1. A method for generating a vertical section of an object surface under inspection by a digital optical-video inspection apparatus movable along a vertical Z axis, comprising: a) obtaining a video image of the object surface; b) overlaying over the video image on the object surface a sectioning band along a section vector to make a vertical section of the object, the band comprising a number of regions of pixels, the center of each region being a sampling point along the section vector; c) generating a series of video images of the object surface at several Z axis positions; d) computing a focus quality measurement Q(n) for each region at each Z axis position Z(n); e) computing a best focus quality measurement from step d); and f) generating a vertical cross-section of the object surface from a set of points x,y,z obtained at each best focus location.