OPTOELECTRONIC SENSOR

Description

[0001] The present invention relates to an optoelectronic sensor comprising a light inlet opening and at least one light receiver for detecting received light signals and for converting the received light signals into electrical received signals, wherein a received light path extends between the light inlet opening and the at least one light receiver, which path has a deflection element with a front and a rear reflection surface, wherein the deflection element is designed such that a part of the received light signals is reflected at the front reflection surface and another part of the received light signals is reflected at the rear reflection surface.

[0002] Generic and similar optoelectronic sensors can be designed in a variety of ways and used for different purposes. Optoelectronic sensor arrangements can, for example, comprise a light transmitter that emits light signals into a monitored area. These signals are reflected or remitted by an object present in the monitored area toward the optoelectronic sensor and detected by the sensor's light receiver. In some embodiments, in addition to the mere presence of an object in the monitored area, certain properties of the object, such as its surface properties or size, can also be detected. Such arrangements are also referred to as light sensors.In other sensor arrangements, a transmitted light beam is emitted toward a reflector, particularly a retroreflector, and reflected by it toward the optoelectronic sensor. An interruption in the light path can be registered by the optoelectronic sensor. Such a sensor arrangement is also referred to as a light barrier. An arrangement of multiple light barriers is referred to as a light curtain or light grid. Further exemplary sensor arrangements include so-called laser scanners, in which the transmitted light signals are periodically deflected in different spatial directions, for example, using rotating or pivoting mirrors. This allows even larger two- or three-dimensional spatial areas to be monitored with spatial resolution.

[0003] In many optoelectronic sensor arrangements, it is also possible to determine the distance of a detected object, for example by determining a light travel time, a phase position or by means of triangulation.

[0004] In optoelectronic sensor arrangements, deflecting mirrors or folding mirrors are often arranged in the transmitted light path and / or the received light path in order to advantageously deflect or fold the optical beam paths. This can in particular reduce the installation space required for the sensor arrangement or adapt it to certain complex installation situations. Furthermore, deflection or folding of the optical beam path may also be necessary in order to incorporate various optical elements into the beam path. A folding mirror is usually understood to be a mirror which is integrated into the optical beam path in such a way that a deflection of usually 180° occurs here, i.e. the beam path is reflected back on itself. Deflecting mirrors usually cause a deflection by an angle other than 180°, preferably by 90° or by other angles in the range between more than 0° and less than 180°.

[0005] EP 1 931 133 A1 describes a method and a device for optically capturing a structure using an image sensor. An optical element arranged in the imaging beam path images the structure in at least two separate and offset regions of the image sensor. This allows a structure with a large longitudinal extension to be divided into several consecutive subsections and captured by the image sensor in a single image. This division can be achieved, for example, using a plane-parallel, doubly reflecting deflection plate.

[0006] Various optoelectronic arrangements in which deflection elements with a front and a rear reflection surface are arranged in the beam path are disclosed, for example, in DE 689 09 663 T2 and JP 2011-193 205 A.

[0007] The object of the invention is to create an optoelectronic sensor with a deflection element in the beam path, the functionality and performance of which is improved compared to conventional sensors.

[0008] The solution is provided by an optoelectronic sensor having the features of claim 1. According to the invention, the front reflection surface at least partially has a filter layer which reflects or transmits received light signals depending on their wavelength and / or polarization direction.

[0009] In the optoelectronic sensor according to the invention, received light signals of a first wavelength and / or polarization direction can thus be reflected at the front reflection surface, while received light signals of a second wavelength and / or polarization direction are reflected at the rear reflection surface. The deflection element is designed such that received light signals reflected at the rear reflection surface are transmitted twice by the front reflection surface, namely on the way to and from the rear reflection surface.By reflecting the received light signals depending on their wavelength and / or polarization direction either at the front or rear reflection surface, the received light signals can be spatially separated from one another, which can be used, for example, to evaluate the received light signals depending on their wavelength and / or polarization direction. It is understood that the front and rear reflection surfaces are spaced apart by a certain amount. The term "light" here, depending on the application, encompasses electromagnetic radiation, particularly from the visible, ultraviolet, and / or infrared wavelength ranges.

[0010] In addition to the aforementioned elements, the optoelectronic sensor may also comprise further optical elements such as lenses, prisms, or mirrors, which are arranged in front of and / or behind the deflection element, relative to the direction of propagation of the received light signals. For example, the aforementioned light entry opening may be defined by an optic or lens arranged in the received light path, or by an aperture.

[0011] The filter layer, which is designed depending on the desired functionality, can be manufactured in a generally known manner. For example, the filter layer can be produced in the form of a single- or multi-layer structure by vapor deposition or vacuum deposition of suitable substances directly on the deflection element. The filter layer can also be applied to the deflection element in the form of a film. The deflection element itself is preferably transparent to the wavelength range of the received light, which is determined, for example, by a light-emitting element that may be used, and can be made of glass or plastic, e.g., PMMA.

[0012] One application example for the optoelectronic sensor according to the invention involves differentiating received light signals according to their polarization direction. This can be used, for example, to make an additional distinction based on the surface properties of light sensors used to detect objects that may be present in a surveillance area. While unpolarized transmitted light is at least partially polarized when reflected from a shiny object, reflection from a matte object surface generally does not change the polarization of the reflected transmitted light.

[0013] The further design of the optoelectronic sensor according to the invention can be realized in a variety of ways, in particular according to the above list of generic and similar optoelectronic sensors, whereby this list is purely exemplary and not exhaustive. The areas of application for generic and similar optoelectronic sensors are known to those skilled in the art, and their structural designs are described in the relevant prior art.

[0014] According to an advantageous embodiment, the optoelectronic sensor comprises a first and a second light receiver, wherein the light receivers and the deflection element are designed and arranged such that received light signals reflected at the front reflection surface are detected by the first light receiver, and received light signals reflected at the rear reflection surface are detected by the second light receiver. This makes it possible to also detect and evaluate the received light signals separated by wavelength and / or polarization direction separately from one another. The two light receivers can be arranged, for example, in a common plane, for example, on a common circuit board, which reduces manufacturing costs.A certain distance can be provided between the first and the second light receiver depending on the design of the deflection element and the geometric arrangement of the elements of the optoelectronic sensor.

[0015] According to a further advantageous embodiment, the filter layer is provided only on at least one partial region of the front reflection surface. The at least one partial region can, for example, be annular, in particular in the form of several concentric rings. Furthermore, a strip-shaped arrangement is also possible, with each strip being regarded as a partial region. Furthermore, a checkerboard-like arrangement of the partial regions is also possible. The remaining part of the front reflection surface does not have a filter layer, although another type of coating can also be provided that is different from the aforementioned filter layer. By coating only one or more partial regions with the filter layer, different detection zones for the received light signals can be realized, for example a division into a near zone and a far zone.

[0016] According to a further advantageous embodiment, the front reflection surface and the rear reflection surface are flat. In this case, the convergence or divergence angle of the received light signals is not influenced by the deflection element. With a convergent beam path, the received light signals are imaged into spaced-apart focal planes or focal points depending on the reflection surface from which they were reflected. The distance between the focal planes depends, among other things, on the length of the optical path within the deflection element.

[0017] According to a further advantageous embodiment, the front reflection surface and the rear reflection surface extend at an angle to one another. This has proven particularly advantageous in connection with the embodiment described above, in which the optoelectronic sensor comprises a first and a second light receiver, in order to apply the received light signals separated according to wavelength and / or polarization direction to both light receivers. Preferably, both reflection surfaces are flat, but due to the inclination, they do not extend parallel to one another. According to an alternative embodiment, however, both reflection surfaces can also extend parallel to one another.

[0018] According to a further advantageous embodiment, at least one of the reflection surfaces, preferably the rear reflection surface, is curved, preferably concave. This makes it possible, in particular, to separate the focal planes, into which the received light signals are imaged depending on their wavelength or polarization direction, more clearly from one another than would be possible, for example, solely through the optical path within the deflection element, which is determined by its angular orientation and thickness. In principle, however, the deflection element can also fulfill a beam-shaping function in addition to its deflecting and separating function, thereby reducing the number of required optical beam-shaping elements and, in particular, also reducing the overall length and installation space.Both reflection surfaces can also be curved, preferably with different radii of curvature, so that the focal lengths of the two reflection surfaces differ from each other.

[0019] According to a further advantageous embodiment, the deflection angle at which the received light signals are deflected is 90° or 180°, or at least substantially 90° or 180°. If the deflection angle is 90°, for example, the deflection element fulfills the function of a conventional deflection mirror, with the incident and outgoing beam paths at a right angle to each other. If the deflection angle is 180°, this corresponds to the function of a folding mirror, in which the outgoing beam path is reflected back onto the incident beam path. This is primarily used to shorten the overall length.

[0020] According to a further advantageous embodiment, the rear reflection surface has a reflective coating, e.g., a vapor-deposited metal layer. This can increase the proportion of received light reflected by the rear reflection surface.

[0021] According to a further advantageous embodiment, the reflection properties of the filter layer can be varied with regard to their selectivity for a wavelength and / or a polarization direction in response to an electrical control signal. Such an active coating of the front reflection surface can then be influenced, for example, by means of an electrical voltage applied to the filter layer in order to adapt the optical properties of the optoelectronic sensor in a desired manner.

[0022] According to a further advantageous embodiment, the rear reflection surface can be designed in a stepped manner. Thus, the optical path within the deflection element also depends on the point of incidence of a received light signal on the deflection element. This allows, for example, additional focal planes to be created.

[0023] The present invention relates, in a further aspect, which is not claimed, to a light transmitter arrangement for emitting transmitted light into a surveillance area, comprising a light exit opening and a first light transmitter, which is configured to generate transmitted light of a first wavelength, and a second light transmitter arranged at a distance from the first light transmitter, which is configured to generate transmitted light of a second wavelength different from the first wavelength, wherein a transmitted light path extends between the light transmitters and the light exit opening, which transmitted light path has a deflection element with a front and a rear reflection surface which extend at an angle to one another, wherein the front reflection surface has a filter layer which reflects or transmits transmitted light depending on its wavelength, and wherein the light transmitters and the deflection element are designed and arranged such thatthat transmitted light generated by the first light transmitter is reflected at the front reflection surface and transmitted light generated by the second light transmitter is reflected at the rear reflection surface in such a way that the transmitted light reflected at the reflection surfaces propagates along a common transmitted light axis.

[0024] Thus, separate sections of the transmitted light path extend between the light transmitters and the deflecting element, each with a different transmitted light axes for each wavelength. These transmitted light paths or transmitted light axes are combined by the deflecting element, so that a common section of the transmitted light path with the common transmitted light axis extends between the deflecting element and the light exit opening. The light transmitter arrangement according to the invention is based on the idea that the basic concept implemented in the optoelectronic sensor according to the invention described above can also be transferred analogously to a light transmitter arrangement, whereby the propagation direction of the light paths is reversed, so to speak.

[0025] The above-described advantageous embodiments of the optoelectronic sensor according to the invention, in particular those relating to the deflection element, can also be applied in a corresponding and advantageous manner to the light transmitter arrangement according to the invention.

[0026] The deflection element can be arranged in a stationary manner or adjustable, in particular rotatable, with respect to other components of the optoelectronic sensor or the light transmitter arrangement.

[0027] Further advantageous embodiments of the invention emerge from the subclaims, the description and the drawings.

[0028] The invention is described below using exemplary embodiments with reference to the drawings.

[0029] They show: Fig. 1 shows a schematic view of an optoelectronic sensor according to a first embodiment; Fig. 2 shows a schematic view of an optoelectronic sensor according to a second embodiment; Fig. 3 shows a schematic view of an optoelectronic sensor according to a third embodiment; Fig. 4 shows a schematic view of an optoelectronic sensor according to a fourth embodiment; and Fig. 5 shows a schematic view of an optoelectronic sensor according to a fifth embodiment.

[0030] In the following, identical or similar elements or components are designated by the same reference numerals.

[0031] Fig. 1 bis 5 show optoelectronic sensors 110 to 510, which comprise a respective deflection element 112 to 512 in different designs. Each deflection element 112 to 512 has a front reflection surface 14 and a rear reflection surface 16 spaced therefrom. Applied to the front reflection surface 14, either completely or in one or more partial areas, is a respective filter layer 18, which reflects or transmits incident light, i.e., received light signals and / or transmitted light signals, depending on their wavelength and / or polarization direction. The rear reflection surface 16 can have a reflective coating 20.

[0032] In Fig. 1 bis 5 Beam paths for received light 28.1, 28.2 detected by the optoelectronic sensors 110 to 510 are shown in a purely schematic manner, wherein the received light 28.1 has a first wavelength and the received light 28.2 has a second wavelength different from the first wavelength. In principle, the received light 28.1 can also have a first wavelength range and the received light 28.2 a second wavelength range, wherein the two wavelength ranges do not overlap. The received light 28.1, 28.2 enters the respective optoelectronic sensor 110 to 510 through a light inlet opening (not designated in more detail). The optoelectronic sensors 110 to 510 each have a receiving optics 22 for beam shaping the incoming received light 28.1, 28.2. Furthermore, the optoelectronic sensors 110 to 510 have either a single light receiver 24 or a first light receiver 24.1 and a second light receiver 24.2, which are configured to convert the incident received light 28.1 or 28.2 into electrical signals. In . Fig. 2 the receiving optics 22 and the light receiver(s) 24, 24.1, 24.2 are not shown.

[0033] In all embodiments, the differences shown between the received light 28.1 and the received light 28.2 relate to their wavelengths. However, the differences between the respective received light 28.1, 28.2 can alternatively or additionally also relate to their polarization direction. For example, the received light 28.1 can have a horizontal polarization and the received light 28.2 a vertical polarization. However, for ease of understanding, reference is made below only to possible different wavelengths or wavelength ranges.

[0034] The received light 28.1, 28.2, possibly focused by the receiving optics 22, strikes the deflection element 112 to 512, wherein the received light 28.1 with the first wavelength is reflected at the front reflection surface 14 and the received light 28.2 with the second wavelength is reflected at the rear reflection surface 16.

[0035] With reference to the individual figures, the specific differences between the optoelectronic sensors 110 to 510 are explained in more detail below.

[0036] In the optoelectronic sensor 110 according to Fig. 1 The deflection element 112 is designed as a plane-parallel plate. Since the received light 28.2 with the second wavelength must pass through the deflection element 112 twice, the focal plane 30.2 of the received light 28.2 is located in front of the focal plane 30.1 of the received light 28.1 with the first wavelength, as seen in the propagation of the light. With the illustrated geometry, the received light 28.1 with the first wavelength is focused, and the received light 28.2 with the second wavelength is defocused and detected by the light receiver 24. Differentiation of the received light 28.1, 28.2 according to wavelength can be achieved, for example, by using a spatially resolving and / or color-resolving light receiver 24 and a corresponding evaluation.

[0037] In the optoelectronic sensor 210 according to Fig. 2 the deflection element 212 differs from the deflection element 112 according to Fig. 1 in that its rear reflection surface 16 is concavely curved. This gives the deflection element 212 an additional beam-shaping function with respect to the received light 28.2, so that the received light 28.2 with a second wavelength reflected at the rear reflection surface 16 is bundled into a focal point 30.2, while the received light 28.1, which was reflected at the front reflection surface 14, maintains its parallel beam path.

[0038] According to an embodiment not shown, as already mentioned above, a light transmitter arrangement in modification of the optoelectronic sensor 210 according to Fig. 2 be created by reversing the propagation direction of the light paths and replacing the light receivers 24.1, 24.2 by respective light transmitters.

[0039] In the optoelectronic sensor 310 according to Fig. 3 a deflection element 312 designed as a plane-parallel plate is used, but not the entire front reflection surface 14 has a filter layer 18, but only an annular partial area 18, which due to the sectional view in Fig. 3 appears as two partial areas 18. As explained above, further partial areas of the front reflection surface 14 can also be provided with a filter layer 18. In this embodiment, too, the received light 28.1, 28.2 has different focal points 30.1, 30.2 depending on the respective reflection surface 14, 16.

[0040] The optoelectronic sensor 410 according to Fig. 4 Instead of a single light receiver, it has a first light receiver 24.1 and a second light receiver 24.2, which are arranged at a distance from one another on a common substrate 32 or a printed circuit board. The front reflection surface 14 and the rear reflection surface 16 of the deflection element 412 are both flat and inclined relative to one another, so that the deflection element 412 has a wedge-shaped configuration.

[0041] The distance between the light receivers 24.1, 24.2, the angle of inclination between the reflection surfaces 14, 16, and the arrangement and orientation of the deflection element 412 in the beam path are selected such that the received light 28.1 is detected by the first light receiver 24.1 and the received light 28.2 by the second light receiver 24.2. The focal points 30.1, 30.2 are located on the respective assigned light receivers 24.1, 24.2.

[0042] The optoelectronic sensor 510 according to Fig. 5 is designed as a (laser) scanner. In addition to the components described above, a housing 34 also contains a light transmitter 38, e.g., a laser, and a rotating deflecting mirror 36, which deflects both the transmitted light 40 emitted by the light transmitter 38 and the received light 28.1, 28.2 by an angle of 90°, so that a flat, circular monitoring area can be periodically scanned. The housing 34 is transparent, at least in the area of ​​the light entry and exit, for the wavelength range of the radiation used. The annular receiving optics 22 has a central recess for accommodating the light transmitter 38.

[0043] The deflection element 512 has, similar to the deflection element 212 of Fig. 2 a concavely curved rear reflection surface 16. The light receiver 24 is arranged between the deflection element 512 and the light transmitter 38, wherein the light transmitter 38, the receiving optics 22, the light receiver 24 and the deflection element 512 are arranged coaxially along an optical axis A. In the optoelectronic sensor 510, the focus points 30.1, 30.2 are located at different distances relative to the light receiver 24, similar to the embodiments according to Fig. 1 bis 3 . Bezuaszeichenliste

[0044] 110 - 510 optoelectronic sensor 112 - 512 deflection element 14 front reflection surface 16 rear reflection surface 18 filter layer 20 coating 22 receiving optics 24, 24.1, 24.2 light receiver 28.1 received light with first wavelength 28.2 received light with second wavelength 30.1, 30.2 focal point 32 substrate 34 housing 36 deflection mirror 38 light transmitter 40 transmitted light Aoptic axis

Claims

1. An optoelectronic sensor (110 - 510) comprising a light entry opening and at least one light receiver (24, 24.1, 24.2) for detecting reception light signals and for converting the reception light signals into electrical reception signals, wherein a reception light path, which has a deflection element (112 - 512) having a front and a rear reflection surface (14, 16), extends between the light entry opening and the at least one light receiver (24, 24.1, 24.2), wherein the deflection element (112 - 512) is configured such that some of the reception signals are reflected at the front reflection surface (14) and the remaining reception signals are reflected at the rear reflection surface (16), wherein the front reflection surface (14) at least partly has a filter layer (18) which reflects or transmits reception light signals in dependence on their wavelength and / or polarization direction, wherein the optoelectronic sensor (110 - 510) comprises a first and a second light receiver (24.1, 24.2), with the light receivers (24.1, 24.2) and the deflection element (112 - 512) being designed and arranged in such a manner that reception light signals reflected at the front reflection surface (14) are detected by the first light receiver (24.1) and reception light signals reflected at the rear reflection surface (16) are detected by the second light receiver (24.2), characterized in that reception light signals which are reflected at the rear reflection surface are transmitted twice by the front reflection surface, namely on the outward path towards and on the return path from the rear reflection surface, and in that the front reflection surface (14) and the rear reflection surface (16) extend inclined with respect to one another.

2. An optoelectronic sensor (110 - 510) according to claim 1, characterized in that the filter layer (18) is only provided on at least one part region of the front reflection surface (14).

3. An optoelectronic sensor (110 - 510) according to one of the preceding claims, characterized in that the front reflection surface (14) and the rear reflection surface (16) are planar.

4. An optoelectronic sensor (110 - 510) according to claim 1 or 2, characterized in that at least one of the reflection surfaces (14, 16), preferably the rear reflection surface (16), is curved, preferably concave.

5. An optoelectronic sensor (110 - 510) according to any one of the preceding claims, characterized in that the deflection angle at which the reception light signals are deflected is 90° or 180°.

6. An optoelectronic sensor (110 - 510) according to any one of the preceding claims, characterized in that the rear reflection surface (16) has a reflective coating (20).

7. An optoelectronic sensor (110 - 510) according to any one of the preceding claims, characterized in that the reflection properties of the filter layer (18) can be varied with respect to their selectivity for a wavelength and / or a polarization direction in response to an electrical control signal.