Position measuring system

Abstract

The invention relates to a position measuring system for determining spatial position information. The invention relates to a position measuring system comprising at least one light source and at least one optical receiving unit, the optical receiving unit having a scanning grating and a photodetector device, the photosensitive surface of which is oriented in the direction of the scanning grating. The invention relates to a detector arrangement for detecting a surface of a motor vehicle, comprising two detector regions which are arranged mirror-symmetrically in a detection plane about a first axis of symmetry which extends in the detection plane through a center of the detector arrangement, the first axis of symmetry is oriented orthogonally to a longitudinal extension direction of the detector regions. The two detector regions each have the shape of an isosceles acute triangle, the triangular tip of which has an apex angle is oriented in the direction of the center of the detector device (Fig. 2a).

Description

Technical Field

[0001] The invention relates to a position measuring system for determining spatial position information. Background Art

[0002] An optical position measuring system is known from WO 01 / 38828 A1, 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 includes a transmitting unit, which is arranged on a measuring object that can be moved in space, and the spatial position and orientation (attitude) of the measuring object are to be determined; for example, a suitable light source can serve as a transmitting unit. On the other hand, one or more optical receiving units are fixedly arranged relative to the movable transmitting unit, and the optical receiving units basically have a scanning grating and a photodetector device, and the photosensitive surface of the photodetector device is oriented in the direction of the scanning grating. With the help of such a system, the position of the transmitting unit in space can be determined by so-called multi-angle measurement. For this purpose, the direction of the line of sight to the transmitting unit is determined by two angle measurements from the perspective of the corresponding receiving unit. When the relative position of the two receiving units is known, the position of the transmitting unit can be determined according to the intersection of the determined lines of sight. This measurement principle can be expanded by adding other transmitting units, so that the spatial attitude of the transmitting unit can also be determined by corresponding measurements. For further details about this measurement principle, explicit reference should be made to the mentioned publications. Summary of the invention

[0003] The object of the present invention is to optimize such a position measuring system with regard to signal generation and thereby to increase the position measurement accuracy.

[0004] This object is achieved according to the invention by a position measuring system having the features of claim 1 .

[0005] Advantageous embodiments of the position-measuring system according to the invention result from the measures listed in the dependent claims.

[0006] 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 optical receiving unit, which has a scanning grating and a photodetector device, the photosensitive surface of which is oriented in the direction of the scanning grating. The detector device has two detector areas, which are arranged in a detection plane in a mirror-symmetrical manner with respect to a first symmetry axis, which extends through the center of the detector device in the detection plane, wherein the first symmetry axis is oriented orthogonally to the longitudinal extension direction of the detector areas. The two detector areas each have the shape of an isosceles acute triangle, the tip of the triangle having the vertex angle of which is oriented in the direction of the center of the detector device.

[0007] Preferably, the detector device has two further detector regions which are designed identically to the first two detector regions and are arranged mirror-symmetrically about a second axis of symmetry which extends through the center of the detector device in the detection plane and is oriented orthogonally to the first axis of symmetry.

[0008] Here, it is possible to:

[0009] the triangles each have a vertex angle γ, for which γ / 2=7.125°+ / -5° applies, and

[0010] - A triangular tip with an apex angle contacts at the center of the detector device.

[0011] In one possible embodiment, a plurality of individual detector elements may be arranged in each detector region periodically and parallel to one another along an arrangement direction which is oriented perpendicularly to a longitudinal extension direction of the detector region.

[0012] In this case, it is advantageous to provide that:

[0013] The detector elements are each designed in a rectangular shape, with the longitudinal axis of the rectangle being oriented parallel to the longitudinal extension direction of the detector region; and

[0014] Every fourth detector element is electrically connected to one another along the arrangement direction, so that four phase-shifted output signals are generated from the scanning of the fringe pattern falling on the detector arrangement for further processing.

[0015] In this case, preferably, the ratio of the detector element width to the detector element period is 1:7.

[0016] It can also be advantageously provided that for a change in the length of the detector elements along the arrangement direction:

[0017] dh_D / dx=+ / -8,

[0018] in

[0019] h_D: = detector element length,

[0020] x: = arrangement direction.

[0021] It is also possible that the scanning grating is arranged in a plane parallel to the detection plane and consists of a periodic arrangement of grid regions along at least one grid direction, wherein the grid direction is at an angle of 45° to the longitudinal extension of the detector region.

[0022] Advantageously, it is provided that the scanning grating is designed as a transmissive, combined amplitude-phase grating, wherein

[0023] - an identically designed, opaque amplitude grating structure is arranged in each grid area, and

[0024] Along each grid direction, a phase shift layer is arranged above the amplitude grating structure in every second grid region.

[0025] In this case, it is possible to design the phase shift layer with regard to material and layer thickness in such a way that a large degree of suppression of the 0th diffraction order and of all even-numbered diffraction orders is produced for a certain wavelength range and for a certain angle of incidence range.

[0026] Furthermore, the amplitude grating structure can be designed such that, for a certain wavelength range, a preferred transmission to + / - 1st diffraction order and a large degree of suppression of odd diffraction orders occurs.

[0027] In one possible embodiment, it can be provided that the scanning grating is arranged on that side of the transparent cover of the receiving unit which is oriented in the direction of the detector arrangement.

[0028] Preferably, the combined amplitude-phase grating has a checkerboard structure with a periodic arrangement of square grid areas along two orthogonal grid directions.

[0029] It may also be advantageous to provide that:

[0030] the amplitude grating structure consists of opaque grating strips which are arranged parallel to one another along the two grating directions and have at least partially different strip widths; and

[0031] The amplitude grating structures in grid regions arranged adjacent to each other along a grid direction are each designed to be mirror-symmetrical about an axis of symmetry which extends along a boundary of adjacent grid regions.

[0032] It is also possible that the light source is designed as an LED which emits radiation in the wavelength range λ=850 nm+ / −20 nm and has a coherence length of less than or equal to 7 μm.

[0033] The measures according to the invention now ensure that signal falsifying influences such as subharmonics, higher harmonics and 2D spatial frequencies that do not conform to the desired values ​​are suppressed or filtered out. It is also ensured that a sufficient signal strength of the detected measurement signal is generated for all detected reception angles within a large range of distances between the light source and the receiving unit. In this way, the accuracy of position measurement in space can be significantly increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Further details and advantages of the invention are explained with reference to the following description of an exemplary embodiment of the device according to the invention in conjunction with the attached drawings.

[0035] in:

[0036] Figure 1 A very schematic principle diagram is shown for explaining the measuring principle of the optical position measuring system according to the invention;

[0037] Figure 2a A top view showing an embodiment of a detector arrangement of an optical position measuring system according to the present invention;

[0038] Figure 2b Shown from Figure 2a An enlarged detailed view of a detector region of a detector arrangement;

[0039] Figure 3 A top view of an embodiment of a scanning grating of an optical position measuring system according to the present invention is shown;

[0040] Figure 4a Shown from Figure 3 A top view of a portion of a scanning grating;

[0041] Figure 4b Shown from Figure 4a A scanning grating is combined with an enlarged detailed view of its cross-section;

[0042] Figure 5 Shown from Figure 2a and Figure 3 Side-by-side illustration of the detector arrangement and scanning grating. DETAILED DESCRIPTION

[0043] in accordance with Figure 1 The basic measuring principle of the optical position measuring system according to the invention and its basic structure will be explained later based on the very schematic illustration in FIG.

[0044] The corresponding optical position measuring system comprises at least one light source LQ and at least one optical receiving unit OE. Here, the light source LQ can be arranged, for example, on a measuring object that can be moved in space, and the spatial position and orientation (attitude) of the measuring object should be determined by means of the fixedly arranged optical receiving unit OE.

[0045] The light source LQ is preferably designed as a nearly point light source, for example as an LED. In an advantageous embodiment, the light source LQ has only a slight coherence length, which is selected to be less than or equal to 7 μm; the light source emits radiation in the wavelength range λ=850 nm+ / -20 nm. In this case, the light source LQ sends a divergent light beam S in the direction of the optical receiving unit OE, i.e. no collimating optical device is arranged upstream of the light source LQ.

[0046] The optical receiving unit OE mainly comprises: a scanning grating AG arranged at the entrance side; and a photodetector device D fixedly arranged downstream of the scanning grating AG in the direction of light beam propagation. The scanning grating AG 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 device D. All components of the receiving unit OE are arranged in a suitable housing, which is Figure 1 The photosensitive surface of the detector device D is oriented in the direction of the scanning grating AG and defines a detection plane DE in the optical receiving unit OE. Figure 1 It can be seen that the detection plane DE is arranged in the receiving unit OE in parallel and at a certain distance d from the scanning grating AG. With regard to a suitable design of the optical receiving unit OE, reference is made here in addition to EP 4145083 A1.

[0047] The interaction of the light beam S emitted divergently by the light source LQ with the scanning grating AG generates a spatially structured light field in the form of a fringe pattern SM in the detection plane DE of the detector device D by grating self-imaging. Figure 1 The lower area of ​​is schematically represented in a partial top view of the detection plane DE of the detector device D. In the event of a relative movement of the light source LQ relative to the optical receiving unit OE, the fringe pattern SM moves in the detection plane DE above the detector device D. Subsequently, via the detection of the position or position change of the fringe pattern by means of the detector device D, the penetration point DP of the connecting line VL between the light source LQ and the detector device D can be determined via the scanning grating AG. From the orientation of the penetration point DP through the scanning grating AG, in combination with the known distance d between the scanning grating AG and the detector device D, a light incidence angle θ with respect to the grating normal GN results.

[0048] exist Figure 1In , only the conditions with respect to the drawing plane are shown, i.e. the drawing plane represents the measurement plane with respect to the light incidence angle θ. In practice, it is advantageous if, in addition to this - as mentioned at the outset - a second angle measurement is also performed along another measurement plane, which is oriented perpendicularly to the drawing plane. In this embodiment of the device according to the invention, a 2D angle measurement between the light source LQ and the optical receiving unit OE is ultimately performed. The two angle measurements are respectively incremental measurements, i.e. when the light source LQ is moved from a first position to a second position, the angular changes produced in these two measurement planes are detected by means of the optical position measuring system according to the invention. In a typical configuration, the signal period of the position-dependent incremental signal generated via the detector device D corresponds to an angular change of several mrad.

[0049] In order to ensure the most accurate possible measurement of the fringe pattern position and to avoid possible signal drops when the distance between the light source LQ and the receiving unit OE changes, a number of measures have proven to be advantageous in the optical position measuring system according to the invention, in particular with regard to the detector arrangement D and the scanning grating AG in the receiving unit OE. These measures are necessary because the sinusoidal gratings that are ideally required for measurement by means of grating self-imaging cannot be used as scanning gratings due to production technology; instead, binary gratings must be used. Here, an ideal sinusoidal grating is one whose transmission varies according to position in the form of sin 2 Gratings with varying shapes. When using such sinusoidal gratings, only the + / -1st diffraction order generated in transmission contributes to the grating self-image in the detection plane. In order to ensure sufficiently precise angle measurements even when using binary gratings, the measures to be explained below are advantageous in order to at least minimize undesirable influences caused by the binary grating. In the following, variants of the detector arrangement D or scanning grating AG are explained in detail, which are optimized by suitable measures for use in the optical position measuring system according to the invention.

[0050] in accordance with Figure 2a , Figure 2b , an advantageous embodiment of a detector arrangement 25 for 2D angle measurement shall first be described.

[0051] exist Figure 2a, a top view of a corresponding detector device 25 of an optical position measuring system according to the invention is shown. In the present example, the detector device 25 has four detector regions 25.1-25.4, each of which has the shape of an isosceles acute triangle. The tips of the triangles, which have the same vertex angle γ, are all oriented in the direction of the center Z of the detector device 25. In this case, the center Z is the geometric center of gravity of the area of ​​the detector device. The arrangement of the detector regions 25.1-25.4 is arranged so that: two detector regions 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 device 25. The symmetry axes S1, S2 extend through the center Z of the detector device 25 in the detection plane and are oriented orthogonally to each other. Specifically, in the example shown, the two detector regions 25.1, 25.2 are arranged mirror-symmetrically with respect to the first symmetry axis S1, and the two detector regions 25.3, 25.4 are arranged mirror-symmetrically with respect to the second symmetry axis S2. The detector regions 25.1, 25.2 or 25.3, 25.4 arranged mirror-symmetrically with respect to one of the two axes of symmetry S1 and S2 have a common longitudinal extension direction y or x, respectively. Figure 2a , the two detector regions 25.1, 25.2 extend along the indicated y direction and the detector regions 25.3, 25.4 extend along the x direction. Thereby, the longitudinal extension direction y of the two detector regions 25.1, 25.2 is oriented orthogonally to the first symmetry axis S1 and the longitudinal extension direction x of the two detector regions 25.3, 25.4 is oriented orthogonally to the second symmetry axis S2.

[0052] The two detector regions 25.1, 25.2 whose longitudinal extension directions are respectively oriented along the indicated y direction are used to detect the movement of the stripe pattern along the measuring direction x; through the other two detector regions 25.3, 25.4 whose longitudinal extension directions are respectively oriented along the x direction, the movement of the stripe pattern along the measuring direction y can be detected.

[0053] In the illustrated embodiment of the detector arrangement 25, it is provided that the triangular tips of the detector regions 25.1-25.4 with the vertex angle γ touch at the center Z of the detector arrangement 25. In this case, in the present example or for a detector having a radius of about 1 m 3 For the present application with a measurement volume of 1.50° and an angle of incidence range of approximately + / -50°, the vertex angle γ is selected in each case such that: γ / 2=7.125°+ / -5° applies. In principle, in the case of changing requirements on the measurement range, different ranges can also be provided for the vertex angle γ, for which γ / 2=7.125°+[-5°,+20°] can apply.

[0054] The length of the detector regions 25.1-25.4 along their longitudinal extension direction x or y is respectively 5.376 mm; the length of the base of the triangular envelope is respectively 1.344 mm.

[0055] exist Figure 2b 1 shows an enlarged detailed view of the detector region 25.1. As can be seen from the figure, within the detector region 25.1, a plurality of individual, rectangular detector elements 25.1_DE are arranged periodically and parallel to one another. Within the detector region 25.1, the periodic arrangement takes place along an arrangement direction x, which is oriented perpendicularly to the longitudinal extension direction y of the detector region 25.1; the arrangement direction x is therefore oriented parallel to the measuring direction x of the detector region 25.1. As can be seen, the rectangular longitudinal axes of the detector elements 25.1_DE are oriented parallel to the longitudinal extension direction y of the detector region 25.1. Photodetector elements in the form of photodiodes, for example, come into consideration as suitable detector elements 25.1_DE.

[0056] If also from Figure 2b As can be seen, within the detector region 25.1, along the arrangement direction x, every fourth detector element 25.1_DE is electrically connected to one another. This is done via four collecting lines 25.1_SL, which respectively electrically connect every fourth detector element 25.1_DE to one another. In this way, from the scanning of the fringe pattern in the detection plane, periodic output signals A, B, C, D are generated which are phase-shifted by 90° and are made available for further processing. With these four collecting lines 25.1_SL of the detector region 25.1, in the detector device 25, four contact terminals 25.1_K are connected outside the detector region 25.1, such as from Figure 2a Visible in.

[0057] Within the framework of further signal processing, in a known manner, the 0° output signal A and the 180° output signal C are combined into a first incremental signal S0 via a push-pull connection; the 90° output signal B and the 270° output signal D are also combined into a second incremental signal S90 via a push-pull connection, which is phase-shifted by 90° relative to the first incremental signal S0.

[0058] In the present exemplary embodiment, the width b of the detector elements 25.1_DE is selected to be b_D=12 μm, and the gaps between the detector elements 25.1_DE have a width of 9 μm. The detector element period P associated with the detector elements P with the same phase is then P_D=84 μm, i.e., b_D:P_D=1:7 applies to the ratio of detector element width b_D to detector element period P_D. A total of 64 detector elements 25.1_DE are provided in the detector region 25.1, resulting in a maximum width of the detector region 25.1 or a base length of the triangular envelope of 1.344 mm.

[0059] Figure 2b The arrangement of the detector elements 25.1_DE in the region of the left bottom corner of the detector region 25.1 is shown in detail. Thus, at the left edge of the detector region 25.1, the detector element providing the output signal B is arranged at a distance 1 / 8·P_D from the upper left corner point of the triangular detector region 25.1. At a distance 1 / 4·P_D, the detector elements 25.1_DE providing the output signals C, D, A, respectively, follow, and so on.

[0060] If also from Figure 2b As can be seen in FIG. 1 , due to the above-described triangular shape of the detector region 25.1, the detector elements 25.1_DE have different detector element lengths h_D along the arrangement direction x; in the section shown, for example, the detector element length h_D increases from left to right until the middle of the detector region 25.1; starting from the middle of the detector region 25.1, the length of the detector elements 25.1_DE then decreases again toward the right. Thus, starting from the left, the first detector element 25.1_DE providing the output signal B has a detector element length h_D=1·P_D; the second detector element (output signal C) has a detector element length h_D=3·P_D; the third detector element (output signal D) has a detector element length h_D=5·P_D, and so on.

[0061] In one advantageous embodiment, for the change in the detector element length h_D along the arrangement direction x, the following applies:

[0062] dh_D / dx=+ / -8,

[0063] in

[0064] h_D: = detector element length,

[0065] x: = arrangement direction.

[0066] Here, within the detector region 25.1, the detector elements 25.1_DE are arranged mirror-symmetrically with respect to a longitudinal axis of symmetry of the detector region 25.1, which extends in the y direction through the tip of the triangle. In this case, on both sides adjacent to this longitudinal axis of symmetry, two detector elements 25.1_DE providing output signals A, B are arranged. On the left side of this axis of symmetry is placed the detector element providing output signal A; on the right side of this axis of symmetry is placed the detector element with output signal B. The corresponding distances from this longitudinal axis of symmetry are + / -1 / 8·P_D. Next, on the left side, at a distance 1 / 4·P_D, is the detector element with output signal D, on the right side, at a distance 1 / 4·P_D, is the detector element with output signal C, and so on.

[0067] Detector region 25 . 2 is designed identically with regard to the arrangement of the detector elements, wherein the detector elements in both detector regions 25 . 1 , 25 . 2 which provide output signals A, B, C, D with the same phase lie opposite each other in mirror-symmetrical fashion with respect to a first axis of symmetry S1 .

[0068] The arrangement of the detector elements in the two detector regions 25.3, 25.4 is provided rotated by 90° relative thereto. In each detector region 25.1-25.4, the design and connection of the detector elements are respectively substantially identical.

[0069] In addition to the design of the scanning grating to be described, this design of the detector device 25 and in particular the arrangement and connection of the detector elements 25.1_DE in the different detector regions 25.1-25.4 contribute to suppressing or filtering out undesirable intensity components of the grating self-image, which otherwise would cause errors in the determination of the 2D angular position of the light source. Such undesirable signal components are, for example, higher harmonics or 2D spatial frequencies, which can be eliminated by the filtering effect of the detector device 25. The corresponding design of the detector regions 25.1-25.4 also ensures that reliable 2D angle measurements can be made over a large range of distances between the light source and the receiving unit; in the present embodiment, the distance between the light source and the receiving unit can be in the range between 0.2 m and 1.5 m. Within this range, the angle of incidence of the light beam from the light source can be measured within an angle range of incidence of + / -50° relative to the normal of the scanning grating.

[0070] Based on the subsequent explanation of the exemplary embodiment of the scanning grating in the optical receiving unit, further measures are described, which are also intended to suppress interference in the device according to the invention. Figure 3 shows a schematic top view of a circular scanning grating 21, Figure 4a , Figure 4bA detailed view of a portion of the scanning grating 21 including a cross-sectional view thereof is shown. Figure 4b The part of the scanning grating 21 shown in φ should also be referred to as the optical cell of the scanning grating 21 used.

[0071] The present scanning grating 21 is designed like the above-mentioned detector device 25 for 2D angle measurement. The scanning grating is designed as a transmissive, combined amplitude-phase grating, which consists of a periodic arrangement of square grid regions 21.1, 21.2 along two orthogonal grid directions GR1, GR2, wherein the grid regions 21.1, 21.2 are designed differently and have different optical effects on the light beam incident thereon. In this case, a combined amplitude-phase grating is to be understood as a grating having both an amplitude grating component and a phase grating component; for the specific design of the scanning grating 21, reference should be made to the further description of the following figures.

[0072] exist Figure 3 , EZ denotes a unit cell of the scanning grating 21, which has a total of four grid regions 21.1, 21.2, from which the scanning grating 21 can be constructed by translation along two grid directions GR1, GR2. In the embodiment shown, the periods P_GR1, P_GR2 along the two grid directions GR1, GR2 are selected to be identical according to P_GR1=P_GR2=222.85 μm.

[0073] exist Figure 4b The optical unit cell of the scanning grating 21 shown in has a period of 157.58 μm; this period determines the signal period of the position-dependent incremental signals generated by the detector arrangement D with respect to the resulting angular changes.

[0074] In each grid area 21.1, 21.2 of the scanning grating 21, an identically designed, non-transparent amplitude grating structure 21.3 is arranged on a carrier substrate 21.4, for example Figure 4b In this case, the amplitude grating structure is composed of opaque grating strips 21.3_G, which are arranged parallel to one another along the two grating directions GR1, GR2 and have at least partially different strip widths.

[0075] In each grid region 21.1, 21.2, the amplitude grating structure is designed to be identical and symmetrical about the center point M of the corresponding grid region. In addition, in the grid regions 21.1, 21.2 arranged adjacently along a grid direction GR1, GR2, the amplitude grating structures are designed to be mirror-symmetrical about the symmetry axes SG1, SG2, SG3, SG4, respectively, which extend along the boundaries of adjacent grid regions 21.1, 21.2. In this way, Figure 4b It can be seen, for example, how the widths of the opaque grating strips in the central grid region 21.2 and the adjacent grid region 21.1 at the bottom left have mirror symmetry with respect to the axis of symmetry SG1; the strip widths in the other three adjacent grid regions 21.1 are designed similarly with respect to the axes of symmetry SG2, SG3 and SG4. Figure 4b This is also clearly visible in the cross-sectional view of the scanning grating at the bottom right in FIG. 2 with respect to the symmetry axis SG1 ; as can be clearly seen therein, the amplitude grating structure in all grid regions 21 . 1 , 21 . 2 is designed identically.

[0076] An amplitude grating structure 21.3 designed in this way ensures that the scanning grating 21 is relatively similar to an ideal sinusoidal grating and produces a preferred transmission to the + / -1st diffraction order for a specific wavelength range; higher odd diffraction orders that could have a negative impact on the quality of the generated signal are thereby largely suppressed.

[0077] In every second grid region 21.2 along the two grid directions GR1, GR2, a phase shift layer 21.5 is arranged over the entire surface above the amplitude grating structure 21.3, as shown in FIG. Figure 4b Thus, the period of the phase shift layer 21.5 corresponds to the period P_GR1 or P_GR2 of the two grid regions 21.1, 21.2 arranged along the two grid directions GR1, GR2.

[0078] For example, tantalum pentoxide Ta with a refractive index of n=2.122 may be used in the scanning grating 21. 2 O 5 , as a suitable material for the phase shift layer 21.5. With a selected height h=351 nm, with this material it is possible to ensure that, for incident radiation in the wavelength range of 850 nm+ / -20 nm and in the angle of incidence range between 0° and 50°, not only the 0th diffraction order but also all even-numbered diffraction orders are suppressed. For an average angle of incidence of approximately 30°, the phase shift layer 21.5 then has a phase shift of 180°. Thus, by means of this design of the grid region 21.2, other diffraction orders which also have a negative impact on the signal quality can be eliminated; therefore, in the device according to the invention, essentially only the + / -1st diffraction order contributes to signal generation.

[0079] from Figure 4b The structure of the scanning grating 21 can be seen in detail in the cross-sectional view in FIG. 2. On the upper side of the carrier substrate 21.4, the above-mentioned amplitude grating structure 21.3 with opaque grating strips 21.3_G is arranged in two grating regions 21.1, 21.2, and / or a phase shift layer 21.5 is arranged in the grating region 21.2. On the opposite side of the carrier substrate 21.4, that is, on the lower side of the carrier substrate, there is also an anti-reflection layer 21.6 on the entire surface.

[0080] in accordance with Figure 5 Finally, it will be explained how the above-mentioned detector device 25 and the scanning grating 21 in the optical receiving unit of the position measuring system according to the invention are preferably arranged relative to each other; the corresponding relative arrangement is a further measure for filtering undesirable influences on the generated signal, especially in the case of 2D angle measurement. For this purpose, Figure 5 A top view of the side-by-side arrangement of the detector arrangement 25 and the scanning grating 21 is shown. Figure 1 As explained, in a practical system, scanning gratings 21 with a periodic arrangement of grid regions 21 . 1 , 21 . 2 along two grid directions GR1 , GR2 are arranged in a plane parallel to the detection plane and spaced apart by a distance d in the housing of the receiving unit.

[0081] according to Figure 5 , the scanning grating is arranged here so that: in the present case, the two grid directions GR1, GR2 are at an angle of 45° to the longitudinal extension directions x, y of the detector regions 21.1-21.4, respectively. By this relative arrangement of the scanning grating 21 and the detector device 25, it is possible to avoid: in certain cases, for a certain angle of incidence of the light source beam to the scanning grating, a complete signal loss can be avoided. That is, by this measure, it is ensured that: a reliable 2D angle measurement can be achieved in the entire measuring range.

[0082] Of course, in addition to the explained embodiments of the device according to the invention, there are also further design options within the scope of the invention.

[0083] Although the above examples enable 2D angle measurement in space, a design of the optical position measuring system according to the present invention is also possible in which 1D angle measurement between the light source and the optical receiving unit is performed only in one measuring plane.

[0084] In this case, on the detector device side, only Figure 2a Two of the four detector regions 25.1-25.4 in the embodiment, ie two opposite detector regions, for example the detector regions 25.1, 25.2 extending along the y-direction.

[0085] For this variant, the scanning grating then consists of a periodic arrangement of grid regions along only one grid direction, wherein these grid regions are in turn designed as combined amplitude-phase gratings. Here, each grid region also has an amplitude grating structure, above which a phase shift layer is arranged in every second grid region. In this case, the amplitude grating structure will not be a two-dimensional structure as described above, but a one-dimensional arrangement of opaque grating strips with partially different strip widths provided along the grid direction. In this case, the grid direction corresponds to the arrangement direction of the detector elements in the two detector regions 25.1, 25.2, i.e. Figure 2a The grating strips are arranged in the direction x in the detector element, whereby the grating strips are oriented parallel to the detector elements. The grating strips are arranged in turn in such a way that, as in the above example, undesirable odd diffraction orders are suppressed. For this purpose, a mirror-symmetrical arrangement of the grating strips with respect to an axis of symmetry is provided, which extends through the boundary of adjacent grid areas.

Claims

1. A position measuring system for determining spatial position information, the position measuring system having at least one light source and at least one optical receiving unit, the optical receiving unit comprising a scanning grating and a photodetector device, the photosensitive surface of the photodetector device being oriented in the direction of the scanning grating, It is characterized in that - the detector device (D; 25) has two detector regions (25.1, 25.2), which are arranged in a detection plane (DE) in a mirror-symmetrical manner with respect to a first symmetry axis (S1), which extends in the detection plane (DE) through a center (Z) of the detector device (D; 25), wherein the first symmetry axis (S1) is oriented orthogonally to a longitudinal extension direction (y) of the detector regions (25.1, 25.2); and The two detector regions (25.1, 25.2) each have the shape of an isosceles acute triangle, the triangle tip of which, with the vertex angle (γ), is oriented in the direction of the center (Z) of the detector arrangement (D; 25).

2. The position measurement system according to claim 1, characterized in that: The detector device (D; 25) has two further detector areas (25.3, 25.4), which are designed to be identical to the first two detector areas (25.1, 25.2) and are arranged in a mirror-symmetrical manner about a second axis of symmetry (S2), which extends in the detection plane (DE) through the center (Z) of the detector device (D; 25) and is oriented orthogonally to the first axis of symmetry (S1).

3. The position measurement system according to claim 1 or 2, characterized in that: - the triangles each have a vertex angle γ, for which γ / 2=7.125°+ / -5° applies, and - The triangular tips with said apex angle (γ) meet at the center (Z) of said detector device (D; 25).

4. Position measuring system according to at least one of the preceding claims, characterized in that In each detector region (25.1-25.4), a plurality of individual detector elements (25.1_DE) are arranged periodically and parallel to one another along an arrangement direction (x, y) which is oriented perpendicular to a longitudinal extension direction (y, x) of the detector region (25.1-25.4).

5. The position measurement system according to claim 4, characterized in that: The detector elements (25.1-DE) are each designed in a rectangular shape, and the longitudinal axis of the rectangle is oriented parallel to the longitudinal extension direction (y, x) of the detector region (25.1-25.4); and - Every fourth detector element (25.1_DE) is electrically connected to one another along the arrangement direction (x, y) so that four phase-shifted output signals (A, B, C, D) are generated from the scanning of the fringe pattern (SM) falling on the detector device (D; 25) for further processing.

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

7.

7. The position measurement system according to claim 5, characterized in that: For the change in the detector element length (h_D) along the arrangement direction (x), the following applies: dh_D / dx=+ / -8, in h_D: = detector element length, x: = arrangement direction.

8. Position measuring system according to at least one of the preceding claims, characterized in that The scanning grating (AG; 21) is arranged in a plane parallel to the detection plane (DE) and consists of a periodic arrangement of grid areas (21.1, 21.2) along at least one grid direction (GR1, GR2), wherein the grid directions (GR1, GR2) are at an angle of 45° with respect to the longitudinal extension directions (y, x) of the detector areas (25.1-25.4).

9. Position measuring system according to at least one of the preceding claims, characterized in that The scanning grating (AG; 21) is designed as a transmissive, combined amplitude-phase grating, wherein - an identically designed, opaque amplitude grating structure (21.3) is arranged in each grid region (21.1, 21.2), and - Along each grid direction (GR1, GR2), a phase shift layer (21.5) is arranged above the amplitude grating structure (21.3) in every second grid region.

10. The position measurement system according to claim 9, characterized in that: The phase shift layer (21.5) is designed with regard to material and layer thickness (h) in such a way that, for a certain wavelength range and for a certain angle of incidence range, a large degree of suppression of the 0th diffraction order and of all even-numbered diffraction orders is produced thereby.

11. The position measurement system according to claim 9 or 10, characterized in that: The amplitude grating structure (21.3) is designed in such a way that, for a certain wavelength range, a preferred transmission to + / -1st diffraction order and a large degree of suppression of odd diffraction orders occurs.

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

13. Position measuring system according to at least one of claims 9 to 11, characterized in that The combined amplitude-phase grating has a checkerboard structure with a periodic arrangement of square grid regions (GR1, GR2) along two orthogonal grid directions (GR1, GR2).

14. The position measurement system according to claim 13, characterized in that: The amplitude grating structure (21.3) consists of opaque grating strips (21.3_G) which are arranged parallel to one another along the two grating directions (GR1, GR2) and have at least partially different strip widths; and - The amplitude grating structures (21.3) in adjacently arranged grid regions (21.1, 21.2) along a grid direction (GR1, GR2) are designed to be mirror-symmetrical about symmetry axes (SG1, SG2, SG3, SG4), respectively, which extend along the boundaries of adjacent grid regions (21.1, 21.2).

15. Position measuring system according to at least one of the preceding claims, characterized in that The light source (LQ) is designed as an LED which emits radiation in the wavelength range λ=850 nm+ / −20 nm and has a coherence length of less than or equal to 7 μm.

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