| 摘要 |
PROBLEM TO BE SOLVED: To provide a double aperture double focus optical reproducing optical device by using only one gradient index lens partially having two kinds of lengths as an objective lens, making a DVD(digital video disk) reproducing laser beam and a CD(compact disk) reproducing laser beam incident on the gradient index lens with different tilts to the optical axis of lens and constituting the gradient index lens so that the entrance end of the laser beam is made to be a plane and so as to have the long length part and the short length part in the lens. SOLUTION: As the objective lens for a double aperture double focus optical reproducing optical device, a gradient index lens whose distribution of refractive index changes in the radial direction is provided, two kinds of apertures is realized by making the tilts of two kinds of laser beams (RD and RC), for reading information corresponding to two kinds of optical recording media, respectively, to the optical axis of the gradient index lens, mutually different (in this case, 0 deg. and -θ0 ) and two kinds of optical paths whose optical path lengths are different from each other are formed. |
