EP3549124B1 - Addressing mode and principle of construction of matrix screens for displaying colour images with quasi-static behaviour - Google Patents

Description

TECHNICAL AREA

The present invention relates to a method of addressing and a principle of making large flat color matrix display screens, and provides solutions to several drawbacks associated with current methods of making and addressing these screens, observed mainly when the addressing of the image elements (in everyday language: pixels), of said screens is said to be multiplexed, or carried out sequentially in time.

Today there are many techniques for producing flat display screens. Among them: Liquid crystal screens which are the most widespread, plasma screens, organic light-emitting diode screens.

The main advantage of these techniques for making flat screens compared to older techniques (screens using cathode ray tubes) is that their thickness, from a few millimeters to several centimeters, depends very little on the size of the screen. screen, but essentially the technique used.

The techniques mentioned above use collective manufacturing methods, the set of pixels constituting the screen being produced on a single substrate, generally made of glass and whose size is in practice today limited to a few meters diagonally.

Light-emitting diode display screens overcome this limitation and use usually an assembly of individual components associated with their control electronics on a printed circuit. The sub-assemblies thus formed, or modules, with a size that can today range up to 25 dm ² , are then combined together to form modular screens of very large size. On the other hand, the resolution of these modules, and therefore of the screens which use them, is limited by the size of the components used to produce them, ie at least a few millimeters in the current state of the art.

As an indication, the documents US 2013/0234175 [4] and US 2007/0262334 [5] describe, without limiting the choices that the designer can make, LED components that can be used to manufacture a screen of this type.

This latter technique is used for the production of large screens which are usually observed from a considerable distance, such as, for example, urban or advertising display supports.

The present invention applies in particular, without this being limiting, to this latter technique for producing screens.

STATE OF THE PRIOR ART

The production of large screens by assembling sub-assemblies or modules is well described in the technical literature and for example in document [1] " Introduction to driving LED Arrays, AV02-3697EN - July 11, 2013 published by Avago Technologies.

A structure widely used to produce and control the various pixels of these modules is described figure 17 of document [1] and figure 1 of this memo. This describes as an example four lines of two color pixels 1 each composed of three red 1A, green 1B and blue 1C sub-pixels produced here using red, green and blue light-emitting diodes (LEDs), denoted Red, Green & Blue, and allowing any color images to be produced. This structure is repeated as much as necessary to reach the desired number of rows, columns and therefore pixels.

The matrix organization in rows and columns of pixels is particularly suited to the display of images and video content, because of the matrix organization itself thereof. It is useful to note that the notion of rows and columns, used in this memorandum remains formal. The role of the rows and of the columns, as these terms are used below, can be exchanged without changing the principle of the addressing modes and principles of embodiment which are described below.

• spatial multiplexing

The addressing mode of such a structure implements a single line selection circuit or module 2 which successively activates the latter over time. In the example of the figure 1 , where the first line of pixels represented is selected, the anodes of the LEDs of the same line are interconnected and receive the same positive control voltage generated by the sub-assembly 3 when the switch of the line concerned is closed.

The cathodes of the LEDs of the same column of sub-pixels are connected to each other and to the same output of a control circuit chosen from among the three possible outputs for the three colors of possible sub-pixels, namely red 4A, green 4B and blue 4C. The current which flows through, and therefore the quantity of light which is emitted by, an LED when the row to which it belongs is selected by the row selection circuit 2 and when the column to which it belongs is selected by the control circuit of the subpixels per color, can therefore be controlled independently of the other LEDs of its own row and independently of the other LEDs belonging to the non-selected rows. The sequential selection of the lines of the screen thanks to the selection circuits 2, thus makes it possible to construct and display any image, in this case a white image resulting from the superposition of all the sub-pixels of the pixels of the same line. over four successive sub-frames.

Depending on the implementation adopted, there may be, indifferently, and without the operating principle being modified, such a control circuit 4A, 4B or 4C per LED color as described in the figure 1 , or a single circuit for, for example, the 6 columns of LEDs. Many manufacturers offer suitable circuits which usually have 16 outputs and are capable of temporally modulating the current flowing through the LEDs and thus producing images with a very large number of color gradations. The data to be displayed are produced by the sub-assembly 5 according to the specifications required by the manufacturer of the control circuit used.

• L'image affichée est formée au cours d'un nombre de sous trames fonction du nombre de lignes de l'écran d'un module d'affichage constitutif de l'écran modulaire. La persistance visuelle de l'œil humain fait que les 4 sous-images ainsi émises par les DELs de chacune des lignes se superposent visuellement pour produire une image complète.
• Il n'est besoin pour contrôler les 4 lignes que d'un seul jeu de circuits de commande 4.

The 4 lines of the screen section represented figure 1 are selected successively in time, or in technical language, multiplexed, which has the following consequences:

• The displayed image is formed over a number of subframes depending on the number of lines of the screen of a display module constituting the modular screen. The visual persistence of the human eye causes the 4 sub-images thus emitted by the LEDs of each of the lines to be visually superimposed to produce a complete image.
• It is only necessary to control the 4 lines of a single set of control circuits 4.

The visual aspect of the 4 sub-images resulting from this addressing mode is described by the figure 2 for a four by four pixel section 1 of the screen, which specifies, for each of the 4 subframes T1 to T4, which are the selected pixels 6 displaying the state and the color determined by the content of the information transferred to and contained in the control circuits 4 and the unselected pixels 7.

The sequence of sub-images thus produced must be fast enough for the human eye not to perceive the independent sub-images. A minimum repetition rate greater than 25 Hz is required.

It is said that such a structure has a multiplexing rate N=4 due to the number of subframes necessary for the constitution of a complete image. The multiplexing rates most frequently encountered in LED screens are 2, 4 and more rarely 8.

Since the N sub-images produced relate to N different groups of pixels, each group of pixels being made up of a row of pixels, the multiplexing is said to be spatial.

It can be seen that such an arrangement has the economic advantage of requiring only N times fewer control outputs than groups of sub-pixels.

On the other hand, it has the disadvantage of requiring an instantaneous current N times greater per control output for the same visual effect. This current being on the other hand applied to N times less pixels, the current remains identical for each sub-frame.

Moreover, the display of the image being dynamic and composed of N distinct and successive sub-images, if a photograph of the screen is taken with a device (Camera or camera) whose exposure time is of the same order of magnitude as the duration of a sub-frame, the image obtained may be that of a sub-image and not be representative of the complete displayed image. This phenomenon is very penalizing when the image of such a screen appears for example in shots or video recordings of a sporting event.

• time division multiplexing

A time-division multiplexing of the color, the red, green and blue sub-pixels of the same pixel, representing the different color components of the display screen, being sequentially displayed to produce the final image, can also be envisaged. .

Documents [2] US 5,812,105 [2], and [3] US 6,734,875 offer addressing modes of this type.

In accordance with the picture 3 , a screen of this type comprises pixels 1 arranged in a matrix and each consisting of different types of optoelectronic devices 1A, 1B, 1C respectively able to diffuse different basic colors (red, green, blue) when an electrical excitation is applied to them , each optoelectronic device 1A, 1B, 1C being connected on the one hand to an electric excitation source corresponding to the color which it diffuses, called color source 3A, 3B, 3C, and on the other hand to a control means 5 making it possible to vary the intensity of the diffusion of the corresponding color.

More precisely, the optoelectronic devices 1A, 1D, 1E diffusing the same color (in this case red for the LEDs referenced 1A, 1D, 1E) are connected by their anode to the corresponding color source 3A (in this case VRED) via a single selection module 2 (see figures 26 to 31 ). The cathodes of the three LEDs constituting the three red 1A, green 1B and blue 1C sub-pixels of the same pixel 1 are interconnected and controlled by a single 3A color output of a color selection module. The display of the image thus consists of the temporal superposition of the three red, green and blue components, corresponding to the three different types or families of sub-pixels. There figure 4 describes the visual appearance of a 4 by 4 pixel section of the screen, describes picture 3 , for each of the 3 sub-frames T1, T2 and T3 in order to display at the end of the three sub-frames, a white screen consisting of the superposition of the screens of red, then green then blue. Each selected pixel thus successively takes on a red 6A, green 6B or blue 6C color, the intensity of which is determined by the content of the information transferred to and contained in the control circuits 4 of the picture 3 , the sub-pixels of each color component being successively selected by the selection circuit 2.

The main advantage of such color multiplexing, where the sub-pixels are grouped into as many groups as there are possible base colors “C” (in this case 3) i.e. groups of sub-pixels of identical color, is that the number of control outputs necessary is divided by C, C being usually equal to 3, the number of sub-pixels or color LEDs constituting an elementary pixel.

• Le courant instantané nécessaire pour afficher une image couleur sera C fois plus important que si aucun multiplexage couleur n'est appliqué. Contrairement au cas précédent, chaque famille de sous-pixels est adressée consécutivement et le courant nécessaire n'est pas constant pour chaque sous-trame comme on peut le constater dans le tableau de la figure 6.
• L'affichage de l'image est dynamique et toute prise de vue réalisée sur l'écran en fonctionnement peut mettre en évidence une des composantes couleur produites. Par exemple et dans le cas d'un écran trichrome rouge, vert et bleu, une image intégralement verte, rouge ou bleu peut résulter d'une prise de vue à faible temps d'exposition.

Its disadvantages are similar to those encountered for spatial multiplexing. In effect :

• The instantaneous current required to display a color image will be C times greater than if no color multiplexing is applied. Contrary to the previous case, each family of sub-pixels is addressed consecutively and the necessary current is not constant for each sub-frame as can be seen in the table of the figure 6 .
• The display of the image is dynamic and any shot taken on the screen in operation may highlight highlight one of the color components produced. For example, and in the case of a red, green and blue three-color screen, an entirely green, red or blue image may result from shooting with a short exposure time.

Document [3] also draws attention to the fact that the working voltages of LEDs generally depend on the color emitted and that to optimize the energy consumption of a screen, it is preferable to provide a different supply voltage. by groups associated with each family of sub-pixels or group of sub-pixels.

In this case, the color time-division multiplexing taught by documents [2] and [3] leads to the choice of distinct voltage sources for each group. There picture 3 describes the resulting block diagram. The peak currents required for each of these voltage sources are C times greater than if no color multiplexing is applied, while the average current remains the same. This constraint leads to the need to oversize these voltage sources and to use more capable and more expensive components.

It is possible to summarize these two types of multiplexing encountered in the literature as follows.

• L'ensemble des pixels, et consécutivement de sous pixels, sont regroupés en N groupes activés successivement au cours de N sous-trames, produisant N sous-images de l'image complète qui, du fait du phénomène de persistance rétinienne, permettent de reproduire celle-ci.
• Chaque sortie des circuits de commande 4 permet de contrôler N groupes de sous-pixels.
• Les circuits de sélection 2 comportent N jeux de sorties, chacun étant associé à une sous-trame.

In the case of a spatial multiplexing of value N:

• All the pixels, and consecutively sub-pixels, are grouped into N groups successively activated during N sub-frames, producing N sub-images of the complete image which, due to the phenomenon of retinal persistence, make it possible to reproduce this one.
• Each output of the control circuits 4 makes it possible to control N groups of sub-pixels.
• The selection circuits 2 comprise N sets of outputs, each being associated with a subframe.

• L'ensemble des sous-pixels sont répartis en C groupes activés successivement au cours de C sous-trames, produisant par exemple les C composantes couleur de l'image complète qui, du fait du phénomène de persistance rétinienne, permettent de reproduire celle-ci.
• Chaque sortie des circuits de commande 4 permet de contrôler C sous pixels.
• Les circuits de sélection 2 comportent C jeux de sorties, chacun étant associé à une sous-trame.

In the case of time division multiplexing of C different color components:

• All the sub-pixels are divided into C groups activated successively during C sub-frames, producing for example the C color components of the complete image which, due to the phenomenon of retinal persistence, make it possible to reproduce this .
• Each output of the control circuits 4 makes it possible to control C sub-pixels.
• The selection circuits 2 comprise C sets of outputs, each being associated with a subframe.

The two types of spatial and temporal multiplexing described above have the major drawback of requiring more instantaneous current than if no multiplexing was performed, and of displaying an image with visual artifacts when shooting this screen with a camera with a short exposure time.

We know the document EP 1 628 285 A1 which discloses a memory management method for display data of a light-emitting display device, which uses the field light emission of organic materials.

We know the document WO 2015/002010 which discloses a display device which is provided with a display unit which includes a plurality of pixels and a driver circuit which drives the display unit according to color assignment rules.

We know the document US 2015/302797 A1 which discloses a passive matrix of LEDs of several colors. For a row of LEDs, the anodes are connected to the same control means. For a column of LEDs, the cathodes of LEDs of the same color are connected to the same current source.

DISCLOSURE OF THE INVENTION

The object of the present invention is to remedy the drawbacks of the known embodiments described above.

It applies to screens whose pixels are made from components of the light-emitting diode type, but can also apply to any matrix screen, whether it is based on electroluminescence or any other electro-optical effect for which a opacity, refractive index, absorption, luminescence or any other optical property can be changed using electrical excitation.

More specifically, the subject of the present invention is a matrix screen for displaying multiplexed color images, the screen being made up of pixels arranged in a matrix and each made up of different types of optoelectronic devices respectively capable of broadcasting different basic colors when a electrical excitation is applied to it, each optoelectronic device being connected on the one hand to an electrical excitation source corresponding to the color which it diffuses, called color source, and on the other hand to a control means making it possible to vary the intensity of the diffusion of the corresponding color, the optoelectronic devices diffusing the same color being connected to the corresponding color source via at least one color source selection module.

The invention is defined by the claims.

BRIEF DESCRIPTION OF FIGURES

• There figure 1 describes a principle for producing spatially multiplexed screens such as can be found in the existing literature.
• There figure 2 describes the visual appearance of a 4 by 4 pixel area of a screen according to the principle of figure 1 and for the different subframes.
• There picture 3 describes the principle of production of color component multiplexed screens such as can be encountered in the existing literature.
• There figure 4 describes the visual aspect of the pixels of a 4 by 4 pixel area of a screen according to the principle of picture 3 and for the different subframes.
• There figure 5 is an example not forming part of the invention which describes for a section of a three-color screen using the addressing method, the percentage of pixels activated by groups of sub-pixels, for C=3 and N=1.
• There figure 6 describes the same situation according to a method of the prior art of figures 3 and 4 .
• There figure 7 describes in the case C=3 & N=2, and for a particular subframe, how 3 groups of subpixels combine to produce the subpicture displayed during that subframe.
• There figure 8 describes for C=3 & N=1 a possible organization of the sub-pixels during the 3 sub-frames, according to particular modes of implementation not forming the invention.
• There figure 9 describes a variant of these embodiments for C=3 & N=1.
• There figure 10 describes, for the 6 frames required, a possible organization of the sub-pixels in the case C=3 & N=2, according to an example not forming part of the invention.
• There figure 11 describes a particular embodiment in the case C=3 & N=1.
• There figure 12 describes an exemplary implementation of the invention in the case C=3 & N=2 and when the sub-pixels consist of light-emitting diodes.
• There figure 13 described in relation to figure 10 & 12 , an example of organization of groups of sub-pixels according to the rows & columns of the screen & the family considered.
• There figure 14 schematically illustrates the wiring of the pixels of the screen whose subframes are represented on the figure 8 , for the sub-frame T1 whose representation is also taken up in figure 15
• THE figures 16 and 17 are analogous to figures 14 and 15 , for the T2 subframe
• THE figures 18 and 19 are analogous to figures 14 and 15 , for the T3 subframe
• THE figures 20 to 25 are analogous to figures 14 to 19 being made for the wiring of the pixels of the screen of the figure 9 according to the invention
• THE figures 26 to 31 are analogous to figures 14 to 19 being made for the wiring of the pixels of the screen of the figure 4 according to the state of the art
• THE figures 32 to 34 are analogous to figures 14 to 19 being made to illustrate the configuration of the control means for displaying any image on the screen.

Definitions

Sub-pixel: optoelectronic device capable of diffusing a color of the visible with a greater or lesser intensity, when an electrical excitation is applied to it, we will speak indifferently of sub-pixel or electronic device, light-emitting diodes, LEDs in this text

Sub-frame: operating phase of a multiplexed matrix screen during which a degraded image (with fewer activated pixels than the image to be displayed) is produced. For a multiplexing rate N, a number of N successive subframes will be required to reconstitute said image to be displayed.

DETAILED EXPLANATION OF PARTICULAR EMBODIMENTS

The invention relates to a matrix screen exhibiting less visual artifacts than a screen of the state of the art when filmed or captured by a device with a low exposure time and which requires less instantaneous current than the known multiplexed screens.

This objective is achieved thanks to an innovative wiring of the sub-pixels of the screen which are organized in different groups so that at each sub-frame, the sub-pixels of all the basic colors of the screen are activated and that on average, at each sub-frame 1/3 of the sub-pixels are activated.

We detail in the following with reference to the figure 14 , the innovative wiring according to the invention for an exemplary embodiment, C = 3, N = 1:
Conventionally, each pixel of the screen 1 consists of several sub-pixels respectively diffusing the basic colors of the screen. In this example, the basic colors are three in number: red, green and blue, this number being denoted C. The sub-pixels of red, green and blue colors are arranged in this order for each of the pixels represented.

The number N governs with the color number C, the number of subframes allowing the constitution of a complete image, which is equal to C*N or three subframes for the example illustrated.

In accordance with the invention and as illustrated in the figure 14 , the screen comprises several selection modules 10, 11, 12 each connected to at least one color source VRED, VGREEN, VBLUE. In the example of this figure 14 , each selection module is connected to the three color sources. In the example of the figure 12 , each selection module 2 is connected to a single color source.

Each selection module 10, 11, 12 comprises different selection terminals 13 each connected to a color source via a switch.

Notion of sub pixel group

The sub-pixels (which are light-emitting diodes in the example shown) are part of different color families (red family F1, green family F2, blue family F3) represented by squares of different colors and/or patterns.

The sub-pixels of the same family are divided into different groups recognizable by the fact that the sub-pixels belonging to the same group are connected to the same connection terminal.

According to the invention, the number of sub-pixel groups depends on the number of basic colors of the screen C, which are three in number in the example illustrated (red, green and blue), and on a positive integer N representing the multiplexing rate which is 1 in the example illustrated.

More precisely, the number of sub-pixel groups is N*C ² i.e. 9 sub-pixel groups, each connected respectively to a number N*C ² selection terminals, and each color family comprises a number of C*N i.e. three groups of sub-pixels of the same color.

In other words, in the example illustrated, there are three groups of sub-pixels per color family.

• le premier groupe G1 est constitué des sous pixels rouges de la première colonne de pixel et de la quatrième colonne de pixel (et de toutes les colonnes suivantes de l'écran respectant cette périodicité, non représentées), ces sous pixels sont tous reliés à la borne de sélection S1 qui est reliée à la source couleur rouge dans le premier module de sélection 10
• le deuxième groupe G2 est constitué des sous pixels rouges de la deuxième colonne de pixel(et de toutes les colonnes suivantes de l'écran respectant cette périodicité, non représentées) qui sont tous reliés à la borne S4 qui est reliée à la source couleur rouge dans le deuxième module
• le troisième groupe G3 est constitué des sous pixels rouges de la troisième colonne de pixel (et de toutes les colonnes suivantes de l'écran respectant cette périodicité, non représentées) qui sont tous reliés à la borne S4 qui est reliée à la source couleur rouge dans le troisième module

Thus, there are three groups of red sub-pixels (shaded square first line of the legend) each connected to the selection terminal corresponding to its color within a selection module:

• the first group G1 is made up of the red sub-pixels of the first pixel column and of the fourth pixel column (and of all the following columns of the screen respecting this periodicity, not shown), these sub-pixels are all connected to the selection terminal S1 which is connected to the red color source in the first selection module 10
• the second group G2 consists of the red sub-pixels of the second pixel column (and of all the following columns of the screen respecting this periodicity, not represented) which are all connected to the terminal S4 which is connected to the red color source in the second module
• the third group G3 consists of the red sub-pixels of the third pixel column (and of all the following columns of the screen respecting this periodicity, not represented) which are all connected to the terminal S4 which is connected to the red color source in the third module

• une colonne sur quatre à partir de la 1^ère (sous pixels référencés H1), qui sont tous reliés à la borne de sélection S2
• une colonne sur quatre à partir de la 2^ème (sous pixels référencés H2) qui sont tous reliés à la borne de sélection S5
• une colonne sur quatre à partir de la 3^ème (sous pixels référencés H3) qui sont tous reliés à la borne de sélection S8

Similarly, there are three groups of green sub-pixels H1, H2 and H3, made up of the green sub-pixels present respectively on:

• one column out of four starting from the ^1st (sub-pixels referenced H1), which are all connected to the selection terminal S2
• one column out of four starting from the ^2nd (under pixels referenced H2) which are all connected to the selection terminal S5
• one column out of four starting from the ^3rd (under pixels referenced H3) which are all connected to the selection terminal S8

• une colonne sur quatre à partir de la 1^ère (sous pixels référencés partiellement I1) qui sont tous reliés à la borne de sélection S3
• une colonne sur quatre à partir de la 2^ème (sous pixels référencés partiellement I2) qui sont tous reliés à la borne de sélection S6
• une colonne sur quatre à partir de la 3^ème (sous pixels référencés partiellement I3) qui sont tous reliés à la borne de sélection S9

And finally, there are three groups of blue sub-pixels (remaining sub-pixels partially referenced I), made up of blue sub-pixels present respectively on:

• one column out of four starting from the ^1st (subpixels partially referenced I1) which are all connected to the selection terminal S3
• one column out of four starting from the ^2nd (subpixels partially referenced I2) which are all connected to the selection terminal S6
• one column out of four starting from the ^3rd (subpixels partially referenced I3) which are all connected to the selection terminal S9

The screen according to the invention comprises a control box which controls the closing of a switch per selection module at each subframe, and thus connects the terminal S of a group of subpixels to the corresponding color source, knowing that the switches whose closure is controlled, are connected to different color sources, so that at each subframe, all the colors are broadcast simultaneously.

Thus, at each subframe, the selection terminals of a group of each family can be activated simultaneously so as to request optoelectronic devices diffusing all the possible colors.

During the following sub-frames, it is the selection terminals of the other groups of sub-pixels which are activated, always making sure to connect the groups of the three color families simultaneously.

In this case, as illustrated in the figure 14 for the frame T1, the switches connected to the terminals S1, S5 and S9 (respectively connected to the color sources red, green and blue) are closed, which makes it possible to connect to their respective color sources, the groups of sub-pixels red G1, green H2 and blue (I3).

During the following subframe T2, these are, as illustrated in the figure 16 , the terminals S2, S6 and S7 whose switches are closed in order to connect the groups of green sub-pixels H2, group of blue sub-pixels I2, group of red sub-pixels G3.

And during the following subframe T3, these are, as illustrated in the figure 16 , the terminals S3, S4 and S8 whose switches are closed in order to connect the groups of green sub-pixels H3, group of blue sub-pixels I1, group of red sub-pixels G2.

It is well understood that at each sub-frame, sub-pixels of different colors, distributed over the whole of the screen (and no longer certain lines of sub-pixels of the same color) can potentially be activated.

To control their activation, control means are provided. Each sub-pixel is in fact connected, opposite its selection terminal, to an output of a control means which can regulate the light diffusion intensity of this sub-pixel between 0 and 100%.

Given that the sub-pixels of the same pixel are never activated at the same time, the same control means output can control the sub-pixels of the same pixel. This is the case of the separate outputs of the control means 14 to 17 of the figure 14 which are each connected to the sub-pixels of the same pixel, thus succeeding in modulating the intensity of the sub-pixel activated during the sub-frame considered.

According to the invention, as will be explained for the case N=2, for the cases N>1, the same control means can advantageously control the sub-pixels of a number of N pixels which are not connected to terminals of selection activated during the same subframe.

THE figure 15 , 17 And 19 which represent the three sub-frames making up an image, illustrate the display of the screen when the control outputs control the active sub-pixels so that they all diffuse the corresponding color at 100%.

At the end of these three sub-frames, a white screen is therefore obtained resulting from the superposition of the three colors displayed by each pixel successively.

Formation of any image on the screen according to the invention To, on the contrary, display any image, such as that illustrated in the header of the figures 32 to 34 , the control means will command the sub-pixels whose selection terminals are activated during the considered sub-frame and whose color and location in the pixel matrix coincide with the color of the image at the corresponding location, a intensity of 100%, and to the other sub-pixels whose selection terminals are activated during this sub-frame but whose colors and locations in the matrix do not correspond, an intensity of 0%.

Distribution of sub pixel groups

In the example of the figures commented on above, the sub-pixels connected to two different selection terminals among those activated simultaneously during the same sub-frame and belonging to two different families are arranged in two adjacent columns (thus during the sub-frame). frame T1, the red sub-pixels of group G1 are arranged in a column and adjacent to the green sub-pixels of group H2), in order to distribute each color through the pixels of the matrix.

To optimize this distribution, it is advantageously provided that the sub-pixels of the same group activated during a sub-frame are also distributed in line and in column so that their closest neighbor is of a different color family.

The invention provides corresponding wiring for these optimized screens illustrated in the figure 20 , 22 , 24 which responds to the same general principles as those set out above.

In this optimized screen, the immediate neighbor in line and in column of a sub-pixel which can be activated during the sub-frame considered, is of one or the other of the other colors.

Description of the operating method of the screen according to the invention, for any numbers N and C. It is recalled here that the invention applies to any matrix screen made up of pixels arranged in rows and columns, each of these pixels being made up of C sub-pixels or groups of sub-pixels of different characteristics and/or colors, belonging to C distinct families denoted F ₁ to Fc.

According to the principle of the invention, each family F _x of sub-pixels of the screen, with 1 ≤ X ≤ C, is subdivided into NC disjoint groups thus constituting NC ² groups of sub-pixels G _{X, Y, Z} , with N ≥ 1, 1 ≤ Y ≤ C and 1 ≤ Z ≤ N, all the sub-pixels of the group G _{X, Y, Z} belonging to the same family F _X , and each group being associated with a common selection means S _{X ,Y,Z} .

These groups are selected and displayed sequentially during NC consecutive sub-frames, the C groups G _1,Y,Z , G _2,Y,Z ... G _C,Y,Z being simultaneously selected, thanks to the selection means S _1,Y,Z , S _2,Y,Z ... S _C,Y,Z , and displayed during the subframe T _Y,Z .

With each subset of N pixels of the screen, made up of NC sub-pixels belonging to the NC groups G _{X, Y, Z} , such as 1 ≤ Y ≤ C and 1 ≤ Z ≤ N, is associated a control means making it possible to independently control the state of the sub-pixel belonging to the group G _X,Y,Z . during the subframe T _Y,Z .

When N = 1, G _C,Y,Z can be denoted in a simplified way G _C,Y and T _Y,Z denoted T _Y .

In order to clearly specify the notion of family of sub-pixels or groupings of sub-pixels, a few examples are given below.

• Constituer 3 familles basées sur la couleur des sous pixels; Une famille pour les sous-pixels rouges, une autre pour le vert et une dernière pour le bleu.
• Ou constituer 2 familles basées sur la tension de fonctionnement des sous pixels : Soit, pour une technologie basée sur l'utilisation de DELs, Les sous pixels rouges d'un côté et d'un autre, les sous-pixels vert & bleus nécessitant une tension d'alimentation supérieure.

If we consider a three-color screen, made up of pixels themselves made up of 3 red, green and blue sub-pixels, we can for example consider:

• Create 3 families based on the color of the sub pixels; A family for the red sub-pixels, another for the green and a last for the blue.
• Or constitute 2 families based on the operating voltage of the sub-pixels: Either, for a technology based on the use of LEDs, the red sub-pixels on one side and on the other, the green & blue sub-pixels requiring a higher supply voltage.

If we consider a screen based on the use of pixels made up of 4 sub-pixels, red, green, blue and white, 4 families based on the color of these sub-pixels could be formed.

• De constituer autant de familles que de sous-pixels, donc quatre.
• De regrouper les deux sous-pixels rouges dans une même famille et ainsi en constituer trois.

Finally, if we consider a screen based on the use of pixels made up of, for example, 4 sub-pixels including 2 red, one green and one blue, we can consider:

• To constitute as many families as there are sub-pixels, therefore four.
• To group the two red sub-pixels in the same family and thus constitute three of them.

It is also possible to group sub-pixels in the same family so that the average consumption of each family thus constituted is similar.

A first advantage of the invention is illustrated by the figure 5 which describes the behavior of a red, green and blue three-color screen, each pixel of which is made up of sub-pixels of these same colors and for which C=3 and N=1.

In this example, the families of sub-pixels are 3 in number, characterized by the color displayed; Red, green or blue, and noted respectively F ₁ , F ₂ & F ₃ .

• 3 groupes pour les sous pixels de couleur rouge; G_1,1, G_1,2 & G_1,3, qui sont affichés au cours des sous-trames T₁, T₂ & T₃,
• De même 3 groupes pour les sous pixels de couleur verte ; G_2,1, G_2,2 & G_2,3,
• Et 3 groupes pour les sous-pixels de couleur bleue ; G_3,1, G_3,2 & G_3,3.

In accordance with the invention and for this example, the sub-pixels are organized into 9 groups:

• 3 groups for red color sub pixels; G _1.1 , G _1.2 & G _1.3 , which are displayed during the subframes T ₁ , T ₂ & T ₃ ,
• In the same way 3 groups for the under pixels of green color; _G2.1 , _G2.2 & _G2.3 ,
• And 3 groups for blue color sub pixels; _G3.1 , _G3.2 & _G3.3 .

The table of the figure 5 presents, for each of the 9 groups and depending on the subframe T ₁ , T ₂ or T ₃ , the percentage of sub-pixels displayed, as well as the sum of these percentages within the same family F1, F2 or F3.

In addition to the figure 5 , there figure 8 illustrates a possible arrangement of these groups of sub-pixels. It can be seen in this figure that during the three sub-frames, each sub-pixel of each pixel will indeed have been selected and displayed, thus making it possible to compose a complete image.

The table of the figure 6 presents the same results for the prior art color component multiplexing method as previously described by figures 3 and 4 .

There figure 4 illustrates the distribution and the evolution of the state of the pixels of the screen relative to the table of the figure 6 .

It is noted that, if for the previously known addressing modes and principles of embodiment and for a screen of identical characteristics, the percentage of sub-pixels displayed in a given family is not constant but is maximum and 100% during a single sub-frame, the addressing mode of the invention makes it possible to ensure that this same percentage remains constant and equal to 1/3 regardless of the sub-frame considered.

• La puissance crête nécessaire pour alimenter chaque famille est divisée par C, ce qui permet de se satisfaire d'une alimentation dont la puissance crête est C fois inférieure.
• La puissance, donc le courant et/ou la tension, nécessaire à chaque famille restent, pour une image affichée donnée, statique dans le temps, ce qui permet d'en faciliter la mesure sans avoir à mettre en œuvre des moyens de filtrage superflus et améliore la durée de vie des composants électroniques utilisés.

If we consider C distinct families, this percentage would be 1/C. This particular property of the process of the invention brings several advantages compared to the processes of the prior art:

• The peak power required to supply each family is divided by C, which makes it possible to be satisfied with a power supply whose peak power is C times lower.
• The power, therefore the current and/or the voltage, necessary for each family remains, for a given displayed image, static over time, which makes it possible to facilitate its measurement without having to implement superfluous filtering means and improves the life of the electronic components used.

• La composition des groupes G_1,1,1, G_2,1,1 et G_3,1,1, relatifs aux familles F₁, F₂ & F₃,
• Le résultat de la sélection et de l'affichage de ces groupes de sous-pixels au cours de la sous-trame T _1,1.

There figure 7 Specifies on an example how different groups combine to display the pattern of subpixels displayed during a subframe. Specifically a portion of a screen with N=1 & C=3 is detailed, showing:

• The composition of the groups G _1,1,1 , G _2,1,1 and G _3,1,1 , relating to the families F ₁ , F ₂ & F ₃ ,
• The result of the selection and display of these groups of sub-pixels during the sub-frame T _1,1 .

It can be noted in this figure that for N=2, only half of the pixels are selected and displayed, which is deduced easily because according to the invention, all of the C families of sub-pixels are displayed during CN sub-frames. Only a fraction 1/N of the set of pixels is therefore selected and displayed at each subframe.

There figure 10 shows the 5 other subframes T _1.2 , T _2.1 , T _2.2 , T _3.1 and T _3.2 associated with the detailed frame T _1.1 figure 7 . In the same way that the latter shows how the groups combine, the groups implemented for these subframes can be easily deduced from the figure 10 , because being constituted for each sub-frame of the 3 groups of sub-pixels associated with each family which compose them.

The previous discussion does not take into account the spatial distribution of groups of sub-pixels during a frame. It is, however, apparent on examination of the figures 8, 9 And 10 , that it is advantageous to do so according to methods specific to the principle of the invention.

Thus, the groups of sub-pixels G _{X, Y, Z} can be spatially organized in such a way that for any sub-frame T _{Y, Z} considered, any group of NC consecutive pixels considered along a line and/or any group of NC consecutive pixels considered according to a column of the screen, contains exactly C pixels, one sub-pixel of which is selected and displayed, each being chosen from a different family F _X from among the C families of sub-pixels of the screen.

There figure 8 illustrates as a first example, a possible distribution in the case C=3 and N=1, and shows, for each subframe, the state of the pixels of the screen depending on whether a representative of the first family is displayed of sub-pixels F ₁ , of the second F ₂ or of the third F ₃ .

In the case illustrated, the groupings 8 of pixels referred to above are evaluated according to the lines of the screen, all the lines of the screen having an identical organization.

There figure 9 illustrates, as a second example, another possible distribution in the case C=3 and N=1, the groupings 8 of pixels being evaluated according to the rows and columns of the screen.

There figure 10 illustrates, finally and by way of example, a possible distribution in the case C=3 and N=2.

Another advantage of the principle of the invention can be seen in these three figures. Indeed, the spatial distribution of the groups of sub-pixels ensures that, for any displayed sub-frame, the local average of the information displayed remains representative of the complete image.

So and for example, any shot of a tri-color, low exposure time display, even though it may not capture the same quality as the full image, never results in an image of a single screen colors as commonly observed with known methods. Even if the image is displayed dynamically during several sub-frames, any instantaneous image remains representative of the complete image and the addressing method of the invention can therefore be qualified as quasi-static.

Advantageously, and particularly in the case where N > 1, for any subframe T _{Y, Z} considered among the possible NCs, the groups of sub-pixels G _{X, Y, Z} are organized in such a way that any pixel whose a representative among the C families F _X of sub-pixels is selected and displayed, is followed, according to the lines or the columns or the lines and the columns of the screen, by N-1 pixels for which none of the sub-pixels n is selected.

A particular organization of the different groups of sub-pixels also makes it possible to distribute them advantageously over time. Thus and according to this particular mode of implementation, the groups of sub-pixels G _{X, Y, Z} are organized in such that any pixel of which a representative among the C families F _X of sub-pixels is selected and displayed during a considered sub-frame, is not displayed during the following N-1 sub-frames.

There figure 10 illustrates a possible arrangement of these preferred modes of implementation in the case C=3 and N=2, the first criterion being applied according to the rows and columns of the screen.

In the case of a classical matrix organization, every pixel is surrounded by 8 close neighbors as visible, for example, on the figure 9 & 10 .

In the case C=3 & N=1, a particular embodiment makes it possible, within the framework of the invention, to provide particular additional advantages. This is described by the figure 11 . The rows and columns of the screen are spatially organized in such a way that the pixels of a particular row are shifted by 1/2 horizontal pitch between each pixel HP with respect to those of the preceding row.

In this configuration, each pixel is surrounded by 6 nearest neighbors. The 9 groups of sub-pixels G _X,Y , are spatially organized in such a way that for any sub-frame T _Y considered, any grouping of 3 neighboring pixels displays a representative of each of the 3 families of sub-pixels of the screen .

There figure 11 describes a first possible organization, a second being also described by inverting the families F2 and F3 of this same figure.

In this particular embodiment, it is advantageous to fix a precise ratio between the horizontal pitch HP between each column of pixels and the vertical pitch VP between each row of pixels. Indeed, if the distance between two pixels of the same line being given by HP, the distance R between a pixel and the neighboring pixels of an adjacent line is given by: $${\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">R</figure-callout>}}^2={\mathit{<figure-callout\; id="2"\; label="VP"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">VP</figure-callout>}}^2+\frac{{\mathit{<figure-callout\; id="2"\; label="HP"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">HP</figure-callout>}}^2}{4}$$

This distance R can be made equal to HP if: $$\mathit{VP}=\frac{\sqrt{3}}{2}\mathit{HP}$$

In this particular configuration, the pixels are arranged in a regular hexagonal pattern, any grouping of 3 neighboring pixels forming an equilateral triangle.

The pixel density D _H is then given by: $$D_H=\frac{4\sqrt{3}}{9{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}$$

For comparison, the average distance R between pixels of a classic matrix organization is given by: $$R=\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="imgf0002.png,imgf0003.png"\; state="\{\{state\}\}">P</figure-callout>}\frac{1+\sqrt{2}}{2}$$

P being equal to the vertical and horizontal pitch between pixels.

The pixel density D _R expressed as a function of R then being given by: $$D_R=\frac{{\left(1+\sqrt{2}\right)}^2}{4{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">R</figure-callout>}}^2}$$

The D _H /D _R ratio is thus, for an identical average distance between pixels, equal to: $$\frac{D_H}{D_R}=\frac{16}{9}\frac{\sqrt{3}}{{\left(1+\sqrt{2}\right)}^2}\sim 0.5283$$

Which, in other words, indicates that to obtain an identical average distance between pixels, the pixel density, therefore the overall cost of the screen can be reduced in proportion. In all the foregoing, the nature of the sub-pixels constituting the families F ₁ , F ₂ , ... F _C can be arbitrary and associate these sub-pixels according to their color, their technology, their service voltage or any other characteristic .

• Dans le cas C=3 et les sous-pixels des familles F₁, F₂ & F₃ étant respectivement de couleur rouge, verte et bleue. Cette configuration permet ainsi d'afficher des images couleurs quelconques.
• Dans le cas C=4 et les sous-pixels des familles F₁, F₂, F₃ F₄ étant respectivement de couleur rouge, verte, bleue et blanche. Cette configuration permet également d'afficher des images couleur quelconques et de pouvoir améliorer la luminance globale et le rendement de l'écran par l'addition de lumière blanche quand l'image à afficher le permet.

The invention finds a particular application in the case where this distribution of the C families is done according to the color. Two particular cases of implementation of the addressing principle of the invention are of practical interest in this case:

• In the case C=3 and the sub-pixels of the families F ₁ , F ₂ & F ₃ being respectively of red, green and blue color. This configuration thus makes it possible to display any color images.
• In the case C=4 and the sub-pixels of the families F ₁ , F ₂ , F ₃ F ₄ being respectively of red, green, blue and white color. This configuration also makes it possible to display any color images and to be able to improve the overall luminance and the performance of the screen by adding white light when the image to be displayed allows it.

The invention also finds a particularly advantageous application in the case of the production of screens based on LEDs.

• Toutes les anodes des diodes électroluminescentes constituant les sous pixels d'un même groupe G_X,Y,Z sont connectées entre elles et à une même sortie des moyens de sélection 2, en comptant N.C², permettant de sélectionner séquentiellement ces groupes au cours de N.C sous-trames consécutives à raison de C groupes distincts G_1,Y,Z, G_2,Y,Z ... G_C,Y,Z par sous-trame T_Y,Z,
• Chaque sortie des circuits de commande 4, permettant de contrôler le courant circulant dans les diodes qui y sont connectés, est également connectée aux C.N cathodes des diodes électroluminescentes constituant les C.N sous-pixels de N pixels distincts, chaque sous-pixel appartenant à un groupe G_X,Y,Z distinct caractérisé par 1 ≤ Y ≤ C et 1 ≤ Z ≤ N.

In this case, each pixel is made up of sub-pixels made up of light-emitting diodes connected as follows:

• All the anodes of the light-emitting diodes constituting the sub-pixels of the same group G _{X, Y, Z} are connected to each other and to the same output of the selection means 2, counting NC ² , making it possible to select these groups sequentially during NC consecutive subframes with C distinct groups G _1,Y,Z , G _2,Y,Z ... G _C,Y,Z per subframe T _Y,Z ,
• Each output of the control circuits 4, making it possible to control the current flowing in the diodes which are connected thereto, is also connected to the CN cathodes of the light-emitting diodes constituting the CN sub-pixels of N distinct pixels, each sub-pixel belonging to a group G _X,Y,Z distinct characterized by 1 ≤ Y ≤ C and 1 ≤ Z ≤ N.

There figure 12 helps to better understand this arrangement in the case N=2 & C=3. It describes a portion of 2 lines of 6 pixels 1 of such an LED screen. The corresponding diagram will be repeated as many times vertically and horizontally as necessary to build a screen module and therefore a complete screen.

There figure 10 describes, for a portion of 6 lines of 6 pixels, the state of the sub-pixels during the different sub-frames. It is useful to refer to it to better understand the diagram of the figure 12 .

The tables of the figure 13 show moreover for each family F1, F2 and F3, and each pixel of the zone considered of the screen, to which group the different sub-pixels belong.

The groups are 2.3 ² in number, ie 18, at the rate of 2.3, ie 6 per family of sub-pixels. The 3 selection circuits 2 of the figure 12 therefore has 18 outputs, denoted S _X,Y,Z , the 3 outputs S _1,Y,Z , S _2,Y,Z and S _3,Y,Z being simultaneously activated during the frame T _Y,Z , thus allowing the control, by means of control circuits 4, of the LEDs whose anodes are connected thereto.

It can clearly be seen, in this particular case of device, that the principle of the invention leads to the use of NC ² selection means, against respectively N and C in the previously known devices.

From the point of view of the cathodes of the LEDs constituting the sub-pixels, it is useful to take a particular example to better understand how the principle of the invention can be applied. For example, the 3 cathodes of the 3 sub-pixels of the pixel belonging to the first row & first column, therefore belonging to the groups G _1,1,1 , G _2,2,1 & G _3,3,1 , as well as the 3 cathodes of the 3 sub-pixels of the neighboring pixel, therefore belonging to the groups G _1,1,2 , G _2,2,2 & G _3,3,2 , are linked together and controlled by a single output of the control circuit 4.

A single output of the control circuits 4 therefore makes it possible to control N.C sub-pixels.

Claims (10)

1. A matrix screen for displaying multiplexed color images, the screen being composed of pixels arranged in a matrix and each consisting of C, C>1, different types of optoelectronic devices respectively capable of diffusing C base colors when an electrical excitation is applied thereto, the screen comprising C electrical excitation sources corresponding to the C base colors, referred to as color sources, and a plurality of control means, each optoelectronic device having a first termination connected to one of the color sources, and a second termination connected to one of the control means for varying the intensity of the diffusion of the corresponding color, the optoelectronic devices diffusing the same color being connected to the corresponding color source via at least one selection module (2) of a color source, the screen being defined:

   - in that it comprises n, n>1 selection modules,

   - in that each selection module comprises different M, C>=M>1, selection terminals (Si), each selection module is connected to M color sources and comprises M switches, each of the M selection terminals being connected to one of the corresponding M color sources by means of one of the M switches,
   the screen being configured so as to activate a single terminal for selection via selection module during the same operating phase of the screen or sub-frame, the activation consisting in controlling a switch so as to connect the selection terminal to a corresponding color source, and in that the optoelectronic devices of the screen belonging to the same color family, i.e. diffusing the same color, are divided into different groups, and:

   - for each selection module, the optoelectronic devices emitting the same color are all connected to the same color selection terminal corresponding to the same selection module,

   the optoelectronic devices of the same group being connected to the same selection terminal,

   the screen being characterized in that:

   - the optoelectronic devices of the same pixel and belonging to different N, N>1 groups are connected to the same control means,

   - the screen is configured to activate simultaneously a control means and a terminal in the selection modules associated with said control means so as to trigger optoelectronic devices diffusing the C base colors during the same sub-frame,
   wherein the screen has a total number of N* C² groups in which are distributed the optoelectronic devices of the screen and a total number of N* C² selection terminals respectively connected to the N* C² groups and distributed in a number C*N of selection modules.
2. The matrix screen according to claim 1, wherein the optoelectronic devices of a number of N pixels are connected to the same control means for a multiplexing rate N.
3. The matrix screen according to either of the preceding claims, wherein the optoelectronic devices of the same group and connected to the same selection terminal are arranged along a column or a row of the pixel matrix constituting the matrix screen, and the optoelectronic devices connected to two different selection terminals from the terminals activated simultaneously during the same sub-frame and belonging to two different families are arranged along two adjacent columns or rows
4. The matrix screen according to any of the preceding claims, wherein the optoelectronic devices of different groups connected to different selection terminals from the terminals activated simultaneously during the same sub-frame are arranged in periodic alternation from one group to another group along the columns and/or rows of the matrix constituting the screen
5. The matrix screen according to any of the preceding claims, such that the horizontal pitch HP of the pixels along the rows of the screen and the vertical pitch VP of the pixels along the columns of the screen are such that $\mathit{VP}=\frac{\sqrt{3}}{2}\mathit{HP}$

   

   and that any grouping of 3 neighboring pixels forms an equilateral triangle.
6. The matrix screen according to any of the preceding claims, wherein the base colors of the screen are 3 in number, C=3, and are red, green and blue, respectively
7. The matrix screen according to any of the preceding claims, wherein the base colors of the screen are 4 in number, C=4, and are red, green, blue and white, respectively
8. The matrix screen according to any of the preceding claims, wherein an optoelectronic device is a light-emitting diode, the anode of which is connected to the corresponding selection terminal and the cathode to the corresponding control means.
9. A display device comprising one or more screens assembled together to constitute said device, said screens being matrix screens produced according to any of the preceding claims.
10. A method for producing the matrix screen for displaying multiplexed color images according to any of claims 1 to 8, characterized in that it comprises:

    - a step of wiring a plurality of selection modules, each one to at least one color source,

    - a step of wiring optoelectronic devices to the same corresponding color selection terminal of the same selection module, said devices being connected to the same selection terminal, forming a group,

    - a step of configuring the selection terminals of a group of each family that can be activated simultaneously so as to trigger optoelectronic devices to diffuse all possible colors during the same sub-frame,
    the optoelectronic devices of the same group are connected to the same terminal for a multiplexing rate N.

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