JP2007293039A - Image display device and image display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the maintenance of brightness of a screen and suppression of power consumption effectively compatible, on the condition that a method of black image insertion be employed to improve a movement blur. <P>SOLUTION: An image display device includes an image display driving means of driving a display panel section where pixels are arrayed in a matrix form for image display and drives it by a hold type image display method; a black image display control means of controlling the image display drive means so that a black image is displayed for a predetermined length of time in a frame cycle; a movement detecting means of inputting an image signal, on which the image displayed by the image display driving means is based and detecting the state of movement of the image; and a black image display time setting means of varying and setting the time length, for which the black image is displayed by the black image display control means, according to the state of movement of the image detected by the movement detecting means. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image display device such as a liquid crystal display device and a method thereof.

JP 2005-122199 A

For example, in order to display an image in a liquid crystal display (LCD) employing a matrix driving method, a so-called hold type as described in Patent Document 1, for example, is known.
In the hold method, an image (line image) is displayed for each scanned horizontal line by driving the vertical line in accordance with the video signal while performing vertical scanning for each predetermined period for a predetermined number of horizontal lines. . Then, the display of the line image for each horizontal line performed in this way is continued (held) for a period corresponding to one field until the horizontal line is next scanned.

  However, in the hold-type display, the image content corresponding to each frame period of the video signal is continuously displayed in any line or pixel. It has been a problem for a long time that a phenomenon called “motion blur” occurs in which a portion appears blurred or blurred.

Therefore, a technique called black image insertion is known as one of countermeasures against the above-mentioned “motion blur” problem.
Black image insertion is based on a hold-type display drive, and an image display period for displaying a normal image and a black display period for displaying black corresponding to a display period per unit time (for example, one frame period). It is something to be divided into. That is, based on the hold-type image display, a period for displaying black without inserting a normal image is inserted.
By inserting the period during which black is displayed during image display as described above, the period during which a normal image is displayed per unit time becomes discontinuous, and this causes movement in human vision. Blur becomes difficult to perceive. That is, motion blur is improved.

However, inserting a black image includes a period during which a normal image is not displayed per unit time and a black image is displayed. Therefore, the brightness of the image perceived by the person viewing the screen is reduced accordingly. Will do. That is, depending on the black image insertion, there is a problem that the display image is perceived as if it looks dark.
As a countermeasure for this, one of the measures is to compensate for the luminance reduced by the black image insertion, and to set the luminance of the original display image itself higher than when the black image is not inserted. It has been broken. For example, in the case of a liquid crystal display device, the brightness of the backlight may be increased.

By doing so, it is possible to compensate for the decrease in luminance due to the black image insertion. However, in this case, for example, when the luminance of the backlight is increased, the power consumption correspondingly increases.
Incidentally, it can be said that the problem relating to the increase in power consumption is particularly noticeable when a still image or an image in a state of motion similar to a still image is displayed. That is, as long as it is limited to a still image or an image close thereto, black image insertion is not necessary. Nevertheless, in the above-described luminance reduction compensation configuration, for example, the brightness of the backlight is steadily increased, and even when a still image or an image close thereto is displayed. This is because the state does not change.
Therefore, the present invention adopts the black image insertion method to improve the “motion blur”, and makes it possible to effectively maintain both the brightness of the screen and the suppression of the power consumption. For the purpose.

In view of the above-described problems, the present invention is configured as an image display apparatus as follows.
In other words, a display panel formed by arranging pixels in a matrix along the horizontal line direction and the vertical line direction is driven for image display, and the horizontal lines are sequentially scanned in a frame cycle. In addition, for each horizontal line scanning period, the pixels constituting the scanned horizontal line are driven based on the image signal to display an image for one horizontal line, and the displayed one horizontal line Image display driving means capable of driving the image portion for a minute until the next pixel on the horizontal line is driven, and a predetermined number based on the frame period for each horizontal line. The black image display control means for controlling the image display driving means so that a black image that is an image corresponding to black is displayed according to a required time length within a unit time. A motion detection unit that detects the motion of the image when the image signal that is the source of the image to be displayed by the image display driving unit is input and the input image signal is displayed and output; and According to the state of motion of the image detected by the motion detection means, a black image display control means is provided to display a black image, and the time length is variably set. .

As an image display device having the above-described configuration, first, a matrix type display panel unit is provided, and as a display drive thereof, a vertical line is driven each time a horizontal line is sequentially scanned, whereby a horizontal line unit is obtained. Images are displayed sequentially. And it drives so that the image for every horizontal line displayed in this way may continue until it switches to the image according to the next frame. That is, a method for display driving called a hold type is adopted. In addition, a black image is displayed for each horizontal line with a certain length of time within a predetermined unit time based on the frame period. In other words, on the premise of the hold type, driving is performed so that display called black image insertion is performed. As a result, the phenomenon called so-called “motion blur” caused by the display drive method being the hold method can be improved.
In addition, the invention of the present application is configured to vary the length of time for which the black image is displayed according to the movement of the image to be displayed on the display panel unit based on the image signal.
By changing the display time length of the black image in accordance with the movement of the image in this way, for example, the black image is displayed in accordance with the state of the image content having a large movement such that the motion blur is conspicuous. It is possible to increase the length of time that should be displayed, and conversely reduce the length of time that the black image should be displayed according to the state of small image content that does not make blurring noticeable become. The change in the length of time for displaying the black image appears as a change in the brightness of the display image perceived by the person viewing the image. The shorter the time length, the higher the perceived brightness of the image.

  For this reason, the present invention ensures a sufficiently high brightness of the display image at least in a state where the necessity of black image insertion is inherently reduced and the image movement is small. It will be possible. That is, it is not necessary to take measures such as an increase in luminance to compensate for a decrease in luminance due to display of a black image, for example. Thereby, as this invention, the effect that the increase in power consumption can be suppressed is acquired, maintaining the brightness | luminance of a display image required and sufficient.

Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described by taking a liquid crystal display device configured to perform image display by an active matrix method as an example.

FIG. 1 is a block diagram showing an example of the overall configuration of the liquid crystal display device 1 of the present embodiment.
In this case, an image signal (video signal) that is a source of the display image is input from the input terminal 10 to the first image processing unit 11 in the form of a digital signal, for example. In the first image processing unit 11, the input image signal is adapted to, for example, conversion processing of a signal format suitable for display on an actual display panel (liquid crystal panel unit) and the number of horizontal / vertical pixels of the display panel. Signal processing for various image quality adjustments, such as resolution conversion processing, is executed and output to the second image processing unit 12.

The second image processing unit 12 is a part for generating an input signal used by the scan driver 13 and the source driver 14 for display driving based on the image signal input from the first image processing unit 11. . The input signal to the scan driver 13 is, for example, a timing signal that indicates the timing for scanning the horizontal line (gate line) in the vertical direction according to the frame period. An input signal to the source driver 14 is data to be applied to pixels (data lines) for one horizontal line corresponding to the scanning timing of the gate line.

The display panel 15 includes a liquid crystal panel unit 15 and a backlight unit 16 provided on the back surface.
The liquid crystal panel unit 15 is formed by enclosing a liquid crystal layer in glass or the like as well known, and by arranging pixel cells (pixel cell driving circuits) corresponding to a predetermined resolution in a matrix by using, for example, a semiconductor substrate. The That is, the liquid crystal panel unit 15 in this case has a structure corresponding to the active matrix system.
In this case, the backlight unit 16 is configured by arranging a predetermined number of discharge lamps (for example, cold cathode tubes) as light sources in a predetermined arrangement pattern. And after diffusing the white light obtained when these discharge lamps light, for example, it irradiates from the back side of the liquid crystal panel part 15 toward the front side.
Further, the discharge lamp provided in the backlight unit 16 is driven to be lit by driving power output from the backlight driving unit 20, for example.

  The pixel cells in the liquid crystal panel unit 15 are located at positions corresponding to the intersections of the gate lines G1 to Gm drawn from the scan driver 13 and the data lines D1 to Dn drawn from the source driver 14. The scan driver 13 and the source driver 14 drive the gate line and the data line at the timing described later, so that the polarization direction of the liquid crystal layer corresponding to the pixel cell changes, and the back surface of the liquid crystal panel unit 15 The light that is transmitted from the light to the front surface is modulated. As a result, an image is displayed on the screen of the liquid crystal panel unit 15.

  In this case, for example, in this case, the moving image analysis unit 18 receives an image signal at a predetermined processing stage in the first image processing unit 11 and detects the amount of movement in units of pixels. This motion amount detection result is used to set a time length for black image insertion, which will be described later.

  The control unit 19 is a part that executes various controls in the liquid crystal display device 1 and is configured as a microcomputer including a CPU and a RAM, for example. In this case, information on the amount of motion detected by the moving image analysis unit 18 is input to the control unit 19. The control unit 19 can execute control related to the time length setting for black image insertion based on the input information on the amount of motion.

Next, a structural example of the liquid crystal panel unit 15 will be described with reference to FIG.
As a basic structure of the liquid crystal panel unit 15 shown in this figure, a required circuit including at least a pixel cell driving circuit arranged in a matrix, for example, is formed on a semiconductor substrate. The semiconductor substrate has a structure in which a counter substrate on which a common electrode is formed is opposed to each other, and liquid crystal is sealed between the semiconductor substrate and the counter substrate. In this figure, the scan driver 13 and the source driver 14 are shown together with the liquid crystal panel unit 15.

First, the circuit configuration of the pixel cell driving circuit 2 formed on the semiconductor substrate will be described by taking as an example a part indicated by wavy lines in FIG.
One pixel cell driving circuit 2 includes a pixel switch S11, a pixel capacitor C11, and a pixel electrode P11 as shown in the drawing.
The pixel switch S11 has a structure as, for example, an FET (field effect transistor). The gate of the pixel switch S11 is connected to the gate line G1, and the drain is connected to the data line D1. Each gate line and data line are also formed on the semiconductor substrate.
The source of the pixel switch S11 is connected to one end of the pixel capacitor C11. The other end of the pixel capacitor C11 is connected to the common electrode. A connection point between the source of the pixel switch and the pixel capacitor C11 is connected to the pixel electrode P11. The pixel cell driving circuit 10 formed in this way is arranged in a matrix along the row direction and the digit direction as shown. In addition, as a semiconductor substrate on which the pixel cell driving circuit 2 is formed in this manner, the pixel electrodes P of each pixel cell driving circuit 2 are arranged and exposed in a matrix.

  The scan driver 13 is formed with a shift register, for example, and is provided for performing scanning in the vertical direction for each row (one horizontal line). That is, at the time of display, the gate lines are scanned by outputting a pulsed scanning signal (scanning pulse) in the order of the gate lines G1, G2,. For example, when the gate line G1 is driven by scanning of the scan driver 13, a gate voltage is applied to the gates of the pixel switches (S11, S12, S13... S1h) for one row connected to the gate line G1. These pixel switches (S11, S12, S13... S1h) are turned on.

In addition, the source driver 14 displays the data lines D1, D2, D3,... Dm as horizontal lines corresponding to the gate lines to be scanned for the data lines D1, D2, D3,. Data corresponding to the image signal to be applied is applied.
Note that the data application to the data line executed by the source driver 14 in accordance with the scanning timing of one gate line is performed simultaneously with, for example, a method of sequentially scanning the data lines D1 to Dm. It is known that it is performed automatically. As this embodiment, either method may be adopted, but here, the latter method of simultaneously applying data is adopted.

  The semiconductor substrate thus formed is disposed so that the counter substrate on which the common electrode to which the common potential Vcom is applied is formed is opposed to the semiconductor substrate. Then, liquid crystal layer 3 is formed by sealing liquid crystal between the semiconductor substrate and the counter substrate.

A basic operation for image display by the liquid crystal panel unit 15 formed in this way, and the scan driver 13 and the source driver 14 will be described with reference to FIG. 3 together with FIG.
As the operations of the scan driver 13 and the source driver 14 at the time of display, the scan driver 13 shifts the output at the timing of each horizontal scanning period Th as shown in FIG. The gate line G1 from the first row to the last gate line Gm is sequentially scanned.
Thus, for example, in the horizontal scanning period Th in which the gate line G1 is scanned, the gate voltage is applied to the pixel switches S11, S12, S13... S1h in the row connected to the gate line G1 to turn it on, and the subsequent horizontal scanning. In a period Th, the pixel switches S11, S12, S13... S1h are turned on, and the pixel switches S21, S22, S23... S2h in the row connected to the next gate line G2 are turned on. It is said. Thereafter, the remaining gate lines are similarly scanned.

Then, the data lines D1 to Dn from the first digit (column) to the last digit are simultaneously driven by the source driver 14 within the horizontal scanning period Th in which one gate line is scanned as described above. Is done. Here, driving the data line means outputting a voltage value corresponding to the pixel data from the source driver 14 to the data line. In the example shown in FIG. 3, a voltage value corresponding to pixel data corresponding to an image signal for performing effective display as an image is applied.
Here, for example, it is assumed that the data lines D1 to Dm are simultaneously driven at a predetermined timing within the horizontal scanning period Th during which the gate line G1 is scanned. At this time, the pixel switches S11, S12, S13,... S1h whose gates are connected to the gate line G1 are turned on. However, the data lines D1 to Dm are driven to drive the gate lines G1. Applied to the data lines D1, D2, D3,... Dm to the pixel capacitors C11, C12, C13,... C1h connected to the pixel switches S11, S12, S13. Charges corresponding to voltage values (data) are accumulated from the drains of the pixel switches S11, S12, S13... S1h through the source. Potentials corresponding to the accumulated charge amount are generated at both ends of the pixel capacitors C11, C12, C13... C1h. That is, data is written to the pixel capacitors C11, C12, C13... C1h. The potentials generated in the pixel capacitors C11, C12, C13... C1h by this data writing are the pixel electrodes P11, P12, P13... Connected to the sources of the same pixel switches S11, S12, S13.・ It also occurs in P1h.

Then, when data writing by the data lines D1, D2, D3... Dm is completed, the data written to the pixel capacitors C11, C12, C13. D1, D2, D3,... Dm are driven. Therefore, in this case, pixel capacitors C11, C12, C13... Connected to the pixel switches S11, S12, S13... S1h at the intersections of the gate line G1 and the data lines D1, D2, D3. Data is written to C1h, and a potential is generated in the pixel electrodes P11, P12, P13... P1h.

Here, as shown in FIG. 2, the common electrode to which the potential Vcom is applied is disposed opposite to the pixel electrode P with the liquid crystal layer 3 interposed therebetween.
When potentials corresponding to data are generated in the pixel electrodes P11, P12, P13,..., P1h as described above, the potentials of the pixel electrodes P11, P12, P13. Depending on the potential difference, the liquid crystal of the liquid crystal layer 3 interposed therebetween reacts and is excited. That is, the pixel cell is driven.

Then, as described above, it is assumed that the source driver 14 simultaneously drives the data lines within the scanning period of the gate line G1, drives the pixels of one horizontal line, and completes the scanning of the gate line G1. The scan driver 13 scans the next gate line G2. Then, within the scanning period of the gate line G2, the source driver 14 drives the data lines at the same time, and similarly drives pixels for one horizontal line.
By performing such an operation for every horizontal line, writing of data for one screen is completed. By repeating this operation, for example, at a frame period, image display is performed.
In addition, the data written for each horizontal line is held until the data corresponding to the next frame is written to that horizontal line. In other words, this is a so-called hold-type display driving operation in which an image for one horizontal line (line image) is held for a time length of one frame period.

However, when display driving by the simple hold type as described above is performed, a phenomenon called “motion blur” tends to occur.
That is, in the hold formula, an image for one frame (frame image) can be viewed as a set of image elements expressed for each pixel by the above-described data writing, but in the hold formula, The image element obtained in response to one data writing is continuously maintained throughout the frame period. For this reason, the afterimage of the previous frame is easily perceived in the moving image portion, and the contour of the image looks unclear. This is called “motion blur”.
Such “motion blur” is a factor in image quality deterioration, and is preferably suppressed as much as possible.

  Therefore, the liquid crystal display device of the present embodiment also adopts a technique called black image insertion in order to suppress the above-mentioned motion blur. Black image insertion here is based on hold-type display driving and corresponds to black instead of an effective image corresponding to the display image signal, for example, for a certain length of time within the frame period. The display drive is performed so as to display the image to be displayed (black image).

A display driving example in the case where the black image insertion as described above is performed by the liquid crystal display device of the present embodiment will be described with reference to a timing chart of FIG.
Here, the timing at which the gate lines G1 to Gm shown in FIG. 4 are scanned and the pixel data corresponding to the effective image is applied, that is, the timing shown as the horizontal scanning period Th is shown in FIG. It has become the same. That is, in FIG. 4, the drive timing for displaying an effective image is the same as that in FIG.

In addition, in FIG. 4, driving for inserting a black image is performed as follows.
For example, taking the driving timing of the horizontal line corresponding to the gate line G1 as an example, first, the horizontal scanning period Th appears at the timing when one frame period starts. That is, as described with reference to FIG. 3, the scan for the gate line G1 is performed by the scan driver 13 during the horizontal scanning period Th, and the data lines D1 to Dn are scanned by the source driver 14 within the same horizontal scanning period Th. Application of data according to the image signal is performed. Thereby, after the data line driving is performed in the horizontal scanning period Th, an effective image display period T1 in which an effective image is displayed is started.

For example, in the case of FIG. 3, one frame period substantially coincides with the effective image display period T1.
On the other hand, in the case of FIG. 4, the black data application period Tbl appears at the timing when a predetermined time elapses in the effective image display period T1 within one frame period. In the black data application period Tbl, the pixels are driven so that the line image of the effective image displayed in the previous effective image display period T1 is displayed as a black image. For this purpose, for example, a voltage value corresponding to pixel data for displaying black is applied from the source driver 14 at the timing of the black data application period Tbl. As a result, the write data (charge) corresponding to the valid image so far is reset, and data writing corresponding to the black image is performed. In this way, the displayed black image is continued until the start timing of the next frame, that is, the next horizontal scanning period Th.
In other words, when one gate line is viewed, an effective image display period T1 of a predetermined time length for displaying a line image corresponding to the effective image and a black line image are displayed following this one frame period. It is divided into a black insertion period T2 having a predetermined time length. Then, such driving for one horizontal line is performed for each horizontal line as shown in FIG. In this case, as the scan driver 13 sequentially scans the gate lines, the timing of the horizontal scanning period Th for each horizontal line is sequentially shifted, but is set for each horizontal line. The time ratio (time length) between the effective image display period T1 and the black insertion period T2 within one frame period is the same. In the description of FIG. 4, it is assumed that the time lengths of the effective image display period T1 and the black insertion period T2 are fixed.

FIG. 5A and FIG. 5B schematically show display state examples obtained as a result of hold-type display driving in which the black insertion period T2 is set as shown in FIG.
If the display driving according to FIG. 4 is repeated at a frame period, for example, as shown in FIGS. 5A and 5B, the entire display image is displayed along the horizontal direction indicated as the black image display area AR2. A black image portion having a certain fixed width in a band shape is constantly displayed, and the remaining area in the entire display image is an effective image display area AR1 in which an effective image is displayed. The black image display area AR2 is displayed in such a manner that an operation of moving from the top to the bottom of the display image in a cycle of one frame circulates. Changes between FIGS. 5A and 5B indicate the movement of the position of the black image display area AR2 as described above.
The ratio of the width W2 in the vertical direction of the black image display area AR2 to the width W1 in the vertical direction of the entire display image is represented by W2 / W1, and this ratio is for one frame period (TF). This coincides with T2 / TF which is a temporal ratio of the black insertion period T2. Further, the fact that a black image is displayed as described above based on this ratio means that, for example, within one frame period, only the time length corresponding to the time ratio represented by T2 / TF (W2 / W1) This means that a black image is displayed instead of an effective image.

  When the black image is displayed as described above, the time for rendering the image element corresponding to the effective image for each pixel is shortened accordingly. For example, in a cathode ray tube display device, motion blur is hardly a problem, as is well known, when an image element is actually displayed only when an electron beam is scanned to excite a phosphor. For this reason, the images of the previous and subsequent frames (fields) are less likely to remain as afterimages. In other words, by performing black insertion, the display of such an image element is approached, and therefore, the phenomenon of motion blur can be suppressed.

However, when a black image is inserted, the display time of the effective image per unit time is shortened, so that the perceived luminance with respect to the display of the effective image decreases. Therefore, in order to compensate for this decrease in luminance, for example, the display luminance of the original effective image itself may be set higher according to the decrease in luminance. In the liquid crystal display device as in the present embodiment, the display luminance of the effective image itself can be increased by increasing the light emission luminance of the discharge lamp in the backlight unit 16.
However, if the emission luminance of the backlight is increased, the power consumption increases accordingly. In particular, when displaying a still image (or an image having a content close to that of a still image), black image insertion is not necessary (or even a short time may be necessary). As a result, the luminance of the backlight is increased. That is, the increase in power consumption due to the increase in the light emission luminance of the backlight is almost wasted, and its irrationality becomes obvious.

Therefore, in the present embodiment, the black image insertion time length is not fixed, but is configured to be variable according to the state of motion of the display image. Hereinafter, this configuration example will be described.

First, an example of display driving for changing the time length of black image insertion in the present embodiment will be described with reference to the timing chart of FIG.
In FIG. 6, the horizontal scanning period Th within the frame period for each of the gate lines G1 to Gm and the black data application period Tblβ indicated by the broken line are the frames for each of the gate lines G1 to Gm shown in FIG. It is assumed that the timing is the same as the horizontal scanning period Th in the period and the black data application period Tbl. Therefore, the time length of the effective image display period T1β and the black insertion period T2β in FIG. 6 (synonymous with the time ratio of the black insertion period T2β to one frame period) is also the same as the effective image display period T1 and the black insertion period T2 of FIG. Is equal to the time length of the black insertion period T2α with respect to one frame period.
In FIG. 6, the black insertion period in one frame period is longer than this from the state in which the black image insertion is performed based on the time ratio of the effective image display period T1β and the black insertion period T2β. If, for example, the black data application period Tblα shown by the solid line in FIG. 6 is to be changed, the one corresponding to the black image in one frame period corresponding to each gate line is used. The timing for applying the pixel data is set earlier than the black data application period Tblβ.
The time length of the effective image display period T1β and the black insertion period T2β formed according to the setting of the black data application period Tblβ (the time ratio of the black insertion period T2β to one frame period) corresponds to the black data application period Tblα. Compared with the time length of the effective image display period T1α and the black insertion period T2α (time ratio of the black insertion period T2α to one frame period), the black insertion period T2β is longer than the black insertion period T2α. The time ratio of the black insertion period T2 to the frame period is also larger when the black insertion period T2β is set. This is the case where the black data application period Tblβ (black insertion period T2β) is set as the time during which a black image is inserted in a unit time based on the frame period (which may be considered as one frame period here). This is longer than when the black data application period Tblα (black insertion period T2α) is set.

FIGS. 5C and 5D show examples of image display states when display driving is performed by setting the timing of the black data application period Tblβ. 5A and 5B are examples of display states corresponding to the setting of the black data application period Tbl shown in FIG. 4, and in FIG. 6, the display corresponds to the timing setting of the black data application period Tblα. Become.
Here, as can be seen by comparing FIGS. 5C and 5D and FIGS. 5A and 5B,
The vertical width W3 of the black image display area AR2 shown in FIGS. 5C and 5D is larger than the width W2 of the black image display area AR2 shown in FIGS. In other words, the ratio (W3 / W1) of the width W3 in the vertical direction of the black image display area AR2 in the case of FIGS. 5C and 5D to the width W1 in the vertical direction of the entire display image is as shown in FIG. In the case of (b), it is larger than (W2 / W1). As can be understood from the description of FIGS. 5A and 5B, the time during which a black image is displayed in one frame period becomes longer as the ratio increases. That is, also in FIG. 5, it is shown that the black image display time in one frame period is longer when the black data application period Tblβ is set than when the black data application period Tblα is set. It is what has been.

As can be understood from the above description, in order to change the time during which the black image is displayed, it is only necessary to change the timing of the black data application period Tbl in the frame period for each gate line. . In order to lengthen the black image display time, as shown in FIG. 6, the timing of the black data application period Tbl is set earlier so that the black insertion period T2 becomes longer (one frame period TF). The time ratio with respect to is increased. On the contrary, if the black image display time is to be shortened, the timing of the black data application period Tbl is set to be delayed so that the black insertion period T2 is shortened (the time ratio with respect to one frame period TF is reduced). You can do it.
In this embodiment, for black image display, for example, the source driver 14 applies pixel data (black data) corresponding to the black image. Therefore, in order to realize the change of the timing (black image display time) of the black data application period Tbl as described above, it is only necessary to configure the timing at which the black data is applied by the source driver 14 to be variable. Become.

In addition, in the present embodiment, the change setting of the black image display time described above is performed by the control unit 19 in accordance with the movement of the effective image obtained as the analysis processing result of the moving image analysis unit 18. The
That is, as a concept of a basic control algorithm relating to the change of the black image display time, the content of the image (effective image) displayed on the display panel 17 is a state of motion in which the visually recognized motion blur is conspicuous. Accordingly, the black image display time is set to be long, and the black image display time is set to be short as the motion blur becomes inconspicuous.
The control unit 19 further sets the execution timing of the black data application period Tbl in one frame period based on the black image display time set in this way, and the set execution timing is set in this case. The second image processing unit 12 is instructed. In response to this, the second image processing unit 12 outputs a timing signal to the source driver 14 so that writing of the black image data is executed during the black data application period Tbl at the instructed execution timing. To be done.

  When the image content is such that motion blur is perceived by executing the algorithm as described above and display driving according to the algorithm, an appropriate time length determined according to the degree of motion blur is used. A black image is displayed, and motion blur can be effectively suppressed. On the other hand, in a still image state where motion blur is not perceived or in a state close to a still image that is difficult to perceive (both states are collectively referred to as a substantially still image state), a black image is displayed. The display is not performed or is set so as to be very short. As a result, in a substantially still image state, for example, a standard brightness is set, for example, without adopting a method of increasing the display brightness by increasing the light emission brightness of the discharge lamp in the backlight unit 16, for example. Even if it is set, it becomes possible to obtain a necessary and sufficient luminance of the image. In other words, for example, at least for substantially still image display, there is no need to increase the light emission luminance, and it becomes possible to eliminate the absurdity described above, It becomes possible to reduce electric power.

As described in the above description, the black image display time is set as a substantially still image state at least in the case of a motion image state that can be regarded as a substantially still image. It may be 0. For this purpose, the black data application period Tbl (black insertion period T2) is set in the frame period corresponding to each gate line (the period from the start of the horizontal scanning period Th to the next horizontal scanning period). For example, driving for displaying only a normal effective image as shown in FIG. 3 may be performed without setting. As described above, if the standard luminance is set as the display luminance in the configuration according to the embodiment described so far, a black image is displayed at least when a substantially still image is displayed. This is because when the time becomes zero, a display state with standard luminance is obtained, and necessary and sufficient image brightness is obtained.
Of course, even in an image state that can be regarded as a still image, display driving may be performed so that a black image display time exists in a short time. Even if the black image display time exists, if the time is within a certain range, it is possible to obtain sufficient luminance that does not impair the display image quality.

Next, a more specific configuration example of the algorithm for changing the black image display time according to the state of image movement according to the present embodiment will be described.
First, detection of the state of movement of an image displayed on the screen of the display panel 17 (liquid crystal panel unit 15) is performed by the moving image analysis unit 18 as described above. In other words, the moving image analysis unit 18 takes in a digital image signal that has been subjected to a predetermined signal processing stage in the first image processing unit 11 and uses a technique such as frame correlation, so-called motion detection. It is assumed that an analysis process for the image signal of the image is executed. Note that the motion detection technology actually employed in the moving image analysis unit 18 has been known so far, including, for example, those based on interlace / progressive conversion processing, encoding technology in the MPEG system, and the like. Technology that will be developed or put to practical use in the future.

Then, the moving image analysis unit 18 of the present embodiment obtains a numerical value as a motion amount for every pixel that is supposed to form a display image as a result of motion detection.
Information on the amount of movement for each pixel obtained by the moving image analysis unit 18 in this way is captured by the control unit 19. Then, the control unit 19 sets the black image display time based on the information on the amount of movement, for example, as described below.

First, the control unit 19 obtains the distribution information of the number of pixels with respect to the motion amount by using the value of the motion amount for each pixel that has been captured. For example, as schematically shown in FIGS. 7A, 7B, and 7C, this can be expressed as a histogram in which the horizontal axis represents the amount of motion and the vertical axis represents the number of pixels. FIGS. 7A, 7B, and 7C show examples of pixel number distributions obtained in accordance with motion detection results of different patterns, which will be described later.
In this embodiment, for example, as shown in FIGS. 7A, 7B, and 7C, a threshold value TH that is matched with the information on the pixel number distribution with respect to the amount of motion is set. The threshold value TH is set for the number of pixels in the histogram, but the threshold value TH is set so as to decrease as the value of the motion amount increases.

Then, after setting the threshold value TH as described above, the setting of the black image display time is basically determined in accordance with the total number of pixels that exceed the threshold value TH in the histogram. In the case of FIG. 6, the threshold value TH indicated by diagonal lines in the region surrounded by the curve indicating the pixel number distribution in FIGS. 7A, 7 </ b> B, and 7 </ b> C shown in each figure. The area of the region on the upper side corresponds to the above-mentioned “total number of pixels that have exceeded the threshold value TH in the histogram”.
Here, when the total number of pixels that exceed the threshold TH in the histogram is 0, for example (when there is no portion exceeding the threshold TH in the curve indicating the pixel number distribution), for example, the substantially still image described above As the state, the black image display time is set to the shortest in the variable range (including the possibility of not setting the black image display time). When the total number of pixels that exceed the threshold TH in the histogram is obtained as a value greater than 0, the black image display time increases in accordance with a predetermined rule as the value increases. It is set as follows. That is, as the total number of pixels that exceed the threshold TH in the histogram increases, it is assumed that the state of the image in which motion blur is conspicuous is perceived, and the degree of motion blur is less than a certain level. The idea is to increase the black image display time.

As described above, in the present embodiment, the value that is changed in accordance with the change in the amount of motion is set for the threshold value TH for the following reason.
For example, the state of the pixel number distribution with respect to the amount of motion as shown in FIG. 7B can be said to be a state in which an image portion with a large amount of motion exists but the number of pixels is not so large. Such a state is, for example, a state in which an image with a considerably large movement is displayed on the entire screen. More specifically, this corresponds to a state in which a tennis ball is moving due to a relay of a tennis game or the like. The motion of an image part like a tennis ball is perceived as a noticeable motion blur in contrast to the fact that the surrounding area is relatively close to a stationary state even though the area occupied on the screen is small. Are known. Therefore, in order to set an appropriate black image display time to adapt to such motion blur, the threshold value TH for the number of pixels decreases as the value of the motion amount increases in the distribution area. It can be said that it is necessary to set.

On the other hand, the state shown in FIG. 7C is a state in which the number of pixels in the distribution area with a large amount of motion is small and the number of pixels in the distribution area with a small amount of motion is large, contrary to FIG. is there. This is a state in which there is almost no image region with relatively large motion, but an image region with a small amount of motion occupies a large proportion of the entire image. Specifically, for example, a scene of an effort such as a sumo relay is a pattern having such a pixel number distribution.
In such an image state, the amount of motion is originally small, and motion blur is less likely to be perceived under the same number of pixels as compared to when the amount of motion is large. However, when the number of pixels increases to a certain extent, motion blur is perceived to a degree that cannot be ignored. Therefore, it is reasonable to set the threshold value TH higher as the amount of motion becomes smaller in the distribution area.
Taking this into consideration, in the present embodiment, the threshold value TH is changed from a higher value to a lower value as the amount of motion changes from a smaller value to a larger value. Is set. As for the relationship between the value of the motion amount and the threshold value TH, for example, the relationship between the actual content of the image signal (that is, the content of the display image) and the perceived state of motion blur was examined. It should be determined above and should not be limited here. For this reason, for example, the relationship between the threshold TH and the amount of motion is not limited to a proportional one as shown in FIG. For example, the correspondence of the threshold value to the amount of movement may be curvilinear or stepwise.

Further, the algorithm for setting the black image display time described with reference to FIG. 7 is merely an example, and various other algorithms can be considered.
For example, for the threshold value TH to be set for the histogram, it may be possible to adopt a simpler method in which a value corresponding to a predetermined number of pixels is fixedly set.
Further, in the description based on FIG. 7, in generating the histogram information, the motion amount for every pixel is obtained. However, for example, it is limited to pixels that form only a partial region in the entire display image. It is also conceivable to obtain the amount of motion of these pixels. An example of this case is a configuration in which the amount of motion is obtained for a pixel in a partial area that is substantially in the center of the entire display image. In general, it is considered that an object to be noted in a display image is likely to be in the center of the screen in consideration of composition and the like. Then, it is possible to take the idea that, with regard to motion blur, for example, if only the main subject on the screen as described above can be suppressed, a correspondingly good image quality can be maintained. Of course, under the present invention, the partial area in the entire display image formed from the pixels for which the amount of motion is to be calculated should not be limited to the center of the screen. The shape to be formed is not limited.
In this way, by limiting the number of pixels for obtaining the motion amount to a partial region in the entire display image, for example, analysis processing in the moving image analysis unit 18 and information on the motion amount in the control unit 19 This will reduce the burden on the processing. As a result, for example, the processing related to the black image display time setting corresponding to the motion of the image can be speeded up and stabilized. Further, when the moving image analysis unit 18 is configured by hardware, the circuit scale can be reduced, which is advantageous in terms of cost, for example.

By the way, as described above, when the black image display time is changed according to the movement of the image, the effective image within one frame period according to the change of the black image display time. The length of time that is displayed also changes. As a phenomenon that is actually perceived, this leads to the fact that the brightness appears to change as time passes when the displayed image is viewed. It is preferable that such a phenomenon is eliminated in consideration of practical use.
Therefore, the liquid crystal display device 1 according to the present embodiment is configured to vary the luminance of the image perceived as an effective image as the black image display time is changed. And in this Embodiment, in changing the brightness | luminance of the image itself perceived as an effective image, it is comprised so that the brightness | luminance of the discharge lamp light-emitted in the backlight part 16 may be variably controlled. Changing the luminance of the discharge lamp in this way is advantageous because it can be realized with a simpler configuration than when the luminance of the display image is varied by, for example, gradation control.

Such light emission luminance control can be realized, for example, when the control unit 19 controls the backlight driving unit 20.
That is, the control unit 19 sets the black image display time, for example, as described above, but in correspondence with the set black image display time, for example, as schematically shown in FIG. Sets the luminance increase rate with respect to the standard luminance. In FIG. 8, as an algorithm for setting the luminance increase rate, when the black image display time is 0, the luminance increase rate is set to 0 and the standard luminance is set, and the black image display time exceeds 0. An example is shown in which the luminance increase rate is increased at a predetermined ratio in proportion to the increase. Note that the relationship between the black image display time and the luminance increase rate shown in FIG. 8 is merely an example, and in actuality, for example, depending on conditions such as the actual black image display time and the degree to which the luminance of the display image is reduced. To be determined.
Then, the control unit 19 controls the light emission driving operation of the backlight driving unit 20 so that the light emission luminance in the backlight unit 16 actually changes in accordance with the luminance increase rate set in this way. To be.

FIG. 9 shows an example of the light emission driving operation by the backlight driving unit 20 in accordance with the control of the control unit 19.
First, the lighting drive for the discharge lamp of the backlight unit 16 by the backlight driving unit 20 here is followed by the discharge period Tdsc and the predetermined period time TC as shown in FIG. 9A. This is performed at a timing having a non-discharge period Trds. In the discharge period Tdsc, for example, a voltage is applied to put the discharge lamp into a discharge state, and the discharge lamp emits light when it enters the discharge state. On the other hand, the non-discharge period Trds is a period in which the voltage application for the above-described discharge is stopped, and thus the light emission of the discharge lamp is stopped in this period. That is, in this case, the discharge lamp is driven such that light emission with a time length corresponding to the discharge period Tdsc and non-light emission with a time length according to the non-discharge period Trds are repeated at a certain cycle time TC. Has been.
Note that, for example, the cycle time TC is at least about several tens of Hz when viewed as a frequency, and depending on the person, the cycle time TC is not perceived as blinking according to the cycle time TC, and is constantly lit. It is something that is perceived.

Here, for example, the time length of the discharge period Tdsc (time ratio (duty) between the discharge period Tdsc and the non-discharge period Trds) shown in FIG. 9A is assumed to be the standard light emission luminance of the backlight unit 16. . Then, for example, under this state, a certain luminance increase rate is given from the control unit 19 to the backlight drive unit 20 in accordance with the black image display time by a certain time length set by the control unit 19. Suppose you are instructed.
In response to this, the backlight drive unit 20 increases the time length of the discharge period Tdsc within the cycle time TC by an amount corresponding to the luminance increase rate, for example, as shown in FIG. The non-discharge period Trds is set short. That is, the time ratio (duty) between the discharge period Tdsc and the non-discharge period Trds in the cycle time TC is changed. This can be regarded as performing PWM (Pulse Width Modulation) control if each of the discharge period Tdsc and the non-discharge period Trds is regarded as a pulse width within a period.
Thus, by performing PWM control, the amount of light visually received by a person per unit time changes. That is, the luminance of the discharge lamp perceived by a person changes. In the case of the transition from FIG. 9A to FIG. 9B, the discharge period Tdsc within one cycle is long, and accordingly, the emission luminance of the discharge lamp perceived by a person is increased accordingly. Then, based on FIG. 8, the longer the black image display time set in the control unit 19, the higher the luminance increase rate is indicated, and the time length of the discharge period Tdsc within one cycle is extended. Will be.
For example, in this manner, the luminance of the display image is changed in accordance with the dynamic change in the black image display time by changing the light emission luminance of the backlight unit 16 (discharge lamp) in accordance with the black image display time. Will be canceled, and for example, it will appear as if image display with stable brightness is being performed.
Further, when the light emission luminance is varied in this way, the light emission luminance is increased as the black image display time becomes longer. The power consumption will increase. However, for example, when the black image insertion is performed with a fixed time length, as compared with the case where a constant luminance increase rate is fixedly maintained, the power consumption in a certain short period is Thus, the case where the light emission luminance is varied is more advantageous because it is reduced.

  Other methods for variably controlling the emission luminance of the backlight (discharge lamp) are also conceivable. For example, when a voltage is applied to the discharge lamp to drive light emission, a discharge current flows from the power source side of the backlight drive unit 20 to the discharge lamp. By controlling the amount of discharge current, the discharge current flows. In addition, it is possible to vary the light emission luminance of the discharge lamp. As the discharge current increases, the light emission brightness of the discharge lamp increases.

Further, the present invention is not limited to the configuration as the embodiment described so far.
For example, there are various basic driving methods for inserting a black image in the display driving by the hold method in addition to those shown in FIG. For example, there is known a technique that displays a black image of all horizontal lines at a predetermined timing based on a frame period. Further, a technique for increasing the speed of one frame period to a normal 1 / n speed is also known and can be applied to such display driving. In the embodiment, when a black image is inserted, the display period of the black image is always set for each frame (field) period, but for example, once every predetermined number of frames. It is conceivable to drive the black image display period at a ratio. That is, the display of the black image may be regarded as being executed at a predetermined timing within a period based on the frame period.

In the description of the embodiments so far, the liquid crystal display device is taken as an example. However, as the present invention, other than the liquid crystal display device, for example, a display device in general that is configured to perform display driving by a hold type. It is possible to apply to.
For example, an organic EL (Electro Luminescence) display can be cited as a display device other than the liquid crystal that is driven by the hold method. Even when the organic EL display is driven by the hold method, the same effect as described above can be obtained by variably setting the black image display time according to the motion detection result based on the present invention. Is obtained. However, since organic EL is self-luminous as is well known, in order to compensate for a decrease in the display luminance of an effective image due to a change in the black image display time, the luminance of the backlight is set as in this embodiment. Variable control is not possible. However, in this case, at the stage of gradation control for displaying an effective image, the display drive may be performed by setting an increase rate with respect to the standard gradation according to the black image display time. .

It is a block diagram which shows the structural example of the liquid crystal display device as embodiment of this invention. It is a figure which shows the circuit structural example of the liquid crystal panel part shown by FIG. 6 is a timing chart showing an example of basic display driving operation as a hold type in the liquid crystal display device of the present embodiment. 6 is a timing chart showing an example of basic display drive operation with black image insertion in the liquid crystal display device of the present embodiment. It is a figure which shows typically the state example of the image displayed as a result of the hold-type display drive accompanied by black image insertion. 5 is a timing chart showing an example of display drive operation for changing a black image display time as an example of display drive operation involving black image insertion in the liquid crystal display device of the present embodiment. It is for explaining an example of an algorithm for setting a black image display time in the present embodiment, and an example of a distribution of the number of pixels with respect to a motion amount obtained based on a motion amount for each pixel obtained from a motion detection result. FIG. It is a figure which shows the example of control of the light emission luminance of the backlight part according to black image display time in this Embodiment by the relationship between black image display time and a luminance increase rate. It is a figure which shows the operation example of the lighting drive by the backlight drive part in this Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Liquid crystal display device, 2 Pixel cell drive circuit, 3 Liquid crystal layer, Vcom opposing base | substrate, 10 Input terminal, 11 1st image processing part, 12 2nd image processing part, 13 Scan driver, 14 Source driver, 15 Liquid crystal panel part, 16 backlight unit, 17 display panel, 18 moving image analysis unit, 19 control unit, 20 backlight drive unit

Claims (5)

A display panel formed by arranging pixels in a matrix along the horizontal line direction and the vertical line direction is driven for image display, and the horizontal lines are sequentially scanned in a frame cycle. At the same time, in every scanning period of one horizontal line, the pixels constituting the scanned horizontal line are driven based on the image signal to display an image for one horizontal line, and this displayed one horizontal line is displayed. Image display driving means capable of being driven so as to continuously display the image portion until the pixels constituting the horizontal line are driven next;
Black image display for controlling the image display driving means so that a black image, which is an image corresponding to black, is displayed for each horizontal line by a required time length within a predetermined unit time based on the frame period. Control means;
A motion detecting means for detecting the motion of the image when the image signal that is the source of the image to be displayed by the image display driving means is input and the input image signal is displayed and output;
Black image display time setting means for displaying the black image by the black image display control means and variably setting the time length according to the state of motion of the image detected by the motion detection means;
An image display device comprising: Luminance control for varying the luminance of the effective image itself other than the black image displayed on the display panel unit according to the length of time for displaying the black image set by the black image display time setting means Means,
The image display apparatus according to claim 1, further comprising: A light source for irradiating light used for image display in the display panel unit;
And further comprising a lighting drive means for lighting the light source,
The brightness control means includes
By controlling the lighting drive means so that the brightness of the light emitted from the light source is variably set according to the time length for displaying the black image set by the black image display time setting means, The brightness of the effective image itself is configured to be variable.
The image display device according to claim 2. The motion detection unit is configured to obtain a motion amount for at least some of the pixels that form a frame image,
The black image display time setting means obtains distribution information indicating the distribution of the number of pixels according to the value of the amount of movement based on the amount of movement for each pixel, and the distribution indicated by the distribution information Set the length of time to display the black image according to the state,
The image display apparatus according to claim 1. A display panel formed by arranging pixels in a matrix along the horizontal line direction and the vertical line direction is driven for image display, and the horizontal lines are sequentially scanned in a frame cycle. At the same time, in every scanning period of one horizontal line, the pixels constituting the scanned horizontal line are driven based on the image signal to display an image for one horizontal line, and this displayed one horizontal line is displayed. An image display driving procedure for driving the image portion to be continuously displayed until the pixels that form the horizontal line are driven next;
Black for controlling the driving by the image display driving procedure so that a black image, which is an image corresponding to black, is displayed for each horizontal line by a predetermined time length within a predetermined unit time based on the frame period. Image display control procedure;
A motion detection procedure for detecting the motion of the image when the image signal that is the source of the image to be displayed by the image display driving procedure is input and the input image signal is displayed and output;
A black image display time setting procedure in which the black image is displayed by the black image display control procedure and the time length is variably set according to the state of motion of the image detected by the motion detection procedure;
The image display method characterized by performing.

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