JP2005352269A - Image display device and light source control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the blinking feel of an image due to a fluctuation in brightness of a back light in control of the brightness of the back light. <P>SOLUTION: An average luminance detector 5 calculates the average luminance per frame of a luminance signal and outputs the same to a light source controller 13 and a light source control decision section 16 out of image signals inputted in an image display device. The light source control decision section 16 makes decision as to whether the brightness of a light source 2 is to be fluctuated or not by the light source controller 13 from the result obtained by comparing the inputted average luminance and the average luminance of the previous frame. If the difference of the average luminance as a result of the decision is below the prescribed value, the light source control decision section notifies the light source controller 13 so as to disable the control of the light source 2 according to a fine change in the average luminance. The light source controller 13 drives and controls the light source 2 in such a manner that the brightness suitable for displaying the frame is attained by the average luminance inputted by the average luminance detector 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transmissive or reflective image display apparatus and a light source control method for dynamically adjusting the luminance of a light source according to a video signal.

  In recent years, in display devices that display images by illuminating a display portion that displays an image depending on the amount of light transmission, such as a liquid crystal display device, by using a light source to improve the visibility, the characteristics of the video signal are extracted. At the same time, an image quality improvement method for improving the image quality by changing the brightness of the light source and a display device that implements the image quality improvement method have been proposed. For example, the technique disclosed in Patent Document 1 controls the brightness of a backlight of a liquid crystal display device according to the average luminance per image frame and the number of pixels that can be regarded as a peak, thereby improving the sharpness, stereoscopic effect, metal Improve glossiness.

  FIG. 21 shows an example of an image display device disclosed in Patent Document 1. The average luminance detecting unit 75 detects the average luminance per frame from the luminance signal included in the input video signal. The peak detection unit 77 compares the luminance signal included in the input video signal with a certain threshold, and if the luminance signal is larger than the threshold, the pixel is regarded as a peak, and the number of pixels that can be regarded as a peak included in one frame is detected.

The backlight control unit 73 controls the brightness of the backlight 72 according to the characteristics shown in FIG. 22 from the average luminance detected by the average luminance detection unit 75 and the number of pixels that can be regarded as the peak detected by the peak detection unit 77. By performing such control, the liquid crystal display unit 74 on which an image is displayed by the display control unit 79 can effectively express sharpness, three-dimensionality, and glossiness, and there is no peak and the entire screen is dark. Black float can be suppressed.
International Publication No. WO 03/038799

  In many images, the above-described control improves the image quality. However, the brightness of the backlight may become excessive due to the type and noise of the input image, resulting in a blinking feeling. For example, when irregular noise enters the signal, the average luminance or the number of pixels that can be regarded as a peak changes due to the noise. If you are affected by such noise in a complete still image or a landscape image with little movement even in a moving image, the average luminance detected by the average luminance detection unit is almost unchanged, even though the displayed image is almost unchanged. Since the number of pixels that can be regarded as a peak detected by the peak detection unit changes, the brightness of the backlight changes, and the change in brightness is recognized by the observer as a blinking sensation.

  A similar decrease can occur depending on the type of input image. For example, in a landscape image with little motion including a water surface that reflects light, the number of pixels that can be regarded as a peak varies due to a subtle change in the reflection of light on the water surface. It also affects the average brightness. In such a case, the entire image is recognized with little movement, but the brightness of the backlight changes due to fluctuations in the average luminance and the number of pixels that can be regarded as the peak. It becomes easy to be caught by the person.

  Therefore, in view of the above problems, the present invention provides an image display device and a light source control method capable of suppressing the blinking feeling of an image due to fluctuations in the brightness of the backlight in the control of the brightness of the backlight. Objective.

  The image display device and the light source control method according to the present invention have the following features in order to solve the above-described problems.

The image display apparatus according to the present invention includes a light source, an image display unit that displays an image by controlling a transmission amount of light from the light source, and a luminance of an arbitrary frame for a video signal input to the image display unit. A luminance detection means for detecting a level characteristic; a detection result of the luminance detection means; a light source control determination means for determining whether or not to control the brightness of the light source based on the latest past detection result; When the light source control determining means determines not to control the brightness of the light source, the control for changing the brightness of the light source is not performed, and when the light source control determining means determines to control the brightness of the light source. And light source control means for performing control to vary the brightness of the light source based on the detection result of the luminance detection means.
The light source control method according to the present invention includes a light source and a light source control method for an image display device that includes an image display unit that displays an image by controlling an amount of light transmitted from the light source. A feature of a luminance level of an arbitrary frame is detected for an input video signal, and it is determined whether or not to control the brightness of the light source based on the luminance level detection result and the latest past detection result, When it is determined that the brightness of the light source is not controlled, control for changing the brightness of the light source is not performed, and when it is determined that the brightness of the light source is controlled, the brightness of the light source is set as the brightness. Control that varies based on the level detection result is performed.

  With the above features, high-quality images with sharpness, three-dimensionality, and glossiness can be displayed by controlling the brightness of the light source, and a stable display can be realized by suppressing flickering due to noise and image characteristics. .

The image display apparatus according to the present invention includes a light source, an image display unit that displays an image by controlling a transmission amount of light from the light source, and a luminance of an arbitrary frame for a video signal input to the image display unit. A luminance detection means for detecting a level feature; a luminance distribution detection means for detecting a luminance distribution of an arbitrary frame of a video signal input to the image display means; a detection result of the luminance detection means; and the luminance distribution A light source control determination unit that determines whether or not to control the brightness of the light source based on the detection result of the detection unit and the detection result of either or both of the most recent past; When it is determined that the brightness of the light source is not controlled, the brightness of the light source is not controlled, and when the light source control determination unit determines to control the brightness of the light source, the brightness of the light source is set. And a light source control unit that performs control to vary based on a detection result of the luminance detection unit and the luminance distribution detection unit.
The light source control method according to the present invention includes a light source and a light source control method for an image display device that includes an image display unit that displays an image by controlling an amount of light transmitted from the light source. A feature of a luminance level of an arbitrary frame is detected from an input video signal, a luminance distribution of an arbitrary frame is detected, a detection result of the luminance level, a detection result of the luminance distribution, and the latest past Whether to control the brightness of the light source based on both or one of the detection results, and when it is determined not to control the brightness of the light source, control to vary the brightness of the light source If it is determined that the brightness of the light source is controlled without performing the control, the brightness of the light source is controlled to vary based on the detection result of the luminance level and the detection result of the luminance distribution. To.

  Due to the above features, by controlling the brightness of the light source by the average brightness, it is possible to display a high-quality image with sharpness, three-dimensionality, and glossiness, while suppressing the flickering feeling caused by noise and image characteristics, and a brighter part Therefore, it is possible to realize a suitable image display in which black floating on a dark screen is suppressed as a whole.

  The image display device according to the present invention is characterized in that the luminance detecting means detects an average luminance level of one arbitrary frame. The light source control method according to the present invention is characterized in that the characteristic of the luminance level is an average of luminance levels of an arbitrary frame.

  With the above characteristics, a high-quality image with a sharpness, a three-dimensional effect, and a glossy feeling can be displayed by controlling the brightness of the light source.

  The image display apparatus according to the present invention is characterized in that the luminance detecting means detects a total luminance level of one arbitrary frame. The light source control method according to the present invention is characterized in that the characteristic of the luminance level is an average of luminance levels of an arbitrary frame.

  With the above feature, the circuit scale and the processing amount can be reduced as compared with the case of detecting the average luminance, and a high-quality image with the same level of sharpness, stereoscopic effect, and glossiness can be displayed.

In the image display device according to the present invention, the light source control determination unit changes a difference between detection results that are temporally continuous based on a detection result by the luminance level feature detection unit and a luminance level feature detection result in the latest past. Based on this, it is determined whether to control the brightness of the light source.
In the light source control method according to the present invention, the brightness of the light source is controlled based on a change in a difference between temporally continuous luminance level features based on the luminance level feature and the latest past luminance level feature. It is characterized by determining whether to do.

In the image display device according to the present invention, the light source control means is based on a change in a difference between temporally continuous detection results based on a detection result by the luminance distribution detection means and a luminance distribution detection result in the latest past. It is characterized by determining whether to control the brightness of the light source.
The light source control method according to the present invention determines whether to control the brightness of the light source based on a change in a difference between temporally continuous luminance distributions based on the luminance distribution and the latest past distribution. It is characterized by doing.

  With the above characteristics, it is possible to suppress a flickering feeling caused by noise and image characteristics and realize a stable display.

The image display device according to the present invention is characterized in that the detection result in the latest past is a detection result of at least two frames.
The light source control method according to the present invention is characterized in that the most recent past luminance level feature and luminance distribution are at least two frames or more.

  Due to the above characteristics, it is possible to display an image with a sharpness, a three-dimensional effect, and a glossy feeling following the change even when monotonously increasing or decreasing.

The image display device according to the present invention is characterized in that the light source control means changes the brightness of the light source within a width of 5% or less when the light source is lit brightest.
The light source control method according to the present invention is characterized in that the brightness of the light source is changed within a width of 5% or less when the light source is lit brightest.

  With the above characteristics, it is possible to suppress a flickering feeling caused by noise and image characteristics and realize a stable display.

  According to the present invention, in an image display device that dynamically adjusts the luminance of a light source according to a video signal, the light source can be adjusted to have a brightness suitable for each frame by detecting the average luminance and luminance distribution of one frame. By controlling, it achieves a high-quality image by expressing sharpness, three-dimensionality, and glossiness, and by detecting the difference from the past frame and limiting the brightness of the light source that changes between frames, noise And flickering caused by image characteristics. Thereby, it is possible to display a suitable image with high quality and no sense of incongruity.

  Embodiments of an image display device according to the present invention will be described below with reference to the drawings.

<First Embodiment>
FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of an image display apparatus according to the invention. The image display device 11 includes a light source 2, a light source control unit 13, a display unit 4, an average luminance detection unit 5, and a light source control determination unit 16.

The display unit 4 is configured by arranging a large number of minute devices that control the amount of light transmission, such as liquid crystal, and displays an image with light and dark gradations generated by controlling the amount of light transmission according to the position. Means. Although it is possible to display an image only with the display unit 4, if the amount of transmitted light is small, the contrast is low and the visibility is poor. Improve image visibility.
The average luminance detection unit 5 calculates the average luminance per frame of the luminance signal among the image signals input to the image display device 11 and outputs the average luminance to the light source control unit 13 and the light source control determination unit 16.

The light source control unit 3 drives and controls the light source 2 so that the brightness is suitable for displaying the frame based on the average luminance input from the average luminance detection unit 5. For example, the drive control method is shown in FIG.
As shown in FIG. 6, the light source 2 is controlled to be bright when the average luminance is small, and the light source 2 is darkened when the average luminance is large.

  By controlling in this way, it is possible to effectively prevent the display image from being felt too bright or conversely too dark and display an easy-to-see screen. Further, compared to the case where the brightness of the light source 2 is kept constant, there is a sharpness between the case where the screen is dark and the case where the screen is bright, and the display has an increased glossiness such as metal.

The light source control determination unit 16 determines whether or not the light source control unit 13 varies the brightness of the light source 2 based on the result of comparing the input average luminance and the average luminance of the previous frame.
The average luminance of one frame obtained when the same image is input is basically the same. However, even if the same image is input, the average luminance may differ due to the influence of noise or the like. For example, in the case of an image showing a water surface or the like, although the same scene is shown, the average luminance varies finely due to a subtle change in reflection on the water surface.

  In such a case, if the brightness of the light source 2 is changed according to the average luminance, the observer will recognize that the screen flickers, causing deterioration in image quality. An example of the change in the average luminance and the brightness of the light source 2 at this time is shown in FIG. The brightness of the light source 2 indicated by the broken line is also changed in synchronization with the change in the average luminance indicated by the solid line.

  In order to prevent this, the light source control determination unit 16 determines that the light source 2 cannot be controlled in accordance with a minute change in average luminance when the difference in average luminance is equal to or smaller than a predetermined value. 13 is notified.

When the light source control unit 13 receives a notification from the light source control determination unit 16 that the control of the light source 2 is disabled, the light source control unit 13 controls the brightness of the light source 2 to be in the same state as the previous frame. An example of the change in the average brightness and the brightness of the light source 2 at this time is shown in FIG. The brightness of the light source 2 indicated by the broken line is kept constant with respect to the fluctuation of the average luminance indicated by the solid line, and flickering of the screen can be avoided.
When the light source control unit 13 receives a notification that the light source 2 can be controlled from the light source control determination unit 16,
Based on the detection result of the average luminance detector 5, the normal light source 2 is controlled.

<Second Embodiment>
Next, a second embodiment of the image display apparatus according to the present invention will be described with reference to FIG. FIG. 5 is a block diagram showing a schematic configuration of the second embodiment of the image display apparatus according to the invention.

In the first embodiment, the method of controlling the brightness of the light source 2 based on the average luminance of one frame of the image has been described. However, the same effect can be obtained by using the total luminance value as a reference instead of the average luminance. That is, as shown in FIG. 2, when the total luminance value is high, the light source is darkened, and when the total luminance value is low, the light source is brightened so that the display image is too bright or conversely too dark. In addition to preventing this effectively, there is a sharpness between when the screen is dark and when it is bright, and it is possible to display an image with increased glossiness such as metal.
The average luminance of one frame is a numerical value obtained by dividing the total luminance by the number of pixels per frame, and both numerical values can be regarded as parameters having equivalent information. In addition, there is an advantage that the circuit scale and the processing amount can be reduced by eliminating the division.

  FIG. 5 shows a block diagram of the image display device 21 that controls the light source 2 based on the total luminance of one frame. The image display device 21 includes a light source 2, a light source control unit 23, a display unit 4, a luminance total detection unit 25, and a light source control determination unit 26. The image display device 21 operates based on the total luminance of one frame detected by the total luminance detection unit 25 instead of the average luminance of one frame. That is, the light source control determination unit 26 determines whether the light source control unit 23 changes the brightness of the light source 2 based on the result of comparing the luminance total value detected by the luminance total detection unit 25 with the luminance total value of the previous frame. It is determined whether or not, and the determination result is notified to the light source control unit 3.

When the light source control unit 23 receives the notification from the light source control determination unit 26 and changes the brightness of the light source 2, the brightness suitable for displaying the frame based on the total luminance value detected by the total luminance detection unit 25. The light source 2 is driven and controlled so as to be the same. When the brightness of the light source 2 is not changed, the brightness of the light source 2 is controlled to be the same as that of the previous frame regardless of the brightness total value detected by the brightness total detection unit 25.
By controlling in this way, it is possible to automatically correct the brightness of the light source 2 in accordance with the characteristics of the image and to display an image that avoids flickering.

<Third Embodiment>
Next, a third embodiment of the image display apparatus according to the present invention will be described with reference to FIG.
FIG. 6 is a block diagram showing a schematic configuration of the third embodiment of the image display apparatus according to the invention. The image display device 31 includes a light source 2, a light source control unit 33, a display unit 4, an average luminance detection unit 5, a light source control determination unit 36, and a luminance distribution detection unit 7.

As shown in FIG. 2, when the average luminance of the luminance signal of one frame is high, the light source is darkened, and when it is low, it is brightened, thereby effectively preventing the display image from being felt too bright or conversely too dark. At the same time, there are sharpness in the case where the screen is dark and bright, and an image with an increased glossiness such as metal can be displayed. However, even images with low average brightness are generally dark, and in images with few particularly bright pixels such as night scenes and fireworks, the so-called black float that causes the part that should be black to appear black appears when the light source is brightened. In some cases, the image quality may be deteriorated.
The above problem can be avoided by detecting the luminance distribution in addition to the average luminance of one frame.

  There is a certain tendency in the luminance distribution of one frame depending on the type of image. An image with a large contrast between light and dark, such as a night view or fireworks, has a bipolar distribution as shown in FIG. On the other hand, the overall dark image has a distribution shape close to the normal distribution as shown in FIG.

  The luminance distribution detection unit 7 detects the distribution shape of the luminance signal of one frame and notifies the light source control unit 33 and the light source control determination unit 36 of the shape. The detection of the distribution shape may not be a subdivided histogram as shown in FIG. 7 or FIG. For example, when histograms of only pixels having higher and lower brightness than α are created with reference to the brightness α in FIGS. 7 and 8, the results are as shown in FIGS. 9 and 10. Even in the normal distribution as shown in FIG. 8, when the peak and α are close to each other, the shape as shown in FIG. 10 can be obtained, but the average luminance differs between the normal distribution shape and the bipolar distribution shape. Therefore, even with the simplified histograms as shown in FIGS. 9 and 10, the above-described black float can be suppressed by making a judgment together with the average luminance. Such a simplified histogram can be easily obtained by simply counting either the number of pixels with a luminance higher than a certain reference value α or the number of pixels with a luminance lower than α if the number of pixels on the entire screen is known. It is done.

  The light source control determination unit 36 compares the average luminance of one frame detected by the average luminance detection unit 5 and the luminance distribution of one frame detected by the luminance distribution detection unit 7 with the previous frame and the difference between them. If the difference is smaller than the set threshold value, the brightness of the light source 2 is changed. If the difference is smaller than the set threshold value, the current brightness is determined to be maintained, and the determination result is notified to the light source control unit 33.

  When the light source control unit 33 adjusts the brightness of the light source 2 according to the determination of the light source control determination unit 36 according to the determination result of the light source control determination unit 36, the average luminance of one frame detected by the average luminance detection unit 5 Then, the light source 2 is controlled so as to obtain an optimum brightness from the luminance distribution of one frame detected by the luminance distribution detecting unit 7. When the brightness of the light source 2 is not adjusted by the determination of the light source control determination unit 36, the light source 2 is controlled so as to maintain the current brightness.

  Instead of detecting the average luminance by the average luminance detecting unit 5, a luminance total detecting unit 25 may be used as shown in FIG. In this case, the light source control determination unit 46 compares the total luminance of one frame detected by the luminance total detection unit 5 and the luminance distribution of one frame detected by the luminance distribution detection unit 7 with both values from the previous frame. If the difference is larger than the set threshold, the brightness of the light source 2 is changed. If the difference is smaller than the set threshold, the current brightness is maintained, and the determination result is notified to the light source controller 33. . Further, the light source control unit 43 controls the brightness of the light source 2 based on the total luminance and luminance distribution of one frame.

<Fourth Embodiment>
Next, a fourth embodiment of the image display device according to the present invention will be described.
The light source control determination units 16, 26, 36, and 46 in the first to third embodiments all determine only by comparison with the previous frame. However, only by comparing with the previous frame, it is not possible to distinguish between the average luminance or luminance total due to noise and image properties, and the fluctuation of luminance distribution, and the monotonically increasing or decreasing monotonically changing. In the case of monotonous decrease, the control may be insufficient.

  In FIG. 12, the average luminance or the total luminance when the average luminance is monotonously decreased is indicated by a solid line, and the change in the brightness of the light source 2 is indicated by a broken line. In the third embodiment, the luminance distribution originally affects the control of the light source, but it is omitted here for simplicity.

When the control is performed only by comparing the two frames before and after, it is determined whether or not the brightness of the light source is changed depending on whether the difference between the average luminance or the total luminance of the two frames is a certain threshold value or less. Therefore, when the average brightness or the monotonic increase / decrease of the total brightness occurs within the change range below the threshold, the brightness of the light source does not change at all, regardless of the change of the average / total brightness signal, and effective control is achieved. It becomes impossible. When the average luminance decreases monotonously as shown in FIG. 12, the brightness of the light source remains dark even if the average luminance decreases, and the above-described image quality improvement effect cannot be obtained.
Therefore, in the present embodiment, whether to change the brightness of the light source or not is determined from the average luminance or the total luminance between the frames in the past several frames and the difference in the luminance distribution.

  A block diagram of this embodiment is shown in FIG. The light source control determination unit 36 of FIG. 6 described in the third embodiment is replaced with a light source control determination unit 56. The light source control determination unit 56 according to the present embodiment determines whether or not the brightness of the light source has been changed based on the average luminance or the total luminance in the latest three frames and the difference in luminance distribution according to the table shown in FIG.

  Differences 1 and 2 in FIGS. 14 and 15 are differences in average luminance or luminance total between the latest three frames, and luminance distribution (number of pixels greater than or equal to the reference value α). The difference between the current frame and the immediately preceding frame is difference 1, and the difference between the immediately preceding frame and the immediately preceding frame is difference 2. FIG. 14 shows an example of a table when the difference is taken as an absolute value, and FIG. 15 shows a table example when the difference is taken with a sign. In FIG. 14 and FIG. 15, the combination that changes the brightness of the light source is 1, and the combination that does not change is 0.

  When the difference is smaller than the threshold value β, it is assumed that the difference is less than the noise and the brightness of the light source is fixed. However, when the difference is completely zero, the brightness of the light source is controlled to change from a slightly fluctuating image below the threshold β to a non-fluctuating image such as a still image. And the brightness of the light source at that time can be changed to an optimum brightness according to the average luminance or the total luminance and the luminance distribution.

  FIG. 16 and FIG. 17 show the relationship between the average brightness or the total brightness and the brightness of the light source when the light source control is performed using the tables of FIGS. 14 and 15 for the same image input as FIG. According to the table in FIG. 14, the light source is controlled so that the optimum brightness is obtained when the continuous average luminance change is stopped as shown in FIG. 16. According to the table of FIG. 15, the brightness of the light source is controlled while following a continuous change as shown in FIG.

  In this embodiment, the case where the presence / absence of the brightness control of the light source is determined based on the difference between the three most recent frames as an example has been described. Thus, it is possible to appropriately determine whether or not to control the brightness of the light source.

  Further, in the present embodiment, the configuration in which the light source control determination unit 36 in FIG. 6 is replaced with the light source control determination unit 56 is illustrated in FIG. 13 as an example, but the image display device 11 illustrated in FIGS. The same effect can be obtained by replacing the light source control determination units 16, 26, 46 of 21 and 41 with the light source control determination unit 56.

<Fifth Embodiment>
Next, a fifth embodiment of the image display apparatus according to the present invention will be described with reference to FIG. FIG. 18 is a block diagram showing a schematic configuration of the fifth embodiment of the image display apparatus according to the invention.

  The cause of the flickering feeling of the screen is that the brightness of the light source changes abruptly in addition to the slight shaking caused by the noise or the like touched in the first embodiment. Compared to the case where it changes gently, the difference in brightness is easily recognized by the observer's eyes, and the flickering feeling is strongly recognized. When the brightness of the light source is controlled by the luminance signal of the image, this sudden change is easy because the average luminance, the total luminance, and the luminance distribution of the image change abruptly at certain frames due to scene switching of the image. Occur.

  In the present embodiment, in order to solve the above-described problem, the light source control smoothing unit 8 suppresses a rapid change in the brightness of the light source, and there is no flickering feeling. The image display device 61 that realizes an increased good image display will be described. The image display device 61 includes a light source 2, a light source control unit 3, a display unit 4, an average luminance detection unit 5, a light source control determination unit 56, a luminance distribution detection unit 7, and a light source control smoothing unit 8.

  The light source control smoothing unit 8 receives the control of the brightness of the light source 2 by the light source control unit 3, and performs conversion so that the change is gentle when the change is abrupt. FIG. 19 shows an example of light source control by the image display device 51 of FIG. 13, and FIG. 20 shows an example of light source control by the image display device 61 of this embodiment. In FIGS. 19 and 20, for simplicity, the brightness of the light source 2 is changed only by a change in average luminance. In both cases, a change in average luminance is indicated by a solid line, and a change in brightness of the light source 2 is indicated by a broken line.

  In the light source control by the image display device 51, it is determined by the average luminance and the luminance distribution. At this time, if the average luminance or luminance distribution of the image suddenly changes due to a scene change or the like, the brightness of the light source also changes discontinuously as shown in FIG. 19, which causes the viewer to be identified and to feel a flickering feeling. .

  The image display device 61 eliminates this by including the light source control smoothing unit 8. The light source control smoothing unit 8 compares the control parameter of the light source control unit 3 with the current control state, and suppresses a rapid change. The light source control smoothing unit 8 continuously changes the brightness of the light source as shown in FIG.

  For example, when the light source 2 is an LED (light emitting diode) and the brightness is changed by PWM (pluse width modulation) control by the light source control unit 3, the light source control smoothing unit 8 limits the amount of change of the pulse width per time. To do. Even when the pulse width is changed from 50% to 100% in order to obtain optimum brightness due to a scene change, it is not changed by 50% at a time but is changed by a small amount. Usually, the average luminance and luminance distribution change greatly at the moment when a scene change or the like occurs, but thereafter, it changes continuously. Further, since the image display device 61 detects the average luminance and the luminance distribution, the pulse width can be basically controlled every frame, that is, every 1/60 seconds, and can be controlled in a sufficiently short period. It was experimentally determined that the amount of change in control pulse width per frame is preferably 5% or less.

  In the present embodiment, the configuration in which the light source control smoothing unit 8 is added to the image display device 51 of FIG. 13 is shown in FIG. 18 as an example, but the image display devices 11, 21, 31, and 41 shown in FIGS. Even if the control smoothing unit 8 is added, the same effect can be obtained.

1 is a block diagram showing a schematic configuration of a first embodiment of an image display device according to the present invention. 5 is a graph showing an example of light source brightness control with respect to average luminance or luminance total in the image display device according to the present invention. It is a graph which shows an example of the relationship between the average brightness | luminance in the conventional image display apparatus, and the brightness of a light source. It is a graph which shows an example of the relationship between the average brightness | luminance and the brightness of a light source in the image display apparatus which concerns on this invention. It is a block diagram which shows schematic structure of 2nd Embodiment of the image display apparatus which concerns on this invention. It is a block diagram which shows schematic structure of 3rd Embodiment of the image display apparatus which concerns on this invention. It is a graph which shows another example of the luminance distribution in 1 frame. It is a graph which shows an example of the luminance distribution in 1 frame. It is a graph which shows the luminance distribution which made the graph of FIG. 8 only two threshold values more than threshold value (alpha) and below (alpha). FIG. 8 is a graph showing a luminance distribution in which the graph of FIG. It is a block diagram which shows schematic structure about another example of 3rd Embodiment of the image display apparatus which concerns on this invention. It is a graph which shows an example of the relationship between average brightness | luminance and the brightness of a light source. It is a block diagram which shows schematic structure of 4th Embodiment of the image display apparatus which concerns on invention. It is a table which shows an example of determination of a light source control determination part. It is a table which shows another example of the determination of a light source control determination part. It is a graph which shows an example of the relationship between the average brightness | luminance when a light source is controlled by the table of FIG. 14, and the brightness of a light source. It is a graph which shows an example of the relationship between the average brightness | luminance when a light source is controlled by the table of FIG. 15, and the brightness of a light source. It is a block diagram which shows schematic structure of 5th Embodiment of the image display apparatus which concerns on this invention. It is a graph which shows an example of the relationship between the average brightness | luminance in the conventional image display apparatus, and the brightness of a light source. It is a graph which shows an example of the relationship between average brightness | luminance and the brightness of a light source. FIG. 10 is a block diagram illustrating an example of an image display device disclosed in Patent Document 1. FIG. 10 is a characteristic diagram of screen luminance with respect to average luminance in backlight brightness control.

Explanation of symbols

2 Light source 4 Display unit 5 Average luminance detection unit 7 Luminance distribution detection unit 8 Light source control smoothing unit 11 Image display device 13 Light source control unit 16 Light source control determination unit 21 Image display device 23 Light source control unit 25 Luminance total detection unit 26 Light source control determination Unit 31 image display device 33 light source control unit 36 light source control determination unit 41 image display device 43 light source control unit 46 light source control determination unit 51 image display device 56 light source control determination unit 61 image display device 72 backlight 73 backlight control unit 74 liquid crystal Display unit 75 Average luminance detection unit 77 Peak detection unit 79 Display control unit

Claims (16)

A light source;
Image display means for displaying an image by controlling the amount of light transmitted from the light source;
Luminance detection means for detecting a feature of luminance level of an arbitrary frame for a video signal input to the image display means;
Light source control determination means for determining whether to control the brightness of the light source based on the detection result of the luminance detection means and the latest past detection result;
When the light source control determination unit determines not to control the brightness of the light source, the control for changing the brightness of the light source is not performed, and the light source control determination unit determines to control the brightness of the light source. A light source control means for performing control to vary the brightness of the light source based on a detection result of the brightness detection means;
An image display device comprising: A light source;
Image display means for displaying an image by controlling the amount of light transmitted from the light source;
Luminance detection means for detecting a feature of luminance level of an arbitrary frame for a video signal input to the image display means;
A luminance distribution detecting means for detecting a luminance distribution of an arbitrary frame for a video signal input to the image display means;
Light source control determination for determining whether to control the brightness of the light source based on the detection result of the luminance detection unit, the detection result of the luminance distribution detection unit, and / or the most recent detection result Means,
When the light source control determination unit determines not to control the brightness of the light source, the control for changing the brightness of the light source is not performed, and the light source control determination unit determines to control the brightness of the light source. A light source control means for performing control to vary the brightness of the light source based on detection results of the brightness detection means and the brightness distribution detection means;
An image display device comprising:   The image display device according to claim 1, wherein the luminance detection unit detects an average luminance level of one arbitrary frame.   The image display device according to claim 1, wherein the luminance detection unit detects a total luminance level of an arbitrary frame.   The light source control determination unit controls the brightness of the light source based on a change in a difference between temporally continuous detection results based on a detection result by the luminance level feature detection unit and a luminance level feature detection result in the latest past. 5. The image display device according to claim 1, wherein it is determined whether or not to perform the operation.   Whether the light source control means controls the brightness of the light source based on a change in a difference between detection results that are temporally continuous based on a detection result by the luminance distribution detection means and a luminance distribution detection result in the latest past. The image display device according to claim 2, wherein the image display device determines whether or not.   7. The image display device according to claim 5, wherein the detection result in the latest past is a detection result of at least two frames.   The image display device according to claim 1, wherein the light source control unit changes the brightness of the light source within a width of 5% or less when the light source is lit brightest. In a light source control method for an image display device comprising a light source and an image display means for displaying an image by controlling the amount of light transmitted from the light source,
A feature of the luminance level of an arbitrary frame is detected from the video signal input to the image display means,
It is determined whether to control the brightness of the light source based on the brightness level detection result and the latest past detection result,
When it is determined that the brightness of the light source is not controlled, control for changing the brightness of the light source is not performed, and when it is determined that the brightness of the light source is controlled, the brightness of the light source is set as the brightness. A light source control method characterized by performing control that varies based on a level detection result. In a light source control method for an image display device comprising a light source and an image display means for displaying an image by controlling the amount of light transmitted from the light source,
For the video signal input to the image display means, the feature of the luminance level of any one frame is detected, and the luminance distribution of any one frame is detected,
It is determined whether to control the brightness of the light source based on the detection result of the luminance level, the detection result of the luminance distribution, and / or the detection result of the most recent past,
When it is determined that the brightness of the light source is not controlled, the brightness of the light source is determined to be controlled without performing the control for changing the brightness of the light source. A light source control method comprising performing control based on a level detection result and a luminance distribution detection result.   11. The light source control method according to claim 9, wherein the characteristic of the luminance level is an average luminance level of one arbitrary frame.   11. The light source control method according to claim 9, wherein the characteristic of the luminance level is a total luminance level of one arbitrary frame.   Determining whether to control the brightness of the light source based on a change in a difference between temporally continuous luminance level features based on the luminance level feature and the latest past luminance level feature. The light source control method according to claim 9.   Whether to control the brightness of the light source is determined based on a change in a difference between temporally continuous luminance distributions based on the luminance distribution and the latest past distribution. The light source control method according to claim 10.   15. The light source control method according to claim 9, wherein the most recent past luminance level feature and luminance distribution are at least two frames or more. 16. The light source control method according to claim 9, wherein the brightness of the light source is changed within a width of 5% or less when the light source is lit brightest.

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