Chromatic confocal sensor and method for determining the coordinates of at least one measured object

Abstract

comprising a confocal chromatic sensor (110) for determining the coordinates of at least one measurement object (112) - at least one first aperture element (114); - at least one lighting device (116) which is designed to generate at least one illuminating light beam (118) and to illuminate the object being measured (112) through the first aperture element (114); - at least one sensor element (120) wherein the sensor element (120) is configured to detect at least one detection light beam (122) emanating from the object being measured (112) and to determine at least one spectral distribution; - at least one second aperture element (124) which is arranged in a propagation direction of the detection light beam (126) in front of the sensor element (120); - at least one multifocal optical element (134) which is configured to generate at least two chromatically confocal measuring areas (138) that are one behind the other in a propagation direction of the illumination light beam (136); - at least one evaluation unit (158) which is set up to determine a height coordinate of the object being measured (112) from the spectral distribution.

Description

Field of the invention

[0001] The invention relates to a confocal chromatic sensor and a method for determining the coordinates of at least one measurement object. The present invention particularly relates to the field of coordinate metrology using a non-contact coordinate measuring machine. State of the art

[0002] Various devices and methods for determining the coordinates of a measurement object are known from the prior art. For example, methods for topographical surveys, such as triangulation methods, are used. For example, measurement methods that divide a measurement area into periods are known, such as interferometers and fringe projectors. Confocal distance sensors are also known. With such sensors, depth is determined by evaluating an intensity distribution along a height coordinate, e.g.

[0003] In contrast to measurement methods in which a measuring range is divided into periods, such as in interferometers or fringe projectors, the number of resolvable depth levels in confocal sensors can be limited, for example to 1000. Thus, with such sensors, either a high resolution with a small measuring range or a low resolution with a large measuring range can be achieved.

[0004] Furthermore, with confocal sensors, the height coordinate z on a surface of the target can be determined by shifting the optical elements, so that measurement data acquisition with multiple images may be necessary. Furthermore, technical problems can arise when implementing fast, high-precision kinematics.

[0005] Confocal chromatic sensors are known, which enable the measurement of the height coordinate z with a single image. Such sensors generally use measuring lenses with chromatic aberration, which focus portions of a light beam with different wavelengths in different focal planes along an optical axis of the sensor. Each wavelength of the light beam can thus be assigned a height coordinate. If a focus of a wavelength is located on a surface of the measurement object, an intensity maximum for this wavelength can be measured on a sensor element of the confocal chromatic sensor, thus determining the depth.

[0006] The maximum achievable depth resolution of a chromatic confocal sensor can be determined by the measurement range and the spectral resolution. The spectral resolution can be limited by the available bandwidth of light sources and the number of pixels available for analysis on a sensor, especially a spectrometer. Especially with so-called multispot sensors, the number of available pixels per spectrum can be limited.

[0007] DE 102 20 824 A1 describes an optical measuring device for measuring the shape of a particularly rough surface of a measurement object. The device comprises a device comprising at least one light source, an illumination optic, a measuring optic, and at least one detection unit for determining the intensity distribution of a measurement radiation reflected from the surface as a function of a focus position relative to the object surface. The measuring optic has an optical probe for generating at least one intermediate image of a surface area under observation.

[0008] FR 2 957156 A1 describes a device comprising a light source for generating an incident beam propagating along an optical axis and a beam-shaping device, i.e., a phase-shift mask, arranged between the light source and a converging lens, i.e., an immersion lens. The beam-shaping device modifies the incident beam to define a focal point and another focal point. The focal points are different from each other. A reflective device, e.g., a deformable mirror, is located midway between focal points to form an isotropic light spot by reflecting one light spot onto another light spot.

[0009] DE 103 56 412 A1 describes a multifocal confocal method and a confocal arrangement, in particular for the shape measurement of less cooperative objects, in particular also for the 3D tooth shape measurement in the mouth of a patient, with a light source, with a test object lens, with means for carrying out a depth scan, so that in the object space the relative position of the images from point light sources to the object surface changes, at least one additional, multifocal imaging system which is arranged at least approximately in the focal plane of the test object lens, which is facing away from the test object.In this confocal method, instead of a confocal signal with only two edges, signals with a large number of edges are generated, so that a confocal signal in a wavelet form is created over the depth and this signal is evaluated with the methods of cross-correlation, the evaluation methods of short-coherence interferometry or by means of wavelet transformation with regard to the depth position of at least one object point.

[0010] DE 10 2014 002 514 A1 describes a method and devices for generating multispectral illumination light with an addressable spectrum, for adaptive multispectral imaging, and for detecting structural and / or topographical information about an object or the distance to an object. The illumination device comprises a multispectral light source and a modulation device for temporally modulating the individual spectral components of the multispectral light source with different modulation frequencies, modulation frequency ranges, and / or modulation sequences.The multispectral light source comprises (i) at least one light source with a continuous, quasi-continuous, or frequency comb spectrum and wavelength-dispersive means, or (ii) an ensemble or array of monochromatic or quasi-monochromatic light sources with mutually different emission wavelengths or emission wavelength bands. The modulation device comprises (i) at least one electrically controllable spatial light modulator or (ii) a plurality of electronic control modules associated with the individual monochromatic or quasi-monochromatic light sources. The illumination device further comprises optical means for combining the individual modulated spectral components to form the multispectral illumination light with an addressable spectrum. Object of the invention

[0011] It is therefore an object of the present invention to provide a chromatic confocal sensor and a method that at least largely avoid the disadvantages of known devices and methods. In particular, it is intended to enable an enlargement of a measuring range without a loss of resolution. Disclosure of the invention

[0012] This object is achieved by a device and a method having the features of the independent patent claims. Preferred embodiments, which can be implemented individually or in combination, are presented in the dependent claims.

[0013] In the following, the terms "have", "have", "comprise" or "include" or any grammatical variations thereof are used in a non-exclusive manner. Accordingly, these terms can refer both to situations in which, apart from the feature introduced by these terms, no other features are present or to situations in which one or more other features are present. For example, the expression "A has B", "A has B", "A comprises B" or "A includes B" can refer both to the situation in which, apart from B, no other element is present in A (i.e., to a situation in which A consists exclusively of B) and to the situation in which, in addition to B, one or more other elements are present in A, for example element C, elements C and D, or even other elements.

[0014] It should also be noted that the terms "at least one" and "one or more," as well as grammatical variations of these terms or similar terms, when used in connection with one or more elements or features and intended to express that the element or feature may be provided once or multiple times, are generally used only once, for example when the feature or element is first introduced. When the feature or element is subsequently mentioned again, the corresponding term "at least one" or "one or more" is generally no longer used, without limiting the possibility that the feature or element may be provided once or multiple times.

[0015] Furthermore, the terms “preferably”, “in particular”, “for example” or similar terms are used hereinafter in connection with optional features, without limiting alternative embodiments. Thus, features introduced by these terms are optional features, and these features are not intended to limit the scope of the claims, and in particular the independent claims. Thus, as those skilled in the art will recognize, the invention can also be carried out using other embodiments. Similarly, features introduced by “in one embodiment of the invention” or by “in an embodiment of the invention” are understood as optional features, without limiting alternative embodiments or the scope of the independent claims.Furthermore, these introductory expressions are intended to leave untouched all possibilities of combining the features introduced thereby with other features, whether optional or non-optional.

[0016] In a first aspect of the present invention, a confocal chromatic sensor for determining coordinates of at least one measurement object is proposed.

[0017] A confocal chromatic sensor can basically be understood as an optical sensor that has at least one confocal chromatic beam path. In the context of the present invention, the term "beam path" can be understood as a path of light rays through optical elements. The chromatic confocal sensor can be configured to focus portions of an illuminating light beam with different wavelengths in different focal planes along an optical axis of the sensor. The confocal chromatic sensor can have an optical axis in the viewing direction of the sensor element. The optical axis can be an axis of the coordinate system, for example the z-axis. Further axes, for example the x-axis and y-axis, can be provided perpendicular to the z-axis.For example, a first portion of the illumination light beam with a first wavelength can be focused in a first focal plane, for example at a first point, in particular a first z-coordinate, on the optical axis, and a second portion of the illumination light beam with a second wavelength, which is different from the first wavelength, can be focused in a second focal plane, for example at a second point, in particular a second z-coordinate, which is different from the first point. Within the scope of the present invention, a "chromatically confocal beam path" can be understood as a beam path in which an illumination beam path and a detection beam path are confocal for at least one wavelength of the illumination light beam.In particular, for at least one wavelength of the illuminating light beam, the condition can be met that a first focus is located on the surface of the measurement object and, at the same time, a second focus is located in an opening, in particular at a point in the opening, of a diaphragm element arranged in front of a sensor element in a propagation direction of a light beam remitted by the measurement object. The confocal chromatic sensor can be configured 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 non-contact distance sensor in the field of coordinate metrology or can be used in a non-contact distance sensor.

[0018] In the context of the present invention, a measurement object can generally be understood as any shaped object to be measured. 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 the context of the present invention, the coordinates of a measurement object can be understood as coordinates on a surface of the measurement object to be measured, in particular height coordinates. For this purpose, one or more coordinate systems can be used. For example, a Cartesian coordinate system or a spherical coordinate system can be used. Other coordinate systems are also conceivable.

[0019] The confocal chromatic sensor includes - at least one first aperture element; - at least one illumination device which is configured to generate at least one illumination light beam and to illuminate the measurement object through the first aperture element; - at least one sensor element, wherein the sensor element is configured to detect at least one detection light beam emanating from the measurement object and to determine at least one spectral distribution; - at least one second aperture element which is arranged in front of the sensor element in a propagation direction of the detection light beam; - at least one multifocal optical element which is designed to generate at least two chromatic confocal measuring areas lying one behind the other in a propagation direction of the illuminating light beam; - at least one evaluation unit which is configured to determine a height coordinate of the measuring object from the spectral distribution.

[0020] In the context of the present invention, an “aperture element” can basically be understood as an optical element or component of the confocal chromatic sensor which is designed to limit the extent of a beam of rays. The designations “first” and “second” aperture element are to be understood as purely designations and in particular provide no information about a sequence or whether the confocal chromatic sensor has further aperture elements. The first aperture element and the second aperture element can be designed as an optical element with at least one opening of any shape and / or adjustability. For example, the opening of the aperture element can have a diameter in the micrometer range, for example the diameter can be 20 µm. For example, the first and second aperture elements can have a so-called pinhole.

[0021] The first aperture element can be configured to limit a light beam generated by the illumination device such that the aperture element acts as a point light source. The first aperture element can be arranged in front of the illumination device. The first aperture element can act as a confocal aperture.

[0022] The confocal chromatic sensor comprises at least one illumination device configured to generate at least one illumination light beam and to illuminate the measurement object through the first aperture element. Within the scope of the present invention, an illumination device can be understood as any device configured to generate at least one light beam. The illumination device can have at least one light source. The illumination device can have at least one polychromatic light source and / or at least one white light source. The light source can have a broad and evenly distributed spectral density.In the context of the present invention, “illuminating the measurement object through” can be understood to mean that the illumination device is configured to illuminate the first aperture element and further to illuminate the surface, in particular a point or an area on the surface, of the measurement object.

[0023] In the context of the present invention, “light” can 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 being referred to as near infrared (NIR), and the range from 15 µm to 1000 µm as far infrared (FIR). The term ultraviolet basically covers a spectral range from 100 nm to 380 nm. In the context of the present invention, visible light, i.e. light from the visible spectral range, is preferably used.

[0024] The term "light beam" can generally be understood as an amount of light emitted and / or sent out in a specific direction. The light beam can be a bundle of rays. The term "illumination light beam" can be understood as a light beam generated by the illumination device and illuminating the measurement object, in particular the surface of the measurement object. "At least one detection light beam emanating from the measurement object" can be understood as a light beam that is remitted by the measurement object, in particular by the surface of the measurement object, and is detectable by the sensor element.

[0025] The detection light beam may have a propagation direction such that the detection light beam illuminates the second aperture element and the sensor element.

[0026] The confocal chromatic sensor comprises at least one sensor element, wherein the sensor element is configured to detect at least one detection light beam emanating from the measurement object and to determine at least one spectral distribution. Within the scope of the present invention, a "sensor element" can be understood as any device configured to detect at least one optical measurement variable, for example an intensity, of the detection light beam and to generate a corresponding signal, for example an electrical signal, for example an analog and / or a digital signal. Determining a spectral distribution can be understood as measuring and / or determining the intensity of the detection light beam as a function of wavelength. The spectral distribution can comprise 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.

[0027] The confocal chromatic sensor comprises at least one second aperture element, which is arranged in front of the sensor element in the propagation direction of the detection light beam. The second aperture element can be configured as a sensor aperture. A sensor element can be arranged on a rear side of the second aperture element. The second aperture element can be arranged such that light remitted by the measurement object can strike the second aperture element. The second aperture element can be configured to illuminate the sensor element. The second aperture element can act as a confocal aperture. For a wavelength of the illumination light beam, a focus can be located on the surface of the measurement object. At the same time, for this wavelength of the detection light beam, a focus can be located at a point in the center of an opening of the second aperture element, so that the intensity on the sensor element is maximum for this wavelength.The second aperture element can be configured to mask out all other spectral components of the detection light beam.

[0028] The confocal chromatic sensor comprises at least one multifocal optical element configured to generate at least two chromatic confocal measurement areas located one behind the other in a propagation direction of the illumination light beam. Within the scope of the present invention, an optical element can be understood as any optical component or part.

[0029] In the context of the present invention, a multifocal optical element can be understood as an optical element that is configured to focus passing light into two or more focal lengths. The multifocal optical element can be selected from the group consisting of: at least one bifocal lens; at least one multifocal lens. The multifocal optical element can comprise at least one refractive and / or at least one diffractive optical element. The multifocal optical element can comprise a lens group and / or a lens system.

[0030] The multifocal optical element is configured to generate at least two consecutive chromatic confocal measurement areas. The multifocal optical element can be configured to focus at least a portion of the illumination light beam having one wavelength along the optical axis into at least two focal planes, in particular into a plurality of focal planes. The multifocal optical element can be configured to focus the portions of the illumination light beam having different wavelengths along the optical axis into different focal planes. The multifocal optical element can be configured to focus the portions of the illumination light beam having different wavelengths in two or more focal planes along the optical axis.The multifocal optical element can be configured to focus the components of the illumination light beam with different wavelengths in at least two focal planes along the optical axis. For example, the multifocal optical element can be configured to focus at least two components of the illumination light beam with different wavelengths in at least two focal planes along the optical axis. The multifocal optical element can be configured to focus the components of the illumination light beam with different wavelengths in a plurality of focal planes along the optical axis. The distance between the focal planes can be smaller than a measurement range defined by a spectrum of the illumination device.Within the scope of the present invention, the term "chromatic confocal measuring range" can be understood as a range along the optical axis in which the components of the illuminating light beam with different wavelengths are each focused once in a respective focal plane. For example, the multifocal optical element can generate a first and a second chromatic confocal measuring range. For example, the multifocal optical element can be configured to generate a plurality of chromatic confocal measuring ranges. The order of the focal planes of the wavelengths in the respective chromatic confocal measuring ranges can be identical; in particular, the order of the focal planes can be periodic.Within the context of the present invention, the term "consecutive" can be understood to mean that the first chromatic confocal measuring region and the second confocal measuring region are arranged one behind the other along the z-axis and / or follow one another. The first chromatic confocal measuring region and the second chromatic confocal measuring region can partially overlap or can be configured completely separate from one another. For example, the chromatic confocal measuring regions can be consecutive or overlap.

[0031] The illumination light beam can have a plurality of wavelengths. For example, the illumination light beam can have a plurality of wavelengths in a range from 380 nm to 780 nm. The multifocal optical element can be a multifocal optical element with chromatic aberration and / or have chromatically aberrative properties. In particular, the multifocal optical element can be configured to focus portions of the illumination light beam with different wavelengths into different focal planes along an optical axis of the sensor element. A focal plane can generally be understood as a plane that is arranged perpendicular to the optical axis and in which a focus of the illumination light beam is arranged. In particular, the focus can be arranged on the optical axis or parallel to the optical axis.

[0032] The confocal chromatic sensor can have at least one transfer device. The transfer device can be configured as part of the multifocal optical element or as a separate element. The transfer device can be configured to guide and / or direct light generated by the illumination device onto the measurement object, in particular onto the surface of the measurement object. Furthermore, the transfer device can be configured to guide and / or direct light remitted and / or reflected by the measurement object onto the second diaphragm element. 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.

[0033] The confocal chromatic sensor comprises at least one evaluation unit configured to determine a height coordinate of the measurement object from the spectral distribution. "An evaluation unit" can generally be understood to mean an electronic device configured to evaluate signals generated by the sensor element. For example, one or more electronic connections can be provided between the sensor element and the evaluation unit 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 configured by programming to control the sensor element.The evaluation unit can further comprise at least one interface, for example, an electronic interface and / or a human-machine interface, such as an input / output device such as a display and / or a keyboard. The evaluation unit can be configured centrally or decentrally, for example. Other configurations are also conceivable.

[0034] The evaluation unit can be configured to determine at least one intensity maximum of the spectral distribution. The spectral distribution can have at least one intensity maximum. The spectral distribution can, in particular, have a plurality of intensity maxima. As explained above, the multifocal optical element can be configured to focus the portions of the illumination light beam into different focal planes along the optical axis, for example, the z-axis. The multifocal optical element can be configured to focus at least a portion of the illumination light beam with one wavelength along the optical axis into at least two focal planes, in particular into a plurality of focal planes.The multifocal optical element can further be configured to focus the portions of the illumination light beam with different wavelengths in a plurality of focal planes along the optical axis, for example, the z-axis, and thus generate a plurality of chromatic confocal measurement ranges. The confocal chromatic sensor can be configured and / or arranged such that the surface of the measurement object is located at the focus of a wavelength of a chromatic confocal measurement range. A sharp light spot can be imaged on the second aperture element when the surface of the measurement object is located at the focus of a wavelength of a chromatic confocal measurement range. The light spot can illuminate the sensor element with maximum intensity, so that the sensor element detects an intensity maximum in the spectral distribution.The second aperture element can be configured to filter out all other spectral components of the detection light beam that do not illuminate the sensor element with maximum intensity. The evaluation unit can be configured to detect the intensity maximum.

[0035] The evaluation unit can be configured to assign a wavelength to the intensity maximum. The evaluation unit can be configured to assign a focal plane and thus a coordinate on the optical axis to the wavelength assigned to the intensity maximum. The coordinate on the optical axis can correspond to a height coordinate of the measurement object. The evaluation unit can be configured to assign a chromatic confocal measurement range to the intensity maximum. Assigning an intensity maximum to a wavelength and a chromatic confocal measurement range can enable a unique determination of a height coordinate of the measurement object. The evaluation unit can be configured to identify the wavelengths of the spectral distribution that have an intensity maximum and to determine a number of these wavelengths in the spectral distribution, thus uniquely assigning a chromatic confocal measurement range to each intensity maximum.

[0036] For example, the multifocal optical element can be configured to generate at least a first and a second chromatic confocal measuring range, which partially overlap. A different number of chromatic confocal measuring ranges is also possible. For example, the illumination light beam can have a first wavelength, a second wavelength, and a third wavelength. The first, second, and third wavelengths can each be focused into a first, second, and third focal plane in the first chromatic confocal measuring range and the second chromatic confocal measuring range. The first, second, and third focal planes can be arranged one behind the other in the respective measuring range in the propagation direction of the illumination light beam along the optical axis, for example in the order mentioned.The first chromatic confocal measuring range can be arranged upstream of the second chromatic confocal measuring range in the propagation direction of the illuminating light beam along the optical axis. For example, the first chromatic confocal measuring range and the second chromatic confocal measuring range can overlap such that the focal plane of the second wavelength of the first chromatic confocal measuring range and the focal plane of the first wavelength of the second chromatic confocal measuring range coincide and / or are identical, and such that the focal plane of the third wavelength of the first chromatic confocal measuring range and the focal plane of the second wavelength of the second chromatic confocal measuring range coincide and / or are identical.If the surface of the measurement object is located in the focal plane of the first wavelength of the first chromatic confocal measurement range, the sensor element can detect a single intensity maximum in the spectral distribution at the first wavelength. The evaluation unit can assign this intensity maximum to the first chromatic confocal measurement range. If the surface of the measurement object is located in the focal plane of the third wavelength of the second chromatic confocal measurement range, the sensor element can detect a single intensity maximum in the spectral distribution at the third wavelength. The evaluation unit can assign this intensity maximum to the second chromatic confocal measurement range.If the surface of the measurement object is located in the common focal plane of the second wavelength of the first chromatic confocal measuring range and the first wavelength of the second chromatic confocal measuring range, the sensor element can detect two intensity maxima in the spectral distribution. The evaluation unit can be configured to detect the intensity maxima and assign each intensity maximum a wavelength, for example, the first wavelength or the second wavelength, and a chromatic confocal measuring range, for example, the first or second chromatic confocal measuring range. For example, the sensor element can detect two intensity maxima in the spectral distribution: a first intensity maximum at the first wavelength and a second intensity maximum at the second wavelength.The evaluation unit can be configured to identify the first wavelength and the second wavelength and to determine that the spectral distribution has two intensity maxima, thus assigning the second chromatic confocal measurement range to the first intensity maximum and the first chromatic confocal measurement range to the second intensity maximum. The evaluation unit can determine that the measurement object is located in the common focal plane of the second wavelength of the first chromatic confocal measurement range and the first wavelength of the second chromatic confocal measurement range, and can unambiguously determine a height coordinate. Overlapping enables a unique assignment of the intensity maxima to the chromatic confocal measurement ranges and thus a unique determination of the height coordinate.If the chromatic confocal measuring areas are designed separately, a clear assignment may be possible using at least one additional piece of information, for example a known nature of the object and / or another measuring method.

[0037] The confocal chromatic sensor may comprise at least one multi-spot sensor. The sensor element may be configured to detect a plurality of detection light beams. For example, the sensor element may comprise a plurality of pixels.

[0038] The confocal chromatic sensor can have an array of chromatic confocal beam paths. The confocal chromatic sensor can have a plurality of illumination light beams. For example, the illumination device can be configured to generate a plurality of illumination light beams. For example, the first diaphragm element can be configured to split a light beam generated by the illumination device into a plurality of illumination light beams, for example using at least one diaphragm system. The multifocal optical element can be configured to focus the illumination light beams into different planes, in particular into different planes parallel to the optical axis. The multifocal optical element can be configured to arrange the chromatic confocal measuring areas one behind the other along the optical axis and in different planes parallel to the optical axis.

[0039] For example, the multifocal optical element can be configured to focus at least two illuminating light beams into at least two different planes parallel to the optical axis and to generate at least two consecutive chromatic confocal measuring ranges, in particular two at least partially overlapping chromatic confocal measuring ranges. For example, the multifocal optical element can be configured to focus at least two illuminating light beams into at least two different planes parallel to the optical axis and to generate a chromatic confocal measuring range each. The chromatic confocal measuring ranges of the at least two illuminating light beams can be configured as consecutive, separate, or partially overlapping measuring ranges, for example, in different planes parallel to the optical axis along the optical axis.The chromatic confocal measurement areas can be arranged separately or partially overlapping. Overlapping allows for a clear assignment of the intensity maxima to the chromatic confocal measurement areas, thus allowing for a clear determination of the height coordinate. With a separate configuration of the chromatic confocal measurement areas, a clear assignment can be possible using at least one piece of additional information, such as a known nature of the object.

[0040] The first aperture element and the second aperture element can have at least one aperture system. The aperture system can be selected from the group consisting of: at least two apertures; an aperture structure; a mask structure, in particular chrome masks, which are arranged on an at least partially transparent body. For example, an aperture structure can be applied to a transparent body. For example, absorbing layers having at least one opening can be applied to the transparent body. For example, chrome masks can be applied to the transparent body, for example a glass plate. The detection light beams can be observed through aperture elements arranged in multiple planes, in particular in different planes parallel to the optical axis. The sensor element can be configured to determine the spectral distribution of the detection light beams.For example, at least one spectrometer area can be provided for each detection light beam.

[0041] In a further aspect, a method for determining the coordinates of at least one measurement object is proposed. The method comprises the following steps: - generating at least one illuminating light beam with at least one illuminating device; - Illuminating the measuring object by at least one first aperture element; - Detecting at least one detection light beam emanating from the measurement object with at least one sensor element, wherein at least one second aperture element is arranged in front of the sensor element in a propagation direction of the detection light beam; - Determining at least one spectral distribution; - generating at least two chromatic confocal measuring areas arranged one behind the other in a propagation direction of the illuminating light beam with at least one multifocal optical element; - Determining a height coordinate of the measuring object from the spectral distribution with at least one evaluation unit.

[0042] The method steps can be performed in the specified order, with one or more of the steps being able to be performed at least partially simultaneously, and with one or more of the steps being able to be repeated multiple times. Furthermore, further steps can be performed additionally, regardless of whether they are mentioned in the present application or not. A confocal chromatic sensor according to the invention can be used in the method. For details regarding the method according to the invention, reference is made to the description of the confocal chromatic sensor according to the invention.

[0043] The device and method according to the invention are advantageous over known methods and devices. The measuring range of chromatic confocal sensors can be increased without loss of resolution and without movement of mechanical parts. At the same time, telecentricity, or perspective, can be maintained. Furthermore, the use of a multi-spot sensor can enable thickness measurement of transparent bodies or step gauge blocks.

[0044] In summary, the following embodiments are particularly preferred within the scope of the present invention: Embodiment 1: Confocal chromatic sensor for determining coordinates of at least one measurement object comprising - at least one first aperture element; - at least one illumination device which is configured to generate at least one illumination light beam and to illuminate the measurement object through the first aperture element; - at least one sensor element, wherein the sensor element is configured to detect at least one detection light beam emanating from the measurement object and to determine at least one spectral distribution; - at least one second aperture element which is arranged in front of the sensor element in a propagation direction of the detection light beam; - at least one multifocal optical element which is designed to generate at least two chromatic confocal measuring areas lying one behind the other in a propagation direction of the illuminating light beam; - at least one evaluation unit which is configured to determine a height coordinate of the measuring object from the spectral distribution. Embodiment 2: Confocal chromatic sensor according to the preceding embodiment, wherein the multifocal optical element is selected from the group consisting of: at least one bifocal lens; at least one multifocal lens. Embodiment 3: Confocal chromatic sensor according to one of the preceding embodiments, wherein the multifocal optical element is a multifocal optical element with chromatic aberration. Embodiment 4: Confocal chromatic sensor according to the preceding embodiment, wherein the multifocal optical element is configured to focus portions of the illumination light beam having different wavelengths in at least two focal planes along an optical axis. Embodiment 5: Confocal chromatic sensor according to the preceding embodiment, wherein a distance of the focal planes is smaller than a measuring range defined by a spectrum of the illumination device. Embodiment 6: Confocal chromatic sensor according to one of the preceding embodiments, wherein the chromatic confocal measuring areas are consecutive or at least partially overlapping. Embodiment 7: Confocal chromatic sensor according to one of the preceding embodiments, wherein the multifocal optical element comprises a lens group and / or a lens system. Embodiment 8: Confocal chromatic sensor according to one of the preceding embodiments, wherein the confocal chromatic sensor comprises at least one transfer device. Embodiment 9: Confocal chromatic sensor according to one of the preceding embodiments, wherein the spectral distribution comprises an intensity distribution depending on a wavelength. Embodiment 10: Confocal chromatic sensor according to one of the preceding embodiments, wherein the sensor element is a spectrally resolving detector. Embodiment 11: Confocal chromatic sensor according to one of the preceding embodiments, wherein the illumination device comprises at least one polychromatic light source and / or at least one white light source. Embodiment 12: Confocal chromatic sensor according to the preceding embodiment, wherein the light source has a broad and evenly distributed spectral density. Embodiment 13: Confocal chromatic sensor according to one of the preceding embodiments, wherein the evaluation unit is configured to determine at least one intensity maximum of the spectral distribution. Embodiment 14: Confocal chromatic sensor according to the preceding embodiment, wherein the control and evaluation unit is configured to assign a wavelength to the intensity maximum. Embodiment 15: Confocal chromatic sensor according to one of the two preceding embodiments, wherein the evaluation unit is configured to assign a chromatic confocal measuring range to the intensity maximum. Embodiment 16: Confocal chromatic sensor according to one of the three preceding embodiments, wherein the evaluation unit is configured to identify wavelengths of the spectral distribution which have an intensity maximum and to determine a number of these wavelengths in the spectral distribution and thus to unambiguously assign a chromatic confocal measuring range to each intensity maximum. Embodiment 17: Confocal chromatic sensor according to one of the preceding embodiments, wherein the confocal chromatic sensor comprises at least one multispot sensor. Embodiment 18: Confocal chromatic sensor according to the preceding embodiment, wherein the confocal chromatic sensor has an array of confocal optical paths. Embodiment 19: Confocal chromatic sensor according to one of the two preceding embodiments, wherein the first diaphragm element and the second diaphragm element comprise at least one diaphragm system, wherein the diaphragm system is selected from the group consisting of: at least two diaphragms; a mask structure. Embodiment 20: Method for determining coordinates of at least one measurement object, the method comprising the following method steps: - generating at least one illuminating light beam with at least one illuminating device; - Illuminating the measuring object by at least one first aperture element; - Detecting at least one detection light beam emanating from the measurement object with at least one sensor element, wherein at least one second aperture element is arranged in front of the sensor element in a propagation direction of the detection light beam; - Determining at least one spectral distribution; - generating at least two chromatic confocal measuring areas arranged one behind the other in a propagation direction of the illuminating light beam with at least one multifocal optical element; - Determining a height coordinate of the measuring object from the spectral distribution with at least one evaluation unit. Short description of the characters

[0045] Further details and features of the invention will become apparent from the following description of preferred embodiments, particularly in conjunction with the subclaims. The respective features can be implemented individually or in combination with one another. The invention is not limited to the embodiments. The embodiments are illustrated schematically in the figures. Identical reference numerals in the individual figures designate identical or functionally identical elements, or elements that correspond to one another in terms of their functions.

[0046] In detail: Fig. 1 is a schematic representation of an embodiment of a confocal chromatic sensor according to the invention; Fig. 2A to 2C each show an assignment of a chromatic confocal measuring range to a spectral distribution; and Fig. 3A and Fig. 3B is a schematic representation of an embodiment of a confocal chromatic sensor according to the invention with a multi-spot sensor and a schematic representation of an aperture system of the confocal chromatic sensor. Examples of implementation

[0047] Fig. 1 shows a schematic representation of an embodiment of a confocal chromatic sensor 110 according to the invention for determining coordinates of at least one measurement object 112. The confocal chromatic sensor comprises at least one first aperture element 114. The first aperture element 114 can be configured as an optical element with at least one arbitrarily shaped and / or adjustable aperture. For example, the aperture of the aperture element can have a diameter in the micrometer range, for example, the diameter can be 20 µm. For example, the first aperture element 114 can have a so-called pinhole.

[0048] The confocal chromatic sensor 110 comprises at least one illumination device 116 configured to generate at least one illumination light beam 118 and to illuminate the measurement object 112 through the first aperture element 114. The first aperture element 114 can be configured to limit a light beam generated by the illumination device 116 such that the first aperture element 114 acts as a point light source. The first aperture element 114 can be arranged in front of the illumination device. The first aperture element 114 can act as a confocal aperture.

[0049] The illumination device 116 may include at least one light source. The illumination device 116 may include at least one polychromatic light source and / or at least one white light source. The light source may have a broad and evenly distributed spectral density.

[0050] The confocal chromatic sensor 110 comprises at least one sensor element 120. The sensor element 120 is configured to detect at least one detection light beam 122 emanating from the measurement object 112 and to determine at least one spectral distribution. The spectral distribution may include an intensity distribution as a function of a wavelength. The sensor element 120 may be and / or include a spectrally resolving detector. In particular, the sensor element 120 may be and / or include a spectrometer.

[0051] The confocal chromatic sensor 110 comprises at least one second aperture element 124, which is arranged in front of the sensor element 120 in a propagation direction 126 of the detection light beam 122. The second aperture element 124 can be configured as a sensor aperture. The sensor element 120 can be arranged on a rear side of the second aperture element 124. The second aperture element 124 can be arranged such that light remitted by the measurement object 112 can strike the second aperture element 124. The second aperture element 124 can be configured to illuminate the sensor element 120. The second aperture element 124 can act as a confocal aperture.

[0052] For a wavelength λ of the illumination light beam 118, a focus may be located on a surface of the measurement object 112. Fig. 1 shows, by way of example, an illumination light beam 118 having a first wavelength 128, a second wavelength 130, and a third wavelength 132. If the focus of a wavelength is located on the surface of the measurement object 112, a focus for this wavelength of the detection light beam 122 can be located at a point in the center of the second aperture element 124, so that the intensity on the sensor element 120 is maximum for this wavelength. The second aperture element 124 can be configured to mask out all other spectral components of the detection light beam.

[0053] The confocal chromatic sensor 110 comprises at least one multifocal optical element 134, which is configured to generate at least two chromatic confocal measuring areas 138 arranged one behind the other in a propagation direction 136 of the illumination light beam 118. The multifocal optical element 134 can be configured to focus passing light into two or more focal lengths. The multifocal optical element 134 can be selected from the group consisting of: at least one bifocal lens; at least one multifocal lens. The multifocal optical element 134 can comprise at least one refractive and / or at least one diffractive optical element. The multifocal optical element 134 can comprise a lens group and / or a lens system.

[0054] The multifocal optical element 134 can be configured to focus at least a portion of the illumination light beam 118 having one wavelength along the optical axis into at least two focal planes, in particular into a plurality of focal planes. The multifocal optical element 134 can be configured to focus the portions of the illumination light beam 118 having different wavelengths along the optical axis into different focal planes. The multifocal optical element 134 can be a multifocal optical element with chromatic aberration and / or can have chromatically aberrative properties. The multifocal optical element 134 can be configured to focus the portions of the illumination light beam 118 in each case in two or more focal planes along an optical axis 140.The multifocal optical element 134 can be configured to focus the portions of the illumination light beam 118 with different wavelengths in at least two focal planes along the optical axis 140. In the embodiment shown in . Fig. In the embodiment shown in Figure 1, the multifocal optical element 134 can be configured to focus the first wavelength 128 into a first focal plane 144, the second wavelength 130 into a second focal plane 146, and the third wavelength 132 into a third focal plane 148 in a first chromatic confocal measuring range 142. Furthermore, the multifocal optical element 134 can be configured to focus the first wavelength 128 into a fourth focal plane 152, the second wavelength 130 into a fifth focal plane 154, and the third wavelength 132 into a sixth focal plane 156 in a second chromatic confocal measuring range 150. The second focal plane 146 and the fourth focal plane 152, as well as the third focal plane 148 and the fifth focal plane 154, can be identical.The first chromatic confocal measurement region 142 and the second chromatic confocal measurement region 150 may at least partially overlap or may be configured to be completely separate from one another. For example, the chromatic confocal measurement regions 138 may be consecutive or overlapping.

[0055] The confocal chromatic sensor 110 comprises at least one evaluation unit 158, which is configured to determine a height coordinate of the measurement object 112 from the spectral distribution. The evaluation unit 158 ​​can, for example, comprise at least one data processing device, for example at least one computer or microcontroller.

[0056] The evaluation unit 158 ​​can be configured to determine at least one intensity maximum of the spectral distribution. The evaluation unit 158 ​​can be configured to assign a wavelength to the intensity maximum. The evaluation unit 158 ​​can be configured to assign a focal plane and thus a coordinate on the optical axis 140 to the wavelength assigned to the intensity maximum. The coordinate on the optical axis 140 can correspond to a height coordinate of the measurement object 112. The evaluation unit can be configured to assign a chromatic confocal measurement range to the intensity maximum. The evaluation unit 158 ​​can be configured to identify the wavelengths of the spectral distribution that have an intensity maximum and to determine a number of these wavelengths in the spectral distribution, thus uniquely assigning a chromatic confocal measurement range to each intensity maximum. Fig. 2A to 2C each show an assignment of a chromatic confocal measuring range 138 to a spectral distribution.

[0057] In the Fig. 2A, left side, the first focal plane 144 of the first wavelength 128 of the first chromatic confocal measuring range 142 can be arranged on the measurement object 112, in particular on the surface of the measurement object 112. The sensor element 120 can determine a spectral distribution. In Fig. 2A, right side, shows the intensity I as a function of the wavelength λ. The sensor element 120 can detect a single intensity maximum in the spectral distribution at the first wavelength 128. The evaluation unit 158 ​​can be configured to identify the first wavelength 128, determine that the spectral distribution has a single intensity maximum, and thus unambiguously assign the first chromatic confocal measurement range 142 to the intensity maximum. The evaluation unit 158 ​​can unambiguously determine a height coordinate from the identified wavelength and the assigned chromatic confocal measurement range.

[0058] In the Fig. 2B, left side, the second focal plane 146 of the second wavelength 130 of the first chromatic confocal measuring range 142, which is identical to the fourth focal plane 146 of the first wavelength 128 of the second chromatic confocal measuring range 150, can be arranged on the measurement object 112, in particular on the surface of the measurement object 112. The sensor element 120 can determine a spectral distribution, see Fig. 2B, right side. The sensor element 120 can detect two intensity maxima in the spectral distribution, a first intensity maximum 160 at the first wavelength 128 and a second intensity maximum 162 at the second wavelength 130. The evaluation unit 158 ​​can be configured to identify the first wavelength 128 and the second wavelength 130, determine that the spectral distribution has two intensity maxima, and thus assign the second chromatic confocal measurement range 150 to the first intensity maximum 160 and the first chromatic confocal measurement range 142 to the second intensity maximum 162. The evaluation unit 158 ​​can determine that the measurement object 112 is located in the common focal plane of the second wavelength 130 of the first chromatic confocal measuring range 142 and the first wavelength 128 of the second chromatic confocal measuring range 150, and can unambiguously determine a height coordinate.

[0059] In the Fig. In the example shown in Figure 2C, left side, the sixth focal plane 156 of the third wavelength 132 of the second chromatic confocal measurement range 150 can be arranged on the measurement object 112, in particular on the surface of the measurement object 112. The sensor element 120 can detect a single intensity maximum in the spectral distribution at the third wavelength 132. The evaluation unit 158 ​​can be configured to identify the third wavelength 132, determine that the spectral distribution has a single intensity maximum, and thus unambiguously assign the second chromatic confocal measurement range 150 to the intensity maximum. The evaluation unit 158 ​​can unambiguously determine a height coordinate from the identified wavelength and the assigned chromatic confocal measurement range.

[0060] Fig. 3A shows a schematic representation of an embodiment of a confocal chromatic sensor 110 according to the invention with a multi-spot sensor 164. The confocal chromatic sensor 110 can have at least one multi-spot sensor 164. The sensor element can be configured to detect a plurality of detection light beams 122. For example, the sensor element 120 can have a plurality of pixels.

[0061] The confocal chromatic sensor 110 can have an array of chromatic confocal beam paths. The confocal chromatic sensor 110 can have a plurality of illumination light beams 118. For example, the illumination device 116 can be configured to generate a plurality of illumination light beams. For example, the first diaphragm element 114 can be configured to split a light beam generated by the illumination device 116 into a plurality of illumination light beams 118, for example, using at least one diaphragm system 166. The multifocal optical element 134 can be configured to focus the illumination light beams 118 into different planes, in particular into different planes parallel to the optical axis 140. Fig. 3A shows an example in which two illumination light beams 118 are focused in two different focal planes 168 one behind the other and in different planes parallel to the optical axis 140. For example, the multifocal optical element 134 can be configured to focus at least two illumination light beams 118 into at least two different planes parallel to the optical axis 140 and to generate at least two consecutive chromatic confocal measurement regions 138 in each case, in particular two at least partially overlapping chromatic confocal measurement regions 138. For example, the multifocal optical element 134 can be configured to focus at least two illumination light beams 118 into at least two different planes parallel to the optical axis 140 and to generate a chromatic confocal measurement region 138 in each case.The chromatic confocal measuring regions 138 of the at least two illumination light beams 118 can be configured as separate, consecutive measuring regions. Overlapping enables a clear assignment of the intensity maxima to the chromatic confocal measuring regions 138 and thus a clear determination of the height coordinate. With a separate configuration of the chromatic confocal measuring regions 138, a clear assignment may be possible using at least one piece of additional information, for example, a known nature of the object and / or another measuring method.

[0062] The confocal chromatic sensor 110 may include at least one transfer device 170. The transfer device 170 may be configured to focus a plurality of detection beams 122 onto the second aperture element 124. The confocal chromatic sensor 110 may include at least one further transfer device 172 configured to guide and / or direct light generated by the illumination device 116 onto the measurement object 112. The further transfer device 172 may be at least one beam splitter.

[0063] Fig. 3B shows an embodiment of a diaphragm element, in particular the first diaphragm element 114 and the second diaphragm element 124. The design of the second diaphragm element 124 is described below by way of example. The first diaphragm element 114 and the second diaphragm element 124 can be configured identically. The second diaphragm element 124 can have at least one diaphragm system 166. The diaphragm system 166 can be selected from the group consisting of: at least two diaphragms; a diaphragm structure; a mask structure, in particular chrome masks, which are arranged on an at least partially transparent body. Fig.Figure 3B shows a diaphragm structure 166 applied to a transparent body 174. For example, absorbing layers 176 having at least one opening 178 can be applied to the transparent body 174. For example, chromium masks can be applied to the transparent body 174, for example, a glass plate. The detection light beams 122 can be observed through diaphragm elements arranged in multiple planes, in particular in different planes parallel to the optical axis 140. List of reference symbols 110 Confocal chromatic sensor 112 measurement object 114 First aperture element 116 Lighting device 118 Illumination light beam 120 sensor element 122 Detection light beam 124 second aperture element 126 Propagation direction of the detection light beam 128 First Wavelength 130 Second Wavelength 132 Third Wavelength 134 Multifocal optical element 136 Direction of propagation of the illuminating light beam 138 Chromatic confocal measuring range 140 Optical axis 142 First chromatic confocal measuring range 144 First focal plane 146 Second focal plane 148 Third focal level 150 Second chromatic confocal measuring range 152 Fourth focal plane 154 Fifth focal plane 156 Sixth focal plane 158 Evaluation unit 160 First intensity maximum 162 Second intensity maximum 164 Multispot sensor 166 aperture system 168 focal plane 170 Transfer device 172 Additional transfer device 174 Transparent Body 176 Absorbent layer 178 Opening

Claims

[1] Confocal chromatic sensor (110) for determining coordinates of at least one measurement object (112) comprising - at least one first aperture element (114); - at least one illumination device (116) which is configured to generate at least one illumination light beam (118) and to illuminate the measurement object (112) through the first aperture element (114); - at least one sensor element (120), wherein the sensor element (120) is configured to detect at least one detection light beam (122) emanating from the measurement object (112) and to determine at least one spectral distribution; - at least one second aperture element (124) which is arranged in front of the sensor element (120) in a propagation direction of the detection light beam (126); - at least one multifocal optical element (134) which is designed to generate at least two chromatically confocal measuring areas (138) lying one behind the other in a propagation direction of the illuminating light beam (136); - at least one evaluation unit (158) which is configured to determine a height coordinate of the measurement object (112) from the spectral distribution. [2] Confocal chromatic sensor (110) according to the preceding claim, wherein the multifocal optical element (134) is selected from the group consisting of: at least one bifocal lens; at least one multifocal lens. [3] Confocal chromatic sensor (110) according to one of the preceding claims, wherein the multifocal optical element (134) is a multifocal optical element (134) with chromatic aberration, wherein the multifocal optical element (134) is configured to focus portions of the illumination light beam (118) with different wavelengths at different focal planes along an optical axis (140) of the sensor element (120). [4] Confocal chromatic sensor (110) according to claim 3, wherein the multifocal optical element (134) is further configured to focus the respective portions of the illumination light beam (118) into at least two successive focal planes. [5] Confocal chromatic sensor (110) according to one of the preceding claims, wherein the sensor element (120) is a spectrally resolving detector. [6] Confocal chromatic sensor (110) according to one of the preceding claims, wherein the illumination device (116) comprises at least one polychromatic light source and / or at least one white light source. [7] Confocal chromatic sensor (110) according to one of the preceding claims, wherein the evaluation unit (158) is configured to determine at least one intensity maximum of the spectral distribution and to assign a wavelength to the intensity maximum. [8] Confocal chromatic sensor (110) according to claim 7, wherein the evaluation unit (158) is configured to assign a chromatic confocal measuring range (138) to the intensity maximum. [9] Confocal chromatic sensor (110) according to claim 7 or 8, wherein the evaluation unit (158) is configured to identify wavelengths of the spectral distribution which have an intensity maximum and to determine a number of these wavelengths in the spectral distribution and thus to unambiguously assign a chromatic confocal measuring range (138) to each intensity maximum. [10] Confocal chromatic sensor (110) according to one of the preceding claims, wherein the confocal chromatic sensor (110) comprises at least one multispot sensor (164). [11] Method for determining coordinates of at least one measurement object (112), the method comprising the following method steps: - generating at least one illumination light beam (118) with at least one illumination device (116); - illuminating the measurement object (112) by at least one first aperture element (114); - detecting at least one detection light beam (122) emanating from the measurement object (112) with at least one sensor element (120), wherein at least one second aperture element (124) is arranged in front of the sensor element (120) in a propagation direction of the detection light beam (126); - Determining at least one spectral distribution; - generating at least two chromatically confocal measuring areas (138) arranged one behind the other in a propagation direction of the illuminating light beam (136) with at least one multifocal optical element (134); - Determining a height coordinate of the measurement object (112) from the spectral distribution with at least one evaluation unit (158).

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