JP2000313627A - Method for molding optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding an optical element, which permits the irregularity of the volume of a supplied optical element material and makes it possible to mold the optical element capable of being faborably built in the barrel tube with a simplified process. SOLUTION: This method for molding an optical element comprises press- molding a thermally softening optical element material, molding the optical function surface of the optical element and simultaneously controlling the outer diameter of the element. Therein, the characteristic comprises forming a radially directed projection 51 at least one portion of the outer peripheral surface 52 of the optical element material 5. It is preferable that an edge portion 103 whose outer diameter is controlled by the projection 51 is molded. It is further preferable that the relation of the following inequality is established between a diameter X at the projection 51 and the inner diameter Y of a mold for controlling the outer diameter. Y(1+Tα2)/(1+Tα1}-0.3<=X<Y (α1: the thermal expansion coefficient of the optical element material, α2: the thermal expansion coefficient of the material of the mold, T: the molding temperature of the optical element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an optical element by heating and softening an optical element material and pressing the material.

[0002]

2. Description of the Related Art As a method of molding an optical element such as a lens, there has been increasing a molding method which does not require a centering operation in a later step. For example, there have been proposed various molding methods and molding devices for optical elements in which an optical element material (preform) is press-molded by a pair of upper and lower molding dies while regulating the outer diameter of the lens by a body mold or an outer diameter mold.

In such a molding method, since the molding portion of the mold forms a closed space, unless the capacity of the optical element material to be supplied is stabilized with high precision, the desired thickness of the lens or the shape of the optical function surface is required. Accuracy cannot be obtained and good optical performance cannot be obtained. Therefore, means for precisely controlling the supply amount of the optical element material is required, and there is a problem that the manufacturing process is complicated and the cost is increased.

[0004] In order to eliminate the need for a centering operation in a post-process and a strict capacitance accuracy of the supplied optical element material,
A method has been proposed in which an optical element is press-molded with a molding die provided with a space capable of accommodating excess optical element material (excess wall) in a part of the molding section.

However, when an optical element manufactured by such a method is incorporated in a lens barrel, it is necessary to provide a space for accommodating excess thickness in the lens barrel, which complicates the lens barrel structure and increases the optical element. There was a risk that the work of assembling the components would be complicated. Further, there is a case where surplus optical element material enters between the molds and causes chipping when the molded optical element is released from the mold.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to produce an optical element which can tolerate variations in the volume of the supplied optical element material and which can be favorably incorporated into a lens barrel by a simplified process. An object of the present invention is to provide a method for molding an optical element.

[0007]

This and other objects are achieved by the present invention which is defined below as (1) to (7).

(1) In a method for molding an optical element, wherein an optical element material which has been heated and softened is molded under pressure to mold an optical functional surface of the optical element and simultaneously regulate an outer diameter, at least a part of an outer peripheral surface of the optical element material A method for molding an optical element, characterized in that a protruding portion that protrudes in the radial direction is formed on the optical element.

(2) The method for molding an optical element according to the above (1), wherein the edge portion whose outer diameter is regulated by the projecting portion is molded.

(3) The optical element according to the above (1) or (2), wherein the projecting portion regulates the outer diameter within a range corresponding to a central angle of 270 ° or more around the optical axis of the optical element. Molding method.

(4) A method according to any one of the above (1) to (3), wherein the relationship of the following formula (I) is established between the thickness d of the edge portion of the optical element and the maximum outer diameter W. Optical element molding method. d ≧ W / 50 (I)

(5) The method according to any one of the above (1) to (4), wherein a relationship represented by the following formula (II) is established between the diameter X at the projecting portion and the inner diameter Y of the mold for regulating the outer diameter. Optical element molding method. {Y (1 + Tα ₂ ) / (1 + Tα ₁ )} − 0.3 ≦ X <Y (II) (α ₁ : coefficient of thermal expansion of optical element material, α ₂ : coefficient of thermal expansion of mold material of mold) , T: molding temperature of optical element)

(6) The method for forming an optical element according to any one of (1) to (5), wherein the protruding portion is formed by grinding.

(7) The method for forming an optical element according to any one of (1) to (6), wherein the optical element material has a tapered portion whose diameter increases toward the projecting portion.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for molding an optical element according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a cross-sectional view showing one embodiment of an optical element material used in the optical element molding method of the present invention.
FIG. 3 and FIG. 3 are longitudinal sectional views showing one example of a molding apparatus used in the optical element molding method of the present invention.

As shown in these figures, the method of molding an optical element according to the present invention comprises press-molding a heat-softened optical element material to form an optical functional surface of the optical element, and at the same time restricting the outer diameter. The optical element material used is characterized in that at least a part of the outer peripheral surface is formed with a protruding portion that protrudes in the radial direction. As described above, by using an optical element material having a shape suitable for press molding, an optical element that does not require strict capacitance accuracy of the optical element material and that can easily perform an assembling operation into a lens barrel and the like. Can be manufactured by a simple process.

Hereinafter, the method for molding an optical element of the present invention will be described in detail. First, the optical element material 5 is transported by the optical element material transporting means (not shown) to the optical element molding apparatus 1 and supplied onto the molding surface 31 of the lower mold 3. The volume of the supplied optical element material 5 is preferably not less than the volume that forms the outer diameter and forms the required effective surface at least in at least a part of the optical element, and is equal to or less than the volume of the perfectly shaped optical element. . The volume of the optical element material 5 can be adjusted by setting dimensions such as an outer diameter dimension, a radius of curvature, and a center thickness of the optical element material 5.

The optical element material 5 has an effective diameter forming portion 50 on the upper surface and the bottom surface, and the outer peripheral surface 52 has a projecting portion 51 having a different diameter and a small diameter portion 54. Effective diameter forming part 5
It is preferable that the diameter at 0, that is, the diameter of the small diameter portion 54 in this embodiment is larger than the effective diameter of the optical element. With such a shape, the optical functional surface can be molded with high precision even if the capacity of the optical element material 5 is slightly varied or the optical element material 5 is supplied at a position eccentric with respect to the molding surface 31. be able to. In particular, when the relationship of the formula (II) is satisfied, the degree of the eccentricity can be reduced even if the optical element material 5 is at an eccentric position. The details will be described later.

When the optical element material 5 is supplied, the movable upper die supporting member 8 moves downward, and approaches so that the upper die 2 does not come into contact with the optical element material 5. An ascending and descending quartz tube 10 is disposed near the movable upper die supporting member 8, and this quartz tube 10 descends as shown in FIG. A surrounding closed space is formed.
In this state, the heater 11 disposed around the quartz tube 10
To heat the entire upper mold 2 and lower mold 3. At this time, it is preferable to introduce an inert gas into the closed space of the quartz tube 10. Thereby, an oxidation reaction or the like of the optical element material 5 and the mold material can be suppressed. Examples of the inert gas to be introduced include a rare gas, a nitrogen gas, and a mixed gas thereof.

The optical element material 5 softens when heated to a temperature higher than the transition point, and expands in diameter due to thermal expansion. Usually, since the optical element material has a larger thermal expansion coefficient than the molding die and the outer diameter mold made of a high hardness material, the outer peripheral surface 5
The difference between each diameter of 2 and the inner diameter of the outer diameter mold 4 is smaller than that before heating. Therefore, for example, even when the optical element material is supplied at a position eccentric to the molding surface 31,
Due to the thermal expansion of the optical element material 5 in the closed cavity, the deviation from the center position on the molding surface 31 can be reduced.

When the thermal expansion of the optical element material 5 is completed, the movable upper die supporting member 8 is further lowered, and the molding surface 21 is adjusted while maintaining a predetermined interval between the dies according to the molding amount. The optical element material 5 is press-formed between and. The heating temperature (molding temperature) of the optical element material 5 is set to a temperature suitable for predetermined molding conditions, and is preferably about 400 to 800 ° C. The pressing pressure is appropriately set depending on the size and number of the optical elements to be molded.
It is preferable to be about 2000 kgf / cm ² .

When the press forming of the optical element material 5 is performed under such conditions, the optical element material 5 is gradually crushed while flowing, and finally reaches the state shown in FIG. In this state, the shapes of the molding surfaces 21 and 31 are transferred to the upper and lower effective diameter molding portions 50 of the optical element material 5, and the optical functional surface of the molded product is formed. The outer peripheral surface 52 is rolled in the radial direction, and comes into contact with the inner peripheral surface of the outer diameter die 4 from the protruding portion 51 to control the outer diameter 103 of the outer diameter die 4.
Is molded.

Further, by using the optical element material 5 having the projections 51 formed thereon, even if the capacity of the optical element material 5 varies, the outer diameter required for assembling into the lens barrel is regulated. Can be molded. For example, when the outer peripheral surface 59 is press-formed using an optical element material having a single diameter as shown in FIG. 9, the supplied optical element material is completely rolled because the outer peripheral surface 59 is uniformly rolled. If the capacity required for forming the optical element is less than the required value, the minimum necessary edge portion cannot be secured, and the optical element may not be able to be incorporated into a lens barrel. On the other hand, when the capacity of the optical element material is excessive, a surplus is generated over almost the entire circumference, and an optical element that is difficult to incorporate into the lens barrel is formed, or the surplus enters the gap of the mold and separates. In some cases, chipping may occur during molding.

Therefore, by using the optical element material 5 having the projections 51 protruding in the radial direction as in the present invention, the optical element material 5 has a capacity necessary for molding a completely shaped optical element. Since the outer diameter is formed from the protruding portion 51 even when the diameter is less than the required value, it is possible to secure the minimum necessary edge portion 103 to be incorporated in the lens barrel. Further, when the optical element material 5 is supplied more than the necessary minimum edge portion 103 can be secured, after the edge portion 103 is formed, the excess is compensated for by the small-diameter portion 54, so that the outer periphery of the optical element is The molding of the optical element can be completed without any excess wall. Therefore, variations in the capacity of the optical element material can be tolerated in a wider range than when the optical element material having no protrusion is used, and the productivity can be greatly improved.

Further, it is preferable that the protrusion 51 regulates the outer diameter within a range corresponding to a central angle of 270 ° or more around the optical axis of the optical element. In the molded optical element, when the range in which the outer diameter is restricted is less than the central angle of about 270 ° in total about the optical axis, when the optical element is inserted into the lens barrel, the outer diameter of the optical element ( In some cases, the maximum amount of axial deviation caused by the clearance between the edge portion and the inner diameter of the lens barrel increases, and the optical accuracy decreases. This will be described in detail with reference to FIG.

FIG. 7 is a diagram showing the relationship between the range in which the outer diameter of the optical element is restricted and the maximum amount of axial deviation. Optical element 10
The case where the cross-sectional shape of 0 and the lens barrel 103 is circular will be described as an example. The outer periphery corresponding to the central angle 90 ° (<PO′Q) from the center point O ′ of the optical element 100 has a straight line PQ.
And the outer diameter is not regulated. The outer diameter of the other outer peripheral portion, that is, the portion corresponding to the central angle of 270 ° is regulated. The dotted line indicates the center point of the lens barrel 103 and the optical element 1
The position of the optical element 103 when the center point coincides with 00 is shown.

In this case, the maximum axial deviation amount S of the optical element 100 in the lens barrel 103 is represented by the distance between the center point O of the lens barrel 103 and the center point O ′ of the optical element 100 shown by a solid line. Is done. Therefore, the maximum axis deviation amount S of the optical element 100 due to the range in which the outer diameter is restricted, that is, the center angle about the optical axis O 'is calculated from the cosine theorem for △ PO'O by the following equation (III). .

[0029] S = 1/2 × (φ 1 cosθ + (φ 1 2 cos 2 θ-φ 1 2 + φ 2 2) 1/2) ··· (III) (φ 1 is the outer diameter of the optical element 100, phi ₂ is the inner diameter of the lens barrel 103, and θ is the angle of <PO'O. Note that φ ₁ = 2r ₁ ,
φ ₂ = 2r ₂ , r ₁ represents the radius of the optical element 100, and r ₂ represents the radius of the lens barrel 103. The central angle 270 of the portion where the outer diameter of the optical element 100 is restricted is 270.
In the case of the range corresponding to °, since <PO′Q = 90 °, θ = １ ／ × (360 ° −90 °) = 135 °.

For example, φ ₁ = 12.00 mm, φ ₂ = 12.
When the distance is 01 mm, from the above equation (III), the maximum axis deviation amount S is 0.007 mm, and sufficient optical axis accuracy can be maintained even when incorporated in a lens barrel. From this,
If the outer diameter of the molded optical element is regulated within a range of a central angle of 270 ° or more with respect to the optical axis of the optical element as a center, sufficient optical axis accuracy can be maintained even when the optical element is mounted on the lens barrel. The maximum axial deviation S decreases as the center angle increases. In addition, the portion whose outer diameter is restricted may be divided and formed on the outer periphery of the optical element, and the total of the respective central angles may be 270 ° or more.

In the optical element 100 to be molded, it is preferable that the relationship represented by the following formula (I) is established between the thickness d of the edge portion 103 and the maximum outer diameter W.

D ≧ W / 50 (I) When d <W / 50, when the optical element is mounted on the lens barrel, rattling or the like may occur and the optical axis accuracy may not be maintained.

Further, it is preferable that the following formula (II) is established between the diameter X of the protrusion 51 of the optical element material 5 and the inner diameter Y of the mold for regulating the outer diameter of the optical element.

{Y (1 + Tα ₂ ) / (1 + Tα ₁ )} − 0.3 ≦ X <Y (II) (α ₁ : coefficient of thermal expansion of optical element material, α ₂ : mold material of mold) Thermal expansion coefficient, T: molding temperature of optical element) By establishing the relationship of equation (II) between X and Y,
For example, even when the optical element material 5 is placed at an eccentric position with respect to the molding surface 31 of the optical element as shown in FIG. 8, as described above, the optical element material 5 is heated in the closed cavity. By the expansion, at least in the protruding portion 51, the deviation from the center position on the molding surface 31 can be reduced, and the edge portion can be easily molded.

Further, by satisfying the relationship of the formula (II), it is possible to more reliably regulate the outer diameter within a range corresponding to a central angle of 270 ° or more around the optical axis O by expansion and press molding by heating. Achieved. Therefore, the optical element can be molded with high accuracy without requiring precise positioning of the optical element material 5 with respect to the molding surface 31, and the manufacturing cost can be reduced.

The protrusion 51 may be provided by any method, for example, grinding, polishing, or the like.
Alternatively, a method of directly forming from molten glass may be mentioned, but grinding is preferred. According to the grinding process, the formation position, the protrusion amount, and the like of the protrusion 51 on the outer peripheral surface 52 can be easily adjusted. Therefore, it is easy to provide the edge portion 103 of the optical element 100 to be formed at a desired position.

The optical element material 5 may be a glass material or a resin material, but more preferably a material containing glass as a main component. Thereby, an optical element having higher accuracy and excellent heat resistance can be molded.

In order to prevent sink marks caused by thermal shrinkage of the optical element material in the cooling process after completion of press molding using the optical element material 5 as described above, and to maintain the surface accuracy of the optical functional surface of the optical element. It is preferable to maintain the pressurized state. After the molding, the quartz tube 10 is raised to open the closed space, and the molded optical element 100 is taken out. The optical element 100 molded in this manner has, on at least a part of the outer peripheral portion thereof, an edge portion 103 whose outer diameter is regulated as shown in FIG. 1, for example.

The molding device used in the present invention may be any device as long as its outer diameter can be regulated. For example, the optical element molding apparatus 1 shown in FIG. 2 and FIG. 3 has a pair of upper and lower molding dies (upper die 2 and lower die 3) and an outer diameter die 4, and heats and softens the optical element material 5. It is configured so that the optical function surface and outer diameter of the optical element can be simultaneously regulated by press molding.

The upper mold 2 and the lower mold 3 have molding surfaces 21 and 31 for molding the optically functional surface of the optical element, respectively. The molding surfaces 21 and 31 have a shape corresponding to the final molding lens surface, and are mirror-finished so that the maximum surface roughness (Rmax) is 0.02 μm or less. The outer diameter of the molding surfaces 21 and 31 is set to be larger than the effective diameter of the optical element 100 by a predetermined amount.

The constituent materials of the upper mold 2 and the lower mold 3 include:
Those made of a high-hardness material are preferable, for example, silicon carbide,
Use of carbides such as silicon nitride, titanium carbide, titanium nitride, and tungsten carbide, tungsten carbide cemented carbide, metals such as molybdenum, tungsten, and tantalum; oxide ceramics such as alumina and zirconia; and nitride ceramics. Can be. Thereby, durability, heat resistance, corrosion resistance, and the like of the optical element molding apparatus 1 can be significantly improved. In addition, galling, one-sided contact, biting, and the like that occur in the sliding portion of the molding die during molding of the optical element can be prevented.

Further, the molding surfaces 21 and 31 have P
It is preferable to provide a protective film made of a noble metal material such as t, Au, and Rh, a ceramic material, or a mixed material containing a noble metal material and a ceramic material. When the protective film is provided, the heat resistance, oxidation resistance, wet resistance, and the like of the molding surface 31 can be improved. The protective film can be provided by, for example, a sputtering method, an ion plating method, a chemical vapor deposition method (CVD), and the like, and its thickness is preferably about 0.1 to 5 μm.

In the vicinity of the molding surface 31 of the lower mold 3, an annular outer diameter mold 4 for regulating the outer diameter of the optical element is mounted. Thereby, the outer diameter of the optical element is regulated, so that the centering step after molding can be omitted, and the manufacturing cost can be reduced. As the constituent material of the outer diameter mold 4, the upper mold 2
And the same material as the constituent material of the lower mold 3.

Further, the upper body mold 62 and the lower body mold 63
Are arranged so that their central axes coincide. Thereby, the center axes of the molding surface 21 and the molding surface 31 can be made coincident, and the axial deviation and inclination between the optical function surfaces of the optical element to be molded are suppressed.

The upper body die 62 and the lower body die 63 are detachably fixed to the movable upper die supporting member 8 and the fixed lower die supporting member 7 by fixing means such as bolts (not shown). The movable upper die supporting member 8 is driven up and down along a central axis by a driving mechanism (not shown). When a plurality of optical elements are molded by one molding apparatus, for example, a spacer 9 for adjusting the thickness of the optical element may be interposed between the lower mold 3 and the fixed lower mold support member 7. More preferred.

FIG. 4 is a cross-sectional view showing a second embodiment of the optical element material used in the optical element molding method of the present invention. In the drawings, the same items as those of the optical element material in FIG. 1 described above are denoted by the same reference numerals, and detailed description thereof will be omitted.

The optical element material 5 shown in FIG.
Protruding portion 5 formed by, for example, grinding near the center of
1 and tapered portions 53 and 55 whose diameter increases toward the protruding portion 51. By providing the tapered portion in this way, when the protrusion 51 and the peripheral portion of the protrusion 51 are rolled to form the edge portion, the amount of deformation becomes excessive, and the optical element is formed after molding by the action of stress due to press molding. Cracking can be avoided. Further, the glass preform does not enter between the molding die and the outer diameter die, and it is possible to prevent the occurrence of chip when the optical element is taken out from the molding die. Further, it is preferable that the relationship of the above formula (II) is established between the diameter X of the protrusion 51 and the inner diameter Y of the mold that regulates the outer diameter, as in the first embodiment.

When the optical element material 5 is press-molded, an edge portion 103 having a restricted outer diameter is formed substantially at the center of the outer periphery of the optical element as shown in FIG. Furthermore, the first
As in the case of the embodiment, the protrusion 51 is
It is preferable to regulate the outer diameter in a range corresponding to a central angle of 270 ° or more with respect to the optical axis of the optical element 100 in total, as described above between the thickness d of the edge portion 103 of the optical element 100 and the maximum outer diameter W. It is preferable that the relationship of the formula (I) is satisfied.

FIG. 5 is a sectional view showing a third embodiment of the optical element material used in the optical element molding method of the present invention. The optical element material 5 shown in FIG. 5 has a protruding portion 51 formed by, for example, a grinding process on an outer peripheral surface 52 near one effective diameter forming portion 50, and goes from the other effective diameter forming portion 50 to the protruding portion 51. A tapered portion 57 whose diameter increases is formed. Further, between the diameter X of the protruding portion 51 and the inner diameter Y of the mold that regulates the outer diameter, as in the case of the first embodiment,
It is preferable that the relationship of the above formula (II) is satisfied.

When the optical element material 5 is press-molded, an edge portion 103 having a restricted outer diameter is formed as shown in FIG. Further, similarly to the case of the first embodiment, the projection 51 has a total central angle of 2 around the optical axis of the optical element 100.
It is preferable that the outer diameter is restricted within a range of 70 ° or more, and the relationship of the formula (I) is established between the thickness d of the edge portion 103 of the optical element 100 and the maximum outer diameter W as described above. Is preferred.

FIG. 6 is a cross-sectional view showing a fourth embodiment of the optical element material used in the optical element molding method of the present invention. The optical element material 5 shown in FIG. 6 has a protruding portion 51 formed by, for example, grinding near the center of an outer peripheral surface 52, and has small diameter portions 54a and 54b on both sides thereof.

It is preferable that the relationship of the above-mentioned formula (II) is established between the diameter X of the protrusion 51 and the inner diameter Y of the mold for regulating the outer diameter, as in the first embodiment.
The small diameter portions 54a and 54b may have the same diameter or different diameters. When the optical element material 5 is press-molded, an edge portion 103 having a restricted outer diameter is formed substantially at the center of the outer periphery of the optical element as shown in the figure. As in the case of the first embodiment, it is preferable that the outer diameter of the protruding portion 51 be regulated within a range corresponding to a central angle of 270 ° or more with respect to the optical axis of the optical element 100.
It is preferable that the relationship of the formula (I) be established as described above between the thickness d and the maximum outer diameter W.

The method for molding an optical element according to the present invention has been described above with reference to the illustrated embodiments. However, the present invention is not limited to these, and the optical element material may be formed with a protrusion having the same function. Any shape may be used as long as it is done. When the tapered portion is provided, the inclination may be provided at an arbitrary angle, and the tapered surface may be a curved surface.

Further, the molding die used is not limited to the one whose outer diameter is restricted by the inner peripheral surface of the outer diameter mold 4 as shown in the figure, but the one whose outer diameter is restricted by the inner peripheral surfaces of the body dies 62 and 63. It may be. Further, the optical element molded by the molding method of the present invention is not limited to a convex lens, and includes, for example, a concave lens, an aspherical lens, a cylindrical lens, and the like.

[0055]

Next, specific examples of the present invention will be described. Example 1 Using the optical element material 5 shown in FIG. 1, an optical element (a biconvex lens) was molded by the optical element molding apparatus 1 shown in FIGS. The optical element material 5 (thermal expansion coefficient α ₁ : 94 × 10 ⁻⁷ [deg]) made of optical glass L-BAL35 (manufactured by OHARA CORPORATION) has a diameter X at the protrusion 51.
Was 11.960 mm, the effective diameter of the optical element for molding the small diameter portion 54 was 11.300 mm, 11.300 mm, and the thickness of the projection 51 was 1.0 mm. WC (thermal expansion coefficient α ₂ : 48 × 10 ^-7 [deg]) The outer diameter type 4 has an inner diameter Y of 12.0
00 mm.

From the above values, it was confirmed that when the molding temperature T was 580 ° C., the following formula (II) was satisfied. {Y (1 + Tα ₂ ) / (1 + Tα ₁ )} − 0.3 ≦ X <Y (II) The optical element material 5 (preform) is placed on the molding surface 31 and the molding surface of the upper mold 2 is formed. After lowering the movable upper die supporting member 8 so that the distance between the effective diameter forming portion 50 of the optical element material 5 and the optical element material 5 becomes 0.5 mm, the quartz tube 10 is lowered to form the molding surface 2.
The quartz tube 10 was covered with N ₂ gas atmosphere.

Heating is performed by energizing the heater 11,
The mold temperature was monitored by thermocouple 12. Mold temperature is 580 ° C
, The optical element material 5 softened and thermally expanded, and the diameter of the outer peripheral surface 52 of the optical element material 5 expanded. Assuming that the diameter of the protruding portion after expansion is X ′ and the inner diameter of the outer diameter mold 4 after expansion is Y ′, X ′ = X (1 + Tα ₁ ) = 12.025 [mm], Y ′ = Y (1 + Tα ₂ ) = 12.033 [mm]. Before heating, the difference between the inner diameter Y of the outer diameter mold 4 and the diameter X at the protruding portion 51 was YX = 40 [μm], but the difference between the two due to heating was Y′−X ′ = 8. [μm], which was very small.

Therefore, even if the optical element material 5 is placed at an eccentric position on the molding surface 31 before heating, when heated, the deviation from the center position on the molding surface 31 due to thermal expansion is reduced. I was able to. Further, it was found that by performing the press molding in this state, the edge portion whose outer diameter was regulated was sufficiently formed.

The movable upper die supporting member 8 was further lowered, and press molding of the optical element material 5 was started. At this time, the molding temperature was 580 ° C., and the pressure during molding was 200 kgf / cm ² . The softened optical element material 5 was rolled in the radial direction along the molding surfaces 21 and 31 according to the pressing by the upper and lower molds. After the protruding portion 51 comes into contact with the inner peripheral surface of the outer diameter mold 4, it is further rolled up and down to form an optical element whose outer diameter is restricted as shown in FIGS. 1 and 3.

After press molding, the quartz tube 10 was raised to open the closed space, the movable upper die supporting member 8 was raised, and the formed optical element 100 was taken out. Obtained optical element 1
At 00, the edge portion 103 is provided around the entire circumference of the optical element (central angle 36
0 °). In addition, the thickness d of the edge portion 103 is 1.1 mm, and the maximum outer diameter W is 12 mm, which satisfies the relationship d ≧ W / 50. Therefore, this optical element could be stably held in the lens barrel. . On the other hand, the diameter of the small diameter portion 54 after thermal expansion was 11.362 mm, and did not come into contact with the inner peripheral surface of the outer diameter mold 4 even after press molding.

Example 2 An optical element was produced in the same manner as in Example 1 except that an optical element material (X = 11.960 [mm]) having a shape as shown in FIG. 4 was used. In the obtained optical element 100, the edge portion 103 was formed on the entire circumference (central angle of 360 °) of the optical element. The edge portion 103
Has a thickness d of 0.6 mm, a maximum outer diameter W of 12 mm, and d ≧
The relationship of W / 50 was satisfied.

Example 3 An optical element material (X = 7.970 [mm]) having the shape shown in FIG. 5 was used, and an outer diameter mold 4 having an inner diameter Y of 8.000 [mm] was used. Produced an optical element in the same manner as in Example 1. Obtained optical element 10
In the case of 0, the edge portion 103 is provided around the entire circumference of the optical element (central angle 360
°). The thickness d of the edge portion 103 is equal to 0.
4 mm and the maximum outer diameter W was 8 mm, which satisfied the relationship d ≧ W / 50.

Example 4 An optical element material having a shape as shown in FIG. 6 was used (X = 29.905 [mm]), and the inner diameter Y
An optical element was prepared in the same manner as in Example 1 except that an outer diameter mold 4 having a diameter of 30.000 [mm] was used. Also, considering the engagement portion when incorporating the optical element into the lens barrel, the protrusion 5
1 was 1.1 mm thick. In the obtained optical element 100, the edge portion 103 has the entire circumference of the optical element (central angle 360 °).
Formed. The thickness d of the edge portion 103 is 1.2 m.
m, the maximum outer diameter W was 30 mm, and the relationship of d ≧ W / 50 was satisfied.

Each of the optical elements molded in Examples 1 to 4 was molded into a desired shape, was excellent in dimensional accuracy and molding accuracy of the optical functional surface, and did not require centering in a later step. In addition, since each optical element has an edge formed with a restricted outer diameter with high precision, the optical axis and the outer diameter axis can be easily and precisely incorporated into the lens barrel without eccentricity. Was.

[0065]

As described above, according to the optical element molding method of the present invention, the optical element molded by regulating the outer diameter of the optical element by the outer diameter mold 4 requires a centering step. Therefore, the manufacturing cost can be reduced. In addition, by using an optical element material having a protruding portion protruding in the outer diameter direction on the outer peripheral surface, not only does not require strict capacity accuracy of the optical element material but also strict positioning is required, and the lens outer diameter and lens thickness are not required. An optical element having excellent dimensional accuracy, optical axis accuracy, and transfer accuracy of an optical functional surface can be formed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of an optical element material used in a method for molding an optical element of the present invention.

FIG. 2 is a longitudinal sectional view showing an example of a molding apparatus used in the optical element molding method of the present invention.

FIG. 3 is a longitudinal sectional view showing an example of a molding apparatus used in the optical element molding method of the present invention.

FIG. 4 is a longitudinal sectional view showing a second embodiment of the optical element material used in the optical element forming method of the present invention.

FIG. 5 is a longitudinal sectional view showing a third embodiment of an optical element material used in the optical element molding method of the present invention.

FIG. 6 is a longitudinal sectional view showing a fourth embodiment of an optical element material used in the optical element molding method of the present invention.

FIG. 7 is a diagram illustrating a relationship between a range in which the outer diameter of the optical element is restricted and a maximum axial deviation amount.

FIG. 8 is a diagram illustrating the position of the optical element material on the molding surface and the optical element to be molded.

FIG. 9 is a longitudinal sectional view showing a conventional optical element material.

[Explanation of symbols]

 2 Upper die 21 Molding surface 24 Flange 3 Lower die 31 Molding surface 32 Step part 4 Outer diameter mold 41 Rough surface part 43 Fitting part 5 Optical element material 50 Effective diameter molding part 51 Projection part 52 Outer peripheral surface 54 Small diameter part 53, 55, 57 Tapered portion 59 Outer peripheral surface 62 Upper trunk die 63 Lower trunk die 7 Fixed lower die support member 8 Movable upper die support member 9 Spacer 10 Quartz tube 11 Heater 12 Thermocouple 100 Optical element 103 Edge part

Claims (7)

[Claims] 1. A method of molding an optical element, wherein a heat-softened optical element material is pressure-molded to form an optical functional surface of the optical element and simultaneously regulate an outer diameter. A method for molding an optical element, wherein a protruding portion projecting in a radial direction is formed. 2. The method for forming an optical element according to claim 1, wherein the edge portion whose outer diameter is regulated by the projecting portion is formed. 3. The method of molding an optical element according to claim 1, wherein the protrusion regulates the outer diameter within a range corresponding to a central angle of 270 ° or more with respect to an optical axis of the optical element. 4. The molding of the optical element according to claim 1, wherein a relationship represented by the following formula (I) is established between the thickness d of the edge portion of the optical element and the maximum outer diameter W. Method. d ≧ W / 50 (I) 5. The optical element according to claim 1, wherein a relationship represented by the following expression (II) is established between a diameter X of the projecting portion and an inner diameter Y of the mold that regulates the outer diameter. Molding method. {Y (1 + Tα ₂ ) / (1 + Tα ₁ )} − 0.3 ≦ X <Y (II) (α ₁ : coefficient of thermal expansion of optical element material, α ₂ : coefficient of thermal expansion of mold material of mold) , T: molding temperature of optical element) 6. The method according to claim 1, wherein the protrusion is formed by grinding. 7. The method of molding an optical element according to claim 1, wherein the optical element material has a tapered portion whose diameter increases toward the protruding portion.