JP2005097099A - Method of manufacturing optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of efficiently manufacturing an optical device by press-forming a preform in a proper quantity (volume) neither too much nor too less in the method of manufacturing the optical device having a prescribed shape from a preliminary formed base material through a press-forming and a coring process. <P>SOLUTION: In the manufacturing method, when the optical device to be obtained has a convexo convex shape or a convex meniscus shape, the forming base material having a weight 110-155% of that of the optical device obtained after coring is used and when the optical device to be obtained has a concavo concave shape or a concave meniscus shape, the forming base material having a weight 180-240% of that of the optical device obtained after coring is used. The optical device having a prescribed shape is obtained by press-forming after heating to soften the preliminary formed base material obtained by cooling and coring the resultant press formed article by dropping or making the molten glass to flow from a nozzle. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an optical element, in which an optically functional surface is formed by transferring a molding surface to a heat-softened molding material using a precision processed mold. In particular, the present invention relates to a method of manufacturing an optical element, wherein the center axis of the optical element is determined by performing a centering process after precision pressing, or a mounting portion or the like to another member is formed on the outer periphery of the optical element. About.

  As a method for manufacturing an optical element, a precision press for forming an optical element such as a lens by press-molding a preformed molding material such as a glass preform in a heat-softened state is known. The optical functional surface of the optical element obtained by precision pressing does not require post-processing such as grinding and polishing, and can be precisely formed into a desired shape by press molding. This is useful in that the optical functional surface can be precisely formed. The molded product thus formed is centered (by cutting the periphery of the molded product or the like so that the central axis with respect to the outer diameter matches the optical axis) to determine the central axis. In some cases, during centering, a flat part perpendicular to the central axis or a flat part perpendicular to the central axis is formed on the outer periphery of the lens, and a lens mounting part or a part serving as a reference surface for lens attachment is provided. It can be a product.

In JP-A-11-1000021 (Patent Document 1), when pressing a glass material, the extra volume necessary for conveying the glass material is made unnecessary or reduced, thereby reducing the man-hours in the subsequent process. It is disclosed. However, this method only proposes to eliminate or reduce the excess volume of the material related to conveyance, and does not consider the volume (or weight) necessary for the centering process.
Japanese Patent Laid-Open No. 11-1000021

  Since an optical element such as a lens needs to satisfy the optical performance required for its application, it is designed using a known lens design method so as to satisfy the desired optical performance. Thereby, a spherical surface or an aspherical surface formula that defines the shape of the lens diameter, lens thickness, convex surface, concave surface, or the like is determined. Furthermore, in order to obtain a lens having a desired optical performance, it is also important to use a molding material having an appropriate optical constant in combination with the lens design. Usually, after determining the final lens shape, the shape, weight and the like of the molding material for manufacturing the lens are determined.

  As the molding material, a material preformed into a predetermined shape in advance, such as a glass preform, can be used. Hereinafter, the “preliminarily molded material” is also referred to as “preform” in the present specification. For example, the preform can be preformed into a spherical shape, a biconvex curved shape, a disc shape, a cylindrical shape, or the like. Usually, the shape of the molding material is preferably close to the shape of the lens to be obtained from the viewpoint of ease of press molding.

Here, in the lens manufacturing method in which the centering process is performed after the press molding, the peripheral portion of the molded product is cut in the centering process. Therefore, the weight (or volume) of the preform to be prepared needs to be larger than the weight (or volume) of the lens to be obtained. However, the weight (volume) of the preform has conventionally been determined by trial and error. For this reason, if the weight (volume) of the preform is unnecessarily large, not only is the material wasted, but the man-hours for centering increase, and the waste of glass powder increases the environmental load. Further, it has been found that when the preform volume is larger than a predetermined range, the load during pressing is likely to be applied unevenly, resulting in poor surface accuracy. Further, if the volume (weight) of the preform is too small, the lens mounting portion cannot be sufficiently removed, or the optical functional surface is insufficient due to slight uneven thickness during pressing, which causes deterioration in yield.
Therefore, it has been necessary to determine an appropriate weight (volume) preform without excess or deficiency in press molding without repeating trial and error of press molding.

  By the way, as a glass preform, a glass material capable of obtaining a lens having desired optical performance (for example, refractive index nd, Abbe number νd) is selected, and the selected type of glass material is preformed into an appropriate shape. Is produced. The glass type is, for example, a glass type, which depends on the glass composition.

  However, there are upper and lower limits to the weight of glass that can be preformed as a glass preform, and the upper and lower limits vary depending on the glass composition. Further, the value varies depending on the preform shape to be preformed.

  For example, glass preforms are hot-formed (molten glass is dropped or flowed down from a nozzle to a receiving mold, and cooled in an appropriate holding state (for example, a floating state by an air flow), so that a spherical shape having no surface defects or both When preforming a convex curved surface shape), if the weight of the glass exceeds a certain range, it becomes difficult to perform appropriate dripping (or flow-down) and molding after dripping (or flow-down). In addition, striae may occur in the preform obtained due to the composition and physical properties of the glass material used, and it is difficult to obtain a high-quality lens even when such a preform is subjected to press molding.

In addition, when hot forming a glass preform, even if the amount of dripping (or flowing down) from the nozzle is kept to a minimum, in order to maintain the weight accuracy within a certain range, the weight includes individual glass compositions. There is a lower limit depending on the preform shape.
In recent years, lenses having a higher refractive index have been demanded as lenses used in imaging optical equipment such as digital cameras. For this purpose, preforms are obtained by hot forming from a glass material having a high refractive index. Has been tried. However, glass materials with a high refractive index tend to have high wettability between the molten glass and the nozzle, and have a low viscosity during melting. It has often been difficult to obtain a preform having a desired weight (volume) by molding as desired.

Normally, when obtaining a lens with the desired optical performance, a glass material having an appropriate optical constant in terms of lens design is determined, and the lens shape is designed by a known lens design method based on the optical constant of the glass material. To do. The volume of the designed lens can be calculated by lens design software, and the weight of the glass of that volume can be calculated from the specific gravity of the glass material used. By adding the weight (volume) cut by centering to the weight (volume) of the lens to be obtained (assuming this can be accurately predicted), the weight of the required preform can be calculated. it can.
On the other hand, as described above, the glass weight that can be preformed as a preform by hot forming has an upper limit and a lower limit. Therefore, if the calculated weight of the preform is outside the range of glass weight that can be preformed as a glass preform, such a lens cannot be molded. In this case, the lens design that provides equivalent optical performance must be redone or modified again. This is very complicated.

  Therefore, the first object of the present invention is to minimize the amount of centering in a method of manufacturing an optical element from a preformed molding material through a press molding and centering process, In addition, the weight of the molding material is determined within a range in which there is no problem of insufficient optical function and poor surface accuracy due to uneven thickness and the like, and an optical element is efficiently manufactured.

  The second object of the present invention is to determine an appropriate weight (volume) preform without excess or deficiency in press molding without repeating trial and error of press molding or lens design, and efficiently use optical elements. Is to manufacture.

Means for achieving the above object are as follows.
[Claim 1] An optical element including a molding step of press-molding a preformed molding material in a heat-softened state, and a centering step of centering the obtained press-molded product to obtain an optical element of a predetermined shape In the manufacturing method,
When the optical element to be obtained has a biconvex shape or a convex meniscus shape, a molding material having a weight in the range of 110 to 155% of the weight of the optical element of the predetermined shape is used as the molding material.
When the optical element to be obtained has a biconcave shape or a concave meniscus shape, a molding material having a weight within a range of 180 to 240% of the weight of the optical element having the predetermined shape is used as the molding material. The manufacturing method of an optical element.
[Claim 2] The method according to claim 1, wherein the preformed molding material is obtained by dropping or flowing molten glass from a nozzle and cooling.
[Claim 3] The method according to claim 1 or 2, wherein the molding material has a refractive index (nd) of 1.7 or more.
[Claim 4] The method according to any one of claims 1 to 3, wherein the molding material is made of phosphate glass.
5. The method according to claim 3, wherein the weight of the preformed molding material is in the range of 10 to 8000 mg.
6. The method according to claim 5, wherein the preformed molding material has a spherical shape and has a weight in the range of 10 to 1000 mg.
7. The method according to claim 5, wherein the preformed molding material has a biconvex curved surface shape and a weight in the range of 150 to 8000 mg.
[Claim 8] Dropping or flowing molten glass from a nozzle, cooling the molten glass, preforming a molding material, press-molding the preformed molding material in a heat-softened state, and then obtaining In the manufacturing method of an optical element including centering the obtained press-formed product, obtaining a biconvex or convex meniscus optical element,
A method for producing an optical element, wherein the shape of the optical element obtained by the centering is determined according to the following (1) to (3):
(1) Based on the optical performance of the lens to be obtained, determine the type of glass to be used,
(2) Find the weight range or volume range of the molding material that can pre-form that kind of glass,
(3) The shape of the optical element is determined so that the weight or volume of the optical element finally obtained is within the range of 100/110 to 100/155 of the weight or volume within the range.
[Claim 9] Dropping or flowing molten glass from a nozzle, preliminarily forming a molding material by cooling the molten glass, press-molding the preformed molding material in a heat-softened state, and then obtaining In the manufacturing method of an optical element including centering the obtained press-molded product to obtain a biconcave or concave meniscus optical element,
A method for producing an optical element, wherein the shape of the optical element obtained by the centering is determined according to the following (1) to (3):
(1) Based on the optical performance of the lens to be obtained, determine the type of glass to be used,
(2) Find the weight range or volume range of the molding material that can pre-form that kind of glass,
(3) The shape of the optical element is determined so that the weight or volume of the finally obtained optical element falls within the range of 100/180 to 100/240 of the weight or volume within the range.

  According to the first aspect of the present invention, it is possible to perform press molding using a preform having a weight (or volume) that is not excessive or insufficient in accordance with the lens shape to be obtained. Moreover, since press molding can be performed without excessively removing a portion to be removed by centering, man-hours for centering after press molding can be minimized. Furthermore, press molding can be performed using a preform having a weight (or volume) that does not cause shortage of the optical functional surface due to uneven thickness, and a lens is molded by applying an appropriate load over the entire optical functional surface. Therefore, a high quality lens with high surface accuracy can be obtained.

  Furthermore, according to the invention described in claims 8 and 9, since the lens (optical element) is designed in consideration of restrictions on the molding material used for press molding, an appropriate weight (volume) without excess or deficiency is designed. Reform can be decided without repeating press molding and lens design trial and error, and lens production with high production efficiency can be achieved.

The present invention relates to an optical element including a molding step of press-molding a preformed molding material in a heat-softened state, and a centering step of performing centering of the obtained press-molded product to obtain an optical element of a predetermined shape. It relates to a manufacturing method.
In the manufacturing method of the present invention, when the optical element to be obtained has a biconvex shape or a convex meniscus shape, 110 to 155 of the weight (or volume) of the optical element having a predetermined shape obtained by centering as the molding material. It is characterized by using a molding material having a weight (or volume) in the range of%. Preferably, it is 110 to 140%, more preferably 110 to 135% for the biconvex shape, and 115 to 140% for the convex meniscus shape.
If the weight (or volume) of the preformed molding material is less than 110% of the weight (or volume) of the optical element obtained by centering, the lens mounting part cannot be removed sufficiently, or a slight uneven thickness during pressing. Therefore, there is a problem that the surface accuracy is lowered because the optical function surface is insufficient, or the lens cannot be molded by applying an appropriate load over the entire area of the optical function surface. In addition, when the weight (or volume) of the preformed molding material is larger than 155% of the weight (or volume) of the optical element obtained by centering, the material is wasted and the man-hour for centering increases. The problem arises that productivity deteriorates. Furthermore, an unbalanced press load is likely to be applied to the preform, and surface accuracy may be deteriorated. Furthermore, there arises a problem that waste such as glass powder increases the environmental load.

  In the manufacturing method of the present invention, an optical functional surface can be formed by press molding with an appropriate load distribution using a preform with a weight (or volume) that is not excessive or insufficient. The surface accuracy is high even without performing polishing or the like. Therefore, the production method of the present invention is suitable for a precision press molding method, which is a method of forming an optical functional surface by transferring a molding surface to a heat-softened molding material using a precision-molded mold. It is.

In the present invention, when an optical element is obtained by precision press molding, it is not necessary to consider the glass weight (or volume) removed by polishing because polishing is not required. Therefore, considering the part removed by the centering, the weight (or volume) of the part is in the range of 10 to 55% of the weight (or volume) of the final product (optical element after centering). The press molding may be performed. This point will be described with reference to FIG. FIG. 1 is a schematic view of a press-formed product including a portion removed by centering when a biconvex lens is manufactured.
For example, when a biconvex lens as shown in FIG. 1 is manufactured, the shape and weight (or volume) of the portion removed by centering can be determined as shown below. (In FIG. 1, the shaded portion is the portion removed by centering.)
The lens effective diameter and the final lens outer diameter are determined by the application and the optical system using the lens in order to satisfy the required optical performance of the lens and the accuracy of mounting on the apparatus. Outside the effective diameter, a lens-shaped extension 11 having a substantially constant width can be provided regardless of the lens diameter. The shape of the lens shape extension portion 11 is defined by a line that extends or substantially extends a curve (or straight line) that defines the optical function surface shapes of the first surface and the second surface in FIG. The lens shape extension is a necessary part for applying a sufficient and substantially uniform load over the entire optical functional surface during press molding. The width of the lens shape extension is preferably 0.2 to 0.4 mm regardless of the lens shape or outer diameter, which is the minimum necessary width. More preferably, it is in the range of 0.25 to 0.35 mm. Note that “width” refers to the width on the projection plane onto a plane perpendicular to the central axis (the same applies hereinafter).

  In the present invention, it is preferable to provide a chamfered portion on the mold as shown in FIG. 2 so that the corners of the mold are not damaged. FIG. 2 is a schematic view of a chamfered portion of a mold that can be used in the production method of the present invention. The chamfering can be performed by a known method. However, if the portion in contact with the chamfered portion during press molding is included in the lens after centering, the portion in contact with the chamfered portion becomes thick, which may hinder lens mounting. On the other hand, if the above-described lens shape extension is provided and press molding is performed so that the portion that contacts the chamfered portion of the mold is included in the lens shape extension, such a problem can be avoided.

  Further, it is preferable to provide a flat portion 12 having a certain width on the outer side of the lens shape extension portion 11. The flat portion 12 is a flat surface or a gentle curved surface that is substantially perpendicular to the central axis of the lens, and is used to smoothly connect the lens shape extension portion 11 to the outer edge portion 13 described later. . Further, if a flat portion 12 as a smooth transfer surface is provided at this position, the ring-shaped position by the flat portion 12 can be confirmed by visually observing the lens after molding (before centering). . By this, before entering the centering process, it is possible to easily find a lens with uneven thickness and exclude it as a defective product before the centering process. Can be avoided. The flat portion 12 may be provided on the first surface, the second surface, or both. Regardless of the shape and outer diameter of the lens to be obtained, the width of the flat portion is preferably 0.2 to 0.4 mm, which is the minimum necessary width. More preferably, it is in the range of 0.25 to 0.35 mm. This is an appropriate width because it is easy to visually confirm the relative position with respect to the outer diameter of the ring-shaped lens.

  Further, the outer edge portion 13 can be provided outside the lens shape extension portion 11 when there is no flat portion 12 and outside the flat portion 12 when there is the flat portion 12. The outer edge portion 13 is a portion that includes a free surface that is solidified without being in contact with the mold during press molding, and defines the press diameter of the lens. This portion can have a width necessary for connecting both the flat portion 12 on the first surface side and the second surface side (or the lens shape extension portion 11 when the flat portion 12 is not provided). This width correlates with the thickness of the lens in that portion, and is preferably 0.25 to 0.35 times the thickness, preferably 0.28 to 0.32 times the width.

  In this way, the shape of the lens shape extension portion 11, the flat portion 12, and the outer edge portion 13 after molding (before centering) can be determined. The volume of the lens shape extension portion 11, the flat portion 12, and the outer edge portion 13 can be calculated as a rotating body by plotting the cross-sectional shape on coordinates.

  On the other hand, the volume of the lens after centering, that is, the lens to be obtained can be obtained from its shape, and specifically, can be calculated by the same method or lens design software as described above. The total volume (or weight) of the calculated lens shape extension part, flat part and outer edge part is added to the volume (or weight) of the lens to be obtained, so that the volume of the molded product before centering (or Weight). In this way, the volume (or weight) before and after centering can be determined. As described above, when precision press molding is performed in the present invention, the weight (or volume) of the portion removed by the centering is in the range of 10 to 55% of the weight (or volume) of the optical element after the centering. Thus, press molding is performed.

On the other hand, in the manufacturing method of the present invention, when the optical element to be obtained has a biconcave shape or a concave meniscus shape, the weight (or volume) of the optical element having a predetermined shape obtained by centering as the molding material is 180. It is characterized by using a molding material having a weight (or volume) within a range of ˜240%. In particular, in the case of a concave meniscus shape, it is 200 to 235%.
If the weight (or volume) of the preformed molding material is less than 180% of the weight (or volume) of the optical element obtained by centering, the lens mounting part cannot be removed sufficiently, or a slight uneven thickness during pressing. Therefore, there is a problem that the surface accuracy is lowered because the optical function surface is insufficient, or the lens cannot be molded by applying an appropriate load over the entire area of the optical function surface. Further, when the weight (or volume) of the preformed molding material is larger than 240% of the weight (or volume) of the optical element obtained by the centering, the material is wasted and the man-hour for centering is increased. The problem arises that productivity deteriorates. Furthermore, an unbalanced press load is applied to the preform, which may cause surface accuracy defects. Furthermore, there arises a problem that waste such as glass powder increases the environmental load.

As described above, the manufacturing method of the present invention is suitable for obtaining an optical element by precision press molding. In the present invention, when an optical element having a biconcave shape or a concave meniscus shape is obtained by precision press molding, it is not necessary to consider the glass weight (or volume) removed by polishing because polishing processing is unnecessary. Therefore, in consideration of the part removed by the centering, the weight (or volume) of the part is in the range of 80 to 140% of the weight (or volume) of the final product (optical element after centering). The press molding may be performed. Hereinafter, this point will be described with reference to FIG. FIG. 3 is a schematic view of a press-formed product including a portion to be removed by centering when a concave meniscus lens is manufactured.
For example, when a concave meniscus lens as shown in FIG. 3 is manufactured, the weight (or volume) of the portion removed by the centering is in the range of 80 to 140% of the weight (or volume) of the final product. In consideration of the above, the shape of the portion can be determined as follows. (In FIG. 3, the shaded portion is the portion removed by centering.)
In FIG. 3 (vertical sectional view of the lens), a lens shape extension 21 is provided outside the surface diameter D2 on the second surface (concave surface) side. This width can be, for example, 0.2 to 0.4 mm. The shape of the lens shape extension portion 21 can be determined in consideration so that a load can be appropriately applied to the optical function surface of the second surface so that contact with a relay portion described later can be appropriately made. preferable. This portion is defined by a line that extends or substantially extends a curve (or straight line) that defines the optical functional surface shape of the second surface. The shape of this portion is preferably a curved surface having an inflection point on the outer periphery (contact point with the relay portion) and having a curvature opposite to that of the optical function surface of the second surface.

  The lens shape extension on the first surface side is defined by a line that extends or substantially extends a curve (or straight line) that defines the optical functional surface of the first surface. This portion is necessary because a sufficient load is applied to the entire area of the optical functional surface during press molding, and is preferably 0.2 to 0.4 mm regardless of the lens shape and lens diameter. More preferably, the width is 0.25 to 0.35 mm.

  A relay portion 24 can be provided outside the lens-shaped extension 21 on the second surface. This part is a communication part with the outer edge part 23 further outside. The relay portion 24 extends with a predetermined curvature, and the tangent line is substantially horizontal outside the surface diameter D1 of the first surface (preferably 0.2 to 0.4 mm outside the point D1), and communicates with the outer edge portion. Is preferred. The preform volume can be controlled by adjusting the shape of the relay portion 24. However, if the volume of the relay portion 24 is excessively small, the curvature on the mold side for transferring the surface becomes tight and the surface processing becomes difficult. On the other hand, if this part is excessively enlarged, the volume of the preform increases, making it difficult to apply an appropriate load over the entire effective diameter in the pressing process, making it difficult to achieve high surface accuracy. become. 0.5-10 mm is preferable and, as for the curvature radius of a relay part, 3-7 mm is more preferable.

  An outer edge portion 23 can be provided outside the relay portion 24. The outer edge portion 23 is a portion that determines the press diameter of the lens, and all or most of the outer edge portion 23 is a free surface depending on the structure of the mold. The width of the outer edge portion 23 is preferably 0.25 to 0.35 times, preferably 0.28 to 0.32 times the thickness of the portion in contact with the relay portion.

  In the case of a concave meniscus lens as shown in FIG. 3, it is useful to form the flat portion described above. In FIG. 3, the aspect which provided the flat part 22 in the 1st surface side is shown. The width of this portion is preferably set to 0.25 to 0.35 mm as in the biconvex lens described above.

In the production method of the present invention, a nozzle is formed by hot forming, that is, molten glass (glass heated to a high temperature so as to have an appropriate viscosity, or glass adjusted to have a proper viscosity from a molten state). It is preferable to perform preforming of the molding material by dropping or flowing down a predetermined amount from and cooling in an appropriate holding state.
In precision press molding, the surface of the preform is often deformed and becomes a part of the surface of the optical element, which is the final product. However, by hot forming, it is possible to produce a preform having no defects near the surface, and therefore it is possible to provide high-quality optical elements with high productivity by precision press molding. In particular, in the present invention, if the molten glass dropped or flown from the nozzle is floated by an air flow and cooled in a substantially non-contact state with the floating jig, the entire surface is formed by solidification of the molten glass. A molding material consisting of a free surface can be obtained. Moreover, at the time of cooling, it is preferable to solidify at a selected cooling rate while floating on the gas. By doing in this way, the preform without a surface defect can be obtained.

  According to such hot forming, a high-quality glass preform can be preformed from various types of optical glass. However, the difficulty of preforming differs depending on the type of glass. For example, depending on the composition, the glass type having a low viscosity at high temperature, or the wettability to the nozzle when dripping (or flowing down) molten glass is large. For glass types that have glass types and low viscosity at high temperatures and glass types that have high wettability to the nozzle, the weight range in which preforming can be performed with high weight accuracy tends to be narrow. In the case of an optical element that performs centering processing, the weight accuracy of the preform is preferably ± 2% or less.

As described above, the weight (or volume) of a preform that can be preformed by hot forming has an upper limit and a lower limit depending on the type of glass and the shape of the molding material to be obtained. Therefore, in the production method of the present invention, the type of glass to be used is determined based on the optical performance of the optical element to be obtained, and the weight of the preform that can be preformed by hot forming (or the type of glass) It is preferable to determine the weight (or volume) of the preform so that the volume is within the range.
The weight (or volume) range of the preform that can be preformed by hot forming can be predicted from the liquidus temperature of the glass and the viscosity at that temperature. However, because some glass types may cause striae even within the weight (or volume) range predicted by the liquidus temperature and viscosity, the exact upper and lower limits are actually formed. This is preferably confirmed.

  The production method of the present invention is effective for obtaining an optical element having a high refractive index, and the molding material used in the production method of the present invention preferably has a refractive index (nd) of 1.7 or more. However, a glass having a refractive index (nd) of 1.7 or more contains a considerable amount of a high refractive index component (for example, Ti, W, Nb, or Zr), so that the viscosity at the time of melting tends to decrease. In addition, striae are likely to occur during hot forming, and the stability of the glass is low, so that the formable region is narrow. In the production method of the present invention, when a molding material having a refractive index (nd) of 1.7 or more is used, striae is generated if the preform has a weight in the range of 10 to 8000 mg, preferably 100 to 8000 mg. Therefore, the preforming can be performed with high weight accuracy. In addition, when a molding material having a refractive index (nd) of 1.8 or more is used, if the preform has a weight in the range of 100 to 7000 mg, the preform can be preformed with high weight accuracy. The weight range that can be preformed is also affected by the shape of the molding material, and the moldable range of the biconvex curved glass preform tends to shift to the larger side compared to the spherical glass preform. There is. The spherical glass preform has a weight in the range of 10 to 1000 mg, and the biconvex curved glass preform has a weight in the range of 50 to 10000 mg, more preferably 100 to 8000 mg.

  The molding material used in the production method of the present invention can be made of phosphate glass (here, the main skeleton component is phosphoric acid; the same applies hereinafter). Phosphate glass has high wettability with nozzles that drop (or flow down) molten glass, so it is formed by hot forming compared to glass such as borate glass, silicate glass, and borosilicate glass. It is often difficult to preform the material. In the case of using a molding material made of phosphate glass, if the preform has a weight in the range of 100 to 8000 mg, it can be preformed with high weight accuracy. When using phosphate glass, it is preferable that the spherical glass preform has a weight in the range of 100 to 1000 mg, and the biconvex curved glass preform has a weight in the range of 150 to 8000 mg. Furthermore, when using high refractive index glass whose nd is 1.7 or more with phosphate glass, it is preferable to set it as the range of 100-4000 mg.

  In the production method of the present invention, a molding material made of borate glass, silicate glass, or borosilicate glass can also be used. When borate glass, silicate glass, or borosilicate glass is used, the weight of the preform can be in the range of 10 to 10,000 mg. In this case, it is more preferable that the spherical glass preform has a weight in the range of 10 to 1000 mg and the biconvex curved glass preform has a weight in the range of 50 to 10000 mg because the weight accuracy is high.

  In the production method of the present invention, when optical glass having a specific gravity of 4.0 or more is used as a molding material, if the preform has a weight in the range of 50 mg to 8000 mg, more preferably 100 to 7000 mg, the weight accuracy is high. This is preferable because a preform can be produced.

  There is a possibility that the upper limit value and the lower limit value of the weight at which the molding material can be preformed change with the progress of the preform molding technology, and the degree of freedom becomes wide. Further, as described above, when determining the shape of the molding material, it should be noted that the pre-moldable range varies depending on the shape of the glass preform. That is, compared with a spherical glass preform, the moldable range of the biconvex curved glass preform tends to shift to a larger weight. Therefore, for example, when a glass preform of 1000 mg or more is used, it is preferable to select a biconvex curved surface shape.

  In the production method of the present invention, the molding step of press molding the preformed molding material in a heat-softened state can be performed by a known method. In the present invention, the shape of the portion to be removed by centering is determined in advance by the method described above, and then a molding die corresponding to the shape is produced, and press molding is performed using the molding die. Is preferred.

  In the production method of the present invention, the centering step of obtaining an optical element by centering from the obtained press-molded product can also be performed by a known method. In the present invention, the centering process can be minimized. Specifically, the machining allowance (grinding amount) of the centering can be reduced, and the centering processing time can be shortened. That is, according to the manufacturing method of the present invention, it is possible to manufacture a press-molded product having a minimum machining allowance in which the press-molded product does not have a weight (or volume) deficiency, or a lens thickness does not cause a shortage of the optical function surface.

The present invention also relates to the following method.
The molten glass is dropped or flown from the nozzle, the molten glass is cooled, the molding material is preformed, the preformed molding material is press-molded in a heat-softened state, and then the obtained press-molded product is obtained. In the method for manufacturing an optical element, including centering and obtaining a biconvex or convex meniscus optical element,
A method for producing an optical element, wherein the shape of the optical element obtained by the centering is determined according to the following (1) to (3):
(1) Based on the optical performance of the lens to be obtained, determine the type of glass to be used,
(2) Find the weight range or volume range of the molding material that can pre-form that kind of glass,
(3) The shape of the optical element is determined so that the weight or volume of the optical element finally obtained is within the range of 100/110 to 100/155 of the weight or volume within the range.

The present invention further relates to the following methods.
The molten glass is dropped or flown from the nozzle, the molten glass is cooled, the molding material is preformed, the preformed molding material is press-molded in a heat-softened state, and then the obtained press-molded product is obtained. In the method of manufacturing an optical element, including centering and obtaining a biconcave or concave meniscus optical element,
A method for producing an optical element, wherein the shape of the optical element obtained by the centering is determined according to the following (1) to (3):
(1) Based on the optical performance of the lens to be obtained, determine the type of glass to be used,
(2) Find the weight range or volume range of the molding material that can pre-form that kind of glass,
(3) The shape of the optical element is determined so that the weight or volume of the finally obtained optical element falls within the range of 100/180 to 100/240 of the weight or volume within the range.

A more specific method will be described using a glass lens as an example.

When producing a biconvex lens or a convex meniscus lens, first, the type of glass to be used is determined based on the optical performance of the lens to be obtained.
Usually, in order to obtain a lens having a desired optical performance, an appropriate one is selected from various optical glasses. The selection criteria are mainly optical constants (refractive index, dispersion), but other chemical and mechanical durability, coloring degree, etc. may be referred to. In many cases, the selection can be made based on the specifications of the optical apparatus to which the lens is applied.

  Once the type of glass is determined, the weight (or volume) range of the molding material that can be preformed is determined for that type of glass. The weight (or volume) range of the molding material that can be preformed can be predicted from the liquidus temperature and the viscosity of the glass, as described above. However, because some glass types may cause striae even within the weight (or volume) range predicted by the liquidus temperature and viscosity, the exact upper and lower limits are actually formed. This is preferably confirmed. The weight (or volume) range of the molding material that can be preformed varies depending on the shape of the molding material (for example, glass preform) to be preformed. The shape is preferably determined together. The weight (or volume) range of the molding material that can be preformed is preferably obtained in advance for each type of optical glass and each preform shape, and is preferably retained as data.

  The preform shape may be restricted depending on the lens shape to be obtained. For example, when the curvature of the convex surface of the lens to be obtained is larger than the curvature of the convex surface of the preform (the radius of curvature is small), the gas trapped between the preform and the molding surface during press molding is There is a concern that the lens shape may be damaged without being discharged. Accordingly, it is preferable to select the preform shape so that the curvature of the convex surface of the preform is larger than the curvature of the convex surface of the lens. In such a case, it is preferable to select a spherical preform. However, as described above, since the biconvex curved flat sphere shape is easier to pre-form a large preform than the spherical shape, it is preferable to take this point into consideration. Thus, it is preferable to grasp the rough lens shape in consideration of the moldability of the preform before final determination of the lens shape to be obtained.

Once the weight (or volume) range of the molding material that can be preformed for that type of glass is determined, preferably within the range of 100/110 to 100/155 of the weight (or volume) within that weight (or volume) range, preferably Determines the lens shape so that the weight (or volume) of the obtained lens is within the range of 100/110 to 100/140.
By the above operation, the weight (or volume) of the preform is determined so as to be within a range that can be preformed by hot forming, and the centering process can be minimized, and due to uneven thickness. A lens shape having desired optical performance can be determined within a range that does not cause problems such as a lack of optical function.

  In practice, the weight (or volume) range of the molding material that can be preformed is converted into a volume from the specific gravity of the optical glass of that type, and the volume within the range is within the range of 100/110 to 100/155. The final lens shape can be determined by designing the shape of a lens having a desired optical performance so that the volume finally becomes the volume of the lens to be obtained. The determination of the lens shape includes determination of the shapes of the optical functional surfaces of the first surface and the second surface of the lens. This can be performed by a known lens design technique based on the optical constant of the material used and the desired optical performance.

  Based on the determined shape of the optical functional surface, the molding surface shape of the molding die for forming the first surface and the second surface of the optical element is determined, and a molding die having the molding surface of the determined shape is prepared, and the molding is performed. Using a mold, a molding material in a heat-softened state is press-molded, and the obtained molded body is centered and a desired optical element can be obtained.

Also in the case of a biconcave lens or a concave meniscus lens concave lens system ( biconcave or concave meniscus ), the weight (or volume) of the lens to be obtained is 100 of the weight (or volume) within the weight (or volume) range of the preform. / 180 to 100/240, especially in the concave meniscus shape, the same as above except that it is more preferably 100/200 to 100/235.

  When the optical element obtained by the production method of the present invention is a lens (common to biconvex lenses, convex meniscus lenses, biconcave lenses, and concave meniscus lenses), the effective diameter is preferably about 2 mm to 28 mm. If the effective diameter of the lens is within this range, a lens having high surface accuracy can be obtained by precision press molding. Moreover, the effect of this invention can be acquired notably if it is in this range.

  The lens obtained by the present invention may be a spherical lens or an aspheric lens, and preferably has at least one aspheric surface.

The use of the lens obtained by the production method of the present invention is not particularly limited. The lens obtained by the production method of the present invention can be suitably used as a biconvex lens, a convex meniscus lens, or a concave meniscus lens used in an imaging optical device such as a camera (including a digital camera and a VTR camera).
As described above, the glass material is used as the molding material, and the glass lens is used as the optical element, but the present invention is not limited thereto.

Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these embodiments.

[Example 1: Production of biconvex lens]
The shape of the lens finally obtained by centering the press-molded product was a biconvex shape, and press molding of a biconvex lens made of glass E shown in Table 3 was performed in the following procedure.
First, a lens was designed by a known lens design method based on the optical constant of a glass material. Then, the volume of the biconvex lens was calculated by lens design software, and the weight of the glass corresponding to the volume, that is, the weight of the biconvex lens to be obtained was calculated from the specific gravity of the glass material used.
Next, assuming that the weight of the biconvex lens to be obtained is 100, a plurality (seven types) of biconvex in which the weight of the glass preform for obtaining the biconvex lens is 105, 110, 126, 140, 155, 162, 175. A curved glass preform was formed by hot forming.
Next, in a state where each glass preform was heated and softened, the glass preform was pressed with a predetermined load by a mold for forming a convex lens to form a press-molded product. As shown in FIG. 1, the general shape of this press-molded product is a shape having a lens shape extension portion 11, a flat portion 12, and an outer edge portion 13 on the outer periphery of the central portion (lens outer diameter D) that is the final product. However, these weights are different. The molding conditions other than the weight of the glass preform were the same.
Next, in order to remove the internal distortion of the press-formed product and adjust the refractive index, each press-formed product was annealed at a temperature not higher than the glass transition point Tg.
Next, each press-molded product was centered, and the outer edge of the molded product was excised and the center axis was determined. In the centering step, the lens was held by a bell clamp method, and the lens outer peripheral end surface was processed to obtain a lens shape. The centering processing time is 20 seconds / piece. About the obtained seven types of biconvex lenses, the appearance, performance, and centering man-hours were evaluated. The evaluation results are shown in Table 1.

In Table 1, with respect to appearance inspection and performance inspection, those with an incidence of defects of less than 10% are indicated with ◯, those with 10% or more are indicated with ×, and the centering man-hours satisfy the allowable range converted from the manufacturing cost. A thing is indicated by ○, and a thing exceeding the allowable range is indicated by ×.
As can be seen from Table 1, the biconvex lens obtained from the preform having a weight ratio of 105 could not obtain a desired shape due to insufficient volume, and both the appearance inspection and the performance inspection were evaluated as x.
For biconvex lenses obtained from preforms having a weight ratio of 110 to 155, no problem occurred with any of the evaluation items having a defect rate of less than 10%, but the biconvex lenses obtained from weight ratios of 162 and 175 were As a result, asperity failure and eccentricity failure occurred due to uneven thickness, and further, the processing time required for centering exceeded the allowable range, and the performance inspection and the evaluation of the centering man-hours were x.
By the above verification, when the weight of the optical element finally obtained is 100, a biconvex lens having a stable quality can be obtained by using a molding material (glass preform) having a weight within a range of 110 to 155%. It can be said that it can be produced efficiently.

[Example 2: Production of concave meniscus lens]
The shape of the lens finally obtained by centering the press-molded product was a concave meniscus shape, and press molding of a concave meniscus lens made of glass A in Table 3 was performed in the following procedure.
First, a lens was designed by a known lens design method based on the optical constant of a glass material. Then, the volume of the concave meniscus lens was calculated by the lens design software, and the weight of the glass corresponding to the volume, that is, the weight of the concave meniscus lens to be obtained was calculated from the specific gravity of the glass material used, and was 150 mg. It was.
Next, when the weight of the concave meniscus lens to be obtained is 100, a plurality of (seven types) glass preforms for obtaining the concave meniscus lens have a weight of 172, 180, 200, 218, 235, 244, 260. A spherical glass preform was formed by hot forming.
Next, in a state where the respective glass preforms were heated and softened, the glass preforms were pressed with a predetermined load by a concave meniscus forming die to form press-formed products. As shown in FIG. 3, the shape of this press-molded product is as follows: a lens-shaped extension portion 21, a relay portion 24, a flat portion 22, and an outer edge portion 23 following the central portion (lens outer diameter D) that is the final product. However, the glass preforms had different weights. The molding conditions other than the weight of the glass preform were the same.
Next, in order to remove the internal distortion of the press-formed product and adjust the refractive index, each press-formed product was annealed at a temperature not higher than the glass transition point Tg.
Next, centering was performed on each press-formed product. The centering processing time is within 65 seconds / piece.
And the concave meniscus lens of the substantially same shape was produced, and the external appearance, performance, and centering man-hours were evaluated about the obtained seven types of concave meniscus lenses, respectively. The evaluation results are shown in Table 2.

In Table 2, with regard to appearance inspection and performance inspection, those with an incidence of defects of less than 10% are indicated with ◯, those with 10% or more are indicated with ×, and the centering man-hours satisfy the allowable range converted from the manufacturing cost. A thing is indicated by ○, and a thing exceeding the allowable range is indicated by ×.
As can be seen from Table 2, the concave meniscus lens obtained from the preform having a weight ratio of 172 was evaluated as x in both the appearance inspection and the performance inspection.
In addition, with respect to the concave meniscus lens obtained from the preform having a weight ratio of 180 to 240, the defect rate was less than 10% for all the evaluation items, but there was no problem, but it was obtained from the preform having the weight ratio of 244. The concave meniscus lens has a processing time exceeding the allowable range for centering, and the concave meniscus lens obtained from the preform with a weight ratio of 260 has a surface with poor astigmatism and eccentricity due to uneven thickness. Defects occurred at 10% or more, and the evaluation of performance inspection and centering man-hours was x.
From the above verification, when the weight of the optical element finally obtained is 100, a concave meniscus lens having a stable quality can be obtained by using a molding material (glass preform) having a weight in the range of 180 to 240%. It can be said that it can be produced efficiently.

[Example 3: Determination of lens shape]
When the final lens shape is a biconvex shape or a convex meniscus shape, use a glass preform whose weight is in the range of 110 to 155% of the weight of the final product, or finally When the shape of the lens obtained is a biconcave shape or a concave meniscus shape, the appearance shape and optical performance can be obtained by using a glass preform whose weight is in the range of 180 to 240% of the weight of the final product. Based on the knowledge that a desired lens can be obtained with high efficiency and a relatively low centering man-hour, lens weight tolerance range data by material and shape as shown in Table 3 was created.

ガラスＢは、Nb、W、Zrを含有。
ガラスE、Fは、Ti、Nb、Wを含有。

Glass B contains Nb, W, and Zr.
Glasses E and F contain Ti, Nb, and W.

In Table 3, the term “preform weight” indicates the upper and lower limits that can be formed when hot forming a spherical shape and a biconvex curved preform shape (PF shape) using each molding material. A spherical preform can be formed relatively small, and a biconvex curved preform can be formed relatively large.
The term of the lens weight range is appropriate for obtaining a lens with good quality and manufacturing cost based on the above-mentioned knowledge when molding a convex lens or a concave lens from each preform molded by material and shape. The weight range is shown.

For example, when the molding material glass A is selected based on the optical characteristics of the lens to be obtained, and a small convex lens is manufactured from the molding material A, a spherical preform suitable for the small lens can be molded in a range of 50 mg to 1000 mg. It is. This spherical preform is press-molded in a heat-softened state, the press-molded product is centered, and the weight range of the finally obtained convex lens is 32 to 909 mg from Table 3, so this weight range If the lens is designed in this way, the design can be determined without trial and error.
As described in Example 1, when the weight of the biconvex lens (or the convex meniscus lens) is 100, the optimum weight of the preform is in the range of 110 to 155%, so the preform weight is 50 mg. When the lens weight is ˜1000 mg, the lens weight of the desired performance can be obtained if the lens weight is calculated back to 100/155 to 100/110 of the preform weight, that is, the lens weight of the minimum value 32 mg to the maximum value 909 mg. .

In addition, for example, when the molding material glass D is selected based on the optical characteristics of the lens to be obtained, and a relatively large-diameter concave meniscus lens is manufactured from this material, the molding range of a biconvex curved preform is possible. Is 100 mg to 8000 mg. The preform is press-molded in a softened state, the press-molded product is centered, and the weight range of the concave lens finally obtained is 42 to 4450 mg from Table 3. If a lens is designed, the design can be determined without trial and error.
As described in Example 2, when the weight of the concave meniscus lens (or biconcave lens) is 100, the optimal weight of the preform is in the range of 180 to 240%, so the weight of the preform is 100 mg. In the case of ˜8000 mg, the lens weight can be obtained by calculating back the lens weight as long as the preform weight is 100/240 to 100/180, that is, the lens weight of the minimum value 42 mg to the maximum value 4450 mg. .

  The manufacturing method of the present invention can be used to manufacture spherical lenses and aspherical lenses. The lens obtained by the production method of the present invention can be suitably used as a biconvex lens, a convex meniscus lens, or a concave meniscus lens used in an imaging optical device such as a camera (including a digital camera and a VTR camera).

It is the schematic of the press-molded product including the part removed by centering in the case of manufacturing a biconvex lens. It is the schematic of the chamfering part of the shaping | molding die which can be used in the manufacturing method of this invention. It is the schematic of the press molded product including the part removed by centering in the case of manufacturing a concave meniscus lens.

Claims (9)

In a method of manufacturing an optical element, including a molding step of press molding a preformed molding material in a heat-softened state, and a centering step of centering the obtained press-molded product to obtain an optical element of a predetermined shape,
When the optical element to be obtained has a biconvex shape or a convex meniscus shape, a molding material having a weight in the range of 110 to 155% of the weight of the optical element of the predetermined shape is used as the molding material.
When the optical element to be obtained has a biconcave shape or a concave meniscus shape, a molding material having a weight within a range of 180 to 240% of the weight of the optical element having the predetermined shape is used as the molding material. The manufacturing method of an optical element. The method according to claim 1, wherein the preformed molding material is obtained by dropping or flowing molten glass from a nozzle and cooling. The method according to claim 1 or 2, wherein the molding material has a refractive index (nd) of 1.7 or more. The method according to claim 1, wherein the molding material is made of phosphate glass. The method according to claim 3 or 4, wherein the weight of the preformed molding material is in the range of 10 to 8000 mg. The method of claim 5, wherein the preformed molding material has a spherical shape and has a weight in the range of 10 to 1000 mg. The method according to claim 5, wherein the preformed molding material has a biconvex curved shape and a weight in the range of 150 to 8000 mg. The molten glass is dropped or flown from the nozzle, the molten glass is cooled, the molding material is preformed, the preformed molding material is press-molded in a heat-softened state, and then the obtained press-molded product is obtained. In the method for manufacturing an optical element, including centering and obtaining a biconvex or convex meniscus optical element,
A method for producing an optical element, wherein the shape of the optical element obtained by the centering is determined according to the following (1) to (3):
(1) Based on the optical performance of the lens to be obtained, determine the type of glass to be used,
(2) Find the weight range or volume range of the molding material that can pre-form that kind of glass,
(3) The shape of the optical element is determined so that the weight or volume of the optical element finally obtained is within the range of 100/110 to 100/155 of the weight or volume within the range. The molten glass is dropped or flown from the nozzle, the molten glass is cooled, the molding material is preformed, the preformed molding material is press-molded in a heat-softened state, and then the obtained press-molded product is obtained. In the method of manufacturing an optical element, including centering and obtaining a biconcave or concave meniscus optical element,
A method for producing an optical element, wherein the shape of the optical element obtained by the centering is determined according to the following (1) to (3):
(1) Based on the optical performance of the lens to be obtained, determine the type of glass to be used,
(2) Find the weight range or volume range of the molding material that can pre-form that kind of glass,
(3) The shape of the optical element is determined so that the weight or volume of the finally obtained optical element falls within the range of 100/180 to 100/240 of the weight or volume within the range.

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