KR20050052192A - Error diffusion device for display panel - Google Patents

Abstract

An error diffusion device for a display panel of the present invention includes: a quantization unit for quantizing and outputting input data by a predetermined threshold value; A subtractor for calculating an error by subtracting the data after quantization from the data before quantization; An error diffusion filter that propagates the error to peripheral pixels; An error diffusion weight determination unit adapted to vary the weight of the error diffusion filter adaptively to the gray level of the input data; And an adder for adding the input data and the output of the error diffusion filter and outputting them to the quantization unit.

According to the panel driving apparatus of the present invention, in the conventional error diffusion used in the PDP, by using the same filter at all times regardless of the gray scale, the problem that an abnormal pattern occurs in a specific gray scale is solved. That is, by applying the optimized error filter adaptively according to the gray level of the input data, it is possible to remove the abnormal pattern generated in the specific gray level.

Description

Error diffusion device for display panel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a display panel such as a plasma display panel (PDP), and more particularly to an error diffusion device for performing error diffusion in a panel driving device.

1 is a view showing the structure of a conventional three-electrode surface discharge plasma display panel.

Referring to FIG. 1, between the front and rear glass substrates 100 and 106 of a conventional surface discharge plasma display panel 1, address electrode lines A ₁ , A ₂ ,..., A _m , Dielectric layers 102 and 110, Y electrode lines Y ₁ , ..., Y _n , X electrode lines X ₁ , ..., X _n , fluorescent layer 112, barrier rib 114, and As a protective layer, the magnesium monoxide (MgO) layer 104 is provided, for example.

The address electrode lines A ₁ , A ₂ ,..., A _m are formed in a predetermined pattern on the front side of the rear glass substrate 106. The lower dielectric layer 110 is applied in front of the address electrode lines A ₁ , A ₂ ,..., A _m . In front of the lower dielectric layer 110, barrier ribs 114 are formed in a direction parallel to the address electrode lines A ₁ , A ₂ ,..., A _m . The partition walls 114 function to partition the discharge area of each display cell and to prevent optical interference between the display cells. The fluorescent layer 112 is formed between the partition walls 114.

The X electrode lines X ₁ , ..., X _n and the Y electrode lines Y ₁ , ..., Y _n are address electrode lines A ₁ , A ₂ , ..., A _m . It is formed in a predetermined pattern on the back of the front glass substrate 100 to be orthogonal to the. Each intersection sets a corresponding display cell. Each X electrode line (X ₁ , ..., X _n ) and each Y electrode line (Y ₁ , ..., Y _n ) are transparent electrode lines (X _na ) made of a transparent conductive material such as indium tin oxide (ITO). , Y _na ) and metal electrode lines X _nb and Y _nb for increasing conductivity may be formed. The front dielectric layer 102 is formed by applying the entire surface to the rear of the X electrode lines (X ₁ ,..., X _n ) and the Y electrode lines (Y ₁ ,..., Y _n ). A protective layer 104 for protecting the panel 1 from a strong electric field, for example, a magnesium monoxide (MgO) layer, is formed by applying a front surface to the back of the front dielectric layer 102. The plasma forming gas is sealed in the discharge space 108.

A driving scheme generally applied to such a plasma display panel is a method in which initialization, address, and display holding steps are sequentially performed in a unit sub-field. In the initialization step, the charge states of the display cells to be driven are made uniform. In the address step, the charge state of display cells to be selected and the charge state of display cells not to be selected are set. In the display holding step, display discharge is performed in the display cells to be selected. At this time, a plasma is formed from the plasma forming gas of the display cells performing display discharge, and the fluorescent layer 112 of the display cells is excited by ultraviolet radiation from the plasma to generate light.

2 illustrates a general driving device of the plasma display panel of FIG. 1.

Referring to the drawings, a typical driving device of the plasma display panel 1 includes an image processor 200, a controller 202, an address driver 206, an X driver 208, and a Y driver 204. The image processing unit 200 converts an external analog image signal into a digital signal, and internal image signals, for example, 8-bit red (R), green (G) and blue (B) image data, clock signals, vertical and horizontal, respectively. Generate synchronization signals. The controller 202 generates the driving control signals SA, SY, and SX according to the internal image signal from the image processor 200. The address driver 206 processes the address signal SA among the drive control signals SA, SY, and SX from the controller 202 to generate a display data signal, and generates the display data signal through the address electrode lines. To apply. The X driver 208 processes the X driving control signal SX among the driving control signals SA, SY, and SX from the controller 202 and applies the X driving control signal SX to the X electrode lines. The Y driver 204 processes the Y driving control signal SY among the driving control signals SA, SY, and SX from the controller 202 and applies the Y driving control signal SY to the Y electrode lines.

FIG. 3 illustrates a conventional address-display separation driving method for Y electrode lines of the plasma display panel of FIG. 1.

Referring to the drawings, a unit frame may be divided into a predetermined number, for example, eight subfields SF1, ..., SF8 to realize time division gray scale display. Each subfield SF1, ..., SF8 is divided into a reset section (not shown), an address section A1, ..., A8, and a sustain discharge section S1, ..., S8. do.

In each address section A1, ..., A8, a display data signal is applied to the address electrode lines AR1, AG1, ..., AGm, ABm in FIG. Scan pulses corresponding to..., Yn) are sequentially applied.

In each sustain discharge section S1, ..., S8, pulses for display discharge alternately in the Y electrode lines Y1, ..., Yn and the X electrode lines X1, ..., Xn. Is applied to cause display discharge in discharge cells in which wall charges are formed in the address periods A1, ..., A8.

The luminance of the plasma display panel is proportional to the number of sustain discharge pulses in the sustain discharge sections S1, ..., S8 occupied in the unit frame. When one frame forming one image is represented by eight subfields and 256 gray levels, each subfield is sequentially held at a ratio of 1, 2, 4, 8, 16, 32, 64, and 128 in order. The number of pulses can be assigned. In order to obtain luminance of 133 gray levels, cells may be addressed and sustained and discharged during the subfield 1 period, the subfield 3 period, and the subfield 8 period.

The number of sustain discharges allocated to each subfield may be variably determined according to the weights of the subfields according to the APC (Automatic Power Control) step. In addition, the number of sustain discharges allocated to each subfield is. Various modifications are possible in consideration of gamma characteristics or panel characteristics. For example, the gradation level assigned to subfield 4 may be lowered from 8 to 6, and the gradation level assigned to subfield 6 may be increased from 32 to 34. In addition, the number of subfields forming one frame can be variously modified according to design specifications.

The error spreader in the PDP is used to express a larger number of gray scales with a limited number of bits. The error spreader propagates the error generated during quantization to the surroundings so that a local average is maintained. The PDP applies an error diffusion device when quantizing 12-bit image data into 8 bits after inverse gamma correction.

4 is a block diagram for explaining a conventional error diffusion device, and includes an adder 402, a quantizer 406, a subtractor 404, and an error diffusion filter 400. As shown in FIG. FIG. 5 illustrates a Float-steinberg filter as an example of the error diffusion filter 400 illustrated in FIG. 4. In this case, for example, the filter of FIG. 5 is fixedly applied to the error diffusion filter 400 irrespective of input data. In the conventional error diffusion used in the PDP, there is a problem that an abnormal pattern occurs in a specific gray level by always using the same filter regardless of the gray level.

An object of the present invention is to provide an error diffusion device for a display panel that propagates an error adaptively to input data.

An error diffusion device for a display panel of the present invention for achieving the above technical problem, the quantization unit for outputting the quantized input data by a predetermined threshold value; A subtractor for calculating an error by subtracting the data after quantization from the data before quantization; An error diffusion filter that propagates the error to peripheral pixels; An error diffusion weight determination unit adapted to vary a weight of the error diffusion filter adaptively to the gray level of the input data; And an adder for adding the input data and the output of the error diffusion filter and outputting the input data to the quantization unit.

The error diffusion weight determination unit may determine a weight of the error diffusion filter adaptively to the gray level of the input data by using a lookup table.

When the input data is the lowest gray scale, the error diffusion weight determination unit is a weight of the error diffusion filter, which is 6/16 for the right pixel of the current pixel, 3/16 for the lower left pixel of the current pixel, and the bottom of the current pixel. 3/16 may be used for the pixel, and 4/16 may be used for the lower right pixel of the current pixel.

Hereinafter, the configuration and operation of an error diffusion device for a display panel according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The basic concept of panel driving according to the present invention is to perform error diffusion by differently determining the weight of the error filter according to the gray level of the input data.

FIG. 6 is a block diagram illustrating an error diffusion means according to an exemplary embodiment of the present invention. The diffusion filter part 604 is provided.

The quantization unit 608 quantizes and outputs the input data according to a predetermined threshold value. The threshold may be an intermediate value of the input gray level or an average signal level. In the PDP, in order to express a larger number of gray scales with a limited number of bits, inverse gamma correction generally uses a 12-bit lookup table and quantizes 12 bits into 8 bits. This quantization occurs with a data error of 4 bits.

The subtractor 610 subtracts the data after passing through the quantization unit 608 from the data before passing through the quantization unit 608 and outputs the data as errors 612 and E ^* .

FIG. 7 is a filter to which the weight determined by the error diffusion weight determining unit 600 shown in FIG. 6 is applied. The error diffusion filter 604 allows the error to be spread as shown in Equations 1 to 4 below, for example, when the filter of FIG. 7 is applied.

Here, IN2 is an adder 606 output, which is an input of the quantization unit 608.

The error diffusion weight determination unit 600 determines and outputs an adaptive weight according to the gray level of the input data IN. The error diffusion weight determination unit 600 may store the adaptive weight value according to the gray level as a lookup table shown in Table 1, for example.

W0 W1 W2 W3 Gradation 1 W _{0_1} W _{1_1} W _{2_1} W _{3_1} Gradation 2 W _{0_2} W _{0_2} W _{0_2} W _{0_2} … … … … … Gradation n-1 W _{0_n-1} W _{0_n-1} W _{0_n-1} W _{0_n-1} Gradation n W _{0_n} W _{0_n} W _{0_n} W _{0_n}

Referring to Table 1, gradation 1 to gradation n of the vertical axis are the gradation expressed after quantization. Considering the case where the quantization unit 608 quantizes the 12-bit input into 8 bits, for example, the error diffusion determining unit 600 determines the weight by referring to the upper 8 bits of the input data IN. Therefore, in this case, the final gradation n may be 255.

8 is an example of a frame or a local low gray scale input image (IN). The inner lattice pattern consists of data of gradation 1 when four bits are input to the error diffusion weight determination unit 600.

FIG. 10 illustrates an abnormal pattern generated when the conventional fixed error filter of FIG. 5 is applied to the low grayscale input data of FIG. 8. The quantization output in this case generates regular abnormal patterns that are deflected in the direction of the arrow. In other words, if (W0, W1, W2, W3) = (7/16, 3/16, 5/16, 1/16) is always applied equally as the weight of the error filter, the overall uniform low gray scale input data With respect to, the error spread unevenly to the surrounding pixels becomes noticeable to the human eye in an oblique direction.

FIG. 9 is an example of an error filter that may be applied to a specific pattern as shown in FIG. 8. For input data having a low gray level, FIG. 9 serves as a filter that spreads an error evenly to peripheral pixels.

FIG. 11 is a quantized output image when the low gradation error filter of FIG. 9 is applied to the low gradation input data of FIG. 8. As the error is spread evenly without being deflected, it can be seen that, for the uniform input data of low gradation, it looks relatively even without deflection.

As described above, when an optimized error filter that does not generate patterns in each gray scale is determined and a lookup table is applied, and an error filter is adaptively applied according to the gray scale of the input data, abnormalities occurring in a specific gray scale when a fixed error filter is used. Solve the problem of fringes.

The panel driving apparatus according to the present invention is made by a schematic or ultra high-speed integrated circuit hardware description language (VHDL) or the like on a computer, and is connected to a computer and programmed by an integrated circuit, for example, a field programmable gate array (FPGA). It can be implemented as a circuit.

The error diffusion device for the display panel of the present invention may be applied after performing inverse gamma correction, white balance correction, or the like on RGB input data. The error spreader in the PDP is used to express a larger number of gray scales with a limited number of bits. The error spreader propagates the error generated during quantization to the surroundings so that a local average is maintained. In the PDP, an error diffusion device is applied when quantizing 12-bit image data, for example, 8 bits after inverse gamma correction. The error diffusion device for the display panel according to the present invention may be implemented by being included in the logic controller 202 shown in FIG. 2 when applied to a PDP, for example.

The best embodiments have been disclosed in the drawings and specification above. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not used to limit the scope of the present invention as defined in the meaning or claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

As described above, according to the panel driving apparatus of the present invention, in the conventional error diffusion used in the PDP, by using the same filter at all times regardless of the gradation, the problem that an abnormal pattern occurs in a specific gradation is solved.

That is, by applying the optimized error filter adaptively according to the gray level of the input data, it is possible to remove the abnormal pattern generated in the specific gray level.

The invention is not limited to the examples described above and represented in the drawings. Those skilled in the art taught by the above-described embodiments, many modifications to the above-described embodiments are possible by substitution, erasure, merging, etc. within the scope and object of the present invention described in the following claims.

1 is a view showing the structure of a conventional three-electrode surface discharge plasma display panel.

FIG. 2 shows a typical driving apparatus of the plasma display panel shown in FIG. 1.

FIG. 3 shows a conventional address-display separation driving method for Y electrode lines of the plasma display panel of FIG. 1.

4 is a block diagram for explaining a conventional error diffusion means.

FIG. 5 illustrates a Float Steinberg filter as an example of the error diffusion filter illustrated in FIG. 4.

6 is a block diagram illustrating an error diffusion means according to an embodiment of the present invention.

FIG. 7 is a filter to which the weight determined by the error diffusion weight determining unit 600 shown in FIG. 6 is applied.

8 is an example of one frame or local low gradation input image.

FIG. 9 is an example of an error filter that may be applied to a specific pattern as shown in FIG. 8.

FIG. 10 illustrates an abnormal pattern generated when the conventional fixed error filter of FIG. 5 is applied to the low grayscale input data of FIG. 8.

FIG. 11 is a quantized output image when the low gray level error filter of FIG. 9 is applied to the low gray level input data of FIG. 8.

Claims (3)

A quantizer for quantizing and outputting the input data by a predetermined threshold value; A subtractor for calculating an error by subtracting the data after quantization from the data before quantization; An error diffusion filter that propagates the error to peripheral pixels; An error diffusion weight determination unit adapted to vary a weight of the error diffusion filter adaptively to the gray level of the input data; And And an adder configured to add the input data and the output of the error diffusion filter and output the output data to the quantization unit. The method of claim 1, wherein the error diffusion weight determination unit, And a lookup table to determine a weight of the error diffusion filter adaptively to the gray level of the input data. 3. The error diffusion weight determining unit of claim 2, wherein the error diffusion weight determination unit is a weight of the error diffusion filter. 6/16 for the right pixel of the current pixel, The lower left pixel of the current pixel has 3/16, The lower pixel of the current pixel is 3/16, Error diffusion device for a display panel, characterized in that 4/16 is used for the lower right pixel of the current pixel.