Coded aperture imagers extend the pinhole camera concept, which requires no lenses, has unlimited depth of focus, and can image radiation of any wavelength. The proposed reconstruction method can be used for any planar arrangement of discrete sources and is thus capable of comparing the performance of various source point distributions. Compressive coded aperture superresolution image reconstruction. This paper appeared in a longer version in in t zand 1992. In this system, a separable mask was used to reduce the complexity of calibration and the computational burden of image reconstruction. Camera systems have been proposed that allow for recording allfocus images, or for extracting depth, but to record both simultaneously has required more extensive hardware and reduced spatial resolution. However, the optical field from the scene could be modulated using a coded aperture. The aperture code optimization problem is shown to be analogous to the optimization of a constrained. Compressive sensing image sensorshardware implementation. Code aperture optimization for spectrally agile compressive imaging.
It is shown that a nine redundant source code provides for better reconstructions than a twelve circular array and a twelve nonredundant array of same inertia. Spectral image estimation for coded aperture snapshot. The mlem algorithm is built on the poisson statistics of photon emission and detection processes. Codedmask imaging is basically a twostep procedure. The coded aperture keyed exposure cake sensing paradigm we describe in this paper is designed to allow nonlinear highresolution video reconstruction from relatively few measurements in more general settings. Assuming the coded aperture moves linearly during d t such that stnt, the images temporal spectrum is given by. A new approach of 3d spect reconstruction for nearfield coded. An optimization approach to design the structure of the coded apertures in a multiple source compressive xray tomosynthesis imaging system is presented. Coded apertures are placed in front of the xray source in caxct so as to obtain patterned projections onto a detector array. The reconstruction of coded aperture images using an optical scanning heterodyne processor is described for a class of apertures which can be synthesized by two beam interference.
A coded aperture gamma camera based on a novel imaging model which decomposes the mask projections as a superposition of two separable functions was proposed for nearfield highresolution gammaray imaging. Compressive coded aperture keyed exposure imaging with. Sep 01, 2012 image plane coded aperture for terahertz imaging image plane coded aperture for terahertz imaging 20120901 00. Image and depth from a conventional camera with a coded aperture.
Spect imaging of 2d and 3d distributed sources with near. Highrank coded aperture projection for extended depth of field. Compressive coded aperture aperture superresolution image reconstruction slide 0. The first technique is called coded aperture imaging, which is a technique of tomographic. Compressive coded aperture keyed exposure imaging with optical flow reconstruction zachary t. Spatiotemporal compressed sensing with coded apertures. Partial reconstruction of 3d image stack from single projection. Coded aperture imaging concept astrophysics science division. Probability of correct reconstruction in compressive. Spect imaging of 2d and 3d distributed sources with nearfield. Coded aperture pairs for depth from defocus and defocus. The function generator moves the coded aperture and triggers camera acquisition with signals from its function and sync outputs, respectively.
We have calculated imaging with fresnel zone plate and multiple pinhole apertures to produce coded shadows and reconstruction of these shadows using correlation, fresnel. Extra software modules are available for special functions e. We show in this paper that the use of a circular aperture severely restricts the accuracy of dfd. Radionuclide imaging with coded apertures and three. The traditional correlation method for coded apertures cannot. One may analyze the expected temporal resolution of the coded data by considering the fourier transform of eq. Comparisons of coded aperture imaging using various. Compressive coded apertures recent studies by the authors19,20 and others21 address the accurate reconstruction of a high resolution static image which has a sparse representation in some basis from a single low resolution observation using compressive coded aperture cca imaging. This study focuses on the coded aperture design and its optimization for xray tomosynthesis. Compressed sensing cs reconstruction algorithms are then used to recover the threedimensional data cube. Box 90291, durham, north carolina 27708, usa 2departments of radiology and electrical engineering, washington university, box 1127, st. Coded aperture compressive 3d lidar achuta kadambi,1 petros t. Jun 15, 2012 these active imaging systems consist of a heterodyne source and receiver pair, image forming optics, a coded aperture, data acquisition hardware, and image reconstruction software.
Coded apertures or coded aperture masks are grids, gratings, or other patterns of materials opaque to various wavelengths of electromagnetic radiation. A scanning optical technique is described and used to reconstruct coded aperture images obtained with four different kinds of arrays. Coded aperture imaging has the advantage that all of the threedimensional information is contained in a single image, whereas computed tomography requires several images or projections. Image and depth from a conventional camera with a coded. Image plane coded aperture for terahertz imaging, optical. Coded aperture xray computed tomography caxct is a novel xray imaging system capable of reconstructing high quality images from a reduced set of measurements. Coded aperture correlation holography coach is a recently developed 3dimaging technology. A postscript version of the complete paper original version, without figures is available 220 kb. Compressive coded aperture superresolution image reconstruction roummel f. Scanning heterodyne reconstruction of coded aperture images. Coded aperture snapshot spectral imaging cassi provides a mechanism for capturing a 3d spectral cube with a single shot 2d measurement. Rank minimization code aperture design for spectrally selective compressive imaging abstract. Spectral calibration is requisite for spectroscopy to obtain the spectrum information exactly.
Scintillator based codedaperture imaging has proven to be effective when applied for x and gammaray detection. It places a coded aperture in front of an xray source in order to obtain 2d patterned projections of a threedimensional object onto a detector plane. Given a sparsity condition for signal representation, the minimum number of shots for reconstruction is determined by the variance of the representation basis and the variance of the random structure of the. Scanning optical reconstruction of coded aperture images. For optimal reconstruction, the coded aperture patterns must be designed with p 0,5 or equivalent with a transmittance of fifty percent. To understand them it is useful to understand pinhole apertures. Jun 06, 2016 image and depth from a conventional camera with a coded aperture siggraph 2007 presentation duration. Therefore, each sensor in the array represents a pixel of the image. After the accumulation of spatially coded detector data, the second step involves. Efficient light field acquisition using a coded aperture camera is the target problem considered in this paper. In the anger camera described in chapter 4, the pinhole aperture or the. The properties of the original radiation sources can then be mathematically reconstructed from this shadow. In contrast to conventional apertures, coded apertures i. Lensless codedaperture imaging with separable doubly.
The following list concerns papers that deal with the principle and details of coded aperture imaging i. Our methods apply these coded mask designs to each video frame and use compressive sensing optimization techniques for enhanced resolution digital video recovery. Nayar abstract the classical approach to depth from defocus dfd uses lenses with circular apertures for image capturing. Think of coded aperture as a way to produce shadows on an image.
Compressive coded apertures for highresolution imaging. Specifically, the entire light field, which consists of many images, should be reconstructed from only a few images that are captured through different aperture patterns. Willett department of electrical and computer engineering, duke university, durham, nc 27708 abstract nonlinear image reconstruction based upon sparse representations of images has recently received widespread attention. Nearfield coded aperture imaging is known to have superior image resolution and count sensitivity over conventional parallelhole collimated nuclear imaging. Antenna phase error compensation for terahertz coded. The multishot system thus requires the design of a sequence of code aperture patterns. Highrank coded aperture projection for extended depth of field chenguang ma1, jinli suo1, qionghai dai1, ramesh raskar2, gordon wetzstein2 1department of automation, tsinghua university, 2mit media lab abstract projectors require large apertures to maximize light throughput. As a promising imaging technology, terahertz coded aperture imaging tcai has the advantages of both terahertz imaging 1,2,3 and coded aperture imaging 4,5. Aperture is a java framework for extracting and querying fulltext content and metadata from various information systems file systems, web sites, mail boxes.
In decoding, the gradient projection for sparse reconstruction gpsr method was used in previous work to. Multiangular coded aperture projections are acquired and a stack of 2d images is reconstructed separately from each of. This optical bandpass retains more frequencies and more image details are reconstructed. Keita takahashis page research computational camera. Image reconstruction software for nearfield coded mask. Pdf compressive coded aperture keyed exposure imaging with. Compressive coded aperture keyed exposure imaging with optical flow reconstruction article pdf available june 20 with 99 reads how we measure reads. We propose to use a heuristic algorithm to remove the defocused artifacts and to improve the tomographic resolution. Reconstruction methods codedmask imaging is basically a twostep procedure. Compressive coded aperture video reconstruction request pdf. Osa coded aperture optimization for compressive xray.
Learning to capture light fields through a coded aperture camera. The analysis of fresnel zone apertures indicates that a lateral and longitudinal tomographic resolution close to the theoretical limit is achievable. Aug 04, 2011 coded aperture camera imaging concept c jean in t zand, 1992, 1996. Scintillator based coded aperture imaging has proven to be effective when applied for x and gammaray detection. In many applications selective spectral imaging is sought since relevant information. In this article, the authors present a novel method of 3d single photon emission computerized tomography spect reconstruction for nearfield coded aperture imaging. In the astronomical applications for which coded aperture imaging was originally. An excellent web site on the topic can be found at coded aperture imaging in highenergy astronomy, which also has an extensive bibliography. Coded aperture spectroscopy allows for sources of large field to be efficiently coupled into dispersive spectrometers by replacing the traditional input slit with a patterned mask. It is a nonlinear method that is fundamentally different from the decoding methods built on the linear and deterministic model, as described above. This technique has been implemented by other using photographic film as an image recording medium and optical reconstruction or decoding of the images. Comparison to traditional coded aperture method the dynamic reconstruction method can handle relative motion between the detector system and the scene. In this paper, we described the spectral calibrations principle and methods of coded aperture spectral imaging, and.
The wavelengths are usually highenergy radiation such as xrays and gamma rays. Adaptation of the same method for neutron imaging has resulted in a number of propitious systems, which could be potentially employed for neutron detection in security and nuclear decommissioning applications. Coded aperture imaging was introduced by dicke 1 and ables 2 in the 1960s, and the field developed rapidly for astronomical xray and gammaray imaging. Since coded aperture can view an object with a large solid angle, it can provide some tomographic resolution for threedimensional object. It began as a regular inline, twobeam interference holography and has evolved into an interferenceless technique based on a working principle entirely different from techniques of conventional holography. Medical imaging with coded apertures technical report. Willett, senior member, ieee abstractthis paper describes a coded aperture and keyed exposure approach to compressive video measurement which.
In contrast to traditional conebeam xray tomography, coded aperture xray tomosynthesis places a coded aperture between the xray source and the 3d object, by which certain xrays will pass or be blocked. While static coded apertures are easier to realize and less expensive, adaptive coded apertures are more effective. Coded aperture imaging manuel martinello school of engineering and physical sciences heriotwatt university a thesis submitted for the degree of philosophi. Spectral calibration of the coded aperture spectra imaging. Jul 03, 2008 to overcome this problem, we apply a coded aperture whose fourier transform has less low magnitudes initially. Rank minimization code aperture design for spectrally. This list is a personal nonexhaustive compilation of papers which in my mind are most relevant mainly to astrophysical applications. Coded aperture imaging uses many pinholes to increase the snr for intrinsically weak sources when the radiation can be neither reflected nor refracted. Thus, reconstruction could be improved by using multiple images. Using a statistical model of images, we can recover both depth information and an allfocus image from single photographs. The text is regularly updated for new developments in the field. Advacam minipix tpx3 xray diffraction for nondestructive. Coded aperture projection max grosse, oliver bimbery bauhausuniversity weimar figure 1.
To overcome this problem, we apply a coded aperture whose fourier transform has less low magnitudes initially. Osa fast optimization of coded apertures in xray computed. Coded aperture imaging coded aperture imaging has been presented recently in the context of computational photography 5, 6, and has been applied previously in astronomy and medical imaging. By using different coded apertures in a multiple source system, multiplexed projections can be. Our modification is to insert a patterned occluder within the aperture of the camera lens, creating a coded aperture. Image and depth from a conventional camera with a coded aperture siggraph 2007 presentation duration. Then, compressive sensing cs reconstruction algorithms are used to reconstruct the linear attenuation. The dynamic reconstruction method builds up an image as events are accumulated. Tcai uses a coded aperture antenna to modulate the phase of incident terahertz wave to produce a spatiotemporal independent radiation field in the imaging area.
Coded apertures are used in x and gamma ray imaging systems, because these hi. Recent developments in coded aperture mask designs have led to the reconstruction of static images from a single, lowresolution, noisy observation image. The feasibility and advantages of the technique are demonstrated experimentally. Coded aperture snapshot spectral imaging cassi system encodes the 3d hyperspectral image hsi within a single 2d compressive image and then reconstructs the underlying hsi by employing an. It is clear that codedaperture based reconstruction of the circular 241am source. Coded apertures or codedaperture masks are grids, gratings, or other patterns of materials opaque to various wavelengths of electromagnetic radiation. The power spectra of a gaussian psf a and of the psf of a coded aperture b. The pixet pro software used for detector operation is provided for free.
Willett department of electrical and computer engineering duke university research supported by darpa and onr icassp 2008. Both approaches significantly improve depthoffield through inverse light filtering when compared to circular aperture stops. Coded aperture spect reconstruction via mlem algorithm. The utility of coded aperture imaging of radioisotope distributions in nuclear medicine is in its ability to give depth information about a three dimensional source. We show that deconvolution with coded apertures leads to the reconstruction of signi. The new approach thus replaces the static code aperture in the cassi system by a digital micromirror devicedmd that permits changes in the code pattern, enabling the design of a multishot cassi system.
We introduce highrank coded aperture projectorsa new computational display technology that combines optical designs with computationalprocessing to overcome depth of. Index terms image reconstruction, image resolution, compressive sensing, coded aperture 1. Mcam cadbased software was used for the design of the aperture and. Effectively, the signal is multiplexed onto an image and then decoded, often by a computer, to form a reconstructed image. Highrank coded aperture projection for extended depth of. As mentioned, the work presented in this paper is an extension of our previous effort on nearfield coded aperture imaging. With a specific random pattern, one can detect light coming from a certain angle because it produces a certain signature on the camera focal plane array. A novel threedimensional image reconstruction method for. Coded aperture pairs for depth from defocus and defocus deblurring changyin zhou stephen lin shree k. Superresolution image reconstruction superresolution image reconstruction conventionally is the process by which several low resolution, noisy, slightly shifted observations are used to reconstruct an image of the underlying high resolution scene 1.
Coded aperture imaging seminal work in coded aperture imaging includes the development of masks based on hadamard transform optics 29 and pseudorandom phase masks 30. Radiation dose is a concern in xray tomographic imaging. This page is based largely on the article new family of binary arrays for coded aperture imaging by stephen r. The coded aperture snapshot spectral imager cassi is an architecture realizing csi where the reconstruction image quality relies on the design of a 2d set of binary coded apertures which block. After the accumulation of spatially coded detector data, the second step involves the decoding of this data, in other words the reconstruction of the observed part of the sky. Fourier magnitudes that are too low are clipped black, which causes ringing artifacts. Lensless codedaperture imaging with separable doublytoeplitz. It aims at the optimization of code aperture sets such that a group of compressive spectral measurements is constructed, each with.
Designed the model of ct equipment with xray cone beam, programed algorithm and constraint for image reconstruction using matlab, and optimized the code for coded aperture computed tomography. The objective lens images the continuous scene f onto the piezopositioned mask. By blocking radiation in a known pattern, a coded shadow is cast upon a plane. We introduce a criterion for depth discriminability which we use to design the preferred aperture pattern. Coded aperture correlation holography features mar 2020. In one of the configurations, the target is measured in transmission, while in the other it is measured in reflection. Osullivan2 1fitzpatrick institute for photonics and department of electrical and computer engineering, duke university, p. Typical cameras use pinhole apertures and lenses to focus the incoming light from the object onto the sensor array. Recent research developed in the area try to focus in extends the concept of cassi to a system admitting multiple shot measurements which leads not only to higher quality of reconstruction, but also to spectrally selective imaging when the sequence of code aperture patterns is optimized. A new code aperture design framework for multiframe code aperture snapshot spectral imaging cassi system is presented. Spect reconstruction software provided by the microspect system. A conventional camera captures blurred versions of scene information away from the plane of focus. In the absence of detector arrays, a single pixel coupled with an image plane coded aperture has been shown to be a practical solution to imaging problems in the terahertz and submillimeter wave domains. Nearfield highresolution coded aperture gammaray imaging.
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