Device and method for detecting the position of a body, as well as coordinate measuring machine

Abstract

Device (10) for detecting the position of a body (12), in particular for detecting errors in several degrees of freedom, wherein the device (10) comprises a transmitter unit (14), at least one spatially resolving sensor (16), an evaluation and control unit (18), and a target element (20) with three retroreflectors (22), wherein the transmitter unit (14) is configured to emit three parallel light beams (24), wherein the retroreflectors (22) are configured to reflect one of the three light beams (24) back to the transmitter unit (14) as a retroreflected light beam (26), wherein the at least one spatially resolving sensor (16) is configured to detect a first signal, wherein the transmitter unit (14) is configured to detect a second signal from the three retroreflected light beams (26), and wherein the evaluation and control unit (18) is configuredto determine, by means of the first signal and the second signal, six degrees of freedom of the body (12) exhibiting a position error (48), a first translation error (50), a second translation error (52), a roll error (54), a yaw error (56) and a pitch error (58), wherein the evaluation and control device (18) is configured to determine, by means of the first signal, the first translation error (50), the second translation error (52) and the roll error (54) and, by means of the second signal, the position error (48), the yaw error (56) and the pitch error (58).

Description

[0001] The present invention relates to a device for detecting the position of a body, a coordinate measuring machine and a method for detecting the position of a body.

[0002] In general, the present disclosure relates, at least in exemplary embodiments, to measuring systems, in particular coordinate measuring machines, with a substrate that is movable relative to a frame of the measuring system / measuring device.

[0003] From WO 01 / 88471 A1, a device for determining the 3D shape of an object is known, comprising a 3D coordinate measuring machine, a mechanical object movement system, at least one reference object in the form of a marker, and a computer for linking the measured areas of the object, wherein the detection of the at least one marker is optical, and wherein at least one tactile sensor is additionally provided for tactile probing. In other words, WO 01 / 88471 A1 discloses a so-called multi-sensor coordinate measuring machine.

[0004] German patent DE 10 2016 124 549 A1 discloses a measuring system for the dimensional measurement of an object, comprising a slide for holding the object to be measured, several optical markers arranged on the slide and / or the object, and a first sensor for tactile, optical, and / or tomographic scanning of the object. The first sensor generates a first measurement signal. The measuring system further includes a second optical sensor for detecting the position and location of the object based on the optical markers. A second measurement signal is generated by the second sensor, containing information on the location and position of the optical markers. The second sensor is connected to the first sensor via a mechanically rigid connection.Furthermore, the measuring system includes an evaluation unit which is designed to determine the position and spatial orientation of the object to be measured relative to the first sensor from the second measurement signal and to determine a geometry of the object being measured from the first signal.

[0005] Further exemplary devices and methods for measuring several degrees of freedom of an object are known from the following publications: DE 11 2009 003 495 T5, US 2012 / 0050712 A1 and DE 101 18 392 A1.

[0006] Measuring systems for the dimensional measurement of an object are known in a wide variety of designs from the state of the art. In dimensional metrology, a wide range of measuring methods are used to measure the geometry and dimensions of objects of all kinds.

[0007] Coordinate measuring machines for industrial use are generally quite complex in design to reliably guarantee the desired accuracy during measurement / surveying. Coordinate measuring machines typically have multiple driven axes with corresponding guides. These axes and their guides are regularly assigned dimensional standards that enable the determination of absolute and / or relative positions / movements.

[0008] The design of coordinate measuring machines often involves providing a specific measuring volume (such as a cube or cuboid with defined length, width, and height) within which measurements can be taken with a certain accuracy. However, this leads to considerable complexity, especially when the measuring volume reaches a certain size required for industrial applications. Frequently, the sensors used to probe the object have a very small measuring range, making it essential to move the sensors relative to the object and determine corresponding travel distances and / or angles.

[0009] Since a coordinate measuring machine typically has several axes that can move relative to each other for movements between the object being measured and the sensor(s), the accuracy usually decreases with an increasing measurement volume and with an increasing number of degrees of freedom, because in the worst case the errors of the individual axes add up to a total error.

[0010] A general objective for the development and design of measuring systems, especially coordinate measuring machines for industrial use, is to increase accuracy, increase productivity, and improve suitability for use in industrial environments. Furthermore, improved properties should be achievable with minimal additional cost.

[0011] Measurement systems are regularly subject to errors. They typically exhibit errors in multiple degrees of freedom, particularly in all six degrees of freedom, which can be attributed, for example, to misaligned movements in the respective degree of freedom. Such misaligned movements can be caused by bearing play, drive backlash, geometric errors, or similar factors. There is a desire to detect these errors and at least partially compensate for them.

[0012] It is therefore an object of the present disclosure to specify a device for detecting the position of a body, with which the accuracy can be increased in the operation of a measuring system. Furthermore, a coordinate measuring machine equipped with such a device and a method for detecting the position of a body are to be specified.

[0013] At least with regard to exemplary aspects, the present disclosure is based on the objective of providing a measuring system, in particular a coordinate measuring machine, for the dimensional measurement of an object, with which high measurement accuracies can nevertheless be achieved, whereby the manufacture of the measuring system should, if possible, not involve increased structural complexity. The measuring system should be suitable for industrial applications, especially with regard to performance (measurements per unit of time) and flexibility (performance of a wide variety of measurement tasks).

[0014] Preferably, the measuring system is capable of ensuring measurement accuracies in the sub-micrometer range for large measuring volumes, which are frequently required in industrially used coordinate measuring machines.

[0015] According to a first aspect of the present disclosure, the problem described in the disclosure is solved by a device for detecting the position of a body, in particular for detecting errors in several degrees of freedom. The device comprises a transmitter unit, at least one position-resolving sensor, an evaluation and control unit, and a target element with three retroreflectors. The transmitter unit is configured to emit three parallel light beams. The retroreflectors are configured to reflect each of the three light beams back to the transmitter unit as a retroreflected light beam. The at least one position-resolving sensor is configured to detect a first signal. The transmitter unit is configured to detect a second signal from the three retroreflected light beams.The evaluation and control unit is configured to determine, using the first and second signals, six degrees of freedom of the body, which exhibit a position error, a first translation error, a second translation error, a roll error, a yaw error, and a pitch error. The evaluation and control unit is configured to determine the first translation error, the second translation error, and the roll error using the first signal, and to determine the position error, the yaw error, and the pitch error using the second signal.

[0016] The device is exemplified as being assigned to a motion axis (such as X, Y, or Z) of a coordinate measuring machine. Such a motion axis comprises, for example, a guide and a carriage that can be moved along the guide by a drive mechanism. If the device is assigned to the guide or carriage, any errors can be easily and accurately detected and compensated for as needed. In this way, even with backlash in the motion axis, a highly accurate movement is achieved, which forms the basis for the measurement. Thus, the device can be used to further enhance and / or increase the accuracy of a coordinate measuring machine. However, this should not be interpreted as a limitation.

[0017] Position can refer to a position relative to a measurement environment. It can relate to positioning and / or orientation. Position can involve one or more degrees of freedom of the body. These degrees of freedom can be selected from a group consisting of a position (e.g., an X-coordinate), one or two translations (e.g., a Y-coordinate and / or a Z-coordinate), yaw, pitch, and roll.

[0018] The device is configured, for example, to detect errors in the positioning of a body, such as a positional error, and / or one or two translational errors, and / or a yaw error, and / or a pitch error, and / or a roll error. The device can, in particular, be configured to detect errors in a coordinate measuring machine, at least along one axis of motion. By detecting these errors, corrections, such as systematic errors, can be made. A positional error is a misposition along a direction of motion (e.g., the X-coordinate). A translational error is a misposition along a first axis and / or along a second axis. The first and second axes are perpendicular to each other and perpendicular to the direction of motion. Roll is a rotation about the axis of motion. Yaw is a rotation about the first axis.Nodding is a rotation around the second axis.

[0019] The new device allows the determination of errors in each degree of freedom. Consequently, the time-consuming design-related minimization of these errors during the development and / or manufacturing of a coordinate measuring machine can be avoided, at least partially. This is economically advantageous.

[0020] The device is designed, for example, to detect systematic errors. These detected systematic errors can then be used to correct them later in a company.

[0021] The object being measured can be a measurement object, a reference target, a marker, a workpiece holder, or a workpiece support. In any case, if the measurement object is positioned on a workpiece support or similar, its position / orientation can be indirectly determined by measuring the position / orientation of the support.

[0022] The transmitter unit can be a device that emits and receives electromagnetic waves, particularly light beams. In other words, the transmitter unit does not serve exclusively as a transmitter, but also partially as a receiver, at least in exemplary embodiments. The transmitter unit can include an optical arrangement. The optical arrangement can include a laser and / or a mirror and / or a lens and / or a filter and / or a detector. The transmitter unit can include a transmitter element. The transmitter element can be configured to emit electromagnetic waves, particularly light beams. The transmitter element can, for example, be a diode laser.

[0023] The spatially resolving sensor can be configured to perform two-dimensional detection, in particular two-dimensional detection of an incident light beam. The spatially resolving sensor can be configured to generate an optical image. The device can have several spatially resolving sensors, for example, three spatially resolving sensors. For example, three spatially resolving sensors can be configured as a single element. The evaluation and control unit can be configured to perform the disclosed method. The evaluation and control unit can include one or more processors. The spatially resolving sensor can be configured to detect spatial coordinates of an incident light beam, for example, two coordinates.

[0024] The target element is, for example, the body itself, or an element attached to it. The target element can also be described as the measurement objective.

[0025] The retroreflector can be configured to reflect incident light rays back in the direction of incidence, largely independent of the direction of incidence. A retroreflector has the advantage that the retroreflected light beam should reliably return to the transmitter unit after being emitted from the transmitter unit to the retroreflector. Using a retroreflector, compared to a reflective surface such as a planar mirror, can be advantageous because a light beam traveling from the transmitter unit to the target element will also return to the transmitter unit, particularly regardless of the geometric arrangement of the transmitter unit relative to the target element. This is especially beneficial, or even essential, for detecting deviations in the arrangement of the transmitter unit relative to the target element.With a planar mirror, the angle of an incident light ray to the planar mirror corresponds to an angle of the reflected light ray, but at deviations of 90° in different directions. If the incident light ray does not strike the planar mirror perpendicularly, the light ray reflected by the planar mirror could miss the sending unit. When using a retroreflector, a reflected ray returns to the sending unit at greater deviations from the perpendicular than with a planar mirror, such as a planar reflective surface. The retroreflector can be configured to reflect a light ray parallel to the incident light ray. A light ray reflected by the retroreflector can be aligned parallel to a light ray striking the retroreflector, but in opposite directions.The back-reflected light ray, also called the retroreflective light ray, can be spaced apart from the light ray striking the retroreflector, in particular parallel to it. Alternatively, the back-reflected light ray and the light ray striking the retroreflector can have identical paths, but in opposite directions.

[0026] The transmitter unit can be configured to emit at least three, in particular six, light beams, in particular laser beams, and / or to receive at least three, in particular six, light beams, in particular laser beams.

[0027] The transmitter unit may have a housing. The light beam may be a beam of an electromagnetic wave with a narrow frequency band. The light beam may be a laser beam. Alternatively, the light beam may have a broad frequency band. The light beam may be a chromatic light beam. For example, the light beam may be at least partially visible light. Alternatively or additionally, the light beam may contain light with frequencies outside the visible spectrum. The light beam may contain radar radiation and / or X-rays.

[0028] The first signal can comprise two spatial coordinates of the position-resolving sensor. The second signal can be an interference signal. The second signal can exhibit a phase difference. Alternatively or additionally, the second signal can have a frequency spectrum. The second signal can also contain one or two spatial coordinates, for example, the position coordinates of a position-resolving sensor. The second signal can be acquired using a photodiode and / or using the position-resolving sensor and / or using another position-resolving sensor.

[0029] The device can be configured to simultaneously detect at least two, in particular at least four, for example five, and in particular six degrees of freedom of the body. Simultaneous detection here means detection at the same time. For example, the device according to the disclosure can be used to simultaneously detect all degrees of freedom of the body and / or all defects of a body. This can result in time savings and / or cost savings.

[0030] The device may include an interferometer arrangement. The interferometer arrangement may be configured to detect the distance between the body and the transmitter unit. The interferometer arrangement may be configured to interfere with two laser beams and to detect an interference signal, for example, the second signal. The interferometer arrangement may be a three-beam interferometer. The interferometer arrangement may be configured to optically detect distances and / or changes in distance. Alternatively or additionally to the interferometer arrangement, the device may include an arrangement for chromatic confocal distance measurement.

[0031] The retroreflector can be part of the interferometer setup. The interferometer setup can include a Michelson interferometer. The interferometer setup can include one or more beam splitters. The interferometer setup can include a photodiode, particularly a fast photodiode. The photodiode can be configured to detect an interference signal, for example, the second signal.

[0032] The evaluation and control unit is designed, for example, to detect a distance from the second signal, such as the distance between the transmitter unit and the body. The interferometer arrangement can be configured to interfere with the retroreflected light beam with another light beam. This second light beam can have the same frequency or a different frequency, for example, a light beam directed towards the retroreflector. The photodiode can detect the superposition of the retroreflected light beam and the second light beam. The photodiode can be an avalanche photodiode.

[0033] The target element can be movable relative to the transmitter unit, and in particular, its movement can be controlled by the evaluation and control unit. The target element can be a carriage or mounted on a carriage. The carriage can be mounted on a rail. The target element can be configured to move along a trajectory by means of a guide. Movement of the target element relative to the transmitter unit can be controlled by the evaluation and control unit. The possibility of controlled movement of the target element relative to the transmitter unit allows the device to detect errors in a coordinate measuring machine at various positions.

[0034] For example, all elements of the target element that influence the light rays can be passive. These elements could include, for example, a retroreflector, a mirror, and / or sensors. The target element can consist solely of passive optical elements. In the context of this disclosure, "passive" means that each element does not require a power supply. Using only passive elements within the target element simplifies assembly and operation, as no wire connections to the target element are necessary.

[0035] The target element can include the position-resolving sensor. In this case, the target element would not consist solely of passive elements. This can be advantageous for increasing the accuracy of the device.

[0036] The device can have at least three retroreflectors, in particular at least six retroreflectors. Preferably, the target element can have at least three retroreflectors, in particular at least six retroreflectors. The retroreflectors can be used, for example, for interferometric distance measurements and / or for chromatic confocal distance measurements and / or for translation measurements. Additionally, the device, in particular the target element, can have a mirror. The mirror can be configured to reflect light rays at the same angle to a fixed spatial coordinate at which the incident light ray strikes the target element.

[0037] The target element can have three retroreflectors and three position-resolving sensors. In particular, the target element can have exactly three retroreflectors and exactly three position-resolving sensors. The three retroreflectors can be configured to reflect three interferometer beams back to the transmitter unit. This allows for the determination of a position error, yaw error, roll error, and / or pitch error. Specifically, the distance between the target element and the transmitter unit can be determined, for example, by averaging. By comparing the three interferometer beams, a yaw error and / or a position error can be detected.The three position-resolving sensors can be configured to detect the impact positions of three light beams emitted by the transmitter unit, for example, to determine a first translation error and a roll error and / or a second translation error and a roll error. This allows all six degrees of freedom to be detected, preferably simultaneously.

[0038] The transmitter unit can have at least one photodiode, in particular at least two photodiodes, and in particular at least three photodiodes. The photodiode can be a fast photodiode. The fast photodiode can, in particular, be designed such that an interference signal can be resolved in order to detect a distance and / or a change in distance.

[0039] The target element can have six retroreflectors. The transmitter unit can include the position-resolving sensor. The transmitter unit can have a total of three position-resolving sensors. This allows the target element to be designed as a passive element. The six retroreflectors can, for example, be configured to reflect at least three interferometer beams and at least three light beams for position-resolving detection. For example, three of the six retroreflectors can form a cooperating pair with the three position-resolving sensors of the transmitter unit, and three of the six retroreflectors and three photodiodes of the target element can form a cooperating pair. A pair can be understood here as a light beam being reflected from one retroreflector of the target element to another element of the pair.

[0040] The spatially resolved sensor is selected, for example, from a sensor group consisting of an image sensor, a camera chip, and a 4Q diode. The image sensor can be configured to capture a two-dimensional image. The camera chip can be a CCD (charge-coupled device) sensor. The 4Q diode is a four-quadrant diode. Using the spatially resolved sensor, for example, two coordinates of the point of impact of a retroreflected light beam can be detected. The use of quadrant diodes enables significantly faster defect detection, especially compared to the use of camera chips.

[0041] The retroreflector can be selected from a group of reflectors consisting of a lens reflector, a cat's eye reflector, a Lüneburg lens, an angle reflector, a triple mirror, a corner cube, a triple prism, a retroreflective film, and a back reflector. For example, the retroreflector can have two mirrors positioned perpendicular to each other. Each of the mirrors can be at an angle of approximately 45° to an incident light beam. This allows retroreflection to be generated. Furthermore, a parallel displacement of the incident light beam can be detected by a position-resolving sensor on the transmitter unit. A corner cube comprises three flat mirrors positioned perpendicular to each other.

[0042] The device can be configured such that a first degree of freedom can be determined from the retroreflected light beam using the spatially resolved sensor, and a second degree of freedom can be determined using the same retroreflected light beam by exploiting an interference effect. This means that only three retroreflectors are required on the target element to detect six different degrees of freedom. This can lead to cost savings.

[0043] For example, the device can have three beam splitters, in particular to split three retroreflected beams, specifically to direct one partial beam to a diode for reading an interference signal and one partial beam to a spatially resolving sensor or to a common spatially resolving sensor for acquiring spatial coordinates. This allows all six degrees of freedom and / or their errors to be determined using only three retroreflectors on the target element. This can result in cost savings.

[0044] The device comprises, by way of example, three elements arranged in a plane at the vertices of a triangle. The triangle is, for example, an equilateral triangle. The three elements can be selected from a group consisting of three retroreflectors, three spatially resolved sensors, three beam splitters, three filters, three photodiodes, three laser sources, three mirrors, three lenses, and three beam outputs, and combinations thereof. The three elements arranged in a plane at the vertices of a triangle can, for example, be located on or within the target element and / or on or within the transmitter unit.

[0045] The three elements are identically designed, at least in exemplary configurations. For example, the target element has three retroreflectors arranged in a plane, each at the vertices of a first equilateral triangle. The target element also has three further retroreflectors arranged in a plane, for example, the same plane, each at the vertices of a second equilateral triangle. The first and second equilateral triangles can share the same center point and be rotated relative to each other by 60°, at least in exemplary configurations. It is understood that a non-equilateral configuration of the triangle is also conceivable.

[0046] Alternatively or additionally, besides the three retroreflectors of the first equilateral or otherwise shaped triangle, the target element can have three position-resolving sensors arranged in a plane at the vertices of the second triangle. By arranging them at the vertices of an equilateral or otherwise shaped triangle, information about all six degrees of freedom can be acquired. Arranging three elements in a plane at the vertices of a triangle, particularly an equilateral triangle, can achieve a special symmetry that can simplify calculations for the evaluation and control unit. For example, the transmitter unit can have three laser sources and / or three light beam exit points arranged at the vertices of an equilateral or otherwise shaped triangle.

[0047] In one exemplary embodiment, the device is configured such that the three light beams from each laser source are directed to each retroreflector and / or each to a spatially resolving sensor. This allows for a symmetrical design. Such a design is clear and offers advantages in terms of assembly and / or adjustment. Furthermore, the installation space requirements can be reduced.

[0048] The filters could be, for example, polarizing filters. A polarizing filter can be used to control the intensity ratio of two partial beams after they have passed through a beam splitter.

[0049] According to a further aspect, the problem of the present disclosure is solved by a coordinate measuring machine comprising a device according to at least one embodiment described herein. In this way, advantageously designed measuring systems can be realized.

[0050] The coordinate measuring machine is designed, for example, to determine a geometric property of a measured object tactilely. Alternatively or additionally, the coordinate measuring machine is designed to determine a geometric property of a measured object optically. In exemplary embodiments, the coordinate measuring machine is designed as a so-called multi-sensor measuring device, i.e., it includes various sensors for tactile and / or optical probing.

[0051] The coordinate measuring machine can, for example, have several devices as disclosed, such as two devices, and in particular three devices. Each device is assigned to an axis (e.g., X, Y, Z). The devices can, for example, be oriented differently, in particular at an angle between 45° and 135°, and in particular at an angle between 85° and 95° with respect to the emitted light rays. This can increase the accuracy of error determination, for example by averaging, and / or enable its use with larger error ranges. In an exemplary embodiment, at least two of the axes (X, Y, Z) and the devices assigned to them are orthogonal to each other.Since every device is designed for detection in multiple degrees of freedom, in particular for detection of errors in multiple degrees of freedom, at least some of the degrees of freedom can be monitored doubly, at least in exemplary embodiments.

[0052] In other words, in exemplary configurations, the coordinate measuring machine does not use the device directly or only partially for measurement, but at least partially also for minimizing errors in the axes of motion. In this way, for example, a coordinate measuring machine with a certain amount of guide play in at least one of the axes of motion can be operated more accurately than would be possible purely structurally with a given guide accuracy. This should not be understood as a limitation.

[0053] According to a further aspect of the present invention, the problem is solved by a method for detecting the position of a body, in particular for detecting errors in several degrees of freedom, comprising the steps of: - Providing a device for detecting the position of the body comprising a transmitter unit, at least one spatially resolving sensor, an evaluation and control unit and a target element with three retroreflectors; - Emitting three parallel beams of light using the transmitter unit; - Reflecting the three light beams as retroreflected light beams back to the transmitter unit, with each of the three retroreflectors reflecting one of the three light beams; - Detection of a first signal by means of the at least one spatially resolving sensor and a second signal from the three retroreflected light beams by means of the transmitter unit; and - Determining the six degrees of freedom of the body, which exhibit a position error, a first translation error, a second translation error, a roll error, a yaw error and a pitch error, by the evaluation and control device using the first signal and the second signal, wherein the first translation error, the second translation error and the roll error are determined from the first signal, and wherein the position error, the yaw error and the pitch error are determined from the second signal.

[0054] The disclosed device and method offer several advantages, at least in exemplary embodiments. Using the new method and device, the position of a body with respect to all six degrees of freedom can be determined with precisely one setup and one measurement step. No modifications by personnel are necessary to determine the six degrees of freedom. A typical sampling rate for the interferometer setup can be in the megahertz range.

[0055] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of this disclosure.

[0056] Exemplary embodiments of the disclosure are shown in the drawing and are explained in more detail below. They show: Fig. 1. An exemplary representation to illustrate the degrees of freedom of a body; Fig. 2A a schematic side view to illustrate an embodiment of a device according to the invention; Fig. 2B a simplified representation of a target element for use in the arrangement according to Fig. 2A; Fig. 2C, Fig. 2D and Fig. 2E Exemplary states of an exemplary design of a device based on Fig. 2A to illustrate how it works; Fig. 3A a simplified representation of a target element of a further embodiment of a device according to the invention; Fig. 3B a schematic side view for illustration to further illustrate the exemplary embodiment according to Fig. 3A; Fig. 3C a simplified schematic representation of a measurement order to illustrate the recording of a translation of the body according to the based on the Fig. 3A and Fig. 3B illustrated example; Fig. 4A a schematic, perspective partial representation of a further embodiment of a device according to the invention; Fig. 4B another schematic representation of the based on Fig. 4A described embodiment; and Fig. 5 A perspective view to illustrate an exemplary embodiment of a coordinate measuring machine.

[0057] Fig. Figure 1 shows a perspective view of a body 12, to illustrate the degrees of freedom of the body 12. The position of the body 12 is illustrated using a three-dimensional coordinate system. Fig. Figure 1 illustrates in particular a position error 48, a translation error 50, a translation error 52, a roll error 54, a yaw error 56 and a pitch error 58. The error contributions 48, 50, 52, 54, 56, 58 are each assigned to a degree of freedom. Fig. Figure 1 further illustrates a guide 60 along which the body 12 is movable. The body 12 is, for example, a sled that is movable along the guide 60, the guide 60 defining a principal direction of movement. For instance, the guide 60 is configured to guide the body 12, in particular a target element 20 applied thereto, along a direction of movement 48, in particular controlled by the evaluation and control unit 18 (see Figure 1). Fig. 2A.

[0058] The Fig. 2A, Fig. 3B and Fig. Figure 4B shows exemplary embodiments of a device designated 10 for position detection, in particular for detecting errors in various degrees of freedom. The device 10 serves to detect the position of the body 12. In the illustrated embodiment, the device 10 comprises a transmitter unit 14, a position-resolving sensor 16, an evaluation and control unit 18, and a target element 20 with a retroreflector 22. The transmitter unit 14 is configured to emit a light beam 24. The retroreflector 22 is configured to reflect the light beam 24 back to the transmitter unit 14 as a retroreflected light beam 26. The position-resolving sensor 16 is configured to detect a first signal. The transmitter unit 14 is configured to detect a second signal from the retroreflected light beam 26.The evaluation and control unit 18 is configured to determine the position of the body 12 using the first and second signals. It is understood that the evaluation and control unit 18 can be a higher-level unit; see [reference to be added]. Fig. 5.

[0059] Fig. Figure 2A illustrates a first embodiment of a device 10 according to the disclosure by means of a simplified representation. The device 10 has a guide 60. The guide 60 is configured to guide the body 12 along the direction of movement 48 in a controlled manner through the evaluation and control unit 18. The device 10 may also have a drive for moving the body 12 relative to the guide 60. The drive may include a motor. The drive may be configured to move the body 12 in a controlled manner through the evaluation and control unit 18.

[0060] The target element 20 can be arranged on the body 12. The target element 20 can be fixedly connected to the body 12. Other, indirect connections are also conceivable. The device 10 has a transmitter unit 14. The transmitter unit 14 can be fixedly connected to an environment 61, for example a table, for example by means of a support 62. The transmitter unit 14 can have a laser source 44, at least in exemplary embodiments. The transmitter unit 14 and / or the target element 20 can be connected to the evaluation and control unit 18 via an interface 64.

[0061] The device 10 includes, by way of example, an interferometer arrangement 30. For example, the transmitter unit 14 is configured to send a light beam 24 from the transmitter unit 14 to the target element 20. The target element 20 may include the retroreflector 22. The device 10 comprises, for example, two sub-devices.

[0062] The first part comprises, for example, the transmitter unit 14. The transmitter unit 14 can, for example, have three laser sources 44. A diode laser can serve as the laser source 44. The diode laser can emit a light beam 24, which can be split into three light beams 24. Thus, a single diode laser acts like three laser sources 44. According to an alternative embodiment, the device 10 has three diode lasers. The transmitter unit 14 is, for example, fixedly arranged on a frame 61 (or a hierarchically superior carriage). The transmitter unit 14 is designed to be immovable, in particular, along the direction of movement 48 of the target element 20.

[0063] The second part includes, for example, the target element 20. The target element 20 can have reflectors, in particular retroreflectors 22. The target element 20 can move or be movable relative to the environment 61, for example a table or frame, and consequently relative to the transmitter unit 14. The movement takes place in a main direction of movement 48. The movement is controlled, for example, by the evaluation and control unit 18.

[0064] The laser sources 44 can, for example, be arranged in a housing of the transmitter unit 14. The transmitter unit 14 is designed to emit three light beams 24, which run parallel in the space between the transmitter unit 14 and the target element 20. For example, the ends of these three light beams 24 can span a plane, forming, for example, an equilateral or otherwise shaped triangle. The plane can be perpendicular to the light beams 24. The ends of the plane can be located at the vertices of a triangle.

[0065] Depending on the arrangement of the laser sources 44, the target element 20 can have a corresponding arrangement of retroreflectors 22. The device 10 can, in particular, be designed such that the light beams 24 are reflected back parallel to themselves upon striking the retroreflectors 22, especially to enable interferometric measurement.

[0066] The evaluation and control unit 18 can be configured to determine relative distances and / or absolute distances after evaluating the three retroreflected light beams 26, depending on the measuring principle. From the relative and / or absolute distances, a position deviation can be determined by averaging, and / or a yaw movement 56, in particular a yaw error 56, and / or a pitch movement 58, in particular a pitch error 58, can be determined by calculating differences between the relative and / or absolute distances obtained using the retroreflected light beams 26. Fig. 1.

[0067] Fig. Figure 4A illustrates a possible design of a target element 20 with three retroreflectors 22 and three beam outputs 46 arranged as described above, as well as three parallel light beams 24 and retroreflected light beams 26 reflected back into themselves.

[0068] Fig. Figure 2B shows an embodiment of a target element 20 for an exemplary embodiment of the device 10, in which the transmitter unit 14 has three further laser sources 44, in addition to the three laser sources 44, whose light beams 24 also run parallel in space. These light beams 24 can run parallel to the three light beams 24 described above, in particular in spaces between the three light beams 24 described above.

[0069] In addition to the retroreflectors 22 described above, which enable position detection, the target element 20 can have spatially resolving sensors 16, for example, three 4-quadrant diodes and / or three camera chips 34. Alternatively to the ones described in Fig. In Figure 2B, the target element 20 can have only a single spatially resolving sensor 16, which is equipped, for example, as a camera chip (or at least similar to a camera chip) and can be dimensioned in such a way that the spatial coordinates of the points of impact of three retroreflected light beams can be detected.

[0070] For example, the retroreflectors 22 can be arranged at the vertices of an equilateral or otherwise shaped triangle. The position-resolving sensors 16 can also be arranged at points of an equilateral or otherwise shaped triangle, wherein the two equilateral triangles are rotated relative to each other by 60° or a similar angle, with both triangles having the same center point. In an exemplary embodiment, the distances between the retroreflectors 22 and / or the position-resolving sensors 16 are known and can be used by the evaluation and control unit 18 to calculate the position of the body 12.

[0071] Positions at which the light rays 24 hit the target element 20, in particular the spatially resolving sensors 16, can be calculated, for example, by center of gravity calculation and / or circle or ellipse fitting to a 2D intensity profile using the evaluation and control unit 18.

[0072] Fig. 2C, Fig. 2D and Fig. Figure 2E shows, by way of example, how translational or rolling errors 54 during a movement of the target element 20 along the direction of movement 48 can affect an impact point 66 on a position-resolving sensor 16. Translational and / or rolling errors 54 during a movement of the target element 20 along the direction of movement 48 can manifest as a variation in the impact points 66 of the light rays 24 on the position-resolving sensor 16.

[0073] When using position-resolving sensors 16 on the target element 20 and three light beams 24 for fault detection, translational and / or rolling movements can be calculated using the evaluation and control unit 18 as described below.

[0074] The three light beams 24, which strike position-resolving sensors 16, each provide an X-position and a Y-position (along the area spanned by the sensor, compare Fig. 2C). The translation of the body 12 in the X-direction corresponds, for example, to a displacement of a light beam 24 incident on a position-resolving sensor 16. To determine a translation of the body 12, an average value can be calculated from two or three X and / or Y positions of light beams incident on position-resolving sensors 16. A rolling motion 54 of the body 12 can correspond to an arctangent of the projected difference of the determined X and Y positions of the incident light beams, perpendicular to the vector distance between the two light beams 24. This method can also be used if quadrant diodes 34 are used instead of camera chips.

[0075] Only the acquisition of the X and / or Y position of the light beams 24 incident on the target element 20 needs to be adjusted accordingly when using quadrant diodes instead of one or more camera chips 34. If more than two additional laser beams are used for translational and / or roll measurement, for example, three additional laser beams, it is recommended to determine the errors by best fitting them through translational and rotational transformation of the reference arrangement to the detected positions, for example, by a rigid-body transformation. When using multiple quadrant diodes or multiple camera chips 34, these can be aligned and / or calibrated relative to each other using a suitable strategy, for example, before initial commissioning.

[0076] The Fig. 3A, Fig. 3B and Fig. Figure 3C shows a further embodiment of the device 10 according to the invention. In contrast to the first embodiment shown in the Fig. In the second embodiment of the device 10 for determining the translations and the rolling motion of the target element 20 described in sections 2A to 2E, the second embodiment of the device 10 for determining the translations and the rolling motion of the target element 20 has no active components, i.e., no components that require power and / or signal interfaces. This is advantageous for certain applications because it significantly simplifies the design.

[0077] The inventors have realized that, for the construction of a device 10 with a purely passive target element 20, the camera chips 34 and / or quadrant diodes of the target element 20 of the first embodiment can be replaced by retroreflectors 22. Thus, by means of six retroreflectors 22 of the target element 20, six incident light rays 24 can be reflected from the target element 20 as retroreflected light rays 26 back to the transmitter unit 14.

[0078] Retroreflectors 22 typically have the property of reflecting incident light rays 24 back in the same direction in which they struck the retroreflector 22. If the ray diameter of a light ray striking a retroreflector 22 corresponds to the aperture of the retroreflector 22, or if the ray diameter is larger than the aperture of the retroreflector 22, the light ray 24 is reflected back parallel to itself. However, if the ray diameter is significantly smaller than the aperture of the retroreflector 22, the incident light ray 24 is reflected parallel to itself, but not back to itself, as is the case, for example, in Fig. 3C shown.

[0079] Fig. Figure 3C shows a beam path of incoming light rays 24 and retroreflected light rays 26 for two different positions of the target element 20. Fig. 3C illustrates how a position error of 48 ( Fig. 1) of the body 12 leads to a beam offset 70 between the retroreflected light beams 26 from two different positions of the target element 20. In the Fig. In the example shown in Figure 3C, the beam offset 70 between the incident light beam 24 and the retroreflected light beam 26 corresponds exactly to twice the translation of the target element 20 between the two. Fig. Positions shown in 3C.

[0080] The inventors have recognized that pitch and / or yaw movements of the target element 20 can also influence the beam offset 70 of the retroreflected light beam 26, but that these result in cosine deviations which can be neglected for small angles and / or can be calculated and compensated for by means of the evaluation and control device 18 via the already carried out detection of the yaw and pitch movements.

[0081] The second embodiment of the device 10 according to the disclosure has six retroreflectors 22 on the target element 20. In this embodiment, both the beam source 44, or multiple beam sources 44, and the spatially resolving sensors 16, for example configured as camera chips 34 or quadrant diodes, are arranged in the transmitter unit 14. Thus, the target element 20 is designed entirely as a passive component. The transmitter unit 14 serves not only as a transmitter but also as a receiver.

[0082] The in Fig. The transmitter unit 14 shown in Figure 3B has, by way of example, a beam splitter 42. For example, a light beam 24 can be directed to the target element 20 by transmission at the beam splitter 42 of the transmitter unit 14. After retroreflection at the target element 20, the retroreflected light beam 26 can be reflected and expanded at the beam splitter 42, for example by means of a spatially resolving sensor 16. Alternatively, a light beam 24 can be guided from the transmitter unit 14 to the target element 20 by reflection at the beam splitter 42, and then the retroreflected light beam 26 can be transmitted and expanded at the beam splitter 42, for example by means of a spatially resolving sensor 16 or by means of a photodiode 32. By means of the beam splitter 42, a light beam 24 directed towards the target element 20 and a light beam 26 retroreflected from the target element 20 can be spatially separated.The beam splitter 42 can be used alternatively or additionally to split a retroreflected light beam 26 and to evaluate it both interferometrically and by means of a spatially resolving sensor 16.

[0083] As in the first embodiment of the device 10, in the second embodiment of the device 10 at least some of the evaluation elements, for example a spatially resolving sensor 16 and / or a photodiode 32, can also be linked to each other by means of an adjustment and / or a measurement strategy and / or a calibration. The transmitter unit 14 has, by way of example, a housing 72. The housing 72 is in Fig. 3B is represented by dashed lines.

[0084] The Fig. 4A and Fig. Figure 4B shows a third embodiment of the device 10 according to the invention. In this third embodiment, the target element 20 is also passively designed. Elements for detecting translation and roll motion are arranged in the transmitter unit 14 and can be coupled in or out via a beam splitter 42. In contrast to the first two embodiments, only three light beams 24 are now required to guide the target element 20. For example, only three light sources and / or light exit apertures 46 are required in the transmitter unit 14. The laser beams for position measurement can also be used for interferometric measurement, particularly using the beam splitters 42, especially for measuring translation and roll motion. Thus, the embodiment according to the Fig. 4A and Fig. 4B requires only three retroreflectors 22, three laser sources 44, and three beam splitters 42. This reduces costs and installation space requirements.

[0085] Fig. Figure 5 shows an embodiment of a coordinate measuring machine 74. The coordinate measuring machine 74 has, for example, a measuring head 78 mounted on a boom 76. Furthermore, the coordinate measuring machine 74 includes, for example, a column 80 and a base 84. The coordinate measuring machine 74 also includes a workpiece holder 82 for a workpiece. The workpiece holder 82 can also be referred to as a support or table for a workpiece. For example, the column 80 is movable relative to the workpiece holder 82, or vice versa. Alternatively or additionally, the workpiece holder 82 can be movable relative to the measuring head 78. Typically, the coordinate measuring machine provides at least three translational axes for the relative movement between the workpiece holder 82 and the measuring head 78. Each of these axes includes, for example, at least one guide and an element movable along the guide, such as a slide.

[0086] Errors can occur in one or more degrees of freedom on each axis. For example, error components exist in all six degrees of freedom (three translational degrees of freedom and three rotational degrees of freedom); see [reference]. Fig. 1. The measuring head 78 can, for example, have a tactile sensor 86 and / or an optical sensor 88. The coordinate measuring machine 74 is designed, by way of example, to determine a geometric property of a measured object, for example the body 12, tactilely and / or optically.

[0087] The coordinate measuring machine 74, in its exemplary embodiment, comprises a device 10 for position detection according to at least one exemplary embodiment described herein. The device 10 includes, by way of example, a transmitter unit 14 and a target element 20. The target element 20 is, by way of example, arranged on the workpiece holder 82 (in Fig.(5 shown only schematically). The transmitter element 14 is arranged on the column 80 by way of example. The coordinate measuring machine 74 is configured by way of example to move the target element 20 relative to the transmitter element 14.

[0088] The device 10 is designed, for example, to detect erroneous movements of the coordinate measuring machine 74, in particular of its workpiece holder 82. Preferably, the device 10 is designed to detect errors in at least three degrees of freedom, preferably in six degrees of freedom.

[0089] Device 10 can be used for the actual dimensional measurement / acquisition, for example, to determine the specific position along the respective axis. Additionally, device 10 can be used for multidimensional error detection of the affected axis. Overall, this allows for the realization of a highly accurate measuring system.

Claims

[1] Device (10) for detecting the position of a body (12), in particular for detecting errors in several degrees of freedom, wherein the device (10) comprises a transmitter unit (14), at least one spatially resolving sensor (16), an evaluation and control unit (18) and a target element (20) with three retroreflectors (22), wherein the transmitter unit (14) is configured to emit three parallel light beams (24), wherein the retroreflectors (22) are configured to reflect one of the three light beams (24) back to the transmitter unit (14) as a retroreflected light beam (26), wherein the at least one spatially resolving sensor (16) is configured to detect a first signal, wherein the transmitter unit (14) is configured to detect a second signal from the three retroreflected light beams (26), and wherein the evaluation and control unit (18) is configuredto determine, by means of the first signal and the second signal, six degrees of freedom of the body (12) exhibiting a position error (48), a first translation error (50), a second translation error (52), a roll error (54), a yaw error (56) and a pitch error (58), wherein the evaluation and control device (18) is configured to determine, by means of the first signal, the first translation error (50), the second translation error (52) and the roll error (54) and, by means of the second signal, the position error (48), the yaw error (56) and the pitch error (58). [2] Device according to claim 1, wherein the device (10) comprises an interferometer arrangement (30). [3] Device according to claim 2, wherein the three retroreflectors (22) are part of the interferometer arrangement (30). [4] Device according to one of claims 1 to 3, wherein the target element (20) is movable relative to the transmitter unit (14). [5] Device according to one of claims 1 to 4, wherein the target element (20) has the at least one spatially resolving sensor (16). [6] Device according to claim 5, wherein the at least one spatially resolving sensor (16) comprises three spatially resolving sensors (16). [7] Device according to any one of claims 1 to 4, wherein all elements (22) of the target element (20) influencing the light rays (24) are passive. [8] Device according to one of claims 1 to 7, wherein the transmitter unit (14) has a photodiode (32), in particular at least two photodiodes (32), in particular at least three photodiodes (32). [9] Device according to any one of claims 1 to 8, wherein the target element (20) has six retroreflectors (22) and wherein the transmitter unit (14) has at least one spatially resolving sensor (16). [10] Device according to any one of claims 1 to 9, wherein the device (10) has three elements arranged in a plane at vertices of a triangle, wherein the three elements are selected from a group consisting of the three retroreflectors (22), three spatially resolving sensors (16), three beam splitters (42), three filters, three photodiodes (32), three laser sources (44), three mirrors, three lenses and three beam outputs (46), and combinations thereof. [11] Coordinate measuring machine with a device (10) according to any one of claims 1 to 10. [12] Coordinate measuring machine according to claim 11, wherein the coordinate measuring machine (74) is further configured to determine a geometric property of a measuring object tactilely and / or optically. [13] Method for detecting the position of a body (12), in particular for detecting errors in several degrees of freedom, comprising the steps: - Providing a device (10) for detecting the position of the body (12) comprising a transmitter unit (14), at least one spatially resolving sensor (16), an evaluation and control unit (18), and a target element (20) with three retroreflectors (22); - Emitting three parallel light beams (24) by means of the transmitter unit (14); - Reflecting the three light rays (24) as retroreflected light rays (26) back to the transmitter unit (14), with each of the three retroreflectors (22) reflecting one of the three light rays (24) at each of the three retroreflectors (22); - Detection of a first signal by means of the at least one spatially resolving sensor (16) and of a second signal from the three retroreflected light beams (26) by means of the transmitter unit (14); and - Determining the six degrees of freedom of the body (12), which exhibit a position error (48), a first translation error (50), a second translation error (52), a roll error (54), a yaw error (56) and a pitch error (58), by the evaluation and control device (18) using the first signal and the second signal, wherein the first translation error (50), the second translation error (52) and the roll error (54) are determined from the first signal, and wherein the position error (48), the yaw error (56) and the pitch error (58) are determined from the second signal.

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