Ultra-smooth polishing method for NiP modified reflector

Abstract

The invention discloses an ultra-smooth polishing method for a NiP modified reflector, the processing method comprising: preparing a NiP modified layer, and performing ultra-precision turning and ultra-smooth polishing on the NiP modified layer until the index requirements are met. In the processing method of the invention, ultra-precision turning and ultra-smooth polishing are used to process the NiP modified reflector blank workpiece, which can not only effectively eliminate the surface defects generated during the processing of the NiP modified reflector blank workpiece, but also help improve the processing efficiency, and can effectively suppress the medium and high frequency errors on the reflector surface, thereby significantly improving the surface shape accuracy and surface quality of the processing, and can process the NiP modified reflector blank workpiece into a higher quality NiP modified reflector, which has the advantages of less processing defects, high processing quality, high processing efficiency, good repeatability, etc., and is of great significance for promoting the wide application of NiP modified reflectors in the field of short-wavelength optics.

Description

Technical Field

[0001] The invention belongs to the technical field of ultra-precision processing of optical elements and relates to an ultra-smooth polishing processing method of a NiP modified reflecting mirror. Background Art

[0002] In an optical reflector, the surface roughness of the reflector will cause surface scattering that varies with the energy of the incident light. In order to effectively reflect the incident light, the surface of the reflector must be smooth enough. The quality of the optical reflector plays a critical role in the performance of the optical system. The shorter the application spectrum band of the optical system, the higher the surface quality requirements for the reflector in the system. Therefore, in order to enable the reflector to be applied to applications in the short wavelength band, higher requirements are placed on the surface quality of the reflector.

[0003] In the existing reflectors made of light metal materials such as aluminum and beryllium, by plating a NiP modified layer on the surface of the reflector, scratches, pits and other defects can be avoided during processing. At the same time, the NiP modified layer can be made into an optical mirror surface by ultra-precision turning. Furthermore, by performing magnetorheological polishing and shaping processing on the NiP modified reflector, the mirror surface quality can be further improved, but the reflector obtained in this way can only be used in applications in the visible light band, and cannot be used in applications in shorter wavelength bands. Therefore, in order to meet higher usage requirements, it is necessary to further process the reflector surface to obtain a higher quality reflector.

[0004] In the prior art, some researchers have proposed a method for machining grazing-incidence sub-nanometer mandrels using magnetorheological shaping and manual conformal smoothing. The mandrel surface is plated with nickel-phosphorus alloy, which has the following defects: (1.1) The surface roughness can only reach RMS 0.6nm, which cannot meet the requirements of short-wavelength bands; (1.2) Alumina is used as a polishing abrasive, and scratch damage on the coating surface is difficult to control, which is not conducive to obtaining high-quality machined surfaces; (1.3) Manual conformal smoothing is highly dependent on manual experience, and the process repeatability is poor, which is not conducive to industrial applications. In view of the above-mentioned defects, the inventors of the present application proposed a chemical mechanical polishing liquid for NiP modified layer and a processing method for obtaining high-quality NiP modified layer using the polishing liquid in their preliminary research. Although the processing method can achieve ultra-precision processing of NiP modified layer, effectively improving the surface accuracy and surface quality of NiP modified layer and significantly improving process repeatability, there are still areas for improvement in the following aspects: (2.1) The polishing processing method using magnetorheological shaping and automatic conformal smoothing is subject to many adverse factors during the processing, making it difficult to improve the processing efficiency. (2.2) The magnetorheological polishing fluid used has poor compatibility with the NiP modified layer, resulting in a processing time of up to 45 minutes, which is not conducive to improving processing efficiency; (2.3) The polishing fluid used has poor compatibility with the NiP modified layer, resulting in a difficult balance between mechanical removal and chemical action during the polishing process, which easily produces processing defects such as scratches and pits on the surface of the NiP modified layer, making it difficult to improve the surface quality of the NiP modified reflector. As a result, the surface roughness of the final NiP modified reflector is still relatively high, making it difficult to be widely used in applications in the short wavelength band.

[0005] Therefore, obtaining an ultra-smooth polishing method for a NiP modified reflector with high processing efficiency, good processing quality and good process repeatability is of great significance for obtaining a NiP modified reflector with higher quality. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide an ultra-smooth polishing method for a NiP modified reflector with high processing efficiency, good processing quality and good process repeatability.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A super-smooth polishing method for a NiP modified reflector comprises the following steps:

[0009] Step S1, preparing a NiP modified layer on the surface of a reflector substrate to obtain a NiP modified reflector blank workpiece;

[0010] Step S2, performing ultra-precision turning on the NiP modified reflector blank workpiece to obtain a NiP modified reflector;

[0011] Step S3, performing wavefront interference detection on the NiP modified reflecting mirror to obtain the initial surface shape of the mirror surface of the NiP modified reflecting mirror;

[0012] Step S4, performing ultra-smooth polishing on the NiP modified reflector using an ultra-smooth polishing liquid according to the initial surface shape of the NiP modified reflector;

[0013] Step S5, performing wavefront interference detection and white light interference detection on the ultra-smooth polished NiP modified reflector. If the index requirements are not met, jump to step S4, otherwise the processing is terminated, and the processing of the NiP modified reflector is completed.

[0014] The above-mentioned ultra-smooth polishing method is further improved, in step S4, the ultra-smooth polishing liquid comprises the following raw material components in terms of mass percentage:

[0015] Polishing abrasive 10%~15%,

[0016] Oxidant 1%~3%,

[0017] Complexing agent 1%~2%,

[0018] Surfactant 1%~2%,

[0019] Metal surface defect improver 1% to 2%,

[0020] pH adjuster 0.5%~2%, the rest is water.

[0021] The above-mentioned ultra-smooth polishing method is further improved, wherein the metal surface defect improving agent is at least one of ethylene glycol, 1,4-butanediol, and glycerol.

[0022] The above-mentioned ultra-smooth polishing method is further improved in that the polishing abrasive is silicon oxide.

[0023] The above-mentioned ultra-smooth polishing method is further improved in that the oxidant is hydrogen peroxide.

[0024] The above-mentioned ultra-smooth polishing processing method is further improved, and the complexing agent is at least one of malic acid, acetic acid, citric acid, salicylic acid, lactic acid, glycine, and alanine.

[0025] The above-mentioned ultra-smooth polishing processing method is further improved, wherein the surfactant is at least one of sodium stearate, potassium stearate, and sodium dodecylbenzene sulfonate.

[0026] The above-mentioned ultra-smooth polishing processing method is further improved, wherein the pH regulator is at least one of potassium hydroxide, sodium hydroxide, sodium acetate, sodium carbonate, and sodium borate.

[0027] The above-mentioned ultra-smooth polishing processing method is further improved. In step S4, the process parameters of the ultra-smooth polishing processing are: the polishing disc used is an asphalt polishing disc or a damping cloth polishing disc, the size of the polishing disc is one-quarter to one-sixteenth of the size of the NiP modified reflector, the shape of the polishing disc is adapted to the NiP modified reflector, so that the polishing disc and the NiP modified reflector are fitted together, the processing path used is a grating or spiral scanning path, the rotation speed of the polishing head used is 80 rpm to 120 rpm, and the polishing gas pressure is 0.01 MPa to 0.5 MPa.

[0028] The above-mentioned ultra-smooth polishing method is further improved, in step S1, preparing a NiP modified layer on the surface of the reflector substrate, comprising the following steps:

[0029] Step S1-1, preparing a NiP modified layer on the surface of the reflector substrate;

[0030] Step S1-2, inspect the NiP modified layer. If the NiP modified layer has quality defects, remove the NiP modified layer on the surface of the reflector substrate and jump to execute step S1-1 until the quality of the NiP modified layer meets the index requirements.

[0031] The above-mentioned ultra-smooth polishing processing method is further improved. In step S1-1, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating; the thickness of the NiP modified layer is 80 μm to 120 μm; and the phosphorus content in the NiP modified layer is 9 wt % to 14 wt %.

[0032] The above-mentioned ultra-smooth polishing processing method is further improved in that the material of the reflector substrate is light metal; the light metal includes at least one of aluminum alloy, beryllium, and aluminum-beryllium alloy.

[0033] The above-mentioned ultra-smooth polishing processing method is further improved. In step S1-2, a microscope is used to detect the NiP modified layer, and the detection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether there are holes, whether there are gaps, and whether there are cracks; the quality of the NiP modified layer meets the index requirements, including meeting the following indicators: the surface of the NiP modified layer is free of impurities, flat and smooth, uniform and dense, without holes, without gaps, and without cracks.

[0034] The above-mentioned ultra-smooth polishing processing method is further improved, and after step S1-2 is completed, it also includes the following processing: selecting a heat treatment method according to relevant standards and the type of reflector substrate, and heat treating the NiP modified layer whose quality meets the index requirements to reduce hydrogen embrittlement and improve bonding strength.

[0035] The above-mentioned ultra-smooth polishing method is further improved in that in step S2, a diamond turning tool is used when ultra-precision turning the NiP modified layer; the front angle of the diamond turning tool is 0°.

[0036] The above-mentioned ultra-smooth polishing method is further improved, in step S2, the radius of the arc of the tip of the diamond turning tool is 0.5 mm to 2 mm; the radius of the blunt circle of the cutting edge of the diamond turning tool is 20 nm to 50 nm.

[0037] The above-mentioned ultra-smooth polishing processing method is further improved. In step S2, the process parameters of the ultra-precision turning processing are: the machine tool spindle speed is 1200 rpm~1600 rpm, the feed rate is 1 μm / r~10 μm / r, and the cutting depth is 1 μm~5 μm.

[0038] The above-mentioned ultra-smooth polishing processing method is further improved, and step S3 also includes: detecting whether the surface of the NiP modified reflector meets the ultra-precision turning index requirements, if not, jumping to executing step S2, otherwise jumping to executing step S4.

[0039] Compared with the prior art, the advantages of the present invention are:

[0040] (1) In view of the shortcomings of the existing polishing methods of NiP modified reflectors, such as many processing defects and low processing efficiency, and the resulting processing accuracy and surface quality are difficult to meet the application requirements of short-wavelength optical systems, the present invention creatively proposes an ultra-smooth polishing method for NiP modified reflectors, firstly preparing a NiP modified layer on the surface of the reflector substrate to obtain a NiP modified reflector blank workpiece, and then performing ultra-precision turning on the NiP modified reflector blank workpiece to make the surface of the NiP modified reflector blank workpiece become an optical reflective mirror surface, which can be used for interference measurement, and then obtaining NiP by detection. The initial surface shape of the NiP modified reflector is obtained by calculating the initial surface shape of the NiP modified reflector. On this basis, according to the initial surface shape of the NiP modified reflector, the NiP modified reflector is ultra-smoothly polished, and the surface shape error of the NiP modified reflector is deterministically modified through ultra-smooth polishing. The mechanical and chemical effects during processing are controlled and balanced, so that the medium and high frequency errors on the reflector surface can be effectively suppressed, and the surface shape accuracy and surface quality of the NiP modified reflector can be significantly improved, thereby realizing ultra-precision processing of the NiP modified reflector, so that the NiP modified reflector can meet the application requirements of short-wavelength optical systems. In the ultra-smooth polishing processing method of the NiP modified reflector of the present invention, ultra-precision turning and ultra-smooth polishing are used to process the NiP modified reflector blank workpiece, which can not only effectively eliminate the surface defects generated in the processing of the NiP modified reflector blank workpiece, which is beneficial to improving the processing efficiency, but also effectively suppress the medium and high frequency errors on the reflector surface, thereby significantly improving the processed surface shape accuracy and surface quality, and can process the NiP modified reflector blank workpiece into a higher quality NiP modified reflector, which has the advantages of few processing defects, high processing quality, high processing efficiency, good repeatability, etc., and is of great significance for promoting the wide application of NiP modified reflectors in the field of short-wavelength optics.

[0041] (2) In view of the defects such as the incompatibility between the existing smooth polishing liquid and the NiP modified layer and the resulting shortcomings such as poor processing quality and low processing efficiency, the ultra-smooth polishing processing method of the NiP modified reflector of the present invention provides an ultra-smooth polishing liquid, which comprises the following raw material components in terms of mass percentage: 10 wt% to 15 wt% of polishing abrasive, 1 wt% to 3 wt% of oxidizing agent, 1 wt% to 2 wt% of complexing agent, 1 wt% to 2 wt% of surfactant, 1 wt% to 2 wt% of metal surface defect improving agent, 0.5 wt% to 2 wt% of pH adjusting agent, and the rest is deionized water. In the present invention, under the joint action of an oxidant and a pH regulator, a chemical reaction between the polishing liquid and the workpiece material can be achieved, and an easily removable oxide layer is generated on the surface of the workpiece, and then the oxide layer is mechanically removed under the action of a polishing abrasive; by adding a complexing agent, acid-base balance is easily achieved, the chemical reaction of the oxidant on the workpiece material can be stabilized, and the molecular binding force between the components in the formed complex is much smaller than the molecular binding force between the components in the NiP modified layer, thereby promoting the removal of the workpiece surface material by the polishing abrasive; by adding a surfactant, the dispersibility of the polishing abrasive can be effectively improved, and its agglomeration can be avoided, which is conducive to the rapid removal of the oxide layer by the polishing abrasive, and under the protection of the metal surface defect improving agent, the processing defects on the surface of the modified layer are reduced, thereby effectively improving the surface quality of the ultra-smooth polished NiP modified reflector, and realizing ultra-precision processing of the NiP modified layer. In particular, when the amount of oxidant in the ultra-smooth polishing liquid is small, the mechanical removal rate of the workpiece by the polishing abrasive is greater than the chemical reaction rate between the polishing liquid and the modified layer, resulting in mechanical over-processing, which is prone to scratches. When the amount of oxidant is too much, the mechanical removal rate of the workpiece by the polishing abrasive is less than the chemical reaction rate between the polishing liquid and the NiP modified layer, and a large number of abrasive particles and polishing liquid gather at the concave points on the surface of the workpiece, causing the concave points to continue to grow and form corrosion pits. In addition, when the amount of polishing abrasive is too small, the material removal effect on the workpiece surface is poor and the processing efficiency is low. When the amount of polishing abrasive is too much, over-processing will occur, destroying the chemical mechanical effect. Balance, deteriorating processing quality. In addition, excessive or insufficient use of pH adjuster will change the pH of the polishing liquid, and excessive or insufficient use of chelating agent will also destroy the acid-base balance of the polishing liquid. Generally speaking, the pH value of the polishing liquid is related to the chemical reaction rate between the workpiece material and the processing surface quality. Inappropriate acid-base levels will cause the oxidant in the polishing liquid to decompose and lose its oxidizing ability, or enhance the oxidizing ability of the oxidant, causing excessive corrosion to the workpiece surface. When the amount of metal surface defect improver is too small, the improvement effect on surface defects is not obvious, and when the amount of metal surface defect improver is too large, it will affect the stability of the polishing liquid and other properties.The ultra-smooth polishing liquid of the present invention has good adaptability to the NiP modified layer. Through the effective combination of various effective components, the chemical corrosion and mechanical grinding effects of the ultra-smooth polishing liquid on the NiP modified layer can be significantly enhanced. When used for ultra-smooth polishing, it can not only improve the processing efficiency of ultra-smooth polishing, but also effectively improve the processing quality of the ultra-smooth polished NiP modified reflector, and realize ultra-precision processing of the NiP modified layer. At the same time, by optimizing the dosage of various effective components, the performance of the ultra-smooth polishing liquid can be further improved, so that the chemical corrosion and mechanical grinding effects of the ultra-smooth polishing liquid on the NiP modified layer are relatively balanced. While improving the processing quality and processing efficiency, it can also further suppress the generation of processing defects, which is conducive to obtaining higher quality surface quality. It can be widely used in the ultra-smooth polishing of the NiP modified layer, and has a promoting effect on the wide application of the NiP modified reflector in application occasions such as shorter wavelength bands. It has high use value and good application prospects. It can be seen that in the present invention, by optimizing the raw material components of the ultra-smooth polishing liquid and the amount of each component, the adaptability between the ultra-smooth polishing liquid and the NiP modified layer is good, which is beneficial to improving the processing quality and efficiency of ultra-smooth polishing; at the same time, by optimizing the process parameters of ultra-smooth polishing, the surface accuracy and surface quality of the processing can be further improved, so that the defects of the processed surface are reduced, and thus a higher quality NiP modified reflector can be obtained.

[0042] (3) In the ultra-smooth polishing method of the NiP modified reflector of the present invention, the ultra-precision turning mechanism and process of the NiP modified reflector are studied and explored. By preparing a high-phosphorus content amorphous NiP modified layer that meets the processing requirements on the surface of the reflector substrate and optimizing the process parameters of the ultra-precision turning, the ultra-precision turning can be used to achieve high-quality, low-defect processing of the NiP modified layer, which is beneficial to improving the processing efficiency and processing quality of the NiP modified reflector, as well as improving the process repeatability, and can ensure that a higher quality reflector surface can be obtained after ultra-smooth polishing. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0044] Figure 1 1 is a process flow chart of ultra-smooth polishing of a NiP modified reflector in an embodiment of the present invention.

[0045] Figure 2 Surface roughness diagram of the NiP modified layer after ultra-precision turning in an embodiment of the present invention.

[0046] Figure 3Schematic diagram of the structure of the ultra-smooth polishing device used in the embodiment of the present invention.

[0047] Figure 4 Schematic diagram of the removal principle of the ultra-smooth polishing device used in an embodiment of the present invention.

[0048] Figure 5 The XPS Ni 2p of the NiP modified layer after ultra-smooth polishing in the embodiment of the present invention 3 / 2 picture.

[0049] Figure 6 XPS P 2p of the NiP modified layer after ultra-smooth polishing in the embodiment of the present invention 3 / 2 picture.

[0050] Figure 7 Schematic diagram of the reaction principle of the ultra-smooth polishing liquid used in the embodiment of the present invention.

[0051] Figure 8 Schematic diagram of the complex formed during the ultra-smooth polishing process in an embodiment of the present invention.

[0052] Fig. 9 This is a surface roughness diagram of the NiP modified layer after the first ultra-smooth polishing process in an embodiment of the present invention.

[0053] Fig.10 Surface roughness diagram of the NiP modified layer after the second ultra-smooth polishing process in an embodiment of the present invention.

[0054] Fig.11 Surface roughness diagram of the NiP modified layer after the third ultra-smooth polishing process in the embodiment of the present invention.

[0055] Fig.12 This is a surface roughness diagram of the NiP modified layer after the fourth ultra-smooth polishing process in an embodiment of the present invention.

[0056] Fig.13 This is a surface roughness diagram of the NiP modified layer after the fifth ultra-smooth polishing process in an embodiment of the present invention.

[0057] Fig.14 This is a surface roughness diagram of the NiP modified layer after the sixth ultra-smooth polishing process in an embodiment of the present invention.

[0058] Fig.15 Graph showing the PSD analysis of the NiP modified layer after ultra-smooth polishing in an embodiment of the present invention.

[0059] Fig.16 1 is a graph showing the surface morphology and surface roughness of the NiP modified layer after polishing with a polishing solution without adding a metal surface defect improving agent in an embodiment of the present invention.

[0060] Fig.17 This is a graph showing the surface tension test results of polishing liquids with different formulations in the embodiments of the present invention.

[0061] Fig.18 Graph showing the contact angle measurement results of polishing liquids with different formulations in the embodiments of the present invention.

[0062] Fig.19 Graph showing the particle size distribution of the polishing abrasive in liquid No. 2 in an embodiment of the present invention.

[0063] Fig. 20 Graph showing the particle size distribution of the polishing abrasive in liquid No. 3 in the embodiment of the present invention.

[0064] Fig.21 Graph showing the particle size distribution of the polishing abrasive in liquid No. 4 in the embodiment of the present invention.

[0065] Fig. 22 Graph showing the surface morphology and surface roughness of the NiP modified layer after polishing using asphalt as the polishing pad in an embodiment of the present invention.

[0066] Fig.23 Graph showing the surface morphology and surface roughness of the NiP modified layer after polishing using polyurethane as the polishing pad in an embodiment of the present invention.

[0067] Fig.24 Graph showing the surface morphology and surface roughness of the NiP modified layer after polishing using the damping cloth as the polishing pad in an embodiment of the present invention. DETAILED DESCRIPTION

[0068] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments of the specification, but the protection scope of the present invention is not limited thereby. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0069] The "range" disclosed in the present invention can be defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and any end value can be included or excluded independently, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are also listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present invention, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.

[0070] In the present invention, "plurality", "multiple" and the like, unless otherwise specified, refer to a number greater than or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0071] If not otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution.

[0072] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present invention. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments. Reference to "implementations" herein has a similar understanding.

[0073] Those skilled in the art will appreciate that, in the methods of various embodiments or examples, the order in which each step is written does not mean a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible internal logic. If there is no special explanation, all steps of the present invention can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0074] In the present invention, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0075] In the present invention, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel solutions of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0076] Aiming at the shortcomings of the existing polishing method of NiP modified reflector, such as many processing defects and low processing efficiency, and the resulting processing accuracy and surface quality are difficult to meet the application requirements of short-wavelength optical systems, the present invention also provides a super-smooth polishing method of NiP modified reflector, comprising the following steps:

[0077] Step S1, preparing a NiP modified layer on the surface of a reflector substrate to obtain a NiP modified reflector blank workpiece;

[0078] Step S2, performing ultra-precision turning on the NiP modified reflector blank workpiece to obtain a NiP modified reflector;

[0079] Step S3, performing wavefront interference detection on the NiP modified reflecting mirror to obtain the initial surface shape of the mirror surface of the NiP modified reflecting mirror;

[0080] Step S4, performing ultra-smooth polishing on the NiP modified reflector using an ultra-smooth polishing liquid according to the initial surface shape of the NiP modified reflector;

[0081] Step S5, performing wavefront interference detection and white light interference detection on the ultra-smooth polished NiP modified reflector. If the index requirements are not met, jump to step S4, otherwise the processing is terminated, and the processing of the NiP modified reflector is completed.

[0082] Further improved, the ultra-smooth polishing method of the present invention uses an ultra-smooth polishing liquid comprising the following raw material components in terms of mass percentage:

[0083] Polishing abrasive 10%~15%,

[0084] Oxidant 1%~3%,

[0085] Complexing agent 1%~2%,

[0086] Surfactant 1%~2%,

[0087] Metal surface defect improver 1% to 2%,

[0088] pH adjuster 0.5%~2%, the rest is water.

[0089] It can be understood that the mass percentage refers to the mass fraction of the component in the ultra-smooth polishing liquid.

[0090] In some embodiments, the mass percentage of the polishing abrasive in the ultra-smooth polishing liquid of the present invention is 10% to 15%. It can be understood that the mass fraction of the polishing abrasive in the ultra-smooth polishing liquid is 10 wt% to 15 wt%. As an example, the mass percentage of the polishing abrasive in the ultra-smooth polishing liquid can be 10%, 10.5%, 11%, 12%, 12.5%, 13%, 14%, 15%, or can be within the range of any two of the above point values ​​as end values. Optionally, the mass percentage of the polishing abrasive in the ultra-smooth polishing liquid is 11% to 14%.

[0091] In some embodiments, the mass percentage of the oxidant in the ultra-smooth polishing liquid of the present invention is 1% to 3%. As an example, the mass percentage of the oxidant in the ultra-smooth polishing liquid can be 1%, 1.2%, 1.4%, 1.5%, 1.8%, 2%, 2.4%, 2.5%, 2.7%, 2.8%, 2.9%, 3%, or can be within the range of any two of the above point values ​​as end values. Optionally, the mass percentage of the oxidant in the ultra-smooth polishing liquid is 1.2% to 2.8%.

[0092] In some embodiments, the mass percentage of the complexing agent in the ultra-smooth polishing liquid of the present invention is 1% to 2%. As an example, the mass percentage of the complexing agent in the ultra-smooth polishing liquid can be 1%, 1.1%, 1.2%, 1.4%, 1.5%, 1.8%, 1.9%, 2%, or can be within the range of any two of the above point values ​​as end values. Optionally, the mass percentage of the complexing agent in the ultra-smooth polishing liquid is 1.1% to 1.8%.

[0093] In some embodiments, the mass percentage of the surfactant in the ultra-smooth polishing liquid of the present invention is 1% to 2%. As an example, the mass percentage of the surfactant in the ultra-smooth polishing liquid can be 1%, 1.1%, 1.2%, 1.4%, 1.5%, 1.8%, 1.9%, 2%, or can be within the range of any two of the above point values ​​as end values. Optionally, the mass percentage of the surfactant in the ultra-smooth polishing liquid is 1.1% to 1.8%.

[0094] In some embodiments, the mass percentage of the metal surface defect improver in the ultra-smooth polishing liquid of the present invention is 1% to 2%. As an example, the mass percentage of the metal surface defect improver in the ultra-smooth polishing liquid can be 1%, 1.1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 1.9%, 2%, or can be within the range of any two of the above point values ​​as end values. Optionally, the mass percentage of the metal surface defect improver in the ultra-smooth polishing liquid is 1.1% to 1.8%.

[0095] In some embodiments, the mass percentage of the pH adjuster in the ultra-smooth polishing liquid of the present invention is 0.5% to 2%. As an example, the mass percentage of the pH adjuster in the ultra-smooth polishing liquid can be 0.5%, 0.6%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 1.9%, 2%, or any two of the above point values ​​as end values. Optionally, the mass percentage of the pH adjuster in the ultra-smooth polishing liquid is 0.6% to 1.8%.

[0096] In some embodiments, the metal surface defect improving agent used is at least one of ethylene glycol, 1,4-butanediol, and glycerol.

[0097] In some embodiments, the polishing abrasive used is silicon oxide.

[0098] In some embodiments, the oxidizing agent employed is hydrogen peroxide.

[0099] In some embodiments, the complexing agent used is at least one of malic acid, acetic acid, citric acid, salicylic acid, lactic acid, glycine, and alanine.

[0100] In some embodiments, the surfactant used is at least one of sodium stearate, potassium stearate, and sodium dodecylbenzene sulfonate.

[0101] In some embodiments, the pH adjuster used is at least one of potassium hydroxide, sodium hydroxide, sodium acetate, sodium carbonate, and sodium borate.

[0102] In some embodiments, in step S4, the process parameters of the ultra-smooth polishing process are: the polishing disc used is an asphalt polishing disc or a damping cloth polishing disc, the size of the polishing disc is one-quarter to one-sixteenth of the size of the NiP modified reflector, the shape of the polishing disc is adapted to the NiP modified reflector, so that the polishing disc and the NiP modified reflector fit together, the processing path used is a grating or spiral scanning path, the rotation speed of the polishing head used is 80 rpm to 120 rpm, and the polishing gas pressure is 0.01 MPa to 0.5 MPa.

[0103] In some embodiments, in step S1, preparing a NiP modified layer on the surface of a reflector substrate comprises the following steps:

[0104] Step S1-1, preparing a NiP modified layer on the surface of the reflector substrate;

[0105] Step S1-2, inspect the NiP modified layer. If the NiP modified layer has quality defects, remove the NiP modified layer on the surface of the reflector substrate and jump to execute step S1-1 until the quality of the NiP modified layer meets the index requirements.

[0106] In some embodiments, in step S1-1, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating.

[0107] In some embodiments, the thickness of the NiP modified layer is 80 μm to 120 μm.

[0108] In some embodiments, the content of phosphorus in the NiP modified layer is 9 wt % to 14 wt %.

[0109] In some embodiments, the material of the reflector substrate is a light metal.

[0110] In some embodiments, the light metal includes at least one of aluminum alloy, beryllium, and aluminum-beryllium alloy.

[0111] In some embodiments, in step S1-2, the NiP modified layer is inspected using a microscope, and the inspection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether it has holes, whether it has gaps, and whether it has cracks.

[0112] In some embodiments, the quality of the NiP modified layer meets the index requirements, including meeting the following indexes: The surface of the NiP modified layer is free of impurities, flat and smooth, uniform and dense, and has no holes, no gaps, and no cracks.

[0113] In some embodiments, after step S1-2 is completed, the following processing is also included: selecting a heat treatment method according to relevant standards and the type of the reflector substrate, and heat treating the NiP modified layer whose quality meets the index requirements to reduce hydrogen embrittlement and improve bonding strength.

[0114] In some embodiments, in step S2, a diamond turning tool is used when ultra-precision turning is performed on the NiP modified layer; the front angle of the diamond turning tool is 0°.

[0115] In some embodiments, in step S2, the radius of the arc of the tip of the diamond turning tool is 0.5 mm to 2 mm; the radius of the blunt circle of the cutting edge of the diamond turning tool is 20 nm to 50 nm.

[0116] In some embodiments, in step S2, the process parameters of ultra-precision turning are: the spindle speed of the machine tool is 1200 rpm to 1600 rpm, the feed rate is 1 μm / r to 10 μm / r, and the cutting depth is 1 μm to 5 μm.

[0117] In some embodiments, step S3 further includes: detecting whether the surface of the NiP modified reflector meets the ultra-precision turning index requirements, if not, jumping to executing step S2, otherwise jumping to executing step S4.

[0118] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0119] The workpiece to be processed in this embodiment is a NiP modified plane reflector with a diameter of 100 mm, and the substrate is 6061 aluminum alloy. The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, and the processing method used in the present invention is further explained.

[0120] like Figure 1 As shown, the ultra-smooth polishing method of the NiP modified reflector of this embodiment comprises the following steps:

[0121] Step S1, preparing a NiP modified layer on the surface of a reflector substrate.

[0122] Step S2, inspect the NiP modified layer. If the NiP modified layer has quality defects, remove the NiP modified layer on the surface of the reflector substrate, and jump to step S1 until the quality of the NiP modified layer meets the index requirements and execute the next step.

[0123] Step S3, heat-treating the NiP modified layer to obtain a NiP modified reflector blank workpiece.

[0124] Step S4, performing ultra-precision turning on the NiP modified reflector blank workpiece, so that the reflection effect of the NiP modified layer on the surface of the reflector substrate meets the mirror reflection requirement, and obtaining the NiP modified reflector.

[0125] Step S5: Perform wavefront interference detection on the NiP modified reflecting mirror to obtain the initial surface shape of the mirror surface of the NiP modified reflecting mirror.

[0126] Step S6: According to the initial surface shape of the NiP modified reflector, the NiP modified reflector is subjected to ultra-smooth polishing processing by using an ultra-smooth polishing liquid.

[0127] Step S7, performing wavefront interference detection and white light interference detection on the ultra-smooth polished NiP modified reflector. If the index requirements are not met, jump to step S5, otherwise the processing is terminated, and the processing of the NiP modified reflector is completed.

[0128] In this embodiment, the material properties of the NiP modified layer directly affect the processing performance of ultra-precision turning. For example, during the chemical nickel plating process in step S1, if the plating process is not properly controlled, impurities are easily deposited on the surface of the NiP modified layer. At the same time, due to the small bonding force between the impurities and the NiP modified layer, when the NiP modified layer is subjected to ultra-precision turning, the impurities are driven by the turning tool to separate from the surface of the NiP modified layer, forming pit defects on the surface of the modified layer, or the turning tool drives the impurities to form scratches on the surface of the modified layer.

[0129] In view of the above problems, in steps S1 and S2 of the present embodiment, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating. After the chemical nickel plating is completed, the NiP modified layer is inspected by a microscope. The inspection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether there are holes, whether there are gaps, and whether there are cracks. If the NiP modified layer has any of the above quality defects, the NiP modified layer on the surface of the reflector substrate is removed, and the process jumps to step S1, and the NiP modified layer is continued to be prepared on the surface of the reflector substrate by chemical nickel plating until the quality of the NiP modified layer meets the index requirements. Specifically, by observing under a strong light and using an ultra-depth of field microscope, it is ensured that the surface of the NiP modified layer is free of impurity deposition, flat and smooth, uniform and dense, and has no defects such as holes, gaps, and cracks. In this step, the quality of the NiP modified layer meets the index requirements, which can be determined according to actual conditions, such as impurity-free deposition means that there are no impurities on the surface of the NiP modified layer; generally speaking, chemical plating is an equal thickness deposition, so the preparation by chemical nickel plating can basically ensure that the NiP modified layer is flat and smooth; uniform density requires that the Ni element and the P element are randomly and uniformly distributed, because the NiP modified layer is an amorphous NiP modified layer, it is also easier to achieve; voids and cracks are usually easy to observe, they belong to very bad conditions, and they are scrapped when they appear, so once defects such as voids and cracks appear, the modified layer needs to be re-plated; holes are formed by hydrogen generated in chemical nickel plating, and their size and depth are required not to exceed the value of the cutting depth during ultra-precision turning.

[0130] In step S2 of this embodiment, the NiP modified layer plated on the 6061 aluminum alloy substrate meets the quality requirements, has a thickness of 100 μm, and a phosphorus content of 11 wt %, which is a high-phosphorus-content amorphous NiP modified layer.

[0131] In addition, during the chemical nickel plating process in step S1, not all chemical reaction products are beneficial to the formation of the NiP modified layer. For example, hydrogen will be generated during the chemical nickel plating, and hydrogen will form pores in the NiP modified layer, reducing the toughness and load capacity of the modified layer, affecting the bonding strength between the NiP modified layer and the reflector substrate, and further, when the NiP modified layer is subjected to ultra-precision turning, the NiP modified layer is prone to peeling and falling off.

[0132] In order to eliminate hydrogen embrittlement and enhance the bonding strength between the NiP modified layer and the substrate, it is also necessary to select a heat treatment method according to relevant standards and the type of reflector substrate, and heat treat the NiP modified layer whose quality meets the index requirements in step S1 to reduce hydrogen embrittlement and improve the bonding strength. Specifically: in step S3 of this embodiment, the NiP modified layer whose quality meets the index requirements plated on the 6061 aluminum alloy substrate is heat treated to reduce hydrogen embrittlement and improve the bonding strength. After testing by a tensile testing machine, the bonding strength between the substrate and the modified layer can reach 40 MPa after heat treatment to reduce hydrogen embrittlement and heat treatment to improve the bonding strength, which meets the requirements.

[0133] In step S4 of this embodiment, the NiP modified layer obtained after heat treatment in step S3 is subjected to ultra-precision turning, wherein a diamond turning tool is used when the modified layer is subjected to ultra-precision turning, wherein the rake angle of the diamond turning tool is 0°, the tool tip arc radius is 0.5 mm, the cutting edge blunt circle radius is 20 nm, the feed rate range is 10 μm / r, and the cutting depth is 5 μm; the machine tool spindle speed is 1500 rpm, so that the reflection effect of the NiP modified layer on the surface of the reflector substrate meets the mirror reflection requirements, and a NiP modified reflector is obtained.

[0134] In step S5 of this embodiment, it is detected whether the surface of the NiP modified reflector meets the ultra-precision turning index requirements. If it does not meet the index requirements, the process jumps to step S4, otherwise it jumps to step S6 to perform the next ultra-smooth polishing process.

[0135] In step S5 of this embodiment, a wavefront interferometer is used to perform wavefront interference detection on the NiP modified reflector after ultra-precision turning to obtain the initial surface shape of the NiP modified reflector; a white light interferometer is used to perform white light interference detection on the NiP modified reflector after ultra-precision turning, and the result is as follows: Figure 2 shown. Figure 2 The right picture is the height profile of the left picture at the center line. Figure 2 It can be seen that the surface roughness Ra of the NiP modified mirror obtained after ultra-precision turning is 2.267 nm.

[0136] In step S6 of this embodiment, a schematic diagram of an ultra-smooth polishing device is used, as shown in FIG. Figure 3As shown, during the polishing process, the fixture is installed on the rotating table, the worktable rotates with the C axis, the workpiece is clamped by the fixture, the polishing disc is connected to the cylinder through a flexible ball joint, and the working pressure is applied to the polishing disc through the cylinder. The upper end of the cylinder is connected to a double rotor mechanism, and the polishing disc can be controlled to perform revolution, rotation, and revolution and rotation according to processing needs. Since the material removal rate under the mechanical action during polishing can be adjusted by controlling the size of the cylinder pressure and the speed of the polishing disc during ultra-smooth polishing, this is conducive to controlling the balance between mechanical action and chemical reaction, and realizing ultra-smooth polishing of NiP modified reflectors with nano-level material removal.

[0137] In step S6 of this embodiment, according to the initial surface shape of the NiP modified reflector, the NiP modified reflector is subjected to ultra-smooth polishing by using an ultra-smooth polishing liquid. The detailed steps include:

[0138] Step S6-1, the polishing liquid is the medium between the polishing tool and the workpiece during the ultra-smooth polishing process, so it is necessary to prepare a high-performance ultra-smooth polishing liquid. The composition of the ultra-smooth polishing liquid is: 12 wt% polishing abrasive, 2 wt% oxidant, 1.5 wt% complexing agent, 1 wt% surfactant, 1.5 wt% metal surface defect improving agent, and 1 wt% pH regulator.

[0139] Step S6-2, according to the initial surface shape of the reflector after ultra-precision turning, the size and shape of the polishing disk are selected, the processing path is selected, the polishing parameters are set, and the numerical control code is generated to perform ultra-smooth polishing.

[0140] In step S6-1, in the ultra-smooth polishing liquid, the polishing abrasive is silicon oxide; the oxidant is hydrogen peroxide; the complexing agent is malic acid; the surfactant is sodium stearate; the metal surface defect improving agent is ethylene glycol; and the pH adjusting agent is potassium hydroxide.

[0141] In step S6-2, during the ultra-smooth polishing process, an asphalt polishing disc is used as the polishing disc, the size of the polishing disc is one-quarter to one-sixteenth of the workpiece size, the shape of the polishing disc is adapted to the NiP modified reflector, so that the shape of the polishing disc needs to ensure good adhesion to the surface of the workpiece, and the processing path is a raster scanning path. When ultra-smooth polishing of the NiP modified reflector, it is necessary to control the mechanical removal effect and the chemical reaction to reach a balanced equilibrium state to obtain a high-quality, low-defect reflector surface, wherein the chemical effect is achieved by controlling the composition of the polishing liquid, and the mechanical effect is achieved by controlling the polishing process parameters, wherein the process parameters during polishing are set to: the polishing head rotation speed is 100 rpm, and the polishing gas pressure is 0.02 MPa.

[0142] In step S6 of this embodiment, ultra-smooth polishing is based on the principle of chemical mechanical polishing (CMP). In the ultra-smooth polishing process, there is a chemical reaction between the polishing liquid and the NiP modified layer and a mechanical removal effect of the polishing abrasive. Therefore, when the ultra-smooth polishing process is used to polish the NiP modified reflector, the prerequisite for obtaining an ultra-smooth optical surface is to achieve a balance between the chemical action and mechanical removal in the processing process.

[0143] like Figure 4 As shown in the figure, the mechanical action is responsible for the workpiece material removal task. Under the mechanical removal action, the material removal amount of a single polishing abrasive per unit time is for:

[0144] (1).

[0145] In the above formula, υ is the relative speed between the abrasive and the workpiece surface, P a is the average contact pressure on each polishing pad protrusion, D is the equivalent diameter of the abrasive.

[0146] Material removal rate MRR for:

[0147] (2).

[0148] In the above formula, A t is the actual contact area between the polishing pad and the workpiece, A n is the theoretical contact area between the polishing pad and the workpiece, χ is the concentration of abrasive particles embedded in the polishing pad.

[0149] When the NiP modified reflector is ultra-smoothly polished, a chemical reaction will occur between the ultra-smooth polishing liquid and the NiP modified layer on the reflector surface. The chemical state of the elements after the chemical reaction is analyzed by X-ray photoelectron spectroscopy (XPS). The results are as follows: Figure 5 and Figure 6 As shown. Figure 5 and Figure 6It can be seen that when the NiP modified reflector is ultra-smoothly polished, a chemical reaction will occur between the ultra-smooth polishing liquid and the NiP modified layer on the reflector surface to generate Ni oxide and P oxide. Therefore, during the ultra-smooth polishing process of the NiP modified reflector, a chemical reaction will occur between the workpiece material and the polishing liquid to generate an oxide layer, and then the material is removed by the abrasive in the polishing liquid. By analyzing the mechanical removal and chemical reaction between the NiP modified layer and the polishing liquid, the ultra-smooth polishing mechanism of the NiP modified reflector can be revealed. The schematic diagram of the polishing mechanism is shown in the figure. Figure 7 shown.

[0150] Depend on Figure 7 It can be seen that the smoothing and polishing process of NiP modified metal reflector can be divided into four stages. The first stage is the stage in which the NiP modified metal reflector workpiece forms an oxide layer under the action of the polishing liquid. The second stage is the stage in which the oxide layer is hydrolyzed. + Under the action of ions and polishing liquid, NiO and Ni2O3 react with the polishing liquid to generate Ni 2+ Ions and Ni 3+ Ions, P2O3 react with the polishing liquid to generate The third stage is Ni 2+ Ions and Ni 3+ The stage where ions react with the complex in the polishing liquid, Ni 2+ Ions and Ni 3+ Ions can react with hydroxyl groups in the complex to form a complex. Ni ions and hydroxyl groups can form a variety of long-chain molecular complexes with different structures. Figure 8 As shown, Ni 2+ Ions and Ni 3+ Schematic diagram of the product after the complex reaction between ions and hydroxyl groups. The fourth stage is the stage in which the polishing abrasive in the polishing liquid removes the oxide layer on the surface of the NiP modified layer. After the oxide layer is removed, the exposed NiP modified layer substrate continues to react with the polishing liquid, thus continuously circulating until the processing is completed.

[0151] In step S6 of this embodiment, six ultra-smooth polishing processes are performed. After each process is completed, the surface quality of the NiP modified reflector after ultra-smooth polishing is measured using a white light interferometer. The results are as follows: Figures 9 to 14 shown. Figures 9 to 14 The right picture is the height profile of the left picture at the center line. Figure 9-14It can be seen that after six times of ultra-smooth polishing, the turning marks on the surface of the NiP modified reflector can be completely removed, wherein the surface roughness Ra of the NiP modified reflector reaches 0.183 nm, and it is not easy to produce processing defects such as tiny scratches and pits, and has better processing quality. In addition, according to the test, in this embodiment, the total time for six times of ultra-smooth polishing is 60 minutes, while the time required for three times of conventional self-preserving smoothing is as high as 135 minutes. It can be seen that the ultra-smooth polishing method of the present invention can significantly improve the processing efficiency.

[0152] In order to study the change of surface error of NiP modified reflector during ultra-precision turning and ultra-smooth polishing, the surface error of NiP modified reflector workpiece after processing was analyzed by power spectral density (PSD) method. PSD analysis method is to divide the square of Fourier transform corresponding to the surface error of optical parts by its corresponding spatial frequency bandwidth, which can analyze the frequency band distribution characteristics of surface error of optical components and better reflect the error distribution of optical components surface than peak-to-valley value and root mean square value.

[0153] The PSD analysis curve of NiP modified reflector during ultra-precision turning and ultra-smooth polishing is shown above. Fig.15 As shown. Fig.15 It can be seen that in the NiP modified reflector after ultra-precision turning, there are many peaks in the PSD distribution curve of the surface error. The frequency bands where these peaks are located correspond to the frequency bands where the periodic turning tool marks are located. With the increase of the number of ultra-smooth polishing, these peaks gradually decrease, indicating that ultra-smooth polishing can effectively suppress some mid-frequency errors and all high-frequency errors on the workpiece surface, thereby improving the surface quality of the NiP modified reflector.

[0154] Control group: The NiP modified reflector was ultra-smoothly polished using a polishing liquid without adding a metal surface defect improving agent. Other conditions were the same as those in this example. The results are as follows: Fig.16 As shown. Fig.16 It can be seen that when no metal surface defect improving agent is added to the polishing liquid, defects such as scratches and pits are easily generated on the surface of the NiP modified layer.

[0155] In addition, the performance of polishing liquids with different formulations was also investigated in the examples of the present invention, as follows:

[0156] In order to compare and analyze the performance of the ultra-smooth polishing liquid of the present invention, four polishing liquids were prepared, wherein liquid No. 1 was deionized water, liquid No. 2 was a silica polishing liquid prepared by adding silica to deionized water, and the mass concentration of silica in the polishing liquid was 12 wt %; liquid No. 3 was a polishing liquid prepared by adding hydrogen peroxide to liquid No. 2, and the mass concentration of hydrogen peroxide in the polishing liquid was 3 wt %; liquid No. 4 was the ultra-smooth polishing liquid used in step S6 of this embodiment, and the surface tension, contact angle and particle size distribution of the four polishing liquids were tested and analyzed, and the results are as follows: Figures 17 to 21 shown.

[0157] Depend on Fig.17 It can be seen that the surface tension values ​​of these four polishing fluids are not much different.

[0158] In order to further analyze the wetting properties of the polishing liquid, the contact angles of the above four liquids were measured. The results are as follows: Fig.18 As shown. Fig.18 It can be seen that the contact angle of liquid No. 1 is 75.5°, the contact angle of liquid No. 2 is 82.2°, the contact angle of liquid No. 3 is 86.0°, and the contact angle of liquid No. 4 is 73.9°. The contact angle of liquid No. 4 is the smallest, indicating that the ultra-smooth polishing liquid used in the present invention has the best wetting performance.

[0159] The particle size test results of liquids No. 2, No. 3 and No. 4 are as follows: Figures 19 to 21 shown.

[0160] Depend on Figure 19-21 It can be seen that the average particle sizes of the polishing abrasives in liquids No. 2, No. 3 and No. 4 are 93.15 nm, 95.58 nm and 86.64 nm respectively, and the particle size distribution of the polishing abrasives in liquid No. 4 is more concentrated, indicating that the ultra-smooth polishing liquid of the present invention has the best dispersibility. In addition, by comparing the test results of the wetting performance and dispersibility of the polishing liquid, it can be seen that the ultra-smooth polishing liquid of the present invention has more excellent dispersibility and stability.

[0161] In addition, the effects of different types of polishing pads on the polishing effect are also investigated in the embodiments of the present invention, as follows:

[0162] In the ultra-smooth polishing process, asphalt, polyurethane and damping cloth were used as polishing pads to perform ultra-smooth polishing on the NiP modified reflector. The processing time was 40 minutes and it was performed once in total. The wavefront interferometer was used to perform wavefront interference detection on the NiP modified reflector after ultra-smooth polishing to obtain the surface morphology of the NiP modified reflector. The white light interferometer was used to perform white light interference detection on the NiP modified reflector after ultra-smooth polishing. The results are as follows: Figure 22 to Figure 24 shown.

[0163] from Fig. 22 It can be seen that when asphalt is used as the polishing pad, there is no defect on the surface of the processed NiP modified metal mirror, the surface roughness Ra is 1.171 nm, and the surface quality is good.

[0164] from Fig.23 It can be seen that when polyurethane is used as the polishing pad, the surface roughness value Ra of the processed NiP modified metal mirror is 4.163 nm, and deep scratches and pits are generated on the surface. This is because the hardness of polyurethane is relatively high. Under the action of polyurethane, the polishing abrasive is embedded in the surface of the NiP modified layer to form pits. After the pits are generated, the polishing liquid gathers. The polishing liquid is more likely to react chemically with the NiP modified layer in the pits and be removed, causing the pits to continue to expand.

[0165] from Fig.24 It can be seen that when the damping cloth is used as the polishing pad, the surface roughness Ra of the processed NiP modified layer is 1.507 nm, and scratches are generated on the surface. This is because the damping cloth is soft and easily squeezed with the workpiece, and the damping cloth has a weak ability to hold the abrasive particles. The fluff structure of the damping cloth easily absorbs the abrasive particles and causes agglomeration, and scratches are easily generated when polishing the NiP modified layer.

[0166] Depend on Figure 22-24 It can be seen from the results in that using asphalt as the polishing pad material for polishing NiP modified metal reflectors is more conducive to obtaining high-quality NiP modified metal reflectors.

[0167] From the above results, it can be seen that the ultra-smooth polishing processing method of the NiP modified reflector of the present invention uses an ultra-smooth polishing liquid to perform ultra-smooth polishing on the NiP modified reflector, which can achieve sub-nanometer surface roughness polishing of the NiP modified reflector, and can effectively suppress the medium and high frequency errors on the surface of the reflector, and greatly improve the surface quality of the NiP modified reflector. Therefore, the processing method of the present invention can overcome the shortcomings of many optical reflectors in material processing characteristics, achieve low-defect and high-quality ultra-smooth polishing of the NiP modified reflector, and promote the wide application of NiP modified reflectors in the optical field, especially in the short-wavelength band optical field.

[0168] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for ultra-smooth polishing of a NiP modified reflector, characterized in that: The following steps are involved: Step S1, preparing a NiP modified layer on the surface of a reflector substrate to obtain a NiP modified reflector blank workpiece; Step S2, using a diamond turning tool to perform ultra-precision turning on the NiP modified reflector blank workpiece to obtain a NiP modified reflector; the rake angle of the diamond turning tool is 0°; the radius of the tip arc of the diamond turning tool is 0.5 mm to 2 mm; the blunt radius of the cutting edge of the diamond turning tool is 20 nm to 50 nm; the process parameters of the ultra-precision turning are: the machine tool spindle speed is 1200 rpm to 1600 rpm, the feed rate is 1 μm / r to 10 μm / r, and the cutting depth is 1 μm to 5 μm; Step S3, performing wavefront interference detection on the NiP modified reflecting mirror to obtain the initial surface shape of the mirror surface of the NiP modified reflecting mirror; Step S4: According to the initial surface shape of the NiP modified reflector, the NiP modified reflector is subjected to ultra-smooth polishing by using an ultra-smooth polishing liquid; the ultra-smooth polishing liquid comprises the following raw material components in terms of mass percentage: Polishing abrasive 10%~15%, Oxidant 1%~3%, Complexing agent 1%~2%, Surfactant 1%~2%, Metal surface defect improver 1%~2%, The pH regulator is 0.5% to 2%, and the rest is water; the metal surface defect improving agent is at least one of ethylene glycol and 1,4-butanediol; Step S5, performing wavefront interference detection and white light interference detection on the NiP modified reflector after ultra-smooth polishing. If the index requirements are not met, jump to step S4, otherwise the processing is terminated, and the processing of the NiP modified reflector is completed; In step S1, a NiP modified layer is prepared on the surface of the reflector substrate, comprising the following steps: Step S1-1, preparing a NiP modified layer on the surface of the reflector substrate; the phosphorus content in the NiP modified layer is 9 wt % to 14 wt %; Step S1-2, inspecting the NiP modified layer. If the NiP modified layer has quality defects, the NiP modified layer on the surface of the reflector substrate is removed, and the process jumps to step S1-1 until the quality of the NiP modified layer meets the index requirements. The quality of the NiP modified layer meets the index requirements, including meeting the following indicators: the surface of the NiP modified layer is free of impurities, flat and smooth, uniform and dense, and has no holes, no gaps, and no cracks; After step S1-2 is completed, the following processing is also included: a heat treatment method is selected according to relevant standards and the type of the reflector substrate, and the NiP modified layer whose quality meets the index requirements is heat treated to reduce hydrogen embrittlement and improve bonding strength.

2. The ultra-smooth polishing method according to claim 1, characterized in that: The polishing abrasive is silicon oxide; the oxidant is hydrogen peroxide; the chelating agent is at least one of malic acid, acetic acid, citric acid, salicylic acid, lactic acid, glycine, and alanine; the surfactant is at least one of sodium stearate, potassium stearate, and sodium dodecylbenzene sulfonate; and the pH adjuster is at least one of potassium hydroxide, sodium hydroxide, sodium acetate, sodium carbonate, and sodium borate.

3. The ultra-smooth polishing method according to claim 2, characterized in that: In step S4, the process parameters of the ultra-smooth polishing processing are: the polishing disc used is an asphalt polishing disc or a damping cloth polishing disc, the size of the polishing disc is one-quarter to one-sixteenth of the size of the NiP modified reflector, the shape of the polishing disc is adapted to the NiP modified reflector, so that the polishing disc and the NiP modified reflector are fitted, the processing path used is a grating or spiral scanning path, the rotation speed of the polishing head used is 80 rpm to 120 rpm, and the polishing gas pressure is 0.01 MPa to 0.5 MPa.

4. The ultra-smooth polishing method according to any one of claims 1 to 3, characterized in that: In step S1-1, a NiP modified layer is prepared on the surface of the reflector substrate by chemical nickel plating; the thickness of the NiP modified layer is 80 μm to 120 μm; the material of the reflector substrate is light metal; the light metal includes at least one of aluminum alloy, beryllium, and aluminum-beryllium alloy.

5. The ultra-smooth polishing method according to claim 4, characterized in that: In step S1-2, the NiP modified layer is inspected using a microscope, and the inspection items include: whether the surface of the NiP modified layer has impurities, whether it is flat, whether it is uniform and dense, whether it has holes, whether it has gaps, and whether it has cracks.

6. The ultra-smooth polishing method according to any one of claims 1 to 3, characterized in that: Step S3 also includes: detecting whether the surface of the NiP modified reflector meets the ultra-precision turning index requirements, if not, jumping to executing step S2, otherwise jumping to executing step S4.

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