Abstract: An MgF2 optical thin film is formed on an optical surface of a base material. The MgF2 optical thin film includes MgF2 particles and an amorphous silicon oxide-based binder which exists on the surfaces of the MgF2 particles and between the MgF2 particles. Owing to this amorphous silicon oxide-based binder, the optical thin film can have high mechanical strength and high adhesion to the base material, while having excellent environment resistance and a lower refractive index.

Abstract: An MgF2 optical thin film is formed on an optical surface of a base material. The MgF2 optical thin film includes MgF2 particles and an amorphous silicon oxide-based binder which exists on the surfaces of the MgF2 particles and between the MgF2 particles. Owing to this amorphous silicon oxide-based binder, the optical thin film can have high mechanical strength and high adhesion to the base material, while having excellent environment resistance and a lower refractive index.

Abstract: An MgF2 optical thin film is formed on an optical surface of a base material. The MgF2 optical thin film includes MgF2 particles and an amorphous silicon oxide-based binder which exists on the surfaces of the MgF2 particles and between the MgF2 particles. Owing to this amorphous silicon oxide-based binder, the optical thin film can have high mechanical strength and high adhesion to the base material, while having excellent environment resistance and a lower refractive index.

Abstract: Optical multi-layer thin film comprises: an outermost layer stacked above an optical surface of an optical substrate having a lower refractive index than the optical substrate; and at least a certain refractive index layer disposed between the optical substrate and the outermost layer, and having a refractive index adjustable in a predetermined range higher than that of the outermost layer. The outermost layer is formed by a wet film-formation method using: low-refractive-index fine particles made of a low-refractive-index material; and a first binder, and the certain refractive index layer is formed by a wet film-formation method using: high-refractive-index fine particles made of a high-refractive-index material; and a second binder which has a refractive index different from that of the high-refractive-index material.

Abstract: An MgF2 optical thin film is formed on an optical surface of a base material. The MgF2 optical thin film includes MgF2 particles and an amorphous silicon oxide-based binder which exists on the surfaces of the MgF2 particles and between the MgF2 particles. Owing to this amorphous silicon oxide-based binder, the optical thin film can have high mechanical strength and high adhesion to the base material, while having excellent environment resistance and a lower refractive index.

Abstract: Embodiment of the present invention is to provide an optical member composed of calcium fluoride (fluorite) and being capable of preventing deterioration and demonstrating a long life even in use under severe conditions. An optical member of a preferred embodiment has a base material having an entrance face into which light is incident, a total reflection face totally reflecting the incident light, and an exit face from which the totally reflected light emerges to the outside, and made of a calcium fluoride crystal; and a protecting layer to control deterioration of the total reflection face by the light, which is provided on a surface outside the total reflection face in this base material.

Abstract: An optical multi-layer thin film comprises: an outermost layer (13) which is stacked above an optical surface (11) of an optical substrate (10), and which has a lower refractive index than that of the optical substrate (10); and at least certain refractive index layer (14) which is disposed between the optical substrate (10) and the outermost layer (13), and which has a refractive index adjustable in a predetermined range higher than that of the outermost layer (13), wherein the outermost layer (13) is formed by a wet film-formation method using: low-refractive-index fine particles (15) made of a low-refractive-index material having a lower refractive index than that of the optical substrate (10); and a first binder (16), and the certain refractive index layer (14) is formed by a wet film-formation method using: high-refractive-index fine particles (18) made of a high-refractive-index material having a higher refractive index than that of the low-refractive-index material; and a second binder (19) which has a

Abstract: An MgF2 optical thin film is formed on an optical surface of a base material. The MgF2 optical thin film includes MgF2 particles and an amorphous silicon oxide-based binder which exists on the surfaces of the MgF2 particles and between the MgF2 particles. Owing to this amorphous silicon oxide-based binder, the optical thin film can have high mechanical strength and high adhesion to the base material, while having excellent environment resistance and a lower refractive index.

Abstract: A projection optical system, which forms a reduced image of a first surface onto a second surface, has excellent optical performance without substantially being affected by birefringence despite the use of optical material having intrinsic birefringence. This is done by suitably arranging certain crystal axes of radiation transmissive members that make up the projection optical system relative to the optical axis of the projection optical system, and by suitably arranging the certain crystal axes of the radiation transmissive members relative to the crystal axes of other radiation transmissive members in the projection optical system.

Abstract: A projection optical system, which forms a reduced image of a first surface onto a second surface, has excellent optical performance without substantially being affected by birefringence despite the use of optical material having intrinsic birefringence. This is done by suitably arranging certain crystal axes of radiation transmissive members that make up the projection optical system relative to the optical axis of the projection optical system, and by suitably arranging the certain crystal axes of the radiation transmissive members relative to the crystal axes of other radiation transmissive members in the projection optical system.

Abstract: A projection optical system has excellent optical performance without substantially being affected by birefringence despite the use of an optical material with intrinsic birefringence such as fluorite, for example. A projection optical system forms a reduced image of a first surface onto a second surface . A first group of radiation transmissive members is formed such that a crystal axis [100] and the optical axis nearly align and similarly a second group of radiation transmissive members is formed such that the crystal axis [100] and the optical axis nearly align. The first grout of radiation transmissive members and the second group of radiation transmissive members have a positional relationship rotated relatively 45 degrees around the center of the light axis. Both the first group of radiation transmissive members and the second group of radiation transmissive members are arranged in an optical path between a pupil position on the second surface side and the second surface.