A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

We report an imaging method, termed Fourier ptychographic microscopy (FPM), which iteratively stitches together a
number of variably illuminated, low-resolution intensity images in Fourier space to produce a wide-field, high-resolution
complex sample image. By adopting a wavefront correction strategy, the FPM method can also correct for aberrations and
digitally extend a microscope’s depth of focus beyond the physical limitations of its optics. As a demonstration, we built a
microscope prototype with a resolution of 0.78 µm, a field of view of ∼120 mm^2 and a resolution-invariant depth of focus
of 0.3 mm (characterized at 632 nm). Gigapixel colour images of histology slides verify successful FPM operation. The
reported imaging procedure transforms the general challenge of high-throughput, high-resolution microscopy from one
that is coupled to the physical limitations of the system’s optics to one that is solvable through computation.

Wide-field, high-resolution Fourier ptychographic microscopy

A self-scanned 1024 element photodiode array and minicomputer are used to measure the phase (wavefront) in the interference pattern of an interferometer to lambda/100. The photodiode array samples intensities over a 32 x 32 matrix in the interference pattern as the length of the reference arm is varied piezoelectrically. Using these data the minicomputer synchronously detects the phase at each of the 1024 points by a Fourier series method and displays the wavefront in contour and perspective plot on a storage oscilloscope in less than 1 min (Bruning et al. Paper WE16, OSA Annual Meeting, Oct. 1972). The array of intensities is sampled and averaged many times in a random fashion so that the effects of air turbulence, vibrations, and thermal drifts are minimized. Very significant is the fact that wavefront errors in the interferometer are easily determined and may be automatically subtracted from current or subsequent wavefrots. Various programs supporting the measurement system include software for determining the aperture boundary, sum and difference of wavefronts, removal or insertion of tilt and focus errors, and routines for spatial manipulation of wavefronts. FFT programs transform wavefront data into point spread function and modulus and phase of the optical transfer function of lenses. Display programs plot these functions in contour and perspective. The system has been designed to optimize the collection of data to give higher than usual accuracy in measuring the individual elements and final performance of assembled diffraction limited optical systems, and furthermore, the short loop time of a few minutes makes the system an attractive alternative to constraints imposed by test glasses in the optical shop.

Digital wavefront measuring interferometer for testing optical surfaces and lenses

Have you ever felt that the very title, Progress in Optics, conjured an image in your mind? Don’t you see a row of handsomely printed books, bearing the editorial stamp of one of the most brilliant members of the optics community, and chronicling the field of optics since the invention of the laser? If so, you are certain to move the bookend to make room for Volume 16, the latest of this series. It contains seven chapters on widely diverging topics, written by well-known authorities in their fields. These are: 1) Laser Selective Photophysics and Photochemistry by V. S. Letokhov, 2) Recent Advances in Phase Profiles (sic) Generation by J. J. Clair and C. I. Abitbol, 3 ) Computer-Generated Holograms: Techniques and Applications by W.-H. Lee, 4) Speckle Interferometry by A. E. Ennos, 5 ) Deformation  Invariant, Space-Variant Optical  Pattern Recognition by D. Casasent and D. Psaltis, 6) Light Emission from High-Current Surface-Spark Discharges by R. E. Beverly, and 7) Semiclassical Radiation  Theory within a  QuantumMechanical Framework by I. R. Senitzkt. The  breadth of topic  matter  spanned  by  these  chapters makes it impossible, for this reviewer at least, to pass judgement on the comprehensiveness, relevance, and completeness of every chapter. With an editorial board as prominent as that of Progress in Optics, however, it seems hardly likely that such comments should be necessary. It should certainly be possible to take the authority of each author as credible. The only remaining judgment to be  made on these chapters is their readability. In short, what are they like to read? The first sentence of the first chapter greets the eye with an obvious typographical error: “The creation of coherent laser light source, that have tunable radiation, opened the . . . .” Two pages later we find: “When two types of atoms or molecules of different isotopic composition ( A and B ) have even one spectral line that does not overlap with others, it is pos-

Progress in optics

Quantitative phase imaging (QPI) has emerged as a valuable method for investigating cells and tissues. QPI operates on unlabelled specimens and, as such, is complementary to established fluorescence microscopy, exhibiting lower phototoxicity and no photobleaching. As the images represent quantitative maps of optical path length delays introduced by the specimen, QPI provides an objective measure of morphology and dynamics, free of variability due to contrast agents. Owing to the tremendous progress witnessed especially in the past 10–15 years, a number of technologies have become sufficiently reliable and translated to biomedical laboratories. Commercialization efforts are under way and, as a result, the QPI field is now transitioning from a technology-development-driven to an application-focused field. In this Review, we aim to provide a critical and objective overview of this dynamic research field by presenting the scientific context, main principles of operation and current biomedical applications. Over the past 10–15 years, quantitative phase imaging has moved from a research-driven to an application-focused field. This Review presents the main principles of operation and representative basic and clinical science applications.

Quantitative phase imaging in biomedicine

We report on a novel layout capable of dual-mode imaging in real time with different magnifications and resolution capabilities in lensless microscopy. The concept is based on wavelength multiplexing for providing two illuminations with different wavefront curvatures: one is collimated, allowing a large field of view (FOV) with a poor resolution limit, and the other is divergent, to achieve a better resolution limit (micron range) over a small FOV. Moreover, our recently reported concept of MISHELF microscopy [M. Sanz, J. A. Picazo-Bueno, L. Granero, J. Garcia and V. Mico, Sci. Rep., 2017, 7, 43291] is applied to the divergent illumination case, improving the image quality by noise averaging and twin image minimization. The performance of this novel dual-mode lensless microscopy imaging platform is validated through experiments using both static amplitude (resolution test targets) and dynamic complex (flowing microbeads and live sperm cells) samples. The proposed imaging platform represents the background technology for a new generation of lensless microscopes with improved performance and capabilities.

Dual-mode holographic microscopy imaging platform.

Recently proposed lensless object scanning holography (LOSH) [Opt. Express20, 9382 (2012)] is a fully lensless method capable of improving the image quality in digital Fourier holography applied to one-dimensional (1D) reflective objects and it involves a very simplified experimental setup. LOSH is based on the recording and digital postprocessing of a set of digital lensless Fourier transform holograms, which finally results in a synthetic image with improved resolution, field-of-view (FOV), signal-to-noise ratio (SNR), and depth of field. In this paper, LOSH is extended to the cases of two-dimensional (2D) mirror-like and 1D diffuse-based objects. For 2D mirror-like objects, the experimental results show an impressive image quality improvement over a factor of 3 in FOV, SNR, and resolution, as good as that obtained for the 1D case but in two dimensions. For 1D diffuse-based objects, in general the speckle affects the image resolution, which will not be only a function of the aperture size. In this case, increasing the aperture produces a decrease of the speckle size. Moreover, due to the overlapping of speckles between successive images, different types of digital processing can be applied to obtain the final synthetic image: fully incoherent, fully coherent, and partially coherent. The last, arising from the incoherent sum of several independent sets of coherently added images, provides the best improvement in the resolution. Experimental results for both types of objects are presented.

Lensless object scanning holography for two-dimensional mirror-like and diffuse reflective objects

Method for determining the proper expansion center and order for Mellin radial harmonic filters

Quantitative phase imaging needs of a holographic setup in order to retrieve the sample phase distribution. Often this new phase information is obtained at the cost of reducing the useful range in other parameters of the imaging system such as field of view or resolution. We devised an experimental setup that allows complex amplitude evaluation and phase image quantification of three-dimensional (3-D) samples in wide- field digital holographic microscopy. The basis is a common-path interferometric configuration that can be implemented in two configurations depending on the position and the basic period of the grating: static grating and windowed Fourier filtering method or with phase-shifting moving grating. Both configurations allow complex amplitude recovery and, thus, quantitative phase imaging of the sample under test. Moreover, by combining the basic setup with tilted illumination and time multiplexing, it is possible to generate a synthetic aperture enlargement that improves the final image resolution. Experimental results validated our concepts.

/pdf/quantitative-phase-imaging-by-common-path-interferometric-2xmt4dzyyp.pdf

Quantitative phase imaging by common-path interferometric microscopy: application to super-resolved imaging and nanophotonics

https://www.uv.es/~gpoei/articulos/(2003)_OC_217_Detection_and_orientation_evaluation_for_3D_object.pdf

Javier Garcia

Papers

Dual-mode holographic microscopy imaging platform.

Lensless object scanning holography for two-dimensional mirror-like and diffuse reflective objects

Method for determining the proper expansion center and order for Mellin radial harmonic filters

Quantitative phase imaging by common-path interferometric microscopy: application to super-resolved imaging and nanophotonics

Detection and orientation evaluation for three-dimensional objects