Quantitative phase imaging system and method based on Bessel beam illumination

Abstract

The invention discloses a quantitative phase imaging system and method based on Bessel beam illumination, and the method comprises the steps: enabling laser output by a laser device to be coupled through a beam splitting 1 * 2 single-mode optical fiber through a light source and a beam splitting module, filtering a high-order mode, and splitting the laser into object light and reference light; through a Bessel beam generation module, object light is collimated by a short-focus lens to form a plane wave, the plane wave is incident to a spatial light modulator, phase distribution of an axis prism is loaded, the plane wave is modulated into a Bessel beam, the Bessel beam is subjected to beam contraction through an objective lens and a tube lens in sequence, the Bessel beam passes through a scattering medium, an effective area covered by a central main lobe serves as an imaging area, a sample to be detected is irradiated, and the target object is detected. Outputting central main lobe object light; the reference light is collimated into a plane wave through a short-focus lens, the incident angle of the plane wave is adjusted through a reflector, then the intensity of the reference light is adjusted through a linear polarizer, and interference fringes with the optimal contrast are obtained; and the signal acquisition and processing module converts data extracted from the interference fringes into three-dimensional height information of the sample, so that high-precision quantitative phase imaging is realized.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging, specifically relating to a quantitative phase imaging system and method based on Bessel beam illumination. Background Technology

[0002] In the field of optical phase imaging, accurately acquiring the complex amplitude distribution of the light field (including amplitude and phase information) is crucial for high-precision measurement and analysis. The technique of simultaneously reconstructing amplitude and phase using numerical methods is known as quantitative phase imaging (QPI). This technique enables non-destructive, high-precision measurement of the optical properties of samples and has demonstrated significant application value in fields such as disease diagnosis, cell biology, and material characterization.

[0003] Since Gabor proposed holography in the 1940s, numerous researchers and engineers have continuously promoted its development and application. Currently, this technology is widely used in holographic display, optical measurement, and holographic storage. Among these, digital holographic microscopy (DHM), based on off-axis holography, has become one of the core technologies in the field of QPI (Quantity Imaging Processing), possessing advantages such as high measurement accuracy and strong real-time data recovery, and showing broad application prospects in high-speed imaging and dynamic process monitoring. In recent years, research based on DHM systems has further expanded to emerging directions such as three-dimensional refractive index reconstruction and high-speed classification and analysis of live cells, and has spurred the development of commercial products such as novel DHM-based imaging flow cytometers.

[0004] The Bessel beam, a novel laser mode first proposed by Durnin in 1987, is a propagation-invariant solution to the Helmholtz equation and possesses two major characteristics: diffraction-free and self-healing. The main lobe hardly broadens during long-distance propagation, maintaining a stable optical field structure, i.e., diffraction-free. Even after partial obstruction during propagation, the beam can recover to its initial intensity distribution after a certain distance, i.e., self-healing. Thanks to these superior properties, Bessel light has achieved greater imaging depth and penetration depth in fields such as multiphoton fluorescence microscopy, light sheet fluorescence imaging, and Raman scattering microscopy, and has demonstrated unique advantages in optical communication and precision materials processing.

[0005] However, current QPI techniques are commonly used for single-cell or thin samples in microscopic imaging, and plane waves are typically used for illumination. When imaging thick scattering media (such as biological tissue), scattering significantly reduces the coherence of the object light and leads to uneven illumination intensity distribution, thereby weakening or even losing sample information and affecting the formation of interference fringes. This problem greatly limits the application of QPI techniques in complex biological samples.

[0006] While some studies have attempted to improve imaging quality in scattering environments, most methods require specific optical equipment, additional processing algorithms, or neural network-assisted image reconstruction. Furthermore, many of these methods are only applicable to specific imaging techniques and are difficult to generalize. Notably, research has shown that Bessel light exhibits better propagation stability in scattering media than Gaussian light, offering a potential solution and application prospect for phase microscopy, especially for phase imaging and quantitative analysis of targets in scattering environments. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a quantitative phase imaging system and method based on Bessel beam illumination, which solves the limitation of traditional methods in the prior art that can only image single cells and thin samples.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] A quantitative phase imaging system based on Bessel beam illumination includes a light source and spectrometer module, a Bessel beam generation module, a sample illumination module, a reference beam module, and a signal acquisition and processing module; among which...

[0010] The light source and beam splitting module are used to generate the light source and split the beam into object light and reference light;

[0011] The Bessel beam generation module is used to load the phase map of the axial prism after the object light is split into beams through a spatial light modulator to generate a Bessel beam, and then perform beam reduction processing.

[0012] The sample illumination module uses a reduced Sell beam to illuminate the sample under test and outputs an imaging area covered by the main lobe of the object beam center.

[0013] The reference light module is used to process the reference light output from the light source and the beam splitter module and match it with the light intensity of the main lobe of the object beam center to obtain interference fringes with the best contrast.

[0014] The signal acquisition and processing module is used to acquire and process interference fringes, extract complex amplitude information of the sample light, and finally convert the acquired complex amplitude information of the sample light into three-dimensional height information of the sample to achieve quantitative phase imaging.

[0015] The light source and beam splitting module includes a laser and a 1×2 single-mode fiber coupler. The laser generates the light source, and the 1×2 single-mode fiber coupler couples the laser output from the laser, splitting the light source into object light and reference light.

[0016] The Bessel beam generation module includes a short focal length lens, a spatial light modulator, a beam splitter, a tube mirror, and an objective lens. The object light passes through the short focal length lens and the beam splitter in sequence, and then enters the spatial light modulator to generate a Bessel beam, which is then reduced in size by the objective lens and the tube mirror.

[0017] The sample illumination module includes a scattering medium positioned above the sample to be tested, and an objective lens and a tube lens positioned below the sample to be tested. The effective area covered by the main lobe of the Bessel beam after beam reduction serves as the imaging area. After the sample to be tested is illuminated by the scattering medium, it is magnified by the objective lens and the tube lens, and then reflected by the second beam splitter before being output to the signal acquisition and processing module.

[0018] The reference light module includes a short focal length lens, a reflector, and a linear polarizer. After passing through the short focal length lens, the incident angle of the reference light is adjusted by the reflector, and then the intensity of the reference light is adjusted by the linear polarizer to match the intensity of the main lobe of the object light, so as to obtain interference fringes with optimal contrast, and then enters the signal acquisition and processing module.

[0019] The signal acquisition and processing module includes a camera and two lenses with different focal lengths. The two lenses with different focal lengths magnify the interference fringes. The camera acquires the light field of the interference fringes with and without the sample as experimental data and reference background. Then, the light field information is recovered and the true phase distribution is obtained. The data is converted into the three-dimensional height information of the sample to achieve high-precision quantitative phase imaging.

[0020] The quantitative phase imaging method based on Bessel beam illumination includes the following steps:

[0021] Step 1: Couple the laser output from the laser through a 1×2 single-mode fiber to filter out higher-order modes and split the beam into object light and reference light;

[0022] Step 2: The object light is collimated by the short focal length lens to form a plane wave, which is then incident on the spatial light modulator. The phase distribution of the loading axis prism is applied to modulate it into a Bessel beam, which is then passed through the objective lens and the tube lens in sequence for beam reduction.

[0023] Step 3: After the beam is reduced, the Bessel beam passes through the scattering medium, and the effective area covered by its central main lobe is used as the imaging area to illuminate the sample to be tested. The beam is then magnified by the objective lens and the tube lens, and the central main lobe object beam is output.

[0024] Step 4: The reference light is collimated into a plane wave by a short focal length lens. Its incident angle is adjusted by a mirror so that it has a small angle with the object light of the central main lobe. Then, a linear polarizer is used to adjust the intensity of the reference light so that it matches the intensity of the object light of the central main lobe to obtain interference fringes with the best contrast.

[0025] Step 5: Acquire the interference results. First, use the Fourier filter digital holographic reconstruction algorithm to extract the complex amplitude information from the interference results. Then, unwrap the folded phase data to restore the phase distribution of the light field to be measured and convert it into the three-dimensional height information of the sample to achieve high-precision quantitative phase imaging.

[0026] In step 1, the splitting ratio is set to 3:1.

[0027] In step 2, the phase function is φ = -k·r·NA, where k is the wave number and NA is the numerical aperture of the axial prism.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The quantitative phase imaging system based on Bessel beam illumination proposed in this invention can obtain clear interference fringes even when imaging thick scattering samples, thereby realizing the imaging of the target object and the recovery of light field information, and further converting it into quantitative analysis of physical parameters such as the height and refractive index of the measured object.

[0030] 2. This system is an optimization based on the traditional off-axis digital holographic microscope, without increasing the time overhead of the information recovery process. Therefore, it still has high-speed imaging capabilities and can meet the needs of real-time dynamic sample imaging.

[0031] 3. Theoretically, this scheme can be extended to other types of quantitative phase imaging systems, and therefore has broad application prospects and expansion value in in vivo tissue imaging, pathological analysis and complex sample detection. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of a quantitative phase imaging system based on Bessel beam illumination.

[0033] Figure 2 This is the phase diagram of the axial prism used to generate the Bessel beam.

[0034] Figure 3 This diagram illustrates the effect of scattering on the final interference light field when illuminated by a plane wave.

[0035] Figure 4 This diagram illustrates the effect of Bessel light scattering on the final interference light field.

[0036] Figure 5 A comparison chart showing the results of the ball's height recovery.

[0037] Figure 1The markings in the diagram represent: 1. Laser; 2. 1×2 single-mode fiber coupler; 3. First short-focal-length lens; 4. First beam splitter; 5. Spatial light modulator; 6. First tube lens; 7. First objective lens; 8. Second short-focal-length lens; 9. Mirror; 10. Linear polarizer; 11. Sample under test; 12. Second objective lens; 13. Second tube lens; 14. Second beam splitter; 15. First lens; 16. Second lens; 17. Camera; 18. Computer. Detailed Implementation

[0038] The structure and working process of the present invention will be further described below with reference to the accompanying drawings.

[0039] A quantitative phase imaging system based on Bessel beam illumination includes a light source and spectrometer module, a Bessel beam generation module, a sample illumination module, a reference beam module, and a signal acquisition and processing module; among which...

[0040] The light source and beam splitting module are used to generate the light source and split the beam into object light and reference light;

[0041] The Bessel beam generation module is used to load the phase map of the axial prism after the object light is split into beams through a spatial light modulator to generate a Bessel beam, and then perform beam reduction processing.

[0042] The sample illumination module uses a reduced Sell beam to illuminate the sample under test and outputs an imaging area covered by the main lobe of the object beam center.

[0043] The reference light module is used to process the reference light output from the light source and the beam splitter module and match it with the light intensity of the main lobe of the object beam center to obtain interference fringes with the best contrast.

[0044] The signal acquisition and processing module is used to acquire and process interference fringes, extract optical complex amplitude information, and finally obtain the three-dimensional height information of the sample under test to achieve quantitative phase imaging.

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the following embodiments are only used to explain the technical principles and implementation methods of this invention and do not constitute a limitation on the scope of protection. All technical features involved in this invention can be combined with each other as long as there is no contradiction or conflict, and all such combinations fall within the scope of protection of this invention.

[0046] Specific embodiments, such as Figures 1 to 5 As shown:

[0047] A quantitative phase imaging system based on Bessel beam illumination, the specific hardware components of which are as follows: Figure 1 As shown, it includes a light source and beam splitting module, a Bessel beam generation module, a sample illumination module, a reference light module, and a signal acquisition and processing module; among which,

[0048] A light source and beam splitting module are used to generate the light source and split it into object light and reference light. The light source and beam splitting module includes a laser 1 and a 1×2 single-mode fiber coupler 2. The laser 1 generates the light source, and the 1×2 single-mode fiber coupler 2 splits the light source into object light and reference light. The single-mode fiber can effectively filter out higher-order modes, allowing only high-order modes to transmit. The splitting ratio is set to 3:1 to ensure intensity matching between the object light and reference light during interference, facilitating subsequent contrast optimization.

[0049] A Bessel beam generation module is used to generate a Bessel beam by loading an axial prism phase map onto a spatial light modulator after the object light has been split, and then perform beam reduction processing. The Bessel beam generation module includes a first short focal length lens 3, a spatial light modulator 5, a first beam splitter 4, a first tube mirror 6, and a first objective lens 7. The object light passes sequentially through the first short focal length lens 3 and the first beam splitter 4, and then enters the spatial light modulator 5 to generate a Bessel beam, which is then reduced in size by the first objective lens 7 and the first tube mirror 6. The high-intensity splitting path (i.e., the object light) is collimated by the first short focal length lens to form a plane wave and then enters the spatial light modulator (SLM). The phase distribution of the axial prism loaded on the SLM is shown in the figure. Figure 2 The phase function is φ = -k·r·NA, where k is the wavenumber and NA is the numerical aperture of the axial prism. After SLM modulation, a Bessel beam is generated, which is then beam-constricted by a 4f system consisting of the first objective and the first tube mirror. The magnification of the first objective, the focal length of the first tube mirror, and the NA parameter of the axial prism phase are adjustable to ensure that the sample is located within the diffraction-free region of the Bessel beam and to match the sample size with the camera field of view.

[0050] The sample illumination module uses a Bessel beam with a reduced beam size to illuminate the sample 11 under test, outputting the imaging area covered by the main lobe of the object beam. The module includes a scattering medium positioned above the sample 11, and a second objective lens 12 and a second tube mirror 13 positioned below the sample. The effective area covered by the main lobe of the reduced-bessel beam serves as the imaging area. After illuminating the sample 11 through the scattering medium, the beam is magnified by the second objective lens 12 and the second tube mirror 13 before being output to the reference light module. The Bessel beam, used as the object beam to illuminate the sample, exhibits higher anti-scattering capability in the scattering medium compared to traditional plane waves. Even if the light field is disturbed by scattering phase, its main lobe maintains a near-planar phase and stable intensity distribution, thus maintaining high coherence. Selecting only the effective area covered by the main lobe as the imaging area during acquisition significantly reduces the impact of scattering noise. The object beam is magnified by the second objective lens and the second tube mirror, and then output to the signal acquisition and processing module after passing through the second beam splitter.

[0051] The reference light module is used to process the reference light output from the light source and the beam splitter module, and then match the intensity of the main lobe of the object beam to obtain interference fringes with optimal contrast. The reference light module includes a second beam splitter 14, a second short-focal-length lens 8, a reflector 9, and a linear polarizer 10. After passing through the second short-focal-length lens 8, the incident angle of the reference light is adjusted by the reflector 9, and then the intensity of the reference light is adjusted by the linear polarizer 10 to match the intensity of the main lobe of the object beam, obtaining interference fringes with optimal contrast. The reference light then enters the signal acquisition and processing module through the second beam splitter 14. The lower-intensity beam splitter (i.e., the reference light) is collimated into a plane wave by the second short-focal-length lens, and its incident angle is adjusted by the reflector to create a small angle with the object beam. Then, the intensity of the reference light is adjusted by the linear polarizer to match the intensity of the main lobe of the object beam, thereby obtaining interference fringes with optimal contrast.

[0052] The signal acquisition and processing module is used to acquire and process interference fringes, extract complex amplitude information, and ultimately obtain the three-dimensional height information of the sample under test, achieving quantitative phase imaging. The module includes a camera 17, a computer 18, and two lenses with different focal lengths, namely a first lens 15 and a second lens 16. These lenses amplify the interference fringes to ensure compliance with the Nyquist sampling theorem. The camera acquires the interference fringes light field with and without the sample as experimental data and a reference background. The computer 18 then recovers the light field information and obtains the true phase distribution, converting the data into the three-dimensional height information of the sample to achieve high-precision quantitative phase imaging. The camera acquires the interference pattern and avoids overexposure by adjusting the exposure time. The acquired interference data is processed by the computer. First, the complex amplitude information is extracted using a digital holographic reconstruction algorithm with Fourier filtering. Then, the phase data is unwrapped to recover the phase distribution of the light field under test, which can be further converted into the three-dimensional height information of the sample to achieve high-precision quantitative phase imaging.

[0053] In this embodiment, the second beam splitter does not have a specific function for the reference light; it simply propagates along the same path at the end.

[0054] The following example further illustrates the imaging method of this quantitative phase imaging system based on Bessel beam illumination. By utilizing the non-diffraction and anti-scattering properties of Bessel light, sample imaging and quantitative phase information acquisition under scattering medium conditions are achieved. The specific steps include:

[0055] Step 1: Using a 532nm wavelength laser as the light source, the sample to be tested is a standard polystyrene microsphere with a diameter of 15μm (its size is close to the diameter of a typical eukaryotic cell, 10-20μm). The laser output is input into a single-mode fiber with a 1:3 splitting ratio via a 1×2 single-mode fiber coupler. This fiber only allows Gaussian modes to pass through, acting as a mode filter and beam splitter. The outgoing light field is collimated into plane waves by two lenses with a focal length of 50mm. The beam with the higher intensity is used as the object beam, and the other is used as the reference beam.

[0056] Step 2: In the object-light path, the plane wave is first split by a beam splitter (BS) and then illuminates the spatial light modulator, onto which an axial prism phase map is loaded to generate a Bessel beam. The generated Bessel beam is then processed by a beam-contraction system consisting of a 300mm focal length lens and a 20× magnification objective lens, ensuring that the sample under test is located within the diffraction-free region of the Bessel beam. The length of the diffraction-free region after beam consolidation is 1 / M of the original length. 2 Where M is the beam reduction ratio. Considering beam splitting loss and subsequent amplification, a 1:3 splitting ratio can effectively ensure the balance between the intensity of the object beam and the reference beam.

[0057] Step 3: The Bessel beam, after being reduced to a single beam, illuminates the sample under test, and a thin scattering object is placed directly above it to simulate the scattering medium. Experiments show that after a normal plane wave passes through this medium, the intensity distribution of the interference light field becomes severely uneven, and the coherence is significantly reduced (see...). Figure 3 Under the same conditions, the Bessel optical main lobe region still maintains high coherence and uniform intensity distribution (see...). Figure 4 This indicates its excellent anti-scattering properties.

[0058] Step 4: The imaging section uses a 40× magnification objective lens and a 200mm focal length lens to form a magnification system, focusing and magnifying the sample. The reference beam is adjusted to a tilted plane wave by a tilting lens, and its intensity is adjusted by a linear polarizer to match the intensity of the main lobe of the object beam, thus obtaining interference fringes with good contrast. To meet the Nyquist sampling conditions, a lens group with focal lengths of 50mm and 75mm is added in front of the camera to form a magnification system, further amplifying the interference light field.

[0059] Step 5: The camera acquires interference light fields with and without the sample as experimental data and a reference background, respectively. Then, a holographic digital reconstruction method based on Fourier filtering is used to recover the light field information, and the true phase distribution is obtained using the Goldstein phase unwrapping algorithm. When the sample structure is homogeneous, the phase information can be further converted into height information. Comparative results show that, under scattering conditions, the imaging results obtained by the quantitative phase imaging system based on Bessel illumination are significantly better than those of the traditional plane wave illumination digital holographic microscopy system (see...). Figure 5 ).

[0060] Therefore, it can be seen that the quantitative phase imaging system based on Bessel beam illumination proposed in this invention effectively overcomes the limitation of traditional methods that can only image transparent samples. It can obtain clear interference fringes even in scattering tissues, thereby achieving imaging of the target object and recovery of light field information, and further transforming it into quantitative analysis of physical parameters such as sample height and refractive index. This system is an optimization based on traditional off-axis digital holographic microscopy without increasing the time overhead of the information recovery process, thus still possessing high-speed imaging capabilities and meeting the needs of real-time dynamic sample imaging. At the same time, Bessel beam illumination has good versatility. Although this invention uses off-axis digital holographic microscopy as an example, this scheme can theoretically be extended to other types of quantitative phase imaging systems, thus having broad application prospects and expansion value in in vivo tissue imaging, pathological analysis, and complex sample detection.

[0061] Through the above implementation scheme, the present invention successfully reconstructs the height information of a 15μm standard polystyrene microsphere under scattering conditions, verifies the stability and applicability of the quantitative phase imaging system based on Bessel beam illumination in complex optical environments, and significantly expands the application scope of quantitative phase imaging technology.

[0062] It should be understood that this solution is not limited to the specific embodiments described above. Devices and structures not described in detail herein should be understood as being implemented in a manner common to the art. Any person skilled in the art can make many possible variations and modifications to this solution, or modify it into equivalent embodiments, without departing from the scope of this solution, using the methods and techniques disclosed above. This does not affect the substantive content of this solution. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this solution, without departing from its scope, still fall within the protection scope of this solution.

Claims

1. A quantitative phase imaging system based on Bessel beam illumination, characterized in that: It includes a light source and beam splitting module, a Bessel beam generation module, a sample illumination module, a reference light module, and a signal acquisition and processing module; among which, The light source and beam splitting module are used to generate the light source and split the beam into object light and reference light; The Bessel beam generation module is used to load the phase map of the axial prism after the object light is split into beams through a spatial light modulator to generate a Bessel beam, and then perform beam reduction processing. The sample illumination module uses a reduced Sell beam to illuminate the sample under test and outputs an imaging area covered by the main lobe of the object beam center. The reference light module is used to process the reference light output from the light source and the beam splitter module and match it with the light intensity of the main lobe of the object beam center to obtain interference fringes with the best contrast. The signal acquisition and processing module is used to acquire and process interference fringes, extract complex amplitude information of the sample light, and finally convert the acquired complex amplitude information of the sample light into three-dimensional height information of the sample to achieve quantitative phase imaging.

2. The quantitative phase imaging system based on Bessel beam illumination according to claim 1, characterized in that: The light source and beam splitting module includes a laser and a 1×2 single-mode fiber coupler. The laser generates the light source, and the 1×2 single-mode fiber coupler couples the laser output from the laser, splitting the light source into object light and reference light.

3. The quantitative phase imaging system based on Bessel beam illumination according to claim 1, characterized in that: The Bessel beam generation module includes a short focal length lens, a spatial light modulator, a beam splitter, a tube mirror, and an objective lens; The object beam passes through a short focal length lens and a beam splitter in sequence, and then enters the spatial light modulator to generate a Bessel beam, which is then reduced in size by the objective lens and the tube lens.

4. The quantitative phase imaging system based on Bessel beam illumination according to claim 1, characterized in that: The sample illumination module includes a scattering medium positioned above the sample to be tested, and an objective lens and a tube lens positioned below the sample to be tested. The effective area covered by the main lobe of the Bessel beam after beam reduction serves as the imaging area. After the sample to be tested is illuminated by the scattering medium, it is magnified by the objective lens and the tube lens, and then reflected by the second beam splitter before being output to the signal acquisition and processing module.

5. The quantitative phase imaging system based on Bessel beam illumination according to claim 1, characterized in that: The reference light module includes a short focal length lens, a reflector, and a linear polarizer. After passing through the short focal length lens, the incident angle of the reference light is adjusted by the reflector, and then the intensity of the reference light is adjusted by the linear polarizer to match the intensity of the main lobe of the object light, so as to obtain interference fringes with optimal contrast, and then enters the signal acquisition and processing module.

6. The quantitative phase imaging system based on Bessel beam illumination according to claim 1, characterized in that: The signal acquisition and processing module includes a camera and two lenses with different focal lengths. The two lenses with different focal lengths magnify the interference fringes. The camera acquires the light field of the interference fringes with and without the sample as experimental data and reference background. Then, the light field information is recovered and the true phase distribution is obtained. The data is converted into the three-dimensional height information of the sample to achieve high-precision quantitative phase imaging.

7. A quantitative phase imaging method based on Bessel beam illumination, characterized in that: Includes the following steps: Step 1: Couple the laser output from the laser through a 1×2 single-mode fiber to filter out higher-order modes and split the beam into object light and reference light; Step 2: The object light is collimated by the short focal length lens to form a plane wave, which is then incident on the spatial light modulator. The phase distribution of the loading axis prism is applied to modulate it into a Bessel beam, which is then passed through the objective lens and the tube lens in sequence for beam reduction. Step 3: After the beam is reduced, the Bessel beam passes through the scattering medium, and the effective area covered by its central main lobe is used as the imaging area to illuminate the sample to be tested. The beam is then magnified by the objective lens and the tube lens, and the central main lobe object beam is output. Step 4: The reference light is collimated into a plane wave by a short focal length lens. Its incident angle is adjusted by a mirror so that it has a small angle with the object light of the central main lobe. Then, a linear polarizer is used to adjust the intensity of the reference light so that it matches the intensity of the object light of the central main lobe to obtain interference fringes with the best contrast. Step 5: Acquire the interference results. First, use the Fourier filter digital holographic reconstruction algorithm to extract the complex amplitude information from the interference results. Then, unwrap the folded phase data to restore the phase distribution of the light field to be measured and convert it into the three-dimensional height information of the sample to achieve high-precision quantitative phase imaging.

8. The quantitative phase imaging method based on Bessel beam illumination according to claim 7, characterized in that: In step 1, the splitting ratio is set to 3:

1.

9. The quantitative phase imaging method based on Bessel beam illumination according to claim 7, characterized in that: In step 2, the phase function is φ = -k·r·NA, where k is the wave number and NA is the numerical aperture of the axial prism.

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