Clad glass composition and mother glass rod for gradient-index rod lens formed using the same, gradient-index rod lens and method of manufacturing the same, rod lens array, and image processor

Abstract

The present invention provides a clad glass composition that is excellent in devitrification resistance and that prevents the whole mother glass rod from devitrifying by preventing a core glass composition from devitrifying in forming a mother glass rod using a concentric crucible drawing method. The clad glass composition forms a clad of a mother glass rod for a gradient-index rod lens having a core / clad structure. The clad glass composition includes the following components, indicated by mol %: 45 to 65% SiO2; 0.5 to 10% TiO2; 0 to 15% B2O3; 0 to 7% Al2O3; 0.1 to 10% Bi2O3; 0 to 5% Li2O; 5 to 30% Na2O; 0 to 10% K2O; 0 to 15% MgO; 0 to 10% CaO; 0 to 10% SrO; 0.5 to 10% BaO; 0 to 10% Cs2O; 0 to 10% ZnO; 0 to 7% Y2O3; 0 to 7% Nb2O5; 0 to 7% In2O3; 0 to 7% La2O3; 0 to 10% Ta2O5; 0 to 7% ZrO2; and 0 to 1% Sb2O3, where the total of Li2O+Na2O+K2O is in the range of 5 to 35 mol %, the total of MgO+CaO+SrO+BaO is in the range of 2 to 20 mol %, the total of Li2O+Na2O+K2O+MgO+CaO+SrO+BaO is in the range of 7 to 50 mol %, and the total of Cs2O+ZnO+Y2O3+Nb2O5+In2O3+La2O3+ZrO2+Ta2O5 is in the range of 0 to 15 mol %. In the clad glass composition, at least two molar ratios selected from the group consisting of MgO / (MgO+CaO+SrO+BaO); CaO / (MgO+CaO+SrO+BaO); SrO / (MgO+CaO+SrO+BaO); and BaO / (MgO+CaO+SrO+BaO) are at least 0.1. The clad glass composition is substantially free from lead and has a refractive index in the range of 1.56 to 1.68.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to a glass composition (a clad glass composition) that forms a clad of a mother glass rod for gradient-index rod lens having a core / clad structure, and a mother glass rod for a gradient-index rod lens formed using the same. The present invention also relates to a gradient-index rod lens formed of the mother glass rod and a method of manufacturing the same as well as a rod lens array and an image processor that include the rod lens. [0003] 2. Related Background Art [0004] A gradient-index rod lens (hereinafter also referred to simply as a “rod lens”) is a rod-shaped optical element having a refractive index distribution from its center to its periphery in the section thereof. The rod lens can exhibit lens functions such as, for instance, an imaging function even when both the end faces thereof are flat, and has many features including one that facilitates the production of lens...

AI Technical Summary

Benefits of technology

[0029] The present invention is intended to provide a clad glass composition that is different in composition from such a conventional clad glass composition but is excellent in devitrification resistance and prevents a core glass composition from devitrifying to make it possible to prevent a mother glass rod as a whole from devitrifying in forming the mother glass rod using the concentric crucible drawing method.

Problems solved by technology

The direct drawing method, however, has a disadvantage that the molten glass 101 tends to devitrify when being cooled gradually inside the nozzle 104.

Particularly, molten glass that is free from lead (whose typical composition is PbO) tends to devitrify when being drawn by the direct drawing method using a crucible.

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