Showing papers on "Edge enhancement published in 1983"

Optical correlator using electronic image preprocessing

Abstract: An optical processing system uses spatial filtering to recognize two-dimensional functions and images. Images of real objects are captured with a television camera. The electronic signals representing the two-dimensional function or image are electronically preprocessed, such as by edge enhancement techniques or by applying a curvature function, and displayed on a narrow-band-phosphor cathode ray tube or television monitor. The monitor image is used directly as the input to an incoherent holographic correlator. Alternatively, the monitor image is used to modulate a source of coherent radiation such as a laser via a spatial light modulator to generate a modulated optical signal which is the input to a coherent holographic correlator. Analyzer circuitry with an optical detector at the correlation plane analyzes the shape of the correlation function to determine the intensity and position of its peak. The input to the CRT or monitor may also be in the form of non-optically generated electronic signals representative of a two-dimensional function for display in graphic form by the CRT or monitor.

Enhanced image mammography.

Abstract: A blurred mass subtraction technique has been developed for mammography that will enhance 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 parts of the breast is increased by compression into the high-contrast part 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.

An image processing approach to fast, efficient proximity correction for electron beam lithography

Abstract: A limitation on the quality of electron beam lithography is the proximity effect. This produces exposure of the resist at locations remote from the point of incidence of the electron beam. One of the techniques used to mitigate this problem is to precompensate the applied beam dose. Traditional approaches to this problem have required extensive calculations which occasionally fail to produce satisfactory results. However, the proximity correction problem is quite similar to the edge enhancement problem which arises in pattern recognition. Furthermore, the issue of data base compaction for the precompensated lithography is quite similar to bandwidth compression in image transmission. In this paper, we examine the application of image processing methods to the proximity correction problem. We find that, while the match between these disciplines is not perfect, the idea appears quite promising.

An Investigation of Digital Mammographic Imaging

Abstract: Measurements and theoretical calculations of the limitations of film-screen mammography have been made. The results show that the use of mammographic film-screen systems to image the breast has three major drawbacks: 1) insufficient contrast enhancement for the visualization of subtle tumours and microcalcificatons; 2) limited latitude, i.e. in some patients, structures in thin and thick or dense regions of the breast are not clearly visible on the same film; and 3) dose inefficiency, since most mammograms are not quantum-limited. Digital techniques may overcome these problems by decoupling the image recording and display processes, allowing for contrast enhancement without loss of dynamic range. Using digitized film mammograms and phantom images, we have made a preliminary study of whether image processing can improve visualization of breast lesions. Contrast enhancement by histogram equalization and linear scaling with clipping, and edge enhancement by unsharp masking allowed the extraction of more information than was originally perceived on the film. In these images, however, film grain noise accounts for at least one-third of the total image noise, and thus limits the degree to which the images can be enhanced. To investigate the feasibility of recording digital mammographic images directly, an x-ray image intensifier (XRII) was evaluated. With the use of geometric magnification and small focal spot x-ray tubes, the XRII can produce images with sufficient resolution for mammography. Noise power spectra of both XRII and film-screen images were measured. The XRII was found to have better sensitivity and, if structural mottle can be removed, a higher signal-to-noise ratio than mammographic film-screen systems; however, it is limited by the high attenuation of the front input window at mammographic energies.

Side-scan sonar mapping and computer-aided interpretation in the Santa Barbara Channel, California

Abstract: We have experimented with digital processing of side scan sonar data taken in a 14 sq-km area of continental shelf offshore Southern California. The data were FM tape recorded during the survey and digitized and processed later in the laboratory. The digital image processing included both image correction and image enhancement. Geometric corrections were applied to correct for image distortions due to variable ship position and speed and sonar slant range. Enhancements that were tried included contrast stretching, band-pass filtering, image restoration (inverse filtering), and various edge enhancements such as density slicing and standard deviation filters. Interpretive procedures were also attempted and included digital mosaicking, stereoscopic viewing, and falsecolor display. The most effective processing was geometric correction combined with contrast stretching. Mosaicking proved difficult due to imprecise navigation (±50 m), but was very effective in increasing the understanding of the geologic structure in the survey area.

Efficient algorithm for image enhancement

Abstract: The problem of smoothing, point, line and edge detection in image processing is considered. It has been shown that computation in each case can be speeded up considerably by looking at the redundancy. The methods are simple and can be implemented easily in software or hardware.

Image enhancement in a dithered picture

Abstract: A technique called ordered dither for displaying continuous tone pictures on a bilevel display or a display with limited levels has been investigated. In a dithered picture with many pseudo halftones, edges are blurred and letters or drawings are indistinct. A technique for edge enhancement to display dithered pictures of high quality is presented. The method partially controls the contrast of the dithered picture. The displayed picture can be easily enhanced by changing the thresholds of the dither matrices. The method has the advantages of simple processing, simple hardware construction, and high quality picture display. It is a very powerful and flexible image processing method.

Intelligent Image Digitizing Subsystems

Abstract: An image scanner/digitizer has been developed which utilizes solid state array sensors to achieve high-speed, high-resolution scanning of black and white images. The internal 68000 microprocessor-controlled unit is desk-top sized, easy to interface, and simple to operate. It incorporates the following features: o Flat bed input platen o Two selectable input scan widths o Cursor cropping of scanned area to minimize digital data storage requirements o Eight bit per pixel digitization of imagery o One bit per pixel digitization of line art o Reflected or transmitted white light scanning o Automatic pre-scan sensor calibration The scanner provides high fidelity digitization of imagery for a variety of applications, including CAD/CAM and medical image enhancement. It is currently being used to input line graphics and photographs to an all-electronic image assembly subsystem. Proprietary software provides a powerful, user-friendly menu of the image processing and page layout functions required for electronic page composition. Simple operator interactions with a data tablet invoke and control the operations of: o Contrast/brightness enhancements o Image placement and rotation o Software-interpolated image sizing o Outlining o Cropping and stripping o Edge enhancement o Small area modifications o Graphic creation and modification o Application of spot colors from a user-defined color palette© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Dual Image Processing For Stereoscopic Display

Abstract: For an in-depth study of features of the celestial surface, stereoscopic imaging technique serves as a powerful and efficient tool as it brings in depth information onto the images displayed. A system registering the stereo pair of satallite images, processing the dual images for enhancement and restoration and displaying them in twin picture tubes for stereo visualization is described. As an example, edge enhancement, median filtering and histogram equalization techniques are applied to the experimental stereo pair of images to show a considerable improvement in the quality of the 3D image visualized. Bicircularly polarized viewing system is used in the stereoscopic display system enabling the display for mass viewing. A method of generating the range image and stereoscopic image pair is also indicated.

Oblique Illumination And Matched High Spatial Frequency Cut-Off For Edge Enhancement

Abstract: Referring to edge enhancement effect obtained with detuned interference filters already reported, a model is discussed where the source is made of a narrow annular aperture in the front focal plane of a lens, producing a narrow spatial frequency band illumination with circular symmetry in the back focal plane. Such a plane is made to coincide with the object plane of a 4-f optical processor. In the Fourier plane of the processor a circular aperture is placed, to perform low-pass spatial frequency filtering whose cut-off matches the spatial frequency of the illuminating configuration. In reasonable operating conditions the overall processing turns out to be described by a directional Hilbert transform of the object transparency along radial lines of the Fourier plane. Computation and experimental evidence are presented for the case of a simple object as a slit, showing up edge enhancement and background attenuation according to the image intensity distribution which consists of two equally energetic terms, the one associated to the geometrical image and the other to the sharp edge effect.

Some Techniques for Image Enhancement, Edge Detection and Smoothing

Abstract: Any image processing technique, such as enhancement, edge detection, smoothing etc. should incorporate the respense function of human visual system. A transfer function has been developed here using the property that the brightness perceived by human visual system follows a logarithmic response to light intensity incident on eye. For edge detection, a space-variant thresholding function has been found using the same property. Also, a weighted neighbourhood averaging technique has been developed to remove noise, where weighting co-efficient is obtained considering the homogeneity of neighbouring area.