Sensor device for surface measurement

Abstract

To provide a sensor device that detects the characteristics of a surface of an object, and that is made simple and compact and can perform precise detection of an object.SOLUTION: A sensor device 10 detects the characteristics of a surface 1.1 of an object 1 located on a first plane T1, and has: a light source 12 that generates light; a beam splitting element 14 that deflects or passes the light from the light source 12 toward the object 1; a detection element 16 that detects light reflected on the object 1 and passing through the beam splitting element 14 or light reflected on the beam splitting element 14; and a lattice element 18 that generates an intensity pattern on a surface 16.1 of the beam sensitivity of the detection element 16 located on a second plane T2, and is arranged between the detection element 16 and the beam splitting element 14. The sensor device is provided with a first lens system 20.1 forming an image of the first plane T1 on the second plane T2, and the first lens system 20.1 is arranged on a detection optical path between the detection element 16 and the object 1.SELECTED DRAWING: Figure 1a

Description

[Technical field]

[0001] The invention relates to a sensor device for detecting a property of the surface of an object located in a first plane according to the preamble of claim 1. [Background technology]

[0002] A typical sensor arrangement is known from DE 10 200 03 133 A1. The sensor arrangement is used to measure the shape of an optical element and the resulting aberrations for the different light paths. The sensor arrangement comprises a combination of a grating and a structured detector. The sensor arrangement also comprises a beam splitter which combines (merges) the illumination and detection light paths. The grating is formed as a crossed grating.

[0003] The measurement principle of the sensor device is as follows: the object to be tested (i.e. the test specimen) is illuminated with a plane wave, which upon reflection is modified by the optical properties of the object. With each deviation of the reflected (modified) wave from the plane wave it is possible to deduce the optical properties of the object. The combination of a grating and a structured detector allows the reconstruction of the wavefront modified by the object surface. This in turn makes it possible to determine the optical properties of the object. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] China Patent Application Publication No. 111751012 [Patent Document 2] European Patent Application Publication No. 1081457 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem underlying the invention is to provide a sensor device for detecting properties of the surface of an object located in a first plane, which is of simple and compact construction and allows for precise detection of the object. [Means for solving the problem]

[0006] This problem is solved according to the invention by a sensor arrangement having the features of claim 1.

[0007] A sensor device formed according to the invention is used for detecting a characteristic of a surface of an object located in a first plane. The sensor device comprises a light source generating light. The sensor device comprises a beam splitting element for deflecting or passing the light of the light source towards the object. The sensor device comprises a sensing element for detecting light reflected at the object and passing through the beam splitting element or light reflected at the beam splitting element. The sensor device comprises a grating element arranged between the sensing element and the beam splitting element, which generates an intensity pattern on a beam sensitive surface of the sensing element located in a second plane. The sensor device comprises a first lens system for imaging the first plane onto the second plane. The first lens system is arranged in a detection optical path between the sensing element and the object.

[0008] Preferably, the first lens system is an afocal lens system.

[0009] It is advantageous if the first lens system is formed to provide a magnification of the imaging of the first plane into the second plane, and if the magnification is in the range 1-10, in the range 1.5-8 or in the range 2-6.

[0010] It is advantageous if the first lens system comprises a first lens element and a second lens element, the first lens element being arranged between the beam splitting element and the object, and the second lens element being arranged between the detection element and the beam splitting element.

[0011] Preferably, the beam splitting element is disposed in the detection optical path between the detection element and the object. For example, the beam splitting element is disposed in the detection optical path between the first lens element and the second lens element. Alternatively, the beam splitting element can be disposed in the detection optical path between the first lens element and the object. Alternatively, the beam splitting element can be disposed in the detection optical path between the detection element and the second lens element.

[0012] Instead of the first lens element, a first lens element group can be provided, and instead of the second lens element, a second lens element group can be provided, and the first and second lens element groups can each be a combined doublet (achromatic lens) or a complete (objective) lens.

[0013] It is advantageous if the first lens element has a first focal point on the image side and if the second lens element has a second focal point on the object side, if the first focal point and the second focal point coincide at a common point and if the common point is located between the second lens element and the beam splitting element or between the beam splitting element and the first lens element.

[0014] It is also advantageous if the grating elements are arranged in a third plane, if the third plane and the second plane are arranged at a predetermined distance from each other, and if the predetermined distance is less than 1 / 2 or 1 / 4 of the Talbot distance, depending on the period of the grating elements.

[0015] Preferably, the grid elements are formed as pure amplitude grids, in particular linear grids or two-dimensional grids (for example cross grids or checkerboard grids).

[0016] Preferably, the light source is an incoherent light source (eg, an LED).

[0017] A machine tool with a sensor arrangement according to the invention is defined in claim 15. The machine tool comprises a tool receptacle and a housing part connected to the tool receptacle. The sensor arrangement is integrated in the housing part. The housing part is arranged between the tool receptacle and the object.

[0018] The first plane may also be referred to as the object plane, and the second plane may also be referred to as the image plane.

[0019] The invention allows for precise detection of the surface characteristics of an object (e.g. the reconstructed height or the reconstructed height profile after a low-pass filter that removes high-frequency roughness) with a sensor device that is simply and compactly constructed. The detection of the object is performed in particular for relatively large wave periods and wave amplitudes of the object's surface (e.g. wave periods in the range of 0.1-2 mm; wave amplitudes in the range of 0.8-20 μm). For this purpose, a lens system (i.e. a first lens system) is provided that is arranged in the detection beam path of the sensor device. The first lens system provides a desired imaging between a first plane (i.e. the object plane) and a second plane (i.e. the image plane). For example, the imaging or imaging parameters (e.g. the magnification) are adapted to the object's surface (e.g. the surface angle). This allows for a high accuracy of the detection of the object, or even for the first time detection of the surface characteristics of the object, in particular in the presence of the above-mentioned exemplary wave periods and wave amplitudes. In addition, the invention allows for the realization of a desired imaging together with a collimated illumination of the object's surface. This essentially results in an optimized illumination and detection light path of the sensor device for detecting an object.

[0020] The sensor device according to the invention can also be understood as a light field camera, which makes it possible to simultaneously obtain not only the location information of the object image but also the angle information, which is coded in the intensity / stripe pattern.

[0021] Advantageous developments of the invention can be seen from the respective dependent claims.

[0022] Further details and advantages of the invention will become apparent from the following description of an embodiment of the invention in conjunction with the drawings. [Brief description of the drawings]

[0023] [Figure 1a] FIG. 2 shows a sensor arrangement according to a first embodiment, comprising a first lens system for imaging a first plane into a second plane. [Figure 1b] FIG. 1b shows an alternative illustration of the detection light path caused by the first lens system according to FIG. 1a. [Diagram 2] FIG. 11 is a diagram showing a sensor device according to a second embodiment. [Diagram 3] FIG. 2 is a schematic diagram illustrating the condition for the angle of the incident beam, where the incident beam strikes a second plane. [Figure 4a] FIG. 1 shows an exemplary intensity pattern and an exemplary intensity progression that are detected or determined upon imaging of a first plane onto a second plane via a detection optical path, the detection optical path exiting a smooth (flat) surface of an object. [Figure 4b] FIG. 13 shows an exemplary intensity pattern and an exemplary intensity progression that are detected or determined upon imaging of a first plane onto a second plane via a detection optical path, the detection optical path exiting from a wavy surface of an object. [Diagram 5] FIG. 4b shows an exemplary intensity profile corresponding to the intensity profile according to FIG. 4b. [Figure 6] FIG. 2 is a block diagram of an exemplary evaluation unit. [Figure 7] FIG. 13 shows an exemplary machine tool with a sensor arrangement according to a third embodiment, the sensor arrangement being integrated into a housing part of the machine tool. [Figure 8] FIG. 13 is a diagram showing a sensor device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In the drawings, identical or functionally identical elements are provided with the same reference numbers.

[0025] Based on figures 1a and 2, a first and a second embodiment are described below. The sensor device 10 according to the first and the second embodiment is respectively used to detect a property (e.g. a reconstructed height) of a surface 1.1 of an object 1 located in a first plane T1. The surface 1.1 of the object 1 has in particular a corrugated portion (wave irregularity) (e.g. a wave period in the range of 0.1-2 mm, a wave amplitude in the range of 0.8-20 μm).

[0026] In each figure, an optical axis O1 is shown. The optical axis O1 corresponds to the symmetry axis of at least a part of the detection light path of the sensor device 10. In addition, in each figure, a coordinate system (X, Y, Z) is shown. A first coordinate axis (X-axis) is perpendicular to the optical axis O1 and parallel to the paper surface. A second coordinate axis (Y-axis) is perpendicular to the paper surface. A third coordinate axis (Z-axis) is parallel to the optical axis O1. A first plane T1 is perpendicular to the optical axis O1.

[0027] The sensor device 10 according to Fig. 1a comprises a light source 12 for generating light. In particular, the light source 12 is an incoherent light (e.g. an LED). The sensor device 10 according to Fig. 1a also comprises a beam splitting element 14 for deflecting the light of the light source 12 towards the object 1. As shown in Fig. 1a, a first light path 13.1 (i.e. an illumination light path) is formed between the light source 12 and the object 1.

[0028] The sensor arrangement according to FIG. 1a comprises a sensing element 16 which detects light reflected at the object 1 and passing through the beam splitting element 14. The sensor arrangement 10 according to FIG. 1a also comprises a grating element 18 arranged between the sensing element 16 and the beam splitting element 14, which generates an intensity pattern (e.g. intensity pattern 101-1, 101-2 according to FIG. 4a, 4b) on a beam-sensitive surface 16.1 of the sensing element 16 located in a second plane T2. The second plane T2 is parallel to the first plane T1. As shown in FIG. 1a, a second (virtual) light path 13.2 is formed between the sensing element 16 and the object 1. The second light path 13.2 corresponds to a sensing light path from a smooth (virtual) surface 1.2 of the object 1. It is also shown in FIG. 1a that a third light path 13.3 is formed between the sensing element 16 and the object 1. The third light path 13.3 corresponds to a sensing light path from a wavy surface 1.1 of the object 1.

[0029] The sensor arrangement 10 according to Fig. 1a comprises a first lens system 20.1 for imaging (mapping) a first plane T1 into a second plane T2. The first lens system 20.1 is arranged between the sensing element 16 and the object 1. The first plane T1 corresponds to the object plane. The second plane T2 corresponds to the imaging plane (projection plane).

[0030] Advantageously, the first lens system 20.1 is configured as an afocal lens system.

[0031] The first lens system 20.1 is configured to produce a magnification (parameter m) of the imaging of the first plane T1 onto the second plane T2, for example parameter m being in the range 1 to 10, in the range 1.5 to 8 or in the (preferred) range 2 to 6.

[0032] In Fig. 1a, the angle α (i.e., the surface angle) between the first plane T1 and the local tangent 1.11 at the indicated point of the surface 1.1 of the object 1 is shown. Also in Fig. 1a, the angle 2α (i.e., twice the reflection angle) between the incident beam of the first optical path 13.1 (the incident beam strikes the first plane T1) and the reflected beam of the third optical path 13.3 (the reflected beam comes from the first plane T1) is shown. In addition, in Fig. 1a, the angle β between the incident beam of the second optical path 13.2 and the incident beam of the third optical path 13.3 (each of these incident beams strikes the second plane T2) is shown. As shown in Fig. 1a, the incident beam of the first optical path 13.1 striking the first plane T1 and the incident beam of the second optical path 13.2 striking the second plane T2 are each parallel to the optical axis O1.

[0033] As can be seen in FIG. 1a, the angle 2α is equal to twice the angle α, and the angle β is given by the following relationship:

[0034]

number

[0035] If m>1, then the angle β is smaller than the angle 2α. The case m=1 corresponds to 1:1 imaging.

[0036] The first lens system 20.1 includes a first lens element 22.1 and a second lens element 22.2. The first lens element 22.1 is disposed between the beam splitting element 14 and the object 1. The second lens element 22.2 is disposed between the sensing element 16 and the beam splitting element 14.

[0037] The first lens element 22.1 has a first focus P1 on the image side. The second lens element 22.2 has a second focus P2 on the object side. The first focus P1 and the second focus P2 coincide at a common point P. In a first embodiment, the common point P is located between the second lens element 22.2 and the beam splitting element 14.

[0038] The sensor arrangement 10 according to FIG. 1a comprises a reflecting element 24, which deflects the light of the light source 12 towards the beam splitting element 14. The sensor arrangement 10 according to FIG. 1a also comprises a second lens system 20.2, which is arranged between the light source 12 and the reflecting element 24. The second lens system 20.2 has an intermediate focus P'. In a first embodiment, the intermediate focus P' is arranged between the reflecting element 24 and the beam splitting element 14. The intermediate focus P' corresponds to the image-side focal length F1 of the first lens element 22.1. The first lens element 22.1 is formed to collimate the light from the intermediate focus P'.

[0039] As shown in Fig. 1a, the second lens system 20.2 includes a third lens element 22.3 and a fourth lens element 22.4. By means of the second lens system 20.2 in association with the first lens element 22.1, a collimated illumination of the object 1 is achieved.

[0040] In addition, the first lens system 20.1 achieves that the reflected beam of the second optical path 13.2 (the reflected beam comes from the first plane T1) and the incident beam of the second optical path 13.2 (the incident beam hits the second plane T2) each run parallel to the optical axis O1. This essentially achieves an infinity-to-infinity imaging, while avoiding a sharp image of the light source 12 on the detection element 16 that would interfere with the reconstruction or evaluation.

[0041] As shown in FIG. 1a, the distance between the first lens element 22.1 and the first plane T1 corresponds to the focal length F1 of the first lens element 22.1. The image-side focal length F1 of the first lens element 22.1 and the object-side focal length F1 of the first lens element 22.1 are the same size. Also, in FIG. 1a, the distance between the second plane T2 and the second lens element 22.2 corresponds to the image-side focal length F2 of the second lens element 22.2. The image-side focal length F2 of the second lens element 22.2 and the object-side focal length F2 of the second lens element 22.2 are the same size. Alternatively, the image-side and object-side focal lengths F1 and F2 listed immediately above may be different from each other (for example, in the case of an (objective) lens).

[0042] According to Fig. 1a, the grating elements 18 are arranged in a third plane T3. The third plane and the second plane T2 are arranged at a predefined distance L from each other. The second plane T2 and the third plane T3 are parallel to each other. Advantageously, the predefined distance L is less than 1 / 2 or 1 / 4 of the Talbot distance, which depends on the period D1 of the grating elements 18. This results in suitable conditions for the angle β. This is explained in more detail below on the basis of Fig. 3.

[0043] As shown diagrammatically in Fig. 1a, the beam-sensitive surface 16.1 of the sensing element 16 has a predetermined period D2. Preferably, the predetermined period D2 is smaller than 1 / 2, 1 / 4 or 1 / 10 of the period D1 of the grating element 18. This makes it possible to separate higher harmonics from the carrier frequency in the frequency spectrum of the measurement (i.e. the detected intensity pattern).

[0044] It is advantageous if the sensing elements 16 are formed such that their Nyquist frequency corresponds to an odd multiple of 1 / 2 or 1 / 4 of the spatial frequency of the intensity pattern (e.g. intensity patterns 101-1, 101-2 in Figures 4a, 4b) produced by the grating elements 18, which depends on the period D1 of the grating elements 18. In this case, the above mentioned rather high harmonics can be accurately mapped back to the carrier frequency.

[0045] In Fig. 1b, an alternative illustration of the detection light path caused by the first lens system 20.1 according to Fig. 1a is shown. In Fig. 1b, the surface 1.1 of the object 1 is depicted as a micromirror (see first plane T1) that is offset and tilted with respect to one another. With the illustration according to Fig. 1b, the surface area of ​​the beam-sensitive surface 16.1 of the detection element 16 (see second plane T2; element 16.1 not shown)

[0046]

number

[0047] ,

[0048]

number

[0049] the surface extent of the object 1 (see the first plane T1) generated by the first lens system 20.1 to

[0050]

number

[0051] ,

[0052]

number

[0053] The afocal imaging of is explained. Also, the spatial magnification is shown in Fig. 1b.

[0054]

number

[0055] ,

[0056]

number

[0057] (

[0058]

number

[0059] ,

[0060]

number

[0061] , where

[0062]

number

[0063] ,

[0064]

number

[0065] ) and simultaneous angle reduction

[0066]

number

[0067] ,

[0068]

number

[0069] (

[0070]

number

[0071] ,

[0072]

number

[0073] , where:

[0074]

number

[0075] ,

[0076]

number

[0077] ) is explained. Furthermore, the illustration according to FIG. 1b reveals the Δx shifts (i.e. Δx1, Δx2) of the local gradient intensity pattern (see FIG. 5, parameter Δx).

[0078] In FIG. 1b, the index "O" represents the feature / characteristic (surface extent, location information or angle information) of the object 1, and the index "R" represents the reflection angle. Furthermore, the index "K" represents the feature / characteristic (surface extent, location information) of the sensing element 16.

[0079]

number

[0080] ,

[0081]

number

[0082] Angles β1 and β2 in FIG. 1b correspond to angle β in FIG. 1a.

[0083] In Fig. 1b, exemplary intensity patterns 201-1 (circles) and 201-2 (circles with dots) are shown. The intensity patterns 201-1 and 201-2 in Fig. 1b correspond to exemplary intensity patterns 101-1 and 101-2 (striped patterns) described below with reference to Figs. 4a and 4b. The illustration of the intensity patterns 201-1 and 201-2 in Fig. 1b explains the parameter ΔX (Δx shift). In Fig. 1b, the illumination light path is omitted for clarity.

[0084] The sensor device 10 according to the second embodiment differs from the sensor device 10 according to the first embodiment in that the light source 12 is a diverging light source and is arranged at a predetermined position P″ upstream of the light of the beam splitting element 14 (see FIG. 2). The predetermined position P″ corresponds to the image-side focal length F1 of the first lens element 22.1. The first lens element 22.1 is formed to collimate the light from the predetermined position P″. Thus, a collimated illumination of the object 1 is achieved by the first lens element 22.1.

[0085] The sensor arrangement 10 according to Fig. 2 comprises a diaphragm element 32 arranged in a common inner focal plane I of the first lens system 20.1. The diaphragm element 32 has an adjustable aperture 32.1 which limits the optical path (i.e. the second or third optical path 13.2, 13.3 of the first lens system 20.1). The common inner focal plane I is parallel to the first to third planes T1 to T3 and extends through a common point P.

[0086] By means of the diaphragm element 32 it is possible to make a separation between a relatively large angle (angle 2α) and a relatively small angle (angle 2α). Typically, the relatively large angles are assigned to undesirable (high frequency) roughness of the object 1. Typically, the relatively small angles are assigned to (long period) waviness of the object 1 which is to be detected. Due to the above-mentioned separation it is possible to largely avoid errors in the evaluation (or reconstruction).

[0087] In the second embodiment it is also possible to omit the throttling element 32. The throttling element 32 can also be used in the first or third embodiment.

[0088] In FIG. 3, a schematic diagram is shown to explain the conditions for the angle β (see FIG. 1a and FIG. 2). In FIG. 3, an incident beam 13.31 is exemplarily shown. The incident beam 13.31 impinges on a second plane T2. The second plane T2 is arranged at a first distance L1 from the third plane T3. The first distance L1 corresponds to the given distance L in FIG. 1a and FIG. 2. As can be seen from FIG. 3, the incident beam 13.31 impinges on the second plane T2 in a first uniqueness range 2.1. For this, the following conditions should be fulfilled (first case):

[0089]

number

[0090] Also shown in Figure 3 is the following: the second (imaginary) plane T2a is disposed at a second distance L2 from the third plane T3. The second distance L2 is greater than the first distance L1. The second (imaginary) plane T2b is disposed at a third distance L3 from the third plane T3. The third distance L3 is greater than the second distance L2.

[0091] As can be seen from figure 3, the incident beam 13.31 impinges on the second (imaginary) plane T2a in the first uniqueness range 2.1 (i.e. at the border of the first uniqueness range 2.1). For this, the following conditions should be met (second case):

[0092]

number

[0093] Also, as can be seen from Fig. 3, the incident beam 13.31 impinges on the second (imaginary) plane T2b in the second uniqueness range 2.2 (i.e. outside the first uniqueness range 2.1). This is an impermissible case. In other words, the incident beam 13.31 no longer impinges on the second (imaginary) plane T2b in the first uniqueness range 2.1. In this (impermissible) case, the following condition is fulfilled (third case):

[0094]

number

[0095] The first and second uniqueness ranges 2.1, 2.2 are defined as follows: the incident beam 13.31 passes through the first grating opening (dimension D1 / 2) (see FIG. 3). A first grating web is arranged adjacent to the first grating opening (and below the first grating opening in FIG. 3). The first uniqueness range 2.1 is defined by the lower edge of the first grating web and the upper edge of the first grating opening (see dashed line parallel to the Z axis in FIG. 3). A first grating opening and a second grating web are arranged adjacent to the first grating opening (and below the first grating opening in FIG. 3). The first uniqueness range 2.2 is defined by the lower edge of the second grating web and the upper edge of the second grating opening (similar to the first uniqueness range 2.1).

[0096] In Fig. 4a an exemplary intensity pattern 101-1 and an exemplary intensity progression 103-1 derived therefrom are shown. The intensity pattern 101-1 and the intensity progression 103-1 are assigned to the imaging of the first plane T1 into the second plane T2 via the second optical path 13.2 (see Figs. 1a and 2). The intensity progression 103-1 corresponds to the intensity I as a function of the X coordinate, i.e. I=I(X). The intensity progression 103-1 is obtained by integration of the intensity pattern 101-1 over the Y coordinate (Y). As shown in Fig. 4a, the intensity progression 103-1 is periodic in the X direction.

[0097] In Fig. 4b an exemplary intensity pattern 101-2 and an exemplary intensity progression 103-2 derived therefrom are shown. The intensity pattern 101-2 and the intensity progression 103-2 are assigned to the imaging of the first plane T1 into the second plane T2 via the third optical path 13.3 (see Figs. 1a and 2). The intensity progression 103-2 is the intensity I as a function of the X coordinate, i.e. I=I(X). The intensity progression 103-2 is obtained by integration of the intensity pattern 101-2 over the Y coordinate (Y). In Fig. 4b dashed lines are shown. The dashed lines in Fig. 4b correspond to the intensity pattern 101-1 or the intensity progression 103-1 according to Fig. 4a. As shown in Fig. 4b, the intensity progression 103-2 is locally displaced in the X direction with respect to the dashed lines (i.e. locally expanded or compressed).

[0098] In Fig. 5 an exemplary intensity profile 103-2 is shown which corresponds to the intensity profile 103-2 according to Fig. 4b. In particular, the local displacement (parameter ΔX) of the intensity profile 103-2 is shown in Fig. 5. As shown diagrammatically in Fig. 5, the parameter ΔX is the distance from the first intensity maximum I max,1 and the second intensity maximum I max,2 The deviation of the grating elements 18 from periodicity is represented by the parameter ΔX, which can be understood as the relative phase (the so-called Takeda phase).

[0099] The parameter ΔX is obtained, for example, from a Fourier evaluation of the intensity progression 103-2 (derived from the intensity pattern 101-2 or from the stripe pattern), for example based on the so-called Takeda algorithm.

[0100] In Fig. 6 a block diagram of an exemplary evaluation unit 26 is shown. The evaluation unit 26 comprises a unit 28 and a unit 30. The unit 28 is arranged to determine phase information 107 depending on a signal 105 representative of an intensity pattern (e.g. the intensity patterns 101-1, 101-2 in Fig. 4a, 4b). The unit 30 is arranged to determine a reconstructed height 109 as a property of the surface 1.1 of the object 1 depending on the phase information 107. In Fig. 6 the signal 105 is denoted S~I(X). The phase information 107 is denoted φ(i). The reconstructed height 109 is denoted h(X). The reconstructed height 109 is determined by the evaluation unit 26 using the following relationship:

[0101]

number

[0102] where φ(i) is the phase information 107; Δξ is the pixel size of the detector element 16; L is a predetermined distance between the second plane T2 and the third plane T3; D1 is the period of the grating element 18; m is the magnification of the image; and N is the total number of pixels of the detector element 16.

[0103] In Fig. 7, an exemplary machine tool 200 with a sensor arrangement 10 according to a third embodiment is shown. The sensor arrangement 10 according to the third embodiment is integrated into a housing part 204 of the machine tool 200. The sensor arrangement 10 according to the third embodiment differs from the sensor arrangement 10 according to the first embodiment in that the common point P is arranged between the beam splitting element 14 and the first lens element 22.1. In addition, in the third embodiment, an intermediate focus P' is arranged between the beam splitting element 14 and the first lens element 22.1. As shown diagrammatically in Fig. 7, the common point P and the intermediate focus P' coincide.

[0104] As shown in Fig. 7, the machine tool 200 comprises a tool receptacle 202. The tool receptacle 202 and a housing part 204 are connected to each other. By integrating the sensor device 10 according to the third embodiment into the housing part 204, a compact construction is achieved.

[0105] According to Fig. 7, the housing part 204 has a first dimension A1 in the Z direction. Also, the housing part 204 has a second dimension A2 in the X direction. The first dimension A1 is essentially given by the parameters F1, F2 (see Fig. 7). The second dimension A2 is smaller than the first dimension A1. Also according to Fig. 7, the reflecting element 24 of the sensor device 10 is arranged in the vicinity of the second lens system 20.2 such that the dimension of the housing part 204 in the Z direction is smaller than the first dimension A1 at least in the area of ​​the reflecting element 24. This optimizes the compactness of the construction.

[0106] 8 shows a sensor device 10 according to a fourth embodiment. The sensor device 10 according to the fourth embodiment differs from the sensor device 10 according to the first embodiment in that the reflecting element 24 is not provided.

[0107] In the fourth embodiment, a beam splitting element 14 is used to pass the light of the light source 12 to the object 1 (see the first plane T1; element 1 not shown). As shown in FIG. 8, the combination of the light source 12 and the second lens system 20.2 is arranged centered with respect to the axis of symmetry of the illumination light path. Also in the fourth embodiment, a detection element 16 is used to detect the light reflected at the object 1 and at the beam splitting element 14. In other words, here, on the one hand, illumination of the object 1 by passing through the beam splitting element 14 takes place. Here, on the other hand, detection of the object 1 by reflection at the beam splitting element 14 takes place.

[0108] In the fourth embodiment, the sensor device 10 is formed so that it can project through 90°. Also in the fourth embodiment, as already mentioned above, the reflecting element 24 is not necessary.

[0109] 1a, the grating elements 18 are formed as simple amplitude gratings, which allows easy and cheap production of the grating elements 18. The gratings can be linear or two-dimensional (e.g. cross gratings or checkerboard gratings).

[0110] Alternatively, the grating elements 18 can be formed as linear mixed amplitude-phase gratings, whereby the grating elements 18 advantageously have a scale factor of TP AS In the amplitude structure within the width b of the opaque web S B S =1 / 3TP AS Furthermore, in each second opaque gap region of the amplitude structure, a phase-shifted subregion with a phase shift φ=π is arranged. In this regard, reference is made to the description of US Pat. No. 5,999,333, in particular to Figs. 2a and 2b.

[0111] In the first and third exemplary embodiments, it is also possible to omit the reflecting element 24. In this case, the light source 12 and the second lens system 20.2 are for example arranged such that the first light path 13.1 enters the beam splitting element 14 at an angle of 90° to the optical axis O1.

[0112] Alternatively, the light source 12 and the second lens system 20.2 can be arranged such that the first light path 13.1 enters the beam splitting element 14 obliquely (i.e. at an angle different from 90°, e.g. 60° or 45°) relative to the optical axis O1. In this case, the tilt / rotation of the beam splitting element 14 should be adapted accordingly.

[0113] In the first and third embodiments, the second lens system 20.2 can also consist of only one lens element, for example the third lens element 22.3. In this case, the fourth lens element 22.4 can be omitted. This is a cheaper alternative, but requires a greater adjustment effort.

[0114] For reasons of clarity, in FIG. 1b a second plane T2 is shown that does not have element 16.1, in FIG. 7 a first plane T1 is shown that does not have element 1, and in FIG. 8 a first plane T1 that does not have element 1, a second plane T2 that does not have element 16.1 and a third plane T3 that does not have element 18 are shown.

[0115] The invention has the following advantages in particular: Due to the first lens system 20.1, preferably formed as an afocal lens system, it is possible, unlike the prior art, to measure relatively large phase differences of technical surfaces (i.e. corrugation period and corrugation amplitude). Also, unlike the prior art, the use of incoherent light sources (e.g. LEDs) is significantly cheaper, energy-saving and less maintenance-intensive. Furthermore, due to the incoherent light source, it is possible to significantly reduce so-called speckle in the detected intensity pattern. In addition, the sensor device 10 can be formed as a wireless system with radio and accumulator (battery). The use of wireless technology for data transmission also allows the use of the sensor device 10 in areas of use that are difficult to access, such as for example the machining space of a machine tool. Furthermore, it is also possible to integrate the sensor device 10 into an automated feedback loop system for the mechanical determination of technical surfaces (cutting or adding).

Claims

1. A sensor device (10) for detecting a characteristic of a surface (1.1) of an object (1) located in a first plane (T1), comprising: A light source (12) for generating light; a beam splitting element (14) for deflecting or passing the light of the light source (12) to the object (1); a sensing element (16) for detecting light reflected from the object (1) and passing through the beam splitting element (14) or light reflected from the beam splitting element (14); a grating element (18) arranged between said detector element (16) and said beam splitting element (14), which generates an intensity pattern (101-1; 101-2) on a beam-sensitive surface (16.1) of said detector element (16) located in a second plane (T2); In the sensor device (10), The sensor device (10) comprises a first lens system (20.1) for imaging the first plane (T1) into the second plane (T2), the first lens system (20.1) being arranged in a detection optical path between the detection element (16) and the object (1).

2. 2. The sensor arrangement (10) according to claim 1, characterized in that the first lens system (20.1) is an afocal lens system.

3. 3. The sensor arrangement (10) according to claim 1 or 2, characterized in that the first lens system (20.1) is formed to provide a magnification (m) of the imaging of the first plane (T1) into the second plane (T2), the magnification (m) being in the range of 1 to 10, in the range of 1.5 to 8 or in the range of 2 to 6.

4. The sensor device (10) according to any one of claims 1 to 3, characterized in that the first lens system (20.1) comprises a first lens element (22.1) and a second lens element (22.2), the first lens element (22.1) being arranged between the beam splitting element (14) and the object (1) and the second lens element (22.2) being arranged between the detection element (16) and the beam splitting element (14).

5. 5. The sensor device (10) according to claim 4, characterized in that the sensor device (10) comprises a reflecting element (24) which deflects the light of the light source (12) towards the beam splitting element (14), the sensor device (10) comprises a second lens system (20.2) arranged between the light source (12) and the reflecting element (24), the second lens system (20.2) having an intermediate focus (P'), the intermediate focus (P') being arranged between the reflecting element (24) and the beam splitting element (14) or between the beam splitting element (14) and the first lens element (22.1), the intermediate focus (P') corresponding to a point distance (F1) on the image side of the first lens element (22.1), the first lens element (22.1) being formed to collimate the light from the intermediate focus (P').

6. 5. The sensor device (10) according to claim 4, characterized in that the light source (12) is a diverging light source (12) and is arranged at a predetermined position (P'') upstream of the light of the beam splitting element (14), the predetermined position (P'') corresponding to an image-side focal length (F1) of the first lens element (22.1), the first lens element (22.1) being formed to collimate the light from the predetermined position (P'').

7. The sensor device (10) according to any one of claims 1 to 6, characterized in that the grating element (18) is arranged in a third plane (T3), the third plane (T3) and the second plane (T2) are arranged at a predetermined distance (L) from each other, and the predetermined distance (L) is shorter than 1 / 2 or 1 / 4 of a Talbot distance, which depends on a period (D1) of the grating element (18).

8. 8. The sensor device (10) according to claim 1, characterized in that the beam-sensitive surface (16.1) of the sensing element (16) has a predetermined period (D2), which is shorter than 1 / 2, 1 / 4 or 1 / 10 of the period (D1) of the grating element (18).

9. 9. The sensor device (10) according to claim 1, characterized in that the sensing elements (16) are formed such that the Nyquist frequency of the sensing elements (16) corresponds to a few multiples of ½ or an odd multiple of ¼ of the spatial frequency of the intensity pattern (101-1; 101-2) generated by the grating elements (18), depending on the period (D1) of the grating elements (18).

10. 10. The sensor arrangement (10) according to claim 1, characterized in that the grating element (18) is formed as a pure amplitude grating.

11. 10. The sensor arrangement (10) according to any one of the preceding claims, characterized in that the grating elements (18) are formed as linear mixed amplitude phase gratings.

12. The sensor device (10) according to any one of claims 1 to 11, characterized in that the sensor device (10) comprises a diaphragm element (32) arranged in a common inner focal plane (I) of the first lens system (20.1), the diaphragm element (32) having an adjustable opening (32.1) which limits the optical path of the first lens system (20.1).

13. 13. The sensor arrangement (10) according to claim 1, characterized in that the sensor arrangement (10) comprises an evaluation unit (26) which is formed to determine phase information (107) depending on a signal (105) representative of the intensity pattern (101-1; 101-2) and to determine a reconstructed height (109) depending on the phase information (107) as a property of the surface (1.1) of the object (1).

14. The sensor device (10) according to any one of the preceding claims, characterized in that the light source (12) is an incoherent light source (12).

15. A machine tool (200) having a sensor device (10) according to any one of claims 1 to 14, characterized in that the machine tool (200) comprises a tool holding portion (202) and a housing portion (204) connected to the tool holding portion (202), the sensor device (10) being integrated into the housing portion (204), and the housing portion (204) being arranged between the tool holding portion (202) and the object (1).

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