A laser-ultrasound detection method and device based on elliptical longitudinal singular points

Abstract

An elliptical longitudinal phase singularity based laser ultrasonic detection method, comprising: generating an elliptical longitudinal phase singularity structure as a detection light field to be used; the elliptical longitudinal phase singularity interacts with the detected acoustic surface wave to load the acoustic wave signal on the detection light field; the elliptical longitudinal phase singularity light field after loading the detection signal is diffracted through a detection mask to form a diffracted light field; the diffracted light field is processed through an optical path, and the light field is analyzed; the intensity fluctuation of the light spot obtained after analysis is measured by using a photoelectric detector, and the measured signal is processed by a computer. The application improves the increase of signal sensitivity in the detection direction, refreshes the acoustic surface wave detection frequency limit, and further improves the imaging resolution of the laser ultrasonic microscopic imaging technology.

Description

A laser ultrasonic detection method and device based on the longitudinal singularity of an ellipse Technical Field

[0001] This invention relates to the field of laser ultrasonic microscopy, specifically to a laser ultrasonic detection method and apparatus based on an optical longitudinal phase singularity. Background Technology

[0002] Laser ultrasonic microscopy is similar to XRD (Extreme Ratio Density Detection) in that it offers a large field of view, low resolution, and high speed, making it valuable for material structure inspection, such as the inspection of turbine blades. Its main principle is to focus a pulsed laser beam onto the surface of an alloy. By locally heating the alloy with the laser, acoustic surface waves are generated at the heated point due to the alloy's thermal expansion and contraction, and these waves propagate along the alloy surface. Subsequently, another continuous laser beam is used to detect these acoustic surface waves. By analyzing the detected acoustic surface wave signals (frequency, velocity, etc.), information such as defects and cracks in the alloy can be detected.

[0003] Currently, the most commonly used technology in this industry is "knife-edge detection," which involves illuminating a material surface with a Gaussian beam, converting the acoustic surface wave signal into a displacement of the Gaussian beam. Then, a knife edge is used to partially block the Gaussian beam, causing a change in the energy of the beam crossing the blade when it undergoes a minute displacement. This allows for the detection of the Gaussian beam displacement and, consequently, the detection of the acoustic surface waves. To further improve detection accuracy, an even more advanced method is to use singularity diffraction. This replaces the interaction between the Gaussian beam and the sound wave with the interaction between the singularity and the sound wave, significantly improving detection precision.

[0004] However, smaller material structures generate higher-frequency acoustic signals, resulting in greater transmission losses on material surfaces and smaller deformations caused by these acoustic waves. This necessitates higher precision in laser detection of surface deformation. Therefore, improving the accuracy of acoustic surface wave detection has become a crucial issue for the industry. Currently, detection schemes with higher sensitivity have not yet been researched.

[0005] In conclusion, in order to enable laser ultrasonic microscopy to meet the application requirements of higher precision, the research on new laser ultrasonic detection schemes is particularly urgent. Summary of the Invention

[0006] The present invention aims to overcome the above-mentioned shortcomings of the prior art by providing a laser ultrasonic detection method and device based on the longitudinal phase singularity of an ellipse.

[0007] This invention utilizes the asymmetric phase gradient change of the elliptical phase singularity to improve the detection accuracy of acoustic signals in a specific direction, thereby increasing the resolution limit of laser ultrasonic microscopy.

[0008] A laser ultrasonic detection method based on an elliptical longitudinal phase singularity includes the following steps:

[0009] 1. Generate an elliptical longitudinal phase singularity structure as the probe light field to be used;

[0010] 2. The interaction between the longitudinal phase singularity of the ellipse and the detected acoustic surface wave loads the acoustic signal onto the detection optical field;

[0011] 3. The elliptical longitudinal phase singularity light field after the detection signal is loaded is diffracted through the detection mask to form a diffracted light field;

[0012] 4. The diffracted light field is processed through an optical path to analyze the light field;

[0013] 5. Use a photodetector to measure the intensity fluctuations of the light spot obtained after analysis, and then process the measured signal with a computer.

[0014] Furthermore, the generation of the elliptical longitudinal phase singularity structure in step 1 includes: generating laser light using a continuous wave laser; converting the generated laser light into circularly polarized laser light by modulating it with a 1 / 4 glass plate through a polarizer; modulating the circularly polarized laser light into a circularly polarized elliptical phase singularity through a mask; and obtaining a linearly polarized elliptical phase singularity light field as a probe light field by modulating the modulated circularly polarized laser light through a polarizer.

[0015] Furthermore, the complex transmittance function of the mask is t = exp(i * atan(x * 2 / y)), where i is the imaginary unit, atan is the arctangent function, and (x, y) is a rectangular coordinate system;

[0016] Furthermore, the interaction between the elliptical longitudinal phase singularity and the detected acoustic surface wave in step 2 includes: a microscope objective focuses the probe light field onto the surface of the object to be detected; the acoustic wave signal on the surface of the object to be detected causes a small deformation on the surface of the object to be detected; during the reflection process of the probe light field illuminating the object to be detected, the small deformation on the surface of the object to be detected is converted into a small displacement of the probe light field, thereby realizing the transfer of the acoustic wave signal to the probe light field signal, and obtaining the elliptical longitudinal phase singularity light field after loading the probe signal.

[0017] Furthermore, the complex transmittance function of the detection mask mentioned in step 3 is:

[0018] t1=im2bw(abs(x),a)*exp(i*b*r 2), where abs represents the absolute value function, im2bw represents the binary function with a threshold of a, that is, abs(x)>a is 0 and abs(x)<a is 1, exp is the exponential function with base e, i is the imaginary unit, b is the focus adjustment factor, and r is the radial coordinate variable in the polar coordinate system. The detected light field will diffract into a double-spot light field through the detection mask. The position of the spot along the propagation direction is adjusted by the parameter b, and the length of the spot is adjusted by the parameter a. In this process, the acoustic signal loaded in the detected light field is converted into the fluctuation of the spot energy.

[0019] Preferably, the parameter a is set to 0.1 mm, and the parameter b is set to 1.

[0020] Furthermore, the processing optical path of the diffracted light field in step 4 includes using a knife-edge to block the double spots to generate a single spot, thus excluding the interference of the energy fluctuation signal of the other spot. The single spot is regulated by a one-dimensional beam shrinking system composed of two cylindrical lenses to obtain a quasi-circular spot, and the quasi-circular spot is focused by a lens into a light point. The fluctuation of the light point energy records the acoustic signal.

[0021] Furthermore, the photodetector in step 5 receives the light point in step 4, records the fluctuation of the light point energy, and transmits the signal to a computer for processing to realize the detection of the acoustic signal.

[0022] The present invention also relates to a laser ultrasonic detection device based on an elliptical longitudinal phase singularity, which includes a continuous wave laser. The laser emits laser light that is converted into linearly polarized laser light by 1 polarizer. The linearly polarized laser light is converted into circularly polarized laser light by 1 quarter-wave plate. A liquid crystal plate is used to write a mask t to modulate the circularly polarized laser light to obtain the elliptical phase singularity light field; then 1 polarizer is used to modulate the polarization state of the elliptical phase singularity light field into linear polarization as the detected light field. The detected light field passes through a beam splitter cube and a microscope objective and irradiates the surface of the sample to load an acoustic signal. The laser light reflected by the sample passes through the same microscope objective and irradiates the beam splitter cube. The beam splitter cube separates the detected light from the reflected light loaded with the acoustic signal. The separated reflected light diffracts through an amplitude-phase modulation detection mask to form a double-spot light beam. The detection mask can be implemented by loading a transmittance function t1 onto a spatial light modulator. The double-spot light beam is further blocked by a knife-edge to form a single-spot light beam. The single-spot light beam uses a 4-f system composed of two cylindrical lenses to focus on the long side of the light beam, thereby generating a quasi-circular spot that is coupled to a photodetector for detection.

[0023] Furthermore, the wavelength of the continuous wave laser is 532 nm.

[0024] Furthermore, the magnification of the microscope objective is 10 times and the working distance is 30 mm.

[0025] The beneficial effects of the present invention are as follows: Compared with the prior art, the laser ultrasonic detection scheme based on the longitudinal singularity of an ellipse can improve the signal sensitivity in the detection direction, thereby breaking the frequency limit of acoustic surface wave detection, and thus improving the imaging resolution of laser ultrasonic microscopy, expanding the application fields and scope of laser ultrasonic microscopy. Attached Figure Description

[0026] Figure 1 is a flowchart of a laser ultrasonic detection method based on the longitudinal singularity of an ellipse according to the present invention.

[0027] Figure 2 shows the intensity and phase distribution of the light field at the elliptical phase singularity. From left to right, these are the intensity distribution of the light field at the longitudinal singularity of the ellipse and the phase distribution of the light field at the longitudinal singularity of the ellipse.

[0028] Figures 3a-3c show the probe optical path mask and the optical field distribution. Figure 3a is the phase distribution diagram of the probe mask, Figure 3b is the diffraction field intensity distribution diagram when the singularity has not shifted, and Figure 3c is the diffraction field intensity distribution diagram when the singularity has shifted.

[0029] Figure 4 is a schematic diagram of the structure of a laser ultrasonic detection device based on the longitudinal singularity of an ellipse according to the present invention.

[0030] Figure 5 is a comparison of the displacement sensing accuracy obtained by the present invention with that obtained using ordinary singularity detection. The dots represent the energy fluctuations of the photodetector when the light field of the present invention moves; the square dots represent the detection data obtained by the traditional method when the light field of the ordinary singularity moves. The higher slope of the curve demonstrates that the detection sensitivity of the present invention is higher. Detailed Implementation

[0031] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this invention should not be considered as limited to the specific forms stated in the embodiments. The scope of protection of this invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

[0032] The technical solution of this invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0033] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0035] Example 1

[0036] As shown in Figure 1, a laser ultrasonic detection method based on the longitudinal phase singularity of an ellipse includes the following steps:

[0037] 1. Generate an elliptical longitudinal phase singularity structure as the probe light field to be used;

[0038] 2. The interaction between the longitudinal phase singularity of the ellipse and the detected acoustic surface wave loads the acoustic signal onto the detection optical field;

[0039] 3. The elliptical longitudinal phase singularity light field after the detection signal is loaded is diffracted through the detection mask to form a diffracted light field;

[0040] 4. The diffracted light field is processed through an optical path to analyze the light field;

[0041] 5. Use a photodetector to measure the intensity fluctuations of the light spot obtained after analysis, and then process the measured signal with a computer.

[0042] The generation of the elliptical longitudinal phase singularity structure described in Step 1 includes: a continuous-wave laser generates laser light; the generated laser light is modulated and converted into circularly polarized laser light through a polarizer and a quarter-wave plate; the circularly polarized laser light is modulated into a circularly polarized elliptical phase singularity through a mask with a complex transmittance function of t = exp(i*atan(x*2 / y)), where i is the imaginary unit, atan is the arctangent function, and (x, y) is the rectangular coordinate system; the modulated circularly polarized laser light is modulated through a polarizer to obtain a linearly polarized elliptical phase singularity optical field as the detection optical field. As shown in the first and second figures on the left side of Figure 2, they are the intensity and phase distributions of the elliptical phase singularity generated in the specific implementation.

[0043] The interaction between the elliptical longitudinal phase singularity described in Step 2 and the sound wave to be detected includes: a microscope objective lens focuses the detection optical field on the surface of the object to be detected. The sound wave signal on the surface of the object to be detected causes a small deformation on the surface of the object to be detected. The small deformation on the surface of the object to be detected during the reflection process of the detection optical field irradiating the object to be detected is converted into a small displacement of the detection optical field, thereby achieving the transfer of the sound wave signal to the detection optical field signal, and obtaining the elliptical longitudinal phase singularity optical field loaded with the detection signal.

[0044] The complex transmittance function of the detection mask described in Step 3 is: t1 = im2bw(abs(x), a)*exp(i*b*r 2 ), where abs represents the absolute value function, im2bw represents the binary function with a threshold of a, that is, abs(x)>a is 0, abs(x)<a is 1, exp is the exponential function of e, i is the imaginary unit, b is the focus adjustment factor, and r is the radial coordinate variable in the polar coordinate system). The detection optical field will diffract a double-spot optical field through the detection mask. The position of the spot along the propagation direction is adjusted by the parameter b, and the length of the spot is adjusted by the parameter a. In the specific implementation, the value of the parameter a is 0.1 mm, and the value of the parameter b is 1. The obtained detection mask is shown in Figure 3a. In this process, the sound wave signal loaded by the detection optical field is converted into the fluctuation of the spot energy. As shown in Figures 3b and 3c, during the movement of the detection optical field, the energy contrast of the two spots is significantly different.

[0045] The processing optical path for the diffracted optical field described in Step 4 includes a knife-edge to block the double spots to generate a single spot, thereby excluding the interference of the energy fluctuation signal of the other spot. The single spot is regulated by a 1D beam shrinking system composed of two cylindrical lenses to obtain an approximately circular spot, and the approximately circular spot is focused into a light point by a lens. The fluctuation of the light point energy records the sound wave signal.

[0046] The photodetector described in Step 5 receives the light point in Step 4 and records the fluctuation of the light point energy, and transmits the signal to the computer for processing, thereby achieving the detection of the sound wave signal.

[0047] A laser ultrasonic detection method based on an optical longitudinal phase singularity was obtained using the parameters provided in Embodiment 1. The measurement results are shown in Figure 5. The dots represent the energy fluctuations of the photodetector when the detection light field of the present invention moves; the square dots represent the detection data obtained by the traditional method when the ordinary singularity light field moves. The higher slope of the curve proves that the detection sensitivity of the present invention is higher.

[0048] Example 2

[0049] This embodiment relates to a laser ultrasonic detection device based on an elliptical longitudinal phase singularity, used to implement the method of Embodiment 1. The optical path schematic diagram is shown in Figure 4.

[0050] The system includes a continuous-wave laser

[001] (wavelength 532nm). The laser emitted by the laser

[001] is converted into a linearly polarized laser by a polarizer

[002] . The linearly polarized laser is converted into a circularly polarized laser by a quarter-glass slide

[003] . A liquid crystal

[004] is used to write a mask t to modulate the circularly polarized laser to obtain the elliptical phase singularity light field. A polarizer

[005] is further used to modulate the polarization state of the elliptical phase singularity light field into linear polarization as the probe light field. The probe light field is irradiated onto the sample surface by a beam splitter cube

[006] and a microscope objective

[007] (magnification 10x, working distance 30mm) to load an acoustic signal. The signal is reflected by the sample. The laser beam is irradiated onto a beam splitter cube

[006] through the same microscope objective

[007] . The beam splitter cube

[006] separates the probe beam from the reflected light carrying the acoustic signal. The separated reflected light is diffracted into a dual-spot beam after passing through an amplitude-phase modulation probe mask

[009] . The probe mask

[009] can be implemented by loading a spatial light modulator with a transmittance function t1. The dual-spot beam is further blocked by a knife edge

[010] to form a single-spot beam. The single-spot beam is focused on the long side of the beam using a 4-f system composed of cylindrical lenses

[011] and

[012] , thereby generating a near-circular spot that is coupled to a photodetector

[013] for detection. The focal length of the cylindrical lens

[011] is 40 cm and the focal length of the cylindrical lens

[012] is 3.5 cm.

[0051] Figure 5 shows the measurement results of a laser ultrasonic detection method and device based on an optical longitudinal phase singularity, obtained using the parameters provided in Examples 1 and 2. The dots represent the energy fluctuations of the photodetector when the detection light field of this invention moves; the square dots represent the detection data obtained by the conventional method when the ordinary singularity light field moves. The higher slope of the curve demonstrates that the detection sensitivity of this invention is higher.

[0052] Example 3

[0053] This embodiment is a companion embodiment to Embodiment 2, and relates to a laser ultrasonic detection device based on an elliptical longitudinal phase singularity, used to implement the method of Embodiment 1. The optical path schematic diagram is shown in Figure 4.

[0054] The system includes a continuous-wave laser

[001] (wavelength 532nm). The laser emitted by the laser

[001] is converted into a linearly polarized laser by a polarizer

[002] . The linearly polarized laser is converted into a circularly polarized laser by a quarter-glass slide

[003] . A liquid crystal

[004] is used to write a mask t to modulate the circularly polarized laser to obtain the elliptical phase singularity light field. A polarizer

[005] is further used to modulate the polarization state of the elliptical phase singularity light field into linear polarization as the probe light field. The probe light field is irradiated onto the sample surface by a beam splitter cube

[006] and a microscope objective

[007] (magnification 10x, working distance 30mm) to load an acoustic signal. The signal is reflected by the sample. The laser beam is irradiated onto the beam splitting cube

[006] through the same microscope objective

[007] . The beam splitting cube

[006] separates the probe beam from the reflected light carrying the acoustic signal. The separated reflected light is diffracted into a dual-spot beam after passing through an amplitude-phase modulation probe mask

[009] . The probe mask

[009] can be implemented by loading a spatial light modulator with a transmittance function t1. The dual-spot beam is further blocked by a knife edge

[010] to form a single-spot beam. The single-spot beam is focused on the long side of the beam using a 4-f system composed of a cylindrical lens

[011] and a cylindrical lens

[012] , thereby generating a near-circular spot that is coupled to a photodetector

[013] for detection.

[0055] Unlike Embodiment 2, the focal length of the cylindrical lens

[011] is 80cm and the focal length of the cylindrical lens

[012] is 10cm, ensuring that the near-circular light spot can be completely coupled to the photodetector

[013] , thus achieving the measurement results shown in Figure 5. Any changes to the lens focal length based on this invention fall within the scope of protection of this invention.

[0056] The laser ultrasonic detection scheme based on the longitudinal singularity of an ellipse described above is merely one specific embodiment of the present invention and should not be construed as limiting the scope of protection of the present invention. It should be noted that those skilled in the art can make various modifications and improvements to the specific implementation details proposed in this patent without departing from the basic idea of ​​the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A laser ultrasonic detection method based on elliptical longitudinal phase singularities, comprising the following steps:

1. Generate an elliptical longitudinal phase singularity structure as the detection light field to be used; 2. The elliptical longitudinal phase singularity interacts with the detected acoustic surface wave to load the acoustic wave signal onto the detection light field; 3. The elliptical longitudinal phase singularity light field after loading the detection signal forms a diffraction light field through diffraction by a detection mask; the complex transmittance function of the detection mask is: t1 = im2bw(abs(x), a)*exp(i*b*r 2 ), where abs represents the absolute value function, im2bw represents the binary function with a threshold of a, that is, abs(x)>a is 0, abs(x)<a is 1, exp is the exponential function of e, i is the imaginary unit, b is the focus adjustment factor, and r is the radial coordinate variable in the polar coordinate system; the elliptical longitudinal phase singularity light field after loading the detection signal will diffract a double-spot light field through the detection mask, and the position of the spot along the propagation direction is adjusted by the parameter b, and the length of the spot is adjusted by the parameter a; in this process, the acoustic wave signal loaded on the detection light field is converted into the fluctuation of the spot energy; 4. Process the diffraction light field through the optical path and analyze the light field; the processing optical path of the diffraction light field includes a knife-edge to block the double spot to generate a single spot, thus excluding the interference of the energy fluctuation signal of the other spot, and the single spot is regulated by a one-dimensional beam shrinking system composed of two cylindrical lenses to obtain a quasi-circular spot, and the quasi-circular spot is focused by a lens into a light point; the fluctuation of the light point energy records the acoustic wave signal; 5. Use a photodetector to measure the intensity fluctuation of the spot obtained after analysis, and hand the measured signal to a computer for processing.

2. The laser ultrasonic detection method based on an elliptical longitudinal phase singularity as described in claim 1, characterized in that, Step 1, which involves generating an elliptical longitudinal phase singularity structure, includes: generating laser light using a continuous wave laser; converting the generated laser light into circularly polarized laser light by modulating it with a 1 / 4 glass plate using a polarizer; modulating the circularly polarized laser light into a circularly polarized elliptical longitudinal phase singularity using a mask; and using the modulated circularly polarized elliptical longitudinal phase singularity light field obtained by modulating it with a polarizer as a probe light field.

3. The laser ultrasonic detection method based on an elliptical longitudinal phase singularity as described in claim 2, characterized in that, The complex transmittance function of the mask is t=exp(i*atan(x*2 / y)), where i is the imaginary unit, atan is the arctangent function, and (x, y) is a rectangular coordinate system.

4. The laser ultrasonic detection method based on an elliptical longitudinal phase singularity as described in claim 1, characterized in that, The interaction between the elliptical longitudinal phase singularity and the detected acoustic surface wave in step 2 includes: a microscope objective focuses the probe light field onto the surface of the object to be detected; the acoustic wave signal on the surface of the object to be detected causes a small deformation on the surface of the object to be detected; during the reflection process of the probe light field illuminating the object to be detected, the small deformation on the surface of the object to be detected is converted into a small displacement of the probe light field, thereby realizing the transfer of the acoustic wave signal to the probe light field signal, and obtaining the elliptical longitudinal phase singularity light field after loading the probe signal.

5. The laser ultrasonic detection method based on an elliptical longitudinal phase singularity as described in claim 1, characterized in that, Parameter a is set to 0.1 mm, and parameter b is set to 1.

6. The laser ultrasonic detection method based on an elliptical longitudinal phase singularity as described in claim 1, characterized in that, The photodetector described in step 5 receives the energy fluctuations of the light spot recorded in step 4 and transmits the signal to the computer for processing, thereby realizing the detection of the sound wave signal.

7. A laser ultrasonic detection device based on an elliptical longitudinal phase singularity, characterized in that: It includes a continuous-wave laser. The laser beam emitted by the laser is converted into linearly polarized laser through a polarizer. The linearly polarized laser is converted into circularly polarized laser through a quarter-wave plate. A liquid crystal plate is used to write the mask template t to modulate the circularly polarized laser to obtain the elliptical longitudinal phase singularity optical field. Then, a polarizer is used to modulate the polarization state of the elliptical longitudinal phase singularity optical field into linear polarization as the detection optical field. The detection optical field is irradiated onto the sample surface to load an acoustic signal through a beam-splitting cube and a microscope objective. The laser reflected by the sample is irradiated onto the beam-splitting cube through the same microscope objective. The beam-splitting cube separates the detection optical field from the reflected light of the loaded acoustic signal. The reflected light of the loaded acoustic signal after separation is diffracted through an amplitude-phase modulation detection mask template to form a double-spot beam. The detection mask template is implemented by loading a complex transmittance function t1 onto a spatial light modulator. The double-spot beam is further blocked by a knife edge to form a single-spot beam. The single-spot beam is focused on the long side of the beam by a 4-f system composed of two cylindrical lenses, so as to generate a quasi-circular spot and couple it to a photodetector for detection. The complex transmittance function of the detection mask template is: t1 = im2bw(abs(x), a)*exp(i*b*r 2 ), where abs represents the absolute value function, im2bw represents the binary function with a threshold of a, that is, abs(x)>a is 0, abs(x)<a is 1, exp is the exponential function of e, i is the imaginary unit, b is the focus adjustment factor, and r is the radial coordinate variable in the polar coordinate system. The reflected light of the loaded acoustic signal will diffract a double-spot optical field through the detection mask template. The position of the spot along the propagation direction is adjusted by the parameter b, and the length of the spot is adjusted by the parameter a. In this process, the acoustic signal loaded by the detection optical field is converted into the fluctuation of the spot energy.

8. The laser ultrasonic detection device based on an elliptical longitudinal phase singularity as described in claim 7, characterized in that: The wavelength of the continuous wave laser is 532nm, the magnification of the microscope objective is 10x, and the working distance is 30mm.

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