JP5220491B2 - Optical element manufacturing method - Google Patents

Description

  The present invention relates to a method of manufacturing an optical element that obtains a non-rotationally symmetric optical element by molding a heat-softened molding material with a molding die.

  In a photographing camera optical system, an observation optical system, and the like, a plurality of optical elements such as lenses and prisms are used. For these optical elements, there is a demand for higher performance and higher functionality, for example, by improving the performance by changing the optical surface shape to an aspherical shape. Further, in the scene of mass production of optical elements having an aspherical shape, a manufacturing method is adopted in which a heat-softened molding material is pressed with a molding die.

  Furthermore, from the viewpoint of reducing the size, reducing the thickness, and improving the mounting density, the outer shape of the optical element is a D shape in which a cross-sectional shape (outer shape) perpendicular to the optical axis is cut out of a circular shape, or A non-rotationally symmetric body such as a rectangular shape may be used. In such a case, in general, the optical element obtained by molding in advance is cut or cut into a desired outer shape.

Further, as a method for manufacturing an optical element only by a molding process, for example, a technique described in Patent Document 1 is known.
In Patent Document 1, a collar portion is provided on the outer peripheral portion of the optical element, and a positioning surface is formed on the collar portion. In order to form this surface, projections are provided on the upper and lower molds, and the glass molding material placed inside the mold is heated and softened to form the collar on the optical element. At the same time, a positioning surface is formed.
JP-A-1-183611

However, in a general manufacturing method that obtains a non-rotationally symmetric optical element by cutting or scraping an optical element obtained by molding, the number of steps is increased to form the outer shape.
Moreover, in patent document 1, since the glass heat-softened by the formation process exists in a state with high viscosity, the freedom degree of a deformation | transformation is not so high. For this reason, it is difficult to freely set the outer shape of the optical element including the positioning surface.

  Furthermore, even if the shape is moldable, the volume variation increases depending on the molding material to be used, and part of the outer shape is not formed or a molding flash is likely to be caused, thereby causing molding defects.

  The present invention has been made to solve such a problem, and provides an optical element manufacturing method capable of simultaneously and accurately molding the optical functional surface and the outer shape of an optical element of a non-rotationally symmetric body. For the purpose.

In order to achieve the object, the invention according to claim 1
In the method of manufacturing an optical element that obtains a non-rotationally symmetric optical element by molding a heat-softened glass molding material with an upper mold, a lower mold, and an auxiliary mold,
The molding material has a single spherical shape,
A molding surface is formed on each of the upper mold and the lower mold,
The auxiliary mold is provided with a deformation restricting portion, and the cross section of the deformation restricting portion has a shape connected by combining a straight side, an arc side, or a combination thereof,
The length of the perpendicular line from the center of gravity of the cross section of the deformation restricting portion to each side is defined as RL = Lmax / Lmin when the ratio of the minimum perpendicular length Lmin and the perpendicular maximum length Lmax is RL = Lmax / Lmin.
1 ≦ RL ≦ 1.3
Is satisfied,
The molding material has a ratio of the volume Vm and the volume Vc in the space formed by the molding surfaces of the upper mold and the lower mold and the deformation restricting portion when the molding is completed, and RV = Vm / Vc. ,
0.6 ≦ RV ≦ 1
Is satisfied,
Arranging the molding material in a space surrounded by the molding surface of the upper mold, the molding surface of the lower mold, and the deformation restricting portion;
While the heat-softened molding material is pressed with the upper mold and the lower mold, the space surrounded by the molding surface of the upper mold, the molding surface of the lower mold, and the deformation regulating portion is filled. And a molding step.

The invention according to claim 2 is the method of manufacturing an optical element according to claim 1,
When the thickness of the deformation restricting portion is d, the relationship with the minimum length Lmin of the perpendicular from the center of gravity of the cross section to each side is d ≦ 1.34 × Lmin.
It is characterized by satisfying.

The invention according to claim 3 is the method of manufacturing an optical element according to claim 1 or 2 ,
A cross section of the deformation restricting portion is a regular polygon.

  According to the present invention, the optical functional surface and the outer shape of the optical element of the non-rotation symmetric body can be molded simultaneously and with high accuracy.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 is a diagram showing a partial concept of an optical element manufacturing apparatus in a thermoforming state.

The optical element manufacturing apparatus 10 can be operated under atmospheric pressure or under the substitution of an inert gas (Ar gas or the like) or nitrogen gas (N ₂ or the like) and does not require a vacuum apparatus. The manufacturing apparatus 10 includes an upper plate 12 and a lower plate 14 that are arranged to face each other, and a pressurizing device 21 that presses the upper plate 12 toward the lower plate 14 (in the direction of arrow A). . Then, the mold assembly 20 in which the molding material 30 (see FIG. 2) is accommodated is carried and sandwiched between the upper plate 12 and the lower plate 14.

  The lower plate 14 is fixed to the base 15, and the upper plate 12 is connected to the pressure device 21. An upper cartridge heater 16 is built in the upper plate 12. The lower plate 14 has a lower cartridge heater 18 built therein. The mold assembly 20 is heated by the cartridge heaters 16 and 18 via the lower plate 14 and the upper plate 12. Instead of the cartridge heaters 16 and 18, an infrared lamp or the like may be arranged around the side surface of the mold assembly 20.

  For example, in the molding process, the mold assembly 20 is pressure-molded by the pressure device 21 while being sandwiched between the upper plate 12 and the lower plate 14. In this way, the mold assembly 20 is subjected to the steps of heating, molding, and cooling to mold the molding material 30 and obtain the optical element 32 (see FIG. 2C).

Next, the configuration of the mold assembly 20 and the optical element 32 will be described.
FIG. 2A is a view showing an assembled state of the mold assembly 20 at room temperature, FIG. 2B is a view showing a state after the mold assembly 20 is molded under heating, and FIG. 4 is a sectional view of an element 32. FIG. 3A is a sectional view taken along line III-III in FIG. 2A, FIG. 3B is a sectional view taken along line III-III in FIG. 2B, and FIG. 3C is a plan view of the optical element 32. 4A is a plan view of the auxiliary mold 27, and FIG. 4B is a side sectional view thereof.

  2A and 3A, the mold assembly 20 includes an auxiliary die 27 in addition to an upper die 22, a lower die 24, and a sleeve 26 as a body die. The sleeve 26 has a cylindrical shape that is long in the vertical direction (pressing direction). The upper die 22 and the lower die 24 are respectively inserted into the sleeve 26 from both opening sides.

In a state where the upper mold 22 and the lower mold 24 are fitted, the central axes O of the upper mold 22, the lower mold 24, and the sleeve 26 are set to coincide with each other.
The upper mold 22 and the lower mold 24 are formed with molding surfaces 22a and 24a on opposite surfaces, respectively. The outer peripheral portions of the molding surfaces 22a and 24a are formed as flat surfaces 22b and 24b (non-optical functional surfaces), respectively. The molding surfaces 22a and 24a correspond to the optical functional surfaces 32a and 32b (see FIGS. 2C and 3C) of the optical element 32, respectively, and the flat surfaces 22b and 24b correspond to the non-optical functional surfaces 32a ′ and 32b of the optical element 32, respectively. This corresponds to 32b ′ (see FIGS. 2C and 3C). The molding surface 22a and the flat surface 22b, and the molding surface 24a and the flat surface 24b are integrally formed, respectively.

Each molding surface 22a, 24a is formed into a spherical surface or an aspherical surface, and these molding surfaces 22a, 2 are formed.
It is formed so that the top of the surface as the center of the spherical surface or the aspherical surface is located on the central axis of 4a.

In the present embodiment, the molding surfaces 22a and 24a are formed in a concave shape corresponding to the biconvex optical functional surfaces 32a and 32b (see FIGS. 2C and 3C) of the optical element.
The auxiliary mold 27 is provided with a deformation restricting portion 29 having an oval cross-sectional opening to restrict the outer shape of the optical element 32.

Then, the molding material 30 is arranged in a space surrounded by the molding surface 22 a of the upper mold 22, the molding surface 24 a of the lower mold 24, and the deformation restricting portion 29 of the auxiliary mold 27.
Next, as shown in FIGS. 2B and 3B, an intermediate molded product 31 having a desired shape is molded by heating and softening the molding material 30 and pressurizing the mold assembly 20 with the pressurizing device 21.

  In the intermediate molded product 31, the molding surfaces (22 a, 24 a) of the upper mold 22 and the lower mold 24 are transferred, and a desired outer shape is formed by being regulated by the deformation regulating portion 29 of the auxiliary mold 27. Is done.

  Thereafter, the mold assembly 20 is cooled to a predetermined temperature and disassembled, so that the optical functional surfaces 32a and 32b, the non-optical functional surfaces 32a ′ and 32b ′, and the outer shape are obtained as shown in FIGS. 2C and 3C. The desired optical element 32 having the side surface 32c is finally obtained. The optical element 32 has an oval shape in plan view (see FIG. 3C).

Next, the auxiliary mold 27 will be described.
As shown in FIGS. 4A and 4B, the auxiliary die 27 is placed on the flat surface 24 b around the molding surface 24 a of the lower die 24 while being fitted to the inner peripheral surface of the sleeve 26.

  An opening 28 is formed in the auxiliary mold 27, and the inner peripheral surface serves as a deformation restricting portion 29. The cross section of the deformation restricting portion 29 has a straight side, an arc side, or a combination of these.

  In the present embodiment, this cross section has an oval shape in which both sides of a circular radial direction are cut out. That is, this cross section has a shape in which two straight sides and two arc sides are connected. By this deformation restricting portion 29, the outer side surface 32c (see FIGS. 2C and 3C) of the optical element 32 is formed.

Next, setting conditions regarding the shape of the cross section of the deformation restricting portion 29 will be described.
4A, let OPi be the length of a perpendicular line that extends from the center of gravity Ow of the cross section of the deformation restricting portion 29 to each side.

  Among the lengths OPi, when the minimum length is Lmin (= OP1), the maximum length is Lmax (= OP2), and the ratio is RL = Lmax / Lmin, the cross section of the deformation restricting portion 29 has the following relationship: Set to satisfy the expression. The reason will be described later.

1 ≦ RL ≦ 1.3 ......... Formula (1)
In the present embodiment, the center of gravity Ow of the cross section of the deformation restricting portion 29 is arranged on the center axis O of the outer shape of the auxiliary die 27.

When the deformation restricting portion 29 has an oval cross section, the minimum length Lmin is the half-value width of the oval cutout portion.
The maximum length Lmax is the radius of the oval circular portion.

The thickness d of the cross section of the auxiliary die 27 (deformation restricting portion 29) is set so as to satisfy the following relational expression using the minimum length Lmin of the cross section.
d ≦ 1.34 × Lmin (2)
The material of the upper mold 22, the lower mold 24, the sleeve 26, and the auxiliary mold 27 is made of cemented carbide, silicon carbide, stainless steel, or the like. Furthermore, the shape of the molding surfaces 22a and 24a can be manufactured by selecting an appropriate process from cutting, grinding, polishing and the like.

A single molding material 30 disposed between the upper mold 22 and the lower mold 24 is made of optical glass as a thermoplastic material. In this embodiment, as optical glass (L-BSL7 manufactured by OHARA)
(Glass transition point 498 ° C., yield point 549 ° C.). The shape of the molding material 30 is a ball shape (spherical shape).

The ball-shaped molding material 30 is manufactured by polishing a material obtained from a molten glass by a dropping method, or by subjecting a cut material to a heat deformation treatment and then polishing the material.
This ball-shaped molding material 30 is very convenient for volume control because of its high dimensional accuracy. Furthermore, the manufacturing costs are relatively low.

In addition, since the entire surface of the ball shape is finished to a mirror surface, the appearance of the obtained molded product can be easily finished to a good state.
The volume Vm of the molding material 30 is made to coincide with the volume of the optical element 32 to be manufactured.

  Furthermore, the ratio RV = Vm / Vc between the volume Vc of the space surrounded by the molding surface 22a of the upper mold 22, the molding surface 24a of the lower mold 24, and the deformation restricting portion 28 and the volume Vm of the molding material 30 is as follows. Set to satisfy.

RV ≦ 1 ……… Formula (3)
Next, the operation of the method for manufacturing an optical element by glass molding in the present embodiment will be described.
The manufacturing process of the optical element of the present embodiment includes an assembly process of the mold assembly 20, a heating process, a molding process, and a cooling process.

First, the assembly process of the mold assembly 20 will be described.
2A and 3A described above, the auxiliary mold 27 is placed on the flat surface 24b around the molding surface 24a of the lower mold 24, and the position is set so that the central axis of the lower mold 24 and the central axis of the auxiliary mold 27 coincide. Match.

Next, the ball-shaped molding material 30 is put into the opening 28 of the auxiliary mold 27 and placed on the molding surface 24 a of the lower mold 24.
At this time, positioning is performed so that the center of the ball-shaped molding material 30 is arranged on the central axis of the lower mold 24.

In this state, the sleeve 26 and the auxiliary die 27 are fitted to the lower die 24, and the upper die 22 is fitted so that the molding surface 22 a faces the molding material 30 on the lower die 24.
When the upper die 22, the lower die 24, and the auxiliary die 27 are inserted into the sleeve 26, the central axes of the upper die 22, the lower die 24, and the auxiliary die 27 coincide with the central axis of the sleeve 26.

The center of the ball-shaped molding material 30 coincides with the central axis of the upper mold 22.
Thus, the molding material 30 is composed of the upper mold 22 and the lower mold 24 that are inserted to face the sleeve 26.
Is used to obtain the mold assembly 20.

Next, the heating process of the mold assembly 20 will be described.
In FIG. 1, a mold assembly 20 in which a molding material 30 is assembled is carried between a lower plate 14 and an upper plate 12 of an optical element manufacturing apparatus 10.

Via the lower plate 14 and the upper plate 12, the mold assembly 20 and the molding material 30 inside are heated for a predetermined time so as to reach a molding temperature corresponding to the molding material 30.
This molding temperature is set to a temperature higher than the yield point of the glass material of the molding material 30 and lower than the softening point.

As a result, the molding material 30 is in a softened state at the molding temperature.
Next, the molding process will be described.
The mold assembly 20 is sandwiched and pressed between the lower plate 14 and the upper plate 12 while being held at the molding temperature described above.

  In the mold assembly 20, the molding material 30 sandwiched between the lower mold 24 and the upper mold 22 is softened and deformed, while the molding surface 24 a of the lower mold 24, the molding surface 22 a of the upper mold 22, and the deformation restricting portion. The space surrounded by 29 is filled.

  As the deformation of the molding material 30 proceeds, the shapes of the molding surfaces 22a and 24a are transferred to the molding material 30 to mold the optical functional surfaces 32a and 32b and the non-optical functional surfaces 32a ′ and 32b ′ of the optical element 32. (See FIGS. 2C and 3C).

Furthermore, when the deformed molding material 30 reaches each side of the deformation restricting portion 29, the shape of the outer side surface 32c on the outer periphery of the optical element 32 is molded (see FIGS. 2C and 3C).
If the pressing of the upper plate 12 is stopped at the stage when the molding material 30 is molded into a desired shape, the molding is completed.

  In order to pressurize the molding material 30 and obtain a desired shape, when the mold assembly 20 is pressed between the upper plate 12 and the lower plate 14 as described above, the amount of movement of the upper plate 12 is set. It may be controlled, or it may be controlled by setting a pressing force and a pressurizing time.

Next, the cooling process after forming the molding material 30 into a desired shape will be described.
In the cooling step, the heated molding material 30 is shifted from the softened state to the solidified state, and the shape of the molded optical element 32 is stabilized.

In this step, the mold assembly 20 is cooled by a cooling device (not shown).
During cooling, a pressurized state may be necessary to ensure transfer accuracy of the molded optical element 32 and reduce internal strain.

The pressure applied during cooling is set within a range that does not cause cracks in a molded product such as an optical element.
The cooling is completed when the mold assembly 20 and the molded optical element 32 are cooled to near room temperature. After the cooling is completed, the upper die 22 is removed from the mold assembly 20 and the molded product is taken out, so that an optical element 32 having an oval outer shape can be obtained.

Here, the role of the deformation restricting portion 29 of the auxiliary die 27 will be described with reference to FIG. 2A (FIG. 3A) to FIG. 2C (FIG. 3C).
At the initial stage of deformation, the soft ball-shaped molding material 30 is spread from the center of the molding surface 24 a of the lower mold 24 (the top position of the optical function surface) toward each side of the deformation restricting portion 29. Since the molding material 30 is in a uniformly softened state, it spreads in a circular shape toward the outside in a direction perpendicular to the pressing direction (the central axis direction of the mold).

  When the expanded molding material 30 reaches each side of the deformation restricting portion 29, outward deformation at that portion stops. Depending on the progress of the deformation of the molding material 30, the opening 28 changes from the radial direction to the thickness direction and the circumferential direction at the opening 28.

  When the molding is completed, the outer side surface (32c) of the intermediate molded product 31 surrounded by each side of the deformation restricting portion 29 is formed. Under the molding temperature, the viscosity of the glass is relatively high, so that it is not a momentary deformation but a gentle deformation flow state. With this gentle deformation, the degree of freedom with respect to the deformable shape is not high.

For this reason, it is preferable to set the cross section of the deformation | transformation control part 29 to the shape which can follow the flow at the time of the deformation | transformation of the molding raw material 30 fully.
Here, in FIG. 4A, when the difference between the maximum length Lmax and the minimum length Lmin is large with respect to the length OPi of the perpendicular line extending from the center of gravity Ow of the cross-sectional shape of the deformation restricting portion 29 to each side, when the molding is completed. The possibility that an unfilled state in which the molding material 30 is not filled in the portion having the maximum length Lmax is increased. In addition, there is an increased possibility that an overfilling state in which the molding material 30 overflows at the minimum length and becomes a molding burr will occur.

Next, the ratio RL between the minimum length Lmin and the maximum length Lmax will be examined.
Assume that the molding material 30 spreads outward in a circular shape.
As shown in FIGS. 5 and 6, the length from the center of the molded product 32 to the outer side surface 32c is compared with and without the auxiliary die 27. FIG.

For the sake of simplicity, the molding surfaces 22a and 24a of the upper mold 22 and the lower mold 24 are flat surfaces.
In FIG. 5, when the cross section of the deformation restricting portion 29 in the auxiliary die 27 is circular, the molded product 42 has a cylindrical shape (see FIG. 7).

At this time, the length from the center of the molding material 30 to the circumferential portion is the radius of the cylinder, which is L1. The thickness is d.
As shown in FIG. 6, when the diameter of the opening 28 of the auxiliary mold 27 in FIG. 5 is increased, that is, when the auxiliary mold 27 is removed so that the molding material 30 can be freely deformed, the outer shape of the molded product 52 Becomes a barrel-like columnar shape bulging outward (see FIG. 8).

  At this time, as shown in FIGS. 8 and 9 (a cross-sectional view obtained by enlarging FIG. 8 and rotated by 90 °), the cross-sectional shape of both end faces of the barrel-shaped molded product 52 is a semicircular shape, and a semicircular portion from the center. The length to the end of is L2.

  It is assumed that the cylindrical shaped product 42 and the barrel cylindrical shaped product 52 have the same thickness d and volume V. The barrel-like cylindrical shaped product 52 has a shape in which the middle is rectangular and semicircular shapes are added to both ends thereof.

Therefore, consider again the length ratio Ra = L2 / L1 described above.
The volume V of the cylindrical shaped product 42 in FIG. 7 is V = π × L1 ² × d.
Further, the volume V of the barrel-shaped cylindrical shaped product 52 in FIG.
If the coordinate axes are taken as shown in FIG. 9, the curve y = f (x) connecting the points Q, R, and S (points on the semicircle) is
y = (L2−d / 2) + √ ((d / 2) ² −x ² )
It is represented by

Therefore, the volume V of the three-dimensional product 52 is expressed by the following equation.
V = 2 × ∫ ₀ ^{d / 2} y ² πdx = 2π∫ ₀ ^{d / 2} {(L2−d / 2) + √ ((d / 2) ² −x ² )} ² dx
Then, if it calculates using said formula, the volume V of the molded article 52 will be calculated | required.

In the case of the above premise, a form that does not exist in the actual molding process is formed, but a cylinder and a sphere having the same thickness are in one extreme state.
At this time, the ratio Ra = L2 / L1 is as follows.

1 ≦ Ra ≦ √ (3/2) (≈1.23)... (4)
In the actually confirmed range, a certain amount of free flow occurs in the glass of the molding material 30. Therefore, according to experiments, the upper limit of the ratio Ra is expanded to about 1.3 as a practical condition range.

If this Ra is greater than 1.3, the glass will be insufficiently filled. If Ra is less than 1, the glass will be overfilled.
As described above, in the deformation restricting portion 29 of the auxiliary die 27, the ratio RL between the minimum length Lmin and the maximum length Lmax satisfies the expression (1).

The ratios RL and Ra can be considered by replacing them with corresponding conditions.
If the deformation restricting portion 29 satisfies the expression (1), the forming material 30 can be deformed so as to reach each side constituting the cross section of the deformation restricting portion 29 at the stage of forming the ball-shaped forming material 30. it can.

Next, conditions regarding the thickness d of the auxiliary die 27 (deformation restricting portion 29) are arranged.
In order to place the ball-shaped molding material 30 inside the opening 28, the radius r of the molding material 30 must be smaller than the minimum length Lmin.

From this relationship, an upper limit is set for the thickness d of the deformation restricting portion 29 when the molding surface is formed.
Let us consider a case where a cylindrical molded product is molded from the ball-shaped molding material 30 with r = Lmin.

The upper limit of the thickness d1 of the cylinder is as follows.
d1 ≦ 4/3 × r (≈1.34r) (5)
As described above, the thickness d of the auxiliary die 27 and the minimum length Lmin of the cross-sectional shape of the opening 28 satisfy Expression (2).

The thickness d of the auxiliary mold 27 and the thickness d1 of the cylinder can be replaced by considering the conditions.
If the auxiliary mold 27 satisfies the formula (2), the ball-shaped molding material 30 can be used to mold the optical functional surface of the molded product in the widest possible range.

Next, conditions for the volume Vm of the ball-shaped molding material 30 are arranged.
Let Vc be the volume of the molding space surrounded by the molding surface 22a of the upper mold 22, the molding surface 24a of the lower mold 24, and the opening 28.

The ideal state is when the molding material 30 is deformed to completely fill the molding space.
However, since the viscosity of the glass is relatively high at the molding temperature, a part of the molding material 30 is likely to protrude from the upper part of the auxiliary die 27 at the portion where the deformation is restricted.

It is necessary to manage the volume of the molding material 30 to prevent the protrusion within a range satisfying the expression (3) so that it is not necessary to scrape off the protruding portion after the molding.
In the present embodiment, the shape of the molded optical element 32, the type of glass constituting the ball-shaped molding material 30 (or the optical element), the order of the manufacturing process, and the like are not limited to the above-described examples. .

  For example, the shape of the outer side surface 32 c of the optical element 32 may be a D-cut shape in which only one end of a circle is cut out in addition to the substantially oval shape surrounded by the cross section of the opening 28 of the auxiliary die 27.

Further, the shape of the optical functional surfaces 32a and 32b and the shape of the non-optical functional surfaces 32a ′ and 32b ′ of the optical element 32 can be changed according to the required optical performance and specifications.
Furthermore, although the upper mold | type 22 and the lower mold | type 24 each showed as an example the case comprised with a single component, you may comprise it combining several separate components.

  Further, in the optical element manufacturing process exemplified in the present embodiment, an example in which an assembly process, a heating process, a molding process, and a cooling process are combined has been shown. However, when combined with an automatic assembly apparatus, the order of the assembly process and the heating process is shown. Can also be replaced, and they may be manufactured in the order in which the assembly process is performed after the heating process.

Furthermore, when a function such as antireflection is added to the optical element 32, the surface of the optical element 32 may be coated in a later step.
According to the present embodiment described above, an optical element 32 having a non-rotationally symmetric outer shape can be obtained by using a single molding material 30 made of glass. Further, since the ball-shaped molding material 30 is used, it is easy to suppress the volume variation, and it is possible to prevent the occurrence of defective products and obtain the optical element 32 with stable quality. Further, the optical functional surfaces 32a and 32b, the non-optical functional surfaces 32a ′ and 32b ′, and the outer side surface 32c of the optical element 32 are simultaneously and accurately molded according to the condition range set in the deformation restricting portion 29 of the auxiliary die 27. be able to.

[Second Embodiment]
10A to 10C are diagrams illustrating a second embodiment. In addition, the same code | symbol is attached | subjected and demonstrated to the member which is the same as that of 1st Embodiment, or is equivalent.

The basic configuration is the same as that of the first embodiment.
The difference from the first embodiment is that the cross section of the deformation restricting portion 29 has a rectangular shape.
The conditions of the lower limit value for the volume Vm of the ball-shaped molding material 30 are arranged.

The volume of the molding space surrounded by the molding surface 22a of the upper mold 22, the molding surface 24a of the lower mold 24, and the deformation restricting portion 29 is Vc, and the ratio is RV = Vm / Vc.
For the sake of simplicity, the cross-sectional shape of the deformation restricting portion 29 is an equilateral triangle having the minimum number of sides.

  In FIG. 11, because of the relationship between a triangular prism having a regular triangle (side length s) and a cylinder (radius r) inscribed in the triangular prism and having the same thickness, s = 2√3r. The lower limit value of the volume ratio RV is obtained as a condition that the outer side surface portion cannot be formed when it is widely formed.

The volume ratio RV is as follows.
RV ≧ π / (3√3) (≈0.6) Equation (6)
Moreover, although description is abbreviate | omitted, in the case of a square, the lower limit of volume ratio RV will be about 0.8.

Furthermore, it is necessary to control the volume of the molding material 30 to prevent the protrusion within a range that satisfies the following conditions so that it is not necessary to scrape off the protruding portion after molding.
RV ≦ 1 ......... Formula (7)
The volume ratio RV can prevent unfilling or overfilling beforehand by satisfying the following relationship that combines both conditions.

0.6 ≤ RV ≤ 1 ......... Formula (8)
According to this embodiment, as compared with the first embodiment, the outer shape of the optical element 32 that can be molded can be expanded into a polygon.
[Third Embodiment]
12A to 12C are diagrams illustrating a third embodiment. In addition, the same code | symbol is attached | subjected and demonstrated to the member which is the same as that of 1st Embodiment, or is equivalent.

The basic contents are the same as in the first embodiment.
The difference from the first embodiment is that the cross section of the deformation restricting portion 29 is a regular hexagon.
According to this embodiment, as compared with the first embodiment, the outer shape of the optical element 32 that can be molded can be expanded to a regular polygon.

  Moreover, compared with 2nd Embodiment, the cross section of the opening part 28 is a regular polygon, and a cross section becomes close to a circular shape by the number of sides increasing. For this reason, it has the advantage that the external shape of the optical element 32 can be shape | molded stably.

It is a figure which shows the partial concept of the manufacturing apparatus of an optical element. It is a figure which shows the assembly state of the metal mold assembly in normal temperature. It is a figure which shows the state after shaping | molding under a heating. It is sectional drawing of the obtained optical element. It is sectional drawing which follows the III-III line of FIG. 2A. It is sectional drawing which follows the III-III line of FIG. 2B. It is a top view of an optical element. It is a top view of an auxiliary type. It is side surface sectional drawing same as the above. It is a figure which shows the assembly state of a metal mold assembly. It is a figure which shows the assembly state (without an auxiliary die) of a metal mold assembly. It is an external view of a cylindrical molded product. It is sectional drawing of a molded article of a barrel-shaped column shape. It is an enlarged view same as the above. It is sectional drawing of the assembly state whose opening part is rectangular shape. It is sectional drawing of the state after shaping | molding whose opening part is rectangular shape. It is a top view of a molded product. It is a figure which shows the Example whose opening part makes an equilateral triangle. It is sectional drawing of the assembly state whose opening part is a regular hexagon. It is sectional drawing of the state after an opening shape | molds a regular hexagon. It is a top view of a molded product.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical element manufacturing apparatus 12 Upper plate 14 Lower plate 15 Base 16 Upper cartridge heater 18 Lower cartridge heater 20 Mold assembly 21 Pressurizer 22 Upper mold 22a Molding surface 22b Flat surface 24 Lower mold 24a Molding surface 24b Flat surface 26 Sleeve 27 Auxiliary mold 28 Opening 29 Deformation restricting portion 30 Molding material 31 Intermediate molded product 32 Optical element 32a Optical functional surface 32b Optical functional surface 32a 'Non-optical functional surface 32b' Non-optical functional surface 32c External side surface 42 Molded product 52 Molded products

Claims (3)

In the method of manufacturing an optical element that obtains a non-rotationally symmetric optical element by molding a heat-softened glass molding material with an upper mold, a lower mold, and an auxiliary mold,
The molding material has a single spherical shape,
A molding surface is formed on each of the upper mold and the lower mold,
The auxiliary mold is provided with a deformation restricting portion, and the cross section of the deformation restricting portion has a shape connected by combining a straight side, an arc side, or a combination thereof,
The length of the perpendicular line from the center of gravity of the cross section of the deformation restricting portion to each side is defined as RL = Lmax / Lmin when the ratio of the minimum perpendicular length Lmin and the perpendicular maximum length Lmax is RL = Lmax / Lmin.
1 ≦ RL ≦ 1.3
Is satisfied,
The molding material has a ratio of the volume Vm and the volume Vc in the space formed by the molding surfaces of the upper mold and the lower mold and the deformation restricting portion when the molding is completed, and RV = Vm / Vc. ,
0.6 ≦ RV ≦ 1
Is satisfied,
Arranging the molding material in a space surrounded by the molding surface of the upper mold, the molding surface of the lower mold, and the deformation restricting portion;
While the heat-softened molding material is pressed with the upper mold and the lower mold, the space surrounded by the molding surface of the upper mold, the molding surface of the lower mold, and the deformation regulating portion is filled. A process for molding the optical element. When the thickness of the deformation restricting portion is d, the relationship with the minimum length Lmin of the perpendicular from the center of gravity of the cross section to each side is d ≦ 1.34 × Lmin.
An optical element manufacturing method characterized by satisfying: The method of manufacturing an optical element according to claim 1, wherein a cross section of the deformation restricting portion is a regular polygon.