In fringe projection profilometry, phase unwrapping has long been a critical issue. Unwrapping methods can be classified as spatial unwrapping methods and temporal unwrapping methods. The spatial unwrapping method applies only to the surface of continuous objects. The temporal unwrapping method is more widely used and can be used on discontinuous or isolated objects. Nevertheless, the temporal unwrapping methods are suffering from time-consuming, such as the large number of pictures required (standard temporal unwrapping method, phase shift plus Gray code method), and high algorithm complexity (such as periodic encoding method, Fourier transform Method) Etc. Therefore, we propose a temporal unwrapping method using only three projection patterns. In this method, two linear gray scale increasing and decreasing pictures are used to obtain the cores global phase map and uniform illumination background. Another sine fringe image and the above uniformly illuminated background image are used to obtain the wrapped phase. Then the absolute phase can be achieved with the coarse global phase distribution and the wrapped phase. Experimental results prove that this method can measure three-dimensional scenes containing isolated objects.