second semiconductor laser ld 2 is converted into the parallel light flux by the coupling lens cul after reflecting by the first dichroic prism dp 1 and passing the second dichroic prism dp 2 and the polarized beam splitter pbs then passes u03bb 4 wavelength plate qwp is regulated its light flux diameter by a diaphragm not shown and becomes a spot formed on the information recording surface through the protective layer of dvd by the objective lens obj the objective lens obj conducts the focusing or tracking by 2 axis actuator not shown arranged in the periphery of that the reflected light flux modulated by the information pit on the information recording surface of dvd after transmits again the objective lens obj and u03bb 4 wavelength plate qwp and the coupling lens cul reflected by the polarized beam splitter pbs astigmatism is added by the sensor lens sn and is converged on the light receiving surface of the photo detector pd then by using the output signal of the photo detector pd the information recorded in dvd can be read in the optical pickup apparatus pu 1 when the recording reproducing of the information is conducted on cd the third semiconductor laser ld 3 is light emitted the divergent light flux emitted from the third semiconductor laser ld 3 is converted into the parallel light flux by the coupling lens cul after reflecting by the second.