Showing papers on "Image resolution published in 1980"

Range-Doppler Imaging of Rotating Objects

Abstract: During the integration time required to obtain fine Dopplerfrequency resolution in a range-Doppler imaging radar, a point on a rotating object may move through several range and Doppler resolution cells and produce a smeared image. This motion can be compensated by storing the appropriately processed return pulse, and the angular coordinates are determined by the angular coordinates of the radar antenna. The resulting stored data represents the three-dimensional Fourier transform of the object reflectivity density, and hence can be processed by an inverse Fourier transformation. Also included is an analysis of the three-dimensional radar/object geometry with separate source and receiver locations. The effects of various system aberrations are investigated and experimental results from a microwave test range which demonstrate the image improvement are presented.

Method of and apparatus for processing a radiation image

Abstract: A method and apparatus for processing a radiation image in a radiation image recording system in which a stimulable phosphor is stimulated with a scanning stimulating beam and the light emitted from the stimulable phosphor upon stimulation by the stimulating beam is detected by a detector which generates an output which is processed and used for recording a visible image on a recording material. In the processing of the detected output, an operation represented by a formula S'=Sorg+β (Sorg--Sus) is conducted, where Sorg is the original image signal detected by the detector, β is an emphasis coefficient, and Sus is an unsharp mask signal corresponding to a super-low spatial frequency at every scanning point. The unsharp masking process may be performed together with a gradation process, reduction of image size, smoothing process and the like. Further, the emphasis coefficient may be varied with either the original image signal Sorg or the unsharp mask signal Sus.

Real-time edge enhancement using the photorefractive effect

Abstract: Edge enhancement, a type of optical image processing, is performed in a photorefractive material in real time and with low incident-light intensities (10−3 W/cm2). We calculate the expected images using two different four-wave mixing geometries, which show good agreement with the images that we experimentally observe using a single-domain crystal of BaTiO3 as the photorefractive material.

Quantitation in positron emission computed tomography: 3 Effect of sampling.

Abstract: Effect of insufficient transverse sampling on quantitative positron emission computed tomography (ECT) was investigated with computer simulation and measurements on parallel bar and line source phantoms. Aliasing artifacts were observed and were found to be dependent on both the configuration and the location of imaged objects. Images of parallel bar phantoms were found to have aliasing artifacts similar in characteristics to aliasing on one-dimensional signals. In line source images, aliasing effects were manifested as variations in amplitude and full width at half maximum resolution (FWHM) for sources at even slightly different locations in the field of view. It was found that employing sampling distances smaller than one-third of the intrinsic detector FWHM eliminated noticeable aliasing artifacts. Image resolution was also found to be affected by the sampling distance. For a sampling distance equal to one-half of the intrinsic detector FWHM, the imaging FWHM is about 10% worse than the intrinsic FWHM. Selection of sampling distance in noisy environments is discussed. Parallel bar phantoms are shown to have advantages over line sources in the evaluation of sampling and resolution performance of ECT scanners.

Digital Processing of Ultrasonic Data by Deconvolution

Abstract: Abstrocr-Digital deconvolution of ultrasonic echo signals improves resolution and quality of ultrasonic images. Filtering usual B-scan images with a special digital fdter increases the lateral resolution by 50 percent. The filter is constructed from the measured signal amplitudes across the transmitter beam. By an empirical approach, it is optimized for low noise and high resolution. This method for lateral filtering produces good results for a great variety of test objects. The quality of the filter is maintained over a great range of depth, where the original beamwidth varies about 30 percent. This filtering method has high stability, such that application on measured profdes that are heavily disturbed does not increase noise nor produce disturbances.

Method of and apparatus for processing a radiographic image

Abstract: A method of and apparatus for processing a radiographic image in a radiographic image copying system in which an original radiograph scanned with the light beam and the image information of the radiograph is read out by a detector which gives an output to be processed and used for reproducing an image on a recording material. In the processing of the detected output, an operation represented by a formula D'=Dorg+β(Dorg-Dus) is conducted, where Dorg is the original image density detected by the detector, β is an emphasis coefficient, and Dus is an unsharp mask density corresponding to a super-low spatial frequency at every scanning point. The unsharp masking process may be performed together with a gradation process, reduction of image size, smoothing process and the like. Further, the emphasis coefficient may be varied with either the original image density Dorg or the unsharp mask signal Dus.

Aperture Synthesis by Object Rotation in Coherent Imaging

Abstract: Doppler processing is an established method for obtaining spatial resolution of objects which exhibit radial motion relative to an observing sensor. When applied to rotating objects, Doppler processing yields resolution in cross-range along an axis normal to both object rotation and line-of-sight axes. In this case, the cross-range resolution performance is dictated by the angular interval over which the data are observed and processed. This paper treats a tomographic extension of Doppler processing in the case of a rotating object (or a rotating planar array of point scatterers). It uses a stationary, continuous-wave (CW) irradiating source and sensor, co-located in the plane being imaged. The processing of data from a rotating object is shown to be equivalent to synthesizing an aperture which is a segment of a circle, however, processing over large angular rotations requires a focusing correction. Angular rotations up to and including 2? radians are considered. For this latter condition the system simulates an annular aperture which encloses the object. With this technique, high resolution may be obtained in all directions in the object plane without the use of a wideband signal, and equal point-objects separated by a quarter wavelength may be resolved. The imaging process provides high resolution for sparse arrays of objects of similar strength which are small in comparison to a wavelength. The imaging capability in the case of dense object arrays or large objects is limited and has a restricted dynamic range.

Performance Analysis of Three Camera Configurations for Single Photon Emission Computed Tomography

Abstract: The performance of three camera-based detector configurations for single photon emission computed tomography (SPECT) have been compared for system sensitivity and spatial resolution in the reconstructed images. These configurations are the flat detector with parallel channel collimation, the flat detector with focused channel collimation, and the fan-curved detector with focused channel collimation. The analysis was done by simulation of the projection data collection process in the collimator-detector assembly and subsequent image reconstruction for each configuration. Generally the results indicate that both the system sensitivity and image spatial resolution can be simultaneously improved by using largearea detectors with focused collimators. Except for short focal length cases, differences in performance between the two focused configurations are minimal.. Although the depth-dependence of collimator spatial resolution introduces point spread function (psf) shape anisotropy along the radius, varying both in the radial and azimuthal crirections, it does not significantly degrade reconstructed image quality.

High-resolution imaging by wave-front conjugation.

Abstract: Conjugate-wave-front generation by degenerate four-wave mixing is used to produce images with a resolution better than 500 lines/mm with 514.5-nm light.

Hybrid optical and electronic image processing for strain measurements by speckle photography

Abstract: A Young's fringe processor for speckle photographs is described. It automatically measures fringe separation and orientation with an accuracy of 1% and 1 degrees , respectively. The fringe evaluation is fast and computer controlled. Fringe densities of one to twenty fringes within the diffraction pattern can be treated with the same resolution. Application to displacement and strain measurements by focused image speckle photography is reported. Local strains can be determined with an accuracy of ~E = 10(-5) for displacements between 10 and 100 microm and a spatial resolution of 10 mm.

Coded-aperture imaging of the heart.

Abstract: Coded-aperture imaging of the heart combines the advantages of tomography with good sensitivity, high resolution, and accurate size scaling. Since the images are multiplexed, the method may be adapted to small, portable cameras for bed-side use without sacrificing image resolution. A new coded aperture designed especially for cardiac imaging has been constructed and tested. This aperture incorporates significant improvements over previous designs. Longitudinal tomograms are calculated at 1-cm intervals using a modified ART algorithm. Experimental lateral resulution at 140 keV with a portable scintillation camera is 3.8 mm FWHM at 4 cm, and 7.8 mm FWHM at 12 cm. Dpth resolution determined from a sloping line source is 1.1 cm FWHM at 4 cm, and 2.9 cm at 12 cm. The calculated point-source sensitivities in air at 4 cm and 12 cm, respectively, are 20 and 8 cps/microCi. Images of good diagnostic quality have been obtained in phantoms and in a dog model of acute myocardial infarction, using thallium-201, technetium-99m pyrophosphate, and gated ventricular blood-pool imaging with Tc-labeled red blood cells. Preliminary studies in humans confirm the good results in animals.

Real-time digital heterodyne interferometry: a system

Abstract: A system for obtaining real-time optical path difference maps is described. Results of applications to characterize thermally driven optical phenomena and active optical components are presented. Demonstrated performance parameters include a serial data acquisition rate of 50-microsec/point, spatial resolution to 500 points/line, and phase accuracy of lambda/70.

Synthetic formation of defect-free images - by superimposed blurring images of defect on reconstituted multiple perspective images

Abstract: A method and arrangement for tomographic synthetic image formation involve passing light through the object (6) from several positions to form perspective images (11) on a recording medium (10). The images are smapled by placing a lens at the source positions so as to superimpose them on a light sensitive layer, thus recording the visual image. The arrangement is designed to produce a natural locking image without defects. The perspective image is partially overlayed by a blurred image derived from the perspective image and of an intensity corresp. to that of the defect present in the image. The blurred image may be conducted by superimposing several visual images lying in front of and/or behind the layer image. This may involve moving the recording medium, lens and/or light sensitive film along the optical system axis.

Direct Digitization System for Quantification in Ion Microscopy.

Abstract: : A system for the quantification of secondary ion mass spectrometric images produced by an ion microscope is presented. The Microscopic Image Digital Acquisition System (MIDAS) developed in this laboratory by coupling a CAMECA IMS-300 ion microscope, a low light level TV camera, a video color graphics system and digital image processing techniques, is described. Ion images detected by the television camera are converted in real time into matrices of point intensities, maintaining the spatial resolution of the original image. These image matrices may then be converted to ion intensity space, or by the use of standards, to concentration. The use of ion implantation to fabricate image standards is presented as an evaluation of MIDAS. Applications of color display as a means of conveying compositional morphological information are demonstrated. (Author)

Tomography of hydrogen with nuclear magnetic resonance.

Abstract: A nuclear magnetic resonance (NMR) imager with a 6.5-cm aperture is described. Spatial resolution is 0.47 X 2.0 mm with a slice thickness of 8.4 mm. Contrast resolution is 3% for a 4-minute image. Because of the excellent spatial resolution and high contrast between soft tissues, the images provide a great deal of detail and reconstruction artifacts due to motion are avoided. Blood flow can be observed, and selected enhancement of lesions thorough the modification of software-controlled operational parameters is demonstrated.

Penetrating radiant energy imaging system with multiple resolution

Abstract: Radiation imaging means are disclosed for producing plural images exhibiting different resolution or contrast. As a pencil beam of radiation scans an object to be examined and is detected, its cross sectional size is periodically changed; and imaging means synchronously display signals obtained by detection of the respective beams of different cross section.

Use of Position Sensitive Detectors in Positron Imaging

Abstract: The use of Anger-type bar cameras for positron imaging results in a totally stationary system. In addition, the design is cost effective since the Anger principle will provide many resolution elements using only a few crystals and photomultipliers. Pulse shortening techniques are used to solve countrate problems associated with Anger-type detectors. When compared to an array of BGO detectors, a bar camera with equal sensitivity has superior spatial resolution.

Extracting linear features from images using pyramids

Abstract: : A method is described of extracting linear features from images. The approach is to construct a series of lower-resolution versions of the original image (a pyramid), and to look for lines in these images. A line in a low- resolution image corresponds to a thicker linear feature in a high-resolution image. The position and extent of this linear feature is calculated from the low-resolution image, and a threshold is found which, when applied in the neighborhood of the feature in the high-resolution image, segments the linear feature from its background. Advantages of the method are that only the parts of the image in the neighborhood of linear features need be thresholded, and that different thresholds may be used to extract the various linear features in the image.

Clinical and experimental investigation of a smoothed CT reconstruction algorithm.

Abstract: The usefulness of a smoothed reconstruction CT algorithm was studied using raw data from the EMI Mark I head scanner. The reconstruction algorithm operated on an off-line computer, independent of the EMI algorithm. This technique greatly reduces image noise and improves the visibility of very low-contrast structures, but at the cost of reduced spatial resolution. Phantom tests with contrasts as low as 0.14% demonstrated the validity of the images. Clinical results showed greatly improved visualization of gray and white matter with no increase in dose. It was necessary to expand the CT density scale so that the range from air to water was divided into 2,000 parts.

Image magnification and demagnification system

Abstract: A control system for controlling the size of the image produced by pixels generated by a raster scanner employing a binary rate multiplier for image size control along the X-axis, the multiplier being programmed to the size image desired to vary the frequency of the pixel clock signals output by the multiplier, together with a control flip-flop astride the image pixel stream and driven by the multiplier clock signals to speed up or reduce the rate at which image pixels are output. For image size control along the Y-axis, a phase lock loop is provided for controlling scanning carriage speed in response to the frequency of the signals output by a programmable frequency generator.

Improved techniques for multicolour reflection holograms

Abstract: It is shown that much brighter images are obtained with bleached reflection holograms recorded on separate plates with each of the wavelengths used and put together in register. A further improvement in image luminance is possible if holograms are recorded of a real image of the object projected by an optical system whose effective aperture is limited in the vertical plane by a suitably shaped stop.

High resolution acoustic probe

Abstract: A novel ultrasonic probe for the measurement of field distributions in water is described. In an arrangement using a metal cone tip as the antenna and an acoustic lens with conventional large diameter transducer as the detector, a spatial resolution of λ/4 was achieved. Experimental results for a 4 MHz design are presented.

Device for reducing faults in layer images of a three-dimensional object formed by means of penetrating radiation

Abstract: A device for reducing artefacts in layer images. Several layer images are formed of an object layer by irradiation from different directions. The same points of these layer images are compared in order to obtain a corrected layer image: when corresponding image information is present in all image points compared, the image information is transferred to corresponding layer image points in a corrected layer image; when the image information in the compared image points is not the same, that information is at least partly suppressed.

The spatial resolving power of earth resources satellites: A review

Abstract: The significance of spatial resolving power on the utility of current and future Earth resources satellites is critically discussed and the relative merits of different approaches in defining and estimating spatial resolution are outlined. It is shown that choice of a particular measure of spatial resolution depends strongly on the particular needs of the user. Several experiments have simulated the capabilities of future satellite systems by degradation of aircraft images. Surprisingly, many of these indicated that improvements in resolution may lead to a reduction in the classification accuracy of land cover types using computer assisted methods. However, where the frequency of boundary pixels is high, the converse relationship is found. Use of imagery dependent upon visual interpretation is likely to benefit more consistently from higher resolutions. Extraction of information from images will depend upon several other factors apart from spatial resolving power: these include characteristics of the terrain being sensed, the image processing methods that are applied as well as certain sensor characteristics.

A New Photocathode for X-ray Image Intensifies Operating in the 1–50 keV Region

Abstract: Publisher Summary This chapter discusses a new photocathode for X-ray image intensifiers. The X-ray image intensifier is a device extensively used in scientific research, industry, and medicine. The detection process of an X-ray in a low density layer is rendered schematically. While accurate measurement of the spatial resolution response functions of an X-ray image intensifier at high spatial frequencies is a matter of some difficulty, it was felt that some indication of the likely spatial resolution of a low density X-ray cathode could be deduced from previously studies. Degradation of the spatial resolution can be expected to arise from two causes: the physical spread of the photoelectrons released by the X-ray in the layer and the lateral spread of the induced charged cloud as it drifts through the layer. The calculation of the limits to the spatial resolution set by the X-ray absorption processes is achieved with reasonable precision by referring to the work done by Bateman on xenon gas proportional counters.