DE102020134604B4 - Device and method for position determination - Google Patents

Abstract

The present invention relates to a device and a method for position determination by detecting at least one reference mark of a material measure. In order to present a solution that reduces the sensitivity of the detection to signal interference, it is proposed to carry out the position determination based on a detector signal and a window signal, which are based on at least three detection signals, with the detector signal being based on two of the detection signals and the detection signals based on another one the window signal is determined. As a result, the window signal can be determined independently of the detector signal, which leads to better resolution of the position determination.

Description

The present invention relates to the field of position measuring devices for detecting a reference mark and in particular but not exclusively to a device for optical position determination for detecting a movement or rotation of a scale relative to a measuring head.

A position-measuring device includes a measuring head and a measuring standard that can be moved in a measuring direction for this purpose. The material measure has a periodic scale, in particular an optical grating extending in the measuring direction, and at least one reference mark. The measuring head detects an incremental relative movement of the scale in the measuring direction to generate mostly sinusoidal periodic signals. In addition, at least one reference mark is detected and at least one reference pulse is generated, as a result of which the absolute position in the measuring direction relative to the measuring head can be determined. For this purpose, the measuring head has a detector arrangement for detecting the scale and a detector arrangement for detecting the reference mark.

Generic devices, such as those from the publications U.S. 2016/0231144 A1 or DE 10 2018 108 347 A1 are known are in many cases optical encoders. Such an optical encoder comprises a light source for applying light to the scale, which is reflected from the scale to said detectors or which reaches the detectors in transmission through the scale. However, there are also generic encoders for detecting relative movements that are based on other principles, for example inductive magnetic encoders, as for example in the publication DE 43 06 634 A1 called. The method according to the invention can also be used in this field.

To detect a reference position, for example, in writing EP 0 361 457 B1 proposed to use two detectors that generate two offset signals. A signal is generated at the crossing point of the two signals, which indicates the reference position. However, this method has the disadvantage that the crossing point can vary with fluctuations in the signal level and therefore cannot be determined with sufficient accuracy. In addition, the document gives no indication of how the reference signal can be exactly related to a periodic incremental signal.

document WO 2017/203210 A1 relates to an encoder having a read head movable relative to a scale, configured to generate a position signal and a reference mark signal when the read head passes over a reference mark on the scale, and configured to process the reference mark signal generation process in response to to automatically adapt to a change of circumstances in order to track at least the maintenance of a given relationship between the position and reference mark signals.

In WO 2020/053566 A1 proposes an incremental measurement encoder comprising a scale and a readhead, the scale comprising a periodic series of features forming an incremental track and at least one reference mark, the readhead comprising a structured light source and a reference mark photodetector array and the at least one Reference mark comprises at least one imaging element which is configured to generate an image of the structured light source on the reference mark photodetector array.

another in US 6,175,109 B1 The proposed device for detecting rotational movement includes three detectors arranged transversally to the measuring direction, which detect three different measuring tracks that have reference marks that are coded differently in the measuring direction. The detectors each emit square-wave high or low signals. However, this device is not suitable for high-resolution position determination in the nanometer range.

High-resolution position measuring devices with a high-resolution reference mark are, for example, from the patents EP 2 525 195 B1 and US 2003/0047674 A1 known. In this case, the reference mark has a so-called chirped grating structure, which generates a modulated interference signal which is detected by the detector arrangement consisting of three or four reference detectors arranged in the measuring direction. Through suitable interconnection, e.g. B. Amplification and summation of the individual detector signals, a high-resolution reference pulse is generated.

However, such or comparable devices have several disadvantages: The chirped grating structure is designed as a diffractive optical element (DOE) and must be manufactured with the same precision as the incremental grating and have an exact positional relationship with narrow manufacturing tolerances to this. Such structures are complex and expensive to produce. The phase relationship of the reference pulse to the periodic signal is determined by its physical position in the direction of measurement and the location of the detectors and is therefore not adjustable. Nevertheless, the position of the reference pulse can be affected by the interferometrically generated pattern can be very susceptible to fluctuations in the alignment of the detector to the scale and can change during operation, in particular when the detector is rotated. On the other hand, a targeted adjustment of the position and width of the reference pulse is only possible to a limited extent. Furthermore, the desired shape of the signal pulse is only generated by several electronic summations.

Furthermore, devices and methods are known in which reference marks are attached to the material measure as simple markings without any special structure. The expansion of the reference mark in the measuring direction extends over several periods of the incremental scale. Comparable devices, such as those in EP 1 050 742 A2 or in U.S. 2016/0231144 A1 are described include two detectors offset in the measuring direction or two detector groups for detecting the reference mark. The detectors or detector groups each generate two overlapping analog detector signals offset in the measurement direction, the width of which is much greater than one period of the periodic signal. A difference signal with a typical signal shape with a steep and straight edge is generated from these two signals (e.g. shown in 5B the EP 1 050 742 A2 ). Depending on the process, for example, the zero crossing is now determined and set in phase relation to the incremental signal, or the passing of these thresholds is evaluated using two fixed or adjustable threshold values and a logical high-low signal is generated from this, which has several edges and square-wave pulses of different widths. Since the difference signal with its typical signal form has several zero crossings or passes the threshold values several times, another window signal is required to select a defined pulse from the high-low signal, the width of which is smaller than one period of the incremental signal. For this purpose, the sum of the two detector signals is also formed and again compared with a further threshold value, as a result of which a window signal is generated with which a defined reference pulse can be generated from the high-low signal.

The disadvantages of such and similar methods and devices are as follows: On the one hand, in addition to calculating the difference, a summation is necessary, which has to be implemented using electronic components in an evaluation unit and is lossy. Furthermore, both the sum signal and the difference signal lead back to the same two detector signals. A disturbance in the difference signal, for example a change in the ambient light, automatically also leads to a disturbance in the sum signal, as a result of which this disturbance has a double effect. Finally, the shape and width of the sum signal is determined by the physical arrangement and dimensions of the detectors or detector groups, which also generate the differential signal. The position and width of the window signal can therefore not be tuned independently of and in a targeted manner to the difference signal, except by the threshold value for the sum signal. For example, it is desirable to make the window signal as narrow as possible. However, a corresponding design would also result in narrow detector signals that no longer overlap sufficiently to generate the necessary typical shape of the difference signal, which in such a case would have a saddle point instead of a steep edge.

The present invention is based on the object of specifying a position measuring device for detecting at least one reference position and a method for generating at least one reference signal in which the problems or limitations of the conventional approaches do not occur or at least occur to a lesser extent.

According to the invention, according to a first aspect, a device for position determination by detecting at least one reference mark of a material measure is proposed, as defined in claim 1, namely with at least one signal source, which is designed to emit a scanning signal, at least three detector units, which are relatively offset from one another and arranged at a respective predetermined position relative to the signal source, the detector units each being configured to output a detection signal on the basis of a response signal emanating from the reference mark in response to the scanning signal, the detection signals being independent of one another, and a signal processing unit which is designed to determine a detector signal on the basis of two of the three detection signals and to determine a window signal on the basis of the other of the three detection signals or the other of the three detection signals le to use as a window signal, wherein the signal processing unit is further configured to determine the position of the reference mark based on the detector signal and the window signal.

According to the invention, according to a second aspect, a method for determining a position by detecting at least one reference mark of a material measure is proposed, as defined in claim 16, namely with the steps of emitting a scanning signal through a signal source of a device for determining the position, the interaction of the scanning signal with the reference mark , leaving a reply sig nal is present, the detection of the response signal by at least three detector units, which are offset relative to one another along a measurement direction and are arranged at a respective predetermined position relative to the signal source in order to output a respective detection signal to a signal processing unit, the determination, by the signal processing unit, of a detector signal Based on two of the three detection signals and a window signal based on the other of the three detection signals or using the other of the three detection signals as the window signal, and determining the position of the reference mark based on the detector signal and the window signal.

One aspect of the present invention is that a third detector is used to generate a window signal, which generates a third detector signal so that no sum signal has to be generated, this third detector signal being independent of the signals from the other detectors as a result of the separate detector.

Part of the background to the present invention is found in the following considerations.

If the device has at least three detector units, each configured to output a detection signal based on a response signal emanating from the reference mark in response to the scanning signal, the detection signals being independent of one another, and a signal processing unit configured based on two of the three Detection signals to determine a detector signal and to determine a window signal based on the other of the three detection signals or to use the other of the three detection signals as a window signal, as well as to determine the position of the reference mark on the basis of the detector signal and the window signal, the window signal can be independent of the detector signal to be determined. As a result, the window signal used is not coupled to the difference signal, which means that the error in determining the window signal can be reduced. By decoupling the window signal from the differential signal, independent adjustability and thus an enlarged adjustment range as well as reduced sensitivity to signal interference, for example due to fluctuations in the ambient light, is achieved and the disadvantages of the prior art are overcome. This leads to an improvement in the resolution of the position determination.

The present invention can make it possible to determine the position of at least one reference position in relation to the high-resolution incremental scale as precisely as possible. This means that the reference signal does not extend over more than one period of the incremental signal. This creates a reference point for the high-resolution incremental position measurement and thus enables an absolute position to be determined. For this purpose, the signals from the detectors for detecting the reference mark must be assigned to an exact period of the signals from the detectors for detecting the incremental periodic scale.

In principle, due to the measuring principle, the incremental relative movement of the periodic scale can be recorded with a much lower resolution than the recording of a reference marking.

It is therefore advantageous to present a solution by which the reference signal can be associated with a single period of the incremental periodic signal, so that the absolute position of the reference mark can be determined with the same resolution as the relative position.

It is preferred that the device has a signal source that emits a scanning signal, the at least three detector units being designed in such a way that they each detect a response signal on the basis of the one scanning signal. Alternatively, the device can also have more than one, e.g. two or three, signal sources that emit more than one, e.g. two or three, scanning signals, with the at least three detector units being designed in such a way that they each detect a response signal on the basis of the scanning signals and each output a detection signal, which are independent of each other. It is conceivable that, e.g. in the case of three signal sources, a scanning signal from a signal source is detected as a response signal from one of the at least three detector units, or that a combination of multiple scanning signals from the multiple signal sources is detected as a response signal from the at least three Detector units is detected, the output detection signals of the at least three detector units are independent.

In an advantageous configuration of one aspect of the invention, the signal source is designed to emit an electromagnetic scanning signal, in particular an optical scanning signal, to emit an electrical scanning signal and/or to emit a magnetic scanning signal, and the detector units are designed to detect a corresponding response signal. The scanning signal preferably has electromagnetic radiation, with the detector units being designed to assign a response signal as a function of an intensity of the electromagnetic radiation detect and output a detection signal. Alternatively, the response signal can also depend on other properties of the electromagnetic radiation, for example the phase. Preferably, the scanning signal comprises electromagnetic radiation having wavelengths in the visible range of the spectrum. For example, the scanning signal may comprise white light, ie electromagnetic radiation having a variety of different wavelengths in the visible part of the spectrum, or colored light, ie having wavelengths from a small part of the visible spectrum. In these cases, the scanning signal is an optical scanning signal and the detector units are preferably photodiodes which, depending on the intensity of the light, emit an electrical signal, eg an electrical current, as a detection signal. The scanning signal can also have electromagnetic radiation from other ranges of the spectrum, the detector units then being designed such that they are sensitive to the scanning signal depending on the wavelength range, ie for example detecting a response signal depending on the intensity of the radiation and outputting a detection signal. In addition or as an alternative to an optical scanning signal, an electrical or magnetic signal can also be used as the scanning signal, with the respective detector units being designed to additionally or alternatively detect a response signal from the electrical or magnetic signal and to output a detection signal.

In another advantageous embodiment of an aspect of the invention, the signal source and the detector units are arranged relative to one another for the response signal to emanate from the reference mark on the basis of the scanning signal by transmission or reflection. If a response signal as a response to a scanning signal emitted by the signal source reaches a detector unit by transmission at the reference mark, the signal source and the at least three detector units are preferably designed in such a way that a scanning signal from the signal source is transmitted directly to the reference mark, i.e. in the direction of propagation of the Scanning signal from the signal source reaches the at least three detector units. If a response signal as a response to a scanning signal emitted by the signal source reaches a detector unit through reflection at the reference mark, the signal source and the at least three detector units are preferably designed in such a way that a scanning signal from the signal source is reflected against the direction of propagation of the scanning signal from the reference mark the signal source reaches the at least three detector units. In this case, the signal source and the at least three detector units are preferably arranged in one plane relative to one another. A combination of reflection and transmission is also conceivable, in that part of the scanning signal from the signal source reaches one or more detector units directly by transmission and part of the scanning signal reaches one or more detector units by reflection. In a preferred embodiment, the signal source and the at least three detector units are arranged relative to one another for outputting the response signal from the reference mark on the basis of the scanning signal by reflection, it being further preferred that the signal source and the at least three detector units are arranged in one plane. This has the advantage that all units of the device according to the invention can be arranged on one side relative to a reference mark.

In a further advantageous embodiment of an aspect of the invention, two of the three detector units are arranged on a line that extends in the measuring direction, with the other of the three detector units being arranged offset with respect to the line.

In a preferred variant of the above embodiment, the signal processing unit is designed to determine the detector signal on the basis of the detection signals of the two of the three detector units and the window signal on the basis of the detection signal of the other three detector units or the detection signal of the other three detector units as the window signal to use. This arrangement of the two of the three detector units on a line has the advantage that the two detector units can output two identical detection signals when the device moves relative in the measuring direction and a detector signal can be determined on the basis of two identical detection signals. In addition, because the other of the three detector units is offset from the line, the detection signal on the basis of which the window signal is determined can have different properties than the detection signal on the basis of which the detector signal is determined. In particular, the two detector units can be arranged in such a way that the two associated detection signals are designed so that a detector signal is determined on the basis thereof, and that the further detector unit is arranged such that the associated detection signal is designed to generate a window signal on its basis is determined. By using the further detector unit, the respective detection signal can thus be optimized via the arrangement of the detector units, so that it is adapted either for determining the detector signal or for determining the window signal.

In another advantageous embodiment of an aspect of the invention, two of the three detector units are of identical design and differ from the other of the three detector units, in particular with regard to their dimensions. It is also preferred here to determine the detector signal on the basis of the detection signals of the two of the three detector units and the window signal on the basis of the detection signal of the other three detector units or to use the detection signal of the other three detector units as the window signal. This aspect also enables the respective detection signals to be better adapted, for example depending on whether they are used to determine the detector signal or to determine the window signal. For example, the two detector units can have the same sensitivity for the scanning signal and the response signal, respectively, which, however, differs from the sensitivity of the further detector unit. It can also be advantageous for the detection signal of the two detector units to be greater than that of the further detector unit. In the case of an optical detection, this can be realized by the area of the two detector units being larger than that of the further detector unit. The shape of the surface of the detector units can also be different, it also being preferred that the surface of the two detector units is of the same shape. For example, it is desirable to make the window signal as narrow as possible, which can be implemented in this embodiment by appropriately dimensioning the additional detector unit without narrowing the detector signal. However, it is also conceivable that the two detector units, on the basis of which the detector signal is determined, or the at least three detector units, differ in arrangement and dimensions.

In another advantageous embodiment of an aspect of the invention, the signal processing unit is designed to compare a difference signal of the two of the three detection signals with a first and a second threshold value in order to determine the detector signal as a linked comparator signal, the signal processing unit being further designed to further of the three detection signals to a third threshold to determine the window signal. By comparing a signal with a threshold value, the values of the signals, which often have a distribution, e.g. a normal distribution, of different values, can be sorted according to whether they fall below or exceed the respective threshold value. For example, a signal that can be described by a sine function can be converted into a square-wave function with two levels, e.g. 0 and 1. The signal can be converted into a digital signal, so to speak. In the case of calculating a difference between two detection signals and then comparing them with two threshold values, a three-level function can also be determined. In such a case, two of the levels can be equated. For example, a threshold T1 is less than a threshold T2. Then all values of the difference signal which are smaller than T1 are assigned a level 0, all values which are larger than T1 but smaller than T2 are assigned a level 1 and all values which are larger than T2 are also assigned a level 0 . As a result, a square-wave signal with two levels is also determined after a comparison of the difference signal of the two detection signals with a first and a second threshold value. This can then be used by the signal processing unit as a detector signal, i.e. as a linked comparator signal, and used together with the window signal to determine a position of a reference mark.

In a further advantageous embodiment of an aspect of the invention, the signal source, the detector units and the signal processing unit are arranged together in a measuring head. This has the advantage that the device according to the invention can be provided in one component.

In another advantageous embodiment of an aspect of the invention, the device has at least three additional detector units, which are offset relative to one another along a measurement direction and are arranged at a respective predetermined position relative to the signal source, with the additional detector units each being configured on the basis of one of the Reference mark to output an additional detection signal in response to the scanning signal outgoing response signal, wherein the additional detection signals are independent of each other. This can be an advantage, for example, if a position of more than one reference mark is to be determined. In this case, the device has at least three detector units in each case in order to determine the position of a reference mark in each case.

In another advantageous embodiment of an aspect of the invention, the device is part of a system that also has a measuring standard with at least one reference mark, the measuring standard and the device being designed such that the device is equipped with one of the three detector units or a further detector unit at one relative movement of the device and scale detects a periodic incremental signal. It is possible to determine the position of the reference mark of the material measure using the device according to the invention an absolute position determination of the device in relation to the material measure.

In an advantageous embodiment of an aspect of the invention relating to the proposed system, the further of the three detection signals is narrower than one period of the incremental signal. This can be achieved, for example, by suitably selecting the at least three detector units. For example, the dimension of the detector unit, on the basis of which the window signal is determined, can be chosen such that the associated detection signal of the detector unit is narrower than a period of the incremental signal. In addition, in particular independently of this, the detector units on the basis of which the detector signal is determined can be selected, e.g. with regard to their arrangement relative to one another or their dimensions. This achieves a certain adjustability of the three detection signals, in particular of the detection signal on the basis of which the window signal is determined. A detection signal on the basis of which the window signal is determined, the detection signal being narrower than one period of the incremental signal, leads to a position determination of the reference mark with an improved resolution, in particular the same resolution that can be achieved when measuring the incremental scale.

In a further advantageous embodiment of an aspect of the invention in relation to the proposed system, the material measure has a periodic grid or a periodic scale.

The periodic grating or the periodic scale advantageously allows high-resolution generation or use of incremental signals, with this periodic grating or the periodic scale itself not being used for the detection signal or the window signal.

In a further preferred variant of the above configuration of the system, the at least one reference mark is offset relative to the grid or the scale transversely to the measuring direction. This has the advantage that the detection of the grid or the scale can be spatially separated from the detection of the reference mark. This can be used, for example, to the extent that the detection structure for detecting the grid or the scale and that for detecting the reference mark can also be arranged spatially separate from one another.

If several reference marks are provided distributed in the measuring direction, which as such represent several reference positions, there is an advantage in that referencing does not have to be moved so far, so that an absolute position can be determined at shorter measuring distances, for example.

Within the scope of the present invention, several reference marks can also be detected one after the other. However, the reference marks themselves do not form a periodic grid in the sense of the increment determination.

It can also be provided that the multiple reference marks are designed to be distinguishable from one another, for example by additional markings in the vicinity of the respective reference mark or by properties of the reference marks themselves. However, it can also be provided that an intervention or data input from the outside a distinction between otherwise identically designed reference marks is achieved.

In another advantageous embodiment of an aspect of the invention in relation to the proposed system, a distance between the two of the three detector units whose detection signals are used to determine the detector signal corresponds in the measuring direction to a one to twofold extension of the reference mark in the measuring direction. This leads to a particularly suitable form of the detection signal.

In another advantageous embodiment of an aspect of the invention in relation to the proposed system, the detector unit, whose detection signal is used as a window signal or for determining the window signal, has a dimension in the measuring direction that corresponds to a half to one extension of the reference mark in the measuring direction. This leads to a particularly suitable form of the window signal. The position and width of the window signal can thus be determined not only by the threshold values but also by the dimensions and position of the detector unit, which outputs the detection signal, on the basis of which the window signal is determined, relative to the two detector units that output the detection signals, on the basis of which the detector signal is determined will be discontinued. This means that properties such as dimensions and/or arrangements of the at least three detector units of the device according to the invention can be optimally selected for the window signal and the detector signal.

Features of advantageous embodiments of the invention are defined in particular in the dependent claims, with further advantageous features, designs and configurations for the person skilled in the art also being inferred from the above explanation and the following discussion.

• 1 eine schematische Darstellung zur Illustration eines ersten Ausführungsbeispiels des erfindungsgemäßen Systems mit einer erfindungsgemäßen Vorrichtung und einer Maßverkörperung,
• 2 eine schematische Darstellung von drei beispielhaften Erfassungssignalen, die von drei Detektoreinheiten ausgegeben werden,
• 3 eine schematische Darstellung von einem beispielhaften Erfassungssignal und einem beispielhaften Differenzsignal, das von der Signalverarbeitungseinheit bestimmt wird,
• 4 eine schematische Darstellung eines beispielhaften Komparatorsignals, das von der Signalverarbeitungseinheit bestimmt wird,
• 5 eine schematische Darstellung einer beispielhaften Schaltungsanordnung einer Signalverarbeitungseinheit und Detektoreinheiten gemäß der erfindungsmäßen Vorrichtung,
• 6 eine schematische Darstellung zur Illustration eines weiteren Ausführungsbeispiels einer Maßverkörperung des erfindungsgemäßen Systems,
• 7 eine schematische Darstellung zur Illustration eines weiteren Ausführungsbeispiels der erfindungsgemäßen Vorrichtung,
• 8 eine schematische Darstellung zur Illustration eines weiteren Ausführungsbeispiels der erfindungsgemäßen Vorrichtung, und
• 9 ein schematisches Ablaufdiagramm eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens zur Positionsbestimmung einer Referenzmarke.

The present invention is further illustrated and explained below with reference to exemplary embodiments shown in the figures. Here shows

• 1 a schematic representation to illustrate a first exemplary embodiment of the system according to the invention with a device according to the invention and a material measure,
• 2 a schematic representation of three exemplary detection signals that are output by three detector units,
• 3 a schematic representation of an exemplary detection signal and an exemplary difference signal that is determined by the signal processing unit,
• 4 a schematic representation of an exemplary comparator signal that is determined by the signal processing unit,
• 5 a schematic representation of an exemplary circuit arrangement of a signal processing unit and detector units according to the device according to the invention,
• 6 a schematic representation to illustrate a further exemplary embodiment of a material measure of the system according to the invention,
• 7 a schematic representation to illustrate a further embodiment of the device according to the invention,
• 8th a schematic representation to illustrate a further embodiment of the device according to the invention, and
• 9 a schematic flowchart of an embodiment of the method according to the invention for determining the position of a reference mark.

In the accompanying drawings and the explanations of such drawings, where appropriate, corresponding or related elements are designated by corresponding or similar reference characters, even though they may be found in different embodiments.

1 shows a schematic representation to illustrate a first embodiment of the system according to the invention with a device 100 according to the invention and a material measure 200. In this embodiment, the device 100 according to the invention comprises a measuring head with a signal source 110, which is a light source in this embodiment, a detector arrangement 120 for detection a high-resolution incremental signal, three detector units 130, 140 and 150 offset in the measuring direction for detecting the reference mark 220 and a signal processing unit 160, which in this embodiment is designed as an analog-digital signal processing unit. The signal processing unit 160 can be integrated into the measuring head, as in 1 shown, but the measuring head can also be connected to an external signal processing unit 160, for example by cable. The signal source 110 is used to generate a scanning signal 300, which in this embodiment is shown as a light cone, but which can alternatively also be implemented, for example, as a bundle of rays. The scanning signal 300, ie the light cone here, is used to illuminate a measuring standard 200 that is movable in direction x, which corresponds to a measuring direction x, relative to the measuring head. The material measure 200 has an incremental scale 210, which is designed as a periodic grid, and a reference mark 220, which is applied to a separate track that is offset from the incremental scale 210 in direction y, which runs transversely to the measuring direction x.

The sample signal 300 emitted by the signal source 110 is reflected off the incremental scale 210 in this embodiment. The reflected signal reaches the detector arrangement 120, which periodically generates incremental signals when the scale 200 and thus the incremental scale 210 move relative to the measuring head. The mapping and generation of the incremental signals are, for example, in the application DE 10 2018 108 347 A1 described and not the subject of this invention. In addition to this, the device according to the invention and the method can also be used in combination with all types of position measuring devices for detecting incremental relative movements of a scale.

The light reflected from the reference mark 220 is detected by three detector units 130, 140, 150 at different intensities. When the scale 200 moves in the measuring direction x, the reference mark 220 moves over the center positions of the three detector units 130, 140, 150 in the x direction one after the other. The strength of the respective detection signal is greatest when the reference mark 220 is exactly at the respective position x _j of the respective detector unit 130, 140, 150. In this embodiment, each detector unit 130, 140, 150 is connected to a respective current-voltage converter 611, 612, 613, which is 5 are shown. The current-to-voltage converters 611, 612, 613 can be transimpedance amplifiers, operational amplifiers or other suitable electronic components or circuits. However, it is also conceivable that the detection signals are output directly and without conversion and from the subsequent circuit components are further processed. With a continuous, uniform movement of the material measure 200 in the measuring direction x, three detection signals that are offset in the measuring direction x are generated 2 are shown.

2 shows a schematic representation of three exemplary detection signals A, B, C, which are output by three detector units, eg the detector units 130,140,150. The horizontal axis in 2 (and also in the 3 and 4 ) indicates the direction x, ie the measurement direction x, the vertical axis indicates the strength U of the detection signal. The detection signal A can be the signal generated by the detector unit 130 , the detection signal B can be the signal generated by the detector unit 140 , and the detection signal C can be the signal generated by the detector unit 150 . Alternatively, the detection signals A, B and C are the voltage signals converted by the current-voltage converters 611, 612 and 613. Each of the three detection signals A, B and C is wider than one period of an incremental signal in the measuring direction x.

3 FIG. 12 shows a schematic representation of an example detection signal and an example difference signal that is determined by a signal processing unit. The detection signal B is shown in the upper part of the graph, with a difference signal D being shown in the lower part, which is determined, for example, by the signal processing unit 160, ie by an analog/digital signal processing unit. The difference signal D can be calculated by calculating the difference of the detection signals A and C, eg with the formula D = A - C.

If the signal processing unit is designed as an analog-digital signal processing unit, as is shown in 5 is shown, the difference signal D can be formed by a circuit element 620 . The circuit element 620 can be a differential amplifier, for example. Furthermore, the analog-digital signal processing unit 5 a comparator 631 in which the difference signal D is compared to a first threshold value T1, and a further comparator 633 in which the difference signal D is compared to a second threshold value T2, each of the comparators 631, 633 producing square-wave output signals dependent on the comparison provides. The square-wave output signals of the comparators 631, 633 are combined in a first logic stage 641, which performs a logical AND operation and outputs a combined comparator signal 410, which is in 4 is shown.

The threshold values T1, T2 of the comparators 631, 633 determine the position of the linked comparator signal 410 in the measuring direction x and thus also the position in relation to the incremental periodic signal. The threshold values T1, T2 can be set during operation or they can be preset. Furthermore, the width of the mean rectangular pulse in the linked comparator signal 410 in the measuring direction x is set by the threshold values T1, T2 and thus the exact positional relationship to a defined period of the incremental periodic signal.

It becomes clear that a steep, straight edge in the difference signal D is a prerequisite for sufficient adjustability of the linked comparator signal 410 by means of the threshold values T1, T2. The signal form of the difference signal D is mainly determined by the width and the overlap of the signals A and C, which in turn are determined by the extension and the distance between the associated detector units, in this example the detector units 130 and 150, in the measuring direction x and by the width of the reference mark 220 in the measuring direction x. If the signals A and C are too narrow, for example, or the overlap is too small, then the difference signal D has a saddle point. If the signals A and C are too wide or the overlap is too large, the difference signal D also has a saddle point or the edge steepness is not sufficient.

Exemplary embodiments with particularly advantageous ratios of the dimensions of the detectors to the reference mark are explained further below.

4 FIG. 4 shows a schematic representation of an exemplary comparator signal 410 that is determined by the signal processing unit. In order to generate a reference pulse 410.1 from the linked comparator signal 410, the linked comparator signal 410 is windowed so that the mean rectangular pulse can be filtered out of the linked comparator signal 410. For this purpose, the signal B is compared in a third comparator 632 with a third threshold value T3. The third comparator 632 generates the window signal 420. The signals 410 and 420 are applied to a second logic stage 642. The reference pulse 410.1 is generated by a logical AND operation.

Based on 3 and 4 it becomes clear that the signal level as well as the width and position in the measurement direction x of the signal B are decisive for the position and width of the window signal 420 in relation to the linked comparator signal 410. The signal B is decisive for the size of the associated detector unit, in the example above of the detector unit 140, in the measuring direction x in relation to the size of the reference mark 220 is determined. If the signal B is too wide, more than the middle rectangular pulse is windowed, as a result of which the reference pulse 410.1 would not be unambiguous. If signal B is too narrow, reference pulse 410.1 is artificially reduced or cut off. The position of the signal B and thus of the window signal 420 in the measurement direction x is also decisive for correct windowing.

In summary, the device according to the invention is characterized in that the signal B is generated by a third detector unit, e.g. the detector unit 140, so that the position and width in the measuring direction x is independent of the signals A and C, which are generated e.g. by the detector units 130 and 150 are generated and which result in the difference signal D, as a result of which the window signal is not coupled to the signal to be windowed.

5 shows a schematic representation of an exemplary circuit arrangement of a signal processing unit and detector units according to the device according to the invention, wherein 5 has already been described in connection with the embodiment described above. In this circuit arrangement, the detector units 130, 140, 150 are implemented as photodiodes, which detect a light signal 301 as the scanning signal.

In the embodiment in FIG 1 the signal source 110 and the detector units 130, 140, 150 are arranged on the same side relative to the material measure 200. In this case, the detection is based on a reflection of the scanning signal on the material measure, in particular the incremental scale 210 and the reference mark 220. However, the invention is not limited to reflective measurements. For example, from the document U.S. 2016/0231144 A1 Devices are known in which the light transmitted through the material measure is detected. An exemplary embodiment of the device according to the invention, which is based on transmission, can be characterized in that the detector units for detecting the reference mark and optionally also the detector units for detecting the incremental scale are arranged on the opposite side of the measuring scale from the signal source and detect a transmitted signal.

Furthermore, the in 1 invention shown is not limited to reflective reference marks. The reference mark can be designed to be reflective on an absorbent background or absorbent on a reflective background. For the arrangement in transmission, the reference mark can be designed to be transmissive on a reflective or absorbent background, or alternatively reflective or absorbent on a transmissive background. The detection signals of the detector units, eg signals A, B and C, are inverted in the case of a shadowing or absorbing reference mark, which changes the sign of the threshold values, eg threshold values T1, T2 and T3, in the windowing process.

The invention (method and device) can also be applied to position measuring devices in which the reference mark is not arranged on a separate track, as is shown in 1 is shown, but in which the reference mark is embedded in the incremental track, such as from EP 1 766 334 B1 , 9 known.

In addition, the method according to the invention can be applied to the devices mentioned at the outset, in which so-called chirped reference marks are detected. In this case, a sum signal is not generated and instead, as described, a difference signal and a window signal independent thereof are generated according to the invention.

A further embodiment in which light is used as the scanning signal is characterized in that imaging optics or collimating optics can be used to image the light onto the detectors.

Furthermore, the invention is not limited to light sources that generate a light cone or a divergent bundle of rays. Further conceivable designs are characterized in that different light sources are optionally used to act on the reference mark and the incremental scale, one or more elements are used to split the light into at least two partial beams, collimation optics are used to collimate the light, a light source with a highly collimated emission characteristic, in particular a VECSEL or a laser, is used and/or, as is the case, for example, in DE 10 2018 108 347 A1 is described, light guides are used to guide the light.

Furthermore, as mentioned above, the invention is not limited to optical position measuring devices. The invention or at least the method according to the invention can be applied in particular to magnetic or inductive position measuring devices in which magnetic or electric detectors are used in order to detect electric or magnetic signals instead of light signals.

In particular, the invention is not limited to a single reference position. example wise there are material measures with several distance-coded reference marks in the measuring direction x. Each reference mark is detected one after the other, as described above for an individual reference mark.

Furthermore, a system according to the invention is not limited to the number of one reference track on the scale. For example, it can be advantageous to use material measures with two reference tracks, as shown in 6 is shown.

6 shows a schematic representation to illustrate a further exemplary embodiment of a material measure of the system according to the invention. 6 is a top view, so to speak from direction z, of an embodiment of a material measure 200 of an advantageous embodiment of the system according to the invention with two reference tracks, which are arranged left and right next to the incremental scale 210 in this view, and each have a reference mark 221,222.

In addition, the arrangement and/or dimensions of the detector units are not limited to the arrangement as indicated in connection with the embodiment 1 is shown, limited.

7 shows a schematic representation to illustrate a further embodiment of the device according to the invention. The selection of different dimensions and distances between the at least three detector units 130, 140, 150 can be particularly advantageous. It shows 7 , so to speak from direction z, the top view of an advantageous embodiment of the device 100 according to the invention in the form of a measuring head, which comprises a signal source 110, three detector units 130, 140, 150 and a detector arrangement 120. The device in 7 is characterized in that the dimension of the detector unit 140, which can be used, for example, to generate the signal B, differs from the dimension of the detector units 130, 150. Furthermore, it can be advantageous if the detector unit 140 is offset in the measuring direction or transversely to the measuring direction in relation to the two other detector units 130, 150. As a result, the signal level and signal width, for example of signal B, differs from the signal levels and signal widths, for example of signals A and C. The detector units, for example detector unit 140, can also be offset in the measuring direction x.

Without restricting generality, the detector units 130, 140, 150 can also be designed as detector groups, which consist of a number of detector elements or in which a number of detectors are connected in series to form a group in each case.

For example shows 8th a schematic representation to illustrate a further embodiment of the device according to the invention, wherein 8th represents a plan view of the device from direction z. The device 100 off 8th can, for example, be used to determine the position of the reference marks 221, 222 of the material measure 200 in 7 be applied. In addition to a signal source 110 and two detector arrangements 121, 122, the device comprises a first detector group with at least two detector units 131, 132, a second detector group with at least two detector units 141, 142 and a third detector group with at least two detector units 151, 152 for detecting two reference tracks. The detector arrays 121, 122 for detecting the incremental signal can also be designed as detector groups, with an embodiment with only one of the detector arrays 121 or 122 being conceivable.

A further particularly advantageous embodiment results from a suitable selection of the width and the spacing of the detector units in the measuring direction x. The overlap of the detection signals A and C and thus the signal form D is determined by the arrangement and dimensions of the detector units that output the detection signals A and C in relation to the width of the reference mark in the measuring direction x. If the arrangement and dimensions of the detector units are selected appropriately, the signal form shown there has the steepest possible edge. A distance between the detector units, which emit the detection signals A and C, in the measuring direction x, which corresponds to one to twice the extent of the reference mark in the measuring direction x, is particularly advantageous. A particular advantage is a respective width of the detector units, which output the detection signals A and C, in the measuring direction x, which corresponds to half to one time the extension of the reference mark in the measuring direction x. The detector units are preferably diodes, in particular photodiodes, which are sensitive to the scanning signal of the signal source.

The detection signals A and C are the signals on the basis of which the detector signal is determined.

9 shows a schematic flowchart of an embodiment of the method according to the invention for determining the position of a reference mark. The method according to the invention is characterized in that, in order to generate a window signal, a third signal, independent of the two detection signals A and C with regard to signal level, shape and position in the measuring direction x pending, detection signal B is used. In a first step S1 of the method, a signal source of a device, for example the device 100, transmits a scanning signal for position determination, which in a step S2 interacts with a reference mark, so that a response signal is present. The response signal is detected in a step S3 by at least three detector units, e.g. eg the signal processing unit 160 to output. In a step S4, the signal processing unit then determines a detector signal based on two of the three detection signals and a window signal based on the other of the three detection signals or uses the other of the three detection signals as a window signal and determines a position of the reference mark on the basis of the detector signal in a step S5 and the window signal.

Even if different aspects or features of the invention are shown in combination in the figures, it is obvious to the person skilled in the art--unless stated otherwise--that the combinations shown and discussed are not the only possible ones. In particular, mutually corresponding units or complexes of features from different exemplary embodiments can be exchanged with one another.

The present invention relates to a device and a method for determining a position by detecting at least one reference mark of a material measure. In order to present a solution that reduces the sensitivity of the detection to signal interference, it is proposed to carry out the position determination based on a detector signal and a window signal, which are based on at least three detection signals, with the detector signal being based on two of the detection signals and the detection signals based on another one the window signal is determined. As a result, the window signal can be determined independently of the detector signal, which leads to better resolution of the position determination.

Reference List

100

contraption

110

signal source

120, 121, 122

detector array

130, 131, 132, 140, 141, 142, 150, 151, 152

detector unit

160

signal processing unit

200

material measure

210

incremental scale

220, 221, 222

reference mark

300

scanning signal

301

light signal

410

linked comparator signal

410.1

reference pulse

420

window signal

611, 612, 613

current-voltage converter

620

circuit element

631, 632, 633

comparator

641

first link level

642

second link level

A, B, C

detection signal

T1, T2, T3

threshold

Claims (16)

Device (100) for position determination by detecting at least one reference mark (220, 221, 222) of a material measure (200), the device (100) having: at least one signal source (110), which is designed to emit a scanning signal (300), at least three detector units (130,140,150) which are offset relative to one another along a measurement direction and are arranged at a respective predetermined position relative to the signal source (110), the detector units (130,140,150) each being configured on the basis of a response from the reference mark (220,221,222). outputting a detection signal (A,B,C) based on the response signal emanating from the scanning signal (300), the detection signals (A,B,C) being independent of one another, and a signal processing unit (160) which is designed to determine a detector signal on the basis of two of the three detection signals (A,B,C) and to determine a window signal (420) on the basis of the other three detection signals (A,B,C) or to use the other of the three detection signals (A, B, C) as a window signal (420), the signal processing unit (160) also being designed to determine the position of the reference mark (220, 221, 222) on the basis of the detector signal and the window signal (420). . Device (100) according to claim 1 , wherein the signal source (110) is designed to emit an electromagnetic scanning signal, in particular an optical scanning signal, to emit an electrical scanning signal and/or to emit a magnetic scanning signal, and the detector units (130, 140, 150) are designed to detect a corresponding response signal. Device (100) according to any one of the preceding claims, wherein the signal source (110) and the detector units (130,140,150) are arranged relative to one another for an emanation of the response signal from the reference mark (220,221,222) on the basis of the scanning signal by transmission or reflection. Device (100) according to one of the preceding claims, wherein two of the three detector units (130,140,150) are arranged on a line extending in the measuring direction, the other of the three detector units (130,140,150) being arranged offset with respect to the line. Device (100) according to one of the preceding claims, wherein two of the three detector units (130,140,150) are of identical design and differ from the other of the three detector units (130,140,150), in particular with regard to their dimensions. Device (100) according to claim 4 or 5 , wherein the signal processing unit (160) is designed to determine the detector signal on the basis of the detection signals of the two of the three detector units (130,140,150) and the window signal (420) on the basis of the detection signal of the other three detector units (130,140,150) or to determine the detection signal of the further of the three detector units as the window signal (420). Device (100) according to one of the preceding claims, wherein the signal processing unit (160) is designed to compare a difference signal of the two of the three detection signals (A, B, C) with a first and a second threshold value (T1, T2) in order to to determine the detector signal as a linked comparator signal (410), the signal processing unit (160) being further configured to compare the other of the three detection signals (A, B, C) with a third threshold value (T3) in order to close the window signal (420). determine. Device (100) according to one of the preceding claims, wherein the signal source (110), the detector units (130, 140, 150) and the signal processing unit (160) are arranged together in a measuring head. Device (100) according to any one of the preceding claims, with at least three additional detector units which are offset relative to one another along a measurement direction and are arranged at a respective predetermined position relative to the signal source (110), the additional detector units each being configured on the basis of a signal read from the reference mark (220,221,222) in response to the scanning signal ( 300) to output an additional detection signal on top of the outgoing response signal, the additional detection signals being independent of one another. System with a device (100) according to one of the preceding claims and a measuring standard (200) with at least one reference mark (220, 221, 222), wherein the measuring standard (200) and the device (100) are designed so that the device (100) with a the three detector units (130,140,150) or a further detector unit (131,132,141,142,151,152) detects a periodic incremental signal during a relative movement of the device (100) and measuring standard (200). system after claim 10 , where the other of the three detection signals is narrower than a period of the incremental signal. system according to one of the Claims 10 or 11 , wherein the material measure (200) has a periodic grid or a periodic scale. system after claim 12 , wherein the at least one reference mark (220,221,222) is offset relative to the grid or the scale transversely to the measuring direction. system according to one of the Claims 10 until 13 , a distance between the two of the three detector units (130,140,150), whose detection signals (A,B,C) are used to determine the detector signal, in the measuring direction corresponding to a one to twofold extension of the reference mark (220,221,222) in the measuring direction. system according to one of the Claims 10 until 14 , wherein the detector unit, the detection signal of which is used as a window signal (420) or for determining the window signal (420), has a dimension in the measuring direction that corresponds to half to one extension of the reference mark (220,221,222) in the measuring direction. Method for determining the position by detecting at least one reference mark (220, 221, 222) of a material measure (200), the method comprising the steps: transmission of a scanning signal (300) by a signal source (110) of a device (100) for determining the position, interaction of the scanning signal (300) with the reference mark (220,221,222) so that a response signal is present, detecting the response signal by at least three detector units (130,140,150) which are offset relative to one another along a measurement direction and are arranged at a respective predetermined position relative to the signal source (110) in order to detect a respective detection signal (A,B,C) to a signal processing unit (160), determining, by the signal processing unit (160), a detector signal based on two of the three detection signals (A,B,C) and a window signal (420) based on the further of three detection signals (A,B,C) or use of the other three detection signals signals (A,B,C) as the window signal (420), and determining the position of the reference mark (220,221,222) based on the detector signal and the window signal (420).

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