Dark-field confocal microscopy measurement device and method based on spiral spectrum extraction

Abstract

The present invention discloses a dark-field confocal microscopic measurement device and method based on spiral spectrum extraction, belonging to the technical field of optical precision measurement. It includes a vortex illumination light generation module, a beam scanning illumination module, and a spiral spectrum extraction module; by loading a fork grating phase modulation on the liquid crystal spatial light modulator for the light beam reflected by the sample to the detection path, and at the same time using an aperture stop to block the central light intensity of the annular light detection spot, the intensity of the spiral spectrum component corresponding to the vortex order is extracted. It can extract the three-dimensional distribution information of subsurface scratches, wear, subsurface cracks, bubbles and other defects; analyzing the spiral spectrum of the reflected light can obtain information such as the phase of the sample; it can accurately identify and classify the phase defects and amplitude defects of optical elements.

Description

Technical Field

[0001] The present invention relates to the field of optical precision measurement technology, and more specifically, to a dark-field confocal microscopic measurement device and method based on spiral spectrum extraction. Background Art

[0002] High-performance optical components and optical materials have extensive applications in precision instrument manufacturing and major optical engineering research, and are the foundation of the performance of optical systems. Therefore, high-resolution precision detection of the mechanical structure, chemical composition, and lattice structure defects of optical components and optical materials in the surface and subsurface plays an important role. Among them, the phase defect of an optical component will cause the incident light beam to form a focused light field locally, causing local overheating of the component and irreversible damage.

[0003] The dark-field confocal microscopic measurement technology has advantages such as good optical tomography ability, high imaging resolution, and high imaging contrast brought by a dark background, and has become an important means for non-destructive three-dimensional detection of optical components. The ordinary optical dark-field confocal microscopic measurement technology can only detect the geometric defects of samples, such as scratches and bubbles, but its response rate to phase defects is low, and it cannot accurately obtain other physical and chemical properties of the phase defects in optical components.

[0004] Therefore, how to more comprehensively characterize the defect characteristics of optical components and materials, and accurately identify and classify the phase defects and amplitude defects of optical components is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a dark-field confocal microscopic measurement device and method based on spiral spectrum extraction. While obtaining the structural information of the microstructure sample and the defect information such as scratches and wear on the surface of industrial optical samples through dark-field confocal under the illumination of first-order vortex light, the chiral information of the micro-nano structure is obtained by analyzing the vortex scattering dichroic spectrum, providing a new way for micro-nano structure detection. It solves the bottleneck that the ordinary dark-field confocal technology has a single imaging mode and cannot realize phase defect detection, and realizes the physical property detection and analysis of defects to a certain extent.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a dark-field confocal microscopic measurement device based on spiral spectrum extraction, including a vortex illumination light generation module, a beam scanning illumination module, and a spiral spectrum extraction module;

[0008] The vortex illumination light generation module is used to generate a low-order vortex beam for illumination;

[0009] The beam scanning illumination module is used to transmit the low-order vortex beam generated by the vortex illumination light generation module to the sample to be measured to generate the signal light of the sample to be measured;

[0010] The spiral spectrum extraction module is used to receive the signal light of the sample to be measured, and load a fork grating on the liquid crystal spatial light modulator to phase-modulate the signal light, so as to obtain the spiral spectrum of the sample to be measured containing the corresponding order vortex component.

[0011] Further: The vortex illumination light generation module sequentially includes, in the light propagation direction: a laser, a half-wave plate, a first polarizer, a first non-polarizing beam splitter, and a first liquid crystal spatial light modulator.

[0012] Further: The beam scanning illumination module sequentially includes, in the light propagation direction: a first aperture stop, a second non-polarizing beam splitter, a two-dimensional scanning galvanometer, a scanning lens, a tube lens, an objective lens, and the sample to be measured.

[0013] Further: The spiral spectrum extraction module sequentially includes, in the light propagation direction: a second polarizer, a third non-polarizing beam splitter, a second liquid crystal spatial light modulator, a second aperture stop, a focusing lens, a single-mode optical fiber, and a PMT detector.

[0014] Further: The laser is used to emit linearly polarized light, and the half-wave plate and the first polarizer are used to adjust the beam polarization direction of the linearly polarized light to be parallel to the liquid crystal e-axis of the first liquid crystal spatial light modulator. The adjusted linearly polarized light is incident on the first liquid crystal spatial light modulator after being reflected by the first non-polarizing beam splitter.

[0015] Further: A low-order fork grating of a fixed order is loaded on the first liquid crystal spatial light modulator, and a corresponding low-order vortex beam is output.

[0016] Further: The second polarizer is used to adjust the signal light of the sample to be measured collected by the beam scanning illumination module, so that the beam polarization direction of the signal light is parallel to the liquid crystal e-axis of the second liquid crystal spatial light modulator. The signal light passes through the third non-polarizing beam splitter and is incident on the second liquid crystal spatial light modulator.

[0017] Further: ±n-order fork gratings are sequentially loaded on the second liquid crystal spatial light modulator, where n = 0, 1, 2, 3,... 10, and the period of the fork grating is the length of 5-10 pixel points. The second liquid crystal spatial light modulator generates vortex light containing the corresponding order vortex component.

[0018] Further: The aperture of the second aperture stop is complementary and matched with the vortex light containing the corresponding order vortex component generated by the second liquid crystal spatial light modulator, and only allows the spot center of the vortex light containing the corresponding order vortex component to pass through the second aperture stop.

[0019] Further: The PMT detector is used to record the spiral spectrum obtained from the sample to be measured.

[0020] On the other hand, the present invention discloses a dark-field confocal microscopy measurement method based on spiral spectrum extraction, which is realized by a dark-field confocal microscopy measurement device based on spiral spectrum extraction. The specific steps are as follows:

[0021] Step a: After the linearly polarized light emitted by the laser is adjusted by a half-wave plate and a polarizer 1, the polarization direction of the linearly polarized light beam is parallel to the liquid crystal e-axis of the liquid crystal spatial light modulator 1.

[0022] Step b: The adjusted linearly polarized light is reflected by a non-polarizing beam splitter 1 to the liquid crystal spatial light modulator 1, and a fixed low-order fork grating phase is loaded on the liquid crystal spatial light modulator 1 to generate a corresponding low-order vortex beam by the liquid crystal spatial light modulator 1.

[0023] Step c: Control the inclination angle of the non-polarizing beam splitter 1 so that the low-order vortex beam generated by the liquid crystal spatial light modulator 1 can pass through the non-polarizing beam splitter 1 and is isolated by an aperture stop 1.

[0024] Step d: After the isolated low-order vortex beam passes through the non-polarizing beam splitter 2, it is reflected by a two-dimensional scanning galvanometer. The reflected low-order vortex beam passes through a scanning lens, a tube lens, and an incident objective lens in sequence and forms a focused spot on the sample to be measured, realizing the illumination of the sample to be measured.

[0025] Step e: The signal light generated by the sample to be measured returns to the incident objective lens, the tube lens, the lens, and the two-dimensional scanning galvanometer in sequence, and is reflected by the non-polarizing beam splitter 2. The reflected signal light is adjusted by a polarizer 2 to adjust the polarization direction of the signal light beam to be parallel to the liquid crystal e-axis of the liquid crystal spatial light modulator 2.

[0026] Step f: The adjusted signal light passes through the non-polarizing beam splitter 3 and is incident on the liquid crystal spatial light modulator 2. A variable ±n-order fork grating is loaded on the liquid crystal spatial light modulator 2 to generate a vortex light containing corresponding-order vortex components.

[0027] Step g: Control the inclination angle of the non-polarizing beam splitter 3 so that the vortex light containing corresponding-order vortex components generated in step f can be reflected by the non-polarizing beam splitter 3, and the reflected vortex light containing corresponding-order vortex components enters the aperture stop 2, and the beam center of the vortex light containing corresponding-order vortex components coincides with the aperture center of the aperture stop 2.

[0028] Step h: Adjust the aperture of the aperture stop 2 so that only the spot center of the vortex light containing corresponding-order vortex components passes through the aperture stop 2.

[0029] Step i: The vortex light containing corresponding-order vortex components adjusted by the aperture stop 2 is focused onto a single-mode optical fiber through a focusing lens and is transmitted by the single-mode optical fiber to a PMT detector for recording.

[0030] Step j: successively change the order values of the ±n - order fork gratings loaded on the second liquid crystal spatial light modulator, and repeat Steps a - i to obtain the helical spectrum of the sample to be measured.

[0031] As can be seen from the above - mentioned technical solutions, compared with the prior art, the present invention discloses a dark - field confocal microscopic measurement device and method based on helical spectrum extraction, which has the following beneficial effects.

[0032] First, according to the first - order spectral components of the extracted helical spectrum, ordinary dark - field measurement of the sample can be realized; according to the analysis of the high - order spectral components of the extracted helical spectrum, the phase information of the fixed - structure sample can be obtained. At the same time, the amplitude information of the sample with a fixed phase distribution can also be acquired.

[0033] Second, the device uses Gaussian light illumination, avoiding the requirement of the traditional dark - field confocal measurement that the light - passing aperture of the objective lens is larger than the inner diameter of the annular light, which is beneficial to using an objective lens with a large numerical aperture for high - resolution dark - field imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0035] Figure 1 It is a schematic structural diagram of a dark - field confocal microscopic measurement device based on helical spectrum extraction provided by the present invention;

[0036] In the figure: 1 laser, 2 half - wave plate, 3 first polarizer, 4 first non - polarized beam splitter, 5 first liquid crystal spatial light modulator, 6 first aperture diaphragm, 7 second non - polarized beam splitter, 8 two - dimensional scanning galvanometer, 9 scanning lens, 10 tube lens, 11 objective lens, 12 sample to be measured, 13 second polarizer, 14 third non - polarized beam splitter, 15 second liquid crystal spatial light modulator, 16 second aperture diaphragm, 17 focusing lens, 18 single - mode optical fiber, 19 PMT detector. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] In the following, exemplary embodiments of the present invention will be described in conjunction with the accompanying drawings. For the sake of clarity and conciseness, not all features of the actual embodiments are described in the specification. However, it should be understood that many implementation-specific decisions must be made during the development of any such actual embodiment in order to achieve the specific goals of the developer, for example, to comply with those limitations related to the system and the business, and such limitations may vary with different embodiments. In addition, it should also be understood that although the development work may be very complex and time-consuming, for those skilled in the art who benefit from the disclosure of the present invention, such development work is merely a routine task.

[0038] Here, it should also be noted that in order to avoid obscuring the present invention with unnecessary details, only the device structures and / or processing steps closely related to the solution according to the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0039] Embodiment 1: As shown in the attached Figure 1 This embodiment provides a dark-field confocal microscopy measurement device based on spiral spectrum extraction, which is used to realize the dark-field measurement function of the phase defect of the sample.

[0040] It includes a vortex illumination light generation module, a beam scanning illumination module, and a spiral spectrum extraction module;

[0041] The vortex illumination light generation module is used to generate a low-order vortex beam for illumination;

[0042] The beam scanning illumination module is used to transmit the low-order vortex beam generated by the vortex illumination light generation module to the sample to be measured to generate the signal light of the sample to be measured;

[0043] The spiral spectrum extraction module is used to receive the signal light of the sample to be measured, and use a liquid crystal spatial light modulator to load a fork grating to phase-modulate the signal light, and obtain the spiral spectrum of the sample to be measured containing the corresponding-order vortex component.

[0044] The vortex illumination light generation module, in the order of the light propagation direction, is: laser 1, half-wave plate 2, polarizer 1 3, non-polarizing beam splitter 1 4, and liquid crystal spatial light modulator 1 5;

[0045] Laser 1 emits linearly polarized light, the polarization state is adjusted by half-wave plate 1 2 and polarizer 3, and it is incident on liquid crystal spatial light modulator 5 through non-polarizing beam splitter 1 4, and vortex light is generated by loading a fork grating on liquid crystal spatial light modulator 5;

[0046] Specifically: The laser 1 emits linearly polarized laser light. The half-wave plate 2 and the first polarizer 3 are used to adjust the polarization direction of the linearly polarized light beam to be parallel to the liquid crystal e-axis of the first liquid crystal spatial light modulator 5, so that the diffracted light energy of the linearly polarized light passing through the first non-polarizing beam splitter 4 and incident on the first liquid crystal spatial light modulator 5 is concentrated on the first-order diffraction.

[0047] A fixed low-order fork grating is loaded on the first liquid crystal spatial light modulator 5, specifically the superposition of the exp(imφ) phase and the blazed grating. The phase order of the low-order fork grating is m-th order, where m = 0, 1, 2, and the emitted light beam is the vortex beam of the m-th order accordingly. The period of the low-order fork grating is 5 - 10 pixel lengths.

[0048] The beam angle modulated by the first liquid crystal spatial light modulator 5 is controlled by the first non-polarizing beam splitter 4. The inclination angle of the first non-polarizing beam splitter 4 is adjusted so that the first-order diffracted light of the first liquid crystal spatial light modulator 5 enters the subsequent optical path (the optical path for generating the signal light of the sample to be measured), and the first aperture stop 6 isolates the diffracted light of other orders.

[0049] The first aperture stop 6 filters out the vortex beam (specifically the first-order diffracted light in this embodiment) generated by the liquid crystal spatial light modulator 5, and through the two-dimensional scanning galvanometer 8, the scanning lens 9, the tube lens 10, it is incident on the objective lens 11 to achieve two-dimensional point scanning illumination of the sample to be measured 12.

[0050] The beam scanning illumination module is in the order of the light propagation direction: the first aperture stop 6, the second non-polarizing beam splitter 7, the two-dimensional scanning galvanometer 8, the scanning lens 9, the tube lens 10, the objective lens 11, and the sample to be measured 12.

[0051] The helical spectrum extraction module is in the order of the light propagation direction: the second polarizer 13, the third non-polarizing beam splitter 14, the second liquid crystal spatial light modulator 15, the second aperture stop 16, the focusing lens 17, the single-mode optical fiber 18, and the PMT detector 19.

[0052] The objective lens 11 collects the signal light of the sample to be measured, which is reflected by the second non-polarizing beam splitter 7 and enters the helical spectrum extraction module. After the polarization state is adjusted by the second polarizer 13, it is incident on the second liquid crystal spatial light modulator 15 through the third non-polarizing beam splitter 14. By loading a fork grating on the second liquid crystal spatial light modulator 15, the vortex component of the corresponding order is extracted. The second aperture stop 16 blocks the annular vortex light, and the light spot center is transmitted. The focusing lens 17 focuses the scattered light onto the single-mode optical fiber 18, and is recorded by the PMT detector 19.

[0053] More specifically:

[0054] The second polarizer 13 adjusts the polarization direction of the signal light beam collected by the objective lens 11 to be parallel to the liquid crystal e-axis of the second liquid crystal spatial light modulator 15, that is, observing the emitted light beam to make its energy concentrated on the first-order diffraction, and the signal light passes through the third non-polarizing beam splitter 14 and is incident on the second liquid crystal spatial light modulator 15.

[0055] The sample retroreflection carries a helical spectrum reflecting sample information. Successively load an nth-order fork grating phase (n = 0, 1, 2, 3, …) on the liquid crystal spatial light modulator two 15. If there is an -nth-order helical component in the sample retroreflection, then the central light intensity of the spot modulated by the liquid crystal spatial light modulator two 15 is the intensity of the component of the incident light beam at the corresponding helical order. If the sample retroreflection does not contain an -nth-order helical component, then the central light intensity of the spot modulated by the liquid crystal spatial light modulator two 15 is 0, and the light intensity shows an annular distribution.

[0056] More specifically: The aperture of the aperture stop two 16 is set to 0.5 mm - 1 mm, allowing only the center of the spot modulated by the liquid crystal spatial light modulator two 15 to pass through the aperture stop two 16. After passing through the aperture stop two 16, it is collected and detected by the single-mode optical fiber 18 and the PMT detector 19.

[0057] Embodiment 2: This embodiment provides a dark-field confocal microscopic measurement method based on helical spectrum extraction for realizing the dark-field confocal detection and chirality detection functions of a sample. Specific steps:

[0058] Step a: The laser beam emitted by the laser 1 passes through the half-wave plate 2 and the polarizer one 3 to adjust the polarization direction to be parallel to the liquid crystal e-axis of the liquid crystal spatial light modulator one 5.

[0059] Step b: The linearly polarized light is incident on the liquid crystal spatial light modulator one 5 through the non-polarizing beam splitter one 4, and a fixed mth-order fork phase with a lower order (m = 0, 1, 2) is loaded on the liquid crystal spatial light modulator one 5 to make its output beam a vortex light of the corresponding order.

[0060] Step c: Control the inclination angle of the non-polarizing beam splitter one 4 to make the optical axis of the first-order diffracted light generated by the liquid crystal spatial light modulator one 5 coincide with the subsequent optical path (the optical path for generating the signal light of the sample to be measured), and the aperture stop one 6 isolates the diffracted light of other orders.

[0061] Step d: The vortex light is reflected by the non-polarizing beam splitter two 7 and the two-dimensional scanning galvanometer 8, and then passes through the scanning lens 9 and the tube lens 10 and is incident on the objective lens 11 to form a focused spot on the sample to be measured 12, realizing the illumination of the sample to be measured 12.

[0062] Step e: The sample signal light is collected by the objective lens, returned along the original illumination optical path, reflected by the non-polarizing beam splitter two 7, and then adjusted by the polarizer two 13 into a linearly polarized light with a polarization state parallel to the liquid crystal e-axis of the liquid crystal spatial light modulator two 15.

[0063] Step f: The signal light passes through the non-polarizing beam splitter three 14 and is incident on the liquid crystal spatial light modulator two 15, and a ±nth-order fork phase (n = 0, 1, 2, 3, …) is loaded on the liquid crystal spatial light modulator two 5.

[0064] Step g: Control the inclination angle of the non-polarizing beam splitter III 14 so that the vortex light containing the corresponding-order vortex component generated by the liquid crystal spatial light modulator II 15 enters the subsequent optical path (the spiral spectrum generation optical path), and the beam center coincides with the aperture stop II 16;

[0065] Step h: Adjust the aperture of the aperture stop II 16 to 1 mm to block the annular light and pass through the center of the light spot of the vortex light containing the corresponding-order vortex component;

[0066] Step i: Focus the vortex light containing the corresponding-order vortex component adjusted by the aperture stop II 16 through the focusing lens 17 onto the single-mode optical fiber 18, and transmit it through the single-mode optical fiber 18 to the PMT detector 19 for recording;

[0067] Step j: Sequentially change the order values of the ±n-order fork gratings loaded on the liquid crystal spatial light modulator II 15, and repeat steps a-i to obtain the spiral spectrum of the sample to be measured.

[0068] More specifically, in the embodiment of the present invention, the wavelength of the laser beam emitted by the laser 1 is 400 nm - 620 nm.

[0069] Although the disclosed embodiments of the present invention are as above, the content thereof is only an embodiment adopted for facilitating the understanding of the technical solution of the present invention, and is not used to limit the present invention. Any person skilled in the art within the technical field to which the present invention pertains can make any modifications and changes in the form and details of the implementation without departing from the core technical solution disclosed by the present invention. However, the protection scope defined by the present invention shall still be subject to the scope defined by the appended claims.

[0070] In this specification, each embodiment is described in a progressive manner. The key point of each embodiment is to illustrate the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0071] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A dark-field confocal microscopic measurement device based on spiral spectrum extraction, characterized in that: It includes a vortex illumination light generation module, a beam scanning illumination module, and a helical spectrum extraction module; The vortex illumination light generation module is used to generate a low-order vortex beam for illumination; The vortex illumination light generation module sequentially includes, in the light propagation direction: a laser (1), a half-wave plate (2), a first polarizer (3), a first non-polarizing beam splitter (4), and a first liquid crystal spatial light modulator (5); The beam scanning illumination module is used to transmit the low-order vortex beam generated by the vortex illumination light generation module to a sample to be measured to generate a signal light of the sample to be measured; The beam scanning illumination module sequentially includes, in the light propagation direction: a first aperture stop (6), a second non-polarizing beam splitter (7), a two-dimensional scanning galvanometer (8), a scanning lens (9), a tube lens (10), an objective lens (11), and a sample to be measured (12); The helical spectrum extraction module is used to receive the signal light of the sample to be measured, and uses a liquid crystal spatial light modulator to load a fork grating to phase-modulate the signal light, and obtain the helical spectrum of the sample to be measured containing the corresponding order vortex component; The helical spectrum extraction module sequentially includes, in the light propagation direction: a second polarizer (13), a third non-polarizing beam splitter (14), a second liquid crystal spatial light modulator (15), a second aperture stop (16), a focusing lens (17), a single-mode optical fiber (18), and a PMT detector (19).

2. The dark-field confocal microscopic measurement device based on spiral spectrum extraction according to claim 1, characterized in that: The laser (1) is used to emit linearly polarized light, and the beam polarization direction of the linearly polarized light is adjusted by the half-wave plate (2) and the first polarizer (3) to be parallel to the liquid crystal e-axis of the first liquid crystal spatial light modulator (5). The adjusted linearly polarized light is incident on the first liquid crystal spatial light modulator (5) after being reflected by the first non-polarizing beam splitter (4).

3. The dark-field confocal microscopic measurement device based on spiral spectrum extraction according to claim 2, characterized in that: A low-order fork grating of a fixed order is loaded on the first liquid crystal spatial light modulator (5), and a corresponding low-order vortex beam is output.

4. The dark-field confocal microscopic measurement device based on spiral spectrum extraction according to claim 1, wherein: The second polarizer (13) is used to adjust the signal light of the sample to be measured collected by the beam scanning illumination module, so that the beam polarization direction of the signal light is parallel to the liquid crystal e-axis of the second liquid crystal spatial light modulator (15), and the signal light passes through the third non-polarizing beam splitter (14) and is incident on the second liquid crystal spatial light modulator (15).

5. The dark-field confocal microscopic measurement device based on spiral spectrum extraction according to claim 4, wherein: ±n-order fork gratings are sequentially loaded on the second liquid crystal spatial light modulator (15), where n = 0, 1, 2, 3,... 10, the period of the fork grating is the length of 5-10 pixel points, and the second liquid crystal spatial light modulator (15) generates a vortex light containing the corresponding order vortex component.

6. The dark-field confocal microscopic measurement device based on spiral spectrum extraction according to claim 5, wherein: The aperture of the second aperture stop (16) is complementary and matched with the vortex light containing the corresponding order vortex component generated by the second liquid crystal spatial light modulator (15), and only allows the spot center of the vortex light containing the corresponding order vortex component to pass through the second aperture stop (16).

7. A dark-field confocal microscopy measurement method based on spiral spectrum extraction, characterized in that: The specific steps include: Step a, after the linearly polarized light emitted by the laser (1) is adjusted by the half-wave plate (2) and the first polarizer (3), the beam polarization direction of the linearly polarized light is parallel to the liquid crystal e-axis of the first liquid crystal spatial light modulator (5); Step b: The adjusted linearly polarized light is reflected by the first non-polarizing beam splitter (4) to the first liquid crystal spatial light modulator (5), and a fixed low-order fork grating phase is loaded on the first liquid crystal spatial light modulator (5) to generate a corresponding low-order vortex beam by the first liquid crystal spatial light modulator (5). Step c: Control the inclination angle of the first non-polarizing beam splitter (4) so that the low-order vortex beam generated by the first liquid crystal spatial light modulator (5) can pass through the first non-polarizing beam splitter (4) and is isolated by the first aperture diaphragm (6). Step d: After the isolated low-order vortex beam passes through the second non-polarizing beam splitter (7), it is reflected by the two-dimensional scanning galvanometer (8). The reflected low-order vortex beam sequentially passes through the scanning lens (9), the tube lens (10), and the incident objective lens (11) and then forms a focused spot on the sample to be measured (12), realizing the illumination of the sample to be measured (12). Step e: The signal light generated by the sample to be measured (12) sequentially returns to the incident objective lens (11), the tube lens (10), the lens (9), and the two-dimensional scanning galvanometer (8), and then is reflected by the second non-polarizing beam splitter (7). The reflected signal light is adjusted by the second polarizer (13) to adjust the beam polarization direction of the signal light to be parallel to the liquid crystal e-axis of the second liquid crystal spatial light modulator (15). Step f: The adjusted signal light passes through the third non-polarizing beam splitter (14) and then is incident on the second liquid crystal spatial light modulator (15). A variable ±n-order fork grating is loaded on the second liquid crystal spatial light modulator (15) to generate a vortex light containing vortex components of the corresponding order. Step g: Control the inclination angle of the third non-polarizing beam splitter (14) so that the vortex light containing vortex components of the corresponding order generated in step f can be reflected by the third non-polarizing beam splitter (14), and the reflected vortex light containing vortex components of the corresponding order enters the second aperture diaphragm (16), and the beam center of the vortex light containing vortex components of the corresponding order coincides with the aperture center of the second aperture diaphragm (16). Step h: Adjust the aperture of the second aperture diaphragm (16) so that only the spot center of the vortex light containing vortex components of the corresponding order passes through the second aperture diaphragm. Step i: The vortex light containing vortex components of the corresponding order after being adjusted by the second aperture diaphragm (16) is focused onto the single-mode fiber (18) through the focusing lens (17) and is transmitted by the single-mode fiber (18) to the PMT detector (19) for recording. Step j: Sequentially change the order values of the ±n-order fork gratings loaded on the second liquid crystal spatial light modulator (15), and repeat steps a - i to obtain the helical spectrum of the sample to be measured.

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