Panasonic Corporation

Matsushita Electric Industrial Co., Ltd.

Panasonic Corporaton

Minoru Onoda

Tomokazu Tokunaga

Kazuhiko Ishimaru

Kunio Hibino

Toshiaki Takano

Shoji Nakamura

Kazuaki Takagi

Fujio Okuyama

Eiichi Nagaoka

An optical glass composition contains, in % by mole, 0% or more and 25.0% or less of SiO, 20.0% or more and 40.0% or less of BO, 0% or more and 5.0% or less of LiO, 3.0% or more and 15.0% or less of ZnO, 0% or more and 10.0% or less of ZrO, 2.0% or more and 7.0% or less of TaO, 6.0% or more and 25.0% or less of LaO, 5.0% or more and 22.0% or less of GdO, 66.5% or less of LaO+GdO+BOand 26.0% or more of LaO+GdO, and has nd of 1.83 or higher and 1.86 or lower, vd of 43 or higher and 46 or lower and a liquidus temperature of 1300&#xb0; C. or lower, and a preform and an optical element are formed from the optical glass composition.

Optical glass composition, preform and optical element

A prism () is in the form of a polygonal prism and has a first optical surface (), a second optical surface () and a third optical surface () formed on different surfaces of the prism. A light entrance region () is provided at the center of the first optical surface (), a light exit region () is provided at the center of the second optical surface () and a substantially flat light reflecting region () is provided at the center of the third optical surface (). Suppose that there is a virtual surface between the light reflecting region () and the first optical surface (), the virtual surface is positioned more inward in the prism than a peripheral region of the third optical surface () extending from the light reflecting region () to an edge () between the third optical surface () and the first optical surface ().

Prism and optical device

An optical glass composition contains, in % by weight, 1.0% or more and 12.0% or less of SiO, 8.0% or more and 18.0% or less of BO, 0% or more and 6.0% or less of ZnO, 1.0% or more and 10.0% or less of ZrO, 25.0% or more and 47.0% or less of LaO, 0% or more and 5.0% or less of RO (here, R is at least one of Li, Na and K), 0% or more and 15.0% or less of NbO, 0% or more and 7.0% or less of TiO, 0% or more and 15.0% or less of TaO, 1.0% or more of NbO+TiO+TaO, 0% or more and 25.5% or less of GdO, 0.5% or more and 15.0% or less of WOand 0.5% or more and 26.0% or less of GdO+WO, and has nd of 1.88 or higher and 1.92 or lower and &#x3bd;d of 33 or higher and 37 or lower, and a preform and an optical element are formed from the optical glass composition.

An optical glass composition contains, in % by mole, 14.0% or more and 31.0% or less of SiO, 19.0% or more and 40.0% or less of BO, 0% or more and 5.0% or less of LiO, 0% or more and 12.0% or less of ZnO, 0% or more and 12.0% or less of ZrO, 15.0% or more and 26.0% or less of LaO, 22.0% or more and 38.0% or less of LaO+ZrO, 2.0% or more and 5.0% or less of TaOand 4.0% or more and 16.0% or less of GdO, and has nd of 1.83 or higher and 1.87 or lower and &#x3bd;d of 43 or higher and 47 or lower, and a preform and an optical element are formed from the optical glass composition.

A prismincludes a prism body. The prism bodyis formed into a polygonal column. At least one of a plurality of ridgesof the prism bodyis formed into an R-plane.

Prism, imaging device and lighting device including the same, and prism manufacturing method

A prismincludes a prism bodyformed into a polygonal column. At least one ridgeof a plurality of ridgesof the prism bodyis formed into a flat face. A joint partbetween the flat faceand at least oneof the facesof the prism bodywhich are adjacent to each other with the ridgein the flat faceinterposed is formed into an R-plane.

A glass material ( ) is placed in a forming die including a pair of upper and lower dies ( ) and a control member ( ) for controlling the space between the upper and the lower die, and then heated, softened, and molded by pressure into a glass substrate in the shape of a parallel plate. The amount of thermal contraction of the control member is smaller than that of the glass material. Therefore, the glass substrate is released from the die when cooled after molding. The present invention can provide a glass substrate that is excellent in smoothness and form accuracy of the surface, and that is suitable for recording media such as magnetic disks that are inexpensive and suitable for mass production.

Growing community of inventors

Osaka, Japan

Minoru Onoda