Optical sensor

Abstract

Optical sensor (1) with a housing (2) in which at least one sensor component designed for object detection and electronic components are arranged, wherein at least one electronic component generates an output signal depending on sensor signals of the sensor component, characterized in that sections of the housing (2) made of thermally conductive material are connected to an electronic component and / or the sensor component via thermally conductive layers (15), so that heat generated in these is dissipated to the outside via the housing (2).

Description

[0001] The invention relates to an optical sensor.

[0002] Such optical sensors are generally used to detect objects. For this purpose, the optical sensor incorporates sensor components and electronic components integrated into a housing.

[0003] Typically, the optical sensor has as sensor components a transmitter unit that emits light rays and a receiver unit that receives light rays reflected back from an object.

[0004] At least one of the electronic components forms an evaluation unit in which an output signal is generated depending on sensor signals from the sensor component.

[0005] The optical sensor can be used to detect objects in a surveillance area. In this case, the optical sensor generates an object detection signal as an output signal, which indicates whether or not an object is present in the surveillance area.

[0006] The optical sensor can also be used, in particular, to detect codes such as barcodes or 2D codes, i.e., the optical sensor then functions as a code reader. In this case, the code information contained in the sensor signals from the receiver unit is decoded in the evaluation unit, so that the detected code can be output as an output signal.

[0007] Particularly in an embodiment in the form of a code reader, the receiver unit is designed in the form of an image sensor, i.e., an imager. Advantageously, the image sensor is associated with a transmitter unit in the form of a lighting unit, which, for example, comprises a multiple arrangement of light-emitting diodes.

[0008] The image sensor is preferably connected to a computer unit forming the evaluation unit via MIPI lines. MIPI lines are serial interface lines standardized by the MIPI consortium that offer high and fast data transfer rates.

[0009] One problem here is that such MIPI lines are highly susceptible to interference at longer lengths.

[0010] Another general problem with optical sensors is that their interior is heated by the heating power of the electronic components and sensor components, which can lead to functional impairments or even failures of the optical sensor.

[0011] The invention is based on the object of designing an optical sensor of the type mentioned above in such a way that it has a low susceptibility to interference.

[0012] 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.

[0013] The invention relates to an optical sensor comprising a housing in which at least one sensor component designed for object detection and electronic components are arranged. At least one electronic component generates an output signal depending on sensor signals from the sensor component. Sections of the housing made of thermally conductive material are connected to an electronic component and / or the sensor component via thermally conductive layers, so that heat generated in these sections is dissipated to the outside via the housing.

[0014] A key advantage of the invention is that the heat generated in the interior due to the heating power of the sensor and electronic components can be efficiently dissipated to the outside, i.e., to the environment of the optical sensor, via the housing. This prevents overheating of the electronic and sensor components and the resulting malfunctions or even failures of the optical sensor.

[0015] A key aspect of the invention is that the housing is made entirely or at least partially of a thermally conductive material, i.e., a material with high thermal conductivity. This allows heat to be dissipated to the outside via thermal conduction through the housing of the optical sensor.

[0016] Another key aspect of the invention is that the housing structure of the optical sensor housing is designed such that housing segments extend directly to electronic components and / or sensor components and are connected to them via thin thermally conductive layers. This achieves direct heat transfer from the electronic component or sensor component via the thermally conductive layer to the housing segment and thus to the entire housing, ensuring direct dissipation of heat generated in the area of ​​the electronic component or sensor component.

[0017] The housing segment(s) may protrude from the inside of the housing walls and from there be guided directly to the electronic components or sensor components.

[0018] Particularly advantageous is that the housing is made of a thermally conductive metallic material.

[0019] Metallic materials have very high thermal conductivity values ​​and are therefore particularly suitable for dissipating heat from the interior of the housing.

[0020] According to an advantageous embodiment, the metallic material is a zinc or aluminum die-cast.

[0021] Housings made of zinc or aluminum die-cast parts can be manufactured efficiently. Another advantage is that they can also be used to create complex housing geometries.

[0022] The thermally conductive layers generally have thin layers, ideally in the µm range. This ensures good heat transfer to the housing structures.

[0023] It is advantageous to use a thermal pad or thermal paste as the thermal conduction layer.

[0024] The circuit board, as a large, flat component, generates considerable heat during operation of the optical sensor, especially other electronic components located on the circuit board.

[0025] By directly coupling the circuit board via the heat-conducting layers to the housing cover or a housing wall, which are both heat-conducting, heat generated in the area of ​​the circuit board can be efficiently dissipated from the interior of the housing.

[0026] In general, the surface of the circuit board itself or the surface of another electronic component placed on the circuit board can be directly connected to the thermally conductive layer.

[0027] According to a further advantageous embodiment, a heat sink, which is made of thermally conductive material and is a component of the housing, opens out on the inner sides of housing wall segments made of thermally conductive material. The heat sink is in contact with at least one electronic component via at least one thermally conductive layer.

[0028] In particular, the heat sink is in contact with the top side of the circuit board via at least one thermally conductive layer.

[0029] The geometry of the heat sink as a component of the housing is optimized in such a way that it is directly connected to the sensor components of an electronic component to be cooled, in particular to the circuit board, so that heat can be directly dissipated via it and led outwards via the housing wall.

[0030] The heat sink has a sufficiently large surface area so that large amounts of heat can be dissipated.

[0031] In this case too, the thermally conductive layer can be directly connected to a surface of the circuit board or another electronic component placed on it.

[0032] According to an advantageous embodiment, the optical sensor comprises an image sensor and a lens as sensor components.

[0033] The image sensor, ie imager, can be formed, for example, by a matrix-shaped CMOS or CCD array, the lens consists in a known manner of a lens arrangement.

[0034] In this case, the optical sensor can be designed as a code reader that can read barcodes and 2D codes.

[0035] Advantageously, the image sensor and lens are mounted on top of the circuit board.

[0036] Advantageously, the heat sink has cooling fins that run radially towards the lens surrounding the image sensor.

[0037] The lens and the image sensor are mounted in a tube that is fixed in position by means of the cooling fins.

[0038] The heat sink with the cooling fins thus fulfills a dual function in that it not only serves to dissipate heat, but also to fix the position of the lens with the image sensor.

[0039] The tube is conveniently connected to the cooling fins by a clamp connection or a screw connection.

[0040] Both variants lead to a secure fixation of the tube in its position.

[0041] According to an advantageous embodiment, the heat sink has centering pins that can be inserted into holes in the circuit board.

[0042] The centering pins are used to position the image sensor with the lens relative to a hole in the circuit board that forms a camera mount.

[0043] The holes are machined into the circuit board in the desired position in advance, particularly with the assistance of image processing, so that a highly precise positioning of the image sensor in the camera mount is ensured by subsequently inserting the centering pins.

[0044] According to an optional embodiment, sensor components in the form of light-emitting diodes that emit light rays are mounted on the top side of the circuit board, forming a lighting unit.

[0045] The illumination units are thus arranged on the same side of the circuit board as the image sensor with the lens, preferably directly adjacent to them. The light beams emitted by the LEDs illuminate the image sensor's field of view.

[0046] The LEDs are advantageously located in recesses in the cooling fins.

[0047] The recesses of the heat sink serve as a diaphragm and prevent crosstalk, i.e. direct radiation of the light rays from the LEDs into the lens and the image sensor.

[0048] Furthermore, the heat sink can fulfill an additional function in that it carries a lens plate which serves to shape the light beams emitted by the LEDs.

[0049] According to an advantageous embodiment, a computer unit forming an electronic component is mounted on the underside, forming an evaluation unit in which the output signal is generated. The computer unit and the image sensor are arranged opposite each other on either side of the circuit board.

[0050] In particular, the computing unit is a microcontroller.

[0051] The positioning of the computer unit on the underside of the circuit board is optimally adapted to the positioning of the image sensor on the top, so that the image sensor can be connected to the computer unit via very short cables.

[0052] This is particularly advantageous when the computer unit and the image sensor are connected via MIPI lines.

[0053] Because the MIPI lines can be very short, unwanted interference during data transmission via these MIPI lines is avoided.

[0054] The invention is explained below with reference to the drawings. They show: Fig. 1: Embodiment of the optical sensor according to the invention. Fig. 2: Individual representation of components of the optical sensor according to Fig. 1. Fig. 3: Schematic sectional view of the optical sensor according to Fig. 1.

[0055] Fig. 1 shows an embodiment of the optical sensor 1 according to the invention. Components of the optical sensor are shown in Fig. 2 shown. Fig. 3 is a highly schematic, not to scale sectional view of the optical sensor 1 along a narrow side of the optical sensor 1.

[0056] In this case, the optical sensor 1 is designed as a code reader with which barcodes and 2D codes can be detected and decoded.

[0057] The optical sensor 1 has a housing 2 in which the electronic components and sensor components of the optical sensor 1 are integrated. The housing 2 is made of a material with high thermal conductivity. For this purpose, the housing 2 is made of a metallic material. In this case, the housing 2 consists of two zinc or aluminum die-cast parts, namely a housing body 2a and a housing cover 2b, which closes off an opening on the underside of the housing body 2a.

[0058] A connector cover 3 with electrical connections 4 is attached to the side of the housing body 2a. The connector cover 3 can also be made of a zinc or aluminum die-cast part.

[0059] The central electronic component is a printed circuit board 5, which is attached to the inside of the housing walls 6 of the housing 2.

[0060] Mounted on the top side of the circuit board 5 are an image sensor 7 and a lens 8 associated with it. The lens 8 is housed in a tube 9, which is attached to the top side of the circuit board 5. The tube 9 is made of opaque material and is open at its top.

[0061] The image sensor 7 preferably consists of a matrix-shaped CCD or CMOS array. The lens 8 consists of an array of lenses.

[0062] Mounted on the top side of the circuit board 5 are light-emitting LEDs 10, which form an illumination unit. The light rays from the illumination unit illuminate the field of view of the image sensor 7.

[0063] The light-emitting diodes 10 are assigned a lens plate 11 with lens elements 12, by means of which the light beams are shaped.

[0064] A window 13 transparent to the light rays is inserted into an opening on the top of the housing 2.

[0065] A microcontroller 14 is mounted on the underside of the circuit board 5. It forms a computing unit and thus an electronic component of the optical sensor 1. Other processors can also be provided instead of the microcontroller 14. The microcontroller 14 is located directly opposite the image sensor 7. The image sensor 7 is connected to the microcontroller 14 via MIPI lines (not shown). Sensor signals from the image sensor 7 are read into the microcontroller 14 via the MIPI lines, which forms an evaluation unit for evaluating the sensor signals.

[0066] To detect codes, the light beams from LEDs 10 are guided through the window 13 of the optical sensor 1 into a detection zone. Light beams reflected by a code are guided via the window and lens 8 to the image sensor 7. The sensor signals generated in the image sensor 7, which contain the code information, are evaluated in the microcontroller 14 to decode the code. The decoded code is output by the optical sensor as an output signal.

[0067] According to the invention, the housing 2 made of thermally conductive material serves to dissipate heat from the interior of the optical sensor 1.

[0068] For this purpose, sections of the housing 2 are connected directly, ie without intervening air gaps, to electronic components or sensor components via heat-conducting layers 15, so that heat generated there is dissipated via the heat-conducting layer 15 and the housing 2 and led to the outside, ie into the environment of the optical sensor 1.

[0069] The thermally conductive layers 15 have layer thicknesses in the µm range and can consist of thermally conductive pads or thermally conductive pastes.

[0070] In the present case, direct contact is made with the housing cover 2b via heat-conducting layers 15 on the underside of the printed circuit board 5 or the microcontroller 14, so that heat generated in the printed circuit board 5 or the microcontroller 14 is dissipated to the outside via the heat-conducting layers 15 present there and the housing cover 2b in contact with the heat-conducting layers 15.

[0071] Furthermore, a heat sink 16 is provided on the inner sides of the housing walls 6, which heat sink is formed integrally with these housing walls 6 and is a component of the housing body 2a.

[0072] The heat sink 16 extends in a plane perpendicular to the housing walls 6, where it terminates. The heat sink 16 is dimensioned such that it rests flat on the circuit board 5, with additional thermally conductive layers 15 located between the circuit board 5 and the heat sink 16. Thus, heat generated in the area of ​​the circuit board 5 is dissipated directly to the outside via the thermally conductive layers 15, the heat sink 16, and the housing walls 6.

[0073] The heat sink 16 has cooling fins 17 that extend radially toward the tube 9. The cooling fins 17 serve to fix the position of the tube 9, with the tube 9 being secured to the cooling fins 17 by means of a clamp connection. Alternatively, the heat sink 16 can form an annular segment with an internal thread into which the tube 9 is screwed.

[0074] As is particularly evident from Fig. As can be seen in Figure 3, the heat sink 16 has recesses 18 in which the LEDs 10 are mounted. Additional (not shown) heat-conducting layers 15 may be present in the area of ​​the recesses 18, creating a heat-conducting connection between the LEDs 10 and the heat sink 16.

[0075] According to an advantageous further development, the heat sink 16 can have centering pins which can be inserted into holes in the printed circuit board 5.

[0076] The image sensor 7 with the lens 8 is positioned by means of the centering pins relative to a hole in the circuit board 5 forming a camera receptacle.

[0077] The centering pins and holes are not shown in the figures. List of reference symbols 1 optical sensor 2 housings 2a Housing body 2b Housing cover 3 plug cover 4 Connection 5 circuit board 6 Housing wall 7 image sensor 8 lens 9 tube 10 LEDs 11 Lens plate 12 lens elements 13 windows 14 microcontrollers 15 Thermally conductive layer 16 heat sinks 17 cooling fins 18 recess

Claims

[1] Optical sensor (1) with a housing (2) in which at least one sensor component designed for object detection and electronic components are arranged, wherein at least one electronic component generates an output signal depending on sensor signals of the sensor component, characterized by that sections of the housing (2) consisting of thermally conductive material are connected to an electronic component and / or the sensor component via thermally conductive layers (15), so that heat generated in these is dissipated to the outside via the housing (2). [2] Optical sensor (1) according to claim 1, characterized by that the housing (2) is made of a thermally conductive metallic material. [3] Optical sensor (1) according to claim 2, characterized by that the metallic material is a zinc or aluminum die-cast. [4] Optical sensor (1) according to one of claims 1 to 3, characterized bythat a thermally conductive pad or a thermally conductive paste is provided as the thermally conductive layer (15). [5] Optical sensor (1) according to one of claims 1 to 4, characterized by that a printed circuit board (5) is provided as the electronic component, the underside of which is connected via at least one heat-conducting layer (15) to a housing cover (2b) made of heat-conducting material or to a housing wall (6) made of heat-conducting material. [6] Optical sensor (1) according to one of claims 1 to 5, characterized by that a heat sink (16) which consists of thermally conductive material and is a component of the housing (2) opens out on the inside of housing wall segments consisting of thermally conductive material, and that the heat sink (16) is in contact with at least one electronic component via at least one thermally conductive layer (15). [7] Optical sensor (1) according to one of claims 5 or 6, characterized bythat the heat sink (16) is in contact with the top side of the circuit board (5) via at least one heat-conducting layer (15). [8] Optical sensor (1) according to one of claims 1 to 7, characterized by that the sensor components are an image sensor (7) and a lens (8). [9] Optical sensor (1) according to claim 8, characterized by that the image sensor (7) and the lens (8) are mounted on the top of the circuit board (5). [10] Optical sensor (1) according to one of claims 8 or 9, characterized by that the heat sink (16) has cooling fins (17) which run radially towards the lens (8) surrounding the image sensor (7). [11] Optical sensor (1) according to one of claims 8 to 10, characterized by that the lens (8) and the image sensor (7) are mounted in a tube (9) which is fixed in position by means of the cooling fins (17). [12] Optical sensor (1) according to claim 11, characterized bythat the tube (9) is connected to the cooling fins (17) by a clamp connection or a screw connection. [13] Optical sensor (1) according to one of claims 5 and 6, characterized by that the heat sink (16) has centering pins which can be inserted into holes in the printed circuit board (5). [14] Optical sensor (1) according to claim 13, characterized by that by means of the centering pins the image sensor (7) with the lens (8) is positioned relative to a hole in the circuit board (5) forming a camera receptacle. [15] Optical sensor (1) according to one of claims 8 to 13, characterized by that light-emitting diodes (10) forming sensor components and emitting light rays are mounted on the top side of the printed circuit board (5), which form a lighting unit. [16] Optical sensor (1) according to claim 15, characterized by that the light-emitting diodes (10) are located in recesses (18) of the cooling fins (17). [17] Optical sensor (1) according to one of claims 5 to 16, characterized by that on the underside of the printed circuit board (5) there is mounted a computer unit forming an electronic component, which forms an evaluation unit in which the output signal is generated. [18] Optical sensor (1) according to claim 17, characterized by that the computer unit is a microcontroller (14). [19] Optical sensor (1) according to claim 18, characterized by that the computer unit and the image sensor (7) are connected via MIPI lines. [20] Optical sensor (1) according to one of claims 1 to 19, characterized by that this is a code reader.

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