Patent ID: 7173897

Claim:
An optical pickup apparatus, comprising: a first light source for emitting a first light flux having a first wavelength for reproducing or recording information from or onto a first optical information recording medium having a first transparent substrate and a first information recording plane, the first transparent substrate having a first thickness; a second light source for emitting a second light flux having a second wavelength for reproducing or recording information from or onto a second optical information recording medium having a second transparent substrate and a second information recording plane, the second transparent substrate having a second thickness, the first wavelength being different from the second wavelength, and the first thickness being different from the second thickness; a converging optical system comprising a first diffractive portion, and a second diffractive portion farther from an optical axis of the converging optical system than the first diffractive portion; a photo detector for receiving light flux reflected from the first information recording plane or the second information recording plane; wherein in case that the first light flux passes through at least a part of the first diffractive portion to generate at least one diffracted ray, an amount of first n-th ordered diffracted ray of the first light flux is greater than an amount of any other ordered diffracted ray of the first light flux, and in case that the second light flux passes through at least a part of the first diffractive portion to generate at least one diffracted ray, an amount of the second n-th ordered diffracted ray of the second light flux is greater than an amount of any other ordered diffracted ray of the second light flux, where n stands for one integer other than zero, and where the n of the first n-th ordered diffracted ray is equal to the n of the second n-th ordered diffracted ray; wherein the converging optical system converges the first n-th ordered diffracted ray of the first light flux passing through the first diffractive portion and a diffracted ray of the first light flux passing through the second diffractive portion on the first information recording plane of the first optical information recording medium through the first transparent substrate so as to reproduce or record information from or onto the first optical information recording medium; and wherein the converging optical system converges the second n-th ordered diffracted ray of the second light flux passing through the first diffractive portion on the second information recording plane of the second optical information recording medium through the second transparent substrate so as to reproduce or record information from or onto the second optical information recording medium.