Objective optical system, optical pickup apparatus and optical information recording and reproducing apparatus
AssigneeKonica Minolta Opto, Inc.
InventorTohru Kimura
Life of this patent
Estimating the term…
Abstract
An objective optical system for use in an optical pickup apparatus for converging first and second parallel light fluxes includes: a first lens group having a phase structure; and a second lens group, wherein the first lens group and the second lens group are arranged in the objective optical system in this order from a longer conjugate distance side of the objective optical system, and a wavefront aberration of the first lens group WL1λ1, a wavefront aberration of the second lens group WL2λ1, a magnification of the second lens group M, a wavefront aberration of the second lens group WL2λ2, a wavefront aberration of the objective optical system WOBJλ2 are satisfy predescribed expressions.
Claims16
An objective optical system for use in an optical pickup apparatus for converging a first parallel light flux with a diameter φ1and a first wavelength λ1 on an information recording surface of a first optical disk having a protective layer with a thickness t1 within a numerical aperture NA1, and converging a second parallel light flux with a diameter φ2 (φ2<φ1) and a second wavelength λ2 (λ2>λ1) on an information recording surface of a second optical disk having a protective layer with a thickness t2 (t2>t1) within a numerical aperture NA2 (NA2<NA1), the objective optical system comprising:
- a first lens group having a phase structure;
- and a second lens group,
- wherein the first lens group and the second lens group are arranged in the objective optical system in this order from a longer conjugate distance side of the objective optical system, and
- the objective optical system satisfies following expressions:
- WL1λ1≦0.05 λRMS(λ=λ1) (1)
- WL2λ1≦0.05 λRMS(λ=λ1) (2)
- −0.03≦M≦0.13 (3)
- WL2λ2>0.30 λRMS(λ=λ2) (4)
- WOBJλ2≦0.05 λRMS(λ=λ2) (6)
- where WL1λ1 is a wavefront aberration of the first lens group when the first parallel light flux enters into the first lens group,
- WL2λ1 is a wavefront aberration of the second lens group within the numerical aperture NA1 for the first parallel light flux,
- M is a magnification of the second lens group when WL2λ1 has a minimum value,
- WL2λ2 is a wavefront aberration of the second lens group whose magnification is M, within the numerical aperture NA2 for the second parallel light flux, and
- WOBJλ2 is a wavefront aberration of the objective optical system within the numerical aperture NA2 when the second parallel light flux enters into the objective optical system,
- wherein each of WL2λ1, WL2λ2, and WOBJλ2 is a wavefront aberration whose defocus component is removed,
- WL2λ1 is measured with the protective layer having a thickness t1 included, and
- each of WL2λ2 and WOBJλ2 is measured with the protective layer having a thickness t2 included,
- wherein the objective optical system further satisfies
- |PL1/PL2|≦0.2 (7)
- where PL1 is a paraxial power of the first lens group for the first parallel light flux, and
- PL2 is a paraxial power of the second lens group for the first parallel light flux, and
- wherein the objective optical system further satisfies following expressions:
- WS1=WC2−WC1<0.01 λRMS(λ=λ1) (8)
- WS2=WC4−WC3>0.02 λRMS(λ=λ2) (9)
- where WC1 is a coma amount of the objective optical system within the numerical aperture NA1 for the first parallel light flux and is measured with the first lens group, the second lens group and the protective layer with a thickness t1 arranged along one optical axis,
- WC2 is a coma amount of the objective optical system within the numerical aperture NA1 for the first parallel light flux and is measured with the second lens group and the protective layer with a thickness t1 arranged along one optical axis and with an optical axis of the first lens group shifted 10 μm to an optical axis of the second lens group,
- where WC3 is a coma amount of the objective optical system within the numerical aperture NA2 for the second parallel light flux and is measured with the first lens group, the second lens group and the protective layer with a thickness t2 arranged along one optical axis,
- WC4 is a coma amount of the objective optical system within the numerical aperture NA2 for the second parallel light flux and is measured with the second lens group and the protective layer with a thickness t2 arranged along one optical axis and with an optical axis of the first lens group shifted 10 μm to an optical axis of the second lens group,
- WS1 is a difference between WC1 and WC2, and
- WS1 is a difference between WC3 and WC4.
An objective optical system for use in an optical pickup apparatus for converging a first parallel light flux with a diameter φ1 and a first wavelength λ1 on an information recording surface of a first optical disk having a protective layer with a thickness t1 within a numerical aperture NA1, and converging a second parallel light flux with a diameter φ2 (φ2<φ1) and a second wavelength λ2 (λ2>λ1) on an information recording surface of a second optical disk having a protective layer with a thickness t2 (t2>t1) within a numerical aperture NA2 (NA2<NA1), the objective optical system comprising:
- a first lens group having a phase structure;
- and a second lens group,
- wherein the first lens group and the second lens group are arranged in the objective optical system in this order from a longer conjugate distance side of the objective optical system, and
- the objective optical system satisfies following expressions:
- WL1λ1≦0.05 λRMS(λ=λ1) (1)
- WL2λ1≦0.05 λRMS(λ=λ1) (2)
- −0.03≦M≦0.13 (3)
- WL2λ2>0.30 λRMS(λ=λ2) (4)
- WOBJλ2≦0.05 λRMS(λ=λ2) (6)
- where WL1λ1 is a wavefront aberration of the first lens group when the first parallel light flux enters into the first lens group,
- WL2λ1 is a wavefront aberration of the second lens group within the numerical aperture NA1 for the first parallel light flux,
- M is a magnification of the second lens group when WL2λ1 has a minimum value,
- WL2λ2 is a wavefront aberration of the second lens group whose magnification is M, within the numerical aperture NA2 for the second parallel light flux, and
- WOBJλ2 is a wavefront aberration of the objective optical system within the numerical aperture NA2 when the second parallel light flux enters into the objective optical system,
- wherein each of WL2λ1, WL2λ2, and WOBJλ2 is a wavefront aberration whose defocus component is removed,
- WL2λ1 is measured with the protective layer having a thickness t1 included, and
- each of WL2λ2 and WOBJλ2 is measured with the protective layer having a thickness t2 included,
- wherein the objective optical system further satisfies
- |PL1/PL2|≦0.2 (7)
- where PL1 is a paraxial power of the first lens group for the first parallel light flux, and
- PL2 is a paraxial power of the second lens group for the first parallel light flux, and
- wherein the objective optical system further satisfies following expressions:
- WT1=WC5−WC1<0.02 λRMS(λ=λ1) (10)
- WT2=WC6−WC3≦0.02 λRMS(λ=λ2) (11)
- where WC1 is a coma amount of the objective optical system within the numerical aperture NA1 for the first parallel light flux and is measured with the first lens group, the second lens group and the protective layer with a thickness t1 arranged along one optical axis,
- WC5 is a coma amount of the objective optical system within the numerical aperture NA1 for the first parallel light flux and is measured with the second lens group and the protective layer with a thickness t1 arranged along one optical axis arranged and with an optical axis of the first lens group tilted 5 minutes to an optical axis of the second lens group,
- where WC3 is a coma amount of the objective optical system within the numerical aperture NA2 for the second parallel light flux and is measured with the first lens group, the second lens group and the protective layer with a thickness t2 arranged along one optical axis,
- WC6 is a coma amount of the objective optical system within the numerical aperture NA2 for the second parallel light flux and is measured with the second lens group and the protective layer with a thickness t2 arranged along one optical axis and with an optical axis of the first lens group tilted 5 minutes to an optical axis of the second lens group,
- WT1 is a difference between WC5 and WC1, and
- WT2 is a difference between WC6 and WC3.
Dependencies are inferred from the claim text.