Patent ID: 7613095

Claim:
An optical pickup apparatus capable of compatibly employing a high-density recording medium, which uses a celadon light and is slimmer than a digital versatile disc (DVD), and at least one low-density recording medium, the optical pickup apparatus comprising: an optical unit for projecting a plurality of lights of different wavelengths, the lights including a celadon light, toward a recording medium and receiving the lights reflected from the recording medium to thereby detect an information signal and an error signal; and a compatible objective lens for focusing a light projected from the optical unit to thereby form an optical spot on a recording surface of the recording medium and applicable for at least three lights having different wavelength ranges to be compatibly used for both the high-density and the low-density recording mediums; wherein the low-density recording medium comprises the DVD and a compact disc (CD); and wherein the optical unit comprises: a first light source for projecting the celadon light for the high-density recording medium; a 2-wavelength light source module for projecting an infrared light for the CD and the red light for the DVD and receiving the lights being reflected to thereby detect a signal; a first light detector for receiving the light projected by the first light source and reflected from the recording medium to thereby detect a signal; a first optical path converter for changing a path of the light projected by the first light source; a second optical path converter for changing a path of the light projected by the 2-wavelength light source module; and a first monitoring light detector which receives the lights of different wavelengths, projected by the 2-wavelength light source module to monitor output of the 2-wavelength light source module; wherein the first monitoring light detector and the 2-wavelength light source module are mounted so that optical axes of the lights being projected and incident with respect to the first monitoring light detector and the 2-wavelength light source module form substantially 90°.