JP2019045500A - Coordinate measuring machine for determining at least one coordinate of at least one measuring object - Google Patents

Abstract

A coordinate measuring machine is provided for determining at least one coordinate of at least one measurement object. A coordinate measuring machine (110) is proposed for determining at least one coordinate of at least one measurement object (112). The coordinate measuring machine (110) comprises at least one optical element (114). The optical element (114) is configured to set the imaging magnification of at least one pixel according to the distance of the same pixel from the optical axis (116) of the optical element (114). A coordinate measuring machine (110) includes at least one imaging device (118) configured to generate at least one image of pixels. The coordinate measuring machine (110) comprises at least one evaluation unit (120). The evaluation unit (120) is configured to correct the distortion of the image. The evaluation unit (120) is configured to determine the coordinates of the measurement object (112) from the corrected image. [Selected figure] Figure 1

Description

  The present invention relates to a coordinate measuring machine which determines at least one coordinate of at least one measurement object and a method of determining at least one coordinate of at least one measurement object. The invention relates in particular to the field of coordinate measurement technology using non-contact coordinate measuring machines.

  Various devices and methods are known from the prior art for determining the coordinates of an object to be measured (e.g. turbine blades, vehicle body sheets, seals or printed circuit boards). Tactile and optical coordinate measuring machines are known as an example. A coordinate measuring machine of this type can, for example, be configured as a gantry-type measuring machine. The gantry type measuring machine includes a gantry having two vertical rows and a cross beam connecting the two rows in the upper region. The gantry is mounted so as to be horizontally movable on the body for supporting the workpiece to be measured. A measuring slide is mounted so as to be movable along the cross beam, and a vertically movable sleeve is mounted on the measuring slide. A sensor, in particular a tactile or optical sensor, is arranged at the lower end of the sleeve, by means of which the surface of the measurement object can be scanned or imaged in a contactless manner. The sensor can be moved in all coordinate directions x, y, z relative to the measurement object by means of the described gantry mechanism.

  However, on the one hand high-resolution measurements and on the other hand large measuring fields or rough recordings are necessary for optical coordinate measuring machines. In the case of large measuring fields, known coordinate measuring machines need to have no resolution for a larger measuring range. Furthermore, in known coordinate measuring machines, the ratio of the measuring range (so-called spread) is introduced by means of a so-called zoom system. Here, the imaging magnification may be set by adjusting the lens position, for example in a cascade of imaging lens elements or groups. As a result, in the zoom system it is possible to select which target segment is to be imaged on the camera. However, this type of zoom system can be disadvantageous. As an example, the optical mechanism for moving the lens is expensive and prone to wear. Playing with this mechanism can result in measurement instability and / or inaccuracies. This type of system tends to have a large structure. Changes in the heat input arising from the motor, controller and friction of the drive can occur, so that this type of system can only be thermally controlled with high complexity.

  Furthermore, it is known to realize the enlargement of the measurement field by increasing the number of pixels of the camera chip. Nevertheless, chip enlargement and / or pixel densification to maintain resolution while expanding the measurement range may not be suitable for all applications. As an example, a spread of 4: 1 or more is desirable for various applications. The expansion of chips and / or the densification of the pixels by such magnifications have never occurred even in the context of advances in the semiconductor industry, or these chips are not preferred for use in the industrial field. It is in particular necessary to enlarge the diameter of the imaging optical unit in order to fulfill the enlargement of the chip by the imaging optical unit. However, such imaging optical units are heavy, large and expensive.

  Furthermore, the '095 patent processes an image according to an optical element, an image sector element coupled to it, the image sector element configured to divide the field of view into a plurality of areas, and And an image processing processor configured to:

U.S. Patent Application Publication No. 2008/0158226 A1

  It is therefore an object of the present invention to provide a coordinate measuring machine and method which at least largely avoids the disadvantages of the known devices and methods. In particular, the intention is to enable measurements with the largest possible resolution and the largest possible measurement field.

  This object is achieved by an apparatus and method having the features of the independent claims. Advantageous developments which can be realized individually or in combination are presented in the dependent claims.

  In the following, the terms "present", "have", "include" or "include" or all grammatical variants thereof are used in a non-exclusive manner. Thus, these terms may refer to any situation where there is no other feature besides the features introduced by these terms, or where one or more other features exist. For example, the expressions "A presents B", "A has B", "A contains B" or "A contains B" provides any other element within A except B. In A, and one or more other elements (eg, element C, elements C and D, or another element) in addition to B. Can refer to both

  Furthermore, the terms "at least one", "one or more" and grammatical variations or similar terms of these terms are used in connection with one or more elements or features, the same elements or features being alone It is pointed out that if it is intended to represent the fact that one or more may be provided, it will usually only be used once, for example when a feature or element is first introduced. When the same feature or element is subsequently mentioned again, the terms "at least one" or "one or more" are generally no longer used without limitation of the possibility that the feature or element is provided singly or in multiples I will not.

  Furthermore, the terms "preferably", "in particular", "as an example" or similar terms are used hereinafter in connection with optional features without limitation of alternative embodiments. In this regard, the features introduced by these terms are optional features and are not intended to limit the scope of protection of the claims, particularly the independent claims, by these features. In this regard, as one of ordinary skill in the art will appreciate, the present invention may also be practiced using other configurations. Similarly, features introduced by "in an embodiment of the invention" or "in an exemplary embodiment of the invention" are thereby limited in scope of protection in another configuration or in the independent claims. Are understood as optional features without the intention. Furthermore, all possibilities of combining features introduced by these introductory expressions with other features are intended to remain unaffected by said introductory expressions, whether or not they are optional features. ing.

  In one aspect of the invention, a coordinate measuring machine is proposed for determining at least one coordinate of at least one measurement object.

  In this case, the measurement object can usually be understood in the context of the present invention as meaning an arbitrarily shaped measurement object. As an example, the measurement object can be selected, for example, from the group consisting of a test specimen of a motor vehicle, a workpiece to be measured and a component to be measured. The measurement object may be a three-dimensional measurement object (e.g. at least one turbine blade, at least one vehicle body sheet, at least one seal, or at least one printed circuit board). In particular, the measurement object may be at least one end or may have at least one end. Edge in the context of the present invention may be understood to mean a surface having a limit of less than 1 mm or a contour having a radius of curvature of less than 1 mm. However, other measurement objects can also be considered.

  "Coordinate measuring machine" may be understood to mean an apparatus configured to determine at least one coordinate of a measurement object. The coordinate measuring machine may be an optical coordinate measuring machine. The coordinate measuring machine may be a coordinate measuring machine including an imaging measurement system. The coordinate measuring machine may be, for example, a gantry type measuring machine or a bridge type measuring machine. The coordinate measuring machine may include a measurement table having at least one bearing surface for carrying the measurement object. The coordinate measuring machine has at least one gantry having at least one first vertical row, at least one second vertical row, and a cross beam connecting the first vertical row and the second vertical row. obtain. At least one vertical row selected from the first and second vertical rows may be horizontally movable on the measurement table. The horizontal direction may be, for example, a direction along the y-axis. The coordinate measuring machine may have a coordinate system, for example a Cartesian coordinate system or a polar coordinate system. Other coordinate systems are also conceivable. The origin or zero of the coordinate system can be defined, for example, by the sensor of the coordinate measuring machine. The x-axis may extend perpendicularly to the y-axis in the plane of the bearing surface of the measuring table. The z-axis may extend vertically, perpendicular to the plane of the bearing surface. The vertical rows may extend along the z-axis. The cross beam may extend along the x-axis.

  The coordinate measuring machine comprises at least one optical element. The optical element is configured to set the imaging magnification of at least one pixel according to the distance of the same pixel from the optical axis of the optical element. The coordinate measuring machine includes at least one imaging device configured to generate at least one image of pixels. The coordinate measuring machine comprises at least one evaluation unit. The evaluation unit is configured to correct the distortion of the image. The evaluation unit is configured to determine the coordinates of the measurement object from the corrected image.

ここで、ｚはサジタル高さ、ρは頂点曲率、ｈは光軸に垂直な距離、κは円錐定数、ｃ_ｋは補正多項式の係数、ｉは自然数である。光学素子は少なくとも２つの非球面レンズを含み得る。非球面レンズは同一または異なる方法で構成され得る。 "Optical element" in the context of the present invention may be understood to mean any optical component part or any optical component. As an example, the optical element may include multiple components. In this case, the parts can be configured in a spatially separated manner from one another. As an example, the optical element may include an optical system having a plurality of optical components (e.g., one or more lenses and / or lens groups and / or another optical component). The optical element may include at least one aspheric lens. An "aspheric lens" may be understood to mean an optical element having at least one aspheric surface (i.e. a surface that deviates from a circular shape and / or a planar shape). The aspheric surface can be described by the following equation.

Here, z is a sagittal height, ρ is a vertex curvature, h is a distance perpendicular to the optical axis, κ is a conical constant, _ck is a coefficient of the correction polynomial, and i is a natural number. The optical element may include at least two aspheric lenses. Aspheric lenses may be configured in the same or different manner.

  "Imaging magnification", also referred to as magnification, may be understood to mean the ratio of the image size of the optical imaging of the measurement object to the actual object size. Pixels can be understood as meaning points in the image plane of the measurement object. The entire pixel is sometimes referred to as the imaging of the measurement object (also called an image). “Imaging” can be understood in principle to mean the generation of an image of the measurement object. The optical element may transmit part of the energy emanating from the measurement object in the visible spectral range into the image plane. As an example, energy may be generated by the measurement object itself, for example in the case of an autoluminescent measurement object, and / or energy may be generated by irradiation of the measurement object, which can be transmitted in the measurement object, for example by reflection. It can be converted to energy. The image may be an image of a partial region of the measurement object or an image of the entire measurement object.

  The optical axis may be a common optical axis of the components of the optical element. “The distance of the pixel from the optical axis” may be understood to mean the distance perpendicular to the optical axis in the image plane of the measurement object. The optical axis may, for example, define the z-axis, to which the image plane perpendicular to it may form the xy plane. Setting the imaging magnification according to the distance of the pixel from the optical axis may be understood to mean that the optical element is configured such that the magnification of the pixel decreases with increasing distance from the axis. The optical element may have geometrical image aberrations. In particular, the optical element may comprise a distortion optical unit. The optical element may include a foveal optical unit. The optical element may be configured to set a first imaging magnification for the near-axis measurement field area and a second imaging magnification for the axis-remote measurement field area. . The optical element may be configured to simultaneously set a first imaging magnification for the paraxial measurement field area and a second imaging magnification for the far axis measurement field area. The first imaging magnification may be greater than the second imaging magnification. The paraxial and far-axis measurement field regions may extend rotationally symmetrically or non-rotationally symmetrically in the image plane radially outward from the optical axis. "Paraxial" may be understood to mean a measurement field area having a smaller radius from the optical axis as compared to the "far axis" measurement field area. For zero axial distance, the term "optical axis" is used. The term "zone" is used for axial distances of 2/3 or less of the field diagonal. The term "margin" is used for axial distances from the outer area to 3/3 of the diagonal field. The paraxial measurement field area may in particular be present in the area of the zone, while the far axis measurement field area may be present in the area of the edge. The far-axis measurement field area may surround the paraxial measurement field area. The size (in particular the area) of the paraxial and far-axis measurement field areas can be determined by the components of the optical element. The optical element may be configured to set a spread of 4: 1 or more (preferably 5: 1 or more) with respect to the paraxial measurement field region and the far-axis measurement field region.

The optical element may be configured to telecentrically image the paraxial measurement field area on the imaging device. Telecentricity may decrease with increasing distance from the axis. As explained above, the optical element may be configured to simultaneously set a first imaging magnification for the paraxial measurement field area and a second imaging magnification for the far axis measurement field area. In this regard, sharp z-focusing of the working distance of the optical unit near the axis with small depth of field can also be transferred to the far-axis image area. With this sharp z-focus it is possible to significantly minimize the effect of telecentricity loss on the xy measurement accuracy of the far-axis measurement area (depth of field ̃NA ² ).

  The imaging device may include at least one sensor element. As an example, the sensor elements may be configured rotationally symmetric. The optical element may be configured such that the strain profile is the same in all radial directions. The distortion profile may correspond to the field height in each direction.

  As an example, the sensor elements may be configured non-rotationally symmetric. As an example, the sensor element may be rectangular, for example with an aspect ratio of 4: 3. The optical element may be configured to generate a non-uniform distortion profile. As an example, the optical elements may be configured such that the strain profiles are different in different radial directions (ie non-rotationally symmetrical in a way that matches the field geometry). The optical element may be configured such that the strain profile is non-rotationally symmetric. As an example, in the short field direction, the maximum magnification may only be needed to a correspondingly small field height, which may already drop thereafter. In the diagonal direction, the magnification can be kept constant up to a larger radius. The optical element may be configured such that the distortion profile is non-rotationally symmetric, so that in the case of a fixed field height distortion profile in the object, the associated field height in the image is the spread of the sensor element in the corresponding direction Have the same azimuthal dependence (in particular, azimuthal dependence with four minima and maxima). The optical element may comprise at least two near-field free form double aspheric surfaces. The optical element may comprise at least two non-rotationally symmetric free form double aspheric surfaces.

  "Imaging device" may be understood to mean an optional device configured to generate at least one image of a pixel. The imaging device may include at least one sensor element. The “sensor element” in the context of the present invention detects, for example, at least one optical measurement variable of the detection light beam emanating from the measurement object and generates a corresponding signal, for example an electrical signal (eg analog and / or digital signal) It can be understood to mean any device configured in. The sensor element may include a plurality of pixels. The imaging device may include at least one camera. As one example, the imaging device may include at least one camera chip having a plurality of pixels. As an example, the camera chip may be a camera chip of about 10 million pixels or more and 1 inch or more. For example, the average pixel size may be 3 μm. As an example, the pixel size may be 3 to 7 micrometers, and the number of pixels may be 2 million pixels to 5 million pixels. As an example, the image feed rate may preferably be 25 to 50 Hz.

  An "evaluation unit" may generally be understood to mean an electronic device configured to evaluate a signal generated by an imaging device, in particular a sensor element. As an example, one or more electronic connections between the sensor element and the evaluation unit may be provided for this purpose. The evaluation unit may, for example, comprise at least one data processing device (e.g. at least one computer, microcontroller). The data processing device may have one or more volatile and / or non-volatile data memories, and may be configured to drive sensor elements, for example in terms of programming. The evaluation unit may further include at least one interface (e.g. an electronic interface and / or a human machine interface such as an input / output device such as a display and / or a keyboard). The evaluation unit may, for example, be constructed in a centralized or otherwise decentralized manner. Other configurations are also conceivable. The evaluation unit may, for example, be configured to read out from the camera chip of the imaging device at a certain read rate. The readout rate may be several tens of Hz or more. Data transmission may occur, for example, in a cable-based manner via optical waveguides and / or wirelessly.

  The evaluation unit may be configured to correct the distortion of the image. The evaluation unit may include an image processing device. The image processing device may be provided at least partially as part of an imaging device (e.g. as an "embedded platform"). "At least partially as part of an imaging device" may be understood as meaning that at least a part of the imaging device is arranged as a component of the imaging device, another part of the imaging device is also It can be arranged outside the imaging device, for example connected to the imaging device via at least one connection, in particular a data transmission. The image processing device may be configured to perform near-sensor pre-processing. The image processing apparatus may be configured to correct for distortion.

  The image processing apparatus may include software for correcting distortion. The image processing apparatus selects and / or compresses an image region at least one "region of interest" (ROI) and / or an image segment of the image ("image cropping") in the image. Can be configured as follows. The image processing device may be configured to select at least two measurement field areas with different imaging magnifications, in particular at least one near-axis measurement field area and / or at least one far-axis measurement field area. The image processing apparatus may be configured to select ROI or image cropping depending on whether paraxial detail (far-axis cropping) is desired or if outline without detail (paraxial compression) is desired. . As an example, the evaluation unit may include a graphic user interface for selecting the spatial spacing to be represented.

  The connection of the optical systems described for camera proximity imaging or image preprocessing (so-called embedded processing platform) may be particularly advantageous. In this way, at least one correction of significant distortion can be shifted upstream so that after correction the existing open loop and closed loop control electronics of the coordinate measuring machine or their algorithms can all be adopted without modification . More extensive image processing methods may also be shifted upstream in the imaging device. As an example, the image area needed for the measurement that is actually needed may be filtered out, while the rest of the image has already been discarded near the camera. In this way, the volume of data sent to the measurement image processing and thus the required bandwidth of the feed can be reduced. This may in particular make it possible to increase the measuring frequency. A reduction in heat input associated with data transmission may also be possible. As an example, the image processing up to so-called "feature extraction" (eg edge detection) may be shifted upstream in the imaging device so that finally only the point cloud (ie small sized ASCII file) is imaged It is transmitted from the device to the evaluation unit of the coordinate measuring machine. The sensor thus embodied comprising an optical element having an imaging device and a foveal optical unit may be used in a standard change interface for automated tool changes.

Correction of distortion (especially radial distortion) may be performed, for example, by use of the Brown-Conrady model. In this case, for example, the seventh-order distortion image coordinates x _s can be described by the following equation.
x _s = k ₀ x ₀ + k ₁ x ₀ ³ + k ₂ x ₀ ⁵ + k ₃ x ₀ ⁷
Here, x ₀ is a distortion free coordinate, and k is a magnification factor. The distortion free factor M _L may then be described by the following equation:

  Correction of distortion with low or high order is also conceivable.

  The image processing device may be configured to determine the offset between individual records of different areas of the measurement object. As an example, a low resolution outline area may be used to determine the offset between individual records, for example by correlation. These methods allow ultra-high accuracy of offset determination in a relatively simple manner, so that also general images that tend to have more features to be correlated are better suited for detail recording. These correlations make it possible to significantly increase the accuracy of the axial scale of the machine without increasing the cost of the actual machine structure and to enable offset measurement accuracy in the submicron range.

  The evaluation unit may be configured to determine the coordinates of the measurement object from the corrected image. The evaluation device may include metrology image processing configured to dimensionally measure the measurement object. In the context of the present invention, the coordinates of the measurement object can be understood as meaning the coordinates (in particular the distance coordinates) on the measurement object surface (especially on the edge) of the measurement object. One or more coordinate systems may be used for this purpose. As an example, a Cartesian or polar coordinate system may be used. Other coordinate systems are also conceivable. The optical axis of the optical element may be the axis of the coordinate system (e.g. z-axis). Distance coordinates may be understood to mean coordinates along the z-axis. Another axis (e.g. x-axis, y-axis) perpendicular to the z-axis may be provided. The determination of the distance coordinates can be understood as meaning in particular the determination of the distance between the measurement object and the respective determined position of the optical element and / or the imaging device.

In another aspect, a method of determining at least one coordinate of at least one measurement object is proposed in the context of the present invention. This method is
-Setting the imaging magnification of at least one pixel by the same optical element according to the distance of the pixel from the optical axis of the at least one optical element;
Imaging the pixels with at least one imaging device;
Correcting the distortion of the image by means of at least one evaluation unit;
Determining the coordinates of the measurement object from the corrected image by means of the evaluation unit.

  In this case, the method steps may be performed in a defined order, one or more of the method steps may be performed at least partially simultaneously, and one or more of the method steps may be repeated multiple times. . Furthermore, other steps may additionally be performed, whether or not mentioned in the present application.

  A coordinate measuring machine according to the invention can be used in the method. For details regarding the method according to the invention, reference is made to the description of the coordinate measuring machine according to the invention.

  The coordinate measuring machine according to the invention and the method according to the invention are advantageous compared to known methods and devices. The optical elements make it possible, in particular, to be dispensed with without moving groups, thus making it possible to simplify the structure, eliminating the motor with the controller and the leads and improving the measurement stability.

  In summary, in the context of the present invention, the following embodiments are particularly preferred:

  Embodiment 1: A coordinate measuring machine for determining at least one coordinate of at least one measurement object, the coordinate measuring machine including at least one optical element, the optical element comprising an imaging magnification of at least one pixel A coordinate measuring machine configured to set according to the distance of the same pixel from the optical axis of the optical element, the coordinate measuring machine including at least one imaging device configured to generate at least one image of the pixels; A coordinate measuring machine comprising at least one evaluation unit, wherein the evaluation unit is adapted to correct the distortion of the image, the evaluation unit being adapted to determine the coordinates of the measurement object from the corrected image.

  Embodiment 2: The optical element is configured to set a first imaging magnification for the paraxial measurement field region and to set a second imaging magnification for the far-axis measurement field region. Coordinate measuring machine described in.

  Embodiment 3: The coordinate measuring machine according to Embodiment 2, wherein the first imaging magnification is larger than the second imaging magnification.

  Embodiment 4: The coordinate measurement machine of any one of embodiments 2-3, wherein the optical element is configured to set a spread of 4: 1 or more with respect to the paraxial measurement field region and the far axis measurement field region. .

  Embodiment 5: The coordinate measuring machine according to any one of the embodiments 1 to 4, wherein the optical element has geometrical image aberration.

  Embodiment 6 The coordinate measurement machine of any one of embodiments 1 to 5, wherein the optical element comprises a foveal optical unit.

  Embodiment 7 The coordinate measurement machine of embodiment 6, wherein the optical element comprises at least one aspheric lens.

  Embodiment 8: The coordinate measuring machine according to any one of the embodiments 1 to 7, wherein the imaging device comprises at least one sensor element.

  Embodiment 9: The coordinate measurement machine of embodiment 8, wherein the sensor element comprises a plurality of pixels.

  Embodiment 10: The coordinate measuring machine of any one of embodiments 1 to 9, wherein the imaging device comprises at least one camera.

  Embodiment 11: A coordinate measuring machine according to any of embodiments 1-10, wherein the evaluation unit comprises an image processing device configured to correct for distortion.

  Embodiment 12: The coordinate measurement machine of embodiment 11, wherein the image processing device is at least partially configured as part of an imaging device, and the image processing device is configured to perform near-sensor preprocessing.

Embodiment 13: A method for determining at least one coordinate of at least one measurement object, comprising:
-Setting the imaging magnification of at least one pixel by the optical element according to the distance of the pixel from the optical axis of the at least one optical element;
Imaging the pixels with at least one imaging device;
Correcting the distortion of the image by means of at least one evaluation unit;
Determining the coordinates of the measurement object from the corrected image by means of an evaluation unit.

  Embodiment 14 The method according to embodiment 13, wherein the coordinate measuring machine according to any one of the embodiments 1-12 relating to a coordinate measuring machine is used.

  Further details and features of the invention emerge from the following description of preferred exemplary embodiments, in particular in conjunction with the independent claims. In this case, each feature may be realized by itself or as a plurality in combination with one another. The invention is not limited to the exemplary embodiments. Exemplary embodiments are schematically illustrated in the attached drawings. In this case, identical reference symbols in the individual figures indicate identical or functionally identical elements or element groups which correspond to one another with regard to their function.

Fig. 2 shows a schematic view of a coordinate measuring machine. 2A to 2C show an image of the measurement object without distortion, an image of the measurement object with distortion, and a corrected image. 3A-3C illustrate the imaging of a distortion free measurement object, the imaging of a distortion measurement object, and the simulation of a corrected image.

  FIG. 1 shows a schematic view of a coordinate measuring machine 110 for determining at least one coordinate of at least one measurement object 112. Coordinate measuring machine 110 may be an optical coordinate measuring machine. The coordinate measurement machine 110 may be a coordinate measurement machine including an imaging measurement system. Coordinate measuring machine 110 may be, for example, a gantry type measuring machine or a bridge type measuring machine. Coordinate measuring machine 110 may include a measurement table having at least one bearing surface for carrying measurement object 112. A coordinate measurement machine 110 comprises at least one gantry having at least one first vertical row, at least one second vertical row, and a cross beam connecting the first vertical row and the second vertical row. It can have At least one vertical row selected from the first and second vertical rows may be horizontally movable on the measurement table. The horizontal direction may be, for example, a direction along the y-axis. Coordinate measuring machine 110 may have a coordinate system, such as a Cartesian coordinate system or a polar coordinate system. Other coordinate systems are also conceivable. The origin or zero of the coordinate system may be defined, for example, by the sensor of coordinate measuring machine 110. The x-axis may extend perpendicularly to the y-axis in the plane of the bearing surface of the measuring table. The z-axis may extend perpendicularly to the plane of the bearing surface in the vertical direction. The vertical rows may extend along the z-axis. The cross beam may extend along the x-axis.

  Coordinate measuring machine 110 includes at least one optical element 114. The optical element 114 is configured to set the imaging magnification of at least one pixel in accordance with the distance of the same pixel from the optical axis 116 of the optical element 114. Coordinate measurer 110 includes at least one imaging device 118 configured to generate at least one image of pixels. The coordinate measuring machine 110 comprises at least one evaluation unit 120. The evaluation unit 120 is configured to correct the distortion of the image. The evaluation unit 120 is configured to determine the coordinates of the measurement object 112 from the corrected image.

ここで、ｚはサジタル高さ、ρは頂点曲率、ｈは光軸に垂直な距離、κは円錐定数、ｃ_ｋは補正多項式の係数、ｉは自然数である。 As one example, optical element 114 may include multiple components. In this case, the parts can be configured in a spatially separated manner from one another. As an example, the optical element may include an optical system having a plurality of optical components (e.g., one or more lenses and / or lens groups and / or another optical component). Optical element 114 may include at least one aspheric lens 122. Optical element 114 may include a plurality of aspheric lenses. Aspheric lenses may be configured in the same or different manner. The aspheric surface can be described by the following equation.

Here, z is a sagittal height, ρ is a vertex curvature, h is a distance perpendicular to the optical axis, κ is a conical constant, _ck is a coefficient of the correction polynomial, and i is a natural number.

FIG. 1 shows an optical element 114 that includes two aspheric lenses, a first aspheric lens 124 and a second aspheric lens 126. The first aspheric lens 124 may have, for example, a height of 4.562 mm (i.e. a spread perpendicular to the optical axis 116) and a width of 2.173 mm (i.e. a spread parallel to the optical axis 116). The second aspheric lens 126 may for example have a height of 5.786 mm and a width of 6.498 mm. The first aspheric lens 124 may have a first aspheric surface 128 and the second aspheric lens 126 may have a second aspheric surface 130. The following table shows the coefficients c _k of the correction polynomial of the example of FIG.

  Optical axis 116 may be the common optical axis of the components of the optical element. The optical axis 116 may, for example, define the z-axis, and the image plane perpendicular to it may form the xy plane. Optical element 114 may have geometrical image aberrations. In particular, optical element 114 may include a distortion optical unit. Optical element 114 may include a foveal optical unit. The optical element 114 may be configured to set a first imaging magnification for the paraxial measurement field area 132 and to set a second imaging magnification for the far-axis measurement field area 134.

  FIG. 2A shows an image of the measurement object 112 without distortion (shown here as a circle). FIG. 2B shows an image of the measurement object, the paraxial measurement field area 132 is imaged at a first imaging magnification, and the far axis measurement field area 134 is imaged at a second imaging magnification. The optical element 114 may be configured to simultaneously set a first imaging magnification for the paraxial measurement field area 132 and a second imaging magnification for the far axis measurement field area 134. The first imaging magnification may be greater than the second imaging magnification. The paraxial measurement field area 132 and the far axis measurement field area 134 may extend radially outward from the optical axis 116 rotationally symmetrically or non-rotationally symmetrically in the image plane. Far-axis measurement field area 134 may surround paraxial measurement field area 132. The size (in particular the area) of the paraxial and far-axis measurement field areas can be determined by the components of the optical element. Optical element 114 may be configured to set a spread of 4: 1 or more (preferably 5: 1 or more) with respect to paraxial measurement field region 132 and far-axis measurement field region 134.

The optical element 114 may be configured to telecentrically image the paraxial measurement field area 132 onto the imaging device 118. Telecentricity may decrease with increasing distance from the axis. As described above, the optical element 114 is configured to simultaneously set the first imaging magnification for the paraxial measurement field area 132 and the second imaging magnification for the far axis measurement field area 134. obtain. In this regard, the sharp z-focus of the working distance of the optical unit near the axis with a small depth of field can also be transferred to the far-axis image area. With this sharp z-focusing, it is possible to significantly minimize the effect of telecentricity loss on the xy measurement accuracy of the far-axis measurement region 134 (depth of field ̃NA ² ).

  The imaging device 118 may include at least one sensor element. The sensor element may include a plurality of pixels. Imager 118 may include at least one camera. As one example, the imaging device 118 may include at least one camera chip having a plurality of pixels. As an example, the camera chip may be a camera chip of about 10 million pixels or more and 1 inch or more. For example, the average pixel size may be 3 μm.

  Evaluation unit 120 may evaluate the signal generated by imaging device 118. As an example, one or more electronic connections between the sensor element and the evaluation unit 120 may be provided for this purpose. Evaluation unit 120 may include, for example, at least one data processing apparatus (eg, at least one computer, microcontroller). The data processing device may have one or more volatile and / or non-volatile data memories, and may be configured to drive sensor elements, for example in terms of programming. Evaluation unit 120 may further include at least one interface (eg, an electronic interface and / or a human-machine interface such as an input / output device such as a display and / or a keyboard, for example). The evaluation unit 120 may, for example, be constructed in a centralized or otherwise decentralized manner. Other configurations are also conceivable. The evaluation unit 120 may, for example, be configured to read out from the camera chip of the imaging device 118 at a certain read rate. The readout rate may be several tens of Hz or more.

  The evaluation unit 120 may be configured to determine the coordinates of the measurement object 112 from the corrected image. The evaluation device 120 may include metrology image processing configured to dimensionally measure the measurement object.

  The evaluation unit 120 may be configured to correct the distortion of the image. Evaluation unit 120 may include an image processor 136. The image processing device 136 may be provided as part of the imaging device 118, for example as a "embedded platform". Image processor 136 may be configured to correct for distortion. Image processing unit 136 may include software for distortion correction. Image processing unit 136 may be configured to select and / or perform compression of the image region at least one “region of interest” (ROI) and / or an image segment of the image (“image cropping”) in the image. The image processing device 136 may be configured to select at least two measurement field areas (especially at least one near-axis measurement field area 132 and / or at least one far-axis measurement field area 134) having different imaging magnifications. The image processor 136 is configured to select either the ROI or the image cropping depending on whether paraxial detail (far-axis cropping) is desired or if outline without detail (paraxial compression) is desired. obtain. As an example, evaluation unit 120 may include a graphic user interface for selecting the spatial spacing to be represented.

  Correction of distortion (especially radial distortion) may be performed, for example, by use of the Brown-Conrady model. FIG. 2C shows an image of the distortion-corrected measurement object 112.

  3A to 3C show the results of simulation of distortion of the embodiment conceptually shown as in FIG. FIG. 3A shows a simulation of the image of the measurement object 112 (here a regular point pattern) without distortion. FIG. 3B shows an image of the measurement object 112 with distortion, and FIG. 3C shows a corrected image.

DESCRIPTION OF SYMBOLS 110 Coordinate measuring machine 112 Measuring object 114 Optical element 116 Optical axis 118 Imaging device 120 Evaluation unit 122 Aspheric lens 124 1st aspheric lens 126 2nd aspheric lens 128 1st aspheric surface 130 2nd aspheric surface 132 paraxial measurement field area 134 far-axis measurement field area 136 image processing apparatus

Claims (14)

A coordinate measuring machine (110) for determining at least one coordinate of at least one measurement object (112), comprising:
The coordinate measuring machine (110) comprises at least one optical element (114)
The optical element (114) is configured to set an imaging magnification of at least one pixel according to a distance of the pixel from an optical axis (116) of the optical element (114).
The coordinate measuring machine (110) comprises at least one imaging device (118) configured to generate at least one image of the pixels;
The coordinate measuring machine (110) comprises at least one evaluation unit (120)
The evaluation unit (120) is configured to correct the distortion of the image;
Coordinate measuring machine (110), wherein the evaluation unit (120) is configured to determine the coordinates of the measurement object (112) from the corrected image.   The optical element (114) is configured to set a first imaging magnification for the paraxial measurement field area (132) and to set a second imaging magnification for the far axis measurement field area (134). A coordinate measuring machine (110) according to claim 1, wherein:   The coordinate measuring machine (110) according to claim 2, wherein the first imaging magnification is greater than the second imaging magnification.   The optical element (114) is configured to set a spread of at least 4: 1 with respect to the paraxial measurement field area (132) and the far axis measurement field area (134). Coordinate measuring machine (110) according to claim 1.   The coordinate measuring machine (110) according to any of the preceding claims, wherein the optical element (114) has geometrical image aberrations.   The coordinate measuring machine (110) according to any of the preceding claims, wherein the optical element (114) comprises an optical unit of a fovea.   A coordinate measurement machine (110) according to claim 6, wherein the optical element (114) comprises at least one aspheric lens (122).   A coordinate measuring machine (110) according to any of the claims 6 to 7, wherein the optical element (114) is configured such that the strain profile is non-rotationally symmetric.   Coordinate measuring machine (110) according to any of the preceding claims, wherein the imaging device (118) comprises at least one sensor element.   A coordinate measuring machine (110) according to claim 9, wherein the sensor element comprises a plurality of pixels.   A coordinate measuring machine (110) according to any of the preceding claims, wherein the evaluation unit (120) comprises an image processing device (136) configured to correct distortion.   The image processing device (136) is at least partially configured as part of the imaging device (118), and the image processing device (136) is configured to perform near-sensor pre-processing. Coordinate measuring machine (110). A method for determining at least one coordinate of at least one measurement object (112), comprising
-Setting the imaging magnification of at least one pixel by said optical element (114) according to the distance of said pixel from the optical axis (116) of at least one optical element (114);
Imaging the pixels with at least one imaging device (118);
Correcting the distortion of the image by means of at least one evaluation unit (120);
Determining the coordinates of the measurement object from the corrected image by the evaluation unit (120).   The method according to claim 13, wherein a coordinate measuring machine (110) according to any of the preceding claims is used for a coordinate measuring machine.

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