Keith S. Pennington

Grid coding: A preprocessing technique for robot and machine vision

Abstract The problem of machine vision as evidenced in the various robot projects in existence is attacked by analogy with the supposed nature of human visual processing in that edges are enhanced, texture is examined and various heuristic approaches are studied. This paper describes a non-anthropomorphically based method of decomposing a scene subjected to a special form of illumination into elementary planar areas. The method consists in coding the various planar areas as the modulation on a spatial frequency carrier grid so that the extraction of the planar areas becomes a matter of linear frequency domain filtering. The paper also addresses the application of grid coding to other problems in recording and extracting information from 3-D images.

Grid coding: A novel technique for image processing

The encoding of information as the modulation of a grid is explored as the means for allowing the extraction of relevant details or features from images. A major aspect of this approach is the replacement of the heuristics in certain image processing tasks by simple Fourier filtering. Specific examples and particular implementations of coding schemes are described in order to show the wide applicability of the concept. The examples chosen fall in the domains of scene analysis, difference extraction from successive images, automatic extraction of range, extraction of features such as planes, recording of three-dimentional imagery, and the processing of a single coded view to give a set of stereo related pairs.

Digital halftoning of images

Most printers and some display devices are bilevel (black or white) and therefore not capable of reproducing continuous tone pictures. Digital halftoning algorithms transform digital gray scale images into bilevel ones which give the appearance of containing various shades of gray. A halftoning algorithm is presented in which novel concepts are combined resulting in an output image in which moire patterns are suppressed and, at the same time, the edges are enhanced. Various other artifacts associated with the halftoning process, such as contouring due to coarse quantization or to textural changes, are also absent from the output images in the proposed scheme. The algorithm separates the image into many small clusters which are processed independently and, therefore, it is capable of parallel implementation.

Series/1-based videoconferencing system

Discussed is a new videoconferencing system that has been developed and deployed at several IBM locations. This system transmits high-quality monochrome, freeze-frame images over dial-up telephone lines between two (or three) dedicated videoconferencing rooms. There are two main system components. An IBM Series/1 provides control, communication, data compression, and storage, and a Grinnell GMR-270 image processing display system implements image acquisition, processing, and video buffering functions. Conference participants may choose either a basically black and white rendering of an image for fast transmission or a continuous-tone rendering with a longer transmission time. Details are given regarding the system configuration, function, and operation.

Graphics image coding for freeze-frame videoconferencing

A technique is presented for coding images that are bilevel in nature but have been captured in continuous-tone format. Following various stages of image processing, a three-level image is generated, and compressed to about 0.1 to 0.2 b/pixel. The technique has been implemented in the IBM freeze-frame videoconferencing system. >

Making negatives and plates for printing by electroerosion: II. larger-scale fabrication and testing

The principles of producing direct negatives and direct plates by electroerosion writing were given in Part 1 of the present series of papers. Part II is concerned with larger-scale fabrication techniques, characterization methods, and the results of tests, together with their interpretation. Major problems which were encountered are also presented with their solutions. sheet material for the direct negative/direct plate (DNP) was made by 1) Coating polyester rolls with an underlayer. The underlayer coating fluid contained silica, a cellulosic binder, a saturated polyester dispersant, and an isocyanate cross-linker. The coating fluid was carefully milled to control silica particle size before coating. 2) Curing the rolls either at ambient or elevated temperature. 3) Calendering the underlayer. 4) Vacuum-depositing an aluminum film. 5) Coating with an overlayer containing graphite and a binder. Maintenance of good control of material characteristics was found essential for acceptable functional performance. Among the parameters requiring control were underlayer thickness and surface roughness, aluminum thickness, and overlayer thickness, as well as the composition of the various components. After fabrication, functional testing of the DNP material was carried out on the IBM 4250 printer in order to study the major performance problems of scratching, writing failure, head wear, gouging, and head fouling. Scratching could be suppressed by decreasing the surface roughness and increasing the thickness of the overlayer. Writing efficiency could be improved by increasing the roughness, decreasing the overlayer thickness, decreasing the aluminum thickness, and increasing the pulse length. Head wear could be suppressed by calendering and reducing the roughness. Gouging and excessive head wear could be suppressed by adequate milling, dispersing and filtering of the underlayer coating fluid, and calendering and curing of the coated web, while ensuring good underlayer-substrate adhesion. Fouling was reduced by decreasing the overlayer thickness and reducing the writing pulse length.

Making negatives and plates for printing by electroerosion: III. use of the direct negative and direct plate

Issues related to the practical usage in the pressroom of both the direct negative and direct plate are discussed. Two concerns associated with the usage of the direct negative during platemaking are treated: 1) the effect of light transmission through defects (voids) in the aluminum film, and 2) the effect of light transmission directly through the aluminum. These concerns may be addressed respectively by careful fabrication of the material and careful control of the exposure conditions during platemaking. Two aspects of the usage of the direct plate are considered: 1) the need for a simple prepress “activation” treatment, and 2) press-life limitations caused by wear of the direct plate on the press. Passing a direct plate through an activator solution immediately prior to mounting it on the press prevented scumming in the image area and blinding in the background (nonimage) area. The life on the press of the direct plate is limited by the wearing away of the aluminum from the background areas, thereby causing scumming. Changes in the structure of the direct plate which could prolong press life were investigated.

Making negatives and plates for printing by electroerosion: I. physical principles

Electroerosion printing involves removal of the aluminum overlayer from selected areas of a black-coated paper. “Direct negatives” as well as “direct plates” for use in offset lithographic printing may also be generated by electroerosion if a clear polymer sheet is used as the substrate instead of paper, and the black base layer is omitted. If such a substrate is metallized and written by electroerosion, the desired direct negative is created in principle since the metal stops transmitted light and the polyester does not. The direct plate is simultaneously created in principle since the aluminum is hydrophilic and the polyester is hydrophobic. Practical realization of these concepts required studies of the physical principles of the processes involved, which led to techniques for avoidance of mechanical scratching of the aluminum film during writing. For this purpose a mechanically hard underlayer was applied to the substrate under the aluminum, while a very thin lubricating overlayer having some electrical conductivity was applied over the aluminum. The underlayer consisted of silica particles in an organic binder, while the overlayer consisted of graphite particles in a binder. Although scratching is less for smooth than for rough underlayers, rough underlayers were preferred because they offered better writing reproducibility. In particular, debris created during writing was scoured away from the styli in rough-underlayer samples. For writing, a two-phase driver was used, in which the first phase provided a high current for Joule heating with consequent breaking of direct local aluminum-stylus contacts, while the second phase provided an arc which removed the remainder of the aluminum under the stylus.

Improved Materials for Fabrication of Direct Negatives and Plates by Electro-Erosion Printing.

The Direct Negative/Direct Plate (DNP) technology was developed for use with the IBM 4250 electro-erosion printer. This new printer supply allows either negatives or offset printing plates to be printed out directly from the IBM 4250 without any chemical processing. Since the introduction of the original DNP product , under the tradename electroNeg, we have continued to make major improvements in the functional characteristics of the material. These improvements encompass a) Improved optical quality, b) Reduced scratching, c) Increased press life and d) Far greater resistance to handling and environmental corrosion.

Parameters Associated with Fabrication of an Improved Direct Negative and Plate: Methods and Measurements.

The Direct Negative/Direct Plate technology employs electro-erosion printing techniques to directly generate negatives and offset printing plates suitable for use in many printing and publishing applications. Recently we have been developing materials which yield functional characteristics which are considerably improved over the first product (IBM electroNeg) to use this process. The physical parameters that govern the suitability of materials for use in the demanding environment of both electro-erosion printing and offset printing is discussed and some results and techniques for measuring these parameters described.