DE102018201211B4 - Chromatic confocal multi-spot sensor for determining the coordinates of a measurement object - Google Patents

Abstract

Objective (112) for a chromatic confocal multi-spot sensor (110), the objective (112) having at least one first lens group (114) and at least one second lens group (116), the first lens group (114) at least one in the direction of propagation (118) The first illuminating light beam (120) and at least one second illuminating light beam (122) are arranged in front of a pupil (124) and the second lens group (116) is arranged behind the pupil (124), the objective (112) being arranged in the direction of propagation (118) of the first illuminating light beam ( 120) and the second illuminating light beam (122) behind the second lens group (116) has at least one deflection device (126) which is set up to change the direction of propagation (118) of the illuminating light beams (120, 122), the first lens group (114) and the second lens group (116) have chromatically aberrative properties, wherein the first lens group (114) and the second lens group (116) ei are directed to focus portions of the first illuminating light beam (120) depending on the wavelength at at least two first measuring points (128) along an optical axis (130) of the objective (112) and portions of the second illuminating light beam (122) depending on the wavelength to focus at at least two second measuring points (132) along the optical axis (130) of the objective (112), wherein the first lens group (114) is set up to generate a first longitudinal chromatic aberration, wherein the second lens group (116) is set up a to generate second longitudinal chromatic aberrations, the first longitudinal chromatic aberration and the second longitudinal chromatic aberration differing considerably, the first lens group (114) and the second lens group (116) being set up to generate a lateral chromatic aberration such that the at least two first measuring points (128) and the at least two second measuring points (132) at each measuring depth essentially parallel to the optical Ac hse (130) extending straight lines (140) are arranged.

Description

Field of invention

The invention relates to an objective for a chromatic confocal multi-spot sensor, a chromatic confocal multi-spot sensor and a method for determining coordinates of at least two different destinations of at least one measurement object. The present invention relates in particular to the field of coordinate measuring technology using a non-contact coordinate measuring device.

State of the art

Various devices and methods for determining coordinates of at least two different destinations of a measurement object, in particular an extended measurement object, are known from the prior art. For example, methods for topography measurements, such as triangulation methods, deflectometry or fringe projections, are known. These methods can be used for full-area measurements over larger areas up to square meters. However, with such methods no accuracies required for coordinate metrology, for example down to the nanometer range, can be achieved.

Confocal and confocal chromatic distance sensors, so-called confocal chromatic point sensors, are also known. With sensors of this type, the depth is determined by evaluating an intensity distribution along a distance coordinate z, also called a height coordinate. Confocal chromatic sensors enable the distance coordinate z to be measured with a single image. In principle, measurement objectives with chromatic aberration are used in such sensors, which focus portions of a light beam with different wavelengths in different focal planes along an optical axis of the sensor. A distance coordinate can thus be assigned to each wavelength of the light beam. If a focus of a wavelength is on a surface of the measurement object, an intensity maximum can be measured for this wavelength on a sensor element of the confocal chromatic sensor and the depth can thus be determined.

Also known are confocal chromatic multi-spot sensors which enable parallelized depth measurement at many different measuring points at the same time. For example, as in FR 2 950 441 A1 described, a telecentric arrangement of the beams to the measuring points on the object side is used. Such an arrangement ensures that a measuring grid is the same at every depth, and an angle of incidence is the same for all measuring points. Describes further US 8 477 320 B2 a method for measuring the shape of a section of a semitransparent object with a light source with a broadband spectrum in a device for generating a multifocal illumination pattern, a lens with a large chromatic aberration for the imaging of foci of the illumination pattern on the object and a detection device for determining the wavelength spectra the focal points, which are imaged confocally onto the object via the lens, a position of a spectral peak for each focus being determined from the respective wavelength spectrum, from which an extent of the object in the direction of the imaging beam (Z coordinate) is calculated.

In the case of a telecentric confocal-chromatic multi-spot sensor on the object side, however, the diameter of an optical system closest to the field is already determined by a working distance, the size of a measuring field in the radial direction and in z, and the numerical aperture. For example, when using a deflecting prism with NA = 0.1, working distance 5 mm and measuring range 10 × 10 × 10 mm, an edge length of a first prism of approximately 16 mm results. When the object-side telecentricity is abandoned, the edge length of the prism can be reduced with otherwise unchanged properties, without a design of the confocal-chromatic multi-spot sensor being significantly changed. However, it is disadvantageous that the size of the measuring field changes with depth. Without further measures, the main rays essentially coincide, so that with a smaller distance the field is correspondingly smaller, or for the greatest distance the measuring field has to be enlarged accordingly, which reduces the grid density.

DE 10 2012 223 873 A1 describes a chromatic point sensor system comprising a first confocal optical path with a longitudinally diffusing element configured to focus different wavelengths at different distances in the vicinity of a workpiece; a second optical path configured to focus different wavelengths at substantially the same distance in the vicinity of the workpiece; a light source connected to the first confocal optical path; a light source connected to the second optical path; a first confocal optical path deactivation element; a deactivation element of the second optical path; and CPS electronics comprising a CPS wavelength detector that provides output spectral profile data. The output spectral profile data of the second optical path can be used for output spectral profile data of the first confocal optical path in relation to a Compensate for distance-independent profile components that have errors due to workpiece material effects.

Hillenbrand M. et al., "Parallelized chromatic confocal sensor systems," Proc. SPIE 8788, Optical Measurement Systems for Industrial Inspection VIII, 87880V (13 May 2013) ; doi: 10.1117 / 12.2020334, describes a chromatic confocal distance sensor for the parallel evaluation of several lateral positions. The multi-point measurement is carried out with a one or two-dimensional detector array. A first sensor combines concepts of confocal matrix sensing and snapshot hyperspectral imaging to obtain a two-dimensional array of laterally distant points in one image.

Object of the invention

It is therefore the object of the present invention to provide an objective for a chromatic confocal multi-spot sensor, a chromatic confocal multi-spot sensor and a method which at least largely avoid the disadvantages of known devices and methods. In particular, a reduction in the size of chromatic confocal multi-spot sensors is to be made possible.

Disclosure of the invention

This object is achieved by a device and a method with the features of the independent patent claims. Preferred configurations, which can be implemented individually or in combination, are presented in the dependent claims.

In the following, the terms “have”, “have”, “comprise” or “include” or any grammatical deviations therefrom are used in a non-exclusive manner. Accordingly, these terms can relate both to situations in which, besides the feature introduced by these terms, no further features are present, or to situations in which one or more further features are present. For example, the expression “A has B”, “A has B”, “A includes B” or “A includes B” can refer to the situation in which, apart from B, there is no other element in A (ie on a situation in which A consists exclusively of B), as well as on the situation in which, in addition to B, one or more further elements are present in A, for example element C, elements C and D or even further elements .

Furthermore, it should be noted that the terms “at least one” and “one or more” as well as grammatical modifications of these terms or similar terms, if these are used in connection with one or more elements or features and are intended to express that the element or feature simply or can be provided several times, usually only used once, for example when the feature or element is introduced for the first time. If the feature or element is subsequently mentioned again, the corresponding term “at least one” or “one or more” is generally no longer used, without restricting the possibility that the feature or element can be provided once or several times.

Furthermore, the terms “preferably”, “in particular”, “for example” or similar terms are used below in connection with optional features, without this limiting alternative embodiments. Features introduced by these terms are optional features, and it is not intended to use these features to restrict the scope of protection of the claims and in particular of the independent claims. Thus, as the person skilled in the art will recognize, the invention can also be carried out using other configurations. In a similar way, features which are introduced by “in an embodiment of the invention” or by “in an exemplary embodiment of the invention” are understood as optional features, without this being intended to limit alternative configurations or the scope of protection of the independent claims. Furthermore, by means of these introductory expressions, all possibilities of combining the features introduced in this way with other features, be it optional or non-optional features, remain untouched.

In a first aspect of the present invention, an objective for a chromatic confocal multi-spot sensor is proposed. An objective can in principle be understood to mean an optical system, in particular a real imaging optical system, with at least one optical element. A chromatic confocal multi-spot sensor can be understood to be a chromatic confocal sensor in which a measurement object to be examined is illuminated at several destinations at the same time and thus allows longitudinal coordinates to be determined at several destinations at the same time. Chromatic confocal multi-spot sensors enable parallelized depth measurement at many points at the same time. A chromatic confocal sensor can in principle be understood to mean an optical sensor which has at least one Has confocal chromatic beam path. In the context of the present invention, the term “beam path” can be understood to mean a course of light rays through optical elements. A “chromatic confocal beam path” can be understood in the context of the present invention as a beam path in which an illuminating beam path and a detection beam path are confocal for at least one wavelength of an illuminating light beam. In particular, the condition can be met for at least one wavelength of the illuminating light beam that a first focus is located on a destination on a surface of the measurement object and, at the same time, a second focus is located at a point in a center of a diaphragm element which is in a direction of propagation of one of the Measurement object remitted light beam is arranged in front of a sensor element. The confocal chromatic sensor can be set up to measure a measurement object, in particular a surface and / or a surface contour of a measurement object. In particular, the confocal chromatic sensor can be a contactless distance sensor in the field of coordinate measuring technology or can be used in a contactless distance sensor.

In the context of the present invention, a measurement object can generally be understood to mean an object to be measured of any shape. For example, the measurement object can be selected from the group consisting of a test object, a workpiece to be measured and a component to be measured, for example a motor vehicle. However, other measurement objects are also conceivable. In particular, the measurement object can be a flat measurement object, for example with an extensive surface. The surface can be at least partially reflective. Partially reflective can be understood to mean that the surface of the measurement object is set up to reflect and / or reflect at least a portion of an illuminating light beam.

The objective has at least one first lens group and at least one second lens group. The first lens group is arranged in the direction of propagation of at least one first illuminating light beam and at least one second illuminating light beam in front of a pupil and the second lens group is arranged behind the pupil. The objective has at least one deflection device behind the second lens group in the direction of propagation of the first illuminating light beam and the second illuminating light beam, which deflection device is set up to change the direction of propagation of the illuminating light beams. The first lens group and the second lens group have chromatically aberrative properties. The first lens group and the second lens group are set up to focus portions of the first illuminating light beam depending on the wavelength at at least two first measuring points along an optical axis of the objective and portions of the second illuminating light beam depending on the wavelength at at least two second measuring points along the optical axis Focus on the axis of the lens. “To focus along the optical axis” can be understood to mean focusing in the direction of the optical axis, in particular on the optical axis or parallel to the optical axis. The first lens group is set up to produce a first longitudinal chromatic aberration. The second lens group is set up to generate a second longitudinal chromatic aberration. The first longitudinal color defect and the second longitudinal color defect differ considerably. The first lens group and the second lens group are set up to generate a lateral chromatic aberration in such a way that the at least two first measuring points and the at least two second measuring points are arranged at each measuring depth on straight lines running essentially parallel to the optical axis.

A lens group can be understood to mean an optical element which has at least two lens elements. The first lens group can be referred to as first imaging optics and the second lens group as second imaging optics. The first and second lens groups can include a plurality of lens elements. The lens elements can be selected from the group consisting of: at least one concavo-convex lens, at least one convex-concave lens, at least one biconvex lens, at least one plano-convex lens. The terms “first” and “second” are to be understood as pure designations and in particular do not provide any information about a sequence or whether the objective has further optical elements, in particular lens groups. The objective can have a multiplicity of lens elements, in particular lens groups or individual lens elements, for example a third and a fourth lens group.

The first lens group is arranged in the direction of propagation of the at least one first illuminating light beam and the at least one second illuminating light beam in front of the pupil and the second lens group is arranged behind the pupil. A pupil can be understood to mean a diaphragm which limits a radiation cone of the illuminating light beam, or an image thereof, i.e. the pupil can be a real or virtual pupil. The designation “before” or “after” refers to the beam path in the direction of illumination.

The objective points in the direction of propagation of the first illuminating light beam and the second illuminating light beam behind the second Lens group on at least one deflecting device. The deflection device is set up to change the direction of propagation of the illuminating light beams, in particular to deflect it into a predetermined or predeterminable direction. The deflecting device can be set up to deflect the illuminating light beams perpendicular to the direction of propagation. However, other changes of direction are also conceivable. A deflection device can be understood to mean any optical element which is set up to change the direction of propagation of the illuminating light beams in a predetermined or predeterminable direction. The deflecting device can have an element selected from the group consisting of: a prism, in particular a deflecting prism, a mirror. For example, the deflection device can be a prism with an edge length of 16 mm. The edge length can preferably be less than 16 mm, for example the edge length can be 12 mm. However, other edge lengths are also conceivable, in particular shorter edge lengths. For example, the edge length in relation to the size of the measurement volume can be <1.2 as here in the exemplary embodiment, ideally even <1.

The first lens group and the second lens group have chromatically aberrative properties. The expression “chromatic aberrative” properties can be understood to mean that the lens groups can be set up to separate portions of the illuminating light beam as a function of the wavelength. For example, the first lens group and the second lens group can have at least one lens with chromatic aberration. The first lens group and the second lens group are set up to focus portions of the first illuminating light beam depending on the wavelength at at least two first measuring points along an optical axis of the objective and portions of the second illuminating light beam depending on the wavelength at at least two second measuring points along the optical axis Focus on the axis of the lens. A “measuring point” can be understood to mean a point at which a portion of one of the illuminating light beams is focused. The terms “first” and “second” measuring points are to be understood as pure designations and in particular do not provide any information about a sequence or whether further measuring points are provided. The first lens group and the second lens group can form a hyperchromatic optical system. The at least two first measuring points can be arranged in different focal planes. The at least two second measuring points can be arranged in different focal planes. A focal plane, also called focal plane, can be understood as a plane perpendicular to the optical axis in which at least one focal point, also called focal point, of the hyperchromatic optical system is arranged for at least one wavelength. In particular, the hyperchromatic optical system can be set up to focus a large number of components of the illuminating light beams as a function of the wavelength at a large number of different focal planes along the optical axis. For example, a first portion of the first illuminating light beam with a first wavelength can be focused in a first focal plane, for example at the first first measuring point, in particular a first z coordinate, and a second portion of the first illuminating light beam with a second wavelength, which differs from the first The wavelength is different can be focused in a second focal plane, for example the second first measuring point, in particular a second z coordinate which is different from the first first measuring point. For example, a first portion of the second illuminating light beam with a first wavelength can be focused in a first focal plane, for example at the second first measuring point, in particular a first z coordinate, and a second portion of the second illuminating light beam with a second wavelength, which differs from the first The wavelength is different can be focused in a second focal plane, for example the second second measuring point, in particular a second z-coordinate which is different from the second first measuring point. The lens can be chromatically uncorrected.

In the context of the present invention, “light” can be understood to mean electromagnetic radiation in at least one spectral range selected from the visible spectral range, the ultraviolet spectral range and the infrared spectral range. The term visible spectral range basically covers a range from 380 nm to 780 nm. The term infrared (IR) spectral range basically covers a range from 780 nm to 1000 µm, with the range from 780 nm to 1.4 µm as near infrared (NIR), and the range from 15 µm to 1000 µm is called far infrared (FIR). The term ultraviolet basically comprises a spectral range from 100 nm to 380 nm. In the context of the present invention, preference is given to using visible light, that is to say light from the visible spectral range. The term “light beam” can basically be understood to mean an amount of light that is emitted and / or sent out in a specific direction. The light beam can be a bundle of rays. The term “illuminating light beam” can be understood to mean a light beam which illuminates the measurement object, in particular the surface of the measurement object. The first and second illuminating light beams can be generated by an illuminating device. For example, the first and second illuminating light beam can be separate, in particular spatially separate, light beams are generated by the lighting device. For example, the lighting device can be set up to generate an illuminating light beam which can be divided into at least two illuminating light beams using optical elements, for example diaphragm elements with a plurality of hole elements.

The first lens group is set up to produce a first longitudinal chromatic aberration. The second lens group is set up to generate a second longitudinal chromatic aberration. A longitudinal chromatic aberration can be understood as an imaging property such that two parts of a light beam with different wavelengths are focused at two different focal points as a function of the wavelength. The first longitudinal color defect and the second longitudinal color defect differ considerably. “Significantly different” can be understood to mean that the first longitudinal color error and the second longitudinal color error have opposite signs and / or differ by at least a factor of 3. The longitudinal color error generated by the lens groups before and after the pupil, or the groups closest to the field, can differ by at least a factor of 3, preferably by a factor of 5 and particularly preferably by a factor of 10. An embodiment can be particularly preferred in which the first longitudinal color error and the second longitudinal color error have opposite signs. The first lens group and the second lens group can further be set up to meet additional conditions for a secondary spectrum.

The first lens group and the second lens group are set up to generate a lateral chromatic aberration in such a way that the at least two first measuring points and the at least two second measuring points are arranged at each measuring depth on straight lines running essentially parallel to the optical axis. A lateral chromatic aberration can be understood to mean an imaging property that an imaging scale depends on the wavelength of the incident light. In particular, the lateral chromatic aberration can be measured in a fixed reference plane, as is generally the case. With regard to this reference plane, the beam heights of the main rays can be different, even if the image size is actually the same in the best focal plane in each case. For example, the lens groups, the system comprising the first lens group and the second lens group, can be set up to generate images of different sizes for different wavelengths. A measurement depth can be understood to mean a distance from the objective, in particular a longitudinal coordinate along the optical axis. “Essentially parallel” can be understood to mean a parallel course, with deviations from a parallel course of 10%, preferably 5% and particularly preferably 1% being possible. Deviations from a parallel course can depend on production and adjustment. “Arranged on a straight line” can be understood to mean an arrangement of the first measurement points and the second measurement point in which the first measurement points and the second measurement points lie on a straight line, deviations from the straight line, in particular through a secondary spectrum, being possible. In particular, the first measurement points and the second measurement points lie essentially on a straight line if there are more than two wavelengths or depth levels. The objective can be set up to allow a correction of the secondary spectrum, in particular to correct deviations from an arrangement on the straight line. In particular, the objective can have means for correcting the secondary spectrum, for example special glasses with anomalous partial dispersion. “On straight lines running essentially parallel to the optical axis” can be understood to mean that the at least two first measuring points and the at least two second measuring points have an identical longitudinal coordinate for identical wavelengths. In particular, the measuring points are located on an identical grid at each measuring depth. For example, the first illuminating light beam and the second illuminating light beam can each have a component with a first wavelength λ ₁ and a component with a second wavelength λ ₂ . The objective, in particular the first and the second lens group, can be set up to focus the portion of the first illuminating light beam with the first wavelength at a first first measuring point f ₁ with a longitudinal coordinate z ₁ and the portion of the first illuminating light beam with the second wavelength to focus a first second measuring point f ₂ with a longitudinal coordinate z _2. The objective, in particular the first and second lens groups, can be set up to focus the portion of the second illuminating light beam with the first wavelength at a second first measuring point f ₃ with the longitudinal coordinate z ₁ and the portion of the second illuminating light beam with the second wavelength to focus on a second second measuring point f ₄ with the longitudinal coordinate z _2. The measuring points f ₁ and f ₂ can be arranged in such a way that they lie on a first straight line which runs essentially parallel to the optical axis. The measuring points f ₃ and f ₄ can be arranged in such a way that they lie on a second straight line which runs essentially parallel to the optical axis. The objective can have an optical axis. The optical axis can be an optical axis of one or more of the optical elements of the objective. The optical axis can point in the viewing direction of a sensor element. The optical axis can be an axis of a coordinate system of the lens, for example the z-axis. A longitudinal coordinate, in particular a distance coordinate, can be understood to mean a coordinate along the z-axis. Further axes, for example the x-axis and y-axis, can be provided perpendicular to the z-axis. As stated above, the objective has a deflection device. The optical axis can be an optical axis of the deflecting device.

In particular, the lateral chromatic aberration can be greater than 10% of the product of the numerical aperture NA of the objective and a depth measurement range. A “depth measuring range” can be understood to mean a predetermined and / or adjustable and / or predeterminable measuring range in which the longitudinal coordinate is determined. The objective can be set up to provide a measurement volume of 10 × 10 × 10 mm ³ . The lateral chromatic aberration can correspond to a product of non-telecentricity and the depth measurement range. “Non-telecentricity” can be understood to mean a deviation from an axially parallel course of main rays in the objective, in particular an angle difference. For example, lateral color errors can be determined from: lateral color error [mm] = tan (angle difference) · depth measuring range [mm].

The first and second lens groups can be arranged in such a way that the first illuminating light beam and the second illuminating light beam, in particular their main rays, run non-telecentrically on the object side. The lens can be a non-telecentric lens. The objective can be set up to introduce so many lateral color errors in addition to the longitudinal color error that the at least two first measurement points and the at least two second measurement points continue to lie on a grid that is essentially identical at each measurement depth. “Essentially identical grid” can be understood to mean that the at least two first measurement points and the at least two second measurement points are located on an identical grid at each measurement depth, with deviations from the identical grid, in particular due to a secondary spectrum, being possible. “Non-telecentric on the object side” can be understood to mean that on the object side a deviation from an axially parallel course of main rays in the objective is possible. “On the object side” refers to the object to be measured and not to the object in the sense of the optical image, the image of which lies on the measurement object.

As stated above, the objective can have a multiplicity of lens elements, in particular lens groups or individual lens elements, for example a third and a fourth lens group. The further lens elements can be set up to generate a lateral color error and / or a longitudinal color error. For example, a further lens element can be arranged in front of the first lens group in the direction of propagation of the illuminating light beam and a further lens element can be arranged behind the second lens group in the direction of propagation of the illuminating light beam. The further lens groups can be set up, for example, to increase the lateral color error and / or the longitudinal color error generated by the first and second lens group. For example, the further lens groups can generate a lateral color error with the same sign and thus generate longitudinal color errors with the opposite sign.

The objective can have at least one illumination diaphragm with at least two illumination diaphragm hole elements. The illumination aperture may have a plurality of illumination aperture hole elements. In the context of the present invention, a “diaphragm” can in principle be understood to mean an optical element or component of the objective which is set up to limit the extent of a beam. A “lighting screen” can be understood to mean a screen which is arranged, for example, in front of the lighting device and is illuminated by the lighting device. In the context of the present invention, a “hole element” can be understood to mean an opening of basically any shape. The objective can have at least one confocal diaphragm, also called detection pinhole, with at least two confocal pinhole elements. The illumination diaphragm and the confocal diaphragm can be designed as optical elements with at least two openings of any shape and / or adjustable and / or adjustable. The illumination diaphragm and / or the confocal diaphragm can have a multiplicity of perforated elements, for example a perforated grid made up of a plurality of holes. The confocal diaphragm may have a plurality of confocal diaphragm hole elements. A “confocal diaphragm” can be understood to mean any diaphragm which is arranged in a plane conjugate to the illumination diaphragm, in particular at the same distance from the first lens group as the illumination diaphragm, against the direction of illumination in front of a sensor element and is set up to defocus portions of a detection light beam, in particular Fade out strongly defocused parts and let through focused parts. An arrangement, in particular a position, of the confocal diaphragm can be dependent on the measurement object, an amount of light and a desired resolution, for example a lateral resolution and / or resolution of the distance determination. “A detection light beam” can be understood to mean a light beam which is remitted from the measurement object, in particular from the surface of the measurement object, and can be detected by a sensor element. the Detection light beam can have a direction of propagation so that the detection light beam illuminates the confocal diaphragm and the sensor element.

The lateral chromatic aberration in an image plane, as a transverse deviation in a central plane, can be greater than the diameter of an image of one or both confocal diaphragm hole elements. For a maximum z-resolution, a diameter of the holes can typically be in the range of the diameter of the diffraction disk. A distance between two hole elements of the illumination diaphragm and / or the confocal diaphragm can be such that confocality conditions are met. Confocality conditions can be understood as the condition that defocused portions of the detection light beam are masked out and only focused portions fall into a hole element and are allowed through. In particular, the distance between two adjacent hole elements can be such that heavily defocused light does not fall into an adjacent hole element and is allowed to pass through. The distance between two hole elements can be chosen such that spectra of the hole elements overlap.

The objective can have at least one transfer device. The transfer device can be designed as part of one of the lens groups or as a separate element. The transfer device can be set up to guide and / or direct light generated by the lighting device onto the measurement object, in particular onto the surface of the measurement object. Furthermore, the transfer device can be set up to guide and / or direct light remitted and / or reflected by the measurement object onto the confocal diaphragm. The transfer device can be selected from the group consisting of: at least one beam splitter; at least one lens, at least one lens group.

In a further aspect, a chromatic confocal multi-spot sensor is proposed for determining longitudinal coordinates of at least two different destination locations of at least one measurement object. The chromatic confocal multi-spot sensor comprises at least one objective according to the invention according to one of the embodiments described above or below. For details with regard to the chromatic confocal multi-spot sensor, reference is made to the description of the objective according to the invention.

In the context of the present invention, the term “destination” can be understood to mean any location, in particular a point or an area, on the surface of the measurement object to be measured, at which a longitudinal coordinate is determined. For example, a destination can be a measurement point on the surface of the measurement object. In the context of the present invention, “different destinations” can be understood to mean a spatial separation, for example in at least one spatial direction, of the destinations on the surface, wherein the destinations may at least partially overlap. “At least partially overlap” can be understood to mean that the destinations are not completely congruent. In the context of the present invention, coordinates of a measurement object can be understood to mean coordinates on the surface of the measurement object to be measured, in particular distance coordinates. One or more coordinate systems can be used for this purpose. For example, a Cartesian coordinate system or a spherical coordinate system can be used. Other coordinate systems are also conceivable. A determination of a coordinate can be understood to mean, in particular, a determination of a distance between the respective destination of the measurement object and the chromatically confocal multi-spot sensor, for example a distance between the respective destination of the measurement object and at least one element of the chromatically confocal multi-spot sensor, in particular the sensor element and / or at least a confocal diaphragm. The chromatically confocal multi-spot sensor can be set up to determine at least one coordinate in each case at a plurality of destinations, in particular at the same time.

The chromatic confocal multi-spot sensor can have at least one lighting device which is set up to generate at least one illuminating light beam. The lighting device can have at least one polychromatic light source and / or at least one white light source and / or at least one spectrally broadband light source. In the context of the present invention, a lighting device can be understood to mean any device which is set up to generate at least one light beam. The lighting device can have at least one light source. The lighting device can have at least one polychromatic light source and / or at least one white light source and / or at least one broadband light source. The light source can have a broad and evenly distributed spectral density. The lighting device can be set up to illuminate the measurement object through the illumination diaphragm. “To illuminate the measurement object through” can be understood in the context of the present invention that the lighting device is set up to illuminate the illumination diaphragm and furthermore to illuminate the surface, in particular a point or an area on the surface, of the measurement object. The lighting device can furthermore have at least one have further optical element, in particular a lens, which is set up to focus the light beam generated by the light source.

The chromatic confocal multi-spot sensor has at least one sensor element, the sensor element being set up to detect at least two detection light beams reflected from the two destinations. The confocal diaphragm can be set up to illuminate the sensor element. A focus can be located on the surface of the measurement object for at least one wavelength of the illuminating light beam. At the same time, a portion of the detection light beam for this wavelength can be focused in at least one hole element, in particular in exactly one hole element, of the confocal diaphragm in such a way that the intensity on the sensor element is maximal. The confocal diaphragm can be set up to mask out all further unfocused spectral components of the detection light beam. In the context of the present invention, a “sensor element” can be understood to mean any device which is set up to detect at least one optical measured variable, for example an intensity, of the detection light beam and to generate a corresponding signal, for example an electrical signal, for example a analog and / or a digital signal.

The chromatic confocal multi-spot sensor can have at least one evaluation unit which is set up to determine at least one spectral intensity distribution of the detection light beams and to determine a longitudinal coordinate of the respective destination of the measurement object from the respective spectral intensity distribution. A “spectral intensity distribution” can be understood to mean a distribution of the intensity of the detection light beam as a function of the wavelength. The evaluation unit can be set up to determine a maximum of the respective spectral intensity distribution, to assign it to a wavelength and to determine the longitudinal coordinate of the destination of the measurement object from the assigned wavelength. The sensor element can be set up to determine at least one spectral distribution. The evaluation unit can be set up to determine at least one intensity maximum of the spectral distribution and to assign a wavelength to the intensity maximum. A determination of a spectral distribution can be understood to mean a measurement and / or determination of the intensity of the detection light beam as a function of the wavelength. The spectral distribution can include an intensity distribution as a function of a wavelength. The sensor element can be and / or comprise a spectrally resolving detector. In particular, the sensor element can be and / or comprise a spectrometer. The sensor element can have at least one multi-spectral sensor.

“An evaluation unit” can generally be understood to mean an electronic device which is set up to evaluate signals generated by the sensor element. For example, one or more electronic connections between the sensor element and the evaluation unit can be provided for this purpose. The evaluation unit can for example comprise at least one data processing device, for example at least one computer or microcontroller. The data processing device can have one or more volatile and / or non-volatile data memories, wherein the data processing device can, for example, be set up in terms of programming to control the sensor element. The evaluation unit can furthermore comprise at least one interface, for example an electronic interface and / or a man-machine interface such as an input / output device such as a display and / or a keyboard. The evaluation unit can, for example, have a central or decentralized structure. Other configurations are also conceivable. The evaluation unit can be fully or partially integrated into the sensor element. The sensor element can, for example, be connected directly or indirectly to the evaluation unit. Alternatively or additionally, however, the evaluation unit can also be arranged wholly or partially at the location of the sensor element, for example in the form of a microcontroller, and / or can be wholly or partially integrated into the sensor element.

As stated above, the distance between two hole elements can be selected in such a way that spectra of the hole elements overlap. The evaluation unit can be set up to separate overlapping spatial and spectral information, in particular with at least one algorithmic method.

• - Erzeugen mindestens eines ersten Beleuchtungslichtstrahls und eines zweiten Beleuchtungslichtstrahls mit mindestens einer Beleuchtungsvorrichtung;
• - Beleuchten des Messobjekts mit den Beleuchtungslichtstrahlen durch eine Beleuchtungsblende mit mindestens zwei Beleuchtungslochelementen an den mindestens zwei Bestimmungsorten;
• - Fokussieren von Anteilen des ersten Beleuchtungslichtstrahls in Abhängigkeit von der Wellenlänge an mindestens zwei ersten Messpunkten entlang einer optischen Achse des Objektivs und Fokussieren von Anteilen des zweiten Beleuchtungslichtstrahls in Abhängigkeit von der Wellenlänge an mindestens zwei zweiten Messpunkten entlang der optischen Achse des Objektivs; wobei die erste Linsengruppe und die zweite Linsengruppe chromatisch aberrative Eigenschaften aufweisen;
• - Erzeugen eines ersten Farblängsfehler mit der ersten Linsengruppe und Erzeugen eines zweiten Farblängsfehlers mit der zweiten Linsengruppe, wobei sich der erste Farblängsfehler und der zweite Farblängsfehler erheblich unterscheiden,
• - Erzeugen eines Farbquerfehlers mit der ersten Linsengruppe und der zweite Linsengruppe derart, dass die mindestens zwei ersten Messpunkte und die mindestens zwei zweiten Messpunkte in jeder Messtiefe auf im Wesentlichen parallel zur optischen Achse verlaufenden Geraden angeordnet sind.

In a further aspect, a method for determining longitudinal coordinates of at least two different destinations of at least one measurement object is proposed. The procedure comprises the following procedural steps:

• Generating at least a first illuminating light beam and a second illuminating light beam with at least one lighting device;
• - Illuminating the measurement object with the illuminating light beams through an illuminating diaphragm with at least two illuminating hole elements at the at least two destination locations;
• - Focusing portions of the first illuminating light beam as a function of the wavelength at at least two first measuring points along an optical axis of the objective and focusing portions of the second illuminating light beam as a function of the wavelength at at least two second measuring points along the optical axis of the objective; wherein the first lens group and the second lens group have chromatically aberrative properties;
• - Generating a first longitudinal color defect with the first lens group and generating a second longitudinal color defect with the second lens group, the first longitudinal color defect and the second longitudinal color defect differing considerably,
• Generating a transverse chromatic aberration with the first lens group and the second lens group in such a way that the at least two first measuring points and the at least two second measuring points are arranged at each measuring depth on straight lines running essentially parallel to the optical axis.

Here, the method steps can be carried out in the specified order, with one or more of the steps also being able to be carried out at least partially simultaneously and with one or more of the steps being able to be repeated several times. Furthermore, further steps can additionally be carried out regardless of whether they are mentioned in the present application or not.

In the method, at least one detection light beam reflected from the destinations can be detected with a sensor element. In the method, at least one spectral intensity distribution of the detection light beams can be determined and a longitudinal coordinate of the respective destination of the measurement object can be determined from the respective spectral intensity distribution.

A chromatic confocal multi-spot sensor according to the invention can be used in the method. For details with regard to the method according to the invention, reference is made to the description of the chromatic confocal multi-spot sensor according to the invention.

The device according to the invention and the method according to the invention are advantageous over known methods and devices. By allowing lateral color errors, a reduction in the size of chromatic confocal multi-spot sensors can be made possible. By giving up telecentricity on the object side, it is possible to reduce the edge length of a deflecting device. For example, it may be possible to use a prism as a deflecting device with a reduced edge length of 12 mm while maintaining the same depth measuring range.

• Ausführungsform 1: Objektiv für einen chromatisch konfokalen Multispotsensor, wobei das Objektiv mindestens eine erste Linsengruppe und mindestens eine zweite Linsengruppe aufweist, wobei die erste Linsengruppe in Ausbreitungsrichtung mindestens eines ersten Beleuchtungslichtstrahls und mindestens eines zweiten Beleuchtungslichtstrahls vor einer Pupille und die zweite Linsengruppe hinter der Pupille angeordnet ist, wobei das Objektiv in Ausbreitungsrichtung des ersten Beleuchtungslichtstrahls und des zweiten Beleuchtungslichtstrahls hinter der zweiten Linsengruppe mindestens eine Umlenkvorrichtung aufweist, welche eingerichtet ist, die Ausbreitungsrichtung der Beleuchtungslichtstrahlen zu ändern, wobei die erste Linsengruppe und die zweite Linsengruppe chromatisch aberrative Eigenschaften aufweisen, wobei die erste Linsengruppe und die zweite Linsengruppe eingerichtet sind, Anteile des ersten Beleuchtungslichtstrahls in Abhängigkeit von der Wellenlänge an mindestens zwei ersten Messpunkten entlang einer optischen Achse des Objektivs zu fokussieren und Anteile des zweiten Beleuchtungslichtstrahls in Abhängigkeit von der Wellenlänge an mindestens zwei zweiten Messpunkten entlang der optischen Achse des Objektivs zu fokussieren, wobei die erste Linsengruppe eingerichtet ist, einen ersten Farblängsfehler zu erzeugen, wobei die zweite Linsengruppe eingerichtet ist, einen zweiten Farblängsfehler zu erzeugen, wobei sich der erste Farblängsfehler und der zweite Farblängsfehler erheblich unterscheiden, wobei die erste Linsengruppe und die zweite Linsengruppe eingerichtet sind, einen Farbquerfehler zu erzeugen derart, dass die mindestens zwei ersten Messpunkte und die mindestens zwei zweiten Messpunkte in jeder Messtiefe auf im Wesentlichen parallel zur optischen Achse verlaufenden Geraden angeordnet sind. Ausführungsform 2: Objektiv nach der vorhergehenden Ausführungsform, wobei die mindestens zwei ersten Messpunkte und die mindestens zwei zweiten Messpunkte in jeder Messtiefe auf einem identischen Raster liegen.
• Ausführungsform 3: Objektiv nach einer der vorhergehenden Ausführungsformen, wobei die erste Linsengruppe und die zweite Linsengruppe derart angeordnet sind, dass der erste Beleuchtungslichtstrahl und der zweite Beleuchtungslichtstrahl objektseitig nicht-telezentrisch verlaufen.
• Ausführungsform 4: Objektiv nach einer der vorhergehenden Ausführungsformen, wobei das Objektiv chromatisch unkorrigiert ist.
• Ausführungsform 5: Objektiv nach einer der vorhergehenden Ausführungsformen, wobei das Objektiv mindestens eine Beleuchtungsblende mit mindestens zwei Beleuchtungsblendenlochelementen aufweist.
• Ausführungsform 6: Objektiv nach der vorhergehenden Ausführungsform, wobei die Beleuchtungsblende eine Vielzahl von Beleuchtungsblendenlochelementen aufweist.
• Ausführungsform 7: Objektiv nach einer der vorhergehenden Ausführungsformen, wobei das Objektiv mindestens eine Konfokalblende mit mindestens zwei Konfokalblendenlochelementen aufweist, wobei der Farbquerfehler in einer Bildebene größer ist als der Durchmesser eines Bildes eines oder beider Konfokalblendenlochelemente.
• Ausführungsform 8: Objektiv nach der vorhergehenden Ausführungsform, wobei die Konfokalblende eine Vielzahl von Konfokalblendenlochelementen aufweist.
• Ausführungsform 9: Objektiv nach einer der vier vorhergehenden Ausführungsformen, wobei ein Abstand zwischen zwei Lochelementen der Beleuchtungsblende und der Konfokalblende derart ist, dass Konfokalitätsbedingungen erfüllt sind.
• Ausführungsform 10: Objektiv nach einer der vorhergehenden Ausführungsformen, wobei der Farbquerfehler größer als 10% des Produktes aus Numerischer Apertur NA des Objektivs und eines Tiefenmessbereichs ist.
• Ausführungsform 11: Objektiv nach einer der vorhergehenden Ausführungsformen, wobei der Farbquerfehler einem Produkt aus Nichttelezentrie und dem Tiefenmessbereich entspricht.
• Ausführungsform 12: Objektiv nach einer der vorhergehenden Ausführungsformen, wobei die von den Linsengruppen vor und nach der Pupille erzeugten Farblängsfehler ein entgegengesetztes Vorzeichen aufweisen oder sich bei gleichem Vorzeichen um mindestens einen Faktor 3, bevorzugt um einem Faktor 5 und besonders bevorzugt um einen Faktor 10 unterscheiden.
• Ausführungsform 13: Chromatisch konfokaler Multispotsensor zur Bestimmung von longitudinalen Koordinaten von mindestens zwei verschiedenen Bestimmungsorten mindestens eines Messobjekts umfassend mindestens ein Objektiv nach einer der vorhergehenden Ausführungsformen.
• Ausführungsform 14: Chromatisch konfokaler Multispotsensor nach der vorhergehenden Ausführungsform, wobei der chromatisch konfokale Multispotsensor mindestens eine Beleuchtungsvorrichtung aufweist, welche eingerichtet ist, mindestens einen Beleuchtungslichtstrahl zu erzeugen.
• Ausführungsform 15: Chromatisch konfokaler Multispotsensor nach einer der zwei vorhergehenden Ausführungsformen, wobei die Beleuchtungsvorrichtung mindestens eine polychromatische Lichtquelle und/oder mindestens eine Weißlichtquelle und/oder mindestens eine spektral breitbandige Lichtquelle aufweist.
• Ausführungsform 16: Chromatisch konfokaler Multispotsensor nach einem der drei vorhergehenden Ausführungsformen, wobei die Beleuchtungsvorrichtung eingerichtet ist, das Messobjekt durch die Beleuchtungsblende zu beleuchten.
• Ausführungsform 17: Chromatisch konfokaler Multispotsensor nach einem der drei vorhergehenden Ausführungsformen, wobei der chromatisch konfokale Multispotsensor mindestens ein Sensorelement aufweist, wobei das Sensorelement eingerichtet ist, mindestens zwei von den zwei Bestimmungsorten reflektierten Detektionslichtstrahlen zu detektieren.
• Ausführungsform 18: Chromatisch konfokaler Multispotsensor nach der vorhergehenden Ausführungsform, wobei der chromatisch konfokale Multispotsensor mindestens eine Auswerteeinheit aufweist, welche eingerichtet ist, jeweils mindestens eine spektrale Intensitätsverteilung der Detektionslichtstrahlen zu bestimmen und aus der jeweiligen spektralen Intensitätsverteilung eine longitudinale Koordinate des jeweiligen Bestimmungsortes des Messobjekts zu bestimmen.
• Ausführungsform 19: Chromatisch konfokaler Multispotsensor nach der vorhergehenden Ausführungsform, wobei die Auswerteeinheit eingerichtet ist, um ein Maximum der jeweiligen spektralen Intensitätsverteilung zu bestimmen, einer Wellenlänge zuzuordnen und aus der zugeordneten Wellenlänge die longitudinale Koordinate des Bestimmungsortes des Messobjekts zu bestimmen.
• Ausführungsform 20: Verfahren zur Bestimmung von longitudinalen Koordinaten mindestens zweier verschiedener Bestimmungsorte mindestens eines Messobjekts, wobei das Verfahren die folgenden Verfahrensschritte umfasst:
  • - Erzeugen mindestens eines ersten Beleuchtungslichtstrahls und eines zweiten Beleuchtungslichtstrahls mit mindestens einer Beleuchtungsvorrichtung;
  • - Beleuchten des Messobjekts mit den Beleuchtungslichtstrahlen durch eine Beleuchtungsblende mit mindestens zwei Beleuchtungslochelementen an den mindestens zwei Bestimmungsorten;
  • - Fokussieren von Anteilen des ersten Beleuchtungslichtstrahls in Abhängigkeit von der Wellenlänge an mindestens zwei ersten Messpunkten entlang einer optischen Achse des Objektivs und Fokussieren von Anteilen des zweiten Beleuchtungslichtstrahls in Abhängigkeit von der Wellenlänge an mindestens zwei zweiten Messpunkten entlang der optischen Achse des Objektivs; wobei die erste Linsengruppe und die zweite Linsengruppe chromatisch aberrative Eigenschaften aufweisen;
  • - Erzeugen eines ersten Farblängsfehlers mit der ersten Linsengruppe und Erzeugen eines zweiten Farblängsfehlers mit der zweiten Linsengruppe, wobei sich der erste Farblängsfehler und der zweite Farblängsfehler erheblich unterscheiden,
  • - Erzeugen eines Farbquerfehlers mit der ersten Linsengruppe und der zweite Linsengruppe derart, dass die mindestens zwei ersten Messpunkte und die mindestens zwei zweiten Messpunkte in jeder Messtiefe auf im Wesentlichen parallel zur optischen Achse verlaufenden Geraden angeordnet sind.
• Ausführungsform 21: Verfahren nach der vorhergehenden Ausführungsform, wobei jeweils mindestens ein von den Bestimmungsorten reflektierter Detektionslichtstrahl mit einem Sensorelement detektiert wird, wobei jeweils mindestens eine spektrale Intensitätsverteilung der Detektionslichtstrahlen bestimmt wird und aus der jeweiligen spektralen Intensitätsverteilung eine longitudinale Koordinate des jeweiligen Bestimmungsorts des Messobjekts bestimmt wird.
• Ausführungsform 22: Verfahren nach einem der zwei vorhergehenden Ausführungsformen, wobei ein chromatisch konfokaler Multispotsensor nach einem der vorhergehenden einen chromatisch konfokalen Multispotsensor betreffenden Ansprüche verwendet wird.

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

• Embodiment 1: objective for a chromatic confocal multi-spot sensor, the objective having at least one first lens group and at least one second lens group, the first lens group being arranged in the direction of propagation at least one first illuminating light beam and at least one second illuminating light beam in front of a pupil and the second lens group behind the pupil is, wherein the objective in the direction of propagation of the first illuminating light beam and the second illuminating light beam behind the second lens group has at least one deflection device which is set up to change the direction of propagation of the illuminating light beams, the first lens group and the second lens group having chromatically aberrative properties, the first Lens group and the second lens group are set up, components of the first illuminating light beam as a function of the wavelength at at least two first measuring points kten to focus along an optical axis of the objective and to focus portions of the second illuminating light beam as a function of the wavelength at at least two second measuring points along the optical axis of the objective, the first lens group being set up to generate a first longitudinal chromatic aberration, the second lens group is set up to generate a second longitudinal color error, the first longitudinal color error and the second longitudinal color error differing significantly, the first lens group and the second lens group being set up to generate a lateral color error such that the at least two first measurement points and the at least two second measurement points are arranged at each measurement depth on straight lines running essentially parallel to the optical axis. Embodiment 2: Objective according to the preceding embodiment, wherein the at least two first measuring points and the at least two second measuring points are located on an identical grid at each measuring depth.
• Embodiment 3: Objective according to one of the preceding embodiments, wherein the first lens group and the second lens group are arranged in such a way that the first The illuminating light beam and the second illuminating light beam run non-telecentrically on the object side.
• Embodiment 4: Objective according to one of the preceding embodiments, the objective being chromatically uncorrected.
• Embodiment 5: Objective according to one of the preceding embodiments, the objective having at least one illumination diaphragm with at least two illumination diaphragm hole elements.
• Embodiment 6: The objective according to the preceding embodiment, wherein the illumination diaphragm has a plurality of illumination diaphragm hole elements.
• Embodiment 7: Objective according to one of the preceding embodiments, the objective having at least one confocal diaphragm with at least two confocal diaphragm hole elements, the lateral chromatic aberration in an image plane being greater than the diameter of an image of one or both confocal diaphragm hole elements.
• Embodiment 8: The objective according to the preceding embodiment, wherein the confocal diaphragm has a plurality of confocal diaphragm hole elements.
• Embodiment 9: Objective according to one of the four preceding embodiments, a distance between two hole elements of the illumination diaphragm and the confocal diaphragm being such that confocality conditions are met.
• Embodiment 10: Objective according to one of the preceding embodiments, wherein the lateral chromatic aberration is greater than 10% of the product of the numerical aperture NA of the objective and a depth measuring range.
• Embodiment 11: Objective according to one of the preceding embodiments, the lateral color error corresponding to a product of non-telecentricity and the depth measuring range.
• Embodiment 12: Objective according to one of the preceding embodiments, wherein the longitudinal color errors generated by the lens groups before and after the pupil have opposite signs or differ by at least a factor of 3, preferably by a factor of 5 and particularly preferably by a factor of 10, if they have the same sign .
• Embodiment 13: Chromatic confocal multi-spot sensor for determining longitudinal coordinates of at least two different destinations of at least one measurement object comprising at least one objective according to one of the preceding embodiments.
• Embodiment 14: Chromatic confocal multi-spot sensor according to the preceding embodiment, the chromatic confocal multi-spot sensor having at least one lighting device which is set up to generate at least one illuminating light beam.
• Embodiment 15: Chromatic confocal multi-spot sensor according to one of the two preceding embodiments, the lighting device having at least one polychromatic light source and / or at least one white light source and / or at least one spectrally broadband light source.
• Embodiment 16: Chromatic confocal multi-spot sensor according to one of the three preceding embodiments, wherein the lighting device is set up to illuminate the measurement object through the lighting diaphragm.
• Embodiment 17: Chromatic confocal multi-spot sensor according to one of the three preceding embodiments, the chromatic confocal multi-spot sensor having at least one sensor element, the sensor element being set up to detect at least two detection light beams reflected from the two destinations.
• Embodiment 18: Chromatic confocal multi-spot sensor according to the previous embodiment, the chromatic confocal multi-spot sensor having at least one evaluation unit which is set up to determine at least one spectral intensity distribution of the detection light beams and to determine a longitudinal coordinate of the respective destination of the measurement object from the respective spectral intensity distribution .
• Embodiment 19: Chromatic confocal multi-spot sensor according to the previous embodiment, the evaluation unit being set up to determine a maximum of the respective spectral intensity distribution, to assign it to a wavelength and to determine the longitudinal coordinate of the destination of the measurement object from the assigned wavelength.
• Embodiment 20: A method for determining longitudinal coordinates of at least two different destinations of at least one measurement object, the method comprising the following method steps:
  • - Generating at least a first illuminating light beam and a second illuminating light beam with at least one lighting device;
  • - Illuminating the measurement object with the illuminating light beams through an illuminating diaphragm with at least two illuminating hole elements at the at least two destination locations;
  • Focusing of portions of the first illuminating light beam as a function of the wavelength at at least two first measuring points along an optical axis of the objective and focusing of portions of the second illuminating light beam as a function of the wavelength at at least two second measuring points along the optical axis of the objective; wherein the first lens group and the second lens group have chromatically aberrative properties;
  • - generating a first longitudinal color defect with the first lens group and generating a second longitudinal color defect with the second lens group, the first longitudinal color defect and the second longitudinal color defect differing considerably,
  • Generating a transverse chromatic aberration with the first lens group and the second lens group in such a way that the at least two first measuring points and the at least two second measuring points are arranged at each measuring depth on straight lines running essentially parallel to the optical axis.
• Embodiment 21: Method according to the preceding embodiment, in which in each case at least one detection light beam reflected from the destinations is detected with a sensor element, in which case at least one spectral intensity distribution of the detection light beams is determined and a longitudinal coordinate of the respective destination of the measurement object is determined from the respective spectral intensity distribution .
• Embodiment 22: Method according to one of the two preceding embodiments, wherein a chromatic confocal multi-spot sensor according to one of the preceding claims relating to a chromatic confocal multi-spot sensor is used.

Figure list

Further details and features of the invention emerge from the following description of preferred exemplary embodiments, in particular in conjunction with the subclaims. The respective features can be implemented individually or in combination with one another. The invention is not restricted to the exemplary embodiments. The exemplary embodiments are shown schematically in the figure.

• 1 eine schematische Darstellung eines Ausführungsbeispiels eines erfindungsgemäßen chromatisch konfokalen Multispotsensors.

In detail shows:

• 1 a schematic representation of an embodiment of a chromatic confocal multi-spot sensor according to the invention.

Embodiments

1 shows a schematic representation of an embodiment of a chromatic confocal multi-spot sensor according to the invention 110 . The chromatic confocal multi-spot sensor has an objective 112 on. The objective 112 has at least a first lens group 114 and at least one second lens group 116 on. The first group of lenses 114 is in the direction of propagation 118 at least one first illuminating light beam 120 and at least one second illuminating light beam 122 in front of a pupil 124 and the second lens group 116 located behind the pupil. The first group of lenses 114 and the second lens group 116 may have a plurality of lens elements. The lens elements can be selected from the group consisting of: at least one concavo-convex lens, at least one convex-concave lens, at least one biconvex lens, at least one plano-convex lens. The objective 112 can have a multiplicity of lens elements, in particular lens groups or individual lens elements, for example a third and a fourth lens group.

The objective 112 points in the direction of propagation 118 of the first illuminating light beam 120 and the second illuminating light beam 122 behind the second lens group 116 at least one deflection device 126 on. The deflection device 126 is set up, the direction of propagation of the illuminating light rays 120 , 122 to change, in particular to deflect in a predetermined or predeterminable direction. The deflection device 126 can be set up the illuminating light beams 120 , 122 perpendicular to the direction of propagation 118 redirect. However, other changes of direction are also conceivable. The deflection device 116 can have an element selected from the group consisting of: a prism, in particular a deflecting prism, a mirror. For example, the deflection device can be a prism with an edge length of 16 mm. The edge length can preferably be less than 16 mm, for example the edge length can be 12 mm. However, other edge lengths are also conceivable.

The first group of lenses 114 and the second lens group 116 show chromatically aberrative Properties on. The first group of lenses 114 and the second lens group 116 , in particular a system from the first lens group 114 and second lens group 116 , are set up, portions of the first illuminating light beam 120 depending on the wavelength at at least two first measuring points 128 along an optical axis 130 of the lens 112 to focus and portions of the second illuminating light beam 122 depending on the wavelength at at least two second measuring points 132 along the optical axis 130 to focus. The first group of lenses 114 and the second lens group 116 show chromatically aberrative properties. In 1 an embodiment is shown in which the first lens group 114 and the second lens group, in particular the system comprising the first and second lens groups, the first illuminating light beam 120 at three first measuring points and the second illuminating light beam 122 focused at three second measuring points. The first group of lenses 114 and the second lens group 116 can form a hyperchromatic optical system. The at least two first measuring points 128 can be arranged in different focal planes. The at least two second measuring points 132 can be arranged in different focal planes. In particular, the hyperchromatic optical system can be set up to include a large number of components of the illuminating light beams 120 , 122 depending on the wavelength at a large number of different focal planes along the optical axis 130 to focus. For example, a first portion of the first illuminating light beam 120 with a first wavelength in a first focal plane, for example at the first first measuring point 134 , in particular a first z coordinate, and a second portion of the first illuminating light beam 120 with a second wavelength, which is different from the first wavelength, can be in a second focal plane, for example the second first measuring point 136 , in particular a second z coordinate, which is from the first first measuring point 134 is different, be focused. For example, a first portion of the second illuminating light beam 122 with a first wavelength in a first focal plane, for example at the second first measuring point 134 , in particular a first z coordinate, and a second portion of the second illuminating light beam 122 with a second wavelength, which is different from the first wavelength, can be in a second focal plane, for example the second second measuring point 136 , in particular a second z coordinate, which is from the second first measuring point 134 is different, be focused. The objective 112 can be chromatically uncorrected.

The first beam of illuminating light 120 and second illuminating light beam 122 can from a lighting device 138 be generated. For example, the first illuminating light beam 120 and second illuminating light beam 122 as separate, in particular spatially separate, light beams from the lighting device 138 be generated. For example, the lighting device 138 be set up to generate an illuminating light beam which can be divided into at least two illuminating light beams using optical elements, for example diaphragm elements with a plurality of hole elements. The chromatic confocal multi-spot sensor 110 can enable parallelized depth measurement at many points at the same time. The lighting device 138 can be set up to generate a plurality of illuminating light beams, for example two, three, four, ten or more. In the figure, an embodiment with two illuminating light beams is shown as an example with a light bundle to the field edge and a light bundle to the center of the field.

The chromatic confocal multi-spot sensor 110 can the at least one lighting device 138 exhibit. The lighting device 138 can have at least one polychromatic light source and / or at least one white light source and / or at least one spectrally broadband light source. The lighting device 138 can have at least one light source. The lighting device 138 can have at least one polychromatic light source and / or at least one white light source and / or at least one broadband light source. The light source can have a broad and evenly distributed spectral density. The lighting device 138 can furthermore have at least one further optical element, in particular a lens, which is set up to focus the light beam generated by the light source.

The first group of lenses 114 is set up to generate a first longitudinal color error. The second group of lenses 116 is set up to generate a second longitudinal color error. The first longitudinal color defect and the second longitudinal color defect differ considerably. The first group of lenses 114 and the second lens group 116 are set up to generate a lateral chromatic aberration in such a way that the at least two first measuring points 128 and the at least two second measurement points 132 at every measuring depth essentially parallel to the optical axis 130 running straight lines 140 are arranged. The first longitudinal color error and the second longitudinal color error can have opposite signs and / or differ by at least a factor of 3. That of the lens groups, especially of the first lens group 114 and the second lens group 116 , before and after the pupil 124 , or the groups closest to the field Longitudinal color errors can differ by at least a factor of 3, preferably by a factor of 5 and particularly preferably by a factor of 10. For example, the lens groups 114 , 116 , especially the system from the first lens group 114 and second lens group 116 , be set up to generate images of different sizes for different wavelengths. The at least two first measuring points 128 and the at least two second measurement points 132 for identical wavelengths can have an identical longitudinal coordinate. In particular, the measuring points are located on an identical grid at each measuring depth 142 . For example, the first illuminating light beam 120 and the second illuminating light beam 122 each have a portion with a first wavelength λ1 and a portion with a second wavelength λ2. The objective 112 , especially the first group of lenses 114 and the second lens group 116 , can be set up, the portion of the first illuminating light beam 120 with the first wavelength at a first first measuring point f1 with a longitudinal coordinate z1 and the portion of the first illuminating light beam 120 with the second wavelength at a first second measuring point f2 with a longitudinal coordinate z2. The objective 112 , especially the first lens group 114 and the second lens group 116 , can be set up, the proportion of the second illuminating light beam 122 with the first wavelength at a second first measuring point f3 with the longitudinal coordinate z1 and the portion of the second illuminating light beam 122 to focus with the second wavelength at a second second measuring point f4 with the longitudinal coordinate z2. The measuring points f1 and f2 can be arranged in such a way that they are on a first straight line 144 lie, which are essentially parallel to the optical axis 130 runs. The measuring points f3 and f4 can be arranged in such a way that they are on a second straight line 146 lie, which are essentially parallel to the optical axis 130 runs.

The optical axis 130 can be an optical axis of one or more of the optical elements of the objective 112 being. The optical axis can be viewed in the direction of view of a sensor element 148 show. The optical axis 130 can be an axis of a coordinate system of the objective, for example the z-axis. Further axes, for example the x-axis and y-axis, can be provided perpendicular to the z-axis. As stated above, the lens 112 a diverter 126 on. The optical axis 130 can be an optical axis of the deflecting device 126 being.

In particular, the lateral chromatic aberration can be greater than 10% of the product of the numerical aperture NA of the objective and a depth measurement range. The objective 112 can be set up a measurement volume 150 of 10 × 10 × 10 mm ^{3 to be provided} . The lateral chromatic aberration can correspond to a product of non-telecentricity and the depth measurement range. The first group of lenses 114 and the second lens group 116 can be arranged such that the first illuminating light beam 120 and the second illuminating light beam 122 , in particular their main rays, are non-telecentric on the object side. The objective 112 can be a non-telecentric lens. The objective 112 can be set up to introduce so many lateral color errors in addition to the longitudinal color error that the at least two first measuring points 128 and the at least two second measurement points 132 continue on a grid that is identical at every measuring depth 142 lie.

The objective 112 can have a multiplicity of lens elements, in particular lens groups or individual lens elements, for example a third and a fourth lens group. The further lens elements can be set up to generate a lateral color error and / or a longitudinal color error. For example, a further lens element can be used in the direction of propagation of the illuminating light beam 120 , 122 before the first lens group 114 be arranged and a further lens element in the direction of propagation of the illuminating light beam 120 , 122 behind the second lens group 116 be arranged. The further lens groups can be set up, for example, to increase the lateral color error and / or the longitudinal color error generated by the first and second lens group. For example, the further lens groups can generate a lateral color error with the same sign and thus generate longitudinal color errors with the opposite sign.

The objective 112 can have at least one lighting panel 152 with at least two lighting aperture hole elements 154 exhibit. The lighting screen 152 can have a variety of lighting aperture hole elements 154 exhibit. The objective 112 can have at least one confocal aperture 156 , also called detection pinhole, with at least two confocal pinhole elements 158 exhibit. The lighting screen 152 and the confocal diaphragm 156 can be designed as optical elements with at least two arbitrarily shaped and / or adjustable and / or adjustable openings. The lighting screen 152 and / or the confocal diaphragm 156 can have a multiplicity of hole elements, for example a hole pattern made up of several holes. The confocal diaphragm may have a plurality of confocal diaphragm hole elements. The confocal diaphragm 156 can be arranged in a plane conjugate to the illumination diaphragm and be set up, defocused portions of a detection light beam 160 , especially strongly defocused parts, to fade out and to let through focused parts. A distance between two perforated elements of the illumination panel 152 and / or the confocal diaphragm 156 can be such that confocality conditions are met.

The lateral chromatic aberration in an image plane, as a transverse deviation in a central plane, can be greater than the diameter of an image of one or both confocal diaphragm hole elements.

The objective 112 can have at least one transfer device 162 exhibit. The transfer device 162 can be designed as part of one of the lens groups or as a separate element. The transfer device 162 can be set up by the lighting device 138 to guide and / or direct generated light onto a measurement object, in particular onto the surface of the measurement object. The transfer device 162 be set up to guide and / or direct light remitted and / or reflected by the measurement object onto the confocal diaphragm. The transfer device 162 can be selected from the group consisting of: at least one beam splitter; at least one lens; at least one lens group.

The chromatic confocal multi-spot sensor 110 has the at least one sensor element 148 on, the sensor element 148 is set up, at least two of two destinations reflected detection light beams 162 to detect. The confocal diaphragm 156 can be set up, the sensor element 148 to illuminate. For at least one wavelength of the illuminating light beam 120 , 122 there may be a focus on the surface of the measurement object. At the same time, a portion of the detection light beam 162 for this wavelength be focused in at least one hole element, in particular in exactly one hole element, of the confocal diaphragm, that the intensity is on the sensor element 148 becomes maximum. The confocal diaphragm 156 can be set up to include all further unfocused spectral components of the detection light beam 162 fade out. The sensor element 148 can be an intensity of the detection light beam 162 detect and generate a corresponding signal, for example an electrical signal, for example an analog and / or a digital signal.

The chromatic confocal multi-spot sensor 110 can have at least one evaluation unit 164 which is set up to each have at least one spectral intensity distribution of the detection light beams 162 to determine and from the respective spectral intensity distribution to determine a longitudinal coordinate of the respective destination of the measurement object. The evaluation unit 164 can be set up to determine a maximum of the respective spectral intensity distribution, to assign it to a wavelength and to determine the longitudinal coordinate of the destination of the measurement object from the assigned wavelength. The sensor element 148 can be set up to determine at least one spectral distribution. The evaluation unit 164 can be set up to determine at least one intensity maximum of the spectral distribution and to assign a wavelength to the intensity maximum. The spectral distribution can include an intensity distribution as a function of a wavelength. The sensor element 148 can be and / or comprise a spectrally resolving detector. In particular, the sensor element 148 be and / or comprise a spectrometer. The sensor element 148 can have at least one multi-spectral sensor.

Between the sensor element 148 and the evaluation unit 164 one or more electronic connections can be provided. The evaluation unit 164 can for example comprise at least one data processing device, for example at least one computer or microcontroller. The data processing device can have one or more volatile and / or non-volatile data memories, wherein the data processing device can, for example, be set up in terms of programming to control the sensor element. The evaluation unit 164 can furthermore comprise at least one interface, for example an electronic interface and / or a man-machine interface such as an input / output device such as a display and / or a keyboard. The evaluation unit 164 can for example be set up centrally or decentrally. Other configurations are also conceivable. The evaluation unit 164 can be wholly or partially in the sensor element 148 be integrated. The sensor element 148 can for example directly or indirectly with the evaluation unit 164 be connected. Alternatively or additionally, the evaluation unit 164 however, also wholly or partially at the location of the sensor element 148 be arranged, for example in the form of a microcontroller, and / or can be fully or partially integrated into the sensor element.

List of reference symbols

110

Multi-spot sensor

112

lens

114

First lens group

116

Second lens group

118

Direction of propagation

120

First illuminating light beam

122

Second illuminating light beam

124

pupil

126

Deflection device

128

First measuring points

130

Optical axis

132

Second measuring points

134

First first measuring point or first second measuring point

136

Second first measuring point or second second measuring point

138

Lighting device

140

Straight lines

142

Grid

144

First straight

146

Second straight

148

Sensor element

150

Measurement volume

152

Lighting screen

154

Lighting aperture hole element

156

Confocal diaphragm

158

Confocal aperture hole element

160

Detection light beam

162

Transfer device

164

Evaluation unit

Claims (10)

Objective (112) for a chromatic confocal multi-spot sensor (110), the objective (112) having at least one first lens group (114) and at least one second lens group (116), the first lens group (114) at least one in the direction of propagation (118) The first illuminating light beam (120) and at least one second illuminating light beam (122) are arranged in front of a pupil (124) and the second lens group (116) is arranged behind the pupil (124), the objective (112) being arranged in the direction of propagation (118) of the first illuminating light beam ( 120) and the second illuminating light beam (122) behind the second lens group (116) has at least one deflection device (126) which is set up to change the direction of propagation (118) of the illuminating light beams (120, 122), the first lens group (114) and the second lens group (116) have chromatically aberrative properties, wherein the first lens group (114) and the second lens group (116) ei are directed to focus portions of the first illuminating light beam (120) depending on the wavelength at at least two first measuring points (128) along an optical axis (130) of the objective (112) and portions of the second illuminating light beam (122) depending on the wavelength to focus at at least two second measuring points (132) along the optical axis (130) of the objective (112), wherein the first lens group (114) is set up to generate a first longitudinal chromatic aberration, wherein the second lens group (116) is set up a to generate second longitudinal chromatic aberrations, the first longitudinal chromatic aberration and the second longitudinal chromatic aberration differing considerably, the first lens group (114) and the second lens group (116) being set up to generate a lateral chromatic aberration such that the at least two first measuring points (128) and the at least two second measuring points (132) at each measuring depth essentially parallel to the optical Ac hse (130) extending straight lines (140) are arranged. Objective (112) according to the preceding claim, wherein the at least two first measuring points (128) and the at least two second measuring points (132) lie at each measuring depth on an identical grid (142). Objective (112) according to one of the preceding claims, wherein the first lens group (114) and the second lens group (116) are arranged such that the first illuminating light beam (120) and the second illuminating light beam (122) run non-telecentrically on the object side. Objective (112) according to one of the preceding claims, wherein the objective (112) has at least one confocal diaphragm (156) with at least two confocal diaphragm hole elements (158), the lateral chromatic aberration in an image plane being greater than the diameter of an image of one or both confocal diaphragm hole elements (158) ). Objective (112) according to one of the preceding claims, wherein the lateral chromatic aberration is greater than 10% of the product of the numerical aperture NA of the objective (112) and a depth measuring range. Lens (112) according to one of the Claims 3 until 5 , where the lateral chromatic aberration corresponds to a product of non-telecentricity and the depth measurement range. Objective (112) according to one of the preceding claims, wherein the longitudinal color errors generated by the lens groups before and after the pupil (124) have an opposite sign or with the same sign by at least a factor of 3, preferably by a factor of 5 and particularly preferably by one Differentiate by a factor of 10. Chromatic confocal multi-spot sensor (110) for determining longitudinal coordinates of at least two different destinations of at least one measurement object, comprising at least one objective (112) according to one of the preceding claims. Chromatic confocal multi-spot sensor (110) Claim 8 , wherein the chromatic confocal multi-spot sensor (110) has at least one sensor element (148), the sensor element (148) being set up to detect at least two detection light beams (160) reflected by the two destinations, the chromatic confocal multi-spot sensor (110) at least one Evaluation unit (164) which is set up to determine at least one spectral intensity distribution of the detection light beams (160) and to determine a longitudinal coordinate of the respective destination of the measurement object from the respective spectral intensity distribution. Method for determining longitudinal coordinates of at least two different destinations of at least one measurement object, the method comprising the following method steps: - generating at least a first illuminating light beam (120) and a second illuminating light beam (122) with at least one illuminating device (138); - Illuminating the measurement object with the illuminating light beams (120, 122) through an illuminating diaphragm (152) with at least two illuminating hole elements (154) at the at least two destination locations; - Focusing portions of the first illuminating light beam (120) depending on the wavelength at at least two first measuring points (128) along an optical axis (130) of the objective (112) and focusing portions of the second illuminating light beam (122) depending on the wavelength at at least two second measuring points (132) along the optical axis (130) of the objective (112), the first lens group (114) and the second lens group (116) having chromatically aberrative properties; - Generation of a first longitudinal color defect with the first lens group (114) and generation of a second longitudinal color defect with the second lens group (116), the first longitudinal color defect and the second longitudinal color defect differing considerably, - Generating a transverse color error with the first lens group (114) and the second lens group (116) in such a way that the at least two first measuring points (128) and the at least two second measuring points (132) are essentially parallel to the optical axis (130 ) extending straight lines (140) are arranged.

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