Optical position measuring device

Abstract

The invention relates to an optical position measuring device for detecting the relative position of two scales, which can be moved relative to one another in a plurality of measurement directions and are arranged in different planes and cross one another. The two scales each have a measurement division. The longitudinal extension of the scales is oriented parallel to a first and a second measurement direction. A third measurement direction is perpendicular to the first and second measurement direction. An illumination beam emitted by a light source is split at the first scale into at least two partial beams. The partial beams subsequently impinge on a second scale which is arranged obliquely with respect to the horizontal movement plane about its longitudinal extension, the partial beams undergo a back reflection in the direction of the first scale at the second scale. The partial beams then impinge again on the first scale and are combined again, a signal beam resulting therefrom propagates in the direction of a detection unit. Via the detection unit a plurality of phase-shifted scanning signals can be generated about the relative movement of the scales in the third measurement direction and in the first or second measurement direction.

Description

TECHNICAL FIELD

[0001] The present application relates to an optical position measuring device which is suitable for high-precision position measurement of two objects which are moved relative to one another along at least two measurement directions. Here, the two objects are each associated with a scale. BACKGROUND

[0002] Optical position measuring devices are known which are based on the interference scanning principle, wherein an illumination beam is split into different partial beams by diffraction at a measurement scale. After suitable partial beam combination, a periodic signal is obtained in a detection unit by interference of the two partial beams when the scale is moved relative to another scale. By counting the signal periods in the detection unit, it is possible to infer the extent of the displacement of the two scales or of the objects associated with the scales.

[0003] Such optical position measuring devices are used, for example, for high-precision position measurement in the semiconductor industry, where, for example, an exposure mask for photolithography is moved relative to a wafer at speeds of more than one meter per second; here, the positioning accuracy must be maintained in the range of a few nanometers and below. A significant advantage of grating-based position measuring devices over interferometers is that the partial beams of the interference only have to pass very short distances. As a result, the partial beams are hardly impaired by environmental influences such as fluctuations in air pressure, temperature fluctuations and humidity fluctuations, which can distort the measurement, for example, via fluctuations in the refractive index of the air.

[0004] From WO 2008 / 138501 Al, an optical position measuring device is known which comprises two intersecting scales which each have a measurement scale with periodically arranged lines or grating regions transverse to a common measurement direction. With the aid of such a position measuring device, it is possible to detect the position of a worktable which is movable in two directions along a first measurement direction x independently of the position of the worktable along a further second measurement direction y. If two such position measuring devices which are arranged orthogonal to one another are used, it is also possible to detect the position of the worktable along the second measurement direction y independently of the position of the worktable along the first measurement direction x. A disadvantage of the position measuring device disclosed in WO 2008 / 138501 Al is that a movement of the worktable perpendicular to the worktable plane or a movement of the worktable along a further third measurement direction z is not possible to determine by means of measurement technology.

[0005] For detecting the position of the worktable in the worktable plane along the first and second measurement directions x, y, a position measuring device with a scale is also known, which has a two-dimensional measurement graduation in the form of a cross grating, which is scanned at a plurality of positions, so that a lateral movement and a rotation in the worktable can be measured. It is proposed in EP 1 019 669 B1 with respect to such a position measuring device to use an additional spacing sensor with which a movement perpendicular to the worktable plane, i.e. along a third measurement direction z, can be detected, and thus all six movement degrees of freedom of the worktable. However, the spacing sensors proposed there, for example touch or capacitive measuring probes, do not meet the accuracy requirements of current and future production facilities in the semiconductor industry. Furthermore, a high-precision, expanded cross grating is expensive to manufacture.

[0006] An optical position measuring device is described in EP 1 762 828 A2, which, in addition to allowing measurement along the main horizontal measurement direction x, additionally allows measurement of the so-called scanning spacing perpendicular to the measurement direction x, i.e. a position measurement between the scale and the scanning unit along the measurement direction z with other components of the position measuring device. This is intended to measure an additional movement degree of freedom along the vertical measurement direction z. For this purpose, a light beam is directed onto a reflective measurement graduation of the scale by means of a transparent scanning plate with different optical structures. The light separated into two partial beams then migrates back and forth between the scanning plate and the scale several times. The partial rays of the partial beams here extend asymmetrically with respect to a plane perpendicular to the horizontal measurement direction x and have different path lengths. In the course of the scanning beam path, the partial beams interact with different optically effective structures, i.e. for example with gratings for separating or combining light rays of different diffraction orders and with structures of mirrors for reflection and lenses for targeted deflection of light. Finally, these partial beams are combined with one another, the partial beams interfere with one another, so that a periodic scanning signal is generated in a plurality of photodetectors of a detection unit upon relative movement between the scale and the scanning unit. Due to the asymmetric course of the partial beams, a periodic scanning signal is obtained in the detection unit, from which the horizontal and vertical displacement of the scale and the scanning unit, and thus the relative displacement of the two mutually moving objects along the two measurement directions x and z, can be extracted. However, due to the structure of the scanning plate of the position measuring device described in EP 1 762 828 A2, the scanning plate cannot be used in a system with a cross scale as described above. The scanning plate cannot be expanded to a second scale, which can be moved laterally with respect to the second scale without interfering with the measurement.

[0007] Therefore, an optical position measuring device is proposed in EP 2 450 673 A2, which comprises a scanning scale with a first grating-shaped measurement division and a scale with a second grating-shaped measurement division, wherein the scanning scale extends along a first or a second measurement direction of two measurement directions x, y and the scale extends along the respective other measurement direction of the two measurement directions y, x. Here, the scale is arranged offset by a scanning pitch relative to the scanning scale in a third measurement direction z perpendicular to the first and second measurement directions. Furthermore, the optical position measuring device has a light source, which emits an illumination beam, which penetrates the first measurement division on the scanning scale at the intersection of the scanning scale and the scale in order to impinge on the second measurement division on the scale and from there back to the scanning scale and further to a detection unit. Here, the light is separated by diffraction at the optically effective structures of the scanning scale and the scale and is combined again, wherein by the interference of the partial beams combined with one another a periodic signal is generated in the detection unit upon displacement between the scanning scale and the scale along the first measurement direction x. Here, the optical position measuring device is configured such that in the event of a change in the scanning pitch between the scanning scale and the scale a periodic signal can likewise be generated in the detection unit along the third measurement direction z. Now, the optical position measuring device can achieve the detection of a relative movement along at least two measurement directions x, z, but is independent of possible fluctuations of the light wavelength; such fluctuations can be caused, for example, by temperature and / or humidity changes in the ambient air and lead to errors in the determination of the position-dependent scanning signal. SUMMARY

[0008] The object on which the invention is based is to provide a high-precision optical position measuring device with a cross-arranged scale, which, in addition to at least one position measurement along a measurement direction parallel to the longitudinal extension direction of one of the scales, is also able to achieve a position measurement along a further measurement direction perpendicular to both scales.

[0009] The optical position measuring device according to the application serves for detecting the relative position of two scales which are movable relative to one another in a plurality of measurement directions, which scales are arranged in different planes and are arranged crosswise to one another. Here, the two scales each have a measurement scale which has periodically arranged grating regions with different optical properties. The longitudinal extension of the scales is oriented parallel to a first and a second measurement direction, wherein a horizontal movement plane is spanned by the first and the second measurement direction; a third measurement direction is oriented perpendicular to the first and the second measurement direction. At the first scale, an illumination beam emitted by a light source is split into at least two partial beams. The partial beams are then loaded onto the second scale, which is arranged obliquely about its longitudinal extension relative to the horizontal movement plane. Here, the partial beams undergo a back reflection in the direction of the first scale at the second scale. The back reflected partial beams are re-projected onto the first scale and are combined there again, so that a subsequently generated signal beam propagates in the direction of a detection unit via which a plurality of phase-shifted scanning signals can be generated with respect to the relative movement of the scales along the third measurement direction and the first or the second measurement direction.

[0010] Preferably, the second scale is arranged obliquely about its longitudinal extension relative to the horizontal movement plane, so that in the plane spanned by the split partial beams at the first scale, the angle bisector between the split partial beams is perpendicular to the connecting line between the points of intersection of the partial beams at the second scale.

[0011] In a possible embodiment, the two measurement scales on the scales are each configured as reflective phase gratings having periodically arranged grating regions with different phase shift effects.

[0012] Here, the two scales can each comprise a carrier on which the measurement scale is arranged, wherein the carrier is made of a material having a thermal expansion coefficient CTE ~ 0.

[0013] Furthermore, at least one of the two measurement scales can be configured as a geometric phase grating which polarizes the two partial beams orthogonally to one another.

[0014] Furthermore, it is possible for the measurement scale of the second scale to be configured as a Littrow grating, so that

[0015] - the partial beam incident thereupon undergoes a back reflection opposite to the direction of incidence,

[0016] - or the partial beam projected into a plane spanned by the normal to the second measurement scale and the diffraction direction of the first measurement scale undergoes a back reflection opposite to the direction of incidence.

[0017] Advantageously, the longitudinal extensions of the first and the second scale are oriented orthogonally to one another.

[0018] In a possible embodiment it is proposed that

[0019] - the first scale has a length along its longitudinal extension direction which corresponds to the displacement path of the first scale along its associated measurement direction, and

[0020] - the second scale has a length along its longitudinal extension direction which corresponds to the displacement path of the first scale along its associated measurement direction.

[0021] Alternatively thereto it is possible that

[0022] - the first scale has a length along its longitudinal extension direction which corresponds to the displacement path of the second scale along its associated measurement direction, and

[0023] - the second scale has a length along its longitudinal extension direction which corresponds to the displacement path of the second scale along its associated measurement direction.

[0024] It is possible that the light source and the detection unit are jointly arranged in the scanning head.

[0025] Herein it is possible that

[0026] - the scanning head is connected with the second scale, and

[0027] - the first scale is arranged to be relatively movable with respect to the scanning head along the first, second and third measurement directions, and

[0028] - the first scale is arranged obliquely with respect to a horizontal movement plane around its longitudinal extension direction.

[0029] Further, herein the signal beam and the illumination beam can be oriented counter-parallel.

[0030] In another embodiment it is possible that

[0031] - the scanning head is arranged to be neither connected with the first scale nor with the second scale and to be relatively movable with respect to the first scale along the first measurement direction, and

[0032] - the second scale is arranged to be relatively movable with respect to the first scale along the second and third measurement directions.

[0033] Further possible is that

[0034] - the scanning head is connected with the first scale, and

[0035] - the second scale is arranged to be relatively movable with respect to the scanning head along the first, second and third measurement directions.

[0036] Alternatively thereto, it is further possible that

[0037] - the scanning head is arranged to be connectable neither to the first scale nor to the second scale and to be movable relative to the second scale along the first measurement direction, and

[0038] - the first scale is arranged to be relatively movable relative to the second scale along the second and third measurement directions.

[0039] Finally possible is a manufacturing device which is constructed with four position measuring devices according to the application, wherein

[0040] - the manufacturing device comprises a tool and a work table, the work table being arranged to be movable relative to the tool along three measurement directions, and

[0041] - the scanning head and the second scale of the position measuring devices are connected to the tool, respectively, and

[0042] - the first scales of the position measuring devices are connected to the work table, respectively,

[0043] - so that the spatial position of the work table relative to the tool in all six spatial degrees of freedom can be determined from the scanning signals of the position measuring devices.

[0044] From now on, via the measures according to the application, a highly precise position measurement is possible also along another measurement direction in an optical position measuring device with intersecting scales, which is oriented perpendicular to the two scales. Thus, for example, the movement of a work table in a manufacturing device for semiconductor manufacturing can be detected in all six degrees of freedom in a measurement-technical manner.

[0045] Furthermore, in an advantageous embodiment, the position measurement is independent of possible fluctuations of the light wavelength, which are caused, for example, by changes in the air temperature or the air humidity. Thereby, the requirements on the light source to be used in terms of coherence properties and drift behavior are reduced, i.e. a low-cost light source can be used.

[0046] In addition, the number of required components and the weight of the position measuring devices on the movable object, for example the work table of a manufacturing device, can be kept low. Thereby, the complexity of the corresponding devices is low. BRIEF DESCRIPTION OF DRAWINGS

[0047] Further details and advantages of the application are explained below on the basis of a description of embodiments of the device according to the application in connection with the drawings.

[0048] The drawings show

[0049] Figure 1a , 1b schematic sectional views of the scanning beam path of a first embodiment of an optical position measuring device according to the application, respectively;

[0050] Figure 2a , 2b top view of the two measurement scales used in the scale in the first embodiment of the optical position measuring device according to the application.

[0051] Figure 3 schematic view of the scanning head of the first embodiment of the optical position measuring device according to the application;

[0052] Figure 4a , 4b schematic cross-sectional view of the scanning beam path with the second embodiment of the optical position measuring device according to the application;

[0053] Figure 5a , 5b top view of the two measurement scales used in the scale in the second embodiment of the position measuring device according to the application;

[0054] Figure 6a , 6b schematic cross-sectional view of the scanning beam path with the third embodiment of the optical position measuring device according to the application;

[0055] Figure 7a , 7b schematic cross-sectional view of the scanning beam path with the fourth embodiment of the optical position measuring device according to the application;

[0056] Figure 8 extremely schematic top view of a manufacturing device with a plurality of position measuring devices according to the application;

[0057] Figure 9a , 9b schematic cross-sectional view of a part of the scanning beam path with another embodiment of the optical position measuring device according to the application. DETAILED DESCRIPTION

[0058] Before specific embodiments of the optical position measuring device according to the application and of a manufacturing device with a plurality of such position measuring devices are described in the following, first the basic theoretical considerations are set out in accordance with Figure 9a , 9b The underlying theoretical considerations are set out in the context of the present application.

[0059] Two Figure 9a , 9bDifferent sectional views showing a part of the scanning beam path of an optical position measuring device according to the application with two scales M1, M2 arranged crosswise. The scales M1, M2 are arranged so as to be movable relative to one another in different planes along a plurality of measurement directions x, y, z. The relative position of the scales M1, M2 is detected along at least two different measurement directions x, y, z by means of the position measuring device. In practice, objects movable relative to one another are connected to the two scales M1, M2, the relative position of which is to be determined in a plurality of spatial degrees of freedom, for example corresponding machine parts; in the drawing, these objects are not shown. With the scanning signals generated by the position measuring device according to the application, a machine control device downstream is able to position the corresponding machine parts appropriately.

[0060] The two scales M1, M2 each have a measurement scale or grating with periodically arranged grating regions having different optical properties; for reasons of clarity, the measurement scale is not shown in Figure 9a , 9b . The longitudinal extension of the scales M1 and M2 is oriented parallel to the second and first measurement directions y, x, wherein a horizontal movement plane is spanned by the first and second measurement directions x, y. The third measurement direction z is oriented perpendicular or vertically to the first and second measurement directions x, y.

[0061] At the first scale M2, an illumination beam B emitted by a light source (not shown in the drawing) is split into at least two partial beams. Subsequently, the partial beams load the second scale M1, which is arranged obliquely about its longitudinal extension, which here is oriented in the y direction, relative to the horizontal movement plane. Here, the partial beams undergo a back reflection at the second scale M1 in the direction of the first scale M2. The back reflected partial beams strike the first scale M2 again and are combined there again, so that the resulting signal beam S then propagates in the direction of a detection unit (also not shown). Via this, a plurality of phase-shifted scanning signals about the relative movement of the scales M1, M2 along the third measurement direction z and the first or second measurement direction x, y can be generated.

[0062] Thus, with this optical position measuring device, the relative position change between the two scales M1, M2 is measured, on which scales the measurement scale is arranged. In order to be able to achieve as large a movement range as possible in the horizontal xy movement plane, it is necessary to expand the first scale M2 over this plane. In order to ensure achromatic, i.e. wavelength-independent, position measurement, it is necessary that the scanning beam path of the two partial beams has the same optical path length between the splitting and the recombination.

[0063] As Figure 9a , 9bIf the second scale M1, onto which the separated partial beams are directed, is arranged obliquely about its longitudinal extension direction y, the measurement direction in the horizontal movement plane can be freely chosen; at the same time, the measurement sensitivity with respect to the relative movement along the vertical measurement direction z is ensured. That is, the generated scanning signal contains information about the relative movement along the third measurement direction z in addition to the information about the relative movement along the measurement directions x or y in the horizontal movement plane. Here, if the angle bisector between the two separated partial beams is oriented as a normal to the scale plane onto which the two separated partial beams are directed, it is ensured that the path lengths of the two partial beams are equal and the scanning is achromatic, i.e. not sensitive with respect to possible wavelength fluctuations, as shown below.

[0064] If the beam is diffracted at an optical diffraction grating, the beam experiences a directional change proportional to the gradient of the phase of the grating Here, m denotes the diffraction order of the grating:

[0065]

[0066] If the first linear grating is displaced in the x direction with respect to the second grating by a value the position phase Φ of the partial beam at the first grating changes by:

[0067]

[0068] It can be seen from this that in the case of a displacement of the second grating by a displacement value the phase Φ of the position measurement device changes by

[0069]

[0070] In this respect, the respective first footnotes indicate the first or second diffractive branch L1, L2 depending on Figure 9a , 9b The footnotes I indicate the grating contact of the respective diffractive partial beam.

[0071] Thus, again, ΔΦ ≠ 0, and furthermore, if the condition

[0072]

[0073] and

[0074]

[0075] there is a sensitivity with respect to a change in position along the z direction.

[0076] Therefore, to make a grating-based position measurement device sensitive in the z-direction, at least one grating used for signal generation must be arranged obliquely with respect to the xy-plane.

[0077] Achromatic position measurement is basically understood to be a position measurement whose measurement result in the form of a position phase Φ is independent of the wavelength λ of the light to first order:

[0078]

[0079] Therefore, for the wavelength-independent determinacy of the scan according to the application it is decisive that the two partial beams have no optical path length difference ΔΛ between the splitting and the recombination, wherein according to

[0080] ΔΛ = Λ2 - Λ1

[0081] The optical path length difference is obtained, wherein Λ1 : = optical path length of the first partial beam, Λ2 : = optical path length of the second partial beam.

[0082] It is shown below that for Figure 9a , 9b the condition is met for the scan shown in that the optical path lengths of the two partial beams are identical there between the splitting and the recombination.

[0083] Therefore, according to Figure 9a , 9b the optical path length difference ΔΛ of the two partial beams between the splitting and the recombination is given by

[0084] ΔΛ = 2 · (L2 - L1)

[0085] Here, L1 and L2 denote the lengths of the partial beams between the splitting point P0 on the first scale M2 and the meeting points P11 or P12 on the second scale M1.

[0086] The connecting line of the two points P0 and Ps is denoted in Figure 9a by L0. Here, P0 denotes the splitting point and Ps denotes the intersection of the angle bisector of the two partial beams with the surface of the second scale M1.

[0087] It can be seen from this that the lengths L1 and L2 of the partial beams are identical and furthermore that the optical path length difference ΔΛ = 0 when the angle bisector is perpendicular to the connecting line of the two meeting points P11 and P12. Therefore only the following applies:

[0088] L1 = L0 / cos(α1) = L2 = L0 / cos(α2) mit α1 = α2

[0089] Here, α1 denotes the angle of the first diffractive branch L1 with respect to the angle bisector and α2 denotes the angle of the second diffractive branch L2 with respect to the angle bisector.

[0090] In the following, a first embodiment of an optical position measuring device according to the application is explained with reference to Figure 1a , 1b , 2a, 2b and 3. Herein, Figure 1a , 1b different sectional views with a scanning beam path are shown, Figure 2a , 2b a top view of a measurement division of a scale used is shown, and Figure 3 a view of a scanning head of the position measuring device is shown.

[0091] By means of this embodiment of an optical position measuring device according to the application, a wavelength-independent scanning can be realized, in which the relative movement of the two scales 10, 20 or (schematically indicated) of the machine parts 1, 2 connected therewith along the measurement directions y and z can be detected in a measurement-technical manner.

[0092] In the following, the direction indicated with x in the drawing will be referred to as the first measurement direction, and the direction y orthogonal thereto as the second measurement direction. At present, a horizontal movement plane is spanned by the measurement directions x, y; in this movement plane or parallel thereto the first scale 20 is movably arranged. A vertical direction z is oriented perpendicular to the first and second measurement directions x, y or orthogonal to the horizontal movement plane, which vertical direction will be referred to in the following as the third measurement direction z; the first scale 20 is also arranged movable along this direction.

[0093] At this point it should be noted that the terms horizontal, vertical, first, second and third measurement direction as well as upper and lower used in this application are of course not to be understood as limiting.

[0094] Thus, in the present embodiment, the first scale 20 is arranged movable along the three measurement directions x, y, z relative to a fixed scanning head 30, which in turn is connected with the second scale 10. The scanning head 30 further comprises further light sources as well as a detection unit, wherein in Figure 1a , 1b details are not shown in detail in connection therewith. Further details of the scanning head 30 are explained in the further description according to Figure 3 .

[0095] In the example shown, the longitudinal extension of the first scale 20 is oriented parallel to the second measurement direction y, and the longitudinal extension of the second scale 10 is oriented parallel to the first measurement direction x. Thus, the longitudinal extensions of the two scales 10, 20 are oriented orthogonal to each other.

[0096] The first scale 20 has a length along its longitudinal extension direction y which corresponds to the displacement path of the first scale 20 along its associated measurement direction y. The second scale 10 has a length along its longitudinal extension direction x which corresponds to the displacement path of the first scale 20 along its associated measurement direction x.

[0097] It is further apparent from Figure 1a and 1b that the second scale 10 is arranged obliquely about its longitudinal extension direction relative to a horizontal movement plane which is spanned by the first and second measurement directions x, y. With regard to the oblique arrangement of the second scale 10, reference is made to the further description of this embodiment.

[0098] Furthermore, in the present first embodiment, the first scale 20 is arranged obliquely about its longitudinal extension direction in the y direction relative to its horizontal movement plane, as is also apparent from the description of the other embodiments, however, which is not an essential measure of the application here.

[0099] In Figure 1a and Figure 1b , the measurement graduation provided on the scales 10, 20 is not shown, which is composed of periodically arranged grating regions with different optical properties, respectively. In Figure 2a and 2b , top views of the two scales 20, 10 with the respective measurement graduation 21, 11 are shown. In this embodiment, a reflective phase grating is provided as the measurement graduation 21, 11 on the scales 20, 10, which has periodically arranged grating regions 21a, 21b or 11a, 11b with different phase shift effects.

[0100] The scales 20, 10 comprise a carrier 22, 12, respectively, on which the measurement graduation 21, 11 is arranged. Here, the carrier 22, 12 is preferably made of a material with a thermal expansion coefficient CTE ~ 0, for example from a glass ceramic such as microcrystalline glass.

[0101] The measurement graduation 11, 21 arranged on the carrier has a multilayer structure. This multilayer structure can be composed of, for example, a metallic or dielectric mirror layer, a phase shift layer and a structured reflection layer arranged on the carrier 12, 22.

[0102] In the case of the first scale 20, Figure 2a The measurement graduation 21 shown with the grating regions 21a, 21b is configured as a so-called cross grating. In this embodiment, this cross grating is generated from the superposition of two linear gratings. A first of these linear gratings has a diffractive effect in the y direction here, the second linear grating has a diffractive effect in the y direction, but with lower intensity than the first linear grating; in addition, the second linear grating has a diffractive component in the x direction.Figure 2a The view in the image shows the binarized form of the cross grating resulting from the superposition of two linear gratings.

[0103] In the second scale 10, the grating regions 11a and 11b of the measurement scale 11 are projected onto the xy plane according to their projections. Figure 2b The second scale 10 is periodically arranged perpendicular to the longitudinal extension direction x and then periodically arranged along the second measurement direction y. In the current embodiment, the measurement division 21 of the second scale 10 is constructed as a so-called Littrow grating, such that the beam incident upon it undergoes retroreflection opposite to the incident direction. Alternatively, the beam projected onto the plane of the beams separated at the first scale may also undergo retroreflection opposite to the incident direction.

[0104] The scanning beam path of the first embodiment of the optical position measuring device according to the present invention will now be described.

[0105] An illumination beam B emitted from a light source in the scanning head 30 at point P0, parallel to the first measurement direction x, strikes the first scale 20 at point P1, where it is split into at least two beams or diffraction orders via the first measurement division 21. At the first measurement division 21, diffraction at the first diffraction order via a first linear grating can be separated from diffraction along the y-direction alone, and diffraction at the first diffraction order via a second linear grating can be separated from diffraction along both the y and x directions. The split beams are then aligned with the normal. The same angle α1 or α2 propagates and is projected onto the xz projection on the surface of the inclined second scale 10. Figure 1b There is no beam shearing in the direction of the second scale 10. In other words, in the plane through which the split beams are deployed at the first scale 20, perpendicular to the line connecting the meeting points P21 and P22 of the split beams at the second scale 10, there are angular bisectors between the separated split beams. At the meeting points P21 and P22, the split beams are thus loaded onto the second scale 10 or the second measurement division 11. The split beams are reflected back from the meeting points P21 and P22 via the measurement division 11 of the second scale 10, which is constructed as a Littoral grating, opposite to the incident direction to the first scale 20, and then recombined at point P3 on the first scale 20. Subsequently, the resulting signal beam S and the recombined or superimposed split beams propagate in the direction of the illumination beam B parallel to the direction of the scanning head 30, and strike the detector unit arranged there at point P4. The detection unit and the detection signal beam can generate multiple phase-shift detection signals regarding the relative movement of scales 10 and 20 along the second measurement direction y and the third measurement direction z.

[0106] With regard to the generation of the scanning signals via the probe unit, reference is made to the schematic diagram of the scanning head 30 in Figure 3 . Adjacent to the illumination unit 31 having the light source 31.1 and the collimating optics 31.2 arranged upstream for generating the illumination beam B, a probe unit 32 is arranged in the scanning head 30 for generating a plurality of phase-shifted scanning signals from the signal beam S. To this end, the probe unit 31 comprises a separating element 32.3, for example configured as a grating, which separates the incident signal beam S into three partial beams which then propagate in the direction of polarizers 32.2a-32.2c, respectively, and then to the probe elements 32.1a-32.1c arranged downstream of the respective polarizers 32.2a-32.2c. By means of the probe elements 32.1a-32.1c, the partial beams are converted into three phase-shifted periodic scanning signals, for example into three scanning signals which are phase-shifted by 120° from one another; the scanning signals can then be further processed in a known manner and method by a machine control device arranged downstream.

[0107] The illustrated scanning beam path of the first embodiment of the optical position measuring device according to the application provides scanning signals as illustrated above which are sensitive to relative displacements of the second scale 20 along the second measurement direction y as well as the third measurement direction z. This is represented in Figure 1a via the so-called sensitivity vector ; this sensitivity vector illustrates along which measurement direction(s) the grating-based optical position measuring device is sensitive with regard to position changes. As can be seen from the figure: the sensitivity vector here has components in the y-direction and the z-direction, i.e. thus, the respective position measuring device is sensitive with regard to position changes in these measurement directions.

[0108] In addition to the desired sensitivity of the position measurement along the two measurement directions y and z, the illustrated first embodiment of the optical position measuring device according to the application also ensures wavelength independence of the position measurement. This is ensured by a suitable inclination of the second scale 10 such that in the plane developed by the partial beams split at the first scale 20, the angle bisector between the split partial beams is perpendicular to the connecting line between the points of encounter P21, P22 of the partial beams at the second scale 10.

[0109] In a variant of the first embodiment, it is also possible to integrally arrange the beam splitter element in the scanning head 30 according to Figure 3 . In addition, it can be ensured that the signal beam B propagating in the direction of the scanning head 30 from the first scale 20 impinges on the probe unit at a point P4 which is spatially separate from the point P0 of the emitted signal beam S.

[0110] Furthermore, it is possible for one of the scales to have a measurement division which has a polarizing effect on the beam incident thereon, such that the partial beams diffracted thereon produce different polarization states. To this end, one of the measurement divisions can be configured as a geometric phase grating which causes the partial beams diffracted thereby to have mutually orthogonal polarizations.

[0111] In the following, a second embodiment of an optical position measuring device according to the application will be explained with reference to Figure 4a , 4b and Figures 5a and 5b. Like the first embodiment, this drawing shows a schematic sectional view for illustrating the path of the scanning beam and a plan view of the scales used or the corresponding projection view in the xy plane.

[0112] By means of this embodiment of an optical position measuring device according to the application, a wavelength-independent scanning can be achieved, in which the relative movement of the two scales 110, 120 or (again schematically indicated) of the machine parts 101, 102 connected therewith along the measurement directions x and z can be detected in a measurement-technological manner.

[0113] In this example, the direction denoted by x in the drawing is referred to as the first measurement direction, and the direction orthogonal thereto is referred to as the direction y, wherein a horizontal movement plane is spanned by the measurement direction x and the direction y. At present, the second scale 110 is arranged displaceably along the direction y in this movement plane or parallel thereto. Furthermore, the second scale 110 is also arranged displaceably along a third measurement direction z which is again oriented perpendicular to the other two directions x, y.

[0114] The first scale 120 is connected with the fixed machine part 102. Unlike in the previous embodiment, here the scanning head 130 is connected with a further machine part 103 which is displaceable along the first measurement direction x. With regard to the structure and function of the scanning head 130, reference is made to the previous example.

[0115] In this embodiment, the longitudinal extension of the first scale 120 is oriented parallel to the first measurement direction x, and the longitudinal extension of the second scale 110 is oriented parallel to the second direction y; here, the longitudinal extensions of the two scales 110, 120 are again oriented orthogonally to one another.

[0116] In this embodiment, the first scale 120 has a length along its longitudinal extension x which corresponds to the displacement path of the second scale 110 along its measurement direction x. The second scale 110 has a length along its longitudinal extension y which corresponds to the displacement path of the second scale 110 along its measurement direction y.

[0117] As can be seen from Figure 4aIn the case of the embodiment shown in Fig. 1 1, the second scale 1 10 is arranged in the path of the scanning beam relative to the first scale 120 and the horizontal movement plane extending through the first measurement direction x and the direction y obliquely in the y direction about its longitudinal extension. With regard to the obliquity of the second scale 1 10, reference is made to the explanations of the previous embodiments.

[0118] In the case of the embodiment shown in Fig. 1 1, the second scale 1 10 is arranged in the path of the scanning beam relative to the first scale 120 and the horizontal movement plane extending through the first measurement direction x and the direction y obliquely in the y direction about its longitudinal extension. With regard to the obliquity of the second scale 1 10, reference is made to the explanations of the previous embodiments. Figure 5a In Fig. 1 1, a top view of the first scale 120 with the corresponding measurement graduation 121 is shown; in Fig. 1 2, the projection of the second scale 1 10 with its measurement graduation 1 1 1 is shown in projection in the xy plane, similar to the previous examples. In this embodiment, the reflective phase gratings are also arranged as measurement graduation 121, 1 1 1 on the scales 120, 1 10, which have grating regions 121 a, 121 b or 1 1 1 a, 1 1 1 b with different phase shift effects arranged periodically. Figure 5b

[0119] The scales 120, 1 10 in turn comprise a carrier 122, 1 12 on which the measurement graduation 121, 1 1 1 is arranged, which can in principle be configured as in the first embodiment. In this example, the carrier 122, 1 12 is also preferably made of a material with a thermal expansion coefficient CTE ~ 0.

[0120] It can be seen from Fig. 1 1 that, on the scale 120, the grating regions 121 a, 121 b of the measurement graduation 121 are arranged periodically along the longitudinal extension direction x of the scale 120. In the second scale 1 10, the grating regions 1 1 1 a, 1 1 1 b of the measurement graduation 1 1 1 are arranged periodically perpendicular to the longitudinal extension direction y and thus along the third measurement direction z, according to the explanations of the previous embodiments. Figure 5a Figure 5b It can be seen from Fig. 1 1 that, on the scale 120, the grating regions 121 a, 121 b of the measurement graduation 121 are arranged periodically along the longitudinal extension direction x of the scale 120. In the second scale 1 10, the grating regions 1 1 1 a, 1 1 1 b of the measurement graduation 1 1 1 are arranged periodically perpendicular to the longitudinal extension direction y and thus along the third measurement direction z, according to the explanations of the previous embodiments.

[0121] In this embodiment, the measurement graduation 121 of the second scale 120 is also configured as a Littrow grating, so that a beam incident thereon undergoes a back reflection opposite to the direction of incidence.

[0122] By suitably selecting the graduation period TP G2 of the measurement graduation 1 1 1 of the second scale 1 10, it is ensured here that the ray direction component in the y direction remains unchanged when the partial beam incident thereon is diffracted and back reflected. To this end, the graduation period TP G2 is selected as follows:

[0123] TP G2 = TP G1 • (cos β) / 2

[0124] Here, TP G1 denotes the graduation period of the measurement graduation 121 on the first scale 120, and according to the explanations of the previous embodiments. Figure 4a ​​β indicates the angle of the second scale 110 arranged inclined with respect to the horizontal.

[0125] In the following, the scanning beam path of a second embodiment of the optical position measuring device according to the application is explained.

[0126] The illumination beam B emitted at the point P0 by the light source in the scanning head 130 impinges at the point P1 on the first scale 120 or on the measurement graduation 121 arranged thereon, wherein, in contrast to the first embodiment, an inclined illumination of the first scale 120 is provided here. Like in the first embodiment, the illumination beam B is split into at least two partial beams or diffraction orders via the first measurement graduation 121. Then, the split partial beams propagate in the xz projection plane in the direction of the second scale 110 at the same angle a1 or a2 with respect to the normal to the surface of the inclined arranged scale 110 Figure 4a The same angle a1 or a2 with respect to the normal to the surface of the inclined arranged scale 110. Subsequently, the partial beams load the second scale 10 or the second measurement graduation 11 at the meeting points P21, P22. From the meeting points P21, P22, the partial beams are reflected in the xz projection plane in the direction of the first scale 120 opposite to the direction of incidence via the measurement graduation 111 of the second scale 110 configured as a Littrow grating and subsequently recombined in the point P3 on the scale 120. Subsequently, the generated signal beam S with the recombined or superimposed partial beams propagates in the direction of the scanning head 130 anti-parallel to the illumination beam B and impinges in the point P4 on the detection unit arranged there. Via the detection unit and the detection signal beam a plurality of phase-shifted scanning signals can be generated about the relative movement of the scales 110, 120 along the first measurement direction x and the third measurement direction z.

[0127] This is again illustrated in Figure 4a Fig. 6 via the sensitivity vector of this embodiment of the optical position measuring device according to the application. It can be seen from this figure that the sensitivity vector here has components in the x direction and in the z direction.

[0128] In addition to the desired sensitivity of the position measurement along the two measurement directions x and z, this embodiment of the optical position measuring device according to the application also ensures wavelength independence of the position measurement. This is again ensured by a suitable inclination of the second scale 110 in the scanning beam path, similar to the first embodiment.

[0129] Due to the deflection of the partial beams perpendicular to the measurement direction x in this embodiment, a beam splitter element is also not required here, via which the signal beam B propagating in the direction of the scanning head 130 from the first scale 120 is to be made to impinge on the detection unit at a point which is spatially separate from the point of emission of the signal beam S.

[0130] In the following, the scanning beam path of a second embodiment of the optical position measuring device according to the application is explained.​Figure 6a and 6b A third embodiment of the optical position measuring device according to the present invention is illustrated. Similar to the other two embodiments, these figures show schematic cross-sectional views to illustrate the scanning beam path.

[0131] This embodiment of the optical position measuring device according to the invention also ensures wavelength-independent scanning; thus, the relative movement of the two scales 210, 220, or the machine parts 201, 202 connected thereto, along the measuring directions x and z is detected in a measurement-technical manner.

[0132] In the attached diagram, the direction represented by x is referred to hereinafter as the first measurement direction, and the direction orthogonal to it is referred to as direction y. The horizontal moving plane is further extended by the measurement directions x and y. Currently, a second scale 210 is movably arranged along the first and second measurement directions x and y in or parallel to this moving plane. Furthermore, the second scale 210 is also arranged to be movable along a third measurement direction z, which is perpendicular to the other two directions x and y.

[0133] The first scale 220 is connected to the fixed machine component 202 relative to the second scale 210. In this embodiment, the scanning head 230 is also connected to the fixed first scale 220. For the structure and function of the scanning head 230, refer to the first embodiment described above.

[0134] In this embodiment, the longitudinal extension direction of the first scale 220 is parallel to the first measurement direction x, and the longitudinal extension direction of the second scale 210 is parallel to the second direction y; therefore, the longitudinal extension directions of the two scales 210 and 220 are orthogonal to each other.

[0135] In this embodiment, the first scale 220 has a length along its longitudinal extension direction x, which corresponds to the displacement path of the second scale 210 along its respective measurement direction x. The second scale 210 has a length along its longitudinal extension direction y, which corresponds to the displacement path of the second scale 210 along its respective measurement direction y.

[0136] according to Figure 6a In this embodiment, the second scale 210 is also arranged obliquely in the y-direction relative to the first scale 220 and the horizontal moving plane about its longitudinal extension direction. The horizontal moving plane extends through the first and second measurement directions x and y. Regarding the obliqueness of the second scale 210, refer to the description of the first embodiment.

[0137] The scales 210 and 220 and the measurement graduations used in the third embodiment correspond to the scales and measurement graduations in the second embodiment. Figure 5a and 5bare shown in the figures and explicitly referred to herein.

[0138] In the following, the scanning beam path of a third embodiment of the optical position measuring device according to the application is set forth.

[0139] The illumination beam B emitted at the point P0 by the light source in the scanning head 230 impinges at the point P1 on the reflector region 215 arranged at the second scale 220, at which the illumination beam is deflected in the direction of the first scale 220. Then, at the point P2, the illumination beam B impinges on the first scale 220, where, similar to the previous embodiments, it is split into at least two partial beams or diffraction orders via the first measurement division. The split partial beams then propagate in the direction of the second scale 210 at the same angle a1 or a2 with respect to the normal to the surface of the tilted arrangement of the second scale 210 Figure 6a The same angle a1 or a2 with respect to the normal to the surface of the tilted arrangement of the second scale 210 Subsequently, the partial beams load the second scale 210 or the second measurement division at the meeting points P31, P32. From the meeting points P31, P32, the partial beams are reflected in the direction of the first scale 220 in the xz projection plane opposite the direction of incidence via the measurement division of the second scale 210 configured as a Littrow grating and subsequently combined again in the point P4 on the scale 220. The resulting signal beam S with the combined or superimposed partial beams then propagates counter-parallel to the illumination beam B towards the reflector region 215 at the second scale 210, where it impinges at the point P5. There, a deflection in the direction of the scanning head 230 is generated, where the signal beam S impinges in the point P6 on the detection unit arranged there. Via the detection unit and the detection signal beam S, a plurality of phase-shifted scanning signals about the relative movement of the scales 210, 220 along the first measurement direction x and the third measurement direction z can then be generated.

[0140] Figure 6a In the following, the sensitivity vector Explanation: From this it follows that this embodiment of the optical position measuring device according to the application is sensitive with respect to a position change along which measurement direction. According to Figure 6a , the sensitivity vector Here has components in the x direction and in the z direction.

[0141] In addition to the desired sensitivity of the position measurement along the two measurement directions x and z, this embodiment of the optical position measuring device according to the application also ensures wavelength independence of the position measurement. This is ensured again by a suitable tilting of the second scale 210, similar to the first embodiment.

[0142] Finally, according to Figure 7a and 7b ​A fourth embodiment of the optical position measuring device according to the application is illustrated, which shows a schematic sectional view similar to the other embodiments to illustrate the scanning beam path.

[0143] In this embodiment of the optical position measuring device according to the application, wavelength-independent scanning is also ensured. By this means, the relative movement of the two scales 310, 320 or of the machine parts 301, 302 connected therewith along the measuring directions y and z is detected in a measurement-technical manner.

[0144] The direction indicated by x in the drawing is referred to as the first measuring direction in the following and the direction orthogonal thereto is referred to as the direction y, wherein a horizontal movement plane is again developed by the measuring directions x, y. In this embodiment, a scanning head 330 connected with the machine part 303 is movably arranged along the first measuring direction x in this movement plane or parallel thereto; here, the scanning head 330 is arranged at the machine part 303 which is movable along the measuring direction x. In this embodiment, therefore, the scanning head 330 is neither connected with the first scale 320 nor with the second scale 310. With regard to the structure and function of the scanning head 230, reference is made to the first embodiment explained above.

[0145] The first scale 320 is movably arranged at the machine part 302 relative to the second scale 310, wherein the first scale 320 is provided with a movability along the second measuring direction y at present. The second scale 310 is connected with the fixed machine part 301.

[0146] In this embodiment, the longitudinal extension of the first scale 320 is oriented parallel to the second measuring direction y and the longitudinal extension of the second scale 310 is oriented parallel to the first measuring direction x; therefore, the longitudinal extensions of the two scales 310, 320 are again oriented orthogonal to one another.

[0147] In this embodiment, the first scale 320 has a length along its longitudinal extension y which corresponds to the displacement path of the first scale 320 along its measuring direction y. The second scale 310 has a length along its longitudinal extension x which corresponds to the displacement path of the first scale 320 along its measuring direction x.

[0148] According to Figure 7a In this embodiment, the second scale 310 is arranged inclined about its longitudinal extension in the x direction relative to the first scale 310 and the horizontal movement plane developed along the first and second measuring directions x, y, wherein the horizontal movement plane is developed along the first and second measuring directions x, y. With regard to the inclination of the second scale 310, reference is made to the description of the first embodiment.

[0149] The scales 310, 320 and the measuring division used in the fourth embodiment are identical to those explained in the first embodiment.

[0150] The scanning beam path of a fourth embodiment of an optical position measuring device according to the application is set out below.

[0151] The illumination beam B emitted in point P0 by the light source in the scanning head 330 parallel to the first measuring direction x impinges on the first scale 320 in point P1, where it is split into at least two partial beams or diffraction orders via the first measuring graduation. The split partial beams then propagate in the direction of the first scale 320 opposite to the direction of incidence via the measuring graduation of the first scale 320 and subsequently in points P2, P3 load the second scale 310 or the second measuring graduation. The same angle a1 or a2 propagates in the direction of the second scale 310. Subsequently, the partial beams load the second scale 310 or the second measuring graduation in the meeting points P21, P32. The partial beams are reflected again in the direction of the first scale 320 opposite to the direction of incidence via the measuring graduation of the first scale 320 from the meeting points P21, P22 and subsequently again combined in point P3 on the first scale 320. The resulting signal beam S with the again combined or superimposed partial beams then propagates in the direction of the scanning head 330 anti-parallel to the illumination beam B and impinges in point P4 on the detection unit arranged there. Via the detection unit and the detection signal beam a plurality of phase-shifted scanning signals can be generated about the relative movement of the scales 310, 320 along the second and third measuring directions y, z.

[0152] Likewise, in the Figure 7a sensitivity vector Explanation: From this it follows that this embodiment of the optical position measuring device according to the application is sensitive with regard to a position change along which measuring direction. According to Figure 7a the sensitivity vector Here with a component in the y direction and in the z direction.

[0153] In addition to the desired sensitivity of the position measurement along the two measuring directions y and z, this embodiment of the optical position measuring device according to the application also ensures the wavelength independence of the position measurement. This is ensured again by a suitable tilting of the second scale 310, similar to the first embodiment.

[0154] According to the above-described embodiments of the optical position measuring device according to the application, on the one hand, displacement information is provided with respect to the first measuring direction x or the second measuring direction y, respectively; the two measuring directions x, y are each oriented orthogonally to one another in a horizontal movement plane. In addition to this, there is a respective measuring device which is sensitive to a positional change along a third measuring direction z, which is oriented perpendicularly to the orthogonal movement plane. This means that, on the other hand, displacement information is also provided with respect to the third measuring direction z. Thus, by means of each of the position measuring devices described, two linear spatial movement degrees of freedom of two mutually movable objects can be detected in a measurement-technical manner, respectively. Furthermore, by means of a suitable combination of a plurality of position measuring devices according to the application, all six possible movement degrees of freedom of two mutually movable objects in space can be detected in a measurement-technical manner, which are translational movements along the measuring directions x, y, z and rotational movements about the measuring directions x, y, z. According to Figure 8 In the following, by way of example, a highly schematic view is sketched in which, for example, in the case of a manufacturing device, the relative position of a tool T with respect to a work table W can be detected in all six spatial movement degrees of freedom by means of four position measuring devices according to the application. The manufacturing device can be, for example, a lithography system in which a semiconductor wafer arranged on the work table W is positioned with respect to a tool T which is configured as an exposure optical device.

[0155] In the manufacturing device shown, a total of four position measuring devices according to the above-described first embodiment are provided for detecting the spatial position of the tool T with respect to the work table W in all six spatial degrees of freedom. Here, the work table W is arranged to be movable with respect to the tool along three measuring directions x, y, z; here, the measuring directions x, y represent the main movement directions, along which a smaller displacement is possible along the measuring direction z. Furthermore, small rotational movements of the work table about the three measuring directions x, y, z are possible.

[0156] Here, the first position measuring device comprises a scanning head AK1, a first scale M11 which extends in the y direction and a second scale M142 which is inclined and extends in the x direction. The first scale M11 is arranged at a first side of the work table W; the scanning head AK1 and the second scale M142 are connected with the tool T. By means of the first position measuring device, position or measurement variables ml, m2 are determined; here, there is a respective sensitivity of the first position measuring device with respect to a relative movement of the tool T and the work table W along the measuring directions y and z.

[0157] The second position-measuring device comprises a scanning head AK2, a first scale M231 extending in the x direction and a tilted second scale M22 extending in the y direction. The first scale M231 is arranged at the second side of the work table W; the scanning head AK2 and the second scale M22 are connected with the tool T. By means of the second position-measuring device the position or the measurement variables m3, m4 are determined; here there is a sensitivity of the respective second position-measuring device with respect to the relative movement of the tool T and the work table W along the measurement directions x and z.

[0158] The third position-measuring device comprises a scanning head AK3, a first scale M231 extending in the x direction and a tilted second scale M32 extending in the y direction. Thus, the second position-measuring device and the third position-measuring device jointly use the same scale M231 as first scale in the scanning beam path, which is arranged at the second side of the work table W. The scanning head AK3 and the second scale M32 are connected with the tool T. By means of the third position-measuring device the position or the measurement variables m5, m6 are determined. Here there is a sensitivity of the respective third position-measuring device with respect to the relative movement of the tool T and the work table W along the measurement directions x and z.

[0159] The fourth position-measuring device comprises a scanning head AK4, a first scale M31 extending in the y direction and a tilted second scale M142 extending in the x direction. Thus, the first position-measuring device and the fourth position-measuring device jointly use the same scale M142 as tilted second scale in the scanning beam path. The first scale M31 is arranged at the third side of the work table W. The scanning head AK4 and the second scale M142 are connected with the tool T. By means of the third position-measuring device the position or the measurement variables m7, m8 are determined. Here there is a sensitivity of the respective fourth position-measuring device with respect to the relative movement of the tool T and the work table W along the measurement directions y and z.

[0160] Thus, it is possible to determine the spatial position of the tool T relative to the work table W in all six spatial degrees of freedom from the obtained position or measurement variables ml - m8 and combinations thereof.

[0161] Here, it is also particularly advantageous that only at three sides of the work table W functional faces are required, at which the first scales M11, M231, M41 of the different position-measuring devices are respectively arranged. In addition, no further elements for position detection are required at the work table W.

[0162] Of course, the above-described position-measuring device according to the application can also be used in a plurality of manufacturing devices. Figure 8The described arrangement is to be understood as exemplary only. Furthermore, there are various other possibilities for the arrangement and combination of the position measuring devices according to the invention with each other or with other known position measuring devices that can be used in corresponding manufacturing apparatuses and machines to detect the relative positions of movable parts in multiple spatial degrees of freedom using a measurement technique.

[0163] In addition to the specific embodiments described, other design possibilities for the optical position measuring device according to the present invention certainly exist within the scope of the present invention.

[0164] Therefore, it is feasible to use measurement graduations on a scale, which are constructed as polarization gratings or geometric phase gratings that polarize the two beams orthogonally to each other. In this way and by this method, polarization optics can be used to generate phase-shifted signals. For the corresponding measurement graduations, refer to the applicant's German patent application No. 102019 206 9373.1.

Claims

1. An optical position measuring device with two scales for detecting the relative position of the two scales, the scales being movable relative to one another along a plurality of measurement directions, the scales being arranged in different planes and crossing one another, wherein - the two scales each have a measurement scale with periodically arranged grating regions having different optical properties, and the longitudinal extension of the scales is oriented parallel to a first measurement direction and a second measurement direction, with a horizontal movement plane being spanned by the first measurement direction and the second measurement direction, and a third measurement direction being oriented perpendicular to the first measurement direction and the second measurement direction, and - at the first scale an illumination beam (B) emitted by a light source (31.1) is split into at least two partial beams, and - the partial beams subsequently impinge on a second scale, which is arranged obliquely with respect to the horizontal movement plane about the longitudinal extension of the second scale, wherein the partial beams at the second scale undergo a back reflection in the direction of the first scale, and - the back reflected partial beams reimpinge on the first scale and are combined again at the first scale, so that a subsequently generated signal beam (S) propagates in the direction of a detection unit (32), via which a plurality of phase-shifted scanning signals about the relative movement of the scales along the third measurement direction and along the first measurement direction or the second measurement direction can be generated. The second scale is arranged obliquely with respect to the horizontal movement plane about the longitudinal extension of the second scale, so that in the plane spanned by the partial beams split at the first scale, the angle bisector between the split partial beams is perpendicular to the connecting line between the points of intersection of the partial beams at the second scale. The two measurement scales on the scales are each configured as reflective phase gratings with periodically arranged grating regions having different phase shift effects. The two scales each comprise a carrier (12, 22) on which the measurement scale is provided, and the carriers (12, 22) are made of a material having a thermal expansion coefficient CTE ~ 0. At least one of the two measurement scales is configured as a geometric phase grating, which polarizes the two partial beams orthogonally to one another. The measurement scale of the second scale is configured as a Littrow grating, 2. The optical position measuring device of claim 1, wherein, so that a partial beam incident on the Littrow grating undergoes a back reflection opposite to the direction of incidence, 3. The optical position measuring device according to claim 1 or 2, wherein or so that a partial beam projected into a plane spanned by the normal to the second measurement scale and the diffraction direction of the first measurement scale undergoes a back reflection opposite to the direction of incidence.

4. The optical position measuring device of claim 3, wherein, The longitudinal extensions of the first scale and the second scale are oriented orthogonally to one another.

5. The optical position measuring device according to claim 1 or 2, wherein 8. The optical position measuring device according to claim 1 or 2, wherein - the first scale has a length along the longitudinal extension of the first scale, which length corresponds to the displacement path of the first scale along the measurement direction assigned to the first scale, and - the second scale has a length along the longitudinal extension of the second scale, which length corresponds to the displacement path of the second scale along the measurement direction assigned to the second scale.

6. The optical position measuring device according to claim 1 or 2, wherein 9. The optical position measuring device according to claim 1 or 2, wherein - the first scale has a length along the longitudinal extension of the first scale, which length corresponds to the displacement path of the first scale along the measurement direction assigned to the first scale, and - the second scale has a length along the longitudinal extension of the second scale, which length corresponds to the displacement path of the second scale along the measurement direction assigned to the second scale. ​ ​ 7. The optical position measuring device according to claim 1 or 2, wherein ​ ​ ​ The second scale has a length in the longitudinal extension of the second scale which corresponds to the displacement path of the first scale in the associated measurement direction.

9. The optical position measuring device according to claim 1 or 2, wherein the first scale has a length in the longitudinal extension of the first scale which corresponds to the displacement path of the second scale in the associated measurement direction, and the second scale has a length in the longitudinal extension of the second scale which corresponds to the displacement path of the second scale in the associated measurement direction.

10. The optical position measuring device of claim 1 or 2, wherein, The light source (31.1) and the detection unit (32) are jointly arranged in a scanning head.

11. The optical position measuring device according to claim 10, wherein the scanning head is connected with the second scale, and the first scale is arranged to be relatively movable with respect to the scanning head along the first, second and third measurement directions, and the first scale is arranged obliquely with respect to a horizontal movement plane around the longitudinal extension of the first scale.

12. The optical position measuring device of claim 11, wherein, The signal beam (S) is oriented counter-parallel to the illumination beam (B).

13. The optical position measuring device according to claim 10, wherein the scanning head is neither connected with the first scale nor with the second scale, and the scanning head is arranged to be relatively movable with respect to the first scale along the first measurement direction, and the second scale is arranged to be relatively movable with respect to the first scale along the second and third measurement directions.

14. The optical position measuring device according to claim 10, wherein the scanning head is connected with the first scale, and the second scale is arranged to be relatively movable with respect to the scanning head along the first, second and third measurement directions.

15. The optical position measuring device according to claim 10, wherein the scanning head is neither connected with the first scale nor with the second scale, and the scanning head is arranged to be relatively movable with respect to the second scale along the first measurement direction, and the first scale is arranged to be relatively movable with respect to the second scale along the second and third measurement directions.

16. A manufacturing device having four optical position measuring devices according to claim 11, wherein the manufacturing device comprises a tool (T) and a work table (W) which is arranged to be linearly movable with respect to the tool (T) along the first, second and third measurement directions, and to be movable in rotational motion around the first, second and third measurement directions, and the scanning heads and the second scales of the position measuring devices are respectively connected with the tool (T), and the first scales of the position measuring devices are respectively connected with the work table (W), to determine the spatial position of the worktable (W) in all six spatial degrees of freedom relative to the tool (T) from the scanning signals of the position measuring device.

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