Abstract: A method for determining the relative motion of a surface with respect to a measurement device including placing a partially transmitting object, which is part of the measuring device, adjacent to the surface; illuminating the surface with incident illumination, which does not constitute an interference pattern, such that the illumination is reflected from portions of the surface, wherein at least part of at least one of the incident and reflected illumination passes through the object; detecting the illumination reflected from the surface, and generating a detected signal; and determining the relative motion of the surface parallel to the surface, from the detected signal.

Abstract: A method of detecting the passage of an edge of a moving sheet of material at a position comprising: monitoring a state of motion at a position; and determining a time of an edge of the sheet at a position as a time at which a change in a state of motion at the position is detected.

Abstract: A method for determining the relative motion of a surface with respect to a measurement device, comprising: illuminating the surface with incident illumination, having a coherence length, such that the illumination is reflected from portions of the surface, wherein at least part of at least one of the incident and reflected illumination passes through a partially transmitting object that is part of the measuring device; detecting the illumination reflected from the surface, to generate a detected signal; and determining the relative motion of the surface parallel to the surface, from the detected signal, wherein the object and the surface are situated within a distance that is less than the coherence length of the detected illumination.

Abstract: A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface with incident illumination; detecting illumination reflected from the surface to form at least one detected signal; and determining the amount of relative motion parallel to the surface from said at least one detected signal, characterized in that said determining includes correcting for the effects of relative motion perpendicular to the surface.

Abstract: A method for determining the relative motion of a surface with respect to a measurement device comprising: illuminating the surface from a source with incident illumination, such that illumination is reflected from portions of the surface toward a detector; spatially filtering the reflected illumination such that the phase of the detected optical illumination from a given scatterer on the surface is substantially constant or linearly related to the translation of the surface; generating a signal by the detector responsive to the illumination incident on the detector; and determining the relative motion of the surface from the signal.