JP4784454B2 - Optical element manufacturing method and manufacturing apparatus - Google Patents

Description

  The present invention relates to an optical element manufacturing method and a manufacturing apparatus for obtaining a glass optical element by pressure molding molten glass with a mold.

  Today, glass optical elements are widely used as digital camera lenses, optical pickup lenses such as DVDs, mobile phone camera lenses, optical communication coupling lenses, various mirrors, and the like. Such glass optical elements are often manufactured by a press molding method in which a glass material is pressure-molded with a molding die. In particular, an optical element having an aspheric surface as an optical surface is not easily formed by grinding / polishing, and therefore is generally manufactured by a press molding method using a molding die. Among them, a direct press method for obtaining a glass optical element by directly pressure-molding molten glass with a molding die is attracting attention because high production efficiency can be expected.

  As a method for obtaining a glass optical element by directly pressure-molding molten glass with a molding die, the molten glass from the nozzle tip is retained in the support member, and then the support member is withdrawn from the nozzle tip. A method of pressure-molding a glass gob with an upper mold and a lower mold is known (see, for example, Patent Document 1).

  However, the rate at which the molten glass is cooled during the molding process differs between the upper and lower surfaces of the molten glass, or the center and edges, and the amount of shrinkage due to cooling becomes uneven. It was difficult to form. In particular, it has been very difficult to form a highly accurate optical surface on the lower surface side where the molten glass first contacts with the support member and is rapidly cooled.

  In addition, after conveying the molten glass supplied to the receiving mold onto the lower mold, only the upper optical surface on which the temperature of the molten glass is relatively stable is formed by pressing with the upper and lower molds. There has been proposed a method of manufacturing a glass lens by forming a molding surface by transfer and forming an optical surface on the lower surface side by additional processing (grinding / polishing) (see, for example, Patent Document 2).

In Patent Document 2, the distribution of the cooling rate in the radial direction of the lens is reduced by forming the receiving surface of the lower mold so that the thickness of the molded lens is uniform over the entire surface. It is disclosed that a highly accurate optical surface can be obtained on the side.
JP-A-6-206730 JP-A-8-208248

  However, when the surface to be formed by molding among the optical surfaces of the optical element is a convex surface, a highly accurate optical surface cannot be obtained due to the following problems.

  Of the optical surfaces of the optical element, when the surface to be formed by molding is a convex surface, the molding surface of the upper mold corresponding to this is a concave surface. Therefore, in order to make the thickness of the molded body obtained by molding uniform over the entire surface, it is necessary to make the receiving surface of the lower mold convex. However, if the receiving surface is a convex surface, the position of the supplied molten glass becomes unstable. For this reason, the cooling rate of the molten glass varies, and a highly accurate optical surface cannot be obtained.

  Further, when manufacturing a relatively large optical element having an outer diameter of, for example, φ20 mm or more, it is necessary to store a large amount of molten glass on the receiving surface of the lower mold, so that the outer diameter for regulating the outer diameter of the molten glass is limited. It is necessary to use a molding die provided with an outer diameter regulating member having a diameter regulating surface. In such a case, if the receiving surface is a convex surface, the supplied molten glass first flows outward and accumulates from the outer side of the receiving surface toward the center side. The molten glass that has flowed to the outside comes into contact with the outer diameter regulating surface of the outer diameter regulating member and is rapidly cooled from the contact surface. As described above, when a molding die having an outer diameter regulating member is used, there is a large difference in the cooling rate between the center portion and the end portion of the molten glass, so that the amount of shrinkage of the molten glass during molding is uniform. Therefore, it has become more difficult to obtain a highly accurate optical surface on the upper surface side of the optical element.

  The present invention has been made in view of the technical problems as described above, and an object of the present invention is to reduce the cooling rate of the center and end of the molten glass even if the molding surface of the upper mold is a concave surface. An object of the present invention is to provide an optical element manufacturing method and a manufacturing apparatus capable of manufacturing an optical element having a highly accurate optical surface with high production efficiency by making it uniform.

  In order to solve the above problems, the present invention has the following features.

1. A molding die comprising a lower mold having a receiving surface for receiving molten glass and an upper mold having a concave molding surface for forming the first optical surface of the optical element is lower than the temperature of the molten glass. A heating step of heating to a predetermined temperature; a molten glass supply step of supplying the molten glass to the receiving surface of the lower mold; and pressure molding of the molten glass with the molding die, and transfer of the molding surface of the upper mold Forming a molded body having a first optical surface, wherein the receiving surface of the lower mold is concave or flat at the center, and outside the concave or flat surface, The molten glass having a region whose height is lower than the end portion of the concave surface or the flat surface, the molten glass supplied in the molten glass supply step is collected in a central portion of the receiving surface, and then supplied to the region having a low height. are manufactured side of the optical element characterized Rukoto .

2 . 2. The method of manufacturing an optical element according to 1 above, further comprising an additional processing step of forming a second optical surface on the back surface side of the first optical surface of the molded body by additional processing after the molding step. .

3 . The molding die includes an outer diameter regulating member having an outer diameter regulating surface for regulating the outer diameter of the molten glass, and the molten glass supplied to the receiving surface of the lower mold in the molten glass supply step The method of manufacturing an optical element according to any one of 1 and 2 , wherein the outer diameter regulating surface of the outer diameter regulating member is in contact with the outer diameter regulating surface.

4 . A molding die provided with a lower die having a receiving surface for receiving molten glass and an upper die having a concave molding surface for forming the first optical surface of the optical element, and the molding die as molten glass A heating means for heating to a predetermined temperature lower than the temperature of the molten glass, a molten glass supply means for supplying the molten glass to the receiving surface of the lower mold, and the molten glass by pressure molding with the molding die. And a pressing means for forming a molded body having a first optical surface onto which the molding surface of the upper mold is transferred, and the receiving surface of the lower mold has a concave or flat central portion And the outer side of the concave surface or plane has a region whose height is lower than the end of the concave surface or plane, and the molten glass supplied by the molten glass supply means is a central portion of the receiving surface. the reservoir, Turkey is then supplied to the low-level-area Apparatus for producing an optical element characterized.

  According to the method for producing an optical element of the present invention, the cooling rate of the molten glass supplied to the molding die is made uniform, and the shrinkage amount of the molten glass at the time of molding can be made uniform. Therefore, even if the molding surface of the upper mold is concave, it is possible to obtain a molded body in which at least the optical surface on the upper surface side is formed with high accuracy by molding, and an optical element having a high accuracy optical surface is high. It can be manufactured with production efficiency.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Optical element)
FIG. 1 is a diagram illustrating an example of an optical element manufactured in the present embodiment. FIG. 1A shows a biconvex lens 120, and FIG. 1B shows a meniscus lens 130. The biconvex lens 120 has a first optical surface 121 formed by molding and a second optical surface 122 formed by additional machining. Similarly, the meniscus lens 130 has a first optical surface 131 formed by molding and a second optical surface 132 formed by additional machining. The present invention is directed to an optical element in which the first optical surface formed by molding as described above is a convex surface.

  In the case of a biconvex lens, there is no particular limitation as to which one of the two optical surfaces is the first optical surface formed by molding. However, if one of the two optical surfaces of the biconvex lens is a so-called aspherical surface that is difficult to form by additional machining, and the other surface is a general spherical surface, the former Is a first optical surface formed by molding, and the latter is a second optical surface formed by additional machining, from the viewpoint of productivity. However, when the optical element to be manufactured is an object having only one optical surface such as a mirror, the surface may be formed by molding as the first optical surface.

  FIG. 2 is a diagram illustrating an example of a molded body obtained in the molding process. 2A shows a molded body 123 for manufacturing the biconvex lens 120, and FIG. 2B shows a molded body 133 for manufacturing the meniscus lens 130. As indicated by the wavy lines in the figure, the second optical surfaces 122 and 132 are formed by additional processing, and the edge surfaces 124 and 134 are further formed to complete the target optical element. At this time, if the first optical surfaces 121 and 131 have the same shape, a biconvex lens 120 can be manufactured by manufacturing one type of molded body and additionally processing it, or a meniscus lens 130 can be manufactured. You can also

(Molding equipment)
FIG. 3 is a diagram illustrating an example of a molding apparatus used in the present embodiment.

  In the present embodiment, molten glass is supplied from the nozzle 5 provided at the lower part of the melting tank 2 to the receiving surface of the lower mold 11 of the molding die 10 heated to a predetermined temperature lower than the temperature of the molten glass. At this time, the melting tank 2 and the nozzle 5 are each heated to a predetermined temperature by the heater 3. The lower mold 11 to which the molten glass is supplied moves to a position below the upper mold 12, the molten glass is pressure-molded by the lower mold 11 and the upper mold 12, and the molding surface of the upper mold 12 is transferred to the first mold 11. A molded body having an optical surface is obtained. Then, an optical element is completed by forming a 2nd optical surface by an additional process in the back surface side of a 1st optical surface.

(Molding mold)
FIG. 4 is a view showing a molding die 10 used in the present embodiment. The molding die 10 is a molding die for molding the molded body 123 for the biconvex lens 120. The molding die 10 includes a lower die 11 and an upper die 12, and further includes an outer diameter regulating member 13. The lower mold 11 has a receiving surface 17 for receiving molten glass, and the upper mold 12 has a molding surface 18 for forming a first optical surface of the optical element. The outer diameter regulating member 13 has an outer diameter regulating surface 19 for regulating the outer diameter of the molten glass, and is fixed in combination with the lower mold 11. The lower mold 11, the upper mold 12, and the outer diameter regulating member 13 have heaters 14a, 15a, 16a and temperature sensors 14b, 15b, 16b as heating means, respectively.

  The outer diameter regulating member 13 is not necessarily an essential member in the manufacturing method of the present invention. However, for example, when a relatively large optical element having an outer diameter of φ20 or more is manufactured, a large amount is provided on the receiving surface 17 of the lower mold 11. Since it is necessary to store molten glass, it is preferable to include an outer diameter regulating member 13 having an outer diameter regulating surface 19 for regulating the outer diameter of the molten glass. As shown in FIG. 4, the outer diameter regulating member 13 may be constituted by a member separate from the lower mold 11, or a receiving surface 17 and an outer diameter regulating surface 19 are formed on the same member, so that the lower mold 11 and the outer diameter regulating member 13 are formed. A member having both functions of the member 13 may be used.

  The lower mold 11, the upper mold 12, and the outer diameter regulating member 13 are formed by press-molding a glass optical element such as a super hard material mainly composed of tungsten carbide, silicon carbide, silicon nitride, aluminum nitride, carbon, or the like. As a molding die for this purpose, it can be appropriately selected from known materials according to the use. Moreover, what formed protective films, such as various metals, ceramics, and carbon, on the surface of these materials can also be used. The lower mold 11, the upper mold 12, and the outer diameter regulating member 13 may all be made of the same material, or may be made of different materials.

  The molding surface 18 of the upper mold 12 has a shape corresponding to the first optical surface 121 of the biconvex lens 120. On the other hand, since the second optical surface 122 of the biconvex lens 120 is formed by additional machining after molding, the receiving surface 17 of the lower mold 11 does not need to have a shape corresponding to the second optical surface 122.

  The receiving surface 17 of the lower mold 11 of this embodiment has a concave portion 17a at the center, and a region 17b having a height lower than that of the end portion 17c of the concave surface 17a. The supplied molten glass first accumulates on the concave surface 17a and then gradually flows to the outer region 17b to complete the supply. Therefore, the molten glass does not flow to the outside at the initial stage of supply and does not come into contact with the outer diameter regulating surface 19 of the outer diameter regulating member 13, and the molten glass and the outer diameter regulating surface 19 are not formed until the last stage of supply. Contact. Therefore, the problem that the molten glass is rapidly cooled by coming into contact with the outer diameter regulating surface 19 and a large difference in the cooling rate between the central portion and the end portion of the molten glass can be minimized.

  The center of the receiving surface may be a flat surface instead of a concave surface. The concave surface or flat surface of the central portion of the receiving surface may be only a part of the receiving surface or the entire receiving surface, and it is effective that the molten glass comes into contact with the outer diameter regulating surface at the initial stage of supply. It is preferable that there is a size that can be prevented.

  On the other hand, if the concave surface or flat surface of the central portion of the receiving surface is large, the thickness of the end of the resulting molded body becomes too thin compared to the thickness of the central portion depending on the shape of the molded body, so In some cases, the difference in cooling rate between the center portion and the end portion of the glass becomes large. Therefore, it is preferable that the receiving surface of the lower mold has a region whose height is lower than the end portion of the concave surface or the plane outside the concave surface or plane of the central portion. As a result, the molten glass can be effectively prevented from coming into contact with the outer diameter regulating surface at the initial stage of supply, and the thickness of the end of the molded body can be prevented from becoming too thin. The amount of shrinkage can be made more uniform.

  5 and 6 show another example of a lower mold that can be used in the present invention. A heater and a temperature sensor as heating means are not shown.

  As for the lower mold | type 21 shown to Fig.5 (a), the whole receiving surface 27 is the concave surface 27a. Moreover, the receiving surface 37 of the lower mold | type 31 shown in FIG.5 (b) has the concave part 37a in the center part, and the outer side becomes a plane of the same height as the edge part of the concave surface 37a.

  By using the lower mold 21 and the lower mold 31, the supplied molten glass first accumulates in the center of the receiving surface, and effectively prevents the molten glass from coming into contact with the outer diameter regulating surface in the initial stage of supply. Therefore, the amount of shrinkage of the molten glass during molding can be made uniform, and an optical element having a highly accurate optical surface can be obtained.

  The receiving surface 47 of the lower mold 41 shown in FIG. 6A has a concave surface 47a at the center, and has a region 47b whose height is lower than that of the end portion 47c of the concave surface 47a. Moreover, the receiving surface 57 of the lower mold | type 51 shown in FIG.6 (b) has the area | region 57b whose center part is the plane 57a, and whose height is lower than the edge part 57c of the plane 57a on the outer side.

  By using the lower mold 41 and the lower mold 51, it is possible to effectively prevent the molten glass from coming into contact with the outer diameter regulating surface in the initial stage of supply, and the thickness of the end portion of the molded body is thin. Since it can prevent becoming too much, the shrinkage | contraction amount of the molten glass at the time of shaping | molding can be made further uniform, and the optical element which has a highly accurate optical surface can be obtained.

(Heating process)
The heating step is a step of heating the molding die to a predetermined temperature lower than the temperature of the molten glass. As shown in FIG. 4, the molding die 10 includes a lower die 11 and an upper die 12, and may further include an outer diameter regulating member 13 as necessary.

  The lower die 11, the upper die 12, and the outer diameter regulating member 13 have heaters 14a, 15a, 16a and temperature sensors 14b, 15b, 16b as heating means, respectively. Thus, it is good also as a structure which can adjust temperature of each member independently, and it is good also as a structure which heats the whole shaping die collectively with one or several heaters. The heater can be appropriately selected from known various heaters. For example, a cartridge heater that is used by being embedded inside the member, or a sheet heater that is used while being in contact with the outside of the member can be used. In addition to various thermocouples, known means such as a platinum resistance thermometer and various thermistors can be used as the temperature sensor.

  Of the molding die 10, the heating temperature of the upper die 12 needs to be set in a temperature range in which the shape of the molding surface 18 can be satisfactorily transferred to the molten glass. Usually, it is preferable to make it the temperature range of Tg (glass transition point) -100 degreeC of glass to shape | mold to about Tg + 100 degreeC. If the heating temperature is too low, it becomes difficult to transfer the shape of the molding surface 18 to the molten glass. On the contrary, it is not preferable to raise the temperature more than necessary from the viewpoint of preventing fusion between the glass and the molding die and the life of the molding die. In practice, the appropriate temperature is determined taking into account various conditions such as the glass material to be molded, the shape and size of the molded body, the material of the molding die, the type of protective film, the position of the heater and temperature sensor, etc. To do.

  Unlike the upper mold 12, the heating temperature of the lower mold 11 and the outer diameter regulating member 13 does not need to consider the transferability of the molding surface, but affects the cooling rate of the molten glass. Furthermore, it is preferable that the glass to be molded has a temperature range of about Tg-100 ° C to about Tg + 100 ° C.

(Molten glass supply process)
The molten glass supply step is a step of supplying molten glass to the receiving surface 17 of the lower mold 11. The supplied molten glass comes into contact with the receiving surface 17 of the lower mold 11 and is cooled. When the molding die is provided with the outer diameter regulating member 13 having the outer diameter regulating surface 19 for regulating the outer diameter of the molten glass, it is also cooled by contacting the outer diameter regulating surface 19.

  However, since the receiving surface 17 of the lower mold 11 has a concave portion 17a at the center, the supplied molten glass first accumulates at the center of the receiving surface 17, and then gradually flows to the outside to complete the supply. Therefore, the molten glass does not flow to the outside at the initial stage of supply and does not come into contact with the outer diameter regulating surface 19 of the outer diameter regulating member 13, and the molten glass and the outer diameter regulating surface 19 are not formed until the last stage of supply. Contact.

  There is no restriction | limiting in particular about the method of supplying molten glass, A well-known method can be selected suitably and can be used. For example, in a state where a molten glass droplet falls from the tip of the nozzle due to its own weight, the lower die 11 is brought close to the nozzle tip and a predetermined amount of molten glass is retained on the receiving surface 17, and then the lower die 11 is pulled down. It is also preferable to use a method of cutting molten glass (see Patent Document 1). Alternatively, a method of cutting a molten glass with a metal blade after a predetermined amount of molten glass is retained in the lower mold 11 in a state where the molten glass flows out from the nozzle tip in a liquid state.

There is no restriction | limiting in particular in the kind of glass which can be used, The well-known glass used for an optical use can be selected and used according to a use. For example, phosphate glass, lanthanum glass, etc. (molding process)
The molding step is a step of forming a molded body having a first optical surface on which the molding surface of the upper mold is transferred by pressure-molding molten glass with a molding die.

  The pressurizing means is not particularly limited, and known pressurizing means such as an air cylinder, a hydraulic cylinder, and an electric cylinder using a servo motor can be appropriately selected and used.

  Cooling of the molten glass further proceeds during pressing. After being cooled to a temperature at which the molten glass is sufficiently solidified, the pressure is released and the molded body is taken out from the molding die. The temperature of the molded body at the time of releasing the pressure depends on the type of glass, the size and shape of the molded body, the required accuracy, and the like, but it may be usually cooled to a temperature in the vicinity of Tg of the glass. Necessary pressurization time and load vary depending on various conditions, but normally, an appropriate value may be selected from the range of pressurization time of 10 seconds to 300 seconds and load of 500 N to 20000 N.

  Note that pressurization may be performed while the molten glass and the outer diameter regulating member are in contact with each other, or the outer diameter regulating member is retracted before the molding process to release the contact between the molten glass and the outer diameter regulating member. After that, pressurization may be performed. In the latter case, it is necessary to retract the outer diameter regulating member after cooling until the viscosity reaches a level at which the molten glass does not flow outside.

  In addition, a step of annealing the molded body can be provided in order to remove distortion remaining in the obtained molded body and to make the quality such as the refractive index uniform and to obtain a more accurate optical element.

(Additional process)
The additional processing step is a step of forming the second optical surface on the back side of the first optical surface of the molded body after the molding step.

  In general, an optical surface can be formed by a process such as a roughing process using a high-speed grinding machine (curve generator), a fine grinding process using diamond pellets, or a polishing process for finishing the surface with an abrasive. However, the present invention is not limited to this, and a known method can be appropriately selected and used.

  Moreover, you may provide the process of forming the outer diameter surface of an optical element by grinding etc.

(Example 1)
A molded body was produced using the molding apparatus shown in FIG. 3, and the shape accuracy of the first optical surface formed by transferring the molding surface of the upper mold was evaluated. A molding die 123 shown in FIG. 2A was produced using the molding die 10 shown in FIG. The first optical surface 121 is usually an aspheric surface in many cases, but here a spherical surface having a curvature radius of 30 mm is used for easy evaluation.

  The outer diameter of the molded body 123 was 25 mm, and the wall thickness at the center was 8 mm. The receiving surface 17 of the lower mold 11 is a concave surface 17a having a radius of curvature of 30 mm at the center, and has a region 17b whose height is lower than that of the end portion 17c of the concave surface 17a. The concave surface 17a has a diameter of 15 mm, and the difference in height between the end 17c and the region 17b is 2 mm at the maximum. The lower mold 11, the upper mold 12, and the outer diameter regulating member 13 are all made of a super hard material mainly composed of tungsten carbide. The heating temperature was set to 520 ° C. for the lower die 11 and the outer diameter regulating member 13, and 430 ° C. for the upper die 12.

  Phosphoric glass was used as the glass material. The nozzle tip is heated to 1000 ° C., and the molten glass drops fall under its own weight, the lower die 11 is brought close to the nozzle tip and the molten glass is retained on the receiving surface 17, and then the lower die 11 is moved downward. The molten glass was cut by pulling down, and a molten glass having the same volume as the compact was supplied. Then, the lower mold | type 11 was moved to the position facing the upper mold | type 12, and the molten glass was pressurized for 70 second with the load of 1800N.

  The shape accuracy of the optical surface 121 of the molded body taken out was evaluated. For evaluation, the maximum value of the deviation from the spherical surface was obtained using a surface shape measuring instrument PGI840 manufactured by Taylor Hobson Co., Ltd., and the maximum value of the deviation from the spherical surface was 150 nm or less. The case where it was large and 300 nm or less and good was rated as ○, and the case where the problem was larger than 300 nm was marked as x.

  The evaluation results are shown in Table 1. The shape accuracy of the optical surface 121 was 55 nm, and a high-precision optical surface could be formed by molding.

(Examples 2 to 5)
In Example 2, the lower mold 21 shown in FIG. 5A was used as the lower mold. The receiving surface 27 is a concave surface having a curvature radius of 30 mm.

  In Example 3, the lower mold 31 shown in FIG. 5B was used as the lower mold. The receiving surface 37 is a concave surface 37a having a radius of curvature of 30 mm at the center. The concave surface 17a had a diameter of 15 mm. The outer side of the concave surface 37a is a flat surface having the same height as the end of the concave surface 37a.

  In Example 4, the lower mold 41 shown in FIG. 6A was used as the lower mold. The receiving surface 47 is a concave surface 47a having a radius of curvature of 30 mm at the center, and a region 47b having a height lower than that of the end portion 47c of the concave surface 47a. The concave surface 47a has a diameter of 15 mm, and the height difference between the end 47c and the region 47b is 2 mm at the maximum.

  In Example 5, the lower mold 51 shown in FIG. 6B was used as the lower mold. The receiving surface 57 has a flat surface 57a at the center and a region 57b having a height lower than that of the flat surface 57a on the outer side. The flat surface 57a has a diameter of 15 mm, and the maximum height difference between the flat surface 57a and the region 57b is 2 mm.

  Except having used each said lower mold | type, the molded object was produced on the same conditions as Example 1, and the shape accuracy of the optical surface of the taken-out molded object was evaluated. Evaluation was performed in the same manner as in Example 1. The evaluation results are also shown in Table 1. In any case, a high-precision optical surface could be formed by molding.

(Comparative Example 1)
A lower mold was used in which the receiving surface was a convex surface with a curvature radius of 30 mm over the entire surface. A molded body was produced under the same conditions as in Example 1, and the shape accuracy of the optical surface of the removed molded body was evaluated. Evaluation was performed in the same manner as in Example 1.

  The evaluation results are also shown in Table 1. Unlike the cases of Examples 1 to 5, the shape accuracy of the optical surface was larger than 300 nm, and a high-precision optical surface could not be formed.

Sectional drawing which shows the example of the optical element manufactured by the method of this invention Sectional drawing which shows the example of the molded object obtained at the formation process The figure which shows an example of the shaping | molding apparatus used with the method of this invention Sectional view of the molding die used in the present invention Sectional drawing which shows the example of another lower mold | type which can be used by this invention Sectional drawing which shows the example of another lower mold | type which can be used by this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding apparatus 10 Molding die 11, 21, 31, 41, 51 Lower mold 12 Upper mold 13 Outer diameter regulating member 17, 27, 37, 47, 57 Receiving surface 17a, 27a, 37a, 47a Concave surface 17b, 47b, 57b Regions 17c, 47c, 57c having a lower height than the end of the concave surface or plane 17c, 47c, 57c End portions of the concave surface or plane 18 Molding surface 19 Outer diameter regulating surface 57a Plane 120, 130 Optical element 121, 131 First optical surface 122, 132 Second optical surface 123, 133 molded body

Claims (4)

A molding die comprising a lower mold having a receiving surface for receiving molten glass and an upper mold having a concave molding surface for forming the first optical surface of the optical element is lower than the temperature of the molten glass. A heating step of heating to a predetermined temperature;
A molten glass supply step of supplying the molten glass to the receiving surface of the lower mold;
Pressing the molten glass with the molding die, and forming a molded body having a first optical surface onto which the molding surface of the upper mold is transferred, and
The receiving surface of the lower mold has a central portion that is a concave surface or a flat surface, and has an area outside the concave surface or the flat surface that is lower in height than the end portion of the concave surface or the flat surface,
Wherein the molten glass supplied in molten glass supplying step, accumulates in the central portion of the receiving surface, the manufacturing method of the subsequent optical elements in which the height is characterized Rukoto is supplied to a lower area. 2. The optical element manufacturing method according to claim 1, further comprising an additional processing step of forming a second optical surface on the back surface side of the first optical surface of the molded body by additional processing after the molding step. Method. The molding die includes an outer diameter regulating member having an outer diameter regulating surface for regulating the outer diameter of the molten glass,
In the molten glass supplying step, the molten glass supplied to the receiving surface of the lower mold, the outer size specification system any one of claims 1 or 2, characterized in that contact with the outer size specification system surface of the member The manufacturing method of the optical element of description. A molding die comprising a lower mold having a receiving surface for receiving molten glass, and an upper mold having a concave molding surface for forming the first optical surface of the optical element;
Heating means for heating the molding die to a predetermined temperature lower than the temperature of the molten glass;
Molten glass supply means for supplying the molten glass to the receiving surface of the lower mold,
Pressurizing the molten glass with the molding die, and forming a molded body having a first optical surface to which the molding surface of the upper mold is transferred, and
The receiving surface of the lower mold has a central portion that is a concave surface or a flat surface, and has an area outside the concave surface or the flat surface that is lower in height than the end portion of the concave surface or the flat surface,
Wherein the molten glass supplied by molten glass supply means, collects in the center of the receiving surface, apparatus for producing a subsequent optical elements in which the height is characterized Rukoto is supplied to a lower area.

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