OPTOELECTRONIC SENSOR

Description

[0001] The present invention relates to an optoelectronic sensor for detecting objects in a surveillance area according to the triangulation principle, comprising a transmitting arrangement for transmitting transmitted light signals into the surveillance area along a transmitted light path, wherein the transmitting arrangement comprises at least one light source and a transmitting optical system configured to focus the transmitted light signals generated by the at least one light source into a transmitted light spot, and comprising a receiving arrangement comprising a receiving optical system configured to focus received signals generated by an object present in the surveillance area by remission of incident transmitted light signals into a received light spot, and a spatially resolving light receiver configured to detect the received light spot,wherein the point of incidence of the received light spot on the light receiver with respect to a triangulation direction depends on the distance of the object from the optoelectronic sensor.

[0002] In such an optoelectronic sensor, which can also be referred to as a triangulation light sensor or generally as a triangulation sensor, the light source and the light receiver on the one hand, and the transmitting optics and receiving optics on the other, are each laterally offset from each other in the so-called triangulation direction, so that the transmitting axis and the receiving axis do not coincide. This type of optoelectronic sensor configuration is also referred to as a biaxial arrangement.

[0003] In an optoelectronic sensor operating according to the triangulation principle, the light receiver consists of at least two photosensitive receiving elements or is designed as a so-called line sensor with at least one line of photosensitive elements.

[0004] Depending on the distance between the sensor and a remitting object, the position of a received light spot, which is generated by the receiving optics by shaping the remitted light, i.e. light diffusely or specularly reflected from the object, on the light receiver, changes in the triangulation direction. There is a clear geometric relationship between the point of incidence of the received light spot on the light receiver and the distance to the detected object. By evaluating the light distribution on the light receiver, which can be detected, for example, by the photosensitive elements of a line sensor that are lined up next to one another in a line along the triangulation direction, the distance between the sensor and the object can be determined or it can be established whether or not a detected object is at a specified distance from the optoelectronic sensor.

[0005] Triangulating sensors are used to detect any objects present in a monitoring area detectable by the sensor, taking into account the distance of an object from the sensor. For this purpose, a corresponding evaluation unit can be provided, which is connected at least to the light receiver and is configured to process electrical reception signals generated by the light receiver by converting detected received light signals into electrical signals, and to generate a corresponding object detection signal based on the electrical reception signals. Such an object detection signal can, for example, include information about the aforementioned distance of the object or it can be generated based on a comparison with a distance threshold.Such a comparison may, for example, include checking whether a determined object distance is greater or smaller than a predefined distance threshold or whether the determined object distance lies within or outside a predefined distance range.

[0006] For reliable object detection, it is desirable for the transmitted light signals to be as focused as possible on the object to be detected, i.e. that the transmitted light spot generated on the object by the transmitted light signals has the smallest possible extent. This is the only way to ensure good detectivity even with inhomogeneously remitting or reflecting objects. A further positive effect that can be achieved is that a received light spot generated by the receiving optics on the light receiver, which represents an image of the transmitted light spot generated on the object, has sufficient light intensity or energy density. The location at which the transmitted light spot generated on the object has a minimal extent can be referred to as the focal point of the transmitted light path.If an object to be detected is located in front of or behind this focal point, a blurred transmitted light spot is generated, with the size of the transmitted light spot increasing with the object's distance from the focal point. Therefore, it is desirable for the transmitting optics to have the largest possible depth of field in order to keep the blur-related magnification of the transmitted light spot within acceptable limits within the largest possible distance range.

[0007] To achieve this goal, a transmitter optic with a comparatively long focal length can be used, as these offer a greater depth of field than short-focal-length optics with the same aperture. However, the use of long-focal-length transmitter optics requires a comparatively large installation space. Such an increase in installation space is undesirable, since in many applications, a sensor design that is as compact as possible is desired due to space constraints.

[0008] DE 10 2007 050 096 A1 discloses a triangulation sensor that has optics for homogenizing the transmitted light beam. This optics can, in particular, comprise cylindrical lenses or multifocus lenses.

[0009] DE 10 2014 105 746 A1 shows a sensor for detecting shiny objects with a transmitter line and a receiver line that are rotated by 90° relative to each other.

[0010] From EP 2 442 141 B1 a triangulation sensor is known in which a transmitter line with several LEDs arranged on a substrate is arranged parallel to a separating web of a position-sensitive detector.

[0011] EP 2 159 599 B1 describes an optical sensor in a triangulation arrangement with several light sources arranged next to one another in the triangulation direction.

[0012] DE 197 32 376 C1 describes a method and device for distance measurement based on the triangulation principle. Several laser light sources are provided as transmitters, each focused by its own lens at different measuring distances. The resulting multiple scanning spots are imaged on the sensor's position-sensitive detector as concentric circles of different diameters. The light sources are modulated differently so that they can be individually identified from the concentric superposition. During distance measurement, the measuring light spot with the smallest diameter is evaluated in order to minimize measurement inaccuracies due to the scanning spot size. The detector is aligned according to the Scheimpflug condition.

[0013] EP 1 947 477 B1 shows a triangulation sensor in which the receiving light path is designed in a Scheimpflug arrangement.

[0014] DE 20 2021 101 693 U1 discloses a triangulation sensor with a spatially resolving light receiver and a microlens array arranged upstream of the light receiver. A multiplicity of pinhole apertures is arranged between the light receiver and the microlens array, with each microlens being assigned a pinhole aperture with a pinhole diameter that is smaller than the diameter of the microlens associated with the pinhole aperture. The pinhole apertures are offset in the triangulation direction from the microlenses assigned to them. The transmitted light path is deflected by 90° between the transmitted light source and the monitored area.

[0015] DE 10 2019 200 664 B3 shows a triangulation sensor in which a light source initially emits the transmitted light in a direction away from the monitored area. This transmitted light beam is then redirected toward an object to be detected by means of a deflecting mirror.

[0016] DE 10 2018 222 231 A1 relates to a device for optically measuring an inner contour of a spectacle frame.

[0017] JP 2009 264784 A discloses a distance-measuring sensor operating according to the triangulation principle. A deflection element is provided in the transmitted light path, which deflects the transmitted light by 90°. The light source and light receiver are arranged adjacent to each other on the side of the monitoring area.

[0018] It is the object of the invention to provide an optoelectronic sensor of the type mentioned above which has compact dimensions and enables reliable object detection with high sensitivity.

[0019] The object is achieved by an optoelectronic sensor having the features of claim 1. An optoelectronic sensor according to the invention for detecting objects in a surveillance area according to the triangulation principle comprises a transmitting arrangement for emitting transmitted light signals into the surveillance area along a transmitted light path, wherein the transmitting arrangement comprises at least one light source and a transmitting optics which is configured to focus the transmitted light signals generated by the at least one light source into a transmitted light spot, and a receiving arrangement which comprises a receiving optics which is configured to focus received signals generated by objects present in a surveillance area by remission of incident transmitted light signals into a received light spot, and a spatially resolving light receiver which is configured to detect the received light spot,The location of the received light spot on the light receiver, relative to a triangulation direction, depends on the distance of the object from the optoelectronic sensor. The light receiver faces the monitoring area, and the at least one light source is arranged facing away from the monitoring area. The transmitting arrangement comprises at least one deflecting element configured to deflect the transmitted light signals, initially emitted by the at least one light source in a direction away from the monitoring area, toward the monitoring area.

[0020] According to the triangulation principle, the transmitting optics and the receiving optics are arranged laterally spaced apart from one another along the triangulation direction. The at least one light source, i.e., a single light source or an arrangement of multiple light sources or partial light sources, is preferably designed as a divergent light source, in particular as a point light source, preferably as an LED or vertical-cavity surface-emitting laser (VCSEL). The transmitting optics can comprise one or more reflective, refractive, and / or diffractive beam-shaping elements, for example, concave mirrors, optical lenses with spherical, aspherical, cylindrical, or astigmatic shapes, as well as Fresnel lenses or diffractive optical elements. The transmitting optics can, in particular, also comprise a combination of the beam-shaping elements listed here as examples or other suitable beam-shaping elements.

[0021] A particular advantage of the present invention is that the light receiver and the at least one light source point in different directions relative to the monitoring area. While the light receiver arranged facing the monitoring area, i.e. its light-sensitive side, "looks" directly into the monitoring area, the at least one light source arranged away from the monitoring area, i.e. its light-emitting side, initially radiates in the opposite or essentially opposite direction. This initially appearing unfavorable design, in conjunction with the at least one deflection element, however, enables the available installation space, which is generally limited by the desired compact housing shape of the optoelectronic sensor, to be used optimally by folding the entire transmitted light path.

[0022] The folding of the transmitted light path is preferably performed at an angle of approximately 180°. Compared to other conceivable deflections, e.g., a 90° deflection of the transmitted light path, which is already known from the prior art, this results in better use of space. In particular, this also allows the lateral expansion of the sensor, i.e., an expansion perpendicular to the transmitted or received light path, to be minimized.

[0023] This optimized use of installation space allows, in particular, the focal length of the transmitting optics to be significantly extended compared to a comparable fold-free transmitting arrangement. As explained above, this increases the depth of field compared to a short-focal-length transmitting optics with a comparable aperture. This has a positive effect on the sensitivity and accuracy of object detection.

[0024] According to the invention, the at least one light source and the light receiver are arranged on a common, flat carrier card, wherein the carrier card has a first side facing the monitored area and forming a front side of the carrier card, and a second side facing away from the monitored area and forming a rear side of the carrier card, and wherein the light receiver is arranged on the first side and the at least one light source is arranged on the second side. The carrier card forms a carrier module for both the light receiver and the at least one light source and has a flat design. The carrier card can in particular be a printed circuit card, printed circuit board or electronic card.Since such carrier cards represent a not insignificant cost factor, a significant cost reduction can be achieved by the combined use of a common carrier card for both the light receiver and the at least one light source.

[0025] According to a further preferred embodiment, the at least one deflecting element is arranged in the transmitted light path between the at least one light source and the transmitting optics. In principle, it is not necessary for the transmitting optics and the deflecting element to be designed as two completely separate components. For example, the deflecting element, or if multiple deflecting elements are present, some of the deflecting elements, can form a component of the transmitting optics. For example, the deflecting element can additionally have beam-shaping, in particular focusing, properties that interact with another component of the transmitting optics, for example a lens. This will be explained in more detail below in connection with a further preferred embodiment.

[0026] According to a further preferred embodiment, the receiving optics have an optical plane, a section of the transmitted light path running behind the deflection element(s) as viewed in the propagation direction of the transmitted light signals runs in a transmission plane, and a light entry surface of the light receiver runs in a reception plane, with the transmission plane, the optical plane, and the reception plane intersecting in a common intersection line. This optical plane can also be referred to as the main extension plane or main plane of the receiving optics. According to this embodiment, the light receiver, the receiving optics, and the transmitted light path are arranged such that the conditions of Scheimpflug's rule are met. In this configuration, in other words, the transmission axis or the optical axis of the section of the transmitted light path running behind the deflection element(s) lies in the transmission plane.Thus, depending on the object distance, the possible locations where a received light spot can be generated on an object are located in the transmitting plane, which can thus also be referred to as the optical object plane of the receiving light path. Accordingly, due to the fulfillment of the Scheimpflug rule, a respective transmitted light spot is sharply imaged into the receiving plane and thus onto the light receiver, regardless of its distance from the optoelectronic sensor. The receiving plane can also be referred to as the optical image plane of the receiving light path.

[0027] With such a Scheimpflug arrangement, a very large working distance range, i.e. a range between a minimum and a maximum distance of a detectable object from the sensor, can be covered without the received light spot formed by the receiving optics being blurred due to the distance and accordingly being imaged with an enlarged extent on the light receiver, which would impair the detection accuracy.

[0028] The condition "intersecting" in the feature, according to which the transmitting plane, the optical plane and the receiving plane intersect in a common intersection line, is not to be understood here in a narrow mathematical sense, but rather as an approximation, i.e., particularly within the framework of usual design or manufacturing tolerances.

[0029] According to a further preferred embodiment, it is provided that a partial section of the transmitted light path running behind the deflection element(s), viewed in the propagation direction of the transmitted light signals, runs in a transmission plane, and that a light entry surface of the light receiver runs in a reception plane, wherein the angle enclosed between the transmission plane and the reception plane is more than 90°. The included angle is understood to be the angle that is less than 180°. Preferably, the included angle is more than 100°, particularly preferably more than 115° and in particular more than 120°. Such a configuration has proven particularly useful in combination with the above-described arrangement of the optical plane, the transmission plane and the reception plane in a Scheimpflug arrangement.The inclination of the receiving plane with respect to the transmitting plane by more than 90° makes it possible, in particular, to arrange the receiving optics such that their optical plane or main plane runs at right angles to the transmitting plane and, in particular, also parallel to the optical plane of the transmitting optics. In other words, the optical planes of the transmitting optics and the receiving optics can run in a common plane or at least parallel to one another, preferably parallel to a housing surface of a housing surrounding the optoelectronic sensor or a supporting structure inside the sensor. Such a configuration offers design and manufacturing advantages compared to a possible alternative embodiment with a receiving plane running perpendicular to the transmitting plane, in which the optical plane of the receiving optics would have to be inclined to fulfill the Scheimpflug condition. A further advantage of the inclined arrangement of the transmitting plane orthe carrier card also arises in connection with a further preferred embodiment described below.

[0030] According to a further preferred embodiment, in a configuration with a common carrier card for the light source and light receiver, a light entry surface of the light receiver runs parallel to the first side of the carrier card. Accordingly, the carrier card or the first side of the carrier card can be aligned parallel to the receiving plane. This results in the advantage that the light receiver does not have to be mounted tilted relative to the main extension plane of the carrier card, in particular if, according to the embodiments described above, a Scheimpflug arrangement including a vertical alignment of the optical plane of the receiving optics to the transmitting plane is to be implemented.

[0031] According to a further preferred embodiment, in a configuration with a common carrier card for the light source and light receiver, a main radiation direction of the at least one light source runs perpendicular to the second side of the carrier card. The main radiation direction of the at least one light source is understood to be the radiation direction having the greatest energy density per unit angle. In the case of a divergently emitting light source, this main radiation direction generally represents the axis of symmetry of the radiation region. This has the advantage that the light source does not have to be mounted tilted or inclined with respect to the main extension plane of the carrier card. The main radiation direction preferably also runs perpendicular to the reception plane.In connection with the embodiment already described above, according to which the angle enclosed between the transmitting plane and the receiving plane is more than 90°, there is the further advantage that the section of the transmitted light path that lies immediately behind the light source and in front of the deflecting element—as viewed in the direction of propagation of the transmitted light—runs at an angle to the transmitting plane. This makes it possible to use only a single deflecting element.If the receiving plane and thus the carrier card aligned parallel to it were to form an angle of exactly 90° with the transmitting plane and at the same time the main radiation direction of the light source pointing away from the monitored area were to run perpendicular to the carrier card, at least two deflection elements would be required to direct the transmitted light path around the carrier card in the direction of the monitored area, which would increase the material and assembly costs and thus also create an additional source of error during adjustment.

[0032] According to a further preferred embodiment, the transmission arrangement comprises a plurality of light sources arranged along a straight line running perpendicular to the triangulation direction, or the transmission arrangement comprises a single longitudinally extending light source whose main extension direction runs perpendicular to the triangulation direction. The plurality of light sources can preferably be arranged on a common semiconductor substrate or chip, for example in the form of LED structures or multi-VCSEL structures. With this configuration, a linear transmission light spot can be generated, whereby the light intensity contained in the transmission light spot can be increased. An alternative solution for increasing the energy density would consist in using a light source with greater light output.However, particularly when using LEDs, this would simultaneously increase the light exit area, which would inevitably increase the extent of the transmitted light spot in the triangulation direction with the usual imaging of the light source into the transmitted light spot to an undesirable extent. The advantageous generation of a linear transmitted light spot exploits the fact that typical light receivers, for example line receivers, also have a certain extent transverse to the triangulation direction. Preferably, the longitudinal extent of the arrangement of multiple light sources or of the individual longitudinally extended light source is selected such that, taking into account the focal lengths of the optics and other geometric parameters, the corresponding received light spot generated by imaging the transmitted light spot on the light receiver has a longitudinal extent corresponding to the width of the light receiver transverse to the triangulation direction.

[0033] In this context, it has proven advantageous if the transmitting optics are designed as astigmatic optics, which are configured and arranged such that the multiple light sources are imaged sharply at a predetermined working distance relative to the triangulation direction and blurred in a direction transverse to this. Such an astigmatic optic has different focal lengths in the meridional and sagittal planes and consequently has the property that a point light source is imaged in two focal lines lying one behind the other in the direction of light propagation and running perpendicular to each other. The aforementioned predetermined working distance can be described by a focal length or image length, at which the transmitted light spot should have its greatest possible sharpness in the triangulation direction. A working distance range of the sensor generally extends in front of and behind this predetermined working distance.The multiple point light sources are now focused in such a way that their associated front focal lines run perpendicular to the triangulation direction and overlap in their longitudinal direction, forming the transmitted light spot at the specified working distance. The rear focal lines, which run parallel to the triangulation direction, are advantageously located outside the working area. This homogenizes the transmitted light spot in its longitudinal extent perpendicular to the triangulation direction. The astigmatic nature of the transmitting optics does not serve to create a linear transmitted light spot in the first place, which is already achieved in this case by the multiple light sources, but rather serves to improve the quality of the transmitted light spot by avoiding the occurrence of individual intensity peaks corresponding to the number of individual light sources.

[0034] The desired astigmatic characteristics of the transmitting optics can be achieved in a variety of ways. For example, a corresponding astigmatic single lens or lens arrangement can be used, which can also be referred to as a focal or multifocal lens. In principle, a combination of a rotationally symmetric spherical lens and a cylindrical lens can also be used. Another exemplary implementation can be achieved by additionally giving the deflecting element beam-shaping or focusing properties. For example, the deflecting element can be designed as a concave mirror with a cylindrical shape and the transmitting optics can comprise a spherical lens. The reverse case, with the deflecting element designed as a spherical concave mirror and the use of a cylindrical lens in the transmitting optics, is also conceivable.As already mentioned above, the astigmatic nature of the transmitting optics can be implemented alternatively or additionally by using diffractive elements such as Fresnel lenses.

[0035] Preferably, the aperture of the transmitted light path, in particular the aperture of the transmitted optics, can have an asymmetry, wherein the extent of the aperture in the triangulation direction deviates from the extent perpendicular to the triangulation direction. Preferably, the extent in the triangulation direction is smaller than the extent perpendicular to the triangulation direction. An asymmetric enlargement of the aperture achievable in this way only in the direction transverse to the triangulation direction can at least partially compensate for a reduction in light efficiency caused by a reduction in the aperture angle when selecting a comparatively long focal length transmitted optics, without simultaneously reducing the depth of field in the triangulation direction. The aperture can, for example, have an elliptical shape with different lengths of main axes or a rectangular shape with different edge lengths, in particular a slit shape.

[0036] According to a further preferred embodiment, the receiving optics have an asymmetric aperture which, relative to the main axis of the receiving optics, is smaller on the side of the main axis facing the transmitted light path than on the side of the main axis facing away from the transmitted light path. The term "main axis" refers in particular to the optical axis of the receiving optics, i.e., a receiving lens or a receiving lens arrangement. This is the axis running through the optical lens center perpendicular to the optical plane. In other words, in this embodiment, an edge surface delimiting the aperture is smaller on the side facing the transmitted light path than on the side facing away from the transmitted light path. The aperture of the receiving optics thus has an asymmetry in the triangulation direction.

[0037] Particularly in conjunction with a receiving plane inclined by more than 90° relative to the transmitting plane, an asymmetric aperture of the receiving optics, which is smaller on the side of the main axis facing the transmitted light path than on the side of the main axis facing away from the transmitted light path, prevents certain received light rays from striking the light receiver at a very shallow angle. Such shallowly incident light rays can cause undesirable effects due to crosstalk on neighboring light-sensitive elements of the light sensor, which can impair the signal quality during electronic detection of the received light spot.In comparison to a light receiver whose receiving plane runs parallel to the optical plane of the receiving optics and in which, with a circular aperture, all edge light rays hit the light receiver at the same angle of incidence, in a light receiver arranged at an angle to the optical plane, those light rays which are refracted at a certain distance from the main axis of the receiving optics on the side of the main axis facing the transmitted light path fall onto the light receiver at a flatter angle than those light rays which are refracted at the same distance but on the opposite side of the main axis facing away from the transmitted light path.

[0038] By asymmetrically reducing the aperture of the receiving optics on the side of the principal axis facing the transmitted light path, the light rays arriving at a particularly shallow angle are, so to speak, cut off. The associated reduction in the aperture area of ​​the receiving optics compared to a corresponding uncut circular aperture area can be accepted. The degree of asymmetry of the two aperture halves can be adapted to the inclination angle of the receiving plane, i.e. the angle enclosed between the transmitting plane and the receiving plane, and other parameters. As a rule, a greater inclination of the receiving plane relative to the principal plane of the receiving optics also requires a greater asymmetry, whereby the specific sensitivity of the light receiver to undesirably flat incident rays should also be taken into account.

[0039] In this context, it has proven advantageous if the asymmetric aperture of the receiving optics is formed by the extent of the optically effective surface of the receiving optics relative to the main axis of the receiving optics being smaller on the side of the main axis facing the transmitted light than on the side of the main axis facing away from the transmitted light path. Accordingly, the asymmetry is achieved by, in other words, "cutting off" a portion of a symmetrically designed optic or lens on the side facing the transmitted light path. The term "cut off" is not to be understood literally, but can also be taken into account during the manufacture of the lens, for example, in the injection molding process.

[0040] Reducing the optically effective area of ​​the receiving optics does not preclude the possibility of the optics or lens extending beyond the area limited by the aperture, for example, in the case of a plastic lens, to create a kind of frame for mounting the lens or optics in a suitable holder. However, such an overhanging area does not contribute to the generation of the receiving light spot and is therefore considered optically ineffective.

[0041] Alternatively, the asymmetric aperture can be formed by assigning an aperture stop to the preferably rotationally symmetrical receiving optics, the opening of which, relative to the main axis of the receiving optics, is smaller on the side of the main axis facing the received light path than on the side of the main axis facing away from the transmitted light path. In this configuration, the asymmetric limitation of the aperture can be achieved cost-effectively by means of an asymmetric aperture stop arranged in front of or behind the receiving optics. This eliminates the need for cost-intensive custom-made receiving optics.

[0042] In addition, an asymmetry of the receiving optics perpendicular to the triangulation direction can also be provided.

[0043] Further advantages of the optoelectronic sensor according to the invention and advantageous embodiments will become apparent from the following description of the drawings. The drawings illustrate exemplary embodiments of the invention. The drawings, the description, and the claims contain numerous features in combination. Those skilled in the art will expediently consider these features individually and combine them into useful further combinations. They show: Fig. 1 shows a schematic cross-sectional view of an optoelectronic sensor according to a first embodiment in a first sectional plane; and Fig. 2 a schematic cross-sectional view of a transmitted light path of the optoelectronic sensor of Fig. 1 in a second cutting plane.

[0044] Fig. 1shows an optoelectronic sensor 10 according to an embodiment, which is configured to detect objects in a monitoring area 12 according to the triangulation principle.

[0045] The optoelectronic sensor comprises a transmitting arrangement 14 for transmitting transmitted light signals into the monitoring area along a transmitted light path 16, which Fig. 1 and 2 simplified as a transmitted light axis. In the present embodiment, the transmitted light arrangement 14 comprises four light sources 18, for example, designed as LEDs or VCSELs, which are arranged along a straight line running perpendicular to a triangulation direction T. Since this straight line in Fig. 1 perpendicular to the plane of the drawing, the four light sources 18 appear in the schematic sectional view of Fig. 1 as superimposed light sources, so that in Fig. 1only one light source 18 is visible. However, in a modification not shown, the use of only one light source 18 is also possible, for example if it is linear and perpendicular to the plane of the drawing of the Fig. 1 extends.

[0046] The optoelectronic sensor 10 further comprises a receiving arrangement 30 with receiving optics 32, which is configured to focus received light signals or received light beams 38 into a received light spot. The received light signals or received light beams 38 are generated by an object (not shown) present in the monitored area 12 through remission, i.e., through specular and / or diffuse reflection, of incident transmitted light signals. The receiving arrangement 30 further comprises a spatially resolving light receiver 34, which is configured for spatially resolved detection of the received light spot. The light receiver 34 can, for example, be designed as a line sensor with several adjacent photosensitive elements arranged next to one another, parallel to the plane of the drawing.

[0047] The transmitting arrangement 14 and the receiving arrangement 30 are arranged at a distance from one another in the triangulation direction T, so that according to the triangulation principle, the point of incidence of the received light spot on the light receiver 34 with respect to the triangulation direction depends on the distance of a detected object from the optoelectronic sensor 10.

[0048] The optoelectronic sensor 10 comprises a flat carrier card 36, which is generally designed as a carrier module, but preferably as an electronics card or printed circuit board, and carries both the light sources 18 and the light receiver 34. Additional electronic components (not shown) can also be arranged on the carrier card 36. The carrier card 36 can be connected to a display and control unit 46, which is arranged on a structural element 44, for example, a section of a housing of the optoelectronic sensor 10. The connection can be made, for example, via a flexible cable 48.

[0049] The carrier card 36 has a first side facing the monitored area 12 and a second side facing away from the monitored area 12, with the light receiver 34 arranged on the first side and the light sources 18 on the second side. Thus, the transmitted light emitted by the light sources 18 is initially emitted in a direction away from the monitored area 12. In order to redirect the transmitted light toward the monitored area 12, the transmitting arrangement 14 has a deflecting element 26, which in the present embodiment is designed as a mirror. Thus, after emerging from the light sources 18, the transmitted light is first redirected and subsequently focused into a transmitted light spot by means of a transmitting optics 22.

[0050] By folding the transmitted light path 16, the maximum possible object distance, ie the maximum possible distance between the light sources 18 and the transmitting optics 22, is increased for a given installation space (e.g., for a given housing depth of the optoelectronic sensor 10) compared to an unfolded beam path. To illustrate this, Fig. 1 and 2 In addition to the light sources 18, corresponding virtual light sources 20 are shown, the position of which would result for an unfolded transmitted light beam path with the same object distance. As in Fig. 1As can be clearly seen, this position is on a side of the structural element 44 facing away from the monitoring area 12 and thus already outside a housing of the optoelectronic sensor 10. In order to be able to arrange one or more light sources at a position corresponding to the position of the virtual light sources 20 without using deflection elements, the installation depth of the housing would have to be significantly increased.

[0051] While in Fig. 1 the optoelectronic sensor 10 is shown in an XZ plane, Fig. 2the transmission arrangement 14 with the associated transmission light path 16 in a YZ plane perpendicular thereto. Accordingly, the virtual light sources 20 are no longer shown one above the other, but next to each other. For better clarity, the associated real light sources 18 and the deflection element 26 are not shown. Likewise, for this reason, the rays are also only shown for the two outer virtual light sources 20 and for the two inner virtual light sources 20 only indicated by short dashed lines. Both representations of the Fig. 1 and 2 are generally not to scale and serve only to illustrate the described effects.

[0052] As can be seen from a comparison of Fig. 1 and Fig. 2As can be seen, the transmitting optics 22 are designed as an astigmatic optics, which is designed and arranged in such a way that the plurality of light sources 18 are imaged sharply at a predetermined working distance relative to the triangulation direction Z and blurred in a transverse direction thereto. In contrast to Fig. 1 is in Fig. 2 The transmitting optics 22 are shown slightly enlarged in order to better illustrate the effect of the astigmatic design of the receiving optics 22. The point-shaped light sources 18 or the associated virtual light sources 20 are imaged into two respective focal lines 24, 25 arranged one behind the other and extending perpendicular to each other.

[0053] The front focal lines 24, which partially overlap in the longitudinal direction, generate a linear transmitted light spot on an object present there, the cross section of which has a minimum in the triangulation direction T with respect to the object distance ( Fig. 1 ). The front focal lines 24 define a target distance or predetermined working distance, which is also referred to as the working point. A working distance range of the sensor 10 extends in front of and behind this working point, whereby the size of a reasonable working distance range can be determined from a just tolerable blur of the transmitted light spot. Due to the astigmatic design of the receiving optics 22, the front focal lines 24 have a blur-related extension in a direction perpendicular to the triangulation direction T ( Fig. 2). This blurring results in a homogenization of the linear received light spot compared to a non-astigmatic image.

[0054] The respective rear focal lines 25, which in Fig. 1 overlap and are therefore only shown as one line and in Fig. 2 are shown as respective intersection points with the drawing plane, are sensibly outside the working distance range of the sensor 10.

[0055] The distance of the operating point defined by the focal lines 24 from the transmitting optics 22, which corresponds to the front image distance of the transmitting optics 22, depends on the optical path length between the light sources 18 and the transmitting optics 22, ie the object distance, and the focal length of the transmitting optics 22.

[0056] However, since the folding of the transmission light path 16 enables the use of a long-focal-length transmission optics 22, the usable working distance range is larger than with a short-focal-length transmission optics with a comparable aperture. The reduction in the light intensity of the transmission optics 22 caused by the increase in focal length is compensated by the use of the longitudinally extended arrangement of multiple light sources 18.

[0057] In the schematic representation of Fig. 1 For reasons of clarity, the image width of the transmitted light spot 24 is shown in a greatly shortened form and does not correspond to the course of the received light rays 38, which in Fig. 1 for an object located at an approximately infinite distance from the optoelectronic sensor 10.

[0058] According to Fig. 1The section of the transmitted light path 16 located behind the deflection element simultaneously defines a transmission plane 16, which corresponds to a plane running perpendicular to the plane of the drawing. The receiving optics 32 has an optical plane 40, which corresponds to a main extension plane or main plane of the receiving optics 32. The light receiver 34 has a light entry surface, which runs in a receiving plane 42. The optical plane 40 and the receiving plane 40 also run perpendicular to the plane of the drawing and intersect the transmission plane 16 in a common intersection axis 50, which also runs perpendicular to the plane of the drawing and is therefore shown as a point. The receiving plane 16, the optical plane 40, and the receiving plane 42 thus fulfill Scheimpflug's condition.Therefore, a transmitted light spot, which is generated by the transmitted light rays when they hit an object, is always sharply imaged on the light receiver 34, regardless of the distance of the object from the optoelectronic sensor 10 or the image width.

[0059] To implement this Scheimpflug arrangement, in the exemplary embodiment, the optical plane 40 runs perpendicular to the transmitting plane 16, while the receiving plane 42 is inclined relative to the optical plane 40 by an angle of approximately 25°. Consequently, the angle enclosed between the transmitting plane 16 and the receiving plane 42 in the exemplary embodiment is approximately 115°. The angle specifications mentioned here are purely exemplary. The angle of inclination or the included angle can also be selected to be larger or smaller. For example, the angle of inclination can also be only 15 to 20°, which would correspond to an included angle of 105 to 110° between the transmitting plane 16 and the receiving plane 42.

[0060] Since the light sources 18 emit the transmitted light perpendicular to the rear surface of the carrier card 36, the inclined arrangement of the carrier card 36 enables the transmitted light, which is emitted at an angle relative to the section of the transmitted light path 16 located behind the deflection element, to be easily directed around the carrier card in the direction of the transmitted optics 22 by means of the one deflection element 26. Thus, it is not necessary to provide multiple deflection elements 26, although this would also be possible in principle with a different geometric arrangement of the components of the optoelectronic sensor 10.

[0061] The receiving optics 32 has an asymmetric aperture, which is formed in that the extent of the optically effective surface of the receiving optics 32 relative to a main axis 52 of the receiving optics 32 is smaller on the side of the main axis 52 facing the transmitted light path 16 than on the side of the main axis 52 facing away from the transmitted light path 16. Due to this asymmetry of the receiving aperture, those received light beams are blocked out which would strike the light receiver 34 at a comparatively flat angle, i.e. a small angle between the beam and the receiver surface, and could cause a deterioration in the signal quality through crosstalk to neighboring receiving elements. The asymmetric aperture of the receiving optics thus only allows those received light beams 38 to pass which are in Fig. 1are shown as solid lines. Those received light rays 38' that would strike the light receiver 34 at a particularly flat angle and are represented by a dashed line are masked out.

[0062] According to a modification, instead of the asymmetrically designed receiving optics 22 according to Fig. 1 A symmetrical receiving optics can also be used, to which an aperture stop is assigned, the aperture of which has a corresponding asymmetry.

[0063] Overall, the various measures reduce both the blur-related expansion of the transmitted light spot and the blur-related expansion of the received light spot, each relative to the triangulation direction T, over a larger working distance range compared to conventional comparable sensors. This increases the distance sensitivity of the sensor. List of reference symbols

[0064] 10 optoelectronic sensor 12 monitoring area 14 transmitting arrangement 16 transmitting light path, transmitting plane 18 light source 20 virtual light source 22 transmitting optics 24 front focal line 25 rear focal line 26 deflecting element 30 receiving arrangement 32 receiving optics 34 light receiver 36 carrier card 38, 38' receiving light beam 40 optical plane 42 receiving plane 44 structural element 46 display and control unit 48 cable 50 section axis 52 main axis Triangulation direction

Claims

1. An optoelectronic sensor (10) for detecting objects in a monitored zone (12) in accordance with the triangulation principle, said optoelectronic sensor (10) comprising a transmission arrangement (14) for transmitting transmission light signals into the monitored zone (12) along a transmission light path (16), wherein the transmission arrangement (14) comprises at least one light source (18) and a transmission optics (22) which is configured to focus the transmission light signals generated by the at least one light source (18) into a transmission light spot, and a reception arrangement (30) - which comprises a reception optics (32) which is configured to focus reception light signals, which are generated by an object present in the monitored zone (12) by a remission of incident transmission light signals, into a reception light spot, and - a spatially resolving light receiver (34) which is configured to detect the reception light spot, wherein the point of incidence of the reception light spot on the light receiver (34) with respect to a triangulation direction (T) depends on the distance of the object from the optoelectronic sensor (10), wherein the light receiver (34) faces the monitored zone (12) and the at least one light source (18) is arranged facing away from the monitored zone (12), and wherein the transmission arrangement (14) comprises at least one deflection element (26) which is configured to deflect the transmission light signals, which are initially transmitted in a direction facing away from the monitored zone (12) by the at least one light source (18), in the direction of the monitored zone (12), wherein the at least one light source (18) and the light receiver (34) are arranged on a common carrier board (36) of a planar design, characterized in that the carrier board (36) has a first side facing the monitored zone (12) and forming a front side of the carrier board (36) and a second side facing away from the monitored zone (12) and forming a rear side of the carrier board (36), with the light receiver (34) being arranged at the first side and the at least one light source (18) being arranged at the second side.

2. An optoelectronic sensor (10) according to claim 1, characterized in that a light entry surface of the light receiver (34) extends parallel to the first side of the carrier board (36).

3. An optoelectronic sensor (10) according to one of the claims 1 or 2, characterized in that a main radiation direction of the at least one light source (18) extends perpendicular to the second side of the carrier board (36).

4. An optoelectronic sensor (10) according to any one of the preceding claims, characterized in that the at least one deflection element (26) is arranged in the transmission light path (16) between the at least one light source (18) and the transmission optics (22).

5. An optoelectronic sensor (10) according to any one of the preceding claims, characterized in that the reception optics (32) has an optics plane (40), in that a partial section of the transmission light path (16) extending behind the deflection element(s) (26), viewed in the propagation direction of the transmission light signals, extends in a transmission plane (16), and in that a light entry surface of the light receiver (34) extends in a reception plane (42), with the transmission plane (16), the optics plane (40) and the reception plane (42) intersecting in a common intersection line (50).

6. An optoelectronic sensor (10) according to any one of the preceding claims, characterized in that a partial section of the transmission light path (16) extending behind the deflection element(s) (26), viewed in the propagation direction of the transmission light signals, extends in a transmission plane (16), and in that a light entry surface of the light receiver (34) extends in a reception plane (42), with the angle included between the transmission plane (16) and the reception plane (42) amounting to more than 90°.

7. An optoelectronic sensor (10) according to any one of the preceding claims, characterized in that the transmission arrangement (14) comprises a plurality of light sources (18) which are arranged along a straight line extending perpendicular to the triangulation direction (T), or in that the transmission arrangement (14) comprises a single longitudinally extended light source (18) whose main direction of extent extends perpendicular to the triangulation direction (T).

8. An optoelectronic sensor (10) according to claim 7, characterized in that the transmission optics (22) is configured as an astigmatic optics which is designed and arranged such that the plurality of light sources (18) are imaged sharply at a predefined working distance with respect to the triangulation direction (T) and out of focus in a transverse direction thereto.

9. An optoelectronic sensor (10) according to any one of the preceding claims, characterized in that the reception optics (32) has an asymmetrical aperture which, with respect to the main axis (52) of the reception optics (32), is smaller at the side of the main axis (52) facing the transmission light path (16) than at the side of the main axis (52) facing away from the transmission light path (16).

10. An optoelectronic sensor (10) according to claim 9, characterized in that the asymmetrical aperture is formed in that the extent of the optically effective area of the reception optics (32) with respect to the main axis (52) of the reception optics (32) is smaller at the side of the main axis (52) facing the transmission light path (16) than at the side of the main axis (52) facing away from the transmission light path (16).

11. An optoelectronic sensor (10) according to claim 9, characterized in that the asymmetrical aperture is formed in that the reception optics (32), which is preferably rotationally symmetrical, is assigned an aperture diaphragm whose opening with respect to the main axis (52) of the reception optics (32) is smaller at the side of the main axis (52) facing the transmission light path (16) than at the side of the main axis (52) facing away from the transmission light path (16).