FR2662291A1 - METHOD OF ADJUSTING THE LUMINANCE OF AN ALTERNATIVE PLASMA PANEL - Google Patents

Abstract

The invention relates to a method for adjusting the luminance of an AC plasma panel. The method of the invention makes it possible in particular to act on the luminance per line with a view to creating localized highlights or sub-shines. The method consists in controlling an "written" state or an "erased" state of cells (C1 to C36) arranged in n lines (L1 to L4), then in applying to the cells maintenance signals in order to activate the cells. in the "registered" state. According to one characteristic of the invention, the method consists in inhibiting the transmission of one or more sustain signals (SE, SAE) to the cells of at least one row (L1 to L9), so as to reduce the luminance of this line in relation to the other lines.

Description

METHOD FOR ADJUSTING THE LUMINANCE OF A

ALTERNATIVE PLASMA PANEL

  The invention relates to a method for adjusting the luminance of a screen of the alternative plasma panel type, in particular for acting in lines or strips in order to create localized highlights or sub-glosses of the screen. Alternative type plasma panels, called

  in the following description "Pa P Ac", present a

  memory property that allows to dissociate the addressing functions (command write or erase information), the maintenance of light discharges that serves to produce most of the useful light Also, a method conventional adjustment of the overall luminance of the screen is to adjust the frequency of maintenance signals that perform the maintenance of landfills, maintenance by which

  cells in the "inscribed" state produce light.

  The operation and structure of "Pa P Ac" are in themselves well known The panels are for example of the type with two crossed electrodes to define a discharge cell, as described for example in a French patent in the name of THOMSON-CSE published with NO 2 417 848; addressing discharges and maintenance discharges being performed between the same two electrodes These panels can also be of the coplanar maintenance type, with for example three electrodes crossed to define a cell, so that addressing discharges and discharges may be carried out between different electrodes, as described in particular in a European patent application EP-A-0135 382 and in a published French patent application

with No. 2,629,265.

  In the "Pa P Ac" coplanar maintenance or not, the addressing of a given cell (that is to say, its inscription or erasure) is achieved by the selection of the two corresponding crossed electrodes, which are applied to appropriate voltage slots to create, between these two electrodes, a potential difference such that it generates

  a discharge of registration or erasure.

  A conventional method of addressing is to operate line by line: in this case all the cells of a line are controlled to be put all in the same state, the "erased" state for example (semiselective operation) and this operation is followed by a selective operation during which one or more selected cells of this same line are "registered". Semi-selective and selective operations are performed for each line during an addressing phase, with a time shift from one line to a next line that

  corresponds to the duration of a line cycle.

  In each line cycle, generally the addressing phase is followed by a specific maintenance phase, so that, for each line of cells, between two consecutive addressing phases, the cells in the "registered" state

  are activated by the maintenance signals.

  It should be noted that generally addressing by semi-selective and selective operation and performed by superposition of addressing slots on basic slots, as explained for example in the French patent applications in the name of THOMSON-CSE No. 88 11 248 and No. 88 11247, the latter patent application to be considered as

  forming part of this description.

  Taking the coplanar maintenance "Pa P Ac" as examples, these panels generally comprise an array of electrodes called column electrodes, whose function is only an addressing function and which are crossed with pairs of maintenance electrodes. ; each pair being formed of an addressing-maintenance type electrode having an addressing function plus a maintenance function, and an electrode having only a maintenance function Each crossing of a column electrode with a pair of electrodes defines a cell, such that cells are arranged in rows and columns; at each row of cells corresponds

  a pair of maintenance electrodes.

  Selective addressing is performed between a column electrode and an address-talk electrode; semi-selective addressing (one whole line) can be done between the two electrodes of the same pair. Maintenance discharges are obtained by applying maintenance signals to both

electrodes of the same pair.

  Usually the maintenance is ensured by creating simultaneously, or at least at close moments, a voltage front rising on one of the electrodes, the addressing-maintenance electrode for example and a voltage front falling on the only maintenance electrode these two

  variations are added and generate a maintenance discharge.

  This is generally achieved by using cyclic voltage slots which are applied to the two electrodes of the same pair with opposite polarities and which constitute the maintenance signals. Thus, voltage slots are permanently applied to all the cell lines, which slots form maintenance signals during the maintenance phases, and which constitute basic slots during the addressing phases; addressing slots (performing the inscription or erasure) are superimposed on these basic slots only on the addressing-maintenance electrode of the addressed line. The base slots have substantially the same amplitude as the slots for signals. in such a way that they can generate at least one light discharge. It should be noted that the maintenance addressing electrodes are individualized, whereas, on the other hand, the maintenance-only electrodes simultaneously receive slots.

  identical and are generally interconnected.

  In the "Pa P Ac", the luminance is usually set in two distinct and complementary ways: either globally (for the entire screen) by adjusting the frequency of the maintenance signals; the luminances of each of the points are then the same they are proportional to the frequency of maintenance; either point by point, by temporal framing as described for example in the French patents published with Nos. 2 519 170 and 2 536 565; intermediate levels of luminance (called "shades of gray") are thus obtained which, in the displayed images, allow the effects of degrading or, in the case for example of computer menus, the presentation

  uniform areas with reduced luminance.

  These two methods do not make it possible to obtain, in a simple manner, intermediate cases, such as the setting of

  luminance in bands or in line packets.

  The method of the invention is simple to implement and it applies as well to the luminance adjustments in the intermediate cases mentioned above as to adjust

the overall luminance.

  The method of the invention finds a particularly interesting application in "Pa P Ac"

  polychrome, for color balancing.

  According to the invention, a method of controlling an alternating plasma panel, said panel comprising a plurality of cells arranged in rows and columns, the method consisting in controlling the "registered" state or the "erased" state of the cells. and to apply to the cells maintenance signals so as to activate the cells in the "registered" state, is characterized in that it consists in inhibiting the transmission of one or more maintenance signals to the cells of the cells. at least one line so as to reduce luminance

of this line.

  The invention will be better understood and other advantages

  that it provides will appear on reading the description which

  follows, given by way of non-limiting example with reference to the appended figures in which: Figure 1 shows schematically, and by way of non-limiting example, a plasma-alternative panel to which the method according to the invention; Figures 2a, 2b, 2c illustrate the operation of a coplanar plasma panel operating under the control of the method of the invention; Figures 3 to 3 e illustrate the possibilities offered by the method of the invention; Figures 4a, 4b, 4c illustrate the application of the method of the invention to the control of a plasma panel to

  two crossed electrodes to define a cell.

  FIG. 1 shows an alternative plasma panel 1 to which a preferred embodiment of the method of FIG.

the invention.

  In the nonlimiting example described the panel 1 is of the coplanar maintenance type It comprises an array of column electrodes XI to X 4 which are crossed in a conventional manner with pairs of electrodes P1 to P9 arranged in rows Each pair P1 to P9 of electrodes comprises an address-maintenance electrode Y1 to Y9 and a maintenance only electrode E1 to E9: the address-maintenance electrodes Y1 to Y9 fill on the one hand an addressing function in cooperation with the column electrodes Xi to X 4 and, secondly, a maintenance function with the electrodes only maintenance Therefore, these addressing-maintenance electrodes Y1 to Y 9 must be individualized and they are each connected to a separate output of an addressing register line 3, which delivers

  SAE signals useful for addressing and maintenance.

  The maintenance electrodes El to E 9 only provide a maintenance function, they can all be connected to the same output of a pulse generator 4,

  from which they receive SE maintenance signals.

  The column electrodes X1 to X4 provide an addressing function, they are therefore individualized and each connected to a separate output of a column addressing register 5

  delivering SA addressing signals.

  The operating commands and the synchronization of the two addressing registers 3, 5 and of the generator 4 are managed in a traditional manner by a control device 12. Each crossing of a column electrode X 1 to X 4 with a pair P1 to P 9 of electrodes defines a cell C1 to C36, the cells thus being arranged in lines Li to L 9 and in columns.

  In the nonlimiting example of the description

  only 4 columns X1 to X4 and 9 pairs P1 to P9 forming 9 lines LI to L9 are shown, which define a screen of 36 cells, but in the spirit of the invention different numbers of rows and columns can be used and the screen may have many more lines, for example

480, 1000 or more.

  In a first version of the method of the invention, a feature of the method consists in eliminating, that is to say not to apply, at least one line Li to L 9 of cells, the maintenance signals SE delivered by the pulse generator 4; this being achieved by not applying these maintenance signals to the maintenance electrode only E1 to E9

corresponding.

  If these signals are not applied to the electrodes E1 to E9 only maintenance of all lines Li to L 9, it removes maintenance discharges and thus reduces globally the luminance of the screen; and we increase so

  overall this luminance when applying these signals again.

  If we do not act on all the lines of the screen, but only on some of them for example grouped in packets, we obtain localized effects of under-shine

or highlight.

  For example, if the second, third, seventh and eighth maintenance electrodes E 2, E 3, E 7 and E 8 are not fed with maintenance signals, no maintenance discharges are performed for the cells formed by the pairs P 2, P 3, P 7, P 8, that is to say the lines L 2, L 3, L 7, L 8. The cells of these lines produce less light and constitute screen of the sub-shine areas, relative to the lines of cells LM, L 4, L 5, L 9 which are

normally powered.

  Thus, by removing the maintenance signals applied to some maintenance-only electrodes, the coplanar maintenance is suppressed for the corresponding lines LM to L 9, and the light produced by the cells of these lines is then due solely to the discharges produced. between the electrodes

  columns X1 to X4 and the addressing-maintenance electrodes Y1 to Y9.

  To obtain localized highlighting, for example lines L 2, L 3, L 7, L 8, it is necessary to act in the opposite way, by applying the maintenance signals to these lines L 2, L 3, L 7, L 8 and by not applying it to the other lines LM, L 4, L 5, L 6, L 9. These two levels of luminance can be obtained in a simple manner, for example by actuating a simple switch It disposed between the generator of 4 and the electrodes only maintenance El to E 9, whereas until now it was known to act on the maintenance signals of

  complex way by playing on the frequency of these signals.

  In fact, in the method of the invention, the maintenance signals SE are not suppressed, but they are inhibited.

transmission to the cells.

  The transition from one luminance level to another can be done globally for the whole screen, it is then sufficient to cut off the general transmission of the maintenance signal SE or

  establish it using the switch Il for example.

  Luminance changes can also be accomplished in packets of one or more contiguous lines as already explained above, for lines whose

  positions are predetermined or not.

  In the case of predetermined lines, it is possible to separate these lines from the others, and for example to connect them by same packets to the generator 4 via, for example, a second switch I 2 for each packet, as shown

  in Figure 1 with the lines only maintenance E 3, E 4.

  Another method consists in implanting maintenance-only electrodes for the lines L1 to L9 that we want to be more luminous. For example, if it is expected that the second and third lines L 2, L 3 will be brighter, then implants only the second and third electrodes only

  maintenance E 2, E 3 and not others.

  It is also possible to act in software, with the possibility of action on all lines L1 to L9 or only a few of them For this purpose, it is possible to have in series with all electrodes only maintenance El to E 9, an electronic switching element, a transistor Tl to T 9 for example (symbolized by a dashed line) These switching elements are connected (in a manner in itself not shown) to the control device 12, whereby the maintenance electrodes El to E 9, to which will be applied, are electrically selected.

SE maintenance signals.

  Another interesting possibility offered by the method of the invention applies to the color adjustment of a polychrome panel. Indeed, if cells of the same colors are grouped together in the same packets of electrodes only for maintenance, Each Pain can be given two levels of intensity. For example, the cells of the lines Li, L 4, L 7 may correspond to the blue color B; the cells of lines L 2, L 5, L 8 with the red color and the cells of the lines L 3, L 6 and L 9 V with the green color If these three groups of lines are connected to the generator 4 each by the intermediate of a switch (not shown), one can obtain two

  Intensity levels for each color.

  The fact of not transmitting to some or all electrodes maintenance only E1 to E9, the maintenance signals SE delivered by the generator 4, has the effect of reducing the potential difference generated between the two electrodes of the pairs Corresponding P1 to P9, that is to say, to reduce the amplitude of the above-mentioned rising or falling edges, to the point that no discharge is

produced between these two electrodes.

  Also, according to another version of the method of the invention, the aforementioned effect is obtained by acting on at least one of the addressing-maintenance electrodes Y1 to YE 9 by not transmitting to this electrode a part

  SAE signals useful for maintenance.

  FIGS. 2a, 2b and 2c to be read at the same time, illustrate by way of nonlimiting example the maintenance signals applied to the pairs P1 to P, FIG. 2a represents the SAE signals applied to the addressing electrodes. maintenance Y1 to Y9; FIG. 2b shows the signals SE applied to the maintenance only electrodes E1 to 9 and FIG. 2c illustrates the potential differences SAE-SE generated between the two electrodes of the same pair P1 to P9.

  by the application of these signals or one of these signals.

  At a time t O: the signal SAE is at a potential + Vi stable, positive with respect to a reference voltage VR the signal SE is at a stable potential -V 2 negative with respect to the reference voltage VR; the potential difference SAE-SE is positive with a value + V 3 equal to the sum of the voltages

Vl and V 2 (V 3 = V 1 + V 2).

  At a time t1, the signal SAE goes to a negative potential -Vl and generates a negative variation of the potential difference SAE-SE which passes to a value V 5 corresponding to

V 2-Vl (V 5 = V 2 VI).

  At a time tl 'which follows and which is close to the moment tl, the signal SE reverses and goes from the negative voltage -V 2 to a positive voltage + V 2, which generates a new negative variation of the difference SAESE which passes to a negative value -V 3, a variation which is added to that already produced at time tl and which generates a maintenance discharge

(not shown)

  At time t 2, the signal SE reverses and goes to -V 2, which causes a positive variation of the difference SAE-SE

  which passes to the value V 5 (V 5 = V 2 Vl).

  At a time following t 2 'close to t 2, the signal SAE goes from -V1 to + V1 and causes a new positive variation of the difference SAE-SE which passes to + V 3, which results in a

new discharge of maintenance.

  At time t 3, there are variations comparable to those produced at time t1: the signal SAE goes to -Vl

  and the difference SAE-SE goes to the value V 5.

  In the conventional operation, at a time t 3 'close to the instant t 3, there must occur a positive slot of the signal SE (represented in dotted lines) which must cause at this instant t 3' and at a time t 4 the same effects that those

  mentioned for instants tl 'and t 2.

  If, in accordance with the invention, this voltage slot of the signal SE is not transmitted to one or to only maintenance electrodes E1 to E9, the maintenance discharges of the instants t 3 'and t 4 are eliminated for the pairs Correspondingly, because at each of these instants t 3 'and t 4 there is only one edge coming from the signal SAE, the maintenance is "truncated" and if the voltages are correctly

  set, the light discharge does not occur.

  Also, the difference signal SAE-SE is maintained at the value V 5 (V 5 = V 2 Vl) from the moment t 3 until a time t 4 'where it passes to + V 3, as a result of variation

  positive signal SAE which then passed to + Vl.

  This does not affect the proper functioning of the discharge cell to the next cycle (the memory required for proper operation is retained) and can be found at times t 5, t 5 ', t 6, t 6' which follow the same operation only

instants ti, ti ', t 2, t 2'.

  However, as mentioned above, it is possible to act in a similar manner on the Y 1 to Y 9 maintenance addressing electrodes, by not transmitting the SAE signal to one or more of these electrodes. to generate one or more successive "truncated interviews", the inhibition of the transmission of the SAE signal then being carried out for example directly in the addressing register

line 3.

  Thus, in the prior art, the instant t 8 'corresponds to a positive variation of the signal SAE from -Vi to + Vl, and the instant following t 9 corresponds to a negative variation of this signal from + Vl to -Vi, these variations being shown in Figure 2a in dashed lines But according to the invention this signal is not applied to at least one of the addressing-maintenance electrodes Yi to Y 9, so that for the pair Pl to Corresponding P 9 is performed a "truncated maintenance": there are no light discharges at time t 8 ', that is to say that the difference SAE-SE remains at the value V 5 = V 2 Vi from an instant t 8 until a moment t 1 O

  despite the existence of variations of the signal SE at time t 8.

  Of course, the principle of "truncated maintenance" by the SAE signal applied to the addressing-servicing electrodes can be applied to the entire panel. But it can also be applied selectively electrode electrode, or package per package of electrodes we find all the possibilities already mentioned above about electrodes only maintenance, but with greater facility for

  finer settings by playing on the number of deleted edges.

  FIGS. 3 a to 3 e illustrate by way of nonlimiting example a case where the maintenance, for three pairs of electrodes Pi, P 2, P 3 for example, is performed differently for each pair by playing on the SE signals applied to

  electrodes only maintenance El, E 2, E 3.

  FIG. 3a represents addressing signals SA applied to column electrodes X1 to X9; FIG. 3b shows the SAE signals applied simultaneously and in the same way to all the addressing-maintenance electrodes Y 1 to Y 9; FIGS. 3c, 3d, 3e respectively represent signals SE 1, SE 2, SE 3 applied to the first, the second and the

  third electrodes only maintenance El, E 2, E 3.

  The transmission of the maintenance signals S El to the electrode El has been totally inhibited in this case the light discharges of the line L1 are reduced to those generated solely between the column electrodes and the addressing-maintenance electrodes, and the luminance of this line

  is minimum, for example Lmin equals 30 cd / m 2.

  The maintenance signals SE 2 transmitted to the second maintenance only electrode E 2 are at the maximum number, and consequently the luminance of the second line L 2 is maximum, by

example Lmax equals 100 cd / m 2.

  The maintenance signals SE 3 transmitted to the third maintenance-only electrode E 3 are in an intermediate number, 2 to 5, for example in this case the luminance of the third line L 3 is equal to the minimum luminance Lmin +

2/5 Lmax-Lmin, or 58 cd / m 2.

  It should be noted that the invention can also be applied to non-coplanar panels, that is to say panels having only two crossed electrodes to form a cell. Such a plasma panel could be represented by FIG. all electrodes only maintenance For such a plasma panel, whose row electrodes would be grouped for example in two packets one of which would receive the maximum number of maintenance signals and the other would receive 2 out of 5 signals, the lines with higher luminance would for example have 30 cd / m_ and lines with lower luminance would have about 12 cd / m 2. But in the case of these panels with two electrodes per cell and unlike the case of coplanar panels, the setting of luminance per line interferes with the addressing function in that the addressing function is provided by the same type of electrodes as the one on which the removal of maintenance fronts is concerned However, it is necessary that the setting of the interviews be completed in

out of the addressing cycles.

  In practice, the addressing cycles represent an important part of the frame time, for example, for a screen of 480 lines refreshed every 20 ms, the addressing takes up approximately 480 x 20 ps / line, ie 9.6 ms which represent 48% of the total time It follows that the possibilities of adjustment of the interviews are relatively limited This constraint can be turned by interposing between the phases

  addressing, reduced maintenance cycles.

  FIGS. 4a, 4b and 4c illustrate such an organization, which can be applied particularly, but not exclusively, to the case of two-way alternative plasma panels.

cross electrodes per cell.

  FIG. 4a shows SX addressing signals applied to the column electrodes. FIG. 4b shows addressing signals and maintenance signals applied to a line electrode, corresponding to a line Li for which the maximum luminance La is desired. FIG. 4c shows addressing and maintenance signals applied to the line electrode of a subsequent Li + 1 line for which reduced luminance is desired. In the signals applied to each of the lines, there are PA addressing phases between which are

  interposed PE maintenance phases.

  In a manner that is conventional in itself, each addressing phase comprises an erase base slot C Be within an erasure cycle CE, followed by a registration cycle CI comprising a slot of registration base C Bi The addressing phases PA 1, PA 2 have a duration of the order of 20 us and in the case for example of a 480-line panel, the time available for the maintenance phases PE is 21.6 s; this allows a maximum of 4 consecutive C 51 to C 54 maintenance cycles, each of which has a shorter duration than an erase or CE marking cycle, which allows 5 levels

luminance.

  In the case of the line Li (FIG. 4 b), it is assumed that the first addressing phase P Al serves for the addressing of this line, and consequently and in a conventional manner, on the one hand, a pulse of erase IE is superimposed on the erase window Cbe and, on the other hand, an inscription pulse It is superimposed on the base registration window C Bi The first addressing phase P Al is followed, for the line Li, 4 maintenance cycles C 51 to C 54 Then the PEI maintenance phase is followed by a second PA 2 addressing phase, and so on. In the nonlimiting example shown in FIG. 4c, the line Li + 1 also sees the addressing phase P Al, followed by a PEI maintenance phase, itself followed by a second PA addressing phase. 2, etc .; the addressing of the line Li + 1 being

  performed during the second PA 2 addressing phase.

  According to the invention, in order to reduce the luminance of the line Li + 1, the number of transmission cycles C 51 to C 54 transmitted is less than that transmitted for the transmission.

Li line.

  Of course, this last version of the method of the invention can also be applied to the case of polychromatic plasma panels, for the purpose of electronically balancing the colors. It should be noted that the "line" and "column" names given to the electrodes do not necessarily prejudge the horizontal or vertical orientation of these electrodes, even though a horizontal row of cells is most often

called "line".

Claims (1)

1 A method of controlling an alternating plasma panel, said panel (1) comprising a plurality of cells (C1 to C36) arranged in lines (L1 to L9) and in columns, the method of controlling the state "enrolled" or the "erased" state of the cells and to apply to the cells maintenance signals so as to activate the cells in the "registered" state, characterized in that it consists in inhibiting the transmission of a or a plurality of maintenance signals (SE, SAE) to the cells (C1 to C36) of at least one line (L1 to L9) so as to reduce the luminance of that line. Method according to claim 1, characterized in that it consists in inhibiting the transmission of the maintenance signals to several lines (L1 to L9) or packets of lines so as to constitute zones having different luminances. 3 Process according to claim 2, characterized in that it consists in inhibiting the transmission of signals (SE, SAE) simultaneously to several lines (L1 to L9) and differently between at least two lines. 4 Process according to claim 1, characterized in that it consists in inhibiting the transmission of the maintenance signals (SE, SAE) in the same way for all the lines (L1 to L9) of the panel (1). Method according to one of the preceding claims, the plasma panel being of the coplanar maintenance type having address-maintenance electrodes (Y 1 to Y 9) and maintenance-only electrodes (E 1 to E 9), characterized in that what it consists of intervening on the transmission of the maintenance signals (SAE) applied to the addressing-maintenance electrodes. 6. Method according to one of the preceding claims, the plasma panel being of the coplanar maintenance type comprising column electrodes (X1 to X4) crossed with addressing-maintenance electrodes (Y 1 to Y 9) and with electrodes. only maintenance (El to E 9), characterized in that it consists in intervening on the transmission of the maintenance signals (SE) applied to the electrodes only maintenance (El to E 9). 7 Process according to claim 6, characterized in that it consists in providing at least one line (Ll to L 9) with a lower luminance and in producing this line with only one addressing-maintenance electrode (Y 1 to Y 9 ) crossed with the column electrodes (X1 to X4). 8 Process according to claim 6, characterized in that it consists in arranging at least one switching element (10) in series with the supply of maintenance signals of at least one maintenance-only electrode (El to E 9). Process according to any one of the claims   1 to 4, characterized in that the plasma panel is of the type to   two crossed electrodes to define a cell.   Method according to one of the claims   characterized in that the plasma array is of the polychrome type comprising cells having at least two different colors, and in that it consists in arranging the cells so that each line (Li to L 9) is formed by cells of the same color.