Classifications

• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
  • G09G3/28—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels
  • G09G3/288—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels using AC panels
  • G09G3/296—Driving circuits for producing the waveforms applied to the driving electrodes
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/2007—Display of intermediate tones
  • G09G3/2018—Display of intermediate tones by time modulation using two or more time intervals
  • G09G3/2022—Display of intermediate tones by time modulation using two or more time intervals using sub-frames
  • G09G3/2029—Display of intermediate tones by time modulation using two or more time intervals using sub-frames the sub-frames having non-binary weights
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2310/00—Command of the display device
  • G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
  • G09G2310/0202—Addressing of scan or signal lines
  • G09G2310/0205—Simultaneous scanning of several lines in flat panels
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2320/00—Control of display operating conditions
  • G09G2320/02—Improving the quality of display appearance
  • G09G2320/0261—Improving the quality of display appearance in the context of movement of objects on the screen or movement of the observer relative to the screen
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2320/00—Control of display operating conditions
  • G09G2320/02—Improving the quality of display appearance
  • G09G2320/0266—Reduction of sub-frame artefacts
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G2320/00—Control of display operating conditions
  • G09G2320/02—Improving the quality of display appearance
  • G09G2320/0285—Improving the quality of display appearance using tables for spatial correction of display data
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
  • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
  • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
  • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
  • G09G3/28—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using luminous gas-discharge panels, e.g. plasma panels

Definitions

• a method of encoding video for a plasma display panel is provided. More particularly, the invention relates to the coding of the gray levels of a panel of the type with separate display and maintenance.
• PAP Plasma display panels
• PAPs generally include two insulating slabs (or substrate), each carrying one or more networks of electrodes and delimiting between them a space filled with gas. The slabs are assembled to each other so as to define intersections between the electrodes of said arrays. Each intersection of electrodes defines an elementary cell to which corresponds a gas space partially delimited by barriers and in which an electric discharge occurs when the cell is activated. The electric discharge causes an emission of UV rays in the elementary cell.
• Luminophores red, green or blue
• PAPs of the alternative type there are two types of cell architecture, one is called matrix, the other is called coplanar. Although these structures are different, the functioning of an elementary cell is essentially the same.
• Each cell can be in the on or off state. Maintaining in one of the states is done by sending a succession of so-called maintenance pulses for the entire duration during which one wishes to maintain this state.
• the ignition, or addressing, of a cell is done by sending a larger pulse, commonly called addressing pulse.
• the extinction, or erasure, of a cell is done by cancellation of the charges inside the cell using a damped discharge.
• a first addressing mode called addressing during the display (or Addressing While Displaying) consists of addressing each cell line while the other cell lines are held, the addressing being done line by line in an offset manner.
• a second addressing mode called Addressing and Display Separation, consists of addressing, maintaining and erasing all the cells of the panel during three distinct periods.
• FIG. 1 shows the basic time distribution of the addressing mode with separate display for displaying an image.
• the total display time Ttot of the image is 16.6 or 20 ms depending on the country.
• eight sub-scans SB1 to SB8 are carried out in order to allow 256 gray levels per cell, each sub-scan making it possible to illuminate or not an elementary cell during an illumination time Tec multiple of a value To.
• the total duration of a subscanning includes an erasing time Tef, a time d addressing Ta, and the lighting time Tec specific to each subscanning.
• the addressing time Ta is also decomposable into n times an elementary duration Tae which corresponds to the addressing of a line.
• Figure 1 corresponds to a binary decomposition of the lighting time. This binary representation has many drawbacks. A problem of false contouring (or "contouring”) has been identified for a long time.
• the problem of false contours comes from the proximity of two zones whose gray levels are very close but whose moments of illumination are decorrelated.
• the worst case corresponds to a transition between levels 127 and 128: Indeed, the gray level 127 corresponds to an illumination during the first seven sub-scans SB1 to SB7 while the level 128 corresponds to the illumination of the eighth sub-scan. SB8 scan. Two areas of the screen placed next to each other, having levels 127 and 128, are never lit at the same time. When the image is static and the viewer's eye does not move on the screen, integration temporal is done relatively well (if we do not take into account a possible flicker effect) and we observe two zones with relatively close gray levels.
• the integration time window changes screen zone and is moved from one zone to another for a number of cells.
• the displacement of the time window for integrating the eye from a level 127 area to a level 128 area leads to integration on cells that are off for the duration of a frame, which results in the appearance of 'a dark outline of the area.
• the displacement of the time window for integrating the eye from a level 128 area to a level 127 area results in integration of cells lit for the duration of a frame, which results in the appearance of a clear outline of the area.
• Ttot m * (Tef + n * Tae) + Tmax remains fixed, which results in a decrease in the time Tmax (because Tef and Tae are incompressible durations) and therefore a maximum screen brightness decrease. It is possible to use up to 10 subscans while having the correct brightness. With 10 subscans, the maximum lighting time Tmax is currently 30% of the total time while the erasing and addressing time is around 70%.
• FIG. 2 represents an example of addressing using 10 sub-scans SB1 to SB10 in which the most significant are broken in half. In order to reduce important transitions and increase the number of sub-scans without reducing the screen brightness, one technique consists in simultaneously scanning two successive lines for certain lighting values.
• Ttot m (Tef + n * Tae) + m 2 * (Tef + n / 2 * Tae) + Tmax.
• the erasure time Tef being negligible compared to an * Tae, we have the equivalence Ttot ⁇ (m, + m ⁇ ) * (Tef + n * Tae) + Tmax.
• the sub-scans S1 and S2 corresponding to the lowest lighting times are carried out on two lines at the same time in order to obtain an overall addressing time for these two sub-scans which is equal to the addressing time of a single underscan. If we perform sub-scans common to two successive lines for the weights 1, 2, 4, and 8 of illumination, it is possible to obtain 12 sub-scans in order to suppress the transitions of weights 64. The problem of this solution is however the loss of resolution due to the simultaneous scanning of two lines.
• FIG. 4 illustrates a coding with rolling code using twelve sub-scans S1 to S12 with which the following lighting weights are associated: 1, 2, 4, 6, 10, 14, 18, 24, 32, 40, 48 and 56
• An effect of the rolling code is to soften the switching of most significant by reducing the number of weights switched during the switching of a most significant.
• a simultaneous scan of two lines is carried out for the weights 2, 6, 14 and 24.
• NG1 VS1 + VC
• NG2 VS2 + VC
• VS1 ⁇ * NG1
• a second limitation of such a coding method comes from the dispersion of the different codings for the same value.
• the coding variations no longer depend on each cell but on each pair of cells independently of the neighboring pair.
• the false contour phenomenon is greatly attenuated within the pair of cells, but the attenuation of the false contour is less with the neighboring pairs.
• EP-A-0 945 846 that in order to minimize this limitation, it is advisable to use the largest possible common part which has the effect of increasing the probability of error due to the limitation resulting from the deviation from the maximum value.
• the invention provides a new scanning technique aimed at improving the use of rolling code.
• the gray level coding method which is the subject of the invention achieves a coding which favors a choice from two possible codes depending on the gray levels associated with each cell.
• the two codes use equivalent criteria so that the disparity between the two codes is minimized.
• the highest gray level is coded as a priority over all of the sub-scans. If the coding on all of the sub-scans is not suitable, the lowest gray level is coded on the sub-scans common to the two cells of the pair. In both cases, priority is given to the sub-scans corresponding to the low light weight.
• Such a method performs different codings for the same value while keeping a close proximity between the different codes.
• E1 coding of the highest gray level NG1 over all of the sub-scans, favoring the sub-scans with the lowest lighting time;
• E2 extraction of the specific value VS1 corresponding to the coding of step E1;
• step E3 coding of the lowest gray level using the common value VC resulting from step E1 if the specific value VS1 extracted in step E2 is greater than the difference NG1 - NG2. In some cases, the following step is carried out:
• the common value VC is equal to the lowest gray level NG2
• the specific value VS1 is equal to the maximum value encodable on the first subscans.
• the value 1 is optionally added and / or subtracted from one or both of the gray levels NG1 and NG2 so that the difference NG1 - NG2, a multiple of five.
• the display durations associated with the first sub-scans correspond to the product of an elementary duration respectively by the factors: 5, 10, 20, 30, 40, 45, and in that the durations d display associated with the second subscans correspond to the product of the elementary duration by the factors respectively: 1, 2, 4, 7, 13, 17, 25, 36.
• a first coding circuit for coding the highest gray level NG1 over all of the sub-scans, favoring the sub-scans with the lowest lighting time
• a means for extracting a common value VC and a specific value VS1 leaving the first coding circuit a selection and calculation circuit for coding the lowest gray level using the common value VC leaving the first coding circuit if the specific value VS1 extracted from the first coding circuit is greater than the difference NG1 - NG2 .
• the other particularities of the process are also transposed on the device.
• FIGS. 1 to 4 represent temporal distributions of sub-scans during the display of an image according to the state of the art
• FIG. 5 represents the temporal distribution of sub-scans according to a preferred embodiment
• FIG. 6 represents a gray level coding algorithm according to the invention
• FIG. 7 represents a processing circuit implementing the coding algorithm according to the invention
• FIGS. 8 to 10 represent details of the circuit of FIG. 7
• FIG. 11 represents a plasma display screen implementing the invention.
• the temporal distribution of the sub-scans uses significant proportions which do not correspond to an exact linear scale.
• FIG. 5 represents a preferred time distribution for which an embodiment will be described.
• This time distribution includes first PSB sub-scans specific to each line which make it possible to address each cell of the screen individually.
• first PSB sub-scans with which the respective illumination weights 5, 10 20 30 40 and 45 are associated.
• Such a choice makes it possible to have a maximum difference value of 150 over 256 levels of gray.
• a statistical study on video images makes it possible to determine that the probability of error due to the maximum value of difference is much less than 5%.
• Second DSB subscans simultaneously address two adjacent lines.
• the method of coding the gray levels for each pair of cells will now be described using the algorithm of FIG. 6.
• the algorithm begins with two known gray levels NG1 and NG2 associated with a first and a second cell.
• a first step 101 the absolute value of the difference between NG1 and NG2 is calculated.
• is then rounded to five to minimize the error, the rounded difference being called D below.
• a second step 102 the values V1 and V2 corresponding to the levels NG1 and NG2 are calculated respectively. These values V1 and V2 are determined on the one hand as a function of the rounding performed on the difference
• the encoding carried out consists in carrying out on the one hand the coding of the value V1 on all of the sub-scans PSB and DSB by favoring the sub-scans corresponding to the low light weights and on the other hand by coding of the value V2 on the second DSB sub-scans by favoring the sub-scans corresponding to the low light weights.
• there is a 6-bit SPEMAX word which corresponds to the first PSB sub-scans used to code the value V1.
• the word SPEMAX is associated with the value corresponding to the sum of the weights of the first subscans activated in SPEMAX.
• COMMAX there is also an 8-bit COMMAX word which corresponds to the second DSB sub-scans used to code the value V1.
• the word COMMAX is associated with the value corresponding to the sum of the weights of the second subscans activated in COMMAX.
• COMMIN is associated with the value corresponding to the sum of the weights of the second subscans activated in COMMIN.
• the second test 106 checks whether the value which corresponds to SPEMAX is less than or not the difference D. If the value of SPEMAX is less than the difference D then a fifth step 107 is carried out, otherwise a sixth step 108 is carried out.
• the fourth to sixth steps 105, 107 and 108 are assignment steps which determine three words Si, Sj and COM.
• the word Si is a six-bit word which corresponds to the coding of the first PSB sub-scans for the cell having the highest gray level.
• the word Sj is a six-bit word which corresponds to the coding of the first sub-scans PSB for the cell having the lowest gray level.
• the word COM is an eight-bit word which corresponds to the coding of the second DSB sub-scans which are common to the two cells.
• the fourth step 105 assigns the word Si so that it corresponds to the realization of all the first sub-scans PSB, the word Sj so that it corresponds to the realization of none of the first sub-scans PSB, and the word COM so that it is identical to the word COMMIN.
• the fifth step 107 affects the word Si so that it corresponds to the realization of the first sub-scans PSB whose total illumination weight corresponds to the difference D.
• the fifth step 107 also affects the word Sj so that it corresponds to none of the first PSB sub-scans, and the word COM so that it is identical to the word COMMIN.
• the sixth step 108 assigns the word Si so that it is identical to the word SPEMMAX, and the word COM so that it is identical to the word COMMAX.
• the word Sj is defined to correspond to an illumination corresponding to the value of the word SPEMAX minus the difference D.
• a third test 109 is carried out to determine which gray level NG1 or NG2 is the highest in order to match in the seventh and eighth steps 110 and 111 the words Si and Sj to the words S1 and S2 which correspond to the first sub-scans PSB for the levels NG1 and NG2 respectively.
• the difference D is less than DMAX and D is less than SPEMAX, it is the sixth step 108 which is carried out, there will therefore be:
• SPEMMAX 5 + 10 + 20 + 30
• level 130 is coded on the twelve least significant sub-scans.
• level 130 is coded according to sixteen different codes, the distribution of the sub-scans remains grouped and homogeneous, which eliminates any false contour effect. In 22% of possible cases, one of the two most significant sub-scans is used to code the value 130. However, the different codings have homogeneous distributions on the eleven least significant sub-scans which minimize the effect of false outline.
• FIG. 7 shows an encoding device 200, according to the invention, used to code the gray levels in code control for the different PSB and DSB sub-scans.
• a plasma display panel may include one or more devices of this type depending on the calculation time required and the number of cells present on said panel.
• the encoding device 200 has first and second input buses, for example eight bits for receiving the gray levels NG1 and NG2 corresponding to two cells sharing the same second DSB sub-scans.
• the gray levels NG1 and NG2 can come from either an image memory containing the entire image, or from a decoding device which decodes a video signal and which translates it into gray level for each cell.
• the encoding device 200 has three output buses which supply the words COM, S1 and S2 which correspond respectively to ignition or non-ignition codes for the second DSB sub-scans, for the first PSB sub-scans. associated with the first gray level NG1 and for the first sub-scans associated with the second gray level NG2.
• the encoding device 200 comprises a difference circuit 201 which receives the two gray levels NG1 and NG2 to be encoded and provides on a first output the absolute value of the difference between NG1 and NG2. In addition, on a second output of said difference circuit 201, an information bit SelC indicates what is the gray level NG1 or NG2 which is to be considered as greater than the other.
• the difference circuit 201 is for example constituted as shown in FIG. 8.
• First and second subtraction circuits 301 and 302 receive the gray levels NG1 and NG2 on opposite inputs, so that the first subtraction circuit 301 provides on a result output the difference NG1 - NG2 and that the second subtraction circuit 302 provides the difference NG2 - NG1 on a result output.
• the second subtraction circuit also has an overflow output (also known as a carry output) which makes it possible to know whether the result of the subtraction is positive or negative and therefore provides the information bit SelC.
• a multiplexer 303 receives the SelC information bit on a selection input and has first and second inputs connected to the result outputs of the first and second subtraction circuits 301 and 302 respectively. The multiplexer 303 selects the positive result as a function of the information bit SelC so that the output of the multiplexer 303 corresponds to the output of the difference circuit 201.
• the encoding device 200 further comprises a first comparison circuit 202 which compares the absolute value of the difference
• the first comparison circuit 202 provides a first selection signal SelA which corresponds to the result of the first test 104.
• SelA a first selection signal
• a rounding circuit 203 receives the absolute value of the difference
• a first exit provides the difference rounding D and a second output provides a rounding control bus.
• the rounding control bus indicates how the values V1 and V2 should be changed.
• the rounding circuit 203 can be produced using a correspondence table of which a part of the output bits corresponds to the rounded difference D and another part of the output bits corresponds to a command code.
• a calculation circuit 204 receives the gray levels NG1 and NG2 and supplies the values V1 and V2 which will be used for coding.
• the calculation circuit 204 receives for this purpose the information bit SelC to make the highest level NG1 or NG2 correspond to the value V1 and the lowest level NG1 to the value V2.
• the calculation circuit 204 also receives the control bus coming from the rounding circuit 203 to carry out, if necessary, an addition or a subtraction of a unit on V1 and / or V2.
• a first coding circuit 205 receives the value V1 and provides complete coding of this value over all of the sub-scans PSB and DSB.
• a six-bit bus supports the word SPEMAX corresponding to the first PSB subscans and an eight-bit bus supports the word COMMAX corresponding to the second DSB subscans.
• a correspondence table is used which contains optimum coding.
• a second coding circuit 206 receives the value V2 and provides coding of this value on the second DSB sub-scans only.
• the output bus of this second coding circuit 206 supports the word COMMIN.
• This second coding circuit can also be carried out using a correspondence table. Those skilled in the art will note that only a limited number of different values are actually to be coded and that it is therefore not necessary to use a table having more than seven input bits.
• a second comparison circuit 207 receives on the one hand the rounded difference D and on the other hand the word SPEMAX. This second comparison circuit will compare the value associated with the word SPEMAX with the rounded difference D in order to provide on a first output a second selection signal SelB which corresponds to the result of the second test 106. The second comparison circuit also provides on a second output a six-bit word corresponding to the first sub-scans and having an associated illumination which corresponds either to the rounded difference D or to the illumination associated with SPEMAX from which the rounded difference D has been removed.
• An exemplary embodiment of the second comparison circuit 207 is shown in FIG. 9.
• the second comparison circuit 207 comprises a decoding circuit 401, a subtraction circuit 402, a multiplexer 403 and a coding circuit 404.
• the decoding circuit 401 is for example a correspondence table receiving the six bits of the word SPEMAX and providing an eight-bit word corresponding to the value representative of the illumination associated with the word SPEMAX.
• the subtraction circuit 402 has two inputs receiving respectively the rounded difference D and the word leaving the decoding circuit 401, so that it provides on its output the result of the difference corresponding to the value of SPEMAX minus D.
• the circuit 402 has an overflow or holdout output that indicates whether the result of the subtraction is positive or negative. Said overflow output thus provides the second selection signal SelB.
• the multiplexer 403 has two input buses receiving respectively D and the result leaving the subtraction circuit 402.
• a selection input of the multiplexer 403 receives the second selection signal so that the output bus of the multiplexer 403 provides D if D is greater than the value of SPEMAX or the result leaving the subtraction circuit 402 otherwise.
• the coding circuit is a correspondence table which has an input connected to the output of the multiplexer 403 to receive either D or SPEMAX - D, in order to provide a six-bit code corresponding to the coding of the input value using the first PSB subscans.
• the encoding device 200 comprises a selection circuit 208 which receives on the one hand the different words COMMIN, COMMAX, SPEMAX and the word leaving the second comparison circuit, and on the other hand the first and second selection signals SelA and SelB.
• Said selection circuit provides, on first and second outputs, first and second words Si and Sj of six bits corresponding to the codings of the first sub-scans for the two gray levels NG1 and NG2, and, on a third output, a third eight-bit COM word corresponding to the common coding of the second sub-scans for the two gray levels NG1 and NG2.
• the circuit 208 comprises a decoder 501 and three multiplexers 502 to 503.
• the decoder circuit 401 receives the first and second selection signals SelA and Sel B and provides the commands necessary for the three multiplexers 502 to 504 to carry out the connections defined in the fourth to sixth steps 105, 107 and 108.
• the multiplexer 502 has two inputs which receive the words COMMIN and COMMAX and one output which supplies the word COM.
• the word COM corresponds either to COMMIN when the first selection signal SelA indicates that D is greater than DMAX or when the second selection signal SelB indicates that the value of SPEMAX is less than D, or to COMMAX when the first and second signals indicate that D is not greater than DMAX and that the value of SPEMAX is not less than D.
• Multiplexer 503 has two inputs and one output.
• One of said inputs receives the six-bit word from the second comparison circuit 207
• the other of said inputs receives a six-bit word corresponding to the zero value encoded for the first subscans
• the output provides the word Sj.
• the word Sj corresponds either to the zero value coded on six bits when the first selection signal SelA indicates that D is greater than DMAX or when the second selection signal SelB indicates that the value of SPEMAX is less than D, or to the word leaving the second comparison circuit 207 COMMAX when the first and second signals SelA and SelB indicate that D is not greater than DMAX and that the value of SPEMAX is not less than D.
• Multiplexer 504 has first to third inputs and an output.
• the first input receives a word corresponding to DMAX, ie corresponding to the maximum possible illumination using the first PSB sub-scans.
• the second entry receives the word SPEMAX.
• the third input receives the outgoing word from the second comparison circuit 207.
• the output provides the word Si which corresponds either to the word corresponding to DMAX when the first signal SelA indicates that D is greater than DMAX, or to SPEMAX when the first and second signals SelA and SelB indicate that D is not greater than DMAX and that SPEMAX is not less than D, that is to say the word leaving the second comparison circuit when the signals SelA and SelB indicate that D is not greater than DMAX and that SPEMAX is less than D.
• the encoding device 200 comprises an output circuit 209 which receives the words Si and Sj to make them correspond either to the words S1 and S2 respectively, or to the words S2 and S1 respectively according to the information bit SelC.
• the encoding device 200 is then incorporated into a display panel 600 to allow the display of image 601, as shown in FIG. 11.
• Such an encoding device 200 can be produced according to different variants.
• a person skilled in the art considers that the computation time is too low, it is for example possible to adopt a structure of the pipeline type. To this end, it is possible, for example, to add storage registers 210 as indicated in FIG. 7 to perform the calculation in two stages, which allows an overall reduction in the calculation time for an image.
• correspondence tables are used to carry out the coding and decoding for reasons of simplicity of implementation and therefore of reliability. It goes without saying that these correspondence tables can be replaced by calculation circuits, in particular if it is chosen to implement such a device using circuits of the microcontroller type.
• one can for example use a coding for sixteen sub-scans comprising four first sub-scans whose respective weights are 5, 10, 20 and 35 and ten second sub-scans whose respective weights are 1, 2, 4, 6, 9, 12, 15, 19, 23, 27, 31 and 36, taking care to modify the different quantities (DMAX value, number of coding bits) which have been used in the description.

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• Control Of Indicators Other Than Cathode Ray Tubes (AREA)
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