JPH04330403A - Glass optical element - Google Patents

Abstract

PURPOSE:To eliminate offcentering and to enhance centering accuracy as well as to facilitate alignment by press-forming a lens to have annular grooves or projections on the outside of the effective diameter of the lens on both surfaces of the lens. CONSTITUTION:This glass optical element is formed by press forming the lens 1 so as to have the annular grooves 2 on both surfaces on the outside of the effective diameter of the lens. A softened glass cob 5 is inserted between a punch 3 and die 4 for lens molding having the annular projections (grooves are equally well but the projections are typical and most effective) 6 and is press-formed. The optical element 1 is fixed by applying plural supporting rods 10 to the positions corresponding to the optical axis of the annular grooves 2 for this purpose, by which the optical element is surely fixed. Then, the center misalignment is prevented at the time of centering the element by pressing the side faces thereof to a cutter 11 having the plane parallel to the optical axis and rotating the optical element together with the supporting rods.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass optical element obtained by press molding.

0002

2. Description of the Related Art In lens precision machining, eccentricity (tilt eccentricity and parallel eccentricity) and centering accuracy are always important issues. Many techniques have been proposed in the past as techniques for obtaining precisely centered lenses without eccentricity. For example, JP-A-63-60114, JP-A-63-297233, JP-A-1-126232, JP-A-1-183611, JP-A-1-18
Publication No. 3612 discloses a technique relating to a mold having eccentricity, centering, a surface serving as an assembly reference, or a jig thereof, and an optical element obtained from the mold. There is no mention of how to achieve them.

Correction of eccentricity has conventionally been carried out through repeated trial and error of making a lens, making corrections, and making and making corrections, but this operation is extremely complicated.

0004

SUMMARY OF THE INVENTION An object of the present invention is to obtain an optical lens that is free from eccentricity and has high centering accuracy through simple operations.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a press-molded glass optical element having ring-shaped grooves or protrusions on both sides of the lens outside the effective diameter of the lens, and a method for manufacturing the same. The optical element (1) of the present invention is shown in FIG. (2) shows a ring-shaped groove.

In order to obtain the glass optical element of the present invention, a softened glass gob (5) is formed into a ring-shaped protrusion (5) as shown in FIG.
6) Lens molding upper mold (3) and lower mold (4) having (grooves may be used, but protrusions are typical and most effective, so the protrusions will be explained below) (there is no need to particularly distinguish between the two) (hereinafter simply referred to as a mold) and press-forming. At this time, the temperature of the glass gob (5) should be above the softening point of the glass, but if the temperature is too high, it will take time to cool down in the mold, or there will be distortion due to shrinkage or shrinkage due to the temperature difference with the mold. Alternatively, since the formation of navels is to be observed, it is preferable to set the gob surface to a temperature slightly lower than the softening temperature and the inside to a temperature slightly higher than the softening temperature. The temperature is usually about 750 to 500°C, more preferably about 550 to 500°C.

The temperature of the mold is determined by the softening point of the glass.
The temperature is set at 00 to 450°C, more preferably 500 to 450°C. Press molding may be performed by initially raising the temperature of the mold higher than the glass softening temperature and cooling the entire mold to below the softening temperature.

[0008] Molding is preferably carried out in the presence of an inert gas, such as nitrogen gas, and the ambient temperature is slightly higher than the softening temperature of the glass, for example 30-50% of the glass softening point.
It is also possible to set the temperature at a high temperature, correct eccentricity, and then cool and mold. The molding pressure is preferably about 2.0 to 5.0 kg/cm2, particularly about 3 kg/cm2.

Upper mold for molding (3) and lower mold for molding (4)
may have any shape so that the lens functional surface can be formed into a spherical surface, an aspherical surface, or any other freely curved surface.

The upper mold (3) and lower mold (4) are shown in FIG.
As shown in the figure, it is provided so as to be movable in both the horizontal direction (x-axis direction) and the θ direction. This allows correction of parallel eccentricity and tilt eccentricity.

When the upper mold (3) and the lower mold (4) are tilted and eccentric as shown in FIG. 3, the grooves on both surfaces of the optical element are not observed as circles. Therefore, for example, the lower die (4) is controlled so that the groove on one side becomes an accurate circle. When there is tilt eccentricity, the other surface naturally becomes an ellipse, so its long axis,
That is, by measuring the radius a and short axis b of the circle, the amount of tilt eccentricity can be determined using the following equation. θ=cos-1b/a

Therefore, based on this value, for example, the upper type (
3) Alternatively, after correcting the tilt eccentricity by moving the lower die (4) in the θ direction, measure the parallel eccentricity. For example, as shown in Figure 4, a ring-shaped groove (
7) and the ring-shaped groove (8) on the lower surface have a parallel eccentricity by d, eliminate the parallel eccentricity by moving the upper mold (3) or the lower mold (4) in parallel by d. Can be done.

[0013] These observations can be easily carried out visually, but may also be carried out by means such as directly measuring the amount of deviation (numerical value) using a high-magnification microscope.

The accuracy of both the equilibrium eccentricity and the tilt eccentricity can be improved by making the width of the ring-shaped groove of the lens as small as possible and making the tip thereof sharp and shallow.

In order to form such a ring-shaped groove, the material of the mold must have low thermal expansion at the glass softening temperature (molding temperature), be unsusceptible to chemical and physical changes, and have high rigidity and low brittleness. Preferably, the material has the following properties. An example of such a material is stainless steel.

The protrusions provided on the mold may be obtained by cutting the mold surface from both sides as shown in FIG. 6 using an ultra-precision cutting blade (9) as shown in FIG. 5, for example.

[0017] The ring-shaped protrusion (6) provided on the mold is
As shown in FIG. 7, it is preferable to have a triangular shape with a pointed tip; square, circular, or elliptical shapes are not preferable in terms of accuracy. The length of the ring-shaped protrusion is 1.5 to 5
．． 0 μm, more preferably 1.5 to 3.0 μm, and the length of the base of the triangle is 0.5 to 6.0 μm, preferably 1.0 to 3.0 μm, and the apex of the right-angled cross section of the ring-shaped protrusion is Preferably, the angle is between 20° and 60°, particularly between 30° and 50°. If it is smaller than 20°, sufficient strength cannot be obtained,
Furthermore, after the lens is molded, it becomes difficult to remove the lens from the mold. On the other hand, if the angle is larger than 60°, the ring-shaped groove becomes thick, making it difficult to eliminate eccentricity with high precision.

Furthermore, by providing a ring-shaped projection on the mold, it becomes possible to know the position of the optical element with respect to the mold.

Since the optical element of the present invention has a ring-shaped groove on the peripheral edge of the lens, it is possible to reduce variations in centering accuracy and improve the accuracy itself. That is, as shown in FIG. 8, when the optical element (1) is fixed by applying a plurality of support rods (10) to optical axis symmetrical positions of the ring-shaped groove (2), the optical element is firmly fixed. When centering the optical element by applying the side surface to a cutter (11) having a surface parallel to the optical axis and rotating the optical element together with the support rod,
The core never shifts. Therefore, high centering accuracy can be obtained regardless of the shape of the lens, such as a concave lens, a convex lens, or a meniscus lens.

When the optical element of the present invention is assembled into a lens barrel, high assembly accuracy can be achieved by using a ring-shaped groove. For example, as shown in FIG. 9, an optical element (1) is placed in its ring-shaped groove (2), and a plurality of support rods (as shown in FIG.
10) and a lens barrel (13) having protruding teeth (12).
The outer periphery (14) of the ring-shaped groove (2) is fixed to the protruding tooth (12) with adhesive (15), and the fixing member (16) is further inserted into the lens barrel to secure the optical element. to be fixed. In this method, as long as there is surface precision inside the lens barrel, a plurality of optical elements can be assembled quickly and the alignment can be performed accurately.

[0021]

Effects of the Invention The optical element of the present invention can eliminate eccentricity easily and with high precision during molding, can achieve high centering accuracy, and can be easily aligned when assembled.

[Brief explanation of drawings]

[Fig. 1] A cross-sectional view showing an outline of a specific example of the optical element of the present invention

[Figure 2] Schematic cross-sectional view of a glass gob press molding machine

[Figure 3] Schematic cross-sectional view of a tilted and decentered optical element

[Figure 4
] Schematic diagram of a parallel decentered optical element

[Figure 5] Schematic cross-sectional view of ultra-precision cutting blade

[Figure 6] Schematic diagram showing the direction of movement of the ultra-precision cutting blade

[Figure 7] Diagram showing the ring-shaped protrusion of the mold and the ring-shaped groove of the optical element

[Figure 8] Schematic diagram of optical element fixing device

[Figure 9]
Schematic diagram of incorporating optical elements into lens barrel

[Explanation of symbols]

1: Lens 2: Ring-shaped groove 3: Upper mold 4: Lower mold 5: Glass gob 6: Ring-shaped projection 7: Ring-shaped groove on the top surface of the optical element 8: Ring-shaped groove on the bottom surface of the optical element 9: Ultra precision cutting blade 10: Support rod 11: Cutter 12: Protruding teeth 13: Lens barrel 14: Optical element outer periphery 15: Adhesive 16: Lens fixing member

Claims (3)

[Claims] 1. A press-molded glass optical element having ring-shaped grooves or protrusions on both surfaces of the lens outside the effective diameter of the lens. 2. A glass optical element in which the ring-shaped groove is a triangular groove with a depth of 1.5 to 3.0 μm and a maximum width of 1.0 to 3.0 μm. 3. A softened glass gob is sandwiched between upper and lower molds for lens molding, which have ring-shaped projections or grooves in the portions of the lens where the grooves or projections are to be formed;
A method for manufacturing glass optical elements using press molding.