Magneto-optical head with a three prism beam splitter to split a reflected beam into three beams

A magneto-optical head for reading information recorded on a reflective medium comprising;

• (a) a laser source for generating a laser beam;
• (b) a polarization beam splitter mounted between said laser source and said reflective medium for deflecting the laser beam;
• (c) an actuator means for directing the laser beam to said reflective mediums:
• (d) a convex lens for receiving a reflected laser beam from said reflective medium;
• (e) a second beam splitter comprising a rectangular shaped prism, including three triangular cubic prisms and a coating, for receiving the laser beam reflected from said reflective medium and for splitting the reflected laser beam into three orthogonal light beams, each orthogonal to each other, a first reflected beam used for tracking photodetection, a transmitted beam for data reproducing photodetection, and a beam for focusing;
• and
• (f) a half plate for rotating said polarized beam splitter and said second beam splitter wherein said second beam splitter includes a coating satisfying the following condition;
• T.sub.p .gtoreq.80%
• R.sub.S .gtoreq.5%
• R.sub.S +T.sub.S .congruent.1
• where, T.sub.P is the transmittance of a horizontal polarization beam transmitted through said second beam splitter, R.sub.S is the reflectance of a vertical polarization beam reflected from said second beam splitter, and T.sub.S is the transmittance of a vertical polarization beam transmitted through said second beam splitter.

A magneto-optical information system of reflected light path of a WORM optical head for splitting a light beam reflected from an optical disk into three light beams for tracking, data reproducing and focusing the respectively, comprising

• (a) a convex lens for receiving and focusing the light beam reflected from the optical disk;
• and
• (b) a beam splitter for receiving the light beam coming from said convex lens and splitting said reflected light beam into three orthogonal light beams, said beam splitter including a coated prism formed by three triangular cubic prisms, wherein a side angle in one of the triangular cubic prisms for reflecting the light path of said focus signal photo detection is 45.degree., and wherein beam splitter has a coating satisfying the following conditions:
• R>5%
• R+T.congruent.1
• where, R is the reflectance of a beam reflected from said beam spitter, and T is the transmittance of a vertical polarization beam transmitted through said beam splitter.