Composited color-coded sinusoidal fringe pattern for absolute phase measurement

A novel color-coded sinusoidal fringe pattern for absolute phase measurement is proposed in this letter. We used composited color sinusoidal fringe to calculate the wrapped phases and fringe orders without other assistant gratings. A novel algorithm was used to map wrapped phase to absolute phase. Three different colors were employed to mark to fringe orders, and then 27 fringes could be encoded by 4-bits codeword in three gratings with a phase shift of 2π/3. Gray values of the color-coded sinusoidal fringe are employed to calculate the wrapped phases by phase shift method, and then we used wrapped phases to obtain the lowest bit of codewords. Color information were used to decide three high bits of codewords. With codewords of 4 bits, the fringe orders can be found from a lookup table, and then the wrapped phased could be mapped to absolute phase. Moreover, shortcomings of channels coupling in color grating measurement are also circumvented. The experimental results showed the validity of our algorithm.