Multi-directional 3D flame chemiluminescence tomography based on lens imaging.

Flame chemiluminescence tomography (FCT) has been widely used in flame diagnostics for three-dimensional (3D), spatially resolved measurements of instantaneous flame geometry and, to some extent, of species concentrations. However, in most studies, tomographic reconstructions are based on a traditional parallel projection model. Due to the light collection characteristics of a lens, a parallel projection model is not appropriate for the practical optical setups that are used for emission imaging, particularly at small F-numbers.

Theoretical analysis and experimental verification of six-step spatial phase-shifting shearing interferometry by double gratings.

In order to measure the phase projection in moiré tomography, in this paper we present a new spatial phase-shifting shearing interferometry that consists only of a crossed grating and a linear grating. With it, six phase-shifted interferograms can be acquired simultaneously. The intensity distributions of these six interferograms are derived based on the scalar diffraction theory.

Two-step spatial phase-shifting radial shearing interferometery with circular gratings.

This Letter presents a simple radial shearing interferometery with circular gratings to measure the radial first-order derivative of arbitrary wavefront phase. Two spatial phase-shifted radial shearing interferograms can be simultaneously obtained by the system, and a two-step phase-shifting algorithm with arbitrary phase-shift value is proposed for phase retrieval. The measurement for spherical wave has shown the feasibility and validity, and the optical system is used to measure the radial first-order derivative of projection wavefront phase of a propane flame with plane incident wave.

Volume moiré tomography based on double cross gratings for real three-dimensional flow field diagnosis.

Since the advantages of noncontact, strong antidisturbing capability and wide measurement range, moiré tomography has been considered a powerful diagnostic tool for flow fields. In this paper, the volume computerized tomography is introduced to obtain the real three-dimensional reconstruction based on moiré deflectometry. In order to realize volume moiré tomography (VMT), double cross gratings are applied in the moiré deflected system to gain the shearing phase distribution of the moiré deflected projection in two mutually perpendicular directions simultaneously.

Theoretical analysis for moiré effect of circular gratings for volume optical computerized tomography.

Obtaining the radial derivatives of wavefronts in projections is a critical step for volume optical computerized tomography. In this paper, the moiré effect of two identical circular gratings in acquiring the first-order radial derivative of a wavefront is analyzed. Based on scalar diffraction theory, the formation mechanism of circular gratings' moiré fringes is derived.

Influence of pressure distribution on flow field temperature reconstruction.

This research proposes an issue that has previously been omitted in flow field temperature reconstruction by optical computerized tomography (OCT). To prove that it is not reasonable to always assume an isobaric process occurs when OCT is adopted to obtain the temperature distributions of flow fields, a propane-air flame and an argon arc plasma are chosen as two practical examples for experiment. In addition, the measurement of the refractive index is achieved by moiré deflection tomography.

Complex refractive index measurement of biological tissues by attenuated total reflection ellipsometry.

To apply reflection ellipsometry to determine the real and imaginary parts of the refractive index of biological tissues simultaneously, we combine reflection ellipsometry with total internal reflection to warrant minimal influences by the strong scattering and absorption of biological tissues. A K9 glass prism with refractive index 1.51468 at wavelength 632.

Extension of the Gladstone-Dale equation for flame flow field diagnosis by optical computerized tomography.

An extended model of the original Gladstone-Dale (G-D) equation is proposed for optical computerized tomography (OCT) diagnosis of flame flow fields. For the purpose of verifying the newly established model, propane combustion is used as a practical example for experiment, and moiré deflection tomography is introduced with the probe wavelength 808 nm. The results indicate that the temperature based on the extended model is more accurate than that based on the original G-D equation.

[Extracting projections from laser moire interference spectra].

Laser Moire Interference spectra of rocket exhausted plumes were analyzed. Projections for reconstruction were figured out, and air density distribution was reconstructed. Moire deflectograms of the plumes were produced and captured with a home-made, wide-range, high-sensitivity Moire deflectometer.

Applicability of moiré deflection tomography for diagnosing arc plasmas.

The argon arc plasma whose central temperature, 1.90x10(4) K, is used as a practical example for an experiment to research the applicability of moiré deflection tomography in arc plasma flow-field diagnosis. The experimental result indicates that moiré deflection of the measured argon arc plasma is very small, even smaller than that of a common flame with the maximal temperature of nearly 1.

[Simple self-correlative algebraic reconstruction technique].

A new improvement was brought forward in algebraic reconstruction technique (ART), named simple self-correlative algebraic reconstruction technique (SSCART), and its reconstructive result was discussed in detail. With numerical simulation technique, both ART and SSCART were numerically simulated with computer, and discussed in terms of simulated result and reconstructive accuracy with error indexes such as mean-square error (MSE), absolute value error (AVE) and peak error (PE). As a result, the accuracy of SSCART was markedly improved.

[Analyzing the effect of field frequencies on reconstructive accuracy of rebuilt field with spectroscopy].

The field to be reconstructed was simulated with numerical simulation technique. The effect of a three-dimensional field's characteristics, especially, its frequency components, on the reconstructive accuracy was discussed with spectroscopy. A double-peaked field model was built with Gaussian function, and its frequency components were analyzed by Fourier transform.

[Analyzing the methods to smooth field reconstructed by algebraic reconstruction technique with spectroscopy].

The effects of filters and filtering methods on the field reconstructed by algebraic reconstruction technique (ART) is discussed with spectroscopy. The field to be constructed was simulated with numerical simulation technique. The effects of many kinds of filters and filtering methods on the field reconstructed by ART were analyzed with spectroscopy.

[Doppler effect on width of characteristic line in plasma induced by pulsed laser ablating Al].

Aluminum (Al) plasma was induced with a pulsed Nd: YAG laser beam ablating Al target in Ar. Time-resolved information of the plasma radiation was taken with time-resolved technique, and the spectra of the radiation were recorded with an optical multi-path analyzer (OMA III ), whereupon, time-resolved spectra of the plasma radiation induced by pulsed laser were acquired. Based on the experiment data, Al resonant double lines, Al I 396.

[Study on time-resolved spectra shape of aluminum plasma's characteristic radiation].

Aluminum plasma was obtained with a Nd:YAG pulsed laser beam ablating target aluminum. The radiation information of the plasma was recorded on a time and space resolution basis. So the time-resolved spectra of Al plasma were obtained with a time delay of 10 to 10,000 ns.