Diffractive optical element, method for manufacturing diffractive optical element, optical device, display device, and imaging device

Abstract

To provide a diffraction optical element which can reduce or prevent deterioration of optical characteristics when a circular diffraction grating and an arcuate diffraction grating are provided in plan view, and a method for manufacturing the diffraction optical element.SOLUTION: A diffraction optical element has a substrate having a surface provided with a diffraction grating, and a resin layer provided so as to cover the diffraction grating on the surface of the substrate. In plan view in an optical axis direction, the diffraction grating includes a circular first diffraction grating and an arcuate second diffraction grating arranged outside the first diffraction grating. The diffraction optical element has an optical effective region, and a non-optical effective region surrounding the optical effective region. An arcuate end of the second diffraction grating is positioned in the non-optical effective region, and thickness of the resin layer provided in the non-optical effective region is thicker than thickness of the resin layer provided in the optical effective region.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a diffractive optical element, a method for manufacturing a diffractive optical element, an optical device, a display device, and an imaging device.

Background Art

[0002] Conventionally, a method of reducing chromatic aberration of a lens system by providing a diffractive optical element having a diffractive action in a part of an optical system is known. In addition to correcting chromatic aberration, it is known that a diffractive optical element has an aspherical effect by appropriately changing the grating pitch of its periodic structure. Also, in a diffractive optical element used for a lens of an optical system, it is known that by closely arranging two diffraction gratings and appropriately setting the material and grating height constituting each diffraction grating, high diffraction efficiency can be obtained in a wide wavelength band.

[0003] Patent Document 1 describes a diffractive optical element including a substrate made of a first optical material and having a diffraction grating on its surface, and an optical adjustment layer made of a second optical material and provided on the substrate so as to cover the diffraction grating. In the diffractive optical element described in Patent Document 1, the optical adjustment layer made of the second optical material containing resin has a uniform thickness in the normal direction from an envelope surface that is a curved surface passing through the tip of the diffraction grating. Thereby, in the diffractive optical element described in Patent Document 1, cracks due to stress generated in the optical adjustment layer due to curing shrinkage of the second optical material during manufacturing are prevented.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Patent Document 1 discloses a technique for preventing cracks from occurring due to local concentration of stress during curing shrinkage by making the thickness of an optical adjustment layer, which is a resin layer on a substrate, constant. However, in the case of an arc shape where the substrate is a part of a circular lens shape cut out, the diffraction grating on the substrate is circular on the inner side and arc-shaped on the outer side in a plan view seen in the optical axis direction. In the case of an arc-shaped diffraction grating, the curing shrinkage behavior of the resin formed on the diffraction grating is different from that in the case of only a circular diffraction grating. Therefore, in the case of a diffractive optical element in which a circular diffraction grating and an arc-shaped diffraction grating are provided on a substrate, even if the thickness of the resin layer on the substrate is made constant as in the technique disclosed in Patent Document 1, a decrease in diffraction efficiency due to the density difference of the resin layer occurs, and the optical characteristics tend to deteriorate.

[0006] An object of the present invention is to provide a diffractive optical element and a method for manufacturing the diffractive optical element that can reduce or prevent deterioration of optical characteristics when a circular diffraction grating and an arc-shaped diffraction grating are provided in a plan view.

Means for Solving the Problems

[0007] According to one aspect of the present invention, there is provided a diffractive optical element including a substrate having a surface on which a diffraction grating is provided, and a resin layer provided on the surface of the substrate so as to cover the diffraction grating. In a plan view seen along the optical axis direction, the diffraction grating includes a circular first diffraction grating and an arc-shaped second diffraction grating disposed outside the first diffraction grating. The diffractive optical element has an optically effective region and a non-optically effective region surrounding the optically effective region. The arc ends of the second diffraction grating are located in the non-optically effective region, and the thickness of the resin layer provided in the non-optically effective region is thicker than the thickness of the resin layer provided in the optically effective region.

[0008] According to another aspect of the present invention, there is provided a method for manufacturing a diffractive optical element having a substrate with a surface provided with a diffraction grating and a resin layer provided on the surface of the substrate so as to cover the diffraction grating. In a plan view as viewed in the optical axis direction, the diffraction grating includes a circular first diffraction grating and an arc-shaped second diffraction grating disposed outside the first diffraction grating. The diffractive optical element has an optically effective region and a non-optically effective region surrounding the optically effective region. The arc ends of the second diffraction grating are located in the non-optically effective region, and the resin layer provided in the non-optically effective region is provided so as to be thicker than the resin layer provided in the optically effective region. A method for manufacturing a diffractive optical element is provided.

Effects of the Invention

[0009] According to the present invention, when a circular diffraction grating and an arc-shaped diffraction grating are provided in a plan view, deterioration of optical characteristics can be reduced or prevented.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0011] [First Embodiment] A diffractive optical element and a method for manufacturing the diffractive optical element according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4.

[0012] First, the configuration of the diffractive optical element according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic view showing a diffractive optical element 10 according to the present embodiment. The upper part of FIG. 1 is a plan view showing the diffractive optical element 10 according to the present embodiment in a plan view as viewed in the optical axis direction. The lower part of FIG. 1 is a cross-sectional view taken along line A-A' in the plan view of the upper part of FIG. 1. FIG. 2 is a cross-sectional view showing an enlarged diffractive grating 13 in the diffractive optical element 10 according to the present embodiment.

[0013] As shown in FIG. 1, the diffractive optical element 10 according to the present embodiment has, as two optical elements, a substrate 11 that is a base and a resin layer 12. The diffractive optical element 10 according to the present embodiment is used in optical devices such as digital cameras, video cameras, binoculars, and head-mounted displays. A diffractive grating 13 is provided on one surface of the substrate 11. The resin layer 12 is provided so as to cover the diffractive grating 13 on the surface of the substrate 11 where the diffractive grating 13 is provided.

[0014] The substrate 11 is, for example, a substrate having a convex lens shape, and may be a resin substrate formed by injection molding or a glass substrate. Note that the shape of the substrate 11 may be a concave lens shape in addition to the convex lens shape, or may be a convex spherical shape, a concave spherical shape, an aspherical shape, a planar shape, or the like. Further, the material constituting the substrate 11 is not particularly limited as long as it is a transparent material having permeability to light such as visible light targeted by the diffractive optical element 10. Note that transparent means, for example, that the transmittance of light in the wavelength range of 420 nm or more and 700 nm or less is 10% or more.

[0015] The substrate 11 has a planar shape including a non-circular shape surrounded by an arc and a chord connecting both ends of the arc, and a rectangular shape connected to the non-circular shape, in a plan view seen in the optical axis direction of the diffractive optical element 10. The non-circular shape of the substrate 11 is a shape surrounded by a major arc with a central angle exceeding 180° and a chord connecting both ends of the major arc. The center of the circle of the non-circular shape is the optical center of the diffractive optical element 10. The rectangular shape connected to the non-circular shape of the substrate 11 has the chord of the non-circular shape as the longitudinal side. The substrate 11 has a first portion 111 having a planar shape of the non-circular shape and a second portion 112 having a planar shape of the rectangular shape. The first portion 111 has a shape in which a shape such as the above-described lens shape is cut along the optical axis direction at the position of the chord. The second portion 112 has a plate-like shape protruding from the center of the cut portion at the position of the chord of the first portion 111. Note that the shape including the planar shape of the substrate 11 is not limited to the shape shown in FIG. 1, and can be an appropriate shape according to the use of the diffractive optical element 10 and the like.

[0016] The diffractive optical element 10 including the substrate 11 has an optically effective region 14 which is a region within the optically effective diameter, and a non-optically effective region 15 which surrounds the optically effective region 14 outside the optically effective diameter. The optically effective region 14 is a region through which light targeted by the diffractive optical element 10 passes, and the non-optically effective region 15 is a region outside the optically effective region 14. The non-optically effective region 15 includes an arc portion 113 which is an end portion on the arc side of the first portion 111, and a chord portion 114 which is constituted by an end portion on the chord side of the first portion 111 and the second portion 112.

[0017] The diffraction grating 13 is provided concentrically on one surface of the first portion 111 having the planar shape of the non-circular shape of the substrate 11, with the center of the non-circular shape through which the optical axis of the diffractive optical element 10 passes as the center. The diffraction grating 13 is formed, for example, such that a slope and a wall surface are continuously repeated from the element center passing through the optical axis toward the outer periphery (see FIG. 2 described later).

[0018] Since the first portion 111 of the substrate 11 has an elliptical planar shape, the diffraction grating 13 includes a circular diffraction grating 13a inside the substrate 11 and an arc-shaped diffraction grating 13b outside the substrate 11. The diffraction grating 13b outside the substrate 11 is interrupted at the end of the chord portion 114 of the first portion 111 of the substrate 11, so it is arc-shaped. The arc ends of the arc-shaped diffraction grating 13b are located on the chord portion 114 which is a non-optically effective region 15.

[0019] The resin layer 12 is provided so as to cover the diffraction grating 13 on one surface of the first portion 111 and the second portion 112 of the substrate 11. The resin constituting the resin layer 12 is not particularly limited as long as it is a transparent resin having transparency to light such as visible light targeted by the diffractive optical element 10, but from the viewpoint of ease of manufacture, it is preferably a photocurable resin or a thermosetting resin.

[0020] As shown in Fig. 2(a), the resin layer 12 is formed on the substrate 11 so as to be in close contact with the substrate 11 and fill the concave portions between the convex portions of the diffraction grating 13. Thereby, the resin layer 12 has a diffraction grating 16 formed so as to cover the diffraction grating 13 adjacent to the diffraction grating 13 of the substrate 11.

[0021] Note that a transparent inorganic film 17 may be provided between the substrate 11 and the resin layer 12 as shown in Fig. 2(b). That is, the transparent inorganic film 17 may be provided on the diffraction grating 13 of the substrate 11, and the resin layer 12 may be provided on the substrate 11 via the transparent inorganic film 17. In this case, the transparent inorganic film 17 is a thin film made of a transparent inorganic material having transparency to light such as visible light targeted by the diffractive optical element 10. Examples of the inorganic material include aluminum oxide (Al2O3), silicon oxide (SiO2, SiO), titanium oxide (TiO x )), tantalum oxide (TaO x ), niobium oxide (NbO x)Examples include the like. The transparent inorganic film 17 can be provided so as to cover the grating surface along the grating surface of the diffraction grating 13. Note that the transparent inorganic film 17 can be provided using various film-forming methods such as vacuum evaporation and sputtering. By providing the transparent inorganic film 17, when the substrate 11 is made of resin, penetration and dissolution of the resin material between the substrate 11 and the resin layer 12 can be reduced or prevented, and deterioration of the diffraction efficiency can be reduced or prevented. Furthermore, the transparent inorganic film 17 may be provided such that the thickness of the transparent inorganic film 17 at the grating tip of the diffraction grating 13 is greater than the thickness of the transparent inorganic film at the grating surface other than the grating tip of the diffraction grating 13. Thereby, while suppressing the influence on the initial optical performance by the transparent inorganic film to a small extent, deterioration of the diffraction efficiency due to penetration and dissolution of the resin material at the grating tip of the diffraction grating 13 can be reduced or prevented.

[0022] The resin layer 12 is provided so as to have substantially the same thickness tc with respect to the envelope surface, which is the surface passing through the tip of the diffraction grating 13, in the optical effective region 14, which is the region within the optical effective diameter. On the other hand, the resin layer 12 is provided with a thickness greater than the thickness tc in the optical effective region 14 in the non-optical effective region 15, which is the region outside the optical effective diameter.

[0023] Specifically, the resin layer 12 is provided with a thickness t1 greater than the thickness tc at the chord portion 114 in the non-optical effective region 15. Also, the resin layer 12 is provided with a thickness t2 greater than the thickness tc at the arc portion 113 in the non-optical effective region 15.

[0024] Note that the thickness tc can be the average thickness of the resin layer 12 provided in the optical effective region 14 from the envelope surface of the diffraction grating 13. Also, the thickness t1 can be the average thickness of the resin layer 12 provided at the chord portion 114 in the non-optical effective region 15. Also, the thickness t2 can be the average thickness of the resin layer 12 provided at the arc portion 113 in the non-optical effective region 15. The thickness of the resin layer 12 can be measured using a shape measuring machine or the like. The thickness of the resin layer 12 can be obtained by taking the difference between the measured value of the surface shape of the diffractive optical element 10 by a shape measuring machine or the like and the shape of the substrate 11.

[0025] As described above, the thicknesses t1 and t2 of the resin layer 12 provided in the non - optical effective region 15 are greater than the thickness tc of the resin layer 12 provided in the optical effective region 14. This is to consider the shrinkage during the curing of the resin constituting the resin layer 12 and to suppress the density difference of the resin due to curing to a small value.

[0026] The phenomenon of the density difference of the resin due to curing will be described with reference to FIGS. 3 and 4 in conjunction with the manufacturing method of the diffractive optical element 10 according to the present embodiment. FIG. 3 is a schematic cross - sectional view showing the steps of the manufacturing method of the diffractive optical element 10 according to the present embodiment. FIG. 4 is a schematic view showing the shrinkage of the resin during curing.

[0027] In manufacturing the diffractive optical element 10 according to the present embodiment, first, as shown in FIG. 3(a), a liquid resin 121 is discharged onto a mold 21 for forming the resin layer 12, and the resin 121 on the mold 21 and the surface of the substrate 11 provided with the diffraction grating 13 are brought into contact with each other. Note that in FIGS. 3(a) to 3(c), a substrate 11 having a cross - sectional shape different from that of FIG. 1 is shown. Next, as shown in FIG. 3(b), while controlling the distance between the mold 21 and the substrate 11, the space therebetween is filled with the resin 121. Next, as shown in FIG. 3(c), the filled resin 121 is cured to form a resin layer 12 composed of the cured resin 121. As the resin 121 used at this time, a photocurable resin or a thermosetting resin is preferable. When a photocurable resin is used as the resin 121, light L such as ultraviolet rays for curing the resin 121 is irradiated onto the resin 121 between the mold 21 and the substrate 11 by a light irradiator 22. In particular, a photocurable resin is more preferable because of its high curing speed and excellent cost performance. Examples of the photocurable resin include resins such as acrylic, methacrylic, epoxy, thiol, and episulfide resins. In this way, the resin layer 12 can be provided by molding the resin 121 on the substrate 11 using the mold 21. Next, the resin layer 12 made of the cured resin 121 is integrally separated from the substrate 11 from the mold 21. In this way, the diffractive optical element 10 can be manufactured.

[0028] Figures 4(a) to 4(c-2) show the shrinkage during curing of the resin 121 that constitutes the resin layer 12 in the diffractive optical element 10. Figure 4(a) shows a plan view of the diffractive optical element 10 in a plan view along the optical axis direction, together with a cross-sectional view and a side view of the diffractive optical element 10. In Figure 4(a), the lower figure with respect to the plan view corresponds to the cross-sectional view along the line A-A' in Figure 1, and the right figure with respect to the plan view is a side view of the diffractive optical element 10 seen from the chord portion 114 side. Note that the scales of the cross-sectional view and the side view in Figure 4(a) are different from the scale of the cross-sectional view in Figure 1 for the purpose of explanation. Also, the line B-B' shown in Figure 4(a) is a cutting line that cuts the arc portion perpendicular to the diffraction grating 13. Further, the line C-C' shown in Figure 4(a) is a cutting line that cuts the boundary between the first portion 111 and the second portion 112 perpendicular to the chord portion 114.

[0029] Also, Figures 4(b-1) and 4(c-1) are cross-sectional views showing the shrinkage of the resin 121 that constitutes the resin layer 12 during the manufacture of a diffractive optical element according to a comparative example in which the thickness of the resin layer 12 is substantially constant from the center to outside the optically effective diameter. Figure 4(b-1) shows the cross-section during manufacture corresponding to the cross-section of the line B-B' in Figure 4(a), and Figure 4(c-1) shows the cross-section during manufacture corresponding to the cross-section of the line C-C' in Figure 4(a). On the other hand, Figures 4(b-2) and 4(c-2) are cross-sectional views showing the shrinkage of the resin 121 that constitutes the resin layer 12 during the manufacture of the diffractive optical element 10 according to the present embodiment. Figure 4(b-2) shows the cross-section during manufacture corresponding to the cross-section of the line B-B' in Figure 4(a), and Figure 4(c-2) shows the cross-section during manufacture corresponding to the cross-section of the line C-C' in Figure 4(a).

[0030] In the manufacturing method as shown in FIG. 3 described above, the outside of the substrate 11 is restrained during the curing of the resin 121 that constitutes the resin layer 12. Therefore, during the curing of the resin 121, in the diffractive optical element 10, the resin 121 mainly shrinks in the radial direction from the outer periphery to the inner periphery as indicated by the solid line arrow in FIG. 4(a). Further, in the chord portion 114, since the cross section of the diffraction grating 13b is exposed, in addition to the radial shrinkage, the resin 121 shrinks in the direction along the diffraction grating 13b as indicated by the broken line arrow in FIG. 4(a). The direction of the broken line arrow in FIG. 4(a) is the direction from the depth to the front of the paper surface of FIG. 4(c-1). Therefore, in the case of the comparative example where the film thickness of the resin layer 12 is substantially constant, as shown in FIG. 4(c-1), the resin 121 in the chord portion 114 and its vicinity becomes less dense, and as a result, the refractive index of the resin layer 12 in the chord portion 114 and its vicinity changes from the design value.

[0031] In the diffractive optical element 10 according to the present embodiment, the thickness of the resin layer 12 provided in the non-optical effective region 15 outside the optical effective diameter is made thicker than the thickness of the resin layer 12 provided in the optical effective region 14. For this reason, in the present embodiment, the mold 21 for providing the resin layer 12 is a mold in which the resin layer 12 in the non-optical effective region 15 is provided thickly. Therefore, as shown in FIGS. 4(b-2) and 4(c-2), the resin 121 can be supplied from the non-optical effective region 15 to the optical effective region 14. Thereby, in the present embodiment, the radial shrinkage of the resin 121 can be improved, and the shrinkage of the resin 121 in the chord portion 114 and its vicinity can also be improved. Thus, in the present embodiment, by improving the shrinkage of the resin 121, the occurrence of a refractive index difference due to a density difference of the resin layer 12 constituted by the resin 121 can be suppressed or prevented, and a decrease in the diffraction efficiency of the resin layer 12 can be suppressed or prevented to a small extent.

[0032] Note that the shrinkage of the resin 121 in the chord portion 114 tends to be larger than the shrinkage of the resin 121 in the arc portion 113. For this reason, it is preferable that the thickness t1 of the resin layer 12 provided in the chord portion 114 in the non-optical effective region 15 is thicker than the thickness t2 of the resin layer 12 provided in the arc portion 113 in the non-optical effective region 15, that is, t1 > t2.

[0033] Also, if the thickness t1 is too thick, a large curing stress may be generated in the thickness direction during the curing process of the resin 121, which may cause deformation of the diffractive optical element 10. The length from the optical center to the end of the substrate 11 is shorter in the chord portion 114 than in the arc portion 113. Therefore, although the substrate 11 is more advantageous for deformation in the chord portion 114 than in the arc portion 113, the thickness t1 is preferably suppressed to less than three times the thickness t2, that is, t1 / t2 < 3.

[0034] Also, assuming that the width of the resin layer 12 provided in the chord portion 114 is w1 and the width of the resin layer 12 provided in the arc portion 113 is w2, considering these widths from the above viewpoints, it is preferable that 1 < (t1 × w1) / (t2 × w2) < 3. The width w1 and the width w2 can each be an average value.

[0035] Also, assuming that the grating height of the diffraction grating 13 is d, it is preferable that 3 < (t1 - tc) / d < 80. Note that the grating height d is the height from the boundary between the convex portion and the base of the diffraction grating 13 to the tip of the convex portion of the diffraction grating 13. The grating height d can be an average value for the diffraction grating 13 provided on the substrate 11.

[0036] Also, if the thickness t1 becomes too thick with respect to the thickness of the resin layer 12 at the center of the diffractive optical element 10, it is assumed that the diffractive optical element 10 becomes thick and heavy. Therefore, the thickness t1 is preferably 1000 μm or less.

[0037] As described above, according to this embodiment, when the circular diffraction grating 13a and the arc-shaped diffraction grating 13b are provided, deterioration of the optical characteristics of the diffractive optical element 10 can be reduced or prevented. Regarding the optical characteristics of the diffractive optical element 10, as an initial evaluation, for example, the diffraction efficiency in a desired wavelength region such as a wavelength region from 420 nm to 700 nm can be measured and evaluated. In this case, for example, when the change in the diffraction efficiency is 2% or less compared to the design value, since there is no significant influence on the optical characteristics, it can be evaluated that the optical characteristics are good.

[0038] [Second Embodiment] The diffractive optical element according to the second embodiment of the present invention will be described with reference to FIG. 5. Components similar to those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted or simplified.

[0039] FIG. 5 is a schematic view showing the diffractive optical element 10 according to the present embodiment. The upper part of FIG. 5 is a plan view showing the diffractive optical element 10 according to the present embodiment in a plan view as viewed in the optical axis direction. The lower part of FIG. 5 is a cross-sectional view taken along line D-D' in the plan view of the lower part of FIG. 5.

[0040] The diffractive optical element 10 according to the present embodiment is substantially the same as the configuration according to the first embodiment. The diffractive optical element 10 according to the present embodiment is different from the configuration according to the first embodiment in that the substrate 11 is composed of only the first portion 111 and does not have the second portion 112.

[0041] In the present embodiment, the chord portion 114 does not include the second portion 112. A resin layer 12 is provided on such a chord portion 114 so as to protrude to the outside of the first portion 111.

[0042] As in the present embodiment, the substrate 11 does not necessarily have to have both the first portion 111 and the second portion 112, and may be composed of only the first portion 111. In the present embodiment, the distance r2 from the optical center of the resin layer 12 to the end on the chord portion 114 side of the resin layer 12 is longer than the distance r1 from the optical center of the substrate 11 to the chord portion 114, and r1 < r2. By not providing the second portion 112 that supports the resin layer 12 on the substrate 11 at the chord portion 114 in this way, a smaller and lighter diffractive optical element 10 can be provided.

[0043] [Examples] Next, examples will be specifically described for the diffractive optical element and the method for manufacturing the diffractive optical element according to the above embodiment.

[0044] (Example 1) The diffractive optical element according to Example 1 and the method for manufacturing the diffractive optical element will be described with reference to FIGS. 1 and 3. In Example 1, a diffractive optical element 10 having the shape shown in FIG. 1 was manufactured.

[0045] In Example 1, first, as the substrate 11, a substrate formed by injection molding a polycarbonate-based resin material (EP4500, manufactured by Mitsubishi Gas Chemical) was prepared. The substrate 11 had an outer diameter of φ46 mm, an optical effective diameter of Φ42 mm, and a central thickness of 2.5 mm. One surface had a convex shape, and the other surface was flat, and a diffraction grating 13 with a grating height of 10 μm was provided. This diffraction grating 13 was arranged concentrically with respect to the center of the outer diameter of the substrate 11, and the grating pitch decreased from the center toward the outer periphery. The substrate 11 had an elliptical first portion 111 in a plan view when viewed in the optical axis direction, and the outer peripheral diffraction grating 13b was cut at a chord portion 114 16 mm from the center. Outside the chord portion 114 of the first portion 111 in the substrate 11, a flat second portion 112 with a width of 2.0 mm and a thickness of 2.0 mm was provided.

[0046] Next, the resin layer 12 was molded using the mold 21 by the process shown in FIG. 3. As the resin 121 used at this time, an episulfide-based resin material of a photocurable resin was used. The mold 21 had an outer diameter of φ48 mm, and in the portion corresponding to the optically effective region 14, an aspherical shape corresponding to the envelope surface through which the apexes of the diffraction gratings 13 provided on the substrate 11 passed was provided. Further, the mold 21 had a shape such that the thickness of the resin layer 12 in the non-optically effective region 15 was 100 μm thicker at the arc portion 113 and 300 μm thicker at the chord portion 114 than the thickness of the resin layer 12 in the optically effective region 14. For such a mold 21, the resin 121 was dropped as shown in FIG. 3(a). Next, as shown in FIG. 3(b), the resin 121 was filled between the mold 21 and the substrate 11 so that the thickness of the resin layer 12 from the envelope surface of the diffraction grating 13 became 100 μm. At this time, the filling region of the resin 121 was larger than the optically effective radius 21 mm of the substrate 11 in the arc portion 113 and had a size between the radius 23 mm of the outer periphery of the substrate 11, and the outer edge of the filling region was preferably contained between 21.1 mm and 22.5 mm. Further, the filling region of the resin 121 was larger than the optically effective radius 16 mm up to the chord portion 114 of the substrate 11 in the chord portion 114 and had a size between the radius 18 mm of the substrate 11, and the outer edge of the filling region was preferably contained between 16.1 mm and 17.5 mm. Then, as shown in FIG. 3(c), light was irradiated from the light irradiator 22 to cure the resin 121 and form the resin layer 12. Next, the diffraction optical element 10 having the shape shown in FIG. 1 was manufactured by separating the resin layer 12 integrally with the substrate 11 from the mold 21.

[0047] Regarding the diffraction optical element 10 according to Example 1 manufactured as described above, shape measurement was performed after demolding from the mold 21. For the shape measurement, a surface shape roughness measuring instrument Form Talysurf (manufactured by Taylor Hobson) was used. In order to measure the thickness of the resin layer 12, the surface shape on the resin layer 12 side of the diffraction optical element 10 was measured at least at three locations each for the chord portion and the other regions from the optical axis center to the end.

[0048] When the thickness t1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the thicknesses t1 at the three locations were 450 μm, 350 μm, and 410 μm respectively, and the average value of these was about 400 μm. Also, when the width w1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the widths w1 at the three locations were 1.1 mm, 0.9 mm, and 1.05 mm respectively, and the average value of these was about 1.0 mm. On the other hand, when the thickness t2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the thicknesses t2 at the three locations were 150 μm, 210 μm, and 230 μm respectively, and the average value of these was about 200 μm. Also, when the width w2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the widths w2 at the three locations were 0.8 mm, 1.1 mm, and 1.2 mm respectively, and the average value of these was about 1.0 mm. In addition, when the thickness tc of the resin layer 12 in the optical effective region 14 was measured in the same manner, the average value of the thickness tc was 100 μm.

[0049] As an initial evaluation of the diffractive optical element 10 according to Example 1, the diffraction efficiency in the wavelength range from 420 nm to 700 nm was measured. In the initial evaluation, when the change in the diffraction efficiency was 2% or less compared to the design value, it was evaluated as good because there was no significant influence on the optical performance. As a result, as shown in Table 1, it was confirmed that the diffraction efficiency was good.

[0050] [Example 2] In Example 2, the same substrate as in Example 1 was used as the substrate 11. Also, in Example 2, regarding the shape of the mold 21, the thickness of the resin layer 12 in the non-optical effective region 15 was changed to a shape such that it was 300 μm thicker than the thickness of the resin layer 12 in the optical effective region 14 in both the arc portion 113 and the chord portion 114. The resin layer 12 was molded in the same manner as in Example 1 except for this point, and the diffractive optical element 10 was manufactured.

[0051] For the diffractive optical element 10 according to Example 2, shape measurement was performed in the same manner as in Example 1 after demolding. When the thickness t1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the thicknesses t1 at the three locations were 300 μm, 510 μm, and 400 μm, respectively, and the average value thereof was about 400 μm. Also, when the width w1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the widths w1 at the three locations were 0.45 mm, 0.55 mm, and 0.52 mm, respectively, and the average value thereof was about 0.5 mm. On the other hand, when the thickness t2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the thicknesses t2 at the three locations were 420 μm, 350 μm, and 440 μm, respectively, and the average value thereof was about 400 μm. Also, when the width w2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the widths w2 at the three locations were 0.49 mm, 0.53 mm, and 0.47 mm, respectively, and the average value thereof was about 0.5 mm. Incidentally, when the thickness tc of the resin layer 12 in the optical effective region 14 was measured in the same manner, the average value of the thickness tc was 100 μm.

[0052] As an initial evaluation of the diffractive optical element 10 according to Example 2, the diffraction efficiency was measured and evaluated in the same manner as in Example 1. As shown in Table 1, it was confirmed that the diffraction efficiency was good.

[0053] [Example 3] In Example 3, the same substrate as in Example 1 was used as the substrate 11. Also, in Example 3, regarding the shape of the mold 21, the thickness of the resin layer 12 in the non-optical effective region 15 was changed to a shape such that it was 200 μm thicker than the thickness of the resin layer 12 in the optical effective region 14 in the arc portion 113 and 700 μm thicker in the chord portion 114. The resin layer 12 was molded in the same manner as in Example 1 except for this point, and the diffractive optical element 10 was manufactured.

[0054] For the diffractive optical element 10 according to Example 3, shape measurement was performed in the same manner as in Example 1 after demolding. When the thickness t1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the thicknesses t1 at the three locations were 610 μm, 910 μm, and 870 μm, respectively, and the average value of these was approximately 800 μm. Also, when the width w1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the widths w1 at the three locations were 0.095 mm, 0.11 mm, and 0.09 mm, respectively, and the average value of these was approximately 0.1 mm. On the other hand, when the thickness t2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the thicknesses t2 at the three locations were 370 μm, 240 μm, and 300 μm, respectively, and the average value of these was approximately 300 μm. Also, when the width w2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the widths w2 at the three locations were 0.105 mm, 0.11 mm, and 0.09 mm, respectively, and the average value of these was approximately 0.1 mm. In addition, when the thickness tc of the resin layer 12 in the optical effective region 14 was measured in the same manner, the average value of the thickness tc was 100 μm.

[0055] As an initial evaluation of the diffractive optical element 10 according to Example 3, the diffraction efficiency was measured and evaluated in the same manner as in Example 1. As shown in Table 1, it was confirmed that the diffraction efficiency was good.

[0056] [Example 4] The diffractive optical element according to Example 4 and the method for manufacturing the diffractive optical element will be described with reference to FIGS. 3 and 5. In Example 4, a diffractive optical element 10 having the shape shown in FIG. 5 was manufactured.

[0057] In Example 4, first, as the substrate 11, a substrate made of glass provided with a diffraction grating by a mold or the like was prepared. The substrate 11 had an outer diameter of φ40 mm, an optical effective diameter of Φ36 mm, and a central thickness of 5 mm. One surface had a convex shape, and the other surface was flat, and a diffraction grating 13 with a grating height of 30 μm was provided. This diffraction grating 13 was arranged concentrically with respect to the center of the outer diameter of the substrate 11, and the grating pitch decreased from the center toward the outer periphery. The substrate 11 was composed only of the first partial 111 having an elliptical shape in a plan view along the optical axis direction, and the outer peripheral diffraction grating 13b and the substrate 11 were cut at a chord portion 114 15 mm from the center.

[0058] Next, the resin layer 12 was molded using the mold 21 by the process shown in FIG. 3. As the resin 121 used at this time, an episulfide-based resin material of a photocurable resin was used. The mold 21 had an outer diameter of φ44 mm, and an aspherical shape corresponding to the envelope surface passing through the apexes of the diffraction gratings 13 provided on the substrate 11 was provided in the portion corresponding to the optically effective region 14. Also, the mold 21 had a shape such that the thickness of the resin layer 12 in the non-optically effective region 15 was 50 μm thicker at the arc portion 113 and 100 μm thicker at the chord portion 114 than the thickness of the resin layer 12 in the optically effective region 14. With respect to such a mold 21, the resin 121 was dropped as shown in FIG. 3(a). Next, as shown in FIG. 3(b), the space between the mold 21 and the substrate 11 was filled with the resin 121 so that the thickness of the resin layer 12 from the envelope surface of the diffraction grating 13 was 200 μm. At this time, the filling region of the resin 121 was made larger than the optically effective radius 18 mm of the substrate 11 and up to the radius 20 mm of the outer periphery of the substrate 11 at the arc portion 113, and the outer edge of the filling region was made to fall within the range of 18.1 mm to 19.8 mm as much as possible. Also, the filling region of the resin 121 was made larger than the distance 15 mm from the optical center of the substrate 11 to the chord portion 114 and up to the radius 18 mm of the mold 21 at the chord portion 114, and the outer edge of the filling region was made to fall within the range of 15.1 mm to 17.5 mm as much as possible. Then, as shown in FIG. 3(c), light was irradiated from the light irradiator 22 to cure the resin 121 and form the resin layer 12. Next, the diffraction optical element 10 having the shape shown in FIG. 5 was manufactured by separating the resin layer 12 from the mold 21 integrally with the substrate 11.

[0059] Regarding the diffractive optical element 10 according to Example 4 manufactured as described above, after demolding from the mold 21, shape measurement was performed in the same manner as in Example 1. When the thickness t1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the thicknesses t1 at the three locations were 240 μm, 310 μm, and 340 μm respectively, and the average value of these was approximately 300 μm. Also, when the width w1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the widths w1 at the three locations were 1.44 mm, 1.39 mm, and 1.36 mm respectively, and the average value of these was approximately 1.4 mm. On the other hand, when the thickness t2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the thicknesses t2 at the three locations were 180 μm, 270 μm, and 310 μm respectively, and the average value of these was approximately 250 μm. Also, when the width w2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the widths w2 at the three locations were 1.55 mm, 1.65 mm, and 1.61 mm respectively, and the average value of these was approximately 1.6 mm. In addition, when the thickness tc of the resin layer 12 in the optical effective region 14 was measured in the same manner, the average value of the thickness tc was 200 μm.

[0060] As an initial evaluation of the diffractive optical element 10 according to Example 4, the diffraction efficiency was measured and evaluated in the same manner as in Example 1. As shown in Table 1, it was confirmed that the diffraction efficiency was good.

[0061] [Comparative Example 1] In Comparative Example 1, the same substrate as in Example 1 was used as the substrate 11. Also, in Comparative Example 1, regarding the shape of the mold 21, the shape was changed so that the thickness of the resin layer 12 in the non-optical effective regions 15 of the arc portion 113 and the chord portion 114 became the same as the thickness of the resin layer 12 in the optical effective region 14. The resin layer 12 was molded in the same manner as in Example 1 except for this point, and the diffractive optical element 10 was manufactured.

[0062] For the diffractive optical element 10 according to Comparative Example 1, shape measurement was performed in the same manner as in Example 1 after release. When the thickness t1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the thicknesses t1 at the three locations were 100 μm, 80 μm, and 130 μm respectively, and the average value thereof was about 100 μm. Further, when the width w1 of the resin layer 12 outside the optical effective diameter in the chord portion 114 was measured at three locations, the widths w1 at the three locations were 1.05 mm, 0.85 mm, and 1.1 mm respectively, and the average value thereof was about 1.0 mm. On the other hand, when the thickness t2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the thicknesses t2 at the three locations were 70 μm, 110 μm, and 120 μm respectively, and the average value thereof was about 100 μm. Further, when the width w2 of the resin layer 12 outside the optical effective diameter in the arc portion 113 was measured at three locations, the widths w2 at the three locations were 1.07 mm, 0.79 mm, and 1.15 mm respectively, and the average value thereof was about 1.0 mm. In addition, when the thickness tc of the resin layer 12 in the optical effective region 14 was measured in the same manner, the average value of the thickness tc was 100 μm.

[0063] As an initial evaluation of the diffractive optical element 10 according to Comparative Example 1, the diffraction efficiency was measured and evaluated in the same manner as in Example 1. As shown in Table 1, it was confirmed that the diffraction efficiency deteriorated.

[0064] The measurement results and evaluation results for Examples 1 to 4 and Comparative Example 1 described above are shown in Table 1 below. In Table 1, the calculated results of t1 / t2, (t1 × w1) / (t2 × w2), and (t1 - tc) / d calculated from the grating height d of the diffraction grating 13, the thicknesses t1 and t2 of the resin layer 12, and the widths w1 and w2 of the resin layer 12 are also shown.

[0065]

Table 1

[0066] [Third Embodiment] The diffractive optical element 10 according to the first and second embodiments can be applied to various devices and apparatuses such as optical devices, display devices, and imaging devices. In the present embodiment, as specific application examples of the diffractive optical element 10 according to the first and second embodiments, optical devices, display devices, and imaging devices will be described.

[0067] (Optical device) Specific application examples of the diffractive optical element 10 according to the first and second embodiments include lenses constituting an optical device (imaging optical system) for a camera or a video camera, lenses constituting an optical device (projection optical system) for a liquid crystal projector, and the like. Further, it can also be used for a pickup lens of a DVD recorder or the like. These optical systems are composed of at least one lens disposed in a housing, and the diffractive optical element 10 according to the first embodiment can be used for at least one of those lenses.

[0068] (Display device) FIGS. 6(a) to 6(c) are schematic views showing the configuration of a head-mounted display (HMD) 100, which is an example of a preferred embodiment of a display device using the diffractive optical element 10 according to the first and second embodiments. FIG. 6(a) is a side view showing the HMD 100. FIG. 6(b) is a side view showing the HMD 100. FIG. 6(c) is a schematic view showing the optical system of the HMD 100.

[0069] As shown in FIGS. 6(a) and 6(b), the HMD 100 has a housing 101, a mounting tool 102, and display units 103 for the left and right eyes. Each display unit 103 is provided in the housing 101. The HMD 100 is mounted on the user's head H by the mounting tool 102 such that the display units 103 for the left and right eyes are respectively positioned corresponding to the user's left and right eyes.

[0070] As shown in FIG. 6(c), each display unit 103 has a display panel 104, an optical system 105, and a diffractive optical element 10 according to the first or second embodiment. The display panel 104 is a display unit such as an organic electroluminescence (EL) panel or a liquid crystal panel, and displays a corresponding video for the left eye or the right eye. The optical system 105 is for imaging the video light emitted from the display panel 104 at the position of the user's eye E. The optical system 105 may include a transmissive optical element such as a convex lens or a concave lens, a reflective optical element such as a concave mirror, an optical path changing element such as a mirror or a polarizing beam splitter (PBS), etc., according to the design of the HMD 100. The diffractive optical element 10 is installed so as to be located between the optical system 105 and the eye E, and corrects the chromatic aberration of the video light that is emitted from the optical system 105 and imaged on the eye E through the diffractive optical element 10. The diffractive optical element 10, together with the optical system 105, constitutes an optical system that guides the video light, which is the light emitted from the display panel 104, to the user's eye E, and functions as at least one of the lenses in the optical system.

[0071] Here, although the display device has been described using an HMD, the diffractive optical element 10 can be similarly used for a projector or the like.

[0072] (Imaging device) FIG. 7 is a schematic diagram showing the configuration of a single-lens reflex digital camera 200, which is an example of a preferred embodiment of an imaging device using the diffractive optical element 10 according to the first embodiment. In FIG. 7, a camera body 202 and a lens barrel 201, which is an optical device, are coupled. The lens barrel 201 is a so-called interchangeable lens that is detachable from the camera body 202.

[0073] Light from the subject is photographed through an optical system including a plurality of lenses 203, 205, etc. arranged on the optical axis of the photographing optical system inside the housing 220 of the lens barrel 201. The diffractive optical element 10 according to the first embodiment can be used for, for example, the lenses 203, 205. Here, the lens 205 is supported by an inner cylinder 204 and is movably supported with respect to the outer cylinder of the lens barrel 201 for focusing and zooming.

[0074] During the observation period before shooting, the light from the subject is reflected by the main mirror 207 inside the housing 221 of the camera body, passes through the prism 211, and then the photographed image is projected onto the photographer through the viewfinder lens 212. The main mirror 207 is, for example, a half mirror, and the light passing through the main mirror 207 is reflected by the sub mirror 208 in the direction of the AF (auto focus) unit 213. For example, this reflected light is used for distance measurement. In addition, the main mirror 207 is mounted and supported on the main mirror holder 240 by adhesion or the like. During shooting, the main mirror 207 and the sub mirror 208 are moved out of the optical path through a drive mechanism (not shown), the shutter 209 is opened, and the imaging element 210 receives the light that has entered from the lens barrel 201, passed through the imaging optical system, and forms a photographed optical image. Further, the aperture 206 is configured to be able to change the brightness and depth of focus during shooting by changing the aperture area.

[0075] Here, although the imaging device has been described using a single-lens reflex digital camera, the diffractive optical element 10 can be similarly used in a smartphone, a compact digital camera, a drone, or the like.

[0076] The disclosure of the present embodiment includes the following configurations and methods. (Configuration 1) A substrate having a surface provided with a diffraction grating, A resin layer provided on the surface of the substrate so as to cover the diffraction grating, and a diffractive optical element having the resin layer, In a plan view along the optical axis direction, the diffraction grating includes a circular first diffraction grating and an arc-shaped second diffraction grating disposed outside the first diffraction grating. The diffractive optical element has an optically effective region and a non-optically effective region surrounding the optically effective region. The arc ends of the second diffraction grating are located in the non-optically effective region. The thickness of the resin layer provided in the non-optically effective region is thicker than the thickness of the resin layer provided in the optically effective region. A diffractive optical element characterized by this. (Configuration 2) The substrate includes a first portion having a plane shape of an incomplete circular shape surrounded by an arc and a chord connecting both ends of the arc in the plan view. The non-optical effective region has an arc portion that is an end portion on the arc side of the first portion and a chord portion that includes an end portion on the chord side of the first portion. The diffractive optical element according to Configuration 1, characterized in that. (Configuration 3) When the thickness of the resin layer provided on the chord portion is t1 and the thickness of the resin layer provided on the arc portion is t2, t1 > t2. The diffractive optical element according to Configuration 2, characterized in that. (Configuration 4) t1 / t2 < 3. The diffractive optical element according to Configuration 3, characterized in that. (Configuration 5) When the width of the resin layer provided on the chord portion is w1 and the width of the resin layer provided on the arc portion is w2, 1 < (t1 × w1) / (t2 × w2) < 3. The diffractive optical element according to Configuration 3 or 4, characterized in that. (Configuration 6) When the thickness of the resin layer provided in the optical effective region is tc and the height of the diffraction grating is d, 3 < (t1 - tc) / d < 80. The diffractive optical element according to any one of Configurations 3 to 5, characterized in that. (Configuration 7) The thickness t1 is 1000 μm or less. The diffractive optical element according to any one of Configurations 3 to 6, characterized in that. (Configuration 8) The substrate includes a second portion provided on the chord side of the first portion. The second portion has a rectangular plane shape in the plan view. The chord portion includes the second portion. The diffractive optical element according to any one of Configurations 2 to 7, characterized in that. (Configuration 9) Let the distance from the optical center of the substrate to the chord portion be r1, and the distance from the optical center of the resin layer to the end portion on the side of the chord portion of the resin layer be r2. Then, r1 < r2 The diffractive optical element according to any one of Configurations 2 to 8, characterized in that (Configuration 10) The resin layer is made of a photocurable resin The diffractive optical element according to any one of Configurations 1 to 9, characterized in that (Configuration 11) The photocurable resin is an episulfide-based resin The diffractive optical element according to Configuration 10, characterized in that (Configuration 12) Having an inorganic film provided between the substrate and the resin layer The diffractive optical element according to any one of Configurations 1 to 11, characterized in that (Configuration 13) The substrate is a resin substrate or a glass substrate The diffractive optical element according to any one of Configurations 1 to 12, characterized in that (Configuration 14) An optical device having a housing and an optical system having at least one lens disposed within the housing, wherein At least one of the lenses is a diffractive optical element according to any one of Configurations 1 to 13, characterized in that (Configuration 15) A display device having a housing, an optical system having at least one lens disposed within the housing, and a display unit that emits light guided by the optical system, wherein At least one of the lenses is a diffractive optical element according to any one of Configurations 1 to 13, characterized in that (Configuration 16) An imaging device having a housing, an optical system having at least one lens disposed within the housing, and an imaging element that receives light that has passed through the optical system, wherein An imaging device, wherein at least one of the lenses is a diffractive optical element according to any one of Configurations 1 to 13. (Method 1) A substrate having a surface provided with a diffraction grating, A method for manufacturing a diffractive optical element, comprising a resin layer provided so as to cover the diffraction grating on the surface of the substrate, In a plan view as viewed in the optical axis direction, the diffraction grating includes a circular first diffraction grating and an arc-shaped second diffraction grating disposed outside the first diffraction grating, The diffractive optical element has an optically effective region and a non-optically effective region surrounding the optically effective region, The arc ends of the second diffraction grating are located in the non-optically effective region, The resin layer is provided such that the thickness of the resin layer provided in the non-optically effective region is thicker than the thickness of the resin layer provided in the optically effective region. A method for manufacturing a diffractive optical element, characterized by the above. (Method 2) A resin is molded on the substrate using a mold to provide the resin layer. A method for manufacturing a diffractive optical element according to Method 1, characterized by the above.

Explanation of Reference Numerals

[0077] 11 Substrate 12 Resin layer 13 Diffraction grating 14 Optically effective region 15 Non-optically effective region 16 Diffraction grating 17 Transparent inorganic film 21 Mold 22 Light irradiation machine 111 First part 112 Second part 113 Arc part 114 Chord part 121 Resin

Claims

1. A diffraction optical element having a substrate with a surface provided with a diffraction grating, and a resin layer provided on the surface of the substrate so as to cover the diffraction grating, wherein: In a plan view along the optical axis direction, the diffraction grating includes a circular first diffraction grating and an arc-shaped second diffraction grating disposed outside the first diffraction grating; The diffraction optical element has an optically effective region and a non-optically effective region surrounding the optically effective region; The arc ends of the second diffraction grating are located in the non-optically effective region; The thickness of the resin layer provided in the non-optically effective region is greater than the thickness of the resin layer provided in the optically effective region; The substrate includes a first portion having a truncated circular planar shape surrounded by an arc and a chord connecting both ends of the arc in the plan view; The non-optically effective region has an arc portion that is an end portion on the arc side of the first portion and a chord portion that includes an end portion on the chord side of the first portion; When the thickness of the resin layer provided in the chord portion is t1 and the thickness of the resin layer provided in the arc portion is t2, t1 > t2; A diffraction optical element, characterized by the above.

2. t1 / t2 < 3; The diffraction optical element according to claim 1, characterized by the above.

3. When the width of the resin layer provided in the chord portion is w1 and the width of the resin layer provided in the arc portion is w2, 1 < (t1 × w1) / (t2 × w2) < 3; The diffraction optical element according to claim 1 or 2, characterized by the above.

4. When the thickness of the resin layer provided in the optically effective region is tc and the height of the diffraction grating is d, 3 < (t1 - tc) / d < 80; The diffraction optical element according to claim 1 or 2, characterized by the above.

5. The thickness t1 is 1000 μm or less; The diffraction optical element according to claim 1 or 2, characterized by the above.

6. A diffraction optical element having a substrate with a surface provided with a diffraction grating, and a resin layer provided on the surface of the substrate so as to cover the diffraction grating, wherein: In a plan view along the optical axis direction, the diffraction grating includes a circular first diffraction grating and an arc-shaped second diffraction grating disposed outside the first diffraction grating; The diffraction optical element has an optically effective region and a non-optically effective region surrounding the optically effective region; The arc ends of the second diffraction grating are located in the non-optically effective region; ​ The thickness of the resin layer provided in the non-optical effective region is greater than the thickness of the resin layer provided in the optical effective region. The substrate includes a first portion having a plane shape of a defective circular shape surrounded by an arc and a chord connecting both ends of the arc in the plan view, and a second portion provided on the chord side of the first portion. The non-optical effective region has an arc portion that is an end portion on the arc side of the first portion and a chord portion that includes an end portion on the chord side of the first portion. The second portion has a plane shape of a rectangular shape in the plan view. The chord portion includes the second portion. A diffractive optical element characterized by the above.

7. The resin layer is composed of a photocurable resin. The diffractive optical element according to claim 1, 2 or 6, characterized in that.

8. The photocurable resin is an episulfide-based resin. The diffractive optical element according to claim 7, characterized in that.

9. Having an inorganic film provided between the substrate and the resin layer. The diffractive optical element according to claim 1, 2 or 6, characterized in that.

10. The substrate is a resin substrate or a glass substrate. The diffractive optical element according to claim 1, 2 or 6, characterized in that.

11. An optical device having a housing and an optical system having at least one lens disposed in the housing, An optical device, characterized in that at least one of the lenses is the diffractive optical element according to claim 1, 2 or 6.

12. A display device having a housing, an optical system having at least one lens disposed in the housing, and a display unit that emits light guided by the optical system, A display device, characterized in that at least one of the lenses is the diffractive optical element according to claim 1, 2 or 6.

13. An imaging device having a housing, an optical system having at least one lens disposed in the housing, and an imaging element that receives light that has passed through the optical system, An imaging device, characterized in that at least one of the lenses is the diffractive optical element according to claim 1, 2 or 6.

14. A substrate having a surface provided with a diffraction grating, A method for manufacturing a diffractive optical element having a resin layer provided so as to cover the diffraction grating on the surface of the substrate, In a plan view seen in the optical axis direction, the diffraction grating includes a circular first diffraction grating and an arc-shaped second diffraction grating disposed outside the first diffraction grating. The diffractive optical element has an optically effective region and a non-optically effective region surrounding the optically effective region, The arc ends of the second diffraction grating are located in the non-optically effective region, The substrate includes a first portion having a plane shape of an incomplete circular shape surrounded by an arc and a chord connecting both ends of the arc in the plan view, The non-optically effective region has an arc portion that is an end portion on the arc side of the first portion and a chord portion that includes an end portion on the chord side of the first portion, The thickness of the resin layer provided in the non-optically effective region is made thicker than the thickness of the resin layer provided in the optically effective region. When the thickness of the resin layer provided in the chord portion is t1 and the thickness of the resin layer provided in the arc portion is t2, the resin layer is provided so that t1 > t2. A method for manufacturing a diffractive optical element, characterized by the above.

15. A method for manufacturing a diffractive optical element, comprising: a substrate having a surface provided with a diffraction grating; A resin layer provided on the surface of the substrate so as to cover the diffraction grating, In a plan view seen in the optical axis direction, the diffraction grating includes a circular first diffraction grating and an arc-shaped second diffraction grating disposed outside the first diffraction grating, The diffractive optical element has an optically effective region and a non-optically effective region surrounding the optically effective region, The arc ends of the second diffraction grating are located in the non-optically effective region, The substrate includes a first portion having a plane shape of an incomplete circular shape surrounded by an arc and a chord connecting both ends of the arc in the plan view, and a second portion provided on the chord side of the first portion, The non-optically effective region has an arc portion that is an end portion on the arc side of the first portion and a chord portion that includes an end portion on the chord side of the first portion, The second portion has a plane shape of a rectangular shape in the plan view, The chord portion includes the second portion, The resin layer is provided so that the thickness of the resin layer provided in the non-optically effective region is made thicker than the thickness of the resin layer provided in the optically effective region. A method for manufacturing a diffractive optical element, characterized by the above.

16. The resin is molded on the substrate using a mold to provide the resin layer. A method for manufacturing a diffractive optical element according to claim 14 or 15, characterized by the above.

Images