Citizen Holdings Company, Ltd.

Shinya Sato

Masayuki Iwasaki

Nobuhiro Sato

Seiichi Osawa

Shuji Naka

Yoshiharu Takane

Takeshi Toyoda

A liquid crystal optical element having a crystal liquid optical element adapted to positively function as a diffraction element and an optical pickup apparatus including the liquid crystal optical element are disclosed. A transparent electrode having a diffraction pattern is arranged on one of a pair of transparent substrates. A liquid crystal panel has a transparent opposed electrode arranged on the other one of the pair of the transparent substrates. A driving unit generates a phase difference distribution in the liquid crystal layer by generating a potential difference between the transparent electrode and the transparent opposed electrode and causes the liquid crystal panel to function as a diffraction element for diffracting the incoming light beam transmitted therethrough. The diffraction pattern or the transparent opposed electrode is divided into a plurality of regions. The driving unit adjusts the potential difference for each of the regions.

Liquid crystal optical element and optical pickup apparatus

The present invention is directed to the provision of an optical pickup apparatus in which a liquid crystal optical element constructed by combining an aberration correcting liquid crystal panel and an n&#x3bb;/4 liquid crystal panel in an integral fashion is mounted in a tilted position. More specifically, the invention provides a liquid crystal optical element includes a first liquid crystal layer having a first rubbing direction and for correcting aberration, a second liquid crystal layer having a second rubbing direction and combined with the first liquid crystal layer in an integral fashion, and a transparent electrode for generating a potential difference across the second liquid crystal layer in order to control an amount of phase difference for the light beam passing through the second liquid crystal layer, and wherein the angle (&#x3c8;) that the second rubbing direction makes with the first rubbing direction is determined in accordance with the tilt angle (&#x3b1;) so that the second liquid crystal layer functions as an n&#x3bb;/4 plate. The invention also provides an optical pickup apparatus incorporating such a liquid crystal optical element.

A first electrode of a liquid crystal cell () is composed of a plurality of concentric electrodes (to) of a concentrically circular shape, the plurality of concentric electrodes are divided into a first group of concentric electrodes () near the center and a second group of concentric electrodes () near the periphery, and a concentric electrode between the two groups is an independent single electrode (). A first correction unit that corrects spherical aberration of a high density DVD is composed of the two groups and a second correction unit that corrects aberration of a conventional DVD is composed of the first group of concentric electrodes (). In the case of correcting the aberration of the conventional DVD, the independent concentric electrode () is supplied with a voltage between the voltages respectively supplied to adjacent concentric electrodes (), (). In the case of correcting the aberration of the high density DVD, the independent concentric electrode () is supplied with a voltage equal to the voltage supplied to the concentric electrode immediately lateral thereto ().

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Koganei, Japan

Shinya Sato