JP2015210389A - Display device, method for driving display device, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the degradation of picture quality while reducing power consumption.SOLUTION: A reproduction color space is divided in plurality by a hue, and different values are set to at least two of a plurality of divided spaces as limit values that are upper limits to the ratio, to a total number of pixels, of the number of pixels exceeding the maximum value of the luminosity of the reproduction color space in a combination of hue and saturation values. A first limit value for the case of a color included in an area that is set on the basis of the case of at least one color among six specific colors where the signal value of a component, among the red, blue, and green components of an input signal, whose value is maximum and the signal value of a component whose value is minimum are different, and the signal value of a component whose value is intermediate and the signal value of the component whose value is maximum or the signal value of the component whose value is minimum are the same, is set to be higher than a second limit value for the case of the other color. An expansion coefficient α for the input signal is calculated within the range in which the ratio of the number of pixels exceeding the maximum value of luminosity to the total number of pixels does not exceed the limit values.

Description

  The present invention relates to a display device having an image display unit provided with an image display region, a display device driving method, and an electronic apparatus.

  In recent years, there has been a growing demand for display devices for mobile devices such as mobile phones and electronic paper. In a display device, one pixel includes a plurality of sub-pixels, each of the plurality of sub-pixels outputs light of a different color, and the display of the sub-pixel is switched on and off, whereby one pixel can perform various operations. The color is displayed. Some of such display devices use four sub-pixels including white as one pixel (see Patent Documents 1 and 2).

In Patent Document 1, an image display panel in which pixels composed of first, second, third, and fourth subpixels are arranged in a two-dimensional matrix, an input signal is input, and an output signal is output. A display device including a signal processing unit is described. The display device can expand the HSV color space more than the case of the three primary colors by adding the fourth color to the three primary colors. The signal processing unit stores the maximum value V _max (S) of lightness with the saturation S as a variable, obtains the saturation S and the lightness V (S) based on the signal value of the input signal, and V _max (S ) / V (S) based on at least one of the values, the expansion coefficient α ₀ is obtained, and the output signal value to the fourth subpixel is input to at least the first, second and third subpixels. Based on the signal value, output signal values to the first, second, and third subpixels are calculated based on the input signal value, the expansion coefficient α ₀ , and the fourth output signal value.

Patent Document 2 discloses a display panel provided with a plurality of pixels each including a sub-pixel having red, green, and blue color filters and a sub-pixel for controlling transmission of white light, A backlight unit having green, blue, and white light sources, an image switching circuit that switches between displaying the display panel in a moving image mode or a still image mode, and a backlight according to an image signal in the moving image mode And a display control circuit that controls the luminance of red, green, and blue in a portion and controls the luminance of a white light source in a backlight portion in accordance with an image signal in a still image mode. . In Patent Document 3, the signal processing unit obtains the saturation S and the brightness V (S) in the plurality of pixels based on the input signal values of the sub-pixels in the plurality of pixels, and expands the brightness V (S) and the brightness. The expansion coefficient α ₀ is determined so that the ratio of the pixels where the value of the expanded brightness obtained from the product of the coefficient α ₀ exceeds the maximum value V _max (S) to all the pixels is equal to or less than a predetermined value (β ₀ ). To do.

JP 2010-33009 A JP 2011-248352 A JP 2011-154323 A

  As shown in Patent Document 1 to Patent Document 3, an image corresponding to an HSV color space expanded by one subpixel (basically a white subpixel) based on an image signal among a plurality of subpixels. By extending the signal, the light amount of the light source can be reduced and a desired image can be reproduced. In addition, the image can be brightened without increasing the amount of light from the light source.

  However, when the image signal is expanded, the image quality may be reduced (deteriorated). On the other hand, although the degradation of image quality can be suppressed by determining the expansion coefficient using the display device described in Patent Document 3, the effect of reducing power consumption may be reduced. .

  The present technology has been made in view of such problems, and an object of the present technology is to provide a display device capable of reducing power consumption while suppressing deterioration in image quality, an electronic device including the display device, and a display device driving method. It is to provide.

  The display device of the present invention displays a first subpixel that displays a first color, a second subpixel that displays a second color, a third subpixel that displays a third color, and a fourth color. An image display panel in which pixels including a fourth sub-pixel are arranged in a two-dimensional matrix, and an input value of an input signal for the first color, the second color, the third color, and the fourth color A signal processing unit that converts and generates a reproduction value of a reproduction color space (for example, HSV color space) that is reproduced in color, and outputs the generated output signal to the image display panel. , Dividing the reproduction color space into a plurality of hues, and for at least two of the divided spaces, the maximum value of the lightness of the reproduction color space in a combination of hue and saturation values Set a different value as the limit value that is the upper limit of the ratio of the width exceeding the maximum value, Among the three components of the first color (for example, red), the second color (for example, blue), and the third color (for example, green) of the input signal, the signal value and the value of the component having the maximum value are the minimum. The signal values of the six components are different from each other and the signal value of the intermediate component is the same as the signal value of the component having the maximum value or the signal value of the component having the minimum value. A first limit value in the case of a color included in an area set based on at least one specific color is set higher than a second limit value in the case of another color, and each subpixel of the input signal is set. In the range where the ratio of the number of pixels exceeding the maximum value of lightness to the total number of pixels among the values obtained by multiplying the signal by the expansion coefficient α does not exceed the limit value, the expansion coefficient α for the input signal is calculated, Based on at least the input signal of the first sub-pixel and the expansion coefficient α, the first sub-image The output signal of the second subpixel is calculated based on at least the input signal of the second subpixel and the expansion coefficient α, and output to the first subpixel. To calculate the output signal of the third subpixel based on at least the input signal of the third subpixel and the expansion coefficient α, and output to the third subpixel. The input signal of the first subpixel The output signal of the fourth subpixel is calculated based on the input signal of the second subpixel and the input signal of the third subpixel, and is output to the fourth subpixel.

  An electronic apparatus according to the present invention includes any of the display devices described above and a control device that supplies the input signal to the display device.

  The present invention provides a first sub-pixel that displays a first color, a second sub-pixel that displays a second color, a third sub-pixel that displays a third color, and a fourth sub-pixel that displays a fourth color. An image display panel in which pixels including pixels are arranged in a two-dimensional matrix, and an input value of an input signal is reproduced in the first color, the second color, the third color, and the fourth color And a signal processing unit that converts and generates a reproduction value of a reproduced color space (for example, HSV color space) and outputs the generated output signal to the image display panel. The reproduction color space is divided into a plurality of hues, and for at least two of the divided spaces, the maximum value for the maximum value of the reproduction color space in a combination of hue and saturation values. Set a different value as the limit value, which is the upper limit of the ratio of the width exceeding the value. And the ratio of the number of pixels exceeding the maximum value of brightness among the values obtained by multiplying the signal of each sub-pixel of the input signal by the expansion coefficient α in a range not exceeding the limit value, Calculating an expansion coefficient α for the input signal; calculating an output signal of the first subpixel based on at least the input signal of the first subpixel and the expansion coefficient α; and outputting the output signal to the first subpixel. Calculating an output signal of the second subpixel based on at least the input signal of the second subpixel and the expansion coefficient α and outputting the calculated signal to the second subpixel; and at least the input signal of the third subpixel and the Based on the expansion coefficient α, the output signal of the third subpixel is calculated and output to the third subpixel, the input signal of the first subpixel, the input signal of the second subpixel, and the third subpixel. Based on the input signal of the fourth sub-pixel. Calculating a force signal and outputting it to the fourth sub-pixel, wherein the limit value is a signal value and a value of a component having the maximum value among the three components of red, blue and green of the input signal Is a value different from the signal value of the component with the smallest value, and the signal value of the component with the intermediate value is the same as the signal value of the component with the largest value or the signal value of the component with the smallest value The first limit value in the case of a color included in an area set based on at least one of the colors is set higher than the second limit value in the case of other colors.

FIG. 1 is a functional block diagram showing an example of the configuration of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a wiring diagram of the image display panel unit in the liquid crystal display device shown in FIG. FIG. 3 is a functional block diagram around the signal processing unit in the liquid crystal display device according to the embodiment of the present invention. FIG. 4 is a conceptual diagram of a reproduction HSV color space that can be reproduced by the display device of the present embodiment. FIG. 5 is a conceptual diagram showing the relationship between the hue and saturation of the reproduction HSV color space. FIG. 6 is a schematic diagram showing the color balance of six specific colors. FIG. 7 is a conceptual diagram showing the relationship among the hue, saturation, and limit value areas of the reproduction HSV color space. FIG. 8 is a conceptual diagram showing the relationship between the saturation and lightness of the reproduction HSV color space. FIG. 9 is a flowchart illustrating an example of the control operation of the display device. FIG. 10 is a flowchart illustrating an example of the control operation of the display device. FIG. 11 is a conceptual diagram showing the relationship between the input signal and the output signal. FIG. 12 is a conceptual diagram illustrating the relationship among the hue, saturation, and limit value areas of the reproduction color space. FIG. 13 is a conceptual diagram illustrating the relationship among the hue, saturation, and limit value areas of the reproduction color space. FIG. 14 is a conceptual diagram showing the relationship between the hue, saturation, and limit value area of the reproduction color space. FIG. 15 is a conceptual diagram showing the relationship among the hue, saturation, and limit value areas of the reproduction color space. FIG. 16 is a diagram illustrating an example of an electronic apparatus including the display device according to the embodiment of the invention. FIG. 17 is a diagram illustrating an example of an electronic apparatus including the display device according to the embodiment of the present invention. FIG. 18 is a diagram illustrating an example of an electronic apparatus including the display device according to the embodiment of the present invention. FIG. 19 is a diagram illustrating an example of an electronic apparatus including the display device according to the embodiment of the present invention. FIG. 20 is a diagram illustrating an example of an electronic apparatus including the display device according to the embodiment of the present invention. FIG. 21 is a diagram illustrating an example of an electronic apparatus including the display device according to the embodiment of the present invention. FIG. 22 is a diagram illustrating an example of an electronic apparatus including the display device according to the embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the disclosure is merely an example, and those skilled in the art can easily conceive of appropriate modifications while maintaining the gist of the invention are naturally included in the scope of the present invention. In addition, the drawings may be schematically represented with respect to the width, thickness, shape, and the like of each part in comparison with actual aspects for the sake of clarity of explanation, but are merely examples, and the interpretation of the present invention is not limited. It is not limited. In addition, in the present specification and each drawing, elements similar to those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description may be omitted as appropriate. In this embodiment, a liquid crystal display device is described as an example of a display device. However, the present invention is not limited to the liquid crystal display device and can be applied to various display devices.

  FIG. 1 is a functional block diagram showing an example of the configuration of the liquid crystal display device according to this embodiment. FIG. 2 is a wiring diagram of the image display panel unit in the liquid crystal display device shown in FIG.

  The display device 10 according to the present embodiment includes a signal processing unit 20, an image display panel driving unit 30, an image display panel 40, a planar light source device control unit 50, and a planar light source device 60. In the display device 10, the signal processing unit 20 sends a signal to each unit of the display device 10, and the image display panel driving unit 30 controls the driving of the image display panel 40 based on the signal from the signal processing unit 20. 40 displays an image based on a signal from the image display panel driving unit 30, and the planar light source device control unit 50 controls driving of the planar light source device 60 based on a signal from the signal processing unit 20, The planar light source device 60 illuminates the image display panel 40 from the back based on a signal from the planar light source device control unit 50 to display an image. The display device 10 has the same configuration as the image display device assembly described in JP 2011-154323 A, and various modifications described in JP 2011-154323 A can be applied. is there.

As shown in FIG. 2, the image display panel 40 has pixels 48 arranged in a two-dimensional matrix with P ₀ × Q ₀ (P _{0 in} the row direction and Q _{0 in} the column direction). The example shown in FIG. 2 shows an example in which a plurality of pixels 48 are arranged in a matrix in an XY two-dimensional coordinate system. In this example, the row direction is the X-axis direction, and the column direction is the Y-axis direction. The row direction may be the Y-axis direction and the column direction may be the X-axis direction.

  The pixel 48 includes a first sub-pixel 49R, a second sub-pixel 49G, and a third sub-pixel 49B or a fourth sub-pixel 49W. The first sub-pixel 49R displays a first primary color (for example, red). The second subpixel 49G displays a second primary color (for example, green). The third subpixel 49B displays a third primary color (for example, blue). The fourth subpixel 49W displays a fourth color (for example, white). Hereinafter, the first sub-pixel 49R, the second sub-pixel 49G, the third sub-pixel 49B, and the fourth sub-pixel 49W are referred to as sub-pixels 49 when it is not necessary to distinguish them from each other.

  More specifically, the display device 10 is a transmissive color liquid crystal display device. The image display panel 40 is a color liquid crystal display panel, in which a first color filter that passes the first primary color is disposed between the first sub-pixel 49R and the image observer, and the second sub-pixel 49G, the image observer, A second color filter that allows the second primary color to pass therethrough is disposed, and a third color filter that allows the third primary color to pass is disposed between the third sub-pixel 49B and the image observer. In the image display panel 40, no color filter is disposed between the fourth sub-pixel 49W and the image observer. The fourth subpixel 49W may be provided with a transparent resin layer instead of the color filter. As described above, by providing the transparent resin layer, the image display panel 40 can suppress the occurrence of a large step in the fourth subpixel 49W by not providing the color filter in the fourth subpixel 49W.

  In the example shown in FIG. 2, in the image display panel 40, the first sub-pixel 49R, the second sub-pixel 49G, the third sub-pixel 49B, and the fourth sub-pixel 49W are arranged in an arrangement similar to the stripe arrangement. . Note that the configuration and arrangement of sub-pixels included in one pixel are not particularly limited. For example, in the image display panel 40, the first sub-pixel 49R, the second sub-pixel 49G, the third sub-pixel 49B, and the fourth sub-pixel 49W may be arranged in an arrangement similar to a diagonal arrangement (mosaic arrangement). . Further, for example, it may be arranged by an arrangement similar to a delta arrangement (triangle arrangement) or an arrangement similar to a rectangle arrangement. In general, an arrangement similar to the stripe arrangement is suitable for displaying data and character strings on a personal computer or the like. On the other hand, an arrangement similar to the mosaic arrangement is suitable for displaying a natural image on a video camera recorder, a digital still camera, or the like.

  Referring again to FIG. 1, the signal processing unit 20 is an arithmetic processing circuit that controls operations of the image display panel 40 and the planar light source device 60 via the image display panel driving unit 30 and the planar light source device control unit 50. is there. The signal processing unit 20 is connected to the image display panel driving unit 30 and the planar light source device control unit 50.

  The signal processing unit 20 processes an input signal input from an external application processor (host CPU, not shown) to generate an image processing signal and a planar light source device control signal SBL. The signal processing unit 20 converts the input value of the input signal into a reproduction value of a reproduction color space (for example, HSV color space) reproduced in the first color, the second color, the third color, and the fourth color (for example, HSV color space). Image processing signal). Then, the signal processing unit 20 outputs the generated image processing signal to the image display panel driving unit 30. Further, the signal processing unit 20 outputs the generated planar light source device control signal SBL to the planar light source device control unit 50. In the present embodiment, the reproduction color space is an HSV color space, but is not limited to this, and may be an XYZ color space, a YUV space, or another coordinate system.

  FIG. 3 is a schematic diagram illustrating an outline of the configuration of the signal processing unit according to the present embodiment. As illustrated in FIG. 3, the signal processing unit 20 includes an input unit 21, a signal generation unit 23, and an output unit 25.

  The input unit 21 receives an input signal from an external application processor. The input signal has, for example, an input signal compression unit, a RAM, and an input signal expansion unit. The input signal data is compressed and temporarily stored in the RAM, and the data stored in the RAM is read and expanded. May be.

  The signal generation unit 23 reads the input signal input to the input unit 21 and generates an image processing signal. The signal generation unit 23 includes an α calculation unit 23a and an expansion processing unit 23b. Here, the α calculation unit 23a and the expansion processing unit 23b are not particularly limited as long as the functions are realized by either hardware or software. In addition, even if each component of the signal generation unit 23 is configured by hardware, it is not necessary to distinguish each circuit physically independently. The function may be realized. The α calculation unit 23a calculates the expansion coefficient α. In addition, the α calculating unit 23a calculates 1 / α. The process for calculating the expansion coefficient α will be described later.

  The expansion processing unit 23b performs the expansion process of the input signal using the expansion coefficient α calculated by the α calculation unit 23a and the input signal input to the input unit 21. That is, the decompression processing unit 23b converts the input value of the input signal into a reproduction value (image processing signal) of a reproduction color space (for example, HSV color space), and generates an image display signal. The decompression process will be described later.

  The output unit 25 outputs the image processing signal generated by the signal generation unit 23 to the image display panel drive unit 30.

  Referring to FIGS. 1 and 3 again, the image display panel drive unit 30 includes a signal output circuit 31 and a scanning circuit 32. The image display panel driving unit 30 holds the video signal by the signal output circuit 31 and sequentially outputs it to the image display panel 40. More specifically, the signal output circuit 31 outputs an image output signal having a predetermined potential corresponding to the image processing signal to the image display panel 40. The signal output circuit 31 is electrically connected to the image display panel 40 through a signal line DTL. The scanning circuit 32 controls ON / OFF of a switching element (for example, TFT) for controlling the operation (light transmittance) of the sub-pixel 49 in the image display panel 40. The scanning circuit 32 is electrically connected to the image display panel 40 by the wiring SCL.

  The planar light source device 60 is disposed on the back surface of the image display panel 40 and illuminates the image display panel 40 by irradiating light toward the image display panel 40. The planar light source device 60 irradiates light toward the image display panel unit 30. The planar light source device 60 includes, for example, a light guide plate and a light source disposed in the vicinity of the end face of the light guide plate. As the light source, an LED as a point light source arranged in parallel at a predetermined interval along one direction or a cold cathode tube can be used. Further, in the planar light source device 60, optical sheets may be disposed on the exit surface side of the light guide plate, and a reflective sheet may be disposed on the surface opposite to the exit surface of the light guide plate. The planar light source device 60 is not a so-called side light type in which light is incident from the side surface of the light guide plate, and a light source may be disposed on the back surface of the light guide plate. Further, the planar light source device 60 may not include a light guide plate. The planar light source device 60 irradiates the entire surface of the image display panel 40 with light to brighten the image display panel 40.

  The planar light source device controller 50 controls the amount of light output from the planar light source device 60. Specifically, the planar light source device controller 50 applies PWM (Pulse Width Modulation) to the voltage supplied to the planar light source device 60 based on the planar light source device control signal SBL output from the signal processor 20. The amount of light (light intensity) irradiating the image display panel 40 is controlled by adjusting with the above.

(Processing operation of signal processor)
Next, processing operations executed by the signal processing unit 20 will be described with reference to FIGS. 4 and 5. FIG. 4 is a reproduction HSV color space conceptual diagram that can be reproduced by the display device of the present embodiment. FIG. 5 is a conceptual diagram showing the relationship between the hue and saturation of the reproduction HSV color space. In the present embodiment, a case where the color space is processed in the HSV color space will be described. However, the same applies to color spaces other than the HSV color space.

The signal processing unit 20 receives an input signal, which is information about an image to be displayed, from an external application processor. The input signal includes information on an image (color) displayed at the position for each pixel as an input signal. Specifically, for the (p, q) -th pixel (where 1 ≦ p ≦ I, 1 ≦ q ≦ Q _{0 )} , the first subpixel having a signal value of x _{1− (p, q)} It contains input signals 49R, the second input signal of the sub-pixel 49G of ₂ signal values _{x (p, q),} and the signal value _{x 3- (p, q)} is the input signal of the third sub-pixel 49B of A signal is input to the signal processing unit 20.

The signal processing unit 20 processes the input signal to output the first subpixel output signal (signal value X ₁₋ 1) as a signal for the first subpixel for determining the display gradation of the first subpixel 49R. _{(P, q)} ), the output signal of the second sub-pixel as a signal for the second sub-pixel for determining the display gradation of the second sub-pixel 49G (signal value _{X2- (p, q)} ), The third subpixel output signal (signal value X _{3- (p, q)} ) as the signal for the third subpixel for determining the display gradation of the third subpixel 49B, and the fourth subpixel 49W An output signal (signal value X _{4− (p, q)} ) of the fourth subpixel as a signal for the fourth subpixel for determining the display gradation of the image is generated, and the image display panel driving is performed as the image processing signal. To the unit 30.

  Here, the display device 10 includes the fourth sub-pixel 49 </ b> W that outputs the fourth color (for example, white) to the pixel 48, so that the dynamic range of the brightness in the reproduction HSV color space is as shown in FIG. 4. It has been spread. In other words, as shown in FIG. 5, the maximum value of the lightness decreases as the saturation increases on the cylindrical color space that can be displayed by the first subpixel, the second subpixel, and the third subpixel. The shape in the cross section including the axis and the brightness axis is a shape on which a solid body having a substantially trapezoidal shape with a hypotenuse being a curve is placed. The signal processing unit 20 uses the signal processing unit 20 to obtain a maximum value Vmax (S) of brightness with the saturation S in the reproduction HSV color space expanded by adding a fourth color (for example, white) as a variable. Desired. That is, the signal processing unit 20 obtains the maximum brightness value Vmax (S) for each coordinate (value) of saturation and hue for the three-dimensional shape of the HSV color space shown in FIG. Here, since the input signal is composed of the input signals of the first sub-pixel 49R, the second sub-pixel 49G, and the third sub-pixel 49B, the HSV color space of the input signal has a cylindrical shape, that is, the reproduced HSV color. It becomes the same shape as the cylindrical portion of the space. In the present embodiment, the case where the color space is the HSV color space will be described. As described above, the color space is not limited to the HSV color space. In addition, the signal processing unit 20 stores a maximum value Vmax (S) of lightness as a table with the saturation S in the reproduction HSV color space expanded by adding a fourth color (for example, white) as a variable. But you can.

The signal processing unit 20 uses the expansion processing unit 23b to output the first subpixel output signal (signal value) based on at least the input signal (signal value _{x1- (p, q)} ) of the first subpixel and the expansion coefficient α. X _{1− (p, q)} ), and an output signal (signal value) of the second subpixel based on at least the input signal (signal value x _{2− (p, q)} ) of the second subpixel and the expansion coefficient α. X _{2- (p, q)} ), and the output signal (signal value) of the third sub-pixel based on at least the input signal (signal value x _{3- (p, q)} ) of the third sub-pixel and the expansion coefficient α. _{X3- (p, q)} ) is calculated.

  Specifically, the output signal of the first subpixel is calculated based on the input signal of the first subpixel, the expansion coefficient α, and the output signal of the fourth subpixel, and the input signal of the second subpixel, the expansion coefficient α, and The output signal of the second subpixel is calculated based on the output signal of the fourth subpixel, and the output signal of the third subpixel is calculated based on the input signal of the third subpixel, the expansion coefficient α, and the output signal of the fourth subpixel. Is calculated.

That is, the signal processing unit 20 uses the (p, q) -th pixel (or the first sub-pixel 49R, the second sub-pixel 49G, and the third sub-pixel 49B when χ is a constant depending on the display device 10. Output signal value X _{1− (p, q)} of the first subpixel, output signal value X _{2− (p, q)} of the second subpixel, and output signal value X ₃₋ of the third subpixel. _{(P, q)} is obtained from the following equations (1), (2), (3).
_{X1- (p, q)} = [alpha] .x1- _{(p, q)-[} chi] .X4- _{(p, q)} (1)
_{X2- (p, q)} = [alpha] .x2- _{(p, q)-[} chi] .X4- _{(p, q)} (2)
X _{3-(p, q)} = α · x _{3-(p, q)} -χ · X _{4-(p, q)} (3)

  The signal processing unit 20 obtains the maximum value Vmax (S) of the brightness with the saturation S in the HSV color space expanded by adding the fourth color as a variable, and the input signal of the sub-pixel 49 in the plurality of pixels 48. Based on the values, the saturation S and the lightness V (S) in the plurality of pixels 48 are obtained. Then, the signal processing unit 20 calculates the expansion coefficient α based on the lightness maximum value Vmax (S) and the lightness V (S) in the α calculation unit 23a. The signal processing unit 20 is configured to store the maximum value Vmax (S) of lightness with the saturation S in the reproduction HSV color space expanded by adding a fourth color (for example, white) as a table. But you can.

  Here, the signal processing unit 20 obtains the maximum value Vmax (S) of the brightness with the saturation S in the HVS color space (reproduction HSV color space) expanded by adding the fourth color as a variable, Based on the input signal value of the sub-pixel in the pixel, the saturation S and the lightness V (S) in these pixels are obtained, and the expanded lightness value obtained from the product of the lightness V (S) and the expansion coefficient α. The expansion coefficient α is determined so that the ratio of pixels exceeding the maximum value Vmax (S) to all the pixels is equal to or less than the limit value β (Limit value). Here, the limit value β is an upper limit value (ratio) of the ratio of the width exceeding the maximum value with respect to the maximum brightness value of the reproduction HSV color space in a combination of hue and saturation values.

Here, the saturation S and the lightness V (S) are represented by S = (Max−Min) / Max and V (S) = Max. The saturation S can take a value from 0 to 1, the lightness V (S) can take a value from 0 to (2 ⁿ −1), and n is the number of display gradation bits. Max is the maximum value of the input signal values of the three subpixels of the first subpixel 49R to the pixel 48, the input signal value of the second subpixel 49G, and the input signal value of the third subpixel 49B. It is. Min is the minimum value of the input signal values of the three subpixels, that is, the input signal value of the first subpixel 49R to the pixel 48, the input signal value of the second subpixel 49G, and the input signal value of the third subpixel 49B. .

  The signal processing unit 20 divides the reproduction color space (for example, HSV color space) shown in FIG. 4 into a plurality of spaces (color spaces) using the hue H as a reference, and sets a limit value β for each region. ing. Here, the hue H is represented by 0 ° to 360 ° as shown in FIG. The hue H of this embodiment is from 0 ° to 360 °, red at 0 °, yellow at 60 °, green at 120 °, cyan at 180 °, 240 °. Blue at Blue, Magenta at 300 °, and Red at 360 ° (0 °). In the present embodiment, colors with hue angles of 0 °, 60 °, 120 °, 180 °, 240 °, and 300 ° are defined as specific colors.

In the present embodiment, the signal processing unit 20 uses the expansion processing unit 23b based on the input signal of the first subpixel 49R, the input signal of the second subpixel 49G, the input signal of the third subpixel 49B, and the expansion coefficient α. The output signal value X _{4- (p, q)} of the fourth sub-pixel 49W is obtained. More specifically, the signal processing unit 20 outputs Min (the input signal value of the first subpixel 49R to the pixel, the input signal value of the second subpixel 49G, and the input signal value of the third subpixel 49B). The signal value X _{4− (p, q)} is obtained from the minimum value of the input signal value), the expansion coefficient α, and the fourth subpixel correction value WG. Specifically, the signal processing unit 20 obtains a signal value X _{4- (p, q)} based on the following equation (4). In Expression (4), the product of Min _{(p, q)} and the expansion coefficient α is divided by χ, but the present invention is not limited to this. χ will be described later.

X _{4− (p, q)} = Min _{(p, q)} · (α / χ) (4)

Generally, in the (p, q) th pixel, the input signal of the first sub-pixel 49R (signal value _{x 1- (p, q))} , the input signal of the second sub-pixel 49G (signal value _{x 2-(p , Q)} ) and the input signal (signal value _{x3- (p, q)} ) of the third sub-pixel 49B, saturation S _{(p, q)} and brightness V in the cylindrical color space. (S) _{(p, q)} can be obtained from the following equations (5) and (6).

S _{(p, q)} = (Max _{(p, q)} −Min _{(p, q)} ) / Max _{(p, q)} (5)

V (S) _{(p, q)} = Max _{(p, q)} (6)

Here, Max _{(p, q)} is an input signal value of three sub-pixels 49 of (x _{1- (p, q)} , x _{2- (p, q)} , x _{3- (p, q)} ). Min _{(p, q)} is an input of three subpixels 49 (x _{1-(p, q)} , x _{2-(p, q)} , x _{3-(p, q)} ) 3 This is the minimum signal value. In this embodiment, n = 8. That is, the number of display gradation bits is 8 bits (the display gradation value is 256 gradations from 0 to 255).

For example, no color filter is disposed in the fourth sub-pixel 49W that displays white. The fourth sub-pixel 49W that displays the fourth color, when irradiated with the same light source lighting amount, the first sub-pixel 49R that displays the first color, the second sub-pixel 49G that displays the second color, Brighter than the third sub-pixel 49B that displays the third color. A signal having a value corresponding to the maximum signal value of the output signal of the first subpixel 49R is input to the first subpixel 49R, and the signal value corresponding to the maximum signal value of the output signal of the second subpixel 49G is input to the second subpixel 49G. When a signal having a value is input and a signal having a value corresponding to the maximum signal value of the output signal of the third subpixel 49B is input to the third subpixel 49B, the pixel 48 or the group of pixels 48 includes The luminance of the aggregate of the first sub-pixel 49R, the second sub-pixel 49G, and the third sub-pixel 49B is BN _1-3 . The luminance of the fourth subpixel 49W when a signal having a value corresponding to the maximum signal value of the output signal of the fourth subpixel 49W is input to the fourth subpixel 49W included in the pixel 48 or the group of pixels 48. the assume when the BN _4. That is, the maximum luminance white is displayed by the aggregate of the first sub-pixel 49R, the second sub-pixel 49G, and the third sub-pixel 49B, and this white luminance is represented by BN _1-3 . Then, when χ is a constant depending on the display device 10, the constant χ is represented by χ = BN ₄ / BN _1-3 .

Specifically, a signal value x _{1− (p, q) is} input to the aggregate of the first subpixel 49R, the second subpixel 49G, and the third subpixel 49B as an input signal having the next display gradation value. = 255, relative to the signal value _{x 2- (p, q) =} 255, the white luminance _{BN 1-3} at the time when the signal value _{x 3- (p, q) =} 255 is input, the fourth subpixel 49W For example, the luminance BN ₄ when the input signal having the display gradation value 255 is input is 1.5 times. That is, in this embodiment, χ = 1.5.

By the way, when the signal value X _{4- (p, q)} is given by the above-described equation (4), Vmax (S) can be expressed by the following equations (7) and (8).

If S ≦ S ₀ :
Vmax (S) = (χ + 1) · (2 ⁿ −1) (7)

If S ₀ <S ≦ 1:
Vmax (S) = (2 ⁿ −1) · (1 / S) (8)
Here, S ₀ = 1 / (χ + 1), and the saturation S in FIG. 4 starts to decrease in brightness from the maximum brightness.

  The maximum value Vmax (S) of brightness obtained by using the saturation S in the reproduction HSV color space expanded by adding the fourth color as a variable is, for example, a kind of signal processing unit 20. It is stored as a lookup table. Alternatively, the maximum value Vmax (S) of lightness with the saturation S in the enlarged HSV color space as a variable is obtained in the signal processing unit 20 each time.

Next, signal values X _{1- (p, q)} , X _{2- (p, q)} , X _{3- (p, q)} , X ₄₋ which are output signals at the (p, q) -th pixel 48. _A method for _{obtaining (p, q)} (extension processing) will be described. The next processing is the luminance of the first primary color displayed by (first subpixel 49R + fourth subpixel 49W), the luminance of the second primary color displayed by (second subpixel 49G + fourth subpixel 49W), ( This is performed so as to maintain the luminance ratio of the third primary color displayed by the third subpixel 49B + the fourth subpixel 49W). In addition, the color tone is maintained (maintained). Furthermore, the gradation-luminance characteristics (gamma characteristics, γ characteristics) are maintained (maintained). Further, when any of the input signal values is zero or small in any one of the pixels 48 or the group of pixels 48, the expansion coefficient α may be obtained without including such a pixel 48 or the group of pixels 48. .

(First step)
First, the signal processing unit 20 obtains the saturation S and the lightness V (S) in the plurality of pixels 48 based on the input signal values of the sub-pixels 49 in the plurality of pixels 48. Specifically, a signal value x _{1− (p, q)} that is an input signal of the first subpixel 49R to the (p, q) th pixel 48, and a signal value that is an input signal of the second subpixel 49G. Based on x _{2− (p, q)} , signal value x _{3− (p, q)} that is an input signal of the third sub-pixel 49B, S _{(p, q)} , V from Formula (5) and Formula (6) (S) _{Find (p, q)} . The signal processing unit 20 performs this process for all the pixels 48.

(Second step)
Next, the signal processing unit 20 obtains the expansion coefficient α (S) based on Vmax (S) / V (S) obtained in the plurality of pixels 48.

  α (S) = Vmax (S) / V (S) (9)

Then, the values of the expansion coefficients α (S) obtained in a plurality of pixels (all P ₀ × Q ₀ pixels in the present embodiment) are arranged in ascending order, and P ₀ × Q ₀ expansion coefficients are arranged. The expansion coefficient α (S) corresponding to β × P ₀ × Q ₀ from the minimum value among the values of α (S) is defined as the expansion coefficient α. In this way, the ratio of the pixels where the value of the expanded brightness obtained from the product of the brightness V (S) and the expansion coefficient α exceeds the maximum value Vmax (S) to all the pixels is equal to or less than the predetermined value (β). The elongation factor α can be determined.

  In this embodiment, it is preferable that the limit value β is, for example, 0 or more and 0.2 or less (0% or more and 20% or less), and 0.0001 or more and 0.20 or less (0.01% or more and 20% or less). Or less), more preferably 0.003 or more and 0.05 or less (0.3% or more and 5% or less). The value of β is determined by performing various tests.

When the minimum value of Vmax (S) / V (S) is the expansion coefficient α, the output signal value with respect to the input signal value does not exceed (2 ⁸ −1). However, if the expansion coefficient α is not the minimum value of Vmax (S) / V (S) and is determined as described above, the expansion coefficient α is multiplied by a pixel whose expansion coefficient α (S) is less than the expansion coefficient α. Therefore, the expanded brightness value exceeds the maximum value Vmax (S). As a result, so-called “gradation collapse” occurs. However, as described above, by setting the value of β to, for example, 0.003 to 0.05, it is possible to prevent the occurrence of a phenomenon in which gradation collapse is conspicuous and an unnatural image is formed. On the other hand, when the value of β exceeds 0.05, it was confirmed that an unnatural image with conspicuous gradation collapse was obtained in some cases. When the output signal value exceeds the limit value (2 ⁿ −1) by the decompression process, the output signal value may be set to the limit value (2 ⁿ −1).

  By the way, normally, the value of the expansion coefficient α (S) exceeds 1.0 and gathers in the vicinity of 1.0. Therefore, when the minimum value of Vmax (S) / V (S) is the expansion coefficient α, the degree of expansion of the output signal value is small, and it is often difficult to achieve low power consumption of the display device. However, for example, by setting the value of β to 0 or more and 0.2 or less, the value of the expansion coefficient α of at least a part of the space can be increased. As described later, the luminance of the planar light source device 60 is increased. Since (1 / α) times is sufficient, it is possible to achieve low power consumption of the display device.

(Third step)
Next, the signal processing unit 20 converts the signal value X _{4- (p, q)} in the (p, q) -th pixel 48 to at least the signal value x _{1- (p, q)} , the signal value x ₂₋ It is determined based on _{(p, q)} and the signal value x _{3- (p, q)} . In the present embodiment, the signal processing unit 20 determines the signal value X _{4- (p, q) based} on Min _{(p, q)} , the expansion coefficient α, and the constant χ. More specifically, as described above, the signal processing unit 20 obtains the signal value X _{4- (p, q) based} on the above equation (4). The signal processing unit 20 obtains a signal value X _{4− (p, q)} in all of the P ₀ × Q ₀ pixels 48.

(4th process)
Thereafter, the signal processing unit 20 converts the signal value X _{1- (p, q)} in the (p, q) -th pixel 48 into the signal value x _{1- (p, q)} , the expansion coefficient α, and the signal value X _{4. - (p, q)} obtained based on, the (p, q) th pixel 48 the signal value _X 2 in _{- (p, q)} and the signal value _{x 2 - (p, q)} , expansion coefficient α and the signal value X _{4- (p, q)} , the signal value X _{3- (p, q)} at the (p, q) -th pixel 48 is converted into the signal value x _{3- (p, q)} , the expansion coefficient α, and _Obtained based on the signal value X _{4− (p, q)} . Specifically, the signal processing unit 20 outputs the signal value X _{1- (p, q)} , the signal value X _{2- (p, q),} and the signal value X _{3- ( p, q)} is obtained based on the above formulas (1) to (3).

The signal processing unit 20 expands the value of Min _{(p, q)} by the expansion coefficient α as shown in Expression (4). As described above, the value of Min _{(p, q)} is expanded by the expansion coefficient α, so that not only the luminance of the white display subpixel (the fourth subpixel 49W) is increased, but also the red color as shown in the above formula. The luminance of the display subpixel, the green display subpixel, and the blue display subpixel (corresponding to the first subpixel 49R, the second subpixel 49G, and the third subpixel 49B, respectively) also increases. For this reason, the problem that the dullness of color generate | occur | produces can be avoided. That is, as compared with the case where the value of Min _{(p, q)} is not expanded, the value of Min _{(p, q)} is expanded by the expansion coefficient α, so that the luminance of the entire image becomes α times. Therefore, for example, an image display such as a still image can be performed with high luminance, which is preferable.

  The maximum value Vmax (S) of lightness obtained by adding the fourth color in the HSV color space obtained by adding the fourth color as a variable is, for example, a kind of look for the signal processing unit 20. It is stored as an uptable, or is obtained by the signal processing unit 20 each time.

  Further, as described above, the display device according to the present embodiment divides the HSV color space into a plurality of spaces, and sets a limit value (Limit value) β for each divided space, thereby maintaining the image quality. A value that can reduce power consumption can be used as the expansion coefficient.

The display device 10 according to this embodiment includes a signal value X _{1- (p, q)} , a signal value X _{2- (p, q)} , and a signal value X _{3- (p, q} ) in the (p, q) -th pixel. ₎ Is extended α-fold. Therefore, the luminance of the planar light source device 60 may be reduced based on the expansion coefficient α in order to obtain the same image luminance as that of the unexpanded image. Specifically, the luminance of the planar light source device 60 may be (1 / α) times. Thereby, the power consumption of the planar light source device 60 can be reduced. The signal processing unit 20 outputs (1 / α) to the planar light source device control unit 50 (see FIG. 1) as the planar light source device control signal SBL.

  Next, a method for setting the limit value β will be described with reference to FIGS. FIG. 6 is a schematic diagram showing the color balance of six specific colors. FIG. 7 is a conceptual diagram showing the relationship among the hue, saturation, and limit value areas of the reproduction HSV color space. FIG. 8 is a conceptual diagram showing the relationship between the saturation and lightness of the reproduction HSV color space. In the present embodiment, a case where the color space is processed in the HSV color space will be described. However, the same applies to color spaces other than the HSV color space.

  As shown in the color balances 120a, 120b, and 120c in FIG. 6, the color that turns red when the hue angle is 0 ° has the same values for the green component and the blue component among the three components of red, blue, and green. In value, the values of the green component and the blue component are smaller than the values of the red component. In addition, as shown in the color balances 122a, 122b, and 122c in FIG. 6, the color that becomes green when the hue angle is 120 ° is the value of the red component and the blue component among the three components of red, blue, and green. Are the same value, and the value of the red component and the value of the blue component are smaller than the value of the green component. Further, the color that becomes blue when the hue angle is 240 ° is the value of the red component and the green component among the three components of red, blue, and green, as shown in the color balances 124a, 124b, and 124c in FIG. Are the same value, and the red component value and the green component value are smaller than the blue component value. In addition, as shown in the color balance 126a, 126b, and 126c in FIG. 6, the color that becomes cyan when the hue angle is 180 ° is the value of the green component and the blue component among the three components of red, blue, and green. Are the same value, and the value of the green component and the value of the blue component are larger than the value of the red component. Further, the color that becomes magenta when the hue angle is 300 ° is the value of the red component and the blue component among the three components of red, blue, and green, as shown in the color balances 128a, 128b, and 128c in FIG. Are the same value, and the value of the red component and the value of the blue component are larger than the value of the green component. Further, the color that becomes yellow when the hue angle is 60 ° is the value of the red component and the green component among the three components of red, blue, and green, as shown in the color balances 129a, 129b, and 129c in FIG. Are the same value, and the value of the red component and the value of the green component are larger than the value of the blue component.

  In the present embodiment, as shown in FIG. 7, based on the hue H angle, the hue H area 101 is divided into areas 102 a, 102 b, 102 c, 102 d, 102 e, 102 f and other areas 104. The region 102a is a region included in a predetermined angle around a line segment in which the angle of the hue H that is red among the specific colors is 0 °. The region 102b is a region included in a predetermined angle around a line segment in which the angle of the hue H that is yellow among the specific colors is 60 °. The region 102c is a region included in a predetermined angle around a line segment in which the angle of the hue H that is green among the specific colors is 120 °. The region 102d is a region included in a predetermined angle centered on a line segment where the angle of the hue H that is cyan among the specific colors is 180 °. The region 102e is a region included in a predetermined angle around a line segment in which the angle of the hue H that is blue among the specific colors is 240 °. The region 102f is a region included in a predetermined angle around a line segment in which the angle of the hue H of magenta among the specific colors is 300 °. The angle regions of the regions 102a, 102b, 102c, 102d, 102e, and 102f are preferably 3.5 ° or less, that is, 7 ° or less from the central line segment.

  In the present embodiment, among the three components of red, blue, and green of the input signal, the signal value of the component having the maximum value is different from the signal value of the component having the minimum value, and the component having the intermediate value The three specific colors having the same signal value and the signal value of the component having the smallest value are red (R), green (G), and blue (B), respectively. In addition, among the three components of the input signal red, blue, and green, the signal value of the component with the largest value is different from the signal value of the component with the smallest value, and the signal value of the component with the intermediate value The three specific colors having the same signal value of the component with the maximum value are cyan (C), magenta (M), and yellow (Y), respectively. The areas 102a, 102b, 102c, 102d, 102e, and 102f are set based on these six specific colors, and are separated from the other areas 104, and limit values are set. The specific color is Vmax = Vmid or Vmin = Vmid, where Vmax is the maximum signal value of the red, blue and green components of the input signal, Vmid is the intermediate signal value, and Vmin is the minimum signal value. Vmax ≠ Vmin. For example, when the region 102a is red, the region 102b is yellow, the region 102c is green, the region 102d is cyan, the region 102e is blue, and the region 102f is magenta.

  In the present embodiment, the first limit value β1 of the brightness (V) of the reproduction color space is set for the colors included in the regions 102a, 102b, 102c, 102d, 102e, and 102f, and the colors included in the region 104 are set. To set the second limit value β2. The first limit value β1 is higher than the second limit value β2.

  Therefore, as shown in FIG. 8, the signal processing unit 20 uses the maximum value line indicating the maximum value Vmax (S) of the brightness with the saturation S in the HSV color space expanded by adding the fourth color as a variable. 66 is set. Furthermore, it exceeds the first maximum value line 68 in which the upper limit of the ratio of the number of pixels exceeding the maximum value line 66 to the total number of pixels is equal to or less than the first limit value β1, and the maximum value line 66 indicating the maximum value of brightness V. Two second maximum value lines 69 are set such that the upper limit of the ratio of the number of pixels to the total number of pixels is equal to or less than the second limit value β2. The signal processing unit 20 switches whether to apply the first limit value β1 or the second limit value β2 based on the hue of the pixel to be processed. Here, in FIG. 8, circles are values of the input signal, and stars are values after being expanded. The example of FIG. 8 shows a case where the second maximum value line 69 is applied. That is, the second maximum value line 69 expanded by setting the expansion coefficient α such that the upper limit of the ratio of the number of pixels exceeding the maximum value line 66 to the total number of pixels is equal to or less than the second limit value β2 is selected. .

  As described above, when the hue is an area based on six specific colors, the signal processing unit 20 sets the limit value β1 higher than in the other areas. Thereby, a signal can be extended more suitably. As shown in FIG. 6, the six specific colors have the same size of the two components. Therefore, even if the expansion coefficient is increased, the image quality deterioration is not noticeable. The signal processing unit 20 sets the regions 102a, 102b, 102c, 102d, 102e, and 102f, and increases the expansion coefficient by setting a specific color and a color close to the specific color to a higher limit value than other colors. Can do. As a result, the expansion coefficient can be increased while suppressing the deterioration of the image quality, so that the power consumption can be reduced while maintaining the image quality. As described above, even in an image including a specific color, the expansion coefficient can be increased while maintaining the image quality. Therefore, even when displaying an image with high saturation, for example, an artificial image with many primary colors, power consumption can be reduced.

  Next, an example of the control operation of the display device will be described with reference to FIGS. 9 and 10. 9 and 10 are flowcharts illustrating an example of the control operation of the display device. The display device 10 implements the processing illustrated in FIGS. 9 and 10 by executing arithmetic processing mainly by the signal processing unit 20.

  The signal processing unit 20 divides the reproduction HSV color space into a plurality (step S12), and sets a limit value for each of the divided spaces (step S14). The signal processing unit 20 reads the stored data to divide the reproduction HSV color space and set a limit value.

  After setting the limit value, the signal processing unit 20 acquires the input signal (step S16), and determines the expansion coefficient based on the acquired input signal, the reproduction HSV color space (maximum value of brightness), and the limit value ( Step S18). Here, the signal processing unit 20 determines whether the color of the pixel is within the specific color area (step S30). If the signal processing unit 20 determines that the pixel color is included in the specific color region (Yes in step S30), the signal processing unit 20 adopts the first limit value β1 (step S32), and the pixel color is included in the specific color region. If it is determined that it is not included (No in step S30), the second limit value β2 is adopted (step S34). The signal processing unit 20 determines the expansion coefficient α based on the set limit value β. The signal processing unit 20 calculates the expansion coefficient for each pixel, and based on the calculated result, the ratio of the number of pixels in which the expanded output signal exceeds the reproduction color space (the maximum value of brightness) to the total number of pixels is Obtain the expansion coefficient that does not exceed the limit value.

  Thereafter, the signal processing unit 20 determines and outputs the output signal of each subpixel based on the input signal and the expansion coefficient (step S20), and further adjusts the output of the light source (step S22). That is, the signal processing unit 20 outputs the expanded output signal to the image display panel driving unit 30, and uses the light source (planar light source device 60) output condition calculated corresponding to the expanded result as the light source device control signal. And output to the planar light source device controller 50.

  After adjusting the output of the light source, the signal processing unit 20 determines whether to end the image display (step S24). If the signal processing unit 20 determines that the image display is not finished (No in step S24), the signal processing unit 20 proceeds to step S16. Thereby, the signal processing unit 20 determines the expansion coefficient according to the input signal (image) until the display of the image is finished, generates an output signal based on the expansion coefficient, and supports the expansion of the signal. Then, the process of adjusting the light quantity of the planar light source device 60 is repeated. If the signal processing unit 20 determines to end the display of the image (Yes in step S24), the signal processing unit 20 ends the process. The signal processing unit 20 employs the first limit value β1 for the specific color set in the areas 102a, 102b, 102c, 102d, 102e, and 102f. A plurality of different values may be set according to the area.

  The display device 10 can obtain the above-described effects by performing the above processing. Even when the display device 10 includes the fourth subpixel, the display device 10 may include a mode for displaying an image without using the fourth subpixel.

  Here, FIG. 11 is a conceptual diagram showing the relationship between the input signal and the output signal. The display device 10 becomes a color space 130 that can be displayed on the display device 10. The display device 10 performs the above processing, and when the input signal 132 is input, when the signal is composed only of colors included in the specific color region, the decompressed signal becomes the waveform 134. In addition, by performing the above processing, when the input signal 132 is input, if the signal is composed only of colors that are not included in the specific color area, the expanded signal becomes the waveform 136. In the case of an actual image, the expansion coefficient changes depending on the hue even with the same saturation. In this way, by setting the limit value to a different value depending on the hue, and for a specific color, by setting the expansion coefficient to be large and the signal output to be large, in the vicinity of the specific color where deterioration in image quality is not noticeable The color expansion coefficient of the area can be increased. Thereby, the output of the planar light source device can be further reduced, and the power consumption can be reduced.

  Here, the setting of the area based on the specific color is not limited to the angle range based on the line of the specific color as described above. FIG. 12 is a conceptual diagram showing the relationship among the hue, saturation, and limit value areas of the reproduction HSV color space. In the present embodiment, a case where the color space is processed in the HSV color space will be described. However, the same applies to color spaces other than the HSV color space. The region 141 of hue H shown in FIG. 12 is divided into regions 142a, 142b, 142c, 142d, 142e, 142f and other regions 144, 146. The region 142a is a region that is included in a predetermined angle centered on a line segment where the angle of the hue H that is red among specific colors is 0 °, and the saturation is equal to or greater than a threshold value. The region 142b is a region that is included in a predetermined angle centered on a line segment where the angle of the hue H that is yellow among the specific colors is 60 °, and the saturation is equal to or greater than a threshold value. The region 142c is a region that is included in a predetermined angle centered on a line segment where the angle of the hue H that is green among the specific colors is 120 °, and the saturation is equal to or greater than a threshold value. The region 142d is a region that is included in a predetermined angle centered on a line segment where the angle of the hue H that is cyan among the specific colors is 180 °, and in which the saturation is equal to or greater than a threshold value. The region 142e is a region that is included in a predetermined angle centered on a line segment where the angle of the hue H that is blue among the specific colors is 240 °, and the saturation is equal to or greater than a threshold value. The region 142f is a region that is included in a predetermined angle centered on a line segment in which the hue H of magenta among the specific colors is 300 °, and the saturation is equal to or greater than a threshold value. The region 144 is a region whose saturation is equal to or greater than a threshold and is not included in the specific color region. The region 146 is a region where the saturation is less than the threshold value.

  As described above, the regions 142a, 142b, 142c, 142d, 142e, and 142f in which the first limit value β1 is set may be limited to colors that are in the vicinity of the specific color and whose saturation is equal to or higher than the threshold value. Thereby, the expansion coefficient of the region where it is difficult to increase the expansion coefficient can be increased. Further, when dividing as in the area 141, different limit values may be set in the areas 142a, 142b, 142c, 142d, 142e, 142f, the area 144, and the area 146. At this time, the relationship between the limit values of the region 144 and the region 146 can be an arbitrary relationship. The first limit value β1 may be set to a plurality of different values depending on each color gamut. Note that the first limit value β1 of the regions 142a, 142b, 142c, 142d, 142e, and 142f is set higher than the second limit value β2 of the region 144.

  FIG. 13 is a conceptual diagram showing the relationship among the hue, saturation, and limit value areas of the reproduction HSV color space. In the present embodiment, a case where the color space is processed in the HSV color space will be described. However, the same applies to color spaces other than the HSV color space. A region 151 of hue H shown in FIG. 13 is divided into regions 152a, 152b, 152c, 152d, 152e, and 152f and other regions 154. Note that the regions 152a, 152b, 152c, 152d, 152e, and 152f in FIG. 13 are shown wider than the preferable angle range described later. The area 151 shown in FIG. 13 is the same as the area 101 except for the angle range based on the line segment at the center of the areas 152a, 152b, 152c, 152d, 152e, and 152f. The angle of the region is the largest in the green region 152c, and decreases in the order of the blue region 152e, the magenta region 152f, the red region 152a, the cyan region 152d, and the yellow region 152b. Here, the angle region of the region 152a centering on the line segment in which the angle of the hue H that becomes red among the specific colors is 0 ° is set to 2.0 ° or less, that is, 4 ° or less from the center line segment. preferable. Of the specific colors, the angle region of the region 152b centered on the line segment where the angle of the hue H that is yellow is 60 ° is preferably 1.0 ° or less, that is, 2 ° or less from the center line segment. Of the specific color, the angle region of the region 152c centering on the line segment where the angle of the hue H that becomes green is 120 ° is preferably 3.5 ° or less, that is, 7 ° or less from the center line segment. Of the specific color, the angle region of the region 152d centered on the line segment where the angle of the hue H of cyan is 180 ° is preferably 1.5 ° or less, that is, 3 ° or less from the center line segment. Of the specific colors, the angle region of the region 152e centering on the line segment where the angle of the hue H that is blue is 240 ° is preferably 3.0 ° or less, that is, 6 ° or less from the center line segment. Of the specific colors, the angle region of the region 152f centering on the line segment where the angle of the hue H that becomes magenta is 300 ° is preferably 2.5 ° or less, that is, 5 ° or less from the center line segment.

  As shown in FIG. 13, the size of the range is set to be different depending on the specific color, and each specific color has at least one different size so that the color change of each specific color is easily noticeable. The region can be set according to the size, and the deterioration of the image quality can be further suppressed.

  FIG. 14 is a conceptual diagram showing the relationship among the hue, saturation, and limit value areas of the reproduction HSV color space. In the present embodiment, a case where the color space is processed in the HSV color space will be described. However, the same applies to color spaces other than the HSV color space. The region 161 of hue H shown in FIG. 14 is divided into regions 162a, 162b, 162c, 162d, 162e, 162f and other regions 164. An area 161 shown in FIG. 14 is the same as the area 101 except that the angle range based on the line segment at the center of the areas 162a, 162b, 162c, 162d, 162e, and 162f changes depending on the saturation. In the areas 162a, 162b, 162c, 162d, 162e, and 162f, the angle with respect to the area increases as the saturation decreases. Specifically, in the regions 162a, 162b, 162c, 162d, 162e, and 162f, a line segment that is an end portion in the rotation direction of the range is a line parallel to the center of the range. In this way, the expansion coefficient can be further increased by increasing the regions 162a, 162b, 162c, 162d, 162e, and 162f as the saturation decreases. Further, since the color change is not conspicuous in the low saturation region, it is possible to suppress the deterioration of the image quality even if the expansion coefficient is increased.

  FIG. 15 is a conceptual diagram showing the relationship among the hue, saturation, and limit value areas of the reproduction HSV color space. In the present embodiment, a case where the color space is processed in the HSV color space will be described. However, the same applies to color spaces other than the HSV color space. The region 171 of hue H shown in FIG. 15 is divided into regions 172a, 172b, 172c, 172d, 172e, 172f and other regions 174. An area 171 shown in FIG. 15 is the same as the area 101 except that the angle range based on the line segment at the center of the areas 172a, 172b, 172c, 172d, 172e, and 172f changes depending on the saturation. In the regions 172a, 172b, 172c, 172d, 172e, and 172f, the angle with respect to the region increases as the saturation decreases. Specifically, the regions 172a, 172b, 172c, 172d, 172e, and 172f are lines whose distance from the center of the range becomes wider as the saturation becomes lower. Become. As described above, the expansion coefficient can be further increased by increasing the regions 172a, 172b, 172c, 172d, 172e, and 172f as the saturation decreases. Further, since the color change is not conspicuous in the low saturation region, it is possible to suppress the deterioration of the image quality even if the expansion coefficient is increased.

  In the above-described embodiment, areas are set for all six specific colors, and the limit values of the respective areas of the six specific colors are set higher than the limit values of the other areas. However, the present invention is not limited to this. . The display device 10 may set the limit value of the region based on at least one specific color among the six specific colors to a value higher than the limit values of the other regions. In this way, by increasing the limit value for at least one specific color, it is possible to increase the expansion coefficient in the range of the specific color, and to easily increase the reduction amount of the output of the planar light source device. Moreover, in the said embodiment, although the color balance was made into the signal value, you may use a brightness | luminance. Note that the color balance signal values are values that are set so as to obtain so-called six specific colors in the case of the relationship shown in FIG.

  Next, with reference to FIGS. 16 to 22, an electronic apparatus including the display device 10 according to the above embodiment and a control device that controls the display device 10 will be described. 16 to 22 are diagrams each illustrating an example of an electronic device including the display device 10 according to the above embodiment. The display device 10 can be applied to electronic devices in various fields such as a television device, a digital camera, a notebook personal computer, a mobile terminal device such as a mobile phone, or a video camera. In other words, the display device 10 can be applied to electronic devices in all fields that display a video signal input from the outside or a video signal generated inside as an image or video.

(Application example 1)
The electronic device illustrated in FIG. 16 is a television device to which the display device 10 is applied. The television apparatus has, for example, a video display screen unit 510 including a front panel 511 and a filter glass 512, and the display device 10 is applied to the video display screen unit 510. The screen of the television device has a function of detecting a touch operation in addition to a function of displaying an image.

(Application example 2)
The electronic apparatus shown in FIG. 17 is a digital camera to which the display device 10 is applied. This digital camera has, for example, a display unit 522, a menu switch 523, and a shutter button 524, and the display device 10 is applied to the display unit 522. Therefore, the display unit 522 of the digital camera has a function of detecting a touch operation in addition to a function of displaying an image.

(Application example 3)
The electronic device shown in FIG. 18 represents the appearance of a video camera to which the display device 10 is applied. This video camera has, for example, a main body 531, a subject photographing lens 532 provided on the front side surface of the main body 531, a start / stop switch 533 during photographing, and a display 534. The display device 10 is applied to the display unit 534. Therefore, the display unit 534 of the video camera has a function of detecting a touch operation in addition to a function of displaying an image.

(Application example 4)
An electronic apparatus illustrated in FIG. 19 is a notebook personal computer to which the display device 10 is applied. This notebook personal computer has, for example, a main body 541, a keyboard 542 for inputting characters and the like, and a display unit 543 for displaying an image. The display unit 10 is applied to the display unit 543. Therefore, the display unit 543 of the notebook personal computer has a function of detecting a touch operation in addition to a function of displaying an image.

(Application example 5)
The electronic device illustrated in FIG. 20 is a mobile phone to which the display device 10 is applied. This mobile phone is, for example, a device in which an upper housing 551 and a lower housing 552 are connected by a connecting portion (hinge portion), and has a display 554. The display device 10 is attached to the display 554. Therefore, the display 554 of the mobile phone has a function of detecting a touch operation in addition to a function of displaying an image.

(Application example 6)
The electronic device illustrated in FIG. 21 is a so-called smartphone, to which the display device 10 or the like is applied. This mobile phone has a touch panel 562 on the surface of a substantially rectangular thin plate-like casing 561, for example. The touch panel 562 includes the display device 10 and the like.

(Application example 7)
The electronic device shown in FIG. 22 is a meter unit mounted on a vehicle. A meter unit (electronic device) 570 illustrated in FIG. 22 includes a plurality of liquid crystal display devices 571 such as a fuel gauge, a water temperature gauge, a speedometer, and a tachometer. The plurality of liquid crystal display devices 571 are all covered by a single exterior panel 572.

  Each of the liquid crystal display devices 571 shown in FIG. 22 has a configuration in which a liquid crystal panel 573 as liquid crystal display means and a movement mechanism as analog display means are combined with each other. The movement mechanism has a motor as driving means and a pointer 574 rotated by the motor. As shown in FIG. 22, the liquid crystal display device 571 can display a scale display, a warning display, etc. on the display surface of the liquid crystal panel 573, and the pointer 574 of the movement mechanism is on the display surface side of the liquid crystal panel 573. It is possible to rotate. Display device 10 according to the present embodiment is applied to liquid crystal display device 571.

  In FIG. 22, a plurality of liquid crystal display devices 571 are provided in one exterior panel 572, but the present invention is not limited to this. One liquid crystal display device may be provided in a region surrounded by the exterior panel, and a fuel gauge, a water temperature gauge, a speedometer, a tachometer, or the like may be displayed on the liquid crystal display device.

DESCRIPTION OF SYMBOLS 10 Display apparatus 20 Signal processing part 21 Input part 23 Signal generation part 23a (alpha) calculation part 23b Decompression processing part 25 Output part 30 Image display panel drive part 31 Signal output circuit 32 Scan circuit 40 Image display panel 48 Pixel 49R First subpixel 49G Second subpixel 49B Third subpixel 49W Fourth subpixel 50 Light source device controller 60 Planar light source device

Claims (10)

A pixel including a first subpixel that displays a first color, a second subpixel that displays a second color, a third subpixel that displays a third color, and a fourth subpixel that displays a fourth color An image display panel arranged in a two-dimensional matrix;
An input value of an input color space of an input signal is converted into a reproduction value of a reproduction color space that is reproduced with the first color, the second color, the third color, and the fourth color. A signal processing unit that outputs the generated output signal to the image display panel,
The signal processing unit
The reproduction color space is divided into a plurality of hues, and for at least two of the divided spaces, the maximum value for the maximum value of the reproduction color space in a combination of hue and saturation values. Set a different value as the limit value that is the upper limit of the ratio of the number of pixels exceeding the value to the total number of pixels,
Among the three components of the first color, the second color, and the third color of the input signal, the signal value of the component having the maximum value is different from the component of the signal value having the minimum value. In addition, with reference to the case of at least one specific color among the six specific colors in which the signal value of the component having the intermediate value and the signal value of the component having the maximum value or the signal value of the component having the minimum value are the same The first limit value for the color included in the set area is set higher than the second limit value for the other colors;
In a range where the ratio of the number of pixels exceeding the maximum value of brightness to the total number of pixels does not exceed the limit value, the expansion coefficient α for the input signal is calculated,
Calculating an output signal of the first subpixel based on at least an input signal of the first subpixel and the expansion coefficient α and outputting the output signal to the first subpixel;
Calculating an output signal of the second subpixel based on at least the input signal of the second subpixel and the expansion coefficient α, and outputting the output signal to the second subpixel;
Calculating an output signal of the third subpixel based on at least the input signal of the third subpixel and the expansion coefficient α, and outputting the output signal to the third subpixel;
Calculating an output signal of the fourth subpixel based on an input signal of the first subpixel, an input signal of the second subpixel, and an input signal of the third subpixel, and outputting the output signal to the fourth subpixel; A display device.   The display device according to claim 1, wherein the signal processing unit applies the one limit value to all of the six specific colors.   The display device according to claim 1, wherein the region is a region of 3.5 ° or less from the reference in the hue of the HSV color space.   4. The display device according to claim 1, wherein the area has a size different from that of at least one of the six specific color areas. 5.   The display device according to claim 1, wherein the angle of the region changes according to saturation.   The display device according to claim 5, wherein the angle of the region increases as the saturation increases.   The display device according to claim 1, wherein an angle of the region changes according to lightness.   The display device according to claim 1, wherein the signal processing unit applies the one limit value only in the case of the six specific colors. A display device according to any one of claims 1 to 8,
And a control device for supplying the input signal to the display device. A pixel including a first subpixel that displays a first color, a second subpixel that displays a second color, a third subpixel that displays a third color, and a fourth subpixel that displays a fourth color Reproduces the input value of the input color space of the input signal as the first color, the second color, the third color, and the fourth color. And a signal processing unit that converts the generated reproduction color space into a reproduced value and generates the output signal and outputs the generated output signal to the image display panel.
The reproduction color space is divided into a plurality of hues, and for at least two of the divided spaces, the maximum value for the maximum value of the reproduction color space in a combination of hue and saturation values. Setting a different value as a limit value that is an upper limit of the ratio of the number of pixels exceeding the value to the total number of pixels;
Calculating the expansion coefficient α for the input signal in a range in which the ratio of the number of pixels exceeding the maximum value of brightness to the total number of pixels does not exceed the limit value;
Calculating an output signal of the first subpixel based on at least an input signal of the first subpixel and the expansion coefficient α and outputting the output signal to the first subpixel;
Calculating an output signal of the second subpixel based on at least the input signal of the second subpixel and the expansion coefficient α, and outputting the output signal to the second subpixel;
Calculating an output signal of the third subpixel based on at least the input signal of the third subpixel and the expansion coefficient α, and outputting the output signal to the third subpixel;
Calculating an output signal of the fourth subpixel based on an input signal of the first subpixel, an input signal of the second subpixel, and an input signal of the third subpixel, and outputting the output signal to the fourth subpixel; And including
The limit value includes the signal value of the component having the maximum value and the signal value of the component having the minimum value among the three components of the first color, the second color, and the third color of the input signal. Are different values, and the signal value of the intermediate component and the signal value of the component having the maximum value or the signal value of the component having the minimum value are at least one specific color among the six specific colors A driving method of a display device, wherein the first limit value in the case of a color included in a region set on the basis of the case of the above is set higher than the second limit value in the case of another color.

Images