Optical sensor

Abstract

Optical sensor (1) with at least one light beam emitting transmitter (3), at least one light beam receiving receiver (4) and an evaluation unit designed for evaluating received signals from the receiver (4), wherein the light beams (2) are guided through at least one sensor window (13) of a housing (6), characterized in that the sensor window (13) consists of a component having various components with which areas of different optical properties are formed for the light beams (2).

Description

[0001] The invention relates to an optical sensor.

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

[0003] For this purpose, such an optical sensor comprises at least one light-emitting transmitter and at least one light-receiving receiver as sensor components. Furthermore, the optical sensor includes an evaluation unit in which an object detection signal is generated from the received signals of the receiver.

[0004] These components of the optical sensor are housed in at least one casing.

[0005] An example of such an optical sensor is an area distance sensor, i.e., a scanning distance sensor. Light beams emitted by the transmitter are deflected by a deflection unit and thus periodically guided within the monitoring area, or the transmitter is rotated using a rotary device. All components of the area distance sensor are housed in a single casing.

[0006] The area distance sensor is used for monitoring the protective field. The evaluation unit generates a binary switching signal as an object detection signal; its switching states indicate whether an object is located within the monitored protective field or not. The distances to the objects can also be measured.

[0007] In order to guide the light rays emitted by the transmitter into the monitoring area and to guide light rays, in particular those reflected by an object in the monitoring area, to the receiver, at least one sensor window must be provided in the housing through which the light rays are guided, i.e. the sensor window is transparent to the light rays in contrast to the housing wall.

[0008] It is known to use apertures in such optical sensors. An aperture associated with the transmitter can shape the light rays emitted by the transmitter. An aperture associated with the receiver can be used to adjust what proportion of the light rays are directed to the receiver. Furthermore, such an aperture can reduce the amount of stray light reaching the receiver.

[0009] In principle, apertures can be mounted as separate components on brackets within the housing. However, this requires increased design complexity, additional assembly steps, and a larger optical sensor form factor.

[0010] It is also known to print apertures onto the sensor window, for example using pad printing. However, this printing method only allows for thin layers to be applied to the sensor window, which can impair the aperture function. Furthermore, printing on curved sensor windows is problematic. Additionally, all surfaces to be printed must be accessible.

[0011] The invention is based on the objective of providing an optical sensor with improved functionality.

[0012] The features of claim 1 are provided to solve this problem. Advantageous embodiments and expedient further developments of the invention are described in the dependent claims.

[0013] The invention relates to an optical sensor with at least one light-emitting transmitter, at least one light-receiving receiver, and an evaluation unit configured to evaluate received signals from the receiver. The light beams are guided through at least one sensor window of a housing. The sensor window consists of a component comprising various elements that create areas with different optical properties for the light beams.

[0014] The optical sensor according to the invention has at least one sensor window which has multiple functionalities.

[0015] The sensor window serves in a known manner as mechanical protection together with the housing, preventing the ingress of dirt, moisture and the like into the interior of the optical sensor.

[0016] In a manner still known, light rays emitted by the transmitter, or light rays directed to the receiver, are guided through the sensor window, which, unlike the housing, is at least partially transparent to the light rays.

[0017] According to the invention, the sensor window consists of only one component, which has areas with different optical properties. These areas enable different functions to be implemented, thereby expanding the functionality of the optical sensor.

[0018] A key advantage here is that additional optical functions can be implemented with just one component, which forms the sensor window. No further components, auxiliary structures, or the like are required.

[0019] Since the component forming the sensor window provides the additional functions on its own, without any further design modifications, the number of individual parts of the optical sensor can be kept to a minimum. This also allows for easy assembly of the optical sensor.

[0020] In general, the sensor window can have areas with different transmission, absorption, reflection, or remission properties.

[0021] This allows a wide variety of functions to be implemented with the component forming the sensor window.

[0022] According to an initial embodiment, the sensor window has several areas that are selectively transparent to light rays of different wavelengths.

[0023] This embodiment is particularly advantageous if the optical sensor has a transmitter that emits light rays in the invisible wavelength range, especially the infrared range, for object detection, and furthermore has an alignment transmitter that emits visible alignment light rays for aligning the optical sensor.

[0024] The sensor window then has a first area that is transparent only to the light beams from the transmitter, and a second area that is transparent only to the alignment light beams. This allows the beam paths of the light beams and alignment light beams to be separated, preventing mutual interference.

[0025] According to a second, particularly advantageous embodiment, areas of the sensor window form an aperture.

[0026] In this case, one area is transparent to the light rays emitted by the transmitter or directed towards the receiver, while at least a second area of ​​the sensor window is opaque to the light rays and thus forms an aperture. The shape of the aperture can be freely chosen with any geometry, so that the aperture function can be optimally adapted to the respective requirements. The aperture can be assigned to the transmitter as a transmitter-side aperture or to the receiver as a receiver-side aperture.

[0027] This embodiment is particularly advantageous when the optical sensor additionally includes window monitoring, which checks the sensor window for contamination that could affect the transmitted or received light. For this purpose, the sensor window is monitored by at least one further optical sensor, consisting of at least one additional transmitter and at least one additional receiver inside the housing and a reflective or retroreflective reference target outside the housing. At least one aperture in the sensor window allows interfering light reflections from outside the sensor to be selectively blocked for window monitoring, so that they do not affect the window monitoring signals.

[0028] In general, the sensor window of the optical sensor is designed such that the areas of the component are volume regions.

[0029] These volume areas, as integral components, exhibit higher stability than coatings on components and define optical properties more precisely and reproducibly than coatings on components.

[0030] Another significant advantage of the areas designed in this way is that they can be incorporated into components with any geometry, especially components with flat or curved surfaces.

[0031] According to an advantageous embodiment, the component forms a housing or a housing part.

[0032] The sensor window takes on an additional function due to the housing design. This reduces the number of parts in the optical sensor and further simplifies its assembly.

[0033] Particularly advantageous is the component which forms the sensor window according to the invention consisting of a cast part or an injection-molded part.

[0034] In this case, the component consists of one or more plastics.

[0035] A casting is produced using a casting process in which a plastic is poured into a mold without pressure.

[0036] In an injection molded part, a plastic is injected under pressure into a mold.

[0037] According to an advantageous embodiment of the sensor window according to the invention, the areas of the component exhibiting different optical properties are made of different materials.

[0038] According to one variant, an insert in a casting or injection-molded part forms a first area. A second area consists of the casting material of the casting or injection-molded part.

[0039] The insert and the plastic casting compound have different optical properties.

[0040] For example, the insert can form a baffle, while the plastic is transparent to the light rays.

[0041] According to another variant, the component is manufactured using a multi-component injection molding or multi-component casting process. Areas of the component consisting of different components exhibit different optical properties.

[0042] The areas of the forming components can consist of different materials.

[0043] For example, a first component can consist of non-transparent plastic and form an aperture, while a second component consists of transparent plastic.

[0044] Different plastics can also be used that are transparent to light in different wavelength ranges.

[0045] Alternatively, the components forming the areas can consist of the same base material with different additives.

[0046] The additives allow for targeted modification of the optical properties. For example, if the base material is a transparent plastic, non-transparent additives such as carbon black particles can be added to it in defined areas to create apertures.

[0047] Finally, it is possible to create different optical properties through different geometries and / or surface roughness of the areas.

[0048] According to an advantageous embodiment, the optical sensor is designed as a safety sensor.

[0049] To meet the normative safety requirements, the safety sensor has a fail-safe design. This is achieved by the safety sensor having a multi-channel evaluation unit for evaluating sensor signals.

[0050] An optical sensor, such as an area distance sensor or a LIDAR sensor, is particularly advantageous.

[0051] Furthermore, it is possible that the optical sensor is a light switch, a code reader, a light barrier, a reflective light barrier or a light curtain.

[0052] The invention will be explained below with reference to the drawings. The drawings show: Fig. 1: First embodiment of the optical sensor according to the invention. Fig. 2: Second embodiment of the optical sensor according to the invention. Fig. 3: Housing with a sensor window for the optical sensor according to Fig. 2 a) Perspective view. b) Side view. Fig. 4a: Sectional view of the housing according to Fig. 3. Fig. 4b: Enlarged detail view of Fig. 4a Fig. 5: Example of a sensor window for an optical sensor a) in a perspective view. b) in a sectional view. c) in top view.

[0053] The Fig. 1 and Fig. Figure 2 shows schematic and not to scale embodiments of the optical sensor 1 according to the invention.

[0054] Fig. Figure 1 shows an embodiment of an optical sensor 1 in the form of an area distance sensor, that is, a scanning distance sensor. For performing distance measurements, the optical sensor 1 has a light beam 2 emitting transmitter 3 and a light beam 2 receiving receiver 4. The transmitter 3 emits light beams 2 in the form of light pulses. How Fig. As shown in Figure 1, the light rays 2 are reflected at a target object 5 to be detected, whereby the corresponding light travel time of the light pulses to the target object 5 and back to the optical sensor 1 is evaluated for the distance determinations.

[0055] How Fig. As shown in Figure 1, the sensor components of the optical sensor 1 are integrated into a housing 6, with the transmitter 3 and the receiver 4, each with a transmitting optic and receiving optic 7 respectively, being stationary within the housing 6. The optical sensor 1 detects objects within a planar detection area by periodically deflecting the light rays 2 using a deflection unit 8. The deflection unit 8 is motor-driven and comprises an angled mirror 9 rotatable about a rotational axis D, by which the light rays 2 are deflected.

[0056] Fig. Figure 2 shows a variant of the area distance sensor according to Fig. 1. In this case, the periodic deflection of the light rays 2 is achieved by arranging the transmitter 3 and the receiver 4 in a measuring head 10 rotatable about a rotational axis D with the housing 6, wherein the measuring head 10 is rotatably mounted on a base 11.

[0057] In general, the optical sensor 1 has an evaluation unit (not shown) in which the received signals from the receiver 4 can be evaluated. The optical sensor 1 is advantageous according to the Fig. 1 or 2 a safety sensor.

[0058] For use in the field of safety technology, the safety sensor has a fail-safe design, which can be implemented, for example, by a redundant evaluation unit in the form of two processors that cyclically monitor each other.

[0059] The safety sensor is advantageously used according to Fig. 1 or 2 a protective field monitoring was carried out.

[0060] Depending on whether the safety sensor detects a safety-critical object, such as a person, within the protective field, it generates an object detection signal, typically in the form of a binary switching signal. The switching states of this signal indicate whether a safety-critical object is present within the protective field. If the safety sensor detects a safety-critical object within the protective field, the corresponding switching signal triggers a safety function, which, in particular, brings a system monitored by the safety sensor into a safe state. Specifically, the system is shut down.

[0061] The Fig. 3a, Fig. 3b, Fig. 4a, Fig. Figure 4b shows a housing 6 designed for an optical sensor 1 as described in the Fig. 1, Fig. 2 outlined, can be used.

[0062] The housing 6 according to the Fig. 3a, Fig. 3b, Fig. 4a, Fig. 4b is a component in the form of a multi-component injection molded part, consisting of two different plastics.

[0063] A base area of ​​the housing 6 is formed with a plastic that is not transparent to the light rays 2 of the optical sensor 1, which takes on the function of an aperture 12.

[0064] An upper area of ​​the housing 6 is formed with a plastic that is transparent to the light rays 2 of the optical sensor 1, forming a sensor window 13 through which the light rays 2 of the optical sensor 1 are guided.

[0065] Alternatively, the manufacturing process of the housing 6 can be varied using an injection molding process such that only a plastic transparent to the light rays 2 is formed. Additives consisting of non-transparent particles, such as soot particles, are mixed into the plastic only to form the aperture 12.

[0066] The Fig. 5a, Fig. 5b, Fig. Figure 5c shows an embodiment of a sensor window 13, which is formed in the form of a plate-shaped, flat component.

[0067] This sensor window 13 can be inserted into a front edge of a cubic housing 6 with a rectangular cross-section of an optical sensor 1 such as a light switch and in particular be assigned to its receiver 4.

[0068] In this case, too, the sensor window 13 consists of a plastic injection molded part, with a cover 12 being inserted as an insert during the injection molding of the plastic injection molded part into the mold.

[0069] The sensor window 13 is made of a transparent plastic, the aperture 12 of a non-transparent plastic.

[0070] In this case, aperture 12 has a circular aperture opening 15, although this is not mandatory. The aperture opening 15 is made of transparent plastic. Reference symbol list 1 optical sensor 2 light beam 3 channels 4 receivers 5 Target object 6 cases 7 Receiving optics 8 Deflection unit 9 Corner mirrors 10 measuring head 11 sockets 12 aperture 13 sensor windows 15 aperture D axis of rotation

Claims

[1] Optical sensor (1) with at least one light beam emitting transmitter (3), at least one light beam receiving receiver (4) and an evaluation unit designed for evaluating received signals from the receiver (4), wherein the light beams (2) are guided through at least one sensor window (13) of a housing (6), characterized by , that the sensor window (13) consists of a component which has various components with which areas of different optical properties are formed for the light rays (2). [2] Optical sensor (1) according to claim 1, characterized by , that the sensor window (13) has areas with different transmission, absorption, reflection or remission properties. [3] Optical sensor (1) according to claim 2, characterized by , that areas of the sensor window (13) form an aperture (12). [4] Optical sensor (1) according to claim 2, characterized by, that the sensor window (13) has several areas that are selectively transparent to light rays (2) of different wavelengths. [5] Optical sensor (1) according to any one of claims 1 to 4, characterized by that the areas of the component are volume areas. [6] Optical sensor (1) according to any one of claims 1 to 5, characterized by , that the component forms a housing (6) or a housing part. [7] Optical sensor (1) according to any one of claims 1 to 6, characterized by that the component has curved and / or flat surfaces. [8] Optical sensor (1) according to any one of claims 1 to 7, characterized by that the component is a casting or an injection-molded part. [9] Optical sensor (1) according to any one of claims 1 to 8, characterized by that the component consists of one or more plastics. [10] Optical sensor (1) according to any one of claims 1 to 9, characterized by, that the areas of the component exhibiting different optical properties are made of different materials. [11] Optical sensor (1) according to claims 8 and 9, characterized by , that an insert in a casting or injection molded part forms a first area, and that a second area consists of a casting compound of the casting or injection molded part. [12] Optical sensor (1) according to one of claims 8 and 9, characterized by , that the component is manufactured using a multi-component injection molding or multi-component casting process, whereby areas of the component consisting of different components have different optical properties. [13] Optical sensor (1) according to claim 12, characterized by that the components forming the areas consist of different materials. [14] Optical sensor (1) according to claim 12, characterized bythat the components forming the areas consist of the same base material with different additives. [15] Optical sensor (1) according to any one of claims 1 to 14, characterized by , that different optical properties are caused by different geometries and / or surface roughness of the areas. [16] Optical sensor (1) according to any one of claims 1 to 15, characterized by that this is a security sensor. [17] Optical sensor (1) according to any one of claims 1 to 16, characterized by that this is an area distance sensor or a LIDAR sensor. [18] Optical sensor according to any one of claims 1 to 16, characterized by that this is a light switch, a code reader, a light barrier, a reflective light barrier or a light curtain.

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