JP4139189B2 - Liquid crystal display - Google Patents

Liquid crystal display Download PDF

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Publication number
JP4139189B2
JP4139189B2 JP2002323711A JP2002323711A JP4139189B2 JP 4139189 B2 JP4139189 B2 JP 4139189B2 JP 2002323711 A JP2002323711 A JP 2002323711A JP 2002323711 A JP2002323711 A JP 2002323711A JP 4139189 B2 JP4139189 B2 JP 4139189B2
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Japan
Prior art keywords
liquid crystal
crystal display
backlight
display device
light source
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JP2002323711A
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Japanese (ja)
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JP2004062134A (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]
JP-A-11-109921
[0017]
[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, the image display period is shortened, and the display state of the hold-type drive is approximated to the display of the impulse-type drive such as the CRT. Is.
[0018]
Incidentally, CRT peak luminance is one of the technical elements for displaying a moving image with high image quality. As shown in FIG. 21, the CRT has a feature that the peak luminance changes dynamically according to the content of the image to be displayed. This results in a sharpness in the image quality of the moving image and realizes a high image quality. It has been known.
[0019]
On the other hand, in the case of a general liquid crystal display device, as shown in FIG. 21, since the amount of light of the backlight is always constant regardless of the display image content, the peak luminance does not change and the image quality is not sharp. Not only will the video display (poor contrast), but the backlight light source is always lit, so the lifetime of the backlight light source is shortened and power consumption cannot be reduced. .
[0020]
The present invention has been made in view of the above problems, and a backlight light source according to the content of a display image. The drive of It is an object of the present invention to provide a liquid crystal display device capable of easily realizing image quality improvement by peak luminance modulation in addition to image quality improvement by preventing motion blur by controlling movement.
[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. Means for detecting a feature amount of an image signal, and based on the detected feature amount, the size of the simultaneous light emitting area of the backlight source is variably controlled in units of one vertical period To modulate peak brightness And a means for performing.
[0022]
According to a second invention of the present application, in the first invention, the backlight light source emits flash over the entire surface every vertical period in synchronization with a vertical synchronization signal supplied to the liquid crystal display panel. Features.
[0023]
A third invention of the present application is the above-mentioned third invention. 2 In the invention of Switching the backlight source that emits light simultaneously every vertical period It is characterized by that.
[0024]
The fourth invention of the present application is: In the first aspect of the invention, the backlight light source sequentially scans and lights a plurality of light emitting areas in synchronization with a vertical synchronization signal and a horizontal synchronization signal supplied to the liquid crystal display panel. It is characterized by that.
[0025]
The fifth invention of the present application is: In the fourth aspect of the invention, the backlight source that simultaneously emits light in each of the plurality of light emitting regions is switched every vertical period. It is characterized by that.
[0026]
The sixth invention of the present application is: The feature amount of the image signal is obtained by one or a combination of two or more of average luminance, maximum luminance, minimum luminance, and luminance distribution within one vertical period. It is characterized by that.
[0027]
A seventh 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, and detects a feature amount of an image signal in a vertical period to be displayed on the liquid crystal display panel. And the size of the simultaneous light emitting area of the backlight light source variably controlled in units of one vertical period based on the detected feature amount To modulate peak brightness And a means for performing.
[0030]
According to the liquid crystal display device of the present invention, , Painting Backlight depending on features such as brightness and darkness of image Same light source Hour lighting area Size of By appropriately switching automatically, the backlight light quantity (peak luminance) is variably controlled to achieve the same peak luminance characteristics as CRT. , C As with RT, sharp and high-quality images can be easily realized.
[0032]
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.
[0033]
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 a light source control unit 4 that performs intermittent drive control of turning off / on the backlight light source 3 within one vertical period.
[0034]
Furthermore, an APL detection unit 5 for detecting an average luminance level (APL) per screen as a feature amount of the input image signal is provided, and the detected average luminance level is output to the light source control unit 4. . The light source control unit 4 controls the timing for turning on / off the backlight light source 3 based on the vertical synchronization signal of the input image signal and the average luminance level.
[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 in accordance with the average luminance level (image brightness) of the image detected by the APL detection unit 5, thereby interlocking with the display image content. To change the light intensity (peak luminance) of the backlight. Specifically, the backlight lighting period (lighting timing / lighting timing) is variably controlled so as to be the same as the peak luminance characteristic of the CRT shown in FIG.
[0038]
That is, when the average luminance level of the input image is small, after delaying by a predetermined liquid crystal response period, the backlight beam 3 is turned on immediately, and the backlight is turned on until the next frame scanning period starts. Hold the period. Conversely, when the average luminance level of the input image is large, the backlight lighting period is shortened by delaying the backlight lighting timing or by delaying the backlight lighting timing.
[0039]
In the present embodiment, the image signal for one frame needs to be written and scanned 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. The frame frequency of the input image signal is converted to a high frequency by a frequency converter (not shown) and then input to the electrode driver 2.
[0040]
Here, in order to ensure a sufficient backlight lighting period, for example, as shown in FIG. 3, the frame frequency of the input image signal may be converted to a higher frequency to shorten the image writing scanning period. When the average luminance level of the image signal is small, 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 in accordance with the average luminance level of the image, the degree of freedom in setting the backlight lighting period can be greatly improved.
[0041]
As described above, in the liquid crystal display device of the present embodiment, when motion blur is prevented by using a full-flash-type backlight lighting method to approach the display state of impulse-type driving, the back-up according to the content of the display image is performed. Since the lighting period (timing) of the light source is controlled, it is possible to easily realize a sharp image quality in the same way as a CRT, in addition to improving the image quality by preventing motion blur. Further, when the average luminance of the image is high, the backlight lighting period is controlled to be shortened, so that the lifetime of the backlight light source can be extended and the power consumption can be reduced.
[0042]
In the above embodiment, the case where the lighting time of the backlight light source 3 is variably controlled based on the average luminance level of the input image signal as a feature of the display image content has been described. The lighting time of the backlight light source 3 may be variably controlled based on the maximum luminance level, the minimum luminance level, the luminance generation distribution (histogram), or a feature amount obtained by appropriately combining these. Further, the lighting time of the backlight light source 3 may be variably controlled using a use environment condition such as an external light illuminance (ambient brightness) in addition to the feature amount of the input image signal.
[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 4 controls the timing for sequentially scanning and lighting each light emitting area based on the vertical / horizontal synchronization signal of the input image signal and the average luminance level.
[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, the backlight lighting period of each light emitting area indicated by the shaded portion in FIG. 4 is set to the average luminance level (APL) within one frame of the input image signal detected by the APL detection unit 5, that is, the brightness of the image. By varying in response, the amount of light (peak luminance) of the backlight is changed in conjunction with the display image content. Specifically, the backlight lighting period (lighting timing / lighting timing) is variably controlled so as to be the same as the peak luminance characteristic of the CRT shown in FIG.
[0047]
That is, when the average luminance level of the input image is small, the backlight lighting period in each light emitting area is set large. Conversely, when the average luminance level of the input image is large, the backlight lighting period in each light emitting area 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 of the input image signal may be converted to a high frequency in order to ensure a sufficient backlight lighting period in each light emitting area. That is, as the average luminance level of the input image decreases, the writing scanning period of the image signal can be shortened by variably controlling the frame frequency of the input image signal to be higher, and the backlight lighting period is correspondingly reduced. Can be increased.
[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, each light emission is performed according to the content of the display image. Since the backlight lighting period of the area is controlled, it is possible to easily realize a sharp image quality in the same manner as the CRT, in addition to improving the image quality by preventing motion blur. Further, when the average luminance of the image is high, the backlight lighting period is controlled to be shortened, so that the lifetime of the backlight light source can be extended and the power consumption can be reduced.
[0050]
In the above embodiment, the case where the lighting time in each light emitting area of the backlight light source 3 is variably controlled based on the average luminance level of the input image signal as a feature of the display image content has been described. The lighting time in each light emitting area of the backlight light source 3 is variable based on the maximum luminance level, the minimum luminance level in one frame, the luminance generation distribution (histogram), or the feature amount obtained by appropriately combining them. You may control. Further, the lighting time of the backlight light source 3 may be variably controlled using a use environment condition such as an external light illuminance (ambient brightness) in addition to the feature amount of the input image signal.
[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 prevents motion blur that occurs during moving image display by a scanning backlight lighting method, as in the second embodiment described above. On the basis of this, it is characterized in that peak luminance modulation is realized by variably controlling the simultaneous light emission region (the number of backlights that are lit simultaneously 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. The region is variably controlled according to the average brightness level (brightness of the image) of the image detected by the APL detection unit 5, so that it becomes almost the same as the peak brightness characteristic of the CRT shown in FIG. Change the amount of light (peak luminance) of the backlight. 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 average luminance level of the input image detected by the APL detection unit 5 is in the range indicated by c in FIG. 10, each of the three fluorescent lamps is always lit at the same time as shown in FIG. The fluorescent lamp 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 average luminance level of the input image changes in the direction of decreasing and falls within the range indicated by b in FIG. 10, the four fluorescent lamps are always lit simultaneously as shown in FIG. The lighting / extinguishing of each fluorescent lamp is controlled to sequentially scan 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 average luminance level of the input image changes in a direction that further decreases and falls within the range indicated by a in FIG. 10, the number of fluorescent lamps that are turned on simultaneously is increased to five, and each fluorescent lamp is increased. The lamps are scanned and turned on sequentially from top to bottom within one frame (simultaneous emission area is 5/8 of the entire screen). On the other hand, when the average luminance level of the input image changes in the direction of increasing and falls within the range indicated by d in FIG. 10, the number of fluorescent lamps that are turned on simultaneously is reduced to two, and each fluorescent lamp lamp is Scan lighting is performed sequentially from top to bottom within one frame (simultaneous light emission area is a quarter of the entire screen).
[0059]
As described above, by varying the size of the simultaneous light emitting area according to the average luminance level of the image, it becomes possible to appropriately control the light amount (peak luminance) of the backlight in multiple stages, as shown in FIG. An image can be displayed with characteristics approximate to the peak luminance characteristics of CRT.
[0060]
Of course, also 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 LED light sources and EL light sources are used. Further, it is possible to perform multi-level peak luminance control. 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, when the moving backlight is prevented by using the scanning backlight lighting method to approach the display state of the impulse-type drive, simultaneous light emission is performed according to the display image content. Since the area is controlled, in addition to improving the image quality by preventing motion blur, it is possible to easily realize a sharp image quality similar to the CRT. Furthermore, when the average luminance of the image is high, the backlight lighting period is shortened, so that the lifetime of the backlight light source can be extended and the power consumption can be reduced.
[0062]
In the above embodiment, the case where the size of the simultaneous light emitting area of the backlight light source 3 is variably controlled based on the average luminance level of the input image signal as a feature of the display image content has been described. The size of the simultaneous light emission region in the backlight source 3 is variable based on the maximum luminance level or minimum luminance level in one frame, the occurrence distribution (histogram) of luminance, or the feature amount obtained by appropriately combining these. You may control. Further, the size of the simultaneous light emission region of the backlight source 3 may be variably controlled using the use environment conditions such as the illuminance of the outside light (ambient brightness) in addition to the feature amount of the input image signal. .
[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 of the present embodiment, like the third embodiment described above, prevents motion blur that occurs during moving image display from the scanning backlight lighting method, and based on the feature amount of the input image, The peak luminance modulation similar to the CRT is realized by variably controlling the simultaneous light emission area (the number of backlights that are simultaneously turned on 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 average luminance level of the input image detected by the APL detection unit 5 is extremely small, as shown in FIG. 12 (a), all four fluorescent lamps in the fluorescent lamp groups 3a to 3d in the respective light emitting areas are displayed. While lighting, 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 average luminance level of the input image is slightly small, as shown in FIG. 12 (b), three fluorescent lamps among the four fluorescent lamp lamps in the fluorescent lamp lamp groups 3a to 3d in the respective light emitting areas. While selecting and lighting the lamp, each light emitting area is sequentially scanned from top to bottom in one frame cycle. 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 average luminance level of the input image is slightly high, as shown in FIG. 12C, two fluorescent lamp lamps out of 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 selecting and lighting. 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]
Further, when the average luminance level of the input image is extremely high, as shown in FIG. 12D, one fluorescent lamp lamp among 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 selecting and lighting. 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, the amount of backlight light (peak luminance) can be increased by varying the size of the simultaneous light emitting area according to the average luminance level of the image, as in the third embodiment. It is possible to appropriately control in stages, and an image can be displayed with characteristics approximate to the peak luminance characteristics of the CRT shown in FIG. Therefore, in addition to improving the image quality by preventing motion blur, it is possible to easily realize a sharp image quality similar to the CRT. Furthermore, when the average luminance of the image is large, 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, 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 a direct type LED light source is used. Further, it is possible to perform multi-level peak luminance control. 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 embodiment, the case where the size of the simultaneous light emitting area of the backlight light source 3 is variably controlled based on the average luminance level of the input image signal as a feature of the display image content has been described. The size of the simultaneous light emission region in the backlight source 3 is variable based on the maximum luminance level or minimum luminance level in one frame, the occurrence distribution (histogram) of luminance, or the feature amount obtained by appropriately combining these. Needless to say, it may be controlled. Further, the size of the simultaneous light emission region of the backlight source 3 may be variably controlled using the use environment conditions such as the illuminance of the outside light (ambient brightness) in addition to the feature amount of the input image signal. It is clear.
[0078]
In the fourth embodiment, in the scanning backlight lighting method, the number of simultaneously lighting backlights is varied in conjunction with the APL of the input image signal, but this is applied to the full-flash type backlight lighting method. This case will be described with reference to FIG. 13 as a fifth embodiment of the present invention, but 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 of the present embodiment prevents motion blur that occurs during moving image display from the full-flash type backlight lighting method, and simultaneously emits light from the backlight light source 3 based on the feature amount of the input image ( By variably controlling the number of backlights that are lit simultaneously at a certain time, peak luminance modulation similar to that of a CRT 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 average luminance level of the input image detected by the APL detection unit 5 is extremely small, as shown in FIG. 13A, after the image writing scan is completed, it is delayed by a predetermined liquid crystal response period. , Turn on all 16 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 average luminance level of the input image is slightly small, as shown in FIG. 13B, after the writing scan of the image is completed, it is delayed by a predetermined liquid crystal response period, and then the 16 fluorescent lights. Among the lamp lamps, 12 fluorescent lamps are selected and turned on. 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]
Further, when the average luminance level of the input image is slightly high, as shown in FIG. 13C, after the completion of the writing scan of the image, after delaying by a predetermined liquid crystal response period, 16 fluorescent lamps are used. 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 average luminance level of the input image is extremely high, as shown in FIG. 13D, after the writing scan of the image is completed, after delaying by a predetermined liquid crystal response period, 16 fluorescent lamps are used. Four of the fluorescent lamps are selected and lit. 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, the amount of backlight light (peak luminance) can be increased by varying the size of the simultaneous light emitting area according to the average luminance level of the image, as in the fourth embodiment. It is possible to appropriately control in stages, and an image can be displayed with characteristics approximate to the peak luminance characteristics of the CRT shown in FIG. Therefore, in addition to improving the image quality by preventing motion blur, it is possible to easily realize a sharp image quality similar to the CRT. Furthermore, when the average luminance of the image is large, 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 those described above, and the size of the simultaneous light-emitting area is particularly fine when a direct type LED light source is used. It is also possible to perform multi-level peak luminance 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 embodiment, the case where the size of the simultaneous light emitting area of the backlight light source 3 is variably controlled based on the average luminance level of the input image signal as a feature of the display image content has been described. The size of the simultaneous light emission region in the backlight source 3 is variable based on the maximum luminance level or minimum luminance level in one frame, the occurrence distribution (histogram) of luminance, or the feature amount obtained by appropriately combining these. Needless to say, it may be controlled. Further, the size of the simultaneous light emission region of the backlight source 3 may be variably controlled using the use environment conditions such as the illuminance of the outside light (ambient brightness) in addition to the feature amount of the input image signal. It is clear.
[0091]
Furthermore, although the sixth embodiment of the present invention will be described with reference to FIGS. 14 and 15, 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 kept in the normal lighting state, and the black display signal write scan (reset scan) is performed in succession to the image display signal write scan 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 APL detection unit 5, the control CPU 8 varies the writing timing of the black display signal by the electrode driving 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 average luminance level (APL) within one frame of the input image, that is, the brightness of the image.
[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]
In this way, by varying 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 and linked to the display image content. Thus, the light amount (peak luminance) of the backlight can be changed. Specifically, the black display period (black writing timing) is variably controlled so as to be the same as the peak luminance characteristic of the CRT shown in FIG.
[0097]
For example, when the average luminance level of the input image is small, the black writing timing with respect to the image writing timing in each horizontal line is sufficiently delayed. Conversely, when the average luminance level of the input image is large, the black writing timing is advanced, the black display period in 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 the improvement of the image quality by preventing the motion blur, it is possible to easily realize a sharp image quality similar to the CRT. 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 present embodiment, the case where the black display period, that is, the size of the image display period is variably controlled based on the average luminance level of the input image signal as a characteristic of the display image content has been described. The size of the image display period may be variably controlled based on the feature amount obtained by using the maximum luminance level or minimum luminance level in the frame, the luminance generation distribution (histogram), or appropriately combining these. Needless to say. Furthermore, the size of the image display period may be variably controlled using the use environment conditions such as the illuminance of the outside light (ambient brightness) in addition to the feature amount of the input image signal.
[0100]
【The invention's effect】
Since the liquid crystal display device of the present invention is configured as described above, the backlight source of the backlight light source is selected according to the display image content. Simultaneous lighting area size By controlling The Thus, it is possible to easily improve the image quality by the peak luminance modulation.
[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 average luminance level of the input image 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 transition of peak luminance of CRT and LCD.
[Explanation of symbols]
1 LCD panel
2 Electrode driver
3 Backlight light source
4 Light source controller
5 APL detector

Claims (7)

  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,
    Means for detecting a feature quantity of an image signal in the vertical period to be displayed;
    Means for modulating peak luminance by variably controlling the size of the simultaneous light emitting region of the backlight light source in units of one vertical period based on the detected feature amount. Display device.
  2.   The liquid crystal display device according to claim 1, wherein the backlight light source emits flash light on the entire surface every vertical period in synchronization with a vertical synchronization signal supplied to the liquid crystal display panel.
  3.   The liquid crystal display device according to claim 2, wherein the backlight light sources that emit light simultaneously are switched every vertical period.
  4.   2. The liquid crystal display according to claim 1, wherein the backlight light source sequentially scans and lights a plurality of light emitting areas in synchronization with a vertical synchronizing signal and a horizontal synchronizing signal supplied to the liquid crystal display panel. apparatus.
  5.   5. The liquid crystal display device according to claim 4, wherein backlight light sources that simultaneously emit light in each of the plurality of light emitting regions are switched every vertical period.
  6.   The feature amount of the image signal is obtained by one or a combination of two or more of average luminance, maximum luminance, minimum luminance, and luminance distribution within one vertical period. The liquid crystal display device according to any one of 1 to 5.
  7. A liquid crystal display device in which a direct backlight light source is arranged on the back surface of the liquid crystal display panel,
    Means for detecting a feature amount of an image signal in a vertical period to be displayed on the liquid crystal display panel;
    Means for modulating peak luminance by variably controlling the size of the simultaneous light emitting region of the backlight light source in units of one vertical period based on the detected feature amount. Display device.
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