1. Field of the Invention
The present invention relates to an optical pickup device for optically recording information on an optical disk and/or reproducing information from the optical disk.
2. Related Background Art
In an optical pickup device, the objective lens is driven in two axial directions: a direction perpendicular to the optical disk (hereinafter referred to as “focusing direction”) and a disk radial direction (hereinafter referred to as “tracking direction”). This driving of the objective lens is effected in order to correct focusing deviation due to vertical movement of the recording surface attributable to warpage of the optical disk, side-runout of the spindle motor for rotating the optical disk, etc., and tracking deviation due to eccentricity of the optical disk, eccentricity of the chucking portion for connecting the optical disk to the spindle motor, etc. In an optical disk recording and/or reproducing apparatus (hereinafter referred to as “optical disk recording-reproducing apparatus”) including the above optical pickup device, the optical disk can warp since it is formed of a resin such as polycarbonate. When the disk has any warpage, it generates inclination of the optical axis of the objective lens with respect to the disk surface (hereinafter referred to as “tilt”). Due to the inclination of the optical axis with respect to the optical disk, upon light incidence, an optical aberration is generated, which leads to deterioration in the signal at the time of recording and reproduction. In view of this, tilt control is generally conducted, in which the inclination of the optical disk with respect to the optical axis of the objective lens is detected by an optical sensor or the like and the objective lens is inclined by that inclination amount for angular correction.
As a tilt driving method for a conventional tilt control device, there has been proposed a method in which, as disclosed, for example, by Japanese Patent Application Laid-Open No. H9-22537, a lens holder is supported by four bar-shaped support members and in which there are provided four focusing coils and four tracking coils, the objective lens being driven by superimposing a tilt drive signal on a focusing drive signal. However, in the above-described conventional arrangement, not only is the magnetic circuit configuration rather complicated, but also the control is rather complicated and difficult due to the superimposition of the tilt drive signal on the focusing drive signal.
As a second conventional example to overcome this problem, there has been proposed a method, in which, as disclosed by Japanese Patent Application Laid-Open No. H8-249695, the entire optical pickup device is rotatably mounted on a carriage and in which the guide shaft of the carriage is rotated by a motor to tilt drive the optical pickup device, which is connected to the guide shaft by a gear.
However, the construction of the above second conventional example has a problem in that the carriage including the optical pickup device has to be rather large, making it impossible to meet the recent requirement for a reduction in the size and thickness of optical disk recording-reproducing apparatuses.