Display device and source driver

Abstract

The present invention provides a display device capable of performing image quality adjustment without causing gradation collapse when images having different gradation are displayed in a partial region in a display screen. The image data signal output unit has a gamma setting data generation unit that generates gamma setting data, which is setting information for gamma correction corresponding to at least one partial region of a display screen of a display panel, on the basis of image data for the at least one partial region. The source driver includes: a gamma curve generation unit that receives supply of gamma setting data and generates a local gamma correction curve, which is a gamma correction curve corresponding to at least one partial region, on the basis of the gamma setting data; a decoder unit that performs gamma correction of gradation voltages corresponding to the plurality of pieces of pixel data for each of the at least one partial region on the basis of the local gamma correction curve; and an output unit that outputs a pixel driving voltage on the basis of the gamma-corrected gradation voltage.

Description

Technical Field

[0001] The invention relates to a display device and a source driver. Background Art

[0002] In a display device including a display element such as a liquid crystal or an organic electroluminescence (EL) (organic light-emitting diode (OLED)), brightness correction (gamma correction) using a gamma curve is performed. As a circuit for performing such gamma correction, a gamma correction circuit is proposed, in which a grayscale voltage generator selects a grayscale voltage corresponding to a specific situation, and the selected grayscale voltage is finely adjusted by changing a first reference base voltage and a second reference base voltage set in a setting register, thereby performing gamma correction consistent with a desired gamma correction curve (for example, Patent Document 1).

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2009-25665 Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] In recent years, in the display of television (TV) conference systems, multiple images with different sources are displayed in a display. When there are images with different average brightness in the multiple images, the image quality is adjusted by allocating more grayscale near each average brightness. For example, when there are both images with blocked up shadows and images with blown out highlights among the multiple images, more grayscale is allocated to the black area and the white area, respectively.

[0008] However, when such grayscale distribution is performed, there is a problem that the grayscale values ​​near the middle grayscale of the black area and the white area are degraded, the gradation becomes rough, and the so-called grayscale collapse occurs.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a display device capable of adjusting the image quality without causing grayscale collapse when displaying an image with different grayscales in a partial area within a display screen.

[0010] [Technical means to solve the problem]

[0011] The display device of the present invention comprises: a display panel having a plurality of source lines and a plurality of gate lines, and a plurality of pixel portions arranged in a matrix at each of the intersections of the plurality of source lines and the plurality of gate lines; an image data signal output portion receiving an input of image data and outputting the image data signal including a sequence of a plurality of pixel data slices based on the image data; and a source driver receiving a supply of the image data signal from the image data signal output portion and outputting a pixel driving voltage applied to the plurality of pixel portions based on the image data signal, the image data signal output portion having a gamma setting data generating portion, the gamma setting data generating portion generating a gamma setting data for the display panel; At least one partial area of ​​the display screen of the display panel is displayed, and setting information of gamma correction corresponding to the at least one partial area is generated based on the image data, namely, gamma setting data. The source driver comprises: a gamma curve generating unit, which receives the supply of the gamma setting data and generates a gamma correction curve corresponding to the at least one partial area, namely, a local gamma correction curve based on the gamma setting data; a decoder unit, which performs gamma correction of the grayscale voltage corresponding to the multiple pixel data pieces for each of the at least one partial area based on the local gamma correction curve; and an output unit, which outputs the pixel driving voltage based on the grayscale voltage after the gamma correction.

[0012] The source driver of the present invention is connected to a display panel having multiple source lines and multiple pixel parts connected to the multiple source lines, receives an image data signal including a sequence of multiple pixel data pieces, and outputs a pixel driving voltage applied to the multiple pixel parts based on the image data signal. The source driver is characterized in that it has: a gamma curve generating unit, which receives input of setting data for gamma correction corresponding to at least one partial area of ​​a display screen of the display panel, i.e., gamma setting data, and generates a gamma correction curve corresponding to the at least one partial area, i.e., a local gamma correction curve based on the gamma setting data; a decoder unit, which performs gamma correction on the grayscale voltage corresponding to the multiple pixel data pieces for each of the at least one partial area based on the local gamma correction curve; and an output unit, which outputs the pixel driving voltage based on the grayscale voltage that has undergone the gamma correction.

[0013] [Effects of the Invention]

[0014] According to the display device of the present invention, when an image with different grayscales is displayed in a partial area within a display screen, image quality adjustment can be performed without causing grayscale collapse. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a block diagram showing the structure of a display device according to an embodiment of the present invention.

[0016] Figure 2 The diagram shows an example of a display screen in which different images are displayed in a plurality of windows.

[0017] Figure 3 It is a block diagram showing the configuration of a timing controller and a source driver.

[0018] Figure 4 This is a block diagram showing the configuration of an image data latch circuit, a decoder circuit, and a decoder selection circuit.

[0019] Figure 5A Yes means Figure 2 A diagram showing an example of a gamma curve for an entire image.

[0020] Figure 5B It means Figure 2 Figure 2. An example of a gamma correction curve corresponding to the first window.

[0021] Figure 5C It means Figure 2 Figure 2 is a graph of an example of a gamma correction curve corresponding to the second window.

[0022] [Explanation of Symbols]

[0023] 100: Display device

[0024] 11: Display Panel

[0025] 12: Timing controller

[0026] 13: Gate Driver

[0027] 14: Source driver

[0028] 21: Overall image quality adjustment circuit

[0029] 22: Partial area setting

[0030] 23: Image data control circuit

[0031] 24A, 24B: Local image analysis circuit

[0032] 25A, 25B: Gamma curve adjustment circuit

[0033] 31: Image data latch circuit

[0034] 32: Gamma curve generation circuit

[0035] 33: Decoder circuit

[0036] 34: Decoder selection circuit

[0037] 35: Output circuit DETAILED DESCRIPTION

[0038] Hereinafter, preferred embodiments of the present invention will be described in detail. In the following description of the embodiments and the accompanying drawings, substantially the same or equivalent parts are denoted by the same reference numerals.

[0039] Figure 1 1 is a block diagram showing the structure of a display device according to an embodiment of the present invention. The display device 100 is an active matrix liquid crystal display device. The display device 100 includes a display panel 11, a timing controller 12, a gate driver 13, and source drivers 14-1 to 14-k.

[0040] The display panel 11 includes a plurality of pixel portions P 11 ~P nm And pixel switch M 11 ~M nm (n, m: a natural number greater than or equal to 2) is a semiconductor substrate arranged in a matrix. The display panel 11 includes n gate lines GL1 to GLn as scanning lines extending in the horizontal direction, and m source lines SL1 to SLm as data lines arranged to intersect with the gate lines. 11 ~Pixel part P nm And pixel switch M 11 ~Pixel switch M nm Provided at intersections of gate lines GL1 to GLn and source lines SL1 to SLm.

[0041] Pixel switch M 11 ~Pixel switch M nm The gate driver 13 controls the gates to be turned on or off according to gate signals Vg1 to Vgn supplied thereto.

[0042] Pixel part P 11 ~Pixel part P nm The source drivers 14-1 to 14-k receive the supply of grayscale voltages (driving voltages) corresponding to the image data. Specifically, the source drivers 14-1 to 14-k output pixel driving voltage signals Vd1 to Vdm to the source lines SL1 to SLm, and the pixel switches M 11 ~Pixel switch M nm When each is turned on, the pixel driving voltage signal Vd1 to the pixel driving voltage signal Vdm are applied to the pixel portion P 11 ~Pixel part P nm Thus, the pixel portion P 11 ~Pixel part P nm Each pixel electrode is charged and the brightness is controlled.

[0043] Pixel part P 11 ~Pixel part Pnm They respectively include: a transparent electrode, a pixel switch M 11 ~Pixel switch M nm The source lines SL1 to SLm are connected; and the liquid crystal is sealed between the transparent electrode and the opposing substrate, which is arranged opposite to the semiconductor substrate and has a transparent electrode formed on the entire surface. For the backlight inside the display device, the transmittance of the liquid crystal depends on the backlight applied to the pixel portion P 11 ~Pixel part P nm Display is performed by changing the potential difference between the grayscale voltage (driving voltage) and the voltage on the opposite substrate.

[0044] The timing controller 12 generates a sequence (serial signal) of pixel data pieces PD, for example, representing the brightness level of each pixel with 8-bit 256-level brightness grayscale, based on the image data VS. In addition, the timing controller 12 generates a clock signal CLK of an embedded clock method having a certain clock cycle based on the synchronization signal SS. The timing controller 12 generates a serial signal, namely, an image data signal VDS, which is an integration of the sequence of pixel data pieces PD and the clock signal CLK, and supplies it to the source driver 14-1 to the source driver 14-k, thereby performing display control of the image data. The image data signal VDS is configured as a serialized image data signal according to the number of transmission paths for each of the specified number of source lines.

[0045] In this embodiment, n pixel data slice groups each including m pixel data slices PD are connected in series, thereby constituting one frame of image data signal VDS. Each of the n pixel data slice groups is a pixel data slice group including pixel data slices corresponding to grayscale voltages, and the grayscale voltages are supplied to pixels on each horizontal scan line (i.e., each of gate lines GL1 to GLn). Based on the m×n pixel data slices PD, the n×m pixel units (i.e., pixel units P) are applied via the source lines through the actions of source drivers 14-1 to 14-k. 11 ~Pixel part P nm ) as the pixel driving voltage signal Vd1 to the pixel driving voltage signal Vdm to be supplied.

[0046] The timing controller 12 generates a frame synchronization signal FS indicating the timing of each frame of the image data signal VDS based on the synchronization signal SS, and supplies the frame synchronization signal FS to the source driver 14. The timing controller 12 generates a gate control signal GS for controlling the operation of the gate driver 13, and supplies the gate driver 13 with the frame synchronization signal FS.

[0047] The gate driver 13 operates by receiving the gate control signal GS from the timing controller 12, and sequentially supplies the gate signals Vg1 to Vgn to the gate lines GL1 to GLn based on the clock timing included in the gate control signal GS. The supply of the gate signals Vg1 to Vgn selects the pixel portion P for each pixel row. 11 ~Pixel part P nm Then, the pixel driving voltage signals Vd1 to Vdm are applied to the selected pixel portions from the source drivers 14 - 1 to 14 - k, so that the grayscale voltage is written to the pixel electrode.

[0048] In other words, through the operation of the gate driver 13, the m pixel portions arranged along the extension direction of the gate line (i.e., in a horizontal column) are selected as the supply targets of the pixel driving voltage signals Vd1 to Vdm. The source drivers 14-1 to 14-k apply the pixel driving voltage signals Vd1 to Vdm to the selected pixel portions in the horizontal column, and display the color corresponding to the voltage. While selectively switching the pixel portions in the horizontal column selected as the supply targets of the pixel driving voltage signals Vd1 to Vdm, this is repeated along the extension direction of the source line (i.e., in the vertical direction), thereby displaying a screen of one frame.

[0049] Source drivers 14-1 to 14-k are provided for each of the predetermined number of data lines divided from source lines SL1 to SLm. Source drivers 14-1 to 14-k are formed in separate semiconductor integrated circuit (IC) chips. For example, when each source driver has 960 outputs and the display panel includes one data line for each pixel column, a 4K panel uses 12 source drivers to drive the source lines, and an 8K panel uses 24 source drivers to drive the source lines. Source drivers 14-1 to 14-k receive the frame synchronization signal FS, and the serial signal integrated with the clock signal CLK and the image data signal VDS from the timing controller 12 on separate transmission paths. When the transmission path between the timing controller 12 and each data driver is one pair (two lines), image data VD corresponding to the number of outputs of the source driver is supplied as a serialized differential signal during one data period.

[0050] In this embodiment, a plurality of windows are displayed on a screen (hereinafter referred to as a display screen DS) displayed on the display panel 11, and a plurality of images having different sources are displayed in the plurality of windows. In the following description, the area where these windows are displayed is referred to as a partial area of ​​the display screen DS. For example, when a TV conference is conducted using a computer connected to the display device 100, or when a navigation screen and an image of a rear camera are displayed simultaneously using a car navigation device connected to the display device 100, such a display is performed.

[0051] Figure 2 1 is a diagram showing an example of a display screen DS in which different images are displayed in a plurality of partial regions (a plurality of windows). Here, an example is shown in which images in which different persons are respectively captured are displayed in the first window W1 and the second window W2.

[0052] The first window W1 displays an image with a dark background and a strong black grayscale as a whole, while the second window W2 displays an image with a bright background and a strong white grayscale as a whole.

[0053] The display device 100 of this embodiment has a function of performing image quality adjustment corresponding to the case where an image with different grayscales is displayed on such a display screen. The function will be described below.

[0054] Figure 3 This is a block diagram showing the configuration of the portion related to the image quality adjustment function of the timing controller 12 and the source drivers 14-1 to 14-k. Here, only the source driver 14-1 and the source driver 14-2 are extracted and shown among the source drivers 14-1 to 14-k.

[0055] The timing controller 12 includes an overall image quality adjustment circuit 21, a partial region setting unit 22, and an image data control circuit 23. The overall image quality adjustment circuit 21 performs overall image quality adjustment of the image data VS.

[0056] The partial area setting unit 22 sets a partial area in the display screen DS of the display panel 11 and an area where an image is displayed as a partial area based on the image data VS. For example, the partial area setting unit 22 sets the partial area based on the information of the display position and grayscale when the image data contained in the image data VS is displayed on the display screen DS. Figure 2 In the example of FIG. 5 , the areas in the display screen DS where the first window W1 and the second window W2 are displayed are respectively set as partial areas.

[0057] The image data control circuit 23 supplies the image data signal VDS generated based on the image data VS to the source driver 14 - 1 and the source driver 14 - 2 together with the information of the partial area set by the partial area setting unit 22 .

[0058] In addition, the timing controller 12 has a plurality of local image analysis circuits and a gamma curve adjustment circuit. Figure 3 , only the local image analysis circuit 24A, the local image analysis circuit 24B and the gamma curve adjustment circuit 25A, the gamma curve adjustment circuit 25B are shown.

[0059] The local image analysis circuit 24A performs grayscale analysis on the local image, which is an image displayed in one or more partial areas set by the partial area setting unit 22. The gamma curve adjustment circuit 25A generates gamma setting data GSD, which is setting information of a gamma correction curve corresponding to the partial area, based on the analysis result of the local image analysis circuit 24A. The gamma curve adjustment circuit 25A supplies the generated gamma setting data GSD to the source driver 14-1 and the source driver 14-2.

[0060] Similarly, the local image analysis circuit 24B performs grayscale analysis on the local image displayed in the partial area different from the local image analyzed by the local image analysis circuit 24A. The gamma curve adjustment circuit 25B generates gamma setting data GSD based on the analysis result of the local image analysis circuit 24B and supplies it to the source driver 14-1 and the source driver 14-2.

[0061] The source driver 14-1 includes an image data latch circuit 31, a gamma curve generation circuit 32, a decoder circuit 33, a decoder selection circuit 34, and an output circuit 35. A plurality of gamma curve generation circuits 32 and a plurality of decoder circuits 33 are provided.

[0062] The image data latch circuit 31 sequentially takes in a sequence of pixel data pieces PD included in the image data signal VDS supplied from the timing controller 12. The image data latch circuit 31 supplies the taken-in pixel data pieces PD to the decoder circuit 33 each time it takes in the number (m) of pixel data pieces PD corresponding to the grayscale voltage signal supplied to the source driver 14-1 among the pixel data pieces PD of one horizontal scan line.

[0063] The gamma curve generation circuit 32 generates a local gamma correction curve corresponding to a partial region based on the gamma setting data GSD supplied from the timing controller 12. When there are a plurality of partial regions, a plurality of local gamma correction curves are generated by a plurality of gamma curve generation circuits.

[0064] The plurality of decoder circuits 33 are provided respectively corresponding to the plurality of gamma curve generating circuits 32 . The decoder selecting circuit 34 selects any one of the plurality of decoder circuits 33 based on the pixel data piece PD output from the image data latch circuit 31 and the information of the partial region supplied from the timing controller 12 .

[0065] The decoder circuit 33 receives the supply of the pixel data piece PD from the image data latch circuit 31, and receives the supply of the local gamma correction curve from the gamma curve generation circuit 32. The decoder circuit 33 performs digital-analog (DA) conversion of the pixel data piece PD while performing gamma correction corresponding to a partial area using the local gamma correction curve. That is, the decoder circuit 33 selects a grayscale voltage corresponding to the brightness shown in the pixel data piece PD supplied to itself from the grayscale voltage supplied from the grayscale voltage generation unit (not shown). The decoder circuit 33 performs gamma correction of the grayscale voltage based on the local gamma correction curve supplied from the gamma curve generation circuit 32.

[0066] The output circuit 35 amplifies the grayscale voltage signal reflecting the gamma correction performed by the decoder circuit 33 and outputs it as a pixel driving voltage signal Vd.

[0067] Figure 4 3 is a block diagram showing the configuration of the image data latch circuit 31 , the decoder circuit 33 , and the decoder selection circuit 34 .

[0068] The image data signal VDS supplied from the timing controller 12 is input to the source driver 14 - 1 via the interface 51 , and is supplied to each data latch in the image data latch circuit 31 .

[0069] The gamma setting data GSD is supplied from the timing controller 12 and stored in the register 52 via the interface 51 , and is supplied to the gamma curve generation circuits 32 - 1 to 32 - 3 .

[0070] Image data latch circuit 31 includes data latches 41A to 41F. Data latches 41A to 41F are provided for each channel, and sequentially take in a sequence of pixel data pieces PD included in image data signal VDS via interface 51 .

[0071] The decoder circuit 33 includes first decoders D1A to D1F, second decoders D2A to D2F, and third decoders D3A to D3F. That is, the decoder circuit 33 includes three decoders for each channel.

[0072] Gamma curve generation circuits 32-1 to 32-3 are provided corresponding to the first to third decoders. The gamma curve generation circuit 32 generates a gamma correction curve based on the gamma setting data GSD read from the register 52. The gamma curve generation circuit 32-1 supplies the gamma correction curve to the first decoder D1A to the first decoder D1F, the gamma curve generation circuit 32-2 supplies the gamma correction curve to the second decoder D2A to the second decoder D2F, and the gamma curve generation circuit 32-3 supplies the gamma correction curve to the third decoder D3A to the third decoder D3F.

[0073] The decoder selection circuit 34 includes selection circuits 44A to 44F. The selection circuits 44A to 44F are provided for each channel and select a decoder for each channel.

[0074] The output circuit 35 is provided for each channel, and outputs a pixel driving voltage signal Vd for each channel from an output terminal ST based on the grayscale voltage signal subjected to gamma correction performed in the decoder selected by the decoder selection circuit 34 .

[0075] In addition, although channels A to F are extracted and shown here, there are actually more channels, and the same structure is provided for each channel.

[0076] As described above, in the display device 100 of this embodiment, partial regions are set, and a local gamma correction curve is generated for each partial region. Gamma correction of the grayscale voltage is performed based on the generated gamma correction curve, thereby generating a pixel driving voltage signal Vd.

[0077] Figure 5A 1 is a diagram showing a gamma correction curve of the entire display screen DS, which is different from the local gamma correction curve described above. The gamma correction curve is determined by the characteristics of the display panel 11 and has a shape that is not biased toward either the black side or the white side.

[0078] Figure 5B It means Figure 2 FIG. 1 is a diagram of a local gamma correction curve corresponding to a partial area where the first window W1 of the display screen DS is located. The partial image displayed in the first window W1 is a dark image, so the portion of the grayscale on the black side of the local gamma correction curve surrounded by the dotted line becomes steeper. By performing gamma correction using the local gamma correction curve, the image of the first window W1 highlights the grayscale on the black side.

[0079] Figure 5C It means Figure 2FIG. 1 is a diagram of a local gamma correction curve corresponding to a partial area where the second window W2 of the display screen DS is located. The partial image displayed in the second window W2 is a bright image with white, so the grayscale portion of the white side of the local gamma correction curve surrounded by the dotted line becomes steeper. By performing gamma correction using the local gamma correction curve, the image of the second window W2 highlights the grayscale on the white side.

[0080] Thus, in the display device 100 of the present embodiment, a local gamma correction curve is generated for each partial region image, and gamma correction is performed according to the grayscale of the partial image displayed in the partial region. Therefore, the following problem, which occurs when gamma correction is performed using only one gamma correction curve corresponding to the entire display screen for a display screen including images with greatly different grayscales, i.e., the so-called grayscale collapse problem in which the gradation near the middle grayscale becomes coarse, does not occur.

[0081] Therefore, according to the display device 100 of this embodiment, when an image with different grayscales is displayed in a partial area within the display screen, image quality adjustment can be performed without causing grayscale collapse.

[0082] Furthermore, the present invention is not limited to the contents shown in the embodiments. Figure 2 In the embodiment, the first window W1 and the second window W2 are displayed in a plurality of partial regions of the display screen DS, and images with different grayscales are displayed in each window. However, the number of divided regions in the display screen is not limited thereto, and the display device 100 of this embodiment can be applied to a case where there is at least one partial region. In this case, it is sufficient to generate a gamma correction curve corresponding to the at least one partial region and perform gamma correction for each partial region.

[0083] In addition, Figure 4 In the description, the case where three decoders, namely the first decoder to the third decoder, are provided for each channel is taken as an example, but the number of decoders is not limited to this.

[0084] In addition, in the above-described embodiment, the timing controller 12 is described as having the overall image quality adjustment circuit 21, the partial area setting unit 22, the image data control circuit 23, the local image analysis circuit 24A, the local image analysis circuit 24B, and the gamma curve adjustment circuit 25A, the gamma curve adjustment circuit 25B. However, these functions may be provided in the image data signal output unit other than the timing controller 12, for example, in a single chip system (System on Chip, SoC).

[0085] In the above-described embodiment, the display device 100 is described as an example in which the display device 100 is an active matrix liquid crystal display device. However, the display device 100 may be an organic EL (OLED) display device.

Claims

1. A display device, characterized in that: have: A display panel having a plurality of source lines and a plurality of gate lines, and a plurality of pixel portions arranged in a matrix at each of the intersections of the plurality of source lines and the plurality of gate lines; An image data signal output unit receives input of image data and outputs an image data signal including a sequence of a plurality of pixel data slices based on the image data; as well as a source driver receiving the image data signal from the image data signal output unit and outputting a pixel driving voltage applied to the plurality of pixel units based on the image data signal, The image data signal output unit includes a gamma setting data generating unit, which generates gamma correction setting information corresponding to at least one partial area of ​​the display screen of the display panel based on the image data, i.e., gamma setting data. The source driver comprises: a gamma curve generating unit, receiving the supply of the gamma setting data, and generating a gamma correction curve corresponding to the at least one partial area, namely, a local gamma correction curve based on the gamma setting data; a decoder unit, which performs gamma correction of grayscale voltages corresponding to the plurality of pixel data pieces for each of the at least one partial area based on the local gamma correction curve; as well as An output unit outputs the pixel driving voltage based on the grayscale voltage that has undergone the gamma correction.

2. The display device according to claim 1, characterized in that The image data signal output unit includes a local image analysis unit that analyzes the grayscale of the image displayed in the at least one partial area, that is, the local image, based on the image data. The gamma setting data generating section generates the gamma setting data based on the analysis result obtained by the partial image analyzing section.

3. The display device according to claim 1, characterized in that The gamma curve generation unit and the decoder unit are provided with a plurality of channels for each of the channels including the plurality of source lines. The source driver includes a decoder selection circuit that selects one of the plurality of decoder sections for each channel.

4. A source driver connected to a display panel having a plurality of source lines and a plurality of pixel units connected to the plurality of source lines, receiving an image data signal including a sequence of a plurality of pixel data pieces, and outputting a pixel driving voltage applied to the plurality of pixel units based on the image data signal, wherein the source driver is characterized by: a gamma curve generating unit, receiving input of setting data of gamma correction corresponding to at least one partial area of ​​the display screen of the display panel, namely, gamma setting data, and generating a gamma correction curve corresponding to the at least one partial area, namely, a local gamma correction curve based on the gamma setting data; a decoder unit, which performs gamma correction of grayscale voltages corresponding to the plurality of pixel data pieces for each of the at least one partial area based on the local gamma correction curve; as well as An output unit outputs the pixel driving voltage based on the grayscale voltage that has undergone the gamma correction.

5. The source driver according to claim 4, characterized in that: The gamma curve generation unit and the decoder unit are provided with a plurality of channels for each of the channels including the plurality of source lines. The source driver includes a decoder selection circuit that selects one of the plurality of decoder sections for each channel.

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