Position measurement system

Abstract

To optimize a general position measurement system with respect to signal generation, thus increasing accuracy of position measurement.SOLUTION: This position measurement system comprises at least one light source and at least one light receiving unit. The light receiving unit comprises a scanning grating and a photoelectron detector array. A photosensitive surface of the photoelectron detector array is oriented in the direction of the scanning grating. The detector array has two detection regions arranged in a detection plane in mirror symmetry about a first symmetry axis line. The first symmetry axis line extends in the detection plane through the center of the detector array, where the first symmetry axis line is disposed orthogonal to the longitudinal extending direction of the detection regions. The two detection regions have the form of isosceles triangles and acute triangles, respectively, where the tips having top angles of the triangles are oriented toward the center of the detector array.SELECTED DRAWING: Figure 2a

Description

[Technical field]

[0001] The present invention relates to a position measurement system for determining spatial position information. [Background technology]

[0002] From WO 01 / 38828 A1, an optical position measuring system is known which is designed as a spatial 2D angle measuring system and can be used to determine spatial position information. On the one hand, the position measuring system comprises a transmitting unit, which is arranged on a measuring object movable in space, the spatial position and orientation (pose) of which has to be determined, for example a suitable light source can serve as a transmitting unit. On the other hand, one or more receiving units are fixedly arranged opposite the movable transmitting unit, which receiving units essentially comprise a scanning grating and an optoelectronic detector array, respectively, the light-sensitive surface of the optoelectronic detector array being oriented in the direction of the scanning grating. With such a system, the position of the transmitting unit in space can be determined by so-called multiangulation. To this end, the direction of the line of sight towards 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 position of the transmitting unit can be determined from the intersection of the specific lines of sight. This measurement principle can be extended by adding further transmitting units, so that the spatial orientation of the transmitting units can also be determined by corresponding measurements. For further details of this measurement principle, please refer to the aforementioned publication. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] WO 01 / 38828 [Patent Document 2] European Patent No. 4145083 Summary of the Invention [Problem to be solved by the invention]

[0004] The object of the invention is to optimize a general position measuring system with regard to signal generation and thus to increase the accuracy of the position measurement. [Means for solving the problem]

[0005] This problem is solved according to the invention by a position measuring system having the features of claim 1.

[0006] Advantageous embodiments of the position measuring system according to the invention result from the measures recited in the dependent claims.

[0007] The position measuring system according to the invention is used to determine spatial position information. The position measuring system comprises at least one light source and at least one light receiving unit, which comprises a scanning grid and a photoelectron detector array, the photosensitive surface of which is oriented in the direction of the scanning grid. The detector array has two detection areas arranged in a detection plane with mirror symmetry with respect to a first symmetry axis, which extends through the center of the detector array in the detection plane, the first symmetry axis being oriented perpendicular to the longitudinal extension of the detection areas. The two detection areas each have the form of an isosceles, acute triangle, the apex angle of which is oriented with the tip angle towards the center of the detector array.

[0008] Preferably, the detector array has two further detection areas formed similarly to the two first detection areas and arranged mirror-symmetrically with respect to a second axis of symmetry that extends through the centre of the detector array in the detection plane and is oriented orthogonal to the first axis of symmetry.

[0009] in this case, - each triangle has a vertex angle γ such that γ / 2 = 7.125° ± 5°; - the apex points of the triangles touch each other at the center of the detector array; It is possible.

[0010] In one possible embodiment, in each detection region, a plurality of individual detection elements may be arranged periodically and parallel to one another along an array direction, which is oriented perpendicular to the longitudinal extension direction of the detection region.

[0011] In this case, advantageously, the detector elements are each rectangular in shape and the longitudinal axis of the rectangle is oriented parallel to the longitudinal extension of the detector area; - every fourth detector element is electrically connected to each other along the array direction, so that scanning of the stripe pattern impinging on the detector array results in four phase-shifted output signals for further processing; It is intended that.

[0012] In this case, preferably the ratio of detector element width to detector element period is 1:7.

[0013] Advantageously, for a change in detector element length along the array direction: dh_D / dx=+ / -8 holds true, h_D:=detection element length, x:=arrangement direction It can be contemplated that.

[0014] Furthermore, the scanning grating can be arranged in a plane parallel to the detection surface and can consist of a periodic arrangement of grating regions along at least one grating direction, whereby the grating direction can be at an angle of 45° to the longitudinal extension of the detection area.

[0015] Advantageously, it is provided that the scanning grating is formed as a complex amplitude-phase grating in transmission, At that time, - an identically formed opaque amplitude grating structure is disposed in each grating region; and Along each grating direction, a phase shift layer is arranged in every second grating region above the amplitude grating structure.

[0016] In this case, the phase shift layer, in terms of material and layer thickness, is configured to further significantly suppress the zeroth diffraction order and all even diffraction orders for a particular wavelength range and a particular range of incidence angles.

[0017] Furthermore, the amplitude grating structure may be formed to provide favorable transmission in the diffraction orders + / -1 for a particular wavelength range, and significant suppression of the odd diffraction orders.

[0018] In one possible embodiment, it may be envisaged that the scanning grating is arranged on the side of the transparent cover plate of the light receiving unit that is oriented in the direction of the detector array.

[0019] Preferably, the compound amplitude phase grating has a checkerboard structure with a periodic arrangement of square grating regions along two orthogonal grating directions.

[0020] Advantageously, - the amplitude grating structure consists of opaque grating webs which are arranged parallel to one another along two grating directions and have at least partially different web widths, the amplitude grating structures in adjacent grating regions arranged along the grating direction are formed mirror-symmetrically with respect to an axis of symmetry extending along the boundary between adjacent grating regions, It may be contemplated that.

[0021] Furthermore, it is possible for the light source to be formed as an LED emitting radiant energy in the wavelength range λ=850 nm±20 nm and having a coherence length of less than or equal to 7 μm.

[0022] The measures according to the invention ensure that the effects of signal distortions, such as undesired subharmonics, harmonics, 2D spatial frequencies, etc., are suppressed or filtered. Furthermore, a sufficient signal strength of the determined measurement signal is guaranteed to result in a large distance range between the light source and the receiving unit for all determined reception angles. In this way, it is possible to significantly increase the accuracy of the position measurement in space.

[0023] Further details and advantages of the invention are explained in the following description and in conjunction with the drawings, which are an example embodiment of the device according to the invention. [Brief description of the drawings]

[0024] [Figure 1] 1 is a highly schematic diagram for explaining the measurement principle of an optical position measuring system according to the invention; [Figure 2a] 2 is a plan view of one embodiment of a detector array of an optical position measurement system according to the present invention; [Figure 2b] FIG. 2b is an enlarged, detailed view of the detection area of ​​the detector array of FIG. 2a. [Diagram 3] 2 is a plan view of one embodiment of a scanning grating of an optical position measurement system according to the present invention; [Figure 4a] FIG. 4 is a plan view of a portion of the scanning grating of FIG. [Figure 4b] 4b and 4c show enlarged details and cross-sectional views of the scanning grating of FIG. 4a. [Diagram 5] FIG. 4 is an aligned view of the detector array and scanning grid of FIGS. 2a and 3; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The basic measurement principle of the optical position measuring system according to the invention and its basic structure are explained below on the basis of the highly schematic diagram of FIG.

[0026] A corresponding optical position measuring system comprises at least one light source LQ and at least one receiving unit OE, where the light source LQ can for example be arranged on a measurement object which is movable in space, the spatial position and orientation (pose) of which should be determined using a fixedly arranged receiving unit OE.

[0027] Preferably, the light source LQ is formed as an approximately point light beam, for example an LED. In an advantageous embodiment, the light source LQ has only a small coherence length selected to be less than or equal to 7 μm and emits radiation in the wavelength range λ=850 nm±20 nm. In this case, the light source LQ transmits a diverging beam S in the direction of the receiving unit OE, i.e. no collimation optics are arranged in front of the light source LQ.

[0028] The receiving unit OE essentially comprises a scanning grating AG arranged at the entrance side and an optoelectronic detector array D arranged fixedly downstream of the scanning grating AG in the beam propagation direction. The scanning grating AG is arranged on the side of a transparent cover plate DP of the receiving unit OE that is oriented in the direction of the detector array D. All components of the receiving unit OE are arranged in a suitable housing, which is not shown in detail in FIG. 1. The light-sensitive surface of the detector array D is oriented in the direction of the scanning grating AG and defines a detection plane DE in the receiving unit OE. As can be seen from FIG. 1, the detection plane DE is arranged in the receiving unit OE parallel to the scanning grating AG and at a certain distance d from the scanning grating AG. With regard to a suitable configuration of the receiving unit OE, reference is further made here to EP 4145083 A1.

[0029] The interaction of the light beams S emitted divergently by the light source LQ with the scanning grating AG results in a spatially structured light field in the detection plane DE of the detector array D by self-imaging of the grating in the form of a stripe pattern SM, which is shown diagrammatically in the lower area of ​​FIG. 1 in a partial plan view of the detection plane DE of the detector array D. When the light source LQ moves relative to the receiving unit OE, the stripe pattern SM in the detection plane DE moves over the detector array D. By knowing the position of the stripe pattern or the change in the position of the stripe pattern using the detector array D, it is possible to determine the intersection point DP of the connecting line VL between the light source LQ and the detector array D through the scanning grating AG. The location of the intersection point DP through the scanning grating AG in combination with the known spacing d between the scanning grating AG and the detector array D gives the angle of incidence θ of the light relative to the grating normal GN.

[0030] In FIG. 1, only the relationship to the drawing plane is shown, i.e. the drawing plane represents the measurement plane for the light incidence angle θ. In fact, in addition to this, as mentioned at the beginning, it is advantageous if a second angle measurement is also performed along another measurement plane that is oriented perpendicularly to the drawing plane. Thus, in such an embodiment of the inventive device, a 2D angle measurement is finally performed between the light source LQ and the receiving unit OE. Both angle measurements are incremental, i.e. in the case of a movement of the light source LQ from a first position to a second position, the resulting angular changes in the two measurement planes are ascertained using the optical position measuring system according to the invention. In a typical configuration, the signal period of the incremental position-dependent signal generated by the detector array D corresponds to an angular change of several mrad.

[0031] In order to ensure that the position of the stripe pattern is measured as accurately as possible and to avoid possible signal drops at different distances between the light source LQ and the receiving unit OE, some measures in the optical position measuring system according to the invention prove to be advantageous, in particular measures at the side of the detector array D and the scanning grating AG in the receiving unit OE. These measures are mainly necessary because an ideal sinusoidal grating, which is required for measurements with self-imaging of the grating, is not available as a scanning grating due to the manufacturing technology, and a binary grating must be used instead. In this case, an ideal sinusoidal grating means a grating whose transmittance varies sinusoidally depending on the position. When using such a sinusoidal grating, only the diffraction order + / -1, which gives rise to the transmittance, contributes to the self-imaging of the grating in the detection plane. In order to ensure sufficiently accurate angle measurements despite the use of a binary grating, the measures to be described below are advantageous in order to minimize undesirable effects caused by the binary grating at least as far as possible. In the following, variants of the detector array D or the scanning grating AG, optimized by suitable measures, for use in the optical position measuring system according to the invention are described in detail.

[0032] Based on Figs. 2a and 2b, an embodiment of an advantageous detector array 25 for 2D angle measurement will first be described.

[0033] In FIG. 2a, a plan view of a detector array 25 corresponding to an optical position measuring system according to the invention is shown. In this embodiment, the detector array 25 has four detection areas 25.1 to 25.4, each of which has the shape of an isosceles triangle, a triangular apex angle. The tips of the triangles, each of which has the same apex angle γ, are oriented towards the center Z of the detector array 25. The center Z represents the geometric center of gravity of the surface of the detector array. The arrangement of the detection areas 25.1 to 25.4 is designed such that each two detection areas 25.1, 25.2 or 25.3, 25.4 are arranged mirror-symmetrically with respect to one of the two symmetry axes S1, S2 of the detector array 25. The symmetry axes S1, S2 extend in the detection plane through the center Z of the detector array 25 and are oriented orthogonal to each other. In particular, the described embodiment has two detection areas 25.1, 25.2 arranged mirror-symmetrically with respect to a first axis of symmetry S1, whereas the two detection areas 25.3, 25.4 are arranged mirror-symmetrically with respect to a second axis of symmetry S2. The detection areas 25.1, 25.2 or 5.3, 25.4 arranged mirror-symmetrically with respect to one of the two axes of symmetry S1 or S2 have a common longitudinal extension direction y or x, respectively. Thus, according to FIG. 2a, the two detection areas 25.1, 25.2 extend along the indicated y direction and the detection areas 25.3, 25.4 extend along the x direction. The longitudinal extension direction y of the two detection areas 25.1, 25.2 is therefore oriented perpendicular to the first axis of symmetry S1, and the longitudinal extension direction x of the two detection areas 25.3, 25.4 is oriented perpendicular to the second axis of symmetry S2.

[0034] Two detection areas 25.1, 25.2, whose longitudinal extension directions are each oriented along the mentioned y direction, are used to determine the movement of the stripe pattern along the measurement direction x, and via the other two detection areas 25.3, 25.4, whose longitudinal extension directions are each oriented along the x direction, the movement of the stripe pattern along the measurement direction y can be determined.

[0035] In the illustrated embodiment of the detector array 25, the triangular apex angles γ of the detection areas 25.1 to 25.4 are arranged to contact each other at the center Z of the detector array 25. 3 For the present application, where the incidence angle is about ±50°, the apex angle γ is selected such that γ / 2=7.125°±5°. Essentially, if the measurement area requirements change, different areas can be provided for the apex angle γ, where γ / 2=7.125°+[−5°,+20°].

[0036] The length of the detection areas 25.1 to 25.4 along the longitudinal extension direction x or y is 5.376 mm, respectively, and the basic length of the triangular envelope is 1.344 mm.

[0037] An enlarged detailed view of the detection area 25.1 is shown in Fig. 2b. As can be seen, in this detection area 25.1, a number of individual rectangular detection elements 25.1_DE are arranged periodically and parallel to one another. The periodic arrangement takes place in the detection area 25.1 along an arrangement direction x which is oriented perpendicular to the longitudinal extension direction y of the detection area 25.1 and thus is oriented parallel to the measurement direction x of this detection area 25.1. As can be seen, the rectangular longitudinal axis of the detection element 25.1_DE is oriented parallel to the longitudinal extension direction y of the detection area 25.1. A suitable detection element 25.1_DE comprises an optoelectronic detection element in the form of a photodiode.

[0038] Also, as can be seen from Fig. 2b, every fourth detector element 25.1_DE is electrically connected to each other in the detector area 25.1 along the array direction x. This is done via four bus cables 25.1_SL, which electrically connect every fourth detector element 25.1_DE to each other. In this way, four periodic output signals A, B, C, D, phase shifted by 90°, are generated from the scanning of the stripe pattern in the detector plane and are available for further processing. As can be seen from Fig. 2a, in the detector array 25, four contact terminals 25.1_K outside this detector area 25.1 are connected to four bus cables 25.1_SL in the detector area 25.1.

[0039] During signal processing, the 0° output signal A and the 180° output signal C are combined in a known manner via a push-pull connection to form a first incremental signal S0, and the 90° output signal B and the 270° output signal D are also combined via a push-pull connection to form a second incremental signal S90 that is 90° out of phase with the first incremental signal S0.

[0040] In this embodiment, the width b of the detector elements 25.1_DE is selected according to b_D=12 μm, the spacing between the detector elements 25.1_DE has a width of 9 μm, and the period P of the detector elements for the in-phase detector elements P is P_D=84 μm, i.e. the ratio of the detector element width b_D to the detector element period P_D is b_D:P_D=1:7. A total of 64 detector elements 25.1_DE are provided in the detector area 25.1, and the maximum width or basic length of the triangular envelope of the detector area 25.1 is 1.344 millimeters.

[0041] Figure 2b shows in detail the arrangement of the detector elements 25.1_DE in the region of the bottom left corner of the detection area 25.1. Thus, the detector element providing the output signal B is located at the left edge of the detection area 25.1 and has a distance 1 / 8·P_D from the upper left corner point of the triangular detection area 25.1. At a distance 1 / 4·P_D respectively follows the detector elements 25.1_DE, which provide output signals C, D, A, etc.

[0042] Also, as can be seen from Fig. 2b, based on the above-mentioned triangular morphology of the detection area 25.1, the detection elements 25.1_DE have different detection element lengths h_D along the array direction x, where in the depicted part the detection element length h_D increases from left to right up to the center of the detection area 25.1, and the length of the detection elements 25.1_DE decreases again from the center of the detection area 25.1 towards the right. Thus, the first detection element 25.1_DE from the left supplying the output signal B has a detection element length h_D=1·P_D, the second detection element (output signal C) has a detection element length h_D=3·P_D, the third detection element (output signal D) has a detection element length h_D=5·P_D, etc.

[0043] In one advantageous embodiment, for a change in length h_D of the detector element along the array direction x, dh_D / dx=+ / -8, holds true, h_D:=length of the detection element, x:=array direction.

[0044] In the detection area 25.1, the detector elements 25.1_DE are arranged mirror-symmetrically with respect to the longitudinal axis of symmetry of the detection area 25.1, which runs along the y-direction through the tip of the triangle. In this case, the two detector elements 25.1_DE providing output signals A, B are arranged on either side of the longitudinal axis of symmetry. To the left of the axis of symmetry, the detector element providing output signal A is arranged, and to the right of the axis of symmetry, the detector element providing output signal B is arranged. The respective spacing with respect to the longitudinal axis of symmetry is + / - 1 / 8·P_D. Then, to the left, the detector element providing output signal D follows with a spacing of 1 / 4·P_D, and to the right, the detector element providing output signal C, etc. follows with a spacing of 1 / 4·P_D.

[0045] The detection areas 25.2 are also constructed identically with regard to the arrangement of the detection elements, the detection elements in the two detection areas 25.1, 25.2 providing in-phase output signals A, B, C, D and arranged opposite each other in mirror symmetry with respect to a first axis of symmetry S1.

[0046] In contrast, the arrangement of the detection elements in the two detection regions 25.3 and 25.4 is rotated by 90°. In each of the detection regions 25.1 to 25.4, the configuration and interconnection of the detection elements are basically the same.

[0047] In addition to the later-described development of the scanning grating, such development of the detector array 25, in particular the arrangement and interconnection of the detector elements 25.1_DE in the various detection areas 25.1-25.4, contributes to the suppression or filtering of undesired brightness components of the self-imaging of the grating, which would otherwise cause errors in the determination of the 2D angular position of the light source. Such undesired signal components are, for example, harmonics or 2D spatial frequencies, which can be removed by the filter effect of the detector array 25. Furthermore, this development corresponding to the detection areas 25.1-25.4 ensures that reliable 2D angle measurements are possible in a wide spacing range between the light source and the receiving unit, in the present embodiment a spacing between the light source and the receiving unit in the range of 0.2 m to 1.5 m is possible. In this range, the incidence angle of the light beam from the light source can be measured in the range of incidence angles of ±50° with respect to the normal of the scanning grating.

[0048] Further measures, which are also aimed at suppressing interference in the device according to the invention, are explained below with reference to an embodiment of a scanning grating in the receiving unit, where Fig. 3 shows a schematic plan view of a circular scanning grating 21 and Figs. 4a, 4b show detailed views of a part of the scanning grating 21 including a cross-section. The part of the scanning grating 21 shown in Fig. 4b is also referred to below as the optical unit cell of the scanning grating 21 used.

[0049] The scanning grating 21 of the present invention is designed for 2D angle measurements, like the above-mentioned detector array 25. It is formed as a transparent compound amplitude-phase grating consisting of a periodic arrangement of square grating areas 21.1, 21.2 along two orthogonal grating directions GR1, GR2, where the grating areas 21.1, 21.2 are formed differently and have different optical effects on the light rays incident on them. A compound amplitude-phase grating is understood here to be a grating having an amplitude grating component and a phase grating component; for the exact configuration of the scanning grating 21, please refer to the further description of the figures below.

[0050] 3, an elementary cell of the scanning grating 21 is indicated by EZ with a total of four grating regions 21.1, 21.2 in which the scanning grating 21 can be constructed by translation along the two grating directions GR1, GR2. In the described embodiment, the periods P_GR1, P_GR2 along the two grating directions GR1, GR2 are selected to be identical according to P_GR1=P_GR2=222.85 μm.

[0051] The optical unit cell of the scanning grating 21 (described in FIG. 4b) has a periodicity of 157.58 μm, which determines the signal period of the position-dependent incremental signal generated via the detector array D in terms of the resulting angular change.

[0052] In each grating region 21.1, 21.2 of the scanning grating 21, an identically configured and opaque amplitude grating structure 21.3 is arranged on a carrier substrate 21.4, as can be seen, for example, from Fig. 4b, where the amplitude grating structure consists of opaque grating webs 21.3_G which are arranged parallel to one another along the two grating directions GR1, GR2 in each case and which at least partially have different web widths.

[0053] In each grating region 21.1, 21.2, the amplitude grating structure is identical and configured symmetrically with respect to the center point M of the respective grating region. Moreover, in the grating regions 21.1, 21.2 arranged adjacent to each other along the grating directions GR1, GR2, the amplitude grating structure is formed mirror-symmetrically with respect to the symmetry axes SG1, SG2, SG3, SG4 extending along the boundaries of the adjacent grating regions 21.1, 21.2, respectively. For example, FIG. 4b is clear, for example, that the width of the opaque grating webs in the central grating region 21.2 and the lower left adjacent grating region 21.1 are mirror-symmetric with respect to the symmetry axis SG1, and similarly, the widths of the webs in the other three adjacent grating regions 21.1 are configured with respect to the symmetry axes SG2, SG3, and SG4. This is also clearly seen with respect to the symmetry axis SG1 in the cross-sectional view of the scanning grating in the lower right of FIG. 4b, where the amplitude grating structure is configured identically in all grating regions 21.1, 21.2.

[0054] The amplitude grating structure 21.3 configured in this manner results in the scanning grating 21 being relatively similar to an ideal sine grating, providing favorable transmission in the diffraction orders + / -1 for a particular wavelength range, while the odd higher diffraction orders, which in some cases may adversely affect the quality of the generated signal, are significantly suppressed.

[0055] As can be seen from the cross-sectional view of Fig. 4b, for every second grating region 21.2 along the two grating directions GR1, GR2, a phase-shift layer 21.5 is arranged over the entire amplitude grating structure 21.3. The periodicity of the phase-shift layer 21.5 thus corresponds to a periodicity P_GR1 or P_GR2, by which the two grating regions 21.1, 21.2 are arranged along the two grating directions GR1, GR2.

[0056] As a suitable material for the phase shift layer 21.5, for example, tantalum pentoxide Ta2O5 with a refractive index n=2.122 can be used for the scanning grating 21. At the selected height h=351 nm, this material ensures that both the 0th and even diffraction orders are suppressed for incident radiation energy in the wavelength range λ=850 nm±20 nm and in the range of angles of incidence between 0° and 50°. For an average angle of incidence of about 30°, the phase shift layer 21.5 has a phase shift of 180°. Thus, by such a design of the grating area 21.2, another diffraction order can be excluded, which also has a negative effect on the signal quality; in other words, in the device according to the present embodiment, only the diffraction order + / - 1 contributes to the signal generation.

[0057] The cross-sectional view of Fig. 4b shows in detail the structure of the scanning grating 21. On the upper side of the carrier substrate 21.4, the above-mentioned amplitude grating structure 21.3 with the opaque grating webs 21.3_G is arranged in the two grating areas 21.1, 21.2, or a phase shift layer 21.5 is arranged in the grating area 21.2. On the opposite side of the carrier substrate 21.4, i.e. on the lower side of the carrier substrate 21.4, there is additionally an antireflection layer 21.6 over the entire surface.

[0058] Finally, based on the description of Fig. 5, it is explained how the above-mentioned detector array 25 and the scanning grating 21 in the receiving unit of the position measuring system according to the invention are preferably arranged relative to each other, where the corresponding relative arrangement represents a further means for filtering out undesired influences on the generated signal, especially in the case of 2D angle measurements. In this regard, Fig. 5 shows a plan view of the side-by-side arrangement of the detector array 25 and the scanning grating 21. As explained with reference to Fig. 1, in the basic system, the scanning grating 21 with a periodic arrangement of grating areas 21.1, 21.2 along the two grating directions GR1, GR2 is arranged in a plane parallel to the detection surface and spaced apart by a distance d in the housing of the receiving unit.

[0059] According to the representation in Fig. 5, the scanning grating is arranged in the present case such that the two grating directions GR1, GR2 are each at an angle of 45° to the longitudinal extension directions x, y of the detection areas 21.1-21.4. With such a relative arrangement of the scanning grating 21 and the detector array 25, it is possible to avoid a complete signal loss at a certain angle of incidence of the light beam of the light source on the scanning grating. By this measure, it is thus guaranteed that reliable 2D angle measurements are possible over the entire measurement range.

[0060] In addition to the described embodiment of the device according to the invention, there are of course further design options within the scope of the invention.

[0061] Although the above described embodiments allow for 2D angle measurements in space, it is also possible to configure an optical position measuring system according to the invention in which only 1D angle measurements are made between the light source and the receiving unit in the measurement plane.

[0062] In this case, only two of the four detection areas 25.1-25.4 in FIG. 2a must be used, i.e. the two opposing detection areas such as detection areas 25.1, 25.2 extending along the y direction, on one side of the detector array.

[0063] In such a variant, the scanning grating consists of a periodic arrangement of grating areas along only one grating direction, whereby the grating areas are configured as a composite amplitude phase grating. Each grating area also has an amplitude grating structure, and for every second grating area a phase shift layer is arranged above the amplitude grating structure. In this case, the amplitude grating structure is not a two-dimensional structure as described above, but a one-dimensional arrangement of opaque grating webs arranged along the grating direction and having partially different web widths. In this case, the grating direction corresponds to the arrangement direction of the detector elements in the two detector areas 25.1, 25.2, i.e. the direction x in FIG. 2a, and therefore the grating webs are aligned parallel to the detector elements. The arrangement of the grating webs is such that, as in the above-mentioned embodiment, odd unwanted diffraction orders are suppressed. For this purpose, a mirror-symmetric arrangement of the grating webs with respect to an axis of symmetry extending through the boundary between adjacent grating areas is provided.

Claims

1. A position measurement system for determining spatial position information, comprising at least one light source and at least one light receiving unit, The light receiving unit comprises a scanning grating and a photoelectron detector array, the photosensitive surface of the photoelectron detector array being oriented in the direction of the scanning grating; In the position measurement system, said detector array (D; 25) comprises two detection areas (25.1, 25.2) arranged in a detection plane (DE) with mirror symmetry with respect to a first axis of symmetry (S1), said first axis of symmetry (S1) running through the centre of said detector array (D; 25) in said detection plane (DE), said first axis of symmetry (S1) being oriented perpendicular to the longitudinal extension (y) of said detection areas (25.1, 25.2); the two detection areas (25.1, 25.2) each have the form of an isosceles, acute triangle, the apex of said triangle having an apex angle (γ) oriented towards the centre of the detector array; A position measurement system comprising:

2. said detector array (D; 25) further comprises two further detection areas (25.3, 25.4) which are formed similarly to the two first detection areas (25.1, 25.2) and which are arranged mirror-symmetrically with respect to a second axis of symmetry (S2), which extends through the center (Z) of the detector array (D; 25) in the detection plane (DE) and is oriented orthogonal to the first axis of symmetry (S1); 2. The position measurement system according to claim 1 .

3. - each triangle has an apex angle γ such that γ / 2 = 7.125° ± 5°; and - the tips of the triangle with its apex angle (γ) touch each other at the center (Z) of the detector array (D; 25); 3. A position measuring system according to claim 1 or 2.

4. in each detection area (25.1-25.4), a plurality of individual detection elements (25.1_DE) are arranged periodically and parallel to one another along an arrangement direction (x, y), which is oriented perpendicular to the longitudinal extension direction (y, x) of the detection area (25.1-25.4); A position measuring system according to at least one of claims 1 to 3.

5. the detector elements (25.1_DE) are each rectangular in shape and the longitudinal axis of the rectangle is oriented parallel to the longitudinal extension (y, x) of the detector areas (25.1-25.4); every fourth detector element (25.1_DE) is electrically connected to each other along the array direction (x, y), so that a scan of the stripe pattern impinging on the detector array (D; 25) results in four phase-shifted output signals (A, B, C, D) for further processing; 5. The position measurement system according to claim 4.

6. the ratio of detector element width (b_D) to detector element period (P_D) is 1:7; 6. The position measurement system according to claim 5.

7. With respect to the change in the detector element length (h_D) along the array direction (x), dh_D / dx=+ / -8 holds true, h_D:=detection element length, x:=arrangement direction, 6. The position measurement system according to claim 5.

8. the scanning grating (AG; 21) is arranged in a plane parallel to the detection surface (DE) and consists of a periodic arrangement of grating areas (21.1, 21.2) along at least one grating direction, said grating directions (GR1, GR2) being at an angle of 45° to the longitudinal extension (y, x) of the detection areas (25.1-25.4); A position measuring system according to at least one of the preceding claims.

9. The scanning grating (AG; 21) is formed as a complex amplitude-phase grating in transmission, At that time, an identically shaped opaque amplitude grating structure (21.3) is arranged in each grating area (21.1, 21.2), and along each grating direction (GR1, GR2) and for each second grating region, a phase shift layer (21.5) is arranged above the amplitude grating structure (21.3); A position measuring system according to at least one of the preceding claims.

10. the phase shift layer (21.5) is configured with respect to material and layer thickness (h) to substantially suppress the zeroth and all even diffraction orders for a particular wavelength range and a particular range of incidence angles; 10. The position measuring system according to claim 9,

11. The amplitude grating structure (21.3) is shaped to provide favorable transmission in the diffraction orders + / - 1 for a particular wavelength range and significant suppression of odd diffraction orders.

11. A position measuring system according to claim 9 or 10.

12. The scanning grating (AG; 21) is arranged on the side of the transparent cover plate (DP) of the receiving unit (OE) that is oriented in the direction of the detector array (D; 25); A position measuring system according to at least one of the preceding claims.

13. A position measurement system according to at least one of claims 9 to 11, characterized in that the composite amplitude-phase grating has a checkerboard structure with a periodic arrangement of square grating regions (GR1, GR2) along two orthogonal grating directions (GR1, GR2).

14. - the amplitude grating structure (21.3) consists of opaque grating webs (21.3_G) which are arranged parallel to one another along the two grating directions (GR1, GR2) and which have at least partially different web widths, and the amplitude grating structures (21.3) in adjacent grating regions (21.1, 21.2) arranged adjacent to each other along the grating direction (GR1, GR2) are formed mirror-symmetrically with respect to respective symmetry axes (SG1, SG2, SG3, SG4) extending along the boundary between adjacent grating regions (21.1, 21.2), 14. The position measurement system according to claim 13.

15. The light source (LQ) is formed as an LED emitting radiant energy in the wavelength region λ = 850 nm ± 20 nm and having a coherence length of 7 μm or less; A position measuring system according to at least one of the preceding claims.

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