Herein, an improved phase correction method is proposed to address insufficient correction when a monotone method is applied to phase noise in the shadow area of binocular vision systems. The absolute phase information on the workpiece surface is solved using a four-step phase shift and multi-frequency heterodyne, and the phase noise is corrected using a monotone nonreduction method. We then analyze the characteristics of phase noise with insufficient correction of multiple sets of different experimental objects. Discrete phase noise is corrected based on the frequency at which non-zero phase occurs over a fixed interval calculated by the phase frequency matrix, and the continuous phase is corrected using the difference between the actual and predicted phases of the adjacent discontinuous points. The integrity of workpiece information is ensured by calculating and judging the slope between the discontinuous points and the fitting slope of the non-zero phase on both sides, and using the linear method to compensate the partial phase that is set to zero because of the random noise. Experiments are also given to demonstrate that the proposed method effectively corrects phase noise in the shadow area and can be applied to different experimental objects. The cylindrical wooden workpiece has an average measurement error of 0.0859 mm, which meets the accuracy requirements of pose estimation for target grabbing.