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EP4555271A1 - Appareil de mesure confocale chromatique de distances - Google Patents

Appareil de mesure confocale chromatique de distances

Info

Publication number
EP4555271A1
EP4555271A1 EP23735765.2A EP23735765A EP4555271A1 EP 4555271 A1 EP4555271 A1 EP 4555271A1 EP 23735765 A EP23735765 A EP 23735765A EP 4555271 A1 EP4555271 A1 EP 4555271A1
Authority
EP
European Patent Office
Prior art keywords
pixel
light
spatial filter
light pattern
generating device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP23735765.2A
Other languages
German (de)
English (en)
Inventor
Laura VIETZE
Christoph Dietz
Frauke Roellinghoff
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Precitec Optronik GmbH
Original Assignee
Precitec Optronik GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Precitec Optronik GmbH filed Critical Precitec Optronik GmbH
Publication of EP4555271A1 publication Critical patent/EP4555271A1/fr
Pending legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/026—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness by measuring distance between sensor and object
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2210/00—Aspects not specifically covered by any group under G01B, e.g. of wheel alignment, caliper-like sensors
    • G01B2210/50—Using chromatic effects to achieve wavelength-dependent depth resolution

Definitions

  • the invention relates to a device for chromatically confocal measurement of distances at several points, preferably arranged along a line, on surfaces of workpieces and other objects.
  • Devices for chromatic confocal measurement of distances have been used in industrial measurement technology for many years when distances to workpieces or other objects need to be measured without contact and with high accuracy.
  • wall thicknesses or other thicknesses can also be measured with such devices, since a distance can usually be determined for each optical interface and the thickness results from the difference between the measured distances.
  • Conventional devices for chromatically confocal distance measurement contain a light source that generates polychromatic measuring light and directs it onto a pinhole that has a very small aperture.
  • the aperture opening is imaged onto the surface to be measured by imaging optics. At least part of the imaging optics has a significant longitudinal chromatic aberration. Different colored images of the aperture opening are therefore arranged one behind the other on the optical axis of the imaging optics. Only the spectral portion of the measuring light, in which the image of the aperture opening lies exactly on the surface to be measured, is reflected back by it in such a way that it can enter the same aperture opening or an aperture opening arranged optically conjugate to it. The wavelength of this spectral component is recorded using a spectrometer.
  • Each wavelength is assigned a specific distance from the imaging optics.
  • the other spectral components are also partially reflected by the object surface, but cannot be focused by the imaging optics into the same aperture or an optically conjugate aperture and therefore do not contribute significantly to the part of the measuring light that is spectrally analyzed by the spectrometer.
  • a chromatic confocal measuring device is known with which the distances or thicknesses at several points can be measured at the same time.
  • the otherwise usual pinhole is replaced here by a linear or flat arrangement of ends of optical fibers. If the distances or thicknesses are measured in multiple locations at the same time, this will significantly reduce the measurement time. A complete surface profile can then be created in a short time, even for larger surfaces.
  • the lateral resolution of such a multi-point measuring device i.e. the density of the measuring points on the surface of the object, is limited by the fact that measuring light reflected from the object, which hits the end of an optically conjugated optical fiber, must not also hit an adjacent optical fiber at the same time . If such optical crosstalk occurs, clear distance values can no longer be assigned to the individual measuring points.
  • One factor that contributes to optical crosstalk is that, even with optimally corrected imaging optics, the image of a fiber end can never be exactly sharp for physical reasons, but rather, due to diffraction phenomena, has the shape of a flat, extended diffraction disk that has several clearly recognizable secondary maxima.
  • the fiber ends are at a relatively large distance, which is why a high density of measuring points is not possible.
  • the object of the invention is to provide a device for chromatically confocal measurement of distances to several points on a surface of an object, which has a high lateral resolution.
  • this object is achieved by a device for chromatically confocal measurement of distances at several points on a surface of an object, which has a light source that is set up to generate polychromatic measuring light.
  • a light pattern generating device is set up to generate a light pattern from the measuring light, which extends in a first plane along one dimension or along two dimensions.
  • a chromatically uncorrected lens is designed to produce images of the light pattern in image planes whose axial position is wavelength-dependent due to chromatic longitudinal aberration.
  • a static spatial filter is arranged in a second level and has a filter function corresponding to the light pattern (but not necessarily identical), the second level being optically conjugate to the first level.
  • a preferably non-polarizing beam splitter cube is arranged in the light path between the light pattern generating device and the objective and directs measurement light that has been reflected from the surface and has passed through the objective to the spatial filter.
  • a spectrometer has several input channels that are set up to spectrally analyze reflected measuring light that has passed through a point of the static spatial filter assigned to the respective input channel.
  • An evaluation device is set up to calculate distances from points on the surface to the measuring device from wavelengths measured by the spectrometer.
  • the device also has a spatial filter that can be switched pixel by pixel, which has a plurality of pixels and either forms the light pattern generating device or is arranged in a third level which is optically conjugate to the first level and the second level, with each pixel in a first switching state , in which the pixel blocks measuring light, and can be converted into a second switching state in which the pixel does not block measuring light.
  • a spatial filter that can be switched pixel by pixel, which has a plurality of pixels and either forms the light pattern generating device or is arranged in a third level which is optically conjugate to the first level and the second level, with each pixel in a first switching state , in which the pixel blocks measuring light, and can be converted into a second switching state in which the pixel does not block measuring light.
  • the spatial filter which can be switched pixel by pixel, makes it possible to dim or deflect part of the measuring light that would lead to optical crosstalk at a time during the measurement so that it cannot reach the spectrometer. At another time, another part of the measuring light is suppressed. In this way, a very high lateral resolution can be achieved by combining several successive measurements.
  • the spatial filter which can be switched digitally on a pixel-by-pixel basis, is controlled in such a way that it switches between a first switching configuration and a second switching configuration during a measurement, whereby in the first switching configuration no two neighboring pixels are in the same switching state, and whereby the second switching configuration is complementary to the first switching configuration. This means that only two individual measurements are required.
  • n 2, 3, ... pixels in an inactive switching position . n+1 different switching configurations must then follow each other until all pixels were in an active switching position.
  • control with different switching configurations can be made dependent not only on the required lateral resolution, but also on the properties of the object surface to be measured.
  • more crosstalk can possibly be tolerated, so that half or even all pixels of the spatial filter can be in the active second switching state at a certain point in time.
  • optical conjugation between the third level, in which the pixel-by-pixel digitally switchable spatial filter is located, and the first level, in which the light pattern generation unit is located ensures that pixels of the pixel-by-pixel digitally switchable spatial filter can be clearly assigned to the individual measuring points.
  • Planes that can be converted into one another through an optical image are called optically conjugate.
  • optical conjugation can also be achieved by other optical systems.
  • An example of this are the opposite ends of optical fibers, both of which are called optical conjugates can be viewed because the point-like light distribution is identical at both ends.
  • Optical images can therefore also be created using bundles of optical fibers, as is known from endoscopes, for example. Two planes immediately behind one another can also be viewed as optically conjugate in a broader sense.
  • the pixel-by-pixel digitally switchable spatial filter is arranged independently of the light pattern generating device and in the third level, it can be located in the light path between the light pattern generating device and the beam splitter cube. Such an arrangement is favorable because the image of the light pattern is sharper than after being imaged again through the lens.
  • the device then preferably has imaging optics which images the first level onto the third level.
  • imaging optics are particularly advantageous when the light pattern generating device comprises an arrangement of ends of optical fibers or a diaphragm with at least one opening.
  • the measuring light usually emerges from the fibers or the opening in a strongly diverging manner.
  • the spatial filter which can be digitally switched pixel by pixel, is arranged directly at the fiber ends or in front of the opening of a diaphragm, optical conjugation in the broader sense is achieved.
  • many particularly suitable spatial filters that can be digitally switched pixel by pixel such as micromirror arrays, cannot be arranged so close to the light pattern generating device that one can still speak of optical conjugation.
  • the imaging optics allow, on the one hand, the use of a large numerical aperture and, on the other hand, the use of micromirror arrays and other switchable spatial filters, which can only be arranged at a greater distance from the light pattern generating device due to beam folding or the required installation space.
  • the light pattern can comprise several two-dimensionally distributed light points or at least one continuous light line or one composed of light points.
  • the division of a continuous light line into individual measuring points is caused by the pixels of the switchable spatial filter.
  • the light pattern generating device comprises a planar array of micro-collecting lenses.
  • the converging lenses focus the measuring light on the assigned pixels of the switchable spatial filter and thereby bring about optical conjugation in a broader sense.
  • the spatial filter which can be switched digitally on a pixel-by-pixel basis, forms the light pattern generating device.
  • Such a structure is particularly simple and allows the use of spatial filters in the form of micromirror arrays without the need for additional imaging optics.
  • the spatial filter should then be illuminated with light that has an angular distribution matched to the numerical aperture of the chromatically uncorrected objective. This works particularly well if the measuring light spreads out as a free beam between the light source and the spatial filter, which can be switched digitally on a pixel-by-pixel basis.
  • the spatial filter which acts as a light pattern generating device, should be illuminated by the light source in such a way that as much light as possible hits the spatial filter.
  • a simple collecting optic is sufficient to bundle the light emanating from an exit surface of the light source so that it hits the spatial filter with little loss.
  • the collecting optics can be a cylindrical lens or anamorphic in some other way.
  • a collimator is arranged in the light path between the light pattern generating device and the beam splitter cube, which collimates measuring light entering the beam splitter cube. Due to the confocal imaging, the measuring light reflected from the object then passes through the beam splitter cube in a collimated manner.
  • a collimated transmission is advantageous because the beam splitter cube does not produce any spherical aberration.
  • the spatial filter which can be switched digitally on a pixel-by-pixel basis, is preferably a micromirror array. Alternatively, it can also be a transmissive MEMS component, as described, for example, in US 8,054,527 B2.
  • An LCD panel can also be considered as a spatial filter that can be digitally switched pixel by pixel, but has disadvantages due to its polarizing properties. For the same reason, it is useful if the beam splitter cube is not polarizing. The division ratio of the beam splitter cube then does not depend on the polarization state and therefore on the properties of the object surface.
  • the polychromatic light source contains a luminophore, as is known from EP 3 764 056 A1 (corresponds to US 10,731,965 B1).
  • a light source preferably has an elongated light exit surface. If optical fibers are used to guide light, their ends can form a rectangular or circular arrangement and receive light that is emitted from an adjacently arranged square or circular light exit surface of the luminophore.
  • a pump source which is usually a laser or an LED, excites a phosphor called a luminophore, which emits light through a physical process, in particular phosphorescence, fluorescence or scintillation.
  • a light source has the advantage that it can illuminate the entire confocal aperture and has high efficiency and high luminous efficacy.
  • further spatial filters can be arranged at positions that are optically conjugate to the first, second and third planes.
  • the spectrometer can be synchronized with the spatial filter that can be switched digitally on a pixel-by-pixel basis in such a way that input channels that are assigned to pixels in the second switching state are logically or physically deactivated. This prevents measurement light that reaches neighboring input channels due to crosstalk from being taken into account in the evaluation.
  • the easiest way to deactivate the relevant input channels is to ensure that the intensities recorded there are not read out.
  • a further pixel-by-pixel digitally switchable spatial filter can be arranged in the light path between the beam splitter cube and the spectrometer in a fourth level, which is optically related to the first level and the second level is conjugated.
  • Each pixel of the further spatial filter which can be switched digitally on a pixel-by-pixel basis, can be converted into a first switching state in which the pixel blocks measuring light and into a second switching state in which the pixel does not block measuring light.
  • the background to this measure is that the image of the light pattern loses sharpness with each optical image. If, for example, two neighboring diffraction disks only overlap negligibly on the object surface, the overlap can already be significant after being imaged again through the lens at the height of the spectrometer.
  • the additional spatial filter which can be switched digitally on a pixel-by-pixel basis, can help here by trimming the light bundles in question so that there is no crosstalk on the spectrometer even after imaging again.
  • Figure 1 shows a device according to the invention for distance measurement according to a first exemplary embodiment in a schematic meridional section
  • Figure 2 shows a top view of a pinhole diaphragm used as a light pattern generating device in the device according to Figure 1;
  • Figures 3a and 3b show a transmissive MEMS spatial filter contained in the device according to Figure 1 in an enlarged schematic section in different switching configurations;
  • FIG. 4 shows another exemplary embodiment of a pinhole diaphragm that can be used as a light pattern generating device in the device according to FIG. 1 in a top view;
  • Figure 5 shows a further exemplary embodiment of a pinhole diaphragm that can be used as a light pattern generating device in the device according to Figure 1, in a top view;
  • Figure 6 shows a device according to the invention for distance measurement according to a second exemplary embodiment in a schematic meridional section;
  • Figures 7a and 7b show a reflective MEMS spatial filter contained in the device according to Figure 6 in an enlarged schematic section in different switching configurations;
  • Figure 8 is a schematic representation of an exemplary embodiment in which the light pattern generating device is formed by a linear arrangement of microlenses
  • Figures 9a and 9b further options for possible switching configurations in schematic representations based on Figures 3a and 3b;
  • Figure 10 shows a detail from a further variant with two transmissive MEMS spatial filters.
  • FIG. 11 shows a device according to the invention for distance measurement according to a third exemplary embodiment in a schematic meridional section, in which the spatial filter, which can be switched digitally on a pixel-by-pixel basis, forms the light pattern generating device.
  • Figure 1 shows a device according to the invention and designated overall by 10 for distance measurement according to a first exemplary embodiment in a schematic meridional section.
  • the device 10 has a light source 12 which generates polychromatic measuring light ML.
  • the measuring light ML preferably has a continuous spectrum.
  • the use of comb spectra or other discrete spectra is fundamentally just as if considered, provided the wavelength peaks are sufficiently close together.
  • the light source 12 comprises a superluminescent diode 14 and a converging lens 16 arranged behind it in the light propagation direction.
  • the measuring light ML generated by the light source 12 strikes a light pattern generating device 18, which generates a light pattern from the incident measuring light ML.
  • the light pattern generating device 18 comprises a pinhole 20, which is shown in plan view in FIG.
  • the pinhole 20 has a plurality of aperture openings 22 which are arranged along a line. When illuminated with the measuring light ML, the aperture openings represent 22 point light sources from which the measuring light ML emerges divergently.
  • the aperture openings 22 are arranged in a first plane E1, which coincides with an object plane of an imaging optics 24.
  • the imaging optics 24 are designed as 4f-0 optics.
  • a transmissive MEMS spatial filter 26 is arranged in the image plane E2 of the imaging optics 24, MEMS being an acronym for micro-electro-mechanical system.
  • Such filters 26 include a plurality of regularly arranged elements or pixels 28 that can be individually mechanically moved to selectively clear or block the light path. Suitable examples of such MEMS filters are known per se and are described, for example, in US 2006/0012781 A1. Alternatively, an LCD panel can also be used, although it has a polarizing effect, which can be disadvantageous for some measuring tasks.
  • Figures 3a and 3b show the transmissive MEMS spatial filter 26 in an enlarged schematic section.
  • the pixels 28 of the transmissive MEMS spatial filter 26 are arranged along a line so that each pixel 28 is assigned exactly one aperture 22 of the light pattern generating device 18. This assignment results from the imaging of the aperture openings 22 onto the pixels 28 caused by the imaging optics 24.
  • the individual switchability of the individual pixels 28 is indicated in FIG. 3a by light and dark backgrounds.
  • a pixel 28 with a dark background is in a first switching state in which the pixel 28 blocks measuring light ML.
  • a pixel 28 with a light background is in a second switching state in which the pixel 28 is transparent to measuring light.
  • the switching states of the pixels 28 are specified by a control and evaluation device 30. The change between different switching states, as becomes clear from a comparison of Figures 3a and 3b, typically takes place within a few microseconds.
  • the pixel 28 shown on the far left in Figure 3a which is in the second switching state, it is indicated by further rays that the angular distribution of the measuring light ML is maintained when it passes through the transmissive MEMS spatial filter 26.
  • the transmissive MEMS spatial filter 26 therefore only filters in spatial space, but not in angular space. Consequently, the measuring light ML emerges at the output of the pixel 28 with the numerical aperture NA of the imaging system 24.
  • the pixels 28 of the transmissive MEMS spatial filter 26 thus also represent point light sources, which, however, in contrast to the aperture openings 22 of the light pattern generating device 18, can be switched on and off individually.
  • Figures 3a and 3b illustrate two different switching configurations that can be switched between in this exemplary embodiment.
  • the first switching configuration which is shown in FIG. 3a
  • no two neighboring pixels 28 are in the same switching state.
  • the switching state therefore alternates from pixel to pixel.
  • the second switching configuration according to FIG. 3b is complementary to the first switching configuration of FIG. 3a.
  • no two neighboring pixels 28 are the same Switching state that alternates from pixel to pixel.
  • the switching pattern is offset by one pixel, so that you can switch between the two switching configurations according to Figures 3a and 3b by switching to the other switching state at each pixel 28.
  • a collimator lens 32 is arranged in the light path behind the transmissive MEMS spatial filter 26, the front focal plane of which coincides with the plane E2. The beams of rays emerging from the pixels 28 are therefore collimated as they pass through the collimator lens 32.
  • the collimated beams of rays impinge on a non-polarizing beam splitter cube 33 which has a beam splitter surface 34 arranged at an angle of 45° to the optical axis.
  • a predetermined proportion of the incident light e.g. 50%, is reflected on the beam splitter surface and is lost for the measurement.
  • the remaining measuring light ML passes through the beam splitter cube without deflection due to the collimated beam path and hits a chromatically uncorrected objective 36, which has an object plane lying at infinity.
  • the objective 36 together with the imaging optics 24 and the collimator lens 32, the objective 36, due to its chromatic longitudinal aberration, images the aperture openings 22 arranged in the plane E1 in image planes B1 to B3, the axial positions of which are wavelength-dependent. In Figure 2, this is indicated by different dashed lines. Each wavelength is assigned exactly one image plane. If - as in the present exemplary embodiment - the spectrum generated by the light source 12 is continuous, a continuous sequence of image planes is consequently created.
  • the image of an aperture opening 22 lies in an image plane at the height of which there is an at least partially reflecting surface 38 of an object 40, the light beam striking there is reflected back into itself and travels the same way via the lens 36 back to the beam splitter surface 34 of the beam splitter cube 33.
  • this requirement is met, for example, for the aperture opening 22 located on the optical axis OA of the device 10 at a wavelength for which the image of the aperture 22 lies in the image plane B2.
  • the object 40 which has passed through another aperture opening 22, this requirement is fulfilled for the object 40 assumed here at a different wavelength, for which the image of the relevant aperture opening 22 lies in the image plane B1.
  • the object 40 assumed here at a different wavelength, for which the image of the relevant aperture opening 22 lies in the image plane B1.
  • not only light of a single wavelength is reflected on the surface 38. However, there is only one wavelength at which the measuring light beam is reflected because the focus is exactly on the surface 38 for only this wavelength.
  • a predetermined portion of the reflected measurement light ML is reflected by 90° and focused by a converging lens 42 onto a static spatial filter 44, which is arranged in a third plane E3 and has a filter function corresponding to the light pattern.
  • the static spatial filter 44 is transparent to measuring light ML at individual locations (or reflective in the case of a reflective spatial filter), while it blocks the measuring light ML at the remaining locations.
  • the static spatial filter 44 is the same pinhole that was used for the light pattern generating device 18, possibly reduced or enlarged by the image scale of the optics in between. The entire optics in the light path between the light pattern generating device 18 and the static spatial filter 44, i.e.
  • the imaging optics 24, the collimator lens 32, the objective 36 and the focusing lens 42, cause the light pattern generating device 18 to be imaged onto the static spatial filter 44 .
  • the planes E1, E2 and E3 are therefore optically conjugate. Intermediate images are created at the level of the transmissive MEMS spatial filter 26 and in the image planes B1 to B3 on the surface 38 of the object 40.
  • the static spatial filter 44 ensures that only measuring light beams that have been reflected on the surface 38 with a very specific wavelength can be further evaluated. Measuring light ML that does not meet this condition is dimmed by the static spatial filter 44 in accordance with the chromatic-confocal measuring principle.
  • a spectrometer 46 In the light path behind the static spatial filter 44, a spectrometer 46 with several input channels is arranged, which spectrally reflects reflected measuring light ML, which has passed through a point of the static spatial filter 44 assigned to the respective input channel analyze.
  • the spectrometer 46 typically contains a dispersive optical element, for example an optical grating or a prism 47, and a line-like arrangement 48 of light-sensitive cells for each input channel, as indicated schematically in FIG. 1. Since spectrometers 46 of this type are known, further explanations are unnecessary at this point.
  • the control and evaluation device 30 calculates distances from points on the surface 38 to the measuring device 10 from wavelengths measured by the spectrometer 46, as is known per se for chromatic confocal measuring devices. These points are images of the point light sources, i.e. the aperture openings 22. Each point light source is assigned its own input channel, so that the distance measurement can in principle be carried out for all point light sources at the same time.
  • the control and evaluation device 30 controls the transmissive MEMS spatial filter 26 in such a way that the measurement is divided into two partial measurements.
  • the pixels 28 of the transmissive MEMS spatial filter 26 are in one of the two switching configurations shown in FIGS. 3a and 3b.
  • the pixels 28 are in the other switching configuration.
  • the adjacent light bundle LB ' which is indicated with dashed lines in section C of FIG LB' are not assigned; This applies accordingly to the other light bundle, which is not indicated in the section C and is adjacent to the light bundle LB on the other side.
  • the spectrometer 46 is synchronized with the spatial filter 26, which can be switched digitally on a pixel-by-pixel basis, so that the two input channels that are assigned to the adjacent aperture openings 22" are deactivated.
  • the proportion of the light bundle LB that falls on the light-sensitive cells of these two input channels is therefore not evaluated.
  • control and evaluation device 30 can be programmed so that this mode is only used for measurements in which a high lateral resolution is required and the object has a surface that particularly favors optical crosstalk. If the requirements for the lateral resolution are lower, only one measurement is carried out with one of the switching configurations shown in Figures 3a and 3b.
  • FIG Pinhole 20 can be used as a light pattern generating device 18. Measuring light ML, which would lead to optical crosstalk, is also prevented from spreading here with the help of the transmissive MEMS spatial filter 26.
  • FIG 5 shows, in a representation based on FIGS the 2D pinhole 20" is distributed in a uniform two-dimensional grid.
  • the transmissive MEMS spatial filter 26 must then have a corresponding two-dimensional arrangement of pixels 28 so that each aperture opening 22" is assigned a switchable pixel.
  • the static spatial filter 44 and the spectrometer 46 must also be expanded in two dimensions accordingly, as is the case when stationary known to technology.
  • Figure 6 shows a second exemplary embodiment of a measuring device, which is designated overall by 10'. This exemplary embodiment differs from the device 10 according to FIG. 1 primarily in the following points:
  • the light source 12 used is not a superluminescent diode, but rather a luminophore 52, which in the exemplary embodiment shown has an elongated light exit surface and is illuminated by a pump source 54, which can be a laser, for example.
  • a pump source 54 which can be a laser, for example.
  • the polychromatic measuring light emerging from the light exit surface of the luminophore 52 is first collimated and then coupled into the ends of a linear arrangement of parallel optical fibers 56 using a cylindrical lens 55.
  • the Luminophor 52 a particularly high light intensity can be achieved.
  • the luminophore 52 has a round or square light exit surface.
  • the ends of the optical fibers 56 then do not form a linear arrangement, but rather a round or square arrangement;
  • the cylindrical lens 55 is omitted in this variant.
  • the measuring light ML guided in the optical fibers 56 exits at the opposite ends of the fibers 56. These ends are arranged along a line running perpendicular to the plane of the paper and at the same time represent the light pattern generating device 18.
  • the imaging optics 24 images the fiber ends via a flat deflection mirror 58 onto a switchable spatial filter 26 ', which in the exemplary embodiment shown is a one-dimensional digital micromirror array (DMD , digital micromirror device).
  • DMD digital micromirror array
  • the micromirror array extends perpendicular to the paper plane in Figure 6.
  • the static spatial filter 44 is also formed by a linear arrangement of ends of optical fibers 60, the line here also extending perpendicular to the plane of the paper.
  • the optical fibers 60 direct the measuring light to the spectrometer 46.
  • Optical fiber connectors 62, 62', 64, 64' can be integrated into the optical fibers 56, 60. In this way, the parts of the device 10 'outlined with dashed lines can be accommodated in separate housings, which form a mobile measuring head 66 and a stationary control device 68.
  • FIGs 7a and 7b illustrate the two switching configurations of the reflective switchable spatial filter 26 'in representations based on Figures 3a and 3b.
  • Each pixel 28 is formed by a micromirror that can assume two stable switching states. Pixels 28 with a gray background are in the second switching state and reflect the incident measuring light ML so that it falls on an absorber. The pixels 28 with a white background reflect the incident measuring light ML in such a way that it can enter the lens 36 via the beam splitter cube 33.
  • the light source includes a collimator lens 72, which collimates the measuring light onto the microlenses 70. These each focus the measuring light ML onto an assigned pixel 28 of the transmissive switchable spatial filter 26. In this exemplary embodiment, no imaging optics 24 are therefore required. Since the microlenses 70 are arranged directly in front of the transmissive switchable spatial filter 26, the plane falls E1 of the microlenses 70 is virtually together with the plane E2, which corresponds to an optical conjugation. The numerical aperture NA of the microlenses 70 is adapted to the numerical aperture NA of the lens 36.
  • Figures 9a and 9b illustrate further possibilities for possible switching configurations in schematic representations based on Figures 3a and 3b. If the images of the point light sources at the height of the static spatial filter 44 are particularly large, it may happen that these images extend not only over the immediately adjacent aperture openings 22 ', but over two or even three adjacent aperture openings 22'. In this case, the measurement should be divided into not two, but three or more individual measurements in order to prevent optical crosstalk.
  • Figure 10 shows a detail of another variant; the parts of the device 10 not shown in Figure 10 correspond to those in Figure 1.
  • a further transmissive MEMS spatial filter 74 is arranged in a fourth level E4 in the light path between the beam splitter cube 33 and the spectrograph 46, which is optically conjugate to the first level E1 and the second level E2.
  • Another imaging optics 75 images the further transmissive MEMS spatial filter 74 in the plane E4 onto the static spatial filter 44 in the plane E3.
  • the pixels of the further transmissive MEMS spatial filter 74 also have the property of being able to be converted into a first switching state in which the pixel blocks measuring light ML and into a second switching state in which the pixel does not block measuring light ML.
  • the static spatial filter 44 is omitted; The entrance slot of the spectrograph 46 is then located in level E3.
  • Such a further transmissive MEMS spatial filter 74 is advantageous if the input channels in the spectrograph cannot be individually deactivated and the images of the point light sources are partially on the static spatial filter 44 behind the objective 34 despite the MEMS spatial filter 26 arranged at the front of the beam path would overlap.
  • the further transmissive MEMS spatial filter 74 “cleanses” the light distribution and in this way ensures that there is no overlap of the images of the point light sources on the static spatial filter 44.
  • the switching configurations of the further transmissive MEMS spatial filter 74 are always at the Switching configurations of the front transmissive MEMS spatial filter 26 adjusted.
  • the additional MEMS spatial filter 74 can be dispensed with.
  • the spatial filter 26 which can be switched digitally on a pixel-by-pixel basis, forms the light pattern generating device 18.
  • the spatial filter 26 which can be switched digitally on a pixel-by-pixel basis, forms the light pattern generating device 18.
  • the measuring light ML generated by the light source 14 is first collimated by a converging lens 16.
  • a further converging lens 16' concentrates the measuring light ML in such a way that it just completely illuminates the spatial filter 26", which can be switched digitally on a pixel-by-pixel basis.
  • the spatial filter 26" which can be digitally switched pixel by pixel is square and a circularly delimited area is illuminated by the measuring light ML.
  • the converging lens 16' can be designed as a cylindrical lens or as another anamophotic optical element that has a different refractive power along orthogonal directions In this way, the linear spatial filter can be illuminated in stripes to minimize light losses.
  • a light source with an elongated exit surface can be used, which is imaged onto the linear spatial filter that can be digitally switched pixel by pixel and illuminates it accordingly.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Microscoopes, Condenser (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Measurement Of Optical Distance (AREA)

Abstract

L'invention concerne un appareil de mesure confocale chromatique de distances à partir d'une pluralité de points sur une surface réfléchissante (38) d'un objet (40). L'appareil comprend : une source de lumière (12) qui génère une lumière de mesure polychromatique (ML) ; et un dispositif de génération de motif de lumière (18) qui génère un motif de lumière à partir de la lumière de mesure. Une lentille objectif (36) non corrigée de manière chromatique génère des images du motif lumineux dans des plans d'image (B1, B2, B3), la position axiale desdits plans d'image dépendant de la longueur d'onde en raison de l'aberration chromatique longitudinale. L'appareil comprend également un filtre spatial statique (44), un cube séparateur de faisceau (33) et un spectromètre (46) qui analyse de manière spectrale la lumière de mesure réfléchie par la surface (38). Selon l'invention, l'appareil comprend également un filtre spatial (26 ; 26' ; 26'') qui peut être commuté numériquement pixel par pixel et qui comporte une pluralité de pixels (28), et qui soit forme le dispositif de génération de motifs lumineux (18), soit est situé dans un plan (E2) qui est optiquement conjugué par rapport au filtre spatial statique (44). Chaque pixel (28) peut être converti dans un premier état de commutation, dans lequel le pixel (28) bloque la lumière de mesure (ML), et dans un second état de commutation, dans lequel le pixel (28) ne bloque pas la lumière de mesure (ML).
EP23735765.2A 2022-07-13 2023-06-28 Appareil de mesure confocale chromatique de distances Pending EP4555271A1 (fr)

Applications Claiming Priority (2)

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DE102022117536.7A DE102022117536A1 (de) 2022-07-13 2022-07-13 Vorrichtung zur chromatisch konfokalen Messung von Abständen
PCT/EP2023/067657 WO2024012878A1 (fr) 2022-07-13 2023-06-28 Appareil de mesure confocale chromatique de distances

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JP (1) JP2025521999A (fr)
KR (1) KR20250033300A (fr)
CN (1) CN119487356A (fr)
DE (1) DE102022117536A1 (fr)
WO (1) WO2024012878A1 (fr)

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DE102022120069A1 (de) 2022-08-09 2024-02-15 Precitec Optronik Gmbh Vorrichtung zum Messen von Abständen an mehreren Messpunkten auf einem Werkstück

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Publication number Priority date Publication date Assignee Title
US5923466A (en) 1993-10-20 1999-07-13 Biophysica Technologies, Inc. Light modulated confocal optical instruments and method
KR20050086953A (ko) 2003-01-15 2005-08-30 마이크로닉 레이저 시스템즈 에이비 결함 픽셀을 탐지하는 방법
US20060012781A1 (en) 2004-07-14 2006-01-19 Negevtech Ltd. Programmable spatial filter for wafer inspection
DE102006007170B4 (de) 2006-02-08 2009-06-10 Sirona Dental Systems Gmbh Verfahren und Anordnung zur schnellen und robusten chromatisch konfokalen 3D-Messtechnik
US8054527B2 (en) 2007-10-23 2011-11-08 Qualcomm Mems Technologies, Inc. Adjustably transmissive MEMS-based devices
US10591279B2 (en) 2014-12-09 2020-03-17 Asentys Sas Integrated optical device for contactless measurement of altitudes and thicknesses
JP7408265B2 (ja) 2017-06-13 2024-01-05 株式会社キーエンス 共焦点変位計
DE102019001498A1 (de) * 2019-03-06 2020-09-10 Precitec Optronik Gmbh Vorrichtung zur optischen Vermessung und Abbildung eines Messobjekts sowie Verfahren
US11287626B2 (en) * 2019-05-17 2022-03-29 Hong Kong Applied Science and Technology Research Institute Comoanv Limited Chromatic confocal system and a method for inspecting an object
DE102019118600A1 (de) 2019-07-09 2021-01-14 Precitec Optronik Gmbh Phosphor-Lichtquelle für CLS oder Multipoint

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WO2024012878A1 (fr) 2024-01-18
KR20250033300A (ko) 2025-03-07
CN119487356A (zh) 2025-02-18
JP2025521999A (ja) 2025-07-10
DE102022117536A1 (de) 2024-01-18

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