Temporal-spatial encoding binary fringes toward three-dimensional shape measurement without projector nonlinearity

Abstract

Projector nonlinearity is a common problem for digital structured light-based three-dimensional (3-D) shape measurement techniques. A temporal-spatial binary encoding method is presented for the purpose of eluding it. We build a 3-D shape measurement scheme by combining our proposed method with phase measurement profiling. A standard sinusoidal fringe pattern is divided into more than two binary fringe patterns using specially designed temporal and spatial binary encoding rule based on intensity hierarchic quantification, and then are in-focus projected onto the measured object at a time sequence to reconstruct a frame phase-shifting fringe image. On account of the projected binary fringe pattern strictly consisting of zeros and ones, the influence of the projector nonlinearity on the measurement result can be effectively ruled out and simultaneously enables high-quality sinusoidality. In-depth investigations by theoretical analysis and experiments are conducted to demonstrate the performance of this method.

Analysis and reduction of phase errors caused by nonuniform surface reflectivity in a phase-shifting measurement system

“…[1][2][3][4] Among these techniques, digital fringe projection and phase-shifting methods can acquire 3-D coordinates for every image pixel, and thus they have the advantages of high resolution and high measurement speed. [5][6][7][8] The measurement accuracy of phase-shifting methods would be adversely affected by phase errors that are considered to be mainly caused by the nonlinear response of the projector and camera. 9 Many methods have been proposed to calibrate the nonlinear response of the projector and camera or to compensate the phase errors caused by them.…”