JP3447568B2 - Display device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device for reproducing a halftone by intra-frame modulation, and an AC type PD.
It is suitable for display by P (Plasma Display Panel).

[0002] A PDP is a thin self-luminous display device having a substrate pair as a support, and has been widely used for applications such as television images and computer monitors with the practical use of color screens. One of the challenges of PDP
One is the reduction of background brightness.

[0003]

2. Description of the Related Art An AC PDP has a structure in which a main electrode is covered with a dielectric so as to have a so-called memory function of maintaining a lighting state by utilizing wall charges. When displaying,
Line-sequential addressing is performed in which only cells to be lighted (emits light) are charged, and thereafter, a lighting sustaining voltage Vs having an alternating polarity is applied to all the cells at once. The lighting sustain voltage Vs satisfies the expression (1).

Vf-Vwall <Vs <Vf (1) Vf: discharge start voltage Vwall: wall voltage In a cell in which wall charges are present, the wall voltage Vwall is superimposed on the lighting sustaining voltage Vs, so the effective voltage applied to the cell ( Veff (also referred to as cell voltage) exceeds the discharge start voltage Vf to cause discharge. If the application period of the lighting sustaining voltage Vs is shortened, an apparently continuous lighting state can be obtained. The brightness of the display depends on the number of discharges per unit time. Therefore, the halftone is reproduced by appropriately setting the number of discharges of one frame for each cell according to the gradation level. Color display is a kind of gradation display, and the display color is determined by the combination of the luminances of the three primary colors.

As a gradation display method of the PDP, one frame is composed of a plurality of subfields weighted by luminance (that is, the number of discharges), and the total number of discharges of one frame is determined by a combination of presence / absence of lighting in subfield units. The intra-frame modulation method for setting is widely known (Japanese Patent Laid-Open No. 4-1 / 1992).
95188). Generally, so-called "binary weighting", in which the weight is represented by 2 ⁿ (n = 0, 1, 2, 3, ...) Is performed for each subfield. For example, if the number of subfields is 8, the gradation level is “0” to “255”.
It is possible to display 256 gradations.

Binary weighting has no redundancy in weighting and is suitable for multi-gradation. However, in order to make the gradation width (luminance difference of one step of gradation) uniform over the entire gradation range, addressing must be performed for each subfield. Further, it is necessary to perform a reset process (addressing preparation process) for equalizing the charged state of the entire screen prior to addressing for each subfield. If the reset process is omitted, the discharge condition differs between the cell in which the wall charge remains (previously lighted cell) and the other cell (previously non-lighted cell), and it becomes difficult to perform reliable addressing. Since the reset process and the addressing are accompanied by discharge, it is desirable that the number of times is smaller from the viewpoint of contrast and power consumption. In particular, in a PDP having a large number of display pixels, such as an HDTV, the load on the circuit components for addressing is large, and therefore it is desired to reduce the number of addressing in terms of heat generation.

Therefore, conventionally, a predetermined number of subfields are divided into a plurality of subfield groups, and the weights of the subfields belonging to each subfield group are equalized.
A driving method has been proposed in which the reset process is performed once for each subfield group (Japanese Patent No. 2639311). According to this driving method, both the number of reset processes and the number of addressing are reduced from the number of subfields to the number of subfield groups, so that it is possible to improve contrast and power consumption.

[0008]

However, in the conventional display device, the number of subfield groups is constant. Therefore, when displaying an entirely dark frame, there has been a problem that the background portion, which occupies most of the screen, shines and appears slightly due to the discharge for reset processing and addressing. In the case of a relatively bright frame, even if the background part is slightly bright, there are many brighter parts and it is not noticeable.

An object of the present invention is to realize a display with a good contrast regardless of the brightness of the frame.

[0010]

According to the present invention, a histogram of pixel values representing luminance (luminance distribution) is calculated to discriminate a frame, and the frame structure related to gradation display is switched according to the discrimination result. For example, if the distribution is biased to low-luminance pixels, a frame configuration with a small number of subfield groups is applied, and the reduction of background luminance is prioritized over the number of gradations. If the distribution spreads from the lowest brightness to the highest brightness,
The frame structure with the largest number of subfield groups is applied to enhance gradation reproducibility.

[0011]

[0012]

According to the apparatus of the invention of claim 1 , one frame is illuminated.
It consists of 3 or more subfields weighted by degrees,
Addressing period and points that set whether or not to turn on each cell
For each subfield, the lighting maintenance period for maintaining the lighting condition
Allocation and set of the subfields for one frame
Is divided into one or more subfield groups,
At the beginning of the group, an address that equalizes the charge state of the entire screen
Is a display device that assigns a preparatory period for gradation display.
Therefore, the brightness distribution of one or more frames including the frame of interest
Set distribution calculation means to calculate and calculated brightness distribution
The ratio of the number of pixels in the range to the total number of pixels and the setting threshold
Brightness discriminating means for discriminating by comparing the
Different number of subfield groups depending on different results
Select one of the frame configurations of
And a control unit applied to the gradation display of the frame.

In the display device according to the second aspect of the present invention, the distribution calculation means calculates the luminance distribution on a frame-by-frame basis.
In the display device according to the third aspect of the present invention, the distribution calculation means calculates the luminance distribution in units of a plurality of frames.

In the display device of the fourth aspect of the present invention, when the input signal is an interlaced signal, the luminance distribution of one or more frames calculated by the distribution calculation means is an even or odd number which constitutes each frame. It is calculated from the brightness distribution of either one of the fields.

The display device of the invention of claim 5, when the similarity determination means for determining whether at least one of the frame is similar frame of interest and adjacent thereto of the frame arranged in series, of the frame of interest A distribution calculation means for calculating a brightness distribution and a brightness distribution of a plurality of consecutive frames including the target frame, a brightness determining means for determining the calculated brightness distribution in accordance with a setting condition, and the target frame and its adjacent When the frame is not similar, one of a plurality of frame configurations in which the number of subfield groups is different is selected according to the result of the determination of the luminance distribution of the frame of interest to display the gradation of the frame of interest. If the target frame is similar to the adjacent frame, the result of the determination of the luminance distribution of a plurality of consecutive frames is applied. Depending on, it comprises a control means for applying to the gradation display of the frame of interest by selecting one of a plurality of said frame structure, a.

In the display device of the sixth aspect of the present invention, the luminance discriminating means compares at least one of the luminance distribution of the target frame and the luminance distribution of the plurality of consecutive frames with a feature amount and a set threshold value. Determine.

In the display device of the invention of claim 7 , the brightness discriminating means sets at least one of the brightness distribution of the frame of interest and the brightness distribution of the plurality of consecutive frames as the number of pixels having a value within a set range. It is determined by comparison with the set threshold.

In the display device of the eighth aspect of the invention, the luminance discriminating means sets at least one of the luminance distribution of the frame of interest and the luminance distribution of the plurality of consecutive frames to all pixels having a value within a set range. It is determined by comparing the ratio with respect to the number and the set threshold.

In the display device of the ninth aspect , the frame is a color image composed of three planes having different display colors, the distribution calculation means calculates a luminance distribution for each plane, and the control means: The frame configuration is selected according to the result of the determination of the brightness distribution of the plane having the widest brightness distribution range.

[0021] In the display device of the present invention 請 Motomeko 10, wherein the set threshold value, the a maximum value or a value close to that of the reproducible luminance in each frame structure.

In the display device of the invention of claim 11 ,
When the input signal is an interlaced signal, the brightness distribution of the frame of interest and the brightness distribution of a plurality of frames including the frame of interest are calculated from the brightness distribution of either an even field or an odd field forming each frame. To be done.

[0023]

1 is a block diagram of a plasma display device 100 according to the present invention. Plasma display device 100
Is composed of an AC type PDP 1 which is a matrix type color display device, and a drive unit 80 for selectively turning on a large number of cells C which form a screen. It is used as a monitor for machines and computer systems.

In the PDP 1, the first and second main electrodes X and Y forming a pair are arranged in parallel, and in each cell C, the main electrodes X and
This is a PDP having a three-electrode surface discharge structure in which Y and an address electrode A as a third electrode are arranged in an intersecting manner. The main electrodes X and Y extend in the row direction (horizontal direction) of the screen, and one main electrode Y is used as a scan electrode for selecting cells in row units during addressing. The address electrode A extends in the column direction (vertical direction) and is used as a data electrode for selecting cells in column units. The area where the main electrode group and the address electrode group intersect is a screen.

The drive unit 80 includes a controller 81,
In addition to the basic constituent elements of the frame memory 82, the data processing circuit 83, the subfield memory 84, the power supply circuit 85, the X driver 86, the Y driver 87, and the address driver 88, three constituent elements (luminance distribution) unique to the present invention are also included. It has a calculation circuit 91, a luminance distribution determination circuit 92, and a similarity determination circuit 93). Frame data DF in pixel units indicating the luminance level (gradation level) of each color of R, G, B is input to the drive unit 80 from an external device such as a TV tuner computer together with various synchronization signals.

The frame data DF is stored in the frame memory 8
After being temporarily stored in 2, the data is sent to the data processing circuit 83. The data processing circuit 83 is a data conversion unit that sets a combination of subfields to be turned on, and outputs subfield data DSF according to the gradation level indicated by the frame data DF. The subfield data DSF is stored in the subfield memory 84. The value of each bit of the sub-field data DSF is information indicating whether or not the cell in the sub-field is required to be lit, more specifically, whether or not address discharge is required.

The X driver circuit 86 applies a drive voltage to the main electrode X, and the Y driver circuit 87 applies a drive voltage to the main electrode Y. The address driver 88 applies a drive voltage to the address electrode A according to the subfield data DSF. A predetermined power is supplied from the power supply circuit 85 to these driver circuits.

The frame data DF is input to the brightness distribution calculation circuit 91 and the similarity determination circuit 93 in parallel with the storage in the frame memory 82. Brightness distribution calculation circuit 9
Reference numeral 1 is a histogram that counts pixels of each brightness level for each of the R, G, B planes, and brightness distribution data (luminance histograms) D91r, D91g, D91 for each plane.
b is output to the brightness distribution determination circuit 92. The luminance distribution is calculated not only for a single frame of interest but also for a plurality of frames (for example, five frames) including the frame of interest. The similarity determination circuit 93 uses j
It is determined whether or not the (arbitrary integer) th frame (frame of interest) is similar to the immediately preceding (j−1) th frame. The determination data D93 indicating the determination result is input to the luminance distribution determination circuit 92. The luminance distribution discriminating circuit 92 discriminates the luminance distribution for each frame in a manner described later, and outputs discrimination data D92 indicating the result to the controller 81. The controller 81 switches to instruct the data processing circuit 83 to apply one frame configuration according to the value of the discrimination data D92 from a plurality of types (three types in this example) of frame configurations stored in advance. A signal Ssf is given. The frame data DF is converted to the subfield data DSF according to the switching signal Ssf.

FIG. 2 is an exploded perspective view showing the internal structure of the PDP 1 according to the present invention. The PDP 1 is a pair of substrate structures 1
It consists of 0 and 20. In the PDP 1, the main electrodes X and Y are arranged in pairs for each row on the inner surface of the glass substrate 11 which is the base material of the substrate structure 10 on the front side. Rows are horizontal cell columns. Each of the main electrodes X and Y is composed of a transparent conductive film 41 and a metal film (bus conductor) 42, and has a thickness of 30 μm.
It is covered with a dielectric layer 17 of about m. Dielectric layer 17
A protective film 18 made of magnesia (MgO) and having a thickness of several thousand angstroms is provided on the surface of the. The address electrodes A are arranged on the inner surface of the glass substrate 21 which is the base material of the substrate structure 20 on the back side, and are covered with the dielectric layer 24. Above the dielectric layer 24, the height is 150μ.
The partition walls 29 each having a linear band shape m in a plan view are provided between the address electrodes A one by one. The discharge spaces 30 are sub-pixels (unit light emitting regions) in the row direction due to the barrier ribs 29.
The discharge space 30 is defined for each space, and the gap size of the discharge space 30 is defined. Then, the phosphor layers 28R, 28 of three colors of R, G, B for color display are provided so as to cover the inner surface on the back side including the side surfaces of the partition walls 29 and above the address electrodes A.
G and 28B are provided. The discharge space 30 is filled with a discharge gas in which neon, which is a main component, is mixed with xenon, and the phosphor layers 28R, 28G, and 28B are locally excited by the ultraviolet rays emitted by xenon at the time of discharge to emit light.
One pixel (pixel) for display is composed of three sub-pixels arranged in the row direction. The structure in each sub-pixel is a cell (display element) C. Since the arrangement pattern of the barrier ribs 29 is a stripe pattern, the portion of the discharge space 30 corresponding to each column is continuous in the column direction across all the rows L.

Hereinafter, the PDP in the plasma display device 1 will be described.
The driving method of No. 1 will be described. FIG. 3 is a diagram showing a first frame structure. Each time-series frame F, which is an input image, is reproduced in 16 subfields SF1, SF2, SF3, SF4, SF in order to reproduce gradation by binary lighting control.
5, SF6, SF7, SF8, SF9, SF10, SF
11, SF12, SF13, SF14, SF15, SF
Divide into 16. In other words, the frame F is replaced with a set of 16 subfields SF1 to SF16 for display. In each of the subfields SF1 to SF16, an addressing period TA and a sustain period (display period) TS
And assign. Then, in order to reduce the number of times of addressing, a plurality (3 in the example) of subfield groups SFG1, SFG2, S16 are provided.
It is classified into FG3. A set of five subfields SF1 to SF5 from the beginning to the fifth in the display order is defined as a first subfield group SFG1, and a set of five subfields SF6 to SF10 from the sixth to tenth is defined. The second subfield group SFG2 is defined as the remaining 11th to 16th subfields SF11.
The set of SF16 to SF16 is defined as a third subfield group SFG3. An addressing preparation period TR is assigned to each of the subfield groups SFG1 to SFG3. In the present embodiment, the brightness weights of all the subfields belonging to the first subfield group SFG1 are set to the minimum “1”,
The brightness weights of all the subfields belonging to the second subfield group SFG2 are set to "6", and the brightness weights of all the subfields belonging to the third subfield group SFG3 are set to "36". Here, the weight of each subfield in the second and third subfield groups SFG2, SFG3 is an integer multiple of the minimum weight (“1”) and is a value obtained by adding 1 to the sum of the weights smaller than that. . That is, 6 = 1 × 5 + 1 and 36 = 1 × 5 + 6 × 5 + 1
Is. According to such a weighted frame structure,
By combining the presence / absence of lighting of the sub-fields, the gradation widths of the gradation levels “0” to “251” can be made uniform.
It is possible to realize display with 52 gradations. Therefore,
When this first frame structure is applied, the number of colors that can be displayed is 252 ³ .

The subfield groups SFG1 to SF
In G3, all weights do not necessarily have to be the same, and can be appropriately selected. For example, one subfield SF1 of the third subfield group SFG3
The weight of 3 is set to "35", and when obtaining the brightness of the weight of "36", the subfield SF13 of the weight of "35" and one subfield SF1 of the weight of "1" may be turned on. Further, it is not necessary to display the weights in order. For example, optimization can be performed such that a subfield having a large weight is arranged in the middle of the frame period. In order to prevent false contours in moving image display, it is desirable to avoid an extremely continuous lighting or non-lighting. However, the subfields belonging to each of the subfield groups SFG1 to SFG3 are continuously displayed, and the subfields of another group are not inserted between the subfields of a certain group.

The addressing preparation period TR is provided at the front of each of the subfield groups SFG1 to SFG3,
In the case of the erase address drive, in the addressing preparation period TR, a charge forming process for charging all the cells with wall charges necessary for maintaining lighting is performed by a drive sequence described later. Therefore, if the lighting sustaining voltage is applied while the charge forming process is performed, all cells are lit. In the addressing period TA of each subfield,
Erase addressing for erasing wall charges is performed only for cells that do not require lighting. The cell from which the wall charges have been erased does not light up even if the lighting sustaining voltage is applied until the charge forming process is performed again. In the sustain period TS, the lighting sustaining voltage of alternating polarity is simultaneously applied to all cells, and the lighting state of the cells in which the wall charges remain is maintained. N (5 or 6) in each subfield group SFG1 to SFG3
For gradation level cells that light m (0 ≦ m <n) subfields of the subfields,
The wall charges are erased in the (m + 1) th addressing period TA. The wall charge is not erased for the gray level cells that light the n sub-fields.

For example, in order to reproduce the gradation level "3",
The cells may be turned on during the sustain period TS of the three subfields SF1 to SF3 having a weight of 1.
In this case, charges are formed on the entire screen in the addressing preparation period TR of the first subfield group SFG1, and charges are erased in the corresponding cell in the addressing period TA of the fourth subfield SF4. When reproducing the gradation level “2”, the third
Addressing period TA of the th subfield SF3
The electric charge is erased in, and the corresponding cell is not lit in the sustain period TS of the third to fifth subfields SF3 to SF5.

In this way, each subfield group SFG1.about.
By changing the period of charge erasing according to the gradation level to be reproduced for each SFG3, the number of charge forming processes of the entire screen can be reduced to the number of subfield groups, and the number of addressing times is less than or equal to the number of subfield groups. Can be reduced to Since the addressing is of the erasing type, the addressing is unnecessary when the gradation level to be reproduced is "251", which is the maximum.

FIG. 4 is a diagram showing the second frame structure. Similar to the frame structure described above, each time-series frame F
Is divided into 16 subfields SF1 to SF16,
An addressing period TA and a sustain period TS are assigned to each of the subfields SF1 to SF16. In the second frame structure, subfields SF1 to SF
16 to two subfield groups SFG1b, SFG2b
Divide into. A set of eight subfields SF1 to SF8 from the beginning to the eighth in the display order is defined as a first subfield group SFG1b, and a set of eight subfields SF9 to SF16 from the ninth to sixteenth is defined. Second
Subfield group SFG2b. An addressing preparation period TR is assigned to each of the subfield groups SFG1b and SFG2b. First subfield group SFG
The luminance weights of all the subfields belonging to 1b are set to the minimum "1", and the luminance weights of all subfields belonging to the second subfield group SFG2b are set to "9". According to such weighting, the gradation levels from "0" to
It is possible to realize display of 81 gradations having a uniform gradation width of "80".

When the second frame structure is applied, the number of colors that can be displayed is 81 ³ , but since the number of subfield groups is 2, the background brightness is 67% of that of the display by the first frame structure. It can be reduced to the extent.

FIG. 5 is a diagram showing the third frame structure. Similar to the first and second frame configurations described above, each time-series frame F is divided into 16 subfields SF1 to SF.
It is divided into 16 parts, and an addressing period TA and a sustain period TS are assigned to each of the subfields SF1 to SF16. In the third frame structure, all the subfields SF1 to SF16 are combined into one subfield group S.
Summarize to FG1c. An addressing preparation period TR is assigned to the subfield group SFG1c. The brightness weights of all the subfields SF1 to SF16 are set to the minimum "1". With such weighting, it is possible to realize a display of 17 gradations having a uniform gradation width of gradation levels “0” to “16”.

When the third frame structure is applied, the number of colors that can be displayed is 17 ^3. However, since the number of subfield groups is 1, the background luminance is 33% of the display in the first frame structure. It can be reduced to the extent.

FIG. 6 is a voltage waveform diagram showing an example of the driving sequence. Here, the first frame configuration is shown as a representative, but the drive waveforms of the periods TR, TA, and TS are the same in the second and third frame configurations. However, the number of pulses in the sustain period TS is almost proportional to the weight of brightness.

In the addressing preparation period TR,
By the first step of applying the positive voltage pulse Pr to the main electrode X and the second step of applying the positive voltage pulse Prx to the main electrode X and the negative voltage pulse Pry to the main electrode Y. , Wall charges having a predetermined polarity are formed in the previously lighted cell and the previously unlighted cell. In the first process, the address electrode A is biased to a positive potential to prevent unnecessary discharge between the address electrode A and the main electrode X. Following the second process, in order to improve the uniformity of charging, a positive voltage pulse Prs is applied to the main electrode Y to cause surface discharge in all cells. This surface discharge reverses the charging polarity. After that, the potential of the main electrode Y is gradually reduced in order to avoid the disappearance of charges.

In the addressing period TA following the addressing preparation period TR, a negative scan pulse Py is applied to the main electrode Y to be selected in order to select each line one by one from the head line. Simultaneously with the selection of the line, a positive address pulse Pa is applied to the address electrode A corresponding to the cell to be unlit (the non-lit cell this time). In the cell to which the address pulse Pa is applied in the selected line, the opposing discharge occurs between the main electrode Y and the address electrode A, and the dielectric layer 17
Wall charge disappears. Since positive wall charges exist near the main electrode X at the time of applying the address pulse Pa,
The address pulse Pa is canceled by the wall voltage, and no discharge occurs between the main electrode X and the address electrode A. Unlike the writing method, the erasing type addressing does not require charge reformation and thus is suitable for speeding up.

In the sustain period TS, all the address electrodes A are biased to the positive potential in order to prevent unnecessary discharge, and the positive sustain pulse Ps is first applied to all the main electrodes X. After that, the sustain pulse Ps is alternately applied to the main electrode Y and the main electrode X. In this embodiment, the final sustain pulse Ps is applied to the main electrode Y. By the application of the sustain pulse Ps, surface discharge is generated in the cell in which the wall charge remains in the addressing period TA (currently lit cell).

In the addressing period TA following the sustain period TS, the voltage pulse Pr is applied to the main electrode X and the voltage pulse Prs is applied to the main electrode Y for the purpose of adjusting the charge distribution. Then, similarly to the addressing preparation period TR, the potential of the main electrode Y is gradually reduced,
After that, line-sequential addressing is performed as in the first addressing period TA.

Next, a description will be given of how to select the frame structure applied to the display of each frame F. FIG. 7 is a diagram for explaining a method of discriminating the luminance distribution. In the example of FIG. 7, it is determined which of the first to third frame configurations should be applied to the luminance distribution based on the characteristic amount of the luminance distribution. For example, when the 90% point of the luminance histogram is the feature amount, the feature amount is smaller than the first threshold value (16) in the distribution (a) biased near the lowest luminance. This threshold is the maximum brightness that can be represented by the third frame configuration in FIG. The third frame configuration is applied to the frame having such a distribution (a). In the distribution (b) biased to the low luminance side, the feature amount is a value between the threshold value (16) and the threshold value (80). Distribution (b)
The second frame structure is applied to the frame.
In the distribution (c) extending from low brightness to high brightness, the feature amount is larger than the threshold value (80). The first frame structure is applied to the frames of this distribution (c).

The feature amount is not limited to the 90% point, and the frame structure may be selected based on another point such as the 95% point or the 100% point. Further, the threshold value is not limited to 16 and 80, and may be any value close to the maximum value of the brightness that can be expressed in each frame configuration. However, when the value is set to a value larger than the maximum value, the gradation on the higher brightness side is rounded to the maximum value, so it is desirable to set it to a value smaller than the maximum value. The matters regarding these threshold values are similarly applied to the following determination method. As a form of calculating the luminance distribution, it may be calculated in a unit of one frame or in a unit of a plurality of frames. In the latter case, there is the following effect in addition to the reduction of the background brightness. That is, when paying attention to a plurality of consecutive frames, it is possible to avoid the flicker of the background luminance caused by switching the frame configuration for each frame when the feature amount varies near the threshold value.

By the way, in the present embodiment, as described above, the luminance distribution is calculated for each color of R, G, B for one frame F. The frame configuration is selected based on one of the luminance distributions for each color.

FIG. 8 is a diagram showing an example of the luminance distribution of three colors. When selecting the frame configuration, it is determined whether the characteristic amount (for example, 90% point) of the luminance distribution for each color of R, G, and B falls within the range of less than 16, more than 16 and less than 80, or more than 80. Then, the frame configuration for the frame F is selected by paying attention to the luminance distribution of the color whose range including the feature amount is the highest luminance side. In the example of FIG. 8, attention will be paid to the brightness distribution of B in which the 90% point is 80 or more.

9 and 10 are diagrams for explaining another example of the method of discriminating the luminance distribution. First, for each of the preset threshold values (16) and (80), the ratio of the number of pixels having a luminance lower than that to the total number of pixels is obtained. In the illustrated example, the former is 20% and the latter is 97%. Next, the magnitude relationship between the calculated ratio and the ratio setting threshold of 90% is checked. Since the relationship between the 90% point of the luminance distribution and the threshold values (16) and (80) is known from the magnitude relationship, the frame configuration is selected according to the relationship, as in the example of FIG. 7. In the example of FIG. 9, the 90% point is from the threshold value (16) to the threshold value (8
The second frame configuration is selected because it is within the range up to 0). Note that instead of obtaining the ratio of the number of pixels having the luminance equal to or lower than the threshold to the total number of pixels, a method of comparing the number of pixels having the luminance equal to or lower than the threshold with the set threshold may be adopted. Figure 1
In the example of 0, the 90% point of the histogram is within the range from the threshold (16) to the threshold (80) for R and G, and within the range from the threshold (80) to the predetermined value (251) for B. Therefore, in this case, the first frame configuration is selected.

FIG. 11 and FIG. 12 are diagrams showing an example of the luminance distribution with different number of target frames. Plasma display device 1
In, the luminance distribution to be determined is switched depending on whether the target frame is similar to the adjacent frame (this is equivalent to switching the target frame for calculating the luminance distribution). That is, when the degree of similarity is greater than the threshold and the determination data D93 indicates similarity (a series of frames is regarded as a video of a continuous scene), the frames are calculated based on the luminance distribution calculated for a plurality of frames. A configuration is selected. On the other hand, when the determination data D93 indicates dissimilarity (when the scene changes significantly), the frame configuration is selected based on the brightness distribution calculated only for the target frame. In this way, by changing the selection form of the frame configuration according to the result of the similarity determination,
In continuous scenes, it is possible to avoid image distortion due to a change in the brightness of the background portion when the image feature amount changes in the vicinity of the threshold for frame configuration selection.

According to the above embodiment, the result of the frame similarity determination is reflected in the switching of the frame structure.
It is possible to realize a display with less disorder. However,
The similarity determination circuit 93 may be omitted, and the optimum frame configuration may be selected only according to the result of the determination of the luminance distribution. Further, it is not always necessary to select the frame configuration for each frame, and it is possible to reduce the background brightness even if the frame configuration is selected in units of two or more frames. Although erase addressing is illustrated in the above embodiment, the present invention is also applicable to write addressing.

Objects to be displayed according to the present invention include interlaced images represented by television images. In the NTSC system, one frame F is composed of an odd field f1 and an even field f2 as shown in FIG. In the display by PDP1, each field is divided into a predetermined number of subfields.

By the way, the image signal of the odd-numbered field f1 and the image signal of the even-numbered field f2 are very similar to each other, and the luminance distribution obtained from either one of the image signals is the image for one frame composed of both fields. The brightness distribution obtained from the signal is almost the same. Therefore, when the input signal to the plasma display device 100 is an interlaced signal, it is sufficient to calculate the luminance distribution based on the image signal of any one field forming one frame. The method of calculating the luminance distribution of the frame of interest by paying attention to only the image signal of one field is advantageous in that the scale of the calculation circuit can be reduced and the calculation time can be shortened.

[0053]

According to the first to eleventh aspects of the present invention, it is possible to realize a display having a good contrast regardless of whether the frame is bright or dark.

According to the fifth aspect of the present invention, it is possible to avoid the display disturbance due to the change in the brightness of the background portion in continuous scenes. According to the invention of claim 4 or claim 11 , when the input signal is an interlaced signal, the circuit cost can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a plasma display device according to the present invention.

FIG. 2 is an exploded perspective view showing an internal structure of a PDP according to the present invention.

FIG. 3 is a diagram showing a first frame configuration.

FIG. 4 is a diagram showing a second frame configuration.

FIG. 5 is a diagram showing a third frame configuration.

FIG. 6 is a voltage waveform diagram showing an example of a drive sequence.

FIG. 7 is a diagram for explaining a method of discriminating a luminance distribution.

FIG. 8 is a diagram showing an example of luminance distribution of three colors.

FIG. 9 is a diagram for explaining another example of the method of discriminating the luminance distribution.

FIG. 10 is a diagram for explaining another example of the method of discriminating the luminance distribution.

FIG. 11 is a diagram showing an example of a luminance distribution in which the number of target frames is different.

FIG. 12 is a diagram showing an example of a luminance distribution in which the number of target frames is different.

FIG. 13 is a diagram showing a calculation form of a luminance distribution in the case of an interlaced signal.

[Explanation of symbols]

100 Plasma display device (display device) F frame SF1-16 subfield C cell TA addressing period TS sustain period (lighting maintenance period) TR addressing preparation period 91 Brightness distribution calculation circuit (distribution calculation circuit) 92 Luminance distribution discrimination circuit (distribution discrimination means) 81 controller (control means) 93 similarity determination circuit (similarity determination means)

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-11-231825 (JP, A) JP-A-11-219152 (JP, A) JP-A-11-119730 (JP, A) JP-A-10- 161589 (JP, A) JP 10-42137 (JP, A) JP 7-298161 (JP, A) JP 7-49663 (JP, A) JP 6-259034 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G09G 3/20 641 G09G 3/20 612 G09G 3/20 642 G09G 3/28

Claims (11)

(57) [Claims] 1. One frame is composed of three or more subfields weighted with brightness, and an addressing period for setting necessity of lighting of each cell and a lighting maintaining period for maintaining a lighting state are provided for each subfield. allocation, and divides the set of subfields of one frame into one or more sub-field group, performs gradation display by assigning a first address preparation period for equalizing charge state of the entire screen of the subfolder I Rudo group A display device, a distribution calculation means for calculating a luminance distribution of one or more frames including a frame of interest, and a total number of pixels having a value within the set range of the calculated luminance distribution.
And a set threshold value, and one of a plurality of frame configurations in which the number of subfield groups is different is selected according to the result of the determination of the brightness distribution. A display device comprising: a control unit applied to gradation display. Wherein said distribution calculating means, according to claim 1 Symbol placement of the display device calculates the luminance distribution in each frame. Wherein said distribution calculating means, according to claim 1 Symbol placement of the display device calculates a luminance distribution in a plurality frames. 4. One or more frames are weighted by 3 or more.
It consists of sub-fields and sets whether or not each cell needs to be turned on
Addressing period and lighting state
Allocating period and sub-field for each sub-field and 1 frame
Minute sub-field set to one or more sub-fields
Divide into groups and charge the entire screen at the beginning of the subfield group
Allocating an addressing preparation period to equalize the state
A display device that performs gradation display, and calculates the luminance distribution of one or more frames including a target frame
And a brightness that determines the calculated brightness distribution according to the setting conditions.
The number of subfield groups depending on the discrimination means and the result of discrimination of the luminance distribution.
Select one of several frame configurations with different
Equipped with control means applied to the gradation display of the frame of interest
If the input signal is an interlaced signal, the brightness distribution of one or more frames calculated by the distribution calculating means is calculated from the brightness distribution of either the even field or the odd field that constitutes each frame. A display device characterized by the above. 5. One frame is composed of three or more subfields weighted with brightness, and an addressing period for setting the necessity of lighting of each cell and a lighting maintaining period for maintaining a lighting state are provided for each subfield. allocation, and divides the set of subfolder I Rudo for one frame into one or more sub-field group, the gray scale display by assigning an address preparation period for initially equalizing the charge state of the entire screen of the subfolder I Rudo group A display device for performing the similarity determination means for determining whether or not a frame of interest among frames arranged in time series is similar to at least one frame adjacent thereto, a luminance distribution of the frame of interest, and Distribution calculation means for calculating the brightness distribution of a plurality of consecutive frames including frames, and brightness for judging the calculated brightness distribution according to the setting conditions. One of a plurality of frame configurations in which the number of subfield groups is different according to the result of the determination of the luminance distribution of the target frame when the degree determining unit and the frame adjacent to the target frame are not similar to each other. Is applied to the gradation display of the target frame, and when the target frame and the adjacent frames are similar, the plurality of frames are determined according to the result of the determination of the luminance distribution of the plurality of consecutive frames. A display device comprising: a control unit that selects one of the configurations and applies the gray scale display of the target frame. 6. The display according to claim 5 , wherein the brightness determining means determines at least one of the brightness distribution of the frame of interest and the brightness distribution of the plurality of consecutive frames by comparing the feature amount with a set threshold value. apparatus. 7. The brightness determining means determines at least one of the brightness distribution of the frame of interest and the brightness distribution of the plurality of consecutive frames by comparing the number of pixels having a value within a setting range with a setting threshold. The display device according to claim 5 . 8. The brightness determining means sets at least one of the brightness distribution of the frame of interest and the brightness distribution of the plurality of consecutive frames as a ratio of a ratio of pixels having a value within a setting range to the total number of pixels and a setting threshold. Claims determined by comparison
5. The display device according to item 5 . 9. A frame is a color image composed of three planes having different display colors, the distribution calculation means calculates a luminance distribution for each plane, and the control means controls a plane having the widest luminance distribution range. depending on the result of the determination of the luminance distribution, the display device according to any one of claims 1 to 8 for selecting a said frame structure. 10. The set threshold value is a maximum value of luminance reproducible in each of the frame configurations or a value close thereto.
1 or the display device according to any one of claims 6 to 8 . 11. When the input signal is an interlaced signal, the brightness distribution of the frame of interest and the brightness distribution of a plurality of frames including the frame of interest are either even or odd fields forming each frame. The display device according to claim 5 , wherein the display device is calculated from the luminance distribution.