Die processing method, die, objective lens, and optical pick-up device

Abstract

Disclosed is a die processing method which makes it possible to inexpensively process a die for moulding an objective lens having a multilevel structure for use in an optical pick-up device. A method for processing a material for a die for moulding an objective lens which is formed with a multilevel structure on the curved surface thereof and is intended for shared use in an optical pick-up device in which different optical disks can be substituted for use and for focusing a light beam onto the information recording surface of each optical disk, wherein the transfer surface of the objective lens is cut by means of an implement having a cutting face, the outline of which comprises a linear first edge part, a linear second edge part extending in a direction which intersects the first edge part at an acute angle thereto, and a third edge part which joins the end of the first edge part and the end of the second edge part, while the die material is rotated about the axis thereof, in a state in which the first edge part and / or the second edge part of said implement is inclined with respect to the abovementioned axis and while said implement is moved only in the abovementioned axial direction and in the direction which intersects said axis.

Description

technical field [0001] The invention relates to a mold processing method, a mold, an objective lens and an optical pick-up device. Background technique [0002] In recent years, an optical pickup device that uses a blue-violet semiconductor laser with a wavelength of about 400 nm to record and / or reproduce information on a high-density optical disc (hereinafter, "record and / or reproduce" is referred to as "record / regenerate") has been developed. , and has been sold in the market. As an example of a high-density optical disc, in NA0.85, an optical disc for recording / reproducing information with a light source wavelength of 405nm, so-called Blu-ray Disc (hereinafter referred to as BD), can be compatible with DVD (NA0.6, The wavelength of the light source is 650nm, and the storage capacity is 4.7GB). A disc with a diameter of 12cm of the same size can record 25GB of information on each layer. [0003] However, for this type of high-density optical disc, it is not enough as a ...

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Problems solved by technology

[0004] As a method for appropriately recording / reproducing information while maintaining compatibility with any of high-density optical discs, DVDs, and even CDs, it may be considered to selectively switch according to the recording density of the optical disc for recording / reproducing information. The optical system for high-density optical discs and the optical system for DVD or CD, however, requires multiple optical systems, which is not conducive to miniaturization and increases the cost

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