Abstract: A wavelength conversion element includes a wavelength conversion layer configured to convert first light in a first wavelength band into second light in a second wavelength band different from the first wavelength band, the wavelength conversion layer including a scattering element no higher than 5% in volume ratio and having a first surface, a second surface intersecting the first surface, and a third surface intersecting the second surface and different from the first surface, an optical element including glass having a first refractive index lower than a second refractive index of the wavelength conversion layer, the optical element having contact with the first surface and the second surface, and a low-refractive index layer having a third refractive index lower than the first refractive index of the glass, the low-refractive index layer having contact with the third surface.

Abstract: A wavelength. conversion device includes a motor having a rotation axis and a hollow space, a wavelength converter converting incident first light in a first wavelength band to second light in a second wavelength band that is different from the first wavelength band, and a coupling member thermally coupled to the wavelength converter. At least a part of the coupling member is arranged in the hollow space. The motor changes a position of incidence of the first light on the wavelength converter relatively with respect to the wavelength converter.

Abstract: A phosphor particle is configured to emit fluorescence longer in wavelength than excitation light entering the phosphor particle. The phosphor includes a concave portion which is no smaller than 0.1 times as large as the wavelength of the fluorescence and no larger than 10 times as large as the wavelength of the fluorescence. The concave portion is disposed on a surface of the phosphor particle.

Abstract: A wavelength conversion element includes a phosphor layer having phosphor particles and a binder, and a holding member including alumina, configured to hold the layer. The binder includes glass and is configured to bind a part the adjacent particles. The holding member has a pore, defining an apparent porosity thereof as X, bending strength A of the holding member fulfills A=?7.11X+316.52, an elastic modulus B of the holding member fulfills B=?6.26X+288.43, and defining an elastic modulus of the glass as C, 1/B+1/C=D, and a product of a difference between a linear expansion coefficient of the holding member and a linear expansion coefficient of the glass and a transition point of the glass as Y, Y<(A)(D)(0.001) when the linear expansion coefficient of the glass is smaller than the linear expansion coefficient of the holding member in a temperature range from the transition point of the glass to a room temperature.

Abstract: The wavelength conversion element includes a phosphor layer having a plurality of phosphor particles and a binder configured to bind one of the phosphor particles adjacent to each other and another of the phosphor particles adjacent to each other out of the plurality of phosphor particles, an antireflection layer disposed on an incident side of the excitation light with respect to the phosphor layer, and a substrate provided with the phosphor layer, wherein the binder includes glass, and the binder binds a part of a surface of the one of the phosphor particles and a part of a surface of the another of the phosphor particles to each other.

Abstract: The wavelength conversion element includes a phosphor layer having a plurality of phosphor particles and a binder configured to bind one of the phosphor particles adjacent to each other and another of the phosphor particles adjacent to each other out of the plurality of phosphor particles, and a substrate provided with the phosphor layer, wherein the binder includes glass, and the binder binds a part of a surface of the one of the phosphor particles and a part of a surface of the another of the phosphor particles to each other.

Abstract: A light source device includes a light source configured to emit excitation light, a wavelength conversion section configured to perform wavelength conversion on the excitation light to generate fluorescence having a wavelength longer than a wavelength of the excitation light, a substrate opposed to the wavelength conversion section, and an air gap disposed between the wavelength conversion section and the substrate, wherein the wavelength conversion section has a first surface opposed to the substrate, the substrate has a second surface opposed to the first surface, a thickness dimension of the air gap as a dimension in a direction from the first surface toward the second surface is defined by a sum of a roughness of the first surface and a roughness of the second surface, and the thickness dimension of the air gap is no smaller than a wavelength of the fluorescence.

Abstract: A wavelength conversion element includes a wavelength conversion layer having a first surface on which excitation light is incident, a second surface located on the side opposite the first surface, a plurality of phosphor particles that convert the excitation light in terms of wavelength to produce fluorescence, and a binder that holds the plurality of phosphor particles. The plurality of phosphor particles have a particle diameter distribution, and the minimum particle diameter in the particle diameter distribution of a plurality of the phosphor particles contained in a first region located on the side facing the first surface is greater than the minimum particle diameter in the particle diameter distribution of a plurality of the phosphor particles contained in a second region located on the side facing the second surface.

Abstract: A wavelength conversion element includes a wavelength conversion layer containing a plurality of phosphor particles and an inorganic binder that bonds the phosphor particles to each other and a substrate that holds the wavelength conversion layer and contains alumina and air cavities. The substrate has an apparent air cavity ratio that is greater than or equal to 10% and smaller than or equal to 30%. The substrate has a median diameter of particles of the alumina that is greater than or equal to 0.1 ?m and smaller than or equal to 1.0 ?m.

Abstract: A light source device includes a first light source configured to emit excitation light having a first wavelength band, a wavelength conversion member having a plurality of surfaces and configured to convert the excitation light made incident from the first light source into converted light having a second wavelength band different from the first wavelength band, and a first light transmissive member provided between the first light source and the wavelength conversion member and configured to transmit the excitation light. The wavelength conversion member includes a first surface on which the excitation light from the first light source is made incident. The first light transmissive member includes, on a surface opposed to the first surface of the wavelength conversion member, a first reflection layer that transmits the excitation light and reflects the converted light. A gap is provided between the first surface and the first reflection layer.

Abstract: A light source device includes a first light source configured to emit excitation light in a first wavelength band and a wavelength conversion member having a plurality of surfaces and configured to convert the excitation light made incident from the first light source into converted light in a second wavelength band different from the first wavelength band. The wavelength conversion member includes a first surface on which the excitation light is made incident, a second surface opposed to the first surface, and a third surface that emits the converted light. A first reflection layer that transmits the excitation light and reflects the converted light is provided on the first surface.

Abstract: A wavelength conversion element includes a base material and a phosphor layer that contains a phosphor emitting fluorescence upon incidence of excitation light and is provided on the base material, in which the phosphor layer includes a first surface on which excitation light (blue light) is incident and a second surface facing the base material, and a plurality of regions with different absorption coefficients of the excitation light between the first surface and the second surface.

Abstract: A light source apparatus includes a light source that outputs excitation light, and a rotating light emitting device in which a wavelength conversion element that emits light when irradiated with the excitation light is provided on a rotating disk. A spot of the excitation light on the wavelength conversion element has a shape that is long in a radial direction of the rotating disk and short in a circumferential direction of the rotating disk. Alternatively, an orthogonally projected length of the spot in the radial direction is greater than an orthogonally projected length of the spot in the circumferential direction.

Abstract: A light source device according to the invention includes a light source, a light separating/combining element including a dichroic layer, a wavelength conversion layer, and a diffusely reflecting element. A bundle of light beams emitted from the light source includes a first light bundle and a second light bundle. The first light bundle enters the wavelength conversion layer via the dichroic layer. The second light bundle enters the diffusely reflecting element without entering the dichroic layer, and is converted into diffusely reflected light. The dichroic layer combines the third light bundle from the wavelength conversion layer and the diffusely reflected light from the diffusely reflecting element with each other.

Abstract: A fluorescence light emitting element includes a phosphor layer that includes phosphors and a binder made of an inorganic material. A thermal conductivity B of the binder is larger than 1.88 times a thermal conductivity A of the phosphors. When the volume of the phosphors included in the phosphor layer is X and the volume of the binder included in the phosphor layer is Y, a relationship of X/Y>1/2 is satisfied.

Abstract: A light source apparatus includes a light emitting device that has a first light emitting region outputting first excitation light and a second light emitting region outputting second excitation light, a phosphor layer that is so provided that the phosphor layer coincides with the first light emitting region in a plan view and emits fluorescence light, a reflector that is provided on the opposite side of the phosphor layer to the light emitting device, transmits the fluorescence light, and reflects the excitation light, and a light guide section that is disposed on an optical path between the phosphor layer and the reflector, and guides the second excitation light reflected off the reflector such that at least part of the reflected second excitation light enters the phosphor layer.

Abstract: A screen in which observation distance may be adjusted while maintaining image brightness and a projection system using the screen. In a light control layer of a screen, a first angle region that determines a diffusion distribution of a reflected light is different according to the screen position in a control direction in which light diffusion control is performed. Accordingly, a diffusion distribution of image light emitted from a screen surface is adjusted to be tilted downward by an upper end and upward by a lower end according to the screen position. Thus, for example, a size of a diffused angle range is maintained to be 30°, and a direction in which the image light is diffusion-emitted corresponds to an assumed position of an observer. The projection image can be observed while maintaining brightness of an image and the observation distance L can be adjusted to be short.

Abstract: A projector includes a light source, a first light separation optical system adapted to separate light emitted from the light source into first light and second light, a second light separation optical system adapted to separate the first light into third light and fourth light, separate the second light into fifth light and sixth light, and emit the third light, the fourth light, the fifth light, and the six light in directions intersecting with a plane including a light axis of the light emitted from the light source and a light axis of the first light, and a light modulation element which the third light, the fourth light, the fifth light, and the sixth light enter.

Abstract: A screen which reflects light emitted from a projector includes a light diffusion layer through which light incident from a specific angular region is diffused and transmitted and through which light incident from the other angular region is transmitted straight; area pairs having a mirror forming area and a non-mirror forming area; a light transmissive layer having a back surface, on which the area pairs are disposed, and an opposite surface being bonded to a back side of the light diffusion layer; and a specular reflection film formed on a back surface of each mirror forming area. An inclination of the mirror forming area with respect to a normal line of the screen close to the projector becomes larger than the inclination of the mirror forming area far from the projector within a cross section perpendicular to the mirror forming areas inside the screen.

Abstract: A screen in which observation distance may be adjusted while maintaining image brightness and a projection system using the screen. In a light control layer of a screen, a first angle region that determines a diffusion distribution of a reflected light is different according to the screen position in a control direction in which light diffusion control is performed. Accordingly, a diffusion distribution of image light emitted from a screen surface is adjusted to be tilted downward by an upper end and upward by a lower end according to the screen position. Thus, for example, a size of a diffused angle range is maintained to be 30°, and a direction in which the image light is diffusion-emitted corresponds to an assumed position of an observer. The projection image can be observed while maintaining brightness of an image and the observation distance can be adjusted to be short.