US Patent 7545726 Optical disc drive

An optical disc drive includes a light source and an objective optical system for condensing a light from the light source onto a recording surface of an optical disc. A chassis which is movable radially of the optical disc supports both the light source and the objective optical system. The light source includes a red/infrared unit having a red/infrared LD and a blue LD. The red/infrared LD generates both a red beam and an infrared beam. The blue LD generates a blue beam. The objective optical system includes a first and a second object lenses whose focal distances are different. The first and the second object lenses are disposed on a circumferential line of the optical disc.