JP2017122777A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image display device capable of suppressing deterioration of image quality even if a buffer area of a time aperture is reduced.SOLUTION: An image display device 1 includes: a display part 10; a video input part 11 to which a video signal is inputted; an extraction part 121 for taking out two frames with a time difference from the inputted video signal and for extracting movement of a subject recorded in the frames; a division part 122 for dividing a frame area into a moving area and a still area, based on the extraction result; and a control part 16 for displaying frames on the display part 10 by reducing emission time of the moving area shorter than that of the still area, providing a buffer area adjacent to both of the still area and the moving area, and gradually reducing emission time closer to the moving area in the buffer area. The control part 16 controls an emission period such that centers of gravity of emission time in the moving area, still area, and buffer area are consistent.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image display device that displays an image.

  An image display device using an active matrix such as a liquid crystal display and an organic EL (Electroluminescence) display continuously displays the same video for one frame period. Such an image display device is called a hold-type image display device. In the hold-type image display device, it is known that when the displayed object moves on the screen, the user follows the object and the image looks blurred due to the eye integration effect.

  In order to prevent such blurring, a technique for increasing the frame rate of the image display apparatus and a technique for shortening the light emission time aperture during one frame period have been proposed. A normal hold-type image display device continues to emit light over the entire frame period. However, in the method of shortening the light emission time aperture, as shown in FIG. 7, a non-light emission period is provided in a part of one frame period. Inserting. Thereby, blurring of the video when the user follows the object is suppressed, and the moving image quality is improved.

  On the other hand, when shortening the light emission time aperture during one frame period, it is necessary to increase the instantaneous luminance during the light emission period in order to maintain the brightness of the displayed image. For example, when the light emission period is halved compared to normal, the instantaneous luminance needs to be doubled compared to normal. By the way, in the organic EL display, the brightness is increased in proportion to the amount of current supplied to the organic EL element, and the lifetime is shortened in proportion to the power of the amount of current supplied to the organic EL element. Therefore, in the organic EL display, when the instantaneous luminance is increased, the lifetime may be accelerated. Therefore, a technique for adaptively shortening the light emission time aperture in one frame period has been proposed (see Patent Document 1 and Non-Patent Document 1).

JP 2004-144928 A

Takeharu Asai et al., “Examination of image quality improvement method in aperture control drive of organic EL display”, ITE Technical Report, Vol. 39, No2, IDY2015-10 (Jan. 2015), pp71-74

By the way, when the time aperture is changed for each region in the display surface in the image display device, regions having different instantaneous luminances are adjacent even at the same video level. In this case, when the user moves his / her line of sight between regions having different instantaneous luminances, the video level appears to fluctuate due to the effect of tracking visual integration.
For example, as shown in FIG. 8, it is assumed that a region A having a light emission intensity of 100 and a time aperture of 100% and a region B having a light emission intensity of 400 and a time aperture of 25% are adjacent to each other. At this time, as shown in FIG. 8A, when the user looks without moving his / her line of sight, both areas A and B appear to have the same brightness. However, as shown in FIG. 8B, when the user moves his / her line of sight in the up / down direction, the image for one frame appears to be integrated. As a result, the image quality is deteriorated such that the vicinity of the boundary between the regions A and B looks dark.

  In the method of Non-Patent Document 1, in order to suppress this image quality deterioration, a buffer region for gently changing the time aperture is introduced. However, although the image quality deterioration is reduced by taking a sufficient buffer area, the effect of suppressing the life deterioration has been reduced.

  An object of the present invention is to provide an image display device capable of suppressing image quality degradation even if the buffer area of the time aperture is shortened.

  An image display apparatus according to the present invention extracts an image display module, an input unit to which a video signal is input, and two frames that are temporally shifted from the video signal input by the input unit, and extracts the two frames Based on the extraction unit that extracts the movement of the subject recorded in the frame, and based on the extraction result of the extraction unit, the frame region is moved to the moving region where the subject is supposed to move, and the subject moves A dividing unit that divides the moving region into a stationary region, a light emitting time of the moving region that is shorter than a light emitting time of the stationary region, and a buffer region that is adjacent to both the stationary region and the moving region. A control unit that causes the image display module to display a frame so as to gradually shorten the light emission time as it approaches the moving region in the buffer region, Serial control unit, the moving area, controls the light emission period so as to match the center of gravity of light emission time in the still region and the buffer region.

  The dividing unit obtains a ratio of the number of pixels in which the subject moves for each horizontal line constituting the frame based on a result of extraction by the extraction unit, and moves the horizontal line exceeding the threshold among the ratios for each horizontal line. It is good also considering a horizontal line below a threshold among the said ratio for every horizontal line as an area | region, and making it the said static area.

  The control unit may control the emission intensity to be higher when the emission time is shorter.

  The image display module may be an active matrix organic EL display module.

  According to the present invention, image quality degradation can be suppressed even if the buffer area of the time aperture is shortened.

It is a block diagram which shows the function structure of the image display apparatus which concerns on embodiment. It is a figure which illustrates the change of the time aperture in the buffer area | region which concerns on embodiment. It is a figure which shows the structure of the row drive driver part which concerns on embodiment. It is a figure which shows an example of operation | movement of the row drive driver part which concerns on embodiment. It is a figure which shows two types of change patterns of the time aperture used for simulation. It is the graph which showed the change rate of the integral value of the brightness | luminance calculated | required by simulation. It is a figure which shows an example of the method of shortening a light emission time aperture. It is a figure explaining image quality degradation by tracking visual integration.

Hereinafter, an example of an embodiment of the present invention will be described.
FIG. 1 is a block diagram illustrating a functional configuration of the image display apparatus 1 according to the present embodiment.

  The image display device 1 includes a display unit 10, a video input unit 11, a moving region extraction unit 12, a time aperture control unit 13, a row drive driver unit 14, and a column drive driver unit 15. The time aperture control unit 13, the row drive driver unit 14, and the column drive driver unit 15 are functional units constituting the control unit 16.

  The display unit 10 is a hold-type image display module. As a more specific example, the display unit 10 is an organic EL display module including an active matrix display panel 111.

  The video input unit 11 receives a video signal. The video input unit 11 includes a buffer that temporarily stores frames included in the video signal. The video input unit 11 stores the frame in the buffer, and then supplies the frame In stored in the buffer and the temporally previous frame In-1 to the moving region extraction unit 12.

The moving area extracting unit 12 includes an extracting unit 121 and a dividing unit 122.
The extraction unit 121 extracts the movement of the subject recorded in the frame based on the two frames that move forward and backward in time. That is, the extraction unit 121 extracts the amount of movement of the subject in the frame In based on the frame In and the temporally previous frame In-1.

For example, the extraction unit 121 acquires a movement amount that is the magnitude of the movement of the subject of each pixel between frames based on two frames that are temporally changed. As a specific example, the extraction unit 121 extracts a block of 16 pixels × 16 pixels from a frame and performs block matching between the frames, thereby acquiring the motion amount of the subject of each pixel.
Here, it is assumed that the amount of movement of the subject in the pixel Pn (x, y) of the frame In is Vn (x, y). Note that x satisfies the relationship of 0 <x ≦ Nx (Nx: the number of pixels in the horizontal direction). Moreover, y satisfies the relationship of 0 <y ≦ Ny (Ny: number of pixels in the vertical direction).

  The dividing unit 122 divides the frame region into a moving region in which the subject moves for each horizontal line and a still region in which the subject does not move based on the extraction result by the extracting unit 121. To do. That is, the dividing unit 122 obtains the ratio of the number of pixels that the subject moves for each horizontal line corresponding to the horizontal direction of the frame based on the extraction result by the extracting unit 121. Then, the dividing unit 122 sets a horizontal line exceeding the threshold among the ratios for each horizontal line as a moving area. In addition, the dividing unit 122 sets a horizontal line that is equal to or less than a threshold among the ratio of each horizontal line as a still area.

  Specifically, the dividing unit 122 creates a histogram Hn (l) of the subject motion amount for each horizontal line based on the subject motion amount Vn extracted by the extraction unit 121. Here, l represents the number of the horizontal line.

  More specifically, the dividing unit 122 first obtains the number of pixels in which the amount of motion Vn of the subject when the horizontal line number is y = 1 exceeds the first threshold value Vth. Here, as an example, the first threshold value Vth is 4 pixels / frame. In this case, the dividing unit 122 obtains the number of pixels having a subject motion exceeding 4 pixels per frame for each horizontal line. Subsequently, the dividing unit 122 sets Hn (l) as a value obtained by dividing the obtained number of pixels by the number of pixels Nx (the number of pixels in the horizontal direction) constituting one horizontal line. Next, the dividing unit 122 sets a horizontal line that exceeds the second threshold Hth (for example, Hth = 0.05) in the histogram Hn (l) as a moving region. Further, the dividing unit 122 sets a horizontal line equal to or lower than the second threshold value Hth as a still region for the histogram Hn (l).

  The time aperture control unit 13 receives information on a stationary region or a moving region for each horizontal line divided by the dividing unit 122. The time aperture control unit 13 sets the still region to emit light for a predetermined period of one frame period. In addition, the time aperture control unit 13 sets the moving region to emit light for a period shorter than a predetermined period. In the present embodiment, as an example, the time aperture control unit 13 sets the time aperture of light emission in the still region to 100% (predetermined period = 1 frame period), and sets the time aperture of light emission in the moving region to 25%. It should be noted that the light emission time in the moving area is appropriately set so that the blur of the video is difficult to understand.

In addition, the time aperture control unit 13 is adjacent to both the stationary region and the moving region in order to reduce image quality degradation as shown in FIG. 8 in which the space between the stationary region and the moving region appears dark due to the vertical movement of the line of sight. A buffer region is provided, and the light emission time is gradually shortened as the buffer region approaches the moving region from the stationary region. That is, the time aperture control unit 13 resets a part of the stationary area adjacent to the moving area, a part of the moving area adjacent to the stationary area, or an area including the boundary between the stationary area and the moving area as a buffer area. The adjustment is made so that the rate of change of the time aperture in the buffer region is kept within a certain range.
Further, the time aperture control unit 13 controls the light emission period so that the centers of light emission time in the moving area, the stationary area, and the buffer area coincide with each other.

  FIG. 2 is a diagram illustrating the change of the time aperture in the buffer region according to the present embodiment.

  In the time aperture, for example, the start point and the end point of light emission in one frame period may change linearly as shown in FIG. 2A from an aperture ratio of 100% to an aperture ratio of 25%, or FIG. It may be changed by an exponential function as shown in FIG. 2 or a curve determined by a sine wave as shown in FIG.

Note that these curves are examples, and a predetermined function may be used as appropriate.
In this way, the buffer region is provided, and the center of gravity of the light emission period coincides at the same time in all the horizontal lines, so that the phenomenon that the luminance integral changes greatly when the line of sight moves up and down is suppressed.

Further, when the time aperture of light emission changes, the apparent luminance also changes, so it is necessary to change the light emission intensity according to the time aperture. Therefore, the time aperture control unit 13 converts the image data based on the following expression (1) in order to increase the light emission intensity as the light emission time becomes shorter.
Output data = input data × 100 / hour aperture [%] (1)
Here, the input data is a luminance value for each pixel recorded in the video signal.

As an example, if the time aperture of the moving area is 25%, the output data has a value that is four times the input data. In other words, the time aperture control unit 13 performs control so that each pixel emits light by increasing the light emission intensity of the moving region by four times as compared with the case where the light emission intensity is not changed.
The time aperture control unit 13 supplies data relating to the moving area and the stationary area, and output data to the subsequent stage.

  A plurality of data signal lines arranged in the vertical direction are connected to the column drive driver unit 15. The column drive driver unit 15 supplies the output data signal of each pixel to each of the plurality of data signal lines.

  A plurality of selection signal lines arranged in the horizontal direction are connected to the row drive driver unit 14. The row drive driver unit 14 supplies a selection signal to each of the plurality of selection signal lines. The row drive driver unit 14 is connected to a plurality of light emission time control signal lines along the horizontal direction. Each light emission time control signal line is connected with a plurality of light emission time control transistors existing in a region along the horizontal direction where the light emission time control signal line is arranged.

FIG. 3 is a diagram illustrating a configuration of the row drive driver unit 14 according to the present embodiment.
In the drawing, an example is described in which the number of horizontal lines is 100, but the number of horizontal lines is not limited to 100.

  The row drive driver unit 14 includes a pixel selection shift register 141, an AND circuit 142, a pixel selection amplifier 143, a light emission time control shift register 144, a latch 145, and a light emission time control amplifier 146.

  The pixel selection shift register 141 sequentially outputs a selection signal for controlling whether or not to select an organic EL element to the display panel 111 for each of a plurality of horizontal lines (selection signal lines) constituting the display panel 111. .

  The AND circuit 142 is arranged for each horizontal line (selection signal line). The AND circuit 142 calculates the logical product of the selection signal output from the pixel selection shift register 141 and the gate pulse, and supplies the calculation result to the selection signal line via the pixel selection amplifier 143.

  The light emission time control shift register 144 controls the light emission time of the organic EL elements for all of the plurality of horizontal lines (100 rows) every time the pixel selection shift register 141 outputs a selection signal for one horizontal line. The light emission time control signal is sequentially output.

  The latch 145 sequentially accumulates the data output from the light emission time control shift register 144, and all of the accumulated data at a predetermined timing in the period in which the pixel selection shift register 141 outputs a selection signal for one horizontal line. The light emission time control signal is supplied to the light emission time control signal line via the light emission time control amplifier 146.

Next, the operation of the row drive driver unit 14 will be described.
FIG. 4 is a diagram illustrating an example of the operation of the row drive driver unit 14 according to the present embodiment.

  FIG. 4A is a diagram illustrating a signal input to the AND circuit 142 and a signal input to the pixel selection shift register 141 during one frame period. FIG. 4B shows a signal input to the pixel selection shift register 141, a signal input to the latch 145, and a light emission time control when a signal is supplied to one horizontal line (one row driving period). It is a figure which shows the signal input into the shift register 144 for a signal. FIG. 4C illustrates a signal input to the latch 145 and a signal input to the light emission time control shift register 144 in one row driving period.

As shown in FIG. 4A, gate pulses are sequentially input to one input of the AND circuit 142.
In addition, a gate signal is input to the pixel selection shift register 141 at the beginning of one frame period, and a first clock signal (CLK1) is sequentially input over one frame period.

As shown in FIG. 4B, during the one-row driving period, one first clock signal (CLK1) is input to the pixel selection shift register 141, and an AND circuit 142 corresponding to the first clock signal. Is inputted with 1 gate pulse. In addition, a data signal for controlling the light emission time for all the plurality of horizontal lines is input to the light emission time control shift register 144 in synchronization with the second clock signal (CLK2) during one row driving period. Is done. Since FIG. 3 shows an example in which 100 horizontal lines are arranged, FIG. 4C also shows an example in which 100 data are input.
The latch 145 receives data signals for all of the plurality of horizontal lines, and then receives one latch signal during one row driving period.
Note that the gate pulse, the gate signal, the first clock signal, the data signal, the second clock signal, and the latch signal are generated in the control unit 16.

The pixel selection shift register 141 receives a gate signal for controlling the timing of writing data to each horizontal line, and outputs a write control pulse to the corresponding AND circuit 142 line by line. The AND circuit 142 calculates the logical product of the input write control pulse and the gate pulse, and outputs the calculation result as a selection signal.
The light emission time control shift register 144 receives current control data for all of the plurality of horizontal lines when a data signal of 100 clocks synchronized with the second clock signal is input to control the current flowing through each horizontal line. The data is sequentially output to the latch 145.

  When the current control data is input from the light emission time control shift register 144, the latch 145 stores the current control data for all the plurality of horizontal lines. When the current control data is stored for all the horizontal lines, the latch 145 determines the current for all horizontal lines. A light emission time control signal based on the control data is output.

  That is, the row drive driver unit 14 outputs a selection signal to one horizontal line (selection signal line) and emits light to all the plurality of horizontal lines (light emission time control signal lines) in one row drive period. Outputs a time control signal. As a result, power is supplied only to the horizontal line that should emit light, and the time aperture is controlled.

  In this way, the row drive driver unit 14 controls the light emission timing that differs for each horizontal line. In a horizontal line with a time aperture of 100%, the aperture control data is turned on immediately after writing, and remains on until the next writing. In a horizontal line with a time aperture of less than 100%, the time aperture control data is turned on after a delay time that differs depending on each time aperture so that the center of light emission becomes constant.

As a result, even if the buffer area where the time aperture changes is reduced, the variation in the tracking visual integration is reduced as compared with the case where there is no delay time, and image quality deterioration is further suppressed. In addition, since the buffer region is reduced, the life of the display element can be expected to be improved.
Hereinafter, the effect of the present embodiment will be described by a simulation using actual image data.

FIG. 5 is a diagram showing two types of change patterns of the time aperture used in the simulation.
FIG. 5A shows a case where there is no delay time until the aperture control data is turned on (light emission is started). In the buffer area, the time aperture is linear from 100% to 25% in the vertical direction of the screen. It has changed.
FIG. 5B shows a case where the delay time until the aperture control data is turned on (light emission is started) is controlled and the light emission center of gravity of each horizontal line is temporally matched. In the vertical direction, the time aperture varies linearly from 100% to 25%.

FIG. 6 is a graph showing the change rate of the integral value of luminance obtained by simulation.
The horizontal axis indicates the horizontal line number of the display. The vertical axis represents the rate of change in luminance when the line of sight moves in the vertical direction of the screen at a speed of (10 pixels / 1 frame period) when the buffer area is 40 rows and 100 rows.
In pattern A, a buffer area of about 100 rows was required to suppress the luminance change to within 5%, but in pattern B, the luminance change can be suppressed to within 5% in the buffer area of about 40 rows. Met.

According to the present embodiment, the image display apparatus 1 performs the aperture control that shortens the light emission time for the moving area other than the stationary area, so that it is possible to suppress the occurrence of blurring when displaying a moving image. In addition, since the image display device 1 gradually shortens the light emission time as it approaches the moving area in the buffer area adjacent to the moving area, it is possible to suppress image quality deterioration in which the space between the stationary area and the moving area looks dark.
Further, at this time, the image display device 1 performs aperture control so that the light emission centroids coincide with each other in time, thereby reducing the amount of change in the tracking visual integration and reducing the image quality even if the time aperture buffer region is shortened. It becomes possible to suppress.

  Further, the image display device 1 obtains the ratio of the number of pixels that the subject moves for each horizontal line that constitutes the frame, sets the horizontal line that exceeds the threshold among the ratios for each horizontal line as a moving region, and out of the ratio for each horizontal line A horizontal line that is equal to or less than the threshold is set as a still area. Thereby, the image display device 1 can easily classify the moving area and the stationary area from the input video signal.

  The image display device 1 performs control so that the light emission intensity is higher in the region where the light emission time is shorter. As a result, the image display device 1 increases the light emission intensity for only a part of one frame, and thus suppresses a decrease in luminance due to aperture control, and particularly in an active matrix organic EL display module or the like. Lifetime deterioration can be suppressed.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to embodiment mentioned above. Further, the effects described in the present embodiment are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the present embodiment.

DESCRIPTION OF SYMBOLS 1 Image display apparatus 10 Display part (image display module)
11 Video input section (input section)
DESCRIPTION OF SYMBOLS 12 Moving region extraction part 13 Time aperture control part 14 Row drive driver part 15 Column drive driver part 16 Control part 111 Display panel 121 Extraction part 122 Dividing part

Claims (4)

An image display module;
An input unit for inputting a video signal;
An extraction unit that extracts two frames that are temporally moved forward and backward from the video signal input by the input unit, and extracts a movement of a subject recorded in the frame based on the two extracted frames;
A dividing unit that divides a region of the frame into a moving region in which the subject is moving and a stationary region in which the subject is not moving based on a result of extraction by the extracting unit;
The light emission time of the moving region is made shorter than the light emission time of the stationary region, and a buffer region adjacent to both the stationary region and the moving region is provided, and the light emitting time is gradually increased as the moving region approaches the moving region. A control unit that causes the image display module to display a frame,
The said control part is an image display apparatus which controls a light emission period so that the gravity center of the light emission time in the said movement area | region, the said stationary area | region, and the said buffer area | region may correspond. The dividing unit is
Based on the result of extraction by the extraction unit, obtain the ratio of the number of pixels that the subject moves for each horizontal line constituting the frame,
A horizontal line that exceeds a threshold value in the ratio for each horizontal line is defined as the moving area,
The image display apparatus according to claim 1, wherein a horizontal line that is equal to or less than a threshold value among the ratio of each horizontal line is set as the still area.   The image display device according to claim 1, wherein the control unit controls the light emission intensity to be higher when the light emission time is shorter.   The image display device according to claim 1, wherein the image display module is an active matrix organic EL display module.

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