Iterative Angular Spectrum Research Articles

DESIGN OF A TRANSDUCER FOR FRAGMENTING LARGE KIDNEY STONES USING BURST WAVE LITHOTRIPSY.

Burst wave lithotripsy (BWL) is a potential noninvasive treatment for breaking kidney stones. BWL requirements of high-pressure output, limited aperture for acoustic window, and specific focal length and frequency constrain the focal beam width. However, BWL is most effective only on stones smaller than the beam width. We tested a porous piezoelectric material (PZ36) to increase the output power and designed acoustic lenses that broaden the beam. A weighted iterative angular spectrum approach was used to calculate the source phase distribution needed to generate desired cross sectional focal beam profiles each of 12 mm width. The phase calculations were then 3D printed as holographic lenses placed over a circular aperture of 80-mm diameter, 350 kHz PZ36 to produce the desired beam at 85 mm depth. The difference in simulated beam width and that measured by hydrophone was <1 mm, and the structural-similarity index value was greater than 0.65. The differences in structures were due not to shape and size of the 6-dB contours but to amplitude distribution within the contour. In conclusion, this design approach combined with 3D printing provides a way to tailor focal beam profiles for lithotripsy transducers.

基于背景校正和图像分割定量分析光学元件表面疵病的新算法

A hybrid iterative algorithm which combines the transport of intensity equation (TIE)with the iterative angular spectrum propagation algorithm is studied.In the simulations and experiments,the phase retrieval performances by the TIE algorithm and the hybrid iterative algorithm at different defocusing distances are compared. The results indicate that,if compared with those by the TIE algorithm,the accuracy at large defocusing distance and spatial resolution of the phase retrieval by the hybrid iterative algorithm are improved.This algorithm provides a solution to the phase retrieval with high accuracy.

Design of a New Diffractive Optical Element for Flattening the Gaussian High-Repetition-Rate Transversely Excited Atmospheric-Pressure CO2 Laser Beam Using an Iterative Angular Spectrum Algorithm through MATLAB

The editorial board announced this article has been retracted on December 21, 2012. If you have any further question, please contact us at: mas@ccsenet.org Article Title: Design of a New Diffractive Optical Element for Flattening the Gaussian High-Repetition-Rate Transversely Excited Atmospheric-Pressure CO2 Laser Beam Using an Iterative Angular Spectrum Algorithm through MATLAB Author/s: Alireza Heidari, Mehrnoosh Zeinalkhani, Abolhasan Nabatchian, Mohammad Amin Zare Soltani, Tahere Godarzvand Chegini, Mohammadreza Seifi Aghdam Malakabad & Mohammadali Ghorbani Journal Title: Modern Applied Science ISSN 1913-1844 (Print) E-ISSN 1913-1852 Volume and Number: Vol. 6, No. 5, 2012 Pages: 82-90 DOI: 10.5539/mas.v6n5p82 Mr. Mohammadali Ghorbani (Corresponding Author) formally apologizes to his dear and respected colleagues and journal editorial board. He gave deceiving them and got abuse their names, brilliant academic records, and reputations. His dear and respected colleagues have no knowledge or fault. He is a legal and moral responsibility to get this problem.

Iterative Wiener deconvolution based method for phase retrieval from noisy intensities

To retrieve the phase from the noisy measured intensities in the diffraction planes, an iterative Wiener deconvolution based method is proposed. With the same iterative scheme as the iterative angular spectrum method (IAS), the propagation of the optical wave function between the input plane and the diffraction planes is calculated by Wiener deconvolution in this method. The angular spectrum convolution kernel used in the iterative angular spectrum method is incorporated into the Wiener filter. The simulation experiments show that the proposed method can reduce the impact of the noise on the retrieved phase and performed better than the pre-denoising method. Furthermore, the proposed method exhibits great advantage compared to IAS for retrieving the complicated phase distribution from two measured intensities.

Comparison of iterative angular spectrum and optimal rotation angle methods in designing beam-fanners

We compare the iterative angular spectrum (IAS) and the optimal rotation angle (ORA) methods in designing two-dimensional finite aperture diffractive optical elements (FADOEs) used as beamfanners. The transfer functions of both methods are compared analytically in the spatial frequency domain. We have designed several structures of 1-to-4 and 1-to-6 beamfanners to investigate the differences in the performance of the beamfanners designed by ORA method for near field operation. Using the three-dimensional finite difference time-domain (3-D FDTD) method with perfect matched layer (PML) absorbing boundary condition (ABC), the diffraction efficiency is calculated for each designed FADOE and the corresponding values are compared.

Hybrid iterative phase retrieval algorithm based on fusion of intensity information in three defocused planes

Study of phase retrieval technology is quite meaningful, for its wide applications related to many domains, such as adaptive optics, detection of laser quality, precise measurement of optical surface, and so on. Here a hybrid iterative phase retrieval algorithm is proposed, based on fusion of the intensity information in three defocused planes. First the conjugate gradient algorithm is adapted to achieve a coarse solution of phase distribution in the input plane; then the iterative angular spectrum method is applied in succession for better retrieval result. This algorithm is still applicable even when the exact shape and size of the aperture in the input plane are unknown. Moreover, this algorithm always exhibits good convergence, i.e., the retrieved results are insensitive to the chosen positions of the three defocused planes and the initial guess of complex amplitude in the input plane, which has been proved by both simulations and further experiments.

Limits of scalar diffraction theory and an iterative angular spectrum algorithm for finite aperture diffractive optical element design

We have designed high-efficiency finite-aperture diffractive optical elements (DOE's) with features on the order of or smaller than the wave-length of the incident illumination. The use of scalar diffraction theory is generally not considered valid for the design of DOE's with such features. However, we have found several cases in which the use of a scalar-based design is, in fact, quite accurate. We also present a modified scalar-based iterative design method that incorporates the angular spectrum approach to design diffractive optical elements that operate in the near-field and have sub-wavelength features. We call this design method the iterative angular spectrum approach (IASA). Upon comparison with a rigorous electromag-netic analysis technique, specifically, the finite difference time-domain method (FDTD), we find that our scalar-based design method is surprisingly valid for DOE's having sub-wavelength features.