Abstract: A two axis linear motor for carrying the objective lens for optical focusing and optical tracking in an optical recording system has a stationary structure for providing a magnetic field and a moving armature structure. The stationary structure may have two permanent magnets and several pole pieces to properly shape the field with respect to the armature. In one embodiment, a central elongated pole piece and two parallel adjacent elongated pole pieces which are associated with two permanent magnets to form flux gaps with the central pole piece. Flux returns to the magnets through a lower pole piece to which the central pole piece is attached. The central and lower pole pieces have an aperture through which the laser beam may pass on its way to and from the objective lens.

Abstract: Apparatus for precisely machining the surface of a workpiece comprises a rotating plate with a flat, horizontal abrasive-laden surface against which the workpiece surface is forced by gravity. The workpiece is carried on the free end of an arm pivotably supported remote from the end of the arm carrying the workpiece. Loading of the workpiece work surface can be varied by shifting weights along the length of the arm or transverse to the length of the arm. The workpiece itself can comprise a bar on which several magnetic transducing heads have been deposited. Machining the workpiece surface to a preferred position accurately defines a dimension of choice, such as the throat height of these transducers.

Abstract: A data recovery circuit useful in magnetic data recording systems employs doublet pulses to at least partially encode data. Measurement of the slope of the transition between doublet pulse half-cycle peaks and of the amplitude of this transition allows rejection of high frequency low amplitude noise and high amplitude low frequency noise. The use of nearly the entire peak-to-peak voltage swing of doublet pulses makes identifying them relatively reliable.

Abstract: In the process for manufacturing the ferrite cores used in magnetic data transducer heads, a novel stacking of the bars from which the core pieces are cut allows these bars to mutually shield each other's back gap areas during the alumina sputtering step which sets the lengths of the read/write flux gaps. An inexpensive fixture supports the bars in the desired position during the sputtering operation.