Abstract: In a Schottky emitter or a thermal field emitter using a hexaboride single crystal, side emission from portions other than an electron emission portion is reduced. An electron source according to the invention includes: a protrusion (40) configured to emit an electron when an electric field is generated; a shank (41) that supports the protrusion (40) and has a diameter decreasing toward the protrusion (40); and a body (42) that supports the shank (41), in which the protrusion (40), the shank (41), and the body (42) are each made of a hexaboride single crystal, and a part including the shank (41) and the body (42) excluding the protrusion (40) is covered with a material having a work function higher than that of the hexaboride single crystal.

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 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 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: 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: 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 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: 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 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 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 wavelength conversion element according to the invention includes a wavelength conversion layer including a plurality of phosphor particles made of an yttrium aluminum garnet (YAG) type phosphor material including cerium (Ce) as a activator agent, and a binder made of glass adapted to hold the plurality of phosphor particles, and the refractive index of the binder is higher than the refractive index of the phosphor particles.

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 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 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 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.