Patent ID: 8144398

Claim:
A polarizing element, comprising: a glass substrate; and fine metal particles provided in a plurality of regions dispersed in the glass substrate; wherein: the fine metal particles are obtained by heat-treating the glass substrate in a reducing atmosphere to reduce substantially needle-shaped metal halide fine particles present in the glass substrate prior to the heat-treatment; prior to the heat-treatment the substantially needle-shaped metal halide fine particles are oriented and dispersed in the glass substrate so that lengthwise directions of the substantially needle-shaped metal halide fine particles are substantially the same; the plurality of regions in which the fine metal particles are provided correspond to regions occupied by the substantially needle-shaped metal halide fine particles prior to the heat-treatment; two or more fine metal particles are present in at least some of plurality of regions; 90% or more of the plurality of regions have a volume of 2,500 to 2,500,000 nm 3 ; and 90% or more of the plurality of regions include a fine metal particle having a volume of 4 to 40% of a volume of the region in which the particle is provided.