Abstract: A non-contact gauge and method of use is provided for optical measurement of an object or objects. The apparatus and methods may comprise a laser providing a projected laser beam; a work-piece holder for holding the object to be measured; a light sensitive sensor located to sense the beam as the beam is diffracted by at least one edge of the object and as the beam forms a near field Fresnel diffraction fringe pattern upon elements of the sensor. The laser and the sensor are located to enable near-field Fresnel diffraction. A fringe pattern signal analyzer may be included for computing mathematical algorithms to determine the position (X0) of at least one edge of the object based upon the diffraction pattern sensed by the sensor wherein the fringe pattern signal analyzer is structured to refine sensed fringe pattern edge position data to be more accurate based upon a theoretical diffraction compensation factor.