Detection of undersampling from measured phase-shifting data

Single-shot deflectometry for dynamic 3D surface profile measurement by modified spatial-carrier frequency phase-shifting method

We propose a new concept of single-shot deflectometry for real-time measurement of three-dimensional surface profile using a single composite pattern. To retrieve an accurate phase from one-frame composite pattern, we adapt the Fourier Transform (FT) method and the spatial carrier-frequency phase-shifting (SCPS) technique to our proposed deflectometry. Based on Lissajous figure and ellipse fitting method, we also correct the phase extraction error in SCPS technique by reducing the effect of background and modulation variations. The proposed technique is verified by comparing our measurement results with phase-shifting deflectometry, and the maximum difference between two measurement results is less than 30 nm rms. We also test the robustness to vibration and the measurement capability for dynamic object.

Phase recovery from a single undersampled interferogram

A new method of phase determination from a single undersampled interferogram is described. Two low-fringe-density synthetic interferograms corresponding to the phase differences along orthogonal directions are obtained from neighboring pixels of the aliased measured data. The only assumption is that the illumination background, the modulation intensity, and the searched phase are smooth and continuous functions. The synthetic interferograms are demodulated by use of either standard frequency or spatial-domain procedures to obtain the phase differences. The phase is then recovered by integration of the phase differences with a least-squares method. The proposed method is demonstrated to be noise tolerant.

Efficient noncollinear parametric amplification of weak femtosecond pulses in the visible and near-infrared spectral range

We report measurement of efficient amplification of weak femtosecond supercontinuum seed pulses by use of a noncollinear optical parametric process in BBO crystal pumped with 150-fs pulses from a frequency-doubled regenerative-amplified Ti:sapphire laser at 390nm . The highest amplification factor, 10(8) , was achieved for 3x10(-16)J energy seed pulses at wavelength of 560nm.

Dispersive interferometric profilometer

The usual automated interferometric profilometers suffer from phase-unwrapping problems. We discuss a one-dimensional method for the absolute determination of the path difference in interferometers to obtain unique surface profiles with high accuracy.