A rhombic prism polishing method of a narrow and long shape

Abstract

The present application relates to a kind of rhombic prism polishing method of narrow long shape in the field of optical prism processing technology, steps are as follows: polishing the first face of rhombic prism→photo glue body photo glue is on photo glue pad, the second face of rhombic prism is processed→180 ° overturn photo glue body, the second face of rhombic prism photo glue is on photo glue pad, the third face of rhombic prism is processed→ lower tray, photo glue body is glued, cleaning→the first face of rhombic prism photo glue is on photo glue pad, the fourth face of rhombic prism is processed→polishing is completed.The present application utilizes 45 ° tool, high degree of compensation sheet, auxiliary prism strip, realizes the polishing processing of rhombic prism facet, completes the effective control of rhombic prism angle processing precision;By the precision of tool is copied to rhombic prism, solve the problem that rhombic prism facet is difficult to grind and polish rhombic prism facet when rhombic prism facet is polished;Strong operability, short processing time, through strict process parameter control, can improve the processing rhombic prism angle value precision.

Description

Technical Field

[0001] This invention belongs to the field of optical prism processing technology, specifically relating to a polishing method for a narrow and elongated rhomboid prism. Background Technology

[0002] A rhombus prism is a prism with a parallelogram cross-section and four parallel working faces. Rhombus prisms are commonly used to deflect laser beams without changing their direction. In imaging applications, a rhombus prism will deflect the optical axis without flipping the image. The lateral displacement is equal to the length of the prism. A high-precision rhombus prism has a parallelism between the input and output beams within 30″, while those beyond 30″ are considered low- to medium-precision. Typically, in narrow, elongated rhombus prisms, the distances between any two parallel faces vary considerably. Figure 1 As shown, assuming the distance between the two parallel small faces (i.e., the second and third faces) of the rhombic prism is a, and the distance between the two parallel large faces (i.e., the first and fourth faces) is b, when a÷b≥2, it is called a narrow and long rhombic prism.

[0003] In existing technologies, the photopolymerization method is often used to polish narrow and elongated rhomboid prisms. The photopolymerization method utilizes the attraction between molecules to bring the polished surfaces of two optical rhomboid prisms into close contact and adhesion. The rhomboid prisms and the tool are photopolymerized together to form a photopolymer, which is then photopolymerized onto a photopolymer pad to form a mirror disk. At this point, the surface of the rhomboid prism to be processed is parallel to the lower surface of the photopolymer pad. By controlling the parallelism between the surface to be processed and the lower surface of the pad, the precision of the tool is replicated onto the rhomboid prism.

[0004] However, due to the unique shape of narrow and elongated rhombic prisms, the small facets are prone to detachment during polishing when processed using the photoresist method because their center of gravity is suspended. Furthermore, the small contact area between the facets and the polishing mold makes polishing very difficult; typically, when the ratio of the processed area to the mirror disk area is less than 40%, the polishing process becomes challenging. Therefore, there is an urgent need to find a new polishing method better suited for processing narrow and elongated rhombic prisms. Summary of the Invention

[0005] To address the above issues and solve the problems of difficult facet joint and easy delamination during the polishing of narrow and elongated rhomboid prisms, as well as the urgent need to improve the polishing accuracy of rhomboid prisms, this invention provides a polishing method for narrow and elongated rhomboid prisms, the technical solution of which is as follows:

[0006] A polishing method for a narrow, elongated rhombic prism, comprising the following steps:

[0007] S1. Place the first face of the rhombic prism, which has a parallelogram structure in longitudinal section, onto the mounting mold. Use sealing wax to bond the fourth face of the rhombic prism to the flat mold. After cooling, separate the mirror plate from the mounting mold. Then, the first face of the rhombic prism can be finely ground and polished.

[0008] S2. After the first face of the rhombic prism is machined, remove the rhombic prism from the flat mold. Apply photopolymer adhesive to the bottom of the right-angled base of the 45° tool, whose longitudinal section forms an isosceles right triangle. Then, apply photopolymer adhesive to the first face of the rhombic prism and the large hypotenuse of the 45° tool, ensuring that the third face of the rhombic prism after photopolymer adhesive application is higher than the lower surface of the tool height compensation piece, leaving a certain machining allowance. This step can be accomplished with the help of a photopolymer adhesive block. Next, use photopolymer adhesive to bond the fourth face of the rhombic prism to the large hypotenuse of the auxiliary prism strip, whose longitudinal section forms an isosceles right triangle, ensuring that the upper right-angled surface of the auxiliary prism strip is flush with the second face of the rhombic prism. Combine the tool height compensation piece, the 45° tool, the rhombic prism, and the auxiliary prism strip into a single photopolymer adhesive body. Then, apply photopolymer adhesive to the bottom surface of the tool height compensation piece of the photopolymer adhesive body onto a photopolymer adhesive pad to form a mirror plate, which can then be used for fine grinding and polishing of the second face of the rhombic prism.

[0009] S3. After the second surface of the rhombic prism is processed, flip the optical adhesive and apply the auxiliary prism strip and the second surface of the rhombic prism to the optical adhesive pad to form a mirror plate. Then the third surface of the rhombic prism can be finely ground and polished.

[0010] S4. After the third face of the rhombic prism is processed, the optical adhesive is removed, and the rhombic prism is separated from the 45° tool and auxiliary prism strip. Then, the first face of the rhombic prism is optically glued onto the optical adhesive pad to form a mirror plate. Then, the fourth face of the rhombic prism can be finely ground and polished.

[0011] S5. After all four faces of the rhombic prism have been processed, polishing is completed. The rhombic prism is then removed from the optical adhesive pad for cleaning. After passing inspection, it is transferred to the next process.

[0012] Furthermore, in step S1, multiple rhombic prisms can be placed on the mounting mold at one time. Since the flatness of the mounting mold is within 0.005mm, it ensures that the first face of each rhombic prism is on a reference plane. The sealing wax needs to be heated to bond the fourth face of the rhombic prism to the flat mold, so that the rhombic prism, sealing wax and flat mold form a mirror plate. Then, after cooling for 2 hours, the mirror plate is separated from the mounting mold.

[0013] Furthermore, in step S2, the 45° tool that makes up the photocolloid is required to have a 45° angle error of ±5″, a surface shape of N≤0.5 and ΔN≤0.2, and its actual angle value is measured and marked with a precision goniometer; the tool height compensation piece is required to have a parallelism of ±5″, a surface shape of N≤0.5 and ΔN≤0.2, and its thin and thick ends are measured and marked with a precision goniometer.

[0014] Furthermore, in step S2, the third surface of the rhombic prism after photoresist coating is suspended above the lower surface of the tool height compensation plate, with a preferred machining allowance of about 0.05mm.

[0015] Furthermore, in step S2, during the fine grinding of the second face of the rhombic prism and before polishing the lower plate, a micrometer must be used for measurement and self-inspection to ensure that the parallelism difference of the mirror plate is ≤0.001mm.

[0016] Furthermore, in step S3, during the fine grinding of the third surface of the rhombic prism and before polishing the lower plate, a micrometer must be used for measurement and self-inspection to ensure that the parallelism difference of the mirror plate is ≤0.001mm.

[0017] Furthermore, in step S4, during the fine grinding of the fourth face of the rhombic prism and before polishing the lower plate, a micrometer must be used for measurement and self-inspection to ensure that the parallelism difference of the mirror plate is ≤0.001mm.

[0018] Furthermore, in step S4, after separating the rhombic prism, it is necessary to clean the rhombic prism and then apply optical adhesive to the first surface of the rhombic prism onto the optical adhesive pad.

[0019] Furthermore, in each step, the gluing pad is preferably made of φ220mm~φ300mm, with a surface shape N≤0.5 and ΔN≤0.2. Only one side needs to be polished, and it is necessary to use a micrometer to measure and check to ensure that the thickness difference between different positions on opposite sides is ≤0.001mm. In each gluing process in the above steps, the ambient temperature between the gluing pads is required to be 22℃~24℃.

[0020] The present invention also includes other components that enable its normal use, all of which are conventional means in the art. In addition, devices or components not limited in the present invention, such as: 45° tools, tool height compensation plates, auxiliary prism strips, optical adhesive pads, and polishing machines, goniometers, micrometers, etc. used in the fine grinding and polishing process, all adopt the prior art in the art.

[0021] The basic principle of this invention is as follows:

[0022] The present invention provides a polishing method for narrow and long rhomboid prisms, which uses a 45° tool for photoresist replication to ensure that the 45° angle of the rhomboid prism has high angular accuracy, while solving the problem of easy delamination when the center of gravity is suspended during polishing of small faces.

[0023] To address the issues of small contact area and difficulty in polishing the small facets of rhombic prisms, auxiliary prism strips need to be bonded to the small facets of the rhombic prisms to increase the polishing area.

[0024] The purpose of making a suitable tool height compensation piece is to ensure that the tool height compensation piece is ground simultaneously when machining the third face of the rhomboid prism, so as to ensure that there is a sufficient machining area during the polishing process, avoid the difficulty of running-in during the polishing process, and also avoid grinding a 45° tool.

[0025] Regarding the choice of bonding method between the auxiliary prism strip and the rhombic prism: In the existing technology, the auxiliary strip and the rhombic prism are usually bonded with 502 glue or hot wax glue during the polishing process. However, after polishing, due to factors such as temperature, humidity and vibration, the auxiliary strip and the rhombic prism will have slight displacement. As a result, the polished surfaces of the auxiliary strip and the rhombic prism are no longer on the same plane, which makes it impossible to smoothly apply the flipping gluing (i.e., the second surface of the gluing rhombic prism is processed on the third surface of the rhombic prism).

[0026] Therefore, this invention uses photosensitive adhesive to fix the auxiliary strip and the rhombic prism together, thereby forming a photocolloid; then the photocolloid is photo-adhesively applied to a photocolloid pad to form a mirror disk. At this time, the surface of the rhombic prism to be processed is parallel to the lower surface of the photocolloid pad. By controlling the parallelism between the surface to be processed and the lower surface of the pad, the precision of the tool is replicated onto the rhombic prism.

[0027] The beneficial effects of this invention are as follows:

[0028] This invention provides a polishing method for narrow and elongated rhombic prisms. Utilizing a 45° tool, a height compensation plate, and auxiliary prism strips, it successfully polishes the facets of rhombic prisms, effectively controlling the angular processing accuracy of the rhombic prisms. It solves the problems of difficult facet break-in and easy delamination during polishing. The method is highly operable, with a short processing time. Through strict process parameter control, it can achieve very high angular accuracy (45° angle accuracy can reach 5″, and angle and edge differences can both reach 2″). Furthermore, this method can be applied to the processing of other rhombic prisms, demonstrating significant application and promotion value. Attached Figure Description

[0029] Figure 1 (a) and (b) are the front view and top view of the rhomboid prism described in the background art, respectively.

[0030] Figure 2 This is a schematic diagram of the structure of the photocolloid described in this invention.

[0031] Figure 3 This is a schematic diagram of the process of mounting the rhomboid prism, the mold, and the flat mold during the processing of the first surface.

[0032] Figure 4 This is a schematic diagram of the process of mounting the photocolloid and the photocolloid pad on the second surface.

[0033] Figure 5 This is a schematic diagram of the process of mounting the photocolloid onto the photocolloid pad after it is flipped over during the processing of the third side.

[0034] Figure 6 This is a schematic diagram of the mounting process between the rhombic prism and the optical adhesive pad when processing the fourth face.

[0035] Figure 7 This is a flowchart illustrating the overall process flow of the polishing method for narrow and elongated rhomboid prisms described in this invention.

[0036] Figure 8 (a) and (b) are the front view and top view of the rhombic prism processed in the embodiment, respectively.

[0037] Figure 9 This is a schematic diagram of the structure of the photoresist block described in the embodiment.

[0038] Figure 10 This is a schematic diagram of the large-area gluing process of the first face of the rhombic prism and the 45° tool in the embodiment. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0040] Example

[0041] like Figure 8 As shown, the accuracy requirements for this narrow, elongated rhomboid prism include an accuracy of ±5″ for the two 45° angles and an angle difference of θ. Ⅰ 7″, edge difference θ Ⅱ It is 7″.

[0042] like Figure 2-7 As shown, the polishing method for this narrow and elongated rhomboid prism includes the following steps:

[0043] S1. Processing the first face of the rhombic prism: Place the first face of the rhombic prism 100, which has a parallelogram structure in longitudinal section, onto the mounting mold 500. Use sealing wax 600 to bond the fourth face of the rhombic prism to the flat mold 700. After cooling, separate the mirror plate from the mounting mold. Then, use a polishing machine to finely grind and polish the first face of the rhombic prism.

[0044] A plurality of rhombic prisms can be placed on the mounting die at one time. Since the flatness of the mounting die is within 0.005mm, the first surfaces of all rhombic prisms are ensured to be on a reference plane. The fourth surface of the rhombic prism needs to be bonded to the flattening jig with heated sealing wax, so that the rhombic prism, the sealing wax and the flattening jig form a lens pan, and then the lens pan is separated from the mounting die after cooling for 2 hours.

[0045] S2. Machining the second surface 2 of the rhombic prism: after the first surface of the rhombic prism is machined, the rhombic prism is taken down from the flattening jig; then an optical cement assembly is formed to prepare for polishing the second surface;

[0046] The formation process of the optical cement assembly: optically cement the tool height compensation plate 300 to the lower side of the right-angle bottom edge of the 45° tool 200 with a longitudinal section of isosceles right triangle structure; ensure that the 45° angle accuracy after optical cementing is better than 5 arcseconds;

[0047] Then the first surface of the rhombic prism and the large inclined surface of the 45° tool are optically cemented together. This step can be completed with the aid of the optical cement stopper 900, as shown in Figure 9 , the optical cement stopper is composed of a "V"-shaped base 901 and a "⊂"-shaped clamping frame 902; wherein the "V"-shaped base includes two right-angle triangular stoppers, and one acute angle part of the two right-angle triangular stoppers is horizontally butted to form the "V"-shaped base; the "⊂"-shaped clamping frame is arranged in the "V"-shaped groove in the middle of the "V"-shaped base in an inclined matching manner; as shown in Figure 10 , when the first surface of the rhombic prism is optically cemented to the large surface of the 45° tool, the bottom surface of the tool height compensation plate below the 45° tool abuts against the lower inner wall of the "⊂"-shaped clamping frame, and the second surface of the rhombic prism abuts against the upper inner wall of the "⊂"-shaped clamping frame. At this time, it can be ensured that the third surface of the rhombic prism after optical cementing is suspended higher than the lower surface of the tool height compensation plate, leaving a machining allowance of about 0.05mm. After the rhombic prism and the 45° tool are optically cemented and combined, the optical cement stopper can be removed. The height of the optical cement stopper is the distance between the two small surfaces of the rhombic prism before machining plus 0.05mm. Assuming that the distance between the two small surfaces before machining is 35.65mm, the height dimension is 35.65 + 0.05 = 35.7mm;

[0048] Then use a photosensitive adhesive (preferably NOA61 photosensitive adhesive, which is more sensitive to ultraviolet light with a wavelength of 350~380nm) to bond the fourth surface of the rhombic prism to the large inclined surface of the auxiliary prism bar 400 with a longitudinal section of isosceles right triangle structure, and ensure that the upper right-angle surface of the auxiliary prism bar is flush with the second surface of the rhombic prism; so that the tool height compensation plate, the 45° tool, the rhombic prism and the auxiliary prism bar form an integrated optical cement assembly;

[0049] Then, the bottom surface of the tool height compensation piece of the optical colloid is optically coated onto the optical colloid pad 800 to form a mirror plate, which can then be used to finely grind and polish the second face of the rhombic prism. During the fine grinding of the second face of the rhombic prism and before polishing, a micrometer must be used for measurement and self-inspection to ensure that the parallelism difference of the mirror plate is ≤0.001mm. After processing, a protective glue is applied, and then it is ready to process the third face of the rhombic prism.

[0050] The 45° tool that makes up the photocolloid requires a 45° angle error of ±5″, a surface shape of N≤0.5 and ΔN≤0.2, and its actual angle value is measured and marked using a precision goniometer (preferably a Prismmaster precision goniometer); the tool height compensation piece requires a parallelism of ±5″, a surface shape of N≤0.5 and ΔN≤0.2, and its thickness end is measured and marked using a precision goniometer.

[0051] To ensure the accuracy of the 45° angle after gluing, when the 45° angle of the 45° tool is greater than 45°, the 45° edge of the tool is on the same side as the thick end of the compensation piece, and gluing is performed; when the 45° angle of the tool is less than 45°, the 45° edge of the tool is on the same side as the thin end of the compensation piece, and gluing is performed.

[0052] The process of bonding the fourth face of the rhombic prism to the auxiliary prism strip: Use photosensitive adhesive (recommended model NOA61) to bond the fourth face of the rhombic prism and the large face of the auxiliary prism strip together, keeping the right-angled face of the auxiliary strip flush with the second face of the rhombic prism (when bonding, apply the photosensitive adhesive to the fourth face of the rhombic prism, adhere the auxiliary strip to the fourth face of the rhombic prism, and at the same time, have the right-angled face of the auxiliary strip and the second face of the rhombic prism face down, then irradiate with a UV lamp for 5 minutes for initial curing).

[0053] S3. Processing the third face of the rhombic prism: After the second face of the rhombic prism is processed, rotate the optical adhesive 180° and apply the auxiliary prism strip and the second face of the rhombic prism to the optical adhesive pad to form a mirror plate. Then, the third face of the rhombic prism can be finely ground and polished. During the fine grinding of the third face of the rhombic prism and before polishing, a micrometer must be used for measurement and self-inspection to ensure that the parallelism difference of the mirror plate is ≤0.001mm. After processing, apply protective adhesive.

[0054] S4. Processing the fourth face of the rhombic prism: After the third face of the rhombic prism is processed, the optical adhesive is removed, and the rhombic prism is separated from the 45° tool and auxiliary prism strip. The rhombic prism is cleaned, and then the first face of the rhombic prism is optically glued onto the optical adhesive pad to form a mirror plate. Then the fourth face of the rhombic prism can be finely ground and polished.

[0055] During the fine grinding of the fourth face of the rhombic prism and before polishing the lower plate, a micrometer must be used for measurement and self-inspection to ensure that the parallelism difference of the mirror plate is ≤0.001mm. After processing, a protective glue is applied.

[0056] During the polishing process, the thin and thick ends of the mirror disk are sampled and tested. The thick end of the mirror disk is pressed with a load. Before removing the mirror disk, the parallelism difference of the mirror disk is checked with a micrometer and is ≤0.001mm.

[0057] S5. After all four faces of the rhombic prism have been processed, polishing is completed. The rhombic prism is then removed from the optical adhesive pad for cleaning. After passing inspection, it is transferred to the next process.

[0058] Specifically, in all the above steps, the glossy adhesive pads are all φ220mm~φ300mm glossy adhesive pads. The surface shape requirements are N≤0.5 and ΔN≤0.2. Only one side needs to be polished. Furthermore, it is necessary to use a micrometer to measure and check to ensure that the thickness difference between different positions on opposite sides is ≤0.001mm.

[0059] Requirements for optical adhesive pads: As a basic tooling for the processing of optical rhombic prisms, the surface shape and thickness differences of optical adhesive pads will affect the parallelism control of the mirror disk.

[0060] Requirements for 45° tools and tool height compensation plates: The angular accuracy of the 45° tool and the parallelism accuracy of the compensation plate both affect the 45° accuracy of the rhombic prism;

[0061] During the processing, the parallelism difference of the mirror disk is controlled to be ≤0.001mm: Because the processing method of this invention uses the optical adhesive replication method to process the rhombic prism, the angular accuracy of the tool is indirectly copied onto the rhombic prism by controlling the parallelism difference of the mirror disk during the processing.

[0062] Specifically, the ambient temperature between the photopolymer layers is required to be 22℃~24℃ during each of the above steps. The composition of the photopolymer is key to this invention. In addition, the control of various process parameters ensures that the angular accuracy of the rhombic prism reaches a high level. Specifically, the main functions of controlling each process parameter are as follows:

[0063] The environmental temperature and humidity requirements are related to the quality of the photopolymerization process. The quality of the photopolymerization affects the angular accuracy and surface defects of the rhombic prism, which is very important for the polishing of high-precision optical rhombic prisms.

[0064] The processing method of this invention is applicable to the precision polishing of high-precision optical rhombic prisms, which can improve the angular accuracy of rhombic prisms and significantly reduce the difficulty of controlling the angular accuracy of such parts.

[0065] Note 1: The protective adhesive applied to the non-processed surface is used to protect the surface defects of the rhombic prism. The protective adhesive is acetal resin, which is existing technology and will not be described in detail here.

[0066] 2. Cleaning is the process of washing away the protective adhesive on the surface of the rhomboid prism. The cleaning agent used is industrial ethanol, which is existing technology and will not be described in detail here.

[0067] In summary, the overall process flow of the narrow and elongated rhombic prism polishing method provided by this invention is roughly as follows: polishing the first surface of the rhombic prism → applying optical adhesive to the optical adhesive pad and processing the second surface of the rhombic prism → rotating the optical adhesive 180° so that the second surface of the rhombic prism is coated with optical adhesive on the optical adhesive pad and processing the third surface of the rhombic prism → removing the adhesive from the lower plate and the optical adhesive and cleaning → applying optical adhesive to the first surface of the rhombic prism on the optical adhesive pad and processing the fourth surface of the rhombic prism → polishing completed.

[0068] The technical solutions of the present invention are not limited to the specific embodiments described above. Without departing from the scope and spirit of the described embodiments, many modifications and changes will be obvious to those skilled in the art. Any technical modifications made within the spirit and principles of the present invention will fall within the protection scope of the present invention.

Claims

1. A method for polishing a narrow, elongated rhomboid prism, characterized in that, The steps are as follows: S1. Place the first face of the rhombic prism, which has a parallelogram structure in longitudinal section, onto the mounting mold. Use sealing wax to bond the fourth face of the rhombic prism to the flat mold. After cooling, separate the mirror plate from the mounting mold. Then, the first face of the rhombic prism can be finely ground and polished. S2. After the first face of the rhombic prism is machined, remove the rhombic prism from the flat mold. Apply photopolymer adhesive to the bottom of the right-angled base of the 45° tool, whose longitudinal section forms an isosceles right triangle. Then, apply photopolymer adhesive to the first face of the rhombic prism and the large hypotenuse of the 45° tool, ensuring that the third face of the rhombic prism after photopolymer adhesive application is higher than the lower surface of the tool height compensation piece, leaving a certain machining allowance. Next, use photopolymer adhesive to bond the fourth face of the rhombic prism to the large hypotenuse of the auxiliary prism strip, whose longitudinal section forms an isosceles right triangle, ensuring that the upper right-angled surface of the auxiliary prism strip is flush with the second face of the rhombic prism. Combine the tool height compensation piece, the 45° tool, the rhombic prism, and the auxiliary prism strip into a single photopolymer adhesive body. Then, apply photopolymer adhesive to the bottom surface of the tool height compensation piece of the photopolymer adhesive body onto a photopolymer adhesive pad to form a mirror plate, which can then be used for fine grinding and polishing of the second face of the rhombic prism. S3. After the second surface of the rhombic prism is processed, flip the optical adhesive and apply the auxiliary prism strip and the second surface of the rhombic prism to the optical adhesive pad to form a mirror plate. Then the third surface of the rhombic prism can be finely ground and polished. S4. After the third face of the rhombic prism is processed, the optical adhesive is removed, and the rhombic prism is separated from the 45° tool and auxiliary prism strip. Then, the first face of the rhombic prism is optically glued onto the optical adhesive pad to form a mirror plate. Then, the fourth face of the rhombic prism can be finely ground and polished. S5. After all four faces of the rhombic prism have been processed, polishing is completed. The rhombic prism is then removed from the optical adhesive pad for cleaning. After passing inspection, it is transferred to the next process.

2. The polishing method for a narrow, elongated rhombic prism according to claim 1, characterized in that: In step S1, multiple rhombic prisms can be placed on the mounting mold at one time, ensuring that the first face of each rhombic prism is on a reference plane. The sealing wax needs to be heated to bond the fourth face of the rhombic prism to the flat mold, so that the rhombic prism, sealing wax and flat mold form a mirror plate. After cooling for 2 hours, the mirror plate is separated from the mounting mold.

3. The polishing method for a narrow, elongated rhombic prism according to claim 1, characterized in that: In step S2, the 45° tool that makes up the photocolloid is required to have a 45° angle error of ±5″, and a surface shape of N≤0.5 and ΔN≤0.2; the tool height compensation piece is required to have a parallelism of ±5″, and a surface shape of N≤0.5 and ΔN≤0.

2.

4. The polishing method for a narrow, elongated rhombic prism according to claim 1, characterized in that: In step S2, the third surface of the rhombic prism after photoresist coating is suspended above the lower surface of the tool height compensation plate, with a machining allowance of 0.05mm.

5. The polishing method for a narrow, elongated rhombic prism according to claim 1, characterized in that: In step S2, during the fine grinding of the second face of the rhombic prism and before polishing the lower plate, a measurement self-inspection must be performed to ensure that the parallelism difference between the mirror and the plate is ≤0.001mm.

6. The polishing method for a narrow, elongated rhombic prism according to claim 1, characterized in that: In step S3, during the fine grinding of the third surface of the rhombic prism and before polishing the lower plate, a measurement self-inspection must be performed to ensure that the parallelism difference between the mirror and the plate is ≤0.001mm.

7. The polishing method for a narrow, elongated rhombic prism according to claim 1, characterized in that: In step S4, during the fine grinding of the fourth face of the rhombic prism and before polishing the lower plate, a measurement self-inspection must be performed to ensure that the parallelism difference between the mirror and the plate is ≤0.001mm.

8. The polishing method for a narrow and elongated rhombic prism according to claim 1, characterized in that: In step S4, after separating the rhombic prism, it needs to be cleaned, and then the first surface of the rhombic prism is coated with optical adhesive onto the optical adhesive pad.

9. A polishing method for a narrow, elongated rhombic prism according to any one of claims 1-7, characterized in that: The glossy adhesive pad uses a φ220mm~φ300mm glossy adhesive pad with a surface shape N≤0.5 and ΔN≤0.

2. Only one side needs to be polished, and self-inspection is required to ensure that the thickness difference between different positions on the two opposite sides is ≤0.001mm.

10. A polishing method for a narrow, elongated rhombic prism according to any one of claims 1-7, characterized in that: During each photoresist process, the ambient temperature between photoresists should be 22℃~24℃.

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