  Conventional dual-frequency fringe projection algorithm often suffers from
phase unwrapping failure when the frequency ratio between the high frequency
and the low one is too large. Zhang et.al. proposed an enhanced two-frequency
phase-shifting method to use geometric constraints of digital fringe
projection(DFP) to reduce the noise impact due to the large frequency ratio.
However, this method needs to calibrate the DFP system and calculate the
minimum phase map at the nearest position from the camera perspective, these
procedures are are relatively complex and more time-cosuming. In this paper, we
proposed an improved method, which eliminates the system calibration and
determination in Zhang's method,meanwhile does not need to use the low
frequency fringe pattern. In the proposed method,we only need a set of high
frequency fringe patterns to measure the object after the high frequency is
directly estimated by the experiment. Thus the proposed method can simplify the
procedure and improve the speed. Finally, the experimental evaluation is
conducted to prove the validity of the proposed method.The results demonstrate
that the proposed method can overcome the main disadvantages encountered by
Zhang's method.
