Patent ID: 7961583

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 DVD; a second light source for emitting a second light flux having a second wavelength for reproducing or recording information from or onto a CD, the first wavelength being different from the second wavelength; an objective lens comprising a diffraction surface comprising diffracting annular bands, the objective lens being a single plastic lens; and a photo detector for receiving light flux reflected from an information recording plane of the DVD or an information recording plane of the CD; wherein in case that the first light flux passes through at least a part of the diffraction surface to generate at least one diffracted ray, an amount of 1st ordered diffracted ray of the first light flux is greater than that 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 diffraction surface to generate at least one diffracted ray, an amount of 1 st ordered diffracted ray of the second light flux is greater than that of any other ordered diffracted ray of the second light flux, the first wavelength being different from the second wavelength; wherein the objective lens converges the 1st ordered diffracted ray of the first light flux on the information recording plane of the DVD so as to reproduce or record information from or onto the DVD; wherein the objective lens converges the 1st ordered diffracted ray of the second light flux on the information recording plane of the CD so as to reproduce or record information from or onto the CD; wherein at least a part of the diffraction surface is formed so that a diffraction efficiency of a light flux having a predetermined wavelength which is longer than the first wavelength and shorter than the second wavelength is larger than each of a diffraction efficiency of a light flux having the first wavelength and a diffraction efficiency of a light flux having the second wavelength; and wherein following formulas are satisfied: −0.0002/° C.<Δ n/ΔT<− 0.00005/° C. 0.05 nm/° C.<Δλ1/Δ T< 0.5 nm/° C. wherein ΔT is a temperature change of the objective lens, Δn is a change in refractive index, of the objective lens at the time that the temperature change ΔT takes place, and Δλ1 is a change in wavelength of the first light source at the time that the temperature change ΔT takes place.