Phase Retrieval with Application to Intensity Correlation Interferometers

Phase Retrieval with Application to Intensity Correlation Interferometers
Author: Russell Edward Trahan
Publisher:
Total Pages: 92
Release: 2013
Genre:
ISBN:

As astronomers and astrophysicists seek to view ever-increasingly distant celestial objects, the desired angular resolution of telescopes is constantly being increased. Classical optics, however, has shown a proportional relationship between the size of an optical telescope and the possible angular resolution. Experience has also shown that prohibitive cost accompanies large optical systems. With these limitations on classical optical systems and with the drastic increase in computational power over the past decade, intensity correlation interferometry (ICI) has seen renewed interest since the 1950's and 60's when it was initially conceived by Hanbury Brown and Twiss. Intensity correlation interferometry has the advantage of less stringent equipment precision and less equipment cost when compared to most other forms of interferometry. ICI is thus attractive as a solution to the desire for high angular resolution imaging especially in space based imaging systems. Optical interferometry works by gathering information about the Fourier transform of the geometry of an optical source. An ICI system, however, can only detect the magnitude of the Fourier components. The phase of the Fourier components must be recovered through some computational means and typically some a priori knowledge of the optical source. This thesis gives the physics and mathematical basis of the intensity correlation interferometer. Since the ICI system cannot detect the phase of an optical source's Fourier transform, some known methods for recovering the phase information are discussed. The primary method of interest here is the error-reduction algorithm by Gerchberg-Saxton which was adapted by Fienup to phase retrieval. This algorithm works by using known qualities of the image as constraints; however, sometimes it can be difficult to know what these constraints are supposed to be. A method of adaptively discovering these constraints is presented, and its performance is evaluated in the presence of noise. Additionally, an algorithm is presented to adapt to the presence of noise in the Fourier modulus data. Finally, the effects of the initial condition of the error-reduction algorithm are shown and a method of mitigating its effect by averaging several independent solutions together is shown. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148155

Phase Estimation in Optical Interferometry

Phase Estimation in Optical Interferometry
Author: Pramod Rastogi
Publisher: CRC Press
Total Pages: 364
Release: 2014-11-21
Genre: Science
ISBN: 1466598328

This book covers the essentials of phase-stepping algorithms used in interferometry and pseudointerferometric techniques. It presents the basic concepts and mathematics needed for understanding modern phase estimation methods. The book first focuses on phase retrieval from image transforms using a single frame. It then examines the local environment of a fringe pattern, the phase estimation approach based on local polynomial phase modeling, temporal high-resolution phase evaluation methods, and methods of phase unwrapping. It also discusses experimental imperfections liable to adversely influence the accuracy of phase measurements.

Advanced theory of optical wave propagation and interferometric sensors for topography measurement

Advanced theory of optical wave propagation and interferometric sensors for topography measurement
Author: Markus C. Schake
Publisher: BoD – Books on Demand
Total Pages: 182
Release: 2014-01-01
Genre: Technology & Engineering
ISBN: 3737608407

This manuscript provides a compendium for the application of the nonuniform wave model to standard problems of two beam interference and addresses common educational issues associated with wave propagation at attenuating interfaces. It also reports scientific advances in interferometric applications focusing on an interferometric point sensor with optical path length modulation and an areal measuring RGB-interferometer for fast topography measurements in the sub millisecond regime.

Iterative Phase Estimation Algorithms in Interferometric Systems

Iterative Phase Estimation Algorithms in Interferometric Systems
Author: Wesley E. Farriss
Publisher:
Total Pages: 191
Release: 2021
Genre:
ISBN:

"Coherent optical interferometry has a long history of enabling extremely precise measurements at length scales of less than the wavelength of light used in the interferometer. It is the ability of these systems to measure both the relative phase and amplitude information of the optical field that makes them so useful. As the name would imply, measuring phase and amplitude is accomplished by interfering two or more beams of light. Interferometric techniques have been adopted for use in both imaging/sensing technologies. For imaging systems under ideal conditions, the ability to measure both phase and amplitude information in one transverse plane allows for the calculation of that field's phase and amplitude distribution in any other transverse plane. However, the presence of atmospheric turbulence unpredictably alters the index of refraction in the propagation medium thereby adversely affecting the reliability of calculation of phase and amplitude in other transverse planes. To address this problem, we demonstrate iterative sharpness maximization (ISM) correction of anisoplanatic turbulence effects in simulated range-compressed holography (RCH) fields and their corresponding range images. Our turbulence correction estimated four phase screens placed along the path of optical propagation using nonlinear optimizations aided by the method of sieves technique. We conducted a study of range images created from simulated single speckle realization 3D RCH fields subjected to twenty different turbulence profiles at five different strengths of turbulence, D/r0 = 7, 14, 21, 28, and 36. Range images showed significant improvement for all strengths of turbulence. To assist in correction, we introduced a novel constraint limiting the spread of energy in the corrected pupil. Corrected range images were qualitatively very similar to unaberrated range images in all but the most severe turbulence case, D/r0 = 36. Additionally, our algorithm was tested for fields affected by shot noise. Mean target photons per speckle ranged from 10 -2 to 10 2 in these simulations. For an effective D/r0 = 36, range images corrected from fields with 102 mean photons per speckle had very similar RMSE when compared to corrected noiseless range images. On average, corrected range images created from fields with 1 mean target photon per speckle differed by less than 5% RMSE from noiseless corrected range images. We went on to construct a RCH system in a laboratory setting using a linear frequency modulated CW laser and a high frame rate camera which allowed us to create 3D images of laboratory targets. Data was collected both with and without the effects of turbulence. In the former, multiple Lexitek turbulence screens were used to aberrate the image fields of our lab target at two different effective strengths of anisoplanatic turbulence, D/r0 = 7 and D/r0 = 16, respectively. Both of these sets of real aberrated image fields showed profound improvement in quality after correction with our phase ISM turbulence mitigation algorithm. Novel interferometric systems are also being developed which enable modal analysis of an optical field. This generalized optical interferometry (GOI) treats coherent optical fields as a linear superposition of transverse modes and recovers the amplitudes of modal weighting coefficients. In order to maximize the utility of these systems, we used phase retrieval by nonlinear optimization to recover the phase of these modal weighting coefficients. Algorithms were developed both for use with an array detector and for use with a bucket detector. Information diversity increased the robustness of both algorithms by better constraining the solutions. In our array detection phase retrieval, the algorithm was able to recover nearly all coefficient phases for simulated fields consisting of up to 21 superpositioned Hermite Gaussian modes from simulated data and proved to be resilient to shot noise. Similarly, the algorithm we developed using data from a simulated bucket detector was able to consistently recover better than 95% of coefficient phases for simulated random fields consisting of up to 21 superpositioned Hermite Gaussian modes using between three and seven measurements per unknown phase coefficient. With shot noise, the algorithm achieved performance on par with noiseless simulations with 106 mean signal photons per measurement. The role played by number of measurements per unknown (mpu), photons per unknown per measurement (ppu), and order of superposition in the bucket detection algorithm's performance was also explored"--Pages xvi-xix

Phase Retrieval Using an Imaging Sensor

Phase Retrieval Using an Imaging Sensor
Author: Charles V. Scull
Publisher:
Total Pages: 66
Release: 1979
Genre:
ISBN:

This research study is concerned with spatial (relative) phase reconstruction using an imaging sensor. Specifically, work was completed which investigates the retrieval of the spatial phase of the aperture wavefront from sampled intensity data in the focal plane of an imaging sensor, where phase is not explicitly present. Techniques investigated are not interferometric methods, but are signal processing techniques that use the Fourier transform properties of a lens, analytics, and numerics to retrieve the spatial phase of the aperture field from intensity measurements in the focal plane of an imaging sensor. The techniques investigated include an analytic approach which is used to develop several numerical approaches, and the Gerchberg-Saxton Algorithm which is adapted to solve this specific phase retrieval problem. Finally, the results from simulations of these methods are compared yielding the Gerchberg-Saxton Algorithm as the most promising method to approximate the relative phase in the aperture plane. (Author).

PHASE RETRIEVAL FROM TWO DEFOCUSED IMAGES BY THE TRANSPORT OF INTENSITY EQUATION FORMALISM WITH FAST FOURIER TRANSFORM.

PHASE RETRIEVAL FROM TWO DEFOCUSED IMAGES BY THE TRANSPORT OF INTENSITY EQUATION FORMALISM WITH FAST FOURIER TRANSFORM.
Author:
Publisher:
Total Pages:
Release: 2001
Genre:
ISBN:

The problem of phase retrieval from intensity measurements plays an important role in many fields of physical research, e.g. optics, electron and x-ray microscopy, crystallography, diffraction tomography and others. In practice the recorded images contain information only on the intensity distribution I(x, y)=[Psi]*[Psi]=[vert-bar]A[vert-bar][sup 2] of the imaging wave function[Psi]= A*exp( -i[var-phi]) and the phase information[var-phi](x, y) is usually lost. In general, the phase problem can be solved either by special holographic/interferometric methods, or by non-interferometric approaches based on intensity measurements in far Fraunhofer zone or in the Fresnel zone at two adjacent planes orthogonal to the optical axis. The latter approach uses the transport-of-intensity equation (TIE) formalism, introduced originally by Teague[1] and developed later in[2]. Applications of TIE to nonmagnetic materials and magnetic inductance mapping were successfully made in[3,4]. However, this approach still needs further improvement both in mathematics and in practical solutions, since the result is very sensitive to many experimental parameters.

Interferometry in Speckle Light

Interferometry in Speckle Light
Author: Pierre Jacquot
Publisher: Springer Science & Business Media
Total Pages: 684
Release: 2000
Genre: Medical
ISBN: 9783540679431

The Proceedings contain state-of-the-art reviews and original materials related to up-to-date developments in a wide range of optical control methods. They are devoted in particular to shape, displacement and deformation measurement, strain analysis, mechanical behavior evaluation, inspection and non-destructive testing. Three principal classes of methods are under consideration: speckle photography, holographic interferometry and speckle interferometry. Both the state-of-the-art practices and the actual leading-edge techniques are discussed within a single volume, with reference to theoretical backgrounds common to all methods. Usually, similar information is distributed over many specialised works. The book presents both conceptual and practical aspects: theoretical considerations are fully analysed and applications illustrate the emphasis on many experimental aspects.