A diamond NV color center magnetometer imaging method and system

Abstract

The present invention belongs to the field of magnetic field imaging measurement, and provides a diamond NV center magnetometer imaging method and system, including: calibration and chromatic aberration elimination, focus positioning, high-pass filter filtration, and image capture. Through the structure of an achromatic lens, a wedge prism group, and a diamond NV center, the present invention reduces the laser spot size and improves the spatial resolution of the magnetometer.

Description

Technical Field

[0001] The present invention relates to the field of magnetic field imaging measurement, and particularly to a diamond NV center magnetometer imaging method and system. Background Art

[0002] During the imaging process of a diamond NV center magnetometer, the number of NV centers that can be simultaneously excited mainly depends on the size of the laser spot. Therefore, the spatial resolution of imaging is limited by the spot size. Currently, many diamond NV center magnetometers use an optical fiber to simultaneously transmit laser and fluorescence signals to the detection area. However, due to the diffraction effect in the optical fiber, the laser spot is usually large, which limits the improvement of resolution. In order to optimize the spatial resolution, in recent years, super-resolution imaging techniques have been widely applied.

[0003] But these techniques usually use special optical elements or design complex optical paths, or rely on post-processing of data to extract super-resolution images, increasing the complexity and cost of the system. Currently, there are few simple and efficient optical path designs that can achieve high-spatial-resolution magnetic field measurement of a diamond NV center magnetometer by precisely controlling the focusing of the laser beam. Summary of the Invention

[0004] In order to overcome the deficiencies of the prior art, the purpose of the present invention is to provide a diamond NV center magnetometer imaging method and system to reduce the laser spot to improve the spatial resolution ability of the magnetometer.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] A diamond NV center magnetometer imaging method, comprising:

[0007] Using an achromatic lens to correct and eliminate chromatic aberration of the laser beam emitted by the light source;

[0008] Using a wedge prism group to locate the focus of the laser beam output by the achromatic lens on the surface of the diamond NV center;

[0009] Transmitting the laser beam output by the diamond NV center to a high-pass filter through an optical fiber for filtering;

[0010] Transmitting the fluorescence signal output by the high-pass filter to the detector for image capture to obtain a spot image.

[0011] Preferably, the calculation formula for the spot radius at the focus is: where ω′ 0 is the spot radius at the focus; ω 0$w_0$ is the beam waist radius of the incident laser for the achromatic lens; $F$ is the focal length of the achromatic lens; $f$ is the Rayleigh length of the incident laser; $L$ is the distance from the beam waist position of the incident laser beam to the achromatic lens.

[0012] Preferably, the wavelength of the laser beam emitted by the light source is 532 nm; the NV centers in the diamond NV centers are distributed on the diamond surface layer; the wavelength distribution range of the fluorescence signal excited by the diamond NV centers is from 637 nm to 800 nm.

[0013] Preferably, the beam waist radius is 2 mm; the focal length is 50 mm; the spot diameter at the focus is 8.47 μm.

[0014] Preferably, a diamond NV center magnetometer imaging system includes: a phototube, an achromatic lens, a wedge prism group, a diamond NV center, an optical fiber, a high-pass filter, and a detector;

[0015] The output plane of the wedge prism group and the input plane of the diamond NV center are parallel to each other; the optical fiber is arranged between the output plane of the diamond NV center and the high-pass filter; the high-pass filter is fixed at the input end of the detector;

[0016] The achromatic lens is used to correct, eliminate chromatic aberration, and collimate the laser beam emitted by the phototube, and form a small spot with a diameter in the micron range at the focal length according to the calculation formula of the spot radius at the focus, so as to obtain a collimated beam; the wedge prism group is used to position the collimated beam on the upper surface of the diamond NV center by adjusting the direction of the collimated beam.

[0017] The present invention discloses the following technical effects:

[0018] The present invention provides a diamond NV center magnetometer imaging method and system, which solves the defects of complex existing magnetometer imaging methods and high costs through the structures of an achromatic lens, a wedge prism group, and a diamond NV center, and realizes the reduction of the laser spot. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 It is a schematic diagram of the imaging process of the diamond NV center magnetometer provided by the embodiment of the present invention;

[0021] Figure 2 Schematic diagram of the diamond NV - center magnetometer imaging system provided by the embodiment of the present invention;

[0022] Figure 3 Schematic diagram of the surface light spot of the diamond NV - center provided by the embodiment of the present invention. Specific embodiments

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] The object of the present invention is to provide a diamond NV - center magnetometer imaging method and system, which reduces the laser spot to improve the spatial resolution ability of the magnetometer.

[0025] To make the above - mentioned objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0026] Figure 1 Schematic diagram of the imaging process of the diamond NV - center magnetometer provided by the embodiment of the present invention. As Figure 1 shown, the present invention provides a diamond NV - center magnetometer imaging method, including:

[0027] Step 100: Use an achromatic lens to correct and eliminate chromatic aberration of the laser beam emitted by the light source;

[0028] Step 200: Use a wedge prism group to position the focus of the laser beam output by the achromatic lens on the surface of the diamond NV - center;

[0029] Step 300: Transmit the laser beam output by the diamond NV - center to a high - pass filter through an optical fiber for filtering;

[0030] Step 400: Transmit the fluorescence signal output by the high - pass filter to a detector for image capture to obtain a spot image.

[0031] Specifically, the calculation formula for the spot radius at the focus is: where, ω′ 0 is the spot radius at the focus; ω 0 is the beam waist radius of the laser incident on the achromatic lens; F is the focal length of the achromatic lens; f is the Rayleigh length of the incident laser; L is the distance from the beam waist position of the incident laser beam to the achromatic lens.

[0032] Optionally, the wavelength of the laser beam emitted by the light source is 532 nm; the NV centers in the diamond NV centers are distributed on the surface layer of the diamond; the wavelength distribution range of the fluorescence signal excited by the diamond NV centers is from 637 nm to 800 nm.

[0033] Preferably, the beam waist radius is 2 mm; the focal length is 50 mm; the spot diameter at the focus is 8.47 um.

[0034] Reference Figure 2 , a diamond NV center magnetometer imaging system, comprising: a phototube, an achromatic lens, a wedge prism group, a diamond NV center, an optical fiber, a high-pass filter, and a detector;

[0035] The output plane of the wedge prism group and the input plane of the diamond NV center are parallel to each other; an optical fiber is arranged between the output plane of the diamond NV center and the high-pass filter; the high-pass filter is fixed at the input end of the detector;

[0036] The achromatic lens is used to correct the laser beam emitted by the phototube, eliminate chromatic aberration, and collimate the beam, and form a small spot with a diameter of micron level at the focal length according to the calculation formula of the spot radius at the focus, so as to obtain a collimated beam; the wedge prism group is used to position the collimated beam on the upper surface of the diamond NV center by adjusting the direction of the collimated beam.

[0037] Specifically, the optical path method for reducing the laser spot on the surface of the diamond NV center magnetometer includes the following steps:

[0038] S1: Correct the laser beam emitted by the light source through the achromatic lens, eliminate chromatic aberration, and at the same time form a small spot with a diameter of micron level at the focal length and collimate the beam;

[0039] S2: Precisely adjust the direction of the collimated beam through a group of wedge prisms to accurately position the focus of the laser beam on the upper surface of the diamond NV center;

[0040] S3: Transmit the fluorescence signal emitted by the diamond NV center to the detector through the optical fiber connected to the prism, and add a high-pass filter in the detector to only allow the fluorescence signal to pass through.

[0041] In step S1, the formula for the spot radius of the laser beam at the focal length after passing through the achromatic lens is:

[0042]

[0043] ω 0 That is, the minimum spot radius before the lens, ω′ 0 That is, the newly obtained minimum spot radius.

[0044] Furthermore, the Rayleigh length of the incident laser λ is the wavelength of the incident laser. Since the incident light is collimated into parallel light, the distance from the beam waist position of the incident laser to the lens can be ignored. Therefore, Therefore, the spot diameter at the focal point after the laser passes through the lens is 8.47 μm.

[0045] Specifically, the spatial resolution of the diamond NV center magnetometer is determined by the number of diamond NV centers excited within the laser spot. Therefore, the smaller the spot, the higher the spatial resolution. The position of the spot is precisely adjusted through a set of wedge prisms, and the spot with the minimum spot radius is positioned on the upper surface of the diamond NV center to achieve a higher spatial resolution.

[0046] Furthermore, when the spot size is large in magnetic field imaging, the signals of individual NV centers within the spot cannot be distinguished, and the finally measured value is the average of these signals, resulting in the field averaging effect. Reducing the spot size can reduce the field averaging effect, thereby improving the spatial resolution of magnetic field imaging.

[0047] Preferably, the fluorescence signal is transmitted through an optical fiber from the diamond NV center to the detector. There is no need to transmit the laser beam and the fluorescence signal simultaneously, avoiding the laser spot from becoming larger due to the diffraction effect.

[0048] Specifically, a high-pass filter is used to filter the fluorescence signal emitted by the diamond NV center, allowing only light with a wavelength higher than the set threshold to pass through, blocking the interference of the excitation light and low-wavelength stray light, and improving the signal-to-noise ratio of the fluorescence signal.

[0049] Furthermore, the specific implementation process of the method designed in this embodiment is as follows: First, a parallel laser with a wavelength of 532 nm is incident, and the beam is corrected by an achromatic lens with a focal length of 50 mm to eliminate the focal shift of light with different wavelengths. Refer to Figure 2 , the convex surface of the lens is aligned with the light source, ensuring the parallel incidence of the laser and enabling it to form a small spot with a diameter on the micron scale at the focal length. To further improve the laser focusing quality, the beam is collimated to improve the stability and uniformity of the beam. On this basis, the spot radius at the focal point is accurately calculated based on the following formula:

[0050]

[0051] To further reduce the spot size and optimize the spatial resolution, the focal spot must be precisely positioned on the surface of the diamond NV center. However, since the laser signal may be affected by diffraction and refraction effects during the transmission in a traditional optical fiber, resulting in the expansion of the spot size, additional optical adjustment techniques are introduced. By using a set of wedge prisms, the propagation direction of the laser beam is precisely adjusted to ensure that the laser can be precisely focused on the upper surface of the diamond NV center. By precisely adjusting the angles of the wedge prisms, micrometer-level control of the spot position is achieved, effectively reducing the field averaging effect and significantly improving the spatial resolution of magnetic field imaging.

[0052] The diamond NV center generates fluorescence signals under the irradiation of the laser, and these fluorescence signals are guided into the optical fiber after passing through the wedge prism. To avoid the interference of the excitation light and stray light, a high-pass filter is added between the optical fiber and the detector, allowing only the fluorescence signals above the set threshold to pass through. The design of the high-pass filter matches the wavelength of the excitation light (532 nm) of the system and the wavelength range (637 nm to 800 nm) where the fluorescence signals are mainly distributed, ensuring the selective filtering of the signals. The use of the high-pass filter not only significantly improves the signal-to-noise ratio but also enhances the detection ability of the system for weak fluorescence signals. The results are shown in Figure 3 。

[0053] The beneficial effects of the present invention are as follows:

[0054] By introducing an optical path design based on wedge prisms and achromatic lenses, the present invention can optimize the propagation path and focal point positioning of the laser beam, not only significantly reducing the laser spot size but also effectively simplifying the system structure, reducing the complexity and cost. This design provides a practical technical solution for improving the performance and wide application of the diamond NV center magnetometer.

[0055] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other.

[0056] Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, there will be changes in the specific implementation manner and application scope according to the idea of the present invention. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A diamond NV color center magnetometer imaging method, characterized in that: include: The laser beam emitted by the light source is corrected and the chromatic aberration is eliminated by using an achromatic lens; The focus of the laser beam output by the achromatic lens is positioned on the surface of the diamond NV color center by using a wedge prism group; the calculation formula of the spot radius at the focus is: Wherein, ω'0 is the spot radius at the focus; ω0 is the beam waist radius of the incident laser of the achromatic lens; F is the focal length of the achromatic lens; f is the Rayleigh length of the incident laser; L is the distance from the incident laser beam waist position to the achromatic lens; Transmitting the laser beam output by the diamond NV color center to a high-pass filter through a light guide for filtering; The fluorescence signal output by the high-pass filter is transmitted to the detector for image capture to obtain a light spot image.

2. A diamond NV color center magnetometer imaging method according to claim 1, characterized in that: The wavelength of the laser beam emitted by the light source is 532 nm; the NV color center in the diamond is distributed on the surface of the diamond; the wavelength distribution range of the fluorescence signal excited by the diamond NV color center is 637 nm to 800 nm.

3. A diamond NV color center magnetometer imaging method according to claim 1, characterized in that: The beam waist radius is 2 mm; the focal length is 50 mm; and the spot diameter at the focus is 8.47 um.

4. A diamond NV color center magnetometer imaging system, characterized in that: A diamond NV color center magnetometer imaging method applied to claim 1, the system comprising: a phototube, an achromatic lens, a wedge prism group, a diamond NV color center, a light guide, a high-pass filter and a detector; The output plane of the wedge prism group and the input plane of the diamond NV color center are parallel to each other; the light guide is arranged between the output plane of the diamond NV color center and the high-pass filter; the high-pass filter is fixed at the input end of the detector; The achromatic lens is used to correct, eliminate chromatic aberration and collimate the laser beam emitted by the photoelectric tube, and form a small light spot with a diameter of micrometers at the focal length according to the calculation formula of the light spot radius at the focus to obtain a collimated light beam; the wedge prism group is used to position the collimated light beam on the upper surface of the diamond NV color center by adjusting the direction of the collimated light beam.

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