JP2002062416A - Method for manufacturing optical device or method for manufacturing device, and optical system, device for photographing and device for observation having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical device having good release property, a method for manufacturing a device, an optical system, a photographing device and an observation device having the above device. SOLUTION: In the method for manufacturing an optical device including a step of forming a pattern having ridge lines on a raw material by using a die, the raw material is softened and then the raw material in the softened state is pressurized to such a degree that the raw material does not intrude into the deepest part of the die corresponding to the ridge line so as to form the pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical element or a method for manufacturing an element, an optical system having these elements, a photographing apparatus, and an observation apparatus. The present invention relates to a method for manufacturing a diffractive optical element or the like including a step of transferring a fine diffraction grating pattern to glass by press-molding a softened glass material.

[0002]

2. Description of the Related Art At present, a technique of manufacturing a lens by pressing a glass material without a polishing step eliminates the complicated steps required in the conventional manufacturing and easily and inexpensively manufactures a lens. Made it possible to do In particular, in recent years, a press molding method has come to be used not only for manufacturing optical elements such as an aspherical lens but also for prisms and other various optical elements.

In such a press molding method, generally, a glass material is inserted into a mold having an upper mold member and a lower mold member for molding, and the atmosphere is changed to a non-oxidizing atmosphere such as a nitrogen atmosphere in order to prevent oxidation of the mold. As a predetermined temperature suitable for molding, that is, until the glass material becomes 10 ⁸ to 10 ¹² dPaS, press molding is performed on the glass material at a predetermined pressure,
The shape of the molding surface of the mold is transferred to the surface of the glass material. Then, the mold and the molded glass optical element are cooled to a temperature sufficiently close to the transition temperature of the glass material. Thereafter, the pressing pressure is removed and the mold is opened to take out the molded glass optical element.

Next, as an example of a method for manufacturing an optical element by a press molding method, Japanese Patent Application Laid-Open No. Sho 62-203101 discloses a mold having an irregular fine pattern on the surface of a heat-resistant metal, ceramic or cermet. A method for press forming an optical element is disclosed. Also, JP-A-62-303
No. 1 discloses a method of forming glass using a mold cut with a diamond tool, and it is presumed that there is no disclosure of processing a fine pattern using the mold.
As a method of forming an optical element having a ridge line, Japanese Utility Model Application Laid-Open No. 62-191837 discloses a method of forming a ridge line of a prism using a combined mold.

[0005]

The diffractive optical element includes an element (blazed element) having a sawtooth-shaped fine pattern (diffraction grating). It is conceivable to cut a mold shown in Japanese Patent Application Laid-Open No. Sho 62-3031 to form a fine saw-tooth pattern on its working surface, and to form a blazed element using this mold. Incidentally, the fine pattern of the blazed element includes an annular pattern and a straight band pattern depending on the application.

The fine pattern of a blazed device is formed by repeating a non-functional surface parallel to a light beam incident on the device and a functional surface where the light beam causes a diffraction phenomenon. It is desirable that the ridge line formed by the functional surface and the non-functional surface be sharp. This is because the diffraction efficiency decreases as the radius of curvature R of the tip of the ridge increases, and the optical function is not satisfied. The cutting edge of a diamond cutting tool for cutting a mold can be manufactured even if the tip R has a radius of about 50 nm, and the diffraction grating (fine pattern) of a blazed element can be manufactured.
Is enough for the production of. However, if a groove is formed in the mold with such a sharp edge, and softened glass is pressed there to form a ridge, the mold separation is extremely poor, and in some cases the bottom (deepest) of the groove It was found that the glass was fused, and the shape of the ridgeline was rather worse.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing an optical element having good releasability, a method for manufacturing an element, an optical system having these elements, a photographing apparatus, and an observation apparatus.

[0008]

According to the present invention, there is provided a method for manufacturing an optical element or a method for manufacturing an element having the following constitutions (1) to (13). An optical system, a photographing device, and an observation device are provided. (1) A method for manufacturing an optical element, comprising a step of forming a pattern having a ridge line on a material with a mold, wherein the material is in a softened state, and a deepest portion corresponding to the ridge line of the mold with respect to the material in the softened state. And forming the pattern by applying a pressure that does not allow the material to enter the portion. (2) The method for manufacturing an optical element according to (1), wherein the ridge line of the pattern has a curvature radius of a cross section of 0.2 μm or more and 2.0 μm or less. (3) The method for manufacturing an optical element according to (1) or (2), wherein the optical element is a diffractive optical element. (4) The method for manufacturing an optical element according to (3), wherein the pattern is a blazed diffraction grating. (5) The method for manufacturing an optical element according to any one of (1) to (4), wherein the pressure is a pressure that does not substantially lower the optical performance of the pattern after molding. (6) The method for producing an optical element according to any one of (1) to (5), wherein a pressure is applied at a predetermined molding temperature during the molding. (7) A method for manufacturing an element, comprising a step of forming a pattern having a ridge line on a material using a mold, wherein a pressure is applied to the material such that the material does not enter the deepest portion corresponding to the ridge line of the mold. In addition, a method for manufacturing an element, wherein the pattern is formed. (8) A method for manufacturing an element, comprising forming a pattern having a ridge line on a material by a mold, wherein the material does not enter the deepest portion corresponding to the ridge line of the mold with respect to the material, and A method for manufacturing an element, comprising applying a pressure that does not substantially lower the function to form the pattern. (9) The method for manufacturing an element according to (7) or (8), wherein the element is an optical element. (10) The method according to any one of the above (7) to (9), wherein a pressure is applied at a predetermined molding temperature during the molding. (11) An optical element manufactured by the method for manufacturing an optical element according to any one of (1) to (6) or a method for manufacturing an element according to any one of (7) to (10). An optical system comprising an element manufactured by the above method. (12) An imaging device comprising the optical system according to (11). (13) An observation device comprising the optical system according to (11).

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS By applying the above configuration,
Although it is possible to achieve the object of the present invention described above,
It is based on the following findings of the present inventors. That is, in forming a blazed diffraction grating using a mold, attention was paid to the fact that fusion is likely to occur at the ridge portion of the diffraction grating, and the pressure applied to the softened material was devised.

For example, when a pattern having a ridge line is formed on a glass with a mold, if the glass is filled in the deepest portion corresponding to the ridge line in the mold, the mold releasability deteriorates or fusion occurs. The reason for this is that when molding, pressure concentrates on that part and the adhesion between the mold and the glass increases,
Further, it is considered that the thermal stress based on the difference in the thermal expansion coefficient between the glass and the mold at the time of mold release is small in a narrow groove portion such as the deepest part, and the mold is not easily released. Therefore, in order to prevent fusion from occurring at the ridge line portion, the shape of the groove portion of the mold forming the ridge line portion should be such that there is no narrow portion or the shape of the groove portion of the mold should be sharp. However, it has been found that it is sufficient to control the glass completely so as not to transfer the groove shape under molding conditions such as pressure and temperature.

[0011] From the above, if the glass is completely filled in the groove of the mold forming the ridge portion of the sharp edge, the releasability is likely to be deteriorated. Therefore, in the present invention, the glass is completely filled in the bottom of the groove. The mold releasability was improved by making the mold and the glass non-contacting with each other without filling. At this time, the radius of curvature of a narrow pattern region (hereinafter referred to as a free surface of the diffraction grating pattern ridge portion) in the mold for forming the diffraction grating pattern ridge portion is R0.2 μm.
By setting it within the range of -R2.0 µm, it is possible to obtain better results. That is, if the radius of curvature is less than 0.2 μm, the glass enters the narrow portion of the groove of the mold, so that the releasability is deteriorated or fusion occurs. On the other hand, if the thickness exceeds 2.0 μm, the diffraction efficiency is lowered and the optical function is not satisfied.

The diffraction efficiency indicates the ratio of the intensity of the first-order diffracted light that contributes to the image formation in the diffracted light coming out of the diffraction element. If the radius of curvature exceeds 2.0 μm, the blazed shape collapses, so the influence of scattered light from the collapsed portion increases, and the diffraction efficiency decreases, and the optical function is not satisfied. Supplementing the range of the radius of curvature defined here, R = 0.2 μm means that the cross-sectional shape of the free surface at the tip of the ridge is a perfect circle with R = 0.2 μm, and that the curve is true. This includes the case where it deviates from the circle in a dull direction.

In the embodiment of the present invention, when the above-described method for manufacturing an optical element is applied, the fluidity of the glass changes depending on the molding temperature. It is desirable to set a desired press pressure from the relation of the state of filling of the glass. At this time, as a method of changing the transfer state to the fine part of the mold, the transfer state can be changed by controlling the viscosity of the glass by changing the temperature of the glass. However, if the temperature is changed too high, the specularity deteriorates due to the reaction at the interface between the mold and the glass, and if the temperature is too low, the glass is crushed or impossible to deform and has an adverse effect. . As another method, the transfer state can be influenced by the capacity of the glass. However, since the capacity of the glass material is unavoidable, in order to obtain a desired transfer state stably, at the above-mentioned constant temperature,
The method by pressure adjustment is more preferable.

In the present invention, the optical element obtained from the above-described means, for example, a blazed diffraction grating molded product is used not only as a single element but also as a part of a composite element formed by joining a plurality of elements. It goes without saying that you can do it. Further, according to the present invention, an improved optical system, a photographing apparatus having the improved optical system, and an improved optical system can be used as one optical element of an optical system including a plurality of optical elements. Various optical devices such as an observation device having

[0015]

Embodiments of the present invention will be described below. [Embodiment 1] FIG. 1 is a view showing a mold structure according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes an upper die whose lower functional surface is a plane, 2 denotes a lower die whose upper functional surface is a fine pattern for forming a blazed diffraction grating, and 3a denotes an upper body into which the upper die enters. The mold, 3b is a lower body mold in which the lower mold is inserted, 4 is a ring-shaped frame, and 5 is a diffractive optical element press-molded with the mold shown. FIG. 2 shows the diffractive optical element 5. FIG. 3 is an enlarged view of an arbitrary ridge line portion of the diffractive optical element 5. In FIG. 3, 7 denotes a non-functional surface, 8 denotes a functional surface, and 9 denotes a free surface.

In this embodiment, a glass which can be formed at a relatively low temperature of nd = 1.56911 and Tg = 368 ° C. is used as a glass for forming the element 5, and this glass is heated to form a preform. Diameter 25.
A disk having a thickness of 8 mm and a thickness of 2.03 mm was prepared. A diffractive optical element having one surface flat and the other surface n having a blazed diffraction grating pattern is formed from the glass material. The diffractive optical element 5 to be formed has a diameter of 26 mm, a thickness of 2 mm, an effective diameter of the diffraction grating pattern of 24 mm, a depth of the diffraction grating h = 0.92 μm, a pitch p1 = 946 μm, and p2 = 3.
93 μm, p3 = 302 μm,..., P133 = 42 μ
m. The lower mold 2 of FIG. 1 has a functional surface finished with a blazed diffraction grating fine pattern by cutting with a diamond tool.

A glass material was put into the mold shown in FIG. 1 and heated until the mold temperature reached 430 ° C. in a molding apparatus kept in a vacuum atmosphere. Next, pressing was performed by applying a pressing pressure to transfer the diffraction grating pattern of the lower mold 2 to glass. After a predetermined time, the mold was cooled in a state where the press pressure was reduced. After the mold was cooled to a temperature lower than the glass transition point, the mold was released and the molded product was taken out. This operation was performed at various press pressures, and the state of transfer of the blazed diffraction grating pattern to glass was examined. Table 1 shows the results.

[0018]

[Table 1] In Table 1, "radius of curvature" is the curvature of the free surface of the ridge of the formed diffraction grating. NO. The molded products of Nos. 1 and 2 had good releasability, but the amount of scattered light was large and the diffraction efficiency was lowered, and the optical functions were not satisfied. NO. Sample No. 9 tried to release at or below the transition point, but could not release, and was taken out after cooling to room temperature. NO. 10 is the ridgeline of the blazed diffraction grating (tip)
Were fused, and the glass as a material remained at the deepest part of the mold. On the other hand, the NO. 3-9
The molded product of No. had a portion that was not in contact with the mold at the ridge portion of the diffraction grating pattern, and the optical performance was good.

[Embodiment 2] FIG. 4 is a diagram showing a mold structure according to Embodiment 2 of the present invention. In the figure, reference numeral 10 denotes an upper mold having a lower functional surface which is a spherical surface, 11 denotes a lower mold whose upper functional surface is a fine pattern for forming a blazed diffraction grating on a spherical surface, and 12a denotes an upper mold 10 therein. , A lower body mold 12b into which the lower mold 11 enters, a ring frame 13 and a molded diffractive optical element 14. FIG. 5 shows the diffractive optical element 14. FIG. 6 shows the diffractive optical element 14.
FIG. 7 is an enlarged view of an arbitrary ridge portion of FIG.
Indicates a non-functional surface, 17 indicates a functional surface, and 18 indicates a free surface.

Also in this embodiment, the same material as the glass shown in Embodiment 1 is used as a glass for forming a diffractive optical element, and this glass is processed to obtain a preform of 0.5%.
A cc glass gob was made. One side is R1 from the above material
A diffractive optical element having a blazed diffraction grating pattern is formed on a spherical surface of 6.8 and a spherical surface on one side of R16.4. The diffractive optical element to be molded has a diameter of 14 mm and a center thickness of 4.5 m.
m, a biconvex diffraction lens having a diffraction pattern effective diameter of 12 mm. The lower mold 11 in FIG. 4 has a blazed diffraction grating-like fine pattern finished by cutting the functional surface with a diamond tool.

The glass material was put into the mold shown in FIG. 4 and heated until the mold temperature reached 430 ° C. in a molding apparatus kept in a vacuum atmosphere. Next, pressing was performed by applying a pressing pressure, and the diffraction grating-like fine pattern of the lower mold 11 was transferred to glass. The mold was cooled in a state where the press pressure was reduced for a predetermined time, and after the mold was cooled below the glass transition point, the mold was released and the molded product was taken out. This operation was performed at various press pressures, and the state of transfer of the blazed pattern to glass was examined. Table 2 shows the results.

[0022]

[Table 2] In Table 2, “radius of curvature” is the curvature of the free surface of the ridge of the formed diffraction grating. NO. The molded products of Nos. 1 and 2 had good releasability, but the amount of scattered light was large and the diffraction efficiency was lowered, and the optical functions were not satisfied. NO. Sample No. 9 tried to release at or below the transition point, but could not release, and was taken out after cooling to room temperature. NO. In No. 10, the tip of the ridge line was fused and glass remained in the mold. On the other hand, N according to Embodiment 2 of the present invention
O. The molded products of Nos. 3 to 9 had non-contact portions with the mold at the ridge portions of the diffraction grating pattern, and had good optical performance.

The diffractive optical elements according to Embodiments 1 and 2 described above are optical systems of various optical devices such as a photographing device such as a camera, an observation device such as eyeglasses and a microscope, and a projection device such as a stepper and a liquid crystal projector. And an improved optical system and optical apparatus with high performance can be obtained.

[0024]

As described above, according to the present invention,
It is possible to realize a method for manufacturing an optical element or a method for manufacturing an element, which has good releasability from a pattern and can satisfy optical performance, and an optical system, a photographing apparatus, and an observation apparatus having these elements.

[Brief description of the drawings]

FIG. 1 is a diagram showing a mold structure according to a first embodiment of the present invention.

FIG. 2 is a diagram of a diffractive optical element according to the first embodiment of the present invention.

FIG. 3 is an enlarged view of a ridge portion of the diffractive optical element according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a mold structure according to a second embodiment of the present invention.

FIG. 5 is a diagram of a diffractive optical element according to a second embodiment of the present invention.

FIG. 6 is an enlarged view of a ridge portion of the diffractive optical element according to the second embodiment of the present invention.

[Explanation of symbols]

1: Upper flat mold 2: Lower mold having a fine pattern for forming a blazed diffraction grating 3a: Upper barrel mold 3b: Lower trunk mold 4: Ring frame 5: Molded product 6: Diffractive optical element 7: Non Functional surface 8: Functional surface 9: Free surface 10: Upper surface of spherical surface 11: Lower die having a fine pattern for forming a blazed diffraction grating 12a: Upper trunk type 12b: Lower trunk type 13: Ring frame 14: Molded product 15: Diffractive optical element 16: Non-functional surface 17: Functional surface 18: Free surface

Claims (13)

[Claims] 1. A method of manufacturing an optical element, comprising: forming a pattern having a ridge line on a material with a mold, wherein the material is in a softened state, and the material in the softened state corresponds to the ridge line of the mold. Forming a pattern by applying a pressure that does not allow the material to enter the deepest part of the optical element. 2. The method according to claim 1, wherein the ridge line of the pattern has a radius of curvature of a cross section of 0.2 μm or more and 2.0 μm or less. 3. The method for manufacturing an optical element according to claim 1, wherein the optical element is a diffractive optical element. 4. The method according to claim 3, wherein the pattern is a blazed diffraction grating. 5. The method for manufacturing an optical element according to claim 1, wherein the pressure is a pressure that does not substantially lower the optical performance of the pattern after molding. 6. The method of manufacturing an optical element according to claim 1, wherein a pressure is applied at a predetermined molding temperature during said molding. 7. A method for manufacturing an element, comprising a step of forming a pattern having a ridge line on a material by using a mold, wherein the material has such an extent that the material does not enter the deepest portion corresponding to the ridge line of the mold. A method for manufacturing an element, wherein the pattern is formed by applying pressure. 8. A method for manufacturing an element, comprising a step of forming a pattern having a ridge line on a material with a mold, wherein the material does not enter a deepest portion corresponding to the ridge line of the mold with respect to the material, and A method for manufacturing an element, comprising applying a pressure that does not substantially lower the function of a pattern to form the pattern. 9. The method according to claim 7, wherein the element is an optical element. 10. The method according to claim 7, wherein a pressure is applied at a predetermined molding temperature during said molding. 11. An optical element manufactured by the method for manufacturing an optical element according to any one of claims 1 to 6 or a method for manufacturing an element according to any one of claims 7 to 10. An optical system comprising an element manufactured by the above method. 12. An imaging apparatus comprising the optical system according to claim 11. 13. An observation apparatus comprising the optical system according to claim 11.