Simple magneto-optic rewritable head for roughedized environments

Claim 1

Optical apparatus for use in reading and writing data onto a recording medium comprising: prism means having first, second, third and fourth surfaces, the first surface having polarizing beam splitting material thereon which material is highly reflective to radiation polarized in a first sense while transmissive to a majority of radiation polarized in a second sense, the second surface being highly reflective to radiation, the third and fourth surfaces being radiation transmissive; first means for transmitting a beam of polarized radiation as an input and arranged so that a majority of the input passes to a first portion of the first surface and through the beam splitting material into the prism as radiation polarized in the second sense and thence to the second surface where it is reflected back to a second portion of the first surface where it is split into first and second beams, the first beam containing the majority of the radiation is transmitted out of the prism as a first output and the second beam containing a minority of the radiation is reflected to the third surface where it is transmitted out of the prism to power monitoring means; second means for transmitting the first output beam to the recording medium for use in recording data thereon and for receiving radiation reflected therefrom containing information recorded on the medium, the second means transmitting the reflected radiation to the first surface where it is split into third and fourth beams, the third beam containing a minority of the radiation being reflected from the first surface toward data signal receiving means and the fourth beam containing the majority of the radiation being transmitted through the beam splitting material and through the prism to the second surface for reflection to the fourth surface where it is transmitted out of the prism toward focus detecting means.