| 摘要 |
PROBLEM TO BE SOLVED: To realize optimum visual acuity correction by controlling refractive index characteristics under different conditions, such as far viewing and near viewing. SOLUTION: Incident light 3 on spectacles is subjected to selection of linearly polarized light components by a polarizing film 4 and is subjected to switching of a polarization state between two orthogonal directions by the presence or absence of AC voltage impression in a liquid crystal cell constituted by transparent electrodes 51 and 52 and a liquid crystal layer 6. The light is then guided to two pieces of birefringent optical material lenses 7 and 8 of the birefringent optical axes intersecting orthogonally with each other. The refractive indices of the respective lenses 7 and 8 for transmitted rays are either of no or ne to ordinary rays and extraordinary rays and required numerical values of the refracting power of combined lenses including directions can be selected by switching of the polarization directions of the incident rays. The optimum visual acuity correction when the spectacles are used under the different conditions, such as far viewing and near viewing can thus be realized.
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