An exemplary optical pick-up apparatus of the invention includes: a first light source configured to emit a light beam of a first wavelength; a second light source configured to emit a light beam of a second wavelength, the second wavelength longer than the first wavelength; a third light source configured to emit a light beam of a third wavelength, the third wavelength longer than the second wavelength, wherein the first, second, and third light sources emit light beams one at a time during a reading or writing operation; a first dichroic element configured to transmit the light beam of the first wavelength and to reflect the light beam of the second wavelength; a second dichroic element configured to reflect the light beams of the first and second wavelengths and to transmit the light beam of the third wavelength; and an objective lens configured to transmit light beams of the first and second wavelengths, that have interacted with the first and second dichroic elements, to transmit the third wavelength, that has interacted with the second dichroic element, and to project one light beam onto a disk. |