PROCEEDINGS
OF THE TOMSK POLYTECHNIC INSTITUTE
NAMED AFTER S. M. KIROV,
ORDER OF THE OCTOBER REVOLUTION
AND ORDER OF THE RED BANNER OF LABOR

Volume 266　　　　　　　　　　　　　　　　　　　　　　　　　1976

KEY COMPONENTS AND CLASSIFICATION

OF SIGN-BASED INDICATORS

(Review)

V. I. ZHULMIN, V. M. RAZIN

A pressing task in information theory and computer technology is to solve the problem of closer interaction between man and machine. In order to turn the machine from a calculator and data repository into an amplifier of human intelligence, it is necessary to make it possible to issue commands to the machine in alphanumeric and graphic form; to obtain from the machine, in the required format, data, graphs, and suggestions concerning further steps; and, with the machine’s constant participation (through appropriate real-time feedback), to make decisions and change the direction of one’s actions. Such close contact between man and machine will become possible only if reliable, inexpensive, high-speed indicators are available.

At present this task has not been fully solved, but devices have already been created or are being developed that make it possible to solve part of the tasks posed.

Most authors prefer to classify sign-based indicators according to the characteristics of the signals reproduced or according to the method of forming visual symbols. Classification of sign-based indicators according to the principle of technical implementation makes it possible to provide the most complete information for purposes of their further practical use. Visual information for the operator may be reproduced regularly or on demand; in this case it becomes possible, as necessary, to replace obsolete or unnecessary information with new information.

When constructing sign-based indicators, attention must be paid to the method of reproduction and the method of fixing visual symbols, the method of indicating the location of letters of the visual alphabet, and the principle of distinguishing visual symbols from the elements of the visual part of sign-based indicators.

All sign-based indicators, according to the method of constructing the visual part, can be divided into coordinate and projection types (Fig. 1). To create a volumetric image, three-coordinate sign-based indicators are used. The latter, according to the method of formation, are divided into stereoscopic and natural ones [3, 4]. Stereoscopic sign-based indicators are characterized by the reproduction of data on one or two screens; to create a volumetric image it is necessary to reproduce the images in such a way that they are perceived by the retinas of the left and right eyes.

For natural sign-based indicators, volumetric screens are used. Screens for such indicators are built as both electronic [5] and electromechanical [2]. Electronic indicators contain no mechanical elements and, consequently, have high speed; however, the brightness of the indicated signs is rather low.

According to the method of fixing visual symbols on the screen, two-coordinate sign-based indicators can be divided into devices with one-time and cyclic recording [6, 7]. To store information in devices with one-time recording, special CRTs with “memory” are used. In devices with cyclic recording, the data are indicated at intervals determined by the flicker-fusion frequency. To increase the amount of indicated data, the symbol reproduction frequency is reduced, but in doing so one must take into account the critical frequency at which the operator perceives information without substantial irritation.

Fig. 1. Classification scheme of sign-based indicators

When determining the position of a symbol on the indicator screen, discrete or analog sign-based indicators may be used. According to the principle of selection of the elements forming the visual symbol, discrete sign-based indicators are divided into devices with sign-cell [3] and raster screens. In sign-cell indicators the screen is assembled from elements of various shapes that are combined into autonomous cells. In raster indicators the screen is a set of elements identical in shape and size.

For most analog sign-based indicators, CRTs or special electroluminescent screens are used. Control of the information reproduced on indicators of this type is carried out by generating time-varying voltages or currents. Symbols are reproduced on the screen of analog indicators by profiling [6], raster, or functional methods.

Profiling devices include special sign-based CRTs (charactrons, typotrons, etc.), in which the electron beam, passing through

the aperture in the matrix, takes the form of a visual symbol. In raster reproduction of symbols, a strictly defined sequence of pulses illuminates the electron beam at specific points of the television raster, the totality of which forms the reproduced symbol.

These sign-based indicators can be divided into devices with a common raster and with a raster autonomous for each letter of the visual alphabet. In the first case the electron beam is scanned over the entire working part of the CRT. In the second case the raster is created only on the area of the symbol being reproduced. Visual symbols can be created by means of dot or line rasters. In the first case the symbol consists of a set of straight-line segments of different lengths.

In the functional method of reproducing symbols, voltages or currents are generated that create a field which, in turn, acts on the electron beam, and with the aid of the beam the necessary symbols are traced.

The following methods may be used to form voltages and currents:

1) the voltage or currents vary according to the method of Lissajous figures;
2) the voltage or currents are obtained by expanding functional dependencies in a Fourier series;
3) the voltage or currents vary according to the law of step approximation;
4) the voltage or currents vary according to the law of piecewise-linear approximation [8].

According to the method of creating the projection image, sign-based indicators can be divided into electro-optical [1] and photoprojection indicators. In electro-optical indicators, projection is carried out

Fig. 2. Photoprojection method of image creation

through a fixed template with the aid of incandescent lamps and condensers of a light beam; in this case only one of the lamps lights up.

To create images on large screens, it is possible to use

photoprojection method (Fig. 2). Such an indication system may include a character generator that converts digital information into symbols of a definite form—letters and numerals; a vector graph for reproducing graphic information; an image generator, which must arrange the symbols and vectors so as to obtain the required image, which is then projected onto a screen; a photographic device, which must photograph and process slides or film from the images obtained; a magazine for storing them; a device for feeding the required slides to the projector; and a projection device, which must provide simultaneous projection, onto the viewing screen, of the image obtained from the computer and the background in the form of a map.

An analysis of the review of sign-based indicators for presenting information at the output of electronic digital computers shows that at present a sufficiently varied arsenal of technical means for displaying information for visual perception has been developed. At the same time, it must be stated that work in the field of improving existing types of sign-based indicators and creating new means of displaying information for human visual perception has in recent years been developing ever more broadly. One may hope that, as a result of intensive work in this new area of technology, qualitatively new results may be obtained, especially taking into account the latest achievements in engineering psychology.

REFERENCES

1. V. Kh. Dei. Elektronika, 1962, No. 2.
2. F. V. Darn. In the collection: Electronic Information-Display Systems. Moscow, Voenizdat, 1966.
3. V. S. Govorov. Tekhnika i vooruzhenie, 1965, No. 9.
4. P. V. Shmakov. Fundamentals of Color Stereoscopic Television. Moscow, Sov. Radio Publishing House, 1954.
5. R. D. Zito. Elektronika, 1963, No. 2.
6. I. E. Soloveichik, P. M. Anishchenko. Sign-Based Indication and Its Application in Modern Radar Systems. Moscow, Sov. Radio Publishing House, 1960.
7. N. I. Orlov. Electroluminescence and Prospects for Its Application. Proceedings of the Scientific and Technical Conference on the Application of Luminescence. Tallinn, 1960.
8. V. S. Govorov. In the collection: Instrument Engineering. Kiev, 1966, No. 2.