Manufacturing method of an objective lens for an optical pickup apparatus and the optical pickup apparatus

Abstract

A method of manufacturing an optical pickup apparatus, comprising steps of selecting one type objective lens from plural types of objective lenses different in specification of respective optical path difference providing structures in accordance with an oscillation wavelength of a laser light source; and assembling the selected type objective lens and the laser light source into the apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing the structure of the optical pickup apparatus of the present embodiment by which the recording/reproducing of the information can be adequately conducted on HD, DVD and CD which are different optical information recording media (called also optical disk).

FIG. 2 is a perspective view of the molded objective lens OBJ.

FIG. 3 is a flowchart showing the manufacturing method of the optical pickup apparatus according to the present embodiment.

FIGS. 4( a)-4(d) are sectional views typically showing several examples of the optical path difference providing structure provided in objective optical element OBJ according to the present invention.

Claims

1. A method of manufacturing an optical pickup apparatus, comprising steps of: selecting one type objective lens from plural types of objective lenses different in specification of respective optical path difference providing structures in accordance with an oscillation wavelength of a laser light source; andassembling the selected type objective lens and the laser light source into the apparatus.

2. The method described in claim 1, further comprising: preparing the plural types of objective lenses different in specification of respective optical path difference providing structures.

3. The method described in claim 1, wherein the light source is a light source having an oscillation wavelength of 500 nm or less.

4. The method described in claim 1, wherein the objective lens is made of a plastic, is provided with an optical path difference providing structure on at least one surface thereof and satisfies the following expression: 0.01≦|δSA3obj/δλ|<0.1 (λrms/nm)where δSA3obj/δλ represents the wavelength dependency of the 3rd order spherical aberration of the objective lens when an oscillation wavelength is fluctuated between ±2 nm from a reference wavelength of 500 nm or less.

5. The method described in claim 1, wherein the objective lens is structure with a single lens.

6. A method of manufacturing an optical pickup apparatus, comprising steps of: selecting one light source from plural laser light sources different in oscillation wavelength in accordance with a specification of an optical path difference providing structure of an objective lens; andassembling the objective lens and the selected laser source into the apparatus.

7. The method described in claim 6, further comprising: preparing plural types of objective lenses different in specification of respective optical path difference providing structures, and wherein the one light source is selected from the plural laser light sources different in oscillation wavelength in accordance with a specification of an optical path difference providing structure of an objective lens selected from the prepared plural types of objective lenses.

8. The method described in claim 6, wherein the light source is a light source having an oscillation wavelength of 500 nm or less.

9. The method described in claim 6, wherein the objective lens is made of a plastic, is provided with an optical path difference providing structure on at least one surface hereof and satisfies the following expression: 0.01≦|δSA3obj/δλ|<0.1 (λrms/nm)where δSA3obj/δλ represents the wavelength dependency of the 3rd order spherical aberration of the objective lens when an oscillation wavelength is fluctuated between ±2 nm from a reference wavelength of 500 nm or less.

10. The method described in claim 6, wherein the objective lens is structure with a single lens.

11. A method of manufacturing an optical pickup apparatus, comprising steps of: classifying plural objective lenses which are made of a plastic, have respective optical path difference providing structures on at least one surface and satisfy the following expression, into plural types in accordance with the specification of the respective optical path difference providing structures;selecting one type objective lens from the plural types in accordance with an oscillation characteristic of a laser light source to be used; andassembling the laser source and the selected type objective, 0.01≦|δSA3obj/δλ|<0.1 (λrms/nm)where δSA3obj/δλ represents the wavelength dependency of the 3rd order spherical aberration of the objective lens when an oscillation wavelength is fluctuated between ±2 nm from a reference wavelength of 500 nm or less.

12. The method described in claim 11, wherein when a delivery lot of the manufactured optical pickup apparatus is inspected, the following expression is satisfied. σSA3≦σλ·δSA3/δλwhere, σSA3 (λrms) represents the standard deviation of the 3rd order spherical aberration SA3 of the light-converging optical system (from the light source to the information recording surface) including the objective lens of the optical pickup apparatus for the wavelength when the laser light source is oscillated at the reference temperature with the reference output in respective optical pickup apparatus, in the delivery lot of the optical pickup apparatus,σλ (nm) represents the standard deviation of the oscillation wavelength at the reference temperature with the reference power of the laser included in the delivery lot of the optical pickup apparatus, andδSA3/δλ (λrms/nm) represents the wavelength dependency of the 3rd order spherical aberration of the light-converging optical system (from the light source to the information recording surface) including the objective lens included in the delivery lot of the optical pickup apparatus.

13. The method described in claim 11, wherein the objective lenses are provided with respective identification marks for each different type.

14. The method described in claim 11, wherein the objective lenses satisfy the following expression. 0.02≦|SA3obj/δλ|<0.1 (λrms/nm)

15. The method described in claim 11, wherein the objective lenses satisfy the following expression: |SA3obj|≦0.030 (λrms)where SA3obj represents the 3rd order spherical aberration of the objective lens for the oscillation wavelength when a laser light source incorporated in the optical pickup apparatus oscillates with a reference output under a reference temperature.

16. The method described in claim 11, wherein the objective lenses satisfy the following expression. |δSA3obj/δT|≦0.002 (λrms/° C.)where |δSA3obj/δT| represents the temperature dependency of the 3rd order spherical aberration of the objective lens when an wavelength fluctuation for a temperature change in an oscillation wavelength of 500 nm or less is made +0.05 nm/° C.

17. The method described in claim 11, wherein the optical pickup apparatus comprises a first light source having an oscillation wavelength λ1 of 500 nm or less and a second light source having an oscillation wavelength λ2 (λ1<λ2), and the objective lens converges a light flux from the first light source through a protective substrate having a thickness t1 onto an information recording surface of a first information recording medium so as to conduct recording and/or reproducing information and converges a light flux from the second light source through a protective substrate having a thickness t2 (t1<t2) onto an information recording surface of a second information recording medium so as to conduct recording and/or reproducing information, and wherein the objective lens is made of a plastic and includes a diffractive structure on at least one surface in which a diffraction order having the maximum diffraction efficiency is different between a case that a light flux from the first light source passes through and a case that a light flux from the second light source passes through.

18. The method described in claim 11, wherein the objective lenses have an image side maximum numerical aperture of 0.8 or more.

19. The method described in claim 11, wherein the objective lenses are structured with a single lens.

20. An optical pickup apparatus, comprising: the laser light source, andthe objective lens selected by the method described in claim 11.