JP2009162944A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the cost by integration of a double speed converting circuit and an overdrive circuit by simultaneously performing a dark/light system double speed converting processing and overdrive processing in a liquid crystal display device. <P>SOLUTION: This liquid crystal display device includes: an image data storage part 181 for storing image data of one frame before prior to double speed conversion; a conversion table storage part 182 storing first and second look-up tables for generating high gray level data and low gray level data showing higher gray level than that of image data of a current frame, which are two-dimensional look-up tables where the gray levels of a predetermined number contrasted with the image data of the current frame before double speed conversion is related with the gray levels of a predetermined number contrasted with the image data of one frame before; and a double speed converting part 183 for generating high gray level data and low gray level data to the image data of the current frame with reference to the first and second look-up tables using the image data of one frame before and the image data of the current frame. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device having a double speed conversion function and an overdrive function.

  Conventionally, overdrive processing or double speed conversion processing has been used in order to improve the response speed of liquid crystal display devices and reduce the afterimage phenomenon. In Patent Document 1, image data generated by performing complementary processing on two preceding and following image data is inserted into image data with a frame rate of 60 Hz, the frame rate is converted to 120 Hz, and over 120 Hz image data. A technique for performing drive processing is disclosed.

  On the other hand, in Patent Document 2, image data once stored in a memory is read twice continuously to convert the frame rate to 120 Hz, and after being converted to 120 Hz, the polarity is inverted every frame. Thus, a technique is disclosed in which overdrive processing is simultaneously performed during forward rotation driving (when changing from dark to light) and during inversion driving (when changing from light to dark). However, Patent Document 2 relates to a liquid crystal display device in which a pixel electrode and a counter electrode are arranged on the same substrate and generates a voltage in parallel with the substrate.

  Further, in Patent Document 3, image data is doubled by scanning N times (for example, four times) during one field period of the video signal, and the image data is not directly given to the liquid crystal display panel. By comparing the image data of the frame with the image data of the current frame, referring to a look-up table (LUT) according to the difference, and giving the corrected image data to the liquid crystal display panel, the responsiveness of the liquid crystal display device is improved. Techniques for improving are disclosed.

  According to the technology disclosed in Patent Document 1, when there is no change or small image, such as a still image or a slow-moving image, overdrive processing is not performed, and gradation is disturbed in a still image or the like. There is nothing. However, according to Patent Document 1, for example, when an image is changed by panning or tilting by a camera, there is a problem in that image data for complementation is lost at the periphery of the screen and the image is distorted. ing. In addition, the calculation processing for creating complementary image data is complicated. In addition, a CPU capable of high-speed arithmetic processing is required, which increases costs.

  According to the technique disclosed in Patent Document 2, in order to prevent the overdrive process from being performed when there is no image change like a still image, the image data of the previous frame and the image data of the current frame are compared. However, the overdrive process is complicated.

  According to the technique disclosed in Patent Document 3, a look-up table is referred to according to the difference between the image data of the previous frame and the image data of the current frame. In addition to being able to perform processing, it is possible to prevent overdrive processing from being performed when the change in the image is small, such as a still image. However, since the double-speed conversion image data is corrected by referring to a lookup table and the corrected image data is given to the liquid crystal display panel, the double-speed conversion circuit and the overdrive circuit are configured separately. As a result, the circuit configuration becomes complicated and the cost increases.

  In recent years, as a new method of double speed processing, two consecutive image data (high gradation data) each showing a gradation higher and lower than the gradation indicated by the image data from one frame of image data before double speed conversion. In addition, a so-called light / dark double speed conversion has been proposed in which the frame rate is doubled.

  If the double-speed conversion processing and overdrive processing of the light / dark method are performed by separate circuits, the image data after the double-speed conversion repeats light and dark for each frame, so that overdrive processing is always performed even for still images. As a result, the average gradation of the two image data after the overdrive processing is the same as the average gradation of the two image data that has not been overdriven due to the asymmetry of the rising and falling characteristics of the liquid crystal display panel. Must not. That is, the gradation characteristic of the still image is disturbed by the overdrive process. When the overdrive process is not performed, the gradation characteristics of the still image are not deteriorated, but there is a conflicting problem that the afterimage feeling is enhanced in the moving image.

JP 2006-349952 A JP 2006-285092 A JP-A-5-73005

  The present invention was made in order to solve the problems in the above-described liquid crystal display device that performs double-speed conversion processing and overdrive processing of the light and dark method, and can perform double-speed conversion processing and overdrive processing at the same time. An object of the present invention is to provide a liquid crystal display device that does not perform overdrive processing when there is little change in an image such as a still image, and that can reduce costs by integrating a double speed conversion circuit and an overdrive circuit.

In order to achieve the above object, the invention of claim 1 is characterized in that, from one frame of image data before double-speed conversion, two consecutive high gradations each showing a gradation higher and lower than the gradation indicated by the image data. Liquid crystal that generates data and low gradation data, expresses the gradation of the current frame by the average gradation of the high gradation data and the low gradation data, and performs so-called light / dark double speed conversion that converts the frame rate to twice. In the display device,
An image data storage unit that stores image data of one frame before the current frame among the image data before double speed conversion;
A two-dimensional lookup table associating a predetermined number of gradation levels compared with image data of a current frame before double speed conversion and a predetermined number of gradation levels compared with image data of one frame before, A first lookup table for generating high gradation data indicating a gradation higher than the gradation indicated by the image data of the frame, and low gradation data indicating a gradation lower than the gradation indicated by the image data of the current frame. A conversion table storage unit that stores a second lookup table for generating;
High gradation data for the image data of the current frame by referring to the first look-up table and the second look-up table using the image data of the previous frame and the image data of the current frame stored in the image data storage unit, respectively. And a double speed conversion unit for generating low gradation data.

  According to a second aspect of the present invention, in the liquid crystal display device according to the first aspect, a liquid crystal display panel in which high gradation data and low gradation data are output as each value of the first lookup table and the second lookup table. The characteristic is characterized in that the value is determined in consideration of the response characteristic.

  According to the first aspect of the present invention, the high speed data and the low gradation data are not directly generated from the image data of the current frame by the double speed conversion unit, but the image data of the current frame and the image data of the previous frame are referred to. However, since the high gradation data and the low gradation data are generated in consideration of the value of the image data, that is, whether or not the gradation changes greatly, it is possible to perform the double speed conversion process and the overdrive process at the same time. In addition, the cost can be reduced by integrating the double speed conversion circuit and the overdrive circuit. Further, when the values of the first look-up table and the second look-up table are determined, the image data has not changed or the change is small between the image data of the current frame and the image data of the previous frame like a still image. A value can be set so as not to perform overdrive processing. Therefore, when there is little change in an image such as a still image, overdrive processing is not performed, and disturbance of the gradation characteristics of the still image can be prevented.

  According to the invention of claim 2, each value of the first look-up table and the second look-up table takes into account the response characteristics of the liquid crystal display panel to which high gradation data and low gradation data are output, Since the value is determined, the response speed can be improved more effectively by the overdrive process.

  When a liquid crystal display panel is purchased from another company as a component, the response characteristic of the liquid crystal display panel is unknown on the television (hereinafter referred to as TV) receiver side. It is provided on the display panel side. On the other hand, the double speed conversion circuit differs depending on the double speed conversion method, and is therefore provided on the TV receiver side. Therefore, the present invention can be realized only when the liquid crystal display panel is manufactured in an integrated manner.

  A liquid crystal display device according to an embodiment of the present invention will be described with reference to the drawings. As an example of the liquid crystal display device according to the present embodiment, a schematic configuration of a television (TV) receiver 1 using a liquid crystal display panel is shown in FIG.

  The TV receiver 1 includes a liquid crystal display panel 11, a drive unit 12 that drives the liquid crystal display panel 11, a speaker 13 that can output sound, a control unit 14 that controls the operation of each unit of the TV receiver 1, and an external device. A tuner 15 that selects a desired TV broadcast program received by the antenna, a terminal portion 16 that is provided so as to be exposed to the outside of the housing of the TV receiver 1, an apparatus main body, Consists of a receiving unit 17 for receiving an operation signal transmitted from a separate remote control device 9 and the like. Under the control of the control unit 14, the TV receiver 1 displays, for example, a TV broadcast program selected by the tuner 15 or an image / sound input from an external input device connected to the terminal unit 16 on a liquid crystal display. Viewing is possible through the panel 11 and the speaker 13. The terminal unit 16 is connected to an external device such as a DVD recorder 2 via an HDMI (High-Definition Multimedia Interface) cable or the like.

  The control unit 14 includes an image processing circuit 18, an audio processing circuit 19, and the like composed of a CPU, a ROM, a RAM, and other electronic components. The video signal of the program selected by the tuner 15, for example, the terminal unit 16 Based on a video signal or the like input from the connected DVD recorder 2, the drive unit 12 is controlled to display an image on the liquid crystal display panel 11.

  FIG. 2 shows a block configuration of the image processing circuit 18, particularly the image processing circuit 18 having a double speed conversion function and an overdrive function. The image processing circuit 18 stores an image data storage unit 181 for storing image data one frame before the current frame among the image data before double speed conversion, and a first lookup table and a second lookup table described later. The conversion table storage unit 182 and the double speed conversion unit 183 that performs overdrive processing as needed simultaneously with the double speed conversion processing.

  In the present embodiment, as the double speed conversion processing, two consecutive image data (high gradation data) each indicating a gradation higher and lower than the gradation indicated by the image data from one frame of image data before the double speed conversion. And low gradation data), and the so-called light / dark double speed conversion is performed to convert the frame rate to twice. When the overdrive process is not performed, the high gradation data and the low gradation data are stored so that the average gradation of the high gradation data and the low gradation data matches the gradation indicated by the image data of one frame before the double speed conversion. Each is decided.

  FIG. 3 is a waveform diagram showing an example of double speed conversion processing and overdrive processing by the image processing circuit 18. In FIG. 3, a broken line is image data (for example, a 60 Hz signal waveform) indicating the gradation of a specific pixel before double speed conversion, and a solid line is high gradation data and low gradation data (120 Hz) of the specific pixel after double speed conversion. Signal waveform).

  In FIG. 3, when the image data of the current frame before double speed conversion is D2, and the image data D2 of the current frame is compared with the image data D1 of the previous frame, both are not changed. Therefore, when the current frame image data D2 is double-speed converted, the overdrive process is not performed, and the high-tone data H2 and the low-tone data L2 after the double-speed conversion corresponding to the image data D2 of the current frame are one frame before. It is set to the same value as the high gradation data H1 and the low gradation data L1 after double speed conversion corresponding to the image data D1.

  If the time for one frame has passed and the current frame image data before double speed conversion is D3, the current frame image data D3 has changed from the previous frame image data D2. Therefore, when the current frame image data D2 is double-speed converted, an overdrive process is performed, and the double-speed converted high gradation data H3 and low gradation data L3 corresponding to the current frame image data D3 are one frame before. It is set to be higher or lower than the high gradation data H2 and the low gradation data L2 after double speed conversion corresponding to the image data D2.

  Further, when the time for one frame has passed and the image data of the current frame before double speed conversion is D4, the image data D4 of the current frame has not changed from the image data D3 of the previous frame. Therefore, when the image data D4 of the current frame is converted at double speed, overdrive processing is not performed, and the high gradation data H4 and the low gradation data L4 after the double speed conversion corresponding to the image data D4 of the current frame are the high gradation data H4. The average gradation of the low gradation data L4 is determined so as to match the gradation indicated by the image data D4 of the current frame before the double speed conversion. FIG. 3 illustrates the case where the gradation of the specific pixel changes so as to increase (from dark to light), but conversely the case where the gradation of the specific pixel changes so as to decrease (from light to dark). Is the same.

  The double speed conversion unit 183 uses the image data of the previous frame stored in the image data storage unit 181 and the image data of the current frame, and uses the first look-up table and the second look-up table stored in the conversion table storage unit 182. By referring to the uptable, the double speed conversion process and the overdrive process are simultaneously performed.

  FIG. 4 shows an example of the input / output characteristics of the liquid crystal display panel when overdrive is not considered (that is, still images). In FIG. 4, the horizontal axis represents the input signal, and the vertical axis represents the output signal. In FIG. 4, the curve labeled “Hi” indicates the input / output characteristics of the liquid crystal display panel when changing from a low gradation level to a high gradation level (from dark to bright), and is denoted as “Lo”. The curve shows the input / output characteristics of the liquid crystal display panel when changing from a high gradation level to a low gradation level (from light to dark).

  In the present embodiment, since the overdrive processing is performed as described above, the image data of the current frame and the image data of the previous frame are compared, and the overdrive process is performed according to the difference, that is, the change amount of the image data. It is necessary to add a correction for this. The conversion table storage unit 182 has a two-dimensional look in which a predetermined number of gradation levels compared with the image data of the current frame before double speed conversion and a predetermined number of gradation levels compared with the image data of the previous frame are associated with each other. A first look-up table for generating high gradation data indicating a gradation higher than the gradation indicated by the image data of the current frame, and a gradation lower than the gradation indicated by the image data of the current frame A second look-up table for generating low gradation data indicating the above is stored. For example, if one frame of image data is expressed at 16 levels (16 gradations), the first lookup table and the second lookup table are each composed of 16 × 16 = 256 numerical data. Has been.

  5 and 6 are graphs obtained by three-dimensionally visualizing the numerical data of the first lookup table and the second lookup table, respectively. Each intersection on the curved surface in FIGS. 5 and 6 represents numerical data in the first lookup table and the second lookup table. Further, the curves labeled “Hi” and “Lo” correspond to the curves “Hi” and “Lo” in FIG. 4. The waviness of the curved surface in FIGS. 5 and 6 reflects the correction for overdrive. As described above, the values of the first look-up table and the second look-up table are determined in consideration of the response characteristics of the liquid crystal display panel that outputs high gradation data and low gradation data. .

  For example, in the area surrounded by an ellipse A in FIG. 6, the gradation of the image data of the previous frame is low, the gradation of the image data of the current frame is higher than that, and the luminance of the pixel is changed from dark to bright. Since it has changed greatly, it can be seen that correction by overdrive is taken into account.

  In this way, the double speed conversion unit 183 does not generate high gradation data and low gradation data directly from the image data of the current frame, but refers to the image data of the current frame and the image data of the previous frame, and the image data Since the high gradation data and the low gradation data are generated in consideration of the value of the value, that is, whether or not the gradation is greatly changed, the overdrive processing is performed at the same time as performing the double speed conversion processing. It is possible. In other words, when there is little change in an image such as a still image, overdrive processing is not performed, and the gradation characteristics of the still image can be prevented from being disturbed. In addition, the double speed conversion unit 183 has a double speed conversion function and an overdrive function, so that the double speed conversion circuit and the overdrive circuit are substantially integrated, and the cost can be reduced by simplifying the circuit configuration. is there.

1 is a block diagram showing a schematic configuration of a TV receiver using a liquid crystal display panel as an example of a liquid crystal display device according to an embodiment of the present invention. The block block diagram of the image processing circuit provided with the double speed conversion function and overdrive function in the said one Embodiment. The wave form diagram which shows an example of the double speed conversion process and overdrive process by an image processing circuit. The graph which shows an example of the response characteristic of a liquid crystal display panel in case overdrive is not considered. The graph which visualized three-dimensionally the 1st look-up table for producing | generating the data in the case of changing from the low gradation level to the high gradation level in the said one Embodiment. The graph which visualized the 2nd look-up table for producing | generating the data in the case of changing from the high gradation level in the said one embodiment to a low gradation level three-dimensionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Television (TV) receiver 11 Liquid crystal display panel 18 Image processing circuit 181 Image data storage part 182 Conversion table storage part 183 Double speed conversion part D1-D4 (Before double speed conversion) Image data H1-H4 (After double speed conversion) High gradation data L1-L4 Low gradation data (after double speed conversion)

Claims (2)

From one frame of image data before double speed conversion, two continuous high gradation data and low gradation data respectively indicating a gradation higher and lower than the gradation indicated by the image data are generated, In the liquid crystal display device that represents the gradation of the current frame by the average gradation of the low gradation data and performs the double-speed conversion of the so-called light-dark method that converts the frame rate to twice,
An image data storage unit that stores image data of one frame before the current frame among the image data before double speed conversion;
A two-dimensional lookup table associating a predetermined number of gradation levels compared with image data of a current frame before double speed conversion and a predetermined number of gradation levels compared with image data of one frame before, A first lookup table for generating high gradation data indicating a gradation higher than the gradation indicated by the image data of the frame, and low gradation data indicating a gradation lower than the gradation indicated by the image data of the current frame. A conversion table storage unit that stores a second lookup table for generating;
High gradation data for the image data of the current frame by referring to the first look-up table and the second look-up table using the image data of the previous frame and the image data of the current frame stored in the image data storage unit, respectively. And a double-speed converter for generating low gradation data.   The values of the first look-up table and the second look-up table are determined in consideration of the response characteristics of a liquid crystal display panel that outputs high gradation data and low gradation data. The liquid crystal display device according to claim 1.

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