JPH0615414B2 - Lens molding method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens molding method used in a pickup system of an optical device such as a compact disc device.

2. Description of the Related Art FIG. 5 shows the principle of an optical system used for a compact disc or the like. Light P emitted from a laser emission source 51 passes through a cover glass 52 and a condenser lens 53 along an optical axis 0.
The light is incident on the first lens surface 54, travels through the condenser lens 53 as indicated by the arrow, exits the second lens surface, and is condensed on the disk 56. The information reproducing light enters the condenser lens 53 again as phase modulated light and vibration modulated light by the bit surface of the disk 56 and is transmitted to subsequent signal reproducing means. That is, only the lens effective optical path portion 57 of the condenser lens 53 is used as a function necessary for condensing the laser light.

Therefore, the excess portion 58 shown by the hatched portion in the figure is basically unnecessary, but has the shape of FIG. 5 because of the necessity of the reference surface for attachment to the device. However, compact discs, etc., read the signal on the disc surface accurately and at high speed when using equipment, so the condenser lens must be activated at high speed, and the weight of the condenser lens itself can be used to satisfy this purpose. It is necessary to reduce as much as possible. As a glass lens molding apparatus using glass as a lens material, for example, as proposed in Japanese Patent Publication No. 54-38126, a method of pressing a glass lens material heated to a predetermined temperature with a pair of molding dies is used. .

However, the above-mentioned method requires a centering step (grinding operation) for making the lens outer diameter constant after the lens is molded, and in order to reduce the weight of the lens itself, the effective optical path portion of the lens is as much as possible. There is also a method of grinding up to the vicinity, but it requires a large number of man-hours, increases the cost, and is likely to damage the lens surface in the work process, which is not preferable.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention The present invention solves the above-mentioned drawbacks of the prior art, allows a large range of volume variation of the lens material to be supplied, eliminates the need for centering work after lens molding, and reduces the weight. The purpose is to take the molded lens.

Means for Solving the Problems In order to solve the above problems, the lens molding method of the present invention is
At the time of lens molding, by maintaining the relationship that the punch set temperature on the lens surface side with a large lens effective diameter is higher than the punch set temperature on the lens surface side with a smaller lens effective diameter by a predetermined amount, For example, it is possible to obtain a lens having a substantially conical free molding surface in the vicinity of the outer peripheral portion of the effective optical path of the lens, or sharing a free molding surface and a predetermined molding reference outer diameter surface.

Operation The present invention having the above-mentioned configuration can reduce the weight of the molded lens itself, is advantageous for high-speed activation of the laser condenser lens used for the compact disc, and further activates the condenser lens. It is possible to give the pickup flexibility in design. In addition, centering after molding is unnecessary, and it can be directly incorporated in the device side (pickup), and the number of assembling steps can be reduced at the same time.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 are sectional views showing the concept of an apparatus for producing a molded glass lens of the present invention, and FIGS. 3 and 4 are moldings of the present invention shown in the apparatus of FIG. A sectional view of a glass lens is shown. In FIG. 1 and FIG. 2, the upper punch 1 and the lower punch 2 are formed by forming a predetermined metal material into a cylindrical shape and arranged so that their axes are the same, and one end surface of each punch has a punch shaft. A predetermined molded lens surface shape is formed accurately with a shape orthogonal to the center. It has molding die surfaces 11 and 12, and the molding die surface is finished to a predetermined mirror surface.

In the embodiment of the present invention, in order to obtain a convex lens, the mold surface shape is a concave surface, and the molding die surface 11 has a small lens effective diameter.
Is the upper punch 1 and the molding die surface 1 has a large lens effective diameter.
2 was placed as lower punch 2. Due to the shape of the cylindrical sleeve or the like, a plurality of through holes 4 are provided at equal intervals on the side surface of the metallic body die 3, and the inner diameter of the body die 3 slides with the outer diameters of the upper punch 1 and the lower punch 2. As much as possible, it fits nicely,
Manufactured to a specified accuracy. That is, the body mold 3 plays a role of regulating the outer diameter of the glass lens to be molded and the lens thickness of the glass lens when the molding is completed during molding of the glass lens. A through hole 4 for air escape is provided in the body mold 3 so as to be arranged at a predetermined position near the molding die surface 11 on the upper punch 1 side. Further, the upper punch 1 is fixed (not shown) to a mold plate 7 having a heater 6 incorporated therein, and pressurization is performed via the mold plate 7 by means of, for example, air, a hydraulic cylinder, etc. A mechanism (not shown) is pressed against the lens material 5 in the arrow direction. The lower punch 2 is fixed (not shown) to a template 9 having a heater 8 incorporated therein, and the pressing force is received by the template 9.

The lens molding process is as follows. First, a glass lens material 5 is placed in an internal space formed by the upper punch 1, the lower punch 2 and the barrel die 3. In the case of this embodiment, the glass lens material 5 is weighed in a predetermined amount smaller than the internal space volume.

The supplied glass lens material 5 has a spherical shape, which is the punch mold surface 11, 1 for obtaining a predetermined convex lens.
Since both 2 are concave surfaces, when the glass lens material 5 is pressed by the upper and lower punches 1 and 2, the air in the internal space smoothly escapes to the outside through the through hole 4 provided in the body mold 3. This is because. Upper and lower punches 1, which form the molding die
If both the molding die surfaces 11 and 12 of 2 are convex, a simple disk-shaped glass material may be supplied, but in the case of a convex surface on one side like a meniscus lens and a convex surface on the die side, as in this embodiment. It is desirable to supply a spherical glass material.

When the glass lens material 5 placed on the lower punch 2 reaches a predetermined softening temperature, the upper punch 1 is pressed in the direction of the arrow until the flange portion of the upper punch 1 contacts the upper end surface of the barrel die 3. Press. After a predetermined time, the heater 6
8 is turned off, and the molded glass lens is cooled and fixed to a predetermined temperature.

FIG. 2 is a cross-sectional view of a main part showing a glass lens after molding,
The temperature of the upper punch 1 is 500 ° C and the temperature of the lower punch 2 is 52 ° C.
0 ℃, pressure 20kgf, glass lens material 5 is SF-6
Glass lens molding was performed using (lead glass). By contacting the upper punch 1 with the upper end surface of the barrel die 3, the desired lens thickness and the desired lens 31 shape shown in FIG. 3 are obtained. That is, the temperature of the upper punch 1 is equal to that of the lower punch 2
The temperature is lower by a predetermined temperature, so that the glass lens material 5 has a predetermined heat transfer from the lower punch 2 side than that on the upper punch 1 side. This means that the amount of deformation of the glass lens material on the side of the lower punch 2 is larger than the amount of deformation on the side of the upper punch 1, and the formed lens shape is generally a truncated cone shape. By forming this conical shape as desired, the molded glass lens 31 has a molding free surface 32 substantially along the effective optical path shown by the alternate long and short dash line in FIG. The weight can be reduced.

FIG. 4 shows that the upper punch 1 has a temperature of 500 ° C. and the lower punch 2 has a temperature of 530 ° C.
A molded glass lens 41 obtained by further providing a temperature difference between them, that is, a molding free surface 42,
Moreover, the weight shared in the state of being connected to the molding reference outer diameter surface 43 parallel to the optical axis is similar, and a molded glass lens which can be easily attached to a device can be obtained.

In the present embodiment, the glass lens material having a spherical shape has been described, but the glass lens material 61 having the shape shown in FIG. 6 may be supplied. Further, it goes without saying that a plastic material such as acrylic, polycarbonate, etc. other than glass may be used as the lens material, and the lens shape forming means may be any means other than the press molding. .

EFFECTS OF THE INVENTION The molded glass lens obtained by the above configuration can reduce the weight of the lens itself, and is also suitable for high speed actuation of a laser focusing lens used for a compact disc. Further, the degree of freedom in designing the device side (pickup) for performing the actuation is larger than that of the lens having the conventional shape, so that a compact disc device having good performance can be obtained.

[Brief description of drawings]

1 and 2 are cross-sectional views of a principal part showing an apparatus for producing a molded glass lens in one embodiment of the present invention, FIGS. 3 and 4 are cross-sectional views of a molded glass lens obtained by the present invention, FIG. 5 is a cross-sectional view of an essential part for explaining the principle of an optical system used for a compact disc or the like, and FIG. 6 is a cross-sectional view of a glass lens material for explaining another embodiment. 1, 2 ... Punch, 3 ... Body type, 4 ... Through hole, 5 ...
Glass lens material, 6, 8 ... Heater, 7, 9 ...
... Mold plate, 32 ... molding free surface, 43 ... molding reference outer diameter surface, 58 ... surplus portion.

Claims (3)

[Claims] 1. A lens molding method for heating a lens material to a predetermined temperature and press-molding it into a desired lens shape by using a barrel die and an upper punch and a lower punch fitted to the barrel die. The lens forming method, wherein the set temperature of the lower punch is set to be higher than the set temperature of 1. by a predetermined temperature to obtain a lens having a predetermined shape. 2. The lens molding method according to claim 1, wherein the temperature difference between the upper punch and the lower punch is 10 ° C. or more. 3. A lens effective diameter having a first surface and a second lens effective diameter.
The lens forming method according to claim 1, wherein the lens forming method has an outer peripheral surface such that a substantially conical shape is formed in the vicinity of the lens effective optical path connecting the lens effective diameter of the surface.