Single-point diamond turning device and method for lens based on vacuum piston

Abstract

The single-point diamond turning device comprises a bottom plate, a circumferential sealing component installed on the bottom plate and the lens arranged on the circumferential sealing component, a plurality of countersunk threaded holes are formed in the bottom plate in an array mode, a vacuum connector is formed in the center position of the bottom plate, and the vacuum connector is connected with the circumferential sealing component. A piston support is slidably connected into a countersunk threaded hole in the circumferential sealing component, the top of the piston support abuts against the lower surface of the lens, and the upper surface of a piston of the piston support, the lower surface of the lens, the inner wall of the circumferential sealing component and the upper surface of the bottom plate jointly define a closed cavity. The device is suitable for supporting the large-diameter-thickness-ratio curved surface contour lens, it can be guaranteed that all positions of the lower surface of the lens are effectively supported in the machining process on the premise that an active adjusting device and operation are not needed, the mirror surface deformation area is small and the deformation amplitude is small when the lens is machined, and the surface shape precision of the machined mirror surface is further guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-precision machining, and particularly to a single-point diamond turning machining device and method for lenses based on a vacuum piston. Background Art

[0002] Free-form surfaces have higher degrees of freedom in optical surface design, are easier to correct aberrations, and improve the performance of optical systems. At the same time, free-form surface optical elements are lighter in mass, smaller in external dimensions, and a single element can achieve the functions of original multiple elements, making the system simple and compact. These free-form surface optical elements are widely used in modern optical fields such as lighting, optical imaging, and biomedical engineering. Currently, ultra-precision machining technology is the mainstream technology for manufacturing free-form surface optical elements, and its basic technology is single-point diamond turning.

[0003] When manufacturing an optical surface using diamond turning, it is necessary to reduce the elastic deformation and vibration of the optical surface during machining to ensure the surface shape accuracy and surface roughness of the mirror surface. This requires the optical element to have a certain stiffness. Therefore, the thickness of the optical element generally cannot be too thin, and a certain diameter-to-thickness ratio is used to increase the stiffness of the element and reduce deformation and vibration.

[0004] However, thinner free-form surface lenses are the basis for giving full play to the advantages of lightness, small size, and compactness of free-form surface optical systems. For such lenses with a large diameter-to-thickness ratio, effective back support is required to make up for the insufficient stiffness of the lens itself, so as to achieve the effect of reducing the elastic deformation and vibration of the optical surface during machining. For lenses with a large diameter-to-thickness ratio whose back surfaces are flat or spherical, effective surface support can be achieved by installing them on a flat or complementary spherical support body. However, for lenses with a large diameter-to-thickness ratio whose both surfaces are free-form surfaces, when machining each surface, it is necessary to first use single-point turning to machine the complementary contour support body on the back surface, and then install and further machine the front surface of the lens. The machining process is complex and time-consuming, and it is difficult to ensure the fitting between the support body and the back surface of the lens.

[0005] CN109676420A combines the magnetorheological fluid technology with the jet support technology, uses the jet impact force on the back surface of the lens to offset part of the machining force on the front surface, and further controls the magnetic field strength to support the workpiece with instantaneously solidified magnetorheological fluid.

[0006] Invention patents such as CN201810341311.2, CN201810341293.8, and CN201610630977.0 adjust the height of each support pillar to be consistent with the height of the back contour of the thin sheet element by controlling the ball screw mechanism, and further fix the thin sheet element using the suction cup on the top of the support pillar. The above existing methods rely on active control devices such as magnetorheological fluid, jet devices, or adjustment mechanisms and motors. The relationships between the mechanisms are complex, it is difficult to arrange the support device on the main shaft, and it is difficult to give full play to the advantages of single-point diamond turning machining.

[0007] Currently, no one has proposed an effective passive conforming support device and method for single-point diamond turning of large-diameter-thickness ratio lenses, and the problem that the support of large-diameter-thickness ratio free-form surface lenses in the existing single-point turning technology depends on complex active adjustment devices has not been effectively solved. Summary of the Invention

[0008] The main technical problem to be solved by the present invention is to provide a single-point diamond turning processing device and method for lenses based on a vacuum piston, which realizes effective support of large-diameter-thickness ratio lenses in single-point turning on the premise of avoiding active adjustment devices, so that the mirror deformation area is small and the deformation amplitude is small during single-point diamond turning of lenses, reduces low-frequency deformation, weakens intermediate-frequency vibration, and further ensures high surface shape accuracy and good surface roughness of the mirror surface after processing.

[0009] To solve the above technical problem, a technical solution adopted by the present invention is: a single-point diamond turning processing device for lenses based on a vacuum piston, including: a bottom plate, a circumferential sealing member installed on the bottom plate, and a lens disposed on the circumferential sealing member. A plurality of countersunk threaded holes are arranged in an array on the bottom plate, a vacuum interface is provided at the central position of the bottom plate, a piston support is slidably connected in the countersunk threaded holes in the circumferential sealing member, the top of the piston support abuts against the lower surface of the lens, and a closed chamber is jointly formed by the upper surface of the piston of the piston support, the lower surface of the lens, the inner wall of the circumferential sealing member, and the upper surface of the bottom plate. The vacuum interface is connected to an external vacuum air path to maintain the vacuum state of the closed chamber.

[0010] In a preferred embodiment of the present invention, the upper end of the circumferential sealing member has a stepped portion, the lower end of the circumferential sealing member is attached to the bottom plate and has mounting legs, through holes are provided on the mounting legs, and the circumferential sealing member is fixedly connected to the bottom plate by screws passing through the through holes.

[0011] In a preferred embodiment of the present invention, the inner wall contour of the stepped portion matches the outer contour of the lens, and the two are connected in a clearance fit.

[0012] In a preferred embodiment of the present invention, the piston support includes a piston and a support rod fixedly connected to the upper end of the piston. The upper end of the support rod contacts the lower surface of the lens, and a fillet is provided at the upper end of the support rod.

[0013] In a preferred embodiment of the present invention, the upper end of the support rod is made of a material with soft texture, high lubricity, and non-stickiness.

[0014] In a preferred embodiment of the present invention, the countersunk threaded hole includes a countersunk hole and a threaded hole extending downward along the countersunk hole, and the piston is slidably connected with the countersunk hole.

[0015] In a preferred embodiment of the present invention, the countersunk threaded hole located at the center of the array on the bottom plate serves as a spare vacuum interface.

[0016] In a preferred embodiment of the present invention, the upper surface of the lens is subjected to atmospheric pressure to apply a downward pressure on the lens, so that the lens is adsorbed on the stepped portion of the circumferential sealing member. The lower surface of the piston support is connected to the atmosphere, and an upward pressure is applied to the piston support through the atmospheric pressure received by the lower surface of the piston, so as to realize the effective support of the piston support for the lower surface of the lens.

[0017] The present invention also provides a processing method for a single-point diamond turning device for lenses based on a vacuum piston, including the following steps: Step 1: Perform high-precision machining on the upper surface and the lower surface of the bottom plate, the circumferential surface of the piston of the piston support, and the countersunk hole, so as to ensure the sliding fit between the countersunk hole and the piston and the airtightness of the connection; Step 2: Design and machine the circumferential sealing member according to the lens contour shape so that the inner wall shapes of the two are the same and in complementary clearance fit. Install the circumferential sealing member on the bottom plate so that the lower surface of the circumferential sealing member is in close contact with the upper surface of the bottom plate. Use screws to pass through the through holes on the mounting legs to lock the circumferential sealing member on the bottom plate; Step 3: Install the piston support in the unobstructed countersunk hole inside the area surrounded by the circumferential sealing member on the bottom plate, so that the piston is slidably connected with the countersunk hole. Use a stud to seal the threaded hole part of the countersunk threaded hole, and assemble it into a single-point diamond turning device; Step 4: Install the assembled single-point diamond turning device on the spindle or linear guide of the turning machine tool, connect the machine tool vacuum pipeline to the vacuum interface of the bottom plate, complete the effective support for the lower surface of the lens, and facilitate turning processing.

[0018] In a preferred embodiment of the present invention, a sealing washer made of a soft material is provided inside the stepped portion of the circumferential sealing member. The upper surface of the piston of the piston support, the lower surface of the lens, the inner wall of the circumferential sealing member, and the upper surface of the bottom plate jointly enclose a closed chamber.

[0019] The beneficial effects of the present invention are as follows: Without the need for an active adjustment device, effective support for large-diameter-to-thickness-ratio lenses in single-point turning is achieved. As a result, during the single-point diamond turning of the lens, the mirror deformation area is small, the deformation amplitude is small, the low-frequency deformation is reduced, and the medium-frequency vibration is weakened. Furthermore, the surface shape accuracy of the mirror after processing is high, and the surface roughness is good. It also has the advantages of a small device volume, simple composition, being convenient to use inside a single-point diamond lathe, simple processing of the specific components required for the device, and the reusability of the device body. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention, among which: Figure 1 It is a schematic structural diagram of a single-point diamond turning device for large-diameter-to-thickness-ratio lenses;

[0021] Figure 2 It is the piston support structure in a single-point diamond turning device for large-diameter-to-thickness-ratio lenses;

[0022] Figure 3 It is the bottom plate structure in a single-point diamond turning device for large-diameter-to-thickness-ratio lenses;

[0023] Figure 4 It is the shape diagram of a free-form surface lens with a large diameter-to-thickness ratio provided in a specific embodiment;

[0024] Figure 5 It is the circumferential sealing component structure obtained in a specific embodiment;

[0025] Figure 6 It is the structural assembly diagram of a single-point diamond turning device for a curved surface lens in a specific embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] Please refer to Figure 1-6, embodiments of the present invention include: a single-point diamond turning processing device and method for lenses based on a vacuum piston, comprising: a bottom plate 1, a circumferential sealing member 3 mounted on the bottom plate, and a lens 4 disposed on the circumferential sealing member. A plurality of countersunk threaded holes 104 are arranged in an array on the bottom plate, and a vacuum interface 101 is provided at the center position of the bottom plate. A piston support 2 is slidably connected to the countersunk threaded holes inside the circumferential sealing member. Specifically, the upper end of the circumferential sealing member has a stepped portion 302, the lower end of the circumferential sealing member is in contact with the bottom plate and has mounting legs 303, and through holes 304 are provided on the mounting legs. The circumferential sealing member is fixedly connected to the bottom plate by screws 5 passing through the through holes. The piston support includes a piston 202 and a support rod 203 fixedly connected to the upper end of the piston. The upper end of the support rod is in contact with the lower surface of the lens, and a rounded corner 204 is provided at the upper end of the support rod, which is not likely to cause damage to the lower surface of the lens when in contact with it. After installation, the top of the piston support abuts against the lower surface of the lens. The upper surface 201 of the piston of the piston support, the lower surface 401 of the lens, the inner wall 301 of the circumferential sealing member, and the upper surface 102 of the bottom plate jointly enclose a closed chamber. The vacuum interface is connected to an external vacuum air path to maintain the vacuum state of the closed chamber.

[0028] Further, the inner wall contour of the stepped portion matches the outer contour of the lens, and the two are connected in a clearance fit. The upper surface of the lens is subjected to atmospheric pressure to apply a downward pressure on the lens, so that the lens is adsorbed on the stepped portion of the circumferential sealing member. The lower surface 205 of the piston of the piston support is connected to the atmosphere, and an upward pressure is applied to the piston support through the atmospheric pressure received by the lower surface of the piston to achieve effective support of the piston support for the lower surface of the lens. The upper end of the support rod is made of a material with a soft texture, high lubricity, and non-stickiness to avoid damage or contamination to the lower surface of the lens. The piston 202 needs to be in a sliding fit with the countersunk hole 104a. As an alternative embodiment, on the premise of the above dimensions and tolerances, a 30-micron molybdenum disulfide lubricating layer is plated on the circumferential surface of the piston 202, which can ensure both sliding fit and airtightness.

[0029] Preferably, a sealing gasket made of a soft material can be provided inside the stepped portion of the circumferential sealing member to achieve the effects of protecting the lens and sealing. As an alternative embodiment, the stepped portion 302 of the circumferential sealing member is covered with raw tape; the lower surface 401 of the lens is installed on the step 302 of the circumferential sealing member, and the vacuum switch on the machine tool spindle is turned on to connect with the vacuum interface.

[0030] Further, the piston support has a piston motion relationship with the bottom plate. The countersunk threaded hole 104 includes a countersunk hole 104a and a threaded hole 104b extending downward along the countersunk hole. The piston support is installed in the unobstructed countersunk hole inside the area surrounded by the circumferential sealing member on the bottom plate, so that the piston is slidably and matingly connected with the countersunk hole, and the countersunk threaded hole 104 with obstruction in the area of the circumferential sealing member 3 is sealed to ensure the connection airtightness. As an alternative embodiment, a stud is screwed in to seal the countersunk threaded hole 104 to ensure the airtightness in the area of the circumferential sealing member. In addition, the hole at the center of the array of the countersunk threaded holes 104 on the bottom plate does not install the piston support, and the countersunk threaded hole at the center position serves as a spare vacuum interface 101, which can be sealed with a stud when not in use.

[0031] In a preferred embodiment, as Figure 4 shown, the surface shapes of the upper surface 402 and the lower surface 401 of the lens are both non-rotationally symmetric free-form surfaces. The aperture of the lens 4 is 400 mm, the thickness is 20 mm, and the diameter-thickness ratio is 20:1. The circumferential sealing member 3 is designed and processed according to the outer contour shape of the lens 4. The wall thickness of the circumferential sealing member 3 is 15 mm, the outer wall diameter is 207.5 mm, and the inner wall 301 diameter is 192.5 mm. A step 302 is provided on the upper side of the circumferential sealing member 3. The circular inner wall diameter of the step 302 is 200 mm and the height is 10 mm. The outer edge of the lower surface 401 of the lens is consistent with and complementary to the upper surface shape of the step 302 of the circumferential sealing member. Further, the upper surface 102 and the lower surface 103 of the bottom plate 1 are parallel, with a thickness of 60 mm, a length of 500 mm, and a width of 500 mm; the bottom plate 1 is provided with an array of countersunk threaded holes 104. The aperture of the countersunk hole 104a of the countersunk threaded hole 104 is 10 mm (the tolerance range is +0 mm / +0.02 mm), the height is 50 mm, and the threaded hole 104b is an M6 through hole. The number of arrays is 25×25, and the spacing is 20 mm. As an alternative embodiment, the bottom plate 1 is prepared from Al6061 material, and the upper plane 102, the lower plane 103, and the countersunk hole 104a of the bottom plate 1 are machined with high precision to ensure the connection airtightness and the sliding fit between the countersunk hole 104a and the piston 202.

[0032] The present invention also provides a processing method for a single-point diamond turning processing device for a lens based on a vacuum piston, including the following steps: Step 1: High-precision machining is performed on the upper surface and the lower surface of the bottom plate, the piston circumferential surface of the piston support, and the countersunk hole to ensure the sliding fit between the countersunk hole and the piston and the connection airtightness; Step 2: Design and process the circumferential sealing member according to the lens contour shape so that the inner wall shapes of the two are consistent and complementary with a clearance fit. Install the circumferential sealing member on the bottom plate so that the lower surface of the circumferential sealing member is in close contact with the upper surface of the bottom plate, and use screws to pass through the through holes on the mounting legs to lock the circumferential sealing member on the bottom plate; Step 3: Install the piston support in the unobstructed counterbore inside the area enclosed by the circumferential sealing component on the bottom plate, making the piston slidably and fittingly connected with the counterbore, and use studs to seal the threaded part of the counterbore threaded hole to assemble a single-point diamond turning device; Step 4: Install the assembled single-point diamond turning device on the spindle or linear guide of the turning machine tool, and connect the machine tool vacuum pipeline to the vacuum interface of the bottom plate to complete the effective support of the lower surface of the lens, facilitating turning processing.

[0033] The beneficial effects of a single-point diamond turning device and method for lenses based on a vacuum piston according to the present invention are as follows: (1) High manufacturing accuracy of the optical mirror surface: The single-point diamond turning device and method for large-diameter and thick-thickness ratio lenses based on a vacuum piston in this application can ensure that all positions on the lower surface of the lens are effectively supported during the processing, so that the mirror surface deformation area and deformation amplitude are small during the single-point diamond turning of the lens, reducing low-frequency deformation and weakening medium-frequency vibration, and further ensuring high surface shape accuracy and good surface roughness of the mirror surface after processing; (2) Small device volume and simple composition: The single-point diamond turning device for large-diameter and thick-thickness ratio lenses based on a vacuum piston in this application only includes a circumferential sealing component, a bottom plate, and a piston support. After assembly, the volume is small, approximately equal to the lens being processed, which is convenient for use in a single-point diamond lathe. The device composition is simple, does not rely on a motor for adjustment, does not require a circulating device for magnetorheological fluid, etc., and only requires vacuum for fixation and support, and the support device can be arranged on the spindle; (3) The special components required for the device are simple to process, and the device main body can be reused: When processing large-diameter and thick-thickness ratio lenses with free-form surfaces on both sides using traditional methods, it is necessary to first use single-point turning to process the complementary contour body of the back free-form surface, and then install and process the front surface of the lens. The processing process is complex and time-consuming, and it is difficult to ensure the fitting of the body and the back surface of the lens. The single-point diamond turning device for large-diameter and thick-thickness ratio lenses based on a vacuum piston in this application only requires the circumferential sealing component to be designed and processed according to the lens contour. The circumferential sealing component cooperates with a soft cushion material only for sealing and local support, and does not require ultra-precision processing. The rest of the bottom plate, piston support, screws, studs, etc. can be reused.

[0034] The above are only embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structural or equivalent process transformation made using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. A single-point diamond turning device for lenses based on a vacuum piston, characterized in that: include: A base plate, a circumferential sealing component installed on the base plate, and a lens arranged on the circumferential sealing component, the base plate is provided with a plurality of countersunk threaded holes arranged in an array, a vacuum interface is provided at the center of the base plate, a piston support is slidably connected in the countersunk threaded hole in the circumferential sealing component, the top of the piston support abuts against the lower surface of the lens, the upper surface of the piston of the piston support, the lower surface of the lens, the inner wall of the circumferential sealing component and the upper surface of the base plate together enclose a closed chamber, and the vacuum interface is connected to an external vacuum air circuit to maintain the vacuum state of the closed chamber.

2. A vacuum piston-based single-point diamond turning device for lenses according to claim 1, characterized in that: The upper end of the circumferential sealing component has a step portion, the lower end of the circumferential sealing component is in contact with the bottom plate and has a mounting leg, the mounting leg is provided with a through hole, and the circumferential sealing component is fixedly connected to the bottom plate by screws passing through the through holes.

3. A vacuum piston-based single-point diamond turning device for lenses according to claim 2, characterized in that: The inner wall profile of the step portion matches the outer profile of the lens, and the two are connected with a clearance fit.

4. The single-point diamond turning device for lenses based on a vacuum piston according to claim 1, characterized in that: The piston support comprises a piston and a support rod fixedly connected to the upper end of the piston, the upper end of the support rod is in contact with the lower surface of the lens, and the upper end of the support rod is provided with a rounded corner.

5. The single-point diamond turning device for lenses based on a vacuum piston according to claim 4, characterized in that: The upper end of the support rod is made of a soft material with high lubricity and non-stickiness.

6. The single-point diamond turning device for lenses based on a vacuum piston according to claim 4, characterized in that: The countersunk threaded hole comprises a countersunk hole and a threaded hole extending downwardly from the countersunk hole, and the piston is connected with the countersunk hole in a sliding fit.

7. The single-point diamond turning device for lenses based on a vacuum piston according to claim 1, characterized in that: The countersunk threaded hole on the bottom plate located at the center of the array serves as a spare vacuum interface.

8. The single-point diamond turning device for lenses based on a vacuum piston according to claim 1, characterized in that: The upper surface of the lens is subjected to atmospheric pressure, which applies downward pressure to the lens, so that the lens is adsorbed on the step portion of the circumferential sealing component. The lower surface of the piston of the piston support is connected to the atmosphere, and the atmospheric pressure on the lower surface of the piston applies upward pressure to the piston support, so as to achieve effective support of the lower surface of the lens by the piston support.

9. A processing method for a single-point diamond turning device for a lens based on a vacuum piston, characterized in that: The following steps are involved: Step 1: The upper surface and the lower surface of the bottom plate, the piston circumferential surface of the piston support, and the countersunk hole are processed with high precision to ensure the sliding fit between the countersunk hole and the piston and the air tightness of the connection; Step 2: Design and process the circumferential sealing component according to the contour shape of the lens so that the inner wall shapes of the two are consistent and the gaps are complementary, install the circumferential sealing component on the bottom plate, make the lower surface of the circumferential sealing component closely contact with the upper surface of the bottom plate, and use screws to pass through the through holes on the mounting legs to lock the circumferential sealing component on the bottom plate; Step 3: Install the piston support in an unobstructed countersunk hole in the area enclosed by the circumferential sealing component on the bottom plate, make the piston and the countersunk hole slidingly connected, use a stud to seal the threaded hole part of the countersunk threaded hole, and assemble into a single-point diamond turning processing device; Step 4: Install the assembled single-point diamond turning device on the spindle or linear guide of the turning machine, and connect the vacuum air circuit of the machine to the vacuum interface of the base plate to complete the effective support of the lower surface of the lens and facilitate turning.

10. The processing method of the single-point diamond turning device for lenses based on a vacuum piston according to claim 9, characterized in that: A sealing gasket made of soft material is arranged in the step portion of the circumferential sealing component. The upper surface of the piston supported by the piston, the lower surface of the lens, the inner wall of the circumferential sealing component and the upper surface of the bottom plate together form a closed chamber.

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