The roundness profile extraction strategy of the cylindricity measuring instrument (CMI) only uses 5-10 cross-section to evaluate the cylindricity, which can not exactly express the catachrestic of the cylindrical surface error. On the contrary, the measurement result of the stitching interferometry has the advantage of high resolution and high precision, which is able to meet the requirement of bird-cage extraction. So, in this paper, we build a two-dimensional (2D) Gaussian filter weighting function to extract the cylindrical profile, according to its special shape characteristic. Besides, an experiment has been carried out by taking a ceramic plug gauge as the workpiece. The extracted results of 1-50 undulation per revolution (UPR) in circumference direction and 1-10 UPR in generatrix direction demonstrate a good performance of our method.
Due to the unique mechanical and optical characteristics, it is difficult to carry out experimental research and online measurement for large-aperture ICF frequency converters. To analyze and optimize the performance of the frequency converters under complex process loads, we present an integrated optomechanical method that correlates actual process loads with laser critical characteristics. Based on the established optomechanical model, the key factor that induces the loss of harmonic generation efficiency is identified. In addition, the proposed method is conductive to rapid evaluation, prediction, and optimization of comprehensive performance of frequency converters. Thereby, we propose an adaptive frequency conversion system (AFCS). The results indicate that AFCS can not only minimize the phase mismatching of second harmonic generation doubler but also significantly improve the quality of far-field focal spot.
KEYWORDS: General packet radio service, Fringe analysis, Data modeling, Process modeling, Interferometry, Distortion, Computer generated holography, Modeling, Metrology, Statistical modeling
Interferometric techniques are very important in the metrology field, while the quality of the interferogram will directly affect the retrieval phase of the tested object. This paper presents a method to improve the quality of the interferogram including restoration of noise aliasing and moiré distortion by using the Gaussian Process Regression (GPR). Through choosing a suitable covariance function to describe the relationship between points and points in the fringe pattern, we build a Gaussian process regression model of interferogram, denoise the interferogram and improve the resolution at the same time. The treated interferogram can predict and compensate the part of the fringe distortion and enlarge the depth range of the interferometric measurement. Besides, with the resolution elevated of the hologram, a wider spectrum range can be obtained. In order to verify the possibility of this method, several simulations have been done, which showed a good performance in the enhancement of the quality of interferogram.
Electronic Speckle Interferometry (ESPI) is a common method for deformation measurements by introducing a phase shift technique. The traditional method needs to subtract the distribution of the phase before and after deformation to get the deformation information. During this process, the noise of the object wavefront will partially remain in the deformation signal. In order to solve this problem, this paper proposes a 5+5 phase-shifting algorithm to suppress the influence of the error from the calculation. In this algorithm, the deformed phase map is directly obtained by combining the interferograms before and after the deformation. Several experiments have been carried out to verify this method. Finally, the results show a better characteristic to quantify deformation than the traditional method. In addition, the algorithm also has better redundancy
Recovering the phase of radiation is of general interest in material and biomedical science, and in nanotechnology. Commercial interferometers have been widely used in a variety of applications, if equipped with a spatial light modulator or a computer generate hologram, theoretically the interferometer can measure a variety of surface objects. At present, the new non-interferometric quantitative phase recovery method based on Transport of Intensity Equations (TIE) is widely used in the field of microstructure measurement and bioimaging. Compared with interferometric measurement, the Transport of Intensity Equations does not need additional reference light, and has good ability of anti-vibration. In this paper, the ubiquitous interferometer and the new d’Nanoimager based on the Transport of Intensity Equations (TIE) are compared with respect to measuring larger objects of different profiles. These two methods are compared with respect of their accuracy and resolution of measurement and speed of acquiring data and other experimental consideration. In addition, a large number of subjects are selected for specific applications include flat surface such as the display screen of smartphones, to lens testing both spherical and cylindrical lenses and specific application such as corrosion pitting of aluminum disks. The comparative advantages and dis-advantages of the two methods are explored, as well as their application.
The multi-grid method is a common method for solving the transport of intensity equation (TIE). Transport of intensity equation can retrieve phase information from the directly measured intensity image. When using multi-grid method to solve the TIE, firstly, the phase distribution is directly solved on the coarsest layer. The solved phase distribution is regard as the initial value on the finest grid layer to increase the convergence speed of the algorithm. Residual error on the finest grid can be obtained, then, using the restrict operators transfer the residual error from finer grid to coarser grid, until the solution on the coarsest grid is obtained. the solution on coarser grid transfer to finer grid by using prolongation operator, until the accurate phase distribution solution obtained on the finest grid. The Simulation experiments show that this method has a better convergence rate and retrieves complicated phase with higher accuracy.
This paper compares two kinds of cylinder stitching algorithm: global error homogenization stitching algorithm and Legendre Fourier polynomial fitting algorithm. The former uses the overlapping regions between adjacent sub-apertures, which can obtain high accurate results but need more time on data acquisition; Legendre-Fourier polynomial fitting stitching algorithm without overlapping regions need less aperture and short measure time but lack of high frequency information. Its stitching results easily affected by the position error of sub aperture, which is more suitable for in-situ measurement.
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