for example, be a microcylindrical lens structure. A plurality of such microcylindrical lenses are arranged flatly on the light scattering element 9.

[0057] According to Fig. 11, the light scattering element 9 has scattering particles 18 within the volume of the scattering light element 9. The scattering particles 18 can be, for example, micro-bodies that are spatially distributed within the light scattering element 9. For example, the micro-bodies are bodies with any irregular shape, bodies with geometric shapes, and / or bodies with three-dimensional shapes. For example, the scattering particles 18 are microspheres. A plurality of such scattering particles 18 are spatially arranged within the light scattering element 9.

[0058] For example, the light-scattering element 9 has scattering means designed to scatter light only in one direction. This allows the expansion of the scattered light to be limited in only one direction.

[0059] According to Fig. 12, the scattering agent is a cylindrical lens structure 17. The cylindrical lens structure 17 can, for example, be a micro-cylindrical lens structure.

[0060] A plurality of such microcylinder lenses are arranged flatly on the light scattering element 9.

[0061] For example, one direction is along the receiving unit 6. This means that the light scattering only occurs in the direction along the receiving unit 6.

[0062] For example, the detection area is enlarged in the y-direction, i.e., a direction parallel to the light grid's extension, by the light scattering element 9. This allows the opening 10 or hole moving in the z-direction to be detected even outside the direct field of view of the light grid. This means that the opening 10 or hole can be detected even though the hole is smaller than the resolution of the light grid 1. This means that an opening located directly between two light receivers 7 is also detected, or an opening 10 that is not directly in front of a light receiver 7 is detected.

[0063] For example, one direction is perpendicular to the receiving unit 6. As a result, the light scattering only occurs in the direction perpendicular to the receiving unit 6.

[0064] For example, the detection area in the z-direction, i.e., in a direction perpendicular to the light grid's extension, is enlarged by the light scattering element 9. This allows the opening 10, or hole, which moves in the z-direction to be detected even outside the direct field of view of the light grid. This means that the activity of an active light receiver 7 can be utilized over a longer period of time.

[0065] For example, the detection range of a light grid 1 without a light scattering element 9 is defined by the aperture of the optics; a typical value here is a lens diameter of, for example, 5 mm. If the light scattering element 9 has a size of, for example, 50 mm in the z-direction, i.e., perpendicular to a longitudinal axis of the light grid housing, the object can have a speed ten times higher.

[0066] For example, the light scattering element 9 has scattering means which are designed to form a light scattering in two mutually orthogonal directions.

[0067] For example, the detection area is enlarged in the z-direction, i.e. a direction transverse to the light grid extension and in a direction longitudinal to the light grid extension by the light scattering element 9.

[0068] For example, several light scattering elements 9 are cascaded one behind the other. This can improve the light scattering effect and scatter the light more widely over a shorter light path. The cascaded light scattering elements 9 can be designed differently according to the above principles.

[0069] According to Fig.13, the light scattering element 9 is designed to be remitting and / or reflective. The light changes direction after remission or reflection. This allows the receiving side or receiving unit 6 to be designed more compactly. Reference symbol: 1 light grid 2 objects 3 Monitoring area 4 Transmitter unit 5 light transmitters 6 Receiving unit 7 light receivers 8 Control and evaluation unit 9 Light scattering element 10 openings 11 Scatter film 12 Windscreen 13 Microstructure 14 stochastic structure 15 Lens structure 16 Prism structure 17 Cylindrical lens structure 18 scattering particles 20 housings

Claims

[1] Light grid (1) for detecting openings in objects (2) within a monitoring area (3), with a transmitting unit (4) with light transmitters (5) emitting light beams, with a receiving unit (6) with light receivers (7) receiving light beams and with a control and evaluation unit (8) in which object detection signals are generated as a function of received signals at the outputs of the light receivers (7), wherein an object detection signal is generated by the control and evaluation unit (8) in the event of a beam interruption in the monitoring area (4), characterized bythat at least one light scattering element (9) is arranged between the object (2) and the receiving unit (6), whereby light which penetrates through openings (10) in the object (2) is scattered by the light scattering element (9) and falls on at least one light receiver (7), whereby blind areas of the light grid, i.e. blind spots between the light receivers, are eliminated and whereby an object hole detection signal is generated. [2] Light grid (1) according to claim 1, characterized by that the light scattering element (9) is part of the receiving unit (6). [3] Light grid (1) according to one of the preceding claims, characterized by that the light scattering element (9) is a scattering film (11). [4] Light grid (1) according to one of the preceding claims, characterized by that the light scattering element (9) forms a front panel (12) of the receiving unit (6). [5] Light grid (1) according to one of the preceding claims, characterized bythat the light scattering element (9) has a microstructure (13). [6] Light grid (1) according to claim 5, characterized by that the microstructure (13) has a stochastic structure (14). [7] Light grid (1) according to claim 5, characterized by that the microstructure (13) has a lens structure (15). [8] Light grid (1) according to claim 5, characterized by that the microstructure (13) has a prism structure (16). [9] Light grid (1) according to claim 5, characterized by that the microstructure (13) has a cylindrical lens structure (17). [10] Light grid (1) according to one of the preceding claims, characterized by that the light scattering element (9) has scattering particles (18) in the volume of the light scattering element (9). [11] Light grid (1) according to one of the preceding claims, characterized by that the light scattering element (9) has scattering means which are designed to scatter light only in one direction. [12] Light grid (1) according to claim 11, characterized by that one direction is along the receiving unit (6). [13] Light grid (1) according to claim 11, characterized by that one direction is transverse to the receiving unit (6). [14] Light grid (1) according to one of the preceding claims, characterized by that the light scattering element (9) has scattering means which are designed to form a light scattering in two mutually orthogonal directions. [15] Light grid (1) according to one of the preceding claims, characterized by that several light scattering elements (9) are cascaded one behind the other. [16] Light grid (1) according to one of the preceding claims, characterized by that the light scattering element (9) is designed to be remitting and / or reflective. [17] Method for detecting openings in objects (2) within a monitoring area (3) with a light grid (1), with a transmitting unit (4) with light transmitters (5) emitting light beams, with a receiving unit (6) with light receivers (7) receiving light beams and with a control and evaluation unit (8) in which object detection signals are generated as a function of received signals at the outputs of the light receivers (7), wherein an object detection signal is generated by the control and evaluation unit (8) in the event of a beam interruption in the monitoring area (4), characterized bythat at least one light scattering element (9) is arranged between the object (2) and the receiving unit (6), whereby light which penetrates through openings (10) in the object (2) is scattered by the light scattering element (9) and falls on at least one light receiver (7), whereby blind areas of the light grid, i.e. blind spots between the light receivers, are eliminated and whereby an object hole detection signal is generated.

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