DE102018251727A1 - Contaminant and defect resistant optical rotary position encoder configuration for providing displacement signals - Google Patents

Abstract

An optical encoder configuration includes a rotation scale, a lighting source, and a photodetector configuration. The illumination source is configured to output collimated light to the scale at a first illumination region, which is then output to the scale at a second illumination region from which the scale outputs a scale light forming a detector strip pattern comprising high and low intensity periodic bands which extend over a relatively longer dimension along the rotational direction and are relatively narrow and periodic along a detected strip movement direction transverse to the direction of rotation. The high and low intensity bands move along the detected strip motion direction as the scale grid shifts along the rotational direction. The photodetector configuration is configured to detect a shift of the high and low intensity bands and provide respective spatial phase shift signals indicative of the rotational scale shift.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation part of U.S. Patent Application Serial No. 15 / 942,135 titled "CONTAMINATION AND DEFECT RESISTANT OPTICAL ENCODER CONFIGURATION FOR PROVIDING DISPLACEMENT SIGNALS", filed March 30, 2018, which is a continuation subseq U.S. Patent Application Serial No. 15 / 858,218 entitled "CONTAMINATION AND DEFECT RESISTANT OPTICAL ENCODER CONFIGURATION FOR PROVIDING DISPLACEMENT SIGNALS", filed December 29, 2017; a partial continuation of the U.S. Patent Application Serial No. 15 / 702,520 entitled "CONTAMINATION AND DEFECT RESISTANT OPTICAL ENCODER CONFIGURATION FOR PROVIDING DISPLACEMENT SIGNALS", filed September 12, 2017; a partial continuation of the U.S. Patent Application Serial No. 15 / 637,750 entitled "CONTAMINATION AND DEFECT RESISTANT OPTICAL ENCODER CONFIGURATION FOR PROVIDING DISPLACEMENT SIGNALS", filed Jun. 29, 2017, the disclosures of which are hereby incorporated by reference in their entirety.

BACKGROUND

Technical area

The invention generally relates to instruments for precise position or displacement measurement, and more particularly to a coder configuration with signal processing that is error resistant and can be associated with a soiled or defective portion of a scale.

Description of the Related Art

Optical position sensors determine the displacement of a read head with respect to a scale comprising a pattern detected by the read head. Typically, position encoders use a scale that includes at least one scale track that has a periodic pattern, and the signals that originate from that scale track are periodic as a function of the displacement or position of the read head along the scale track. Absolute encoders can use multiple scale tracks to provide a unique combination of signals in any position along an absolute scale.

Optical encoders can use scale structures with incremental or absolute positions. A scale structure with incremental positions makes it possible to determine the displacement of a read head with respect to a scale by cumulating incremental displacement units starting at a starting point along the scale. Such encoders are suitable for certain applications, especially those where mains power is available. For low power applications (eg, battery powered gauges or the like), it is more desirable to use absolute position scale structures. Absolute position scale structures provide a unique output signal or a combination of signals at each position along a scale, thus enabling various energy saving measures. The U.S. Patent Nos. 3,882,482 ; 5,965,879 ; 5,279,044 ; 5,886,519 ; 5,237,391 ; 5,442,166 ; 4,964,727 ; 4,414,754 ; 4,109,389 ; 5,773,820 ; and 5,010,655 disclose various encoder configurations and / or signal processing techniques relevant to absolute position encoders and are hereby fully incorporated by reference.

Some encoder configurations offer certain advantages by using a light diffraction grating of the illumination source in a lighting section of the encoder configuration. The U.S. Patents No. 8,941,052 ; 9,018,578 ; 9,029,757 ; and 9,080,899 , which are all incorporated herein by reference, disclose such encoder configurations. Some of the configurations disclosed in these patents may also be characterized as using super-resolution moiré imaging.

In various applications, scale manufacturing defects or contaminants, such as dust or oils, on a scale track can interfere with the pattern detected by the read head and produce errors in the resulting position or displacement measurements. In general, the size of defects due to a defect or contaminant may depend on factors such as the size of the defect or contaminant, the wavelength of the periodic pattern on the scale, the size of the readhead detector region, the relationship between these quantities, and depend on the like. Various methods are known for responding to abnormal signals in an encoder. Almost all of these procedures are based on deactivating the encoder signals or providing an "error signal" to alert the user, or to adjust the intensity of a light source to amplify weak signals, or the like. However, such methods do not provide a means to continue accurate measurements, despite the abnormal signals resulting from certain types of scale defects and contaminants. Therefore, the usefulness of these methods is limited. A well-known method that actually reduces the effects of scale contaminants or defects on the measurement accuracy is disclosed in Japanese Patent Application JP2003-065803 (Application '803). The '803 application teaches a method in which two or more photodetectors output periodic signals having the same phase and each input to respective signal stability judging means. The signal stability judging means outputs only signals judged to be "normal", and "normal" signals are combined as a basis for the position measurement. Signals that are "abnormal" are excluded from the position measurement calculations. However, the methods of judging "normal" and "abnormal" signals disclosed in the '803 application have certain disadvantages that limit the usefulness of the teachings of the' 803 application.

The U.S. Patent No. 8,493,572 ('572 patent) discloses a stain and defect resistant optical encoder configuration that provides a means to select signals from photodetector elements that are not subject to fouling. However, the '572 patent relies on elaborate signal processing, which may be less desirable in some applications.

Improved methods of providing accurate measurements that avoid or mitigate abnormal signals resulting from certain types of scale defects or fouling without the need for elaborate signal processing would be desirable.

SUMMARY

A fouling and defect resistant optical rotary position encoder configuration for providing displacement signals includes a rotation scale, a lighting source, and a photodetector configuration. The rotary scale extends along a rotational direction about an axis of rotation. The rotary scale includes a rotary scale grille comprising scale grid bars disposed on a rotating surface along the rotational direction. The scale grid bars are narrow along the rotational direction and elongated along a direction of the rotary scale bars transverse to the rotational direction, and are graduated in scale P _SF arranged periodically along the rotational direction. The illumination source includes a light source that outputs collimated light to a first illumination region on the rotation scale that is configured to input the light and structured illumination along an optical path LP to output to a second illumination region on the rotation scale, wherein the structured illumination comprises an illumination strip pattern comprising strips which are narrow along the rotational direction and are elongated along an illumination pattern direction which is oriented transversely to the rotational direction. The photodetector configuration includes a set of N spatial phase detectors with a detector spacing PD along a detected strip movement direction transverse to the measuring axis direction, each spatial phase detector configured to provide a respective spatial phase detector signal, and at least a majority of the respective spatial phase detectors extend over a relatively longer dimension along the rotation direction and along the detected strip movement direction across The rotation direction is relatively narrow, and the set of N spatial phase detectors in a spatial phase sequence along the detected strip movement direction is arranged. The rotary lattice grating is configured to input the illumination strip pattern at the second illumination region and to output scale light forming a fringe pattern to the photodetector configuration, the fringe pattern comprising high and low intensity periodic bands extending over a relatively longer dimension along the rotational direction and relative narrow and periodic with a detected fringe period PDF along the detected strip movement direction transverse to the direction of rotation. The direction of the rotary lattice bars is oriented with respect to the axis of rotation at a yaw angle ψ not equal to zero. The detected strip period PDF and the detected strip movement direction are transverse to the direction of rotation and are at least partially dependent on the yaw angle ψ not equal to zero. The high and low intensity bands move along the detected strip movement direction transverse to the direction of rotation as the scale grid rotates about the axis of rotation. The photodetector configuration is configured to detect displacement of the high and low intensity bands along the detected strip movement direction transverse to the direction of rotation and to provide respective spatial phase shift signals indicative of the rotation scale offset.

list of figures

• 1 ein unvollständiges schematisches auseinandergezogenes Diagramm einer verschmutzungs- und defektbeständigen optischen Codiererkonfiguration zum Bereitstellen von Verschiebungssignalen.
• 2 ein unvollständiges schematisches Diagramm einer verschmutzungs- und defektbeständigen optischen Codiererkonfiguration zum Bereitstellen von Verschiebungssignalen.
• 3 ein unvollständiges schematisches Diagramm einer Fotodetektorkonfiguration einer verschmutzungs- und defektbeständigen optischen Codiererkonfiguration.
• 4A ein schematisches Diagramm eines Abschnitts einer Fotodetektorkonfiguration einer verschmutzungs- und defektbeständigen optischen Codiererkonfiguration.
• 4B ein schematisches Diagramm eines Abschnitts einer Fotodetektorkonfiguration einer verschmutzungs- und defektbeständigen optischen Codiererkonfiguration.
• 5 ein unvollständiges schematisches Diagramm einer zusätzlichen Umsetzung einer verschmutzungs- und defektbeständigen optischen Codiererkonfiguration zum Bereitstellen von Verschiebungssignalen, wobei sich ein Detektorstreifenmuster während der Verschiebung des optischen Codierers quer zur Messachsenrichtung bewegt.
• 6A ein schematisches Diagramm, das eine erste Ansicht von Skalenlichtkomponenten darstellt, die ein Detektorstreifenmuster in der Nähe einer Fotodetektorkonfiguration bilden, die räumliche Phasendetektoren umfasst, die ungefähr entlang der Messachsenrichtung länglich sind und quer zur Messachsenrichtung periodisch angeordnet sind.
• 6B ein schematisches Diagramm, das eine zweite Ansicht von Skalenlichtkomponenten darstellt, die ein Detektorstreifenmuster in der Nähe einer Fotodetektorkonfiguration bilden, die räumliche Phasendetektoren umfasst, die ungefähr entlang der Messachsenrichtung länglich sind und quer zur Messachsenrichtung periodisch angeordnet sind.
• 7 eine Grafik der Eigenschaften eines verschmutzungs- und defektbeständigen optischen Codierers ähnlich wie der in 5 und 6 dargestellte optische Codierer, der eine detektierte Streifenperiode statt eines Beleuchtungsstreifen-Gierwinkels umfasst.
• 8 ein schematisches Diagramm einer beispielhaften Fotodetektorkonfiguration, die in einem verschmutzungs- und defektbeständigen optischen Codierer ähnlich wie der in 5 und 6 dargestellte optische Codierer verwendbar ist, wobei die Fotodetektorkonfiguration räumliche Phasendetektoren umfasst, die ungefähr entlang der Messachsenrichtung länglich sind und quer zur Messachsenrichtung periodisch angeordnet sind.
• 9A ein ausführliches schematisches Diagramm eines Teilabschnitts einer anderen beispielhaften Fotodetektorkonfiguration eines verschmutzungs- und defektbeständigen optischen Codierers, die ähnlich wie die in 8 gezeigte Fotodetektorkonfiguration ist.
• 9B ein ausführliches schematisches Diagramm eines Teilabschnitts einer anderen beispielhaften Fotodetektorkonfiguration eines verschmutzungs- und defektbeständigen optischen Codierers, die ähnlich wie die in 8 gezeigte Fotodetektorkonfiguration ist.
• 10 ein unvollständiges schematisches Diagramm einer zusätzlichen Umsetzung einer verschmutzungs- und defektbeständigen optischen Codiererkonfiguration.
• 11A ein schematisches Diagramm eines ersten Beugungsgitters einer Beleuchtungsquelle.
• 11B ein schematisches Diagramm eines zweiten Beugungsgitters einer Beleuchtungsquelle.
• 12 ein unvollständiges schematisches Diagramm einer zusätzlichen Umsetzung einer verschmutzungs- und defektbeständigen optischen Codiererkonfiguration.
• 13A ein schematisches Diagramm, das eine erste Ansicht von Skalenlichtkomponenten darstellt, die ein Detektorstreifenmuster in der Nähe einer Fotodetektorkonfiguration bilden.
• 13B ein schematisches Diagramm, das eine zweite Ansicht von Skalenlichtkomponenten darstellt, die ein Detektorstreifenmuster in der Nähe einer Fotodetektorkonfiguration bilden.
• 13C ein schematisches Diagramm, das eine dritte Ansicht von Skalenlichtkomponenten darstellt, die ein Detektorstreifenmuster in der Nähe einer Fotodetektorkonfiguration bilden.
• 13D ein schematisches Diagramm, das eine vierte Ansicht von Skalenlichtkomponenten darstellt, die ein Detektorstreifenmuster in der Nähe einer Fotodetektorkonfiguration bilden.
• 14 ein unvollständiges schematisches Diagramm einer ersten Umsetzung einer verschmutzungs- und defektbeständigen optischen Drehpositionsgeberkonfiguration zum Bereitstellen von Verschiebungssignalen.
• 15 ein schematisches Diagramm eines Abschnitts des Drehskalengitters aus 14, das zusätzliche Einzelheiten zeigt.
• 16 ein unvollständiges schematisches Diagramm einer zweiten Umsetzung einer verschmutzungs- und defektbeständigen optischen Drehpositionsgeberkonfiguration zum Bereitstellen von Verschiebungssignalen.

The foregoing aspects and many of the attendant advantages will be more readily appreciated as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. Show it:

• 1 an incomplete schematic exploded diagram of a contamination and defect resistant optical encoder configuration for providing displacement signals.
• 2 an incomplete schematic diagram of a contamination and defect resistant optical encoder configuration for providing displacement signals.
• 3 an incomplete schematic diagram of a photodetector configuration of a contamination and defect resistant optical encoder configuration.
• 4A a schematic diagram of a portion of a photodetector configuration of a contamination and defect-resistant optical encoder configuration.
• 4B a schematic diagram of a portion of a photodetector configuration of a contamination and defect-resistant optical encoder configuration.
• 5 an incomplete schematic diagram of an additional implementation of a pollution and defect resistant optical encoder configuration for providing displacement signals, wherein a detector strip pattern moves during the displacement of the optical encoder transversely to the measuring axis direction.
• 6A 12 is a schematic diagram illustrating a first view of scale light components that form a detector strip pattern in the vicinity of a photodetector configuration that includes spatial phase detectors that are elongated approximately along the measurement axis direction and periodically disposed transverse to the measurement axis direction.
• 6B 12 is a schematic diagram illustrating a second view of scale light components forming a detector strip pattern in the vicinity of a photodetector configuration that includes spatial phase detectors that are elongated approximately along the measurement axis direction and periodically disposed transverse to the measurement axis direction.
• 7 a graph of the properties of a pollution- and defect-resistant optical encoder similar to that in 5 and 6 illustrated optical encoder comprising a detected stripe period instead of a lighting stripe yaw angle.
• 8th 12 is a schematic diagram of an exemplary photodetector configuration used in a fouling and defect resistant optical encoder similar to that in FIG 5 and 6 illustrated optical encoder, wherein the photodetector configuration comprises spatial phase detectors which are elongated approximately along the measuring axis direction and periodically arranged transversely to the measuring axis direction.
• 9A 12 is a detailed schematic diagram of a portion of another exemplary photodetector configuration of a contamination and defect resistant optical encoder similar to that of FIG 8th is shown photodetector configuration.
• 9B 12 is a detailed schematic diagram of a portion of another exemplary photodetector configuration of a contamination and defect resistant optical encoder similar to that of FIG 8th is shown photodetector configuration.
• 10 an incomplete schematic diagram of an additional implementation of a pollution and defect resistant optical encoder configuration.
• 11A a schematic diagram of a first diffraction grating of a lighting source.
• 11B a schematic diagram of a second diffraction grating of a lighting source.
• 12 an incomplete schematic diagram of an additional implementation of a pollution and defect resistant optical encoder configuration.
• 13A 12 is a schematic diagram illustrating a first view of scale light components forming a detector strip pattern in the vicinity of a photodetector configuration.
• 13B 12 is a schematic diagram illustrating a second view of scale light components forming a detector strip pattern in the vicinity of a photodetector configuration.
• 13C 12 is a schematic diagram illustrating a third view of scale light components forming a detector strip pattern in the vicinity of a photodetector configuration.
• 13D 12 is a schematic diagram illustrating a fourth view of scale light components that form a detector strip pattern in the vicinity of a photodetector configuration.
• 14 an incomplete schematic diagram of a first implementation of a pollution and defect resistant optical rotary position encoder configuration for providing displacement signals.
• 15 a schematic diagram of a portion of the rotary scale grating 14 showing additional details.
• 16 an incomplete schematic diagram of a second implementation of a contamination and defect-resistant optical rotary position encoder configuration for providing displacement signals.

DETAILED DESCRIPTION

1 Figure 4 is an incomplete schematic exploded diagram of a contamination and defect resistant optical encoder configuration 100 for providing displacement signals. The encoder configuration 100 includes a scale grid 110 , a lighting section 120 and a photodetector configuration 160 ,

1 shows the orthogonal X - Y - and Z Directions according to a convention used here. The X - and Y Directions are parallel to the plane of the scale grid 110 , where the X Direction parallel to a measuring axis direction MA (eg at right angles to elongated pattern elements of the scale grid 110 ). The Z Direction is perpendicular to the plane of the scale grid 110 ,

At the in 1 The implementation shown is the scale grid 110 a permeable grid. The scale grid 110 extends along a measuring axis direction MA and includes a periodic pattern including bars along the measuring axis direction MA are narrow and along a direction leading to the measuring axis direction MA (ie the Y Direction) are rectangular, oblong, and along the measuring axis direction MA are arranged periodically.

The lighting section 120 includes a source of illumination 130 , a first lighting grid 140 and a second lighting grid 150 , The illumination source 130 includes a light source 131 and a collimation lens 132 , The light source 131 is configured to source light 134 to the collimating lens 132 issue. The collimation lens 132 is configured to source light 134 to receive and collimated source light 134 ' to the first lighting grid 140 issue. The first lighting grid 140 receives the source light 134 ' and bends the source light 134 ' towards the second lighting grid 150 , The second lighting grid 150 receives the source light 134 ' and bends the source light 134 ' continue towards the scale grid 110 along an original beam path SOLP , The scale grid 110 gives the source light 134 ' along the original beam path SOLP and gives scale light, which is a periodic scale light pattern 135 includes, along a Skalenstrahlengang SCLP to the photodetector configuration 160 out. The photodetector configuration 160 receives the periodic scale light pattern 135 from the scale grid 110 along the scale beam path SCLP , The periodic scale light pattern 135 shifts to the photodetector configuration 160 passing, indicating a relative shift between the scale grid 110 and the photodetector configuration 160 along the measuring axis direction MA equivalent. An example of a photodetector configuration similar to the photodetector configuration 160 is in 3 shown in detail. The photodetector configuration 160 includes a set of N spatial phase detectors operating in a spatial phase sequence along a direction transverse to the measuring axis direction MA (ie the Y Direction) are arranged, wherein N is an integer that is at least 6, and the spatial phase sequence comprises two outer spatial phase detectors at the beginning and end of the sequence along the direction transverse to the measurement axis and an inner group of spatial phase detectors located between the two outer spatial phase detectors , At the in 1 The implementation shown includes the sentence of N spatial phase photodetectors 3 Subsets of spatial phase detectors S ₁ . S ₂ and S ₃ which have the same subset of the spatial phase sequence.

At least a majority of the respective spatial phase detectors are along the measuring axis direction MA relatively oblong and along the direction to the measuring axis direction MA (ie the Y Direction) is rectangular, relatively narrow, and includes scale light receiving areas along the measuring axis direction MA are spatially periodic and correspondingly positioned to a respective spatial phase of this spatial phase detector with respect to the periodic scale light pattern, and is configured to provide a respective spatial phase detector signal. Each spatial phase detector in the inner group is included in the spatial phase sequence by spatial phase detectors having respective spatial phases different from and different from each other in this spatial phase detector.

In various applications, the photodetector configuration 160 and the lighting section 120 be mounted in a fixed relationship to each other, eg in a readhead or meter housing (not shown), and become along the measuring axis direction MA with reference to the scale grid 110 passed through a storage system according to known techniques. The scale grid 110 may be attached to a movable plate or a meter spindle or the like in various applications.

It is understood that the stain and defect resistant optical encoder configuration 100 is just one example of a stain and defect resistant optical encoder configuration according to the principles disclosed herein. In alternative implementations, various optical components may be used, such as a telecentric imaging system, restrictive apertures, and the like. In alternative implementations, a lighting section may comprise only a single lighting grid.

2 FIG. 10 is an incomplete schematic diagram of a contamination and defect resistant optical encoder configuration. FIG 200 for providing displacement signals. The optical encoder configuration 200 is similar to the encoder configuration 100 , Similar reference numbers 2XX in 2 and 1 XX in 1 may refer to similar elements unless otherwise indicated by the context or description. In the 2 shown encoder configuration 200 is a reflective configuration. The scale 210 is a reflective scale grid.

3 is an incomplete schematic diagram of a photodetector configuration 360 a contamination and defect resistant optical encoder configuration 300 , The stain and defect resistant optical encoder configuration 300 can be similar to the stain and defect resistant optical encoder configuration 100 or the stain and defect resistant optical encoder configuration 200 his. The photodetector configuration 360 includes a set of N spatial phase detectors operating in a spatial phase sequence along a direction transverse to the measuring axis direction MA are arranged, wherein N is an integer that is at least 6, and the spatial phase sequence comprises two outer spatial phase detectors at the beginning and end of the sequence along the direction transverse to the measurement axis and an inner group of spatial phase detectors located between the two outer spatial phase detectors , At least a majority of the respective spatial phase detectors are along the measuring axis direction MA relatively oblong and along the direction to the measuring axis direction MA is rectangular, relatively narrow, and includes scale light receiving areas along the measuring axis direction MA are spatially periodic and correspondingly positioned to a respective spatial phase of this spatial phase detector with respect to the periodic scale light pattern, and is configured to provide a respective spatial phase detector signal. Each spatial phase detector in the inner group is included in the spatial phase sequence by spatial phase detectors having respective spatial phases different from and different from each other in this spatial phase detector.

In some implementations, the sentence of N spatial phase photodetectors at least M Subsets of spatial phase detectors, wherein M is an integer that is at least equal to 2, and where each of the M Subsets comprise spatial phase detectors that provide each of the respective spatial phases included in the set of N spatial phase photodetectors are included. In some implementations can M at least equal to 3. In some implementations can M at least equal to 6. In some implementations, each of the M Subsets of spatial phase detectors comprise spatial phase detectors which provide the same respective spatial phases arranged in the same subset of the spatial phase sequence. 3 shows an implementation with M Subsets of spatial phase detectors using S ₁ to S _M are indicated. The subset S ₁ includes the spatial phase detectors SPD _1A . SPD _1B . SPD _1C and SPD _1D , The subset S ₂ includes the spatial phase detectors SPD _2A . SPD _2B . SPD _2C and SPD _2D , The subset S _M includes the spatial phase detectors SPD _MA . SPD _MB . SPD _MC and SPD _MD , Each of the spatial phase detectors in 3 is shown as he K Has scale light receiving areas. As an example of the scale light receiving areas is the spatial phase detector SPD _MD with the scale light receiving areas SLRA _M1 and SLRA _MK designated. In some implementations can K be an even value.

At the in 3 As shown, the spatial phase sequence is indicated by spatial phase detectors, which are the subscripts A . B . C and D include (eg the spatial phase detectors SPD _1A . SPD _1B . SPD _1C and SPD _ID ). The spatial phase detectors with subscripts A and D For example, the two outer spatial phase detectors are at the beginning and end of each instance of the spatial phase sequence. The spatial phase detectors with subscripts B and C are the inner groups.

The spatial phase detectors SPD _1A . SPD _1B . SPD _1C and SPD _1D give respective spatial phase detector signals A ₁ . B ₁ . C ₁ and D ₁ out. The spatial phase detectors SPD _2A . SPD _2B . SPD _2C and SPD _2D give respective spatial phase detector signals A ₂ . B ₂ . C ₂ and D ₂ out. The spatial phase detectors SPD _MA . SPD _MB . SPD _MC and SPD _MD give respective spatial phase detector signals A _M . B _M . C _M and D _M out.

A contamination and defect resistant optical encoder configured in accordance with the principles disclosed herein provides a simple design suitable for contaminants (eg wire bonding contamination) up to 100 micrometers in size and scale defects up to 300 micrometers are big, can be tolerant. Contaminants or defects on a scale typically create a common mode error component on adjacent spatial phase detectors that can be canceled in signal processing (eg, quadrature processing). Spatial phase detectors along the measuring axis direction MA relatively oblong and along the direction to the measuring axis direction MA rectangular, relatively narrow, provide better resistance to contamination and defects. The signal levels may change more slowly by the frequency of the structure of the spatial phase detectors along the measuring axis direction MA is reduced. Further, such an encoder does not require complex signal processing to provide tolerance to fouling and defects. Signals by the sentence of N spatial phase detectors can be processed according to standard techniques known to those skilled in the art.

In some implementations, such as in 3 shown implementation is N at least equal to 8, and each subset of spatial phase detectors may comprise 4 spatial phase detectors having respective spatial phases separated by 90 degrees. In alternative implementations, each subset of spatial phase detectors may comprise three spatial phase detectors comprising respective spatial phases separated by 120 degrees.

At the in 3 The implementation shown includes the photodetector configuration 360 Compounds configured to combine spatial phase detector signals corresponding to the same respective spatial phase and to output each such combination as a respective spatial phase position signal. The photodetector configuration 360 is configured to output four spatial phase position signals corresponding to spatial phases separated by 90 degrees. The spatial phase signals with the same letter designation (eg A ₁ . A ₂ and A _M ) are combined (eg summed) to the spatial phase signals ΣA . .sigma..sub.B . ΣC and ΣD provide. In alternative implementations, a photodetector configuration may be configured to output three spatial phase position signals corresponding to spatial phases separated by 120 degrees. In both cases, the spatial phase position signals may also be used to determine displacement signals, eg by quadrature or three-phase signal processing.

In some implementations, each of the respective spatial phase detectors may be along the measuring axis direction MA relatively oblong and along the direction to the measuring axis direction MA is rectangular, relatively narrow, and may include scale light receiving areas along the measuring axis direction MA are spatially periodic and correspondingly positioned to a respective spatial phase of this spatial phase detector with respect to the periodic scale light pattern, and may be configured to provide a respective spatial phase detector signal.

In some implementations, one dimension YSLRA the scale light receiving areas of each of the N spatial phase detectors along the Y Direction at most 250 microns. In some implementations can YSLRA at least 5 microns.

In some implementations, a separation distance YSEP between the scale light receiving areas of each adjacent pair of N spatial phase detectors along the Y Direction at most 25 microns.

In some implementations, one dimension YSLRA the scale light receiving areas of each of the N spatial phase detectors along the Y Direction be the same. In some implementations, a separation distance YSEP between the scale light receiving areas of each adjacent pair of N spatial phase detectors along the Y Direction be the same.

It is understood that it, although a great value of N provides a greater robustness against pollution, thereby compromising that it may be a great value of N provides smaller signal levels within each individual spatial phase detector.

4A Figure 12 is a schematic diagram of a portion of a photodetector configuration 460A a contamination and defect resistant optical encoder configuration 400A , For simplicity's sake 4A only a subset of spatial phase detectors S ₁ with two spatial phase detectors SPD _1A and SPD _1B , It is understood that the photodetector configuration 460A at least six spatial phase detectors in accordance with the principles disclosed herein, but only two are shown for simplicity. At the in 4A Each implementation includes the implementation shown N spatial phase detectors (eg the spatial phase detectors SPD _1A and SPD _1B ) a photodetector (eg the photodetectors PD _1A and PD _1B , which are indicated by dashed lines), which is covered by a spatial phase mask (eg the phase masks PM _1A and PM _1B ), which prevents the photodetector from receiving the periodic scale light pattern except through the openings contained in the spatial phase mask. In this case, the scale light receiving areas include areas of the photodetectors (eg, the photodetectors PD _1A and PD _1B ) passing through the openings in the respective spatial phase masks (eg the spatial phase masks PM _1A and PM _1B ) are exposed through. At the in 4A The conversion shown are the scale light receiving areas (ie, the openings) of the phase mask PM _1B with respect to the scale light receiving areas of the phase mask PM _1A along the measuring axis direction MA offset by 90 degrees. It is understood that although the spatial phase masks PM _1A and PM _1B in 4A schematically depicted as separate sections, in some implementations, they may conveniently be made of the same material in the same process to eliminate any positioning errors.

4B Figure 12 is a schematic diagram of a portion of a photodetector configuration 460B a contamination and defect resistant optical encoder configuration 400B , For simplicity's sake 4B only a subset of spatial phase detectors S ₁ ' with two spatial phase detectors SPD _1A ' and SPD _1B ' , It is understood that the photodetector configuration 460B at least six spatial phase detectors in accordance with the principles disclosed herein, but for simplicity only two are shown. At the in 4B Each implementation includes the implementation shown N spatial phase detectors (eg the spatial phase detectors SPD _1A ' and SPD _1B ' ) a periodic grid of electrically interconnected photodetector areas that receive the periodic scale light pattern. In this case, the scale light receiving areas include the photodetector areas of the periodic grid of photodetectors. At the in 4B The implementation shown are the photodetector areas of the spatial phase detector SPD _1B ' with respect to the photodetector areas of the spatial phase detector SPD _1A 'along the measuring axis direction MA offset by 90 degrees.

5 FIG. 10 is an incomplete schematic diagram of additional implementation of a stain and defect resistant optical encoder configuration. FIG 500 for providing displacement signals. In the encoder configuration 500 includes the periodic scale light pattern 535 which is detected, a detector strip pattern 535 comprising straps oriented to extend over a relatively longer dimension along the measuring axis direction MA and extending transversely to the measuring axis direction along a detected strip movement direction DFMD during the displacement of the optical encoder.

The encoder configuration 500 includes a scale 510 , a source of illumination 520 and a photodetector configuration 560 , The scale 510 extends along a measuring axis direction MA and includes a scale grid, the grid bars GB includes, in a scale plane SP are arranged, which are the Meßachsenrichtung MA nominally parallel, with the bars GB along the measuring axis direction MA are narrow and along a grid bar direction GBD transverse to the measuring axis direction MA are elongated, and with a graduation P _SF along the measuring axis direction MA are arranged periodically. The illumination source 520 includes a light source 530 , the light 534 ' issues, and a section 533 to generate a structured lighting that is configured to light 534 ' to enter and a structured lighting 534 '' to a lighting region IR at the scale level SP spend the structured lighting 534 '' a lighting strip pattern IFP comprising strips along the measuring axis direction MA narrow and along a lighting strip direction IFD to the measuring axis direction MA in one Illuminating strip yaw angle ψ not equal to zero with respect to the grating bar direction GBD oriented transversely, are elongated. The light source 530 includes a point source 531 and a collimation lens 532 , The point source 531 spend light 534 to the collimating lens, then the light 534 collapsed to the light 534 ' provide. The illumination strip yaw angle ψ non-zero can be achieved in various implementations by adding one or more elements of the section 533 to generate a structured lighting (eg one of the elements 540 and or 550 ) to the Z -Axis around to a desired angle with respect to the Y -Axis is turned. In some embodiments, the non-zero illumination strip yaw angle auch may also be achieved or extended by adjusting the grating bar direction GBD to the Z -Axis around to a desired angle with respect to the Y -Axis is turned.

The photodetector configuration 560 includes a set of N spatial phase detectors with a detector spacing PD (in 6A and 6B shown) along a detected strip movement direction DFMD transverse to the measuring axis direction MA are arranged periodically, wherein each spatial phase detector is configured to provide a respective spatial phase detector signal, and at least a majority of the respective spatial phase detectors over a relatively longer dimension along the measuring axis direction MA extends and along the detected strip movement direction DFMD is relatively narrow across the measuring axis, and the theorem of N spatial phase detectors in a spatial phase sequence along the detected strip motion direction DFMD is arranged as below with reference to 8th . 9A and 9B will be described in more detail.

The scale 510 is configured to reflect the illumination strip pattern at the illumination region IR and input the scale light components along a scale beam path SCLP to output the detector strip pattern 535 at the photodetector configuration 560 to build. The detector strip pattern 535 includes periodic high and low intensity bands extending over a relatively longer dimension along the measuring axis direction MA extend and are relatively narrow and with a detected fringe period PDF along the detected strip movement direction DFMD transverse to the measuring axis direction MA are periodic, as described below with reference to 6 will be described in more detail. As a way to describe their orientation, the bands extend over a relatively longer dimension along the measuring axis direction MA However, in various implementations, this does not mean that they must be aligned along the measuring axis direction. In various exemplary implementations, the bands may be oriented at a medium or small angle with respect to the measuring axis direction, as described below with reference to FIGS 6 is explained.

The detected stripe period PDF and the detected strip movement direction DFMD transverse to the measuring axis direction MA are at least partially dependent on the illumination strip yaw angle ψ not equal to zero, as described below with reference to FIG 7 is addressed. The high and low intensity bands move along the detected strip motion direction DFMD transverse to the measuring axis direction MA if the scale is 510 along the measuring axis direction MA shifts. The photodetector configuration 560 is configured to shift the high and low intensity bands along the detected strip motion direction DFMD transverse to the measuring axis direction MA detect and provide respective spatial phase shift signals indicative of the scale shift.

At the in 5 The implementation shown in the section covers 533 for generating a structured illumination, a first light diffraction grating 540 the illumination source and a second light diffraction grating 550 the illumination source. In some implementations, the first light diffraction grating 540 the illumination source and the second light diffraction grating 550 the illumination source be phase grating. Phase gratings provide better power efficiency by reducing light losses.

A contamination and defect resistant optical encoder constructed according to the principles described with reference to 5 to 9B can be described, provides a simple design that can be tolerant to contaminants (eg wire bonding contamination) up to 100 microns in size and scale defects up to 300 microns in size. Contaminants or defects on a scale that are similar to or larger than the detection strip period typically produce a common mode error component on adjacent spatial phase detectors that may be canceled in signal processing (eg, quadrature processing). That is, the effect of contamination moving along the measuring axis direction tends to be shared with the adjacent spatial phase detectors and moves along the measuring axis direction at these adjacent spatial phase detectors as the scale or read head configuration moves along the measuring axis direction. Because the fouling effect is a common mode effect across adjacent spatial phase detectors, and because the spatial phase detectors have a dimension along the measuring axis direction which is the size of the Can significantly exceed the effect of contamination, are relatively elongated, the effect of contamination on the accuracy of the displacement signal can be significantly reduced. Another advantage is that, in the event of a possible non-common mode residual error, when the photodetector configuration becomes 560 with reference to the scale 510 shifts portions of the detector strip pattern 535 , which correspond to a defect, move much more slowly from one spatial phase detector to the other, allowing a more effective compensation of the spatial phase shift signals. Such an encoder does not require extensive signal processing to provide tolerance for fouling and defects. The spatial phase shift signals generated by the set of N spatial phase detectors can be processed according to standard techniques known to those skilled in the art.

6A Fig. 12 is a diagram schematically illustrating a first view of the scale light components SL1 and SL2 representing a detector strip pattern 635 similar to or identical to the detector strip pattern 535 is that near a photodetector configuration 660 shown is similar to the photodetector configuration 560 in 5 is. The detector strip pattern 635 can be provided by an optical encoder similar to the optical encoder configuration 500 is that with respect to 5 was addressed. 6A shows a cross section of the scale light, which the detector strip pattern 635 in a plane formed by a measuring axis direction MA and a scale beam path SCLP is defined as before with reference to 5 shown. As in 6A As shown, the scale light components include a first scale light component SL1 and a second scale light component SL2 (indicated by dashed lines representing high intensity bands) each comprising parallel beams, the parallel beams of the first scale light component SL1 along one direction with one in relation to the scale beam path SCLP lie opposite angle orientation. The first scale light component SL1 and the second scale light component SL2 overlap around the detector strip pattern 635 according to known principles. The first scale light component SL1 and the second scale light component SL2 may be formed of different diffraction orders from a section for generating a structured illumination. The detector strip pattern 635 includes dark or low intensity interference bands 635D , which are indicated by bold lines, and bright or high intensity interference bands 635L , which are indicated by dashed outlines.

6B Fig. 12 is a diagram schematically showing a second view of the scale light components SL1 and SL2 represents the striped pattern 635 form. 6A shows a cross section of the detector strip pattern 635 in a plane passing through a measuring axis direction MA and a Y Direction is defined as above with reference to 5 shown close to the photodetector configuration 660 lies. The detector strip pattern 635 includes dark or low intensity interference bands 635D , which are indicated by bold lines, and bright or high intensity interference bands 635L , which are indicated by dashed lines, with a detected stripe period PDF along the detected strip movement direction DFMD are periodic, as in 6B shown. The detected strip movement direction is generally transverse to the direction of the interference bands 635D and 635L with a small rotation equal to the illumination strip yaw angle ψ not equal to zero with respect to the Y direction.

7 is a graphic 700 the properties of a stain and defect resistant optical encoder similar to the optical encoder configuration 500 , in the 5 and 6 showing a detected fringe period PDF instead of a lighting strip yaw angle ψ. The graphic 700 FIG. 12 shows data for a fouling and defect resistant optical encoder having a structured illumination generating portion with a first light diffraction grating of the illumination source, which has a grating pitch. FIG P ₁ a second light diffraction grating of the illumination source having a pitch P ₂ and a scale representing a scale graduation P _SF which satisfies the following expression includes: $$\frac{1}{P_2}-\frac{1}{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="DE102018251727A1\_0014.png,DE102018251727A1\_0020.png"\; state="\{\{state\}\}">P</figure-callout>}}_1}=\frac{1}{P_{SF}}$$

The detected stripe period PDF is then related to the illumination strip yaw angle ψ by the following expression: $$PDF=\frac{P_{SF}}{4sin\left(\raisebox{1ex}{$\Psi $}\!\left/ \!\raisebox{-1ex}{$2$}\right.\right)}$$

It is generally desirable that a stain and defect resistant optical encoder be configured such that the detected fringe period PDF is large (eg, greater than 7 microns, or greater than 40 microns in some implementations), which requires a small value for the illumination stripe yaw angle ψ (eg, less than 7 degrees). A larger detected fringe period PDF Provides a better tolerance for measurement errors due to misalignment between a scale, a photodetector configuration, and a lighting source. Errors resulting from tilting and rolling of a scale with respect to a source of illumination and / or a photodetector configuration are inversely proportional to the detected fringe period PDF , Therefore, represents a larger detected fringe period PDF better robustness for measurement errors caused by scale ripple.

8th is a schematic diagram 800 an exemplary photodetector configuration 860 usable in a stain and defect resistant optical encoder similar to the optical encoder configuration 500 is that in 5 and 6 wherein the photodetector configuration comprises spatial phase detectors which are approximately oblong or coarse along the measuring axis direction and periodically arranged transversely to the measuring axis direction. Similar reference numbers 8XX in 8th and 5 XX in 5 may refer to similar elements unless otherwise indicated by the context or the description.

The photodetector configuration 860 includes a set of N spatial phase detectors operating in a spatial phase sequence along the detected strip motion direction DFMD are arranged, wherein N is an integer that is at least 6, and the spatial phase sequence includes two outer spatial phase detectors at the beginning and end of the sequence along the direction transverse to the measuring axis direction MA and an inner set of spatial phase detectors located between the two outer spatial phase detectors. Each spatial phase detector in the inner group is included in the spatial phase sequence by spatial phase detectors having respective spatial phases other than this spatial phase detector and different from one another. Each spatial phase detector includes scale light receiving areas along the detected strip moving direction DFMD spatially periodically and a respective spatial phase of this spatial phase detector with respect to the periodic scale light pattern are positioned accordingly. Each spatial phase detector in the inner group is included in the spatial phase sequence by spatial phase detectors having respective spatial phases other than this spatial phase detector and different from one another.

In some implementations, the sentence of N spatial phase photodetectors at least M Subsets of spatial phase detectors, wherein M is an integer that is at least equal to 2, and where each of the M Subsets comprise spatial phase detectors that provide each of the respective spatial phases included in the set of N spatial phase photodetectors are included. In some implementations can M at least equal to 4. In some implementations can M at least equal to 6. In some implementations, each of the M Subsets of spatial phase detectors comprise spatial phase detectors which provide the same respective spatial phases arranged in the same subset of the spatial phase sequence. 8th shows an implementation with M Subsets of spatial phase detectors using S ₁ to S _M are indicated. The subset S ₁ includes the spatial phase detectors SPD _1A . SPD _1B . SPD _1C and SPD _1D , The subset S ₂ includes the spatial phase detectors SPD _2A . SPD _2B . SPD _2C and SPD _2D , The subset S _M includes the spatial phase detectors SPD _MA . SPD _MB . SPD _MC and SPD _MD ,

At the in 8th The implementation shown is the spatial phase sequence by the spatial phase detectors, which are the subscripts A . B . C and D include (eg the spatial phase detectors SPD _1A . SPD _1B . SPD _1C and SPD _1D ). The spatial phase detectors with subscripts A and D For example, the two outer spatial phase detectors are at the beginning and end of each instance of the spatial phase sequence. The spatial phase detectors with subscripts B and C are the inner groups.

The spatial phase detectors SPD _1A . SPD _1B . SPD _1C and SPD _1D give the respective spatial phase detector signals A ₁ . B ₁ . C ₁ and D ₁ out. The spatial phase detectors SPD _2A . SPD _2B . SPD _2C and SPD _2D give the respective spatial phase detector signals A ₂ . B ₂ . C ₂ and D ₂ out. The spatial phase detectors SPD _MA . SPD _MB . SPD _MC and SPD _MD give the respective spatial phase detector signals A _M . B _M . C _M and D _M out.

In some implementations, such as in 8th shown implementation is N at least equal to 8 and each subset of spatial phase detectors may comprise four spatial phase detectors having respective spatial phases separated by 90 degrees. In alternative implementations, each subset of spatial phase detectors may comprise three spatial phase detectors having respective spatial phases separated by 120 degrees.

At the in 8th The implementation shown includes the photodetector configuration 860 Compounds configured to combine spatial phase detector signals corresponding to the same respective spatial phase and to output each such combination as a respective spatial phase position signal. The photodetector configuration 860 is configured to output four spatial phase position signals corresponding to spatial phases separated by 90 degrees. The spatial phase signals with the same letter designation (eg A ₁ . A ₂ and A _M ) are combined (eg summed) to the spatial phase signals ΣA . .sigma..sub.B . ΣC and ΣD provide. In alternative implementations, a photodetector configuration may be configured to output three spatial phase position signals corresponding to spatial phases separated by 120 degrees. In both cases, the spatial phase position signals may continue to be used to determine displacement signals, for example, by quadrature or three-phase signal processing.

In some implementations, a separation distance YSEP between the scale light receiving areas of each adjacent pair of N spatial phase detectors along the detected strip motion direction DFMD at most 25 microns. In some implementations, the separation distance is YSEP between the scale light receiving areas of each adjacent pair of N spatial phase detectors along the detected strip motion direction DFMD the same.

8th additionally shows a detector axis THERE with respect to the measuring axis direction MA , The detector axis is a direction parallel to the specific longitudinal direction of the spatial phase detectors. In general, it is desirable that the detector axis THERE orthogonal (or nearly orthogonal) to the detected strip motion direction DFMD Although it is not necessary that this is exactly the case, on the condition that good displacement signals can be obtained. Therefore, in some implementations, the detector axis may be relative to the measuring axis direction MA at an angle α be rotated, in particular if the detected strip movement direction DFMD to the measuring axis direction MA is not right-angled. Since it is desirable to have a small illumination strip yaw angle ψ to use (as related to 7 described), the angle can be α can be quite small, and in some cases it can with a very small value of the illumination strip yaw angle ψ be that it is not necessary, the detector axis D in relation to the measuring axis direction MA to turn.

9A FIG. 12 is a detailed schematic diagram of a portion of another exemplary photodetector configuration. FIG 960A a contamination and defect resistant optical encoder 900A that are similar to those in 8th is shown photodetector configuration. For simplicity's sake 9A only a subset of the spatial phase detectors S ₁ with two spatial phase detectors SPD _1A and SPD _1B , It is understood that the photodetector configuration 960A may comprise further spatial phase detectors according to the principles disclosed herein, but only two are shown for the sake of simplicity. At the 9A Each implementation includes the implementation shown N spatial phase detectors (eg the spatial phase detectors SPD _1A and SPD _1B ) a photodetector (eg the photodetectors PD _1A and PD _1B , which are indicated by dashed lines), with a spatial phase mask (eg the phase masks PM _1A and PM _1B ) which prevents the photodetector from receiving the periodic scale light pattern except through openings contained in the spatial phase mask. In this case, the scale light receiving areas include areas of the photodetectors (eg, the photodetectors PD _1A and PD _1B ) passing through the openings in the respective spatial phase masks (eg the spatial phase masks PM _1A and PM _1B ) are exposed through. At the in 9A The conversion shown are the scale light receiving areas (ie, the openings) of the phase mask PM _1B with respect to the scale light receiving areas of the phase mask PM _1A along the detected strip movement direction DFMD offset by 90 degrees. It is understood that they, although the spatial phase masks PM _1A and PM _1B in 9A schematically depicted as separate sections, in some implementations may conveniently be made of the same material in the same process to eliminate any positioning errors.

9B FIG. 12 is a detailed schematic diagram of a portion of another exemplary photodetector configuration. FIG 960B a contamination and defect resistant optical encoder 900B that are similar to those in 8th shown photodetector configuration 860 is. For simplicity's sake 9B only a subset of spatial phase detectors S ₁ ' with two spatial phase detectors SPD _1A ' and SPD _1B '. It is understood that the photodetector configuration 960B may comprise further spatial phase detectors according to the principles disclosed herein, but only two are shown for the sake of simplicity. At the in 9B Each implementation includes the implementation shown N spatial phase detectors (eg the spatial phase detectors SPD _1A ' and SPD _1B ' ) a periodic grid of electrically interconnected photodetector areas that receive the periodic scale light pattern. In this case, the scale light receiving areas include the photodetector areas of the periodic grid of photodetectors. At the in 9B The implementation shown are the photodetector areas of the spatial phase detector SPD _1B ' with respect to the photodetector areas of the spatial phase detector SPD _1A ' along the detected strip movement direction DFMD offset by a spatial phase shift of 90 degrees.

In some implementations of the photodetectors, similar to the photodetector configurations 960A or 960B are, it is beneficial that each of the N spatial phase detectors comprises an even number of scale light receiving areas. 0th-order scale light components may cause a variation in intensity between alternating stripes within the scale light. Therefore, the fact that one has an even number of the scale light receiving areas compensates for this variation.

10 FIG. 10 is an incomplete schematic diagram of additional implementation of a stain and defect resistant optical encoder configuration. FIG 1000 for providing displacement signals. In the encoder configuration 1000 includes the periodic scale light pattern 1035 which is detected, a detector strip pattern 1035 comprising straps oriented to extend over a relatively longer dimension along a measuring axis direction MA and extending transversely to the measuring axis direction along a detected strip movement direction DFMD during the displacement of the optical encoder.

The optical encoder configuration 1000 includes a scale 1010 , a source of illumination 1020 and a photodetector configuration 1060 , The scale 1010 extends along a measuring axis direction MA and includes a scale grid, the grid bars GB includes, in a scale plane SP are arranged, which are the Meßachsenrichtung MA nominally parallel. The scale lattice bars GB are along the measuring axis direction MA narrow and along a scale grid bar direction DBMS transverse to the measuring axis direction MA oblong, and are along the measuring axis direction MA with a scale graduation P _SF arranged periodically. The illumination source 1020 includes a light source 1030 , the light 1034 ' issues, and a section 1033 to generate a structured lighting that is configured to light 1034 ' to enter and a structured lighting 1034 '' along a source beam path SOLP to a lighting region IR at the scale level SP spend the structured lighting 1034 '' a lighting strip pattern IFP comprising strips along the measuring axis direction MA narrow and along a lighting strip direction IFD , which are transverse to the measuring axis direction MA is oriented, are elongated. The light source 1030 includes a point source 1031 and a collimation lens 1032 , The point source 1031 spend light 1034 to the collimating lens, then the light 1034 collapsed to the light 1034 ' provide.

The photodetector configuration 1060 comprises a set of N spatial phase detectors with a detector spacing PD (as in 6A and 6B shown in detail) along a detected strip movement direction DFMD transverse to the measuring axis direction MA are arranged periodically, each spatial phase detector configured to provide a respective spatial phase detector signal and at least a majority of the respective spatial phase detectors over a relatively longer dimension along the measuring axis direction MA extends and along the detected strip movement direction DFMD is relatively narrow across the measuring axis, and the theorem of N spatial phase detectors in a spatial phase sequence along the detected strip motion direction DFMD is arranged as described in more detail with reference to 8th . 9A and 9B described.

Similar to the encoder configuration 500 is the scale 1010 configured to illuminate the illumination strip pattern at the illumination region IR input and scale light components along a scale beam path SCLP to output the detector strip pattern 1035 at the photodetector configuration 1060 to build. The detector strip pattern 1035 includes periodic high and low intensity bands extending over a relatively longer dimension along the measuring axis direction MA extend and relatively narrow and with a detected fringe period PDF along the detected strip movement direction DFMD transverse to the measuring axis direction MA are periodic, as previously described in more detail with reference to 6 described.

The scale grid bar direction DBMS is in a yaw angle ψ _SC nonzero with respect to a read head plane RHP passing through the source beam path SOLP and a scale beam path SCLP is defined, oriented.

The section 1033 To generate a structured illumination comprises a first diffraction grating 1040 the illumination source and a second diffraction grating 1050 the illumination source used in 11A and 11B be shown in more detail. In some implementations, the first diffraction grating 1040 the illumination source and the second diffraction grating 1050 the illumination source be phase grating.

The detected stripe period PDF and the detected strip movement direction DFMD transverse to the measuring axis direction MA are at least partially of the yaw angle ψ _SC nonzero dependent as previously with respect to 7 addressed. The high and low intensity bands move along the detected strip motion direction DFMD transverse to the measuring axis direction MA if the scale is 1010 along the measuring axis direction MA shifts. The photodetector configuration 1060 is configured to shift the high and low intensity bands along the detected strip motion direction DFMD transverse to the measuring axis direction MA detect and provide respective spatial phase shift signals indicative of the scale shift.

11A is a schematic diagram of the first diffraction grating 1040 the illumination source. 11B is a schematic diagram of the second diffraction grating 1050 the illumination source. In various implementations, it is desirable to have the optical encoder configuration 1000 to minimize errors in the displacement signals resulting from gap variations between the scale 1010 , the lighting source 1020 and the photodetector configuration 1060 result.

As in 11A shown includes the first diffraction grating 1040 the illumination source first index grid bars, which with a first index division P ₁ are arranged periodically in a first index plane, the first index grid bars being narrow along the measuring axis direction and along a first grid bar direction transverse to the measuring axis direction and in relation to the reading head plane RHP at an angle ψ ₁ is turned, are elongated. As in 11B shown includes the second diffraction grating 1050 the illumination source second illumination source lattice bars having a second index division P ₂ are periodically arranged in a second index plane parallel to the first index plane, the second index gratings being narrow along the measuring axis direction and along an index grating second direction transverse to the measuring axis direction and an angle relative to the reading head plane RHP ψ ₂ is turned, are elongated.

In various optical encoders, such as the optical encoder configuration 500 , dynamic gap errors can arise due to scale ripple, which is a distance between the illumination section 520 and the scale 510 along the source beam path SOLP changes. A change in a light path length along the Skalenstrahlengang SCLP causes changes in the relative phases of interfering beams that are related to the detector strip pattern 1035 contribute. In various applications can ψ ₁ and ψ ₂ be selected such that they give a dynamic gap error having the same magnitude and the opposite sign. The phases of two interfering beams of the interfering beams leading to the detector strip pattern 1035 can contribute through Φ ₊ and Φ _- be expressed. The light coming from the light source 1030 is output, has a wavelength λ on. A dynamic gap error DGE depends on a gap variation Δg along a direction to the measuring axis direction MA and the scale grid bar direction DBMS (ie the Z Direction) is perpendicular, by the following expression: $$DGe=\frac{P_{SF}}{4\pi }\frac{\left({\Phi }_{+}-{\Phi }_{-}\right)}{\partial \Delta G}$$

gegeben, wobei ein Faktor Ω definiert ist durch den Ausdruck: $$\mathrm{\Omega }=\frac{4\pi \lambda }{P_{SF}^2}\text{sin}\left(V\right)\left({\left({\text{cos}}^2\left(V\right)-\frac{{\lambda }^2}{P_{SF}^2}\right)}^{-3/2}-{\text{cos}}^{-3}\left(V\right)\right)+\frac{8\pi }{\lambda }\text{tan}\left(V\right)$$

More precisely, the difference term is the expression $$\frac{\partial \left({\mathrm{\Phi }}_{+}-{\mathrm{\Phi }}_{-}\right)}{\partial \Delta G}=\mathrm{\Omega }\left[\frac{-\lambda }{P_1}sin\left({\Psi }_1\right)+\frac{\lambda }{P_2}sin\left({\Psi }_2\right)\right]-\frac{4\pi }{P_{SF}}sin\left({\Psi }_{SC}\right)\text{tan}\left(V\right)$$

given, being a factor Ω is defined by the expression: $$\mathrm{\Omega }=\frac{4\pi \lambda }{P_{SF}^2}\text{sin}\left(V\right)\left({\left({\text{cos}}^2\left(V\right)-\frac{{\lambda }^2}{P_{SF}^2}\right)}^{-3/2}-{\text{cos}}^{-3}\left(V\right)\right)+\frac{\mathrm{8th}\pi }{\lambda }\text{tan}\left(V\right)$$

eine Fehlerkomponente, die sich aus dem Gieren jedes von dem ersten Beugungsgitter 1040 der Beleuchtungsquelle und dem zweiten Beugungsgitter 1050 der Beleuchtungsquelle ergibt. Der zweite Term $\frac{4\pi }{P_{SF}}sin\left({\Psi }_{SC}\right)\text{tan}\left(V\right)$

ist eine Fehlerkomponente, die sich aus dem Gierwinkel ψ_SC ergibt. Durch das absichtliche Einführen von Fehlerkomponenten mit dem Winkel ψ₁ und dem Winkel ψ₂ ist es möglich, die Fehlerkomponenten aus dem zweiten Term zu kompensieren.In Equation 4, the first term $\mathrm{\Omega }\left[\frac{-\lambda }{P_1}sin\left({\Psi }_1\right)+\frac{\lambda }{P_2}sin\left({\Psi }_2\right)\right]$

an error component resulting from the yawing of each of the first diffraction gratings 1040 the illumination source and the second diffraction grating 1050 the illumination source results. The second term $\frac{4\pi }{P_{SF}}sin\left({\Psi }_{SC}\right)\text{tan}\left(V\right)$

is an error component resulting from the yaw angle ψ _SC results. By intentionally introducing error components with the angle ψ ₁ and the angle ψ ₂ it is possible to compensate for the error components from the second term.

In some implementations, the scale includes 1010 a scale grid, which is a reflective grid. As 10 shown, the source beam path SOLP in relation to a direction which is perpendicular to the scale plane, at an angle V be oriented. To the desired detected fringe period PDF can provide the yaw angle ψ _SC fulfill the following expression: $${\Psi }_{SC}={\text{sin}}^{-1}\left[P_{SF}\left(\frac{1}{2PDF}-\frac{\text{sin}\left({\Psi }_2\right)}{{\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="DE102018251727A1\_0014.png,DE102018251727A1\_0020.png"\; state="\{\{state\}\}">P</figure-callout>}}_1}+\frac{\text{sin}\left({\Psi }_2\right)}{P_2}\right)\right]$$

To the dynamic gap error DGE can cancel, as shown in equation 3, the angle ψ ₁ and the angle ψ ₂ fulfill the following expression: $$\frac{-\text{sin}\left({\Psi }_1\right)}{{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="DE102018251727A1\_0014.png,DE102018251727A1\_0020.png"\; state="\{\{state\}\}">d</figure-callout>}}_1}+\frac{\text{sin}\left({\Psi }_2\right)}{d_2}=\frac{2\pi \text{tan}\left(V\right)\text{cos}\left(V\right)}{PDF\left(\Omega \lambda -4\pi \text{tan}V\right)}$$

In a typical example of an optical encoder, similar to the optical encoder configuration 500 with a P _SF Value of 2 microns, one P ₁ Value of 2 microns, one P ₂ Value of 1 micron, a V value of 30 degrees, a λ value of 660 nanometers and a PDF value of 120 microns is configured then ψ _SC have a value of 0.48 degrees. This can give a dynamic gap error of 4.8 nanometers of a position measurement error per micron of the gap variation Δg. In a typical example of an optical encoder, similar to the optical encoder configuration 100 with the same parameters as previously configured can ψ _SC be equal to 0.94 degrees, ψ ₁ can be equal to -0.46 degrees, and ψ ₂ can be equal to 0.0 degrees. The yaw angle ψ ₁ can have a dynamic gap error component of -9.4 nanometers of position measurement error per micrometer of gap variation Δg contribute, and the yaw angle ψ ₂ may have a dynamic gap error component of 9.4 nanometers of position measurement error per micron of gap variation Δg contribute. The two dynamic gap errors balance each other out to provide a net dynamic gap error of zero.

12 FIG. 10 is an incomplete schematic diagram of additional implementation of a stain and defect resistant optical encoder configuration. FIG 1200 for providing displacement signals. In the encoder configuration 1200 includes the periodic scale light pattern 1235 , which is detected, a detector strip pattern comprising bands oriented to a relatively longer dimension along a measuring axis direction MA extend and transverse to the Meßachsenrichtung MA along a detected strip movement direction DFMD during the displacement of the optical encoder. The scale light pattern 1235 can by a similar optical encoder as the optical encoder configuration 1000 related to 10 was addressed.

The optical encoder configuration 1200 includes a scale 1210 , a source of illumination 1220 and a photodetector configuration 1260 , The scale 1210 extends along a measuring axis direction MA and includes a scale grid, the grid bars GB includes, in a scale plane SP to the measuring axis direction MA nominally parallel, are arranged. The scale lattice bars GB are along the measuring axis direction MA narrow and along a scale grid bar direction DBMS transverse to the measuring axis direction MA oblong, and are with a graduation P _SF along the measuring axis direction MA arranged periodically. The illumination source 1220 includes a light source 1230 , the light 1234 ' issues, and a section 1233 to generate a structured lighting that is configured to light 1234 ' to enter and a structured lighting 1234 '' along a source beam path SOLP to a lighting region IR to spend at the scale level SP, with the structured lighting 1234 '' a lighting strip pattern IFP comprising strips along the measuring axis direction MA narrow and along a lighting strip direction IFD , which are transverse to the measuring axis direction MA is oriented, are elongated. The light source 1230 includes a point source 1231 and a collimation lens 1232 , The point source 1231 spend light 1234 to the collimating lens, then the light 1234 collapsed to the light 1234 ' provide.

The photodetector configuration 1260 comprises a set of N spatial phase detectors with a detector spacing PD (similar to the photodetector configuration 860 , in the 8th shown in detail) along a detected strip movement direction DFMD transverse to the measuring axis direction MA are arranged periodically, wherein each spatial phase detector is configured to provide a respective spatial phase detector signal, and at least a majority of the respective spatial phase detectors over a relatively longer dimension along the measuring axis direction MA extends and along the detected strip movement direction DFMD transverse to the measuring axis direction MA is relatively narrow, and the sentence of N spatial phase detectors in a spatial phase sequence along the detected strip motion direction DFMD is arranged as previously with reference to 8th . 9A and 9B described in more detail.

Similar to the encoder configuration 500 is the scale 1210 configured to illuminate the illumination strip pattern at the illumination region IR input and scale light components along a scale beam path SCLP to output the scale light pattern 1235 at the photodetector configuration 1260 to build. The scale light pattern 1235 includes periodic high and low intensity bands extending over a relatively longer dimension along the measuring axis direction MA extend and relatively narrow and with a detected fringe period PDF along the detected strip movement direction DFMD transverse to the measuring axis direction MA are periodic, as before with reference to 6A and 6B described in more detail.

The scale grid bar direction DBMS is with respect to a read head level RHP passing through the source beam path SOLP and a scale beam path SCLP is defined, in a yaw angle ψ _SC nonzero oriented.

The detected stripe period PDF and the detected strip movement direction DFMD transverse to the measuring axis direction MA are at least partially of the yaw angle ψ _SC nonzero dependent as previously with respect to 7 addressed. The high and low intensity bands move along the detected strip motion direction DFMD transverse to the measuring axis direction MA if the scale is 1210 along the measuring axis direction MA shifts. The photodetector configuration 1260 is configured to shift the high and low intensity bands along the detected strip motion direction DFMD transverse to the measuring axis direction MA detect and provide respective spatial phase shift signals indicative of the scale shift.

A vertical RHPN the reading head level RHP is with respect to the measuring axis direction MA with a tilt angle Φ nonzero oriented.

13A FIG. 10 is a schematic diagram illustrating a first view of scale light components that is a scale light pattern. FIG 1235 form a photodetector configuration similar to the photodetector configuration 1260 in 12 is. More specifically shows 13A a cross section of a portion SIG of the scale light pattern 1235 in a plane passing through a measuring axis direction MA and a Y Direction, which is close to the photodetector configuration 1260 located, defines the. The section SIG the scale light pattern 1235 is a set of stripes caused by the overlap of the scale light components SL1 and SL2 is formed with regard to 6B to understand. The section SIG the scale light pattern 1235 includes dark or low intensity interference bands 1235SIGD , which are indicated by bold line, and bright or high intensity interference bands 1235SIGL , which are indicated by dashed outlines. The section SIG is analogous to the detector strip pattern 635 The section of the scale light pattern 1235 which results in spatial phase shift signals indicating the scale shift. More specifically, the photodetector configuration is 1260 configured to shift the interference bands 1235SIGD and 1235SIGL along the detected strip movement direction DFMD transverse to the measuring axis direction MA detect and provide respective spatial phase shift signals indicative of the scale shift.

In various implementations, the detector strip pattern 635 In addition, zeroth-order light includes variations in the intensity of the high-intensity interference bands 635L caused. More specifically, the interference between the zero-order scale light and the scale light components SL1 and SL2 to bands of low and high intensity bands of interference leading to the low intensity bands of interference 635D and the high-intensity interference bands 635L are parallel. This results in streaks in the detector strip pattern 635 having a pattern of a variation of alternating stripes, resulting in near-field errors in spatial phase-shift signals. The stain and defect resistant optical encoder configuration 1200 is configured to suppress these errors as described below. Specifically, the interference between zero-order scale light and light, which results in the 6B shown scale light components SL1 and SL2 would correspond to stripes of dark and light intensity bands leading to light, the scale light components SL1 and SL2 would be parallel, and during the displacement of the optical encoder along the detected strip movement direction DFMD would move.

It is understood that 13A to D a section of the scale light pattern 1235 in a reference frame pointing to the photodetector configuration 1260 is aligned, show. In general, a photodetector configuration, such as the photodetector configuration, should be used 1260 , be oriented such that the spatial phase detectors respond to the fringe pattern produced by the low and high intensity interference fringes 1235SIGD and 1235SIGL is defined along the detected strip movement direction DFMD , which are transverse to the measuring axis direction MA is aligned, but not exactly on the Y Direction are aligned.

13B FIG. 12 is a schematic diagram illustrating a second view of scale light components that is a scale light pattern. FIG 1235 form a photodetector configuration similar to the photodetector configuration 1260 in 12 is. More specifically shows 13B a cross section of a section PZ the scale light pattern 1235 in a plane passing through a measuring axis direction MA and a Y Direction defined in the vicinity of the photodetector configuration 1260 located. The section PZ the scale light pattern 1235 is a set of stripes caused by the overlap of a zero-order scale light component and the scale light component SL1 be formed. The section PZ the scale light pattern 1235 includes dark or low intensity interference bands 1235PZD indicated by bold lines and bright or high intensity interference bands 1235PZL , which are indicated by dashed outlines.

Due to the inclination angle Φ non-zero are the interference bands 1235PZD and 1235PZL oriented such that it does not travel along the detected stripe direction DMFD are aligned and thus not on the interference bands 1235SIGD and interference bands 1235SIGL are aligned.

13C FIG. 12 is a schematic diagram showing a third view of the scale light components that is a scale light pattern. FIG 1235 form a photodetector configuration similar to the photodetector configuration 1260 in 12 is. More specifically shows 13C a cross section of a section MZ the scale light pattern 1235 in a plane passing through a measuring axis direction MA and defining a Y-direction that is proximate to the photodetector configuration 1260 located. The section MZ the scale light pattern 1235 is a set of stripes caused by the overlap of a zero-order scale light component and the scale light component SL2 be formed. The section MZ the scale light pattern 1235 includes dark or low intensity interference bands 1235MZD indicated by bold lines and bright or high intensity interference bands 1235MZL , which are indicated by dashed outlines.

Due to the inclination angle Φ non-zero are the interference bands 1235MZD and 1235MZL oriented such that it does not travel along the detected stripe direction DMFD aligned, and thus they are not on the interference bands 1235SIGD and interference bands 1235SIGL aligned.

13D FIG. 10 is a schematic diagram illustrating a fourth view of scale light components that is a scale light pattern. FIG 1235 form a photodetector configuration similar to the photodetector configuration 1260 in 12 is. More specifically shows 13D a cross section of each of the sections PZ . MZ and SIG of the scale light 1235 , When the angle of inclination Φ would be zero, would be the interference bands of the sections PZ and MZ with respect to the detected strip movement direction DFMD angularly not otherwise oriented, but instead would be parallel to the interference bands 1235SIGD and 1235SIGL , resulting in a variation of the intensity between alternating interference bands of the high interference bands 1235SIGL of the section SIG which would cause near field errors in the spatial phase shift signals. As in 13D shown overlap, however, for the case an inclination angle Φ nonzero, the low-intensity interference bands 1235PZD and 1235MZD the sections PZ and MZ in the low-intensity regions LO , and the high-intensity interference bands 1235PZL and 1235MZL overlap in the high-intensity regions HI , The regions LO and HI are along a direction transverse to the detected strip movement direction DFMD aligned. The intensity of 1235 in the regions LO and HI equals along the direction transverse to the detected strip movement direction DFMD resulting in a variation in intensity between alternating stripes within the scale light 1235 along the detected strip movement direction DFMD is suppressed. This averaging reduces short-range errors in spatial phase shift signals caused by zero-order scale light associated with the section SIG of the scale light 1235 interferes.

In some implementations of the stain resistant optical encoder 1200 can Φ greater than 0.3 degrees and less than 2.0 degrees.

In some implementations of the stain resistant optical encoder 1200 Anyone can do that N spatial phase detectors comprise an even number of scale light receiving areas.

In some implementations of the stain resistant optical encoder 1200 can the section 1233 for generating a structured illumination, a first diffraction grating of the illumination source (eg, the first diffraction grating 1040 the illumination source) and a second diffraction grating of the illumination source (eg, the second diffraction grating 1050 the illumination source). The first diffraction grating of the illumination source may comprise first illumination source grating bars having a first index pitch P ₁ are arranged periodically in a first index plane, wherein the first index grid bars along the measuring axis direction are narrow and along a first lattice rod direction, which is transverse to the measuring axis direction and in relation to the read head RHP by an angle ψ ₁ is turned, are elongated. The second diffraction grating of the illumination source may comprise second illumination source grating bars having a second index pitch P ₂ are periodically arranged in a second index plane parallel to the first index plane, the second index grid bars being narrow along the measuring axis direction and along a second index grid direction transverse to the measuring axis direction and relative to the reading head plane RHP at an angle ψ ₂ is turned, are elongated. In some implementations (eg as previously with reference to 10 described) can the scale 1210 a scale grating which is a reflective grating, the source beam path SOLP can be relative to a direction leading to the scale plane SP is vertical, at an angle V be oriented, and the yaw angle ψ _SC can satisfy the equation (6). In some implementations, the light emitted by the light source 1230 is output, a wavelength λ have a factor Ω can be defined by equation (5), and the angle ψ ₁ and the angle ψ ₂ can satisfy equation (7). In some implementations, the first diffraction grating of the illumination source light and the second diffraction grating of the illumination source light may be phase gratings. In some implementations, the detected stripe period PDF at least 40 microns.

14 FIG. 10 is an incomplete schematic diagram of a first implementation of a contamination and defect resistant optical rotary position encoder configuration. FIG 1400 for providing displacement signals. The encoder configuration 1400 includes a rotary scale 1410 , a source of illumination 1420 and a photodetector configuration 1460 , 15 is a schematic diagram of a section of the rotary scale 1410 out 14 showing additional details. At the in 14 The implementation shown includes the rotary scale 1410 a permeable grid.

In the encoder configuration 1400 includes the periodic scale light pattern 1435 which is detected, a detector strip pattern 1435 comprising straps oriented to extend over a relatively longer dimension along the measuring axis direction MA and during translation of the optical encoder transversely of the rotational direction of measurement, along a detected strip movement direction DFMD move.

The rotation scale 1410 extends along a rotational direction θ around a rotation axis RA around. The rotation scale 1410 includes a turnstile lattice, the scale lattice bars GB includes, in a rotating surface along the rotational direction θ are arranged, wherein the scale grid bars GB along the direction of rotation θ narrow and along a direction of the turnstile lattice bars RSGBD transverse to the direction of rotation 9 are elongated, and with a graduation P _SF along the direction of rotation θ are arranged periodically. The illumination source 1420 includes a light source, the collimated light 1434 to a first illumination region IR1 on the rotary scale 1410 which is configured to input the light 1434 and a structured lighting 1434 ' along a ray path LP to a second illumination region IR2 on the rotary scale 1410 spend the structured lighting 1434 ' a lighting strip pattern IFP includes, comprising strips along the direction of rotation 9 narrow and along a lighting strip direction IFD , which are transverse to the direction of rotation θ is oriented, are elongated.

The encoder configuration 1400 may also be either a first mirror 1471 and a second mirror 1472 to the structured lighting 1434 ' to reflect, or a first grid 1473 and a second grid 1474 to the structured lighting 1434 ' to the second lighting region IR2 to judge. In some implementations then the structured lighting 1434 ' near the axis of rotation RA nominally focused. In some implementations, the structured lighting goes 1434 ' in the free space between the first mirror 1471 and the second mirror 1472 , In other implementations, the first mirror 1471 and the second mirror 1472 be a monolithic optical material in which the structured lighting 1434 ' is reflected by internal reflections inside the monolithic optical material.

The photodetector configuration 1460 is similar to the photodetector 560 and is related to 6A and 6B to understand. The photodetector 1460 includes a set of N spatial phase detectors with a detector spacing PD (in 6A and 6B shown) along a detected strip movement direction DFMD are arranged periodically transverse to the direction of rotation.

The rotation scale 1410 is configured to match the lighting strip pattern IFP at the second illumination region IR2 to input and output scale light, which is a stripe pattern at the photodetector configuration 1460 wherein the fringe pattern comprises high and low intensity periodic bands extending over a relatively longer dimension along the rotational direction 9 extend and are relatively narrow and with a detected fringe period PDF along the detected strip movement direction DFMD transverse to the direction of rotation θ are periodic.

The direction RGBB the rotary lattice bars is with respect to the axis of rotation RA in a yaw angle ψ nonzero oriented. The detected stripe period PDF and the detected strip movement direction DFMD lie transverse to the direction of rotation θ and are at least partially of the yaw angle ψ non-zero dependent, similar as with respect to 7 described. The high and low intensity bands move along the detected strip motion direction DFMD transverse to the direction of rotation θ when the rotation scale 1410 around the axis of rotation RA turns around. The photodetector configuration 1460 is configured to shift the high and low intensity bands along the detected strip motion direction DFMD transverse to the direction of rotation θ detect and provide respective spatial phase shift signals indicative of the rotational scale shift.

In some implementations, Equation 6 may be adapted to an optical rotary position encoder configuration, such as the optical rotary position encoder configuration 1400 , be adjusted. In this case, the scale represents 1410 the equivalent of the first and second diffraction gratings 540 and 550 the illumination source light, wherein P ₁ and P ₂ now equal to the graduation P _SF are. The scale lattice bars GB are with respect to the light 1434 and the structured lighting 1434 ' at the respective first illumination region IR1 and the second illumination region IR2 oriented in opposite angles. In other words ψ ₁ equal -ψ ₂ , Because the light 1434 and the structured lighting 1434 ' Now only go through the two grids, simplified for the optical encoder configuration 1400 Equation 5, to provide an equation, the yaw angle ψ with the detected strip division PDF to connect: $$\Psi ={\text{sin}}^{-1}\left(\frac{P_{SF}}{PDF}\right)$$

Double the lighting 1434 and 1434 ' pointing to the rotation scale 1410 is incident (ie at the first illumination region IR1 and the second illumination region IR2 ), allows higher resolution of displacement measurements as well as the correction of a rotational offset perpendicular to a line passing through the first illumination region IR1 and the second illumination region IR2 goes.

16 FIG. 10 is an incomplete schematic diagram of a first implementation of a contamination and defect resistant optical rotary position encoder configuration. FIG 1600 for providing displacement signals. The optical rotary encoder configuration 1600 is similar to the encoder configuration 1400 , Similar reference numbers 14XX in 14 and 16 XX in 16 may refer to similar elements unless otherwise indicated by the context or the description. As in 16 includes the optical rotary position encoder configuration 1600 a rotary scale 1610 which includes a reflective grid.

While preferred implementations of the present disclosure have been illustrated and described, many variations of the illustrated and described arrangements of features and sequences will be apparent to those skilled in the art based on the present disclosure. Various alternative forms may be used to implement the principles disclosed herein. In addition, the various reactions described above can be combined to provide further reactions. All US patents and US patent applications referred to in the present specification are hereby incorporated by reference in their entirety. Aspects of the implementations may be changed as needed to use the concepts of the various patents and applications to provide further implementations.

These and other changes may be made to the implementations in light of the description previously given. In general, in the following claims, the terms used are not to be construed to limit the claims to the specific implementations disclosed in the specification and claims, but are intended to cover all possible implementations, along with the full scope of equivalents thereof these claims are entitled to include.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

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Claims (9)

A fouling and defect resistant optical rotary position encoder configuration for providing displacement signals, comprising: a rotary scale extending along a rotational direction about an axis of rotation, the rotary scale comprising a rotary scale grating comprising scale grid bars disposed in a rotary surface along the rotary measuring direction; Scale grating bars are narrow along the rotational direction and are elongated along a direction of the rotary grate bars transverse to the rotation measuring direction and are periodically arranged with a scale pitch P _SF along the rotation measuring direction; an illumination source comprising a light source outputting collimated light to a first illumination region on the rotation scale configured to input the light and output structured illumination along a beam path LP to a second illumination region on the rotation scale, the structured illumination entering An illumination strip pattern comprising strips narrow along the rotational direction and elongate along a illumination pattern direction oriented transverse to the direction of rotation; and a photodetector configuration comprising a set of N spatial phase detectors periodically spaced at a detector spacing PD along a detected strip move direction transverse to the rotation direction, each spatial phase detector configured to provide a respective spatial phase detector signal, and at least a majority of the respective ones spatial phase detectors over a relatively longer dimension along the rotational direction and is relatively narrow along the detected strip movement direction transverse to the rotational direction, and the set of N spatial phase detectors is arranged in a spatial phase sequence along the detected strip movement direction; wherein: the rotation-scale grille is configured to input the illumination-stripe pattern at the second illumination region and output scale light forming a stripe pattern on the photodetector configuration, the stripe pattern comprising high and low intensity periodic bands extending over a relatively longer dimension along the rotational direction extend and are relatively narrow and periodic with a detected fringe period PDF along the detected strip movement direction transverse to the direction of rotation; the direction of the rotary lattice bars is oriented with respect to the axis of rotation at a yaw angle ψ not equal to zero; the detected strip period PDF and the detected strip movement direction are transverse to the direction of rotation and at least partially dependent on the yaw angle ψ not equal to zero; the high and low intensity bands move transversely to the direction of rotation of the scan along the detected strip movement direction as the scale grid rotates about the axis of rotation; and the photodetector configuration is configured to detect a shift of the high and low intensity bands along the detected strip movement direction transverse to the rotation direction and to provide respective spatial phase shift signals indicative of the rotation scale offset. Pollution and defect resistant optical rotary position encoder configuration Claim 1 wherein each of the N spatial phase detectors comprises an even number of scale light receiving areas. Pollution and defect resistant optical encoder configuration according to Claim 1 wherein the detected stripe period PDF is at least 40 microns. Pollution and defect resistant optical encoder configuration according to Claim 1 , wherein the rotary grate is a permeable grating. Pollution and defect resistant optical encoder configuration according to Claim 1 wherein the rotary grate is a reflective grating. Pollution and defect resistant optical encoder configuration according to Claim 1 , where the yaw angle ψ the relationship: $$\Psi ={\text{sin}}^{-1}\left(\frac{P_{SF}}{PDF}\right)$$

Fulfills. Pollution and defect resistant optical encoder configuration according to Claim 1 further comprising a first mirror and a second mirror for directing the structured illumination to the second illumination region. Pollution and defect resistant optical encoder configuration according to Claim 7 wherein the first mirror and the second mirror are surfaces of a monolithic optical material. Pollution and defect resistant optical encoder configuration according to Claim 1 further comprising a first grid and a second grid for directing the structured illumination to the second illumination region.

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