Patent ID: 8134907

Claim:
An optical head, comprising: a first light source for emitting a first laser beam having a first wavelength λ 1 ; a second light source for emitting a second laser beam having a second wavelength λ 2 that is larger than the first wavelength λ 1 ; a first planar optical element for transmitting and reflecting the first laser beam at a predetermined ratio; a second planar optical element disposed between the second light source and the first planar optical element, for transmitting and reflecting the second laser beam at a predetermined ratio and substantially transmitting the first laser beam; a first objective lens for converging the first laser beam reflected by the first planar optical element onto an information recording surface of a first information recording medium; a second objective lens for converging the second laser beam reflected by the second planar optical element onto an information recording surface of a second information recording medium of a type that is different from the first information recording medium; a first photodetector for receiving reflected light from the information recording surface of the first information recording medium and creating an information signal or an error signal; and a second photodetector for receiving transmitted light from the first planar optical element and creating an automatic power control signal for controlling an output of the first light source, wherein the first planar optical element includes a first surface which the first laser beam emitted from the first light source enters, and a second surface facing the first surface, the first surface and the second surface are mutually parallel, a reflective coat for transmitting and reflecting the first laser beam at a predetermined ratio is formed on the first surface, and an antireflection coat having prescribed reflectance and transmittance for the first laser beam is formed on the second surface.