Optical head apparatus

• US 20050018554A1
• Filed: 05/20/2004
• Published: 01/27/2005
• Est. Priority Date: 05/22/2003
• Status: Active Grant

• Current Assignee: Dimensional Dynamics, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Nidec Sankyo Corporation (Nidec Corporation)
• Inventors: Shiba, Kazuo
• Granted Patent: US 7,372,784 B2
• Time in Patent Office: Days
• US Class Current: 369/44.240
• CPC Class Codes: G11B 7/1374 Objective lenses optical objectives per se G02B9/00
• CPC Class Codes: G11B 7/1381 Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops G11B7/1353 - G11B7/1369 take precedence
• CPC Class Codes: G11B 7/139 Numerical aperture control means

Abstract

The present invention proposes an optical head apparatus provided with light-blocking structure that can reliably prevent nonessential light from reaching the photo detector, without being an impediment to miniaturization and flattening, moreover, without increasing manufacturing cost. In an optical head apparatus, and in a lens holder, light-blocking section is provided that blocks nonessential light from passing outside the effective diameter of objective lens. This light-blocking section is constructed so that it extends only in tracking direction T of objective lens 5. Further, light-blocking face of light-blocking section slants at an angle of 1° or more toward the face orthogonal to the optical axis, consequently, nonessential light is reflected in a direction other than the direction of photo detector.

Claims

1. An optical head apparatus comprising:

a light source;

a lens holder for retaining objective lens that converges emitted light emitted from said light source on optical recording medium;

a lens drive apparatus for driving said lens holder in the tracking direction at the least; and

a photo detector for receiving reflected light from said optical recording medium;

wherein said objective lens or said lens holder includes a light-blocking section that has spread out on both sides of the tracking direction and that is capable of blocking nonessential light from the said light source proceeding toward said optical recording medium by passing outside the effective diameter of said objective lens.

2. The optical head apparatus of claim 1 wherein said objective lens is constructed so that incident light flux comprises light rays made parallel by a collimating lens;

and

wherein a light-blocking face located on said light source side in said light-blocking section is slanted at an angle of 1°

or more toward the face orthogonal to the optical axis of said objective lens.

3. The optical head apparatus of claim 1 wherein dimensions at both ends in the tracking direction of said light-blocking section are such that light-blocking of said nonessential light is possible in the entire range of movement of said lens holder in the tracking direction.

4. The optical head apparatus of claim 1 wherein dimensions at both ends in the tracking direction of said light-blocking section are such that light-blocking of said nonessential light is possible in the entire range of movement of said lens holder in the tracking direction.

5. The optical head apparatus of claim 2 which is configured so that when dimensions at both ends in the tracking direction of said light-blocking section, effective diameter of said collimating lens, and maximum amount of movement of said objective lens in the tracking direction are designated W, C, K, respectively, and wherein W, C, K are selected to satisfy the following formula:

W>

C+2K.

6. The optical head apparatus of claim 1 wherein, said light-blocking section is a part constructed as one with said lens holder.

7. The optical head apparatus of claim 2 wherein said light-blocking section is a part constructed as one with said lens holder.