JPH10101350A - Manufacture of optical element and optical element manufactured thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacture by which high-precision optical element can be manufactured at a low cost. SOLUTION: This manufacture comprises a first stage for placing a glass material 13 above a surface of a mold 11, that corresponds to the optical- functional surface of this optical element, (surface corresponding to the optical- functional surface), a second stage for heating the glass material 13 to a prescribed temp., and a third stage for deforming the softened glass material 13 on the surface corresponding to the optical-functional surface while allowing the material 13 to contact with the mold 11 successively from its central part to its peripheral part by the gravity of the material 13, to form one formed surface. Further, in the third stage, the weight of the glass material 13, that exerts on the surface corresponding to the optical-functional surface, is adjusted by using a glass material holding member 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical element having an optically functional surface such as a lens and a mirror.

[0002]

2. Description of the Related Art Conventionally, an optical element having an optical function surface such as a lens and a mirror has been manufactured from a predetermined glass material through a grinding and polishing process. In recent years, glass has been directly added using a mold. A manufacturing method of pressing has been proposed. In the manufacturing method using such a mold, an optical element is manufactured by using a mirror-finished mold, heating and softening a glass material having a predetermined shape, and press-molding with a mold in a softened state. ing.

[0003]

In the manufacturing method using the mold described above, the major points are the shape accuracy of the optically functional surface of the manufactured optical element and the life of the mold. That is, in order to improve the shape accuracy of the optical function surface, in other words, the transferability of the mirror surface mold, it is necessary to perform molding at high temperature and high pressure during pressure molding. However, when pressure molding is performed at high temperature and high pressure, physical and chemical damage to the mold is large, and the life of the mold is significantly shortened. As described above, when the life of the mold is shortened, the cost of the optical element is increased, which is not desirable. In addition, mold materials that can be press-molded at high temperature and high pressure are very limited, and there is a problem that glass materials and shapes of optical elements to be manufactured are greatly restricted.

[0004] In view of the above problems, an object of the present invention is to provide a method of manufacturing an optical element capable of manufacturing an inexpensive and high-precision optical element.

[0005]

In order to achieve the above object, a method for manufacturing an optical element according to the present invention is directed to a method for manufacturing an optical element by heating and softening a glass material and molding it using a mold to obtain an optically functional surface. A manufacturing method, comprising: a first step of placing a glass material above a surface corresponding to an optical function surface of the mold; and a second step of heating the glass material to a predetermined temperature.
And a third step of sequentially deforming the softened glass material to a surface corresponding to the optically functional surface of the mold by its own weight from the center of the mold to obtain one molding surface. It is characterized by.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] FIG. 1 is a sectional view showing a schematic configuration of a manufacturing apparatus to which an optical element manufacturing method according to a first embodiment is applied. In FIG. 1, the manufacturing apparatus according to the first embodiment generally includes a mold 11, a glass material holding member 12, a mold holding member 15, and the like.

The mold 11 has a molding surface for molding a mirror-finished optical function surface disposed on the upper side, and the mold holding member 1
5. The mold holding member 15 is formed of a material having good thermal conductivity, and a through hole is formed in the inside thereof so that the glass material holding member 12 can be moved in the vertical direction. Also, the mold holding member 15
The cartridge heater 14 incorporated therein generates heat when drive power is applied thereto via a control circuit (not shown), and applies heat to the mold 11 via the mold holding member 15.

The glass material holding member 12 has a glass material holding portion having an opening larger than the diameter of the mold at an upper portion, and holds a substantially flat glass material 13 in this portion.
Further, the lower side of the glass material holding member 12 has a leg portion for supporting the glass material holding portion, and the leg portion is disposed through a through hole formed inside the mold holding member 15. Therefore, the glass material holding member 12 can move up and down as a whole.

Next, the production of an optical element by the production apparatus having the above-described configuration will be described by taking as an example a case where an optically functional surface is formed on one surface of a glass lens. First, a mold 11 having a shape corresponding to a lens shape to be manufactured and having a mirror-finished surface having a predetermined surface roughness, and a glass material holding member 12 having a predetermined shape are prepared. set. The material of the mold 11 may be a ceramic material such as silicon carbide, a metal material such as platinum, gold, rhodium, or an alloy thereof, a material in which a protective film of platinum or gold is added to the surface of silicon carbide, or the like. The material is not particularly limited as long as it is chemically stable at the temperature at the time of molding the glass material 13 and has low reactivity with glass.

Next, a flat plate or a glass material 13 having a predetermined shape is placed on the glass material holding member 12 (first step). The glass material 13 is basically a flat or spherical member whose surface facing the mold 11 is mirror-finished to a predetermined surface roughness, but the shape of the surface facing the mold 11 is finally obtained. It may be set appropriately according to the lens shape to be obtained. In addition, the surface accuracy of the surface facing the mold 11 does not necessarily need to be mirror-finished, and even if the surface is ground, the molding conditions (temperature, holding time, and the like) of each of the subsequent steps are also required.
By appropriately setting, it is possible to finally obtain a mirror surface.

Further, the glass material 13 placed on the glass material holding member 12 is heated to a predetermined temperature (second step). In the present embodiment, the mold 11 is heated by a cartridge heater built in the mold holding member 15, and the mold 11 is heated.
The method of heating the glass material 13 by the heat generated from is adopted. Other methods for heating the glass material 13 include a method in which the manufacturing apparatus is closed and a heating atmosphere gas is introduced to heat the glass material 13 and the mold 11 simultaneously, or a heater is disposed near the glass material 13. Alternatively, a method of directly heating the glass material 13 itself may be used, or these methods may be combined. Further, the predetermined temperature may be a temperature at which the glass material 13 is softened to the extent that the glass material 13 can be molded. Since this temperature naturally differs for each glass material 13, it is necessary to set each temperature to an optimum value.

Further, the glass material holding member 12 is moved downward, and the glass material 13 softened by heating is brought into contact with its own weight in order from the center of the surface corresponding to the optical function surface of the mold 11 (third step). . At this time, it is important to make contact from the center of the surface corresponding to the optical function surface of the mold 11. Contrary to the central portion, when the glass material 13 comes into contact with the peripheral portion first, the gas is confined in the central portion, so that the central portion of the mold 11 and the softened glass material 13 cannot be brought into contact. , It becomes impossible to obtain a desired shape.

In response to the above point, in the third step, when the surface to be molded is concave (when the surface of the mold 11 is convex), the uniformly heated glass material 13 is deformed by its own weight. Then, there is no problem because the contact is made from the center of the mold 11. On the contrary, when the surface to be molded is a convex surface (the mold 1).
When the surface of the glass material 13 is concave, the glass material 13 needs to have a smaller radius of curvature than the mold 11 at the time of contact with the mold 11.

In the present embodiment, the glass material holding member 12
Of the glass material 13 by appropriately adjusting the distance between the mold 11 and the glass material 13 from the state during heating, so that the glass material 13 comes into contact with the glass material 13 in order from the center of the mold. Is controlling. In addition, it is necessary to consider the shapes of the mold 11 and the glass material 13 so that they can come into contact with each other in order from the center.

Finally, after the third step, the temperature of the mold 11 is changed to the glass transition point (Tg) of the formed glass material 13.
Cool to the following temperature (fourth step). In the fourth step, it is desirable to cool the glass material 13 so as to satisfy the following conditions at least until the ambient temperature is cooled to a temperature equal to or lower than the glass softening point (At) of the formed glass material 13. Ta−Tm ≧ 20, where Ta: ambient temperature (° C.) Tm: mold temperature (° C.)

Cooling the mold 11 and the glass material 13 so as to satisfy the above-mentioned conditional expression means that the surface to be molded which is in contact with the mold 11 is in contact with the mold 11. It means to cool before the non-side surface.
By cooling in this way, the target optical functional surface can be cured first, so that there is an effect that the shrinkage of the glass generated during cooling is concentrated on the surface opposite to the optical functional surface. Therefore, it is possible to cool the glass material 13 while maintaining the surface accuracy of the optical function surface. Since the shape change of the glass material 13 hardly occurs below the glass softening point (At), it is not necessary to satisfy this condition if the glass material 13 is cooled to the glass softening point (At) or lower.

The optical element made of glass manufactured by the above process can be formed into any shape such as a concave or convex spherical shape or an aspherical shape by manufacturing the mold 11 with high precision. It is possible and the shape is not particularly limited. In addition, since only a pressure of about the weight of the glass material 13 is applied to the mold 11, damage is small.
The mold life can be greatly improved. Also, since the damage of the mold 11 is small, the shape of the optical function surface,
The degree of freedom such as the type of the glass material 13 can be increased.

[Second Embodiment] The second embodiment is a modification of the above-described first embodiment, and is an embodiment using the same manufacturing apparatus as the first embodiment. Therefore,
In the following description, only differences from the first embodiment will be described, and redundant description will be omitted.

FIG. 2 is a diagram showing a schematic configuration of a mold 21 used in the method of manufacturing an optical element according to the second embodiment.
The mold 21 is located on the circumference of the periphery of the optical element after molding.
Six through holes 22 are formed at six equal positions. In the second embodiment, in the third step of the first embodiment, in addition to the fact that the glass material 13 is deformed by its own weight, by applying a negative pressure to the through hole 22 of the mold 21, the mold 21 is formed. The action of pulling the glass material 13 toward the mold 21 is performed. By applying a negative pressure through the through-hole 22 in this way, the glass material 13 is deformed by its own weight.
Deformation is promoted and the processing time can be shortened, which is desirable.

The negative pressure applied to the through hole 22 is suitably from a very small amount to about -50 kPa, and may be appropriately determined according to the hardness of the glass material 13 at the molding temperature. Also, the through hole 2
The number of 2 may be one or more. For example, it may be formed by dispersing fine pores throughout the mold.

[Third Embodiment] FIG. 3 is a sectional view showing a schematic configuration of a manufacturing apparatus to which an optical element manufacturing method according to a third embodiment is applied. In FIG. 3, the manufacturing apparatus according to the first embodiment generally includes a mold 31, a glass material holding member 32 on which a glass material 33 is placed, a mold holding member 35 having a cartridge heater 34 built therein, and a sealed container 37. And so on. Among these, the configurations of the mold 31, the glass material holding member 33, the mold holding member 35, and the like are the same as those of the first embodiment.
Since the configuration is the same as that of the embodiment, the description is omitted.

In the manufacturing apparatus to which the method for manufacturing an optical element according to the third embodiment is applied, the entire molded portion is built in the closed container 37. Glass material 33 inside closed container 37
A nichrome wire heater capable of directly heating the glass material 33 is provided in a portion opposed to the above. Also,
A gas injection pipe 37a for introducing gas into the molded part is formed at the upper part of the closed vessel 37.
A nichrome wire heater 38 for heating the gas to be injected is disposed around the heater.

Next, the manufacture of an optical element by the manufacturing apparatus having the above-described configuration will be described by taking as an example a case where an optically functional surface is formed on one surface of a glass lens, as in the first embodiment. However, the method of manufacturing the optical element of the third embodiment also includes substantially the same steps as those of the first embodiment, and therefore, in the following description, only the differences from the first embodiment will be described.

First, a mold 31 having a shape corresponding to the shape of a lens to be manufactured and mirror-finished to a predetermined surface roughness is prepared and set on a mold holding member 35.
Further, the glass material 33 is set on the glass material holding member 32 (first step).

Next, the above-described mold holding member 32 and the like are built in the closed container 37, oxygen is discharged from the closed container 37 to make a nitrogen atmosphere, and then the cartridge heater 34 and the nichrome wire heater 36 are used. Then, the glass material 33 is heated to a predetermined temperature (second step). In this embodiment,
In order to heat the glass material 33 efficiently, the nichrome wire heater 36 disposed near the glass material 33 is used to heat the glass material 33 in addition to the cartridge heater built in the mold holding member 35. Can be.

Further, when the glass material 33 is softened and deformed, nitrogen heated to a predetermined temperature by the nichrome wire heater 38 is blown at a predetermined flow rate from the upper surface side of the glass material 33 to accelerate the deformation. (3rd step). When the deformation is completed, the blowing of nitrogen is terminated, and the glass material is cooled as in the case of the first embodiment.

As described above, in the third embodiment, the deformation of the glass material 33 is promoted by the gas blown from the upper surface.
It is desirable because the deformation of No. 3 can be promoted and the processing time can be shortened. The gas to be blown is not limited to nitrogen, but may be an inert gas such as helium or air.

[Fourth Embodiment] FIG. 4 is a sectional view showing a schematic configuration of a manufacturing apparatus to which an optical element manufacturing method according to a fourth embodiment is applied. In FIG. 4, a manufacturing apparatus according to the first embodiment has a configuration similar to that of the apparatus described in the first embodiment, and includes a first mold 41 and a first glass material holding member 42 on which a glass material 43 is placed. A second mold 46 above a first mold holding portion including a first mold holding member 45 having a cartridge heater 44 therein, and a second mold holding having a cartridge heater 48 therein. A second mold holding portion, which is constituted by a member 47 and the like and has substantially the same configuration as the first mold holding portion, is arranged. The configuration and operation of the first mold holding unit are the same as those of the above-described first embodiment, and a description thereof will be omitted.

The second mold holding portion can move integrally in the vertical direction. In the third step of the first embodiment, when the glass material starts to deform, it moves downward, The second mold 46 is brought into contact with the upper surface of the substrate to promote deformation due to its own weight.

The shape of the second mold 46 may be a concave or convex spherical surface or a flat surface in accordance with the shape of the optical element to be finally formed.
It is effective if the shape of the upper surface of the glass material is deformed so that the material loss of the glass material when processing the other surface after forming one surface is reduced. The surface accuracy of the second mold 46 is not particularly required to transfer the surface shape of the mold onto the glass surface, so it is not necessary to perform mirror finishing, and a ground surface is sufficient.

Further, the pressure applied to the glass material by the second mold 46 is smaller than the pressure required for double-sided molding.
Desirably small enough. That is, it is not preferable to increase the pressure of the second mold 46 to shorten the life of the mold 41 in order to bring the glass material 43 along the first mold 41.

[Other Embodiments] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and can be appropriately changed without departing from the spirit of the invention. It is. For example, the shape of the surface to be formed can correspond to any shape such as not only a rotationally symmetric surface but also a toric surface, a cylindrical surface, a non-axisymmetric surface, and a free-form surface. In addition, as an optical element, not only a refraction type lens is formed, but also a mirror having the power of a toric surface or a cylindrical surface is manufactured by vapor-depositing a light reflecting material on the formed surface shape. By adding a functional material such as a wavelength selective reflection film or a polarization reflection film to the surface, a prism or an optical functional device can also be manufactured.

[0033]

Next, numerical examples based on the above embodiment will be described. [Example 1] Example 1 is a numerical example corresponding to the above-described first embodiment. Using a manufacturing apparatus shown in FIG. 1, a mold is formed via a glass material holding member 12 above a mold 11 having a concave aspherical surface made of silicon carbide which is mirror-finished to a maximum roughness of 0.01 μm or less. A flat lanthanum-crown glass material 13 having a diameter of 80 mm and a thickness of 10 mm, whose surface opposite to 11 was polished, was arranged. Mold 1
1 has an effective diameter of 75 mm and a paraxial radius of curvature of 100 mm. In the initial setting, the distance between the mold 11 and the glass material 13 was 15 mm.

Next, the cartridge heater 14 incorporated in the mold holding member 15 was driven to heat the mold 11 and the glass material 13 to 690 ° C. Five minutes after the mold 11 and the glass material 13 reach 690 ° C., the glass material 13
Started softening, and the glass material holding member 12 was moved toward the mold 11 at a speed of 1 mm / min such that the glass material 13 came into contact sequentially from the center of the mold 11 with the start of softening.

After 10 minutes have passed since the glass material 13 was completely separated from the glass material holding member 12, the mold 11 and the glass material 13 were cooled to 550 ° C. at a rate of 1 ° C./min. It was cooled at a rate of 10 ° C / min to 200 ° C or less. Note that a series of steps were all performed in a nitrogen atmosphere.

It was confirmed that the molding surface of the obtained glass material had a shape accuracy within 1.2 μm and a maximum roughness of 0.02 μm or less within the effective diameter, and had a cloudless aspheric shape.
After the same process was performed 500 times, the surface of the mold 11 was not particularly changed.

Example 2 Example 2 is a numerical example corresponding to the above-described second embodiment. Using the manufacturing apparatus shown in FIG. 1, the same shape as the mold 11 of the first embodiment is used. As shown in FIG.
The mold 21 having the through hole 22 formed therein was installed. The same glass material 1 as the glass material 13 used in Example 1 described above.
3, and the glass material 13 and the mold 21 are 690 ° C.
5 minutes after reaching, a negative pressure of −10 kPa was applied to the through hole 22 of the mold 21 for 1 minute, and then cooled as in Example 1.

The molding surface of the obtained glass material has a through hole 2
Except for the part corresponding to 2, the shape accuracy is 0.9 within the effective diameter.
It was confirmed that the film had an aspherical shape with no cloud and a maximum roughness of 0.02 μm or less. After the same process was performed 500 times, the surface of the mold 21 was not particularly changed.

Example 3 Example 3 is a numerical example corresponding to the third embodiment described above. Using the manufacturing apparatus shown in FIG. 3, a mold is formed via a glass material holding member 32 above a mold 31 having a concave aspherical surface made of silicon carbide mirror-finished to a maximum roughness of 0.01 μm or less. A lanthanum-crown-type glass material 33 having a diameter of 80 mm and a thickness of 10 mm and having a polished surface opposite to 31 was disposed.

After the glass material 33 is disposed, the glass material 33 is housed in a closed container 37 and a nitrogen atmosphere is introduced.
The mold 31 and the glass material 33 were heated to 690 ° C. by the nichrome wire heater 36. Five minutes after the mold 31 and the glass material 33 reach 690 ° C., the glass material 33 starts to soften, and when the softening starts, the glass material 3
The glass material holding member 32 was moved to the mold 11 side at a speed of 1 mm / min such that 3 contacted sequentially from the center of the mold 31.

Ten minutes after the glass material 33 was completely separated from the glass material holding member 32, nitrogen gas heated to 690 ° C. by the nichrome wire heater 38 was supplied from the upper portion at a flow rate of 2 liter / minute. It was sprayed on the glass material 33 for 10 minutes. Further, the mold 31 and the glass material 33 are set at 1 °.
Cool to 550 ° C at a rate of C / min, then 10 ° C
/ Minute to 200 ° C or less. Note that a series of steps were all performed in a nitrogen atmosphere.

It was confirmed that the molding surface of the obtained glass material had an accuracy of 1.2 μm or less and a maximum roughness of 0.02 μm or less within the effective diameter, and had an aspherical shape without clouding.
After the same process was performed 500 times, the surface of the mold 11 was not particularly changed.

[Embodiment 4] Embodiment 4 is a numerical example corresponding to a modification of the third embodiment. Using the manufacturing apparatus of FIG. 3, the same steps as those of the third embodiment are performed until the nitrogen gas is blown using the same mold 31 and glass material 33 as those of the third embodiment.

In Example 4, 10 minutes after the glass material 33 was completely separated from the glass material holding member 32, the nitrogen gas heated to 690 ° C. by the nichrome wire heater 38 was supplied from the upper part to 2 liter / liter. The glass material 33 was sprayed at a flow rate of 1 minute for 5 minutes. After that, the mold 31 and the glass material 33 are heated by the cartridge heater 35 to 69
While maintaining the temperature at 0 ° C, the nichrome wire heaters 36 and 38 are
The mold 31 and the glass material 33 are cooled at a rate of 1 ° C./min to 550 ° C. while maintaining the temperature difference at 20 ° C., and further cooled at a rate of 10 ° C./min. 2
It was cooled to below 00 ° C. Note that a series of steps were all performed in a nitrogen atmosphere.

It was confirmed that the formed surface of the obtained glass material had an accuracy of 0.6 μm or less within the effective diameter, a maximum roughness of 0.02 μm or less, and had an aspheric shape without clouding.
After the same process was performed 500 times, the surface of the mold 11 was not particularly changed.

[Embodiment 5] Embodiment 5 is a numerical example corresponding to the above-described fourth embodiment. Using the manufacturing apparatus of FIG. 4, via a glass material holding member 42, above a first mold 41 having a concave aspherical surface made of silicon carbide mirror-finished to a maximum roughness of 0.01 μm or less, First mold 4
80mm in diameter and 10mm in thickness polished on the surface facing 1
Lanthanum-based glass material 1
3 was placed. The effective diameter of the surface formed by the first mold 41 is 75 mm, and the paraxial radius of curvature is 100 mm. In the initial setting, the first mold 41 and the glass material 43 are used.
Was 15 mm.

Next, the cartridge heater 44 incorporated in the first mold holding member 45 was driven to heat the first mold 41 and the glass material 43 to 690 ° C. First mold 41
Five minutes after the glass material 43 reaches 690 ° C., the glass material 43 starts to soften, and the glass material is held in such a manner that the glass material 43 comes into contact in order from the center of the first mold 41 as the softening starts. The member 42 was moved toward the first mold 41 at a speed of 1 mm / min.

When 10 minutes have passed since the glass material 43 completely separated from the glass material holding member 42 and the glass material 43 substantially conformed to the shape of the first mold 41, the second metal heated to 690 ° C. A mold 46 is prepared and pressed from the upper surface of the glass material 43. The second mold 46 has a convex shape and the surface is a ground surface. The pressure applied by the first and second molds is 30
Deformation was promoted by applying a pressure of 0 kgf for 5 minutes.

After elapse of 5 minutes from the pressurization, the first and second molds 41 and the glass material 43 are separated by 550 at a rate of 1 ° C./min.
Cool to 200 ° C at a rate of 10 ° C / min.
It cooled to below C. Note that a series of steps were all performed in a nitrogen atmosphere.

It was confirmed that the molded surface of the obtained glass material had an accuracy of 0.3 μm or less within the effective diameter, a maximum roughness of 0.02 μm or less, and had an aspherical shape without clouding.
Further, no change was observed on the surface of the first mold 41 after the same process was performed 500 times.

[Embodiment 6] Embodiment 6 is a numerical example corresponding to the first embodiment. Using the manufacturing apparatus of FIG. 1, a mold having the same shape as in Example 1 was prepared using a platinum alloy containing 5% gold, and was molded under exactly the same conditions as in Example 1.

It was confirmed that the molding surface of the obtained glass material had an accuracy of 1.2 μm or less within the effective diameter, a maximum roughness of 0.02 μm or less, and an aspherical shape without clouding.
After the same process was performed 200 times, no particular change was observed on the surface of the mold.

[0053]

As described above, according to the present invention,
Since pressure molding is not performed at high temperature and high pressure, physical and chemical damage to the mold is small, and the life of the mold can be extended. Therefore, a high-precision optical element can be manufactured at low cost. Further, since pressure molding is not performed at high temperature and high pressure, there is no restriction on the mold material and the glass material and shape of the optical element.

[Brief description of the drawings]

FIG. 1 is a manufacturing apparatus used in a method for manufacturing an optical element according to a first embodiment.

FIG. 2 shows a mold used in the method for manufacturing an optical element according to the second embodiment.

FIG. 3 is a manufacturing apparatus used in a method for manufacturing an optical element according to a third embodiment.

FIG. 4 is a manufacturing apparatus used in a method for manufacturing an optical element according to a fourth embodiment.

[Explanation of symbols]

 11, 21, 31, 41: Mold (first mold) 12, 32, 42: Glass material holding member 22: Through hole 46: Second mold

Claims (8)

[Claims] 1. A method for producing an optical element in which a glass material is heated and softened and molded using a mold to obtain an optically functional surface, wherein a glass is provided above a surface corresponding to the optically functional surface of the mold. A first step of placing a material, a second step of heating the glass material to a predetermined temperature, and applying the softened glass material to a surface corresponding to the optical function surface of the mold from the center of the mold. In order to deform by its own weight,
And a third step of obtaining one molding surface. 2. The optical device according to claim 1, wherein in the third step, the weight of the glass material on the surface corresponding to the optically functional surface of the mold is adjusted using a glass material holding member. Device manufacturing method. 3. The method according to claim 1, wherein the mold is formed of a material having pores, and in the third step, a negative pressure is applied to the glass material through the pores of the mold. A method for manufacturing an optical element. 4. The method according to claim 3, wherein in the third step, deformation of the glass material is promoted by blowing a gas heated to a predetermined temperature from a side opposite to a surface of the glass material on which an optical function surface is to be formed. The method for manufacturing an optical element according to claim 1. 5. A method according to claim 5, further comprising: disposing a second mold so as to face a surface corresponding to the optical function surface of the mold. In the third step, the glass material is deformed and the optical property of the mold is changed. 2. The optical device according to claim 1, wherein after pressing along a surface corresponding to the functional surface, pressure is applied by the second mold from a side opposite to a surface of the glass material on which an optical functional surface is to be formed. 3. Device manufacturing method. 6. After the third step, a fourth step of cooling the temperature of the mold to a temperature equal to or lower than a glass transition point of a molded glass material is performed, and in the fourth step, 2. The method for manufacturing an optical element according to claim 1, wherein cooling is performed so as to satisfy the following conditions at least until the ambient temperature is cooled to a temperature equal to or lower than the glass softening point of the formed glass material. Tm ≧ 20, where Ta: ambient temperature (° C.) Tm: mold temperature (° C.) 7. The method according to claim 1, wherein the material of the mold is platinum or an alloy containing platinum. 8. An optical element manufactured by a method for manufacturing an optical element by heating and softening a glass material and molding using a mold to obtain an optically functional surface, wherein the optical element corresponds to the optically functional surface of the mold. A first step of placing a glass material above the surface, a second step of heating the glass material to a predetermined temperature, and placing the softened glass material on a surface corresponding to the optical function surface of the mold. A third step of obtaining one molding surface by sequentially deforming from the center of the mold by its own weight.