WO2021009203A1

WO2021009203A1 - Devices and methods for magnetic field-dependent optical detection

Info

Publication number: WO2021009203A1
Application number: PCT/EP2020/069959
Authority: WO
Inventors: Ulrich Vogl; Nils Trautmann; Petr SIYUSHEV; Bernhard Schwarz; Lorenz Lechner
Original assignee: Carl Zeiss Ag
Priority date: 2019-07-16
Filing date: 2020-07-15
Publication date: 2021-01-21
Also published as: DE102019119212A1

Abstract

The aim of the invention is to improve devices and methods for magnetic field-dependent optical detection and to make their handling easier. For this purpose, an objective lens for a microscope has, in a beam path of the objective lens, a solid state element with at least one NV center. A microscope for confocal microscopy has a solid state element with a plurality of NV centers, the NV centers being scanned in a method for three-dimensionally determining a magnetic field.

Description

description

Devices and methods for magnetic field-dependent optical detection

The invention is in the field of the determination of magnetic fields as well as

Magnetic field-dependent optics and relates in particular to an objective for a microscope, a device with a microwave antenna arrangement, a microscope, a use of a microscope and a method for three-dimensional determination of a magnetic field.

Magnetic fields can be determined optically by means of NV centers - that is to say by means of color centers, for example, which can be optically excited depending on a magnetic field effective at the respective color center and which emit emission light. For this purpose, a microscope, for example, can be converted in order to optically excite such color centers and to detect the emission light emitted by the color centers in an imaging manner. In addition, further modifications to the microscope or extensions for a measurement setup with a microscope may be necessary in order to influence the color centers in a certain way - for example by means of microwave radiation - so that they can be optically excited depending on the magnetic field or emit emission light depending on the magnetic field.

Conversely, fluorescence or phosphorescence (or more generally luminescence, henceforth briefly referred to as “fluorescence”) from NV centers - for example in applications such as medical imaging or biosensors, in which NV centers can be used as a fluorescent substance, or in the Quantum cryptography or for quantum computer systems - depending on the magnetic field effective there and any other influencing variables. For example, such an NV center could serve as an emitter in a solid-state-based single photon source at room temperature.

In addition to applications in the academic environment, such NV centers and measurement setups are also interesting for various commercial fields such as the investigation of electrical circuits or for an optically integrated biosensor due to the controllable fluorescence, a high achievable sensitivity and / or a large achievable range on an optically detected (microwave) resonance of an NV center. For example, such an optically integrated biosensor is described in US Pat. No. 8,193,808 B2. There is a need, devices and methods for magnetic field-dependent optical

To improve detection and / or a construction or conversion of appropriate

To facilitate devices - such as a microscope - and, in particular, to make such measurement setups and methods more reliable and efficient.

The invention meets this need by an objective for a microscope, by a device with a microwave antenna arrangement, by a microscope, by the

Use of a microscope and a method for three-dimensional determination of a magnetic field in accordance with the teaching of one of the main claims. Beneficial

Embodiments, developments and variants of the present invention are in particular the subject of the subclaims.

A first aspect of the invention relates to an objective for a microscope, the objective having a solid-state element with at least one NV center which can be arranged in a beam path of the objective.

In the context of the invention, an “NV center” is to be understood as at least one color center, the color center being dependent on a magnetic field effective there by means of a

Excitation light is optically excitable and emission light can be emitted from the excited color center. Such a color center can be a defect in a matrix structure, in particular in a (possibly crystalline) solid. An intensity of the emission light can also be dependent on a resonant microwave absorption, the resonant

Microwave absorption is dependent on the magnetic field at the color center. Such a NV center can also be a nitrogen vacancy center in a diamond lattice, for example a so-called [NV] ^_ center, which is the subject of current research. In such a [NV] ^_ center, a model is currently based on a multi-electron system, which is a 3-level system with a triplet ground state and an excited triplet state and at least one energetically between the ground state and the excited state Intermediate state - especially a singlet state - (or about two intermediate states according to Doherty, Marcus W .; Manson, Neil B .; Delaney, Paul; Jelezko, Fedor; Wrachtrup, Jörg; Hollenberg, Lloyd CL (2013-07-01). "The nitrogen-vacancy color center in diamond". Physics Reports. The nitrogen-vacancy color center in diamond. 528 (1): 1-45). With such a [NV] center, an electron spin resonance can also be energetically excited between several

different states in the triplet ground state, which are due to a spin Differentiate energetically between interaction and any magnetic field acting at the NV center. Microwave radiation of a suitable frequency can be used to excite the electron spin resonance, so that the electron system is raised from an energetically lower state of the triplet ground state to an energetically higher state of the triplet ground state by means of energy from the microwave radiation. Furthermore, such an NV center can be a color center in a diamond matrix, such as an ST1 or “Stuttgart T” color center. The matrix structure can also be made from 4H-SiC and, for example, a solid-state matrix, in particular a crystal lattice, made from 4H-SiC. Such a matrix structure made of 4H-SiC can be a color center such as a so-called "VcVsi DiVacancy" or a so-called "NV Nitrogene Vacancy" or a so-called "hexagonal lattice site Silicon vacancy (VSi)" (see for example NATURE COMMUNICATIONS | (2019) 10: 1954 | https://doi.org/10.1038/s41467-019-09873 | High-fidelity spin and optical control of single silicon-vacancy centers in Silicon Carbide), especially in the crystal lattice.

One advantage of arranging the solid-state element with at least one NV center can in particular be that a magnetic field-dependent emission from the NV center can be detected via the objective using a microscope. A commercially available microscope can be fitted with such an objective - for example for the respective microscope

has appropriate threads or similar for fastening - equip it without the need for an additional solid-state element with NV centers. The solid-state element can also be rigidly or movably connected to the objective in such a way that, in a connection position for detecting the at least one NV center, the NV center is fixedly arranged in the beam path of the objective, in particular in an image area relative to the rest of the objective NV center can be assigned to a specific position in the image area. A microscope set up for this purpose can also be used to shift an object to be imaged relative to the objective so that different areas of the object are imaged in the image area, with the position of the NV center moving relative to the object and thus the NV center at different levels of the respective mapped area can be arranged on the object.

A second aspect of the invention relates to a device with a

Microwave antenna assembly. The device has a diamond plate with at least one NV center. Alternatively, the device is an objective for a microscope, in particular according to the first aspect of the invention. As a further alternative, the device is a slide for a microscope. The possible advantages, embodiments or variants of the first aspect of the invention also apply accordingly to the device with a microwave antenna arrangement. The device with diamond plate, the objective and microscope slide can be used for

Use magnetic field-dependent optical detection, whereby - in some embodiments - energetic states of the at least one NV center in the basic state or in the (optically) excited state, which differ in energy due to the magnetic field effective there, can be excited by means of the microwave antenna arrangement. One advantage of having the microwave antenna arrangement can in particular be that the number of different parts for converting a (commercially available) microscope for magnetic field-dependent optical detection is reduced and handling is thus simplified. With some variants of such a lens, both with

Solid-state elements with an NV center as well as with a microwave antenna arrangement both interact synergistically and further simplify handling. The at least one NV center and the microwave antenna arrangement - that is to say, for example, frequencies and spatial field profiles of electric fields that can be achieved by means of the microwave antenna arrangement - can also be adapted to one another, thereby further simplifying the

Handling and / or increased reliability and / or efficiency are made possible.

A third aspect of the invention relates to a microscope which is set up for 2-pi or 4-pi microscopy and has a solid-state element with at least one NV center in a focal point.

The possible advantages, embodiments or variants of the preceding aspects of the invention also apply accordingly to the microscope for 2-pi or 4-pi microscopy with the at least one NV center. If the at least one NV center is arranged in the focal point, the sensitivity - that is to say in particular the light yield with respect to the emission light of the NV center - and thus the efficiency can advantageously be increased. The spatial resolution can also be improved if there are several NV centers in the solid element.

In some variants, the microscope has one as the solid-state element

Diamond platelets with one or more NV centers.

A fourth aspect of the invention relates to a use of a microscope for the imaging determination of a magnetic field based on an optical detection of a

Electron spin resonance at at least one NV center. The microscope is designed according to the third aspect of the invention or the microscope has an objective according to the first or a device according to the second aspect of the invention. The possible advantages, embodiments or variants of the preceding aspects of the invention also apply accordingly to the use of the microscope. An advantage of determining a magnetic field by means of NV centers or the at least one NV center and the microscope can in particular be that an imaging determination with a - corresponding to such a microscope - high optical resolution - for example compared to methods for determining magnetic fields by means of Coils - as well as, in the case of several NV centers, simultaneous detection of the magnetic field at several positions (according to the number and position of the respective NV centers, in particular a simultaneous one

Imaging for these multiple positions) and / or a high sensitivity and / or a large dynamic range can be made possible.

A fifth aspect of the invention relates to a method for three-dimensional determination of a magnetic field. The method comprises arranging a solid-state element with a plurality of NV centers in the magnetic field to be determined. The method also includes three-dimensional scanning of the solid-state element by means of a confocal microscope, with one NV center or several NV centers of the plurality of NV centers being excited at a respective focal point during scanning, microwave radiation for an electron spin resonance at the respective NV Centers is emitted and is detected by light emitted at the respective focal point by the NV centers as a function of the electron spin resonance. Finally, the method includes detecting light emitted by the NV centers at the respective focal point as a function of the

Electron spin resonance.

The possible advantages, embodiments or variants of the preceding aspects of the invention also apply accordingly to the method for three-dimensional determination of a magnetic field.

Further advantages, features and possible applications result from the

following detailed description of exemplary embodiments and / or from the figures.

The invention is explained in more detail below with reference to the figures on the basis of advantageous exemplary embodiments. Identical elements or components of the

Exemplary embodiments are essentially identified by the same reference symbols, unless otherwise described or if nothing else results from the context. To this end show, partly schematically:

1 shows a model of a [NV] - center;

2 shows an energy diagram for an NV center;

3 shows an objective having a movable solid-state element with an NV center according to one embodiment;

4 shows a further objective according to an embodiment;

Fig. 5 shows a device with a diamond plate and a

Microwave antenna arrangement and several NV centers in the diamond plate according to one embodiment;

6 shows a microscope for 2-pi microscopy according to an embodiment;

7 shows a further objective according to an embodiment;

8 shows a use of a microscope for the imaging determination of a

Magnetic field according to one embodiment;

9 shows a measurement setup for three-dimensional determination of a magnetic field by means of a confocal microscope and a plurality of NV centers after a

Embodiment; and

10 shows a flow diagram of a method for three-dimensional determination of a magnetic field according to an embodiment.

The figures are schematic representations of various embodiments and / or exemplary embodiments of the present invention. Elements and / or components shown in the figures are not necessarily shown true to scale. Rather, the various elements and / or components shown in the figures are reproduced in such a way that their function and / or their purpose can be understood by a person skilled in the art. Connections and couplings shown in the figures between the functional

Units and elements can also be called indirect connections or couplings

implemented. In particular, data connections can be wired or wireless, that is to say in particular as radio connections. Certain

Connections, such as electrical connections, for example for energy supply, the

Not be shown for the sake of clarity. Furthermore, optical connections - for example between optical elements - which can be represented in particular as a straight light beam, can also be implemented in some variants by means of a light guide and / or optical elements such as mirrors for deflecting light beams, such connections for the sake of clarity are not necessarily shown.

1 schematically illustrates an atomic structure of an NV center such as a nitrogen vacancy center with a ball-and-stick model of a [NV] - center (140) without a surrounding diamond lattice. There are three carbon atoms 146 in three places of the

Diamond lattice, while one of these three carbon atoms 146

(immediate / nearest neighbor) adjacent lattice site there is a defect 144 (vacancy: V) - this lattice site is therefore not occupied - as well as a nitrogen atom 142 (nitrogen: N) instead of a carbon atom in a lattice site adjacent to it (immediate / nearest neighbor) is arranged. In addition, FIG. 1 shows a vector for an external magnetic field 80 and an axis of the NV center 148 - with respect to which a spin is

Multi-electron system of the NV center is defined - shown. It goes without saying that, in addition to the external magnetic field 80, a magnetic field due to the magnetic moments of the atomic nuclei is also effective on electrons of the multi-electron system or these magnetic fields are superimposed, with - unless reference is made separately to these additional magnetic moments - in the sense of According to the invention, the “magnetic field effective there” is to be understood as the magnetic field which occurs there, i.e. at the respective NV center, due to the external magnetic field.

2 shows an energy diagram 40 for an NV center such as a [NV] center according to current modeling (cf., for example, Rogers, L. J .; Armstrong, S .; Sellars, M. J .; Manson,

N. B. (2008). "Infrared emission of the NV center in diamond: Zeeman and uniaxial stress studies". New Journal of Physics. 10 (10): 103024.) (cf. e.g. Doherty, Marcus W .; Manson,

Neil B .; Delaney, Paul; Jeletsko, Fedor; Wrachtrup, Jörg; Hollenberg, Lloyd CL (2013-07-01). "The nitrogen-vacancy color center in diamond". Physics Reports. The nitrogen-vacancy color center in diamond. 528 (1): 1-45.). The multi-electron system of the NV center has a triplet ground state | g>, an excited triplet state | e> and two Intermediate states | ze> and | zg>, which energetically lie between the ground state | g> and the excited state | e>. Two of the electrons of the multi-electron system can be aligned parallel or antiparallel with regard to their spin in the triplet ground state, so that the multi-electron system has a spin +1 (m _s = +1) or -1 (m _s = -1) or a spin 0 (m _s = 0). Due to their spin interaction, the electrons have a higher energy level with spin +1 and -1 than with an anti-parallel alignment with spin 0. In addition - not shown in FIG. 2 - the energy levels for m _s = + 1 and m _s = -1 differ from each other due to an interaction with the magnetic moments of the atomic nuclei (cf. hyperfine structure), whereby this split, i.e. a difference between the energy levels for m _s = + 1 and m _s = -1, is usually much smaller than an energy difference between the energy levels for m _s = + 1 / m _s = -1 compared to the energy level for m _s = 0.

Proceeding from FIG. 2, an optical detection of a magnetic field - or more generally a magnetic field-dependent optical detection - based on an NV center can be carried out

corresponding to FIG. 1 and / or with regard to energy levels corresponding to FIG. 2 as follows

illustrate. By means of excitation light 46 with sufficient energy per photon, i.e. a green laser with a wavelength less than about 532 nm - such as, as shown, with a wavelength of 515 nm - the [NV] - center can be reduced from the ground state | g> (initially possibly into vibronic bands and then from there) into the excited state | e>, whereby the spin of the multi-electron system is retained, i.e. when the ground state | g> is excited with m _s = + 1, correspondingly as an excited state | e> with m _s = +1 is reached. The NV center can then, with the emission of a photon, i.e. emission light 56 and thus fluorescence, return to the corresponding state of the triplet ground state - i.e. from the excited state | e> with m _s = + 1 to the ground state | g> with m _s = +1 - get; at a [NV] ^_ center, for example, a photon with 637 nm, i.e. red emission light, can be emitted. This transition is also called a radiating transition or optical transition, with the (emission / fluorescence) light emitted here usually being detected optically.

In addition to this radiant transition there is also another transition over the

Intermediate states | ze> and | zg> possible, with a photon with a longer wavelength being emitted at the transition from | zg> to | ze>, i.e. a photon with 1042 nm at a [NV] ^_ center. In other models there is only one intermediate state

assumed that no corresponding photon is emitted. In the case of these transitions, there is therefore no emission of photons or at least one emission 58 of photons with a different, in particular with a greater wavelength, and these transitions occur also called non-radiating transitions. In the case of these non-ray transitions, the spin of the multi-electron system is not necessarily retained, with the rate or the

The probability of a transition from an excited state with m _s = + 1 or m _s = -1 of the excited triplet state | e> to the state with m _s = 0 of the triplet ground state is greater than the rate or the probability for one Transition from the excited state | e> with m _s = 0 to one of the ground states with m _s = + 1, 0 or -1. The further transition via the intermediate states | ze> and | zg> competes with the radiant transition. Thus, if an NV center has a spin m _s = 0, it emits more emission light than with a spin m _s = + 1 or m _s = -1, since there is a transition at m _s = + 1 or m _s = -1 about the intermediate states

takes place (relatively) more frequently. In addition, in the case of an NV center, repeated excitation can increase the population probability for the ground state and / or for the excited state with m _s = 0, since over the further transition the ground state | g> with m _s = 0 (and then after possibly renewed excitation the excited state | e> with m _s = 0) is reached - this is also called spin polarization.

Through certain measures - such as radiation with a certain energy

(in particular per radiation quantum), which corresponds to an energy difference between | g> with m _s = 0 and | g> with m _s = ± 1 or an energy difference between | e> with m _s = 0 and | e> with m _s = ± 1 corresponds to - the occupation probability for the ground state and / or the excited state can be increased with m _s = + 1 or -1 for an NV center. In the case of an [NV] center (without an external magnetic field), a transition from the ground state | g> with m _s = 0 to one of the

Ground states are excited resonantly with m _s = ± 1, so an electron spin resonance can be achieved - that is, in the context of the invention, in particular a resonant absorption of the

(Microwave) radiation through the NV center with transition from | g> with m _s = 0 to | g> with m _s = + 1 or -1. In a broader sense, electron spin resonance can also include such an excitation while varying the (external) magnetic field and measuring the

Magnetic field-dependent absorption of microwave radiation can be understood (see e.g. https://de.wikipedia.org/wiki/Elektronenspinresonanz). By creating an external

Magnetic field shifts the energy levels of the ground state with m _s = + 1 and the ground state with m _s = -1 (the same applies to the states of the excited

Triplet state | e> with m _s = ± 1). Thus, for the transition from | g> with m _s = 0 to | g> with m _s = -1, a different frequency of the microwave radiation is required than for the transition from | g> with m _s = 0 to | g> with m _s = + 1. When a [NV] - center is irradiated (initially without an external magnetic field) with microwave radiation with a frequency of around 2870 MHz, the probability for the states with m _s = ± 1 is increased, which means that the fluorescence, i.e. the emitted emission light, decreases. The frequency required for the electron spin resonance is shifted by an external magnetic field, which acts at the NV center, whereby the probability for the states with m _s = ± 1 is less or not increased and thus the fluorescence does not decrease or increase again.

The change in fluorescence at the NV center is therefore dependent on the particular one

Measure to increase the probability of occupation for states with m _s = ± 1 - i.e. roughly the frequency of the incident microwave radiation - as well as the (external) magnetic field effective at the NV center. Thus, based on a change in the

Fluorescence or the emitted emission light determine an effective (external) magnetic field at the NV center. Other variants based on the NV center are also possible for determining the magnetic field, such as a variation of the frequency of the

Microwave radiation, so that the fluorescence remains the same, the external magnetic field being determined based on the respective variation. In addition, depending on the method selected, a calibration may be required in order to orient the axis 148 of the NV center and / or a magnetic field that acts on the basis of the magnetic moments of the NV center (for example from the atomic nuclei of the NV center) and which interacts with the superimposed on the external magnetic field.

Conversely, the fluorescence can be controlled by applying a magnetic field and / or by means of other influencing variables that change the occupation probability for states with m _s = ± 1 - such as microwave radiation of a suitable frequency - which makes it advantageous to use materials such as particles with NV centers as (externally) controllable

Fluorescent substances together with appropriate methods and devices - such as appropriately equipped microscopes - are made possible.

3 shows an objective 100 for a microscope, the objective having an NV center 140, according to an embodiment of the present invention.

In one embodiment, the objective 100 has a connecting device 102 which is set up for connection to the microscope, a housing 110 and a carrier plate 120 which is movably connected to the housing 110 by means of a movement device 112 of the objective 100. In some variants, the movement device 112 has one Plain bearings on or consists of it. In some variants, the connecting device 102 has or consists of a thread and is formed on a side of the housing 110 facing the microscope. By connecting the objective 100 to the microscope by means of the connecting device 102, a beam path of the objective and a beam path of the microscope can be aligned in such a way that a common beam path is formed. In some variants, the housing 110 has further optical elements 116, such as lenses, which are arranged in the beam path of the objective 100.

The carrier plate 120 has a first lens 122, a solid-state element 124 and a second lens 126. The solid-state element 124 has at least one NV center 140 and is integrally and optically permeable to the first lens 122, for example by means of an optical adhesive 123. Correspondingly, in some variants, the first lens 122 and the second lens 126 can also be combined with the carrier plate 120, which for example have an optical

transparent material is made, in particular consists of glass, be integrally and optically permeable connected. The carrier plate 120 and the movement device 112 are set up to move the carrier plate 120 relative to the housing 110 into a first connection position for detecting the at least one NV center 140 by means of a movement such that the first lens 122, the solid-state element 124 and the NV- Center 140 are arranged in a fixed position in the beam path of the objective. In addition, they are

Carrier plate 120 and the movement device 112 set up by means of a movement to move the carrier plate 120 relative to the housing 110 in such a way into a second connection position for detecting an object which is arranged on a side of the objective facing away from the beam path from the microscope for imaging by means of the microscope that the second lens 126 is arranged in a fixed position in the beam path and directs light from the object into the beam path or, conversely, directs light that runs from the microscope through the beam path to the object.

In some variants - such as shown in FIG. 3 - the first lens 122 is semispherically shaped on a side facing the microscope with respect to the beam path, whereby the light yield, in particular the light emitted by the NV center, can advantageously be increased. In some variants, the carrier plate 120 has a first optical element 128 which is arranged and set up relative to the first lens 122 when it is in the first connection position together with the first lens 122, the solid-state element 124 and the NV center 140 in the beam path of the objective is arranged to compensate for a spherical aberration due to the semispherically shaped first lens 122. This first optical element 128 can advantageously be used for the second connection position by means of the movement Remove the solid-state element 124 with the NV center 140 from the beam path together with the semispherically shaped first lens 122, so that they do not interfere with an image of the object using the second lens 128 and, in particular, a sharp image is made possible.

In Fig. 4, a further objective 100 according to an embodiment of the present invention is shown as a schematic section.

In one embodiment, the further objective 100 has a housing 110, a

Connecting device 102 and possibly one or more further optical elements 116 in a beam path of the objective. In this case, the further objective 100 is designed in some variants similar to the objective from FIG. 3, wherein the connecting device 102 can have a thread so that the objective 100 can be connected to a commercially available microscope by means of the thread 102.

The further objective 100 also has a solid-state element 124, which is designed as a front lens of the objective and, with respect to the beam path, on a side of the objective facing away from the microscope, in particular as the last optical element along the beam path from the microscope via the objective to a possible microscope Object, is arranged and shaped in such a way that when an object at the lens for

Microscopy is arranged, light from this object is guided into the beam path. The front lens 124 has at least one — or, as shown — several NV centers 140, which are arranged in such a way that light is guided from these NV centers 140 into the beam path and thus when the (further) lens 100 is connected to a microscope , imaged by means of the microscope and possibly with an image acquisition device, in particular in an imaging manner.

In some variants, the front lens 124 consists of diamond - in particular of precisely one monocrystalline diamond -, the NV centers 140 being nitrogen defect centers, in particular [NV] ^_ centers. In this advantageous way, good optical

Properties in the visible range of the electromagnetic spectrum both for microscoping an object via the front lens and for detection of light emitted by the NV centers, and good mechanical properties - in particular low scratch sensitivity - achieve as well as magnetic field-dependent optical detection Enable excitation and emission light in the visible range at NV centers with largely known properties. The further lens 100 also has a microwave antenna arrangement 280, which is set up to emit microwave radiation to the NV centers 140 in a frequency range for electron spin resonance of the NV centers, this frequency range being in the gigahertz range in some variants, for example for variants with [NV] ^_ centers than the NV centers 140 is in a range at 2.87 GHz and the microwave antenna arrangement 280 is accordingly set up approximately to emit microwave radiation between 2.5 GHz and 3.5 GHz. In some variants, the microwave antenna arrangement 280 is arranged at the front lens, that is to say in the solid-state element 124 with the NV centers 140, in order to enable a stronger coupling of the microwave antenna arrangement 280 to the NV centers 140 in comparison with an arrangement further away. In some variants, the microwave antenna arrangement 280 is also arranged in the housing 110 in order, in particular, to protect the microwave antenna arrangement 280, to enable a compact lens 100 and / or to facilitate the handling of the lens 100.

The further objective 100 has - as shown - in some variants a

Magnetic field device 180, which is set up a static or low frequency

Generate bias field for the NV centers 140. The magnetic field device 180 can also be arranged in some variants in accordance with the microwave antenna arrangement 280 in the front lens 124 and / or in the housing 110. In some variants, the magnetic field device 180 and the microwave antenna arrangement 280 are also designed as a common microwave magnetic field device which is set up to emit both a static or low-frequency bias field and microwave radiation for electron spin resonance of the NV centers. In some variants the

common microwave-magnetic field device (or correspondingly the

Magnetic field device 180 or the microwave antenna arrangement 280) also set up to emit electromagnetic radiation in the megahertz range for generating eddy currents in a test object. In some variants, the common microwave magnetic field device (or correspondingly the magnetic field device 180 or the

Microwave antenna arrangement 280) has a coil arrangement or consists thereof. In some variants, the coil arrangement is embodied in an annular manner around the beam path and / or the front lens 124. In some variants of this, a coil or several coils of the coil arrangement are coreless, in particular designed as an air coil, with an electrical conductor of the coil / coils winding around the beam path and / or the front lens 124. This makes it possible to achieve good coupling and / or to disrupt the optical

Properties - e.g. due to parts of the magnetic field device 180 / Microwave antenna arrangement 280 / microwave magnetic field device in the beam path - avoid.

In some variants, the housing 110 has connection elements 282, 284 for the

Microwave antenna arrangement 280 and / or connection elements 182, 184 for the

Magnetic field device 180. In some variants, these are linked to the

Connecting device 102 integrated or arranged in this, in particular to provide a simple-to-use connection both of the objective 100 to the microscope and a simultaneous connection of the magnetic field device 180 and / or the

Microwave antenna arrangement 280 with corresponding systems for generating signals for the microwave radiation, the bias field and / or the

To enable electromagnetic radiation in the megahertz range - for example via other connecting elements arranged on the microscope.

5 outlines a device 200 with a diamond plate 240 according to a

Embodiment of the present invention.

In one embodiment, the diamond plate 240 has a nitrogen vacancy center, in particular a [NV] ^_ center, as at least one NV center 140. In some variants, the diamond plate 240 is made from polycrystalline diamond, which in particular enables simple production. In particular, the properties of [NV] ^_ centers are retained in polycrystalline diamond.

In one embodiment, the device 200 has a microwave antenna arrangement 280 as well as a first connection element 282 and a second connection element 284 for the microwave antenna arrangement 280. In some variants, the

Microwave antenna arrangement 280 has a structure with an electrical conductor, which is arranged in a meandering manner on one side of the diamond plate 240. In some variants, the electrical conductor is vapor-deposited onto the diamond plate 240 or the electrical conductor is mechanically connected as a wire to the diamond plate 240, for example via an adhesive connection.

6 shows a microscope 300 for 2-pi microscopy according to an embodiment of the present invention. In one exemplary embodiment, the microscope 300 has an objective 100 with a diamond plate 240 as a solid-state element and a microwave antenna arrangement 280. Alternatively, in some variants, the microscope 300 has an objective 100 and, separately, a solid-state element 124 - for example a diamond plate 240. The diamond plate 240 or the solid-state element 124 has a plurality of NV centers 140, which for

Magnetic field-dependent optical detection can be arranged in a focal point of the microscope 300 or in an image area of the microscope.

Furthermore, the microscope 300 has in some variants a light source 340, in particular a laser, which is set up to generate an excitation light 304 for the NV centers 140. In some variants thereof with [NV] ^_ centers as NV centers, the light source 340 is designed as a green laser, in particular with a wavelength of 515 nm. Furthermore, the microscope 300 has in some variants an image acquisition device 350, in particular with an electronic image sensor, which is set up to acquire an emission light 305 from the NV centers 140 in an imaging manner. In some variants thereof with [NV] ^_ centers as NV centers, the image capture device 350 has an image sensor which is sensitive to red light, in particular with a wavelength of 637 nm. In some variants, the microscope 300 also has a beam splitter device 330 which is set up to couple excitation light 304 - for example from a light source 340 - into a beam path of the microscope 300, and emission light 305 emitted from one of the NV centers into the beam path to a beam path exit of the Microscope - in which, for example, an image acquisition device 350 is arranged - to guide. In some variants, the beam splitter device 330 is designed as a dichroic mirror.

In one embodiment - as shown in FIG. 6 - the diamond plate 240 is coated on a side facing the microscope with respect to the beam path with an anti-reflective coating 244 for the light emitted by the NV centers. In this advantageous way, multiple reflections can be avoided and the image quality can thus be increased.

In one embodiment - as shown in FIG. 6 - the diamond plate 240 is coated on a side facing away from the microscope with respect to the beam path with a coating 245 that reflects the light emitted by the NV centers. In this advantageous way, the light 305 emitted in the direction of the opposite side can also be guided into the beam path and thus a light yield and thus the sensitivity can be increased. In some variations, the NV centers 140 in the diamond plate 240 are close to a surface of the diamond plate arranged at the reflective coating 245 - about less than 100 nm, in particular less than 20 nm away from the surface, whereby

in particular can reduce double images due to the reflection and thus increase the image quality.

In some variants, the antireflective coating 244 is designed to be antireflective for the excitation light 304 as well, as a result of which, in particular, the efficiency during the excitation can be increased. In some variants, the reflective coating 245 is embodied as a dichroic coating, which is antireflective for the excitation light 304, which in particular makes it possible to avoid back reflection. The reflective coating 245 can also be antireflective for other wavelengths of light, as a result of which, in particular, an object behind this coating 245 can be detected at least for those wavelengths at which the coating 245 does not reflect the light.

In one embodiment - as shown in Fig. 6 - the lens 100 is as

Mirror lens formed. In some variants, the mirror lens 100 can be used as

Schwarzschild lens be designed. In some variants, the mirror objective 100 has a concave mirror 130 and a convex mirror 132. In some variants, the convex mirror 132 is dichroic and at the same time permeable to the excitation light 304 as well as reflective / specular for the emission light 305, whereby in particular a direct

Excitation of NV centers 140 - in particular without imaging via mirror objective 100 - is made possible by means of excitation light 304, while emission light 305 is imaged by means of mirror objective 100 - for example starting from a focal point or from an image area. The convex mirror 132 can also be reflective for the excitation light 304 and for the emission light 305, which in particular enables focusing on a focal point - for example for confocal microscopy.

The mirror objective 100 is designed in some variants - as shown in FIG. 7 - in such a way that it has an end mirror 134 - for example comprising diamond - in which the NV centers or the at least one NV center - in particular in the vicinity of a Side of the end mirror 134, which faces an object to be microscoped during microscopy - are formed. In this advantageous way, the separate convex mirror and the solid-state element or the diamond plate can be omitted, their function being combined in the end mirror 134. In some variants, one side of the end mirror which faces an object to be microscoped during microscopy is coated with a coating 244 that reflects the emission light 305. In some variants there is a Side of the end mirror, which faces away from an object to be microscoped during microscopy, is coated with a coating 245 that is antireflective for the excitation light 304 or with a coating 245 that is reflective for the emission light 305, in particular with a dichroic coating 245, which increases the efficiency of the excitation by means of excitation light 304 can be increased and / or - any interspersed - light components, in particular along the beam path to the NV centers, can be reduced, that is to say, for example, background noise in the spectral range of the emission light 305 can be reduced.

One advantage of the mirror objective can in particular lie in the fact that it is achromatic over a large bandwidth or a large range of wavelengths and thus chromatic distortions occur even in the case of emission light 305, which is large

Spectral bandwidth - about 100 nm for [NV] ^_ centers - can be reduced.

8 shows a use of a microscope for the imaging determination of a

Magnetic field illustrated.

In one exemplary embodiment, an electronic chip 574, which is attached to a circuit board 572 in a base 576, is analyzed and currents flowing in the electronic chip 574 are determined by determining the magnetic field. The electronics chip 574 is connected to other components on the circuit board 572 and / or to a

Experimental set-up for feeding in and / or reading out certain voltages or currents. For example, the chip 574 can - in its usual function - be operated on the circuit board 572 or can be manipulated in a targeted manner by feeding in certain voltages / currents. The chip 574 has a device with a diamond plate 240, a microwave antenna arrangement 280 and connections 282, 284 for the

Microwave antenna assembly attached. In some variants of the use, a housing of the electronic chip 574 at the top - i. H. in particular on a side opposite the board - be open, which is also referred to as “decapitated”, which enables better coupling of the diamond plate 240 placed on this side. Due to the electrical currents flowing in the chip 574, a (location-dependent)

Induced magnetic field which influences at least one NV center of the diamond plate in such a way that an electron spin resonance at the at least one NV center is amplified or weakened for a certain frequency by a microwave radiation radiated by means of the microwave antenna arrangement 280, whereby the fluorescence of the is increased when excited by excitation light at least one NV center, i.e. the emitted emission light is reduced or increased. By moving the board 572 together with the Electronics chip 574 over a multitude of positions by means of actuators 372, a locally acting magnetic field at the NV center for the multitude of positions can be determined via the fluorescence or its change, and thus an overall magnetic field and, accordingly, an electrical current density, which such Total magnetic field generated, determine. In some variants, the actuators 372 are designed as piezo actuators or have such. The actuators 372 can also be set up to move the circuit board 572 or, accordingly, another object to be analyzed / examined by a so-called “slip and stick motion”. In some variants with a “decapitated” electronic chip, this chip 574 can also be polished on the open side, which enables particularly good contact and thus particularly good coupling of the magnetic field into the diamond plate. Some variants are also set up to frame an image area to be analyzed by means of the microwave antenna arrangement 280, whereby the electron spin resonance is mainly and efficiently in this area (with a suitable microwave frequency in

Depending on the locally acting magnetic field).

With a corresponding use, a corresponding measurement set-up can be used which has a device for generating eddy currents, for example the

Microwave antenna arrangement is set up, in addition to electromagnetic radiation in the microwave range, also to generate electromagnetic radiation in the megahertz range, in order to examine an object having a conductive material. Such an object can be a metallic workpiece - for example from a 3-D printing process. The

Device for generating eddy currents can be set up to generate the eddy currents in a certain material depth or up to a certain material depth. One advantage of this use can lie in the fact that an electrical conductivity in the object - for example at the specific material depth - can be determined in a spatially resolved manner, the electrical conductivity allowing conclusions to be drawn about the quality of the conductive material. For example, inclusions or poorly formed metallic connections - the extent of which is usually in the range of micrometers - can be determined in a metallic workpiece produced using a 3-D printing process based on a change in the inducible eddy currents and thus a magnetic field resulting therefrom.

9 shows a measurement setup 500 according to an embodiment of the present invention, which is set up for the three-dimensional determination of a magnetic field by means of a confocal microscope 530. In one exemplary embodiment, the measurement setup 500 has the confocal microscope 530. In addition, in one exemplary embodiment, the measurement setup 500 has a solid-state element 540 with a plurality of NV centers 140, the NV centers spatially extending over all three dimensions in the solid-state element 540. In some variations, the solid element is made 540 of a monocrystalline or polycrystalline diamond, the NV centers are 140 corresponding to [NV ^_] centers.

In addition, FIG. 9 shows an object 570 to be examined, which is not necessarily part of the measurement setup 500, but is there for measurement, i.e. H. to determine the magnetic field - in particular such a magnetic field which is generated by the object 570 - can be arranged. Another object can be arranged there accordingly.

In one embodiment, the confocal microscope 530 has a

Beam splitter device 330 and further optical elements 116, which are set up to bundle excitation light 304 in a beam path of confocal microscope 530 onto a focal point, and light 305 emitted by the focal point, in particular

To guide emission light, which is emitted from one NV center of the plurality of NV centers 140, into the beam path. In this case, the beam splitter device 330 is set up to split the beam path with respect to the excitation light 304 and the light 305.

In one embodiment, the measurement setup 500 furthermore has a green laser 340 as a light source for exciting the NV centers, in particular with a wavelength of 515 nm, as well as a photodiode 350 for the detection of emission light emitted at the focal point, in particular with a high sensitivity for a wavelength of 637 nm. In alternative variants, the measurement set-up can also have another light source and / or an image acquisition device 350 instead of the photodiode, these generating a corresponding excitation light or being sensitive to a corresponding emission light depending on the NV centers used in the measuring set-up.

Using the confocal microscope 530, various positions in the

Scanning solid state element 540, d. H. focus the focal point on such a position. For three-dimensional determination of the magnetic field, such

Scanned positions at which one of the NV centers 140 is arranged. By means of a microwave antenna arrangement (not shown in FIG. 9) a

Excite electron spin resonance of the NV center there, with the excitation or the The (microwave) frequency required for this is dependent on the magnetic field effective at this NV center. After such an electron spin resonance again leads to a reduction in fluorescence, the magnetic field effective there can be determined from a change in fluorescence.

In addition to a three-dimensional determination of a magnetic field via the solid-state element 540, in which the large number of NV centers extend over all three dimensions, a corresponding measurement setup 500 with a corresponding method can also be used for a two-dimensional determination, with NV centers in a two-dimensional Area are scanned and about a diamond plate is used in which the NV centers in a plane - are arranged approximately in the vicinity of a surface of the diamond plate. A particularly high resolution can be achieved by means of confocal microscopy.

FIG. 10 shows a flow diagram of a method 400 for three-dimensional determination of a magnetic field according to an embodiment of the present invention.

In one embodiment, the method 400 has the method steps 420, 430, 432, 434, 436, 442, 446, 448 and 480 as well as the method conditions 410 and 416. Method 400 begins at method start 402 and ends at method end 404.

In this case, in some variants, a measurement setup according to the invention, in particular a measurement setup described with reference to FIG. 9, can be used.

In method step 420, a solid-state element with a plurality of NV centers is arranged in the magnetic field to be determined. Such a magnetic field can be generated in some variants by an object to be examined. In some variants, such a magnetic field can also be induced in the object to be examined, for example with a device for generating eddy currents. In some variants, the method can be used to examine a metallic workpiece - for example when manufacturing or processing with 3-D printing, welding or a casting process.

In method step 430, the solid element is scanned three-dimensionally by means of a confocal microscope. For this purpose, in method step 430, method steps 432, 434 and 436 are carried out iteratively until, in accordance with method condition 410, a sufficient number of volume elements in the solid element and thus / or a sufficient number of NV centers of the multitude of NV centers has been recorded.

In method step 432, a first or, in the case of further iterations, a corresponding further focal point is focused and there one NV center of the plurality of NV centers is optically excited by means of excitation light.

In method step 434, microwave radiation is emitted to the NV center, which has a frequency for exciting the electron spin resonance of the NV center.

In method step 436, an emission light emitted by the NV center at the respective focal point is detected as a function of the electron spin resonance, and method steps 442 and 446 are used for a large number of specific values for this purpose

The bias field, which is superimposed on the magnetic field to be determined, executed, the determined values defining a strength and a spatial orientation of the bias field.

In method step 442, the bias field is generated with one of the plurality of specific values.

In method step 446, the emission light of the NV center at the respective focal point or its change is detected for the value of the plurality of values of the premagnetization field.

In process condition 416, it is checked whether all values of the

Bias magnetic field an emission light has been detected at the respective focal point, and if this is the case - symbolized by <y> - the method 400 is continued at method condition 410. Otherwise, if the emission light is to be detected for further values - symbolized by <n> - the method 400 is continued in method step 442 for a value of the plurality of specific values for the bias field for which the emission light at the respective focal point is not yet has been captured. In some variants, the bias field is thus varied across all specific values for the bias field. Alternatively, in some variants, the emission light can only be used for one value of the

Bias field or without a bias field are detected, with which

Method step 442 and method condition 416 can be omitted and method step 430 corresponds to method step 446. In method condition 410, a check is made as to whether a sufficient number of

Volume elements in the solid element and thus / or a sufficient number of NV centers of the plurality of NV centers has been recorded, and if this is the case - symbolized by <y> - method 400 is continued at method step 480. Otherwise - symbolized by <n> - the method 400 in method step 432 is for a further focal point, that is to say in particular for a focal point in a not yet scanned one

Volume element, continued.

The number required in each case can depend on the desired spatial resolution, the total number of NV centers, their arrangement and / or a structure of the magnetic field. For example, for a low spatial resolution and a largely homogeneous magnetic field or a magnetic field with weak gradients, a smaller number of NV centers to be recorded is required than for a high spatial resolution or a highly inhomogeneous magnetic field, in which magnetic field gradients also extend over small spatial sections - about a few micrometers - change significantly. In addition, the number required can depend on the total volume over which the magnetic field is to be determined. For example, for a larger volume, a higher number of volume elements correspondingly distributed over this larger volume is required than for a smaller volume in which the magnetic field is to be determined. The (sufficient) number of

Volume elements and, accordingly, at NV centers, are defined in some variants using a grid. For example, a first step size can be defined along a first axis through the solid-state element, a second step size along a second axis and a third step size along a third axis, wherein the step sizes can be the same or different. For example, the step size for the first and second axes can be 50 nm and the step size for the third axis - for which a lower spatial resolution is required and / or the magnetic field changes to a lesser extent - can be 2 pm.

In method step 480, the magnetic field is determined based on the light emitted in each case at the NV centers. To this end, method step 448 is carried out in the case of variants in which a bias field is varied. In method step 448, a magnetic field vector is determined by initially using the dependence of the emission light emitted at the respective focal point from the respective NV center on the electron spin resonance to apply a local magnetic field, in particular a local magnetic field

Magnetic field strength is determined and then based on a change in this locally Acting local magnetic field strength for different strengths and orientations of the

Bias magnetic field, which is superimposed there with the local magnetic field, a respective magnetic field vector is determined. For example, the overall local magnetic field strength acting there decreases if the magnetic field to be examined and the bias magnetic field are destructively superimposed there - i.e. have opposite directions. Correspondingly, in variants without a bias field, the magnetic field or its strength is determined based on the emission light and its dependence on the electron spin resonance. In some variants, the dependence on the electron spin resonance can also be the

Frequency of the microwave radiation can be varied.

In some variants, after method step 480, data relating to the magnetic field

identify - for example a vector model of the magnetic field - stored in a storage device or a representation thereof output at a user interface.

The method 400 can be used for further objects to be examined or for further ones

investigating magnetic fields are repeated beginning at method step 420.

In some variants, the method 400 can also have one or more calibration steps in which a light emitted at respective volume elements is determined for the solid-state element or for a further solid-state element, one or more specific bias fields being generated and / or other magnetic fields

be shielded. Light emitted initially can also be determined without excitation of NV centers in order to determine a background noise and possibly this background noise from a later detected light, which both components of

Has background noise as well as emission light to subtract.

While some exemplary embodiments have been described with respect to one or more [NV] ^_ centers, those skilled in the art can also adapt these for other NV centers. For example, in some modifications with a so-called "hexagonal lattice site silicon vacancy (VSi)", a light with a wavelength of at most 861 nm, i.e. an excitation light with a wavelength of 730 nm, is generated with a laser diode and as light from the Spatial area or from the respectively selected spatial section, in particular the emission light for a wavelength at least in the range between 875 nm and 890 nm, and a microwave radiation with a frequency in the range of 4.5 MHz is generated as microwave radiation. With the above, the following statements also result and / or are exemplified with the above.

In some embodiments of the objective, a front lens of the objective consists of the solid-state element or has the solid-state element. One advantage of the front lens made from the solid-state element can in particular be that no transitions are required between different materials in the front lens, which means that

Image quality can be increased. In addition, the at least one NV center thus arranged in the front lens makes it possible to simplify an optical structure of the lens and thus its manufacture.

In some embodiments, a lens of the objective is connected integrally and optically permeable to the solid-state element, whereby the image quality can in particular be increased.

In some embodiments, the solid-state element comprises or consists of diamond. The diamond has a nitrogen vacancy center as the at least one NV center. One advantage of the nitrogen void center can in particular be that it has largely known properties and is therefore particularly well suited for magnetic field-dependent optical detection, especially in commercial use.

In some embodiments, the solid-state element is or is a lens with the

Solid-state element shaped semispherically on a side facing the microscope with respect to the beam path, whereby in particular the light yield, ie in particular the yield of emission light from the at least one NV center, can be increased.

In some embodiments in which a lens or the solid-state element is semispherically shaped, the objective has an optical element which is set up in the beam path to compensate for a spherical aberration due to the semispherically shaped lens or the semispherically shaped solid-state element.

In some embodiments, particularly those which are semispherically shaped

Solid-state element or a semi-spherically shaped lens are those

Solid-state element or this lens and an optical element for compensating for a spherical aberration can be removed from the beam path. In some embodiments, the device has a microwave antenna arrangement - for example the objective, the device with the diamond plate or a slide for

Microscope - or the lens without a microwave antenna arrangement

Magnetic field device that is set up static or low frequency

Generate bias field.

In some embodiments, the microwave antenna arrangement is configured

To emit microwave radiation in the gigahertz range for electron spin resonance in at least one NV center and electromagnetic radiation in the megahertz range for generating eddy currents in a test object.

In some embodiments, the solid-state element of the lens or the

Diamond platelets are coated with a reflective coating which is reflective for a light for exciting the NV centers or for a light that the NV centers emit due to their excitation.

In some embodiments, the solid-state element of the lens or the

Diamond platelets coated with an anti-reflective coating for the light emitted.

In some embodiments, the objective is designed as a mirror objective.

In some embodiments, the method for three-dimensional determination of a magnetic field further comprises: varying a bias magnetic field, which is superimposed on the magnetic field to be determined; detecting a variation of the light emitted in each case during scanning due to the varying bias field; as well as a

Determine magnetic field vectors at the NV centers based on the variation of the emitted light. In this way, the magnetic field can advantageously be determined as a three-dimensional vector field.

The aforementioned devices and methods for magnetic field-dependent optical detection can advantageously be used in some variants for the following: A three-dimensional determination of magnetic fields in the process control, with magnetic fields being advantageously only weakly shielded by materials compared to electrical fields; Thus, in process control - for example in the manufacture of products - a material composition can be determined via the three-dimensional determination of magnetic fields determine a product produced in a production process controlled by the process control below its surface, that is to say in the product itself and not just on the surface; If, for example, the material of the product is partially magnetic, magnetizable or electrically conductive, static magnetic fields and / or eddy currents can be detected and used for process control; In particular, such a method with confocal microscopy enables a particularly high spatial resolution, including a resolution into the depth of the product or material to be examined; In this way, a spatial resolution can be achieved which, for example in the case of a solid-state element comprising diamond, corresponds approximately to the distance between the solid-state element and the product to be examined, at least for distances greater than 1 μm. Correspondingly, the three-dimensional determination of magnetic fields can also be used for quality control in a 3-D printing process, during welding or during a casting process. The

Use magnetic field-dependent optical detection for biosensors or for the analysis of electronic circuits, whereby the fluorescence can advantageously be controlled via the magnetic field. In some variants, a high dynamic range and / or a high sensitivity of the fluorescence with respect to the magnetic field are also advantageous. A sensitivity of approximately 10 ⁹ to 10 ¹² Tesla / sqrt (Hz) with respect to a variation of the irradiated can be used for determining a magnetic field or a magnetic field strength

Achieve microwave radiation.

While exemplary embodiments, possible applications and application examples have been described in detail, in particular with reference to the figures, it should be pointed out that a large number of modifications are possible. It should also be pointed out that the exemplary designs and applications are merely examples that are not intended to limit the scope of protection, the application and the structure in any way. Rather, the preceding description provides the person skilled in the art with guidelines for the implementation and / or application of at least one exemplary embodiment, with various modifications, in particular alternative or additional features and / or modifications of the function and / or arrangements of the described components, as desired by the person skilled in the art can be made without losing any of the subject matter specified in the attached claims or its legal

Equivalents are deviated from and / or the scope of protection is left.

Claims

1. Method (400) for three-dimensional determination of a magnetic field, comprising:

- (420) arranging a solid-state element with a plurality of NV centers in the magnetic field to be determined;

- (430) Three-dimensional scanning of the solid-state element by means of a

Confocal microscope and each:

- (432) exciting one or more NV centers of the plurality of NV centers at a respective focal point;

- (434) radiating microwave radiation for electron spin resonance at the respective NV centers; such as

- (436) detecting light emitted at the respective focal point by the NV centers as a function of the electron spin resonance; and

- (480) determining the magnetic field based on the light emitted in each case at the NV centers and its dependence on the electron spin resonance.

2. The method (400) according to claim 1, further comprising:

- (442) Varying a bias field, which with the to

superimposed determining magnetic field;

- (446) detecting a variation of the light emitted in each case during scanning due to the varying bias field; and

- (448) Determining magnetic field vectors at the NV centers based on the variation of the emitted light.

3. Objective (100) for a microscope, having a solid-state element (124) which can be arranged in a beam path of the objective and has at least one NV center (140).

4. Objective (100) according to claim 3, wherein a front lens of the objective from the

Solid element (124) consists.

5. Objective (100) according to claim 3, wherein a lens (122) of the objective with the solid-state element (124) is integrally and optically transparent.

6. The objective (100) according to any one of claims 3 to 5, wherein the solid-state element (124) comprises a diamond and the diamond has a nitrogen vacancy center as the at least one NV center (140).

7. Objective (100) according to one of claims 3 to 6, wherein the solid-state element or a lens (122) with the solid-state element (124) is semispherically shaped on a side facing the microscope with respect to the beam path.

8. The objective (100) according to claim 7, which has an optical element (128) which is set up in the beam path to cause a spherical aberration due to the semispherically shaped solid-state element or the semispherically shaped lens (122)

compensate.

9. Objective (100) according to claim 8, wherein the solid-state element (124) and the optical element (128) can be removed from the beam path.

10. Device (100, 200) with a microwave antenna arrangement (280), the device having a diamond plate (240) with at least one NV center (140), an objective (100) for a microscope, in particular according to one of claims 3 to 9, or is a slide for a microscope.

11. The device (100, 200) according to claim 10, further comprising a

Magnetic field device (180) which is set up to be static or low-frequency

Generate bias field.

12. The device (100, 200) according to claim 10 or 11, wherein the

Microwave antenna arrangement (280) is set up to emit microwave radiation in the gigahertz range for electron spin resonance at at least one NV center (140) and electromagnetic radiation in the megahertz range for generating eddy currents in a test object.

13. Objective (100) according to one of claims 3 to 9 or device (200) with the diamond plate according to one of claims 10 to 12, wherein the solid-state element (124) of the objective or the diamond plate (240) with a reflective coating (245 ) is coated, which is reflective for a light to excite the NV centers or for a light that the NV centers (140) emit due to their excitation.

14. Objective (100) or device (200) with diamond plate according to claim 13, which is further coated with an anti-reflective coating (244) for the emitted light.

15. Lens (100) or device (200) according to one of claims 3 to 14, which is designed as a mirror lens.

16. A microscope (300) which is set up for 2-pi or 4-pi microscopy and has a solid-state element (124, 240) with at least one NV center (140) in a focal point.

17. Use of a microscope (300) according to claim 15 or a microscope with an objective (100) according to one of claims 3 to 9 or 13 to 15 or with a device (200) according to one of claims 10 to 15, wherein the microscope for

imaging determination of a magnetic field based on an optical detection of an electron spin resonance at at least one NV center (140) is used.