JP7451299B2 - Diffractive optical elements, optical instruments and imaging devices - Google Patents

Description

This invention relates to diffractive optical elements used as lenses in cameras, videos, etc. The present invention also relates to an optical device and an imaging device using the diffractive optical element.

BACKGROUND ART A diffractive optical element in which two types of resins having different optical properties are laminated in close contact with each other has been known as a diffractive optical element used in lenses and the like. Such a diffractive optical element is manufactured by a manufacturing method as disclosed in Patent Document 1. Specifically, first, a first resin layer having a lattice shape is formed on a base material using a mold having a lattice shape. Next, a second resin layer having optical properties different from those of the first resin layer is formed on the first resin layer using a flat mold.

Japanese Patent Application Publication No. 2003-320540

However, in the diffractive optical element manufactured by the manufacturing method disclosed in Patent Document 1, the diffraction efficiency at the periphery of the element is significantly lower than that at the center of the element, depending on the height of the grating and the thickness of the resin layer. There was a problem that it ended up happening.

A diffractive optical element for solving the above problems has a first resin layer and a second resin layer laminated in order, and when viewed from above, at least one of the interfaces between the first resin layer and the second resin layer is laminated. A diffractive optical element in which a concentric diffraction grating is formed in a portion thereof, and the diffraction grating includes a first region including a center of the diffraction grating and a first region surrounding the first region when viewed in plan. a second region having a grating with a height lower than that of the second region, the grating height of the diffraction grating in the second region decreases toward an outer edge of the diffraction grating , and in the second region, When the height of the m-th grating (m is an integer greater than 2) from the center to the outer edge of the diffraction grating is dm, the relationship 0.50≦d _m /d _m−1 ≦0.98 is satisfied. It is characterized by

According to the present invention, it is possible to provide a diffractive optical element with a small difference in diffraction efficiency between the ends and the center of the element.

1 is a schematic diagram showing one embodiment of a diffractive optical element of the present invention. FIG. 2 is an enlarged view of the diffractive optical element of FIG. 1; FIG. 2 is a schematic diagram showing a change over time in the refractive index of a conventional diffractive optical element. 1 is a schematic diagram showing one embodiment of a diffractive optical element of the present invention. 1 is a schematic diagram showing one embodiment of a method for manufacturing a diffractive optical element of the present invention. 1 is a schematic diagram showing an embodiment of an imaging device of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

[Diffractive optical element]
FIG. 1 is a schematic plan view and a schematic cross-sectional view showing a diffractive optical element according to a first embodiment. FIG. 2 is an enlarged view of the end portion of the diffractive optical element, which is an enlarged view of the dotted line portion in FIG. As shown in FIGS. 1 and 2, the diffractive optical element 20 has a first resin layer 2 and a second resin layer 3 laminated in this order on a first base material 1.

(First base material)
The first base material 1 can be made of transparent resin or transparent glass. It is preferable to use glass for the first base material 1, and for example, common optical glasses such as silicate glass, borosilicate glass, and phosphate glass, quartz glass, and glass ceramics can be used.

The shape of the first base material 1 is not particularly limited, and the shape of the surface in contact with the first resin layer 2 can be selected from a concave spherical surface, a convex spherical surface, an axially symmetric aspherical surface, a flat surface, and the like. Moreover, it is preferable that the outer shape of the first base material 1 is circular when viewed from above.

(First resin layer/second resin layer)
The first resin layer 2 and the second resin layer 3 are transparent resins having different optical properties, and the refractive index and Abbe number are designed so that the diffractive optical element 20 has desired optical properties. In order to obtain high diffraction efficiency in a wide wavelength band, it is preferable that one of the first resin layer 2 and the second resin layer 3 has a low refractive index and high dispersion, and the other has a high refractive index and low dispersion. Here, the low refractive index and the high refractive index refer to the relative relationship between the refractive indexes (d-line refractive index) of the first resin layer 2 and the second resin layer 3. Similarly, high dispersion and low dispersion refer to the relative relationship between the dispersion characteristics (Abbe number νd) of the first resin layer 2 and the second resin layer 3. In other words, the fact that the first resin layer 2 has a high refractive index and low dispersion with respect to the second resin layer 3 means that the refractive index Nd1 of the first resin layer 2, the Abbe number ν1, the refractive index Nd2 of the second resin layer 3, and This means that the Abbe number ν2 satisfies Nd1>Nd2 and ν1>ν2.

The first resin layer 2 and the second resin layer 3 are cured products of resin compositions. The resin composition that is the raw material for the first resin layer 2 is the first resin composition 2a, and the resin composition that is the raw material for the second resin layer 3 is the second resin composition 3. It is preferable that the first resin composition 2a and the second resin composition 3a contain an energy-curable resin. Among energy-curable resins, ultraviolet-curable resins are more preferred. As the ultraviolet curable resin, for example, acrylic resin or epoxy resin can be used. Furthermore, the first resin composition 2a and the second resin composition 3a may contain organic or inorganic substances other than resin in order to adjust optical properties and mechanical properties.

The first resin layer 2 and the second resin layer 3, which are two resin layers laminated on the first base material 1, have a concentric diffraction grating formed on at least a part of their interface when viewed from above. ing. Specifically, the grating portion 10 exists between the base portion 11 of the first resin layer and the base portion 12 of the second resin layer, and a diffraction grating is formed in the lamination direction of the two resin layers. The diffraction grating may be formed on a part of the interface in the stacking direction, or may be formed on the entire surface. The shape of the diffraction grating includes an inclined surface 15A that is gently inclined in the radial direction from the center O of the element (the center of the first resin layer 2 and the second resin layer 3) toward the outer periphery (periphery), and a slope that extends a predetermined distance. Incidentally, this is a repeating pattern of the wall surface 15B that suddenly changes in the opposite direction of the slope. The interval between the repeating patterns (pitch interval) decreases continuously from the center toward the outer periphery. Further, the inclined surface does not need to be smooth, and may have a fine step-like inclination of less than the wavelength of visible light.

(lattice shape)
FIG. 3 is a schematic diagram showing an end portion of a prior art diffractive optical element. In the diffractive optical element 20X, a first resin layer 2X and a second resin layer 3X are sequentially laminated on a first base material 1X. Further, when the first resin layer 2X and the second resin layer 3X are viewed in plan, a concentric diffraction grating is formed at least in part of the interface thereof. Specifically, a grating portion 10X exists between the base portion 11X of the first resin layer and the base portion 12X of the second resin layer, and a diffraction grating is formed in the lamination direction of the two resin layers. The shape of the diffraction grating consists of an inclined surface 15XA that gently slopes in the radial direction from the center of the first resin layer 2X and the second resin layer 3X toward the outer periphery, and after a predetermined distance, the slope suddenly changes in the opposite direction. This is a repeating pattern of wall surface 15XB. However, the diffractive optical element 20X differs from the diffractive optical element 20 in that the height of the diffraction grating (the height of the grating portion 10X) is substantially uniform. The configuration of this diffractive optical element 20X is the same as that of the diffractive optical element disclosed in Patent Document 1.

The inventor of the present application has discovered that the diffraction efficiency of the diffractive optical element 20X at the periphery of the element is significantly lower than that at the center depending on the height of the grating section 10X and the thickness of the first resin layer 2X and the second resin layer 3X. I discovered that The mechanism will be described below, taking as an example a case where the height of the grid portion is high and the thickness of the first resin layer and the second resin layer is thin.

First, using a mold, uncured resin is cured on the first base material 11X to form the first resin layer 1X. If the height of the lattice portion 10X of the first resin layer is too high, the amount of curing shrinkage will differ greatly between the vicinity of the apex of the lattice and the base portion. If the amount of curing shrinkage differs, the density of the resin also changes, resulting in a difference in refractive index near the apex of the lattice and at the base. At this time, if the base part is thick enough, the difference in refractive index that occurs can be alleviated to some extent, but if the thickness of the base part is thin relative to the height of the grating part, the difference in refractive index that occurs becomes large. It ends up.

Furthermore, when the first resin layer is molded with a mold, the refractive index difference has a greater influence on the peripheral portion surrounding the center than on the central portion including the center of the element. This is because if there is a thin region at the periphery of the lattice shape, when uncured resin is cured, the lattice stress at the periphery increases due to less supply of uncured resin from the periphery. be. Furthermore, not only a refractive index difference occurs, but also a deterioration in the shape accuracy of the diffraction grating.

These phenomena also apply to the second resin layer. If the base portion of the second resin layer 3X is thin, a difference in refractive index will occur between the vicinity of the lattice apex of the second resin portion 3X and the base portion.

Therefore, the present invention provides a first region including the center of the diffraction grating, and a second region surrounding the first region and consisting of a plurality of gratings having heights lower than the first region, when the shape of the diffraction grating is viewed in plan. A region was established. Furthermore, a configuration is adopted in which the grating height of the diffraction grating in the second region is lowered toward the outer edge of the diffraction grating.

FIG. 2 is an enlarged view of the end region of the diffractive optical element 20 in FIG. 1 surrounded by dotted lines. In FIG. 2, the center O of the diffractive optical element 20 is on the left side, and the right side shows the periphery. The first region 13 is a region including the center of the diffraction grating. Its radial length (width) is A. The second region 14 is a region adjacent to the first region 13 and surrounding the first region 13 . The height of the grating in the second region 14 is smaller than the height of the grating in the first region 13 . Furthermore, the lattice in the second region 14 has a plurality of height values, and the height becomes lower in stages from the center toward the outer edge.

By configuring the shape of the diffraction grating in this way, the diffractive optical element 20 can first suppress the residual stress generated at the peripheral edge of the first resin layer 2 when the first resin layer 2 is molded. can. This is because the height of the lattice in the second region 14 is lowered stepwise, so that the influence of the stress generated at the peripheral edge can be gently transmitted inward (toward the center). Furthermore, since the stress generated in the second region 14 is small, the influence of stress transmitted to the first region 13, which has the center of the diffraction grating, is also reduced. As a result, refractive index distribution due to residual stress is less likely to occur throughout the first resin layer 2.

Furthermore, residual stress generated at the peripheral edge of the second resin layer 3 when molding the second resin layer 3 can be suppressed. This is because the lattice in the second region 14 becomes lower in stages, so that the influence of stress generated at the peripheral edge can be transmitted inwardly. Furthermore, since the stress generated in the second region 14 is small, the influence of stress transmitted to the first region 13, which has the center of the diffraction grating, is also reduced. As a result, refractive index distribution due to residual stress is less likely to occur throughout the second resin layer 3.

The height of the diffraction grating in the first region 13 preferably satisfies the following relationship (Equation 1).

0.99≦d _n /d _n-1 ≦1.01 (Formula 1)
Here, d _n is the height of the n-th grating (n is an integer of 2 or more) from the center to the outer edge of the diffraction grating. That is, in the first region, the height of the grid is approximately constant, with the height of the grid near the center being within a range of 0.99 times or more and 1.01 times or less of the height of the neighboring grid on the outer circumference side. It is preferable that The first region 13 is an optically effective region, and if the height of the grating is substantially constant, it is easier to design the optical performance of the diffractive optical element 20.

Furthermore, it is preferable that the height of the diffraction grating in the second region 14 satisfy the following relationship (Equation 2).

0.50≦d _m /d _m-1 ≦0.98 (Formula 2)
Here, d _m is the height of the m-th grating (m is an integer greater than n) from the center of the diffraction grating toward the outer edge. That is, in the second region, it is preferable that the height of the adjacent lattice on the outer peripheral side is in a range of 0.50 to 0.98 times the height of the lattice near the center. If this value is less than 0.50 times, the change in the grating height is too large, resulting in a difference in the amount of curing shrinkage near the peaks of the grating, which may cause a refractive index distribution. On the other hand, if it is larger than 0.98 times, the change in grating height will be small and the effect of relaxing stress will be small, and there is a possibility that a refractive index distribution will occur from the periphery toward the center.

Further, it is preferable that the radial length A of the first region 13 and the radial length B of the second region 14 satisfy the following relationship (Equation 3).

0.018≦B/A≦0.10 (Formula 3)
When A and B satisfy (Formula 3), a sufficient stress relaxation effect can be obtained and the device can be easily miniaturized. If B/A is less than 0.018, the area of the second region 14 is small, so there is a possibility that a sufficient stress relaxation effect cannot be obtained. On the other hand, if B/A is larger than 0.10, the area of the second region 14 having the optically ineffective area becomes large, so there is a possibility that the device becomes large.

Note that there may be a portion without a diffraction grating at a position surrounding the second region 14. This portion may have a bank-like shape with a flat height, or may have a tapered shape (slope shape) where the thickness continuously decreases toward the outer periphery.

The height of the diffraction grating (the height of the grating section 10) is preferably in the range of 5 μm or more and 30 μm or less. If the height of the diffraction grating is within this range, it is easy to obtain sufficient optical performance and the grating is less likely to be deformed during demolding. Further, the pitch of the diffraction grating is, for example, 100 μm or more and 5 mm or less. In particular, it is preferable that the interval between the outermost lattice of the first region and the innermost lattice of the second region is in the range of 100 μm or more and 500 μm or less. If the interval is less than 100 μm, the stress in the second region will be greatly affected, and there is a possibility that a difference in refractive index will occur inside the grating in the first region. If the interval is larger than 500 μm, the area of the second region 14 having the optically ineffective area becomes large, so there is a possibility that the device becomes large.

The average thickness of the base portion 11, which is the portion of the first resin layer 2 excluding the lattice shape, is preferably in the range of 1 μm or more and 50 μm or less. If it is less than 1 μm, when the first resin layer 2 is cured and formed, stress will be excessively generated between the apex and the base of the lattice, making the lattice shape unstable, resulting in a decrease in diffraction efficiency. There is a risk that the product may become damaged. On the other hand, if it is thicker than 50 μm, the entire resin layer becomes thick as a diffractive optical element, and the optical characteristics may easily change due to temperature fluctuations.

The average thickness of the base portion 12 of the portion of the second resin layer 3 excluding the lattice shape is preferably in the range of 10 μm or more and 400 μm or less. If it is less than 10 μm, when the second resin layer 3 is cured and formed, excessive stress will be generated in the stepped portion of the grating, resulting in an unstable shape, which may result in a decrease in diffraction efficiency. . On the other hand, if it is thicker than 400 μm, the entire resin layer becomes thick as a diffractive optical element, and the optical characteristics may easily change due to temperature fluctuations.

(Modified example)
The diffractive optical element applicable to the present invention is not limited to the forms shown in FIGS. 1 and 2. For example, the first resin layer 2 and the second resin layer 3 may be laminated on the first base material 1 in the order of the second resin layer 3 and the first resin layer 2.

Further, as shown in FIG. 4, the diffractive optical element 20 has a second base material 4 provided on the second resin layer 3, and the two resin layers are placed between the first base material 1 and the second base material 4. A configuration in which it is sandwiched between the two is also acceptable. At this time, like the first base material 1, the second base material 4 can be made of transparent resin or transparent glass. It is preferable to use glass for the second base material 4, and for example, common optical glasses such as silicate glass, borosilicate glass, and phosphate glass, quartz glass, and glass ceramics can be used. Like the first base material 1, the shape of the second base material 4 is not particularly limited, and the shape of the surface in contact with the second resin layer 3 can be selected from a concave spherical surface, a convex spherical surface, an axisymmetric aspheric surface, a flat surface, etc. . However, it is preferable that the shape of the surface of the second base material 4 in contact with the second resin layer 3 is substantially the same as the shape of the surface of the first base material 1 in contact with the first resin layer 2. Further, the outer shape of the second base material 4 when viewed from above is preferably circular like the first base material 1. Note that the effects of the present invention are more prominently exhibited in the diffractive optical element having the second base material 4. This is because when the second base material 4 is present, when the second resin layer 3 is cured and formed, the stress generated at the steps of the lattice (steps between the apex of the lattice and the base part) is restrained by the second base material 4 and relaxed. This is because it is difficult to release and more likely to remain.

[Method for manufacturing diffractive optical element]
Next, a method for manufacturing a diffractive optical element will be explained. FIG. 5 is a schematic diagram showing one embodiment of the method for manufacturing a diffractive optical element of the present invention.

First, a glass base material is prepared as the first base material 1. In order to improve the adhesion with the resin layer to be laminated, it is preferable to pre-treat the surface of the glass substrate that will be in close contact with the resin layer. Preferably, the glass surface is subjected to a coupling treatment using a silane coupling agent that has good affinity with the resin layer. Specific coupling agents include hexamethyldisilazane, methyltrimethoxysilane, trimethylchlorosilane, triethylchlorosilane, and the like.

Next, a first resin layer 2 is formed on the first base material 1. As shown in FIG. 5(a), an energetic hardening resin is dropped onto the grid mold 5 as a first resin composition 2a, which is a precursor of the first resin layer 2. As shown in FIG. Next, the first base material 1 is placed on the ejector 7 and placed facing the grid mold 5. The grating type 5 used here has an inverted shape of the desired diffraction grating shape on its surface, and is cut by a precision processing machine using, for example, NiP plating or oxygen-free copper plating on a metal base material such as stainless steel or steel. It can be made by doing this.

Next, as shown in FIG. 5(b), the ejector 7 is lowered to fill the space between the grid mold 5 and the first base material 1 with energy-curable resin. Thereafter, the shutter 9 is retracted and the energy curable resin is irradiated with energy rays using the lamp 8 to cure the energy curable resin and form the first resin layer 2.

Thereafter, as shown in FIG. 5(c1), the ejector 7 is raised to remove the cured first resin layer 2 from the grid mold 5, thereby releasing the mold. Note that heating annealing, additional irradiation with energy rays, heating in an oxygen-free atmosphere, irradiation with energy rays, etc. may be performed before and after demolding. Here, the lattice shape formed may be a convex lattice shape as shown in FIG. 5(c1) or a concave lattice shape as shown in FIG. 5(c2).

Next, the second resin layer 3 is formed. As shown in FIG. 5(d), an energy-curable resin is dropped onto the flat mold 6 as a second resin composition 3a, which is a precursor of the second resin layer 3. As shown in FIG. Then, the first base material 1 and the first resin layer 12 are placed on the ejector 7 and placed facing the flat mold 6. Next, as shown in FIG. 5(e), the ejector 7 is lowered to fill the space between the flat mold 6 and the first resin layer 2 with energy ray-curable resin. Thereafter, the shutter 9 is retracted and the energy ray curable resin is irradiated with energy rays from the lamp 8 to form the second resin layer 3. Through the above steps, the diffractive optical element 20 in which the first resin layer 2 and the second resin layer 3 are laminated in close contact with each other on the first base material 1 can be manufactured.

Note that the obtained diffractive optical element 20 may be subjected to heat annealing, additional irradiation with energy rays, heating in an oxygen-free atmosphere, irradiation with energy rays, etc. so as not to leave unreacted resin.

Further, when the second base material 4 is provided on the second resin layer 3, the second base material 4 may be used instead of the flat mold 6.

[Imaging device]
FIG. 6 shows the configuration of a single-lens reflex digital camera, which is an example of a preferred embodiment of the imaging device of the present invention. In FIG. 6, a camera body 602 and a lens barrel 601, which is an optical device, are combined, and the lens barrel 601 is a so-called interchangeable lens that can be attached to and detached from the camera body 602.

Light from the subject passes through an optical system including a plurality of lenses 603 and 605 arranged on the optical axis of the photographing optical system in the housing 620 of the lens barrel 601, and is received by the image sensor 610. The diffractive optical element of the present invention can be used for the lens 605, for example.

Here, the lens 605 is supported by an inner tube 604 inside the housing, and is movably supported relative to the outer tube of the lens barrel 601 for focusing and zooming.

During the observation period before photographing, light from the subject is reflected by the main mirror 607 in the housing 621 of the camera body, passes through the prism 611, and then the photographed image is projected to the photographer through the finder lens 612. The main mirror 607 is, for example, a half mirror, and the light transmitted through the main mirror is reflected by a submirror 608 in the direction of an AF (autofocus) unit 613, and this reflected light is used, for example, for distance measurement. Further, the main mirror 607 is mounted and supported by a main mirror holder 640 by adhesive or the like. During photographing, the main mirror 607 and the sub-mirror 608 are moved out of the optical path through a drive mechanism (not shown), the shutter 609 is opened, and the photographing light image incident from the lens barrel 601 is formed on the image sensor 610. Further, the diaphragm 606 is configured so that brightness and depth of focus during photographing can be changed by changing the aperture area.

The present invention will be explained in more detail below using Examples. First, a method for evaluating a diffractive optical element will be explained.

(Grid height, resin layer thickness, lattice pitch, radial length of the first region and second region)
A plane passing through the center O of the diffractive optical element (a plane passing through the center of the optical axis) was cut in the stacking direction. The cross section of the cut diffractive optical element was observed at a magnification of 1000 times (eyepiece: 10 times, objective lens: 100 times) using a metallurgical microscope (ECLIPSE ME600P, manufactured by Nikon Corporation). The grating height, the thickness of the resin layer, the grating pitch, and the radial lengths of the first region and the second region were each measured from the feed amount of the XY stage.

The lattice height is defined as the surface (laminated surface) of the first base material that is in contact with the first resin layer with respect to the straight line connecting the two bottom parts (two places on the base part) adjacent to the vertices of the lattice from the apex of the lattice. The length in the normal direction was measured. The first region and the second region were identified from the grid height.

The thickness of the resin layer was determined by measuring the length in the normal direction of the laminated surface of the first base material from the straight line connecting the bottoms of the lattice to the laminated surface of the first base material. The thickness of the first resin layer and the thickness of the second resin layer are determined by dividing the combined resin width (radial length) of the first region and the second region into 10 equal parts, and measuring the resin thickness at the center of each divided region. was measured and calculated from the average value. The difference between this calculated value and the grid height was defined as the thickness of the base portion.

The grating pitch was determined by measuring the length of the two bottoms adjacent to the top of the grating in the direction perpendicular to the optical axis.

The radial lengths of the first region and the second region were calculated by summing the lattice pitches of the lattices included in each region.

(d-line refractive index measurement)
The first base material 11 and/or the second base material 14 were peeled off from the diffractive optical elements of Examples and Comparative Examples, and the resin was taken out and measured. The refractive index of the obtained sample at a wavelength of 587.6 nm (d-line) was measured using a precision refractometer (KPR-30, Shimadzu Corporation).

(Diffraction efficiency of diffractive optical element)
The average diffraction efficiency was measured by entering measurement light with a diameter of 2 mm and a wavelength of 400 nm to 700 nm into the outer circumference of the grating shape, and detecting the intensity of the first-order diffracted light emitted from the element. In this measurement, the diffraction efficiency at the center of the first region was measured in a region from 8 gratings to 11 gratings from the center to the outer periphery of the diffractive optical element. In this measurement, the diffraction efficiency at the outer periphery of the first region was measured in a region from 1st grating to 9th grating from the outer periphery to the center of the first region. Among the manufactured diffractive optical elements, those in which the ratio of the diffraction efficiency of the outer peripheral part of the first region to the central part of the first region is less than 0.993 are designated as C, and those that are 0.993 or more and less than 0.995 are designated as B and 0.995. The above items were rated A. A and B were judged as passing, and C was judged as failing.

(Example 1)
As the first base material, a concave spherical glass lens made of S-TIM8 (manufactured by Ohara Corporation) with a diameter of 60 mm, one surface being flat, and the other surface having a radius of curvature R of 190 mm was used. The second base material 4 is a glass lens made of S-FSL5 (manufactured by Ohara Corporation), diameter 58 mm, convex spherical shape with radius of curvature R of 70 mm on one surface, and convex spherical shape on the other surface with radius R of 190 mm. . The lattice type and flat type were obtained by cutting a NiP layer plated on a metal base material using a precision processing machine to form a desired lattice shape, a flat shape, and an inverted shape of the outer peripheral shape.

A first resin composition 2a of an ultraviolet curable acrylic resin was filled between the grid mold 5 and the first base material 1. Thereafter, the first resin composition 2a was cured by irradiating the entire surface with ultraviolet light having a wavelength of 365 nm and an intensity of 10 mW/ ^cm2 for 200 seconds, and the mold was released to form a first resin layer 2 on the first base material 1. .

Next, the intermediate obtained by demolding was placed in an oven and heated at 80° C. for 24 hours. Subsequently, a second resin composition 3a of an ultraviolet curable acrylic resin is filled between the intermediate body and the second base material 4, and the entire surface is irradiated with ultraviolet rays for 200 seconds to cure the second resin composition 3a. A zygote was obtained. Thereafter, the entire surface of the obtained bonded body was irradiated with ultraviolet light having a wavelength of 365 nm and an intensity of 30 mW/cm ² for 1000 seconds. Finally, the obtained bonded body was placed in an oven and heated at 80° C. for 72 hours to produce the diffractive optical element of Example 1.

The first resin layer of the diffractive optical element of Example 1 had a d-line refractive index of 1.62 and an Abbe number νd of 40.0, and a second resin layer had a d-line refractive index of 1.59 and an Abbe number of 29. It was .0.

The grating shape of the diffractive optical element of Example 1 had a gentle convex slope with respect to a concave spherical surface with an radius of 190 mm. The grating pitch of the first grating closest to the center of the element was 3.5 mm, the grating pitch of the second grating was 1.5 mm, and the grating pitches became narrower successively. The grating pitch is 0.54 mm for the 10th grating, 0.39 mm for the 20th grating, 0.32 mm for the 30th grating, 0.28 mm for the 40th grating, 0.25 mm for the 50th grating, and 0.2 mm for the 60th grating. It was 24 mm. The outermost lattice was the 65th lattice, and the lattice pitch was 0.23 mm. Further, the height 10 of the grating portion is 23.8 μm for the first grating, 23.7 μm for the 10th grating, 23.6 μm for the 20th grating, 23.5 μm for the 30th grating, and 23.3 μm for the 40th grating. The 50th grating was 23.2 μm, and the 60th grating was 23.0 μm. Further, the 61st grating was 20.7 μm, the 62nd grating was 18.6 μm, the 63rd grating was 16.8 μm, the 64th grating was 15.1 μm, and the 65th grating was 13.6 μm. From this, the first region was from the center to the 60th lattice, and the second region was from the 61st lattice to the outermost periphery. Further, the radial length A of the first region was 25.8 mm, and the radial length B of the second region was 1.2 mm.

Further, the average thickness of the base portion of the first resin layer excluding the grid height was 27.0 μm. Further, the average thickness of the base portion of the second resin layer excluding the grid height was 50.0 μm.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Example 2)
The second embodiment differs from the first embodiment in the shape of the lattice type. A diffractive optical element of Example 2 was produced in the same manner as in Example 1 except for the above.

The diffractive optical element of Example 2 had the following grating shape.

The grating heights were 23.8 μm for the first grating, 23.0 μm for the 63rd grating, 22.5 μm for the 64th grating, and 22.1 μm for the 65th grating. That is, the first region was from the center to the 63rd lattice, and the second region was from the 64th lattice to the outermost periphery. The radial length A of the first region was 26.5 mm, and the radial length B of the second region was 0.5 mm.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Example 3)
The third embodiment differs from the first embodiment in the shape of the lattice type. The diffractive optical element of Example 3 was produced in the same manner as in Example 1 except for the above.

The diffractive optical element of Example 3 had the following grating shape.

The grating heights were 23.8 μm for the first grating, 23.0 μm for the 63rd grating, 11.5 μm for the 64th grating, and 5.8 μm for the 65th grating. That is, the first region was from the center to the 63rd lattice, and the second region was from the 64th lattice to the outermost periphery. The radial length A of the first region was 26.5 mm, and the radial length B of the second region was 0.5 mm.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Example 4)
Example 4 differs from Example 1 in the shape of the lattice type and the compositions of the first resin layer and the second resin layer. A diffractive optical element of Example 4 was produced in the same manner as in Example 1 except for the above.

As for the physical properties of the resin layer of the diffractive optical element of Example 4, the first resin layer has a refractive index of 1.63 and an Abbe number of 44.0, and the second resin layer has a refractive index of 1.57 and an Abbe number of 19. It was 3.

The diffractive optical element of Example 4 had the following grating shape.

The grating pitch was 3.1 mm for the first grating and 1.2 mm for the second grating, and the pitch became narrower successively, and was 0.12 mm for the 55th grating and 0.11 mm for the 65th grating. The grating height is 8.2 μm for the first grating, 8.0 μm for the 55th grating, 7.7 μm for the 56th grating, 7.4 μm for the 57th grating, 7.1 μm for the 58th grating, and 6 μm for the 59th grating. .8 μm, 60th grating 6.5 μm, 61st grating 6.3 μm, 62nd grating 6.0 μm, 63rd grating 5.8 μm, 64th grating 5.5 μm, 65th grating 5.3 μm Met. That is, the first region was from the center to the 55th lattice, and the second region was from the 56th lattice to the outermost periphery. The radial length A of the first region was 25.8 mm, and the radial length B of the second region was 1.2 mm.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Example 5)
Example 5 differs from Example 1 in the shape of the lattice type. A diffractive optical element of Example 5 was manufactured in the same manner as in Example 1 except for the above.

The diffractive optical element of Example 5 had the following grating shape.

The grating heights were 23.8 μm for the first grating, 22.9 μm for the 63rd grating, 11.5 μm for the 64th grating, and 4.6 μm for the 65th grating. That is, the first region was from the center to the 63rd lattice, and the second region was from the 64th lattice to the outermost periphery. The radial length A of the first region was 26.8 mm, and the radial length B of the second region was 0.2 mm.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Example 6)
Example 6 differs from Example 1 in the shape of the lattice type. A diffractive optical element of Example 6 was produced in the same manner as in Example 1 except for the above.

The diffractive optical element of Example 6 had the following grating shape.

The grating heights were 23.8 μm for the first grating, 23.0 μm for the 63rd grating, 22.8 μm for the 64th grating, and 22.5 μm for the 65th grating. That is, the first region was from the center to the 63rd lattice, and the second region was from the 64th lattice to the outermost periphery. The radial length A of the first region was 26.5 mm, and the radial length B of the second region was 0.5 mm.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Example 7)
Example 7 differs from Example 1 in the shape of the lattice type. A diffractive optical element of Example 7 was produced in the same manner as in Example 1 except for the above.

The diffractive optical element of Example 7 had the following grating shape.

The grating heights were 23.8 μm for the first grating, 23.0 μm for the 63rd grating, 9.2 μm for the 64th grating, and 3.7 μm for the 65th grating. That is, the first region was from the center to the 63rd lattice, and the second region was from the 64th lattice to the outermost periphery. The radial length A of the first region was 26.5 mm, and the radial length B of the second region was 0.5 mm.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Example 8)
Example 8 differs from Example 1 in the shape of the lattice type. Further, the second resin layer was formed using a flat mold with a convex spherical surface of R190 mm without using the second base material. A diffractive optical element of Example 8 was produced in the same manner as in Example 1 except for the above.

The diffractive optical element of Example 8 had the following grating shape.

The grating height is 24.5 μm for the first grating, 23.7 μm for the 60th grating, 21.3 μm for the 61st grating, 19.2 μm for the 62nd grating, 17.3 μm for the 63rd grating, and 15 μm for the 64th grating. .5 μm, and the 65th grid was 14.0 μm. That is, the first region was from the center to the 60th lattice, and the second region was from the 61st lattice to the outermost periphery. The radial length A of the first region was 25.8 mm, and the radial length B of the second region was 1.2 mm.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Example 9)
Example 9 differs from Example 1 in the shape of the lattice type. The diffractive optical element of Example 9 was produced in the same manner as in Example 8 except for the above.

The diffractive optical element of Example 9 had the following grating shape.

The grating heights were 24.5 μm for the first grating, 23.7 μm for the 63rd grating, 23.2 μm for the 64th grating, and 22.8 μm for the 65th grating. That is, the first region was from the center to the 63rd lattice, and the second region was from the 64th lattice to the outermost periphery. The radial length A of the first region was 26.5 mm, and the radial length B of the second region was 0.5 mm.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Comparative example 1)
Comparative Example 1 differs from Example 1 in the shape of the lattice type. A diffractive optical element of Comparative Example 1 was produced in the same manner as in Example 1 except for the above.

The diffractive optical element of Comparative Example 1 had the following grating shape.

The grating heights from the first grating to the 65th grating were all 22.9 μm. That is, the second region did not exist in the diffractive optical element of Comparative Example 1. The first region had a radial length A of 27.0 mm from the center to the outermost periphery.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(Comparative example 2)
Comparative Example 2 differs from Example 8 in the shape of the lattice type. A diffractive optical element of Comparative Example 2 was produced in the same manner as in Example 8 except for the above.

The diffractive optical element of Comparative Example 2 had the following grating shape.

The grating heights from the first grating to the 65th grating were all 23.7 μm. That is, the second region did not exist in the diffractive optical element of Comparative Example 1. The first region had a radial length A of 27.0 mm from the center to the outermost periphery.

Table 1 summarizes the measurement results of the shape of the diffractive optical element, and Table 2 summarizes the evaluation results of the diffractive optical element.

(evaluation)
From Tables 1 and 2, in all of the diffractive optical elements of Examples 1 to 9, the ratio of the diffraction efficiency at the outer periphery of the first region to the diffraction efficiency at the center of the first region was 0.993 or more. Further, Examples 1 to 3, 8 and 9, which had particularly good diffraction efficiency ratios of 0.995 or more, all satisfied the following formula.

0.99≦d _n /d _n-1 ≦1.01 (Formula 1)
0.50≦d _m /d _m-1 ≦0.98 (Formula 2)
0.018≦B/A≦0.10 (Formula 3)
On the other hand, in both Comparative Examples 1 and 2, the ratio of the diffraction efficiency at the outer periphery of the first region to the diffraction efficiency at the center of the first region was less than 0.993. The diffractive optical elements of Comparative Examples 1 and 2 did not have a second region where the diffraction grating becomes lower toward the outer edge of the diffraction grating. Therefore, it is thought that the refractive index variation that occurs from the outer circumferential direction to the inside of the diffractive optical element is large, and as a result, the difference between the diffraction efficiency near the center and the diffraction efficiency at the periphery becomes large.

The diffractive optical element of the present invention can be used for lenses such as camera lenses, liquid crystal projector lenses, and pickup lenses for DVDs, CDs, and the like.

1 First base material 2 First resin layer 2a First resin composition 3 Second resin layer 3a Second resin composition 4 Second base material 5 Grid type 6 Flat type 7 Ejector 8 Lamp 9 Shutter 10 Grid part 11 First Base portion of resin layer 12 Base portion of second resin layer 13 First region 14 Second region 20 Diffractive optical element 600 Imaging device (digital camera)
601 Optical equipment (lens barrel)
602 Camera body 603 Lens 605 Lens

Claims (14)

A diffraction pattern in which a first resin layer and a second resin layer are laminated in order, and a concentric diffraction grating is formed on at least a part of the interface between the first resin layer and the second resin layer when viewed from above. An optical element,
The diffraction grating has a first region including the center of the diffraction grating when viewed in plan, and a second region surrounding the first region and having a grating lower in height than the first region,
The grating height of the diffraction grating in the second region decreases toward the outer edge of the diffraction grating ,
In the second region, if the height of the m-th grating (m is an integer greater than 2) from the center to the outer edge of the diffraction grating is dm,
0.50≦d _m /d _m-1 ≦0.98
A diffractive optical element characterized by satisfying the following relationship . In the first region, if the height of the n-th grating (n is an integer of 2 or more) from the center to the outer edge of the diffraction grating is _dn ,
0.99≦d _n /d _n-1 ≦1.01
The diffractive optical element according to claim 1, which satisfies the following relationship. When viewed in plan, when the radial length of the first region is A, and the radial length of the second region is B,
0.018≦B/A≦0.10
The diffractive optical element according to claim 1 or 2, which satisfies the following relationship. The diffractive optical element according to any one of claims 1 to 3, wherein the height of the grating in the first region is in a range of 5 μm or more and 30 μm or less. 5. The distance between the outermost lattice, which is a lattice in contact with the second region of the first region, and the outermost lattice is in the range of 100 μm or more and 500 μm or less. Diffractive optical element. The diffractive optical element according to any one of claims 1 to 5, wherein the thickness of the base portion of the first resin layer is in a range of 1 μm or more and 50 μm or less. The diffractive optical element according to any one of claims 1 to 6, wherein the thickness of the base portion of the second resin layer is in the range of 10 μm or more and 400 μm or less. The diffractive optical element has a first base material and a second base material,
The diffractive optical element according to any one of claims 1 to 7, wherein the first base material, the first resin layer, the second resin layer, and the second base material are laminated in this order. 9. The diffraction grating element according to claim 1, wherein the grating pitch of the diffraction grating in the second region becomes narrower from the center to the outer edge of the diffraction grating. An optical device comprising a housing and an optical system having a plurality of lenses within the housing,
An optical instrument characterized in that at least one of the plurality of lenses is the diffractive optical element according to any one of claims 1 to 9. An imaging device comprising a housing, an optical system having a plurality of lenses in the housing, and an imaging element that receives light passing through the optical system,
An imaging device characterized in that at least one of the plurality of lenses is the diffractive optical element according to any one of claims 1 to 10. The imaging device according to claim 11, wherein the imaging device is a camera. A method for manufacturing a diffractive optical element in which a concentric diffraction grating is provided on at least a part of the interface between a laminated first resin layer and a second resin layer when viewed in plan,
providing a resin composition on the lattice shape of the first resin layer provided with the lattice shape;
curing the resin composition to form a second resin layer;
The lattice shape provided in the first resin layer has a first region including the center of the lattice shape and a lattice surrounding the first region and having a height lower than the first region when viewed in plan. a second region;
The grating height of the diffraction grating in the second region decreases toward the outer edge of the diffraction grating,
In the second region, if the height of the m-th grating (m is an integer greater than 2) from the center to the outer edge of the diffraction grating is dm,
0.50≦d _m /d _m-1 ≦0.98
A method for manufacturing a diffractive optical element characterized by satisfying the following relationship. 13. The method of manufacturing a diffraction grating optical element according to claim 12, further comprising the step of providing the first resin layer having a grating shape on the first base material.

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