JP2001142409A - Video display device and illumination control method in the video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power consumption required for illumination. SOLUTION: At least one LED as a light source which emits illuminating light irradiating a liquid crystal panel is arranged at least one by one for plural divided areas. An LED control circuit 34 controls driving of LEDs on a back light panel 2 in the unit of divided areas so that only picture areas requiring illuminating light may be irradiated with illuminating light in accordance with a video signal. Picture areas which don't require to be illuminated are not irradiated with illuminating light fundamentally to reduce the power consumption required for illumination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video display device for displaying a video by modulating illumination light in accordance with a video signal, and a lighting control method in the video display device.

[0002]

2. Description of the Related Art Conventionally, there is an image display device that displays an image using a liquid crystal display element (hereinafter, referred to as a liquid crystal panel) as a light modulation element. As a type of a liquid crystal panel used for an image display device, there are a transmissive panel that transmits irradiated light and a reflective panel that reflects irradiated light. In recent years, a video display device using such a liquid crystal panel (hereinafter, referred to as a “liquid crystal display device”) has been used in various devices including information devices such as a portable personal computer (personal computer). . Here, for example, in a liquid crystal display device using a transmissive liquid crystal panel, the liquid crystal panel is irradiated with illumination light, and the illumination light is modulated according to a video signal in the liquid crystal panel and selectively transmitted. Accordingly, an image is displayed. As an illumination system in such a liquid crystal display device, a backlight system in which illumination light is emitted from the back of a liquid crystal panel is often used. A fluorescent tube is mainly used as a light source in the backlight system.

[0003]

However, in the conventional method of illuminating a liquid crystal display device, the entire screen is illuminated irrespective of the image display state, for example, even when an image is displayed only on a part of the screen. Therefore, there is a problem that power consumption for lighting becomes unnecessarily large. In particular, in information devices such as portable personal computers that often use a battery as a power source, a large percentage of the power consumed for lighting affects the usable time of the device. Desirably less.

Further, the fluorescent tube used as a light source for illumination has a drawback that its life is shortened when it is repeatedly turned on / off, a drawback that a high voltage is required for lighting, and a glass material. However, there is a disadvantage that the degree of freedom of the shape due to the configuration is small.

Recently, white and blue light emitting diodes (hereinafter referred to as “LEDs (Light Emitting Diodes)”) have been developed and commercialized, and these LEDs are used as light sources instead of fluorescent tubes. Is becoming possible. LEDs can be driven at a lower voltage than fluorescent tubes, have lower power consumption, and have better performance than fluorescent tubes, such as longer lifespan.Therefore, LEDs are used as light sources in liquid crystal display devices instead of fluorescent tubes. The use can solve some problems of the fluorescent tube. However, as described above, in the conventional lighting method in the liquid crystal display device, the entire screen is illuminated regardless of the display state of the image, and therefore, the low power consumption LED is used as the light source.
Even if is used, the effect of reducing power consumption is limited and not sufficient.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a video display device and a lighting control method in the video display device, which can reduce power consumption required for lighting. It is in.

[0007]

According to the present invention, there is provided an image display apparatus comprising: a light modulation element for forming an image corresponding to a video signal on a display screen by modulating irradiated illumination light according to the video signal; At least one light source is provided for each of a plurality of divided areas obtained by dividing the display screen, and a plurality of light emitting units that emit illumination light to irradiate the light modulation element, and at least illumination light is required according to a video signal. And a control circuit for controlling the driving of the plurality of light emitting means in units of divided regions so that the pixel region is irradiated with illumination light.

The illumination control method in the video display device according to the present invention modulates the irradiated illumination light by a light modulation element according to a video signal so as to form an image according to the video signal on a display screen. A lighting control method for a video display device, comprising: arranging at least one light emitting unit for emitting illumination light for irradiating a light modulation element for each of a plurality of divided areas obtained by dividing a display screen, according to a video signal. The driving of the light-emitting means is controlled in units of divided areas so that at least a screen area requiring the illumination light is irradiated with the illumination light.

In the video display apparatus and the illumination control method in the video display apparatus according to the present invention, at least one light-emitting means for emitting illumination light for irradiating the light modulation element is provided for each of a plurality of divided areas obtained by dividing the display screen. At the same time, the light emitting means is driven and controlled in units of divided regions so that at least a screen region requiring the illumination light is irradiated with the illumination light in accordance with the video signal.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] FIG. 2 is a sectional view showing a main structure of a liquid crystal display device as a video display device according to a first embodiment of the present invention. As shown in the figure, the liquid crystal display device according to the present embodiment is a liquid crystal panel 1 that forms an image corresponding to a video signal on a display surface 5 by optically modulating illumination light according to a video signal. And a backlight panel 2 that is arranged to face the liquid crystal panel 1 and irradiates illumination light from the back of the liquid crystal panel 1.
And As shown in FIG. 1B, in the liquid crystal display device according to the present embodiment, the illumination light from the backlight panel 2 is further made uniform between the liquid crystal panel 1 and the backlight panel 2. May be provided. Here, the liquid crystal panel 1 corresponds to a specific example of “light modulation element” in the present invention.

The liquid crystal panel 1 is, for example, a TFT (Thin F).
It is driven by an active matrix system such as an ilm transistor (thin film transistor) type, and includes a liquid crystal layer and an electrode substrate for applying a voltage to the liquid crystal layer (not shown). Here, the TFT type liquid crystal panel has a configuration in which thin film transistors functioning as switching elements are arranged in a matrix at intersections of row electrodes arranged in a row direction and column electrodes arranged in a column direction. In a TFT-type liquid crystal panel, by controlling thin-film transistors arranged in a matrix and selectively applying a voltage to the liquid crystal layer independently for each pixel, the incident light is optically modulated to display an image. Is performed. As the liquid crystal panel 1, for example, STN (super twisted nem)
An element driven by a simple matrix method such as an atic (super twisted nematic) type may be used. The STN type liquid crystal panel has a configuration in which two electrode substrates having row electrodes and column electrodes arranged in a matrix on the surface are opposed to each other with a liquid crystal layer interposed therebetween. In an STN type liquid crystal panel, incident light is optically modulated in response to an effective voltage value of a drive voltage applied between a row electrode and a column electrode, and an image is displayed.

A backlight panel 2 has a plurality of LEDs on its side facing the liquid crystal panel 1 as a light source for emitting illumination light.
3 has a substrate 4 on which it is arranged. The LED 3 emits white light from the back of the liquid crystal panel 1,
White LED that emits white light by itself or red (Red = R), green (Green = G), blue (Blue =
It is composed of a combination of LEDs of three colors B). The LEDs 3 are connected to the switching elements in, for example, a predetermined divided area unit, and drive control is performed in a predetermined divided area unit, as described later. If a problem arises because individual light emitted from the plurality of LEDs 3 becomes uneven, a light diffusing plate 6 is provided between the liquid crystal panel 1 and the backlight panel 2 as shown in FIG. Are desirably arranged to make the light amount uniform. Where L
The ED 3 corresponds to a specific example of “light emitting unit” in the present invention. In addition, each LED of each color in the case where the LED 3 is configured by an LED of each color of R, G, and B that can be driven independently corresponds to a specific example of “light emitting element” in the present invention.

FIG. 3 shows each pixel and L in the liquid crystal panel 1.
It is explanatory drawing which shows the relationship with ED3. 3A shows the arrangement of each pixel in the liquid crystal panel 1, and FIG.
3 is shown. Note that in (A), one rectangular area P corresponds to one pixel.

In the liquid crystal panel 1, as shown in FIG. 1A, a pixel has m rows and n columns (m and n are integers of 2 or more).
Are arranged in a matrix. On the other hand, LED3 is
At least one is provided for each of a plurality of divided areas obtained by dividing the display screen formed by the liquid crystal panel 1. In the example of FIG. 3B, the arrangement surface of the LED 3 is divided into two in the horizontal direction (X direction in FIG. 4) and in the vertical direction (Y direction in FIG. 4), and divided into a total of four regions 20A to 20D. An example in which six LEDs 3 are arranged at equal intervals in each divided area is shown. Further, in the present embodiment, the LED 3 is driven and controlled in each divided area according to a video signal, and can partially illuminate the liquid crystal panel 1 in each divided area.

The number of divided areas and the number of LEDs 3 arranged in each divided area can be set to an arbitrary number in consideration of the size of the entire display screen, the total number of pixels, and the like. It is not limited. For example, when the size of the entire display screen is small, it is possible to set the number of LEDs 3 arranged in each divided area to be smaller than when the display screen is large. Also, in the figure, an example is shown in which each divided region is set to a rectangular shape and the size of each divided region is all the same, but the shape and size of each divided region are not limited to those illustrated, It is also possible to set the size of each divided region so that the size is partially different, or to set the shape of each divided region to another shape such as a polygon other than a rectangle.

FIG. 1 is a block diagram showing a circuit configuration of a control system of the liquid crystal display device according to the present embodiment. The liquid crystal display device according to the present embodiment includes, as control circuits, a signal drive circuit 11 for applying a signal voltage corresponding to a video signal to the liquid crystal panel 1 via a data line 13, and a liquid crystal panel via a data line 14. 1, a scan drive circuit 12 that cyclically applies a scan voltage, a horizontal drive circuit 21 that applies a control signal for controlling the LED 3 of the backlight panel 2 via a data line 23, and a data drive line 24. A vertical drive circuit 22 for applying a control signal for controlling the LEDs 3 of the backlight panel 2.

The liquid crystal display device according to the present embodiment further includes a video signal processing circuit 31 for performing signal processing so that the input video signal Vs becomes a signal suitable for driving the liquid crystal panel 1, and a video signal processing circuit. A video memory 32 for temporarily storing a video signal of a predetermined unit (for example, one frame or one line) processed by the circuit 31;
2, a liquid crystal panel control circuit 33 for controlling the driving of the liquid crystal panel 1 via the signal driving circuit 11 and the scanning driving circuit 12 based on the video signal stored in the LCD panel 2, and a backlight via the horizontal driving circuit 21 and the vertical driving circuit 22. An LED control circuit 34 for driving and controlling the panel 2 and a video signal processing circuit 3
1. Liquid crystal panel control circuit 33 and LED control circuit 34
And a controller 35 for controlling the components of each part of the liquid crystal display device including the above.

Here, the horizontal drive circuit 21, the vertical drive circuit 22, the LED control circuit 34 and the controller 35
This corresponds to a specific example of the “control circuit” in the present invention.

The data lines 13 and 14 are connected to electrodes for applying a voltage to the liquid crystal layer of the liquid crystal panel 1, respectively. A plurality of data lines 13 are provided corresponding to the number of pixels in the horizontal direction (X direction in the drawing) of the liquid crystal panel 1, and one data line 13 extends in the same column direction (Y direction in the drawing) of the liquid crystal panel 1. It is possible to apply a signal voltage from the signal drive circuit 11 to a certain pixel. A plurality of data lines 14 are provided corresponding to the number of pixels in the vertical direction (Y direction in the drawing) of the liquid crystal panel 1, and one data line 14 extends in the same row direction (X direction in the drawing) of the liquid crystal panel 1. It is possible to apply a scanning voltage from the scanning drive circuit 12 to a certain pixel. In the liquid crystal panel 1, a pixel located at the intersection of the data line 13 to which the signal voltage is applied and the data line 14 to which the scanning voltage is applied is driven. This makes it possible to drive the liquid crystal panel 1 on a pixel-by-pixel basis in accordance with a video signal.

The liquid crystal panel control circuit 33 controls the scan drive circuit 12 so that a scan voltage is sequentially applied from the scan drive circuit 12 to the plurality of data lines 14 at a constant scan cycle. Further, the liquid crystal panel control circuit 33 includes:
The video signal stored in the video memory 32 is read at a predetermined cycle, and a signal voltage based on the video signal is selectively applied from the signal drive circuit 11 to the plurality of data lines 13 based on the read video signal. , And the signal drive circuit 11.

Each of the data lines 23 and 24 is connected to an electrode for applying a voltage to the LED 3 of the backlight panel 2. The data line 23 is the number of divisions (two in the example of FIG. 3) in the horizontal direction (X direction in FIG. 3) of the division area set as the drive unit of the backlight panel 2.
Are provided in correspondence with. The data lines 24 correspond to the number of divisions (two in the example of FIG. 3) in the vertical direction (Y direction in FIG. 3) of the divided regions set as the drive units of the backlight panel 2.
) Are provided. In the backlight panel 2, the LEDs 3 in the divided region located at the intersection of the data line 23 to which the control signal from the horizontal drive circuit 21 is applied and the data line 14 to which the control signal from the vertical drive circuit 22 is applied are connected. Driven. Thus, in the backlight panel 2, the LEDs 3 can be driven in units of divided areas.

The LED control circuit 34 controls the horizontal drive circuit 21 and the vertical drive circuit 22 such that the LED 3 in the divided area corresponding to the pixel area where illumination light is required is driven in accordance with the driving of the liquid crystal panel 1. Is controlled.

The controller 35 controls the liquid crystal panel control circuit 33 and the LED control circuit 34 synchronously so that the LEDs 3 of the backlight panel 2 are driven in synchronization with the driving cycle of the liquid crystal panel 1.

Next, the operation of the liquid crystal display having the above configuration will be described. The following description also serves as a description of the illumination control method in the present embodiment.

The video signal Vs input to the video signal processing circuit 31 is subjected to signal processing by the video signal processing circuit 31 so as to be a signal suitable for driving the liquid crystal panel 1.
Output to the video memory 32. The video memory 32 temporarily stores a video signal of a predetermined unit (for example, one frame or one line) processed by the video signal processing circuit 31. The liquid crystal panel control circuit 33 includes a video memory 32
Is read out at a predetermined cycle, and the liquid crystal panel 1 is drive-controlled via the signal drive circuit 11 and the scan drive circuit 12 based on the read out video signal.

The scanning drive circuit 12 sequentially applies a scanning voltage to the plurality of data lines 14 at a constant scanning cycle under the control of the liquid crystal panel control circuit 33. Signal drive circuit 11
Selectively applies a signal voltage corresponding to a video signal to the plurality of data lines 13 under the control of the liquid crystal panel control circuit 33. In the liquid crystal panel 1, the pixel located at the intersection of the data line 13 to which the signal voltage is applied and the data line 14 to which the scanning voltage is applied is driven, and responds to the video signal with respect to the illumination light incident on the liquid crystal layer. Optical modulation is performed.

The LED control circuit 34 controls the liquid crystal panel 1 via the horizontal drive circuit 21 and the vertical drive circuit 22 so that at least the pixel area where the illumination light is required is irradiated with the illumination light in accordance with the video signal. The LED 3 in the backlight panel 2 is drive-controlled for each set divided area. In the backlight panel 2, a data line 23 to which a control signal from the horizontal drive circuit 21 is applied and a data line 14 to which a control signal from the vertical drive circuit 22 is applied
LED 3 in the divided area located at the intersection with is driven,
From the driven LED 3 toward the back of the liquid crystal panel 1,
Illumination light is emitted for each set divided area. The controller 35 controls the liquid crystal panel control circuit 33 and the LED control circuit 34 synchronously so that the LEDs 3 of the backlight panel 2 are driven in synchronization with the driving cycle of the pixels in the liquid crystal panel 1.

Next, referring to FIG. 4, the driving control of the pixels in the liquid crystal panel 1 and the LEDs in the backlight panel 2 which are characteristic parts of the liquid crystal display device according to the present embodiment will be described.
The control relationship with drive control 3 will be described in more detail. FIG. 2A shows an example of a display screen 50 displayed on the display surface 5 (FIG. 2) of the liquid crystal panel 1. FIGS. 3B and 3C correspond to FIGS. 3A and 3B, respectively. In FIG. 3C, black areas 20B to 20D indicate that the LED 3 is not lit, and an area 20A that is not black is the LED 3
Indicates that is lit. Hereinafter, a case will be described in which the liquid crystal display device 1 performs monochrome image display in a so-called normally black mode. In the liquid crystal panel 1 operating in the normally black mode, the screen has a black level display in a normal state where no voltage is applied to the liquid crystal layer. When a voltage is applied to the liquid crystal layer, light is transmitted through the liquid crystal layer and the screen is displayed. It operates so as to display a white level.

Here, as shown in FIG. 3A, only the pixel portion located at the address (α, β) is displayed in white level (bright display), and the other pixel portions are displayed in black level (dark display). Display) of a one-frame display screen 50
A case of displaying on the display surface 5 (FIG. 2) of the liquid crystal panel 1 will be described. When displaying the display screen 50 as shown in FIG. 5A, the liquid crystal panel control circuit 33 (FIG. 1) controls the addresses (α, β) on the liquid crystal panel 1 as shown in FIG. ), The signal drive circuit 11 and the scan drive circuit 12 are controlled so that only the illumination light incident on the liquid crystal layer corresponding to the address (α, β) is transmitted.

At this time, in the backlight panel 2, all the Ls in the divided area corresponding to the address (α, β)
ED3 is driven. For example, as shown in FIG. 3C, when the driving unit of the LED 3 in the backlight panel 2 is equally divided into four divided areas 20A to 20D, the address (α, β) is controlled by the LED control circuit 34. )
The horizontal drive circuit 21 and the vertical drive circuit 22 are controlled such that only the LEDs 3 in the divided area 20A corresponding to the above are driven to emit light. In the liquid crystal panel 1, since the pixels other than the address (α, β) are not driven, the illuminating light incident on the liquid crystal layer other than the address (α, β) does not pass through the liquid crystal layer. A display screen 50 as shown in FIG. In this way, when the display screen 50 of one frame as shown in FIG. 5A is displayed, the address (α, β) of the four divided areas 20A to 20D is set in one frame unit. Only the LEDs 3 in the corresponding divided area 20A are driven.

In the conventional liquid crystal display device, the entire screen is always illuminated with the illumination light regardless of the display state of the image. Therefore, as shown in FIG. Is displayed, the illumination light is always applied to the entire screen. On the other hand, in the liquid crystal display device of the present embodiment, as described above, the LEDs 3 in the backlight panel 2 are selectively driven and controlled according to the image to be displayed, so that at least illumination light is required. Since the illumination light is partially applied only to the pixel region, the power consumption required for the illumination is reduced. In the example shown in FIG. 4, as compared with the case where the entire screen is irradiated with illumination light,
Illuminating light is illuminated only in the area of
4 = 75% power reduction.

Next, referring to FIG. 5 and FIG.
The relationship between the number of divided regions serving as the driving unit 3 and the power consumption of the LED 3 will be described in more detail. In FIGS. 5 and 6, for simplification of the drawings, illustration of the LEDs 3 in the divided areas set in the backlight panel 2 is omitted.

In the example shown in FIG. 4, a case has been described in which a pixel area for which illumination light is required is only one pixel in a one-frame screen. It is considered that images are often displayed in a dispersed manner. At this time, if the number of divided regions is small, the effect of reducing power consumption may not be obtained.

For example, as shown in FIG.
When the display image 51 is displayed so as to extend over all of the four divided areas 20A to 20D which are the drive units of D3, as shown in FIG.
Since all the LEDs 3 within ２０20D are turned on, the effect of reducing power consumption cannot be obtained. However, even in the case where images are dispersedly displayed on the entire screen,
The effect of reducing power consumption can be obtained by further dividing the divided area.

FIG. 6 is a diagram showing the L in the backlight panel 2.
The divided area as a drive unit of the ED3 is equally divided into eight in the horizontal direction (X direction in the same drawing) and six in the vertical direction (Y direction in the same drawing) with respect to the display screen, for a total of 48 divisions. An example of the setting is shown. In the drawing, a rectangular area indicated by reference numeral 20 is one divided area. When the display area 51 is displayed by setting the divided areas in this way, the LED 3 that needs to be driven is displayed on the display image 51 as shown in FIG. LED3 in a total of 22 divided areas in the central area 20-1 of the screen corresponding to
It is not necessary to drive the LEDs 3 in the total of 26 divided areas in the other areas 20-2 and 20-3. Therefore, in this case, the power is reduced by 26/48 = 60.9% as compared with the case where the entire screen is irradiated with the illumination light.

As described above, by subdividing the divided areas, the effect of power saving can be enhanced even when performing a complicated image display in which images are dispersed over the entire screen. By setting one divided region for one pixel, the effect of power consumption reduction is substantially maximized. However, the size of one pixel in the liquid crystal panel 1 used for a portable personal computer or the like is the same as the current LED3.
Since the size is considerably smaller than the size of the pixel, usually, one LED 3 illuminates a plurality of pixels, and it is difficult to set one divided region for one pixel.
However, it is needless to say that the number of divided regions can be set to one for each pixel when the size of one pixel is large or depending on improvement of device technology.

As described above, according to the liquid crystal display device of the present embodiment, at least one LED 3 serving as a light source for illuminating the liquid crystal panel 1 is provided for each of the plurality of divided areas. In addition, the LED 3 is driven and controlled in units of divided areas so that the illumination light is emitted only to the screen area where illumination light is required at least in accordance with the video signal. Can be prevented from irradiating illumination light, and power consumption required for illumination can be reduced. As a result, especially for information devices such as portable personal computers that often use a battery as a power source,
An excellent effect that the usable time of the battery can be extended can be obtained.

Further, according to the liquid crystal display device of the present embodiment, normally, the pixel portion for performing the black level display is not irradiated with the illuminating light, so that the light reaches the pixel portion where the illuminating light is not required. It is possible to reduce so-called leaked light that leaks, and it is possible to lower the brightness of the black level. As a result, the contrast in image display can be improved, and good image display can be performed.

[Second Embodiment] Next, a second embodiment of the present invention will be described.
An embodiment will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof will not be repeated.

Usually, the size of one pixel in the liquid crystal panel 1 is considerably smaller than the size of one LED 3.
Therefore, the size of one pixel in the liquid crystal panel 1 is usually sufficiently small with respect to each divided area which is a driving unit of the LED 3. When there is such a relationship between the size of the pixel and the size of the divided region, in the first embodiment, only the divided region corresponding to the pixel region where the illumination light is required is set as the drive target. Therefore, even if there is a slight change in the displayed image, the divided region to be driven moves. Therefore, when the image changes frequently, the divided area to be driven frequently changes, and the area irradiated with the illumination light frequently changes. However, if the area to be irradiated with the illumination light is frequently switched, unnecessary flickering to the human eye may occur, which may cause discomfort.

First, with reference to FIG. 7, a description will be given of the flicker caused by the change in the image described above. In the following description, a case will be described in which the liquid crystal display device 1 displays a monochrome image in the normally black mode, as in the first embodiment. In the figure, as shown in (B), the addresses of the pixels in the liquid crystal panel 1 in the horizontal direction (X direction in the figure) are sequentially set to 0h, 1 from the left end of the screen.
h, 2h, 3h, 4h,..., and the addresses of the pixels in the vertical direction (Y direction in the figure) are sequentially set to 0v, 1 from the upper end of the screen.
v, 2v, 3v, 4v,... Also, in the same figure, as shown in (C), the size of one divided region that is a driving unit of the LED 3 is “3 pixels in the horizontal direction” × “3 pixels in the vertical direction” = 9 pixels in total. Is set to
FIG. 2 shows only a partial area at the upper left of the screen.

Here, for example, a case where a display screen 50C as shown in FIG. 5A is displayed in the first frame and a display screen 50D as shown in FIG. Will be described as an example. In the display screen 50C shown in FIG. 9A, only the pixel portion at the address (2h, 2v) is displayed in the white level. In the display screen 50D shown in FIG. 3D, only the pixel portion at the address (3h, 2v) adjacent to the address (2h, 2v) by one pixel in the horizontal direction is displayed in the white level.

When such display screens 50C and 50D are continuously displayed, it appears that the display pixels have moved only one pixel in the horizontal direction. At this time, the displayed addresses (2h, 2v) and Address (3h, 2v)
Are located at the ends of the divided area at the address (1, 1) and the divided area at the address (2, 1). , (F), the divided area to be driven is switched. As described above, if the state in which the pixel to be displayed frequently moves from the end to the end of the adjacent divided region, the region irradiated with the illumination light is frequently switched, and the flicker occurs. Not preferred. In the present embodiment, a liquid crystal display device for solving such a problem will be described.

FIG. 8 is an explanatory diagram for describing the control operation of illumination light in the liquid crystal display device according to the present embodiment. The arrangement of the addresses of the pixels of the liquid crystal panel 1 and the arrangement of the addresses of the divided areas and the size of each divided area in FIG. 7 are the same as those in FIG.

In the first embodiment, only the divided areas corresponding to the pixels to be actually displayed in the white level are to be driven, but in the present embodiment, the pixels to be actually displayed in the white level are to be driven. A pixel area extended by a predetermined area is set, and the divided area corresponding to the pixel to be actually displayed in white level and the divided area corresponding to the extended pixel area are also to be driven. For example, in the example of FIG. 8, an address range extended by ± 1 in the horizontal and vertical directions with respect to the address of the pixel to be actually displayed in the white level is set as the extended pixel area 60. Fig. (B)
In the example of (1), the address of the pixel to be actually displayed in the white level is (2h, 2v), and the surrounding (1h, 1v),
(2h, 1v), (3h, 1v), (1h, 2v),
(3h, 2v), (1h, 3v), (2h, 3v),
Pixels at eight addresses (3h, 3v) are pixels set as an extended pixel area. On the other hand, the address of the pixel to be actually displayed as the white level is changed from (2h, 2v) to (3
h, 2v), (2h, 1v), (3h, 1) around the address (3h, 2v) in the example of FIG.
v), (4h, 1v), (2h, 2v), (4h, 2
v), (2h, 3v), (3h, 3v), (4h, 3
The pixel at the address of v) is set as an extended pixel.

As described above, when the extended pixel area 60 is set, the divided area to be driven is, as shown in FIG.
As shown in FIG. 3C, the divided area of the address (1, 1) corresponding to the pixel of the address (2h, 2v) to be actually displayed as the white level is to be driven, and the surrounding area is further driven. The divided areas of the addresses (2, 1) and (1, 2) (2, 1) are to be driven. That is, a total of four divided areas are set as driving targets. The divided area to be driven is expanded even if the address of the pixel to be actually displayed as the white level moves from (2h, 2v) to (3h, 2v) as in the example of FIG. Pixel area 60
Is the same because Therefore, by setting the extended pixel area 60, a situation in which the divided area to be driven is switched by only moving the display pixel by one pixel as in the example of FIG. 7 is prevented. Thereby, even if the pixel to be displayed frequently moves from the end to the end of the adjacent divided region, it is suppressed that the region irradiated with the illumination light is frequently switched,
Flicker can be reduced.

In the present embodiment, the drive control using the extended pixel area 60 is performed on the LEDs 3 in the backlight panel 1, and the drive control of the pixels in the liquid crystal panel 1 is performed by the first control. This is the same as the embodiment. The setting of the extended pixel region 60 and the control of the LEDs 3 based on the extended pixel region 60 are performed by the LED control circuit 34 (FIG. 1).

FIG. 8 shows a case where the range to be extended is set to the pixels within the address range of ± 1 in the horizontal and vertical directions with respect to the address of the driving pixel. However, the present invention is not limited to this. At this time, it is desirable that the range to be extended be determined in consideration of the relative relationship between the pixels and the size of each divided region, the frequency of occurrence of flicker, the power saving effect, and the like. For example, when priority is given to the effect of power saving, the range to be extended is set smaller. Conversely, if the range in which the pixels are expanded is set to be large, the power saving effect is reduced, but the frequency of flicker can be reduced.

As described above, according to the liquid crystal display device of the present embodiment, the LED control circuit 34
An extended pixel area is set by extending the pixel area where illumination light is required by a predetermined area, and according to a video signal, L is arranged in a divided area corresponding to the pixel area where illumination light is required.
The ED3 is caused to emit light, and the LE3 is arranged to emit light in the LED3 arranged in the divided area corresponding to the extended pixel area.
Since the drive control of D3 is performed, the frequency of switching the divided regions to be driven is reduced, and unnecessary flickering accompanying image display can be improved.

The other configurations, operations, and effects of this embodiment are the same as those of the first embodiment.

The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, the LEDs 3 that emit illumination light to irradiate the liquid crystal panel 1 may be configured by combining LEDs of each color of R, G, and B that can be driven independently, and the LEDs may be controlled independently for each color. Thereby, it is possible to control the illumination light to irradiate the liquid crystal panel 1 so as to have a color desired by the user.
For example, the combined light from the LEDs of each color can be controlled to a desired illumination color such as reddish white having a low color temperature, bluish white or greenish white having a high color temperature. When the external light is blue light such as fluorescent light, or when the external light is extremely red light such as sodium light,
When illuminating the liquid crystal panel 1 with the same color of illumination light under different external illumination, the screen becomes difficult to see depending on the type of external illumination. However, if the color of the illumination light applied to the liquid crystal panel 1 is changed according to the type of external illumination, Thus, the visibility of the display screen can be improved. In this way, by controlling the LEDs independently for each color, the color temperature of the display screen can be adjusted according to the external lighting environment, and a display state with good visibility can be provided. .

At this time, the display surface 5 of the liquid crystal panel 1
, An optical sensor for detecting external light may be provided, and control may be performed to automatically adjust the light amount of each color LED based on the detection result of this optical sensor. This makes it possible to provide a display state in which the visibility is automatically optimized according to the external environment.

Further, in each of the above-described embodiments, a case has been described in which a black-and-white image is displayed in a normally black mode in which the liquid crystal panel 1 displays a black level in a normal state. However, the present invention is not limited to this. Without being
For example, the present invention can be applied to a display method in a so-called normally white mode in which a white level is displayed in a normal state. When the present invention is applied to a case where the liquid crystal panel 1 operates in the normally white mode, the relationship between the driving of the pixels of the liquid crystal panel 1 and the driving of the LEDs 3 in the normally black mode described in each of the above embodiments is described. Is reversed. For example, in the normally white mode, the LED 3 corresponding to the driven pixel is not driven, and the LED corresponding to the pixel other than the driven pixel is not driven.
3 is controlled to emit light. Further, in each of the above embodiments, the case of displaying a monochrome image has been described for the sake of simplicity, but the present invention is also applicable to the case of displaying a color image.

[0055]

As described above, according to the illumination control method for a liquid crystal display device according to any one of claims 1 to 4 or the illumination control method for a liquid crystal display device according to claim 5, illumination applied to a light modulation element. At least one light emitting unit that emits light is arranged for each of a plurality of divided areas obtained by dividing the display screen, and illumination light is applied to at least a screen area where illumination light is required according to a video signal. As described above, since the driving of the light emitting means is controlled in units of the divided areas, it is possible to prevent the illumination light from being emitted to the screen area which does not need to be illuminated, and the power consumption required for the illumination is This has the effect of being able to reduce.

In particular, according to the liquid crystal display device of the second aspect, in the liquid crystal display device of the first aspect, the control circuit expands a pixel region where illumination light is required by a predetermined region. In accordance with the video signal, the light emitting means arranged in the divided area corresponding to the pixel area where illumination light is required emits light, and the light emitting means arranged in the divided area corresponding to the extended pixel area emits light. As described above, since the driving of the plurality of light emitting units is controlled, the switching frequency of the divided areas to be driven can be reduced, and unnecessary flicker accompanying image display can be improved.

According to a third aspect of the present invention, in the liquid crystal display device of the first aspect, the plurality of light emitting means are constituted by a plurality of light emitting elements each emitting light of a different color. Since the control circuit can control the light-emitting means for each light-emitting element, for example, the color temperature of the display screen can be adjusted according to the external lighting environment, and a display state with good visibility can be provided. This has the effect of becoming

Further, according to the display device of the fourth aspect,
2. A liquid crystal display device according to claim 1, wherein a light diffusing plate for equalizing illumination light from the light emitting means is provided between the light modulation element and the plurality of light emitting means. In the case where there is unevenness in the individual illumination light emitted from, there is an effect that the unevenness of the illumination light can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a liquid crystal display device as a video display device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a main structure of the video display device shown in FIG.

FIG. 3 is an explanatory diagram showing the relationship between the arrangement of LEDs and pixels in the video display device shown in FIG.

FIG. 4 is an explanatory diagram for explaining an illumination light control operation in the video display device shown in FIG. 1;

FIG. 5 is an explanatory diagram for describing a relationship between an image displayed on the video display device shown in FIG. 1 and a driving range of an LED.

FIG. 6 is another explanatory diagram for describing a relationship between an image displayed in the video display device shown in FIG. 1 and a driving range of the LED.

FIG. 7 is an explanatory diagram showing a comparative example of the control operation of the illumination light in the liquid crystal display device according to the second embodiment of the present invention.

FIG. 8 is an explanatory diagram illustrating an operation of controlling illumination light in a liquid crystal display device according to a second embodiment of the present invention.

[Explanation of symbols]

1: liquid crystal panel, 2: backlight panel, 3: LE
D, 5: display surface, 6: light diffusion plate, 11: signal drive circuit,
12 scanning drive circuit, 21 horizontal drive circuit, 22 vertical drive circuit, 31 video signal processing circuit, 32 video memory, 33 liquid crystal panel control circuit, 34 LED control circuit, 35 controller, 60 expansion Pixel area.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H093 NA07 NA16 NC29 NC34 NC44 NC45 NC49 NC59 ND04 ND09 ND39 NE06 NF05 NF13 5C006 AA01 BB14 BF45 EA01 FA22 FA47 5G435 AA16 BB12 BB15 CC09 CC12 EE26 LL08

Claims (5)

[Claims] A light modulation element that forms an image corresponding to a video signal in a display screen by modulating the irradiated illumination light in accordance with the video signal; and a plurality of divided areas obtained by dividing the display screen. A plurality of light emitting means for emitting illumination light for irradiating the light modulation element, and irradiating at least a pixel area where illumination light is required with the video signal in accordance with the video signal And a control circuit for controlling the driving of the plurality of light emitting units in units of the divided areas. 2. The control circuit sets an extended pixel area obtained by expanding a pixel area in which the illumination light is required by a predetermined area, and sets the extended pixel area in a pixel area in which the illumination light is required in accordance with the video signal. The plurality of light emitting units are driven and controlled such that the light emitting units arranged in the corresponding divided regions emit light and the light emitting units arranged in the divided regions corresponding to the extended pixel regions emit light. The video display device according to claim 1. 3. The light emitting device according to claim 1, wherein the plurality of light emitting units include a plurality of light emitting devices each emitting light of a different color, and the control circuit is capable of controlling the light emitting unit for each of the light emitting devices. The video display device according to claim 1. 4. A light diffusing plate provided between the light modulating element and the plurality of light emitting means for equalizing illumination light from the light emitting means. 2. The image display device according to 1. 5. An illumination control method in an image display device, wherein an emitted illumination light is modulated by a light modulation element according to an image signal to form an image according to the image signal on a display screen. A light emitting unit that emits illumination light for irradiating the light modulation element,
The light-emitting unit is arranged such that at least one of the plurality of divided areas is divided into the display screen, and the screen area where at least illumination light is required is irradiated with the illumination light in accordance with the video signal. A lighting control method in the video display device, wherein the driving control is performed for each divided area.