Optical position measuring device

Abstract

To provide an optical position measuring device which enables a simplified assembly of components of a scanning unit.SOLUTION: A first object 01 is connected to a first track having an incremental measuring scale 11 and a second track having an absolute measuring scale 12. A second object 02 is connected to an absolute detector arrangement structure 27 for detecting an aperiodic light pattern transmitted from the absolute measuring scale 12 onto a detection plane and an incremental detector arrangement structure 26 for detecting a periodic light pattern transmitted from the incremental measuring scale 11 onto the detection plane. Additionally, a fiber optic plate 23 composed of a large number of optical fibers is arranged as an integrated component in front of the absolute detector arrangement structure 27 and the incremental detector arrangement structure 26.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical position measuring device, which is suitable for determining the position of a first object relative to a second object. [Background technology]

[0002] A similar position measuring device is known, for example, from DE 10 200 03 133 A1. This device is used to determine the position of a first object with respect to a second object, which are arranged so as to be movable relative to one another along at least one measuring direction. On the one hand, a scale is provided which extends along the measuring direction and is connected to the first object. The scale has a first track with an incremental measuring graduation which consists of a number of graduation sections with different optical properties. The graduation sections are arranged so as to have a measuring graduation periodicity P INC The measuring scales are arranged along the measuring direction alternately with a period P INC gives the sum of the widths of adjacent different graduation sections. Furthermore, the scale has a second track with an absolute measurement graduation, which consists of a number of graduation sections with different optical properties arranged aperiodically along the measuring direction and which have a coding for determining the absolute position. Furthermore, the position measuring device has a scanning unit connected to the second object. The scanning unit has at least a detector with an absolute detector array for detecting the aperiodic light pattern transmitted from the absolute measurement graduation to a detection surface and an incremental detector array for detecting the periodic light pattern transmitted from the incremental measurement graduation to the detection surface, and a light source. Furthermore, the scanning unit has a fiber optic plate consisting of a number of optical fibers arranged side by side, with their image entrance surface facing the scale and their image exit surface facing the detector.

[0003] Such a position measuring device makes it possible, for example, to determine the position of a movable machine element in a machine relative to a stationary machine frame opposite it. The movable machine element on the one hand and the stationary machine frame on the other hand thus function as two objects which can be moved relative to each other. A higher-level machine control serves as the subsequent electronics, which uses the generated position-dependent signals, for example to position the movable machine element.

[0004] In the described embodiment of the document, the fiber optic plate used in the scanning unit is used for scanning the coded absolute measurement graduation. That is, during the measurement operation, the light pattern generated by the interaction of the light beam emitted by the light source with the absolute measurement graduation is transmitted via the fiber optic plate to the detection surface of the detector. In order to scan the incremental measurement graduation on the scale, a separate scanning plate with a suitable scanning grid is arranged adjacent to the fiber optic plate in the scanning unit. In such a configuration, the use of the fiber optic plate and the scanning plate requires that the two components must be aligned or mounted very precisely with respect to the respective detector arrangement during assembly of the scanning unit. Due to the manufacturing conditions and the different thicknesses of the fiber optic plate and the scanning plate, edges are also formed between the adjacently arranged components. On these edges, dirt can accumulate during the measurement operation, which can thereby jeopardize the function of the position measuring device.

[0005] The use of a fiber-optic plate in a scanning unit of an optical position measuring device is further known from DE 10 200 03 133 A1. However, the position measuring device described in this document does not have a measuring standard with different tracks for the incremental and absolute measuring graduations, so that the above-mentioned problems do not occur with this position measuring device, and therefore this document does not provide any suggestions for optimizing the position measuring device discussed at the beginning or for solving the above-mentioned problems. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] DE 102016211150 [Patent Document 2] European Patent Application Publication No. 3633323 Summary of the Invention [Problem to be solved by the invention]

[0007] The invention has the object of providing an optical position measuring device of the type described at the outset, which allows for a simplified assembly of the components of the scanning unit and at the same time is as resistant as possible to possible contamination. [Means for solving the problem]

[0008] This problem is solved according to the invention by an optical position measuring device having the features of claim 1.

[0009] Advantageous embodiments of the optical position measuring device according to the invention are obtained by the measures set forth in the dependent claims.

[0010] The optical position measuring device according to the invention is used for determining the position of a first object with respect to a second object which is movable relative to the first object along at least one measuring direction. The device comprises a scale extending along the measuring direction and connected to the first object. The scale comprises a first track with an incremental measuring graduation, which comprises graduation sections with different optical properties arranged alternately along the measuring direction with a period according to a measuring graduation periodicity, the measuring graduation periodicity giving the sum of the widths of the different graduation sections adjacent to each other. The scale further comprises a second track with an absolute measuring graduation, which comprises graduation sections with different optical properties arranged aperiodically along the measuring direction and has a coding for determining the absolute position. The position measuring device further comprises a scanning unit connected to the second object. The scanning unit is provided with at least one light source and a detector comprising an absolute detector arrangement for detecting a non-periodic light pattern transmitted from the absolute measuring graduation to a detection surface and an incremental detector arrangement for detecting a periodic light pattern transmitted from the incremental measuring graduation to the detection surface. The scanning unit further comprises a fiber optic plate, which consists of a number of optical fibers arranged side by side, with their image entrance faces facing the scale and their image exit faces facing the detector, and which is arranged as an integral part in front of the absolute detector array and the incremental detector array, so that both the absolute track information and the incremental track information are transmitted to the respective detector faces via the fiber optic plate.

[0011] The fiber optic plate preferably includes a scanning grid in the area in front of the incremental detector array structure.

[0012] Here, the scanning grid may be formed as an amplitude grating and may consist of a plurality of transparent and opaque linear grating sections arranged alternately along the measurement direction, the grating sections of the scanning grid being arranged with a period according to the scanning grid periodicity, which gives the sum of the widths of adjacent transparent and opaque grating sections.

[0013] Advantageously here, the optical fibers in the fiber optic plate are arranged along the measuring direction in a mesh with an average fiber periodicity, with respect to which P AG / 2>P Fx but, P Fx :=average fiber periodicity along the measurement direction x P AG := scan grid periodicity This holds true.

[0014] Furthermore, it is also possible for a scanning grid to be arranged on the image-entering side of the fiber optic plate facing the scale.

[0015] In addition, a flat, opaque covering layer may be arranged at least partially on the image-incident surface of the fiber optic plate facing the scale, the covering layer having an incremental scanning window and an absolute scanning window, the incremental scanning window having a scanning grid arranged therein.

[0016] Additionally, the scan grid periodicity may be selected to be different than the measurement graduation periodicity of the incremental measurement graduation.

[0017] For example, the scan grid periodicity is P AG =(k P DET P INC ) / (k P DET + / - P INC ) According to P AG:= scan grid periodicity P INC :=Incremental measuring scale periodicity P DET :=Detector periodicity of incremental detector array structure k:=3,4 may be selected as

[0018] Furthermore, at this time, n P AG =P DET but, P AG := scan grid periodicity P DET :=Detector periodicity of incremental detector array structure n:=1,2,3,… It is also acceptable for the above to hold true.

[0019] Alternatively, the scan grid periodicity may be selected to be equal to the measurement graduation periodicity of the incremental measurement graduation, at least within the scan grid area.

[0020] Advantageously, the incremental detector array structure comprises a plurality of light-sensitive detector elements arranged along the measurement direction with a period according to a detector periodicity, the detector periodicity giving the width of the detector elements along the measurement direction.

[0021] Here, three or four detection elements may be arranged along the measurement direction within one period of the periodic light pattern transmitted from the incremental measuring scale to the detection surface.

[0022] Furthermore, the incremental detector array structure and the absolute detector array structure may be integrated into an Opt-ASIC arranged in a recess in the holding member, and the upper surface of the Opt-ASIC may protrude from the upper surface of the holding member.

[0023] Here, a fiber optic plate may be disposed on the upper surface of the Opt-ASIC, and a gap medium may exist at least between the image exit surface of the fiber optic plate and the detector array structure.

[0024] An important advantage of the solution according to the invention is that when assembling the scanning unit, now only a single part needs to be aligned and attached to the detectors, since an integral fiber optic plate is provided in front of the two detector arrangements. The fiber optic plate formed as an integral part has a surface that is free of bumps and edges, the presence of which could potentially allow impurities to accumulate.

[0025] Further details and advantages of the invention will be explained on the basis of the following description of an embodiment of the device according to the invention in conjunction with the drawings. [Brief description of the drawings]

[0026] [Figure 1] 1 shows a highly simplified cross-sectional view of an embodiment of an optical position measuring device according to the invention; [Diagram 2] 2 is a three-dimensional view of a fiber optic plate of the position measuring device of FIG. 1. FIG. [Diagram 3] 2 is a cross-sectional view of the position measuring device of FIG. 1 on an enlarged scale in the region of the incremental detector array structure; [Figure 4] 6 shows a diagram of an incremental detector arrangement and a portion of a scanning grid in yet another variant of the optical position measuring system according to the invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] A schematic cross-sectional view of an embodiment of a position measuring device according to the invention is shown in figure 1, further details of this device are shown in figures 2 and 3. In the following, the embodiment will be explained on the basis of the various figures.

[0028] The position measuring device according to the invention is used to determine the position of a first object O1 with respect to a second object O2 which is movable relative to the first object along at least one measuring direction x. One object O1, for example a first machine element (machine component), is here connected to a scale 10 of the position measuring device, which extends along the measuring direction x. The other object O2, for example a second machine element (machine component), is movable along the measuring direction x relative to the first machine element and is connected to a scanning unit 20 of the position measuring device. In the present embodiment, both objects O1, O2 are assumed to move relative to each other along a linear measuring direction x, which is oriented perpendicular to the plane of the paper in FIG. 1.

[0029] With the position measuring device according to the invention, position-dependent signals are generated by optical scanning of the scale 10 with respect to the positions of the two objects O1, O2 which are movable relative to one another or of corresponding machine elements and are transmitted to a subsequent electronic device (not shown) which may, for example, be a higher-level machine control which uses the position-dependent signals for positioning the machine elements.

[0030] The scale 10 consists of a transparent supporting substrate, for example made of glass, on whose upper surface in this embodiment a first track with an incremental measuring graduation 11 extending along the measuring direction x and a second track parallel to this with an absolute measuring graduation 12 are arranged. The incremental measuring scale 11 has a measuring scale periodicity P INC The scale has a plurality of graduations with different optical characteristics that are arranged alternately along the measurement direction x at a period according to the measurement graduation periodicity P INC gives the sum of the widths of two adjacent different graduation sections. In the illustrated example, the incremental measuring scale 11 is configured as an amplitude grating, i.e. the different graduation sections each have a different light transmittance, on the one hand there are opaque graduation sections (e.g. made of chrome) and on the other hand there are transparent graduation sections. The absolute measuring graduation 12 has a coding section for determining the absolute position and consists of a number of graduation sections with different optical properties that are arranged aperiodically along the measuring direction x. Similar to the incremental measuring graduation 11, the different graduation sections of the absolute measuring graduation 12 have different light transmittances. The aperiodic coding section of the absolute measuring graduation 12 can, for example, be formed as a pseudorandom code (PRC).

[0031] In the position measuring device according to the invention, coarse absolute position information is obtained by optically scanning the absolute measuring graduation 12 and this information is precisely recalculated using high-resolution incremental position information generated by optically scanning the incremental measuring graduation 11. As a result, high-resolution absolute position information of the two objects O1, O2 is available at the output and can be further processed, for example by a downstream machine control.

[0032] Further components required in the position measuring device according to the invention for optically scanning the scale 10 or the two graduations 11, 12 and generating position-dependent signals are arranged on the side of the scanning unit 20. These include a light source 21 arranged on one side of the scale 10, for example in the form of an LED (light emitting diode) and emitting light with a wavelength of, for example, 850 nm. A collimation optics 22 is arranged in front of the light source 21 in the direction of light travel in order to collimate the light bundle emitted by the light source 21 in the direction of the scale 10.

[0033] Further components are arranged in the scanning unit 20 on the opposite side of the scale 10, which are used to optically scan the two graduations 11, 12 and generate position-dependent signals. For this purpose, a fiber optic plate 23 is provided there, which consists of a number of optical fibers arranged side by side, whose image input faces face the scale 10 and whose image output faces a downstream detector comprising an incremental detector arrangement 26 and an absolute detector arrangement 27. The incremental detector arrangement 26 is used here to detect the periodic light pattern transmitted to the detection surface by the incremental measuring graduation 11; the absolute detector arrangement 27 is used to detect the non-periodic light pattern transmitted to the detection surface by the absolute measuring graduation 12. Via the fiber optic plate 23, information from the two graduations 11, 12 is transmitted to the detection surfaces of the corresponding detector arrangements 26, 27.

[0034] In the illustrated embodiment, the incremental detector array structure 26 and the absolute detector array structure 27 are integrated in an Opt-ASIC 28, which is arranged in a recess in a holding member 29, e.g., a suitable circuit board or wiring board, in the scanning unit 20. In the Opt-ASIC 28, the detected signals are first processed before being transmitted to the subsequent electronics (not shown). As can be seen in FIG. 1, the upper surface of the Opt-ASIC 28 protrudes from the upper surface of the holding member 29.

[0035] Between the image exit surface of the fiber optic plate 23 and the light-sensitive surface of the detector array structures 26, 27 integrated in the Opt-ASIC 29, a gap medium 30 is further arranged. It is selected in such a way that the light beams emerging from the image exit surface of the fiber optic plate 23 undergo less refraction on their way to the respective detector array structures 26, 27 than they would in the absence of the gap medium. In addition to minimizing the refractive index jumps and the associated reflections at the interface, this ensures that in particular a light pattern with the highest possible contrast is provided at the detection surface of the incremental detector array structure 26 and the absolute detector array structure 27. A further point regarding the gap medium 30 is that it prevents the area between the fiber optic plate 23 and the Opt-ASIC 29 from becoming dirty. For example, a glue with an appropriately selected refractive index is conceivable as a material for the gap medium 30. For further details of the gap medium 30, reference is made to the above-mentioned US Pat. No. 5,399,313.

[0036] In order to avoid the problems discussed at the beginning, the optical position measuring device according to the invention is designed such that the fiber optic plate 23 thus arranged in the scanning unit 20 is arranged as an integral part in front of the absolute detector array 27 and the incremental detector array 26 or in front of their light-sensitive surfaces. In this way, both the absolute track information and the incremental track information are transmitted via the fiber optic plate 23 to the respective detection surfaces of the corresponding detector arrays 26, 27. In contrast, in DE 10 200 04 13 236 the fiber optic plate is only used for transmitting the light pattern from the coded absolute measurement graduation to the detection surface of the absolute detector array. In this document, a separate scanning plate with a scanning grid integrated therein is arranged in the scanning light path between the incremental measurement graduation and the incremental detector array for generating the incremental signal.

[0037] Therefore, when assembling the position measuring device according to the invention, only one component has to be correctly aligned and mounted in comparison with the known solutions, which significantly reduces the assembly work. The surface of the fiber optic plate 23 facing the scale 10 is flat all over and does not have edges, which are unavoidable in the case of an additional scanning plate for incremental scanning. As a result, no dirt can accumulate on this surface during the measuring operation. Furthermore, if this surface can be used to evacuate a suitable positioning device, the fiber optic plate 23 can be handled more easily during the assembly process. Furthermore, the thickness of the fiber optic plate 23 can be selected freely in principle. By dimensioning the fiber optic plate 23 in this way, it is possible to ensure mechanical protection of sensitive components arranged downstream in the optical path.

[0038] The fiber optic plate 23 used consists of a number of optical fibers arranged side-by-side, which are fused together and cut and polished to form a plane-parallel plate. Fiber optic plates of this kind are commercially available under the name "Fiber Optic Faceplates".

[0039] As regards the function of the fiber optic plate 23 for scanning the absolute measuring graduation 12 and transmitting the absolute track information to the detection surface of the absolute detector array 27, reference is made to US Pat. No. 5,399,633.

[0040] In order to be able to transmit the incremental track information also via the fiber optic plate 23 to the detection surface of the incremental detector array 26, a further configuration of the position measuring device according to the invention proves to be advantageous. A scanning grid 24 is thus arranged on the fiber optic plate 23 in the area in front of the incremental detector array 26. In the present exemplary embodiment, it is provided that the scanning grid 24 is arranged on the image-entrance side of the fiber optic plate 23 facing the scale 10. The scanning grid 24 is here configured as an amplitude grating. It consists of a number of transparent and opaque linear grating sections arranged periodically in the measuring direction x, with their longitudinal direction oriented perpendicular to the measuring direction x. The scanning grid periodicity P AG Hereinafter, x denotes the width of adjacent transparent and opaque grating portions in the scan grid 24.

[0041] In a possible embodiment of the optical position measuring device according to the invention, the scanning grid periodicity P AG is the average fiber periodicity P Fx This periodicity gives a measure of the average periodicity of the mesh of optical fibers along the measurement direction x in the fiber optic plate 23. These two periodicities are then preferably arranged to satisfy the following relationship: P AG / 2>P Fx (Formula 1) Where: P Fx :=average fiber periodicity along the measurement direction x P AG := scan grid periodicity

[0042] Two periodicities P AG ,P Fx This sizing ensures that as many optical fibers as possible in the transparent grating portion of the scanning grid 24 contribute to the transmission of the signal.

[0043] The corresponding fiber-optic plate 23 is shown in a perspective view in FIG. 2. The upper side of the fiber-optic plate 23 here represents the image input side facing the scale in the position measuring device according to the invention. As can be seen, a flat, opaque coating layer 31 with two rectangular scanning windows 32, 25 is arranged on the upper side of the fiber-optic plate 23. On the one hand, the incremental scanning window 32 is then provided in the coating layer 31, in which the scanning grid 24 is arranged. On the other hand, the coating layer 31 is provided with an absolute scanning window 25, which is made essentially transparent. The incremental scanning window 32 is arranged in the region of the fiber-optic scanning plate 23 in front of the incremental detector arrangement 26, and the absolute scanning window 25 is arranged in the region of the fiber-optic scanning plate 23 in front of the absolute detector arrangement 27.

[0044] In the position measuring device according to the invention, this fiber optic plate 23 is followed by a detector which comprises an absolute detector arrangement 27 and an incremental detector arrangement 26 .

[0045] The absolute detector array structure 27 then consists of a periodic arrangement along the measuring direction x of light-sensitive individual detector elements, for example a suitable CCD array.

[0046] The incremental detector array structure 26 has a detector periodicity P along the measurement direction x. DET The detector has a plurality of light-sensitive detector elements arranged at a period according to the detector periodicity P DET gives the width of the detector element along the measurement direction x. In this connection, reference is made to the description of FIG. 3, which shows a schematic and enlarged side view of the position measuring device of the invention in the region between the incremental detector array structure 26 and the scanning grid 24.

[0047] In the illustrated embodiment of FIG. 3, the measuring scale 10 has a measuring graduation periodicity PINC The scanning grid 24 on the image-incident surface of the fiber optic plate 23 has a scanning grid periodicity P AG = 19.512 μm, resulting in a measurement scale periodicity P INC The periodic light pattern resulting from the interaction of the light beam with the incremental measuring graduation 11 and the scanning grid 24 is transmitted through the fiber optic plate 23 to the detector surface of the incremental detector array structure 26, where the pattern is represented by a light pattern periodicity P LM 3, within one period of the light pattern, four detector elements 26.1-26.4 are arranged along the measuring direction x, which, in the case of a relative movement of the scale 10 and the scanning unit 20, result in phase-shifted incremental signals with the illustrated relative phases 0°, 90°, 180°, 270°; DET In this embodiment, P DET = 200 μm.

[0048] In the following, we basically consider the selected scanning grid periodicity P AG Now, different variants of the optical position measuring device according to the invention will be considered in detail.

[0049] In a first variant, the scanning grid periodicity P AG is chosen in the same way as in the example of FIG. 3 described above, i.e. the measurement scale periodicity P INC Different scanning grid periodicity P AG , that is, P AG ≠P INC is selected.

[0050] In this case, the light beam emitted by the light source interacts with the incremental measuring scale and the scanning grid to produce a light pattern periodicity P LM In this case, a periodic (vernier) light pattern with a light pattern periodicity P LM is given by the following relation: P LM=+ / -P AG P INC / (P AG -P INC ) (Formula 2) Where: P LM :=Light pattern periodicity P AG := scan grid periodicity P INC := Measurement scale periodicity

[0051] Within one light pattern period, an incremental detector array structure typically has three or four detector elements evenly distributed. These generate three 120° or four 90° phase-shifted incremental signals during the relative movement of the scale and the scanning unit. Typically, a number (N) of light pattern periods are scanned with the incremental detector array structure. For each phase of the incremental signal, a number (N) of detector elements connected in parallel contribute to generating a signal. Thus, if k(3,4) detector elements are used per light pattern period, the following holds: k P DET =+ / -P AG P INC / (P AG -P INC ) (Formula 3) where: k:=3,4 P DET :=detector periodicity P LM :=Light pattern periodicity P AG := scan grid periodicity P INC := Measurement scale periodicity

[0052] Required scan grid periodicity P AG is the periodicity of a given measurement scale P INC and the detector periodicity P DET From these relationships, P AG =(k P DET P INC ) / (k P DET + / - P INC) (Equation 4) where: P AG := scan grid periodicity P INC :=Incremental measuring scale periodicity P DET :=Detector periodicity of incremental detector array structure k:=3,4 is obtained by

[0053] The P who conducted the study AG ≠P INC In the first variant of the scanning grid periodicity P AG and the measurement scale periodicity P INC It is also important to note how much the opaque grid portions contribute to the generation of a signal per detector element.

[0054] As in the previous example of FIG. 3, the scan grid periodicity P AG and the measurement scale periodicity P INC If there is only a small difference between the phase shifts, then for each detector element capturing a signal, a similar number of opaque grating sections of the scanning grid will be contributed by each detector element of different phase; the resulting phase-shifted incremental signals will then be substantially no different in terms of their offset and in terms of their amplitude and phase relationships.

[0055] In contrast, the scanning grid periodicity P AG and the measurement scale periodicity P INCIf n differs significantly, it may happen that for each detector element capturing the signal, a different number of opaque grid sections of the scanning grid will contribute. As a result, the resulting phase-shifted incremental signals will have obvious differences in amplitude and phase relationships with respect to their offsets, which may lead to errors in localization. To address this issue, a further condition on the design of the scanning grid may be provided such that for each detector element, the same n number of opaque grid sections of the scanning grid must contribute to the capture of the signal, i.e., the following further condition must be met: n P AG =P DET (Formula 5) where: P AG := scan grid periodicity P DET :=Detector periodicity of incremental detector array structure n:=1,2,3,…

[0056] As a consequence of this additional condition, in the corresponding position measuring device, the detector periodicity P DET or light pattern periodicity P LM Only certain permitted values ​​are possible for , which are governed by the following conditions: P DET =+ / -P INC / k+n·P INC (Formula 6) where P DET :=Detector periodicity of incremental detector array structure P INC :=Incremental measuring scale periodicity k=3,4 n=1,2,3,…

[0057] In the ideal case, the detector periodicity P of the incremental detector array structure is DET Also, the measurement scale periodicity P INCshould be chosen as a natural multiple of , since in that case the image of the scale structures transferred through the fiber optic plate would be filtered. According to equation 6), this condition cannot be realized further.

[0058] Measured scale periodicity P at k=4 INC = 20 μm, detector periodicity P DET or light pattern periodicity P LM For example, we get the following possible values:

[0059] [Table 1] and so on.

[0060] As mentioned above, P DET = n P AG and P DET =i P INC Since an ideal solution with n,i > 0 is not possible within the bounds of the vernier scan, one can try to find an optimal compromise: for example, n and i may not be chosen as natural numbers, but instead be replaced by real-valued factors fn and fi that are as close to natural numbers as possible.

[0061] Conditional Expressions P AG =fn·P DET (Formula 7a) and P INC =fi·P DET (Formula 7b) Using equation 3, we get: k P DET =+ / -fn·fi·P DET / (fn-fi) (Eq. 8) where k=3,4, Therefore, k=fi / (1-fi / fn) (Eq. 9) It becomes.

[0062] This allows P DET and PAG or P INC There is a beat between each of these, and the periodicity can be described as: S AG =abs(P DET P AG / (P DET -P AG )) (Equation 10a) or S INC =abs(P DET P AG / ((P DET -P INC )) (Equation 10b)

[0063] It is further advantageous that the total length L of the incremental detector array structure INC but, L INC = N k P DET (Formula 11) (N: number of vernier periods to be scanned) and the two beat periodicities S AG and S INC with natural number factors M1 and M2: L INC =M1 S AG (Formula 12a) L INC =M2 S INC (Formula 12b)

[0064] In the following, a second variant of the position measuring device according to the invention will be considered; in this variant, the scanning grid periodicity P AG is the measurement scale periodicity P of the incremental measurement scale at least within the scanning grid area. INC So that P AG =P INC4 shows a diagram of the scanning grid and part of the incremental detector array 126 of such a variant of the optical position measuring device according to the invention, which is arranged to generate incremental signals which are phase shifted by 90° with k=4. As can be seen, n=2 opaque grid sections 124.1-124.8 are assigned to each detector element 126.1-126.4 of the incremental detector array 126. The width or periodicity P of the incremental detector array 126 along the measuring direction x is DET Within the scanning grid area corresponding to INC The corresponding scanning grid periodicity P AG Between the opaque grid sections 124.1-124.8 provided for adjacent detector elements 126.1-126.4, there is a P AG +1 / 4P AG Similarly, for an incremental signal with k=3 and phase shifted by 120°, the interval is P AG +1 / 3P AG It becomes.

[0065] In this type of variant, the scanning grid periodicity P AG is the detector periodicity P DET If the size is selected to be comparable to that of P AG =P INC =P DET so that only a single (n=1) opaque grid section of the scanning grid is provided for each detector element of the incremental detector array. Again, between the opaque grid sections for adjacent detector elements, P AG +1 / 4P AG There is an interval of

[0066] In addition to the embodiments specifically described, there are, of course, still other possible embodiments within the scope of the invention.

[0067] In this way, the position measuring device according to the invention can be made not only for detecting relative movements along a linear measuring direction, but also for detecting relative movements in rotation about a rotation axis.

[0068] Alternatively to the example described, the scanned graduation can also be formed as a phase grating etc.

Claims

1. 1. An optical position measuring device for determining a position of a first object with respect to a second object movable relative to the first object along at least one measurement direction (x), comprising: a scale extending along a measuring direction (x) and connected to a first object, Measurement scale periodicity (P ＩＮＣ The scale has a plurality of graduations with different optical characteristics that are alternately arranged along the measurement direction (x) at a period according to the measurement graduation periodicity (P ＩＮＣ ) has a first track with incremental measurement graduations providing a sum of widths of adjacent distinct graduations; The second track has an encoding portion for specifying an absolute position and has an absolute measurement scale consisting of a plurality of scale portions having different optical characteristics that are non-periodically arranged along the measurement direction (x). Equipped with a standard scale, a scanning unit connected to a second object, At least one light source; a detector comprising an absolute detector array for detecting a non-periodic light pattern transmitted to a detection surface from an absolute measurement graduation, and an incremental detector array for detecting a periodic light pattern transmitted to a detection surface from an incremental measurement graduation; a fiber optic plate comprising a number of optical fibers arranged adjacent to each other, the image input surfaces of the optical fibers facing the scale and the image output surfaces of the optical fibers facing the detector; Equipped with a scanning unit In an optical position measuring device, An optical position measuring device characterized in that the fiber optic plate (23) is arranged as an integral part in front of the absolute detector array structure (27) and the incremental detector array structure (26), such that both absolute track information and incremental track information are transmitted to their respective detection surfaces via the fiber optic plate (23).

2. 2. The optical position measuring device according to claim 1, characterized in that the fiber optic plate (23) is provided with a scanning grid (24) in the area in front of the incremental detector arrangement (26).

3. The scanning grid (24) is formed as an amplitude grid and consists of a plurality of transparent and opaque linear grating sections arranged alternately along the measurement direction (x), and these grating sections of the scanning grid (24) have a scanning grid periodicity (P ＡＧ ) and are arranged with a period according to the scan grid periodicity (P ＡＧ 3. The optical position measuring device of claim 2, wherein: n is a sum of the widths of adjacent transparent and opaque grating portions.

4. The optical fibers in the fiber optic plate (23) have an average fiber periodicity (P Ｆｘ ) are arranged along the measurement direction (x), and the average fiber periodicity (P Ｆｘ ) P ＡＧ / 2>P Ｆｘ but, P Ｆｘ :=average fiber periodicity along the measurement direction x P ＡＧ := scan grid periodicity 4. The optical position measuring device according to claim 3, wherein the above formula is satisfied.

5. 3. The optical position measuring device according to claim 2, further comprising a scanning grid (24) arranged on the image-entering side of the fiber-optic plate (23) facing the scale (10).

6. 3. The optical position measuring device according to claim 2, characterized in that on the image-entering side of the fiber optic plate (24) facing the scale (10), a flat, opaque covering layer (31) is arranged at least partially with an incremental scanning window (32) and an absolute scanning window (25), and a scanning grid (24) is arranged in the incremental scanning window (32).

7. Scan grid periodicity (P ＡＧ ) is the measurement scale periodicity (P ＩＮＣ 4. The optical position measuring device according to claim 3, wherein said optical position measuring means is selected to be different from said optical position measuring means.

8. Scan grid periodicity (P ＡＧ )teeth, P ＡＧ =(k・P ＤＥＴ ・P ＩＮＣ ) / (k・P ＤＥＴ + / -P ＩＮＣ ) According to P ＡＧ := scan grid periodicity P ＩＮＣ : = Measurement scale periodicity of incremental measurement scale P ＤＥＴ :=detector periodicity of incremental detector array structure k:=3,4 8. The optical position measuring device according to claim 7, wherein the optical position measuring means is selected as follows:

9. moreover, n・P ＡＧ =P ＤＥＴ but, P ＡＧ := scan grid periodicity P ＤＥＴ :=detector periodicity of incremental detector array structure n:=1, 2, 3,...

9. The optical position measuring device according to claim 8, wherein the above formula holds true.

10. Scan grid periodicity (P ＡＧ ) is the measurement graduation periodicity (P ＩＮＣ 4. The optical position measuring device according to claim 3, wherein the optical position measuring means is selected to be equal to the optical axis.

11. The incremental detector array structure (26) has a detector periodicity (P ＤＥＴ ) with a detector periodicity (P ＤＥＴ 11. Optical position measuring device according to claim 1, characterized in that: 126.1-126.4; 126.1-126.4 denotes the width of the detector element (26.1-26.4; 126.1-126.4) along the measuring direction (x).

12. One period (P ＬＭ 12. The optical position measuring device according to claim 11, characterized in that three or four detector elements (26.1-26.4; 126.1-126.4) are arranged in the measuring direction (x) within the measuring element (26.1-26.4; 126.1-126.4).

13. An optical position measuring device as described in any one of claims 1 to 12, characterized in that the incremental detector array structure (26) and the absolute detector array structure (27) are integrated into an Opt-ASIC arranged in a recess of the holding member (29), and the upper surface of the Opt-ASIC protrudes from the upper surface of the holding member (29).

14. 14. The optical position measuring device according to claim 13, characterized in that a fiber optic plate (23) is arranged on the upper surface of the Opt-ASIC, and a gap medium (30) is present at least between the image exit surface of the fiber optic plate (23) and the detector array structure (26, 27).

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