DE102022112765A1 - Detection unit for the spectral analysis of a laser-induced plasma and laser-induced plasma spectrometer - Google Patents

Abstract

There is a detection unit (21) for a spectrometer system (1) for the spectral analysis (LIBS) of a plasma light (3A) emitted by a laser-induced plasma (3), the plasma (3) being coupled with a laser beam (5A) propagating along a beam axis (5A). 5) is generated on a surface (7A) of a sample (7). The detection unit (21) comprises a lens holder (23) and a plurality of lenses (25A, 25B, 25C, 25D) held by the lens holder (23). Each of the lenses (25A, 25B, 25C, 25D) is assigned a detection cone (35), which forms a plasma detection area (39) in an overlap area (37) with the laser beam (5), from which in the case of a plasma detection area (39) present plasma (3) a measurement component (33) of the plasma light (3A) is detected by the lens (25A, 25B, 25C, 25D). The lenses (25A, 25B, 25C, 25D) are arranged and aligned in the lens holder (23) in such a way that the plasma detection areas (39) are arranged offset along the beam axis (5A) and together form a viewing area (41) of the detection unit (21). form. The increased depth of field using the multifocal detection concept can shorten the measuring process of the spectral analysis.

Description

The present invention relates to systems for laser-induced plasma spectroscopy, in particular a detection unit for the spectral analysis of a laser-induced plasma. The invention further relates to a spectrometer system, in particular with a light guiding system comprising a plurality of optical fibers.

Laser-induced plasma spectroscopy - also known as LIBS (laser induced breakdown spectroscopy) or LIPS (laser induced plasma spectroscopy) - is used to determine an element-specific composition of a sample using a plasma. The plasma is generated on the surface of the sample using high-intensity, focused laser radiation. Light emitted by the plasma is detected and spectrally evaluated in order to determine the elemental composition of the sample.

LIBS systems are known from the prior art, which measure a height profile of the sample in order to correctly focus the laser radiation on the surface and adjust the distance of the spectrometer accordingly. An automatic focusing device is e.g. Am CN 107783242 A disclosed. Furthermore, portable devices with e.g. B. one or more spectrometers known, see e.g. b. US 11,085,882 B1.

Advantages of LIBS, and of laser-based optical emission spectroscopy in general, include non-contact analysis, which can be carried out at a distance from the sample of e.g. B. 100 mm, 200 mm or 500 mm and is free of ionizing radiation. Exemplary areas of application of one of the LIBS-based material identification disclosed herein include an analysis of homogeneous and heterogeneous samples on a stationary system or an analysis of continuous samples, for example (online) metal analysis of samples transported on a conveyor belt. Material identification can be used as a preparatory step for material sorting. The quick evaluation of the detected spectra can, for example, B. allow feed speeds of a few m/s in conveyor belt systems. Due to the contact-free analysis, LIBS systems can be designed to be insensitive and error-resistant in industrial working environments.

In general, the present disclosure is directed at improving, at least in part, one or more aspects of known LIBS-based systems. One aspect of this disclosure is based on the task of enabling the use of LIBS with easy sample handling. In particular, a quick and reliable analysis of samples with structured, undefined (and therefore unknown) surface contours is essential for the integration of LIBS into industrial workflows. Another aspect of this disclosure is based on the task of providing sufficiently strong detection signals in the context of LIBS, especially when analyzing samples with a structured, undefined surface profile. A further aspect of this disclosure is based on the task of specifying an optical system, in particular for LIBS, which eliminates the disadvantages of the prior art, particularly with regard to samples with a structured, undefined surface shape. A further aspect of this disclosure is based on the task of specifying a light guidance system for a LIBS system that enables simple transmission of plasma light to an optical spectrometer.

At least one of these tasks is solved by a detection unit according to claim 1 and by a spectrometer system according to claim 11. Further developments are specified in the subclaims.

In one aspect, a detection unit for a spectrometer system for spectral analysis of a plasma light emitted by a laser-induced plasma, wherein the plasma is generated on a surface of a sample with a laser beam propagating along a beam axis (and in particular a spectral splitting of the plasma light for the spectral analysis in an optical spectrometer), a lens mount and several lenses held by the lens mount. Each of the lenses is assigned a detection cone, which forms a plasma detection area in an overlapping area with the laser beam, from which, in the case of a plasma present in the plasma detection area, a measurement portion of the plasma light is detected by the objective. In other words, tips of the detection cones lie just behind the laser axis, causing the detection cones to “hug” a possible plasma in the plasma detection area. The lenses are arranged and aligned in the lens holder in such a way that the plasma detection areas are arranged offset along the beam axis and together form a viewing area of the detection unit.

In general, the field of view of the detection unit is an area along the beam axis from which the detection unit can detect plasma light in the form of measurement components from individual lenses. The detection unit can in particular comprise two to 25, for example four, five, eight, nine or 15 lenses.

In a further aspect, a spectrometer system for the spectral analysis of a plasma light emitted by a laser-induced plasma has a laser beam source for emitting a, in particular pulsed, laser beam, wherein the plasma is generated on a surface of a sample with the laser beam propagating along a beam axis. Furthermore, the spectrometer system includes focusing optics for focusing the laser beam onto the surface of the sample, a detection unit disclosed herein, and an optical spectrometer for spectral analysis of a plasma light detected by the detection unit. Plasma detection areas of the detection unit are arranged in a section along the beam axis. Furthermore, the laser beam source and the focusing optics are designed to generate a plasma in each of the plasma detection areas when the surface of the sample is positioned. For this purpose, for example, beam parameters of the laser beam, including in particular the pulse duration and pulse energy of a pulsed laser beam, are set or adjustable depending on the material of the sample.

In some developments, the plasma detection areas can partially overlap along the beam axis, merge into one another or be spaced apart from one another. Alternatively or additionally, the plasma detection areas can each extend over 0.1 mm to 15 mm (for example 0.1 mm to 10 mm) and/or over 1/10 to 1/4 of the viewing area along the beam axis. Alternatively or additionally, the lens holder can provide an optical through-opening through which the beam axis runs, wherein a position of the beam axis can be fixed in particular in the middle of the optical through-opening. The lens holder can in particular have a mounting plate in which a plurality of lens holder openings for receiving the lenses and the optical passage opening for the laser beam are provided. The lens holder openings can be arranged around the optical through-opening, and in particular azimuthally distributed around the optical through-opening. The lens mounting openings can be designed as through openings or recesses, with apertures of the lenses of the detection unit for receiving light generally being arranged on one side of the mounting plate and light outputs of the lenses for coupling light into the light guidance system can be arranged on the other side.

In some developments, each of the detection cones (starting from the aperture of an associated objective) can extend along an observation axis that runs at an observation angle in the range of approximately 0° to approximately 90° to the beam axis. The observation angles can in particular be the same, not differ from each other by more than 3° or be distributed in an angular range of 45°. The lens holder can in particular have a mounting plate in which an optical passage opening for the laser beam is provided, the beam axis extending orthogonally to the mounting plate. At least one of the detection cones can extend (starting from the aperture of an associated objective) along an observation axis which is at an observation angle in a range of approximately 0° to approximately 90°, in particular in a range of approximately 3° to approximately. 60°, for example in the range from approx. 5° to approx. 25°, to the beam axis.

In some developments, the lenses can be arranged azimuthally (in particular azimuthally with respect to the beam axis) spaced around the beam axis. The lenses can in particular be arranged with the same azimuth distribution around the beam axis. In other words, observation axes of the lenses can run from the respective center of the aperture of an objective in the direction of the beam axis and accordingly define planes that run through the beam axis and the respective observation axis. Each of the planes can be assigned a specific azimuthal angle with respect to the beam axis. For four lenses with the same azimuthal distribution, the azimuthal angles of adjacent lenses differ by 90°, for example.

In some developments, the detection unit can further comprise an optical light guide system that has a plurality of optical inputs and an optical output. Each of the optical inputs can be optically connected to one of the lenses and designed to record the measurement portion recorded with the associated lens. The optical output can be designed to output the measurement components recorded with the lenses. In other words, the optical output of the light guide system can be designed as a common functional output for emitting the measurement components recorded with the objective.

In some developments, the optical light guide system can have several optical fibers. In each case a light entry surface of one of the optical fibers can form one of the optical inputs and the lens assigned to the optical input can be designed and arranged (in particular aligned) to image the plasma detection area of the assigned lens onto the light entry surface. The light exit surfaces of the optical fibers can form the optical output, whereby the light exit surfaces can in particular be arranged in a row, adjacent or spaced apart from one another. Furthermore, can the light exit surfaces can be arranged in a row, in particular according to the sequence of the plasma detection areas in the viewing area. In some developments, the optical fibers can be lined up linearly on the output side, in particular for alignment along an entrance slit of an optical spectrometer, in which, for example, a spectral splitting of the plasma light for the spectral analysis of a plasma light detected by the detection unit takes place. In particular, there can be a parallel fiber orientation on the output side for the rectified delivery of the measurement components.

In some developments, a light guide zone of an optical fiber can have a diameter of e.g. B. in the range from approx. 100 µm to approx. 1,000 µm (or more), in particular in the range from approx. 100 µm to approx. 300 µm, in the range from approx. 150 µm to approx. 250 µm or in the range from approx 750 µm to approx. 850 µm.

In some embodiments of the spectrometer, this may include an optical light guide system, which is designed to forward measurement components of the plasma light detected by the detection unit to the optical spectrometer and includes a plurality of optical inputs and an optical output. Each of the optical inputs can be optically assigned to one of the lenses and designed to record the measurement portion recorded with the assigned lens. The optical output can be designed to couple measurement components recorded with the lenses into the optical spectrometer. In particular, at least one of the lenses can be designed and arranged in the lens holder in such a way that a measurement portion of the plasma light, which is detected in the detection cone of the lens, is imaged onto the optical input assigned to the lens.

In some developments, each of the measuring components emerging from the optical light guide system can be assigned a beam axis, and the beam axes can run parallel to one another or no more than at an angle of up to approximately 1° or up to approximately 3° to one another.

In some developments, the optical spectrometer can include an entrance aperture, in particular an entrance slit, a dispersive optical element, in particular a grating, prism or grating prism, and a detector, wherein the measurement components can be coupled into the optical spectrometer through the entrance aperture and via the dispersive optical Element can be guided to the detector in a spectrally resolved manner in order to output a spectral distribution assigned to the lenses of the detection unit.

Examples of samples/materials to be examined according to the invention include homogeneous and inhomogeneous materials, which are characterized in particular by an uneven, non-uniform spatial surface contour. Possible samples/materials to be examined include solids, powders or granules such as metals, glass, sand, salt, minerals, slag, rock, flour, sugar, (agricultural) soil samples, gypsum, clay, lime, marl, cement, coal, coke, Ore, emulsions, sludges and especially thick/viscous samples such as melts, e.g. B. from glass, aluminum, iron and pig iron, salt, etc.

In the context of the lenses disclosed herein, a detectable volume extends from the lens apparatus (generally, a lens includes one or more focusing optical elements, such as a focusing lens or a focusing mirror, and optionally defocusing optical elements, such as a defocusing lens or a defocusing mirror, which are held in a housing) in the direction of the plasma to be detected. The volume detectable with an objective is referred to herein as the detection cone (and is also known as the “light cone” of an objective). In the context of the present disclosure, a detection cone thus generally corresponds to a volume from which light can be detected by an objective and forwarded to an optical spectrometer. In the case of a round objective aperture, the detectable volume is conical in the narrow sense, i.e. H. with a circular cross section. Within the scope of the present disclosure, a detection cone also includes a cone geometry that deviates from rotational symmetry and therefore does not have a round cross-sectional geometry. The axis of the detection cone is also referred to herein as the observation axis and generally defines an observation direction of the objective.

In LIBS, an overlap area of the detection cone with the laser beam represents a plasma detection area of a lens. The detection cone usually extends over the plasma that is generated by the laser beam in the area of the beam axis of the laser beam, and thus extends beyond the beam axis to be in the area of the plasma to have a cross section adapted to the size of the plasma in order to detect the largest possible measurement portion of the plasma light.

In other words, each lens can capture plasma light from a plasma at a predetermined solid angle relative to a focal point of the lens. The prerequisite is that the plasma lies in the detection cone/light cone of the lens that defines the solid angle of the detectable light, preferably at the pointed end of the lens Detection cone/light cone. Possible dimensions of the cross section of the detection cone at the position of the plasma to be detected can be such that at the position of the plasma to be detected there is a length in the direction of propagation of the detection cone, which is z. B. in the range of 10% to 25% of the length of the viewing area to be provided by the detection unit (in the direction of propagation) and, for example, in the range of 0.1 mm to 10 mm or z. B. can be up to 15 mm.

As part of the LIBS disclosed herein, samples are examined which have a three-dimensional contour on the side of the incident laser beam, so that - when carrying out the measurement on different surface areas - a surface of the sample is not in a fixed location in the direction of the beam axis of the laser beam, on which the laser beam could be focused. The three-dimensional shape of the sample means that the plasma does not form at a fixed location in the direction of the beam axis, but can vary in its position along the beam axis of the laser beam. The extent of the possible variation in the location of a plasma that can be used for spectral analysis (herein also referred to as the laser induced plasma excitation area) depends - in addition to the shape of the surface of the sample in the direction of the beam axis and the coupling ability (absorption) of the Material - on the focusing of the laser beam, and in particular on the intensity profile of the laser beam in the focus area. With appropriate beam parameters (focus diameter and focus length) and laser parameters (laser power, laser pulse energy, laser pulse duration...), the possible plasma ignition range in the direction of the beam axis can range from a fraction of a millimeter to a few millimeters (e.g. 2 mm to 4 mm) or even up to a few 10 cm, e.g. B. extend up to 20 cm.

In some embodiments, implementation of the multifocal concept may have the following advantages. With regard to the detection of plasma light, a depth of field, here in the sense of a detectable depth range along the laser propagation direction, given by the arrangement of the lenses, is significantly increased. This makes it possible or easier to examine samples with irregular surface shapes. In this way, the detection of plasma light across the ignition area becomes independent of a mechanical movement of the detection unit or the sample in the laser beam direction. This results in a greater tolerance with regard to the position of the sample/sample surface and thus the surface geometry of the sample. Furthermore, sample preparation such as smoothing a powder or pressing a surface smooth can be omitted.

When designing a detection device, the depth of field can be increased through the optical design of a single lens. A greater depth of field caused by the optical design of a single objective can result in an increase in the distance to the sample, thereby reducing the amount of light captured by the objective (reduction in the solid angle/light cone of the objective). To compensate for this, a lens with a larger aperture (larger light cone) can be used.

In contrast to such designs/optical configurations of lenses, the inventive multifocal concept achieves a depth of field extending over a larger area through the use of multiple lenses with offset plasma detection areas. The offset plasma detection areas mean that plasma light can be detected from a greater depth range. It is not necessary to change the distance, so the amount of light captured remains the same.

Due, among other things, to a greater tolerance with regard to the location at which a plasma to be detected is generated, the multifocal detection approach proposed here can be used to carry out a substantially sample preparation-free analysis of (homogeneous and heterogeneous) samples on a stationary system or an analysis of samples in transit.

In some embodiments of the multifocal concept - even with a more structured three-dimensional surface shape of a sample - a spectrometric examination can be carried out without or, if at all, with only a rudimentary height adjustment preceding the measurement process.

In some embodiments, implementation of the multilateral concept may have the following advantages. A plasma can be viewed simultaneously from different observation directions, with the sum of all “observation directions” forming a common spectral optical (output) measurement signal. Even if one of the observation directions is blocked due to the surface shape of the sample or another obstacle, a sufficient measurement portion can still be available for the spectral analysis.

In some embodiments of the optical light guide system, the combination of n>1 fibers (e.g. n=2, 3, 4...10...15) on a (functional) fiber output can advantageously feed multiple lenses into an optical spectrometer allow. Advantages of such an n-fold ratio This can be seen in the implementation of the multifocal concept and the multilateral concept.

• 1 eine schematische Übersicht eines LIBS-Systems,
• 2 eine Skizze zur Verdeutlichung des multifokalen Konzepts,
• 3 eine perspektivische Ansicht eines beispielhaften LIBS-Messkopfs,
• 4A und 4B eine Aufsicht auf eine erste beispielhafte Halterungsplatte und eine perspektivische Ansicht einer Detektionseinheit (multifokales Konzept),
• 5A und 5B eine Aufsicht auf eine zweite beispielhafte Halterungsplatte und eine perspektivische Ansicht einer Detektionseinheit (multifokales Konzept),
• 6A und 6B eine Aufsicht auf eine beispielhafte Halterungsplatte und eine perspektivische Ansicht einer Detektionseinheit (multilaterales Konzept),
• 7A bis 7E schematische Skizzen zur Verdeutlichung eines beispielhaften mehrere Lichtleitfasern umfassenden Lichtleitsystems,
• 8A bis 8C schematische Skizzen zur Verdeutlichung einer Einkopplung des Lichtleitsystems aus 6 in ein optisches Spektrometer,
• 9A und 9B eine Illustration beispielhafter spektrale Intensitätsverläufe mit zugehöriger Messkonstellation (multifokales Konzept, Plasma in einem Plasmadetektionsbereich),
• 10A und 10B eine Illustration beispielhafter spektrale Intensitätsverläufe mit zugehöriger Messkonstellation (multifokales Konzept, Plasma innerhalb zweier Plasmadetektionsbereichen),
• 11A und 11B eine Illustration beispielhafter spektrale Intensitätsverläufe mit zugehöriger Messkonstellation (multilaterales Konzept, ohne Abschattung),
• 12A und 12B eine Illustration beispielhafter spektrale Intensitätsverläufe mit zugehöriger Messkonstellation (multilaterales Konzept, mit Abschattung),
• 13A bis 13C schematische Illustrationen industrieller Anwendungen am Beispiel des multifokalen Konzepts und
• 14A bis 14C zwei Flussdiagramme und eine Skizze zur Erläuterung von beispielhaften Messvorgängen.

Concepts are disclosed here that make it possible to at least partially improve aspects of the prior art. In particular, further features and their expediencies emerge from the following description of embodiments based on the figures. Of the figures show:

• 1 a schematic overview of a LIBS system,
• 2 a sketch to illustrate the multifocal concept,
• 3 a perspective view of an exemplary LIBS measuring head,
• 4A and 4B a top view of a first exemplary mounting plate and a perspective view of a detection unit (multifocal concept),
• 5A and 5B a top view of a second exemplary mounting plate and a perspective view of a detection unit (multifocal concept),
• 6A and 6B a top view of an exemplary mounting plate and a perspective view of a detection unit (multilateral concept),
• 7A until 7E schematic sketches to illustrate an exemplary light guide system comprising several optical fibers,
• 8A until 8C schematic sketches to illustrate coupling of the light guide system 6 into an optical spectrometer,
• 9A and 9B an illustration of exemplary spectral intensity curves with the associated measurement constellation (multifocal concept, plasma in a plasma detection area),
• 10A and 10B an illustration of exemplary spectral intensity curves with the associated measurement constellation (multifocal concept, plasma within two plasma detection areas),
• 11A and 11B an illustration of exemplary spectral intensity curves with the associated measurement constellation (multilateral concept, without shading),
• 12A and 12B an illustration of exemplary spectral intensity curves with the associated measurement constellation (multilateral concept, with shading),
• 13A until 13C schematic illustrations of industrial applications using the example of the multifocal concept and
• 14A until 14C two flowcharts and a sketch to explain exemplary measurement processes.

Aspects described here are partly based on the knowledge that the use of several lenses in combination with an optical spectrometer enables an expansion of the detectable solid angle component in LIBS. If the lenses are arranged and aligned accordingly, a captured depth of field area can be enlarged along the beam axis (multifocal concept). Alternatively or additionally, the proportion of detected plasma light emitted by a plasma at one location can also be increased (multilateral concept).

The inventors have recognized that using the concepts proposed herein, it is possible to capture plasma light over a field of view along the beam axis that is longer than that provided with only a single lens under comparable conditions. In the field of vision, the detection unit can provide a depth of field along an ignition area provided by the laser, which brings about a tolerance with regard to the position of the sample and thus the position of the plasma on the surface of the sample. Instead of height compensation according to the prior art by a mechanical method of the detection unit or the sample (or a mechanical adjustment of the sample surface to a focal point/to a punctiform ignition area), the multifocal concept uses several plasma detection areas that are arranged along the ignition area provided by the laser.

Here, a plasma detection area is determined by an observation axis and a solid angle, which are assigned to a lens. In order to provide comparable conditions for detecting plasma light, in particular for several lenses (or, for example, in the sense of a symmetrically implemented structure of a detection unit), the observation axes of the different lenses can be directed at the beam axis at a substantially same observation angle, but in the case of multifocal concept offset in the direction of the beam axis.

Due to the depth of field provided along the beam axis according to the multifocal concept disclosed herein, plasma light can be detected (without repositioning or regulating the spectrometer system) for sections of the surface profile of the sample in the correspondingly covered depth of field area, which is then spectrally recorded can be measured in a (common) optical spectrometer. The detectable signal contribution can thus be increased, whereby the measuring process can take less time than if only one lens is used for detection in a plasma detection area/at a position in the propagation direction.

The inventors have also observed that when using a single lens, there can be at least temporary spatial shadowing of a detection cone and the plasma to be detected in it. The shading is z. B. caused by the surface shape of the sample in space, as it exists in the environment of the plasma. The inventors have now realized that using multiple lenses makes it possible to capture plasma light that is emitted in different directions and analyze it with a (common) optical spectrometer. This can reduce the influence of shading effects.

In order to obtain comparable signal information from each of the lenses, in one embodiment the observation angles of the lenses that are as similar as possible (e.g. essentially identical) can be provided in relation to the direction of propagation of the laser beam. In the case of a spatially larger plasma, this can also prevent different plasma areas with possibly different spectral components from being combined into one signal.

The inventors have further recognized that, in an advantageous embodiment, an optical fiber bundle can be used to bring together the measurement components of the different lenses and to couple them together - at a functional fiber output of the optical fiber bundle - through a gap of an optical spectrometer into the optical spectrometer for spectral analysis. For this purpose, the optical fibers record the measuring portion of one of the lenses at one end during operation. At the other end, the optical fibers are brought together and held in an optical connector and form the common functional fiber output. The optical fibers preferably deliver at least a large portion of the measurement components to the same zones of the detector in order to achieve the highest possible signal strengths. For example, the optical fibers can emit their measurement components at the functional fiber output in the same direction. In some embodiments, the ends of the optical fibers can be aligned in the same way, in particular run as parallel as possible. Furthermore, the optical fibers can, for example, be lined up linearly and aligned along the gap when installed. In order to achieve the most localized possible location of the functional fiber output and thus the coupling of the measurement components into the optical spectrometer, the optical fibers in the optical connector can run close to one another, preferably directly next to one another.

In some embodiments, the ends of the optical fibers in the optical connector can run at angles to one another, the angles being coordinated with the geometry of the spectrometer (optical paths in the spectrometer) in such a way that the measurement components of the lenses on the detector of the optical spectrometer are also, if possible, in their maximums - e.g. B. in the direction of the linear array - can be placed on top of each other.

The various inventive concepts are explained below by way of example in conjunction with the figures.

1 shows a schematic overview of a spectrometer system 1 (LIBS system) for the spectral analysis of a plasma light 3A emitted by a laser-induced plasma 3 (schematically indicated as a filled circle). Detectable plasma light 3A is, for example, in the wavelength range of UV light, visible light, near infrared light and/or infrared light; In particular, plasma light to be detected can be in the spectral range from approximately 190 nm to approximately 920 nm. In LIBS, the plasma 3 is generated with a laser beam 5 on a surface 7A of a sample 7.

To generate the, e.g. B. pulsed laser beam 5, the spectrometer system 1 comprises a laser beam source 9. The laser beam source 9 is designed to provide laser beam parameters required for plasma generation; Examples of laser beam parameters for the material analysis of minerals, salts, ferrous and non-ferrous metals, etc. include, for example: B. Laser pulse energies in the range from <1 mJ to >100 mJ, laser pulse durations in the range from <1ns to >100 ns and a central laser wavelength e.g. B. in the infrared (IR) range (for example around 1064 nm), in the ultraviolet (UV) range or in a wavelength range in between or in several wavelength ranges, ie, for example, in a combination of several wavelengths, as well as fixed or adjustable repetition rates or laser pulse burst -Settings. The laser beam 5 is z. B. fed via an optical fiber 9A (optionally optically active, such as spectrally broadening or amplifying) to a focusing optics 11 and focused by this onto the surface 7A of the sample 7. The focusing optics 11 can in particular be designed as a laser head component with a focusing function, such as an active laser component with a focusing function that acts in particular on the spectrum or the pulse duration or the pulse energy. The propagation of the laser beam 5 between focusing optics 11 and Sample 7 is taken along a beam axis 5A. Exemplary focus diameters (1/e ² beam diameter in the beam waist) in the range from <50 µm to >250 µm and exemplary focus lengths (e.g. double Rayleigh length) are in the range from <5 mm to >1,000 mm.

Laser parameters can in particular be set/selected such that a region in which plasma generation can take place (also referred to as a possible ignition region), for example over a length in the range of approximately 0.2 mm to approximately 50 mm, for example over a length of 2 mm, 5 mm, 20 mm, 200 mm or 500 mm, extends along the beam axis 5A.

1 shows schematically a focus zone 11A elongated along the beam axis 5A, as formed in the area of the surface 7A of the sample 7. The plasma 3 forms due to the interaction of the laser radiation with the material on the surface of the sample 7A. In LIBS, the usual dimensions (average diameter) of a plasma 3 are in the range of z. B. 0.1 mm to 5 mm (depending on sample material and laser parameters).

The spectrometer system 1 further includes an optical spectrometer 13 for spectral analysis of the plasma light 3A. The optical spectrometer 13 is in 1 shown as an example as a grid spectrometer. In general, the spectrometer 13 comprises at least one dispersive element 13A, e.g. B. a grid, a prism or a grating prism, and a pixel-based detector 13B, onto which the plasma light strikes in a spectrally expanded manner. Spectral components of the plasma light 3A to be analyzed are assigned to the pixels of the detector 13B. The detector 13B outputs intensity values of the irradiated pixels to an evaluation unit 15, usually a computer with a processor and a memory. The evaluation unit 15 outputs a measured spectral distribution 17 and compares it, for example, with stored comparison spectra in order to assign the elements contributing to the plasma light 3A and thus to the examined sample 3 and output them as the result of the spectral examination.

In the spectrometer 13, a (spectral-dependent) beam input for the plasma light to be analyzed is defined by an entrance aperture 19, usually an entrance slit 19A.

The spectrometer system 1 further comprises a detection unit 21 with a lens holder 23 and a plurality of lenses 25A, 25B, 25C, which are held by the lens holder 23. As an example, three lenses are shown in the figures, two in the image plane and one behind it. The concepts disclosed herein are implemented with more than one lens in the lens mount 23. The number of lenses used can be selected depending on spatial and optical parameters as well as parameters of the material of the sample to be examined; it lies e.g. B. in the range from 2 to 20, for example with 4, 5, 8, 9 or 15 lenses.

The spectrometer system 1, in particular the detection unit 21, further comprises an optical light guide system 27, which optically connects the lenses 25A, 25B, 25C with the spectrometer 13. The light guide system 27 provides a plurality of optical inputs 29, each of which is optically assigned to one of the lenses 25A, 25B, 25C, and an optical output 31 (functional, common to the lenses), which is optically assigned to the entrance aperture 19.

Each of the lenses 25A, 25B, 25C is designed to capture a measurement portion 33 of the plasma light 3A and includes at least one focusing optical element (such as a converging lens usually arranged in a light-tight housing or a concave mirror). A detection cone 35 is assigned to each of the lenses 25A, 25B, 25C. The beam axis 5A runs through the detection cones 35, the detection cones 35 having a set minimum size in the area of the laser beam 5. Each of the detection cones 35 includes a plasma detection area 39 in an overlap area with the laser beam 5, which is assigned to the corresponding objective 25A, 25B, 25C. For example, the detection cones 35 have a length from an entrance aperture of an objective to the laser beam in the range of 100 mm to 500 mm. An example is given in 1 the plasma 3 is generated in the plasma detection area 39 of the lens 25B, so that the associated measurement component 33 of the plasma light 3A is detected by the lens 25B and imaged onto the associated optical input 29 of the light guide system 27. Measurement components 33 detected by one or more lenses are guided by the optical light guide system 27 to the common optical output 31 and coupled through the entrance aperture 19 into the optical spectrometer 13 for spectral analysis.

1 shows an example of three lenses 25A, 25B, 25C, which are arranged (azimuthally distributed) around the beam axis 5A. The lenses 25A and 25B lie on opposite sides of the beam axis 5A and are thus directed onto the beam axis 5A from opposite sides. The lens 25C is directed from behind onto the beam axis 5A. Another lens (in 1 not shown) can, for example, be directed from the front onto the beam axis 5A or directed along the beam axis 5A onto the focus zone 11A using a beam splitter be. For clarification are in 1 the detection cones 35 are indicated by dashed lines tapering conically towards the beam axis 5A, with the focus zone 11A, the plasma 3 and the plasma detection areas 39 being shown oversized compared to the detection cones 35 for clarity.

2 shows a mounting plate 23A of the detection unit 21 of the LIBS system to illustrate the arrangement and orientation of the lenses 25A, 25B, 25C. For stationary mounting of the lenses, the mounting plate 23A has lens mounting openings for receiving the lenses 25A, 25B, 25C. The lens holder openings are each arranged at a radial distance from the beam axis 5A and are designed for an oblique alignment of the lenses 25A, 25B, 25C to the beam axis 5A. To illustrate the oblique alignment, observation axes 35A of the lenses 25A, 25B, 25C are shown. In the example shown, the observation axes 35A run at an observation angle α to the beam axis 5A.

To implement the multifocal concept, the lenses 25A, 25B, 25C are mounted in the mount plate 23A (generally located and aligned in the mount 23) such that the plasma detection areas 39 are offset along the beam axis 5A. In particular, with comparable observation angles α, the offset in the direction of the beam axis 5A can be achieved by varying the radial distance of the lenses 25A, 25B, 25C from the beam axis 5A (optionally with varying insertion). Examples include different radial distances R1 and R2 for the lenses 25A and 25B in 2 indicated. Alternatively (optionally with a comparable radial distance) the observation angle of at least some of the lenses can be adjusted to the desired offset of the plasma detection areas 39 in the direction of the beam axis 5A (see, for example, 5B) . Mixed configurations are also possible.

In general, the observation angle α can be in the range from 0° (via beam splitters along the laser beam) to 90° (observation orthogonal to the laser beam). The observation angles α shown as examples within the scope of the disclosure are in the range from 3° to 60°, for example in the range from 5° to 25°. The observation axes 35A of adjacent lenses 25A, 25B, 25C approach the beam axis 5A from different azimuthal directions (azimuthal angle in the plane perpendicular to the beam axis 5A). Im in 2 In the case shown, the observation angles α are comparable for all lenses and do not differ more than e.g. B. 5° or 1° from each other (deviation given, for example, by permitted manufacturing tolerances of the lens holder openings and lenses). However, the arrangement varies 2 the radial distances to the beam axis 5A. Accordingly, comparable spectra can be recorded from the plasma detection areas 39 of the different objectives for a sample at different positions of the surface of the sample along the beam axis 5A (corresponding to different measurement constellations within the scope of a measurement process), for example from the objective 25B with a surface course according to the solid line ( Surface 7A of sample 7 1 ) or from the lens 25A in the case of a surface gradient according to the dash-dotted line 7A' or from the lens 25C in the case of a surface gradient according to the dashed line 7A''.

As in 2 indicated, the plasma detection areas 39 together form a viewing area 41 of the detection unit 21. The viewing area 41 extends along the beam axis 5A in the area of the focus zone 11A.

Each of the plasma detection areas 39 is assigned a measurement depth along the beam axis 5A. The measuring depth corresponds to: 2 e.g . B. a diameter of the circles that illustrate the plasma detection areas 39. For a lens, the measurement depth is a specific characteristic that is given by optical parameters such as focus length and aperture of the lens as well as by the arrangement and orientation of the lens (e.g. geometric position parameters of the lens with respect to the beam axis 5A - distance and angle). For example, the plasma detection areas 39 can each extend along the beam axis 5A over a measuring depth of approximately 0.1 mm to approximately 15 mm, in particular over a measuring depth of approximately 0.5 mm to approximately 10 mm or approximately 0.5 mm to approx. 5 mm. In some embodiments, the plasma detection areas 39 may extend along the beam axis 5A over 1/10 to 1/4 of the viewing area 41. In 2 In the multifocal concept, the offset plasma detection areas 39 are arranged along the beam axis 5A, for example, at a distance D in the order of magnitude of the measuring depth (here approximately twice the diameter of the plasma detection areas 39). Alternatively, the plasma detection areas 39 can adjoin one another or partially overlap (for example in the range of 10% of the measuring depth). In this way, the lenses can detect plasma light from different sections of the viewing area 41 along the beam axis 5A. (In contrast, in the multilateral concept, plasma detection areas essentially cover the same section along the beam axis 5A, so that the lenses detect plasma light from this same section. See for example 11B with associated description.)

Furthermore, you can see in 2 an optional protective window 43A, which can be provided in the area of an optical through opening 43 in the holder plate 23A in order to be able to direct the laser beam through the holder 23 and past the lenses 25A, 25B, 25C onto the sample 7.

3 shows a perspective view of an exemplary LIBS measuring head 51, which is connected to a laser beam source via an optical fiber 9A. The holder 23 of the LIBS measuring head 51 comprises a longitudinal support plate 23B, on the input side of which an attachment for the optical fiber 9A and the focusing optics 11 (laser head with beam shaping) is provided. The optical spectrometer 13 is also attached to the longitudinal support plate 23B and the mounting plate 23A for the four lenses 25A, 25B, 25C, 25D (generally n>1-fold entrance optics) is provided. The lenses 25A, 25B, 25C, 25D are set up to detect measurement components of plasma light from plasma detection areas 39, which are arranged offset from one another along the beam axis 5A, and via the light guide system 27 (for example a fiber bundle with n>1 inputs and a functional output - “n-on-1 fiber bundle”) to the spectrometer 13 for spectral analysis. Examples are in 3 two optical fibers 45 of the light guiding system 27 are shown, which optically connect the lenses 25B and 25C to the common spectrometer 13. With the light guide system 27, the measurement components in the spectrometer 13 (or optionally before coupling into the spectrometer 13) can be combined for a measurement process.

The n-fold observation of the field of view with several (in 3 four) lenses allow a significant increase in depth of field, given by the arrangement of the plasma detection areas of the lenses. This makes it possible to efficiently analyze samples that are structured and uneven on the surface. Furthermore, the sample is viewed from different angles, which can reduce shadowing effects. The recorded measurement components are brought together at a common output of the light guide system (sum of all observations) and fed to a common spectral analysis.

An n-to-1 fiber bundle allows multiple lenses to be fed into one spectrometer, where multiple n-to-1 bundles can be used to feed multiple spectrometers.

The exemplary implementation of the multifocal concept in the in 2 The detection unit shown is based on the 4A and 4B further clarified. 4A shows a top view of the mounting plate 23A. The optical passage opening 43 in the center allows the laser beam to pass through (laser beam axis 5A). Four lens mounting openings 53A, 53B, 53C, 53D are arranged azimuthally around the through opening 43 with varying radial distances from the beam axis 5A. They are equally distributed azimuthally, so that two lens holder openings are opposite each other in pairs. In the perspective view of the 4B Four identical lenses 25A, 25B, 25C, 25D are inserted into the lens mounting holes 53A, 53B, 53C, 53D. The lenses 25A, 25B, 25C, 25D were inserted at different distances into the lens holder openings 53A, 53B, 53C, 53D, so that depending on the radial distance, the associated plasma detection areas 39 are arranged next to each other in the direction of the beam axis and thus the viewing area 41 given by the depth of field Form detection unit 21.

An alternative implementation of the multifocal concept is presented in the 5A and 5B clarified. In the top view of the mounting plate 23A, four lens mounting openings 55A, 55B, 55C, 55D can be seen, which are arranged symmetrically at the same radial distance from the through opening 43 and, for example, evenly distributed around it. As in the perspective view of the 5B is indicated, the offset of the plasma detection areas 39 in the direction of the beam axis 5A is caused by different observation angles of the lenses 25A, 25B, 25C, 25D used. For example, the observation angles can be in the range of 3° to 15° at a radial distance of 30 mm, so that the viewing area 41 is formed at a distance of approximately 100 mm from the mounting plate 23A. With different observation angles (and optionally viewing heights) the detected spectral distributions can vary in a large-volume plasma. However, particularly in the case of a small-volume plasma, as is usually generated for LIBS, these differences in the spectral distribution are negligible, since essentially the entire plasma lies in a plasma detection area 39.

An exemplary implementation of the multilateral concept is presented in the 6A and 6B clarified. Under the supervision of 6A An exemplary mounting plate 23A' of a lens mount 23' can be seen, similar to in 5A , four lens mount holes 57A', 57B', 57C', 57D' provided in the mount plate 23A'. The lens holder openings 57A ', 57B', 57C', 57D' are arranged symmetrically at the same radial distance from the through opening 43. In the case of 6A For example, they are arranged evenly distributed, that is, they lie opposite each other in pairs. The lens holder also provides an optical passage opening 43 through which the beam axis 5A runs. In particular, one location was... Beam axis 5A is placed centrally in the optical passage opening 43.

As in 6B shown, lenses 25A', 25B', 25C', 25D' are held in the lens mount holes 57A', 57B', 57C', 57D' of the lens mount 23'. In contrast to the orientation of the lenses 25A, 25B, 25C, 25D in 5B As part of the multilateral concept, the lenses 25A', 25B', 25C', 25D' are directed at the beam axis at a substantially identical observation angle, so that they form a common plasma detection area 59. Each of the lenses 25A', 25B', 25C', 25D' is assigned a detection cone 35', the lenses 25A', 25B', 25C', 25D' being arranged and aligned in the lens holder in such a way that the detection cones 35' are in form a common plasma detection area 59 in an overlap area with the laser beam. That is, in the case of a plasma present in the plasma detection area 59, a measurement portion of the plasma light can be detected by each of the four lenses 25A', 25B', 25C', 25D', with the detection cones 35' measuring portions of the plasma light of the plasma emitted in different solid angles capture. Each of the detection cones 35' extends along an observation axis 35A', which runs at an observation angle in the range of up to 90° (observation orthogonal to the laser beam) to the beam axis 5A. The observation angles shown as examples within the scope of the disclosure are in the range from 1° to 60°. The observation angles are essentially the same (within, for example, 1° or 2°, for example production-related tolerance) or can differ from one another, for example in order to observe from different directions (observation angle differences up to 90°, for example up to 45°).

You recognize in 6B that the observation axes 35A' of adjacent lenses 25A', 25B', 25C', 25D' are arranged azimuthally spaced around the beam axis. For example, the observation axes 35A' of the lenses 25A', 25B', 25C', 25D' lie on a conical surface.

Further explanations of the multilateral concept follow in connection with the 11A until 12B .

In the spectrometer systems proposed here for multifocal and/or multilateral observation, a light guide system is generally used to guide measurement components of the detected plasma light from the detection unit to the optical spectrometer. In addition to the following in connection with the 7A until 7E and 8A to 8C explained light guide systems based on several optical fibers, the measurement components can also be guided from the lenses to the input aperture of the optical spectrometer via a free beam system using, for example, mirrors and lenses. Alternatively, light guide systems can be based, for example, on several optical fibers, which are combined into one fiber on the output side.

The schematic sketches of the 7A until 7E illustrate an exemplary light-guiding system 27 with several optical fibers 45A, 45B, 45C, 45D, which are designed to guide the measurement components of the detected plasma light to the optical spectrometer in light-guiding areas. Exemplary optical fibers are adapted to the spectral ranges to be carried (UV, VIS, IR, NIR) and can include, for example, the following types of optical fibers: step index fibers, gradient index fibers, hollow core fibers, photonic crystal fibers as well as single-mode fibers or multi-mode fibers . Diameters of the light-guiding areas are z. B. in the range from 100 µm to 1,000 µm, especially in the range around 800 µm. Assigned light entry surfaces/light exit surfaces have comparable dimensions. Furthermore, variations in the diameter of a light-guiding area between the light entry surface and the light exit surface are possible, as will be explained below using an example.

Each of the optical fibers is fixed on the input side in an optical input connector 61A, for example in an SMA connector ( 7B and 7C ). The light-guiding areas of the optical fibers 45A, 45B, 45C, 45D each have a light entry surface 63 on the input side. An example is in 7C In a front view of the input plug 61A, the light entry surface 63 is indicated centered in a rotationally symmetrical ferrule 64. Each of the light entry surfaces 63 forms one of the optical inputs 29 of the light guide system 27. The input plug 61A can be mounted on one of the lenses of the detection unit in such a way that one of the measurement components is coupled into the light-guiding area. For this purpose, the light entry surface 63 is positioned so that a lens, which detects plasma light emitted from the plasma detection area in the direction of the lens (ie, propagating in the detection cone), images this onto the light entry surface 63 so that it can be passed on by the optical fiber.

As in 7A shown, the optical fibers 45A, 45B, 45C, 45D can be combined on the output side to form a fiber bundle section 65.

On the output side, the optical fibers 45A, 45B, 45C, 45D, which are each assigned to a lens in the multifocal concept and in the multilateral concept, are held in a (common) output plug 61B ( 7D and 7E) . The light-guiding areas of the optical fibers 45A, 45B, 45C, 45D each have a light exit surface 67A, 67B, 67C, 67D on the output side. The light exit surfaces 67A, 67B, 67C, 67D form the optical (functional) output 31 of the light guide system 27. As in 7E shown, the optical fibers 45A, 45B, 45C, 45D in the output plug 61B are held in a ferrule 69, running largely parallel to one another. For example, fiber receiving openings are provided in the ferrule 69, which run parallel to one another and are adapted to the outer diameter of the optical fibers 45A, 45B, 45C, 45D. Preferably, the optical fibers 45A, 45B, 45C, 45D are arranged such that the optical fibers 45A, 45B, 45C, 45D are adjacent to one another or with a spacing of a few percent, e.g. B. 10%, 20%, 30% or 100%, a diameter of the optical fibers 45A, 45B, 45C, 45D, are fixed in the ferrule 69. As in the front view of the output connector 61B in 7E is shown, the light exit surfaces 67A, 67B, 67C, 67D can, for example, be arranged next to each other (linearly) in order to geometrically adapt the optical output 31 for efficient coupling to a slit-shaped entrance aperture of the optical spectrometer.

The 8A until 8C show how the output plug 61B can be mounted on the optical spectrometer 13 for efficient light coupling of the measurement components. Examples are as in 7E the light exit surfaces 67A, 67B, 67C, 67D are lined up linearly and aligned along an entry gap opening 71 running in the Y direction. Correspondingly, a position of the coupling in the X direction is given by a width of the inlet gap opening 71. The position of the coupling in the Y direction is given by the light exit surfaces 67A, 67B, 67C, 67D lying one above the other in the Y direction. The closer the light exit surfaces 67A, 67B, 67C, 67D are to one another, the more the optical paths of the measurement components in the optical spectrometer overlap and lead to equally localized signal contributions on the detector.

In some embodiments, the order of the light exit surfaces 67A, 67B, 67C, 67D corresponds to the sequence of the plasma detection areas 39 in the viewing area 41. As a result, the centrally located plasma detection areas 39 are optimally coupled into the optical spectrometer, so that the associated measurement components contribute most efficiently to the spectral analysis. Referring to the examples of the multifocal concept in 4B and 5B The middle optical fibers in the output connector can also be used for the middle plasma detection areas 39. Referring to the example of the multilateral concept of 6B The sum of the measurement components of all contributing optical fibers is decisive, with different optical fibers contributing depending on the surface shape, so that a corresponding sequence will generally have little or no effect.

In a schematic top view of a section through the “top” optical fiber 45D ( 8A) , a schematic side view of a section through the four lined up optical fibers 45A, 45B, 45C, 45D ( 8B) and a view of the light exit surfaces 67A, 67B, 67C, 67D of the optical fibers in the assembled state ( 8C ), the coupling through an entry slit opening 71 into an optical spectrometer is illustrated. In 8A you can see the optical fiber 45D held in the ferrule 69. The light-guiding region 73D (indicated schematically) extends inside the optical fiber 45D and opens into the light exit surface 67D. The measurement portion of the detected plasma light emerges from this and passes through the elongated entrance slit opening 71 (slit width, e.g. 10µm). Dotted is in 8A a possible beam divergence in the X direction due to the gap opening 71 is indicated.

In the section view of the 8B one can see the four optical fibers 45A, 45B, 45C, 45D arranged one above the other in the Y direction in the ferrule 69, each with a central light-guiding area; The light-guiding area 73D for the optical fiber 45D is indicated. Furthermore, (measurement component) beam axes 75A, 75B, 75C, 75D can be seen, along which the measurement components of the plasma light are emitted from the optical fibers 45A, 45B, 45C, 45D. The beam axes 75A, 75B, 75C, 75D run parallel to one another, for example. This causes the measurement components to pass through the entrance slit opening 71 essentially in the same direction and with comparable divergences in the Y direction and thus hit the dispersive element and the detector for spectral analysis as a quasi light beam.

In 8C one can see schematically the entrance gap opening 71 in an inner wall 77 of the housing of the spectrometer. In the example shown, the optical fibers (with parallel fiber orientations) are lined up linearly, the line being along a longitudinal axis of the entrance gap opening 71 (here along the Y direction). The diameter of the light exit surfaces 67A, 67B, 67C, 67D is usually larger or is in the range of a width of the entrance gap opening 71. Furthermore, in 8C the output plug 61B (outside the housing) is indicated schematically.

Referring to the 9A until 10B The multifocal concept is explained using exemplary measurement constellations and measurement spectra.

9A shows two measurement spectra in the wavelength range from approx. 250 nm to approx. 500 nm and 9B exemplifies the constellation in the LIBS measurement with the spectrometer system 1 1 . The plasma 3 is generated on the surface of the sample 7 with the laser beam. The detection unit 23 of the spectrometer system 1 is set in such a way that the measurement detection areas of the individual lenses do not overlap. It can be seen that a measurement detection area 83A of the objective 25A lies inside the sample 7 (and accordingly the objective 25A “only” observes the sample surface at some distance from the plasma), the measurement detection area 83B of the objective 25B lies on the surface of the sample 7 (and the objective 25B accordingly observes the sample surface in the area of the plasma formation and thus looks directly into the plasma), and the measurement detection area 83C of the objective 25C does not overlap with the sample 7 (and accordingly the objective 25C looks over the plasma and also “only” the sample surface observed at some distance from the plasma).

In the case shown, the extent of the generated plasma 3 is comparable to the extent of the measurement detection areas of the lenses, so that the plasma 3 is essentially only present in the measurement detection area 83B and accordingly only emits light into the detection cone of the objective 25B. This can also be seen in the measurement spectra, which, for clarity, are selective for the measurement components of the lenses 25A and 25B in 9A are shown. The measurement portion of the 25A lens results in hardly any signal contributions. Accordingly, the measurement component leads to a measurement spectrum with very low intensities I (dashed line 81A). It is noted that the objective 25C would have a measurement spectrum similar to that of the objective 25A. Deviating from this, the measurement portion of the objective 25B leads to a specific signal distribution with significant intensities I at specific wavelengths λ in the measurement spectrum (dotted line 81B). These allow an assignment of the elementary components of sample 7 to be determined. It is noted that in order to be able to selectively record and display the measurement components, only the lens to be measured needs to be optically connected to the spectrometer.

If, according to the invention, all lenses are optically connected to the spectrometer to implement the multifocal concept, in the present case the 9B the sum signal corresponds approximately to the measurement component of the lens 25B (dotted line 81B), since at the time of measurement in 9B the measurement detection areas 83A, 83C of the objective 25A and the objective 25C lie in the sample 7 or in front of the sample 7. As a result, essentially only the lens 25A captures a measurement portion of the plasma 3.

10A shows three measurement spectra in the wavelength range from approx. 250 nm to approx. 500 nm and 10B illustrates by way of example the constellation in a LIBS measurement, in which the detection unit 23 of the spectrometer system is set in such a way that neighboring measurement detection areas of the individual lenses partially overlap. It can be seen that the measurement detection area 87A of the objective 25A and the measurement detection area 87B of the objective 25B are close to the surface of the sample 7, with the measurement detection area 87C of the objective 25C being slightly further away in front of the sample 7. The plasma 3 is generated on the surface of the sample 7 with the laser beam. The plasma 3 extends in the example 10B via the measurement detection areas 87A, 87B of the lens 25A and the lens 25B.

The situation of the resulting measurement spectra is in 10A shown, whereby the measurement spectra for the lens 25A and the lens 25B are also shown selectively for clarity. The measurement portion of the 25C lens results in hardly any signal contributions and is in 10A Not shown. It can be seen that the plasma 3 overlaps in a comparable manner with the measurement detection area 87A and the measurement detection area 87B. Accordingly, the measurement components of the objective 25A and the objective 25B lead to comparable measurement spectra with significant intensities I at specific wavelengths λ in the measurement spectrum (dashed line 89A, dotted line 89B). It is noted that in order to be able to selectively record and display the measurement components, only the lens to be measured needs to be optically connected to the spectrometer.

If, according to the invention, all lenses are optically connected to the spectrometer to implement the multilateral concept, this results in the exemplary constellation: 10B a combined sum signal (solid line 91) in which the significant intensities I can be easily resolved at specific wavelengths λ.

Referring to the 11A until 12B The multilateral concept is explained using exemplary measurement data, where: 11B the advantage of a larger recorded solid angle range and 12B shows the advantage when shadows occur due to multilateral observation.

11A shows three measurement spectra in the wavelength range from approx. 250 nm to approx. 500 nm and 11B exemplifies the constellation in a LIBS measurement in which - as in 6B shown - the detection unit 23 of the spectrometer system is set such that the measurement detection areas of the individual lenses coincide with one another and form a common measurement detection area 59. The measurement detection is used Area 59 captured from different spatial directions with the different lenses. It can be seen that the measurement detection area 59 is close to the surface of the sample 7. The laser beam is used to generate the plasma 3 on the surface of the sample 7 in the area of the measurement detection area 59.

The situation of the resulting measurement spectra is in 11A shown, whereby the (comparable) measurement spectra (dashed line 93A, dotted line 93B) for the objective 25A and the objective 25B are also shown selectively for clarity. The measurement portion of the lens 25C results in a comparable signal contribution and is not shown. It is noted that in order to be able to selectively record and display the measurement components, only the lens to be measured needs to be optically connected to the spectrometer.

If, according to the invention, all lenses are optically connected to the spectrometer to implement the multifocal concept, this results in the present case 10B a combined sum signal (solid line 95) in which the significant intensities I can be easily resolved at specific wavelengths λ.

12A shows two measurement spectra in the wavelength range from approx. 250 nm to approx. 500 nm and 12B exemplifies the constellation in a LIBS measurement in which the geometry of sample 7 shades all lenses except one (here lens 25B). The detection unit 23 of the spectrometer system is set according to the multilateral concept in such a way that the measurement detection areas of the individual lenses coincide with one another and form the common measurement detection area 59. The measurement detection area 59 is recorded with the different lenses from different spatial directions. The laser beam is used to generate the plasma 3 on the surface of the sample 7 in the area of the measurement detection area 59.

It can be seen that the measurement detection area 59 is close to the surface of the sample 7, but material from the sample 7 is located between the plasma 3 and the lenses 25A, 25C. Accordingly, plasma light emitted toward the lenses 25A, 25C is shielded from the sample 7 and accordingly cannot be detected by the lenses 25A, 25C.

This can also be seen in the measurement spectra, which, for clarity, are selective for the measurement components of the lenses 25A and 25B in 12A are shown. The measurement portion of the 25A lens results in hardly any signal contributions. Accordingly, the measurement component leads to a measurement spectrum with very low intensities I (dashed line 97A). It is noted that the objective 25C would have a measurement spectrum similar to that of the objective 25A. However, the measurement portion of the objective 25B leads to a specific signal distribution with significant intensities I at specific wavelengths λ in the measurement spectrum (dotted line 97B). These allow an assignment of the elementary components of the sample 7 to be determined despite the shielded lenses 25B, 25C. It is noted that in order to be able to selectively record and display the measurement components, only the lens to be measured needs to be optically connected to the spectrometer.

If, according to the invention, all lenses are optically connected to the spectrometer to implement the multilateral concept, in the present case the 12B the sum signal corresponds approximately to the measurement portion of the lens 25B (dotted line 97B), since only the lens 25A can capture a measurement portion of the plasma 3.

It should be added that subgroups of lenses can be assigned to their own optical spectrometer, with the spectrometers (and optionally the light guide systems) being adapted, for example, to different spectral ranges to be analyzed. For example, four lenses each can supply measurement components to an optical spectrometer in the UV range and four lenses each can supply measurement components to an optical spectrometer in the NIR range via their own light guide systems. Alternatively or additionally, measurement components of a lens can be divided into two light paths, for example, so that with four lenses, for example, eight optical fibers are used, of which four optical fibers have a functional output for an optical spectrometer in the UV range and four optical fibers have a functional output for an optical spectrometer in the UV range Form NIR range.

The multifocal and multilateral concepts of the arrangements of lenses in a detection unit of a spectrometer system presented here show their advantages in particular when recording emission spectra of a moving object (sample) to be analyzed with a surface profile modeled in the beam axis. In comparison with a spatially smaller focal zone, the proportion of surface sections of the sample in which, on the one hand, a plasma is generated and, on the other hand, measured portions of this plasma can be detected by the detection unit, increases due to the field of view being expanded in the direction of the beam axis. Accordingly, the amount of recorded data required to analyze the material is available more quickly. A quick analysis of the material composition is beneficial in various applications.

Examples are given in the 13A until 13C Industrial applications are shown schematically using the example of the multifocal concept, whereby the multilateral concept can also be used accordingly for these industrial applications.

13A shows a stationary system with a spectrometer system 101. The laser beam 5 of the spectrometer system 101 is from above (in 13A along the Z axis) towards a sample vessel 103 (e.g. a sample plate or a sample dish with, for example, a round or rectangular basic shape), in which a sample 105 to be examined is provided for examination. The detection unit 23 of the spectrometer system 101 is arranged with respect to the sample vessel 103 in such a way that a viewing area 41 of the detection unit 23 of the spectrometer system 101 (see also 2 ) extends at a, for example fixed, height (distance in the Z direction) above the bottom (sample vessel bottom surface 103A) of the sample vessel 103 and thus enables detection of measurement components in a predetermined Z range.

By way of example, the sample 105 consists of broken sample pieces 105A. The test pieces 105A form a surface course that varies in the Z direction and is generally undefined, i.e. H. not specified. Accordingly, the surface course includes many measurement surface areas in which the surfaces lie in the predetermined Z value range of the viewing area 41. If a plasma is generated on these surface areas, the plasma lies in the viewing area 41 of the detection unit 23, so that plasma light can be detected accordingly.

The laser beam 5 scans the sample 105 along an (adjustable) trajectory, for example by rotating the sample vessel 103 in the XY plane (indicated by the arrow 107) or by one-dimensional or two-dimensional (for example linear, row-shaped or grid-shaped) scanning linear displacement in the X-Y plane, or a combination of pivoting movement, translational movement and / or rotational movement, so that the trajectory includes many measurement sections (trajectory sections). The measuring sections are assigned measuring surface areas in which detection of plasma light can take place. The detection unit 23 detects plasma light whenever the laser beam 5 generates a plasma on these measuring surface areas along the measuring sections. The larger the viewing area 41 extends in the Z direction, the larger the proportion of the measuring surface areas in the entire surface and the correspondingly larger the proportion of the measuring sections in the trajectory. Thus, the multifocal concept can accelerate data acquisition for spectral analysis.

Furthermore, it can be seen that, for example, with coarse-grained sample pieces 105A on the sample vessel 103, shading effects can occur. This means that a plasma cannot be detected at every observation angle. The multilateral concept disclosed herein (not explicitly in 13A shown, but easily transferable to this industrial application) also provides several observation directions, so that despite possible shadowing, it is possible to capture a measurement component with at least one of several provided lenses. Thus, the multilateral approach can accelerate data collection for spectral analysis.

13B shows a system 111 for LIBS-based sorting of pieces made of different materials. The sorting process for two types of material is shown as an example; for example, pieces 113A made of copper and pieces 113B made of brass should be distributed to two collection points 115A, 115B. The system 111 includes a spectrometer system 117A and a separating device 117B, which, for example, uses an activatable air flow pulse 119 to separate the pieces 113A of copper from a continuous stream of pieces. For this purpose, the separating device 117 uses information about the material composition of the pieces passed by, which is recorded using the spectrometer system 117A. However, the position of the pieces with respect to the field of view of the spectrometer system 117A may not be clearly defined, so that the multifocal concept and/or the multilateral concept may have advantages with regard to the detection of measurement components.

A short detection time, which can be achieved using the multifocal and/or multilateral concepts disclosed herein, allows the pieces 113A, 113B to be measured in terms of material composition even with small pieces and therefore short possible measuring distances per piece, as well as high passing speeds and thus a small number to detect any detectable measurement spectra of suitably located surface sections and thus to implement a fast and/or high-precision sorting process.

13C shows a system 121 for determining the composition of slag. For example, a suitable quality of slag for road construction can be recorded through selection with LIBS. The system 121 has a spectrometer system 123 and a conveyor belt system 125. Slag 127 to be analyzed is placed on a conveyor belt 125A of the conveyor belt system 125 at the Spektro meter system 123 is guided past, the laser beam of the spectrometer system 123 being directed at the conveyor belt 125A and the viewing area 41 of the spectrometer system 123 being positioned at a distance from and above the conveyor belt 125A. Given the varying size and shape of the slag pieces with respect to the field of view of the spectrometer system 123, the multifocal concept and/or the multilateral concept allows measurement components to be advantageously recorded.

A short detection time, which can be achieved using the multifocal and/or multilateral concepts disclosed herein, allows the slag 127 to be recognized in terms of material composition even at a high passing speed and thus to implement a rapid and/or highly precise quality check.

In general, the person skilled in the art will recognize that an alignment of the laser beam with respect to a surface of a sample (e.g. with respect to a normal direction of the surface at the location of the generated plasma) or with respect to a support surface, for example a normal direction of a bottom surface of a sample vessel or a conveyor belt, in an angular range from 0° (incidence parallel to the normal direction) to 90° (lateral incidence) can be selected, with an angular range of 0° to 80°, in particular from 0° to 60°, being able to have advantages with regard to any shading effects. Furthermore, the person skilled in the art will recognize that an alignment of the laser beam with respect to a direction of movement of the sample (e.g. a linear movement or a rotational movement of the sample) in an angular range from 0° (incidence opposite the direction of movement) to 90° (lateral incidence) to 180 ° (incidence in the direction of movement) can be selected.

Below, a measurement process according to the multifocal concept is presented as an example for two measurement points with reference to the 14A and 14B summarized:

Providing (step 131) a detection unit that provides an extended field of view for detecting plasma light using multiple lenses aligned according to the multifocal concept.

Positioning (step 133) a first surface area of a sample, for example stored on a sample vessel, in the field of vision of the detection unit.

Irradiating (step 135) a laser beam to generate a first plasma on the first surface region, wherein plasma light is emitted from the first plasma according to a material of the sample.

Detecting (step 137) a first measurement portion of the plasma light using the detection unit and forwarding the first measurement portion of the plasma light to an optical spectrometer.

Moving (step 139) the sample relative to the viewing area, in particular as part of a continuous relative movement between the sample and the detection unit, for example using a rotation drive and a pivoting drive of the sample vessel, so that a second surface area of the sample is positioned in the viewing area.

Repeating the steps of irradiation (135) and detection (step 137) for the second surface area, so that a second measurement portion of the plasma light of a second plasma is forwarded to the optical spectrometer.

Based on the first measurement portion and the second measurement portion, outputting (step 141) a cumulative optical spectrum to a computing unit and performing a spectral analysis of the cumulative optical spectrum to determine and output the elemental composition of the sample. As part of a measurement process, spectra from different measurement constellations can be collected for a sample and, in particular, evaluated using a filter algorithm until a required quality is achieved with regard to the output analysis.

14B shows a sample 7 which is moved past a pulsed laser beam 5 of a spectrometer system 1 at a (relative) speed v. The sample 7 has a structured surface profile that only partially extends in the viewing area 41 of the spectrometer system 1 (given by the plasma detection areas 39). Due to the pulsed laser beam 5, a sequence of plasmas was generated on the surface of the sample 7 and the plasma light was correspondingly detected and spectrally analyzed. By way of example, a final plasma 3 and the positions of the previously generated plasmas (circles) are indicated along the surface of the sample 7.

Below, a measurement process according to the multilateral concept is presented as an example for two measurement points 14C summarized:

Providing (step 151) a detection unit that provides an extended solid angle range for detecting plasma light using multiple lenses aligned according to the multilateral concept.

Positioning (step 153) a first surface area of a sample, for example stored on a sample vessel, in the field of vision of the detection unit.

Irradiating (step 155) a laser beam to generate a first plasma on the first surface region, wherein plasma light is emitted from the first plasma according to a material of the sample.

Detecting (step 157) a first measurement portion of the plasma light using a first subgroup of lenses of the detection unit and forwarding the first measurement portion of the plasma light to an optical spectrometer.

Moving (step 159) the sample relative to the viewing area, in particular as part of a continuous relative movement between the sample and the detection unit, for example using a rotation drive and a pivoting drive of the sample vessel, so that a second surface area of the sample is positioned in the viewing area.

Repeating the steps of irradiation (155) and detection (step 157) for the second surface area, whereby, due to the geometry of the sample, a second measurement component of a plasma light of a second plasma is carried out using a second subgroup of objectives of the detection unit, which is different from the first subgroup of Lenses of the detection unit are detected, so that the second measurement component is forwarded to the optical spectrometer.

Based on the first measurement portion and the second measurement portion, outputting (step 161) a cumulative optical spectrum to a computing unit and performing a spectral analysis of the cumulative optical spectrum to determine and output the elemental composition of the sample. As part of a measurement process, spectra from different measurement constellations can be collected for a sample and, in particular, evaluated using a filter algorithm until a required quality is achieved with regard to the output analysis.

The two measurement processes described above as examples are not limited to the detection of two plasmas and correspondingly two measurement components, but are carried out, for example, continuously for a large number of generated plasmas/measurement components, as long as the surface of the sample extends into the visible range, and will, should the surface move out of the field of view, continuing as soon as the surface re-enters the field of view.

Some aspects of a light control system are summarized below, such as: B. can be used when implementing the multifocal concept or the multilateral concept.

Aspect A1. Light guide system (27) with several optical fibers (45A, 45B, 45C, 45D), which have several optical inputs (29) for receiving light, in particular measuring components (33) of plasma light, and an optical output (31) for emitting the light, in particular the recorded measurement components (33) in an optical spectrometer (13), wherein first ends of the optical fibers (45A, 45B, 45C, 45D) are each held in a plug (61A) and each have a light entry surface (63) as an optical input (29) and second ends of the optical fibers (45A, 45B, 45C, 45D) each comprise a light exit surface (67A, 67B, 67C, 67D) and are held together in a plug (61B), the light exit surfaces (67A, 67B, 67C, 67D) form the optical output (31).

Aspect A2. Light guide system (27) according to aspect A1, wherein the optical fibers (45A, 45B, 45C, 45D) are lined up linearly on the output side and have essentially parallel fiber orientations, so that the light exit surfaces (67A, 67B, 67C, 67D) are arranged next to one another.

Aspect A3. Light guide system (27) according to aspect A1 or aspect A2, wherein on the output side the light, in particular each of the measurement components (33) emerging from the optical light guide system (27), is assigned a beam axis (75A, 75B, 75C, 75D) and the optical fibers (45A , 45B, 45C, 45D) are arranged such that the beam axes (75A, 75B, 75C, 75D) run parallel to one another or no more than at an angle of up to 1° or up to 3° to one another.

• einer Laserstrahlquelle (9) zur Abgabe eines, insbesondere gepulsten, Laserstrahls (5), wobei das Plasma (3) mit dem sich entlang einer Strahlachse (5A) ausbreitenden Laserstrahl (5) auf einer Oberfläche (7A) einer Probe (7) erzeugt wird,
• einer Fokussieroptik (11) zur Fokussierung des Laserstrahls (5) auf die Oberfläche (7A) der Probe (7), insbesondere einer Laserkopfkomponente mit Fokussierfunktion wie eine insbesondere auf das Spektrum oder die Pulsdauer oder die Pulsenergie einwirkende aktive Laserkomponente mit Fokussierfunktion,
• einer Detektionseinheit (21) mit mehreren Objektiven und einem Lichtleitsystem (27) nach einem der Aspekte A1 bis A3, wobei jedes der Objektive ausgebildet ist, einen Messanteil (33) des Plasmalichts (3A) aus objektiv-spezifischen oder aus einem gemeinsamen Plasmadetektionsbereich (59) zu erfassen und an einen der optischen Eingängen (29) in das Lichtleitsystem (27) einzukoppeln, und
• einem optischen Spektrometer (13) zur Spektralanalyse der mit den Objektiven erfassten Messanteile (33) des Plasmalichts (3A), wobei das optische Spektrometer (13) zur Aufnahme der Messanteile (33) mit dem optischen Ausgang (31) des Lichtleitsystems (27) optisch verbunden ist.

Aspect A4. Spectrometer system (1) for the spectral analysis of a plasma light (3A) emitted by a laser-induced plasma (3).

• a laser beam source (9) for emitting a, in particular pulsed, laser beam (5), the plasma (3) being generated on a surface (7A) of a sample (7) with the laser beam (5) propagating along a beam axis (5A). ,
• a focusing optics (11) for focusing the laser beam (5) onto the surface (7A) of the sample (7), in particular a laser head component with a focusing function such as an active laser component with a focusing function which acts in particular on the spectrum or the pulse duration or the pulse energy,
• a detection unit (21) with several lenses and a light guide system (27) according to one of aspects A1 to A3, wherein each of the lenses is designed to detect a measurement portion (33) of the plasma light (3A) from lens-specific or from a common plasma detection area (59) and to one of the optical inputs (29) in the to couple in the light guide system (27), and
• an optical spectrometer (13) for the spectral analysis of the measurement components (33) of the plasma light (3A) recorded with the lenses, the optical spectrometer (13) for recording the measurement components (33) being optically connected to the optical output (31) of the light guide system (27). connected is.

Some aspects of the multilateral concept are summarized below.

• - eine Objektivhalterung (23'),
• - mehrere von der Objektivhalterung (23') gehaltene Objektive (25A', 25B', 25C', 25D'), wobei jedem der Objektive (25A', 25B', 25C', 25D') ein Detektionskegel (35`) zugeordnet ist und die Objektive (25A', 25B', 25C', 25D') derart in der Objektivhalterung (23') angeordnet und ausgerichtet sind, dass die Detektionskegel (35`) in einem Überlappungsbereich mit dem Laserstrahl (5) einen gemeinsamen Plasmadetektionsbereich (59) ausbilden, aus dem im Fall eines im Plasmadetektionsbereich (59) vorliegenden Plasmas (3) von jedem der Objektive (25A', 25B', 25C', 25D') ein Messanteil (33) des Plasmalichts (3A) erfassbar ist.

Aspect B1. Detection unit (21) for a spectrometer system (1) for the spectral analysis of a plasma light (3A) emitted by a laser-induced plasma (3), the plasma (3) being on a surface (3) with a laser beam (5) propagating along a beam axis (5A). 7A) of a sample (7) is generated (and in particular a spectral splitting of the plasma light (3A) for spectral analysis takes place in an optical spectrometer (13)), comprising:

• - a lens holder (23'),
• - several lenses (25A', 25B', 25C', 25D') held by the lens holder (23'), each of the lenses (25A', 25B', 25C', 25D') being assigned a detection cone (35'). and the lenses (25A', 25B', 25C', 25D') are arranged and aligned in the lens holder (23') in such a way that the detection cones (35') form a common plasma detection area (59) in an overlap area with the laser beam (5). ) from which, in the case of a plasma (3) present in the plasma detection area (59), a measurement portion (33) of the plasma light (3A) can be detected by each of the lenses (25A', 25B', 25C', 25D').

• wobei die Objektivhaltung (23') eine optische Durchgangsöffnung (43) bereitstellt, durch die die Strahlachse (5A) verläuft, wobei eine Lage der Strahlachse (5A) insbesondere mittig in der optischen Durchgangsöffnung (43) festgelegt ist, und
• wobei die Objektivhalterung (23') insbesondere eine Halterungsplatte (23A') aufweist, in der mehrere Objektivhalterungsöffnungen (57A', 57B', 57C', 57D') zur Aufnahme der Objektive (25A', 25B', 25C', 25D') und die optische Durchgangsöffnung (43) für den Laserstrahl (5) vorgesehen sind, und wobei die Objektivhalterungsöffnungen (57A', 57B', 57C', 57D') um die optische Durchgangsöffnung (43) herum angeordnet sind, und insbesondere um die optische Durchgangsöffnung (43) azimutal verteilt sind.

Aspect B2. Detection unit (21') according to aspect B1, wherein the lenses (25A', 25B', 25C', 25D') are arranged and aligned in the lens holder (23') in such a way that the detection cones (35') emitted measurement components in different solid angles (33) of the plasma light (3A) of a plasma (3) detect and/or

• wherein the lens holder (23') provides an optical through-opening (43) through which the beam axis (5A) runs, a position of the beam axis (5A) being fixed in particular centrally in the optical through-opening (43), and
• wherein the lens holder (23') in particular has a mounting plate (23A') in which a plurality of lens holder openings (57A', 57B', 57C', 57D') for receiving the lenses (25A', 25B', 25C', 25D') and the optical through-hole (43) is provided for the laser beam (5), and wherein the lens holder openings (57A', 57B', 57C', 57D') are arranged around the optical through-hole (43), and in particular around the optical through-opening (43) are distributed azimuthally.

Aspect B3. Detection unit (21') according to aspect B1 or B2, wherein each of the detection cones (35`) extends along an observation axis (35A') which runs at an observation angle (α) in the range of 0° to 90° to the beam axis (5A). , wherein the observation angles (α) are in particular the same, do not differ from each other by more than 3° or are distributed in an angular range of 45°, and / or wherein the lens holder (23`) in particular has a mounting plate (23A'), in which a optical passage opening (43) is provided for the laser beam (5), the beam axis (5A) being orthogonal to the mounting plate (23A') and at least one of the detection cones (35`) extending along an observation axis which is at an observation angle (α) in the range from 0° to 90°, in particular 3° to 60°, for example in the range from 5° to 25°, to the beam axis (5A).

Aspect B4. Detection unit (21') according to one of aspects B1 to B3, wherein adjacent lenses (25A', 25B', 25C', 25D') are arranged azimuthally spaced around the beam axis (5A) and/or the observation axes (35A') of the lenses (25A', 25B', 25C', 25D') lie on a cone surface around the beam axis (5A).

• wobei die Objektive (25A', 25B', 25C', 25D') azimutal gleichverteilt um die Strahlachse (5A) angeordnet sind.

Aspect B5. Detection unit (21') according to one of aspects B1 to B4, wherein the detection unit (21) comprises two to 25, preferably four, lenses (25A', 25B', 25C', 25D') and/or

• wherein the lenses (25A', 25B', 25C', 25D') are arranged equally azimuthally distributed around the beam axis (5A).

• mehrere optische Eingängen (29), wobei jeder der optischen Eingänge (29) optisch mit einem der Objektive (25A', 25B', 25C', 25D') verbunden und zur Aufnahme des mit dem zugeordneten Objektiv (25A', 25B', 25C', 25D') erfassten Messanteils (33) ausgebildet ist, und
• einen optischen Ausgang (31) zur Abgabe der mit den Objektiven (25A', 25B', 25C', 25D') erfassten Messanteile (33).

Aspect B6. Detection unit (21) according to one of aspects B1 to B5, further comprising an optical light guide system (27).

• a plurality of optical inputs (29), each of the optical inputs (29) being optically connected to one of the lenses (25A', 25B', 25C', 25D') and for recording the associated lens (25A', 25B', 25C ', 25D') of the recorded measurement component (33) is formed, and
• an optical output (31) for emitting the measurement components (33) recorded with the lenses (25A', 25B', 25C', 25D').

Aspect B7. Detection unit (21) according to aspect B6, wherein the optical light guide system (27) has a plurality of optical fibers (45) and wherein a light entry surface (63) of one of the optical fibers (45) forms one of the optical inputs (29) and that corresponds to the optical input (29 ) assigned lens (25A', 25B', 25C', 25D') images the plasma detection area (39) onto the light entry surface (63).

Aspect B8. Detection unit (21) according to aspect B7, wherein light exit surfaces (67A, 67B, 67C, 67D) of the optical fibers (45) form the optical output (31) and the light exit surfaces (67A, 67B, 67C, 67D), in particular adjacent or spaced apart from one another, are arranged in a row.

• wobei die Lichtleitfasern (45) ausgangsseitig linear aufgereiht sind, insbesondere zur Ausrichtung entlang eines Eintrittsspalt (19A) eines optischen Spektrometers (13), in dem insbesondere eine spektrale Aufspaltung des Plasmalichts (3A) für die Spektralanalyse von einem von der Detektionseinheit (21) erfassten Plasmalicht (3A) erfolgt, und/oder mit parallelen Faserorientierungen angeordnet sind.

Aspect B9. Detection unit (21) according to aspect B7 or B8, wherein light exit surfaces (67A, 67B, 67C, 67D) of the optical fibers (45) are arranged in a row and/or

• wherein the optical fibers (45) are lined up linearly on the output side, in particular for alignment along an entrance slit (19A) of an optical spectrometer (13), in which in particular a spectral splitting of the plasma light (3A) for the spectral analysis of one detected by the detection unit (21). Plasma light (3A) occurs and/or is arranged with parallel fiber orientations.

• einer Laserstrahlquelle (9) zur Abgabe eines, insbesondere gepulsten, Laserstrahls (5), wobei das Plasma (3) mit dem sich entlang einer Strahlachse (5A) ausbreitenden Laserstrahl (5) auf einer Oberfläche (7A) einer Probe (7) erzeugt wird,
• einer Fokussieroptik (11) zur Fokussierung des Laserstrahls (5) auf die Oberfläche (7A) der Probe (7),
• einer Detektionseinheit (21) nach einem der vorhergehenden Aspekte, und
• einem optischen Spektrometer (13) zur Spektralanalyse von einem von der Detektionseinheit (21) erfassten Plasmalicht (3A),

wobei

• - der Plasmadetektionsbereich (59) der Detektionseinheit (21) in einem Abschnitt entlang der Strahlachse (5A) angeordnet ist und
• - die Laserstrahlquelle (9) und die Fokussieroptik (11) derart ausgebildet sind, und insbesondere Strahlparameter des Laserstrahls (5), umfassend insbesondere Pulsdauer und Pulsenergie eines gepulsten Laserstrahls, in Abhängigkeit des Materials der Probe (7) derart eingestellt sind, dass bei Positionierung der Oberfläche (7A) der Probe (7) im Plasmadetektionsbereiche (59) ein Plasma erzeugt wird.

AspectB10. Spectrometer system (1) for the spectral analysis of a plasma light (3A) emitted by a laser-induced plasma (3).

• a laser beam source (9) for emitting a, in particular pulsed, laser beam (5), the plasma (3) being generated on a surface (7A) of a sample (7) with the laser beam (5) propagating along a beam axis (5A). ,
• a focusing optics (11) for focusing the laser beam (5) on the surface (7A) of the sample (7),
• a detection unit (21) according to one of the preceding aspects, and
• an optical spectrometer (13) for the spectral analysis of a plasma light (3A) detected by the detection unit (21),

where

• - the plasma detection area (59) of the detection unit (21) is arranged in a section along the beam axis (5A) and
• - the laser beam source (9) and the focusing optics (11) are designed in such a way, and in particular beam parameters of the laser beam (5), including in particular the pulse duration and pulse energy of a pulsed laser beam, are set depending on the material of the sample (7) in such a way that when positioned a plasma is generated on the surface (7A) of the sample (7) in the plasma detection areas (59).

Aspect B11. Spectrometer system (1) according to aspect B10, wherein the lenses (25A', 25B', 25C', 25D') and correspondingly the detection cones (35') are spatially arranged in such a way that when at least one of the lenses (25A', 25B', 25C', 25D') the measuring component (33') of the plasma light (3A) can be detected with another of the lenses (25A', 25B', 25C', 25D').

• wobei jeder der optischen Eingänge (29) optisch einem der Objektive (25A', 25B', 25C', 25D') zugeordnet und zur Aufnahme des mit dem zugeordneten Objektiv (25A', 25B', 25C', 25D') erfassten Messanteils ausgebildet ist, und
• der optische Ausgang (31) zur Einkopplung von mit den Objektiven (25A', 25B', 25C', 25D') erfassten Messanteilen in das optische Spektrometer (13) ausgebildet ist.

Aspect B12. Spectrometer system (1) according to aspect B10 or B11, further comprising an optical light guide system (27), which is designed to forward measurement components of the plasma light (3A) detected by the detection unit (21) to the optical spectrometer (13) and a plurality of optical inputs ( 29) and an optical output (31),

• wherein each of the optical inputs (29) is optically assigned to one of the lenses (25A', 25B', 25C', 25D') and is designed to record the measurement portion recorded with the assigned lens (25A', 25B', 25C', 25D'). is and
• the optical output (31) is designed to couple measurement components recorded with the lenses (25A', 25B', 25C', 25D') into the optical spectrometer (13).

Aspect B13. Spectrometer system (1) according to aspect B12, wherein each of the lenses (25A', 25B', 25C', 25D') is designed and arranged in the lens holder (23') in such a way that the measurement portion that is in the detection cone (35'). the lens (25A', 25B', 25C', 25D') is captured and imaged onto the optical input (29) assigned to the lens (25A', 25B', 25C').

Aspect B14. Spectrometer system (1) according to one of aspects B10 to B13, wherein a beam axis (75A, 75B, 75C, 75D) is assigned to each of the measuring components (33) emerging from the optical light guide system (27), and the beam axes (75A, 75B, 75C , 75D) are parallel to each other or no more than at an angle of up to 1° or up to 3° to each other.

• wobei die Messanteile (33) durch die Eintrittsapertur (19) in das optische Spektrometer (13) eingekoppelt werden und über das dispersive optische Element (13A) spektral aufgelöst zu dem Detektor (13B) geführt werden, um eine allen Objektiven (25A', 25B', 25C', 25D') der Detektionseinheit (21) zugeordnete spektrale Verteilung (17) auszugeben.

Aspect B15. Spectrometer system (1) according to one of aspects B11 to B14, wherein the optical spectrometer (13) has an entrance aperture (19), in particular an entrance slit (19A), a dispersive optical element (13A), in particular a grating, Prism or grating prism (grisma), and a detector (13B), and

• wherein the measurement components (33) are coupled into the optical spectrometer (13) through the entrance aperture (19) and are guided to the detector (13B) in a spectrally resolved manner via the dispersive optical element (13A) in order to obtain all lenses (25A', 25B ', 25C', 25D') to output the spectral distribution (17) assigned to the detection unit (21).

It is expressly emphasized that all features disclosed in the description and/or the claims are considered to be separate and independent from each other for the purpose of the original disclosure as well as for the purpose of limiting the claimed invention, regardless of the combinations of features in the embodiments and/or the claims should. It is explicitly stated that all range statements or statements of groups of units disclose every possible intermediate value or subgroup of units for the purpose of the original disclosure as well as for the purpose of limiting the claimed invention, in particular also as a limit of a range statement.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• CN 107783242 A [0003]
• US 11085882 [0003]

Claims (15)

Detection unit (21) for a spectrometer system (1) for the spectral analysis of a plasma light (3A) emitted by a laser-induced plasma (3), the plasma (3) being on a surface (3) with a laser beam (5) propagating along a beam axis (5A). 7A) of a sample (7) is generated, comprising: - a lens holder (23), - several lenses (25A, 25B, 25C, 25D) held by the lens holder (23), whereby Each of the lenses (25A, 25B, 25C, 25D) is assigned a detection cone (35), which forms a plasma detection area (39) in an overlap area (37) with the laser beam (5), from which in the case of a plasma detection area (39) present plasma (3) a measurement component (33) of the plasma light (3A) is detected by the lens (25A, 25B, 25C, 25D), and the lenses (25A, 25B, 25C, 25D) are arranged and aligned in the lens holder (23) in such a way that the plasma detection areas (39) are arranged offset along the beam axis (5A) and together form a viewing area (41) of the detection unit (21) form. Detection unit (21). Claim 1 , wherein the plasma detection areas (39) - partially overlap, merge into one another or are spaced apart from one another along the beam axis (5A) and/or - each extend over 0.1 mm to 15 mm along the beam axis (5A) and/or over 1/ 10 to 1/4 of the viewing area (41) and / or wherein the lens holder (23) provides an optical passage opening (43) through which the beam axis (5A) runs, with a position of the beam axis (5A) in particular in the middle of the optical Through opening (43) is fixed, and wherein the lens holder (23) in particular has a mounting plate (23A) in which a plurality of lens holder openings for receiving the lenses (25A, 25B, 25C, 25D) and the optical through opening (43) for the laser beam ( 5) are provided, and wherein the lens holder openings are arranged around the optical through-opening (43), and in particular azimuthally distributed around the optical through-opening (43). Detection unit (21). Claim 1 or 2 , wherein each of the detection cones (35) extends along an observation axis (35A) which runs at an observation angle (α) in the range from 0° to 90° to the beam axis (5A), the observation angles (α) being in particular the same deviate from each other by more than 3° or are distributed in an angular range of 45°, and/or the lens holder (23) in particular has a holder plate (23A) in which an optical passage opening (43) is provided for the laser beam (5), wherein the beam axis (5A) extends orthogonally to the mounting plate (23A) and at least one of the detection cones (35) extends along an observation axis (35A) which is at an observation angle (α) in the range from 0° to 90°, in particular 3° to 60°, for example in the range from 5° to 25°, to the beam axis (5A). Detection unit (21) according to one of the Claims 1 until 3 , wherein the lenses (25A, 25B, 25C, 25D) are arranged azimuthally spaced around the beam axis (5A) and / or wherein the lenses (25A, 25B, 25C, 25D) are arranged azimuthally equally distributed around the beam axis (5A). Detection unit (21) according to one of the Claims 1 until 4 , wherein the detection unit (21) comprises two to 25, in particular four, lenses (25A, 25B, 25C, 25D). Detection unit (21) according to one of the Claims 1 until 5 , further with an optical light guide system (27) comprising a plurality of optical inputs (29), each of the optical inputs (29) being optically connected to one of the lenses (25A, 25B, 25C, 25D) and for receiving the associated lens (25A , 25B, 25C, 25D). Detection unit (21). Claim 6 , wherein the optical light guide system (27) has a plurality of optical fibers (45) and wherein a light entry surface (63) of one of the optical fibers (45) forms one of the optical inputs (29) and the lens (25A, 25B) assigned to the optical input (29). , 25C, 25D) is designed and arranged to image the plasma detection area (39) of the associated lens (25A, 25B, 25C, 25D) onto the light entry surface (63). Detection unit (21). Claim 7 , wherein light exit surfaces (51A, 51B, 51C, 51D) of the optical fibers (45) form the optical output (31) and the light exit surfaces (51A, 51B, 51C, 51D), in particular adjacent or spaced apart, are arranged in a row. Detection unit (21). Claim 7 or 8th , wherein light exit surfaces (67A, 67B, 67C, 67D) of the optical fibers (45), in particular according to the sequence of the plasma detection areas (39) in the viewing area (33), are arranged in a row and / or the optical fibers (45) on the output side lined up linearly, in particular for alignment along an entrance slit (19A) of an optical spectrometer (13), in which in particular a spectral splitting of the plasma light (3A) takes place for the spectral analysis of a plasma light (3A) detected by the detection unit (21), and/ or are arranged with parallel fiber orientations. Detection unit (21) according to one of the Claims 7 until 9 , wherein a light guide zone of an optical fiber has a diameter in the range from 100 µm to 1,000 µm, in particular in the range from 100 µm to 300 µm, in the range from 150 µm to 250 µm or in the range from 750 µm to 850 µm. Spectrometer system (1) for the spectral analysis of a plasma light (3A) emitted by a laser-induced plasma (3). a laser beam source (9) for emitting a, in particular pulsed, laser beam (5), the plasma (3) being generated on a surface (7A) of a sample (7) with the laser beam (5) propagating along a beam axis (5A). , a focusing optics (11) for focusing the laser beam (5) on the surface (7A) of the sample (7), a detection unit (21) according to one of the preceding claims, and an optical spectrometer (13) for the spectral analysis of a plasma light (3A) detected by the detection unit (21), where - Plasma detection areas (39) of the detection unit (21) are arranged in a section along the beam axis (5A) and - The laser beam source (9) and the focusing optics (11) are designed such that a plasma is generated in each of the plasma detection areas (39) when the surface (7A) of the sample (7) is positioned. Spectrometer system (1). Claim 11 , further with an optical light guide system (27), which is designed to forward measurement components of the plasma light (3A) detected by the detection unit (21) to the optical spectrometer (13) and a plurality of optical inputs (29) and an optical output (31) comprises, wherein each of the optical inputs (29) is optically assigned to one of the lenses (25A, 25B, 25C, 25D) and is designed to record the measurement portion (33) recorded with the assigned lens (25A, 25B, 25C, 25D), and the optical output (31) is designed to couple measurement components (33) recorded with the lenses (25A, 25B, 25C, 25D) into the optical spectrometer (13). Spectrometer system (1). Claim 12 , wherein at least one of the lenses (25A, 25B, 25C, 25D) is designed and arranged in the lens holder (23) in such a way that a measuring component (33) of the plasma light (3A) which is in the detection cone of the lens (25A, 25B, 25C , 25D), is imaged onto the optical input (29) assigned to the lens (25A, 25B, 25C, 25D). Spectrometer system (1). Claim 12 or 13 , wherein each of the measuring components (33) emerging from the optical light guide system (27) is assigned a beam axis (75A, 75B, 75C, 75D), and the beam axes (75A, 75B, 75C, 75D) are parallel to one another or no more than below at an angle of up to 1° or up to 3° to each other. Spectrometer system (1) according to one of the Claims 11 until 14 , wherein the optical spectrometer (13) comprises an entrance aperture (19), in particular an entrance slit (19A), a dispersive optical element (13A), in particular a grating, prism or grating prism, and a detector (13B), and wherein the measurement components ( 33) are coupled into the optical spectrometer (13) through the entrance aperture (19) and are guided to the detector (13B) in a spectrally resolved manner via the dispersive optical element (13A) in order to produce one of the lenses (25A, 25B, 25C, 25D). to output the spectral distribution (17) assigned to the detection unit (21).

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