Mould pressing method of large-diameter glass aspheric lens

Abstract

The invention discloses a mold pressing method for a large-diameter glass aspheric lens. The mold pressing method comprises the following steps of feeding, wherein a mold pressing mold with a glass blank is fed into a mold pressing cavity; preheating: a preheating shaft abuts against the mold pressing mold and integrally heats the mold pressing mold until the glass blank is heated to a softened state; high-temperature mold pressing is conducted, specifically, an upper heating plate of the forming shaft abuts against an upper mold core of the mold pressing mold, the upper heating plate of the forming shaft exerts forming pressure on the upper mold core till the forming pressure reaches the forming pressure value, the upper heating plate stops moving, and pressure maintaining is conducted on the upper heating plate under the forming pressure value; cooling, wherein a cooling shaft cools the mold pressing mold until the temperature of the mold pressing mold reaches a preset temperature value; and blanking: moving out the mould pressing mould, and taking out the glass aspheric lens formed by mould pressing. By means of the design, the pv value error of the glass aspheric lens with the caliber larger than 30 mm can be controlled within 1.5 micrometers, and the PV value control precision of the large-caliber glass aspheric lens is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of glass lens molding, and particularly relates to a molding method for a large-aperture glass aspherical lens. Background Art

[0002] An aspherical lens is a lens with an aspherical symmetric curved surface shape, and its curvature may be different in different directions. The advantages of an aspherical lens compared to a spherical lens are spherical aberration correction, system miniaturization, and weight reduction. These advantages make the imaging performance and imaging quality of an aspherical lens better than that of a spherical lens.

[0003] The surface shape of an aspherical lens can be described by a series of parameters. One commonly used parameter is pv (peak-to-valley), that is, the peak-valley value; pv represents the vertical distance between the highest point and the lowest point at the location where the curvature changes the most. For a given aspherical lens, its pv value can be set by measuring the surface height distribution. Usually, a reference flat reference plane is selected and defined as zero; then a set of measurement points is selected on this reference plane, and the height difference from each point to the surface of the aspherical lens is measured; by setting the maximum and minimum values of these height differences, the pv value of the aspherical lens can be obtained.

[0004] In an aspherical lens system, the surface shape of the aspherical lens directly affects the propagation direction and focal length of the incident light beam after passing through the lens. When the surface shape parameter pv of the aspherical lens is large, its curvature changes greatly and the radius of curvature changes rapidly; this means that at a given incident angle, the light beam propagating through the aspherical lens will be greatly deflected. When the surface shape parameter pv of the aspherical lens is small, its curvature changes little and the radius of curvature changes slowly; this means that the light beam propagating through the aspherical lens will be slightly deflected. Therefore, in the processing of glass aspherical lenses, to ensure the quality of glass aspherical lenses, it is necessary to strictly control the pv value of glass aspherical lenses and ensure that the error of the pv value of glass aspherical lenses is within the allowable range of design.

[0005] Existing glass aspherical lenses are generally formed by high-temperature molding of glass materials in a molding die. Due to the expansion phenomenon of the molding die and the glass material at high temperature, the pv value of the glass aspherical lens obtained by high-temperature molding inevitably has an error. When the aperture of the glass aspherical lens to be prepared is larger, the error of the pv value of the glass aspherical lens is also larger. For the existing molding method of glass aspherical lenses, it is difficult to control the error of the pv value of the glass aspherical lens within 1.5 microns for a glass aspherical lens with a larger aperture, and there is a problem of relatively low control accuracy of the pv value of the glass aspherical lens. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the defect of low PV value control accuracy in the existing large-diameter glass aspherical lens by molding, so as to provide a molding method for large-diameter glass aspherical lenses.

[0007] To solve the above technical problem, the technical solution of the present invention is as follows:

[0008] A molding method for large-diameter glass aspherical lenses, comprising the following steps:

[0009] Loading: evacuate the molding cavity to vacuum, and send the molding die with the glass blank placed therein to the loading station of the molding cavity;

[0010] Preheating: transfer the molding die with the glass blank placed therein to the preheating station of the molding cavity, so that the molding die faces the preheating shaft, the preheating shaft abuts against the molding die and heats the whole molding die until the glass blank is heated to a softened state;

[0011] High-temperature molding: transfer the preheated molding die to the molding station of the molding cavity, so that the molding die faces the forming shaft. After the forming shaft abuts against the molding die, the upper heating plate of the forming shaft abuts against the upper mold core of the molding die, and the upper heating plate of the forming shaft applies a forming pressure to the upper mold core until the forming pressure reaches the forming pressure value, then the upper heating plate stops moving, and the upper heating plate holds the pressure at the forming pressure value;

[0012] Cooling: transfer the molded molding die to the cooling station of the molding cavity, so that the molding die faces the cooling shaft. After the cooling shaft abuts against the molding die, cool the upper and lower mold cores of the molding die until the temperatures of the upper and lower mold cores of the molding die reach the preset temperature value;

[0013] Unloading: transfer the cooled molding die to the unloading station of the molding cavity, separate the upper and lower mold cores of the molding die, and take out the molded glass aspherical lens from the molding die.

[0014] Further, in the preheating step, the preheating shaft heats the whole molding die and the glass preform to a temperature above the softening temperature point of the glass preform +10°.

[0015] Further, in the preheating step, set the preheating time according to the surface shape and outer diameter of the glass aspherical lens to be molded;

[0016] When the glass aspherical lens is biconvex and the outer diameter is greater than 30 mm, the preset time is set above 160 s;

[0017] When the glass aspherical lens is biconcave and the outer diameter is greater than 30 mm, the preset time is set above 230 s;

[0018] When the glass aspherical lens is concave-convex and the outer diameter is greater than 30 mm, the preset time is set above 190 s.

[0019] Furthermore, in the step of hot embossing, the holding pressure time of the embossing mold during hot embossing is set according to the outer diameter of the glass aspherical lens to be embossed, the temperature during hot embossing, and the heat conduction rate of the embossing mold.

[0020] Furthermore, in the step of hot embossing, the forming pressure value of the embossing mold during hot embossing is set according to the surface shape and outer diameter of the glass aspherical lens to be embossed;

[0021] When the glass aspherical lens is biconvex and the outer diameter is greater than 30 mm, the forming pressure value is above 0.25 MPa;

[0022] When the glass aspherical lens is biconcave and the outer diameter is greater than 30 mm, the forming pressure value is above 0.4 MPa;

[0023] When the glass aspherical lens is concave-convex and the outer diameter is greater than 30 mm, the forming pressure value is above 0.3 MPa.

[0024] Furthermore, in the step of cooling down, the cooling holding pressure time of the embossing mold during cooling down is set according to the outer diameter of the glass aspherical lens to be embossed and the heat conduction rate of the embossing mold.

[0025] Furthermore, in the step of cooling down, the holding pressure value of the embossing mold during cooling down is set according to the surface shape and outer diameter of the glass aspherical lens to be embossed;

[0026] When the glass aspherical lens is biconvex and the outer diameter is greater than 30 mm, the initial holding pressure value is 0.25 MPa, and the holding pressure increases by 0.02 - 0.04 MPa in each pressurization cycle, and the pressurization cycle is less than 1 s;

[0027] When the glass aspherical lens is biconcave and the outer diameter is greater than 30 mm, the initial holding pressure value is 0.4 MPa, and the holding pressure increases by 0.03 - 0.05 MPa in each pressurization cycle, and the pressurization cycle is less than 0.6 s;

[0028] When the glass aspherical lens is concave-convex and the outer diameter is greater than 30 mm, the initial holding pressure value is 0.3 MPa, and the holding pressure increases by 0.01 - 0.03 MPa in each pressurization cycle, and the pressurization cycle is less than 0.6 s.

[0029] Further, before the feeding step, it further includes preparation before molding: selecting the upper mold core, lower mold core, and mold sleeve of the molding die according to the coefficient of thermal expansion of the glass preform to be molded, wherein the linear expansion coefficients of the upper mold core, lower mold core, and mold sleeve are all greater than that of the glass preform to be molded; the linear expansion coefficients of the upper mold core and the lower mold core are both greater than that of the mold sleeve.

[0030] Wherein, the lower part of the upper mold core and the upper part of the lower mold core are located inside the mold sleeve; the side surface of the upper mold core facing the lower mold core is the upper forming surface, the side surface of the lower mold core facing the upper mold core is the lower forming surface, and both the upper forming surface and the lower forming surface are aspherical surfaces; the inner wall of the mold sleeve is adapted to define the outer diameter of the glass aspherical lens, and the upper forming surface, the lower forming surface, and the inner wall of the mold sleeve enclose to form a molding cavity for the glass aspherical lens.

[0031] Further, in the feeding step and the discharging step, a manipulator is used to realize automatic feeding and automatic discharging of the molding die.

[0032] Further, the preheating step, the high-temperature molding step, and the cooling and temperature reduction step can be cycled multiple times in the molding cavity.

[0033] The technical solution of the present invention has the following advantages:

[0034] 1. The molding method of the large-aperture glass aspherical lens provided by the present invention sets the preheating time in the preheating step, the molding pressure value in the high-temperature molding step, and the holding pressure value in the cooling and temperature reduction step according to the surface shape and outer diameter of the glass aspherical lens to be molded, and the holding pressure value gradually increases in gradients; it can control the pv value error of the large-aperture glass aspherical lens with a diameter greater than 30 mm within 1.5 microns, improving the control accuracy of the PV value of the large-aperture glass aspherical lens. Description of the Drawings

[0035] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1 It is a flowchart for implementing the molding method of the large-aperture glass aspherical lens in the embodiment of the present invention. Specific Embodiments

[0037] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work shall fall within the protection scope of the present invention.

[0038] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0040] A molding method for a large-diameter glass aspherical lens, comprising the following steps:

[0041] Loading step: evacuating the molding cavity to a vacuum, and sending a molding die with a glass blank into the loading station of the molding cavity;

[0042] Preheating step: transferring the molding die with the glass blank to the preheating station of the molding cavity, making the molding die face the preheating shaft, the preheating shaft abut against the molding die and heat the whole molding die until the glass blank is heated to a softened state;

[0043] High-temperature molding step: transferring the preheated molding die to the molding station of the molding cavity, making the molding die face the forming shaft. After the forming shaft abuts against the molding die, the upper heating plate of the forming shaft abuts against the upper mold core of the molding die. The upper heating plate of the forming shaft applies a forming pressure to the upper mold core until the forming pressure reaches the forming pressure value, and then the upper heating plate stops moving. The upper heating plate maintains the pressure at the forming pressure value;

[0044] Cooling and temperature reduction step: Transfer the molded molding die to the cooling station of the molding cavity, align the molding die with the cooling shaft. After the cooling shaft abuts against the molding die, cool the upper mold core and the lower mold core of the molding die until the temperatures of the upper mold core and the lower mold core of the molding die reach the preset temperature value;

[0045] Blanking step: Transfer the cooled molding die to the blanking station of the molding cavity, separate the upper mold core and the lower mold core of the molding die, and take out the molded glass aspherical lens from the molding die.

[0046] Before feeding, first perform the preparatory operations before molding. First, select a glass preform with a low melting point, and then select the upper mold core, the lower mold core, and the mold sleeve of the molding die according to the thermal expansion coefficient of the glass preform. Among them, the linear expansion coefficients of the upper mold core, the lower mold core, and the mold sleeve are all greater than the linear expansion coefficient of the glass preform to be molded; the linear expansion coefficients of the upper mold core and the lower mold core are both greater than the linear expansion coefficient of the mold sleeve. According to the thermal expansion coefficients of the selected glass preform, upper mold core, lower mold core, and mold sleeve, and the dimensions of the upper mold core, lower mold core, and mold sleeve, after heating, give parameters such as the designed preheating temperature, heat preservation time, and pressure holding pressure through expansion.

[0047] Among them, the lower part of the upper mold core and the upper part of the lower mold core are located inside the mold sleeve; the side surface of the upper mold core facing the lower mold core is the upper forming surface, the side surface of the lower mold core facing the upper mold core is the lower forming surface, and both the upper forming surface and the lower forming surface are aspherical surfaces; the inner wall of the mold sleeve is suitable for defining the outer diameter of the glass aspherical lens, and the upper forming surface, the lower forming surface, and the inner wall of the mold sleeve enclose to form the molding cavity of the glass aspherical lens.

[0048] In the feeding step, use a manipulator to take out the upper mold core, place the glass preform in the lower mold core, and then gently place the upper mold core back into the mold sleeve until the glass preform just touches the upper mold core, and finally place the whole set of molds on the feeding table at the feeding station of the molding cavity.

[0049] In the preheating step, the preheating shaft heats the whole molding die and the glass preform to a temperature above the softening temperature point of the glass preform +10°. Set the preheating time according to the surface shape and outer diameter of the glass aspherical lens to be molded; when the glass aspherical lens is biconvex and the outer diameter is greater than 30 mm, the preset time is set above 160 s; when the glass aspherical lens is biconcave and the outer diameter is greater than 30 mm, the preset time is set above 230 s; when the glass aspherical lens is convex-concave and the outer diameter is greater than 30 mm, the preset time is set above 190 s.

[0050] In the step of hot embossing, set the embossing holding time of the embossing mold during the hot embossing process according to the outer diameter of the glass aspherical lens to be embossed, the temperature during hot embossing, and the heat conduction rate of the embossing mold. Among them, the forming pressure value of the embossing mold during the hot embossing process can be set according to the surface shape and outer diameter of the glass aspherical lens to be embossed; when the glass aspherical lens is double convex and the outer diameter is greater than 30 mm, the forming pressure value is above 0.25 MPa; when the glass aspherical lens is double concave and the outer diameter is greater than 30 mm, the forming pressure value is above 0.4 MPa; when the glass aspherical lens is convex-concave and the outer diameter is greater than 30 mm, the forming pressure value is above 0.3 MPa.

[0051] In the step of cooling down, set the cooling holding time and the holding pressure value of the embossing mold during the cooling process according to the outer diameter of the glass aspherical lens to be embossed and the heat conduction rate of the embossing mold. Among them, the holding pressure value of the embossing mold during the cooling process is set according to the surface shape and outer diameter of the glass aspherical lens to be embossed; when the glass aspherical lens is double convex and the outer diameter is greater than 30 mm, the initial holding pressure value is 0.25 MPa, and the holding pressure increases by 0.02 - 0.04 MPa in each pressurization cycle, and the pressurization cycle is less than 1 s; when the glass aspherical lens is double concave and the outer diameter is greater than 30 mm, the initial holding pressure value is 0.4 MPa, and the holding pressure increases by 0.03 - 0.05 MPa in each pressurization cycle, and the pressurization cycle is less than 0.6 s; when the glass aspherical lens is convex-concave and the outer diameter is greater than 30 mm, the initial holding pressure value is 0.3 MPa, and the holding pressure increases by 0.01 - 0.03 MPa in each pressurization cycle, and the pressurization cycle is less than 0.6 s.

[0052] In the step of blanking, first use a manipulator to transfer the cooled embossing mold to the blanking station of the embossing cavity, then separate the upper mold core and the lower mold core of the upper mold core embossing mold, and use a vacuum adsorption means to take out the embossed glass aspherical lens from the embossing mold and place it in the finished product box.

[0053] In some embodiments of the present invention, the preheating step, the hot embossing step, and the cooling step can be cycled multiple times in the embossing cavity. Both the preheating step and the cooling step can be carried out in gradients.

[0054] The embossing method for large-aperture glass aspherical lenses provided by the present invention sets the preheating time in the preheating step, the forming pressure value in the hot embossing step, and the holding pressure value in the cooling step according to the surface shape and outer diameter of the glass aspherical lens to be embossed, and the holding pressure value gradually increases in gradients; it can control the pv value error of large-aperture glass aspherical lenses with a diameter greater than 30 mm within 1.5 microns, and improve the PV value control accuracy of large-aperture glass aspherical lenses.

[0055] Obviously, the above embodiments are merely examples given for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for molding a large-aperture glass aspherical lens, characterized in that, It includes the following steps: Loading: Evacuate the molding cavity to a vacuum and send the molding die with the glass blank into the loading station of the molding cavity; Preheating: Transfer the molding die with the glass blank to the preheating station of the molding cavity so that the molding die faces the preheating shaft. The preheating shaft presses against the molding die and heats the whole molding die until the glass blank is heated to a softened state; High-temperature molding: Transfer the preheated molding die to the molding station of the molding cavity so that the molding die faces the forming shaft. After the forming shaft presses against the molding die, the upper heating plate of the forming shaft abuts against the upper mold core of the molding die. The upper heating plate of the forming shaft applies a forming pressure to the upper mold core until the forming pressure reaches the forming pressure value and then the upper heating plate stops moving. The upper heating plate holds the pressure at the forming pressure value; Cooling and temperature reduction: Transfer the molded molding die to the cooling station of the molding cavity so that the molding die faces the cooling shaft. After the cooling shaft presses against the molding die, the upper and lower mold cores of the molding die are cooled until the temperatures of the upper and lower mold cores of the molding die reach the preset temperature value; Unloading: Transfer the cooled molding die to the unloading station of the molding cavity, separate the upper and lower mold cores of the molding die, and take out the molded glass aspherical lens from the molding die.

2. The molding method of the large-aperture glass aspherical lens according to claim 1, characterized in that, In the step of the preheating, the preheating shaft heats the whole molding die and the glass preform to a temperature above the softening temperature point of the glass preform + 10°; 3. The molding method of the large-aperture glass aspherical lens according to claim 1, characterized in that, In the step of the preheating, set the preheating time according to the surface shape and outer diameter of the required molded glass aspherical lens; When the glass aspherical lens is biconvex and the outer diameter is greater than 30 mm, the preset time is set above 160 s; When the glass aspherical lens is biconcave and the outer diameter is greater than 30 mm, the preset time is set above 230 s; When the glass aspherical lens is convex-concave and the outer diameter is greater than 30 mm, the preset time is set above 190 s.

4. The molding method of the large-aperture glass aspherical lens according to claim 1, characterized in that, In the step of the high-temperature molding, set the molding holding pressure time of the molding die during the high-temperature molding according to the outer diameter of the required molded glass aspherical lens, the temperature during the high-temperature molding, and the heat conduction rate of the molding die; 5. The molding method of the large-aperture glass aspherical lens according to claim 1, characterized in that In the step of the high-temperature molding, set the forming pressure value of the molding die during the high-temperature molding according to the surface shape and outer diameter of the required molded glass aspherical lens; When the glass aspherical lens is biconvex and the outer diameter is greater than 30 mm, the forming pressure value is above 0.25 MPa; When the glass aspherical lens is biconcave and the outer diameter is greater than 30 mm, the forming pressure value is above 0.4 MPa; When the glass aspherical lens is convex-concave and the outer diameter is greater than 30 mm, the forming pressure value is above 0.3 MPa.

6. The molding method of the large-aperture glass aspherical lens according to claim 1, characterized in that In the step of the cooling and temperature reduction, set the cooling holding pressure time of the molding die during the cooling and temperature reduction according to the outer diameter of the required molded glass aspherical lens and the heat conduction rate of the molding die; 7. The molding method of the large-aperture glass aspherical lens according to claim 1, characterized in that In the step of the cooling and temperature reduction, set the holding pressure value of the molding die during the cooling and temperature reduction according to the surface shape and outer diameter of the required molded glass aspherical lens; When the glass aspherical lens is biconvex and the outer diameter is greater than 30 mm, the initial value of the holding pressure is 0.25 MPa, and the holding pressure increases by 0.02 - 0.04 MPa in each pressurization cycle, and the pressurization cycle is less than 1 s; When the glass aspherical lens is biconcave and the outer diameter is greater than 30 mm, the initial value of the holding pressure is 0.4 MPa, and the holding pressure increases by 0.03 - 0.05 MPa in each pressurization cycle, and the pressurization cycle is less than 0.6 s; When the glass aspherical lens is convex-concave and the outer diameter is greater than 30 mm, the initial value of the holding pressure is 0.3 MPa, and the holding pressure increases by 0.01 - 0.03 MPa in each pressurization cycle, and the pressurization cycle is less than 0.6 s.

8. The molding method of the large-aperture glass aspherical lens according to claim 1, characterized in that Before the step of loading, it also includes preparation before molding: select the upper mold core, lower mold core, and mold sleeve of the molding die according to the thermal expansion coefficient of the glass preform to be molded. The linear expansion coefficients of the upper mold core, lower mold core, and mold sleeve are all greater than the linear expansion coefficient of the glass preform to be molded; the linear expansion coefficients of the upper mold core and the lower mold core are both greater than the linear expansion coefficient of the mold sleeve; Wherein, the lower part of the upper mold core and the upper part of the lower mold core are located inside the mold sleeve; the side surface of the upper mold core facing the lower mold core is the upper molding surface, the side surface of the lower mold core facing the upper mold core is the lower molding surface, and both the upper molding surface and the lower molding surface are aspherical surfaces; the inner wall of the mold sleeve is adapted to define the outer diameter of the glass aspherical lens, and the upper molding surface, the lower molding surface, and the inner wall of the mold sleeve enclose to form a molding cavity for the glass aspherical lens.

9. The molding method of the large-aperture glass aspherical lens according to claim 1, characterized in that, In the steps of loading and unloading, a manipulator is used to realize automatic loading and unloading of the molding die.

10. The molding method of the large-aperture glass aspherical lens according to claim 1, characterized in that, The preheating step, the high-temperature molding step, and the cooling step can be cycled multiple times in the molding cavity.

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