A processing method for preparing a C-lens by using a glass ball blank

Abstract

The application relates to the technical field of precision machining of optical communication passive devices, and discloses a machining method for preparing a C-Lens by using a glass ball blank, which comprises the following steps: S1, semi-sphere blank preparation, selecting an optical glass round ball as a base material, pre-adhering the glass ball to the surface of an optical flat disc through photosensitive glue, removing part of the spherical material through grinding and polishing machining, and forming a semi-sphere blank with a preset curvature radius and consistent surface precision; and S2, double-side film plating, loading the semi-sphere blank into a clamp, and enabling the edge non-optical area of the semi-sphere blank to be limited and supported by the clamp. The machining method for preparing the C-Lens by using the glass ball blank can effectively solve the problem in the prior art that the lens is first molded and then plated, the lens is subjected to edge grinding and core setting machining, and then is subjected to film plating treatment, so that the plated film layer is extremely prone to friction, scratching, bumping and damage in the subsequent sorting and assembling process, the optical performance of the lens is lost, and the product rejection rate is high.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology for passive optical communication devices, and specifically to a machining method for preparing C-Lens using glass spherical blanks. Background Technology

[0002] C-Lens are core optical components of optical communication devices such as fiber collimators, optical couplers, and optical switches. Their spherical surface accuracy, curvature consistency, coaxiality, and film integrity directly determine the insertion loss, coupling efficiency, and long-term stability of optical devices.

[0003] Currently, the mainstream mass production of C-Lens in the industry adopts glass rod pendulum grinding process and traditional spherical modification process. However, the traditional pendulum grinding process relies on the mechanical pendulum arm trajectory for grinding and shaping, and the motion trajectory has inherent deviations. It cannot uniformly shape the lens spherical surface, resulting in the product's local surface shape accuracy not meeting the standard. The batch R value has large dispersion, and the yield of high-precision products is low, which cannot meet the assembly and use requirements of high-end optical devices. In addition, the industry's conventional mature process is to first core and shape the lens, and then coat it. After the lens completes the outer edge grinding and core setting process, it is coated. This makes the coated film layer very easy to be rubbed, scratched, and damaged by bumps during subsequent sorting and assembly, resulting in the failure of the lens's optical performance and a high product scrap rate. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a processing method for preparing C-Lens using glass spherical preforms. This method effectively solves the problem in existing technologies where the conventional and mature process involves first core shaping and then coating, followed by edge grinding and core setting before coating. This process leads to the coated layer being easily damaged by friction, scratches, and impacts during subsequent sorting and assembly, resulting in lens optical performance failure and a high product scrap rate.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a processing method for preparing C-Lens using glass sphere preforms, comprising the following steps: S1. Preparation of hemispherical blank: Optical glass spheres are selected as the substrate. The glass spheres are arranged in an array and pre-bonded to the surface of the optical disk with photosensitive adhesive. A constant pressure fixture is used to press down and position the glass spheres so that the bonding height of all glass spheres is consistent. After grinding and polishing, some of the sphere material is removed to form a hemispherical blank with a preset radius of curvature and consistent surface accuracy. S2. Double-sided coating: The hemispherical blank is loaded into the fixture, so that the non-optical area of ​​the edge of the hemispherical blank is limited and supported by the fixture. The effective optical surfaces of the spherical surface and the plane are not obstructed. While the hemispherical blank is kept in the clamped state and is not removed, optical coating is performed on its spherical and plane ends in sequence to complete the double-sided coating. S3. Core taking and edge grinding: After double-sided coating is completed, the original positioning state of the hemispherical blank in the fixture is maintained. The fixture containing the hemispherical blank is directly transferred to the core taking processing station. Based on the positioning reference of the fixture, the outer circumferential surface and flat end of the hemispherical blank are ground and shaped to remove excess material to form a standard cylindrical side surface, and a C-Lens semi-finished product with no film residue on the cylindrical side surface is obtained. S4. Precision cleaning and finished product inspection: Remove the C-Lens semi-finished product from the fixture and perform cleaning, drying and finished product inspection in sequence.

[0006] Furthermore, in step S1, the hemispherical blank obtained after grinding and polishing has a local surface shape error ΔN of no more than 0.3.

[0007] Furthermore, in step S2, the optical coating is an optical antireflection film system adapted to the optical communication band.

[0008] Furthermore, in step S3, a diamond grinding wheel is used to grind the outer periphery of the hemispherical blank, and after forming, there is no coating residue on the side of the cylinder.

[0009] Furthermore, in step S2, the fixture adopts an array-type workstation arrangement, and its structure is adapted to an automated feeding device to automatically clamp the hemispherical blank through mechanical suction.

[0010] A fixture for C-Lens machining includes an upper plate and a lower plate; The surface of the lower plate is provided with countersunk grooves, and multiple countersunk grooves are arranged in an array along the center surface of the lower plate. The countersunk grooves are used to support the flat edge of the hemispherical blank. The surface of the upper plate is provided with limiting circular holes that correspond one-to-one with the positions of the countersunk grooves. The limiting circular holes are used to cooperate with the countersunk grooves to limit and fix the spherical side edge of the hemispherical blank.

[0011] Furthermore, it also includes a limiting unit for locking and fixing the upper plate and the lower plate; The limiting unit includes a plug rod fixedly installed on the outer side of the upper plate. The plug rods are arranged in a circular array along the center line of the upper plate. An annular locking groove is formed on the outer circumferential surface of the plug rod. Locking blocks corresponding to the plug rods are fixedly installed on the outer side of the lower plate. The locking blocks have plug holes that are clearance-fitted with the outer circular surface of the plug rods. A conical hole communicating with the plug hole is also formed on the lower plate.

[0012] Furthermore, the outer circumferential surface of the locking block is provided with a radially penetrating slot, and a spring plate is installed in the slot. Multiple spring plates are provided and distributed in a circumferential array along the central axis of the locking block. The side of the spring plate facing the insertion hole is provided with a snap-fit ​​protrusion, and the side of the spring plate away from the insertion hole is provided with a conical push block.

[0013] Furthermore, an abutment ring is slidably sleeved on the outer side of the locking block. The inner end face of the abutment ring abuts against the conical surface of the conical push block. A guide rod is fixedly installed on the end face of the abutment ring. The guide rod passes through the end wall of the locking block and extends outward. Multiple guide rods are provided and arranged in a circumferential array along the central axis of the abutment ring. A return spring is sleeved on the guide rod. One end of the return spring is fixedly installed on the outer circumferential surface of the guide rod, and the other end of the return spring is fixedly installed on the outer side of the locking block. A magnetic element is embedded in the end face of the abutment ring. The magnetic element is used to attract the end face of the locking block to maintain the locking state.

[0014] The technical solution provided by this invention has the following advantages compared with the prior art: 1. Optical glass spheres are used as the substrate and a flat plate wax or glue ball milling process is used to prepare hemispherical blanks. The glass sphere substrate molding process is mature and has strong structural stability. The lens spherical molding accuracy can be precisely controlled, and the batch surface shape consistency is excellent. It can stably control the local surface shape of the spherical surface within 0.3N, which fully meets the high-precision surface shape requirements of high-end customers and completely solves the problems of unstable surface shape, difficulty in meeting standards, and large batch dispersion of traditional plate milling process.

[0015] 2. The conventional process flow of the industry, which involves first forming the shape and then coating, has been changed to a process flow of hemispherical forming, double-sided coating, and core picking from the same fixture, which solves the problem of scratching the film layer and causing optical performance failure during subsequent edge grinding.

[0016] 3. The design incorporates an integrated fixture with upper and lower components. One fixture is compatible with the two core processes of double-sided coating and core grinding, eliminating the need for secondary disassembly and positioning. While retaining the advantages of traditional processes without coating edge protection, it completely eliminates secondary clamping and positioning errors, significantly improving the coaxiality and batch consistency of finished products.

[0017] 4. Abandoning the outdated mode of traditional single-point clamping and manual feeding, this invention adopts a regular array-type integrated fixture with a regular and uniform workstation layout that is compatible with mechanical suction structure. It can be directly used with automated suction equipment to complete batch automatic feeding and automatic alignment clamping without manual operation of each item. This solves the pain point of traditional coating processes being unable to be automated, and greatly improves feeding efficiency and workstation consistency.

[0018] 5. Double-sided coating is completed in the hemispherical semi-finished state. At this time, the lens has not formed a cylindrical side structure. The core is then ground to form a cylindrical surface. There is no excess film residue on the cylindrical side of the finished product, and the glass substrate is cleanly exposed. This solves the problem of poor adhesion and easy delamination caused by excess film in traditional finished product coating from the source of the process, and improves the long-term stability of the device. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0020] Figure 1 This is a process flow diagram of an embodiment of the present invention; Figure 2 This is a schematic diagram of the optical glass sphere and flat plate being coated with wax according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the hemispherical blank structure according to an embodiment of the present invention; Figure 4 This is a three-dimensional structural diagram of the fixture according to an embodiment of the present invention; Figure 5 This is a three-dimensional structural diagram of the countersunk head lower plate according to an embodiment of the present invention; Figure 6 This is a cross-sectional view of the upper and lower plates according to an embodiment of the present invention; Figure 7 This is an embodiment of the present invention. Figure 6 A magnified structural diagram of part A in the middle; Figure 8 This is a schematic diagram of the three-dimensional separation structure of the locking block and the plug rod in an embodiment of the present invention.

[0021] The labels in the diagram represent: 1. Fixture; 11. Upper plate; 111. Limiting hole; 12. Lower plate; 121. Countersunk groove; 13. Limiting unit; 131. Insert rod; 132. Locking groove; 133. Locking block; 1331. Slot; 1332. Spring plate; 1333. Protrusion; 1334. Conical block; 1335. Abutment ring; 1336. Guide rod; 1337. Return spring; 1338. Magnetic component; 134. Insertion hole; 135. Conical hole. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] The present invention will be further described below with reference to embodiments. Example

[0024] Please see Figures 1-8 This invention provides a technical solution: a processing method for preparing C-Lens using glass sphere preforms, comprising the following steps: S1. Preparation of hemispherical blank: Optical glass spheres are selected as the substrate. The glass spheres are arranged in an array and pre-bonded to the surface of the optical disk with photosensitive adhesive. A constant pressure fixture is used to press down and position the glass spheres so that the bonding height of all glass spheres is consistent. After grinding and polishing, some of the sphere material is removed to form a hemispherical blank with a preset radius of curvature and consistent surface accuracy. S2. Double-sided coating: The hemispherical blank is loaded into the fixture 1, so that the non-optical area of ​​the edge of the hemispherical blank is limited and supported by the fixture 1, and the optical effective surfaces of the spherical surface and the plane are not obstructed. While the hemispherical blank is kept in the clamped state and is not removed, optical coating is performed on its spherical surface and plane end in sequence to complete the double-sided coating. S3. Core taking and edge grinding: After double-sided coating is completed, the original positioning state of the hemispherical blank in the fixture 1 is maintained. The fixture 1 containing the hemispherical blank is directly transferred to the core taking processing station. Based on the positioning reference of the fixture 1, the outer circumferential surface and flat end of the hemispherical blank are ground and shaped to remove excess material to form a standard cylindrical side surface, and a C-Lens semi-finished product with no film residue on the cylindrical side surface is obtained. S4. Precision cleaning and finished product inspection: Take the C-Lens semi-finished product out of fixture 1 and clean, dry and inspect the finished product in sequence.

[0025] In step S1, the hemispherical blank obtained after grinding and polishing has a local surface shape error ΔN of no more than 0.3.

[0026] In step S2, the optical coating is an optical antireflection coating system adapted to the optical communication band.

[0027] In step S3, a diamond grinding wheel is used to grind the outer periphery of the hemispherical blank, and no coating residue remains on the side of the cylinder after forming.

[0028] In step S2, fixture 1 adopts an array-style workstation arrangement, and its structure is adapted to the automated feeding device. The automatic clamping of the hemispherical blank is completed by mechanical suction.

[0029] A fixture for C-Lens machining includes an upper plate 11 and a lower plate 12; The surface of the lower plate 12 is provided with countersunk grooves 121, and multiple countersunk grooves 121 are provided and arranged in an array along the center surface of the lower plate 12. The countersunk grooves 121 are used to support the flat edge of the hemispherical blank. The surface of the upper plate 11 is provided with limiting holes 111 that correspond one-to-one with the positions of the countersunk grooves 121. The limiting holes 111 are used to cooperate with the countersunk grooves 121 to limit and fix the spherical side edge of the hemispherical blank.

[0030] It also includes a limiting unit 13, used to lock and fix the upper plate 11 and the lower plate 12; The limiting unit 13 includes a plug rod 131 fixedly installed on the outside of the upper plate 11. The plug rod 131 is arranged in a circular array along the center line of the upper plate 11. An annular locking groove 132 is opened on the outer circumferential surface of the plug rod 131. A locking block 133 corresponding to the plug rod 131 is fixedly installed on the outside of the lower plate 12. The locking block 133 is provided with a plug hole 134 that is clearance-fitted with the outer circular surface of the plug rod 131. A conical hole 135 communicating with the plug hole 134 is also opened on the lower plate 12.

[0031] The outer circumferential surface of the locking block 133 is provided with a radially penetrating slot 1331. A spring plate 1332 is installed in the slot 1331. Multiple spring plates 1332 are provided and distributed in a circumferential array along the central axis of the locking block 133. A snap-fit ​​protrusion 1333 is provided on the side of the spring plate 1332 facing the insertion hole 134, and a conical push block is provided on the side of the spring plate 1332 away from the insertion hole 134.

[0032] A locking block 133 has a sliding abutment ring 1335 on its outer side. The inner end face of the abutment ring 1335 abuts against the conical surface of the conical push block. A guide rod 1336 is fixedly installed on the end face of the abutment ring 1335. The guide rod 1336 passes through the end wall of the locking block 133 and extends outward. Multiple guide rods 1336 are arranged in a circumferential array along the central axis of the abutment ring 1335. A return spring 1337 is sleeved on the guide rod 1336. One end of the return spring 1337 is fixedly installed on the outer circumferential surface of the guide rod 1336, and the other end of the return spring 1337 is fixedly installed on the outer side of the locking block 133. A magnetic element 1338 is embedded in the end face of the abutment ring 1335. The magnetic element 1338 is used to attract the end face of the locking block 133 to maintain the locking state.

[0033] The principle and advantages of this processing method for preparing C-Lens using glass preforms: Optical glass spheres of uniform size and stable material are selected as the substrate. Using hot-melt optical wax or a highly stable adhesive, the glass spheres are neatly arranged and pre-bonded to the surface of an optical disk with ultra-high flatness. Subsequently, a cylinder-pressing positioning mechanism applying constant pressure uniformly compacts all the bonded glass spheres. This process ensures that the bonding height of each glass sphere is consistent, the force is evenly distributed, and eliminates tilting, offset, and voids, thereby establishing a unified processing benchmark for the entire disk.

[0034] Next, the fixed glass spheres are ground using precision grinding equipment to remove excess material, initially forming a hemispherical blank with a preset radius of curvature. Then, a high-precision polishing disc is used to perform overall fine polishing on the hemispherical surface, aiming to eliminate grinding marks and microscopic defects, achieving a surface finish that meets optical coating standards. Finally, a reflective appearance inspection process is used to screen out defective products with scratches, pitting, chipping, or out-of-tolerance surface shapes, obtaining qualified hemispherical blanks.

[0035] The key to this process lies in the "spherical modification" process of flat plate bonding combined with constant pressure flattening, which can ensure the high uniformity of the processing benchmark of the entire plate, thereby stably controlling the local surface accuracy of the hemispherical blank within 0.3N, and making the radius of curvature R of batch products have excellent consistency, which is significantly better than the traditional upper pendulum grinding process.

[0036] The qualified hemispherical blank is placed in fixture 1, which is designed with a regular array arrangement structure. Its workstation layout is standardized and can be directly adapted to automated picking equipment to realize the mechanical automatic picking, unloading, and alignment clamping of the hemispherical blank, eliminating the dependence on manual operation one by one and laying the foundation for automated mass production. The specific clamping process is as follows: The qualified hemispherical blank is placed with its flat end facing down in the countersunk groove 121 of the lower plate 12. The countersunk groove 121 is designed to both support and avoid the flat coating area. Then, the upper plate 11 is fastened. The surface of the upper plate 11 has a limiting circular hole 111 corresponding to the position of the countersunk groove 121. The two work together to limit and fix the spherical side edge of the hemispherical blank.

[0037] During this locking process, a locking unit within the clamp 1 is utilized. The four corner plug rods 131 of the upper plate 11 are aligned with the tapered holes 135 on the outer side of the lower plate 12 and inserted. The tapered holes 135 have an automatic alignment function, ensuring that the center of the plug rod 131 is coaxial with the plug hole 134 in the locking block 133, achieving precise alignment of the upper and lower plates 12. During locking, a controllable magnetic repulsion force is generated between the magnetic element 1338 on the abutment ring 1335 and the permanent magnet mounted on the locking block 133. In this invention, the magnetic element 1338 is an electromagnet, which is easy for the operator to control. This drives the abutment ring 1335 to slide along the guide rod 1336 and press the tapered block 1334 on the outer side of the spring plate 1332, forcing the spring plate 1332 to undergo elastic deformation, causing the protrusion 1333 on its inner side to engage in the locking groove 132 of the plug rod 131, thereby quickly and reliably locking the clamp 1.

[0038] In traditional precision machining, the alignment of the upper plate 11 and lower plate 12 often relies on the operator's experience or cumbersome auxiliary positioning pins, which is inefficient and prone to human error. In this invention, during the engagement of the upper plate 11 and lower plate 12, the cooperation between the insertion rod 131 and the tapered hole 135 constitutes an automatic alignment system. According to the geometric positioning principle, the tapered hole 135 has a tapered structure with the large end facing upwards and the small end communicating with the insertion hole 134. When the insertion rod 131 is inserted, the spherical design at its end first contacts the inner wall of the large end of the tapered hole 135. At this time, the normal component of the tapered surface is automatically decomposed into an axial guiding force, forcing the insertion rod 131 to slide along the tapered surface until it falls into the bottom insertion hole 134. This process uses geometric constraints to automatically correct horizontal displacement deviations, ensuring that the axes of the insertion rod 131 and the insertion hole 134 are coaxial. This enables high-precision automatic alignment of the upper and lower plates 12 without manual fine alignment intervention. Precise alignment can be achieved without repeated position adjustments, greatly reducing the threshold for manual operation and significantly improving the clamping efficiency and positioning accuracy of automated production lines.

[0039] The fixture 1 only supports and limits the non-optically effective edge areas of the hemispherical blank, leaving the optically effective surfaces (spherical and planar) completely exposed and unobstructed, ensuring no edge defects during the coating process. The assembled fixture 1 is then moved into the vacuum coating equipment, where optical antireflection coatings for the optical communication band are sequentially deposited on the spherical and planar ends of the hemispherical blank. After single-sided coating, pre-cleaning can be performed at the fixture 1 station, followed by coating of the second side, completing the double-sided coating process.

[0040] After double-sided coating, the hemispherical blank remains in its original positioning within the integrated fixture 1 without any disassembly or secondary clamping. The fixture 1 containing the hemispherical blank is then directly transferred to the core-removal machining station. Using the precise positioning reference provided by the fixture 1 itself, the core is automatically cored using a core-removal machine. Subsequently, the outer circumferential surface and flat end of the hemispherical blank are precision ground to remove excess material, forming a standard cylindrical side surface. This process, performed after coating, offers two key advantages: First, by using the same set of fixtures to connect the coating and edge-grinding processes, the coaxiality deviation caused by workpiece disassembly and secondary clamping in traditional processes is completely eliminated, ensuring excellent coaxiality and dimensional consistency of the finished product. Second, the edge-grinding process removes excess material from the hemispherical blank, resulting in the final C-Lens cylindrical surface being an exposed glass substrate without any optical coating. This addresses the issue from the source that residual coating on the cylindrical side of traditional finished products can lead to poor adhesion and easy delamination during subsequent assembly, thus improving the long-term stability of the device.

[0041] The C-Lens semi-finished product is removed from fixture 1 and subjected to a multi-tank ultrasonic cleaning process using a special optical cleaning solution. This process sequentially completes precision cleaning steps including dewaxing (or de-adhesive removal), removal of grinding dust, oil removal, and removal of coating residue. Finally, it undergoes dehydration with high-purity anhydrous ethanol and constant-temperature drying to ensure a highly clean product surface. Subsequently, the finished product undergoes comprehensive performance and dimensional testing, covering key indicators such as appearance defects, outer diameter, length, radius of curvature R-value, local spherical surface shape, optical transmittance, and insertion loss. Defective products are rejected, and qualified finished products are packaged and stored.

[0042] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A processing method for preparing C-Lens using glass sphere preforms, characterized in that, Includes the following steps: S1. Preparation of hemispherical blank: Optical glass spheres are selected as the substrate. The glass spheres are arranged in an array and pre-bonded to the surface of the optical disk with photosensitive adhesive. A constant pressure fixture is used to press down and position the glass spheres so that the bonding height of all glass spheres is consistent. After grinding and polishing, some of the spherical material is removed to form a hemispherical blank with a preset radius of curvature and consistent surface accuracy. S2. Double-sided coating: The hemispherical blank is loaded into the fixture (1), so that the non-optical area of ​​the edge of the hemispherical blank is limited and supported by the fixture (1). The effective optical surfaces of the spherical surface and the plane are not blocked. While the hemispherical blank is in the clamped state and is not removed, optical coating is performed on its spherical surface and plane end in sequence to complete the double-sided coating. S3. Core taking and edge grinding: After double-sided coating is completed, the original positioning state of the hemispherical blank in the fixture (1) is maintained. The fixture (1) containing the hemispherical blank is directly transferred to the core taking processing station. Based on the positioning reference of the fixture (1), the outer circumferential surface and flat end of the hemispherical blank are ground and shaped to remove excess material to form a standard cylindrical side surface, and a C-Lens semi-finished product with no film residue on the cylindrical side surface is obtained. S4. Precision cleaning and finished product inspection: Take the C-Lens semi-finished product out of the fixture (1) and clean, dry and inspect the finished product in sequence.

2. The processing method for preparing C-Lens using glass sphere preforms according to claim 1, characterized in that: In step S1, the hemispherical blank obtained after grinding and polishing has a local surface shape error ΔN of no more than 0.

3.

3. The processing method for preparing C-Lens using glass sphere preforms according to claim 1, characterized in that: In step S2, the optical coating is an optical antireflection film system adapted to the optical communication band.

4. The processing method for preparing C-Lens using glass sphere preforms according to claim 1, characterized in that: In step S3, a diamond grinding wheel is used to grind the outer periphery of the hemispherical blank, and after forming, there is no coating residue on the side of the cylinder.

5. The processing method for preparing C-Lens using glass sphere preforms according to claim 1, characterized in that: In step S2, the fixture (1) adopts an array-type workstation arrangement, and its structure is adapted to the automated feeding device. The automatic clamping of the hemispherical blank is completed by mechanical suction.

6. A fixture for C-Lens machining, characterized in that: Including the upper plate (11) and the lower plate (12); The surface of the lower plate (12) is provided with countersunk grooves (121), and multiple countersunk grooves (121) are provided and arranged in an array along the center surface of the lower plate (12). The countersunk grooves (121) are used to support the flat edge of the hemispherical blank. The surface of the upper plate (11) is provided with limiting holes (111) that correspond one-to-one with the positions of the countersunk grooves (121). The limiting holes (111) are used to cooperate with the countersunk grooves (121) to limit and fix the spherical side edge of the hemispherical blank.

7. The C-Lens machining fixture according to claim 6, characterized in that: It also includes a limiting unit (13) for locking and fixing the upper plate (11) and the lower plate (12). The limiting unit (13) includes a plug rod (131) fixedly installed on the outside of the upper plate (11). The plug rod (131) is arranged in a circular array along the center line of the upper plate (11). The outer circumferential surface of the plug rod (131) is provided with an annular locking groove (132). The outer side of the lower plate (12) is fixedly installed with a locking block (133) corresponding to the plug rod (131). The locking block (133) is provided with a plug hole (134) that is clearance-fitted with the outer circumferential surface of the plug rod (131). The lower plate (12) is also provided with a conical hole (135) that communicates with the plug hole (134).

8. The C-Lens machining fixture according to claim 7, characterized in that: The locking block (133) has a radially penetrating slot (1331) on its outer circumference. A spring plate (1332) is installed in the slot (1331). The spring plate (1332) has multiple spring plates arranged in a circumferential array along the central axis of the locking block (133). The side of the spring plate (1332) facing the insertion hole (134) has a snap-fit ​​protrusion (1333), and the side of the spring plate (1332) away from the insertion hole (134) has a conical push block.

9. The C-Lens machining fixture according to claim 8, characterized in that: The locking block (133) has a sliding abutment ring (1335) on its outer side. The inner end face of the abutment ring (1335) abuts against the conical surface of the conical push block. A guide rod (1336) is fixedly installed on the end face of the abutment ring (1335). The guide rod (1336) passes through the end wall of the locking block (133) and extends outward. Multiple guide rods (1336) are provided and arranged in a circumferential array along the central axis of the abutment ring (1335). A return spring (1337) is sleeved on the guide rod (1336). One end of the return spring (1337) is fixedly installed on the outer circumference of the guide rod (1336), and the other end of the return spring (1337) is fixedly installed on the outside of the locking block (133). A magnetic element (1338) is embedded in the end face of the abutment ring (1335). The magnetic element (1338) is used to attract the end face of the locking block (133) to maintain the locking state.

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