Nippon Sheet Glass Company, Limited

Yukio Noguchi

Takashi Yamagishi

Noboru Akazawa

Masayoshi Shimizu

Takasi Yamagishi

Masakiyo Tachibana

A thallium-containing optical glass composition which comprises the following oxides in the indicated proportions in mole %: SiO.sub.2 35-80, Tl.sub.2 O 1-30, Tl.sub.2 O+R.sub.2 O (R being an alkali metal) 1-35, ZnO 0-35, GeO.sub.2 0-30, BaO 0-25, TiO.sub.2 0-20, MgO 0-20, B.sub.2 O.sub.3 0-less than 10, ZrO.sub.2 0-2, Al.sub.2 O.sub.3 0-8, SnO 0-5, CaO 0-10, SrO 0-10, PbO 0-10, La.sub.2 O.sub.3 0-5, Bi.sub.2 O.sub.3 0-8, and Ta.sub.2 O.sub.5 0-2, and satisfies the following relations:

Thallium-containing optical glass

A thallium-containing optical glass composition which contains the following oxides in the indicated proportions in mole %:

Thallium-containing optical glass composition

A cesium-containing optical glass comprising, by weight, 32-56% of SiO.sub.2, 6-25% of K.sub.2 O, 6-32% of Cs.sub.2 O, 0-30% of BaO, 0-2.5% of MgO, 5-34% of ZnO, 0-3% of ZrO.sub.2 and 0-5% of SnO.sub.2, provided that the total proportion of BaO, MgO and ZnO is 8-40% and the total proportion of ZrO.sub.2 and SnO.sub.2 is 0.2-6%. When this cesium-containing optical glass is treated in a molten bath containing potassium nitrate, the cesium ion in the glass is easily exchanged with a potassium ion and therefore, the cesium ion concentration gradually decreases radially outwardly from the central axis and the potassium ion concentration gradually increases in that direction. Thus, there is obtained a light converge-type lens in which the refractive index gradually decreases in the same direction.

Cesium-containing optical glass

The present invention provides a converging light transmitting glass body whose refractive index gradually changes from its central portion to its surface in a direction transverse to a path of light, said glass body containing at least three cations constituting modifying oxides of the glass, a first and a second cation among said cations showing concentration changes of converse gradients from its central portion toward its peripheral surface, and a third cation showing no substantial concentration change at the central portion of the glass body but showing a substantial continuous concentration charge outwardly thereof toward its peripheral surface. The present invention also provides a process for producing the light transmitting glass body which comprises contacting a glass body containing a modifying oxide of a first cation with an ion source containing the second cation to produce a pre-produced glass body, and then contacting the pre-produced glass body with an ion source containing the third cation, or which comprises contacting a glass body containing a modifying oxide of a first cation with an ion source containing a second cation and a third cation. The converting light transmitting glass body of the present invention has an ideal refractive index distribution.

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Toyonaka, Japan

Yukio Noguchi