Measuring system and processing device for polishing elements, operating procedures

Abstract

The invention relates to a measuring system (1) for testing a polishing surface (2) of a polishing element (3), in particular a pitch bowl, comprising a carrier (4) that can be displaced in a plane and on which the polishing element (3) can be arranged, and comprising at least one sensor device (8, 9, 10) that has a sensor (11) for measuring distances along a sensor axis (12) and is associated with or can be assigned to the carrier (4) such that the sensor axis (12) is oriented at least substantially perpendicular to the displacement plane of the carrier (4). It is provided that at least two sensor devices (8, 9, 10), each with an optical sensor (11), are present, the sensor axes (12) of which are spaced apart and arranged parallel to each other and distributed transversely to the displacement direction of the carrier (4).

Description

The present invention relates to a measuring system for testing a polishing surface of a polishing element, in particular a pitch dish, having a carrier which can be displaced in a plane and on which the polishing element can be arranged, and having at least one sensor device which has a sensor for measuring distance along a sensor axis and is arrangeable or assigned to the carrier in such a way that the sensor axis is aligned at least substantially perpendicular to the displacement plane of the displaceable carrier.The invention further relates to a method for operating such a measurement system.The invention also relates to an apparatus for processing a polishing surface of a polishing element, having at least one controllable processing device for processing the polishing surface of the polishing element and having a measurement system as has been described above.Measuring systems of the type mentioned at the beginning are known from the prior art. In the production and optimization of optical elements, it is known to process the surfaces with particularly high precision. In this case, mechanical and mechanical-chemical grinding processes are used, among other things, which use polishing elements and optionally polishing agents, in particular liquids, which interact with the optical elements. In order for the polishing elements to lead to the desired result, they themselves must be checked regularly for their state of use, in particular for wear and changes in shape. For this purpose, measurement systems are used, as described, for example, in the laid-open specification U.S. Pat. No. 5,974,679 B1. From this publication it is known to provide a sensor device which faces the polishing element and detects in a sensor axis the distance to the polishing element or to the polishing surface of the polishing element at different locations of the polishing surface, in order to also detect therefrom the wear and / or changes in shape of the polishing element. In order to detect the distance at different locations, the sensor device and / or the polishing element are arranged displaceably. For this purpose, the sensor device has a sensor which is designed to operate mechanically or optically. Thus, the cited publication proposes configuring the sensor as a position sensor, in particular as a linear variable transformer or as a laser sensor. A similar measuring system is also disclosed in the laid-open specification U.S. Pat. No. 8,123,593 B2.The known measuring systems can detect the wear of a polishing element in the form of removal and / or shape errors. A shape error or a shape deviation is understood in particular to mean a deviation of the surface shape of the polishing element from an expected or desired surface shape. Thus, the shape deviation can be due to individual or local shape errors in the polishing element or else to uneven wear or removal of the polishing surface, such that, for example, a curvature or inclination of the polishing surface results over a larger region of the polishing surface.The object of the present invention is to provide an improved measurement system which enables a simplified determination of a removal and / or a shape error of a polishing element, in particular without a user having to evaluate measured value data. The improved measurement system is preferably intended to enable a more rapid and detailed detection of the wear, in particular removal and / or shape errors, in comparison with known measurement systems.The object on which the invention is based is achieved by a measuring system having the features of claim 1.According to the invention, the measuring system has at least two sensor devices each having an optical sensor, wherein the sensor axes of the sensors are arranged spaced apart and parallel to one another and distributed transversely to the displacement direction of the carrier. When the carrier is displaced, the polishing surface is thus advantageously scanned by the two sensors on different movement paths over the polishing surface, whereby removal and changes in shape can be determined reliably and precisely. By providing at least two sensor devices, shape deviations can be detected particularly quickly by comparing the measured values of the two sensor devices with one another. This makes it possible to dispense with a complex calibration of the measurement system before startup, since calibration is not necessary due to the plurality of sensor devices.According to a preferred development of the invention, at least three sensor devices are provided, each with an optical sensor, the sensor axes of which are arranged spaced apart and parallel to one another and distributed transversely to the displacement direction of the carrier. By providing at least one further sensor or at least one further sensor device, it is achieved that the measurement results of the sensor devices can be verified or checked for plausibility with one another. The plausibility check ensures that a shape error or a shape deviation, which is detected by one of the measuring devices, can be assigned to the correct measuring device. By comparing the measurement signals with one another, the measurement reliability is thus advantageously increased.The respective sensor is preferably designed as a confocal sensor. A confocal sensor is characterized by a particularly precise distance measurement. Here, two optical systems or optical paths with a common focal point are used for each confocal sensor. Particularly preferably, a chromatic-confocal sensor is used as the confocal sensor, which is characterized in that not white light, but rather light separated according to wavelengths is focused at different distances or at different focal points along the optical sensor axis. Usually, the focal point or focal point for blue light is closer to the optics and the focal point for red light is farther away along the sensor axis. This allows a surface to be imaged and measured at different distances at the same time. As a result, a chromatic-confocal sensor does not require a scanning movement along the optical axis; the scanning along the surface or the polishing surface of the test object, in the present case the polishing element, is sufficient.Particularly preferably, each of the sensor devices has a measuring glass which can be arranged on the polishing surface and lies in the respective sensor axis. The measurement glass has the particular advantage that the multiple focal points of the chromatic confocal sensor can be used advantageously. The respective measuring glass compensates for small shape errors or irregularities in the polishing surface and results in a type of averaged measurement value at the top side of the measuring glass.Preferably, the respective measuring glass has an underside which can be deposited on the polishing surface and an upper side which is aligned parallel thereto and faces the sensor.Particularly preferably, the distance from the top side to the underside of the measuring glass or the thickness of the measuring glass in the direction of the sensor axis is selected as a function of the focal points of the respective confocal sensor in such a way that one focal point lies on the top side and a further focal point lies on an underside of the respective measuring glass. Alternatively or additionally, the respective confocal sensor is designed such that the focal points are adapted to the distance of the upper side from the lower side of the respective measuring glass. The fact that, on the one hand, the upper side and, on the other hand, the lower side of the measuring glass are detected by the respective sensor device results in the advantage that, on the one hand, a total removal of the polishing element can be advantageously detected because small unevennesses are compensated by the measuring glass, and that, on the other hand, shape errors or shape deviations on the lower side of the measuring glass can be advantageously determined and evaluated, so that both the information relating to the removal and the information relating to even relatively small shape errors are advantageously detected in a measurement process.Particularly preferably, the carrier is rotatably mounted, wherein the sensor axes are arranged distributed along a radial extending from a rotation center. Thereby, the sensor axes are located on different peripheries of the polishing member with respect to the rotation center. If the carrier is set in rotation, the sensor devices advantageously scan the polishing element on the respective peripheral line. By using at least three sensor devices, this already results in an advantageous measurement result, which allows a breakdown for removal and shape deviations.Particularly preferably, at least one controllable actuator is assigned to the carrier for its displacement, so that its movement in the displacement plane can be carried out automatically. In particular, the carrier is rotatably mounted in the plane, wherein a rotational speed can be fixed, which enables an advantageous and reliable evaluation.Particularly preferably, at least one of the sensor devices is mounted so as to be displaceable along the radial. The sensor devices are held, for example, by a carrier arm extending radially from the center of rotation. At least one of the sensor devices is mounted displaceably along the carrier arm in order to radially displace the sensor axis and thereby enable scanning of the polishing element on different circumferential lines. Optionally, a plurality of the sensor devices are arranged such that they can be displaced or displaced accordingly. This can increase the measurement precision and the accuracy of the evaluation. In addition, the measuring system can thereby advantageously be adapted to polishing elements of different sizes, in particular polishing elements of different sizes.Particularly preferably, a control device is present which is specifically designed to actuate the sensor devices and the at least one actuator in order to record the removal of the polishing element and / or shape deviations of the polishing element. The control unit ensures automated detection of removal and / or shape deviations. In particular, the control device is designed to execute the method described further below when used as intended.The control device is preferably configured to compare distances to the top side and / or to the bottom side detected by means of the sensor devices with one another in order to detect ablation and / or shape deviations.The method according to the invention for operating the measuring system is characterized by the features of claim 11 in that an ablation of the polishing element is determined by comparing the distances to the top side of the measuring glasses. Preferably, the removal of the polishing element is measured indirectly via the absolute position of the peak of the glass top side of the respective measuring glass, optionally with polishing agent present on the polishing surface.Furthermore, it is preferably provided that alternatively or additionally a shape error of the polishing element is determined by comparing the distances to the underside of the measuring glasses. By comparing the measured values of the focal points on the glass underside, shape errors or shape deviations of the polishing element can be directly detected.The device according to the invention having the features of claim 12 is characterized in that the processing device is controlled by the control unit as a function of measurement data of the measurement system. This results in automatic utilization of the acquired measurement data for the subsequent processing of the polishing surface, in that the processing device is controlled as a function of acquired measurement data to compensate shape errors acquired by the measurement system. In particular, the machining device has a dressing glass which is positioned as a function of the measurement data of the measurement system in order to achieve a shape correction of the polishing element, in particular of the pitch shell.The machining device preferably has at least one displaceable machining element, in particular a dressing glass. In particular, the processing element for processing the polishing element can be placed thereon or pressed against the latter with an adjustable force in order to process the polishing element.Further advantages and preferred features and combinations of features emerge in particular from the description above and from the claims. The invention will be explained in more detail below with reference to the drawings. This is shown by FIG. 1 shows an advantageous measurement system in a simplified representation, FIG. 2 shows an enlarged illustration of the measurement system, FIG. 3 shows a measurement result of the measurement system, FIG. 4 shows an exemplary application of the measuring system, and FIG. 5 shows an apparatus for processing a polishing surface of a polishing element with the measurement system in a simplified illustration.FIG. 1 shows, in a simplified representation, an advantageous measuring system 1 for checking a polishing surface 2 of a polishing element 3 shown here only by way of example. According to the present exemplary embodiment, the polishing element 3 is designed in the form of a circular disk and is arranged on a carrier 4, which is likewise designed in the form of a circular disk and is mounted rotatably about a rotation center 5, which results from a central rotation axis 6 of the carrier 4. The polishing element 3 is likewise placed centrally on the carrier 4 and can thus likewise be rotated about its center of rotation by means of the carrier 4. For this purpose, the carrier 4 is assigned an actuatable actuator 7, in particular an electric motor.The measurement system 1 in the present case furthermore has three sensor devices 8, 9, 10, which are of identical design. The embodiment of the sensor device 10 described below with reference to the sensor device 10 is thus equally understood for the sensor devices 8 and 9.The sensor device 10 has an optical sensor 11 which is designed as a chromatic-confocal sensor. The optical sensor 11 has a sensor axis 12 in its detection direction, wherein the sensor axis 12 is oriented perpendicular to the rotational plane of the carrier 4 and thus at least substantially perpendicular to the polishing surface 2 of the polishing element 3 located on the carrier 4. The actual relative orientation of the sensor axis 12 to the polishing surface 2 depends on the nature of the polishing surface 2 that is to be detected by the measurement system 1. In this respect, the sensor axis 12 is aligned exactly perpendicular to the polishing surface 2 only if it extends exactly parallel to the carrier 4 or in the plane of rotation. Depending on the detection point on the polishing surface 2, the orientation of the sensor axis 12 to the polishing surface 2 can thus change if the latter has, for example, a curvature, a notch or the like. When viewing the entire polishing surface 2, however, it can be assumed that the sensor axis 12 is oriented at least on average perpendicular to the polishing surface 2.The sensor device 10 furthermore has a measurement glass 13 which rests or is placed on the polishing surface 2 of the polishing element 3 for a measurement.FIG. 2 shows the sensor devices 8, 9, 10 in an enlarged representation for this purpose. By configuring the sensors 11 as chromatic-confocal sensors, these have a plurality of focal points along the sensor axis 12, but at least two focal points F 1 and F 2, which are situated at different distances from the sensor 11. The sensor 11 and the measuring glass 13 are matched to one another in such a way that the focal point F 1 is assigned to an underside 14 of the measuring glass 13 resting on the polishing surface 2, and the focal point F 2 is assigned to an upper side 15 of the measuring glass 13 facing away from the underside 14. By configuring the respective sensor 11 as a chromatic confocal sensor, the focal points or focal points F 1, F 2 can thus be adapted to the upper side 15 and the lower side 14.For a measurement, the three sensors 8, 9, 10 are controlled by a control device to record the position of the measuring glasses 13 or the polishing surface 2 in the focal points F 1 and F 2, respectively.FIG. 3 shows a measurement result in a simplified manner in a diagram for this purpose. The intensity of the reflection radiation detected by the sensor 11 at the respective focal point F 1, F 2 is shown at two different measurement points a and b.By means of the advantageous measurement, the shape or shape deviation and removal of the polishing element 3 can be determined during operation. In particular, the removal of the polishing element 3 is measured indirectly by the three sensor devices 8, 9, 10 by the absolute position of the peak of the top side 15 of the measuring glasses 13, and shape errors or shape deviations of the polishing surface, in particular of an exactly planar polishing surface, are detected directly by means of the measurement value comparison at the focal points F 1 or the glass bottom side 14 of the measuring glasses 13.In principle, the measuring system 1 can be used for all planar surface processes, such as foil polish, pitch polish or the like. In the present case, the polishing element 3 is in particular a so-called pitch shell. The advantageous method and the advantageous measurement system 1 make it superfluous to check the measured values by employees and avoid problems which could arise during subjective checking by employees.FIG. 4 shows an application example in which the polishing surface 2 has a decreasing thickness or height toward its outer edge. The advantageous measurement system 1 recognizes on the upper side of the measurement glasses 13 that overall wear, in the present case non-uniform wear, has occurred. By comparing the measured values at the underside of the measuring glasses at the focal point F 1, shape errors are detected which are in particular smaller than the respective measuring glass 13. While the test glasses advantageously neutralize smaller unevennesses in the polishing surface 2 and thus advantageously allow the wear of the polishing element 3 to be detected at the focal point F 2, local flaws are advantageously detected at the focal point F 1.FIG. 5 shows an advantageous device 20 which is designed to process a polishing element 3. In particular, the device 20 has the aforementioned measurement system 1, so that the device 20 also has the carrier 4, by means of which the polishing element 3 is rotatable. Whereas the sensor devices 8, 9 and 10 are now arranged on an angle segment of the polishing element 3 or of the carrier 4, a processing device 21 is provided, for example, in another angle segment of the carrier 4, which processing device has a processing element 22, which is designed, for example, as a dressing glass and can be pressed onto the polishing surface 2 of the polishing element 3. Depending on the measurement data acquired by the measurement system 1, the machining device 21 is controlled to compensate for the unevennesses by means of the dressing glass or the machining element 22. If the carrier 4 is rotated and thus also the polishing element 3 is rotated relative to the dressing glass, the dressing glass or the machining element 22 has the result that the dimensional deviation previously detected by the measurement system 1 is compensated.The sensor devices 8, 9, 10 are advantageously held on a support rail 23 which extends radially over the support 4 towards the center of rotation 5, as shown by way of example in FIG. 2. As a result, the sensor elements 8, 9, 10 are arranged distributed along a radial starting from the rotational axis 6 or the rotational center 5. In particular, the sensor elements 8, 9, 10 are arranged distributed uniformly along the radial line. Optionally, at least one of the sensor devices 8, 9, 10 is mounted displaceably on the support rail 23, as shown by way of example by a double arrow 24 in FIG. 2. As a result, the measuring system 1 can be advantageously adapted to different polishing elements 3 or polishing element sizes, for example.LIST OF REFERENCE CHARACTERS1 Measuring system 2 Polishing surface 3 Polishing element 4 Carrier 5 Rotation center 6 Rotation axis 7 Actuator 8 Sensor device 9 Sensor device 10 Sensor device 11 Sensor 12 Sensor axis 13 Measuring glass 14 Underside 15 Upper side 20 Apparatus 21 Processing device 22 Processing element 23 Mounting rail 24 Double arrow F 1 Focal point F 2 Focal pointReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedU.S. Pat. No. 5,974,679 B1

[0004] U.S. Pat. No. 8,123,593 B2

[0004]

Claims

Measurement system (1) for checking a polishing surface (2) of a polishing element (3), in particular a pitch dish, having a carrier (4) which can be displaced in a plane and on which the polishing element (3) can be arranged, and having at least one sensor device (8, 9, 10) which has a sensor (11) for measuring the distance along a sensor axis (12) and is alignable or associated with the carrier (4) in such a way that the sensor axis (12) is aligned at least substantially perpendicularly to the displacement plane of the carrier (4), characterized in that at least two sensor devices (8, 9, 10) are present each having an optical sensor (11), the sensor axes (12) of which are arranged at a distance from one another and parallel to one another and are arranged at a distribution transversely to the displacement direction of the carrier (4).Measurement system according to claim 1, characterised in that three sensor devices (8, 9, 10) are provided each with an optical sensor (11), the sensor axes (12) of which are arranged spaced apart and parallel to one another and are arranged distributed transversely to the displacement direction of the carrier (4).Measurement system according to one of the preceding claims, characterized in that the respective sensor (11) is designed as a confocal sensor, in particular as a chromatic confocal sensor.Measuring system according to one of the preceding claims, characterized in that each of the sensor devices (8, 9, 10) has a measuring glass (13) which can be arranged on the polishing surface and lies in the respective sensor axis (12), wherein the respective measuring glass (13) has an underside (14) which can be deposited on the polishing surface (2) and an upper side (15) which is aligned parallel thereto and faces the respective sensor (11).Measurement system according to one of the preceding claims, characterized in that the distance of the upper side (15) from the lower side (14) in the direction of the sensor axis (12) is selected as a function of focal points (F1, F2) of the respective confocal sensor, such that one focal point (F2) lies on the upper side (15) and a further focal point (F1) lies on the lower side (14).Measurement system according to one of the preceding claims, characterized in that the carrier (4) is rotatably mounted, wherein the sensor axes (12) are arranged distributed along a radial extending from a rotation center (5).Measurement system according to one of the preceding claims, characterized in that the carrier (4) is assigned at least one controllable actuator (7) for its displacement.Measurement system according to one of the preceding claims, characterized in that at least one of the sensor devices (8, 9, 10) is mounted so as to be displaceable along the radial.The measurement system according to any one of the preceding claims, characterized in that a control device is provided which is configured to control the sensor devices (8, 9, 10) and the at least one actuator (7) in order to detect a removal of the polishing element (3) and / or a shape deviation of the polishing element (3).Measurement system according to one of the preceding claims, characterized in that the control device is configured to compare distances to the upper side (15) detected by means of the sensor devices (8, 9, 10) and / or the detected distances to the lower side (14) with one another.Method for operating a measurement system according to one of Claims 1 to 10, characterized in that removal of the polishing element (3) is determined by comparing the distances from the upper side (15) of the measurement glasses (13), and / or in that a shape error of the polishing element (3) is determined by comparing the distances from the lower side (14) of the measurement glasses (13).Apparatus (20) for processing a polishing surface (2) of a polishing element (3), having at least one controllable processing device (21) for processing the polishing surface (2) of the polishing element (3) and having a measurement system (1) according to one of Claims 1 to 12, characterized in that the processing device (21) is controlled, in particular by the control device according to Claim 9, as a function of measurement data of the measurement system (1).Device according to claim 12, characterised in that the machining device (21) has at least one displaceable machining element (22), in particular a dressing glass.

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