Abstract: Tracking control apparatus includes a magnetic recording medium (disk or tape) comprising a dedicated servo track having recorded thereon a servo signal having a fixed spatial wavelength, and magnetic playback apparatus comprising a servo tracking head having an elongated tapered transducing gap transverse to the dedicated servo track. The transducing gap has (1) a relatively small magnetic gap length, at a first end of the gap, which is less than the spatial wavelength of the recorded signal, and (2) a relatively large magnetic gap length, at a second opposing end of the gap, which is greater than the spatial wavelength of the recorded servo signal. The servo head is in a desired tracking position when the segment of the tapered gap aligned with the servo track has a magnetic gap length that is equal to the spatial wavelength of the servo signal.

Abstract: Apparatus for, and a method of, duplicating magnetically recorded information by contact transfer from a master medium to a slave medium in the absence of a transfer field. The slave medium comprises a dilute concentration of magnetic particles productive of a demagnetization field that is negligible compared to an external magnetic field of the master medium in its contact-transfer zone. The absence of an appreciable demagnetization field in the slave medium enables the external magnetic field of the master medium to be virtually unopposed in effecting the magnetization of the slave medium.

Abstract: The invention in one embodiment utilizes a pair of identical high energy permanent magnet dipoles mounted on parallel rotatable shafts. The magnetic dipoles lie in a plane perpendicular to the rotatable shafts, and the shafts are coupled to a drive motor for rotation in opposite directions. The magnetic dipoles gives rise to a resultant field which is the sum of the fields due to the individual dipole magnetic moments. With the dipoles aligned, a field having only a longitudinal component is generated, "longitudinal" being defined as being along the direction of initial alignment. The longitudinal components of the two dipoles add, being in the same direction, while the transverse (i.e. perpendicular to the longitudinal direction) components of the dipole cancel, as they point in opposite directions. In the region of space adjacent to the longitudinally defined direction, the longitudinal oriented field components still add, and the transverse components substantially, if not completely, cancel.

Abstract: A thin film magnetometer includes first and second thin film magnetoresistive elements and first and second thin film laminated flux collectors. The first magnetoresistive element is located in a gap formed by the flux collectors, and the second magnetoresistive element is subtantially magnetically shielded by the flux collectors, and acts as a thermistor. The magnetoresistive elements are connected in a bridge circuit whereby any signal component due to thermal effects on the magnetoresistive elements is removed from the signal produced by the first magnetoresistive element.

Abstract: A thin film magnetic record/playback head having suitably thin layers of soft, high permeability magnetic material, such as permalloy, electrically insulated from each other by very thin layers of a magnetic material having suitably high resistivity, such as NiZn ferrite. The improved magnetic record/playback head is capable of reading and writing much higher bit densities (up to about 100 kfci) and at much higher frequencies (100 MHz or higher) than prior art devices while remaining fully compatible with existing electronic circuitry.

Abstract: Apparatus, for duplicating magnetically recorded information by contact transfer from a master medium in the form of a magnetic rotatable drum to a slave medium in the form of a magnetic tape, includes a magnetic head, for initially recording the information to be duplicated on the magnetic drum, having a media-contact surface the curvature of which conforms to the curvature of the drum. The magnetic head is mounted with its media-contact surface essentially parallel with the surface of revolution of the drum, thereby enhancing signal-to-noise performance by suppressing spacing losses.

Abstract: Apparatus, for recording information on a flexible magnetic slave disk by contact transfer of information recorded on a flexible magnetic master disk, includes a U-shaped electromagnetic device terminating, respectively, in a first planar pole tip axially aligned with a second movably mounted planar pole tip, to define predominately a single closed-loop flux-conducting path extending through a contact-transfer zone between the pole tips. A linear actuator, coupled to the movable pole tip, serves for releasably mounting the master disk in intimate facing relationship with the slave disk in the contact-transfer zone between the planar pole tips. Control circuitry applies an alternating electrical signal to the U-shaped electromagnetic device to develop an alternating magnetic field in the closed-loop flux-contacting path that produces a corresponding alternating magnetic transfer field extending axially in the contact-transfer zone between the planar pole tips.

Abstract: A magnetometer includes a magnetoresistive element and first and second high-permeable laminated flux collectors of height H partially overlapping, respectively, opposing lateral edges of the magnetoresistive element, wherein the flux collectors are separated laterally by a gap of length G which the magnetoresistive element spans. The two laminated flux collector and the magnetoresistive element cooperatively form an open-loop flux-conducting path of total height 2H+G, that is capable of collecting flux of a magnetic field being measured and, in response to the flux collected, developing a magnetometive force across the gap G that is functionally related to the height of the flux collectors.

Abstract: An improved radiographic imaging screen is disclosed in which microscopic high-Z metal particles are coated with or dispersed in luminescent material and formed as a layer on a substrate. The complete surrounding of each particle with the luminescent material assures that secondary electrons emitted from the particles from absorption of incident radiation photons will encounter the luminescent material regardless of the direction of emission of the electrons.

Abstract: A close packed planar array corner cube surface is employed in making an x-ray image intensifier screen. The corner cube surface is produced from single cube silicon crystal using a photoresist pattern of an array of triangle openings aligned with the <110> directions of the cube in a {111} plane facial surface of the wafer. Corner cube cells are etched in the wafer surface with an anisotropic etchant preferentially etching the {100} planes of the cubic lattice. A method for producing a retro-reflective surface from the etched silicon wafer for making the x-ray phosphor imaging screen is described.

Abstract: In a recording system utilizing a cross-field head, rather than excite both the field gap and the recording gap with signal and bias excitation as taught in the prior art, the present invention teaches applying bias excitation to both the field gap and the recording gap (as known in the prior art), but applying the signal excitation solely to the recording gap. By following this teaching of the invention, the record zone length is decreased to allow shorter wavelength recording, while the short wavelength recorded signal level is increased by effectively eliminating opposing recorded regions of magnetization in the vertical signal component.

Abstract: A yoke-type magneto-resistive head employs a thin magnetic film structure to bridge a gap in the flux conducting structure of the head and thereby sense magnetic flux. The invention provided means for reducing the magnetic reluctance of the interface between the magnetic film structures and the flux conducting structure of the head, to improve the coupling of magnetic flux from the flux conducting structure to the magnetic film structure and thereby increase the sensitivity of the magneto-resistive head.

Abstract: An apparatus is disclosed having means for shunting demagnetization fields to prevent "magnetostrictive knockdown" of a signal recorded on an isotropic recording medium.

Abstract: The disclosure hereof calls for the shearing of a thin film dispersion of magnetic particles. Magnetic fields, selectively perpendicular to the plane of shear or the direction of shear, control the degree of clumping experienced by the dispersion particles.

Abstract: To lessen thermal noise in a magneto-resistive head employing a slotted magneto-resistive sensing element, the present invention provides for such element to be plated with a highly thermally conductive film (e.g. gold, silver, copper, aluminum, etc.) exclusively in the slotted portion of the element. By restricting such plating to the slotted portion of the sensing element, the film thereon will be precluded from electrically short circuiting the magneto-resistive sensing element . . . while, at the same time, serving as an energy-spreading heat sink.

Abstract: Given that there is a limit to the extent to which a record head may be excited before its pole tips saturate (gap fuzziness) while overwriting a second set of information signals atop a first set of information signals recorded in a high coercivity recording medium, the present invention concerns the discovery that if the record gap is dimensioned to equal approximately the flux change length that corresponds with a 2 f signal (FCL.sub.2) recorded atop a 1 f signal, i.e. if the record gap is somewhere between about 0.7 and 1.5 times the flux change length associated with the 2 f signal, erasure of the 1 f signal (as well as other signals) will be most effective.

Abstract: To avoid ambiguity in the tracking of a magnetic head to a data track, the invention calls for the selection of a single given signal polarity, as recorded, as the source of positional control for a tracking servo. Difference and sum signals associated with the two longitudinal halves of a data track constitute, respectively, the servo error signal and the data signal.

Abstract: A magnetic head has an array of cores the transducer gaps of which are aligned in a row. Each core--unlike most prior art cores--has a high reluctance back gap; and bridging the back gap of all such cores is a common magnetic wire. Pursuant to the invention, a domain wall is created in the film on the magnetic wire; and such domain wall is thereafter caused to propagate along the length of the wire. Whenever the domain wall resides in the back gap of a given core in the array of cores, that back gap has low reluctance, thereby turning ON the core in question. All other cores remain OFF until the propagating domain wall resides at their respective back gaps.

Abstract: Flux sensitive apparatus, in one form thereof, employs paired thin single domain magnetic film structures, the easy magnetization axes of which are canted with respect to the direction of sense current flow therewithin. The magnetization vectors of the film structures are opposite with respect to each other, thereby to preclude, or at least lessen, demagnetization fields associated with the structures. By special connections between the thin film structures, the respective sense currents therein are provided with the same spatial direction of flow; and mutual biasing of the structures is thereby avoided.

Abstract: By recording an alternating signal in an ancillary recording medium having high coercivity, such medium will exhibit an external field of a given strength. The ancillary medium is placed in proximation to the record zone of a signal-carrying magnetic head cooperative with a primary magnetic recording medium of lesser coercivity, the fields of the head and ancillary medium algebraically adding to effect signal recording in the primary medium. When the field of the ancillary medium has a strength approximating the coercivity of the primary medium, the signal current applied to the magnetic head may be quite small.