JP2001141918A - Diffractive optical element and method of manufacturing the same - Google Patents

Abstract

(57) Abstract: A laminated diffractive optical element having a laminated structure is obtained. SOLUTION: In the laminated diffractive optical element 1, a glass substrate 2 is provided.
a, a diffractive optical element 3 made of a resin, and a diffractive optical element 4 molded of another resin having the same pitch on a glass substrate 2b are provided with a concave portion 3a provided in the diffractive optical element 3 and a convex portion provided in the diffractive optical element 4. It is joined together with the fitting by the part 4a. An air gap G of 1.5 μm is provided between the diffractive optical elements 3 and 4. The diffractive optical elements 3 and 4 have a blazed grating. The diffractive optical element 3 is formed of a high-cured resin having a high refractive index and a large dispersion, and the diffractive optical element 4 is formed of a high-cured resin having a low refractive index and a small dispersion. Have been.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diffractive optical element having a grating structure in which all luminous fluxes in a used wavelength region concentrate on diffracted light of a specific order, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, chromatic aberration of an optical system has been corrected by combining a plurality of optical elements made of glass materials having different dispersions. Further, chromatic aberration correction using a refraction and diffraction optical system instead of a refraction optical system (lens) is disclosed in SPIE VOL.

When a diffractive surface having a diffractive effect is added to an optical system, it is important to maintain a high diffraction efficiency at a design order (generally, a first order) within a used wavelength range.
This is because light of an order other than the design order has a larger diffraction angle as the order departs from the design order, a larger difference in focal length, and appears as defocus. In particular, when a high-luminance light source is present, side lobes may be seen.

Further, as disclosed in Japanese Patent Application Laid-Open No. 9-127322, a laminated diffractive optical element having a laminated structure of two or more diffraction gratings can be used in a wide wavelength region to correct chromatic aberration. It is known that, when used in an optical system that requires, the diffraction efficiency of the order different from the design order is reduced and the diffraction efficiency of the design order is improved in the wavelength region to be used. Therefore, when this laminated diffractive optical element is applied to an optical system, improvement in the quality of images and optical information can be expected.

[0005]

However, if there is a misalignment between a plurality of stacked diffraction gratings, the diffraction efficiency of light of an order different from the design order increases, resulting in a significant decrease in image quality. become. Therefore, in order to manufacture a laminated diffractive optical element, it is necessary to perform adjustment for positioning a plurality of laminated diffraction gratings with high accuracy.

In general, an optical axis adjustment method for joining two refraction lenses is achieved by rotating the two joined lenses with respect to the optical axis to reduce the amount of eccentricity of transmitted light. However, for example, a diffraction grating used as a diffractive lens uses the achromatic effect, which is its advantage, and therefore has a long focal length and a small amount of eccentricity of transmitted light as a lens, so that it is difficult to use this method.

Further, alignment marks can be formed on each diffraction grating and the alignment marks can be adjusted to a reference. However, when this step is performed manually, the adjustment is inefficient and requires a lot of time. In addition, adjustment by automation utilizing image processing requires a high production cost due to an increase in equipment cost.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a diffractive optical element capable of performing positioning in a shorter time and at lower cost than before, and a method of manufacturing the same.

[0009]

According to a first aspect of the present invention, there is provided a diffractive optical element having a plurality of diffraction grating surfaces laminated thereon, wherein the projection is formed outside one of the diffraction grating surfaces. The pair of diffraction grating surfaces is positioned by fitting the concave portion and / or the convex portion formed outside the other diffraction grating surface, and the pair of diffraction grating surfaces pass therethrough. So that the maximum optical path length difference given between the light beams is an integral multiple of the wavelength for a plurality of wavelengths.
A diffractive optical element characterized by being formed in a kinoform or a blazed or binary shape and height close to the kinoform on materials having different refractive indexes and dispersions.

According to a second aspect of the present invention, in a diffractive optical element having a plurality of diffraction grating surfaces stacked, a convex portion and / or a concave portion formed outside the optically effective area of one of the diffraction grating surfaces has the other diffraction grating surface. A pair of diffraction grating surfaces is positioned by fitting into a concave portion and / or a convex portion formed outside the optically effective area of the surface, and the pair of diffraction grating surfaces is provided between light beams passing therethrough. In order that the maximum optical path length difference may be an integral multiple of each wavelength for a plurality of wavelengths, the refractive index and the dispersion are different from each other, and quinoform or a blazed or binary shape and height close to it are formed. Is a diffractive optical element.

According to a third aspect of the present invention, in a diffractive optical element having a plurality of diffraction grating surfaces stacked, a convex portion and / or a concave portion formed outside one of the diffraction grating surfaces is formed outside the other diffraction grating surface. A pair of diffraction grating surfaces is positioned by fitting into the formed concave portions and / or convex portions, and the pair of diffraction grating surfaces has a diffraction efficiency of diffracted light of a specific order of about 100% with respect to a plurality of wavelengths. A diffractive optical element characterized by being formed in a material having a different refractive index and dispersion from a kinoform or a shape and a height close to the kinoform.

According to a fourth aspect of the present invention, in the diffractive optical element in which a plurality of diffraction grating surfaces are stacked, the convex portion and / or the concave portion formed outside the optically effective area on one of the diffraction grating surfaces has the other diffraction grating surface. A pair of diffraction grating surfaces is positioned by fitting into a concave portion and / or a convex portion formed outside the optically effective area on the grating surface side, and the pair of diffraction grating surfaces is used for diffracting light of a specific order. Diffraction efficiency is about 100 for multiple wavelengths
%. A diffractive optical element characterized by being formed of a kinoform or a shape and a height close to those of a kinoform material having different refractive indices and dispersions so that the refractive index and the dispersion ratio are different from each other.

According to a fifth aspect of the present invention, in the diffractive optical element according to any one of the first to fourth aspects, the pair of diffraction grating surfaces face each other via a space. It is.

According to a sixth aspect of the present invention, there is provided the diffractive optical element according to any one of the first to fifth aspects, wherein each of the concavities and convexities has a triangular, trapezoidal or semicircular cross-sectional shape.

According to a seventh aspect of the present invention, in the diffractive optical element in which a plurality of diffraction grating surfaces are stacked, a cross section formed on one of the diffraction grating surfaces has a triangular, trapezoidal, or semicircular convex and / or concave portion. A diffraction optical element characterized in that a pair of diffraction grating surfaces are aligned by fitting a triangular, trapezoidal, or semicircular concave or convex portion with a cross section formed on the diffraction grating surface. is there.

According to an eighth aspect of the present invention, in the diffractive optical element in which a plurality of diffraction grating surfaces are stacked, the cross section formed outside the optically effective area on one of the diffraction grating surfaces has a triangular, trapezoidal, or semicircular convex shape. The cross section formed outside the optically effective area on the other diffraction grating surface side of the portion and / or the concave portion fits into a triangular, trapezoidal, or semicircular concave or convex portion, so that a pair of diffraction grating surfaces can be aligned. It is a diffractive optical element characterized by being formed.

According to a ninth aspect of the present invention, in the method for manufacturing a diffractive optical element according to any one of the first to eighth aspects, the convex portion formed on the one diffraction grating side includes A method for manufacturing a diffractive optical element, comprising a step of fitting the concave portion formed on the other diffraction grating surface side into the concave portion.

The present invention according to claim 10 is the invention according to claims 1 to 8
The method for manufacturing a diffractive optical element according to any one of claims 1 to 3, further comprising a step of forming one diffraction grating surface and then forming a remaining diffraction grating surface using a mold, wherein the one diffraction grating is provided. The projections and / or depressions formed on the surface side are fitted into the depressions and / or projections formed in the mold for the remaining diffraction grating surface, thereby aligning the two, and the remaining diffraction grating surface Forming a diffractive optical element.

According to an eleventh aspect of the present invention, each of the diffraction gratings constituting the laminated diffraction grating has a positioning fitting portion in a radial direction which is coaxial with the optical axis and has a small and small radius, and is provided in the optical axis direction. Is a method for manufacturing a diffraction grating, comprising abutting portions of opposite shapes for determining the height of the grating.

According to a twelfth aspect of the present invention, the shape of the positioning fitting portion in each radial direction of the laminated diffraction grating is such that the diffraction grating side having a concave spherical component has a convex shape with a small diameter and a convex spherical component opposite thereto. The method of manufacturing a diffraction grating according to claim 11, wherein the diffraction grating has a concave shape with a large diameter.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 is a cross-sectional view of the laminated diffractive optical element 1 (diffractive lens) according to the first embodiment, and FIG. The laminated diffractive optical element 1 has a diffraction grating 3 made of a resin formed on a glass substrate 2a and a diffraction grating 4 formed of another resin having the same pitch as the diffraction grating 3 on a glass substrate 2b. And are joined. An air gap G of 1.5 μm is provided between the diffraction gratings 3 and 4.

The diffraction gratings 3 and 4 in this embodiment have a diffraction grating surface having a blazed, kinoform or stepped (so-called binary) cross section. The diffraction grating 3 has a high refractive index and a high refractive index. The diffraction grating 4 is formed of a large photocurable resin, and is formed of a photocurable resin having a low refractive index and a small dispersion. Regarding the selection of each resin, the diffraction efficiency of the diffracted light of a specific order (for example, the first order) of the diffractive optical element including the diffraction gratings 3 and 4 becomes substantially 100% over the entire used wavelength region (for example, the visible region). Is determined by a combination of two or more kinds of resins depending on the optical design. Further, the grid shape such as the grid height and the pitch also depends on the application and the material.

The resin of the diffraction grating 3 in the present embodiment includes:
A methacrylate-based ultraviolet curable resin is used, the refractive index after curing is 1.635, and the Abbe number is 23. Also,
The resin of the diffraction grating 4 is a urethane-modified polyester acrylate ultraviolet curing resin, and has a refractive index of 1.525 after curing and an Abbe number of 50.8.

In the laminated diffractive optical element 1 used for an optical device such as a camera, a light beam in a working wavelength range, for example, a c-line having a first design wavelength λ = 565.27 nm, and a second design wavelength λ = 435. At the g-line of 83 nm, the lattice shape must be determined for each material so as to concentrate on a specific order (usually one of ± first orders, but other orders are also possible) and obtain a high diffraction efficiency of 95 to 100%. Must. In theory, to obtain 100% diffraction efficiency, the diffraction gratings 3, 4
Is determined such that the maximum optical path length difference given between rays passing therethrough is an integral multiple of each wavelength for the c-line and the g-line. Specific formulas and design examples relating to this determination are described in, for example, Japanese Patent Application Laid-Open No. H11-04481.

[0025]

[0026]

In this embodiment, the diffraction grating 3 has a grating height of 6.74 μm, and the diffraction grating 4 has a grating height of 9.5.
0 μm. The grating pitch of the periodic structure for generating the diffraction effect is the same in the diffraction gratings 3 and 4, and becomes smaller as the distance from the center of the diffraction gratings 3 and 4, and the minimum pitch is less than about 40 μm. Also, three or more concave portions 3a and convex portions 4a which are provided in an annular shape or independently provided around the outside of the optically effective portions of the diffraction gratings 3, 4 are fitted.

FIG. 3 is a cross-sectional view of a molding die 11 for forming the diffraction grating 3, and FIG. 4 is an enlarged cross-sectional view of the molding die 11 in the vicinity of the outer periphery. The forming die 11 is manufactured by applying KN plating with a thickness of several μm to a super steel and cutting the plated film using a diamond bite. A convex portion 12 for forming the concave portion 3a is provided outside the optically effective portion of the mold 11 by cutting.

Similarly, FIG. 5 is a sectional view of a molding die 21 for molding the diffraction grating 4, and FIG. 6 is an enlarged sectional view of the molding die 21 in the vicinity of an outer peripheral portion thereof. Is provided with a concave portion 22 for forming the convex portion 4a. The positions of the convex portion 12 and the concave portion 22 from the center of the diffractive lens (the centers of the diffraction gratings 3 and 4) need to be equal to each other. In actual cutting, the difference can be within 1 μm.

The convex portion 12 and the concave portion 22 may be formed by combining a semicircular portion with a V-shaped cross section. However, the actual positioning of the contact point between the surface and the circle depends on the processing and the gap between the diffraction gratings. Is difficult to set. Therefore, in this embodiment, the convex portion 12 is formed into a mountain shape, and the concave portion 22 is formed.
Are formed so as to form a V-shaped groove, and a flat portion 22a of 5 μm is provided at the apex of the V-shaped groove so that the molded product is hardly damaged. In addition, the cross-sectional shape of the convex portion 4a, the concave portion 3a, the convex portion 12, and the concave portion 22 is not limited to a triangular shape, but may be a trapezoidal shape or a semicircular shape.

First, a controlled amount of a methacrylate ultraviolet curable resin serving as a diffraction grating is dropped into the center of the molding surface of the mold 11 by a dispenser. However, pitch 40
In the case of a lattice shape having a lattice height of 10 μm and a lattice height of 10 μm, when the resin is diffused on the molding die 11, air is taken into the fine shape and a shape defect of the molded product is generated. After diffusing to the convex portion 12 outside the optically effective portion, it is preferable to reduce the pressure to about 10 mmHg in a vacuum vessel to perform a defoaming treatment.

After this defoaming treatment, a very small amount of resin is dropped at the center of the glass substrate 2a serving as the substrate of the molded product, and the resin is brought into contact with the resin on the molding die 11, and the glass substrate 2a is gradually removed. It is lowered and fixed at a position where a desired film thickness is obtained.

Subsequently, since the resin used in this embodiment is a photocurable resin, it is temporarily cured by irradiating ultraviolet rays from the glass substrate 2a side as shown in FIG. 7, and the periphery of the glass substrate 2a is pulled up. As a result, the mold 11
Then, the diffraction grating 3 with the concave portion 3a can be formed on the glass substrate 2a as shown in FIG. Further, in order to improve the adhesiveness with the resin on the glass substrate 2a, a process of applying a silane coupling agent using a spinner on the surface of the glass substrate 2a in advance and then drying in a oven is performed.

A similar series of steps is performed in the same manner using a urethane-modified polyester acrylate-based UV-curable resin for the molding die 21 so that the projections 4 are formed on the glass substrate 2b.
The diffraction grating 4 with a can be formed.

In the molding method of this embodiment, when the resin is cured, the diffraction gratings 3, 4 and the entire glass substrates 2a, 2b are deformed due to shrinkage. There are restrictions. In the present embodiment, since the resin film thickness is 50 μm, the height of the unevenness is 80 μm.

Next, one of the diffraction gratings 3 and 4 formed by the above-described method is fixed using a fixing jig. A thixotropic light-curing adhesive having low fluidity is dripped outward at a plurality of locations in the circumferential direction by the concave portions 3a or the convex portions 4a, and the other diffraction gratings are directed to the molding surface side and are superimposed so that they are centered with each other. Thereby, the laminated diffractive optical element 1 having a laminated structure can be obtained. At this time, interference fringes can be observed at the laminated portion of the diffraction gratings 3 and 4, and coarse adjustment may be performed to position the center of one diffraction grating to the center of the other diffraction grating with the interference fringes as a guide. . Then, after assembling so that the circle of the concave part 3a and the convex part 4a may overlap,
The laminated diffractive optical element 1 can be obtained by irradiating and curing ultraviolet rays.

FIG. 9 is a sectional view of a laminated diffractive optical element 31 according to the second embodiment. In the first embodiment, the two diffraction gratings 3 and 4 are joined via an air layer to produce the laminated diffractive optical element 1 having a laminated structure. In the present embodiment, however, the first layer diffraction grating is provided. The laminated diffractive optical element 31 is formed by directly laminating the second-layer diffraction grating 33 on the second diffraction grating 32.

In the case of lamination molding, when forming the diffraction grating 33 of the second layer, the thickness of the resin of the second layer is set to the first layer.
If the thickness of the diffraction grating 32 is smaller than the height of the
And the diffraction grating 32 of the first layer may be damaged. Therefore, a diffraction grating having a low grating height is used as the first layer on the base side. Further, when designing an optical element, the order of layers to be laminated does not depend on the theory, so that there is no problem even when any of the optical elements is placed above.

First, as in the first embodiment, a diffraction grating 32 is formed on a glass substrate 2 using a molding die (not shown). Further, a concave portion 32a is formed outside the optically effective portion of the glass substrate 2 outside the diffraction grating 32. continue,
The height of the lattice shape of the mold 34 for molding the diffraction grating 33 is set to 2.76 μm, which is obtained by subtracting the grating height of the diffraction grating 32, and a convex portion 34 a similar to that of the first embodiment is provided.

The recess 32a provided in the diffraction grating 32
And the convex portion 34a provided on the molding die 34, the positioning of the molding die 34 becomes possible.
The resin can be filled between the mold 34 and the mold 34 to form the diffraction grating 33. Further, as shown in FIG.
4 is separated from the glass substrate 2 by diffraction.
2, 33 can be formed by lamination.

After the diffraction grating 33 is released from the mold 34,
Since it is necessary to adhere to the diffraction grating 32 as the first layer,
The bonding between the diffraction gratings 32 and 33 requires an adhesive strength that does not release the mold, but the mold 34 is immersed in a release agent that has been sufficiently diluted in advance, and is then washed with steam or the like. Care must be taken that the release agent does not disturb the fine shape,
It is necessary to improve the releasability by performing a release treatment.

In general, the thickness of the diffraction grating 33 formed in the second layer becomes thicker, and the viscosity is reduced by heating, or is reduced to 0 in a region other than the grating pitch even when pressed and formed. It is not possible. However, if the film thickness is uniform in the laminated diffractive optical element 31, the same effect is exerted on the entire transmitted light flux, so that there is no problem for the laminated diffractive optical element 31. Rather, it is important to take measures to make the film thickness uniform. If an optical element with a short focus is considered, the angle of view becomes large. Sisters,
Since the correction effect is reduced, it is important to reduce the thickness of the resin as much as possible and to design the element in consideration of the angle of view and the thickness of the resin.

In the first and second embodiments, the concave portion or the convex portion in the mold is formed by machining, but there are other methods. For example, first, a mold of either a concave portion or a convex portion for combination is prepared by cutting. The obtained concave or convex mold is transferred using a photocurable resin or the like on a glass substrate. Further, a vapor deposition film is provided on the surface of the obtained molded product, and nickel plating is performed to manufacture an electroformed product. Next, a fine shape is applied to the optically effective area on the mold of the concave portion or the convex portion formed first. Also, fine processing is similarly performed on the surface of the completed electroformed product. At this time,
By forming a mark at the center so that the center position can be accurately adjusted, a molding die can be obtained.

FIG. 11 is a partial cross-sectional view showing a state in which two diffraction gratings having a spherical power whose one surface is concave and the other surface is convex are laminated in the third embodiment. This is a diffraction grating (diffraction lens) having spherical power (negative focal length), and has a height t1 from the optical axis center e to the diameter φa. Also, the diameter φa ~
The height between grids φb is the same as the top of the lattice, and a step having a height t4 is provided between the diameters φb to φc. A chamfered portion 42 is provided on the optical axis center e side of the diameter φc as necessary. A convex step having a height t6 is provided outside the diameter φc.

The element 43 facing one element 41 is a diffraction grating (diffraction lens) having a convex spherical power (positive focal length). Height t2 from shaft center e to diameter φa
Are formed. The outer circumference has the same height as the lattice top from the diameter φa to φb, and a step having a height t5 is provided between the diameters φb to φc.

As described above, the element 41 having a concave spherical power and the element 43 having a convex spherical power are
The contact at 4 makes it possible to form a laminated structure having a gap of a thickness t3 (= t4 + t5) between lattice vertices of the elements 41 and 43. In addition, by setting the diameter φc of the element 43 to the fitting step 45 in the radial direction by a very small amount of about 1 μm, for example, from the diameter φc of the element 41, the element 41 having a concave spherical power and the element 43 Can be assembled with substantially the same optical axis. At this time, the outer side of the diameter φc of the element 43 having the convex spherical power is configured such that the height t7 in the optical axis direction becomes the gap d so as not to contact the element 41 having the concave spherical power.

FIG. 12 is a sectional view showing a case where only the element 51 having a concave spherical power has the step of the thickness t3 between lattice vertices in FIG. In this case, the effective outside of the diameters φa to φc of the element 52 having the convex spherical power can be constituted by straight lines, and the processing becomes easier than the elements 41 and 43 in FIG.

FIG. 13 shows a modification of FIG. 12, in which a radial fitting portion 5 of an element 52 'having a convex spherical power is provided.
3 has a convex shape with a width w1. Naturally, the gap d of the outer peripheral portion having the diameter φc becomes wide as t7 ′, and when the element 51 having the concave spherical power and the element 52 ′ having the convex spherical power are fitted in the fitting portion 53 in the intermediate fitting state. In addition, the element can be made elastic so that it can be elastically deformed by a small amount and fitted.

FIG. 14 is a cross-sectional view of a molding die used for molding two elements having one concave spherical power and the other having a convex spherical power. FIG. 3 shows a cross-sectional view of a mold 61 for forming a semiconductor device, and has a shape opposed to the element 41. In a state in which the mold 61 is attached to a rotating mechanism (not shown) having the optical axis center e as a center of rotation and is rotated, a sharp cutting tool 62 made of diamond or the like having a traverse angle θ1 is provided so as not to interfere with the grating slope. Following the shape to be formed, the dotted line portion 63 having the thickness t8 is cut and removed from the outer portion toward the inner peripheral portion to create the shape of the mold 61.

In FIG. 14, the cutting tool 62 is positioned at the center of the optical axis e.
When the machining is performed from the rotation center toward the outer periphery, the surface of the mold 61 is in a peeled state, but when the machining is performed from the outer periphery to the inner periphery, the surface condition of the machining surface can be favorably machined.

FIG. 15 is a sectional view of a mold 71 for molding the element 43 having a convex spherical power in FIG. In the type 71, the part indicated by the area 72 is byte 7
Reference numeral 3 denotes a portion to be cut and removed. The mold 71 is shown in FIG.
4, which is different from the convex shape of the convex shape 61, the removal processing is performed from the rotation center e side toward the outer peripheral side according to the desired shape. The cutting tool 73 has a transverse cutting edge angle θ2 so as not to interfere with the lattice slope. Byte 73 is also shown in FIG.
Similarly to 4, when processing is performed from the outer peripheral portion toward the inner peripheral portion, a peeled state is obtained. However, when processing is performed from the inner peripheral portion toward the outer peripheral portion, the surface of the processed surface can be satisfactorily processed.

Next, as shown in FIGS. 11 to 13, the diffractive optical elements 41 and 51 having concave spherical power have a convex fitting portion 53 in the radial direction, and a diffractive optical element having convex spherical power. Element 43, 52, 52 ′ side radial fitting portion 53
The concave shape has the following advantages.

Diffractive optical element 4 having concave spherical power
In Nos. 1 and 51, a cutting tool 6 having a transverse cutting angle θ1
1, the chamfered portion 42 can be machined as shown in FIG. 11 or a cylinder having a diameter φc parallel to the optical axis center e.
In the cutting tool 73 having the opposite transverse cutting angle θ2 shown in FIG. 5, the cutting tool interferes with the processing surface and cannot be processed.

Conversely, in the diffractive optical elements 43, 52, and 52 'having convex spherical power, the cutting tool 62 having the transverse cutting edge angle θ1 causes interference at the radial fitting portion and is processed into a cylindrical shape. Can not.

FIG. 11 shows a diffractive optical element 41.
Although the chamfered portion 42 is an R-shaped chamfer, it may be a tapered chamfer. The diffractive optical element 43 having a convex spherical power is not chamfered.
There is no problem if the chamfer is smaller than 1 chamfer.

Although the radial fitting portion 53 of the diffractive optical element 52 'in FIG. 13 is a step portion having a width w1, the gap t
The shape does not matter as long as there is a fitting portion with the diffractive optical element 51 with a step smaller than 7 '.

The laminated diffractive optical element obtained by the above-described embodiment is applied to a photographing optical system of a camera (not shown), a finder optical system, an objective and / or eyepiece optical system of binoculars or a telescope, and has a high performance. Can be applied.

【The invention's effect】

As described above, the diffractive optical element and the method of manufacturing the same according to the present invention can simplify a diffraction grating having a concave spherical power and a diffraction grating having a convex spherical power which constitute a laminated type diffractive optical element. Because it can be made into a laminated structure by fitting, it is low cost and has good mass productivity.
It becomes possible to produce a laminated diffractive optical element.

The diffractive optical element and the method of manufacturing the same according to the present invention can produce a laminated diffractive optical element in a short time and at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view of a laminated diffractive optical element according to a first embodiment.

FIG. 2 is an enlarged cross-sectional view near the outer peripheral portion of the laminated diffractive optical element.

FIG. 3 is a sectional view of a molding die.

FIG. 4 is an enlarged sectional view of the vicinity of an outer peripheral portion of a molding die.

FIG. 5 is a sectional view of a molding die.

FIG. 6 is an enlarged sectional view of the vicinity of an outer peripheral portion of a molding die.

FIG. 7 is an explanatory view of a resin curing means.

FIG. 8 is a sectional view of a glass substrate and a diffraction grating.

FIG. 9 is a sectional view of a mold and a laminated diffractive optical element according to a second embodiment.

FIG. 10 is a sectional view of a laminated diffractive optical element.

FIG. 11 is a sectional view of a laminated diffractive optical element according to a third embodiment.

FIG. 12 is a sectional view of a laminated diffractive optical element.

FIG. 13 is a sectional view of a laminated diffractive optical element.

FIG. 14 is a sectional view of a molding die.

FIG. 15 is a sectional view of a molding die.

[Explanation of symbols]

1, 31 laminated diffractive optical element 2 glass substrate 3, 4, 32, 33, 41, 43, 51, 52, 52 '
Diffraction grating 3a, 32a Concave part 4a Convex part 11, 22, 34 Mold 12 Concave part 22, 34a Convex part 42 Chamfer part 44 Abutment part 45 Fitting part step 53 Fitting part 61, 71 Mold 62, 73 Part-Time Job

Claims (12)

[Claims] 1. A diffractive optical element having a plurality of diffraction grating surfaces stacked, wherein a convex portion and / or a concave portion formed outside one diffraction grating surface is a concave portion and / or a convex portion formed outside the other diffraction grating surface. A pair of diffraction grating surfaces is positioned by being fitted in the portion, and the maximum difference in optical path length given between light beams passing therethrough is an integral multiple of the wavelength for a plurality of wavelengths. A diffractive optical element formed of a kinoform or a blazed or binary shape and a height close to the kinoform from materials having different refractive indices and dispersions. 2. In a diffractive optical element having a plurality of diffraction grating surfaces stacked, a convex portion and / or a concave portion formed outside the optically effective region of one diffraction grating surface is outside the optically effective region of the other diffraction grating surface. A pair of diffraction grating surfaces is positioned by fitting into a concave portion and / or a convex portion formed in the pair, and the pair of diffraction grating surfaces has a maximum optical path length difference given between light beams passing therethrough. In order to be an integer multiple of each wavelength with respect to a plurality of wavelengths, materials having different refractive indices and dispersions,
A diffractive optical element formed of a kinoform or a blazed or binary shape and a height similar thereto. 3. A diffractive optical element in which a plurality of diffraction grating surfaces are stacked, wherein a convex portion and / or a concave portion formed outside one of the diffraction grating surfaces is a concave portion and / or a convex formed outside the other diffraction grating surface. A pair of diffraction grating surfaces is positioned by being fitted in the portion, and the pair of diffraction grating surfaces has a diffraction efficiency of diffracted light of a specific order of about 100 for a plurality of wavelengths.
%. A diffractive optical element characterized by being formed in a material having a different refractive index and dispersion so as to have a kinoform or a shape and a height close to kinoform. 4. In a diffractive optical element having a plurality of diffraction grating surfaces stacked, a convex portion and / or a concave portion formed outside an optically effective region on one diffraction grating surface side has an optical effective region on the other diffraction grating surface side. A pair of diffraction grating surfaces is positioned by fitting into a concave portion and / or a convex portion formed outside the region, and the pair of diffraction grating surfaces has a diffraction efficiency of diffracted light of a specific order with respect to a plurality of wavelengths. A diffractive optical element characterized in that it is formed of a kinoform or a shape and a height close thereto with materials having different refractive indexes and dispersions so as to be about 100%. 5. The diffractive optical element according to claim 1, wherein the pair of diffraction grating surfaces face each other via a space. 6. The diffractive optical element according to claim 1, wherein a cross-sectional shape of each of the irregularities is a triangle, a trapezoid, or a semicircle. 7. A diffractive optical element in which a plurality of diffraction grating surfaces are stacked, wherein a cross section formed on one diffraction grating surface has a triangular, trapezoidal, or semicircular projection and / or recess formed on the other diffraction grating surface. A diffractive optical element wherein a pair of diffraction grating surfaces are aligned by fitting into a concave or convex part having a triangular, trapezoidal or semicircular cross section. 8. A diffractive optical element in which a plurality of diffraction grating surfaces are stacked, and a cross section formed outside the optically effective area on one of the diffraction grating surfaces has a triangular, trapezoidal, or semicircular convex portion and / or
Alternatively, the cross-section formed outside the optically effective area on the other diffraction grating surface side in the triangular, trapezoidal, or semicircular concave or convex portion allows positioning of the pair of diffraction grating surfaces. A diffractive optical element. 9. The method for manufacturing a diffractive optical element according to claim 1, wherein the convex portion formed on the one diffraction grating side is provided on the other diffraction grating surface side. A method for manufacturing a diffractive optical element, comprising a step of fitting into the formed concave portion. 10. A method for manufacturing a diffractive optical element according to claim 1, wherein after forming one diffraction grating surface, the remaining diffraction grating surface is formed using a mold. A step of fitting the convex and / or concave portion formed on the one diffraction grating surface side to the concave and / or convex portion formed in the mold for the remaining diffraction grating surface. To form the remaining diffraction grating surface. 11. Each of the diffraction gratings constituting the laminated diffraction grating has coaxial with the optical axis thereof, and has a radial positioning fitting portion having a small and small radius, and determines the height of the grating in the optical axis direction. A method for manufacturing a diffraction grating, comprising: abutting portions having opposite shapes. 12. The shape of the positioning fitting portion in each radial direction of the laminated diffraction grating is such that the diffraction grating side having a concave spherical component has a convex shape with a small diameter, and the diffraction grating side having a convex spherical component opposite has a concave shape having a large diameter. The method according to claim 11, wherein the diffraction grating is formed in a shape.