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Full-Text Articles in Engineering

Using Practical Supergain For Passive Imaging With Noise, Martin Siderius Dec 2011

Using Practical Supergain For Passive Imaging With Noise, Martin Siderius

Electrical and Computer Engineering Faculty Publications and Presentations

Recent work has shown that endfire beamforming of ocean noise can be used to produce images of the seabed layering [Siderius et al., J. Acoust. Soc. Am. 120, 1315–1323 (2006)]. This initial noise imaging technique used conventional beamforming and was later extended to adaptive beamforming that is theoretically optimal. However, there can be problems with adaptive methods, which include extreme sensitivity to random errors, the required averaging time, and computational complexity. Here, the concept of supergain is used to show that delay and sum beamforming can produce nearly the same results as the optimal adaptive methods without the drawbacks.


Decomposition Of Reversible Logic Function Based On Cube-Reordering, Martin Lukac, Michitaka Kameyama, Marek Perkowski, Pawel Kerntopf Dec 2011

Decomposition Of Reversible Logic Function Based On Cube-Reordering, Martin Lukac, Michitaka Kameyama, Marek Perkowski, Pawel Kerntopf

Electrical and Computer Engineering Faculty Publications and Presentations

We present a novel approach to the synthesis of incompletely specified reversible logic functions. The method is based on cube grouping; the first step of the synthesis method analyzes the logic function and generates groupings of same cubes in such a manner that multiple sub-functions are realized by a single Toffoli gate. This process also reorders the function in such a manner that not only groups of similarly defined cubes are joined together but also don’t care cubes. The proposed method is verified on standard benchmarks for both reversible and irreversible logic functions. The obtained results show that for functions …


Application Of Genetic Algorithm For Synthesis Of Large Reversible Circuits Using Covered Set Partitions, Maher Mofeid Hawash, Baker Abdalhaq, Amjad Hawash, Marek Perkowski Dec 2011

Application Of Genetic Algorithm For Synthesis Of Large Reversible Circuits Using Covered Set Partitions, Maher Mofeid Hawash, Baker Abdalhaq, Amjad Hawash, Marek Perkowski

Electrical and Computer Engineering Faculty Publications and Presentations

We present the results of application of Evolutionary Algorithms to the problem of synthesizing quantum circuits which belong to the class of reversible circuits, represented as an input/output mapping vectors. The paper specifically focuses on large quantum circuits where many valid solutions exist in an exponentially inflating search space. Valid solutions represent the set of all input vector permutations (arrangements) which satisfy the circuit specification. The search space for circuits with large number of variables grows exponentially making it impossible to discover the set of optimal solutions. The paper compares three methods for selecting valid solutions of input vector sequences: …


Efficient Design And Synthesis Of Decimation Filters For Wideband Delta-Sigma Adcs, Rajaram Mohan Roy Koppula, Sakkarapani Balagopal, Vishal Saxena Sep 2011

Efficient Design And Synthesis Of Decimation Filters For Wideband Delta-Sigma Adcs, Rajaram Mohan Roy Koppula, Sakkarapani Balagopal, Vishal Saxena

Electrical and Computer Engineering Faculty Publications and Presentations

A design methodology for synthesizing power-optimized decimation filters for wideband Delta Sigma (ΔΣ) analog-to-digital converters (ADCs) for next-generation wireless standards is presented. The decimation filter is designed to filter the out-of-band quantization noise from a fifth-order continuous-time ΔΣ modulator, with 20 MHz signal bandwidth and 14-bits resolution. The modulator employs an oversampling ratio (OSR) of 16 with a clock rate of 640 MHz. Retiming, pipelining, Canonical Signed Digits (CSD) encoding has been utilized along with an optimized halfband filter to realize the power savings in the overall decimation filter. A process flow to rapidly design the optimized filters in MATLAB, …


Towards Improved Paper-Based Election Technology, Elisa H. Barney Smith, Daniel Lopresti, George Nagy, Ziyan Wu Sep 2011

Towards Improved Paper-Based Election Technology, Elisa H. Barney Smith, Daniel Lopresti, George Nagy, Ziyan Wu

Electrical and Computer Engineering Faculty Publications and Presentations

Resources are presented for fostering paper-based election technology. They comprise a diverse collection of real and simulated ballot and survey images, and software tools for ballot synthesis, registration, segmentation, and ground-truthing. The grids underlying the designated location of voter marks are extracted from 13,315 degraded ballot images. The actual skew angles of sample ballots, recorded as part of complete ballot descriptions compiled with the interactive ground-truthing tool, are compared with their automatically extracted parameters. The average error is 0.1 degrees. These results provide a baseline for the application of digital image analysis to the scrutiny of electoral ballots.


Evaluation Of Voting With Form Dropout Techniques For Ballot Vote Counting, Elisa H. Barney Smith, Shatakshi Goyal, Robbie Scott, Daniel Lopresti Sep 2011

Evaluation Of Voting With Form Dropout Techniques For Ballot Vote Counting, Elisa H. Barney Smith, Shatakshi Goyal, Robbie Scott, Daniel Lopresti

Electrical and Computer Engineering Faculty Publications and Presentations

Vote counting accuracy has become a well-known issue in the vote collection process. Digital image processing techniques can be incorporated in the analysis of printed election ballots. Current image processing techniques in the vote collection process are heavily dependent on the anticipated, geometric positioning of the vote. These techniques don’t account for markings made outside of the requested field of input. Using various form dropout techniques, however, every mark on the form can be extracted and used by the machine to make an intelligent decision. Most methods will still miss a few marks and result in a few false alarms. …


Wireless Sensor Network For Aircraft Cabin Environment Sensing, Joshua Kiepert, Sin Ming Loo, Derek Klein, Michael Pook Jul 2011

Wireless Sensor Network For Aircraft Cabin Environment Sensing, Joshua Kiepert, Sin Ming Loo, Derek Klein, Michael Pook

Electrical and Computer Engineering Faculty Publications and Presentations

Wireless sensor networks consist of physically distributed autonomous sensor nodes that cooperatively monitor physical or environmental conditions. One of the greatest benefits of wireless sensor networks is that they are capable of generating a more complete view of the sensed environment by acquiring larger quantities of correlated data than independent sensor monitors. The aircraft cabin is a highly dynamic environment which necessitates the use of more advanced sensing systems. It is with the motivation of painting a better picture of the aircraft cabin environment that such a wireless sensor network is being designed and prototyped. This paper discusses the design …


Survey Of Sensor Technology For Aircraft Cabin Environment Sensing, Derek Klein, Sin Ming Loo, Joshua Kiepert, Michael Pook, Jim Hall Jul 2011

Survey Of Sensor Technology For Aircraft Cabin Environment Sensing, Derek Klein, Sin Ming Loo, Joshua Kiepert, Michael Pook, Jim Hall

Electrical and Computer Engineering Faculty Publications and Presentations

The aircraft cabin environment is unique due to the proximity of the passengers, the need for cabin pressurization, and the low humidity. All of these aspects are complicated by the fact that the aircraft is a semi-enclosed structure. There is an increased desire to monitor the aircraft cabin environment with various sensors for comfort and safety. However, the aircraft cabin environment is composed of a large number of factors. Some of these factors can include air quality, temperature, level of pressurization, and motion of the aircraft. Therefore, many types of sensors must be used to monitor aircraft environments. A variety …


Striation-Based Beamforming For Estimating The Waveguide Invariant With Passive Sonar, Lisa M. Zurk, Daniel Rouseff Jul 2011

Striation-Based Beamforming For Estimating The Waveguide Invariant With Passive Sonar, Lisa M. Zurk, Daniel Rouseff

Electrical and Computer Engineering Faculty Publications and Presentations

The waveguide invariant summarizes the pattern of constructive and destructive interference between acoustic modes propagating in the ocean waveguide. For many sonar signal-processing schemes, it is essential to know the correct numerical value for the waveguide invariant. While conventional beamforming can estimate the ratio between the waveguide invariant and the range to the source, it cannot unambiguously separate the two terms. In the present work, striationbased beamforming is developed. It is shown that the striation-based beamformer can be used to produce an estimate for the waveguide invariant that is independent of the range. Simulation results are presented.


Redesign Of Freshman Electrical Engineering Courses For Improved Motivation And Early Introduction Of Design, Phillip Wong, Melinda Holtzman, Branimir Pejcinovic, Malgorzata Chrzanowska-Jeske Jun 2011

Redesign Of Freshman Electrical Engineering Courses For Improved Motivation And Early Introduction Of Design, Phillip Wong, Melinda Holtzman, Branimir Pejcinovic, Malgorzata Chrzanowska-Jeske

Electrical and Computer Engineering Faculty Publications and Presentations

The student experience during the freshman year has been recognized as one of the keys to not only attracting more students into engineering and improving retention, but also to forming some significant attributes of successful engineering graduates. Portland State University is an urban university, and its Electrical and Computer Engineering (ECE) department serves a relatively large and very diverse student population including a large fraction of transfer and part-time students. Traditionally, all engineering disciplines within our Maseeh College of Engineering and Computer Science had a similar freshman year curriculum. The common entry course – Engineering and Applied Science (EAS) 101 …


Hydrodynamic Modeling Of Surface Plasmon Enhanced Photon Induced Current In A Gold Grating, Alex English, Cheng-Wen Cheng, Lloyd Lowe Ii, Min-Hsiung Shih, Wan Kuang May 2011

Hydrodynamic Modeling Of Surface Plasmon Enhanced Photon Induced Current In A Gold Grating, Alex English, Cheng-Wen Cheng, Lloyd Lowe Ii, Min-Hsiung Shih, Wan Kuang

Electrical and Computer Engineering Faculty Publications and Presentations

The current induced by incident photons on an gold grating slab is investigated numerically and experimentally. A semi-classical electrodynamic model is developed under the weak nonlinearity approximation. Electrons in the conduction band are treated as an electron gas in the presence of a self-consistent electromagnetic field. The model is solved by the finite element method and compared with measurements. The calculated current density as a function of incident angle and wavelength is found to be in qualitative agreement with the experimental measurements. The results show that increasing surface plasmon spatial variation enhances photon induced current.


Terahertz Material Detection From Diffuse Surface Scattering, Scott Schecklman, Lisa M. Zurk, Samuel C. Henry, Gabriel Paul Kniffin May 2011

Terahertz Material Detection From Diffuse Surface Scattering, Scott Schecklman, Lisa M. Zurk, Samuel C. Henry, Gabriel Paul Kniffin

Electrical and Computer Engineering Faculty Publications and Presentations

The potential for terahertz (THz) spectroscopy to detect explosives and other materials of interest is complicated by rough surface scattering. Our previous work has demonstrated that by averaging over diffuse observation angles and surfaces, spectral features could be recovered from laboratory measurements and numerical computer simulations. In addition to averaging, a low-pass cepstrum filter was used to reduce noise due to the random rough surface. This paper expands on these concepts by using the cepstrum of both the random rough surface and the material properties of the target material to choose an optimal cutoff frequency for the filter. The utility …


Quantum Phase Estimation Using Multivalued Logic, Marek Perkowski, Vamsi Parasa May 2011

Quantum Phase Estimation Using Multivalued Logic, Marek Perkowski, Vamsi Parasa

Electrical and Computer Engineering Faculty Publications and Presentations

We generalize the Quantum Phase Estimation algorithm to MVL logic. We show the quantum circuits for QPE using qudits. We derive the performance requirements of the QPE to achieve high probability of success. We show how this leads to logarithmic decrease in the number of qudits and exponential decrease in error probability of the QPE algorithm as the value of the radix d increases.


Synthesis Of Reversible Synchronous Counters, Marek Perkowski, Mozammel H.A. Khan May 2011

Synthesis Of Reversible Synchronous Counters, Marek Perkowski, Mozammel H.A. Khan

Electrical and Computer Engineering Faculty Publications and Presentations

In this paper, we concentrate on design of synchronous counters directly from reversible gates.


Improved Complexity Of Quantum Oracles For Ternary Grover Algorithm For Graph Coloring, Marek Perkowski, Yushi Wang May 2011

Improved Complexity Of Quantum Oracles For Ternary Grover Algorithm For Graph Coloring, Marek Perkowski, Yushi Wang

Electrical and Computer Engineering Faculty Publications and Presentations

The Graph Coloring Grover Algorithm has several applications in logic synthesis, scheduling, allocation, planning, robot motion, robot communication, resource allocation, conflict resolution, floor-planning, and many others.

It can serve as a “generic CSP solver” similar to a general SAT solver.


Structural Study Of Ag-Ge-S Solid Electrolyte Glass System For Resistive Radiation Sensing, Ping Chen, Mahesh Ailavajhala, Maria I. Mitkova, Dmitri A. Tenne, Ivan Sanchez Esqueda, Hugh Barnaby Apr 2011

Structural Study Of Ag-Ge-S Solid Electrolyte Glass System For Resistive Radiation Sensing, Ping Chen, Mahesh Ailavajhala, Maria I. Mitkova, Dmitri A. Tenne, Ivan Sanchez Esqueda, Hugh Barnaby

Electrical and Computer Engineering Faculty Publications and Presentations

Solid electrolytes based on chalcogenide glasses have been one of the most promising candidates for the next generation non-volatile memories. Here we propose a new application of chalcogenide solid electrolytes for low cost, high performance microelectronic radiation sensor that reacts to γ-radiation to produce an easily measurable change in electrical resistance. The active layer material is Ag-doped GeS thin film glasses and several compositions of GeS base glasses were tested for best resistive sensing capability. Energy-dispersive X-ray spectroscopy (EDS) was used for elemental analysis and Raman scattering spectroscopy was measured to determine the structural details and radiation induced structural changes. …


Enhancement Of Historical Printed Document Images By Combining Total Variation Regularization And Non-Local Means Filtering, Laurence Likforman-Sulem, Jérôme Darbon, Elisa H. Barney Smith Apr 2011

Enhancement Of Historical Printed Document Images By Combining Total Variation Regularization And Non-Local Means Filtering, Laurence Likforman-Sulem, Jérôme Darbon, Elisa H. Barney Smith

Electrical and Computer Engineering Faculty Publications and Presentations

This paper proposes a novel method for document enhancement which combines two recent powerful noise-reduction steps. The first step is based on the total variation framework. It flattens background grey-levels and produces an intermediate image where background noise is considerably reduced. This image is used as a mask to produce an image with a cleaner background while keeping character details. The second step is applied to the cleaner image and consists of a filter based on non-local means: character edges are smoothed by searching for similar patch images in pixel neighborhoods. The document images to be enhanced are real historical …


Soft Error In Fpga-Implemented Asynchronous Circuits, Weidong Kuang, Yu Bai Apr 2011

Soft Error In Fpga-Implemented Asynchronous Circuits, Weidong Kuang, Yu Bai

Electrical and Computer Engineering Faculty Publications and Presentations

In this paper, we investigate the mechanism of soft error generation and propagation in asynchronous circuits which are implemented on FPGAs. The effects of the soft errors on Quasi-delay-insensitive (QDI) asynchronous circuits are analyzed. The results show that it is much easier to detect the soft error in asynchronous circuits implemented on FPGAs so that FPGAs can be reprogrammed, compared with traditional synchronous circuits.


Synthesis Of Quantum Circuits In Linear Nearest Neighbor Model Using Positive Davio Lattices, Marek Perkowski, Martin Lukac, Dipal Shah, Michitaka Kameyama Apr 2011

Synthesis Of Quantum Circuits In Linear Nearest Neighbor Model Using Positive Davio Lattices, Marek Perkowski, Martin Lukac, Dipal Shah, Michitaka Kameyama

Electrical and Computer Engineering Faculty Publications and Presentations

We present a logic synthesis method based on lattices that realize quantum arrays in One-Dimensional Ion Trap technology. This means that all gates are built from 2x2 quantum primitives that are located only on neighbor qubits in a onedimensional space (called also vector of qubits or Linear Nearest Neighbor (LNN) architecture). The Logic circuits designed by the proposed method are realized only with 3*3 Toffoli, Feynman and NOT quantum gates and the usage of the commonly used multi-input Toffoli gates is avoided. This realization method of quantum circuits is different from most of reversible circuits synthesis methods from the literature …


Modal Logic And Its Applications, Explained Using Puzzles And Examples, Marek Perkowski Mar 2011

Modal Logic And Its Applications, Explained Using Puzzles And Examples, Marek Perkowski

Electrical and Computer Engineering Faculty Publications and Presentations

1.We shall be concerned, at first, with alethicmodal logic, or modal logic tout court. 2.The starting point, once again, is Aristotle, who was the first to study the relationship between modal statements and their validity. 3.However, the great discussion it enjoyed in the Middle Ages. 4.The official birth date of modal logic is 1921, when Clarence Irving Lewis wrote a famous essay on implication.


A Faceted Magnetron Concept Using Field Emission Cathodes, Jim Browning, Jack Watrous Mar 2011

A Faceted Magnetron Concept Using Field Emission Cathodes, Jim Browning, Jack Watrous

Electrical and Computer Engineering Faculty Publications and Presentations

A magnetron concept using field emission cathodes has been modeled with the Air Force Research Laboratory particle-in-cell code ICEPIC and the 2D particle trajectory simulation Lorentz2E. In this approach, field emitters are used to provide a distributed cathode in place of a traditional thermionic cathode. The emitters are placed below the interaction space in a shielded structure. The cathode is comprised of facet plates with slits to protect the emitters. Simulation of an L-band rising sun magnetron shows that the faceted magnetron will oscillate using both five and ten facet cathodes. The startup times are very similar to that of …


Characterizing Challenged Minnesota Ballots, George Nagy, Daniel Lopresti, Elisa H. Barney Smith, Ziyan Wu Jan 2011

Characterizing Challenged Minnesota Ballots, George Nagy, Daniel Lopresti, Elisa H. Barney Smith, Ziyan Wu

Electrical and Computer Engineering Faculty Publications and Presentations

Photocopies of the ballots challenged in the 2008 Minnesota elections, which constitute a public record, were scanned on a high-speed scanner and made available on a public radio website. The PDF files were downloaded, converted to TIF images, and posted on the PERFECT website. Based on a review of relevant image-processing aspects of paper-based election machinery and on additional statistics and observations on the posted sample data, robust tools were developed for determining the underlying grid of the targets on these ballots regardless of skew, clipping, and other degradations caused by high-speed copying and digitization. The accuracy and robustness of …


A Mask-Based Enhancement Method For Historical Documents, Elisa H. Barney Smith, Jerôme Darbon, Laurence Likforman-Sulem Jan 2011

A Mask-Based Enhancement Method For Historical Documents, Elisa H. Barney Smith, Jerôme Darbon, Laurence Likforman-Sulem

Electrical and Computer Engineering Faculty Publications and Presentations

This paper proposes a novel method for document enhancement. The method is based on the combination of two state-of-the-art filters through the construction of a mask. The mask is applied to a TV (Total Variation) -regularized image where background noise has been reduced. The masked image is then filtered by NLmeans (Non-Local Means) which reduces the noise in the text areas located by the mask. The document images to be enhanced are real historical documents from several periods which include several defects in their background. These defects result from scanning, paper aging and bleed-through. We observe the improvement of this …


Descreening Of Color Halftone Images In The Frequency Domain, C. J. Stanger, Thanh Tran, Elisa H. Barney Smith Jan 2011

Descreening Of Color Halftone Images In The Frequency Domain, C. J. Stanger, Thanh Tran, Elisa H. Barney Smith

Electrical and Computer Engineering Faculty Publications and Presentations

Scanning a halftone image introduces halftone artifacts, known as Moiré patterns, which significantly degrade the image quality. Printers that use amplitude modulation (AM) screening for halftone printing position dots in a periodic pattern. Therefore, frequencies relating halftoning are easily identifiable in the frequency domain. This paper proposes a method for descreening scanned color halftone images using a custom band reject filter designed to isolate and remove only the frequencies related to halftoning while leaving image edges sharp without image segmentation or edge detection. To enable hardware acceleration, the image is processed in small overlapped windows. The windows are filtered individually …


Electron Hop Funnel Measurements And Comparison With The Lorentz-2e Simulation, Charles Lester, Jim Browning, Lael Matthews Jan 2011

Electron Hop Funnel Measurements And Comparison With The Lorentz-2e Simulation, Charles Lester, Jim Browning, Lael Matthews

Electrical and Computer Engineering Faculty Publications and Presentations

Electron hop funnels have been fabricated using a Low Temperature Co-Fired Ceramic (LTCC). Measurements of the hop funnel I-V curve and electron energy distribution have been made using gated field emitters as the electron source. The charged particle simulation Lorentz 2E has been used to model the hop funnel charging and to predict the I-V and energy characteristics. The results of this comparison indicate that the simulation can be used to design hop funnel structures for use in various applications.


Elimination Theory For Nonlinear Parameter Estimation, John Chiasson, Ahmed Oteafy Jan 2011

Elimination Theory For Nonlinear Parameter Estimation, John Chiasson, Ahmed Oteafy

Electrical and Computer Engineering Faculty Publications and Presentations

The work presented here exploits elimination theory (solving systems of polynomial equations in several variables) [1][2] to perform nonlinear parameter identification. In particular show how this technique can be used to estimate the rotor time constant and the stator resistance values of an induction machine. Although the example here is restricted to an induction machine, parameter estimation is applicable to many practical engineering problems. In [3], L. Ljung has outlined many of the challenges of nonlinear system identification as well as its particular importance for biological systems. In these types of problems, the model developed for analysis is typically a …


Development Of Dna Based Active Macro-Materials For Biology And Medicine: A Review, Frank Xue Jiang, Bernard Yurke, Devendra Verma, Michelle Previtera, Rene Schloss, Noshir A. Langrana Jan 2011

Development Of Dna Based Active Macro-Materials For Biology And Medicine: A Review, Frank Xue Jiang, Bernard Yurke, Devendra Verma, Michelle Previtera, Rene Schloss, Noshir A. Langrana

Electrical and Computer Engineering Faculty Publications and Presentations

DNA was first discovered as the carrier of genetic information for the majority of the known living organisms, encoding the secret of life. Its delicate design based upon double helical structure and base pairing offers a stable and reliable media for storing hereditary codes, laying the foundation for the central dogma (Watson et al. 2003). The impact of this molecule is far reaching into scientific community and our society, as manifested in many fields, for instance, forensics (Budowle et al. 2003), besides medicine. To date, a great deal of research effort has been directed towards understanding


Extraction Of Small Boat Harmonic Signatures From Passive Sonar, George Lloyd Ogden, Lisa M. Zurk, M. E. Jones, M. E. Peterson Jan 2011

Extraction Of Small Boat Harmonic Signatures From Passive Sonar, George Lloyd Ogden, Lisa M. Zurk, M. E. Jones, M. E. Peterson

Electrical and Computer Engineering Faculty Publications and Presentations

This paper investigates the extraction of acoustic signatures from small boats using a passive sonar system. Noise radiated from a small boats consists of broadband noise and harmonically related tones that correspond to engine and propeller specifications. A signal processing method to automatically extract the harmonic structure of noise radiated from small boats is developed. The Harmonic Extraction and Analysis Tool (HEAT) estimates the instantaneous fundamental frequency of the harmonic tones, refines the fundamental frequency estimate using a Kalman filter, and automatically extracts the amplitudes of the harmonic tonals to generate a harmonic signature for the boat. Results are presented …


Edge Noise Removal In Bilevel Graphical Document Images Using Sparse Representation, Thai V. Hoang, Elisa Barney Smith, Salvatore Tabbone Jan 2011

Edge Noise Removal In Bilevel Graphical Document Images Using Sparse Representation, Thai V. Hoang, Elisa Barney Smith, Salvatore Tabbone

Electrical and Computer Engineering Faculty Publications and Presentations

A new parametric method for edge noise removal in graphical document images is presented using geometrical regularities of the graphics contours that exists in the images. Denoising is understood as a recovery problem and is done by employing a sparse representation framework with a basis pursuit denoising algorithm for denoising and curvelet frames for encoding directional information of the graphics contours. The optimal precision parameter used in this framework is shown to have linear relationship with the level of the noise. Experimental results show the superiority of the proposed method over existing ones in terms of image recovery and contour …


Quantitative Carré Differential Interference Contrast Microscopy To Assess Phase And Amplitude, Donald D. Duncan, David G. Fischer, Amanda Dayton, Scott A. Prahl Jan 2011

Quantitative Carré Differential Interference Contrast Microscopy To Assess Phase And Amplitude, Donald D. Duncan, David G. Fischer, Amanda Dayton, Scott A. Prahl

Electrical and Computer Engineering Faculty Publications and Presentations

We present a method of using an unmodified differential interference contrast microscope to acquire quantitative information on scatter and absorption of thin tissue samples. A simple calibration process is discussed that uses a standard optical wedge. Subsequently, we present a phase-stepping procedure for acquiring phase gradient information exclusive of absorption effects. The procedure results in two-dimensional maps of the local angular (polar and azimuthal) ray deviation. We demonstrate the calibration process, discuss details of the phase-stepping algorithm, and present representative results for a porcine skin sample.