A processing method for making linear light guides completely free of gate residues

Abstract

This invention discloses a processing method for linear light guides that completely eliminates gate residue, comprising the following steps: S1, using an injection mold to injection mold one or more light guide blanks in a single process; S2, transferring the light guide blanks to the positioning fixture of a laser cutting equipment; S3, the laser cutting equipment identifies the gate position through a vision recognition system and controls the emitted laser to cut off all non-functional process segments of the light guide blank, obtaining a finished linear light guide product with only the light guide functional segment. Using this processing method, the resulting linear light guide product has the advantages of no gate residue or optical defects, improved cutting accuracy and efficiency, increased yield, good versatility, environmental friendliness and economy, elimination of stress concentration and fracture risk in the finished linear light guide product, and increased design freedom for the linear light guide.

Description

Technical Field

[0001] This invention relates to the field of optical component processing methods, specifically to a processing method that completely eliminates gate residue in linear optical guides. Background Technology

[0002] Linear ambient lighting is the most widely used type of ambient lighting, and linear light guides are one of the core components of linear ambient lighting.

[0003] Please see Figure 1 and Figure 2 Existing linear light guides typically place the gate in the middle or at the end of the light guide, and the existing processing method is to cut off the gate after the linear light guide is formed. The applicant of this invention has discovered in production practice that linear light guides processed by existing methods have the following defects:

[0004] 1. Gate residue problem: Gates are generally cut manually or by laser. The cut gate is not only prone to problems such as rough and tilted cross-section, but if the residual height is ≥0.2mm, it will cause abnormal local light reflection of the linear light guide.

[0005] 2. Cutting process defects: It is difficult to ensure the consistency of the gate cutting and the roughness of the cut is also difficult to control. When lit, bright spots will be formed, which will destroy the uniformity of the overall light emission of the linear light guide and seriously affect the optical and lighting effects.

[0006] 3. Difficulty in controlling cutting precision: If the laser cutting distance is close, the heat-affected zone is large, and the linear light guide surface is very prone to "air marks" (micro-cracks, carbonization, yellowing); if the cutting distance is far, the residual size of the gate is prone to be too large, resulting in bright spots or light leakage risks on the surface.

[0007] 4. Stress concentration and fracture risk: Stress concentration is prone to occur at the gate location, which may lead to fracture risk at the gate location during production and assembly.

[0008] 5. Restrictions on gate location: To ensure the fluidity of the injection molding process and improve the yield of injection molding, the gate is usually located on the arc-shaped surface of the circumferential sidewall of the linear light guide. However, laser cutting is a straight-line cutting, which causes the thickness in the middle of the gate location to be inconsistent with the thickness on both sides. This not only easily causes local assembly problems, but also has the problem of local bright spot abnormalities.

[0009] 6. High production cost: To avoid bright spots when the gate is lit, black ink or UV glue is usually applied manually to the gate to absorb stray light and solve the problem of bright spots. This not only increases the production process and affects production efficiency, but also increases production cost.

[0010] 7. Limitations on application scope: High-end models require linear light guides to have an optical uniformity of over 70%. The linear light guides produced by existing technologies cannot completely solve the problem of poor uniformity caused by gate residue, resulting in poor yield.

[0011] 8. Optical design limitations: To avoid bright spots when the gate is lit, the light guide teeth / microstructures corresponding to the gate area are usually weakened during the light distribution design stage to reduce the light intensity. This not only imposes greater limitations on optical design, but also places higher requirements on the injection molding process. Summary of the Invention

[0012] In view of this, the present invention provides a processing method that makes the linear light guide completely free of gate residue.

[0013] The technical solution is as follows:

[0014] The first aspect of this application relates to a processing method that completely eliminates gate residue from linear light guides, comprising the following steps:

[0015] S1. One or more light guide blanks are obtained by injection molding in one injection molding process using an injection mold. The light guide blank includes a light guide functional segment and non-functional process segments integrally formed at one or both ends of the light guide functional segment. Each non-functional process segment is integrally formed with a gate.

[0016] S2. Transfer the optical guide blank to the positioning fixture of the laser cutting equipment;

[0017] S3. The laser cutting equipment identifies the gate position through a vision recognition system and controls the emitted laser to cut off all non-functional process sections of the light guide blank, resulting in a linear light guide finished product with only the light guide functional section.

[0018] The above processing method, which completely eliminates gate residue in linear light guides, achieves the following technical effects:

[0019] 1. The resulting linear light guide product is free of gate residue and optical defects: The end of the linear light guide is extended to form a non-functional process section, and the gate is set in the non-functional process section. After injection molding, the entire non-functional process section is cut off, avoiding the bright spot problem caused by gate residue in traditional designs. The bright spot elimination rate is 100%, which improves the overall uniformity of light emission of the linear light guide and improves the optical and lighting effects.

[0020] 2. Improved cutting precision and efficiency: Laser cutting not only offers high precision but also ensures consistent cutting, resulting in smooth cuts with low roughness, no material buildup, and stable optical performance, thus enhancing the appearance and optical performance of the light guide. Furthermore, laser cutting equipment can be integrated into automated production lines, making it particularly suitable for batch cutting and achieving more efficient processing.

[0021] 3. Improved yield: The cutting process has become much simpler, which not only shortens the cutting time per piece, but also eliminates the need to adjust the cutting parameters separately for gates of different curvatures or sizes. This increases the tolerance for errors in the cutting parameters and significantly improves the yield of cut products, enabling the yield of cut products to reach over 95%.

[0022] 4. Good versatility: It can be applied not only to linear light guides with various cross-sectional shapes (circular, polygonal, irregular), but also to the manufacture of other precision optical components such as light guide plates, prisms, and lens arrays.

[0023] 5. Environmentally friendly and economical: The gate no longer needs to be blackened, which improves the production efficiency of linear light guides, enhances the environmental friendliness of the manufacturing process, and reduces production costs.

[0024] 6. Eliminate stress concentration and fracture risk of the obtained linear light guide product: Since the linear light guide product does not have a gate position, it effectively solves the problem of fracture risk at the gate position caused by stress concentration during production and assembly. At the same time, since the gate is far away from the light guide functional section during injection molding, the stress concentration phenomenon during injection molding will also be reduced, and the warpage deformation will be reduced by more than 40%.

[0025] 7. It is the first to add a non-functional process section for injection molding to the linear light guide, so that the light guide functional section can fully serve the optical performance. This breaks through the industry perception that "the gate should be set in the light guide functional section" and creatively proposes the concept of "completely cutting off the non-functional process section after injection molding".

[0026] 8. Increased design freedom for linear light guides: Since the gate position is designed to be "completely cut off from non-functional process sections after injection molding", it is possible not only to design the gate at any position in the non-functional process section, improving the flexibility of injection mold design, but also to completely ignore the gate position design of the light guide functional section, making the shape design of the light guide functional section more free and the optical design more flexible. Attached Figure Description

[0027] Figure 1 A schematic diagram of a linear light guide with two light-introducing and light-mixing units obtained by injection molding using existing processing methods;

[0028] Figure 2 A schematic diagram of a linear light guide with one light-introducing and light-mixing unit obtained by injection molding using existing processing methods;

[0029] Figure 3 This is a flowchart of the processing method of the present invention;

[0030] Figure 4This is a schematic diagram of the structure of the optical guide blank obtained by injection molding according to the processing method of the present invention in Example 1;

[0031] Figure 5 This is a schematic diagram of the structure of the optical guide blank obtained by injection molding according to the processing method of the present invention in Example 2;

[0032] Figure 6 A schematic diagram of the structure of the linear optical guide finished product after removing non-functional process sections from the optical guide blank of Example 1 or Example 2;

[0033] Figure 7 This is a schematic diagram of the structure of the optical guide blank obtained by injection molding according to the processing method of the present invention in Example 3;

[0034] Figure 8 This is a schematic diagram of the linear optical guide finished product after cutting off the non-functional process sections from the optical guide blank in Example 3.

[0035] Figure 9 This is a schematic diagram of the structure of the optical guide blank obtained by injection molding according to the processing method of the present invention in Example 4;

[0036] Figure 10 This is a schematic diagram of the structure of the optical guide blank obtained by injection molding according to the processing method of the present invention in Example 5;

[0037] Figure 11 This is a schematic diagram of the structure of the linear optical guide finished product after removing non-functional process sections from the optical guide blank in Example 4 or Example 5. Detailed Implementation

[0038] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0039] like Figure 3 As shown, a processing method for making linear light guides completely free of gate residue is carried out according to the following steps:

[0040] S1. Inject molten optical grade resin into an injection mold, and use the injection mold to form one or more light guide blanks 1 in one injection molding process. The specific number depends on the structure of the mold.

[0041] The optical grade resin can be commonly used resins such as PMMA / PC. The light guide blank 1 includes a linear light guide functional segment 11 and non-functional process segments 12 integrally formed at one or both ends of the light guide functional segment 11. Each non-functional process segment 12 is integrally formed with a gate 13.

[0042] Taking PMMA resin as an example, the process parameters for injection molding include: mold temperature controlled at 60℃~90℃, injection pressure at 80MPa~120MPa, holding pressure at 60%~80% of the injection pressure, holding time at 2s~5s, and cooling time at 10s~30s.

[0043] For the above-mentioned injection molding process parameter design, controlling the mold temperature can effectively avoid the problem of stress concentration; at the same time, by reasonably matching the holding pressure and cooling time, the problem of warping deformation of the light guide blank 1 can be effectively reduced.

[0044] Furthermore, the PMMA resin is preferably high-transmittance PMMA (transmittance ≥92%, haze ≤1.5%), and its drying conditions are 80℃±5℃ for more than 4 hours. By drying the resin, defects such as bubbles and silver streaks can be effectively prevented, and the consistency of optical performance can be improved.

[0045] Specifically, the optical guide blank has the following multiple implementation methods:

[0046] Optical guide blank Example 1: Please refer to Figure 4 The light guide functional section 11 of the light guide blank 1 is a linear light guide structure with a light-introducing and light-mixing unit. Specifically, the light guide functional section 11 includes a light-emitting unit 111 and a light-introducing and light-mixing unit 112 integrally formed at one end of the light-emitting unit 111. The light-emitting unit 111 is a linear structure, and the sidewall of the light-emitting unit 111 has optical patterns 111a distributed along its length direction. The optical patterns 111a can be common optical patterns 111a such as optical teeth, leather texture, and frosted texture. The end face of the light-introducing and light-mixing unit 112 away from the light-emitting unit 111 is the light-introducing end face. The light emitted by the LED enters the light-introducing and light-mixing unit 112 through the light-introducing end face. The light-introducing and light-mixing unit 112 also has a light-mixing function to eliminate the non-uniformity of light distribution and ensure the softness and consistency of the light emitted by the light-emitting unit 111.

[0047] A non-functional processing segment 12 is integrally formed at the end of the optical guide functional segment 11 furthest from the light-incoming mixing unit 112. Cutting marks 121 are integrally formed at the boundary between the non-functional processing segment 12 and the optical guide functional segment 11. Therefore, by setting the cutting marks 121, subsequent laser cutting can ensure good cutting consistency, a smooth cut, low roughness, no material accumulation, and stable optical performance, thus improving the appearance quality and optical performance of the optical guide. The finished product after cutting is as follows... Figure 6 As shown.

[0048] Furthermore, the non-functional process segment 12 is designed at the end of the light guide functional segment 11 that is far away from the light-incoming mixing unit 112, so that the light-incoming end face of the light-incoming mixing unit 112 is directly formed during injection molding, rather than formed by laser cutting. This design can better ensure the flatness of the light-incoming end face, thereby ensuring the optical effect of the light guide blank 1.

[0049] The length of the non-functional process section 12 is generally 8mm-20mm. In this embodiment, the length of the non-functional process section 12 is preferably 10mm-15mm, which can accommodate the gate and positioning structure without causing material waste.

[0050] It should be noted that the cross-sectional dimensions of the non-functional process section 12 are the same as or slightly larger than those of the light-guiding functional section 11. In this embodiment, the circumferential outer wall of the non-functional process section 12 preferably protrudes 0.05mm to 0.2mm from the circumferential outer wall of the light-guiding functional section 11. This design can compensate for the injection molding shrinkage rate and ensure the flatness of the laser-cut rear end face.

[0051] Typically, the cutting mark 121 is formed on the non-functional process segment 12. By using the cutting method of the cutting mark 121, the optical guide functional segment 11 obtained after cutting can be free of defects in appearance and function.

[0052] The gate 13 is integrally molded on the non-functional process section 12. Therefore, after injection molding, the entire non-functional process section 12 is cut off, avoiding the bright spot problem caused by the gate 13 residue in the traditional design. The bright spot elimination rate is 100%, which improves the uniformity of the overall light emission of the linear light guide and improves the optical and lighting effects.

[0053] Furthermore, the gate 13 is integrally formed on the circumferential sidewall or end face of the corresponding non-functional process segment 12. It is preferably designed at the center of the circumferential sidewall or the center or edge of the end face of the non-functional process segment 12. That is, the gate 13 can be designed at any position in the non-functional process segment as needed (mold layout and flow balance requirements), which improves the flexibility of injection mold design.

[0054] Specifically, the gate 13 can be a side gate, a fan-shaped gate, a submarine gate, or a point gate. In this embodiment, the gate 13 is preferably a submarine gate, with an entrance angle of 30° to 60°, a depth of 0.5mm to 1.2mm, and a width of 1.0mm to 2.5mm. When a multi-cavity mold is used, each cavity is fed evenly through a hot runner system to ensure the consistency of the forming of each light guide blank.

[0055] Furthermore, the cutting mark 121 is a linear groove structure formed on the optical guide blank 1 in a circumferential direction. This linear groove structure can surround the optical guide blank 1 completely or extend only a short section, as long as it serves to guide the cutting position. Moreover, the linear groove structure can serve as a laser pre-cutting groove structure, which can better ensure the consistency of cutting and the flatness of the cut.

[0056] Optical guide blank Example 2: Please refer to Figure 5 The main structure of the light guide blank 1 is exactly the same as that of the light guide blank in Example 1, except that the cutting mark 121 is a linear rib structure extending circumferentially on the light guide blank 1. This linear rib structure can surround the light guide blank 1 completely or extend only a short section, as long as it guides the cutting position. This design improves the fluidity of the fluid flowing towards the light guide functional section 11 during injection molding, which can slightly improve the injection molding efficiency.

[0057] The finished product after cutting looks like Figure 6 As shown.

[0058] Optical guide blank Example 3: Please refer to Figure 7 The main structure of the light guide blank 1 is exactly the same as that of the light guide blank in embodiment 1, except that the cutting mark 121 is at least one circumferentially distributed protrusion or recess on the light guide blank 1. Typically, only one protrusion or recess is needed for identification. Furthermore, because the protrusion or recess is small, it is less likely to leave residue after cutting, further improving the yield of the finished product. In addition, the non-functional process segment 12 is integrally formed at the end of the light-introducing and mixing unit 112 away from the light guide functional segment 11.

[0059] The finished product after cutting looks like Figure 8 As shown.

[0060] Example 4 of optical guide blank: Please refer to Figure 9 The main structure of the light guide blank 1 is exactly the same as that of the light guide blank embodiment 1, except that the light guide functional segment 11 is a linear light guide structure with two light-introducing and light-mixing units 112.

[0061] Typically, when the length of the light guide functional segment 11 is relatively long, two light-introducing and light-mixing units 112 are provided to ensure the brightness and uniformity of light emission of the light guide functional segment 11. Specifically, the light guide functional segment 11 includes a light-emitting unit 111 and light-introducing and light-mixing units 112 integrally formed at both ends of the light-emitting unit 111.

[0062] In this embodiment, a non-functional process segment 12 is integrally formed at the end of each of the two light-incoming and light-mixing units 112 away from the light-guiding functional segment 11, and a gate 13 is integrally formed on the non-functional process segment 12. This design can improve the efficiency and yield of injection molding.

[0063] The finished product after cutting looks like Figure 11 As shown.

[0064] Optical guide blank Example 5: Please refer to Figure 10 The main structure of the light guide blank 1 is exactly the same as that of the light guide blank in embodiment 4. The only difference is that only one of the light-introducing and light-mixing units 112 has a non-functional process section 12 integrally formed at the end away from the light guide functional section 11, while the other light-introducing and light-mixing unit 112 does not have a non-functional process section 12 at the end away from the light guide functional section 11.

[0065] This design, when applied to the injection molding of linear light guides where the length of the light guide functional segment 11 is not very long but the brightness requirement is high, can reduce mold investment costs while ensuring injection molding efficiency and yield.

[0066] The finished product after cutting looks like Figure 11 As shown.

[0067] S2. Transfer the optical guide blank 1 to the positioning fixture of the laser cutting equipment.

[0068] Specifically, after the light guide blank 1 cools down, it is transferred to the positioning fixture of the laser cutting equipment. The positioning fixture can fix one or more light guide blanks 1 at a time, and the specific number depends on the structure of the positioning fixture and the cutting design of the laser cutting equipment.

[0069] In the existing technology, linear light guides usually cannot be reliably positioned on the positioning fixture, especially the non-functional process segment 12 which is not positioned, resulting in low cutting accuracy, difficulty in ensuring cutting consistency, and difficulty in controlling the roughness of the cut, which further aggravates the problems of appearance and optical performance.

[0070] To address the aforementioned issues, in this embodiment, a cutting and positioning structure 123 is integrally formed on each non-functional process segment 12. Therefore, by providing the cutting and positioning structure 123 on the non-functional process segment 12 (excluding the optical guide functional segment 11), and correspondingly providing a fixing structure adapted to the cutting and positioning structure 123 on the positioning fixture, the optical guide blank 1 can be reliably fixed and positioned. This ensures cutting accuracy, good cutting consistency, low kerf roughness, and improves the final product's appearance quality and optical performance. Furthermore, it eliminates the need for a positioning structure on the optical guide functional segment 11, further ensuring the final product's optical performance.

[0071] It should be noted that the cutting positioning structure 123 can take many forms, as long as it can be used with the positioning fixture to achieve reliable positioning. For example, the cutting positioning structure 123 can be several planar structures formed along the length direction on the circumferential sidewall of the non-functional process segment 12, several protruding structures formed on the non-functional process segment 12, or several recessed structures formed on the non-functional process segment 12. Simultaneously, the cutting positioning structure 123 can also be designed on the end face of the non-functional process segment 12.

[0072] Furthermore, in order to further improve the accuracy and reliability of positioning and improve the cutting precision, several light guide positioning structures 113 are integrally formed on the light guide functional segment 11 to further improve the reliability of positioning light guide blank 1. At the same time, the light guide positioning structure 113 can also be used as the installation positioning structure of linear light guide, realizing the effect of dual use in one piece.

[0073] Furthermore, the light guide positioning structure 113 is preferably a protrusion structure integrally formed on the circumferential sidewall of the corresponding light-incoming and light-mixing unit 112. Compared with the groove structure, it can allow more light to enter the light-emitting unit 111, thereby improving the brightness of the light-emitting unit 111.

[0074] S3. The laser cutting equipment identifies the position of the gate 13 through a vision recognition system and controls the emitted laser to cut off all non-functional process segments 12 of the light guide blank 1, resulting in a linear light guide finished product with only the light guide functional segment 11. The laser used is a high-precision CO2 or ultraviolet laser.

[0075] Furthermore, since each non-functional process segment 12 and the functional process segment 11 of the optical guide blank 1 are integrally formed with cutting marks 121, in step S3, the laser emitted by the laser cutting equipment identifies the cutting marks 121 through the visual recognition system and cuts off each non-functional process segment 12 along the cutting marks 121, which further improves the cutting accuracy and thus obtains a completely residue-free optical guide product.

[0076] Specifically, if the cutting mark 121 is a linear groove structure extending circumferentially between the non-functional process segment 12 and the optical guide functional segment 11, or if the cutting mark 121 is at least one pit structure distributed circumferentially on the non-functional process segment 12, the laser emitted by the laser cutting equipment directly cuts the linear groove structure or pit structure until the non-functional process segment 12 is completely cut off.

[0077] If the cutting mark 121 is a linear rib structure extending circumferentially on the non-functional process segment 12, or if the cutting mark 121 is at least one circumferentially distributed protrusion structure on the non-functional process segment 12, the cutting mark 121 needs to be set immediately adjacent to the boundary line between the non-functional process segment 12 and the optical guide functional segment 11, and all cutting marks 121 are located on the side of the boundary line closer to the non-functional process segment 12. Therefore, the laser emitted by the laser cutting equipment identifies the cutting mark 121 through the visual recognition system, and cuts off the non-functional process segment 12 close to the side of the cutting mark 121 near the optical guide functional segment 11, which can make the cut surface of the optical guide functional segment 11 smoother and reduce defects.

[0078] S4. Clean and destaticate the cut end face of the linear optical guide product. Specifically, first clean the cut end face of the linear optical guide product obtained in step S3 to remove dust and other impurities, and then destaticate the linear optical guide product.

[0079] S5. Inspect the cut end face of the finished linear light guide: if it passes, remove the finished linear light guide from the production line; if it fails, proceed to the next step.

[0080] Typically, a microscopic visual inspection system is used to inspect the cut end face for the first, middle and last pieces. The inspection items include: end face flatness (allowable deviation ≤ ±20μm), presence of burrs (height > 10μm is considered unacceptable), and presence of microcracks (length > 50μm is considered unacceptable).

[0081] S6. After processing the defects on the cut end face of the linear optical guide product, return to step S5. Methods for processing the defects on the cut end face of the linear optical guide product include polishing, grinding, and flame treatment.

[0082] In this embodiment, flame polishing is preferably used to treat the slight burrs or uneven areas on the cut end face of the linear optical guide product. Specifically, it includes: using an oxyhydrogen flame to spray at a flow rate of 0.3L / min to 0.6L / min, at a distance of 3mm to 8mm from the end face, and at a moving speed of 10mm / s to 20mm / s, and then returning to step S5 after processing.

[0083] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A processing method that completely eliminates gate residue in linear light guides, characterized in that, Follow these steps: S1. One or more light guide blanks are obtained by injection molding in one injection molding process using an injection mold. The light guide blank includes a light guide functional segment and non-functional process segments integrally formed at one or both ends of the light guide functional segment. Each non-functional process segment is integrally formed with a gate. S2. Transfer the optical guide blank to the positioning fixture of the laser cutting equipment; S3. The laser cutting equipment identifies the gate position through a vision recognition system and controls the emitted laser to cut off all non-functional process sections of the light guide blank, resulting in a linear light guide finished product with only light guide functional sections. The optical guide blank is integrally formed with a cutting and positioning structure adapted to the positioning fixture, and the positioning fixture positions and / or locks non-functional process segments through the cutting and positioning structure. The cutting and positioning structure is as follows: Several planar structures formed along the length of the circumferential sidewall of the non-functional process section; or, Several protrusions are formed on the non-functional process section; or, Several depressions are formed in the pit structure of the non-functional process section; The light guide functional segment is integrally formed with several light guide positioning structures. The positioning fixture positions and / or locks the light guide functional segment through the light guide positioning structures. The light guide positioning structure is a protruding structure integrally formed on the circumferential sidewall of the light-incoming mixing unit.

2. The processing method according to claim 1, characterized in that, Each non-functional process segment and the optical guide functional segment has a cutting mark integrally formed on the optical guide blank. In step S3, the laser emitted by the laser cutting equipment identifies the cutting mark through a visual recognition system and cuts off each non-functional process segment along the cutting mark.

3. The processing method according to claim 2, characterized in that, The cutting mark is a linear groove structure that extends circumferentially and is formed between the non-functional process section and the optical guide functional section; or, The cutting mark is at least one circumferentially distributed pit structure on a non-functional process section.

4. The processing method according to claim 2, characterized in that, The cutting marks are all adjacent to the boundary line between the non-functional process section and the optical guide functional section, and are located on the side of the boundary line closer to the non-functional process section. In step S3, the laser emitted by the laser cutting equipment identifies the cutting marks through the visual recognition system, and cuts off the non-functional process section close to the side of the cutting marks near the optical guide functional section.

5. The processing method according to claim 4, characterized in that, The cutting mark is a linear rib structure that extends circumferentially and is formed on a non-functional process section; or, The cutting mark is at least one convex structure distributed circumferentially on a non-functional process segment.

6. The processing method according to claim 1, characterized in that, Also includes: S4. Clean and destaticate the cut end face of the linear optical guide product.

7. The processing method according to claim 6, characterized in that, Also includes: S5. Inspect the cut end face of the finished linear optical guide: if qualified, remove the finished linear optical guide from the production line; If it fails, proceed to the next step; S6. After processing the defects on the cut end face of the linear optical guide product, return to step S5.

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