JP2010044194A - Image-displaying device and backlight-controlling circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image-displaying device and a backlight-controlling circuit which each prevent a person from being dazzled even when a screen suddenly becomes bright. <P>SOLUTION: The image-displaying device 1 includes: a backlight 14; a display device 16 which modulates illumination light from the backlight 14, according to video signals, to display an image; a light quantity computing part 12 which increases or decreases the light quantity of the backlight 14 in accordance with the intensity of the brightness of the displayed image based on the video signals; and so on. The light quantity computing part 12 determines the light quantity of the backlight 14 so that the degree of the increase of the illumination light from the backlight 14 may be restrained on the basis of an alleviation function for restraining the degree of the increase of the illumination light which corresponds to the increase of the brightness of the displayed image based on the video signals. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an image display device including a backlight and a backlight control circuit.

  A liquid crystal display device displays an image on a screen using illumination light from a backlight disposed on the back of a liquid crystal panel. In a liquid crystal display device, the light quantity of the backlight affects the brightness of the entire screen. For this reason, in recent years, there have been many cases in which the amount of light of the backlight is adjusted according to the brightness of the image (see, for example, Patent Document 1).

One such technique is called dynamic backlight control. This dynamic backlight control determines whether the scene displayed on the screen is dark or bright using an average luminance level (APL; Average Picture Level) of the read video signal. For example, as shown in FIG. By reducing the amount of light from the backlight in a dark scene where the APL is low, and increasing the amount of light from the backlight in a bright scene where the APL is high, it is possible to create a sharp picture.
JP 2007-299001 A

  However, in the conventional liquid crystal display device that performs the dynamic backlight control as described above, a phenomenon of dazzling may occur when an extremely bright scene is displayed on the screen. That is, when a frame with a very high APL compared to the immediately preceding frame is displayed (for example, when moving from a frame that displays the entire black to a frame with a high APL), the amount of light from the backlight is also linked accordingly. Become extremely large. For this reason, the entire screen becomes brighter than necessary, and the amount of light entering the user's eyes increases rapidly, causing the user to feel dazzling. Conventionally, however, no countermeasure has been taken against this problem.

  The present invention has been made in view of such problems, and an object thereof is to provide an image display device and a backlight control circuit capable of preventing the user from feeling dazzled even when the screen is rapidly brightened. It is in.

  The image display device of the present invention includes a backlight, a display element that modulates illumination light from the backlight according to a video signal and displays an image, and a brightness of a display image based on the video signal. Control means for performing control so as to increase or decrease the amount of light of the backlight. This control means sets a mitigation function for suppressing the degree of increase in illumination light according to the increase in brightness of the display image based on the video signal, and based on this mitigation function, the illumination light from the backlight is set. It has a function of performing control so as to suppress the degree of increase.

  The backlight control circuit of the present invention is a detection means for obtaining the brightness of a display image in an image display device including a backlight and a display element that displays an image by modulating illumination light from the backlight according to a video signal. And control means for performing control so as to increase or decrease the amount of light of the backlight according to the brightness level of the display image detected by the detection means. This control means sets a mitigation function for suppressing the degree of increase in illumination light according to the increase in brightness of the display image based on the video signal, and based on this mitigation function, the illumination light from the backlight is set. Control is performed so as to suppress the degree of increase.

  In the image display device or the backlight control circuit of the present invention, the light amount of the backlight is controlled according to the brightness of the display image obtained from the video signal. At that time, the light amount of the backlight is adjusted so as to suppress the degree of increase of the illumination light according to the increase in the brightness of the display image using a preset reduction function. Then, image display is performed using the adjusted backlight illumination light.

  According to the image display device and the backlight control circuit of the present invention, the light amount adjustment is performed by using the reduction function so as to suppress the increase in the backlight illumination light according to the increase in the brightness of the display image. Therefore, the dazzling phenomenon can be suppressed. That is, even when the display image suddenly becomes brighter, the amount of light entering the user's eyes does not increase abruptly, and it can be prevented from feeling dazzling.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<First Embodiment>
FIG. 1 shows a schematic configuration of an image display apparatus provided with a backlight control circuit according to a first embodiment of the present invention. FIG. 2 shows an example of a mitigation function used for backlight light quantity control in this image display device, and FIG. 3 shows an example of backlight light quantity control.

  As illustrated in FIG. 1, the image display device 1 includes an image processing unit 10, an average luminance level detection unit 11, a light amount calculation unit 12, a backlight control unit 13, a backlight 14, a display device control unit 15, and a display device 16. I have.

  The image processing unit 10 performs various types of image processing, such as contrast enhancement processing and color balance correction processing, on the input video signal.

  The average luminance level detector 11 detects an average luminance level (APL) for each frame of the image signal subjected to image processing, and outputs it as APL information S0. Here, APL corresponds to a specific example of “brightness of display image” of the present invention. Further, the average luminance level detection unit 11 corresponds to a specific example of “detection means” of the present invention.

  The light quantity calculation unit 12 constitutes a specific example of the “control unit” in the present invention together with the backlight control unit 13 and corresponds to the brightness level of the display image detected by the average luminance level detection unit 11. Thus, control for increasing or decreasing the amount of light of the backlight 14 is performed. Specifically, the light quantity calculation unit 12 stores a mitigation function 20 (FIG. 2) for suppressing the degree of increase in illumination light according to the increase in brightness of the display image based on the video signal in a memory (not shown). Based on this mitigation function, a backlight light amount value that suppresses the degree of increase in illumination light from the backlight 14 is calculated and supplied to the backlight control unit 13. ing. Details thereof will be described later.

  The backlight control unit 13 adjusts the amount of light of the backlight 14, for example, along the line L <b> 1 in FIG. 3 so that the amount of light determined by the light amount calculation unit 12 can be obtained. The backlight 14 can be configured using, for example, a CCFL (Cold Cathode Fluorescent Lamp), but in addition, a plurality of LEDs that output white light or a plurality of LEDs that output R, G, and B color lights. Can be arranged and configured. Further, a plurality of such LEDs and a light guide plate may be combined.

  The display device control unit 15 outputs drive signals to a data driver and a gate driver (not shown) of the display device 16 based on the video signal input from the image processing unit 10. The display device 16 displays an image by modulating illumination light from the backlight 14 by driving a data driver and a gate driver based on the video signal. The display device 16 is a display element that requires a backlight, and for example, a liquid crystal display panel or the like is used. Here, the display device 16 corresponds to a specific example of “display element” of the invention.

  Next, the operation of the image display apparatus 1 having the above configuration will be described with reference to FIGS. 4A shows the relationship between time (horizontal axis) and APL (vertical axis), and FIG. 4B shows the relationship between time (horizontal axis) and the amount of light of the backlight 14 (vertical axis). To express.

[Overall operation]
First, the overall operation of the image display apparatus 1 will be described.
The image processing unit 10 performs various types of image processing on the input video signal, and then outputs the video signal to the average luminance level detection unit 11 and the display device 16. After detecting the APL for each frame of the video signal, the average luminance level detection unit 11 outputs the detection result to the light amount calculation unit 12.

  The light quantity calculation unit 12 calculates the light quantity of the backlight 14 according to APL using the reduction function 20 (FIG. 2). In the example illustrated in FIG. 2, the light amount calculation unit 12 obtains a reduction coefficient for each region of 0 ≦ APL <k1, k1 ≦ APL <k2, k2 ≦ APL <k3, k3 ≦ APL, and uses the obtained reduction coefficient. Based on this, the light quantity of the backlight 14 is obtained. Details thereof will be described later.

  The backlight control unit 13 acquires the backlight light amount determined based on the reduction function 20 from the light amount calculation unit 12, and performs control so as to suppress the degree of increase in illumination light from the backlight 14 based on this. Do. When the mitigation function has a function form as shown in FIG. 2, the amount of light from the backlight changes along the solid line L1 in FIG. 3, and the degree of increase in the amount of light from the backlight 14 is suppressed in the high luminance region. Be controlled. Accordingly, if the APL changes with time as shown in FIG. 4A, for example, the light quantity of the backlight 14 changes as shown by a solid line L4 shown in FIG. 4B, for example.

  Note that the broken line L0 in FIG. 3 indicates a comparative example that does not suppress the increase in the amount of light of the backlight in accordance with APL (when the reduction function (FIG. 2) in which the value decreases in the high luminance region is not applied, in other words, the reduction This shows the change in the amount of backlight when the function form has a constant value regardless of the magnitude of APL. A broken line L3 in FIG. 4B shows how the backlight light amount changes with time when the increase in the light amount of the backlight is not suppressed according to APL.

  As can be seen from FIGS. 3 and 4, the light amount of the backlight 14 is lower than the comparative example in the maximum value of the light amount of the backlight 14 that changes over time.

  The display device control unit 15 and the display device 16 modulate the illumination light from the backlight 14 based on the video signal input from the image processing unit 10 and display an image. At this time, since the maximum value of the amount of illumination light from the backlight 14 is lower than that of the comparative example, the user feels dazzled even if the display image changes from a dark scene to a bright scene. Can be prevented.

[Determination of backlight intensity]
Next, a method for determining the light amount of the backlight 14 will be described in detail with reference to FIGS.

  When the light amount calculation unit 12 calculates the light amount of the backlight 14, first, the mitigation function 20 (FIG. 2) for suppressing the degree of increase in the light amount of the backlight 14 according to the increase in APL is referred to. .

  In FIG. 2, the horizontal axis represents the APL of the display image, and the vertical axis represents a reduction coefficient that determines the suppression ratio of the increase in the amount of light of the backlight 14. A small reduction coefficient means that the degree of increase in the amount of light is more strongly suppressed, and a reduction coefficient of “1” means that the increase in the amount of light is not suppressed. In the example shown here, in order to smoothly change the degree of increase in the amount of light of the backlight 14, the APL change area is divided into four areas (0 ≦ APL <k1, k1 ≦ APL <k2, k2 ≦ APL <k3, k3 ≦ APL), the function form of the mitigation function 20 is varied for each region, and the function values are continuous between the regions. Here, k1, k2, and k3 are appropriately set according to characteristics of the display device 16, an image quality mode, a glare suppression pattern, and the like to be described later. Note that k1, k2, and k3 satisfy the relationship that 0 ≦ k1, k2, k3 <the maximum value of APL.

  The mitigation function 20 is a value (a mitigation coefficient) as shown in the equations (1) to (4) depending on the cases of 0 ≦ APL <k1, k1 ≦ APL <k2, k2 ≦ APL <k3, k3 ≦ APL. S).

0 ≦ APL <k1; S = 1 (1)
k1 ≦ APL <k2; S = 1 − ((1−s2) / (k2−k1)) × (APL−k1) (2)
k2 ≦ APL <k3; S = s2 − ((s2−s1) / (k3−k2)) × (APL−k (3)
k3 ≦ APL; S = s1 (4)

  Here, s1 and s2 are appropriately set according to the characteristics of the display device 16, the image quality mode, the glare control pattern, and the like. Note that s1 and s2 satisfy the relationship 0 <s1, s2 ≦ 1.

The light quantity calculation unit 12 obtains the light quantity of the backlight 14 by the following equation (5) using the reduction coefficient S obtained from the reduction function 20 according to the APL of the video signal.
Light amount of the backlight 14 = reduction coefficient S × normalization coefficient N × APL (5)
Note that the normalization coefficient N is for adjusting the APL to the brightness of the backlight 14 in a scaled manner.

  The increase tendency of the light amount of the backlight 14 calculated in this way is as shown by a solid line L1 in FIG. Here, in k1 ≦ APL <k2 and k2 ≦ APL <k3, the light quantity of the backlight 14 is a quadratic function with APL as a variable, and a part of the parabola is drawn.

  As shown in FIG. 3, in the comparative example (broken line L0), the amount of light from the backlight increases in proportion to the increase in APL, as in the case shown in FIG. On the other hand, in the present embodiment in which the light amount of the backlight 14 is adjusted using the reduction coefficient, when the APL is k1 or more, the increase in the light amount is suppressed as compared with the comparative example, and the APL is The higher the light intensity of the backlight 14, the stronger the suppression.

  As described above, according to the present embodiment, the light amount of the backlight 14 is calculated using the mitigation function 20, and the degree of increase of the illumination light of the backlight 14 is suppressed according to the increase of APL. Therefore, even when the display screen suddenly changes to a bright scene, the user can be prevented from feeling dazzling. Further, since the backlight 14 does not become too bright, it is possible to avoid consuming more power than necessary.

<Second Embodiment>
Next, a second embodiment of the invention will be described.
FIG. 5 shows a schematic configuration of the image display apparatus according to the second embodiment. In the present embodiment, a light amount calculation unit 22 is provided instead of the light amount calculation unit 12 in the first embodiment (FIG. 1). Unlike the light amount calculation unit 12 that always calculates the backlight light amount by using one reduction function fixedly, the light amount calculation unit 22 selects an optimum reduction function according to control information given from the outside. The amount of backlight light is calculated using the selected reduction function. Details will be described below.

  The light quantity calculation unit 22 receives the APL information S0 from the average luminance level detection unit 11, and receives the image quality mode information S1 and the glare suppression pattern information S2 from the outside. The image quality mode information S1 is information representing the image quality of the video displayed on the display device 16. The image quality mode includes, for example, a “dynamic” mode, a “standard” mode, a “cinema” mode, and a “custom” mode. The “dynamic” mode is an image quality mode that is adjusted for high brightness and high contrast, mainly used in stores, and the “standard” mode is designed for general broadcast viewing at home, with colors and brightness. This is an image quality mode that suppresses slightly. The “cinema” mode is an image quality mode suitable for movie viewing, and the “custom” mode is an image quality mode that exposes various image quality parameters so that the user can adjust the image quality. The glare suppression pattern information S2 is information indicating a suppression pattern when the degree of increase in the amount of light of the backlight 14 is suppressed. As a dazzling suppression pattern, for example, as described later (FIGS. 6 to 8), a “strong suppression pattern” that strongly suppresses the light amount of the backlight 14 for each image quality mode, and a moderate light amount suppression “ There are a “medium suppression pattern”, a “weak suppression pattern” that performs light amount suppression weakly, and “off” that does not perform light amount suppression.

  The light quantity calculation unit 22 holds a plurality of reduction functions having different function forms, and an optimal reduction among the plurality of reduction functions based on the APL information S0, the image quality mode information S1, and the glare suppression pattern information S2. A function is selected, and the amount of light of the backlight 14 is determined using a reduction coefficient obtained from the selected reduction function. The specific method will be described later. The image quality mode information S1 and the glare suppression pattern information S2 may be set, for example, by the user of the image display device 1, or program information (for example, EPG (Electric Program Guide)) is received by the television receiver. Then, it may be automatically set based on the program information.

  Other configurations are the same as those in FIG. 1, and a description thereof will be omitted.

  In the present embodiment, the light amount calculation unit 22 determines the image quality mode and the glare suppression pattern based on the given image quality mode information S1 and the glare suppression pattern information S2, and the determined image quality mode and the glare suppression pattern. In accordance with, a mitigation function is selected from a plurality of mitigation functions held. Then, the light amount calculation unit 22 calculates the light amount of the backlight 14 using the reduction coefficient obtained from the selected reduction function, and outputs the calculation result to the backlight control unit 13. As a result, the backlight 14 is suppressed from increasing in light quantity in an optimal manner determined from the image quality mode and the glare suppression pattern.

  Specific examples of the mitigation function are as follows, for example.

  6A to 6D show reduction functions when the image quality mode is the dynamic mode. 6A is when the glare suppression control is off, FIG. 6B is when the glare suppression is weak (weak suppression pattern), and FIG. 6C is when the glare suppression is medium ( (Medium suppression pattern), FIG. 6 (D) shows a reduction function when the glare suppression is strongly performed (strong suppression pattern).

  When the image quality mode is dynamic, it is used at the store, so the brightness of the backlight 14 is originally high to make a vivid image even in a bright store, so the glare suppression control is off. Even in this case (FIG. 8A), the increase in the amount of light of the backlight 14 is suppressed in the high luminance level region. Moreover, the range of the area | region which divides | segments APL and the value of a reduction coefficient differ for every glare suppression pattern, and as shown to FIG.7 (B)-(D), the rank (suppression intensity) of a glare suppression pattern The higher the value is, the stronger the rate of increase in illumination light from the backlight 14 is suppressed.

  FIGS. 7A to 7D show reduction functions when the image quality mode is the standard mode. 7A is when the glare suppression control is off, FIG. 7B is when the glare suppression is weakly performed, FIG. 7C is when the glare suppression is medium, FIG. 7D. Indicates a reduction function when the dazzling suppression is strongly performed.

  Even when the image quality mode is standard, as in the case of the dynamic mode, since the brightness of the backlight 14 is high on the premise of viewing in a general living room, glare suppression is turned off. However, the light quantity of the backlight 14 is suppressed in the high luminance level region. However, in the standard mode, when the dazzling suppression patterns of the same rank are compared, the low luminance region (the region where the reduction coefficient is a constant value “1”) that does not perform the dazzling suppression is wider than in the dynamic mode ( To a higher luminance range). Also, in the case of the standard mode, the range of the area where the APL is divided and the reduction coefficient differ for each glare suppression pattern, and as shown in FIGS. 8B to 8D, the rank of the glare suppression pattern The higher the value is, the more the rate of increase in illumination light from the backlight 14 is suppressed. However, in the standard mode, when the dazzling suppression patterns of the same rank are compared, the dazzling suppression strength is weaker (a reduction factor is larger) than in the dynamic mode.

  FIGS. 8A to 8D show reduction functions when the image quality mode is the cinema mode or the custom mode. 8A is when the glare suppression control is off, FIG. 8B is when the glare suppression is weakly performed, FIG. 8C is when the glare suppression is medium, FIG. 8D. Indicates a reduction function when the dazzling suppression is strongly performed.

  When the image quality mode is cinema or custom mode, the brightness of the backlight 14 is lower than that in the case of dynamic or standard for making a picture suitable for movie viewing or for default setting. When the glare suppression control is off, the light intensity increase suppression control is not performed at all regardless of the value of APL (the reduction coefficient is a constant value “1”). For this reason, the relationship between APL and the amount of light of the backlight is as shown in FIG. On the other hand, when the glare suppression control is other than OFF (FIGS. 8B to 8D), as in the other image quality modes, the range and reduction of the area where the APL is divided for each glare suppression pattern The coefficients are different, and as the glare suppression pattern is strengthened, the rate of increase in illumination light from the backlight 14 is more strongly suppressed. However, in cinema or custom mode, when comparing dazzling suppression patterns of the same rank, low brightness areas that do not suppress dazzling (areas where the reduction factor is a constant value “1”) are higher than in standard mode. Wide (so that it extends to a higher luminance region). In the cinema or custom mode, when the dazzling suppression patterns of the same rank are compared with each other, the dazzling suppression strength is weaker (the reduction coefficient is larger) than in the standard mode. As described above, when the image quality mode is the cinema mode or the custom mode, the increase in the amount of light of the backlight is selectively suppressed depending on whether or not the glare suppression pattern is “off”. It may or may not be done).

  While the present invention has been described with reference to some embodiments, the present invention is not limited to the above embodiments, and various modifications can be made.

  For example, in the above embodiment, the case where the APL is divided into four regions has been described. However, the APL may be divided into regions other than the four regions, and the mitigation function may be set for each region. You may make it set one mitigation function (for example, monotone decreasing function) to the whole, without dividing | segmenting.

  In the above embodiment, the case where APL is detected for each frame of the video signal has been described. However, the display area of one frame is divided into a plurality of areas, the APL is detected for each divided display area, and divided display is performed. You may make it apply a mitigation function for every area | region.

  In the above embodiment, a case has been described in which a mitigation function whose function form is a straight line is applied to each area obtained by dividing the APL, but a mitigation function whose function form is a curve is applied to each area. You may make it do. Further, as shown in FIG. 9, a reduction function (for example, a quadratic curve) having a functional form that forms a single curve may be applied without dividing the APL.

  In the above embodiment, a case has been described in which a reduction function is set such that function values are continuous between regions obtained by dividing the APL. However, as shown in FIG. A function (for example, a step function) may be applied.

  In the second embodiment, a case where any one of a plurality of reduction functions held in advance is selected based on image quality mode information S1 and glare suppression pattern information S2 given from the outside. As described above, a necessary reduction function may be supplied together with the video signal from the outside, and this may be used to suppress an increase in the amount of light of the backlight 14.

  In the second embodiment, the case where the reduction function is selected according to the type of the video signal has been described. However, the reduction function may be selected regardless of the type.

1 is a block diagram illustrating a schematic configuration of an image display device according to a first embodiment of the present invention. It is a graph showing an example of a mitigation function. It is a graph showing the relationship between APL and a backlight light quantity. It is a graph showing an example of the time change of APL and the time change of a backlight light quantity. It is a block diagram showing schematic structure of the image display apparatus which concerns on the 2nd Embodiment of this invention. It is a graph showing four examples of the reduction function when the image quality mode is dynamic. It is a graph showing four examples of the reduction function when an image quality mode is standard. It is a graph showing four examples of the reduction function when the image quality mode is cinema and custom. It is a graph showing the reduction function whose function form is a curve. It is a graph showing the reduction function whose function form is step shape. It is a graph showing the relationship between APL and the light quantity of a backlight in the conventional image display apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image display apparatus, 10 ... Image processing part, 11 ... Average brightness level detection part, 12, 22 ... Light quantity calculation part, 13 ... Backlight control part, 14 ... Backlight, 15 ... Display device control part, 16 ... Display Device, 20 ... reduction function, S0 ... APL, S1 ... image quality mode information, S2 ... glare suppression pattern information.

Claims (7)

With backlight,
A display element that displays an image by modulating illumination light from the backlight according to a video signal;
Control means for performing control so as to increase or decrease the amount of light of the backlight according to the brightness level of the display image based on the video signal,
The control means determines the degree of increase in illumination light from the backlight based on a mitigation function for suppressing the degree of increase in the illumination light according to the increase in brightness of the display image based on the video signal. An image display device having a function of performing control to suppress. The image display device according to claim 1, wherein the control unit divides the entire display region into a plurality of regions and increases or decreases the amount of light of the backlight in each divided region according to the brightness level of the display image. The control means selectively performs control for suppressing increase in the amount of light of the backlight.
The image display device according to claim 1. The control means performs selective suppression control for increasing the amount of light of the backlight based on the type of video signal.
The image display device according to claim 3. The control means selects any one of a plurality of different mitigation functions prepared for each type of video signal, and performs suppression control for increasing the amount of light of the backlight for each type of video signal. The image display device described. The control means sets a plurality of suppression patterns when suppressing the increase degree of the illumination light, and suppresses the increase degree of the illumination light based on a reduction function corresponding to each suppression pattern. The image display device according to claim 1, wherein control is performed. Detection means for obtaining brightness of a display image in an image display device including a backlight and a display element that displays an image by modulating illumination light from the backlight according to a video signal;
Control means for performing control to increase or decrease the amount of light of the backlight according to the brightness level of the display image detected by the detection means,
The control means determines the degree of increase in illumination light from the backlight based on a mitigation function for suppressing the degree of increase in the illumination light according to the increase in brightness of the display image based on the video signal. A backlight control circuit having a control to suppress.

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