JPH0360975A - Method for forming glass optical element - Google Patents

Abstract

PURPOSE:To form a glass material approximately in a final shape by a method wherein an anode is applied on a conductive grinding tool the machining surface of which is formed in the same shape as that of the desired curvature of a work, a cathode is applied on electrodes keeping a specified distance between the machining surface of the conductive grinding tool and the electrode, and a weak electric coolant is fed between the conductive grinding tool and the cathode. CONSTITUTION:An anode is applied on a conductive grinding tool 4 having a machining surface 4a formed in the same shape as that of the desired curvature of a work 2. A cathode is applied on an electrode 7 keeping a specified distance between the machining surface 4a of the grinding tool 4 and the electrode. The surface of a glass material 2 is formed in a shape similar to a final shape as a weak electric coolant fed through a pipe 8 is located between the conductive grinding tool 4 and the cathode 7 and smooth machining is applied. After the glass material is heated and cured, the glass material is press-molded in a given shape by using a pair of molds, and the glass material is cooled down to a given temperature to produce a desired optical element, e.g. lens.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of molding a glass optical element, in which an optical element such as a lens is manufactured by press molding.

[Conventional technology]

Conventionally, the following inventions have been disclosed as methods for obtaining glass materials used in press molding of glass optical elements.

For example, in the invention described in Japanese Patent Publication No. 63-37043, the surface of a glass material is smoothed by a general polishing process using a polishing plate.
In the invention described in Japanese Patent Publication No. 146723, the surface of a lens material that has been ground into a spherical shape is treated with an acid to give a predetermined mirror surface.
In the invention described in Publication No. 1, a non-polished glass gob is obtained by dropping molten glass from the tip of a nozzle and allowing it to fall until the surface temperature of the glass droplet becomes lower than the softening temperature.

[Problem to be solved by the invention]

However, the above-mentioned conventional technology has the following drawbacks.

In the invention described in Japanese Patent Publication No. 63-37043,
Smooth processing of glass materials requires complicated steps such as pasting, polishing, and peeling, and depending on the shape of the glass material, one piece may be processed, resulting in high processing costs.

In the invention described in JP-A-61-146723, the material is selectively eroded from the crank on the surface of the material before acid treatment,
It is easy to cause waviness on the surface, and there are also safety problems in handling the acid, and cost problems related to the disposal of the acid treatment solution.

In the invention described in JP-A-61-146721, the glass gob has a spherical shape, and it is necessary to cause a large flow during press molding to form the final product shape. For this reason, the press molding time becomes longer, the life of the mold becomes shorter, and the molding cost increases.

Therefore, the present invention was developed in view of the drawbacks of the prior art, and aims to provide a method for molding a glass optical element that eliminates the drawbacks of the prior art and has low processing cost.

[Means and effects for solving the problem] The present invention approximates the final shape of the glass surface by a curve generator type spherical surface generating grinding method, which will be described later, and heats and softens the smoothed glass material to form a pair. This is a molding method in which the material is placed between molds, press-molded into a predetermined shape, and cooled to a predetermined temperature.

FIG. 1a is a conceptual diagram of a device used for curve generator type spherical surface generation grinding, and FIG. 1A is a diagram showing the arrangement of a tool holding shaft and electrodes in the same device.

A spherical member 2 is coaxially secured to the tip of a rotatable collet 1. The processed surface 2a of the spherical member 2 has a desired curvature RA.

The rotatable tool holding shaft 3 is disposed so as to face the axis of the rotary shaft at a swivel angle α with respect to the axis of the spherical member 2. At the tip of the tool holding shaft 3, a conductive grinding tool 4 made of a sintered alloy made of a heat-treated mixture of abrasive grains such as diamond powder and metal powder such as Cu-3n-Fe is attached. The processed surface 4a of the conductive grinding tool 4 is formed to have a curvature RA so as to correspond to the processed surface 2a of the spherical member 2. In addition, a blank 5 is provided so as to be in contact with the tool holding shaft 3, and (through this blank 5) (
+) A conductive grinding tool in which the electrode 7 is formed to have a curvature RA-1 that approximates the curvature RA of the machined surface 2a of the 0-spherical member 2 so that the electrode can be applied to the conductive grinding tool 4. It is provided with a slight gap 1 between it and the processed surface 4a of No. 4, and the (-) pole from the DC type a6 is applied thereto. Furthermore, a vibrator 8 is provided in the gap 1 between the conductive grinding tool 4 and the electrode 7 to spray a weakly conductive coolant.

The grinding process performed by the device used in the generation grinding method described above is performed by applying weakly electric coolant to the conductive grinding tool 4 and the electrode 7 while spouting it from the vibrator 8, and 4a is brought into contact with the spherical member 2, and the cutting trajectory 9
Grinding is performed by moving the conductive grinding tool 4 according to the direction of the arrow.

At this time, the processed surface 4a of the conductive grinding tool 4 is dressed by electrolysis. This eliminates uneven wear of the conductive grinding tool 4 and avoids the upper part (belly button). Furthermore, since the interval of the gap l is always kept constant along the curvature of the machining surface 4a of the conductive grinding tool 4, the machining surface 4a of the conductive grinding tool 4 can be dressed evenly and uniformly, resulting in stable machining. can.

Conventionally, grinding tools using fine diamond abrasive grains were clogged and the machining capacity was significantly reduced, but with the above method, dressing can be done evenly and uniformly, allowing machining while maintaining machining capacity. The surface roughness of objects can be dramatically improved.

Further, by using the curve generator method, it is possible to uniformly form the radius of curvature, thickness, etc. of the glass material to be created to predetermined values that approximate the final shape. This glass material can be used as a preform for glass press lenses, which is obtained by heating and press-molding and precisely transferring the mold shape, so this glass material is softened by heating and molded into the desired shape with a pair of molds. By press molding and cooling to a predetermined temperature, it is possible to obtain a glass optical element having an arbitrary surface shape with the mold shape reversed.

〔Example〕

Hereinafter, embodiments of the method for molding a glass optical element of the present invention will be described in detail with reference to the drawings.

(First Example) FIGS. 2a, b, c, d, and e are side views showing a first example of the method for molding a glass optical element of the present invention.

A spherical member 2 such as a pressing material is attached to the tip of the freely rotatable collet 1.
The machined surface 2a of the 0-spherical member 2, which is coaxially locked, has a desired curvature of RA. The rotatable tool holding shaft 3 is disposed so as to face the axis of the rotary shaft at a swivel angle α with respect to the axis of the spherical member 2. The tip of the tool holding shaft 3 is equipped with abrasive grains such as diamond powder (desirably #6000 to #8000 abrasive grains) and Cu.
.

A conductive grinding tool 4, which is made of a metal such as Su or Fe or a conductive resin as a binding material and is entirely conductive in the shape of a cup, is coaxially attached. The processed surface 4a of the conductive grinding tool 4 is formed to have a curvature RA so as to correspond to the processed surface 2a of the spherical member 2.

Further, a brush 5 is provided so as to be in contact with the tool holding shaft 3, and (+
) can be applied to the conductive grinding tool 4. DC type 1! X6 is a direct power supply for electrolytic processing and generates pulse voltage. The electrode 7, which is formed to have a curvature RA+f that is approximately the same as the curvature RA of the processed surface 2a of the spherical member 2, has a slight and uniform gap l(
The gap 2 is provided with a gap (preferably 0.1 to 0.2 mm) in between, and the (-) pole from the DC power source 6 is applied thereto. Furthermore, a vibrator 8 is provided in the gap 1 between the conductive grinding tool 4 and the electrode 7 to spray a weakly conductive coolant.

The grinding process using the apparatus used in the generation grinding method described above is performed by applying a pulse voltage from the DC power supply 6 to the conductive grinding tool 4 and the electrode 7 while spouting a weakly conductive coolant from the pipe 8. The processing surface 4a of the conductive grinding tool 4 is brought into contact with the processing surface 2a of the spherical member 2, and the conductive grinding tool 4 is moved along the cutting locus 9 (in the direction of the arrow) to perform the grinding process. At this time, the processed surface 4a of the conductive grinding tool 4 is dressed by electrolysis.

When grinding is performed in this manner, the conductive grinding tool 4 is The displacement of the machined surface 4a is small, and the upper part (belly button) at the center of the spherical member 2 can be avoided. In addition, since the machined surface 4a of the conductive grinding tool 4 can maintain a constant shape, the gap i between the machined surface 4a and the electrode 7 can always maintain a uniform interval, so that the machined surface 4a of the conductive grinding tool 4 is always It allows constant and even dressing and stable spherical surface generating grinding.

The surface roughness of the machined surface 2a of the spherical member 2 thus created is a mirror surface with R□ of 0.03 μm. next,
The back surface of the spherical member 2 is similarly subjected to spherical surface generation grinding, and processed into a mirror-like state with a predetermined radius of curvature RB and a surface roughness of R1,0.03μ. By setting the depth of cut, the second
As shown in Figure (b), a preform 1O formed with a predetermined medium thickness t is obtained.

FIGS. 2c and 2d show the process of obtaining an aspherical optical element by press working from the preform 10 obtained by the above-mentioned spherical generating grinding process.

11 is a heating furnace, and this heating furnace 11 has a heater 12 installed therein. The heating mold 11 is coaxially disposed opposite to the upper mold 1.
3 and a lower mold 14 that is vertically movable. 15 is a transfer arm, and this transfer arm 15 places the preform 10 in a mounting hole 15a, and is configured to be movable between the heating furnace 11 and the molding molds 13 and 14 by a drive device (not shown). There is.

In the press working process having the above configuration, first, the preform 10 is placed in the placement hole 15a of the transfer arm 15.

The preform 10 is locked to a step 15b formed inside the mounting hole 15a and is accommodated in the mounting hole 15a. Next, the preform lO is heated and softened in the heating furnace 11 to a predetermined temperature near its softening point, and then transported by the transport arm 15 between the forming molds 13 and 14. Upper mold of the forming mold 13.
The molding heads 13a and 14a of the lower mold 14 are precisely mirror-finished (for example, into an aspherical shape), and are constantly heated by a heater (not shown) to the transition temperature of glass or a temperature close to it. Then, the lower mold 1 of the molding die
4 is raised by a drive mechanism (not shown), and the preform 10 is pushed up and pressed into contact with the upper mold 13 of the molding die to be press-molded.

After a predetermined holding time has elapsed and the preform IO is cooled and solidified between the molding molds 13 and 14, the lower mold 14 is lowered to obtain the glass optical element 16 shown in FIG. 2(e). .

According to this embodiment, the process of approximating the final shape of the surface of the glass material and the process of smoothing it can be greatly simplified.

Although the present embodiment has been described with respect to a convex meniscus shape, other shapes can be implemented in the same manner.

(Second Example) FIG. 3 is a side view showing a second example of the method for molding a glass optical element of the present invention.

The method for forming a glass optical element shown in this embodiment differs from the configuration of the heating furnace 11 in the first embodiment in terms of heating conditions, and the other configurations are the same. They are numbered and their explanations are omitted.

20 is a heating furnace, this heating furnace 20 has a heater 21 installed therein, and an interior 20a of the heating furnace 20 is a preform 1.
It is configured to be close to the R surfaces 10a and 10b of 0.

From the above configuration, the temperature of the heater 21 of the heating furnace 20 is as follows:
The temperature is set sufficiently higher than the predetermined heating temperature (for example, 200° C. higher than the predetermined heating temperature). Therefore, heating of the preform 10 is performed in a shorter time than in the first embodiment, and only the surface of the preform 10 is heated by 103"".
This results in heating and softening to a viscosity of 6 bores.

As a result, even if the surface accuracy of the ground surface subjected to the spherical surface creation process in this example is rougher than the surface accuracy in the first example, the surface roughness can be improved in the heating process to a level that does not pose a problem as an optical element. becomes possible.

According to this embodiment, it is possible to cope with the case where the amount of machining removal is large in the spherical surface generating grinding process and the surface roughness is not sufficiently reduced.

(Third Example) FIG. 4 is a side view showing a third example of the method for molding a glass optical element of the present invention.

The method for molding a glass optical element shown in this example differs from the first example in the press working process, and a description of the process for approximating the surface of the glass material to the final shape will be omitted.

Reference numeral 30 denotes a sleeve, and this sleeve 30 is formed into a cylindrical shape from a material (such as a superalloy) having a coefficient of linear expansion smaller than that of glass.

A pair of molding molds consisting of an upper mold 31 and a lower mold 32 coaxially arranged opposite to each other are slidably fitted into the sleeve 30. Molding head 3 of upper mold 31 and lower mold 32
1a and 32a are precisely mirror-finished (for example, into an aspherical shape).

Further, a coil-shaped heater 33 is provided on the outer peripheral surface of the sleeve 30.
is attached, and the temperature can be controlled to a predetermined temperature.

A preform 10 processed by the same process as in the first embodiment to approximate the final shape of the glass material surface is placed in the acid mold 31.
32, and the molding molds 31 and 32 are inserted into the sleeve 30.

Next, the sleeve 30 is heated by the heater 33, and the preform 10 and the molding molds 31, 32 are uniformly heated to a predetermined temperature near the yielding point of the glass.

Then, the upper mold 31 is pressed by the weight of the upper mold 31 of the molding die or by a pressure mechanism (not shown), and after a predetermined holding time has elapsed, the heater 33 is controlled to gradually cool the mold and the applied pressure is removed. After cooling and solidifying, the glass optical element 34 is taken out.

According to this embodiment, a glass optical element having an arbitrary shape can be obtained by inverting the molding die as in the first embodiment.

Further, in this embodiment as well, similar implementation is possible with shapes other than the convex meniscus shape.

〔Effect of the invention〕

As described above, according to the method for molding a glass optical element of the present invention, it is possible to approximate the final shape of the glass material surface and to significantly simplify the smooth processing process, resulting in a glass with low processing cost. The bottom shape of the optical element is realized.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of the method for molding the glass optical element of the present invention;
Figures 2 a, b, c, d, and e are side views showing the first embodiment, Figure 3 is a side view showing the second embodiment, and Figure 4 is a side view showing the third embodiment. In the figure: 1... Collet 2... Spherical member 3... Tool holding shaft 4... Conductive grinding tool 6... DC power supply 7... Electrode 8... Vibrator... Heating furnace 2 .13...Heater 3.31...Upper mold 4.32...Lower mold

Claims (2)

[Claims] (1) Applying an anode to a conductive grinding tool whose machining surface is formed to have the same shape as the desired curvature of the workpiece, and applying a cathode to an electrode that maintains a certain distance from the machining surface of the conductive grinding tool; A weakly conductive coolant is passed between the conductive grinding tool and the cathode so that the surface approximates the final shape, and the smoothed glass material is heated and softened, and then placed between a pair of molds and shaped into a predetermined shape by this mold. 1. A method for forming a glass optical element, which comprises press-molding it into a shape and cooling it to a predetermined temperature. (2) Applying an anode to a conductive grinding tool whose machined surface has the same shape as the desired curvature of the workpiece, and applying a cathode to an electrode that maintains a certain distance from the machined surface of the conductive grinding tool to conduct conductivity. A slightly electrically conductive coolant is passed between the magnetic grinding tool and the cathode to approximate the final shape, and the smoothed glass material is placed between a pair of molds, then heated and softened at the same time as the molds, and then press-formed. A method for molding a glass optical element, the method comprising: cooling the glass optical element to a predetermined temperature.