Patent ID: 8615128

Claim:
A method for 3D scanning of a surface of an object by means of optical double triangulation using a phase shifting process, the method comprising: performing at least two 3D scans of the object at different triangulation angles (θ1, θ2) yielding for each triangulation angle (θ1, θ2) at least one phase related image (φ1(x,y), φ2(x,y)) containing a plurality of pixels (B i ) with coordinates (x i ,y i ), wherein a first one of the triangulation angles is known and a second one of the triangulations angle is at least approximately known, and each phase related image (φ1(x,y), φ2(x,y)) has a uniqueness range (E1, E2) depending, inter alia, on at least one of the triangulation angles (θ1, θ2), for each pixel (B i ) in a first phase related image (φ1(x,y)), determining a wave number using a second phase related image (φ2(x,y)) whose integral portion is equal to an order (n) of the uniqueness range (E1) in which at least one respective pixel (B i ) is located, optimizing the wave number such that at least for a random sample of m pixels (B i ) a non-integral portion of the wave number is minimized, and performing at least one of the following based on the optimized wave number: determining a relief image (H1(x,y)) of said object, by forming, for each pixel (B i ), a sum of the phase related image (φ1(x i ,y i )) at this pixel (B i ) and 2n times a corresponding wave number and multiplying the sum by a scaling factor (S1), determining a ratio (r) of scaling factors (S1, S2) which map the phase related images (φ1,φ2) onto metric relief values h and determining a drift (q) between a phase position of a pattern in the phase related images (φ1(x,y), φ2(x,y)) for use as initial values for optimization of a next relief image (H(x,y)) during a next 3D scan of said object, or creating a second metric relief image (H2(x,y)) from the second phase related image (φ2(x,y)).