Diamond NV color center magnetometer imaging method and system

Abstract

The invention belongs to the field of magnetic field imaging measurement, and provides a diamond NV color center magnetometer imaging method and system, and the method comprises the steps: correction and chromatic aberration elimination, focus positioning, high-pass optical filter filtering, and image shooting. Through the structure of the achromatic lens, the wedge-shaped prism and the diamond NV color center, laser spots are reduced, and the spatial resolution capability of the magnetometer is improved.

Description

Technical Field

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

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

[0003] However, these techniques usually use special optical components or design complex optical paths, or rely on post-processing to extract super-resolution images, which increases 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 measurements of diamond NV color center magnetometers 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 object of the present invention is to provide a diamond NV color center magnetometer imaging method and system to reduce the laser spot to enhance the spatial resolution capability of the magnetometer.

[0005] To achieve the above object, the present invention provides the following solutions: A diamond NV color center magnetometer imaging method, comprising: The laser beam emitted by the light source is corrected and the chromatic aberration is eliminated by using an achromatic lens; Using a wedge prism to position the focus of the laser beam output by the achromatic lens on the surface of the diamond NV color center; 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.

[0006] Preferably, the calculation formula for the spot radius at the focus is: ;in, is the spot radius at the focus; is the beam waist radius of the incident laser of the achromatic lens; is the focal length of the achromatic lens; is the Rayleigh length of the incident laser; is the distance from the incident laser beam waist position to the achromatic lens.

[0007] Preferably, 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; and the wavelength distribution range of the fluorescence signal excited by the diamond NV color center is 637 nm to 800 nm.

[0008] Preferably, the beam waist radius is 2 mm; the focal length is 50 mm; and the spot diameter at the focus is 8.47 um.

[0009] Preferably, a diamond NV color center magnetometer imaging system comprises: a phototube, an achromatic lens, a wedge prism, a diamond NV color center, a light guide, a high pass filter and a detector; The centers of the phototube, the achromatic lens and the wedge prism are distributed on the same straight line; the output plane of the wedge prism 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; and the high-pass filter is fixed at the input end of the detector.

[0010] The present invention discloses the following technical effects: The present invention provides a diamond NV color center magnetometer imaging method and system, which solves the defects of the existing magnetometer imaging method being complicated and costly through the structure of an achromatic lens, a wedge prism and a diamond NV color center, and realizes the reduction of the laser spot. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0012] Figure 1 A schematic diagram of the imaging process of a diamond NV color center magnetometer provided in an embodiment of the present invention; Figure 2 A schematic diagram of a diamond NV color center magnetometer imaging system provided by an embodiment of the present invention; Figure 3 Schematic diagram of the surface light spot of the diamond NV color center provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] The purpose of the present invention is to provide a diamond NV color center magnetometer imaging method and system to reduce the laser spot to improve the spatial resolution capability of the magnetometer.

[0015] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] Figure 1 A schematic diagram of the imaging process of a diamond NV color center magnetometer provided in an embodiment of the present invention is shown in FIG. Figure 1 As shown, the present invention provides a diamond NV color center magnetometer imaging method, comprising: Step 100: using an achromatic lens to correct and eliminate chromatic aberration of the laser beam emitted by the light source; Step 200: using a wedge prism to locate the focus of the laser beam output by the achromatic lens on the surface of the diamond NV color center; Step 300: transmitting the laser beam output by the diamond NV color center to a high-pass filter for filtering through a light guide; Step 400: Transmit the fluorescence signal output by the high-pass filter to the detector for image capture to obtain a light spot image.

[0017] Specifically, the calculation formula for the spot radius at the focus is: ;in, is the spot radius at the focus; is the beam waist radius of the incident laser of the achromatic lens; is the focal length of the achromatic lens; f is the Rayleigh length of the incident laser; is the distance from the incident laser beam waist to the achromatic lens.

[0018] Optionally, 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; and the wavelength distribution range of the fluorescence signal excited by the diamond NV color center is 637 nm to 800 nm.

[0019] Preferably, the beam waist radius is 2 mm; the focal length is 50 mm; and the spot diameter at the focus is 8.47 um.

[0020] refer to Figure 2, a diamond NV color center magnetometer imaging system, comprising: a phototube, an achromatic lens, a wedge prism, a diamond NV color center, a light guide, a high pass filter and a detector; The centers of the phototube, the achromatic lens and the wedge prism are distributed on the same straight line; the output plane of the wedge prism and the input plane of the diamond NV color center are parallel to each other; a light guide is arranged between the output plane of the diamond NV color center and the high-pass filter; and the high-pass filter is fixed at the input end of the detector.

[0021] Specifically, the optical path method for reducing the laser spot on the surface of a diamond NV color center magnetometer comprises the following steps: S1: The laser beam emitted by the light source is corrected through an achromatic lens to eliminate chromatic aberration, and at the same time a small light spot with a diameter of micrometers is formed at the focal length, and the beam is collimated; S2: The direction of the collimated beam is precisely adjusted through a set of wedge-shaped prisms to accurately position the laser beam focus on the upper surface of the diamond NV color center; S3: The fluorescence signal emitted by the diamond NV color center is transmitted to the detector through a light guide connected to the prism, and a high-pass filter is added to the detector to allow only the fluorescence signal to pass.

[0022] In step S1, the formula for the spot radius of the laser beam at the focal length after passing through the achromatic lens is: That is, the minimum spot radius before the lens, That is the newly obtained minimum spot radius.

[0023] Furthermore, the Rayleigh length of the incident laser , is the wavelength of the incident laser. Since the incident light is collimated into parallel light, the distance from the incident laser waist position to the lens can be ignored, so , so the spot diameter at the focal point after the laser passes through the lens is 8.47um.

[0024] Specifically, the spatial resolution of the diamond NV color center magnetometer is determined by the number of diamond NV color centers excited within the laser spot range, so the smaller the spot, the higher the spatial resolution. The spot position is precisely adjusted through a set of wedge prisms to position the spot with the minimum spot radius on the upper surface of the diamond NV color center to achieve higher spatial resolution.

[0025] Furthermore, in magnetic field imaging, when the spot size is large, the signals of each NV color center in the spot cannot be distinguished, and the average value of these signals is finally measured, resulting in a field averaging effect. Reducing the spot size can reduce the field averaging effect, thereby improving the spatial resolution of magnetic field imaging.

[0026] Preferably, the fluorescence signal is transmitted from the diamond NV color center to the detector through a light guide, and there is no need to transmit the laser beam and the fluorescence signal at the same time, thus avoiding the enlargement of the laser spot due to the diffraction effect.

[0027] Specifically, a high-pass filter is used to filter the fluorescence signal emitted by the diamond NV color center, allowing only light with a wavelength higher than a set threshold to pass through, blocking interference from the excitation light and low-wavelength stray light, and improving the signal-to-noise ratio of the fluorescence signal.

[0028] Furthermore, the specific implementation process of the method designed in this embodiment is as follows: first, a parallel laser with a wavelength of 532nm is used for incident light, and the light beam is corrected by an achromatic lens with a focal length of 50mm to eliminate the focus offset of light with different wavelengths. 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 of micrometers at the focal length. In order 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 focus is accurately calculated based on the following formula: In order 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 traditional optical transmission, resulting in an expansion of the spot size, additional optical adjustment technology is introduced. By using a set of wedge-shaped 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 angle of the wedge-shaped prism, micron-level control of the spot position is achieved, thereby effectively reducing the field averaging effect and greatly improving the spatial resolution of magnetic field imaging.

[0029] The NV color center in diamond will generate fluorescence signals under the irradiation of laser. These fluorescence signals are guided into the light guide after passing through a wedge-shaped prism. In order to avoid interference from excitation light and stray light, a high-pass filter is added between the light guide and the detector, allowing only fluorescence signals above the set threshold to pass through. The design of the high-pass filter matches the wavelength of the system's excitation light (532nm) and the wavelength range (637nm to 800nm) where the fluorescence signal is mainly distributed, ensuring selective filtering of the signal. The use of high-pass filters not only significantly improves the signal-to-noise ratio, but also enhances the system's ability to detect weak fluorescence signals. See the results. Figure 3 .

[0030] The beneficial effects of the present invention are as follows: The present invention introduces an optical path design based on a wedge prism and an achromatic lens, which can optimize the propagation path and focus positioning of the laser beam, not only greatly reducing the laser spot size, but also effectively simplifying the system structure, reducing complexity and cost. This design provides a practical technical solution for the performance improvement and wide application of diamond NV color center magnetometers.

[0031] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0032] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting 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; Using a wedge prism to position the focus of the laser beam output by the achromatic lens on the surface of the diamond NV color center; 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 calculation formula of the spot radius at the focus is: ;in, is the spot radius at the focus; is the beam waist radius of the incident laser of the achromatic lens; is the focal length of the achromatic lens; is the Rayleigh length of the incident laser; is the distance from the incident laser beam waist position to the achromatic lens.

3. 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.

4. A diamond NV color center magnetometer imaging method according to claim 2, 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.

5. A diamond NV color center magnetometer imaging system, characterized in that: include: Phototube, achromatic lens, wedge prism, diamond NV color center, light guide, high pass filter and detector; The centers of the phototube, the achromatic lens and the wedge prism are distributed on the same straight line; the output plane of the wedge prism 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; and the high-pass filter is fixed at the input end of the detector.

Images