Method for obtaining the translation and rotation of a computer-controlled machine

Abstract

Method for obtaining the translation and rotation of a first part relative to the translation and rotation of a second part of a computer-controlled machine with at least one movable support (3) for changing the position of the first machine part relative to that of the second machine part, the method comprising Providing a pattern generator (6) attached to the first machine part (4), Providing a first lighting device (7) attached either to the first machine part (4) or the second machine part (5) and optically configured to illuminate the pattern generator (6) to together create a three-dimensional pattern (8) of light in space; providing a first camera (9) attached to the second machine part (5) and optically configured to capture the pattern images of the three-dimensional pattern (8) of light in space. Providing a second lighting device (7) or a second camera (9), Providing a range of effective optical distances of a first optical configuration (11A) in which light is propagated along optical paths from one of the first or second illumination devices via the pattern generator (6) to one of the first or second cameras to capture a first image of the three-dimensional pattern (8) of light in space, wherein the range of effective optical distances does not overlap with a range of effective optical distances of a second optical configuration (11B) in which light is propagated along optical paths from one of the first or second illumination devices via the pattern generator (6) to one of the first or second cameras to capture a second image of the three-dimensional pattern (8) of light in space, Configuring each of the first or second illumination devices configured to illuminate the pattern generator (6) with light of a coherence length longer than a maximum optical path length difference within each of the optical configurations (11A, 11B), and Configuring the sensor device (1) to capture either a) the first image of the three-dimensional pattern (8) of light in space using a combination of the first lighting device and the first camera, and the second image of the three-dimensional pattern (8) of light in space using a combination of the first lighting device and the second camera, or b) of the first image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the first lighting device, and of the second image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the second lighting device, or c) of the first image of the three-dimensional pattern (8) of light in space using a combination of the first lighting device and the first camera, and of the second image of the three-dimensional pattern (8) of light in space using a combination of the second lighting device and the second camera, wherein at each position of the movable carrier the first and second are controlled by the lighting device (7) or the first and second of the camera to operate alternately, so as not to capture the first and second images simultaneously and only in different optical configurations.

Description

BACKGROUND OF THE INVENTION / DESCRIPTION OF THE STATE OF THE ART.

[0001] The present invention relates to the field of devices and methods for finding exact translations and rotations within computer-controlled machines such as machine tools, opto-mechanical measuring devices, coordinate measuring machines (CMMs), robots, and position encoders. In particular, the invention relates to solid-state translation and rotation calibration at a plurality of machine part positions or simultaneous translation and rotation reading within such devices.

[0002] With reference to XYZ coordinate axes, the translation of a part refers to the X, Y, Z coordinates of a specific location on that part. The rotation of the same part refers to the Rx, Ry, Rz rotation angles of the part, where Rx, Ry, and Rz are the rotation angles about the given X, Y, and Z axes, respectively. The position of a part, in a broader sense, refers to either the combined translation and rotation, the translation, or the rotation of the part. Typically, the machines mentioned above use translation reading devices, called encoders, to read the exact translation of different parts of the machine. If, for example, such a machine is built with three translational degrees of freedom, XYZ, and one rotational degree of freedom, θ, linear encoders are placed on each of the three respective X, Y, and Z beams, and an angle encoder is placed on a rotational axis of a θ beam of the machine.These encoders are typically located away from the machine's workspace (or work area); otherwise, they would interfere with the machine's workspace operations. Consequently, to determine the translation of a particular machine part or tool within the workspace, translations and rotations of multiple machine parts must be determined from measurements taken by the respective encoders. By using geometric information and performing geometric calculations based on these measurements, the translation and rotation of the specific machine part, or typically the translation and rotation of a tool located within the machine's workspace, are derived. However, mechanical irregularities, clearances, and / or play affect machine part movements.Consequently, translational and rotational offsets between the encoder read positions and the work area operation positions introduce difficult-to-measure offsets associated with each respective degree of freedom, whose offsets are not taken into account in the geometric calculations, and which in turn leads to a degree of uncertainty and error in the determined machine part positions.

[0003] To measure and calibrate the 3D (three-dimensional) positioning of, for example, machine tools, opto-mechanical devices, and encoders, so-called probes are typically used. A probe can be installed in the tool holder of the machine tool and moved for measurement purposes to contact the calibrated position of measuring instruments such as steel balls or rods. This is a time-consuming part of the pointing process and requires the installation and use of expensive dimensionally calibrated measuring instruments.

[0004] Typically, an encoder measures the 1D (one-dimensional) translations along a rod or, to read a rotation angle, the 1D rotation on the circumference of a rotating shaft. Extending these same processes to simultaneously read both translations and rotations for some or all of the 6 (3 translations + 3 rotations) possible mechanical degrees of freedom of a solid can be complicated and expensive. Current encoders, due to accuracy limitations, may not be well-suited for reading the difference between, for example, the translations along two rods and potentially extrapolating the difference translations into values ​​for translations at locations far beyond the rods.

[0005] In the literature, such as Christopher J. Dainty (ed.) in Laser Speckle and Related In Phenomena, Springer Verlag, Berlin 1974, a number of so-called speckle photography and speckle interferometry techniques are described. The focus of these techniques is on measuring object-internal deformations and surface topography. Speckle photography techniques are unable to measure both local translational and rotational angular displacements at a multitude of partial positions in 3D space. Consequently, and additionally, interferometric techniques are sensitive to vibrations and, in many cases, not well suited for industrial applications.

[0006] Later, Ichirou Yamaguchi and Tadashige Fujita, for example, in Yamaguchi I., Fujita T.: Laser speckle rotary encoder. Appl. Opt. 28, pp. 4401-4406, 1989, and Vijay Shilpiekandula in his master's thesis, Massachusetts Institute of Technology, Feb. 2004, describe how a defocused or focused camera can be used to create a rotation angle reader encoder by recording the speckle displacement using, for example, a camera. This technique also lacks the ability to measure both local translational and rotational displacements at a multitude of partial positions in 3D space.

[0007] European Patent EP 1 924 400 A1 describes a device and method for finding and identifying part position relationships of components in mechanical and opto-mechanical machining and quality control systems. These techniques include correlation methods for finding image displacement of a focused surface structure. However, this technique lacks the ability to measure both translational and rotational displacements at a multitude of part positions in 3D space.

[0008] CN101655352A discloses a method for three-dimensional speckle strain measurement, comprising: (1) speckle preparation; (2) camera calibration; (3) acquisition of state information; (4) computational domain determination; (5) setting of starting points; (6) speckle fitting; (7) three-dimensional reconstruction; and (8) strain calculation. The above steps provide a three-dimensional speckle strain measurement method that enables the measurement of material properties. However, this technique lacks the ability to measure both translational and rotational displacements at a multitude of partial positions in 3D space.

[0009] US4967093A discloses a method and device for deformation measurement in which a portion of an object's surface is irradiated with a laser beam before and after deformation to obtain speckle patterns. The extent of the object's deformation is determined based on the cross-correlation function between the speckle patterns. This technique also lacks the ability to measure both translational and rotational displacements at a multitude of partial positions in 3D space. US 2013 / 0235389A1 discloses a method for position correction using a speckle field, but employing only one light source and one detector. This technique also lacks the ability to measure both translational and rotational displacements at a multitude of partial positions in 3D space.

[0010] JP H09-178 475 A discloses a position measuring unit that uses two cameras and a light source. This technique also lacks the ability to measure both translational and rotational displacements at a multitude of partial positions in 3D space.

[0011] Consequently, known mechanical and optical devices and methods for detecting translations and rotations within computer-controlled machines lack sufficient measurement capability, or they are too sensitive or prone to error. Furthermore, they typically require time-consuming and / or expensive calibration. TASKS OF INVENTION

[0012] One object of the invention is to improve the accuracy of determining either partial translation or rotation, or both partial translation and rotation, within the workspace of computer-controlled machines. Another object of the invention is to reduce the time required for calibrating computer-controlled machines. A further object of the invention is to provide computer-controlled machines with translation and / or rotation correction data, or to provide solutions that function directly as advanced translation and / or rotation encoders. SUMMARY

[0013] These and other tasks and advantages, which can be understood from the following description of the present invention, are achieved by the methods according to the attached independent claims. Further aspects of the invention are defined in the dependent claims. The invention relates to a method for achieving the translation and rotation of a first part relative to the translation and rotation of a second part of a computer-controlled machine with at least one movable support (3) for changing the position of the first machine part relative to that of the second machine part, the method comprising providing a pattern generator (6) attached to the first machine part (4), providing a first lighting device (7) attached either to the first machine part (4) or the second machine part (5) and optically configured to illuminate the pattern generator (6) in order to together create a three-dimensional pattern (8) of light in space, and providing a first camera (9) attached to the second machine part (5) and optically configured to capture the pattern images of the three-dimensional pattern (8) of light in space.Providing a second lighting device (7) or a second camera (9), providing a range of effective optical distances of a first optical configuration (11A) in which light is propagated along optical paths from one of the first or second lighting devices via the pattern generator (6) to one of the first or second cameras to capture a first image of the three-dimensional pattern (8) of light in space, wherein the range of effective optical distances does not overlap with a range of effective optical distances of a second optical configuration (11B) in which light is propagated along optical paths from one of the first or second lighting devices via the pattern generator (6) to one of the first or second cameras to capture a second image of the three-dimensional pattern (8) of light in space, configuring each of the first or second lighting devices that are configured,to illuminate the pattern generator (6) with light of a coherence length longer than a maximum optical path length difference within each of the optical configurations (11A, 11B), and to configure the sensor device (1) to detect either a) the first image of the three-dimensional pattern (8) of light in space using a combination of the first illumination device and the first camera, and the second image of the three-dimensional pattern (8) of light in space using a combination of the first illumination device and the second camera, or b) the first image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the first illumination device, and the second image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the second illumination device,or c) of the first image of the three-dimensional pattern (8) of light in space using a combination of the first lighting device and the first camera, and of the second image of the three-dimensional pattern (8) of light in space using a combination of the second lighting device and the second camera, wherein at each position of the movable carrier the first and second are controlled by the lighting device (7) or the first and second of the camera to operate alternately in order not to capture the first and second images simultaneously and only in different optical configurations.

[0014] A first further development of the invention relates to the method, further comprising moving the movable carrier into a plurality of positions and at each position recording carrier position data (31, 32) in connection with the position of the movable carrier in conjunction with a configuration of the sensor device.

[0015] A second embodiment of the invention relates to the method according to the invention or the first embodiment of the method according to the invention, wherein images are taken at each position of the movable carrier using a plurality of cameras (9), wherein the cameras are configured to take images in different object planes.

[0016] A second invention relates to a method for deriving data for calibrating or improving the positioning of a computer-controlled machine comprising a movable carrier for changing the position of a first machine part relative to that of the second machine part, wherein the method comprises: providing a sensor device for a computer-controlled machine (2) with a movable carrier (3) for changing the position of a first machine part (4) relative to that of a second machine part (5), wherein the sensor device (1) comprises: a pattern generator (6) attached to the first machine part (4), a first illumination device (7) for coherent light attached either to the first machine part (4) or the second machine part (5) and optically configured to illuminate the pattern generator (6) with coherent light to together create a three-dimensional pattern (8) of light in space,a first camera (9) attached to the second machine part (5) and optically configured to capture the pattern images of the three-dimensional pattern (8) of light in space, the sensor device (1) further comprising: either a) a second camera (9) and the sensor device is configured to capture a first image of the three-dimensional pattern (8) of light in space using a combination of the first coherent light illumination device and the first camera, and a second image of the three-dimensional pattern (8) of light in space using a combination of the first illumination device and the second camera, wherein an area of ​​effective optical distances of a first optical configuration (11A) in which light is propagated along optical paths from the first illumination device via the pattern generator (6) to the first camera to capture the first image,not overlapping with a range of effective optical distances of a second optical configuration (11B) in which light is propagated along optical paths from one of the first illumination devices via the pattern generator (6) to the second camera to capture the second image, and wherein the first illumination device is configured to illuminate the pattern generator (6) with light of a coherence length longer than a maximum optical path length difference within each of the optical configurations (11A, 11B), or b) a second coherent light illumination device (7) and a sensor device (1) configured to capture a first image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the first coherent light illumination device,and a second image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the second coherent light illumination device, wherein a region of effective optical distances of a first optical configuration (11A), in which light is propagated along optical paths from the first illumination device via the pattern generator (6) to the first camera to capture the first image, does not overlap with a region of effective optical distances of a second optical configuration (11B), in which light is propagated along optical paths from one of the first illumination devices via the pattern generator (6) to the first camera to capture the second image, and wherein each of the first or second illumination devices is configured to illuminate the pattern generator (6) with light of a coherence length,which is longer than a maximum optical path length difference within each of the optical configurations (11A, 11B), or c) a second camera (9) and a second coherent light illumination device (7) and the sensor device (1) is configured to capture a first image of the three-dimensional pattern (8) of light in space using a combination of the first coherent light illumination device and the first camera, and a second image of the three-dimensional pattern (8) of light in space using a combination of the second coherent light illumination device and the second camera, wherein a range of effective optical distances of a first optical configuration (11A) in which light is propagated along optical paths from the first illumination device via the pattern generator (6) to the first camera to capture the first image,not overlapping with a range of effective optical distances of a second optical configuration (11B) in which light is propagated along optical paths from the second illumination device via the pattern generator (6) to the second camera to capture the second image, and wherein each of the first and second illumination devices is configured to illuminate the pattern generator (6) with light of a coherence length longer than a maximum optical path length difference within each of the optical configurations (11A, 11B), moving the movable carrier to a plurality of carrier positions such that the position of the first machine part changes relative to that of the second machine part for each of the plurality of positions, and at each carrier position,Acquiring positional data related to the position of the movable carrier and operating the sensor device to acquire a pair of first and second images of the three-dimensional pattern of light in space in corresponding first and second optical configurations, and comparing the acquired image data with image data from a reference database comprising interconnected image and positional data related to the three-dimensional pattern of light in space of the pattern generator and finding pairs of similar images, deriving image translation offset data for each pair of similar images, and deriving translation and rotation data for calibrating or improving the positioning of the computer-controlled machine based on image translation offset data related to the optical configurations.

[0017] According to one aspect of the invention, a sensor device for use in a computer-controlled machine with a movable carrier for changing the position of a first machine part relative to a second machine part located in the workspace of the computer-controlled machine comprises a pattern generator attachable to the first machine part, at least one lighting device configured to illuminate the pattern generator to together create a combined three-dimensional light diffraction and interference pattern in the workspace, hereinafter referred to as a light pattern or a pattern of light, and at least one camera attachable to the second machine part. The camera is advantageously configured to capture sample images of the three-dimensional pattern of light in the workspace.In one embodiment, the sensor device further comprises storage means for receiving image data from the at least one camera and position data of the carrier, and is configured to capture images in at least one first and second different optical configurations of the at least one illumination device, the at least one camera, and the pattern generator. The effective distance, which is the inverse of the harmonic sum of the distance of the illumination divergence center from the pattern generator, the camera object plane distance from the pattern generator, and the effective focal length of the pattern generator in the first optical configuration, differs from the effective distance of the second optical configuration. According to one aspect of the invention, the at least one illumination device is configured to illuminate the pattern generator with at least partially coherent light.The higher the degree of coherence of the light, the wider the three-dimensional light pattern extends in space. A system according to any aspect of the invention comprises a sensor device according to any of the above aspects and a storage means for carrying a reference database. The reference database comprises linked image and carrier position data representing the exact translation and rotation of a reference machine part relative to the pattern generator. The provision of the reference database makes it possible to associate image samples acquired in a first computer-controlled machine with image samples acquired before or after in a second computer-controlled machine. The second machine is a reference machine that uses the same optical configurations as the first machine.According to one aspect, the system further includes a processing unit configured to compare the acquired image data with image data from the reference database and to find pairs of similar images in order to derive image translation offset data for each pair of similar images and to derive calibration data for the computer-controlled machine based on image translation offset data associated with a variety of different optical configurations. The processing unit enables the system to automatically compare the images and derive data for calibrating the computer-controlled machine.

[0018] Another aspect describes a method for recording data related to the relative The translation and rotation of a first and a second part of a computer-controlled machine are associated. The computer-controlled machine includes movable supports for changing the position of the first machine part relative to the second machine part. The method comprises the steps of moving the support to a multitude of positions. At each position, at least one lighting device is used to illuminate a pattern generator attached to the first machine part, such that at least one three-dimensional pattern of light is created in space. At each position, images of the at least one three-dimensional light pattern are also captured in at least two different optical configurations of the pattern generator, the at least one lighting device, and the at least one camera.Such a method enables fast and accurate sampling of data associated with the translation and rotation of the first machine part relative to the translation and rotation of the second machine part. Consequently, the method allows for dense sampling of translational and rotational offsets in a computer-controlled machine, such as a machine tool or a coordinate measuring machine.

[0019] According to one aspect, the procedure includes the further procedural step of recording the position of the carriers at each location.

[0020] According to one aspect, a large number of lighting devices are controlled at each position to illuminate the pattern generator alternately.

[0021] According to one aspect, images are captured at each position using a variety of cameras configured to capture images at different object levels.

[0022] According to one aspect, a method for deriving data for the calibration of a computer-controlled A machine is provided. The computer-controlled machine includes a movable carrier for changing the position of a first machine part relative to a second machine part. This process includes the steps of moving the carrier to a multitude of carrier positions, such that the position of the first machine part relative to the second machine part changes for each position. At each carrier position, at least one lighting device is operated to illuminate a pattern generator attached to the first machine part, thus creating at least one three-dimensional light pattern in space. Positional data related to the carrier's position are also recorded at each carrier position.Furthermore, at each carrier position, images of the at least one three-dimensional light pattern created in space are captured in at least two different optical configurations of the at least one lighting device, the pattern generator, and the at least one camera. For each carrier position, pairs of similar images are found by comparing the captured image data with image data from a reference database. The image data from the reference database comprises linked image and position data associated with the unique light pattern in space reflected or transmitted by the pattern generator. The similar images are then analyzed to derive image translation offset data for each pair of similar images.Furthermore, data for the calibration of the computer-controlled machine are derived based on image translation offset data associated with a variety of different optical configurations.

[0023] According to one aspect, the pattern generator is illuminated with at least partially coherent light. The coherence of light makes it possible to produce the three-dimensional light pattern in space.

[0024] According to another aspect of the invention, the acquisition of reference light patterns and the use of these reference light patterns are performed on different machines. Furthermore, it is also possible for one machine to serve as the reference for its subsequent performance. Another aspect of the invention is to find and calibrate the translation and rotation of the computer-controlled machine, wherein the present invention associates differently configured acquisitions of light patterns with encoder position readings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic side view drawing illustrating a first embodiment of a milling machine equipped with a system comprising a sensor device according to the present invention. Fig. Figure 2 is a schematic side view drawing illustrating a first embodiment of a coordinate measuring machine equipped with a system comprising a sensor device according to the present invention. This machine collects the reference data used by the milling machine, as described by Fig. 1 shown. Fig. Figure 3 is a schematic drawing of the side view, showing optical paths and effective distances of the milling machine. Fig. 1 and the coordinate measuring machine from Fig. 2 represents. Fig. Figure 4 is a schematic drawing of the side view of the milling machine from Example 1, which is equipped with an alternative system comprising sensor devices according to the present invention. The use of these sensor devices makes it possible to determine all 6 degrees of freedom (3 translations + 3 rotations) of a solid motion in a multitude of positions for the milling machine relative to a coordinate measuring machine with similarly configured sensor devices. Fig. Figure 5 is a schematic drawing of the side view of the milling machine from Example 1, which is, however, equipped with an alternative system comprising sensor devices according to the present invention. The use of these sensors makes it possible to separate the mechanical construction of the sensor device into two lighting device-camera housings, which can also be operated separately. Fig. Figure 6 is a schematic drawing of the projection view illustrating a second embodiment of the support details of a numerically controlled computer machine equipped with a system comprising a sensor device according to the present invention. This solution enables the system to function as an advanced translation and rotation encoder. Fig. Figure 7 is a schematic drawing of the projection view illustrating the second embodiment of the support details of a calibration reference machine equipped with a system comprising a sensor device according to the present invention. This machine collects the reference data used by the numerically controlled computer machine, as described by Fig. 6 shown. Fig. Figure 8 is a schematic drawing of the projection view illustrating an alternative second embodiment of the carrier details of a numerically controlled computer machine equipped with a system comprising a sensor device according to the present invention. This solution enables the system to function as an advanced translational and rotational encoder, representing the exact positioning of two independent carriers. Fig. Figure 9 is a schematic side view drawing illustrating a third embodiment of the support details of an axle joint equipped with a system comprising a sensor device according to the present invention. This solution enables the system to function as an advanced translation and rotation encoder, making it possible to determine the exact translation and rotation of a robot arm tip. ADVANTAGES.

[0025] The method of this invention enables fast and accurate scanning of data associated with the translation and rotation of a first machine part relative to the translation and rotation of a second machine part. Consequently, the method enables dense scanning of translational and rotational offsets in a computer-controlled machine, such as a machine tool or a coordinate measuring machine, relative to those of a reference machine.Comparing data with the reference database—comprehensive, interconnected image and position data associated with the spatial optical characteristics of the pattern generator—makes it possible to compare the position of image samples acquired in a first computer-controlled machine with image samples acquired before or after in a computer-controlled reference machine, such as a coordinate measuring machine or a calibration setup, using the same optical configurations. This allows for the rapid determination of translational and rotational offsets at each sample position and the use of these offset data to derive calibration data for the first computer-controlled machine.The calibration data can be used to control the movement of the first computer-controlled machine, so that its movement is corrected by the movement of the reference machine that was used to record the reference data.

[0026] By associating exact positions and angles of optical configurations of cameras and lighting devices with the position and angle of a physical part, hereinafter referred to as the pattern generator, the present invention enables the exact toolholder translation and rotation to be found in a computer-controlled machine by transferring the pattern generator or an exact sister copy of the pattern generator from one machine (reference) to another and by observing the light patterns created by sensor devices, which are defined by the same optical configurations. This achieves a high degree of reliability and accuracy.

[0027] The pattern generator essentially serves the same purpose as, for example, the encoder glass rod of a commercially available encoder. Consequently, the present invention enables the recording of translations and rotations of 3D light patterns in free space outside the pattern generator and uses this information to determine the exact translational and rotational offset conditions of machine parts.

[0028] The sensor device enables fast and accurate acquisition of data associated with the translation and rotation of the first machine part relative to the translation and rotation of the second machine part. Consequently, the device allows for the dense scanning of translational and rotational offsets in a computer-controlled machine, such as a machine tool or a coordinate measuring machine. The provision of two different optical configurations makes it possible to derive reliable information on the translation of the first part relative to the translation of the second part separately from the rotation of the first part relative to the rotation of the second part.Since the effective distance of the first optical configuration differs from the effective distance of the second optical configuration, it is also possible to acquire two clearly defined images of the three-dimensional light pattern, which together contain sufficient translational and rotational information at each sample position. This makes it possible to... The system rapidly determines translational and rotational offsets at each sample position and uses this data to compensate for positioning in the first computer-controlled machine. This ensures that the positioning in the first machine matches the positioning in the reference machine used to acquire the reference data. Consequently, the sensor device more or less eliminates the effects of mechanical irregularities, bearing gaps, and / or mechanical play that create machine part positioning errors.

[0029] Recording carrier positions makes it possible to associate captured image data with captured carrier positions, thus associating positions referenced to the coordinate system of a computer-controlled reference machine, such as a laboratory machine, with positions referenced to the coordinate system of another computer-controlled machine—that is, the computer-controlled machine currently in use. This enables the production of precise translation and rotation data associated with pattern generators, which will work together as advanced encoders.

[0030] This invention utilizes a multitude of different optical configurations for each available camera, thus making it possible to use even a single camera. Furthermore, a greater number of optical configurations enables the measurement of translations and rotations of multiple degrees of freedom and results in higher accuracy when determining translational and rotational offsets. DETAILED DESCRIPTION OF INVENTION EXAMPLE 1.

[0031] A sensor device 1 according to an embodiment of the invention is now described with reference to Fig. 1 described. The sensor device 1 is suitable in this example for the alignment and calibration of a milling machine 2. In Fig. In the present embodiment, the milling machine 2 comprises the work area table 4, the tool holder 5, the support parts 100-1, 100-2, and 100-3, and the carriers 3-1 and 3-2. When the carriers 3-1 and 3-2 of the milling machine 2 are mounted, their axes must be aligned to be orthogonal to each other. Even after the carriers 3-1 and 3-2 have been mechanically aligned to align as closely as possible with an internal coordinate system 100-4 of the milling machine 2, residual errors may still occur when the carriers are moved. These errors must be taken into account if high machining precision is required. The sensor device 1 is used to detect these errors. In the present embodiment, these errors are represented as translational and rotational offsets from corresponding reference data acquired separately using a CMM (coordinate measuring machine) 2-R, as described by Fig. 2 shown. These errors are related to the positions of the moving parts of the milling machine 2. In the present example, the milling machine has an internal 3D machine coordinate system 100-4, to which the X, Y and Z beam positions refer (it should be noted that for the sake of simplicity only the X beam axis 3-1 and the Z beam axis 3-2 are shown in Fig. (1 shown schematically). The purpose of the present embodiment is to find a set of translational and rotational offset data associated with a multitude of 3D positions within the working volume of the milling machine. This offset data is used by the machine manufacturer to improve assembly and alignment, or by the CNC (computer numerical control) of the machine to compensate for errors in the actual XYZ carrier movements that physically place the tool into the intended positions in space.

[0032] Fig. Figure 1 shows a schematic drawing of the milling machine 2 together with an embodiment of the present invention. The sensor device 1 comprises two lighting devices 7A and 7B and a camera 9. We distinguish between two optical configurations 11A and 11B. In a configuration where the lighting device 7A is made ready to illuminate the pattern generator 6, we say that the camera belongs to optical configuration A and call it camera 9A. In a configuration where the lighting device 7B is made ready to illuminate the pattern generator 6, we accordingly say that the camera belongs to optical configuration B and call it camera 9B. In this example, the lighting devices 7A, 7B, and the camera 9 are attached to the tool holder 5, and the pattern generator 6 is attached to the workpiece holder 4.It should be noted that another possible configuration, which would work equally well, would be to attach the first and second lighting devices 7A, 7B and the camera 9 to the workpiece holder 4 and the pattern generator 6 to the tool holder 5. The pattern generator 6 is a light-diffusing surface suitable for reflecting at least some of the light emitted by the lighting devices 7A, 7B in one direction towards the camera 9. The lighting devices 7A, 7B are configured to illuminate the pattern generator 6 to create three-dimensional light patterns 8A, 8B in the space between the workpiece holder 4 and the tool holder 5. The camera is configured to capture two-dimensional pattern images of the three-dimensional light patterns 8A, 8B in space.The sensor device 1 is configured to capture images in at least one first 11A and one second 11B different optical configuration. The first optical configuration 11A defines the path from the illumination device 7A via the pattern generator 6 to the camera 9A. The second optical configuration 11B defines the path from the illumination device 7B via the pattern generator 6 to the camera 9B. Each respective optical configuration is thus defined by the relative position of the pattern generator 6, the camera 9, and the illumination devices 7A and 7B. Consequently, images captured by the camera 9 in the different optical configurations identified by the parameters A and B, respectively, will be unique and directly related to the relative position of the pattern generator 6, the camera 9, and the illumination devices 7A and 7B.In addition to the sensor device 1, the complete system according to this particular embodiment also includes a computer hard disk 10 or a similar data storage device for storing the linked carrier positions 31, 32 from the milling machine 2 and pattern images 30A, 30B from the camera 9A, 9B. The computer also includes a processor 12 configured to compare previously acquired carrier reference position data 31-R, 32-R with the carrier position data 31, 32 coming from the milling machine 2 and to compare separately acquired and previously acquired reference pattern image data 30A-R, 30B-R with the acquired pattern image data 30A, 30B coming from the camera 9. Fig. 1 are the collected data 33 received by the processor 12 from the hard disk 10, the series of corresponding previously recorded carrier reference position data 31-R, 32-R, the carrier position data 31, 32, the previously recorded reference pattern image data 30A-R, 30B-R and the captured pattern images 30A, 30B. The previously recorded carrier reference position data 31-R, 32-R and the previously recorded reference pattern image data 30AR, 30B-R were previously recorded in the separate CMM, as by Fig. 2 shown, stored on hard drive 10-R and copied to hard drive 10. Fig. 1 transferred.

[0033] The lighting devices 7A, 7B are of a type capable of emitting light suitable for illuminating the pattern generator 6 to create the 3D light patterns 8A, 8B in space. Typically, lighting devices capable of emitting substantially coherent light are suitable for this purpose. For the purposes of the present invention, we define the coherence length of a lighting device 7 as the maximum optical path length difference that creates a degree of coherence greater than 50% complete coherence. In this particular embodiment, the lighting devices are laser-emitting diodes with a coherence length greater than the maximum path length differences within each of the optical configurations A and B. Light emitted by each of the lighting devices 7A, 7B follows infinitely many different paths. For optical configuration A, in Fig. 3. For illustrative purposes, two examples of the paths are shown. The first path is indicated by the dot-dash line that coincides with a first optical axis of the illumination device 16A, extending from the first illumination device 7A to the pattern generator 6, and continues along the dot-dash line that coincides with an optical axis of the camera 20A, extending from the pattern generator 6 to the camera 9A. The second path is indicated by the fully drawn double line 21A, extending from the first illumination device 7A to the pattern generator 6, and continues along the fully drawn double line 22A, extending from the pattern generator to the camera 9A.Taking into account all possible optical paths and path lengths from the first illumination device 7A via the pattern generator 6 to the camera 9A, the laser diode source of the illumination device 7A should emit light with a coherence length greater than the maximum length difference between these optical paths. The same coherence condition should also be met separately by configuration B, which includes the second illumination device 7B, the pattern generator 6, and the camera 9B. The camera 9 is typically a 2D video camera of the CCD (charge-coupled device) or CMOS type, preferably with a resolution of 1000x1000 pixels or better. The pattern generator 6 is suitably provided by a flat stainless steel plate.Other materials, such as aluminum and glass, could be used within the scope of the invention to provide the pattern generator 6, provided that the reflective surface of the pattern generator 6 is suitable for creating the intended 3D light patterns 8A, 8B in space. The pattern generator 6 could also be provided by a reflective hologram, or by a metal surface pattern vapor-deposited onto a glass plate surface, or by an imprint from a primary surface onto another suitable surface. However, a key requirement is that the surface details should not change over time, for example, due to corrosion, handling, or similar factors.In the present embodiment, the reflective surface of the steel plate has a surface roughness comparable to the laser light wavelength emitted by the illumination devices 7A, 7B, thereby creating a sufficient angular range of scattering angles and a sufficient amount of light detectable by the camera 9. In this embodiment, a computer includes the hard disk 10 and the processor 12. To receive the carrier position data 31, 32, the computer is connected to the milling machine, CNC, via an Ethernet cable, and the computer receives pattern images 30A, 30B from the camera 9 using a USB port cable connection or a FireWire port cable connection. The reference position data 31-R, 32-R and reference pattern images 30A-R, 30B-R are transferred from the reference hard disk 10-R to the hard disk 10 using a USB-type memory stick or similar portable data storage device.

[0034] The following describes a method according to one embodiment of the invention with reference to the Fig. 1, Fig. 2, Fig. 3 and Fig. 4 described. The sensor device 1 described above, or a sensor device 1-R containing the same optical configurations, is used to record the reference data stored on the hard disk 10-R, the storage medium 10-R from Fig. 2, are stored. To record reference pattern images 30A-R, 30B-R and reference carrier position data 31-R, 32-R, we rely in the present embodiment on a calibrated coordinate measuring machine, hereinafter referred to as the CMM 2-R. Schematically, the CMM 2-R is similar to the milling machine 2, but by Fig. Figure 2 illustrates this. This CMM is programmed to move stepwise between sample / recording positions in a fixed 3D matrix of positions. The number of positions would depend heavily on the user and their application. If the milling machine 2 is only to be checked for arrangement quality, 5x5x5 positions may suffice. On the other hand, if detailed feedback correction data for the CNC is required, a higher number such as 1000x1000x1000 may be needed. In the present example, these positions cover a volume of 400x400x400 mm. For each of these positions, the computer hard drive 10-R stores two images, one for each optical configuration 11AR, 11B-R, along with the corresponding carrier position data 31-RA, 32-RA, 31-RB, and 32-RB. Assuming that the CMM is mechanically stable during image acquisition, position 31-RA is the same as position 31-RB and carrier position 32-RA is the same as carrier position 32-RB.This data is the reference data for the subsequent production / service alignment activities of milling machine 2 and is retrieved in a timely manner from hard drive 10-R (. Fig. 2) to hard drive 10 ( Fig. 1) transferred. The first and second illumination devices 7A-R, 7B-R are laser diodes of the same type and coherence characteristics, for later use in the milling machine 2. In the present embodiment, and as in Fig. 2 schematically indicated, and also according to the configuration of the milling machine in Fig. 1. The focus position of the first illumination device 7A-R is located between the first illumination device 7A-R and the pattern generator 6-R. The laser light diverges from this focus position 17A-R to the pattern generator 6-R. The second illumination device 7B-R, as also shown schematically in Fig. The element shown in Figure 1 contains optics to create collimated light that propagates to the pattern generator 6-R. That is, its divergence center is set to infinity in this example and therefore cannot be located within the extent shown in the drawing. Fig. 2 will be shown. Fig. Figure 3 schematically shows the illumination / observation geometries of the two optical configurations A and B and represents the optical configurations that are used on both the milling machine 2, schematically represented by the drawing of Fig. 1, as well as on the CMM 2-R, are schematically represented by the drawing of Fig. 2. For the sake of clarity, both centers of divergence are defined as being within the extent of Fig. 3 shown, although the divergence center 17B of the second illumination device 7B is set to infinity in the present embodiment. As also shown in Fig. As shown in Figure 3, the imaging characteristics of the camera are defined by an object plane position and size 15A, 15B and a corresponding depth of field 19A, 19B centered on this object plane. The depth of field extends from the planes 19A1, 19B1 to the respective planes 19A2, 19B2. In the present example, the object plane is located between the camera 9 and the pattern generator 6. Each of the optical axes of the camera 20A, 20B is defined to pass through two points in space, the first point being the center of the entrance lens of the camera 9A, 9B and the second point being their respective object plane centers 15A, 15B. These optical axes of the camera 20A, 20B extend to define a point 23 where the optical axes 20A, 20B of the camera 9 intersect the pattern generator 6. As also shown in Figure 3, the optical axes 20A, 20B of the camera 9 intersect the pattern generator 6. Fig. As shown in Figure 3, the optical characteristics of the illumination devices are defined by divergence centers 17A, 17B and a corresponding depth of field 18A, 18B centered on these respective divergence centers. The depth of field of illumination device 7A extends from plane 18A1 to plane 18A2. Accordingly, the depth of field of illumination device 7B extends from plane 18B1 to plane 18B2. For clarity, the divergence centers in this example are located between the respective illumination devices 7A, 7B and the pattern generator 6. Each of the optical axes of the illumination device 16A, 16B is defined to pass through two points in space; their respective divergence centers 17A, 17B converge at point 23, where the respective optical axis of the camera 20A, 20B intersects the pattern generator.The divergence center distances diA 40, diB 41 of the illumination device are measured along their respective optical axes 16A, 16B from the divergence centers 17A, 17B to the reflection surface point 23 on the pattern generator 6. The object plane distances dcA 42, dcB 43 of the camera are measured along their respective optical axes 20A, 20B from the reflection surface point 23 on the pattern generator 6 to the object planes 15A, 15B.

[0035] It should be noted that these geometries change during the reference recording of the CMM 2-R and measurements of the milling machine 2 as the CMM carriers 3-1-R, 3-2-R and milling machine carriers 3-1, 3-2 move. The defined axis(es), positions, and distances will change during these processes. The effective distance of the first optical configuration A is given by the equation deA = diA*dcA / (diA+dcA), and similarly, the effective distance of the second optical configuration B is given by the equation deB = diB*dcB / (diB+dcB). If the pattern generator 6 is curved or contains a lensing effect on transmission, diA and diB in the above equations should be replaced by the respective equations diA*f / (diA+f) and diB*f / (diB+f), where f is the equivalent focal length of an equivalent pattern generator in which the surface of the pattern generator 6 is replaced by an optically smooth surface without roughness.If, for example, the pattern generator 6 is curved with a specified radius of curvature of R, the focal length f would be equal to R / 2. For each of these optical configurations, the depth of field defines a region in which an object is assumed to be in focus. In this example, these regions extend from the respective field planes 19A1, 19B1 to the field planes 19A2, 19B2, such that the object plane distance dcA 42, dcB 43 ranges from dcA1=dcB1 to dcA2=dcB2. Accordingly, the illumination devices can cover various distances ranging from the respective divergence plane 18A1 to 18A2 and from 18B1 to 18B2, such that the divergence center distances diA 40, diB 41 range from diA1 to diA2 and diB1 to diB2, respectively. Substituting dcA1, diA1, dcA2, and diA2 into the equation for the first effective distance deA, we obtain a range of effective distances extending from deA1 to deA2.

[0036] Accordingly, if we substitute dcB1, diB1, dcB2, ​​and diB2 into the equation for the first effective distance deB, we obtain a range of effective distances extending from deB1 to deB2. Typically, the depth of field considered for the cameras and lighting equipment is ±(2*Lambda*F*F), where Lambda is the optical wavelength and F is the effective optical F-number, which refers to page 6 of the pattern generator. By effective F-number, we mean the F-numbers that define the angular measure of the exit lenses of the lighting equipment and the entry lenses of the camera by the equation F = 1 / [2*sin(v / 2)], where v is the angular measure of these lenses as observed from the divergence centers and object planes. However, it should be noted that the lighting equipment and camera may be configured with different F-numbers.It should also be noted that the illumination devices 7A, 7B may contain astigmatic foci in alternative optical configurations, so that the divergence centers 17A, 17B at different illumination device distances diA (40 in . Fig. 3) and diB (41 in Fig. 3) can be when observed in a transverse direction, say parallel to the X-axis, and at the corresponding divergence center distances when observed in the orthogonal transverse directions. In other alternative optical configurations, the same applies to the imaging properties of the camera that determine the object plane positions 15A and 15B at different object plane distances dcA (42 in Fig. 3) and dcB (43 in Fig. 3) Position the camera when focused on features in two orthogonal transverse directions. Astigmatic performance is typically achieved by incorporating cylindrical optics into the illumination setup and / or observation paths. Optical configurations A and B are configured such that their effective distances do not overlap; that is, for each location of sensor device 1, any effective distances ranging from deA1 to deA2 should not be equal to any distances ranging from deB1 to deB2. If alternative optical configurations include astigmatic divergence centers 17A and 17B or astigmatic object plane positions 15A and 15B, the requirement is that the effective distance for optical configurations A and B should not overlap for each of the separately evaluated directions. For improved image analysis performance, the range of effective distances should be separated.Increasing the distance between the effective distances makes it easier to distinguish between translational and rotational offsets, thereby reducing the influence of measurement errors.

[0037] Since the pattern generator 6 is illuminated by laser light, a structurally stable light pattern 8 is created in the 3D space above the pattern generator 6. This light pattern 8 is observed by the camera 9. Each of the optical configurations A and B creates a light pattern that differs from the other. Typically, these light patterns are unique for all the different recording positions. If the carriers 3-1, 3-2 and 3-1-R, 3-2-R are controlled to record at a first recording position at a first time point T1, then moved to record at subsequent recording positions, and finally moved back to exactly the first position at a second time point T2, the pattern images recorded at time point T1 are reproduced exactly at time point T2.But even very small positional offsets between the first and second time of recording, such as 0.1 µm, can influence the pattern image positions and are therefore detectable.

[0038] After the CMM reference recordings are completed, the collected reference data 33-R, recorded on the hard disk 10-R, are used, with the aid of the sensor device 1-R according to the present embodiment or a similarly optically configured sensor device 1, to quantify misalignments occurring during the assembly, use, or maintenance of the milling machine 2. Once quantified, the misalignments are used to improve machine alignment and / or control of subsequent CNC movements of the milling machine 2. This achieves better positioning regardless of any mechanical translational and rotational irregularities in the milling machine 2 that cannot be corrected using conventional calibration and alignment methods.The sensor device 1, which contains the same optical configurations A, B as were used in acquiring the reference data from CMM 2-R, is used. Fig. Figure 1 shows a schematic representation of the milling machine 2. In the present embodiment, the pattern generator 6-R is moved to the milling machine and is called the pattern generator 6. However, the present embodiment would work just as well if both the pattern generator 6-R and the pattern generator 6 were exact copies of the same template. The new positions of the lighting device-camera assembly 7A, 9, 7B relative to the pattern generator 6 should reproduce those of the CMM machine as accurately as possible. To achieve this, the lighting device-camera assembly 7A, 9, 7B and the pattern generator 6 must be pre-aligned.

[0039] For this purpose, the use of pre-positioned mechanical locators or an iterative mechanical alignment of the position of the pattern generator 6 must be performed. The CNC control of the milling machine 2 is then used to move the lighting device-camera arrangement 7A, 9, 7B to the vicinity of one of the previously recorded positions of the CMM 2-R relative to the pattern generator 6, then the offsets are optically observed / measured, then the pattern generator 6 is mechanically moved, and then the alignment process is repeated until the positions are reasonably aligned.

[0040] Alternatively, it is possible to mechanically align the lighting device-camera arrangement 7A, 9, 7B relative to the pattern generator 6 by manually using rulers / buttons or other alignment tools such as a touch probe or similar.

[0041] After pre-alignment, this setting of milling machine 2 is ready to find its exact orientation as measured relative to the reference images of the CMM 2-R. The collected reference data 33-R, represented by the series of corresponding reference carrier position data 31-R, 32-R and reference pattern image data 30A-R, 30B-R, are copied to the hard drive 10. The milling machine 2 is then instructed to move nominally between the previous nominal positions, which correspond to those recorded by the reference CMM 2-R. For each of these positions, the computer hard drive 10 receives from the camera 9 the two pattern images 30A, 30B and the corresponding carrier positions 31, 32, recorded under the conditions of the two optical configurations A and B, respectively.The translation and rotation of the lighting device-camera arrangement 7A, 9, 7B relative to the translation and rotation of the pattern generator 6 should be nominally equal to the corresponding translation and rotation used during the reference shots of the CMM 2-R. Consequently, the new pattern images 30A, captured in the milling machine 2 in optical configuration A, will be similar to the corresponding reference pattern images 30A-R of the CMM 2-R, also captured in optical configuration A. The same will be true for the corresponding B shots. In particular, the images will be similar enough to be recognized as the same pattern, albeit with some offset and possible minor decorrelation. However, with respect to the light-sensitive surface of camera 9, the images will generally be shifted by relatively small amounts.Referring to the light-sensitive surface, we call these 2D image translation offsets (DAX, DAY) and (DBX, DBY), respectively. To calculate these offsets, each reference pattern image 30A-R, 30B-R is mathematically 2D cross-correlated with the corresponding pattern images 30A, 30B of milling machine 2 (for cross-correlation calculations, see, for example, the book by Athanasios Papoulis, entitled Systems and Transforms with Applications in Optics, 1968, McGraw-Hill Book Company, New York). For each of the carrier positions 31, 32, the positions of maximum cross-correlation determine the image offset (DAX, DAY) and (DBX, DBY) of the two optical configurations A and B.Since the encoders of the reference CMM-2-R carriers 3-1-R, 3-2-R can return slightly different carrier positions 31-R, 32-R from the assigned carrier positions 31, 32 of carriers 3-1, 3-2 of machine 2, the carrier positions or the measured image translation offsets should be corrected for these possible differences, even for the same nominal carrier positions. In the present example, we apply these corrections to the image translation offset and denote the corresponding corrected image translation offsets (dAx, dAy) and (dBx, dBy). These corrected image translation offsets are caused by a combination of translational offsets (Dx, Dy) and rotational angle offsets (Tx, Ty) of the illumination device-camera assembly 7A, 9, 7B relative to the pattern generator 6. That is to say,The corrected image translation offsets are caused by translational offsets (Dx, Dy) and rotational angle offsets (Tx, Ty) of the workpiece holder 4 of the milling machine 2 relative to the tool holder 5, using the first partial position 4-R relative to the second partial position 5-R of the CMM 2-R as references. Dx and Dy represent translational offsets in the x and y directions, respectively, while Tx and Ty represent rotational angle offsets about the x and y axes. These offsets are referenced to the milling machine coordinate axis 100-4. Fig. 1. The reference carrier positions 31-R, 32-R refer to the coordinate axis 100-4-R of the CMM 2-R.

[0042] In a linear approximation of the relationship between the image translation offsets (dAx, dAy) and (dBx, dBy) and the relative partial translation offsets (Dx, Dy) and rotation angle offsets (Tx, Ty), the four equations dAx=m11*Dx+m12*Dy+m13*Tx+m14*Ty, dAy=m21*Dx+m22*Dy+m23*Tx+m24*Ty, dBx=m31*Dx+m32*Dy+m33*Tx+m34*Ty, dBy=m41*Dx+m42*Dy+m43*Tx+m44*Ty are expressed. In these equations, the respective factors (m11, m12, m13, m14, m21, m22, m23, m24, m31, m32, m33, m34, m41, m42, m43, m44) are given by the exact illumination observation geometries of the first and second optical configurations A and B, respectively.As long as the effective distance deA for creating the pattern images 30A, 30A-R of optical configuration A differs from the effective distance deB for creating the pattern images 30B, 30B-R of optical configuration B, then the above equations are reversed to find the translational and rotational angular offsets of the workpiece holder 4 relative to the tool holder 5, as expressed by the values ​​of the translational offsets (Dx, Dy) and rotational angular offsets (Tx, Ty). As a numerical example, we assume that the illumination distance diA 40 is equal to 60 mm, the camera distance dcA 42 is equal to 100 mm, the illumination distance diB 41 is at infinity, the camera distance dcB 43 is also equal to 100 mm, and the XYZ coordinate axis is parallel to the corresponding XYZ coordinate axis 100-4 (. Fig. 1) of the milling machine 2 and that the origin is at point 23 ( Fig. 3) is positioned where the optical axis 20A, 20B of camera 9 intersects the pattern generator 6. For numbers representing the distances, see Fig. 3. We also assume that the optical axes of the lighting device 16A, 16B are coaxial with the optical axes of the camera 20A, 20B, that the camera magnification is equal to -1 / 3, and that the X and Y axes of the light-sensitive camera surface are parallel to the corresponding X and Y axes of the machines, as defined by the milling machine coordinate axis 100-4 ( Fig. 1) and CMM coordinate axis 100-4-R ( Fig. 2) specified. In a linear approximation, these configuration parameters for the factors (m11, m12, m13, m14, m21, m22, m23, m24, m31, m32, m33, m34, m41, m42, m43, m44) would yield the respective values ​​(-0.8889, 0.0, 0.0 mm, -66.667 mm, 0, -0.8889, 66.6667 mm, 0.0 mm, -0.3333, 0.0, 0.0 mm, -66.6667 mm, 0.0, -0.3333, 66.6667 mm, 0.0 mm). We also assume that no corrections are made due to the difference between the corresponding carrier positions 31, 32 and the reference carrier positions 31-R, 32-R. It is then found that the corrected image translation offsets (dAx, dAy, dBx, dBy) are each equal to (-59.6, -4.0, -30.7, +2.7) µm. These expressions can then be reversed to yield the desired values ​​for the respective translation offsets (Dx, Dy) as (52.0, 12.0) µm and rotation angle offsets (Tx, Ty) as (100, 200) µradians. The linear expressions described above represent the optical illumination, diffraction, and observation processes.In real-world applications, the m-factors described above may need to account for non-linear deviations. Alternatively, the complete non-linear equations can be iterated to find the exact solution.

[0043] The translation and rotation data 34, represented by the carrier positions 31, 32, the associated partial translation offsets (Dx, Dy) and the associated rotation angle offsets (Tx, Ty), become the calibration data for subsequent production, maintenance or alignment activities of the milling machine. Alternatively, the CNC control of the milling machine 2 uses this data to compensate for the combined error movements of the carriers 3-1, 3-2 during milling.

[0044] Generally, two optical configurations A and B are required to simultaneously locate the translational and rotational components separately. However, although two different optical configurations are provided in this embodiment, a higher number of optical configurations could be provided in further embodiments. A higher number of optical configurations provides more information and a greater number of spatial references, but also requires greater computational capacity for analyzing the acquired data. The exact setting of the optical configurations is varied within the scope of the invention, as long as the light pattern is repeatable, meaning it is always reproduced. An example that allows all six degrees of freedom (three translations + three rotations) of a solid motion to be located for all applied support positions 31 and 32 is shown in [reference]. Fig. Figure 4 shows schematically. According to the embodiment, two different optical configurations A and B, two separate cameras 9A-1 and 9B-1 in combination with a lighting device 7 are also used. See the separate cameras 9A-1 and 9B-1 shown in Figure 4. Fig. 4 together with a lighting device 7, called 7A-1 and 7B-1, are optically configured. In yet another example, according to one embodiment, two separate lighting devices are used in combination with two cameras to provide two different optical configurations A and B. See an example in Fig. 5, in which the illumination device 7A, the pattern generator 6, and the camera 9A belong to configuration A, and the illumination device 7A, the pattern generator 6, and the camera 9A belong to configuration B. In this case, they could be grouped as two different sensor heads, each with its own illumination device and camera. If more than one illumination device is used in combination with the same camera, the illumination devices are preferably operated to illuminate the pattern generator 6 alternately, so that a multitude of different optical light patterns are created based on the origin of the emitted light, and, if more than one illumination device emits light simultaneously, also based on the interference of emitted light waves.In further embodiments, at least one lighting device is attached to a part 4, immovably relative to the pattern generator 6, which is also attached to the part 4, wherein the cameras are attached to a further machine part 5 so that they are movable relative to the pattern generator 6 and the lighting device. In further embodiments, a plurality of pattern generators are provided and combined with several optical configurations A, B of camera(s) and lighting device(s). Since the positioning of most CNC-controlled machines is highly repeatable, in further embodiments it may also be possible to first collect all pattern images 30A of optical configuration A and then collect all pattern images 30B of optical configuration B. In this case, the repeatability error of the computer-controlled machine would complement the final result.However, the flexibility of shooting with one optical configuration after another could outweigh this disadvantage.

[0045] Instead of using the CMM of this example as a reference machine, other alternatives are either to use a laboratory machine as the reference, or to use the best machine in a production series as a reference, or to record the initial state of a machine for later reference during subsequent maintenance.

[0046] Since the characteristics of low-cost pattern generators depend on the production process, such as milling or electrical erosion, the surface structure details of the pattern are random but unique for each generator. However, it is possible, for example, by using holographic replication techniques, to replicate the optical characteristics of a pattern generator, thus enabling the mass production of sufficiently identical models. It is also possible to create a mask using a photographic technique or an embossing process that can produce multiple identical copies of the template. Both of these masks can function as reflectors. EXAMPLE 2.

[0047] This embodiment functions as an absolute position encoder capable of calibrating for translational and rotational offsets. In this context, an absolute encoder is one that reads and knows the carrier positions without necessarily tracking their positions relative to a home position. Variations of this embodiment are described in Fig. 6, Fig. 7 and Fig. 8 illustrated. Fig. Figure 6 schematically shows some of the parts of an advanced single-carrier encoder. In this figure, the pattern generator 6 is attached to a machine part 4, and the lighting devices 7A, 7B, and camera 9 are attached to the machine part 5, where camera 9A is identical to camera 9B but belongs to different optical configurations A and B, respectively. To achieve a high sampling rate, camera 9 is a 2D CMOS video camera with a resolution of only 50x50 pixels but a sampling rate of 10,000 frames per second. The carrier 3-1 with two parallel carrier carriages is shown in Figure 5. Fig. 6 enables the machine to move part 5 relative to part 4 in a direction parallel to the Y-axis. A traditional encoder sensor head 101, which reads the Y-position 31 of the carrier, is also provided. For each carrier position 31, this embodiment is able to find the translational (Dy, Dz) and rotational angular offsets (Ty, Tz) of part 5 relative to part 4. The translational and rotational data 34, represented by the carrier positions 31, the associated part translational offset (Dx, Dy), and the associated rotational angular offset (Tx, Ty), become the encoder data to be used by the machine in which this advanced single-carrier encoder is installed.

[0048] In the present embodiment, a carefully prepared calibration reference machine is shown schematically in Fig. Figure 7 shows the machine used to create the collected reference data 33-R. This calibration reference machine is optically as similar as possible to the advanced single-carrier encoder from [reference missing]. Fig. 6 configured, but to obtain high rotational offset accuracy, its mechanics incorporate larger distances between the two precision carriers 3-1-R and between the carriers 3-1-R and the moving part 5-R, in both the Z and Y directions. This calibration reference machine provides the collected reference data 33-R, represented by the reference carrier position 31-R and reference pattern image data 30A-R, 30B-R, by characterizing the exact translation and rotation of part 5-R relative to part 4-R. A small embedded computer contains the processor 12 ( Fig. 6) The collected reference data 33-R is copied to a USB flash drive. The USB flash drive is inserted into the embedded computer and the data is copied to internal memory 10 within that embedded computer. As described in Fig. As specified in 6, the carrier position data 31 and the pattern image data 30A, 30B are also copied to the internal memory 10. Using the same calculations as described in Example 1, the processor 12, knowing the collected data 33, the corresponding reference carrier position 31-R and carrier positions 31, and the corresponding reference pattern image data 30A-R, 30B-R and pattern image data 30A, 30B, calculates the (Dy, Dz) translational offset and (Ty, Tz) rotational angle offset of part 5 relative to part 4 in real time for each carrier position 3-1. In this context, real time means an update rate necessary for the CNC machine in which this embodiment of a single-carrier encoder is installed to operate at an appropriate speed.

[0049] If only Y-translations and rotational angle offsets around the Y-axis are required, this embodiment is alternatively equipped with a 1D line scan camera with a resolution of 500 pixels instead of the 2D camera, wherein the pixel line is parallel to the Y-axis and the sampling rate is 10,000 per second. For each carrier position 31, this embodiment is then able to find the translational offset (Dy) and rotational angle offset (Tz) of part 5 relative to part 4 if the photosensitive line surface of the line scan camera is parallel to the Y-axis, or the translational offset (Dz) and rotational angle offset (Ty) of part 5 relative to part 4 if the photosensitive line surface of the line scan camera is parallel to the Z-axis.

[0050] In the first case, involving a 1D line-scan camera, a linear approximation of the relationship between the image translation offsets (dAy) and (dBy) and the relative partial translation offset (Dy) and rotation angle offset (Tz) is expressed by the two equations dAy = m11*Dy + m12*Tz, dBy = m21*Dy + m42*Dy + m22*Tz. In these equations, the respective four factors (m11, m12, m21, m22) are given by the exact illumination observation geometries of the first and second optical configurations A and B, respectively.

[0051] Fig. Figure 8 shows an alternative encoder, which we call an advanced two-carrier encoder, installed within a computer-controlled machine with carriers 3-1, 3-2, and which moves part 5 relative to part 4 in both the Y and Z directions. This embodiment is also capable of determining the (Dy, Dz) translational offset and (Ty, Tz) rotational angular offset of part 5 relative to part 4. Another use of this embodiment is its installation in a machine tool such as the milling machine 2, described in Example 1. Then, simultaneous measurements of translations and rotations during machining, or simultaneous measurement of the effect of tool load and tool speed, or simultaneous measurement of thermal changes are performed.

[0052] In the embodiments described in Example 2, the carrier position data 31 from the encoder sensor head 101 help to speed up the retrieval of the correct pattern image data 30A, 30B, since the reference carrier positions 31-R, and, if applicable, 32-R, assist in pointing to the appropriate pattern image data 30A, 30B. Although the reference encoder sensor head 101-R is required to associate the reference pattern data 30A-R, 30B-R with the reference carrier positions such as 31-R and 31-R, all devices according to the present invention can function just as well without access to the carrier positions 31, 32. In this case, processor 12 must first search for pattern images 30A, 30B that match the reference pattern images 30A-R, 30B-R before performing the detailed image correlations that find the partial translations and rotations.In the embodiments of the present Example 2, the speed of the encoder may be critical, but the embodiments of Example 1 can function almost as accurately without using carrier positions 31 or carrier positions 31, 32. The reason they do not function as accurately is due to the fact that in these cases, the processor 12 does not have access to small corrections between the carrier position 31, 32 specified by the CNC and the carrier position actually read (see the description of compensation of the corrected image translation offsets from Example 1). EXAMPLE 3.

[0053] This embodiment functions as an absolute angle encoder for a robot joint. This encoder is capable of calibrating for translational and rotational offsets. This is demonstrated in Fig. 9 schematically illustrated. Fig. Figure 9 shows some of the mechanical parts of a robot joint and an embodiment of the present invention. In this figure, the pattern generator 6 is attached to a machine part 4, and the lighting device 7 and cameras 9A, 9B are attached to the machine part 5. Here, 7A indicates that the lighting device 7 belongs to optical configuration A, and 7B indicates that it belongs to optical configuration B. The pattern generator 6 is a flat and polished glass plate with a detailed mirror pattern evaporated onto its surface. If the pattern is randomized, all pattern images 30A, 30B will be different. If the pattern is periodic, the patterns can repeat at different carrier positions 31, and the processor 12 needs access to the carrier positions 31 to distinguish between patterns.This pattern generator 6 was created from a drawing, which made it possible to create a large number of optically identical copies. This makes it possible to create another copy reference pattern 6-R from the drawing template, which is used in a reference robot joint. However, the pattern must be detailed enough to diffract light from the lighting device 7A to the camera 9A and from the lighting device 7B to the camera 9B. The reference robot joint is not shown in any drawing, but could be represented, except for the processor 12 and the translation and rotation data 34, by... Fig. 9 is represented, in which all numbers and character combinations end with -R (see Fig. 2 and Fig. 7 for the similar conventions in spelling). The carrier 3-1, which in Fig. The 9 bearings shown allow the machine part 5 to rotate around the X-axis relative to part 4.

[0054] A traditional angle encoder sensor head 101, which reads the carrier rotation angle from a segmented glass line pattern 102 that also rotates about the X-axis, is also shown. For each rotation angle about the X-axis, the embodiment of the present example is able to find the local (Dy, Dz) translational offset and (Ty, Tz) rotational angle offset of part 5 relative to part 4. Since both the translational offset (Dy, Dz) and the rotational angle offset (Ty, Tz) at the robot joint are found with high accuracy, the translation and rotation of the robot arm tip are also found with high accuracy by extrapolation.

Claims

[1] Method for obtaining the translation and rotation of a first part relative to the translation and rotation of a second part of a computer-controlled machine having at least one movable support (3) for changing the position of the first machine part relative to that of the second machine part, the method comprising Providing a pattern generator (6) which is attached to the first machine part (4), Providing a first illumination device (7) which is attached to either the first machine part (4) or the second machine part (5) and which is optically configured to illuminate the pattern generator (6) to jointly create a three-dimensional pattern (8) of light in space, Providing a first camera (9) which is attached to the second machine part (5) and which is optically configured to record the pattern images of the three-dimensional pattern (8) of light in space, Providing a second lighting device (7) or a second camera (9), Providing a range of effective optical distances of a first optical configuration (11A) in which light is propagated along optical paths from one of the first or second illumination devices via the pattern generator (6) to one of the first or second cameras to capture a first image of the three-dimensional pattern (8) of light in space, wherein the range of effective optical distances does not overlap with a range of effective optical distances of a second optical configuration (11B) in which light is propagated along optical paths from one of the first or second illumination devices via the pattern generator (6) to one of the first or second cameras to capture a second image of the three-dimensional pattern (8) of light in space, Configuring each of the first or second illumination devices configured to illuminate the pattern generator (6) with light of a coherence length that is longer than a maximum optical path length difference within each of the optical configurations (11A, 11B), and Configuring the sensor device (1) to capture either a) the first image of the three-dimensional pattern (8) of light in space using a combination of the first illumination device and the first camera, and the second image of the three-dimensional pattern (8) of light in space using a combination of the first illumination device and the second camera, or b) the first image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the first illumination device, and the second image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the second illumination device, or c) the first image of the three-dimensional pattern (8) of light in space using a combination of the first illumination device and the first camera, and the second image of the three-dimensional pattern (8) of light in space using a combination of the second illumination device and the second camera, wherein at each position of the movable support, the first and second of the illumination device (7) or the first and second of the camera are controlled to operate alternately so as not to capture the first and second images simultaneously and only in respectively different optical configurations. [2] The method of claim 1, further comprising moving the movable carrier to a plurality of positions and at each position recording carrier position data (31, 32) associated with the position of the movable carrier in conjunction with a configuration of the sensor device. [3] A method according to any one of claims 1 or 2, wherein images are taken at each position of the movable support using a plurality of cameras (9), the cameras being configured to take images in respective different object planes. [4] A method for deriving data for calibrating or improving the positioning of a computer-controlled machine comprising a movable support for changing the position of a first machine part relative to that of the second machine part, the method comprising: Providing a sensor device for a computer-controlled machine (2) with a movable support (3) for changing the position of a first machine part (4) relative to that of a second machine part (5), wherein the sensor device (1) comprises: a pattern generator (6) attached to the first machine part (4), a first illumination device (7) for coherent light, which is attached to either the first machine part (4) or the second machine part (5) and which is optically configured to illuminate the pattern generator (6) with coherent light to jointly create a three-dimensional pattern (8) of light in space, a first camera (9) which is attached to the second machine part (5) and which is optically configured to record the pattern images of the three-dimensional pattern (8) of light in space, wherein the sensor device (1) further comprises: either a) a second camera (9), and the sensor device is configured to capture a first image of the three-dimensional pattern (8) of light in space using a combination of the first illumination device for coherent light and the first camera, and a second image of the three-dimensional pattern (8) of light in space using a combination of the first illumination device and the second camera, wherein a range of effective optical distances of a first optical configuration (11A), in which light is propagated along optical paths from the first illumination device via the pattern generator (6) to the first camera to capture the first image, does not overlap with a range of effective optical distances of a second optical configuration (11B), in which light is propagated along optical paths from one of the first illumination devices via the pattern generator (6) to the second camera,to capture the second image, and wherein the first illumination device is configured to illuminate the pattern generator (6) with light of a coherence length that is longer than a maximum optical path length difference within each of the optical configurations (11A, 11B), or, b) a second illumination device (7) for coherent light and a sensor device (1) configured to capture a first image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the first illumination device for coherent light, and a second image of the three-dimensional pattern (8) of light in space using a combination of the first camera and the second illumination device for coherent light, wherein a range of effective optical distances of a first optical configuration (11A), in which light is propagated along optical paths from the first illumination device via the pattern generator (6) to the first camera to capture the first image, does not overlap with a range of effective optical distances of a second optical configuration (11B),in which light is propagated along optical paths from one of the first illumination devices via the pattern generator (6) to the first camera to capture the second image, and wherein each of the first or second illumination devices is configured to illuminate the pattern generator (6) with light of a coherence length that is longer than a maximum optical path length difference within each of the optical configurations (11A, 11B), or c) a second camera (9) and a second illumination device (7) for coherent light, and the sensor device (1) is configured to capture a first image of the three-dimensional pattern (8) of light in space using a combination of the first illumination device for coherent light and the first camera, and a second image of the three-dimensional pattern (8) of light in space using a combination of the second illumination device for coherent light and the second camera, wherein a range of effective optical distances of a first optical configuration (11A), in which light is propagated along optical paths from the first illumination device via the pattern generator (6) to the first camera to capture the first image, does not overlap with a range of effective optical distances of a second optical configuration (11B),in which light is propagated along optical paths from the second illumination device via the pattern generator (6) to the second camera to capture the second image, and wherein each of the first and second illumination devices is configured to illuminate the pattern generator (6) with light of a coherence length that is longer than a maximum optical path length difference within each of the optical configurations (11A, 11B), Moving the movable support into a plurality of support positions such that the position of the first machine part changes relative to that of the second machine part for each of the plurality of positions, and at each carrier position, recording position data associated with the position of the movable carrier and operating the sensor device to record a pair of first and second images of the three-dimensional pattern of light in space in corresponding first and second optical configurations, and comparing the recorded image data with image data of a reference database comprising interlinked image and position data associated with the three-dimensional pattern of light in space of the pattern generator and finding pairs of similar images, deriving image translation offset data for each pair of similar images, and Deriving translation and rotation data to calibrate or improve the positioning of the computer-controlled machine based on image translation offset data associated with the optical configurations.

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