Optical receiving unit

Abstract

To provide an optical receiving unit for a position measuring system for determining spatial position information, the optical receiving unit certainly preventing faulty measurement even under mechanical and / or thermal stress.SOLUTION: The present invention relates to an optical receiving unit for a position measuring system for determining spatial position information. The receiving unit has a measuring cell. The measuring cell includes a base plate, a transparent cover plate with a scanning grating, one or more spacers between the base plate and the cover plate, and an optoelectronic detector whose light-sensitive surface is oriented in the direction of the cover plate. The detector is arranged on the base plate of the measuring cell via a self-centering compensating element.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] From Patent Document 1, an optical position measurement system configured as a spatial 2D angle measurement system and capable of being used for specifying spatial position information is known. On the one hand, this system has a transmission unit provided on a measurement target that can move within a space where the spatial position and orientation, that is, the posture, are specified. As the transmission unit, for example, a suitable light source can play that role. On the other hand, one or more optical reception units are provided in a stationary state with respect to the moving transmission unit, and most of these optical reception units are equipped with a scanning grid and a photoelectronic detector, but further details about the corresponding structure of the reception unit are not known from the above document. By using such a system, the posture of the transmission unit within the space can be specified by so-called multiangulation. For this purpose, the direction of the line of sight (Sichtlinie) from each reception unit to the transmission unit is specified by two angle measurements. If the relative positions of two reception units are known, the posture of the transmission unit can be determined from the intersection point of the specified lines of sight. For further details of such a measurement principle, refer to the above document.

[0003] Similar measurement systems are also known from Patent Document 2. Figure 2 of this document also shows a possible structure of the optical receiving unit used therein. This unit consists of a measurement cell with a base plate on which a detector is positioned on top, and a cover plate with a scanning grid provided at a certain distance from the detector via a spacer. If such a measurement cell is mounted, for example, by screwing it to an object, the measurement cell may be mechanically deformed, which negatively affects the accuracy of positioning. In other words, deformation of the measurement cell may result in, for example, a change in the distance between the detector and the scanning grid. Furthermore, it may result in a lateral positional change between the detector and the scanning grid, or deformation of the scanning grid, or at least one of the above. Similar effects can also occur due to temperature changes. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 01 / 38828 [Patent Document 2] European Patent Application Publication No. 3557182 [Patent Document 3] European Patent Application Publication No. 3739287 [Patent Document 4] European Patent Application Publication No. 3175949 [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to provide an optical receiving unit for a position measurement system that identifies spatial position information, which ensures that it does not produce erroneous measurements even when mechanical and / or thermal strain is applied. [Means for solving the problem]

[0006] This problem is solved by the present invention, which provides an optical receiving unit equipped with the features of claim 1.

[0007] Advantageous embodiments of the optical receiving unit according to the present invention will become apparent from the configurations described in the dependent claims.

[0008] The optical receiving unit according to the present invention can be used in a position measurement system that identifies spatial position information. The optical receiving unit comprises a measuring cell, the measuring cell having a base plate, a transparent cover plate with a scanning grid, one or more spacers between the base plate and the cover plate, and an optoelectronic detector, the photosensitive surface of which faces the cover plate. The detector is positioned on the base plate of the measuring cell via a self-centering compensation member.

[0009] When thermal or mechanical influences act on the base plate, rotation of the detector around an axis perpendicular to the detector surface, as well as changes in its lateral position, can be prevented through the configuration of the compensation member.

[0010] To the advantage, - The compensating member consists of multiple adjacent stays surrounding a closed surface area. - Each of these stays comprises at least one detector mounting area and multiple tapered areas, - The compensation member comprises a plurality of additional measurement cell mounting areas, each of which is formed at the boundary area of ​​an adjacent stay. It is designed in that way.

[0011] Here, - The compensation member is positioned above the recess of the base plate via the measurement cell mounting area. - The compensating member has four stays, each with four tapered sections. - A single measuring cell mounting area is formed at each corner of the compensation member, and the compensation member is mounted on the base plate adjacent to the recess via these measuring cell mounting areas. - Each stay has one detector mounting area between two central tapered regions. - Each stay has two additional tapered regions on the outside, adjacent to the measurement cell mounting area. It is possible.

[0012] moreover, - The compensation member is bonded to the base plate surfacely via the measurement cell mounting area. - The detector is bonded to the compensation member surfacely via the detector mounting area. It may be provided in such a way.

[0013] Preferably, the photosensitive surface of the detector is positioned flush with the side of the base plate facing the scanning grid.

[0014] In an advantageous embodiment, the measuring cell may be supported and positioned within a mounting casing via a plurality of flex-joint bipods, which ensure kinematically fixed support of the measuring cell within the mounting casing.

[0015] At this time, - The flex-joint bipod has two legs, each leg comprising multiple leg sections and multiple flex-joints. - The flexure joint bipod is connected to the measuring cell at the connection area of ​​both legs and to the mounting casing by the free ends of both legs. - The flexure joint bipod is positioned tangentially to the outer circumference of the measuring cell. It is possible.

[0016] Advantageously, each flex-joint bipod is constructed such that two translational degrees of freedom are constrained, and only mobility is permitted with respect to a third translational degree of freedom and three rotational degrees of freedom.

[0017] It is possible for three flexure joint bipods to be arranged at an angular interval of 120° around the center of the measurement cell so that the measurement cell cannot move freely in any spatial direction by the cooperation of the three flexure joint bipods.

[0018] Here, advantageously, it has been found that the flexure joint bipod is advantageous when the rigidity along the tangential arrangement direction with respect to the measurement cell is higher than the rigidity in the direction perpendicular to this direction.

[0019] The flexure joint bipod can be formed from invar.

[0020] It is preferable that the base plate, at least one spacer, and the cover plate are made of the same material.

[0021] Furthermore, it is advantageous that the scanning grid is arranged on the side of the cover plate facing the detector.

[0022] Therefore, an optical position measurement system can be configured to identify the position and orientation of a measurement object that can move within a space equipped with a plurality of distinguishable light sources, and the system has one or more optical reception units according to the present invention arranged in a stationary state.

[0023] Thus, by the solution means of the present invention, it is guaranteed to minimize the measurement error in spatial position identification that may occur due to mechanical and / or thermal effects on the optical reception unit. This is achieved by always providing a stable relative position of the detector with respect to the scanning grid regardless of mechanical and / or thermal effects. Furthermore, distortions of the scanning grid, detector, and measurement cell that may similarly lead to measurement errors are avoided.

[0024] Further details and advantages of the present invention will become apparent from the following description in connection with the figures of an embodiment of the device according to the present invention. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic diagram of a position measurement system that identifies spatial position information using multiple optical receiving units according to the present invention. [Figure 2] This is a cross-sectional view of an embodiment of the optical receiving unit according to the present invention. [Figure 3] Figure 2 is a partial perspective view of the measurement cell of the optical receiving unit. [Figure 4] Figure 2 is a perspective view of the compensation member of the measurement cell in the optical receiving unit. [Figure 5] Figure 2 shows a perspective view of the entire measurement cell of the optical receiving unit connected to two flex-joint bipods. [Figure 6a] This is a side view of the flexure joint bipod of the optical receiving unit according to the present invention. [Figure 6b] This is a perspective view of the flexure joint bipod of the optical receiving unit according to the present invention. [Figure 7a] This is a diagram illustrating how the flexure joint bipod operates in the optical receiving unit according to the present invention. [Figure 7b] This is a diagram illustrating how the flexure joint bipod operates in the optical receiving unit according to the present invention. [Modes for carrying out the invention]

[0026] Figure 1 shows a fairly schematic representation of an optical position measurement system suitable for determining the position and orientation (hereinafter also referred to as the orientation of the object to be measured) of an object that can move in space, or for determining spatial position information. In this example, a measuring head 10 is provided as the object to be measured, and this measuring head is positionable in space via a kinematic mechanism 20, which is only schematically shown, and its orientation is determined using the optical position measurement system. As the measuring head 10, for example, a known switching probe that is positioned via a kinematic mechanism 20 in the machining area of ​​a machine tool to measure a manufactured workpiece by tactile probing can be used.

[0027] In this embodiment, the position measurement system consists of multiple spatial 2D angle measurement systems, which are basically known from, for example, Patent Document 1, cited at the beginning. For supplementary information, Patent Documents 3 and 4 are also mentioned. Both of these documents demonstrate the use of this type of 2D angle measurement system in a special optical position measurement system. The disclosures of these documents and the details of suitable 2D angle measurement systems contained therein are explicitly referenced here.

[0028] A suitable position measuring system has, on the one hand, a plurality of identifiable light sources 31.1-31.6 located on the measuring head 10 to determine orientation. 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 at 90° offsets around the measuring head 10, and only six of these light sources 31.1-31.6 are visible in the figure. On the other hand, the position measuring system has a plurality of light receiving units 40.1, 40.2 according to the present invention, which are stationary relative to the light sources 31.1-31.6 on the movable measuring head 10 side. In the illustrated embodiment, only two such light receiving units 40.1, 40.2 are provided, but of course, more such units may be used in this type of position measuring system, and similarly, the number of light sources used can naturally be changed. The light receiving units 40.1, 40.2 are located on a suitable stationary object, for example, on a machine frame (not shown).

[0029] By using the optical receiving units 40.1 and 40.2, which are described in more detail below, the incident 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 for each of the corresponding receiving units 40.1 and 40.2. Furthermore, if the relative positions of the two stationary receiving units 40.1 and 40.2 are known to each other, the orientation of the measuring head 10 can be determined from the identified incident direction or the intersection of the lines of sight to the light sources 31.1-31.6. To do this, the signals generated by the optical receiving units 40.1 and 40.2 are processed by the signal processing unit 50 and transferred to the orientation calculation unit 60, from which the orientation calculation unit determines the orientation or spatial position and orientation of the measuring head 10. Next, this information is made available to the mechanical control unit 70 to appropriately position the measuring head 10 in space via the kinematic mechanism 20.

[0030] An embodiment of the optical receiving unit 140 according to the present invention will be described in detail below with reference to further drawings. Here, Figure 2 shows a cross-sectional view of the receiving unit 140 with a measuring cell 141 and a mounting casing 160, Figures 3 and 5 show perspective views of the measuring cell 141 of the receiving unit 140, respectively, and Figures 4, 6a and 6b show yet another component of the receiving unit 140.

[0031] The receiving unit 140 includes, as a standard functional element, a measuring cell 141 housed within a mounting casing 160, the individual components of which are highlighted with hatching in Figure 2. Both the measuring cell 141 and the mounting casing 160 are cylindrical in shape, with the measuring cell 141 kinematically supported and positioned within the mounting casing 160. The mounting casing 160 includes a transparent cover 162 above the measuring cell 141, which essentially serves to protect the delicate measuring cell 141. The receiving unit 140 can be detachably mounted to an object via this mounting casing 160; for this purpose, one or more cylindrical holes 161 are provided on the outer circumference of the mounting casing 160, through which the casing can be attached to a stationary object by screw connections.

[0032] The measurement cell 141 basically comprises a base plate 142, a transparent cover plate 143 with a scanning grid 144, one or more spacers 145 between the base plate 142 and the cover plate 143, and an optoelectronic detector 146, the photosensitive surface of the detector facing either the cover plate 143 or the scanning grid 144. The scanning grid 144, shown schematicly only in Figure 2, is located on the side of the transparent cover plate 143 facing the detector 146.

[0033] The base plate 142, spacer 145, and cover plate 143 of the measuring cell 141 are all made of the same material, preferably having the smallest possible coefficient of thermal expansion. In this example, quartz glass is selected as the material for these components of the measuring cell, but other materials, such as BK7, are also considered suitable. This provides, on the one hand, a robust structure for the measuring cell 141, and on the other hand, ensures that the measured quantity detected by the measuring cell 141 is hardly altered by heat, because the different components are made of the same material. In other words, a certain degree of stability against thermal effects is ensured. This means, for example, that if the temperature rises uniformly, the distance between the detector 146 and the scanning grid 144 expands to the same extent as the scanning grid 144 positioned on the cover plate 143 expands, increasing its grid constant, thanks to the same coefficient of thermal expansion for all components of the measuring cell. In this way, even if the temperature changes, the angular position of the light source relative to the receiving unit 140, as identified by the receiving unit 140, remains unchanged.

[0034] The periodic fringe pattern formed on the detection surface is detected using an optoelectronic detector 146. This pattern arises from the interaction between the light beam emitted from the light source and the scanning grid 144. Since the position of the fringe pattern on the detector 146 depends on the direction of incidence of the light from the light source being measured to the receiving unit 140, the angular position of the light source can be determined from the position of the fringe pattern on the detection surface. Preferably, the scanning grid 144 of the receiving unit 140 is formed as a two-dimensional cross-grid, and the optoelectronic detector 146 is formed as a two-dimensional detector with optoelectronic detection elements arranged in rows and columns.

[0035] In this way, from the position of the generated two-dimensional fringe pattern on the detector 146, two incident angles with directionality relative to the main direction of the two-dimensional scanning grid 144 can be identified. In other words, by analyzing the position of the fringe pattern on the detector 146, it is possible to detect, from a measurement technique perspective, the incident direction of the light rays coming from each light source or the angular position of the light source being measured for the corresponding receiving unit 140. For these reasons, it is also called a spatial 2D angle measurement system in relation to the corresponding position detection device.

[0036] To further process the signal generated by the detector 146, several signal processing modules 151.1-151.5 are arranged within the optical receiving unit 140 on the circuit board 150 located beneath the base plate 142 of the measurement cell 140. These modules can be, for example, amplifiers, A / D converters, or line drivers.

[0037] To avoid the aforementioned problems when the optical receiving unit 140 is affected by heat, the detector 146 is positioned on the base plate 142 of the measurement cell 141 via a self-centering compensation member 147, in particular to prevent temperature-induced changes in the distance and / or relative position between the detector 146 and the scanning grid 144. This configuration avoids undesirable temperature-induced changes in the relative positional relationship between the detector 146 and the scanning grid 144, which are caused by the different thermal expansion coefficients of the silicon material of the detector, the quartz glass material of the measurement cell, and, in some cases, the substrate material of the detector. Otherwise, these changes are likely to be incorporated into the determination of the angular position of the light source as measurement errors.

[0038] The self-centering compensation member 147 used ensures, through its form, that it prevents both changes in the lateral relative position between the base plate 142 and the detector 146, and rotation of the detector 146 about an axis perpendicular to the detector surface. Such movements are thought to occur when thermal or mechanical influences act on the base plate 142 of the measuring cell 141. For example, if the detector 146 expands relative to the base plate 142 of the measuring cell 141 due to temperature, the self-centering compensation member 147 in the solution according to the present invention absorbs the corresponding mechanical deformation, while neither the detector 146 nor the measuring cell 141 deforms.

[0039] Although rotation of the detector 146 around the rotation axis within the detection surface is still basically possible due to the configuration of the compensation member 147, such movement of the detector 146 does not significantly affect the measurement accuracy.

[0040] In this embodiment, the compensating member 147 shown in the perspective view in Figure 4 consists of four adjacent stays 147.1-147.4 that surround a single closed surface area. While Invar is assumed here as the compensating member 147, other materials, such as aluminum or steel, are also considered suitable alternatives. In the illustrated example, the four stays 147.1-147.4 are all of the same length, so that these stays surround a square surface area, but of course, alternative modifications to this shape are also possible. Each of the individual stays 147.1-147.4 is equipped with detector mounting areas 147.1a-147.4a and multiple tapered sections 147.1_i, 147.1_ii, 147.1_iii, 147.1_iv. For clarity, in Figure 4, only the four tapered sections 147.1_1, 147.1_2, 147.1_3, and 147.1_4 of stay 147.1 provided in this example are labeled, while the labels for the remaining three stays 147.2-147.4 are omitted.

[0041] Furthermore, measurement cell mounting areas 147.1b-147.4b are provided in the boundary regions of adjacent stays 147.1-147.4, respectively. The compensation member 147 is bonded to the detector 146 by surface adhesion via the detector mounting areas 147.1a-147.4a, and the compensation member 147 is bonded to the base plate 142 of the measurement cell 141 by further surface adhesion in the measurement cell mounting areas 147.1b-147.4b.

[0042] In the illustrated example, each stay 147.1-147.4 of the compensation member 147 is provided with two central tapered sections 147.1_2 and 147.1_3, between which the respective detector mounting areas 147.1a-147.4a are located. In addition, each stay 147.1-147.4 is further provided with two outer tapered sections 147.1_1 and 147.1_4 adjacent to the measurement cell mounting areas 147.1b-147.4b.

[0043] In this embodiment, the compensating member 147 is positioned on a square recess 142.1 or a recess in the base plate 142. Here, the area of ​​the recess 142.1 is selected to be slightly larger than the area of ​​the detector 146 attached to the compensating member 147. The square surface area surrounded by the four stays 147.1-147.4 of the compensating member 147 is rotated by 45° relative to the square recess 142.1 in the base plate 142. For this purpose, the four measuring cell mounting areas 147.1b-147.4b are each bonded to the base plate 142 outside the recess 142.1 at the height of the center of the recess's edge. Thus, in this example, the side edges of the square detector 146 are aligned parallel to the edges of the recess in the base plate 142.

[0044] The adhesive bonding described above is provided on the side of the detector mounting area 147.1a-147.4a and the side of the measurement cell mounting area 147.1b-147.4b facing the base plate 142 of the measurement cell 141. Therefore, the photosensitive surface of the detector 146 is positioned on the side of the base plate 142 facing the scanning grid 144, which means that the detection surface of the detector 146 is at the same height as the upper surface of the base plate 142 outside the recess 142.1. Thanks to this configuration of the detector 146, when the temperature changes, their positional state is kept constant, and as a result, the distance between the detector 146 and the scanning grid 144 does not change, and measurement errors are not guaranteed to occur.

[0045] Further means are provided to prevent the optical receiving unit 140 and, in particular, the measuring cell 141 according to the present invention from undergoing mechanical deformation due to attachment to a stationary object. Specifically, the measuring cell 141 is connected to the assembly housing 160 via a hexapod structure consisting of a plurality of flex joint bipods 150.1, 150.2, and 150.3. In this example, the mechanically fixed support of the measuring cell 141 within the mounting casing 160 is ensured via the three flex joint bipods 150.1, 150.2, and 150.3, which are tangentially arranged around the outer circumference of the cylindrical measuring cell 141. In this way, the measuring cell 141 is positioned separately from the mounting casing 160 within the receiving unit 140, thereby preventing any possible mechanical influences on the mounting casing 160 from acting on the measuring cell 141. For example, if the receiving unit 140 is screwed to a non-flat mounting surface with different torques via multiple screw connections through the mounting casing 160, the structure and shape of the flexure joint bipods 150.1, 150.2, and 150.3 ensure that the measuring cell 141 does not deform.

[0046] In addition to reducing mechanical influence on the measuring cell 141, this type of separation between the measuring cell 141 and the mounting casing 160 also ensures further minimization of thermal influences, for example, when the mounting casing heats up through contact with the mechanical frame.

[0047] Figures 6a and 6b illustrate in detail one of the three flexure joint bipods provided, 150.1. In this example, invar is used as the material for each of the flexure joint bipods 150.1. As can be seen from the figures, each flexure joint bipod has two legs 150.1a and 150.1b, and these legs are equipped with leg sections 150.1a_1, 150.1a_2, 150.1a_3, 150.1b_1, 150.1b_2, 150.1b_3 and a plurality of flexure joints 151.a_1-151.a_4, 151.b_1-151.b_4 in the form of leaf springs. Each of the leg sections 150.1a and 150.1b is provided with three leg sections 150.1a_1, 150.1a_2, 150.1a_3, 150.1b_1, 150.1b_2, and 150.1b_3, and two pairs of flexure joints 151.a_1-151.a_4 and 151.b_1-151.b_4, which are oriented in pairs and perpendicular to each other.

[0048] The flex-joint bipod 150.1 is connected to the measuring cell at the connection area 152 of both legs 150.1a and 150.1b, and at the free ends 153.a and 153.b of both legs 150.1a and 150.1b, the flex-joint bipod 150.1 is connected to or mounted to appropriate mounting points on the mounting casing. This mounting is done via a pin provided on this part of the flex-joint bipod 150.1, and the measuring cell or mounting casing has a recess that fits the pin. Flexible joints 151.a_1, 151.a_4, 151.b_1, and 151.b_4 are provided between each of the outer leg sections 150.1a_1, 150.1a_3, 150.1b_1, and 150.1b_3 of the flexible joint bipod and the connecting sections 152, 153a, and 153.b, respectively.

[0049] Thus, through the flexure joint bipod configured in this way, two translational degrees of freedom of the measuring cell and the mounting casing connected to it, namely translation along the directions labeled z and y in Figure 6b, can be constrained. In contrast, relative movement between the measuring cell and the mounting casing is permitted in the remaining four degrees of freedom, which are translational motion along the x direction and rotational motion around the three directions x, y, and z.

[0050] The optical receiving unit according to the present invention has three flex-joint bipods 150.1, 150.2, and 150.3 of this type arranged at 120° angular intervals around the center of the measurement cell 141, arranged such that the longest extension direction of each flex-joint bipod 150.1, 150.2, and 150.3 is tangential to the measurement cell 141. The cooperation of the three flex-joint bipods 150.1, 150.2, and 150.3 ensures that the measurement cell 141 cannot move freely in any spatial direction. In Figure 7b, arrows 201, 202, and 203 represent the constrained degrees of freedom of the measurement cell 141 in the plane of the paper, and the black circles 301, 302, and 303 represent the constrained degrees of freedom of the measurement cell 141 perpendicular to the plane of the paper.

[0051] Each flex-joint bipod possesses particularly high rigidity along the z-direction, so that the measuring cell is uniquely fixed in space against translation along the z-direction and rotation around the x and y directions. In addition, each flex-joint bipod also possesses high rigidity tangentially to the measuring cell, so that the measuring cell cannot rotate around the z-direction. Moreover, by positioning the flex-joint bipods at 120° to the center of the measuring cell and tangentially, the translational degrees of freedom along the x and y directions are also constrained.

[0052] Therefore, the measurement cell as a whole is uniquely determined in all six degrees of freedom in space. In other words, the measurement cell cannot move freely in any spatial direction. As a result, the natural frequency of the measurement cell supported in this way becomes very high, actually reaching about 2 kHz. A particular advantage of kinematically supporting the measurement cell in this way is that, as a result of all the flex-joint bipods being very flexible radially from the perspective of the measurement cell, only very small forces act on the measurement cell. For this, please refer to Figure 7a, where arrows 401, 402, and 403 indicate the flexible directions of the three flex-joint bipods. As is clear from comparing Figure 7a and Figure 7b, the flex-joint bipods have higher rigidity along their tangential arrangement directions 201, 202, and 203 than in the directions 401, 402, and 403 perpendicular to them. The advantage of this is that the attachment points of the legs of the flex-joint bipod remain in place even if they may shift due to external forces acting on the mounting casing or due to thermal expansion.

[0053] Displacement motion of the mounting point, which may occur due to thermal or mechanical causes, is possible in all six degrees of freedom at this time because these displacement motions are elastically absorbed by each flexure joint bipod through a soft leaf spring, and no reaction force is generated in the measuring cell.

[0054] The reaction force from the flex-joint bipod to the measuring cell remains low despite the displacement of the mounting point due to the extremely low stiffness of the flex-joint in those directions. High stiffness exists only along the longitudinal extension of the leg section. Therefore, the measuring cell does not deform. As a result, the distance between the detector and the scanning grid within the measuring cell remains constant, and the scanning grid is not subjected to unexpected strain due to expansion or compression.

[0055] In addition to the embodiments of the apparatus according to the present invention described, there are of course further possible embodiments within the scope of the present invention.

Claims

1. An optical receiving unit for a position measuring system for determining spatial position information, the measuring cell having a base plate, a transparent cover plate with a scanning grating, one or more spacers between the base plate and the cover plate, and an optoelectronic detector, the photosensitive surface of the optical receiving unit facing the cover plate, An optical receiving unit, characterized in that the detector (146) is arranged on a base plate (142) of the measuring cell (141) via a self-centering compensation member (147).

2. 2. An optical receiving unit as described in claim 1, characterized in that, when thermal or mechanical influences act on the base plate (142), rotation of the detector (146) around an axis perpendicular to the detector surface as well as lateral position changes are prevented through the configuration of a compensation member (147).

3. 3. The optical receiving unit according to claim 1, the compensation element (147) consists of a number of adjacent stays (147.1-147.4) encircling a closed surface area, - each of these stays (147.1-147.4) comprises at least one detector mounting area (147.1a-147.4a) and a number of tapered areas (147.1_1-147.1_4); the compensation element (147) comprises a number of further measuring cell attachment areas (147.1b-147.4b), which are respectively formed in the border areas of adjacent stays (147.1-147.4); An optical receiving unit characterized by:

4. 4. The optical receiving unit according to claim 3, the compensation element (147) is arranged above the recess (142.1) of the base plate (142) via the measuring cell mounting area (147.1b-147.4b), the compensation element (147) has four stays (147.1b-147.4b) each with four tapered regions (147.1_1-147.1_4), the compensation element (147) is provided at each of its corners with a measuring cell mounting area (147.1b-147.4b) by means of which the compensation element (147) is mounted on the base plate (142) adjacent to the recess (142.1); Each stay (147.1-147.4) comprises one detector mounting area (147.1a-147.4a) between two central tapered areas (147.1_2, 147.1_3), Each stay (147.1-147.4) is provided with two further tapered regions (147.1_1, 147.1_4) on the outside, adjacent to the measuring cell mounting region (147.1b-147.4b). An optical receiving unit characterized by:

5. 4. The optical receiving unit according to claim 3, the compensation element (147) is surface-bonded to the base plate (142) via the measuring cell attachment areas (147.1b-147.4b); The detector (146) is face-bonded to the compensation element (147) via the detector attachment areas (147.1a-147.4a) An optical receiving unit characterized by:

6. 3. The optical receiving unit according to claim 1, An optical receiving unit, characterized in that the photosensitive surface of the detector (146) is arranged flush with the side of the base plate (142) facing the scanning grating (144).

7. 2. The optical receiving unit according to claim 1, An optical receiving unit, characterized in that the measurement cell (141) is supported and arranged in a mount casing (160) via a plurality of flexure joint bipods (150.1-150.3), the flexure joint bipods (150.1-150.3) ensuring a kinematically determined support of the measurement cell (141) in the mount casing (160).

8. 8. The optical receiving unit according to claim 7, - flexure joint bipods (150.1-150.3) each having two legs (150.1a, 150.1b) with a number of leg sections (150.1a_1, 150.1a_4, 150.1b_1, 150.1b_4) and a number of flexure joints (151.a_1-151.a_4, 151.b_1-151.b_4); the flexure joint bipod (150.1-150.3) is connected in the connection areas of both legs (150.1a, 150.1b) to the measuring cell (141) and by the free ends of both legs (150.1a, 150.1b) to the mounting casing (160); - the flexure joint bipod (150.1-150.3) is arranged tangentially to the outer circumference of the measuring cell (141) An optical receiving unit characterized by:

9. 9. The optical receiving unit according to claim 7, The flexure joint bipods (150.1-150.3) are each configured such that two translational degrees of freedom are constrained and only mobility is permitted with respect to a third translational degree of freedom and three rotational degrees of freedom. An optical receiving unit characterized by:

10. 9. The optical receiving unit according to claim 7, An optical receiving unit, characterized in that three flexure joint bipods (150.1-150.3) are arranged at angular intervals of 120° around the center of a measuring cell (141) so that the three flexure joint bipods (150.1-150.3) work together to prevent the measuring cell (141) from moving freely in any spatial direction.

11. 11. The optical receiving unit according to claim 10, The flexure joint bipods (150.1-150.3) are each characterized in that their stiffness along their tangential orientation with respect to the measuring cell (141) is higher than their stiffness in the direction perpendicular to this orientation.

12. 9. The optical receiving unit according to claim 7, An optical receiving unit, characterized in that the flexure joint bipod (150.1-150.3) is made of Invar.

13. 2. The optical receiving unit according to claim 1, An optical receiving unit, characterized in that the base plate (142), the at least one spacer (145) and the cover plate (143) are made of the same material.

14. 2. The optical receiving unit according to claim 1, An optical receiving unit, characterized in that the scanning grating (144) is arranged on the side of the cover plate (143) facing the detector (146).

15. 13. An optical position measuring system for determining the position and orientation of a moving object in a space in which a plurality of distinguishable light sources are arranged, the optical position measuring system comprising one or more optical receiving units (140) according to claim 1 arranged in a stationary state.

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