KR20080040253A - Image processing method for display device - Google Patents

Abstract

A method for processing images of a display device is provided to determine the magnitude and applying time of data voltages by analyzing the contents of images inputted from the outside. Image data of a frame is received and a gray scale value corresponding to the image data is extracted(310,320). By comparing the extracted gray scale value with a reference gray scale value, the number of pixels within a reference gray scale range are counted(330). It is determined whether the image data has one gray scale value or plural gray scale values based on the counted pixel numbers(340,350). When the image data has the one gray scale value, a first voltage is outputted during a first frame sustain time. When the image data has plural gray scale values, a second voltage less than the first voltage is outputted during a second frame sustain time longer than the first frame sustain time(360a,360b,360c). Images are displayed in response to the first and second voltages(370a,370b,370c).

Description

  Image processing method of display device {IMAGE PROCESSING METHOD FOR DISPLAY DEVICE}

In order to more fully understand the drawings used in the detailed description of the invention, a brief description of each drawing is provided.

1 is a partial cross-sectional view showing an example of a display device according to the present invention.

FIG. 2 is a block diagram illustrating an example of the display device illustrated in FIG. 1.

3 is a floor chart illustrating a method of driving the display device shown in FIG. 2.

FIG. 4 is a diagram illustrating waveforms of voltages output from the data driving circuit shown in FIG. 2.

The present invention relates to a method of driving an electrophoretic display device, and more particularly, to a method of driving an electrophoretic display device driven at low power.

An electrophoretic display is a display device having a bistable display type that substantially maintains an image without consuming power after image updating. The electrophoretic display displays frames corresponding to several to several tens of images on the display screen in order to display a plurality of gray scale images, for example, 16 gray scale images. That is, various gray levels are expressed according to the length of time that a voltage having a constant magnitude is applied to a corresponding pixel.

Therefore, in order to increase the number of gradation levels or the accuracy of the gradation levels, more frame sections must be secured. However, as the frame period increases, the time for which the voltage is applied increases. As a result, the total power consumption of the electrophoretic display device is increased.

Accordingly, an object of the present invention is to provide an image processing method of a display device which can reduce power consumption.

In order to achieve the above technical problem, the display device driving method of the present invention receives image data of one frame and extracts a gray value corresponding to the image data in pixel units. The number of pixels corresponding to the reference gray scale range is counted by comparing the extracted gray scale value with a preset reference gray value. Subsequently, it is determined whether the input image data is image data having one gray level value or image data having a plurality of gray level values based on the counted number of pixels. If the corresponding image data is image data having one gray level value, the preset first voltage is output for a first frame holding time corresponding to the gray level value of the image data having one gray level value. If the corresponding image data is image data having a plurality of gray scale values, the image data is less than the first voltage for a second frame holding time longer than the first frame holding time corresponding to the gray scale values of the plurality of gray scale values. The second preset voltage is output. An image is displayed in response to any one of the first voltage and the second voltage.

According to the image processing method according to the present invention, it is possible to reduce the total power consumption of the electrophoretic display device by adjusting the size and the application time of the data voltage according to the content of the input image.

In order to fully understand the present invention, the operational advantages of the present invention, and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings which illustrate preferred embodiments of the present invention and the contents described in the accompanying drawings. In understanding the drawings, it should be noted that like parts are intended to be represented by the same reference numerals as much as possible. In addition, in the following description, numerous specific details, such as specific processing flows, are described to provide a more general understanding of the invention. Incidentally, detailed descriptions of well-known functions and configurations that are determined to unnecessarily obscure the subject matter of the present invention will be omitted.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

BACKGROUND ART As a display device without its own light emitting means, an electrophoretic display device using an electrophoretic phenomenon is widely known. Here, the electrophoresis phenomenon is a phenomenon in which microcapsules in which fine particles (electrophoretic particles) are dispersed in a dispersion medium are moved by an external electric field.

In such an electrophoretic display device, a microcapsule in which one electrode and the other electrode are opposed to each other at predetermined intervals, and the electrophoretic particles are enclosed therebetween is disposed. In addition, the electrophoretic display includes a driving unit for applying an electric field to the microcapsules.

1 is a partial cross-sectional view showing an example of a display panel provided in the electrophoretic display of the present invention.

Referring to FIG. 1, the display panel includes a first substrate 100 and a second substrate 200 facing the first substrate 100. On the first substrate 100, a plurality of pixel electrodes 104 arranged in a matrix form is provided. On the second substrate 200, a common electrode 201 is provided. The first substrate and the second substrate are spaced at regular intervals, and are disposed to face each other so that the electrode surfaces face each other. In this interval, microcapsules 15 are provided that are divided into predetermined sizes for pixels, which are display units of an image, and contain electrophoretic particles.

The microcapsules may include various types of electrophoretic particles and a dispersion medium 11. For example, black electrophoretic particles 12b having negative charges and white electrophoretic particles 12w having electrostatic charges are used as the electrophoretic particles 12.

As for the dispersion medium 11, additives, such as surfactant, are added as needed. The specific gravity of the dispersion medium 11 and the specific gravity of the electrophoretic particles 12 are set to be substantially the same so as to avoid precipitation due to gravity of the electrophoretic particles 12. As such, the region in which the electrophoretic particles 12 can be moved is limited inside the microcapsules 15. As a result, it is possible to prevent the phenomenon of pulling the electrophoretic particles 12 in the microcapsules and agglomeration into large lumps.

On the surface of the first substrate 100, a peripheral area provided with a display area and a peripheral circuit is provided. On the display area, a thin film transistor (hereinafter referred to as TFT) serving as a scanning line, a data line and a switching driving element described later is provided. On the peripheral region of the first substrate 100, a gate driving circuit, a data driving circuit, and the like described later are provided.

Hereinafter, the operation in the case where a voltage is applied to the pixel electrode 104 will be described.

When a potential difference occurs between the electrode of the pixel electrode 104 and the common electrode 201, the electrophoretic particles 12 charged along the direction of the electric field move to either electrode. Here, when the electrophoretic particles 12 are composed of colored particles and a material having transparency is used as the common electrode 201 and the second substrate 200, the electrophoretic particles 12 arranged on the second substrate 200 side. ) Will be visible. Therefore, an image can be displayed by controlling the voltage applied to each electrode.

Hereinafter, the principle of the gray scale display of the electrophoretic display device will be described.

In order to update from an existing image to a new image, the electrophoretic display performs a kind of reset operation. In this reset operation, electrophoretic particles 12 are arranged on either electrode. At this time, when a negative voltage is applied to the pixel electrode 104 on the basis of the voltage of the common electrode 201, the white electrophoretic particles 12w that are surely charged are arranged on the pixel electrode 104 and charged with positive charge. The black electrophoretic particles 12b are arranged on the common electrode 201.

When a voltage of polarity corresponding to an arbitrary gradation level is applied to the pixel electrode 104, the electrophoretic particles 12 move toward both electrodes according to the electric field.

When the electric field between both electrodes is removed after a certain time has elapsed, the electrophoretic particles 12 are stopped by the viscous resistance of the dispersion medium 11. At this time, the moving speed of the electrophoretic particles 12 is determined according to the electric field strength, that is, the applied voltage. The moving distance of the electrophoretic particles 12 is determined according to the applied voltage and the applied time. Therefore, if application time is made constant, the position in the up-down direction of the electrophoretic particle 12 can be controlled by adjusting an application voltage.

Light incident through the common electrode 201 is reflected by the electrophoretic particles 12, and the reflected light is again observed through the common electrode 201.

Incident light and reflected light are absorbed in accordance with the dispersion medium 11, and the degree of absorption is proportional to the optical path length. Therefore, when observed from the common electrode 201, the gradation can be determined according to the position of the electrophoretic particle 12. As mentioned above, since the position of the electrophoretic particle 12 is determined according to the applied voltage, desired gradation display can be performed by adjusting the applied voltage.

FIG. 2 is a block diagram illustrating an example of the electrophoretic display shown in FIG. 1.

Referring to FIG. 2, an electrophoretic display device (hereinafter, referred to as a display device) according to the present invention includes a display panel 100, a controller 300, and a scan provided with a plurality of pixels 22 arranged in a matrix. The driving circuit 400 and the data driving circuit 500 are included.

The scan driving circuit 400 is electrically connected to the plurality of pixels through the scan electrode 42. The data driving circuit 500 is electrically connected to the plurality of pixels through the data electrodes 52.

The controller 300 is electrically connected to the scan driving circuit 400 and the data driving circuit 500, respectively. The controller 300 transmits command signals to the scan driving circuit 400 and the data driving circuit 500, and controls the scan driving circuit 400 and the data driving circuit 500 through the command signals.

The plurality of pixels 22 are provided with a constant potential when selected by the scan driving circuit and the data driving circuit. And it is activated by placing the predetermined charge 34 at either polarity of the pixel PX, while the common electrode 26 exhibits zero volts or other suitable potential.

Each of the plurality of pixels forms a capacitor consisting of a pixel electrode 104 and a common electrode 201 opposite the pixel electrode 104. The pixel will transition from one optical state to another while this capacitor is charged.

Each electrophoretic pixel 22 in the electrophoretic pixel array 100 is electrically connected on one side to a common electrode 26 based on, for example, ground or zero volts. The predetermined charge 34 is disposed on the pixel electrode 36 on the other side of the electrophoretic pixel 22 to drive the electrophoretic pixel 22 to the desired optical state. For example, the positive charge 34 of the pixel PX electrode causes the pixel PX to be white, while the negative charge 34 disposed on the electrophoretic pixel electrode 104 causes the pixel to be dark. do. Removal of charge by discharge freezes the pixel in the obtained optical state.

Hereinafter, a driving method of the display device according to the present invention will be described.

 In the present specification, the display device is referred to as a driving method. However, the display device may be an image updating method of a display device that changes from an existing image to a new image. In addition, the display device to which the driving method according to the present invention is applied will be described as being limited to the display device having the 16 gray scale. However, it is a matter of course that the idea of the present invention can be sufficiently applied to a display device having a larger gray scale scale, for example, 256 gray scale.

3 is a floor chart illustrating a method of driving the display device illustrated in FIG. 2, and FIG. 4 is a view illustrating waveforms of voltages output from the data driving circuit 300 included in the display device of the present invention.

3 and 4, according to an image processing method of a display device according to an exemplary embodiment of the present disclosure, when image data is input from an external system (S310), a gray value corresponding to the input image data is pixel-based. Extracted to (S320). External systems include conventional graphics controllers (not shown) or any other system that generates and outputs graphical information.

 Thereafter, the extracted grayscale value is compared with a preset reference grayscale value to count the number of pixels corresponding to the reference grayscale range (S330). The input image is composed of one grayscale based on the number of counted pixels. It is determined whether the image is data or a plurality of gray scales.

In detail, when the number of counted pixels is smaller than the number of reference pixels, the corresponding image is determined as an image having one gray level. If the number of counted pixels is greater than the reference number of pixels, the corresponding image determines an image having a plurality of gray levels (S340).

In other words, the image including the text is composed of only one single gray scale, which is a black gray scale. An image, such as an image image, is composed of a plurality of gradations including gray scales.

If the corresponding image is determined as an image having a plurality of gray scales, it is determined whether the lowest gray level value of the corresponding video is '0' (S350).

When the input image data is determined as image data having the same gray value, that is, a character image, a preset first voltage DS1, for example, a maximum data voltage (about 15 V) is provided from the data driving circuit 500 to the display panel. do. In this case, the maximum data voltage (the first voltage set in advance) is provided to each pixel of the display panel for a predetermined time period as the first frame holding time FT1 (S360a).

As described above, in the conventional electrophoretic display, various gray levels are expressed depending on the application time of the voltage. For example, in order to express black gradation, a data voltage of about 7V is continuously applied to each pixel for 16 frame sections, thereby finally implementing black gradation. However, according to the image processing method of the present invention, if it is determined that the input image is an image composed of one black gradation such as text, as shown in FIG. Instead, the holding time at which a voltage of 15V is provided to the pixel is greatly reduced. In other words, it is more economical in terms of power consumption to maintain a voltage of 15 volts only for a short period of about 2 to 3 frames than to maintain a voltage of 7 volts for 16 frames.

On the other hand, if the corresponding image data is image data having a plurality of gray scale values, the second frame holding time (longer than the first frame holding time FT1 corresponding to the gray scale values of the image data having a plurality of gray scale values ( During the FT2, a preset second voltage DS2 smaller than the first voltage DS1 is output (S360b and S360c).

When the input image data is determined as image data having a plurality of gray scale values, that is, image images, a preset second voltage DS2, for example, a data voltage of 7 volts, is provided from the data driving circuit 500 to the display panel. In this case, the data voltage of the 7 volts (the preset second voltage) is provided to each pixel of the display panel for a preset time as the second frame holding time FT1 (S360b and S360c).

Here, when the lowest gray value of the input image is not '0', the data voltage DS2 of the above 7 volt is provided from the data driving circuit 40 to the display panel 10 only until a frame in which the gray level can be expressed. .

If the lowest gray value of the input image is '0', the data is provided from the data driving circuit 40 to the display panel 10 in accordance with a preset gray scale expression method using the voltage magnitude of the second voltage.

The display panel displays a corresponding image in response to any one of the first voltage DS1 and the second voltage DS2 provided through S360a, S360b, and S360c (S370a, S370b, and S370c).

According to the driving method of the electrophoretic display device according to the present invention as described above, it is possible to reduce the total power consumption of the electrophoretic display device by adjusting the magnitude and the application time of the data voltage according to the content of the input image.

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

Claims (6)

Receiving image data of one frame and extracting a gray value corresponding to the image data in pixel units; Counting the number of pixels corresponding to a reference gradation range by comparing the extracted gradation value with a preset reference gradation value; Determining whether the input image data is image data having one gray scale value or image data having a plurality of gray scale values based on the counted number of pixels; If the corresponding image data is image data having one gray level value, an image of a preset first voltage is output for a first frame holding time corresponding to the one gray level value, and the image data has a plurality of gray values. Outputting a predetermined second voltage corresponding to the plurality of gray values and being smaller than the first voltage for a second frame holding time longer than the first frame holding time; And And displaying an image in response to any one of the first voltage and the second voltage. The image processing method of claim 1, wherein the first frame holding time is shortened as the magnitude of the first voltage increases. The display apparatus of claim 1, wherein the image data having one gray level value is image data corresponding to a text image, and the image data having a plurality of gray level values is image data corresponding to an image image. Image processing method. 4. The image processing method of claim 3, wherein the one gray value is a value corresponding to a black gray level.  The method of claim 1, wherein the first voltage is about 15 volts and the second voltage is about 7 volts. The method of claim 1, And the reference gray scale ranges from 10% to 90% of the entire gray scale range.

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