Abstract: A scanned imaging system includes a lens system for directing radiation from a scene to be scanned onto external reflecting surfaces of a rotating polygon and onto a detector, the external reflecting surfaces including primary and secondary flat facets which rotate together on a common axis, the lens system including an image space lens system for focusing an image of the scene to be scanned in the vicinity of a primary facet, and further including an optical system for directing radiation from a primary facet to a focus at a point on or adjacent an associated secondary facet and to reflect the radiation from the secondary facet to the detector, the arrangement being such that a beam of radiation is incident on substantially the whole width of a primary facet and sweeps round with that facet as the polygon rotates.

Abstract: A method is described for determining a shear wave velocity of a transversely isotropic region of an earth formation traversed by a wellbore with a non-zero relative dip angle between a longitudinal axis of the wellbore and an axis of symmetry of the TI region. A sonic tool is used to measure shear velocities in the TI region with polarizations orthogonal to the longitudinal axis of the wellbore. One of the shear velocities is identified as a quasi-shear velocity. A shear wave velocity is calculated, as a function of the quasi-shear velocity, for propagation in a direction along the axis of symmetry of the TI region. Where the orientation of the sonic tool is not known and the measured shear velocities comprises a fast shear velocity and a slow shear velocity, the method comprises identifying either the fast or the slow shear velocity as a quasi-shear mode.

Abstract: A method is described for determining a shear wave velocity of a transversely isotropic region of an earth formation traversed by a wellbore with a non-zero relative dip angle between a longitudinal axis of the wellbore and an axis of symmetry of the TI region. A sonic tool is used to measure shear velocities in the TI region with polarisations orthogonal to the longitudinal axis of the wellbore. One of the shear velocities is identified as a quasi-shear velocity. A shear wave velocity is calculated, as a function of the quasi-shear velocity, for propagation in a direction along the axis of symmetry of the TI region. Where the orientation of the sonic tool is not known and the measured shear velocities comprises a fast shear velocity and a slow shear velocity, the method comprises identifying either the fast or the slow shear velocity as a quasi-shear mode.