JP2008052131A - Liquid crystal backlight driving device - Google Patents

Liquid crystal backlight driving device Download PDF

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Publication number
JP2008052131A
JP2008052131A JP2006229557A JP2006229557A JP2008052131A JP 2008052131 A JP2008052131 A JP 2008052131A JP 2006229557 A JP2006229557 A JP 2006229557A JP 2006229557 A JP2006229557 A JP 2006229557A JP 2008052131 A JP2008052131 A JP 2008052131A
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Japan
Prior art keywords
display
video
signal
light source
light output
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JP2006229557A
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Japanese (ja)
Inventor
Kazuo Asanuma
Yasuo Hosaka
Akinobu Maekawa
Hidefumi Nakagome
Mamoru Sakamoto
Masato Tanaka
秀文 中込
康夫 保坂
晃伸 前川
守 坂本
和夫 浅沼
正人 田中
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Micro Space Kk
Taiyo Yuden Co Ltd
マイクロスペース株式会社
太陽誘電株式会社
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Abstract

【Task】
An effective method for realizing power consumption reduction by backlight control is provided.
[Solution]
A light control signal processing circuit 320 that processes the light control signal Dim output from the image processing circuit 202 to the backlight control circuit 304, and an inverter circuit 322 that drives the backlight 308 based on the processed light control signal Dim ′. The dimming signal processing circuit 320 processes the dimming signal Dim output from the image processing circuit 202 based on the video signal VD output from the image processing circuit 202, and outputs the result to the inverter circuit 322. The inverter circuit 322 generates AC power PWR based on the processed dimming signal Dim ′, and supplies the generated power to the backlight 308.
[Selection] Figure 2

Description

  The present invention relates to a liquid crystal backlight driving device, and more particularly to a liquid crystal backlight driving device effective for reducing power consumption.

  As a technique for reducing power consumption of a liquid crystal display typified by a liquid crystal TV, there is known a technique called APL-AGC (Average Picture Level Automatic Gain Control) that controls the brightness of a backlight according to the average brightness of an image. This technique is described in, for example, Patent Documents 1 to 4.

  These documents describe effective methods of backlight control linked to video scenes, but in order to realize these methods in actual products, they are changed to image processing circuits composed of LSIs. Therefore, it is difficult to cope with variations in the image processing LSI because the correspondence varies depending on the configuration and control method of the backlight drive unit.

In addition, in order to further reduce power consumption, it is necessary to upgrade the backlight control method itself and combine various backlight control methods one after another, which is a large-scale image processing circuit that requires enormous development costs. It is difficult to meticulously respond within the company.
JP 2002-156951 A JP 2002-258401 A JP 2002-357810 A JP 2004-059661 A

  Therefore, the present invention provides a method effective for realizing power consumption reduction by backlight control.

  In order to achieve the above object, the invention described in claim 1 is a video display device that displays an image by controlling light output emitted from a light source with a plurality of display elements. A dimming signal generation circuit for generating the dimming signal, and a dimming signal processing circuit for processing the dimming signal based on a signal different from the dimming signal.

  With such a configuration, arbitrary light source control linked to the video can be realized outside the image processing circuit, so that it is possible to promote the incorporation of a low power consumption function by combining various controls, and the image processing circuit Since it is possible to add a necessary function variation for each model in a common state, it is possible to develop a suitable model.

  In particular, when it is desired to add control such as APL-AGC that does not require interlocking between the light source and the display element, a configuration in which only the light source control unit can be realized by an external circuit of the image processing circuit as in this configuration is suitable. It is.

  Here, as the display element, a reflective or transmissive liquid crystal element, a micro mirror device, or the like can be used, and a plurality of display elements are provided depending on the number of pixels. Further, in the case of color display, these display elements are provided corresponding to each of RGB, or RGB are lighted in time sequence. For example, these display elements display an image that can be perceived by the viewer by controlling gradation of the amount of reflection or transmission of light emitted from the light source with a modulation degree according to the image.

  As the light source, a fluorescent tube such as a hot cathode tube or a cold cathode tube, or a semiconductor device such as LED or EL can be used, and these light sources are driven by an inverter circuit, a DCDC converter circuit, or the like. The amount of light output emitted from the light source is determined in accordance with the degree of modulation of the display element, and is output to the aforementioned inverter circuit or DCDC converter circuit as a dimming signal.

  As a method of processing the dimming signal based on a signal different from the dimming signal, a method of controlling the light output amount of the light source in conjunction with the video is effective. For example, a bright scene with high average luminance By reducing the amount of light output, the control method that reduces the glare perceived by the viewer and saves power, and the amount of light from the backlight is reduced at the same time in dark scenes with a low average luminance or low luminance peak, and the reflection of the display element By increasing the rate or transmittance, it is possible to use a control method that obtains a power saving effect without changing the appearance.

  In addition, as a method of controlling the light output amount of the light source in conjunction with the image, the light output amount is reduced in a bright scene with high average luminance, thereby reducing glare perceived by the viewer and obtaining a power saving effect. Using a control method that obtains a power saving effect without changing the appearance by reducing the amount of backlight light and simultaneously increasing the reflectance or transmittance of the display element in a dark scene with a low average luminance or luminance peak it can.

  According to a second aspect of the present invention, in the video display device that displays an image by controlling the light output emitted from the light source with a plurality of display elements, the first adjustment as a reference of the light output amount of the light source. Means for generating an optical signal; means for generating a second dimming signal that serves as a reference for the light output amount of the light source; and the first and second dimming signals and the dimming signals are different from each other. And a means for generating a third dimming signal based on the signal and a means for controlling the light output amount of the light source based on the third dimming signal.

  With such a configuration, even when a plurality of dimming signals are independently generated, these dimming signals can be cooperated, so that more effective power saving control can be performed. Become. For example, when it is desired to add the detection result of the external light sensor as a dimming element to the dimming signal generated by the image processing circuit, this configuration in which the dimming signals are combined is effective.

  According to a third aspect of the present invention, in a video display device that displays an image by controlling the light output emitted from the light source with a plurality of display elements, a dimming signal that serves as a control reference for the light output amount of the light source Dimming signal generating means for generating the light source, means for controlling the light source in the first and second modes based on the dimming signal, and the first mode based on a signal different from the dimming signal And means for determining the distribution of the second method.

  In this way, by allocating the light source control method according to the video, it is possible to perform control suitable for the characteristics of the light source. For example, it is possible to perform control suitable for a light source such as a fluorescent tube by increasing the control ratio based on the pulse width in a bright scene and increasing the control ratio of the current amount in a dark scene.

  According to a fourth aspect of the present invention, in a video display device that displays an image by controlling the light output emitted from the light source with a plurality of display elements, a dimming signal that serves as a control reference for the light output amount of the light source. A dimming signal generating unit for generating the dimming signal, and a unit for adjusting a light output period indicated by the dimming signal based on a signal different from the dimming signal.

  Thus, when the dimming signal is expressed in the light output period of the light source, the light amount suitable for obtaining the power saving effect is calculated according to the content of the video, and the dimming signal is calculated based on the result. Various power saving controls can be easily added by adjusting the light output period and re-outputting.

  According to a fifth aspect of the present invention, in a video display device that displays video by controlling the light output emitted from the light source with a plurality of display elements, the light output of the light source is based on the input video signal. The apparatus is characterized by comprising means for controlling the force and processing the video signal and means for controlling the display element based on the processed video signal.

  In this way, by processing the video signal itself simultaneously with the control of the light source based on the video signal, it is possible to perform more advanced power saving control. For example, by changing the luminance information, color information, RGB ratio, etc. included in the video signal in accordance with the change in the light output amount of the light source, it is possible to improve the power saving effect without a sense of incongruity of the video.

  This configuration is a control method for obtaining a power saving effect without changing the appearance, for example, by reducing the light amount of the backlight in a dark scene with a low average luminance or a luminance peak and simultaneously increasing the reflectance or transmittance of the display element. It is valid.

  According to a sixth aspect of the present invention, in a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements, the display elements and / or Or a means for generating a control signal for controlling the light source; and means for controlling the light output amount of the light source based on the video signal and processing the control signal.

  As described above, it is possible to perform more advanced power saving control by processing the signal for controlling the display element and / or the light source simultaneously with the control of the light source based on the video signal. For example, when this configuration is applied to a liquid crystal display, a liquid crystal luminance control signal is obtained from a control circuit such as a microcomputer that performs control of the operation system, and a backlight control signal is created from the video signal, and these signals are integrated. The liquid crystal brightness command processed in real time may be output to the image processing circuit. In addition, it is good also as a structure which acquires a liquid-crystal luminance command directly from control circuits, such as a microcomputer, processes this, and re-outputs.

  According to a seventh aspect of the present invention, in the video display device that displays an image by controlling the light output emitted from the light source with a plurality of display elements, a dimming signal that is a control reference for the light output amount of the light source A dimming signal generating unit for generating a control command, a control command generating unit for generating a control command including control information of the display element and / or the light source, and the dimming signal based on a signal different from the dimming signal And a means for processing the control command.

  As described above, it is possible to perform more advanced power saving control by processing the control command for controlling the display element and / or the light source in accordance with the processing of the dimming signal. This configuration is effective when the video signal input to the image processing circuit is branched and used for light source control.

  According to an eighth aspect of the present invention, in a video display device that displays video by controlling the light output emitted from the light source with a plurality of display elements, the light output amount of the light source based on the input video signal And a means for processing and re-outputting the video signal and a means for controlling the display element based on the processed video signal.

  In this way, it is possible to perform more advanced power saving control by processing the video signal itself along with the control of the light source. This configuration is effective when light source control is performed in the preceding stage of the image processing circuit.

  According to a ninth aspect of the present invention, in the video display device that displays an image by controlling the light output emitted from the light source with a plurality of display elements, the first adjustment that serves as a reference for the light output amount of the light source. Based on the means for generating an optical signal, the means for generating a second dimming signal serving as a reference for the light output amount of the light source, and the first and second dimming signals, a third dimming is performed. And means for generating a signal, and means for controlling the light output amount of the light source based on the third dimming signal.

  With such a configuration, even when a plurality of dimming signals are independently generated, these dimming signals can be cooperated, so that more effective power saving control can be performed. Become.

  According to a tenth aspect of the present invention, in a video display device that displays an image by controlling light output emitted from a light source with a plurality of display elements, a dimming signal that serves as a control reference for the light output amount of the light source. Dimming signal generating means for generating the light source, means for controlling the light source by the first and second methods, and means for determining the distribution of the first method and the second method. Features.

  In this way, control suitable for the characteristics of the light source can be performed by appropriately allocating the light source control method.

  The invention described in claim 11 controls the light output emitted from the plurality of light sources provided corresponding to each of the plurality of divided display areas by the plurality of display elements provided for each display area. In the video display device for displaying the video, the means for evaluating the input luminance information for each display area, and the light output amount of each light source and / or each display element based on the evaluation result And a means for controlling.

  In this way, by performing light source control linked to the image for each divided area, even on the same image, the glare is suppressed more for bright areas and the light output amount for dark areas Therefore, the degree of modulation can be further increased and the degree of modulation can be further increased, so that it is easier to see and easier to see than a uniform reduction in the amount of light in the entire image, and a greater power saving effect can be expected.

  The invention according to claim 12 controls the light output emitted from the plurality of light sources provided corresponding to each of the plurality of divided display areas by the plurality of display elements provided for each display area. In the video display device for displaying video by this, means for evaluating the input video signal or luminance information for each display area, and means for controlling the light output amount of each light source based on the evaluation result The light sources are controlled such that the relationship between adjacent display areas falls within a certain constraint.

  In this way, by making the light quantity relationship between adjacent areas constant, it is possible to reduce a sense of discomfort between images that may occur when each area is independently dimmed. Desirably, control is performed so that the light amount difference or ratio between adjacent areas is within a certain range.

  The invention according to claim 13 controls the light output emitted from the plurality of light sources provided corresponding to each of the plurality of divided display areas by the plurality of display elements provided for each display area. In the video display device for displaying video by controlling the light output amount of each light source, means for generating a certain luminance gradient between at least adjacent display areas, and the input video signal or luminance information And a means for determining the value of the inclination based on the above.

  In this way, by keeping the light quantity relationship between adjacent areas within a certain condition, it is possible to reduce the sense of discomfort between the areas that may occur when each area is independently dimmed. Desirably, the light quantity difference or light quantity ratio of the light sources between adjacent areas is controlled within a certain range.

  According to a fourteenth aspect of the present invention, light output emitted from a plurality of light sources provided corresponding to each of a plurality of divided display areas is controlled by a plurality of display elements provided for each display area. In the video display device for displaying the video by the above, the light output amount of each light source is controlled to add a constant luminance gradient between the display areas, and the added gradient is an input It is characterized by being set to a constant value regardless of the received video signal.

  In this way, by adding a fixed luminance gradient, it is possible to further reduce the amount of light in a portion where the luminance change is not conspicuous on the screen, so a higher power saving effect can be expected. For example, if it is difficult to detect even if the lower side of the screen is somewhat dark due to the lighting position or eye characteristics, adding a brightness gradient that gradually decreases the light amount from the upper side to the lower side of the screen will give the image a sense of incongruity The power saving effect can be enhanced.

  According to a fifteenth aspect of the present invention, in a video display device that displays an image by controlling the light output emitted from the light source by a plurality of display elements, the light output of the light source is based on the input video signal. It is characterized by comprising means for controlling the amount of force and means for emphasizing the change in the light output amount corresponding to the change in the video signal.

  In this way, by emphasizing the change in the light output amount corresponding to the change in the image, the change in the luminance of the image that has passed through the display element is mitigated on the contrary, and the power saving effect is gentler to the eyes. A high control method can be provided. The enhancement of the change in the light output amount preferably has a predetermined time constant that takes into account the perceptual characteristics and adaptation characteristics of the retina.

  According to a sixteenth aspect of the present invention, in the video display device that displays video by controlling the light output emitted from the light source by a plurality of display elements, the light source is based on the input first video signal. And means for compensating for the difference between the control response delay and the video display delay based on the second video signal having a time difference from the first video signal. It is characterized by that.

  In this way, since it is possible to predict changes in video brightness in advance by using the time difference between a plurality of video signals, the light output amount of the light source is reduced at the same time as the video changes or during the change. It becomes possible. As a result, it is possible to provide a control method that is more eye-friendly and has a high power saving effect. As a method of using a video signal having a time difference, for example, a method of intentionally creating a time difference video signal using a memory or a time difference video signal naturally generated in the course of image processing can be used.

  According to a seventeenth aspect of the present invention, in the video display device that displays video by controlling the light output emitted from the light source by a plurality of display elements, the light source based on the input first video signal. The change in the light output amount is emphasized before and after the change in the first video signal based on the means for controlling the light output amount and the second video signal having a time difference from the first video signal. Means.

  In this way, by emphasizing the change in the light output amount before and after the change of the video signal, it becomes possible to mitigate the change including the pre-movement, so the luminance change is made more gradual and the eyes are more gentle and power saving. A highly effective control method can be provided.

  According to an eighteenth aspect of the present invention, in a video display device that displays an image by controlling the light output emitted from the light source by a plurality of display elements, the light output of the light source is based on the input video signal. If the luminance distribution is different even when the average luminance of the video signal is the same, the light output amount with respect to the luminance distribution And a means for changing the control characteristic.

  Thus, by changing the control characteristic of the light output amount based on the luminance distribution of the video, the amount of light can be reduced more comfortably according to the video content. For example, when performing APL-AGC, a luminance evaluation value is created by giving a non-linearity to a video signal, and even if the average luminance is the same, the response is different depending on whether the average is dark and the extremely bright part has a small area Let

  According to a nineteenth aspect of the present invention, in a video display device that displays video by controlling the light output emitted from the light source with a plurality of display elements, the light output of the light source is based on the input video signal. Means for controlling the amount of force, and after performing non-linear conversion processing on the video signal, the average luminance is obtained, and the light output amount is controlled by the average luminance, thereby depending on the luminance distribution of the video signal. It is characterized in that the control characteristic of the light output amount is changed.

  For example, after performing non-linear transformation processing such as slicing a dark part below a certain luminance of the input video signal or increasing the level of a dazzling part above a certain luminance, the average in the screen is obtained as the luminance evaluation value, It is effective to control the light source based on this, and to directly control the luminance distribution state, so that the control characteristic has a difference depending on the luminance distribution state.

In this way, by changing the control characteristic of the light output amount depending on the luminance distribution of the video, the amount of light can be reduced more comfortably according to the video content. For example, when performing APL-AGC, if it is dark on average, the luminance is not reduced so much that the details are easy to see, and if part of the same average luminance is extremely bright, to suppress glare It is possible to obtain characteristics that reduce the luminance more.

  According to a twentieth aspect of the present invention, in a video display device that displays a video by controlling light output emitted from a light source by a plurality of display elements, the display element is controlled based on an input video signal. And a means for controlling the light output amount of the light source, wherein the control means controls the light source based on a peak value of luminance information included in the video signal and outputs the light from the light source. When the ability is reduced, text information included in or superimposed on the video signal is ignored, and the degree of modulation of the display element is increased.

  Thus, the power saving effect can be further enhanced by ignoring text information such as captions and controlling the light source and increasing the modulation factor. For example, in a method of expanding the luminance modulation range by linking and modulating the light source according to the peak luminance of the video, the luminance information of the subtitle portion is ignored when detecting the peak luminance, and the signal amount of the subtitle portion is further increased. Leave even if saturated. As a result, there is an effect of automatically suppressing the original brightness when there is a dazzling subtitle in a dark scene without processing the subtitle, and it is easy to see the subtitle, power saving effect, modulation of the original scene other than the subtitle A range can be secured, and smoothness of gradation and contrast can be secured.

  As an example of a method for detecting subtitles, it is possible to improve accuracy for closed captions such as digital broadcasting by using data before superimposing synthesis as it is. In this case, an effect of preventing even saturation can be expected if the synthesis is performed after modulation control of the liquid crystal element.

  According to a twenty-first aspect of the present invention, in a video display device that displays video by controlling light output emitted from a light source by a plurality of display elements, the display element is controlled based on an input video signal. And a means for controlling the light output amount of the light source, wherein the control means increases the modulation degree of the display element and reduces the high frequency of the video signal when the light output amount of the light source is reduced. It is characterized by emphasis.

  In this way, by simultaneously performing high-frequency emphasis (sharpness) in conjunction with a decrease in light intensity and an increase in modulation in dark scenes, it is possible to improve the visibility by providing contrast in dark areas. The amount of light can be reduced. The sharpness may be increased 2 to 3 times in conjunction with a dark scene.

  According to a twenty-second aspect of the present invention, in a video display device that displays video by controlling light output emitted from a light source by a plurality of display elements, the display elements are controlled based on an input video signal. And a means for reducing a change in display luminance of the video represented by the video signal by controlling a light output amount of the light source, and a means for detecting a luminance change speed of the video signal. The means corresponds to the case where the change speed is high by controlling the display element, and the case where the change speed is slow corresponds to the control of the light source.

  In this way, by changing the specific gravity of the control according to the luminance change speed of the video signal, the change is mitigated by giving a sudden change component to the liquid crystal modulation degree side for a rapidly changing scene. When displaying an easy video, it becomes possible to control with high accuracy with little time lag. The invention described in claim 23 is a video display device that displays an image by controlling the light output emitted from the light source with a plurality of display elements, and the light control amount in which the light output amount of the light source is defined by a pulse signal. A dimming signal generating means for generating a signal; a means for causing a plurality of pulse signals to exist in a unit frame that is a reference for video display frequency based on the dimming signal; and a light source for the light source based on the plurality of pulse signals. Means for performing light output control.

  As described above, since the dimming signal generated based on the dimming information of the original dimming signal or uniquely generated is a plurality of pulse signals per frame, the fundamental wave component ratio of the light source blinking can be reduced. Even if the video frame frequency is 50 Hz or 60 Hz, flicker can be reduced. This configuration is particularly effective in the case of performing a sequential lighting method in which the light source is divided in the vertical direction of the screen and the synchronous lighting is sequentially performed in the same direction as the scanning of the display element. This sequential lighting method is also described in Japanese Patent Laid-Open No. 2005-099367.

  According to a twenty-fourth aspect of the present invention, in a video display device that displays video by controlling light output emitted from a light source by a plurality of display elements, based on luminance information included in the input video signal. And means for generating a plurality of pulse signals in a unit frame serving as a reference of the video signal, and means for performing light output control of the light source based on the plurality of pulse signals. As described above, a plurality of dimming signals may be generated in one frame based on the video signal.

  According to a twenty-fifth aspect of the present invention, in a video display device that displays video by controlling light output emitted from a light source by a plurality of display elements, the display element is controlled based on an input video signal. Means for generating a plurality of pulse signals in synchronization with a frame signal included in the video signal, and means for controlling the light output of the light source based on the plurality of pulse signals. The generation of the signal is performed by preferentially avoiding the state transition period of the display element and determining the width and / or phase of each pulse signal.

  As described above, by performing pulse division in synchronization with the video frame and arranging the pulse signal while avoiding the state transition period of the display element, higher image quality and lower power consumption can be improved. This configuration is effective for the above-described sequential lighting method.

  As an example of pulse division, for example, when the burst signal for controlling the lighting period of the light source is synchronized with the video frame and is always continuously generated, and when the duty is lowered from the full duty, first, the interval corresponding to the liquid crystal transition time from the rising edge of the burst signal In order to avoid the color distortion for the transition time and increase the contrast, improve the substantial response time of the liquid crystal and improve the video response by lowering the time aperture ratio. By increasing the interval between burst signals, the increase of the fundamental wave component is suppressed, and the occurrence of flicker is suppressed. When further narrowing down, the two burst signals are narrowed down to further improve the video response.

  According to a twenty-sixth aspect of the present invention, in a video display device that displays a video by controlling light output emitted from a light source by a plurality of display elements, the display element is controlled based on an input video signal. Means for generating a plurality of pulse signals in synchronization with a frame signal included in the video signal, and means for performing light output control of the light source based on the plurality of pulse signals, The generation of the pulse signal is performed by determining the width and / or phase of each pulse signal according to a predetermined relationship.

  As described above, by performing pulse division in synchronization with the video frame and controlling the width and / or phase of the pulse signal according to a predetermined relationship, occurrence of beats can be suppressed. This configuration is effective for the above-described sequential lighting method. As a method for controlling the pulse signal, it is possible to control the division ratio and interval of each pulse signal.

  According to a twenty-seventh aspect of the present invention, in a signal processing circuit incorporated in an image display device that displays an image by controlling the light output emitted from the light source with a plurality of display elements, the reference of the light output amount of the light source And a means for processing the dimming signal based on a signal different from the video signal.

  According to a twenty-eighth aspect of the present invention, in the liquid crystal backlight control device for controlling the light output of the backlight light source provided on the back surface of the plurality of liquid crystal elements, a dimming signal serving as a control reference for the backlight light source is generated. And means for processing the dimming signal based on a signal different from the dimming signal.

  According to a twenty-ninth aspect of the present invention, there is provided a liquid crystal backlight control method for controlling a light output of a backlight light source provided on the back surface of a plurality of liquid crystal elements, and a dimming signal serving as a control reference for the backlight light source is generated. And a step of processing the dimming signal based on a signal different from the dimming signal.

  In each of the above inventions, the video signal used for controlling the light source may be analog or digital, and the form of the signal may be any form of RGB signal, YC signal, composite signal, and component signal.

Also, the video signal is the tuner output signal, terminal output signal, signal before image processing, signal after partial image processing, signal after image complete processing, signal after liquid crystal control, control circuit As long as it is a signal including luminance information, such as a signal passing through, it may be obtained from anywhere.

  As described above, according to the present invention, it is more natural and easy to see by controlling various light sources, suppressing glare in bright scenes, suppressing sudden luminance changes, and suppressing flicker. Power consumption can be reduced simultaneously with video display.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments described below, and can be modified as appropriate.

  FIG. 1 is a block diagram showing the configuration of the video display apparatus according to the first embodiment. As shown in the figure, the video display apparatus includes a front end unit 100 for inputting a video signal from the outside, a video processing unit 200 for processing the input video signal, and video display based on the processed signal. And display unit 300 to be performed.

  The front end unit 100 is provided with a tuner 102 that receives an analog broadcast or a digital broadcast and decodes a compressed signal, and an interface for inputting a video signal such as RGB, D terminal, HDMI (High Definition Media Interface) terminal. The selector 104 selects an externally input video signal from a tuner functioning as an input interface, an RGB terminal, a D terminal, and an HDMI terminal, and outputs the selected video signal to the image processing circuit 202.

  The video processing unit 200 is provided with an image processing circuit 202 that processes various video signals input from the front end unit 100 and a control circuit 204 that performs overall control within the operation system and the apparatus.

  The image processing circuit 202 performs processes necessary for image formation, such as color space conversion, IP conversion (conversion from interlaced scanning to sequential scanning), scaling (resolution conversion), image quality improvement, and adjustment processing. An operation instructed via the external remote controller 400 or a user interface (not shown) is converted into a predetermined control command and output to the image processing circuit 202, the liquid crystal control circuit 302, the backlight control circuit 304, and the like. In the figure, a signal output to the backlight control circuit 304 is indicated by a control signal A, and a signal output to the image processing circuit 202 is indicated by a control signal B. The control signals A and B include luminance information. For example, the backlight control circuit 304 controls the light source based on the luminance information.

  The display unit 300 is provided in the liquid crystal panel 306, a liquid crystal panel 306 including a predetermined number of liquid crystal elements, a backlight 308 disposed on the back surface of the liquid crystal panel and irradiating the liquid crystal elements with light from the back surface. The liquid crystal control circuit 302 that controls the transmittance of the liquid crystal element, the backlight control circuit 304 that controls the light output amount of the backlight 308, and the brightness of outside light are detected, and the result is directly detected (solid line in the figure). Alternatively, an external light sensor 310 that outputs to the backlight control circuit via the control circuit (dotted line in the figure) is provided.

  The backlight 308 includes a plurality of backlight light sources BL1 to BL4, and these light sources are controlled collectively or independently by the backlight control circuit 304.

  FIG. 2 is a block diagram showing a peripheral configuration of the backlight control circuit shown in FIG. The backlight control circuit 304 shown in the figure includes a dimming signal processing circuit 320 for processing the dimming signal generated by the control circuit 204 or the image processing circuit 202 shown in the previous figure, and the processed dimming signal. Based on this, an inverter circuit 322 for driving the backlight 308 is provided. In the example shown in the figure, it is assumed that the control signal A includes a dimming signal.

  The dimming signal processing circuit 320 is included in the control signal A output from the control circuit 204 based on the luminance information included in the video signal output from the front end unit 100 or the image processing circuit 202 shown in the previous figure. The light control signal or the light control signal output from the image processing circuit 202 is processed, and the result is output to the inverter circuit 322 as a processed light control signal.

  The inverter circuit 322 generates AC power based on the processed dimming signal, and supplies the generated power to the backlight 308 shown in the previous figure.

  FIG. 3 is a conceptual diagram showing an example of processing performed by the dimming signal processing circuit shown in FIG. As shown in the figure, the dimming signal processing circuit performs a process of reducing the luminance of the backlight in response to an increase in the input average luminance level of the video. The input average luminance level of the video used in this process can be calculated by averaging the luminance information of each pixel included in the video signal. As shown in the figure, the contrast in dark scenes can be improved by setting the backlight dimming start point to be equal to or higher than a certain input average luminance.

  FIG. 4 is a circuit diagram illustrating an example of a method for calculating the input average luminance level. When the video signal is output in RGB, as shown in the figure, each of the RGB signals is synthesized via resistors Rr, Rg, and Rb to generate a luminance signal. Then, by inputting the luminance signal to the nonlinear circuit 350, a grace characteristic that does not start dimming in a dark image below a certain level, and a progressive gain characteristic is given to a high-luminance portion with priority. After performing an optimal non-linear conversion such as the above, the input average luminance level can be obtained by averaging with the low-pass filter 352.

  Here, the ratio that each RGB signal contributes to the brightness can be adjusted by the resistors Rr, Rg, and Rb, and more natural APL-AGC control is performed by optimizing these ratios. Can do. The circuit for calculating the input average luminance level is provided at the subsequent stage of the image processing circuit 202 shown in FIG. 1 or at an intermediate output obtained by performing a part of the image processing, or at the RGB terminal of the front end unit 100. You may connect.

  FIG. 5 is a timing chart showing an operation example of the backlight control circuit shown in FIG. In the example shown in the figure, the video signal is updated at a rate of 60 frames per second, and is input to the dimming signal processing circuit in the order of video data Frame1, Frame2, Frame3,... Every 1/60 seconds. At the same time, the dimming signal is input to the dimming signal processing circuit as a burst signal indicating the lighting period of the backlight.

  Here, as shown in the figure, when the input average luminance level calculated from the video signal by the dimming signal processing circuit increases in the order of Frame1, Frame2, and Frame3, the backlight is adjusted in accordance with the increase of the average luminance level. A processed dimming signal with a processed pulse width is generated in the direction in which the amount of light decreases.

  At this time, a calculation delay of the input average luminance level occurs with respect to the video signal, and therefore the timing at which the backlight is actually controlled is delayed by one to several frames, but the video signal is also delayed to the same extent until the display. There is no time difference that makes the video feel uncomfortable. This figure shows an example in which the width of the processed dimming signal becomes narrower as the input average luminance level increases.

  The AC power output from the inverter circuit is output during a period when the processing dimming signal is ON, and power is supplied to the backlight light source during this ON period.

  In the figure, the dimming signal or the processed dimming signal is in the form of a pulse and the backlight dimming information is shown by its width. However, if the backlight luminance information is shown, analog voltage or pulse density is used. Any format such as modulation, pulse frequency modulation, parallel or serial digital code may be used. The same applies to the following embodiments.

  FIG. 6 is a timing chart showing the relationship between the increase of the input average luminance level, the reduction of the backlight luminance, and the video display luminance. As shown in the figure, when the input average luminance level increases, the amount of light of the backlight is reduced and the backlight luminance is reduced.

  As a result, a video with an increased input average luminance level and a backlight output with a reduced amount of light are combined, and the video display luminance displayed on the display is higher than the display luminance (dotted line in the figure) when this control is not performed. As a result, the glare is alleviated and a power saving effect is obtained.

  FIG. 7 is a block diagram showing a configuration of a backlight control circuit according to the second embodiment. In the description of the present embodiment, differences from the first embodiment described above will be described, and the portions that are not described are configured in the same manner as in the first embodiment.

  In this embodiment, as shown in the figure, the dimming signal processing circuit 320 receives the dimming signal input from the image processing circuit 202 based on the illuminance signal input from the external light sensor 310 shown in the previous figure. The inverter circuit 322 is driven by the processed dimming signal after processing.

  FIG. 8 is a conceptual diagram showing a processing example performed by the dimming signal processing circuit shown in FIG. As shown in the figure, the dimming signal processing circuit performs a process of increasing the luminance of the backlight in response to an increase in the external light illuminance indicated by the illuminance signal. Thus, sufficient backlight luminance is ensured when viewing in a bright environment, and power saving and glare reduction are achieved by reducing backlight luminance when viewing in a dark environment.

  FIG. 9 is a timing chart showing an operation example of the backlight control circuit shown in FIG. The example shown in the figure is an example of processing the dimming signal generated by the image processing circuit based on the illuminance signal.

  As shown in the figure, the dimming signal processing circuit reduces the amount of backlight light by processing the pulse width of the dimming signal at that time when the illuminance signal decreases at Frame 2 of the video signal. As a result, it is possible to output a backlight light amount that is easy to see even when the surroundings are dark and that can provide a power saving effect. In addition, in the figure, it was described to follow after one frame so that it is easy to understand, but in reality it is not necessary for slight changes in outside light that only a person walks or reflection of the image of his screen in the room. It is desirable to suppress the reaction sensitivity by giving the illuminance signal a time constant response characteristic of, for example, about several seconds so that it does not react sensitively.

  FIG. 10 is a block diagram illustrating a configuration of a backlight control circuit according to the third embodiment. In the description of the present embodiment, differences from the above-described embodiments will be described, and portions that are not described are configured in the same manner as in each embodiment. In this embodiment, as shown in the figure, the dimming signal is processed in consideration of the video signal in addition to the illuminance signal from the external light sensor 310.

  FIG. 11 is a conceptual diagram showing a processing example performed by the dimming signal processing circuit shown in FIG. As shown in the figures, the dimming signal processing circuit performs a process of reducing the luminance of the backlight in response to an increase in the input average luminance level of the video ((a) in the figure), and the illuminance signal indicates A process of increasing the brightness of the backlight in accordance with the increase in the illuminance of the external light is performed ((b) in the figure). As a result, it is possible to reduce glare when viewing an image with a high average luminance level or in a dark environment and to save power. In this example, since both the processes in FIGS. 5A and 5B are applied simultaneously, the most power saving effect is obtained when a bright image is viewed in a dark environment, and the glare is reduced. .

  FIG. 12 is a timing chart showing an operation example of the backlight control circuit shown in FIG. In the example shown in the figure, the dimming signal generated by the image processing circuit is processed based on the input average luminance level and the illuminance signal.

  As shown in the figure, the dimming signal processing circuit processes the pulse width of the dimming signal based on the increase in the input average luminance level and the decrease in the illuminance signal in the frame 2 of the video signal to reduce the amount of backlight. As a result, it is possible to output a backlight light amount that is easy for the viewer to see and can provide a power saving effect. In the figure, an example is shown in which an input average luminance level that changes step by step for each frame is used. However, as shown in FIG. 5, an input average luminance level that changes continuously may be used.

  FIG. 13 is a block diagram showing a configuration of a backlight control circuit according to the fourth embodiment. In the description of the present embodiment, differences from the above-described embodiments will be described, and portions that are not described are configured in the same manner as in each embodiment. In this embodiment, as shown in the figure, dimming signal synthesis and dimming method redistribution are performed.

  The dimming method redistribution circuit 320 shown in the figure performs redistribution of a plurality of dimming methods according to the content of the video and the information of the processed dimming signal after processing. For example, analog dimming means that modulates the value of the current flowing through the backlight or the high-frequency carrier duty ratio of the current and controls the average current, and the current is turned on with a long period of time such as several tens to several hundred hertz, It has digital dimming means that repeats off-flashing and visually modulates with its duty ratio, and when the processed dimming signal after processing is above a predetermined level, only analog dimming can be changed to a predetermined level In the following cases, only digital dimming is made variable, and processing such as desired dimming is performed in its entirety.

  FIG. 14 is a conceptual diagram showing an example of processing performed by the dimming signal processing circuit shown in FIG. The dimming signal processing circuit shown in the previous figure performs processing to reduce the luminance of the backlight in response to an increase in the input average luminance level of the video. Here, the dimming method redistribution circuit is shown in FIG. As shown, analog dimming and digital dimming are performed according to the processed dimming signal indicating the amount of light of the backlight.

  In the example shown in the figure, the digital dimming duty is increased at a constant ratio in the interval in which the processed dimming signal increases from D1 to D2, and the analog dimming is increased in the interval in which the processed dimming signal increases from D2 to D3. Increase the amount of current at a constant rate. As a result, the brightness of the backlight is controlled to a value obtained by multiplying the product of the digital light control amount and the analog light control amount by a predetermined coefficient, and as a result, the desired brightness is realized by the distribution of the digital light control and the analog light control. The

  Note that the product of the analog dimming curve and the digital dimming curve only needs to be the desired dimming control characteristics, and there are parts that change at the same time in the distribution with analog dimming and digital dimming. It is not limited to the curve or its distribution ratio.

    FIG. 15 is a timing chart showing an operation example of the backlight control circuit shown in FIG. In the example shown in the figure, the dimming signal is processed based on the input average luminance level, and analog dimming and digital dimming are distributed based on the processed dimming signal.

  As a result, from the inverter circuit, as indicated by the AC power in the figure, during the period in which the analog dimming amount is changed (Frame 1 and Frame 2 in the figure), AC power with a change in amplitude is generated according to the analog dimming signal. During the period in which the digital dimming amount is output (after Frame 3 in the figure), the AC power having the amplitude indicated by the analog dimming signal is output while the digital dimming signal is ON. The backlight brightness is controlled. In this example, the digital dimming signal is always set to ON during the period for changing the analog dimming amount, and the analog dimming signal is set to the minimum value during the period for changing the digital dimming. Instead, control such as simultaneously changing the digital light control amount and the analog light control amount may be performed.

  FIG. 16 is a block diagram illustrating a configuration of a video display apparatus according to the fifth embodiment. In the description of the present embodiment, differences from the above-described embodiments will be described, and portions that are not described are configured in the same manner as in each embodiment. In this embodiment, as shown in the figure, the backlight control circuit 304 processes the control signal output from the control circuit 204, so that the liquid crystal modulation gain is controlled simultaneously with the control of the backlight light quantity.

  In this configuration, the video signal from the front end unit 100 is branched and input to the backlight control circuit 304 via the selector 104, and the backlight light amount control and the liquid crystal modulation gain control are performed based on the branched video signal. Is done.

  FIG. 17 is a block diagram showing a configuration of the backlight control circuit shown in FIG. As shown in the figure, the dimming signal generation circuit 321 generates a dimming signal based on the luminance information included in the video signal received from the front end unit 100 shown in the previous figure and outputs it to the inverter circuit 322. At the same time, the liquid crystal modulation gain information included in the control signal A received directly from the control circuit 204 or via the IF relay circuit 326 is processed.

  Then, a control signal A ′ including the processed liquid crystal modulation gain information in the original control signal A is output to the image processing circuit 202 or the liquid crystal control circuit 302 shown in the previous figure via the IF relay circuit 326.

  The liquid crystal control circuit 302 that has received the processed liquid crystal modulation gain directly or via the image processing circuit 202 controls the liquid crystal elements provided in the liquid crystal panel 306 in accordance with the processed liquid crystal modulation gain. As a result of these series of controls, power saving control is performed in conjunction with backlight control and liquid crystal control.

  In the IF relay circuit 326, a control signal for directly controlling the image processing circuit 202 is passed from the control circuit 204, and those related to backlight control and liquid crystal modulation are once received by the dimming signal generation processing circuit 321 as appropriate. Process. The overall processed control signal A ′ including the processed information is output in a format that the image processing circuit 202 can receive.

  FIG. 18 is a conceptual diagram illustrating an example of processing performed by the dimming signal generation circuit illustrated in FIG. As shown in FIG. 6A, the dimming signal generation circuit performs a process of reducing the luminance of the backlight in response to a reduction in the input peak luminance or the input average luminance level of the video, and FIG. As shown in FIG. 5, by increasing the liquid crystal modulation degree in conjunction with the decrease in the backlight luminance, it is possible to save power in a dark scene without changing the visual image. Also, in this case, increasing the liquid crystal modulation gain increases the number of gradations in the dark area, and in conjunction with this, lowering the backlight brightness makes it possible to reproduce black well, improving the dark area contrast. .

  Note that the gain of the display brightness of the image displayed by the combination of the backlight and the liquid crystal is the product of the backlight brightness and the liquid crystal modulation gain, as shown in FIG. A constant value is set so as not to give a sense of incongruity.

  FIG. 19 is a conceptual diagram showing another example of processing performed by the dimming signal generation circuit shown in FIG. As the processing performed by the dimming signal generation circuit, as shown in the respective drawings, it is possible to combine the processing of FIG. 3 shown by a dotted line and the processing of FIG. 18 shown by a solid line. These controls are performed independently, and the effects of both processes can be obtained according to the level of the input peak luminance and the input average luminance, respectively. A synergistic effect can also be expected.

  FIG. 20 is a block diagram illustrating a configuration of a video display apparatus according to the sixth embodiment. In the description of the present embodiment, points different from the above-described embodiments will be described, and the portions that are not described are configured in the same manner as in the other embodiments. In this embodiment, as shown in the figure, the video signal output from the front end unit 100 is once received by the backlight control circuit 304, and the video signal is processed here and then input to the image processing circuit 202. .

  FIG. 21 is a block diagram showing a configuration of the backlight control circuit shown in FIG. As shown in the figure, the luminance control signal generation circuit 332 generates a luminance control signal based on the luminance information included in the video signal received from the front end unit 100 shown in the previous figure, and this generated luminance control. The signal is output to the video signal processing circuit 330 and the dimming signal processing circuit 320.

  The dimming signal processing circuit 320 processes the dimming signal included in the control signal A received from the control circuit 204 based on the luminance control signal, and outputs a new processed dimming signal generated by the processing.

  At the same time, the video signal processing circuit 330 processes the video signal based on the luminance control signal and outputs the processed video signal after the processing to the image processing circuit 202. The image processing circuit 202 controls the liquid crystal element based on the processed video signal.

  In this example, the video signal before the image processing circuit is processed by the backlight control circuit, but the output video signal of the image processing circuit may be processed and sent to the liquid crystal control circuit. The video signal obtained from the middle may be sent back to the next processing stage in the image processing circuit after processing.

  FIG. 22 is a timing chart showing an operation example of the backlight control circuit shown in FIG. As shown in the figure, the APL-AGC control described with reference to FIG. 5 can also be performed in this embodiment.

  FIG. 23 is a block diagram showing a configuration of a backlight control circuit according to the seventh embodiment. In the description of the present embodiment, differences from the above-described embodiments will be described, and portions that are not described are configured in the same manner as in each embodiment. In this embodiment, as shown in the figure, the four light sources BL1 to BL4 provided in the backlight 308 are independently controlled.

  In this configuration, the dimming signal processing circuit 320 processes the dimming signal included in the control signal A based on the luminance information included in the video signal, and processes dimming for controlling the light sources BL1 to BL4. Generate signals 1-4.

  The inverter circuit 322 generates AC power PWR1 to PWR4 based on the dimming signals Dim1 'to Dim4', and independently drives the light sources BL1 to BL4. In addition, the structure which drives the light sources BL1-BL4 independently in this way is applicable also to other embodiment.

  24 is a conceptual diagram showing an example of processing performed by the dimming signal processing circuit shown in FIG. As shown in the figure, the dimming signal processing circuit calculates the average luminance level APL of the video areas Area1 to Area4 divided in correspondence with the illumination ranges of the light sources BL1 to BL4, and calculates this for each video area. Area-specific APL-AGC control is performed to reduce the luminance of the backlight corresponding to the increase in the average input luminance level.

  In the example shown in the figure, the average luminance levels of the video areas Area1 and Area2 on the upper side of the screen are as high as 90 and 80, respectively. Setting to 65 and 75 suppresses glare. In addition, the average luminance levels of the video areas Area3 and Area4 on the lower side of the screen are reduced to 40 and 30, respectively. Accordingly, the backlight luminance is set to 90 and 100, respectively, so that the dark portion and the bright portion are respectively set. Adjust the brightness so that it is easy to see. As a result, as compared with the case where the entire screen is performed collectively, an effect such as backlight correction that improves the visibility of both the dark part and the bright part is brought about, and more effective power saving can be achieved.

  At this time, it is not desirable to create an extreme backlight luminance difference between adjacent video areas because the change in brightness is stepped and unnatural. For this reason, the backlight luminance between adjacent video areas is limited so as to fall within a certain difference or ratio range. Further, the moment of the input average luminance of each video area may be obtained and a luminance gradient corresponding thereto may be given. For example, as shown in BL brightness example 2 in the figure, in a bright image on the upper side of the screen, the brightness of the light source is gradually increased at a constant inclination, such as 70, 80, 90, 100 in the order of Area 1, Area 2, Area 3, and Area 4. Let Thereby, the same effect can be acquired with a more natural image.

  FIG. 25 is a timing chart showing an operation example of the backlight control circuit shown in FIG. As shown in the figure, the process light control signals 1 to 4 for controlling the light sources BL1 to BL4 and the AC powers 1 to 4 are sequentially controlled to be turned on with a predetermined phase difference within one frame of the video signal. Note that the lighting control of the light sources BL1 to BL4 may be simultaneous lighting control of the same phase in all areas, instead of sequentially lighting.

  FIG. 26 is a timing chart showing the basic operation of APL-AGC. As shown in the figure, the APL-AGC reduces the display brightness by reducing the backlight brightness from 100% to 70%, for example, when the video suddenly changes from 30% to 100% brightness. This is a technique to keep it at 70%.

  FIG. 27 is a timing chart showing an example of perceptual adaptation control when the video display apparatus according to each of the embodiments described above can be executed, and the brightness of the video changes. In this control example, as shown in the figure, when the input average luminance level rapidly increases, the luminance of the backlight is lowered to be larger than the original target value of APL-AGC, and then has a predetermined time constant. In this way, it converges to the original target value of APL-AGC while creating a visual adaptation period in which the luminance is gradually increased.

  As a result, the display brightness of the image synthesized with the liquid crystal element and the backlight output light is provided with a period in which the display brightness gradually increases with the adaptation period. For example, for example, when the video image suddenly changes from 30% to 100% brightness, the normal APL-AGC suppresses the change from 100% to 70%. To 70% and then gradually reduce to 70%. The obtained display brightness is temporarily suppressed from 30% to change to 50% and then gradually reaches 70%. As a result, it is possible to eliminate the sense of incongruity and fatigue such as a sudden scene change in the human eye and to expect effective power saving.

  If there is a difference between the backlight control delay time when the video brightness changes and the video display time delay at the timing shown in the figure, the resulting display luminance is unnatural at the input average luminance change point. Therefore, it is desirable to correct the time difference.

  This delay correction can be performed using a time difference signal of the front end unit or the video processing unit. For example, the APL calculation is performed by using the advanced NTSC signal output in parallel with the high-definition signal to eliminate the APL response delay, thereby obtaining a more natural video effect and power saving effect for the eyes. be able to. In that case, when the APL is relatively advanced because the original or time difference video signal is used, the delay difference can be eliminated by delaying the APL control signal in units of frames.

  FIG. 28 is a timing chart showing an example of processing that can be executed by the video display device according to each of the above-described embodiments, in which an adaptation period is provided before and after the brightness of the video changes. In this control example, as shown in the figure, the backlight brightness is changed before and after the increase of the average brightness level APL, and the adaptation period is extended to provide a control that is gentler on the eyes and has a higher power saving effect. .

  For example, if it is found that the next video changes from 30% to 100% brightness by using the time difference signal, the backlight luminance is gradually increased in advance for the video of 30% brightness ( In the figure, the adaptation period A), at the timing when the brightness of the image changes to 100%, in the normal APL-AGC, the place where it is suppressed from 90% to 70% is temporarily emphasized and then reduced to 50%. 70% (Adaptation period B in the figure). The obtained display brightness gradually changed from 30% to 40% before the brightness of the image changed, and increased from 40% to 50% at the same time as the brightness of the image changed, and the brightness of the image changed. After 50% gradually reaches 70%. As a result, it is possible to eliminate the sense of incongruity and fatigue such as a sudden scene change in the human eye and to expect effective power saving.

  In the explanation in the figure, at the timing when the brightness of the image changes, the change in the brightness of the image is expressed by leaving the change component from 40% to 50% as the change in display luminance. However, it may be changed gradually and smoothly from 30% to 70% before and after the change without leaving such a change component. Further, the amount to be left as a change component may be set as appropriate according to the length of the adaptation period and the brightness change degree of the video.

  FIG. 29 is a processing example that can be executed by the video display device according to each of the embodiments described above, and is a conceptual diagram illustrating an example in which the control characteristics of APL-AGC are changed according to the luminance distribution state in the screen. It is. In this control example, as shown in the figure, the control characteristics of the video in which the luminance distribution in the screen spreads uniformly (the curve indicated by “Brightness distribution uniform video” in the figure) and the luminance distribution are biased. Different characteristics are given depending on the control characteristics of the video (the curve indicated by “brightness distribution concentrated video” in the figure).

  For example, even if the images have the same average brightness, it is possible to suppress glare when higher brightness areas are concentrated by giving different responses when the average is dark and when the extremely bright area is a small area. And natural image quality.

  FIG. 30 is a block diagram illustrating a configuration of a video display device when caption processing is performed. In the example shown in the figure, the video signal VD output from the front end unit 100 is input to the dimming signal generation circuit 321, and the text signal TEXT output from the front end unit 100 is input to the image processing circuit 202.

  The dimming signal generation circuit 321 generates a dimming signal based on the peak luminance or input average luminance of the video signal excluding text information, drives the inverter circuit 322 with this signal, and processes the video signal to generate an image. Output to the processing circuit 202. As another example, the video signal is branched and input to the image processing circuit as it is before processing (dotted line in the figure), and the dimming signal generation circuit is linked with the backlight to the image processing circuit or the liquid crystal control unit. This can also be achieved by sending a liquid crystal modulation gain signal (in parentheses in the figure).

  Here, when the backlight luminance is reduced for the purpose of power saving control, the image processing circuit 202 ignores the subtitle portion even if it is saturated and increases the modulation degree. That is, in the method of expanding the luminance modulation range by interlocking modulation of the liquid crystal modulation gain and the backlight according to the peak luminance, the luminance information of the subtitle portion is ignored when detecting the peak luminance, and the subtitle portion Even if the signal level is saturated, leave it alone. As a result, it is possible to ensure easy-to-view captions, power saving effects, and modulation ranges according to the brightness of the image without processing the captions.

  As an example of a method for detecting captions, for closed captions such as digital broadcasting, data before superimposition synthesis is used as it is to improve accuracy. In this case, the effect of preventing even saturation can be expected by combining after LCD modulation control.

  FIG. 31 is a conceptual diagram showing an example of processing performed by the apparatus shown in FIG. In this example, as shown in FIG. 6A, when the peak luminance or the input average luminance is small, the luminance of the backlight is reduced to save power, and as shown in FIG. The liquid crystal modulation gain is increased in a direction to compensate for the decrease in backlight luminance.

  At this time, since the subtitle portion is saturated even if the modulation degree is increased due to the increase in the liquid crystal modulation gain, as shown in FIG. In the area on the left side of the “subtitle saturation point” indicated by the dotted line, there is a portion where the subtitle luminance decreases, but since this region is a dark scene, the subtitle luminance decreases, so that the video is easier to see.

  FIG. 32 is a conceptual diagram illustrating an example of processing performed by the apparatus illustrated in FIGS. 17 and 21 and an example of control for enhancing the sharpness of the dark portion. In this example, as shown in FIG. 6A, when the peak luminance is small, the backlight luminance is reduced to save power, and as shown in FIG. The liquid crystal modulation gain is increased in a direction to compensate for the decrease.

  At this time, as shown in FIG. 5C, the sharpness is also emphasized in the region where the liquid crystal modulation gain is increased, thereby providing a sense of contrast and improving the visibility of the dark part. Alternatively, the power saving effect may be improved by further reducing the backlight brightness in conjunction with sharpness enhancement with the same visibility.

  FIG. 33 is a conceptual diagram showing an example of processing performed by the apparatus shown in FIGS. 17 and 21 and a control example in the case of following a high-speed change in video. In this example, as shown in FIG. 6A, in the moving image display in which the peak luminance or the input average luminance level is long and gradually changes with time and short and sudden changes are mixed as shown in FIG. The long and gradual change component corresponds to the luminance change of the backlight (time t1 to t6), and the short and rapid change component is changed by the change of the liquid crystal modulation gain as shown in FIG. Correspond (time t2, t3, t4, t5). As a result, the accuracy of the difference between the video and the delay time with respect to the high-speed change component can be easily obtained, and a suitable video change mitigation effect and power saving effect can be obtained.

  In this example, a short and rapid change in the input luminance peak occurs in the video at times t2, t3, t4, and t5 in the figure, and a long and gentle change in the input luminance peak occurs in the video from time t1 to t6. An example is shown. In addition, the liquid crystal modulation gain in the periods t1 to t2, the periods t2 to t3, the periods t3 to t4, the periods t4 to t5, and the periods t5 to t6 are at a speed (inclination in the figure) that reduces the backlight luminance in each period. By correspondingly increasing the display luminance, the display luminance in each period is maintained constant.

  FIG. 34 is a timing chart showing an example of control that can be executed by the video display device according to each of the above-described embodiments, in the case of performing pseudo high-speed driving by dividing the dimming signal. In this control example, as shown in the figure, the dimming signal pulse output from the image processing circuit is divided into two to generate a plurality of new processed dimming signal pulses existing in one frame of the video signal. The fundamental wave component of 50 Hz or 60 Hz of the burst signal that controls the lighting period of the light source is reduced, and the flicker prevention effect is improved. The processed dimming signal may be divided into three or four. Also, instead of processing the dimming signal pulse output from the image processing circuit, a plurality of dimming signal pulses existing in one frame of the video signal are generated from the beginning based on the luminance information included in the video signal. Also good.

  In this control example, as shown in the figure, when the dimming signal pulse output from the image processing circuit is divided into two to generate a new processed dimming signal pulse ′, by avoiding the transition period of the liquid crystal, Enables higher-quality video display. This control example is preferably implemented with the sequential lighting control configuration shown in FIG.

  As an example of the dimming signal division, for example, when the burst signal pulse for controlling the lighting period of the light source is synchronized with the video frame and is always set to two consecutive times, and when decreasing from full duty, first, the rising edge of the burst signal pulse (in the figure) In the case where the interval corresponding to the liquid crystal transition time is increased from “t1” and the duty is further reduced, the interval between two burst signal pulses existing in the frame (“G1-1, G1-2, G1 in the figure”). -3 ") also suppresses an increase in the fundamental wave component. When further narrowing down, the interval between the rising edge of the burst signal pulse and the burst signal is increased evenly. Further, the pulse signal width ("W1-1, W1-2, W1-3, W2-1, W2-2, W2-3" in the figure) and / or the phase is controlled in accordance with a predetermined relationship, so that the beat Can be suppressed. This configuration is effective for the above-described sequential lighting method. As a method for controlling the width and phase of the burst signal pulse, it is possible to control the division ratio and interval of each burst signal pulse. In the figure, “G2-1, G2-2” indicates an interval between the last pulse of a plurality of pulses existing in a frame unit and the head pulse of a plurality of pulses present in the following frame. The pulse interval between different frames may be controlled.

  FIG. 35 is a conceptual diagram showing a first control example of burst signal pulses in the timing chart shown in FIG. In the figure, the horizontal axis indicates a change in duty required for a burst signal pulse in the digital dimming method, and the vertical axis indicates a time change in one frame.

The example shown in the figure is an example in which the leading edges t1 and t3 of each burst signal pulse are fixed, and the trailing edges t2 and t4 of each burst signal pulse are simultaneously changed at a constant ratio according to the change in duty. In this example, the occurrence of flicker is suppressed by providing constant intervals G1 and G2 for each burst signal pulse.

  FIG. 36 is a conceptual diagram showing a second control example of burst signal pulses in the timing chart shown in FIG. The example shown in the figure is an example in which the trailing edges t2 and t4 of each burst signal pulse are fixed, and the leading edges t1 and t3 of each burst signal pulse are simultaneously changed at a constant ratio according to the change in duty. In this example, the occurrence of flicker is suppressed by providing constant intervals G1 and G2 for each burst signal pulse.

  FIG. 37 is a conceptual diagram showing a third control example of the burst signal pulse in the timing chart shown in FIG. In the example shown in the figure, duty control is performed to avoid the transition time of the liquid crystal element by fixing the leading edge t1 of the leading pulse of the plurality of pulses present in the frame over the entire duty.

  In this control, when the duty is reduced from 100% to 75%, the duty is trimmed from the trailing edge t4 of the last pulse among a plurality of pulses present in the frame. The duty is reduced while preferentially securing a period during which the state of the liquid crystal element is stable.

  Further, when the duty is reduced from 75% to 50%, the duty 50 which is most likely to cause flicker is generated by scraping the trailing edge t2 of the leading pulse with the leading edge t3 and trailing edge t4 of the last pulse fixed. A sufficient flicker suppression interval G1, G2 is provided in the vicinity of%.

  Further, when the duty is reduced from 50% to 10%, the leading edge t3 and trailing edge t4 of the last pulse and the trailing edge t2 of the leading pulse are each trimmed at a constant ratio, thereby providing flicker suppression intervals G1 and G2. Decrease the duty.

  FIG. 38 is a conceptual diagram showing a fourth control example of burst signal pulses in the timing chart shown in FIG. In the example shown in the figure, duty control that avoids the transition time toward the next frame of the liquid crystal element by fixing the leading edge t4 of the leading pulse of the plurality of pulses existing in the frame over the entire duty. Done.

  In this control, when reducing the duty from 100% to 75%, the duty is reduced from the leading edge t1 of the first pulse among the plurality of pulses present in the frame. The duty is reduced while preferentially securing a period during which the state of the liquid crystal element is stable.

  Further, when the duty is reduced from 75% to 50%, the duty 50 that is most likely to cause flicker is generated by scraping the trailing edge t3 of the last pulse with the leading edge t1 and trailing edge t2 of the leading pulse fixed. A sufficient flicker suppression interval G1, G2 is provided in the vicinity of%.

  Further, when the duty is reduced from 50% to 10%, the leading edge t1 and trailing edge t2 of the leading pulse and the leading edge t3 of the trailing pulse are respectively trimmed at a constant ratio, thereby providing flicker suppression intervals G1 and G2. Decrease the duty.

  FIG. 39 is a block diagram showing an example of an input average luminance calculation circuit that can be incorporated in the apparatus shown in FIG. In the example shown in the figure, the input average luminance calculation circuit has a crosstalk characteristic from the surrounding area so that the difference or ratio between adjacent areas falls within a certain range. Here, the surrounding area includes the top and bottom of the screen, the left and right, and the time axis of the video frame.

  Specifically, the input average luminance information for each area Area 1 to 4 shown in FIG. 24 is mixed with the input average luminance information of the surrounding area to obtain the final input average luminances APL1 to APL4 of each area.

  Alternatively, as shown in FIG. 40, the LPF in FIG. 4 is sampled as a one-dimensional or two-dimensional low-pass filter having an appropriate impulse response for sequentially input video signals, and the output is sequentially sampled. Thus, the block input average luminances APL1 to APL4 in a state in which signals of blocks around the block are mixed are obtained.

  As a result, it is automatically maintained within an appropriate maximum difference or ratio without providing a means for limiting the backlight luminance difference or ratio between adjacent blocks.

  According to the present invention, more advanced backlight control is possible, so application to a large liquid crystal display that is required to reduce power consumption is expected.

It is a block diagram which shows the structure of the video display apparatus which concerns on 1st Embodiment. FIG. 2 is a block diagram showing a peripheral configuration of the backlight control circuit shown in FIG. 1. It is a conceptual diagram which shows the process example which the light control signal processing circuit shown in FIG. 2 performs. It is a circuit diagram which shows the example of the method of calculating an average luminance level. 3 is a timing chart showing an operation example of the backlight control circuit shown in FIG. 2. 6 is a timing chart showing a relationship between an increase in average luminance level APL, a reduction in backlight, and video luminance. It is a block diagram which shows the structure of the backlight control circuit which concerns on 2nd Embodiment. It is a conceptual diagram which shows the process example which the light control signal processing circuit shown in FIG. 2 performs. 8 is a timing chart illustrating an operation example of the backlight control circuit illustrated in FIG. 7. It is a block diagram which shows the structure of the backlight control circuit which concerns on 3rd Embodiment. It is a conceptual diagram which shows the process example which the light control signal processing circuit shown in FIG. 10 performs. 11 is a timing chart illustrating an operation example of the backlight control circuit illustrated in FIG. 10. It is a block diagram which shows the structure of the backlight control circuit which concerns on 4th Embodiment. It is a conceptual diagram which shows the process example which the light control signal processing circuit shown in FIG. 13 performs. 14 is a timing chart illustrating an operation example of the backlight control circuit illustrated in FIG. 13. It is a block diagram which shows the structure of the video display apparatus which concerns on 5th Embodiment. It is a block diagram which shows the structure of the backlight control circuit shown in FIG. It is a conceptual diagram which shows the process example which the light control signal processing circuit shown in FIG. 17 performs. It is a conceptual diagram which shows the other process example which the light control signal processing circuit shown in FIG. 17 performs. It is a conceptual diagram which shows the structure of the liquid crystal backlight drive device which concerns on 6th Embodiment. FIG. 21 is a block diagram showing a configuration of a backlight control circuit shown in FIG. 20. 22 is a timing chart showing an operation example of the backlight control circuit shown in FIG. It is a block diagram which shows the structure of the backlight control circuit which concerns on 7th Embodiment. It is a conceptual diagram which shows the process example which the light control signal processing circuit shown in FIG. 23 performs. 24 is a timing chart illustrating an operation example of the backlight control circuit illustrated in FIG. 23. It is a timing chart which shows the basic operation | movement of APL-AGC. It is a timing chart which shows the example of a process which the video display apparatus concerning each embodiment mentioned above can perform, and shows the example of perceptual adaptation control when the brightness of a picture changes. 6 is a timing chart showing an example of processing that can be executed by the video display device according to each of the embodiments described above, in which an adaptation period is provided before and after the brightness of the video changes. It is a conceptual diagram which shows the example at the time of changing the control characteristic of APL-AGC according to the content of an image | video, which is the process example which can be performed by the video display apparatus concerning each embodiment mentioned above. It is a block diagram which shows the structure of the video display apparatus in the case of performing a caption process. It is a conceptual diagram which shows the example of a caption process which the apparatus shown in FIG. 30 performs. FIG. 22 is a conceptual diagram illustrating an example of processing performed by the apparatus illustrated in FIGS. 17 and 21 and an example of control for enhancing sharpness in a dark portion. FIG. 22 is a conceptual diagram illustrating a processing example performed by the apparatus illustrated in FIGS. 17 and 21 and a control example in the case of following a high-speed change in video. 6 is a timing chart showing a control example that can be executed by the video display device according to each of the above-described embodiments, and in which pseudo high-speed driving is performed by dividing a dimming signal. FIG. 35 is a conceptual diagram showing a first control example of burst signal pulses in the timing chart shown in FIG. 34. FIG. 35 is a conceptual diagram showing a second control example of burst signal pulses in the timing chart shown in FIG. 34. FIG. 35 is a conceptual diagram showing a third control example of burst signal pulses in the timing chart shown in FIG. 34. FIG. 35 is a conceptual diagram showing a fourth control example of burst signal pulses in the timing chart shown in FIG. 34. FIG. 24 is a block diagram illustrating an example of an input average luminance calculation block that can be incorporated into the apparatus illustrated in FIG. 23. It is a timing chart which shows the other example of an input average brightness | luminance calculation process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Front end part, 102 ... Tuner circuit, 104 ... Selector, 200 ... Video processing part, 202 ... Image processing circuit, 204 ... Control circuit, 300 ... Display part, 302 ... Liquid crystal control circuit, 304 ... Backlight control circuit, 306 ... Liquid crystal panel, 308 ... Back light, 310 ... External light sensor, 320 ... Dimming signal processing circuit, 321 ... Dimming signal generation circuit, 322 ... Inverter circuit, 324 ... Dimming method redistribution circuit, 326 ... IF relay Circuit: 330 ... Video signal processing circuit, 332: Luminance control signal generation circuit, 350 ... Nonlinear circuit, 352 ... Low pass filter, 354 ... Register, 356 ... Timing control circuit, 400 ... Remote control

Claims (29)

  1. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    A dimming signal generation circuit for generating a dimming signal that serves as a reference for the light output amount of the light source;
    A dimming signal processing circuit for processing the dimming signal based on a signal different from the dimming signal;
    An image display device comprising:
  2. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for generating a first dimming signal that serves as a reference for the light output amount of the light source;
    Means for generating a second dimming signal that serves as a reference for the light output amount of the light source;
    Means for generating a third dimming signal based on the first and second dimming signals and a signal different from each of the dimming signals;
    Means for controlling the light output amount of the light source based on the third dimming signal.
  3. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    A dimming signal generating means for generating a dimming signal as a control reference for the light output amount of the light source;
    Means for controlling the light source in a first and second manner based on the dimming signal;
    An image display apparatus comprising: means for determining distribution of the first method and the second method based on a signal different from the dimming signal.
  4. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    A dimming signal generating means for generating a dimming signal as a control reference for the light output amount of the light source;
    And a means for adjusting a light output period indicated by the dimming signal based on a signal different from the dimming signal.
  5. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Based on the input video signal, the light output amount of the light source is controlled, and means for processing the video signal;
    And a means for controlling the display element based on the processed video signal.
  6. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for generating a control signal for controlling the display element and / or the light source based on an input video signal;
    An image display apparatus comprising: means for controlling a light output amount of the light source based on the image signal and processing the control signal.
  7. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    A dimming signal generating means for generating a dimming signal as a control reference for the light output amount of the light source;
    Control command generating means for generating a control command including control information of the display element and / or the light source;
    An image display device comprising: means for processing the light control signal and processing the control command based on a signal different from the light control signal.
  8. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for controlling the light output amount of the light source based on the input video signal, and processing and re-outputting the video signal;
    And a means for controlling the display element based on the processed video signal.
  9. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for generating a first dimming signal that serves as a reference for the light output amount of the light source;
    Means for generating a second dimming signal that serves as a reference for the light output amount of the light source;
    Means for generating a third dimming signal based on the first and second dimming signals;
    Means for controlling the light output amount of the light source based on the third dimming signal.
  10. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    A dimming signal generating means for generating a dimming signal as a control reference for the light output amount of the light source;
    Means for controlling the light source in a first and second manner;
    An image display device comprising: means for determining distribution of the first method and the second method.
  11. In a video display device that displays video by controlling light output emitted from a plurality of light sources provided corresponding to each of a plurality of divided display areas with a plurality of display elements provided for each display area ,
    Means for evaluating the input luminance information for each display area;
    An image display apparatus comprising: means for controlling a light output amount of each light source and / or each display element based on the evaluated result.
  12. In a video display device that displays video by controlling light output emitted from a plurality of light sources provided corresponding to each of a plurality of divided display areas with a plurality of display elements provided for each display area ,
    Means for evaluating the input video signal or luminance information for each display area;
    And a means for controlling the light output amount of each light source based on the evaluated result,
    The video display device is characterized in that the control of each light source is performed so that the relationship between adjacent display areas falls within a certain constraint.
  13. In a video display device that displays video by controlling light output emitted from a plurality of light sources provided corresponding to each of a plurality of divided display areas with a plurality of display elements provided for each display area ,
    Means for controlling a light output amount of each light source to cause a constant luminance gradient at least between adjacent display areas;
    And a means for determining the value of the inclination based on the input video signal or luminance information.
  14. In a video display device that displays video by controlling light output emitted from a plurality of light sources provided corresponding to each of a plurality of divided display areas with a plurality of display elements provided for each display area ,
    By controlling the light output amount of each light source, it comprises means for adding a constant luminance gradient between the display areas,
    The video display apparatus characterized in that the added slope is set to a constant value regardless of the input video signal.
  15. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for controlling the light output amount of the light source based on the input video signal;
    Means for emphasizing a change in the light output amount in response to a change in the video signal.
  16. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for controlling the light output amount of the light source based on the input first video signal;
    A video display apparatus comprising: means for compensating for a difference between the control response delay and the video display delay based on a second video signal having a time difference from the first video signal.
  17. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for controlling the light output amount of the light source based on the input first video signal;
    And means for emphasizing the change in the light output amount before and after the change of the first video signal based on the second video signal having a time difference from the first video signal. Video display device.
  18. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for controlling the light output amount of the light source based on the input video signal;
    Means for detecting the luminance distribution of the input video signal;
    An image display device comprising: means for changing control characteristics of the light output amount with respect to the luminance distribution when the luminance distribution is different even if the average luminance of the video signal is the same.
  19. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Based on the input video signal, comprising means for controlling the light output amount of the light source,
    After nonlinear conversion processing is performed on the video signal, the average luminance is obtained, and the light output amount is controlled by the average luminance, thereby changing the control characteristic of the light output amount depending on the luminance distribution of the video signal. A video display device characterized by being provided.
  20. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Based on the input video signal, the display element is controlled and the light output amount of the light source is controlled.
    The control means controls the light source based on a peak value of luminance information included in the video signal, and reduces or reduces the light output amount of the light source. An image display device characterized in that the degree of modulation of the display element is increased by ignoring the text information.
  21. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Based on the input video signal, the display element is controlled and the light output amount of the light source is controlled.
    When the light output amount of the light source is decreased, the control means increases the modulation degree of the display element and emphasizes the high frequency range of the video signal.
  22. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Based on the input video signal, the display element is controlled and the light output amount of the light source is controlled to reduce a change in display luminance of the video represented by the video signal;
    Means for detecting a luminance change rate of the video signal,
    The mitigating means responds by controlling the display element when the change speed is fast, and responds by controlling the light source when the change speed is slow.
  23. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    A dimming signal generating means for generating a dimming signal in which the light output amount of the light source is defined by a pulse signal;
    Means for causing a plurality of pulse signals to exist within a unit frame that is a reference for video display frequency based on the dimming signal, and means for performing light output control of the light source based on the plurality of pulse signals. A characteristic video display device.
  24. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for generating a plurality of pulse signals in a unit frame serving as a reference of the video signal based on luminance information included in the input video signal;
    An image display apparatus comprising: means for performing light output control of the light source based on the plurality of pulse signals.
  25. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for controlling the display element based on an input video signal;
    Means for generating a plurality of pulse signals in synchronization with a frame signal included in the video signal, and means for controlling light output of the light source based on the plurality of pulse signals,
    The image display apparatus according to claim 1, wherein the pulse signal is generated by preferentially avoiding a state transition period of the display element and determining a width and / or phase of each pulse signal.
  26. In a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for controlling the display element based on an input video signal;
    Means for generating a plurality of pulse signals in synchronization with a frame signal included in the video signal;
    Means for performing light output control of the light source based on the plurality of pulse signals,
    The image display device according to claim 1, wherein the pulse signal is generated by determining a width and / or a phase of each pulse signal according to a predetermined relationship.
  27. In a signal processing circuit incorporated in a video display device that displays video by controlling light output emitted from a light source with a plurality of display elements,
    Means for generating a dimming signal that serves as a reference for the light output amount of the light source;
    A signal processing circuit comprising: means for processing the dimming signal based on a signal different from the video signal.
  28. In a liquid crystal backlight control device that controls the light output of a backlight light source provided on the back of a plurality of liquid crystal elements,
    Means for generating a dimming signal to be a control reference of the backlight light source;
    Means for processing the light control signal based on a signal different from the light control signal.
  29. In a liquid crystal backlight control method for controlling the light output of a backlight light source provided on the back of a plurality of liquid crystal elements,
    Generating a dimming signal as a control reference for the backlight source;
    And a step of processing the dimming signal based on a signal different from the dimming signal.
JP2006229557A 2006-08-25 2006-08-25 Liquid crystal backlight driving device Pending JP2008052131A (en)

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