阅读说明：本技术 借助于激发荧光进行表面测量 (Surface measurement by means of fluorescence excitation ) 是由 托马斯·延森 杨征 J·斯蒂格瓦尔 于 2019-06-11 设计创作，主要内容包括：借助于激发荧光进行表面测量。一种测量物体的测量装置,其包括测距单元,该测距单元具有：射束发射单元,该射束发射单元生成测量辐射；和检测器(12),该检测器检测在物体表面上反射的测量辐射,所述检测器具有至少一个第一传感器。所述测距单元生成距离测量数据,并可以根据三角测量原理,借助所述测量辐射和所述反射测量辐射来生成反射测量数据作为第一距离测量数据。可以生成具有这样的波长谱的所述测量辐射,即,能够通过所述测量辐射与所述物体材料的相互作用激发荧光并且可以发射荧光,所述荧光的光谱和所述测量辐射的波长谱不同。所述检测器检测所述荧光,并且可以基于所述荧光来生成荧光测量数据作为第二距离测量数据。(Surface measurements are made by means of exciting fluorescence. A measuring apparatus for measuring an object, comprising a ranging unit having: a beam emission unit generating measurement radiation; and a detector (12) which detects the measuring radiation reflected on the object surface, said detector having at least one first sensor. The distance measuring unit generates distance measurement data and may generate reflection measurement data as first distance measurement data by means of the measurement radiation and the reflection measurement radiation according to the triangulation principle. The measuring radiation can be generated with a wavelength spectrum by which fluorescence can be excited by interaction with the object material and fluorescence can be emitted, the spectrum of the fluorescence being different from the wavelength spectrum of the measuring radiation. The detector detects the fluorescence and may generate fluorescence measurement data as second distance measurement data based on the fluorescence.)

1. A measuring device (1) for measuring an object (2), the measuring device (1) comprising a distance measuring unit (10) having:

a beam emission unit (11) configured to generate measurement radiation (13, 13a, 13b) having a prescribed wavelength spectrum; and

a detector (12) configured to detect reflected measurement radiation (14, 14a, 14b), in particular diffusely reflected measurement radiation, on a surface of the object, the detector having at least one first sensor (17, 17a, 17b),

wherein the distance measuring unit (10) is designed to generate distance measurement data and to generate reflection measurement data as first distance measurement data by emitting the measurement radiation (13, 13a, 13b) and detecting the reflection measurement radiation (14, 14a, 14b) according to the principle of triangulation,

it is characterized in that the preparation method is characterized in that,

-being able to generate said measurement radiation (13, 13a, 13b) with a wavelength spectrum: fluorescence can be excited and fluorescence (15) can be emitted by interaction of the measuring radiation (13, 13a, 13b) with the material of the object, wherein the fluorescence has a spectrum that differs from a wavelength spectrum of the measuring radiation,

the detector (12) is designed to detect the fluorescence, and

-being able to generate fluorescence measurement data as second distance measurement data based on the detection of the fluorescence (15).

2. Measuring device (1) according to claim 1,

it is characterized in that the preparation method is characterized in that,

the center wavelength of the wavelength spectrum is selected from the range between 250nm and 500nm, in particular 405nm or 450 nm.

3. Measuring device (1) according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the detector (12) comprises a first filter assembly (16) and the first filter assembly (16) provides a wavelength dependent separation of the reflected measurement radiation and the fluorescence in cooperation with the first sensor, in particular wherein the first filter assembly (16) is designed as a spatially distributed polychromatic filter, in particular as an RGB filter.

4. Measuring device (1) according to one of the claims 1 to 3,

it is characterized in that the preparation method is characterized in that,

the detector (12) comprises a second filter assembly and the second filter assembly is designed as a two-part alternating filter with a first filter region (16a) and a second filter region (16b), wherein,

the first filter region (16a) provides a transmission substantially exclusively for the wavelength spectrum, in particular for a central wavelength of the wavelength spectrum,

the second filter region (16b) is transmissive to the spectrum of the fluorescence, and

the first filter region (16a) and the second filter region (16b) can be arranged alternately, in particular sequentially, in the field of view of the first sensor (17).

5. The measuring device (1) according to any one of claims 1 to 4,

it is characterized in that the preparation method is characterized in that,

the beam emission unit comprises a first beam source (11a) and a second beam source (11b), and the measurement radiation (13) can be generated as a combination, in particular as a superposition, of the measurement radiation (13a) having a defined wavelength spectrum, which can be generated with the first beam source (11a), and a further measurement radiation (13b) having a further wavelength spectrum, which differs from the defined wavelength spectrum, which can be generated with the second beam source (11b),

in particular wherein the presence of a catalyst is preferred,

-the distance measuring unit (10) is designed to activate the first beam source (11a) and the second beam source (11b) as follows: the measurement radiation (13a) having the defined wavelength spectrum and the further measurement radiation (13b) having the further wavelength spectrum can be emitted alternately and successively at specific intervals, and

the ranging unit (10) is designed to activate the detector (12) as follows: first and second detections can be performed sequentially in synchronization with activation of the first and second beam sources.

6. The measuring device (1) according to any one of claims 1 to 5,

it is characterized in that the preparation method is characterized in that,

the detector (12) comprises a second sensor (17b) and is configured such that the reflected measurement radiation (14, 14a, 14b) can be detected with the first sensor (17, 17a) and the fluorescence (15) can be detected with the second sensor (17b), in particular wherein one filter unit (16a, 16b) is assigned to each of the first sensor (17, 17a) and the second sensor (17b) and each filter unit (16a, 16b) can provide a transmission substantially exclusively for the reflected measurement radiation or the fluorescence, respectively.

7. The measuring device (1) according to any one of claims 1 to 6,

it is characterized in that the preparation method is characterized in that,

the detector (12) comprises a beam splitter (19), and the beam splitter (19) is particularly designed dichroic for wavelength-dependent separation of the reflected measurement radiation (14, 14a, 14b) from the fluorescence (15).

8. The measuring device (1) according to any one of claims 1 to 7,

it is characterized in that the preparation method is characterized in that,

the at least one first sensor (17, 17a) comprises a first detection area and a second detection area, in particular spatially separated, and the detector (12) is configured to: the reflected measurement radiation (14, 14a, 14b) is detectable by interaction with the first detection zone and the fluorescence (15) is detectable by interaction with the second detection zone.

9. The measuring device (1) according to any one of claims 1 to 8,

it is characterized in that the preparation method is characterized in that,

the measuring device (1) comprises a control and processing unit, which is particularly configured to perform the method according to any one of claims 12 to 14.

10. Measuring device (1) according to claim 9,

it is characterized in that the preparation method is characterized in that,

the control and processing unit has a data fusion function configured to, upon execution,

continuously monitoring the detection for the measurement radiation and the detection for the fluorescence,

continuously deriving respective intensity information for respective detections of said measurement radiation and said fluorescence, and

generating a point cloud representing the surface of the object by selectively processing the reflectance measurement data and the fluorescence measurement data based on the intensity information, in particular wherein the distance measurement data is processed for respective object points for which a greater intensity is derived.

11. Measuring device (1) according to claim 9 or 10,

it is characterized in that the preparation method is characterized in that,

the control and processing unit includes a switching function configured to, when executed,

continuously detecting the measurement radiation or the fluorescence,

generating corresponding reflectance or fluorescence measurement data respectively,

continuously monitoring the detection for the measurement radiation or the detection for the fluorescence with respect to signal intensity,

continuously comparing said signal strength with a defined threshold value, and

switching between the detection for the measurement radiation and the detection for the fluorescence depending on the comparison.

12. A hybrid measurement method of measuring an object (2) comprising a material that fluoresces for a known wavelength range, the hybrid measurement method comprising the steps of:

generating and emitting measurement radiation (13, 13a, 13b) having a defined wavelength spectrum;

-scanning the irradiated object region with the measuring radiation (13, 13a, 13 b);

-detecting reflected measurement radiation (14, 14a, 14b), in particular diffuse reflected measurement radiation, on the surface;

generating reflection measurement data as first distance measurement data based on the detection of the reflection measurement radiation (14, 14a, 14b) according to triangulation principles,

it is characterized in that the preparation method is characterized in that,

-generating said measurement radiation (13, 13a, 13b) having the following wavelength spectrum: in the region of the scanning irradiation, fluorescence is excited as a result of the interaction of the measuring radiation (13, 13a, 13b) with the material of the object and fluorescence (15) is emitted at the object,

detecting the fluorescence (15), and

-generating fluorescence measurement data as second distance measurement data based on the detection of the fluorescence (15) according to triangulation principles.

13. The method of measurement according to claim 12,

it is characterized in that the preparation method is characterized in that,

generating a reflection point cloud (53) based on the reflection measurement data (51),

generating a fluorescence point cloud (63) based on the fluorescence measurement data (61), and

generating a representation of the surface of the object by combining the reflected point cloud and the fluorescent point cloud.

14. The measuring method according to claim 12 or 13,

it is characterized in that the preparation method is characterized in that,

-analyzing said reflectance measurement data (51) and said fluorescence measurement data (61) with respect to their respective qualities, in particular density, as a function of position with respect to the detection of said object region,

-performing a segmentation (70) of the object region based on the analysis,

-performing a combination of at least a part of the reflectance measurement data (51) and at least a part of the fluorescence measurement data (61) based on the segmentation.

15. A computer program product stored on a machine-readable carrier or embodied by electromagnetic waves, in particular when executed on a control and processing unit of a measurement apparatus (1) according to any one of claims 1 to 11, controlling and/or executing at least the following steps of the measurement method according to any one of claims 12 to 14:

-detecting the reflected measurement radiation (14, 14a, 14 b);

generating reflectance measurement data;

detecting the fluorescence (15); and

generating fluorescence measurement data.

Technical Field

The present invention relates to a measuring device and a method for measuring the surface of an object based on a hybrid measurement technique using the fluorescence effect.

Background

In many technical application fields there is a requirement to measure objects with high accuracy or for their composition. This applies in particular to the manufacturing industry, for which measuring and inspecting the surface of a workpiece is of high importance, in particular for quality control purposes.

For example, coordinate measuring machines that enable precise measurement of the geometry of an object surface, typically with micron-scale accuracy, are used for such applications. The objects to be measured may be, for example, engine blocks, gearboxes and tools. Known coordinate measuring machines measure a surface by establishing mechanical contact and scanning the surface. Examples thereof are gantry measuring machines such as described in DE 4325337 or DE 4325347. Another system is based on the use of an articulated arm, the measuring sensor of which can be moved along the surface, the measuring sensor being arranged at the end of a multi-part arm. Articulated arms in general are described, for example, in US 5,402,582 or EP 1474650.

Coordinate surface measurements permit determination of geometric deviations on the workpiece from corresponding target values. Therefore, a high accuracy specification of the manufacturing accuracy can be made with respect to the geometric deviation. It can thus be determined whether the shape and dimensions of the produced part are within specified tolerances and whether the assembly is to be regarded as a waste or good piece.

In the prior art, for example, a tactile sensor is used with such coordinate measuring devices as a standard measuring sensor, which consists of a ruby sphere mounted on a measuring rod. The deflection of the tactile sensor (in the case of a coordinate measuring machine designed for three-dimensional measurements in three directions X, Y and Z perpendicular to each other) is determined during scanning by means of a switching or distance measuring component. The position of the contact and hence the surface coordinates are calculated based on the switching point or deflection distance.

Furthermore, contactless measuring methods are known, in particular with optical sensors. By means of such an optical sensor, the surface topography can be measured very accurately with the emitted measuring beam, in particular a laser beam. The resolution of measuring the surface profile with an optical measuring sensor can be significantly higher than with a tactile measuring sensor. The simultaneous introduction of optical sensors into metrology with coordinate measuring machines is based, for example, on the emission of laser light onto the surface of an object for interferometric measurement (EP 2037214). Methods based on white light interferometry (DE 102005061464) and color confocal methods (FR 2738343) have also been proposed.

The equally effective method for optical surface measurement is based on the use of optical sensors whose measuring function is based on the principle of triangulation. For this purpose, the measuring radiation is directed onto the object to be measured and diffusely scattered on the object. After a corresponding reflection at a certain angle on the object surface, a portion of the emitted measuring light is detected with a detector at the sensor. To this end, the sensor of the detector may capture a depiction (e.g., as an image) of the illumination resulting from the incidence of the measurement radiation on the surface of the object. The distance may be calculated based on the position of the illumination depicted in the image according to a known relative arrangement of the beam emitter and detector.

The measuring radiation can be emitted in the form of lines, and the image sensor imaging the projected lines can be designed as a surface sensor. In this way, not only one item of distance information can be generated at one point, but also a plurality of measurement values can be detected.

Furthermore, such triangulation sensors may be designed as scanners. In this embodiment variant, the measuring radiation, whether as a moving point or line, can be guided along a scanning movement over the surface to be measured, while the corresponding distance is derived on the basis of the reflection generated in this case. The distance measurement data (e.g., Z-coordinate) is then correlated with the corresponding lateral object position (X-coordinate and Y-coordinate) based on the relative movement with respect to the object surface. As a result of this measurement, a point cloud may be obtained, which may represent the surface of the measured object in spatial dimensions and shape.

One advantage of using triangulation sensors in general is the relatively high measuring speed and the simultaneous contactless measurement.

One disadvantage of this measurement principle, for example, results in the need to measure surfaces that are not diffusely reflective or only diffusely reflective to a limited extent. For example, if a reflective or transparent area of the object is to be measured, there may be no measurement radiation along the detector direction that needs to be reflected for this purpose, since diffuse scattering or reflection usually does not occur on the surface. The measurement can only be successful here with a special arrangement of the sensors relative to the surface, which is, however, generally absent or unguided.

Furthermore, diffuse scattering due to surface defects such as scratches or dust may dominate, thereby greatly reducing measurement accuracy.

The measurement of objects therefore gives rise to the further disadvantage that the surface of the object is only partially diffusely reflective, while in other parts it is reflective or transparent. For optical measurements of such surfaces, very specific boundary conditions have to be met locally in each case. This is associated with a considerable technical effort and results in correspondingly long measurement times.

The above limitations make optical (triangulation) sensors appear to be unsuitable for measuring many components in the field of automotive construction or aircraft construction.

Disclosure of Invention

It is therefore an object of the present invention to provide an improved measuring device for surface measurement of an object, in which the above-mentioned disadvantages are overcome or reduced.

In particular, it is an object of the invention to specify a measuring device which offers enhanced robustness and reliability for surface measurements, in particular a wider range of use.

The invention is based on the following concept: in addition to the typical triangulation by means of reflected measuring radiation (e.g. laser radiation), the fluorescence effect and in this case the emitted fluorescence radiation are also utilized to generate additional distance information by means of the fluorescence radiation. Thus, the fluorescent radiation is captured in such a way with a detector (for example with a CCD or CMOS) positioned with respect to the known arrangement of the beam source: fluorescence-based distance measurement data can also be derived from triangulation principles.

In particular, plastic-based or glass-based materials absorb light in the UV range or in the violet or blue spectral range, whereby electrons in the material temporarily occupy a higher energy level and fall back to the original energy level again. The absorbed energy is then re-emitted in the form of spontaneous emission of fluorescence as a result of returning to a lower energy level. The fluorescence has a larger wavelength than the radiation used for excitation. Thus, radiation originating from transparent or reflective glass or plastic surfaces can be generated and detected by means of adapted detection.

Thus, for example, a surface provided with a reflective or non-diffusely reflective coating may become capable of corresponding measurements.

Also, materials such as polymethyl methacrylate (PMMA) or polyethylene terephthalate (PET) and glass ceramic materials are mentioned, for example. The absorption spectrum of the material is formed in such a way that a relatively large absorption capacity for electromagnetic radiation in the UV, violet or blue spectral range is provided and fluorescence is induced and/or excited upon absorption of the respective radiation. In this case, the excitation of fluorescence is based on the characteristics of the organic compounds present in the material.

As indicated before, it is preferred to excite fluorescence using radiation with a central wavelength in the blue or ultraviolet range between about 250nm and 450 nm.

In general, those materials having a sufficiently high absorption coefficient for the measurement wavelength used and a sufficiently high emission coefficient for the fluorescence can be measured with such an embodiment.

Furthermore, the differentiation of the detected radiation may be performed with the method according to the invention. This results in a significantly more reliable and accurate distance measurement based on different origins and characteristics of radiation originating from the object. The reflected measuring light is reflected on the surface, whereby the triangulated reference point is directly the surface point on the object. However, fluorescence is mostly generated inside the object material, whereby the reference point of the distance measurement can no longer be unambiguously associated with the surface. Furthermore, the spatial length distribution (e.g. gaussian distribution) of the measurement radiation is typically different from the spatial length distribution of the fluorescence radiation (the fluorescence radiation intensity is reduced and the distribution is broader with respect to the penetration depth of the measurement radiation into the material).

Therefore, distinguishing the detected radiation is advantageous for deriving accurate distance values.

The invention thus relates to a hybrid measuring device for measuring an object, wherein the measuring device comprises a distance measuring unit. The distance measuring unit has: a beam emission unit configured to generate measurement radiation having a prescribed wavelength spectrum; and a detector configured to detect, in particular diffusely reflected, measuring radiation reflected on the object surface, the detector having at least one first sensor. The distance measuring unit is further designed to generate distance measurement data, wherein reflection measurement data can be generated as first distance measurement data by means of emitting the measurement radiation and detecting the reflection measurement radiation according to the triangulation principle.

The measuring radiation can be generated with a wavelength spectrum such that fluorescence can be generated by interaction of the measuring radiation with the object material and can be emitted. The ability to excite fluorescence also typically depends on which material the object comprises. Thus, in particular, it is indicated that the wavelength of the incident measuring radiation is tuned to the object material to generate fluorescence. It is preferred that it is at least partially known from which material the object to be measured is made or composed, and that the measuring radiation used is selected accordingly. Preferably, the spectrum of the fluorescence and the wavelength spectrum of the measuring radiation are different.

Furthermore, the detector is designed to detect fluorescence, i.e. to be sensitive to light having a fluorescence wavelength. Thus, fluorescence measurement data may be generated as second distance measurement data (by means of triangulation) based on the detection of fluorescence.

The sensor can be designed, for example, as a planar image sensor (CCD or CMOS). Thus, when projecting the measurement radiation as light rays, distance information may be generated not only for one measurement point but for a plurality of measurement points along the line. The information can be provided as lines from a location and from the curve of the measuring radiation in the image that is detected with the sensor and reflected on the object.

The detector may comprise an optical assembly, in particular an objective lens, having one or more optical components (e.g. lenses, apertures, etc.). The detector is designed in particular as a camera.

In one embodiment, the center wavelength of the wavelength spectrum may be selected from the range between 250nm and 500nm, and may specifically be 450 nm. The wavelength of the measuring radiation is preferably in the visible blue range (about 450 nm). In this case, the measuring radiation is generated, for example, by means of a laser diode. Alternatively, the wavelength may be assigned to the UV range, i.e. the wavelength may be <400nm, for example. Using the mentioned wavelengths, fluorescence can be generated in particular in polymer-based or plastic-based materials, but also in glass.

The detector of the measurement device may include a first filter assembly, wherein. The first filter assembly provides wavelength dependent separation of reflected measurement radiation and fluorescence in cooperation with the first sensor. The filter thus enables the separation of two radiations originating from the object. It is advantageous, in particular, if, upon incidence of the measurement radiation, diffuse reflection of the radiation occurs and fluorescence is excited, and thus distance measurement data can be generated by means of both methods. In particular, the first filter assembly is designed as a spatially distributed polychromatic filter, in particular as an RGB filter. This may also be a component of a surface sensor in the form of an RGB matrix.

The filter may be a combination of multiple spatially distributed pixel level color filters with different transmission spectra, or may be implemented with a color camera having a Bayer pattern.

In one variant, the detector may comprise a second filter assembly, wherein the second filter assembly is designed as a two-part alternating filter with a first filter area and a second filter area. The second filter assembly may be alternatively or additionally disposed with respect to the first filter assembly. The first filter region provides a transmission that is substantially specific for the wavelength spectrum, in particular for the central wavelength of the wavelength spectrum. The second filter region provides a transmittance for the spectrum of the fluorescence. The first filter area and the second filter area may be alternately, in particular sequentially, positioned in the field of view of the first sensor. If desired, the light incident on the detector can therefore be filtered in such a way that fluorescence radiation or only reflected measurement radiation is incident on the sensor. The filter assembly may be manually operated or automatically or in a controlled manner.

The beam emission unit may further comprise a first beam source and a second beam source, and the measurement radiation may be generated as a combination, in particular an overlap, of measurement radiation with a defined wavelength spectrum, which may be generated with the first beam source, and another measurement radiation with another wavelength spectrum, which may be generated with the second beam source, which is different from the defined wavelength spectrum.

Instead of using two beam sources, a single beam source can be provided, which emits the measuring radiation, for example, at two different wavelengths.

In this way, a separation (for wavelength) of fluorescence excitation radiation and radiation to be reflected can be provided at the emitter. The detector can, for example, be designed to detect light at a measurement wavelength (for example, by means of a matched filter), wherein, for example, fluorescence is not expected but reflection occurs for this wavelength. Alternatively, the detector may be designed for detecting fluorescence, for example.

In this connection, the distance measuring unit can be designed to activate the first beam source and the second beam source in such a way that measurement radiation having a defined wavelength spectrum and further measurement radiation (fluorescence radiation) having a further wavelength spectrum can be emitted alternately in succession at specific intervals. Furthermore, the ranging unit may be designed to activate the detector in such a way that a first detection and a second detection may be performed sequentially and in synchronization with the activation of the first beam source and the second beam source. In this way, the detector can be designed, for example, to detect two radiation phenomena (reflection and fluorescence), but the detection can be synchronized with the corresponding emission, so that fluorescence or reflected light is detected with image detection only and the detected radiation can be unambiguously distinguished.

The detector may comprise a second sensor and may be configured in such a way that the reflected measurement radiation is detectable with the first sensor and the fluorescence is detectable with the second sensor, in particular wherein one filter unit is associated with each of the first and second sensors and a respective filter unit is substantially exclusively transmissive for the reflected measurement radiation or the fluorescence, respectively.

The detector may comprise a dichroic beam splitter or a dichroic beam splitter, and the beam splitter may be designed for wavelength dependent separation of the reflected measurement radiation from the fluorescence.

In general, other types of beam splitters or filters are also conceivable, which work, for example, according to the interference principle.

In one embodiment, the sensor comprises a first detection area and a second detection area, in particular spatially separated, and the detector may be configured in such a way that the reflected measurement radiation can be detected by interaction with the first detection area and the fluorescence can be detected by interaction with the second detection area. For this purpose, the respective radiation component can be deflected onto the respective detection area.

According to the invention, the measuring device may comprise a control and processing unit, which is particularly configured to carry out the method described hereinafter.

The control and processing unit may include a data fusion function configured in the following manner: upon execution, the detection of the measurement radiation and the fluorescence is continuously monitored, respective intensity information of the respective detection of the measurement radiation and the fluorescence is continuously derived, and a point cloud representing the object surface is generated by selectively processing the reflectance measurement data and the fluorescence measurement data based on the intensity information, in particular wherein distance measurement data deriving a larger intensity is processed for respective object points.

Thus, a database can be used for each detection area of the object surface, from which a more accurate and complete surface delineation can be expected.

The control and processing unit may further comprise a switching function configured in the following manner: upon execution, the measurement radiation or the fluorescence is continuously detected, corresponding reflectance measurement data or fluorescence measurement data, respectively, is generated, the detection of the measurement radiation or the fluorescence is continuously monitored for signal intensity, the signal intensity is continuously compared with a prescribed threshold value, and switching between the detection of the measurement radiation and the detection of the fluorescence is performed depending on the comparison.

Thus, if it is determined that there is no detectable fluorescence signal, a switch can be made to reflectance measurement accordingly, and if it is determined that there is no detectable measurement radiation, a switch can be made to fluorescence measurement accordingly.

Furthermore, the invention relates to a hybrid measuring method for measuring an object, which object comprises a material that fluoresces with respect to a known wavelength range. The measuring method comprises the following steps: generating and emitting at least measurement radiation having a defined wavelength spectrum; scanning the irradiated object region with the measuring radiation; detecting the measuring radiation reflected, in particular diffusely reflected, on the surface of the object; and generating reflectance measurement data as first distance measurement data based on the detected reflectance measurement radiation according to triangulation principles.

In the context of the measuring method, the measuring radiation is generated with a wavelength spectrum such that, in the context of the scanning irradiation, fluorescence is excited as a result of the interaction of the measuring radiation with the object material and fluorescence is emitted at the object. The fluorescence is detected, and fluorescence measurement data is generated as second distance measurement data based on the detected fluorescence according to the principle of triangulation.

In one embodiment, a reflection point cloud may be generated based on the reflection measurement data and a fluorescence point cloud may be generated based on the fluorescence measurement data. A representation of the object surface may then be generated by combining the reflection point cloud and the fluorescence point cloud. It is thus possible to perform data fusion in which, as a result, the surface of the partially transparent object can be completely imaged by means of optical, non-contact measurement.

In particular, the reflectance measurement data and the fluorescence measurement data may be analyzed with respect to the detected object region as a function of location for their respective form, mass or density, wherein segmentation of the object region may be performed based on the analysis. Then, combining at least a portion of the reflectance measurement data with at least a portion of the fluorescence measurement data may be performed based on the segmenting.

The invention also relates to a computer program product stored on a machine-readable carrier or embodied by electromagnetic waves for controlling and/or executing at least the following steps of the above-mentioned measuring method: detecting the reflected measurement radiation; generating reflectance measurement data; detecting fluorescence; and generating fluorescence measurement data. The above-described computer program product can be executed, in particular, on a control and processing unit of a hybrid measuring device.

Drawings

In the following, a method according to the invention and a device according to the invention are described in more detail, purely by way of example, on the basis of specific exemplary embodiments which are schematically illustrated in the drawings, wherein further advantages of the invention are also discussed. In the specific figures:

FIG. 1 illustrates one embodiment of a measuring device for measuring an object according to the present invention;

FIG. 2 shows another embodiment of a measuring device for measuring an object according to the present invention;

FIG. 3 shows another embodiment of a measuring device for measuring an object according to the present invention;

FIG. 4 shows another embodiment of a measuring device for measuring an object according to the present invention;

FIG. 5 shows another embodiment of a measuring device for measuring an object according to the present invention;

FIG. 6 shows another embodiment of a measuring device for measuring an object according to the present invention;

FIG. 7 illustrates an embodiment of a measurement strategy according to the present invention utilizing a hybrid triangulation scanner according to the present invention; and

fig. 8 shows an intensity distribution model for data analysis in the case of fluorescence.

Detailed Description

Fig. 1 shows an embodiment of a measuring device 1 according to the invention for measuring an object 2. The measuring device 1 comprises a distance measuring unit 10 which is designed to generate measurement data by means of triangulation. The ranging unit 10 includes a beam emitting unit 11 and a detector 12. The beam emitting unit 11 and the detector 12 are arranged in a known position and orientation with respect to each other.

The beam transmitter 11 is designed to emit measuring radiation 13, in particular laser radiation. The measuring radiation 13 can be used to provide a specific illumination of the object 2. For example, the measuring radiation 13 may be generated in the form of lines and corresponding rays may be projected on the object 2.

The measuring radiation 13 is generated here as blue laser radiation with a wavelength of 450 nm.

The object 2 to be measured comprises at least part of a material which can be excited to emit fluorescent light. The absorption spectrum of the object material is formed in such a way that fluorescence can be excited, in particular by means of irradiation with electromagnetic radiation having a wavelength from the wavelength range of 250nm to 500nm, in particular from the wavelength range of 300nm to 450 nm. This fluorescent behavior is applicable to many plastic-type materials or plastic-based materials. Therefore, the wavelength exciting the measuring light is preferably selected from the ultraviolet or blue spectral range.

The measuring radiation 13 is incident on the object and interacts with the object material. Depending on the respective measurement characteristic of the currently illuminated object part, i.e. whether the object part is diffusely reflecting or exciting fluorescence or both effects occur simultaneously, on this part of the object part a portion of the measurement radiation 13 is reflected as reflected radiation 14 in the direction of the detector 12 and/or the measurement radiation 13 is (at least partially) absorbed and emits fluorescence radiation 15. The fluorescent radiation 15 can also be detected using the detector 2.

In the measuring example shown, the measuring radiation is diffusely reflected and also excites fluorescence. Thus, both the reflected measuring radiation 14 and the fluorescence 15 can be detected with the detector 12. Both signals can be sampled and selectively detected by means of a polychromatic filter 16 (for example an RGB filter) connected in front of a sensor 17. Such a filter 16 provides wavelength dependent separation of the signals. Fluorescence has a longer wavelength than the (reflected) measurement radiation.

In this way, the measuring device 1 enables distance measurement data to be generated from directly reflected measurement radiation and also on the basis of emitted fluorescence. If the measuring radiation is incident on the object 2, for example as a line, then the line on the object surface 2 can be detected at a wavelength spectrum corresponding to the emission of the measuring radiation 13 on a part of the detector 12, and the (excited) line with a different wavelength spectrum can be detected. The respective images on the sensor 17 can be associated with the respective measuring principle (reflection and fluorescence) on the basis of different spectral characteristics.

Fig. 2 shows a further embodiment of a measuring device 1 according to the invention for measuring an object 2. The measuring device 1 comprises a first beam source 11a and a second beam source 11 b. The first beam source 11a is designed to emit fluorescence-inducing measurement radiation 13a having a wavelength in the blue or ultraviolet spectral range, in particular as a laser diode. The second beam source 11b is designed to emit measuring radiation 13b of a second, longer wavelength (for example in the red spectral range), in particular also as a laser diode.

The beam guide for the respectively emitted radiation can be designed in such a way that both measuring radiations 13a and 13b are emitted coaxially or parallel with respect to a common optical axis. Such a combination of beams may for example be provided by means of a partially transmissive deflection component (e.g. a beam splitter). Thus, the two beams are incident, for example, at the same position or have a defined parallel offset on the object surface.

When the second measuring radiation 13b for direct triangulation can be emitted by means of beam reflection, the first measuring radiation 13a is provided to induce possible fluorescence effects. In the example shown, both direct reflection of the second measuring radiation 13 and induction of fluorescence takes place.

Thus, as a result of the illumination with the two measuring radiations 13a and 13b, the reflected portions 14b of the first measuring radiation 14a and the second measuring radiation and the fluorescent radiation 15 resulting from the interaction with the first measuring radiation 13a result in a radiation component emitted and/or reflected from the object 2. These three components radiate into the measuring device 1 through the observation window and are incident on the detector 12.

A filter assembly 16 is provided, which has a radiation transmittance corresponding to the fluorescence spectrum and the spectrum of the second measurement radiation. The wavelength of the second measuring radiation is preferably selected such that it lies within the expected fluorescence spectrum.

The sensor 17 is designed to detect the corresponding radiation.

The first radiation source 11a and the second radiation source 11ab can be modulated in such a way that the measuring radiation 13a of the first radiation source and the measuring radiation 13b of the second radiation source are emitted alternately and sequentially, i.e. only the first measuring radiation 13a or the second measuring radiation 13b is emitted at all times. The detector 12 can in turn be adjusted correspondingly in such a way that, synchronously with the alternating emission of the two measuring radiations, two exposures of the sensor are detected alternately (sequentially). Thus, the corresponding detection of sensor illumination may be associated with a reflectance measurement or a fluorescence measurement.

In this case, the wavelength of the second measuring radiation 13b is such that preferably no fluorescence occurs when the object is illuminated with this radiation. Specifically, a red laser line is generated with the second beam source 11b, and a blue laser line is generated with the first beam source 11 a.

Thus, the camera 12 can detect light at both wavelengths, thereby allowing both directly reflected light and fluorescent light to be measured. Thus, surfaces that do not contain fluorescence, e.g., metal surfaces, may also be measured. The wavelength of the beam source 11b is preferably not excessively close to the fluorescence excitation wavelength.

The second radiation source 11b thus provides in particular the emission of a second laser light with a longer wavelength (with respect to the first beam source 11a), so that the reflection (absence of fluorescence) that can result therefrom can be measured with the same camera 12.

Fig. 3 shows a further embodiment of a measuring device 1 according to the invention for measuring an object 2. The beam emission unit 11, the possible interaction with the object 2 and the measurement light emitted from the object 2 substantially correspond to the embodiment according to fig. 1.

This embodiment differs in the detection of measurement radiation 14 and 15 comprising object information. The detector 12 comprises a single sensor 17 designed to detect light having a measuring radiation spectrum, in particular a central measuring radiation wavelength, and light having a fluorescence spectrum, in particular a broader frequency band.

For separating the respective signals, the detector 12 comprises a filter unit with two filter components 16a and 16 b. The filter components 16a and 16b may be alternately introduced into the beam path or into the course of the optical axis of the detector or sensor. The actions of both component 16a and component 16b in the detector may be interchanged multiple times. This can be done manually or (automatically) controlled by means of a mechanical positioning device.

The sequential exchange of the filter components can be carried out in particular depending on the measurement method to be used (reflection or fluorescence).

For example, the object may first be measured using typical triangulation methods that utilize measuring the diffuse reflection of radiation on the object. Then, if it is determined during the measurement that a signal with low insufficient intensity is measured on the detector or that the intensity level drops significantly (strongly and rapidly), this may be an indication that a transparent or reflective object region is reached. Furthermore, the operator of the measuring device can determine the transparent area to be measured separately (by visual evaluation of the object 2), for example. In response to one of the above determinations, a change of the filter 16a or 16b, respectively, used so far, may then be initiated or performed. After the change, the corresponding measuring function of the device can also be changed, for example from a reflection measurement to a fluorescence measurement.

The differentiation of the received radiation (i.e. reflected radiation and fluorescence radiation) is relevant for determining the distance data according to the triangulation principle, however, since the reflected radiation is radiated from the object surface and the fluorescence radiation is mainly present in the lower material layers, this radiation origin is to be considered for the signal analysis. For the analysis of the fluorescence, in particular storing specific calibration parameters, the correction parameters also permit an accurate determination of the object surface on the basis of the fluorescence.

Furthermore, it is relevant to distinguish the signals for signal processing and analysis, since the spectrum of the reflected measuring radiation is rather well-defined, in particular in the case of the use of lasers, while the spectrum in the presence of fluorescence deviates significantly from the spectrum of the emitted measuring radiation.

In standard mode (i.e. with beam reflection), typically a thin symmetrical laser line is projected and an image of the line is detected on a part of the detector after reflection on the object. Here, the intensity distribution with respect to the line image is generally a gaussian distribution. The position of the intensity maximum reflects the relevant height coordinate on the object and can be determined by means of a gaussian or parabolic approximation.

For the distance determination by means of fluorescence, an analysis adapted to the fluorescence spectrum is required. An analysis based on the determination of the intensity maxima or intensity foci (as usually occurs in classical reflection) may lead to defective results here, since the intensity distribution depends on the penetration depth of the fluorescence excitation radiation and thus on the location of the occurrence of the fluorescence. Thus, the intensity focus is not correlated to the object surface, but is usually assigned to a lower material layer.

For this purpose, fig. 8 shows by way of example an intensity distribution 81 of fluorescence, as can be detected with the sensor 12 of the measuring device 1 during the measurement of an object that can excite fluorescence. The emitted fluorescence is collected with a sensor and/or a specific camera chip. The intensity is plotted against the penetration depth 83 (here: measured in millimeters) of the radiation into the object material. Line 82 marks the coordinates of the material surface. As can be seen, the location of the intensity maximum or the location of the intensity focus does not correspond to a point on the surface of the object, but indicates coordinates inside the object. Therefore, the analysis of the measurement points detected by means of fluorescence is preferably performed by applying the model or a similar model. Fig. 4 shows a further embodiment of a measuring device 1 according to the invention for measuring an object 2. This embodiment differs from the embodiment of fig. 3 only in the detector.

The detector 12 includes two cameras 18a and 18 b. Each of the cameras 18a and 18b in turn has a sensor, an optical assembly and a filter component 16a or 16b, respectively. The filter components 16a and 16b differ in the transmittance of electromagnetic radiation.

The filter 16a transmits light at the measurement wavelength and thus also transmits its reflection 14. Thus, if a laser beam source is used, the filter can be designed to be narrow band to minimize or eliminate possible external beam effects.

The filter 16b is designed to transmit the generated fluorescence 15. This filter 16b may in particular be configured to measure objects with a specific material, i.e. if the material properties of the object 2 and the excitable fluorescence properties associated therewith are known, the filter 16b may thus be designed to be properly transmissive. Filter 16b is typically a wider band transmission range than filter 16 a.

Thus, the respective camera sensor may be configured to detect reflected light or fluorescent light, respectively, which may be sensitive in a specific wavelength range, for example.

This arrangement thus provides for simultaneous derivation of fluorescence measurement data (by means of camera 18b) and reflectance measurement data (by means of camera 18 a).

Fig. 5 shows a further embodiment of a measuring device 1 according to the invention for measuring an object 2. This embodiment differs from the embodiment of fig. 4 in the construction of the detector 12.

The detector 12 comprises two sensors 17a and 17 b. Furthermore, the detector 12 comprises a beam splitter 19, in particular dichroic and/or dichroic. The beam splitter 19 provides a wavelength selective separation of the reflected measurement radiation 14 incident in the detector 12 from the likewise incident fluorescence 15. The reflected measuring radiation 14 is deflected by means of a beam splitter 19 onto the sensor 17 b. The fluorescent light 15 may be transmitted through the beam splitter 19 (at least a substantial portion) and may be detected (as an image) with the sensor 17 a. Alternatively, it is conceivable that the beam splitter is designed to transmit only light in the wavelength range of the measurement radiation.

With this arrangement, a measurement based on the emitted fluorescent light 15 and a measurement based on the reflected measuring light 14 can be performed. The two measurement options may be operated separately, e.g. alternately over time, or in combination, e.g. simultaneously.

Fig. 6 shows a further embodiment of a measuring device 1 according to the invention for measuring an at least partially transparent or reflective object 2. This embodiment differs from the embodiment of fig. 5 in the construction of the detector 12.

In this case, the detector 12 comprises a single sensor 17 and a beam splitter 19. The signals (fluorescence 15 and reflection 14) are separated by means of a beam splitter 19. Each of the separated signals is deflected by a deflection member (e.g., a mirror) onto a single sensor 17 and is reflected onto a different detection area of the sensor 17. Thus, both the fluorescent radiation 15 and the reflected radiation 14 can be detected as images with one sensor 17.

Due to the spatially separated signal detection, with one sensor 17, an image of each signal (i.e. the profile of the beam reflected from or emitted on the object) can be detected. The topography of the object 2 can then be calculated for the lines in a point-like manner based on the line curves in the image.

Fig. 7 shows an embodiment of a measurement strategy according to the invention, which makes use of a hybrid triangulation scanner according to the invention, in particular according to the configuration shown in one of fig. 1 to 6.

A hybrid triangulation scanner is understood as a measuring device which is designed both to emit measuring radiation and to detect reflected measuring radiation and which is also designed to emit fluorescence excitation radiation (which may be identical to the measuring radiation, in particular with respect to wavelength) and to detect fluorescence. The corresponding distance measurement data can be generated by detecting reflected measurement radiation and also by detecting fluorescence, i.e. for example, the distance to the object can be determined.

The measuring radiation can be emitted in each case in the form of a line. Thus, measurement data can be derived for the entire line. The distance may be calculated from the shape (curve) and position of the line in the image detected at the sensor based on the known relative positioning of the beam source and detector and based on a previous calibration of the sensor.

The line may be movable relative to the object over its surface, i.e. the object may be movable relative to the scanner, which may be movable relative to the object, or the scanner may comprise a deflection device enabling the line to be moved. The object surface can be detected by scanning in this manner.

On the one hand, for detecting the object surface, triangulation is performed by means of the reflection of the measuring radiation 50, wherein corresponding reflection image data 51 are generated.

On the other hand, for detecting the object surface, a (further) triangulation is performed by means of inducing fluorescence 60 and detecting the light generated in this case, wherein corresponding fluorescence image data 61 is generated.

The two raw data sets (reflectance image data 51, fluorescence image data 61) are jointly processed and the segmentation 70 of the object surface (phantom) into reflectance and fluorescence zones is performed automatically on the basis of the overall processing, in particular with correspondingly performed algorithms. For this purpose, for example, an averaging of the signal strengths may be performed.

A corresponding mask 52 and mask 62 can be derived for the surface area associated with one of the measurement methods, respectively. Then, together with the raw dataset, both a reflection point cloud 53 (diffuse reflection surface area) and a fluorescence point cloud 63 (transparent or reflection surface area) may be generated.

In a downstream combining step 71, point cloud 53 and point cloud 63 may be fused to form an overall point cloud 72. In this way, a point cloud 72 is obtained which represents the diffusely reflective parts of the object surface as well as the transparent or reflective parts of the surface, i.e. the object concerned can be represented completely.

Typically, the reflectance measurement data may be embodied by reflectance image data 51 and/or reflectance point cloud 53. Thus, the fluorescence measurement data may be embodied by the fluorescence image data 61 and/or the fluorescence point cloud 63.

It will be apparent that these illustrations are merely schematic illustrations of possible exemplary embodiments. The various methods can also be combined with each other and with prior art triangulation or fluorometry according to the invention.