Holographic alignment system based on metasurface

Abstract

The invention discloses a metasurface-based holographic alignment system, which belongs to the technical field of holographic optics and comprises an observation system, a holographic alignment system shell, an illumination light system and a metasurface holographic reticle, the illumination light system comprises a semiconductor laser, a 1 / 4 wave plate and a reflector; the metasurface holographic reticle is a transmission-type metasurface and is provided with a hologram which uses a metasurface technology and can generate a holographic alignment pattern. The holographic alignment system based on the metasurface is not limited by optical reflection characteristics of a target surface, can work stably in an extreme environment, can provide high-precision and real-time space attitude perception and alignment guide, can overcome inherent defects of existing alignment methods such as laser, and is high in practicability. And the assembly automation level and reliability under complex working conditions are improved.

Description

Technical Field

[0001] The present invention relates to the field of holographic optical technology, and in particular to a holographic alignment system based on a metasurface. Background Art

[0002] In modern industrial manufacturing, especially in industries such as precision machinery, aerospace, automotive manufacturing, and heavy equipment, high-precision component assembly is a key step in ensuring the performance, reliability, and safety of the final product. During the assembly process, accurate spatial posture perception and real-time alignment of parts are crucial to avoiding assembly interference, collisions, and bumps, and achieving perfect fit. However, traditional alignment methods, especially those that rely on optical reflection principles (such as laser alignment), face severe challenges in many complex working conditions, limiting improvements in assembly efficiency and quality.

[0003] Currently, automated or semi-automated assembly systems widely used in industry often employ technologies such as laser tracking, laser scanning, or vision guidance to sense and align part position and posture. These technologies rely primarily on the target part surface's stable reflection of the laser beam or ambient light. However, in many real-world industrial scenarios, part surface conditions often fail to meet this basic requirement, leading to alignment failures or severe degradation of accuracy.

[0004] 1. Challenges in High-Temperature Conditions: During assembly processes involving heat treatment, forging, welding, or additive manufacturing post-processing, parts are often exposed to high temperatures, even becoming incandescent ("red-hot"). During this period, the intense radiation from the high-temperature radiation on the metal surface significantly alters its physical properties, causing its reflection characteristics to become extremely unstable or completely lose its specular reflectivity (appearing as a strong self-luminous object). This prevents laser alignment systems, which rely on reflected signals, from obtaining effective position feedback, forcing the assembly process to be interrupted during the high-temperature phase or requiring low-precision manual operations, significantly reducing production efficiency and automation levels.

[0005] 2. Limitations of complex surface conditions: Even at room temperature, parts may have surfaces that are highly reflective, matte, dark, light-absorbing, oily, rusty, or have complex geometric textures. These factors can interfere with effective laser beam reflection or clear recognition of visual features, reducing the robustness and accuracy of the alignment system.

[0006] 3. Collision Risk and Precision Loss: Due to inaccurate posture sensing or misalignment, accidental collisions or bumps between parts are very likely to occur during assembly. This can not only damage expensive precision parts, resulting in scrap and increased production costs, but can also endanger equipment and operator safety. Furthermore, even small misalignment can be amplified in subsequent processes, ultimately affecting the overall performance and lifespan of the product.

[0007] Therefore, the industry is in urgent need of a metasurface-based holographic alignment system. Summary of the Invention

[0008] The purpose of the present invention is to provide a holographic alignment system based on a metasurface, which is not limited by the optical reflective properties of the target surface, can work stably in extreme environments, and can provide high-precision, real-time spatial posture perception and alignment guidance. It can overcome the inherent defects of existing alignment methods such as lasers and improve the level of assembly automation and reliability under complex working conditions.

[0009] To achieve the above-mentioned object, the present invention provides a metasurface-based holographic alignment system, comprising an observation system, a holographic alignment system housing, an illumination light system, and a metasurface holographic reticle;

[0010] The illumination light system includes a semiconductor laser, a quarter wave plate, and a reflector; the metasurface holographic grating is a transmissive metasurface with a hologram that can generate a holographic alignment pattern using metasurface technology.

[0011] Preferably, the normal direction of the 1 / 4 wave plate is set at 0° to the direction of the light emitted by the semiconductor laser, so that the parallel linear polarized light with an incident angle of 0° is converted into circularly polarized light.

[0012] Preferably, the angle between the main optical axis of the reflector and the light emitted by the semiconductor laser is 22.5°, so as to ensure that the propagation direction of the light emitted by the semiconductor laser changes by 45° after being reflected by the reflector, and the reflector is a plane mirror.

[0013] Preferably, the reflector is placed in the emitting direction of the 1 / 4 wave plate, and the angle between the irradiation direction of the circularly polarized parallel light deflected by the reflector and the normal direction of the metasurface holographic graticule is 0-75°.

[0014] Preferably, the material of the metasurface holographic graticule is silica glass and hydrogenated amorphous silicon.

[0015] Preferably, the thickness of the metasurface holographic grating plate is 1-3 mm, the working area of ​​the metasurface holographic grating plate is a nano-microstructure, and the material of the nano-microstructure is hydrogenated amorphous silicon.

[0016] Preferably, the nanostructure is an elliptical column structure with the following dimensions: semi-major axis a=100-300 nm, semi-minor axis b=40-100 nm, height H=50-200 nm, and the radius of the nanostructure working area circle is 0.05-10 mm.

[0017] Preferably, the wavelength of the light emitted by the semiconductor laser is 500-560 nm or 600-680 nm.

[0018] Preferably, the holographic alignment pattern is a triangular pattern composed of multiple focal points, and the holographic alignment pattern is prepared by first coating a layer of hydrogenated amorphous silicon film on silica glass, and then etching the holographic alignment pattern on the hydrogenated amorphous silicon film by electron beam etching.

[0019] Preferably, the illumination light system and the metasurface holographic graticule are arranged inside a housing of the holographic alignment system, and an observation window is provided on the housing of the holographic alignment system.

[0020] Therefore, the present invention adopts the above-mentioned holographic alignment system based on metasurface, and the beneficial effects are as follows:

[0021] 1) Revolutionary high-temperature adaptability: The metasurface holographic alignment system can be directly applied to align metal parts heated to a red-hot state, because its operation does not rely on the reflected light of the parts, but rather analyzes the distortion or feature points of the actively projected holographic pattern in the presence of a high-temperature target.

[0022] 2) Revolutionary and excellent anti-interference ability: The metasurface holographic alignment system is insensitive to oil, rust, reflection, matte and other conditions on the surface of parts, and maintains high reliability in harsh industrial environments.

[0023] 3) Revolutionary high-precision spatial perception: The metasurface’s holographic alignment system provides real-time high-precision measurement and feedback of six degrees of freedom (position and attitude).

[0024] 4) Revolutionary intuitive guidance and collision avoidance: The metasurface’s holographic alignment system intuitively guides operations by superimposing holographic alignment instructions on the real scene (such as using AR glasses or projection), significantly reducing the risk of collisions and bumps, and improving the success rate of assembly in one go.

[0025] 5) Revolutionary improvement in automation level: The metasurface holographic alignment system paves the way for automated assembly in traditionally “forbidden zones” such as high temperature and complex surfaces.

[0026] 6) Using an artificially designed metasurface as a holographic graticule, based on the principle of PB phase, it can precisely control the wavefront phase of the light beam irradiated on it, thereby precisely controlling the transmission direction of the light beam, and can achieve alignment accuracy far exceeding that of traditional holography.

[0027] 7) The metasurface diffraction pattern that forms the diffraction graticule in the present invention is concentrated in the center of the entire observation window. In the remaining area without the diffraction pattern, only silica glass exists. When the holographic sight is aimed at the target, the light from the target can enter the observation system with minimal attenuation, greatly improving the light transmittance of the observation window and making the observation window brighter.

[0028] 8) The metasurface diffraction pattern that forms the diffraction graticule is precisely designed to greatly improve its light deflection efficiency. This eliminates the need for high-power lasers to ensure that the observation system can observe clear and bright holographic alignment patterns even in strong ambient light. This significantly reduces laser energy consumption and increases the overall battery life of the holographic alignment system.

[0029] 9) Use a small working area, the working area is less than 1mm 2 Therefore, there is no need to expand the light beam generated by the semiconductor laser, fewer components, smaller size, saving assembly space, reducing the weight of the holographic alignment system itself, and can be adapted to a variety of usage scenarios.

[0030] 10) Metasurface holographic graticules can be prepared using nanoimprinting technology. Compared with traditional holographic graticule preparation methods, this technology has great advantages in terms of preparation speed and production cost when meeting the needs of large-scale preparation, and can significantly reduce production costs.

[0031] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a system schematic diagram of an embodiment of a metasurface-based holographic alignment system of the present invention;

[0033] Figure 2 Schematic diagram of the optical path structure of an embodiment of a holographic alignment system based on a metasurface of the present invention;

[0034] Figure 3 This is a diagram showing the results of using a metasurface microstructure to control the phase of a light beam in an embodiment of a metasurface-based holographic alignment system of the present invention;

[0035] Figure 4 This is a far-field optical power diagram of circularly polarized light after passing through a metasurface holographic graticule in an embodiment of a metasurface-based holographic alignment system of the present invention;

[0036] Figure 5 It is a holographic alignment posture sensing measurement pattern of a metasurface holographic reticle in an embodiment of a metasurface-based holographic alignment system of the present invention;

[0037] Figure 6 yes Figure 5 An enlarged schematic diagram of a single pattern in ;

[0038] Figure 7 yes Figure 6 Schematic diagram of a single metasurface nanostructure in .

[0039] Reference numerals

[0040] 1. Semiconductor laser; 2. Quarter wave plate; 3. Reflector; 4. Metasurface holographic reticle; 5. Holographic alignment system housing; 6. Observation system; 7. Holographic alignment system; 8. Components to be assembled; 9. Relative reference element. DETAILED DESCRIPTION

[0041] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0042] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used in the present invention should be the common meanings understood by people with ordinary skills in the field to which the present invention belongs.

[0043] Example 1

[0044] like Figure 1 As shown, the present invention provides a metasurface-based holographic alignment system, including an observation system 6, a holographic alignment system housing 5, an illumination light system, and a metasurface holographic graticule 4.

[0045] Among them, the illumination light system and the metasurface holographic graticule 4 are arranged inside the holographic alignment system housing 5. The holographic alignment system housing 5 is provided with an observation window for observing the target and the holographic alignment pattern. The observation system 6 obtains image information through the observation window.

[0046] The illumination light system includes a semiconductor laser 1, a quarter wave plate 2, and a reflector 3. Among them, the semiconductor laser 1 uses a model with a wavelength of 532nm, which is in the range of 500-560nm, and the light it emits is parallel linear polarized light. The normal direction of the quarter wave plate 2 is set at 0° to the direction of the light emitted by the semiconductor laser 1, thereby converting parallel linear polarized light with an incident angle of 0° into circularly polarized light. The reflector 3 is a plane mirror, and the angle between its main optical axis and the light emitted by the semiconductor laser 1 is set to 22.5°, ensuring that the propagation direction of the light emitted by the semiconductor laser 1 changes by 45° after being reflected by the reflector 3. The reflector 3 is placed in the emitting direction of the quarter wave plate 2, and the angle between the irradiation direction of the circularly polarized parallel light after deflection by the reflector 3 and the normal direction of the metasurface holographic graticule 4 is 45°.

[0047] The metasurface holographic reticle 4 is a transmissive metasurface made of silica glass and hydrogenated amorphous silicon. Its thickness is set at 2 mm, and its working area is a nanostructure made of hydrogenated amorphous silicon. Its specific dimensions are: semi-major axis a = 200 nm, semi-minor axis b = 70 nm, height H = 120 nm, and the radius of the nanostructure's working area is 0.05 mm, resulting in a working area less than 1 mm. 2 .

[0048] At the same time, the metasurface holographic reticle 4 has a hologram that can generate a holographic alignment pattern using metasurface technology. In this embodiment, the holographic alignment pattern is a triangular pattern composed of multiple focal points. The holographic alignment pattern is prepared by first coating a layer of hydrogenated amorphous silicon film on silica glass, and then etching the hydrogenated amorphous silicon film by electron beam etching. Figure 5 The holographic alignment pattern shown.

[0049] Figure 6 This is an enlarged schematic diagram of a single pattern in the holographic alignment posture sensing measurement pattern, which is a schematic diagram of the arrangement of the metasurface nanostructures, where the rotation angle of the nanostructures and the specific size of each nanostructure are accurately calculated by computer. Figure 7 The green structure in Figure 6 Schematic diagram of a single metasurface nanostructure in .

[0050] like Figure 2 The figure shows a schematic diagram of the optical path structure of the system. The holographic alignment system 7 is assembled on the component to be assembled 8. The light emitted by the semiconductor laser 1 passes through the 1 / 4 wave plate 2. The 1 / 4 wave plate 2 converts the incident linear polarized light into circularly polarized light. Then, after being deflected by the reflector 3, the circularly polarized light is irradiated onto the metasurface holographic graticule 4 (containing metasurface holographic information) to form a holographic image of the graticule mark. At this time, the observation system 6 can see the preset holographic alignment pattern in the observation direction. This holographic alignment pattern is a virtual image of the holographic alignment pattern at an approximately infinite distance from the observation system 6. When observed through the observation window, the holographic pattern can reflect the posture of the component to be assembled 8 on which this holographic aiming system is assembled and the position information relative to the reference element 9.

[0051] In this embodiment, the holographic reticle 4 is a metasurface structure. When circularly polarized light is irradiated onto the nanostructures on it, its phase changes according to the rotation direction of the nanostructures. The phase change caused by this reason is called "PB phase". When we precisely control the rotation direction of each nanostructure, we can use the generated PB phase to adjust the output light to the desired holographic alignment pattern. The relationship between the rotation direction of the nanostructure and the PB phase of the light beam is as follows: Figure 3 shown. Figure 4This is the optical power diagram of the simulated circularly polarized light after passing through the metasurface holographic dividing plate 4, where the propagation direction of the far field is deflected. This result proves the feasibility of the metasurface holographic dividing plate 4.

[0052] The specific workflow of the system is as follows:

[0053] 1. Semiconductor laser 1 emits parallel linear polarized light with a wavelength of 532nm. The light propagates along the set direction to 1 / 4 wave plate 2. Under the action of 1 / 4 wave plate 2, the parallel linear polarized light is converted into circularly polarized light.

[0054] 2. The circularly polarized light continues to propagate to the reflector 3. After being reflected by the reflector 3, the propagation direction changes by 45° and is irradiated onto the metasurface holographic graticule 4 at an angle of 45°.

[0055] 3. The metasurface holographic graticule 4 precisely controls the wavefront phase of the light beam incident thereon according to the PB phase principle, thereby generating a specific holographic alignment pattern (a triangular pattern composed of multiple focal points).

[0056] 4. Light with the holographic alignment pattern passes through the observation window and enters observation system 6. When aligning the target, observation system 6 captures the target image with the holographic alignment pattern. By analyzing the distortion or feature points of the holographic pattern in the presence of the target, it achieves real-time, high-precision measurement and feedback of six degrees of freedom (position and attitude). Holographic alignment instructions superimposed on the real scene (e.g., using AR glasses or projection) can also provide intuitive guidance.

[0057] In actual application tests, the holographic alignment system was used to align metal parts heated to a red-hot state. The system was not affected by the high temperature and reflected light on the part surface and was able to work stably.

[0058] In the scenario of aligning parts on surfaces with oil stains and rust, the system also maintains high reliability and provides precise alignment guidance, verifying the excellent performance of the metasurface-based holographic alignment system in this embodiment.

[0059] Therefore, the present invention adopts the above-mentioned metasurface-based holographic alignment system, which is not limited by the optical reflection characteristics of the target surface, can work stably in extreme environments, and can provide high-precision, real-time spatial posture perception and alignment guidance. It can overcome the inherent defects of existing alignment methods such as lasers and improve the level of assembly automation and reliability under complex working conditions.

[0060] It is worth noting that the contents not elaborated in detail in the present invention are all prior art and are well known to those skilled in the art.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A holographic alignment system based on a metasurface, characterized in that: include: Observation system, holographic alignment system housing, illumination light system, metasurface holographic reticle; The illumination light system includes a semiconductor laser, a quarter wave plate, and a reflector; the metasurface holographic grating is a transmissive metasurface with a hologram that generates a holographic alignment pattern using metasurface technology.

2. The metasurface-based holographic alignment system according to claim 1, wherein: The normal direction of the 1 / 4 wave plate is set at 0° to the direction of the light emitted by the semiconductor laser, so that the parallel linear polarized light with an incident angle of 0° is converted into circularly polarized light.

3. The metasurface-based holographic alignment system according to claim 2, wherein: The angle between the main optical axis of the reflector and the light emitted by the semiconductor laser is 22.5°.

4. The metasurface-based holographic alignment system according to claim 3, wherein: The reflector is placed in the emitting direction of the 1 / 4 wave plate, and the angle between the irradiation direction of the circularly polarized parallel light after deflection by the reflector and the normal direction of the metasurface holographic graticule is 0-75°.

5. The metasurface-based holographic alignment system according to claim 4, characterized in that: The material of the metasurface holographic graticule is silicon dioxide glass and hydrogenated amorphous silicon.

6. The metasurface-based holographic alignment system according to claim 5, characterized in that: The thickness of the metasurface holographic grating plate is 1-3 mm, the working area of ​​the metasurface holographic grating plate is a nano-microstructure, and the material of the nano-microstructure is hydrogenated amorphous silicon.

7. The metasurface-based holographic alignment system according to claim 6, characterized in that: The nanostructure is an elliptical column structure with the following dimensions: semi-major axis a=100-300 nm, semi-minor axis b=40-100 nm, height H=50-200 nm, and the radius of the nanostructure working area circle is 0.05-10 mm.

8. The metasurface-based holographic alignment system according to claim 1, wherein: The wavelength of the light emitted by the semiconductor laser is 500-560nm or 600-680nm.

9. The metasurface-based holographic alignment system according to claim 1, wherein: The holographic alignment pattern is a triangular pattern composed of multiple focal points. The holographic alignment pattern is prepared by first coating a layer of hydrogenated amorphous silicon film on silica glass, and then etching the holographic alignment pattern on the hydrogenated amorphous silicon film by electron beam etching.

10. The metasurface-based holographic alignment system according to claim 1, characterized in that: The illumination light system and the metasurface holographic graticule are arranged inside the housing of the holographic alignment system, and an observation window is arranged on the housing of the holographic alignment system.

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