Method and system for determining posture and method for producing diffractive optical element

Abstract

The invention relates to a method and a system for determining gestures that capture at least one two-dimensional diffraction pattern generated in the far field by diffraction of coherent radiation (14) at a diffractive element (30). The diffractive element (30) has an aperiodic volume diffractive structure (31). A posture of the diffractive element (30) is determined based on the at least one two-dimensional diffraction pattern and data dependent on the aperiodic volume diffraction structure (31).

Description

Field of the Invention

[0001] The present invention relates to a method and a system for determining a pose. The present invention also relates to a production method and a production system for producing components for a pose determination system. The present invention particularly relates to a method and a system for determining a pose using electromagnetic radiation and components thereof. Background Art

[0002] The determination of the pose of an element has many applications, for example in manufacturing technology or medical engineering. An exemplary application area is the determination of the pose of a workpiece (i.e., the determination of translational and rotational degrees of freedom). This can be conventionally performed using tactile methods or without contact.

[0003] Techniques for non-contact pose determination of an element require certain trade-offs. For example, in the case of a camera tracking system using multiple cameras or interferometric techniques, there is an interaction between the achievable accuracy and the achievable spatial dynamic range (i.e., the detection volume and / or the solid angle range). Achieving high accuracy over a large detection volume and / or a large solid angle range is challenging.

[0004] For camera-based detection using a single camera, it is generally not possible to clearly distinguish the characteristic markings of deflections in one degree of freedom from deflections in other degrees of freedom. For example, this can be partially overcome by using multiple cameras. In this regard, a camera tracking system with incoherent illumination is an example. Furthermore, in the case of a system with incoherent illumination, relatively high accuracy can typically be achieved in two translational coordinates, but the resolution in the remaining directions is usually much poorer.

[0005] The use of coherent illumination can provide improvements with respect to these disadvantages of incoherent illumination systems. The measurement of the relative phase angles of the involved wave trains also allows the reconstruction of the pose in the depth direction (i.e., along the beam direction) with interferometric accuracy.

[0006] In addition to the accuracy achievable in up to six degrees of freedom, the various conventional methods also differ in terms of the absolute accuracy that can be achieved in each case. Typically, the intrinsic camera parameters and the extrinsic camera parameters are calibrated by known test standards. In a multi-camera system, the absolute positions of the individual cameras can be calibrated from it, and the absolute pose of the target object for pose determination can be obtained accordingly from it. In the case of a single-camera system and a pose determination target including a repeating grating structure, absolute pose determination is usually only possible using additional measurement techniques.

[0007] Therefore, there is still a need for improved methods and systems for determining the pose of an object of interest. In particular, there is a need for systems and methods that provide improvements in achievable accuracy and / or the dynamic range that enables pose determination. In particular, there is a need for such systems and methods that allow for the determination of an absolute pose (absolute translational position and / or rotational position relative to a reference frame) with high accuracy. There is also a need for components that can be used in such pose determination methods, and a method for producing such components. SUMMARY OF THE INVENTION

[0008] According to the present invention, a system and a method as defined in the independent claims are set forth. The dependent claims define preferred and advantageous exemplary embodiments.

[0009] According to one aspect, the present invention relates to a pose determination system. The pose determination system includes the following: a diffraction element including an aperiodic volume diffraction structure; at least one detector designed to detect at least one two-dimensional diffraction pattern generated in the far field by the diffraction of coherent radiation at the diffraction element; and an evaluation device designed to determine the pose of the diffraction element based on the at least one two-dimensional diffraction pattern and data dependent on the aperiodic volume diffraction structure.

[0010] Performing non-contact pose determination using coherent radiation enables high accuracy to be achieved in all degrees of freedom. Using an element including an aperiodic volume diffraction structure enables the absolute value of the pose (i.e., the position value and / or rotation relative to a coordinate system that can be defined by at least one detector) to be determined. Embodiments of the aperiodic structure of the aperiodic volume diffraction structure contribute to determining the pose over a relatively large dynamic range, particularly a relatively large solid angle range.

[0011] Knowledge of the aperiodic volume diffraction structure is used to evaluate the two-dimensional diffraction pattern or the plurality of two-dimensional diffraction patterns. Thus, this technique is different from conventional speckle methods, for example, in which there is no knowledge of the embodiment of the diffraction structure and it is not available for evaluation. For example, data about the aperiodic volume diffraction structure can define the arrangement of scattering centers in the element. Data about the aperiodic volume diffraction structure can be transferred, for example, from a manufacturing system for manufacturing the element or the diffraction structure in the element to the evaluation device.

[0012] The diffraction element can be implemented such that the at least one two-dimensional diffraction pattern that appears at the at least one detector can be uniquely assigned to the pose of the diffraction element in the detection volume.

[0013] For this purpose, for example, an aperiodic volume diffraction structure can be defined in a way that depends on the dimensions of the detection volume, the desired solid angle range of possible rotation of the element, and the detector area of the at least one detector.

[0014] This can ensure that for the corresponding available detector configurations, unique pose determination within the desired dynamic range is possible.

[0015] The diffraction element can be implemented such that it does not produce a repetition of a two-dimensional diffraction pattern of coherent radiation over a predetermined volume and / or over a predetermined solid angle range.

[0016] This can ensure that for the corresponding available detector configurations, unique pose determination within the desired dynamic range is possible.

[0017] The system can include additional redundant measurement systems in order to resolve possible ambiguities of the two-dimensional diffraction pattern.

[0018] The diffraction element can be implemented such that the diffraction element produces a diffraction pattern over a solid angle range of at least 2π, greater than 2π, greater than 3π, or 4π.

[0019] This enables pose determination even when the element rotates within a correspondingly large solid angle range.

[0020] The diffraction element can include a transparent or translucent material in which the scattering centers of the diffraction structure are formed.

[0021] The diffraction element can include a glass or quartz material in which the at least one diffraction structure is formed.

[0022] Thus, good temperature stability of the measurement technique can be achieved.

[0023] The diffraction element can include a material with a CTE value not exceeding 100 ppb / K, not exceeding 50 ppb / K, not exceeding 20 ppb / K, or not exceeding 10 ppb / K at room temperature, such as a glass or quartz material with high temperature stability.

[0024] Thus, good temperature stability of the measurement technique can be achieved.

[0025] The diffraction element can have a faceted surface, such as a surface with one or more polyhedral parts.

[0026] This can facilitate diffraction into a relatively large solid angle range.

[0027] The diffraction structure may include a pseudo-randomly distributed structure, where the data used by the evaluation device depends on this pseudo-randomly distributed structure. In other words, the scattering centers may be randomly or pseudo-randomly distributed during the design process of the element, but the embodiments of the diffraction structure are deterministic in the sense that it is known and can be used to evaluate this two-dimensional diffraction pattern or these two-dimensional diffraction patterns.

[0028] This facilitates the configuration of the element, which enables a unique assignment of the pose to be carried out with high accuracy even over a relatively large dynamic range (e.g., a relatively large detection volume and / or a relatively large solid angle range of possible rotations of the element).

[0029] The evaluation device may be designed to computationally determine at least three degrees of freedom of the diffraction element for pose determination. The evaluation device may be designed to computationally determine three translational degrees of freedom and / or three rotational degrees of freedom of the diffraction element for pose determination.

[0030] Thus, all degrees of freedom relevant to the corresponding application can be determined.

[0031] The evaluation device may be designed to, for pose determination, compare the at least one two-dimensional diffraction pattern with a plurality of two-dimensional reference diffraction patterns determined according to calibration measurement results or computationally verified depending on the aperiodic volume diffraction structure. The evaluation device may be designed to computationally verify the reference diffraction pattern based on data dependent on the diffraction structure. For this purpose, the forward propagation of the coherent radiation can be computationally verified. To reduce the computational complexity, a rough estimate of the pose can be used to reduce the parameter space to be sampled for computationally determining the reference diffraction pattern.

[0032] The evaluation device may be designed to, for pose determination, use a trained machine learning model to process the at least one two-dimensional diffraction pattern captured by the at least one detector. Thus, the pose determination can be performed with the aid of a trained machine learning model without expert knowledge. The machine learning model may include an input layer that receives the pixel values of the at least one two-dimensional diffraction pattern captured by the at least one detector. The machine learning model may include an output layer that outputs information about the pose. The use of the machine learning model can be combined with the above-mentioned forward propagation to calculate the expected reference diffraction pattern. For example, the machine learning model may be configured such that it receives both the captured at least one two-dimensional diffraction pattern and the reference diffraction pattern, and outputs an indication reflecting the probability that the captured at least one two-dimensional diffraction pattern corresponds to the same pose as the reference diffraction pattern as an output.

[0033] The evaluation device can be designed to perform an approximate procedure for pose determination. The approximate procedure can include an iterative procedure. The approximate procedure can include an iterative refinement of the estimation of the pose. The estimation can be provided by another measuring unit of the system, which operates at a lower resolution. Thus, by evaluating at least one captured two-dimensional diffraction pattern and combining data dependent on the diffraction structure, the results of the other measuring unit can be refined. The approximate procedure can also include using an element that, in addition to the aperiodic volume diffraction structure, includes another diffraction structure, which can be periodic and enables the estimation of the pose.

[0034] The system can include at least one source of coherent radiation, which is designed to radiate coherent radiation onto a diffraction element.

[0035] The at least one source of coherent radiation can include a laser, which generates and outputs coherent radiation or at least one wavelength component of coherent radiation.

[0036] The at least one source can be configured to radiate coherent radiation having multiple different wavelengths onto the diffraction element. The coherent radiation can include a first radiation component having a first wavelength and a second radiation component having a second wavelength. The at least one detector can be configured to capture different wavelengths in different channels.

[0037] Thus, the accuracy of pose determination can be further improved.

[0038] The first radiation component and the second radiation component are coherent with each other and can advantageously be phase-stable relative to each other.

[0039] Thus, the accuracy of pose determination can be further improved. In particular, the interference effects between the radiation components can be used to generate one or more synthetic wavelengths and use them in pose determination.

[0040] The at least one source of coherent radiation can include one source that outputs both the first radiation component and the second radiation component. The at least one source of coherent radiation can include a first source and a second source, where the first source generates and outputs the first radiation component and the second source generates and outputs the second radiation component. The at least one source of coherent radiation can be phase-locked. The at least one source of coherent radiation can include a frequency comb generator.

[0041] The use of such a source enables the desired determination of the absolute pose.

[0042] The at least one source may be arranged in a stationary manner relative to the diffraction element. For example, the source (e.g., the end of an optical fiber coupled to a laser or a frequency comb) and the diffraction element may both be attached to the same carrier. For example, the carrier may be a workpiece, a tool, or a medical device, the pose of which in the detection volume is intended to be determinable over a certain spatial rotation range.

[0043] By using a source arranged in a stationary manner relative to the diffraction element, the generation of the diffraction pattern and its evaluation can be facilitated. In particular, it is no longer necessary to update the beam axis of the coherent radiation according to the current translational position of the diffraction element.

[0044] The diffraction element may be arranged in a movable manner relative to the at least one source. The tracking mechanism of the system may be designed to update the beam axis of the coherent radiation such that the coherent radiation is incident on the diffraction element.

[0045] The system may be or include an industrial manufacturing system, an industrial measurement system, or a medical engineering system.

[0046] The system may include a robot or any other actuator or actuator chain, such as a multi-axis robot, which is controllable to change the translational position and / or angular alignment of a workpiece, a tool, or a medical device. The pose of the workpiece, the tool, or the medical device may be determined using the system according to the invention. In this case, the diffraction element may be arranged on the workpiece, the tool, or the medical device, or on a movable part of the robot.

[0047] The system may include a human-machine interface by means of which the results of the pose determination can be output.

[0048] Alternatively or additionally, the system may be designed to use the results of the pose determination to control at least one actuator. The system may be designed such that an industrial manufacturing process, industrial quality control, and / or a medical engineering instrument are affected by the control of the at least one actuator.

[0049] According to another aspect of the invention, a method for producing a diffraction element for pose determination is set forth, wherein the method includes: determining an aperiodic volume diffraction structure, controlling a production apparatus for producing a diffraction element including the aperiodic volume diffraction structure, and providing data dependent on the aperiodic volume diffraction structure for determining the pose of the diffraction element.

[0050] Such a diffraction element is configured to be used in a pose determination system and method according to the invention. Such an element allows for the determination of an absolute pose with high accuracy over a relatively large dynamic range. The production method also provides data for subsequent use in pose determination. The data may include information about the arrangement of the scattering centers of the aperiodic volume diffraction structure.

[0051] The method can be a method for providing a diffractive element and data to be used in determining the pose of the diffractive element. Accordingly, a method for providing a diffractive element and data to be used in determining the pose of the diffractive element can include: determining an aperiodic volume diffraction structure, controlling a production apparatus for producing a diffractive element including the aperiodic volume diffraction structure, and providing data dependent on the aperiodic volume diffraction structure for determining the pose of the diffractive element.

[0052] The following optional features can be applied to a method for producing a diffractive element for pose determination and to a method for providing a diffractive element and data to be used in determining the pose of the diffractive element.

[0053] The aperiodic volume diffraction structure can be determined and produced in such a way that the at least one two-dimensional diffraction pattern occurring at the at least one detector can be uniquely assigned to the pose of the diffractive element in the detection volume.

[0054] For this purpose, for example, the aperiodic volume diffraction structure can be defined in a way that depends on the radius of the detection volume, the desired solid angle range of possible rotations of the element, and the detector area of the at least one detector.

[0055] This can ensure unique pose determination within the desired dynamic range for the respective available detector configurations.

[0056] The aperiodic volume diffraction structure can be determined and produced in such a way that it does not produce a repetition of a two-dimensional diffraction pattern of coherent radiation on a predetermined volume and / or within a predetermined solid angle range.

[0057] This can ensure unique pose determination within the desired dynamic range for the respective available detector configurations.

[0058] The diffractive element can be produced such that the diffractive element produces a diffraction pattern over a solid angle range of at least 2π, greater than 2π, greater than 3π, or 4π.

[0059] This enables pose determination even when the element rotates within a correspondingly large solid angle range.

[0060] The diffractive element can be produced in such a way that it includes a transparent or translucent material in which scattering centers of the diffraction structure are formed.

[0061] This enables pose determination over a relatively large solid angle range. Compared to reflection techniques, the shadow of the element at the location where coherent radiation is diffracted is avoided.

[0062] The diffractive element can be produced in such a way that it has a faceted surface, for example a surface with one or more polyhedral parts.

[0063] This can facilitate diffraction into a relatively large solid angle range.

[0064] The production apparatus can include means for laser writing an aperiodic volume diffraction structure. Alternatively or additionally, the production apparatus can include means for three-dimensionally printing the diffractive element.

[0065] The production method can include fixing the diffractive element to a component of an industrial system or a medical engineering system.

[0066] According to another aspect of the invention, a diffractive element including an aperiodic volume diffraction structure is set forth.

[0067] The diffractive element can be produced by a production method according to one aspect or an exemplary embodiment.

[0068] The diffractive element can be implemented such that the at least one two-dimensional diffraction pattern occurring at the at least one detector can be uniquely assigned to the pose of the diffractive element in the detection volume.

[0069] For this purpose, for example, the aperiodic volume diffraction structure can be defined in a way that depends on the radius of the detection volume, the desired solid angle range of possible rotations of the element, and the detector area of the at least one detector.

[0070] This can ensure unique pose determination within the desired dynamic range for the respective available detector configurations.

[0071] The diffractive element can be implemented such that it does not produce a repetition of the two-dimensional diffraction pattern of coherent radiation over a predetermined volume and / or over a predetermined solid angle range.

[0072] This can ensure unique pose determination within the desired dynamic range for the respective available detector configurations.

[0073] The diffractive element can be implemented such that the diffractive element produces a diffraction pattern over a solid angle range of at least 2π, greater than 2π, greater than 3π, or 4π.

[0074] This enables pose determination even when the element rotates within a correspondingly large solid angle range.

[0075] The diffractive element can include a transparent or translucent material in which the scattering centers of the diffraction structure are formed.

[0076] The diffractive element can have a faceted surface, for example a surface with one or more polyhedral parts.

[0077] This can promote diffraction into a relatively large solid angle range.

[0078] According to another aspect of the invention, a pose determination method is set forth, the pose determination method comprising: capturing, by means of at least one detector, at least one two-dimensional diffraction pattern generated in the far field by the diffraction of coherent radiation at the diffraction element, wherein the diffraction element comprises an aperiodic volume diffraction structure; and determining the pose of the diffraction element based on the at least one two-dimensional diffraction pattern and data dependent on the aperiodic volume diffraction structure.

[0079] The method can be performed by a pose determination system according to an exemplary embodiment.

[0080] Additional optional features of the pose determination method and the effects achieved thereby respectively correspond to the features and effects described with reference to the system.

[0081] According to one aspect, the invention relates to an evaluation device for a pose determination system. The evaluation device comprises: an interface for receiving at least one two-dimensional diffraction pattern generated in the far field by the diffraction of coherent radiation at the diffraction element; and a processing circuit designed to determine the pose of the diffraction element based on the at least one two-dimensional diffraction pattern and data dependent on the aperiodic volume diffraction structure.

[0082] Additional optional features of the evaluation device and the effects achieved thereby respectively correspond to the optional features described with reference to the pose determination system.

[0083] According to another aspect of the invention, machine-readable instruction code is set forth, which, when executed by a programmable computing unit, performs the method according to one aspect or an exemplary embodiment of the invention.

[0084] According to another aspect of the invention, a storage medium having stored thereon machine-readable instruction code is set forth, which, when executed by a programmable computing unit, performs the method according to one aspect or an exemplary embodiment of the invention.

[0085] The methods, systems, and system components according to the exemplary embodiments of the invention achieve various effects. Determination of the absolute pose is possible. The absolute pose determined according to the invention can include up to three translational degrees of freedom and / or up to three rotational degrees of freedom relative to a coordinate system defined by the at least one detector. Compared with various conventional methods for absolute pose determination, the pose determination can be implemented with higher accuracy and in a larger dynamic range.

[0086] These methods, systems, and system components can be used in different fields. This includes pose determination in industrial environments, such as pose determination in industrial manufacturing and / or quality control. These methods, systems, and system components can also be used in the context of medical engineering devices or medical engineering systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Exemplary embodiments of the present invention will now be described with reference to the drawings. In the drawings, like or identical reference numerals denote elements having like or identical embodiments and / or functions.

[0088] Figure 1 A pose determination system according to an exemplary embodiment is shown.

[0089] Figure 2 Shows the Figure 1 system after the optical element has been translated and rotated.

[0090] Figure 3 An evaluation device of the system according to an exemplary embodiment is shown.

[0091] Figure 4 A schematic diagram of a machine learning structure that the evaluation device may optionally include is shown.

[0092] Figure 5 Is a flowchart of a method according to an exemplary embodiment.

[0093] Figure 6 Is a flowchart of a method according to an exemplary embodiment.

[0094] Figure 7 Is a schematic diagram of a diffraction element that can be used in the systems and methods according to exemplary embodiments.

[0095] Figure 8 A pose determination system according to an exemplary embodiment is shown.

[0096] Figure 9 And Figure 10 Shows the operating modes of the pose determination system.

[0097] Figure 11 And Figure 12 Shows the operating modes of the pose determination system.

[0098] Figure 13 And Figure 14 Shows the operating modes of the pose determination system.

[0099] Figure 15 And Figure 16 Shows a radiation source that can be used in the pose determination systems and methods according to the present invention.

[0100] Figure 17 Shows a system according to an exemplary embodiment.

[0101] Figure 18 Shows a flowchart of a production method according to an exemplary embodiment.

[0102] Figure 19 Shows a block diagram for explaining the operation mode of an optical element production method according to an exemplary embodiment.

[0103] Figure 20 Is a schematic diagram of a diffractive element that can be used in the system and method according to the exemplary embodiment. Detailed Description

[0104] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. In the drawings, like or identical reference numerals denote elements having like or identical embodiments and / or functions.

[0105] Although the exemplary embodiments are described in the context of position determination in an industrial environment or medical engineering, the systems and methods described herein are not limited to these application areas.

[0106] The features of the exemplary embodiments can be combined with each other, unless this is explicitly excluded in the following description.

[0107] The pose determination method and system according to the exemplary embodiment allow for determining the absolute pose of an optical element. Determining the absolute pose herein shall be understood to mean determining up to three translational degrees of freedom and / or up to three rotational degrees of freedom relative to a reference system, relative to which the diffractive element can be moved. For example, the reference system can be defined by one or more detectors used for capturing two-dimensional diffractive patterns in the pose determination.

[0108] The determined pose can be the pose of the optical element or the pose of a rigid part (such as a workpiece, tool, or surgical instrument) connected thereto and derived therefrom.

[0109] The pose determination method and system perform pose determination using a two-dimensional diffraction pattern in the far field. In this process, coherent radiation is radiated onto a diffraction element. In the art, the far field of the two-dimensional diffraction pattern generated by the diffraction structure is to be understood here in particular as referring to the distance between the detector and the diffraction structure, which distance allows the use of the Fraunhofer approximation for computationally determining the two-dimensional diffraction pattern. This detector or each detector for capturing the two-dimensional diffraction pattern can be, for example, at a distance of at least twice the wavelength of the coherent radiation, at least three times the wavelength of the coherent radiation, at least five times the wavelength of the coherent radiation, or at least ten times the wavelength of the coherent radiation from the diffraction element. If coherent radiation with multiple wavelengths is used, the aforementioned minimum distance can be determined based on the longest wavelength that is captured by at least one detector and subsequently evaluated by the evaluation device for pose determination.

[0110] The two-dimensional pattern can be a corresponding granular interference pattern.

[0111] Figure 1 The pose determination system 10 is shown. The system 10 is designed to determine the absolute pose of the diffraction element 30 in the detection volume 11. The system 10 can be designed to determine both the translational position and the rotation of the diffraction element 30 relative to a coordinate system 200 defined by at least one detector 12.

[0112] The system 10 includes at least a diffraction element 30, one or more detectors 12, and an evaluation device 20.

[0113] The diffraction element 30 includes an aperiodic volume diffraction structure 31. The aperiodic volume diffraction structure 31 can be formed, for example, by laser writing or three-dimensional printing. In addition to the aperiodic volume diffraction structure 31, the diffraction element 30 can optionally include additional structures, in particular additional diffraction structures. This additional diffraction structure can be periodic and can be used, for example, to confirm an initial estimate of the pose, which is subsequently refined by the techniques described in detail below.

[0114] The one or more detectors 12 are designed to capture at least one two-dimensional diffraction pattern generated by the diffraction of coherent radiation 14 at the diffraction element 30. The one or more detectors 12 are designed to capture this at least one two-dimensional diffraction pattern in the far field in order to facilitate computationally based pose determination. For this purpose, the one or more detectors 12 can be arranged around the detection volume 11 at a distance from the diffraction element 30, in particular at a distance from the aperiodic volume diffraction structure 31. The position of each detector 12 can be defined to ensure that for each pose of the diffraction element 30 in the detection volume 11, the detector 12 captures a two-dimensional diffraction pattern in the far field.

[0115] Each detector 12 may include a two-dimensional arrangement of sensor pixels. These sensor pixels may be arranged in the detector area. Various sensors known in the art may be used. If the coherent radiation 14 includes different radiation components having different wavelengths, each detector 12 may include a plurality of color channels. The plurality of color channels may correspond to different wavelengths, but if the different radiation components are phase-stable relative to each other, the plurality of color channels may also include at least one color channel corresponding to a composite wavelength generated by the coherent superposition of two radiation components that are phase-stable relative to each other.

[0116] The coherent radiation diffracted at the diffraction element 30 is schematically represented as radiation 15 incident on the detector 12.

[0117] The evaluation device 20 is designed to evaluate one or more two-dimensional diffraction patterns captured by the one or more detectors 12. In order to determine the pose based on the at least one two-dimensional diffraction pattern, the evaluation device 20 also uses data that depends on the aperiodic volume diffraction structure 31 and that may define the configuration of the diffraction structure 31. For example, the data used may originate from the production process of the aperiodic volume diffraction structure 31. For example, the data may define the arrangement of scattering centers in the aperiodic volume diffraction structure 31 produced, for example, by laser writing or 3D printing.

[0118] Reference is made below to Figures 3 to 6 describe in more detail further features and operating modes of the evaluation device 20.

[0119] The system 10 may include a radiation source 13 that radiates coherent radiation 14 onto the diffraction element 30. The radiation source 13 may include one or more lasers. The radiation source 13 may be designed to radiate coherent radiation having exactly one wavelength onto the diffraction element 30. The exactly one wavelength may be determinable fixedly or time-dependently.

[0120] The radiation source 13 may be designed to radiate coherent radiation 14 having radiation components including a plurality of different wavelengths onto the diffraction element 30. In this case, each of the different radiation components may include exactly one wavelength. The radiation source 13 may include a plurality of lasers, such as a plurality of mode-locked lasers. The radiation source 13 may include at least one frequency comb generator.

[0121] The system 10 may include one or more components that further utilize the pose confirmed by the evaluation device 20. Figure 1Schematically shows a human-machine interface 19 and a controller 40, which can receive and represent the determined posture from the evaluation device 20, or use the posture for a control process. The controller 40 can be a controller for at least one actuator from an industrial manufacturing system or an industrial quality control system or a medical engineering system.

[0122] The evaluation device 20 can be designed to output the confirmed posture to the human-machine interface 19, for example, in order to visually output the posture.

[0123] The evaluation device 20 can be designed to output the confirmed posture to the controller 40, so that at least one actuator can be controlled according to a control loop.

[0124] The evaluation device 20 can include a network interface and can be designed to transmit the confirmed posture via a local area network or a wide area network. For example, this can be used to record the posture and / or monitor the system 10 from a remote location.

[0125] In Figure 1 In the shown case, the diffraction element 30 is located at position 16 in the coordinate system 200, and the detector 12 is arranged in a stationary manner in this coordinate system. In Figure 1 In the shown case, the diffraction element 30 is in a first rotational orientation in the coordinate system 200.

[0126] Figure 2 Shows the system 1 after the diffraction element 30 has been translationally moved to the second position 17 in the coordinate system 200.

[0127] The translational movement from the first position 16 to the second position 17 causes a change in the two-dimensional diffraction pattern. The system 10 can be designed to determine the first position 16 and the second position 17 in an absolute sense in each case, where the two-dimensional diffraction pattern captured in each case is evaluated. It is not necessary to use the two-dimensional diffraction pattern captured by the detector 12 when the diffraction element is in the first position 16 to determine the second position 17, in particular, the multiple translational coordinates of the second position.

[0128] As Figure 2 As schematically shown, the object coordinate system 18 of the diffraction element 30 can be rotated relative to the coordinate system 200. The rotation relative to the coordinate system 200 can be determined by up to three rotational degrees of freedom. For example, these rotational degrees of freedom can be specified by three Euler angles. The rotational position is also referred to as "orientation" here in order to allow for a simple conceptual distinction from the translational position.

[0129] The system 10 can be designed to determine the orientation of the diffraction element 30 in an absolute sense in each case, where the two-dimensional diffraction pattern captured in each case is evaluated. The first orientation of the diffraction element (Figure 1 ) can be determined based on at least one first two-dimensional diffraction pattern captured when the diffractive element is in a first orientation. A second orientation of the diffractive element ( Figure 2 ) can be determined based on at least one second two-dimensional diffraction pattern captured when the diffractive element is in a second orientation; the second orientation can be determined independently of the at least one first two-dimensional diffraction pattern.

[0130] The pose determination system and the pose determination method performed by the system according to the present invention achieve various advantages over conventional methods using coherent radiation. One such conventional method is so-called speckle localization, in which a partially reflective object is illuminated with coherent radiation and the resulting interference pattern is compared with a reference measurement. The geometry of the partially reflective surface from speckle localization is generally unknown. Therefore, this conventional method requires a reference measurement for absolute pose determination. The partially reflective surface from conventional speckle localization also limits the solid angle on which the pose can be determined. Additionally, on the detector side, speckle localization has the following limitation: for the relevant reconstruction of pose changes, the characteristic interference pattern from the reference measurement can only be shifted by no more than the field of view of the camera, or alternatively, complex additional reference measurements are required.

[0131] On the other hand, the pose determination system and method according to the present invention allow for the determination of an absolute pose without requiring a reference measurement. Data relying on the aperiodic volume diffraction structure 31 can be used to computationally determine one or more expected diffraction patterns for any arbitrary pose within the dynamic range, and then the (multiple) pattern(s) can be compared with the at least one captured two-dimensional diffraction pattern. The high resolution of the coherent measurement method is maintained during this process.

[0132] The pose determination technique according to the present invention particularly has the following effects: maintaining the accuracy of the coherent measurement method, but allowing for a larger solid angle coverage. The technique according to the present invention also allows for the definition of the design specifications and related manufacturing parameters of the diffractive element 30 such that the desired pose determination within the dynamic range is possible. The technique according to the present invention also allows for the implementation of a measurement specification that transfers the accuracy embodied by the diffractive element 30 to the coordinate system 200 of the detector and generally to the pose determination of the diffractive element 30 (in up to 6 degrees of freedom or 6 dimensions of the pose space).

[0133] The diffractive element 30 can be configured such that a diffraction pattern is generated in the far field under coherent illumination. The diffractive element 30 can be configured such that the diffraction pattern generated in the far field allows for a one-to-one assignment of the pose of the diffractive element.

[0134] The diffractive element 30 includes an aperiodic grating or some other aperiodic volume diffractive structure 31. Periodic gratings or some other periodic diffractive structures have the property that the local interference pattern in the detector plane cannot be uniquely assigned to one pose under coherent illumination. This drawback can be overcome with an aperiodic grating or some other aperiodic volume diffractive structure.

[0135] To confirm the suitable configuration of the aperiodic volume diffractive structure, the required information content of the diffractive structure can be estimated as follows: The surface of the detection volume 11 can be subdivided into a plurality of partial regions, each of which has the size of the detector area of one of these detectors 12. Each of these partial regions can be assigned a unique, spatially discrete "target" diffraction pattern. In this context, a useful reference parameter is the pixel size of the detector used. Based on this initial target diffraction pattern, the reciprocal distribution of the required grating volume of the diffractive element 30 corresponding to the coherent illumination can be calculated using the discrete Fourier transform. The minimum producible structure size (which can depend, for example, on the pixel size of the detector 12) and the desired maximum size of the diffractive element 30 into which the diffractive structure is introduced can be used as boundary conditions. Additional boundary conditions can be considered when determining the aperiodic volume diffractive structure.

[0136] As confirmed above, the structure at which the coherent radiation is scattered defines the producible diffractive element. For the diffractive structure, both the far-field diffraction pattern and the scattering centers of the diffractive element can be arranged quasi-randomly. Nevertheless, the diffractive structure is known and fully computable. This represents a difference from speckle localization, where the geometry of the partially reflecting surface is usually unknown.

[0137] For the manufacture of such a diffractive element 30, this allows for a targeted construction and verification of the spatial structure of the diffractive element 30. For example, microscopic methods can be used for this purpose. Additionally or alternatively, it becomes possible to verify the two-dimensional diffraction pattern in one or more detector planes.

[0138] The technical advantage of this procedure is that one or several detectors can be used to determine poses that can cover a large solid angle, optionally even the full solid angle range. For this purpose, the evaluation device 20 can compare the captured two-dimensional diffraction pattern or the captured two-dimensional diffraction patterns with the calculated reference diffraction pattern of the diffractive element. Since the diffractive structure is specifically produced and / or the data defining the diffractive structure is available to the evaluation device 20, the reference diffraction pattern can be calculated by forward propagation.

[0139] Another technical advantage of this technology according to an exemplary embodiment is that the three-dimensional volume diffraction structure can be implemented in materials with a low coefficient of thermal expansion, such as glass or quartz materials. This ensures improved insensitivity to temperature changes. Known glasses with low thermal expansion can be used. For example, it is possible to use a glass or quartz material with a coefficient of thermal expansion (CTE) value not exceeding 100 ppb / K, not exceeding 50 ppb / K, not exceeding 20 ppb / K, or not exceeding 10 ppb / K at room temperature (23 °C). Thus, a diffraction element 30 on the order of 1 cm can achieve an accuracy of <1 nm in the measurement standard within a temperature band of 1 K. When projected onto the detection plane of the detector 12 or these detectors 12, a lateral accuracy of <1 μm in pose can be achieved.

[0140] The diffraction element 30 can be implemented such that it produces a diffraction image within a solid angle range of at least 2π, at least 3π, or a full solid angle of 4π. Shadows can be accepted.

[0141] As will be described even more in detail below, some requirements regarding the diffraction element 30, particularly regarding the aperiodic volume diffraction structure 30, can be relaxed.

[0142] For example, it is not mandatory to form a two-dimensional diffraction pattern on the detection surface of the detector 12 that has a one-to-one association with the pose over the entire surface of the detection volume 11. Ambiguity can be accepted. For example, a redundant measurement system can be used to resolve the ambiguity.

[0143] In addition to the aperiodic volume diffraction structure 31, the diffraction element 30 can include at least one additional diffraction structure, such as a periodic grating, which is used to resolve any ambiguity and / or to determine an initial estimate of the pose. These different diffraction structures can differ in terms of the average distance to the contrast structure elements.

[0144] By using coherent radiation including radiation components having at least two different wavelengths, the technology disclosed herein can be performed independently for multiple color channels. This relaxes the requirements regarding the diffraction structure. Simpler diffraction structures can be used because the combination of diffraction patterns from different color channels can be used for pose determination. If the radiation components with different wavelengths are phase-stable relative to each other, it is also possible to generate a synthetic wavelength by interference that will further improve the accuracy.

[0145] The diffractive element need not be implemented in such a way that it radiates the diffractive pattern over the entire solid angle range of 4π. For example, radiation into a smaller solid angle range (e.g., into a half-space) may be sufficient for many applications. Alternatively, a plurality of diffractive elements 30 may be combined on a carrier, e.g., on different side surfaces of an industrial or medical tool, where each diffractive element 30 radiates into a solid angle range that is less than the 4π solid angle range; however, using the plurality of diffractive elements 30 still enables the pose of the carrier to be determined over the entire solid angle range.

[0146] The operating modes of the evaluation device 20 for the systems and methods according to the exemplary embodiments are described in more detail below.

[0147] Figure 3 An evaluation device 20 of a system according to one exemplary embodiment is shown.

[0148] The evaluation device 20 includes at least one first interface 21 via which one or more two-dimensional diffractive patterns 50 are received. The at least one first interface 21 may be communicatively connected directly or via a data network (e.g., a wireless or wired local area network) to this detector 12 or these detectors 12. Via the at least one first interface 21, the evaluation device 20 may also receive data 60 that depends on the aperiodic volume diffractive structure 31. These data 60 may specify the distribution of the scattering centers in the diffractive structure 31, as defined during the manufacture of the diffractive element 30 and written into the diffractive element 30. The data 60 may include a configuration file for the manufacture of the diffractive element 30, which is used during the manufacturing process.

[0149] The evaluation device 20 includes a processing circuit 24. The processing circuit 24 is designed to computationally process the two-dimensional diffractive pattern 50 and the configuration data 60 that depends on the aperiodic volume diffractive structure 31. This allows the pose in the detection volume 11 to be determined.

[0150] The pose determination 25 performed by the processing circuit 24 may include a processing 26 of the data 60 that can define the aperiodic volume diffractive structure 31. This allows the reference diffractive pattern computationally determined for a hypothesized pose of the diffractive element 30 based on the data 60 to be compared with the captured two-dimensional diffractive pattern 50. The processing 26 of the data 60 may computationally determine reference diffractive patterns for a plurality of candidate poses in order to compare each of these reference diffractive patterns with the captured two-dimensional diffractive pattern 50.

[0151] The result of pose determination 25, in particular the result of processing 26 of the data 60 (such as determining a reference diffraction pattern based on the data 60), can be stored in the storage system 23 of the evaluation device 20 for further use and retrieved therefrom by the processing circuit 24 as needed.

[0152] The processing circuit 24 may include one or more integrated circuits for performing the required processing of the two-dimensional diffraction pattern and the data 60. The one or more integrated circuits may include, for example, any desired one or any desired combination of the following circuits or circuit components: application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), processor, controller, one or more quantum gates, circuits for quantum information processing, additional integrated circuits.

[0153] The result of pose determination can be output via the at least one first interface 21 of the evaluation device 20 or via a second interface 22 different therefrom. For example, the result can be output to a human-machine interface or a controller of an industrial or medical engineering system.

[0154] To perform pose determination, the evaluation device 20 can utilize at least one trained machine learning model 35.

[0155] Figure 4 is a schematic diagram of the machine learning model 35 that can be executed by the evaluation device 20. The machine learning model 35 includes an input layer 36, a plurality of hidden layers 38, and an output layer 37.

[0156] The input layer 36 can be designed to receive the pixel values of the at least one diffraction pattern captured by the at least one detector. The output layer 37 can be designed to output information about the pose.

[0157] In a further embodiment, the input layer 36 can be designed to receive both the pixel values of the at least one two-dimensional diffraction pattern captured by the at least one detector and computationally verified reference pixel values, where the reference pixel values are computationally verified based on the data 60 about the diffraction structure 31. The output layer 37 can then output a probability value indicating whether the captured two-dimensional diffraction pattern corresponds to the same pose for which the reference pixel values have been computationally verified.

[0158] The technical advantage of the technology described herein is that the labeled data required to train the machine learning model 35 can be computationally confirmed in large quantities based on data 60 regarding the diffraction structure 31. For example, for each of the multiple possible poses of the diffraction element 30 in the detection volume 11, the two-dimensional reference diffraction pattern expected at this detector 12 or these detectors 12 for the corresponding pose can be determined computationally by a forward propagation method. The computationally determined reference diffraction pattern can then be labeled with the known pose for which the forward propagation has been performed. During training, where conventional techniques such as gradient-based methods can be utilized, the machine learning model 35 can be trained to the effect of assigning the correct pose to each reference diffraction pattern by setting the adjustable parameters of the machine learning model 35.

[0159] More complex techniques can be used to implement the trained machine learning model 35. For example, a generative adversarial network (GAN) can be used to form and train the machine learning model 35.

[0160] The use of the machine learning model is optional. The evaluation device 20 can solve the inverse problem of the reconstruction from momentum space to position space for determining the pose in a different way.

[0161] The evaluation device 20 can be designed to computationally determine one expected diffraction pattern or multiple expected diffraction patterns (if multiple color channels and / or multiple detectors are used) for any desired candidate pose, for example. A comparison with the captured two-dimensional diffraction pattern can then be made. The expected diffraction pattern (also referred to as the reference diffraction pattern) can be stored in the evaluation device 20 or a separate storage system to minimize the waiting time in pose determination.

[0162] The evaluation device 20 can alternatively or additionally be designed to use machine learning techniques. In this case, the associations resulting from the pose in the detection volume 11 can be fully or partially identified. Possible implementations have been described above.

[0163] The evaluation device 20 can alternatively or additionally be designed to use approximation methods. In this case, the initial estimate of the pose, which does not need to rely on the diffraction pattern of the non-periodic volume diffraction structure 31, can be further refined. The initial estimate can be generated from an additional measurement system with a coarser resolution or with an additional diffraction structure, as will be described in more detail with reference Figure 7 and Figure 8 more specifically. The initial estimate can also be obtained from the actuation signals of at least one actuator.

[0164] The evaluation device 20 can alternatively or additionally be designed to perform an iterative procedure for determining the pose. The estimate of the pose can be repeatedly further refined.

[0165] The above - mentioned technologies can be combined with each other.

[0166] Figure 5 A flowchart of a method 70 according to an exemplary embodiment is shown. The method 70 can be automatically executed by an evaluation device 20.

[0167] At 71, the evaluation device 20 receives at least one two - dimensional diffraction pattern. The at least one two - dimensional diffraction pattern is captured by a detector 12 and is the result of the diffraction of coherent radiation at an aperiodic volume diffraction structure 31.

[0168] At 72, the two - dimensional diffraction pattern is processed. Data related to the configuration of the aperiodic volume diffraction structure 31 is also used for pose determination.

[0169] At 73, the determined pose is provided. This can include output via a man - machine interface 19 or providing the pose to at least one controller 40.

[0170] Figure 6 A flowchart of a method 80 according to an exemplary embodiment is shown. The method 80 can be automatically executed by an evaluation device 20.

[0171] At 81, a pose is estimated. The pose can be estimated by using an additional measurement system with lower resolution. Alternatively, multiple diffraction structures can be provided in the diffraction element 30 to first confirm the pose estimate and then refine it with the diffraction pattern generated by the diffraction at the aperiodic volume diffraction structure 31.

[0172] At 82, the pose estimate is refined. This can be done in various ways, in particular by using data 60 that defines the diffraction structure 31 or otherwise depends on the diffraction structure 31.

[0173] At 83, it can be checked whether a desired target accuracy has been reached. The check can include confirming an error metric that quantifies the difference between the captured diffraction pattern and the computationally - verified diffraction pattern for a candidate pose. Any suitable difference metric for images can be used to quantify the difference.

[0174] If the desired target accuracy has not been reached, the method can return to step 82.

[0175] Otherwise, at step 84, the determined pose can be provided, as explained with reference to step 73.

[0176] In addition to the aperiodic volume diffraction structure, the diffraction element 30 can also include additional features that can facilitate or be used for pose determination.

[0177] Figure 7Schematically shows a diffraction element 30, which includes an aperiodic volume diffraction structure 31 and at least one additional diffraction structure 32. The at least one additional diffraction structure 32 may be a periodic diffraction structure. The diffraction pattern generated by diffraction at the at least one additional diffraction structure 32 can be used to estimate the pose. Subsequently, the estimation of the pose can be refined.

[0178] As an alternative or supplement to using the additional diffraction structure 32 in the diffraction element 30, additional non-contact measurement and / or tactile measurement systems can also be used to obtain an estimate of the pose.

[0179] Figure 8 Shows a system 10, in addition to the components referred to Figure 1 and Figure 2 described, the system further includes an additional measurement system 90 for pose determination. The resolution of the additional measurement system 90 may not be as accurate as the resolution obtainable by evaluating the at least one interference diffraction pattern. The additional measurement system 90 may be a system that makes measurements non-contact, particularly a system that uses optical methods for measurement.

[0180] The evaluation device 20 can use the estimated pose of the diffraction element 30 confirmed by the additional measurement system 90 to refine the estimate. For example, the evaluation device 20 can limit the determination of the computationally expected reference diffraction pattern according to the known configuration of the diffraction structure 31, such that only a part of the pose space near the pose estimate confirmed by the additional measurement system 90 is sampled in a targeted manner. Thus, the processing time can be reduced.

[0181] The additional measurement system 90 can include an additional radiation source 93. The additional radiation source 93 can be a coherent or incoherent radiation source. The additional radiation source 93 can include at least one additional laser or an additional frequency comb.

[0182] The additional measurement system 90 can include an additional detector 92 or multiple additional detectors 92. The additional measurement system 90 can be, for example, a triangulation system that operates with incoherent illumination, or can use coherent radiation.

[0183] If the additional measurement system 90 has a lower resolution in a first spatial direction among three spatial directions compared to two orthogonal spatial directions, the evaluation of the diffraction pattern captured by the detector 12 for pose determination can be used in a targeted manner to increase the resolution of the pose determination in the first spatial direction. For this purpose, the radiation source 13 and / or the detector 12 can be arranged relative to the components of the system 90 such that in any case, for those spatial directions for which the additional measurement system 90 produces a lower resolution, a high measurement accuracy obtained by processing the diffraction pattern of the coherent radiation is achieved.

[0184] The system 10 can be designed to combine angular and lateral directions.

[0185] For this purpose, for example, the additional measurement system 90 can be designed to determine the distance relative to the target body, where the target body can be the diffraction element 30 or some other optical element, such as a reflector, connected to it in a stationary manner.

[0186] This distance measurement can be carried out in various ways, for example by using time-of-flight techniques, lidar techniques or using at least one frequency comb generator. For example, with the aid of lidar, the additional measurement system 90 can perform a distance measurement that does not necessarily have a high resolution but is unambiguous for all distances in the detection volume 11. This measurement is supplemented by an interferometrically accurate determination using coherent radiation in the system 10. For this purpose, the radiation source 13 can include a frequency comb generator 13. These two measurement methods can be implemented in an integrated (e.g., photonically integrated) form. This enables a compact and robust implementation.

[0187] Another advantage of the combination of the additional measurement system 90 with a system using coherent radiation and thus using interferometric methods (e.g., using a frequency comb generator) is that permanent self-calibration of the system can be achieved. For this purpose, for example, the optical frequency and / or the modulation frequency of an FMCW lidar can be continuously compared with a time standard. For example, such a time standard can be obtained via a time distribution network. This makes it possible to dispense with transfer standards during the factory calibration of the system 10. The need for repeated factory calibration can even be completely eliminated.

[0188] The light beam of the additional measurement system 90 required for distance measurement can be collimated and tracked. However, it can also be defocused so that the need for tracking can be avoided. Additionally, only an open-air section can be introduced for distance measurement, where an optical fiber (e.g., a light-guiding optical fiber) can be used for one of the paths between the additional measurement system 90 and the target object. As a result of the evaluation of the diffraction pattern, by a radio-based method, the phase coherence of the light between the target object and the base unit with the additional detector 92 can be generated, and the distance will be measured relative to this additional detector. For this purpose, in the base unit of the additional measurement system 90, the possibility of rotating the polarization plane of the local light field can additionally be provided, since the polarization plane of the incident light can generally be oriented in any desired manner.

[0189] The availability of coherent radiation 14 with a fully known frequency and thus wavelength in system 10 provides an additional advantage: By using coherent radiation, based on at least one two-dimensional diffraction pattern, good resolution of both the position and orientation of the diffraction element 30 can be achieved. In system 10, the coherent radiation 14 is used to generate the spatial granular light distribution captured by the at least one detector 12. The detector 12 or these detectors can be implemented as a multi-spectral camera or an array of single-photon detectors (SPAD = "single-photon avalanche diode"). In combination with the multi-spectral illumination of the diffraction structure 31, this has the effect that the measurement of the position and orientation can be achieved with high accuracy. Optionally, the pose can be reconstructed based on the known laser wavelength used by the radiation source 13, through the multi-spectral measurement of the diffraction pattern.

[0190] Instead of a frequency comb generator, the radiation source 13 can also include one or more laser diodes.

[0191] The additional measurement system 90 is optional, as already referenced Figures 1 to 3 described.

[0192] Reference will be made to Figures 9 to 14 the operating mode of system 10 in more detail. These figures illustrate the operating mode of a possible embodiment in which the radiation source 13 is not carried during the movement of the diffraction element 30 ( Figure 9 , Figure 10 , Figure 11 and Figure 12 ), and another embodiment in which the radiation source 13 is connected to the diffraction element 30 in a stationary manner such that during the translational movement and / or rotation of the diffraction element 30, the incident direction of the coherent radiation 14 on the diffraction element 30 remains unchanged. The last-mentioned embodiment will be described in more detail with reference to Figure 13 and Figure 14 .

[0193] Figure 9 and Figure 10Illustrates the determination of the rotational posture (i.e., orientation) of the diffraction element 30 in the coordinate system defined by this detector 12 or these detectors 12. By way of example, the capture of one detector is shown, and such capture is sufficient to determine the orientation of the diffraction element 30. As Figure 9 shown, the diffraction of the coherent radiation 14 at the aperiodic volume diffraction structure 31 produces a diffraction pattern 51 in the detector plane of the detector 12. The orientation of the diffraction element 30 can be determined based on the diffraction pattern 51 in combination with the data defining the aperiodic volume diffraction structure 31. For example, this can include determining three Euler angles.

[0194] As Figure 10 shown, if the orientation of the diffraction element 30 relative to the detector 12 changes, the diffraction patterns 51, 52 in the detector plane change. The orientation of the diffraction element 30 can again be determined based on the diffraction pattern captured by the detector. For example, this can include determining three additional Euler angles. In this way, the orientation of the coordinate system 18 associated with the diffraction element 3 relative to the stationary coordinate system defined by at least one detector 200 can be determined.

[0195] As Figure 9 and Figure 10 shown, even when the radiation source 13 is not fixedly attached to the diffraction element 30, the determination of the orientation can be performed using only one detector 12.

[0196] Figure 11 and Figure 12 show the determination of the translational position of the diffraction element 30 in the detection volume when the radiation source 13 is not fixedly attached to the diffraction element. In this case, the propagation direction of the coherent radiation 14 is tracked. This can be done in a control loop (e.g., based on the captured intensity) or based on the pose estimation captured by an additional measurement system.

[0197] At least two detectors can be used to determine the translational pose. More detectors can also be used. By way of example, three detectors 12a, 12b, and 12c are shown. Based on the diffraction patterns 51a, 51b, 51c captured by these detectors, the position of the diffraction element 30 in the reference coordinate system (e.g., the coordinate system defined by at least one detector 200) can be determined.

[0198] The translational movement 101 of the diffraction element in the detection volume causes a change in the diffraction pattern in the detector plane. This change is schematically represented by the additional diffraction patterns 52a, 52b, and 52c in Figure 12 . Based on the diffraction patterns captured by the detectors 12a, 12b, and 12c, the pose of the diffraction element 30 in the detection volume can be calculated in each case, where the data regarding the configuration of the diffraction element 30 is used to calculate the pose (in particular, the position).

[0199] The detection volume can be spherical, as Figure 11 and Figure 12 shown. The radius 100 of the detection volume can be greater than 1 m, greater than 1.5 m, or greater than 2 m.

[0200] Figure 13 and Figure 14 shows the case where the incident beam of the coherent radiation 14 for irradiating the aperiodic volume diffraction structure 31 also moves during the movement of the diffraction element 30. In other words, the following embodiment of the system 10 is used: wherein the radiation source 13 (in this case, for example, can also relate to the exit field of an optical fiber) is fixedly positioned relative to the diffraction element 30. This positioning can be achieved, for example, using a common carrier 110 or a coupling element 110. The carrier 110 or the coupling element 110 is advantageously formed of a material having low thermal expansion. For example, invar alloy or a material having a similar low thermal expansion can be used for the carrier 110 or the coupling element 110. The carrier 110 or the coupling element 110 can have, for example, a linear expansion coefficient of 10·10 -6 / K or less.

[0201] In a manner similar to that described in reference Figure 9 and Figure 10 it is possible to calculate the absolute rotational pose in each case based on the diffraction pattern captured by a single detector 12. In a manner similar to that described in reference Figure 11 and Figure 12 the translational position in the detection volume can be implemented, for example, using multiple detectors.

[0202] The radiation source 13 generates coherent radiation having one or more wavelengths. The radiation source 13 is sufficiently frequency stable to allow the diffraction pattern to have a well-defined phase angle during the relevant measurement period of capturing the diffraction pattern.

[0203] Figure 15 Shows an embodiment of a radiation source 13 that outputs radiation components 121, 122 having different wavelengths. If multiple wavelengths are used, color demultiplexing can be used. Thus, an additional degree of freedom is used in the detection. The diffraction pattern can be evaluated for different color channels of the detector. This can be done as described above. The data 60 that can define the configuration of the aperiodic volume diffraction structure 31 can be used to calculate the expected diffraction pattern separately for different wavelengths.

[0204] These different radiation components 121, 122 can be phase-stable relative to each other. This additionally allows the use of synthetic wavelengths that can be generated by the different radiation components 121, 122. In a manner similar to digital holography, this can achieve good accuracy.

[0205] The different radiation components 121, 122 can be output by the same physical unit. For example, the radiation source 13 can include a frequency comb generator that outputs the radiation components 121, 122.

[0206] As Figure 16 shown, the system can also include physically separate radiation sources. For example, a first radiation source 13a that outputs a radiation component 121 having a first wavelength can be provided, as well as at least one additional radiation source that outputs a radiation component 122 having a second wavelength. The first radiation source 13a can include a first laser diode. The second radiation source 13b can include a second laser diode. The radiation sources 13a, 13b can be coupled to introduce phase stability between the radiation components 121, 122.

[0207] The systems and methods described in detail can be used for pose determination in industrial manufacturing plants and / or quality control systems or medical engineering systems. The determined pose can be provided to a controller 40, which actuates at least one actuator based on the determined pose.

[0208] Figure 17 is a schematic diagram of a system 10 that includes a robotic arm 41. Instead of the robotic arm 41, other mechanisms can also be used to move a target object 42 in a work area.

[0209] The pose determined by the evaluation device 20 can be supplied to a controller 40, which is designed to generate at least one control signal for an actuator (such as of a robotic arm) based on the determined pose. In this way, the pose of the target object 42 (such as a workpiece, tool, or surgical instrument) can be checked and, if necessary, adjusted.

[0210] As Figure 17 shown, the diffraction element 30 can be firmly connected to the target object 42 or integrally formed with the target object. Since the diffraction element 3 is typically arranged offset with respect to a predefined point of the target object 42 (such as the volume center point, center of gravity, or tool tip), it is generally necessary to determine all three translational coordinates and all three rotational coordinates of the diffraction element 30 in order to determine the position of the predefined point of the target object 42 in the detection volume.

[0211] The pose determination system and method use a diffraction element 30 that is designed in a purposeful manner. The non-periodic volume diffraction structure can be formed in such a way that if the data defining the configuration of the non-periodic volume diffraction structure is available for evaluation, the non-periodic volume diffraction structure allows for a unique assignment of any desired pose in the detection volume based on at least one diffraction pattern. This data can be provided during the production of the diffraction element 30 for use by the pose determination system or method.

[0212] Figure 18It is a flowchart of method 130. Method 130 can be automatically executed by a manufacturing system of diffractive element 30.

[0213] At 131, a diffractive optical element having a volumetric aperiodic diffractive structure is produced. Step 131 can include determining the aperiodic volumetric diffractive structure. As described above, the diffractive structure can be determined, for example, by defining corresponding desired reference diffractive patterns for a plurality of possible positions of the detector area of detector 12. This plurality of possible positions of the detector covers the entire surface area of detection volume 11 or a solid angle range corresponding to the desired dynamic range for orientation confirmation. The diffractive structure that will produce these reference diffractive patterns can be confirmed by back-calculation. Other techniques can also be used. For example, based on the surface area of the detection volume, the detector area of each detector 12, and the pixel size of each detector 12, it can be estimated what information content the diffractive structure needs to have to allow a unique pose assignment to exactly one captured diffractive pattern in each case. Then the diffractive structure can be generated pseudo-randomly such that the diffractive structure has this required information content (that is, for example, the corresponding entropy).

[0214] At 132, data dependent on the configuration of the aperiodic volumetric diffractive pattern is provided. This data can be used by system 10 for pose determination. In this case, the data dependent on the configuration of the diffractive pattern can be used in various ways, as has been described in detail. For example, the expected reference diffractive pattern can be calculated for any desired pose and then compared with the captured diffractive pattern.

[0215] Figure 19 It is a schematic block diagram showing system 140 that can be used to define and produce diffractive element 30.

[0216] A computer 143 that performs the determination of the aperiodic volumetric diffractive pattern receives both information about detection volume 141 and characteristics 142 of one detector 12 or a plurality of detectors 12 used as input variables. For example, the characteristics 142 of this detector 12 or these detectors 12 can include detector area and pixel size. The characteristics 142 can also include a plurality of different color channels.

[0217] Then, computer 143 determines the aperiodic volumetric diffractive structure based on the mentioned input variables. For this purpose, for example, the three-dimensional arrangement of scattering centers in a glass or quartz material can be determined.

[0218] The configuration of the determined aperiodic volumetric diffractive structure is used to control manufacturing device 144. Manufacturing 144 can be designed to produce the aperiodic volumetric diffractive structure, for example, by laser writing or by 3D printing.

[0219] The configuration of the determined aperiodic volume diffraction structure is also available to the evaluation device 20, which is designed to computationally use the known configuration of the diffraction structure in pose determination.

[0220] The production of the diffraction element 30 can also include quality control. Thus, the system 140 can additionally include a checkpoint that, for some poses, checks whether the produced diffraction element 30 actually yields the expected diffraction pattern. The checkpoint can include a microscope for visually inspecting the manufactured diffraction structure.

[0221] The diffraction element 30 can have different surface shapes and geometries. For example, the diffraction element 30 can have a geometry that contributes to radiating the diffraction pattern over a desired solid angle range. For this purpose, the diffraction element 30 can be implemented, for example, as having a faceted surface. The diffraction element 30 can have a surface including polyhedral regions.

[0222] Figure 20 is a schematic view of the diffraction element 30, which is produced (in particular, shaped) such that its surface has polyhedral regions 33. Thus, a characteristic can be achieved such that the diffraction pattern is radiated over a relatively large solid angle range 150.

[0223] As already described with reference to the drawings, the pose determination system and method use a diffraction element. The diffraction element includes an aperiodic diffraction structure 31 such that in the detection region, no repeating diffraction pattern appears over an area region corresponding to or larger than the detector area of the detector 12. The diffraction element has a structure that can be generated randomly or pseudo-randomly during production (e.g., to obtain a desired information content), but the structure is known and follows reproducible design rules. This is different from diffraction structures using random interference at two-dimensional surfaces or three-dimensional structures. The diffraction image produced by the diffraction element can cover a solid angle of at least 2π, at least 3π, or 4π. Due to the design of the diffraction element and its application, shadows can be tolerated.

[0224] As described, the aperiodic volume diffraction structure 31 can be implemented depending on the configuration of the system 10, in particular depending on the size of the detection volume 10 and depending on the detector area and / or pixel size and / or number of color channels of the at least one detector 12. By way of example, the aperiodic volume diffraction structure 31 can have an effective average grating constant and dimensions that depend on the detection volume 11 and the image field of the detector 12.

[0225] The intensity distribution generated by the coherent illumination of the diffraction structure 31 in the detection volume can be calculated. For this purpose, for example, the Gerchberg - Saxton method or some other technique that takes into account the angular range of irradiation and / or detection capable of coherent radiation can be used.

[0226] The diffractive element may include a plurality of different diffractive structures. These diffractive structures may have different effective average grating constants. The diffractive element may include an aperiodic volume diffractive structure 31 as the main structure in order to obtain a one-to-one correspondence for pose determination in the detection volume 11. Additionally, a secondary structure (e.g., a superimposed grating) may be provided in order to be able to simplify the estimation of the pose with a less accurate resolution.

[0227] The configuration of the diffractive element 30 is known from a design perspective, e.g., from the production method. For example, the tolerances of the desired configuration can be quantified by means of inverse calculation of diffractive images or confocal microscopy.

[0228] The diffractive element is advantageously formed of a mechanically stable and / or thermally stable material. In particular, the diffractive element may be formed of glass or quartz material or some other material having low thermal expansion. Thus, a high reliability of pose determination is achieved even in the case of temperature variations of a few Kelvin that may be caused, for example, by coherent radiation 14 or by fluctuations in the ambient temperature.

[0229] The source of the coherent radiation may optionally be firmly connected to the diffractive element 30 via a mechanical coupling element 110. For example, the coupling element may be made of a material such as invar or some other material having low thermal expansion (e.g., comparable to or less than the thermal expansion of invar).

[0230] The diffraction pattern may be captured by at least one detector 12. A plurality of detectors 12 may be positioned along the surface of the detection volume. The surface normals of the detector areas may be inclined relative to each other. The detector may be in the form of a camera, e.g., a lensless camera.

[0231] A plurality of detectors 12 may be used in order to cover all degrees of freedom, in particular all three translational degrees of freedom and all three rotational degrees of freedom.

[0232] These systems and methods can be used not only for determining the pose of the diffractive element, but also for verifying higher torques. For example, these systems and methods can also be used for verifying translational velocity and / or acceleration and / or rotational velocity and / or acceleration. These can also be output via a human-machine interface 19 or provided to a controller 40.

[0233] These systems and methods can use an estimation of the pose and refine this estimation. The estimation can be achieved as the measurement result of using an additional measurement system 90, which can also perform measurements without contact (e.g., optically). Alternatively or additionally, the estimation can be obtained from the kinematic chain of an actuator, to which an evaluation device 20 can be communicatively connected and which changes the pose of the diffractive element 30.

[0234] The diffractive element 30 can be produced by laser writing or other techniques such as 3D printing. Such techniques allow for the formation of aperiodic volume diffractive structures that can have dimensions less than 5 cm, less than 3 cm, less than 2 cm, less than 1 cm, less than 5 mm, less than 3 mm, less than 1 mm, less than 0.5 mm, less than 0.3 mm, or less than 0.1 mm. However, by using a conventional detector area and pixel size, the aperiodic volume diffractive structure can allow for a one-to-one correspondence between the pose and the diffraction pattern over a detection volume with a radius of at least 1 cm, at least 3 cm, at least 5 cm, at least 10 cm, at least 30 cm, at least 50 cm, at least 1 m, at least 2 m, at least 3 m, or greater.

[0235] While the exemplary embodiments have been described with reference to the drawings, modifications can be implemented in additional exemplary embodiments. For example, the following modifications can be used alternatively or cumulatively:

[0236] - Fewer than three rotational coordinates and / or fewer than three translational coordinates can be determined. For example, if high accuracy is only a concern for the angular degrees of freedom, the coherent illumination can be positioned such that the diffractive element moves relative to it. Then, a coarse tracking of the coherent radiation is sufficient.

[0237] - If at least one additional measurement system 90 is used to determine the pose at a lower resolution, the requirement for a one-to-one assignment between the pose and the diffraction pattern can be relaxed.

[0238] - The diffraction image can cover the full solid angle, but this is not mandatory. For example, a half-space or a smaller angular range can be sufficient for the desired pose determination for the corresponding application. This allows for a reduction in the illuminated volume of the diffractive element.

[0239] While descriptions of exemplary embodiments that can be used in systems for industrial manufacturing or quality control or medical engineering have been given, the disclosed techniques can also be used in other application areas.

[0240] This disclosure also encompasses embodiments having any combination of the features elucidated or shown with respect to the different embodiments. This disclosure also encompasses the individual features in the drawings, even if they are shown there in combination with other features and / or are not mentioned above or below. Alternatives to the embodiments described in the drawings and the specification, as well as individual alternatives of their features, can also be excluded from the subject matter of the present invention or the disclosed subject matter.

[0241] The terms "comprising" and "having" and their derivatives refer to a non-exhaustive relationship and do not exclude the presence of other elements or steps. The indefinite article "a" or "an" and their derivatives do not exclude the presence of a plurality of corresponding elements. The functions of the plurality of features set forth in the claims may be implemented by units or steps.

[0242] Machine-readable instruction codes that may be executed by a programmable circuit for the purpose of performing a method according to an exemplary embodiment may be stored and / or distributed on a suitable medium, such as an optical storage medium or a solid-state medium, which is provided together with or as part of other hardware. The instruction codes may also be distributed in other forms, for example, in the form of a modulated data signal sequence.

[0243] Exemplary embodiments of the present invention provide improved techniques for pose determination that allow for the determination of an absolute pose (in particular up to six degrees of freedom) with interferometric accuracy.

Claims

1. A pose determination system (10), comprising: a diffraction element (30), which includes an aperiodic volume diffraction structure (31), at least one detector (12; 12a-c), which is designed to capture at least one two-dimensional diffraction pattern (51, 52; 51a, 51b, 52a, 52b, 52c, 52d) generated in the far field by the diffraction of coherent radiation (14) at the diffraction element (30), and an evaluation device (20), which is designed to determine the pose of the diffraction element (30) based on the at least one two-dimensional diffraction pattern (51, 52; 51a, 51b, 52a, 52b, 52c, 52d) and data (60) dependent on the aperiodic volume diffraction structure (31).

2. The system (10) according to claim 1, wherein, The diffraction element (30) is implemented such that the at least one two-dimensional diffraction pattern (51, 52; 51a, 51b, 52a, 52b, 52c, 52d) occurring at the at least one detector (12; 12a-c) can be uniquely assigned to the pose of the diffraction element (30) in the detection volume (11).

3. The system (10) according to claim 1 or claim 2, wherein, The diffraction element (30) is implemented such that the diffraction element does not produce a repetition of the diffraction pattern (51, 52; 51a, 51b, 52a, 52b, 52c, 52d) of the coherent radiation (14) over a predetermined volume and / or over a predetermined solid angle range.

4. The system (10) according to any one of the preceding claims, wherein, The diffraction element (30) is implemented such that the diffraction element produces a diffraction pattern (51, 52; 51a, 51b, 52a, 52b, 52c, 52d) over a solid angle range of at least 2π, greater than 2π, greater than 3π or 4π.

5. The system (10) according to any one of the preceding claims, wherein, The diffraction structure (31) includes a pseudo-randomly distributed structure, wherein the data (60) used by the evaluation device (20) depends on the pseudo-randomly distributed structure.

6. The system (10) according to any one of the preceding claims, wherein, The evaluation device (20) is designed to computationally determine six degrees of freedom of the diffraction element (30) for pose determination.

7. The system (10) according to any one of the preceding claims, wherein, The evaluation device (20) is designed to perform one or more of the following procedures for pose determination: comparing the at least one two-dimensional diffraction pattern (51, 52; 51a, 51b, 52a, 52b, 52c, 52d) with a plurality of two-dimensional reference diffraction patterns determined according to calibration measurement results or computationally confirmed according to the aperiodic volume diffraction structure (31); using a trained machine learning model (35) to process the at least one two-dimensional diffraction pattern (51, 52; 51a, 51b, 52a, 52b, 52c, 52d) captured by the at least one detector (12; 12a-c); an approximation procedure for pose determination.

8. The system (10) according to any one of the preceding claims, further comprising at least one source (13) of the coherent radiation (14), which is designed to radiate the coherent radiation (14) onto the diffraction element (30).

9. The system (10) according to claim 8, wherein, The at least one source (13) is connected to the diffraction element (30) in a stationary manner.

10. The system (10) according to claim 8 or claim 9, wherein, The at least one source (13) is configured to radiate coherent radiation (14) having a plurality of different wavelengths onto the diffraction element (30).

11. The system (10) according to any one of the preceding claims, wherein, The system (10) is or comprises an industrial manufacturing system, an industrial measuring system or a medical engineering system.

12. A method for producing a diffractive element (30) for pose determination, wherein, The method comprises:[[]] determining an aperiodic volume diffraction structure (31), controlling a production device (144) for forming the aperiodic volume diffraction structure (31), and providing data (60) dependent on the aperiodic volume diffraction structure (31) for determining the pose of the diffraction element (30).

13. The method according to claim 12, wherein, The production device (144) comprises a device for laser writing the aperiodic volume diffraction structure (31) or for three-dimensional printing.

14. A method for determining a pose, comprising: capturing, by means of at least one detector (12; 12a-c), at least one two-dimensional diffraction pattern (51, 52; 51a, 51b, 52a, 52b, 52c, 52d) generated in the far field by the diffraction of coherent radiation (14) at the diffraction element (30), wherein the diffraction element (30) comprises an aperiodic volume diffraction structure (31), and determining the pose of the diffraction element (30) based on the at least one two-dimensional diffraction pattern (51, 52; 51a, 51b, 52a, 52b, 52c, 52d) and data (60) dependent on the aperiodic volume diffraction structure (31).

15. The method according to claim 14, wherein, The method is performed by the system (10) according to any one of claims 1 to 11.

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