Light reception unit

Abstract

To provide a light reception unit for a position measurement system that determines spatial position information.SOLUTION: A light reception unit for a position measurement system that determines spatial position information, comprises: a measurement cell including a scanning grating and a photoelectron detector with a photosensitive surface thereof oriented in the direction of the scanning grating. The measurement cell is arranged in an assembly casing having a transparent cover element 162 which is transparent to a measurement wavelength in a region of the scanning grating. The cover element 162 has an electrically conductive layer 1 conductively connected to the assembly casing.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an optical receiving unit that can be used in a position measurement system for determining spatial position information. [Background technology]

[0002] From the document WO 2005 / 023333 an optical position measuring system is known which is configured as a spatial 2D angle measuring system and can be used to determine spatial position information. On the one hand, this system comprises a transmitting unit, which can be, for example, a suitable light source, arranged on a movable measuring object in space, the spatial position and orientation of which and thus its attitude are to be determined. On the other hand, one or more optical receiving units are provided stationary relative to the movable transmitting unit, each of which usually comprises a scanning grating and an optoelectronic detector, although further details regarding the suitable structure of the receiving units are not included in the aforementioned document. With such a system, the attitude of the transmitting unit in space can be determined by so-called multiangulation. For this purpose, the direction of the line of sight to the transmitting unit from each receiving unit is determined by two angle measurements. If the relative positions of the two receiving units are known, the attitude of the transmitting unit can be determined from the intersection of the determined lines of sight. For further details of such a measurement principle, reference is made to the aforementioned document.

[0003] A suitable configuration of an optical receiving unit for such a measuring system is known from DE 199 1 43 51 A1. It consists of a measuring cell, which includes a base plate on which the detector is arranged and is arranged in an assembly casing, above which a cover plate with a scanning grating is provided, spaced at a specified distance from the detector via spacers. A transparent cover element arranged thereon protects the interior of the measuring cell from contamination. These publications do not disclose further details regarding suitable measures for reducing disturbing influences on the measuring signal to be generated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO 01 / 38828 [Patent Document 2] DE 102021209393 [Patent Document 3] European Patent Application Publication No. 3739287 [Patent Document 4] European Patent Application Publication No. 3175949 Summary of the Invention [Problem to be solved by the invention]

[0005] It is an object of the present invention to provide an optical receiving unit for a position measuring system for determining spatial position information, which optical receiving unit has the smallest possible disturbing influence on the measuring signal to be generated. [Means for solving the problem]

[0006] According to the invention, this task is achieved by an optical receiving unit having the features of claim 1. Advantageous embodiments and further developments are set out in the respective dependent claims.

[0007] The optical receiving unit according to the invention can be used in a position measuring system for determining spatial position information. The optical receiving unit comprises a measuring cell including a scanning grating and a photoelectron detector with a photosensitive surface oriented in the direction of the scanning grating. The measuring cell is arranged in an assembly casing with a cover element transparent to the measuring wavelength in the region of the scanning grating. The cover element comprises at least one conductive layer conductively connected to the assembly casing.

[0008] Such a configuration of the cover element can reliably ensure electromagnetic shielding against electromagnetic interference.

[0009] Advantageously, it is envisaged that the cover element comprises a carrier substrate having opposite sides, at least one electrically conductive layer and at least one anti-reflective layer being laminated to the two sides of the carrier substrate.

[0010] An anti-reflective layer can be used to optimize the signal-to-noise ratio in the generated measurement signal, since the disturbing effects of scattered light can thereby be minimized.

[0011] In a preferred embodiment of the optical receiving unit according to the invention, the carrier substrate of the cover element consists of a filter glass plate, preferably with a thickness of 0.7 mm to 7 mm, which plate can be hardened, unhardened or partially hardened, transparent or structured, as well as colored and thus translucent or opaque for a given wavelength range.

[0012] In this case, there can be a conductive connection between the conductive layer of the first side and the conductive layer of the second side via the contact element.

[0013] It may further be contemplated that a conductive layer is disposed between the carrier substrate and the anti-reflective layer.

[0014] Preferably, the conductive layer is formed as a conductive oxide (TCO) that is transparent to the electromagnetic radiation used for the measurements.

[0015] Advantageously, the conductive oxide is aluminum doped zinc oxide (ZnO:Al) or indium tin oxide (ITO).

[0016] The conductive layer can be deposited on the carrier substrate using a thin film process, for example by a sputtering process.

[0017] Preferably, the antireflection layer comprises at least a first and a second sub-layer, The first partial layer comprises silicon dioxide (SiO2), and The second partial layer contains silicon (Si) or tantalum pentoxide (Ta2O5).

[0018] The first and second sub-layers of the antireflection layer can also be deposited using thin film technology processes.

[0019] Advantageously, the cover element is designed in such a way that at least one partial layer of the contact element is arranged between the conductive layer and the antireflection layer.

[0020] It proves to be advantageous if the layer thickness of the conductive layer and, additionally or alternatively, the thickness of the antireflection layer are configured such that for the electromagnetic radiation used for the measurement, a minimum reflectance and a maximum transmittance are obtained at an angle of incidence between 0° and 50° with respect to an axis extending perpendicular to the plane of symmetry of the carrier substrate.

[0021] It may further be envisaged that the conductive layer is directly laminated onto the carrier substrate.

[0022] An optional bond layer between the carrier substrate and the conductive layer or the conductive layer and the antireflective layer is not required.

[0023] Preferably, the contact element is formed circumferentially on the cover element.

[0024] The contact elements may consist of an aluminum chromium alloy (AlCr) or an aluminum-titanium-gold stack (AlTiAu).

[0025] If contact elements that are particularly stable against environmental influences are required, an aluminium-titanium-gold stack can be used.

[0026] Advantageously, the cover element is connected to the casing assembly via the contact element by means of an electrically conductive adhesive or a solder connection.

[0027] In an advantageous embodiment, the carrier substrate may be formed to be transparent only to wavelengths above 780 nm.

[0028] Preferably, the cover element is formed exactly symmetrically relative to the plane of symmetry of the carrier substrate.

[0029] The invention is explained in more detail below with respect to further features and advantages on the basis of a description of an embodiment and with reference to the attached schematic drawings. [Brief description of the drawings]

[0030] [Figure 1] 1 is a schematic diagram of a position measurement system for determining spatial position information in which multiple optical receiving units according to the present invention are used; [Diagram 2] 1 is a cross-sectional view of an embodiment of an optical receiving unit according to the present invention; [Diagram 3] 3 is a cross-sectional view of a transparent cover element of the measuring cell of the optical receiving unit of FIG. 2. [Figure 4] 4 illustrates a detailed view of a portion of the crystal element of FIG. 3. [Diagram 5] 1 shows in detail a portion of a transparent cover element used for the measuring cell. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Some particular embodiments of the invention are described in more detail below with reference to the drawings.

[0032] In Fig. 1, an optical position measuring system suitable for determining spatial position information or for determining the position and orientation of a measuring object moving in space is described in very schematic form. In the following, the orientation of the measuring object is also referred to. In the present embodiment, a measuring head 10 is provided as measuring object, which can be positioned in space via a merely schematic kinematics 20, the orientation of which is determined with the aid of the optical position measuring system. For example, a known switching probe can be used as measuring head 10, which is positioned in the machining area of ​​a machine tool via a kinematics 20 in order to measure a workpiece produced by tactile probing.

[0033] In an embodiment of the present application, the position measuring system consists of a plurality of spatial 2D angle measuring systems, as is basically known, for example from the patent document 2 cited at the outset. Furthermore, by way of supplement, reference is made to patent documents 3 and 4, which each show the application of such 2D angle measuring systems in special optical position measuring systems. Here, explicit reference is made to the disclosure content of these publications and the information contained therein for details of such 2D angle measuring systems.

[0034] The corresponding position measuring system comprises, on the one hand, a number of distinguishable light sources 31.1-31.6 arranged on the measuring head 10 in order to determine the attitude. In the illustrated example, a total of eight light sources 31.1-31.6 are provided on the measuring head 10, which are arranged in pairs around the measuring head 10 offset by 90°, so that only six light sources 31.1-31.6 are visible in the figure. On the other hand, the position measuring system according to the invention comprises a number of optical receiving units 40.1, 40.2, which are arranged fixedly on the measuring head 10 opposite the movable light sources 31.1-31.6. In the described embodiment, only two such optical receiving units 40.1, 40.2 are provided. Of course, more such units can be used in such a position measuring system and the number of light sources used can also be varied. The optical receiving units 40.1, 40.2 are arranged on a suitable fixed object, for example on a machine frame (not shown).

[0035] With the optical receiving units 40.1, 40.2, which shall be explained in more detail below, the incidence direction of the light beam coming from the light sources 31.1-31.6 or the measured angular position of the light sources 31.1-31.6 can be detected with respect to the corresponding receiving units 40.1, 40.2, respectively. In addition, if the relative positions of the two fixed receiving units 40.1, 40.2 with respect to each other are known, the attitude of the measuring head 10 can be determined from the intersection of the lines of sight to the particular incidence direction or light sources 31.1-31.6. For this purpose, the signals generated by the optical receiving units 40.1, 40.2 are processed via the signal processing unit 50 and forwarded to the attitude calculation unit 60, which uses it to determine the spatial position and orientation or attitude of the measuring head 10. This information can then be used by the machine control device 70 for the appropriate positioning in space of the measuring head 10 via the kinematics 20.

[0036] An embodiment of the optical receiving unit 140 according to the invention is explained in detail below with reference to the other figures, whereby Fig. 2 shows a cross-sectional view of the receiving unit 140 with the measuring cell 141, the assembly casing 160 and the transparent cover element 162, Fig. 3 shows a cross-sectional view of the cover element 162 of the measuring cell 141 of the receiving unit 140, and Figs. 4 and 5 show detailed views of the cover element 162.

[0037] As an essential functional element, the receiving unit 140 comprises a measuring cell 141 arranged in an assembly casing 160, the individual components of which are highlighted in FIG. 2 by hatching. The measuring cell 141 and the assembly casing 160 are each designed cylindrically, the measuring cell 141 being arranged in the interior of the assembly casing 160 in a kinematically appropriate manner. Above the measuring cell 141, the assembly casing 160 comprises a cover element 162 which is transparent for the measuring wavelength λ and which is essentially used to protect the sensitive measuring cell 141, the following description being referred to for the appropriate configuration of the cover element 162 in the optical receiving unit 140 according to the invention. The receiving unit 140 can be removably attached to an object via the assembly casing 160, for which purpose one or more cylindrical holes 161 are provided on the outer circumference of the assembly casing 160, via which the assembly casing can be attached to the object by means of a screw connection.

[0038] The measuring cell 141 essentially comprises a base plate 142, a transparent cover plate 143 with a scanning grating 144, one or more spacers 145 between the base plate 142 and the cover plate 143, and an optoelectronic detector 146, the light-sensitive surface of which is oriented towards the cover plate 143 or towards the scanning grating 144. The scanning grating 144, which is only shown diagrammatically in FIG. 2, is arranged on the side of the transparent cover plate 143 which is oriented towards the detector 146.

[0039] The base plate 142, the spacer 145 and the cover plate 143 of the measuring cell 141 each consist of the same material, preferably with a coefficient of thermal expansion as small as possible. In the present embodiment, quartz glass is selected as the material for these measuring cell components, alternatively, other materials, for example BK7 glass, are also suitable. This results in a very rigid structure of the measuring cell 141, while the identical material of the various components ensures, on the other hand, a high thermal constancy of the measurement variables to be detected via the measuring cell 141, i.e. a reliable stability against thermal influences is guaranteed. This means, for example, that in the case of a uniform temperature increase, due to the identical thermal expansion coefficients of all measuring cell components, the distance between the detector 146 and the scanning grating 144 increases in the same way that the scanning grating 144, which is arranged on the cover plate 143, expands and thereby increases its lattice constant. In this way, even in the case of a change in temperature, the angular position of the light source relative to the receiving unit 140, determined via the receiving unit 140, remains unchanged.

[0040] With the aid of the optoelectronic detector 146, the resulting periodic stripe pattern in the detection plane is detected, which results from the interaction of the beam emitted by the light source with the scanning grating 144. The position of the stripe pattern on the detector 146 depends on the incident direction of the light source radiation measured with respect to the receiving unit 140, so that the angular position of the light source can be determined from the position of the stripe pattern in the detection plane. Preferably, the scanning grating 144 of the receiving unit 140 is configured as a two-dimensional cross grating and the optoelectronic detector 146 is configured as a two-dimensional detector with optoelectronic detector elements arranged in columns and rows.

[0041] Thereby, two angles of incidence can be determined from the position of the generated two-dimensional stripe pattern on the detector 146, which angles of incidence are aligned with respect to the main direction of the two-dimensional scanning grating 144. This means that by evaluating the position of the stripe pattern on the detector 146, the direction of incidence of the light beam coming from the respective light source or the measured angular position of the light source can be detected for the corresponding receiving unit 140. For this reason, in this context, the corresponding position detection device is also called a spatial 2D angle measurement system.

[0042] For further processing of the signal generated via the detector 146, in the optical receiving unit 140 several signal processing modules 151.1 to 151.5 are arranged on a circuit board 150 below the base plate 142 of the measuring cell 141. These (signal processing modules) may be, for example, amplifier modules, A / D converter modules or line driver modules.

[0043] In order to avoid the above-mentioned disturbing influences on the optical receiving unit 140, it is provided for the cover element 162 to be conductively connected to the assembly casing 160 of the measuring cell 141. For this purpose, the cover element 162 has a configuration according to the invention with several layers, including at least one conductive layer which is transparent for the wavelengths used for the measurement, see the following description of figures 3 to 5 for further details in this regard. In this way, the interior of the measuring cell 141 is completely surrounded by a conductive shell consisting of the assembly casing 160 and the conductive layer 1 acting as a Faraday cage, which can be used to reliably shield the interior of the measuring cell against disturbing external electromagnetic fields. In particular in the case of the photoelectron detector 146, a high electromagnetic compatibility (EMC) can be ensured in this way. The use of the optical receiving unit 140 according to the invention is therefore also possible in environments with larger electromagnetic fields, for example in the working area of ​​a machine tool.

[0044] The cover element 162 of the optical receiving unit 140 according to the invention comprises, in addition to the conductive layer, also at least one antireflection layer 2. This is formed in such a way that, for the wavelength used for the measurement, a minimum reflectance and a maximum transmission value are obtained. If, for example, electromagnetic radiation with the measurement wavelength λ reaches on the antireflection layer of the cover element 162 inside the measuring cell 141, it does not reflect back to the detector 146, but is transmitted through the cover element 162 and leaves the measuring cell 141. This ensures that no signal-distorting scattered light reaches the photoelectron detector 146. In this way, the signal-to-noise ratio of the generated measuring signal can be significantly optimized.

[0045] By minimum reflectance is meant a minimum reflectance of the electromagnetic radiation reflected by the cover element 162. This minimum can be a minimum within a certain wavelength range of the incident electromagnetic radiation, for example between 750 nm and 950 nm. In the present embodiment, the reflectance minimum can be, for example, λ=850 nm. This results in a maximum transmittance throughout all layers 1, 2 including the carrier substrate 4 only for electromagnetic radiation having a wavelength of λ=850 nm. Advantageously, the reflectance at the minimum reflectance in the incidence angle range of 0°-50° is less than 2%, in particular less than 1%, advantageously less than 0.5%.

[0046] In this case, the angle of incidence means the internal angle formed between an incident electromagnetic wave and an axis A extending perpendicular to the plane of symmetry S of the carrier substrate 4 .

[0047] In this case, the plane of symmetry S extends centrally and parallel to the side faces 4.1, 4.2 through the carrier substrate 4. Furthermore, there may be rotational symmetry about an axis A extending perpendicularly to the plane of symmetry S.

[0048] In the illustrated embodiment of the optical receiving unit according to the invention, the cover element 162 shown in the cross-section of Fig. 3 consists of a planar carrier substrate 4 with opposite side surfaces 4.1, 4.2, in which a conductive layer 1 and an antireflection layer 2 are laminated flat against both opposite sides 4.1, 4.2, respectively. For example, a filter glass plate having a thickness in the range of 0.7 mm to 7 mm, which is configured to be transparent only for wavelengths above 780 nm, can be used as the carrier substrate. In this case, the layers 1, 2 on the opposite sides 4.1, 4.2, respectively, are formed in such a way that the conductive layer 1 is arranged between the carrier substrate 4 and the antireflection layer 2.

[0049] The conductive layer 1 is deposited on the carrier substrate 4, for example by a thin film process, for example by a suitable sputtering process. Preferably, a conductive oxide (TCO) that is transparent to the electromagnetic radiation used for the measurements is used as material for the conductive layer 1. In this example, a layer of aluminium doped zinc oxide (ZnO:Al) with a thickness of about 100 nm and a resistivity of 5·10 -6 Ω~6·10 -6 Ωm is contemplated as the preferred conductive oxide, although indium tin oxide (ITO) is alternatively suitable.

[0050] In the illustrated embodiment, the antireflection layer 2 arranged on the conductive layer 1 comprises a first partial layer 2.1 of silicon dioxide (SiO2) having a layer thickness of approximately 190 nm and a second partial layer 2.2 of silicon (Si) having a layer thickness of approximately 4 nm; alternatively, tantalum pentoxide (Ta2O5) can also be used for the second partial layer 2.1.

[0051] The lateral regions of the cover element 162 are provided with contact elements 5, which are formed around the cover element 162 and allow a conductive connection between the conductive layer 1 of the first side 4.1 and the conductive layer 1 of the second side 4.1. In this case, partial regions of the contact elements 5 are integrated into the stack of the cover element 162 in such a way that they are located between the conductive layer 1 and the antireflection layer 2. As a result, a contact area is formed between the antireflection layer 2 and the contact elements 5, which is configured in such a way that a sufficient electrical conductivity is formed in its area and the conductive layer 1 is simultaneously protected against corrosion in this area. In particular, this means that the conductive layer 1 is "embedded" or encapsulated below the antireflection layer 2 and laterally via the contact elements 5. The conductive layer 1 is thus reliably protected against corrosion even if the optical receiving unit according to the invention is used in a wet environment.

[0052] The contact element 5 may be formed from a number of superimposed partial layers of the same or different metals. In particular, electrically conductive metals that are also resistant to environmental influences are particularly suitable for this purpose. In particular, the contact element 5 may be formed in the form of a bondable aluminum-titanium-gold stack (AlTiAu). In this case, all partial layers of the stack can be formed with the same layer thickness or with respectively different layer thicknesses.

[0053] Alternatively, the contact element 5 may be made in the form of a bondable aluminium-chromium alloy (AlCr).

[0054] Preferably, the conductive layer 1 extends over the entire surface of the first and second side surfaces 4.1, 4.2 of the carrier substrate 4 and is applied directly to the carrier substrate by a thin-film process, as already mentioned. The contact elements 5 are then applied to the conductive layer 1, for example by sputtering, so that electrically conductive contacts are formed at the edge regions of the carrier substrate 4 or of the cover element 162.

[0055] In this example, electromagnetic radiation with a wavelength λ=850 nm is used for the measurements. For angles of incidence between 20° and 50°, the minimum reflectance occurs at this wavelength or in a defined range around this wavelength for both the conductive layer 1 and the two-part antireflection layer 2, thereby allowing maximum transmission through the conductive layer 1 and the two-part antireflection layer 2.

[0056] Within the scope of the present invention, it is possible to flexibly adjust the conductivity and / or resistance of the conductive layer 1 according to requirements. This is achieved by appropriately selecting the layer thickness of the conductive layer 1. Then, when designing the entire system of stacks, the layer thickness of the antireflection layer 2 arranged thereon must be adapted to the selected layer thickness of the conductive layer 1 in order to ensure the desired reflection and transmission properties of this layer.

[0057] For example, in environments with particularly disruptive electromagnetic fields, it may be necessary for the conductive layer 1 to have a higher conductivity and therefore a higher layer thickness in order to ensure reliable shielding of the inner space of the measuring cell. Correspondingly, in this case, the layer thickness of the antireflection layer 2 is also adapted so that there is still a noticeable minimum reflectance for the wavelength λ used for the measurement.

[0058] As can be seen from Fig. 3, a symmetrical construction of the cover element 162 with respect to a plane of symmetry S, which runs centrally and parallel to the side surfaces 4.1, 4.2 through the carrier substrate 4, is intended. This construction ensures, on the one hand, a minimization of reflections at the wavelength λ used for the measurement to the external and internal space of the measurement cell 141. On the other hand, a distortion-free construction of the cover element 162 is ensured by the symmetrical construction, which avoids optical distortions of the signal. In addition to the already mentioned symmetry of the cover element 162 with respect to the plane of symmetry S, there may additionally be a rotational symmetry with respect to an axis A, which is oriented perpendicular to the plane of symmetry S and runs through the center of the circular cover element 162.

[0059] As can be seen from Fig. 4, the partial regions of the contact elements 5 are formed to extend outwardly and parallel to the conductive layer 1 beyond the edge region. In this case, the parallel transition of the partial regions of the contact elements 5 is limited to a few millimeters, so that contact zones are formed only in the vicinity of the edge region. The antireflection layer 2, which is deposited on the conductive layer 1, extends over the entire remaining surface of the conductive layer 1 and forms an overlap region 6 with the contact elements 5. In the overlap region 6, the antireflection layer 2 extends over the partial regions of the contact elements 5. In this case, the antireflection layer 2 can cover the entire partial regions of the contact elements 5 (not shown), but preferably does not completely cover the partial regions of the contact elements 5, so that an open region 8 remains (see Fig. 4).

[0060] The cover element 162 is conductively connected to the assembly casing 160 via a conductive adhesive or solder connection, as shown diagrammatically in Fig. 5. In this case, the connection is preferably made via the free surface 8 of the contact element 5. Alternatively, however, any other surface of the contact element 5 can be used. In the case of an adhesive connection, a conductive adhesive is particularly suitable, which can be arranged partially or continuously between the contact element 5 and the assembly casing.

Claims

1. 1. An optical receiving unit for a position measuring system for determining spatial position information, comprising: the receiving unit comprises a measuring cell including a scanning grating and a photoelectron detector with a photosensitive surface oriented in the direction of the scanning grating; The measuring cell is arranged in an assembly casing with a cover element transparent to the measuring wavelength in the area of ​​the scanning grating, said cover element (162) comprises at least one conductive layer (1) conductively connected to said assembly casing (160); An optical receiving unit characterized by:

2. 2. The optical receiving unit according to claim 1, characterized in that the cover element (162) comprises a carrier substrate (4) having opposite sides (4.1, 4.2), and at least one conductive layer (1) and at least one anti-reflection layer (2) are laminated flat on both sides (4.1, 4.2).

3. 3. An optical receiving unit according to claim 2, characterized in that there is a conductive connection between the conductive layer (1) of the first side (4.1) and the conductive layer (1) of the second side (4.2) via a contact element (5).

4. 4. An optical receiving unit according to claim 2 or 3, characterized in that the conductive layer (1) is arranged between the carrier substrate (4) and the antireflection layer (2).

5. 5. The optical receiving unit according to at least one of claims 1 to 4, characterized in that the conductive layer (1) is configured as a conductive oxide (TCO) which is transparent to the electromagnetic radiation used for the measurement.

6. 6. The optical receiving unit according to claim 5, wherein the conductive oxide is aluminum-doped zinc oxide (ZnO:Al) or indium tin oxide (ITO).

7. the antireflection layer (2) comprises at least one first sub-layer (2.1) and at least one second sub-layer (2.2), The first partial layer (2.1) is made of silicon dioxide (SiO ２ ), and The second partial layer (2.2) is made of silicon (Si) or tantalum pentoxide (Ta ２ O ５ ), An optical receiving unit according to at least one of claims 2 to 6, characterized in that it is

8. The optical receiving unit according to at least one of claims 3 to 7, characterized in that the cover element (162) is formed such that at least a portion of the contact element (5) is arranged between the conductive layer (1) and the antireflection layer (2).

9. 9. The optical receiving unit according to at least one of claims 2 to 8, characterized in that the layer thicknesses of the conductive layer (1) and / or the antireflection layer (2) are formed in such a way that for the electromagnetic radiation used for the measurements, a minimum reflectance and a maximum transmittance are obtained for an angle of incidence between 0° and 50° with respect to an axis (A) extending perpendicularly to a plane of symmetry (S) of the carrier substrate (4).

10. 10. Optical receiving unit according to at least one of claims 2 to 9, characterized in that the conductive layer (1) is deposited directly on the carrier substrate (4).

11. Optical receiving unit according to at least one of claims 3 to 10, characterized in that the contact element (5) is formed circumferentially around the cover element (162).

12. Optical receiving unit according to at least one of claims 3 to 11, characterized in that the contact element (5) consists of an aluminium chromium alloy (AlCr) or an aluminium-titanium-gold stack (AlTiAu).

13. An optical receiving unit according to any one of claims 3 to 12, characterized in that the cover element (162) is connected to the assembly casing (160) via the contact element (5) by means of a conductive adhesive or a solder connection (7).

14. 14. An optical receiving unit according to any one of the preceding claims, characterized in that the carrier substrate (4) is made so as to be transparent only for wavelengths above 780 nm.

15. 15. An optical receiving unit according to any one of the preceding claims, characterized in that the cover element (162) is formed symmetrically with respect to a plane of symmetry (S) of the carrier substrate (4).

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