JPH05349B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a lens manufacturing method for manufacturing lenses used as objective lenses, collimating lenses, etc. of optical pickups by pressing or the like.

[Prior art]

FIG. 3 shows a plano-convex lens 1 used as an objective lens or collimating lens for a compact disc player, or as an optical element for an optical memory device. Recently, lenses of this type have been molded by injection molding, compression molding, or injection compression molding in order to reduce manufacturing costs.

6 and 7 show the conventional process of molding the plano-convex lens 1 using a press. Reference numeral 2 is an upper mold, and 3 is a lower mold. There are 4 nests in the upper mold.
However, a nest 5 is held in the lower die 3, and a cavity 6 is formed between both the nests 4 and 5. The molding surface 4a on the lower side of the nest 4 is concave in order to form the convex optical surface 1a of the plano-convex lens 1.

In the manufacturing process of the plano-convex lens 1, an optical material 10 such as glass or resin is placed in the cavity 6 (the state shown in FIG. 6), and the inserts 4 and 5 are pressurized to form the plano-convex lens 1.
(state shown in Figure 7).

[Problem that the invention seeks to solve]

However, with conventional lens molds,
No gas vent is provided to avoid formation of protrusions on the optical surface 1a of the lens.

However, in the mold shown in FIGS. 6 and 7, when the optical material 10 is injected, gas G is generated in the cavity 6.
In many cases, they have no place to escape and remain behind. This gas G is caused by air or volatile components of the optical material 10 that has been heated and softened. If the nests 4 and 5 are pressurized while this gas G remains, the optical surface 1a of the molded plano-convex lens 1 will have irregularly shaped surfaces 1b such as wrinkles and irregularities due to the influence of the gas G. In a lens, the precision of the optical surface 1a greatly changes the optical characteristics. Therefore, if such an irregularly shaped surface 1b occurs, the performance of the optical system will be deteriorated.

The present invention solves the above-mentioned conventional problems, and when the optical surface is molded using a mold, an irregularly shaped surface due to gas is not formed on the optical surface, and furthermore, the optical characteristics are not deteriorated. The purpose of the present invention is to provide a lens manufacturing method that can manufacture lenses without any defects.

[Means for solving problems]

A lens manufacturing method according to the present invention includes providing a gas vent on a curved molding surface of a lens mold, molding an optical material using this molding surface, and manufacturing a lens in which a protrusion that has entered the gas vent is present on the optical surface. It is characterized by:

[Effect]

In the above means, by providing a gas vent in the mold for molding the optical material, gas in the cavity can be vented, and irregularly shaped surfaces such as irregularities and wrinkles can be prevented from occurring on the optical surface. On the contrary, the protrusion formed by the gas vent is left on the optical surface with a size that does not deteriorate the optical performance.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

1A and 1B show lenses manufactured by the lens manufacturing method according to the first embodiment of the present invention, and FIGS. 2A and 2B show lenses manufactured by the lens manufacturing method of the second embodiment. It shows a lens.

1A to 2B show a plano-convex lens 1 used as an objective lens or collimating lens for an optical pickup in a compact disc player, or as an optical element for an optical memory device.

In the plano-convex lens 1 shown in FIGS. 1A and 1B, projections 1c are provided in the form of dots at the optical axis position of a convexly curved optical surface 1a. Similarly, the plano-convex lens 1 shown in FIGS. 2A and 2B has a linear projection 1c on the optical surface 1a. This linear protrusion 1c includes the optical axis and extends almost the entire length in the diametrical direction of the lens. These protrusions 1c are formed by a gas vent of the type described below.

Next, the method for manufacturing a molded lens according to the present invention will be explained step by step with reference to FIGS. 4 and 5.

The mold used in this manufacturing method consists of an upper mold 2 and a lower mold 3. The upper die 2 holds a nest 4, and the lower die 3 holds a nest 5. Both nests 4
A cavity 6 is formed between and 5. The lower surface of the upper nest 4 has an optical surface 1 of the plano-convex lens 1.
A concave molding surface 4a for molding a is formed. Also, the upper nest 4 has a gas vent 4.
b is drilled. This gas vent 4b is a round hole located on the optical axis when molding the plano-convex lens 1 shown in FIGS. 1A and 1B;
When molding the plano-convex lens 1 shown in FIG. 2B, the gas vent 4b is formed into a slit containing the optical axis. In any case, the gas vent 4b is formed with an opening area that is sufficiently smaller than the area of the plano-convex lens 1.

In the lens molding process, first, an optical material 10 such as glass or resin is heated and softened and injected into the cavity 6 . At this time, as shown in FIG. 4, a gas G consisting of air, volatile components of the optical material 10, etc. remains in the cavity 6. However, as the nests 4 and 5 are pressurized, this gas G escapes to the outside through the gas vent 4b, and in the clamped state shown in FIG. 5, the plano-convex lens 1 is not affected by the gas G.
The optical surface 1a of is reliably molded. At the same time, a protrusion 1c (see FIGS. 1B and 2B) corresponding to the shape of the gas vent 4b is formed on the surface of the optical surface 1a.

When used as an optical element for an optical pickup or an optical memory device, the protrusion 1c is not removed and the plano-convex lens 1 is used as shown in FIGS. 1B and 2B. When the plano-convex lens 1 is used in a laser optical system or a small optical system for a screen, as in these devices, the optical performance of the plano-convex lens 1 depends more on the performance of the entire optical system than on the small protrusions. and the amount of transmitted light. That is, in the case of the plano-convex lens 1, the accuracy of forming the curved optical surface 1a is a more important factor than the presence of the minute protrusions 1c. In addition, when focusing on the decrease in the amount of transmitted light due to the presence of the protrusion 1c, it is found that 0.5mm
Even if the protrusion 1c of the same diameter remains, the decrease in the amount of light is about 1% based on the area ratio, and it can be said that there is almost no effect.

〔effect〕

As described above, according to the present invention, the following effects can be achieved.

(1) Since a mold with a gas vent is used,
The gas in the cavity is allowed to escape through the gas vent, preventing wrinkles and unevenness from forming on the optical surface. Therefore, it becomes possible to always mold lenses having highly accurate optical surfaces, and the number of defective lenses that do not meet the specifications is reduced. Therefore, the yield in processing is improved and costs can be reduced.

(2) Since the optical surface can be formed with high precision, even if the optical surface is provided with protrusions, the optical characteristics will not be significantly degraded. Therefore, even when used as an optical element in an optical pickup or an optical memory device, it can exhibit sufficient optical functions.

[Brief explanation of the drawing]

FIG. 1A is a sectional view showing a lens manufactured by the lens manufacturing method according to the first embodiment of the present invention, FIG. 1B is a perspective view thereof, and FIG. 2A is a sectional view showing a lens manufactured by the second embodiment. , FIG. 2B is a perspective view thereof, and FIG. 3 is a side view of a conventional molded lens.
4 and 5 are cross-sectional views showing each step of the lens mold used in the lens manufacturing method of the present invention, and FIG.
7 are cross-sectional views showing a mold for molding a conventional molded lens at each step. 1... Molded lens, 1a... Optical surface, 1c...
Projection, 4b...Gas vent.

[Claims]

1 Synthesize glass particles by subjecting raw material gas to a flame hydrolysis reaction, deposit the glass particles on a substrate to synthesize a cylindrical or cylindrical soot base material, and heat and sinter the soot base material. In the method of converting the soot base material into transparent vitrification, the soot base material is shrunk by at least 20% or more relative to the diameter of the soot base material in a chlorine-containing atmosphere in a furnace having a furnace length that can heat the entire length of the soot base material. The soot base material is dehydrated at a temperature and for a time that allows the soot to be transparent, and then the soot base material is inserted into a temperature range where transparent vitrification is possible from one end in a pure He gas atmosphere, and transparent vitrification is performed. A method for manufacturing a base material for optical fiber. 2. The method for producing a fiber base material according to claim 1, wherein the dehydration treatment temperature is 1400°C or less. 3. The method for manufacturing an optical fiber base material according to claim 1, wherein the soot base material diameter is 80 mmφ or more. 4 The above dehydration treatment and transparent vitrification are integrated.