Considering the relatively low price, convenience and potential high accuracy of Digital Fringe Projection techniques (DFP), it has begun widely to use in static or even in dynamic scene for object three-dimensional reconstruction. A conventional DFP system utilizes projector to project a sinusoidal fringe patterns onto object surface, which is generated by computer. By further fringe analysis, it could retrieve the phase for reconstruction. However, this technique is not trouble free for various factors such as camera noise, nonlinear intensity response between camera and projector, especially Gamma effect, which seriously distort the sinusoidal wave. Since 1-bit binary structure patterns would not be affected by Gamma effect, S Lei proposed squared binary defocusing techniques to overcome the limitation of DFP techniques above. However, by defocusing the projector, squared binary defocusing technique has low SNR property, whose precision will be affected by various error factors easily. This paper proposes two types of error elimination algorithms of squared binary defocusing techniques. Principle of each technique will be presented, and the experimental results show the differences between the two algorithms.