Zinc selenide aspheric lens and numerical control polishing process thereof

Abstract

The invention relates to the technical field of optical processing, and provides a zinc selenide aspherical lens and a numerical control polishing process thereof, a numerical control polishing machine is used for carrying out the main steps of rough polishing, fine polishing, fine trimming and the like, process parameters are adjusted according to the characteristics of zinc selenide, and therefore the zinc selenide aspherical lens with the diameter smaller than 320 mm can be polished. By means of a numerical control polishing machine tool, the overall PV of the zinc selenide aspherical lens is controlled to be 0.3 mu m or below, white zinc metal particles generated by heating of the surface of the lens in the polishing process are removed, and the surface smoothness of a finished product reaches 60 / 40 and reaches the laser level. And reference significance is also achieved for surface polishing of zinc selenide with the thickness of 320 mm or above.

Description

Technical Field

[0001] The invention relates to the technical field of optical processing, in particular to a zinc selenide aspheric lens and a numerical control polishing process thereof. Background Art

[0002] Aspherical lenses have shapes such as parabolas, quadratic curves, cubic curves or higher-order curves. When designing, it is necessary to consider correction factors such as lens aberration, chromatic aberration and spherical aberration. Usually, one aspherical lens can effectively replace multiple spherical lenses, thereby reducing the number of lenses, improving the accuracy and clarity of the lens, enhancing color reproduction, reducing light reflection, and reducing the size of the lens. Aspherical lenses have the characteristics of high zoom, short object distance and large aperture. High zoom can simplify the types of lenses, short object distance is suitable for close-up photography, and large aperture can be used in dark environments. Therefore, its application field is becoming increasingly wide.

[0003] Zinc selenide material is a yellow transparent polycrystalline material with a crystalline particle size of about 70μm and a light transmission range of 0.5 to 15μm. Zinc selenide synthesized by chemical vapor deposition (CVD) has almost no impurity absorption and extremely low scattering loss. Because of its extremely low absorption rate of 10.6μm wavelength light, zinc selenide has become the preferred material for optical devices in high-power CO2 laser systems. In addition, it is also widely used in various optical systems throughout the entire light transmission band. Zinc selenide has a strong ability to withstand thermal shock, making it an ideal optical material for high-power CO2 lasers. However, its hardness is only 2 / 3 of that of multi-spectral grade ZnS, the material is soft and easy to scratch, and the material has a large refractive index, so it is necessary to plate a high-hardness anti-reflection film on the surface to protect its surface and improve transmittance. At the same time, in the commonly used spectral range, the scattering of zinc selenide materials is very low. When used as a high-power laser device, the body absorption and internal structural defects of the material need to be strictly controlled.

[0004] CN1785560A discloses a method for processing aspheric optical elements, which is mainly used for processing zinc selenide and zinc sulfide aspheric optical elements. Its main technical features are: using a computer numerical control lathe and a diamond arc tool to cut zinc selenide and zinc sulfide. However, it is difficult to control the finish of zinc selenide aspheric lenses to reach laser level by single-point turning. In addition, the pitting problem on the polished surface of zinc selenide aspheric surfaces has always been a problem in the infrared industry. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a zinc selenide aspheric lens and a CNC polishing process thereof. The CNC polishing process uses a CNC polishing machine to polish the zinc selenide aspheric surface, and can polish the zinc selenide aspheric lens with a diameter of less than 320 mm, and can reduce the intermediate frequency error of the zinc selenide aspheric surface, so that the global surface type PV of the zinc selenide aspheric lens is controlled to less than 0.3 μm, and the surface finish reaches the laser level. It is also of reference significance for the surface polishing of zinc selenide above 320 mm.

[0006] The technical solution of the present invention is:

[0007] A CNC polishing process for zinc selenide aspheric lenses, based on a CNC polishing machine, comprises the following steps:

[0008] Step 1: Scan the profile of the zinc selenide aspherical lens to obtain a profile model;

[0009] Step 2: Rough polishing of the zinc selenide aspheric lens using a CNC polishing machine according to the contour model;

[0010] Step 3: Perform profile scanning on the zinc selenide aspheric lens after rough polishing to obtain a new profile model;

[0011] Step 4: Use a CNC polishing machine to fine-polish the zinc selenide aspheric lens according to the contour model obtained in step 3;

[0012] Step 5: Refine and get the finished product.

[0013] In actual application, the present application adopts a polishing method to obtain zinc selenide with a surface finish reaching laser grade, and adjusts the setting parameters of the CNC polishing machine according to the lens and polishing liquid to avoid the CNC polishing machine damaging the zinc selenide aspheric lens and causing irreparable defects.

[0014] In the above-mentioned CNC polishing process of zinc selenide aspheric lens, if the surface PV of the contour model in step 3 is greater than the drawing requirements, return to step 2; if the surface PV is less than the drawing requirements, enter step 4.

[0015] In the above-mentioned CNC polishing process of zinc selenide aspheric lenses, the polishing liquid used for rough polishing is a mixed solution of 1-2 μm aluminum oxide, ammonium dichromate, oily suspension and pure water, wherein the ratio of aluminum oxide: ammonium dichromate: oily suspension: pure water is 40:1:60:299.

[0016] In the above-mentioned CNC polishing process of zinc selenide aspheric lens, the step 5 transfers the zinc selenide aspheric lens to the grinding and polishing machine, adds ammonium dichromate solution to the zinc selenide aspheric lens for wetting, rotates the zinc selenide aspheric lens at a speed of 100 to 200 RPM, and then uses polishing leather to fine-tune the zinc selenide aspheric lens at a pressure of 4 to 6 kPa, and continuously drips polishing liquid and ammonium dichromate solution during the process.

[0017] In the above-mentioned CNC polishing process for zinc selenide aspheric lenses, before step 1, milling is used to prepare zinc selenide aspheric lenses with a surface type PV≤2μm, and sharp edges at the edges of the zinc selenide aspheric lenses are removed.

[0018] In the above-mentioned CNC polishing process for zinc selenide aspheric lenses, in step 2, the actual indentation diameter is compared with the theoretical calculated indentation size, and the rough polishing tooling height is adjusted according to the difference to make the theoretical indentation equal to the actual indentation size.

[0019] In the above-mentioned CNC polishing process for zinc selenide aspheric lenses, the parameter setting of the CNC polishing machine satisfies the following conditions:

[0020] Setting a, when the particle size of the polishing liquid is 0.5-1 μm and the lens diameter is set to be less than 150 mm, the speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 800-1000 RPM, and the downward pressure is 0.5-0.7 mm;

[0021] Setting b, when the particle size of the polishing liquid is 0.5-1 μm and the lens diameter is set to be greater than 150 mm, the speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 300-500 RPM, and the downward pressure is 0.5-0.7 mm;

[0022] Setting c, when the particle size of the polishing liquid is 1-2 μm and the lens diameter is set to be less than 150 mm, the speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 300-500 RPM, and the downward pressure is 0.2-0.4 mm;

[0023] Setting d. When the particle size of the polishing liquid is 1-2 μm and the lens diameter is set to be greater than 150 mm, the speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 150-300 RPM, and the downward pressure is 0.2-0.4 mm.

[0024] In the above-mentioned CNC polishing process for zinc selenide aspherical lenses, the remaining settings of the CNC polishing machine in step 2 are as follows:

[0025] The size of the polishing head is one third to one quarter of the diameter of the lens;

[0026] Correction is set to -30% to -60%;

[0027] The track-pitch value in the path data is one percent of the set lens diameter;

[0028] The unit of oscillation-time is seconds, and its value is 3 to 5 times the set lens diameter;

[0029] The filter width in extrapolate is 1% of the set lens diameter, the point distance is 1% of the set lens diameter, and the target diameter is the effective diameter plus 5 to 10 mm;

[0030] Smoothing is performed, and the smoothing value is 2 to 3 μm;

[0031] Adjust the removal-coefficient and oscillation-time values ​​and set the feedmin. value to 10 mm / min.

[0032] In the above-mentioned CNC polishing process for zinc selenide aspherical lenses, the settings of the CNC polishing machine in step 4 are as follows:

[0033] The particle size of the polishing liquid is 0.5-1μm, the downward pressure is 0.1-0.2mm, and the other setting requirements are the same as rough polishing.

[0034] In addition, the present application also provides a zinc selenide aspheric lens, the diameter of the zinc selenide aspheric lens is less than 320 mm, and is manufactured using the above-mentioned zinc selenide aspheric lens CNC polishing process.

[0035] The polishing process of the present application is capable of polishing zinc selenide aspheric lenses with a diameter of less than 320 mm. With the help of a CNC polishing machine, the global surface profile PV before optimization can be reduced to less than 0.3 μm, and the surface finish can be 60 / 40, reaching the laser grade.

[0036] One of the above technical solutions of the present invention has at least one of the following advantages or beneficial effects:

[0037] The polishing process of the present invention and the present application can polish zinc selenide aspheric lenses with a diameter of less than 320 mm. With the help of a CNC polishing machine, the optimized front PV can be reduced to less than 0.3 μm, and the white zinc metal particles generated by heating the lens surface during the polishing process can be removed, so that the surface finish of the finished product reaches 60 / 40, reaching the laser level and can be used for lasers.

[0038] At the same time, compared with single-point turning, the use of polishing to process zinc selenide aspheric lenses can improve processing efficiency and surface finish, and can also save the cost of frequent tool replacement.

[0039] In addition, the present application can also more accurately control the stability of the polishing surface by controlling the amount of downward pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is the optical surface diagram of the aspheric lens after milling in Example 1 of the present invention;

[0041] Figure 2 The optical surface diagram of the aspheric lens obtained in Example 1 of the present invention;

[0042] Figure 3 The optical surface diagram of the aspheric lens obtained in Example 3 of the present invention;

[0043] Figure 4 This is an optical surface diagram of the aspheric lens obtained in Comparative Example 1 of the present invention;

[0044] Figure 5 This is an optical surface diagram of the aspheric lens obtained in Comparative Example 2 of the present invention;

[0045] Figure 6 This is an optical surface diagram of the aspheric lens obtained in Comparative Example 3 of the present invention;

[0046] Figure 7 This is the appearance of the aspheric lens prepared in Comparative Example 5 of the present invention under a microscope;

[0047] Figure 8 It is a schematic diagram of the cooperation between the polishing head and the lens in the fine finishing of the present invention;

[0048] Fig. 9 Schematic diagram of the calculated theoretical indentation of the present invention.

[0049] Fig.10 It is a processing flow diagram of the present invention.

[0050] Description of reference numerals:

[0051] 1. Polishing head; 2. Lens. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of 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.

[0053] In the following examples, the model of the CNC polishing machine is Satis Loh SPS-200; the model of the CNC milling machine is Satis Loh SPM-200; the model of the profilometer is LUPHOSCAN 260HD 3D. In addition, the drawing requires PV < 5.

[0054] Explanation of the parameter settings of the CNC polishing machine in the article:

[0055] correction: edge retention rate; track-pitch value in path data: spiral pitch; oscillation-time: the time required for one round of polishing; filter width in extrapolate: sampling spiral pitch; point distance: sampling point distance; target diameter: target diameter; smooth: smoothing processing; min.Height: removal amount; removal-coefficient: residence time; feed min.: minimum moving speed of the polishing head.

[0056] Example 1

[0057] refer to Figure 1 , 2 , a CNC polishing process for zinc selenide aspheric lens, in this embodiment, the actual diameter of the zinc selenide aspheric lens is 118 mm, and its composition includes a mixed solution of aluminum oxide, ammonium dichromate, an oily suspension and pure water, and is prepared in a ratio of 40:1:60:299; Fig.10 As shown, the following steps are included:

[0058] Milling: Use CNC milling machine to adjust the surface shape of zinc selenide aspheric lens to less than 2μm, otherwise there will be medium and high frequency surface shape errors during polishing, and it is difficult to control the surface shape after polishing to less than 0.5μm. It is also necessary to chamfer or sandpaper grind the edge to remove the sharp edges to prevent cutting the polished skin; the surface shape after milling is as follows Figure 1 shown.

[0059] Profile scanning: perform profile scanning on the zinc selenide aspheric lens with a surface area of ​​≤2μm to obtain the first profile model;

[0060] Rough polishing: Fix the zinc selenide aspheric lens and its tooling in the CNC polishing machine, import the first contour model into the CNC polishing machine to calculate the rough polishing program and start rough polishing;

[0061] Contour scanning: Perform a contour scan on the zinc selenide aspheric lens after rough polishing to obtain a second contour model; and determine the subsequent processing flow based on the surface shape of the second contour model. The determination process is as follows:

[0062] When the PV of the surface is less than the requirements of the drawing, it will enter fine polishing;

[0063] When the PV of the surface is greater than the requirements of the drawing, first observe whether the contour model has astigmatism. The reason is that the hardness of single crystal silicon is different and anisotropic, and the removal efficiency in different places is different, which is easy to cause astigmatism and deformation;

[0064] If there is astigmatism, perform astigmatism correction, and perform contour scanning again after astigmatism correction;

[0065] If there is no astigmatism, the rough polishing procedure is calculated again using the second contour model and rough polishing is performed;

[0066] Repeat the above judgment process until the surface shape of the zinc selenide aspheric lens is smaller than the drawing requirements and enter fine polishing.

[0067] In this embodiment, the following points need to be explained for rough polishing:

[0068] 1. The settings of the CNC polishing machine for rough polishing are as follows:

[0069] The particle size of the selected polishing liquid is 1 μm and since the lens diameter is set to be less than 150 mm, it meets setting a or c; in this embodiment, setting c is used, so the rotation speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 400 RPM and the rotation direction of the polishing head and the workpiece axis are the same, and the downward pressure is 0.4 mm; it should be noted that in actual applications, setting a is used: the rotation speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 900 RPM, and the downward pressure is 0.6 mm. It can also process a good aspheric surface, but there is a slight difference in processing efficiency.

[0070] The lens diameter is set to the actual lens diameter plus 10mm, that is, the lens diameter is set to 128mm. The reason is that there is a phenomenon of edge collapse in the CNC polishing process, and the edge surface shape has a sudden change that cannot be controlled. Therefore, when walking the polishing track, the polishing head moves a little further outside the lens to reduce the edge collapse phenomenon.

[0071] The size of the polishing head is one-third of the set lens diameter, and the polishing leather is gray GR-35 polyurethane polishing leather; the polishing liquid flow rate is adjusted to the maximum and sprayed on the center of the lens;

[0072] correction is set to -30%; the track-pitch value in path data is 1% of the set lens diameter, i.e. 1.28; the unit of oscillation-time is seconds, and its value is 3 to 5 times the set lens diameter, which is set to 500 in this embodiment; the filter width in extrapolate is 1% of the set lens diameter, i.e. 1.28; the point distance is 1% of the set lens diameter, i.e. 1.28; the target diameter is 48mm; smoothing is performed, and the smoothing value is 2μm; the min.height is set to 0.1μm, and the feed min. value is adjusted to 10mm / min by adjusting the removal-coefficient and oscillation-time values ​​to obtain the final rough polishing program.

[0073] 2. There are two ways to correct astigmatism in the polishing of single-crystal silicon non-spherical surfaces. One is to use the 3D correction software proact provided by the CNC polishing machine to extend the dwell time to eliminate the protruding parts of the surface, but this method is time-consuming. The other method is manual repair, in which the staff polishes the protruding parts of the surface and does not polish the concave parts of the surface.

[0074] Fine polishing: fix the zinc selenide aspheric lens and its tooling in the CNC polishing machine again, import the second contour model obtained by rough polishing into the CNC polishing machine to calculate the fine polishing program and start fine polishing to obtain a semi-finished product; in actual application, take out the zinc selenide aspheric lens after fine polishing, drip hand sanitizer on the lens surface while rinsing with pure water, then wipe it with soaked absorbent cotton dipped in hand sanitizer, and finally wipe the surface stains and moisture of the lens with alcohol and citric acid, and then perform contour scanning on the zinc selenide aspheric lens. If the surface shape is larger than the drawing requirements, repeat fine polishing with the contour model until the surface shape of the semi-finished product is smaller than the drawing requirements, and then enter fine finishing;

[0075] In this embodiment, the following points need to be explained about fine polishing:

[0076] 1. The settings of the CNC polishing machine for fine polishing are as follows:

[0077] The particle size of the polishing liquid selected is 0.5μm; the speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 250RPM, and the downward pressure is 0.2mm; the lens diameter is set to the actual lens diameter plus 10mm, that is, the lens diameter is set to 128mm; the size of the polishing head is one-third of the set lens diameter, and the orange LP-66 polishing leather is selected.

[0078] The polishing liquid flow rate is adjusted to the maximum and sprayed to the center of the lens; correction is set to -30%; the track-pitch value in path data is 1% of the set lens diameter, that is, 1.28; the unit of oscillation-time is seconds, and its numerical value is 3 to 5 times the set lens diameter, which is set to 500 in this embodiment; the filterwidth in extrapolate is 1% of the set lens diameter, that is, 1.28; the point distance is 1% of the set lens diameter, that is, 1.28; the target diameter is 123mm; no smoothing is performed; the min.height is set to 0.1μm, and the feed min. value is adjusted to 10mm / min by adjusting the removal-coefficient and oscillation-time values ​​to obtain the final fine polishing program.

[0079] Fine repair: transfer the semi-finished product to the grinding and polishing machine for manual repair; rotate the semi-finished product at a speed of 150RPM, first wet the lens with ammonium dichromate solution, control the dust-free cloth polishing leather to provide 6kpa pressure on the lens, and drip the polishing liquid and ammonium dichromate solution in turn (the function of ammonium dichromate solution is to remove the white zinc metal particles generated by the heat on the lens surface during the polishing process, and another function is to increase friction), and hand repair for 5 minutes. The above operation can remove deep scratches and residual white spots on the lens surface. Then, drip hand soap onto the lens surface while rinsing with pure water, then wipe it with soaked absorbent cotton dipped in hand soap, and finally wipe the lens clean with alcohol and citric acid. Observe whether there are visible scratches on the surface of the lens. If there are scratches, repeat the above finishing operation again; then observe the surface finish through a microscope with a magnification of 14 times. If there are no white spots and scratches, the surface finish is considered qualified; if the finish does not meet the requirements, repeat the finishing operation again; if the surface shape is also qualified, the zinc selenide aspheric polishing is completed, and the surface is coated with protective paint to prevent scratches. It should be noted that the speed range of the workpiece during finishing is 100-200RPM, the purpose is to ensure efficiency and avoid the polishing liquid from being thrown out; the pressure on the lens is between 4-6kpa, because zinc selenide is a ceramic material with a soft texture. The scratches produced in the previous rough polishing and fine polishing processes are relatively deep, and the manual repair pressure must be increased to remove the scratches.

[0080] The polishing liquid used in the finishing process is a mixture of 0.25μm diamond powder, aluminum oxide, silicon dioxide, oily suspension and pure water in a ratio of 2:1:2:6:29; the concentration of the ammonium dichromate solution used is 1%, and the polishing pad is a dust-free cloth or a damping cloth. It should be noted that the area covered by the polishing pad when the lens rotates one circle needs to be larger than the surface area of ​​the lens, such as Figure 8 shown.

[0081] In addition, reference Fig. 9 In order to improve the processing accuracy, in practical applications, the theoretical indentation is calculated, and the tooling height in the non-CNC polishing machine is adjusted by the difference between the theoretical indentation and the actual indentation to make the theoretical indentation equal to the actual indentation.

[0082] The theoretical indentation is calculated as follows:

[0083]

[0084] Where: L0 = bL e ; we can get L e =2R0b-b 2 / 2R e +2R0-2b;

[0085] Combining the above two equations, we get:

[0086]

[0087] Simplifying, we get:

[0088]

[0089] Among them, R e is the radius of the aspherical surface; R0 is the radius of curvature of the polishing head; b is the amount of downward pressure; Y s is the theoretical indentation diameter.

[0090] Example 2

[0091] The process is basically the same as that in Example 1, except that: the actual lens diameter is 200 mm, and the particle size of the selected polishing liquid is 1 μm, which meets the setting b or d. In this embodiment, setting b is used. It should be noted that in actual application, setting d is used: the rotation speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 300 RPM, and the downward pressure is 0.2 mm. A good aspheric surface can also be processed, but there is a slight difference in processing efficiency.

[0092] Therefore: in the rough polishing, the rotation speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 400RPM, and the downward pressure is 0.6mm; the lens diameter is set to the actual lens diameter plus 10mm, that is, the lens diameter is set to 210mm; the track-pitch value in the path data is 1% of the set lens diameter, that is, 2.1; the unit of oscillation-time is second, and its value is 3 to 5 times the set lens diameter, which is set to 850 in this embodiment; the filter width in extrapolate is 1% of the set lens diameter, that is, 2.1; the point distance is 1% of the set lens diameter, that is, 2.1; the target diameter is 190mm, and the rest remains unchanged.

[0093] In fine polishing, the track-pitch value in path data is 1% of the set lens diameter, that is, 2.1; the unit of oscillation-time is second, and its value is 3 to 5 times the set lens diameter, which is set to 190 in this embodiment; the filter width in extrapolate is 1% of the set lens diameter, that is, 2.1; the point distance is 1% of the set lens diameter, that is, 2.1; the target diameter is 190mm, and the rest remains unchanged.

[0094] Example 3

[0095] refer to Figure 3 , which is basically the same as Example 1, except that smoothing is not performed during rough polishing.

[0096] Comparative Example 1

[0097] refer to Figure 4 , which is basically the same as Example 1, except that: during milling, the edges of the lens are not ground or chamfered.

[0098] Comparative Example 2

[0099] refer to Figure 5 , which is basically the same as Example 1 and meets setting c, except that the rotation speeds of the polishing head and the workpiece axis of the CNC polishing machine are both set to 800RPM.

[0100] Comparative Example 3

[0101] refer to Figure 6 , which is basically the same as Example 1 and meets setting c, but the pressing amount is 0.6 mm.

[0102] Comparative Example 4

[0103] It is basically the same as Comparative Example 3, but the pressing amount is 0.1 mm.

[0104] Comparative Example 5

[0105] refer to Figure 7 , which is basically the same as Example 1 and meets setting c, but no ammonium dichromate solution is dropped during refinement.

[0106] Result analysis:

[0107] refer to Figure 2 , both Examples 1 and 2 can obtain single crystal silicon aspheric lenses with qualified surface shapes and surface finishes of 60 / 40, but the number of repeated rough polishing is different. Figure 3 In Example 3, there is occasional mid-frequency error. The reason is that the surface of the lens after milling is rough and has many burrs. The surface shape shows that the waviness is particularly large. If it is used directly without smoothing, it will cause a particularly serious mid-frequency error in the first round of rough polishing, making the subsequent process impossible. Therefore, in actual production, it is preferred to perform smoothing to reduce defective products.

[0108] refer to Figure 4 The middle part of the face of Example 1 is bulging, and it is speculated that the reason is that the polishing leather is worn away by the edge of the lens.

[0109] refer to Figure 5 The surface of comparative example 2 is concave in the middle because the particle size of the polishing liquid is large and the rotation speed of the polishing head and the working shaft is high.

[0110] refer to Figure 6 , the downward pressure in comparative example 3 is relatively large. Although the polishing efficiency is high, it brings serious mid-frequency errors. Moreover, due to the large downward pressure, the contact between the lens and the polishing liquid is insufficient, and deep scratches and pits will appear on the surface of the lens.

[0111] The efficiency of Comparative Example 4 is too slow because the pressing amount is small and the polishing time is very long. Considering the economic benefits, it is not suitable for production activities.

[0112] refer to Figure 7 The surface finish of comparative example 5 did not meet the standard, and obvious white spots were found through 14 times magnification observation under a microscope.

[0113] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A CNC polishing process for zinc selenide aspheric lenses, based on a CNC polishing machine, characterized in that: The steps include: Step 1: Scan the profile of the zinc selenide aspherical lens to obtain a profile model; Step 2: Rough polishing of the zinc selenide aspheric lens using a CNC polishing machine according to the contour model; Step 3: Perform profile scanning on the zinc selenide aspheric lens after rough polishing to obtain a new profile model; Step 4: Use a CNC polishing machine to fine-polish the zinc selenide aspheric lens according to the contour model obtained in step 3; Step 5: Refine and get the finished product.

2. The CNC polishing process for zinc selenide aspheric lenses according to claim 1, characterized in that: If the surface PV of the contour model in step 3 is greater than the drawing requirement, return to step 2; if the surface PV is less than the drawing requirement, go to step 4.

3. The CNC polishing process for zinc selenide aspheric lenses according to claim 1, characterized in that: The polishing liquid used in the rough polishing is a mixed solution of 1-2 μm aluminum oxide, ammonium dichromate, oily suspension and pure water, wherein the ratio of aluminum oxide: ammonium dichromate: oily suspension: pure water is 40:1:60:

299.

4. The CNC polishing process for zinc selenide aspheric lenses according to claim 1, characterized in that: In the step 5, the zinc selenide aspheric lens is transferred to a grinding and polishing machine, and an ammonium dichromate solution is added to the zinc selenide aspheric lens to wet it, so that the zinc selenide aspheric lens rotates at a speed of 100 to 200 RPM, and then the zinc selenide aspheric lens is finely trimmed with a polishing leather at a pressure of 4 to 6 kPa, and polishing liquid and ammonium dichromate solution are continuously dripped during the process.

5. The CNC polishing process for zinc selenide aspheric lenses according to claim 1, characterized in that: Before step 1, a zinc selenide aspheric lens with a surface type PV≤2 μm is prepared by milling, and sharp edges at the edges of the zinc selenide aspheric lens are removed.

6. The CNC polishing process for zinc selenide aspheric lenses according to claim 1, characterized in that: In the step 2, the actual indentation diameter is compared with the theoretical calculated indentation size, and the rough polishing tool height is adjusted according to the difference to make the theoretical indentation equal to the actual indentation size.

7. The CNC polishing process for zinc selenide aspheric lenses according to claim 1, characterized in that: The parameter setting of the CNC polishing machine meets the following conditions: Setting a, when the particle size of the polishing liquid is 0.5-1 μm and the lens diameter is set to be less than 150 mm, the speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 800-1000 RPM, and the downward pressure is 0.5-0.7 mm; Setting b, when the particle size of the polishing liquid is 0.5-1 μm and the lens diameter is set to be greater than 150 mm, the speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 300-500 RPM, and the downward pressure is 0.5-0.7 mm; Setting c, when the particle size of the polishing liquid is 1-2 μm and the lens diameter is set to be less than 150 mm, the speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 300-500 RPM, and the downward pressure is 0.2-0.4 mm; Setting d. When the particle size of the polishing liquid is 1-2 μm and the lens diameter is set to be greater than 150 mm, the speed of the polishing head and the workpiece axis of the CNC polishing machine are set to 150-300 RPM, and the downward pressure is 0.2-0.4 mm.

8. The CNC polishing process for zinc selenide aspheric lenses according to claim 7, characterized in that, The remaining settings of the CNC polishing machine in step 2 are as follows: The size of the polishing head is one third to one quarter of the diameter of the lens; Correction is set to -30% to -60%; The track-pitch value in the path data is one percent of the set lens diameter; The unit of oscillation-time is seconds, and its value is 3 to 5 times the set lens diameter; The filter width in extrapolate is 1% of the set lens diameter, the point distance is 1% of the set lens diameter, and the target diameter is the effective diameter plus 5 to 10 mm; Smoothing is performed, and the smoothing value is 2 to 3 μm; Adjust the removal-coefficient and oscillation-time values ​​and set the feedmin. value to 10 mm / min.

9. The CNC polishing process for zinc selenide aspheric lenses according to claim 8, characterized in that: The settings of the CNC polishing machine in step 4 are as follows: The particle size of the polishing liquid is 0.5-1μm, the downward pressure is 0.1-0.2mm, and the other setting requirements are the same as rough polishing.

10. A zinc selenide aspherical lens, wherein the diameter of the zinc selenide aspherical lens is less than 320 mm, characterized in that: The aspheric zinc selenide lens is made by the CNC polishing process as claimed in any one of claims 1 to 9. The global surface PV is less than 0.3 μm, and the surface finish is 60 / 40, reaching the laser grade.

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