Chromatic confocal measuring system for high-speed distance measurement

Abstract

To provide a chromatic confocal measuring device that uses an efficient and long-lifetime broadband light source.SOLUTION: There is provided a chromatic confocal measuring device in which a beam path for imaging of a pump light source (1) onto a luminophore (5), and a beam path for imaging of the luminophore (5) onto a surface (8a) of a fiber or fiber bundle partially match each other. The measuring device comprises a dichroic beam splitter (3) arranged so as to separate the beam path for imaging of the luminophore (5) onto the end (8a) of the fiber or fiber bundle from the beam path for imaging of the pump light source (1) onto the luminophore (5).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention is a chromatic confocal measurement device that uses a pump light source in the wavelength range of 350 nm to 500 nm, and a broadband light source, a pump light source, in the wavelength range from the visible wavelength range to the near-infrared range, particularly in the wavelength range of 400 nm to 900 nm. Light source a first optical system for imaging onto the optical fiber, such that at least a portion of the broadband light is coupled into a fiber or fiber bundle; Light source a second optical system for imaging the broadband light onto the surface (8a) of the fiber or fiber bundle, such that at least a portion of the broadband light is coupled into the fiber or fiber bundle; Light source The present invention relates to a chromatic confocal measurement device, which includes a second optical system for imaging the light coupled into the fiber or fiber bundle onto a plane (8a) of the fiber or fiber bundle, and the light coupled into the fiber or fiber bundle is used as measurement light for the chromatic confocal measurement device. The present invention also relates to a light source for use in such a chromatic confocal measurement device. [Background technology]

[0002] From French patent application FR 3006758 B1 a chromatic confocal multipoint measuring device is known which can provide distance or thickness information along a line. From US patent application 2010 / 0097779 A1 a chromatic confocal sensor for Light source The use of a light source based on a reflective surface is known. Light source U.S. Patent No. 10,731,965 B1 describes a chromatic confocal sensor using a broadband light source realized by optically exciting a Light source A broadband light source based on the hologram is described.

[0003] From Volker Hagemann, Albrecht Seidl, Guenter Weidmann, “Static ceramic phosphor assemblies for high power high luminance SSL-light sources for digital projection and specialty lighting,” Proc. SPIE 11302, Light-Emitting Devices, Materials, and Applications XXIV, 113021N (hereinafter referred to as NPL1), it is known that the illumination limit and therefore the maximum intensity of the emitted light of phosphor converter ceramics is limited by thermal quenching.

[0004] The academic paper, Anastasiia Krasnoshchoka, Anders Kragh Hansen, Anders Thorseth, Dominik Marti, Paul Michael Petersen, Xu Jian, and Ole Bjarlin Jensen, “Phosphor material dependent spot size limitations in laser lighting,” Opt. Express 28, 5758-5767 (2020) (hereafter referred to as NPL2), Light source The limiting properties of the .lambda. and their dependence on the spot size of the excitation light are described.

[0005] High resolution optical line scanners require long-life broadband light sources with high intensity. Phosphor converters are increasingly being used as powerful broadband sources for light sources in, for example, automated microscopy.

[0006] The use of such broadband sources is also increasing in metrology (see U.S. Pat. No. 10,180,355 B2 and U.S. Patent Application Publication No. 2010 / 0097779 A1). However, heat generation presents a problem, leading to a preference for dynamic solutions that distribute heat generation by moving the phosphor, thus reducing localized heating. As described in U.S. Patent Application Publication No. 2010 / 0097779 A1, higher intensities can, in principle, be achieved. However, mechanical movement entails a certain amount of wear and therefore a shortened service life. In addition, to improve mechanical stability, thicker phosphor layers must be used, leading to a lower illumination limit (see NPL1), thereby again negating some of the intensity increase achieved by movement. Additionally, movement and the resulting movement artifacts increase the effective emission area, which in area-limited systems, such as chromatic confocal measurement methods, leads to either a lower intensity being achieved or a constant intensity that must be achieved with reduced resolution.

[0007] In summary, up to now only a portion of the emitted radiation is used in the measurement system, however the unused photons also contribute to heating and therefore limit the intensity and lifetime of the white light source. Summary of the Invention [Problem to be solved by the invention]

[0008] It is therefore an object of the present invention to provide a chromatic confocal measurement device that uses an efficient, long-life broadband light source with an optimized radiation pattern for the chromatic confocal sensor. A high light intensity light source is required, especially in the visible spectral range, due to efficient detectors, which limits the measurement speed of the chromatic confocal signal and measurement device due to the availability of high-speed hardware and software. [Means for solving the problem]

[0009] According to the invention, the object is to Light source This is achieved by using focused illumination of the chromatic confocal measurement system and using the resulting broadband measurement light in a chromatic confocal measurement system. Light source Imaging the pump light source onto the beam path and onto the end of the fiber or fiber bundle Light source The beam paths of the imaging of Light source Light incident on and Light source and used as measurement light follows the same path in the opposite direction about the section. A dichroic beam splitter is used to separate or separate light from the beam path to the pump source, which light is used as measurement light and is coupled into a fiber or fiber bundle for this purpose.

[0010] In a preferred embodiment, Light source The optical path for imaging the pump light source onto the end of the fiber or fiber bundle. Light source The coincidence of the optical paths of the imaging is achieved by the first optical system and the second optical system including at least one common imaging optical element, in particular a lens.

[0011] A chromatic confocal measurement device is claimed according to claim 1, and a light source for use in a chromatic confocal measurement device is claimed according to claim 14 or 15. A chromatic confocal single-point or multi-point measurement device is proposed having a long-life, powerful broadband light source from the visible to near-infrared wavelength range for measuring the distance / thickness of an object to be measured. Optical measurement devices based on chromatic confocal or interferometric measurement principles are known.

[0012] Light source The base light source is a luminescent material (e.g., a luminescent substance) that emits light by a physical process, especially fluorescence, phosphorescence, or luminescence. Light source A pump source (typically a laser or LED) is understood to be a light source used to excite a Light source is generally a radiation conversion material.

[0013] In a preferred embodiment, Light sourceThe excitation of the laser is optimized to produce an optimal radiation pattern for coupling into the measurement system, taking into account volume scattering and associated changes in the illumination and emission areas (see NPL2).

[0014] A preferred embodiment is Light source The emission area of ​​the irradiated light is typically larger than the area illuminated by the pump light (see NPL2). Light source The illumination area is less than or equal to the lateral extent of the face of the fiber bundle or fiber, and / or the illumination area is less than or equal to the lateral extent of the face of the fiber. Light source is selected so that the imaging of the illuminated area is less than its lateral dimension.

[0015] On the other hand, this is Light source The small lighting area of Light source This ensures that heat generation is reduced so that a long service life and high optical performance of the broadband light source are achieved.

[0016] At the same time, it is ensured that the lateral dimensions of the emission surface do not or only slightly limit the amount of light that can be coupled into the fiber or fiber bundle. In order to be able to couple out a large angular range of emitted light, the numerical aperture of the optical system in the light source and in the receiving path of the fiber or individual fibers of the fiber bundle is typically selected to be a high value, with the numerical aperture of the fiber being the limiting factor in most cases.

[0017] In another embodiment of the chromatic confocal measurement device, the light source is provided by appropriate selection of the first optical element or by using an additional optical element in front of the dichroic mirror, which additional optical element is used to introduce spherical aberration into the wavefront.

[0018] The following embodiments are particularly preferred: The first optical element (including, among other things, a lens) is selected to produce spherical aberration at the dominant wavelength of the pump light source. Spherical aberration can be further introduced by inserting a glass plate in front of the first optical element. Furthermore, spherical aberration can be produced by additional optical elements such as lenses or correctors.

[0019] The above possibilities are particularly relevant when spherical aberration is Light source Further, the spherical aberration may be generated only by the second optical element.

[0020] Additionally or alternatively, to enlarge a particular spot or Light source to optimize the beam profile by the propagation invariance of optical aberrations so that the illuminated area of ​​the beam has a uniform intensity beam profile or a radial position-dependent beam profile with a rotationally symmetric intensity distribution, in particular an annular beam profile, an intensity profile consisting of several rings or a flat-top profile, Light source can be shifted axially relative to the focal point of the illumination path.

[0021] In a further embodiment of the chromatic confocal measurement device, Light source diffractive optical elements are introduced into the light source, the dichroic mirror or the beam splitter so that the illuminated area of ​​has a rotationally symmetric intensity distribution with a dependence on the radial position, in particular an annular beam profile, an intensity profile consisting of several rings or a flat-top profile.

[0022] In another embodiment of the chromatic confocal measurement apparatus, the one or more axicons in the light source are: Light source It is used as an optical element to generate Bessel-Gaussian beams in the region of

[0023] In another embodiment of the chromatic confocal measurement device, the light source comprises: Light sourceThe present invention operates with multiple pump sources illuminating non-overlapping or partially overlapping regions of a pump source. In the embodiment shown in FIG. 2, the pump sources are arranged to pass through the same optical element, but the beam paths differ in position and angle. Similarly, a beam splitter can be used to combine the beam paths of the pump sources used to the extent that all beam paths pass through a second optical element. Similarly, a polarization-dependent beam splitter can be used to combine the beam paths of multiple polarized pump sources with little loss of light intensity.

[0024] Similarly, by using a single pump source and splitting its beam into multiple beam paths by optical elements, in particular diffractive optical elements, beam splitters or gratings, Light source Multiple non-overlapping or partially overlapping regions in the image can be illuminated.

[0025] In a preferred embodiment of the present invention, broadband light is coupled into a fiber bundle, and the side of the fiber bundle opposite the coupling side of the fiber bundle is arranged at different positions on the object to be measured, suitable for measuring multiple thicknesses or thicknesses. In this case, the coupling side is the side of the fiber into which light coming from the light source is coupled. On this side, the fibers are preferably arranged as spatially close as possible to efficiently capture the light to be imaged. The opposite side is the measurement head side. Particularly preferably, the fibers are arranged in a row on the measurement head side to enable measurement along a line.

[0026] In an alternative embodiment of the chromatic confocal measurement device, the light source Light sourceis illuminated in the same manner as described above, but the converted light is coupled into a multimode fiber instead of a fiber bundle. The light guided by the multimode fiber is split into a line, discrete points, or other arrangement outside the light source and applied to measure multiple thicknesses of the target or thickness at different locations on the target. Splitting the light guided by the multimode fiber into a line can be achieved, for example, by a cylindrical lens in the measurement head. Splitting into discrete points can be achieved, for example, by using a shadow mask in the optical path downstream of the multimode fiber. For example, it is also possible to combine a cylindrical lens in the measurement head with a shadow mask to obtain a line of discrete points.

[0027] An alternative embodiment provides a chromatic confocal single-point measurement device for measuring the distance or thickness of an object to be measured, the light source of which is realized as described above, the difference being that a single fiber having a diameter of less than 300 μm, preferably less than 50 μm, is used.

[0028] One possible embodiment of the chromatic confocal single point measurement device is: Light source is characterized in that the illumination area is smaller or only slightly larger than the fiber surface.

[0029] Another possible embodiment of a chromatic confocal measurement device is described in the unpublished German patent application DE 102020116215. This patent application describes an optical measurement device including a measurement head with imaging optics and an evaluation unit, where the measurement head is connected to the evaluation unit by two light-conducting fibers. The evaluation unit includes a light source, whose light is guided to the measurement head through a first light-conducting fiber, and light reflected from the measurement object passes through the measurement head and is guided to a second light-conducting fiber by a beam splitter so that the outgoing and returning light are separated, the fiber ends being in mutually conjugate positions. The fiber ends acting as the beam splitter and the aperture are arranged together in connectors that are separately connected to the measurement head.

[0030] The above device can be combined with speckle reduction techniques such as reducing the amount of coherence by using a wider broadband pump source or by introducing frequency or phase modulation into the pump source, for example by changing the ambient temperature or diode current.

[0031] The above device can be extended by a cylindrical lens so that the astigmatism prevailing in the light source is corrected. In particular, if the pump light source has asymmetric radiation characteristics—as is the case for example with LEDs, whose divergence angle is strongly direction-dependent—this effect can be at least partially corrected by a cylindrical lens. The cylindrical lens is used to correct the astigmatism prevailing in the pump light source and Light source However, in preferred embodiments, the cylindrical lens can be positioned at a different position in the beam path between the first optical element and the dichroic beam splitter. Preferably, the cylindrical lens is oriented to act parallel to the axis with a small divergence angle of the pump light source.

[0032] In an alternative embodiment, the above apparatus may be designed to use free beam optics instead of fibers or fiber bundles to direct the measurement light from the light source to the measurement head.

[0033] The present invention also relates to a light source for use in a chromatic confocal measurement device, Light source (5) Imaging the beam path of the pump light source (1) onto the end of the fiber or fiber bundle (8a) Light source The beam paths of the imaging (5) are partially coincident and the light source is a light source on the end of a fiber or fiber bundle (8a). Light source (5) The optical path of the image is Light source (5) includes a dichroic beam splitter (3) arranged to separate the pump light source (1) from the optical path of imaging onto the pump light source (1).

[0034] In an alternative embodiment of a light source for use in a chromatic confocal measurement apparatus, the pump light source comprises a plurality of Light source The image is captured on a combination of Light source A combination of two or more Light sourceare layered on top of each other, or the beam path is split by a dichroic mirror or beam splitter, and the first and second Light source and the first and second Light source The light emitted from the first and second electrodes is recombined by a dichroic mirror or beam splitter.

[0035] Further features and advantages of the invention will become apparent from the following description of embodiments based on the drawings. [Brief explanation of the drawings]

[0036] [Figure 1] 1 shows a first advantageous embodiment of a chromatic confocal measurement device. [Figure 2] 2 shows a second advantageous embodiment of a chromatic confocal measurement device. DETAILED DESCRIPTION OF THE INVENTION

[0037] FIG. 1 shows a first advantageous embodiment of a chromatic confocal measurement device. As an example, a chromatic confocal measurement device includes a broadband light source ranging from the visible wavelength range to the near infrared range.

[0038] The light source includes a pump light source 1 in the wavelength range of 350 nm to 500 nm, which is collimated by a first optical element 2 and reflected by a dichroic mirror or beam splitter 3; Light source The first optical element 2 and the second optical element 4 focus the pump light source 1. Light source Together they form a first optical system that images onto the 5.

[0039] Light source The emission area 102 is preferably larger than the illumination area 101. Thus, the broadband light is emitted over the total area 102. Light source is emitted from

[0040] Light sourceThe broadband light emitted by 5 is then collimated again by the second optical element 4. Thus, the emitted light again follows the same path as the incident light. After passing through the dichroic mirror or beam splitter 3 again and being transmitted instead of reflected, and thus separated, it is coupled by the third optical element 7 into a fiber bundle or fiber 8 due to the dichroic nature of the beam splitter 3 and the shift in the spectral distribution of the light. Optical elements 4 and 7 Light source 5 onto the fiber surface 8a. Thus, the entire emission area 102 is imaged onto the fiber surface 8a. Advantageously, the extent of the imaging of the emission area 102 onto the fiber surface 8a roughly corresponds to the extent of the fiber surface. In this way, it is ensured that the entire fiber surface is illuminated and light losses during coupling are minimized. Therefore, in a preferred embodiment, the image of the illumination area 101, which is smaller than the emission area 102, is also smaller than the fiber surface 8a.

[0041] When a fiber bundle 8 is used, the fiber plane 8a is the plane of all of the individual fibers of the fiber bundle 8. Such a plane of a fiber bundle is shown in FIG.

[0042] In general, the optical elements may include lenses or lens groups or equivalent elements (eg, imaging mirrors), respectively.

[0043] 2 shows another embodiment of the chromatic confocal measurement device. In this embodiment, the chromatic confocal measurement device includes a broadband light source from the visible wavelength range to the near-infrared range. The light source includes, for example, two pump light sources 1, which are coupled to a first optical element 2 and a second optical element 4 via a dichroic mirror. Light source The image is captured on 5. Light source is placed on the heat sink 6, Light sourceLight emitted from 5 is imaged onto face 8a of fiber bundle 8 using a second optical system including second optical element 4 and third optical element 7. The fibers of fiber bundle 8 are arranged, for example, in a circular area at first fiber end 8a and, for example, along a line at the other fiber end. Light exiting fiber face 8b propagates, for example, to homogenizer 9, is reflected by beam splitting element 10, and is then focused onto target 12 by optical element 11, which exhibits dispersive behavior and generates different focal points depending on the wavelength of the light.

[0044] Further embodiments of the chromatic confocal measurement device include combinations of individual features from FIGS.

Claims

1. A chromatic confocal measurement device, comprising: a broadband light source from the visible wavelength range to the near-infrared range, in particular in the wavelength range of 400 nm to 900 nm, using a pump light source (1) in the wavelength range of 350 nm to 500 nm; a first optical system for imaging the pump light source (1) onto a luminophore (5); a second optical system for imaging the luminophores onto the surface (8a) of the fiber or fiber bundle so that at least a portion of the broadband light is coupled into the fiber or fiber bundle; Including, The light coupled into the fiber or fiber bundle (8) is used as measurement light for the chromatic confocal measurement device, - the beam path of the imaging of the pump light source (1) onto the luminophore (5) and the beam path of the imaging of the luminophore (5) onto the surface (8a) of the fiber or fiber bundle partially coincides; the measuring device includes a dichroic beam splitter (3) arranged to separate the beam path of the imaging of the luminophores (5) onto the end (8a) of the fiber or fiber bundle from the beam path of the imaging of the pump light source (1) onto the luminophores (5); A chromatic confocal measurement device characterized by:

2. Chromatic confocal measurement device according to claim 1, characterized in that the first optical system and the second optical system comprise at least one common imaging optical element, in particular a lens (4).

3. the illumination area (101) of the luminophores (5) is less than or equal to the lateral extent of the coupling side of the fiber bundle or fiber (8), and / or the image of the illumination area of ​​the luminophores on the coupling side (8a) of the fiber bundle or fiber (8) is smaller than the lateral dimension of the coupling side (8a) of the fiber bundle or fiber; 3. The chromatic confocal measurement device according to claim 1, wherein:

4. spherical aberration is introduced into the wavefront by further optical elements in front of the dichroic mirror (3), and / or spherical aberration is introduced into the wavefront by optical elements downstream of the dichroic mirror (3), and / or Chromatic confocal measurement device according to any one of claims 1 to 3, characterized in that the luminophore (5) is axially displaced with respect to the focus of the illumination path.

5. Chromatic confocal measurement device according to any one of claims 1 to 4, characterized in that several pump sources (1) are used which illuminate non-overlapping or only partially overlapping areas on the luminophore (5).

6. A chromatic confocal measurement device as described in any one of claims 1 to 4, characterized in that the pump light is split into multiple beam paths by optical elements such as diffractive optical elements, beam splitters or gratings, and non-overlapping or only partially overlapping areas on the luminophores are illuminated thereby.

7. 7. A chromatic confocal measurement device according to claim 1, characterized in that the broadband light is coupled into a fiber bundle (8) and the side of the fibers of the fiber bundle opposite the coupling side (8a) of the fiber bundle is arranged in an arrangement suitable for measuring multiple thicknesses of the object to be measured or thicknesses at different positions of the object to be measured, in particular in a line.

8. 7. A chromatic confocal measurement device according to any one of claims 1 to 6, characterized in that coupling into a single multimode fiber is performed, and the coupled light, after leaving the fiber (8), is split into lines, discrete points or other spatially extending arrays and applied to measure multiple thicknesses of the object to be measured or thicknesses at different positions of the object to be measured.

9. Chromatic confocal measurement device according to any one of claims 1 to 6, characterized in that a single fiber having a diameter of less than 300 μm, preferably less than 50 μm, is used and a single point of the target is measured.

10. 10. The chromatic confocal measurement device according to claim 1, wherein an apparatus is used that includes first and second fibers and a beam splitter cube, and the first fiber is in particular the fiber (8) into which the broadband measurement light is coupled, whereby the first fiber guides the measurement light from the light source towards a measurement head of the measurement device, the measurement head guides the measurement light to the measurement object and returns light reflected and returned or backscattered by the measurement object to the beam splitter, the beam splitter combines the measurement light with the light propagating back from the measurement object, and the second fiber of the apparatus guides the light coming from the measurement object and propagating through the beam splitter to a spectrometer of the chromatic confocal measurement device.

11. Chromatic confocal measurement device according to any one of claims 1 to 10, characterized in that speckle reduction techniques are used, in particular reduction of the magnitude of coherence by using a broader band pump source or by introducing frequency or phase modulation into the pump source, for example by changing the ambient temperature or diode current.

12. Chromatic confocal single-point or multipoint measuring device according to any one of claims 1 to 11, characterized in that astigmatism present in the pump light source (1) is corrected by a cylindrical lens.

13. Chromatic confocal single-point or multi-point measuring device according to any one of claims 1 to 12, characterized in that instead of the fiber or fiber bundle (8), the measuring light is guided from the light source to the measuring head through free beam optics.

14. A light source for use in a chromatic confocal measurement device, emitting light in the visible wavelength range to the near-infrared range, in particular in the wavelength range of 400 nm to 900 nm, comprising: a pump light source (1) in the wavelength range of 350 nm to 500 nm; a first optical system suitable for imaging said pump light source (1) onto a luminophore (5); a second optical system suitable for imaging the luminophores onto the end (8a) of the fiber or fiber bundle, so that at least a portion of the broadband light is coupled into the fiber or fiber bundle; In a light source including the beam path of the imaging of the pump light source (1) onto the luminophore (5) and the beam path of the imaging of the luminophore (5) onto the end (8a) of the fiber or fiber bundle partially coincide; the light source includes a dichroic beam splitter (3) arranged to separate the beam path of the imaging of the luminophores (5) onto the end (8a) of the fiber or fiber bundle from the beam path of the imaging of the pump light source (1) onto the luminophores (5); A light source characterized by:

15. A light source for use in a chromatic confocal measurement device, emitting light in the visible wavelength range to the near-infrared range, in particular in the wavelength range of 400 nm to 900 nm, comprising: a pump light source (1) in the wavelength range of 350 nm to 500 nm; a first optical system suitable for imaging said pump light source (1) onto a combination of multiple luminophores; a dichroic mirror or beam splitter (3), a second optical system suitable for imaging the luminophores onto the end (8a) of the fiber or fiber bundle, so that at least a portion of the broadband light is coupled into the fiber or fiber bundle; In a light source including The combination of the lumophores is realized such that two or more lumophores are layered on top of each other; or The realization of the combination of luminophores is such that a beam path is split by a dichroic mirror or beam splitter and illuminates a first and a second luminophor, and the light emitted from the first and second luminophores is recombined by the dichroic mirror or the beam splitter.

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