Patent ID: 7619713

Claim:
A liquid crystal optical element as a variable focus gradient-index lens for a light beam incident from a light source, comprising: a first planar substrate; a second planar substrate; a liquid crystal provided between said first and second planar substrates; an electrode pattern formed on one of said first and second planar substrates and having a plurality of regions each for varying an effective refractive index for a light beam; and a counter electrode, formed on the other one of said first and second planar substrates, for applying a voltage with respect to said electrode pattern, wherein the effective refractive index for a light beam varies with the square of distance from the center of said liquid crystal optical element along a radial direction across said liquid crystal optical element when the voltage is applied between said electrode pattern and said counter electrode, and the amount by which each of said plurality of regions causes the effective refractive index to change is set substantially constant across said plurality of regions, or potential difference between each of said plurality of regions is set substantially constant across said plurality of regions.