Abstract: A magneto-optic transducer for providing an optical indication of variations in magnetization in a magnetic storage medium located along a predetermined path. The transducer has a thin film of magneto-optic material with an edge positionable closely adjacent the storage medium path so that the magneto-optic film is magnetized in accordance with the magnetization in the storage medium. The magneto-optic film is supported such that polarized light projected along an incident optical path, convergent with the storage medium path at an acute angle, intercepts the magneto-optic film substantially normally and is reflected back generally along the incident optical path.

Abstract: An optical recording media as well as methods and apparatus for reading and writing on the novel media are provided. The novel media has the property of birefringence, and information is stored thereon by modifying the birefringence of the storage media at selected locations and leaving the birefringence of the storage media intact at other selected locations. Alternatively, information is stored by inducing birefringence onto the storage media only at selected locations. The information may be stored either in a binary format, or in a multi-level (or analog) format. In a birefringent material wherein birefringence is formed by stretching, a pulse from a focused laser is utilized to modify the birefringence at selected locations by the application of thermal energy. The recorded information is read by passing polarized light through the material and ascertaining whether the polarized light was modulated as it passed through the various selected locations.

Abstract: An optical information processing apparatus comprises an information recording medium, a semiconductor laser diode for issuing a laser beam and an optical system adapted to direct the issued laser beam from the semiconductor laser diode toward the information recording medium and then return the reflected laser beam from the medium to the diode and provided with means capable of rotating the plane of polarization of the reflected laser beam from the medium by 90.degree. relative to the plane of polarization of the issued laser beam.

Abstract: Methods and apparatus for reversibly altering magnetic characteristics or domains of ferrimagnetic material by photomagnetic means, particularly by electron spin reversal (spin-flip). Photomagnetic electron spin reversal and inversion creating cylinder domains and their surrounding toroid domains of oppositely directed intrinsic magnetization in ferrimagnetic thin film material are achieved by means of signal modulated circularly polarized laser radiation. Three different stable conditions are detectable. The invention has particular application as a fundamentally new aproach to erasable digital data storage, providing means and methods for photomagnetically alterable and erasable data storage which can be detected by observing polarization of optical radiation directed through the ferrimagnetic material.

Abstract: A magneto-optic memory medium comprises a reflector exhibiting reflectance for light used for information reproduction and a magneto-optic magnetization film disposed on the reflector. When light is applied for information reproduction, the light impinges on the magnetization film and reaches the reflector. The light reflected through the reflector and the magnetization film is of use for information reproduction. In a preferred form of the magneto-optic memory medium, there is deposited on a transparent substrate a magnetic film having an axis of easy magnetization perpendicular to its surface. The magnetization film is overlaid with a reflective coating which is shaped into a strip configuration.

Abstract: The instant invention is directed to a method for writing and erasing images in the surface of a photosensitive glass which demonstrates photoanisotropic behavior at a mega Hz or higher rate. This is accomplished by utilizing an erasing beam of linearly-polarized red light having about a 45.degree. change in the direction of polarization from that of the writing beam. Also, this invention provides a method for preventing the alteration of an image written into said glass surface, the method involving exposing the area of the image to ultraviolet radiation.

Abstract: Information is converted from electrical-signal form to recorded form, or from recorded form to electrical-signal form. A beam of light emitted by a light source is split into two component light beams each having a different respective polarization plane, and the differently polarized component light beams are projected side by side onto respective adjoining portions of a recording medium.

Abstract: An optical detector for magnetic fields detects rotations in the polarization of a beam of polarized light caused by the magnetic fields. A modulator responsive to a fixed frequency signal introduces a fixed frequency of oscillation in the polarization of the light beam. The output signal of a polarization detector is filtered by a band pass filter and is fed, along with the fixed frequency signal, to a phase detector. The output of the phase detector is inverted and used as a feed-back signal to the modulator to cancel the rotation in polarization caused by the magnetic field. This feedback signal is also the final output signal of the detector.