Mobile-phone antenna design

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Mobile-phone antenna design

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Joint optimization of source, mask, and pupil in optical lithography

Mask topography effects need to be taken into consideration for more advanced resolution enhancement techniques in optical lithography. However, rigorous 3D mask model achieves high accuracy at a large computational cost. This work develops a combined source, mask and pupil optimization (SMPO) approach by taking advantage of the fact that pupil phase manipulation is capable of partially compensating for mask topography effects. We first design the pupil wavefront function by incorporating primary and secondary spherical aberration through the coefficients of the Zernike polynomials, and achieve optimal source-mask pair under the condition of aberrated pupil. Evaluations against conventional source mask optimization (SMO) without incorporating pupil aberrations show that SMPO provides improved performance in terms of pattern fidelity and process window sizes.published_or_final_versio

Multiple frequency band and high isolation mobile device antennas using a capacitive slot

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Super-resolution imaging in optical scanning holography using structured illumination

As a specific digital holographic microscopy system, optical scanning holography (OSH) is an appealing technique that makes use of the advantages of holography in the application of optical microscopy. In OSH system, a three-dimensional object is scanned with a Fresnel zone plate in a raster fashion, and the electrical signals are demodulated into a complex hologram by heterodyne detection. Then the recorded light wavefront information contained in the hologram allows one to digitally reconstruct the specimen for multiple purposes such as optical sectioning, extended focused imaging as well as three-dimensional imaging. According to Abbe criterion, however, akin to those conventional microscopic imaging systems, OSH suffers from limited resolving power due to the finite sizes of the objective lens and the aperture, i.e., low numerical aperture. To bypass the diffraction barrier in light microscopy, various super-resolution imaging techniques have been proposed. Among those methods, structured illumination is an ensemble imaging concept that modulates the spatial frequency by projecting additional well-defined patterns with different orientation and phase shift onto the specimen. Computational algorithms are then applied to remove the effect of the structure and to reconstruct a super-resolved image beyond the diffraction-limit. In this paper, we introduce this technique in OSH system to scale down the spatial resolution beyond the diffraction limit. The performance of the proposed method is validated by simulation and experimental results.link_to_subscribed_fulltex

Nonlinear image reconstruction in block-based compressive imaging

A block-based compressive imaging (BCI) system with sequential architecture is presented in this paper. Feature measurements are collected using the principal component analysis (PCA) projection vectors. Then, we discuss an object prior learning framework based on the Field-of-Expert (FoE) model, and provide its implementation in the BCI reconstruction problem. Experimental results are used to demonstrate the reconstruction performance of the FoE-based method. © 2012 IEEE.published_or_final_versionThe 2012 IEEE International Symposium on Circuits and Systems (ISCAS), Seoul, Korea, 20-23 May 2012. In IEEE International Symposium on Circuits and Systems Proceedings, 2012, p. 2917-292

Robust source and mask optimization compensating for mask topography effects in computational lithography

Mask topography effects need to be taken into consideration for a more accurate solution of source mask optimization (SMO) in advanced optical lithography. However, rigorous 3D mask models generally involve intensive computation and conventional SMO fails to manipulate the mask-induced undesired phase errors that degrade the usable depth of focus (uDOF) and process yield. In this work, an optimization approach incorporating pupil wavefront aberrations into SMO procedure is developed as an alternative to maximize the uDOF. We first design the pupil wavefront function by adding primary and secondary spherical aberrations through the coefficients of the Zernike polynomials, and then apply the conjugate gradient method to achieve an optimal source-mask pair under the condition of aberrated pupil. We also use a statistical model to determine the Zernike coefficients for the phase control and adjustment. Rigorous simulations of thick masks show that this approach provides compensation for mask topography effects by improving the pattern fidelity and increasing uDOF.published_or_final_versio

Comparison of Kasai autocorrelation and maximum likelihood estimators for Doppler optical coherence tomography

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Enhancing a mobile and personalized learning platform through facial analytics and interactive quizzes

Conference Theme: Mobile Learning, Emerging Learning Design and Learning 2.0Learning analytics techniques to capture learners’ real-time responses can be computationally intensive for mobile devices. Yet with the diversity of many online educational videos such as the Ted Talks, YouTube or other open educational resources, the mobile learning platform intrinsically presents an opportunity for learners and instructors to analyze the pace and quality of learning. In a previous work, the PErsonalized Teaching And Learning (PETAL) platform was developed to monitor the learner’s progress in viewing educational videos through a carefully designed facial analytics technique to detect learners’ attention levels and their proximity to the screen of the mobile device. The PETAL application will alert a learner if (s)he is not paying attention while viewing an educational video. In this work, we propose to further improve the original PETAL by using online and interactive quizzes to more precisely evaluate the learner’s level of understanding while viewing the educational videos. The interactive quizzes can be flexibly added by an instructor by modifying a simple configuration file. When a learner gives an incorrect answer to a particular quiz question, (s)he will be requested to revise a specific section of the concerned video. All the data about the learner’s progress is uploaded and stored securely on a password-protected cloud platform to guarantee data privacy for future analyzes. There were some initial and positive students’ feedback collected from an empirical evaluation of the enhanced PETAL system. Clearly, the enhanced PETAL platform provides many promising directions for future extensions.published_or_final_versionThe 2016 International Mobile Learning Festival (IMLF), Bangkok, Thailand, 27-28 May 2016. In Conference Proceedings, 2016, p. 40-4

Placement sensitivity to aberration in optical imaging

Theories are developed to quantify the shift of image intensity extremum (/spl Delta/x) due to aberration. The theory on real, one-dimensional mask spectrum has been extended to complex, two-dimensional mask spectrum under coherent and partially coherent imaging. Verification of the formulae was performed on alternating phase-shifting mask (PSM) and contact array. Balanced third-order coma was used to illustrate the validity of the theories. It is found that the image shift due to aberration of alternating PSM decreases when the partial coherence factor increases. In general, the theories can be applied to any mask spectra and aberration functions.published_or_final_versio