Showing papers on "Image resolution published in 1978"
TL;DR: The ECAT was designed and developed as a positron imaging system capable of providing high contrast, high resolution, quantitative images in two-dimensional (2-D) and tomographic formats and significantly reduces errors caused by motion and detector instability.
Abstract: The ECAT was designed and developed as a positron imaging system capable of providing high contrast, high resolution, quantitative images in two-dimensional (2-D) and tomographic formats. The flexibility in its variety of imaging problems. High (HR), medium (MR), and low (LR) tomographic resolutions are 0.95 +/- 0.1, 1.3 +/- 0.1, and 1.7 +/- 0.1 cm FWHM; high, medium, and low resolutions in 2-D images are 0.85 +/- 0.1, 1.3 +/- 0.1 and 1.7 +/- 0.1, depending on resolution mode employed. ECT system efficiency is 30,100, 15,900, and 9,200 c/sec/muCi/cc with a 20-cm diameter phantom at LR, MR, and HR. Because of the geometric, detector, electronic and shielding design of the system, count-rate capability and linearity are high, with minimum detection of scattered radiation and random coincidence. Measured error agrees well with theoretical statistical predictions down to a level of 1.4% standard deviation. The redundant sampling scheme of this system significantly reduces errors caused by motion and detector instability. Scan times are variable from 10 sec to several min/slice and multiple levels are automatically performed by computer control of patient bed. A variety of human studies illustrate image quality, resolution, and efficiency of both ECT and 2-D imaging mode. Examples of the noninvasive study method have been made possible through development of ECT.
280 citations
TL;DR: In this paper, a multimode planar optical waveguide of homogeneous refractive index can produce real one-dimensional self-images by interference of the waveguide modes, and the authors discuss the image formation, the linespread function, and its apodisation and optimization.
Abstract: A multimode planar optical waveguide of homogeneous refractive index can produce real one-dimensional self-images by interference of the waveguide modes. We discuss the image formation, the linespread function, and its apodisation and optimization. Under optimum conditions, the theoretical linear resolution can reach 0.25(W λf)1/2, where W is the slab thickness and λf is the wavelength in the slab material.
126 citations
TL;DR: The degradation in acquisition probability that occurs when cross correlation is used to determine the offset of two images of the same scene that differ by a relative geometric distortion is presented.
Abstract: The degradation in acquisition probability that occurs when cross correlation is used to determine the offset of two images of the same scene that differ by a relative geometric distortion is presented. The geometric distortions considered can be represented by a general affine transformation of image coordinates. The analysis shows that for a given geometric distortion there is an image size and shape that minimizes the probability of false acquisition. The results are derived for images modeled as random patterns with arbitrary auto-correlation functions. The results are illustrated for images with Gaussian autocorrelation functions.
56 citations
TL;DR: A Fourier deconvolution technique is described for obtaining three-dimensional medical images that uses a generalized matrix inversion by singular value decomposition to modify the low frequency Fourier components.
Abstract: A positron camera consisting of two high density proportional chambers is described. It provides a spatial resolution of 2.4 mm FWHM, a maximum data rate of 3000 c.p.s. and a sensitivity of 25 c.p.s. per ?Ci. Results of its application to angular correlation studies of condensed matter and to phantom and in vivo medical imaging are presented. A Fourier deconvolution technique is described for obtaining three-dimensional medical images. It uses a generalized matrix inversion by singular value decomposition to modify the low frequency Fourier components.
45 citations
TL;DR: In this paper, the effect of geometric distortion on the local accuracy of the image registration algorithms using cross correlation is presented using a probabilistic model describing images as homogeneous random patterns, expressions for the mean and covariance of the local error vector in terms of image and noise autocorrelation functions, geometric distortion, and reference image area are derived.
Abstract: The effect of geometric distortion on the local accuracy of the image registration algorithms using cross correlation is presented. Using a probabilistic model describing images as homogeneous random patterns, expressions for the mean and covariance of the local error vector in terms of image and noise autocorrelation functions, geometric distortion, and reference image area are derived. The geometric distortions considered are those represented by an affine transformation of image coordinates. It is shown that for a fixed geometric distortion there is an image size (integration area) that minimizes the local error. The optimum area decreases with increasing geometric distortion.
43 citations
TL;DR: In this paper, a coherent optical method was proposed to measure the partial derivatives of the contour of an object with respect to the direction of shearing, where the object is immersed in a refractive medium and imaged by a camera with a shearing device.
Abstract: This paper presents a new coherent optical method whereby the partial derivatives of the contour of an object are measured. The object to be studied is immersed in a refractive medium and is imaged by a camera with a shearing device. The processed photographic plate which has been doubly exposed in the image plane with the refractive medium changed between the exposures can be Fourier filtered to yield a fringe pattern depicting derivatives of the surface contour with respect to the direction of shearing. This new method enjoys the advantages of being simple and less demanding in vibration isolation, coherence of light source, and film resolution.
43 citations
TL;DR: In conclusion, 3-D color images composed of thirty-five elements in the horizontal direction and seen from four directions are successfully transmitted and reconstructed with clear parallax and are seen by the naked eye.
Abstract: Theoretical and experimental investigations on the real-time transmission of 3-D images formed by parallax panoramagrams are described. At the image-taking station, a 3-D image is optically decomposed into line images, which can be directly handled by a high resolution TV set. By registering a lenticular sheet to the reproduced line images on a monitor screen, the reconstructed 3-D image is seen by the naked eye. By using an ordinary color TV set with a 350-line resolution and a cylindrical lens array with a 3-mm pitch, 3-D color images composed of thirty-five elements in the horizontal direction and seen from four directions are successfully transmitted and reconstructed with clear parallax.
41 citations
TL;DR: In this paper, a halftone screen function is used to specify configurations of binary image elements; their area determines the local average image irradiance and information about the spatial image irradiances variations is relfected in their boundaries.
Abstract: The halftone technique, which converts a continuous-tone picture into a binary image, is examined. A halftone screen function is used to specify configurations of binary image elements; their area determines the local average image irradiance and information about the spatial image irradiance variations is relfected in their boundaries. A halftone ring geometry is suggested to improve spatial image resolution. Experiments are reported to verify this prediction.
34 citations
Patent•
08 May 1978
TL;DR: In this article, an approach and method for producing image combinations in which the image to be copied are digitally stored and a mask is produced for manually superimposing the images with each other with one of the images and the mask being scanned and wherein the coordinates of the image which is to be transferred into the other image are measured as x and y values.
Abstract: Apparatus and method for producing image combinations in which the image to be copied are digitally stored and a mask is produced for manually superimposing the images with each other with one of the images and the mask being scanned and wherein the coordinates of the image which is to be transferred into the other image are measured as x and y values and the two images are combined by utilizing the x and y values to form a composite total image.
33 citations
TL;DR: The feasibility of three specific coding schemes for compact storage or fast transmission of radiographic images is investigated and the dependence of the compression ratio on image resolution and the feasibility of adaptive coding of bit planes is examined.
Abstract: The feasibility of three specific coding schemes for compact storage or fast transmission of radiographic images is investigated. These schemes are: the synthetic high system, the block-coding system, and the run-length coding system. The last two techniques are used for encoding bit planes. The dependence of the compression ratio on image resolution and the feasibility of adaptive coding of bit planes are also examined.
30 citations
TL;DR: In this paper, point-to-point resolutions of better than 1·7 A have been obtained for Ti6O11 using ultra-high-resolution objective lens pole-pieces and a specially constructed goniometer.
Abstract: Image-matching techniques are used to demonstrate that point-to-point resolutions of better than 1·7 A have been obtained for Ti6O11 using ultra-high-resolution objective lens pole-pieces and a specially constructed goniometer. However, it is important to distinguish between instrumental and structure image resolution. Whereas the former may be as low as 1·6 A, the latter is approximately 2·8 A for C8 = 0·7 mm at 100 kV. It is shown that to take advantage of 1·6 A instrumental resolution and obtain useful defect structure information, lengthy calculations and demanding experimental requirements must be met. On the other hand, 2·8 A structure imaging is far less demanding experimentally (focused illumination may be used for example) and the truncated projected-charge-density approximation may be used, at least in the preliminary stages of defect-structure refinement.
TL;DR: An X-ray imaging detector with good energy resolution, good spatial accuracy and high counting rate has been built for medical application as discussed by the authors, which requires, on the contrary to proportional counters, a high degree of gas purity but produces a significant improvement in energy resolution.
TL;DR: In this article, a generalised matrix inversion technique was used to limit noise amplification to a level related to the spatial resolution of the imaging system, and results were presented on the imaging of an extended, three-dimensional object distribution.
Abstract: A major problem with the reconstruction of three-dimensional object distributions from focused tomographic images using Fourier transforms is the amplification of statistical noise in certain frequency components. The use of a generalised matrix inversion technique to limit noise amplification to a level related to the spatial resolution of the imaging system is described. The reconstruction method is applied to a simulated positron camera, and results are presented on the imaging of an extended, three-dimensional object distribution. A significant improvement in the elimination of the background is achieved.
TL;DR: Results are shown for coherent optical processing by computer-controlled Fourier plane filtering and real-time image correlation, and signal processing systems are described which couple the PROM with an acousto-optic raster recorder to perform spectrum analysis and correlation on radio frequency signals.
Abstract: The PROM is a solid-state, rapidly recyclable, image storage device having a number of applications in image and signal processing. Some of its important characteristics include 1/10-wave optical surface quality, 100-1p/mm three-bar resolution, 10 ergs/cm2 light sensitivity, and image plane contrast of 10 4 :1. One of the unique features of the PROM is that the bias level of stored patterns can be adjusted through application of an external voltage, resulting in image contrast inversion or enhancement. This same operation (baseline subtraction) is used to null the zero order in an optical Fourier transform, achieving a Fourier plane signal-to-noise ratio approaching 106:1. This paper reports on the current status of this device and a number of applications for which it has been tested in several areas of image and signal processing. Results are shown for coherent optical processing by computer-controlled Fourier plane filtering and real-time image correlation, and signal processing systems are described which couple the PROM with an acousto-optic raster recorder to perform spectrum analysis and correlation on radio frequency signals.
TL;DR: In this paper, seven radar-brightness and altitude images of the equatorial belt of Venus are presented, each of a small circular region within the equator belt of the planet.
Patent•
03 Jul 1978
TL;DR: In this paper, an optical read-write system including a first laser scanner for linearly scanning an object and generating a digital signal for the line scan is described, where the digital signal is stored in a buffer at a read clock rate which is correlated to the scan of the first scanner.
Abstract: Disclosed is an optical read-write system including a first laser scanner for linearly scanning an object and generating a digital signal for the line scan. The digital signal is stored in a buffer at a read clock rate which is correlated to the scan of the first laser scanner. The digital signal is read-out of the buffer at a write clock rate and is applied as a control signal for a second laser scanner which linearly scans an image plane to develop an image. The second scanner scans at the same scan rate and distance as the first scanner, and the size of the image compared to the object size is determined by the differential of the read clock rate and the write clock rate.
TL;DR: In this article, a gamma-ray camera consisting of two 3.2×3.2 × 1 cm3 HPGe detectors has been assembled and a square hole collimator has been fabricated with design parameters that exploit the unique characteristics of the detector.
Abstract: A gamma-ray camera consisting of two 3.2×3.2×1-cm3 HPGe detectors has been assembled. Shallow orthogonal grooves define 512 2×2-mm2 elements. Square hole collimators have been fabricated with design parameters that exploit the unique characteristics of the detector. Intrinsic spatial resolution is a square function with 2-mm width, and energy resolution is approximately 2.5% FWHM at 140 keV. Evidently superior images are obtained when this instrument is compared to state-of-the-art scintillation cameras.
TL;DR: The double-star image presented indicates that the bulk of the atmospherically induced wave-front phase change occurred within 2 kilometers of the telescope, which implies that, at least for conditions similar to those of the authors' measurement, real-time correction can be accomplished simultaneously for a region at least several arc seconds in angular size.
Abstract: Atmospherically induced phase perturbations have for years limited the resolution of large optical astronomical telescopes. A prototype telescope system with six movable elements has successfully corrected these phase perturbations. This use of real-time image sharpening has restored stellar images to the diffraction limit (in one dimension) for a 30-centimeter telescope. The double-star image presented indicates that the bulk of the atmospherically induced wave-front phase change occurred within 2 kilometers of the telescope. This implies that, at least for conditions similar to those of our measurement, real-time correction can be accomplished simultaneously for a region at least several arc seconds in angular size. With the present apparatus the technique should be practical for objects as dim as fifth magnitude, and with improvements the technique holds the promise of active image restoration for objects as dim as ninth magnitude.
TL;DR: Quantitative relationships were found concerning the spatial resolution for objects of varying sizes, concerning the partial volume effect and the thickness of the section for object of varying size, and concerning the relationship between resolution and partialVolume effect for small objects.
Abstract: The present work deals with the problem of demonstrating tissue changes of small volume by computer tomography. Measurements were carried out with the Somatom computer tomograph and evaluated by the Evaluscope (both Siemens); fourteen test situations were devised, using plexiglass rods of varying diameter and different penetration into the level being sectioned. Quantitative relationships were found concerning the spatial resolution for objects of varying sizes, concerning the partial volume effect and the thickness of the section for objects of varying size, and concerning the relationship between resolution and partial volume effect for small objects.
TL;DR: A description will be given of the image forming process in which diffraction at the penultimate mask and at the aperture of the lens are the critical features, and rules for maximum edge sharpness are given, so that the tolerance demands on the production process can be relaxed.
Abstract: Optical projection of masks is a very troublesome task if dimensions are in the submicron range. It is difficult to get an undistorted image in the resist. This problem can be overcome by introducing corrections in the penultimate mask. Till now this has been done by a trial and error method in which an acceptable pattern is made only after a time consuming iterative process. In this paper a description will be given of the image forming process in which diffraction at the penultimate mask and at the aperture of the lens are the critical features. Based upon this theory correction formulas are derived for the direct design of penultimate masks. Rules for maximum edge sharpness are given, so that the tolerance demands on the production process can be relaxed. Extensive experimental measurements are in good agreement with theory. It will be shown theoretically as well as practically that by asymmetrical arrangement of the optical system images of gratings with 0.2–0.3 μm linewidth can be obtained.
TL;DR: In this article, the multiwire proportional chamber is compared to photographic film for protein crystallography and the acquired information per photon incident on the specimen is higher and a much better time resolution can be achieved.
TL;DR: Reconstructed images of test objects show spatial resolution uniformity, and attenuation corrections enable estimation of relative activity densities to within 10--15% rms errors, thus demonstrating quantitative imaging capabilities of emission CT.
Abstract: Emission computed tomography (ECT) studies were performed on test objects and dogs. Conjugate views were obtained for 60 to 120 projections equispaced around 360° by rotation of the subjects in front of a gamma camera. A convolution reconstruction algorithm in which gamma ray attenuation corrections are included in the backprojection step were used to reconstruct the emission images. Reconstructions of x-ray transmission data provided data for gamma ray attenuation corrections of the emission images of 99mTc-pyrophosphate uptake in dogs. Reconstructed images of test objects show spatial resolution uniformity, and attenuation corrections enable estimation of relative activity densities to within 10–15% rms errors, thus demonstrating quantitative imaging capabilities of emission CT.
TL;DR: It is demonstrated that the position sensitive detector system achieves a marked improvement of measurement speed, S/N ratio, and sensitivity, and the system also realized an improvement of spatial resolution while retaining energy resolution.
Abstract: A position sensitive detector system composed of a channel plate, a vidicon TV camera, and a computer is utilized for multichannel detection of ESCA spectra. It is demonstrated that the system achieves a marked improvement of measurement speed, S/N ratio, and sensitivity. The system also realized an improvement of spatial resolution while retaining energy resolution.
TL;DR: In this article, a photoplastic transducer was used as an incoherent-to-coherent transducers to insert data into a coherent optical processor in real time.
Abstract: The photoconductor-thermoplastic, or photoplastic, recording medium can serve as an incoherent-to-coherent transducer to insert data into a coherent optical processor in real time. The photoplastic transducer is characterized by good exposure sensitivity, high resolution, and simple construction, and it is well suited to applications requiring image retention before and during readout. In our investigations we measured exposure sensitivities of less than 50 ergs/cm2 , and achieved a write cycle of charge, expose, and develop in less than 10 msec. Because of the band-pass nature of the recording medium, a spatial frequency offset was provided by overlaying the image with a grating. Images were recorded with incoherent light and read out with coherent light with good fidelity, and the transducer was tested as the input to a matched filter processor.
TL;DR: In this article, the authors describe the construction and performance of an atom-probe field-ion microscope which uses a time-gated microchannel plate as a single-ion detector with spatial resolution.
Abstract: The paper describes the construction and performance of an atom-probe field-ion microscope which uses a time-gated microchannel plate as a single-ion detector with spatial resolution. The instrument has a mass resolution Delta m/m in the range 1/15 to 1/25, and a spatial resolution of the order of 1 nm. It is particularly suitable for the detection of segregation at grain boundaries, and an example (oxygen in molybdenum) is given.
TL;DR: A gamma camera made of multiple multiwire proportional chambers with thin converter foils with good imaging of 99Tcm radionuclide distributions and comfirming the predictions of the theory regarding quantum efficiency and spatial resolution is evaluated.
Abstract: A gamma camera made of multiple multiwire proportional chambers with thin convertor foils has been evaluated for clinical application. Results are presented from a small prototype (10 cm*10 cm) showing good imaging of 99Tcm radionuclide distributions and confirming the predictions of the theory regarding quantum efficiency and spatial resolution. The technique is especially aimed at creating a gamma camera with an active area >or approximately=1 m2, a quantum efficiency of 15% and a spatial resolution approximately 3 mm, to be applied in whole body scanning and tomographic applications. The results generated by the current prototype indicate that the above requirements can be met using relatively cheap mass production techniques from the electronic industry.
TL;DR: A new real-time servo controlled sector scanner that produces high resolution images and has functionally programmable features similar to phased array systems, but possesses the simplicity of design and low cost best achievable in a mechanical sector scanner.
01 Jan 1978
TL;DR: Two-dimensional holographic scanners utilizing an auxiliary reflector using multiplexing techniques for increasing the resolution and applications in the visible and other spectra regions including millimeter or microwave and ultrasonic wave are suggested.
Abstract: Two-dimensional holographic scanners utilizing an auxiliary reflector are described. The design equations and procedures are derived and outlined. Multiplexing techniques for increasing the resolution are proposed. Scanners of reasonable size and operating at a moderate speed can achieve a total resolution of 10(7)and a temporal signal of 100 mHz. Applications in the visible and other spectra regions including millimeter or microwave and ultrasonic wave are suggested.
TL;DR: This work is investigating the use of a real-time image transducer, developed by Hughes Research Laboratory, for real- time coherent optical information processing, and describes the response time of the device under various operating conditions.