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James Fienup - University of Rochester. Rochester, NY, US

James Fienup

Robert E. Hopkins Professor of Optics, Professor of Electrical and Computer Engineering, and Professor in the Center for Visual Science | University of Rochester


Fienup is a leading expert in the use of phase retrieval algorithms to carefully align mirrors on NASA satellites once they are in orbit.

Areas of Expertise (10)


Webb Telescope

Imaging with Sparse and Segmented-Aperture Systems

Image Reconstruction

Phase Retrieval

Imaging Science

Unconventional Imaging

Wavefront Sensing

Synthetic-Aperture and Pupil-Plane Active Imaging Systems

James Webb Space Telescope



James Fienup Publication James Fienup Publication James Fienup Publication James Fienup Publication






James R. Fienup is the Robert E. Hopkins Professor of Optics at the Institute of Optics. His research area is imaging science, including phase retrieval, unconventional imaging, image reconstruction, wavefront sensing, imaging with sparse and segmented-aperture systems, and synthetic-aperture and pupil-plane active imaging systems.

Education (2)

Stanford University: PhD, Applied Physics 1975

Stanford University: MS, Applied Physics 1972

Selected Media Appearances (2)

James Webb Space Telescope will rely on Fienup’s algorithms to see clearly

University of Rochester  online


A memorable scene from the movie Apollo 13 shows three astronauts being relentlessly bounced and jostled during their launch. Imagine what all that bouncing does to a finely tuned space telescope when it is lifted off a launch pad! Especially if the telescope is as complicated as the James Webb Space Telescope (JWST). It will be packaged like a table with folding ends for its launch two years from now, then unfolded once it is in orbit—at which time 18 individual hexagonal shaped mirrors will need to be carefully aligned to nanoscale tolerances to deliver sharp images.

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25 years later: Fixing the Hubble Space Telescope

University of Rochester  online


Twenty-five years ago today, the Hubble Space Telescope was launched. The images it has been sending back to Earth for all these years have become iconic, and yet it came very close to being a billion dollar failure. One of the heroes who rescued Hubble from ruin and made it a great science success story is Duncan Moore, Rudolf and Hilda Kingslake Professor of Optical Engineering at the University of Rochester.

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Selected Articles (2)

Phase Retrieval Algorithms: A Comparision

Applied Optics

James Fienup


Iterative algorithms for phase retrieval from intensity data are compared to gradient search methods. Both the problem of phase retrieval from two intensity measurements (in electron microscopy or wave front sensing) and the problem of phase retrieval from a single intensity measurement plus a non-negativity constraint (in astronomy) are considered, with emphasis on the latter. It is shown that both the error-reduction algorithm for the problem of a single intensity measurement and the Gerchberg-Saxton algorithm for the problem of two intensity measurements converge. The error-reduction algorithm is also shown to be closely related to the steepest-descent method. Other algorithms, including the input–output algorithm and the conjugate-gradient method, are shown to converge in practice much faster than the error-reduction algorithm.

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Direct-detection synthetic-aperture coherent imaging by phase retrieval


James Fienup


This paper describes a way to synthesize a larger coherent aperture from smaller apertures combined with motion, when only intensities are measured. It relies on collecting intensity patterns in two planes for each aperture, for example, the aperture plane and an image plane, and using a phase-retrieval algorithm to reconstruct the optical field in the aperture plane. As the sensor moves forward, a larger two-dimensional aperture is synthesized, allowing a much finer resolution image to be reconstructed. An algorithm to correct for the relative pointing (tip and tilt phases) and piston errors between different apertures and at different times is needed to phase up the synthetic aperture. Results of simulations, including the effects of speckle, are shown, and practical considerations are evaluated.

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