DE102016219632A1 - Chromatic confocal sensor for determining coordinates of at least one measurement object - Google Patents

Abstract

A confocal chromatic sensor (110) for determining coordinates of at least one measurement object (112) is proposed. The confocal chromatic sensor comprises: at least a first aperture element (114); - at least one illumination device (116) which is set up to generate at least one illumination light beam (118) and to illuminate the measurement object (112) through the first diaphragm element (114); - At least one sensor element (120), wherein the sensor element (120) is arranged to detect at least one of the measurement object (112) emanating detection light beam (122) and to determine at least one spectral distribution; - At least a second diaphragm 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 adapted to generate at least two in a propagation direction of the illumination light beam (136) one behind the other lying chromatic confocal measuring ranges (138); - At least one evaluation unit (158) which is adapted to determine a height coordinate of the measurement object (112) from the spectral distribution.

Description

Field of the invention

The invention relates to a confocal chromatic sensor and a method for determining coordinates of at least one measurement object. In particular, the present invention relates to the field of coordinate metrology using a non-contact coordinate measuring machine.

State of the art

Various devices and methods for determining coordinates of a measurement object are known from the prior art. For example, methods are used for topography surveys, such as triangulation methods. For example, measuring methods are known which decompose a measuring range into periods, for example interferometers and strip projectors. Also known are confocal distance sensors. In such sensors, a depth determination is carried out by an evaluation of an intensity distribution along a height coordinate z.

In contrast to measuring methods in which a measuring range is decomposed into periods, as for example in interferometers or strip projectors, with confocal sensors a number of resolvable depth steps can be limited, for example to 1000. Thus, such sensors can either have a high resolution with a small measuring range or a low resolution can be achieved with a large measuring range.

Further, in confocal sensors, the height coordinate z on a surface of the measurement object can be determined by displacement of the optical elements, so that a measured value recording with a multiplicity of images may be necessary. In addition, technical problems can occur in the realization of a fast high-precision kinematics.

Known confocal chromatic sensors, which allow a measurement of the height coordinate z with a single image. Basically, chromatic aberration sensing lenses are used in such sensors which focus portions of a light beam having different wavelengths in different focal planes along an optical axis of the sensor. Each wavelength of the light beam can be assigned such a height coordinate. If a focus of a wavelength is located on a surface of the measurement object, an intensity maximum can be measured for a sensor element of the confocal chromatic sensor for this wavelength and thus the depth can be determined.

A maximum achievable depth resolution of a chromatic confocal sensor can be determined by the measuring range and a spectral resolution. The spectral resolution may be limited by an available bandwidth of light sources and an available number of pixels of a sensor, in particular a spectrometer. Especially with so-called multi-spot sensors, a number of the available pixels per spectrum can be limited.

Object of the invention

It is therefore an object of the present invention to provide a chromatically confocal sensor and a method which at least largely avoid the disadvantages of known devices and methods. In particular, an enlargement of a measuring range without a loss of resolution is to be made possible.

Disclosure of the invention

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

Hereinafter, the terms "having", "having", "including" or "including" or any grammatical variations thereof are used in a non-exclusive manner. Accordingly, these terms may refer to situations in which, besides the feature introduced by these terms, there are no other features or situations in which one or more other features are present. For example, the expression "A has B", "A has B", "A includes B" or "A includes B" can both refer to the situation in which, apart from B, there is no further element in A. (ie a situation in which A consists exclusively of B) as well as the situation in which, in addition to B, one or more further elements in A are present, for example element C, elements C and D or even further elements.

It is further to be understood that the terms "at least one" and "one or more" and grammatical variations of these terms or similar terms, when used in conjunction with one or more elements or features, are intended to express that element or feature in a simple manner or may be provided more than once, are usually used only once, for example, at the first introduction of the feature or Element. In a subsequent re-mention of the feature or element, 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 single or multiple.

Furthermore, the terms "preferably", "in particular", "for example" or similar terms are used below in connection with optional features, without restricting alternative embodiments thereof. Thus, features introduced by these terms are optional features, and it is not intended by these features to limit the scope of the claims and, in particular, the independent claims. Thus, as those skilled in the art will recognize, the invention may be practiced using other embodiments. Similarly, features introduced by "in one embodiment of the invention" or by "in one embodiment of the invention" are to be understood as optional features without, however, being construed as limiting alternative embodiments or the scope of the independent claims. Furthermore, these introductory expressions are intended to preserve all possibilities of combining the features introduced thereby with other features, be they optional or non-optional features.

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

Under a confocal chromatic sensor can basically be understood an optical sensor which has at least one confocal chromatic beam path. In the context of the present invention, the term "beam path" can be understood to mean a course of light beams through optical elements. The chromatic confocal sensor may be configured to focus portions of an illuminating light beam having different wavelengths in different focal planes along an optical axis of the sensor. The confocal chromatic sensor may have an optical axis in the direction of the sensor element. The optical axis may be an axis of the coordinate system, for example the z-axis. Perpendicular to the z-axis further axes, such as x-axis and y-axis, may be provided. For example, a first portion of the illumination light beam having 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 at a second wavelength, which differs from the first first wavelength is different, can be focused in a second focal plane, for example a second point, in particular a second z-coordinate, which is different from the first point. In the context 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, the condition can be fulfilled for at least one wavelength of the illumination light beam that there is a first focus on the surface of the measurement object and at the same time a second focus is in an opening, in particular at a point in the opening, of an aperture element which is in a propagation direction 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 may be a non-contact distance sensor in the field of coordinate metrology or may be used in a non-contact distance sensor.

In the context of the present invention, a measuring object can generally be understood to be an arbitrarily 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. Other measurement objects are also conceivable. Coordinates of a measurement object in the context of the present invention can be understood as coordinates on a surface to be measured of the measurement object, in particular height 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.

• – mindestens ein erstes Blendenelement;
• – mindestens eine Beleuchtungsvorrichtung, welche eingerichtet ist, mindestens einen Beleuchtungslichtstrahl zu erzeugen und das Messobjekt durch das erste Blendenelement hindurch zu beleuchten;
• – mindestens ein Sensorelement, wobei das Sensorelement eingerichtet ist, mindestens einen vom Messobjekt ausgehenden Detektionslichtstrahl zu detektieren und mindestens eine Spektralverteilung zu bestimmen;
• – mindestens ein zweites Blendenelement, welches in einer Ausbreitungsrichtung des Detektionslichtstrahls vor dem Sensorelement angeordnet ist;
• – mindestens ein multifokales optisches Element, welches eingerichtet ist, mindestens zwei in einer Ausbreitungsrichtung des Beleuchtungslichtstrahls hintereinanderliegende chromatisch konfokale Messbereiche zu erzeugen;
• – mindestens eine Auswerteeinheit, welche eingerichtet ist, aus der Spektralverteilung eine Höhenkoordinate des Messobjekts zu bestimmen.

The confocal chromatic sensor comprises

• - At least a first panel member;
• At least one illumination device, which is set up to generate at least one illumination light beam and to illuminate the measurement object through the first diaphragm element;
• At least one sensor element, wherein the sensor element is set up to detect at least one detection light beam emanating from the measurement object and to determine at least one spectral distribution;
• - At least a second diaphragm element, which is arranged in a propagation direction of the detection light beam in front of the sensor element;
• At least one multifocal optical element which is set up to generate at least two chromatically confocal measuring ranges arranged one after the other in a propagation direction of the illuminating light beam;
• At least one evaluation unit, which is set up to determine a height coordinate of the measured object from the spectral distribution.

In the context of the present invention, an "aperture element" can basically be understood to mean an optical element or component of the confocal chromatic sensor which is set up to limit an expansion of a radiation beam. The term "first" and "second" diaphragm element are to be understood as pure designations and, in particular, provide no information about an order or whether the confocal chromatic sensor has further diaphragm elements. The first diaphragm element and the second diaphragm element can be designed as an optical element with at least one arbitrarily shaped and / or adjustable and / or adjustable opening. For example, the opening of the diaphragm element may have a diameter in the micrometer range, for example the diameter may be 20 μm. For example, the first and the second diaphragm element may have a so-called pinhole.

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

The confocal chromatic sensor comprises at least one illumination device which is set up to generate at least one illumination light beam and to illuminate the measurement object through the first diaphragm element. In the context of the present invention, a lighting device can be understood as any device which is set up to generate at least one light beam. The lighting device may have at least one light source. The illumination device may have 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. In the context of the present invention, the term "illuminating the test object" can be understood to mean that the lighting device is set up to illuminate the first diaphragm element and furthermore to illuminate the surface, in particular a point or a surface on the surface of the test object.

In the context of the present invention, "light" can be used to select electromagnetic radiation in at least one spectral range 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 generally covers a range from 780 nm to 1000 μm, the range from 780 nm to 1.4 μm being referred to as near infrared (NIR), and the range of 15 μm to 1000 μm is referred to as far infrared (FIR). The term ultraviolet basically comprises a spectral range of 100 nm to 380 nm. Preferably, in the context of the present invention, visible light, ie light from the visible spectral range, is used.

The term "light beam" can basically be understood to mean a quantity of light which is emitted and / or emitted in a specific direction. The light beam can be a beam. The term "illumination light beam" can be understood to mean a light beam which is generated by the illumination device and illuminates the measurement object, in particular the surface of the measurement object. The term "at least one detection light beam emanating from the measurement object" 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 the sensor element.

The detection light beam may have a propagation direction, so that the detection light beam illuminates the second diaphragm element and the sensor element.

The confocal chromatic sensor comprises at least one sensor element, wherein the sensor element is set up to detect at least one detection light beam emanating from the measurement object and to determine at least one spectral distribution. In the context of the present invention, a "sensor element" can be understood to be 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. A determination of a spectral distribution can be understood as meaning 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 may be and / or comprise a spectrometer.

The confocal chromatic sensor comprises at least one second diaphragm element, which is arranged in front of the sensor element in the propagation direction of the detection light beam. The second diaphragm element can be designed as a sensory diaphragm. On a rear side of the second diaphragm element, a sensor element can be arranged. The second diaphragm element may be arranged such that light reflected from the measurement object can strike the second diaphragm element. The second diaphragm element can be set up to illuminate the sensor element. The second diaphragm element can act as a confocal diaphragm. For a wavelength of the illumination light beam, a focus may be 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 a center of an opening of the second diaphragm element, so that the intensity on the sensor element becomes maximum for this wavelength. The second diaphragm element can be set up to hide all other spectral components of the detection light beam.

The confocal chromatic sensor comprises at least one multifocal optical element which is set up to generate at least two chromatically confocal measuring ranges arranged one behind the other in a propagation direction of the illuminating light beam. In the context of the present invention, an optical element can be understood to mean any optical component or any optical component.

In the context of the present invention, a multifocal optical element can be understood to be an optical element which is set up to focus transmitted light in two or more focal lengths. The multifocal optical element may be selected from the group consisting of: at least one bifocal lens; at least one multifocal lens. The multifocal optical element may comprise at least one refractive and / or at least one diffractive optical element. The multifocal optical element may comprise a lens group and / or a lens system.

The multifocal optical element is set up to produce at least two consecutive chromatically confocal measuring ranges. The multifocal optical element may be configured to focus at least a portion of the illumination light beam having a wavelength along the optical axis in at least two focal planes, in particular in a plurality of focal planes. The multifocal optical element may be configured to focus the portions of the illumination light beam of different wavelength along the optical axis into different focal planes. The multifocal optical element may be configured to focus the portions of the illumination light beam having different wavelengths respectively in two or more focal planes along the optical axis. The multifocal optical element can be set up to focus the components of the illumination light beam with different wavelengths in each case in at least two focal planes along the optical axis. For example, the multifocal optical element may be configured to focus at least two portions of the illumination light beam having different wavelengths on at least two focal planes along the optical axis. The multifocal optical element may be configured to focus the portions of the illumination light beam having different wavelengths each in a plurality of focal planes along the optical axis. A distance of the focal planes may be smaller than a measuring range defined by a spectrum of the illumination device. In the context of the present invention, the term "chromatically confocal measuring range" can be understood to mean a region along the optical axis in which the portions of the illumination light beam having different wavelengths are focused once in each case in one focal plane. For example, the multifocal optical element may produce first and second chromatic confocal measurement ranges. For example, the multifocal optical element may be configured to generate a plurality of chromatically confocal measuring ranges. An order of the focal planes of the wavelengths in the respective chromatically confocal measuring ranges may be identical, in particular, the order of the focal planes may be periodic. Within the scope of the present invention, the term "one behind the other" can be understood to mean that the first chromatically confocal measuring range and the second confocal measuring range are arranged one behind the other along the z-axis and / or follow one another. The first chromatic confocal measurement area and the second chromatic confocal measurement area may partially overlap or may be completely separated from one another. For example, the chromatic confocal measuring ranges may be consecutive or overlapping.

The illumination light beam may have a plurality of wavelengths. For example, the illumination light beam may have a plurality of wavelengths in a range of 380 nm to 780 nm. The multifocal optical element can be a multifocal optical element with be chromatic aberration and / or exhibit chromatic aberrative properties. In particular, the multifocal optical element can be set up to focus portions of the illumination light beam having different wavelengths into different focal planes along an optical axis of the sensor element. Here, a focal plane can basically be understood to mean a plane which 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.

The confocal chromatic sensor may include at least one transfer device. The transfer device may be configured as part of the multifocal optical element or as a separate element. The transfer device can be set up to guide and / or direct light generated by the illumination device to the measurement object, in particular to the surface of the measurement object. Furthermore, the transfer device can be set up to guide and / or direct light reflected and / or reflected by the measurement object onto the second diaphragm element. The transfer device may be selected from the group consisting of: at least one beam splitter; at least one lens; at least one lens group.

The confocal chromatic sensor comprises at least one evaluation unit, which is set up to determine a height coordinate of the measurement object from the spectral distribution. In this context, "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 comprise, for example, 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 be set up, for example by programming, to control the sensor element. The evaluation unit may 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 constructed, for example, centrally or decentrally. Other embodiments are conceivable.

The evaluation unit can be set up 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 multiplicity of intensity maxima. As stated above, the multifocal optical element may be configured to focus the components of the illumination light beam into different focal planes along the optical axis, for example the z-axis. The multifocal optical element may be configured to focus at least a portion of the illumination light beam having a wavelength along the optical axis in at least two focal planes, in particular in a plurality of focal planes. The multifocal optical element may be further configured to focus the portions of the illumination light beam having different wavelengths respectively in a plurality of focal planes along the optical axis, for example, the z-axis, to produce a plurality of chromatically confocal measurement areas. The confocal chromatic sensor may be arranged and / or arranged such that the surface of the measurement object is arranged in the focus of a wavelength of a chromatically confocal measurement area. When the surface of the measuring object is in the focus of a wavelength of a chromatically confocal measuring area, a sharp point of light can be imaged on the second screen element. 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 diaphragm element can be set up to hide all other spectral components of the detection light beam that do not illuminate the sensor element with maximum intensity. The evaluation unit can be set up to recognize the intensity maximum.

The evaluation unit can be set up to assign a wavelength to the intensity maximum. The evaluation unit can be set up to associate the wavelength assigned to the intensity maximum with a focal plane and thus a coordinate on the optical axis. The coordinate on the optical axis may correspond to a height coordinate of the measurement object. The evaluation unit can be set up to associate the intensity maximum with a chromatically confocal measuring range. An assignment of an intensity maximum to a wavelength and a chromatically confocal measuring range can enable a clear determination of a height coordinate of the measured object. The evaluation unit can be set up to identify the wavelengths of the spectral distribution which have an intensity maximum and to determine a number of these wavelengths in the spectral distribution and thus unambiguously associate a chromatically confocal measuring range with each intensity maximum.

For example, the multifocal optical element may be configured to generate at least a first and a second chromatic confocal measurement region, which partially overlap. A different number of chromatically confocal measuring ranges is possible. For example, the illumination light beam may have a first wavelength, a second wavelength, and a third wavelength. The first, the second and the third wavelength can each be focused in the first chromatic confocal measuring range and the second chromatically confocal measuring range into a first, second and third focal plane. The first, the second and the third focal plane can be arranged one behind the other in the respective measuring range in the direction of propagation of the illuminating light beam along the optical axis, for example in the stated sequence. The first chromatically confocal measuring range can be arranged in the propagation direction of the illumination light beam along the optical axis in front of the second chromatically confocal measuring range. For example, the first chromatic confocal measuring range and the second chromatic confocal measuring range may 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 identical and 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 identical. If the surface of the measurement object is located in the focal plane of the first wavelength of the first chromatically confocal measurement area, 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 chromatically confocal measuring range. If the surface of the measurement object is located in the focal plane of the third wavelength of the second chromatically confocal measurement area, 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 chromatically confocal measuring range. If the surface of the measurement object is located in the common focal plane of the second wavelength of the first chromatically confocal measurement area and the first wavelength of the second chromatically confocal measurement area, the sensor element can detect two intensity maxima in the spectral distribution. The evaluation unit can be set up to detect the intensity maxima and to associate with each intensity maximum a wavelength, for example the first wavelength or the second wavelength, and a chromatically confocal measuring range, for example the first or second chromatically 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 set up to identify the first wavelength and the second wavelength and to determine that the spectral distribution has two intensity maxima, and thus assign the second chromatic confocal measuring range to the first intensity maximum and the first chromatically confocal measuring range to the second intensity maximum. The evaluation unit may determine that the measurement object is located in the common focal plane of the second wavelength of the first chromatic confocal measurement area and the first wavelength of the second chromatic confocal measurement area, and uniquely determine a height coordinate. An overlap allows an unambiguous assignment of the intensity maxima to the chromatically confocal measuring ranges and thus an unambiguous determination of the height coordinate. In a separate embodiment of the chromatically confocal measuring ranges, an unambiguous assignment using at least one additional piece of information, for example a known quality of the object and / or a further measuring method, may be possible.

The confocal chromatic sensor may include 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 have a multiplicity of pixels.

The confocal chromatic sensor may include an array of chromatically confocal optical paths. The confocal chromatic sensor may include a plurality of illumination light beams. For example, the lighting device may be configured to generate a plurality of illumination light beams. For example, the first diaphragm element can be set up to divide 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 may be configured to focus the illumination light beams in different planes, in particular in different planes parallel to the optical axis. The multifocal optical element can be set up to arrange the chromatically confocal measuring areas along the optical axis one behind the other and in different planes parallel to the optical axis.

For example, the multifocal optical element may be arranged, at least two Focusing illumination light beams in at least two different Ebenden 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. By way of example, the multifocal optical element can be set up to focus at least two illumination light beams in at least two different planes parallel to the optical axis and in each case to generate a chromatically confocal measuring range. The chromatically confocal measuring ranges of the at least two illumination light beams can be configured, for example, in different planes parallel to the optical axis, along the optical axis as separate, partially overlapping measuring ranges lying one behind the other. The chromatically confocal measuring ranges can be arranged separately or partially overlapping. An overlap allows an unambiguous assignment of the intensity maxima to the chromatically confocal measuring ranges and thus an unambiguous determination of the height coordinate. In a separate embodiment of the chromatically confocal measuring ranges, an unambiguous assignment using at least one additional information, for example a known quality of the object, may be possible.

The first diaphragm element and the second diaphragm element can have at least one diaphragm system. The aperture system may be selected from the group consisting of: at least two apertures; a diaphragm structure; a mask structure, in particular chrome masks, which are arranged on an at least partially transparent body. For example, a diaphragm structure can be applied to a transparent body. For example, absorbent layers can be applied to the transparent body, which have at least one opening. For example, chrome masks can be applied to the transparent body, for example a glass plate. The detection light beams can be observed by diaphragm elements arranged in several planes, in particular in different planes parallel to the optical axis. The sensor element may 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.

• – Erzeugen mindestens eines Beleuchtungslichtstrahls mit mindestens einer Beleuchtungsvorrichtung;
• – Beleuchten des Messobjekts durch mindestens eine erstes Blendenelement;
• – Detektieren mindestens eines vom Messobjekt ausgehenden Detektionslichtstrahls mit mindestens einem Sensorelement, wobei mindestens ein zweites Blendenelement in einer Ausbreitungsrichtung des Detektionslichtstrahls vor dem Sensorelement angeordnet ist;
• – Bestimmen mindestens einer Spektralverteilung;
• – Erzeugen mindestens zweier in einer Ausbreitungsrichtung des Beleuchtungslichtstrahls hintereinanderliegender chromatisch konfokaler Messbereiche mit mindestens einem multifokalen optischen Element;
• – Bestimmen einer Höhenkoordinate des Messobjekts aus der Spektralverteilung mit mindestens einer Auswerteeinheit.

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

• Generating at least one illumination light beam with at least one illumination device;
• - Illuminating the test object by at least a first diaphragm element;
• Detecting at least one detection light beam emanating from the measurement object with at least one sensor element, wherein at least one second diaphragm 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 ranges lying one behind the other in a direction of propagation of the illuminating light beam with at least one multifocal optical element;
• - Determining a height coordinate of the measurement object from the spectral distribution with at least one evaluation unit.

In this case, the method steps can be carried out in the order indicated, wherein one or more of the steps can be carried out at least partially simultaneously and wherein one or more of the steps can be repeated several times. In addition, further steps, whether mentioned in the present application or not, may be additionally performed. In the method, a confocal chromatic sensor according to the invention can be used. For details relating to the method according to the invention, reference is made to the description of the confocal chromatic 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. An enlargement of the measuring range of chromatically confocal sensors can be made possible without loss of resolution and without movement of mechanical parts. At the same time, a telecentricity or perspective can be maintained. Further, use of a multi-spot sensor may allow for thickness measurement of transparent bodies or measurement of step gauges.

• – mindestens ein erstes Blendenelement;
• – mindestens eine Beleuchtungsvorrichtung, welche eingerichtet ist, mindestens einen Beleuchtungslichtstrahl zu erzeugen und das Messobjekt durch das erste Blendenelement hindurch zu beleuchten;
• – mindestens ein Sensorelement, wobei das Sensorelement eingerichtet ist, mindestens einen vom Messobjekt ausgehenden Detektionslichtstrahl zu detektieren und mindestens eine Spektralverteilung zu bestimmen;
• – mindestens ein zweites Blendenelement, welches in einer Ausbreitungsrichtung des Detektionslichtstrahls vor dem Sensorelement angeordnet ist;
• – mindestens ein multifokales optisches Element, welches eingerichtet ist, mindestens zwei in einer Ausbreitungsrichtung des Beleuchtungslichtstrahls hintereinanderliegende chromatisch konfokale Messbereiche zu erzeugen;
• – mindestens eine Auswerteeinheit, welche eingerichtet ist, aus der Spektralverteilung eine Höhenkoordinate des Messobjekts zu bestimmen.

In summary, the following embodiments are particularly preferred in the context of the present invention:
Embodiment 1: Confocal chromatic sensor for determining coordinates of at least one measurement object

• - At least a first panel member;
• - At least one lighting device which is adapted to generate at least one illumination light beam and the measurement object to illuminate through the first aperture element;
• At least one sensor element, wherein the sensor element is set up to detect at least one detection light beam emanating from the measurement object and to determine at least one spectral distribution;
• - At least a second diaphragm element, which is arranged in a propagation direction of the detection light beam in front of the sensor element;
• At least one multifocal optical element which is set up to generate at least two chromatically confocal measuring ranges arranged one after the other in a propagation direction of the illuminating light beam;
• At least one evaluation unit, which is set up to determine a height coordinate of the measured object from the spectral distribution.

Embodiment 2: A 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: A confocal chromatic sensor according to any one of the preceding embodiments, wherein the multifocal optical element is a multifocal optical element having chromatic aberration.

Embodiment 4: Confocal chromatic sensor according to the foregoing embodiment, wherein the multifocal optical element is arranged to focus portions of the illumination light beam having different wavelengths in at least two focal planes along an optical axis, respectively.

Embodiment 5: Confocal chromatic sensor according to the previous 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 chromatically confocal measuring ranges 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 has 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 as a function of 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 has at least one polychromatic light source and / or at least one white light source.

Embodiment 12: Confocal chromatic sensor according to the previous 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 set up 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 set up 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 set up in order to associate the intensity maximum with a chromatically confocal measuring range.

Embodiment 16: Confocal chromatic sensor according to one of the three preceding embodiments, wherein the evaluation unit is set up 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 unambiguously assign a chromatic confocal measuring range to each intensity maximum assign.

Embodiment 17: Confocal chromatic sensor according to one of the preceding embodiments, wherein the confocal chromatic sensor has at least one multi-spot sensor.

Embodiment 18: Confocal chromatic sensor according to the previous embodiment, wherein the confocal chromatic sensor comprises an array of confocal optical paths.

Embodiment 19: A confocal chromatic sensor according to one of the two preceding embodiments, wherein the first diaphragm element and the second diaphragm element have at least one diaphragm system, wherein the diaphragm system is selected from the group consisting of: at least two diaphragms; a mask structure.

• – Erzeugen mindestens eines Beleuchtungslichtstrahls mit mindestens einer Beleuchtungsvorrichtung;
• – Beleuchten des Messobjekts durch mindestens eine erstes Blendenelement;
• – Detektieren mindestens eines vom Messobjekt ausgehenden Detektionslichtstrahls mit mindestens einem Sensorelement, wobei mindestens ein zweites Blendenelement in einer Ausbreitungsrichtung des Detektionslichtstrahls vor dem Sensorelement angeordnet ist;
• – Bestimmen mindestens einer Spektralverteilung;
• – Erzeugen mindestens zweier in einer Ausbreitungsrichtung des Beleuchtungslichtstrahls hintereinanderliegender chromatisch konfokaler Messbereiche mit mindestens einem multifokalen optischen Element;
• – Bestimmen einer Höhenkoordinate des Messobjekts aus der Spektralverteilung mit mindestens einer Auswerteeinheit.

Embodiment 20: A method for determining coordinates of at least one measurement object, the method comprising the following method steps:

• Generating at least one illumination light beam with at least one illumination device;
• - Illuminating the test object by at least a first diaphragm element;
• Detecting at least one detection light beam emanating from the measurement object with at least one sensor element, wherein at least one second diaphragm 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 ranges lying one behind the other in a direction of propagation of the illuminating light beam with at least one multifocal optical element;
• - Determining a height coordinate of the measurement object from the spectral distribution with at least one evaluation unit.

Brief description of the figures

Further details and features of the invention will become apparent from the following description of preferred embodiments, in particular in conjunction with the subclaims. In this case, the respective features can be implemented on their own or in combination with one another. The invention is not limited to the embodiments. The embodiments are shown schematically in the figures. The same reference numerals in the individual figures designate the same or functionally identical or with respect to their functions corresponding elements.

In detail show:

1 a schematic representation of an embodiment of a confocal chromatic sensor according to the invention;

2A to 2C in each case an assignment of a chromatically confocal measuring range to a spectral distribution; and

3A and 3B a schematic representation of an embodiment of a confocal chromatic sensor according to the invention with Multispotsensor and a schematic representation of a diaphragm system of the confocal chromatic sensor.

embodiments

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

The confocal chromatic sensor 110 includes at least one lighting device 116 , which is set up, at least one illumination light beam 118 to generate and the measurement object 112 through the first panel element 114 through to illuminate. The first panel element 114 may be configured, one of the lighting device 116 to limit the generated light beam such that the first diaphragm element 114 acts as a point light source. The first panel element 114 can be arranged in front of the lighting device. The first panel element 114 can act as a confocal iris.

The lighting device 116 can have at least one light source. The lighting device 116 may comprise 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.

The confocal chromatic sensor 110 includes at least one sensor element 120 , The sensor element 120 is set up, at least one of the measured object 112 outgoing detection light beam 122 to detect and determine at least one spectral distribution. The spectral distribution may comprise an intensity distribution as a function of a wavelength. The sensor element 120 can be a spectrally resolving detector and / or include. In particular, the sensor element 120 be a spectrometer and / or include.

The confocal chromatic sensor 110 includes at least a second aperture element 124 which is in a propagation direction 126 of the detection light beam 122 in front of the sensor element 120 is arranged. The second aperture element 124 can be designed as a sensory aperture. On a back of the second panel element 124 can the sensor element 120 be arranged. The second aperture element 124 may be arranged such that of the measurement object 112 Remitted light on the second panel element 124 can meet. The second aperture element 124 can be set up, the sensor element 120 to illuminate. The second aperture element 124 can act as a confocal iris.

For a wavelength λ of the illumination light beam 118 may have a focus on a surface of the measurement object 112 are located. 1 shows an example of an illumination light beam 118 which is a first wavelength 128 , a second wavelength 130 and a third wavelength 132 having. Is the focus of a wavelength on the surface of the DUT? 112 , so may for this wavelength of the detection light beam 122 a focus at a point in a center of the second aperture element 124 so that for that wavelength the intensity on the sensor element 120 becomes maximum. The second aperture element 124 can be configured to hide all other spectral components of the detection light beam.

The confocal chromatic sensor 110 comprises at least one multifocal optical element 134 which is set up, at least two in a propagation direction 136 of the illumination light beam 118 consecutive chromatic confocal measuring ranges 138 to create. The multifocal optical element 134 may be arranged to focus transmitted light in two or more focal lengths. The multifocal optical element 134 may be selected from the group consisting of: at least one bifocal lens; at least one multifocal lens. The multifocal optical element 134 may comprise at least one refractive and / or at least one diffractive optical element. The multifocal optical element 134 may include a lens group and / or a lens system.

The multifocal optical element 134 may be arranged at least a portion of the illumination light beam 118 with a wavelength along the optical axis in at least two focal planes, in particular in a plurality of focal planes to focus. The multifocal optical element 134 can be arranged, the proportions of the illumination light beam 118 with different wavelength along the optical axis to focus in different focal planes. The multifocal optical element 134 may be a multifocal optical element with chromatic aberration and / or may have chromatic aberrative properties. The multifocal optical element 134 can be arranged, the proportions of the illumination light beam 118 each in two or more focal planes along an optical axis 140 to focus. The multifocal optical element 134 can be arranged, the proportions of the illumination light beam 118 with different wavelengths in at least two focal planes along the optical axis 140 to focus. In the in 1 In the embodiment shown, the multifocal optical element 134 be set up in a first chromatically confocal measuring range 142 the first wavelength 128 in a first focal plane 144 , the second wavelength 130 in a second focal plane 146 and the third wavelength 132 in a third focal plane 148 to focus. Next, the multifocal optical element 134 be set up in a second chromatically confocal measuring range 150 the first wavelength 128 in a fourth focal plane 152 , the second wavelength 130 in a fifth focal plane 154 and the third wavelength 132 in a sixth focal plane 156 to focus. 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 measuring range 142 and the second chromatic confocal range 150 may at least partially overlap or may be configured completely separated from each other. For example, the chromatically confocal measuring ranges 138 be consecutive or overlapping.

The confocal chromatic sensor 110 comprises at least one evaluation unit 158 , which is set up, a height coordinate of the measured object from the spectral distribution 112 to determine. The evaluation unit 158 For example, it may comprise at least one data processing device, for example at least one computer or microcontroller.

The evaluation unit 158 may be arranged to determine at least one intensity maximum of the spectral distribution. The evaluation unit 158 may be arranged to assign a wavelength to the intensity maximum. The evaluation unit 158 can be set, the intensity maximum associated with the wavelength of a focal plane and thus a coordinate on the optical axis 140 assigned. The coordinate on the optical axis 140 can be a height coordinate of the DUT 112 correspond. The evaluation unit can be set up to Intensity maximum to assign a chromatic confocal measuring range. The evaluation unit 158 can be set up to identify the wavelengths of the spectral distribution having an intensity maximum and to determine a number of these wavelengths in the spectral distribution and thus unambiguously assign a chromatic confocal measuring range to each intensity maximum. 2A to 2C each show an assignment of a chromatic confocal measuring range 138 to a spectral distribution.

In the in 2A , left side, example shown, the first focal plane 144 the first wavelength 128 of the first chromatic confocal measuring range 142 on the test object 112 , in particular on the surface of the measurement object 112 be arranged. The sensor element 120 can determine a spectral distribution. In 2A , right side, the intensity I is shown as a function of the wavelength λ. The sensor element 120 may have a single intensity maximum in the spectral distribution at the first wavelength 128 detect. The evaluation unit 158 can be set up, the first wavelength 128 to identify that the spectral distribution has a single intensity maximum, and thus the intensity maximum the first chromatic confocal measurement range 142 clearly assign. The evaluation unit 158 can uniquely determine a height coordinate from the identified wavelength and the associated chromatic confocal measurement range.

In the in 2 B , left side, example shown may be the second focal plane 146 the second wavelength 130 of the first chromatic confocal measuring range 142 which are identical to the fourth focal plane 146 the first wavelength 128 of the second chromatic confocal measuring range 150 is, on the test object 112 , in particular on the surface of the measurement object 112 be arranged. The sensor element 120 can determine a spectral distribution, see 2 B , right side. The sensor element 120 can have 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 , detect. The evaluation unit 158 can be set up, the first wavelength 128 and the second wavelength 130 to identify that the spectral distribution has two intensity maxima, and thus the first intensity maximum 160 the second chromatic confocal measuring range 150 and the second intensity maximum 162 the first chromatically confocal measuring range 142 assign. The evaluation unit 158 can determine that the measurement object 112 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 uniquely determine a height coordinate.

In the in 2C , left side, example shown, the sixth focal plane 156 the third wavelength 132 of the second chromatic confocal measuring range 150 on the test object 112 , in particular on the surface of the measurement object 112 be arranged. The sensor element 120 can have a single intensity maximum in the spectral distribution at the third wavelength 132 detect. The evaluation unit 158 can be set up, the third wavelength 132 to identify that the spectral distribution has a single intensity maximum, and thus the intensity maximum, the second chromatic confocal measurement range 150 clearly assign. The evaluation unit 158 can uniquely determine a height coordinate from the identified wavelength and the associated chromatic confocal measurement range.

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

The confocal chromatic sensor 110 may have an array of chromatically confocal optical paths. The confocal chromatic sensor 110 can be a variety of illumination light beams 118 exhibit. For example, the lighting device 116 be configured to generate a plurality of illumination light beams. For example, the first aperture element 114 be set up, one of the lighting device 116 generated light beam in a variety of illumination light beams 118 to divide, for example, using at least one aperture system 166 , The multifocal optical element 134 can be set up, the illumination light beams 118 in different planes, in particular in different planes parallel to the optical axis 140 to focus. 3A shows an example in which two illumination light beams 118 in two different focal planes 168 one behind the other and in different planes parallel to the optical axis 140 be focused. For example, the multifocal optical element 134 be set up, at least two illumination light beams 118 in at least two different planes parallel to the optical axis 140 to focus and in each case at least two consecutive chromatic confocal measuring ranges 138 in particular two at least partially overlapping chromatically confocal measuring ranges 138 , For example, the multifocal optical element 134 be set up, at least two illumination light beams 118 in at least two different planes parallel to the optical axis 140 to focus and in each case a chromatically confocal measuring range 138 to create. The chromatically confocal measuring ranges 138 the at least two illumination light beams 118 can be configured as consecutive, separate measuring ranges. An overlap allows an unambiguous assignment of the intensity maxima to the chromatically confocal measuring ranges 138 and so a clear determination of the height coordinate. In a separate embodiment of the chromatically confocal measuring ranges 138 an unambiguous assignment using at least one additional information, for example a known nature of the object and / or a further measuring method, may be possible.

The confocal chromatic sensor 110 can be at least one transfer device 170 exhibit. The transfer device 170 can be set up a variety of detection beams 122 on the second panel element 124 to focus. The confocal chromatic sensor 110 can be at least one more transfer device 172 which is arranged by the lighting device 116 generated light on the measured object 112 to lead and / or direct. The further transfer device 172 can be at least one beam splitter.

3B shows an embodiment of a diaphragm element, in particular of the first diaphragm element 114 and the second panel member 124 , By way of example, the embodiment of the second diaphragm element will be described below 124 described. The first panel element 114 and the second aperture element 124 can be identical. The second aperture element 124 can be at least one aperture system 166 exhibit. The aperture system 166 may be selected from the group consisting of: at least two apertures; a diaphragm structure; a mask structure, in particular chrome masks, which are arranged on an at least partially transparent body. 3B shows an aperture structure 166 pointing to a transparent body 174 is applied. For example, absorbent layers 176 on the transparent body 174 be applied, which has at least one opening 178 exhibit. For example, chrome masks on the transparent body 174 , For example, a glass plate, are applied. The detection light beams 122 can pass through in several planes, especially in different planes parallel to the optical axis 140 , arranged aperture elements are observed.

LIST OF REFERENCE NUMBERS

110

 Confocal chromatic sensor

112

 measurement object

114

 First panel element

116

 lighting device

118

 Illuminating 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

 Propagation direction of the illumination 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 plane

150

 Second chromatic confocal measuring range

152

 Fourth focal plane

154

 Fifth focal plane

156

 Sixth focal plane

158

 evaluation

160

 First intensity maximum

162

 Second intensity maximum

164

 Multi-spot sensor

166

 aperture system

168

 focal plane

170

 transfer device

172

 Further transfer device

174

 Transparent body

176

 Absorbing layer

178

 opening

Claims (11)

Confocal chromatic sensor ( 110 ) for determining coordinates of at least one measurement object ( 112 ) comprising - at least one first diaphragm element ( 114 ); At least one lighting device ( 116 ), which is set up, at least one illumination light beam ( 118 ) and the measurement object ( 112 ) through the first aperture element ( 114 ) through; At least one sensor element ( 120 ), wherein the sensor element ( 120 ) is arranged, at least one of the measured object ( 112 ) outgoing detection light beam ( 122 ) and to determine at least one spectral distribution; At least one second diaphragm element ( 124 ), which in a propagation direction of Detection light beam ( 126 ) in front of the sensor element ( 120 ) is arranged; At least one multifocal optical element ( 134 ) which is arranged at least two in a propagation direction of the illumination light beam (US Pat. 136 ) one behind the other chromatic confocal measuring ranges ( 138 ) to create; - at least one evaluation unit ( 158 ), which is set up, from the spectral distribution a height coordinate of the measurement object ( 112 ). 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. Confocal chromatic sensor ( 110 ) according to any one of the preceding claims, wherein the multifocal optical element ( 134 ) a multifocal optical element ( 134 ) with chromatic aberration, wherein the multifocal optical element ( 134 ), portions of the illumination light beam ( 118 ) with different wavelengths at different focal planes along an optical axis ( 140 ) of the sensor element ( 120 ) to focus. Confocal chromatic sensor ( 110 ) according to the preceding claim, wherein the multifocal optical element ( 134 ) is further set, the respective proportions of the illumination light beam ( 118 ) in each case to focus at least two successive focal planes. Confocal chromatic sensor ( 110 ) according to one of the preceding claims, wherein the sensor element ( 120 ) is a spectrally resolving detector. Confocal chromatic sensor ( 110 ) according to one of the preceding claims, wherein the lighting device ( 116 ) has at least one polychromatic light source and / or at least one white light source. Confocal chromatic sensor ( 110 ) according to one of the preceding claims, wherein the evaluation unit ( 158 ) is arranged to determine at least one intensity maximum of the spectral distribution and to assign a wavelength to the intensity maximum. Confocal chromatic sensor ( 110 ) according to the preceding claim, wherein the evaluation unit ( 158 ) is arranged to provide the intensity maximum a chromatically confocal measuring range ( 138 ). Confocal chromatic sensor ( 110 ) according to one of the two preceding claims, wherein the evaluation unit ( 158 ) is arranged 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 provide each chromaticity maximum a chromatically confocal measuring range ( 138 ). Confocal chromatic sensor ( 110 ) according to one of the preceding claims, wherein the confocal chromatic sensor ( 110 ) at least one multi-spot sensor ( 164 ) having. Method for determining coordinates of at least one test object ( 112 ), the method comprising the following method steps: - generating at least one illumination light beam ( 118 ) with at least one lighting device ( 116 ); - Illumination of the test object ( 112 ) by at least one first aperture element ( 114 ); Detecting at least one of the measured object 112 ) outgoing detection light beam ( 122 ) with at least one sensor element ( 120 ), wherein at least one second diaphragm element ( 124 ) in a direction of propagation of the detection light beam ( 126 ) in front of the sensor element ( 120 ) is arranged; Determining at least one spectral distribution; Generating at least two in a propagation direction of the illumination light beam ( 136 ) one behind the other chromatic confocal measuring ranges ( 138 ) 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 ).

Images