Showing papers on "Edge enhancement published in 1981"

Projection photolithography by wave-front conjugation

Abstract: Conjugate wave-front generation by degenerate four-wave mixing has been employed to project images with submicrometer features onto photoresist-coated substrates. The developed patterns demonstrate a resolution of >800 line pairs per millimeter for 413-nm illumination, consistent with theoretical expectations. The patterns are not degraded by speckle or edge enhancement, and the magnification is within 0.1% of unity. Focusing is accomplished by a novel interferometric procedure.

Optical information processing characteristics of the microchannel spatial light modulator.

Abstract: The microchannel spatial light modulator (MSLM) is a versatile, highly sensitive, and optically addressed modulator that is well suited for low-light level real-time optical information processing. The image processing operations that can be achieved with the MSLM include contrast reversal, contrast enhancement, edge enhancement, image addition and subtraction, analog and digital intensity level thresholding, and binary level logic operations such as AND, OR, EXCLUSIVE OR, and NOR. Several of these operations are demonstrated herein. Recent prototype MSLMs have exhibited a halfwave exposure of 2.2 nJ/cm(2), an optical information storage time of more than two months, and a framing rate of 40 Hz with full modulation depth (200 Hz with 20% modulation depth). The role of secondary electron emission in the operation of the MSLM is discussed, and design modifications that would yield a spatial resolution of ~10 cycles/mm at the 50% point on an MTF curve are proposed.

Digital Boundary Detection Techniques For The Analysis Of Gated Cardiac Scintigrams

Abstract: Boundary detection in conventional nuclear medicine scintigrams is often difficult for several reasons. First, scintigrams generally have a low signal-to-noise ratio. Second, edge structures are poorly defined because of the low resolution of gamma ray cameras; and finally, edge contrast is usually reduced by foreground and background activity. In this paper we report on heuristic approaches we have taken to solve these problems and to develop programs for the display of cardiac wall motion and for the automatic determination of left ventricular ejection fraction. Our approach to processing cardiac scintigrams entails several steps: smoothing, edge enhancement, and contour extraction. We discuss each of these steps in light of the goal of producing cardiac boundaries which are spatially and temporally smooth and continuous. Boundary detection results are presented for some selected clinical images.

Low Frequency Filtering Of Digital Radiographic Images

Abstract: To display the wide range of attenuation values in a computed radiographic image, mathematical processing to suppress low frequency information is often used. This increases the apparent visibility of low contrast structures and permits the simultaneous display of these structures in all areas of the image. Low frequency suppression is performed by subtracting from each pixel in the image a fraction of the weighted mean of a number of surrounding pixels. This produces a degree of edge enhancement which results in an image similar in appearance to that of a Xeroradiograph. The fraction of the weighted mean and the number of surrounding pixels to be used in the filtering process can be varied, thus producing varying degrees of edge enhancement and low frequency suppression. We have investigated the effect of different low frequency filtering parameters on the recognition of low density lung nodules. Digital radiographs of an anthropomorphic phantom which contained lesions ranging in size from 3 to 20 mm were obtained using the GE SV 8800 system. Different filters were applied and images were obtained on film. The detectability of the lesions using the different filter parameters was determined.

Microchannel spatial light modulator

Abstract: The Microchannel Spatial Light Modulator (MSLM), a versatile, highly sensitive, and optically addressed device being developed for real time optical information processing is discussed. The MSLM operates by converting an input optical image into a charge distribution at the surface of an electro-optic crystal. The charge distribution generates an electric field which modulates the refractive index of the crystal and thereby the phase or intensity of an image readout beam. Prototype devices employing 250 micron thick crystals exhibited a spatial resolution of 5 cycles/mm at 50% contrast, an exposure sensitivity of 2.2 nJ/cu cm and framing rates of 40 Hz with full modulation depth. The image processing operations that have been achieved using the internal processing mode of the MSLM include contrast reversal, contrast enhancement, edge enhancement, image addition and subtraction, analog and digital intensity thresholding, and binary level logic operations such as AND, OR, EXCLUSIVE OR, and NOR.

Image Quality Effects In Optical Correlators

Abstract: Three aspects of image quality and their effects in an optical matched spatial filter correlator are described. These concern operation on: digitized imagery, data with low modulation and low space bandwidth product, and synthetic reference imagery. To address these practical problems, we employ: spatial filtering, edge enhancement, use of different apertures, photoreduced imagery, and digital preprocessed data. The first exuerimental data on optical matched spatial filter correlations with synthetic reference imagery and the first comparative data on digitally and optically processed multisensor image correlations are included. From these experiments, we find an optical weighted matched spatial filter correlator to be adequate for most multisensor data and that advanced digital preprocessing operators are necessary when presently available synthetic reference imagery is used.

Image processing for thermal images from an infrared camera.

Abstract: This paper describes the application of computer image processing techniques to thermal images produced by an infrared temperature measurement camera. The camera was used to measure the temperature of materials inside an iron-producing blast furnace. The objective of computer processing of the images was to provide image enhancement that is, improved contrast and reduced noise. Gray-level histogram calculations were performed and it was shown that contrast could be enhanced by manipulation (equalization) of the image histogram. Three types of 2-dimensional digital filtering techniques were demonstrated and applied to the thermal images. These were (1) convolution filtering, (2) discrete transform filtering (Fourier and Walsh-Hadamard) and (3) windowed finite impulse response filtering. For convolution filtering, both noise smoothing and edge enhancement masks were convolved with the original images. Even though both masks were kept relatively small to minimize computation time, they yielded very desirable results. High frequency noise was eliminated with the first mask, and edges (delineating zones of constant temperature) were defined with the second mask. Discrete transform filtering was performed by computing the 2-dimensional Fourier and Walsh-Hadamard transforms of the images, setting the smallest coefficients to zero, and then inverting the transforms to produce the filtered images. Although

Performance Limitations Of The Microchannel Spatial Light Modulator

Abstract: The Microchannel Spatial Light Modulator (MSLM) is a versatile, highly-sensitive and optically-addressed modulator that is well suited for low-light-level, real time, optical information processing. It consists of a photocathode, a microchannel plate, a planar acceleration grid, and an electro-optic plate in proximity focus. The image processing operations that can be achieved with the MSLM include contrast reversal, contrast enhancement, edge enhancement, image addition and subtraction, analog and digital intensity level thresholding, and binary-level logic operations such as AND, OR, EXCLUSIVE OR and NOR. Recent prototype MSLMs have exhibited a half-wave exposure sensitivity of 2.2nJ/cm2, an optical information storage time of more than two months, and a framing rate of 20 Hz with full modulation depth (100 Hz with 20% modulation depth). The materials and device parameters that limit the ultimate performance of the modulator are discussed.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.