A monitoring device and method for measuring the directionality and thickness of an ultrathin nanofilm

Abstract

This invention discloses a monitoring device for measuring the directionality and thickness of ultrathin nanofilms, comprising the following optical paths: an incident optical path, where S-polarized light emitted from an S-polarized source is split into two S-polarized beams by a non-polarized beam splitter; one beam enters a first camera, and the other enters a polarized beam splitter. The incident S-polarized light, after passing through the polarized beam splitter, passes through a quarter-wave plate to form circularly polarized light, which then enters the thin film; a reflected optical path, where the incident light is reflected at the thin film, and after passing through a quarter-wave plate, becomes P-polarized light, which enters the polarized beam splitter and is reflected to a second camera; and a transmitted optical path, where the incident light is transmitted at the thin film, and the transmitted light enters a third camera. This invention's monitoring device for measuring the directionality and thickness of ultrathin nanofilms achieves precise control of directionality, local film surface flatness, and ultrathin thickness measurement through a single system.

Description

Technical Field

[0001] This invention relates to a monitoring device for measuring the directionality and thickness of ultrathin nanofilms, belonging to the field of laser target technology. Background Technology

[0002] In the high repetition rate target ablation process of laser ion acceleration, the ions generated by laser ion acceleration are usually set to exit along the normal of the thin film. Then, a collimating hole is placed at a distance to diagnose the ions behind the target. Therefore, if the normal of the target does not strictly point to the collimating hole, the measured ion signal will be inaccurate.

[0003] Currently, there is no method to integrate the measurement of thin film directivity within the target cavity. For traditional solid thin film targets, the usual practice is to use mechanical fixing devices to align the target angle; however, for novel targets such as liquid thin films that are suspended and self-supporting, it is impossible to measure their angular deviation using mechanical devices or any contact method. Without being able to measure the angular deviation, it is even more impossible to align the target angle.

[0004] In addition, film thickness is also an important parameter in laser ion acceleration. In existing methods, the thickness of the liquid film target is usually measured in advance and then treated as a solid film. However, the liquid film target is a dynamic target and its thickness may change at any time. Therefore, existing technologies cannot achieve real-time measurement of film thickness and lack effective means to monitor and adjust film thickness.

[0005] For the reasons mentioned above, it is necessary to further study the monitoring methods for the orientation and thickness measurement of ultrathin nanofilms in order to solve the aforementioned problems. Summary of the Invention

[0006] To overcome the above problems, the inventors conducted in-depth research and designed a monitoring device for measuring the directionality and thickness of an ultrathin nanofilm. The device includes an S-polarized light source, a non-polarized beam splitter cube, a polarized beam splitter cube, a quarter-wave plate, a first camera, and a second camera at the front end of the film, thus forming the following optical path:

[0007] The incident light path is formed by the emission of S-polarized light from an S-polarized light source. After passing through a non-polarized beam splitter cube, it is split into two S-polarized light beams. One beam enters the first camera, and the other beam enters the polarized beam splitter cube. The incident S-polarized light passes through the polarized beam splitter cube and then passes through a quarter-wave plate to form circularly polarized light. The circularly polarized light is then incident on the thin film.

[0008] The reflected light path is as follows: circularly polarized light incident on the thin film forms reflected light at the thin film. After passing through a quarter-wave plate, the reflected light becomes P-polarized light. The P-polarized light is incident on a polarization beam splitter cube, which reflects the P-polarized light to the second camera.

[0009] In a preferred embodiment, the device further includes a third camera disposed at the rear end of the thin film.

[0010] The optical path also includes a transmission optical path, where circularly polarized light incident on the thin film forms transmitted light at the thin film, and the transmitted light enters the third camera.

[0011] In a preferred embodiment, the S-polarized light source includes a conventional light source, a half-wave plate, a beam-shrinking unit, and a spatial filtering unit.

[0012] Light emitted from a common light source is converted into S-polarized light by passing through a half-wave plate. The S-polarized light is then compressed by a beam-shrinking unit and filtered out by a spatial filter unit to obtain pure S-polarized light.

[0013] This invention also provides a method for adjusting the orientation of ultrathin nanofilms, comprising the following steps:

[0014] S11. Using an S-polarized light transmission polarization beam splitter cube, the transmitted light passes through a quarter-wave plate to form circularly polarized light, and the circularly polarized light is incident on the thin film. The incident circularly polarized light forms reflected light at the thin film, and the reflected light passes through a quarter-wave plate to form P-polarized light. The P-polarized light is incident on the polarization beam splitter cube 4, and the polarization beam splitter cube reflects the P-polarized light to the second camera, and the second camera outputs the reflected light spot.

[0015] S12. Adjust the thin film to minimize the reflected light spot. At this point, the normal direction of the thin film is parallel to the incident circularly polarized light.

[0016] In a preferred embodiment, the adjustment film includes: adjusting the angle of the film.

[0017] In a preferred embodiment, when the film is a liquid film formed by the collision of fluids ejected from two nozzles, the adjustment further includes: adjusting the flow rates of the two nozzles respectively to make the reflected light spots mirror symmetrical.

[0018] In a preferred embodiment, before S12, there is a step S10: performing beam-target coupling: receiving the transmitted light formed by the incident circularly polarized light at the thin film through a third camera at the rear end of the thin film, and outputting the transmitted light spot; adjusting the front and rear positions of the thin film to minimize the transmitted light spot.

[0019] This invention also provides a method for measuring the thickness of ultrathin nanofilms, comprising the following steps:

[0020] S21. An S-polarized light source is split into two S-polarized beams using a non-polarized beam splitter cube. One beam enters the first camera and outputs the incident light spot through the first camera. The other beam is transmitted through a polarized beam splitter cube. The transmitted light passes through a quarter-wave plate to form circularly polarized light, which then enters the thin film. The incident circularly polarized light forms reflected light at the thin film. The reflected light passes through a quarter-wave plate to form P-polarized light, which enters the polarized beam splitter cube. The polarized beam splitter cube reflects the P-polarized light to the second camera, which outputs the reflected light spot through the second camera.

[0021] S22. By comparing the incident light spot and the reflected light spot, the reflectivity of the thin film is obtained;

[0022] S23. Determine the film thickness based on the relationship between reflectivity, incident light wavelength, and film thickness.

[0023] In a preferred embodiment, thin film orientation adjustment is performed before S21.

[0024] In a preferred embodiment, in S23, the relationship between reflectivity, incident light wavelength, and film thickness is as follows:

[0025]

[0026] Where λ represents the wavelength of the incident light, θ represents the incident angle, and h represents the film thickness;

[0027] R(h,λ,θ) represents the reflectivity of the thin film to incident light, R0(λ,θ) represents the reflectivity of the thin film interface as determined by Fresnel's law of reflection, and δ(h,λ,θ) represents the optical path difference of the thin film, which is expressed as:

[0028]

[0029] n(λ) represents the refractive index function of the thin film material.

[0030] The beneficial effects of this invention include:

[0031] (1) A system is used to achieve precise control of directionality, local film surface flatness and ultrathin thickness measurement;

[0032] (2) It can be set in the laser target cavity to measure and monitor the liquid film directionality, film surface flatness and liquid film thickness in real time;

[0033] (3) The polarization-dependent beam splitting cube is cleverly used to eliminate the interference of the reflected light from the element surface on the backlight of the low reflectivity film. Attached Figure Description

[0034] Figure 1This diagram illustrates the structural intent of a monitoring device for measuring the orientation and thickness of an ultrathin nanofilm according to a preferred embodiment of the present invention.

[0035] Figure 2 The reflected light spots of smooth and uneven liquid films are shown;

[0036] Figure 3 The diagram shows a reflected light spot obtained during the flatness adjustment process of an ultrathin nanofilm according to a preferred embodiment of the present invention.

[0037] Figure label:

[0038] 1-film;

[0039] 22-Half-wave plate;

[0040] 23-Beamcontraction Unit;

[0041] 24-Spatial filtering unit;

[0042] 3-Unpolarized beam splitter cubic;

[0043] 4-Polarization beam splitter cubic;

[0044] 5-quarter wave plate;

[0045] 61 - First Camera;

[0046] 62 - Second camera;

[0047] 7-Third camera. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present invention will become clearer and more apparent.

[0049] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0050] This invention provides a monitoring device for measuring the orientation and thickness of ultrathin nanofilms, such as... Figure 1 As shown, an S-polarized light source, a non-polarized beam splitter 3, a polarized beam splitter 4, a quarter-wave plate 5, a first camera 61, and a second camera 62 are arranged at the front end of the thin film 1, thereby forming the following optical path:

[0051] The incident light path is formed by the emission of S-polarized light from the S-polarized light source, which is split into two S-polarized light beams after passing through the non-polarized beam splitter cube 3. One beam enters the first camera 61, and the other beam enters the polarized beam splitter cube 4. The incident S-polarized light passes through the polarized beam splitter cube 3 and then passes through the quarter-wave plate 5 to form circularly polarized light. The circularly polarized light is incident on the thin film 1.

[0052] The reflected light path is as follows: circularly polarized light incident on thin film 1 forms reflected light at thin film 1. The reflected light passes through quarter-wave plate 5 to form P-polarized light. The P-polarized light is incident on polarization beam splitter 4 and reflected by polarization beam splitter 4 to the second camera 62.

[0053] Since the reflected light of thin film 1 is very weak, it is comparable in intensity to the reflected light of other devices in the optical path. However, the reflected light of thin film 1 overlaps with the reflected light of other devices in the optical path, which makes it difficult to accurately measure the reflected light of thin film 1, and thus makes it impossible to detect the directionality of the thin film.

[0054] In this invention, the interference of reflected light from the element surface on the backlight of the low-reflectivity thin film is eliminated by using a polarization-dependent beam-splitting cubic method.

[0055] The polarization beam splitter cube 4 can transmit S-polarized light and reflect p-polarized light. In the incident light path configured above, the reflected light generated by the glass surface of the polarization beam splitter cube 4 is still S-polarized light, which will not enter the second camera but will return along the dotted line, thus not interfering with the second camera's acquisition of the reflected light. Specifically, as... Figure 1 As shown, when s-polarized light is reflected by the right surface of the polarization beam splitter 4, the reflected light is still s-polarized and will return directly along the same path, as indicated by the dashed arrow in the figure, instead of being reflected by the polarization beam splitter 4 into the second camera below. Conversely, the light reflected by the thin film is p-polarized and will enter the second camera 62. This design specifically solves the problem that it is difficult to measure the directionality of thin films with low reflectivity.

[0056] In this invention, the above-described structure enables the simultaneous measurement of the orientation and thickness of the thin film using a single device.

[0057] In a preferred embodiment, the device further includes a third camera 7 disposed at the rear end of the thin film 1.

[0058] The optical path also includes a transmission optical path, where circularly polarized light incident on the thin film 1 forms transmitted light at the thin film 1, and the transmitted light enters the third camera 7.

[0059] The above structure also enables beam-target coupling of the thin film.

[0060] In a preferred embodiment, the S-polarized light source includes a conventional light source, a half-wave plate 22, a beam-shrinking unit 23, and a spatial filtering unit 24.

[0061] Light emitted from a common light source is converted into S-polarized light by passing through a half-wave plate 22. The S-polarized light is then compressed by a beam-shrinking unit 23 and filtered out by a spatial filter unit 24 to obtain pure S-polarized light.

[0062] The beam-concentrating unit 23 can be any unit capable of focusing light, such as a lens or a combination of lenses as the beam-concentrating unit.

[0063] The spatial filtering unit 24 can be any type of filtering unit, such as a combination of a pinhole and a lens, with the pinhole filtering out high-frequency components.

[0064] In a preferred embodiment, a lens is disposed between the polarization beam splitter 4 and the second camera 62. The measurement range and accuracy of the directionality are adjusted by the lens. Specifically, by adjusting the position of the lens, different measurement ranges and accuracies can be achieved according to different object-image relationships.

[0065] The present invention also provides a method for adjusting the orientation of ultrathin nanofilms, preferably using the aforementioned monitoring device for measuring the orientation and thickness of ultrathin nanofilms, comprising the following steps:

[0066] S11. Using an S-polarized light transmission polarization beam splitter cube, the transmitted light passes through a quarter-wave plate to form circularly polarized light, and the circularly polarized light is incident on the thin film. The incident circularly polarized light forms reflected light at the thin film, and the reflected light passes through a quarter-wave plate to form P-polarized light. The P-polarized light is incident on the polarization beam splitter cube 4, and the polarization beam splitter cube reflects the P-polarized light to the second camera, and the second camera outputs the reflected light spot.

[0067] S12. Adjust the thin film to minimize the reflected light spot. At this point, the normal direction of the thin film is parallel to the incident circularly polarized light.

[0068] In high-repetition-rate target ablation using laser-ion acceleration, we need to ensure that the ions generated by the laser-ion acceleration are emitted along the normal to the thin film, meaning that the laser emission direction needs to be parallel to the normal direction of the thin film.

[0069] In a preferred embodiment, adjusting the thin film includes adjusting the angle of the thin film. When the thin film is a flat solid thin film, the size of the reflected light spot can intuitively reflect whether the normal direction of the thin film is parallel to the incident circularly polarized light. When there is an angle between the two, the light spot will increase. The larger the angle, the larger the light spot.

[0070] Furthermore, in high-repetition-rate laser-accelerated target ablation, when the thin film is a liquid film, in addition to requiring the film's normal direction to be parallel to the laser emission direction, the liquid film also needs to have high flatness. Current methods cannot effectively adjust and detect the flatness of the liquid film.

[0071] In this invention, when the film is a liquid film, the liquid film is formed by the collision of fluid ejected from two nozzles. The adjustment also includes adjusting the flow rate of the two nozzles respectively. By adjusting the flow rate, the reflected light spot is made symmetrical, thereby adjusting the flatness of the liquid film.

[0072] Traditionally, it's believed that the smoothness of a liquid film is primarily affected by the dimensions of two nozzles, and that smoothness can be adjusted by fine-tuning the nozzle sizes. Traditional methods involve using a main pump to simultaneously supply liquid to both nozzles, ensuring identical flow rates, and it's assumed that this improves film smoothness. However, this understanding is purely theoretical; currently, there is no method to actually measure film smoothness.

[0073] In this invention, the smoothness of the liquid film is detected by the symmetry of the reflected light spot. The inventors discovered that the higher the smoothness of the liquid film, the more symmetrical its reflected light spot: when the incident light does not irradiate the liquid film perpendicularly, the reflected light spot of a smooth liquid film is a diffraction fringe, such as... Figure 2 As shown in (a), the reflected light spot from the uneven liquid film is as follows: Figure 2 As shown in (b), when the incident light irradiates the liquid film perpendicularly, although diffraction fringes no longer appear in the reflected light spot of the smooth liquid film, the light spot is concentrated, while the reflected light spot of the uneven liquid film is messy and asymmetrical.

[0074] In this invention, unlike the traditional method of adjusting nozzle size, the flow rate of liquid ejected from two nozzles is adjusted separately to adjust the smoothness of the liquid film. This method is quick to adjust and does not require frequent reprocessing of nozzle size. Combined with the reflective light spot, the smoothness of the liquid film can be quickly adjusted.

[0075] According to the present invention, when the film is a liquid film formed by the collision of fluids ejected from two nozzles, the adjustment further includes: adjusting the flow rates of the two nozzles respectively so that the reflected light spots are mirror symmetrical.

[0076] Furthermore, Figure 3 The results obtained during a liquid film flatness adjustment process are shown. It can be seen that as the adjustment is made, the light spot gradually becomes mirror symmetrical, indicating that the liquid film gradually becomes flat. When the light spot is symmetrical and the light spot is at its smallest, it indicates that the liquid film is flat and perpendicular to the incident light.

[0077] In a preferred embodiment, before S12, there is a step S10: performing beam-target coupling. A third camera receives the transmitted light formed at the thin film by the incident circularly polarized light at the thin film's rear end, and outputs a transmitted light spot. The front and rear positions of the thin film are adjusted to minimize the transmitted light spot. At this point, the thin film is located at the optical path focusing position.

[0078] This invention also discloses a method for measuring the thickness of ultrathin nanofilms, preferably using the aforementioned monitoring device for measuring the orientation and thickness of ultrathin nanofilms, comprising the following steps:

[0079] S21. An S-polarized light source is split into two S-polarized beams using a non-polarized beam splitter cube. One beam enters the first camera and outputs the incident light spot through the first camera. The other beam is transmitted through a polarized beam splitter cube. The transmitted light passes through a quarter-wave plate to form circularly polarized light, which then enters the thin film. The incident circularly polarized light forms reflected light at the thin film. The reflected light passes through a quarter-wave plate to form P-polarized light, which enters the polarized beam splitter cube 4. The polarized beam splitter cube reflects the P-polarized light to the second camera, which outputs the reflected light spot through the second camera.

[0080] S22. By comparing the incident light spot and the reflected light spot, the reflectivity of the thin film is obtained;

[0081] S23. Determine the film thickness based on the relationship between reflectivity, incident light wavelength, and film thickness.

[0082] Traditional methods for measuring film thickness typically employ reflectance spectroscopy. According to this method, the reflectance spectrum corresponding to different thicknesses is unique, thus allowing the film thickness to be deduced by measuring the reflectance spectrum. However, the inventors discovered significant limitations. When using conventional light sources, the oscillation of the reflectance spectrum becomes very slow when the film thickness is small, with the oscillation frequency approaching the Gaussian envelope of a typical white light source, leading to substantial errors. Therefore, when the thickness of the film to be measured is less than 150 nm, the measurement accuracy deteriorates significantly, sometimes even becoming unmeasurable. While using a broadband ultraviolet light source can further improve measurement accuracy, the cost is high. Even with a broadband ultraviolet light source, only film thicknesses above 60 nm can be measured, and measurements of film thicknesses below 50 nm are still not possible.

[0083] In this invention, instead of using spectroscopy to measure film thickness, a method is proposed to measure film thickness using the relationship between reflectivity, incident light wavelength, and film thickness.

[0084] In S22, preferably, the ratio of the light intensity integrals of the reflected light spot and the incident light spot is used as the thin film reflectivity by performing light intensity integration on the two light spots respectively.

[0085] In S23, the relationship between reflectivity, incident light wavelength, and film thickness is as follows:

[0086]

[0087] Where λ represents the wavelength of the incident light, θ represents the incident angle, and h represents the film thickness;

[0088] R(h,λ,θ) represents the reflectivity of the thin film, R0(λ,θ) represents the reflectivity of the thin film interface as determined by Fresnel's law of reflection, and δ(h,λ,θ) represents the optical path difference of the thin film, which is expressed as:

[0089]

[0090] n(λ) represents the refractive index function of the thin film material.

[0091] Furthermore, the reflectivity R0(λ,θ) of the thin film interface, as determined by Fresnel's law of reflection, is expressed as:

[0092]

[0093]

[0094]

[0095] Among them, R s (λ,θ), R p (λ,θ) are intermediate variables.

[0096] In a preferred embodiment, prior to S21, the film directivity is adjusted so that the incident light is parallel to the normal direction of the film, i.e., the incident angle θ = π / 2.

[0097] More preferably, the thin film orientation adjustment is performed using the above-described ultrathin nanofilm orientation adjustment method.

[0098] Example

[0099] Example 1

[0100] use Figure 1 The device shown performs thin film orientation adjustment and thickness detection, wherein the thin film orientation adjustment includes the following steps:

[0101] S11. Using an S-polarized light transmission polarization beam splitter cube, the transmitted light passes through a quarter-wave plate to form circularly polarized light, and the circularly polarized light is incident on the thin film. The incident circularly polarized light forms reflected light at the thin film, and the reflected light passes through a quarter-wave plate to form P-polarized light. The P-polarized light is incident on the polarization beam splitter cube 4, and the polarization beam splitter cube reflects the P-polarized light to the second camera, and the second camera outputs the reflected light spot.

[0102] S12. Adjust the thin film to minimize the reflected light spot. At this point, the normal direction of the thin film is parallel to the incident circularly polarized light.

[0103] By shining light directly onto the thin film, the directional deviation of the thin film is obtained by detecting the angle between the reflected light and the direct light: before adjusting the directional deviation of the thin film, the reflection angle of the thin film can reach 3°, and the proton energy obtained after laser target is 8MeV and the proton charge is 4nC; after adjustment, the emission angle of the thin film is close to 0°, and the proton energy obtained after laser target is 10MeV and the proton charge is 10nC.

[0104] Thickness measurement includes the following steps:

[0105] S21. An S-polarized light source is split into two S-polarized beams using a non-polarized beam splitter cube. One beam enters the first camera and outputs the incident light spot through the first camera. The other beam is transmitted through a polarized beam splitter cube. The transmitted light passes through a quarter-wave plate to form circularly polarized light, which then enters the thin film. The incident circularly polarized light forms reflected light at the thin film. The reflected light passes through a quarter-wave plate to form P-polarized light, which enters the polarized beam splitter cube 4. The polarized beam splitter cube reflects the P-polarized light to the second camera, which outputs the reflected light spot through the second camera.

[0106] S22. By comparing the incident light spot and the reflected light spot, the reflectivity of the thin film is obtained;

[0107] S23. Determine the film thickness based on the relationship between reflectivity, incident light wavelength, and film thickness.

[0108] In S23, the relationship between reflectivity, incident light wavelength, and film thickness is as follows:

[0109]

[0110] The final film thickness was 232 nm. The thickness of the film was measured by reflectance spectroscopy, and the result was 238 nm. The error between the two measurements was 2.5%, which proves that the above thickness measurement method is accurate.

[0111] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship in the working state of this invention, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0112] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0113] The present invention has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present invention based on these embodiments, all of which fall within the scope of protection of the present invention.

Claims

1. A monitoring device for the measurement of the directionality and thickness of ultrathin nanofilms, characterized in that it comprises: An S-polarized light source, a non-polarized beam splitter cube (3), a polarized beam splitter cube (4), a quarter-wave plate (5), a first camera (61), and a second camera (62) are arranged at the front end of the thin film (1), thereby forming the following optical path: The incident light path is formed by the emission of S-polarized light from the S-polarized light source. After passing through the non-polarized beam splitter cube (3), it is split into two S-polarized light beams. One beam enters the first camera (61), and the other beam enters the polarized beam splitter cube (4). The incident S-polarized light passes through the polarized beam splitter cube (4) and then passes through the quarter-wave plate (5) to form circularly polarized light. The circularly polarized light is incident on the thin film (1). The circularly polarized light incident on the thin film (1) forms reflected light at the thin film (1). The reflected light passes through the quarter-wave plate (5) and forms P-polarized light. The P-polarized light is incident on the polarization beam splitter (4) and is reflected by the polarization beam splitter (4) to the second camera (62).

2. The monitoring device for measuring the orientation and thickness of ultrathin nanofilms according to claim 1, characterized in that, The device also includes a third camera (7) located at the rear end of the film (1). The optical path also includes a transmission optical path, where circularly polarized light incident on the thin film (1) forms transmitted light at the thin film (1), and the transmitted light enters the third camera (7).

3. The monitoring device for measuring the orientation and thickness of ultrathin nanofilms according to claim 1, characterized in that, The S-polarized light source includes a conventional light source, a half-wave plate (22), a beam-shrinking unit (23), and a spatial filtering unit (24). The light emitted by the ordinary light source is converted into S-polarized light by passing through a half-wave plate (22). The S-polarized light is then compressed by a beam-shrinking unit (23) and then filtered out by a spatial filtering unit (24) to obtain pure S-polarized light.

4. A method for adjusting the orientation of an ultrathin nanofilm, characterized in that, Includes the following steps: S11. Using an S-polarized light transmission polarization beam splitter cube, the transmitted light passes through a quarter-wave plate to form circularly polarized light, and the circularly polarized light is incident on the thin film. The incident circularly polarized light forms reflected light at the thin film, and the reflected light passes through a quarter-wave plate to form P-polarized light. The P-polarized light is incident on the polarization beam splitter cube, and the polarization beam splitter cube reflects the P-polarized light to the second camera, and the second camera outputs the reflected light spot. S12. Adjust the thin film to minimize the reflected light spot. At this point, the normal direction of the thin film is parallel to the incident circularly polarized light. When the film is a liquid film formed by the collision of fluid ejected from two nozzles, the adjustment further includes: adjusting the flow rate of the two nozzles respectively so that the reflected light spots are mirror symmetrical.

5. The method for adjusting the orientation of ultrathin nanofilms according to claim 4, characterized in that, The adjustment film includes: adjusting the angle of the film.

6. The method for adjusting the orientation of ultrathin nanofilms according to claim 4, characterized in that, Before S12, there is also step S10, which involves beam-target coupling: receiving the transmitted light formed by the incident circularly polarized light at the thin film through a third camera at the back end of the thin film, and outputting the transmitted light spot; adjusting the front and back positions of the thin film to minimize the transmitted light spot.

7. A method for measuring the thickness of an ultrathin nanofilm, characterized in that, Includes the following steps: S21. Using a non-polarized beam splitter cube, the S-polarized light source is split into two S-polarized beams. One beam enters the first camera and outputs the incident light spot through the first camera. The other beam is transmitted through a polarized beam splitter cube. The transmitted light passes through a quarter-wave plate to form circularly polarized light, which is incident on the thin film. The incident circularly polarized light forms reflected light at the thin film. The reflected light passes through a quarter-wave plate to form P-polarized light, which is incident on the polarized beam splitter cube (4). The polarized beam splitter cube reflects the P-polarized light to the second camera, which outputs the reflected light spot through the second camera. S22. By comparing the incident light spot and the reflected light spot, the reflectivity of the thin film is obtained; S23. Determine the film thickness based on the relationship between reflectivity, incident light wavelength, and film thickness.

8. The method for measuring the thickness of ultrathin nanofilms according to claim 7, characterized in that, Before S21, thin film orientation adjustment is also performed.

9. The method for measuring the thickness of ultrathin nanofilms according to claim 7, characterized in that, In S23, the relationship between reflectivity, incident light wavelength, and film thickness is as follows: ， in, Indicates the wavelength of the incident light. Indicates the angle of incidence. Indicates film thickness; This indicates the reflectivity of the thin film to incident light. This represents the reflectivity of the thin film interface as determined by Fresnel's law of reflection. The optical path difference of the thin film is expressed as: , This represents the refractive index function of thin film materials.

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