Optical pickup apparatus and objective lens

A lens for use in an optical pickup apparatus for reproducing information from one of different kinds of optical information recording medium, each having a transparent substrate in different thickness, or for recording information onto one of said different kinds of optical information recording medium, the optical pickup apparatus having a first light source for emitting first light flux whose wavelength is λ1, a second light source for emitting second tight flux whose wavelength is λ2 greater than λ1, and a photo detector, the lens comprising:

• an optical axis,
• a first portion,
• a second portion, and
• a third portion,
• wherein the third portion is farther from the optical axis than the first portion, and the second portion is provided between the first portion and the second portion,
• wherein the first portion and the third portion are capable of converging a first light flux of wavelength λ1 from a first light source on a first information recording plane of a first optical information recording medium having a first transparent substrate of thickness t1 to reproduce information recorded in the first optical information recording medium or record information in the first optical information recording medium,
• wherein the first portion and the second portion are capable of converging a second light flux of wavelength λ2 from a second light source on a second information recording plane of a second optical information recording medium having a second transparent substrate of thickness t2 to reproduce information recorded in the second optical information recording medium or record information in the second optical information recording medium, wherein λ2 is greater than λ1 and λ2 is greater than t1, and
• wherein the following conditional formula is satisfied for an amount of the first light flux not less than 30% of the total amount of the first light flux passing the first portion:
• 0.06≧SC1/f1≧0.002
• where, in case that the first portion converges the first light flux on a first information recording plane, SC1 is a sine condition dissatisfaction amount of the first portion of the objective lens for a light flux at a height in the first light flux, and in case that the first portion converges the first light flux on a first information recording plane, f1 is a focal length of the first portion of the objective lens for a first light flux.

An optical information recording medium reproducing or recording apparatus for reproducing information from an optical information recording medium or for recording information onto the optical information recording medium, comprising:

• an optical pickup apparatus comprising
• a first light source for emitting first light flux whose wavelength is λ1;
• a second light source for emitting second light flux whose wavelength is λ2, Wherein λ2 is greater than λ1;
• a converging optical system comprising an objective lens having an optical axis, a first portion, a second portion, and a third portion, the third portion being farther from the optical axis than the first portion, the second portion being provided between the first portion and the second portion, and
• a photo detector,
• wherein the first portion and the third portion are capable of converging the first light flux on a first information recording plane of a first optical information recording medium having a first transparent substrate of thickness t1 to reproduce information recorded in the first optical information recording medium or record information in the first optical information recording medium,
• wherein the first portion and the second portion are capable of converging the second light flux on a second information recording plane of a second optical information recording medium having a second transparent substrate of thickness t2 to reproduce information recorded in the second optical information recording medium or record information in the second optical information recording medium, wherein t2 is greater than t1,
• wherein the photo detector is capable of receiving light flux reflected from the first information recording plane or the second information recording plane, and
• wherein the following conditional formula is satisfied for an amount of the first light flux not less than 30% of the total amount of the first light flux passing the first portion:
• 0.06≧SC1/f1≧0.002
• where, in case that the first portion converges the first light flux on a first information recording plane, SC1 is a sine condition dissatisfaction amount of the first portion of the objective lens for a light flux at a height in the first light flux, and in case that the first portion converges the first light flux on a first information recording plane, f1 is a focal length of the first portion of the objective lens for a first light flux.

A method of reproducing information from one of different kinds of optical information recording medium or of recording information onto one of different kinds of optical information recording medium by an optical pickup apparatus comprising a first light source, a second light source, a photo detector and a converging optical system having an optical axis, a first portion, a second portion and a third portion, the third portion being farther from the optical axis than the first portion, the second portion being provided between the first portion and the second portion, the method comprising steps of:

• emitting a first light flux from the first light source or a second light flux from the second light source, wherein a wavelength of the second light flux λ2 is greater than a wavelength of the first light flux λ1;
• converging the first light flux by the converging optical system on a first information recording plane of a first optical information recording medium or the second light flux by the converging optical system on a second information recording plane of a second optical information recording medium;
• receiving light flux reflected from the optical information recording medium by the photo detector;
• wherein, when reproducing information recorded in a first optical information recording medium having a first transparent substrate of thickness t1, a first light flux which passes through the first portion and a third light flux which passes through the third portion converge on a first information recording plane of the first optical information recording medium through the first transparent substrate to reproduce information recorded in the first optical information recording medium or record information in the first optical information recording medium, and,
• wherein, when reproducing information recorded in a second optical information recording medium having a second transparent substrate of thickness t2, greater than t1, the first light flux and a second light flux which pass through the second portion to converge on a second information recording plane of the second optical information recording medium through the second transparent substrate to reproduce information recorded in the second optical information recording medium or record information in the second optical information recording medium,
• wherein the following conditional formula is satisfied for an amount of the first light flux not less than 30% of the total amount of the first light flux passing the first portion:
• 0.06≧SC1/f1≧0.002
• where, in case that the first portion converges the first light flux on a first information recording plane, SC1 is a sine condition dissatisfaction amount of the first portion of the objective lens for a light flux at a height in the first light flux, and in case that the first portion converges the first light flux on a first information recording plane, f1 is a focal length of the first portion of the objective lens for a first light flux.