Objective lens with center and periphery portions producing reciprocal interference, and optical head and optical disk device using the same

An optical disk device, comprising an optical head, for recording/reproducing information onto/from the information recording surfaces of a first and a second optical disks which have respectively different thicknesses and are used as the first and the second light transmissive flat plates of the optical head,

• the optical head including:
• a light source for emitting a luminous flux;
• an objective lens for converging the luminous flux onto either the information recording surface of a first light transmissive flat plate functioning as a recording medium or the information recording surface of a second light transmissive flat plate also functioning as a recording medium;
• separation means for separating the luminous flux, which has been reflected by or transmitted through either the information recording surface of the first light transmissive flat plate or the information recording surface of the second light transmissive flat plate, into a first luminous flux which has been transmitted through the periphery portion of the objective lens and a second luminous flux which has been transmitted through the center portion of the objective lens;
• and a photodetector for detecting the first and the second luminous fluxes, thereby outputting respective electric signals,
• wherein the objective lens of the optical head converges the luminous flux onto the information recording surfaces of the first and the second optical disks, the periphery portion and the center portion of the objective lens being designed so that a reciprocal interference of the respective luminous fluxes which have passed through the periphery portion and the center portion is produced, and
• the photodetector of the optical head detects the luminous flux, which has been reflected by or transmitted through the information recording surface of the first or the second disk, thereby outputting an electric signal.

An optical disk device, comprising an optical head, for recording/reproducing information onto/from the information recording surfaces of a first and a second optical disks which have respectively different thicknesses and are used as the first and the second light transmissive flat plates of the optical head,

• the optical head including a light source for emitting a luminous flux;
• an objective lens for converging the luminous flux onto either the information recording surface of a first light transmissive flat plate functioning as a recording medium or the information recording surface of a second light transmissive flat plate also functioning as a recording medium;
• and a photodetector for detecting the luminous flux, which has been reflected by or transmitted through the information recording surface of the first or the second light transmissive flat plate, thereby outputting an electric signal, the objective lens including a center portion and a periphery portion surrounding the center portion, an aberration of the periphery portion being corrected such that a light spot is formed by the convergence of the luminous flux which has been transmitted through the periphery portion and then transmitted through the first light transmissive flat plate, and an aberration of the center portion being corrected such that a light spot is formed by the convergence of the luminous flux which has been transmitted through the center portion and then transmitted through the second light transmissive flat plate which is thicker than the first light transmissive flat plate,
• wherein the objective lens of the optical head converges the luminous flux onto the information and recording surfaces of the first and the second optical disks, the periphery portion and the center portion of the objective lens being designed so that a reciprocal interference of the respective luminous fluxes which have passed through the periphery portion and the center portion is produced, and
• the photodetector of the optical head detects the luminous flux, which has been reflected by or transmitted through the information recording surface of the first or the second disk, thereby outputting an electric signal.

An optical disk device, comprising an optical head, for recording/reproducing information onto/from the information recording surfaces of a first and a second optical disks which have respectively different thicknesses and are used as the first and the second light transmissive flat plates of the optical head,

• the optical head including a first light source for emitting a first luminous flux;
• a second light source for emitting a second luminous flux having a wavelength different from a wavelength of the first luminous flux emitted by the first light source;
• an objective lens for converging the first luminous flux onto the information recording surface of a first light transmissive flat plate functioning as a recording medium and for converging the second luminous flux onto the information recording surface of a second light transmissive flat plate also functioning as a recording medium;
• and a photodetector for detecting the luminous flux, which has been reflected by or transmitted through the information recording surface of the first or the second light transmissive flat plate, thereby outputting an electric signal, the objective lens including a center portion and a periphery portion surrounding the center portion, an aberration of the periphery portion being corrected such that a light spot is formed by the convergence of the first luminous flux which has been transmitted through the periphery portion and then transmitted through the first light transmissive flat plate, and an aberration of the center portion being corrected such that a light spot is formed by the convergence of the second luminous flux which has been transmitted through the center portion and then transmitted through the second light transmissive flat plate which is thicker than the first light transmissive flat plate,
• wherein the objective lens of the optical head converges the luminous flux onto the information recording surfaces of the first and the second optical disks, the periphery portion and the center portion of the objective lens being designed so that a reciprocal interference of the respective luminous fluxes which have passed through the periphery portion and the center portion is produced, and
• the photodetector of the optical head detects the luminous flux, which has been reflected by or transmitted through the information recording surface of the first or the second disk, thereby outputting an electric signal.

An optical head comprising:

• a light source for emitting a luminous flux;
• an objective lens for converging the luminous flux onto either the information recording surface of a first light transmissive flat plate functioning as a recording medium or the information recording surface of a second light transmissive flat plate also functioning as a recording medium;
• separation means for separating the luminous flux, which has been reflected by or transmitted through either the information recording surface of the first light transmissive flat plate or the information recording surface of the second light transmissive flat plate, into a first luminous flux which has been transmitted through the periphery portion of the objective lens and a second luminous flux which has been transmitted through the center portion of the objective lens;
• and
• a photodetector for detecting the first and the second luminous fluxes, thereby outputting respective electric signals,
• wherein the periphery portion and the center portion of the objective lens are designed so that a reciprocal interference of the respective luminous fluxes which have passed through the periphery portion and the center portion is produced.

An optical head comprising:

• a first light source for emitting a first luminous flux;
• a second light source for emitting a second luminous flux having a wavelength different from a wavelength of the first luminous flux emitted by the first light source;
• an objective lens for converging the first luminous flux onto the information recording surface of a first light transmissive flat plate functioning as a recording medium and for converging the second luminous flux onto the information recording surface of a second light transmissive flat plate also functioning as a recording medium;
• and
• a photodetector for detecting the luminous flux, which has been reflected by or transmitted through the information recording surface of the first or the second light transmissive flat plate, thereby outputting an electric signal,
• wherein the objective lens includes a center portion and periphery portion surrounding the center portion,
• an aberration of the periphery portion is corrected such that a light spot is formed by the convergence of the first luminous flux which has been transmitted through the periphery portion and then transmitted through the first light transmissive flat plate,
• an aberration of the center portion is corrected such that a light spot is formed by the convergence of the second luminous flux which has been transmitted through the center portion and then transmitted through the second light transmissive flat plate which is thicker than the first light transmissive flat plate, and
• the periphery portion and the center portion of the objective lens are designed so that a reciprocal interference of the respective luminous fluxes which have passed through the periphery portion and the center portion is produced.