FR2516672A1 - Interpolator for observation of curve on TV screen - uses two comparators, line sweep counter, shift register, image memory and XOR-gate - Google Patents

Abstract

A counter (1) sums the line synchronising pulses (3) and is set to zero by a frame synchronising pulse (2). A second counter (4) sums the points along the axes given by a clock signal (6) and is set to zero by a line sync pulse (5). This counter output is stored in a memory (11) and a comparator (7) analyses the two counter outputs. When they are equal, the comparator outputs a pulse (13) to illuminate the spot. A monostable (14) excludes pulses between the successive samples. A second comparator (16) utilises a preceding sample value via a register (19) to provide vertical interpolation via exclusive OR gate (22). A monostable (24) inhibit circuit pulses between samples. A switch (25) and ring counter (26) enable the area to be observed in an envelope generated by the curve.

Description

 The invention relates to a device intended to draw curves as a function of the increasing abscissa on the frame of a television set or of an alpha-digital terminal. This device provides an interpolation line, either between the successive points which correspond to the samples of the quantity to be displayed, or between these points and those of a baseline or of a second curve, in order to visualize their difference. The new product which results therefrom is the combination of the device described with a terminal equipped with a screen of the television type.

 Traces of almost any curves are commonly obtained on a television frame by means of circuits called "graphic screen controllers". These circuits are efficient but expensive, not only by themselves but also by the ancillary components, including page memory which is then important. In addition, they often have to be managed by a microprocessor. They are well suited for industrial computing and general applications.

 Particular applications, of the medical remote surveillance or technical oontr81s type by telephone, can come under the new discipline called "telematics", and also from the mi cro-informatique. These applications are intended for wide distribution and can be addressed to a category of users other than technicians or computer specialists. The visualization of curves of the transmitted signals would be easier to develop if economical solutions were offered on the market.

 When it is a curve plotted in point by point of regularly increasing abscisses, such as those of time, among others, a simple vertical interpolation can suffice. Indeed, between the elementary points along the lines of the scan, the abscissas are very close together. Therefore, the eye perceives little difference between a vector which would be inclined between the points of two successive abscissas, and a simple vertical interpolation.

On the other hand, the logic necessary for vertical interpolation can be much simpler to realize than the generation of any vector. The respective objectives are different.

 In addition, to facilitate visual examination and then certain measurements, it is often useful to highlight a baseline, and sometimes even the area between the curve and this baseline. In other cases it is useful to highlight the difference between this curve and a second curve which replaces the line.

 The device and its variants according to the invention can be associated with a television receiver or an alpba-digital console reduced to its essential elements, without using a microprocessor or a conventional graphic controller. This will result in a new product, in particular to extend the field of application of terminals of the Videotex Teletel type.

 The single figure illustrates the principle of the device which implements the vertical interpolation method described.

 A counter or counter (1) of lines of the television frame provides the value A of the ordinate of the line which is being scanned. For this it is set to zero by the frame synchronization pulse (2), and it counts or counts the line synchronization pulses (3).

 A counter (4) of abscissa points along each of the lines gives the value x or t of the abscissa of the point at each instant in the course of the spot. For this it is set to zero by the line synchronization pulse (5), and counts the pulses of the clock for generating the elementary points (6).

 An ordinate comparator (7) receives, from one side A (8) those from the counter (4), and from the other B (9) the samples of the curve which are read on the data bus (10 ) from the image maintenance memory (11).

When a sample B is found to have the same value as the ordinate A of the line being scanned, the output (12)
A - B of the comparator (7) triggers a pulse (13) which lights the spot at this instant of its course. The monostable (14) is figured to take into account the significant comparisons and to exclude those which are performed during the transient phases between the successive samples.

 This classic configuration gives a dotted curve which is precise but sometimes difficult to read. It can even be ambiguous when the successive ordinates are more hoped than others having relatively close but not contiguous abscissa (es. The proposed innovation consists of a simple process for drawing segments of vertical lines between successive points. A device which implements this method is described by way of example of embodiment.

To obtain the desired vertical interpolation, a second comparator (16) is added. I1 receives on its input A '(17) the current ordered mime A as the first comparator (7). On its input B '(18) it receives the value of the sample which precedes the one processed by the first comparator (7). To do this, a register (19) is interposed between this input B '(18) and the bus d. reading (10) of i memory (17). Each of the two comparators has the usual outputs A <3 and A) B, in addition to that of equality A - B
We use here the outputs A <B (20) and A '<B' (21) respectively, as an example, because the other two, not shown, could also be suitable. When the two values of the samples in progress are larger than the ordinate A of the line being scanned, the two outputs are in the same state. They will be together in the opposite state when the two values B and B 'are less than the ordinate A
On the other hand, when this line A passes between the two ordinates of the samples considered, the states of the outputs (20) and (21) will be opposite at this precise moment of the passage of each of the intermediate scanning lines. Therefore, by combining the states of these outputs in an "OU-EXCLUSIP n" gate (22) we collect in (23) the vertical interpolation pulses of this abscissa. The second monostable (24) has the same function as the first (14).

 It is sometimes useful to visualize a surface of which the curve of the samples constitutes the envelope relative to a baseline. This surface can be easily obtained by replacing the delayed sample B 'with the value of the baseline.

To this end, the switch (25) connects the input (18) of the second comparator (16) to the baseline source, for example coding wheels shown in (26).

 The switch (25) can also replace the register (19) or the encoder wheels (26) by an auxiliary memory area (27) allocated to the samples of a second curve which will be displayed in place of the baseline or the (11) samples delayed. In this case, it is the difference between the two curves which is highlighted by the interpolation surface.

 It is sometimes useful to visualize in dotted lines, without interpolation, the curve and the baseline, or the two curves to compare. This is obtained in a simple way by combining the pulses of the outputs A - B (12) and A '- B' (28) respectively of the two comparators in an OR OR "gate (29).

On the output (30) of @ it one will collect the two distinct sequences of the non-interpolated modulation. The OR gate (29) could be placed upstream of the monostable (14), but the interposition of a separate my @@@ able (31) gives more flexibility to allow a possible distinction of the respective points by their duration / brightness or pure colors
It is sometimes useful to encrypt an order of magnitude for the area viewed. This value can be obtained here by means of a pulse counter placed for the output (35) of the monostable (24). The sign of the surface, relative to the baseline or to the second curve, neut title provided by the states of the outputs (20) or (21) of the comparators.

 It goes without saying that the pulses, mixed here for heavy viewing on an economical black and white screen, connected in (32), can between samples be taken separately and (34, 35, 36) to be distributed between the channels of a television set. colors, in order to identify them clearly.

 The practical embodiment can use the usual integrated and discrete circuits in electronics, or circuits made on demand, to ensure the various functions stated in the description and illustrated as to their connections by the diagram in the single figure.

 read from the point of view of applications, the device described can usefully be combined with a Videotex Teletel terminal. This would allow two interlocutors to complete their verbal dialogue with a graphic marking dialogue on a curve which they must analyze together. In this respect, the alpha-numerical facilities of these terminals provide, in addition to identifications, a convenient means for locating areas or accidents of the curve.

 In this functional combination, the alpha-digital management of the screen remains ensured by the logic of the terminal which supplies the control signals to the graphic device, as well as to the index. The line coupler with the telephone part of the terminal will then serve as an active interface for the proposed device.

For sequences of samples transmitted year to one or up to a few times per second, the standard MCDEM of reception at 1200
Bauds from these terminals (CCITT AVIS-V.23) will probably be suitable. However, these terminals send @ or orally at 75 Bauds.

The addition of an é @@ ssion part to 120C Bauds will allow them a direct dialogue in @lternat. graphic included, as well as a local m @.

 Raw samples transmitted in simple ASCII mode allow resolution on the ordinate of the order of 63 or 64 to 95 or 96 levels. This can often suffice in fact for visual inspection. However, an economical transmission at 1200 Bauds allows only a temporal rate of the order of 100 (sometimes 50) samples per second without data compression.

 When this rate proves to be too low compared to the rates of variation of the ordinates, the readability of the sequence of points is greatly improved by the vertical interpolation proposed.

These conditions may correspond, for example, to those minimum required to transmit an electrocardiogram or an equivalent signal to be visually checked in near real time.

 On the terminals where an access to the elementary point is possible by software, in particular of generation of vector, this process can between accelerated by programming the method of vertical interpolation described. This option, simplified compared to the generation of any vector, makes it possible to raise the limit of the admissible speed of the curve drawing.

Furthermore, when it comes to transmitting signals in real time, some components of which, although at low relative amplitudes, correspond to frequencies which can reach 90 to 100 Hertz, the CCITT recommends the use of MO-
DEMS in accordance with AVIS-V.16. Such MODEMS would therefore be associated with the display device described, via a converter, of course. An AVIS.16 option made compatible with AVIS-V.23 could be considered to be combined with Teletel Videotex terminals. This would solve the aforementioned problem of sending at 1200 Bauds and possibly receiving it back at 75 Bauds.

Claims (8)

 1) Device for vertically interpolating points on the frame of a terminal, characterized by the combination of two comparators, a ordinate counter of 1 line scanned, an offset register, an image maintenance memory and a door "OU-EXCLUSIVE".  2) Device according to claim 1, characterized in that the ordinate of the line being scanned is compared in (20) to the step read in the memory, and in (21) to the preceding sample the latter, thanks to the interposition of the register (26).  3) Device according to claims 1 and 2, characterized in that the states of the two homologous outputs, here AB (20) and A 'B' (21) of the two comparators are not combined in a "OR-EXCLUSIVE" door, or other circuit ensuring the same function with regard to the samples, which gives an impulse for each of the scanning lines situated between the ordinates considered.  4) Device according to claims 1, 2 and 3, characterized in that the value of the delayed sample can be replaced by that of a base line Iron ratio to which is carried out the interpolation of each point of the curve , thus tracing an area bounded by the curve and the baseline0  5) Device according to claim 4, characterized in that the value of the delay8 pu sample from the baseline can be replaced by that of the sample of a second curve whose interpolation shows the distance which separates it from the first curve.  6) Device according to claims 4 and 5, characterized in that a measurement of the area displayed by the interpolation can be obtained by counting the corresponding interpolation pulses.  7) New product according to one or more of the above claims, characterized by the combination of such a device with a digital alpha terminal with television frame, to allow a dialogue of remote monitoring or telemetry displayed in high resolution graph on the initial frame.  8) New product characterized in that it has in the form of an accessory or an additional plug-in card for microcomputer or television, the circuits, devices and methods described in one or more of the above claims.