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AssigneeAsahi Glass Company, Limited
InventorsMitsuo Osawa, Yoshiharu Ooi
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A liquid crystal diffraction lens element and an optical head device, which can switch focal lengths of both of outgoing light and returning light by a single element, are provided. The liquid crystal lens element comprises transparent substrates 1a, 1b, a liquid crystal 4 sandwiched between the transparent substrates 1a, 1b, transparent electrodes 2a, 2b, birefringent Fresnel lens members 3a, 3b each having a Fresnel lens shape and made of a birefringent material, and a seal 5, wherein the extraordinary refractive index direction A of the birefringent Fresnel lens member 3a and the extraordinary refractive index direction B of the birefringent Fresnel lens member 3b are perpendicular to each other, and the alignment direction of the liquid crystal 4 at the interface between the liquid crystal 4 and the transparent substrate 1a is perpendicular to the alignment direction of the liquid crystal 4 at the interface between the liquid crystal 4 and the transparent substrate 1b.
A liquid crystal diffraction lens element comprising a pair of transparent substrates disposed in parallel, a liquid crystal sandwiched between the pair of transparent substrates, transparent electrodes for applying an electric field to the liquid crystal, a first birefringent Fresnel lens member formed between a first one of the transparent substrates and the liquid crystal, having a Fresnel lens shape and made of a birefringent material, and a second birefringent Fresnel lens member formed between a second one of the transparent substrates opposed to the first one of the transparent substrates and the liquid crystal, having a Fresnel lens shape and made of a birefringent material;
Dependencies are inferred from the claim text.