JP4434935B2 - Signal processing circuit and signal processing method for self-luminous display - Google Patents

Description

  The present invention relates to a signal processing circuit and a signal processing method for a self-luminous display.

  A self-luminous display such as an organic EL display has features such as thinness, light weight, and low power consumption, and its application is expanding. However, in applications such as mobile phones and digital still cameras, there is a high demand for further lower power consumption.

In the case of a self-luminous display such as an organic EL display in which a color filter is attached to a white light emitting material, a part of the light is absorbed by the color filter when the light passes through the color filter. It is getting worse. This low light utilization efficiency hinders a reduction in power consumption.
JP 11-295717 A

  In the present invention, a signal processing circuit of a self-luminous display in which one pixel is composed of four RGBW unit pixels, the RGB unit pixels are provided with color filters, and the W unit pixels are not provided with color filters. It is another object of the present invention to provide a signal processing method and a signal processing method for a self-luminous display capable of reducing power consumption.

  The present invention also relates to a signal processing circuit and a signal processing method for a self-luminous display in which X is an arbitrary color other than RGB, and one pixel is composed of four unit pixels of RGBX. It is an object of the present invention to provide a signal processing circuit and a signal processing method for a self-luminous display that can be converted into a signal.

The first aspect of the present invention is a self-luminous type in which one pixel is composed of four RGBW unit pixels, a color filter is provided in the RGB unit pixel, and no color filter is provided in the W unit pixel. This is a display signal processing circuit, and when the RGB input signals are all the same value, the RGB white side reference luminance is set so that the target white can be realized only by RGB, and all of the RGB input signals In the signal processing circuit of the self-luminous display in which the RGBW signal value for realizing the target white is set when is the maximum value, the minimum value of the RGB input signals is subtracted from the RGB input signals. A first means that, based on the RGBW signal value for realizing the target white when all of the RGB input signals are maximum values, The second means for calculating the RGBW signal corresponding to the small value and the RGBW signal calculated by the second means add the subtraction result for each RGB calculated by the first means to the corresponding signal. Thus, a third means for obtaining an RGBW signal is provided.

The second aspect of the present invention is a self-luminous type in which one pixel is composed of four unit pixels of RGBW, the RGB unit pixel is provided with a color filter, and the W unit pixel is not provided with a color filter. This is a display signal processing circuit, and when the RGB input signals are all the same value, the RGB white side reference luminance is set so that the target white can be realized only by RGB, and all of the RGB input signals In a signal processing circuit of a self-luminous display that has RGBW signal values set to achieve the target white when the value is the maximum value, the target white is realized when all the RGB input signals are the maximum value First, the ratio of each RGB signal value to the W signal value is calculated as a feedback rate for each RGB based on the RGBW signal value The second means for calculating the sum of the infinite geometric series with the RGB input signal as the first term and the feedback rate for each RGB as the common ratio for each RGB, the infinite geometric series calculated for each RGB by the second means A third means for subtracting the minimum value of the sum of the RGB input signals from the RGB input signals, based on the RGBW signal values for realizing the target white when all of the RGB input signals are maximum values, The fourth means for calculating the RGBW signal corresponding to the case where all the signals are the minimum value, and the subtraction result for each RGB calculated by the third means with respect to the RGBW signal calculated by the fourth means 5th means which calculates | requires an RGBW signal by adding to a corresponding signal, It is characterized by the above-mentioned.

The third aspect of the present invention is a self-luminous type in which one pixel is composed of four RGBW unit pixels, the RGB unit pixel is provided with a color filter, and the W unit pixel is not provided with a color filter. This is a display signal processing method, and when the RGB input signals are all the same value, the RGB white side reference luminance is set so that the target white can be realized only by RGB, and all of the RGB input signals In the signal processing method of the self-luminous display in which the RGBW signal value for realizing the target white is set when the value is the maximum value, the minimum value of the RGB input signals is subtracted from the RGB input signals. The first step, based on the RGBW signal value to achieve the target white when all of the RGB input signals are maximum values, The second step of calculating the RGBW signal corresponding to the minimum value and the RGBW signal calculated in the second step, the subtraction result for each RGB calculated in the first step is used as the corresponding signal. A third step of obtaining an RGBW signal by adding is provided.

A fourth aspect of the present invention is a signal processing circuit for a self-luminous display in which X is an arbitrary color other than RGB, and one pixel is composed of four unit pixels of RGBX. In a signal processing circuit of a self-luminous display in which RGB signal values capable of realizing chromaticity and maximum luminance are set, RGB-RGBX signal conversion means for converting an RGB input signal into an RGBX signal is provided, and an RGB-RGBX signal The conversion means is an RGB signal component that can be converted from the RGB input signal to the X signal based on the RGB signal value for realizing the chromaticity of X and the maximum luminance, and from the RGB input signal to the X signal. When RGB signal components that can be converted are subtracted, RGB signal components are calculated such that at least one of the RGB subtraction results is 0. The first means, the second means for subtracting the RGB signal component calculated by the first means from the RGB input signal, and outputting the subtraction result as an RGB signal, and X corresponding to the RGB signal component calculated by the first means And a third means for outputting the signal as an X signal.

  According to the present invention, one pixel is composed of four RGBW unit pixels, the RGB unit pixel is provided with a color filter, and the W unit pixel is not provided with a color filter. In the processing circuit and the signal processing method, power consumption can be reduced.

  Further, according to the present invention, in a signal processing circuit and signal processing method for a self-luminous display in which X is an arbitrary color other than RGB and one pixel is composed of four unit pixels of RGBX, RGB signals are converted to RGBX Can be converted into a signal.

  Embodiments of the present invention will be described below with reference to the drawings.

[A] Description of Invention for RGB-RGBW Signal Conversion The present invention is directed to a self-luminous display such as an organic EL display in which a color filter is attached to a white light emitting material. In this way, in the self-luminous display, as shown in FIG. 1, one pixel is composed of four unit pixels, and three unit colors, for example, R (red), G (green), B A color filter for displaying (blue) is arranged. The remaining one unit pixel is dedicated to white (W) display without a color filter.

  In such an RGBW arrangement, the unit pixel dedicated to white display does not have a color filter, so the light utilization efficiency is very high. Therefore, for example, when displaying 100% white, instead of displaying 100% white by emitting unit pixels for RGB display, it is possible to display 100% white by emitting unit pixels dedicated to white display. Thus, the power consumption can be greatly reduced.

  However, in reality, the white chromaticity obtained by the white light emitting material is often not the target white chromaticity, and the white luminescence of the unit pixel dedicated for white display is not suitable for RGB display. It is necessary to add light emission from the unit pixel.

  Therefore, the present invention proposes a signal processing technique for converting an RGB input signal into an RGBW signal when the white chromaticity obtained from the white light emitting material is different from the target white chromaticity.

[1] Description of Configuration of Display Device FIG. 2 shows a configuration of the display device.
A digital RGB input signal is input to the RGB-RGBW signal conversion circuit 1. The RGB-RGBW signal conversion circuit 1 converts an RGB input signal into an RGBW signal. The RGBW signal obtained by the RGB-RGBW signal conversion circuit 1 is converted into an analog RGBW signal by the D / A conversion circuit 2. The RGBW signal obtained by the D / A conversion circuit 2 is sent to the organic EL display 3 in which one pixel is composed of four RGBW unit pixels.

[2] Explanation of basic concept of RGB-RGBW signal conversion An RGB input signal as shown in FIG. 3 is assumed. For convenience of explanation, it is assumed that gamma correction has not been applied to the RGB input signal in advance. In addition, RGB brightness that realizes target white brightness and chromaticity using only RGB is set in advance as RGB white-side reference brightness (white-side reference voltage for RGB of the D / A conversion circuit 2). To do. The white reference luminance of W is adjusted to be the target luminance (W luminance determined in step S4 in FIG. 9 described later) when only W is displayed.

In this example, the RGB input signal value is represented by 8 bits, and R = 200, G = 100, and B = 170. Since the minimum value of the RGB input signal value is 100, the RGB input signal value is set to the minimum value (min (RGB)) as shown in FIG. 4 and the remaining value (input) as shown in FIG. Signal-min (RGB)). In the case of FIG. 4, it is equivalent to the target white W _t (100) when the RGB input signal values are all 100.

If the RGBW signal values for expressing the target white W _t (255) when the RGB input signal values are all 255 are signal values (77, 0, 204, 255) as shown in FIG. The RGBW signal values for realizing the target white W _t (100) when the RGB input signal values are all 100 are as shown in FIG.

  Signal values as shown in FIG. 6 can be obtained from RGB luminance values and RGBW luminance values for realizing the target white. Let RGBR signal values for realizing the target white when the RGB input signal values are all 255 be (R1, G1, B1, W1). The RGB luminance values for realizing the target white luminance and chromaticity are (LR1, LG1, LB1), and the RGBW luminance values for realizing the target white luminance and chromaticity are (LR2, LG2, LB2, LW2). Then, the RGBW signal values for realizing the target white when the RGB input signal values are all 255 are (R1 = 255 × LR2 / LR1, G1 = 255 × LG2 / LG1, B1 = 255 × LB2 / LB1, W1 = 255). In particular, W can be defined only by the RGBW display system, and is uniquely 255. Note that how to obtain the RGB brightness value and the RGBW brightness value for realizing the target white brightness and chromaticity will be described later.

  R, G, B, and W of FIG. 7 are calculated | required by following Formula (1).

R = 77 × 100/255 = 30
G = 0 × 100/255 = 0
B = 204 × 100/255 = 80
W = 255 × 100/255 = 100 (1)

  Therefore, the RGB values in FIG. 4 are replaced with the RGBW values in FIG. Therefore, the RGB values shown in FIG. 3 are converted into the RGBW values shown in FIG. 8 by adding the RGB values of FIG. 5 and the RGBW values of FIG.

  R, G, B, and W of FIG. 8 are calculated | required by following Formula (2).

R = 100 + 30 = 30
G = 0 + 0 = 0
B = 70 + 80 = 150
W = 0 + 100 = 100 (2)

  RGB white side reference luminance (RGB luminance value for realizing target white luminance and chromaticity), RGBW luminance value for expressing target white luminance and chromaticity, and RGB input signal value are all 255 The RGBW signal value for realizing the target white in this case is obtained in advance by panel adjustment processing.

[3] Explanation about RGB-RGBW signal conversion processing

  FIG. 9 shows a panel adjustment processing procedure.

The brightness L _Wt and chromaticity coordinates (x _Wt , y _Wt ) of the target white W _t are set (step S1).

Next, the RGBW chromaticity of the organic EL display 3 is measured (step S2). For example, when measuring the chromaticity of R, only the unit pixel for R display of the organic EL display 3 is caused to emit light, and the chromaticity is measured by an optical measuring instrument. The measured RGBW chromaticity coordinates are (x _R , y _R ), (x _G , y _G ), (x _B , y _B ), and (x _W , y _W ), respectively.

Next, RGB luminance values at the time of white balance (WB) adjustment by RGB are calculated (step S3). That is, the RGB luminance values L _R (corresponding to the above LR1), L _G (above described) when expressing the luminance L _Wt and chromaticity (x _Wt , y _Wt ) of the target white W _t by the three colors of RGB. L B1 (corresponding to LG1) and L _B (corresponding to LB1) are calculated. The luminance values L _R, L _G, L _B is determined from the following equation (3).

However, a _{z R = 1-x R -y} R, z G = 1-x G -y G, z B = 1-x B -y B, z Wt = 1-x Wt -y Wt.

Next, RGBW luminance values at the time of white balance (WB) adjustment by RGBW are calculated (step S4). That is, the 4 colors of RGBW, (corresponding to the LR2) luminance values L _R of RGBW in representing the target white W _t luminance L _Wt and chromaticity _{(x Wt, y Wt),} L G ( the LG 2 (corresponding to LG2), L _B (corresponding to LB2), and L _W (corresponding to LW2) are calculated.

RGBW chromaticity coordinates (x _R , y _R ), (x _G , y _G ), (x _B , y _B ), (x _W , y _W ) and target white W _t chromaticity coordinates (x _Wt , Y _Wt ) have a relationship as shown in FIG. 10, the chromaticity of the target white W _t can be expressed by only three colors of RBW. The 3 colors of RBW, brightness L _Wt and chromaticity (x _Wt, y _Wt) of the target white W _t (corresponding to the LR2) luminance values L _R of RBW in representing the equivalent to L _B (above LB2 ), L _W (corresponding to LW2) is obtained from the following equation (4). In this case the L _G 0 which corresponds to the LG2.

However, a _{z R = 1-x R -y} R, z W = 1-x W -y W, z B = 1-x B -y B, z Wt = 1-x Wt -y Wt.

  Next, RGB white side reference luminance is calculated using the calculation result of step S3 (step S5).

If RGB input signal value is represented by 8 bits, white-side reference luminance of RGB, when input as RGB signals (255, 255, 255), the luminance of the white W _t of the emission luminance and emission color target L _Wt and chromaticity (x _Wt , y _Wt ) are adjusted. That is, when (255, 255, 255) is input as the RGB signal, the RGB white-side reference luminance is set such that the RGB luminances are the luminance values L _R , L _G , and L _B calculated in step S3. Is adjusted. When the RGB white side reference luminance is adjusted in this way, when the input RGB signals have the same value, the emission color always has the target white chromaticity. Note that the white-side reference luminance of W is adjusted to be the target luminance (the luminance value L _{W of} W determined in step S4 in FIG. 9) when only W is displayed.

Note that the RGBW signal value for realizing the target white W _t (255) when the RGB input signal values are all 255 is the luminance value L _R (corresponding to LR1) calculated in step S3 of the panel adjustment process. , L _G (corresponding to LG1), L _B (corresponding to LB1), and the luminance value L _R (corresponding to LR2) calculated in step S4, L _G (corresponding to LG2) , L _B (corresponding to LB2) and L _W (corresponding to LW2).

  FIG. 11 shows a procedure of signal conversion processing for converting an RGB input signal into an RGBW signal.

  First, the minimum value (min (RGB)) in the RGB input signal is determined (step S11). In the example of FIG. 3, min (RGB) = 100.

  Next, min (RGB) is subtracted from each RGB input signal (step S12). In the example of FIG. 3, as shown in FIG. 5, the subtraction results for RGB are 100, 0, and 70, respectively.

Next, min (RGB) is converted into an RGBW signal using the RGBW signal value for expressing the target white W _t (255) when the RGB input signal values are all 255 (step S13). If the RGBW signal value for realizing the target white W _t (255) is a signal value as shown in FIG. 6, the signal value of the RGBW signal corresponding to min (RGB) is shown in the example of FIG. As shown in FIG.

  Next, the RGBW signal corresponding to the RGB input signal is calculated by adding the signal value of the RGBW signal obtained in step S13 to the subtraction value {RGB-min (RGB)} calculated in step S12 ( Step S14). In the example of FIG. 3, the RGBW signal corresponding to the RGB input signal is as shown in FIG.

[4] Description of the first modification of the RGB-RGBW signal conversion process

  When the target white chromaticity can be expressed by only three colors of RBW, when the minimum value in the RGB input signal is the G signal, the processing of steps S11 to S14 in FIG. The RGBW signal in which one signal (G signal) of the RGB signal is 0 is obtained by the -RGBW conversion routine.

  Similarly, when the target white chromaticity can be expressed by only three colors of RGW, even when the minimum value in the RGB input signal is the B signal, steps S11 to S14 in FIG. Through the processing (RGB-RGBW conversion routine), an RGBW signal in which one signal (B signal) of the RGB signals becomes 0 is obtained. Further, when the target white chromaticity can be expressed by only three colors of GBW, the processing in steps S11 to S14 in FIG. 11 is also performed when the minimum value in the RGB input signal is the R signal. By the (RGB-RGBW conversion routine), an RGBW signal in which one signal (R signal) of the RGB signal becomes 0 is obtained.

  However, when the target white chromaticity can be expressed by only three colors of RBW, when the minimum value in the RGB input signal is a signal of a color other than the G signal, the target white chromaticity is When it is possible to express only by three colors of RGW, when the minimum value in the RGB input signal is a signal of a color other than the B signal, the target white chromaticity is expressed by only three colors of GBW. If the minimum value in the RGB input signal is a signal of a color other than the R signal when possible, the processing in steps S11 to S14 in FIG. 11 (RGB-RGBW conversion routine) is performed only once. Then, one signal in the RGB signal in the obtained RGBW signal does not become zero.

  That is, depending on the conditions, one signal in the RGB signal in the obtained RGBW signal does not become 0 only by performing the RGB-RGBW conversion routine once.

  When the RGB input signal is converted to the RGBW signal so that one signal in the RGBW signal in the RGBW signal becomes 0, the size of the W signal increases, the light emission efficiency increases, and the power consumption can be reduced. .

  Therefore, in the first modification, a signal conversion method is proposed in which an RGBW signal is obtained such that one signal in the RGB signal becomes 0 regardless of the conditions.

  FIG. 12 shows a procedure of signal conversion processing for converting an RGB input signal into an RGBW signal.

Assume that the RGBW signal values for expressing the target white W _t (255) when the RGB input signal values are all 255 are signal values as shown in FIG.

  First, the minimum value (min (RGB)) in the RGB input signal is determined (step S21). As shown in FIG. 13, if the RGB input signal values are R = 200, G = 170, and B = 100, min (RGB) = 100 as shown in FIG.

  Next, min (RGB) is subtracted from each RGB input signal (step S22). In the example of FIG. 13, the subtraction results for RGB are 100, 70, and 0, respectively, as shown in FIG. That is, the RGB input signal is decomposed into the RGB signal value of FIG. 14 and the RGB signal value of FIG.

Next, min (RGB) is converted into an RGBW signal using the RGBW signal value for expressing the target white W _t (255) when the RGB input signal values are all 255 (step S23). If the RGBW signal value for realizing the target white W _t (255) is a signal value as shown in FIG. 6, in the example of FIG. 13, the signal value of the RGBW signal corresponding to min (RGB) is 16 (same as FIG. 7).

  Next, the RGBW signal corresponding to the RGB input signal is calculated by adding the signal value of the RGBW signal obtained in step S23 to the subtraction value {RGB-min (RGB)} obtained in step S22. (Step S24). In the example of FIG. 13, the RGBW signal corresponding to the RGB input signal is as shown in FIG.

  R, G, B, and W of FIG. 17 are calculated | required by following Formula (5).

R = 100 + 30 = 130
G = 70 + 0 = 70
B = 0 + 80 = 80
W = 0 + 100 = 100 (5)

  Next, it is determined whether or not the minimum value of the RGB signal in the obtained RGBW signal is 0 (step S25). When the minimum value of the RGB signal in the obtained RGBW signal is 0, the signal conversion process is terminated. That is, the RGBW signal obtained in step S24 is an RGBW output signal.

  If the minimum value of the RGB signal in the obtained RGBW signal is not 0, the obtained RGBW signal is regarded as an input RGBW signal, and the processing (RGB-RGBW conversion routine) performed in steps S21 to S24 is performed. Similar processing is performed again.

That is, when the minimum value of the RGB signal in the RGBW signal is not 0, the obtained RGBW signal is used as the R ₁ G ₁ B ₁ W ₁ input signal as shown in FIG. Then, the minimum value (min (R ₁ G ₁ B ₁ )) in the R ₁ G ₁ B ₁ input signal is determined (step S26). As shown in FIG. 18, assuming that R ₁ G ₁ B ₁ W ₁ input signals are R = 130, G = 70, B = 80, and W = 100, as shown in FIG. 20, min (R ₁ G ₁ B ₁ ) = 70.

Next, min (R ₁ G ₁ B ₁ ) is subtracted from each R ₁ G ₁ B ₁ input signal (step S27). In the example of FIG. 18, as shown in FIG. 19, the subtraction results for RGB are 60, 0, and 10, respectively. That, R ₁ G ₁ B ₁ input signal, the R ₁ G ₁ B ₁ signal values of FIG. 19, is decomposed into R ₁ G ₁ B ₁ signal values of FIG 20.

Next, min (R ₁ G ₁ B ₁ ) is converted into an RGBW signal using the RGBW signal value for expressing the target white W _t (255) when the RGB input signal values are all 255. (Step S28). If the RGBW signal value for realizing the target white W _t (255) is a signal value as shown in FIG. 6, in the example of FIG. 20, the RGBW signal corresponding to min (R ₁ G ₁ B ₁ ). The signal values are as shown in FIG.

  R, G, B, and W in FIG. 21 are obtained by the following equation (6).

R = 77 × 70/255 = 21
G = 0 × 70/255 = 0
B = 204 × 70/255 = 56
W = 255 × 70/255 = 70 (6)

Then, by adding the RGB signal values in the RGBW signals obtained in step S28 to the subtraction value calculated in step _{S27 {R 1 G 1 B 1} -min (R 1 G 1 B 1)} with obtaining the RGB signals, obtaining the W signal by adding the W signal values in RGBW signal obtained in step S28 to W ₁ in R ₁ G ₁ B ₁ W ₁ input signal (step S29). In this way, an RGBW signal is obtained.

  In the above example, the RGBW signal is as shown in FIG. R, G, B, and W of FIG. 22 are calculated | required by following Formula (7).

R = 60 + 21 = 81
G = 0 + 0 = 0
B = 10 + 56 = 66
W = 100 + 70 = 170 (7)

  Next, it is determined whether or not the minimum value of the RGB signal in the RGBW signal obtained in step S29 is 0 (step S30). When the minimum value of the RGB signal in the obtained RGBW signal is 0, the signal conversion process is terminated.

When the minimum value of the RGB signal in the obtained RGBW signal is not 0, the process returns to step S26. That is, the RGB-RGBW conversion routine is repeatedly performed until the minimum value of the RGB signal in the obtained RGBW signal becomes zero.
[5] Explanation of second modification of RGB-RGBW signal conversion processing

  As described in the first modification example, depending on conditions, a signal that is set to 0 by subtracting min (RGB) has a value of 1 or more by subsequent conversion from min (RGB) to RGBW signal. Sometimes. In such a case, the RGB-RGBW conversion routine is repeatedly performed as described in the first modification.

  In the second modification, a signal conversion method is proposed in which an RGBW signal in which at least one of the RGB signals is 0 is obtained regardless of the conditions by executing the RGB-RGBW conversion routine once.

  Focusing on one signal in the RGB signals, the process of signal conversion will be described. When the signal of interest is always handled as min (RGB), and about 0.8% of the converted W signal is fed back to the signal by converting min (RGB) to an RGBW signal. Assuming that, for example, if the initial value is 50, the signal of interest changes according to the number of executions of the RGB-RGBW conversion routine as shown in the following equation (8).

  50 → 40 → 32 → 25.6 → 20.5 → 16.4 → 13.1 ... → 0 (8)

  In this case, the W signal is a value obtained by adding all the numerical values of the above equation (8), and can be obtained as the sum of an infinite geometric series having an initial term of 50 and a common ratio of 0.8. When −1 <common ratio <1, the sum of the infinite geometric series can be simplified as the following equation (9).

  Sum of infinite geometric series = first term / (1-common ratio) (9)

  Therefore, when the infinite geometric series is expressed by the equation (8), the sum of the infinite geometric series is 50 / (1-0.8) = 250.

  In an actual system, the sum of the infinite geometric series as described above is calculated for each RGB signal, and the RGB-RGBW conversion routine is executed once, with the minimum of them being min (RGB). As a result, one of the RGB signals in the obtained RGBW signal is 0, and the other two are 0 or more.

  The case where the RGB input signal values are R = 255, G = 255, and B = 50 will be described as an example.

Assuming a case where the RGBW signal value for expressing the target white W _t (255) when the RGB input signal values are all 255 is as shown in FIG. 6, conversion of min (RGB) to RGBW signal is performed. Therefore, the RGB signal feedback rate is 0.3 (= R in FIG. 6 / W in FIG. 6 = 77/255), 0 (= G in FIG. 6 / W in FIG. 6), 0.8 (= in FIG. 6). B / W in FIG. 6 = 204/255).

  If the sum of the infinite geometric series corresponding to R, G, and B is ΣR, ΣG, and ΣB, ΣR, ΣG, and ΣB are expressed by the following equation (10).

ΣR = 255 / (1-0.3) = 364
ΣG = 255 / (1-0) = 255
ΣB = 50 / (1-0.8) = 250 (10)

  Since the minimum value is 250, when 250 is subtracted from RGB, the subtraction result is as shown in the following equation (11).

R = 255-250 = 5
G = 255-250 = 5
B = 50−250 = −200 (11)

  On the other hand, when min (RGB) (= 250) is converted into an RGBW signal, the following equation (12) is obtained.

R = 250 × 0.3 = 75
G = 255 × 0 = 0
B = 50 × 0.8 = 200
W = 250 (12)

  Therefore, the RGBW output signal is represented by the following equation (13).

R = 5 + 75 = 80
G = 5 + 0 = 5
B = −200 + 200 = 0
W = 250 (13)

  FIG. 23 shows a procedure of signal conversion processing for converting an RGB input signal into an RGBW signal.

The feedback rate of the RGB signal is calculated using the RGBW signal value for expressing the target white W _t (255) when the RGB input signal values are all 255 (step S41). If the RGBW signal value for realizing the target white W _t (255) is a signal value as shown in FIG. 6, the feedback rate of the RGB signal is 0.3 (= 77/255), 0, 0. .8 (= 204/255).

  Next, for each RGB input signal, an infinite geometric series sum ΣR, ΣG, ΣB is calculated with the RGB input signal value as the first term and the feedback rate calculated in step S41 as a common ratio (step S42).

  Next, the minimum value of the sum ΣR, ΣG, ΣB of the infinite geometric series calculated for each RGB input signal is subtracted from the RGB input signal as min (RGB) (step S43).

Next, min (RGB) is converted into an RGBW signal using the RGBW signal value for expressing the target white W _t (255) when the RGB input signal values are all 255 (step S44).

  Next, the RGBW signal corresponding to the RGB input signal is obtained by adding the signal value of the RGBW signal obtained in step S44 to the subtraction value {RGB-min (RGB)} obtained in step S43 ( Step S45).

  By the way, the RGB input signal may be subjected to gamma correction in advance. In such a case, it is preferable that an RGB signal before gamma correction is input to the RGB-RGBW conversion circuit 1 of FIG. 2 for simplification of signal processing. Therefore, as shown in FIG. 24, by performing reverse gamma correction on the RGB input signal that has been subjected to gamma correction in the previous stage of the RGB-RGBW conversion circuit 1, the RGB input signal is converted to RGB before gamma correction. An inverse gamma correction circuit 11 that converts the signal into a signal is arranged, and an RGBW signal output from the RGB-RGBW conversion circuit 1 is provided in a subsequent stage of the RGB-RGBW conversion circuit 1 according to the panel characteristics of the organic EL display 3 It is preferable to arrange a gamma correction circuit 12 that performs gamma correction. In this way, various calculations in the RGB-RGBW conversion circuit 1 can use the calculation methods described in the above embodiment, the first modified example, and the second modified example 2 as they are. That is, the RGB signal output from the inverse gamma correction circuit 11 is used as the “RGB input signal” in the above embodiment, the first modification, and the second modification 2.

[B] Description of Invention Regarding RGB-RGBX (X is an Arbitrary Color) Signal In the above [A], the processing for converting an RGB signal into an RGBW signal has been described. Here, a process for converting an RGB signal into an RGBX signal with X as an arbitrary color other than RGB (an arbitrary color having chromaticity coordinates different from RGB) will be described.

  Here, an embodiment when X = Ye will be described. In the self-luminous display, as shown in FIG. 25, one pixel is composed of four unit pixels, of which three unit colors include three primary colors, for example, R (red), G (green), and B (blue). The color filter for displaying is arranged. A color filter for displaying Ye (yellow) is arranged in the remaining one unit pixel.

[1] Description of configuration of display device

  FIG. 26 shows a configuration of the display device.

  It is assumed that gamma correction is applied in advance to the digital RGB input signal. The inverse gamma correction circuit 21 receives a digital RGB input signal that has been previously subjected to gamma correction. The inverse gamma correction circuit 21 converts the RGB input signal into an RGB signal before gamma correction by performing inverse gamma correction on the RGB input signal.

  The RGB signal obtained by the inverse gamma correction circuit 21 is sent to the RGB-RGBYe signal conversion circuit 22. The RGB-RGBYe signal conversion circuit 22 converts an RGB input signal into an RGBYe signal. The RGBYe signal obtained by the RGB-RGBYe signal conversion circuit 22 is sent to the gamma correction circuit 23.

  The gamma correction circuit 23 performs gamma correction according to the panel characteristics of the organic EL display 25 on the input RGBYe signal. The RGBYe signal obtained by the gamma correction circuit 23 is converted into an analog RGBYe signal by the D / A conversion circuit 24. The RGBYe signal obtained by the D / A conversion circuit 24 is sent to the organic EL display 25 in which one pixel is composed of four unit pixels of RGBYe.

  The RGB-RGBYe signal conversion circuit 22 converts the RGB signal into an RGBYe signal based on the RGB signal value for realizing the chromaticity of Ye (yellow determined by the corresponding color filter) and the maximum luminance. Therefore, first, a method of calculating RGB signal values for realizing Ye chromaticity and maximum luminance will be described.

[2] Description of RGB Signal Value Calculation Method for Realizing Ye Chromaticity and Maximum Luminance FIG. 27 shows the RGB reference adjustment processing procedure.

The brightness L _Wt and chromaticity coordinates (x _Wt , y _Wt ) of the target white W _t are set (step S51).

Next, the RGB chromaticity of the organic EL display 25 is measured (step S52). For example, when measuring the chromaticity of R, only the unit pixel for R display of the organic EL display 25 is caused to emit light, and the chromaticity is measured by an optical measuring instrument. Let the measured RGB chromaticity coordinates be (x _R , y _R ), (x _G , y _G ), and (x _B , y _B ), respectively. Figure 28 shows the chromaticity coordinates of the white W _t of the RGB chromaticity coordinates and target.

Next, RGB luminance values at the time of RGB white balance (WB) adjustment are calculated (step S53). That is, the RGB luminance values L _WR , L _WG , and L _WB for expressing the target white W _t luminance L _Wt and chromaticity (x _Wt , y _Wt ) by the three colors of RGB are calculated. The luminance values L _WR , L _WG , and L _WB are obtained from the following equation (14).

However, a _{z R = 1-x R -y} R, z G = 1-x G -y G, z B = 1-x B -y B, z Wt = 1-x Wt -y Wt.

  Next, RGB white side reference luminance is calculated using the calculation result of step S53 (step S54).

When the RGB input signal value is represented by 8 bits, the RGB white side reference luminance is such that when (255, 255, 255) is input to the RGB-RGBYe conversion circuit 22 as the RGB signal, the emission luminance and emission color are the same. The brightness L _Wt and chromaticity (x _Wt , y _Wt ) of the target white W _t are adjusted. That is, when RGB signals (255, 255, 255) are input to the RGB-RGBYe conversion circuit 22, the RGB luminances are set to L _WR , L _WG , L _WB calculated in step S53, respectively. The white side reference luminance of the image is adjusted.

  FIG. 29 shows a reference adjustment processing procedure for Ye.

The chromaticity of Ye of the organic EL display 25 is measured (step S61). That is, only the unit pixel for Ye display of the organic EL display 24 is caused to emit light, and its chromaticity is measured by the optical measuring instrument. Let the measured chromaticity coordinates of Ye be (x _ye , y _ye ). Figure 30 shows RGB chromaticity coordinates, the chromaticity coordinates of the chromaticity coordinates and Ye target white W _t.

Next, the luminance ratio of RGB at the time of Ye adjustment by RGB is calculated (step S62). That is, the RGB luminance ratios L _yeR , L _yeG , and L _yeB when expressing the chromaticity (x _ye , y _ye ) of Ye by the three colors of RGB are calculated. The luminance ratios L _yeR , L _yeG , and L _yeB are obtained from the following equation (15).

_{However, z R = 1-x R} -y R, z G = 1-x G -y G, z B = 1-x B -y B, a _{z ye = 1-x ye -y} ye.

Next, RGB luminance values L _WR , L _WG , L _WB at the time of RGB white balance (WB) adjustment obtained at step S 53 in FIG. 27, and RGB at the time of Ye adjustment by RGB obtained at step S 62 described above. the luminance ratio _L yeR, L yeG, based on the L _YEB, calculates the RGB luminance when representing chromaticity and the maximum luminance of Ye, RGB signals for realizing the chromaticity and the maximum luminance of Ye A value (RGB signal value equivalent to Ye (255)) is obtained (step S63).

That is, RGB luminances L _yeR ′, L _yeG ′, and L _yeB ′ for expressing Ye (255) are calculated within the RGB luminance range determined when expressing the target white (W _t ).

_{L WR} / L yeR, calculates the _{L WG} / L yeG and _{L WB} / L yeB, the minimum value of the _L yeR, L yeG, by multiplying the L _YEB, RGB for representing Ye (255) Luminance values L _yeR ', L _yeG ', and L _yeB 'are obtained.

For example, the RGB luminances L _WR , L _WG , and L _WB at the time of white balance (WB) adjustment are 30 [cd]: 60 [cd]: 10 [cd], and the RGB luminance ratio L _yeR , If L _yeG and L _yeB are 0.25: 0.6: 0.05, then L _WR / L _yeR = 120, L _WG / L _yeG = 100, and L _WB / L _yeB = 200. Since the minimum value is 100, when L _yeR , L _yeG , and L _yeB are multiplied by 100, RGB luminances L _yeR ', L _yeG ', and L _yeB 'for expressing the chromaticity and maximum luminance of Ye are 25. [cd], 60 [cd], and 5 [cd].

The RGB luminances for expressing the chromaticity and maximum luminance of Ye are (L _yeR ', L _yeG ', L _yeB '), and the RGB luminance values during white balance (WB) adjustment are (L _WR , L _WG , L _WB ), RGB signal values (R _ye , G _ye , B _ye ) for realizing Ye chromaticity and maximum luminance are R _ye = 255 × L _yeR '/ L _WR , G _ye = 255 _{× L yeG '/ L WG,} B ye = 255 × L yeB' a / L _WB.

In the above example, R _ye = 255 × _25/30 = 213, G _ye = 255 × _60/60 = 255, and B _ye = 255 × _5/10 = 128.

Next, the white reference of Ye is adjusted based on the RGB luminance values L _yeR ′, L _yeG ′, and L _yeB ′ for expressing the chromaticity and maximum luminance of Ye obtained in step S63 (step S63). S64). The Ye white side reference voltage (the output voltage of the D / A converter 24 corresponding to Ye = 255), when only Ye is displayed, the luminance is RGB luminance for expressing the chromaticity and maximum luminance of Ye. _Is adjusted so as to be the total value (L _yeR '+ L _yeG ' + L _yeB ').

[3] Explanation of RGB-RGBYe signal conversion processing by the RGB-RGBYe signal conversion circuit 22

  FIG. 31 shows an RGB-RGBYe signal conversion processing procedure by the RGB-RGBYe signal conversion circuit 22.

  Here, an input signal to the RGB-RGBYe signal conversion circuit 22 is referred to as an RGB input signal. An RGB signal component that can be converted from an RGB input signal into a Ye signal, and when an RGB signal component converted from an RGB input signal into a Ye signal is subtracted, at least one of the RGB subtraction results is 0 Such RGB signal components are calculated (step S71).

If the RGB signal values for realizing Ye chromaticity and maximum brightness are R _ye , G _ye , and B _ye , the RGB signal component converted to the Ye signal is α (R _ye , G _ye , B _ye ). expressed. Therefore, first, α is obtained such that when α (R _ye , G _ye , B _ye ) is subtracted from the RGB input signal, at least one of the RGB subtraction results is zero. Specifically, when the RGB input signal is represented by R, G, and B, R / R _ye , G / G _ye , and B / B _ye are calculated, and the minimum value is α. Then, α (R _ye , G _ye , B _ye ) is calculated.

For example, assume that the RGB input signal is as shown in FIG. If the maximum RGB signal values (R _ye , G _ye , B _ye ) for realizing Ye chromaticity and maximum luminance are R _ye = 213, G _ye = 255, and B _ye = 128, the RGB input signal is R = 200, G = 100, B = 170, so R / R _ye = 200/213 = 0.95, G / G _ye = 100/255 = 0.39, B / B _ye = 170/128 = Since it is 1.33, the minimum value is 0.39. Therefore, when α = 0.39, αR _ye = 78, αG _ye = 100, and αB _ye = 67. That is, RGB signal components α (R _ye , G _ye , B _ye ) converted into Ye signals are as shown in FIG.

Next, the RGB signal component α (R _ye , G _ye , B _ye ) converted into the Ye signal is subtracted from the RGB input signal (step S72).

  In the above example, the subtraction result for R is 122 (= 200-78), the subtraction result for G is 0 (= 100-100), and the subtraction result for B is 103 (= 170-67).

  Then, the RGB subtraction results calculated in step S72 are output as RGB signals (step S73).

  Further, 255 × α is output as a Ye signal (step S74). In the above example, the Ye signal is 100 (= 0.39 × 255). That is, in the above example, the RGBYe signal is as shown in FIG.

  In the above embodiment, the case where the RGB signal is converted into the RGBYe signal has been described. However, this method can also be applied to the case where the RGB signal is converted into the RGBX signal with X being an arbitrary color other than RGB. it can.

It is a schematic diagram which shows the example by which 1 pixel is comprised by four units of R, G, B, and W. It is a block diagram which shows the structure of a display apparatus. It is a schematic diagram which shows an example of an RGB input signal. It is a schematic diagram which shows min (RGB). It is a schematic diagram which shows input signal-min (RGB). Showing the signal ratio of the RGBW for representing W _t (255) are schematic views. Showing the signal ratio of the RGBW for realizing W _t (100) are schematic views. It is a schematic diagram which shows the RGBW value calculated | required by adding the RGB value of FIG. 5, and the RGBW value of FIG. It is a flowchart which shows a panel adjustment process procedure. RGBW chromaticity coordinates (x _R , y _R ), (x _G , y _G ), (x _B , y _B ), (x _W , y _W ) and target white W _t chromaticity coordinates (x _Wt , Y _Wt ). It is a flowchart which shows the procedure of the signal conversion process for converting an RGB input signal into an RGBW signal. It is a flowchart which shows the other example of the signal conversion process for converting an RGB input signal into an RGBW signal. It is a schematic diagram which shows an example of an RGB input signal. It is a schematic diagram which shows RGB input signal-min (RGB). It is a schematic diagram which shows min (RGB). It is a schematic diagram which shows the RGBW signal corresponding to min (RGB). It is a schematic diagram which shows the RGBW value calculated | required by adding the RGB value of FIG. 14, and the RGBW value of FIG. The resulting RGBW signals in the case where the R ₁ G ₁ B ₁ W ₁ input signal is a schematic diagram showing the R ₁ G ₁ B ₁ W ₁ input signal. R ₁ G ₁ B ₁ input signal _{-min (R 1 G 1 B 1} ) is a schematic view showing a. It is a schematic diagram showing the _{min (R 1 G 1 B 1} ). is a schematic diagram showing an RGBW signal corresponding to the _{min (R 1 G 1 B 1} ). By adding the R ₁ G ₁ B ₁ W ₁ value of R ₁ G ₁ B ₁ value and 21 in FIG. 19 is a schematic diagram showing the obtained RGBW values. It is a flowchart which shows the further another example of the signal conversion process for converting an RGB input signal into an RGBW signal. It is a block diagram which shows the structure of a display apparatus. It is a schematic diagram which shows the example by which 1 pixel is comprised by four units of R, G, B, and Ye. It is a block diagram which shows the structure of a display apparatus. It is a flowchart which shows the RGB reference adjustment process sequence. It is a schematic diagram illustrating the chromaticity coordinates of the RGB chromaticity coordinates and the target white W _t. It is a flowchart which shows the reference adjustment process sequence of Ye. RGB chromaticity coordinates, is a schematic diagram illustrating the chromaticity coordinates of the chromaticity coordinates and Ye target white W _t. 5 is a flowchart showing an RGB-RGBYe signal conversion processing procedure by an RGB-RGBYe signal conversion circuit 22; It is a schematic diagram which shows an example of an RGB input signal. FIG. ₃₃ is a schematic diagram showing RGB signal components α (R _ye , G _ye , B _ye ) converted into Ye signals when the RGB input signal is a signal as shown in FIG. 32. It is a schematic diagram which shows the RGBYe signal obtained by the RGB-RGBYe signal conversion circuit 22, when an RGB input signal is a signal as shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 RGB-RGBW signal conversion circuit 2 D / A conversion circuit 3 Organic EL display 11 Reverse gamma correction circuit 12 Gamma correction circuit 21 Reverse gamma correction circuit 22 RGB-RGBYe signal conversion circuit 23 Gamma correction circuit 24 D / A conversion circuit 25 Organic EL display

Claims (4)

A signal processing circuit of a self-luminous display in which one pixel is composed of four RGBW unit pixels, the RGB unit pixel is provided with a color filter, and the W unit pixel is not provided with a color filter. When all the RGB input signals have the same value, the white reference luminance of RGB is set so that the target white can be realized only by RGB, and when all the RGB input signals are at the maximum value, In the signal processing circuit of the self-luminous display in which RGBW signal values for realizing white are set,
A first means for subtracting the minimum value of the RGB input signals from the RGB input signals;
Second means for calculating an RGBW signal corresponding to a case where all of the RGB input signals have the minimum value, based on an RGBW signal value for realizing the target white when all of the RGB input signals have the maximum value. And third means for obtaining an RGBW signal by adding the subtraction result for each RGB calculated by the first means to the corresponding signal to the RGBW signal calculated by the second means,
A signal processing circuit for a self-luminous display, comprising: A signal processing circuit of a self-luminous display in which one pixel is composed of four RGBW unit pixels, the RGB unit pixel is provided with a color filter, and the W unit pixel is not provided with a color filter . When all the RGB input signals have the same value, the white reference luminance of RGB is set so that the target white can be realized only by RGB, and when all the RGB input signals are at the maximum value, In the signal processing circuit of the self-luminous display in which RGBW signal values for realizing white are set ,
Based on the RGBW signal value for realizing the target white when all the RGB input signals are maximum values, the ratio of each RGB signal value to the W signal value is calculated as a feedback rate for each RGB. A first means to
A second means for calculating the sum of an infinite geometric series with the RGB input signal as the first term for each RGB and the feedback ratio for each RGB as a common ratio;
A third means for subtracting the minimum value of the sum of the infinite geometric series calculated for each RGB by the second means from the RGB input signals;
Fourth means for calculating an RGBW signal corresponding to a case where all of the RGB input signals have the minimum value, based on an RGBW signal value for realizing the target white when all of the RGB input signals have the maximum value ,and
A fifth means for obtaining an RGBW signal by adding a subtraction result for each RGB calculated by the third means to a corresponding signal to the RGBW signal calculated by the fourth means;
A signal processing circuit for a self-luminous display, comprising: A signal processing method for a self-luminous display in which one pixel is composed of four RGBW unit pixels, the RGB unit pixels are provided with color filters, and the W unit pixels are not provided with color filters. When all the RGB input signals have the same value, the white reference luminance of RGB is set so that the target white can be realized only by RGB, and when all the RGB input signals are at the maximum value, In the signal processing method of the self-luminous display in which the RGBW signal value for realizing white is set,
A first step of subtracting the minimum value of the RGB input signals from the RGB input signals;
A second step of calculating an RGBW signal corresponding to a case where all of the RGB input signals have the minimum value, based on an RGBW signal value for realizing the target white when all of the RGB input signals have the maximum value. , and the relative RGBW signal calculated by the second step, by adding a corresponding signal to the subtraction result for each RGB calculated by the first step, a third step of obtaining a RGBW signal,
Self-luminous display signal processing method which is characterized in that it comprises. A signal processing circuit for a self-luminous display in which X is an arbitrary color other than RGB, and one pixel is composed of four unit pixels of RGBX, in order to realize the chromaticity and maximum luminance of X by the RGB signal In the signal processing circuit of the self-luminous display in which the RGB signal value is set,
RGB-RGBX signal conversion means for converting an RGB input signal into an RGBX signal is provided,
The RGB-RGBX signal conversion means is
RGB signal components that can be converted from the RGB input signal to the X signal based on the RGB signal values for realizing the chromaticity of X and the maximum luminance, and can be converted from the RGB input signal to the X signal A first means for calculating an RGB signal component such that at least one of RGB subtraction results is 0 when the signal component is subtracted;
A second means for subtracting the RGB signal component calculated by the first means from the RGB input signal and outputting the subtraction result as an RGB signal; and
A third means for outputting an X signal corresponding to the RGB signal component calculated by the first means as an X signal;
A signal processing circuit for a self-luminous display, comprising:

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