Optical head for optical disk drive

An optical head for a magneto-optical disk drive, for reading and writing information on a magneto-optical disk, comprising:

• a stem;
• a laser diode fixed to said stem;
• a magneto-optical signal detector fixed to said stem, for detecting a magneto-optical signal from a beam reflected on said magneto-optical disk;
• an error signal detector fixed to said stem, for detecting a focusing error and a tracking error of said laser beam focused on said magneto-optical disk, from said beam reflected on said magneto-optical disk;
• a cap mounted on said stem so as to surround said laser diode, said magneto-optical signal detector, and said error signal detector;
• a beam splitter unit mounted on said cap, said beam splitter unit including a polarization beam splitter, beam separating means formed of a doubly refracting crystal, and a prism;
• and
• a hologram formed on a lower surface of said prism, for diffracting an error signal beam toward said error signal detector.

An optical head for an optical disk drive, for reading and writing information on an optical disk, comprising:

• a stem;
• a laser diode fixed to said stem;
• an optical signal detector fixed to said stem, for detecting an optical signal from a beam reflected on said optical disk;
• an error signal detector fixed to said stem, for detecting a focusing error and a tracking error of said laser beam focused on said optical disk, from said beam reflected on said optical disk;
• a cap mounted on said stem so as to surround said laser diode, said optical signal detector, and said error signal detector;
• a beam splitter unit mounted on said cap, said beam splitter unit including a polarization beam splitter and a prism for reflecting a beam reflected by said polarization beam splitter toward said optical signal detector;
• a hologram formed on a lower surface of said prism, for diffracting said beam reflected by said prism toward said error signal detector;
• and
• a quarter-wave plate located between said optical disk and said beam splitter unit.

An optical head for an optical disk drive, for directing a laser beam onto an optical disk surface and detecting a reflected beam from said optical disk surface to read information recorded on said optical disk surface, comprising:

• a stem;
• a laser diode fixed to said stem;
• an optical signal detector fixed to said stem, for receiving said reflected beam from said optical disk surface to detect an optical signal;
• an error signal detector fixed to said stem, for receiving said reflected beam from said optical disk surface to detect a focusing error and a tracking error of said laser beam focused on said optical disk surface;
• a beam splitter unit mounted above said stem, for separating said reflected beam from said optical disk surface into an optical signal beam incident on said optical signal detector and an error signal beam incident on said error signal detector, said beam splitter unit including a polarization beam splitter and a prism;
• and
• a hologram provided on said beam splitter unit, for separating said error signal beam into a focusing error signal beam and a tracking error signal beam to diffract said focusing error signal beam and said tracking error signal beam toward said error signal detector.