Showing papers on "Edge enhancement published in 1977"

Edge enhancement with incoherent optics.

Abstract: A new approach to optical signal processing has recently been introduced by Gorlitz and Lanzl, Lohmann, and Rhodes. One of the important features of the new approach, the use of a frequency offset, had been previously proposed by Macovski in a related context. This Communication is a first report on independent results in this area and is largely confined to experimental results, with a full account to follow. Operations like edge enhancement are apparently ruled out in incoherent imaging systems because of the constraints on OTFs implied by positive PSFs. The new idea is to employ a pupil plane mask in an imaging system, thereby creating a desired filter response on the unconstrained frequency offset Fig. 1. Top: if a copy of this mask is overlaid the original and shifted so the annulus is centered about the circular hole, the opaque disk in the center of the annulus is just big enough to eclipse the hole.

Detection and Coding of Edges Using Directional Masks

Abstract: This paper describes a new image coding system which combines the detection and coding of visually significant edges in natural images. The edges are defined as amplitude discontinuities between different regions of an image. The edge detection system makes use of 3 x 3 masks, which are well suited for digital implementation. Edge angles are quantized to eight equally spaced directions, suitable for chain coding of contours. Use of an edge direction map improves the simple thresholding of gradient modulus images. The concept of local connectivity of the edge direction map is useful in improving the performance of this method as well as other edge operators such as Kirsch and Sobel. The concepts of an "edge activity index" and a "locally adaptive threshold" are introduced and shown to improve the performance even further.

A Fast Algorithm For Space Variant Contrast Stretching

Abstract: The operation of convolution (for the purpose of edge enhancement) can be decomposed into two terms, one of which varies quite slowly over the image being filtered. By the use of two dimensional interpolation, this spatial redundancy may be exploited in order to achieve a fast two dimensional convolution procedure for a particular class of operators. Viewed in this sense, conventional (linear) edge enhancement may be interpreted as a dynamic shifting of the "local mean". A space variant contrast stretch may then be seen as a non-linear procedure in which both the local mean and the local standard deviation of an image are dynamically shifted. The same fast algorittm may then be applied to the nonlinear space variant case.

New results in computer simulated frequency swept imaging

Abstract: A computer simulation of frequency swept holography is presented. A properly scaled, divergent synthetic aperture generated by frequency sweeping a linear array of synchronous detectors is employed in imaging a rectangular object. An undistorted and edge enchanced image of the object is reconstructed and compared with earlier results. The edge enhancement effect in the image is explained.

Real-Time Spatial Modulators For Optical/Digital Processing Systems

Abstract: The real-time functional features of optically addressed electro-optical spatial modulators such as the Pockels Readout Optical Modulator (PROM) are described and applied to hybrid optical/digital processing of photographic information. The current and predicted performance of developed hardware and R&D devices for optical image sampling, incoherent-to-coherent conversion, stored image manipulation and computer-controlled Fourier plane filtering are presented. The utility in image exploitation of adjusting the dynamic range of a stored image under interactive computer control to effect background suppression, optical density level contouring, image inversion, spatial filtering and edge enhancement is illustrated graphically.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A Method of Adaptive Smoothing and Edge Enhancement

Abstract: : A local operator, 'SWAC', is introduced which identifies image neighborhoods that are noisy and do not contain any boundary. An adaptive smoothing function, guided by the response of SWAC, successfully smooths noisy regions in images without degrading edges. The response of SWAC is also successfully used as a weighting function to suppress spurious responses of an edge detector operating in a noisy environment.

Enhancement Of Solar Corona And Comet Details

Abstract: Finely detailed striae in astronomical images can be important in formulation of theory. Examples are studies of streamers in the solar corona and of dust tails in comets. In both instances, conventional observations fail to reveal much of the structural detail. Digital image processing has been used at LASL for enhancing these images. The corona images have tremendous variations in film density which must be eliminated before fine striae can be seen. These variations can be removed by means of numerical modeling of their spatial relation to the sun. This model can be thought of as a surface of background film density. In the comet images the overall variation is less severe. Further, the large number of comet images makes it infeasible to model them individually. Hence, an extreme low-pass filter was used to create an image which can be used as the background surface. In both cases, the background surface is divided into the original image pixel-by-pixel. This quotient image is then frequency filtered for edge enhancement or noise control. Nonlinear density transformations are then used to enhance contrast. For both types of images, heretofore unmeasurable details become readily visible for analysis.