Method and device for generating hollow light beam and optical tweezers system

Abstract

The invention discloses a method and device for generating a hollow light beam and an optical tweezers system, and belongs to the technical field of optical micro-control. The method comprises the following steps: generating a Gaussian beam, and carrying out beam expansion and collimation processing on the Gaussian beam; designing a phase distribution function of a diffractive optical element DOE, and inputting basic parameters into the phase distribution function phi (r) of the DOE; obtaining a phase distribution diagram of the DOE through a computer design algorithm; and a phase distribution diagram of the DOE is loaded in the spatial light modulator, the light wave after beam expansion and collimation enters the spatial light modulator, and the spatial light modulator modulates the incident light beam to form a hollow light beam with the required inner and outer ring radius. A common Gaussian beam can be shaped into a hollow beam with the dynamically adjustable size, actual machining is not needed, and adjustment is easy.

Description

Technical Field

[0001] The present application relates to the technical field of optical micro-manipulation, and in particular, to a method, an apparatus, and an optical tweezer system for generating a hollow beam. Background Art

[0002] Optical tweezer technology is one of the most widely used technologies in the field of optical micro-manipulation. The light source of a traditional optical tweezer is a solid fundamental mode Gaussian beam. The axial binding force in the beam transmission direction is generally less than the transverse binding force perpendicular to the beam transmission direction. When a microparticle or a cell is captured, an unstable phenomenon is likely to occur. At this time, the microparticle or the cell will be pushed away from the center of the optical trap by a large axial scattering force. Therefore, the research on Gaussian beam shaping technology has become a hot issue in the field of optical micro-manipulation for many years.

[0003] The central intensity of a hollow beam is zero, which can greatly weaken the axial scattering force of the optical trap without affecting the axial gradient force used to capture microparticles or cells. Furthermore, it can reduce the capture optical power and improve the overall capture efficiency of microparticles or cells. At the same time, using a hollow beam as the light source of an optical tweezer can reduce the thermal damage of cells caused by light absorption, making it more suitable for the research on living biological cells.

[0004] Currently, methods for generating hollow beams include Gaussian beam mode conversion method, cone lens method, spiral phase plate method, annular aperture method, optical fiber method, etc. However, the hollow beams generated by these methods have fixed sizes, are difficult to regulate, and have low diffraction efficiency, making it impossible to flexibly capture and manipulate microparticles or cells with different sizes and weights, thus limiting their practical applications. Summary of the Invention

[0005] To facilitate real-time adjustment of the size of a hollow beam, the present application provides a method, an apparatus, and an optical tweezer system for generating a hollow beam.

[0006] A method for generating a hollow beam provided by the present application adopts the following technical solution: First Aspect A method for generating a hollow beam, comprising the following steps: S1: Generate a Gaussian beam and perform beam expansion and collimation processing on the Gaussian beam; S2: Design the phase distribution function of a diffractive optical element DOE. The phase distribution function of the DOE is calculated according to the following formula: where r is the radius of the DOE, f is the focal length of the DOE, ρ1 is the inner ring radius of the hollow beam formed by diffraction of the Gaussian beam, ρ2 is the outer ring radius of the hollow beam formed by diffraction of the Gaussian beam, λ is the wavelength of the incident light, and the wave number Set the constant a to 2.5; Input the phase information of the initial Gaussian beam and the phase information of the required hollow beam into the phase distribution function of the DOE; Simulate the phase distribution diagram of the DOE through a computer-aided design algorithm; Load the phase distribution diagram of the DOE into the spatial light modulator. The light wave after beam expansion and collimation is incident on the spatial light modulator, and the spatial light modulator modulates the incident beam to form a hollow beam with the required inner and outer ring radii. S3: Load the phase distribution diagram of the DOE into the spatial light modulator. The light wave after beam expansion and collimation is incident on the spatial light modulator, and the spatial light modulator modulates the incident beam to form a hollow beam with the required inner and outer ring radii.

[0007] By adopting the above technical solution, a phase distribution function of a new type of DOE is designed The phase modulation principle is simple, which can shape a common Gaussian beam into a hollow beam with dynamically adjustable size in real time, without actual processing and easy to adjust.

[0008] Optionally, the step S2 includes: S21: Create a phase array function, which outputs array phase values according to the phase distribution function of the hollow beam, and determines the wavelength λ of the Gaussian beam; S22: Define the basic parameters of the diffractive optical element DOE, including the focal length f, and select the parameters ρ1 and ρ2 in the DOE phase distribution function according to the size of the required hollow beam in; S23: Input the defined basic parameters of the DOE into the phase distribution function of the DOE ; S24: Determine the image resolution according to the liquid crystal target surface resolution and pixel size of the actually used spatial light modulator; S25: Convert the phase distribution of the DOE into a grayscale image output through a normalization algorithm.

[0009] By adopting the above technical solution, the parameters required by the phase distribution function are easy to obtain, the function calculation is simple, and by adjusting the parameters, a hollow beam with the required size can be effectively and quickly obtained.

[0010] In a second aspect, a device for generating a hollow beam includes: A Gaussian beam generator for generating a Gaussian beam with a required wavelength; A beam expansion and collimation unit for expanding and collimating the Gaussian beam generated by the Gaussian beam generator; A beam splitting unit for changing the propagation direction of the Gaussian beam and splitting the Gaussian beam into a reflected light and a transmitted light; A spatial light modulator loaded with the phase distribution function of the DOE for phase-modulating the incident Gaussian beam and diffracting to generate the required hollow beam; An optical intensity adjustment unit for adjusting the transmittance and reflectance of the optical intensity passing through the beam splitting unit.

[0011] By adopting the above technical solution, the device has a simple structure and can cooperate with the phase distribution function of the DOE to adjust the hollow beam in real time and is also convenient for personnel operation.

[0012] Optionally, the device for generating a hollow beam further includes: A measurement unit for observing the modulated hollow beam and recording its light intensity distribution.

[0013] By adopting the above technical solution, it is used to detect whether the light intensity of the required hollow beam meets the requirements, so that the corresponding parameters can be quickly adjusted according to the actual situation.

[0014] Optionally, the Gaussian beam generator outputs a wavelength of one of 780 - 1100 nm.

[0015] By adopting the above technical solution, after the Gaussian beam with a wavelength in this range is used in combination with the phase distribution function of the DOE a hollow beam that meets the light intensity requirements will be output.

[0016] Optionally, the beam expanding and collimating unit includes a beam expanding objective lens, a filtering pinhole, and a collimating lens arranged in sequence along the optical path transmission direction. The beam expanding objective lens is used to reduce the beam diameter of the Gaussian beam, the filtering pinhole is used to limit and filter the incident Gaussian beam to achieve the selection and suppression of specific signals, and the collimating lens is used to collimate the Gaussian beam.

[0017] Optionally, the beam splitting unit includes a polarization beam splitting prism, which is used to reflect the expanded and collimated Gaussian beam to the spatial light modulator and transmit the hollow beam generated by the spatial light modulator.

[0018] Optionally, the spatial light modulator includes a phase-type reflective spatial light modulator LCOS. After loading the phase distribution diagram of the DOE, the phase-type reflective spatial light modulator LCOS is used to perform phase modulation on the incident light and diffract to generate the required hollow beam.

[0019] Optionally, the optical intensity adjustment unit includes a half-wave plate and a quarter-wave plate. The half-wave plate is arranged between the Gaussian beam generator and the beam expanding and collimating unit, and is used to adjust the polarization direction of the Gaussian beam generated by the Gaussian beam generator so that the expanded and collimated Gaussian beam is reflected by the beam splitting unit. The quarter-wave plate is arranged between the beam splitting unit and the spatial light modulator, and is used to adjust the polarization direction of the hollow beam generated by the spatial light modulator so that the hollow beam is transmitted by the beam splitting unit.

[0020] Second aspect An optical tweezer system includes the device for generating a hollow beam as described above, and further includes a beam shrinking unit, a reflection unit, and a microscopic imaging unit sequentially arranged along the propagation direction of the hollow beam emitted by the beam splitting unit; The beam shrinking unit includes a first beam shrinking lens and a second beam shrinking lens arranged in sequence, and the first beam shrinking lens and the second beam shrinking lens are used for focusing the hollow beam; The reflection unit includes a reflecting mirror and a dichroic mirror arranged in sequence. The reflecting mirror is used for changing the transmission direction of the hollow beam, and the dichroic mirror is used for reflecting the hollow beam to the microscopic imaging unit; The microscopic imaging unit includes a microscopic objective lens, a sample stage, an illumination light source, a filter, and a camera. The hollow beam forms a hollow optical trap after being focused by the microscopic objective lens. The hollow optical trap is used for capturing and manipulating biological samples placed on the sample stage. The illumination light source emits illumination light to be transmitted to the sample stage. The filter filters out the Gaussian beam reflected by the biological sample and other stray light. Finally, the biological sample information and the capture and manipulation conditions of the cells are displayed on the camera in real time.

[0021] In summary, the present application includes at least one of the following beneficial technical effects: 1. The light modulation principle of the diffraction optical element DOE of the present invention is simple, and there is no need to actually process a physical DOE, which is easy to adjust.

[0022] 2. The present invention can shape an ordinary Gaussian beam into a hollow beam with dynamically adjustable size, and the device has a simple structure and convenient operation.

[0023] 3. The device for generating a hollow beam forms an optical tweezer system by combining with the traditional optical tweezer optical path, which can reduce the thermal damage of the optical tweezer to living biological cells and improve the flexibility and applicability of the optical tweezer in its application fields. Description of the Drawings

[0024] Figure 1 It is a method step diagram for generating a hollow beam in the present application.

[0025] Figure 2 It is an algorithm flowchart for how to obtain the DOE phase distribution diagram in the present application.

[0026] Figure 3 It is the DOE phase distribution diagram loaded in the spatial light modulator LCOS in the present application.

[0027] Figure 4 It is a structural schematic diagram of the device for generating a hollow beam in the present application.

[0028] Figure 5 It is a gray-scale diagram of the light intensity distribution of the generated hollow beam measured in the present application.

[0029] Figure 6 is a schematic structural diagram of the optical tweezer system of the present application.

[0030] Explanation of reference numerals: 1. Gaussian beam generator; 2. Light intensity adjustment unit; 21. Half-wave plate; 22. Quarter-wave plate; 3. Beam expansion and collimation unit; 31. Beam expansion objective lens; 32. Filtering pinhole; 33. Collimating lens; 4. Beam splitting unit; 5. Spatial light modulator; 6. Measuring unit; 7. Beam reduction unit; 71. First beam reduction lens; 72. Second beam reduction lens; 8. Reflection unit; 81. Mirror; 82. Dichroic mirror; 9. Microscopic imaging unit; 91. Microscopic objective lens; 92. Specimen stage; 93. Illumination light source; 94. Filter; 95. Camera. Detailed implementation manners

[0031] The following further elaborates on the present application Figures 1-6 in conjunction with the attached drawings.

[0032] In related technologies, methods for obtaining a hollow beam include mode conversion method, geometric optics method, optical holography method, computer holography method, transverse mode selection method, phase plate method, spatial light modulator method, and hollow wave method, etc. Among them, the spatial light modulator method is to simultaneously load the phase information of two beams onto a spatial light modulator and then output to obtain a hollow beam. The core component of the spatial light modulator is a display similar to a holographic phase plate, and its working principle is similar to that of the holography method. First, the phase information of the initial beam and the target beam is input into a computer, and the computer simulates the holographic phase diagram of the two beams. Then, the information of the hologram is loaded onto the display by using Fourier transform. When the initial beam is incident on the spatial light modulator that has been loaded with phase information, the output beam is the required beam.

[0033] The embodiments of the present application disclose a method for generating a hollow beam. Referring to Figure 1 , it includes the following steps: S1: Generate a Gaussian beam and perform beam expansion and collimation processing on the Gaussian beam.

[0034] The phase and amplitude of the Gaussian beam after beam expansion and collimation change less in the transverse direction, which can greatly simplify the complexity of the problem and facilitate theoretical analysis and calculation.

[0035] S2: Design the phase distribution function of the diffractive optical element DOE, and the phase distribution function of the DOE is calculated according to the following formula: Among them, r is the radius of the DOE, f is the focal length of the DOE, ρ1 is the inner ring radius of the hollow beam formed by the diffraction of the Gaussian beam, ρ2 is the outer ring radius of the hollow beam formed by the diffraction of the Gaussian beam, λ is the wavelength of the incident light, and the wave number The constant a is set to 2.5.

[0036] Input the phase information of the initial Gaussian beam and the phase information of the required hollow beam into the phase distribution function of the DOE.

[0037] The phase distribution diagram of the DOE is obtained by simulating through a computer design algorithm.

[0038] Refer to Figure 2 , step S2 specifically includes: S21: Create a phase array function that outputs array phase values according to the phase distribution function of the hollow beam; draw a discrete grid in the function and assign a value to each point on the grid, and this value is calculated through the phase distribution function, so an array phase distribution array can be obtained. Determine the wavelength λ of the initial Gaussian beam.

[0039] S22: Define the basic parameters of the diffraction optical element DOE, including the focal length f, and select the parameters ρ1, ρ2 in the phase distribution function of the DOE according to the size of the required hollow beam.

[0040] S23: Input the defined basic parameters of the DOE into the phase distribution function of the DOE.

[0041] S24: Determine the image resolution according to the liquid crystal target surface resolution and pixel size of the actually used spatial light modulator LCOS.

[0042] S25: Convert the phase distribution of the DOE into a grayscale image output through a normalization algorithm.

[0043] Taking the wavelength λ of the Gaussian beam commonly used in the optical tweezer as 1064 nm, the focal length f of the DOE as 100 mm, the inner and outer ring radii ρ1, ρ2 of the required hollow beam as 0.1 mm and 0.2 mm respectively, and the resolution of the output grayscale image as 1920×1080 and the pixel size as 6.4 μm as an example, as Figure 3 shown is the phase distribution diagram of the DOE at this time. The phase distribution diagram of the DOE is generated by Python calculation, and the reference program is as follows: def platbeam(w,a,px,py,d): k = 2 * math.pi / w f = 100 r1 = 0.1 r2 = 0.2 c = np.sqrt(r2 * r2 - r1 * r1) / (a * r1) xx, yy = meshgrid(px, py, d) r = np.sqrt(xx ** 2 + yy ** 2) m = c * r * np.sqrt((c ** 2 * r ** 2) + 1) n = np.log(c * r + np.sqrt((c ** 2 * r ** 2) + 1)) pha = (k * r1) / (2 * f * c) * (m + n) - (k * r ** 2) / (2 * f) phase = pha % (2 * math.pi) return phase def meshgrid(xx, yy, d): lx = xx * d ly = yy * d fx = np.arange(-lx / 2, lx / 2, d) fy = np.arange(-ly / 2, ly / 2, d) fx, fy = np.meshgrid(fx, fy) return fx, fy if __name__ == '__main__': x_pixels = 1920 y_pixels = 1080 wavelength = 1064 * 1e - 6 dpx = 6.4 * 1e - 3 a = 2.5 res = platbeam(wavelength, a, x_pixels, y_pixels, dpx) temp = res.max() - res.min() result = (res - res.min()) / temp cv2.namedWindow('showresult', 0) cv2.imshow('showresult', result) cv2.namedWindow('showresult', cv2.WINDOW_NORMAL) cv2.imwrite('r1=1.0,r2=2.0,f=100.jpg',255*result) S3: Load the phase distribution diagram of the DOE in the spatial light modulator. The light wave after beam expansion and collimation is incident on the spatial light modulator, and the spatial light modulator modulates the incident light beam to form a hollow light beam with the required inner and outer ring radii.

[0044] Optionally, the spatial light modulator can be a phase-type reflective liquid crystal on silicon (LCOS) spatial light modulator. The phase-type reflective liquid crystal on silicon (LCOS) spatial light modulator adopts a phase modulation method, and realizes the modulation and control of light waves by regulating the phase of light. It is more suitable for application fields that require fine phase control. At the same time, adopting a reflective design, the light utilization efficiency is relatively high, which can reduce the loss of light and improve the brightness and contrast.

[0045] The implementation principle of the method for generating a hollow light beam in an embodiment of the present application is: this DOE phase distribution function The principle is simple. It is not necessary to actually process the DOE to generate a hollow light beam with dynamically adjustable size, and the size of the hollow light beam is easy to adjust, with high flexibility, so that the hollow light beam can meet specific optical requirements in different application scenarios.

[0046] An embodiment of the present application also discloses a device for generating a hollow light beam. This device is based on the method for generating a hollow light beam. Refer to Figure 4 and this device includes: A Gaussian beam generator 1 for generating a Gaussian beam with the required wavelength.

[0047] A beam expansion and collimation unit 3 for expanding and collimating the Gaussian beam generated by the Gaussian beam generator 1.

[0048] A beam splitting unit 4 for changing the propagation direction of the Gaussian beam and splitting the Gaussian beam into a reflected light and a transmitted light.

[0049] A spatial light modulator 5 loaded with the phase distribution function of the DOE for performing phase modulation on the incident Gaussian beam and diffracting to generate the required hollow light beam.

[0050] An optical intensity adjustment unit 2 for adjusting the transmission ratio and reflection ratio of the optical intensity passing through the beam splitting unit 4.

[0051] A measurement unit 6 for observing the modulated hollow light beam and recording its light intensity distribution.

[0052] Among them, the Gaussian beam generator 1 can be a laser, which generates a Gaussian beam; the Gaussian beam generator 1 can also further include a combination of elements such as lenses and diaphragms. In addition, many different physical systems can generate optical modes similar to Gaussian beams. Here, no specific selection of the Gaussian beam generator 1 is limited, as long as it can produce a Gaussian beam.

[0053] Optionally, the Gaussian beam generator 1 outputs a wavelength of one of 780 - 1100 nm. After the Gaussian beam with a wavelength in this range is used in conjunction with the phase distribution function φ(r) of the DOE, a hollow beam that meets the light intensity requirements is output. Specifically, the output wavelength of the Gaussian beam generator 1 is 1064 nm, and this wavelength is suitable for the optical tweezer system.

[0054] Refer to Figure 4 , the beam expanding and collimating unit 3 is arranged at the light output end of the Gaussian beam generator 1. The beam expanding and collimating unit 3 includes a beam expanding objective lens 31, a filtering pinhole 32, and a collimating lens 33 arranged in sequence along the optical path transmission direction. The beam expanding objective lens 31 is used to reduce the beam diameter of the Gaussian beam. In this embodiment, the beam expanding objective lens 31 can be a negative lens type beam expanding objective lens 31. The negative lens type beam expanding objective lens 31 can effectively reduce the diameter of the laser beam and increase its divergence angle to precisely control the divergence angle to obtain a specific processing effect or imaging resolution.

[0055] The filtering pinhole 32 is used to limit and filter the incident Gaussian beam to achieve the selection and suppression of specific signals. The filtering pinhole 32 can be an optical filtering pinhole, a mechanical filtering pinhole, an adjustable filtering pinhole, etc.

[0056] The optical filtering pinhole usually consists of a small hole and a filter 94 with specific filtering characteristics. This type of filtering pinhole 32 selectively transmits or blocks light of specific wavelengths through the filter 94 to achieve the filtering effect on the beam. The mechanical filtering pinhole usually consists of aperture pinholes with different diameters, and each pinhole corresponds to the transmission of light of a specific wavelength. By selecting different aperture pinholes, the filtering effect on light of different wavelengths can be achieved. The adjustable filtering pinhole has certain adjustability and can change its filtering characteristics as needed, such as changing the transmittance or selecting different filtering wavelength ranges. This type of filtering pinhole 32 is usually applied to occasions where dynamic adjustment of filtering characteristics is required.

[0057] The collimating lens 33 is used to collimate the Gaussian beam and convert the Gaussian beam entering the collimating lens 33 into a parallel beam. The collimating lens 33 can be a cylindrical lens or a cylindrical lens group, etc.

[0058] Refer to Figure 4, The beam splitting unit 4 is arranged at the light output end of the beam expanding and collimating unit 3. The beam splitting unit 4 includes a polarization beam splitting prism. In this embodiment, the extinction ratio of the polarization beam splitting prism is >3000:1. The extinction ratio is defined as the ratio of the transmitted or reflected light intensity in a specific polarization direction to the transmitted or reflected light intensity in the perpendicular direction. Ideally, the larger the extinction ratio, the closer the light intensity in the non-polarization direction is to zero, so polarized light can be separated more effectively. Therefore, in other embodiments, a polarization beam splitting prism with a larger extinction ratio can also be used.

[0059] The spatial light modulator 5 is arranged on the reflected light output optical path of the polarization beam splitting prism. The spatial light modulator 5 includes a phase-type reflective spatial light modulator LCOS, and the phase-type reflective spatial light modulator LCOS is loaded with the phase distribution function of the DOE. That is to say, after the light wave is incident on the phase-type reflective spatial light modulator LCOS, the incident light wave can be modulated according to the phase distribution function φ(r), and the output light of the LCOS will be diffracted to form a hollow beam with the required inner and outer ring radii.

[0060] Refer to Figure 4 , The light intensity adjusting unit 2 includes a half-wave plate 21 and a quarter-wave plate 22. The half-wave plate 21 is arranged between the Gaussian beam generator 1 and the beam expanding and collimating unit 3, and is used to adjust the polarization direction of the Gaussian beam generated by the Gaussian beam generator 1, so that the collimated Gaussian beam can be reflected by the beam splitting unit 4 to the spatial light modulator 5 as much as possible. The quarter-wave plate 22 is arranged between the beam splitting unit 4 and the spatial light modulator 5, and is used to adjust the polarization direction of the hollow beam generated by the spatial light modulator 5 so that the hollow beam can be transmitted by the beam splitting unit 4 to the measuring unit 6 as much as possible.

[0061] Refer to Figure 4 and Figure 5 , The measuring unit 6 can be a spot analyzer. The spot analyzer is used to observe the modulated hollow beam and record its light intensity distribution, helping researchers and engineers analyze the modulation characteristics of the beam and optimize the optical system design. In addition, the measuring unit 6 can also be an interferometer, a CCD camera, etc.

[0062] The implementation principle of the device for generating a hollow beam in the embodiment of the present application is: the present application can shape a common Gaussian beam into a hollow beam with dynamically adjustable size, and the device structure is simple and the operation is convenient.

[0063] The embodiment of the present application also discloses an optical tweezer system. Refer to Figure 6 , The optical tweezer system includes the above device for generating a hollow beam. The measuring unit 6 is not provided in the above device for generating a hollow beam. The optical tweezer system further includes a beam reducing unit 7, a reflecting unit 8, and a microscopic imaging unit 9 arranged in sequence along the propagation direction of the hollow beam emitted from the beam splitting unit 4.

[0064] The beam constriction unit 7 includes a first beam constriction lens 71 and a second beam constriction lens 72 arranged in sequence. The first beam constriction lens 71 and the second beam constriction lens 72 are used to focus the hollow beam. The first beam constriction lens 71 and the second beam constriction lens 72 can be convex lenses or microlens arrays, etc.

[0065] The reflection unit 8 includes a reflecting mirror 81 and a dichroic mirror 82 arranged in sequence. The reflecting mirror 81 is used to change the transmission direction of the hollow beam. In this embodiment, after the hollow beam passes through the reflecting mirror 81, the propagation direction of the light changes by 90°. The dichroic mirror 82 is used to reflect the incident hollow beam to the microscopic imaging unit 9 and can transmit the imaging beam of the microscopic imaging unit 9.

[0066] The microscopic imaging unit 9 includes a microscopic objective lens 91, a sample stage 92, an illumination light source 93, a filter 94, and a camera 95. The microscopic objective lens 91, the sample stage 92, and the illumination light source 93 are arranged in sequence on the reflection optical path of the dichroic mirror 82. The filter 94 and the camera 95 are arranged in sequence on the imaging optical path of the microscopic imaging unit 9.

[0067] The hollow beam forms a hollow optical trap after being focused by the microscopic objective lens 91. The hollow optical trap is used to capture and manipulate the biological sample placed on the sample stage 92. The illumination light source 93 emits illumination light and transmits it to the sample stage 92. The illumination light illuminates the biological sample. The imaging beam of the biological sample passes through the dichroic mirror 82 and is incident on the filter 94. The filter 94 filters out the Gaussian beam reflected by the biological sample and other stray light. Finally, the information of the biological sample and the capture and manipulation situation of the cells are displayed in real time on the camera 95.

[0068] The implementation principle of the optical tweezer system in the embodiment of the present application is as follows: The device for generating the hollow beam is combined with the traditional optical tweezer optical path to form a holographic hollow microscopic optical tweezer system. This optical tweezer system can reduce the thermal damage of the optical tweezer to living biological cells and improve the flexibility and applicability of the optical tweezer in its application fields.

[0069] The above are all the preferred embodiments of the present application. The protection scope of the present application is not limited accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for generating a hollow beam, characterized in that, Including the following steps: S1: Generate a Gaussian beam and perform beam expansion and collimation processing on the Gaussian beam; S2: Design the phase distribution function of the diffractive optical element DOE. The phase distribution function of the DOE is calculated according to the following formula: where r is the radius of the DOE, f is the focal length of the DOE, ρ1 is the inner ring radius of the hollow beam formed by the diffraction of the Gaussian beam, ρ2 is the outer ring radius of the hollow beam formed by the diffraction of the Gaussian beam, λ is the wavelength of the incident light, and the wave number The constant a is set to 2.5; Input the phase information of the initial Gaussian beam and the phase information of the required hollow beam into the phase distribution function of the DOE ; Obtain the phase distribution map of the DOE through computer-designed algorithm simulation; S3: Load the phase distribution map of the DOE in the spatial light modulator. The light wave after beam expansion and collimation is incident on the spatial light modulator, and the spatial light modulator modulates the incident beam to form a hollow beam with the required inner and outer ring radii.

2. The method for generating a hollow beam according to claim 1, characterized in that, The step S2 includes: S21: Create a phase array function. This function outputs array phase values according to the phase distribution function of the hollow beam and determines the wavelength λ of the Gaussian beam; S22: Define the basic parameters of the diffractive optical element DOE, including the focal length f, and select the DOE phase distribution function according to the size of the required hollow beam and the parameters ρ1, ρ2 in S23: Phase distribution function of DOE Input the basic parameters of the defined DOE; S24: Determine the image resolution according to the liquid crystal target surface resolution and pixel size of the actually used spatial light modulator; S25: Convert the phase distribution of the DOE into a grayscale image output through a normalization algorithm.

3. A device for generating a hollow beam, based on the method for generating a hollow beam according to claim 1 or 2, characterized in that, Including: A Gaussian beam generator (1) for generating a Gaussian beam with a required wavelength; A beam expansion and collimation unit (3) for expanding and collimating the Gaussian beam generated by the Gaussian beam generator (1); A beam splitting unit (4) for changing the propagation direction of the Gaussian beam and splitting the Gaussian beam into a reflected light and a transmitted light; A spatial light modulator (5) loaded with the phase distribution function φ(r) of the DOE for performing phase modulation on the incident Gaussian beam and diffracting to generate the required hollow beam; An optical intensity adjustment unit (2) for adjusting the transmission ratio and reflection ratio of the optical intensity passing through the beam splitting unit (4).

4. The device for generating a hollow beam according to claim 3, characterized in that: The device for generating the hollow beam further includes: A measurement unit (6) for observing the modulated hollow beam and recording its light intensity distribution.

5. The device for generating a hollow beam according to claim 3, characterized in that: The Gaussian beam generator (1) outputs one wavelength in the range of 780 - 1100 nm.

6. The device for generating a hollow beam according to claim 3, characterized in that: The beam expansion and collimation unit (3) includes a beam expansion objective lens (31), a filtering pinhole (32), and a collimating lens (33) arranged in sequence along the optical path transmission direction. The beam expansion objective lens (31) is used to reduce the beam diameter of the Gaussian beam. The filtering pinhole (32) is used to limit and filter the incident Gaussian beam to achieve the selection and suppression of specific signals. The collimating lens (33) is used to collimate the Gaussian beam.

7. The device for generating a hollow beam according to claim 3, characterized in that: The beam splitting unit (4) includes a polarization beam splitting prism. The polarization beam splitting prism is used to reflect the beam-expanded and collimated Gaussian beam to the spatial light modulator (5) and transmit the hollow beam generated by the spatial light modulator (5).

8. The device for generating a hollow beam according to claim 3, characterized in that: The spatial light modulator (5) includes a phase-type reflective spatial light modulator LCOS. After loading the phase distribution map of the DOE, the phase-type reflective spatial light modulator LCOS is used to perform phase modulation on the incident light and diffract to generate the required hollow beam.

9. The device for generating a hollow beam according to claim 3, characterized in that: The light intensity adjustment unit (2) includes a half-wave plate (21) and a quarter-wave plate (22). The half-wave plate (21) is disposed between the Gaussian beam generator (1) and the beam expanding and collimating unit (3) and is used to adjust the polarization direction of the Gaussian beam generated by the Gaussian beam generator (1) so that the expanded and collimated Gaussian beam is reflected by the beam splitting unit (4). The quarter-wave plate (22) is disposed between the beam splitting unit (4) and the spatial light modulator (5) and is used to adjust the polarization direction of the hollow beam generated by the spatial light modulator (5) so that the hollow beam is transmitted by the beam splitting unit (4).

10. An optical tweezer system, comprising the device for generating a hollow beam according to any one of claims 3-9, characterized in that, It further includes a beam shrinking unit (7), a reflection unit (8), and a microscopic imaging unit (9) which are sequentially disposed along the propagation direction of the hollow beam emitted from the beam splitting unit (4); The beam shrinking unit (7) includes a first beam shrinking lens (71) and a second beam shrinking lens (72) which are sequentially disposed, and the first beam shrinking lens (71) and the second beam shrinking lens (72) are used to focus the hollow beam; The reflection unit (8) includes a reflecting mirror (81) and a dichroic mirror (82) which are sequentially disposed. The reflecting mirror (81) is used to change the transmission direction of the hollow beam, and the dichroic mirror (82) is used to reflect the hollow beam to the microscopic imaging unit (9); The microscopic imaging unit (9) includes a microscopic objective lens (91), a stage (92), an illumination light source (93), a filter (94), and a camera (95). The hollow beam forms a hollow optical trap after being focused by the microscopic objective lens (91). The hollow optical trap is used to capture and manipulate the biological sample placed on the stage (92). The illumination light source (93) emits illumination light and transmits it to the stage (92). The filter (94) filters out the Gaussian beam reflected by the biological sample and other stray light. Finally, the biological sample information and the capture and manipulation conditions of the cells are displayed in real time on the camera (95).

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