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Binary pattern defocused projection is a promising method of measuring 3D shapes. However, deep or long-distance defocus prevents high-accuracy 3D measurement. The triangle pattern is preferred because of its slight defocus and ability to overcome the nonlinear gamma. Thus, a novel method combining triangle pattern slight defocus with phase shifting is proposed. The proposed method has two merits: (1) Compared with the sinusoidal pattern, the proposed method can overcome the nonlinear gamma. (2) Compared with the binary pattern, it has the advantage of slightly defocusing to an ideal sinusoidal pattern in a short distance. Thus, the measurement error caused by nonlinear gamma and deep defocus is reduced. The RMS error of the proposed method is

With the development of optical communication, the optical attenuator becomes an important passive device. It is widely used in power equalization of DWDM system and photo detectors. Here an optofluidic variable optical attenuator (VOA) based on magnetohydrodynamic drive is presented. This chip uses microfluid and compressible air to adjust optical attenuation, where the fluid-drive technology uses magnetohydrodynamic (MHD) drive. The driving pump consists of two electrodes and a permanent magnet (NdFeB) that under the microfluidic channel. Only several volts voltage is needed in operation. There are no movable mechanical parts in this variable optical attenuator, so its volume is small. This variable optical attenuator has a simple structure and a low voltage advantages, and it is easy to control and integrate. The proposed VOA gives a new method for looking for small, low voltage and adjustable VOAs.

A variable optical attenuator (VOA) based on S-shape polymer waveguide is demonstrated at the wavelength λ = 1.55 micron. The VOA consists of straight input and output waveguides, an S-shape waveguide and a pair of deposited electrodes. The cladding material of S waveguide is Poly (methyl methacrylate/disperse red 1) (PMMA/DR1) and the core material of S waveguide is SiON. The refractive index of the polymer cladding at S waveguide is modified by the applied electric voltage. Light scatters at the S waveguide and the VOA has large energy loss in the original state at voltage-off. In the voltage-on state, the refractive index of the polymer of the S waveguide reduces, and energy loss changes as the voltage increases. The attenuation of the VOA can be controled and adjusted by the applied voltage. The beam propagation method(BPM) and finite element analysis are employed to simulate and analyse the VOA. The results show that the VOA has large variable attenuation range of 45.2dB and low insertion loss of 0.8dB.