Abstract: A lower periphery constraint portion [[(15)]] and an upper periphery constraint portion [[(16)]] for molding the periphery of a lens as well as a mirror-finished optical molding surface [[(3a)]] and another mirror-finished optical molding surface [[(9a)]] are formed on a lower mold body [[(3)]] and an upper mold body [[(9)]] of a mold [[(1)]] respectively. The upper periphery constraint portion [[(16)]] and the lower periphery constraint portion [[(15)]] are so formed as to have prescribed thicknesses ?1 and ?2 in a pressure axis direction respectively. A periphery nonconstraint portion [[(17)]] not constraining ceramics when molding a ceramics material is provided between the lower mold body [[(3)]] and the upper mold body [[(9)]]. Thus, a ceramics molded component or the like is prevented from breakage and can be easily detached from the mold, so that the same can be more homogeneously densified.

Abstract: Three lenses formed of ZnS are used in combination. A first lens is a meniscus lens having a middle portion which is convex on an object side. A second lens has a middle portion that is a meniscus, which is concave on an object side and has positive refractive power, and a peripheral portion, which is convex on the object side. The first and second lenses have positive refractive power in combination. A third lens is provided adjacent to the second lens with a distance therebetween 1 mm or less and has a middle portion, which is a convex meniscus on an object side, and a peripheral portion which is concave on the object side. A diffraction surface is formed in either surface of the lens.

Abstract: A far-infrared camera includes three lenses formed of ZnS. A first lens is a biconvex lens, a second lens is a negative meniscus or biconcave lens, and a third lens is a positive meniscus lens. A diffraction surface is formed in either surface of a lens. When a total focal distance f of the lens system is 10 mm to 30 mm and a focal distance f12 of the first and second lenses is 20 mm to 70 mm, 1?f12/f?3.

Abstract: A transparent substrate for an optical engine of a rear-projection television receiver or a liquid crystal image projector, in particular, for protecting an original image forming panel of the optical engine, the transparent substrate characterized by being formed from a transparent highly-thermal-conductive cubic polycrystal plate, exhibiting good transmission of light or the like, good thermal conductivity, and good operability, and a rear-projection television receiver including the transparent substrate. It is favorable that the transparent substrate formed from the transparent highly-thermal-conductive cubic polycrystal and provided with a coating layer on a surface is used. Preferably, the coating layer is a multilayer. It is favorable that the material for the coating is at least two types selected from metal fluorides, metal oxides, and zinc compounds. The optical transparency is improved and the environmental stability is also improved by the coating.