JP2003073135A - Method and mold for forming optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a mold enabling to form a highly precise optical element in a short cycle time. SOLUTION: The method for forming an optical element comprises the steps of heating a glass material 5 in a heating furnace 8 to a temperature corresponding to viscosity of the material of 10<8> dPa.s or lower, transferring the heated glass material 5 into the mold comprising an upper mold 2 and a lower mold 3, forming the glass material 5 as an optical element by the mold set at a temperature corresponding to viscosity of the glass material 5 in the range of 10<15> to 10<12> dPa.s, and taking out the formed optical element from inside the mold, where the surface contour of the mold comprising the upper mold 2 and the lower mold 3 is correctively worked so as to compensate the error in shape against the optically functional surface contour obtained by using the mold before correction and by completion of the above steps to form the optical element.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding method and an optical element molding die for obtaining an optical element by press-molding a glass material softened by heating with a pair of molding dies.

[0002]

2. Description of the Related Art Conventionally, as a method for molding an optical element such as a lens having a highly accurate optical function surface, for example, Japanese Patent Publication No.
A method for manufacturing an optical element disclosed in Japanese Patent Laid-Open No. 32007 is known.

The manufacturing method disclosed in the publication is 10 ⁸ to
A glass material softened to a temperature equivalent to 10 ⁶ poise is pressed at a pressing speed of 10 mm / sec to 250 mm / sec with a mold set to a temperature lower than the glass transition temperature and a temperature equal to or higher than 10 ^14.5 poise. It is what is molded.

[0004]

However, in the case of the method of manufacturing an optical element disclosed in Japanese Patent Publication No. 4-32007, a glass material heated to a temperature corresponding to 10 ⁸ to 10 ⁶ poise is less than the transition point. Since it is rapidly cooled to the temperature of 1, the large heat stress remains in the press-molded glass material.

Therefore, the optical element taken out from the mold does not accurately transfer the surface shape of the mold, and the shape accuracy required for the optical element cannot be obtained. Further, in the case of an optical element such as a concave lens or a meniscus lens, even if the shape accuracy can be obtained after taking out from the mold, the shape accuracy can be improved by performing an annealing treatment to remove the residual stress generated in the molding process. However, it is difficult to obtain a highly accurate optical element having a shape accuracy within 0.2 μm.

The present invention was developed in order to solve the problems of the conventional method for molding an optical element, and a method for molding an optical element and an optical element molding capable of manufacturing a highly accurate optical element in a short cycle time. The purpose is to provide a mold for use.

[0007]

The invention according to claim 1 is
A step of heating the glass material to a temperature corresponding to a viscosity of 10 ⁸ dpa · s or less in a heating furnace, a step of conveying the heated glass material into a mold, and a step of 10 ^{15 to} 10 ¹² dpa · of the glass material. A method for manufacturing an optical element, which includes a step of molding a glass material with a mold set to a temperature corresponding to the viscosity of s to form an optical element, and a step of taking out the molded optical element from the mold. In, the surface shape of the mold is corrected and processed to a shape that cancels a shape error from the shape of the optical function surface of the optical element obtained by completing the above steps using the mold before correction. It is characterized in that the element is molded.

According to the present invention, the shape error between the molding surface of the mold and the optical function surface of the optical element, which occurs in the molding process, can be offset by the corrected molding surface shape of the mold, and high precision is achieved. It is possible to provide a method for manufacturing an optical element capable of manufacturing a simple glass lens in a short cycle time.

According to a second aspect of the present invention, a step of heating the glass material to a viscosity of 10 ⁸ dpa · s or less in a heating furnace, and a step of conveying the heated glass material into a mold,
A step of press-molding the glass material into an optical element by using a mold set to a temperature corresponding to the viscosity of the glass material of 10 ^{15 to} 10 ¹² dpa · s, and the press-molded optical element in the mold. In the method for manufacturing an optical element, including the step of taking out from the mold, and the step of annealing the press-molded optical element after the taking out step, the surface shape of the mold is molded using a mold before correction. Then, the optical element is molded by performing a correction processing to a shape that cancels a shape error from the shape of the optical functional surface of the optical element obtained by completing the annealing step.

According to the present invention, the shape error between the molding surface of the mold and the optically functional surface of the optical element, which occurs in the molding step and the annealing step, can be canceled by the corrected molding surface shape of the mold. It is possible to provide a method of manufacturing an optical element capable of manufacturing a highly accurate glass lens in a short cycle time.

According to a third aspect of the present invention, there is provided an optical element molding die, which comprises a molding surface shape before correction of the mold and an optical functional surface shape of a plurality of optical elements molded by the mold. It is characterized in that it has a molding surface shape that has been subjected to correction processing so as to cancel the average error.

According to the optical element molding die of the present invention,
Molding step in the case of using a mold that is not subjected to correction processing by molding the optical element with this optical element molding mold because it has a molding surface shape that has been corrected so as to cancel the shape error average. It is possible to cancel the shape error between the molding surface and the optical function surface of the optical element, which occurs in
This makes it possible to manufacture highly accurate glass lenses in a short cycle time.

According to a fourth aspect of the present invention, there is provided an optical element molding die, wherein the molding surface shape before correction of the die and the optical functional surfaces of a plurality of optical elements after the molding step and the annealing step by the mold are completed. It is characterized in that it has a molding surface shape that has been subjected to correction processing so as to cancel the shape error average with the shape.

According to the optical element molding die of the present invention,
Molding step in the case of using a mold that is not subjected to correction processing by molding the optical element with this optical element molding mold because it has a molding surface shape that has been corrected so as to cancel the shape error average. It is possible to cancel the shape error between the molding surface and the optical function surface of the optical element, which occurs in the annealing step, and thus it is possible to manufacture a highly accurate glass lens in a short cycle time.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

(Embodiment 1) FIG. 1 is a schematic configuration diagram of an optical element molding apparatus according to Embodiment 1 of the present invention, and illustrates a configuration for molding a convex lens as an example of an optical element.

First, the configuration of the optical element molding apparatus according to the first embodiment will be described with reference to FIG. This optical element molding apparatus includes a molding chamber 4 equipped with an upper mold 2 and a lower mold 3, which are vertically arranged molding molds, on a device base 40, and the molding chamber 4
A heating furnace 8 connected to the heating furnace 8; a heating arm 8 for transferring the heated glass material 5 placed on the rail 7 to the heating furnace 8 and a molding point 11 in the molding chamber 4; The glass lens 5a is carried out by the carry-out arm 13 which carries out the glass lens 5a to the outside of the molding chamber 4.

The optical element molding apparatus has a cylindrical cover body 16 which is erected vertically upward with respect to a lower plate 15 fixed on a flat table 14 arranged on an apparatus base 40, and a cover body 16. The molding chamber 4 is constituted by the upper plate 17 arranged at the upper end of the upper mold 2, and the upper mold 2 and the lower mold 3 are vertically arranged in the molding chamber 4 so as to face each other.

The upper mold 2 is fixed to an upper mold holder 18 fixed on the inner surface of the upper plate 17 via a mounting ring 19, and the lower mold 3 is a bearing 20 fitted to the table 14. It is fixed via a mounting ring 39 to a lower mold holder 38 which is supported so as to be movable up and down. Lower mold holder 3
Reference numeral 8 is connected to a drive source (not shown). Also, lower mold 3
When the lower die 3 is moved up during press molding,
An annular ring 31 for mounting and holding the transport tray 29 is attached. In FIG. 1, reference numerals 22 and 23 denote heating heaters incorporated in the upper die holder 18 and the lower die holder 38, respectively.

The carry-in arm 12 is connected to a drive device (not shown), and as shown in FIG. 2, a glass material holding portion formed in a U-shape so as to match the outer peripheral shape of the carrying tray 29. This glass material holding part 1 is provided with 12a.
The transport tray 29 for transporting the glass material 5 placed on 2a is configured to be transported from a fixed position in the heating furnace 8 to the molding point 11 and can be stopped and controlled.

The glass material 5 is shown in FIG.
The required number is placed and supported on the rail 7 shown in FIG. Then, it is sequentially fed into the heating furnace 8 from a supply chamber (not shown),
An elevating rod 30 supported by the device base 40 and the table 14 so as to be vertically movable and driven by a drive source (not shown).
The glass material 5 is transferred and supported on the glass material holding portion 12a of the carry-in arm 12 by the raising and lowering operation of.

Further, like the carry-in arm 12, the leading end of the carry-out arm 13 has a U-shaped holding portion 13a so as to match the outer peripheral shape of the carrying tray 29, and is connected to a drive source (not shown). And the unloading arm 1 at the forming point 11.
The transport tray 29 placed on the glass lens holding portion 13a at the tip of 3 is configured to be transported from the molding chamber 4 to the position of the unloading point (not shown) and can be stop-controlled.

The heating furnace 8 adjacent to the molding chamber 4 heats the glass material 5 in the carrying tray 29 supported by the rails 7 arranged in parallel in the heating chamber 8a formed in the heating furnace body 8b to a molding temperature. The heating chamber 8a is for softening
On the upper side of the heating chamber and on the lower side of the heating chamber 8a.
Are arranged.

An opening 16a is formed in the side wall of the cover body 16 adjacent to the heating furnace 8 and through which the carry-in arm 12 is inserted.
And an opening 16b for insertion of the carry-out arm 13 are provided symmetrically with respect to the molding point 11. further,
An opening 8c for inserting the carry-in arm 12 and an opening 8d adjacent to the opening 16a are provided symmetrically on the side wall of the heating furnace body 8b.

Next, using the optical element molding apparatus having the above structure,
Optical element made of lanthanum glass material, diameter 15mm
A molding method for molding the biconvex glass lens 5a will be described with reference to FIGS.

First, the glass material 5 processed into a shape similar to that of the glass lens 5a to be molded is accommodated, and the transport tray 29 placed on the rail 7 passes through the heating furnace 8 to cause the glass material 5 to be formed. Is heated to a moldable temperature corresponding to a viscosity of 10 ⁸ dpa · s or less. In Embodiment 1, the glass material 5 is heated to a temperature (650 ° C.) corresponding to 10 ⁷ dpa · s in viscosity. It should be noted that the grain size of the glass material 5 is determined by the amount of pushing of the glass material 5 by molding, and the larger the amount of pushing, the smaller the grain size of the glass material 5 needs to be made. Further, when the pressure is 10 ⁸ dpa · s or more, the pushing amount is almost lost and the formation is impossible.

Next, the carry-in arm 12 is advanced to the heating furnace 8 side, and the elevating bar 30 is raised to lift the carrying tray 29. When the glass material holding portion 12a of the carry-in arm 12 advances to the transfer point of the transfer tray 29 in the heating furnace 8, the elevating rod 30 is lowered to store the glass material 5 in the glass material holding portion 12a. The transport tray 29 is placed.

Thereafter, as shown in FIG. 3, the carry-in arm 1
2 is moved forward, and the upper mold 2 and the lower mold 3 are vertically arranged in the molding chamber 4.
The carry-in arm 12 is stopped at a position where the glass material holding portion 12a faces the molding point 11 where the center of the molding surface and the center of the transport tray 29 coincide with each other. After that, as shown in FIG. 4, the lower mold 3 is driven to move upward toward the upper mold 2, and the glass material 5
The carrying tray 29 holding the above is placed on the holding ring 31 attached to the lower mold 3. By further raising the lower mold 3, the glass material 5 is press-molded under a constant pressure between the upper mold 2 and the lower mold 3 to mold the glass lens 5a.

In the first embodiment, the upper die 2 and the lower die 3 are made of gold.
The mold temperature is 10 depending on the viscosity of the glass material 5. ^13.8dpa ・ s
Is a temperature (550 ° C.) corresponding to This mold temperature setting
The glass material 5 has a grain size of 10¹²dpa
At a temperature corresponding to s or less, fusion between glass and mold is 10
¹⁵Glass formed at temperatures above dpa · s
The occurrence of cracks on the slens 5a increases. Also,
Shape of mold surface and shape of optical function surface of glass lens 5a
When the shape error increases, the optical function surface of the glass lens 5a
Since the shape variation of the
The shape error of the optical function surface of the glass lens 5a is 1.0 mm
It is desirable to set the mold temperature within the range. Gala
During the press forming of the blank 5, the loading arm 12 is retracted.
Driven and retracted to the standby position outside the heating furnace 8 for the next transfer
The standby state for the plate 29 is reached.

After that, the press molding is continued until the glass material 5 and the mold temperature coincide with each other while keeping the mold temperature at the initial setting temperature above the transition point. In the first embodiment, the press continues for 40 seconds from the start.

Thereafter, as shown in FIG. 5, the carry-out arm 1
3 is moved forward, the glass lens holding portion 13a is moved forward to a position facing the molding point 11, and at the same time, the lower mold 3 that has finished the pressing process is driven downward, so that the glass lens formed on the glass lens holding portion 13a is moved. The transport tray 29 holding 5a is placed. In this state, the carry-out arm 13
Is driven backward in the direction of the arrow shown in FIG.
The carrying tray 29 holding the above is carried out to a carrying-out point outside the molding chamber 4 and a collecting process is carried out.

Molding surface shapes of the upper mold 2 and the lower mold 3 when molding the glass lens 5a molded by the above molding process,
6 shows the results of inspecting the shape of the optical function surface of the convex glass lens 5a molded by the upper mold 2 and the lower mold 3 by an interferometer.

The molding surface shapes of the upper mold 2 and the lower mold 3 are those obtained by grinding and polishing the designed shape of the glass lens 5a, and correspond to the molding surface shape and the respective surfaces of the glass lens 5a. Measure several shape errors with the optical functional surface, and based on the average value, the upper surface of the upper mold 2 and the lower mold 3 should have a molding surface shape that cancels the shape error. 2. Correct and process the lower mold 3.

Results of measuring the molding surface shapes of the upper mold 2 and the lower mold 3 which have been corrected by an interferometer, and the upper mold 2 and the lower mold 3 thereof.
FIG. 7 shows a result of measuring the shape of the optical functional surface of the glass lens 5a molded through the above-described molding process using
Are shown in the left and right columns.

Hereinafter, several shape errors between the molding surface shapes of the upper mold 2 and the lower mold 3 and the optical function surfaces corresponding to the respective surfaces of the glass lens 5a are measured, and the shape error is canceled based on the average value. Using the upper mold 2 and the lower mold 3 whose molding surface shapes are corrected to have such a shape, the glass lens 5a is continuously molded in the molding step described above.

Corrected upper mold 2 and lower mold 3 in this case
The left side of FIG. 7 shows the result of measuring the molding surface shape of No. 2 by the interferometer, and the result of measuring the optical functional surface of the glass lens 5a molded using the corrected upper mold 2 and lower mold 3 by the interferometer is 7 As shown in the right column.

As is clear from FIGS. 6 and 7, the glass lens 5a molded by using the upper mold 2 and the lower mold 3 before the correction processing.
The shape of the optical function surface of is a surface shape in which interference fringes are irregularly distributed and has distortion, but the optical function surface of the glass lens 5a molded using the corrected upper mold 2 and lower mold 3 is The shape has a highly precise surface shape in which interference fringes are evenly distributed as shown in the right column of FIG. 7.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS.

The second embodiment shows a method of molding a biconcave glass lens made of a lanthanum glass material and having a diameter of 20 mm. The structure, function and molding conditions of the glass molding apparatus are the same as those in the first embodiment. Therefore, the detailed description thereof will be omitted.

In the second embodiment, a concave lens molded through the same molding process as in the first embodiment is placed in an electric furnace (not shown) and an annealing process is performed to remove the residue generated in the molding process. It removes stress. The annealing treatment condition in this case is heating to an annealing temperature (a temperature 20 ° C. lower than the glass transition point) in 5 hours, and the temperature is set to 5
Hold for time. After that, cooling is performed at a speed of 10 ° C./1 hour, and a predetermined temperature (here, the annealing temperature is set to 1
(Lower temperature of 00 ° C). After this, let it cool naturally. Although the residual stress disappears in the concave lens which has been subjected to such an annealing treatment, the shape change occurs after the completion of the molding process.

The shapes of the molding surfaces of the upper mold 2 and the lower mold 3 at the time of molding are those which are ground and polished into the design shape of the concave lens. In addition, the shape of the optical functional surface of the concave lens after molding with the upper mold 2 and the lower mold 3, and the shape of the optical functional surface of the concave lens after performing the annealing treatment are examined by an interferometer. Shown in the middle and right columns respectively.

Next, several shape errors of the surfaces corresponding to the molding surface shapes of the upper mold 2 and the lower mold 3 and the shape of the optical function surface of the concave lens after the annealing treatment were measured, and the average value thereof was calculated. The molding surfaces of the upper mold 2 and the lower mold 3 are subjected to correction processing so as to cancel the shape. The results of measuring the shapes of the corrected molding surfaces of the upper mold 2 and the lower mold 3 with an interferometer are shown in the left column of FIG.

Further, the upper mold 2, whose molding surface shape is corrected,
Molded using the lower mold 3 through the molding process described above, and
The result of measuring the shape of the optical function surface of the annealed concave lens with an interferometer is shown in the right column of FIG.

As is clear from the right column of FIG. 8 and the right column of FIG. 9,
The shape of the optically functional surface of the concave lens after molding using the upper mold 2 and the lower mold 3 before correction processing and after the annealing treatment is such that interference fringes are irregularly distributed and have distortion. ,
The shape of the optical function surface of the concave lens after the correction processing is performed using the upper mold 2 and the lower mold 3, and the annealing process is performed is highly accurate such that the interference fringes are evenly distributed. It becomes the shape.

Hereinafter, several shape errors between the molding surface shapes of the upper mold 2 and the lower mold 3 and the respective optical function surfaces of the concave lens after the annealing treatment are measured, and the molding surfaces cancel the average value. Using the upper mold 2 and the lower mold 3 whose shape has been corrected, the concave lens is continuously molded in the same molding process as in the first embodiment. Then, the annealing process is performed to manufacture the concave lens.

According to the manufacturing method of the second embodiment, even in the case of a lens such as a concave lens which is likely to be deformed by the annealing process, by using the upper mold 2 and the lower mold 3 corrected as described above, Short molding cycle time and
It is possible to form a highly accurate optical functional surface shape.
In addition to the concave lens, the molding method of the second embodiment described above can also be applied to molding of a lens such as a meniscus lens that is easily deformed by an annealing process.

[0047]

According to the present invention, it occurs in the molding step,
Alternatively, the shape error between the molding surface of the mold and the optical function surface of the optical element, which occurs in the molding step and the annealing step, can be canceled by the molding surface shape of the corrected mold, and a highly accurate glass lens can be obtained. It is possible to provide a method for manufacturing an optical element that can be manufactured in a short cycle time.

Further, according to the present invention, the shape error between the molding surface and the optical functional surface of the optical element, which is generated in the molding step or in the molding step and the annealing step when the mold which is not subjected to the correction processing is used. It is possible to provide a mold for molding an optical element capable of manufacturing a highly accurate offset glass lens in a short cycle time.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an optical element molding apparatus according to a first embodiment of the present invention.

FIG. 2 is a plan view of a carry-in arm according to the first embodiment.

FIG. 3 is a schematic cross-sectional view showing a state where the glass material of the optical element molding apparatus according to the first embodiment is carried into a molding chamber.

FIG. 4 is a schematic cross-sectional view showing a glass material press molding process of the optical element molding apparatus according to the first embodiment.

FIG. 5 is a schematic cross-sectional view showing a step of unloading a glass lens of the optical element molding apparatus according to the first embodiment.

FIG. 6 is an explanatory diagram showing the results of examining the molding surfaces of the upper mold and the lower mold and the optically functional surface of the glass lens according to the first embodiment with an interferometer.

7A and 7B show the results of examining the shapes of the corrected molding surfaces of the upper mold and the lower mold in Embodiment 2 and the shapes of the optical functional surfaces of the glass lenses after molding with the upper mold and the lower mold by an interferometer. It is an explanatory view shown.

FIG. 8 is a view showing the molding surface shapes of the upper mold and the lower mold during molding in Embodiment 2, the shapes of the optical functional surfaces of the concave lens after molding with these upper mold and lower mold, and the concave lens after the annealing treatment. It is explanatory drawing which shows the result of having investigated the shape of the optical function surface by the interferometer.

FIG. 9 is an explanatory diagram showing the results of examining the shapes of the corrected molding surfaces of the upper mold and the lower mold in Embodiment 2 and the shapes of the optical functional surfaces of the concave lens after the annealing treatment by an interferometer.

[Explanation of symbols]

2 Upper mold 3 Lower mold 4 molding room 5 glass material 5a glass lens 6 glass lens 7 rails 8 heating furnace 8a heating chamber 8b heating furnace body 8c opening 8d opening 11 molding points 12 Carry-in arm 12a glass material holder 13 Unloading arm 13a glass lens holder 13a holding part 14 tables 15 Lower plate 16 cover body 16a opening 16b opening 17 Upper plate 18 Upper mold holder 19 Mounting ring 20 bearings 29 Transport tray 30 lifting rod 31 ring 31 retaining ring 32 heater 33 Heater 38 Lower mold holder 39 Mounting ring 40 Device base

Claims (4)

[Claims] 1. The glass material is heated to 10 ⁸ dpa.
A step of heating to a temperature corresponding to a viscosity of s or less, a step of conveying the heated glass material into a mold, and a temperature corresponding to a viscosity of 10 ^{15 to} 10 ¹² dpa · s of the glass material were set. In a method of manufacturing an optical element, including: a step of molding a glass material with a mold to form an optical element; and a step of taking out the molded optical element from the mold, the surface shape of the mold is corrected. An optical element characterized by performing correction processing to a shape that cancels a shape error from an optical functional surface shape of an optical element obtained by completing each of the steps using the former die, and molding the optical element. Device manufacturing method. 2. The glass material is heated to 10 ⁸ dpa.
a step of heating to a viscosity of s or less, a step of transporting the heated glass material into a mold, and a mold set to a temperature corresponding to the viscosity of the glass material of 10 ^{15 to} 10 ¹² dpa · s. A step of press-molding a glass material to form an optical element; a step of taking out the press-molded optical element from the mold; and a step of annealing the press-formed optical element after the taking-out step. In the method of manufacturing an optical element, the surface shape of the mold is molded by using a mold before correction, and a shape error with the optical functional surface shape of the optical element obtained by completing the annealing step is offset. A method for manufacturing an optical element, which comprises performing correction processing to form such a shape to form the optical element. 3. A molding surface corrected so as to cancel the average shape error between the molding surface shape of the mold before correction and the optical functional surface shapes of a plurality of optical elements molded by this mold. A mold for molding an optical element, which has a shape. 4. A correction process is performed so as to cancel the average shape error between the molding surface shape before correction of the mold and the optical functional surface shapes of a plurality of optical elements after the molding step and the annealing step by this mold. A mold for molding an optical element, which has a formed molding surface shape.