Abstract: An electromagnetic radiation read mechanism for reading data stored optically upon an element having a surface and a plurality of tracks, which mechanism includes a source of electromagnetic radiation; an optical coupling system, which optical coupling system is disposed so as to receive radiation output by the source of electromagnetic radiation and spread it into a plane; a prism, which prism is constructed and disposed so as to receive the plane and redirect it to reflect off of the surface of the element, and which prism is further constructed and disposed so as to receive the reflected plane and to redirect it outward; a multi-element optical sensor, which sensor is disposed so as to receive the redirected reflected plane; and a decoder connected to the multi-element optical sensor so as to receive signals therefrom, which decoder allows parallel data reading of all of the tracks of the element simultaneously.

Abstract: A well logging instrument has a plurality of contact arms which are forced against the sidewall of the borehole. The contact arms are pivotally attached to a first collar fixed to a central shaft and are pivotally attached to a second collar slidably mounted on the central shaft. Radial movement of the center of the contact arms moves a slidable collar member over an electrical coil assembly emitting an alternating magnetic flux field. The movement of the slidable collar over the electrical coil assembly alters the eddy current loading of a coil. The position of the contact arms and thus the position of the slidable collar attached thereto can be measured by detecting the eddy current loading of the coil.

Abstract: An improved well logging method and apparatus is provided for more reliable and accurate detection of corrosion in subsurface well casing. Method and apparatus are described for measuring the density of the flux field established inside the casing due to galvanic current flow longitudinally within the casing. A subsurface instrument housing a plurality of flux gates traverses the interior of the casing measuring the flux density within the casing. As the instrument comes proximate a corrosion location there will be detected a change in flux density due to current flowing from the casing into the formation. The detected change is transmitted to a surface location to provide an indication of the location and depth of corrosion.

Abstract: An electromagnetic sensing system is disclosed for sensing the linear distance between two elements and generating a signal related to the distance. The sensing system utilizes a magnetized initiator as one element, and a magnetic fluxgate as the second element. The magnetic fluxgate creates a flux "window" by locating a biased toroidal saturating coil inside a sensing coil, both of which are located inside a non-magnetic sleeve having an opening or "window" to magnetic flux, with the window being focused on the initiator magnet.

Abstract: An elongated borehole logging instrument includes a permanent magnet linear reciprocating motor. The motor powers a sliding sleeve which has attached to its outer perimeter a series of reversible vanes. The vanes engage the mud cake or the borehole wall and thus generate a force opposite to the direction of the vane slant. The motor has a stationary electromagnetic field comprised of a plurality of coils connected to the control electronics. The floating outer sleeve has permanent magnets all oriented in the same direction. As the coils are pulsed alternatingly, the magnets are either repulsed or attracted to thus generate a reciprocating motion which transferred to the vanes moves the tool up or down, depending upon the position of the reversing actuator.