Patent Grant
7522172
This application is based on Japanese Patent Application No. 2005-152058 filed on May 25, 2005, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a display device such as an organic EL (electroluminescence) display device, inorganic EL display device, liquid crystal display device, or plasma display device.
2. Description of Related Art
Display devices like an organic EL display device provided with a self-luminous display panel (self-luminous display) offer advantages of being slim, lightweight, and low-power-consumption, and have been finding increasingly wide application. For application in cellular phones, digital still cameras, and the like, however, such display devices are still to attain lower power consumption.
There have been developed RGB-type organic EL display devices having R, G, and B color filters bonded to a white light emitting material. An RGB-type organic EL display device includes, for each of its R, G, and B unit pixels, an organic EL element. In an RGB-type organic EL display device, when light passes through the color filters, part of the light is absorbed by the color filters. This results in poor light use efficiency, hampering further lowering of power consumption.
Under these circumstances, the applicant of the present application has developed, and has filed patent applications for, RGBW-type organic EL display devices (self-luminous display devices) that permit further lowering of power consumption. An RGBW-type organic EL display device includes, for each of its R, G, B, and W unit pixels, an organic EL element. These organic EL elements emits, for example, white light.
An RGBW-type organic EL display device includes a display panel composed of, as shown in
Having no color filter arranged thereat, the unit pixel for displaying white exhibits extremely high light use efficiency. Accordingly, for example, when white is displayed, it is displayed not by making the unit pixels for displaying R, G, and B emit light but by making the unit pixel for displaying white emit light. This helps greatly reduce power consumption.
If the RGB-signals-to-W-signal conversion rate (the proportion in which RGB signals are converted into a W signal) is 100%, as much of the RGB signals as possible is converted into the W signal, and thus the high-efficiency W pixels (the pixels for displaying white) are made the most of, achieving the lowest power consumption. In a case where RGB signals are each an eight-bit digital signal, and when they all have a value of 255 (assuming that an increase in this value means an increase in brightness), if the RGB-signals-to-W-signal conversion rate is 100%, for example, as shown in
JP-A-2001-109423 (hereinafter “Patent Publication 1”) discloses an RGB-type display device provided with means for controlling the signals applied to adjacent pixels such that the sum of the brightness of the pixels adjacent to a defective pixel equals the brightness that the defective pixel would produce were it not defective.
JP-A-2002-189440 (hereinafter “Patent Publication 2”) discloses an RGB-type display device provided with: a correction data storage portion that stores correction data prescribed according to input signals; and a correction processing portion that, when a defective pixel is found, determines correction data based on input signals and, by using the correction data, corrects the input signals to the pixels around the defective pixel.
Usually, the RGB-signals-to-W-signal conversion rate is set equal (for example, 100%) over the entire the display panel. From the viewpoint of reducing power consumption, it is preferable that the RGB-signals-to-W-signal conversion rate be set as high as possible. If there is a defect among W pixels for displaying white, however, as shown in
The technologies disclosed in Patent Publications 1 and 2 mentioned above are aimed at simply increasing the brightness of pixels around a faulty (defective) pixel, if any, in an RGB-type display device, and therefore cannot be applied, as they are, to an RGBW-type display device where consideration needs to be given to, among other factors, the RGB-signals-to-W-signal conversion rate. Incidentally, in an RGB-type display device, even if a pixel is defective, when white is displayed, it is only a single R, G, or B pixel that fails to emit light. Thus, with no black spot appearing, the defect is comparatively inconspicuous.
In view of the conventionally experienced inconveniences mentioned above, it is an object of the present invention to provide a display device in which a defective pixel, if any, is less conspicuous than ever.
To achieve the above object, according to the present invention, a display device is provided with: an RGB-RGBX conversion circuit that converts RGB signals fed thereto into RGBX signals, where X represents a predetermined color other than R, G, and B; a display panel that displays an image based on the RGBX signals obtained from the RGB-RGBX conversion circuit, the display panel being composed of a plurality of dots each composed of four unit pixels that are an R pixel, a G pixel, a B pixel, and an X pixel; and a defect position specifier that specifies, if a unit pixel is found defective, the position of the defective pixel on the display panel. Here, the RGB-RGBX conversion circuit has a conversion rate controller that controls the conversion rate at which, when the RGB signals are converted into the RGBX signals, the RGB signals are converted into an X signal according to the position specified by the defect position specifier. The conversion rate controller makes the conversion rate for at least one unit pixel adjacent to the defective pixel different from the standard conversion rate set for the entire display panel.
Consider, for example, a case where an X pixel, which would emit white light if not defective, is defective and does not emit light as expected. In this case, if RGB signals are converted into an X signal on the assumption that the defective X pixel emits light as expected, then, as in the display panel 60 shown in
In the configuration described above, however, the conversion rate for at least one unit pixel adjacent to the defective pixel is so controlled as to be different from the standard conversion rate (for example, 90% or 100%) set for the entire display panel. That is, according to the type of the unit pixel found defective, as in the display panel 61 shown in
Specifically, suppose that the RGB signals fed to the RGB-RGBX conversion circuit are composed of an R signal representing the brightness of R pixels, a G signal representing the brightness of G pixels, and a B signal representing the brightness of B pixels; moreover, let the maximum value of the X signal obtained when the RGB signals fed to the RGB-RGBX conversion circuit are converted into the RGBX signals be called the maximum-conversion X signal value, and let the component of the R signal, the component of the G signal, and the component of the B signal that are to be converted into the maximum-conversion X signal value be called the maximum-conversion R signal, the maximum-conversion G signal, and the maximum-conversion B signal, respectively; then the conversion rate controlled by the conversion rate controller represents the ratio of the component of the R signal actually converted into the X signal to the maximum-conversion R signal, the ratio of the component of the G signal actually converted into the X signal to the maximum-conversion G signal, and the ratio of the component of the B signal actually converted into the X signal to the maximum-conversion B signal.
In Numerical Example 3 (
For example, the chromaticity coordinates of the chromaticity obtained as a result of light emission by an X pixel are located, in the chromaticity coordinate system, inside the triangle formed by the chromaticity coordinates of an R pixel, the chromaticity coordinates of a G pixel, and the chromaticity coordinates of a B pixel.
For example, the standard conversion rate is the conversion rate set for all the unit pixels when none of all the unit pixels forming the display panel is found defective.
Specifically, a defective pixel is made inconspicuous by one of the following ways.
For example, if the defective pixel is an X pixel, the conversion rate controller makes the conversion rate for at least one non-X unit pixel adjacent to the defective pixel lower than the standard conversion rate.
In
Alternatively, for example, if the defective pixel is an X pixel, the conversion rate controller makes the conversion rate for the R, G, and B pixels of a dot including at least one unit pixel adjacent to the defective pixel lower than the standard conversion rate.
In
Alternatively, for example, if the defective pixel is an R, G, or B pixel, the conversion rate controller makes the conversion rate for at least one non-X unit pixel adjacent to the defective pixel lower than the standard conversion rate.
In
Alternatively, for example, if the defective pixel is an R, G, or B pixel, and in addition one or more X pixels are adjacent to the defective pixel, the conversion rate controller makes the conversion rate for at least one of the one or more X pixels adjacent to the defective pixel higher than the standard conversion rate.
In
Alternatively, for example, if the defective pixel is an X pixel, and in addition one or more other X pixels are adjacent to the defective pixel, the conversion rate controller makes the conversion rate for at least one X pixel adjacent to the defective pixel higher than the standard conversion rate.
In
Alternatively, for example, if the defective pixel is an X pixel, and in addition one or more other X pixels are adjacent to the defective pixel, the conversion rate controller makes the conversion rate for at least one non-X unit pixel adjacent to the defective pixel lower than the standard conversion rate.
In
Alternatively, for example, if the defective pixel is an X pixel, in addition one or more other X pixels are adjacent to the defective pixel, and in addition the conversion rate for the other X pixels adjacent to the defective pixel is maximal, the conversion rate controller makes the conversion rate for at least one non-X unit pixel adjacent to the defective pixel lower than the standard conversion rate, and makes the conversion rate for at least one non-X unit pixel adjacent to the other X pixels lower than the standard conversion rate.
In
As described above, with a display device according to the present invention, a defective pixel can be made inconspicuous. This helps alleviate degradation in the display quality of the display pixel, and helps reduce the incidence of defective panels.
A first embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
From outside, digital RGB signals Rin, Gin, and Bin are fed to the RGB-RGBW conversion circuit 1. In the following description, these RGB signals Rin, Gin, and Bin are also referred to simply as the “RGB input signals”. Based on pixel defect information fed from the defect position specifier 15 (see
The RGBW signals obtained from the RGB-RGBW conversion circuit 1 are converted into analog RGBW signals by the D/A conversion circuit 2. The display panel 3 is an RGBW-type display panel that displays a color image based on the analog RGBW signals obtained from the D/A conversion circuit 2.
To display a color image, the display panel 3 has a plurality of dots arrayed in rows and columns.
In the following description, R, G, and B pixels are also referred to collectively as “RGB pixels”, and likewise R, G, B, and W pixels are also referred to collectively as “RGBW pixels”.
The RGB input signals fed to the RGB-RGBW conversion circuit 1 are composed of an R signal Rin representing the R (red) component of the image, a G signal Gin representing the G (green) component of the image, and an B signal Bin representing the B (blue) component of the image. In a case where the image is displayed with RGB pixels (three unit pixels, namely R, G, and B pixels), that is, when the image is displayed on an RGB basis, the R, G, and B signals Rin, Gin, and Bin represent the brightness of R, G, and B pixels, respectively.
The RGBW signals outputted from the RGB-RGBW conversion circuit 1 are composed of an R signal Rout, a G signal Gout, a B signal Bout, and a W signal Wout. In a case where the image is displayed with RGBW pixels (four unit pixels, namely R, G, B, and W pixels), that is, when the image is displayed on an RGBW basis, the R, G, B, and W signals Rout, Gout, Bout, and Wout represent the brightness of R, G, B, and W pixels, respectively.
The RGB signals Rin, Gin, and Bin (the R, G, and B signals Rin, Gin, and Bin) are each an eight-bit digital signal (needless to say, these may each be other than an eight-bit digital signal) that takes a value between 0 and 255, an increase in this value meaning an increase in the brightness of the corresponding unit pixel. Likewise, the RGBW signals Rout, Gout, Bout, and Wout (the R, G, B, and W signals Rout, Gout, Bout, and Wout) are each an eight-bit digital signal (needless to say, these may each be other than an eight-bit digital signal) that takes a value between 0 and 255, an increase in this value meaning an increase in the brightness of the corresponding unit pixel. In the following description, for the sake of simplicity, the signal values (that is, the values of the RGB input signals and the values of the RGBW signals) are proportional to display brightness.
Principle of Conversion
Now, the principle on which the RGB-RGBW conversion circuit 1 converts RGB input signals to RGBW signals will be described by way of a first, a second, and a third numerical examples. The principle of conversion described below applies not only to this embodiment but to the second embodiment described later.
First, as a first numerical example, consider a case where RGB input signals are converted into a W signal in a ratio of 1:1:1, that is, where RGB input signals (Rin, Gin, Bin)=(k, k, k) are converted into a W signal having a value of k (that is, Wout=k), where k is an integer between 0 to 255.
Since the ratio in which RGB input signals are converted into a W signal is 1:1:1, the second RGB signal components (100, 100, 100) are converted into a W signal having a value of 100. Adding up (synthesizing) the W signal having a value of 100 and the first RGB signal components shown in graph P2 produces RGBW signal values (120, 80, 0, 100) shown in graph P4. That is, in the first numerical example, RGB input signals are converted into RGBW signals such that (Rout, Gout, Bout, Wout)=(120, 80, 0, 100).
The first numerical example has just been described assuming that the ratio in which RGB input signals are converted into a W signal is 1:1:1. In reality, however, the chromaticity of the white obtained from a white self-luminous material (organic EL elements) is often different from the chromaticity of the targeted white. When RGB input signals (Rin, Gin, Bin)=(k, k, k) are fed in, the chromaticity of the targeted white should be realized. To achieve this, according to the characteristics of the display panel, the ratio in which RGB input signals are converted into a W signal need to be set adequately. How the ratio is calculated according to the characteristics of the display panel will be described later in the section headed “Panel Adjustment”.
Next, as a second numerical example, consider a case where RGB input signals are converted into a W signal in a ratio of 1.00:1.20:1.15, that is, where RGB input signals (Rin, Gin, Bin)=(k/1.00, k/1.20, k/1.15) are converted into a W signal having a value of k, where k is an integer between 0 to 255.
Here, “min(z1, z2, z3)” (where z1, z2, and z3 are arbitrary numbers) is an operational notation that denotes taking the minimum value among z1, z2, and z3. In the following description, except when the ratio in which RGB input signals are converted into a W signal and the maximum-conversion W signal value WMAX are dealt with, all values will be considered (in principle) with their fractional portions discarded.
R1=220×1.00=220 (1)
G1=180×1.20=216 (2)
B1=100×1.15=115 (3)
Subsequently, to calculate the RGB signals as they are after conversion into RGBW signals (that is, to calculate Rout, Gout, and Bout), the component R2 of the R signal Rin, the component G2 of the G signal Gin, and the component B2 of the B signal Bin that are converted into Wout are calculated by formulae (4), (5), and (6) below.
R2=115/1.00=115 (4)
G2=115/1.20=95 (5)
B2=115/1.15=100 (6)
Since 220−115=105, 180−95=85, and 100−100=0, the RGB input signals can be broken down into first RGB signal components (105, 85, 0) shown in graph P6 and second RGB signal components (115, 95, 100) shown in graph P7.
Since the ratio in which RGB input signals are converted into a W signal is 1.00:1.20:1.15, the second RGB signal components (115, 95, 100) are converted into a W signal having a value of 115. Adding up (synthesizing) the W signal having a value of 115 and the first RGB signal components shown in graph P6 produces RGBW signal values (105, 85, 0, 115) shown in graph P8. That is, in the second numerical example, RGB input signals are converted into RGBW signals such that (Rout, Gout, Bout, Wout)=(105, 85, 0, 115).
The second numerical example is an example where the maximum value of the W signal obtained as a result of RGB input signals being converted into RGBW signals (that is, the maximum-conversion W signal value WMAX) is used, as it is, as the Wout (that is, an example where the W signal Wout is maximized), in other words, an example where the W pixel use rate (that is, the RGB-signals-to-W-signal conversion rate, or the W contribution rate) WGAIN is maximized, that is, made equal to 100%. As will be described in detail later, in the RGB-RGBW conversion circuit according to the present invention, the W pixel use rate (that is, the RGB-signals-to-W-signal conversion rate) WGAIN is varied as necessary.
Next, as a third numerical example, consider a case where RGB input signals are converted into a W signal in a ratio of 1.00:1.20:1.15 as in the second numerical example and in addition the W pixel use rate WGAIN is 70%.
Subsequently, to calculate the RGB signals as they are after conversion into RGBW signals (that is, to calculate Rout, Gout, and Bout), the component R2 of the R signal Rin, the component G2 of the G signal Gin, and the component B2 of the B signal Bin that are converted into Wout are calculated by formulae (7), (8), and (9) below.
R2=80/1.00=80 (7)
G2=80/1.20=66 (8)
B2=80/1.15=69 (9)
Since 220−80=140, 180−66=114, and 100−69=31, the RGB input signals can be broken down into first RGB signal components (140, 114, 31) shown in graph P10 and second RGB signal components (80, 66, 69) shown in graph P11.
Since the ratio in which RGB input signals are converted into a W signal is 1.00:1.20:1.15, the second RGB signal components (80, 66, 69) are converted into a W signal having a value of 80 (=115×0.7). Adding up (synthesizing) the W signal having a value of 80 and the first RGB signal components shown in graph P10 produces RGBW signal values (140, 114, 31, 80) shown in graph P12. That is, in the third numerical example, RGB input signals are converted into RGBW signals such that (Rout, Gout, Bout, Wout)=(140, 114, 31, 80).
Now, through a comparison between graph P7 shown in
In the third numerical example, the proportion (ratio) of the component of the R signal that is actually converted into the W signal (in the third numerical example, 80) to the maximum-conversion R signal (in the third numerical example, 115) is 80/115≈70%. This value is equal to the W pixel use rate WGAIN as set. The proportion (ratio) of the component of the G signal that is actually converted into the W signal (in the third numerical example, 66) to the maximum-conversion G signal (in the third numerical example, 95) is 66/95≈70% again. The proportion (ratio) of the component of the B signal that is actually converted into the W signal (in the third numerical example, 69) to the maximum-conversion B signal (in the third numerical example, 100) is 69/100≈70% again.
Thus, the W pixel use rate (the RGB-signals-to-W-signal conversion rate) WGAIN means the proportion (ratio) of the component of the R signal that is actually converted into the W signal to the maximum-conversion R signal, the proportion (ratio) of the component of the G signal that is actually converted into the W signal to the maximum-conversion G signal, and the proportion (ratio) of the component of the B signal that is actually converted into the W signal to the maximum-conversion B signal.
The RGB input signals (in the third numerical example, expressed as (Rin, Gin, Bin)=(220, 180, 100)) minus the RGB signals that are converted into the W signal (in the third numerical example, expressed as (R2, G2, B2)=(80, 66, 69)) leave the RGB signals as they are after conversion into the RGBW signals outputted from the RGB-RGBW conversion circuit 1 (in the third numerical example, expressed as (Rout, Gout, Bout)=(140, 114, 31)).
Detailed Configuration of the Display Device
The RGB-RGBW conversion circuit 1 according to the present invention converts RGB input signals into RGBW signals while adequately controlling (adjusting) the above-mentioned W pixel use rate (the RGB-signals-to-W-signal conversion rate) WGAIN according to pixel defect information fed from the defect position specifier 15.
The RGB-RGBW conversion circuit 1 includes an R-W converter 20R, a G-W converter 20G, a B-W converter 20B, a minimum value calculator 21, a multiplier 22, a W-R converter 23R, a W-G converter 23G, a W-B converter 23B, subtracters 24R, 24G, and 24B, comparators 13 and 14, and a selector 16.
Based on the horizontal synchronizing signal Hsync of the RGB input signals Rin, Gin, and Bin, and based also on a dot signal (dot clock ) CLK, a horizontal counter (H_CNT) 11 outputs a horizontal position signal indicating the horizontal position on the screen (on the display panel 3, or 3a described later) corresponding to the RGB input signals Rin, Gin, and Bin. Based on the horizontal synchronizing signal Hsync and the vertical synchronizing signal Vsync of the RGB input signals Rin, Gin, and Bin, a vertical counter (V_CNT) 12 outputs a vertical position signal indicating the vertical position on the screen (on the display panel 3, or 3a described later) corresponding to the RGB input signals Rin, Gin, and Bin.
Incidentally, the vertical and horizontal synchronizing signals Vsync and Hsync (and the dot signal CLK) are fed also to an unillustrated timing generation circuit, which produces, based on the vertical and horizontal synchronizing signals Vsync and Hsync (and the dot signal CLK), timing signals necessary for image display, which are fed to the D/A conversion circuit 2 and to the display panel 3 (or 3a described later).
The defect position specifier 15 has previously stored therein defect information that identifies the positions (horizontal and vertical) of defective (faulty) unit pixels on the screen. Specifically, when the organic EL display device is fabricated, in an inspection step, every unit pixel is inspected to check whether it emits light as desired, and those pixels which do not emit light as desired (for example, do not emit light at all) are branded as defective, so that defective information that identifies the positions (horizontal and vertical) of those defective pixels (the unit pixels found defective) is stored in the defect position specifier 15 built with a nonvolatile memory or the like.
The comparator 13 compares the horizontal position on the screen corresponding to the RGB input signals, as identified with the horizontal position signal from the horizontal counter 11, with the horizontal position (or the horizontal position near this horizontal position) of the defective pixel as identified with the defect information from the defect position specifier 15, and feeds the result of the comparison to the selector 16. The comparator 14 compares the vertical position on the screen corresponding to the RGB input signals, as identified with the vertical position signal from the vertical counter 12, with the vertical position (or the vertical position near this vertical position) of the defective pixel as identified with the defect information from the defect position specifier 15, and feeds the result of the comparison to the selector 16.
According to the comparison results from the comparators 13 and 14, the selector 16 selects one among a plurality of candidate values, and outputs the selected value as the W pixel use rate (the RGB-signals-to-W-signal conversion rate) WGAIN. As will be seen in the practical numerical examples presented later, the value selected here is, for example, 1 (100%) or 0.75 (75%).
The R-W, G-W, and B-W converters 20R, 20G, and 20B calculate, from the R, G, and B signals Rin, Gin, and Bin, the value R1, G1 and B1 by formulae (10), (11), and (12) noted below. Here, the ratio in which RGB input signals are converted into a W signal is assumed to be “αR:αG:αB”. If, as in the third numerical example described above, (Rin, Gin, Bin)=(220, 180, 100) and αR:αG:αB=1.00:1.20:1.15 (αR=1.00, αG=1.20, αB=1.15), then formulae (10) to (12) noted below agree with formulae (1) to (3), respectively, noted above.
R1=Rin×αR (10)
G1=Gin×αG (11)
B1=Bin×αB (12)
The minimum value calculator 21 calculates the minimum value min(R1, G1, B1) among R1, G1, and B1 calculated by the R-W, G-W, and B-W converters 20R, 20G, and 20B, and outputs the value, as the maximum-conversion W signal value WMAX, to the multiplier 22 provided in the following stage. In the third numerical example described above, the maximum-conversion W signal value WMAX equals 115.
The multiplier 22 multiplies the maximum-conversion W signal value WMAX from the minimum value calculator 21 by the W pixel use rate WGAIN from the selector 16; the multiplier 22 outputs the result of the multiplication as the W signal Wout, and feeds the same result of multiplication to the W-R, W-G, and W-B converters 23R, 23G, and 23B. If, as in the third numerical example described above, WMAX=115 and WGAIN=0.7, then Wout=80 (≈115×0.7).
To calculate the RGB signals as they are after conversion to RGBW signals (that is, to calculate Rout, Gout, ad Bout), the W-R, W-G, and W-B converters 23R, 23G, and 23B calculate the component R2 of the R signal Rin, the component G2 of the G signal Gin, and the component B2 of the B signal Bin that are converted into Wout by formulae (13), (14), and (15) noted below. If, as in the third numerical example described above, Wout=80 and αR:αG:αB=1.00:1.20:1.15, then formulae (13), (14), and (15) noted below agree with formulae (7) to (9), respectively, noted above, and thus, as shown in graph P11 in
R2=Wout/αR (13)
G2=Wout/αG (14)
B2=Wout/αB (15)
The subtracters 24R, 24G, and 24B subtract R2, G2, and B2, which are the results of the calculation by the W-R, W-G, and W-B converters 23R, 23G, and 23B, from the R, G, and B signals Rin, Gin, and Bin, and outputs the result of the subtraction as Rout, Gout, and Bout. Thus, if, as in the third numerical example described above, (Rin, Gin, Bin)=(220, 180, 100) and (R2, G2, B2)=(80, 66, 69), then, as shown in graph P12 in
Next, the configuration inside the display panel 3 shown in
The dot D1 is composed of four unit pixels, namely a W pixel W1, an R pixel R1, a B pixel B1, and a G pixel G1. These unit pixels lie one adjacent to the next in the order of the W pixel W1, then the R pixel R1, then the B pixel B1, and then the G pixel G1 from left to right. The same is true with the other dots D2 to D10. Specifically, each dot Dn, where n represents an integer between 2 and 10, is composed of four unit pixels, namely a W pixel Wn, an R pixel Rn, a B pixel Bn, and a G pixel Gn, and, in the dot Dn, those unit pixels lie one adjacent to the next in the order of the W pixel Wn, then the R pixel Rn, then the B pixel Bn, and then the G pixel Gn from left to right.
In the following description, the W pixel W1, the R pixel R1, the B pixel B1, and the G pixel G1 are also referred to simply as W1, R1, B1, and G1, respectively; likewise, the W pixel Wn, the R pixel Rn, the B pixel Bn, and the G pixel Gn are also referred to simply as Wn, Rn, Bn, and Gn (where n represents an integer between 2 and 10).
As will be clear from the positional relationship described above, W1, R1, B1, G1, W2, R2, B2, G2, W3, R3, B3, and G3 lie one adjacent to the next in this order from left to right; likewise, W4, R4, B4, G4, W5, R5, B5, G5, W6, R6, B6, G6, W7, R7, B7, and G7 lie one adjacent to the next in this order from left to right; likewise, W8, R8, B8, G8, W9, R9, B9, G9, W10, R10, B10, and G10 lie one adjacent to the next in this order from left to right.
Moreover, as shown in
The RGB input signals for the dot D1 are converted into the RGBW signals for the dot D1 by the RGB-RGBW conversion circuit 1. Likewise, the RGB input signals for the dot Dn are converted into the RGBW signals for the dot Dn by the RGB-RGBW conversion circuit 1 (where n represents an integer between 2 and 10).
Examples of Adjustment of W Pixel Use Rate
Next, how the W pixel use rate (the RGB-signals-to-W-signal conversion rate) WGAIN is set to cope with a pixel defect will be described by way of practical examples. In the following description, all unit pixels are assumed to be normally functioning unless explicitly stated as being defective. It is also assumed that a standard conversion rate is previously set for the entire display panel 3 (or 3a described later) so that, if none of all the unit pixels forming the display panel 3 (or 3a described later) is defective, the W pixel use rate WGAIN is kept equal to the standard conversion rate for all the unit pixels. The maximum value of the standard conversion rate is 100%, and the standard conversion rate has, for example, a fixed value. For the sake of simplicity, it is also assumed that, for all the dots D1 to D10, the RGB input signals have values of (Rin, Gin, Bin)=(220, 180, 100) and that αR:αG:αB=1.00:1.20:1.15.
First, a first example of setting will be described. Suppose now that the W pixel W6 is defective (non-luminous). In this case, based on the defect information that identifies the position of the defective W pixel W6, the RGB-RGBW conversion circuit 1 sets the W pixel use rate (the RGB-signals-to-W-signal conversion rate) WGAIN for R5, B5, G5, R6, B6, and G6 at 75%, 50%, 25%, 25%, 50%, and 75%, respectively, as shown in
From the defect position specifier 15, the comparator 13 receives the horizontal position (ADH_W6) of the defective W pixel W6, the horizontal positions (ADH_W6±1) one unit pixel to the left and right of the horizontal position of the defective pixel, the horizontal positions (ADH_W6±2) two unit pixels to the left and right of the horizontal position of the defective pixel, and the horizontal positions (ADH_W6±3) three unit pixels to the left and right of the horizontal position of the defective pixel. The comparator 13 checks whether these seven horizontal positions fed from the defect position specifier 15 agree or disagree with the horizontal position on the screen corresponding to the RGB input signals Rin, Gin, and Bin as fed from the horizontal counter 11, and feeds a signal indicating agreement or disagreement to the selector 16.
From the defect position specifier 15, the comparator 14 receives the vertical position (ADV_W6) of the defective W pixel W6. The comparator 14 checks whether this vertical position fed from the defect position specifier 15 agrees or disagrees with the vertical position on the screen corresponding to the RGB input signals Rin, Gin, and Bin as fed from the vertical counter 12, and feeds a signal indicating agreement or disagreement to the selector 16.
The selector 16 receives, as candidate values, 25%, 50%, 75%, and the standard conversion rate, namely 100%, and sets, according to the outputs of the comparators 13 and 14, WGAIN for each unit pixel as shown in
Now, consider the R pixel R5, for which WGAIN=75%. When WGAIN=75%, as shown in
Now, consider the G pixel G5, for which WGAIN=25%. When WGAIN=25%, as shown in
Now, consider the R pixel R6, for which WGAIN=25%. When WGAIN=25%, as shown in
For each of the other unit pixels including B5, B6, G6, and W7, operations similar to those described above with respect to W5, R5, etc. are performed, so that the B signal Bout corresponding to B5, the B signal Bout corresponding to B6, the G signal Gout corresponding to G6, and the W signal Wout corresponding to W7 have values 51, 51, 109, and 115, respectively. Incidentally, the W signal Wout corresponding to the defective pixel W6 is give, for example, a value of 0.
If no consideration is given to the defect in W6, and WGAIN is set equal to the standard conversion rate, namely 100%, for all of R5, B5, G5, R6, B6, and G6, then, as will be understood from the numerical example described above and from
By contrast, setting WGAIN for pixels around the defective W pixel lower than the standard conversion rate as described above eventually makes the brightness of those nearby pixels comparatively high, and thus makes the defect in the W pixel less conspicuous (in particular, by preventing it from appearing as a conspicuous black spot when white is displayed).
In a case where the W pixel W6 is defective, simply setting WGAIN for at least one of the four unit pixels (G5, R6, B2, and B9) adjacent to the W pixel W6 lower than the standard conversion rate helps make the defect less conspicuous. For example, WGAIN for G5 is set at 25%, and WGAIN for all the other unit pixels are set equal to the standard conversion rate.
Incidentally, the comparators 13 and 14 and the selector 16 function as a conversion rate controller (use rate controller) that controls (sets) the W pixel use rate, that is, the RGB-signals-to-W-signal conversion rate WGAIN, for each unit pixel. The multiplier 22 may also be considered as part of the conversion rate controller.
Next, a second example of setting will be described. Suppose now that the W pixel W6 is defective (non-luminous). In this case, as shown in
This, too, makes the brightness of pixels (B5, G5, R6, B6, B2, and B9) around the defective pixel comparatively high, and thus makes the defect in the W pixel less conspicuous (in particular, by preventing it from appearing as a conspicuous black spot when white is displayed).
From the defect position specifier 15, the comparator 13 receives the horizontal position (ADH_W6) of the defective W pixel W6, and the horizontal positions (ADH_W6±1) one unit pixel to the left and right of the horizontal position of the defective pixel, the horizontal positions (ADH_W6±2) two unit pixels to the left and right of the horizontal position of the defective pixel. The comparator 13 checks whether these five horizontal positions fed from the defect position specifier 15 agree or disagree with the horizontal position on the screen corresponding to the RGB input signals Rin, Gin, and Bin as fed from the horizontal counter 11, and feeds a signal indicating agreement or disagreement to the selector 16.
From the defect position specifier 15, the comparator 14 receives the vertical position (ADV_W6) of the defective W pixel W6 and the vertical positions (ADV_W6±1) one unit pixel above and below the vertical position of the defective W pixel W6. The comparator 14 checks whether these three vertical positions fed from the defect position specifier 15 agree or disagree with the vertical position on the screen corresponding to the RGB input signals Rin, Gin, and Bin as fed from the vertical counter 12, and feeds a signal indicating agreement or disagreement to the selector 16.
The selector 16 receives, as candidate values, 0%, 25%, and the standard conversion rate, namely 100%, and sets, according to the outputs of the comparators 13 and 14, WGAIN for each unit pixel as shown in
As a modification, an adder (unillustrated) may be inserted between the subtracter 24G and the D/A conversion circuit 2 so that a predetermined offset is added to the output from the subtracter 24G corresponding to the G pixel G5 adjacent to the defective pixel and the result is eventually used as the G signal Gout corresponding to the G pixel G5. This helps further increase the brightness of the G pixel G5 and thereby make the defect in the W pixel less conspicuous. Instead of such an adder, a multiplier (unillustrated) may be used so that the output from the subtracter 24G corresponding to the G pixel G5 adjacent to the defective pixel is multiplied by a predetermined value greater than one (for example, 1.1) and the result is eventually used as the G signal Gout corresponding to the G pixel G5.
Likewise, an adder (unillustrated) for adding a predetermined offset may be inserted between the subtracter 24R and the D/A conversion circuit 2 so that the predetermined offset is added to the output from the subtracter 24R corresponding to the R pixel R6 adjacent to the defective pixel and the result is eventually used as the R signal Rout corresponding to the R pixel R6. Instead of such an adder, a multiplier (unillustrated) may be used so that the output from the subtracter 24R corresponding to the R pixel R6 is multiplied by a predetermined value greater than one (for example, 1.1) and the result is eventually used as the R signal Rout corresponding to the R pixel R6.
Likewise, an adder (unillustrated) for adding a predetermined offset may be inserted between the subtracter 24B and the D/A conversion circuit 2 so that the predetermined offset is added to the output from the subtracter 24B corresponding to the B pixel B2 (B9, B5, B6) adjacent to the defective pixel and the result is eventually used as the B signal Bout corresponding to the B pixel B2 (B9, B5, B6). Instead of such an adder, a multiplier (unillustrated) may be used so that the output from the subtracter 24B corresponding to the B pixel B2 (B9, B5, B6) is multiplied by a predetermined value greater than one (for example, 1.1) and the result is eventually used as the B signal Bout corresponding to the B pixel B2 (B9, B5, B6).
Next, a third example of setting will be described. Suppose now that the W pixel W6 is defective (non-luminous). In this case, as shown in
In the third example of setting, the smaller the distance from the defective pixel, the lower the W pixel use rate WGAIN is set, and in addition WGAIN for the nearby pixels in a comparatively wide area is set lower than the standard conversion rate. In this way, by compensating for the defect by using nearby pixels in a wide area and setting WGAIN increasingly low the closer to the defective pixel, it is possible to make the defect in the W pixel less conspicuous (in particular, by preventing it from appearing as a conspicuous black spot when white is displayed).
Incidentally, in the third example of setting, four dots, namely D2, D5, D6, and D9, include unit pixels adjacent to the defective pixel, and WGAIN for all the RGB pixels (or RGBW pixels) included in the dots D2, D5, D6, and D9 is set lower than the standard conversion rate (100%).
Though different from what is shown in
As a modification, adders (unillustrated) may be inserted between the subtracters 24R, 24G, and 24B, respectively, and the D/A conversion circuit 2 so that a predetermined offset is added to the outputs from the subtracters 24R, 24G, and 24B corresponding to the RGB pixels included in the dot D2 (D5, D6, or D9) and the results are eventually used as Rout, Gout, and Bout corresponding to the RGB pixels included in the dot D2 (D5, D6, or D9). This helps further increase the brightness of the RGB pixels included in the dot D2 (D5, D6, or D9) and thereby make the defect in the W pixel less conspicuous. Instead of such adders, multipliers (unillustrated) may be used so that the outputs from the subtracters 24R, 24G, and 24B corresponding to the RGB pixels included in the dot D2 (D5, D6, or D9) are multiplied by a predetermined value greater than one (for example, 1.1) and the results are eventually used as Rout, Gout, and Bout corresponding to the RGB pixels included in the dot D2 (D5, D6, or D9).
Next, a fourth example of setting will be described. Suppose now that a unit pixel other than a W pixel, for example, the B pixel B6, is defective (non-luminous), and assume that the standard conversion rate is set at 90%. In this case, as shown in
In this way, in a case where a unit pixel other than a W pixel (in the fourth example of setting, a B pixel) is defective, WGAIN for the non-W unit pixels adjacent to the defective pixel is set lower than the standard conversion rate set over the entire display panel. Here, WGAIN may be set lower than the standard conversion rate only for one (for example, in the fourth example of setting, the R pixel R6) of the unit pixels adjacent to the defective pixel.
As a modification, an adder (unillustrated) may be inserted between the subtracter 24R (24G) and the D/A conversion circuit 2 so that a predetermined offset is added to the output from the subtracter 24R (24G) corresponding to R6 (G6) adjacent to the defective pixel and the result is eventually used as the R signal Rout (G signal Gout) corresponding to R6 (G6). This helps further increase the brightness of R6 (G6) and thereby make the defect in the B pixel less conspicuous. Instead of such an adder, a multiplier (unillustrated) may be used so that the output from the subtracter 24R (24G) corresponding to R6 (G6) adjacent to the defective pixel is multiplied by a predetermined value greater than one (for example, 1.1) and the result is eventually used as the R signal Rout (G signal Gout) corresponding to R6 (G6).
What is aimed at in the fourth example of setting is to compensate for the defect in B6, which corresponds to blue, with an increase in the brightness of red and green. Since the chromaticity of blue greatly differs from the chromaticities of red and green, however, the part where such compensation is made may appear unnaturally colored.
As a solution to this inconvenience, next, a fifth example of setting will be described. Suppose now that a unit pixel other than a W pixel, for example, the B pixel B6, is defective (non-luminous), and assume that the standard conversion rate is set at 90%. In this case, as shown in
Here, since the chromaticity of W pixels is close to the mean of the chromaticities of blue, red, and green, less unnaturalness is visible than when the defect in B6, which corresponds to blue, is compensated for with an increase in the brightness of red and green as in the fourth example of setting.
In this way, in a case where a unit pixel other than a W pixel (in the fifth example of setting, a B pixel) is defective, WGAIN for the W unit pixels adjacent to the defective pixel is set higher than the standard conversion rate set over the entire display panel. Here, WGAIN may be set higher than the standard conversion rate only for one (for example, in the fifth example of setting, the W pixel W3) of the W pixels adjacent to the defective pixel.
As a modification, an adder (unillustrated) may be inserted between the multiplier 22 and the D/A conversion circuit 2 so that a predetermined offset is added to the output from the multiplier 22 corresponding to W3 (W10) adjacent to the defective pixel and the result is eventually used as the W signal Wout corresponding to W3 (W10). This helps further increase the brightness of W3 (W10) and thereby make the defect in the B pixel less conspicuous. Instead of such an adder, a multiplier (unillustrated) may be used so that the output from the multiplier 22 corresponding to W3 (W10) adjacent to the defective pixel is multiplied by a predetermined value greater than one (for example, 1.1) and the result is eventually used as the W signal Wout corresponding to W3 (W10).
Next, a second embodiment of the present invention will be described in detail with reference to the accompanying drawings.
Like the display panel 3 shown in
Now, the configuration inside the display panel 3a, which has a stripe array, will be described.
The dot D11 is composed of four unit pixels, namely a W pixel W11, an R pixel R11, a B pixel B11, and a G pixel G11. These unit pixels lie one adjacent to the next in the order of the W pixel W11, then the R pixel R11, then the B pixel B11, and then the G pixel G11 from left to right. The same is true with the other dots D12 to D16. Specifically, each dot Dm, where m represents an integer between 12 and 16, is composed of four unit pixels, namely a W pixel Wm, an R pixel Rm, a B pixel Bm, and a G pixel Gm, and, in the dot Dm, those unit pixels lie one adjacent to the next in the order of the W pixel Wm, then the R pixel Rm, then the B pixel Bm, and then the G pixel Gm from left to right.
In the following description, the W pixel W11, the R pixel R11, the B pixel B11, and the G pixel G11 are also referred to simply as W11, R11, B11, and G11, respectively; likewise, the W pixel Wm, the R pixel Rm, the B pixel Bm, and the G pixel Gm are also referred to simply as Wm, Rm, Bm, and Gm (where m represents an integer between 12 and 16).
As will be clear from the positional relationship described above, W11, R11, B11, G11, W12, R12, B12, and G12 lie one adjacent to the next in this order from left to right; likewise, W13, R13, B13, G13, W14, R14, B14, and G14 lie one adjacent to the next in this order from left to right; likewise, W15, R15, B15, G15, W16, R16, B16, and G16 lie one adjacent to the next in this order from left to right.
Moreover, as shown in
The RGB input signals Rin, Gin, and Bin for the dot D11 are converted into the RGBW signals for the dot D11 by the RGB-RGBW conversion circuit 1. Likewise, the RGB input signals Rin, Gin, and Bin for the dot Dm are converted into the RGBW signals for the dot Dm by the RGB-RGBW conversion circuit 1 (where m represents an integer between 12 and 16).
Examples of Adjustment of W Pixel Use Rate
Next, how the W pixel use rate WGAIN is set to cope with a pixel defect will be described by way of practical examples. In the following description, all unit pixels are assumed to be normally functioning unless explicitly stated as being defective. For the sake of simplicity, it is also assumed that, for all the dots D11 to D16, the RGB input signals have values of (Rin, Gin, Bin)=(220, 180, 100) and that αR:αG:αB=1.00:1.20:1.15.
First, as a first example of how WGAIN is set in the second embodiment, a sixth example of setting will be described. Suppose now that the W pixel W14 is defective (non-luminous), and assume that the standard conversion rate is set at 90%. In this case, based on the defect information that identifies the position of the defective W pixel W14, the RGB-RGBW conversion circuit 1 sets the W pixel use rate (the RGB-signals-to-W-signal conversion rate) WGAIN for W12 and W16 adjacently above and below the defective pixel at 100% as shown in
Though different from what is shown in
As a modification, an adder (unillustrated) may be inserted between the multiplier 22 and the D/A conversion circuit 2 so that a predetermined offset is added to the output from the multiplier 22 corresponding to W12 (W16) adjacent to the defective pixel and the result is eventually used as the W signal Wout corresponding to W12 (W16). This helps further increase the brightness of W12 (W16) and thereby make the defect in the W pixel less conspicuous. Instead of such an adder, a multiplier (unillustrated) may be used so that the output from the multiplier 22 corresponding to W12 (W16) adjacent to the defective pixel is multiplied by a predetermined value greater than one (for example, 1.1) and the result is eventually used as the W signal Wout corresponding to W12 (W16).
Next, a seventh example of setting will be described. Suppose now that the W pixel W14 is defective (non-luminous), and assume that the standard conversion rate is set at 90% (it may be set at 100%). In this case, based on the defect information that identifies the position of the defective W pixel W14, the RGB-RGBW conversion circuit 1 sets the W pixel use rate (the RGB-signals-to-W-signal conversion rate) WGAIN for G13 and R14 adjacently to the left and right of the defective pixel at 80% as shown in
In this way, in a case where a W pixel is defective, WGAIN for the non-W unit pixels (in the seventh example of setting, G and R pixels) adjacent to the defective pixel is set lower than the standard conversion rate set over the entire display panel. Here, WGAIN may be set lower than the standard conversion rate only for one (for example, in the seventh example of setting, the G pixel G13) of the unit pixels adjacent to the defective pixel.
As a modification, an adder (unillustrated) may be inserted between the subtracter 24R (24G) and the D/A conversion circuit 2 so that a predetermined offset is added to the output from the subtracter 24R (24G) corresponding to R14 (G13) adjacent to the defective pixel and the result is eventually used as the R signal Rout (G signal Gout) corresponding to R14 (G13). This helps further increase the brightness of R14 (G13) and thereby make the defect in the W pixel less conspicuous. Instead of such an adder, a multiplier (unillustrated) may be used so that the output from the subtracter 24R (24G) corresponding to R14 (G13) adjacent to the defective pixel is multiplied by a predetermined value greater than one (for example, 1.1) and the result is eventually used as the R signal Rout (G signal Gout) corresponding to R14 (G13).
Next, an eighth example of setting will be described. Suppose now that the W pixel W14 is defective (non-luminous), and assume that the standard conversion rate is set at the maximum value, namely 100%. In this case, based on the defect information that identifies the position of the defective W pixel W14, the RGB-RGBW conversion circuit 1 sets the W pixel use rate (the RGB-signals-to-W-signal conversion rate) WGAIN for G11, R12, B13, G13, R14, B14, G15, and R16 at 90%, 90%, 50%, 20%, 20%, 50%, 90%, and 90%, respectively, as shown in
Thus, in the horizontal direction, the smaller the distance from the defective pixel, the lower WGAIN is set. Also in the oblique directions, the smaller the distance from the defective pixel, the lower WGAIN is set. Hence, for example, when white is displayed, brightness gradually increases as one approaches the defective pixel in the horizontal and oblique directions. While the defect in W14 is compensated for with the increased brightness in the pixels around W14, their brightness is increased gradually in different directions. This helps make the defect in W14 less conspicuous. This eighth example of setting is particularly effective in a case where the standard conversion rate is set at its maximum value, namely 100%.
As a modification, an adder (unillustrated) may be inserted between the subtracter 24R (24G) and the D/A conversion circuit 2 so that a predetermined offset is added to the output from the subtracter 24R (24G) corresponding to R14 (G13, R12, G11, R16, and/or G15) and the result is eventually used as the R signal Rout (G signal Gout) corresponding to R14 (G13, R12, G11, R16, and/or G15). This helps further increase the brightness of R14 (G13, R12, G11, R6, and/or G15) and thereby make the defect in the W pixel less conspicuous. Instead of such an adder, a multiplier (unillustrated) may be used so that the output from the subtracter 24R (24G) corresponding to R14 (G13, R12, G11, R16, and/or G15) adjacent to the defective pixel is multiplied by a predetermined value greater than one (for example, 1.1) and the result is eventually used as the R signal Rout (G signal Gout) corresponding to R14 (G13, R12, G11, R16, and/or G15).
In the first to eighth examples of setting, WGAIN for the defective pixel is, for example, fixed (for example, at 0% or equal to the standard conversion rate).
Panel Adjustment
Next, the panel adjustment performed when the organic EL display devices of the first and second embodiments are fabricated will be described. Through this panel adjustment, the values (that is, the individual values of αR, αG, and αB) are determined that set the ratio “αR:αG:αB” in which RGB input signals are converted into a W signal. The determined values (the individual values of αR, αG, and αB) are stored, for example, in an unillustrated memory incorporated in the RGB-RGBW conversion circuit 1, and are used to calculate the RGBW signals Rout, Gout, Bout, and Wout that have been described.
The chromaticity coordinates denote the coordinate components as observed in the xy chromaticity diagram. For example, the brightness LWt is set at 200 cd/m2 (candela per square meter), and the chromaticity coordinates (xWt, YWt) are set at (0.32, 0.33).
Next, the chromaticities of the R, G, B, and W pixels provided in the display panel 3 or 3a are measured (step S2). For example, to measure the chromaticity of the R pixels, they alone are lit, and their chromaticity is measured with a light tester (unillustrated). Let the thus measured chromaticity coordinates of the R, G, B, and W pixels be (xR, yR), (xG, yG), (xB, yB), and (xW, yW), respectively.
Next, the RGB brightness values obtained when white balance (WB) is adjusted on an RGB basis are calculated (step S3). That is, the R pixel brightness value (let this be LR1), the G pixel brightness value (let this be LG1), and the B pixel brightness value (let this be LB1) that achieve “the brightness LWt and the chromaticity coordinates (xWt, yWt)” of the targeted white Wt(255) when the pixels of three colors, namely R, G, and B pixels, alone are lit are calculated. These brightness values LR1, LG1, and LB1 are calculated by matrix formula (16) noted below.
In formula (16) noted above, zR=1−xR−yR, zG=1−xG−yG, zB=1−xB−yB, and zWt=1−xWt−yWt.
Next, the RGBW brightness values obtained when white balance (WB) is adjusted on an RGBW basis are calculated (step S4). That is, the R pixel brightness value (let this be LR2), the G pixel brightness value (let this be LG2), the B pixel brightness value (let this be LB2), and the W pixel brightness value (let this be LW2) that achieve “the brightness LWt and the chromaticity coordinates (xWt, yWt)” of the targeted white Wt(255) when the pixels of four colors, namely R, G, B, and W, are all lit are calculated.
The chromaticity coordinates of the targeted white Wt are located “inside the triangle (or on any of the sides thereof) formed by the chromaticity coordinates of the R, B, and W pixels”, or “inside the triangle (or on any of the sides thereof) formed by the chromaticity coordinates of the G, R, and W pixels”, or “inside the triangle (or on any of the sides thereof) formed by the chromaticity coordinates of the B, G, and W pixels”. Thus, the chromaticity of the targeted white Wt can be obtained by lighting the pixels of three colors, including the W pixels.
For example, in a case where, as shown in
In formula (17) noted above, zR=1−xR−yR, zW=1−xW−yW, zB=1−xB−yB, and zWt=1−xWt−yWt.
Then, based on the brightness values LR1 etc. calculated in steps S3 and S4, the values of αR, αG, and αB that set the ratio in which RGB input signals are converted into a W signal are calculated by formulae (18), (19), and (20) noted below (step S5).
αR=1/(1−LR2/LR1) (18)
αG=1/(1−LG2/LG1) (19)
αB=1/(1−LB2/LB1) (20)
The D/A conversion circuit 2 also receives a “reference voltage for R”, a “reference voltage for G”, a “reference voltage for B” (these are referred to collectively as the “reference voltages for RGB”), and a “reference voltage for W”. With reference to these reference voltages for RGB and for W, the D/A conversion circuit 2 feeds RGBW signals in the form of analog voltages to the individual unit pixels provided in the display panel 3 or 3a. The brightness of each unit pixel varies according to the analog voltage fed thereto.
In step S6, the reference voltages (reference brightness) for RGB are so adjusted that, when RGBW signals having values (Rout, Gout, Bout, Wout)=(255, 255, 255, 0) are fed, the brightness and the chromaticity coordinates of the light emitted by the display panel 3 or 3a equal “the brightness LWt and the chromaticity coordinates (xWt, yWt)” of the targeted white Wt (255), respectively. The reference voltages are adjusted individually for each type of pixel. That is, the “reference voltage for R” is so adjusted that, when RGBW signals having values (Rout, Gout, Bout, Wout)=(255, 0, 0, 0) are fed to the D/A conversion circuit 2, the brightness value of the R pixels equals the brightness value LR1 calculated in step S3; the “reference voltage for G”) is so adjusted that, when RGBW signals having values (Rout, Gout, Bout, Wout)=(0, 255, 0, 0) are fed to the D/A conversion circuit 2, the brightness value of the G pixels equals the brightness value LG1 calculated in step S3; the “reference voltage for B” is so adjusted that, when RGBW signals having values (Rout, Gout, Bout, Wout)=(0, 0, 255, 0) are fed to the D/A conversion circuit 2, the brightness value of the B pixels equals the brightness value LB1 calculated in step S3. Once the reference voltages for RGB are adjusted in this way, the chromaticity of the light emitted by the display panel 3 or 3a when RGB input signals are all equal (that is, Rin=Gin=Bin) always equals the chromaticity of the targeted white Wt.
On the other hand, the reference voltage (reference brightness) for W is so adjusted that, when RGBW signals having values (Rout, Gout, Bout, Wout)=(0, 0, 0, 255) are fed to the D/A conversion circuit 2 to light the W pixels alone, their brightness equals the brightness value LW2 calculated in step S4 (step S6). Incidentally, the RGBW signals (for example, having values (Rout, Gout, Bout, Wout)=(0, 0, 0, 255)) that need to be fed to the D/A conversion circuit 2 to perform the above-described panel adjustment are produced by a test circuit (unillustrated in
It should be understood that the present invention is applicable to display devices of any types other than organic EL display device specifically dealt with in the embodiments described above; that is, the present invention is applicable to various display devices including, among others, inorganic EL display devices provided with inorganic EL display panels as display panels, liquid crystal display devices provided with liquid crystal display panels as display panels, and plasma displays.
The unit pixels that are provided separately from R, G, and B pixels are not limited to W pixels. Let “X” represent any color other than RGB (red, blue, and green), and every occurrence of “W” in the description hereinbefore may be replaced with “X”. That is, the present invention is applicable to various display devices provided with RGBX-type display panels.
It should also be understood that all the specific values given in the description hereinbefore are meant merely to give examples, and thus are not meant to limit in any way the manner the present invention is practiced.
The present invention is suitable for various display devices such as liquid crystal display devices and plasma display devices. The present invention is especially suitable for display devices provided with self-luminous display panels such as organic EL display panels, inorganic EL display panels, and PDPs (plasma display panels).
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-152058 | May 2005 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 5929843 | Tanioka | Jul 1999 | A |
| Number | Date | Country |
|---|---|---|
| 2001-109423 | Apr 2001 | JP |
| 2002-189440 | May 2002 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20060268003 A1 | Nov 2006 | US |
