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X-ray free-electron lasers (FELs) are being recognized as a powerful tool in an ever-increasing number of research fields, but are very limited as to the number of experiments that they can support. This work shows that more beamtime could be made available by using `parasitic' geometries, where a secondary experiment uses the X-ray beam that the primary experiment does not utilize. The first successful ptychography experiment, a scanning coherent diffractive imaging technique, in a parasitic geometry at an X-ray FEL is demonstrated. Utilizing the CXI hutch at the Linac Coherent Light Source (LCLS), it is shown that the obtained data are of high quality and that characterizing the beam using ptychography can be much faster than traditional imprinting methods.

We present a computational accommodation-invariant near-eye display, which relies on imaging with coherent light and utilizes static optics together with convolutional neural network-based preprocessing. The network and the display optics are co-optimized to obtain a depth-invariant display point spread function, and thus relieve the conflict between accommodation and ocular vergence cues that typically exists in conventional near-eye displays. We demonstrate through simulations that the computational near-eye display designed based on the proposed approach can deliver sharp images within a depth range of 3 diopters for an effective aperture (eyepiece) size of 10 mm. Thus, it provides a competitive alternative to the existing accommodation-invariant displays. acceptedVersion

We present results from depth-resolved light scattering measurements of triple transgenic mouse retinas for Alzheimer’s Disease (AD) using a multimodal coherent imaging system. Use of a co-registered angle-resolved low-coherence interferometry (a/LCI) and optical coherence tomography (OCT) system allows unique analysis that is otherwise unavailable using a single modality to provide complementary information on tissue structural changes associated with AD. This abstract summarizes the light scattering parameters drawn using this system at selective retinal layers guided by OCT image segmentation. Future developments of this combined system for human retinal imaging, which involve a low-cost OCT engine, are also discussed.

X-ray ptychography has gained tremendous success in providing quantitative high-resolution imaging for extended samples. Here we report on recent developments in ptychography imaging techniques and the improvement of reconstruction methods to increase ptychographic imaging throughput at the Advanced Photon Source.

We present a high-throughput and cost-effective computational cytometer for rare cell detection, where the target cells are specifically labeled with magnetic particles and exhibit an oscillatory motion under a periodically-changing magnetic field. The time-varying diffraction patterns of the oscillating cells are then captured with a holographic imaging system and are further classified by a customized pseudo-3D convolutional network. To evaluate the performance of our technique, we detected serially-diluted MCF7 cancer cells that were spiked in whole blood, achieving a limit of detection (LoD) of 10 cells per 1 mL of whole blood.

We present a detailed characterization of noise sources in multiple reference optical coherence tomography (MR-OCT) compared to time-domain OCT (TD-OCT). The noise characteristics were modeled based on the TD-OCT noise model and modified for MR-OCT and confirmed with measurements. The MR-OCT sensitivity characteristics are significantly affected by the reflection from the partial mirror, which also introduces a natural attenuation in the reference arm, partially matching the reflectivity intensity profile of human tissue. At optimal balance between sample and reference arm and using balanced detection, the peak sensitivity was measured to be 95 dB, which is close to simple Fourier-domain systems. The results provide a better understanding of the application range for MR-OCT and higher order effects observed, suggesting a nontrivial noise model for MR-OCT. All authors have a financial interest in Compact Imaging, Inc. peer-reviewed

Coherent diffractive imaging of periodic samples is demonstrated with a tabletop, 13.5 nm high-harmonic source. With a novel image reconstruction technique, the record high spatial resolution of 12.6 nm is achieved in the extreme-ultraviolet region.

We propose a computational coherent imaging system based on cylindrical lens’s rotation modulation(RSCL), in which rotation angle is calculated by designed two-step Radon transform(TsRT). This method overcomes longitudinal sampling rate fluctuation in axial multiimage imaging.

A high-efficiency coherent imaging system is designed by using phase modulation. After rotating a known phase mask, three images from rotation modulation are recorded and utilized to accurately reconstruct the complex-value sample. Specially, the system is free from rotation angle calculation, and requires fewer intensity measurements. This method has a superiority in convergence speed and calculation time. Furthermore, the optimal sample-to-sensor distance is searched by auto-focusing criteria. The proposed method is promising for compact biomedicine imaging and 3D measurement.

We consider the problem of imaging small defects embedded in strongly scattering media, often called clutter, using an active array of transducers that can play the dual role of emitters and receivers. Our data is the array response matrix collected by sending short pulses from each source and recording the response at all array elements. Imaging in strong clutter is quite challenging as the array data are dominated by noise due to the multiple scattering of the waves with the medium heterogeneities. To successfully image in this regime using simple coherent imaging functionals, we follow the methodology of coherent signal enhancement through data filtering. We study the performance of the different approaches with extensive numerical simulations, carried out in a non-destructive testing setup.

Sequential speckle reduction methods demand the usage of fast modulators due to the short integration period of human eyes. Here, a nonsequential speckle reduction method by splitting one laser beam with short coherence length into uncorrelated laser subbeams (LSBs) is reported. In order to realize the most efficient speckle reduction, with the help of a polarization beam splitter, we have programmed a reflective spatial light modulator to make the LSBs intensities equivalent. Three uncorrelated LSBs with equivalent light intensity are designed to demonstrate this idea; the speckle contrast ratio is reduced to 0.55, which closes to the expected value of 0.58. This nonsequential speckle reduction method has no requirement of the modulators speed; thus, it has obvious merit comparing with the sequential speckle reduction methods.

An integrated electronic-photonic phase-locked loop (PLL) modulates the frequency of a tunable laser for use in frequency-modulated continuous-wave (FMCW) lidar 3D imaging. The proposed lidar can perform 180k range measurements per second. The rms depth precision is 8 $\mu \text{m}$ at distances of ±5 cm from the range baseline. The range window is 1.4 m, with a precision of 4.2 mm at the edges of the window. Optical circuitry, including input light couplers, waveguides, and photodiodes, is realized on a 3 mm $\times $ 3 mm silicon-photonic chip. The 0.18- $\mu \text{m}$ CMOS ASIC of the same area comprises the front-end transimpedance amplifier, analog electro-optical PLL, and digital control circuitry consuming 1.7 mA from a 1.8 V supply and 14.1 mA from a 5-V supply. The latter includes 12.5-mA bias current for the distributed Bragg reflector section of the tunable laser. The two chips are integrated using through-silicon-vias implemented in the silicon-photonic chip.

Experimentally achieving extreme thermodynamical conditions of temperature, pressure and magnetic field such as the ones found in the interior of planets and stars has been a dream to many scientists seeking to reproduce those conditions on earth to study and produce unconventional materials. The advent of the 4th generation Brazilian synchrotron source (named after the “Sirius” star) allows us to get closer to this dream by implementing a state-of-the-art beamline facility to study samples under extreme thermodynamical conditions by means of a multitude of synchrotron x-ray techniques. The EMA Beamline (Extreme condition Methods of Analysis) will be able to do this by coupling both microfocus (1x1 µm2) and nanofocus (100x100 nm2) beamsizes to x-ray magnetic spectroscopy, x-ray diffraction and x-ray coherent imaging in multiple experimental instruments, placed along the beam path for optimization. Support laboratories (thermodynamical conditions, nuclear materials, laser and optics) were also planned to fulfil all requirements for the experiments under extreme. The EMA beamline, as overviewed here, should open a plethora of opportunities for diverse studies of materials at extreme conditions with synchrotron x-ray techniques.

A proposal for building a Free Electron Laser, EuPRAXIA@SPARC_LAB, at the Laboratori Nazionali di Frascati, is at present under consideration. This FEL facility will provide a unique combination of a high brightness GeV-range electron beam generated in a X-band RF linac, a 0.5 PW-class laser system and the first FEL source driven by a plasma accelerator. The FEL will produce ultra-bright pulses, with up to 10 12 photons/pulse, femtosecond timescale and wavelength down to 3 nm, which lies in the so called &ldquo, water window&rdquo, The experimental activity will be focused on the realization of a plasma driven short wavelength FEL able to provide high-quality photons for a user beamline. In this paper, we describe the main classes of experiments that will be performed at the facility, including coherent diffraction imaging, soft X-ray absorption spectroscopy, Raman spectroscopy, Resonant Inelastic X-ray Scattering and photofragmentation measurements. These techniques will allow studying a variety of samples, both biological and inorganic, providing information about their structure and dynamical behavior. In this context, the possibility of inducing changes in samples via pump pulses leading to the stimulation of chemical reactions or the generation of coherent excitations would tremendously benefit from pulses in the soft X-ray region. High power synchronized optical lasers and a TeraHertz radiation source will indeed be made available for THz and pump&ndash, probe experiments and a split-and-delay station will allow performing XUV-XUV pump&ndash, probe experiments.

As a method to obtain the interference pattern of an object, lensless ghost interference with classical incoherent light source is studied by use of optical coherence theory. It is shown that lensless ghost interference can be regarded as a coherent imaging system. Furthermore, there is a condition to realize lensless ghost interference, and the condition of realizing lensless ghost interference is deduced. Finally, the factors influencing the quality of lensless ghost interference, resolution and contrast, are investigated.

X-ray crystallography has been central to the development of many fields of science over the past century. It has now matured to a point that as long as good-quality crystals are available, their atomic structure can be routinely determined in three dimensions. However, many samples in physics, chemistry, materials science, nanoscience, geology, and biology are noncrystalline, and thus their three-dimensional structures are not accessible by traditional x-ray crystallography. Overcoming this hurdle has required the development of new coherent imaging methods to harness new coherent x-ray light sources. Here we review the revolutionary advances that are transforming x-ray sources and imaging in the 21st century.

We present a coherent imaging setup for extended samples achieving record-high resolution for non-periodic samples. A Siemens star pattern is imaged and the Rayleigh criterion is used to provide a reliable sub-50 nm resolution claim.

In most coherent imaging modality, speckle noise is a major cause that blurs the boundary of tissues and degrades the image contrast. By utilizing the unique properties of supercontinuum (SC) generated by noise-like pulses (NLPs) and a simple multi-frame averaging technique, we achieved significant speckle reduction in spectral domain optical coherence tomography (SD-OCT). We quantitatively compared the speckle of our proposed method with those of conventional swept source OCT (SS-OCT) and SD-OCT based on commercial light sources. The experimental results show that SC pumped by NLPs combined with noncoherent averaging method achieves better denoising performance in terms of contrast to noise ratio (CNR).

We present coherent imaging for acquiring two-dimensional optical image that recovers amplitude and phase simultaneously. With coherent imaging, we detect few-mode-fiber modes with high extinction-ratio, and perform mode decomposition and differential mode delay measurement. Refereed/Peer-reviewed

Acta crystallographica / A 73(4), 282 - 292 (2017). doi:10.1107/S2053273317007902, X-ray tomography at the level of single biological cells is possible in a low-dose regime, based on full-field holographic recordings, with phase contrast originating from free-space wave propagation. Building upon recent progress in cellular imaging based on the illumination by quasi-point sources provided by X-ray waveguides, here this approach is extended in several ways. First, the phase-retrieval algorithms are extended by an optimized deterministic inversion, based on a multi-distance recording. Second, different advanced forms of iterative phase retrieval are used, operational for single-distance and multi-distance recordings. Results are compared for several different preparations of macrophage cells, for different staining and labelling. As a result, it is shown that phase retrieval is no longer a bottleneck for holographic imaging of cells, and how advanced schemes can be implemented to cope also with high noise and inconsistencies in the data., Published by IUCr, Oxford [u.a.]

We demonstrate a sparsity-based phase reconstruction technique implemented in wavelet domain to achieve at least 2-fold reduction in the number of holographic measurements for coherent imaging of samples

We report on the dependence of the spatial properties of high harmonic generation on the harmonic order. We present interesting features in the transverse spatial coherence which may be important for coherent imaging experiments.Research in Optical Sciences © OSA 2014.

A reversal 4f coherent imaging system with phase objects is presented to measure nonlinear refraction of the materials. The modified system can increase the sensitivity compared with the conventional nonlinear-imaging technique with phase objects. The sensitivity enhancement of the modified system is about two times greater than the conventional technique within 0 ≤ ΔφNL ≤ 1. CS2 is used to demonstrate the measurement using the reversal 4f coherent imaging system with phase objects.

Embryonic stem cells are very important for the development of cell-based therapeutic strategies. Since stem cell colonies are nonpigmented and relatively transparent, they do not produce appreciable variation to the amplitude of probe electromagnetic radiation passing through them, necessitating the use of phase contrast imaging techniques for studying them. Here, we used digital holographic interferometric microscopy (DHIM) to observe temporal and spatial evolution of stem cell colonies. Three-dimensional or whole field imaging has yielded important quantitative information about their progression from single cell to colonies. Information on the time and spatial evolution of optical volume and path length change will be an important tool for biologists working in the area of stem cells and their development.

Applying structured illumination microscopy to coherent imaging modalities such as scattering does not yield any additional information beyond that provided by oblique illumination. It thus yields no resolution enhancement over the Abbe diffraction limit, which was derived precisely for that case.

We develop an information-theoretic framework for the quantitative assessment of the maximum amount of information provided by optical coherence imaging through scattering media. We use our approach to investigate the fundamental dependence of the extractable information on the nature of the coherent imaging process, such as on speckle formation. We present nontrivial predictions for the maximum amount of information detected by optical coherence tomography (OCT) from within homogeneous and heterogeneous scattering media and explore its behavior against coherence length and dimension of the detection array. Extension to additional coherent and incoherent light imaging approaches is also discussed.

Measuring atomic-resolution images of materials with x-ray photons during chemical reactions or physical transformations resides at the technological forefront of x-ray science. New x-ray–based experimental capabilities have been closely linked with advances in x-ray sources, a trend that will continue with the impending arrival of x-ray–free electron lasers driven by electron accelerators. We discuss recent advances in ultrafast x-ray science and coherent imaging made possible by linear-accelerator–based light sources. These studies highlight the promise of ultrafast x-ray lasers, as well as the technical challenges and potential range of applications that will accompany these transformative x-ray light sources.

In this communication a comparative study of one to one coherent imaging through double and single hololens configurations have been presented. Resolutions using the two imaging configurations are found to be 28 and 32 lines/mm respectively.

A 0.33THz pulse gyrotron is currently under development at Peking University, which is predicted to generate coherent broadband radiation in each pulse. The pulse gyrotron is designed based on the fundamental harmonic co-rotating TE 62+ (1) mode. The scheme of tuning magnetic field on backward-wave interaction is adopted to realize broadband radiation. The compact pulse gyrotron is promising in the applications of coherent imaging and detection in the medical science and industry.

An optimal track format for a holographic read-only-memory (ROM) disk is proposed that minimizes the intertrack crosstalk and stores conventional optical disk pit patterns with a density equivalent to that of digital versatile discs (DVDs) in a single holographic layer. To quantify the effect of intertrack crosstalk for the cases of variations in track width and pitch, we defined signal-to-crosstalk ratio (SCR) as a criterion to find the optimal track format. A numerical simulation is used to calculate SCR as a function of track width and pitch. The simulation results show that SCR varies with track width, pitch and pit length. When the track width, pitch, and minimum pit length are 0.5, 0.74, and 0.4 m, respectively, we can set a minimum pit length with a maximum SCR so that the storage density of each layer of the holographic ROM is equivalent to that of DVDs.

Coherent imaging with a multi-beam laser is considered as a key technique in ground based imaging. The image quality is directly determined by stability and consistency of each beam in transmitter. Although the stabilities of laser frequency and the drifting compensation methods have been studied previously, they mostly focused on the laser source. In most cases, especially in large transmitter array, however, transmitted beams are always disturbed by different influential factors, such as frequency drift induced by acoustic-optical modulation (AOM) and high power driven amplification. Therefore this kind of frequency drifting needs further rectification. Aiming at this problem, in this paper we propose two new methods called dynamic demodulation and dependence range demodulation. Firstly, the dynamic demodulation takes the whole drifting frequency drift as a changing procedure. It is believed that the beat frequency drifted at any position still carries the target information, so the system demodulates the signal at that drifted position. According to this method, the response speed of the demodulation system should be very high. But in a real system this acquisition is too high to be satisfied. It cannot work as quickly as expected. In computer simulation some slow varying drifts are induced at the beat frequency and the variation is distributed only in three parts of spatial frequency of transmitter interfering array. Simulation results show that this method may well compensate for slow drifting beat frequency. While its response speed is often limited by hardware system. On the other hand, for the dependence range demodulation, the beat drifting range is considered as a useful district, in which all the beat energy is added and demodulated at a preset position. An experiment is carried out to verify this method. The result demonstrates that it can well restrict the beat frequency drift within 100 Hz, which often happens in the procedure of AOM and driving amplification. Besides the laboratory setup research, the field experiments in 200 m and 1.5 km range are also carried out. The dependence range demodulation is proved to be well performed as well. The resolution of the 25 cm simulated target in 1.5 km reaches 0.008 rad. In the consideration of real system, the imaging range is further expanded and the amplifier power is stronger. The field experiments reveal that this demodulation method is applicable in such a condition. Therefore the research in this article provides some new techniques for the remote high resolution imaging in multi-beam laser interfering imaging.

A method is proposed for simulating optical object images formed by oblique or grazing-incidence coherent beams. The theoretical approach relies on the solution of a parabolic equation, which generalises the Fresnel integral. Our numerical results are given for experimental conditions close to those realised when use is made of modern soft X-ray lasers. The newly developed method may also be employed to simulate X-ray imaging systems developed around synchrotron and free-electron laser beams.

This chapter covers the basic principles that are used in Monte Carlo simulation for investigation into microscopy imaging through tissue media. Section 3.1 summarizes the basic formula in a conventional Monte Carlo simulation process. The implementation of this method in reflection and transmission optical microscopes is given in Sect. 3.2. The effect of the polarization states and pulsed illumination of a beam are described in Sects. 3.3 and 3.4. Sections 3.5–3.8 are dedicated to dealing with the various features of turbid media including the effect of the boundary, scatterer size, and aggregation . In Sects. 3.9 and 3.10, Monte Carlo simulation methods for multi-photon fluorescence and coherent imaging processes are discussed.

It is now possible to control the spectral, temporal and polarization of high harmonic x-ray beams for a wide range of applications in imaging and spectroscopy.

The advent of resonant metamaterials with strongly dispersive behavior allowed scientists to design new electromagnetic devices -- including (but not limited to) absorbers, antennas, lenses, holograms, and arguably the most well-known of them all, invisibility cloaks -- exhibiting properties that would otherwise be difficult to obtain. At the heart of these breakthrough designs is our ability to model the behavior of individual metamaterial elements as Lorentzian dipoles, and -- in applications that call for it -- collectively model an entire array of such elements as a homogenous medium with effective electromagnetic properties retrieved from measurements or simulations. Of particular interest in the context of this dissertation is a certain type of metamaterials elements which -- while composed entirely of essentially non-magnetic materials -- respond to a magnetic field, can be modeled as magnetic dipoles, and are able to form a material with effective magnetic response. This thesis describes how such ``magnetic metamaterials'' have been utilized by the author when designing devices for applications in wireless power transfer (WPT) and computational imaging. For the former, I discuss in the thesis a metamaterial implementation of a magnetic `superlens' for wireless power transfer enhancements, and a magnetic reflector for near field shielding. For the latter I detail how we model the imaging capabilities of a recently-introduced class of dispersive metamaterial-based leaky apertures that produce pseudo-random measurement modes, and demonstration of novel Lorentzian-constrained holograms able to tailor their radiation patterns. To design a magnetic superlens for WPT enhancements, we first demonstrate how an array comprising resonant metamaterial elements can act as an effective medium with negative permeability ($\mu$) and enhance near-field transmission of quasi-static non-resonant coil antennas. We implement a new technique to retrieve all diagonal components of our superlens' permeability, including its normal component, which standard techniques cannot retrieve. We study the effect of different components of the $\mu$ tensor on field enhancements using analytical solutions as well as 2D rotationally-symmetric full-wave simulations which approximate the lens as a disc of equal diameter, enabling highly efficient axisymmetric description of the problem. Our studies indicate enhancements are strongest when all three diagonal components of Re$(\mu)$ are negative, which we attribute to the excitation of surface waves.The ability to retrieve permeability's normal component, awarded to us with the implementation of the aforementioned retrieval technique, directly enabled the design of a near field magnetic shield, which -- in contrast to the tripple-negative superlens -- relies on the normal component of $\mu$ assuming values near zero. The thesis discusses the theory behind this phenomenon and explains why such an anisotropic slab is capable of reflecting magnetic fields with component of their wave vector parallel to the slab's surface (fields which contain significant portions of the energy transferred in WPT systems with dipole-like coils). Furthermore, the dispersive nature of the resonant metamaterials used to realize the shield grants us the ability to block certain frequencies while allowing the transmission of other, which can be particularly useful in certain applications; conventional materials used for shielding or electromagnetic interference (EMI) suppression, on the other hand, block frequencies indiscriminately. The thesis also discusses a single-pixel, metamaterial-based aperture we designed for computational imaging purposes. This aperture, termed \textit{metaimager}, forms pseudo-random radiation patterns that vary with frequency by leaking energy from a guided mode via a collection of randomly distributed resonant metamaterial elements. The metaimager, then, is able to interrogate a scene without any moving parts or expensive auxiliary hardware (both are common problems which plague synthetic aperture and phased array systems, respectively). While such a structure cannot be homogenized, when modeling its imaging capabilities we still rely on the fact each of its irises can be modeled analytically as a magnetic dipole using a relatively simple Lorentzian expression. Accurate qualitative modeling of such apertures is of paramount importance in the design and optimization stages, since it allows us to save time and money by avoiding prohibitively slow full-wave simulations of such complex structures and unnecessary fabrication processes. Lastly, the thesis discusses how such an aperture can be viewed as a hologram in which pixels are realized by the metamaterial elements and the reference wave is realized by the fields that excite them. While the current metaimager implementation produces pseudo-random modes, the last section of the thesis discusses how, by accounting for the Lorentzian constraints of each pixel, a novel metamaterial hologram can be designed to yield tailored radiation patterns. An experiment utilizing a Fraunhofer hologram excited in a free-space illumination configuration indicates tailored modes can indeed be formed by carefully choosing the resonance frequency and location of each metamaterial. While this proof-of-concept example is relatively simple, more sophisticated realizations of such holograms can be explored in future works.

The Large Binocular Telescope Interferometer (LBTI) is a strategically important instrument for exploiting the use of the LBT as a 22.7 m telescope. The LBTI has two science cameras (covering the 1.5-5 μm and 8-13 μm atmospheric windows), and a number of observing modes that allow it to carry out a wide range of high-spatial resolution observations. Some simple modes, such as AO imaging, are in routine use. We report here on testing and commissioning of the system for its more ambitious goals as a nulling interferometer and coherent imager. The LBTI will carry out key surveys to Hunt for Observable Signatures of Terrestrial planetary Systems (HOSTS) and an LBTI Exozodi-Exoplanet Common Hunt (LEECH). The current nulling and coherent imaging performance is described.

We report about magnified hard X-ray imaging in cone-beam geometry with a secondary source size of 85 � 95 nm 2 . The small spot size is achieved by focusing with Kirkpatrick–Baez (KB) mirrors at a third-generation synchrotron source. This small and more divergent source projects a magnified sample shadow, overcoming the resolution limit of the detection system. The proposed scheme allows imaging with high resolution and efficiency at the same time. In addition, it should be suitable for coherent imaging experiments. r 2007 Elsevier B.V. All rights reserved.

Characterization of a quantum simulator Ultracold gases can be used to simulate the behavior of more complicated systems, such as solid materials. Senko et al. developed a method similar to nuclear magnetic resonance that can be used to validate the properties of such simulators. They demonstrated the method on an array of interacting trapped ions that simulate magnetism. A modulated magnetic field resonantly enhanced the transfer of the population between the different configurations of the system. The authors varied the modulation frequency to measure the energy of each configuration and mapped the effective interactions. Science , this issue p. 430

The theory of coherent reflection imaging of inclined objects at grazing angles of illumination is developed on the basis of the parabolic wave equation. A new optical transformation connecting image and object field distributions is presented. The codes for simulation the properties of practical optical systems are created. Simulation results for parameters close to an X-ray laser experiment are given.

In this paper theoretical curves for the variation of diffraction efficiency, of thick phase transmission hololenses recorded on dichromated gelatin (DCG), with emulsion thickness (d), depth of refractive-index modulation and fringe spacing at are presented. The results of a comparative study of the theoretical and experimental variations of diffraction efficiency with a change in angle of reconstruction with respect to the Bragg angle for two typical hololenses of fringe spacing and respectively for a fixed value of emulsion thickness and depth of refractive-index modulation are also presented. The present investigation reveals that low-thickness emulsion, high depth of refractive-index modulation and large fringe spacing are quite promising for recording DCG hololenses for coherent imaging systems which can provide appreciable illumination over the entire image of an extended object. Such lenses can be used advantageously in a coherent imaging system for speckle metrology. Dans cet article on presente les courbes theoriques de variation de l'efficacite de diffraction de lentilles holographiques epaisses enregistrees dans la gelatine bichromatee (DCG) avec l'epaisseur de l'emulsion (d), la profondeur de la modulation d'indice et l'interfrange a 0,6328. Les resultats des etudes comparatives de la variation theorique et experimentale de cette efficacite avec le changement d'angle de reconstruction par rapport a l'angle de Bragg pour et , et sont presentees. L'etude actuelle revele qu'une faible epaisseur d'emulsion, une forte profondeur de modulation de l'indice et un grand interfrange sont tres prometteurs pour l'enregistrement de lentilles holographiques DCG qui fourniraient un eclairement appreciable sur l'image entiere d'objets etendus en imagerie coherente. De telles lentilles peuvent etre avantageusement utilisees pour la metrologie speckle.

Dispersive imagers measure multiple speckle realizations of the object to be estimated. This poses a challenge for coherent imaging as classically objects are backpropagated and then despeckled. We present initial findings on an intensity based method for estimating the scattering density.