In order to complete phase unwrapping with a heterodyne of high frequency fringe and achieve high accuracy measurement, a phase unwrapping method of dual frequency heterodyne combined with phase coding was proposed. Firstly, two wrapping phases were obtained by two sinusoidal stripes, and one heterodyne phase was obtained by heterodyne processing; Secondly, the phase coding fringe was used to obtain the fringe order, and the heterodyne phase was unwrapped by fringe order; Finally, the two wrapping phases were unwrapped by continuous heterodyne phases, and the phase information of the object was obtained by using the continuous phase of the highest frequency. The experimental results show that the RMS error of the measurement is 0.038 mm. The period of dual-frequency heterodyne synthesis did not need to cover the whole field of view, thus breaking the limitation of frequency selection in traditional dual-frequency heterodyne method, which could be used for high accuracy measurement with higher frequency fringes. High frequency fringe can be used for high accuracy measurement even if there is error of phase principal value. © 2019, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.
