JP2019028411A - Display - Google Patents

Abstract

To provide a display that can prevent a reduction in visibility of displayed images when performing automatic brightness control.MEANS FOR SOLVING THE PROBLEM: A display comprises: a brightness adjustment value calculation unit that calculates brightness adjustment values of a display panel on the basis of image data; a gradation correction data storage unit that stores a plurality of pieces of gradation correction data in association with the plurality of brightness adjustment values; and an image conversion unit that applies, to the image data, image conversion including brightness adjustment based on the calculated brightness adjustment values and gradation correction based on the gradation correction data according to the calculated brightness adjustment values.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a display device, and more particularly to brightness control of a display device.

  Conventionally, an electronic device including a display device consumes a large amount of power to drive the display device. In general, the higher the luminance of the display panel of the display device, the higher the power consumption required to drive the display device. Therefore, there is a case in which video control called so-called automatic brightness adjustment is performed in which the lighting rate of pixels in the entire screen is calculated according to video data, and the luminance of the entire screen is reduced as the lighting rate increases. Here, the luminance is reduced at a uniform rate for all pixels.

  However, when the lighting rate of the pixels is high on the entire screen, the luminance difference between the pixels is small. Therefore, if the luminance of the entire screen is reduced by a uniform luminance adjustment value (gain), the visibility of the display content is greatly reduced. To do.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a display device that can prevent a decrease in the visibility of display contents when automatic brightness adjustment is performed.

  A display device according to an aspect of the present invention includes a luminance adjustment value calculation unit that calculates a luminance adjustment value of a display panel based on video data, and a plurality of gradation correction data associated with each of the plurality of luminance adjustment values. A video correction including a gradation correction data storage unit for storing, a luminance adjustment based on the calculated luminance adjustment value, and a gradation correction based on the gradation correction data according to the calculated luminance adjustment value, A video conversion unit applied to the video data.

  In one aspect of the present invention, the video data correction unit includes a luminance adjustment unit that performs luminance adjustment by multiplying the calculated luminance adjustment value by each of a plurality of gradation values included in the video data, and a calculation Based on the brightness adjustment value, at least one of the gradation correction data is read from the gradation correction data storage unit, and the read gradation correction data is included in the plurality of gradation values included in the video data And a gradation correction unit that performs the gradation correction.

  Here, the gradation correction data may indicate a larger output gradation value as the input gradation value increases.

  Further, the gradation correction data storage unit may store the gradation correction data for improving the contrast more strongly as the brightness adjustment value becomes smaller.

It is a top view which shows schematically the display apparatus which concerns on this embodiment. It is a figure which shows the equivalent circuit of the display pixel of the display apparatus which concerns on this embodiment. It is a block diagram which shows an example of a structure of the controller for performing the brightness | luminance control operation | movement of the display apparatus which concerns on this embodiment. It is a graph which shows an example of the gradation correction data concerning this embodiment. It is a figure which shows the other example of the gradation correction data based on this embodiment.

  Embodiments of the present invention will be described below with reference to the 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, for the sake of clarity, the drawings may be schematically represented with respect to the width, thickness, shape, etc. of each part as compared to the actual embodiment, 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.

  FIG. 1 is a plan view schematically showing the display device 100 according to the present embodiment. As shown in FIG. 1, the display device 100 includes an organic EL display 1 and a controller 2 that controls the operation of the organic EL display 1.

  The organic EL display 1 includes a display area 3, a scanning line driving circuit 4, and a signal line driving circuit 5.

  The display area 3 includes P × Q display pixels PX arranged in a matrix on an insulating substrate such as glass or resin. The gate lines Gat (1 to P) are arranged along the lines (rows) of the array of the display pixels PX, and are connected to the display pixels PX on each line. In addition, video signal lines Sig (1 to Q) are arranged along the columns of the array of display pixels PX, and are connected to the display pixels PX of each column. Furthermore, a high-potential power line Vdd and a low-potential power line Vss are connected to each display pixel PX.

  The scanning line driving circuit 4 drives the gate lines Gat (1 to P) in line order. The signal line driving circuit 5 drives the video signal wirings Sig (1 to Q). The scanning line driving circuit 4 and the signal line driving circuit 5 are integrally formed on the substrate outside the display area 3 and constitute a control unit 6 together with the controller 2.

  In each line of the display region 3, three types of display pixels PX for red (R) display, green (G) display, and blue (B) display are alternately arranged.

  FIG. 2 is a diagram showing an equivalent circuit of the display pixel PX of the display device 100 according to the present embodiment. The display pixel PX includes an organic EL element 20 that is a self-luminous element and a pixel circuit 10 that supplies a drive current to the organic EL element 20.

  The pixel circuit 10 employs a voltage signal system that controls light emission of the organic EL element 20 in accordance with a video signal composed of a voltage signal. The pixel circuit 10 includes a drive transistor 11, a pixel switch 12, and a storage capacitor 13 as a capacitor.

  In the display device 100 according to the present embodiment, the drive transistor 11 and the pixel switch 12 are constituted by thin film transistors (TFTs) formed by the same process and layer structure. Here, the drive transistor 11 and the pixel switch 12 are N-channel TFTs having the same conductivity type, for example, a top gate TFT using IGZO, a-Si, polysilicon, or the like as a semiconductor layer. Note that the driving transistor 11 and the pixel switch 12 are not limited to the N-channel type, and may be a P-channel type as long as they function as switches.

  The drive transistor 11 and the pixel switch 12 each have a source electrode, a drain electrode, and a gate electrode.

  In the pixel circuit 10, for example, in the display pixel PX for green (G) display, the drive transistor 11 is connected in series with the organic EL element 20 between the high-potential power line Vdd and the low-potential power line Vss. Yes. The power supply line Vdd is set to a potential of 10V, for example, and the power supply line Vss is set to a potential of −4V, for example.

  The drive transistor 11 outputs a drive current having a current amount corresponding to the video signal to the organic EL element 20, and the cathode of the organic EL element 20 is connected to the power supply line Vss.

  The pixel switch 12 has a drain electrode connected to the video signal wiring Sig and a source electrode connected to the gate electrode of the drive transistor 11. The gate electrode of the pixel switch 12 is connected to the gate line Gat, and is turned on / off by a control signal SG supplied from the gate line Gat. The pixel switch 12 controls connection and disconnection between the pixel circuit 10 and the video signal wiring Sig in response to the control signal SG, and takes in the video voltage signal from the corresponding video signal wiring Sig to the pixel circuit 10.

  The storage capacitor 13 has two opposing terminals, is connected between the gate electrode and the source electrode of the drive transistor 11, and holds the control potential between the gate and source of the drive transistor 11 determined by the video signal. .

  On the other hand, the controller 2 shown in FIG. 1 is formed on, for example, a printed circuit board disposed outside the organic EL display 1 and controls the scanning line driving circuit 4 and the signal line driving circuit 5. The controller 2 receives externally supplied digital video data 30 and a synchronizing signal, and generates a vertical scanning control signal for controlling the vertical scanning timing and a horizontal scanning control signal for controlling the horizontal scanning timing based on the synchronizing signal. Let

  The controller 2 supplies the vertical scanning control signal and the horizontal scanning control signal to the scanning line driving circuit 4 and the signal line driving circuit 5, respectively, and the video data 30 is synchronized with the horizontal and vertical scanning timings. To supply.

  The signal line driving circuit 5 converts the video data sequentially obtained in each horizontal scanning period into an analog format under the control of the horizontal scanning control signal, and the red (R) video voltage signal and green (G) signal corresponding to the video data. A gradation voltage signal Vsig having a plurality of gradations including a video voltage signal and a blue (B) video voltage signal is supplied in parallel to the video signal wirings Sig (1 to Q).

  The scanning line driving circuit 4 includes a shift register, an output buffer, and the like, and sequentially transfers a vertical scanning start pulse supplied from the outside to the next stage, as shown in FIGS. 1 and 2, to the display pixels PX of each line. A control signal SG (1 to P) is supplied. As a result, the gate lines Gat (1 to P) are driven by the control signals SG (1 to P).

  FIG. 3 is a block diagram illustrating a configuration example of the controller 2 for executing the luminance control operation of the display device 100 according to the present embodiment. In addition, the controller 2 shown in FIG. 3 is described centering on the part relevant to the luminance control operation.

  The processor 7 provided outside sends the video data 30 and the synchronization signal 31 which are digital video signals to the controller 2. Here, the processor 7 is incorporated in, for example, an electronic device. The device that outputs the video data 30 to the controller 2 is not limited to the processor 7, and may be a memory device, for example.

  The controller 2 performs various types of video conversion including brightness and contrast adjustment processing when using the image quality improvement of the video data 30 transmitted from the processor 7 and the automatic brightness adjustment function. Then, the controller 2 outputs to the organic EL display 1 the video data (converted video data 36) subjected to the video conversion and the timing signal based on the synchronization signal. In the organic EL display 1, the driving circuit (the scanning line driving circuit 4 and the signal line driving circuit 5) drives the display pixels PX in the display area 3 based on the converted video data 36 and the timing signal sent from the controller 2. To display the image.

  As described above, the controller 2 and the drive circuit (the scanning line drive circuit 4 and the signal line drive circuit 5) constitute the control unit 6.

  Next, the configuration of the controller 2 will be described. The controller 2 includes a receiver 40 and a video conversion unit 50.

  The receiver 40 receives the video data 30 for each line from the processor 7 and sends the received video data 30 to the video conversion unit 50 for each line.

  The video conversion unit 50 receives the video data 30 for each line from the receiver 40, and adjusts the luminance of the video data 30 in order to suppress power consumed for display. In addition, the display gradation of the video data 30 is corrected in order to suppress a decrease in contrast due to the brightness adjustment.

  The video conversion unit 50 includes an automatic luminance adjustment value calculation unit 51, a luminance adjustment unit 52, a gradation correction data storage unit 53, a gradation correction unit 54, and a gamma correction unit 55. The automatic luminance adjustment value calculation unit 51 further includes: A line-by-line power consumption calculation unit 51a, a display area power consumption calculation unit 51b, and a luminance adjustment value calculation unit 51c are provided.

The power consumption calculation unit 51a for each line calculates the power consumption for each line according to Equation (1) based on the luminance of the video data 30 for each line. For example, the luminance of the video data 30 for each line in the display area 3 is multiplied by a coefficient for conversion to power consumption.
W _line i = Σ (R _in (i) × K _R + G _in (i) × K _G + B _in (i) × K _B ) (1)

In this equation (1), W _linei is the power consumption related to the video data 30 in the i-th line of the display area 3. The gradation value (pixel value) of the red pixel included in the video data 30 of the i-th line is R _in (i), the gradation value of the green pixel is G _in (i), and the gradation value of the blue pixel is B _in. (i), the coefficient for converting the gradation value of the red pixel into power consumption is K _R , the coefficient for converting the luminance of the green pixel into power consumption is K _G , and the coefficient for converting the luminance of the blue pixel into power consumption is a _{K B.}

The display area power consumption calculation unit 51b calculates the power consumption (display area power consumption 31: W) necessary for displaying the video data 30 in the display area 3 according to Equation (2). For example, the display area power consumption 31 from the first line to the n-th line is the power consumption from the first line to the n-th line among the power consumption per line calculated by the power consumption calculation unit 51a per line. It can be obtained by integrating. Here, n may be the number of the last line in the display area 3.
W = ΣW _linei (2)

The brightness adjustment value calculation unit 51 c calculates the brightness adjustment value 32 for each display frame based on the display area power consumption 31. For example, according to Equation (3), the brightness adjustment value L (reference numeral 32) is a function of the display area power consumption W (reference numeral 31), and is displayed from the display area power consumption W calculated by the display area power consumption calculation unit 51b. The brightness adjustment value L of the area 3 is calculated. Note that the brightness adjustment value L is a value that is small enough to sufficiently suppress the power consumed by the display, for example, a value smaller than 1. For example, the luminance adjustment value L may be 1 when the display area power consumption W is 0, and the luminance adjustment value L may decrease linearly as W increases. Alternatively, when the display area power consumption W is 0, the brightness adjustment value L is 1, and when W exceeds the threshold, the brightness adjustment value L may decrease linearly therefrom.
L = f (W) (3)

  After calculating the brightness adjustment value L, the brightness adjustment value calculation unit 51 c sends the brightness adjustment value L to the brightness adjustment unit 52 and the gradation correction unit 53.

The luminance adjustment unit 52 receives the video data 30 for each line from the receiver 40, and further receives the luminance adjustment value L sent from the luminance adjustment value calculation unit 51c. Then, luminance adjustment video data 33 which is video data to which the luminance adjustment value L is applied to the video data 30 for one frame is calculated according to the equations (4) to (6). That is, the brightness adjustment video data 33 includes a gradation value R _{in_L} of a red pixel, a gradation value G _{in_L} of a green pixel, and a gradation value B _{in_L of a} blue pixel. As shown in Equations (4) to (6), the luminance adjustment unit 52 multiplies each gradation value by a uniform luminance adjustment value L regardless of the magnitude of the value.
_{R in_L = L × R in ...} (4)
G _{in_L} = L × G _in (5)
_{B in_L = L × B in ...} (6)

  The gradation correction unit 53 first receives the luminance adjustment video data 33 from the luminance adjustment unit 52, and further receives the luminance adjustment value L from the luminance adjustment value calculation unit 51c. At this time, based on the brightness adjustment value L, the tone correction data storage unit 54 is requested for tone correction data 34 for performing tone correction of the brightness adjustment video data 33.

  The gradation correction data storage unit 54 stores a plurality of gradation correction data in association with each of the plurality of luminance adjustment values. When the luminance adjustment value L from the gradation correction unit 53 is received, the gradation correction data corresponding to the luminance adjustment value L is selectively read out and sent back. For example, the gradation correction data storage unit 54 may select the gradation correction data associated with the luminance adjustment value closest to the luminance adjustment value L calculated by the luminance adjustment value calculation unit 51c. The gradation correction data indicates the relationship between the input gradation value and the output gradation value, and the gradation correction unit 53 converts the gradation value included in the luminance adjustment video data 33 from the luminance adjustment unit 52 into a gradation. Replace with the output gradation value indicated in the tone correction data.

  The gradation correction video data 35 generated by the gradation correction unit 53 is sent to the gamma correction unit 55. The gamma correction unit 55 performs gamma correction processing on the gradation corrected video data 35 to generate converted video data 36 and sends it to the scanning line driving circuit 4 and the signal line driving circuit 5. In the above embodiment, the luminance adjustment in the luminance adjustment unit 52, the gradation correction in the gradation correction unit 53, and the gamma correction in the gamma correction unit 55 are separately performed. Of course, a part of the processing may be performed collectively.

  The scanning line driving circuit 4 and the signal line driving circuit 5 convert the converted video data 36 into an analog gradation voltage signal Vsig and supply it to the pixel circuit 10 in the display region 3 through the video signal wiring Sig.

  FIG. 4 schematically shows an example of the gradation correction data. In the figure, the horizontal axis represents the input gradation (the gradation before correction, that is, the brightness-adjusted video data 33), and the vertical axis represents the output gradation (the gradation after correction, that is, the gradation-corrected video data 35). A plurality of relationships between the input gradation and the output gradation shown in the figure are associated with the gradation correction value L and stored in the gradation correction data storage unit 54 as gradation correction data.

  In the figure, when the luminance adjustment is not performed in the luminance adjustment unit 52, that is, when the luminance adjustment value L is 1, the gradation correction data indicates a straight line having an inclination of 1, as indicated by a one-dot chain line. When the luminance adjustment is performed in the luminance adjustment unit 52, that is, when the luminance adjustment value L is less than 1, the gradation correction data shows a curve of a profile that varies depending on the magnitude of the luminance adjustment value L.

  That is, when the brightness adjustment value L is less than 1, for example, when the brightness adjustment value L is 0.8, the tone correction data is adjusted while the input tone value is small as shown by the solid line. The value is smaller than the gradation correction data (one-dot chain line) when the value L is 1. Further, it takes the same value as the gradation correction data when the input gradation value is a predetermined value and the luminance adjustment value L is 1. While the input gradation value takes a value larger than the predetermined value, it takes a larger value than the gradation correction data when the luminance adjustment value L is 1. In the figure, the gradation correction data indicated by the solid line is such that the ratio of the output gradation value to the input gradation value increases monotonously.

  Further, when the brightness adjustment value L is even smaller, for example, when the brightness adjustment value L is 0.5, as indicated by the broken line, the tone correction data has a brightness adjustment value while the input tone value takes a small value. It takes a smaller value than the gradation correction data (solid line) when L is 0.8. The gradation correction data when the input gradation value is the predetermined value and the luminance adjustment value L is 1 and the gradation correction data when the luminance adjustment value L is 0.8 are the same. While the input gradation value takes a value larger than the predetermined value, it takes a larger value than the gradation correction data when the luminance adjustment value L is 0.8. In the same figure, the gradation correction data indicated by the broken line also has a monotonically increasing ratio of the output gradation value to the input gradation value. However, the increase rate of the ratio is larger in the gradation correction data indicated by the broken line.

  As shown in FIG. 4, the gradation correction data stores a larger output gradation value as the input gradation value increases. In FIG. 4, the gradation correction data indicated by the broken line improves contrast more strongly than the gradation correction data indicated by the solid line. That is, the gradation correction data storage unit 54 stores gradation correction data that increases the contrast more strongly as the brightness adjustment value L decreases.

  Note that the gradation correction data when the brightness adjustment value L is less than 1 takes a smaller value than the gradation correction data indicated by the alternate long and short dash line until the middle, and more than the gradation correction data indicated by the alternate long and short dashed line. Take a large value. This prevents the power consumption when displaying the video data from fluctuating greatly.

  When the gradation correction data shown in FIG. 4 is used, even when the brightness adjustment value L is small and automatic brightness adjustment works strongly, the process for strongly improving the contrast is executed accordingly, so that the visibility is lowered. There is nothing.

  FIG. 5 is a diagram schematically illustrating another example of the gradation correction data. The gradation correction data corresponding to each luminance adjustment value L shown in the figure also increases the contrast more strongly as the luminance adjustment value L becomes smaller. Further, the gradation correction data when the luminance adjustment value L is less than 1 takes a smaller value than the gradation correction data indicated by the one-dot chain line until the middle, and more than the gradation correction data indicated by the one-dot chain line from the middle. Take a large value. This prevents the power consumption when displaying the video data from fluctuating greatly.

  Unlike the gradation correction data shown in FIG. 4, in the gradation correction data shown in FIG. 5, the ratio of the output gradation value to the input gradation value does not increase monotonously, and the ratio takes the maximum value in the middle. Thereafter, the ratio returns to the original value. However, the maximum value of the ratio increases as the brightness adjustment value L decreases. Even in this case, the contrast can be improved more strongly as the brightness adjustment value L becomes smaller.

  In the scope of the idea of the present invention, those skilled in the art can conceive various modifications and modifications, and it is understood that these modifications and modifications belong to the scope of the present invention. For example, those in which the person skilled in the art appropriately added, deleted, or changed the design of the above-described embodiments, or those in which the process was added, omitted, or changed the conditions are also included in the gist of the present invention. As long as it is provided, it is included in the scope of the present invention.

  In addition, it is understood that other functions and effects brought about by the aspects described in the present embodiment are apparent from the description of the present specification, or can be appropriately conceived by those skilled in the art, are brought about by the present invention. .

1 organic EL display, 2 controller, 3 display area, 4 scanning line drive circuit, 5 signal line drive circuit, 6 control unit, 7 processor, 10 pixel circuit, 11 drive transistor, 12 pixel switch, 13 storage capacitor, 20 organic EL Element, 29 Sync signal, 30 Video data, 31 Display area power consumption, 32 Brightness adjustment value, 33 Brightness adjustment video data, 34 Gradation correction data, 35 Gradation correction video data, 36 Converted video data, 40... Receiver DESCRIPTION OF SYMBOLS 50 ... Video | video conversion part, 51 ... Automatic brightness adjustment value calculation part, 51a ... Power consumption calculation part for every line, 51b ... Display area power consumption calculation part, 51c ... Brightness adjustment value calculation part, 52 ... Brightness adjustment part, 53 ... Floor Tone correction data storage unit 54... Gradation correction unit 55. Gamma correction unit 100. Display device Gat gate gate Sig video signal circuit X ... display pixels, SG ... control signal, Vsig ... gradation voltage signal, Vdd ... high-potential power supply line, Vss ... low-potential power supply line.

Claims (4)

A luminance adjustment value calculation unit for calculating a luminance adjustment value of the display panel based on the video data;
A gradation correction data storage unit that stores a plurality of gradation correction data in association with each of the plurality of brightness adjustment values;
A video conversion unit that applies luminance conversion based on the calculated luminance adjustment value and video conversion including gradation correction based on the gradation correction data corresponding to the calculated luminance adjustment value to the video data;
Display device. The display device according to claim 1,
The video data correction unit
A brightness adjustment unit that performs brightness adjustment by multiplying the calculated brightness adjustment value by each of a plurality of gradation values included in the video data;
Based on the calculated brightness adjustment value, at least one of the gradation correction data is read from the gradation correction data storage, and the read gradation correction data is included in the plurality of gradations included in the video data. And a gradation correction unit that performs the gradation correction by applying to each of the values. The display device according to claim 2,
The display device in which the gradation correction data shows a larger output gradation value as the input gradation value becomes larger. The display device according to any one of claims 1 to 3,
The gradation correction data storage unit stores the gradation correction data for enhancing contrast more strongly as the brightness adjustment value becomes smaller.

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