{"id":3506,"date":"2019-05-23T14:30:03","date_gmt":"2019-05-23T14:30:03","guid":{"rendered":"https:\/\/labsites.wdev.rochester.edu\/fienup\/?page_id=3506"},"modified":"2019-06-06T12:57:04","modified_gmt":"2019-06-06T12:57:04","slug":"lensless-coherent-imaging","status":"publish","type":"page","link":"https:\/\/labsites.rochester.edu\/fienup\/research\/lensless-coherent-imaging\/","title":{"rendered":"Lensless Coherent Imaging"},"content":{"rendered":"\n

Manuel Guizar-Sicairos’ Research<\/h2>\n\n\n\n

Phase retrieval for x-ray coherent lensless imaging<\/h3>\n\n\n\n

Application of phase retrieval algorithms is a very active area of research for lensless imaging at x-ray wavelengths. The small wavelength and high penetration depth of x-rays makes them very attractive for high resolution imaging (on the order of a few nanometers) of biological and material science specimens. However, the difficulty in fabricating good quality focusing optics for these wavelengths limits the application of conventional imaging.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The image above shows an example implementation of coherent lensless \nimaging (also known as coherent diffractive imaging). A coherent \nmonochromatic plane-wave, limited by an aperture, is incident on an \nobject of interest (image of rodent courtesy of brainmaps.org<\/a>). The field transmitted by the object propagates in free space and is measured by a detector array (typically a CCD detector). <\/p>\n\n\n\n

Through this measurement we directly obtain the field intensity, \nbut in order to reconstruct an image one must also recover the phase of \nthis field. The measured intensity pattern is fed to an iterative phase \nretrieval algorithm (along with a set of constraints on the object) to \nrecover the phase associated with the measured intensity and \ncomputationally reconstruct a diffraction-limited image. In this sense, \nphase retrieval algorithms are used as computational lenses.<\/p>\n\n\n\n

My research is mainly focused on the development and testing of new phase retrieval and image reconstruction algorithms.<\/p>\n\n\n\n

Holography with a boundary-wave reference using HERALDO<\/h3>\n\n\n\n

\n\t\t Holography with extended reference by autocorrelation linear \ndifferential operation (HERALDO) is a non-iterative coherent lensless \nimaging technique that allows using the boundary-wave from a sharp \nfeature on an extended reference as a holographic-like reference wave.<\/p>\n\n\n\n

HERALDO, a generalization of an earlier approach by S. G. Podorov\n et al. and Fourier transform holography, can reconstruct the \ncomplex-valued transmissivity of an object in a non-iterative fashion \nthrough the application of a set of derivatives on the field \nautocorrelation.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The image above shows an example setup for reconstruction using \nHERALDO. The object is flood illuminated and a sharp tip is inserted in \nthe path of the beam. The far-field intensity pattern is measured with a\n detector array. The reconstructed image is directly computed from the \nfar-field intensity.<\/p>\n\n\n\n

This approach is robust to noise and is fast and simple to \nimplement. We continue investigating experimental scenarios and sample \ngeometries for which using HERALDO is advantageous compared to other \nlensless imaging techniques. <\/p>\n\n\n\n

Click here for Manuel’s Homepage<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Manuel Guizar-Sicairos’ Research Phase retrieval for x-ray coherent lensless imaging Application of phase retrieval algorithms is a very active area of research for lensless imaging at x-ray wavelengths. The small wavelength and high penetration depth of x-rays makes them very attractive for high resolution imaging (on the order of a few nanometers) of biological and … <\/p>\n

Continue reading “Lensless Coherent Imaging”<\/span><\/a><\/p>\n","protected":false},"author":0,"featured_media":0,"parent":3436,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-3506","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/labsites.rochester.edu\/fienup\/wp-json\/wp\/v2\/pages\/3506","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/labsites.rochester.edu\/fienup\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/labsites.rochester.edu\/fienup\/wp-json\/wp\/v2\/types\/page"}],"replies":[{"embeddable":true,"href":"https:\/\/labsites.rochester.edu\/fienup\/wp-json\/wp\/v2\/comments?post=3506"}],"version-history":[{"count":3,"href":"https:\/\/labsites.rochester.edu\/fienup\/wp-json\/wp\/v2\/pages\/3506\/revisions"}],"predecessor-version":[{"id":4856,"href":"https:\/\/labsites.rochester.edu\/fienup\/wp-json\/wp\/v2\/pages\/3506\/revisions\/4856"}],"up":[{"embeddable":true,"href":"https:\/\/labsites.rochester.edu\/fienup\/wp-json\/wp\/v2\/pages\/3436"}],"wp:attachment":[{"href":"https:\/\/labsites.rochester.edu\/fienup\/wp-json\/wp\/v2\/media?parent=3506"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}