Abstract: A diffractive optical element 10 includes a first diffraction grating 4, a second diffraction grating 5, films 6 formed between the first diffraction grating 4 and the second diffraction grating 5. The DOE 10 satisfies a conditional expression of n2<n1<nha, where nha is an average refractive index of films 6b formed between grating wall surfaces 4b and grating wall surfaces 5b at a wavelength of 550 nm, n1 is a refractive index of the first diffraction grating 4 at a wavelength of 550 nm, and n2 is a refractive index of the second diffraction grating 5 at a wavelength of 550 nm. The films 6b and films 6a that are formed between grating surfaces 4a and grating surfaces 5a satisfy a predetermined relationship.

Abstract: A diffractive optical element (1) includes a first diffraction grating (21) including a first grating surface (21a) and a first grating wall surface (21b), a second diffraction grating (31) including a second grating surface (31a) and a second grating wall surface (31b), and a thin film (11) provided between the first grating wall surface and the second grating wall surface and being in contact with both of the first and second grating wall surfaces, an extinction coefficient of the thin film with respect to a wavelength ? in a use wavelength band is not greater than 0.0005, and with respect to the wavelength ?, refractive indices of materials of the thin film, the first diffraction grating, and the second diffraction grating, a relative diffractive index difference of the thin film and the first diffraction grating, and a width of the thin film satisfy predetermined conditions.

Abstract: A diffractive optical element 10 includes a first diffraction grating 4, a second diffraction grating 5, films 6 formed between the first diffraction grating 4 and the second diffraction grating 5. The DOE 10 satisfies a conditional expression of n2<n1<nha, where nha is an average refractive index of films 6b formed between grating wall surfaces 4b and grating wall surfaces 5b at a wavelength of 550 nm, n1 is a refractive index of the first diffraction grating 4 at a wavelength of 550 nm, and n2 is a refractive index of the second diffraction grating 5 at a wavelength of 550 nm. The films 6b and films 6a that are formed between grating surfaces 4a and grating surfaces 5a satisfy a predetermined relationship.

Abstract: A diffractive optical element (1) includes a first diffraction grating (21) including a first grating surface (21a) and a first grating wall surface (21b), a second diffraction grating (31) including a second grating surface (31a) and a second grating wall surface (31b), and a thin film (11) provided between the first grating wall surface and the second grating wall surface and being in contact with both of the first and second grating wall surfaces, an extinction coefficient of the thin film with respect to a wavelength ? in a use wavelength band is not greater than 0.0005, and with respect to the wavelength ?, refractive indices of materials of the thin film, the first diffraction grating, and the second diffraction grating, a relative diffractive index difference of the thin film and the first diffraction grating, and a width of the thin film satisfy predetermined conditions.

Abstract: A diffractive optical element made by adhering a first diffractive grating and a second diffractive grating to each other, each of which has a blazed structure. At least one of the first and second diffractive gratings is made of a material having a refractive index distribution in a plane normal direction, and the predetermined expressions are satisfied for a wavelength ? in a visible wavelength range.

Abstract: A wavelength selective polarizer includes a substrate that is transparent to light in a visible wavelength band, and an absorption layer configured of a resin composition in which color materials are dispersed and formed on the substrate. The absorption layer includes a plurality of structures that are structured similarly to one another, the plurality of structures being arranged in a predetermined direction with a period shorter than a shortest wavelength in the visible wavelength band. Where a longitudinal direction of each of the plurality of structures is set to a first direction, the predetermined direction is a second direction that is orthogonal to the first direction and parallel to a surface of the substrate, on which the absorption layer is formed. A material of the absorption layer satisfies the predetermined condition.

Abstract: A diffractive optical element includes a first diffraction grating and a second diffraction grating which are made of materials different from each other and are stacked in an optical axis direction, and a thin film which is arranged at least part of an interface between the first diffraction grating and the second diffraction grating, includes a single layer or multiple layers made of a material different from that of each of the first and second diffraction gratings, and is transparent to light of a working wavelength range. nd1<nd2 and 0.5<nd3?nd2<0.8 are satisfied, where nd1 is a refractive index of the material of the first diffraction grating to d-line, nd2 is a refractive index of the material of the second diffraction grating to the d-line, and nd3 is a maximum refractive index of the material of one layer of the thin film to the d-line.

Abstract: A diffractive optical element used as a lens of an optical system includes a first diffractive grating that includes a first grating surface and a first grating wall surface, a reflective member disposed on the first grating wall surface, and a second diffractive grating that includes a second grating surface and a second grating wall surface, and that is disposed so that the second grating surface contacts the first grating surface and the second grating wall surface contacts the reflective member. When off-screen light having an incident angle larger than that of off-axis light flux enters the diffractive optical element at a predetermined incident angle, an emission angle of light having the maximum intensity emitted from the first or second grating wall surface is appropriately set. The maximum width of the reflective member and a grating pitch of each of the first and second diffractive gratings are appropriately set.

Abstract: A diffraction optical element including: a diffractive grating provided with a grating surface and a grating wall surface; and a thin film arranged on the grating wall surface and being transparent with respect to light of a used wavelength range, wherein the following expressions; 0.05<nfd?ngd<0.5 0.01<(nfd?ngd)*wf/?d<0.05 are satisfied, where nfd is a refractive index of the thin film with respect to a d line, ngd is a refractive index of a material of the diffractive grating with respect to the d line, wf is a thickness of the thin film, and ?d is a wavelength of the d line.

Abstract: A diffractive optical element is made by layering first and second diffractive gratings. A difference of an extinction coefficient to d-line between the two materials of each of the first and second diffractive grating is larger than 0.0002 and smaller than 0.002. The following conditional expressions are satisfied 0.05<|?nd1|<0.3, 0.05<|?nd2|<0.3, 20<|??d1|<40, and |??d2|<15, where ?nd1, ?nd2 are differences of a refractive index to the d-line between the two materials of the first and second diffractive gratings, and ??d1, ??d2 are differences of an Abbe number between the two materials of the first and second diffractive gratings.

Abstract: A variable transmittance element includes two substrates, two transparent electrode layers held between the two substrates, an electrochromic layer held between the two transparent electrode layers and having transmittance that is reversibly changed by electric control, and a first dielectric layer provided between one of the two substrates and one of the two transparent electrode layers closest to the one of the two substrates and configured to reduce reflections. The first dielectric layer is a multilayer film made by alternately laminating two or more layers each having a high refractive index and two or more layers each having a low refractive index, a refractive index difference for a wavelength of 550 nm between the layer having the high refractive index and the layer having the low refractive index being 0.2 or more.

Abstract: A diffractive optical element has higher diffraction efficiency of diffracted light of a designed order in a visible wavelength range. The diffractive optical element includes a diffraction grating part provided on a lens surface of an optical system and constituted by laminating first and second diffraction gratings made of two different materials. Each of the first and second diffraction gratings includes a grating surface and a grating wall surface. The grating surfaces of the first and second diffraction gratings are in contact with each other. The diffraction grating part has the designed order of at least +2nd order and has a grating height of at least 6 ?m.

Abstract: A diffractive optical element includes a first diffractive grating including a first grating surface and a first grating wall surface, a light shielding member disposed on the first grating wall surface, and a second diffractive grating including a second grating surface and a second grating wall surface, disposed so that the second grating surface contacts the first grating surface and the second grating wall surface contacts the light shielding member. An extinction coefficient k of a material that constitutes the light shielding member meets the expression of 0.001<k<0.5.

Abstract: A diffractive optical element includes a diffraction grating portion including a first diffraction grating and a second diffraction grating, the first diffraction grating and the second diffraction grating being formed of different materials and being stacked so that grating surfaces thereof are in contact with each other, in which the first diffraction grating is formed of a first grating material having at least three kinds of materials mixed therein, and the following conditions are satisfied: nd1<nd2; ?d1<?d2; ?gF1<(?1.665E?07×?d13+5.213E?05×?d12?5.656E?03×?d1+0.715); ?gF1>(+4.80E?03×?d1+0.33); and ?gF1>(?4.73E?02×?d1+1.31), where nd1, ?d1, and ?gF1 represent a refractive index, an Abbe number, and a partial dispersion ratio, respectively, of the first grating material with respect to a d-line, and nd2 and ?d2 represent a refractive index and an Abbe number, respectively, of a second grating material forming the second diffraction grating with respect to the d-line.

Abstract: A diffractive optical element includes stacked first and second diffraction gratings made of different materials. The materials of the first and second diffraction gratings are glass. The first and second diffraction gratings have grating surfaces contacted to each other. The materials satisfy a predetermined condition when Tg2 and At2 are a transformation point temperature and a yield point temperature of the material of the first diffraction grating, and Tg3 and At3 are a transformation point temperature and a yield point temperature of the material of the second diffraction grating.

Abstract: An image projection apparatus includes light sources 111 to 113 emitting at least two colored lights whose wavelengths are different from each other, a polarization conversion element 2 controlling a polarization direction of the colored light, at least two light modulation elements 41 and 42 modulating incident light, a light guide optical system 31 guiding the at least two colored lights from the polarization conversion element to the at least two light modulation elements in accordance with the polarization direction, and a projection optical system 5. One of the at least two colored light and the other are emitted as lights whose polarization directions are different from each other from the polarization conversion element. A drive unit 6 turns on the light sources so that the one of the colored lights and at least one of the other enter the at least two light modulation elements at the same time.

Abstract: A diffractive optical element is made by layering first and second diffractive gratings. A difference of an extinction coefficient to d-line between the two materials of each of the first and second diffractive grating is larger than 0.0002 and smaller than 0.002. The following conditional expressions are satisfied 0.05<|?nd1|<0.3, 0.05<|?nd2 |<0.3, 20<|??d1|<40, and |??d2|<15, where ?nd1, ?nd2 are differences of a refractive index to the d-line between the two materials of the first and second diffractive gratings, and ??d1, ??d2are differences of an Abbe number between the two materials of the first and second diffractive gratings.

Abstract: An optical system includes an optical element formed of resin. On at least one of optical surfaces on the light incidence side of the optical element formed of resin, a plurality of depressions or protrusions of a size not larger than the wavelengths of visible light is formed without a periodic structure or in a random arrangement.

Abstract: A diffractive optical element includes first and second diffraction gratings. A grating wall surface of the second diffractive grating is located on a surface extending a grating wall surface of the first diffractive grating or on a low refractive index region side of the first diffractive grating with respect to the surface extending the grating wall surface of the first diffractive grating. +1.3×|m|<|m1|<+2.0×|m|, ?1.0×|m|<?|m2|<?0.3×|m|, and 0.94×|m|<|m1+m2|<1.05×|m| are satisfied. Here, m is a designed order, m1=(nd2?nd1)d1/?d, m2=(nd3?nd2)d2/?d, nd1 is a refractive index of the first material to d-line, nd2 is a refractive index of the second material to the d-line, nd3 is a refractive index of the third material to the d-line, ?d is a wavelength of the d-line, d1 and d2 are grating heights of the first and second diffraction gratings.

Abstract: The diffractive optical element includes a first diffraction grating and a second diffraction grating, which are formed of materials different from each other, the first diffraction grating and the second diffraction grating are stacked so as not to provide any air layer therebetween. The diffractive optical element satisfies conditions of nd1<nd2, ?d1<?d2, 1.65?nd1, ?d1?20, 1.73?nd2, and 15??d2?60 where nd1 and ?d1 respectively represent a refractive index and an Abbe constant of the material of the first diffraction grating for a d-line, and nd2 and ?d2 respectively represent a refractive index and an Abbe constant of the material of the second diffraction grating for the d-line. The element is capable of reducing deterioration of a diffraction efficiency by an obliquely incident light, to improve the diffraction efficiency of a designed order light in a use wavelength range.