A three-dimension measurement system using linear LEDs with phase-shifting method

When performing Three-dimension (3D) measurements with phase-shifting method, usually a digital projector, or a translation stage is used to generate phase-shifted fringe patterns. However, in these cases, errors like gamma distortion, lens distortion and random errors caused by mechanisms are inevitable. In order to reduce the effect caused by system errors, simplify calibration procedures as well as further minimizing, in this paper, phase-shifted fringes are generated by linear LED arrays and a Ronchi grating. Phase-shifting will be performed by switching one linear LED array to another. The advanced iteration algorithm which do not require the phase-shifting amount to be known and unified is employed to minimize the calculation error caused by un-unified phase-shifting amount, since the phase-shifting amount produced by this method depends on the distance to the grating plane, which could not be exact 2π/3. Experiment results suggest that the system has a measurement error less than 0.05mm at the working distance of 130mm.