Projector nonlinearity is a common problem for digital structured light-based three-dimensional (3-D) shape measurement techniques. A temporal-spatial binary encoding method is presented for the purpose of eluding it. We build a 3-D shape measurement scheme by combining our proposed method with phase measurement profiling. A standard sinusoidal fringe pattern is divided into more than two binary fringe patterns using specially designed temporal and spatial binary encoding rule based on intensity hierarchic quantification, and then are in-focus projected onto the measured object at a time sequence to reconstruct a frame phase-shifting fringe image. On account of the projected binary fringe pattern strictly consisting of zeros and ones, the influence of the projector nonlinearity on the measurement result can be effectively ruled out and simultaneously enables high-quality sinusoidality. In-depth investigations by theoretical analysis and experiments are conducted to demonstrate the performance of this method.
The proposed four-quadrant Moiré alignment scheme to detect the misalignment between mask and wafer for proximity lithography can achieve the alignment accuracy with nanometer level. When implementing the scheme, however, the distribution of Moiré fringes associated with the mask–wafer gap indeed goes against the alignment, making the gap optimization highly urgent. The optimization model is established, and numerical simulation as well as experimental verification is also provided. Furthermore, an alignment accuracy of ∼3 nm with the illumination wavelength of 632.8 nm is experimentally attained. Simultaneously, the design mechanism of alignment marks for improving the availability of the alignment scheme is discussed.