Optical recording and pickup head for digital versatile disc compatible with read-writable compact disc by adopting flat plate lens having staircase type diffraction grating structure

摘要

An optical recording and pickup head having a flat plate lens of a staircase type diffraction grating structure is compatible with a DVD and a CD-RW. The optical recording and pickup head includes a first optical source for emitting first light having a relatively short wavelength, a second optical source for emitting second light having a relatively long wavelength, a photo detector, an objective lens for focusing the light emitted from the first and second optical sources on the information recording surfaces of the optical discs, respectively, an optical path altering unit for transferring the light emitted from the first and second optical sources to the objective lens and transferring the first and second light reflected from the information recording surfaces of the plurality of discs to the photo detector, respectively, and a flat plate lens for substantially totally transmitting the first light proceeding from the optical path altering unit to the objective lens and diffracting the second light proceeding from the optical path altering unit to the optical axis of the objective lens.