Large phase gradient microlens detection system and detection method

Abstract

The present application relates to a large phase gradient micro-lens detection system, comprising: a sample light path for sample setting; a reference light path for forming interference with the sample light path; a detector for obtaining the interference pattern of the first light beam of the sample light path and the second light beam of the reference light path and performing Fourier transform on the interference pattern to form a frequency spectrum space distribution diagram; a wavefront modulation component arranged on the reference light path and used for modulating the second light beam, so that the frequency spectrum space distribution diagram is completely within the rated frequency spectrum space range of the detector. The present application can realize the detection of micro-lenses with larger numerical aperture without changing the detector.

Description

Technical Field

[0001] This invention relates to the field of optical component testing technology, and in particular to a large phase gradient microlens testing system and method. Background Technology

[0002] Today, technologies used in smart cars, smartphones, and portable display devices are changing and developing at a very rapid pace, with a growing desire to cram more and better functions into increasingly smaller spaces. Despite this, in the field of optical modules, traditional geometric optics-based design schemes face numerous limitations, hindering further technological breakthroughs and applications. With the development of micro-nano photonics, it has become possible to manipulate and control light waves using subwavelength structural units. Effectively arranging these structural units allows for the integration of various complex optical functions onto a single plane; the most representative example is the metasurface, where a metasurface functioning as a lens is called a metalens. Because metalenses are based on a fundamental design, they achieve greater freedom in controlling the light field. Compared to traditional optical lenses, they offer advantages such as thinness (hundreds of nanometers to a few micrometers), miniaturization (tens of micrometers in diameter), and integration, making them potentially valuable in fields such as optical communication, security, autonomous driving, consumer electronics, medical devices, scientific instruments, and sensing.

[0003] Since the concept of metalenses was proposed in 2016, metalens research has become a major cutting-edge research area in micro-nano photonics, attracting numerous researchers both domestically and internationally. Currently, large numerical aperture metalenses, achromatic metalenses, oil-immersed metalenses, variable focal length metalenses, off-axis metalenses, and metalens arrays have been realized, and their operating wavelengths have been further expanded, now encompassing ultraviolet, visible, near-infrared, and mid-infrared. Meanwhile, the applications of metalenses have also attracted widespread attention from high-tech companies. Companies whose main business is metalens products include: Metalenx (USA), Metalenx (China), and Sunward Optoelectronics (China); companies focusing on metalens applications include: Huawei, Oppo, and Xiaomi. Applications are expected in 3D sensing, AR / VR, drone photography modules, LiDAR, sensors, and lighting.

[0004] The optimal way to detect microlenses, such as microlenses and metalenses, is to measure their modulated phase distribution (or wavefront), as described in the authorized invention patent [ZL 2020 1 0305955.3]. However, for microlenses with large numerical apertures, the phase gradient at their edges is extremely large, often exceeding the pixel resolution of the receiving detector, making it difficult to accurately obtain the phase distribution in the corresponding region. Traditional methods for detecting large numerical apertures mainly include the following schemes:

[0005] (1) Direct imaging method: This method uses a resolution plate to directly image the lens and determine its imaging quality, thus characterizing the overall effect of the lens. Because microlenses are on the micrometer scale, direct imaging is not possible. Therefore, this method usually requires indirect imaging using a microscope system. The influence of the microscope system cannot be eliminated, and the larger the numerical aperture, the higher the quality requirements for the microscope system. On the other hand, this method characterizes the overall effect and cannot provide in-depth analysis of the local performance and design of the microlens.

[0006] (2) The method of measuring the focused light field involves measuring the focal point (i.e., the point spread function) of parallel incident light after it has converged through the lens to determine the difference between the focused spot of a large numerical aperture lens and a perfect lens. Although this method can invert the wavefront of a microlens by measuring the light field distribution, it still depends on the quality of the microscope system. At the same time, because the focused light field of a large numerical aperture microlens is very concentrated, it requires a high dynamic range of the camera. Usually, if the focus is not overexposed, other light field position information will be submerged in noise.

[0007] (3) Wavefront sensor method: This method uses a wavefront sensor (microlens array, two-dimensional grating) to directly measure the wavefront distribution controlled by the lens. This method is limited by the pixel spatial density of the wavefront sensor, making it difficult to achieve large gradient wavefront detection. At the same time, for microlenses, this scheme also needs to be based on a microscopic system, and the influence of the system's imaging quality cannot be eliminated.

[0008] (4) Interferometry: Because the phase gradient of a large numerical aperture lens is very large, a standard sample with known phase modulation is needed to modulate the wavefront of the lens and further obtain the corresponding phase distribution of the lens modulation. This method is an effective solution for measuring microlenses, but the detection of large numerical aperture microlenses faces the following problems. On the one hand, it is difficult to design and process a microscopic standard sample (too high cost); on the other hand, it faces the limitation of the number of detector pixels or pixel density, making it difficult to detect very large numerical aperture microlenses. Therefore, in terms of solutions, pixel resolution is usually enhanced by increasing the number of pixels or pixel density. The solution of increasing the number of pixels is to magnify the microlens image, measure only the local phase distribution of the microlens each time, and then perform spatial mapping to obtain the phase distribution of the entire microlens. The solution of increasing pixel density is to select a detector with a higher pixel density (of course, the total number of pixels is also greater) in the same imaging area. This solution is limited by the technology and model of the detectors on the market, and it is usually difficult to select a matching detector (or the cost is too high). Summary of the Invention

[0009] To address the aforementioned problems, this invention provides a large phase gradient microlens detection system and method, which can detect microlenses with larger numerical apertures without changing the detector.

[0010] This invention is achieved through the following scheme: a large phase gradient microlens detection system, comprising:

[0011] Sample optical path for sample setup;

[0012] A reference optical path used to form interference with the sample optical path;

[0013] A detector used to acquire the interference pattern of the first beam of the sample optical path and the second beam of the reference optical path, and to perform a Fourier transform on the interference pattern to form a spectral spatial distribution map;

[0014] A wavefront modulation component is provided on the reference optical path and used to modulate the second beam, such that the spectral spatial distribution is completely within the rated spectral space of the detector.

[0015] A further improvement of the large phase gradient microlens detection system of the present invention is as follows:

[0016] The sample optical path includes a first objective lens, a first lens, and a second beam splitter arranged sequentially.

[0017] The reference optical path includes the wavefront modulation component and the second reflector arranged in sequence. The second reflector is arranged corresponding to the first beam splitter, so that the second beam is reflected by the second reflector into the second beam splitter and merged with the first beam into a single beam and interferes with it.

[0018] The detector is positioned after the second beam splitter along the sample optical path, and an area for setting the sample is reserved in front of the first objective lens on the sample optical path.

[0019] A further improvement of the large phase gradient microlens detection system of the present invention is that the wavefront modulation component includes multiple optical elements, and the second beam is modulated by selecting at least two adapted optical elements and adjusting the distance between at least two optical elements, so that the wavefront of the second beam is the same as the wavefront type of the first beam passing through the sample.

[0020] A further improvement of the large phase gradient microlens detection system of the present invention is that the sample is a large numerical aperture microlens, and the wavefront modulation component includes two adjustment lenses, the distance between the two adjustment lenses satisfying the non-confocal setting of the two adjustment lenses.

[0021] A further improvement of the large phase gradient microlens detection system of the present invention is that the sample is a large numerical aperture vortex lens, the wavefront modulation component includes two adjustment lenses and a vortex waveplate, the distance between the two adjustment lenses satisfies that the two adjustment lenses are non-confocal, and the vortex waveplate is disposed between the two adjustment lenses or on the opposite outer side of one of the adjustment lenses.

[0022] A further improvement of the large phase gradient microlens detection system of the present invention is that it further includes: a monochromatic light source; a beam expander and a first beam splitter disposed at the light outlet of the monochromatic light source, the first beam splitter dividing the light beam of the monochromatic light source into a first beam and a second beam, the reference optical path further including a first reflecting mirror disposed corresponding to the second beam, the second beam being reflected by the first reflecting mirror and then incident into the wavefront modulation component.

[0023] This invention also provides a method for detecting a large phase gradient microlens, comprising the following steps:

[0024] Provides samples of large phase gradient lenses and a large phase gradient microlens detection system as described above;

[0025] The sample is placed in the sample optical path, and the detector acquires the first interference pattern formed by the interference of the first beam and the second beam passing through the sample. The first interference pattern is then subjected to Fourier transform to form a first spectral spatial distribution map.

[0026] Observe whether the first spectral spatial distribution map is completely within the rated spectral spatial range of the detector: if yes, proceed to the next step; if no, adjust the wavefront modulation component until the first spectral spatial distribution map is completely within the rated spectral spatial range of the detector.

[0027] The sample is removed, and a second interference pattern is obtained by the detector through the interference of the first beam without the sample and the second beam. The second interference pattern is then subjected to Fourier transform to form a second spectral spatial distribution map.

[0028] By using off-axis digital holography, the first spectral spatial distribution map is numerically filtered to extract first-order information, and the second spectral spatial distribution map is used as the background for background subtraction, thus obtaining the phase distribution regulated by the sample.

[0029] A further improvement of the large phase gradient microlens detection method of the present invention is that the wavefront modulation component includes multiple optical elements; when adjusting the wavefront modulation component:

[0030] First, select at least two suitable optical elements according to the type of the sample;

[0031] The distance between at least two of the optical elements is then adjusted to modulate the second beam so that the wavefront of the second beam is the same as the wavefront type of the first beam passing through the sample;

[0032] Then, while ensuring that the wavefront of the second beam is the same as the wavefront type of the first beam passing through the sample, the distance between the optical elements is adjusted until the first spectral spatial distribution map is completely within the rated spectral space of the detector.

[0033] A further improvement of the large phase gradient microlens detection method of the present invention is as follows:

[0034] The sample is a large numerical aperture microlens, and the wavefront modulation component includes two adjustment lenses;

[0035] When adjusting the distance between the two adjustment lenses, the distance is such that the two adjustment lenses are set to be non-confocal.

[0036] A further improvement of the large phase gradient microlens detection method of the present invention is as follows:

[0037] The sample is a large numerical aperture vortex lens, and the wavefront modulation assembly includes two adjustment lenses and a vortex wave plate. The vortex wave plate is disposed between the two adjustment lenses or on the opposite outer side of one of the adjustment lenses.

[0038] When adjusting the distance between the two adjustment lenses, the distance is such that the two adjustment lenses are set to be non-confocal.

[0039] This invention provides an effective solution for the detection of large phase gradient lenses. Based on microscopic off-axis digital holographic imaging technology, by selecting a suitable wavefront of the reference beam, it achieves the detection of larger phase gradients within a limited spectral space without changing the detector. This helps to fill the gap in my country's micro-area phase distribution detection technology and provides professional technical guidance for the industrial inspection of microlenses, metalenses, and lens arrays. Attached Figure Description

[0040] Figure 1 The optical path diagram of the large phase gradient microlens detection system of the present invention is shown.

[0041] Figure 2 A comparison diagram of the spectral distribution of the large phase gradient microlens detection system of the present invention is shown.

[0042] Figure 3 A schematic diagram of a modulation embodiment of the wavefront modulation component of the large phase gradient microlens detection system of the present invention is shown.

[0043] Figure 4The diagram shows the measured interference data of the presence or absence of a sample in the large phase gradient microlens detection system of the present invention.

[0044] Figure 5 The diagram shows measured interference data of the presence or absence of a sample when the reference wave of the large phase gradient microlens detection system of the present invention is a plane wave.

[0045] Figure 6 The diagram shows measured interference data of the presence or absence of a sample when the reference wave of the large phase gradient microlens detection system of the present invention is a suitable spherical wave.

[0046] Figure 7 The phase distribution diagram of the filtered microlens of the large phase gradient microlens detection system of the present invention is shown.

[0047] Figure 8 The diagram shows the measured interferometric data of the large phase gradient lens in the large phase gradient microlens detection system of the present invention. Detailed Implementation

[0048] In the detection of phase distribution of microlenses using interferometry, the most crucial elements are the wavefront modulated by the microlens and the wavefront of the reference beam. These two wavefronts interfere and superimpose in front of the detector, and the result is recorded by the detector. In the patent [ZL 2020 10305955.3] for a microlens detection system and method, off-axis digital holography can be used to achieve rapid detection of the phase distribution modulated by microlenses. However, due to limitations in the pixel resolution of the detector, it is difficult to detect the phase distribution of microlenses with large numerical apertures unless the detector is replaced or the microscopic imaging optical path is altered for mapping. A deeper analysis of the underlying physical control mechanism reveals that in off-axis digital holography, pixel resolution affects the size of the spectral space after the Fourier transform of the interference pattern; the stronger the pixel resolution, the larger the corresponding spectral space. For microlenses, the larger the numerical aperture, the larger the spectrum that can be generated. This high-frequency information is mainly concentrated at the edges of the microlens. The refractive power of light increases from the center to the edge of the microlens, resulting in a larger horizontal momentum component, which corresponds to higher frequencies in the spectrum. Without altering the optical path and detector used in microscopic imaging, the size of the spectral space is fixed. The core idea of ​​this invention is to achieve higher frequency phase detection within a limited spectral space.

[0049] The large phase gradient microlens detection system and detection method will be further described below with reference to specific embodiments and accompanying drawings.

[0050] See Figure 1As shown, a large phase gradient microlens detection system includes: a sample optical path for sample setting; a reference optical path for interfering with the sample optical path; a detector 70 for acquiring the interference pattern of a first beam L1 of the sample optical path and a second beam L2 of the reference optical path and performing a Fourier transform on the interference pattern to form a spectral spatial distribution map; and a wavefront modulation component 80 disposed on the reference optical path for modulating the second beam L2, such that the spectral spatial distribution map is completely within the rated spectral space of the detector 70.

[0051] Specifically: both the first beam L1 and the second beam L2 are emitted by a monochromatic light source 10. The output port of the monochromatic light source 10 is provided with a beam splitter 20 and a first beam splitter 31. The first beam splitter 31 splits the beam of the monochromatic light source 10 into the first beam L1 and the second beam L2. The sample optical path is provided with a first objective lens 50, a first lens 60 and a second beam splitter 32 in sequence along the first beam L1. The detector 70 is provided after the second beam splitter 32 along the sample optical path. The reference optical path includes a first reflecting mirror 91, a wavefront modulation component 80 and a second reflecting mirror 92 in sequence. The second beam L2 split by the first beam splitter 31 is reflected by the first reflecting mirror 91 and enters the wavefront modulation component 80. The second reflecting mirror 92 is provided corresponding to the second beam splitter 32. The second beam L2 after passing through the wavefront modulation component 80 is reflected by the second reflecting mirror 92 into the second beam splitter 32 and merges with the first beam L1 into a single beam and interferes. The first beam splitter 31 and the first objective lens 50 have a reserved area for the sample 40 to be placed.

[0052] For a large phase gradient lens (i.e., a sample), the imaging optical path of the sample needs to be magnified onto the detector 70, and a second beam L2 with a suitable wavefront is introduced to interfere with it, so that the interference pattern can be received by the detector. This second beam L2 with a suitable wavefront is modulated by the wavefront modulation assembly 80. Specifically, the wavefront modulation assembly 80 includes multiple optical elements. By selecting at least two suitable optical elements and adjusting the distance between at least two of these optical elements, the second beam L2 is modulated so that the wavefront of the second beam L2 is the same as the wavefront type of the first beam L1 passing through the sample 40. For example, if the sample 40 is a large numerical aperture microlens, the wavefront modulation assembly 80 includes two adjustment lenses, and the distance between the two adjustment lenses satisfies the non-confocal setting of the two adjustment lenses. Specifically, as shown... Figure 3 As shown, since the wavefront of a large numerical aperture microlens is a spherical wavefront, such as Figure 3 From (2) and (3), it can be seen that when the distance between the two lenses satisfies the non-confocal optical path setting (i.e., off-focus O), the resulting wavefront is a spherical wavefront. The direction of deviation affects whether the wavefront is a concave or convex spherical wavefront. When the distance between the two lenses is confocal, the wavefront is a planar wavefront, such as... Figure 3 As shown in (1).

[0053] Of course, using two lenses to modulate the wavefront morphology is only one embodiment. This detection system is applicable to various large phase gradient lens samples. The structural composition of the wavefront modulation component 80 depends on the wavefront form of the sample. For example, if the sample is a large numerical aperture vortex lens, the wavefront modulation component includes two adjusting lenses and a vortex waveplate. The distance between the two adjusting lenses is such that the two adjusting lenses are non-confocal. The vortex waveplate is positioned between the two adjusting lenses or on the opposite outer side of one of the adjusting lenses. The wavefront is modulated into a vortex wavefront by the placement of the vortex waveplate. Of course, the combination of two adjusting lenses and a vortex waveplate is only a preferred combination. Other schemes can also be used, as long as a wavefront of the same type as the sample wavefront is modulated. The wavefront modulation component can include various optical elements, and different combinations of optical elements are selected according to the wavefront type of the sample during use.

[0054] A method for detecting microlenses with large phase gradients, such as Figures 1-3 As shown, the steps include:

[0055] Step 1: Provide a sample 40 of a large phase gradient lens and a large phase gradient microlens detection system as described above.

[0056] Step 2: Place the sample 40 in the sample optical path, and obtain the first interference pattern formed by the interference of the first beam L1 and the second beam L2 passing through the sample 40 through the detector 70. Perform Fourier transform on the first interference pattern to form a first spectral spatial distribution map.

[0057] Step 3: Observe whether the first spectral spatial distribution is completely within the rated spectral spatial range of the detector 70. If yes, proceed to the next step; if no, adjust the wavefront modulation component 80 until the first spectral spatial distribution is completely within the rated spectral spatial range of the detector 70. Specifically, the wavefront modulation component 80 includes multiple optical elements. When adjusting the wavefront modulation component 80: first, select at least two suitable optical elements according to the type of the sample 40; then adjust the distance between the at least two optical elements to modulate the second beam L2, so that the wavefront of the second beam L2 is the same as the wavefront type of the first beam L1 passing through the sample 40; then, while ensuring that the wavefront type of the second beam L2 is the same as the wavefront type of the first beam L1 passing through the sample, continue to adjust the distance between the optical elements until the first spectral spatial distribution is completely within the rated spectral spatial range of the detector 70. Taking the sample 40 as a large numerical aperture microlens as an example: the wavefront modulation component 70 includes two adjustment lenses; when adjusting the distance between the two adjustment lenses, ensure that the distance satisfies the condition that the two adjustment lenses are non-confocal. Using sample 40 as a large numerical aperture vortex lens, the wavefront modulation assembly 80 includes two adjustment lenses and a vortex wave plate, which is disposed between the two adjustment lenses or on the opposite outer side of one of the adjustment lenses; when adjusting the distance between the two adjustment lenses, the distance is made such that the two adjustment lenses are non-confocal.

[0058] Step 4: Take out the sample 40, and use the detector 70 to obtain the second interference pattern formed by the interference of the first beam L1 (excluding the sample 40) and the second beam L2. Perform Fourier transform on the second interference pattern to form a second spectral spatial distribution map.

[0059] Step 5: Using off-axis digital holography, the output first spectral spatial distribution map is numerically filtered to extract first-order information. Then, the output second spectral spatial distribution map is used as the background for background subtraction to obtain the phase distribution regulated by the sample.

[0060] The basic principle of this detection method is as follows: Figure 2 As shown, the sample optical path is typically a plane wavefront when no sample is present. When a miniature lens sample is introduced, the first beam B becomes a spherical wavefront. If an off-axis second beam A interferes with the first beam B, and the interference fringes are recorded with and without the sample, and a Fourier transform is performed on the interference pattern, the following can be obtained: Figure 2 The spectral spatial distribution diagram shown on the right side of the upper middle row. In the absence of a sample, as... Figure 2As shown in the middle image of the top row, the information corresponding to the three points in the spectral space represents the 0th order and ±1st order information after interference (the central point corresponds to the 0th order, and the two points on the sides correspond to the ±1st order respectively). The distance between the three points represents the wave vector difference (referring to the horizontal component projected onto the lens plane), which is the angle between the two beams. The larger the angle, the greater the wave vector difference. Since the second beam A and the first beam B0 without a sample are both plane waves, their wave vectors are fixed, hence the three points. When there is a sample, as shown in the rightmost image of the top row, two very large spots will be generated. The larger the numerical aperture of the microlens, the larger these spots will be. When the spectral space is insufficient, this information cannot be fully acquired.

[0061] By selecting a suitable wavefront for the second beam, the spectral size of the interference pattern can be effectively reduced when a sample is present. Figure 2 As shown in the bottom row. If the second beam A of the spherical wavefront is selected, the spectral space without a sample will change from a point to a spot, while the spectral space with a sample will change from a large spot to a small spot. By selecting a suitable reference wavefront, the sizes of both in the spectral space can be appropriately adjusted to achieve a finite spectral space while measuring a larger spatial frequency signal. The size of the spot represents the wave vector difference (or the difference in momentum parallel components). When both are parallel beams, the wave vector difference is definite and thus appears as a small dot. When one becomes spherical, the wave vector difference becomes a spot, with the maximum wave vector difference corresponding to the spot's boundary. Since the boundary of a large numerical aperture microlens can provide a very large horizontal wave vector component, a large wave vector difference will be generated. Using a suitable reference wavefront can effectively reduce the wave vector difference after interference. This reduced wave vector difference is transferred to the interference pattern between the reference beam and the sample-free beam, thus increasing the size of the corresponding spot in the background spectral space. In this phase distribution measurement scheme, the background interference information (i.e., the phase distribution of the interference between the sample beam and the reference beam without a sample) is subtracted at the end, thus compensating for the wave vector difference again.

[0062] In short, by adjusting the reference wavefront of the second beam, the wave vector difference after interference between the sample wavefront and the reference wavefront is effectively adjusted, reducing the interference wave vector between the sample and the second beam, and increasing the interference wave vector when there is no sample, so that the wave vector difference is within the acceptable spectral range of the system. This allows for the detection of a larger numerical aperture microlens within a limited spatial spectrum.

[0063] To further illustrate the application effects of the large phase gradient microlens detection system and detection method of the present invention, the following embodiments are provided for detailed explanation.

[0064] Example 1

[0065] The sample to be tested is a large numerical aperture metalens with a working wavelength of 532 nm and a lens size of 300 μm * 300 μm. The large phase gradient microlens detection system of this invention is used to detect the sample, which involves imaging and magnifying the sample onto the detector, introducing a reference beam to interfere with it, and recording the interference patterns with and without the sample, as shown in the attached figure. Figure 4 As shown. The interference pattern is subjected to Fourier transform and filtered, and then subjected to inverse Fourier transform. The complex amplitude distributions with and without the sample are compared, and the arc angle is taken to obtain the phase distribution controlled by the corresponding lens sample under test.

[0066] When the reference beam L2 is a plane wave, the obtained spectrum space diagram is as follows: Figure 5 As shown, without a sample, the interference with the reference light corresponds to three points, while with a sample, two large circular fringe spots are generated. These two fringe spots overlap due to their large radii, making it difficult to extract useful information. If local filtering is performed, high-frequency information will be lost, which corresponds to the contribution of the large gradient phase distribution at the edge of the microlens.

[0067] When a suitable reference light wave is selected to interfere with it, such as Figure 6 As shown, by selecting a spherical wavefront, the radius of the obtained spectral spot without a sample is larger than before, while the radius of the spectral spot with a sample is smaller than before, which is beneficial for extracting effective information.

[0068] After numerical filtering, the phase distribution modulated by the large phase gradient lens can be obtained, such as... Figure 7 As shown. Using the same method and selecting a suitable reference wavefront, phase distribution detection with a larger gradient can be obtained, such as... Figure 8 As shown.

[0069] The present invention has been described in detail above with reference to the accompanying drawings and embodiments. Those skilled in the art can make various modifications to the present invention based on the above description. Therefore, certain details in the embodiments should not be construed as limiting the present invention, and the scope of protection of the present invention shall be defined by the appended claims.

Claims

1. A large phase gradient microlens detection system, characterized in that, include: Sample optical path for sample setup; A reference optical path used to form interference with the sample optical path; A detector used to acquire the interference pattern of the first beam of the sample optical path and the second beam of the reference optical path, and to perform a Fourier transform on the interference pattern to form a spectral spatial distribution map; A wavefront modulation assembly is provided on the reference optical path and used to modulate the second beam, such that the spectral spatial distribution is completely within the rated spectral space of the detector; wherein, the wavefront modulation assembly includes a plurality of optical elements, and the second beam is modulated by selecting at least two adapted optical elements and adjusting the distance between at least two optical elements, so that the wavefront of the second beam is the same as the wavefront type of the first beam passing through the sample.

2. The large phase gradient microlens detection system as described in claim 1, characterized in that: The sample optical path includes a first objective lens, a first lens, and a second beam splitter arranged sequentially. The reference optical path includes the wavefront modulation component and the second reflector arranged in sequence. The second reflector is arranged corresponding to the second beam splitter, so that the second beam is reflected by the second reflector into the second beam splitter and combines with the first beam into a single beam and interferes with it. The detector is positioned after the second beam splitter along the sample optical path, and an area for setting the sample is reserved in front of the first objective lens on the sample optical path.

3. The large phase gradient microlens detection system as described in claim 1, characterized in that, The sample is a large numerical aperture microlens, and the wavefront modulation assembly includes two adjustment lenses, the distance between the two adjustment lenses satisfying the non-confocal setting of the two adjustment lenses.

4. The large phase gradient microlens detection system as described in claim 1, characterized in that, The sample is a large numerical aperture vortex lens, and the wavefront modulation assembly includes two adjustment lenses and a vortex wave plate. The distance between the two adjustment lenses satisfies that the two adjustment lenses are non-confocal. The vortex wave plate is disposed between the two adjustment lenses or on the opposite outer side of one of the adjustment lenses.

5. The large phase gradient microlens detection system as described in claim 1, characterized in that, Also includes: Monochromatic light source; A beam expander and a first beam splitter are provided at the light outlet of the monochromatic light source. The first beam splitter splits the light beam of the monochromatic light source into a first beam and a second beam. The reference optical path also includes a first reflector corresponding to the second beam. The second beam is reflected by the first reflector and then enters the wavefront modulation component.

6. A method for detecting a large phase gradient microlens, characterized in that, Including the following steps: Provides a sample of a large phase gradient lens and a large phase gradient microlens detection system as described in claim 1; The sample is placed in the sample optical path, and the detector acquires the first interference pattern formed by the interference of the first beam and the second beam passing through the sample. The first interference pattern is then subjected to Fourier transform to form a first spectral spatial distribution map. Observe whether the first spectral spatial distribution map is completely within the rated spectral spatial range of the detector: if yes, proceed to the next step; if no, adjust the wavefront modulation component until the first spectral spatial distribution map is completely within the rated spectral spatial range of the detector. The sample is removed, and a second interference pattern is obtained by the detector through the interference of the first beam without the sample and the second beam. The second interference pattern is then subjected to Fourier transform to form a second spectral spatial distribution map. Using off-axis digital holography, the output first spectral spatial distribution map is numerically filtered to extract first-order information. Then, the output second spectral spatial distribution map is used as the background for background subtraction to obtain the phase distribution modulated by the sample. When adjusting the wavefront modulation component: First, select at least two suitable optical elements according to the type of the sample; The distance between at least two of the optical elements is then adjusted to modulate the second beam so that the wavefront of the second beam is the same as the wavefront type of the first beam passing through the sample; Then, while ensuring that the wavefront of the second beam is the same as the wavefront type of the first beam passing through the sample, the distance between the optical elements is adjusted until the first spectral spatial distribution map is completely within the rated spectral space of the detector.

7. The method for detecting large phase gradient microlenses as described in claim 6, characterized in that: The sample is a large numerical aperture microlens, and the wavefront modulation component includes two adjustment lenses; When adjusting the distance between the two adjustment lenses, the distance is such that the two adjustment lenses are set to be non-confocal.

8. The method for detecting large phase gradient microlenses as described in claim 6, characterized in that: The sample is a large numerical aperture vortex lens, and the wavefront modulation assembly includes two adjustment lenses and a vortex wave plate. The vortex wave plate is disposed between the two adjustment lenses or on the opposite outer side of one of the adjustment lenses. When adjusting the distance between the two adjustment lenses, the distance is such that the two adjustment lenses are set to be non-confocal.

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