The development of optical 3D shape measurement has been very mature, and has a wide range of applications in industrial manufacturing, biomedical, cultural relic protection and other fields. But sinusoidal fringe used in traditional fringe projection measurement cannot avoid the Gamma effect of projector and camera, which leads to the increase of measurement error. The nonlinear problem is solved by the appearance of binary fringes from the fringe generation, whose discontinuous gray value avoids the influence of nonlinear errors on the measurement results. At the same time, with the development and maturity of digital projection technology, the binary fringes have an absolute advantage in projection speed, compared with gray stripes. Therefore, defocusing projection technology has been widely studied and applied. Based on the brief introduction of the principle of defocus projection and the characteristics of binary fringe, the binary fringe modulation techniques are summarized, and the characteristics and applicable scenarios of different modulation techniques are analyzed. Finally, the future research direction of binary fringe defocused projection is prospected.