This application claims priority from Japanese Application No. 2013-219690, filed on Oct. 22, 2013, the contents of which are incorporated by reference herein in its entirety.
1. Technical Field
The present disclosure relates to a display device including an image display unit having an image display region, a method for driving the display device, and an electronic apparatus.
2. Description of the Related Art
In the related art, display devices have been developed that include a plurality of light-emitting diodes (LEDs) as a linear light source used as a backlight of a liquid crystal display panel (for example, refer to Japanese Patent Application Laid-open Publication No. 2010-175913 and Japanese Patent Application Laid-open Publication No. 2008-051905). In the display devices, a value (also called as luminance or brightness) distribution of image signals is calculated for each of a plurality of partial regions included in an image display region, and an amount of light of the backlight in each image display region is controlled. Due to this, a contrast ratio thereof is enhanced as compared with a non light-emitting display device in the related art.
In the display devices in the related art, when a background of the image display region is a black screen, a phenomenon called “black floating” may occur in some cases. The black floating is a phenomenon in which a luminance difference is caused based on a difference in luminous intensity of the backlight between a black screen in a specific partial region in which a high-saturation image (also called as a high-chroma image) is displayed in part of a partial region in the image display region and a black screen of a partial region in which no image is displayed that is adjacent to the specific partial region. The phenomenon of the black floating may be more remarkable in a red-green-blue-white (RGBW)-type image processing technique, which can display high-saturation images with lower power consumption by using a white (W) sub-pixel, than in a red-green-blue (RGB)-type image display technique using a main pixel including sub-pixels that are a red pixel (R), a green pixel (G), and a blue pixel (B) in the related art.
For the foregoing reasons, there is a need for a display device that can prevent the black floating from occurring even when the high-saturation image is displayed, the method for driving the display device, and the electronic apparatus.
According to an aspect, a display device includes: an image display unit that includes an image display region;
a plurality of light sources that are arranged corresponding to a plurality of partial regions included in the image display region and irradiate the partial regions with light; a light amount correction processing unit that detects that the partial regions are non-display regions in which no image is displayed, and corrects an amount of light of the light sources based on a predetermined threshold when the partial regions adjacent to each other are continuous non-display regions; and a light source control unit that controls the amount of light of the light sources.
According to another aspect, a method for driving a display device, the method includes: detecting that a plurality of partial regions included in an image display region are non-display regions; and correcting an amount of light of light sources that are arranged corresponding to the non-display regions when the partial regions adjacent to each other are continuous non-display regions.
According to another aspect, an electronic apparatus includes: a display device including: an image display unit that includes an image display region; a plurality of light sources that are arranged corresponding to a plurality of partial regions included in the image display region and irradiate the partial regions with light; a light amount correction processing unit that detects that the partial regions are non-display regions in which no image is displayed, and corrects an amount of light of the light sources based on a predetermined threshold when the partial regions adjacent to each other are continuous non-display regions; and a light source control unit that controls the amount of light of the light sources; and a controller that controls the display device.
The following describes an embodiment of the present invention in detail with reference to the attached drawings. In the embodiment, a liquid crystal display device is exemplified as a display device. However, the present invention can be applied to various display devices, not limited to the liquid crystal display device.
As illustrated in
The signal processing unit 20 is an arithmetic processing unit that controls operations of the image display panel unit 30 and the surface light source device 50. The signal processing unit 20 is electrically coupled to the image display panel drive circuit 40 that drives the image display panel unit 30 and the light source device control circuit 60 that drives the surface light source device 50. The signal processing unit 20 executes data processing of the input signal (RGB data) that is received from the outside, outputs an output signal to the image display panel drive circuit 40, and generates and outputs a light source device control signal to the light source device control circuit 60.
The signal processing unit 20 performs predetermined color conversion processing on input signals (Rin, Gin, Bin) serving as RGB data represented by an energy ratio among R (red), G (green), and B (blue). The signal processing unit 20 then generates output signals (Rout, Gout, Bout, Wout) represented by an energy ratio among R (red), G (green), B (blue), and W (white), to which the fourth color W (white) is added. The signal processing unit 20 then outputs the generated output signals (Rout, Gout, Bout, Wout) to the image display panel drive circuit 40, and outputs the light source device control signal to the light source device control circuit 60. In the embodiment, an RGBW-type display device is described in which the signal processing unit 20 generates RGBW output signals. However, the present invention can also be applied to a display device in which the signal processing unit 20 generates RGB-type output signals.
Each of the input signals (Rin, Gin, Bin) is the RGB data indicating a specific color in the standard color gamut. Various standards applied to image display can be used as the standard color gamut. Examples thereof include, but are not limited to, the color gamut of the sRGB standard, the color gamut of the Adobe (registered trademark) RGB standard, and the color gamut of the NTSC standard. The sRGB standard is defined by the International Electrotechnical Commission (IEC). The Adobe (registered trademark) RGB standard is defined by Adobe Systems Incorporated. The NTSC standard is defined by the National Television System Committee.
As illustrated in
In the example illustrated in
The image display panel drive circuit 40 includes a signal output circuit 41 (signal output unit) and a scanning circuit 42. The signal output circuit 41 is electrically coupled to sub-pixels in pixels 48 of the image display panel unit 30 via wiring diode-transistor logic (DTL). The signal output circuit 41 outputs a driving voltage to be applied to a liquid crystal included in each sub-pixel based on the output signals (Rout, Gout, Bout, Wout) output from the signal processing unit 20, and controls transmittance of light emitted from the surface light source device 50 for each pixel. The scanning circuit 42 is electrically coupled, via wiring switch control logic (SCL), to a switching element for controlling an operation of each sub-pixel in each pixel 48 of the image display panel unit 30. The scanning circuit 42 sequentially outputs scanning signals to a plurality of pieces of wiring SCL, and applies each of the scanning signals to the switching element of the sub-pixel in each pixel 48 to turn ON the switching element. The signal output circuit 41 applies the driving voltage to the liquid crystal included in the sub-pixel to which the scanning signal from the scanning circuit 42 is applied. In this way, an image is displayed on the entire image display region 30a of the image display panel unit 30.
The surface light source device 50 is a backlight including various light sources and arranged on the back surface of the image display panel unit 30. The surface light source device 50 illuminates the image display panel unit 30 by emitting light from the light source to the image display panel unit 30.
The light source device control circuit 60 controls lighting quantity and/or a load of the light source in the surface light source device 50 based on the light source device control signal output from the signal processing unit 20, and adjusts an amount of light and intensity of light emitted from the surface light source device 50 to the image display panel unit 30. The light source device control circuit 60 can also control the light source and the intensity of light by controlling the lighting quantity and/or the load of part of the light sources.
Next, the following describes an example of a luminance distribution in the image display region 30a of the image display panel unit 30 with reference to
The partial regions A1 and A3 in the image display region 30a are non-display regions in which no image is displayed (hereinafter, also referred to as a “black screen”). A low-saturation image G1 and an intermediate-saturation image G2 are displayed in the partial regions A4 and A5. A high-saturation image G3 is displayed in the partial region A2. In this case, lighting quantity (load) of the LEDs 54a and 54c that are arranged corresponding to the partial regions A1 and A3 is controlled, for example, to be 25%. The lighting quantity (load) of the LED 54b that is arranged corresponding to the partial region A2 is controlled, for example, to be 100%. The lighting quantity (load) of the LED 54d that is arranged corresponding to the partial region A4 is controlled, for example, to be 70%. The lighting quantity (load) of the LED 54e that is arranged corresponding to the partial region A5 is controlled, for example, to be 65%. As described above, in the example illustrated in
Next, the following describes signal processing in the display device 10 according to the embodiment in detail with reference to
To the α-value generation unit 21, input signals (Rin, Gin, Bin) are input as video signals (RGB data) from the outside. The α-value generation unit 21 calculates an expansion coefficient α from the input signals (Rin, Gin, Bin). The α-value generation unit 21 performs linear conversion as reverse γ correction on the input signals (Rin, Gin, Bin) input from the outside. When the input signals (Rin, Gin, Bin) are the RGB data represented by 8 bits (0 to 255), for example, the α-value generation unit 21 normalizes each value of an R component, a G component, and a B component of the RGB data to be a value of 0 to 1.
The light source lighting pattern determination unit 22 determines lighting patterns of the LEDs 54a to 54e of the light source 54 based on an α-value generated by the α-value generation unit 21.
The lighting quantity correction processing unit 23 determines whether there are continuous black screens in the partial regions A1 to A5 of the image display region 30a. If there are continuous black screens, a black screen continuous flag is set to the LEDs 54a to 54e that are arranged corresponding to the partial regions. The lighting quantity correction processing unit 23 also detects the lighting quantity of the LEDs 54a to 54e to which the black screen continuous flag is set, and corrects the lighting quantity of the LEDs 54a to 54e of a light source control signal based on a difference value of the detected lighting quantity and a threshold set in advance. Due to the correction of the lighting quantity of the LEDs 54a to 54e of the light source control signal, it is possible to prevent the black floating in the image display panel unit 30 based on the luminance difference caused by the difference in the lighting quantity of the LEDs 54a to 54e. The lighting quantity correction processing unit 23 outputs the corrected light source control signal together with the RGBW data to the backlight profile arithmetic unit 24, and also to the light source device control circuit 60.
In the embodiment, the lighting quantity correction processing unit 23 preferably corrects the lighting quantity by scanning the LEDs 54a to 54e arranged in parallel along a certain direction to which the black screen continuous flag is set along a certain direction, and then corrects the lighting quantity by scanning again the LEDs 54a to 54e to which the black screen continuous flag is set along the reverse direction of the certain direction. The lighting quantity correction processing unit 23 compares the difference value of the lighting quantity of the LEDs 54a to 54e to which the black screen continuous flag is set with the threshold set in advance. If the difference value is equal to or smaller than the threshold, the lighting quantity correction processing unit 23 may increase the lighting quantity of the LEDs 54a to 54e the lighting quantity of which is low to be approximated to the lighting quantity of the LEDs 54a to 54e the lighting quantity of which is high. In this way, because the lighting quantity of the LEDs 54a to 54e can be corrected through one reciprocating scanning, an algorithm can be simplified.
The threshold used for correcting the lighting quantity of the LEDs 54a to 54e by the lighting quantity correction processing unit 23 can be set in an arbitrary range from 0% to 100% as a ratio between the luminance and a contrast (luminance/contrast). In this case, when the threshold of luminance/contrast is 0%, the lighting quantity correction processing unit 23 corrects the lighting quantity to be the same among the LEDs 54a to 54e to which the black screen continuous flag is set. When the threshold of luminance/contrast is 100%, the lighting quantity correction processing unit 23 does not correct the lighting quantity of the LEDs 54a to 54e to which black screen continuous flag is set. The black floating tends to be more inconspicuous in a dark environment than that in a bright environment, so that the threshold used for correcting the lighting quantity can be appropriately changed corresponding to a use condition and the like of the display device 10. The following represents examples of the threshold used for correcting the lighting quantity.
threshold 10%=luminance(500 cd/m2)/contrast(1000)
threshold 15%=luminance(500 cd/m2)/contrast(1500)
threshold 20%=luminance(500 cd/m2)/contrast(2000)
threshold 22%=luminance(450 cd/m2)/contrast(2000)
The backlight profile arithmetic unit 24 creates a backlight profile through an arithmetic operation based on the RGB data input from the lighting quantity correction processing unit 23 and the corrected light source device control signal. The backlight profile arithmetic unit 24 outputs the RGB data together with the created backlight profile to the image expansion calculating unit 25.
The image expansion calculating unit 25 generates and expands the RGBW data based on the expansion coefficient α from the backlight profile arithmetic unit 24. The image expansion calculating unit 25 calculates the output signal of the first sub-pixel based on the input signal of the first sub-pixel, the expansion coefficient α, and the output signal of the fourth sub-pixel, calculates the output signal of the second sub-pixel based on the input signal of the second sub-pixel, the expansion coefficient α, and the output signal of the fourth sub-pixel, and calculates the output signal of the third sub-pixel based on the input signal of the third sub-pixel, the expansion coefficient α, and the output signal of the fourth sub-pixel. The image expansion calculating unit 25 outputs the calculated output signals of the first sub-pixel, the second sub-pixel, the third sub-pixel, and the fourth sub-pixel to the image display panel unit 30.
According to the embodiment, the signal processing unit 20 converts the input signals (Rin, Gin, Bin) into the output signals (Rout, Gout, Bout, Wout) to distribute quantity of transmitted light of the surface light source device 50 to the fourth sub-pixel 49W of the pixel 48 based on the W (white) component, so that the light can be transmitted from the fourth sub-pixel 49W the light transmittance of which is the highest. Due to this, transmittance of the entire color filter can be improved, so that quantity of light passing through the color filter can be maintained even when the light output from the surface light source device 50 is reduced, and power consumption of the surface light source device 50 can be reduced while maintaining the luminance of the image.
An external light sensor 26 detects the luminance in the image display region 30a of the image display panel unit 20. Corresponding to the luminance detected by the external light sensor 26, the lighting quantity correction processing unit 23 detects whether there is a non-display region (black screen) in the image display region 30a. The external light sensor 26 may determine the non-display region by comparing the detected luminance with a luminance value that is arbitrarily set by a user. In this case, for example, the non-display region is hardly determined when the user sets a high luminance value, so that the power consumption of the display device 10 can be reduced. The non-display region can be easily determined when the user sets a low luminance value, so that the display quality can be improved.
The functions of the α-value generation unit 21, the light source lighting pattern determination unit 22, the lighting quantity correction processing unit 23, the backlight profile arithmetic unit 24, and the image expansion calculating unit 25 may be implemented by hardware or software, and are not specifically limited. Even if each component of the signal processing unit 20 is configured by hardware, circuits do not need to be physically and independently distinguished from each other, and a plurality of functions may be implemented by a physically single circuit.
Next, the following describes the method for driving the display device according to the embodiment. The method for driving the display device according to the embodiment includes a first step for detecting that the partial regions A1 to A5 included in the image display region 30a of the image display panel unit 30 are non-display regions, and a second step for controlling an amount of light of the light source 54 that is arranged corresponding to the non-display regions when the partial regions A1 to A5 adjacent to each other are continuous non-display regions.
At the first step, the lighting quantity correction processing unit 23 determines whether each of the ten partial regions A1a to A5b in the image display region 30a of the image display panel unit 30 is the black screen, that is, the non-display region (
Subsequently, the lighting quantity correction processing unit 23 detects whether there are two or more continuous partial regions as the black screens, that is, the non-display regions (
Next, the lighting quantity correction processing unit 23 measures the lighting quantity of the LEDs 54a to 54d in a black screen continuous flag area (Step S4), and corrects the lighting quantity of the LEDs 54a to 54d in the black screen continuous flag area of the light source device control signal (Step S5). In the example illustrated in
First, the lighting quantity correction processing unit 23 compares the lighting quantity “25%” of the LED 54a with the lighting quantity “100%” of the LED 54b to both of which the black screen continuous flag is set, and detects that the difference value of the lighting quantity of the LED 54a with respect to that of the LED 54b is “−75%”. The lighting quantity correction processing unit 23 then compares the detected difference value “−75%” with the threshold “25%” set in advance, and determines that the detected difference value is equal to or smaller than the threshold. In this case, the lighting quantity correction processing unit 23 does not correct the lighting quantity of the LED 54a and the LED 54b.
Next, the lighting quantity correction processing unit 23 compares the lighting quantity “100%” of the LED 54b with the lighting quantity “25%” of the LED 54c to both of which the black screen continuous flag is set, and detects that the difference value of the lighting quantity of the LED 54b with respect to that of the LED 54c is “75%”. The lighting quantity correction processing unit 23 then compares the detected difference value “75%” with the threshold “25%” set in advance, determines that the detected difference value is equal to or larger than the threshold, and corrects the lighting quantity of the LED 54c to be increased to “75%” so that the difference value becomes equal to or smaller than the threshold “25%”. Accordingly, in the liquid crystal display device 10, the difference between the lighting quantity of the LED 54b of the partial region A2 including a high-saturation display region and the lighting quantity of the LED 54c of the partial region A3 with no display region is decreased to be equal to or smaller than the threshold “25%”. Due to this, it is possible to reduce a gradation difference between the black screen in the partial region A2 and the black screen in the partial region A3, and prevent the black floating from occurring in the partial region A2.
Next, the lighting quantity correction processing unit 23 compares the corrected lighting quantity “75%” of the LED 54c and the lighting quantity “70%” of the LED 54d to both of which the black screen continuous flag is set, and detects that the difference value of the lighting quantity of the LED 54c with respect to that of the LED 54d is “5%”. The lighting quantity correction processing unit 23 then compares the detected difference value “5%” with the threshold “25%” set in advance, and determines that the detected difference value is equal to or smaller than the threshold. In this case, the lighting quantity correction processing unit 23 does not correct the lighting quantity of the LED 54c and the LED 54d.
Subsequently, the lighting quantity correction processing unit 23 compares the lighting quantity “70%” of the LED 54d with the corrected lighting quantity “75%” of the LED 54c to both of which the black screen continuous flag is set, and detects that the difference value of the lighting quantity of the LED 54d with respect to that of the LED 54c is “−5%”. The lighting quantity correction processing unit 23 then compares the detected difference value “−5%” with the threshold “25%” set in advance, and determines that the detected difference value is equal to or smaller than the threshold. In this case, the lighting quantity correction processing unit 23 does not correct the lighting quantity of the LED 54d and the LED 54c.
Next, the lighting quantity correction processing unit 23 compares the corrected lighting quantity “75%” of the LED 54c with the lighting quantity “100%” of the LED 54b to both of which the black screen continuous flag is set, and detects that the difference value of the lighting quantity of the LED 54c with respect to that of the LED 54b is “−25%”. The lighting quantity correction processing unit 23 then compares the detected difference value “−25%” with the threshold “25%” set in advance, and determines that the detected difference value is equal to or smaller than the threshold. In this case, the lighting quantity correction processing unit 23 does not correct the lighting quantity of the LED 54c and the LED 54b.
Next, the lighting quantity correction processing unit 23 compares the lighting quantity “100%” of the LED 54b with the lighting quantity “25%” of the LED 54a to both of which the black screen continuous flag is set, and detects that the difference value of the lighting quantity of the LED 54a with respect to the LED 54b is “75%”. The lighting quantity correction processing unit 23 then compares the detected difference value “75%” with the threshold “25%” set in advance, determines that the detected difference value is equal to or larger than the threshold, and corrects the lighting quantity of the LED 54a to be increased to “75%” so that the difference value becomes equal to or smaller than the threshold “25%”. Accordingly, in the liquid crystal display device 10, the difference between the lighting quantity of the LED 54b of the partial region A2 including the high-saturation display region and the lighting quantity of the LED 54a of the partial region A1 with no display region is decreased to be equal to or smaller than the threshold “25%”. Due to this, it is possible to reduce the gradation difference between the black screen in the partial region A2 and the black screen in the partial region A1, and prevent the black floating from occurring in the partial region A2.
As described above, the lighting quantity correction processing unit 23 completes the correction of the lighting quantity of the LEDs 54a to 54d of the light source device control signal. Subsequently, the lighting quantity correction processing unit 23 outputs the light source device control signal in which the LEDs 54a to 54d are corrected to the light source device control circuit 60. The light source device control circuit 60 controls actual lighting quantity of the LEDs 54a to 54e based on the corrected light source device control signal input from the lighting quantity correction processing unit 23. The values of the lighting quantity and the threshold described above are exemplary only, and not limited thereto.
In the example of the embodiment described above, the lighting quantity correction processing unit 23 controls the lighting quantity of the LEDs 54a to 54d one by one. Alternatively, the lighting quantity correction processing unit 23 may collectively control the lighting quantity of a plurality of light sources using an average value of the lighting quantity of the light sources. In a case in which the light source device control circuit 60 dividedly drives the LEDs 54a to 54e, the power consumption can be further reduced by correcting the light source device control signal in the LEDs 54a to 54e to be dividedly driven.
As described above, in the display device according to the embodiment, the lighting quantity correction processing unit 23 corrects the lighting quantity of each of the LEDs 54a to 54e when the partial regions A1 to A5 adjacent to each other are continuous non-display regions. Accordingly, the black floating G4 can be prevented from occurring in the image display region 30a even when the high-saturation image G3 is displayed in the image display region 30a.
Preferably, the signal processing unit 20 calculates an amount of light at each position based on the lighting quantity of each of the LEDs 54a to 54e corrected by the lighting quantity correction processing unit 23, and corrects an image signal based on a result thereof. Due to this, an image to be displayed is caused to have high reproducibility.
Next, the following describes an electronic apparatus including the display device 10 according to the embodiment with reference to
The electronic apparatus illustrated in
The electronic apparatus illustrated in
The electronic apparatus illustrated in
The electronic apparatus illustrated in
The electronic apparatus illustrated in
The electronic apparatus illustrated in
The electronic apparatus illustrated in
Each of the liquid crystal display devices 571 illustrated in
In
According to the embodiment, the present invention discloses the following display device, method for driving the display device, and electronic apparatus.
(1) A display device including:
The present invention provides the display device that can prevent the black floating from occurring even when the high-saturation image is displayed, the method for driving the display device, and the electronic apparatus.
Number | Date | Country | Kind |
---|---|---|---|
2013-219690 | Oct 2013 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
20070115246 | Hayashi | May 2007 | A1 |
20100194791 | Ogi et al. | Aug 2010 | A1 |
20100220048 | Yamamura et al. | Sep 2010 | A1 |
20120139885 | Iwasa | Jun 2012 | A1 |
Number | Date | Country |
---|---|---|
2008-009415 | Jan 2008 | JP |
2008-051905 | Mar 2008 | JP |
2010-175913 | Aug 2010 | JP |
Entry |
---|
Japanese Office Action issued Feb. 23, 2016 for corresponding Japanese Application No. 2013-219690. |
Number | Date | Country | |
---|---|---|---|
20150109349 A1 | Apr 2015 | US |