Showing papers on "Standard test image published in 1985"

Digital process and apparatus for convergence correction having adjustment points and correction portions determined by the adjustment point selected

Abstract: A plurality of images superimposed to form a composite image on the screen of a television monitor are brought into convergence (register) by forming a reference image on the screen, the reference image including a plurality of reference points, and superimposing a test image on the reference image. The test image is similar to the reference image and includes a plurality of adjustment points respectively corresponding to the reference points. The test image further includes at least one correction portion corresponding to a given portion of the reference image, the correction portion including a given subset of the adjustment points. An adjustment point is selected within such subset, the position of the selected adjustment point is adjusted with respect to the reference point corresponding thereto, and the positions of the other points within the correction portion are simultaneously and proportionally adjusted, thereby establishing a substantial convergence of the correction portion with respect to the given portion of the reference image. The process is repeated for other corresponding image portions as necessary to establish substantial convergence of all corresponding portions of the two images. In the same manner convergence of a third image with the first two is established.

Image restoration by Wiener deconvolution in limited-view computed tomography

Abstract: In many applications of computed tomography, we cannot acquire the projection data at all angles evenly spaced over 360°. In such cases, the computed tomography images reconstructed using a limited number of projections, measured over a narrow angle range, are characterized by approximately elliptical distortion along the view angles used and poor contrast at angles not used (anisotropic resolution). This systematic geometric distortion is caused by the 2-D point spread function of the reconstruction process. In this paper, we show that such geometric distortion and other artifacts introduced in the reconstruction process can be reduced substantially by deconvolution performed via Wiener filtering using a priori knowledge derived from the given projections. The 2-D system transfer function used in the deconvolution is obtained from the reconstruction of a test image by the same reconstruction algorithm which has been used for reconstructing the unknown object.

Image processing method including image segmentation

Abstract: An image signal is segmented into regions of constant contrast or variance by applying a generalized-likelihood-ratio test to an image difference signal.

Digital image tiles: a method for the processing of large sections.

Abstract: SUMMARY Segmentation of large areas of light microscopic slides into N by N fields, and each of these fields into M digital image tiles, allows the scanning, storage and digital processing of large images. Any of the original N2 fields or composites of M adjacent tiles can be recalled to the video display for analysis. Developed procedures for use on a microscope equipped with a precision scanning stage allow registration of the image coordinates (X-Y) for any original or composite field and the alignment of one of these fields along the depth (Z) axis by means of external, machined fiducial marks in serial sections. To facilitate work whenever unavoidable, we have incorporated methods for digital image panning and zooming (changes of magnification) and discuss their use and implications.

Controlling method of electrophotography

Abstract: PURPOSE:To obtain a stable image by detecting a density of a test developed image whose development potential difference is different, calculating a density variation rate, comparing it with a standard variation rate, and controlling it. CONSTITUTION:When original picture patterns in case an output of a laser has been made comparatively bright, and in case it is dark are written in a photosensitive drum, a test image 17a and 17b whose density is different from each other are formed on a non-image part 16 provided on the way of the outside peripheral surface on the drum 1, and while this image is formed, timing is taken by reading a signal of a drum clock 21. The image density of the test image 17a and 17b is read by sensors 18a, 18b, respectively, brought to digital conversion by an A/D 22a and 22b, respectively, and a density (a) of the time of a development potential difference A and a density (b) of the time of a development potential difference B are read to a microcomputer 20. Subsequently, its density difference is derived, a variation rate of a V-D curve is derived, it is compared with a reference variation rate stored in advance, and if it is larger than the first reference variation rate SM1, a signal for raising the development potential difference is outputted. If said rate is smaller than the second reference variation rate SM2, a signal for lowering the development potential difference is outputted. In this way, an image being stable and having good reproducibility is always obtained.

Color television camera with test image projector and precompensation means for correcting for imaging errors caused by oblique angles of incidence of test images on pickup elements

Abstract: A color television camera has an optical color separation system provided in an optical path for scene light so as to produce pictures of different colors on pickup areas of pickup elements. The scene light extends along optical axes in the system which are central axes of the pickup areas. To synchronize picture signals so that picture coverage is optimized on the joint display thereof, the camera comprises a test image projector and an adjusting circuit. So as to obtain a compact optical system without using a movable reflecting surface for the test image, which surface would be moved in and out of the optical path, the light of the test image is projected at an oblique angle with respect to the optical axes into the color separation system and strikes the pickup areas at an oblique angle. Optical imaging errors produced thereby are precompensated. Optical precompensation means are provided in the form of an obliquely arranged test image slide and a cylindrical plano-convex correction lens. Electrical precompensation means include potentiometers or other adjustable memory circuits.

Method for producing a printing plate

Abstract: A method is proposed for producing a printing plate, in which a scanner scans a halftone image and determines the local density distribution, and in which, as a function of the local density distribution, the halftone image is rastered by means of a computer assigned thereto, and a graphic exposure device is controlled so as to produce the rastered picture. The rastered picture is transferred to a printing plate, taking into account, in generating the raster picture, the tonal value changes, which were determined during an earlier printing operation of a test image having variable area coverages and which can be defined by a polygraphic characteristic curve. The test image is stored in the computer in the form of data and is output to the printing plate via the graphic exposure device. From the printing plate a print is produced, the printed test image being scanned by the scanner in order to establish the local density distribution. The computer uses the scanned data to determine the polygraphic characteristic curve, which is used in rastering the halftone image for the subsequent prints.

Optometer with astigmatism measurement

Abstract: An optometer for the measurement of focussing error and for the detection and measurement of the characteristics of astigmatism giving an external view to allow the eye (2) under test to focus at a known distance, having a test image being a ring with fiducial marks (10c, 10d) superimposable upon the external view (3), said test image being mounted in an axially rotatable member (17) adjustable to provide first and second linear test images at right angles by adjustment of the optometer to a configuration at which the first and second focussing errors of an astigmatic eye may be determined, the radial position of the astigmatism being indicated by rotation of the test image to place the fiducial in the centre of the first or second linear test image.

Evaluation Of Selected 3-D Imaging And 3-D Image Processing Techniques

Abstract: Certain earlier proposed 3-D imaging and 3-D image processing techniques have been evaluated and some improvements are suggested. A method of registering blur-free sectional images of the object for the development of a volumetric 3-D TV is proposed. Also, a method for perception of depth effect from 2-D mono video image is described.