Method and device for controlling a matrix screen displaying gray levels.

p0001The present invention relates to a method and a device for controlling a matrix display screen for displaying images having gray levels. It applies in particular to the control of fluorescent screens with microdots or liquid crystal displays. Images can be black and white or color, the term "gray level" meaning in this case "Color Halftone."

p0002We know that to control the display of images on a matrix screen is generally used the following Scan mode: the lines are successively addressed is to say, brought a suitable potential Vlp another suitable potential Vla a once per frame and for a time T called "time line" which is the same for all the rows, which is equal to the quotient of the duration of an image by the number of lines; simultaneously with the addressing of each row, the columns receive signals for controlling the respective states of picture elements, or pixels, of the line considered, depending on the desired image: a column is raised to an appropriate potential Vac if the corresponding pixel is switched on and at a suitable potential Vce if the corresponding pixel should be, instead, turned off. After the time T, the addressing of the line considered stops and the next line is addressed, the signals received by the dependent columns desired respective states for the pixels of the next line and so on.

p0003Also known two techniques for generating images with gray levels:

p0004One technique is to submit a column to an intermediate potential between VAC and Vce for the corresponding pixel has a brightness intermediate between that corresponding to the lit pixel and one corresponding to the pixel off.

p0005However, especially in the case of a fluorescent screen microdots, it is very difficult to adjust an intermediate voltage Vce between VAC and for a given brightness, due to the stiffness of the voltage-brightness characteristic for such a display.

p0006A second technique is to carry a column potential Vac only during a fraction of the time line, proportional to the desired amount of light to the corresponding pixel and then bring this column potential Vce during the rest of the time line (time modulation the control potential of each column).

p0007However, the relationship between the application time of Vac and the brightness is not perfectly linear, especially in the case of a fluorescent screen microtips, there is a highly non-linear relationship between the time of application and brightness due to the settling time of the voltage across a pixel.

p0008In addition, in the case of either of the two known techniques mentioned above, this settling time of the voltage across a pixel is further dependent of the access resistance to the pixel related to the position thereof on the screen. As a result, the pixel charging time also depends on this position: for the same control potential, for example two pixels at both ends of a same column do not have the same brightness, the pixel nearest contact column which is applied the control voltage having the highest brightness.

p0009The present invention aims a method and a device for controlling a matrix display screen of the gray levels, which uses a temporal modulation of each column control potential and therefore do not present the disadvantage of the first known technique mentioned above and that does not cause either of nonlinearity problem arises as the second te chnical known mentioned above.

p0010Specifically, the present invention firstly provides a method for controlling a display matrix screen for displaying images having gray levels which are identified by integers in growing from 0 to a number integer m at least equal to 1, this screen comprising a plurality of rows and a plurality of columns whose intersections are respectively associated with image elements, in which method, for each image the lines are successively activated for a given time T called time line that is the same for all lines, and, upon activation of each line the columns are respectively controlled by signals to activate the columns, each signal being applied for a time which depends on the level gray of the picture element corresponding to the intersection of the activated line in question and the column controlled by the signal concerned, method characterized in that it subdivides the time line T into N equal time intervals dt, N being an integer at least equal to m in that each gray level i of each line is associated with an integer Nile chosen intervals dt, representing the number of the line in the Nile numbers forming for the entire set, a strictly increasing sequence of the variable i, first term NOI null and last term Nml less than or equal to N and in that said time during which said signal is applied is equal to dt produced by the numbers of said sequence which corresponds to said line and said gray level, said column being deactivated after said time during which said signal is applied , until the activation of the following line, the numbers Nil being selected so as to obtain a determined distribution for the light intensities of the different gray levels.

p0011It is thus seen that the present invention allows to correlate the time of application of the potential Vac during the line time with the voltage-brightness of the current screen.

p0012The use of Nile quantities in the present invention and the ability to choose the quantities that you can balance a posteriori - that is to say, once the screen and the electronic circuits associated with it are ready at work or even have functioning gray levels obtained from each other, or to obtain a particular gray scale, regular or logarithmic, for example, or to compensate for aging of the display assembly circuit or even choose a better compromise between coupling and brightness.

p0013It recalls in this respect that the coupling in question is a phenomenon that is linked to the access resistance to different pixels and that is reflected visually by "smearing" of a screen line on the other.

p0014For every pair of lines l1 and l2, suites and Nil1 Nil2 numbers can be identical (not differentiated lines of the screen, the lines l1 and l2 may not be successive lines.

p0015Then the gray levels can be adjusted as follows: - Forming on the screen at least two zones corresponding to the gray level 0 and level of gray m, - Varying the fraction of line time during which the columns are activated for the image elements to the gray level m, until a desired picture quality on the screen, - Forming on the screen image with a uniform gray level m well defined and we measure the brightness of the uniform image, - Is calculated from the measured brightness value, brightness that is to be obtained for each of the other gray levels 1 to m-1, as a function of a selected scale of gray levels, and - For each of the other gray levels a uniform image having that other gray level is formed on the display and adjusting the number of said sequence corresponding thereto so as to obtain the calculated brightness for this other level Grey.

p0016On the contrary, for some lines l1, l2 of the screen suites Nil1 Nil2 numbers and may not be identical (differentiation of the lines of this screen).

p0017Can then correlate the potential Vac during the time of application the timeline with not only the voltage-brightness characteristic of the current screen as it is already mentioned, but also with the position of the addressed pixel in this screen.

p0018When these Nil1 Nil2 and suites are not identical for certain lines l1, l2 of the screen, maxima of gray levels can be adjusted as follows: - Measuring the respective brightnesses of all lines of the display when these lines are the maximum gray level and it determines the most low light line that is taken for reference, and - For each of the other lines is adjusted Nml the number corresponding to the maximum gray level so that the resulting brightness is equal to the reference brightness.

p0019In this case, the other gray levels 1 to m-1 can then be adjusted as follows: - Is calculated from the value of the reference brightness, the brightness that is to be obtained for each of the other gray levels 1 to m-1, as a function of a selected scale of gray levels, and - For each of the other gray levels and for each row, is formed on the screen the picture of this line having the other gray level and adjusting the number of said sequence corresponding thereto so as to obtain the brightness calculated for the other gray level.

p0020Preferably Nml is less than N, which eliminates the burr phenomenon of a line on the other as will be seen better later.

p0021The present invention also provides a display of a matrix display control device for displaying images having gray levels which are located by integers in increasing from 0 to an integer m at least equal to 1 , this screen comprising a plurality of rows and a plurality of columns whose intersections are respectively associated with image elements, the device comprising: - Means provided for successively activating the lines during a given time T known as time line that is the same for all lines and for each image, and - Control means of the columns, adapted to generate, upon activation of each line, signals to activate the columns respectively, each signal being applied for a time which depends on the gray level of the pixel corresponding to the intersection of the activated line in question and the column under the given signal, device characterized in that the column control means comprises: - Means which are common to all the columns and comprise: . means arranged to generate pulses of period dt equal to T / N, N being an integer at least equal to m, . storage means provided for storing, at least for each gray level i nonzero of each line, information related to an integer Nile selected, the representative number of the line in the Nile numbers forming for the entire set , a strictly increasing sequence of the variable i of last term Nml less than or equal to N, and - Means provided for applying said signal during a time equal to dt produced by the numbers of said sequence which corresponds to said line and said gray level, and to deactivate said column after said time during which said signal is applied, until 'upon activation of the next line, the time of application of any signal corresponding to the display of a pixel gray level 0 is zero, the Nile numbers being selected to achieve a specific distribution for the light intensities of the different gray levels.

p0022In a particular embodiment of the device object of the invention, the column control means further comprises a shift register whose number of positions is equal to the number of columns and which receives as input gray level information for the columns , each position being associated with a given column and occupied during the activation of a line, the gray level information i on this column, the means provided for applying said signal comprises for each column: - A register which receives as input the information contained in the corresponding position of the shift register and which is controlled by start of line signals, and - A comparator with two inputs, whose first input is connected to the output of said register and whose output controls the activation of the corresponding column via amplification means, and means common to all the columns are provided for supplying to the second input of each comparator information representing integers k, such information varying from 0 to m increasingly in the time line so that the corresponding column to this comparator is activated as long as k is lower than i, then deactivated and maintained in the deactivated state as soon as k reaches i until the activation of the following line.

p0023In a first embodiment of the object of the invention device, the Nil1 numbers and Nil2 being equal, for every pair of lines l1 and l2 and for each gray level i, the common means to all columns also include: - A first counter provided to count down, and - A second counter which is reset at the commencement of a line, which is incremented by a signal of end of counting output from the first counter, and sends to the second input of each comparator the information representing the numbers k, the first counter is decremented by the means provided for generating the pulses, the memorizing means comprise at least m registers numbered from 0 to m-1 and an address bus which are sent on the information representing the numbers k, the signal Release of these storage means controls the initialization of the first counter, which takes into account said output signals during the emission of the signal of end of counting, and the information present at the address i memorizing means, i taking any of the values ​​0 to m-1, is equal to the difference between the numbers N (i + 1) and the Nile.

p0024Finally, according to a second embodiment, suites and Nil2 Nil1 numbers are not identical for certain lines l1, l2 of the screen, the common means to all columns also include: - A first counter provided to count down, - A second counter which is reset at the commencement of a line, which is incremented by a signal of end of counting output from the first counter, and sends to the second input of each comparator the information representing the numbers k, and - A third counter which is reset at the start of an image and incremented each start line, the first counter is decremented by the means provided for generating the pulses, the memorizing means comprise at least mxl registers, L being the number of lines, and an address bus to which are sent the information representing the numbers k in the form of binary words in two parts, the most significant part corresponding to the third counter output signals and the low order portion corresponding to the information representing the numbers k, the output signals of these storage means controls the initialization of the first counter which takes into account said output signals during the emission of the signal of end of counting, and the information present at IXL memorizing means, i taking any of the values ​​0 to m-1 and taking any of the values ​​1 to L, is equal to the difference between the numbers N (i + 1) and the Nile.

p0025The invention will be better understood from reading the following description of embodiments given purely indicative and non-restrictive, with reference to the accompanying drawings in which:<ul><li>- Figure 1 illustrates schematically the principle of a display in all or nothing for a fluorescent screen to microtips,</li><li>- Figure 2 illustrates schematically the principle of the invention for such a fluorescent screen to microtips, </li><li>- Figure 3 shows the variations of the electron current based on the voltage between the cathode and the gate for a given screen of the above type,</li><li>- Figure 4 schematically illustrates the interest subdivided, in the present invention, line T of time into a number N of intervals dt, greater than the maximum gray level m,</li><li>- Figure 5 is a schematic view of a first particular embodiment of the device object of the invention, and</li><li>- Figure 6 is a schematic view of a second particular embodiment of this device.</li></ul>

p00261 schematically illustrates the principle of the display in all or nothing in the case of a fluorescent screen particular microtips. For "Display all or nothing" means a display in which each pixel can only be in the off state or the on state, without intermediate state. We see in Figure 1 the successive addressing the first three lines of the screen L1, L2 and L3. Each line passes at one point a potential Vlp = 45V to 90V Vla = potential it retains for the T time line and then back to potential Vlp = 45V to the time the next line changes from potential 45V potential 90V ... When all the lines have been addressed the first east again and so on.

p0027In Figure 1, there is also shown particular signals for addressing the first three columns of the screen C1, C2 and C3, these signals leading to the next image on the screen: the pixels corresponding to the intersections of columns C1 , C2 and C3 with the line L1 are respectively in the oFF states, on and off; the intersections of these same columns with the line L2 respectively lead to pixels in the switched states, off and off and the same intersections with the line L3 respectively lead to pixels in the switched states, off and on. Thus, for example, when the line L1 is on, the potential at the contact column C1 Password Vce = 0V with Vac = 45V then to return to 0V during the successive addressing of the lines L2 and L3.

p0028The method of the invention will now be explained according to the invention, the T line time is divided into N equal intervals dt. Assume that we want to be able to display m + 1 grayscale indicated by the number 0 (off pixel), 1, ..., m (maximum gray level corresponding to a lit pixel). The number N is at least equal to m. In practice, N is greater than m. Is associated with each gray level i of each of the lines of the screen a number of Nile dt intervals. The gray level 0 (off pixel) is in turn associated with 0 interval regardless of the number of the line. In other words, N0L is zero regardless of.

p0029In addition, the number of intervals dt associated with each of the gray levels is strictly increasing with the brightness of the gray level. In other words, for all the set, following the Nile numbers is a strictly increasing sequence of the variable i.

p0030In addition, the maximum gray level m (corresponding to a lit pixel) is associated with a number of intervals Nml less than or equal to N irrespective of.

p0031Addressed to a given line, the column electrode with a pixel must have the gray level brightness i is non-zero range, from the beginning of the T time line, the activation potential VAC (0V for some fluorescent screens microtip), and maintained at this potential during Nile time intervals dt, l being the number of the line in question, after which the electrode is reduced to the potential Vce extinction (45V for these fluorescent screens microtips) and this until the beginning of the next line.

p0032The object of the invention is illustrated by an example in FIG 2, in the case of a fluorescent screen particular microdots in this example, line T of the time is divided into 32 intervals dt (a) to translating 8 gray levels (0 to 7). The numbers N and m are respectively equal to 32 and 7.

p0033It was considered 4 gray levels 0.1, 4, and 7 and, for each of these levels, the timing diagram of the control signal is shown applied to a column of contact to display this level (dotted line) and the behavior of this column (in solid lines) in the time line T. it is noted in Figure 2 that the gray level 7 (items "white" that is to say on) corresponds to 28 intervals dt = N7L (b), representing the number of the row in which the gray level 4 is associated with N4L = 14 intervals dt (c), that the gray level 1 (almost extinct pixel) is associated with N1L = 5 intervals dt (d) and the gray level 0 (black dot that is to say off) is associated with N0L dt = 0 interval (e).

p0034An example demonstrating the improved performance of a microdot fluorescent screen with the object of the invention is given in Table I, which is located at the end of this description and in which the lines are not differentiated: for every pair of lines l1, l2 and for each gray level i, and the Nil1 Nil2 numbers are equal.

p0035In this table, the gray levels are 0 to m = 15, the Nile numbers associated with them in accordance with the present invention will of N0L = 0 = 355 N15l. Furthermore, we compared the gray levels obtained with a uniform distribution over time in accordance with the second known technique referred to above (Vac of application time proportional to the desired brightness) gray levels obtained with an adjusted distribution in accordance with the present invention, for a fluorescent screen microtip whose emission characteristic is shown in Figure 3. the load resistance of each column of the screen is 10 kilo ohms, the ability to load by column is 1 nanofarad, the time line is 64 microseconds and the time line is divided into N = 640 intervals dt equal.

p0036In Figure 3, the variations in the current intensity J e is shown, expressed in milliamperes per square millimeter, depending on the voltage v between a cathode (column) and a gate (row) of the screen expressed in volts.

p0037Table I is indicated for each gray level i, the value for the ratio (percentage) of the brightness Ii corresponding to the gray level to that corresponding to the maximum gray level (15) and, d on the one hand with the invention, by experimentally determining the Nile numbers to obtain an even distribution of brightness, and secondly with the prior art (second known technique mentioned above).

p0038It will be noted that the invention allows to obtain the brightness of reports which substantially grow in arithmetic progression, which is not the case in the prior art.

p0039In addition, with the even distribution of brightness, selected in accordance with the invention in this table I, the coupling is limited to 2.7% of the current emitted by a point of gray level 15 and this coupling is zero for other levels 0-14.

p0040In Figure 4, is schematically shown interest not to award N intervals dt at maximum gray m. Consider a line l of a fluorescent screen microtip and the next row l + 1. PB is assumed that a pixel of the line l is a lighted dot (gray level m) and the PN pixel belonging to the same column as PB and situated on the line l + 1 corresponds to a quenched (level gray 0). In case (a) where N is attributed intervals dt largest gray level, we see that there is a coupling between the LC and PB PN pixels, the corresponding dotted lines to the control signal applied to contact the column in question and the full line corresponding to the behavior of this column during the time T. from line makes this coupling, the light is emitted parasitically on the line l +1. In contrast, in case (b) where the number of intervals dt assigned to the largest gray level is less than N, such interference does not exist.

p0041We will now explain how to determine the number of Nile intervals associated with each gray level i. Consider first the case in which the lines are not differentiated. The Nile numbers can be determined as follows: - Forming on the screen the image of a checkerboard, or a succession of bands alternately lit (maximum gray level) and off (gray level 0). Just actually form an image with a part off and lighted section and more specifically, an image of at least one column a lighted dot immediately followed by an unquenchable.

p0042the timeline fraction is then made to vary during which the column electrodes are maintained at the potential activation for illuminated pixels, or by varying Nml N constant or varying N constant Nml. One seeks in this way the best compromise between the coupling and brightness knowing more Nml / N, the greater the brightness is good but the coupling is strong.

p0043is then formed on the screen a uniform image gray level resulting m the previous compromise and measuring the brightness of the image for example by means of a photometer or by measuring the anode current (in the case a fluorescent screen microtip).

p0044From the brightness value for the gray level m, calculate the brightness that we must get to each other grayscale according to a brightness level that one is fixed (regular or logarithmic scale example).

p0045Finally, for each of these other gray levels, is formed on the screen a uniform image of the other level and adjusting the number of intervals dt associated with this other level so as to obtain the calculated brightness for this previously other level.

p0046Note that the settings are valid for all screens that have the same characteristics, the same number of lines and the same number of columns in the case of screens identical products to the chain, it is not necessary to repeat these settings for each of these screens.

p0047In the case where the lines are differentiated, we can start by setting the maximum gray level of each line as follows:

p0048the weakest brightness line is first determined by measuring the respective brightnesses of all the illuminated lines, successively, for example. The weakest brightness line is usually the last line that is to say, that which is furthest contacts to the addressing columns of the display.

p0049then adjusted for each other online, the number of intervals dt to assign a maximum gray level of the other line so that it has the same brightness said the low brightness, the latter being taken as reference. In this setting, only said other line considered is lit in the screen.

p0050Then, we can calculate, from the value taken as a reference, the brightness that is to be obtained for each of the other gray levels on a scale that one is attached. Thereafter, for each of the other gray levels, is activated on the screen successively display lines is adjusted and the number of intervals dt associated with this other level and the line in question so as to obtain brightness previously calculated for said other level.

p0051Figure 5 schematically shows a first embodiment of the object of the invention device for controlling a matrix display 2, for example a fluorescent screen microdots, for which does not differentiate between the lines point of view of their brightness. This screen comprises a set of parallel lines 4 and between them a set of columns 6 which are mutually parallel and perpendicular to the lines. On the same side of the screen, the end of each line is provided with a contact line. Similarly, one side of the screen, adjacent to the former, the end of each column is provided with a contact column.

p0052The device shown in Figure 5 comprises means 8 for controlling lines and means 10 for controlling the columns. The intersection of a given column and a given row defines a picture element 12 that appears on the screen when the row and column are addressed appropriately.

p0053for example m = 15 is assumed, where 16 gray levels indicated by the numbers 0, 1, ..., 15 that can be encoded in 4-bit binary system. (For m + 1 grayscale, we p bits of code such as these 2^p≧ m + 1).

p0054The device shown in Figure 5 further comprises means 13 arranged to supply the information concerning the gray levels of the pixels, this information being encoded in binary system on 4 bits and denoted GP, and the synchronization pulses, including those of line early.

p0055Moreover, the means 10 comprise: - A shift register 14 having as many positions as there are columns in the display, each having 4-bit position (if m = 15), - For each column, a 16 4-bit register which, in the example shown in Figure 5, is a 4-bit D-type flip-flop, and a comparator 18 and means 20 for amplifying the control signal of the column in question, and - Means 22 which are common to all the columns and which will be described subsequently.

p0056GP information is presented successively to the input of shift register 14 and moved into the register 14 so that at the start of the addressing of a row, each piece of information, which is associated with a pixel, is in the position of shift register which is associated with the column corresponding to this pixel. At the start of the addressing of a row, each GP information is transferred from its position in the register 14 to the D inputs of flip-flop 16 of 4 bits associated with this position. The non-inverting Q outputs of this flip-flop is sent to the P a of the two inputs (4 bits) of the comparator 18 of 2x4 bits, the other input Q (4 bits) of the comparator receiving the GC information that are common to all orders of columns and coded on 4 bits. These GC information, derived from means 22 common to all columns, evolving increasingly over time line T. The output of comparator 18 is connected to the input of the amplification means 20 whose output controls corresponding the corresponding column.

p0057As the GP value is greater than the value GC, the output of comparator 18 remains at logic level 0 and the contact of the column corresponding to the comparator 18 in question is maintained at the potential 0 volts (activation). Once the GC value becomes equal to GP and GP exceeds this value, the output of the comparator 18 passes and remains at logic level 1 and the contact in question is brought to and maintained at 45 volts potential (extinction).

p0058The means 22 that are common to all columns include a first counter 24 of 8 bits, for counting down, a second counter 26 of 4 bits, a clock 28 and a memory 30.

p0059The counters 24 and 26 are for example of the type 74193.

p0060The means 22 further include a first gate 32 AND-type and a second gate 34 also type ET. The output of gate 32 is connected to the clock input CK of the counter 26. The output of gate 34 is connected to the input (inverting) of LD load ( "load") of the counter 24. One input of gate 32 is connected to the output (inverting) of RE retention ( "carry") of the counter 26 and the output (inverting) end downcounting BO ( "borrow") of the counter 24 is connected to the other input of the gate 32 and to an input of the gate 34.

p0061The means 13 are provided for sending a line start information to the means 8 control lines and the counter reset reset input 26. This line start information is also sent to the clock input CK ( "latch") of each flip-flop 16 and to another input of gate 34 via an inverter 36.

p0062We see in Figure 5 as the clock input of latch 16 is inverting: line start pulse (logic 1) is reversed once (logic 0) by the inverter 36 and a second time (logic 1) to the CK input of the latch 16 which thus takes care of the information in the corresponding position of the register 14 when the pulse of the top line is emitted.

p0063The clock 28 is a regular clock of frequency 1 / dt that is to say N / T. The pulses supplied by the clock is sent to the counting input DC ( "down") of the counter 24.

p0064GC information encoded on 4 bits are from the counter 26 and sent from one hand to the input Q of each of the comparators 18 and secondly to the address bus A memory 30 (the contents of counter 26 corresponding so a memory address). This memory 30 is a memory of 15 8-bit words. If the output of this memory 30 are displayed on the counter initialization bus 24.

p0065The counter 26 is reset at the start line and incremented by one end of counting signal from the counter output B0 24. Indeed, at the end of the counting, the counter B0 output 24 passes to state logic 1 and the output RE of the counter 26 being at logic 1, the input CK of the counter 26 receives a pulse. The counter 24 is decremented by the clock 28 and takes into account the outputs of the memory 30 If during the emission of its end counting signal. This signal corresponds in fact to a passage in the meter output BO 24 to logic 1 and, as the output of the inverter is at logic 1, the LD input of the counter 24 receives a pulse.

p0066If the information is placed at i memory and is equal to the number of intervals dt as to pass the number of intervals corresponding to the gray level i the number of intervals corresponding to the gray level i + 1.

p0067For the results shown in Table I, the content of the memory 30 is as follows: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="10" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="15.75mm" colsep="1" /><colspec colnum="2" colname="col2" colwidth="15.75mm" /><colspec colnum="3" colname="col3" colwidth="15.75mm" /><colspec colnum="4" colname="col4" colwidth="15.75mm" /><colspec colnum="5" colname="col5" colwidth="15.75mm" /><colspec colnum="6" colname="col6" colwidth="15.75mm" /><colspec colnum="7" colname="col7" colwidth="15.75mm" /><colspec colnum="8" colname="col8" colwidth="15.75mm" /><colspec colnum="9" colname="col9" colwidth="15.75mm" /><colspec colnum="10" colname="col10" colwidth="15.75mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="left">Address</entry><entry namest="col2" nameend="col2" align="center">0</entry><entry namest="col3" nameend="col3" align="center">1</entry><entry namest="col4" nameend="col4" align="center">2</entry><entry namest="col5" nameend="col5" align="center">3</entry><entry namest="col6" nameend="col6" align="center">4</entry><entry namest="col7" nameend="col7" align="center">5</entry><entry namest="col8" nameend="col8" align="center">6</entry><entry namest="col9" nameend="col9" align="center">7</entry><entry namest="col10" nameend="col10" align="center">8</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">contents</entry><entry namest="col2" nameend="col2" align="right">116</entry><entry namest="col3" nameend="col3" align="right">thirty</entry><entry namest="col4" nameend="col4" align="right">23</entry><entry namest="col5" nameend="col5" align="right">20</entry><entry namest="col6" nameend="col6" align="right">18</entry><entry namest="col7" nameend="col7" align="right">17</entry><entry namest="col8" nameend="col8" align="right">17</entry><entry namest="col9" nameend="col9" align="right">16</entry><entry namest="col10" nameend="col10" align="right">15</entry></row></tbody></tgroup><tgroup cols="10" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="15.75mm" colsep="1" /><colspec colnum="2" colname="col2" colwidth="15.75mm" /><colspec colnum="3" colname="col3" colwidth="15.75mm" /><colspec colnum="4" colname="col4" colwidth="15.75mm" /><colspec colnum="5" colname="col5" colwidth="15.75mm" /><colspec colnum="6" colname="col6" colwidth="15.75mm" /><colspec colnum="7" colname="col7" colwidth="15.75mm" /><colspec colnum="8" colname="col8" colwidth="15.75mm" /><colspec colnum="9" colname="col9" colwidth="15.75mm" /><colspec colnum="10" colname="col10" colwidth="15.75mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="left">Address</entry><entry namest="col2" nameend="col2" align="center">9</entry><entry namest="col3" nameend="col3" align="center">10</entry><entry namest="col4" nameend="col4" align="center">11</entry><entry namest="col5" nameend="col5" align="center">12</entry><entry namest="col6" nameend="col6" align="center">13</entry><entry namest="col7" nameend="col7" align="center">14</entry><entry namest="col8" nameend="col8" align="center">15</entry><entry namest="col9" nameend="col9" /><entry namest="col10" nameend="col10" /></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">contents</entry><entry namest="col2" nameend="col2" align="right">15</entry><entry namest="col3" nameend="col3" align="right">14</entry><entry namest="col4" nameend="col4" align="right">14</entry><entry namest="col5" nameend="col5" align="right">14</entry><entry namest="col6" nameend="col6" align="right">13</entry><entry namest="col7" nameend="col7" align="right">13</entry><entry namest="col8" nameend="col8" align="right">-</entry><entry namest="col9" nameend="col9" /><entry namest="col10" nameend="col10" /></row></tbody></tgroup></table></tables>

p0068In this example, we see that the contents of the address 15 of the memory is irrelevant since it is not considered.

p0069The means 22 thus operate as follows: at the start line, the counter 26 is reset. Its content is then 0. A 0 address, the memory 30 includes the number of dt corresponding to the gray level intervals 1. This number is transferred to the counter 24 is decremented by the clock frequency of 28 1 / dt. When the counter 24 is zero, it sends a pulse to the counter 26 which is incremented because of this impulse. The new content of the counter 26 is then 1. Address 1, memory 30 includes the additional number of intervals after reaching the number of intervals corresponding to the gray level 2. This additional amount is transferred to the counter 24 ... And so on.

p0070When the contents of counter 26 reaches its maximum value (15), its output RE goes to logic 0, blocking it. A new round begins with a new line.

p0071The memory 30 is for example PROM. To make the settings for grayscale mentioned above, which involves changes to the contents of this memory, just replace it with a device called "PROM Emulator," all things being equal and, once settings finished, replace this emulator by the memory 30 in which registered the values ​​obtained with this emulator. In addition, if these adjustments require to vary the number N, it is sufficient for this purpose to change the clock 28.

p0072Figure 6 schematically shows a second embodiment of the object of the invention device, allowing control of the screen with 2 lines of differentiation. schematically the device shown in Figure 6 differs from the device shown in Figure 5 in that it further comprises a third counter 38 whose increment is controlled by the line start pulses (which are sent to the the meter clock CK input 38) and whose reset reset is controlled by a picture start DI signal supplied by the means 13. the number s of output of counter 38 is such that 2^s is at least equal to L (number of lines of the screen). In addition, in the device shown in Figure 6, the memory 30 is replaced with a memory 31, n 8-bit words, n being at least equal to the product of the number of lines of the screen by the number m equal to 15 in the example given.

p0073The words presented on the address bus of the A memory 31 have a low weight part and a high weight. The counter outputs SL 38 is the most significant part of each word whose least significant part is the word output by the counter 26. The memory addresses are identified by words of s + 4 bits .

p0074The devices described with reference to Figures 5 and 6 could be used by the skilled person for driving a liquid crystal matrix screen.

p0075Furthermore, the present invention applies as well to control a black and white screen to control a color screen. <tables id="tabl0002" num="0002"><table frame="all"><title>TABLE I</title><tgroup cols="4" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">i</entry><entry namest="col2" nameend="col2" align="center">Nile Invention</entry><entry namest="col3" nameend="col3" align="center">Ii / I15 (%) Invention</entry><entry namest="col4" nameend="col4" align="center">Ii / I15 (%) Prior Art</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="right">0</entry><entry namest="col2" nameend="col2" align="right">0</entry><entry namest="col3" nameend="col3" align="char" char=",">0</entry><entry namest="col4" nameend="col4" align="char" char=",">0</entry></row><row><entry namest="col1" nameend="col1" align="right">1</entry><entry namest="col2" nameend="col2" align="right">116</entry><entry namest="col3" nameend="col3" align="char" char=",">6.7</entry><entry namest="col4" nameend="col4" align="char" char=",">0.1</entry></row><row><entry namest="col1" nameend="col1" align="right">2</entry><entry namest="col2" nameend="col2" align="right">146</entry><entry namest="col3" nameend="col3" align="char" char=",">13.3</entry><entry namest="col4" nameend="col4" align="char" char=",">1.1</entry></row><row><entry namest="col1" nameend="col1" align="right">3</entry><entry namest="col2" nameend="col2" align="right">169</entry><entry namest="col3" nameend="col3" align="char" char=",">20.0</entry><entry namest="col4" nameend="col4" align="char" char=",">2.5</entry></row><row><entry namest="col1" nameend="col1" align="right">4</entry><entry namest="col2" nameend="col2" align="right">189</entry><entry namest="col3" nameend="col3" align="char" char=",">26.7</entry><entry namest="col4" nameend="col4" align="char" char=",">6.4</entry></row><row><entry namest="col1" nameend="col1" align="right">5</entry><entry namest="col2" nameend="col2" align="right">207</entry><entry namest="col3" nameend="col3" align="char" char=",">33.4</entry><entry namest="col4" nameend="col4" align="char" char=",">15.8</entry></row><row><entry namest="col1" nameend="col1" align="right">6</entry><entry namest="col2" nameend="col2" align="right">224</entry><entry namest="col3" nameend="col3" align="char" char=",">40.2</entry><entry namest="col4" nameend="col4" align="char" char=",">19.8</entry></row><row><entry namest="col1" nameend="col1" align="right">7</entry><entry namest="col2" nameend="col2" align="right">241</entry><entry namest="col3" nameend="col3" align="char" char=",">47.2</entry><entry namest="col4" nameend="col4" align="char" char=",">27.4</entry></row><row><entry namest="col1" nameend="col1" align="right">8</entry><entry namest="col2" nameend="col2" align="right">257</entry><entry namest="col3" nameend="col3" align="char" char=",">54.3</entry><entry namest="col4" nameend="col4" align="char" char=",">41.1</entry></row><row><entry namest="col1" nameend="col1" align="right">9</entry><entry namest="col2" nameend="col2" align="right">272</entry><entry namest="col3" nameend="col3" align="char" char=",">60.9</entry><entry namest="col4" nameend="col4" align="char" char=",">45.4</entry></row><row><entry namest="col1" nameend="col1" align="right">10</entry><entry namest="col2" nameend="col2" align="right">287</entry><entry namest="col3" nameend="col3" align="char" char=",">67.8</entry><entry namest="col4" nameend="col4" align="char" char=",">54.0</entry></row><row><entry namest="col1" nameend="col1" align="right">11</entry><entry namest="col2" nameend="col2" align="right">301</entry><entry namest="col3" nameend="col3" align="char" char=",">74.2</entry><entry namest="col4" nameend="col4" align="char" char=",">68.9</entry></row><row><entry namest="col1" nameend="col1" align="right">12</entry><entry namest="col2" nameend="col2" align="right">315</entry><entry namest="col3" nameend="col3" align="char" char=",">80.7</entry><entry namest="col4" nameend="col4" align="char" char=",">73.2</entry></row><row><entry namest="col1" nameend="col1" align="right">13</entry><entry namest="col2" nameend="col2" align="right">329</entry><entry namest="col3" nameend="col3" align="char" char=",">87.5</entry><entry namest="col4" nameend="col4" align="char" char=",">81.7</entry></row><row><entry namest="col1" nameend="col1" align="right">14</entry><entry namest="col2" nameend="col2" align="right">342</entry><entry namest="col3" nameend="col3" align="char" char=",">93.7</entry><entry namest="col4" nameend="col4" align="char" char=",">95.7</entry></row><row><entry namest="col1" nameend="col1" align="right">15</entry><entry namest="col2" nameend="col2" align="right">355</entry><entry namest="col3" nameend="col3" align="char" char=",">100</entry><entry namest="col4" nameend="col4" align="char" char=",">100</entry></row></tbody></tgroup></table></tables>