JP2008209590A - Driving device of display panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving device of a display panel with which the optimization of white balance is highly accurately performed. <P>SOLUTION: The luminance level in each of first to Nth gradation is determined for each of light emission colors based on the number of times of application sustain pulses within each sustain period of a sub-field and the gradation luminance correspondence data showing the luminance level and each of the first to the Nth gradation while the luminance level is made to correspond to each other is created for each of the light emission colors. Then, on the basis of the gradation luminance correspondence data, the gradation corresponding to the luminance level for each of the light emission colors indicated by an input video signal is determined and the data for performing the driving of the gradation is created as the sub-field data to indicate in which state of lighting mode and light out mode the pixel is to be set for each of sub-fields. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display panel driving device that expresses luminance corresponding to an input video signal in N gradations by the number of times (period) of light emission of a pixel for each unit display period.

  At present, as a thin and large-screen display device, a plasma display device equipped with a plasma display panel (hereinafter referred to as PDP) in which discharge cells corresponding to pixels are arranged in a matrix has been commercialized. At this time, each discharge cell of the PDP has only two states, that is, a lighting state and a light-off state accompanying discharge. Therefore, in order to express halftone luminance according to the input video signal, the subfield method is employed to drive the gradation of display panels such as PDP and ELDP.

  In the subfield method, one field or one frame display period (unit display period) in an input video signal is divided into a plurality of subfields each assigned a light emission count corresponding to a luminance weight. In each subfield, the following address process and sustain process are performed. In the address process, each pixel of the display panel is set to one of a lighting mode and a light-off mode according to the input video signal. In the sustain process, a sustain pulse is applied to each pixel for the number of times corresponding to the luminance weight previously assigned to the subfield, so that only the pixel in the lighting mode state is applied each time the sustain pulse is applied. Discharge light emission. According to this driving method, the intermediate luminance corresponding to the total number of discharge light emission executed in each subfield is visually recognized within the unit display period.

  In addition, as a plasma display device that performs driving according to the subfield method as described above, a sustain to be applied within a unit display period in accordance with a luminance level represented by an input video signal in order to reduce power consumption. There is known one in which the total number of pulses is changed (see, for example, Patent Document 1). At this time, in such a plasma display device, in order to correct the white balance deviation caused by the change in the total number of sustain pulses as described above, the luminance level in the input video signal is changed according to the total number of sustain pulses. Each is adjusted individually.

However, since the total number of sustain pulses and visual luminance are not necessarily in a proportional relationship, such a white balance adjustment method cannot reliably correct the deviation.
Japanese Patent Laid-Open No. 2005-25058

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a display panel driving apparatus that can optimize white balance with high accuracy.

  The display panel driving apparatus according to claim 1 sets the display panel in which a plurality of pixels are formed to one of a lighting mode and a lighting mode according to subfield data based on an input video signal. Driving in a plurality of subfields including an address period to be performed and a sustain period in which a pixel in the lighting mode is caused to emit light by repeatedly applying a sustain pulse to each of the pixels. A display panel driving device that obtains intermediate brightness (N: integer greater than or equal to 2), wherein the first to Nth floors are based on the number of times the sustain pulse is applied within the sustain period of each of the subfields. A luminance level for each tone is obtained for each emission color of the pixel, and the luminance level is shown in association with each of the first to Nth gradations. A gradation luminance measuring means for generating response data for each emission color, and determining a gradation corresponding to the luminance level for each emission color indicated by the input video signal based on the gradation luminance correspondence data, Luminance gradation conversion means for generating data for carrying out driving corresponding to gradation as the subfield data.

  Based on the number of sustain pulses applied within the sustain period of each subfield, the luminance level in each of the first to Nth gradations is obtained for each emission color, and this luminance level and each of the first to Nth gradations are determined. Is generated for each emission color. Then, based on the gradation luminance correspondence data, a gradation corresponding to the luminance level for each emission color indicated by the input video signal is determined, and data for driving the gradation is determined for each subfield. It is generated as subfield data indicating whether the pixel is set to either the on or off mode.

  With this configuration, white balance is optimized based on the luminance level for each gradation estimated from the subfield structure, so white balance is optimized accurately for all the gradations that can be expressed. Will be made.

  FIG. 1 is a diagram showing a configuration of a plasma display apparatus including a driving apparatus according to the present invention.

In FIG. 1, a PDP 10 as a plasma display panel includes a front transparent substrate and a rear substrate (not shown) disposed to face each other with a discharge space in which a discharge gas is sealed. On the front transparent substrate, row electrodes X _{1 to} X _n and row electrodes Y _{1 to} Y _n are formed so as to extend in the horizontal direction (horizontal direction) of the two-dimensional screen. These row electrodes X ₁ to X _n and row electrodes Y ₁ to Y _n, respectively a pair of row electrodes X _i and Y _i: by (i 1 to n), plays a first to n-th display line in the PDP10 Yes. On the back substrate, the column electrodes D are arranged to extend in the vertical direction of the two-dimensional display screen so as to cross the row electrodes X _{1 to} X _n and the row electrodes Y _{1 to} Y _n, respectively. ₁ to D _m are formed. A discharge cell (display cell) P as a pixel is formed at the intersection of each row electrode pair (X, Y) and the column electrode D including the discharge space. That is, the PDP 10 includes (n × m) discharge cells including discharge cells P _{(1,1) in the} first row / first column to discharge cells P _{(n, m) in} the n-th row / m-th column. P is arranged in a matrix.

Of the discharge cells P _{(1,1) to} P _{(n, m)} , the discharge cells belonging to the (3t-2) _-th column (t: an integer from _{1 to m} / 3), that is, the first column, A phosphor that emits red light is formed in the discharge cells P belonging to the fourth, seventh,..., (M−2) -th columns, and emits red display light along with the discharge. In addition, among the discharge cells P _{(1,1) to} P _{(n, m)} , the discharge cells belonging to the (3t-1) th column (t: an integer of 1 to _m / 3), that is, the second column, A phosphor that emits green light is formed in the discharge cells P belonging to the fifth, eighth,..., (M−1) th columns, and emits green display light along with the discharge. In addition, among the discharge cells P _{(1,1) to} P _{(n, m)} , the discharge cells belonging to the (3t) column (t: an integer of _{1 to m} / 3), that is, the third column, the sixth column A phosphor that emits blue light is formed in the discharge cells P belonging to the column, the ninth column,..., The m-th column, and emits blue display light with discharge.

  The A / D converter 1 converts the input video signal into pixel data PD representing the luminance level of, for example, 10 bits for each pixel (discharge cell P) and supplies it to the frame memory 2. The frame memory 2 sequentially writes each of the pixel data PD corresponding to each pixel, reads each of the pixel data PD in the written order, and supplies it to the SF (subfield) data generation circuit 3.

  The SF data generation circuit 3 performs multi-gradation processing including error diffusion processing and dither processing on the pixel data PD sequentially read from the frame memory 2. Further, the SF data generation circuit 3 puts the pixel data PD subjected to the multi-gradation processing into a state in which the discharge cell P is turned on or off in each subfield in one frame display period. It is converted into SF (subfield) data GD indicating whether to set, and supplied to the SF memory 4. At this time, the SF data generation circuit 3 converts the pixel data PD into the SF data GD by a conversion process (described later) according to the SF construction data SFPD supplied from the SF (subfield) construction circuit 11.

  The SF memory 4 sequentially writes each SF data GD for each pixel, and in each subfield SF1 to SF14 in one frame display period as shown in FIG. Perform a read. That is, each written SF data GD for one frame is read, and when each SF data GD indicates that the discharge cell P is set to the extinguishing mode in the subfield, the logic level 1 is set to the lighting mode. In this case, the address data bit DB of logic level 0 is supplied to the address driver 6.

  The SF construction circuit 11 generates various parameter data for constructing the light emission drive sequence as shown in FIG. 2 according to the average luminance level of the image for each frame represented by the input video signal. In this light emission driving sequence, one frame display period is divided into 14 subfields SF1 to SF14, the address process W and the sustain process I are executed in each subfield, and only the first subfield SF1 is changed to the address process W. Prior to this, the reset process R is executed. The SF construction circuit 11 assigns the sustain pulse application times a1 to a14 corresponding to the luminance weights of the subfields to the sustain process I of each of the subfields SF1 to SF14 as follows. That is, first, the SF construction circuit 11 determines the total number of sustain pulses (described later) to be applied within one frame display period in accordance with the average luminance level of the image for each frame represented by the input video signal. To do. At this time, the SF construction circuit 11 reduces the total number of sustain pulses to be applied within one frame display period when the average luminance level is high, compared to when the average luminance level is low, in order to suppress an increase in power consumption. Next, the SF construction circuit 11 distributes the total number of the sustain pulses to each of the subfields SF1 to SF14 with the luminance weight of each subfield, and applies the number of sustain pulses corresponding to each of the subfields SF1 to SF14. It calculates | requires as a1-a14. Further, the SF construction circuit 11 has the address execution period information TW1 to TW14 indicating the period to be spent in the address process W for each of the subfields SF1 to SF14, and the sustain pulse to be applied in the sustain process I peaks from 0 volts. Suspension start period information TS1 to TS14 indicating the period until reaching the level is generated.

  Then, the SF construction circuit 11 shows the sustain pulse application times a1 to a14, the address execution period information TW1 to TW14, and the suspension start period information TS1 to TS14 as shown in FIG. 3 obtained for each subfield SF. The SF construction data SFPD is supplied to the SF data generation circuit 3 and the drive control circuit 20.

  The drive control circuit 20 outputs various control signals for driving the PDP 10 according to the light emission drive sequence as shown in FIG. 2 constructed based on the SF construction data SFPD, that is, the panel driver, that is, the address driver 6, X electrode driver 7 and Y The electrode driver 8 is supplied. The panel driver generates drive pulses according to various control signals supplied from the drive control circuit 20 and supplies them to the column electrodes D and the row electrodes X and Y of the PDP 10.

First, in the reset step R of the leading subfield SF1, with X electrode driver 7 applies a reset pulse RP _X of negative polarity as shown in FIG. 4 to all the row electrodes _X 1 to X _n, Y electrode driver 8 but it applied to all the row electrodes _Y 1 to Y _n to the reset pulse RP _Y of positive polarity as shown in FIG. In response to the application of these reset pulses, reset discharge is generated in all the discharge cells P, and a predetermined amount of wall charges are formed in all the discharge cells P. Thereby, all the discharge cells P are initialized to the state of lighting mode.

Next, in the address process W of each of the subfields SF1 to SF14, the address driver 6 generates a pixel data pulse having a pulse voltage corresponding to the logical level of the address data bit DB supplied from the SF memory 4. For example, the address driver 6 generates a pixel data pulse of a high voltage when the address data bit DB is at logic level 1 and a low voltage when the address data bit DB is at logic level 0. The address driver 6 applies such pixel data pulses to the column electrodes D _{1 to} D _m as a pixel data pulse group DP for each display line (m). Further, in the address process W, the Y electrode driver 8 sequentially applies the negative scan pulse SP to the row electrodes Y ₁ to Y _n at the same timing as the application timing of each pixel data pulse group DP. At this time, the discharge selectively occurs only in the discharge cell P at the intersection of the row electrode to which the scan pulse is applied and the column electrode to which the high-voltage pixel data pulse is applied, and remains in the discharge cell P. The wall charge that has been erased is erased, and the discharge cell P that has lost this wall charge is set to the extinguishing mode. On the other hand, the discharge cell P in which such a discharge has not occurred maintains the state (lighting mode or extinguishing mode state) up to that point.

  The address driver 6 and the Y electrode driver 8 finish the address operation for all the discharge cells P within the address execution period information TW indicated by the SF construction data SFPD in the address process W of each of the subfields SF1 to SF14. In this manner, the pulse widths of the scanning pulse SP and the pixel data pulse are set.

  Next, in the sustain process I of each of the subfields SF1 to SF14, the X electrode driver 7 and the Y electrode driver 8 apply the sustain pulse IP as shown in FIG. 4 to the number of times of application a indicated by the SF construction data SFPD. Is repeatedly applied to the row electrodes X and Y alternately. At this time, the X electrode driver 7 and the Y electrode driver 8 generate a sustain pulse IP having a rising period BT indicated by the sustain rising period information TS in the SF construction data SFPD for each subfield. Only the discharge cell P in which the wall charges remain due to the application of the sustain pulse IP, that is, the discharge cell P in the lighting mode, is subjected to the sustain discharge every time the sustain pulse IP is applied. The light emission state associated with the sustain discharge is maintained.

  Here, according to the light emission drive sequence shown in FIG. 2, the opportunity to change the discharge cell P from the extinguishing mode state to the lighting mode state is only the reset process R of the first subfield SF1. Therefore, once the discharge cell P is set to the extinguishing mode in the address process W of one subfield of each of the subfields SF1 to SF14, the discharge is continued until the last subfield SF14 thereafter. The cell is held in the extinguished mode state.

That is, according to the light emission drive sequence shown in FIG. 2, the sustain of each successive subfield existing between the first subfield SF1 and the subfield where the discharge cell P is to be switched to the extinguishing mode is surely obtained. In step I, a sustain discharge is generated. Therefore, within one frame display period,
1st gradation: pattern without any sustain discharge,
Second gradation: a pattern in which sustain discharge is performed only with SF1,
Third gradation: pattern in which sustain discharge is performed in SF1 and SF2,
Fourth gradation: pattern in which sustain discharge is performed in SF1 to SF3,
5th gradation: pattern in which sustain discharge is performed in SF1 to SF4,
・
・
・
15th gradation: a pattern in which sustain discharge is performed in SF1 to SF14,
The light emission driving of each discharge cell P is performed in the following 15 patterns.

  At this time, the luminance corresponding to the total number of sustain discharges generated within one frame display period is visually recognized. Therefore, according to the driving corresponding to each of the first to fifteenth gradations as described above, the luminance is 0 to the highest. The luminance range up to the luminance can be expressed by the intermediate luminance of 15 levels.

  Next, the white balance optimization operation in the plasma display device shown in FIG. 1 will be described.

  Such white balance optimization is performed in the process of conversion from the pixel data PD to the SF data GD in the SF data generation circuit 3, and is performed for each frame in the input video signal.

  FIG. 5 is a diagram showing an internal configuration of the SF data generation circuit 3.

  As shown in FIG. 5, the SF data generation circuit 3 includes a gradation luminance measurement circuit 31, a luminance linearity calculation circuit 32, a 2.2 power calculation circuit 33, a luminance gradation conversion circuit 34, and a dither processing circuit 35.

  As shown in FIG. 6, the gradation luminance measurement circuit 31 shows the correspondence between the number of sustain pulses applied and the luminance level of display light for each emission color (red, green, blue) emitted from the discharge cell P. A luminance conversion arithmetic processing unit (not shown) is provided that performs arithmetic processing based on actual measurement values.

  Further, as shown in FIG. 7, the gradation luminance measurement circuit 31 has preliminarily stored electron density return rate characteristic data indicating the electron density return rate corresponding to the address execution period length for each emission color (red, green, blue). It is remembered. That is, according to the phosphor characteristics in the discharge cell P, when the sustain discharge is continuously generated, the electron density in the ground state gradually increases, and the density of the electrons excited with each sustain discharge is correspondingly increased. Therefore, the emission luminance due to one sustain discharge gradually decreases. As a result, as shown in FIG. 6, as the number of sustain pulses applied increases, the visible luminance increases, but the increase rate of the luminance decreases. However, an address process W is provided between the sustain processes I of the adjacent subfields SF as shown in FIG. 2, and the sustain discharge is stopped during the execution period of the address process W. Therefore, the density of electrons in the ground state decreases by the amount of the stop period (address execution period). Thereby, at the start of the next sustain step I, the density of electrons excited along with the sustain discharge is increased again, and the light emission luminance associated with each sustain discharge is increased. In other words, the emission brightness of each sustain discharge, which has decreased due to the continuous occurrence of the sustain discharge, transitions to the lowest state in the initial state, that is, the ground state, during the address execution period. The brightness increases and the original state is restored again. The gradation luminance measuring circuit 31 has an electron density indicating the correspondence between the address execution period length and the electron density return rate to the initial state for each emission color (red, green, blue) in the discharge cell P. The return rate characteristic data is stored in advance.

  The gradation luminance measurement circuit 31 is based on the SF construction data SFPD, the correspondence between the number of sustain pulses applied and the luminance level of display light as shown in FIG. 6, and the electron density recovery rate characteristic data as shown in FIG. The luminance level that will be expressed by each of the first to fifteenth gradations is obtained for each emission color.

  Hereinafter, the gradation luminance measurement operation of the gradation luminance measurement circuit 31 will be described by extracting the operation at the time of measuring the gradation luminance in each of the first to fourth gradations in the red light emitting discharge cell P.

The sustain pulse application times a1 to a3 in each of the subfields SF1 to SF3 indicated by the SF construction data SFPD are as follows:
a1: 8
a2: 12
a3: 20
And

Further, according to the electron density return rate characteristic data as shown in FIG. 7, the electron density return rates corresponding to the address execution periods TW2 and TW3 respectively in the subfields SF2 and SF3 indicated by the SF construction data SFPD are respectively obtained.
TW2: 0.5
TW3: 0.2
Suppose that

  First, the gradation luminance measurement circuit 31 extracts a section corresponding to the subfield SF1 from the sustain luminance characteristic curve (shown by a solid line) shown in FIG. That is, since sustain discharge is performed 8 times in the sustain process I of the subfield SF1, the gradation luminance measurement circuit 31 determines the number of times of sustain pulse application “0” to “8” from the sustain luminance characteristic curve of FIG. A sustain luminance characteristic section V1 corresponding to is extracted, and this is used as sustain luminance characteristic curve data corresponding to SF1 as shown in FIG.

  Next, the gradation luminance measurement circuit 31 extracts a section corresponding to the subfield SF2 from the sustain luminance characteristic curve of FIG. In the sustain process I of the subfield SF2, 12 sustain discharges are performed. However, when the sustain discharge is generated in the sustain process I of SF2, the sustain discharge for 8 times is always generated in the sustain process I of the subfield SF1 with the address process W just before that. Therefore, the gradation luminance measurement circuit 31 considers the visual luminance associated with the eighth sustain discharge generated in the sustain process I of SF1 and the electron density return rate based on the address execution period TW2 in the address process W. The following processing is performed. That is, the gradation luminance measurement circuit 31 uses the multiplication result “4” obtained by multiplying the sustain pulse application count “8” of SF1 by the electron density return rate “0.5” in the address execution period TW2 as the initial value in SF2. Use a delimiter value. Further, “11” obtained by subtracting “1” from the number of sustain pulses applied in SF2 is added to the initial delimiter value “4”, and the addition result “15” is used as the final delimiter value in SF2. Then, the gradation luminance measuring circuit 31 has a sustain luminance characteristic section V2 corresponding to the number of sustain pulse application from “4” (initial delimiter value) to “15” (final delimiter value) from the sustain luminance characteristic curve of FIG. Are extracted and connected to a sustain luminance characteristic curve corresponding to SF1 as shown in FIG. Thereby, sustain luminance characteristic curve data corresponding to SF2 as shown in FIG. 8B is obtained.

  Next, the gradation luminance measuring circuit 31 extracts a section corresponding to the subfield SF3 from the sustain luminance characteristic curve of FIG. In the sustain process I of the subfield SF3, 20 sustain discharges are performed. However, when a sustain discharge is generated in the sustain process I of SF3, a total of 20 sustain discharges are always generated in the subfields SF1 and SF2 with respect to the address process W immediately before that. Therefore, the gradation luminance measurement circuit 31 calculates the visual luminance associated with the 20th sustain discharge generated through the subfields SF1 and SF2 and the electron density return rate based on the address execution period TW3 in the address process W of SF3. The following processing in consideration is performed. That is, the gradation luminance measurement circuit 31 multiplies the result “4” obtained by multiplying the total number of sustain pulses applied “20” in SF1 and SF2 by the electron density return rate “0.2” in the address execution period TW3. Is the initial separation value in SF3. Further, “19” obtained by subtracting “1” from the number of sustain pulses applied in SF3 is added to the initial delimiter value “4”, and the addition result “23” is used as the final delimiter value in SF3. Then, the gradation luminance measurement circuit 31 has a sustain luminance characteristic section V3 corresponding to the number of sustain pulse applications from “4” (initial delimiter value) to “23” (final delimiter value) from the sustain luminance characteristic curve of FIG. Is connected to a sustain luminance characteristic curve corresponding to SF2 as shown in FIG. 8B, so that sustain luminance characteristic curve data corresponding to SF3 as shown in FIG. 8C is obtained. Thus, the longer the address execution period, the smaller the electron density recovery rate, and the emission luminance associated with one sustain discharge approaches the initial state (the emission luminance in the lowest ground state electron density). is there. Therefore, as shown in FIG. 8C, the sustain luminance characteristic curve in each of the subfields SF has a convex shape in which the luminance increase rate is initially high and the luminance is increased while gradually decreasing. It becomes.

  That is, as shown in FIG. 6, the gradation luminance measuring circuit 31 indicates the luminance level for each emission color (red, green, blue) radiated from the discharge cell P with respect to the number of times the sustain pulse is applied. It is adjusted according to the electron density return rate according to the address execution period length.

  Next, the gradation luminance measuring circuit 31 determines the luminance at the boundaries of SF1 to SF3 as shown in FIG. 8C, based on the suspension start periods TS1 to TS3 for each subfield indicated by the SF construction data SFPD. The division values Q1 to Q3 (indicated by white circles) are level shifted. That is, since the emission luminance associated with the sustain discharge decreases as the sustain pulse rise period increases, the gradation luminance measurement circuit 31 decreases the luminance partition value Q corresponding to the TS as the sustain rise period TS increases. It is. For example, the gradation luminance measurement circuit 31 multiplies the luminance division value Q1 by a coefficient “1” when the rising period TS1 of the sustain pulse is less than a predetermined period, and is larger than 0 when it is equal to or longer than the predetermined period. And the luminance division value Q1 is multiplied by a coefficient less than 1. Note that, instead of shifting the level of each luminance division value Q, the gradation luminance measurement circuit 31 changes the position of the luminance division value Q, that is, the number of times the corresponding sustain pulse is applied, according to the rising period of the sustain pulse. You may do it. For example, when the sustain pulse rising period indicated by the sustain rising period TS1 is equal to or longer than a predetermined period, the sustain pulse application count “8” of SF1 is multiplied by the coefficient, and the sustain pulse indicated by the multiplication result is obtained. The position on the sustain luminance characteristic curve corresponding to the number of pulse applications is set as a new luminance division value Q1.

  The gradation luminance measuring circuit 31 obtains the luminance division values Q4 to Q14 at the boundaries of SF4 to SF14 by similarly executing the above processing for the subfields SF1 to SF3 for each of SF4 to SF14. . At this time, each of the luminance separation values Q1 to Q14 is a luminance value in each of the second to fifteenth gradations. The gradation luminance measurement circuit 31 obtains luminance values corresponding to the second to fifteenth gradations for the respective emission colors of red, green, and blue.

For example, as shown by white circles in FIG. 9, the gradation luminance measurement circuit 31 has luminance values K1 _{R to} K14 _R corresponding to the second to fifteenth gradations in red light emission and second to second luminances in green light emission. Luminance values K1 _{G to} K14 _G corresponding to the fifteenth gradations and luminance values K1 _{B to} K14 _B corresponding to the second to fifteenth gradations for blue light emission are obtained.

Further, the gradation luminance measuring circuit 31 emits the luminance value for each dither step when the adjacent gradations are separated by, for example, two dither steps based on the luminance values K1 _{G to} K14 _G to emit green light. A corresponding dither luminance value (indicated by a white square mark in FIG. 9) is obtained. Further, the gradation luminance measurement circuit 31 emits the luminance value for each dither step when the adjacent gradations are separated by, for example, two dither steps based on the luminance values K1 _{R to} K14 _R to emit red light. A corresponding dither luminance value (indicated by white triangles in FIG. 9) is obtained. Further, the gradation luminance measurement circuit 31 corresponds to the blue light emission with the luminance value at each dither step when the adjacent gradations are divided by two dither steps based on the luminance values K1 _{B to} K14 _B. The obtained dither luminance value (indicated by a black square mark in FIG. 9) is obtained.

Then, as shown in FIG. 9, the gradation luminance measuring circuit 31 has gradation values K1 _{R to} K14 _R corresponding to red light emission (indicated by white circles) and dither luminance values (white triangles) indicating the luminance values. It provides a corresponding data KY _R in luminance linearity arithmetic circuit 32. Further, as shown in FIG. 9, the gradation luminance measuring circuit 31 has gradation values corresponding to the luminance values K1 _{G to} K14 _G corresponding to green light emission and dither luminance values (white square marks) corresponding to the luminance values KY _G , blue light emission. supplies grayscale luminance corresponding data KY _B indicating brightness value _{K1 B ~K14} B and dither luminance value (black squares) corresponding to the luminance linearity arithmetic circuit 32.

  As shown in FIG. 9, the luminance linearity calculation circuit 32 has luminance values for each color corresponding to lightness (0 to 100%) in white display (red: indicated by a solid line, green: indicated by a wavy line, blue: one point White balance data indicating (indicated by a chain line) is stored in advance.

In FIG. 9, 100% of the white brightness represents the maximum brightness white that can be represented by the pixel data PD. In FIG. 9, the luminance value of red light emission when displaying white brightness of 100% is the maximum luminance value MX _R , the luminance value of green light emission is the maximum luminance value MX _G , and the luminance value of blue light emission is the maximum luminance value MX. This is indicated by _B.

Here, according to the gradation luminance correspondence data KY _R , KY _G , and KY _B as shown in FIG. 9, even if the driving corresponding to the fifteenth gradation which is the maximum luminance gradation is executed, the expressed luminance The value does not reach the luminance value (MX _R , MX _G , MX _B ) at white brightness of 100%.

Therefore, in order to be able to express luminance values (MX _R , MX _G , MX _B ) with white brightness of 100%, the luminance linearity calculation circuit 32 applies to the gradation luminance correspondence data KY _R , KY _G, and KY _B, respectively. The following normalization process is performed.

First, the luminance linearity calculation circuit 32 divides the value obtained by dividing the maximum luminance value MX _G by the luminance value K14 _G by the luminance division value G1 and the value obtained by dividing the maximum luminance value MX _R by the luminance value K14 _R as follows. value G2, the maximum luminance value MX _B luminance values K14 luminance division value the division value in _B G3, respectively as determined.

G1 = MX _G / K14 _G
G2 = MX _R / K14 _R
G3 = MX _B / K14 _B
Next, the luminance linearity calculation circuit 32 sets the largest value among the luminance division values G1 to G3 as the gain value S. In the embodiment shown in FIG. 9, since the largest value among the luminance division values G1 to G3 is the luminance division value G2, this is set as the gain value S.

Next, the luminance linearity calculation circuit 32 obtains the gain value for each luminance value K and dither luminance value indicated by the gradation luminance correspondence data KY for each of the gradation luminance correspondence data KY _R , KY _G and KY _B. by multiplying the S, following such grayscale luminance corresponding data _RA R, to generate the RA _G and RA _B. That is, the luminance linearity arithmetic circuit 32, by multiplying the gain value S luminance value K1 _R ~K14 _R and dither luminance value indicated by the gray-scale luminance corresponding data KY _R in each (open triangle in FIG. 9) Accordingly, it generates grayscale luminance corresponding data RA _R indicating normalized luminance values _{SK1 R ~SK14} R and dither luminance value as shown in FIG. 10 (white triangles in FIG. 10). The luminance linearity arithmetic circuit 32, by multiplying the gain value S luminance value K1 _G ~K14 _G and dither luminance value indicated by the gray-scale luminance corresponding data KY _G each (open square in Fig. 9) Accordingly, it generates grayscale luminance corresponding data RA _G showing normalized luminance values _{SK1 G ~SK14} G and dither luminance value as shown in FIG. 10 (white square marks in Fig. 10). The luminance linearity arithmetic circuit 32, by multiplying the gain value S in each (black square marks in FIG. 9) grayscale luminance corresponding data KY luminance value K1 _B ～K14 _B and dither luminance value indicated by _B Thus, the gradation luminance correspondence data RA _B indicating the normalized luminance values SK1 _{B to} SK14 _B and the dither luminance values (black square marks in FIG. 10) as shown in FIG. 10 is generated.

That is, in this normalization process, the luminance value at the maximum gradation (fifteenth gradation) in the discharge cell P responsible for red emission is the luminance value (MX _R) of red emission in the case of displaying white brightness 100%. to match the), obtaining a gradation luminance corresponding data RA _R as shown in FIG. 10 overall to level shifting each value indicated by the gray-scale luminance corresponding data KY _R. In this case, the gain value S at the time of performing such level shifts, the maximum gradation represented luminance values of the red light emission in the case of performing display of the white brightness 100% (MX _R) at the gradation luminance corresponding data KY _R It is determined by the value (G2) divided by the luminance value (K14 _R ) at (15th gradation). Then, similarly for gradation brightness corresponding data KY _G and KY _B, performs a level shift of each value in the gain value S, the gradation luminance corresponding data RA _G and RA _B as shown in FIG. 10 Get each one.

According to the normalization process, as shown in FIG. 10, the normalized luminance values SK14 _G at the 15 gradation in the gradation brightness corresponding data RA _G, the green emission in the case of performing display of the white brightness 100% It becomes larger than the maximum luminance value MX _G of. Further, as shown in FIG. 10, the normalized luminance values SK14 _R at the 15 gradation in the gradation brightness corresponding data RA _R is the maximum luminance value MX _R emitting red light in the case of performing display of the white brightness 100% Is the same as Further, as shown in FIG. 10, the normalized luminance value SK14 _B at the 15th gradation in the gradation luminance correspondence data RA _B is the maximum luminance value MX _B of blue light emission when displaying with white brightness 100%. Will be greater than.

Therefore, the corresponding gradation luminance obtained by the above-described normalization processing data _{RA R,} RA G, the RA _B, can be displayed in white brightness of 100%.

Next, the luminance linearity arithmetic circuit 32, these gray-scale luminance corresponding data _RA R, RA _G, and supplies the RA _B to a luminance gradation conversion circuit 34.

The 2.2 power calculation circuit 33 multiplies the luminance level (10 bits) for each pixel indicated by the pixel data PD read out from the frame memory 2 to the power of 2.2, and outputs the calculation result for each emission color, that is, red (R). , Pixel data PPD _R , PPD _G and PPD _B represented by 16 bits for each of green (G) and blue (B) are supplied to the luminance gradation conversion circuit 34. That is, the 2.2 power operation circuit 33 performs inverse γ correction on the pixel data PD.

The operations of the gradation luminance measurement circuit 31 and the luminance linearity calculation circuit 32 as described above are performed for each frame during a blanking period as shown in FIG. Therefore, it is of such a blanking grayscale luminance corresponding data RA is generated in the period _R, each RA _G and RA _B is taken into luminance gradation conversion circuit 34.

Luminance gradation conversion circuit 34, as shown in FIG. 10, the grayscale luminance corresponding data RA R indicating the gradation and the luminance value corresponding to the gray scale for each emission _color, based on the RA _G and RA _B, the pixel data _PPD R, the luminance value indicated by the PPD _G and PPD _B respectively, and converts the gradation shows a gray level corresponding to the luminance value data _RPD R, the RPD _G and RPD _B. For example, the luminance gradation conversion circuit 34, when the luminance value indicated by the pixel data PPD _R corresponding to red are Y _R shown in FIG. 10, based on the grayscale luminance corresponding data RA _R corresponding to red, obtaining gradation data RPD _R representing the 11th gray level corresponding to the luminance value _{Y R.} Also, the luminance gradation conversion circuit 34, when the luminance value indicated by the pixel data PPD _G corresponding to green is Y _G shown in FIG. 10, based on the grayscale luminance corresponding data RA _G corresponding to green, obtaining gradation data RPD _G representing the 12th gray level corresponding to the luminance value _{Y G.} Further, when the luminance value indicated by the pixel data PPD _B corresponding to blue is Y _B shown in FIG. 10, the luminance gradation conversion circuit 34, based on the gradation luminance corresponding data RA _B corresponding to blue, obtaining gradation data RPD _B representing the 12th gray level corresponding to the luminance value _{Y B.}

The luminance gradation conversion circuit 34 supplies the gradation data RPD _R , RPD _G , RPD _B to the dither processing circuit 35.

The dither processing circuit 35 performs the following dither processing on each of the gradation data RPD _R , RPD _G , and RPD _B.

That is, first, the dither processing circuit 35 has different dither values for the gradation data RPD _R , RPD _G , RPD _B corresponding to each pixel position in the pixel block for each pixel block of 2 rows × 2 columns. Assign and add. For example, the dither processing circuit 35 adds different first to fourth dither values to the gradation data RPD _R , RPD _G , RPD _B corresponding to the pixel position. Then, the dither processing circuit 35 extracts only the upper bit group of each addition result, and supplies this to the SF memory 4 as SF data GD corresponding to each pixel.

  As described above, the SF data generation circuit 3 first obtains the luminance level for each gradation in the discharge cell according to the number of times of sustain pulse application in each sustain process of each subfield. At this time, the electron density recovery rate of each discharge cell according to the address execution period length in the address process existing between the sustain processes of the adjacent subfields, and the sustain pulse rising period are considered. As shown in FIG. 9, a luminance value for each gradation is obtained for each emission color (red, green, blue). Next, the luminance value at the gradation expressing the maximum luminance is used as a reference point for normalization, and the luminance value for each gradation is level-shifted for each emission color (red, green, blue) as shown in FIG. The data is obtained as gradation luminance correspondence data (RA). Then, based on the correspondence relationship between the luminance represented by the gradation luminance correspondence data and each gradation, a gradation that can express the luminance based on each pixel data is determined, and light emission driving corresponding to the gradation is performed. The power SF data is generated.

  Therefore, according to the SF data conversion process, the white balance based on the luminance level for each gradation estimated from the subfield structure (address execution period for each subfield, number of sustain pulse applications, sustain pulse rising period). Is optimized. Therefore, regardless of the structure of the light emission drive sequence, white balance can be optimized with high accuracy for all the gradations that can be expressed.

In the normalization process in the luminance linearity calculation circuit 32, the grayscale luminance correspondence data KY _R , KY _G and KY _B are level-shifted to the maximum value among the luminance division values G1 to G3 as shown in FIG. However, the gain value S may be set to a value larger than the luminance division values G1 to G3. In short, all of the luminance values (K14 _R , K14 _G , K14 _B ) at the maximum gradation (fifteenth gradation) for each emission color are the maximum luminance values (MX _R , MX _G , If the grayscale luminance correspondence data KY _R , KY _G and KY _B are level-shifted by a gain value S that is larger than MX _B ), a luminance display with white brightness of 100% that can be expressed by the pixel data is obtained. It becomes possible. However, when the luminance value (K14) at the maximum gradation (fifteenth gradation) is larger than the maximum luminance value (MX) at the whiteness of 100%, the luminance from the luminance value 0 to the maximum luminance value (MX). The number of gradations assigned to the range is reduced. For example, as shown in FIG. 10, since the maximum luminance value MX _G in green light emission is larger than the luminance value (K14 _G ) in the 15th gradation, this maximum luminance value MX _G is the 13th gradation. In the case where the luminance value (K12 _G ) is reached, the driving at each of the 14th gradation and the 15th gradation is substantially not performed. That is, in green light emission, the number of gradations assigned to the luminance range of the luminance value 0 to the maximum luminance value MX _G is 13 (first to 13th gradations), which is originally the assignable gradation number of 15 Less than (first to fifteenth gradation).

  However, as shown in FIG. 9 and FIG. 10, if the maximum value among the luminance division values G1 to G3 is the gain value S, the luminance value for at least one of the emission colors is used. All gradations (first to fifteenth gradations) can be assigned to the luminance range of 0 to the maximum luminance value (MX).

In addition, the luminance linearity calculation circuit 32 has a luminance value (K14 _R , K14 _R , _G ) at the maximum gradation (fifteenth gradation) for each emission color indicated by gradation luminance correspondence data (KY _R , KY _G , KY _B ) When all of K14 _G and K14 _B ) are larger than the maximum luminance values MX _R , MX _G , and MX _B corresponding to the respective colors, the normalization process as described above is unnecessary. Thus, this time, the luminance linearity arithmetic circuit 32, the gradation luminance corresponding data _{KY R,} KY G, the KY _B respectively, as the gradation luminance corresponding data _{RA R,} RA G, the luminance gradation conversion circuit 34 as RA _B Supply.

Note that the luminance linearity calculation circuit 32 has luminance values (K14 _R , K14 _R , _G ) at the maximum gradation (fifteenth gradation) for each emission color indicated by gradation luminance correspondence data (KY _R , KY _G , KY _B ). When all of K14 _G and K14 _B ) are smaller than the maximum luminance values MX _R , MX _G , and MX _B corresponding to the respective colors, normalization processing as described below may be performed.

That is, the luminance linearity arithmetic circuit 32, at a gain value corresponding to the smallest becomes the value within the luminance division value G1~G3 as shown in FIG. 9 S (S <1), the gradation luminance corresponding data _KY R, KY _G, and KY _B each gradation brightness by shifting the level of the respective luminance values indicated by the corresponding data _RA R, to generate the RA _G, and RA _B. As a result, as shown in FIG. 10, the luminance value (SK14) at the maximum gradation (fifteenth gradation) indicated by the gradation luminance correspondence data RA corresponding to one of the emission colors (red). ) Is equal to the maximum luminance value MX corresponding to the color. On the other hand, the luminance value (SK14) at the maximum gradation (fifteenth gradation) indicated by the gradation luminance correspondence data RA corresponding to other emission colors (green, blue) is the maximum luminance value corresponding to that color. Greater than MX.

Further, the gradation luminance measurement circuit 31 considers luminance saturation characteristics for each color based on the number of sustain pulses applied for each subfield, thereby indicating luminance gradation correspondence data KY _R indicating the luminance value for each gradation. , KY _G , KY _B are generated, but luminance gradation correspondence data KY _R , KY _G , KY _B may be generated by the following method.

That is, the gradation luminance measurement circuit 31 first displays a one-frame display period of a sustain pulse applied in the subfield SF that causes a sustain discharge at each gradation based on the SF construction data SFPD. Find the total number within. For example, the gradation luminance measuring circuit 31 has a total number M1 to M15 of sustain pulses corresponding to the first to fifteenth gradations as shown in FIG.
M1: 0
M2: number of sustain pulses applied at SF1 M3: total number of sustain pulses applied at each of SF1 and SF2 M4: total number of sustain pulses applied at each of SF1 to SF3 M5: applied at each of SF1 to SF4 Total number of sustain pulses
・
・
M13: Total number of sustain pulses applied in each of SF1 to SF12 M14: Total number of sustain pulses applied in each of SF1 to SF13 M15: Total number of sustain pulses applied in each of SF1 to SF14.

  Next, as shown in FIG. 12, the gradation luminance measuring circuit 31 associates the total number M of the sustain pulses as described above with the gain value S, based on the gain value map shown for each color, for each gradation. The gain value S corresponding to is acquired.

  That is, the luminance saturation characteristics for each color of the phosphor in the PDP 10 are measured in advance, and a gain value map indicating the optimum gain value S corresponding to the total number M of sustain pulses is created based on the measurement result. . This gain value map is stored in advance in a built-in memory (not shown) of the plasma display device. Therefore, the gradation luminance measurement circuit 31 reads the gain value S corresponding to each gradation from the built-in memory for each color (red, green, blue).

Next, the gradation luminance measurement circuit 31 multiplies the total number M1 to M15 of sustain pulses corresponding to each of the first to fifteenth gradations as shown in FIG. As shown in FIG. 4, luminance gradation corresponding data KY _R , KY _G , and KY _B are obtained for each color.

  In the above-described embodiment, an example has been described in which a new luminance division value Q1 is obtained by multiplying each luminance division value Q1 by a coefficient in accordance with the suspension rising periods TS1 to TS3. This is due to the fact that the light emission luminance varies depending on the length of TS. However, this change in light emission luminance is caused not only by the change of the sustain rising period TS but also by the change of the pulse width of the sustain pulse or the change of the pulse waveform.

  Therefore, in consideration of the change in the pulse width of the sustain pulse and the change in the shape of the pulse waveform, the luminance division value is multiplied by a coefficient similar to the above coefficient (hereinafter referred to as coefficient SS) to obtain a new luminance division value. May be.

  As an example of the change in the waveform shape, for example, the waveform of the sustain pulse also changes depending on the light emission load amount of the display panel. Here, the light emission load is the total number of sustain pulses assigned to the subfield set to the lighting mode in the address process. That is, it is the total number of sustain pulses that contribute to gradation display, and the amount of light emission load increases as high-luminance display is performed on the entire screen of the display panel. Here, as the light emission load amount increases, the number of discharge cells in which a sustain discharge is generated in the sustain process increases. In this case, a large number of discharge cells generate discharges substantially simultaneously. At this time, since a large current instantaneously flows, the waveform of the sustain pulse is distorted, and the emission luminance is changed by the waveform distortion of the sustain pulse.

Considering the above points, for example, the light emission load is obtained from the address data for each field, and the coefficient SS is set according to the light emission load amount. For example, when the light emission load amount when the display panel is driven is equal to or less than a predetermined light emission load amount, the coefficient SS is set to “1”, while when the predetermined light emission load amount is exceeded,
0 <coefficient SS <1
The coefficient SS is set within the range. Alternatively, the coefficient SS may be set stepwise within a range of “0” to “1” according to the light emission load amount. In this case, the coefficient SS is set to a smaller value as the light emission load amount increases. Further, when the width of the sustain pulse becomes narrower than a predetermined width, the coefficient SS may be set stepwise within a range of “0” to “1”. Also, the sustain pulse in each subfield is set. However, there may be a difference in the light emission luminance associated with the sustain discharge generated according to each sustain pulse. For example, the light emission luminance associated with the sustain discharge generated in response to the sustain pulse provided at the head may be lower than the light emission luminance associated with the sustain discharge generated in response to the sustain pulse provided at the rear. This is because the amount of charged particles remaining in the discharge space at the stage immediately before the sustain discharge is smaller at the head than at the tail of the sustain process.

  Therefore, the coefficient SS may be set in consideration of the sustain rising period of each sustain pulse, the change in the pulse width, and the change in the shape of the pulse waveform.

  For example, in the example described above, the sustain discharge generated at the beginning of each sustain process has lower emission luminance associated with the discharge than the sustain discharge generated at the rear. Therefore, in setting the coefficient SS, the change in the rising period of the first sustain pulse, the change in the pulse width, and the change in the waveform shape are weighted when the coefficient SS is set compared to the change in the rear sustain pulse. Small. On the other hand, a large weight is used for each of the above-described changes in the rear sustain pulse. That is, the coefficient SS is mainly set based on the change amount of each change in the rear sustain pulse.

It is a figure which shows the structure of the plasma display apparatus containing the drive device by this invention. It is a figure which shows an example of the light emission drive sequence employ | adopted in the plasma display apparatus shown by FIG. It is a figure which shows an example (information on a sustain pulse application number, an address execution period, a suspension start-up period) shown for every subfield in SF construction data SFPD. It is a figure which shows the various drive pulses applied to PDP10 according to the light emission drive sequence shown in FIG. 2, and its application timing. 2 is a diagram showing an internal configuration of an SF data generation circuit 3. FIG. It is a figure which shows the correspondence of the frequency | count of application of a sustain pulse, and visual luminance for every luminescent color. It is a figure which shows the correspondence of address execution period length and an electron density return rate for every luminescent color. It is a figure for demonstrating the operation | movement which calculates | requires the visual luminance estimated for every subfield based on the application frequency and the address execution period length of a sustain pulse. Each gradation and the gradation luminance corresponding data KY R indicating the luminance value for each light emission color by the dither step _is a diagram showing an example of KY _G, and KY _{B. Gradation} luminance corresponding data RA R shown in the normalized luminance for each emission color at each tone and dithering step is a diagram showing an example of a RA _G, and RA _B. It is a figure which shows the total number in 1 frame display period of the sustain pulse applied in the subfield SF which will produce a sustain discharge by the gradation for every gradation. It is a figure which shows an example of the gain value map which shows the gain value S corresponding to the sustain pulse total number M for every color.

Explanation of symbols

3 SF data generation circuit 10 PDP
11 SF construction circuit 20 drive control circuit 31 gradation luminance measurement circuit 32 luminance linearity calculation circuit 34 luminance gradation conversion circuit

Claims (12)

An address period in which each of the pixels is set to one of a lighting mode and a non-lighting mode according to subfield data based on an input video signal, and a sustain pulse is applied to each pixel. Is applied in a plurality of subfields including a sustain period in which the pixel in the lighting mode is caused to emit light by repeatedly applying the first to Nth gradations (N: an integer of 2 or more). A display panel driving device for obtaining brightness,
Based on the number of times of application of the sustain pulse within the sustain period of each of the subfields, a luminance level in each of the first to Nth gradations is obtained for each emission color of the pixel, and the luminance level and the first A gradation luminance measurement means for generating gradation luminance correspondence data indicating each Nth gradation in association with each emission color;
Based on the gradation luminance correspondence data, a gradation corresponding to the luminance level for each light emission color indicated by the input video signal is determined, and data for driving corresponding to the gradation is determined as the subfield data. And a luminance gradation converting means for generating a display panel drive device. Each of the pixels includes a phosphor layer that emits light in one of red, green, and blue.
The gradation luminance measuring means corresponds to the return rate of the phosphor layer with respect to the initial electron density in the ground state corresponding to the period length of the address period of each of the subfields, according to the first to first electron densities in the phosphor layer. 2. The display panel driving apparatus according to claim 1, wherein the brightness level value corresponding to each of the Nth gradations is adjusted for each emission color.   The gradation luminance measuring means stores in advance electron density return rate characteristic data indicating a correspondence relationship between the period length of the address period and the return rate for each light emission color for each of the subfields. The display panel driving device according to claim 2, wherein the driving device is a display panel driving device.   The gradation luminance measuring means adjusts the value of the luminance level corresponding to each of the first to Nth gradations for each emission color according to the rising period of the sustain pulse for each of the subfields. The display panel driving device according to claim 2, wherein:   The gradation luminance measuring means adjusts a luminance level value corresponding to each of the first to Nth gradations for each emission color in accordance with a change in the waveform shape of the sustain pulse for each of the subfields. The display panel driving apparatus according to claim 2, wherein:   The gradation luminance measuring means adjusts a value of a luminance level corresponding to each of the first to Nth gradations for each emission color according to a light emission load amount for each field. 3. A display panel drive device according to 2.   The gradation luminance measuring means adjusts the value of the luminance level corresponding to each of the first to Nth gradations for each emission color according to the pulse width of the sustain pulse for each of the subfields. The display panel driving device according to claim 2, wherein the driving device is a display panel driving device.   6. The display according to claim 5, wherein a luminance level value corresponding to each of the first to Nth gradations is adjusted for each emission color in accordance with a change in each waveform shape of the sustain pulse. Panel drive device Each of the pixels includes a phosphor layer that emits light in one of red, green, and blue.
The gradation luminance measuring means has an Nth gradation luminance level corresponding to the Nth gradation of the luminance levels corresponding to the first to Nth gradations obtained for each emission color. Normalization processing is performed on the value of the luminance level corresponding to each of the first to Nth gradations for each of the emission colors so that the luminance level is equal to or higher than the maximum luminance level in the luminance range indicated by the input video signal. The display panel driving apparatus according to claim 1, wherein:   The normalization processing is characterized by multiplying the value of the luminance level corresponding to each of the first to Nth gradations for each light emission color by the same coefficient for each light emission color. The display panel drive device according to claim 9. Each of the pixels includes a phosphor layer that emits light in one of red, green, and blue.
The gradation luminance measuring means obtains a gain value based on the total number of times the sustain pulse is applied in one field period, and sets the accumulated sustain pulse number corresponding to each of the first to Nth gradations in the one field period. 2. The display panel driving apparatus according to claim 1, wherein the brightness level value corresponding to each of the first to Nth gradations is obtained for each emission color by multiplying the gain value.   12. The display panel driving device according to claim 11, wherein the gain value is individually set for each light emission color based on a light emission characteristic of a phosphor material for each light emission color.

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