"Flexible 3-D shape measurement using projector defocusing," Opt. Lett., (2009)

[20] S Lei* and S Zhang, "Flexible 3-D shape measurement using projector defocusing," Opt. Lett. 34(20),3080-3082, 2009;doi: 10.1364/OL.34.003080

We present a 3-D shape-measurement technique using a defocused projector. The ideal sinusoidal fringe patterns are generated by defocusing binary structured patterns, and the phase shift is realized by shifting the binary patterns spatially. Because this technique does not require calibration of the gamma of the projector, it is easy to implement and thus is promising for developing flexible 3-D shape measurement systems using digital video projectors. 

"Digital sinusoidal fringe generation: defocusing binary patterns VS focusing sinusoidal patterns," Opt. Laser, (2010)

[22] S. Lei* and S. Zhang, "Digital sinusoidal fringe generation: defocusing binary patterns VS focusing sinusoidal patterns,"Opt. Laser Eng. 48, 561-569, 2010; doi: 10.1016/j.optlaseng.2009.12.002

There are two approaches to generate sinusoidal fringe patterns with a digital-light-processing (DLP) projector: defocusing binary patterns (DBP), and focusing sinusoidal patterns (FSP). This paper will compare the potential errors for both methods induced by the following factors: (1) degree of defocusing, (2) exposure time, (3) synchronization, and (4) projector’s nonlinear gamma. Experiments show that in most scenarios, the error for the DBP method is smaller than that of the FSP method. Therefore, generating a sinusoidal fringe image using a DBP method seems to be appealing.