Two-step phase-shifting Fresnel incoherent correlation holography based on discrete wavelet transform

Fresnel incoherent correlation holography(FINCH)has the ability to generate three-dimensional images with a superresolution by using incoherent sources.However,there are unwanted direct current term and twin image in interferograms,so it is of great significance to find a method to eliminate them.Phase-shifting technology is a most widely used technique for this task,but its three-step phase-shifting is not suitable for the instantaneous measurement of dynamic objects,and the quality of reconstructed image with the traditional two-step phase-shifting is lower.In this paper,we present a method of enhancing the resolution through using a two-step phase-shifting technology based on the discrete wavelet transform.After two-step phase-shifting,the resulting hologram is a superposition of multiple forms.The frequency of the resulting hologram is decomposed into different levels through using discrete wavelet transform,then the image is reconstructed after retrieving the low frequency band.Various experiments have verified the effectiveness of this method.

Arbitrary n-step phase-shifting Fourier single-pixel imaging

In this Letter,we innovatively present general analytical expressions for arbitrary n-step phase-shifting Fourier single-pixel imaging(FSI).We also design experiments capable of implementing arbitrary n-step phase-shifting FSI and compare the experimental results,including the image quality,for 3-to 6-step phase-shifting cases without loss of generality.These results suggest that,compared to the 4-step method,these FSI approaches with a larger number of steps exhibit enhanced robustness against noise while ensuring no increase in data-acquisition time.These approaches provide us with more strategies to perform FSI for different steps,which could offer guidance in balancing the tradeoff between the image quality and the number of steps encountered in the application of FSI.

Phase-shifting technique applied to circular harmonic-based joint transform correlator

The phase-shifting technique is applied to the circular harmonic expansion-based jointtransform correlator. Computer simulation has shown that the light efficiency and the discrimination capability are greatly enhanced, and the full rotation invariance is preserved after the phase-shifting technique has been used. A rotation-invariant optical pattern recognition with high discrimination capability and high light efficiency is obtained. The influence of the additive noise on the performance of the correlator is also investigated. However, the anti-noise capability of this kind of correlator still needs improving.

Automated Phase-measuring Profilometry of 3-D Diffuse Objects Using a Single Phase Step Method

The technique of phase measuring profilometry using a single phase step method is proposed.This method can automatically obtain phase value at each pixel by using a discret cosine transform algorithm.The method is able to automatically recognize any position between depression and elevation on an object surface.Theoretical analysis and experimental verification are presented.

Parameter Estimation Approach of FSK/PSK Radar Signal

A parameter estimation approach of reconnaissance hybrid radar signal combined frequency-shift keying （FSK） and phase-shift keying （PSK） is presented. Firstly, the multi-phase difference is adopted to calculate the instantaneous frequency （IF） of FSK/PSK, then the frequency points of FSK are estimated from the histogram of IF. The code rate of PSK is extracted from the locations of phase discontinuity. Finally, the multi-phase difference of the square of the received signal is computed to estimate the code rate of FSK. The presented algorithm has higher accuracy of parameter estimation when the signal-to-noise ratio （SNR） is above 11 dB.

Comparative Analysis of Hybrid Controllers of Done Systems (UPFC) and Interphase Power Regulators Type RPI 30p15 on Contingency Management in Electrical Networks

The aim of this work is to demonstrate that interphase power regulators (IPR) bring new and interesting ultra-solutions that complement those already taken into account by the FACTS (Flexible Alternative Transmission System) in the resolution of the problems related to the power flow in the AC transmission networks. In order to facilitate the understanding of this work, a comparative study of the performances of the two technologies between the UPFC (Unified Power Flow Controller) and RPI was carried out and at the end of which we were able to highlight the preponderance of RPI compared to the UPFC in the bypassing of the short-circuit fault insofar as the latter allows, in particular, an increase in the transformation capacity without an increase in the level of the short-circuit. The decoupled watt-var method has been used to control the UPFC while the RPI is controlled by phase shift. The simulation results are obtained in the Matlab Simulink environment and show the flexibility of the RPI compared to the UPFC in limiting strong contingencies.

Generic and flexible self-correction method for nonlinearity-induced phase error in three-dimensional imaging

In three-dimensional imaging employing phase-shifting profilometry(PSP), the nonlinear response of projector and camera makes the fringe gray distribution non-sinusoidal, which further leads to phase error. Although the double 3-step phaseshifting method is simple and effective, it needs to add an additional set of fringe sequences, which reduces the measurement efficiency. To this end, this paper introduces a generic and flexible self-correction method for nonlinearity-induced phase error.First, according to the nonlinearity-induced phase error model, we introduce an additional wrapped phase with a phase difference of π/3. The error waveform of the two wrapped phases is opposite but not coincident. Then, we introduce an estimation algorithm for the additional wrapped phase offset. Finally, we fuse the two wrapped phases to correct the phase error. Experiments confirm that the root mean squared error of the proposed method is 64.1% lower than that of the traditional method and 13.3% lower than that of the Hilbert transform method. The proposed method does not require any additional fringes or hardware assistance and can be easily extended to 4-step or 5-step PSP.