Process for the production of slab-shaped lens having gradient of refractive index in thickness direction only

Claim 1

A process for producing a slab-shaped optical lens having a gradient of refractive index only in the direction of thickness thereof, which comprises: stuffing a solution comprising a solvent and a dopant into micropores of a plate-shaped porous glass product, the plate-shaped product having length, width and thickness and corresponding axes, leaching said plate-shaped product to unstuff a part of the dopant to form a gradient of dopant concentration in the porous glass product, the gradient being in the thickness and width directions of the porous glass product, precipitating the dopant in the micropores, drying the porous glass product to evaporate the solvent remaining in the micropores, collapsing the micropores by applying a heat treatment to form a gradient of refractive index in the porous glass product, the gradient being in the thickness and width directions of the plate-shaped porous glass product, cutting off a slice from each side of the plate-shaped glass product to decrease the width of the plate-shaped glass product, the width of each slice being large enough such that the refractive index gradient in the width direction of the plate-shaped glass product is eliminated, and a slab-shaped optical lens having a gradient of refractive index only in the direction of thickness thereof is effected, such that light is converged in the direction toward the center of the thickness axis as it flows along the lens.