A method for enlarging absolute phase unwrapping range by active phase setting

An active phase-setting method applied to a frequency-modulated grating is proposed for enlarging the absolute phase unwrapping range. It is found that the absolute phase unwrapping range is related to initial phase of grating. Therefore, the grating is optimized by presetting two different initial phases, which one is constant in frequency-modulation term and the other is related to the ratio of two frequency in linear phase-modulation term. By using absolute phase unwrapping algorithm, which is improved for suiting the new grating, absolute phase unwrapping range successfully is enlarged and achieves the theoretical range. The experimental results show the feasibility and validity of new method.