A cooling device of a projection display apparatus includes a first heat receiving unit including an opening that is rectangular. The first heat receiving unit includes a flow path part that forms the opening. An image display element of the projection display apparatus includes a first front face located in front of a reflective image display, a second front face parallel to the first front face and located behind and outside the first front face, and a first side face located between the first front face and the second front face. The first front face is inserted into the opening, and the flow path part is in contact with the first side face and the second front face via a heat conductive member. The flow path part includes a front face that is flush with or in front of the first front face of the image display element.

An optical system of the disclosure includes: a fluorescent unit that includes a phosphor region excited by a first color light beam to output fluorescent light including at least one color light beam, and outputs the first color light beam in a first period and outputs the fluorescent light in a second period; one or two light valves illuminated by at least one of the first color light beam or the fluorescent light; and a region division element including first and second regions and disposed on an optical path between the fluorescent unit and the one or two light valves, the first region outputting the first color light beam and the fluorescent light from the fluorescent unit to be able to reach the one or two light valves, the second region outputting the fluorescent light from the fluorescent unit to be able to reach the one or two light valves.

A light conversion device is disclosed. The light conversion device includes a substrate and a wavelength conversion element (111). The wavelength conversion element (111) includes an inorganic binder, such as sodium silicate. Also disclosed are phosphor wheels and light engines including such phosphor wheels. Further disclosed are high-power laser projection display systems comprising a laser having a power of from about 60 W and about 300 W and a light conversion device. The use of an inorganic binder permits high thermal stability at reasonable cost.

A light source device according to the present disclosure includes a first light source section for emitting a first light flux, a second light source section for emitting a second light flux, a third light source section for emitting a third light flux, a first reflecting member, a second reflecting member for reflecting the second light flux, and a polarization combining element. With respect to the polarization combining element, the first light flux and the second light flux are light polarized in a first polarization direction, and the third light flux is light polarized in a second polarization direction, and the first and second reflecting members are disposed so that a distance between the first light flux and second light flux becomes smaller after incidence than before the incidence. The polarization combining element combines the first light flux, the second light flux, and the third light flux with each other.

A device includes a light source configured to generate first light, an optical element configured to reflect light incident on the optical element at a first angle of incidence and transmit light incident on the optical element at a second angle of incidence smaller than the first angle of incidence, a first reflecting unit, a second reflecting unit, and a conversion unit on which the first light is incident and which is configured to emit second light, wherein the first light is reflected by the first reflecting unit, passes through the optical element, and is then incident on the second reflecting unit, and wherein the second reflecting unit reflects the first light to the conversion unit.

A light source device according to an embodiment of the present disclosure includes: a first light source section that emits light in a first wavelength region; a wavelength conversion section that is disposed on an optical path of the light in the first wavelength region, and is excited by the light in the first wavelength region emitted from the first light source section to emit light in a second wavelength region different from the first wavelength region; a polarization separation element that is disposed between the first light source section and the wavelength conversion section, and separates incident light on the basis of polarization; and a color separation element that is disposed between the first light source section and the polarization separation element, and separates incident light on the basis of a wavelength region.

To provide an optical element capable of realizing an increase in color range of videos and an improvement in brightness of the videos, a light source device including the optical element, and a projector including the light source device. Provided is an optical element including: a first color conversion layer; a second color conversion layer; and a heat insulating layer, in which the heat insulating layer is disposed between the first color conversion layer and the second color conversion layer, a light source device including the optical element, and a projector including the light source device.

A wavelength conversion element includes a plate, a wavelength conversion layer, and a macromolecular layer. The wavelength conversion layer has a facing surface facing the plate. The wavelength conversion layer contains an inorganic wavelength conversion material that emits light of a wavelength different from the wavelength of incident light. The macromolecular layer is disposed between the plate and the wavelength conversion layer. A part of the facing surface is in contact with the plate. At least a part of another portion of the facing surface is joined to the plate with the macromolecular aver interposed.

A wavelength conversion plate includes a conversion region and a reflection region on a base surface. The conversion region includes a wavelength conversion member configured to receive excitation light and generate a color different from a color of the excitation light. The reflection region is configured to reflect the excitation light. The reflection region includes a transmissive diffusion surface, a transmissive layer, and a reflection surface. The transmissive diffusion surface is configured to diffuse the excitation light. The transmissive layer is configured to transmit the excitation light. The reflection surface is configured to reflect the excitation light. The transmissive diffusion surface is in a position separate from a surface closer to the base surface, of the wavelength conversion member, toward a direction from which the excitation light is incident.

A wavelength conversion element according to the present disclosure includes a wavelength conversion layer having a first surface having a recessed part, and a plurality of air holes, and configured to be excited by light in a first wavelength band to thereby generate light in a second wavelength band different from the first wavelength band, a particle disposed in the recessed part, a light transmissive member disposed so as to cover the recessed part and the particle, a reflecting layer disposed so as to be opposed to the first surface of the wavelength conversion layer, and a base member disposed so as to be opposed to the reflecting layer.