Objective lens driving device and optical disk unit

An objective lens driving device comprising:

• an objective lens for irradiating at least reading light onto a recording surface of an optical disk which is an information recording medium, and for receiving light reflected on said recording surface;
• and
• a driving portion for focusing said objective lens on a focal position;
• said driving portion including:
• a movable body constituted by a lens holder for holding said objective lens, a focusing coil disposed on said lens holder, and a tracking coil disposed on said lens holder;
• supports for supporting said movable body movably in a direction of an optical axis of said objective lens and in a radial direction of said optical disk;
• a fixation member for fixing said supports;
• permanent magnets giving magnetic force to said movable body;
• and
• an inner yoke disposed inside said lens holder, and constituted by a magnetic substance member having at least two sides substantially parallel with the radial direction of said optical disk and at least two sides perpendicular to the radial direction of said optical disk.

An objective lens driving device comprising:

• an objective lens for irradiating at least reading light onto a recording surface of an optical disk which is an information recording medium, and for receiving light reflected on said recording surface;
• and
• a driving portion for focusing said objective lens on a focal position;
• said driving portion including:
• a movable body constituted by said objective lens, a lens holder for holding said objective lens, and a focusing coil and a tracking coil both of which are disposed on said lens holder;
• supports for supporting said movable body movably in a direction of an optical axis of said objective lens and in a radial direction of said optical disk;
• a fixation member for fixing said supports;
• permanent magnets facing each other through said focusing coil and said tracking coil;
• and
• an inner yoke disposed inside said focusing coil, said inner yoke being constituted by a solid magnetic body.

An optical disk drive comprising:

• an optical disk which is an information recording medium;
• a light source for generating laser light;
• an objective lens for collecting light from said light source onto a recording surface of said optical disk;
• a movable body provided with said objective lens, said movable body including a lens holder for holding said objective lens, a focusing coil disposed on said lens holder, and a tracking coil disposed on said lens holder;
• a light detector for detecting a recording/playback signal, a tracking error signal and a focusing error signal on the basis of light reflected from said recording surface;
• and
• a control portion for controlling said movable body and said light source on the basis of outputs of said light detector;
• supports for supporting said movable body movably in a direction of an optical axis of said objective lens and in a radial direction of said optical disk;
• a fixation member for fixing said supports;
• permanent magnets giving magnetic force to said movable body;
• and
• an inner yoke constituted by a magnetic substance member enclosing a light path to said objective lens inside said lens holder;
• wherein an upper end of said inner yoke is positioned between an upper end and a lower end of said lens holder.