WO2009038414A1

WO2009038414A1 - Method for reverse-gamma compensation of plasma display panel

Info

Publication number: WO2009038414A1
Application number: PCT/KR2008/005601
Authority: WO
Inventors: Hee Duk Jo; Yong Duk Kim
Original assignee: Orion Pdp Co., Ltd.
Priority date: 2007-09-20
Filing date: 2008-09-22
Publication date: 2009-03-26
Also published as: KR20090030461A; KR101174717B1

Abstract

Disclosed is a method for reverse-gamma correction of a plasma display panel, which can improve image quality in a low gray scale region by calculating an output of gamma depending on an APL. The method includes selecting a plurality of APL points in an APL curve; calculating the number of sustain pulses for each subfield based on an APL point, calculating a luminance value at each of the APL points based on an SFM level; calculating an output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied; and calculating an output of gamma at each of the APL points based on an input gray scale.

Description

[DESCRIPTION] [Invention Title]

METHOD FOR REVERSE-GAMMA COMPENSATION OF PLASMA DISPLAY PANEL

[Technical Field]

<i> Example embodiments of the present invention relates to a method for reverse-gamma correction of a plasma display panel (PDP), and more particularly, to a method for reverse-gamma correction of a PDP, which can improve image quality in a low gray scale region by calculating an output of gamma depending on an average picture level (APL).

<2>

[Background Art]

<3> A plasma display panel (PDP) is a device that displays an image using visible light generated from phosphors when ultraviolet light generated by gas discharge excites the phosphors. Such a PDP generally has a structure in which upper and lower substrates are sealed together. As described in FIG. 1, the upper substrate is provided with scan electrodes Yl to Yn and sustain electrodes Z, and the lower substrate is provided with address electrodes Xl to Xm. Discharge cells 1 are provided at intersection portions of the scan and sustain electrodes.

<4> Such a PDP employs a method in which the PDP is time-divisionally driven by dividing one frame into several subfields having different light- emission times. Each of the subfields is divided into a reset period for generating uniform discharge, an address period for selecting discharge cells, and a sustain period for realizing gray scales depending on the number of discharge times. For example, when an image with 256 gray scales is displayed, a frame period corresponding to 1/60 second (16.67 ms) is divided into eight subfields. As shown in FIG. 2, each of the eight subfields (SFl, SF2, ...SF8) is also divided into a reset period, an address period and a sustain period. Here, the reset and address periods in each of the subfields are the same for all the subfields. On the other hand, the sustain period and the number of discharge times in each of the subfields are increased at a rate of 2^* (n = 0, 1, 2, 3, 4, 5, 6, 7) at each of the subfields. As such, the sustain periods are different in the respective subfields, thereby realizing gray scales of an image. <5> A subfield map can be constructed based on the fact that the number of sustain pulses is increased at the rate of 2 for each of the subfields, and a larger number of gray scales can be realized by from limited SFM levels using the corresponding subfield map. The following Table 1 is an example of a subfield map, in which subfield weights are allocated to the respective subfields with respect to 55 SFM levels, and the respective subfields are selectively turned on/off, thereby realizing 256 gray scales. For example, if there are 256 R, G and B data each, the corresponding R, G and B data can be expressed using the subfield map of Table 1. For reference, in Table 1, the other gray scales except the 55 SFM levels are realized by performing half-toning. Outputs of gamma, which will be described later, are used in the half-toning.

<6>

<?> [Table 1]

Example of subfield map

<8>

<9>

<10>

R, G and B data inputted to a driving circuit for a PDP are in a gamma- corrected state. Therefore, it is required to allow luminance for a gray scale of an image signal to be linearly changed by performing reverse-gamma correction with respect to the corresponding R, G and B data. At this time, an output of gamma for each of the R, G and B data is calculated by the following Equation 1.

<11> Equation 1

2.2

Ouφut of Gamm∞Max of SFM Levelx {-*££^■)

<12> <13> where "Input" denotes each of the R, G and B data, and "2.2" denotes a gamma value.

<14> The reverse-gamma correction is performed before the subfield map is constructed, i.e., before the subfield mapping is performed, and the subfield mapping is performed by using outputs of gamma calculated by Equation 1, thereby realizing 256 gray scales. Specifically, the integer part of an output of gamma is used in expression of 55 SFM levels, and the decimal part of the output of gamma is used in half-toning for the realization of gray scale. <i5> Meanwhile, a PDP allows power consumption to be constant by using an average picture level (APL) curve shown in FIG. 3. When an image is displayed using conventional outputs of gamma, expression of colors may be degraded at a low gray scale region in which an APL is low. This is because the conventional process of calculating outputs of gamma is performed without considering the APL value.

<16>

[Disclosure]

[Technical Problem]

<i7> Therefore, the present invention has been made in view of the above problems, and provides a method for reverse-gamma correction of a plasma display panel (PDP), which can improve image quality in a low gray scale region by calculating an output of gamma depending on an average picture level (APL).

<18>

[Technical Solution]

<19> In accordance with an aspect of the present invention, there is provided a method for reverse-gamma correction for a plasma display panel (PDP), which includes: selecting a plurality of average picture level (APL) points in an APL curve," calculating the number of sustain pulses for each subfield based on an APL point; calculating a luminance value at each of the APL points based on an SFM level; calculating an output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied; and calculating an output of gamma at each of the APL points based on an input gray scale.

<20> In the calculation of the number of sustain pulses for each of the subfields based on an APL point, the value may be obtained using the following Formula 1, and the number of sustain pulses for each of the subfields at a specific APL point may be calculated by substituting the corresponding value α in the following Formula 2: <2i> Formula 1

_<22> Number of sustain pulses at specific APL point = 2J( SFiWeight^a- 1 )

<23> where α ≥ O and " SF₁We ight " denotes a weight of an i-th subf ield.

<24> Formula 2

_<25> Number of sustain pulses of each SF = SFiWeight - 1

<26> In the calculation of the luminance value at each of the APL points based on an SFM level, the luminance value weights at each of the APL points based on an SFM level may be calculated using a subfield map in which weights are selectively given to the respective subfields to express input gray scales and on/off conditions are set in the respective subfields, a table showing the number of sustain pulses for each of the subfields based on an APL point, which are calculated through the calculation of the number of sustain pulses for each of the sustain pulses based on an APL point, and the following formula, and the luminance value weights at each of the APL points based on an SFM level may be calculated by applying the on/off conditions of the respective subfields set in the subfield map to a table showing the number of sustain pulses for each of the subfields based on an APL point, and substituting the number of sustain pulses for each of the subfields based on an APL point for the following formula:

<27> Ld = Black luminance+∑δ (i)x(Address discharge luminance + Number of sustain pulses of i~th SF x 1 Sustain discharge luminance)

<28> where "δ(i)" denotes a delta function having a value of 1 when the i- th subfield is turned on and a value of 0 when it is turned off, "Black

2 2 luminance" is 0.2 cd/m , "Address discharge luminance" is 1 cd/m , and "1

2

Sustain discharge luminance"is 1 cd/m .

<29> In the calculation of the output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied, the output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied may be calculated by substituting a maximum luminance value and respective input gray scales at each of the APL points in the luminance values calculated through the calculation of the luminance value at each of the APL point based on an SFM level for the following Formula: j. Gamma Value

Lv = Max. Ld of APL point X ( f )

<30> ^ ²⁵⁵ '

<3i> where "Max. Ld of APL point" denotes a maximum luminance value at a specific APL point, "Gamma value" is 2.2, and "Input" denotes R, G, B data values as input gray scales.

<32> The calculation of the output of gamma at each of the APL points based on an input gray scale may be performed using the luminance value at each of the APL points based on an SFM level, the output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied, and the following formula, and the output of gamma at each of the APL points based on an input gray scale may include selecting a luminance value (Lv) corresponding to a specific input gray scale at a specific APL point in the output value for each of the APL points based on an input gray scale to which gamma characteristic are applied; extracting a luminance value (Ld) which is most approximate while being equal to or smaller than the luminance value (Lv) from the luminance value at each of the APL points based on an SFM level in an APL point of the luminance value (Ld) identical to that of the luminance value (Lv); and calculating the output of gamma for each of the APL points based on an input gray scale by substituting the luminance value (Lv), the luminance value (Ld) and an SFM level (K) at each of the APL points for the following Formula:

_Y__ _J*-j Lv—LmφtancdSfM Level K)

Ltminance(SFM LevelK-¥i)-Ltminanc^SFM LevelK)

<33>

<34> where "Lv" denotes a luminance value at a specific input gray scale of a specific APL point in Table 5, "Luminance(SFM Level K)" denotes a luminance value (Ld) equal to or most adjacent while being smaller than Lv in an APL point equal to Lv in table 4, and "SFM Level K" denotes an SFM level at the luminance value (Ld).

[Advantageous Effects] <36> A method for reverse-gamma correction of a plasma display panel (PDP) according to the present invention has the following advantageous effect. <37> A relatively high SFM level is applied in a region in which an average picture level (APL) value is relatively low, thereby improving image quality in a low gray scale region. [Description of Drawings] <38> Fig. 1 is a view showing the configuration of a conventional plasma display panel (PDP). <39> Fig. 2 is a view illustrating a principle of realizing an image in the

PDP.

<40> Fig.3 is a graph showing an average picture level (APL) curve. <4i> Fig. 4 is a block diagram showing the configuration of a driving circuit for implementing a method for reverse-gamma correction of a PDP according to an embodiment of the present invention. <42> Fig. 5 is a flowchart illustrating the method for reverse-gamma correction of the PDP according to the embodiment of the present invention. <43> Fig. 6 is a view showing a subfield map applied to the embodiment of the present invention. <44> FIG. 7 is a graph showing output luminance values at respective APL points based on input gray scales to which gamma characteristics are applied according to the embodiment of the present invention.

<45>

[Mode for Invention]

<46> Hereinafter, a method for reverse-gamma correction of a plasma display panel (PDP) according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

<47> Fig. 4 is a block diagram showing the configuration of a driving circuit for implementing a method for reverse-gamma correction of a PDP according to an embodiment of the present invention. Fig. 5 is a flowchart illustrating the method for reverse-gamma correction of the PDP according to the embodiment of the present invention.

<48> First of all, the driving circuit for implementing the method for reverse-gamma correction of the PDP according to the embodiment of the present invention will be described as follows. As shown in FIG. 4, the driving circuit of a PDP of the present invention includes a signal receiving unit 401, an average picture level (APL) calculation unit 402, a timing control unit 403, a reverse-gamma correction unit 405, a half-toning unit 406, a subfield mapping unit 407 and a data alignment unit 408.

<49> The signal receiving unit 401 receives digital image data, i.e., R, G and B data, inputted through a video board of the PDP. The APL calculation unit 402 includes a read only memory (ROM) in which an APL curve of FIG. 3 is stored. The APL calculation unit 402 calculates an APL using the following Equation 2 and Equation 3, selects the number of sustain pulses corresponding to a specific APL from the APL curve of FIG. 3, and then supplies the selected number of sustain pulses to the timing control unit 403.

<50> Equation 2

T _t( T> C¹ Ti\ Gamma Value

Output ofAPL Gamma = APL Gain X (TT " ^ , )

_<5]> V Max of Input Level J

<52> where "Gamma value" is 2.2. <53> Equation 3

_{A T}-, _T ^ _{Λ π T »x} ZjOutput of APL Gamma{R,G,B)

APL(Average Picture Level) = -= — - — ^v

<5 _4„> Resolution X 5

<55> The timing control unit 403 generates a timing control signal corresponding to the number of sustain pulses inputted from the APL calculation unit 402 in response to the number of sustain pulses, and supplies the corresponding timing control signal to a scan and sustain driving unit 404. For reference, the scan and sustain driving unit supplies sustain pulses to scan and sustain electrodes of the PDP during a sustain period in response to the timing control signal inputted from the timing control unit 403. <56> Using the APL curve stored in the ROM of the APL calculation unit 402, the reverse-gamma correction unit 405 performs calculations of the number of sustain pulses for each subfield based on an APL point, a luminance value of each APL point based on an SFM level, a output luminance value at each APL point based an input gray scale to which gamma characteristics are applied, an output of gamma at each APL point based on an input gray scale, and the like. The reverse-gamma correction unit 405 will be described in detail in the following method for reverse-gamma correction of the PDP according to the embodiment of the present invention.

<57> The half-toning unit 406 performs half-toning with the output of gamma calculated by the reverse-gamma correction unit 405 using either an error diffusion method or a dithering method. The subfield mapping unit 407 maps data inputted from the half-toning unit 406 to a subfield mapping table which has been previously stored, and supplies the mapped data to the data alignment unit 408. The data alignment unit 408 supplies data inputted from the subfield mapping unit 407 to a data driving unit 409. The data driving unit 409 supplies the inputted data to address electrodes.

<58> The driving circuit for implementing the method for reverse-gamma correction of the PDP according to the embodiment of the present invention has been described. Hereinafter, the method for reverse-gamma correction of the PDP according to the present invention will be described in detail.

<59> As described above, in the method for reverse-gamma correction of the PDP according to the embodiment of the present invention, the reverse-gamma correction unit 405 of FIG. 4 calculates a final output of gamma at each APL point based on an input gray scale, using the APL curve stored in the ROM of the APL calculation unit 402. The APL point refers to a plurality of APL values arbitrarily extracted from the APL curve. In the present invention, reverse-gamma correction is performed with respect to the plurality of APL values arbitrarily extracted from the APL curve so as to apply a relatively high luminance value in a period having a relatively small APL value, i.e., in a region having low gray scales. Accordingly, image quality in a low gray scale region can be improved.

<60> Specifically, as shown in FIG. 5, a plurality of APL values are arbitrarily selected from the APL curve of FIG. 3 (S501). For example, 4, 8, 16, 32 and the like may be variously selected as the plurality of APL values. Hereinafter, 16 APL values will be described for convenience of illustration. Each of the plurality of selected APL values are designated by an APL point.

<6i> Meanwhile, the respective selected APL points have the number of sustain pulses corresponding to the number of the APL points through the APL curve of FIG. 3. The number of sustain pulses for each subfield based on APL points can be calculated using the plurality of APL points, the number of sustain pulses corresponding to the APL points and the following Equation 4 and Equation 5 (S502).

<62> Calculation of number of sustain pulses for each subfield based on APL point

<63> First, a value α is obtained using Equation 4. In Equation 4, the number of sustain pulses at a specific APL point can be obtained through the APL curve of FIG. 3, using the weights (SFjWeight) of the respective subfields shown in Table 2. The value α can be obtained using the number of sustain pulses at the specific APL point and the total of the weights (SFjWeight) of the respective subfields.

<64> The value α calculated by Equation 4 is applied to Equation 5, thereby calculating the number of sustain pulses for each of the subfields. In the calculation of Equation 5, a value positioned at the right of the decimal point is rounded off or truncated.

<65> For example, 73, 99, 127, 160, 236, 332, 388, 451, 522, 601, 688, 788, 896 and 1021 are selected as APL points as shown in Table 3, and the number of sustain pulses corresponding to each of the APL points is presented. In this case, the number of sustain pulses for each of the subfields at each of the APL points is calculated by Equation 4 and Equation 5 as shown in Table 3. <66> Equat ion 4

<67> Number of sustain pulses at specific APL point - 2Λ SFiWeight^*- 1) <68> where α ≥ 0 and "SFjWeight" denotes a weight of an i-th subfield.

<69> Equation 5

<70> Number of sustain pulses of each SF = SFiW eight - 1 <71>

<72> [Table 2] Weight for each subfield <73>

<74> [Table 3] Number of sustain pulses for each subfield based on APL point

<75>

<76> In the state that the number of sustain pulses for each of the subfields based on an APL point is calculated as described above, a process of calculating a luminance value at each of the APL points based on an SFM level is performed (S503).

<77> The luminance value at each of the APL points based on an SFM level is calculated using the number of sustain pulses for each of the subfields based on an APL point, the subfield map of FIG. 6 and the following Equation 6.

<78> Specifically, the table showing the number of sustain pulses for each of the subfields based on an APL point in Table 3 is mapped to the subfield map of FIG. 6. Mapping Table 3 to the subfield map of FIG. 6 means that the condition under which the respective subfields are turned on or off is determined by the subfield map of FIG. 6. In the subfield map of FIG. 6, it can be seen that only first and third subfields SFl and SF3 are in a turned- on state and the other subfields are all in a turned-off state in case of an SFM level of 4. In Table 3, this means that only the first and third subfields SFl and SF3 are in a turned-on state and the other subfields are all in a turned-off state in case of an APL point of 1 (APL-73). Accordingly, only five sustain pulses in the third subfield SF3 exhibits actual luminance. If such a matching result is substituted in Equation 6, the luminance value for a SFM level 4 at the APL point of 1 is calculated.

<79> If such a matching result of Table 3 and FIG. 6 is applied to Equation 6 for each APL point and each SFM level, a luminance value (Ld) at each of the APL points based on an SFM level can be calculated as shown in Table 4. For reference, in Equation 6, "Black luminance" denotes a luminance of a PDP screen when a digital image data signal is not applied, "Address discharge luminance" denotes luminance in an address period, and "1 Sustain discharge luminance" denotes luminance when one sustain pulse is applied. In Equation 6, values of the "Black luminance", "Address discharge luminance" and "1 Sustain discharge luminance" may be varied as arbitrary values.

<80> Equation 6

<8i> Ld = Black 1'urninance+∑δ (i)X(Address discharge luminance + Number of sustain pulses of i~th SF x 1 Sustain discharge luminance)

<82> where "δ(i)" denotes a delta function having a value of 1 in a turned- on state and a value of 0 in a turned-off state, "Black luminance" is 0.2 2 2 cd/m , "Address discharge luminance" is 1 cd/m , and "1 Sustain discharge

2 luminance"is 1 cd/m .

<83> [Table 4] Luminance value at each APL point based on SFM level

<84>

Calculation of luminance value at each APL point based on input gray scale to which gamma characteristics are applied

<85> In the state that the luminance value at each of the APL points based on an SFM level is calculated through the aforementioned processes, a process is performed to calculate an output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied (S504) .

<86> The output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied is calculated using the luminance value at each of the APL points based on an SFM level in Table 4 and the following Equation 7. Specifically, if the maximum luminance value at each of the APL points and each input gray scale value are substituted in Equation 7, the output luminance value (Lv) at each of the APL points based on an input gray scale to which gamma characteristics are applied can be calculated as shown in the following Table 5. The output luminance value (Lv) at each of the APL points based on an input gray scale to which gamma character i st ics are appl ied in Table 5 can be shown in a graph of FIG. 7. <87> Equat ion 7

Lv

<89> where "Max. Ld of APL point" denotes a maximum luminance value at a specific APL point, "Gamma value" is 2.2, and "Inpu"t denotes R, G, B data values as input gray scales. <90> [Table 5]

Output luminance value at each APL point based on input gray scale to which gamma characteristics are applied

<91>

<9S>

scale

<96> In the state that the output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied are calculated, a process of calculating an output of gamma at each of the APL points based on an input gray scale is finally performed (S505).

<97> The output of gamma at each of the APL points based on an input gray scale is calculated using the luminance value at each of the APL points based on an SFM level in Table 4, the output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied, and the following Equation 8.

<98> Specifically, a luminance value (Lv) corresponding to a specific input gray scale at a specific APL point is first selected in Table 5, and a luminance value (Ld) equal to or smaller than the corresponding luminance value (Lv) is then looked up in Table 4. At this time, it is assumed that the luminance value (Ld) looked up in Table 4 has the same APL point as the luminance value (Lv) selected in Table 5. When the luminance value (Ld) in Table 4 is smaller than that (Lv) in Table 5, the most approximate luminance value is selected. If the luminance value (Ld) in Table 4 satisfying such conditions is selected, an SFM level (K) of the corresponding luminance value (Ld) can be obtained. If the SFM level (K) is substituted in Equation 8, an output of gamma at each of the APL points based on an input gray scale can be calculated.

<99> For example, a luminance value (Lv) of 0.596 corresponding to an APL point of 1 and an input gray scale of 7 is first selected. Then, a luminance value (Ld) which is most approximate while being equal to or smaller than the luminance value (Lv) of 0.596 is searched in Table 4. At this time, it is assumed that the luminance value (Ld) in Table 4 has the same APL point as the luminance value (Lv) as described above. In Table 4, it can be seen that the luminance value (Ld) is 0.2, which is equal to or smaller than 0.596. At this time, the SFM level (SFM Level K) is 0. Further, it can be seen that the luminance value (Ld) at the next SFM level (SFM level K + 1) is 1.20. Such information is substituted in the following Equation 8.

LuminanceiSFMLevelK+1)-Luminance(SFMLevelK)

<100>

<ioi> = 0 + (0.596-0.20) / (1.20-0.20)

<i02> = 0.396

<iO3> The output of gamma at each of the APL points based on an input gray scale can be calculated through the aforementioned processes, and outputs of gamma at the respect ive APL points based on an input gray level are shown in

Table 6. For reference , it can be seen that the output of gamma in the APL point of 1 and the input gray scale of 7 , calculated above , is 0.396 in Table 6.

<iO4> Equat ion 8

^{Λ ΛT} LuminanceiSFM Level K+l)-Limmance{SFM Lwel JO

<105>

<io6> where "Lv" denotes a luminance value at a specific input gray scale of a specific APL point in Table 5, "Luminance(SFM Level K)" denotes a luminance value (Ld) equal to or most adjacent while being smaller than Lv in an APL point equal to Lv in Table 4, and "SFM Level K" denotes an SFM level at the luminance value (Ld) .

<107>

<io8> [Table 6]

Output of gamma at each APL based on input gray scale

<109>

As described above, the output of gamma at each of the APL points based on an input gray level has been finally calculated through the process of calculating the number of sustain pulses for each of the subfields based on an APL point, the process of calculating a luminance value at each of the APL points based on an SFM level, and the process of calculating an output luminance value at each of the APL pints based on an input gray level to which gamma characteristics are applied.

<110> As shown in Table 6, it can be seen that the output of gamma at each of the APL points based on an input level has an integer part and a decimal part. The integer part indicates an SFM level, and the decimal part indicates a part for expressing half-toning.

<111> When assuming that the same input gray scale is applied, it can be seen that the output of gamma at each of the APL point based on an input gray scale has a relatively high SFM level in a period in which an APL value is relatively small, i.e., in a region in which a large number of low gray scales exist as shown in Table 6. For example, in an input gray scale 87, the output of gamma at an APL point of 1 based on an input gray scale 87 is 20.562, and the output of gamma at an APL point of 16 is 12.921. Accordingly, a relatively high SFM level is applied in a region in which a large number of gray scales exist, thereby improving color expression in the region in which a large number of gray scales exist.

<ii2> The invention has been described in detail with reference to example embodiments thereof. However, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the accompanying claims and their equivalents.

<113>

[Industrial Applicability] <ii4> A method for reverse-gamma correction of a plasma display panel (PDP) according to the present invention has the following advantageous effect. <ii5> A relatively high SFM level is applied in a region in which an average picture level (APL) value is relatively low, thereby improving image quality in a low gray scale region.

Claims

[CLAIMS] [Claim 1] <ii7> A method for reverse-gamma correction of a plasma display panel (PDP), comprising'- <ii8> selecting a plurality of an average picture level (APL) points in an

APL curve; <H9> calculating the number of sustain pulses for each subfield based on an

APL point; <12O> calculating a luminance value at each of the APL points based on an SFM level ; <i2i> calculating an output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied; and <i22> calculating an output of gamma at each of the APL points based on an input gray scale.

<123>

[Claim 2]

<i24> The method as set forth in claim 1, wherein in the calculation of the number of sustain pulses for each of the subfields based on an APL point, a value α is obtained using the following Equation 1, and the number of sustain pulses for each of the subfields at a specific APL point is calculated by substituting the corresponding value α for the following Equation 2:

<125> Equation 1

Number of sustain pulses at specific APL point - χX SFiWeight^- l)

<127> where α ≥ 0 and "SFjWeight" denotes a weight of an i-th subfield. <i28> Formula 2

_<]29> Number of sustain pulses of each SF ⁼ SFiWeight - 1

<130>

[Claim 31 <i3i> The method as set forth in claim 1, wherein in the calculation of the luminance value at each of the APL points based on an SFM level,

<i32> the luminance value weight at each of the APL points based on an SFM level is calculated using a subfield map in which weights are selectively given to the respective subfields to express input gray scales and on/off conditions are set in the respective subfields, a table showing the number of sustain pulses for each of the subfields based on an APL point, which are calculated through the calculation of the number of sustain pulses for each of the sustain pulses based on an APL point, and the following Equation, and

<133> the luminance value weight at each of the APL points based on an SFM level is calculated by applying the on/off conditions of the respective subfields set in the subfield map to a table showing the number of sustain pulses for each of the subfields based on an APL point, and substituting the number of sustain pulses for each of the subfields based on an APL point in the following Equation:

<i34> Ld = Black Luminance+∑ δ (i)x(Address Discharge Luminance + Number of Sustain Pulses of i-th SF x 1 Sustain Discharge Luminance)

<i35> where "δ(i)" denotes a delta function having a value of 1 in a turned- on state and a value of 0 in a turned-off state,, "Black Luminance" is 0.2

2 2 cd/m , "Address Discharge Luminance" is 1 cd/m , and "1 Sustain Discharge

2

Luminance" is 1 cd/m .

<136>

[Claim 4]

<137> The method as set forth in claim 1, wherein in the calculation of the output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied, the output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied is calculated by substituting a maximum luminance value and respective input gray scales at each of the APL points in the luminance values calculated through the calculation of the luminance value at each of the APL point based on an SFM level for the following Equation: Gamma Value

Lv

<139> where "Max. Ld of APL point" denotes a maximum luminance value at a specific APL point, "Gamma value" is 2.2, and "Input" denotes R, G, B data values as input gray scales.

<140>

[Claim 5]

<i4i> The method as set forth in claim 1, wherein the calculation of the output of gamma at each of the APL points based on an input gray scale is calculated using the luminance value at each of the APL points based on an SFM level, the output luminance value at each of the APL points based on an input gray scale to which gamma characteristics are applied, and the following Equation, and the output of gamma at each of the APL points based on an input gray scale comprises:

<i42> selecting a luminance value (Lv) corresponding to a specific input gray scale at a specific APL point in the output value for each of the APL points based on an input gray scale to which gamma characteristic are applied;

<i43> extracting a luminance value (Ld) which is most approximate while being equal to or smaller than the luminance value (Lv) from the luminance value at each of the APL points based on an SFM level in an APL point of the luminance value (Ld) identical to that of the luminance value (Lv); and

<i44> calculating the output of gamma for each of the APL points based on an input gray scale by substituting the luminance value (Lv), the luminance value (Ld) and an SFM level (K) at each of the APL points for the following equation: y «■■ Lv-LμtiφwiceiSFMLevelK)

Lummance($FMLeveliC+1)~Ltmmance(SFMLevelK)

<145>

<i46> where "Lv" denotes a luminance value at a specific input gray scale of a specific APL point in Table 5, "Luminance(SFM Level K)" denotes a luminance value (Ld) equal to or most adjacent while being smaller than Lv in an APL point equal to Lv in table 4, and "SFM Level K" denotes an SFM level at the luminance value.

<147>

[Claim 6]

<i48> The method as set forth in claim 1, further comprising performing subfield mapping using integer and decimal parts of the output of gamma at each of the APL points based on an input gray scale after calculating the output of gamma at each of the APL points based on an input gray scale.