JPH0421528A - Method and device for preparing optical element - Google Patents

Abstract

PURPOSE:To prevent the generation of the strains and cracks of an optical element caused by excessive tightening and the detachment of the element caused by insufficient tightening, by disposing a space between the element and a holding member for holding the element so that the element is tightened with a reasonable force. CONSTITUTION:A raw material 5 is heated with a heating member 12. The element 5 is pressed with a cylindrical mold 15 and with opposed molds 13,14 to form an optical surface. The press-molded element 5 is inserted into a holding member 4 comprising a material having a greater linear expansion coefficient than the element 5. The element 5 and the holding member 4 are subsequently cooled and contracted to hold and fix the element 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and a manufacturing apparatus for manufacturing an optical element such as a lens by pressure molding a material such as a glass material.

[Prior Art] In optical pickups and other various optical devices, a lens held by a holding member (lens barrel) is used. Conventionally, after a lens is manufactured by a polishing process, a pressing process, or a resin molding process, the manufactured single lens is placed in a holding member, positioned, and fixed by means such as adhesive.

However, the above manufacturing method requires a lens manufacturing process, a process of inserting the lens into the holding member, a process of positioning the lens within the holding member, and a process of gluing the lens to the holding member, resulting in a large number of processes. Manufacturing costs increase. Furthermore, it is difficult to position the lens and the holding member, and it is also difficult to improve the positioning accuracy, resulting in a disadvantage that the reliability of the product varies.

Therefore, as an efficient manufacturing method, a lens material such as glass is press-molded within a holding member, and at the same time as the optical element such as a lens is manufactured, the molded optical element is pressed against the inner wall of the holding member, thereby holding it. A possible method is to fix the optical element within the member. FIG. 5 shows an example of using this type of method.

Reference numerals 1 and 2 denote heating bodies that face each other so as to be able to be joined and separated, and a lower mold 3 and an upper mold 6 constituting a facing mold are nested therein.

A support part A is formed at the joint between the heating bodies 1 and 2, and a holding member (lens barrel) 4 is inserted and held in this support part A. The material 5 such as glass is in a preheated state, and the lower mold 3 and the upper mold 6
will be supplied between. Then, the heating body 1.2 is heated by a high frequency coil or the like, and the opposing molds 3 and 6 are heated, and the holding member 4 is heated.
, the material 5 is heated. When the material 5 is heated to a predetermined temperature, when the lower mold 3 and the upper mold 6 are driven in the pressurizing direction, the material 5 is restrained by the holding member 4 around its periphery, and its upper and lower surfaces as shown in the drawing are Each molding surface 3a of the lower mold 3 and upper mold 6
and 68 to form a predetermined lens shape.

At the same time, the material 5 is pressed against the inner wall of the holding member 4.

[Problems to be Solved by the Invention] However, in the method of manufacturing an optical element as shown in FIG. conditions are required. First, if the coefficient of linear expansion of the material of the holding member 4 is too larger than the coefficient of linear expansion of the material 5, the holding member 4 will tighten the material 5 too much in the cooling step after molding.

Therefore, when tightening the molded material 5, that is, the completed optical element such as a lens, the force becomes excessive, causing distortion of the optical surface and changing the optical performance, or causing an extremely large difference in linear expansion coefficient. In some cases, cracks may occur in the material after molding. On the other hand, if the coefficient of linear expansion of the material of the holding member 4 is too smaller than that of the material 5, the pressing force of the material 5 against the holding member 4 (the force of tightening by the holding member 4) will decrease during cooling, and the molding An optical element such as a lens that has been removed is likely to fall off from the holding member 4.

Therefore, in order to avoid such inconveniences, it is necessary to delicately select the combination of linear expansion coefficients to form an appropriate tightening. However, it is virtually impossible to select this material, and even if it could be selected, there would be restrictions on the outer diameter and thickness of the optical element to be manufactured, or the material used to mold the optical element such as a lens. The selection of No. 5 causes problems such as the inability to obtain desired optical characteristics.

The present invention solves the above-mentioned conventional problems, and eliminates the need to select materials and delicate combinations of materials.
, a method for manufacturing an optical element that can reliably hold an optical element such as a lens within a holding member, and that can perform a pressurizing process for manufacturing the optical element and positioning and pressure bonding of the optical element to the holding member in a series of steps; The purpose is to provide manufacturing equipment.

[Means to solve the problem]

The method for manufacturing an optical element according to the present invention includes a step of heating a material, a step of constraining the periphery of the heated material and applying pressure with a mold to form an optical surface, and a step of forming an optical surface using a material having a larger coefficient of linear expansion than the material. Inserting the material after pressure molding into the heated holding member using the formed holding member;
This method is characterized by comprising the steps of cooling the material and the holding member and holding and fixing the material by thermal contraction of the holding member.

Further, the optical element manufacturing apparatus according to the present invention includes a body mold that restrains the periphery of the material, and an opposing mold that moves in the direction of pressurizing the material within the body mold and has a molding surface that molds an optical surface.
A support part that supports a holding member into which the molded material is inserted and is located at a position where the molded material moves when the opposing mold moves in the direction of removal from the body mold, and a heating member that heats the material and the holding member. It is characterized in that it is provided with the following.

[Function] In the method for manufacturing an optical element described above, the holding member is manufactured from a material having a larger coefficient of linear expansion than the material of the optical element such as the lens. The material is then heated and pressurized by a mold.
After being inserted into the holding member, the material and the holding member are cooled, and the molded material is held by thermal contraction of the holding member. Since the material is inserted into the holding member after being pressure-molded with a mold, it is necessary to set the gap between the material and the inner wall of the holding member appropriately according to the difference in linear expansion coefficient between the material and the holding member. Therefore, during cooling, the tightening margin by the holding member can be set to an appropriate amount regardless of the magnitude of the difference in linear expansion coefficient between the material and the holding member, and the material can be fixed by the holding member with an appropriate holding force.

In addition, in the above-mentioned optical element manufacturing apparatus, after the material is pressurized by opposing molds in the body mold to form a shape such as a lens,
Move the opposing mold from inside the body mold. The material thus formed is immediately inserted into the holding member, and the holding member and the material can be cooled. In this way, the material can be molded and transferred to the holding member in a series of steps within the same device.

[Example] Examples of the present invention will be described below with reference to the drawings of FIGS. 1 to 4.

1 to 3 are cross-sectional views showing the optical element manufacturing apparatus according to the present invention in different operating states.

Reference numerals 11 and 12 denote heating bodies that are provided so as to be able to be joined and separated from each other. A lower die 13 and an upper die 14, which are nested, are inserted into the heating bodies 11 and 12 so as to be pressable and releasable, thereby forming opposed dies. Molding surfaces 13a and 14a for molding optical surfaces are formed on the lower mold 13 and the upper mold 14, respectively. The shapes of the molding surfaces 13a and 14a are as follows:
It is selected depending on the external shape of the optical element such as a lens to be molded. For example, in the case of a convex lens, the molding surface 13
a and 14a or one of them is a concave surface, and when a concave lens is molded, the molding surface is a convex surface. Reference numeral 15 denotes a body type, and this body type 15 is held within the heating body 12 on the upper side in the figure. The outer diameter dimensions of the lower mold 13 and the upper mold 14 are both the same, and the inner diameter dimension D1 of the body mold 15 is formed so that the lower mold 13 and the upper mold 14 can slide without any gap. A support part A is formed at the upper part of the heating body 11 on the lower side of the figure, and the holding member (lens barrel) 4 is held within this support part A.

The holding member 4 is attached to the bottom surface 11a of the recess of the heating element 11 and the heating element 12.
The holding member 4 is positioned and held in a state where it is sandwiched between the lower edge 12a of the holding member 4, and the holding member 4 can be taken out from the support portion A by vertically separating the heating bodies 11 and 12.

Reference numeral 16 denotes a high frequency coil, which is connected to a high frequency power source 17. The heating element 11 , 12 and its interior are heated by high-frequency induction heating of the high-frequency coil 16 . A cooling air nozzle 18 is inserted into the lower mold 13, and a cooling air nozzle 19 is similarly inserted into the upper mold 14. Cooling air can be supplied into the lower mold 13 and upper mold 14 by the respective nozzles 18 and 19, and this air supply is controlled by the flow control valve 18.
It is controlled by switching between a and 19a. Furthermore, although not shown, temperature sensors are attached to or inserted into the lower mold 13 and the upper mold 14 so that the temperature of the molds can be detected.

Next, a method for manufacturing an optical element using the above manufacturing apparatus will be explained.

In FIG. 1, reference numeral 5 indicates the material (for example, glass material) of the optical element (lens in the illustrated embodiment).The relationship between the linear expansion coefficient of this material 5 and the linear expansion coefficient of the material of the holding member 4 is 4 is selected to be larger. Further, the outer circumference dimension of the material 5 immediately after pressure molding is determined by the inner diameter dimension of the body mold 15, but the inner diameter dimension D of the holding member 4
2 is set larger than the inner diameter dimension of the barrel mold 15. This dimensional difference, -D, is set according to the difference in linear expansion coefficients between the material 5 and the holding member 4.

That is, when the difference is large, the inner diameter dimension D2 of the holding member 4 is made larger to obtain the dimension difference D 2 D.

(and if the difference in linear expansion coefficient is small, the inner diameter D2 of the holding member 4 is made smaller to make the dimensional difference -D,
Make smaller. As a result, in the cooling process after molding,
The tightening margin between the heat-shrinkable holding member 4 and the material 5 can always be optimally set.

In the manufacturing process, the holding member 4 is inserted into the support part A to be supported, and the preheated material 5 is supplied. Then, a high frequency current is applied from the high frequency power supply 17 to the high frequency coil 16,
The heating bodies 11 and 12 are heated by induction heating. As a result, the mold 13, 14, 15 and the holding member 4 are heated, and the material 5 is further heated from the side by the heating element 12. As shown in FIG. 4, after the heating time T, the temperature of the material 5 reaches the glass softening point or higher, and the temperatures of the lower mold 13 and the upper mold 14 reach the glass transition point or higher, the second As shown in the figure, the lower mold 13 is raised, and the material 5 is pressure-molded by the lower mold 13 and the upper mold 14 in the demolding 15. As a result, with the outer periphery of the material 5 being restrained by the inner wall of the demolding mold 15, the upper and lower surfaces of the material 5 shown in the drawing are press-molded according to the shapes of the molding surfaces 13a and 14a of the lower mold 13 and the upper mold 14. Fourth
As shown in the figure, during pressure molding, the temperature of the heating element 11, 12, lower mold 13, and upper mold 14 is lowered by controlling the high frequency power supply 17 and controlling the cooling air supply from the flow rate control valves 18a and 19a. .

When the temperature of the material 5 falls below the glass transition point, both the lower mold 13 and the upper mold 14 are lowered, and the molded material 5 held in both molds is released. It is removed from the mold 15 and inserted into the holding member 4. Then, the lower mold 13 is first pulled out downward, and the material 5 is pressed into the holding member 4 by the upper mold 14, and the material 5 is pressed and positioned within the holding member 4. Then, the upper mold 14 is pulled out upward from the holding member 4. In FIG. 4, the temperature at the time when the material 5 is inserted into the holding member 4 is indicated by α. After the insertion operation, the temperature is reduced by natural cooling or air cooling by nozzles 18 and 19. At this time, the material 5 is appropriately tightened by the holding member 4 due to the contraction of the holding member 4 made of a material having a larger coefficient of linear expansion than the material 5 and the contraction of the material 5 . After cooling, the holding member 4 and the material 5 held therein are heated by the heating elements 11 and 1.
It is taken out by separation of 2.

〔effect〕

As described above, according to the method for manufacturing an optical element of the present invention,
By setting the gap between the material and the holding member according to the difference in linear expansion coefficient between the materials of the holding member and the material, the material is appropriately tightened by the holding member during cooling. Therefore, the material of the optical element and the material of the holding member can be freely combined, and in this case, for example, by simply setting the inner diameter of the holding member, a moderate tightening force can be obtained, and an excessive tightening force can be obtained. Distortion and cracks in optical elements due to
Also, the optical element will not fall off due to insufficient tightening force.

Further, in the optical element manufacturing apparatus of the present invention, after the material is pressure-molded by the opposing mold, the molded material can be inserted into the holding member by moving the mold. Therefore, it becomes possible to pressurize the material and insert the material into the holding member in a series of steps, making the work more efficient.

[Brief explanation of the drawing]

1 to 4 show embodiments of the present invention, and FIGS. 1 to 3 are cross-sectional views showing the optical element manufacturing apparatus according to the present invention in different operating states, and FIG. 4 shows the present invention. FIG. 5 is a diagram showing the heating temperature in the method of manufacturing an optical element, and FIG. 5 is a sectional view showing the conventional method of manufacturing an optical element. 4... Holding member, 5... Material of optical element, 1112
... Heating body, 13.14 ... Opposing type, 15 ... Demolding, A ... Support part. Figure 2 Figure 3 To Sugijira Figure 4

Claims (1)

[Claims] 1. A step of heating a material, a step of constraining the periphery of the heated material and applying pressure with a mold to form an optical surface, and a step of forming an optical surface using a material having a coefficient of linear expansion larger than that of the material. a step of inserting the pressure-molded material into the heated holding member using a heated holding member; a step of cooling the material and the holding member and holding and fixing the material by heat contraction of the holding member;
2. A method for producing an optical element characterized by comprising: a barrel mold that restrains the periphery of the material; and an opposed mold that has a molding surface that moves in a direction that pressurizes the material within the barrel mold and molds an optical surface. a support part that supports a holding member into which the molded material is inserted and is located at a position where the molded material moves when the opposing mold moves in a direction in which it is removed from the body mold; and a support part that heats the material and the holding member. An optical element manufacturing apparatus characterized by being provided with a heating member.