Showing papers on "Orientation (computer vision) published in 1976"

Early processing of visual information

Abstract: An introduction is given to a theory of early visual information processing. The theory has been implemented, and examples are given of images at various stages of analysis. It is argued that the first step of consequence is to compute a primitive but rich description of the grey-level changes present in an image. The description is expressed in a vocabulary of kinds of intensity change (EDGE, SHADING-EDGE, EXTENDED-EDGE, LINE, BLOB etc.). Modifying parameters are bound to the elements in the description, specifying their POSITION, ORIENTATION, TERMINATION points, CONTRAST, SIZE and FUZZINESS. This description is obtained from the intensity array by fixed techniques, and it is called the primal sketch. For most images, the primal sketch is large and unwieldy. The second important step in visual information processing is to group its contents in a way that is appropriate for later recognition. From our ability to interpret drawings with little semantic content, one may infer the presence in our perceptual equipment of symbolic processes that can define "place-tokens" in an image in various ways, and can group them according to certain rules. Homomorphic techniques fail to account for many of these grouping phenomena, whose explanations require mechanisms of construction rather than mechanisms of detection. The necessary grouping of elements in the primal sketch may be achieved by a mechanism that has available the processes inferred from above, together with the ability to select items by first order discriminations acting on the elements' parameters. Only occasionally do these mechanisms use downward-flowing information about the contents of the particular image being processed. It is argued that "non-attentive" vision is in practice implemented by these grouping operations and first order discriminations acting on the primal sketch. The class of computations so obtained differs slightly from the class of second order operations on the intensity array. The extraction of a form from the primal sketch using these techniques amounts to the separation of figure from ground. It is concluded that most of the separation can be carried out by using techniques that do not depend upon the particular image in question. Therefore, figure-ground separation can normally precede the description of the shape of the extracted form. Up to this point, higher-level knowledge and purpose are brought to bear on only a few of the decisions taken during the processing. This relegates the widespread use of downward-flowing information to a later stage than is found in current machine-vision programs, and implies that such knowledge should influence the control of, rather than interfering with, the actual data-processing that is taking place lower down.

Method for pictorially displaying output information generated by an object imaging apparatus

Abstract: A method for pictorially displaying output information generated in the form of an electrical signal by an apparatus for imaging an object which includes a first display means for visually displaying a working image of the object and a second display means for visually displaying an orientation image of the object. The orientation image is obtained by varying the operating parameters of the apparatus and is displayed simultaneously with the working image. The improvement of the invention comprises the steps of generating the orientation image once, storing the orientation image in an image storage means, and then reproducing the orientation image from the generated image stored in the image storage means.

Metric or non-metric cameras

Abstract: For a comparision of metric and non-metric cameras the reproducibility of the principal distance and the principal point are of primary interest. Such a comparison should take into account the precision requirements for these parameters. Tolerances for the parameters of the elements of inner orientation can be derived from a fictitious camera calibration. The estimations show that the computed values depend only on the opening angle of the camera and the extension of the test field, whereas the size of the camera format is immaterial. Because the tolerances are much larger for nonmal-angle cameras than for wide-angle or super-wide-angle cameras, it is suggested that, for precision measurements, cameras with long focal lengths be applied. A comparision of the computer tolerances with the reproducibility of the principal distance and the principal point indicate that non-metric cameras do fulfill the requirements within certain limits. Problems may arise under certain conditions for the principal point. An accuracy discussion also should include the parameters of exterior orientation. for example, an unfavourable base-to-height ratio or vibrations of the stereocamera might reduce the final measuring precision considerably. Under these conditions small errors of the inner orientation are of minor importance. In general, about the same measuring precision can be reached with metric and non-metric cameras. The data processing for photographs taken with non-metric cameras is practically bound to analytical methods, and sophisticated computer programs are needed. Pictures taken by metric cameras can be restituted with analog plotters. Therefore it is more a question of the restitution method than a matter of precision whether metric or non-metric cameras should be used. /Author/

The Theoretical Basis Of A New Optical Method For The Accurate Measurement Of Small Line-Widths

Abstract: As part of the effort conducted at NBS to solve some of the fundamental problems associated with width measurement of very small (l-5-µm) lines and spaces, the performance of an optical microscope with coherent illumination is investigated. From these studies, the theoretical basis for a new method of accurate width measurements is developed and explored. The new method, in effect, produces an optical transformation in which the image no longer resembles the original line but in which the location of the line-edges is marked by two narrow, dark lines within a bright surround. The correct line-width is then given by the distance between these two lines, a measurement that eliminates the orientation problems normally associated with filar eyepieces and sidesteps the coherence problem that affects shearing eyepieces. Suggestions are made about implementing the technique. Available microscope objectives are not suitable for such a system, and a redesign is recommended.

Experimental heterodyne optical correlator

Abstract: : Over the last several years considerable progress has been made both with regard to the demonstration of the basic concepts of heterodyne optical correlation (HOC) systems as well as the evaluation of the potentials of such a system to achieve automation of the stereocompilation process. This document is the final technical report on a detailed study to test, analyze and achieve optimisation of the experimental HOC system design. The heterodyne optical correlation system is a generalized optical correlation system having significant advantages in its application to stereocompilation. The detection of the regions of conjugate image coincidence between two transparencies through image correlation forms the basis for most automated stereocompilation system. In the HOC system the two transparencies forming the stereopair are relatively oriented and projected onto a common image plane where coincidence is detected. By means of heterodyne optical techniques a normalized correlation coefficient is measured at each element of a photodiode array in the common image plane. The normalized correlation values are then used to define regions of conjugate image coincidence for a given orientation between transparencies.

A new computer program for contour maps of texture functions

Abstract: A Fortran program for plotting contour maps of texture functions is described. The program works at high speed and is very flexible in application. For input the values of the texture function, which have been measured or calculated on a grid of mesh points, are required. From these data, the single-level lines of a contour map are calculated and plotted. Format and caption of the contour map as well as the marking of the level lines can be individually chosen. In the present paper the program is applied to direct and inverse pole figures as well as to a three-dimensional orientation distribution function (ODF) of a silver sheet deformed by 99.3%.

The Role of CT Scanners in Radiotherapy

Abstract: The success of radiation therapy depends upon the correct diagnosis of disease and the accurate delivery of radiation dose to that disease. An important part of radiotherapy is treatment planning in which various possibilities for the type, energy, size, and orientation of therapy beams are considered to insure that the intended volume is adequately irradiated. Treatment planning requires that the shape, size and depth of tumors as well as radiation-sensitive tissues be accurately identified. Furthermore, any distortions to radiation dose distributions caused by the presence of tissue inhomogeneities should be corrected. This paper discusses how computed-tomography scanners may be utilized to advantage in radiotherapy. Major benefits of scanners are described and difficulties associated with using scanner images in radiotherapy treatment planning are indicated.