JPH06115955A - Mold for optical element molding and its production - Google Patents

Abstract

PURPOSE:To provide the subject mold enabling optical elements to be furnished at low cost by making conventional marking operations needless. CONSTITUTION:The optically non-functional surface 13 situated on the molding surfaces of a pair of top and bottom molds serving as a mold 11 for optical elements is provided with small recesses 16, 17; the point group at each of the recesses 16, 17 is designed to represent letters, figures or signs and clarify the correlation with optical element. Besides, in cooling operation after molding, shrinkage difference is developed through the parts as nuclei filled in the point group to develop moderate non-point aberration while maintaining the performance of the entire optical element, thus making conventional marking operations needless.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element molding die used for molding a lens or the like used in an optical device (for example, a compact disc) and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, attempts have been made to form optical lenses and the like by one-shot molding without a polishing step, and at present, each company is in the stage of mass production. The most efficient method is to cast the glass material from the molten state into the mold and press it,
It is difficult to control the shrinkage of the glass during cooling, which is not suitable for precise lens molding. Therefore, it is a general method to pre-process a glass material into a certain shape, supply it between molds, and heat and press-mold it (for example, JP-A-58).
-8413 and JP-A-60-200833).

FIG. 4 is a cross-sectional view of a conventional example showing a state in which a lens is formed by molding a cylindrical glass material. Reference numeral 1 is a molded lens, and 2 and 3 are an upper mold and a pair of molding dies. Lower mold 4 is a barrel mold surrounding the molding portion of the upper mold 2 and the lower mold 3, and 5 and 6 are heating plates having heaters 7 and 8 built therein. The upper mold 2 is attached to the lower surface of the heating plate 5. The lower mold 3 is attached to the upper surface of the heating plate 6. Reference numeral 9 denotes a pressurizing mechanism that supports the heating plate 5 to which the upper mold 2 is attached and pressurizes the glass material of the lens 1, which is movable up and down.
A base 10 receives and supports the lower heating plate 6.

Explaining the operation in the above structure, a glass material is supplied to a forming part between the upper mold 2 and the lower mold 3 and is heated by the heating plates 5 and 6 between the upper mold 2 and the lower mold 3. The glass material is pressed and deformed while being heated to a temperature near the softening point of the glass. After the deformation is completed, the molded lens is gradually cooled to reach a temperature at which the lens can be taken out, the upper mold 2 is opened upward, and the lens is taken out to complete the molding.

The lens obtained by such molding is usually
The aberrations (astigmatism, coma, spherical aberration) and the like that the lens has are extremely small, and the level is high.

[0006]

However, as the number of mass-produced molded lenses increases and the number of mold surfaces used increases, even if the performance of a single lens is satisfied, there will be a slight increase in the subsequent steps (the step of assembling the lens into the pickup). There is a problem that defective products occur. For this problem, it is necessary to quickly find out which mold is used to mold the lens to be a defective product in the subsequent process and take countermeasures. Moreover, when assembling a molded lens into an apparatus, in particular, the directionality of astigmatism must be marked for each lens (usually referred to as asmark) for all molded lenses.

The reason is that by accurately arranging the positional relationship between the asmarks of the lens and the signals (pits) formed on the surface of the disk, crosstalk between pits (between pits in the normal direction) and intersymbol interference (pits). This is to reduce the (between pits in the circumferential direction) and improve the performance of the device.

A great deal of labor is required to solve the above-mentioned two problems, which hinders cost reduction and mass productivity of the lens and is not preferable in industry. The present invention solves such a problem, and an object of the present invention is to eliminate the work of asmark which has been conventionally performed and to provide an optical element at low cost.

[0009]

In order to solve this problem, an optical element molding die of the present invention comprises a non-optical functional surface located on the molding surfaces of a pair of upper and lower molds which are optical element molding dies. The gist of the present invention is to provide a small convex portion or a concave portion in the above and express a letter, a number, or a symbol by the point group of the convex portion or the concave portion. The method for producing a mold for optical element molding of the present invention is a step of polishing an optical functional surface and a non-optical functional surface into a predetermined shape and a mirror surface on the molding surfaces of a pair of upper mold and lower mold to be an optical element molding mold. And a step of processing a convex portion or a concave portion in the polished non-optical functional surface into a point group, and a step of simultaneously forming a release film on the optical functional surface and the non-optical functional surface. It is a summary.

[0010]

As described above, the point group of the convex portions or the concave portions provided on the non-optical function surface makes the correlation with the optical element clear, and the portion filled in the point group of the convex portions or the concave portions serves as the core for cooling. Occasionally, a difference in contraction occurs, and by appropriately generating astigmatism while maintaining the performance of the entire optical element, it is possible to eliminate the conventional asmarking work and provide the optical element at a low cost.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, the molding die 11 has the same dimensions as the lower die 3 used in the conventional example, and the shape provided on the molding surface is similar. This molding die 11 comprises an optical functional surface 12 shown by a region A and a non-optical functional surface 13 shown by a region B in the drawing, which constitutes a molding surface on an end surface of a base material made of a cemented carbide having a cylindrical shape. With a non-optical functional surface
Specimen 13 and a mirror surface were polished with a diamond grindstone so that 13 was provided with an inclined portion 14 and a plane portion 15 extended from the optical function surface 12. The molding die 11 has an outer diameter of 5.0 mm and a thickness of 6.0 mm, and has a cylindrical end surface with a dimension A of 3.0 mm and a dimension B of 1.0 mm.
In the region B, the inclined portion 14 is 0.5 mm, the flat portion 15 is 0.5 mm, and the molding surface is processed so as to obtain desired optical performance. Next, the non-optical function surface 13 was processed so that the inclined portions 14 and the flat surface portion 15 had concave portions in a point cloud shape. Since the working area is very small, the work is performed using a microscope. In this example, a commercially available Vickers hardness meter is used to apply a load of 1 gram to a diamond indenter having a quadrangular pyramid tip to process the recess. I did.
The processed concave portion was a concave pyramid, the surface of which was a mirror surface state, and the size thereof was 4 to 5 microns. By controlling the shape of the indenter and the load applied to the indenter, it is possible to process a recess having an arbitrary size and shape within a certain range by using any mold material. However, in reality, when the amount of the recesses is large, the material rises around the recesses, so it is desirable to reduce the amount of the recesses with a light load. In this example, the concave portion was processed into a point group shape on the molding surface, but if it can express other characters, letters, numbers, and symbols, it is not limited to this example, and any other method can be used as long as it matches the gist of the present invention. You may process.

[0012] For example, by using wire bonding technology as seen in the semiconductor process, precision spot welding technology, plating technology, etc., convex portions are attached in a point cloud shape on the molding surface using a metal material having high heat resistance. It is also possible to process.

FIG. 2 shows a state in which the letter "I" is drawn on the molding die 11 under the above-mentioned conditions by forming a square pyramid concave portion 16 in the flat portion 15 into a group of nine points. The size was large enough to be confirmed by a microscope. Further, as a result of drawing similar characters on the inclined portion 14 under similar conditions, the recesses 17 are similarly formed in the character array.

After that, a release film for preventing glass fusion during molding was formed on the entire molding surface provided with the recesses by a sputtering method. The thickness of the film formed was 2 microns, and it was confirmed by a microscope that the film was evenly formed on the surface of the recess.

As a matter of course, when the recesses showing the letters, numbers and symbols are processed, it is preferable to make the letters, numbers or symbols transferred to the molded lens easy to read. Further, in the present embodiment, the recessed portion was processed before forming the release film, but the same effect can be expected even if it is performed after forming the film.

FIG. 3 shows the molding die of the above-mentioned embodiment and SF.
A molded lens obtained by molding at 520 ° C. in the same manner as in the conventional example using a molding glass material made of −8 (lead glass) is shown. The molded lens 18 has convex portions 19 and 20 formed by the concave portions 16 and 17, respectively. As a result of confirming the transferability of the recessed portion in the molded lens 18 and the optical performance, the transferability of the recessed portion 17 provided in the inclined portion 14 was satisfactory for all of the molded lenses. As for the transferability in the concave portion 16 provided in the flat surface portion 15, an untransferred portion occurred in a part. The reason is that a slight amount of glass material changes in weight and a transfer area changes. Therefore,
It is desirable to provide the concave portion 17 in the inclined portion 14 of the non-optical function surface. The reason is, in addition to the above, the flat surface of the molded lens
This is because 15 is often used as a reference surface for mounting on equipment, and it is difficult to use a flat surface with protrusions as a reference surface.

Further, the transmitted wavefront aberration of the molded lens was measured using a Fizeau interferometer. As a result, the flat portion 15
It was confirmed that the transfer of the concave portion 16 provided on the lens had no effect on the performance of the entire lens. However, the transfer of the concave portion 17 provided in the inclined portion 14 is related to the astigmatism of the lens, and it was confirmed that there is a sink mark difference between the extremely close portion of the concave portion and the other portion when contracting. Moreover, the performance of the entire lens was about 0.03λ, which was sufficient for practical use.

[0018]

As described above, according to the present invention, the point group of the convex portion or the concave portion provided on the non-optical functional surface makes the correlation with the optical element clear, and the point group of the convex portion or the concave portion is filled. The difference in shrinkage occurs at the time of cooling with the part that is the core, and the appropriate astigmatism is generated while maintaining the performance of the entire optical element, eliminating the work of asmarking that has been performed in the past and making the optical element inexpensive. Can be provided to.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an optical element molding die according to an embodiment of the present invention.

FIG. 2 is a perspective view of the optical element molding die.

FIG. 3 is a perspective view of a molded lens molded by using the optical element molding die.

FIG. 4 is a vertical sectional view showing a molding state in a conventional example.

[Explanation of symbols]

 11 Molding die 12 Optically functional surface 13 Non-optically functional surface 14 Inclined portion 15 Flat surface portion 16 Recessed portion 17 Recessed portion 18 Molded lens 19 Convex portion 20 Convex portion

Claims (4)

[Claims] 1. A small convex portion or concave portion is provided on a non-optical functional surface located on a molding surface of a pair of an upper mold and a lower mold, which are optical element molding dies, and a letter, a number, or A mold for molding an optical element characterized by expressing a symbol. 2. The optical element molding die according to claim 1, wherein a small convex portion or a concave portion is provided on an inclined portion of the non-optical functional surface. 3. The optical element molding die according to claim 1, wherein the shape of the small convex portion or the concave portion is a conical shape. 4. A step of polishing an optical functional surface and a non-optical functional surface into a predetermined shape and a mirror surface on a molding surface of a pair of upper mold and lower mold which become an optical element molding mold, and the polished non-optical functional surface. Of the optical element molding die, which comprises a step of processing convex portions or concave portions into a point cloud shape, and a step of simultaneously forming a release film on the optical functional surface and the non-optical functional surface. Production method.