JPS63149602A - Glass lens - Google Patents

Abstract

PURPOSE:To loosen the concentration of stress into a border part between the curved part and plane part of a lens and to prevent the generation of cracks by forming a thick part with a specific shape on the border part. CONSTITUTION:The main face of a glass lens 11 obtained by press molding is formed by as plane and projecting curve and the projection curve side consists of a spherical curved part 12, a plane part 13 on the outer edge part and an inclined plane 14 on the border part between both parts 12, 13. An angle betaformed by intersecting the curved face 12 with the contact plane of the inclined face 14 and an angle gamma formed by intersecting the inclined face 14 with the contact plane of the plane 13 are wider than an angle alpha formed by intersecting the curved face 12 with the contact plane of the plane 13. Consequently, the concentration of stress into the border part can be loosened and the border part can be prevented from generating cracks.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a glass lens used, for example, in various optical instruments such as cameras, or for pickup of compact discs.

[Conventional technology]

In recent years, glass lenses have been widely used that are made by directly press-molding glass, eliminating the need for subsequent cold grinding and polishing (for example, Japanese Patent Laid-Open No. 60-171233).
(Japanese Patent Application Laid-open No. 171236/1983).

FIGS. 7 to 9 show examples of molding of this type of glass lens. FIG. 7 shows a state in which the glass softened by the molding process is press-molded, FIG. 8 is a sectional view of the molded glass lens, and FIG. 9 is a plan view.

The softened glass material is supplied to the lower mold 1. There upper mold 2
is lowered and pressed under pressure to form a glass lens 3 in a predetermined shape.
Form into. Next, the upper mold 2 is raised and the glass lens 3 is taken out. By continuously repeating the above operations, a large number of similar glass lenses can be produced.

[Problem that the invention seeks to solve]

The three glass lenses formed in this way have a spherical or aspherical curved surface part 4 that is effective as a lens, and a flat part 5 made of a glass material with an excess of stone located outside of the curved surface part 4. Cracks 6 are likely to occur at the boundary, causing a drop in the optical precision of the lens. This is because the angle formed by the curved surface part 4 and the flat part 5, that is, the angle α where the tangential planes of the two intersect with each other at the boundary between them, is relatively small, and large stress is concentrated in this part during the forming process. it is conceivable that.

[Means for solving problems]

In the present invention, a built-up portion is provided at the boundary between the curved surface portion and the flat portion of the lens. The angle β where the tangential planes of the curved surface part and the fleshy part intersect, and the angle γ where the tangential planes of the built-up part and the flat part intersect, are both made larger than the angle α where the joint surfaces of the curved surface part and the flat part intersect with each other. .

The built-up portion may be either planar or curved.

[Effect]

Since the curved surface part and the built-up part, and the built-up part and the flat part do not form sharp corners, no significant stress concentration occurs.

〔Example〕

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a plan view thereof. In the glass lens 11 of this embodiment, one of the main surfaces is flat and the other is a convex curved surface.

The main surface on the convex curve side has a spherical curved surface part 12 and a flat part 13 constituting the outer edge part υ, and has a sloped surface 14 at the boundary between the two. Note that the curved surface portion 12 may be an aspherical surface.

Such a glass lens is manufactured by using a lower mold 1 made of tungsten carbide (WC) in a molding apparatus as shown in FIG.
A glass material is supplied to 5, and an upper mold 16 also made of tungsten carbide is lowered thereto to form the glass material. The upper mold 16 has a chamfered portion 19 at the boundary between the curved surface processed portion 17 and the flat surface processed portion 18, and this chamfered portion 19 is transferred to the glass lens 11 during pressing to form the sloped surface 14. do.

Here, as shown in FIG. 4, the curved surface portion 12 is
and the angle β at which the tangent planes of the slope surface 14 intersect, and the slope surface 1
The angle γ at which the tangential planes of the curved surface portion 12 and the flat surface portion 13 intersect is larger than that of the curved surface portion 12 and the flat surface portion 13, so that stress concentration is alleviated compared to the conventional example in which the curved surface portion 12 and the flat portion 13 directly intersect.

Note that the dimensions of the glass lens 11 of this embodiment are the outer diameter DI
= 6.5 m, the effective diameter of the curved surface portion 12, that is, the diameter of the effective portion through which light passes, is D 2 = 4.6111
, the radius of curvature of the curved surface portion 12 is R1=3.7 rtrx%
Center wall thickness t1 = 25mm, wall thickness difference t between outer edge and center
2=1.2 as, and the angle θ=30a. In addition, as a glass material, heavy flint optical glass S
F6 (manufactured by HOYA ■; transition temperature: 435°C) was used.

In the case where the built-up part 20 having the sloped surface 14 is not provided, cracks were generated at the boundary between the curved part 12 and the flat part 13, as shown in FIG. 8, but in this example, there were no cracks at all. It did not occur.

Note that the slope θ of the slope surface 14 is not limited to 306. For example, if the radius of curvature of the curved surface portion 12 is very small, the angle θ is made thicker so that the slope surface 14 and the curved portion 1
Increase the angle β with the tangent plane of 2.

The built-up portion 20 is not limited to a planar shape. Fifth
The figure shows a built-up portion 20A having a spherical surface 21 with a radius of curvature R2=1.0. The glass lens 11A of this embodiment has a curved surface portion 12 and a spherical surface 21, and a spherical surface 21 and a flat portion 1.
The angle formed by each tangential plane of No. 3 is the maximum of 180°, and the effect of alleviating stress concentration is the most excellent. Each other dimension is the fourth
It is exactly the same as the figure.

Although the plano-convex lens has been described above, the present invention
Needless to say, it can also be applied to biconvex lenses.

Similarly, the present invention can also be applied to a meniscus-shaped glass lens 11B as shown in FIG. 6, for example. 14B is a slope surface, 20
B indicates a built-up part.

Further, the glass material is not limited to those mentioned above, and any material that is generally used for forming molded lenses may be used.

In addition to tungsten carbide, materials for type 1 15 and 16 include, for example, silicon carbide (StC), zirconium oxide (Zr 02), stainless steel, cermet,
Silicon nitride (StsN4) or the like may be selected as appropriate depending on the glass material to be formed.

〔Effect of the invention〕

According to the present invention, the built-up portion is provided at the boundary between the curved surface portion and the flat portion of the glass lens, and the tangential plane of the curved surface portion and the flat portion and the built-up portion By making the tangential plane intersect with the tangential plane, cracks can be prevented from forming at the upper boundary, and a molded glass lens with high optical precision can be obtained.

[Brief explanation of the drawing]

Figures 1 to 4 are diagrams showing one embodiment of the present invention,
Figure 1 is a cross-sectional view of the glass lens, Figure 2 is a plan view, and Figure 3 is a cross-sectional view of the glass lens.
The figure is a sectional view during molding, FIG. 4 is a sectional view showing the detailed shape, FIGS. 5 and 6 are sectional views showing other embodiments of the present invention, and FIGS. 7 and 8 are conventional A sectional view showing an example, and FIG. 9 are a plan view of the same. 11, 11A, 11B @-@Φ glass lens, 1
2mm@@curved surface part, 13mm@@flat surface part, 20.2OA
. 20B-Fist... Overfilling part.

Claims (1)

[Claims] In a glass lens in which at least one main surface is composed of a curved surface part and a flat part located outside the curved surface part, a built-up part is provided at the boundary between the curved surface part and the flat part, and the curved surface part and the flat part The angle α where both tangent planes of the curved surface part and the flat part intersect at the boundary part, and the angle β and A glass lens characterized in that, at the boundary between the built-up part and the flat part, the angle γ at which the tangent planes of the built-up part and the flat part intersect are both set to be large.