JP4167474B2 - Liquid crystal display - Google Patents

Liquid crystal display Download PDF

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Publication number
JP4167474B2
JP4167474B2 JP2002323712A JP2002323712A JP4167474B2 JP 4167474 B2 JP4167474 B2 JP 4167474B2 JP 2002323712 A JP2002323712 A JP 2002323712A JP 2002323712 A JP2002323712 A JP 2002323712A JP 4167474 B2 JP4167474 B2 JP 4167474B2
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Prior art keywords
liquid crystal
backlight
crystal display
light
light source
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JP2002323712A
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JP2004157373A (en
Inventor
隆司 吉井
道幸 杉野
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シャープ株式会社
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Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device that displays an image by illuminating a liquid crystal display panel with a backlight light source, and more particularly to a liquid crystal display device that prevents motion blur that occurs when displaying a moving image by bringing it closer to an impulse-type display. is there.
[0002]
[Prior art]
In recent years, flat panel display devices (FPD) such as liquid crystal display devices (LCD) that can realize high definition, low power consumption, and space saving have been actively developed, and in particular, computer display devices and television display devices. The spread of LCDs for such applications is remarkable. However, in contrast to a cathode ray tube (CRT) display device that has been mainly used for such applications, the LCD has a blurred outline of the moving part when a moving image is displayed. It has been pointed out the disadvantage of the so-called “motion blur” that it is perceived.
[0003]
It has been pointed out that the motion blur in moving image display is caused not only by the delay of the optical response time of the liquid crystal but also by the LCD display method itself as described in, for example, Japanese Patent Laid-Open No. 9-325715. In a CRT display device that scans an electron beam and emits phosphors to perform display, each pixel emits light almost in an impulse form although there is a slight afterglow of the phosphors. Yes.
[0004]
On the other hand, in the LCD display device, the charge stored by applying the electric field to the liquid crystal is held at a relatively high rate until the next electric field is applied (particularly in the TFT LCD, the pixel is configured. A TFT switch is provided for each dot to be operated, and since an auxiliary capacitor is usually provided for each pixel, the stored charge is very high in capacity), so that the liquid crystal pixel is based on the image information of the next frame. This is a so-called hold type display system in which light emission is continued until rewriting is performed by applying an electric field.
[0005]
In such a hold-type display device, since the impulse response of the image display light has a temporal spread, the temporal frequency characteristic is deteriorated, and the spatial frequency characteristic is also lowered accordingly, and the visual image is blurred. . Therefore, in the above-mentioned Japanese Patent Laid-Open No. 9-325715, display light is viewed only in the second half of each field period of a display image by controlling on / off of a shutter or a light source lamp (backlight) provided on the display surface. There has been proposed a display device that improves the motion blur of a viewing image by presenting to a person and limiting the temporal spread of the impulse response.
[0006]
This will be described with reference to FIGS. 16 and 17. In FIG. 16, 11 is a light source lamp that can be turned on / off at high speed, such as a strobe lamp, 12 is a power source that supplies power to the light source lamp 11, and 13 is a TFT type that converts an electrical image signal into image display light. A transmissive display element such as a liquid crystal, 16 is a drive circuit for generating a drive signal for driving the display element 13 by an image signal and a synchronization signal, and 17 is a control pulse synchronized with the vertical synchronization of the input synchronization signal. This is a pulse generation circuit for generating and controlling on / off of the power supply 12.
[0007]
When the lighting rate is 50% by supplying pulsed power from the power source 12, the light source lamp 11 is turned off only during the period from the time t1 to the time t2 in the field period T, and only during the period from the time t2 to the time t3. Lights up (see FIG. 17). When the lighting rate is 25% by supplying pulsed power from the power source 12, the light is turned off only during the period from time t1 to time t6 in the field period T, and is lit only during the period from time t6 to time t3 ( FIG. 17).
[0008]
That is, the light emission period of the light source lamp 11 is controlled by the pulse generation circuit 17 and the power source 12. Accordingly, the overall response of the image display light as the image display is, for example, when the lighting rate is 50%, the pulse-on waveform of the time from time t2 to time t3, and the pulse-on waveform of the time from time t4 to time t5 It becomes only. For this reason, the temporal spread of the display overall response is reduced, and the time frequency characteristic is improved to a flatter characteristic, so that the image quality deterioration at the time of moving image display is also improved.
[0009]
Thus, after writing a video signal within one vertical period to be displayed and a predetermined time has elapsed, the backlight light source is turned on entirely to improve image quality degradation such as motion blur that occurs during moving image display. Is called a full-flash type, and is disclosed in, for example, JP-A-2001-201763, JP-A-2002-55657, and the like in addition to the above-mentioned JP-A-9-325715.
[0010]
Further, for example, JP-A-11-202286, JP-A-2000-321551, and JP-A-2001-296838 correspond to a plurality of divided display areas with respect to the above-described full-flash type backlight lighting method. A so-called scanning-type backlight lighting system has been proposed in which the backlight light source is sequentially turned on for each light-emitting divided region to improve image quality degradation such as motion blur that occurs during moving image display.
[0011]
A case where the backlight is blinked at high speed in order to bring the display state of the hold-type drive closer to the display of the impulse-type drive such as a CRT will be described with reference to FIGS. In FIG. 18, a plurality of (four in this case) direct fluorescent lamps (CCFT) 203 to 206 are arranged on the back surface of the liquid crystal display panel 202 in a direction parallel to the scanning lines, and are used as scanning signals of the liquid crystal display panel 202. The lamps 203 to 206 are sequentially lit up and down in synchronization. The lamps 203 to 206 correspond to display areas obtained by dividing the liquid crystal display panel 202 into four in the horizontal direction.
[0012]
FIG. 19 is a diagram showing the lighting timing of the lamp corresponding to FIG. In FIG. 19, a high state indicates a lighting state of the lamp. For example, the video signal is written at the timing of (1) in one frame in the upper 1/4 divided display area in the liquid crystal display panel 202, and is delayed by the liquid crystal response period of (2). At this timing, the fluorescent lamp lamp 203 is turned on. As described above, after the video signal is written, the operation of lighting only one lamp in each divided display area is sequentially repeated within one frame period.
[0013]
As a result, the display state of the liquid crystal hold type drive can be brought close to the display state of the CRT impulse type drive. Therefore, when the moving image is displayed, the video signal of the previous frame is not recognized, and the moving image due to the edge blur is generated. Deterioration of display quality can be prevented. In addition, as shown in FIG. 20, not only the same effect can be obtained by lighting two lamps at a time, but also the lighting time of the backlight can be extended, and the backlight luminance can be increased. Can be suppressed.
[0014]
Further, in this scanning type backlight lighting system, the corresponding light emitting area is lit at the timing when the liquid crystal is optically sufficiently responsive to each of the plurality of divided display areas, so that the backlight is changed from the image writing to the liquid crystal. The period until the light source is turned on can be made uniform regardless of the display screen position (up and down position), and therefore, the motion blur can be sufficiently improved regardless of the position of the display screen. There is.
[0015]
Furthermore, in contrast to the above-described backlight intermittent drive system, for example, Japanese Patent Laid-Open Nos. 9-127717 and 11-109921 disclose that one frame of the backlight light source is not intermittently driven within one frame. By repeatedly writing the video signal and the black signal to the liquid crystal display panel, the pixel emission time (image display period) is shortened from the scanning of a frame of a certain video signal to the scanning of the next frame, A so-called black writing type liquid crystal display device that realizes a pseudo impulse type display has been proposed.
[0016]
[Patent Document 1]
JP-A-9-325715 [Patent Document 2]
JP 2001-201763 A [Patent Document 3]
JP 2002-55657 A [Patent Document 4]
JP-A-11-202286 [Patent Document 5]
JP 2000-321551 A [Patent Document 6]
JP 2001-296838 A [Patent Document 7]
Japanese Patent Laid-Open No. 9-127717 [Patent Document 8]
Japanese Patent Laid-Open No. 11-109921
[Problems to be solved by the invention]
The above-described conventional technique is designed to intermittently drive the backlight within one frame (for example, 16.7 msec in the case of 60 Hz progressive scan) in order to improve image quality degradation due to motion blur that occurs when displaying a moving image on a hold-type display device. Or by writing a black display signal to the liquid crystal display panel following the image display signal to shorten the image display period so that the display state of the hold-type drive is close to that of an impulse-type drive such as a CRT. It is.
[0018]
By the way, in this type of display device, as shown in FIG. 21, the display brightness is variably controlled according to the ambient light illuminance (brightness) in the usage environment of the device, for example, when the display surface is exposed to direct sunlight. Even if the user is viewing or viewing in a dark room, a screen display that is always easy for the user to see is realized.
[0019]
Normally, in a liquid crystal display device, the backlight luminance is appropriately varied by dimming control of the backlight light source according to the illuminance (brightness) of outside light in the usage environment of the device. When the light control is realized independently of the drive control for the impulse-type display described above, there is a problem that the configuration and the operation control process are complicated and inefficient.
[0020]
The present invention has been made in view of the above problems, by controlling the driving motion of the backlight source in accordance with the illuminance of outside light, in addition to improving image quality by preventing motion blur, legible to the user by the display brightness modulation A liquid crystal display device capable of easily realizing image display is provided.
[0021]
[Means for Solving the Problems]
A first invention of the present application is a liquid crystal display device in which an image signal of a vertical period to be displayed is written to a liquid crystal display panel, and a backlight light source is intermittently turned on within one vertical period, and is outside the usage environment of the device. Detection means for detecting light illuminance, and control means for variably controlling the size of the simultaneous light emitting area of the backlight light source in units of one vertical period based on the detected external light illuminance, the control means, the backlight source of simultaneously emitting at the same time the light-emitting region, and switches for each one vertical period.
[0026]
A second invention of the present application is a liquid crystal display device in which a direct-type backlight light source is arranged on the back surface of the liquid crystal display panel, the detecting means for detecting the illuminance of outside light in the use environment of the device, and the detected Control means for variably controlling the size of the simultaneous light emitting area of the backlight light source in units of one vertical period based on the illuminance of outside light, and the control means includes a backlight light source that simultaneously emits light in the simultaneous light emitting area. It is characterized by switching every vertical period .
[0029]
According to the liquid crystal display device of the present invention, depending on the brightness in the use environment of the person the device (the intensity of the ambient light illuminance), by appropriately automatic switching the size of the lighting region of the backlight source, the backlight Since the amount of light (display luminance) is variably controlled, it is possible to easily realize image display that is easy for the user to see.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS. Here, FIG. 1 is a functional block diagram showing a schematic configuration of the main part of the liquid crystal display device of the present embodiment, FIG. 2 is an explanatory diagram for explaining the basic operation principle of the liquid crystal display device of the present embodiment, and FIG. It is explanatory drawing for demonstrating the basic principle of operation in the liquid crystal display device of embodiment.
[0032]
In the present embodiment, as shown in FIG. 1, an active matrix type liquid crystal display panel 1 having a liquid crystal layer and electrodes for applying scanning signals and data signals to the liquid crystal layer, and an input image signal vertically Based on a horizontal synchronizing signal, an electrode driver 2 for driving the data electrodes and scanning electrodes of the liquid crystal display panel 1, a direct type backlight light source 3 disposed on the back surface of the liquid crystal display panel 1, and an input A synchronization signal extraction unit 4 that extracts a synchronization signal from an image signal, and a light source control unit 5 that performs intermittent drive control of turning off / on the backlight light source 3 within one vertical period are provided.
[0033]
Furthermore, the frame frequency conversion unit 6 that converts the frame frequency of the input image signal to a high frequency and outputs the converted signal to the electrode driving unit 2, the illuminance detection unit 7 for detecting the ambient light illuminance in the usage environment of the device, A control CPU 8 that outputs a predetermined control signal to the light source controller 5 and the frame frequency converter 6 according to the detected external light illuminance level is provided.
[0034]
The light source controller 5 controls the timing for turning on / off the backlight light source 3 based on the vertical synchronizing signal extracted by the synchronizing signal extractor 4 and the control signal from the control CPU 8. The frame frequency conversion unit 6 converts the frame frequency of the input image signal to a predetermined frequency based on a control signal from the control CPU 8.
[0035]
The backlight light source 3 may be a direct-type or side-irradiation type LED light source, EL light source, or the like in addition to the direct-type fluorescent lamp. In particular, LEDs (light emitting diodes) have a response speed of several tens to several hundreds ns, and are more responsive than the ms order of fluorescent lamps. Is possible.
[0036]
The liquid crystal display device of the present embodiment prevents motion blur that occurs during moving image display by a full-flash type backlight lighting system. That is, as shown in FIG. 2, after the entire scanning period (image writing) of the display screen is completed, the driving waveform is applied to the backlight light source 3 after being delayed by a predetermined liquid crystal response period. Thus, the backlight light source 3 is turned on all at once (flash emission) on the entire surface of the display screen during the backlight lighting period indicated by the shaded portion in the figure.
[0037]
Here, the backlight lighting period indicated by the shaded portion in FIG. 2 is varied according to the external light illuminance level (ambient brightness) detected by the illuminance detection unit 7, so that the backlight is interlocked with the external use environment. Change the amount of light (display brightness). Specifically, the backlight lighting period (lighting timing / lighting timing) is variably controlled so as to be the same as the display luminance characteristics shown in FIG.
[0038]
That is, when the external light illuminance level is large, after delaying by a predetermined liquid crystal response period, the backlight beam 3 is turned on immediately, and the backlight lighting period is maintained until the next frame scanning period starts. To do. Conversely, when the external light illuminance level is small, the backlight lighting period is shortened by delaying the backlight lighting timing or by accelerating the backlight lighting timing.
[0039]
Here, in this embodiment, it is necessary to write and scan an image signal for one frame over the entire screen of the liquid crystal display panel 1 within a period excluding the liquid crystal response period and the backlight lighting period from one frame period. Therefore, the frame frequency of the input image signal is converted to a high frequency by the frame frequency conversion unit 6 and then input to the electrode driving unit 2.
[0040]
In order to ensure a sufficient backlight lighting period, for example, as shown in FIG. 3, the frame frequency conversion unit 6 converts the frame frequency of the input image signal to a higher frequency, thereby shortening the image writing scanning period. Yes. That is, when the external light illuminance level is large, the backlight lighting period can be increased by variably controlling the frame frequency of the input image signal to be high. Thus, by converting the frame frequency of the input image signal according to the ambient light illuminance level, the degree of freedom in setting the backlight lighting period can be greatly improved.
[0041]
As described above, in the liquid crystal display device according to the present embodiment, when motion blur is prevented by using the full-flash-type backlight lighting method to approach the display state of impulse-type driving, the backlight is set according to the illuminance of outside light. Since the lighting period (timing) of the light source is controlled, in addition to improving the image quality by preventing motion blur, it is possible to easily realize an image display that is easy for the user to see according to the brightness of the usage environment. Furthermore, when the external light illuminance level is small, the backlight lighting period is controlled to be shortened, so that the lifetime of the backlight light source and the reduction in power consumption can be realized.
[0042]
In the above embodiment, the description has been given of the variable control of the lighting time of the backlight light source 3 based on the illuminance level (use environment condition) of the outside light. However, in addition to this, the average luminance level and the maximum of the input image signal The lighting time of the backlight light source 3 may be variably controlled in consideration of the feature amount of the input image signal such as the luminance level, the minimum luminance level, and the luminance distribution (histogram).
[0043]
Next, a second embodiment of the present invention will be described with reference to FIG. 4, but the same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Here, FIG. 4 is an explanatory diagram for explaining the basic operation principle in the liquid crystal display device of the present embodiment.
[0044]
The liquid crystal display device of the present embodiment prevents motion blur that occurs during moving image display by a scanning backlight lighting system, but the basic functional block diagram is the first implementation described above with reference to FIG. It is the same as that of the form. The difference is that among backlight light sources 3 constituted by using a plurality of direct fluorescent lamps arranged in parallel to the scanning line, a plurality of direct or side illumination LED light sources, EL light sources, and the like. The predetermined number (number) is set as one light emitting area, and these are controlled to be sequentially scanned and lighted within one frame. The light source control unit 5 controls the timing for sequentially scanning and lighting each light emitting region based on the vertical / horizontal synchronization signal extracted by the synchronization signal extraction unit 4.
[0045]
That is, in the present embodiment, as shown in FIG. 4, after scanning of a certain horizontal line group (display divided area) (image writing) is completed, the horizontal line group is considered in consideration of the response delay of the liquid crystal. The light emitting area (a certain fluorescent lamp group or LED group) of the backlight source 3 corresponding to is turned on. This is repeated with the next region in the vertical direction. As a result, as indicated by the shaded portion in FIG. 4, the backlight lighting period can be sequentially shifted in units of light emitting regions with the passage of time corresponding to the writing scan location of the image signal.
[0046]
Here, by changing the backlight lighting period of each light emitting area indicated by the shaded portion in FIG. 4 according to the ambient light illuminance level detected by the illuminance detection unit 7, that is, the brightness of the surrounding environment, The amount of backlight light (display brightness) is changed in conjunction with. Specifically, the backlight lighting period (lighting timing / lighting timing) is variably controlled so as to be the same as the display luminance characteristics shown in FIG.
[0047]
That is, when the external light illuminance level is large, the backlight lighting period in each light emitting region is set large. Conversely, when the external light illuminance level is low, the backlight lighting period in each light emitting region is shortened by delaying the backlight lighting timing or by delaying the backlight lighting timing. Here, in order to prevent occurrence of luminance unevenness due to the screen position, the backlight lighting period of each light emitting region is determined for each frame and is not changed within one frame.
[0048]
In the example shown in FIG. 4, since the image signal for one frame is written and scanned over the entire screen of the liquid crystal display panel 1 within one frame period, the frame frequency of the input image signal is changed. However, the frame frequency conversion unit 6 may convert the frame frequency of the input image signal to a high frequency in order to ensure a sufficient backlight lighting period in each light emitting region. That is, as the external light illuminance level increases, the image signal writing scanning period can be shortened by variably controlling the frame frequency of the input image signal to be higher, and the backlight lighting period is increased accordingly. It becomes possible.
[0049]
As described above, in the liquid crystal display device according to the present embodiment, when the moving backlight is prevented by using the scanning backlight lighting method to approach the display state of the impulse type drive, In addition to improving the image quality by preventing motion blur, it is possible to easily realize an image display that is easy to see for the user according to the brightness of the usage environment. Furthermore, when the external light illuminance level is small, the backlight lighting period is controlled to be shortened, so that the lifetime of the backlight light source and the reduction in power consumption can be realized.
[0050]
In the above embodiment, the description has been given of the variable control of the lighting time of the backlight light source 3 based on the illuminance level (use environment condition) of the outside light. However, in addition to this, the average luminance level and the maximum of the input image signal The lighting time of the backlight light source 3 may be variably controlled in consideration of the feature amount of the input image signal such as the luminance level, the minimum luminance level, and the luminance distribution (histogram).
[0051]
In the example shown in FIG. 4, the backlight source 3 is divided into eight light emitting areas (horizontal line groups) and sequentially turned on. However, any number of light emitting divided areas can be used as long as the number is two or more. It is obvious that each light emitting area is not limited to an area obtained by dividing the backlight light source 3 in the horizontal direction (direction parallel to the scanning line). Also in this respect, when the direct type planar LED is used as the backlight light source 3, the setting of the light emission division region can be made with a high degree of freedom.
[0052]
Next, a third embodiment of the present invention will be described with reference to FIGS. 5 to 10, but the same parts as those in the second embodiment are denoted by the same reference numerals, and the description thereof is omitted. Here, FIG. 5 is an explanatory diagram for explaining the basic operation principle in the liquid crystal display device of the present embodiment, and FIGS. 6 and 8 are main parts showing an example of the lighting operation of the backlight light source in the liquid crystal display device of the present embodiment. 7 and 9 are schematic explanatory views showing transition examples of illumination distribution in the liquid crystal display device of the present embodiment, and FIG. 10 is an average luminance level of an input image and a simultaneous lighting light source in the liquid crystal display device of the present embodiment. It is a schematic explanatory drawing which shows the relationship with a number.
[0053]
The liquid crystal display device according to the present embodiment, like the second embodiment described above, prevents motion blur that occurs during moving image display by a scanning backlight lighting method. The present invention is characterized in that display luminance modulation is realized by variably controlling the simultaneous light emission region (the number of backlights that are simultaneously turned on at a certain time) by the backlight light source 3.
[0054]
That is, in FIG. 5, the backlight source 3 is divided into eight light emitting areas (fluorescent lamp groups or LED groups), and these are sequentially scanned and lit in one frame period. 21 is variably controlled in accordance with the ambient light illuminance level (ambient brightness) detected by the illuminance detector 7, so that the amount of light of the backlight is substantially the same as the display luminance characteristics shown in FIG. (Display brightness) is changed. In the example shown in FIG. 5, a simultaneous light emitting region is formed by three light emitting regions (horizontal line group).
[0055]
For example, when eight direct fluorescent lamps arranged in a direction parallel to the scanning line (horizontal direction) are used as the backlight light source 3, and each fluorescent lamp lamp corresponds to each of the eight light emitting areas. A specific operation example will be described in detail with reference to FIGS.
[0056]
When the external light illuminance level detected by the illuminance detection unit 7 is in the range indicated by c in FIG. 10, each fluorescent lamp lamp is always in a state where three fluorescent lamps are always lit simultaneously as shown in FIG. Is turned on / off sequentially from top to bottom in one frame cycle. At this time, as shown in FIG. 7, on the display screen, the horizontal stripe-shaped simultaneous light emitting area (3/8 area with respect to the entire screen) changes vertically and returns to the original state in one frame period. It becomes.
[0057]
Next, when the illuminance level of the external light changes and becomes the range indicated by d in FIG. 10, as shown in FIG. 8, the four fluorescent lamps are always lit at the same time. Control is performed so that lighting / extinguishing of the lamp is sequentially scanned from top to bottom in one frame cycle. At this time, on the display screen, as shown in FIG. 9, the horizontal stripe-shaped simultaneous light-emitting area (1/2 area with respect to the entire screen) changes in the vertical direction and returns to the original state in one frame period. It becomes.
[0058]
Similarly, when the external light illuminance level changes in a direction that further increases and falls within the range indicated by e in FIG. 10, the number of fluorescent lamps that are turned on simultaneously is increased to five, and each fluorescent lamp lamp is set to 1. Scan lighting is performed sequentially from top to bottom within the frame (simultaneous light emission area is 5/8 of the entire screen). On the other hand, when the external light illuminance level changes in the direction of decreasing and falls within the range indicated by b in FIG. 10, the number of fluorescent lamps that are simultaneously turned on is reduced to two, and each fluorescent lamp lamp is within one frame. Then, the scan light is turned on sequentially from top to bottom (simultaneous light emission area is 1/4 of the entire screen). Furthermore, when the ambient light illuminance level changes in the direction of decreasing and falls within the range indicated by a in FIG. 10, the number of fluorescent lamps that are turned on simultaneously is reduced to one, and each fluorescent lamp lamp is within one frame. Then, the scanning is turned on sequentially from top to bottom (simultaneous light emission area is 1/8 of the entire screen).
[0059]
In this way, by changing the size of the simultaneous light emitting area according to the illuminance level of the external light, it becomes possible to appropriately control the amount of light (display luminance) of the backlight in multiple stages, and the CRT shown in FIG. An image can be displayed with characteristics approximate to display luminance characteristics.
[0060]
Of course, also in the present embodiment, the number of fluorescent lamps and the number of light-emitting divided areas are not limited to those described above, and the light-emitting divided areas are set finely, particularly when LED light sources and EL light sources are used. In addition, it is possible to perform display brightness control in further stages. In addition, since the occurrence of luminance unevenness due to the screen position is not caused, the size of the simultaneous light emitting area is determined for each frame and is not changed within one frame.
[0061]
As described above, in the liquid crystal display device according to the present embodiment, the simultaneous light emission region according to the illuminance of outside light is used to prevent motion blur by using a scanning backlight lighting method to approach the display state of the impulse type drive. Therefore, in addition to improving image quality by preventing motion blur, it is possible to easily realize image display that is easy for the user to see according to the brightness of the usage environment. Furthermore, when the illuminance level of the external light is small, the backlight lighting period is shortened, so that the lifetime of the backlight light source and the reduction in power consumption can be realized.
[0062]
In the above-described embodiment, the description has been given of variably controlling the size of the simultaneous light emission area of the backlight source 3 based on the ambient light illuminance level (use environment condition). It is obvious that the lighting time of the backlight light source 3 may be variably controlled in consideration of the feature amount of the input image signal such as the luminance level, maximum luminance level, minimum luminance level, and luminance distribution (histogram). It is.
[0063]
Furthermore, although the fourth embodiment of the present invention will be described with reference to FIGS. 11 and 12, the same parts as those in the third embodiment are denoted by the same reference numerals, and the description thereof is omitted. Here, FIG. 11 is a principal side sectional view showing the configuration of the backlight light source in the liquid crystal display device of the present embodiment, and FIG. 12 is an explanatory diagram for explaining the basic operation principle in the liquid crystal display device of the present embodiment. .
[0064]
The liquid crystal display device according to the present embodiment, like the third embodiment described above, prevents motion blur that occurs during moving image display and reduces the illuminance of the outside light (ambient brightness) from the scanning backlight lighting method. Based on this, the display luminance modulation that is easy to see for the user is realized by variably controlling the simultaneous light emission area (the number of backlights that are simultaneously lit at a certain time) by the backlight light source 3.
[0065]
Here, as the backlight light source 3, for example, as shown in FIG. 11, 16 direct fluorescent lamps arranged in a direction parallel to the scanning line (horizontal direction) are used, and one set of four fluorescent lamps is used. A case will be described in which the four light-emitting divided regions including the fluorescent lamp lamp groups 3a to 3d are sequentially switched and turned on.
[0066]
When the external light illuminance level detected by the illuminance detection unit 7 is extremely high, as shown in FIG. 12A, all the four fluorescent lamp lamps in the fluorescent lamp groups 3a to 3d in each light emitting area are turned on. Each light emitting area is sequentially scanned from top to bottom in one frame period. That is, in the example shown in FIG. 12A, the number of fluorescent lamps that are simultaneously turned on at a certain moment is eight, and the simultaneous light emission area is a half of the entire screen.
[0067]
Next, when the external light illuminance level is slightly high, as shown in FIG. 12 (b), three fluorescent lamp lamps are selected from the four fluorescent lamp lamps in the fluorescent lamp lamp groups 3a to 3d in the respective light emitting areas. Each light emitting area is sequentially scanned from top to bottom in one frame period while being lit. That is, in the example shown in FIG. 12B, the number of fluorescent lamps that are simultaneously turned on at a certain moment is six, and the simultaneous light emitting area is an area of 3/8 of the entire screen.
[0068]
Here, one of the four fluorescent lamp lamps in each of the fluorescent lamp lamp groups 3 a to 3 d is turned off, but a light diffusing action is exerted between the backlight source 3 and the liquid crystal display panel 1. Since the diffusion sheet (not shown) is disposed, spatial luminance unevenness hardly occurs on the screen of the liquid crystal display panel 1. Further, the occurrence of spatial luminance unevenness on the screen is also suppressed by sequentially switching the fluorescent lamp lamps that are turned off among the four fluorescent lamp lamps in each of the fluorescent lamp lamp groups 3a to 3d. .
[0069]
That is, in a certain frame, each of the light emitting areas is sequentially scanned from top to bottom while the fluorescent lamp lamp located at the second from the top among the four fluorescent lamps in each of the fluorescent lamp groups 3a to 3d is turned off. After that, in the next frame, each light emitting area is sequentially scanned from top to bottom while the fluorescent lamp lamp located at the third from the top among the four fluorescent lamps in each of the fluorescent lamp groups 3a to 3d is turned off. Further, in the next frame, each light emitting region is sequentially scanned from top to bottom while turning off the lowest fluorescent lamp among the four fluorescent lamps in each of the fluorescent lamp lamp groups 3a to 3d.
[0070]
As described above, the fluorescent lamp lamps that are extinguished among the four fluorescent lamp lamps in each of the fluorescent lamp lamp groups 3a to 3d are sequentially switched for each frame, so that the brightness unevenness on the screen of the liquid crystal display panel 1 is hardly noticed. It is possible to suppress to a certain extent.
[0071]
When the external light illuminance level is slightly low, two fluorescent lamps are selected from the four fluorescent lamps in the fluorescent lamp groups 3a to 3d in the respective light emitting areas as shown in FIG. Each light emitting area is sequentially scanned from the top to the bottom in one frame period while being lit. That is, in the example shown in FIG. 12C, the number of fluorescent lamps that are simultaneously turned on at a certain moment is four, and the simultaneous light emitting area is a quarter of the entire screen.
[0072]
Here too, the two fluorescent lamp lamps that are extinguished among the four fluorescent lamp lamps in each of the fluorescent lamp lamp groups 3a to 3d are sequentially switched on a frame-by-frame basis, thereby almost eliminating luminance unevenness on the screen of the liquid crystal display panel 1. It is possible to suppress to such an extent that it does not become.
[0073]
Furthermore, when the external light illuminance level is extremely small, as shown in FIG. 12D, one fluorescent lamp lamp is selected from the four fluorescent lamp lamps in the fluorescent lamp lamp groups 3a to 3d in each light emitting region. Each light emitting area is sequentially scanned from the top to the bottom in one frame period while being lit. That is, in the example shown in FIG. 12D, the number of fluorescent lamps that are simultaneously turned on at a certain moment is two, and the simultaneous light emitting area is an area of 1/8 of the entire screen.
[0074]
Here, among the four fluorescent lamp lamps in each of the fluorescent lamp lamp groups 3a to 3d, the three fluorescent lamp lamps to be turned off are sequentially switched for each frame, so that the luminance unevenness on the screen of the liquid crystal display panel 1 is hardly noticed. It is possible to suppress to such an extent that it does not become.
[0075]
As described above, also in the present embodiment, similarly to the third embodiment, the amount of backlight light (display luminance) can be set in multiple stages by changing the size of the simultaneous light emitting area according to the ambient light illuminance level. Control can be appropriately performed, and an image can be displayed with characteristics approximate to the display luminance characteristics of the CRT shown in FIG. Therefore, in addition to improving image quality by preventing motion blur, it is possible to easily realize image display that is easy for the user to see according to the brightness of the usage environment. Furthermore, when the external light illuminance level is small, the number of backlights to be lit is reduced, so that the life of the backlight light source can be extended and the power consumption can be reduced.
[0076]
Of course, in the present embodiment, the number of fluorescent lamps and the number of light-emitting divided regions are not limited to those described above, and the light-emitting divided regions are set finely, particularly when a direct type LED light source is used. In addition, it is possible to perform display brightness control in more stages. In addition, since the occurrence of luminance unevenness due to the screen position is not caused, the size of the simultaneous light emitting area is determined for each frame and is not changed within one frame.
[0077]
In the above-described embodiment, the description has been given of variably controlling the size of the simultaneous light emission area of the backlight source 3 based on the ambient light illuminance level (use environment condition). It is obvious that the lighting time of the backlight light source 3 may be variably controlled in consideration of the feature amount of the input image signal such as the luminance level, maximum luminance level, minimum luminance level, and luminance distribution (histogram). It is.
[0078]
In the fourth embodiment, in the scanning backlight lighting method, the number of simultaneously lit backlights is varied in conjunction with the illuminance of outside light. However, when this is applied to the full-flash type backlight lighting method, Although the fifth embodiment of the present invention will be described with reference to FIG. 13, the same parts as those of the fourth embodiment are denoted by the same reference numerals, and the description thereof is omitted. Here, FIG. 13 is an explanatory diagram for explaining the basic operation principle in the liquid crystal display device of the present embodiment.
[0079]
The liquid crystal display device according to the present embodiment prevents the motion blur that occurs during the moving image display from the full-flash type backlight lighting method, and simultaneously emits light from the backlight light source 3 based on the ambient light illuminance level (for a certain period of time). By variably controlling the number of backlights that are turned on at the same time, display luminance modulation that is easy for the user to see is realized. Here, a case where 16 direct fluorescent lamps arranged in a direction parallel to the scanning line (horizontal direction) are used as the backlight light source 3 will be described.
[0080]
When the external light illuminance level detected by the illuminance detection unit 7 is extremely high, as shown in FIG. 13A, after completion of the image writing scan, after 16 delays by a predetermined liquid crystal response period, Turn on all fluorescent lamps. That is, in the example shown in FIG. 13A, the number of fluorescent lamps that are simultaneously turned on at a certain moment is 16, and the simultaneous light emitting area is equal to the entire screen area.
[0081]
Next, when the external light illuminance level is slightly high, as shown in FIG. 13 (b), after the completion of the image writing scan, after a predetermined liquid crystal response period, the 16 fluorescent lamp lamps Of these, 12 fluorescent lamps are selected and lit. That is, in the example shown in FIG. 13B, the number of fluorescent lamps that are simultaneously turned on at a certain moment is twelve, and the simultaneous light emission area is 2/3 of the entire screen.
[0082]
Here, of the 16 fluorescent lamps, four fluorescent lamps are turned off. A diffusion sheet (not shown) having a light diffusing action is provided between the backlight source 3 and the liquid crystal display panel 1. Due to the arrangement, spatial luminance unevenness hardly occurs on the screen of the liquid crystal display panel 1.
[0083]
Moreover, the occurrence of spatial luminance unevenness on the screen is also suppressed by sequentially switching the fluorescent lamps to be turned off for each frame. Thus, by sequentially switching the fluorescent lamp lamps that are extinguished among the 16 fluorescent lamp lamps for each frame, it is possible to suppress the luminance unevenness on the screen of the liquid crystal display panel 1 to a level that is of little concern. .
[0084]
Also, when the external light illuminance level is slightly small, as shown in FIG. 13C, after the image writing scan is completed, after a predetermined liquid crystal response period, the 16 fluorescent lamp lamps are delayed. Eight fluorescent lamps are selected and lit. That is, in the example shown in FIG. 13C, the number of fluorescent lamps that are simultaneously turned on at a certain moment is eight, and the simultaneous light emission area is a half of the entire screen.
[0085]
In this case as well, it is possible to suppress the luminance unevenness on the screen of the liquid crystal display panel 1 to a level that is hardly noticed by sequentially switching the 8 fluorescent lamp lamps to be turned off among the 16 fluorescent lamp lamps for each frame. It is.
[0086]
Furthermore, when the external light illuminance level is extremely small, as shown in FIG. 13 (d), after completion of the writing scan of the image, it is delayed by a predetermined liquid crystal response period, and then among the 16 fluorescent lamps. Select and illuminate four fluorescent lamps. That is, in the example shown in FIG. 13D, the number of fluorescent lamps that are simultaneously turned on at a certain moment is four, and the simultaneous light emission area is a quarter of the entire screen.
[0087]
Here too, four fluorescent lamp lamps that are extinguished among the 16 fluorescent lamp lamps are sequentially switched for each frame, so that the luminance unevenness on the screen of the liquid crystal display panel 1 can be suppressed to a level that is of little concern. It is.
[0088]
As described above, also in the present embodiment, similarly to the fourth embodiment, the amount of backlight light (display luminance) can be changed in multiple stages by varying the size of the simultaneous light emitting area according to the external light illuminance level. Control can be performed as appropriate, and an image can be displayed with characteristics approximate to the display luminance characteristics shown in FIG. Therefore, in addition to improving the image quality by preventing motion blur, it is possible to easily realize an image display that is easy for the user to see according to the brightness of the usage environment. Furthermore, when the external light illuminance level is small, the number of backlights to be lit is reduced, so that the life of the backlight light source can be extended and the power consumption can be reduced.
[0089]
Of course, also in this embodiment, the number of fluorescent lamps and the number of simultaneously lit lamps are not limited to the above, and particularly when a direct type LED light source is used, the size of the simultaneous light emitting area is finely defined. It is also possible to perform multi-level display brightness control by setting. In addition, since the occurrence of luminance unevenness due to the screen position is not caused, the size of the simultaneous light emitting area is determined for each frame and is not changed within one frame.
[0090]
In the above-described embodiment, the description has been given of the variable control of the size of the simultaneous light emitting area of the backlight source 3 based on the illuminance level (use environment condition) of the outside light. It is obvious that the lighting time of the backlight light source 3 may be variably controlled in consideration of the feature amount of the input image signal such as the luminance level, maximum luminance level, minimum luminance level, and luminance distribution (histogram). It is.
[0091]
Furthermore, although the sixth embodiment of the present invention will be described with reference to FIGS. 14 to 16, the same parts as those of the second embodiment are denoted by the same reference numerals, and the description thereof is omitted. Here, FIG. 14 is an explanatory diagram for explaining the basic operation principle in the liquid crystal display device of this embodiment, and FIG. 15 is a timing chart for explaining the electrode driving operation in the liquid crystal display device of this embodiment.
[0092]
In the liquid crystal display device of this embodiment, the backlight light source is set to the normal lighting state, and the writing scanning (reset scanning) of the black display signal is performed following the writing scanning of the image display signal to the liquid crystal display panel 1 within one frame. The black writing type is performed to prevent motion blur that occurs during moving image display. Based on the detection result of the illuminance detection unit 7, the control CPU 8 changes the writing timing of the black display signal by the electrode drive unit 2. It is characterized by being controlled.
[0093]
That is, in this embodiment, in addition to selecting each scanning line for image display in the electrode driving unit 2, the scanning line is selected again for black display, and the input image signal and the black display signal are accordingly selected as the data line. As shown in FIG. 14, a period of black signal display period (black display period) is generated between one frame image display and the next frame image display by performing a series of operations of supplying to each frame. I am letting. Here, the writing timing (delay time) of the black display signal with respect to the writing timing of the image signal is varied in accordance with the external light illuminance level, that is, the ambient brightness.
[0094]
FIG. 15 is a timing chart regarding the scanning lines (gate lines) of the liquid crystal display panel 1. The gate lines Y1 to Y480 are sequentially raised in order to write an image signal to the pixel cell in one frame period with a slight shift in timing. One frame period is completed by starting all 480 gate lines and writing image signals to the pixel cells.
[0095]
At this time, the gate lines Y1 to Y480 are raised again after a period determined according to the average luminance level of the input image from the rise for writing the image signal, and the data line is connected to each pixel cell. A potential for displaying black is supplied via X. Thereby, each pixel cell is in a black display state. That is, each gate line Y goes high twice in different periods in one frame period. The pixel cell displays image data for a certain period by the first selection, and the pixel cell forcibly displays black by the second selection.
[0096]
As described above, by changing the black display timing, the transmission period of the liquid crystal display panel 1 within one frame of the illumination light from the backlight light source 3, that is, the image display period can be adjusted. It becomes possible to change the amount of light (display luminance) of the backlight. Specifically, the black display period (black writing timing) is variably controlled so as to be the same as the display luminance characteristics shown in FIG.
[0097]
For example, when the external light illuminance level is high, the black writing timing with respect to the image writing timing in each horizontal line is sufficiently delayed. Conversely, when the input external light illuminance level is small, the black writing timing is advanced, the black display period within one frame in each horizontal line is increased, and the image display period is shortened. Here, in order to prevent occurrence of luminance unevenness due to the screen position, the black writing timing (delay time) with respect to the image writing timing of each horizontal line is determined for each frame and is not changed within one frame.
[0098]
As described above, in the liquid crystal display device according to the present embodiment, when motion blur is prevented by using a black writing type display method to approach a display state of impulse type driving, image display is performed according to the display image content. Since the period (black display period) is controlled, in addition to improving image quality by preventing motion blur, it is possible to easily realize image display that is easy for the user to see according to the brightness of the usage environment. Even in the case of the present embodiment, the backlight light source is turned off in conjunction with the black writing timing described above, thereby shortening the backlight lighting period, extending the life of the backlight light source, and reducing the power consumption. Can also be realized.
[0099]
In the above embodiment, the black display period, that is, the image display period is variably controlled based on the ambient light illuminance level (use environment condition). In addition to this, the average luminance level and the maximum of the input image signal are also described. The size of the black display period may be variably controlled in consideration of the feature amount of the input image signal such as the luminance level, the minimum luminance level, and the luminance distribution (histogram).
[0100]
【The invention's effect】
The liquid crystal display device of the present invention is, since the above configuration, by controlling the size of the simultaneous lighting region of the backlight source depending on the ambient light illuminance, to easily achieve the easily viewable image display for Yoo over THE It becomes possible.
[Brief description of the drawings]
FIG. 1 is a functional block diagram illustrating a schematic configuration of main parts of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is an explanatory diagram for explaining a basic operation principle in the first embodiment of the liquid crystal display device of the present invention;
FIG. 3 is an explanatory diagram for explaining a basic operation principle in the first embodiment of the liquid crystal display device of the present invention;
FIG. 4 is an explanatory diagram for explaining a basic operation principle in a second embodiment of the liquid crystal display device of the present invention;
FIG. 5 is an explanatory diagram for explaining a basic operation principle in a third embodiment of the liquid crystal display device of the present invention;
FIG. 6 is a cross-sectional side view of an essential part showing an example of a lighting operation of a backlight light source in a third embodiment of the liquid crystal display device of the present invention.
FIG. 7 is a schematic explanatory view showing an example of transition of illumination distribution in the third embodiment of the liquid crystal display device of the present invention.
FIG. 8 is a cross-sectional side view of an essential part showing an example of a lighting operation of a backlight source in a third embodiment of the liquid crystal display device of the present invention.
FIG. 9 is a schematic explanatory view showing an example of transition of illumination distribution in the third embodiment of the liquid crystal display device of the present invention.
FIG. 10 is a schematic explanatory diagram showing the relationship between the external light illuminance level and the number of simultaneously lit light sources in the third embodiment of the liquid crystal display device of the present invention.
FIG. 11 is a cross-sectional side view of a main part showing a configuration of a backlight light source in a fourth embodiment of the liquid crystal display device of the present invention.
FIG. 12 is an explanatory diagram for explaining a basic operation principle in a fourth embodiment of the liquid crystal display device of the present invention;
FIG. 13 is an explanatory diagram for explaining a basic operation principle in a fifth embodiment of the liquid crystal display device of the present invention;
FIG. 14 is an explanatory diagram for explaining a basic operation principle in a sixth embodiment of the liquid crystal display device of the present invention;
FIG. 15 is a timing chart for explaining an electrode driving operation in a sixth embodiment of the liquid crystal display device of the present invention;
FIG. 16 is a functional block diagram showing a schematic configuration of a main part in a conventional liquid crystal display device (full-flash type).
FIG. 17 is an explanatory diagram showing a display response in a conventional liquid crystal display device (full-flash type).
FIG. 18 is an explanatory diagram showing an arrangement example of a backlight light source with respect to a liquid crystal display panel in a conventional liquid crystal display device (scanning type).
FIG. 19 is an explanatory diagram showing an example of lighting / extinguishing timing of each lamp in a conventional liquid crystal display device (scanning type).
FIG. 20 is an explanatory diagram showing another example of lighting / extinguishing timing of each lamp in a conventional liquid crystal display device (scanning type).
FIG. 21 is an explanatory diagram showing a transition of appropriate display luminance with respect to an external light illuminance level.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel 2 Electrode drive part 3 Backlight light source 4 Synchronization signal extraction part 5 Light source control part 6 Frame frequency conversion part 7 Illuminance detection part 8 Control CPU

Claims (2)

  1. A liquid crystal display device that writes an image signal of a vertical period to be displayed on a liquid crystal display panel and that intermittently lights a backlight light source within one vertical period,
    Detection means for detecting the illuminance of outside light in the usage environment of the device;
    Control means for variably controlling the size of the simultaneous light emission area of the backlight light source in units of one vertical period based on the detected external light illuminance ;
    The liquid crystal display device , wherein the control means switches a backlight light source that simultaneously emits light in the simultaneous light emitting region every vertical period .
  2. A liquid crystal display device in which a direct backlight light source is arranged on the back surface of the liquid crystal display panel,
    Detection means for detecting the illuminance of outside light in the usage environment of the device;
    Control means for variably controlling the size of the simultaneous light emission area of the backlight light source in units of one vertical period based on the detected external light illuminance;
    The liquid crystal display device , wherein the control means switches a backlight light source that simultaneously emits light in the simultaneous light emitting region every vertical period .
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JP2006084710A (en) * 2004-09-15 2006-03-30 Toshiba Matsushita Display Technology Co Ltd Display control circuit, display control method, and liquid crystal display
JP2006147573A (en) * 2004-11-17 2006-06-08 New Power Plasma Co Ltd Surface light source device, display device having it and its control method
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JP2007249011A (en) * 2006-03-17 2007-09-27 Ricoh Co Ltd Image display apparatus and projection type image display apparatus
JP5284571B2 (en) * 2006-06-15 2013-09-11 Necカシオモバイルコミュニケーションズ株式会社 Display control apparatus and program
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JP2008020611A (en) * 2006-07-12 2008-01-31 M & S Fine Tec Kk Liquid crystal display device and method for reducing afterimage in same
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