Abstract: For the purpose of 3D scanning the surface of an object by optical double triangulation using the phase-shifting method, more particularly for dental purposes, at least two 3D scans of the same object (1) are carried out at different triangulation angles (?1, ?2), the first angle of which is known and the second angle of which is known at least approximately. For each pixel (Bi) of the phase related image (?1(x,y)), a wave number (wz(xi,yi) is determined using the second phase related image, the integral portion of which is equal to the order (n) of the uniqueness range (E1) in which the respective pixel (Bi) is located. The wave number (wz(x,y)) is optimized, at least for a random sample of m pixels (Bi), by minimizing a non-integral portion of the wave number (wz (xi,yi)?[wz(xi,yi)]).