JP2011221134A - Image display device and driving method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-quality image display device which is capable of suppressing the degradation in image quality due to brightness unevenness during multi-line driving, with a small memory capacity.SOLUTION: The image display device includes: a display panel having a plurality of light emitting elements; a scanning circuit which sequentially switches scanning lines to which a selection signal is applied, by N lines; a modulation circuit which applies a modulation signal generated based on image data, to each modulation line; and an image processing circuit which outputs image data to the modulation circuit. The image processing circuit includes a storage part in which peculiar brightness of each light emitting element or a value corresponding to the peculiar brightness is stored as light emission characteristic data of the light emitting element, and a correcting operation part which uses correction data calculated from the light emission characteristic data to perform correction for suppressing the variance in brightness among the plurality of light emitting elements with respect to image data. The correcting operation part calculates correction data from an average value of peculiar brightness of N light emitting elements for N lines simultaneously driven by the same modulation signal.

Description

  The present invention relates to a technique for correcting a luminance variation between light emitting elements of an image display device.

As a flat display device (FPD), a liquid crystal display device (LCD), a plasma display device (PDP), a field emission display device (FED), an organic EL display device (OLED), and the like are known.
In such a flat display device, it is necessary to form a large number of light emitting elements on a substrate. The characteristics of these light emitting elements are affected by slight differences in manufacturing conditions and the like. Therefore, in general, it is difficult to make the characteristics of all the light emitting elements included in the flat display device completely uniform. This non-uniformity of the light emission characteristics causes the luminance variation of the display device, and the image quality is deteriorated. For example, in the case of a field emission display device, a surface conduction electron-emitting device, a Spindt type, an MIM type, a carbon nanotube type, or the like is used as an electron-emitting device. If the shape or the like of the electron-emitting device varies depending on the manufacturing conditions of the electron-emitting device, the electron-emitting characteristics of the electron-emitting device also differ. As a result, the luminance variation of the field emission display device occurs, and the image quality deteriorates.

  In response to such a problem, a configuration for correcting an image signal in accordance with the light emission characteristics of each light emitting element has been proposed (luminance variation correction). For example, there is a method in which adjustment ratios (correction data) are prepared in advance for all elements on the screen, and luminance variations are corrected by multiplying input image data.

On the other hand, there is a scanning method in which a plurality of lines are simultaneously driven (emitted). Hereinafter, this scanning method is referred to as N-line driving or multi-line addressing (MLA). By this scanning method, each pixel selection time in one frame period is N times that of the conventional method of sequentially scanning the light emitting lines for each line (hereinafter referred to as single line driving). Can be set to length. Therefore, the light emission luminance of the display panel can be increased approximately N times.
However, since multiple lines are driven simultaneously during multi-line driving, a plurality of light-emitting elements on the same column on the simultaneously driven lines must be driven with the same drive signal. On the other hand, as described above, since the panel has a variation in light emission characteristics for each element, it is necessary to drive the panel with an optimum driving signal corrected for each element. In other words, during multi-line driving, it is not possible to drive with an optimum drive signal corrected for each element, resulting in luminance variations.

Conventionally, as a method for generating correction data in multi-line driving, correction data for single-line driving of any one of N light-emitting elements driven by the same driving signal is used as a representative value for multi-line driving. A method of using the correction data is known. Patent Document 1 proposes a method of using an average value of correction data for single line driving of N light emitting elements as correction data for multiline driving.
However, the conventional method is effective when the luminance variation of the N elements sharing the drive signal is small, but an error occurs when the luminance variation is large. As a result, image quality degradation still occurs due to adjacent variations.
However, it is not preferable to store both the correction data for single line driving and the correction data for multi-line driving in the memory in advance because it causes an increase in memory capacity and cost. This problem is particularly important in the case of an image display device in which the number of lines driven simultaneously is variable.

JP 2005-215140 A

  An object of the present invention is to provide a high-quality image display device that can suppress image quality deterioration due to luminance variations during multi-line driving with a small memory capacity.

  According to a first aspect of the present invention, a display panel having a plurality of scanning wirings and a plurality of modulation wirings arranged in a matrix, a plurality of light emitting elements each connected to the scanning wirings and the modulation wirings, and a selection signal A scanning circuit that sequentially switches scanning lines to be applied by N lines (N is an integer of 1 or more), a modulation circuit that applies a modulation signal generated based on image data to each modulation line, and image data for the modulation circuit Each of the plurality of light emitting elements is driven under the same conditions, and each of the plurality of light emitting elements has a luminance corresponding to a specific luminance or a value corresponding to the specific luminance. Using a storage unit storing light emission characteristic data of the light emitting elements and correction data calculated from the light emission characteristic data, luminance variations of the plurality of light emitting elements with respect to image data are detected. A correction calculation unit that performs correction to control the correction data, and the correction calculation unit is configured to simultaneously drive correction data to be applied to each image data by a modulation signal generated based on the image data. Provided is an image display device that calculates from an average value of intrinsic luminance of N light emitting elements for a line.

  A second aspect of the present invention is a method for driving an image display device, wherein the image display device includes a plurality of scanning wirings and a plurality of modulation wirings arranged in a matrix, and each of the scanning wirings and the modulation wirings. A display panel having a plurality of connected light emitting elements, a scanning circuit for sequentially switching a scanning wiring for applying a selection signal by N lines (N is an integer of 1 or more), and a modulation signal generated based on image data The modulation circuit to be applied to the wiring and the intrinsic luminance that is the luminance of each light emitting element when each of the plurality of light emitting elements is driven under the same conditions, or a value corresponding to the intrinsic luminance is stored as emission characteristic data of each light emitting element. The driving method reads the emission characteristic data from the storage unit, and calculates correction data from the read emission characteristic data. Correcting the image data using the calculated correction data to suppress variations in luminance of the plurality of light emitting elements, and the correction data to be applied to each image data includes the image Provided is a driving method that is calculated from an average value of intrinsic luminance of N light emitting elements for N lines that are simultaneously driven by a modulation signal generated based on data.

  According to the present invention, it is possible to realize a high-quality image display apparatus that can suppress image quality deterioration due to luminance variation during multi-line driving with a small memory capacity.

The block diagram which shows the structure of a brightness variation correction part. The block diagram which shows the structure of the whole image display apparatus. The figure which shows the scanning timing of a double line drive. The figure which shows the pixel arrangement | sequence of a display panel. 4 is a correspondence diagram of 4K2K format data and display panel pixels. FIG. FIG. 3 is a correspondence diagram of 2K1K format data and display panel pixels. (A) is a figure which shows the brightness dispersion | variation in 1 element unit, (B) is a figure which shows the dispersion | variation in brightness in 2 element units. The figure which shows the control flow of 3rd Embodiment. (A) is the conventional, (B) is a diagram showing a data storage example of the third embodiment.

  The present invention is applied to a simple matrix type (passive matrix type) image display device capable of multi-line driving. This type of image display apparatus generally includes a display panel having a plurality of light emitting elements, a drive circuit that drives the display panel, and an image processing circuit that performs necessary processing on image data and outputs the processed data to the drive circuit. Specifically, the display panel includes a plurality of scanning lines and a plurality of modulation lines arranged in a matrix, and a plurality of light emitting elements each connected to the scanning lines and the modulation lines. In addition, the driving circuit applies a modulation signal generated based on the image data and a scanning circuit (scanning driver) that sequentially switches the scanning wiring to which the selection signal is applied by N lines (N is an integer of 1 or more) to each modulation wiring. And a modulation circuit (modulation driver). At the time of driving, the light emitting elements for N lines to which the selection signal is applied emit light at a luminance corresponding to the modulation signal. In the case of multi-line driving (when N ≧ 2), N light emitting elements for N lines in the same column are simultaneously driven by the same modulation signal.

  According to the present invention, in the image display device having the above structure, it is possible to correct the luminance variation due to the nonuniformity of the light emission characteristics for each light emitting element, and to improve the image quality deterioration due to the luminance variation. Simple matrix image display devices include field emission display devices, liquid crystal display devices, plasma display devices, organic EL display devices, and the like, and the present invention can be applied to any display device. Among them, field emission type display devices using light emitting elements composed of electron emitting elements (cold cathode elements) and phosphors (light emitting members) may cause uneven brightness due to variations in emission currents, etc. This is a preferred form to which the present invention is applied.

  In addition, since uneven brightness is easily noticeable when the size (area) of the display panel is large, a large-area image display device is a preferable embodiment to which the present invention is applied. In addition, since the variation in luminance may become a problem as the number of light-emitting elements increases, high-definition image display devices such as 2K1K, 4K2K, and 8K4K are preferable modes to which the present invention is applied. 2K1K has a resolution of about 2000x1000 (equivalent to full HD), 4K2K has a resolution of about 4000x2000 (about 4 times that of full HD), and 8K4K has a resolution of about 8000x4000 (about 16 times that of full HD). Sure.

  In the present invention, correction data corresponding to the number N of simultaneously driven lines is calculated from the light emission characteristic data (specific luminance) of each light emitting element stored in the storage unit. That is, since the same data (light emission characteristic data) can be shared in a plurality of display modes having different numbers N of simultaneously driven lines, an increase in memory capacity can be prevented. Therefore, an image display device having both single-line drive (N = 1) and multi-line drive (N ≧ 2) display modes is a preferred embodiment to which the present invention is applied. For example, in an image display device having a 4K2K high-definition display mode using single-line driving and a 2K1K high-brightness display mode using two-line driving, the luminance variation is suppressed in both display modes without increasing the memory capacity. Quality image display can be realized. As the number of display modes of the image display apparatus increases, such as single line driving, two line driving, three line driving, four line driving,.

[First Embodiment]
The image display apparatus and the driving method thereof according to the first embodiment of the present invention will be specifically described below. Here, a field emission display device using a light emitting element composed of an electron emitting element and a phosphor is exemplified, but the present invention is not limited to this configuration as described above.

(1) Configuration of Image Display Device With reference to FIG. 2, the configuration of the entire image display device, the flow of signals, and the scanning timing will be described.

  FIG. 2 is a block diagram showing the configuration of the entire image display apparatus. Reference numeral 200 denotes a display panel. The display panel 200 has a thin vacuum container, in which a rear plate and a face plate are opposed to each other via a support member called a spacer. The rear plate is a multi-electron source having 4K2K pixels. On the rear plate, 2160 scanning wirings 213 and 11520 (= RGB × 3840) modulation wirings 212 are formed in a matrix, and electron emitting elements 214 ( For example, a surface conduction electron-emitting device) is formed. The face plate has a glass substrate, a plurality of phosphors provided on the glass substrate so as to face the plurality of electron-emitting devices 214, and a metal back that covers the plurality of phosphors.

  The plurality of electron-emitting devices 214 are wired in a simple matrix by a plurality of modulation wirings 212 and a plurality of scanning wirings 213. By applying signals from the modulation driver 210 and the scanning driver 211 to the modulation wiring 212 and the scanning wiring 213, electrons are emitted from a desired electron-emitting device. By using the high voltage power source 216 to raise the potential of the metal back, the emitted electrons are accelerated and pass through the metal back and collide with the phosphor. Thereby, the phosphor emits light and an image (video) is displayed. The configuration and manufacturing method of this type of display panel are disclosed in detail in, for example, Japanese Patent Application Laid-Open No. 2000-250463.

  Next, a configuration of the image processing circuit, in particular, processing from when a video signal (image data) is input to when data is output to the driving circuit will be described. The image display device is connected to, for example, a video signal supply device, and mainly performs processing using a video signal such as the video signal S1 and the synchronization signal T1 and processing using a command signal such as the communication signal C1. It consists of two types of parts to be performed.

  First, a process from the generation of the video signal S1 input from the video signal supply device to the generation of the drive signal S6 input to the modulation driver 210 will be described.

  The video signal S1 is input to the RGB input unit 201. The RGB input unit 201 is a conversion circuit that converts the video signal S1 so that the horizontal resolution, the number of scanning lines, the frame rate, the clock frequency, and the like match those of the display panel 200, and an adjustment that adjusts color temperature, white balance, and the like. Circuit and the like. The RGB input unit 201 performs a predetermined process on the video signal S1 using the conversion circuit and the adjustment circuit, and outputs the processed signal as a signal S2.

When image data 500 in the 4K2K format as shown in FIG. 5A is input to the RGB input unit 201, format conversion is not performed, and the data of each pixel of the image data 500 is used for driving the corresponding pixel of the display panel 200. Is done. That is, data D (0,0), D (1,0),..., D (3839,2159) are pixels (0,0), (1,0),. ). One pixel of the display panel 200 is composed of three RGB sub-pixels (light emitting elements). On the other hand, when image data 501 in the 2K1K format as shown in FIG. 5B is input to the RGB input unit 201, format conversion is performed, and the data of each pixel of the image data 501 is displayed on the display panel 200 (two rows 2). Column). That is, the four pixels (0,0), (0,1), (1,0), (1,1) in FIG. 5A are changed to one pixel (0,0) as shown in FIG. 5B. Format conversion is performed.

The signal S2 is input to the inverse γ correction unit 202. The inverse γ correction unit 202 converts the signal S2 so that the value of the image data is linear with respect to the luminance of the display panel 200, and outputs the signal S3. Since the converted image data has a value proportional to the luminance, it is also called “luminance data”. In general, the input video signal S1 is transmitted or recorded after being subjected to non-linear conversion (gamma conversion) such as 0.45 according to the input-light emission characteristics of the CRT display on the assumption that the input video signal S1 is displayed on the CRT display device. Has been. The inverse γ correction unit 202 performs inverse gamma conversion such as a square to the video signal in order to display such a video signal on a display device having a linear input-light emission characteristic such as FED or PDP. .

  The signal S3 is input to the luminance variation correcting unit 203, which is a feature in the present embodiment. The luminance variation correction unit 203 performs correction for suppressing the luminance variation caused by the variation in the light emission characteristics of the electron-emitting devices 214 of the display panel 200 on the signal S3, and outputs the signal S4. Details of the luminance variation correction unit 203 will be described in detail later. The signal S4 is also referred to as “corrected luminance data”.

  The signal S4 is input to the phosphor correction unit 204. The phosphor correction unit 204 performs linearity correction on the signal S4 so that the selected light emitting element emits light with a luminance proportional to the correction luminance data in consideration of the nonlinearity of the modulation driver 210 and the luminance saturation characteristic of the phosphor. And output as a signal S5. Here, when the luminance saturation characteristics of the phosphors of R, G, and B colors are different, different conversions may be applied to the corrected luminance data for each color.

The signal S5 is input to the drive conversion unit 205. The drive conversion unit 205 rearranges the image data (S5) input in RGB parallel so as to correspond to the RGB phosphor array of the display panel 200. Further, the drive conversion unit 205 converts the image data into data suitable for the input format (for example, Mini LVDS, RSDS, etc.) of the modulation driver 210, and outputs the data as the drive signal S6.

  The operation timing of each signal processing unit (201 to 205) is controlled by a synchronization signal T2 generated by the timing control unit 206 based on the synchronization signal T1 received from the video signal supply device. The operation mode of each signal processing unit (201 to 205) is controlled by the system control unit 207 by setting each parameter via the system bus 209. The system control unit 207 may be configured with only logic logic, or may be configured with a CPU, a microcomputer, and a media processor capable of parallel operation. The program for performing control may be built in the ROM, or may be transferred from the outside via an input / output interface. The parameters vary from a small data size to a large data size. In any case, the parameters need to be stored even when the power is turned off. For this reason, the parameters are stored in a large-capacity nonvolatile memory 208 represented by a flash memory or the like, and are read out and used by the system control unit 207 as necessary. The nonvolatile memory 208 is not limited to a NAND type or NOR type flash memory, but may be a ROM or a hard disk. Moreover, the structure which uses volatile memories, such as SRAM, like a non-volatile memory by battery drive may be sufficient.

  In addition, the system control unit 207 receives various requests such as a start request and an operation mode switching request from the video signal supply device side by the communication signal C1, and controls the image display device according to the request if there is no error. When there is an error, the video signal supply device side is notified of this, and error processing (for example, forced shutdown) of the image display device is performed in a fail-safe manner.

  Next, a process from when the drive signal S6 is output from the drive conversion unit 205 to when the display panel 200 is driven until video display is performed will be described.

The modulation driver 210 receives the drive signal S6 from the drive conversion unit 205. Then, the modulation driver 210 generates a modulation signal S7 from the drive signal S6 according to the timing control signal T3 from the timing control unit 206, and applies the modulation signal S7 to each modulation wiring 212.
The scanning driver 211 sequentially selects lines (scanning wirings) in accordance with the timing control signal T4 from the timing control unit 206. A selection signal of a predetermined selection potential is applied from the scanning driver 211 to the selected scanning wiring.
The drive power source 215 is a voltage source for modulation signals and selection signals output from the modulation driver 210 and the scan driver 211.

As described above, the selection signal is applied to the selection line (scanning wiring 213), and the modulation signal is applied to each column (modulation wiring 212), thereby selecting each electron-emitting device 214 on the selection line. A differential voltage between the signal and the modulation signal is applied. By modulating the pulse width, amplitude, or both of the modulation signal in accordance with the value of the image data (drive signal S6), desired electron emission can be performed from each electron-emitting device 214.
The high-voltage power supply 216 generates an acceleration voltage (8 to 10 kV), and makes the metal back potential high by the acceleration voltage. Thereby, the electrons emitted from the electron-emitting device 214 are accelerated and collide with the phosphor. The phosphor emits light by the collision of electrons with the phosphor.
By sequentially switching the selection lines and repeating the above processing, an image for one screen is formed (displayed) on the display panel 200.

The drive power source 215 and the high voltage power source 216 are preferably configured to be adaptively controlled by control signals C2 and C3 from the system control unit 207. In particular, it is preferable to control the driving sequence of each power source and the step-up / step-down method of the high-voltage power source with an appropriate startup / shutdown sequence at the time of start-up, power-off, and error occurrence.

  Next, N line driving will be described. Here, a description will be given by taking double line driving in the case of N = 2 as an example. FIG. 3 shows an example of scanning timing.

First, the following operation is performed in the 0th scanning period (period shown as scanning period 0 in FIG. 3 (hereinafter the same)).
The modulation driver 210 outputs a modulation signal S7 corresponding to the luminance data for the 0th and 1st rows to the modulation wiring 212 in response to the timing control signal T3 from the timing control unit 206. The scan driver 211 applies selection signals to Y0 and Y1 corresponding to the timing control signal T4 from the timing control unit 206. The electron-emitting device 214 connected to the selected scanning wiring 213 in the 0th and 1st rows and connected to the modulation wiring 212 to which the modulation signal is applied emits electrons according to the modulation signal of the modulation wiring 212. . Thereby, the elements in the 0th and 1st rows emit light.

  Similarly, the following operation is performed in the first scanning period (period shown as scanning period 1 in FIG. 3). The modulation driver 210 outputs a modulation signal S7 corresponding to the luminance data for the second and third rows to the modulation wiring 212 in response to the timing control signal T3. The scan driver 211 applies a selection signal to Y2 and Y3 corresponding to the timing control signal T4. Thereby, the elements in the second and third rows emit light. The same operation is performed for the second and subsequent scanning periods, and the elements emit light every two rows.

In the case of N> 2, it is the same as the double line drive except that the number of scanning wirings to which the selection signal is applied is increased to N. It is also possible to simultaneously drive N lines spaced apart (with a non-selected line in between) as in the 0th and 2nd rows, instead of adjacent Nlines as in the 0th and 1st rows. However, as will be described later, in this embodiment, since the variation in luminance is corrected by paying attention to the total luminance of N elements in the same column, the distance between the selected lines is larger than the distance at which the integration effect of the human eye is obtained. Is set to be smaller. In addition, a part of the selection lines can be overlapped such that the first and second rows are selected next to the 0th and first rows. It is also possible to leave a gap, such as selecting the fourth and fifth rows next to the zero and first rows. In either case, the same modulation signal S7 is applied to the N electron-emitting devices 214 on the same column on the N line that are driven simultaneously.

(2) Necessity of luminance variation correction Next, the necessity of luminance variation correction in the luminance variation correcting unit 203 and the luminance variation correction performed by normal single line driving, which are problems in the present embodiment. Will be explained.

As described above, in the flat display device, the nonuniformity of the characteristics of the light emitting elements causes the luminance variation of the display device, and the image quality deteriorates.
In response to such a problem, a configuration for correcting image data in accordance with the light emission characteristics of each light emitting element has been proposed. For example, there is a method in which all the light emitting elements are driven under the same conditions (that is, with the same value of image data), the luminance of each light emitting element is measured, and the reciprocal of the measured value is used as correction data for each light emitting element. The luminance measured under the same driving conditions takes a value depending on the light emission characteristics of the element. Here, the data is referred to as “light emission data” or “inherent luminance” of the light emitting element, and data obtained by normalizing the light emission data with a predetermined luminance is referred to as “light emission characteristic data”.

The principle of the above method will be described with reference to the configuration of FIG.
Luminance data S3 before luminance variation correction corresponding to each light emitting element (x, y) [0 ≦ x ≦ 11519, 0 ≦ y ≦ 2159 and so on] of the display panel 200 is D (x, y), Let the light emission amount be P (x, y). Further, the light emission characteristic data of each light emitting element is represented by K (x, y).

When correction is not performed, variation in the light emission characteristics of the element affects the image to be displayed, and the display panel 200 has
P (x, y) = D (x, y) ・ K (x, y)
Is formed. Since K (x, y) includes variations depending on the light emission characteristics, this appears to be rough or uneven in the image.

Therefore, the reciprocal of the light emission characteristic data K (x, y) of each element is stored in advance in the nonvolatile memory 208 as correction data Q (x, y), and the luminance data D (x, y) is obtained by the luminance variation correction unit 203. ) Is multiplied by correction data Q (x, y). Then, when the display panel 200 is driven with the corrected luminance data D (x, y) · Q (x, y), the light emission characteristics of the element affect the display panel.
P (x, y) = D (x, y), Q (x, y), K (x, y) ... [Formula 1]
Is formed. Since Q (x, y) is the reciprocal of K (x, y), a uniform image with P (x, y) = D (x, y) in which the variation in the light emission characteristics of each element is canceled can be obtained.

(3) Problem of luminance variation correction at the time of multiline driving Next, the problem of luminance variation correction at the time of multiline driving and the fact that the luminance variation occurs even if the conventional correction method is used will be described.

<About multi-line drive>
Multi-line driving is a scanning method in which a plurality of lines (scanning lines) are simultaneously selected to simultaneously drive light emitting elements on the plurality of selected lines. In multi-line driving, a longer time can be assigned to the horizontal scanning period than in single-line driving. For example, in double line driving, the length of the horizontal scanning period is twice that in single line driving, so that the light emission luminance of the display panel can be approximately doubled.
In the present embodiment, as described with reference to FIG. 3, double line driving that simultaneously drives two adjacent scanning wirings is used.

<Issues with luminance variation correction during double line driving>
Since the two scanning lines are driven simultaneously during the double line driving, the same modulation signal S7 is applied to two light emitting elements connected to the same modulation line. For this reason, unlike the case of single line driving, it is not possible to drive with an optimal modulation signal corrected according to the characteristics of each element, resulting in luminance variations.

For example, consider an example in which R subpixel (0,0) and subpixel (0,1) as shown in FIG. Assuming that the light emission characteristic data of the subpixel (0,0) and subpixel (0,1) are K (0,0) and K (0,1), the correction data Q ( x, y) is the reciprocal of the light emission characteristic data K (x, y) of each element,
Q (0,0) = 1 / K (0,0)
Q (0,1) = 1 / K (0,1)
It becomes.

Consider a case in which luminance data is corrected using correction data Q (0,0) of subpixel (0,0) as a representative value.
When luminance data D (0,0) is given, the total light emission amount P1 (0,0) + P1 (0,1) in the two elements is expressed by [Expression 1]
P1 (0,0) + P1 (0,1) = D (0,0) ・ Q (0,0) ・ K (0,0) + D (0,0) ・ Q (0,0) ・ K (0 , 1)
＝ [{K (0,0) + K (0,1)} / K (0,0)] ・ D (0,0)
It becomes.
On the other hand, the target total light emission amount P0 (0,0) + P0 (0,1) of the two elements is the optimum correction data Q (0,0) and Q (0,1) respectively for the two light emitting elements. Because it is the amount of light emitted when corrected with
P0 (0,0) + P0 (0,1) = D (0,0) ・ Q (0,0) ・ K (0,0) + D (0,0) ・ Q (0,1) ・ K (0 , 1)
= 2 ・ D (0,0)
It becomes.

Therefore, the following coefficient E1
E1 = {K (0,0) + K (0,1)} / K (0,0)
= 1 + K (0,1) / K (0,0) ... [Formula 2]
An error corresponding to is generated.
From the meaning shown in [Formula 2], no error occurs when the values of the light emission characteristic data K (0,0) and K (0,1) are equal, but when the values are different, K (0,1) An error corresponding to the ratio of / K (0,0) occurs. For example,
Assuming that the variation in luminance of all the light emitting elements of the display panel shows a distribution as shown in FIG. 6A,
K (0,0) = 0.7
K (0,1) = 1.0
Then, the coefficient E1 is about 2.428, and the relative error with respect to the target total light emission amount is about 21.4%.

From the above, the following [Conclusion 0] can be derived.
In the method of using the correction data for single line driving of any one of the light emitting elements as the correction data for multiline driving, the luminance variation is deteriorated as compared with the single line driving. [Conclusion 0]

As another method, there is known a method of using an average value of correction data for single line driving as correction data for double line driving.
Similar to the above, consider an example in which the subpixel (0,0) and the subpixel (0,1) as shown in FIG. With this method, correction data for single line drive
Q (0,0) = 1 / K (0,0)
Q (0,1) = 1 / K (0,1)
Is the average of
q1 (0,0) = {1 / K (0,0) + 1 / K (0,1)} / 2
Is used as correction data for double line driving.

In this case, the total light emission amount P2 (0,0) + P2 (0,1) in the two elements is
P2 (0,0) + P2 (0,1) = D (0,0) ・ q1 (0,0) ・ K (0,0) + D (0,0) ・ q1 (0,0) ・ K (0 , 1)
＝ [{K (0,0) + K (0,1)} ² / {2 ・ K (0,0) ・ K (0,1)}] ・ D (0,0)
It becomes.
The target total amount of light emitted by the two elements is the same as above
P0 (0,0) + P0 (0,1) = 2 ・ D (0,0)
It is.

At this time, an error corresponding to the following coefficient E2 occurs.
E2 = {K (0,0) + K (0,1)} ² / {2 ・ K (0,0) ・ K (0,1)}
= {1 + K (0,1) / K (0,0)} ・ {1 + K (0,0) / K (0,1)} / 2 ... [Formula 3]
Substituting [Equation 2] into [Equation 3]
E2 = E1 ・ {1 + K (0,0) / K (0,1)} / 2 ... [Formula 4]
It becomes.
From the meaning shown in [Expression 4], no error occurs when the values of the light emission characteristic data K (0,0) and K (0,1) are equal, but K (0,1) when the values are different. An error occurs according to the ratio of / K (0,0), and the error with respect to the coefficient E1 of the above method changes. For example, assuming that the luminance variation of all the light emitting elements of the display panel shows a distribution as shown in FIG.
K (0,0) = 0.7
K (0,1) = 1.0
Then, the coefficient E2 is about 2.064, and the relative error with respect to the target total light emission amount is about 3.2%.

From the above, the following [Conclusion 1] can be derived.
When the average value of correction data for single-line drive is used as correction data for multi-line drive, brightness variation is worse than that of single-line drive. [Conclusion 1]

(4) Description of Features of the Present Embodiment Next, a correction data calculation method at the time of multi-line driving in the luminance variation correction unit 203 that is a feature of the present embodiment will be described.

  As described above, since the display panel has a variation in light emission characteristics from element to element, it is difficult to drive with an optimal modulation signal in double line driving by the conventional method.

  On the other hand, the input signal format is diversified, and the 2K1K format of full HD as a TV signal format and the 4K2K format as a format for digital cinema are spreading. In the future, it is conceivable that the image display device will further increase in definition such as 4K2K. Therefore, it is naturally required to receive and display the current 2K1K format TV signal on a high-definition display such as 4K2K.

Consider a case where a current 2K1K format signal is input to a 4K2K high-definition display panel of the same size as the 2K1K display panel. In this case, the size of 4 pixels of the 4K2K high-definition display panel is the same as the size of 1 pixel of the 2K1K display panel. Further, as shown in the above (1), the input data in the 2K1K format can be format-converted so as to be input as the same data to the four pixels.
From this, it can be seen that even if data common to the two elements is input, the image quality of the 2K1K format data of the current TV signal can be maintained by viewing the two elements as one subpixel.

  Incidentally, as shown in FIG. 6A, the display panel has variations in luminance due to variations in light emission characteristics. In order to correct all the elements, the intrinsic brightness of the darkest element is set to the target brightness, and the brightness of all the elements is made uniform by darkening the elements brighter than the target brightness. However, if there is an extremely dark element on the display panel, setting the intrinsic luminance of the darkest element as the target luminance will cause the luminance of the entire display panel to become extremely dark. In such a case, it is preferable to set the target luminance based on variations in intrinsic luminance (average μ, standard deviation σ, etc.). For example, as shown in FIG. 6A, the luminance of μ−3σ = 0.4 is set as the target luminance, and the display luminance is corrected according to the target luminance. Thus, if the luminance of μ−3σ is set as the target luminance, 99% or more of the elements can be corrected. Note that an element darker than the target luminance cannot be corrected to the target luminance, so that the correction remains, but there is no practical problem.

  FIG. 6B is a diagram showing the luminance variation in the total luminance of the two elements. Since the same effect as the averaging can be obtained by summing the luminance of the two elements, it can be seen that the variation in luminance is apparently reduced. For this reason, even if the target luminance per light-emitting element is set to the same value 0.4 (0.8 when converted to double line drive) as in single line drive, the remaining correction is greater than in single line drive. Decrease.

From this, the following [Conclusion 2] can be derived.
If correction data for multiline driving is created from the total luminance (or average luminance) of a plurality of elements driven by the same modulation signal, it is possible to reduce the luminance variation compared to single line driving. . [Conclusion 2]

Based on the above examination, the present inventors consider a plurality of light emitting elements driven simultaneously with the same modulation signal as one subpixel, and correct from the total value (or average value) of the intrinsic luminance of the plurality of light emitting elements. A method of calculating data was devised.
According to this method, for example, by performing double line driving on a 4K2K high-definition display panel, a video signal in 2K1K format can be displayed with an image quality equivalent to that of a display panel with 2K1K resolution. In addition, even if an extremely dark light emitting element is included in the display panel, the luminance variation can be further reduced as compared with the conventional correction method.

<Brightness variation correction unit>
Next, the luminance variation correction unit 203 of this embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing details of the luminance variation correcting unit 203 in FIG. The luminance variation correction unit 203 is roughly divided into two processing systems: a light emission characteristic data write / transfer processing system and a light emission characteristic data read calculation processing system. Each processing system will be described in detail below.

(A) Light Emission Characteristic Data Write / Transfer Processing System This processing system sends light emission characteristic data from a low-speed nonvolatile memory 208 to a volatile memory 102 which is a high-speed storage unit as a stage before performing signal processing for correcting luminance variations. It is provided for transferring.

  Specifically, when the power is turned on, the system control unit 207 reads the light emission characteristic data stored in the nonvolatile memory 208 of FIG. 2, and continuously transfers it to the memory write control unit via the system bus 209. . The memory write control unit 100 stores the light emission characteristic data in an internal buffer, converts the format, and writes the data as memory write data M1 in the volatile memory 102 capable of high-speed operation.

  Note that the non-volatile memory 208 of the present embodiment stores the value of the intrinsic luminance when all the elements of the display panel 200 are driven under the same driving conditions as the light emission characteristic data. However, as the light emission characteristic data, a value corresponding to the intrinsic luminance may be used instead of the intrinsic luminance value itself. The value corresponding to the intrinsic luminance is a value that can substantially restore the intrinsic luminance value by performing a predetermined calculation, for example, a value obtained by normalizing the intrinsic luminance with the predetermined luminance, an inverse number of the intrinsic luminance, A value obtained by converting the intrinsic luminance by a predetermined function is applicable.

(B) Light emission characteristic data read calculation processing system This processing system calculates correction data from the light emission characteristic data read from the volatile memory 102, and performs luminance variation correction on the input luminance data S3 using the correction data. It is provided for outputting corrected luminance data S4.

  In (a) above, when the transfer of all the light emission characteristic data to the volatile memory 102 is completed, the system control unit 207 instructs the correction calculation unit 101 to start the correction calculation. The correction calculation unit 101 sequentially reads the light emission characteristic data from the volatile memory 102 as the memory read data M2 in synchronization with the synchronization signal T2 from the timing control unit 206. The correction data creation unit 103 selects the light emission characteristic data of the elements to be driven simultaneously from the read light emission characteristic data, and generates the representative correction data S8 for double line driving from the average value of the light emission characteristic data (inherent luminance). create. The correction data S8 is calculated so as to have a value proportional to the inverse of the average value of the intrinsic luminance. The proportionality constant is appropriately set according to the specifications of the luminance data S3 and the corrected luminance data S4, the minimum value of the average value of the intrinsic luminance, and the like.

  The correction data normalization unit 104 normalizes the correction data S8 with the target luminance, thereby adjusting the correction data S8 to an optimum size so that the correction luminance becomes the target luminance, and outputs the standardized correction data S9. . For example, as shown in FIG. 6B, when the target luminance per element is 0.4 (the total target luminance of two elements is 0.8) as in the case of single line driving, the element pair has a total luminance of 0.8. Each correction data value is multiplied by a coefficient so that the correction data value for 1 becomes 1. That is, the value of each correction data S8 is uniformly multiplied by the reciprocal of the correction data S8 for the element pair having a total luminance of 0.8. However, the correction data normalization unit 104 may be limited so that the value of the correction data after normalization does not exceed 1 (this limited portion corresponds to the remaining correction). The configuration and processing of the correction data normalization unit 104 may be omitted.

  The input data correction unit 105 is a multiplier, and generates the corrected luminance data S4 by multiplying the luminance data S3 by the normalized correction data S9.

As in the case of (3) described above, consider an example in which the subpixel (0,0) and the subpixel (0,1) as shown in FIG. In the present embodiment, representative correction data S8 for double line driving is created from the average value of the light emission characteristic data K (0,0) and K (0,1) for each element. For example,
q2 (0,0) = 2 / {K (0,0) + K (0,1)}
Is used as correction data for double line driving.

In this case, the total light emission amount P3 (0,0) + P3 (0,1) of the two elements is shared with the luminance signal D (0,0) and the correction data q2 (0,0) because of the double line drive. For
P3 (0,0) + P3 (0,1) = D (0,0) ・ q2 (0,0) ・ K (0,0) + D (0,0) ・ q2 (0,0) ・ K (0 , 1)
＝ D (0,0) ・ q2 (0,0) ・ {K (0,0) + K (0,1)}
= 2 ・ D (0,0)
It becomes.
On the other hand, the target total light emission amount P0 (0,0) + P0 (0,1) of the two elements is the optimum correction data Q (0,0) and Q (0,1) respectively for the two light emitting elements. Because it is the amount of light emitted when corrected with
P0 (0,0) + P0 (0,1) = D (0,0) ・ Q (0,0) ・ K (0,0) + D (0,0) ・ Q (0,1) ・ K (0 , 1)
= 2 ・ D (0,0)
It is.

  As described above, according to the luminance variation correction of the present embodiment, the total light emission amount of the two elements in the double line drive can be matched with the target total light emission amount. Therefore, when double line driving is performed, it is possible to improve image quality deterioration due to luminance variation and display a high-quality image. Here, the double line drive has been described as an example. However, even when N> 2 with N> 2, appropriate luminance variation correction can be performed by the method of the present embodiment.

[Second Embodiment]
In the first embodiment, the correction data is standardized based on a fixed target luminance (the same target luminance as that of single line driving). On the other hand, in the second embodiment, the target luminance is changed according to the variation degree of the average value of the intrinsic luminance of the N light emitting elements that are simultaneously driven with the same modulation signal. Thereby, the improvement of the target luminance at the time of multiline driving is realized.

Specific processing in the present embodiment will be described with reference to FIG. 1 as in the first embodiment.
In the present embodiment, when the correction data normalization unit 104 performs normalization, the correction is performed by normalizing μ−3σ as a target luminance. Here, μ (average) and σ (standard deviation) are statistical quantities representing variations in the average value of the intrinsic luminance of the N light emitting elements. For example, considering the example of two elements as shown in FIG. 6B, the value of each correction data is multiplied by a coefficient so that the correction data value for an element pair in which the total luminance of the two elements is equal to μ−3σ is 1. That is, the correction data normalization unit 104 uniformly multiplies the value of each correction data by the reciprocal of the correction data for the element pair with the total luminance of μ−3σ. Also in this case, the correction data normalization unit 104 limits the value of the correction data after normalization so as not to exceed 1. As can be seen from FIG. 6A and FIG. 6B, since the apparent variation is usually reduced by averaging the luminance, the larger the value of N, the larger the value of the target luminance (μ−3σ). That is, the value of the target luminance can be increased without changing the ratio of elements to be corrected (99% or more).

As described above, according to the present embodiment, by determining the target luminance value according to the degree of variation in the average value of the intrinsic luminance, it is possible to further improve the luminance while maintaining the quality of luminance variation correction. It becomes.
The target brightness value may be dynamically calculated by the correction data normalization unit 104 or stored in advance in the nonvolatile memory 208. In addition, the value of the target luminance can be other values obtained from statistics (average, standard deviation, variance, median, mode, etc.) instead of μ−3σ.

[Third Embodiment]
The image display apparatus according to the third embodiment of the present invention has a plurality of display modes in which the value of the number N of simultaneous drive lines is different from each other, and when the display mode is changed, according to the changed value of N. The correction data used for correcting the luminance variation is changed. Hereinafter, a configuration capable of switching between the 4K2K high-definition display mode and the 2K1K high-luminance display mode will be exemplified.

  Conventionally, in order to perform high-precision luminance variation correction in both the 4K2K high-definition display mode and the 2K1K high-brightness display mode, it is necessary to store correction data for each display mode in the nonvolatile memory 208 as shown in FIG. 8A. there were. Reference numeral 800 in FIG. 8A indicates correction data for single line driving, and reference numeral 801 indicates correction data for double line driving. This is not preferable because it increases the memory capacity. The problem becomes more important as the number of display modes increases.

  Therefore, in this embodiment, as shown in FIG. 8B, the light emission characteristic data of each light emitting element is stored in the non-volatile memory 208, and the correction data creation unit 103 (FIG. 1) matches the display mode (sets the value of N). In addition, correction data is created dynamically. As a result, the same light emission characteristic data can be shared between the 4K2K high-definition display mode and the 2K1K high-luminance display mode.

  A specific control method in this embodiment will be described with reference to FIGS. 1, 2, and 7. FIG. 7 is a flowchart showing the features of this embodiment. The difference from the first embodiment is that the system controller 207 has a correction data creation method and a scanning method change instruction function for switching between the 4K2K high-definition display mode and the 2K1K high-brightness display mode.

  When the image display apparatus is powered on, the system control unit 207 in FIG. 2 transfers the light emission characteristic data from the nonvolatile memory 208 to the luminance variation correction unit 203 (S101). Further, the system control unit 207 determines the display mode based on the communication signal C1 input from the video signal supply device. In the video signal supply device, an appropriate display mode is determined in accordance with the user's mode switching request, the type of the input video signal, and the like.

If the display mode is the 4K2K high-definition display mode in S102, the correction data creation unit 103 calculates the correction data for single line driving from the light emission characteristic data K (x, y) in S103.
Q (x, y) = 1 / K (x, y)
Create Then, after processing similar to that of the first embodiment is performed, a drive signal S6 for single line driving is output to the modulation driver 210 (S104). The scanning driver 211 drives the scanning wiring line by line (S105). Thereby, the image display of 4K2K resolution by single line drive is performed.

On the other hand, if the display mode is not the 4K2K high-definition display mode in S102, it is determined in S106 whether the display mode is the 2K1K high-luminance display mode. If the display mode is the 2K1K high-luminance display mode in S106, the correction data creation unit 103 corrects the double line drive from the light emission characteristic data K (x, y), K (x, y + 1) in S107. data
q (x, y) = 2 / {K (x, y) + K (x, y + 1)}
Create Then, after the same processing as that of the first embodiment is performed, a drive signal S6 for double line driving is output to the modulation driver 210 (S108). The scan driver 211 drives the scan wiring line by line (S109). As a result, 2K1K resolution image display by double line driving is performed.

  As described above, in the third embodiment, the display mode is determined, and correction data corresponding to the display mode is created from the light emission characteristic data. As a result, it is not necessary to store correction data for each display mode in the nonvolatile memory 208 as shown in FIG. 8A. Therefore, the memory capacity is not increased as shown in FIG. Brightness variations can be corrected.

  101: Correction calculation unit, 200: Display panel, 203: Brightness variation correction unit, 208: Non-volatile memory, 210: Modulation driver, 211: Scan driver

Claims (7)

A display panel having a plurality of scanning wirings and a plurality of modulation wirings arranged in a matrix, and a plurality of light emitting elements each connected to the scanning wirings and the modulation wirings;
A scanning circuit that sequentially switches the scanning wirings to which the selection signal is applied every N lines (N is an integer of 1 or more);
A modulation circuit for applying a modulation signal generated based on image data to each modulation wiring;
An image processing circuit for outputting image data to the modulation circuit,
The image processing circuit includes:
A storage unit that stores, as light emission characteristic data of each light emitting element, a specific luminance or a value corresponding to the specific luminance that is the luminance of each light emitting element when each of the plurality of light emitting elements is driven under the same conditions;
A correction calculation unit that performs correction for suppressing variation in luminance of the plurality of light emitting elements with respect to image data, using correction data calculated from the light emission characteristic data;
Have
The correction calculation unit calculates correction data to be applied to each image data from an average value of intrinsic luminance of N light emitting elements for N lines that are simultaneously driven by a modulation signal generated based on the image data. An image display device characterized by that. The correction calculation unit is
A correction data creation unit for calculating correction data so as to have a value proportional to the inverse of the average value of the intrinsic luminance of the N light emitting elements;
The image display apparatus according to claim 1, further comprising a multiplier that multiplies the correction data by the image data. The correction calculation unit is
A correction data normalization unit that normalizes the correction data calculated by the correction data generation unit based on a target luminance per light emitting element;
The image display device according to claim 2, wherein the multiplier multiplies the image data by the normalized correction data. The correction data normalization unit
4. The image display device according to claim 3, wherein a target luminance value per light emitting element is determined from a statistic representing a variation in an average value of intrinsic luminance of N light emitting elements. A plurality of display modes having different values of N,
5. The image display device according to claim 1, wherein when the display mode is changed, the correction calculation unit changes the correction data in accordance with the changed value of N. 6. . The said light emitting element is comprised from the light emitting member which light-emits by the cold cathode element which discharge | releases an electron, and the electron discharge | released from the said cold cathode element, The any one of Claims 1-5 characterized by the above-mentioned. Image display device. A driving method of an image display device,
The image display device applies a selection signal to a display panel having a plurality of scanning wirings and a plurality of modulation wirings arranged in a matrix, and a plurality of light emitting elements each connected to the scanning wirings and the modulation wirings. A scanning circuit that sequentially switches the scanning lines by N lines (N is an integer of 1 or more), a modulation circuit that applies a modulation signal generated based on image data to each modulation line, and each of the plurality of light emitting elements under the same conditions A storage unit that stores the intrinsic luminance that is the luminance of each light emitting element when driven or a value corresponding to the intrinsic luminance as light emission characteristic data of each light emitting element,
The driving method is:
Reading light emission characteristic data from the storage unit;
Calculating correction data from the read emission characteristic data;
Using the calculated correction data, performing correction for suppressing variation in luminance of the plurality of light emitting elements on the image data;
Including
Correction data to be applied to each image data is calculated from an average value of intrinsic luminance of N light emitting elements for N lines driven simultaneously by a modulation signal generated based on the image data. Driving method of image display apparatus.

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