Absolute position encoder for a measuring instrument

Abstract

The present invention relates to an absolute position encoder (10) for a measuring instrument, the absolute position encoder comprising a digital scale (20) and a reader (50) movable relative to the digital scale. The digital scale 20 is arranged along the travel direction of the reader 50. The digital scale includes at least one absolute position track (30; 30a, 30b) having a sequence of discrete regions (32; 32a, 32b) clearly separated from each other by separation regions (33; 33a, 33b). The reader (50) includes a first series of detectors (70a-77a) and a second series of detectors (70b-77b) configured to sense the discrete regions (32; 32a, 32b) and the separation regions (33; 33a, 33b) to detect at least one of a first absolute position code and a second absolute position code. The sequence of discrete regions (32; 32a, 32b) and the first series of detectors (70a-77a) and the second series of detectors (70b-77b) are configured such that at each possible position of the reader (50) relative to the digital scale (20), at least one of the first series of detectors and the second series of detectors is not aligned with the transition portion between the discrete regions (32; 32a, 32b) and the separated regions (33; 33a, 33b). The position encoder (10) is configured to select either a first absolute position code or a second absolute position code read by the series of detectors that are not aligned with the transition portion.

Description

Technical Field

[0001] This invention relates to an absolute position encoder for digital measuring instruments and their accessories, particularly for: handheld measuring instruments, such as digital sliding calipers, digital micrometers, and comparators; portable measuring instruments, such as height gauges, measuring probe systems, and geodetic systems; and fixed measuring instruments and their accessories, such as coordinate measuring machines, rotary tables, rotary axes, articulated probe heads, and measuring probes. The measuring instrument may be connected to a measuring device, inspection system, or machine tool, or may be part of such a device, system, or machine tool. Background Technology

[0002] An encoder, which provides the relative position between two elements, is a key component of digital measuring instruments.

[0003] For example, encoders that rely on digital scales with periodic marks spaced at constant pitch are known and disclosed in EP2378252 and EP0872712 to provide the relative position between the reader and the scale. These encoders include readers with sensing elements spaced apart from each other along the measurement path from a portion of the mark pitch to provide sub-pitch measurement accuracy.

[0004] However, a major drawback of these encoders stems from the fact that the maximum defined displacement range (i.e., the segment from which a defined, unique position can be provided) is limited by the pitch between two adjacent marks. This limitation is typically overcome by combining additional tracks with different pitches and / or by considering the number of pitches the reader has already exceeded when moving along the scale from the origin (e.g., zero position). The setting of the zero position and pitch counter (e.g., when the encoder is powered) typically requires the reader's displacement at the origin of the scale.

[0005] Absolute position encoders configured to provide a defined position that always follows the displacement range of the reader are also known. For example, US3820110 describes an absolute position encoder that relies on a scale with tracks having markings arranged on adjacent tracks from which a unique digital code can be read indicating the discrete absolute position of the reader relative to the scale. However, the accuracy of this encoder is strictly related to the size of the markings on the scale and the alignment of the markings on the scale.

[0006] Complementing these methods, CN201225865Y, US5'886'519, US5'939'879, and EP1102040 describe implementations that rely on an absolute position converter that combines coarse absolute and fine relative positions. This converter is configured to sense a unique code used to provide the coarse absolute position of the reader, while the relative fine position is provided by sensing one or more periodic tracks on a scale. In one embodiment of EP1102040, the absolute position converter relies on sensors that couple sensing markers on a first and second track to read the absolute code. These tracks contain the same unique digital code. The markers on the second track provide inverted digits of the numbers provided by the first track to increase read robustness. Summary of the Invention

[0007] The purpose of this invention is to provide an absolute position encoder for applications requiring high precision, such as dimensional measurement.

[0008] Another objective is to provide an absolute position encoder that is more sensitive to inaccurate mark sensing caused by poor positioning of the reader relative to the scale.

[0009] According to the invention, these objectives are achieved by an absolute position encoder for a measuring instrument or an accessory for a measuring instrument, the absolute position encoder comprising a digital scale and a reader movable relative to the digital scale. The digital scale is arranged along the travel direction of the reader. The digital scale includes at least one absolute position track having a sequence of discrete regions (also referred to herein as marks or markings) that are distinctly separated from each other by separation regions, the discrete regions being detectable by detectors. The reader includes a first series of detectors and a second series of detectors configured to sense the discrete regions to detect at least one of a first absolute position code and a second absolute position code, each absolute code representing the absolute position of the reader relative to the digital scale (i.e., always unique and non-repeatable along the digital scale). The sequence of discrete regions and the first and second series of detectors are arranged such that at each possible position of the reader relative to the digital scale, none of the first and second series of detectors is aligned with the transition portion between the discrete region and the separation region. The position encoder is configured to select either a first absolute position code or a second absolute position code to be read by the series of detectors that are not aligned with the transition section. According to the invention, the code can be any information represented in (electrical) analog or digital format (e.g., in the form of one or more analog or digital signals or digital symbols or values).

[0010] In an implementation, selecting the first absolute code or the second absolute code includes testing whether the first absolute position code and the second absolute position code read by the corresponding first series detectors and second series detectors are consistent with the common assumed position of the reader.

[0011] In one embodiment, the digital scale further includes an additional track adjacent to and extending along the at least one absolute position track, which can be detected by a reader. Specifically, the additional track is provided with markings detectable by the reader's detector. The absolute position encoder is configured to select an absolute position code based on a code derived from the additional track. In such an embodiment, the resulting code can advantageously represent spatial or physical information or relationship between the additional track and the at least one absolute position track.

[0012] In this implementation, the additional track is a periodically coded track (also referred to as the incremental track in this document) that provides incremental position codes, which represent the periodic (or cyclic) position of the reader relative to the digital scale. The absolute position encoder is configured to:

[0013] The first absolute position code or the second absolute position code is selected based on the incremental position code (e.g., based on a periodic position associated with the incremental position code), particularly based on the phase of the interpolated incremental position code; and

[0014] A precise absolute position code is provided, comprising the most significant part derived from a selected first or second absolute position code and the least significant part derived from the incremental position code (e.g., from a periodic position associated with the incremental position code), particularly from the interpolated phase. Advantageously, the periodic encoding track is provided with markers regularly spaced (e.g., at a constant pitch) along a digital scale, which can be detected by the reader's detector.

[0015] In one implementation, the first series of detectors and the second series of detectors are arranged at equal intervals along the direction of travel of the reader.

[0016] In one implementation, the digital scale of the absolute position encoder includes a first absolute position track and a second absolute position track. The first absolute position track has a first sequence of discrete regions and separation regions between said discrete regions, and the second absolute position track has a second sequence of discrete regions and separation regions between said discrete regions. The second sequence is a copy of the first sequence shifted along the reader's travel direction, such that the discrete regions of the first absolute position track are offset by a constant pitch relative to the corresponding discrete regions of the second absolute position track. Each detector in the first series of detectors is laterally aligned with a corresponding detector in the second series of detectors relative to the reader's travel direction. The first series of detectors is arranged to move along the first absolute position track, while the second series of detectors is arranged to move along the second absolute position track.

[0017] In one implementation, the digital scale of the absolute position encoder includes a unique absolute position track comprising discrete regions and separation regions between the discrete regions. A first series of detectors and a second series of detectors are respectively positioned along a first row and a second row to detect at least one of the first absolute position code and the second absolute position code, the first row and the second row extending along the travel direction of the reader.

[0018] In one implementation, each detector in the first series of detectors is offset by a constant pitch relative to the corresponding detector in the second series of detectors along the travel direction of the reader.

[0019] In one implementation, the detectors in the first series of detectors are interleaved with those in the second series of detectors to form adjacent detector pairs of the corresponding first and second series of detectors.

[0020] In this implementation, the absolute position encoder is configured as a linear position encoder or an angular position encoder.

[0021] In an implementation, the discrete region of at least one absolute position track differs from the separated region in that it possesses one of the following properties: optical opacity, optical reflectivity, electrical conductivity, magnetization, and magnetic permeability.

[0022] Another aspect of the invention relates to a measuring instrument or an accessory for a measuring instrument, said measuring instrument or accessory comprising an absolute position encoder. The measuring instrument may be a (digital) handheld measuring instrument, such as a (digital) sliding caliper, a (digital) micrometer, or a (digital) comparator. The measuring instrument may be a (digital) portable measuring instrument, such as a height gauge, a measuring probe system, an articulated measuring device, or a geodetic system. The measuring system may be a (digital) fixed measuring instrument, such as a coordinate measuring machine or system. The accessory for the measuring instrument may specifically be a rotary table, a rotary axis, an articulated probe head, or a survey pole.

[0023] In one embodiment, the measuring instrument is configured as a sliding caliper comprising a first jaw fixed relative to a digital scale of an encoder and a second jaw slidable relative to the first jaw and fixed relative to a reader of the encoder. An absolute position encoder provides a value indicating the distance between the first and second jaws.

[0024] In one embodiment, the measuring instrument is configured (in particular, the measuring instrument includes an accessory configured as a survey pole) comprising an absolute position encoder, a first segment fixed relative to the encoder's digital scale, and a second segment slidable relative to the first segment and fixed relative to the encoder's reader. The absolute position encoder provides a value indicating the height of the survey pole.

[0025] Another aspect of the invention relates to a method for determining the position of a reader relative to a digital scale along a direction of travel. The digital scale includes at least one absolute position track comprising a pattern consisting of discrete regions and separation regions between the discrete regions, the pattern being detectable by a plurality of detectors in the reader. The detectors are arranged along a first row and a second row aligned with the direction of travel of the reader. The method includes determining a first absolute position code from detectors in the first row and a second absolute position code from detectors in the second row. The discrete regions and the plurality of detectors are arranged such that at each possible position of the reader relative to the digital scale, at least one of the first and second rows has no detector aligned with a transition portion between the discrete and separation regions. The method further includes selecting an absolute position code provided by a row in which no detector is aligned with the transition portion.

[0026] In this implementation, selecting the absolute position code includes testing whether the first absolute code and the second absolute code are consistent with the reader's common assumed position.

[0027] In one implementation, the test includes: treating the position given by the first absolute position code as a hypothetical position; using the hypothetical position to determine which detectors in the second row are not facing the transition portion of the digital scale; determining an expected value for a bit of the second absolute position code given the hypothetical position; and comparing the expected value with the value of the corresponding bit of the second absolute position code that can be derived from detectors not facing the transition portion.

[0028] In one implementation, the method includes: determining an incremental position code from a periodic encoded track on a digital scale; interpolating the phase value of the incremental position code; using the interpolated phase to select an absolute position code; and providing a precise absolute position code that includes the highest valid portion derived from the selected absolute position code and the lowest valid portion derived from the interpolated phase. Attached Figure Description

[0029] Exemplary embodiments of the present invention are disclosed in the specification and illustrated in the accompanying drawings, wherein:

[0030] - Figure 1 This is a schematic diagram of an absolute position encoder according to an embodiment;

[0031] - Figure 2 and Figure 3 They are Figure 1 A schematic diagram of the reader and digital scale of an absolute position encoder;

[0032] - Figure 4 Schematic illustration of the use of Figure 3 The generation of a sinusoidal signal to determine the fine position within the scale division of a digital scale;

[0033] - Figure 5 Schematic illustration of via Figure 1 The selection between the first absolute position code and the second absolute position code of the absolute position encoder;

[0034] - Figures 6a to 6d This schematically illustrates the movement of the reader along... Figure 1 The sensing sequence of the first and second absolute position tracks at different positions of the digital scale of the absolute position encoder;

[0035] - Figure 7 This is a schematic diagram of a digital scale of an absolute position encoder according to another embodiment;

[0036] - Figure 8 and Figure 9 These are schematic diagrams of a reader and a digital scale for an absolute position encoder according to another embodiment;

[0037] - Figure 10 and Figure 11 These are schematic diagrams of a reader and a digital scale for an absolute position encoder according to another embodiment;

[0038] - Figure 12 This is a schematic diagram of an angular absolute position encoder according to another embodiment;

[0039] - Figure 13 This is a block diagram of a method for providing a reliable absolute position of a reader relative to the track of an absolute position encoder according to any of the above embodiments;

[0040] - Figure 14 This is a schematic diagram of an absolute position encoder according to another embodiment;

[0041] - Figure 15 This is a schematic diagram of the detector and digital scale of a reader for an absolute position encoder according to another embodiment;

[0042] - Figure 16 This is a schematic diagram of the detector and digital scale of a reader for an absolute position encoder according to another embodiment;

[0043] - Figure 17 It is a block diagram of a method for providing a reliable absolute position of a reader relative to the digital scale of an absolute encoder;

[0044] - Figure 18 A sliding caliper including an absolute position encoder according to the present invention is shown; and

[0045] - Figure 19 and Figure 20 Other exemplary uses of absolute position encoders are shown, particularly for geodesy or surveying. Detailed Implementation

[0046] Figures 1 to 3 An absolute position encoder 10 for measuring instruments (particularly for dimensional measuring instruments) or their accessories is shown. The absolute position encoder 10 has a linear accuracy greater than (i.e., an inaccuracy less than) 50 μm, preferably greater than 10 μm. The absolute position encoder 10 includes a digital scale 20 and a reader 50, which is movable relative to the digital scale 20 along a measurement path 2. The reader 50 is configured to sense a first absolute position track 30a and a second absolute position track 30b by reading a first absolute position code and a second absolute position code to provide the absolute position of the reader 50 relative to the digital scale 20 along the measurement path 2.

[0047] The digital scale 20 also includes an incremental track 40 for providing the position of the reader 50 along a first absolute position track 30a within the scale divisions 34, 35, and 36, which extend along the measurement path. Typically, the dimensions of each scale division 34, 35, and 36 are determined along the measurement path to correspond to a maximum displacement range (e.g., pitch P) within which the incremental track 40 can provide an unambiguous position 38, such as... Figure 5 As shown.

[0048] The scale divisions 34, 35, and 36 can be positioned along the measurement path, such that one side 37a of each division corresponds to one side 37b of the adjacent division. Figure 3 As shown. In variations not illustrated, each scale division may be spaced apart from each other along the measurement path, with free space between adjacent divisions. Preferably, each scale division 34, 35, 36 extends the same spatial extension T along the measurement path. The spatial extension T may be, in particular, as shown... Figure 1 The linear spatial extension portion shown in the embodiment of Figure 6, or the curved or angular spatial extension portion according to the variation.

[0049] The incremental track 40 includes a plurality of periodic markers 42, 44, 46 spaced apart from each other along the measurement path to provide a precise position 38 (also referred to herein as a periodic position) within each of these scale divisions 34, 35, 36. Specifically, the periodic markers 42, 44, 46 may be regularly spaced apart from each other along the measurement path by a pitch P. The pitch P substantially corresponds to a spatial extension T, a multiple of the spatial extension T, or a portion of the spatial extension T of the scale division of the first absolute position track 30a. The pitch P may be, in particular, linear, arcuate, or angular. However, according to variations, the periodic markers may be spaced apart from each other by irregular pitches along the measurement path. The irregular pitch may depend, for example, on the position of the periodic markers along the measurement path, such as an increasing, decreasing, logarithmic, exponential, or polynomial pitch, or a combination thereof.

[0050] The scale graduations can also extend along the measurement path into an irregular spatial extension T, which can be a function of, for example, the pitch and / or position of the scale graduations along the measurement path, such as an increasing, decreasing, logarithmic, exponential, or polynomial spatial extension, or a combination thereof. The pitch P and the spatial extension T are advantageously shaped according to the (local) shape of the measurement path.

[0051] The reader 50 includes an incremental sensing unit 80 with multiple detectors 90-97. Each detector is configured to sense periodic markers 42, 44, 46 of the incremental track 40 to derive an incremental position code. Figure 1 In the embodiment shown in Figure 6, the detector of the incremental sensing unit 80 is phase-shifted by a portion of the pitch P along the measurement path in order to generate a signal with a phase shift corresponding to the phase shifted by the pitch P. Figure 4 The periodic sinusoidal signal (u) of the pitch P shown is... cos ,u sin The relationship between these sinusoidal signals (usually based on tan ). -1 or arctan -1 The unique relative position 38 can be provided within the pitch P (and then within the corresponding scale divisions 34, 35, 36), as is known in the art.

[0052] Advantageously, the reader 50 and the digital scale 20 can be configured such that the edges 37a, 37b of each scale division 34, 35, 36 are zero-crossed with one of such phase-shifted sinusoidal signals (see [link]). Figure 4 ).

[0053] As shown in the figure, detectors 90-97 are advantageously grouped into four pairs of sensing elements to reduce uncorrelated sensing errors while compensating for common sensing errors. These groups are phase-shifted by P / 4 to each other. This results in four sinusoidal signals (u cos (+) ,u cos (-) ,u sin (+) ,u sin (-) The sinusoidal signals are phase-shifted by each other P / 4, P / 2, and 3P / 4 (typically represented as 90°-, 180°-, and 270°- phase-shifted signals). The relationship between the sensed values ​​of these sinusoidal signals (i.e., incremental position codes) determines the relative position 38 within the pitch P (and then within the corresponding scale divisions 34, 35, and 36). The reader can be configured to correct the relative position, for example, by applying linear and polynomial corrections to the (incremental) track.

[0054] Each of the first absolute position track 30a and the second absolute position track 30b includes discrete regions 32a, 32b and separated regions 33a, 33b defining a region extending between the two discrete regions. These combinations of discrete and separated regions, which may vary depending on the different embodiments described later, are referred to hereinafter as absolute markers. These regions are associated with the incremental track 40 to provide a coarse absolute position of the encoder's current position, i.e., uniquely identifying or determining which scale division 34, 35, 36 of the first absolute position track 30a the reader 50 is currently positioned on. The first absolute position track 30a and the second absolute position track 30b of the digital scale 20 can be sensed by the reader 50's first absolute sensing unit 60a equipped with sensing elements 70a-77a and the second absolute sensing unit 60b equipped with sensing elements 70b-77b. Therefore, the encoder 10 can determine the precise relative position 38 provided by sensing the incremental track 40. Figure 4 The sensed scale divisions 34, 35, 36 (the absolute reference associated with the sensed scale divisions 34, 35, 36) (i.e., the first absolute position) provide the reader's absolute position 39 relative to the scale. Figures 6a to 6b Advantageously, the absolute position 39 can be provided by adding the precise relative position 38 to the absolute reference associated with the sensed scale divisions 34, 35, 36 in the first absolute position track 30a (or subtracting the precise relative position 38 from the absolute reference associated with the sensed scale divisions 34, 35, 36 in the first absolute position track 30a), i.e., the first absolute position preferably corresponds to one of the opposite sides 37a, 37b of the scale divisions 34-36.

[0055] The determination of the power of each scale division 34 to 36 depends on the arrangement of absolute marks on the first absolute track 30a, so that the reader 50 can sense the first plurality of unique identifiers (A) along the measurement path. 50 A 51 Each unique identifier is different and depends on the positional relationship between the reader and the digital ruler along the measurement path.

[0056] Unique identifiers can be provided within a first plurality of unique identifiers along the measurement path, i.e., each unique identifier appears exactly once as part of a sequence, and a portion of each code partially overlaps with a portion of an adjacent code. Alternatively, the first plurality of unique identifiers can be provided within a series of juxtaposed (i.e., placed side by side without overlap) identifiers along the measurement path.

[0057] As shown in the figure, the absolute marks of the first absolute track 30a can be arranged along the measurement path 2. Alternatively or additionally, multiple sets of absolute marks can be grouped (e.g., defined or aligned) into tracks that are perpendicular or inclined relative to the measurement path 2.

[0058] Advantageously, the first plurality of unique identifiers may correspond to a first plurality of numeric codes, each numeric code being unique and assigned to one of the scale divisions 34 to 36 of the first absolute position track 30a. The numeric codes may be any code having a discrete, discontinuous representation (especially capable of being processed by a computer (e.g., by means of a processor or controller) or its equivalent (e.g., a microprocessor, FPGA, or ASIC)). Preferably, the numeric codes are binary codes having a plurality of digits, preferably having N digits, where N = 3, 4, 5, or greater than 5, to provide N of the first absolute position track 30a. 2 A unique identifier for each different scale division.

[0059] The first multiple digit codes can rely on Gray coding to limit the number of different bits between two adjacent digit codes. This coding is particularly advantageous when individual codes are sensed along a vertical or inclined (virtual) axis relative to the measurement path (e.g., in the case of juxtaposition of codes oriented vertically or inclined relative to the measurement path).

[0060] Alternatively, the first plurality of digital codes may depend on or correspond to (completely or partially) a DeBruijn sequence, wherein each possible code appears exactly once as part of the sequence. This encoding optimally enables sensing of (continuous) code sequences along a measurement path, which is in particular a linear, circular, or even (ring / disc-shaped) circular path.

[0061] exist Figure 1 In the embodiment shown in Figure 6, the first plurality of unique identifiers take the form of a sequence of consecutive numeric codes, each numeric code A N It is unique and assigned to one of the scale divisions 34 to 36 of the first absolute position orbit 30a, as described above.

[0062] like Figures 6a to 6b As shown, the first plurality of digital codes A 50 A 51 It can be a binary code with N digits, where N=9, providing a unique identifier for up to 512 different scale divisions. Each numeric code (A 50 A 51 Each digit in the data is advantageously provided by a detector 70a-77a of the first absolute sensing unit 60a of the reader.

[0063] exist Figure 1In the embodiment shown in Figure 6, the first plurality of digital codes rely on a portion of the DeBruijn sequence to enable a continuous code sequence along the measurement path. Each digital code is extracted (sensed) from such a sequence depending on the relative position of the reader 50 along the measurement path relative to the digital scale 20. The first plurality of digital codes can also be used for linear and angular measuring instruments (see Figure 6). Figure 12 This refers to the circular measurement path along a linear measurement path or even the circular measurement path (ring / disc shape) of an angle measuring instrument.

[0064] Figures 6a to 6b The illustration schematically depicts the sensing of a first absolute position code (in the form of a digital code as part of a first plurality of digital codes) as the reader 50 moves relative to the digital scale 20 from a first relative position to a second relative position. The first position of the reader is located within the center portion of the first scale division 34 of the first absolute position track 30a (i.e., centered), and the second position of the reader is located within the center portion of the second scale division 35 of the first absolute position track (i.e., centered). In this embodiment, the second scale division 35 is adjacent to the first scale division 34.

[0065] Figure 6a The diagram schematically illustrates the sensing of a digit from a first plurality of digit codes when the reader is relatively centered in the first scale division 34, with the reader's position schematically indicated by arrow 39. In this spatial relationship, detectors 70a-77a of the first absolute sensing unit 60a sense subsets of the first absolute markers 32a, 33a located within the sensing volume of each detector, in order to provide information in code A. 50 =100100001, a discretized (individual) signal. This code A 50 Provide a unique identifier for the first scale division 34.

[0066] Therefore, the absolute position 39 of the reader 50 can be determined by adding or mathematically combining the precise relative position provided by the sensing increment track 40 with an absolute reference associated with the first scale division 34 of the first absolute position track 30a. In this embodiment, the absolute reference corresponds to the (lower value) side 37a of the first scale division 34.

[0067] Figure 6b The illustration schematically shows the sensing of a digit code from a first plurality of digit codes when the reader 50 is slightly shifted relative to the center of the first scale division 34. Even though the entire subset of discrete regions 32a of the first absolute markers of the first absolute position track 30a is not entirely within the sensing volume of each detector, the individual signals provided still provide the code A assigned to the first scale division 34. 50Discretization. The absolute position 39 of the reader can still be determined by adding the current precise relative position provided by the sensing increment track 40 to the absolute reference (i.e., the first absolute position) associated with the first scale division 34.

[0068] Figure 6c The diagram schematically illustrates the sensing of a digit code among the first plurality of digit codes when the reader 50 approaches the midpoint between two adjacent scale divisions 34, 35, i.e., the reader 50 is relatively positioned within the (right) peripheral portion of the (first) scale division. In other words, some of the first series of detectors 70a to 77a of the reader 50 are aligned with the transition portion between the separated and discrete regions 32a, 33a. Within this peripheral portion, as the digit code changes from the first code to the second code, some discrete regions 32a of the absolute marker are (substantially) located at half the sensing volume of some detectors (i.e., detectors 70a, 76a) of the first absolute sensing unit. Discretization of the provided signal can lead to unreliable differentiation of the digit code A. X51 Its instantaneous digits may be uncertain or even misclassified. Therefore, the absolute position 39 of the reader cannot be reliably determined because of the difference between the sensed scale division A and the actual position 39. X51 The associated absolute reference (i.e., the first absolute position) may be unstable or even erroneous. The reader's position is part of the unfavorable position.

[0069] Figure 6d The illustration schematically depicts the sensing of a digit from the first plurality of digit codes when the reader is positioned relative to the center portion of another scale division 35. None of the detectors 70a to 77a are aligned with the transition portion between the separation and discrete regions 32a, 33a. In this spatial relationship, a new subset of the absolute markers lies entirely within each sensing volume of the detectors of the first absolute sensing unit to provide (correct) discretization of each instantaneous digit. This discretization results in a new code A that clearly identifies the second scale division 35. 51 =001000011. The absolute position 39 of the reader can still be determined by adding the current precise relative position to the absolute reference 37b associated with the second scale division 35.

[0070] To provide robustness at intermediate positions between two adjacent scale divisions 34 and 35, the reader's sensing element and digital scale are also configured to provide a second absolute position code for the same positioning of the reader 39. This second absolute position code specifically indicates a second absolute position different from the first absolute position, in order to provide reliable positioning in this unfavorable positioning of the reader. In this embodiment, the digital scale is also configured to allow the reader to sense the second position code (especially with multiple unique identifiers B). 50 B51 (One of the forms). Each unique identifier is assigned to the peripheral portion T of each scale division. 2a T 2b ( Figure 5 Specifically, the left and right peripheral portions of two adjacent scale divisions. In these intermediate positions of the encoder, an absolute position 39 can be provided by mathematically combining (e.g., adding or subtracting) the absolute reference (i.e., the second absolute position) associated with the sensed overlapping scale divisions 34', 35', 36' in the second absolute position track 30b with the precise relative position 38. The second absolute position preferably corresponds to one of the edges 37a', 37b', 37c' of the sensed overlapping scale divisions 34' to 36' (the lower or higher one), or to the center position of the sensed overlapping scale divisions.

[0071] Specifically, each unique identifier in the second plurality of identifiers may be assigned to each of the plurality of overlapping scale divisions 34' to 36', which are assigned to scale divisions 34 to 36 of the incremental track 40 and / or the first absolute position track 30b.

[0072] Therefore, multiple overlapping scale divisions are provided on the second absolute position track 30b of the digital scale along the measurement path, each overlapping scale division 34' being spatially aligned with two adjacent scale divisions 34, 35 (both) of the first absolute position track 30a (see...). Figure 1 and Figure 3 The adjacent portions 31a and 31b of the scale overlap. Advantageously, each overlapping scale division includes two adjacent peripheral portions of two adjacent scale divisions, particularly the right peripheral portion of the scale division and the left peripheral portion of the right adjacent scale division. The second absolute position track 30b of the digital scale is configured such that the reader can sense the unique identifier B among the second plurality of identifiers. 60 B 61 (Especially assigned to each of these overlapping scale divisions 34'-36').

[0073] Therefore, the use of overlapping scale divisions provides absolute position detection in the peripheral portion of scale divisions 34 to 36 of the first absolute position track 30a, wherein the unique identifier among the first plurality of identifiers must change from a first value to a second value, thereby constituting an unfavorable positioning of the first absolute position that is likely / may be unreliable by the reader.

[0074] The overlapping scale graduations are shaped according to the shape of the pitch P and / or the shape of the scale graduations of the first absolute position track and / or the (local) shape of the measurement path. Each overlapping scale graduation can be, in particular, a linear, curved, or angled shape along the measurement path.

[0075] Similar to the scale graduations of the first absolute position track, the unique identifiers of the overlapping scale graduations of the second absolute position track are arranged such that the reader can sense multiple unique identifiers B along the measurement path. 60 B 61 According to the scale divisions 34' to 36' of the second absolute position track 30b, the unique identifiers of each intermediate are different (i.e., unique) and depend on the positional relationship between the reader and the scale along the measurement path.

[0076] This implementation ensures that, due to the specific relative arrangement structure between the discrete region sequence 32; 32a, 32b and the first series detectors 70a-77a and the second series detectors 70b-77b, at each possible position of the reader 50 relative to the digital scale, none of the first series detectors and the second series detectors are aligned with the transition portion between the discrete region 32; 32a, 32b and the separated region 33; 33a, 33b.

[0077] Sensing the unique identifier of the first plurality of identifiers and the second plurality of identifiers can rely on a unique absolute position orbit 30 including discrete region 32c and separation region 33c between discrete regions (as in Figures 10 to 11 As shown in the implementation, it depends on the first absolute mark and the second absolute mark provided on the first absolute position track 30a and the second absolute position track 30b (as shown in the implementation). Figure 1 (as shown in Figure 6), or a combination thereof (not shown).

[0078] Overlapping scale divisions 34'-36' can be spaced apart along the measurement path. Alternatively, overlapping scale divisions can be positioned (substantially) one after another along the measurement path (i.e., without overlap and without gaps between divisions) such that the edge of one overlapping scale division substantially corresponds to the edge of the adjacent overlapping scale division.

[0079] Advantageously, the overlapping scale divisions 34'-36' can be (substantially) centered between two adjacent main scale divisions along the measurement path (i.e., corresponding to the midpoint between two adjacent main scale divisions and / or the common edges 37a, 37b) to provide more robust absolute position detection in the various transition sections between discrete and separated regions.

[0080] Alternatively or complementary, each overlapping scale division 34' to 36' extends the same spatial extension T of the main scale divisions 34-36 along the measurement path.

[0081] The reader 50 of the encoder 10 may include a second absolute sensing unit 60b having a plurality of detectors 70b to 77b (e.g., in...). Figures 1 to 2 (as shown in the figure) for sensing discrete region 32b and separation region 33b between discrete regions.

[0082] As mentioned above, a second set of unique identifiers can be technically enabled in a similar manner to the unique identifiers of the first set of multiple identifiers.

[0083] A unique identifier can be provided among a second plurality of identifiers along the measurement path, i.e., each unique identifier among the second plurality of identifiers appears exactly once as part of a sequence. Alternatively, the unique identifier is in the form of a series of juxtaposed identifiers (i.e., placed side by side without overlap) along the measurement path.

[0084] The second plurality of unique identifiers may correspond to a second plurality of numeric codes, each of which is unique and assigned to one of the overlapping scale divisions. Similarly, the numeric codes in the second plurality of numeric codes can be any code having a discrete, discontinuous representation (especially capable of being processed by a computer (e.g., via a processor or controller) or its equivalent (e.g., a microprocessor, FPGA, or ASIC)). Preferably, the second plurality of numeric codes are binary codes having a plurality of digits, preferably having N digits, where N = 3, 4, 5, or greater than 5, in order to provide N 2 A unique identifier for each distinct overlapping scale division. More preferably, the second plurality of numeric codes have the same representation as the first plurality of numeric codes.

[0085] Similar to the first plurality of digit codes, the second plurality of digit codes may rely on Gray coding to limit the number of different bits between two adjacent digit codes, or may (fully or partially) rely on or correspond to the DeBrujin sequence.

[0086] exist Figure 1 In the embodiment shown in Figure 6, the second plurality of unique identifiers adopts a sequence of (continuous) numeric codes (B 60 B 61 In the form of ) the second multiple numeric code B NEach of these is unique and assigned to one of the overlapping scale divisions 34 to 36, as described above. The second plurality of digital codes are binary codes with N digits, N=9, thus providing unique identifiers for up to 512 different scale divisions. The second plurality of digital codes rely on a portion of the DeBruijn sequence to enable a continuous sequence of codes along the measurement path, each digital code being extracted (sensed) from such a sequence depending on the reader's relative position to the scale. Figure 1 In the embodiment shown in Figure 6, the second plurality of numeric codes have the same digital representation as the first plurality of numeric codes and depend on the same code generation; that is, these codes (and their absolute markers) are related, as in Figure 3 As specifically shown in the text.

[0087] Alternatively, the identification of overlapping scale regions may rely on a second plurality of unique identifiers having other numerical representations, which may or may not be related to the numerical representations of the first plurality of unique identifiers. Figure 7 In the embodiment shown, the digital scale 20 includes a second absolute position track 30b, which has a discrete region 32b and a separate region 33c, which are arranged to correspond to the binary inverse code of a first plurality of digital codes.

[0088] exist Figure 1 In Figure 6, the overlapping scale divisions 34'-36' of the second absolute position track 30b are spatially shifted by a spatial period T / 2 (corresponding to half of the spatial extension T of the first scale division) along the measurement path relative to the scale divisions 34-36 of the first absolute position track 30a. In other words, each scale division of the second absolute position track 30b is substantially centered along the measurement path relative to two adjacent scale divisions of the first absolute position track 30a. The markings of the second absolute position track 30b are shifted to the left relative to the markings of the first absolute position track 30a, but according to another embodiment, they can also be shifted to the right.

[0089] Alternative locations, such as Figures 8 to 9 As shown, the digital scale 20 may include a first absolute position track 30a and a second absolute position track 30b. The absolute markings 32a, 33a of the first absolute position track 30a are the same as (or reversed according to a variant not shown) of the second absolute position track 32b, 33b. The first absolute position track 30a and the second absolute position track 30b are aligned along the measurement path. In this embodiment, Figure 8The reader 50 includes a first absolute sensing unit 60a having a first series of detectors 70a-77a and a second absolute sensing unit 60b having a second series of detectors 70b-70b. Each detector of the first absolute sensing unit 60a is offset from the corresponding detector of the second absolute sensing unit 60b by a spatial period T / 2.

[0090] As Figures 8 to 9 In an alternative implementation, the digital scale 20 may include a single absolute position track 30 having identical and aligned absolute markers 32, 33, such as... Figure 11 As shown. In order to provide both the first unique identifier and the second unique identifier, Figure 10 The reader 50 includes two adjacent absolute sensing units 60a and 60b extending along the reader's direction of travel. Figures 8 to 9 In one implementation, each detector of the first absolute sensing unit 60a is offset from the corresponding detector of the second absolute sensing unit 60b by a spatial period T / 2.

[0091] The above embodiments enable robust detection of the absolute position 39 of the reader 50 at each possible location relative to the digital scale 20. These embodiments rely on the digital scale 20, which includes an incremental track 40 for providing the relative position 38 of the reader 50 within a series of scale divisions 34-36 on a first absolute position track 30a. The reader can individually read the first plurality of unique identifiers A. 50 A 51 The second and multiple unique identifiers B 60 B 61 Each of them. The first multiple identifiers A 50 A 51 Each of them is assigned to the (center) portion of the scale division of the first absolute position orbit 30a, while the second plurality of identifiers B 50 B 51 Each of the identifiers is assigned to another portion of the scale division, particularly the (right or left) peripheral portion of the scale division. Preferably, each of the second plurality of identifiers is assigned to overlapping scale divisions, which (continuously) comprise the adjacent peripheral portions of two adjacent scale divisions of the first absolute position track 30a.

[0092] about Figure 1 As shown in the implementation of Figure 6, Figures 6a to 6d The robust effect of the scale divisions 34'-36' of the second absolute position track 30b on the absolute coarse position of the sensor reader 50 is schematically shown.

[0093] When the detector 70a of the first absolute sensing unit of the reader 50 is relatively positioned in the transition region (i.e., in the peripheral portion) between two adjacent scale divisions 34, 35 of the first absolute position track 30a, the detector 70b of the second absolute sensing unit of the reader 50 is then relatively positioned within (especially centered) the edges 37b', 37c' of the overlapping scale divisions 35' (e.g., in their central portion) of the second absolute position track 30b, such as... Figure 6c As shown. The difference between unreliable and master numeric code A. X51 Conversely, because none of the detectors in detectors 70b-77c are aligned with the transition portion between discrete region 32a and separated region 33a, the intermediate digital code B... 61 It can be reliably distinguished and allows for clear identification of related overlapping scale divisions of 35'.

[0094] According to the invention, the central portion of the scale division of the first absolute position track 30a or the unique absolute position track 30 is part of the scale division, wherein the unique identifier can be clearly distinguished by the reader, for example, the absolute mark providing the unique identifier (along the travel direction of the reader) is located relative to the sensing volume of the reader's detector, down to 90% (i.e., equal to or greater than 90%), preferably down to 75% (i.e., equal to or greater than 75%) of the sensing volume.

[0095] According to the invention, the (left and right) peripheral portions of the scale division are part of the scale division, wherein the first unique identifier can be vaguely distinguished by the reader, for example, the absolute mark providing the first unique identifier (along the reader's direction of travel) is located relatively within the sensing volume of the reader's detector (less than 60%, preferably less than 75%).

[0096] Therefore, encoder 10 can provide the absolute position 39 of reader 50 relative to the scale based on the precise relative position 38 provided by sensing incremental track 40 and the scale divisions 34'-36' (the absolute reference associated with the scale divisions 34'-36'). The absolute reference associated with the scale divisions of the second absolute position track 30b can correspond to the (lower or higher) edges 37a', 37b', 37c' of the sensed scale divisions 34'-36' of the second absolute position track 30b. Alternatively, depending on the precise relative position 38 provided by sensing incremental track 40, the absolute reference associated with the scale divisions can selectively correspond to the (lower or higher) edges 37a, 37b, 37c of one of the overlapping scale divisions 34-36, especially to the overlapping edges.

[0097] Similar to the first set of multiple numeric codes, the second set of multiple numeric codes is also affected by edge effects corresponding to code transition portions (e.g., the periphery of overlapping scale divisions). However, these transition portions are misaligned with the transition portions of the first set of multiple numeric codes, such as... Figure 6a and Figure 6d As shown (e.g., B) x61 B x62 ).

[0098] Therefore, the use of overlapping scale divisions 34'-36' of the second absolute position track 30b (each overlapping scale division overlaps with a portion 31a, 31b of each of the two adjacent scale divisions 34-35 (i.e., both) (especially their peripheral portions) of the first absolute position track 30a) provides absolute position detection in a key spatial (i.e., peripheral) region of the scale division, which corresponds to the transition portion region of the (sensed) first plurality of unique identifiers.

[0099] Since the middle area of ​​the overlapping scale division is not aligned with the middle area (edge) of the scale division of the first absolute position track 30a, that is, the peripheral portion of the scale division of the first absolute position track 30a is not aligned with the peripheral portion of the overlapping scale division (preferably not overlapping), the encoder 10 can provide more robust detection by using a first plurality of unique identifiers and a second plurality of unique identifiers that are always along the travel direction of the reader. The first plurality of unique identifiers and the second plurality of unique identifiers are obtained by the reader 50 sensing the marks of both the first absolute position track 30a and the second absolute position track 30b through the corresponding first absolute sensing unit 60a and the second absolute sensing unit 60b.

[0100] Reader 50 is configured to rely on the relative position provided by sensing incremental track 40 (e.g., Figure 5 (As shown) to select one of the first unique identifier and the second unique identifier to determine the absolute position 39 of the reader 50 so as to use a reliable (first or second) absolute position.

[0101] Knowing the relative position of the scale division of the first absolute position track 30 with respect to the (transition) region of the incremental track 40, the encoder 10 relies on the position of the first absolute position or the second absolute position (via the first unique identifier and / or the second unique identifier), which depends on the sensed incremental track, particularly by determining the relative position within the scale division of the first absolute position track 30a. If the relative position is close to or within a portion of the transition section that could affect the reliability of the unique identifier obtained by sensing the first absolute position track (i.e., the encoder estimates that some detectors of detectors 70a-77a may be aligned with the transition section between the separation region and the discrete region), the reader may decide to rely on the second unique identifier instead of the first unique identifier.

[0102] In Figure 5 In the exemplary illustration, each scale division (of which the spatial extension T equals the pitch P) can be divided into four distinct quadrants. Each quadrant can be uniquely identified by the relative position of the reader within the scale division of the first absolute position track 30a. Alternatively or complementaryly, each quadrant can be provided by a series of detectors 90-97 of the reader's incremental sensing unit 80 via sensing incremental track 40. Figure 4 The signs of the four (unbiased) sinusoidal signals are uniquely identified. Therefore, a first unique identifier can be assigned to a subset of these quadrants (e.g., Figure 5 The second unique identifier can be assigned to the remaining subset (e.g., the second quadrant and the third quadrant), and the second unique identifier can be assigned to the remaining subset (e.g., Figure 5 (The first and fourth quadrants). In particular, the central portion T1 of the scale division of the first absolute position orbit 30a can be defined as corresponding to the second and third quadrants, while the (left) peripheral portion T 2a Corresponding to the first quadrant and the (right) peripheral part T 2b It corresponds to the 4th quadrant.

[0103] By sensing the incremental track 40 through the incremental sensing unit 80 (especially via the sensed relative position) and by knowing the spatial relationship between the incremental track and the first absolute position track and the second absolute position track (especially the spatial relationship between their transition portions), the encoder can estimate, for the current position of the reader, whether any of the first series detectors 70a-77a are aligned with the transition portion between the discrete and separated regions and / or whether any of the second series detectors 70b-77b are aligned with the transition portion between the discrete and separated regions. Depending on the estimation results, the encoder can select either the first absolute position code or the second absolute position code provided by the first absolute position track and the second absolute position track, respectively.

[0104] Advantageously, the reader and tag arrangement can be configured to allow sensing of one or more second unique identifiers separately from (and vice versa) sensing of one or more first unique identifiers. This allows the reader to select either the first or second unique identifier used to determine the identifier, particularly based on the determined (or predicted) relative position provided by sensing the incremental trajectory. Advantageously, the first and second absolute positions can be provided simultaneously (i.e., at the same time, i.e., within a time span of less than 0.1 s, preferably less than 10 ms).

[0105] Figure 12 An absolute position encoder 10 is used to provide the absolute position of the reader 50 relative to a circular or arc-shaped track. The track includes an incremental track 40, a first absolute position track 30a, and a second absolute position track 30b. The second absolute position track may lie along a circular (disc-shaped or annular) path on a (disc-shaped) scale 20 to provide the reader's angular absolute position. This angle may be concave or convex. The reader includes: a first absolute position sensing unit 60a and a second absolute position sensing unit 60b for sensing the corresponding first absolute position track 30a and second absolute position track 30b; and an incremental sensing unit 80 for sensing the incremental track 40.

[0106] Therefore, the absolute position encoder 10 can implement a method for providing the absolute position of the reader 50 relative to the digital scale 20.

[0107] The absolute position encoder 10 can be configured to inductively sense at least one subset of the marker arrangement structure. The absolute markers and / or periodic markers can therefore be conductive and / or permeable elements, and the reader 50 can include inductive or eddy current sensing units 60a, 60b, 80 for inductively sensing the absolute markers and / or periodic markers.

[0108] Alternatively or complementaryly, the reader may be configured to capacitively and / or magnetically and / or optically sense at least one (or another) subset of the marker arrangement structure and / or periodic markers, the subset of the marker arrangement structure and / or periodic markers being capable of capacitive and / or resistive and / or magnetic and / or optical sensing.

[0109] refer to Figure 13 The method includes a first step S1, which involves sensing the incremental track 40 of the digital scale 20 by the reader 50.

[0110] The method includes a second step S2, which involves determining or predicting the relative position 38 of the reader 50 within one of the scale divisions 34-36 of at least one absolute position track 30; 30a, 30b (e.g., within one of the scale divisions 34-36 of the first absolute position track) by means of the sensed incremental track. In other words, for the current position of the reader 50 relative to the digital scale 20, if none of the first series of detectors and / or the second series of detectors are aligned with the transition portion between the discrete regions 32; 32a, 32b and the separated regions 33; 33a, 33b, then the second step S2 involves an estimation based on the sensed incremental track 40 (especially based on the determined / predicted relative position).

[0111] The third step S3 includes selecting the first digital code A. N (S4) or the second digital code B N (S5), the first digital code A N (S4) or the second digital code B N (S5) is provided by sensing marks on both the first absolute position track 30a and the second absolute position track 30b based on the determined or predicted relative position 38 of the reader 50. In other words, the third step S3 involves selecting the first absolute position code or the second absolute position code based on an estimate that none of the first or second series of detectors is aligned with the transition section.

[0112] The step of determining the relative position 38 of the reader may include detecting the determined or predicted relative position 38 within the central portion and / or (left and / or right) peripheral portion of the scale graduations of the first absolute position track 30a. First digital code A N Or the second digit code B N The choice can be a function of the center and / or peripheral portion of the scale division of the first absolute position orbit 30a being detected.

[0113] Step S6 includes determining the relative position 38 and the determined digital code A based on the sensed relative position 38. N B N The absolute position 39 of the reader is provided. The step of providing the absolute position 39 of the reader may also include, for example, correcting the relative position by applying linear and polynomial corrections.

[0114] The absolute position encoder 10 and the method can be advantageously implemented and enabled in measuring instruments and / or their accessories, particularly for dimensional metrology (i.e., quantifying one or more physical dimensions or distances from a given object). More specifically, the absolute position encoder 10 and the method can be advantageously implemented and enabled in measuring instruments and / or their accessories, particularly providing one or more of the following metric characteristics: linear dimensions, thickness, radius, inner diameter, or outer diameter of the object; or coordinates, roughness, or surface finish of the object's surface. The measuring instrument can be a handheld measuring instrument (e.g., a digital sliding caliper, a digital micrometer) or a portable measuring instrument (e.g., a height gauge, a measuring probe). The measuring instrument can also be a fixed measuring instrument, such as a coordinate measuring machine (CMM) or a measuring robot (which has a granite (or reference) table on which an object must be placed for measurement) (e.g., a bridging CMM). Accessories can be rotary tables, rotary axes, or articulated probes for orientation (non-contact or contact) probes (particularly relative to moving or fixed parts or components of the measuring instrument). Measuring instruments can be connected to measuring devices, inspection systems, or machine tools, or be part of measuring devices, inspection systems, or machine tools.

[0115] The encoder 10 may also include more than one reader, i.e., multiple readers, each of which is capable of moving individually relative to the (same) scale (especially along the direction of travel of the reader), for example, to provide the position of multiple moving parts of the measuring instrument.

[0116] The surface of the scale on which the encoder can move can be not only (basically) planar, but also non-planar, such as curved or arc-shaped.

[0117] Advantageously, the absolute position encoder may include electronic circuitry 140 (see...) Figure 18 The electronic circuitry is configured to provide the reader's position 39 relative to the scale along the measurement path, and in particular, to provide its digital representation. The electronic circuitry 140 may be part of the reader.

[0118] Electronic circuits may include programmable electronic circuits (such as microcomputers, microcontrollers, or FPGAs) or special-purpose electronic circuits (e.g., ASICs or discrete component circuits).

[0119] Figure 14Another embodiment of an absolute position encoder 10 for less precise applications is shown. The absolute position encoder 10 includes a reader 50 having a first sensing unit 60a and a second sensing unit 60b, which are configured to sense corresponding discrete regions 32a, 32b and separate regions 33a, 33b of corresponding first absolute position tracks 30a and 30b of a digital scale 20. The first absolute position tracks 30a and 30b extend adjacent to each other along the travel direction of the reader 50 to provide first and second absolute positions. This absolute position encoder 10 has no incremental tracks because it is designed for less precise applications.

[0120] Therefore, even if the reader is in an unfavorable position, Figure 14 The absolute position encoder 10 can also provide a reader 50 ( Figures 6a to 6d The position 39 is always dominated by at least one robust absolute position provided by the first absolute position orbit 30a and / or the second absolute position orbit 30b.

[0121] exist Figure 15 In another embodiment, schematically illustrated, the absolute position encoder includes a digital scale 20 having a single mark formed by discrete regions 32 and separation regions 33 between the discrete regions 32. The reader includes a first series of detectors 70a-77a and a second series of detectors 70b-77b. The first and second series of detectors extend along the reader's direction of travel and are adjacent to each other. The position of each detector in the first series 70a-77a is offset relative to a corresponding detector in the second series 70a-77a along the reader's direction of travel. This offset may, for example, correspond to half of the sensing area along the direction of travel. The position encoder is configured to select either a first absolute position code or a second absolute position code read by a series of detectors, where none of the detectors is aligned with the transition portion between the discrete regions 32 and the separation regions 33 of the digital scale 20.

[0122] exist Figure 16In another embodiment schematically illustrated, the absolute position encoder includes a digital scale 20 having a single mark formed by discrete regions 32 and transition regions 33 between the discrete regions 32. The reader includes a first series of detectors 70a-77a and a second series of detectors 70b-77b. Detectors in the first series 70a-77a are interleaved with detectors in the second series 70b-77b to form adjacent detector pairs 70a-70b, 71a-71b, 72a-72b, 73a-73b, 74a-74b, 75a-75b, 76a-76b, and 77a-77b. The position encoder is configured to select either a first absolute position code or a second absolute position code read by a series of detectors, in which no detector is aligned with the transition region between the discrete regions 32 and the transition regions 33 of the digital scale 20.

[0123] Advantageously, the absolute position encoder 10 can be configured to estimate or determine the reliability and / or unreliability of the first absolute position and / or the second absolute position, respectively, to ensure a more reliable position of the reader. The estimation or determination of reliability and / or unreliability can be based on (e.g., verification below): a given spatial relationship between the first and second absolute positions. In fact, if the first and second absolute positions are related to adjacent absolute positions, the first absolute position (and even the second absolute position) can be estimated to be reliable. The absolute position encoder 10 can therefore estimate / determine that the reader may be located in the intermediate zone between the centers of the two scales. Therefore, the reader position 39 can depend on the first absolute position. Alternatively or complementaryly, the reader position 39 can depend on the second absolute position.

[0124] Alternatively or complementaryly, the absolute position encoder 10 may be configured to estimate or determine reliability and / or unreliability based on (e.g., the following verification): a given digital pattern of digital representation or a relationship between digital representations (e.g., a first unique digital identifier and a second unique digital identifier) ​​associated with a first absolute position and / or a second absolute position.

[0125] like Figure 17 As shown, in the event of the aforementioned estimation / determination failure, the absolute position encoder 10 can be configured to estimate or determine whether the reader is in an unfavorable position relative to the second absolute position, i.e., the (sensed) second absolute position is incorrect (because one or more of its detectors are aligned with the transition section). This situation is similar to... Figure 6aThe situation is illustrated. This spatial situation can be verified by checking whether the numerical representation upon which the second position depends exhibits a given pattern. This pattern can correspond to a common number (or an invariant pattern, i.e., a non-transient number) of two adjacent unique numerical identifiers spatially associated with the first absolute position (i.e., whose overlapping scale divisions overlap with the main scale division indicated / linked by the first absolute position). Therefore, the common number corresponds to a bit of the second absolute position code that can be derived from the detectors of the second series detectors 70b-77b that are not oriented towards the transition portion. Using... Figure 6a In the exemplary case shown, considering the first absolute position 37a, the encoder can verify whether the digital representation (B) upon which the second position depends includes the common digits of graduations 34' and 35' (i.e., B). x61 This is used to verify the reliability of the first absolute position 37a.

[0126] In the case of this digital representation including the pattern, the absolute position encoder can therefore estimate / determine that the reader may be positioned in the central region of the scale division of the first absolute position track, which corresponds to the transition region of the overlapping scale divisions (i.e., unfavorable positioning). Therefore, the reader position 39 can rely on the first absolute position, which is considered reliable in contrast to the second absolute position.

[0127] Complementarily or alternatively, especially in the event of the above estimation / determination failure, the absolute position encoder can be configured to estimate or determine whether the reader is in an unfavorable position relative to the first absolute position, i.e., the (sensed) first absolute position is incorrect (because one or more of its detectors are aligned with the transition section).

[0128] This situation is similar to Figure 6c The situation is illustrated below. Similar to the process described above, the spatial situation can be verified by checking whether the numerical representation upon which the first position depends (e.g., the identifier of a first plurality of identifiers) exhibits a given pattern. This pattern can correspond to a common number (i.e., a non-transient number) of two adjacent unique numerical identifiers spatially associated with the second absolute position (i.e., whose scale division overlaps with the overlapping scale division indicated / linked by the second absolute position). In this case, the common number corresponds to a bit of the first absolute position code that can be derived from the detectors of the first series detectors 70a-77a that are not oriented towards the transition portion. Using Figure 6c In the exemplary case shown, considering the first absolute position 37a, the encoder can verify whether the digital representation (A) upon which the first position depends includes the common digits of the scale divisions 34 and 35 of the first absolute position track (i.e., A). X51 This is used to verify the reliability of the second absolute position.

[0129] In the case of this digital representation including the pattern, the absolute position encoder can therefore estimate / determine the junction where the reader may be located between a discrete region and a transitional region (i.e., an unfavorable location) associated with the first absolute position. Therefore, the reader position 39 can rely on a second absolute position that is considered reliable in contrast to the first absolute position.

[0130] Alternatively, the absolute position encoder can estimate / determine the reliability of the first absolute position and / or the second absolute position by verifying a given digital attribute of its digital representation (e.g., its unique digital identifier). The digital attribute can be: a digital signature, a redundancy code, or a cyclic or block redundancy check (e.g., CRC).

[0131] An absolute position encoder can therefore provide a position that depends on the following: 39 Figures 6a to 6d ):

[0132] If the relevant numeric attribute of the first absolute position has been verified, then depend on that first absolute position; and / or

[0133] If the relevant numeric property of the second absolute position has been verified, then the second absolute position is relied upon.

[0134] Figure 18 An exemplary use of an absolute position encoder for dimensional measurement (particularly for sliding calipers) is shown.

[0135] The sliding caliper 100 includes one of the absolute position encoders described above, preferably relying on, for example... Figure 1 The absolute position encoder for the periodic position is shown in the exemplary embodiment of FIG6. The sliding caliper 100 includes a first jaw 102 fixed to the caliper housing 103 and a second jaw 104 connected to a digital scale 120 and slidable relative to the first jaw 102. The sliding caliper 100 also includes a display 106 for displaying, preferably by means of electronic circuitry 140, the distance between the first jaw 102 and the second jaw 104 provided by the absolute position encoder.

[0136] Figure 19 and Figure 20 Many possible uses or applications of the invention are illustrated, with an exemplary use being for geodesy or surveying. As known in the field of geodesy, a target point is surveyed by placing a portable target object (e.g., survey post 270, 270', 270") at the geodetic target point 277. For measuring and / or staking out topographic points, a general survey post system can be used as a device that collaborates with a Ground Positioning System (TPS) 176 (such as a total station or a cooperative or independent Global Navigation Satellite System (GNSS) device). The term survey post system refers at least to a survey post and a survey post having an external (but connected) processing unit.

[0137] That is, the target object includes, for example, a vertical column 270 having a retroreflector 274 for defining a measurement section or measurement point. Another column 270' depicted has, for example, a target plate 274' capable of being measured using a camera of a surveying instrument. Alternatively, column 270" may have a GNSS antenna 274". Combinations of these are also known.

[0138] The measurement or stakeout of target point 277 is an indirect measurement: using methods such as... Figure 20 The TPS 276 shown is used, for example, by using a reflector and measuring the distance and direction from the TPS 276 to the reflector to measure a reference point on the survey post 270. Such a reference point is, for example, the center point of the reflector 274, or, in the case of a GNSS post, a GPS antenna mounted on post 170". Since the tips 275, 275', 275" of the survey posts 270, 270', 270" are placed on the actual target point 77 in the terrain, the location of the target point 277 can be determined from the determinable spatial relationship between the reference point and the tips 275, 275', 275" of the post 270. This method particularly allows for the measurement or stakeout of obstacles (such as...) Figure 20 Point 277 is the wall between TPS276 or GNSS and point 277, which cannot be directly measured or laid out.

[0139] Such indirect measurements may require a free line of sight between the main sensor (e.g., the laser-based optical rangefinder of the TPS 276) and the reflector / antenna. Additionally, the spatial relationship between the measurement center of the reflector or target plate or antenna 274, 274', 274" and the tip of the column 275, 275', 275" needs to be known.

[0140] To provide further flexibility for such obstacle solutions, as shown, the survey posts 270, 270', 270" offer length adjustability, enabling continuously variable post lengths or several different post lengths (the latter, for example, through multiple locking positions). For this purpose, the telescopic structure of posts 270, 270', 270" with at least two elements 272, 272', 272" and 273, 273', 273" capable of moving relative to each other not only provides length adjustability but also relates to the encoder 10 according to the invention for absolute length measurement and determination of actual post length, and optionally also for conversion between measurement units or standards.

[0141] like Figure 19As shown, the length adjustment of the survey post can be achieved in several ways. For example, survey posts 270, 270', and 270" have two telescopic sections, so that, as shown on the exemplary post 270 with reflector 274, the upper telescopic section 272 of the survey rod 271 can be screwed onto the lower section 273 as indicated by the swung arrow (and vice versa). Alternatively, and as shown on post 270" with GNSS antenna 274", the upper tube (section) 272" can be thinner so that it can slide into the lower tube 273", or in another way as shown on post 272', where the lower part 273' can slide into the upper part 272'.

[0142] The columns 270, 270', 270" with continuously variable column height h have built-in measuring units that allow determination of the column height h at each location of the two telescopic sections. Specifically, the length-adjustable survey columns 270, 270', 270" provide their current length using the absolute position encoder 10 according to the invention, i.e., the distance between the length reference point (e.g., the center of the reflecting prism 274 or the target plate 274') and the indicating tips 275, 275', 275"). Thus, as described above, the reader 50 reads the scale 20, thereby allowing determination of the actual rod length and actual column height h at any location. The survey columns 270, 270', 270" can integrate more than one encoder 10, for example, if more than two telescopic sections exist.

[0143] In the posts 270, 270' with retroreflector 274 or target plate 274', the absolute scale 20 extends at least above a portion of the lower portion 273, 273' of the rod 271. The scale 20 extends at least along the entire possible length variation and is read by the reader 50 located in the upper portion 272, 272'. In the exemplary GNSS post 270", this configuration is different because the scale 20 of the encoder 10 is on the inner surface of the hollow lower portion 273" (thereby in... Figure 19 (Not shown in the image). Alternatively, the reader 50 can be placed in or at the lower 273, 273', 273", and the scale 20 can be placed in or at the upper 272, 272', 272".

[0144] The extension of scale 20 in another direction (scale width, e.g., perpendicular to the length change / measurement path) can be chosen, for example, depending on the possible degrees of freedom of movement in that direction. If, for example, the upper 272, 272', 272” and the lower 273, 273', 273” can be fully rotated relative to each other (360° rotation is possible), then scale 20 can be a complete ring structure, thereby encoding the rod length and thus being readable at any position on the entire 360° circumference. Additionally or alternatively, the reader 50 is designed, for example, to be annular, such that scale 20 can be read at any rotational position of the two segments 272, 272', 272” and 273, 273', 273” relative to each other.

[0145] In some embodiments, the scale 20 is embedded in the rod 271. That is, the scale 20 can be (e.g., mechanically or during the assembly process of the rod 271) integrated or incorporated into the structure of one of the segments 272, 272', 272” and 273, 273', 273”.

[0146] As an alternative, some or all of the components are implemented as separate modules. For example, the complete encoder 10 can be provided as an add-on module to upgrade a conventional post. Thus, the scale 20 can, for example, clip onto segments 272, 272', 272” or 273, 273', 273”, and the reader 50 is clamped or secured to another segment 273, 273', 273” or 20, 272', 172”, thereby the encoder 10 preferably provides a self-calibration function. As another example, preferably, if the scale 20 is part of the lower portion 273, 273', 273”, in some embodiments, the lower portion 273, 273', 273” can be replaceable, such that posts 270, 270', 270” can be equipped with different lower portions 273, 273', 273” including different scales. Similarly, the reader 50 or the entire encoder 10 can be replaceable, for example, by a user in the field. As alternatives, units such as communication equipment, power units, or tilt sensors are implemented as (additional) modules, which can be replaceable.

[0147] The encoder 10 allows for continuous determination of the column height h. In some embodiments, the rods 271, 271', 271" are designed to provide several fixed locking positions for secure fixing of different column lengths. In this case, the encoder 10 can be used to control or verify these locking positions. For example, based on encoder measurements, it can be checked whether the locking position is actually installed, and if the locking position is not installed, for example, if the installed column length is only close to the locking position but not actually the locking position, a warning can be issued to the user. This principle can also be used to verify whether the locking position itself is the correct position, i.e., whether the actual locking position corresponds to its nominal position. For example, the locking position may change due to environmental or aging effects (which is particularly critical in the case of telescopic structures); however, the encoder 10 can be used to monitor the locking position. In the above cases, encoder measurements can be used to calibrate such different locking positions, thereby compensating for, for example, rod aging effects. Generally, it is advantageous to prevent measurement errors caused by incorrect assumptions about using the column length (when it is not actually the column length) based on the locking position.

[0148] like Figure 20 As shown, the actual column height h measured using the integrated absolute position encoder 10 can advantageously be automatically transmitted to the measurement unit 276. For example, as depicted, wireless communication 278, such as a wireless or mobile network between the column 270 and the TPS 276, is used to transmit the actual height value to the instrument 276 instantaneously and / or simultaneously with the measurement of the reference point. This value can then be signed with a unique identifier to securely and explicitly link it to the corresponding GNSS or distance measurement. Alternatively, the measured height h or any other measurement structure or processing data can be transmitted to other external instruments or control devices, such as field controllers, smartphones, or communication networks. Additionally or alternatively, as in Figure 19 As shown on the right side of the exemplary column 270, the column may include a display 279, and display operational data or measurement data such as column height h to the user on the display.

[0149] Furthermore, the corresponding communication device (not shown) can be configured to receive requests / demands to trigger (a) signals sent by the communication device and / or (b) codes read by the reader 50. Alternatively, triggering can be performed automatically if a significant change in position is detected. Additionally, or as an alternative, operation or action can be triggered by the operator of columns 270, 270', 270" for example, by pushing buttons provided at levers 273, 273', 273". Such an action is, for example, the command "store point" or "start target search", which is sent by the communication device to TPS 276, enabling remote control of TPS 276 in this manner.

[0150] Signals sent to survey instrument 276 or any other external control device may also optionally be based on the appropriate type of device located at the reference point. For example, the signal may also include information about whether the target type is a prism, certain parameters of the target (such as the amount of additional column length extension), and / or certain assignable parameters of a particular target.

[0151] To optionally further consider the tilt and / or orientation of survey columns 270, 270', 270" , the survey columns 270, 270', 270" may include tilt sensors and / or orientation sensors (not shown). Signals transmitted to total station 276 may also be based on the determined tilt and / or orientation. Either the optional tilt sensor and orientation sensor may, exemplarily, include at least one of an accelerometer, a gyroscope, and a geomagnetic sensor. Additional information about the six degrees of freedom state of the column is useful, for example, in the case of the column tilting against a ceiling or sidewall. Therefore, signals transmitted from columns 270, 270', 270" may include not only information about length or height h, but also information about vertical orientation relative to the gravitational field, tilt information, differential (delta) position and differential orientation information during column movement, and / or the absolute position of columns 270, 270', 270" .

[0152] Posts 270, 270', and 270" may have a power unit for supplying power to reader 50 and other units (such as the optional power-enabled communication equipment described above). In certain cases where survey posts 270, 270', and 270" also have a processing unit, this processing unit may also be supplied by the power unit. The power unit may include at least one of a rechargeable or non-rechargeable battery and, optionally, a power cable for obtaining power from an external source.

[0153] In the case of rechargeable batteries, columns 270, 270', 270" may include or be used for wireless or inductive charging devices. Such devices may include, for example, magnetic coils or NFC units. Alternatively or additionally, columns 270, 270', 270" are at least partially self-powered, as the power unit includes a generator, for example, configured to "harvest" electrical energy from the movement of columns 270, 270', 270" (e.g., when transporting or moving in a field) or the aforementioned length adjustment. This harvesting may be based on induction to convert the power of the length adjustment.

[0154] List of reference numerals

[0155] 2 Measurement Path

[0156] 10 Encoders

[0157] 20 rulers

[0158] 30; 30a, 30b Absolute position orbits

[0159] 32; 32a, 32b Discrete regions

[0160] 33; 33a, 33b Separation regions

[0161] Edges of the marked / transition sections: 37a, 37b, 37c

[0162] 38 Relative / Periodic Positions

[0163] 39 Absolute Position

[0164] 40 Incremental Orbits / Periodic Encoded Orbits

[0165] Marked with 42, 44, and 46

[0166] 50 Readers

[0167] 60a, 60b absolute sensing units

[0168] 70a-77a, 70b-77b detectors

[0169] 80 Incremental Sensing Units

[0170] 90-97 detector

[0171] 100 sliding calipers

[0172] 102 jaws

[0173] 104 jaws

[0174] 270, 270', 270” survey columns

[0175] 271, 271', 271” Surveying rods

[0176] 272", 272', 272" upper pole sections

[0177] 273, 273', 273" Lower pole sections

[0178] 274", 274", 274" retroreflector, target plate, GNSS antenna

[0179] 275", 275', 275” column tips

[0180] 276 Ground Positioning System (TPS)

[0181] 277 Geodetic Target Points

[0182] 278 Wireless Communication

[0183] 279 Monitor

[0184] h Survey column height

[0185] P pitch

[0186] A N Unique Identifier / Unique Numeric Code

[0187] B N Unique Identifier / Unique Numeric Code

[0188] A XN Instantaneous unique identifier / unique numeric code

[0189] B XN Instantaneous unique identifier / unique numeric code

[0190] T-space extension section

Claims

1. An absolute position encoder for a measuring instrument or an accessory for a measuring instrument, the absolute position encoder comprising a digital scale and a reader movable relative to the digital scale, the digital scale being arranged along a direction of travel of the reader, the digital scale comprising at least one absolute position track having a sequence of discrete regions clearly separated from each other by separation regions, and wherein, The reader includes a first series of detectors and a second series of detectors, the first series of detectors and the second series of detectors comprising a plurality of detectors, the first series of detectors and the second series of detectors being configured to sense the discrete region and the separated region to detect at least one of a first absolute position code and a second absolute position code, characterized in that the sequence of the discrete region and the first series of detectors and the second series of detectors are set such that at any possible position of the reader relative to the digital scale, at least one of the first series of detectors and the second series of detectors is not aligned with the transition portion between the discrete region and the separated region, and wherein the absolute position encoder is configured to select the first absolute position code or the second absolute position code read by the series of detectors that is not aligned with the transition portion.

2. The absolute position encoder according to claim 1, wherein, Selecting the first absolute position code or the second absolute position code includes testing whether the first absolute position code and the second absolute position code read by the corresponding first series detector and second series detector are consistent with the common assumed position of the reader.

3. The absolute position encoder according to claim 1, wherein, The digital scale also includes an additional track adjacent to and extending along the at least one absolute position track, and the absolute position encoder is configured to select either the first absolute position code or the second absolute position code based on a code derived from the additional track.

4. The absolute position encoder according to claim 3, wherein, The additional track is a periodic coded track that provides incremental position codes, and the absolute position encoder is configured to: The first absolute position code or the second absolute position code is selected based on the incremental position code; and Provide a precise absolute position code, which includes the highest valid portion derived from a selected first absolute position code or a second absolute position code and the lowest valid portion derived from the incremental position code.

5. The absolute position encoder according to claim 1, wherein, The digital scale includes a first absolute position track and a second absolute position track. The first absolute position track has a first sequence of discrete regions and separation regions between the discrete regions. The second absolute position track has a second sequence of discrete regions and separation regions between the discrete regions. The second sequence is a copy of the first sequence shifted along the travel direction of the reader, such that the discrete regions of the first absolute position track are offset by a constant pitch relative to the corresponding discrete regions of the second absolute position track. Each detector in the first series of detectors is laterally aligned with a corresponding detector in the second series of detectors relative to the travel direction. The first series of detectors is arranged to move along the first absolute position track, while the second series of detectors is arranged to move along the second absolute position track.

6. The absolute position encoder according to claim 1, wherein, The digital scale includes a unique absolute position track, which includes discrete regions and separation regions between the discrete regions. The first series of detectors and the second series of detectors are respectively positioned along a first row and a second row to detect at least one of the first absolute position code and the second absolute position code. The first row and the second row extend along the travel direction of the reader. Each detector in the first series of detectors is offset by a constant pitch relative to the corresponding detector in the second series of detectors along the direction of travel, or The detectors in the first series of detectors are interleaved with the detectors in the second series of detectors to form adjacent detector pairs of the first series of detectors and the second series of detectors.

7. The absolute position encoder of claim 1, wherein the absolute position encoder is configured as a linear position encoder or an angular position encoder.

8. The absolute position encoder according to claim 1, wherein, The discrete region of the at least one absolute position orbit differs from the separated region in that it possesses one of the following properties: optical opacity, optical reflectivity, electrical conductivity, magnetization, and magnetic permeability.

9. The absolute position encoder according to claim 4, wherein, The first absolute position code or the second absolute position code is selected based on the phase of the interpolation of the incremental position code.

10. The absolute position encoder according to claim 9, wherein, The least effective portion is derived from the interpolated phase.

11. A measuring instrument comprising the absolute position encoder of claim 1.

12. The measuring instrument of claim 11, wherein the measuring instrument is configured as a sliding caliper, the sliding caliper including a first jaw fixed relative to the digital scale and a second jaw slidable relative to the first jaw and fixed relative to the reader, wherein the absolute position encoder provides a value indicating the distance between the first jaw and the second jaw.

13. An accessory for a measuring instrument comprising the absolute position encoder of claim 1.

14. A survey post comprising an absolute position encoder according to claim 1, a first segment fixed relative to a digital scale, and a second segment slidable relative to the first segment and fixed relative to the reader, wherein the absolute position encoder provides a value indicating the height of the survey post.

15. A method for determining the position of a reader relative to a digital scale along a direction of travel, wherein, The digital scale includes at least one absolute position track, the at least one absolute position track including a pattern consisting of discrete regions and separation regions between the discrete regions; the pattern is detectable by a plurality of detectors in the reader, wherein the detectors are arranged along a first row and a second row aligned with the travel direction of the reader, the method comprising: determining a first absolute position code from detectors in the first row and determining a second absolute position code from detectors in the second row, characterized in that the discrete regions and the plurality of detectors are arranged such that at each possible position of the reader relative to the digital scale, at least one of the first row and the second row has no detector aligned with the transition portion between the discrete region and the separation region, and the method comprises: selecting either the first absolute position code or the second absolute position code provided by a row in which no detector is aligned with the transition portion.

16. The method according to claim 15, wherein, Selecting the first absolute position code or the second absolute position code includes: testing whether the first absolute position code and the second absolute position code are consistent with the common assumed position of the reader.

17. The method of claim 16, wherein the test comprises: i) treating the position given by the first absolute position code as a hypothetical position, ii) using the hypothetical position to determine which detectors in the second row are not facing the transition portion of the digital scale, iii) determining the expected value of the bit of the second absolute position code given the hypothetical position, and iv) comparing the expected value with the value of the corresponding bit of the second absolute position code that can be derived from the detectors not facing the transition portion.

18. The method of claim 15, wherein the method comprises: i) Determine incremental position codes from periodic encoded tracks on the digital scale; ii) Interpolate the phase values ​​of the incremental position codes; iii) Use the interpolated phase to select the absolute position codes; iv) Provide precise absolute position codes, which include the highest valid portion derived from the selected absolute position codes and the lowest valid portion derived from the interpolated phase.

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