Showing papers on "Edge enhancement published in 1984"

Digital subtraction angiography: principles and pitfalls of image improvement techniques

Abstract: The technology of imaging methods in digital subtraction angiography (DSA) is discussed in detail. Areas covered include function of the video camera in both interlaced and sequential scan modes, digitization by the analog-to-digital converter, logarithmic signal processing, dose rates, and acquisition of images using frame integration and pulsed-sequential techniques. Also discussed are various methods of improving image content and quality by both hardware and software modifications. These include the development of larger image intensifiers, larger matrices, video camera improvements, reregistration, hybrid subtraction, matched filtering, recursive filtering, DSA tomography, and edge enhancement.

Edge enhancement filtering for digital fluorography images

Abstract: For edge enhancement of a digitized fluorographic image, the original image is stored in a full frame memory. When each video vertical blanking pulse occurs time delays are initiated corresponding to shifting whole lines of pixels successively to the left and right and up and down by integral numbers before the pixels are read out of memory. As the pixels are read out for each vertical blanking cycle, they are multiplied by a coefficient related to the pixel shift number and the result is added to to image data from preceding cycles that are summed and stored in a second memory and the new result is returned to the second memory. The final result is an edge map in the second memory constituting digital values corresponding to the frequency components at edges. These are added to corresponding pixels in the original image, resulting in higher and sharper edges in a final digital image. The image is then converted to analog video signals to permit display on a video monitor.

Edge enhancement in scanning optical microscopy by differential detection

Abstract: A simple method of optically producing edge-enhanced images in a scanning optical microscope is described. The method uses a coded photodiode detector from which the conventional unenhanced image may be obtained simultaneously.

Enhanced-image mammography.

Abstract: A blurred-mass subtraction technique has been developed for mammography, which enhances small-object contrast and visibility throughout the breast area. The procedure is easy to implement and requires no additional exposure. Perception of low-contrast objects is improved by eliminating extreme light- and dark-image areas. Contrast of structures within certain portions of the breast is increased by compression into the high-contrast portion of the film characteristic curve. Detail visibility is also increased by the edge enhancement produced by this process. This paper describes the enhancement process and gives an analysis of its capabilities and limitations.

Edge Enhancement by Defocusing of Confocal Images

Abstract: In coherent imaging, the position of an opaque edge may be determined by examining where the intensity has dropped to one-quarter of that far from the edge in the bright region, the precision with which this point may be found depending on the slope of the profile. This is true also for confocal imaging, for which it is found that the slope of the normalized edge image actually increases with defocus. Experimental confirmation of the effect is given. The effect has possible application in the measurement of linewidths in semiconductor microlithography.

An Adaptive Edge And Contrast Enhancement Technique Based On Unsharp Masking

Abstract: An adaptive image filtering scheme is presented for edge and contrast enhancement. This filtering technique is based on a sliding window, which moves across the image in both vertical and horizontal directions. At each step, the density value of the center pixel in the window is transformed to a new value via the filtering equation. This algorithm is superior to that of unsharp masking, a technique reported in the past few years, in the sense that it does not uniformly enhance the high frequency noise components of the image for the sake of edge enhancement. Since the parameters of this filtering algorithm are adaptively adjusted according to the statistics of the local area (window), there are no user (operator) interactions required. The relation between the size of the sliding window, the degree of enhancement, and the stability of the filter are shown in applications concerning visualization of digital angiograms and chest radiographs.

Digital Image Processing for Scanning Acoustic Microscopy

Abstract: Ahrmct-The use of a versatile digital image storage and processing system for scanning acoustic micrmcopy is described. In addition to the data capture and storage functions, different types of image processing functions of particular relevance to scanning acoustic microscopy have been incorporated These ipclude real-time grey scale enhancement and a variety of ofStine edge enhancement, spatial fdtering, and pseudocolor processing algorithms. These facilities can enhance particular aspects of the image or 6lter out unwanted artifacts. Typical results are presented. The further potential of digital processing for scanning acoustic microscopy is discussed. recurring problem associated with the use of imaging apparatus is the production of a display which will do justice to the quality of the data acquired and which is able to take advantage of the powerful electronic techniques for image storage and processing. The image processing described in this paper arose out of necessity, in the course of working with a relatively new form of imaging-scanning acoustic microscopy. Our approach has therefore been to present our results as an example of the application of general image processing techniques to a set of specific problems, arising from this form of microscopy. The scanning acoustic microscope (SAM) was first demonstrated by Quate and Lemons in 1973 [l]. Since then it has been developed sufficiently to allow its use as a tool for investigation of a wide range of materials as well as biological samples. It is particularly appropriate for the examination of the interior of optically opaque media [2] - [4]. In the basic operation of a SAM (reflection or transmission) [5], the object is immersed in a liquid (normally water) and place at the focal plane of an acoustic lens where it is interrogated by a focused ultrasonic beam. The object is subsequently scanned over the entire field of view in a raster manner so that the image is formed point by point. In a typical instrument the two orthogonal displacements of the scanner are measured by means of position encoders. Both amplitude and phase data may be recorded at each point in the scan. As the information and the position encoder outputs are produced in an analog form it was, until recently, accepted practice to resort

Edge Detection In Real-Time

Abstract: A hardware system for real-time image processing is described. The hardware is designed to work at a 10 MHz pixel rate, and will accommodate 512 x 512 images at 25 frames per second. The techniques of parallelism and pipelining are used to achieve the required speed. The system's primary function is the application of an edge detection algorithm to video data in real-time, the algorithm being a 2 x 2 Roberts operator thresholded with a function of local average brightness. The output of the system is a single bit/pixel edge picture which can be directly transferred into the memory of the host computer for further processing. Manipulation of the threshold function allows the system to disregard the edge detection function, and work directly on a greyscale image. The resulting single bit/pixel images can range from simple thresholded greyscale to the display of greyscale intensity contours. The edge detection process, coupled with these additional operational modes, makes the system a powerful tool for image processing.

The Role Of An Image Processing Realtime Digital Disk In A PACS System

Abstract: This paper describes the application of a Realtime Digital Disk (RTDD) with processing capabilities and the increased functionality the RTDD brings to a PACS system. While the display and acquisition of images at 30 frames per second is the obvious advantage of the RTDD in PACS, the image processing and image enhancing functions make its use more effective. Realtime presentations include window and level of greater than 8 bit images, intensity transformation of 8 bit images, shape table and tiling presentation, and subsampling. Movie loop and three dimensional reconstruction sequences are viewed in realtime. Edge enhancement, smoothing, interpolated zoom, unsharp masking and other convolution filtering are near realtime presentations. Compression and decompression, histogram equalization and other transforms are performed in just a few frame times.

Image-plane processing for improved computer vision

Abstract: The proper combination of optical design with image plane processing, as in the mechanism of human vision, which allows to improve the performance of sensor array imaging systems for edge detection and location was examined Two dimensional bandpass filtering during image formation, optimizes edge enhancement and minimizes data transmission It permits control of the spatial imaging system response to tradeoff edge enhancement for sensitivity at low light levels It is shown that most of the information, up to about 94%, is contained in the signal intensity transitions from which the location of edges is determined for raw primal sketches Shading the lens transmittance to increase depth of field and using a hexagonal instead of square sensor array lattice to decrease sensitivity to edge orientation improves edge information about 10%

An Evaluation Of Digital Processing Capabilities For Improving Detection Of Low Contrast Round Objects In A Radiography By Contrast Detail Diagrams

Abstract: In this evaluation contrast-detail diagrams were used to measure the effects on observer performance of several image processing algorithms such as edge enhancement, smoothing and histogram equalization. The observer task was the detection of disk images in a uniform background. A new digital system, DigiRad System One, was used to digitize and postprocess images of a "Rose-Burger" contrast phantom. Results show that detectability of low contrast objects may increase for images taken with standard film/screen combinations. Anticipated changes on the System One may enhance its capabilities significantly.