JP2008281798A - Video display device - Google Patents

Abstract

The present invention provides a technology capable of displaying a high-quality image while favorably suppressing variation phenomenon and luminance reduction.
An image display device according to the present invention is connected to a plurality of scanning lines (51) and one end of the plurality of scanning lines, and sequentially applies a scanning voltage to the plurality of scanning lines ( 5), a plurality of signal lines (41), and a signal line control circuit (4) connected to the plurality of signal lines and applying a signal voltage corresponding to the input video signal to the plurality of signal lines. And a display element (60) disposed at each intersection of the plurality of scanning lines and the plurality of signal lines, to which a scanning voltage from the scanning line control circuit and a signal voltage from the signal line control circuit are applied. With. The signal line control circuit includes a plurality of signal drivers (43a to 43f), and the reference voltage for generating the signal voltage supplied to each signal driver can be individually set.
[Selection] Figure 2

Description

  The present invention relates to an image quality correction technique in a matrix type image display device using, for example, Field Emission Display (hereinafter abbreviated as FED), organic EL (electroluminescence), and the like, which are configured by arranging display elements in a matrix. It is.

  An FED, which is one of display panels used in a matrix type video display device, includes a plurality of electron sources arranged in a matrix, and a signal voltage corresponding to a video signal is applied to the electron source. As a result, electrons are emitted. As a result, an image is formed on the display surface of the FED. In the FED having such a configuration, the electric characteristics of the individual electron sources may be different from each other depending on the manufacturing process and the like. In other words, the amount of electron emission from each electron source varies within the display surface. As a result, even when the same level video signal is applied to each pixel, the luminance between the pixels becomes non-uniform, and so-called luminance variation occurs. In addition, a voltage drop occurs due to the wiring resistance of the wiring (signal line, scanning line) to which the signal voltage or the scanning voltage for selecting the electron source is applied to the electron source, and this voltage drop also causes the luminance described above. Non-uniformity occurs.

  In order to correct such luminance variations, a technique for storing correction data for each pixel in advance and correcting a video signal (video data) using the correction data is described in, for example, Patent Document 1 below.

JP 2005-4118 A

  In Patent Document 1, the luminance variation is corrected by adding correction data to a video signal. That is, in Patent Document 1, since a part of the signal gradation (dynamic range) is used for luminance correction, the effective gradation used for substantial image display is reduced and it becomes difficult to display a fine image. . For example, when a video signal can represent 1024 gradations with 10 bits, if, for example, 100 gradations are used for the luminance correction, only 924 gradations can be used as gradations for video display.

  The present invention has been made in view of such problems, and the object thereof is to display a high-quality image by correcting luminance variations satisfactorily while ensuring effective gradation used for image display. It is to provide possible technology.

  In order to achieve the above object, a video display device according to the present invention includes an improved signal line control circuit and a scanning line control circuit.

  That is, the first feature of the present invention is that a signal line control circuit for generating a signal voltage based on a video signal includes a plurality of signal drivers, and a reference voltage for generating the signal voltage is set for each of the plurality of signal drivers. It can be set individually.

  A second feature of the present invention is that a scanning line control circuit for generating a scanning voltage for selecting a display element (such as an electron source) includes a plurality of scanning drivers, and a reference voltage for generating the scanning voltage is provided. Therefore, it is possible to individually set a plurality of scanning drivers.

  According to the present invention, it is possible to satisfactorily correct luminance variations while ensuring effective gradation used for video display, and high-quality video display is possible.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a passive matrix drive type electron emission element type image display apparatus having an MIM (Metal-Insulator-Metal) type electron source as an electron source will be described as an example. However, this embodiment can be similarly applied to electron sources other than MIM, for example, an SCE (Surface Conduction Electron Emitter) type, a carbon nanotube type, a BSD (Ballistic electron Surface-emitting Device) type, and a Spindt type. Furthermore, the present invention can be similarly applied to a display device using an organic EL element.

  Before describing the embodiment of the present invention, the above-described luminance variation will be described with reference to FIG. In an electron source connected to a scanning line and a signal line, which will be described later, when a driving voltage that is the difference between the scanning voltage and the signal voltage is applied, a current flows between the electrodes of the electron source. When the drive voltage is equal to or greater than the threshold, the amount of current increases almost linearly with respect to the drive voltage. Here, the current flowing by the drive voltage is called a drive current, and the relationship between the drive voltage and the drive current is called a drive current characteristic. This drive current characteristic indicates the operation characteristic of the electron source, and typically has a characteristic as shown by a solid line in FIG. However, each electron source constituting the panel varies in drive current characteristics due to a manufacturing process, a change with time, and the like. As a result, in addition to the drive current characteristic indicated by the solid line in FIG. 1, for example, an electron source having the drive current characteristic indicated by the broken line or the alternate long and short dash line in FIG. In FIG. 1, when the drive voltage V0 is applied, the drive current of each electron source increases in the order of a broken line, a solid line, and a one-dot chain line. Since the brightness of the displayed screen is substantially proportional to the drive current, the brightness increases in the order of the broken line, the solid line, and the alternate long and short dash line, resulting in uneven brightness.

  Furthermore, since the scanning line and the signal line are formed of a very thin metal thin film, a relatively large internal resistance (having wiring resistance) causes a voltage effect corresponding to the position of the electron source. Therefore, the voltage drop in the electron source in which the path of the drive current flows is relatively long compared to the electron source in the relatively short position, and even if the same scanning voltage and signal voltage are applied to these electron sources. The drive voltage applied to the former electron source is lower than the drive voltage applied to the latter electron source due to the influence of the voltage drop. As a result, even if the level of the video signal applied to one screen is equal, luminance unevenness (luminance gradient) is formed in the horizontal direction and / or the vertical direction of the screen.

  The present invention is configured in consideration of the luminance unevenness caused by the above-described variation in drive current characteristics and wiring resistance, and an example thereof will be described below.

  FIG. 2 shows a first embodiment of a video display apparatus according to the present invention. The video signal is input to the video signal input terminal 3 and supplied to the signal processing circuit 7. The signal processing circuit 7 digitally processes the video signal. For example, resolution conversion for matching the definition of the video signal to the resolution of the display panel 20 is performed. Here, the display panel 20 includes the back substrate 6 and the front substrate 30, and details thereof will be described later.

  In addition to the resolution conversion process, the signal processing circuit 7 performs image quality adjustment such as contrast, brightness, and gamma correction. This image quality adjustment may be made to respond to a manual operation by the user. Here, it is assumed that a 10-bit digital video signal is output from the signal processing circuit 7. Therefore, this digital video signal enables 1024 gray scale video representation.

  A synchronization signal corresponding to the video signal is input from the synchronization signal input terminal 1 and supplied to the timing controller 2. In the timing controller 2, a timing pulse synchronized with the synchronization signal is generated and supplied to the scanning line control circuit 5, the signal line control circuit 4, and the signal processing circuit 7.

  On the other hand, the display panel 20 has a back substrate 6 made of a glass substrate and a front substrate 30 also made of a glass substrate. On the rear substrate 6, a plurality of scanning lines 51 extending in the horizontal direction of the screen are arranged side by side in the vertical direction of the screen, and a plurality of signal lines 41 extending in the vertical direction of the screen are arranged in the horizontal direction of the screen. The scanning line 51 and the signal line 41 are orthogonal to each other, and an electron source 60 connected to the scanning line and the signal line is disposed at each intersection.

  A signal line control circuit 4 that is a drive voltage supply unit is connected to the upper end of the signal line 41. As will be described later, the signal line control circuit 4 includes a plurality of signal drivers 43a to 43f and a signal driver reference voltage generation circuit 42 for applying a reference voltage to each signal driver. The signal line control circuit 4 generates a signal voltage based on the video signal processed by the signal processing circuit 7 and the reference voltage generated by the signal driver reference voltage generation circuit 42 and supplies the signal voltage to each signal line 41.

  On the other hand, the scanning line control circuit 5 is connected to the left end of the scanning line 51. As will be described later, the scanning line control circuit 5 includes a plurality of scanning drivers 53a to 53d and a scanning driver reference voltage generation circuit 52 for applying a reference voltage to each scanning driver. The scanning line control circuit 5 synchronizes with the signal of the horizontal cycle from the timing controller 2, and uses the scanning voltage for selecting the scanning lines 51 one by two or the reference voltage from the scanning driver reference voltage generation circuit 52. Is generated based on the above and supplied to the scanning line 51. That is, the scanning line control circuit 5 performs vertical scanning by selecting one or two rows of electron sources in order from the top in the horizontal period. Details of the signal line control circuit 4 and the scanning line control circuit 5 will be described later.

  In this embodiment, the scanning voltage has the same polarity with respect to the signal voltage. That is, both the signal voltage and the scanning voltage are negative or positive. However, the scanning voltage and the signal voltage may have opposite polarities, for example, the driving voltage may be positive and the scanning voltage may be negative.

  When a signal voltage from the signal line control circuit 4 is supplied to each electron source 60 connected to the scanning line selected by the scanning voltage, a potential difference between the scanning voltage and the signal voltage is generated in each electron source 60. . This potential difference becomes the drive voltage, and a drive current flows from the scanning line to the signal line via the electron source. When a drive current flows through the electron source, the electron source emits electrons. This emitted electron current is called emission current, and the emission current is approximately proportional to the drive current.

  In addition, a front substrate 30 is disposed facing the back substrate 6, and phosphors 31 are disposed at positions facing the respective electron sources 60 on the surface of the front substrate 30 facing the back substrate 6. Yes. Further, an acceleration electrode (not shown) is provided on the front substrate 30, and the acceleration electrode is connected to the high voltage control circuit 9 so that a high voltage from the high voltage control circuit 9 is supplied. The space between the back substrate 6 and the front substrate 30 is a vacuum atmosphere. The electrons emitted from the electron source 60 are accelerated by the high voltage supplied from the high voltage control circuit 10 to the accelerating electrode, and proceed in the vacuum to excite the phosphor. As a result, the phosphor emits light, and the light is emitted to the outside through the transparent glass substrate constituting the front substrate 30, and an image is formed on the display panel 20.

  Next, details of the signal line control circuit 4 which is the most characteristic part of the present embodiment will be described.

  FIG. 3 is a block diagram illustrating a configuration example of the signal line control circuit 4. The signal line control circuit 4 according to the present embodiment includes a plurality of (six in this example) signal drivers 43a to 43f and a signal driver reference voltage generation circuit 42 for supplying a reference voltage to the signal drivers 43a to 43f. And. The number of signal drivers 43 is appropriately determined according to the number of output terminals of the signal driver and the horizontal resolution of the display panel 20. Here, each of the signal drivers 43a to 43f is configured by a digital-analog conversion IC (D / A converter) for converting an input digital video signal into an analog signal voltage. An example of the configuration is shown in FIG.

  As shown in FIG. 7, the signal driver 43 includes a digital signal input terminal 71 to which a digital video signal (video data) from the signal processing circuit 7 is input and a plurality of analogs that output analog signals as signal voltages. A signal output terminal 72, a Vcc terminal 73 to which power for operating the signal driver 43 is input, and a reference voltage input to which a plurality of reference voltages corresponding to a plurality of set gradations (D1 to D5) are input Terminals 74a to 74e are provided.

  Here, the reference voltage sets a signal voltage corresponding to a predetermined gradation. For example, when the reference voltage corresponding to the gradation D1 is set to Vr1, the signal driver receives the video signal of D1. Vr1 is output as an analog signal voltage. In general, the number of gradations that can be set by the reference voltage is plural, and in this embodiment, it is assumed that the reference voltages Vr1 to Vr5 can be set for five gradations D1 (low gradation) to D5 (high gradation), respectively. The signal voltage of gradation between Dn and Dn + 1 is generated by linearly interpolating Vn and Vn + 1.

  For example, the reference voltage input terminal 74a has a reference voltage Vr1 corresponding to 0 gradation (gradation D1), 74b has a reference voltage Vr2 corresponding to 256 gradations (gradation D2), and 74c has 512 gradations. The reference voltage Vr3 corresponding to (gradation D3) is 74d, the reference voltage Vr4 corresponding to 768 gradations (gradation D4), and the reference voltage Vr5 corresponding to 1023 gradations (gradation D5) in 74f. It is supplied from the signal driver reference voltage generation circuit 42. The signal driver 43 generates an analog signal voltage from the digital video signal input to the digital signal input terminal 71 based on the plurality of reference voltages input to the reference voltage input terminals 74a to 74f as described above, and outputs the analog signal voltage. To do. For example, when the gradation of the digital video signal is 768, an analog signal voltage of Vr4 is output, and when the gradation of the digital video signal is 512, an analog signal voltage of Vr3 is output. When the gradation of the digital video signal is between 512 and 768, an analog signal voltage between Vr3 and Vr4 is obtained by linear interpolation and output.

  Further, the signal driver reference voltage generation circuit 42 is constituted by, for example, a digital-analog voltage converter, and supplies the reference voltages Vr1 to Vr5 corresponding to the respective gradations D1 to D5 to the signal drivers 43a to 43f.

  Here, a case will be described in which correction data for correcting luminance variations is added to a digital video signal as in Patent Document 1 described above. The signal drivers 43a to 43f are configured by D / A converters as described above, and the number of bits that can be handled by the D / A converters is set in advance. For example, a D / A converter can handle a 10-bit digital signal, and a drive current characteristic of a certain electron source is lower than others, and a video signal corresponding to the electron source is added to the 100th floor as correction data. It is assumed that correction data for adjustment is added. In this case, since the maximum number of gradations that can be supported by the signal drivers 43a to 43f is 1023, an input digital video signal having 923 gradations (a value obtained by subtracting the gradation of the correction data from the maximum gradation) is expressed. I can't. That is, the input digital video signal is saturated at 923 gradations in the electron source, and the dynamic range for 100 gradations of the correction data cannot be used effectively. On the other hand, the gradation of the display video is substantially determined by the level of the analog signal voltage that determines the drive voltage, and the level of the signal voltage corresponding to each gradation of the input digital video signal is the reference voltage Vr1 of each of the signal drivers 43a to 43f. Depends on ~ Vr5.

  Therefore, in the present embodiment, as shown in FIG. 3, the reference voltages V1 to V5 of the signal drivers 43a to 43f can be set independently, and thereby each gradation that can be output from the signal drivers 43a to 43f. The level of the analog signal voltage corresponding to is individually changeable. The reference voltages Vr1 to Vr5 of the signal drivers 43a to 43f are set by the signal driver reference voltage generation circuit 42.

  As described above, the gradation of the displayed video is determined by the analog signal voltage from the signal drivers 43 a to 43 f, and this analog signal voltage depends on the reference voltage provided by the signal driver reference voltage generation circuit 42. Therefore, if this reference voltage is changed, different gradations can be expressed even if the gradation of the input digital video signal is the same. For example, a signal driver corresponding to an electron source that does not require correction of luminance variation (that is, does not need to add correction data) needs to correct the signal driver 43a and luminance variation (that is, needs to add predetermined correction data). Assume that the signal driver corresponding to the electron source is the signal driver 43b. At this time, if the reference voltage of the signal driver 43b is made higher than the reference voltage of the signal driver 43a, the digital video signal input to the signal drivers 43a and 43b is output from the signal driver 43b even if the gradation is the same. The analog signal voltage, that is, the gradation of the display image can be increased.

  Therefore, according to the present embodiment, it is possible to correct the luminance variation without adding correction data to the digital video signal. In this embodiment, there are five reference voltages D1 to D5 supplied to the signal driver 43, but the values of all the reference voltages may be changed, or only one of them, for example, only the value of D5. May be changed, or two or three values may be changed. Furthermore, only the value of the reference voltage D1 may be increased for the signal driver 43 corresponding to the electron source having a low driving voltage characteristic.

  In this embodiment, the output voltages from the signal driver reference voltage generation circuit 42 are individually changed to set the reference voltages D1 to D5 of each signal driver 43. However, the reference voltage input of each signal driver 43 is used. A regulator may be provided for each of the terminals 74a to 74f, and the value of the output voltage from the signal driver reference voltage generation circuit 42 may be individually converted by this regulator.

  In the present embodiment, the case where the number of signal drivers 43 is six has been described as an example. However, the number of signal drivers 43 is not limited to this, and any number may be set according to the number of output terminals of the signal driver 43 and the horizontal resolution of the display panel 20. It is good.

  In the above example, the reference voltage is changed for each of the signal drivers 43a to 23f of the signal line control circuit 4. However, the reference voltage of the scanning driver of the scanning line control circuit 5 may be changed. FIG. 4 is a block diagram illustrating a configuration example of the scanning line control circuit 5 according to the present embodiment. The reference voltage generation circuit 52 is configured by, for example, a digital-analog voltage converter, and supplies a reference voltage for generating a scan voltage to the scan drivers 53a to 53d. The number of scan drivers 53 is appropriately determined according to the number of output terminals of the scan driver and the vertical resolution of the display panel 20. Here, each of the scanning drivers 53a to 53d includes a switching element, and in accordance with the input synchronization signal, the scanning voltage as the selection voltage is selected in the selection period in which one row of electron source groups is selected. Supplies a non-selection voltage to the scanning line 51. The non-selection voltage is supplied from the reference voltage generation circuit 52 or another voltage source to the scan drivers 53a to 53d. That is, the scan drivers 53a to 53d perform a switching operation so that the reference voltage from the reference voltage generation circuit 52 is selected and output as a scan voltage during the selection period, and the non-selection voltage is selected and output during the non-selection period. Do.

  In this embodiment, the reference voltage supplied to each of the scanning drivers 53 a to 53 d is configured to be set individually for each scanning driver 53. The reference voltage is set by a reference voltage generation circuit 52. In this way, different scanning voltages can be output for each scanning driver. FIG. 4 shows the case where there are four scan drivers, but the number of scan drivers may naturally be any number.

  Next, in the above-described configuration, an example of setting a suitable reference voltage in the case where the luminance unevenness such that the upper left of the display panel 20 is dark and the lower right is bright as shown in FIG. 5A will be described.

  It is assumed that the signal driver 43a supplies a signal voltage to the left electron source group of the display panel 20, and the signal driver 43f supplies a signal voltage to the right electron source group of the display panel 20. At this time, the signal driver reference voltage generation circuit 42 sets the reference voltage supplied to each signal driver so that the signal voltage of the signal driver 43a is low and the signal voltage of the signal driver 43f is high.

  On the other hand, since the scanning driver 53a supplies the selection potential to the electron source group on the upper part of the display panel 20 and the scanning driver 53d supplies to the electron source group on the lower part of the display panel 20, the scanning voltage of the scanning driver 53a. The reference voltage supplied to each scan driver is set by the scan driver reference voltage generation circuit 52 so that the scan voltage of the scan driver 53d is low. By setting each reference voltage in this way, the drive voltage at the upper left of the display panel 20 is high and the drive voltage at the lower right is lowered, and as shown in FIG. A substantially uniform image can be displayed. As described above, according to this embodiment, the display gradation is set for the electron source group in which the output luminance is relatively lowered due to the influence of the drive current characteristic of the electron source and the wiring resistance of the scanning line and the signal line. The correction can be made by changing the voltage for driving the IC such as the signal driver or the scanning driver without correcting the video signal by the correction data.

  Further, the signal processing circuit 7 may perform video signal processing for correcting a reference voltage, that is, a luminance step generated at the boundary of each driver, for example, a Gaussian filter or a low-frequency emphasis filter processing. Furthermore, as described in Patent Document 1, correction that adds correction data to a video signal may be used in combination. In this case, high-definition video display can be achieved because fewer gradations are required for correction of luminance variations, that is, less correction data gradations than correction of a video signal as described in Patent Document 1. It becomes possible.

  By setting the driving voltage of each driver in this way, variations in the driving current characteristics of the electron source and luminance variations (non-uniformity in luminance) due to the influence of the wiring resistance of the scanning lines and signal lines can be displayed on the video display. Correction can be performed while ensuring the display gradation to be used.

  Next, a second embodiment of the video display apparatus according to the present invention will be described with reference to FIG. The present embodiment is different from the first embodiment in that a variation correction circuit 8 and a memory 10 are added to the apparatus of the first embodiment, and each reference voltage is controlled by the variation correction circuit 8. Since other elements having the same reference numerals as those in the first embodiment have the same functions, the description thereof is omitted here. Hereinafter, details of the variation correction circuit 8 and the memory 10 will be described.

  The memory 10 holds the drive current characteristics of each block when the panel is divided into an arbitrary number. For example, the number of divided blocks may be the number of scanning drivers in the vertical direction and the number of signal drivers in the horizontal direction. The drive current characteristic of each block held in the memory 10 may be an average value of the drive current characteristics of a plurality of electron sources constituting each block, for example. In addition to the actually measured drive current characteristics, ideal drive current characteristics and luminance characteristics may be retained. Furthermore, the held drive current characteristic may be measured at the time of panel manufacture, or the video display device may have a function of measuring the drive current characteristic and a function of updating the contents held in the memory 10 at any timing. The data may be updated with Furthermore, the memory 10 may hold the characteristics of the emission current of the electron source instead of the driving current characteristics. Furthermore, the memory 10 may hold the drive current characteristic as a drive current of each block corresponding to an arbitrary drive voltage. This arbitrary driving voltage may be, for example, the number of gradations (D1 to D5) corresponding to the reference voltage set in the signal driver.

  Table 1 shows an example of the drive current characteristics held in the memory 10, and Tables 1-1 to 1-5 show the drive currents of the respective blocks at the drive voltages V1 to V5, respectively. Here, it is assumed that the drive voltages V1 to V5 are equal to the gradations D1 to D5 of the signal described above. In each table of Table 1-1 to Table 1-5, five scanning drivers 53a to 53d and six signal drivers 43a to 43f are provided as scanning drivers, and the display panel 20 is provided for each driver. That is, an example is shown in which four blocks in the vertical direction and six blocks in the horizontal direction are divided into a total of 24 blocks. In other words, the 24 numerical values in each table indicate the values of the drive currents held corresponding to the 24 divided blocks, respectively. Table 2 shows an example of an ideal drive current at each of the drive voltages V1 to V5 corresponding to the signal gradations D1 to D5.

表１−１では、左から右(信号ドライバ４３ａから４３ｆの方向)に向かって駆動電流が大きくなっており、また上から下(走査ドライバ５３ａから５３ｄの方向)にも駆動電流が大きくなっている。また表２では駆動電圧Ｖ１における理想の駆動電流が５．００なので左上は理想より暗く右上は理想より明るい輝度となる、例えば図５ａのような輝度むらがあることを示す。

In Table 1-1, the drive current increases from left to right (in the direction of signal drivers 43a to 43f), and also increases from top to bottom (in the direction of scan drivers 53a to 53d). Yes. Table 2 shows that the ideal drive current at the drive voltage V1 is 5.00, so the upper left is darker than ideal and the upper right is brighter than ideal. For example, there is uneven brightness as shown in FIG. 5a.

  On the other hand, the variation correction circuit 8 is based on the data held in the memory 10 as shown in Tables 1-1 to 1-5, and the reference voltages of the signal drivers 43a to 43f and the scan drivers 53a to 53a so as to reduce luminance unevenness. Each reference voltage 53d is calculated.

  Next, an example of reference voltage calculation will be described. First, with reference to Table 1-1 and Table 2, a method of correcting the luminance unevenness in the drive voltage V1, that is, the gradation D1, will be described.

The reference voltages of the signal drivers 43a to 43f are set so that the average current of the block corresponding to each signal driver (block divided in the horizontal direction) increases or decreases by the correction current Idc. The correction current Ic is obtained, for example, as shown in the following equation 1, where Ii is the ideal drive current and Ida is the average current of the block.
(Equation 1) Idc = (Ii−Ida) / 2
For example, the reference voltage corresponding to the gradation D1 of the signal driver 43a is obtained as follows. From Table 2, the ideal current Ii corresponding to the gradation D1 is 5.00, and the average current of the block corresponding to the signal driver 43a in the gradation D1 is 4.64 (4.40, 4.4, 4) from the leftmost column of Table 1-1. Therefore, the correction current Idc is obtained as follows from the equation (1).
Idc = (5.00-4.64) /2=0.18
Therefore, the reference voltage Vr1 corresponding to the gradation D1 of the signal driver 43a is a value obtained by adding the correction current Idc obtained from Equation 1 to the ideal current in Table 2 when a video signal of the gradation D1 is input. That is, the value is corrected and set by the variation correction circuit 8 so that the driving current of 5.18 flows. In order to calculate the reference voltage, for example, the drive current values at the drive voltages V1 and V2 may be linearly complemented.

The reference voltages of the scan drivers 53a to 53d are set so that the average current of the blocks corresponding to the scan drivers (blocks divided in the vertical direction) is increased or decreased by the correction current Isa. The correction current Isc is obtained, for example, as shown in Equation 2 below, where Ii is the ideal drive current and Isa is the average current of the block.
(Equation 2) Isc = (Ii−Isa) / 2
For example, the reference voltage of the scan driver 53a is obtained as follows. From Table 2, the ideal current Ii corresponding to the gradation D1 is 5.00, and the average current of the block corresponding to the scan driver 53a in the gradation D1 is 4.94 (4.40, 4.59) from the upper end of Table 1-1. (Average of 4.80, 5.03, 5.28, 5.56), the correction current Isc can be obtained from Equation 2 as follows.
Isc = (5.00-4.94) /2=0.03
Therefore, the reference voltage corresponding to the gradation D1 of the scan driver 53a is a value obtained by adding the correction current Isc obtained from Equation 2 to the ideal current in Table 2 when a video signal of the gradation D1 is input, that is, The value is corrected and set by the variation correction circuit 8 so that a driving current of 5.03 flows. In order to calculate the reference voltage, for example, the drive current values at the drive voltages V1 and V2 may be linearly complemented.

  By calculating the reference voltage for all the blocks, the reference voltages for the signal drivers and the scan driver are set. As a result, when the video signal D1 is input, the drive voltage of each block becomes a value around V1, the luminance difference of each block is reduced, and the average drive current of all the blocks substantially matches the ideal value.

  The reference voltage Vr2 is calculated in the same manner as described above using the data in Tables 1-2 and 2 and the reference voltage Vr3 is calculated using the data in Tables 1-3 and 2. Since only one reference voltage for the scan driver has already been calculated as described above, it is not necessary to obtain the reference voltage for the scan driver when obtaining the reference voltages Vr2 to Vr5 for the signal driver.

  In this way, the variation correction circuit 8 calculates a correction current for correcting luminance unevenness in each of the gradations D1 to D5, and generates a signal driver reference voltage so as to correct the reference voltage using the correction current (Idc, Ids). The circuit 42 and the scan driver reference voltage generation circuit 53 are controlled. As a result, the luminance unevenness is reduced, and the average luminance at each gradation is substantially equal to the ideal value, and an image display with reduced luminance unevenness as shown in FIG. 5b is possible.

  In the present embodiment, similarly to the first embodiment, the signal processing circuit 7 may perform a Gaussian filter, a low-frequency emphasis filter process, or the like that corrects a luminance step generated at the division boundary. Furthermore, as described in Patent Document 1, correction that adds correction data to a video signal may be used in combination. In this case, high-definition video display can be achieved because fewer gradations are required for correction of luminance variations, that is, less correction data gradations than correction of a video signal as described in Patent Document 1. It becomes possible. Furthermore, the above correction may be performed at the time of manufacture, and may be performed at an arbitrary timing when the video display device has an element for measuring the drive current characteristic.

  In the above embodiment, the signal driver 43 is a D / A converter. However, the present invention can also be applied to drivers other than the D / A converter. For example, the present invention can be applied to a so-called PWM (Pulse Width Modulation) circuit that outputs a pulse signal having a pulse height as a signal voltage and controls the pulse width according to the level of the video signal. That is, the reference voltage for determining the pulse width corresponding to the level of the video signal may be changed for each PWM circuit.

Diagram explaining variation in drive current characteristics The figure which shows 1st Example which concerns on this invention The figure which shows an example of the signal line control circuit which concerns on this invention FIG. 4 is a diagram showing an example of a scanning line control circuit according to the present invention. The figure explaining the example of a display after brightness nonuniformity and brightness nonuniformity correction The figure which shows the 2nd Example which concerns on this invention Diagram showing an example of signal driver

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Synchronization signal input terminal, 2 ... Timing controller, 3 ... Video signal input terminal, 4 ... Signal line control circuit, 5 ... Scanning line control circuit, 6 ... Back substrate, 7 ... Signal processing circuit, 8 ... Variation correction circuit, DESCRIPTION OF SYMBOLS 9 ... High voltage control circuit, 10 ... Memory, 20 ... Display panel, 30 ... Front substrate, 31 ... Phosphor, 41 ... Signal line, 42 ... Signal driver reference voltage generation circuit, 43a-43f ... Signal driver, 51 ... Scanning Line 52... Scan driver reference voltage generation circuit, 53 a to 53 d.

Claims (14)

In the video display device,
A plurality of scan lines;
A scanning line control circuit connected to at least one of the left and right ends of the plurality of scanning lines and sequentially applying a scanning voltage to the plurality of scanning lines;
Multiple signal lines,
A signal line control circuit connected to the plurality of signal lines and applying a signal voltage corresponding to the input video signal to the plurality of signal lines;
A display element disposed at each intersection of the plurality of scanning lines and the plurality of signal lines, to which a scanning voltage from the scanning line control circuit and a signal voltage from the signal line control circuit are applied;
The video display device, wherein the signal line control circuit includes a plurality of signal drivers, and a reference voltage for generating the signal voltage applied to each signal driver can be individually set.   2. The video display device according to claim 1, wherein the scanning line control circuit includes a plurality of scanning drivers, and a reference voltage for generating the scanning voltage applied to each scanning driver can be individually set. A characteristic video display device.   3. The video display device according to claim 2, wherein the signal line control circuit includes a reference voltage generation circuit for distributing the reference voltage to the signal drivers, and the reference voltage generation circuit transmits the reference voltage to the signal drivers. An image display device that sets a level of a reference voltage.   The video display device according to claim 1, wherein the plurality of signal drivers are D / A converters for converting the digital video signal into an analog signal to generate the drive signal, and the reference voltage is: An image display device, characterized in that the reference voltage is a reference voltage for converting the digital image signal into an analog signal.   2. The video display device according to claim 1, wherein when a video signal having a certain level in the horizontal direction of the screen is input, the reference voltage of the signal driver corresponding to a portion where the luminance is relatively low is set to another An image display device, wherein the image display device is set to be higher than the reference voltage of the signal driver.   2. The video display device according to claim 1, wherein the reference voltage is set for each of a plurality of predetermined gradations.   2. The video display device according to claim 1, wherein a memory for storing data for correcting a reference voltage supplied to each of the signal drivers and a correction data stored in the memory are used to correct the reference voltage. And a correction circuit for setting the image display device. In the video display device,
A plurality of scan lines;
A scanning line control circuit connected to at least one of the left and right ends of the plurality of scanning lines and sequentially applying a scanning voltage to the plurality of scanning lines;
Multiple signal lines,
A signal line control circuit connected to the plurality of signal lines and applying a signal voltage corresponding to the input video signal to the plurality of signal lines;
A display element disposed at each intersection of the plurality of scanning lines and the plurality of signal lines, to which a scanning voltage from the scanning line control circuit and a signal voltage from the signal line control circuit are applied;
The scanning line control circuit includes a plurality of scanning drivers, and a reference voltage for generating the scanning voltage given to each scanning driver can be individually set.   9. The video display device according to claim 8, wherein the signal line control circuit includes a plurality of signal drivers, and a reference voltage for generating the signal voltage applied to each signal driver can be individually set. A characteristic video display device.   The video display device according to claim 9, wherein the scanning line control circuit includes a reference voltage generation circuit for distributing the reference voltage to the scan drivers, and the reference voltage generation circuit supplies the reference voltage to the scan drivers. An image display device that sets a level of a reference voltage.   9. The video display device according to claim 8, wherein when a video signal having a certain level in the vertical direction of the screen is input, the reference voltage of the scan driver corresponding to a portion where the luminance is relatively low is set to another level. An image display device, wherein the image display device is set to be higher than the reference voltage of the scanning driver.   9. The video display device according to claim 8, wherein a memory for storing data for correcting a reference voltage supplied to each of the signal drivers is corrected, and the reference voltage is corrected using the correction data stored in the memory. And a correction circuit for setting the image display device.   9. The video display device according to claim 1, wherein the display element is composed of an organic EL.   9. The video display device according to claim 1, wherein the display element is configured by an electric field or an electron-emitting device.

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