JP3695733B2 - Method and apparatus for manufacturing optical element material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method and a manufacturing apparatus for obtaining an optical element material used for molding a glass lens used for a pickup optical system and a camera lens of an optical disk device.
[0002]
[Prior art]
Conventionally, as a method of manufacturing an optical element material, a method of manufacturing a glass sphere by thermal processing using surface tension has been proposed (for example, “Japan Glass Products Industry Association:“ Glass Manufacturing Field Technology ”Vol. 4, 237). Section). As a kind of this manufacturing method, the technique proposed in Japanese Patent Application Laid-Open No. 5-43258 is called a so-called fluidized firing method (processing by surface tension). As shown in FIG. After locally heating by the heating device 55, only the glass of the heated portion is melted to form a spheroidized glass droplet 54 at the tip of the glass rod 53, and then the glass droplet 54 is spontaneously dropped and collected. The spherical glass 57 is produced by collecting with the tool 56. The weight m of the spherical glass 57 is obtained by using the above-described known surface tension processing method, and is approximately mg = 2πrγ (m: weight of glass droplet, g: weight acceleration, 2πr: glass rod diameter, γ: glass (Surface tension). This prior art is to stabilize the physical properties of glass (γ: surface tension of glass), that is, to provide a stable heating means for the glass rod 53 to stabilize the weight of the resulting spherical glass 57. . The desired weight of the spherical glass 57 can adjust the surface tension by adjusting the wire diameter of the glass rod 53.
[0003]
[Problems to be solved by the invention]
As a processing method of the glass rod 53 used for the conventional means, it is common to use a method manufactured by thermal processing or centering. However, there is a problem in that each processing variation occurs. That is, there is a variation in the diameter of the glass rod 53, and even if the control is performed at the precise melting temperature of the prior art described above, a variation in the weight of the spherical glass 57 occurs. In addition, in high-precision glass lens molding, the required weight accuracy of the spherical glass 57 used when forming the outer shape of the lens at the same time as molding is the designed lens volume weight (when this is 100%). 98% to 99% is desirable. In order to obtain such weight accuracy, for example, when the weight of the spherical glass 57 is 100 mg or less, the roundness of the glass rod 53 needs to be several μm or less.
[0004]
Therefore, it is difficult to realize the glass rod 53 manufactured with normal processing accuracy. Therefore, when producing a stable and highly accurate spherical glass 57 with high weight accuracy, the spherical glass 57 produced by the demand for processing accuracy of the glass rod 53 becomes expensive, and the molded glass lens is also expensive. It will be a thing.
[0005]
On the other hand, when a glass rod 53 using, for example, a material containing a large amount of boric acid or an alkali component as a glass material is manufactured by means using glass melting at a high temperature, the volatile component of the glass material adheres to the surface layer portion of the glass rod 53 during melting. However, when glass lens molding is performed using the spherical glass 57 obtained by the glass rod 53, there is a problem that the surface of the molded lens becomes cloudy or glass adheres to the molding die.
[0006]
Further, when the glass rod 43 is manufactured by centering, there is a fine surface roughness on the surface layer portion, and fine scratches remain even if glass lens molding is performed with the spherical glass 47 obtained with the glass rod 43, For this reason, the lens performance has been affected.
[0007]
In order to solve the above-described conventional problems, the present invention provides a manufacturing method and an apparatus for manufacturing the optical element material that enable inexpensive and stable high weight accuracy and surface properties that do not affect optical performance. It was made for the purpose.
[0008]
[Means for Solving the Problems]
An optical element material manufacturing method according to the present invention is a method of manufacturing an optical element material by dropping and solidifying glass droplets formed by melting the glass rod material while passing the glass rod material through a heating furnace. The diameter of the glass rod is measured, and based on the obtained measurement value, the passing speed of the glass rod in the heating furnace is controlled to control the weight of the glass droplet dropped and solidified to be constant. It is characterized by that. By using this method, it is possible to correct the weight variation generated by the processing variation of the glass rod. Therefore, even if the diameter accuracy of the glass rod is not so high, a highly accurate weight-controlled optical element material can be obtained.
[0009]
In the method for producing an optical element material of the present invention, it is preferable to control the temperature of the heating furnace. If the means of the present invention is used, the same effect as described above can be obtained.
Furthermore, in the method for producing an optical element material of the present invention, the glass rod used above is to remove the volatile components adhering by washing the surface of the glass rod in advance. By using the present invention, it is possible to remove volatile components in the surface layer of a glass rod processed by glass melting at a high temperature, and it is possible to obtain an optical element material that does not affect glass lens molding and glass lens performance. .
[0010]
In addition, the optical element material manufacturing apparatus according to the present invention includes a means for cleaning the surface layer of the glass bar to remove the attached volatile components, a driving means for moving the glass bar up and down, and a wire diameter of the glass bar. Measuring means for measuring the pressure, control means for controlling the driving means based on the measured value, heating means for melting the glass rod material to drop glass droplets, collecting means for collecting the glass droplets, collected glass liquid It comprises a drying means for taking out the droplets and drying with hot air. By using the present invention, it is possible to unmanned a series of steps from a glass rod cleaning step to drying of glass droplets produced, and an optical element material can be obtained at low cost.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be specifically described with reference to embodiments.
<First Embodiment>
FIG. 1 is a cross-sectional view showing a method of manufacturing an optical element material in the first embodiment of the present invention. As shown in FIG. 1, in a method for producing an optical element material by solidifying glass droplets 8 formed by melting a glass wire 6, the driving unit 2 holds a glass wire 6 with a ball screw 3. 4, the ball screw 3 is rotated by the driving unit 2, and the holding jig 4 is vertically raised or lowered along the guide 5. A tubular furnace 9 is provided as a heating furnace below the central axis of the glass rod 6, and a length measuring device 7 for measuring the wire diameter of the glass rod 6 is provided in the X and Y directions above the heating furnace 9. Has been placed. The controller 1 can control the drive unit 2 at a descending speed that is a desired weight with respect to the wire diameter of the glass rod 6 measured by the length measuring device 7.
[0012]
FIG. 2 shows the descending speed and weight change of the glass droplet 8 using the glass rod 6 having the same wire diameter. The weight m of the glass droplet 8 generally satisfies the relationship mg = 2πrγ (g: gravitational acceleration, r: wire diameter of the glass rod 6, and γ: surface tension). The surface tension of γ indicates the case where the physical properties of the glass material to be used and the heat energy applied, that is, the melting temperature of the heating furnace 9 is constant. For this reason, as shown in FIG. 2, the weight of the glass droplet 8 is changed by changing the descending speed of the glass rod 6 even when the wire diameter is the same, because the heat applied to the glass rod 6 in the heating furnace 9 is changed. By changing the energy according to the descending speed, that is, by controlling γ, the weight variation due to the wire diameter variation of the glass rod 6 can be corrected.
[0013]
More specifically, the wire diameter when the weight fluctuation with respect to the descending speed in FIG. The glass rod 6 had a length of 250 mm, a wire diameter (diameter: φ) of 1.095 to φ1.105, and the heating furnace 9 was kept constant at 1200 ° C. The measuring condition of the glass rod 6 by the length measuring device 7 is to measure XY at intervals of 5 mm, and send it to the controller 1 each time, and obtain the average wire diameter simultaneously with the fourth measurement (20 mm). The drive unit 2 was controlled so as to be set to an optimum descending speed with respect to the wire diameter. As a result, with respect to the control of the descending speed of 90 to 200 mm / min, the glass droplet 8 weight was within 59.2 mg ± 0.5%, and the wire diameter variation amount φ1.1 ± 40 μm of the glass rod 6 at this time. .
[0014]
As described above, according to the optical element material manufacturing method of the present embodiment, the wire diameter variation required for the weight accuracy ± 0.5% with respect to the wire diameter φ1.1 used this time is required to be ± 5 μm or less. However, it is possible to use even a wire diameter variation as many as 8 times.
[0015]
In addition, although the measurement of the glass rod 6 is performed immediately before melting in the heating furnace 9, it is not necessarily limited, and a configuration using a pre-measured one may be used. In addition, the number of times of measurement and the number of times of control are not necessarily limited, and the more the number of measurements and the number of times of control can be performed, the finer speed control can be performed.
[0016]
Further, although a glass rod length of 250 mm is used, the length is not limited to the length and the wire diameter, and a continuous material such as a roll wound around a roll may be used.
FIG. 3 shows the relationship of the weight change with respect to the temperature change of the heating furnace 9 in the first embodiment. Specifically, the glass rod 6 has a descending speed of 140 mm / min constant, a glass rod 6 φ1.1 ± 2 μm, and the temperature of the heating furnace 6 is changed from 1100 ° C. to 1300 ° C. Although less than the change, it can be seen from FIG. 3 that the weight of the glass droplet 8 can be controlled by changing the melting temperature of the heating furnace 6.
[0017]
Note that the descending speed and dissolution temperature control means used in the first embodiment are not necessarily controlled independently, and means for simultaneous control may be used.
Moreover, the volatile component in the surface layer of the glass rod 6 produced by glass melting | dissolving at high temperature is actively used for the glass rod 6 used for 1st Embodiment using the washing | cleaning means using alkaline detergent. By removing, a glass wire having a high melting point rich layer formed on the surface was used. Specifically, in the glass lens molding confirmation using the glass droplet 8 produced by the glass rod 6 treated by this cleaning means as the optical element material, there is no performance and no deposit on the molding die, It was also confirmed that workability was not affected.
[0018]
The means applied to the high melting point rich layer is not necessarily performed by washing with a detergent, and means capable of obtaining an equivalent effect may be used.
<Second Embodiment>
FIG. 4 is a sectional view showing an optical element material manufacturing apparatus in the second embodiment of the present invention. As shown in FIG. 4, it is a manufacturing apparatus for continuously performing a series of steps provided with the means used in the first embodiment. Specifically, the surface layer of the glass rod 6 is washed to a high level. A means for forming the melting point rich layer, a driving means for moving the glass rod 6 up and down, a measuring means for measuring the wire diameter of the glass rod 6, and the driving means based on the measured value obtained by the measuring means Control means for heating, heating means for melting the glass rod 6 to make glass droplets 8, collecting means for collecting the glass droplets, and drying means for taking out the collected glass droplets 8 and drying them with hot air. The optical element material manufacturing apparatus. More specifically, the glass rod 6 that has been cleaned in a batch manner is first set on the holding jig 4 by a robot (not shown). At the same time when the glass rod 6 is set, the ball screw 3 rotates at a speed set in advance by the controller 1, and the holding jig 4 starts to descend along the guide 5. When the position of the length measuring device 7 at the upper part is reached, the wire diameter is measured. The measured value is transmitted to the controller 1 to obtain the average wire diameter. The drive unit 2 is controlled to an optimum speed at which a desired weight is set in advance with respect to the obtained average wire diameter. The speed-controlled glass rod 6 is guided to the heating furnace 9 having a constant melting temperature to be melted into glass droplets 8, and eventually the glass droplets 8 spontaneously fall and collect the cooling medium 11. Container 10 is inserted. A rolling jig 12 is disposed in the collector 10, and the collected glass droplet 8 rolls downward along the rolling jig 12 and is collected by the collecting jig 13, and then the collecting jig 13. Then, the glass droplet 8 is taken out from the collector 10 (not shown) and conveyed to the entrance of the dryer 14. The glass droplets 8 dried from the outlet of the dryer 14 are arranged on a pallet 15 by a robot (not shown) to form an optical element material 16.
[0019]
As described above, according to the optical element material manufacturing apparatus of the present embodiment, it is possible to unmanned a series of processes from the cleaning process of the glass rod 6 to the drying of the glass droplets 8, and an inexpensive optical element material. 16 can be provided.
[0020]
Although the optical element material 16 is arranged on the final pallet 15, it is not necessarily limited, and it is set in a mold used for glass lens molding, which is the next step. It may be configured to achieve unmanned operation. Moreover, it is not necessarily limited to one glass melting means, and a plurality of glass melting means may be provided.
[0021]
【The invention's effect】
As described above, the method for producing an optical element material according to the present invention provides a high-weight-accuracy optical element material without requiring much wire diameter accuracy by controlling the descending speed suitable for the wire diameter of the glass rod. be able to. The same effect can be obtained by controlling the melting temperature of the heating furnace. In addition, by making the surface layer of the glass rod material a high melting point rich layer, an optical element material having no surface defects at the time of molding a glass lens can be produced. The optical element material manufacturing apparatus can easily unmanned a series of processes. For this reason, it is possible to produce a more inexpensive and highly accurate optical element material, and as a result, it is possible to provide an inexpensive glass lens to the market.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an essential part for explaining a first embodiment of the present invention.
FIG. 2 is a diagram showing the relationship between the descent speed of the glass rod and the weight of the glass droplet in the first embodiment of the present invention.
FIG. 3 is a diagram showing the relationship between the melting temperature of the heating furnace and the weight of glass droplets in the first embodiment of the present invention.
FIG. 4 is a cross-sectional view of a main part for explaining a second embodiment of the present invention.
FIG. 5 is a cross-sectional view of an essential part showing the production of a conventional optical element material.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Controller 2 Drive part 3 Ball screw 4 Holding jig 5 Guide 6 Glass bar 7 Length measuring device (XY axis)
8 Glass droplet 9 Heating furnace (tubular furnace)
DESCRIPTION OF SYMBOLS 10 Collector 11 Cooling medium 12 Rolling jig 13 Collection jig 14 Dryer 15 Pallet 16 Optical element material

Claims (6)

In a method of manufacturing an optical element material by dropping and solidifying glass droplets formed by melting the glass rod while passing the glass rod through a heating furnace,
The diameter of the glass rod is measured, and based on the obtained measurement value, the passing speed of the glass rod in the heating furnace is controlled to control the weight of the glass droplet dropped and solidified to be constant. A method for producing an optical element material characterized by the above.   The method of manufacturing an optical element material according to claim 1, wherein either one of temperature control of the heating furnace and the passing speed is controlled. The method for producing an optical element material according to claim 1 or 2, wherein volatile components adhering to the surface of the glass bar are washed away . Means for cleaning and removing volatile components adhering to the surface of the glass bar;
Driving means for moving the glass rod up and down;
Measuring means for measuring the diameter of the glass rod;
Control means for operating the drive means based on the measurement value obtained by the measurement means;
Heating means for melting the glass rod and dropping glass droplets;
A collecting means for collecting the glass droplet;
An apparatus for producing an optical element material, comprising drying means for taking out the collected glass droplets and drying with hot air.   The optical element material manufacturing apparatus according to claim 4, further comprising a plurality of driving units, a plurality of measuring units, a plurality of heating units, and a plurality of control units.   The optical element material manufacturing apparatus according to claim 4, wherein a pre-measured glass rod is used.

Images