JP6823381B2 - Optical equipment with a diffractive optical element and a diffraction grating and a camera with a diffraction grating - Google Patents

Description

The present invention relates to a diffractive optical element used in an optical device such as a camera.

As described in Patent Document 1, the conventional diffractive optical element has a structure in which a glass substrate, a lattice forming layer optical material, and a flattening layer optical material are laminated in order in the optical axis direction. The diffraction grating is formed between the lattice forming layer and the flattening layer. The glass substrate has a spherical or aspherical uneven shape, and is made of glass or resin. The lattice forming layer optical material and the flattening layer optical material are composed of a photocurable resin or a thermosetting resin having different optical characteristics such as an acrylic resin and an epoxy resin.

The outer peripheral portion of the lattice forming layer is located on the optical axis side of the outer peripheral portion of the adjacent glass substrate. Moreover, the outer peripheral portion of the flattening layer is located on the optical axis side of the outer peripheral portion of the adjacent lattice forming layer. The thickness of the lattice forming layer and the flattening layer in the optical axis direction is 50 μm or more and 400 μm or less, respectively.

The lattice forming layer of the diffractive optical element is formed by photocuring and releasing the lattice forming layer optical material filled between the glass substrate and the mold. Similarly, the flattening layer of the diffractive optical element is also formed by photocuring and releasing the flattening layer optical material filled between the previously formed lattice forming layer and the mold.

Japanese Unexamined Patent Publication No. 2012-218394

However, in the conventional example described in Patent Document 1, there is a problem to be solved that the appearance of the diffractive optical element deteriorates due to the influence of the shapes of the lattice forming layer and the flattening layer forming the diffractive optical element outside the optically effective diameter. there were.

Specifically, two white bright lines are generated on the outer circumference of the diffractive optical element installed in the lens barrel. The two emission lines circulate around the outer circumference of the diffractive optical element while irregularly changing the width of the emission lines and bending in a wavy shape, and the shape of the two emission lines changes depending on the viewing angle. The positions of the two emission lines are outside the optically effective diameter of the lattice forming layer and the flattening layer. The bright lines generated in the diffractive optical element generate conspicuous (conspicuous) irregular scattered light in the optical system such as the lens barrel, which deteriorates the appearance of the optical system including the diffractive optical element.

To solve the above problems, the invention according to a first aspect of the present application,
And the glass substrate,
A first resin layer provided on the glass substrate and having a molding surface having a lattice,
A second resin layer provided on the first resin layer and having a molding surface not in contact with the first resin layer is laminated in order.
A diffraction optical element having a diffraction grating between the first resin layer and the second resin layer .
Each of the previous SL first resin layer and the second resin layer, the radial outer periphery of the inflexion point located on the circumference of a circle positioned at the optical effective diameter around the optical axis of the molding surface It is provided with a tapered portion that becomes thinner toward the end and a terminal portion located at the end of the tapered portion .
Ri thickness 50μm less der than 5μm of the terminal portion,
The end portion has a concave shape recessed in the direction of the optical axis .

According to the present invention, it is possible to reduce bright lines that are irregular scattered light that is noticeable (conspicuous) on the outer periphery of the diffractive optical element, so that it is possible to provide a diffractive optical element having an excellent appearance.

Further, since it is possible to reduce the emission lines which are irregular scattered light from the tapered portion and the terminal portion of the layer for lattice forming, it is possible to provide a diffractive optical element having a more excellent appearance.

Further, since it is possible to reduce the emission lines which are irregular scattered light from the tapered portion and the terminal portion of the layer for lattice forming and the layer for flattening, it is possible to provide a diffractive optical element having a better appearance.

Further, since the emission line which is the reflected light from the tapered portion of the layer for lattice forming and the tapered portion of the layer for flattening can be reduced, it is possible to provide a diffractive optical element having a more excellent appearance.

It is sectional drawing of the diffraction optical element which concerns on embodiment of this invention. It is a figure explaining the manufacturing method of the diffractive optical element which concerns on embodiment of this invention. It is sectional drawing of the diffraction optical element which concerns on embodiment of this invention. It is sectional drawing of the diffraction optical element which concerns on embodiment of this invention. It is sectional drawing of the diffraction optical element which concerns on embodiment of the prior art. It is sectional drawing of the diffraction optical element which concerns on embodiment of this invention. It is sectional drawing of the diffraction optical element which concerns on embodiment of this invention.

As described above, the invention according to a first aspect of the present application,
And the glass substrate,
A first resin layer provided on the glass substrate and having a molding surface having a lattice,
A second resin layer provided on the first resin layer and having a molding surface not in contact with the first resin layer is laminated in order.
A diffraction optical element having a diffraction grating between the first resin layer and the second resin layer.
Each of the first resin layer and the second resin layer is directed from an inflection point located on the circumference of a circle located outside the optical effective diameter centered on the optical axis of the molding surface toward the outer diameter. It is provided with a tapered portion that becomes thinner and a terminal portion located at the end of the tapered portion .
Ri thickness 50μm less der than 5μm of the terminal portion,
The end portion has a concave shape recessed in the direction of the optical axis .
Hereinafter, embodiments of the present invention having such characteristics will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a diffractive optical element according to an embodiment of the present invention. In the diffractive optical element of the present embodiment, the glass substrate 1, the first resin layer 2 for lattice forming, and the second resin layer 3 for flattening are in the direction of the optical axis (indicated by the alternate long and short dash line in the figure). It has a structure in which they are laminated in order. In the diffractive optical element, the intersection line between the molded surface outside the optically effective diameter of the molded surface 6 of the first resin layer 2 and the outer peripheral surface of the first resin layer 2 and the molded surface of the second resin layer 3 Each of the intersecting lines between the molded surface outside the optical effective diameter of No. 6 and the outer peripheral surface of the second resin layer 3 is composed of a series of bending points 7 having the same distance from the optical axis. That is, in the present invention, the "inflection point" is a point at which the inclination of the outer line of the first or second resin layer in the cross section along the optical axis of the diffractive optical element changes discontinuously with that point as a boundary. To say. The first resin layer 2 and the second resin layer 3 of the diffractive optical element have the respective thicknesses of the first resin layer 2 and the second resin layer 3 from each inflection point 7 in the radial outer peripheral direction. Is provided with a tapered portion 4 that gradually or discontinuously thins. Further, the diffractive optical element is provided with a terminal portion 5 having a film thickness of 5 μm or more and less than 50 μm at the end of the tapered portion 4.

FIG. 6 is a cross-sectional view illustrating the form of the terminal portion 5. Reference numeral t in FIG. 6 indicates the shortest length from the intersection of the tapered portion 4 and the terminal portion 5 to the glass substrate 1, that is, the film thickness of the terminal portion 5, and is specifically 5 μm or more and less than 50 μm. Is preferable. The light-shielding layer 11 is formed so as to cover the entire terminal portion 5 and at least a part of the tapered portion 4 (see 11 in FIG. 4) over the entire circumference of the diffractive optical element. However, depending on the light-shielding performance required for the diffractive optical element, as shown in FIG. 6, the light-shielding layer 11 covers the entire terminal portion 5, the entire tapered portion 4, and a part of the first resin layer 2 molded surface. It may be covered. In the figure, d indicates the film thickness of the light-shielding layer 11 in contact with the surfaces of the tapered portion 4 and the terminal portion 5. The light-shielding layer 11 preferably has a film thickness of 5 μm or more in order to obtain sufficient light-shielding performance.

FIG. 2 is a schematic view illustrating an example of a method for manufacturing a diffractive optical element of the present invention. The mold 9 for molding the first resin layer 2 for lattice molding and the mold 10 for molding the second resin layer 3 for flattening constitute an apparatus for manufacturing a diffractive optical element.

Hereinafter, the steps of manufacturing the diffractive optical element of the present invention will be described in order with reference to FIG.
First, an appropriate amount of the uncured optical material 2a for the first resin layer is arranged between the mold 9 for forming the first resin layer 2 for lattice forming and the glass substrate 1 (FIG. 2A). Next, the uncured optical material 2a for the first resin layer is sandwiched between the mold 9 and the glass substrate 1 until the desired layer thickness is obtained, and the optical material 2a is a tapered portion 4 outside the optical effective diameter. Spread until it reaches (Fig. 2 (b)). Next, energy such as light or heat is applied to the uncured optical material 2a for the first resin layer to cure the optical material 2a for the first resin layer. Next, by releasing the optical material 2a for the first resin layer integrated with the glass substrate 1 by curing, a lattice having a tapered portion 4 on the glass substrate 1 and a terminal portion 5 at the end thereof. The first resin layer 2 for molding is molded (FIG. 2 (c)).

Next, uncured optics for forming a second resin layer for flattening between the mold 10 for forming the second resin layer 3 for flattening and the first resin layer 2 for lattice forming. An appropriate amount of the material 3a is arranged (FIG. 2 (d)). Next, the uncured optical material 3a for the second resin layer is sandwiched between the mold 10 and the first resin layer 2 until the desired layer thickness is obtained, and the tapered portion 4 outside the optical effective diameter is formed. Spread until it reaches (Fig. 2 (e)). Next, energy such as light or heat is applied to the uncured optical material 3a for the second resin layer to cure the optical material 3a for the second resin layer. Finally, by releasing the optical material 3a for the second resin layer, which is integrated with the first resin layer 2 by curing, the tapered portion 4 and its termination are formed on the first resin layer 2. A second resin layer 3 for flattening having the end portion 5 is formed (FIG. 2 (f)).
As the first resin and the second resin in the present invention, it is possible to use an energy curable resin including a photocurable resin and a thermosetting resin used as constituent materials of a conventional diffraction optical element. it can.

(Example 1)
The diffractive optical element of this embodiment will be described with reference to FIG.
The diffractive optical element of this embodiment is axisymmetric with respect to the optical axis and is composed of a glass substrate 1, a first resin layer 2 for lattice forming, and a second resin layer 3 for flattening. The diffraction grating 8 is formed at the interface between the first resin layer 2 and the second resin layer 3. The glass substrate 1 is a flat disk glass having a radius of 30 mm. The first resin layer 2 for lattice molding is made of a colorless and transparent photocurable fluoroepoxy resin, and has a film thickness of 200 μm on the optical axis. The second resin layer 3 for flattening is made of a colorless and transparent photocurable sulfur-containing acrylic resin, and has a film thickness of 250 μm on the optical axis.

The inflection point 7 of the first resin layer 2 is located outside the optically effective diameter of a radius of 28 mm in the same molding surface. The inflection point 7 of the second resin layer 3 is located outside the optically effective diameter of a radius of 26 mm in the same molding surface. The optically effective diameter of the diffractive optical element of this embodiment is a radius of 25.5 mm.

A tapered portion 4 is provided so that the film thickness of the first resin layer 2 is continuously thinned from the inflection point 7 of the first resin layer 2 to a position having a radius of 29 mm in the outer peripheral direction of the diameter. Further, the taper portion 4 is provided so that the film thickness of the second resin layer 3 is continuously thinned from the inflection point 7 of the second resin layer 3 to a position having a radius of 27 mm in the outer peripheral direction of the diameter. The surface of each tapered portion 4 of the first resin layer 2 and the second resin layer 3 is a mirror surface.

A terminal portion 5 having a film thickness of 10 μm is provided at the end of the tapered portion 4 of the first resin layer 2. Further, a terminal portion 5 having a film thickness of 20 μm is provided at the end of the tapered portion 4 of the second resin layer 3. The cross-sectional shape of the tapered portion 4 of the first resin layer 2 and the second resin layer 3 is a straight line from the inflection point 7 to the end portion 5. The cross-sectional shape of the terminal portion 5 of the first resin layer 2 and the cross-sectional shape of the terminal portion 5 of the second resin layer 3 in contact with the first resin layer 2 are concave shapes dented in the optical axis direction.

The manufacturing method of the diffractive optical element of this embodiment will be described in order with reference to FIG.
First, the surface of the glass substrate 1 on which the first resin layer 2 for lattice molding is formed is subjected to a silane coupling treatment for strengthening the adhesion with the fluoroepoxy resin.

Next, the glass substrate 1 is placed on the mold 9 with its silane coupling treatment surface facing the mold 9 side, and the fluoroepoxy resin 2a is placed near the center of the mold 9 by a dispenser (not shown). 600 mg is added dropwise (FIG. 2 (a)). Alternatively, the fluorine-based epoxy resin may be dropped near the center of the silane coupling-treated surface of the glass substrate 1.

Next, the glass substrate 1 is pressed against the mold 9 at 10 kgf for 10 seconds, and the fluorine-based epoxy resin 2a is spread and filled between the glass substrate 1 and the mold 9 (FIG. 2B). At this time, the film thickness of the fluorine-based epoxy resin 2a between the glass substrate 1 and the mold 9 along the optical axis is expanded to 200 μm, and the expansion of the fluorine-based epoxy resin 2a is the taper of the outer peripheral portion of the mold 9. It reaches the shape portion, and the film thickness of the end portion 5 of the tapered portion 4 is 10 μm. Here, in order to fill the fluorine-based epoxy resin 2a concentrically between the glass substrate 1 and the mold 9, a step of rotating the glass substrate 1 or the mold 9 around the optical axis may be added.

Next, the fluoroepoxy resin 2a is photocured using an ultraviolet irradiation lamp (not shown). The fluorine-based epoxy resin 2a was irradiated with ultraviolet light having a light intensity of 10 mW / cm ² for 10 minutes through the glass substrate 1.

Next, the first resin layer 2 for lattice forming integrated with the glass substrate 1 is released (FIG. 2 (c)). As a result, the diffraction grating 8 and the tapered portion 4 are transferred to the first resin layer 2 for lattice forming by the mold 9, and the terminal portion 5 is formed at the end of the tapered portion 4.

Next, the glass substrate 1 is placed on the mold 10 with the first resin layer 2 facing the mold 10 side, and then the sulfur-containing acrylic is placed near the center of the mold 10 by a dispenser (not shown). 750 mg of the resin 3a is added dropwise (FIG. 2 (d)). Alternatively, the sulfur-containing acrylic resin may be dropped near the center of the first resin layer 2 on the glass substrate 1.

Next, the glass substrate 1 is pressed against the mold 10 at 10 kgf for 15 seconds, and the sulfur-containing acrylic resin 3a is spread and filled between the first resin layer 2 on the glass substrate 1 and the mold 10. (Fig. 2 (e)). At this time, the film thickness along the optical axis between the first resin layer 2 of the sulfur-containing acrylic resin 3a and the mold 10 is expanded to 250 μm, and the spread of the sulfur-containing acrylic resin 3a is the outer circumference of the mold 10. It reaches the tapered shape portion of the portion, and the film thickness of the terminal portion 5 of the tapered portion 4 is 20 μm. Here, in order to fill the sulfur-containing acrylic resin 3a concentrically between the first resin layer 2 and the mold 10, a step of rotating the glass substrate 1 or the mold 10 around the optical axis may be added. ..

Next, the sulfur-containing acrylic resin 3a is photocured using an ultraviolet irradiation lamp (not shown). The sulfur-containing acrylic resin 3a was irradiated with ultraviolet light having a light intensity of 20 mW / cm ² for 15 minutes through the glass substrate 1 and the first resin layer 2.

Finally, the second resin layer 3 integrated with the glass substrate 1 and the first resin layer 2 is released from the mold (FIG. 2 (f)). As a result, the flat surface and the tapered portion 4 are transferred to the second resin layer 3 for flattening by the mold 10, and the terminal portion 5 is formed at the end of the tapered portion 4.

Since the diffractive optical element of the present embodiment is provided with a tapered portion 4 having a mirror surface and a terminal portion 5 on the outer periphery outside the effective optical diameter, generation of bright lines, which are irregular scattered light, is a problem to be solved in the present invention. Can be reduced. The reason for exerting such a reducing action will be described below.

The light incident on the tapered portion 4 from the periphery of the diffractive optical element is reflected and refracted in a certain direction with respect to the angle of the incident light. Therefore, the light emitted from the tapered portion 4 is observed as a perfectly circular regular emission line with no shading of brightness and no wavy bending. The light incident on the terminal portion 5 from the periphery of the diffractive optical element is scattered by the concave shape of the terminal portion 5. However, since the concave shape of the terminal portion 5 is sufficiently small, the light scattered from the terminal portion 5 is sufficiently weak. The concave shape of the end portion 5 is generated by curing shrinkage during curing of the optical material constituting the first resin layer 2 and the second resin layer 3. Since the volume shrinkage due to the curing reaction of the optical material is concentrated on the terminal portion 5 in contact with the atmosphere during curing molding, the terminal portion 5 is deformed into a concave shape in proportion to the volume shrinkage. Generally, the larger the curing shrinkage rate of the optical material, the larger the end portion 5 is deformed into a concave shape. Further, the thicker the film thickness of the end portion 5, the larger the end portion 5 is deformed into a concave shape. The curing shrinkage of the fluorine-based epoxy resin constituting the first resin layer 2 of this embodiment is 6%, the film thickness of the terminal portion 5 is 10 μm, but the depth of the concave shape of the terminal portion 5 is 3 μm. Met. The curing shrinkage rate of the sulfur-containing acrylic resin constituting the second resin layer 3 of this embodiment is 8%, the film thickness of the terminal portion 5 is 20 μm, but the depth of the concave shape of the terminal portion 5 is 8 μm. Met.

In the diffractive optical element of the prior art, since there is no tapered portion on the outer periphery outside the effective optical diameter and the size of the concave shape of the terminal portion 5 is different, the generation of bright lines, which is irregular scattered light, is a subject of the present invention. Cannot be reduced.

FIG. 5 is a cross-sectional view of a diffractive optical element given as an example of the prior art. The form of the element shown in FIG. 5 and the form of the element according to the present invention are different from each other in the outer peripheral shapes of the first resin layer 2 and the second resin layer 3 outside the optically effective diameter. Since the element of the prior art does not have a portion corresponding to the tapered portion 4 in the present invention, the film thickness of the terminal portion 5 is larger than the film thickness of the terminal portion 5 provided with the tapered portion 4 in the present invention. Further, since the film thickness of the end portion 5 is large, the concave shape formed in the end portion 5 also becomes large. Since the curing shrinkage is concentrated on the end portion 5 which is in contact with the atmosphere during the curing molding of the first resin layer 2 and the second resin layer 3, a plurality of irregularities are irregularly generated on the concave surface of the end portion 5. To do.

The light incident on the terminal portion 5 from the periphery of the diffractive optical element is scattered by the concave shape of the terminal portion 5. Since the concave shape of the end portion 5 is large, a large amount of light is scattered from the end portion 5. Further, since the intensity of the scattered light is distributed in the circumferential direction due to the plurality of irregularities on the concave surface of the terminal portion 5, irregular bright lines with shading in brightness are observed. Further, if the filling shapes of the first resin layer 2 and the second resin layer 3 are not perfectly circular with respect to the optical axis, the terminal portion 5 goes around the outer circumference of the diffractive optical element while bending in a wavy shape in the circumferential direction. Therefore, the emission line due to the terminal portion 5 is also observed in a wavy shape. In the form of the element according to the present invention, even if the end portion 5 is bent in a wavy shape in the circumferential direction of the element, the end portion 5 is sufficiently small, so that the conspicuous (conspicuous) emission line can be significantly reduced. ..

As described above, according to the present embodiment, the emission lines, which are irregular scattered light that is conspicuous (conspicuous) on the outer periphery of the diffractive optical element, are formed on the tapered portion 4 of the first resin layer 2 and the second resin layer 3. Since it can be reduced by the terminal portion 5, it is possible to provide a diffractive optical element having an excellent appearance.

(Comparative Example 1)
In Comparative Example 1, the film thickness of the terminal portion 5 of the first resin layer 2 is different from that of Example 1, and the other configurations are the same. The film thickness of the terminal portion 5 of the first resin layer 2 of Comparative Example 1 is 50 μm, which is thicker than that of Example 1.

According to the configuration of Comparative Example 1, since the film thickness of the end portion 5 of the first resin layer 2 is thick, the scattered light from the end portion 5 is further increased. When the film thickness of the end portion 5 of the first resin layer 2 is 50 μm or more, the irregular bright lines that are noticeable (conspicuous) from the end portion 5 increase, and the appearance of the diffractive optical element is significantly deteriorated. A similar phenomenon was confirmed not only in the case of the first resin layer 2 but also in the second resin layer 3.

(Comparative Example 2)
In Comparative Example 2, the film thickness of the terminal portion 5 of the first resin layer 2 is different from that of Example 1, and the other configurations are the same. The film thickness of the terminal portion 5 of the first resin layer 2 of Comparative Example 2 is 4 μm, which is thinner than that of Example 1.

According to the configuration of Comparative Example 2, since the film thickness of the terminal portion 5 of the first resin layer 2 is thin, the tapered portion 4 and the terminal portion 5 of the first resin layer 2 cannot be molded with high accuracy. Specifically, the thinner the film thickness of the end portion 5, the larger the film thickness ratio between the taper portion 4 and the end portion 5, so that sink marks occur in the taper portion 4 and the end portion 5 due to curing shrinkage, and the portion concerned. The shape of is large and irregularly deformed.

Therefore, according to the configuration of Comparative Example 2, since the tapered portion 4 and the terminal portion 5 do not have a desired shape, irregular scattered light from the tapered portion 4 and the terminal portion 5 is further increased. When the film thickness of the end portion 5 of the first resin layer 2 is less than 5 μm, the irregular emission lines that are noticeable (conspicuous) from the taper portion 4 and the end portion 5 increase, and the appearance of the diffractive optical element is significantly deteriorated. did. A similar phenomenon was confirmed not only in the case of the first resin layer 2 but also in the second resin layer 3.

(Example 2)
The diffractive optical element of this embodiment will be described with reference to FIG.
The diffractive optical element of this embodiment is axisymmetric with respect to the optical axis and is composed of a glass substrate 1, a first resin layer 2 for lattice forming, and a second resin layer 3 for flattening. The diffraction grating 8 is formed at the interface between the first resin layer 2 and the second resin layer 3. The glass substrate 1 is a meniscus lens made of glass and having a radius of 40 mm. The first resin layer 2 is made of a colorless and transparent thermosetting epoxy resin having a refractive index of 1.557, and has a film thickness of 300 μm on the optical axis. The second resin layer 3 is made of a colorless and transparent photocurable fluoroacrylic resin having a refractive index of 1.528, and has a film thickness of 100 μm on the optical axis.

The inflection point 7 of the first resin layer 2 is located outside the optically effective diameter of a radius of 37.4 mm in the same molding surface. The inflection point 7 of the second resin layer 3 is located outside the optically effective diameter of a radius of 37.5 mm in the same molding surface. The optically effective diameter of the diffractive optical element of this embodiment is a radius of 36.5 mm.

A tapered portion 4 is provided in which the film thickness of the first resin layer 2 is continuously thinned from the inflection point 7 of the first resin layer 2 to a position having a radius of 38 mm in the outer peripheral direction of the diameter. A tapered portion 4 is provided in which the film thickness of the second resin layer 3 is continuously thinned from the inflection point 7 of the second resin layer 3 to a position having a radius of 39 mm in the outer peripheral direction of the diameter. The surfaces of the tapered portion 4 of the first resin layer 2 and the second resin layer 3 are mirror surfaces.

A terminal portion 5 having a film thickness of 5 μm is provided at the end of the tapered portion 4 of the first resin layer 2. A terminal portion 5 having a film thickness of 45 μm is provided at the end of the tapered portion 4 of the second resin layer 3. The cross-sectional shape of the tapered portion 4 of the first resin layer 2 and the second resin layer 3 is curved from the inflection point 7 to the end portion 5. The cross-sectional shape of the terminal portion 5 of the first resin layer 2 and the cross-sectional shape of the terminal portion 5 of the second resin layer 3 in contact with the first resin layer 2 are concave shapes dented in the optical axis direction.

The manufacturing method of the diffractive optical element of this embodiment will be described in order with reference to FIG.
First, the concave surface of the glass substrate 1 for forming the first resin layer 2 for lattice forming is subjected to a silane coupling treatment for strengthening the adhesion with the epoxy resin.
Next, the glass substrate 1 is arranged on the mold 9 with the silane coupling treated surface facing the mold 9.

Next, 900 mg of epoxy resin 2a is dropped near the center of the mold 9 by a dispenser (not shown) (FIG. 2 (a)). Alternatively, the epoxy resin 2a may be dropped near the center of the silane coupling-treated surface of the glass substrate 1.

Next, the glass substrate 1 is brought close to the mold 9 at a speed of 20 μm per second, and the epoxy resin 2a is spread and filled between the glass substrate 1 and the mold 9 (FIG. 2B). At this time, the film thickness of the epoxy resin 2a between the glass substrate 1 and the mold 9 along the optical axis is expanded to 300 μm, and the spread of the epoxy resin 2a reaches the tapered shape portion on the outer periphery of the mold 9. The film thickness of the end portion 5 of the taper portion 4 is 5 μm. Here, in order to fill the epoxy resin 2a concentrically between the glass substrate 1 and the mold 9, a step of rotating the glass substrate 1 or the mold 9 around the optical axis may be added.

Next, the epoxy resin is thermoset by heating the epoxy resin at 80 ° C. for 30 minutes using a heating source (not shown).
Next, the first resin layer 2 integrated with the glass substrate 1 is released from the mold (FIG. 2 (c)). The diffraction grating 8 and the tapered portion 4 are transferred to the first resin layer 2 by the mold 9, and the terminal portion 5 is formed at the end of the tapered portion 4.

Next, the glass substrate 1 is arranged on the mold 10 with the first resin layer 2 facing the mold 10.
Next, 300 mg of the fluoroacrylic resin 3a is dropped near the center of the mold 10 by a dispenser (not shown) (FIG. 2 (d)). Alternatively, the fluoroacrylic resin 3a may be dropped near the center of the first resin layer 2 on the glass substrate 1.

Next, the glass substrate 1 is brought close to the mold 10 at a speed of 10 μm per second, and the fluorine-based acrylic resin 3a is spread and filled between the first resin layer 2 and the mold 10 on the glass substrate 1 ( FIG. 2 (e). At this time, the film thickness along the optical axis between the first resin layer 2 and the mold 10 of the fluorine-based acrylic resin 3a is expanded to 100 μm, and the first resin layer 2 is the second resin layer 3. Covered in. The spread of the fluoroacrylic resin reaches the tapered portion of the outer peripheral portion of the mold 10, and the film thickness of the end portion 5 of the tapered portion 4 is 45 μm. Here, in order to fill the fluorine-based acrylic resin concentrically between the first resin layer 2 and the mold 10, a step of rotating the glass substrate 1 or the mold 10 around the optical axis may be added.

Next, the fluoroacrylic resin is photocured using an ultraviolet irradiation lamp (not shown). The fluoroacrylic resin was irradiated with ultraviolet light having a light intensity of 30 mW / cm ² for 10 minutes through the glass substrate 1 and the first resin layer 2.

Finally, the second resin layer 3 integrated with the glass substrate 1 and the first resin layer 2 is released from the mold (FIG. 2 (f)). The flat surface and the tapered portion 4 are transferred to the second resin layer 3 by the mold 10, and the terminal portion 5 is formed at the end of the tapered portion 4.

Since the diffractive optical element of this embodiment is provided with a tapered portion 4 having a mirror surface and a terminal portion 5 on the outer periphery outside the effective optical diameter, and the second resin layer 3 covers the first resin layer 2. It is possible to further reduce the generation of emission lines, which are irregular scattered light, which is a subject of the present invention.

The action of the tapered portion 4 and the terminal portion 5 of the second resin layer 3 in the present embodiment to reduce the emission lines, which are irregular scattered light, is the same as that described in the first embodiment, and is therefore omitted. In this embodiment, in addition, since the second resin layer 3 covers the first resin layer 2, the second resin layers 3 and the first in the tapered portion 4 and the terminal portion 5 of the first resin layer 2 are covered. The difference in the refractive index of the interface composed of the resin layer 2 of the above is reduced. Specifically, the difference in refractive index at the interface between the first resin layer 2 and air is 1.557, whereas the first resin layer 2 and the second resin layer 3 of this embodiment are composed of the first resin layer 2 and the second resin layer 3. The difference in refractive index at the interface is 0.029. As a result, the reflected light and scattered light from the tapered portion 4 and the terminal portion 5 of the first resin layer 2 can be reduced with respect to the incident light on the outer periphery of the diffractive optical element of the present embodiment. The generation of bright lines can be further reduced. The smaller the difference in refractive index between the first resin layer 2 and the second resin layer 3, the more the emission lines from the tapered portion 4 and the terminal portion 5 of the first resin layer 2 can be reduced.

In this embodiment, the cross-sectional shape of the tapered portion 4 from the inflection point 7 to the end portion 5 is a continuous curve, but the same effect can be obtained even with a discontinuous stepped shape.

As described above, according to the present embodiment, the emission lines, which are irregular scattered light that is conspicuous (conspicuous) on the outer periphery of the diffractive optical element, are formed on the tapered portion 4 of the first resin layer 2 and the second resin layer 3. Since it can be further reduced by the terminal portion 5, it is possible to provide a diffractive optical element having a better appearance.

(Example 3)
The configuration of the diffractive optical element of this embodiment is the same as the other configurations except that the surface roughness of the light-shielding layer in contact with the terminal portion 5 and the tapered portion 4 is different from the surface roughness of Example 1.

The cross-sectional structure of the outer peripheral portion of the diffractive optical element of this embodiment will be described with reference to FIG. The light-shielding layer 11 is made of a black photocurable epoxy material and covers at least a part of the terminal portion 5 and the tapered portion 4. The minimum film thickness of the light-shielding layer 11 at the end point 12 on the molding surface 6 side of the terminal portion 5 is 5 μm. The surface roughness of the tapered portion 4 is 10 μm in Ra.

The method for manufacturing the diffractive optical element of this embodiment is the same except that the step of forming the light-shielding layer 11 in contact with the terminal portion 5 is added to the first embodiment.

The light-shielding layer 11 in this embodiment is formed by applying a black photocurable epoxy material to the end portion 5 including the taper portion 4 and the end point 12 and irradiating with ultraviolet rays. It is difficult to form the light-shielding layer 11 on the end point 12 on the molding surface 6 side of the terminal portion 5, but in this embodiment, this is realized by photocuring the epoxy material immediately after applying the epoxy material to the end point 12. did. If the epoxy material is left applied to the end point 5 including the end point 12, the epoxy material on the end point 12 moves to the recess of the end point 5 due to the influence of the surface tension and viscosity of the epoxy material. The desired light-shielding layer 11 cannot be formed on the surface. A 3D printer may be used as a device for forming the light-shielding layer 11.

Further, in order to form the tapered portion 4 having the surface roughness of this embodiment, it is necessary to form a shape having the same surface roughness on the transfer surface of the tapered portion 4 of the mold. The mold having the tapered portion 4 of this embodiment was manufactured by cutting.

The diffractive optical element of this embodiment is provided with a tapered portion 4 having a surface roughness and a terminal portion 5 on the outer periphery outside the effective optical diameter, and the tapered portion 4 and the terminal portion 5 are covered with a light-shielding layer 11. Therefore, it is possible to further reduce the generation of emission lines, which are irregular scattered light, which is a subject of the present invention.

The action of the tapered portion 4 and the terminal portion 5 in the present embodiment to reduce irregular emission lines is the same as that described in the first embodiment, and is therefore omitted. In this embodiment, in addition, since the light-shielding layer 11 covers the tapered portion 4 and the terminal portion 5, the light-shielding layer 11 absorbs partially scattered light and transmitted light from the tapered portion 4 and the terminal portion 5. Can be done. Further, by making the surface of the tapered portion 4 a rough surface, the reflected light from the tapered portion 4 can be reduced.

As described above, according to the present embodiment, the emission lines, which are irregular scattered light that is conspicuous (conspicuous) on the outer periphery of the diffractive optical element, are transmitted to the light-shielding layer 11 of the first resin layer 2 and the second resin layer 3. Since it can be further reduced by the tapered portion 4 and the terminal portion 5 provided, it is possible to provide a diffractive optical element having an excellent appearance.

(Example 4)
The configuration of the diffractive optical element of this embodiment is the same except that the shape of the tapered portion 4 is different from that of the first embodiment. The cross-sectional structure of the outer peripheral portion of the diffractive optical element of this embodiment will be described with reference to FIG. The tapered portion 4 has a tapered shape in which the film thickness decreases toward the outer peripheral direction of the diameter, and has a discontinuous uneven shape on the surface. The uneven shape is a line-and-space structure having a width of 20 μm and a depth of 5 μm.

In the method for manufacturing the diffractive optical element of the present embodiment, in the molding process of the first resin layer 2 and the second resin layer 3, only a mold having a discontinuous uneven shape in the tapered portion is used, and other methods are used. The configuration is the same as in Example 1. In order to form the tapered portion 4 having the discontinuous uneven shape of this embodiment, it is necessary to form an inverted shape having the same structure on the transfer surface of the tapered portion 4 of the mold. The mold having the tapered portion 4 of this embodiment was manufactured by cutting or etching.

Since the diffractive optical element of the present embodiment is provided with a tapered portion 4 and a terminal portion 5 having a discontinuous uneven shape on the outer periphery outside the effective optical diameter, it is an irregular scattered light which is a subject of the present invention. The generation of bright lines can be further reduced.

The action of the terminal portion 5 in the present embodiment to reduce irregular emission lines is the same as that described in the first embodiment, and is therefore omitted. In this embodiment, in addition, by forming the surface of the tapered portion 4 into a discontinuous uneven shape, light incident on the tapered portion 4 can be regularly reflected or diffracted in a plurality of directions. In this embodiment, the uneven shape has a line-and-space structure having a width of 20 μm and a depth of 5 μm, but the shape is not limited to this structure as long as the same effect can be obtained.

As described above, according to the present embodiment, the emission lines, which are irregular scattered light that is noticeable (conspicuous) on the outer periphery of the diffractive optical element, can be further reduced by the tapered portion 4 and the terminal portion 5 having a discontinuous uneven shape. Therefore, it is possible to provide a diffractive optical element having an excellent appearance.

Although a glass substrate is used as the base material in each of the above-described embodiments, the glass substrate is not limited to the inorganic glass substrate, and may be a so-called organic glass substrate (plastic substrate).

1 Glass substrate 2 First resin layer 3 Second resin layer 4 Tapered part 5 Termination part 6 Molding surface 7 Inflection point 8 Diffraction grating 9 Mold 10 Mold 11 Light-shielding layer 12 End point

Claims (9)

With a glass substrate
A first resin layer provided on the glass substrate and having a molding surface having a lattice,
A second resin layer provided on the first resin layer and having a molding surface not in contact with the first resin layer is laminated in order.
A diffraction optical element having a diffraction grating between the first resin layer and the second resin layer .
Each of the previous SL first resin layer and the second resin layer, the radial outer periphery of the inflexion point located on the circumference of a circle positioned at the optical effective diameter around the optical axis of the molding surface It is provided with a tapered portion that becomes thinner toward the end and a terminal portion located at the end of the tapered portion .
Ri thickness 50μm less der than 5μm of the terminal portion,
Diffractive optical element in which the terminal end is characterized concave der Rukoto recessed in the direction of the optical axis. The diffractive optical element according to claim 1, wherein the molded surface of the first resin layer is wider than the molded surface of the second resin layer. The diffractive optical element according to claim 1, wherein the tapered portion and the terminal portion of the first resin layer are covered with the second resin layer. The diffractive optical element according to any one of claims 1 to 3, wherein the molded surface of the second resin layer has a flat portion. Claims, characterized in that the film thickness is formed is 5μm or more light-shielding layer on at least a portion the surface of the end portion of at least one of the tapered portion of the first resin layer and the second resin layer Item 2. The diffractive optical element according to item 1 or 2 . The diffractive optical element according to any one of claims 1 to 5, wherein the surface of at least one of the tapered portion of the first resin layer and the second resin layer is a rough surface. The diffractive optical element according to any one of claims 1 to 5, wherein the surface of at least one of the tapered portion of the first resin layer and the second resin layer has an uneven shape. .. An optical device comprising the diffractive optical element according to any one of claims 1 to 7. A camera provided with the diffractive optical element according to any one of claims 1 to 7.

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