JP2008156177A - Method for manufacturing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical element, by which the optical surface can be easily released after molding and the degree of freedom of the shape of the optical surface can be increased. <P>SOLUTION: The optical surface is formed by pressing an optical workpiece 4 composed of glass with an upper mold and a lower mold in a space between a cylindrical body mold 1, the upper mold inserted into the body mold from above, and the lower mold inserted into the body mold from below while heating the optical workpiece 4. The body mold 1 is formed of a material having a coefficient of linear thermal expansion smaller than that of the optical workpiece 4. The upper mold 2 and lower mold 3 have optical surface forming parts 10, 11 opposite to each other. A nickel layer 12 is provided on the surface of each optical surface forming part. The upper mold 2 and lower mold 3 each have a coefficient of linear thermal expansion larger than that of the optical workpiece 4 and are formed by a material having a coefficient of linear thermal expansion nearly equal to that of the nickel layer 12. The optical surface is formed by pressing the optical workpiece 4 with the upper mold 2 and the lower mold 3, and at least the lower mold 3 is released by the contraction during cooling. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical element such as a lens made of glass, and in particular, a method for manufacturing an optical element that forms an optical surface by heating and pressing an optical material made of glass between a body mold and an upper mold. About.

  As a method for manufacturing an optical element such as a lens, a prism, or a diffraction grating, a method in which glass is heated and softened and then molded by a mold is known. In this method, an optical material made of glass is placed between a cylindrical body mold and an upper mold and a lower mold inserted into the cylindrical body mold and heated to soften the optical material. An optical element having a predetermined shape is formed by pressing the optical material and transferring the shape of the optical surface forming portion formed on the upper die and the lower die to the optical material.

In this method of manufacturing an optical element, the upper mold and the lower mold are generally formed using a hard material such as a cemented carbide and a linear expansion coefficient smaller than that of glass. However, in such a material, since the optical surface forming portion is formed by grinding, it is difficult to form a fine shape with high accuracy. For this reason, it is known that a thin film such as a nickel layer is provided on the surface of the optical surface forming portion by means of plating or the like, and this thin film is subjected to fine processing by cutting. As a method for manufacturing such an optical element, for example, there is a method described in Patent Document 1.
JP-A-5-286727

  However, since a thin film such as a nickel layer that can be machined has a larger linear expansion coefficient than glass, it may be difficult to release after cooling after forming an optical surface on an optical material depending on the shape. Therefore, there is a restriction on the shape of the optical surface.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method of manufacturing an optical element that can be easily released after molding of the optical surface and can increase the degree of freedom of the shape of the optical surface.

In order to solve the above problems, an optical element manufacturing method according to the present invention includes a cylindrical body mold, an upper mold that is inserted into the body mold from above, and a lower mold that is inserted into the body mold from below. In the method of manufacturing an optical element that heats an optical material made of glass and presses the optical material with the upper mold and the lower mold to mold an optical surface,
The body mold is formed of a material having a smaller linear expansion coefficient than the optical material, and the upper mold and the lower mold have optical surface forming portions that face each other, and the optical surface forming portion is provided with a nickel layer on the surface. The upper mold and the lower mold are formed of a material having a larger linear expansion coefficient than the optical material and substantially the same linear expansion coefficient as the nickel layer,
An optical surface is formed by pressing the optical material with the upper mold and the lower mold, and at least the lower mold is released by contraction during cooling.

Further, in the method of manufacturing an optical element according to the present invention, the radius of curvature of the optical surface forming portion formed on the upper mold and the radius of curvature of the optical surface forming portion formed on the lower mold are substantially the same.
The upper mold is previously released from the optical material before cooling, and the lower mold is released by contraction during cooling.

Furthermore, in the method for manufacturing an optical element according to the present invention, the radius of curvature of the optical surface forming portion formed on the upper mold is larger than the radius of curvature of the optical surface forming portion formed on the lower mold,
Both the upper mold and the lower mold are separated from each other by contraction during cooling.

  According to the method of manufacturing an optical element according to the present invention, the body mold is formed of a material having a smaller linear expansion coefficient than the optical material, and the upper mold and the lower mold have optical surface forming portions facing each other, and the optical surface The formation part is provided with a nickel layer on the surface, and the upper mold and lower mold are made of a material having a linear expansion coefficient larger than that of the optical material and substantially the same as the nickel layer. To form an optical surface, and at least the lower mold is released by shrinkage during cooling, so that even if the surface of the optical surface forming part has a nickel layer, it can be released naturally during cooling. Since it can do, the freedom degree of the shape of an optical surface formation part can be made high.

  Further, according to the method for manufacturing an optical element according to the present invention, the curvature radius of the optical surface forming portion formed in the upper mold and the curvature radius of the optical surface forming portion formed in the lower mold are substantially the same, and the upper mold Can be prevented from releasing the molded optical element from the lower mold by contacting the upper mold only by releasing the mold from the optical material before cooling. Thereafter, it can be prevented from being dropped and damaged.

  Furthermore, according to the method of manufacturing an optical element according to the present invention, the radius of curvature of the optical surface forming portion formed in the upper mold is larger than the radius of curvature of the optical surface forming portion formed in the lower mold, and the upper mold and the lower mold In both cases, the molded optical element can be prevented from being released from the lower mold by being released from the mold by shrinkage during cooling. It can prevent falling and breaking.

  Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of the body mold 1, the upper mold 2, the lower mold 3, and the optical material 4 for each optical element manufacturing process according to the first embodiment. FIG. 1A shows a stage before heating. As shown in this figure, with respect to the barrel mold 1 formed in a cylindrical shape, the upper mold 2 and the lower mold 3 are inserted from the upper side and the lower mold 3 from the lower side, respectively. In the space surrounded by 2 and the lower mold 3, a thick plate-shaped optical material 4 is arranged.

  The upper mold 2 has an upper optical surface forming portion 10 formed in the shape of a lens to be formed on the upper surface of the optical material 4 on the lower surface. On the other hand, the lower mold 3 has a lower optical surface forming portion 11 formed in the shape of a lens to be formed on the lower surface of the optical material 4 on the upper surface. Here, the radius of curvature of the lens shape formed in the upper optical surface forming unit 10 is set to be larger than the radius of curvature of the lens shape formed in the lower optical surface forming unit 11. That is, the upper optical surface forming unit 10 has a shallower shape than the lower optical surface forming unit 11. A nickel layer 12 is formed on the surface of each of the upper optical surface forming unit 10 and the lower optical surface forming unit 11, and a precise shape is formed on the nickel layer 12 by cutting.

  Here, the body mold 1 is made of cemented carbide, while the upper mold 2 and the lower mold 3 are made of stainless steel. The body mold 1 is made of a cemented carbide having a smaller coefficient of linear expansion than glass or nickel, while the upper mold 2 and the lower mold 3 are made of stainless steel having a coefficient of linear expansion greater than that of glass and approximately the same as nickel. Is used.

  Although not shown, for example, a heating member made of a high-frequency heating device is arranged on the outer peripheral side of the body mold 1, the upper mold 2 and the lower mold 3, and each member is heated by the heating member, and accordingly, the inside The arranged optical material 4 is heated to a temperature at which it softens. When the body mold 1, the upper mold 2, the lower mold 3, and the optical material 4 are heated, each member expands corresponding to the linear expansion coefficient for each material. In particular, the body mold 1 hardly expands due to a small linear expansion coefficient, while the upper mold 2 and the lower mold 3 expand greatly due to a large linear expansion coefficient.

  FIG. 1B shows a stage where the optical material 4 has been softened by heating. As shown in this figure, when heated, the upper mold 2 expands so as to extend toward the space, that is, downward. A line A in FIG. 1B represents the lower surface position of the upper mold 2 in FIG. 1A, and a line C represents the lower surface position of the upper mold 2 in FIG. The line C in FIG. 1B is below the line A, and the upper optical surface forming part 10 of the upper mold 2 is in a state closer to the optical material 4.

  Further, when the lower mold 3 is heated, it expands so as to extend to the space side, that is, upward. 1B represents the upper surface position of the lower mold 3 in FIG. 1A, and the D line represents the upper surface position of the lower mold 3 in FIG. 1B. The line D in FIG. 1B is above the line B, and indicates that the lower optical surface forming portion 11 of the lower mold 3 has moved upward. Accordingly, the optical material 4 placed on the lower optical surface forming unit 11 is also moved upward.

  After the heating, the optical material 4 is pressed with the upper mold 2 and the lower mold 3 to perform molding. FIG. 1C shows the molding stage. As shown in this figure, the upper mold 2 and the lower mold 3 are driven so as to move in directions close to each other. As a result, the optical material 4 is pressed against the body mold 1, the upper mold 2 and the lower mold 3, the shape of the upper optical surface forming part 10 of the upper mold 2 is formed on the upper surface, and the lower optical surface forming part of the lower mold 3 is formed on the lower surface. The molded lens 5 having the optical surfaces 5a and 5b is formed by transferring the shape of 11 respectively.

  After molding, the upper mold 2 and the lower mold 3 are cooled and contracted, so that the mold is released naturally. FIG.1 (d) has shown the stage where the whole was cooled. Even if the whole is cooled, the body mold 1 having a small linear expansion coefficient hardly deforms. On the other hand, since the upper mold 2 and the lower mold 3 have a large linear expansion coefficient, they shrink in a direction away from the molded lens 5 that has been molded. Accordingly, as shown in FIG. 1 (d), the molded lens 5 is released from the upper mold 2 and the lower mold 3 while the peripheral surface is fixed to the body mold 1.

  Here, since the upper optical surface forming part 10 of the upper mold 2 and the lower optical surface forming part 11 of the lower mold 3 are respectively formed in a concave shape, if the radius of curvature is small, the portion of the nickel layer 12 in the cooling process May shrink, and the upper mold 2 and the lower mold 3 may be in close contact with the molded lens 5 before they are separated from the molded lens 5 and may not be released. The upper optical surface forming part 10 of the upper mold 2 and the lower optical surface forming part 11 of the lower mold 3 are both formed with a radius of curvature that prevents the upper mold 2 and the lower mold 3 from being in close contact with the molded lens 5 during cooling. However, since the curvature radius of the upper optical surface forming portion 10 of the upper mold 2 is smaller than the curvature radius of the lower optical surface forming section 11 of the lower mold 3, the upper mold 2 can be surely released from the lower mold 3. it can. As a result, it is possible to prevent the molded lens 5 from being released from the lower mold 3 and closely attached only to the upper mold 2 and then falling and being damaged. If the molded lens 5 is released from the upper mold 2 and is not in close contact with the lower mold 3, the molded lens 5 is taken out from the lower mold 3 using a jig (not shown).

  As described above, the upper mold 2 and the lower mold 3 are formed of a material having substantially the same linear expansion coefficient as that of the nickel layer 12 on the surface, so that the upper mold 2 and the lower mold 3 are separated from the molded lens 5 during cooling after molding. Since the upper die 2 and the lower die 3 are made of a material having a small linear expansion coefficient such as cemented carbide, curved surfaces having a smaller radius of curvature and fine triangular grooves are formed. It is also possible to form a diffraction grating and the like, and to increase the degree of freedom of the shape of the optical surface.

  Next, a second embodiment of the present invention will be described. FIG. 2 is a cross-sectional view of the body mold 1, the upper mold 2, the lower mold 3, and the optical material 4 for each optical element manufacturing process according to the second embodiment. FIG. 2A shows a stage before heating. As shown in this figure, the body mold 1, the upper mold 2, the lower mold 3, and the optical material 4 of the second embodiment have substantially the same configuration as that of the first embodiment. The difference is that the shape of the upper optical surface forming portion 10 formed on the upper mold 2 is formed so as to have substantially the same radius of curvature as the lower optical surface forming portion 11 of the lower mold 3.

  As shown in FIG. 2 (b), the body mold 1, the upper mold 2, the lower mold 3 and the optical material 4 are heated, and the upper mold 2 and the lower mold 3 expand in a direction approaching each other, and the optical material 4 is softened. The Subsequently, as shown in FIG. 2C, the optical material 4 is pressed and molded, and a molded lens 5 is formed.

  When the molded lens 5 is formed, the upper mold 2 is driven and released from the molded lens 5 in advance before the upper mold 2 and the lower mold 3 are cooled, as shown in FIG. Thereafter, as it is cooled, the lower mold 3 contracts in a direction away from the molded lens 5 as shown in FIG.

  In the second embodiment, the upper mold 2 is released in advance before cooling in this manner, so that the radius of curvature of the upper optical surface forming unit 10 is approximately the same as the radius of curvature of the lower optical surface forming unit 11. Even if it exists, it can prevent that the molding lens 5 adheres only to the upper mold 2 and is released from the lower mold 3, and therefore, when it adheres only to the upper mold 2, it is prevented from being dropped and damaged thereafter. be able to.

  Although the embodiment of the present invention has been described above, the application of the present invention is not limited to this embodiment, and can be applied in various ways within the scope of its technical idea. For example, in the present embodiment, the molded optical element is a molded lens 5 having lenses on both sides, but other diffraction gratings and the like are formed depending on the shapes of the upper optical surface forming unit 10 and the lower optical surface forming unit 11. You can also

It is sectional drawing of the trunk | drum type | mold, upper mold | type, lower mold | type, and optical raw material for every manufacturing process of the optical element in 1st Embodiment. It is sectional drawing of the trunk | drum type | mold, upper mold | type, lower mold | type, and optical raw material for every manufacturing process of the optical element in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Body type | mold 2 Upper mold | type 3 Lower mold | type 4 Optical material 5 Molding lens 10 Upper optical surface formation part 11 Lower optical surface formation part 12 Nickel layer

Claims (3)

Heating the optical material made of glass between a cylindrical body mold, an upper mold inserted into the body mold from above, and a lower mold inserted from below into the body mold, and the upper mold In the method of manufacturing an optical element that molds an optical surface by pressing the optical material with a lower mold,
The body mold is formed of a material having a smaller linear expansion coefficient than the optical material, and the upper mold and the lower mold have optical surface forming portions that face each other, and the optical surface forming portion is provided with a nickel layer on the surface. The upper mold and the lower mold are formed of a material having a larger linear expansion coefficient than the optical material and substantially the same linear expansion coefficient as the nickel layer,
An optical element manufacturing method, wherein an optical surface is formed by pressing the optical material with the upper mold and the lower mold, and at least the lower mold is released by contraction during cooling. The radius of curvature of the optical surface forming portion formed on the upper mold and the radius of curvature of the optical surface forming portion formed on the lower mold are substantially the same,
2. The method of manufacturing an optical element according to claim 1, wherein the upper mold is previously released from the optical material before cooling, and the lower mold is released by contraction during cooling. The radius of curvature of the optical surface forming portion formed on the upper mold is larger than the radius of curvature of the optical surface forming portion formed on the lower mold,
2. The method of manufacturing an optical element according to claim 1, wherein both the upper mold and the lower mold are released by shrinkage during cooling.

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