Polishing device and polishing method for processing calcium fluoride samples in batches

Abstract

The polishing device comprises a rack, a portal frame is arranged above the rack, an upper grinding disc device is arranged on the portal frame, a lower grinding disc is arranged in the middle of the rack, an outer gear ring is arranged on the outer side of the lower grinding disc, and an outer gear ring support is arranged below the outer gear ring. The lower portion of the outer gear ring support is in transmission connection with a first driving mechanism through a rotating sleeve. An inner gear ring is arranged on the inner side of the lower grinding disc; the middle of the inner gear ring is in transmission connection with a second driving mechanism through a hollow shaft; a lower disc hollow shaft is arranged below the lower grinding disc and is in transmission connection with a third driving mechanism; a wandering star wheel is arranged between the outer gear ring and the inner gear ring; a plurality of jig grooves are formed in the surface of the wandering star wheel. The defects in the prior art are overcome, same-thickness double-face polishing and different-thickness single-face polishing can be achieved on the same equipment, and the machining efficiency is greatly improved; and the stress, the wedge angle and the polishing rate of the sample are flexibly adjusted by increasing and reducing the pressure body, so that the introduction of processing stress is greatly avoided.

Description

Technical Field

[0001] The present invention relates to the field of physics, and particularly to the technology of crystal sample polishing. Specifically, it is a polishing device and method for batch processing of calcium fluoride samples. Background Art

[0002] CaF2 single crystal has become an excellent achromatic and apochromatic lens material due to its wide transmission window (0.125μm - 10μm), low refractive index and low dispersion characteristics. In some special application scenarios, such as space-based earth observation imaging systems and objective lens systems for lithography machines, there are relatively high requirements for the optical uniformity, stress, etc. of CaF2 samples. Therefore, it is necessary to conduct a series of test evaluations on the prepared CaF2 crystals for optical uniformity, stress, etc., and select products that meet the requirements for special scenarios such as astronomical observation and lithography.

[0003] However, testing optical uniformity, etc. requires polishing the samples, and generally specific requirements such as wedge angle, surface shape, surface finish, etc. need to be met. In addition, for different application scenarios, the required sample thicknesses are also different.

[0004] Currently, the equipment generally used for large-diameter polishing is a ring polisher, but the ring polisher can only process one side and has a low processing efficiency. For samples with a relatively small diameter (100mm) and consistent thickness, the 9B double-plane polishing equipment has more advantages than the ring polisher. It can achieve double-sided polishing and has a relatively fast processing speed. However, the 9B double-plane polishing equipment cannot meet the polishing requirements for samples with different thicknesses. In summary, both the ring polisher and the 9B double-plane polishing equipment have their own advantages and disadvantages. In addition, the traditional classical polishing process is also often used for large-diameter polishing, but this process highly depends on the experience accumulation of processing personnel, has high requirements for people, and cannot guarantee the repeatability and reliability of processing; at the same time, the processing is slow and the labor cost is high. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the present invention provides a polishing device and method for batch processing of calcium fluoride samples, which overcomes the deficiencies of the prior art, is reasonably designed, can achieve double-sided polishing of the same thickness and single-sided polishing of different thicknesses on the same device, improves the processing efficiency and greatly reduces the production cost of enterprises; and through an additional pressure body, the force on the sample, the wedge angle and the polishing rate can be flexibly adjusted, greatly avoiding the introduction of processing stress.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0007] A polishing device for batch processing of calcium fluoride samples, comprising a frame, above which a gantry is provided, on which an upper grinding disc device is arranged, in the middle of the frame there is a lower grinding disc, outside the lower grinding disc there is an external gear ring, below the external gear ring there is an external gear ring bracket fixedly installed, and the external gear ring bracket is in transmission connection with a first driving mechanism through a rotating sleeve; inside the lower grinding disc there is an internal gear ring, in the middle of the internal gear ring there is a hollow shaft fixedly installed, and the hollow shaft is in transmission connection with a second driving mechanism below; coaxially and fixedly installed below the lower grinding disc there is a lower disc hollow shaft, and the lower end of the lower disc hollow shaft is in transmission connection with a third driving mechanism;

[0008] Between the external gear ring and the internal gear ring there are more than two planetary wheels arranged at intervals, and the planetary wheels are respectively meshed with the external gear ring and the internal gear ring; on the surface of the planetary wheels there are a plurality of fixture grooves.

[0009] Preferably, the upper grinding disc device comprises an upper grinding disc, above which is connected to a bearing seat through an upper support frame, the bearing seat is connected to the outer ring of a bearing, and the inner ring of the bearing is connected to the telescopic end of a telescopic cylinder through a central shaft; the lower surface of the upper grinding disc is directly opposite to the upper surface of the lower grinding disc, in the middle of the lower grinding disc there is a driving dial, coaxially arranged below the driving dial there is a dial driving shaft, and the lower end of the dial driving shaft is in transmission connection with a fourth driving mechanism, and the driving dial and the upper grinding disc are arranged to be separable or dockable.

[0010] Preferably, the first driving mechanism comprises a first gear and a first motor, the first rotating shaft is fixedly sleeved on the lower outer surface of the rotating sleeve, the driving end of the first motor is in transmission connection with the first gear, the second driving mechanism comprises a second gear and a second motor, the second gear is fixedly sleeved on the lower outer surface of the hollow shaft, and the driving end of the second motor is in transmission connection with the second gear; the third driving mechanism comprises a third gear and a third motor, the third gear is fixedly sleeved on the lower outer surface of the lower disc hollow shaft, and the driving end of the third motor is in transmission connection with the third gear.

[0011] The present invention also discloses a polishing method applying the above polishing device for batch processing of calcium fluoride samples, comprising the following steps:

[0012] Step S1: Fine grinding; using a horizontal vertical milling machine, the grinding wheel grit is selected as 350 mesh to process the calcium fluoride crystal sample into a special wedge angle required for optical uniformity testing;

[0013] Step S2: Rough polishing; Place the calcium fluoride crystal sample after the processing in step S1 into the fixture groove in the planetary wheel, and then drop the polycrystalline diamond polishing liquid with the abrasive of W1 particle size on the lower grinding plate; Then start the polishing device, drive the internal gear ring to rotate by the second driving mechanism, and cooperate with the first driving mechanism to drive the external gear ring to rotate, so that the planetary wheel rotates around the centers of the internal gear ring and the external gear ring and rotates self - rotatably, and the calcium fluoride crystal rotates with the planetary wheel; At the same time, the third driving mechanism drives the lower grinding plate to rotate; To grind and polish the calcium fluoride crystal; The polishing time is 30 - 50 min / disc, removing the rough layer on the surface of the calcium fluoride crystal after the fine grinding process.

[0014] Step S3: Fine polishing; Then drop the polycrystalline diamond polishing liquid with the abrasive of 250 nm particle size on the lower grinding plate; Then start the polishing device, and again drive the internal gear ring to rotate by the second driving mechanism, and cooperate with the first driving mechanism to drive the external gear ring to rotate, so that the planetary wheel rotates around the centers of the internal gear ring and the external gear ring and rotates self - rotatably, and the calcium fluoride crystal rotates with the planetary wheel; At the same time, the third driving mechanism drives the lower grinding plate to rotate; To grind and polish the calcium fluoride crystal; The polishing time is 60 - 80 min / disc; To improve the surface finish and surface shape of the sample.

[0015] Step S4: Clean the surface of the processed sample, apply a neutral optical protective paint and stick a protective tape. After the protection process is completed, turn over the sample and return to the rough polishing process in step S2 to polish the unprocessed surface until all the test surfaces of the calcium fluoride crystal reach the polishing index.

[0016] Preferably, before step S2, first classify the calcium fluoride crystals to be processed. According to the sample weight of the calcium fluoride crystals, those with a weight greater than 2 KG are classified as one category, and those less than or equal to 2 KG are classified as the second category; For the samples in the first category, directly place the samples into the fixture groove of the planetary wheel; For the samples in the second category, first paste a metal block with a weight of 0.5 - 1.5 kg on the upper surface of the sample, and then place the sample into the fixture groove of the planetary wheel.

[0017] The present invention provides a polishing device and a polishing method for batch processing calcium fluoride samples. It has the following beneficial effects: By classifying the samples to be processed. The classification is based on the weight of the samples. Samples with a weight greater than 2KG are classified as one category, and those less than or equal to 2KG are classified as the second category. For samples in the first category, since the self-weight of the samples is sufficient, the samples to be polished can be directly placed into the planetary wheel, enabling effective grinding between the sample surface and the disk surface, achieving the purpose of removing dimensions and surface polishing. For samples in the second category, due to their relatively light self-weight, the generated grinding force is insufficient and the processing efficiency is very low. Therefore, a metal block needs to be pasted on the upper surface of the sample with adhesive tape. After pasting, it is placed into the planetary wheel, so that effective grinding is generated between the sample surface and the disk surface of the lower grinding disk, achieving the purpose of removing dimensions and surface polishing; thus, it is possible to flexibly adjust the force, wedge angle, and polishing rate of the sample, greatly avoiding the introduction of processing stress, and while ensuring the processing quality of samples of different specifications, taking into account the processing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for the description of the prior art.

[0019] Figure 1 It is a schematic structural diagram of the polishing device of the present invention;

[0020] Figure 2 It is a schematic cross-sectional view of the polishing device of the present invention;

[0021] Explanation of the reference numerals in the drawings:

[0022] 1, frame; 2, gantry; 3, upper grinding disk device; 4, lower grinding disk; 5, external gear ring; 6, external gear ring bracket; 7, rotating sleeve; 8, first driving mechanism; 9, internal gear ring; 10, hollow shaft; 11, second driving mechanism; 12, lower disk hollow shaft; 13, third driving mechanism; 14, planetary wheel; 15, fixture groove; 31, upper grinding plate; 32, upper support frame; 33, bearing seat; 34, bearing; 35, telescopic cylinder; 36, driving pulley; 37, pulley driving shaft; 38, fourth driving mechanism. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] To make the purpose, technical solutions, and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the present invention with reference to the drawings in the present invention.

[0024] Embodiment 1

[0025] As Figure 1-2As shown, a polishing device for batch processing of calcium fluoride samples comprises a frame 1, a gantry 2 is arranged above the frame 1, an upper grinding disc device 3 is arranged on the gantry 2, a lower grinding disc 4 is arranged in the middle of the frame 1, an outer gear ring 5 is arranged on the outer side of the lower grinding disc 4, an outer gear ring bracket 6 is fixedly installed below the outer gear ring 5, and the lower part of the outer gear ring bracket 6 is connected to the first driving mechanism 8 through a rotating sleeve 7; an inner gear ring 9 is arranged on the inner side of the lower grinding disc 4, a hollow shaft 10 is fixedly installed in the middle of the inner gear ring 9, and the lower part of the hollow shaft 10 is connected to the second driving mechanism 11; a lower plate hollow shaft 12 is fixedly installed coaxially below the lower grinding disc 4, and the lower end of the lower plate hollow shaft 12 is connected to the third driving mechanism 13;

[0026] Two or more planetary wheels 14 are arranged between the outer gear ring 5 and the inner gear ring 9 . The planetary wheels 14 are arranged at intervals and mesh with the outer gear ring 5 and the inner gear ring 9 respectively. A plurality of fixture grooves 15 are arranged on the surface of the planetary wheels 14 .

[0027] Working principle:

[0028] When in use, the sample to be ground and polished is first placed in the fixture groove 15 on the surface of the planetary wheel 14. In this embodiment, due to the uncertainty of crystal growth, it is inevitable to select some blank samples with inconsistent specifications when selecting crystal materials, so it is necessary to classify the samples to be processed. The classification basis is the weight of the sample. The weight greater than 2KG is the first category, and the weight less than or equal to 2KG is the second category. For the first category of samples, the sample weight is sufficient, and the sample to be polished can be directly placed in the fixture groove 15 on the surface of the planetary wheel 14, so that the sample surface and the disk surface are effectively ground, and the purpose of removing size and surface polishing is achieved. For the second category of samples, the sample itself is light in weight, the grinding force generated is insufficient, and the processing efficiency is very low. Therefore, it is necessary to use adhesive tape to stick a 0.5-1.5kg metal block on the upper surface of the sample. After the sticking is completed, it is placed in the fixture groove 15 on the surface of the planetary wheel 14; thereby, the sample force, wedge angle and polishing rate can be flexibly adjusted, and the introduction of processing stress is greatly avoided. While ensuring the processing quality of samples of different specifications, the processing efficiency is taken into account.

[0029] Then, polycrystalline diamond polishing liquid with a particle size of W1 and 250nm is dripped on the lower grinding disc 4 respectively, and then the equipment is started, and the second driving mechanism 11 drives the inner ring gear 9 to rotate, and cooperates with the first driving mechanism 8 to drive the outer ring gear 5 to rotate, so that the planetary wheel 14 rotates and rotates around the center of the inner ring gear 9 and the outer ring gear 5, and the calcium fluoride crystal rotates with the planetary wheel 14; at the same time, the third driving mechanism 13 drives the lower grinding disc 4 to rotate; so as to achieve the rough polishing and fine polishing effects on the sample, and after the fine polishing of a plate of samples is completed, the processed sample surface is cleaned, coated with neutral optical protective paint and affixed with protective tape. After the protection process is completed, the sample is turned over and returned to the rough polishing process to polish the unprocessed surface until all test surfaces of the sample meet the polishing index.

[0030] Embodiment 2, as a further preferred solution of Embodiment 1, the upper grinding disc device 3 includes an upper grinding disc 31. The upper grinding disc 31 is connected to a bearing seat 33 through an upper support frame 32 above. The bearing seat 33 is connected to the outer ring of a bearing 34. The inner ring of the bearing 34 is connected to the telescopic end of a telescopic cylinder 35 through a central shaft. The lower surface of the upper grinding disc 31 is directly opposite to the upper surface of the lower grinding disc 4. A driving dial 36 is arranged in the middle of the lower grinding disc 4. A dial driving shaft 37 is arranged coaxially below the driving dial 36. The lower end of the dial driving shaft 37 is in transmission connection with a fourth driving mechanism 38. The driving dial 36 and the upper grinding disc 31 are arranged to be separable or dockable.

[0031] For a certain type of sample, there is no need to paste a metal block on the sample. Therefore, through the combined action of the upper grinding disc 31 and the lower grinding disc 4, the upper surface and the lower surface of the sample can be ground simultaneously. During use, first place the sample to be ground and polished in the fixture groove 15 on the surface of the planetary wheel 14. Then, drop polycrystalline diamond polishing fluid on the lower grinding disc 4 and the upper surface of the sample. Then, control the telescopic cylinder 35 to drive the upper grinding disc 31 to move downward, so that the middle of the upper grinding disc 31 is docked with the driving dial 36, and then the upper grinding disc 31 and the lower grinding disc 4 are respectively pressed against the upper and lower surfaces of the sample. Then, the second driving mechanism 11 drives the internal gear ring 9 to rotate, and cooperates with the first driving mechanism 8 to drive the external gear ring 5 to rotate, so that the planetary wheel 14 rotates around the centers of the internal gear ring 9 and the external gear ring 5 and rotates itself, so that the calcium fluoride crystal rotates with the planetary wheel 14. At the same time, the third driving mechanism 13 drives the lower grinding disc 4 to rotate, and cooperates with the fourth driving mechanism 38 to drive the driving dial 36 to rotate through the dial driving shaft 37, and then starts the upper grinding disc 31 outside the driving dial 36 to rotate. And in this embodiment, the rotation directions of the upper grinding disc 31 and the lower grinding disc 4 are opposite to the rotation direction of the planetary wheel 14, so as to realize the simultaneous grinding and polishing of the upper and lower surfaces of the workpiece, and achieve the purpose of double-sided grinding and polishing. Then, the same-thickness double-sided polishing and different-thickness single-sided polishing are realized on the same device, improving the processing efficiency and greatly reducing the production cost of the enterprise.

[0032] Embodiment 3, as a further preferred solution of Embodiment 1, the first driving mechanism 8 includes a first gear and a first motor. The first rotating shaft is fixedly sleeved on the lower outer surface of the rotating sleeve 7. The driving end of the first motor is in transmission connection with the first gear. The second driving mechanism 11 includes a second gear and a second motor. The second gear is fixedly sleeved on the lower outer surface of the hollow shaft 10. The driving end of the second motor is in transmission connection with the second gear. The third driving mechanism 13 includes a third gear and a third motor. The third gear is fixedly sleeved on the lower outer surface of the lower plate hollow shaft 12. The driving end of the third motor is in transmission connection with the third gear. In addition, the fourth driving mechanism 13 includes a fourth gear and a fourth motor. The fourth gear is fixedly sleeved on the lower outer surface of the dial driving shaft 37. The driving end of the fourth motor is in transmission connection with the fourth gear. In this embodiment, the first motor, the second motor, the third motor and the fourth motor all adopt servo motors, so that the revolution position and the rotation position of the planet gear 14 can be in a predetermined position by controlling the speed ratio of the first motor, the second motor, the third motor and the fourth motor. Thus, the precision of the rotation speed, the revolution speed and the polishing efficiency of the sample can be traced, and the precise control of the system can be realized.

[0033] Embodiment 4

[0034] The present invention also discloses a polishing method applied to the above-mentioned polishing device for batch processing calcium fluoride samples, including the following steps:

[0035] Step S1: Fine grinding; Use a horizontal vertical milling machine, and select 350-mesh grinding wheel grit to process the calcium fluoride crystal sample to produce the special wedge angle required for optical uniformity testing. According to the requirements of different samples, different methods can be adopted. Generally, when the wedge angle exceeds 15 minutes, a corresponding standard angle tooling needs to be customized. This process is a preparation process and also a prior art, so it will not be elaborated here.

[0036] Step S2: Rough polishing; Put the calcium fluoride crystal sample processed in Step S1 into the fixture groove 15 in the customized-size epoxy resin planet gear 14, and then drop polycrystalline diamond polishing liquid with W1 grit as the abrasive on the lower grinding disc 4. For calcium fluoride crystals, the polycrystalline diamond polishing liquid is diluted in a ratio of 1:2 before use. Then start the polishing device. The second driving mechanism 11 drives the internal gear ring 9 to rotate, and cooperates with the first driving mechanism 8 to drive the external gear ring 5 to rotate, so that the planet gear 14 rotates around the centers of the internal gear ring 9 and the external gear ring 5 and rotates itself, and the calcium fluoride crystal rotates with the planet gear 14. At the same time, the third driving mechanism 13 drives the lower grinding disc 4 to rotate to grind and polish the calcium fluoride crystal. The polishing time is 30 - 50 min / disc to remove the rough layer on the surface of the calcium fluoride crystal after the fine grinding process.

[0037] Step S3: Fine polishing; then drop polycrystalline diamond polishing fluid with a particle size of 250 nm as abrasive on the lower polishing disc 4. For calcium fluoride crystals, it is used after being diluted at a ratio of 1:1; then start the polishing device, and drive the internal gear ring 9 to rotate by the second driving mechanism 11, and cooperate with the first driving mechanism 8 to drive the external gear ring 5 to rotate, so that the planetary gear 14 rotates around the centers of the internal gear ring 9 and the external gear ring 5 and rotates itself, and the calcium fluoride crystal rotates with the planetary gear 14; at the same time, the third driving mechanism 13 drives the lower polishing disc 4 to rotate; to grind and polish the calcium fluoride crystal; the polishing time is 60 - 80 min / disc; to improve the surface finish and surface shape of the sample.

[0038] Step S4: Clean the surface of the processed sample, apply a neutral optical protective paint and stick a protective tape. After the protection process is completed, turn over the sample and return to the rough polishing process in Step S2 to polish the unprocessed surface until all the test surfaces of the calcium fluoride crystal reach the polishing index.

[0039] Among them, before Step S2, first classify the calcium fluoride crystals to be processed. According to the sample weight of the calcium fluoride crystals, those with a weight greater than 2 KG are classified as one category, and those less than or equal to 2 KG are classified as the second category; for samples in the first category, directly put the samples into the planetary gear 14; for samples in the second category, first paste a metal block with a weight of 0.5 - 1.5 kg on the upper surface of the sample, and then put the sample into the planetary gear 14. Thus, by adjusting the pressure-increasing and pressure-reducing body, the thickness of the protective sleeve, the concentration and dosage of the polishing fluid, the stress on the sample, the wedge angle and the polishing rate can be flexibly adjusted, and the introduction of processing stress can be greatly avoided.

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A polishing device for batch processing of calcium fluoride samples, comprising a frame (1), Features: A gantry (2) is arranged above the frame (1), an upper grinding disc device (3) is arranged on the gantry (2), a lower grinding disc (4) is arranged in the middle of the frame (1), an outer gear ring (5) is arranged on the outer side of the lower grinding disc (4), an outer gear ring bracket (6) is fixedly installed below the outer gear ring (5), and the lower side of the outer gear ring bracket (6) is transmission-connected to a first driving mechanism (8) through a rotating sleeve (7); an inner gear ring (9) is arranged on the inner side of the lower grinding disc (4), a hollow shaft (10) is fixedly installed in the middle of the inner gear ring (9), and the lower side of the hollow shaft (10) is transmission-connected to a second driving mechanism (11); a lower plate hollow shaft (12) is coaxially fixedly installed below the lower grinding disc (4), and the lower end of the lower plate hollow shaft (12) is transmission-connected to a third driving mechanism (13); Two or more planetary wheels (14) are arranged between the outer gear ring (5) and the inner gear ring (9), the planetary wheels (14) are arranged at intervals, and the planetary wheels (14) are respectively meshed with the outer gear ring (5) and the inner gear ring (9); and a plurality of fixture grooves (15) are arranged on the surface of the planetary wheels (14).

2. A polishing device for batch processing of calcium fluoride samples according to claim 1, Features: The upper grinding disc device (3) comprises an upper grinding disc (31), the upper part of the upper grinding disc (31) is connected to a bearing seat (33) through an upper support frame (32), the bearing seat (33) is connected to the outer ring of a bearing (34), and the inner ring of the bearing (34) is connected to the telescopic end of a telescopic cylinder (35) through a central axis; the lower surface of the upper grinding disc (31) is vertically opposite to the upper surface of the lower grinding disc (4), a driving paddle wheel (36) is arranged in the middle of the lower grinding disc (4), a paddle wheel driving shaft (37) is coaxially arranged below the driving paddle wheel (36), the lower end of the paddle wheel driving shaft (37) is transmission-connected to a fourth driving mechanism (38), and the driving paddle wheel (36) and the upper grinding disc (31) can be separated or butted.

3. A polishing device for batch processing of calcium fluoride samples according to claim 1, Features: The first driving mechanism (8) comprises a first gear and a first motor, the first rotating shaft is fixedly sleeved below the outer surface of the rotating sleeve (7), and the driving end of the first motor is drivingly connected to the first gear; the second driving mechanism (11) comprises a second gear and a second motor, the second gear is fixedly sleeved below the outer surface of the hollow shaft (10), and the driving end of the second motor is drivingly connected to the second gear; the third driving mechanism (13) comprises a third gear and a third motor, the third gear is fixedly sleeved below the outer surface of the lower plate hollow shaft (12), and the driving end of the third motor is drivingly connected to the third gear.

4. A polishing method using the polishing device for batch processing of calcium fluoride samples according to any one of claims 1 to 3, Features: The following steps are involved: Step S1: Fine grinding; Use a surface vertical milling machine, and select a grinding wheel with a particle size of 350 mesh to process the calcium fluoride crystal sample to produce the special wedge angle required for optical uniformity testing; Step S2: Coarse polishing; Place the calcium fluoride crystal sample processed in Step S1 into the fixture groove (15) of the planetary wheel (14), and then drop polycrystalline diamond polishing liquid with a W1 particle size abrasive on the lower grinding disc (4); Then start the polishing device, drive the internal gear ring (9) to rotate by the second driving mechanism (11), and cooperate with the first driving mechanism (8) to drive the external gear ring (5) to rotate, so that the planetary wheel (14) rotates around the centers of the internal gear ring (9) and the external gear ring (5) and rotates self - rotatably, and the calcium fluoride crystal rotates with the planetary wheel (14); At the same time, the third driving mechanism (13) drives the lower grinding disc (4) to rotate; To grind and polish the calcium fluoride crystal; The polishing time is 30 - 50 min / disc to remove the rough layer on the surface of the calcium fluoride crystal after the fine grinding process; Step S3: Fine polishing; Then drop polycrystalline diamond polishing liquid with a 250 nm particle size abrasive on the lower grinding disc (4); Then start the polishing device, and again drive the internal gear ring (9) to rotate by the second driving mechanism (11), and cooperate with the first driving mechanism (8) to drive the external gear ring (5) to rotate, so that the planetary wheel (14) rotates around the centers of the internal gear ring (9) and the external gear ring (5) and rotates self - rotatably, and the calcium fluoride crystal rotates with the planetary wheel (14); At the same time, the third driving mechanism (13) drives the lower grinding disc (4) to rotate; To grind and polish the calcium fluoride crystal; The polishing time is 60 - 80 min / disc; To improve the surface finish and surface shape of the sample; Step S4: Clean the surface of the processed sample, coat it with a neutral optical protective paint and stick a protective tape. After the protection process is completed, flip the sample and return to the coarse polishing process in Step S2 to polish the unprocessed surface until all the test surfaces of the calcium fluoride crystal reach the polishing index.

5. The polishing method according to claim 4, characterized in that: Before the said Step S2, first classify the calcium fluoride crystals to be processed. According to the sample weight of the calcium fluoride crystals, those with a weight greater than 2 KG are classified as one category, and those less than or equal to 2 KG are classified as two categories; For the samples in the first category, directly place the samples into the fixture groove (15) of the planetary wheel (14); For the samples in the second category, first paste a metal block with a weight of 0.5 - 1.5 kg on the upper surface of the sample, and then place the sample into the fixture groove (15) of the planetary wheel (14).

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