Abstract: A first laser source is arranged on a transmitting side of a polarizing beam splitter, while a second laser source is arranged on a reflecting side of the polarizing beam splitter. The splitting surface of the polarizing beam splitter has a film characteristic of substantially transmitting s-polarization component of the laser light having the first wavelength emitted by the first laser source and substantially reflecting s-polarization component of the laser light having the second wavelength emitted by the second laser source. A plate-like beam splitter serves to introduce laser light reflected off of a signal recording medium into an optical detector by directing the laser light away from the optical path in which the laser sources are located. The plate-like beam splitter includes a splitting surface which has a reflectance that is higher than its transmittance.

Abstract: A lens is provided with a reflective annular zone face that is approximately perpendicular to the lens optical axis, and tilt of the reflective annular zone face is set to be equivalent to coma aberration resulting from the lens.

Abstract: An optical pickup unit comprises a diffraction grating that divides light into at least three luminous fluxes and condenses the three luminous fluxes to apply at least three focusing spots, independent of each other, onto a signal side of a medium. The diffraction grating is divided into at least four regions, a first region, a second region, a third region, and a fourth region.

Abstract: A lens is provided with a reflective annular zone face that is approximately perpendicular to the lens optical axis, and tilt of the reflective annular zone face is set to be equivalent to coma aberration resulting from the lens.

Abstract: A first laser source is arranged on a transmitting side of a polarizing beam splitter, while a second laser source is arranged on a reflecting side of the polarizing beam splitter. The splitting surface of the polarizing beam splitter has a film characteristic of substantially transmitting s-polarization component of the laser light having the first wavelength emitted by the first laser source and substantially reflecting s-polarization component of the laser light having the second wavelength emitted by the second laser source. A plate-like beam splitter serves to introduce laser light reflected off of a signal recording medium into an optical detector by directing the laser light away from the optical path in which the laser sources are located. The plate-like beam splitter includes a splitting surface which has a reflectance that is higher than its transmittance.