Method of manufacturing barrel-integrated lens

A method of manufacturing a barrel-integrated lens, in which a molded glass product is molded integrally with a barrel made of metal by means of a molten glass drop molding method, includes inserting an upper cylindrical die into a through opening from a side of a second cylindrical opening, and press molding the molten glass drop by a lower cylindrical die and the upper cylindrical die such that the molten glass drop is pressure welded to a connection opening.

The present U.S. patent application is a U.S. National Phase Application under 35 U.S.C. §371 of International Application PCT/JP2013/053005 filed on Feb. 8, 2013. This application claims a priority under the Paris Convention of Japanese patent application No. 2012-036184 filed on Feb. 22, 2012, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method of manufacturing a barrel-integrated lens.

BACKGROUND ART

An optical component having a molded glass product formed integrally within a barrel is disclosed in Japanese Laid-Open Patent Publication No. 03-265529 (PTD 1) and Japanese Laid-Open Patent Publication No. 08-75973 (PTD 2).

Both of these documents disclose a manufacturing method of preparing a lens material in a spherical shape, heating the lens material within the barrel to a temperature equal to or higher than the softening point, and applying pressure to the lens material for formation of the molded glass product.

CITATION LIST

Patent Documents

SUMMARY OF INVENTION

Technical Problem

In the above-described methods of manufacturing an optical component, the lens material in a spherical shape needs to be prepared in advance. A step of preparing this lens material is a step of preparing a lens as an optical component, thus requiring advanced manufacturing techniques and manufacturing costs.

In addition, the spherical lens material obtained by the above-described manufacturing step further needs to be subjected to a step of arranging the lens material in a prescribed position within the barrel, as well as a heating and forming step. As a result, numerous steps are required for a manufacturing process.

The present invention was made to solve the above-described problems, and an object of the present invention is to provide a method of manufacturing a barrel-integrated lens that can require fewer manufacturing steps.

Solution to Problem

A method of manufacturing a barrel-integrated lens based on the present invention is a method of manufacturing a barrel-integrated lens, in which a molded glass product is molded integrally with a barrel made of metal by means of a molten glass drop molding method, and the molten glass drop molding method is a method of, using a lower die and an upper die, dropping a molten glass drop on the lower die, and then press molding the molten glass drop by the lower die and the upper die.

The lower die includes a lower cylindrical die, the lower cylindrical die having an optical surface for applying pressure to the molten glass drop on its upper end face and extending toward the upper die, and the upper die includes an upper cylindrical die, the upper cylindrical die being opposed to the lower cylindrical die, having an optical surface for applying pressure to the molten glass drop on its lower end face, and extending toward the lower die.

The barrel includes a through opening extending in an axial direction, and the through opening includes a first cylindrical opening positioned close to the lower die, and receiving the lower cylindrical die inserted therein during molding of the molten glass drop, a second cylindrical opening positioned close to the upper die, receiving the upper cylindrical die inserted therein such that a gap is produced in relation to the circumference of the upper cylindrical die during the molding of the molten glass drop, and having a diameter larger than a diameter of the first cylindrical opening, and a connection opening coupling the first cylindrical opening and the second cylindrical opening together.

The method of manufacturing a barrel-integrated lens includes the steps of inserting the lower cylindrical die into the through opening from a side of the first cylindrical opening of the through opening such that an upper end portion of the lower cylindrical die is positioned part way in the axial direction of the first cylindrical opening to expose a portion of an inner circumferential surface of the first cylindrical opening close to the connection opening, dropping a prescribed amount of the molten glass drop from a side of the second cylindrical opening such that the molten glass drop forms a substantially spherical shape by surface tension, starting from an upper end of the first cylindrical opening of the barrel, while not contacting an exposed opening surface of the connection opening, in a region surrounded by the upper end face of the lower cylindrical die and the exposed opening surface of the first cylindrical opening, and inserting the upper cylindrical die into the through opening from the side of the second cylindrical opening, and press molding the molten glass drop by the lower cylindrical die and the upper cylindrical die such that the molten glass drop is pressure welded to the connection opening.

Advantageous Effects of Invention

According to the method of manufacturing a barrel-integrated lens based on the present invention, a method of manufacturing a barrel-integrated lens that can require fewer manufacturing steps can be provided.

DESCRIPTION OF EMBODIMENTS

Embodiments based on the present invention will be described hereinafter with reference to the drawings. When a reference is made to a number, an amount and the like in the description of the embodiments, the scope of the present invention is not necessarily limited to that number, amount and the like unless otherwise specified.

In the description of the embodiments, the same or corresponding components are designated by the same reference numbers and redundant descriptions thereof may not be repeated.

First Embodiment

Referring toFIGS. 1 to 3, a method of manufacturing a barrel-integrated lens in this embodiment will be described below.FIG. 1is a flowchart of the method of manufacturing a barrel-integrated lens in this embodiment, andFIGS. 2 and 3are schematic diagrams of a manufacturing flow using an apparatus of manufacturing the barrel-integrated lens.FIG. 2shows a state in a step (S104) of dropping a molten glass drop on a lower die, andFIG. 3shows a state in a step (S106) of pressing the dropped molten glass drop by the lower die and an upper die.

The apparatus of manufacturing a molded glass product shown inFIGS. 2 and 3includes a lower die10and an upper die20as a molding die for pressing a molten glass drop50.

Upper die20includes a base material22, which has an upper cylindrical die23being opposed to a lower cylindrical die12provided on lower die10which will be described later and extending toward lower die10. An optical surface (concave surface)23afor pressing molten glass drop50is formed on a lower end face of this upper cylindrical die23. Upper cylindrical die23has a diameter of from about 1.5 mm to about 4 mm.

A material for base material22can be appropriately selected and used depending on the conditions from among known materials for a molding die for press molding molten glass drop50. Examples of preferred usable materials include various types of heat-resistant alloys (such as stainless steel), superhard materials mainly composed of tungsten carbide, various types of ceramics (such as silicon carbide and silicon nitride), and composite materials containing carbon.

Lower die10includes a base material11, which has lower cylindrical die12being opposed to upper cylindrical die23and extending toward upper die20. An optical surface (concave surface)12afor pressing molten glass drop50is formed on an upper end face of this lower cylindrical die12. Lower cylindrical die12has a diameter of from about 1 mm to about 3 mm.

A material for base material11of lower die10may be appropriately selected and used from among materials similar to those for base material22of upper die20. The material for base material11of lower die10and the material for base material22of upper die20may be the same as or different from each other.

Lower die10and upper die20are constructed such that they can be heated to prescribed temperatures by not-shown heating means, respectively. Known heating means can be appropriately selected and used as the heating means. Examples of the heating means include a cartridge heater which is embedded in lower die10and upper die20for use, a sheet-like heater which is contacted with the outer side for use, an infrared heating device, and a high-frequency induction heating device. It is more preferable that lower die10and upper die20be constructed such that their temperatures can be controlled independently of each other.

Lower die10is constructed to be able to move along a guide65(direction of an arrow S inFIGS. 2 and 3) by not-shown driving means, between a position for receiving molten glass drop50(drop position P1) and a position for press molding molten glass drop50opposite to upper die20(pressure application position P2).

Upper die20is constructed to be able to move in a direction to press molten glass drop50(vertical direction (direction of an arrow F) inFIGS. 2 and 3) by not-shown driving means. While only upper die20is described as moving in the pressing direction in this example, this is not restrictive. Lower die10may be constructed to move in the pressing direction, or lower die10and upper die20may both be constructed to move in the pressing direction.

Arranged above drop position P1is a drop nozzle63for dropping molten glass drop50. Drop nozzle63is connected to the bottom of a melting tank62storing a molten glass61, and constructed to drop molten glass drop50from its tip portion when heated by not-shown heating means.

Referring now toFIGS. 4 and 5, the structure of a barrel100used in this embodiment will be described.FIG. 4is a plan view of barrel100used in this embodiment, andFIG. 5is a cross-sectional view of barrel100used in this embodiment, taken along line V-V in a direction of arrows inFIG. 4.

This barrel100has a cylindrical shape, and includes a through opening110extending in the direction of an axis A. Barrel100has a height of from about 3 mm to about 5 mm, and an outside diameter of from about 3 mm to about 6 mm.

Through opening110includes a first cylindrical opening101, a second cylindrical opening102, and a connection opening103. First cylindrical opening101is positioned close to lower die10, and receives lower cylindrical die12inserted therein during the molding of molten glass drop50. Second cylindrical opening102is positioned close to upper die20, receives upper cylindrical die23inserted therein such that a gap is produced in relation to the circumference of upper cylindrical die23during the molding of molten glass drop50, and has a diameter (inside diameter; φD2inFIG. 4) larger than a diameter (inside diameter; φD1inFIG. 4) of first cylindrical opening101. Connection opening103couples first cylindrical opening101and second cylindrical opening102together.

In this embodiment, as connection opening103, a tapered surface having a diameter (inside diameter) that increases from first cylindrical opening101toward second cylindrical opening102is formed.

In this embodiment, first cylindrical opening101has a length of about 1.0 mm, second cylindrical opening102has a length of about 2.5 mm, and connection opening103has a length of about 0.5 mm, in the axial direction.

The same material as that for base material11and base material22can be used as a material for barrel100. Examples of preferred materials include a material having a thermal expansion coefficient close to a thermal expansion coefficient (about 11.3×10−6) of molten glass drop50. For example, austenitic stainless steel (e.g., SUS430 (thermal expansion coefficient: 10.4×10−6)), or ferritic stainless steel (e.g., Shimomura Tokushu Seiko Co., Ltd., product name: SF20T (thermal expansion coefficient: 11.0×10−6)) may be used.

A method of manufacturing the barrel-integrated lens will be described below according to the flowchart shown inFIG. 1and with reference toFIGS. 6 to 9as appropriate.FIG. 6is a cross-sectional view showing a state where a molten glass drop has been dropped, in the method of manufacturing a barrel-integrated lens of this embodiment,FIG. 7is a cross-sectional view showing a state where pressure is being applied to the molten glass drop, in the method of manufacturing a barrel-integrated lens of this embodiment,FIG. 8is a cross-sectional view of the barrel-integrated lens manufactured by the method of manufacturing a barrel-integrated lens of this first embodiment, andFIG. 9shows relation between a time elapsed since the dropping of the molten glass drop and temperature variations of the molten glass drop and the barrel.

First, as shown inFIG. 6, barrel100is supplied on lower die10(step S101). With barrel100being placed on lower die10, lower cylindrical die12is inserted into through opening110. With lower cylindrical die12being inserted into through opening110, an upper end portion of lower cylindrical die12is positioned in a substantially middle portion in the axial direction of first cylindrical opening101of barrel100, to expose a portion of an inner circumferential surface of first cylindrical opening101close to connection opening103. Next, barrel100is heated to a prescribed temperature by heat transferred from lower die10which is controlled to have the prescribed temperature in advance (step S102). In order to prevent the occurrence of axial deviation due to the gap produced between lower cylindrical die12and first cylindrical opening101, a guide member may be provided for positioning barrel100in relation to lower cylindrical die12.

The prescribed temperature may be selected appropriately to ensure that a satisfactory transfer surface (optical surface) can be formed on the molded glass product by press molding. If the temperature of lower die10, upper die20and barrel100is too low, the molded glass product tends to have large wrinkles, and the shape accuracy of the transfer surface may be lowered. Conversely, if the temperature is higher than necessary, lower die10, upper die20and barrel100bend to be fused with the molded glass product, thus shortening the lives of lower die10, upper die20and barrel100.

Since the appropriate temperature actually varies depending on various conditions such as the type, shape and size of the glass, as well as the materials and sizes of lower die10, upper die20and barrel100, it is preferable to experimentally obtain the appropriate temperature. Usually, if glass to be used has a glass transition temperature Tg, the temperature is preferably set in a range from about Tg−100° C. to about Tg+100° C. The heating temperatures of lower die10, upper die20and barrel100may be the same as or different from one another.

Next, lower die10and barrel100are moved to drop position P1(step S103), and molten glass drop50is dropped from drop nozzle63(step S104) (seeFIG. 2). The dropping of molten glass drop50is carried out by heating drop nozzle63connected to melting tank62storing molten glass61to a prescribed temperature. When drop nozzle63is heated to the prescribed temperature, molten glass61stored in melting tank62is supplied to the tip portion of drop nozzle63under its own weight, and retained as a droplet by surface tension. When the molten glass retained at the tip portion of drop nozzle63has a certain mass, the glass is naturally separated from drop nozzle63by gravity and falls down as molten glass drop50.

The mass of molten glass drop50dropped from drop nozzle63can be adjusted by an outside diameter of the tip portion of drop nozzle63and the like. Depending on the type of glass and the like, the molten glass drop of from about 0.1 g to about 2 g can be dropped. Alternatively, the molten glass drop of from 1 mg to 200 mg can be dropped by providing a member, which has a narrow hole of from about 1 mm to about 4 mm in diameter for reducing the size of the molten glass drop, between drop nozzle63and lower die10.

As shown inFIG. 6, in this embodiment, a prescribed amount of molten glass drop50is dropped from the side of second cylindrical opening102. Dropped molten glass drop50forms a substantially spherical shape by surface tension, starting from an upper end of first cylindrical opening101of barrel100(inner circumferential circle which is a border between first cylindrical opening101and connection opening103), while not contacting an inner circumferential surface of connection opening103, in a region surrounded by an upper end face of lower cylindrical die12and the exposed inner circumferential surface of first cylindrical opening101.

Dropped molten glass drop50forms a substantially spherical shape by surface tension starting from the upper end of first cylindrical opening101in this manner because the tapered surface having a diameter (inside diameter) that increases from first cylindrical opening101toward second cylindrical opening102is formed as connection opening103. The presence of connection opening103also makes it easy to obtain a spherical shape coaxial with barrel100starting from the upper end of first cylindrical opening101.

Since dropped molten glass drop50forms a substantially spherical shape by surface tension starting from the upper end of first cylindrical opening101of barrel100as described above, when molten glass drop50is press molded by lower die10and upper die20, molten glass drop50in a spherical shape is pressed, and spread and pressure welded to the portion of connection opening103as shown inFIG. 7. As a result, pressure can be applied readily as compared to an example where the connection opening is not provided, and the molten glass drop is compression bonded to the connection opening, thus increasing bonding strength.

Furthermore, since dropped molten glass drop50forms a substantially spherical shape by surface tension starting from the upper end of first cylindrical opening101, a surface area of dropped molten glass drop50which does not contact the barrel is increased, thus preventing temperature reduction of molten glass drop50caused by the contact with the barrel, as well as the resulting hardening of molten glass drop50. As a result, molten glass drop50is pressurized and spread to connection opening103while maintaining a high temperature and fluidity, thereby obtaining high bonding strength.

The angle of the tapered surface is not particularly limited. In addition, connection opening103does not necessarily need to be the tapered surface having a diameter (inside diameter) that increases from first cylindrical opening101toward second cylindrical opening102as in this embodiment, but may be a radially extending flat surface connecting first cylindrical opening101and second cylindrical opening102together.

The types of usable glass are not particularly limited, and known glass can be selected and used depending on the application. Examples of the usable glass include optical glass such as borosilicate glass, silicate glass, phosphate glass, and lanthanum-based glass. While the glass has a thermal expansion coefficient of about 11.3×10−6as described above, this is not restrictive, and the coefficient may be from about 9 to about 13×10−6.

Next, lower die10is moved to pressure application position P2(step S105), and as shown inFIG. 7, upper die20is moved down to insert upper cylindrical die23into through opening110from the side of second cylindrical opening102of barrel100, and molten glass drop50is press molded by lower cylindrical die12of lower die10and upper cylindrical die23of upper die20such that molten glass drop50is pressure welded to connection opening103(step S106).

Here, in this embodiment, the thermal expansion coefficient of molten glass drop50and the thermal expansion coefficient of barrel100are substantially the same as described above. That the thermal expansion coefficients are substantially the same means that the difference between the thermal expansion coefficients is within 2×10−6.

Accordingly, the step of press molding molten glass drop50by lower cylindrical die12and upper cylindrical die23is performed after a lapse of time during which the temperature of molten glass drop50and the temperature of barrel100reach substantially the same temperature, since the step of dropping molten glass drop50.

As shown inFIG. 9, a difference (TD1) between a glass temperature GT of molten glass drop50and a barrel temperature MT of barrel100immediately after the dropping of molten glass drop50is great. The difference between glass temperature GT and barrel temperature MT of barrel100is a few hundred degrees Celsius. If molten glass drop50is press molded by lower cylindrical die12and upper cylindrical die23while this temperature difference is maintained, a gap tends to be produced between molten glass drop50and barrel100in a process of cooling the dropped molten glass drop, which may result in failure to obtain high joint strength between molten glass drop50and barrel100.

As shown inFIG. 9, as time passes since the dropping of molten glass drop50, glass temperature GT of molten glass drop50decreases sharply soon after the dropping on lower cylindrical die12(heat transfer to lower cylindrical die12and barrel100). On the other hand, the temperature of barrel100increases (heat transfer from molten glass drop50).

When this glass temperature GT and the temperature of barrel100reach appropriate temperatures (substantially the same temperature: approximately the temperature difference indicated by TD2inFIG. 9), molten glass drop50is press molded by lower cylindrical die12and upper cylindrical die23. Accordingly, since molten glass drop50and barrel100have substantially the same thermal expansion coefficient, they shrink at the same ratio in the process of cooling molten glass drop50by press molding.

As a result, between a joint surface of molten glass drop50and a joint surface of barrel100, the joint surfaces are not separated from each other, thereby obtaining high joint strength between molten glass drop50and barrel100.

In this embodiment, the time between the dropping and the start of pressing as shown inFIG. 9is between about three seconds and about four seconds, and the time between the start of pressing (press molding) and the end of pressing is between about two seconds and about three seconds.

When molten glass drop50(molded glass product50after the press molding) is cooled to a prescribed temperature, upper die20is moved up to release the pressure. Depending on the type of the glass, the size and shape of molded glass product50, the required accuracy and the like, it is usually preferable to release the pressure after molten glass drop50has been cooled to a temperature close to Tg of the glass.

A load applied in order to apply pressure to molten glass drop50may be constant at all times, or may be varied with time. The magnitude of the applied load may be set appropriately depending on the size and the like of a molded glass product to be manufactured. Driving means for moving upper die20up and down is not particularly limited, and known driving means such as an air cylinder, a hydraulic cylinder, and an electric cylinder including a servo motor can be selected and used appropriately.

Thereafter, upper die20is moved up and retracted, and a barrel-integrated lens150shown inFIG. 8is collected (step S107), to complete the manufacture of barrel-integrated lens150. If a barrel-integrated lens150is subsequently manufactured, barrel100may be supplied on lower die10again (step S101), followed by the repetition of the subsequent steps.

According to the method of manufacturing a barrel-integrated lens in this embodiment described above, a step of molding a lens optical surface on the molten glass drop and a step of integrating the lens with the barrel can be simultaneously performed. Thus, a method of manufacturing a barrel-integrated lens that can require fewer manufacturing steps can be provided.

Moreover, since molten glass drop50is dropped such that it forms a substantially spherical shape by surface tension, starting from the upper end of first cylindrical opening101of barrel100(inner circumferential circle which is the border between first cylindrical opening101and connection opening103), while not contacting the opening surface of connection opening103, pressure can be applied readily to dropped molten glass drop50, thereby obtaining high joint strength between the pressurized molten glass drop and connection opening103.

Furthermore, since the materials for the molten glass drop and barrel are selected from the viewpoint of thermal expansion coefficient, and the time between the dropping and the start of pressing and the time between the start of pressing and the end of pressing in the pressing step are adjusted, high joint strength can be obtained between the molten glass drop and the barrel.

Second Embodiment

Referring toFIGS. 10 to 14, a method of manufacturing a barrel-integrated lens in this embodiment will be described below. The method of manufacturing a barrel-integrated lens in this embodiment is characterized by a shape of the barrel, and the apparatus and method for manufacturing the barrel-integrated lens are the same as those in the above first embodiment. Accordingly, the structure of a barrel200in this embodiment will be described here in detail.

FIG. 10is a cross-sectional view of barrel200used in this embodiment,FIG. 11is an enlarged cross-sectional view of a region surrounded by XI inFIG. 10,FIG. 12is a cross-sectional view showing a state where a molten glass drop has been dropped, in the method of manufacturing a barrel-integrated lens of this embodiment,FIG. 13is a cross-sectional view showing a state where pressure is being applied to the molten glass drop, in the method of manufacturing a barrel-integrated lens of this embodiment, andFIG. 14is a cross-sectional view of a barrel-integrated lens250manufactured by the method of manufacturing a barrel-integrated lens of this embodiment.

Referring toFIGS. 10 and 11, the structure of barrel200used in this embodiment will be described.FIG. 10corresponds to a cross section taken along line V-V in the direction of arrows inFIG. 4.

This barrel200has a cylindrical shape, and includes a through opening210extending in the direction of axis A. Barrel200has a height of from about 3 mm to about 5 mm, and an outside diameter of from about 3 mm to about 6 mm.

Through opening210includes a first cylindrical opening201, a second cylindrical opening202, and a connection opening203. First cylindrical opening201is positioned close to lower die10, and receives lower cylindrical die12inserted therein during the molding of molten glass drop50. Second cylindrical opening202is positioned close to upper die20, receives upper cylindrical die23inserted therein such that a gap is produced in relation to the circumference of upper cylindrical die23during the molding of molten glass drop50, and has a diameter (inside diameter) larger than a diameter (inside diameter) of first cylindrical opening201. Connection opening203couples first cylindrical opening201and second cylindrical opening202together.

Referring toFIG. 11, in this embodiment, connection opening203includes a tapered surface203aconnected to first cylindrical opening201and having a diameter that increases from first cylindrical opening201toward second cylindrical opening202, and a radially extending flat surface203bconnecting this tapered surface203aand second cylindrical opening202together.

In this embodiment, first cylindrical opening201has a length of about 1.0 mm, second cylindrical opening202has a length of about 2.5 mm, and connection opening203has a length of about 0.5 mm, in the axial direction.

The same material as that for base material11and base material22can be used as a material for barrel200. Examples of preferred materials include a material having a thermal expansion coefficient close to a thermal expansion coefficient (11.3×10−6) of molten glass drop50. For example, austenitic stainless steel (e.g., SUS430 (thermal expansion coefficient: 10.4×10−6)), or ferritic stainless steel (e.g., Shimomura Tokushu Seiko Co., Ltd., product name: SF20T (thermal expansion coefficient: 11.0×10−6)) may be used.

When a barrel-integrated lens is manufactured using barrel200having the above-described structure, as shown inFIG. 12, molten glass drop50forms a substantially spherical shape by surface tension, starting from an upper end of first cylindrical opening201of barrel200(inner circumferential circle which is a border between first cylindrical opening201and connection opening203), while not contacting connection opening203, in a region surrounded by the upper end face of lower cylindrical die12and the exposed inner circumferential surface of first cylindrical opening201, in a manner similar to that of the first embodiment.

Then, as shown inFIG. 13, when molten glass drop50is pressure molded by lower cylindrical die12and upper cylindrical die23, molten glass drop50is spread from tapered surface203atoward flat surface203b.

By providing barrel200with radially extending flat surface203bin this manner, pressure can be applied readily to molten glass drop50during the press molding by lower cylindrical die12and upper cylindrical die23, as compared to the example where the connection opening is formed of only the tapered surface. In addition, as in the first embodiment, the thermal expansion coefficient of molten glass drop50and the thermal expansion coefficient of barrel200are substantially the same, and when glass temperature GT of molten glass drop50and the temperature of barrel100reach appropriate temperatures (substantially the same temperature), molten glass drop50is press molded by lower cylindrical die12and upper cylindrical die23. As a result, in the subsequent cooling step, between a joint surface of molten glass drop50and a joint surface of barrel200, the joint surfaces are not separated from each other, thereby obtaining high joint strength between molten glass drop50and barrel200.

Thereafter, as in the first embodiment, upper die20is moved up and retracted, and barrel-integrated lens250in this embodiment shown inFIG. 14is collected.

According to the method of manufacturing a barrel-integrated lens in this embodiment described above, as in the first embodiment, a step of molding a lens optical surface on the molten glass drop and a step of integrating the lens with the barrel can be simultaneously performed. Thus, a method of manufacturing a barrel-integrated lens that can require fewer manufacturing steps can be provided.

Furthermore, since the materials for the molten glass drop and barrel are selected from the viewpoint of thermal expansion coefficient, and the time between the dropping and the start of pressing and the time between the start of pressing and the end of pressing in the pressing step are adjusted, high joint strength can be obtained between the molten glass drop and the barrel.

Moreover, by providing barrel200with radially extending flat surface203b, high joint strength can be obtained between molten glass drop50and barrel200.

Third Embodiment

Referring toFIGS. 15 to 20, a method of manufacturing a barrel-integrated lens in this embodiment will be described below. The method of manufacturing a barrel-integrated lens in this embodiment is characterized by a shape of the barrel, and the apparatus and method for manufacturing the barrel-integrated lens are the same as those in the above first embodiment. Accordingly, the structure of a barrel300in this embodiment will be described here in detail.

FIG. 15is a cross-sectional view of barrel300used in this embodiment,FIG. 16is an enlarged cross-sectional view of a region surrounded by XVI inFIG. 15,FIG. 17is a cross-sectional view showing a state where a molten glass drop has been dropped, in the method of manufacturing a barrel-integrated lens of this embodiment,FIG. 18is an enlarged cross-sectional view of a region surrounded by XVIII inFIG. 17,FIG. 19is a cross-sectional view showing a state where pressure is being applied to the molten glass drop, in the method of manufacturing a barrel-integrated lens of this embodiment, andFIG. 20is a cross-sectional view of a barrel-integrated lens350manufactured by the method of manufacturing a barrel-integrated lens of this embodiment.

Referring toFIGS. 15 and 16, the structure of barrel300used in this embodiment will be described.FIG. 15corresponds to a cross section taken along line V-V in the direction of arrows inFIG. 4.

This barrel300has a cylindrical shape, and includes a through opening310extending in the direction of axis A. Barrel300has a height of from about 3 mm to about 5 mm, and an outside diameter of from about 3 mm to about 6 mm.

Through opening310includes a first cylindrical opening301, a second cylindrical opening302, and a connection opening303. First cylindrical opening301is positioned close to lower die10, and receives lower cylindrical die12inserted therein during the molding of molten glass drop50. Second cylindrical opening302is positioned close to upper die20, receives upper cylindrical die23inserted therein such that a gap is produced in relation to the circumference of upper cylindrical die23during the molding of molten glass drop50, and has a diameter (inside diameter) larger than a diameter (inside diameter) of first cylindrical opening301. Connection opening303couples first cylindrical opening301and second cylindrical opening302together.

Referring toFIG. 16, in this embodiment, first cylindrical opening301is provided with a radially inwardly projecting convex portion301aat its end portion close to connection opening303. This convex portion301amay be provided annularly on the entire inner circumferential surface of first cylindrical opening301, or may be provided intermittently at a prescribed pitch of arrangement.

In addition, connection opening303includes a sidewall portion303aconnected to convex portion301aand having a diameter (inside diameter) larger than that of first cylindrical opening301and smaller than that of second cylindrical opening302, and a radially extending flat surface303bconnecting this sidewall portion303aand second cylindrical opening302together.

In this embodiment, first cylindrical opening301has a length of about 1.0 mm, second cylindrical opening302has a length of about 2.5 mm, and connection opening303has a length of about 0.5 mm, in the axial direction.

The same material as that for base material11and base material22can be used as a material for barrel300. Examples of preferred materials include a material having a thermal expansion coefficient close to a thermal expansion coefficient (11.3×10−6) of molten glass drop50. For example, austenitic stainless steel (e.g., SUS430 (thermal expansion coefficient: 10.4×10−6)), or ferritic stainless steel (e.g., Shimomura Tokushu Seiko Co., Ltd., product name: SF20T (thermal expansion coefficient: 11.0×10−6)) may be used.

When a barrel-integrated lens is manufactured using barrel300having the above-described structure, as shown inFIG. 17, molten glass drop50forms a substantially spherical shape by surface tension, starting from an upper end of first cylindrical opening301of barrel300(end portion of projection301aclose to connection opening303), while not contacting connection opening303, in a region surrounded by the upper end of lower cylindrical die12and the exposed opening surface of first cylindrical opening301, in a manner similar to that of the first embodiment.

Then, as shown inFIG. 19, when molten glass drop50is pressure molded by lower cylindrical die12and upper cylindrical die23, molten glass drop50is spread toward flat surface303b. Here, convex portion301aprovided on first cylindrical opening301digs into molten glass drop50.

By providing barrel300with radially extending flat surface303bin this manner, pressure can be applied readily to molten glass drop50during the press molding by lower cylindrical die12and upper cylindrical die23. In addition, as in the first embodiment, the thermal expansion coefficient of molten glass drop50and the thermal expansion coefficient of barrel300are substantially the same, and when glass temperature GT of molten glass drop50and the temperature of barrel300reach appropriate temperatures (substantially the same temperature), molten glass drop50is press molded by lower cylindrical die12and upper cylindrical die23. As a result, between a joint surface of molten glass drop50and a joint surface of barrel300, the joint surfaces are not separated from each other in the subsequent cooling step, thereby obtaining high joint strength between molten glass drop50and barrel300.

Furthermore, with convex portion301adigging into molten glass drop50, the pulling resistance of molded glass product50in relation to barrel300can be improved.

Thereafter, as in the first embodiment, upper die20is moved up and retracted, and barrel-integrated lens350in this embodiment shown inFIG. 20is collected.

According to the method of manufacturing a barrel-integrated lens in this embodiment described above, as in the first embodiment, a step of molding a lens optical surface on the molten glass drop and a step of integrating the lens with the barrel can be simultaneously performed. Thus, a method of manufacturing a barrel-integrated lens that can require fewer manufacturing steps can be provided.

Furthermore, since the materials for the molten glass drop and barrel are selected from the viewpoint of thermal expansion coefficient, and the time between the dropping and the start of pressing and the time between the start of pressing and the end of pressing in the pressing step are adjusted, high joint strength can be obtained between the molten glass drop and the barrel.

Moreover, by providing barrel300with radially extending flat surface303band convex portion301awhich is provided on first cylindrical opening301, high joint strength can be obtained between molten glass drop50and barrel300.

While the above embodiments describe using the materials having substantially the same thermal expansion coefficient for molten glass drop50and barrels100,200,300, they are not restrictive. If the thermal expansion coefficient of the barrel is higher than the thermal expansion coefficient of the molten glass drop (the difference between the thermal expansion coefficients being greater than 2×10−6), for example, since the barrel has a shrinkage ratio higher than that of the molded glass product in the cooling step, a structure where the barrel compresses the circumference of the molded glass product can be obtained by adjusting their shrinkage ratios.

Even if the thermal expansion coefficient of the barrel is lower than the thermal expansion coefficient of the molten glass drop (the difference between the thermal expansion coefficients being greater than 2×10−6), a barrel-integrated lens can be manufactured by adjusting their shrinkage ratios. Shrinkage is determined by thermal expansion coefficient×temperature difference. Thus, by appropriately selecting and adjusting the relation between the temperature of the molten glass drop and the temperature of the barrel at the time of press molding by the upper die, the gap produced between the molded glass product and the barrel upon completion of the cooling can be minimized.

The barrel-integrated lens manufactured by the above-described method of manufacturing a barrel-integrated lens can be used as various types of optical elements such as an image pickup lens for a digital camera and the like, an optical pickup lens for a DVD and the like, and a coupling lens for optical communication.

REFERENCE SIGNS LIST