Objective for optical disk, optical pickup, optical disk writer-reader, and optical disk reader
AssigneeVictor Company of Japan, Ltd.
InventorMakoto Itonaga
Life of this patent
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Abstract
An objective for an optical disk is made of a single double-sided aspherical lens having a numerical aperture (NA) equal to or greater than 0.75 and capable of minimizing axial aberration, off-axis aberration, surface-to-surface eccentricity aberration, and chromatic aberration. The objective (11) has a first aspherical surface (1). The vertex of the first surface has a radius of curvature R1 defined as follows: 0.95·A<R1<1.05·A A=B/C B=0.85f(n−1) C=n (0.60866−0.11·t/f−0.1272·d/f)(0.83+0.2·NA) where n is a refractive index of the lens, f is a focal length of the lens, t is a thickness along optical axis through the center of the lens and d is the thickness of a transmission layer of the optical disk.
Claims32
An objective for an optical disk comprising a single lens, wherein the objective has first and second aspherical surfaces, a numerical aperture (NA) of the objective is equal to or greater than 0.75 and a radius of curvature R1 at a vertex of the first surface is defined as follows:
- 0.95·A<R1<1.05·A,
- A=B/C,
- B=0.85f(n−1) and
- C=n (0.60866−0.11·t/f−0.1272·d/f)(0.83+0.2·NA)
- where n is a refractive index of the objective, f is a focal length of the objective, t is a thickness along optical axis through the center of the objective and d is the thickness of a transmission layer of the optical disk.
An objective for an optical disk comprising a single lens, wherein the objective has first and second aspherical surfaces, a numerical aperture (NA) of the objective is equal to or greater than 0.75 and an angle u1′ between a highest ray passing through the objective and an optical axis satisfies the following condition:
- 0.94·K<sin (u1′)<1.06·K and
- K=(0.60866−0.11·t/f−0.1272·d/f)(0.83+0.2NA)·NA/0.85
- where f is a focal length of the objective, t is a thickness along optical axis through center of the objective and d is the thickness of a transmission layer of the optical disk.
An objective for an optical disk comprising a single lens, wherein the lens has first and second aspherical surfaces, a numerical aperture (NA) of the objective is equal to or greater than 0.75 and an angle between a normal to the first surface at a point where a highest ray enters, the first surface and an optical axis is equal to or less than 57 degrees.
An objective for an optical disk comprising a single lens, wherein the objective has first and second aspherical surfaces, a numerical aperture (NA) of the objective is equal to or greater than 0.75 and an angle θ between a normal to the first surface at a point where a highest ray enters the and an optical axis satisfies the following condition:
- θ<57−47.3·(0.85−NA)(degrees).
Dependencies are inferred from the claim text.