VISUALIZATION OF A SEISMIC SECTION ON A CATHODE-RAY TUBE SCREEN

Yu. M. Aichasov, V. B. Terekhin, V. V. Timofeev,
S. S. Krykin, V. N. Sorokin

(Presented by the scientific-technical seminar of the Research Institute of Nuclear Electronics)

To increase labor productivity and the quality of digital processing of seismic information, it is necessary to improve the reliability of computers, increase their speed, and reduce unproductive losses of machine time.

Solving these problems requires not only improvement of the computers themselves and of programming methods, but also further development of their external devices, including devices that provide information exchange between man and machine.

Among devices of this type, devices for operator interaction with a computer are considered highly promising; they contain a cathode-ray indicator used to form the image output from the computer, and a light pen intended for entering into the machine information specified by operators in graphical form, as well as for performing a number of transformations on the displayed image.

These devices output information to a visual screen in the form most convenient for the interpreter, which in many cases makes it possible to avoid additional processing of the output information and to comprehend the results obtained directly.

The specific features of seismic information predetermined, in our case, the choice of a raster principle for scanning information on the display screen. This method provides the fastest output of complex images with comparatively simple image-generation programs. In this method, information called from the computer’s magnetic random-access memory sequentially in time, after conversion into analog form, is laid out trace by trace on the screen of the cathode-ray tube by sweep voltages along the \(X\) axis and the \(Y\) axis in such a way that each raster line on the display screen corresponds to one trace of the seismic section. The distance between traces is chosen by the interpreter.

In accordance with this principle, a block diagram of the display device was developed, shown in Fig. 1, which contains the following main units:

DAC — digital-to-analog converter;

GIZ — generator of pulses requesting information from the digital computer;

SLU — system for logical control of the display device;

AB—analog unit (an amplifier with AGC, low- and high-frequency filters);

HSG—horizontal-sweep generator,

VSG—vertical-sweep generator (includes a device for selecting the desired segment of the trace and for changing the scale of the image being formed);

CRT—cathode-ray-tube system (deflection amplifiers, modulator, CRT power-supply system).

For normal operation of the display device, the computer program must provide the following control signals:

“Ready” to output information means that the computer’s RAM is filled and is ready to output information. If this signal is pulsed, then in continuous operation it must appear at the beginning of each trace; if it is a level signal, then it must exist throughout the time of continuous operation.

Fig. 1. Block diagram of the display device

“End of trace” appears at the end of each trace and is used to bring the electron beam to the required position.

“Start of array” is located at the beginning of the information array being output. It is used to bring the electron beam to its initial position. It may be pulsed or a level signal.

The device operates as follows. When the “ready” command appears, the logical-control system (LCS) of the display device permits operation of the request-pulse indicator of the information request generator (IRG), which begins to call information from the computer. This information is converted into analog form and, after frequency selection, is fed to the horizontal deflection plates of the CRT.

At the same time, the LCS starts the vertical-sweep generator of the electron beam, VSG, whose output voltage unfolds the trace of the seismic section in such a way that each machine “word” corresponds to the selected vertical displacement of the beam. After the required amount of information, determined by the computer program, has been selected from the RAM, the machine sends the command “end of trace,” according to which the LCS resets the voltage of the vertical-sweep generator VSG and starts the horizontal-sweep generator HSG. The CRT electron beam then moves to the position corresponding to the next trace. If the “ready” command has been removed, the LCS inhibits operation of the request-pulse generator of the information request generator IRG. If the “ready” command has not been removed, then on the trailing edge of the “end of trace” signal the LCS starts the IRG and unfolds a new trace on the display screen. After selection of the required information array from the computer, the command “start of array” is received; according to it, the LCS resets the voltage of the VSG and HSG, i.e., returns the CRT beam to its initial position. At this point the device

indication is ready for reproduction of the next frame (information array).

Main Technical Characteristics of the Display Device

1. Methods for reproducing seismic information:
   a) variable amplitude,
   b) variable density.
2. Number of reproduced traces — up to 256.
3. Number of words in one trace — up to 2500.
4. Computer access time — 10 μsec.
5. Working area of the screen — 180×220 mm.

The developed display device can be interfaced with computers of the BESM-4, Minsk-22, M-222, etc., types. It should be noted that, in addition to solving purely seismic problems, this device can be used for operational monitoring of the correctness of the computer’s program execution, operational monitoring of the operation of computer units, and reproduction on the display screen of various graphs, tables, and symbols; moreover, when it is necessary to compare different images, they can be superimposed on one another.

REFERENCES

1. M. Lewin. On graphical terminal devices for digital computers. Translated from English. “TIIER,” 1967, No. 7.

2. Automation of design in electronics. Republican interdepartmental scientific and technical collection. Issue 1. 1970.

3. V. B. Sokolov, B. A. Pozin. Graphical methods of interaction in a human–machine system (review). “Foreign Radio Electronics,” 1968, No. 9.

4. A. M. Zinchenko. Some questions of the technical implementation of display devices for computers, “Instruments and Control Systems,” 1971, No. 3.