| 摘要 |
<P>PROBLEM TO BE SOLVED: To make the optical beam spot and intensity of light beams of the respective wavelengths of signal recording surfaces of a plurality of types of optical disks having protective plates different in thickness. <P>SOLUTION: An optical pickup has a first light source of a first wavelength, a second light source of a second wavelength, a third light source of a third wavelength, an objective lens 33 to focus the optical beams from the first to third light sources on the signal recording surface of an optical disk, a collimator lens 36 disposed between the first to third light sources and the objective lens 33, and an optical diffraction element 34 disposed between the collimator lens and the objective lens 33. The optical diffraction element 34 has a first diffraction section 34a to diffract the optical beam of the second wavelength, and a second diffraction section 34b to diffract the optical beam of the third wavelength. In the second diffraction section 34b, first and second optical ring surfaces are formed continuously, which have radial-direction cross sections formed in free curved shapes. <P>COPYRIGHT: (C)2007,JPO&INPIT |
