Ball measuring device

Abstract

The invention describes a sphere measuring device (10) for optically determining at least one shape parameter (F) of an at least partially reflective sphere (12), wherein the sphere measuring device (10) comprises: a light source (14) for emitting coherent light (16) with a first central wavelength (λ1), a beam splitter (22) arranged to generate measuring light (16.M1) and reference light (16.R1), a measuring arm mirror (24) arranged to reflect at least a portion of the measuring light (16.M1) onto at least a portion of the sphere (12), and a reference arm mirror (30) configured to reflect at least a portion of the reference light (16.R1), wherein the sphere measuring device (10) is configured to superimpose at least a portion of the light (16.R2) reflected by the reference arm mirror (30) with at least a portion of the light reflected by the measuring arm mirror (24). (16.M2) in an interference area (34) such that interference occurs, a detector (40) which is arranged to detect at least one measurement brightness value (I. n ) in at least part of the interference range (34) and is designed such that, based on the measured brightness value (I n ) the at least one shape parameter (F) of the sphere (12) is determinable, wherein the measuring arm mirror (24) has a concave rotational ellipsoid section (26) which is designed such that the sphere (12) can be placed within the rotational ellipsoid section (26) with its center point (M) in a first focal point (B1) of the rotational ellipsoid section (26), namely in a measuring position, and the light source (14) is designed such that a light source point (20) of the light source (14) is located in the second focal point (B2).

Description

[0001] The invention relates to a ball measuring system according to the preamble of claim 1.

[0002] Determining one or more form parameters of a sphere with high precision is important, for example, for calibrating or measuring roundness standards or standards that provide a standard for a specific diameter or volume of a sphere. Furthermore, precise form parameters of spheres are required in coordinate measuring technology, where workpieces are measured precisely, for example, with tactile measuring instruments, to control or optimize manufacturing processes. Reference spheres are often used to calibrate these sensors; their form parameters must be known with high precision, meaning they must have been determined beforehand using a separate measuring instrument.

[0003] It is desirable to be able to determine, for example, the roundness, roundness deviation, diameter, radius, or partial or complete topography of a sphere's surface. This determination should be as cost-effective and rapid as possible to minimize the influence of environmental factors such as fluctuating ambient parameters like pressure, temperature, and / or the composition of the gas (e.g., air) on the measurement results, for example, due to a fluctuating refractive index. Furthermore, the determination should meet a specified accuracy, which, for example, for spheres with diameters between approximately 1 mm and approximately 30 cm, requires a diameter accuracy of at least 1 micrometer, particularly 0.5 micrometers, and / or a roundness deviation accuracy of at least 0.2 micrometers, particularly 0.1 micrometers.

[0004] Disadvantages of known sphere measuring devices for optically determining at least one shape parameter of a partially reflective sphere include, for example, the need for many optical elements with particularly precise optical properties and / or shapes, which increases the costs and effort required for adjustment.

[0005] From FR 3 149 082 A1 a profile measuring device is known in which an ellipsoidal mirror is used to reflect a light beam onto a surface of the object to be measured and to reflect the light beam coming from the object into an optical fiber.

[0006] From CN 106643556 A a device for measuring an ellipsoidal mirror is known, in which a reference sphere of known surface topography is used to retroreflect light rays coming from the ellipsoidal mirror.

[0007] DE 10 2017 222 734 B4 describes a generic sphere measuring device in which a monochromatic, polychromatic or white light source is used to generate an interference pattern from which the surface topography of, for example, a tactile sphere can be determined.

[0008] The invention is based on the objective of reducing disadvantages in the prior art.

[0009] The problem is solved by a ball measuring system with the features of claim 1.

[0010] An advantage of the invention is that an improved sphere measuring device is provided for the optical determination of at least one shape parameter of an at least partially reflective sphere, which can achieve the required accuracy while simultaneously reducing time and costs.

[0011] The advantage of this sphere measuring device is that the time and cost required to determine the absolute shape parameter can usually be reduced, since, on the one hand, fewer optical elements are required than, for example, established sphere interferometer sphere measuring devices, and on the other hand, a larger area fraction of the sphere can be detected or imaged with a single detector recording than, for example, with sphere interferometer sphere measuring devices or non-optical shape measuring devices of spheres.

[0012] Due to the shorter measurement time for determining the shape parameter, a lesser influence from fluctuating environmental factors, which can, for example, cause a fluctuating refractive index, is generally to be expected, or less stabilization effort and / or measurement effort is needed for monitoring and / or compensation.

[0013] Preferably, the light source is designed such that at least a virtual light source point of the light source is located at the second focal point. The advantage of this is that the path of the measuring beam reduces distortion of the interference light.

[0014] The term "shape parameter" refers in particular to a shape and / or shape deviation, especially roundness and / or roundness deviation, a diameter, radius, a topography of at least a portion of the sphere's surface, and / or a volume. For example, the shape parameter includes a diameter at at least one point on the sphere's surface, particularly at two diametrically opposed points, and a topography emanating from that point, which describes, for example, relative or absolute deviations of the sphere's actual shape from the shape of an ideal sphere, for example, on at least 50% of the sphere's surface, preferably on at least 75%, and preferably on at least 90%.

[0015] The requirement that the sphere reflects at least partially means, in particular, that it exhibits a specular reflection of at least 5% on at least 80% of its total spherical surface at the wavelength(s) of light emitted by the light source. Specular reflection is understood to be direct, non-diffuse reflection. Spheres whose shape parameters are to be determined are particularly suitable if their transmittance at the wavelength of the light emitted by the light source is less than 0.1%, preferably less than 0.01%, and / or their roughness is a maximum of 1 micrometer, preferably a maximum of 100 nanometers. Low roughness reduces the diffuse component of the reflection.

[0016] The term "light source" refers in particular to a component or group of components configured to emit coherent light with a first central wavelength. Light emission can be achieved, for example, by emitting photons from a laser or by emitting photons from the exit end of an optical fiber. Preferably, the light source comprises a laser and / or an optical fiber. Coherent light is understood in particular to mean that the emitted light has a coherence length of at least the difference between the optical path length from the beam splitter to the measuring arm mirror and the optical path length from the beam splitter to the reference arm mirror, and in particular at least ten times as long.

[0017] For example, the light source is configured to emit unpulsed light with a minimum duration of 100 milliseconds, particularly at least 500 milliseconds. For example, the light source is configured to emit light with a central wavelength of at least 350 nm, particularly at least 400 nm, and / or at most 2000 nm, particularly at most 1000 nm, and particularly at most 850 nm. Preferably, the light source is configured to emit light with a linewidth of at most 5%, preferably at most 2%, and preferably at most 1% of the central wavelength.

[0018] The term "virtual light source point" refers in particular to a light source exhibiting a divergence that can be extrapolated against the direction of light propagation to a point where the light source point would be located relative to this divergence. Preferably, the light emitted by the light source has an average divergence of at least 100 mrad, preferably at least 200 mrad, between the light source and the beam splitter. It is possible that the light source is, at least to a first approximation, a light source point, for example, the exit end of an optical fiber. It is also possible that the light source point is arranged such that it is not located at the second focal point, but a virtual light source point exists at the second focal point, which would generate an identical light path from the beam splitter to the measuring-arm mirror and from the beam splitter to the reference-arm mirror.For example, the light source is located along a straight line perpendicular to the semi-major axis of an ellipsoid that completes the revolution ellipsoid section of the reference arm mirror to form a complete ellipsoid, for example, inside or outside the ellipsoid. For example, the straight line that can be constructed from the light source to the semi-major axis intersects the semi-major axis at a light source intersection point. In particular, the beam waist distance from a position of a beam waist of the light source from the light source intersection point corresponds to the focal-semi-axis distance, which denotes a distance between the light source intersection point and the second focal point. This is particularly equivalent to the preferred requirement that a light source point of the light source exists at the second focal point, at least a virtual one.

[0019] The beam waist is defined as the point at which the light emitted from the light source has a minimum diameter. The beam waist can be located at the point where the light exits the light source. For example, if the light source is the exit end of an optical fiber, the beam waist is typically located at the exit end.

[0020] If the beam waist, particularly due to the divergence of the light emitted by the light source, can be approximated, at least to a first approximation, as a point light source at the location of the light source point, then the position of the beam waist, which lies particularly between the light source and the beam splitter, is, for example, the virtual light source point. For instance, the beam waist can be approximated as a point light source at the light source point if the beam waist has a maximum diameter of 500 micrometers, particularly a maximum of 200 micrometers, and the divergence between the beam waist and the beam splitter is at least 100 mrad.

[0021] Preferably, the light emitted by the light source has a divergence of at least 50 mrad, preferably at least 100 mrad and / or preferably at least such that at least 30% of the total spherical surface of the sphere is struck by the measuring light from the measuring arm mirror.

[0022] A beam splitter is understood to be, in particular, a component or group of components designed to generate measuring light and reference light, for example, by splitting the light emitted by the light source into at least two components, one of which is the measuring light and the other the reference light. The measuring light refers specifically to that component of the light emitted by the light source that reaches the measuring arm mirror. The reference light refers specifically to that component of the light emitted by the light source that reaches the reference arm mirror. For example, the beam splitter is at least 5% reflective and at least 5% transmissive. For example, the beam splitter is arranged such that a component of the light reflected to the left or right is the measuring light and a transmitted component is the reference light. Alternatively, the reverse is also possible.

[0023] For example, the beam splitter is arranged so that at least 30% of the light emitted by the light source hits the beam splitter.

[0024] If at least a second central wavelength is used to determine the shape parameter, as described below, the beam splitter preferably has values ​​for reflection, transmission, beam displacement, and / or changes in the polarization of the light during reflection and / or transmission that preferably differ from each other by a maximum of 10% for all central wavelengths used and preferably also for wavelengths that deviate from them by at least 10%. In other words, a chromatic influence is negligible for the wavelengths used.

[0025] Preferably, the beam splitter is arranged to superimpose at least a portion of the measuring light and at least a portion of the reference light to form interference light, and preferably to direct the interference light onto the detector. For example, the beam splitter is arranged such that it is located on the semi-major axis of the ellipsoid from which the rotational ellipsoid section of the measuring arm mirror forms a geometric segment. Preferably, the beam splitter is arranged between the first and second focal points, for example, such that a portion of the beam splitter, such as a geometric center and / or a portion thereof extending by a maximum of 20% of the total extent of the beam splitter along one or more directions of extension of the beam splitter, is located at the intersection point of the light sources.

[0026] Preferably, the rotational ellipsoid section of the measuring arm mirror is designed such that its shape satisfies the following formula, where x ell,j ,y ell,i and z ell,j The respective coordinates of the revolution ellipsoid segment along three mutually perpendicular axes are designated, wherein the z-axis runs parallel to, and in particular along, the major semi-axis. Here, a denotes in particular the length of the minor semi-axis and b denotes the length of the major semi-axis of the ellipsoid resulting from completing the revolution ellipsoid segment to form a revolution ellipsoid, wherein in particular there are two minor semi-axes, both preferably having the same length a, and one, in particular a single, major semi-axis of length b: zell,j2a2+xell,j2b2+yell,j2b2=1.

[0027] Here, j is a tracking index. Preferably, the semi-axis ratio (the length of the major semi-axis divided by the length of the minor semi-axis) is at least 1.5, preferably at least 2, preferably at least 3, and preferably at least 4. The advantage of a higher eccentricity is that the distance between the beam splitter and the sphere and the detector is greater, thus simplifying the placement of the optical elements and the sphere. Preferably, the semi-axis ratio is at most 40, preferably at most 30, preferably at most 20, and preferably at most 15. If the eccentricity is not too large, the space required to determine the shape parameter is also advantageously not too large.

[0028] Preferably, the section of the ellipsoid of revolution exhibits deviations from this shape along each of the x, y, and z axes by a maximum of 0.001%, preferably a maximum of 0.0001%, preferably a maximum of 0.00001%. This advantageously allows for a low measurement uncertainty in determining the shape parameter of the sphere.

[0029] Preferably, the section of the ellipsoidal revolution is designed such that the area fraction of the measuring light sphere, which denotes a fraction of the total sphere surface area onto which the measuring light reflected from the section of the ellipsoidal revolution simultaneously strikes, assuming an unchanged relative position of the sphere, is preferably at least 30% of the total sphere surface area, more preferably at least 40%, more preferably at least 49%, and more preferably at least 51%. This applies in particular if the center of the sphere is located at the first focal point closest to the section of the ellipsoidal revolution.

[0030] The section of the ellipsoid of revolution comprises, for example, at least 80% of a complete ellipsoid of revolution along both the x- and y-axes, for example, 100%. The section of the ellipsoid of revolution comprises, for example, at least 5% of a complete ellipsoid of revolution along the z-axis, preferably at least 10%, and / or preferably a maximum of 35%, preferably a maximum of 25%.

[0031] This ensures that a large proportion of the sphere can be illuminated while still leaving sufficient space for the beam splitter, the light source and the reference arm mirror.

[0032] The feature that the section of the ellipsoid of revolution is designed such that the sphere can be placed within the section with its center at a first focus of the section, namely at a measuring position, means in particular that the sphere does not touch the section of the ellipsoid of revolution, but is located within it, when its center lies at the first focus. The first focus is, in particular, the focus closest to the section of the ellipsoid of revolution.

[0033] In particular, the section of the ellipsoid of revolution is concave, so that a cavity exists within the section of the ellipsoid of revolution in which the sphere can be placed.

[0034] Preferably, the semi-axes each have a finite length, in particular not zero or infinity.

[0035] Preferably, the revolution ellipsoid segment has a minor semi-axis whose length is at least 1.7 times, preferably at least twice, and preferably at least three times, the mean diameter of the sphere. For example, if the center of the sphere is located at the first focus, the minimum distance from the sphere's surface to the nearest point of the revolution ellipsoid segment is at least 5% of the sphere's mean diameter, preferably at least 10%, and preferably at least 20%. The advantage of this is that shadowing of parts of the sphere's surface by the sphere itself is reduced if the sphere is not too close to the revolution ellipsoid segment or if the revolution ellipsoid segment is not too small compared to the sphere.

[0036] Preferably, the section of the ellipsoid of revolution is designed such that at least one great circle of a sphere is located within the portion of the sphere surface illuminated by the measuring light. A great circle of a sphere is understood to be, in particular, the largest possible continuous circle on the surface of the sphere, the center of which, assuming the sphere is an ideal sphere, coincides with the center of the sphere and / or divides a volume of the sphere into two hemispheres, which, in particular, have exactly the same volume if the sphere is an ideal sphere.

[0037] Such large-area illumination is particularly advantageous with the dimensions and shape of the rotational ellipsoid section mentioned above. This allows for the determination of at least one shape parameter using one, two, or a few different relative positions of the sphere to the measuring arm mirror. For example, if the shape parameter is a deviation of the sphere from an ideal sphere in a given measurement area fraction of the sphere, then one relative position may suffice. Conversely, if the shape parameter is a diameter or radius topography of the entire sphere or sphere surface, then two or three relative positions may be sufficient.

[0038] In particular, the number of relative positions required to successively illuminate the entire sphere surface with the measuring light may depend on the way the sphere is held in place. The sphere can be held, for example, by means of a pin, preferably a thin one, along its semi-major axis. The pin can be fixed within the section of the ellipsoid of revolution, or it can be inserted through a bore in the section and secured outside of it. Other mounting methods are also possible.

[0039] Preferably, the holder is designed such that it prevents as little of the measuring light reflected from the section of the ellipsoid of revolution as possible from striking the sphere's surface. Preferably, the holder shields a maximum of 2%, preferably a maximum of 1%, preferably a maximum of 0.3%, and preferably a maximum of 0.1% of the total sphere's surface from the measuring light reflected from the section of the ellipsoid of revolution.

[0040] For example, the revolution ellipsoid section has a surface made of gold, silver, and / or copper and / or similarly reflective materials. Preferably, the revolution ellipsoid section is designed such that its reflective surface exhibits low chromatic aberration for all wavelengths of the light source used, preferably with a maximum reflectivity variation of 5%. Preferably, the surface of the revolution ellipsoid section is similarly reflective for all wavelengths of the light source used, preferably with a maximum variation of 5%, more preferably 2%, and more preferably 1%. Preferably, the revolution ellipsoid section has a surface that reflects at least 90% of the measuring light onto the sphere.

[0041] Preferably, the rotational ellipsoid section has a surface that does not have a dielectric coating.

[0042] Preferably, the spherical measuring device between the beam splitter and the measuring arm mirror does not have any transmittive optical elements such as lenses. This has the advantage of avoiding chromatic aberration of the measuring light. The reference arm mirror is understood to be, in particular, a component or group of components designed to reflect a sufficient proportion of the reference light such that interference occurs when it is superimposed with a portion of the measuring light. Specifically, the reference arm mirror has a surface that is at least 10% reflective, preferably oriented such that at least 10% of the reference light incident on the reference arm mirror is reflected.For example, the reference arm mirror is arranged such that at least a portion, preferably at least 10%, of the reflected reference light is reflected back onto a superimposed light, which can in particular be the beam splitter. On this superimposed light, the reflected reference light and the reflected measurement light at least partially overlap to form interference light, which then reaches the detector. It is possible that the spherical measuring device has a superimposed light that is different from the beam splitter and that is arranged to at least partially overlap at least a portion of the reflected measurement light and the reflected reference light to form interference light. Preferably, the reference arm mirror is arranged relative to the superimposed light such that at least a portion, preferably at least 10%, of the reflected reference light is reflected onto the superimposed light.Preferably, the spherical measuring device includes a collimator designed to collimate the reference light before it strikes the reference arm mirror. The collimator is understood to be, in particular, an optical element or group of optical elements designed to reduce the divergence of the reference light to a maximum of, in particular, 15 mrad, preferably a maximum of 5 mrad. The advantage of the collimator is that the reference arm mirror can be planar and is therefore more advantageous than curved mirrors, without introducing distortions that would negatively affect the superposition with the measuring light and the determination of the shape parameter.

[0043] Preferably, the collimator is designed and arranged such that its virtual or actual focal point lies at the location of the virtual or actual light source point of the light source or deviates from it by a maximum of preferably 10% of a focal length of the collimator, preferably a maximum of 5%, preferably a maximum of 2%.

[0044] The superimposition of at least a portion of the light reflected by the reference arm mirror with at least a portion of the light reflected by the measuring arm mirror in an interference region, such that interference occurs, is understood in particular to mean that the measuring light, after having been reflected at least once by the measuring arm mirror and / or the sphere, is superimposed with at least 5% of a reference light component reflected by the reference arm mirror. This is possible, for example, by means of a beam splitter and / or other optical elements such as a superimposer that functions similarly to the beam splitter.The term detector is understood to mean, in particular, a component designed to detect at least one measurement brightness value in at least a part of the interference range and / or designed such that at least one shape parameter of the sphere can be determined from the measurement brightness value. For example, the detector has a detection surface which, when detection light strikes it, generates, for example, an electrical signal that encodes, in particular, a brightness value of the detection light.

[0045] From each brightness value or several brightness values, a phase can be determined, for example, using a method described below for the evaluation unit. Based on this phase, the shape parameter can then be determined, for example, using additional information as described below. For instance, the phase is determined using at least one, preferably at least two, and for example, at least four, five, or more phase-shift brightness values, as described in an example below. Depending on which shape parameter is to be determined, it may be necessary to acquire further brightness values, such as at least one blank brightness value, to detect the detection light when the sphere is not located within the section of the ellipsoid of revolution.

[0046] For example, the detection surface is planar. Alternatively, the detection surface can be curved. Preferably, the detection surface has at least 200x200, more preferably at least 400x500, and more preferably at least 800x900 sub-areas, in each of which the respective brightness value can be detected independently of neighboring sub-areas. The sub-areas are, in particular, pixels. Preferably, the detection surface covers an area and is arranged such that at least 30%, preferably at least 50%, more preferably at least 70%, and more preferably at least 85% of the interference area in which the measuring light and reference light overlap to form interference is detected. It is possible that an imaging optic, which may include optical elements such as lenses, is arranged in front of the detection surface in such a way that it improves the imaging of the interference light onto the detection surface.

[0047] Alternatively, it is possible, for example, to use one, two, or a plurality of sub-areas smaller than those described above and shift them along a plurality of positions so that they preferably cover the aforementioned portions of the interference area as a whole. This shifting can be, for example, a scanning or rasterization process.

[0048] Preferably, a unique assignment of at least one sub-area to each spherical region or spherical point, which designates a section or surface element of the sphere's surface, is possible. An example of such an assignment is given below.

[0049] Preferably, the rotational ellipsoid section of the measuring arm mirror is designed such that, when the sphere is positioned with its center at the first focal point, the measuring light strikes a spherical surface of the sphere perpendicularly. In particular, perpendicularity is defined as an angle at which the measuring light strikes the sphere's surface between 89.51° and 90.49°, provided the sphere's surface has a maximum deviation from an ideal sphere of 0.001%, for example, a maximum deviation of 0.1 micrometers for a sphere with a diameter of 10 centimeters.

[0050] Preferably, the rotational ellipsoid section of the measuring arm mirror is designed such that, when an ideal sphere with its center point is placed at the first focal point, the measuring light hits a spherical surface of the sphere perpendicularly.

[0051] This is achieved, for example, by a sufficiently large short semi-axis of the rotational ellipsoid section compared to the sphere diameter, as well as a sufficiently small shape deviation of the rotational ellipsoid section from an ideal rotational ellipsoid.

[0052] For example, the beam splitter is arranged and the rotational ellipsoid section is designed such that an outermost part of the measuring light hits the rotational ellipsoid section, in particular without hitting an end of the rotational ellipsoid section where the measuring arm mirror no longer has the shape of a rotational ellipsoid.

[0053] Preferably, the sphere measuring device is configured such that a spherical reflection light, which is directly reflected by the ideal sphere without striking the mirror, travels along the major semi-axis of the rotational ellipsoid section, in particular at least until the spherical reflection light strikes the beam splitter. This is especially true for the approximation that the sphere at the point where the measuring light strikes the sphere without having previously struck the measuring arm mirror corresponds to an ideal sphere. Preferably, the sphere measuring device includes a positioning unit for positioning, in particular displacing and / or rotating, the sphere relative to the measuring arm mirror into a plurality of relative positions such that at least the portion of the light reflected by the measuring arm mirror strikes at least partially different sections of the sphere at each of the different relative positions.

[0054] Preferably, the detector is designed to detect at least one measurement brightness value in at least a part of the interference range for each of the relative positions, and / or is designed such that at least one shape parameter of the sphere can be determined from a plurality of measurement brightness values ​​for the plurality of relative positions.

[0055] The feature that the sphere is positioned relatively, in particular displaced and / or rotated, is understood to mean, in particular, that the sphere and / or the measuring arm mirror and the path of the measuring light are changed in such a way that a different area of ​​the sphere's surface is illuminated than in the previous relative position. For example, the positioning unit is configured to rotate only the sphere, for instance, about one, two, or three axes. Alternatively, the same change in relative position can be achieved, for example, by the positioning unit displacing the sphere about two or three axes.

[0056] The areas illuminated by the measuring light at different relative positions can overlap. Preferably, the positioning unit for the relative positioning of the sphere is configured such that the areas illuminated by the measuring light at different relative positions overlap by a maximum of 80%, preferably by a maximum of 60%, preferably by a maximum of 50%, and preferably by a maximum of 30%. Overlap is avoidable in some cases, and less overlap generally results in less redundancy, thus allowing the shape parameter to be determined with fewer relative positions and consequently, usually more quickly.

[0057] Preferably, the positioning unit for the relative positioning of the sphere is such that in each relative position at least one great circle of the sphere is struck by the measuring light.

[0058] In a second aspect, the invention relates to a sphere measuring system with a sphere measuring device as described above and with an evaluation unit configured to determine the at least one shape parameter based on at least one sphere measurement phase. This evaluation unit determines the shape parameter from the at least one measured brightness value, preferably from at least two sphere measurement phases, which correspond to, in particular, two diametrically opposed points on the sphere's surface. An example of how the evaluation unit can determine the shape parameter based on at least one sphere measurement phase is given below. Alternatively, the evaluation unit can be part of the sphere measuring device. The following descriptions of the evaluation unit apply both when it is part of the sphere measuring system and when it is part of the sphere measuring device.

[0059] The evaluation unit has, for example, at least one data interface, preferably configured to receive the at least one measured brightness value from the detector. The evaluation unit has, for example, at least one processor and / or memory configured to process the at least one measured brightness value and to read and store data, which includes, for example, values ​​for the length of the major and minor semi-axes, and / or information about the detector, in particular the number, size, arrangement of the sub-areas, and / or the assignment of the sub-areas to surface elements of the sphere.

[0060] Preferably, the evaluation unit is configured to control a positioning unit such that the positioning unit positions the sphere relative to the measuring arm mirror in a plurality of relative positions such that at least the portion of the light reflected by the measuring arm mirror strikes at least partially different sections of the sphere at different relative positions. Preferably, the evaluation unit is configured to acquire position information that specifies the respective relative position P( α,βThe position of the sphere is encoded. Here, α and β each denote the angle of rotation about an axis of rotation, where, in particular, the axes of rotation with respect to the angles α and β are different from each other, and especially not parallel to each other, and especially perpendicular to each other. It is possible that there are more than two axes of rotation and / or that the axes of rotation are not perpendicular to each other. The position unit is, for example, part of the sphere measuring device and / or the sphere measuring system, but this is not required.

[0061] Preferably, the evaluation unit is configured to assign one or more sub-areas to corresponding spherical regions or points on the sphere's surface, for example, using the method described below. In this example, the detection surface is planar and the sub-areas are arranged two-dimensionally, for example, similarly to a rectangular grid, so that a sub-area position for a sub-area with an integer index i can be determined based on x-values ​​x. i and y-values ​​y iThe ellipsoid can be described as follows, wherein the x-axis, to which the x-values ​​refer, is perpendicular to the y-axis, to which the y-values ​​refer. The number of sub-regions along the x-axis is, for example, at least 0.5 times the number of sub-regions along the y-axis, preferably at least 0.7 times, and / or preferably at most 2 times, preferably 1.5 times, preferably 1.3 times. The x-axis and the y-axis are, in particular, perpendicular to the semi-major axis of the ellipsoid, along which, in particular, a z-axis runs. The individual sub-regions can, for example, be rectangular, in particular square. In particular, a single surface of each of the sub-regions is the same for all sub-regions.

[0062] An offset along the x-axis between the sub-area position and the major semi-axis of the ellipsoid is denoted by x c denoted analogously for the y-axis by y c .

[0063] In the following, the length of the major semi-axis of the ellipsoid will be denoted by b and the length of the minor semi-axis by a.

[0064] In this example, the coordinates of a point on the sphere's surface are given in spherical coordinates, each with a polar angle θ and an azimuthal angle ψ, which, contrary to the usual notation, is not denoted by φ to distinguish the phase. A first point, whose reflected light, for example, strikes the first sub-region, accordingly has the coordinates ψ1, θ1.

[0065] Both the designation of the coordinates of the sub-area position and of the point on the sphere's surface are exemplary and can be replaced by other, preferably unique, coordinate systems.

[0066] For simplicity, a sub-area is designated, for example, in polar coordinates with a radius r and an azimuthal angle ψ1. For instance, the radius r1 is calculated from the sub-area position x1, y1 of a first sub-area and the offset of the first sub-area along the x-axis x. c1 and the y-axis y c1 as determined as follows: r1=s(x1−xc1)2+(y1−yc1)2, where its optional scaling factor specifies a scaling between the coordinates of the sub-area position and the coordinates of the x-, y-, and z-axes if the coordinate scalings of the two coordinate systems do not match. This ensures that the azimuthal angle ψ1 of the sub-area corresponds to the azimuthal angle ψ1 of the point on the sphere's surface. The scaling factor is, for example, a mapping factor.

[0067] The polar angle θ1 can be obtained, for example, using the following formula, in which e denotes the eccentricity of the ellipsoid, where here e=b2−a2 applies: θ1=arctan(re−ba2−r12a) and the azimuthal angle, for example, using the following formula: ψ1=arccos(s(x1−xc)r1).

[0068] The sub-area that corresponds to the point on the surface of the sphere that is exactly diametrically opposite to the point that has radius r1 has radius r2 and can be determined, for example, using the following formula: r2=r1a(b2−e2)(a(b2+e2)+2 b ea2−r12)a2(b2−e2)+4 b2e2r12

[0069] The azimuthal angle ψ2 for the second point is determined, for example, using the following formula: ψ2=(ψ1+π)mod 2π

[0070] From the obtained values ​​for r2 and φ2, the sub-area positions for x2 and y2 for the sub-area that indicates the detection light of the point on the sphere surface opposite the sub-area x1, y1, can be determined using the following formulas, for example: x2=r2scos(ψ2)+xc y2=r2ssin(ψ2)+yc

[0071] The evaluation unit is designed to automatically determine at least one shape parameter of the sphere from the sphere measurement phase and at least one empty phase. The empty phase is determined by the evaluation unit based on at least one empty brightness value detected by the detector when the sphere is in an empty position such that no light reflected from the section of the ellipsoid of revolution strikes the sphere and / or no measurement light reflected from the sphere strikes the detector. In other words, the empty phase is determined by means of an empty measurement in the same sphere measuring device, but without the sphere. For example, for the empty measurement, the sphere is moved from the measurement position to the empty position manually or by means of the positioning unit or another motion unit.

[0072] It is possible, but not necessary, that the sphere in the empty position is not located within the ellipsoid that completes the rotational ellipsoid section of the measuring arm mirror.

[0073] In particular, the difference phase can be determined from the sphere measurement phase and the blank phase, which corresponds to a modulo phase of the sphere diameter at the respective position for the wavelength of the measuring light used. The modulo phase is the remaining phase, the sum of which, with an integer number of integer phases, corresponds to the sphere diameter at the respective position for the wavelength of the measuring light used. For example, the sphere at a given position has a diameter of 1000.2 wavelengths, so the integer number of integer phases there is 1000 wavelengths, and the modulo phase there is 0.2 wavelengths. This modulo phase can be determined as the difference between the sphere measurement phase and the blank phase, as explained below. How, for example, the integer number of integer phases can be determined is explained below.

[0074] For example, the evaluation unit is designed to read out a rough value D. g , which in particular specifies a rough sphere diameter at at least one point or on average. The data is read, for example, from a database and / or based on user input data. Preferably, the evaluation unit is designed to determine an initial rough phase total K. λ1 , which specifies a number of phase transitions of the first central wavelength, especially approximated as an integer, which is included in the approximate value D g fit, from the rough value D g and the first central wavelength λ1, in particular with the formula: Kλ1=Dgλ12.

[0075] The following example illustrates how a diameter, as an example of a shape parameter, can be determined at a specific position on the sphere, for instance, by the evaluation unit. Similarly, the diameter can be determined at other positions on the sphere, for example, at least 100 positions, or at least 1000 positions. Alternatively, other calculation methods are possible. Determining an absolute and / or relative shape deviation of the sphere from an ideal sphere and / or a radius topography of the sphere can be achieved, in particular, from the phase values ​​described below. From the obtained diameter or radius, it is possible, for example, to determine a volume and / or, with given density information, a mass.

[0076] Preferably, the evaluation unit is designed to determine a sphere measurement phase based on the at least one measurement brightness value, in particular for each relative position of the sphere, in particular for a plurality of sub-areas of the detector, in particular for each sub-area of ​​the detector.

[0077] The respective sphere measurement phase for a sub-area is determined, for example, based on the respective measurement brightness value of the sub-area and further comparison brightness values, for example using the Tang algorithm, which is briefly explained below.

[0078] Phase-shift brightness values, detected by the detector in the same sub-range, can serve as reference brightness values. These values ​​are obtained while the sphere remains in the same relative position, and the reference arm mirror is shifted by minute displacements, such that the optical path length difference of the reference light relative to the measurement light changes by less than one whole phase. Alternatively, instead of shifting the reference arm mirror, the optical path length difference between the measurement light and the reference light can be altered in another way, and brightness values ​​can be recorded by the detector for various path length differences.

[0079] For example, the phase-shift brightness values ​​I1, I2, I3, I4 and I5 are recorded for shifts that each correspond to an nth shift interference phase φ(I) changed by 1 / 4. n), with an index n= 1, 2, ..., 5, compared, for example, to a first phase φ0, such that, for example, the following holds: φ(I1)=φ0,φ(I2)=φ0+2π4,φ(I3)=φ0+2π⋅24, φ(I4)=φ0+2π⋅34,φ(I5)=φ0+2π⋅44.

[0080] For example, φ0 is chosen to correspond to the sphere measurement phase. The shift interference phases are adjusted, for instance, by means of an actuator configured to shift the reference arm mirror such that the optical path length from the beam splitter to the reference arm mirror changes to within less than one whole phase. In particular, the brightness value I1 is equal to the brightness value I3, since the shift at brightness value I5 relative to I1 corresponds to one whole phase. It is possible to test and iteratively adjust various actuator step sizes to achieve the aforementioned correspondence I1 = I5 within a specified tolerance and to set correspondingly equal intermediate step sizes between the first and fifth shift interference phases, thus enabling the adjustment of the second, third, and fourth shift interference phases.

[0081] For example, the sphere measurement phase φ messfrom the above recorded brightness values ​​I1, I2, I3, I4 and I5, determined using the following formula: φmeas=arctan(±[2(I4−I2)+(I5−I1)]⋅[2(I4−I2)−(I5−I1)]I1+I5−2 I3)

[0082] For example, whether the sign is positive or negative is determined by the following step: The sign is set as positive if I4 ≥ I2, otherwise as negative. Other phase intervals and formulas for determining the phase that lead to a similar and, in particular, similarly accurate result for the sphere measurement phase are alternatively possible.

[0083] Preferably, the evaluation unit determines an empty phase from the at least one empty brightness value. The empty phase is determined, for example, in the same way as the ball measurement phase, with the ball being in the empty position when the empty brightness values ​​are recorded.

[0084] Preferably, the evaluation unit determines a difference phase as the difference from the sphere measurement phase for a point on the sphere φ. mess,1 , a diametrically opposite point on the sphere φ mess,2 and the empty phase φ leer , for example using the formula: φDiff=φempty−φmeas,1+φmeas,22. In particular, it is possible that the empty phase φ leer by φempty=φempty,1+φempty,22 The value is determined from a first partial empty phase φ. leer,1 and a second-part empty phase φ leer,2 , which are derived from the respective measured brightness values ​​for those two sub-areas of the detector that would correspond to the two opposite points of the sphere, as explained above, if the sphere were located at the focal point.

[0085] The procedure described above is performed, for example, for one, several, or all sub-areas of the detector, such that the sphere measurement phase, blank phase, and difference phase are determined for each sub-area. If different relative positions of the sphere are used, the procedure is preferably repeated for one, several, or each of the relative positions for all sub-areas. It is possible that the sphere is moved to the blank position only once and the blank phase is determined only once, not individually for each of the relative positions, or alternatively, several times, for example, once before the measurements of all relative positions and a second time afterward, in order to estimate and / or compensate for changes and / or influences of an environment's refractive index, such as that of the air.

[0086] If at least one shape parameter includes, for example, a diameter and / or radius, the evaluation unit preferably determines the shape parameter using the following method: Determining the sphere measurement phase and empty phase, for example as described above, each for the first central wavelength and for a second central wavelength. The light with the second central wavelength is provided, for example, by a second light source or by the same light source. In particular, the quotient of the first and second central wavelengths, and vice versa, is not a power of two.

[0087] Preferably, the following applies to the two central wavelengths: 14|λ1−λ2|> A phase measurement uncertainty multiplied by half the central wavelength, with which the phase can be determined. The phase measurement uncertainty depends, for example, on a wavelength measurement uncertainty of the central wavelength λ. 1,2and / or a detector measurement uncertainty of the detector. The wavelength measurement uncertainty is understood in particular to be the uncertainty with which the respective central wavelength is known and / or measurable.

[0088] Preferably, the following applies to the two central wavelengths: λ1λ2<3 orλ2λ1<3.

[0089] Preferably, the following applies to the two central wavelengths: λ1λ2<2 orλ2λ1<2.

[0090] Preferably, each of the above-mentioned conditions applies to the relationship between the two central wavelengths.

[0091] If more than two different central wavelengths are used, the above conditions preferably apply to each relation between any two of the multiple central wavelengths.

[0092] Preferably, the evaluation unit determines from a given rough value D gFor the diameter, the aforementioned total first coarse phase number K λ1 based on the first central wavelength K λ1 .

[0093] Preferably, the evaluation unit determines from the given rough value D g for the diameter a second coarse phase total number K λ2 , which gives a number of phase transitions of the second central wavelength, approximated in integer terms, which is included in the rough value D g fit, from the rough value D g and the second central wavelength λ2, in particular with the formula: Kλ2=Dgλ2 / 2.

[0094] Preferably, the evaluation unit determines a plurality of integer first-correction phase totals M. λ1,f and integer second correction phase totals M λ2,j , each with a correction test diameter D test,j correspond to the first rough phase total number (K) by one or a few integer phase passes. λ1) or the total number of second rough phases (K λ2 ) differs. Preferably, the correction phase totals include both correction phase totals that are smaller and correction phase totals that are larger than the coarse phase total. Here, j is in particular an index.

[0095] Preferably, the total number of first correction phases and the total number of second correction phases is at least three, preferably at least six, preferably a maximum of 500, preferably a maximum of 100.

[0096] In particular, the number of first correction phase totals and second correction phase totals is at most so large that a difference between the smallest and the largest selected correction phase total corresponds at least to the measurement uncertainty of the rough value, preferably at least twice the measurement uncertainty, preferably at least four times the measurement uncertainty.

[0097] For example, a rough value for the first central wavelength is 1000 phase transitions and for the second central wavelength 1261 phase transitions. For example, the evaluation unit determines ten correction phase totals for each of the two central wavelengths, corresponding to 995, 996, 997, 998, 999, 1001, 1002, 1003, 1004 and 1005 phase transitions for the first central wavelength and 1256, 1257, 1258, 1259, 1260, 1262, 1263, 164, 165 and 1266 phase transitions for the second central wavelength.

[0098] It is possible that an additional third central wavelength or further central wavelengths λ are used. k The total coarse phase number and the total correction phase numbers are used, and analogously, the total coarse phase number and the total correction phase numbers are determined. Preferably, no quotient of two central wavelengths is a power of two. Preferably, all central wavelengths are coprime to each other.

[0099] For example, the evaluation unit determines M from the correction phase totals λk,j respective correction test diameter D test,j,k , for each total number of correction phases, for example by means of the difference phase φ Diff and corresponding central wavelength λ k : Dtest,j,k=(Mλk,j+φDiff2π)λk2.

[0100] Preferably, the evaluation unit determines at least one optimal correction test diameter D. test,j=opt , in particular one D each test,j= opt for each central wavelength λ k The optimal correction test diameter is understood to mean, in particular, that the correction test diameter D test,j,k for the different central wavelengths λ k exhibit the slightest deviation from each other, with this deviation being, for example, for two central wavelengths λ k=1,2 It can be determined by means of: Dtest,j1,k=1−Dtest,j2,k=2, and / or where the deviation between them is less than, for example, a specified target measurement uncertainty.

[0101] It is possible to determine the j for which the deviation is minimal using various methods, for example without prior selection by determining the deviation D. test,j1,k=1 - D test,j2,k=2 for all j, or after prior selection only for selected j.

[0102] It is possible that there are multiple optimal correction test diameters, for example, because the values ​​for k=1 and k=2 differ for j=opt. In this case, for example, the evaluation unit determines the shape parameter based on a mean and / or weighted mean of the multiple optimal correction test diameters.

[0103] For example, the evaluation unit determines the optimal diameter as one or more of the shape parameters to be determined. If the shape parameter includes, for example, a radius, a volume, and / or a mass, the evaluation unit preferably determines these from the diameter.

[0104] It is possible for the evaluation unit to perform the above procedure for calculating the total correction phase for one, several, or all points on the sphere's surface, particularly those for which a diametrically opposite point can be determined from a corresponding sub-area of ​​the detector, as described above. It is also possible for the evaluation unit to determine the total correction phase and the optimal diameter at only one or a few points and, based on these absolute diameter results, to determine, for example, the diameter and / or radius topography as form parameters. In the following, the difference phase determined at this point will be referred to as the diameter difference phase. For determining the form deviation, for example, it is not necessary to determine the total correction phase; it is sufficient, for instance, to determine the local difference phase φ. lokto determine and divide these into a length L based on the wavelength λ1 F to be converted according to the local difference phase.

[0105] The local diameter is determined based on the local difference phase φ. lok , the optimal total number of correction phases M λk,j=opt and the wavelength λ1, for example, can be determined using the formula: Dlok=(Mλk,j=opt+φlok2π)λ12

[0106] Preferably, the evaluation unit outputs the specified at least one shape parameter and / or stores it in internal or external memory and / or a database.

[0107] It is possible to determine the correction test diameters and / or the optimal diameter using other formulas. Preferably, if the shape parameter includes the diameter, the diameter is determined using a method that, within a measurement uncertainty of at least two times the described method, yields the same result.

[0108] It is possible that determining the correction test diameters and / or the optimal diameter using other formulas may include a weighting for the different wavelengths, for example due to different measurement uncertainties of the wavelengths λ. k .

[0109] In a third aspect, the invention relates to a method for optically determining at least one shape parameter of an at least partially reflective sphere using at least one sphere measurement phase, which is determined by an evaluation unit from at least one measured brightness value. In particular, the method comprises the steps described above for the evaluation unit.

[0110] The invention will be explained in more detail below with reference to the accompanying figure.

[0111] This shows Fig. 1 a schematic representation of a ball measuring device and a ball measuring system according to the invention, comprising a ball measuring device and an evaluation unit.

[0112] In Fig. Figure 1 shows a schematic representation of a sectional view of a sphere measuring device 10 according to the invention for optically determining at least one shape parameter P of an at least partially reflective sphere 12.

[0113] The sphere measuring device 10 comprises a light source 14 for emitting coherent light 16 with a first central wavelength λ1 and a beam splitter 22, which is arranged to generate measuring light 16.M1 and reference light 16.R1, wherein the light source 14 is configured such that at least a virtual light source point 20 of the light source 14 is located at the second focal point B2. In this example, the light source is an exit end of an optical fiber with an actual light source point 18 at the exit end. In this example, the actual light source point 18 is located in an ellipsoidal region 28.K, laterally folded by 90°, at the position where the second focal point would be located in the folded ellipsoidal region 29.The virtual light source point 20 can be constructed, for example, starting from the point where the light 16 hits the beam splitter 22, where in this example the point is located on the major semi-axis b, based on the divergence of the light 16.

[0114] The sphere measuring device 10 also has a measuring arm mirror 24, which is arranged to reflect at least a part of the measuring light 16.M1 onto at least a part of the sphere 12, wherein the measuring arm mirror 24 has a concave rotational ellipsoid section 26, which is designed such that the sphere 12 can be placed within the rotational ellipsoid section 26 with its center M in a first focal point B1 of the rotational ellipsoid section 26, namely in a measuring position.

[0115] The sphere measuring device 10 also has a reference arm mirror 30, which is configured to reflect at least a part of the reference light 16.R1, wherein the sphere measuring device 10 is configured to superimpose at least a part of the light 16.R2 reflected by the reference arm mirror 30 with at least a part of the light 16.M2 reflected by the measuring arm mirror 24 in an interference area 34 such that interference occurs.

[0116] In this example, the beam splitter 22 is designed to direct the measuring light 16.M1 onto the measuring arm mirror 24 and to direct the reference light 16.R1 onto the reference arm mirror 30.

[0117] For example, the beam splitter 22 is also arranged to superimpose the reference light 16.R2 reflected by the reference arm mirror 30 with the measuring light 16.M2 reflected by the measuring arm mirror 24 to form an interference light 16.U in which interference occurs between at least a part of the measuring light and at least a part of the reference light.

[0118] The sphere measuring device 10 also has a detector 40, which is arranged to detect at least one measurement brightness value I n in at least part of the interference range 34 and is designed in such a way that, based on the measured brightness value I n at least one shape parameter P of the sphere 12 can be determined. In this example, the beam splitter 22 is arranged such that it directs the interference light 16.U to the detector 40.

[0119] In this example, the detector 40 has a detection area 41 which has a plurality of sub-areas 41.U, in particular at least 200x200, in particular at least 400x500, in particular at least 800x900, which are, for example, rectangular pixels and / or arranged in a rectangular grid.

[0120] In this example, at least one imaging optic 42 is arranged in front of the detector 40, which is configured to improve an image, in particular to reduce distortion and / or blurring and / or to improve the ability to assign points on the spherical surface of the sphere 12 to the sub-areas 41.U. The imaging optic 42 has, for example, at least one lens, an objective and / or a collimator.

[0121] In this example, the sphere measuring device 10 also has a collimator 32, which is arranged such that the reference light 16.R1 is collimated before it strikes the reference arm mirror 30. For example, the collimator 32 is arranged such that the focal point of the collimator 32 coincides with a position of the at least virtual light source point 20.

[0122] In this example, the spherical reflection light 16.K, which is reflected directly from the sphere 12 without striking the measuring arm mirror 24 before or after, is reflected back along the same light path, provided that the sphere 12 is shaped like an ideal sphere at the point where the spherical reflection light 16.K strikes it. It is possible that the spherical reflection light 16.K is blocked, for example, by an aperture, either before or after it is reflected from the sphere.

[0123] For example, the beam splitter 22 is arranged and the rotational ellipsoid section 26 is designed such that an outermost part of the measuring light 16.M1.A hits the rotational ellipsoid section 26, in particular without hitting an end 29 of the rotational ellipsoid section 26 where the measuring arm mirror 24 no longer has the shape of a rotational ellipsoid.

[0124] In this example, the sphere measuring device 10 also includes a positioning unit 36 ​​for positioning, in particular moving and / or rotating, the sphere 12 relative to the measuring arm mirror 24 into a plurality of relative positions P such that at least the portion of the light 16.M2 reflected by the measuring arm mirror 24 strikes at least partially different sections of the sphere 12 at different relative positions P. For example, the detector 40 is configured to detect at least one measurement brightness value I. nin at least a part of the interference range 34 for each of the relative positions P, such that based on a majority of the measured brightness values ​​I n for the majority of the relative positions P, at least one shape parameter F of the sphere 12 can be determined.

[0125] Together with the evaluation unit 50, the ball measuring device 10 forms a ball measuring system 60 according to the invention, wherein the evaluation unit 50 is designed to determine the at least one shape parameter F from the at least one brightness value I n , which the detector 40 detects. For example, the evaluation unit 50 is designed to determine the shape parameter F using a method as described above, for example by determining at least one sphere measurement phase φ mess , if the sphere 12 is in the measuring position, that is, with the center M of the sphere at the first focal point B1, and at least one φ leerIdle phase, when the sphere is in an empty position outside the rotational ellipsoid section 26, and preferably for determining one φ each. Diff Difference phase for each sphere measurement phase φ mess Alternatively, it is possible that the ball measuring device 10 has the evaluation unit 50.

[0126] The illustration shown is, for example, a side view. In particular, the ellipsoid 28, the revolution ellipsoid section 26, and the measuring light 16.M1, the latter at least to a first approximation, are rotationally symmetric along the z-axis. For example, the reference light 16.R1 is rotationally symmetric about the x-axis. The schematic representation of the spherical coordinates at the edge of the Fig. Figure 1 serves to illustrate the above-mentioned assignment of a section or surface element of the sphere surface of the sphere 12 to a sub-area 41.U of the detection surface 41 with the polar angle θ and the azimuthal angle ψ. Reference symbol list 10 ball measuring device 12 balls 14 Light source 16 lights 16.K Spherical Reflection Light 16.M1 Measuring light (before it is reflected at the measuring arm mirror) 16.M2 Measuring light (after it is reflected off the measuring arm mirror) 16.R1 Reference light (before it is reflected at the measuring arm mirror) 16.R2 Reference light (after it is reflected off the measuring arm mirror) 16.U Interference light 18 actual light source point 20 virtual light source points 22 beam splitters 24 measuring arm mirrors 26 Rotational ellipsoid section 28 completed ellipsoid 28.K folded ellipsoid area 29 End of the rotational ellipsoid section 30 reference arm mirrors 32 Collimator 34 Interference area P α,βRelative positions of the sphere P Leer Empty position s scaling factor 36 Positioning unit 40 Detector 41 detection area 41.U Sub-areas 42 Imaging optics of the detector 50 evaluation units 60 ball measuring system a minor semi-axis of the ellipsoid b major semi-axis of the ellipsoid e Eccentricity of the ellipsoid B1 first focal point B2 second focal point D g Approximate ball diameter D test,j,k Correction test diameter F abs absolute shape deviation F x,y,2 Shape parameters at the point with the coordinates x, y, z of the sphere In nth brightness value λ k k-th (central) wavelength θ Polar angle ψ Azimuthal angle φ mess Ball measuring phase φ leer Idle period φ Diff Difference phase M Center of the sphere

Claims

[1] Sphere measuring system (60) comprising a sphere measuring device (10) for optically determining at least one shape parameter (F) of an at least partially reflective sphere (12), and an evaluation unit (50), wherein the sphere measuring device (10) comprises the following: (a) a light source (14) for emitting coherent light (16) with a first central wavelength (λ1), (b) a beam splitter (22) arranged to generate measuring light (16.M1) and reference light (16.R1), (c) a measuring arm mirror (24) arranged to reflect at least part of the measuring light (16.M1) onto at least part of the sphere (12), (d) a reference arm mirror (30) designed to reflect at least part of the reference light (16.R1), (e) wherein the sphere measuring device (10) is configured to superimpose at least a part of the light (16.R2) reflected by the reference arm mirror (30) with at least a part of the light (16.M2) reflected by the measuring arm mirror (24) in an interference area (34) such that interference occurs, (f) a detector (40) arranged to (i) Recording at least one measured brightness value (I n ) in at least part of the interference area (34) and is formed in such a way, (ii) that based on the measured brightness value (I n ) of which at least one shape parameter (F) of the sphere (12) can be determined, (g) the measuring arm mirror (24) has a concave rotational ellipsoid section (26) which is designed such that the sphere (12) can be placed within the rotational ellipsoid section (26) with its center point (M) at a first focal point (B1) of the rotational ellipsoid section (26), namely in a measuring position, and (h) the light source (14) is designed such that a light source point (20) of the light source (14) is located at the second focal point (B2), (i) wherein the evaluation unit (50) is configured to determine the at least one shape parameter (F) using at least one sphere measurement phase (φ) mess ), which the evaluation unit (50) from the at least one measured brightness value (I n ) certainly, characterized by , that (j) the evaluation unit (50) is designed to automatically determine at least one shape parameter (F) of the sphere (12) based on the (i) Sphere measuring phase (φ mess ) and (ii) an empty phase (φ leer ), which the evaluation unit (50) determines based on at least one blank brightness value that the detector detects when the sphere (12) is in a blank position (P Leer ) such that the sphere (12) is arranged in such a way that no light reflected from the rotational ellipsoid section (26) hits the sphere (12). [2] Ball measuring system (60) according to claim 1, characterized by , that the measuring arm mirror (24) is designed such that when the sphere (12) is placed with its center (M) at the first focal point (B1), the measuring light (16.M1, 16.M2) strikes a spherical surface of the sphere (12) perpendicularly. [3] Ball measuring system (60) according to one of the preceding claims, characterized by, that the beam splitter (22) is arranged to superimpose at least a part of the measuring light (16.M2) and at least a part of the reference light (16.R2) to form an interference light (16.U) and preferably to direct the interference light (16.U) onto the detector (40). [4] Ball measuring system (60) according to one of the preceding claims, characterized by (a) a positioning unit (36) for positioning the sphere (12) relative to the measuring arm mirror (24) into a plurality of relative positions (P) such that at least the part of the light (16.M2) reflected by the measuring arm mirror (24) strikes at least partially different sections of the sphere (12) at different relative positions (P), (b) wherein the detector (40) is configured to detect at least one measurement brightness value (I n) in at least a part of the interference range (34) for each of the relative positions (P), such that based on a majority of the measured brightness values ​​(I n ) for the majority of the relative positions (P) of the at least one shape parameter (F) of the sphere (12) can be determined. [5] Ball measuring system (60) according to one of the preceding claims, characterized in that the evaluation unit (50) is designed to (a) Controlling a positioning unit (36) such that the positioning unit (36) positions the sphere (12) relative to the measuring arm mirror (24) into a plurality of relative positions (P) such that at least the part of the light (16.R2) reflected by the measuring arm mirror (24) strikes at least partially different sections of the sphere (12) at different relative positions (P), (b) Capturing position information that specifies the respective relative position (P α,β,γ ) the sphere is encoded. [6] Ball measuring system (60) according to one of the preceding claims, characterized by , that (a) the detector (40) has a detection area (41) with at least 500 sub-areas (41.U), in particular pixels, preferably at least 900, and (b) the evaluation unit (50) is designed to assign one or more sub-areas (41.U) to sphere areas or sphere points on the sphere surface of the sphere (12). [7] Ball measuring system (60) according to one of the preceding claims, characterized by , that (a) the light source (14) is designed to emit coherent light (16) with a second central wavelength (λ2) different from the first central wavelength (λ1) and whose quotient (λ1λ2) and their inverse quotient (λ2λ1) is not an integer power of two and / or that the following holds true: 14|λ1−λ2|>0 within a wavelength measurement uncertainty of the central wavelength (λ)1,2 ), (b) wherein the detector (40) is configured to detect the majority of brightness values ​​(I α,β,γ ) for the majority of relative positions (P α,β,γ ) for each of the central wavelengths (λ i ) and (c) the evaluation unit (50) is designed to automatically determine at least one shape parameter (F) of the sphere (12), wherein the determination comprises the following steps: (i) Determining a first rough phase total (K λ1 ), which indicates a number of phase transitions of the first central wavelength, especially approximated as an integer, which is included in the rough value (D g ) fit, from a given approximate value (D g ) and the first central wavelength (λ1) using the formula: Kλ1=Dgλ12, (ii) Determining a second coarse phase total (K λ2), which specifies a number of phase transitions of the second central wavelength (λ2), especially approximated in integer terms, which is included in the rough value (D g ) fit, from the given approximate value (D g ) and the second central wavelength (λ2) using the formula: Kλ2=Dgλ22, 2 and for each of the relative positions (P α,β,γ ) of the ball (12) Perform the following steps: (iii) Determine one sphere measurement phase (φ) mess ) based on the measured brightness value (I α,β,γ ), (iv) Determine each of a difference phase (φ) Diff ) based on the empty phase (φ leer ) and the respective ball measurement phase (φ mess ) of a point and a point diametrically opposite on the sphere (12), (v) Determining a plurality (j1, j2) of distinct first-correction phase totals (M) λ1 , j1) and second correction phase totals (M λ2, j2), each with a correction test diameter (D test,j ) correspond to the first rough phase total number (K) by one or a few phase passes. λ1 ) or the total number of second rough phases (K λ2 ) differs, (vi) Determine the correction test diameter (D) in each case test,j ) to each of the correction phase totals (M λk , j), in particular based on the corresponding central wavelength (λ k ) and the difference phase (φ Diff ), in particular using the formula: Dtest,j,k=(Mλk,j+φDiff)λk2, (vii) Determine at least one optimal correction test diameter (D test,j=opt ), in which the obtained correction test diameters (D test,j,k ) for the different central wavelengths (λ k ) exhibit the slightest deviation from each other, determining at least one shape parameter (F x,y,z ) based on the optimal correction test diameter (D test,j=opt ).

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