A method for manufacturing a subsurface defect calibration plate and a subsurface defect calibration plate

Abstract

This application provides a method for fabricating a subsurface defect calibration plate and the subsurface defect calibration plate itself, belonging to the field of optical inspection and calibration. The method provided includes: processing a simulated defect structure of a first size on the surface of an optical glass substrate using a femtosecond laser; the first size is larger than the actual defect size; dispersing dielectric microspheres in a volatile mixed solvent to form a microsphere dispersion; dropping the microsphere dispersion onto the surface of the optical glass substrate with the simulated defect structure, filling the simulated defect structure through liquid flow; coating the surface of the optical glass substrate after dropping the microsphere dispersion with an optical adhesive, and covering it with a sealing glass for encapsulation and curing. The method for fabricating a subsurface defect calibration plate and the subsurface defect calibration plate provided in this application can solve the problems of existing subsurface defect calibration plates being unable to accurately simulate composite scenarios of embedded impurities within defects, having complex microsphere filling processes, and limited calibration functions.

Description

Technical Field

[0001] This application relates to the field of optical inspection and calibration technology, and in particular to a method for manufacturing a subsurface defect calibration plate and the subsurface defect calibration plate. Background Technology

[0002] Subsurface defects (SSDs) are micrometer- or nanometer-scale damages that form below the surface of optical components during manufacturing. Typical morphologies include scratches and pitting. These defects significantly reduce the laser damage threshold of optical components and generate unwanted stray light, posing a serious threat to the performance and reliability of high-precision optical systems. Therefore, subsurface defect calibration plates used for calibrating and evaluating testing equipment have become a key tool in optical manufacturing and quality control.

[0003] Currently, there are two main approaches to fabricating subsurface defect calibration plates. The first approach involves directly machining a single simulated defect on the surface of the optical substrate, such as creating isolated scratches or pit arrays through mechanical scribing or laser processing. However, such calibration plates can only simulate a single defect morphology and cannot reproduce the more common composite structures of embedded impurities in real optical components (e.g., polishing powder particles remaining in grinding scratches, or bubbles and impurities encased in pits). This composite structure generates complex optical scattering signals that differ from those of a single defect, making it difficult for existing single-morphology calibration plates to meet the requirements of high-fidelity testing and calibration.

[0004] The second approach attempts to introduce microspheres to simulate impurity particles, typically by sandwiching a microsphere layer between two layers of glass. While this method can provide calibration for particulate defects, its inherent structure prevents the microspheres from being precisely positioned within a pre-defined defect contour, making it difficult to construct the composite scenario of microspheres embedded within defects. Furthermore, existing microsphere-filling processes often rely on complex equipment such as negative pressure adsorption and precision micromanipulators to attempt precise directional control of the microspheres. These methods are not only complex and costly, but also inefficient and have unreliable success rates. Therefore, there is an urgent need for a subsurface defect calibration plate and its preparation method that features simplified processes, strong scenario adaptability, and comprehensive calibration functions to fill the technological gap. Summary of the Invention

[0005] In view of this, this application provides a method for manufacturing a subsurface defect calibration plate and a subsurface defect calibration plate, which can solve the problems that existing subsurface defect calibration plates cannot accurately simulate composite scenarios of embedded impurities in defects, and that the microsphere filling process is complex and the calibration function is limited.

[0006] Specifically, this application is implemented through the following technical solution:

[0007] The first aspect of this application provides a method for manufacturing a subsurface defect calibration plate, the method comprising:

[0008] Multiple simulated defect structures of a first size are fabricated on the surface of an optical glass substrate; the first size is larger than the actual defect size.

[0009] The medium microspheres are dispersed in a volatile mixed solvent to form a microsphere dispersion;

[0010] The microsphere dispersion is dropped onto the surface of the optical glass substrate with the simulated defect structure, and the simulated defect structure is filled by the liquid flow.

[0011] An optical adhesive is coated onto the surface of the optical glass substrate after the microsphere dispersion is added, and then a sealing glass is used for encapsulation and curing.

[0012] A second aspect of this application provides a subsurface defect calibration plate, the subsurface defect calibration plate comprising:

[0013] Optical glass substrate;

[0014] Simulated defect structures are disposed on the surface of the optical glass substrate;

[0015] Dielectric microspheres are embedded inside the simulated defect structure and scattered on the surface of the optical glass substrate;

[0016] An optical adhesive layer covers the surface of the optical glass substrate having the dielectric microspheres and the simulated defect structure;

[0017] The cover glass is bonded and encapsulated to the optical glass substrate through the optical adhesive layer.

[0018] The method for fabricating a subsurface defect calibration plate and the subsurface defect calibration plate provided in this application embed subsurface defects within the calibration plate, and the configuration of these defects is microsphere particles. By using simulated defects larger than the actual defect size and a liquid flow-assisted microsphere filling design, the effect of achieving high-fidelity calibration function with simplified operation is achieved. On the one hand, a simulated defect structure larger than the actual defect size is processed using a femtosecond laser. This utilizes the characteristics of the ultrashort pulse of the femtosecond laser to ensure that the defect morphology is regular and the edges are clear. On the other hand, the size enlargement significantly increases the contact probability between the microsphere and the defect. Combined with the fluidity and capillary action of the volatile mixed solvent, the dielectric microspheres can naturally fill into the interior of the defect without complex orientation control equipment. This accurately reproduces the real composite subsurface defect scenario of embedded impurities in optical components, allowing the calibration signal to highly match the optical response characteristics of the actual detection scenario, thereby improving calibration accuracy. On the other hand, the microsphere dispersion uses a specific ratio of anhydrous ethanol and propylene glycol as solvents, combined with ultrasonic treatment to achieve uniform dispersion of microspheres. This avoids microsphere aggregation and allows sufficient time for microsphere filling. Subsequent coating with a low-viscosity optical adhesive and encapsulation with an ultra-thin capping glass not only firmly fixes the microspheres to the defects, ensuring the structural stability of the calibration plate for long-term use, but also minimizes the additional optical path difference introduced by the encapsulation structure, avoiding interference with the calibration signal. At the same time, the microspheres embedded in the defects form composite subsurface defects, while the microspheres remaining on the substrate surface can serve as independent particulate defects. This allows a single calibration plate to simultaneously meet the calibration requirements of two types of defects, effectively covering different detection scenarios and reducing the cost of detection consumables and operational complexity. Furthermore, the entire preparation process does not require complex tooling such as precise alignment and negative pressure adsorption, making it simple to operate and with a low barrier to entry. Attached Figure Description

[0019] Figure 1 A flowchart of an embodiment of the method for fabricating a subsurface defect calibration plate provided in this application;

[0020] Figure 2 This is a side view of the liquid flow direction of a microsyringe shown in this application;

[0021] Figure 3 This is a schematic diagram of the structure of Embodiment 2 of the subsurface defect calibration plate provided in this application;

[0022] Explanation of reference numerals in the attached figures:

[0023] 1: Optical glass substrate;

[0024] 2: Simulate defective structures;

[0025] 21: Side view of the long side of the scratch defect;

[0026] 22: Side view of pitting defects;

[0027] 3: The flow direction of the microsphere dispersion;

[0028] 4: Medium microspheres;

[0029] 5: Optical adhesive layer;

[0030] 6: Cover glass. Detailed Implementation

[0031] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0032] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0033] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0034] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0035] Example 1

[0036] Figure 1 This is a flowchart of an embodiment of the method for fabricating a subsurface defect calibration plate provided in this application. Please refer to... Figure 1 The method provided in this embodiment may include:

[0037] S101. On the surface of an optical glass substrate, a plurality of simulated defect structures of a first size are processed; the first size is larger than the actual defect size.

[0038] It should be noted that before fabricating the simulated defect structure, an optical glass substrate must first be prepared and pretreated. Fused silica glass or K9 optical glass is preferred for the optical glass substrate. Fused silica glass, due to its high transmittance from the ultraviolet to the infrared band, extremely low coefficient of thermal expansion, and excellent chemical stability, is a preferred choice for high-precision optical inspection applications. K9 optical glass, on the other hand, offers good transmittance in the visible light region and is cost-effective, making it suitable for general-purpose inspection and calibration needs. Specifically, the optical glass substrate is designed with dimensions of 25-55mm in length and width to fit the sample stage of mainstream optical inspection systems; the thickness is controlled between 1.5-4mm to balance structural support strength and optical transmittance, avoiding unnecessary transmission loss or optical path difference caused by an excessively thick substrate.

[0039] Furthermore, the obtained optical glass substrate undergoes cleaning and activation treatment. First, ultrasonic cleaning with deionized water (power 250~300W, time 12~18 minutes) effectively removes surface-adhered dust and grease. Subsequently, oxygen plasma cleaning (power 90~130W, time 6~10 minutes) further removes organic residues through physical bombardment and chemical reaction, activates the glass surface, and increases its surface energy, thereby enhancing the adhesion of the UV-cured optical adhesive in subsequent processes. Finally, the surface is dried with high-purity (≥99.99%) nitrogen gas to ensure no residual water stains, providing a clean and dry substrate environment for subsequent precision machining.

[0040] After completing the above preprocessing operations, the processing parameters of the femtosecond laser micromachining process are controlled to form the simulated defect structure with a preset morphology and a first size on one side surface of the optical glass substrate. It should be noted that the preset morphology includes scratch-type and pitted-type defects. The same optical glass substrate surface includes at least a first preset number of scratch-type defects of different sizes and a second preset number of pitted-type defects of different sizes, where the first preset number is greater than the second preset number. Specifically, the scratch-type defects have a linewidth of 3~10μm, a length of 5~12mm, and a depth of 1~3μm; the pitted-type defects have a diameter of 5~15μm and a depth of 2~4μm.

[0041] It's important to note that femtosecond laser pulses have extremely short durations, ranging from 100 to 300 femtoseconds. On this ultra-short timescale, the laser energy can reach extremely high peak power instantaneously and is directly vaporized and removed from the material almost simultaneously with its absorption, through nonlinear effects such as multiphoton ionization. The material is primarily removed directly through nonlinear effects like multiphoton absorption, resulting in a minimal heat-affected zone. This effectively prevents substrate cracking or the formation of microcracks, thus producing defect structures with regular morphology and clear edges. Furthermore, the processing parameters for femtosecond laser micromachining are typically a wavelength of 1064 nm, a pulse width of 100–300 fs, and a processing power of 10–25 W. By precisely controlling these parameters, the geometric dimensions of the defect can be accurately controlled.

[0042] It should be noted that the first size is designed to be larger than the actual subsurface defect size to be simulated. This enlarged design can significantly increase the contact probability between the microsphere and the defect, allowing the microsphere to fall naturally into the defect through the flow of liquid and capillary action. This eliminates the need for complex and expensive microsphere orientation manipulation equipment, greatly simplifying the process and lowering the operating threshold.

[0043] Furthermore, two basic morphologies, scratch-type defects and pitting-type defects, are designed to reproduce the most common defect types in optical components. Scratch-type defects simulate linear scratches, while pitting-type defects simulate point-like pits. By integrating these two morphologies, the calibration plate can simultaneously meet the calibration requirements of the testing system for both linear and point-like defects, improving the equipment's versatility. Specifically, on the same optical glass substrate, at least four different sizes of scratch-type defects and at least three different sizes of pitting-type defects are typically designed. The inclusion of more scratch-type defects than pitting-type defects is primarily to more comprehensively cover the range of scattering signal variations corresponding to linear defects of different lengths and widths, thereby more effectively testing the response performance of the testing system to linear defects of various severity levels. This allows the calibration plate to achieve optimal calibration efficiency and coverage within a limited area.

[0044] Specifically, the simulated defect structure is processed on one side surface of the optical glass substrate. To ensure that the calibration plate can generate clear and interference-free detection signals during use, scratch-type defects and pitting-type defects of different sizes are distributed in a regular array on the upper surface of the substrate. The minimum distance between the edges of adjacent defects is not less than 50μm. This distance limit can prevent the optical scattering signals from overlapping or coupling due to the defect spacing being too close, and ensure that the scattering signal of each defect can be independently and clearly acquired and analyzed.

[0045] Furthermore, scratch-type defects are typically arranged parallel to each other in the same direction. This not only facilitates smooth flow of the liquid along the scratch direction when the microsphere dispersion is subsequently added, but also allows the detection system to scan along the direction perpendicular to the scratch to obtain the strongest contrast of the scattered signal. Pockmark-type defects, on the other hand, are evenly distributed in the gaps between the scratch array. This partitioned and staggered arrangement of scratches and pockmarks effectively avoids excessive spatial concentration of different types of defects, thereby ensuring that the calibration plate maximizes the coverage of defect types and sizes within a limited area.

[0046] It should also be noted that after completing the femtosecond laser processing of the simulated defect structure, the optical glass substrate area containing the defect needs to be targeted cleaned to remove processing residues and create conditions for subsequent microsphere filling. Specifically, firstly, the substrate is ultrasonically cleaned with acetone (power 220~280W, time 8~12 minutes). Utilizing the organic solvent properties of acetone, it effectively dissolves glass micro-debris and residual carbides from the heat-affected zone generated during laser processing. Subsequently, anhydrous ethanol is immediately used for ultrasonic cleaning (power 220~280W, time 5~8 minutes) to replace and remove acetone residues, while simultaneously achieving rapid dehydration. Finally, the cleaned substrate is placed in a vacuum drying oven at a temperature of 65~85℃ and a vacuum degree not exceeding 5×10⁻⁶. -3 Dry under Pa conditions for 1.2 to 2.5 hours to thoroughly remove adsorbed water vapor and trace organic impurities from the microcavities inside the defects and the substrate surface. This prevents these residual substances from hindering the flow, spreading, and filling of the microsphere dispersion in subsequent steps, ensuring that the microspheres can smoothly enter and be positioned inside the defects.

[0047] S102. Disperse the medium microspheres in a volatile mixed solvent to form a microsphere dispersion.

[0048] It should be noted that the medium microspheres are preferably silica microspheres or polystyrene microspheres. Specifically, the process of dispersing the medium microspheres in a volatile mixed solvent to form a microsphere dispersion includes: mixing the medium microspheres of a predetermined particle size with the mixed solvent, wherein the mixed solvent includes at least anhydrous ethanol and propylene glycol; and ultrasonically treating the liquid obtained after mixing.

[0049] It should be noted that the preset particle size is 0.5~2μm, that is, the particle size of the dielectric microspheres is strictly controlled within the range of 0.5~2μm, which is 1 / 5~1 / 3 of the defect size. This design ensures that the microspheres can flow smoothly into the defect with the liquid. At the same time, microspheres within this size range can effectively simulate the optical scattering characteristics of impurity particles embedded in subsurface defects in real optical components.

[0050] To achieve stable dispersion of microspheres and meet process requirements, a volatile mixed solvent with a specific ratio is used as the dispersion medium. This mixed solvent is composed of anhydrous ethanol and propylene glycol mixed at a volume ratio of 95:5. In this process, anhydrous ethanol serves as the main solvent, exhibiting good volatility and facilitating rapid removal in subsequent drying steps. The addition of a small amount of propylene glycol, due to its slightly increased viscosity, moderately slows down the overall evaporation rate of the mixed solvent, providing a necessary time window for the microspheres to fully fill defects during liquid flow. This avoids premature deposition or blockage of microspheres at defect inlets due to excessively rapid solvent evaporation.

[0051] In addition, it should be noted that the concentration of the microsphere dispersion is controlled in a low range of 0.05~0.1wt%. This low concentration can effectively prevent the microspheres from agglomerating in the dispersion due to excessive concentration, thereby ensuring that each microsphere can be independently and uniformly dispersed in the solvent. Secondly, this concentration can ensure that a sufficient number of microspheres participate in filling defects while minimizing the formation of too many irregular residual particles on the substrate surface, making the defect signal of the calibration plate more targeted.

[0052] In practice, the medium microspheres with a preset particle size are first initially mixed with the aforementioned mixed solvent. Then, the resulting liquid is subjected to ultrasonic treatment for 15-20 minutes. This ultrasonic treatment, through its powerful ultrasonic cavitation effect, effectively breaks down any soft aggregates that may exist in the dry powder state of the microspheres, ensuring that each microsphere is fully deagglomerated and uniformly dispersed in the solvent, thereby forming a stable and uniform microsphere dispersion.

[0053] It should be further noted that certain conditions must be met for mixing and ultrasonic treatment to obtain a microsphere dispersion with better dispersion effect. Specifically, when mixing the medium microspheres of the preset particle size with the mixed solvent, the mixture should be stirred at a rate of 200-300 rpm for 20-30 minutes at room temperature (20-25℃). This preliminary mixing process allows the medium microspheres to achieve a preliminary and relatively uniform dispersion in the solvent, laying the foundation for subsequent efficient ultrasonic treatment. Then, when ultrasonicating the pre-mixed liquid, in addition to controlling the duration, the ultrasonic power should be set to 100-200W. Simultaneously, measures such as placing the container holding the liquid in an ice-water bath should be taken during the ultrasonic process to keep the liquid temperature below 30℃. This temperature control avoids excessively high liquid temperatures caused by ultrasonic heat generation, which could lead to changes in the solvent evaporation rate or secondary aggregation of microspheres due to intensified Brownian motion, thus ensuring the stability of the dispersion effect. After ultrasonic treatment, the obtained microsphere dispersion is allowed to stand at room temperature for 5-10 minutes. During this standing period, any small number of large microsphere aggregates that may not have been completely dispersed will naturally settle to the bottom under gravity. The upper layer of homogeneous dispersion is then carefully aspirated for subsequent dropwise addition. This design improves the uniformity of the dispersion and effectively prevents large microsphere aggregates from clogging the entrances to the simulated defect structures or affecting the uniformity of filling during subsequent filling processes.

[0054] S103. The microsphere dispersion is added to the surface of the optical glass substrate with the simulated defect structure, and the simulated defect structure is filled by liquid flow.

[0055] It should be noted that, firstly, the optical glass substrate with the simulated defect structure was placed strictly horizontally to ensure that the subsequently added liquid would spread evenly under gravity, rather than flowing tilted to one side, providing a basic environment for the uniform filling of the dielectric microspheres in each defect. Then, using a 10μL microsyringe with a 0.5mm needle diameter, the prepared microsphere dispersion was precisely guided to the area above the simulated defect structure. Different dropping strategies were adopted for different types of defects. Specifically, for scratch-type defects, the liquid was slowly and continuously dropped along its length at a rate of 0.5~1μL per centimeter. This fully utilizes the groove structure of the scratch as a natural microchannel; driven by capillary action, the liquid spontaneously extends along the groove, carrying the dispersed dielectric microspheres along with it, allowing them to naturally fall into the scratch. For pitted defects, the liquid was dropped directly above each pit at a rate of 1~2μL. After contacting the surface, the droplets quickly penetrated into the pits, and during this process, the flow of the liquid carried the microspheres into the pits. The driving force of the above-mentioned filling process mainly comes from the synergistic effect of the liquid's own flow, capillary action, and gravity. This filling method avoids the use of complex equipment such as negative pressure adsorption and precision alignment microscopes, which greatly reduces the operation threshold and technical costs.

[0056] Figure 2 This is a side view of the liquid flow direction of the micro-syringe shown in this application. Please refer to... Figure 2 An optical glass substrate with simulated defect structures was placed horizontally. Then, a microsyringe was used to precisely guide its needle directly above the scratch-type defect and slowly move it along its length while simultaneously extruding a microsphere dispersion. The droplet rapidly penetrated and filled the scratch groove under capillary action. For pitted defects, the syringe needle was positioned directly above the defect for point-to-point application, with the droplet penetrating the pit due to gravity and wetting. The entire process relies on the synergistic effect of the liquid's own flow, capillary action, and gravity to drive the microspheres in the dispersion into and fill the interior of the simulated defect structure. To better understand this, [further details are needed]. Figure 2 The figures are labeled, where 1 represents the optical glass substrate, 21 represents the long side view of the scratch defect, 22 represents the side view of the pit defect, and 3 represents the flow direction of the microsphere dispersion.

[0057] After the dispersion was added, the entire optical glass substrate was allowed to stand for 5-10 minutes to allow the dielectric microspheres time to move and settle. Under the gradual change in liquid viscosity and the continuous effect of gravity, the dielectric microspheres that had entered the defect were able to settle fully to the bottom of the defect structure, achieving initial fixation. After standing, the substrate was transferred to an oven at 60-70°C for 15-20 minutes to dry. Heating promoted the rapid and complete evaporation of the mixed solvent. After the mixed solvent was removed, the microspheres were firmly retained at the bottom of the defect, achieving initial fixation within the defect and laying the foundation for subsequent permanent encapsulation. Simultaneously, trace amounts of dielectric microspheres remaining on the substrate surface were also fixed during this process; these will serve as additional particulate defects, enriching the functionality of the calibration plate.

[0058] It should be noted that the microsphere filling process achieved through the aforementioned liquid flow and capillary action aims to embed a certain number of dielectric microspheres within the simulated defect structure to construct a composite defect scenario, rather than requiring the complete filling of the defect structure. In practice, the distribution of microspheres within the simulated defect structure can be observed under an optical microscope. Since this filling process mainly relies on the flow, wetting, and subsequent solvent evaporation of the dispersion, the final filling ratio of microspheres in the defect (especially the slender grooves of scratch-type defects) usually does not reach 100%. When dielectric microspheres are observed distributed within the defect, and their filling volume approximately occupies 30% to 60% of the defect structure volume, the process requirements can be considered met. This filling ratio range ensures that the composite defect generates a sufficiently strong and characteristic scattering signal, while avoiding the process complexity and instability that may be introduced by excessively pursuing a high filling rate. It also more realistically simulates the non-uniform distribution of impurities within defects in actual optical components.

[0059] S104. After adding the microsphere dispersion, an optical adhesive is coated on the surface of the optical glass substrate, and a sealing glass is placed over it for encapsulation and curing.

[0060] In practice, a layer of low-viscosity UV-curable optical adhesive is coated on the surface of the optical glass substrate that has been filled and dried with microspheres. The viscosity of the UV-curable optical adhesive is controlled within the range of 5~10 mPa·s. This low viscosity characteristic ensures that the adhesive has excellent flowability and permeability, which can fully penetrate into the interior of the simulated defect structure, wrap and wet the medium microspheres that are fixed therein, and fill the tiny gaps between the medium microspheres and the defect walls, thereby achieving firm anchoring of the medium microspheres and preventing them from shifting or falling off during subsequent use.

[0061] It should be noted that the coating process is preferably carried out using a spin coater at a low speed, such as 800~1000 rpm for 8~12 seconds, to ensure that the adhesive forms a film of uniform thickness (5~8μm), which can completely cover all defects and surface microspheres, and avoid introducing unnecessary optical path differences due to excessive local thickness, thereby minimizing interference with the calibration signal itself.

[0062] Furthermore, a cover glass is bonded to the substrate. The material of the cover glass is consistent with that of the main glass substrate (such as fused silica or K9 glass), and its thickness is reduced to 0.05~0.1mm. Using such an ultra-thin cover glass minimizes the additional optical path introduced by the encapsulation structure, ensuring that the wavefront distortion of the excitation and scattered light from the detection system is minimized when passing through the cover glass. This guarantees accurate detection of the original optical response characteristics of subsurface defects and avoids shielding or interference of the calibration signal by the encapsulation structure itself. Specifically, the length and width of this ultra-thin cover glass match the optical glass substrate, both glass surfaces have a surface finish grade of not less than V, and the refractive index difference is ≤0.015.

[0063] During the bonding process, precise alignment is required using an optical microscope, such as one with a magnification of 50 to 100 times, in conjunction with a precision displacement platform. This ensures that the edge alignment deviation between the cover glass and the optical glass substrate is no more than 50 μm. High-precision alignment is essential to ensure the structural consistency and overall aesthetics of the calibration plate edge area.

[0064] After bonding, UV light with a wavelength of 365nm is used at a concentration of 150~200 mW / cm. 2 Irradiate the adhesive under light intensity for 40-60 seconds to complete the curing process. Under these curing parameters, the adhesive can be fully cross-linked and cured to obtain optimal mechanical strength, while avoiding the accumulation of internal stress caused by excessive light intensity or time, which could affect the flatness of the optical glass substrate or cause minute displacement of the dielectric microspheres.

[0065] Finally, edge trimming and surface cleaning will be performed to remove excess adhesive from the edges, ensuring that the surface finish of the calibration board meets the standards and preventing surface defects from interfering with the detection of subsurface defects.

[0066] The method provided in this embodiment uses femtosecond laser processing to create simulated defect structures larger than the actual defect size, combined with a microsphere dispersion prepared using a volatile mixed solvent. The natural filling of the medium microspheres is achieved through liquid flow and capillary action. After coating with an optical adhesive and encapsulation with an ultra-thin capping glass, the method not only accurately reproduces the real composite subsurface defect scenario of embedded impurities in optical components, ensuring a high degree of consistency between the calibration signal and the actual optical response characteristics, thus improving calibration accuracy, but also eliminates the need for complex microsphere orientation manipulation equipment, significantly simplifying the process, lowering the operational threshold, and reducing industrialization costs. Furthermore, the embedded microspheres form composite defects, while the residual microspheres on the substrate surface constitute independent particulate defects, enabling a single calibration plate to meet the calibration needs of two defect types, effectively covering diverse detection scenarios and reducing the cost of detection consumables. Moreover, the thorough penetration and firm fixation of the low-viscosity adhesive and the precise encapsulation with the ultra-thin capping glass ensure the structural stability of the calibration plate for long-term use, minimizing interference from the encapsulation structure on the calibration signal.

[0067] Based on the foregoing description, this application provides a specific embodiment as follows:

[0068] Fabrication method of composite SSD calibration board based on fused silica glass:

[0069] (1) JGS1 fused silica glass was selected as the main glass substrate, with dimensions of 40mm×40mm×2.5mm, surface finish grade V, and refractive index of 1.458. It was then ultrasonically cleaned with deionized water for 15 minutes (power 280W), oxygen plasma cleaned for 8 minutes (power 110W), and dried with nitrogen.

[0070] (2) Femtosecond laser micromachining defects: wavelength 1064nm, pulse width 200fs, power 15W, scanning speed 200μm / s; machining defects include: scratches with line widths of 3μm, 5μm, 8μm, and 10μm and lengths of 6mm, and pits with diameters of 5μm, 10μm, and 15μm.

[0071] (3) Preparation of microsphere dispersion: 1μm silica microspheres were selected and dispersed in a 95:5 mixture of anhydrous ethanol / propylene glycol at a concentration of 0.08wt%, and ultrasonically treated for 18 minutes.

[0072] (4) Microsphere filling: The main glass substrate is placed horizontally, and a 10μL microsyringe is used to drop the microspheres along the scratch at a speed of 0.8μL / cm, above the pits; after standing for 8 minutes, dry in an oven at 70℃ for 18 minutes;

[0073] (5) Applying adhesive: UV-curable optical adhesive, model NOA73, viscosity 8 mPa·s, refractive index 1.462. Spin coat at 900 rpm for 10 seconds to a thickness of 6 μm;

[0074] (6) Sealing and curing: The ultra-thin sealing glass is 40mm×40mm×0.1mm in size, made of JGS1 material, and aligned with optical microscope. The edge alignment deviation is 35μm. It is cured with 365nm UV light with an intensity of 180mW / cm² for 50 seconds. The surface is cleaned with optical grade isopropanol and 0.5mm micro-beveling is done with diamond tool to obtain the composite SSD calibration board.

[0075] Example 2

[0076] Corresponding to the aforementioned embodiment of a method for fabricating a subsurface defect calibration plate, this application also provides an embodiment of a subsurface defect calibration plate.

[0077] Figure 3 This is a schematic diagram of the structure of Embodiment 2 of the subsurface defect calibration plate provided in this application. Please refer to... Figure 3 The subsurface defect calibration plate provided in this embodiment includes:

[0078] Optical glass substrate 1;

[0079] Simulated defect structure 2 is disposed on the surface of the optical glass substrate 1;

[0080] The dielectric microspheres 4 are embedded inside the simulated defect structure 2 and scattered on the surface of the optical glass substrate 1;

[0081] An optical adhesive layer 5 covers the surface of the optical glass substrate 1, which is provided with the dielectric microspheres 4 and the simulated defect structure 2;

[0082] The cover glass 6 is bonded and encapsulated to the optical glass substrate 1 through the optical adhesive layer 5.

[0083] It should be noted that the optical glass substrate 1 is a transparent flat plate with a certain thickness, serving as the main support for the entire calibration plate, and has an upper and lower surface arranged opposite each other. The simulated defect structure 2 is a concave microstructure processed on the upper surface of the optical glass substrate 1, and its cross-sectional shape includes linear grooves (corresponding to scratch-type defects) and dot-shaped pits (corresponding to pitting-type defects). The dielectric microspheres 4 are spherical particles, part of which are embedded and filled inside the pits of the simulated defect structure 2, and the other part is scattered and attached to the upper surface of the optical glass substrate 1, located in the area outside the simulated defect structure 2. The optical adhesive layer 5 is a transparent thin film-like encapsulation layer covering the entire upper surface of the optical glass substrate 1, and its lower surface is in close contact with the upper surface of the optical glass substrate 1, the inner surface of all simulated defect structures 2, and the surface of all dielectric microspheres 4, completely encapsulating and fixing the latter. The capping glass 6 is an ultra-thin flat plate, which is bonded to the optical glass substrate 1 through the optical adhesive layer 5. Specifically, the lower surface of the cover glass 6 is fully bonded to the upper surface of the optical adhesive layer 5, and its planar contour is basically aligned with the planar contour of the optical glass substrate 1, together forming a complete, sealed flat-shaped package.

[0084] For more details and other related information, please refer to the preceding descriptions; they will not be repeated here.

[0085] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for fabricating a subsurface defect calibration plate, characterized in that, The method includes: By controlling the processing parameters of the femtosecond laser micromachining process, multiple simulated defect structures with a preset morphology and a first size are formed on the surface of an optical glass substrate; the first size is larger than the actual defect size. Medium microspheres with a particle size of 0.5~2μm were mixed with a volatile mixed solvent consisting of anhydrous ethanol and propylene glycol in a volume ratio of 95:

5. The resulting liquid was ultrasonically treated for 15~20 minutes to form a microsphere dispersion with a concentration of 0.05~0.1wt%. The microsphere dispersion is dropped onto the surface of the optical glass substrate with the simulated defect structure, and the simulated defect structure is filled by the liquid flow. An optical adhesive is coated onto the surface of the optical glass substrate after the microsphere dispersion is added, and then a sealing glass is used for encapsulation and curing.

2. The method according to claim 1, characterized in that, The simulated defect structure includes at least scratch-type and pitted-type defects. The same optical glass substrate surface includes at least a first preset number of scratch-type defects of different sizes and a second preset number of pitted-type defects of different sizes, wherein the first preset number is greater than the second preset number; wherein the scratch-type defect has a linewidth of 3~10μm, a length of 5~12mm, and a depth of 1~3μm; and the pitted-type defect has a diameter of 5~15μm and a depth of 2~4μm.

3. The method according to claim 1, characterized in that, The step of dropping the microsphere dispersion onto the surface of the optical glass substrate containing the simulated defect structure includes: An optical glass substrate is placed horizontally, and the microsphere dispersion is guided to the area above each simulated defect structure using a micro-injector. The medium microspheres in the microsphere dispersion are filled into the defect through the flow of the liquid and capillary action.

4. The method according to claim 1, characterized in that, After the microsphere dispersion is dropped onto the surface of the optical glass substrate with the simulated defect structure, the medium microspheres are allowed to stand for 5 to 10 minutes until they sink to the bottom of the simulated defect structure, and then dried at 60 to 70°C.

5. The method according to claim 1, characterized in that, The process of coating an optical adhesive onto the surface of an optical glass substrate after the microsphere dispersion has been added, and then covering it with a sealing glass for encapsulation and curing, includes: A layer of adhesive is applied to cover and fix the dielectric microspheres, which are then bonded to a sealing glass. The adhesive is then cured by light to obtain the encapsulated calibration plate.

6. The method according to claim 5, characterized in that, Curing is performed using UV light with a wavelength of 365nm and a curing light intensity of 150~200mW / cm². 2 The viscosity of the adhesive is 5~10 mPa·s; the thickness of the capping glass is 0.05~0.1 mm.

7. A subsurface defect calibration plate, characterized in that, The subsurface defect calibration plate is prepared based on the method according to any one of claims 1-6, and the subsurface defect calibration plate comprises: Optical glass substrate; Simulated defect structures are disposed on the surface of the optical glass substrate; Dielectric microspheres are embedded inside the simulated defect structure and scattered on the surface of the optical glass substrate; An optical adhesive layer covers the surface of the optical glass substrate having the dielectric microspheres and the simulated defect structure; The cover glass is bonded and encapsulated to the optical glass substrate through the optical adhesive layer.

Images