Showing papers on "Point spread function published in 2009"

Three-dimensional single-molecule fluorescence imaging beyond the diffraction limit using a double-helix point spread function

Abstract: Embodiments of the present invention can resolve molecules beyond the optical diffraction limit in three dimensions. A double-helix point spread function can be used to in conjunction with a microscope to provide dual-lobed images of a molecule. Based on the rotation of the dual-lobed image, the axial position of the molecule can be estimated or determined. In some embodiments, the angular rotation of the dual-lobed imaged can be determined using a centroid fit calculation or by finding the midpoints of the centers of the two lobes. Regardless of the technique, the correspondence between the rotation and axial position can be utilized. A double-helix point spread function can also be used to determine the lateral positions of molecules and hence their three-dimensional location.

Optical diffraction tomography for high resolution live cell imaging

Abstract: We report the experimental implementation of optical diffraction tomography for quantitative 3D mapping of refractive index in live biological cells. Using a heterodyne Mach-Zehnder interferometer, we record complex field images of light transmitted through a sample with varying directions of illumination. To quantitatively reconstruct the 3D map of complex refractive index in live cells, we apply optical diffraction tomography based on the Rytov approximation. In this way, the effect of diffraction is taken into account in the reconstruction process and diffraction-free high resolution 3D images are obtained throughout the entire sample volume. The quantitative refractive index map can potentially serve as an intrinsic assay to provide the molecular concentrations without the addition of exogenous agents and also to provide a method for studying the light scattering properties of single cells.

The Murchison Widefield Array: Design Overview

Abstract: The Murchison Widefield Array (MWA) is a dipole-based aperture array synthesis telescope designed to operate in the 80-300 MHz frequency range. It is capable of a wide range of science investigations, but is initially focused on three key science projects. These are detection and characterization of 3-dimensional brightness temperature fluctuations in the 21cm line of neutral hydrogen during the Epoch of Reionization (EoR) at redshifts from 6 to 10, solar imaging and remote sensing of the inner heliosphere via propagation effects on signals from distant background sources,and high-sensitivity exploration of the variable radio sky. The array design features 8192 dual-polarization broad-band active dipoles, arranged into 512 tiles comprising 16 dipoles each. The tiles are quasi-randomly distributed over an aperture 1.5km in diameter, with a small number of outliers extending to 3km. All tile-tile baselines are correlated in custom FPGA-based hardware, yielding a Nyquist-sampled instantaneous monochromatic uv coverage and unprecedented point spread function (PSF) quality. The correlated data are calibrated in real time using novel position-dependent self-calibration algorithms. The array is located in the Murchison region of outback Western Australia. This region is characterized by extremely low population density and a superbly radio-quiet environment,allowing full exploitation of the instrumental capabilities.

Video rate spectral imaging using a coded aperture snapshot spectral imager

Abstract: We have previously reported on coded aperture snapshot spectral imagers (CASSI) that can capture a full frame spectral image in a snapshot. Here we describe the use of CASSI for spectral imaging of a dynamic scene at video rate. We describe significant advances in the design of the optical system, system calibration procedures and reconstruction method. The new optical system uses a double Amici prism to achieve an in-line, direct view configuration, resulting in a substantial improvement in image quality. We describe NeAREst, an algorithm for estimating the instantaneous three-dimensional spatio-spectral data cube from CASSI’s two-dimensional array of encoded and compressed measurements. We utilize CASSI’s snapshot ability to demonstrate a spectral image video of multi-colored candles with live flames captured at 30 frames per second.

Ghost imaging through turbulent atmosphere

Abstract: Ghost imaging through turbulent atmospheres are theoretically studied. Based on the extended Huygens-Fresnel integral, we obtain an analytical imaging formula. The ghost image can be viewed as the convolution of the original object and a point-spread function (PSF). The imaging quality is determined by the size of the PSF. Increasing the turbulence strength and propagation distance, or decreasing the source size, will increase the size of the PSF, and lead to the degradation of the imaging quality.

Optimal dark hole generation via two deformable mirrors with stroke minimization

Abstract: The past decade has seen a significant growth in research targeted at space-based observatories for imaging exosolar planets. The challenge is in designing an imaging system for high contrast. Even with a perfect coronagraph that modifies the point spread function to achieve high contrast, wavefront sensing and control is needed to correct the errors in the optics and generate a “dark hole.” The high-contrast imaging laboratory at Princeton University is equipped with two Boston Micromachines Kilo-DMs. We review here an algorithm designed to achieve high contrast on both sides of the image plane while minimizing the stroke necessary from each deformable mirror (DM). This algorithm uses the first DM to correct for amplitude aberrations and uses the second DM to create a flat wavefront in the pupil plane. We then show the first results obtained at Princeton with this correction algorithm, and we demonstrate a symmetric dark hole in monochromatic light.

Basic Methods for Image Restoration and Identification

Abstract: Publisher Summary This chapter describes the methods for restoration and identification of image. Many types of motion blur can be distinguished all of which are due to relative motion between the recording device and the scene. This can be in the form of a translation, rotation, sudden change of scale, or some combination of these. The improvement in signal-to-noise ratio is basically a measure that expresses the reduction of disagreement with the ideal image when comparing the distorted and restored image. When applying restoration filters to real images of which the ideal image is not available, often only the visual judgment of the restored image can be relied upon. For this reason it is desirable for a restoration filter to be somewhat tunable to the liking of the user. In many practical cases the actual restoration process has to be preceded by the identification of the point spread function (PSF). A more common situation is that the blur is estimated from the observed image itself. The blur identification procedure starts out by choosing a parametric model for the PSF. Then, the parametric blur model describes the PSF as a (small) set of coefficients within a given finite support. Within this support, the value of the PSF coefficients needs to be estimated.

A fast convolution-based methodology to simulate 2-Dd/3-D cardiac ultrasound images

Abstract: This paper describes a fast convolution-based methodology for simulating ultrasound images in a 2-D/3-D sector format as typically used in cardiac ultrasound. The conventional convolution model is based on the assumption of a space-invariant point spread function (PSF) and typically results in linear images. These characteristics are not representative for cardiac data sets. The spatial impulse response method (IRM) has excellent accuracy in the linear domain; however, calculation time can become an issue when scatterer numbers become significant and when 3-D volumetric data sets need to be computed. As a solution to these problems, the current manuscript proposes a new convolution-based methodology in which the data sets are produced by reducing the conventional 2-D/3-D convolution model to multiple 1-D convolutions (one for each image line). As an example, simulated 2-D/3-D phantom images are presented along with their gray scale histogram statistics. In addition, the computation time is recorded and contrasted to a commonly used implementation of IRM (Field II). It is shown that COLE can produce anatomically plausible images with local Rayleigh statistics but at improved calculation time (1200 times faster than the reference method).

Speckle-field digital holographic microscopy

Abstract: The use of coherent light in conventional holographic phase microscopy (HPM) poses three major drawbacks: poor spatial resolution, weak depth sectioning, and fixed pattern noise due to unwanted diffraction. Here, we report a technique which can overcome these drawbacks, but maintains the advantage of phase microscopy - high contrast live cell imaging and 3D imaging. A speckle beam of a complex spatial pattern is used for illumination to reduce fixed pattern noise and to improve optical sectioning capability. By recording of the electric field of speckle, we demonstrate high contrast 3D live cell imaging without the need for axial scanning - neither objective lens nor sample stage. This technique has great potential in studying biological samples with improved sensitivity, resolution and optical sectioning capability.

Super-resolution orientation estimation and localization of fluorescent dipoles using 3-D steerable filters.

Abstract: Fluorophores that are fixed during image acquisition produce a diffraction pattern that is characteristic of the orientation of the fluorophore’s underlying dipole. Fluorescence localization microscopy techniques such as PALM and STORM achieve super-resolution by applying Gaussian-based fitting algorithms to in-focus images of individual fluorophores; when applied to fixed dipoles, this can lead to a bias in the range of 5–20 nm. We introduce a method for the joint estimation of position and orientation of dipoles, based on the representation of a physically realistic image formation model as a 3-D steerable filter. Our approach relies on a single, defocused acquisition. We establish theoretical, localization-based resolution limits on estimation accuracy using Cramer-Rao bounds, and experimentally show that estimation accuracies of at least 5 nm for position and of at least 2 degrees for orientation can be achieved. Patterns generated by applying the image formation model to estimated position/orientation pairs closely match experimental observations.

Polarization maintaining fiber based ultra-high resolution spectral domain polarization sensitive optical coherence tomography.

Abstract: We present a new ultra high resolution spectral domain polarization sensitive optical coherence tomography (PS-OCT) system based on polarization maintaining (PM) fibers. The method transfers the principles of our previous bulk optic PS-OCT systems to a fiberized setup. The phase shift between the orthogonal polarization states travelling in the two orthogonal modes of the PM fiber is compensated by software in post processing. Thereby, the main advantage of our bulk optics setups, i.e. the use of only a single input polarization state to simultaneously acquire reflectivity, retardation, optic axis orientation, and Stokes vector, is maintained. The use of a broadband light source of 110 nm bandwidth provides improved depth resolution and smaller speckle size. The latter is important for improved resolution of depolarization imaging. We demonstrate our instrument for high-resolution PS-OCT imaging of the healthy human retina.

Confocal Raman microscopy: performance, pitfalls, and best practice.

Abstract: C onfocal Raman microscopy is an extremely useful technique that permits nondestructive, spatially resolved measurements deep within transparent samples simply by focusing the laser beam at the point of interest. Moving the laser focus allows generation of one-dimensional (1D) depth profiles, and 2D and 3D (volumetric) images. However, in order to correctly interpret the data, it is important to understand exactly where the laser beam is focused and to know the volumetric resolution of the probe beam. These are actually non-trivial questions. The objective of this article is to summarize the critical factors that determine the spatial accuracy, resolution, and sensitivity of confocal Raman microscopy and to highlight the precautions that should be taken to collect high quality, quantitative data. No attempt is made to review the applications of Raman microscopy; these are simply too diverse, spanning topics from art conservation to medical diagnosis. However, the same basic principles must be adhered to, irrespective of the application, if reliable conclusions are to be drawn. Two main topics are considered. The first is the need for properly corrected objectives for depth profiling beneath the surface of transparent samples. If this is not done, the confocal profile will have an incorrect depth scale, degraded depth resolution, and reduced spectral intensity and signal-to-noise ratio (S/N). Even if modeling is used to account for the aberrations and to compute corrected profiles, degraded depth resolution and S/N still occur, which limits the performance. The second key issue is that even with a corrected objective operating with the best attainable resolution, the axial point spread function, which determines the depth resolution, has quite broad wings, so weak signals can be detected from regions quite distant (tens of micrometers) from the point of tightest focus. With thick transparent samples, the integrated signal from these out-of-focus domains can be significant or even dominant, resulting in unusual and counterintuitive observations. This effect is noticeable both for confocal profiling and for lateral scanning over cross-sections; in short, one cannot simply assume that data is acquired with a volumetric resolution of ~1 lm. The effect is especially important when one needs to chemically interpret the spectra rather than just view an image or a profile, since this leads to contamination of spectra with spurious bands. Finally, it is important to note that while some of the effects discussed here seem strange when they are first encountered, most have been known since the early days of confocal micro-spectroscopy. Consequently, few of the results discussed here would necessarily surprise a skilled microscopist. However, it is clear from the literature over the last decade or so that many Raman microscopists (the author included) are gradually re-learning these lessons and, as a result, significant advances have been made in the acquisition and interpretation of confocal Raman data. It therefore seems appropriate and timely to summarize these learning points in a review article.

Coded exposure deblurring: Optimized codes for PSF estimation and invertibility

Abstract: We consider the problem of single image object motion deblurring from a static camera. It is well-known that deblurring of moving objects using a traditional camera is ill-posed, due to the loss of high spatial frequencies in the captured blurred image. A coded exposure camera modulates the integration pattern of light by opening and closing the shutter within the exposure time using a binary code. The code is chosen to make the resulting point spread function (PSF) invertible, for best deconvolution performance. However, for a successful deconvolution algorithm, PSF estimation is as important as PSF invertibility. We show that PSF estimation is easier if the resulting motion blur is smooth and the optimal code for PSF invertibility could worsen PSF estimation, since it leads to non-smooth blur. We show that both criterions of PSF invertibility and PSF estimation can be simultaneously met, albeit with a slight increase in the deconvolution noise. We propose design rules for a code to have good PSF estimation capability and outline two search criteria for finding the optimal code for a given length. We present theoretical analysis comparing the performance of the proposed code with the code optimized solely for PSF invertibility. We also show how to easily implement coded exposure on a consumer grade machine vision camera with no additional hardware. Real experimental results demonstrate the effectiveness of the proposed codes for motion deblurring.

Three-dimensional microscopy and sectional image reconstruction using optical scanning holography

Abstract: Fast acquisition and high axial resolution are two primary requirements for three-dimensional microscopy. However, they are sometimes conflicting: imaging modalities such as confocal imaging can deliver superior resolution at the expense of sequential acquisition at different axial planes, which is a time-consuming process. Optical scanning holography (OSH) promises to deliver a good trade-off between these two goals. With just a single scan, we can capture the entire three-dimensional volume in a digital hologram; the data can then be processed to obtain the individual sections. An accurate modeling of the imaging system is key to devising an appropriate image reconstruction algorithm, especially for real data where random noise and other imaging imperfections must be taken into account. In this paper we demonstrate sectional image reconstruction by applying an inverse imaging sectioning technique to experimental OSH data of biological specimens and visualizing the sections using the OSA Interactive Science Publishing software.

Resolution-enhanced integral imaging microscopy that uses lens array shifting

Abstract: A resolution-enhanced integral imaging microscope that uses lens array shifting is proposed in this study. The lens shift method maintains the same field of view of the reconstructed orthographic view images with increased spatial density. In this study, multiple sets of the elemental images were captured with horizontal and vertical shifts of the micro lens array and combined together to form a single set of the elemental images. From the combined elemental images, orthographic view images and depth slice images of the microscopic specimen were generated with enhanced resolution.

Signal-to-noise and radiation exposure considerations in conventional and diffraction x-ray microscopy

Abstract: Using a signal-to-noise ratio estimation based on correlations between multiple simulated images, we compare the dose efficiency of two soft x-ray imaging systems: incoherent brightfield imaging using zone plate optics in a transmission x-ray microscope (TXM), and x-ray diffraction microscopy (XDM) where an image is reconstructed from the far-field coherent diffraction pattern. In XDM one must computationally phase weak diffraction signals; in TXM one suffers signal losses due to the finite numerical aperture and efficiency of the optics. In simulations with objects representing isolated cells such as yeast, we find that XDM has the potential for delivering equivalent resolution images using fewer photons. This can be an important advantage for studying radiation-sensitive biological and soft matter specimens.

3D imaging with axially distributed sensing.

Abstract: A new (to our knowledge) multiperspective 3D imaging architecture is proposed that uses imagers distributed along a common optical axis. In this axially distributed sensing method, either a single imager is translated along its optical axis or objects are moved parallel to the optical axis of a single imager. The 3D information collection capability of the proposed architecture is analyzed and a computational 3D reconstruction algorithm based on ray back-projection is proposed. It is shown analytically and experimentally that the collection capacity of this architecture is not uniform over the field of view. Experimental results are presented to verify the proposed approach. We believe this is the first report on 3D sensing and imaging with axially distributed sensing.

Time-gated perturbation Monte Carlo for whole body functional imaging in small animals

Abstract: This paper explores a time-resolved functional imaging method based on Monte Carlo model for whole-body functional imaging of small animals. To improve the spatial resolution and quantitative accuracy of the functional map, a Bayesian hierarchical method with a high resolution spatial prior is applied to guide the optical reconstructions. Simulated data using the proposed approach are employed on an anatomically accurate mouse model where the optical properties range and volume limitations of the diffusion equation model exist. We investigate the performances of using time-gated data type and spatial priors to quantitatively image the functional parameters of multiple organs. Accurate reconstructions of the two main functional parameters of the blood volume and the relative oxygenation are demonstrated by using our method. Moreover, nonlinear optode settings guided by anatomical prior is proved to be critical to imaging small organs such as the heart.

Optimal single image capture for motion deblurring

Abstract: Deblurring images of moving objects captured from a traditional camera is an ill-posed problem due to the loss of high spatial frequencies in the captured images. Techniques have attempted to engineer the motion point spread function (PSF) by either making it invertible using coded exposure, or invariant to motion by moving the camera in a specific fashion. We address the problem of optimal single image capture strategy for best deblurring performance. We formulate the problem of optimal capture as maximizing the signal to noise ratio (SNR) of the deconvolved image given a scene light level. As the exposure time increases, the sensor integrates more light, thereby increasing the SNR of the captured signal. However, for moving objects, larger exposure time also results in more blur and hence more deconvolution noise. We compare the following three single image capture strategies: (a) traditional camera, (b) coded exposure camera, and (c) motion invariant photography, as well as the best exposure time for capture by analyzing the rate of increase of deconvolution noise with exposure time. We analyze which strategy is optimal for known/unknown motion direction and speed and investigate how the performance degrades for other cases. We present real experimental results by simulating the above capture strategies using a high speed video camera.

What is limiting near-infrared astrometry in the Galactic Center?

Abstract: We systematically investigate the error sources for high-precision astrometry from adaptive optics based near-infrared imaging data. We focus on the application in the crowded stellar field in the Galactic Center. We show that at the level of <=100 micro-arcseconds a number of effects are limiting the accuracy. Most important are the imperfectly subtracted seeing halos of neighboring stars, residual image distortions and unrecognized confusion of the target source with fainter sources in the background. Further contributors to the error budget are the uncertainty in estimating the point spread function, the signal-to-noise ratio induced statistical uncertainty, coordinate transformation errors, the chromaticity of refraction in Earth's atmosphere, the post adaptive optics differential tilt jitter and anisoplanatism. For stars as bright as mK=14, residual image distortions limit the astrometry, for fainter stars the limitation is set by the seeing halos of the surrounding stars. In order to improve the astrometry substantially at the current generation of telescopes, an adaptive optics system with high performance and weak seeing halos over a relatively small field (r<=3") is suited best. Furthermore, techniques to estimate or reconstruct the seeing halo could be promising.

Cone beam micro-CT system for small animal imaging and performance evaluation

Abstract: A prototype cone-beam micro-CT system for small animal imaging has been developed by our group recently, which consists of a microfocus X-ray source, a three-dimensional programmable stage with object holder, and a flat-panel X-ray detector. It has a large field of view (FOV), which can acquire the whole body imaging of a normal-size mouse in a single scan which usually takes about several minutes or tens of minutes. FDK method is adopted for 3D reconstruction with Graphics Processing Unit (GPU) acceleration. In order to reconstruct images with high spatial resolution and low artifacts, raw data preprocessing and geometry calibration are implemented before reconstruction. A method which utilizes a wire phantom to estimate the residual horizontal offset of the detector is proposed, and 1D point spread function is used to assess the performance of geometric calibration quantitatively. System spatial resolution, image uniformity and noise, and low contrast resolution have been studied. Mouse images with and without contrast agent are illuminated in this paper. Experimental results show that the system is suitable for small animal imaging and is adequate to provide high-resolution anatomic information for bioluminescence tomography to build a dual modality system.

The point-spread function measure of resolution for the 3-D electrical resistivity experiment

Abstract: SUMMARY The solution appraisal component of the inverse problem involves investigation of the relationship between our estimated model and the actual model. However, full appraisal is difficult for large 3-D problems such as electrical resistivity tomography (ERT). We tackle the appraisal problem for 3-D ERT via the point-spread functions (PSFs) of the linearized resolution matrix. The PSFs represent the impulse response of the inverse solution and quantify our parameter-specific resolving capability. We implement an iterative least-squares solution of the PSF for the ERT experiment, using on-the-fly calculation of the sensitivity via an adjoint integral equation with stored Green's functions and subgrid reduction. For a synthetic example, analysis of individual PSFs demonstrates the truly 3-D character of the resolution. The PSFs for the ERT experiment are Gaussian-like in shape, with directional asymmetry and significant off-diagonal features. Computation of attributes representative of the blurring and localization of the PSF reveal significant spatial dependence of the resolution with some correlation to the electrode infrastructure. Application to a time-lapse ground-water monitoring experiment demonstrates the utility of the PSF for assessing feature discrimination, predicting artefacts and identifying model dependence of resolution. For a judicious selection of model parameters, we analyse the PSFs and their attributes to quantify the case-specific localized resolving capability and its variability over regions of interest. We observe approximate interborehole resolving capability of less than 1–1.5 m in the vertical direction and less than 1–2.5 m in the horizontal direction. Resolving capability deteriorates significantly outside the electrode infrastructure.

Three-dimensional localization with nanometer accuracy using a detector-limited double-helix point spread function system

Abstract: Accurate estimation of the three-dimensional (3D) position of particles is critical in applications like biological imaging, atom/particle-trapping, and nanomanufacturing. While it is well-known that localization accuracy better than the Rayleigh resolution limit is possible, it was recently shown that, for photon-limited cases, 3D point spread functions (PSFs) can be shaped to increase accuracies over a 3D volume [Pavani and Piestun, Opt. Express 16, 22048 (2008)]. Here, we show that in the detector-limited regime, the gain in accuracy occurs in all three dimensions throughout the axial range of interest. The PSF is shaped as a double helix, resulting in a system with fundamentally better 3D localization accuracies than standard PSF systems, capable of achieving single-image subnanometer accuracies.

Ultrasonic imaging algorithms with limited transmission cycles for rapid nondestructive evaluation

Abstract: Imaging algorithms recently developed in ultrasonic nondestructive testing (NDT) have shown good potential for defect characterization. Many of them are based on the concept of collecting the full matrix of data, obtained by firing each element of an ultrasonic phased array independently, while collecting the data with all elements. Because of the finite sound velocity in the test structure, 2 consecutive firings must be separated by a minimum time interval. Depending on the number of elements in a given array, this may become problematic if data must be collected within a short time, as it is often the case, for example, in an industrial context. An obvious way to decrease the duration of data capture is to use a sparse transmit aperture, in which only a restricted number of elements are used to transmit ultrasonic waves. This paper compares 2 approaches aimed at producing an image on the basis of restricted data: the common source method and the effective aperture technique. The effective aperture technique is based on the far-field approximation, and no similar approach exists for the near-field. This paper investigates the performance of this technique in near-field conditions, where most NDT applications are made. First, these methods are described and their point spread functions are compared with that of the total focusing method (TFM), which consists of focusing the array at every point in the image. Then, a map of efficiency is given for the different algorithms in the nearfield. The map can be used to select the most appropriate algorithm. Finally, this map is validated by testing the different algorithms on experimental data.

A rad-hard CMOS active pixel sensor for electron microscopy

Abstract: Monolithic CMOS pixel sensors offer unprecedented opportunities for fast nano-imaging through direct electron detection in transmission electron microscopy. We present the design and a full characterisation of a CMOS pixel test structure able to withstand doses in excess of 1 Mrad. Data collected with electron beams at various energies of interest in electron microscopy are compared to predictions of simulation and to 1.5 GeV electron data to disentagle the effect of multiple scattering. The point spread function measured with 300 keV electrons is ( 8.1 ± 1.6 ) μ m for 10 μ m pixel and ( 10.9 ± 2.3 ) μ m for 20 μ m pixels, respectively, which agrees well with the values of 8.4 and 10.5 μ m predicted by our simulation.

Polarization sensitive, three-dimensional, single-molecule imaging of cells with a double-helix system

Abstract: Double-helix point spread function photoactivation-localization microscopy allows three-dimensional (3D) superresolution imaging of objects smaller than the optical diffraction-limit. We demonstrate polarization sensitive detection with 3D super-localization of single-molecules and unveil 3D polarization specific characteristics of single-molecules within the intracellular structure of PtK1 cells expressing photoactivatable green fluorescent protein. The system modulates orthogonal polarization components of single-molecule emissions with a single spatial light modulator and detects them separately with a single detector. Information obtained from the two polarization channels demonstrates polarization based contrast in 3D superresolution imaging. Further, we show that the 3D information from the two channels can be optimally combined to yield up to 30% improvement in localization precision relative to a single polarization channel system.

Blind deconvolution for thin-layered confocal imaging.

Abstract: We propose an alternate minimization algorithm for estimating the point-spread function (PSF) of a confocal laser scanning microscope and the specimen fluorescence distribution. A three-dimensional separable Gaussian model is used to restrict the PSF solution space and a constraint on the specimen is used so as to favor the stabilization and convergence of the algorithm. The results obtained from the simulation show that the PSF can be estimated to a high degree of accuracy, and those on real data show better deconvolution as compared to a full theoretical PSF model.

Frequency-resolved high-harmonic wavefront characterization

Abstract: We introduce and demonstrate a novel concept of frequency-resolved wavefront characterization. Our approach is particularly suitable for high-harmonic, extreme-UV (XUV) and soft X-ray radiation. The concept is based on an analysis of radiation diffracted from a slit scanned in front of a flat-field XUV spectrometer. With the spectrally resolved signal spread across one axis and the spatially resolved diffraction pattern in the other dimension, we reconstruct the wavefront. While demonstrated for high harmonics, the method is not restricted in wavelength.