Fourier ptychography
Fourier ptychography is a
Each image is acquired under the illumination of a coherent light source at various angles of incidence (typically from an array of LEDs); the acquired image set is then combined using an iterative phase retrieval algorithm into a final high-resolution image that can contain up to a billion pixels (a gigapixel) with
Fourier ptychography reconstructs the complex image of the object (with quantitative phase information), but contrary to holography, it is a non-interferometric imaging technique and thus often easier to implement.
The name "ptychography" comes from the ancient Greek word πτυχή ("to fold", also found in the word triptych), because the technique is based on multiple "views" of the object.
Image reconstruction algorithms
The image reconstruction algorithms are based on iterative
Advantages
Fourier ptychography can be easily implemented on a conventional optical microscope by replacing the illumination source by an array of LED and improve the optical resolution by a factor 2 (with only bright-field illumination) or more (when including dark-field images to the reconstruction.)
A major advantage of Fourier ptychography is the ability to use a microscope objective with a lower numerical aperture without sacrificing the resolution. The use of a lower numerical aperture allows for larger field of view, larger depth of focus, and larger working distance. Moreover, it enables effective numerical aperture larger than 1 without resorting to oil immersion.[10]
Relation to ptychography
Contrary to Fourier ptychography, (conventional) ptychography swaps the role of the focus element, from an objective to become a condenser, and relies on the acquisition of diffractograms with illumination position diversity. However, the two techniques are both based on the determination of the angular spectrum of the object through a phase retrieval procedure,[11] and inherently reconstruct the same information. Therefore, Fourier ptychography and conventional ptychography provides a bridge between
See also
References
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G. Zheng, R. Horstmeyer and C. Yang (2013). "Wide-field, high-resolution Fourier ptychographic microscopy". Nature Photonics. 7 (9): 739–745. PMID 25243016.
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