US3736375A

US3736375A - Process and apparatus for creating codified cartographic representations of variable quantities

Info

Publication number: US3736375A
Application number: US00083476A
Authority: US
Inventors: B Parnet
Original assignee: Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Industries SA; Compagnie de Saint Gobain SA
Priority date: 1969-10-27
Filing date: 1970-10-23
Publication date: 1973-05-29
Anticipated expiration: 1990-05-29
Also published as: SE363401B; FR2063669A5

Abstract

A process and apparatus for creating a visible coded cartographic representation of a phenomenon, such as luminosity, temperature and the like, which may vary in a given superficial field and is susceptible of expression by a characteristic quantity, the representation comprising differently hatched adjacent areas or zones each representing values of the phenomenon under investigation between selected threshold values thereof, superimposed traces representing one or more of said threshold values for purposes of reference, and superposed transverse contours at selected intervals representing point to point variations in the value of the phenomenon.

Description

United States Patent 1191 Parnet 1 May 29, 1973 54 PROCESS AND APPARATUS FOR 3,294,396 12 1966 Young, Jr. ..178/D1G. 3 CREATING CODIFIEI) 3,441,667 4/1969 Novacek ..178/D1G. 34 (:ARTOGRAPHIC REPRESENTATIONS 3,214,515 10/1965 Ebberline ..178/D1G. 34 3,503,689 3/1970 Miller et a1. ...l78/D1G. 34 0F VARIABLE QUANTITIES 3,580,995 5/1971 Klensch ..178/6.6 B [75] Inventor: Bernard Parnet, Courbevoie, 3,604,846 9/1971 Behane et al.... ..178/6 X prance 3,432,661 3 1969 Hodgkinson ..17s 5 x [73] Assignee: gaint-GFobain Industries, Neu11ly sur Primary Examiner Howard w Brim,

rance Att0rneyDale A. Bauer, John L. Seymour and [22] Filed: Oct. 23, 1970 Bauer & Seymour [21] App1.No.: 83,476 [57] ABSTRACT Foreign Application Priority Data A process and apparatus for creatmg a v1s1ble coded cartographlc representat10n of a phenomenon, such as Oct. 27, 1969 France ..6936743 luminosity, temperature and the like, which may vary in a given superficial field and is susceptible of expresl Cl 34 sion by a characteristic quantity, the representation 1111- C1 1104 comprising differently hatched adjacent areas or zones [58] Field Of Search ..l78/DIG. 34, 6.8, each representing values of the phenomenon under in- 178/D1G- 4 vestigation between selected threshold values thereof, superimposed traces representing one or more of said 1 References Cited threshold values for purposes of reference, and super- UNTED STATES PATENTS posed transverse contours at I selected intervals representmg pomt to pomt var1at1ons 1n the value of 3,25 8,528 6/1966 Oppenheimer ..178/5.4 the phenomenon. 3,354,266 11/1967 Dinenno ...178/D1G. 34 3,337,684 8/1967 Sadler .,178/D1G. 4 26 Claims, 8 Drawing Figures CODE 28 E18 SIGNAL GENERATOR MONO-STABLE OSCILLATORS AND GATE PATENTED 2 it SHEET 1 BF 3 INVENTOR. BERNARD PARNET ATTOREYS PATENTLLTL'IYZSIEITS 6,375

SHEET 2 [1T 3 I :7. CODE 7 m 5 NA G E IIER ATQR v a a LY/8 ET? I Q s 7 ETS m 6 Q 5 ONO-STAB E 4 6 5 v mSO QscILLATQ RS 3,5 m I ad I y s A I} Z F m 5 MIXER 0R GATE 4 4 a ET5 s. I G I 2 3 3 H2 2 Q 4% R S o ET1 TITAP LI EIER 1 m 2 a AND GATE AND GATE Y sAwTooTII GENERATOR 7' auB? OR GATE q INVENTOILI I J BERNARD PAR-NET; THRESHOLD A84 Zf BY I AMPLIFIER mas M85 MONO-STABLE M z OSCILLATOR ATTORNEYS PATENTED HY 29 I975 SHEET 3 OF 3 mm mum 1| may umn mlnm mm mm! lllllll mm "m" I l Illlllll mum mum "mm" INVENTOR BERNARD PARN-ET BY 1 I ATTOR EYS PROCESS AND APPARATUS FOR CREATING CODIFIED CARTOGRAPHIC REPRESENTATIONS F VARIABLE QUANTITIES The present invention relates to a process and devices making it possible to obtain a coded cartographic representation of a phenomenon such as luminosity, temperature, etc., capable of being expressed by a characteristic quantity and affecting a given superficial field. The intensity of such a quantity, which depends upon the location of the point of measurement, can be expressed by a function S of two coordinates of the different points on the field being examined, for example Cartesian x and y coordinates; moreover, it generally also varies with time t. It is therefore impossible to obtain an overall representation which includes all of these three parameters at the same time, but numerous solutions have been devised for the purpose of obtaining partial representations.

In particular, one may seek to obtain successive black-and-white images, which provide representations of a visual nature, but hardly lend themselves to measurement: certain reproduction processes are of the photographic type; in other words, they give a snapshot type analysis, the texture of which is sufficiently fine in order to be able to be considered continuous.

A frequently employed solution consists in effecting periodic scanning by means of a pick-up device which effects linear exploration of the field of observation. This solution gives a field which is generally less fine, but it lends itself more readily to long-distance transmission of the image.

When one examines a rectangular field, to take a frequent example, exploration is decomposed into a succession of horizontal sweeps during the course of which the pick-up scans a line parallel to one of the coordinate axes, the x-axis for example, with these successive sweeps being staggered at frequent intervals by means of vertical" sweep effected in the direction of the y-axis. The scanning done by the transmitter can be achieved by means of electronic processes; this is the solution employed, for example, in television. Recourse can also be had to mechanical processes; this is the solution notably adopted in infrared television or in most radar sets. The vertical scanning is generally periodic; the successive images can be considered instantaneous if the scanning cycle is sufficiently short with respect to the motion of the phenomenon; on the other hand, it can also be continuous and be simply the result of the relative movement of the transmitter with respect to the object examined, with each of the different zones of the field being explored a single time at successive points in time, which in this case provides a spatiotemporal representation.

The receiver may for example comprise a dark-trace screen on which electronic sweep constitutes successive images. Disregarding the engineering signals which might be required by the nature of the measurement or the technological solutions adopted, the data transmitted at this level can be schematized in the form of three synchronized signals: X(t), Y(t) and S(t).

X appears in the form of a short-cycle sawtooth signal which causes the horizontal deflection of the elec tron beam in synchronism with the sweep parallel to the x-axis.

In nearly all applications, Y forms long-cycle saw teeth which correspond to the vertical deflection of the beam. It should be noted that their development should theoretically design a stairway in which the length of each step corresponds to the horizontal sweep cycle.

in actual practice, the distortion introduced by the simplification of the signal ultimately results in a very slight inclination of the sweep toward the x-axis, which generally does not present any drawbacks.

S is the measurement signal which expresses the intensity of the phenomenon being analyzed, in accordance with successive sections through planes y constant; it thus appears in the form of a pseudoperiodic signal which is transmitted to the modulation or Wehnelt grid of the receiving tube.

The images obtained do not provide directly readable quantified data. If one wishes to obtain a measurement rapidly, it is necessary to employ another mode of representation. It is quite easy, for example, periodically to transmit two signals corresponding to X and S on the deflection controls of an oscilloscope, so as to trace on its screen, for different values y, of y, the curve S(s,y representing outlines parallel to the x-axis.

A second approach, on the other hand, consists in making horizontal sections corresponding to suitably selected predetermined values of the intensity S; this leads to a cartographic, or more correctly orographic, representation of the phenomenon. It suffices to trip off the transmission of a secondary signal each time the value of S goes beyond selected thresholds, in order to engender on the viewing screen, during the course of a complete scanning cycle, a corresponding contour line.

The orographic image may be superimposed on the visual image, but visibility becomes mediocre; it can also purely and simply be substituted for it, but in this case it would be necessary, even if only for the purpose of distinguishing the troughs from the peaks, to be able to identify the lines, for example by numbering them on the screen, a possible but complicated solution.

One might also consider replacing the signal S by a signal the intensity of which would vary in successive steps corresponding to the values of the thresholds, but it is found that the result obtained lacks contrast, so that it is ultimately not satisfactory. Another possibility, which has the advantage of giving a very telling representation, is to obtain a colored output; such analog coding has been used in infrared television, but it is complex and consequently expensive.

The procedure which constitutes the solution according to the invention consists in effecting generally rectangular scanning of the field and ascribing code numbers to the values of the characteristic intensity of each zone included between two successive thresholds, crossed by the said intensity, by means of a simple black-and-white signal; in other words, substituting for S a jagged or pulsing signal Z of sufficient cycle or frequency in order to be visible on the image, the form of which is different in each of the threshold intensity zones considered, each sweep line thus forming a broken line of hachures which differs from one threshold zone or range to the next.

According to another characteristic of the invention, each coding signal Z is sent out by an outside clock or generator in synchronism with the sweep signal X and tripped independently of the code signal passage permissions or AND gates, with each threshold range appearing in the form of hachures representative of the base or coding signal.

According to another characteristic of the invention, the division of the horizontal scanning cycle by the code signal cycle results in a different remainder from one zone to the next; thus, the hachures produced during successive scanning or sweep cycles are horizontally offset to give the effect of inclined hatch lines, the inclination of said lines being different in each range.

According to still another characteristic of the invention, the thresholds can be adjusted to various levels; thus, the sensitivity of the apparatus is adjustable and the number of ranges appearing in the field of observation is capable of remaining constant so as to make a satisfactory reading possible.

According to an additional improvement, a secondary impulse is sent out when a selected threshold is crossed; thus only one the threshold level representation is superposed upon the hachure representation and gives the measurement reference level.

According to another improvement, the measurement signal S momentarily replaces the Y signal once per scanning cycle, with the receiver then operating as an oscilloscope. Thus a temperature contour located in an appropriately chosen plane 1 is then superimposed on the hachure image in order to facilitate its interpretation.

A particular form of embodiment of the invention will be described below in detail, simply by way of example, within the framework of an application relating to the measurement and recording of temperatures of glass sheets or ribbon by means of infrared pyrometry, in a suitable area of a processing furnace such as a hardening oven or flattening oven.

This form of embodiment can be utilized, with possible changes in detail, for other technological fields, and in particular for the measurement of the temperatures in the mechanical or thermal processing of metallic parts, for example, or for the measurement of temperatures within an enclosed space, but also for the recording of measurements of relief, electromagnetic fields, etc.

ln'this description, reference will be made to the attached drawings, which show:

FIGS. 1 and 2, plan and end-on views, respectively, of the transmitter;

FIG. 3, curves representing signals W, X, Y and S;

H6. 4, a drawing of the device transforming the S signal into a coded signal;

FIG. 5, a drawing of the circuit controlling the ing tube;

FIG. 6, a drawing pertaining to the synchronization of a coding signal Z with the W signal;

FIG. 7, a diagram showing the zones corresponding to the areas of the ribbon of glass in which the temperatures are comprised within different thresholds;

FIG. 8, a temperature chart for a ribbon of glass upon leaving a drawing well.

In the application chosen by way of example, succesreceivsive transverse lines of a moving ribbon of glass are examined as they pass through a given plane. An infrared-sensitive cell is placed above the ribbon at the output of a flattening oven 11. This cell, provided with an optic l2, observes a narrow field within a range of wavelengths of from 3 to 8 microns, and revolves at the velocity of 960 revolutions per minute about a horizontal axis V located in the median plane of the ribbon. It examines the line uu' in successive spots during approximately one'fifth revolution and thus effects a transverse sweep of the glass ribbon; thus the variation in its transverse temperature contour is detected at each such line. The glass ribbon moves along at a speed of the order of 5 meters per minute, which results in its being scanned longitudinally; the fineness of the field thus corresponds to a pitch of the order of 5 mm.

It is possible to use highly diverse receivers and, for example, film the successive images supplied by an optical fiber line with a fast-moving paper, or use an electrostatic reproduction process.

The more traditional method is to use an ordinary cathode ray tube, but the sweep is too slow in that case to permit direct observation; thus the temperature chart will be obtained by the prolonged exposure of a photographic film, with the exposure time corresponding to the duration of vertical scanning Y.

As a result of the vertical cycle of the receiver, the continuous longitudinal sweep will thus be cut into successive sections, each corresponding to a certain length of ribbon.

Lastly, and this is the solution which will be described below, the image can be observed directly through the use of a memory screen.

The camera 13 will not'be described in detail, since its operation is not directly related to the invention. It shall suffice to know that, in addition to the S signal, it supplies only a scanning signal H and passage permission or triggering signal W for signal H from which sawtooth signal X is developed. Thus a signal Y, having a suitable cycle and uniform mean slope, must be generated separately.

Also, as has already been stated above, a feature of the invention is that the camera revolves in synchronism with the emission of coding signals which form the signal Z, i.e., without any phase drift with respect to them; with a view to achieving this result rigorously, one can synchronize all the components by means of a master clock, but a simple, satisfactory solution is to drive the revolving cell by means of a stabilized directcurrent motor.

Signals W, X, Y and S are represented in FIG. 3.

The period of the X signal is 62.5 ms and corresponds to the scanning or writing of a line. The permission or triggering signal W makes it possible to limit the sawtooth of the X signal to the'time during which the optic head, observing the object under examination, supplies the S signal, or approximately 12 msDuring other operating times the X signal is reduced to a horizontal of zero intensity.

As indicated above, the Y signal is generated separately; the cycle of the sawtooth which constitutes it is 12 seconds, for example, and corresponds to the recording of a complete image on the screen of the receiver; it determines the lengths of the successive sections of ribbon examined, of the order of l m, for example, and when signal Y falls back down, this brings about the erasure of the memory stored.

The device which transforms the analog signal S into a coded pulsing signal 2 in accordance with the invention may be constituted as shown in FIG. 4. A series of adjustable generators supplies the desired coding signals Z the frequency of which is of the order of approximately 10 kHz; they might be, for example, eight in number, indicated as z, to Z thus determining eight coding ranges.

The S signal furnished by the camera is analyzed by a series of seven threshold amplifiers s k to s 7a. Each of these amplifiers delivers two complementary signals s,- and E-"(Booles notation) according as the intensity of the S signal is greater or lower than a selected threshold value.

As soon as the S signal enters a new coding or threshold range, range 3 for example, exceeding the assigned value of threshold s but not yet reaching that of threshold s the combined presence of the triggering signals, here 3 and Z, permits only the impulses emitted by the impulse generator 13 to cross the corresponding permission circuit on AND gate ET 3, while the absence of gsignals in the ET permission or AND gate circuits of a lower order and the absence of s, signals in the ET or AND gate circuits of a higher order inhibit the passage of the other coding impulses.

The entire set of threshold circuits feeds a mixer stage OU which dispatches signal Z here Z toward the cathode ray tube.

One of the threshold amplifiers, s 4/5, for example, is selected to provide a reference. For this purpose, the two

signals

5 and 5 supplied by this threshold amplifier are directed toward two monostable oscillators such as m49 and m50. Each passage of S by the corresponding threshold value causes the triggering of 5 or 5 from to l and trips the corresponding monostable oscillator which delivers a short impulse of adjustable duration; this impulse, sent also to the receiver by circuit OU is superimposed on the output of the successive Z, signals in order to represent the reference isotherm on the screen point by point.

FIG. shows the wiring diagram of the receiver tube 90.

The signal X resulting from the combination of H and W in a permission or AND gate circuit ET 80 is sent to the horizontal deflection grid 91.

The device which transforms the S signal into a coded signal Z in accordance with the invention is schematized here at 81 and Y signal is elaborated at 82.

Normally the vertical deflection grid 92 and the modulation control grid 93 are fed respectively through the gate 83 83' by signals Y and Z, so that the cathode tube operates as a picture tube.

However, the Y signal is likewise sent out to a threshold amplifier s 84 which supplies either signal Y, or Y depending upon whether Y is greater or less than a preselected reference value Y,. These two signals are respectively directed toward monostable circuits m85 and m86 so that when Y passes through the value Y a short pulse is produced which momentarily trips the gate 83 83.

The

grids

92 and 93 are then fed respectively by signals S and W, which signifies that during this short period the tube operates as an oscilloscope, so that one of the horizontal sweeps, corresponding for example to the median line 97 of the image, is replaced on the screen by the corresponding S signal contour 96.

FIG. 6 gives a schematic representation of the synchronization of a coding signal 2, with the W signal. If P is the period of horizontal sweep, and p is the period of the coding pulses, a phase shiftf= P up which represents the remainder of a coding pulse period after the division of P by p appears from one scanning line to the next; it is reflected in the fact that each appearance of the W signal, i.e., each beginning of a scanning line, is progressively shifted with respect to the code signals. Observed on the screen, this phase shift or lag is reflected inversely in the appearance of a system of hachures the slope or inclination of which is characteristic of the algebraic value off.

The form of the Z,- pulses supplied by each of the z,- generators may be selected more or less arbitrarily, and since their rate is independent of the formation of the contour lines of hachures, it can easily be adjusted in such a way that the phase shifts f to f are different from one another, which will result in a difference in the inclination of the hachures as viewed in FIG. 7.

FIG. 7 represents first of all a signal S (yo) successively crossing the three thresholds s s reference threshold, and s 4/5, as well as the series of signals Z (y0) to Z (y0) which come one after the other to take the place of signal S(y0). It also illustrates the scanning line L0 generated by the emission of the successive Z(y0) signals, and the following lines L to L which give rise to the generation of the hachures inclined lines of.

Thus there will be seen to appear successively, from the edges toward the center of the figure, two zones of hachures (2 2) corresponding to the areas of the ribbon of glass in which the temperature is comprised between thresholds s k and 5 two zones 3 3, two zones 4 4' and a central zone 5.

FIG. 8 shows the temperature chart for a ribbon of glass as it issues from a drawing well.

Between the edges 94 one can observe the different zones of hachures schematically represented by hatching, the reference isotherm 95 and the median contour represented by curve 96 which represents temperature variations along the scanning line 97. The isotherms such as 98 can, if it is so desired, be traced directly by the apparatus, as in the case of isotherm 95 itself.

I claim:

1. A process for obtaining a coded cartographic representation of a phenomenon such as luminosity, temperature, and the like, susceptible of expression by a characteristic quantity and concerning a given superficial field which comprises scanning the field to generate a measurement signal characteristic of the intensity of the phenomenon, generating independently of the measurement signal a plurality of coding signals differing in form from each other, and selectively applying said coding signals one at a time to a common outlet in response to selected threshold values of the measurement signal, whereby each coding signal applied to the outlet is representative of a range or zone of measurement signal values between successive threshold values of the measurement signal.

2. A process as defined in claim 1, comprising the step of applying the coding signals on said outlet to the modulation control grid of a cathode ray tube to create hachures on the screen thereof.

3. A process as defined in claim 2 which comprises applying a pulse signal to said common outlet when the measurement signal attains a selected threshold value, whereby to create a contour line on the screen of the tube representative of said selected threshold value.

4. A process as defined in claim 2 comprising intermittently momentarily applying the measurement signal to the vertical deflection grid of the tube while applying a constant signal instead of the coding signals to the modulation control grid to create a contour line representative of the measurement signal values.

5. A process as defined in claim 2 wherein the coding signals are cyclically generated in synchronism with the horizontal sweep signal applied to the horizontal deflection grid of the tube.

6. A process as defined in claim wherein the division of the horizontal sweep signal cycle by the coding signal cycle results in a different remainder from one measurement signal zone to the next, whereby the inclination of the hachures created in successive sweep cycles is different for each zone of measurement signal values.

7. The process of creating a coded cartographic representation of a phenomenon, such as luminosity, temperature and the like, over a superficial field which includes the steps of transversely scanning the field successively along lines spaced longitudinally of the field, generating in response to said scanning an electrical measurement signal which varies in magnitude as the value of the phenomenon at the points of the field being scanned, generating independently of the measurement signal a plurality of alternating code signals differing in form, selectively supplying said code signals, one at a time, to the modulation control grid of a cathode ray tube having a memory screen in response to selected threshold values of said measurement signal, and supplying sawtooth signals to the horizontal and vertical deflection grids of said tube, whereby the tube functions as a picture tube.

8. A process as defined in claim 7 comprising the step of momentarily interrupting the connections to the modulation control grid and the vertical deflection grid, and momentarily connecting the same to receive said measurement signal and a constant signal, respectively, whereby said tube functions momentarily as an oscilloscope to create a trace representing the magnitude of said measurement signal.

9. A process as defined in claim 8 wherein said momentary interruptions are effected in response to a selected magnitude of the sawtooth signal supplied to the vertical deflection grid.

10. A process as defined in claim 9 which comprises applying an additional electrical signal pulse to the modulation control grid of said tube whenever the value of the measurement signal attains a predetermined threshold value to thereby create a generally vertical trace on the memory screen. 11. A process as defined in claim 10 wherein said signal pulses are created by utilization of monostable oscillators connected to complementary outputs of a threshold amplifier responsive to a predetermined threshold value of the measurement signal.

12. A process as defined in claim 7 which includes controlling the connection between each code signal generator by means of an AND gate responsive to predetermined values of the measurement signaL.

13. A process as defined in claim 12 which includes feeding code signals from said AND gates through a common mixer OR gate.

14. A process as defined in claim 12 comprising energizing complementary control terminals of pairs of said AND gates in response to the measurement signal throughparallel connected threshold amplifiers each responsive to said measurement signal at different threshold values thereof and adapted to deliver complementary output signals to said control terminals.

15. Apparatus for creating a codified cartographic representation of a phenomenon such as luminosity, temperature and the like, which is susceptible of ex pression by a characteristic quantity and variable over a superficial field comprising a cathode ray tube having horizontal and vertical deflection grids, a modulation control grid and a memory screen, means for cyclically scanning said field successively along transverse longitudinally spaced lines and for generating an electrical measurement signal during each scanning cycle the magnitude of which varies in accordance with the magnitude of said phenomenon from point to point along said lines, a plurality of coding signal generators, the output signals of which are independent of the measurement signal, means responsive to the measurement signal at selected magnitude thresholds thereof for selectively connecting the outputs of said coding signal generators to said moudulation control grid, and means for supplying a first sawtooth signal to said horizontal deflection grid and a second sawtooth signal to said vertical deflection grid in timed relation with the scanning means cycle.

16. Apparatus as defined in claim 15 wherein the cycle of said first sawtooth signal is short in comparison with the cycle of said second sawtooth signal, whereby the cathode ray makes a plurality of transverse sweeps during each vertical sweep thereof.

17. Apparatus as defined in claim 16 comprising means responsive to a selected magnitude of said second sawtooth signal for momentarily connecting the vertical deflection grid to receive only the measurement signal and simultaneously connecting the modulation control grid to receive a constant signal in lieu of the coding signals. I 7

18. Apparatus as defined in claim 15 comprising an AND gate for controlling the output of each coding signal generator, and a plurality of threshold amplifiers connected in parallel to receive the measurement signal and being responsive to selected threshold magnitudes of the latter, each said amplifier being capable of delivering one signal to a control terminal of one of said AND gates when the magnitude of the measurement signal is below a selected value, and a complementary signal to a control terminal of another of said AND gates when the magnitude of the measurement signal is above said selected value. v

19. Apparatus as defined in claim 18 comprising means including a mixer OR gate for connecting said AND gates to a common output conductor.

20. Apparatus as defined in claim 18 comprising means responsive to the signals delivered by at least one of said amplifiers for applying a pulse to said modulation control grid whenever the" measurement signal attains the selected threshold magnitude to which the amplifier is responsive.

21. In apparatus of the class described, means for generating a measurement signal characteristic of a variable phenomenon, a plurality of threshold amplifiers connected in parallel to said generating means, each said amplifier being responsive to a different threshold value of the measurement signal and being adapted to deliver two complementary signals on different outlets depending upon whether the value of the measurement signal is greater or less than the threshold value to which the amplifier is responsive, a plurality of coding signal pulse generators, means including an AND gate connected to the output of each coding signal generator for selectively connecting the latter to a common conductor, and means for connecting the output terminals of said amplifiers to control terminals of said AND gates, whereby a different AND gate is rendered conductive for each range of measurement signal values between the successive threshold values to which the amplifiers are responsive.

22. Apparatus as defined in claim 21 wherein the output terminals of said AND gates are connected to said common conductor through a mixer OR gate.

23. Apparatus as defined in claim 22 wherein each of the output terminals of at least one of said threshold amplifiers is connected through a rnonostable oscillator and said mixer OR gate to said common conductor.

24. Apparatus as defined in claim 21 wherein said common conductor is connected to a recording device.

tude.

Claims

6. A process as defined in claim 5 wherein the division of the horizontal sweep signal cycle by the coding signal cycle results in a different remainder from one measurement signal zone to the next, whereby the inclination of the hachures created in successive sweep cycles is different for each zone of measurement signal values.

10. A process as defined in claim 9 which comprises applying an additional electrical signal pulse to the modulation control grid of said tube whenever the value of the measurement signal attains a predetermined threshold value to thereby create a generally vertical trace on the memory screen.

11. A process as defined in claim 10 wherein said signal pulses are created by utilization of monostable oscillators connected to complementary outputs of a threshold amplifier responsive to a predetermined threshold value of the measurement signal.

14. A process as defined in claim 12 comprising energizing complementary control terminals of pairs of said AND gates in response to the measurement signal through parallel connected threshold amplifiers each responsive to said measurement signal at different threshold values thereof and adapted to deliver complementary output signals to said control terminals.

15. Apparatus for creating a codified cartographic representation of a phenomenon such as luminosity, temperature and the like, which is susceptible of expression by a characteristic quantity and variable over a superficial field comprising a cathode ray tube having horizontal and vertical deflection grids, a modulation control grid and a memory screen, means for cyclically scanning said field successively along transverse longitudinally spaced lines and for generating an electrical measurement signal during each scanning cycle the magnitude of which varies in accordance with the magnitude of said phenomenon from point to point along said lines, a plurality of coding signal generators, the output signals of which are independent of the measurement signal, means responsive to the measurement signal at selected magnitude thresholds thereof for selectively connecting the outputs of said coding signal generators to said modulation control grid, and means for supplying a first sawtooth signal to said horizontal deflection grid and a second sawtooth signal to said vertical deflection grid in timed relation with the scanning means cycle.

17. Apparatus as defined in claim 16 comprising means responsive to a selected magnitude of said second sawtooth signal for momentarily connecting the vertical deflection grid to receive only the measurement signal and simultaneously connecting the modulation control grid to receive a constant signal in lieu of the coding signals.

18. Apparatus as defined in claim 15 comprising an AND gate for controlling the output of each coding signal generator, and a plurality of threshold amplifiers connected in parallel to receive the measurement signal and being responsive to selected threshold magnitudes of the latter, each said amplifier being capable of delivering one signal to a control terminal of one of said AND gates when the magnitude of the measurement signal is below a Selected value, and a complementary signal to a control terminal of another of said AND gates when the magnitude of the measurement signal is above said selected value.

20. Apparatus as defined in claim 18 comprising means responsive to the signals delivered by at least one of said amplifiers for applying a pulse to said modulation control grid whenever the measurement signal attains the selected threshold magnitude to which the amplifier is responsive.

23. Apparatus as defined in claim 22 wherein each of the output terminals of at least one of said threshold amplifiers is connected through a monostable oscillator and said mixer OR gate to said common conductor.

25. Apparatus as defined in claim 24 wherein the recording device is a cathode ray tube having a modulation control grid connected to said common conductor, and comprising means for supplying sawtooth signals to the horizontal and vertical deflection grids of said tube.

26. Apparatus as defined in claim 25 comprising means for superimposing a pulse signal on the coding signal applied to said modulation control grid whenever the measurement signal attains a preselected magnitude.