Patent ID: 8064141

Claim:
An optical element, comprising: an airtight container having opposing end face walls in a thickness direction, and side walls connecting the end face walls; a first liquid sealed in the container and having polarity or conductivity; a second liquid sealed in the container and not mixed with the first liquid so as to form an interface between the first liquid and the second liquid; and voltage applying means for applying a voltage to the first liquid, wherein the first liquid and the second liquid have the same specific gravity and substantially the same refractive index, and minute particles made of a material that does not transmit light are mixed in the first liquid, such that the first liquid has less light transmittance than the second liquid, in a state in which the voltage is applied to the first liquid, the interface between the first liquid and the second liquid deforms, and a transmitting path of light is formed that passes through the end face walls and propagates in the thickness direction of the container, the refractive index of the first liquid is set by adjusting the content of the minute particles in the first liquid, and wherein a diameter of a region where only the second liquid exists can be increased or decreased by adjusting the voltage, wherein at least three different kinds of liquids having different refractive indices are mixed in the first liquid to form a mixture, and the mixture has substantially the same refractive index as the second liquid.