High precision contouring utilizing the moiré method

The optical methods of contouring are based on a fundamental discipline, Projective Geometry. The 3-D world is projected in 2-D utilizing a camera modeled in the technical literature by a pinhole camera. To get back 3-D information the fundamental property measured is parallax. Parallax is a vector resulting from the difference of the projective coordinates of a point in the space when projected into a plane from two different points. The oldest method used to measure parallax is photogrammetry that at the same time is assumed to be the most precise technique, 10-5 of the largest dimension of the measured object. The paper summarizes the current state of the art of the projection moiré method. Starting from the concept of projection moiré (PM) as a form of photogrammetry, the different optical techniques for parallax determination are discussed. Although the projection moiré method has reached 1 m accuracy in laboratory work, a question remains: can PM become a standardized contouring technique yielding 10-6 m accuracy? The paper is devoted to the analysis of this question, both through theoretical derivations and experimental verifications.