JP3742093B2 - Video display device - Google Patents

Description

  The present invention relates to a video display device, and more particularly to a video display device having hold-type electro-optical conversion characteristics represented by, for example, a liquid crystal display device.

  In a hold-type drive video display device such as an active matrix drive LCD (liquid crystal display device) or organic EL (electroluminescence), moving image quality degradation (tailing, blurring, blurring, blurring) occurs. For example, Non-Patent Document 1 is a document relating to the moving image quality degradation of LCD. It is known that one of the factors that cause deterioration in moving image quality is the effect of retinal afterimage. In the hold-type drive, since images are continuously displayed during one frame period, images of frames with different eyes of the observer are overlapped and recognized as tailing (out-of-focus blurring).

  The principle of generation of LCD tailing will be described with reference to FIG. The items assumed in FIG. 41 are as follows. The object moves at an equal speed of one pixel per frame, which is a video display repeat unit. The moving direction is from the top to the bottom of the screen. As for the size of the object, the vertical length is 3 pixels, and the horizontal length is arbitrary.

  41 (a) is a light emission waveform of the light source, the vertical axis represents the light emission luminance, and the horizontal axis represents the time in frame units. The light source is continuous light emission, and the light emission luminance is constant with respect to time. 41 (b) is a momentary outline of an object displayed on the display screen, the horizontal axis is a space in pixel units, and the vertical axis is luminance. In FIG. 41, part (c) shows how the object moves, with the horizontal axis representing time and the vertical axis representing space. As the object moves, moving objects are sequentially displayed in the cross-hatched part in part (c) of FIG. Since it is a hold type, the change in luminance is held in units of frames with respect to the time axis.

  In addition, the moving object moves in the direction of arrow 1 in part (c) of FIG. 41 with respect to the space axis. However, when the observer follows the object while gazing at the moving object, it is equivalent to the observer observing the object in the direction of the arrow 2. As a result, the images of different frames are overlapped, and the object appears to the observer's eyes as shown in FIG. 41 (d). 41 (e) is the outline of FIG. 41 (d) (the horizontal axis is space, and the vertical axis is luminance), which has an inclination with respect to the space. When the part (b) in FIG. 41 and the part (e) in FIG. 41 are compared, the change in the contour is clear. The observer recognizes this inclination of brightness as an obstruction of blurring, tailing, and blurring.

  There is a method of impulse-lighting a light source as a tail improvement means of the hold type drive. Examples of the prior art of impulse type light emission will be given below.

  In the “image display” of Patent Document 1, a shutter is provided on the optical path of the observer from the light source, and the light emission period is limited to the latter half of one field period of the image signal.

  In “Matrix display system and driving method of such system” of Patent Document 2, display information is addressed in a time shorter than the field period of the video signal, and then the panel is illuminated after the response of the liquid crystal is stabilized. Propose that.

  The principle of improving the tailing of impulse light emission will be described with reference to FIG. The state of the moving object in FIG. 42 is the same as that in FIG. In the impulse-type light emission, the light emission waveform of the light source blinks as shown in FIG. The screen brightness of the LCD is the product of the brightness of the light source and the transmittance of the pixels on the LCD panel, and the screen brightness can be obtained only during the period when the light source is on. Therefore, the cross hatch portion in the portion (c) of FIG. 42 emits light.

  When the observer's eyes integrate the light emission of this screen, it appears as shown in part (d) of FIG. Part (e) of FIG. 42 shows the contour of FIG. 42 (d). Comparing the portion (e) of FIG. 42 and the portion (e) of FIG. 41, the former has a smaller inclined space. Therefore, it can be seen that tailing is reduced.

  The phase of light emission with respect to a video signal in impulse-type light emission, which is a conventional technique, is the latter half of a repetition cycle in which the transmittance of the pixel is updated. Since the time response of the liquid crystal is an exponential function response and has a time constant, the desired transmittance is not instantaneously obtained. Therefore, the best light emission phase of the prior art is the second half of the transmittance update timing, and the liquid crystal in the middle of the change is not easily seen by the observer.

  In the “display device” of Patent Document 3, in the active drive organic EL display device, a separate TFT is inserted between the storage capacitor provided for each pixel and the gate of the TFT for driving the organic EL element. ing. Then, within a period shorter than one frame period immediately after the pixel non-selection time starts, the inserted TFT is turned on to pass a current through the organic EL element, and the TFT is turned off after a predetermined time has elapsed, thereby turning the organic EL element Stop the current. With such a configuration, the light emission characteristics of the hold-type display element are brought close to those of the impulse type to prevent motion blur.

As described above, since organic EL has a high response speed unlike general liquid crystals, a desired current is allowed to flow immediately after the start of the non-selection period, and then light emission is stopped or suppressed by any means, thereby holding-type light emission. In many cases, a method of bringing the light closer to the impulse type light emission is taken.
Japanese Patent Laid-Open No. 9-325715 (Publication date: December 16, 1997) JP-T 8-500915 (Publication date January 30, 1996) JP 2002-287696 A (publication date October 4, 2002) "High-quality video display technology for liquid crystal displays", Monthly Display, June issue, 100 pages, 2003

  However, when the impulse display as described above is performed, image quality interference called flicker (flicker) occurs. This flicker disturbance has a significant adverse effect on the observer, such as causing eye strain. In particular, as the display quality of the LCD, such as an increase in screen brightness and an increase in screen size, is improved, this disturbance is easily recognized by an observer. Since the moving image tailing improvement and flicker interference reduction are in a trade-off relationship, the moving image tailing and flicker interference cannot be solved simultaneously.

  The trade-off relationship will be described with reference to FIGS. 43 (a) to 43 (i). These drawings show the respective light emission pulse waveforms, moving image tailing amounts, and flicker amounts at three types of duty ratios of 25%, 50%, and 75%. 43 (a) to 43 (c) show a case where the duty ratio is 25%, and FIGS. 43 (d) to 43 (f) show a case where the duty ratio is 50%. (G) -FIG. 43 (i) has shown the case where the duty ratio is 75%.

  The pulse waveforms shown in FIGS. 43 (a), 43 (d), and 43 (g) are lighting waveforms of the light source, and the light source is lit while the waveform is High. In these drawings, the luminance (amplitude) is adjusted so that the emission luminances coincide between the duty ratios.

  43 (b), FIG. 43 (e), and FIG. 43 (h) show the trailing amount calculated by the trailing amount calculation method shown in FIG. 42 for each duty ratio. . A steep slope means that the effect of improving the moving image quality is large and the tailing (moving image blur) is less.

  43 (c), 43 (f), and 43 (i) show the flicker amount. The vertical axis represents the spectrum intensity with respect to the frequency, and the horizontal axis represents the frequency. The flicker amount is derived by performing Fourier transform on each pulse waveform of FIGS. 43 (a), 43 (d), and 43 (g) and converting it to the frequency axis.

  For example, if the video signal input to the display device is an NTSC video signal, the pulse waveform is repeated at a period of 60 Hz, so the first harmonic after the Fourier transform operation is also 60 Hz. The larger the ratio of the first harmonic to the DC (direct current) component, the larger the flicker energy and the greater the interference.

  As is clear from FIGS. 43A to 43I, the trailing amount and the flicker amount are in a trade-off relationship. In other words, if the duty ratio is increased to reduce the flicker amount, the amount of tailing increases although the flicker amount is reduced, and the effect of improving the moving image quality is reduced. When the amount of tailing is defined by the luminance gradient of the moving object, the amount of tailing and the duty ratio x are in an inversely proportional relationship, and the effect of improving moving image quality increases as the duty ratio decreases. However, if the duty ratio is reduced in order to reduce the amount of tailing, the amount of flicker increases. The magnitude of the first harmonic of the pulse waveform with the duty ratio x has a relationship of sampling function (sin x) / x, and flicker increases as the duty ratio decreases.

  FIG. 44 is a diagram for explaining the problems of the conventional impulse type intermittent light emission method. In FIG. 44, the horizontal axis indicates the amount of tailing. The amount of tailing is the length of the spatial extent of tailing calculated based on the tailing model described with reference to FIGS. 41 and 42. The smaller the numerical value, the less the motion blur and the higher the image quality.

  In FIG. 44, the vertical axis indicates the amount of flicker. The flicker amount is a value calculated by Fourier-transforming the light emission waveform. The smaller the numerical value, the smaller the blinking energy component and the less the flicker interference.

  In the technique of the conventional intermittent light emission method, the duty ratio (intermittent light emission time ratio with respect to the video period) is adjusted. In this case, the values of the trailing amount and the flicker amount move on the characteristics of the graph shown in FIG. Therefore, if the duty ratio is reduced, the amount of tailing is reduced, but the amount of flicker is increased. On the other hand, if the duty ratio is increased, the flicker amount is reduced but the trailing amount is increased. In order to improve the tailing amount and the flicker amount ideally, it is desired to move the characteristics of the tailing amount and the flicker amount in the direction of the white arrow shown in FIG. Such improvements cannot be made.

  As described above, the relationship between the trailing amount and the flicker amount with respect to the duty ratio is a trade-off, and it is difficult to simultaneously reduce the trailing amount and the flicker amount.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a video display apparatus that can simultaneously improve the moving image tailing and flicker interference that are in a trade-off relationship.

In order to solve the above-described conventional problems, the video display device according to the present invention is a video display device that displays video by modulating the luminance of the pixels based on the video signal, and is a time of D% of the vertical period of the video signal. A first light emitting component having a light emission intensity of S% of the light emission intensity of the pixel displayed within the vertical period, and a time of (100-D)% of the vertical period and the vertical period And a second light-emitting component having a light emission intensity of (100-S)% of the light emission intensity of the pixel displayed in the above, and the values of D and S satisfy the condition A: 62 ≦ S <100 and 0 <D <100 and D <S, or Condition B: 48 <S <62 and D ≦ (S−48) /0.23, and the light emission period related to the first light emission component from the timing at which the vertical period starts The above video of the time to the center of When the ratio of the vertical cycle of No. and P%, a D / 2 ≦ P ≦ (100 -D / 2), and 0 <so that D <100, the first light emission component and the second By controlling the light emission component, the tailing amount and flicker amount in the case of S = 100 are simultaneously reduced .

  According to the above configuration, flicker interference can be suppressed while displaying a clear outline by suppressing tailing of the moving object by the light emitted from the first light-emitting component and the second light-emitting component. .

  Note that the video display device of the present invention can be applied to a transmissive or reflective liquid crystal display device using a liquid crystal element as a non-light emitting element as a display element, or a self-luminous display panel (organic EL panel or the like). It is also applicable to a display device using

Furthermore, in the video display device having the above-described configuration, when the value of P is a constant determined from the response time constant of the video display means,
It is preferable that P = 50 + K (where 0 ≦ K ≦ (50−D / 2)).

  When the response time constant of the image display means (for example, a liquid crystal panel) is relatively large from 2 milliseconds to 5 milliseconds, the optimum value PA of P is PA = 50 + K (where 0 ≦ K ≦ (50−D / 2)). Note that K is a constant if the response time constant is determined. The function for obtaining the constant K from the response time constant is not a simple linear function, but if the response time constant is large, K tends to increase. Therefore, the tailing amount can be optimized by increasing PA when the response time constant is large based on the relational expression between PA and K, that is, by delaying the light emission phase of the first light emission component.

  When the response time constant is as fast as about 1 millisecond, the value of P is optimally about 50. This is because, when the amount of tailing is represented by a tailing model, the gentle slope of the luminance change mainly caused by the second light emitting component can be balanced before and after the first light emitting component.

Furthermore, the values of D and S are
Condition A: 62 ≦ S <100 and 0 <D <100 and D <S, or Condition B: 48 <S <62 and D ≦ (S−48) /0.23 is preferably satisfied.

  The present inventors have examined the amount of tailing and flicker obtained by changing the duty ratio D and the light emission intensity ratio S, and as a result, the duty ratio D and the light emission intensity ratio S should satisfy the condition A or the condition B. It was found that the tailing amount and the flicker amount are simultaneously improved by setting to. Therefore, according to the video display device having the above configuration, the amount of tailing and the amount of flicker can be ideally improved.

  And a light emission period related to the first light emission component from a timing at which the vertical cycle starts, comprising: a video display means for setting the transmittance of the pixel based on the video signal; and a light source body for illuminating the video display means. The ratio P of the time to the center of the vertical period with respect to the vertical period may be controlled by the light source body.

  In this case, the light source body preferably varies the value of P for each area formed by dividing the video display screen.

  In the video display means, the update timing of the pixel transmittance may differ depending on the location of the screen. The effect of the phase difference of the update timing is absorbed by changing the value of P for each area as described above, that is, by shifting the light emission phase of the first light emission component, and the best light emission phase can be obtained. .

  Furthermore, image display means for setting the luminance of a pixel based on the video signal is provided, and the ratio P of the time from the timing at which the vertical cycle starts to the center of the light emission period related to the first light emission component to the vertical cycle This control may be performed by the video display means.

  In this case, the video display means has a memory for holding the video signal for each pixel, and the light emission waveform of each pixel is obtained by referring to the memory a plurality of times per vertical cycle of the video signal. It is preferable to emit light composed of the first light emitting component and the second light emitting component. A memory is a capacitor formed in a pixel, for example.

  According to the above configuration, data is written and updated once per vertical synchronization signal, the information of the video signal is held in the memory for each pixel, and a plurality of the memories are referred to per vertical synchronization signal, so that the light emission of the pixel The light is composed of a first light emitting component and a second light emitting component. Therefore, the amount of tailing and flicker can be reduced without changing the structure of the pixels in the video display means from that of a general configuration in which data is updated once per vertical synchronization signal.

  The above configuration is preferably applied to video display means having a light emitting element for each pixel, for example, an organic EL panel. In a video display device using an organic EL panel, a light emission amount of the light emitting element is controlled based on information held in the memory, thereby generating a first light emission component and a second light emission component, and a tailing amount. In addition, the amount of flicker can be reduced.

  The video display means is supplied with video data rearranged in advance with respect to the time axis, and by selecting the same pixel three times for the vertical period of the video signal, the light emission waveform of each pixel is obtained. A configuration may be adopted in which light emission includes the first light emission component and the second light emission component. Even with this configuration, the amount of tailing and flicker can be reduced without changing the pixel structure in the video display means from that of a general configuration in which data is updated once per vertical synchronization signal. it can.

  Further, the image display means for setting the transmittance of the pixel based on the video signal and a light source body for illuminating the video display means, and between optical paths formed between the video display means and the light source body And controlling the ratio P of the time from the timing at which the vertical period starts to the center of the light emission period related to the first light emission component to the vertical period by controlling the intensity of the illumination light of the light source body. It is good also as a structure provided with the light control means to perform.

  As described above, in the video display device of the present invention, the light emission phase P% and the duty ratio D% of the first light emission component in the first light emission component and the second light emission component are D / 2 ≦ P ≦ (100 −D / 2) and 0 <D <100 is set so as to satisfy the condition, it is possible to achieve both improvement of moving image tailing and reduction of flicker interference. Flicker interference not only causes discomfort to the user, but also has adverse effects such as reduced attention and eye strain. According to the present invention, these adverse effects can be prevented. Furthermore, reducing flicker interference is indispensable for improving the display quality of a video display device with a high brightness and a large screen. Thus, according to the present invention, it is possible to provide an optimal display quality for the observer.

  An embodiment of the present invention will be described with reference to FIGS. 1 to 40 as follows.

Embodiment 1
A video display apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating a light emission waveform of a pixel in a video display device according to an embodiment of the present invention. FIG. 1 shows a light emission waveform for one period of the vertical period T of the video signal to be displayed.

  Moreover, although the (a) part of FIG. 1 and the (b) part of FIG. 1 have shown the same waveform, the division | segmentation method of a light emission waveform differs. That is, in FIG. 1A, the waveform is divided into a portion having a high instantaneous light emission intensity and a portion other than that.

  And in the part (a) of FIG. 1, the part shown with a halftone dot is a 1st light emission component. This first light emitting component has a light emission time duty ratio with respect to the vertical period T of D%, an instantaneous light emission intensity of A [nit], a light emission intensity ratio with respect to the pixel light emission intensity of S%, and light emission after the start of the vertical period. The ratio of the time to the center of the waveform to the vertical period is P%.

Here, pixel light emission at a certain time is referred to as peak light emission value, light emission peak value, instantaneous light emission luminance, instantaneous light emission intensity, instantaneous light emission peak, or simply luminance. Strictly speaking, what is generally called luminance is instantaneous emission luminance, and the unit is [nit] (knit) or [cd / m ² ] (candela per square meter).

  The human eye feels that the instantaneous light emission luminance is integrated and smoothed by the eye, and this is called average luminance, light emission intensity, average screen luminance, screen luminance, average intensity, and average luminance level. Strictly speaking, the unit of the value obtained by integrating the instantaneous light emission luminance is not nit, but the unit of nit is often used equivalently. For example, in an LCD television, the average brightness when white is displayed is used for catalog specifications. A product obtained by multiplying the instantaneous light emission luminance and the time ratio (or time) like S and S1 shown in FIG. 1 is called a light emission intensity ratio (or light emission intensity), a light emission component, and a light emission amount. In FIG. 1, the area surrounded by the vertical axis and the horizontal axis of the light emission waveform corresponds to the light emission intensity.

  In FIG. 1B, the hatched portion is the second light emitting component. In the second light emitting component, the duty ratio of the light emission time is DA + DB = (100−D)%, the instantaneous light emission intensity is B [nit], and the light emission intensity ratio with respect to the pixel light emission intensity is (100−S)%.

  Note that there is a relationship of A> B regarding the instantaneous light emission intensity of the first light emission component and the second light emission component. DA is the vertical period of time from the start of the vertical period (that is, from the pixel selection pulse (gate pulse, scan pulse) based on the vertical synchronization signal) to the start of lighting of the first light emitting component. It is a ratio to. DB is the ratio of the time from the end of lighting of the first light-emitting component to the end of the vertical cycle with respect to the vertical cycle.

  The part (b) of FIG. 1 divides the waveform into intermittent light emission components and other continuous light emission components that generally emit light and raise the luminance. In the part (b) of FIG. 1, the area indicated by the vertical line is the intermittent light emission component. Regarding the intermittent light emission component, the duty ratio of the light emission time with respect to the period T is D%, the instantaneous light emission intensity is C [nit], the light emission intensity ratio with respect to the light emission intensity of the pixels displayed in the vertical period is S1%, and the vertical period is The ratio to the period of time from the start to the center of light emission is P%. The instantaneous light emission intensity C has a relationship of C = A−B.

  In addition, an area indicated by a cross hatch in the part (b) of FIG. 1 is a continuous light emission component. Regarding the continuous light emission component, the duty ratio of the light emission time is 100%, the instantaneous light emission intensity is B [nit], and the light emission intensity ratio with respect to the light emission intensity of the pixels displayed in the vertical period is (100−S1)%.

  Here, S1 = C * D = (A−B) * D. Further, A = S / D and B = (100−S) / (100−D). Therefore, S1 = S− (100−S) / (100−D) * D, and S can be converted into S1. That is, the light emission waveform formed by the first light emission component and the second light emission component may be considered to be substantially equal to the light emission waveform composed of the intermittent light emission component and the continuous light emission component. Therefore, in the following description, the effect of this invention is demonstrated based on the (b) part of FIG.

  FIG. 2 is a block diagram showing a configuration of the video display device 100 according to Embodiment 1 of the present invention. As shown in the figure, the video display device 100 includes a display panel 101, a video controller 102, a data driver 103, a scan driver 104, a column electrode 105, a row electrode 106, a lamp driving circuit 107, a lamp driving circuit 108, a lamp 109, The lamp 110 is configured.

  On the display panel 101, column electrodes 105 arranged in a column shape and row electrodes 106 arranged in a row shape are arranged. Further, the display panel 101 is a transmissive type that transmits and modulates illumination light from a light source. A plurality of pixels (not shown) are formed in a matrix at intersections between the column electrodes 105 and the row electrodes 106.

For example, the display panel 101 is composed of liquid crystal that responds at high speed. Here, the response of the liquid crystal is approximated to an exponential function,
y = A0 * (1-exp (-t / τ)) (where y is transmittance, and A0 is an arbitrary constant)
, It is assumed that the time constant τ (time from response start to response to about 63% of the final value) is about 1 millisecond, and at most 2 milliseconds.

  The data driver 103 drives the pixel based on the data signal 112 and sets the transmittance of the pixel to a state determined by the data signal 112. The scan signal 113 has information on the horizontal synchronization signal and the vertical synchronization signal of the video signal 111. The horizontal synchronization signal is a display unit in the column direction (horizontal direction) of the display screen. The vertical synchronization signal is a display unit in the row direction (vertical direction) of the screen. The frequency of the vertical synchronizing signal is, for example, 60 Hz for an NTSC video signal.

  The scan driver 104 sequentially selects and scans the row electrodes 106 from the top to the bottom of the screen based on the timing of the horizontal synchronization signal of the scan signal 113. Further, the row electrode 106 to be selected is reset to the upper part of the screen based on the timing of the vertical synchronization signal of the scan signal 113.

  When attention is paid to a certain pixel on the display panel 101, the cycle in which the pixel is selected is 16.7 milliseconds. The video controller 102 generates a lamp control signal 114 based on the vertical synchronization signal of the video signal 111 and outputs it to the lamp driving circuit 107. The lamp driving circuit 107 controls the lamp 109. The light emission output of the lamp 109 is intermittent light emission (intermittent light emission component) 115 controlled by the lamp control signal 114. That is, the lamp 109 emits light corresponding to the intermittent light emission component described in the part (b) of FIG. The lamp 109 can be realized by, for example, a single or a plurality of LEDs (light emitting diodes). The intermittent light 115 illuminates the display panel 101.

  The lamp driving circuit 108 controls the lamp 110. The light emission output of the lamp 110 is continuous light emission (sustained light emission component) 116 and emits light irrespective of the video signal 111. That is, the lamp 110 emits light corresponding to the continuous light emission component shown in part (b) of FIG. The lamp 110 can be realized by a fluorescent lamp such as a single or a plurality of CCFLs (cold cathode tubes). Alternatively, similar to the lamp 109, it can be realized by an LED. Similarly to the intermittent emission light 115, the continuous emission light 116 also illuminates the display panel 101.

  FIG. 3 is a cross-sectional view of the video display device 100 of FIG. 3 that have the same functions as those in FIG. 2 are denoted by the same reference numerals. As shown in FIG. 3, the light guide space 201 is a gap between the rear chassis of the video display device 100 and the display panel 101, for example. Further, a lamp 109 and a lamp 110 are disposed below the light guide space 201. A display panel 101 is disposed above the light guide space 201.

  The intermittent emission light 115 that is the output of the lamp 109 and the continuous emission light 116 that is the output of the lamp 110 propagate toward the display panel 101 in the light guide space 201. In the process, both illumination lights are transmitted. The mixed illumination light 202 is mixed. The mixed illumination light 202 illuminates the display panel 101. The illumination light is modulated by the pixels of the display panel 101 and output from the display panel 101 as display video light 203. Further, an observer who observes the video display device 100 recognizes the display video light 203 as a display video.

  FIG. 4 is a timing chart for explaining the operation of the video display apparatus 100 shown in FIGS. 2 and 3, and represents a time change of a signal transmitted through each path and a light emission waveform. The horizontal axis is time, and the time axis is described in units of frames of the video signal 111. A frame is a unit of the display screen of the video signal 111 and is determined by vertical synchronization.

  4A shows the signal waveform of the vertical synchronizing signal of the video signal 111. FIG. 4B shows the signal waveform of the lamp control signal 114, and it can be seen that the lamp control signal 114 repeats on and off in synchronization with the vertical synchronization signal. Part (c) of FIG. 4 shows a light emission waveform of the intermittent light 115, and intermittent light emission is performed in synchronization with the vertical synchronization signal. The vertical axis represents the intensity of instantaneous light emission luminance.

  Further, part (d) of FIG. 4 shows a light emission waveform of the continuous light emission 116, and is always constant irrespective of the vertical synchronization signal. The vertical axis represents instantaneous light emission luminance. 4 shows a light emission waveform of the mixed illumination light 202. FIG. The vertical axis represents instantaneous light emission luminance. Note that the mixed illumination light 202 is obtained by mixing the intermittent light emission 115 in part (c) of FIG. 4 and the continuous light emission 116 in part (d) of FIG. 4 in the light guide space 201.

  Further, part (f) of FIG. 4 shows the transmittance of a pixel when attention is paid to a certain pixel in the display panel 101. FIG. 4 (f) shows a state in which white video is input to the second and fourth frames and black video is input to the first and third frames. The product of the mixed illumination light 202 shown in part (e) of FIG. 4 and the transmittance of the pixel shown in part (f) of FIG. 4 is the display video light 203 shown in part (g) of FIG. The time response waveform of the instantaneous light emission luminance.

  The video display device 100 according to the present embodiment has a plurality of light sources such as a lamp 109 and a lamp 110, and outputs intermittent light 115 and continuous light 116 from each light source. In this point, the display panel 101 is illuminated. The intermittent emission light 115 and the continuous emission light 116 are mixed in the light guide space 202. The intermittent light emission 115 is controlled in synchronization with the vertical synchronizing signal of the video signal 111 and the repetition period and phase of light emission.

  And the video display apparatus 100 of this embodiment can implement | achieve animation tailing improvement and flicker interference reduction simultaneously by illuminating a display panel with the mixed illumination light 202 shown to the (g) part of FIG. .

  FIG. 5 is a diagram for qualitatively explaining the tail improvement and flicker reduction operations of the video display apparatus 100 of the present embodiment. In FIG. 5, it is assumed that the object moves at a constant speed of one pixel per frame, and the moving direction is from the top to the bottom of the screen. Note that the size of the object can be any vertical length of 3 pixels and any horizontal length.

  5A shows a light emission waveform of the mixed illumination light 202. The vertical axis represents instantaneous light emission luminance, and the horizontal axis represents time in frame units. Note that a portion indicated by vertical stripes in the portion (a) of FIG. 5 is a component of the intermittent light emission 115. Further, the portion indicated by cross hatching in the portion (a) of FIG. 5 is the component of the continuous light emission 116.

  A portion (b) in FIG. 5 shows a momentary outline of the moving object displayed on the display panel 101. The horizontal axis represents a space in pixel units, and the vertical axis represents transmittance.

  Part (c) of FIG. 5 shows how the moving object moves on the display screen of the display panel 101 (the horizontal axis is time and the vertical axis is space). Originally, the display screen of the display panel 101 is a two-dimensional plane, but in FIG. 5C, one horizontal axis coordinate is omitted from the two spatial coordinate axes.

  In addition, the moving object displayed moves with time, but the display video light 203 has two types of luminance due to the relationship between the movement and the illumination by the light emission waveform in the portion (a) of FIG. That is, the luminance of the display video light 203 is large during the period in which the intermittent light emission component emits light. In addition, the part shown by a vertical stripe in (c) part of FIG. 5 corresponds to the part where the luminance is increased.

  On the other hand, during the period in which only the continuous light emission component is illuminated, the emission intensity of the mixed illumination light 202 is weak, but it has an intensity sufficient to illuminate the pixels sufficiently. In addition, the part shown by the cross hatching in the part (c) of FIG. 5 corresponds to a period in which only the continuous light emission component is illuminated.

  When the observer follows the moving object along the arrow 2 along the line of sight, the two types of light emission states are integrated, and the state shown in the part (d) of FIG. Moreover, the (e) part of FIG. 5 shows the brightness | luminance outline in the (d) part of FIG. In part (e) of FIG. 5, the horizontal axis represents pixels (spaces) and the vertical axis represents luminance.

  As shown in part (e) of FIG. 5, the luminance contour of the moving object recognized by the observer has three types of inclinations, that is, inclinations 1, 2, and 3. What is important here is that slope 1 and slope 3 shown in part (e) of FIG. 5 are gentle, but slope 2 is steep and has a steep slope.

  The gentle slopes 1 and 3 are not easily recognized by human eyes. This is because the observer's ability to discriminate contrast with respect to a moving object is generally inferior to that of a normal stationary object. Therefore, the contour of the moving object recognized by the observer is inclined 2, and is used for tailing the moving image when the display panel 101 is illuminated with a light source that emits light with respect to time as shown in FIG. On the other hand, it can be seen that the tail improvement can be sufficiently achieved by the video display device 100 of the present embodiment.

  FIG. 6A to FIG. 6I are diagrams for quantitatively explaining the effect of this embodiment, and show the characteristics of three types of light emission patterns.

  Here, FIG. 6A to FIG. 6C show the characteristics of the emission luminance waveform, the amount of tailing, and the amount of flicker when a conventional impulse type emission pattern having a duty ratio of 25% is used. It is shown. FIGS. 6D to 6F show the characteristics of the emission luminance waveform, the amount of tailing, and the amount of flicker when an impulse-type emission pattern having a duty ratio of 40% is used. is there. 6 (g) to 6 (i) show the characteristics of the emission luminance waveform, the amount of tailing, and the amount of flicker when the display panel 101 is illuminated using the video display device 100 of this embodiment. It is shown. In the light emission by the video display device 100 of the present embodiment, the duty ratio D of the intermittent light emission component is set to 20%, and the light emission intensity ratio S1 of the intermittent light emission component is set to 80%.

  In addition, regarding the amount of tailing, the unit is the length in space, and a change from 10% to 90% of the luminance on the vertical axis is defined as the amount of tailing. This definition is made on the basis that the sensitivity of the human eye to the above-described contrast of the moving object is low. In addition, the range of the arrow in FIG.6 (b), FIG.6 (e), and FIG.6 (h) corresponds to this amount of tailing.

  FIG. 6C, FIG. 6F, and FIG. 6I show the flicker amount. This flicker amount is obtained by frequency-converting the emission waveforms shown in FIGS. 6A, 6D, and 6G by Fourier transform, respectively, and obtaining the first harmonic with respect to the zero-order DC component (average value). The ratio of components is calculated. For example, when the vertical synchronization signal is an NTSC video signal of 60 Hz, the first harmonic is 60 Hz. Flicker interference increases as the first harmonic component relative to the zero-order DC component increases.

  Here, in FIG. 6A to FIG. 6I, consideration is given to the light emission intensity of each light emission pattern being the same. That is, in FIG. 6A, FIG. 6D, and FIG. 6G, the values obtained by integrating the luminance with time are the same. Since the emission intensity is the same in this way, the energy amount of each average value component (zero-order DC component) in FIGS. 6C, 6F, and 6I is the same in each emission pattern. Therefore, it is possible to compare the amount of the first harmonic component for each light emission pattern.

  FIG. 7 summarizes the characteristics of the light emission patterns shown in FIGS. 6 (a) to 6 (i). In FIG. 7, the duty ratio D of the intermittent light emission component in the first column is the light emission time ratio of the intermittent light emission component with respect to the pixel update repetition time (vertical period). In addition, the continuous component in the second row is the emission intensity ratio S1 of the intermittent emission component with respect to the entire emission intensity. In the light emission according to the conventional technique, the light emission intensity ratio S1 of the intermittent light emission component is 100%. Further, the amount of tailing in the third column is the length of the arrow line shown in FIGS. 6B, 6E, and 6H. The flicker amount in the fourth column is the ratio of the 60 Hz component (first harmonic) to the average value (0th direct current component). Furthermore, the first to third rows in FIG. 7 correspond to the light emission patterns 1 to 3 in FIG. 6, respectively.

  As shown in part (a) of FIG. 41, in the case of light emission without countermeasures against tailing, the amount of tailing for a change in luminance from 10% to 90% is 0.8. On the other hand, in the conventional example of the first row in FIG. 7, the duty ratio is 25% and the tailing amount is improved to 0.2. Therefore, in the conventional example in the first row, the improvement rate of the trailing amount is 75%. However, the 60 Hz component, which is the main cause of flicker, occurs at a rate of 90%, which is a significant disturbance.

  Here, as shown in the conventional example in the second row of FIG. 7, it is assumed that the duty ratio is increased to 40% in order to reduce flicker. Although the flicker amount can be suppressed to 75% by increasing the duty ratio, the trailing amount increases to 0.32, and the improvement rate of the trailing amount decreases to 60%.

  In this embodiment in the third row, the duty ratio of the intermittent light emission component, which is a feature of the present invention, is 20%, and the light emission intensity ratio is 80%. As is apparent from FIG. 7, it is possible to attenuate the flicker from 90% to 75% and the trailing amount is 0.20 as compared with the conventional example of the first row. Holds improvements to the conventional example of the line.

  As described above, according to the present embodiment, flicker interference can be significantly reduced while ensuring the degree of improvement in tailing, and an optimal quality image can be provided to the viewer.

  FIG. 8 is a diagram showing the characteristics of each light emission pattern of FIG. The horizontal axis in FIG. 8 indicates the amount of tailing, and the smaller the numerical value, the higher the image quality. Also, the vertical axis in FIG. 8 is the flicker amount, and the smaller the numerical value, the smaller the flicker and the higher the image quality.

  In the light emission according to the conventional technique, the values of the trailing amount and the flicker amount move on the locus shown in FIG. 8 by changing the duty ratio D, and do not move in the ideal improvement direction indicated by the white arrow. Therefore, in this case, the flicker amount and the trailing amount are in a trade-off relationship, and both cannot be improved at the same time.

  In contrast, the circles in the figure indicate the light emission characteristics according to the present embodiment, and it can be seen that the amount of tailing and the amount of flicker are simultaneously improved.

  FIG. 9A to FIG. 9F are diagrams for explaining the relationship between the intermittent light emission component duty ratio D and the intermittent light emission phase P. FIG. The intermittent light emission phase is the ratio of the time from the start of the vertical period to the center of the intermittent light emission component with respect to the vertical period (see part (b) of FIG. 1).

  In FIGS. 9A to 9F, the light emission conditions are a duty ratio D = 30% and a light emission intensity ratio S1 = 90%. Further, as described above, it is assumed that the display panel uses a liquid crystal having a high-speed response with a time constant τ = 1 ms. Further, as in FIG. 5, the tailing amount is defined as a tailing amount of 10% to 90% of the tailing luminance change.

  Further, FIG. 9A, FIG. 9C, and FIG. 9E are emission waveforms of P = 30%, 50%, and 70%, respectively. FIG. 9B, FIG. 9D, and FIG. 9F show tailing states when the value of P is 30%, 50%, and 70%, respectively. The tailing state is calculated from the tailing model shown in FIG.

  As is apparent from FIG. 9, the balance of the slopes 1 and 3 described in the part (e) of FIG. 5 is good when P = 50%. Further, when P = 30 and 70%, the inclinations 1 and 3 are biased, but the amount of tailing is the same as when P = 50%, and the tailing improvement effect is the same.

  10 (a) to 10 (f) are diagrams for explaining the relationship between the intermittent light emission component duty ratio D and the intermittent light emission phase P, and the light emission conditions are the same as those in FIGS. 9 (a) to 9 (f). It is. However, FIGS. 10A to 10F show cases where the intermittent light emission phase P is 10%, 50%, and 90%.

  As shown in FIGS. 10B and 10F, when P = 10% and 90%, the tail improvement effect is extremely deteriorated. This is because the light emission waveform is divided into two as shown in FIGS. 10 (a) and 10 (e).

  11 (a) to 11 (f) are diagrams for explaining the relationship between the intermittent light emission component duty ratio D and the intermittent light emission phase P. The light emission conditions are shown in FIGS. 9 (a) to 9 (f) and FIG. 10 (a) to FIG. 10 (f). However, Fig.11 (a)-FIG.11 (f) have shown the case where the intermittent light emission phase P is 15%, 50%, and 85%. As shown in FIGS. 11A to 11F, in this case, the tailing improvement is good.

  The following can be understood from FIGS. 9A to 9F, FIGS. 10A to 10F, and FIGS. 11A to 11F. Since the relationship between the duty ratio D and the light emission phase P is not required if the light emission pulse is not divided within the frame, P is D / 2% or more, or P is (100−D / 2)% or less. is required. In other cases, as shown in FIGS. 10A and 10E, the intermittent light emission component is divided in the frame. When the frame is divided in this way, the slope changes sharply in integration assuming that the human eye follows the edge of the movement of the object as shown in part (c) of FIG. Therefore, the effect of the present invention, that is, the simultaneous reduction effect of the trailing amount and the flicker amount is lost.

Therefore,
D / 2 ≦ P ≦ (100−D / 2) (where 0 <D <100)
The duty ratio D and the intermittent light emission phase P may be managed so as to satisfy the above condition.

  Here, since D = 0% means that the intermittent light emission component is 0, it is excluded here. Also, the case of D = 100% is excluded here because it is a case of a conventional intermittent light emission waveform.

  FIG. 12 is a diagram showing the relationship between the duty ratio D and the intermittent light emission phase P. In FIG. The horizontal axis is D and the vertical axis is P. D and P in the area indicated by halftone dots in the figure satisfy the above condition.

  In FIG. 12, the boundary line on the lower side of the area is a line segment that satisfies the relationship P = D / 2. The boundary line on the upper side of the area is a line segment that satisfies the relationship P = (100−D / 2). From the response speed of the display panel, the type of light source, the mounting method, etc., the values of D and P may be determined in the area indicated by the halftone dots in FIG.

  Fig.13 (a)-FIG.13 (e) are the figures for demonstrating the light emission phase of the light emission waveform of this embodiment. FIG. 13A shows a light emission waveform for one frame of the mixed illumination light 202 of this embodiment, and the horizontal axis indicates time in units of frames. That is, the pixel is selected at time 0 on the time axis, and the next selection is made at the next time 1.

  The light emission waveform conditions are the same as those in the third row of FIG. That is, the duty ratio D of the intermittent light emission component is 20%, and the light emission intensity ratio S1 of the intermittent light emission component is 80%. Further, as described above, the display panel 101 uses a fast response liquid crystal having a time constant of about 1 millisecond. Furthermore, the light emission phase of the intermittent light emission 115 is at the center of the frame period, and the intermittent light emission phase P is 0.5.

  In FIG. 13B, the tailing amount generated when the display panel 101 is illuminated with the mixed illumination light 202 of FIG. 13A is calculated by the simulated tailing amount calculation method shown in FIG. The result is shown. Note that the horizontal axis in FIG. 13B is a space in units of pixels, and here, one pixel is displayed. Furthermore, the definition of the tailing amount is the same as that used in FIG. 6, and the spatial length that changes from 10% to 90% of the luminance change (slope) of the tailing is used as the tailing amount. Here, the amount of tailing is 0.2.

  FIG. 13C shows a light emission waveform according to the present embodiment as in FIG. 13A, but the light emission phase of the intermittent light emission 115 is shifted to the second half of the frame. In addition, the intermittent light emission phase P of the light emission waveform shown in FIG.13 (c) is 75%.

  FIG. 13D shows a tailing waveform when the display panel 101 is illuminated with the mixed illumination light 202 of FIG. In the tailing waveform shown in FIG. 13D, the amount of tailing is 0.33. As described above, the amount of tailing increases due to the change in the intermittent light emission phase P. As shown in FIG. 13D, the balance between the slope 1 and the slope 3 is lost, and the slope portion with the gentle slope 1 is obtained. This exceeds 10% set as the threshold value.

  FIG. 13 (e) shows the intermittent light emission phase P and the amount of tailing in the case of the light emission conditions (duty ratio D = 20%, light emission intensity ratio S1 = 20%) in FIGS. 13 (a) and 13 (c). It is a figure which shows a relationship.

  As is clear from FIG. 13E, in the case of the light emission condition with the duty ratio D = 20% and the light emission intensity ratio S1 = 80%, when the intermittent light emission phase is 50%, that is, the waveform of the intermittent light emission 115 is a frame. It is possible to improve the tailing most when it is the center of repetition.

  For example, from the state of the screen brightness (absolute brightness) of the video display device, viewing environment, etc., the definition of the threshold at which the slopes 1 and 3 shown in FIG. Assume that it is determined that there is a 15% to 85% tailing luminance change. In the case of this definition, the tailing amount in FIG. 13 (d) is equivalent to the tailing amount in FIG. 13 (b).

  In the present embodiment, the effect of improving the tailing amount and the flicker amount is obtained based on the tailing model shown in FIG. 5 and the definition of the flicker amount described in FIGS. 6A to 6I. Although described quantitatively, the image quality of the video display apparatus includes a subjective part, and depends on the viewing environment.

  Therefore, the optimum values of parameters such as the tailing threshold, the duty ratio D, the emission intensity ratio S1 of the intermittent emission component, and the intermittent emission phase P have been described above in consideration of the system conditions of the video display device. It may be determined so as to satisfy D / 2 ≦ P ≦ (100−D / 2).

  FIG. 14 is a diagram for explaining the effect of the present embodiment by subjective evaluation. As for the screen brightness of the video display device, white brightness (screen brightness when white is displayed on the screen) is 450 nits, which is a sufficiently bright level as a television (TV) receiver. In addition, nit (knit, nit) is a unit of luminance. Three types of still images having different APLs (average picture level and average image level) were used as evaluation images.

  The image A is an overall dark image such as a night view. Note that the APL of the image A is 20%, which corresponds to a screen luminance of 100 nits. The image B is an image having an APL of 50% and corresponds to a screen luminance of 250 nits. The image C is a bright image such as a blue sky, and APL is 80% (equivalent to a screen luminance of 350 nits).

  These evaluation images are displayed on a video display device, and can be driven by switching between the light emission waveform of the prior art shown in FIG. 6A and the light emission waveform of the present embodiment shown in FIG. 6C to perceive image flicker. I experimented. Furthermore, if flicker could be perceived, an experiment was conducted to see if it could be disturbed. In addition, the scale of subjective evaluation was made into five steps, and the larger the scale, the higher the image quality.

  From FIG. 14, it can be seen that the flicker reduction effect of the present embodiment with respect to the impulse-type light emission which is the prior art has reached a level acceptable to the observer. Furthermore, this effect is similarly seen with respect to three types of APLs, that is, three types of brightness images.

  As described above, in the tail improvement of the present invention, the low sensitivity of the human eye to the contrast of the moving object is used. Therefore, even if a certain instantaneous value (instantaneous peak luminance) of the screen luminance by illumination of the continuous light 116 is visible to the human eye, it does not affect the tailing improvement performance.

  Rather, the screen luminance based on the instantaneous peak luminance is preferably at a level where it can be easily visually recognized. In FIG. 6G, the continuous light emission component is 20%. Therefore, assuming that the screen brightness of the display panel is 450 nits, 90%, or 20% of that, can be said to be due to the illumination of the continuous light emission 116. The screen brightness of 90 nit is a level that can be sufficiently perceived by human eyes. From the subjective evaluation results shown in FIG. 14, it can be seen that the 20% sustained light emission component functions sufficiently to improve tailing and reduce flicker interference.

  In the present embodiment, the operation method of the video on the display panel can be applied to either progressive scanning or interlace scanning.

  In the video display device 100 of the present embodiment, the light source is not limited to the LED or the CCFL. A light source suitable for intermittent light emission and continuous light emission may be employed.

  Further, in the present embodiment, the display panel 101 in FIG. 2 is described as a transmission type, but the present invention can also be applied to a reflection type that modulates light by reflecting light emitted from a light source.

  Furthermore, in the present embodiment, it has been described that the lamp 109 and the lamp 110 are arranged directly below the display panel 101 in FIG. 2, but the present invention is not limited to this arrangement. Further, in FIG. 3, it is described that light is mixed in the light guide space 201, but intermittent light 115 and continuous light 116 are guided to the display panel 101 by using the light guide plate, for example. In the process, both illumination lights may be mixed. In addition, an electrical signal corresponding to the components of the intermittent emission light 115 and the continuous emission light 116 may be electrically added, and then the light source may be controlled to emit light, and the configuration for mixing the light may be omitted.

  Further, in the present embodiment, the NTSC video signal whose vertical synchronization signal is 60 Hz is given as an example in FIG. 2, but the present embodiment is also applied to a video signal such as 75 Hz of an RGB video signal of a personal computer. Is possible. In this case, the flicker amount may be evaluated by defining a harmonic of 75 Hz with respect to the DC component by Fourier transform of the light emission waveform.

  Furthermore, in the present embodiment, numerical examples of the parameters D and S1 set in the video display device 100 of the present embodiment are described in the third row of FIG. 7, but the present invention is limited by these numerical values. is not.

  Furthermore, in the present embodiment, it has been described that the emission of the continuous light 116 is constant regardless of the video signal 111, but may vary at a frequency of, for example, 150 Hz or more. The observer's eyes are very insensitive to repeated flashing at approximately 150 Hz and have little sensitivity to repeated flashing at frequencies above approximately 300 Hz. In this case, even if the continuous emission light 116 is strictly changing light, the human eye does not follow and is observed as light that emits light with a constant intensity.

  Furthermore, in the present embodiment, the emission intensity ratio between the intermittent emission light 115 and the continuous emission light 116 is described as if it is a fixed value. For example, whether the video signal 111 is a violent movement or a slight movement, Alternatively, it may be determined whether the image is a still image that does not move at all, and based on the information, the emission intensity ratio between the intermittent emission light 115 and the continuous emission light 116 may be varied in association with each other.

  For example, in the case of an intensely moving image, control is performed to increase the emission intensity ratio of the intermittent emission light 115 or decrease the duty ratio. The above-described control may be performed to determine the optimal light emission condition for the display image. Further, the emission intensity ratio may be controlled for each frame.

  As described above, in the present embodiment, the light emission having different characteristics such as the continuous light emission and the intermittent light emission is mixed, and the display panel is illuminated to suppress the tailing of the moving object and display a clear outline. At the same time, flicker interference can be suppressed. In order to improve the tailing of the moving image, the response characteristic of the low sensitivity of the human eye to the contrast of the moving image is used, and the screen luminance due to the emission intensity of the continuous emission light 116 in the instantaneous emission is This level is easily recognizable by an observer.

  In this embodiment, the lamp 109 and the lamp 110 are used to obtain light emission having different characteristics from each other. However, a light source having the characteristics of the lamp 110 is used to form between the display panel and the light source. The light control means may be arranged between the optical paths. The light control means is an optical shutter made of a liquid crystal such as a ferroelectric liquid crystal, and the transmittance is switched between full transmission and semi-transmission by on / off control of an applied voltage. While synchronizing with the vertical synchronization signal of the video, for example, when the voltage is on, the transmittance is 100% and the illumination light of the light source is transmitted to generate intermittent light emission, and when the voltage is off, the transmittance is reduced to 50%. By generating continuous emission light at, an ideal improvement in tailing amount and flicker amount is possible.

  Further, if the screen brightness increases, flicker is easily perceived (Ferry-Porter's law). Therefore, flicker interference is likely to occur due to the high brightness of the video display device. Further, since the human eye is more sensitive to blinking than the cone of photoreceptor cells, that is, the periphery of the visual field is more sensitive to blinking, flicker interference is easily recognized even when the screen size of the video display device is increased. The method for improving the display quality of the video display device according to the present embodiment is particularly effective for increasing the luminance and the screen size of the video display device.

  Further, in the present embodiment, the light emission duty ratio D of the intermittent light emission component and the intermittent light emission phase P satisfy the relationship of D / 2 ≦ P ≦ (100−D / 2). Optimum values such as tail threshold, duty ratio D, intermittent light emission intensity ratio S1, and intermittent light emission phase P, which are parameters of the video display device, are the amount of tailing by subjective evaluation of the video display device, It may be determined so as to satisfy D / 2 ≦ P ≦ (100−D / 2) in consideration of the appearance of the flicker amount and various system conditions.

[Embodiment 2]
A video display apparatus according to still another embodiment of the present invention will be described with reference to FIGS. 15 and 16. FIG. 15 is a diagram for explaining the configuration of a video display apparatus 400 to which the present embodiment is applied. As shown in FIG. 15, the video display device 400 includes a liquid crystal panel (video display means) 401, a liquid crystal controller 402, a source driver 403, a gate driver 404, a source electrode 405, a gate electrode 406, an intermittent light emission drive circuit 407, and continuous light emission. A driving circuit 408, a lamp unit (light emitting means) 409, a lamp 410, a lamp 411, a light guide unit 412, a light guide unit 413, and a light guide unit 414 are provided.

  On the liquid crystal panel 401, a source electrode 405 driven by a source driver 403 and a gate electrode 406 driven by a gate driver 404 are arranged to form a matrix. Pixels (not shown) are arranged at intersections between the source electrode 405 and the gate electrode 406. In FIG. 15, the gate electrode 406 is denoted by reference numerals G1 to G6.

  The liquid crystal controller 402 performs processing necessary for the display operation of the liquid crystal panel 401 based on the video signal 451 and controls the source driver 403 and the gate driver 404.

  The gate driver 404 sequentially selects the gate electrodes 406 and applies a gate signal. The liquid crystal panel 401 is a transmissive type, and when a certain gate electrode is selected, the transmittance of the pixels belonging to the gate electrode is updated.

  The transmittance of the pixel is determined by video information from the source electrode. The frequency of the transmittance update operation is determined based on the vertical synchronization frequency of the video signal 451. For example, the NTSC video signal is 60 Hz. Here, it is assumed that a liquid crystal having a high-speed response in which the time response characteristic of the liquid crystal present in each pixel, that is, the time characteristic (time constant) until the transmittance changes to a desired state, is about 1 millisecond.

  Further, the liquid crystal controller 402 outputs a vertical synchronization signal 452 to the intermittent light emission drive circuit 407. The lamp unit 409 includes a lamp 410 that outputs intermittent light emission and a lamp 411 that outputs continuous light emission. Both the lamp 410 and the lamp 411 can be realized by, for example, a single or a plurality of LEDs. In FIG. 15, three lamp units 409 are illustrated, but the number of lamp units provided in the video display device 400 is not limited to this.

  The intermittent emission light and the continuous emission light are mixed inside the lamp unit 409 and output mixed illumination light 457, mixed illumination light 458, and mixed illumination light 459, respectively. Each of these mixed illumination lights is input to the light guide unit 412, the light guide unit 413, and the light guide unit 414, respectively.

  The light guide units 412 to 414 are printed with a pattern (not shown) for diffusing light, guide and diffuse mixed illumination light input from the end face, and output the mixed illumination light to the liquid crystal panel. . The light guide units 412 to 414 and the lamp unit 409 have a one-to-one correspondence, and are separated by, for example, optical partitions so that the illumination lights are not mixed with each other.

  Each of the three sets of light guide units 412 to 414 and lamp unit 409 (each part divided into a block shape) constitutes an area for partially illuminating the liquid crystal panel 401. The light guide unit 412 illuminates the area at the top of the screen. The light guide unit 413 is the center of the screen, and the light guide unit 414 is the lower part of the screen.

  The intermittent light emission drive circuit 407 creates intermittent pulse signals 453, 454, and 455 from the vertical synchronization signal 452 and supplies them to the lamps 410 of the lamp units 409. The continuous light emission drive circuit 408 supplies a continuous continuous signal 456 that is common to the lamps 411 of the respective lamp units 409 and is irrelevant to the video signal 111.

  FIG. 16 is a timing chart for explaining the operation of the video display apparatus 400 of FIG. A part (a) of FIG. 16 shows a waveform of the vertical synchronizing signal 452. The part (b) of FIG. 16 shows the waveform of the gate signal applied to the gate electrode (G1 or G2) that controls the pixels belonging to the area illuminated by the light guide unit 412. A portion (c) of FIG. 16 shows a light emission waveform of the mixed illumination light 457. FIG. 16D shows the signal waveform of the gate signal applied to the gate electrode (G3 or G4) that controls the pixels belonging to the area illuminated by the light guide unit 413. FIG. A portion (e) of FIG. 16 shows a light emission waveform of the mixed illumination light 458. The part (f) in FIG. 16 shows the waveform of the gate signal applied to the gate electrode (G5 or G6) that controls the pixels belonging to the area illuminated by the light guide unit 414. The (g) part of FIG. 16 shows the light emission waveform of the mixed illumination light 459. The vertical axes of the (c) part, (e) part, and (g) part of FIG.

  Here, one of the features of the video display apparatus 400 of the present embodiment is that the liquid crystal panel is divided into a plurality of areas and each area is illuminated, as shown in FIG. The illumination light is mixed illumination light in which intermittent emission light and continuous emission light are mixed. The light emission phases of the intermittent light emission components between the mixed illumination lights that illuminate each area are different. In the liquid crystal panel 401, the update timing of the transmittance of the pixel differs depending on the location of the screen depending on the selection (addressing) of the gate electrode. The influence of the phase difference of the update timing is absorbed by shifting the emission phase of the intermittent emission light of the plurality of lamp units, and the best emission phase is obtained.

  Also, the vertical synchronization signal 452 in the part (a) of FIG. 16 is the reference timing for the operation of displaying an image on the liquid crystal panel 401. T0 is a repetition time (frame period). Further, the gate electrode driven by the gate signal shown in part (b) of FIG. 16 is located at the upper part of the screen of the display panel 101, and the phase thereof is the same or substantially the same as that of the vertical synchronization signal 452.

  The emission phase of the intermittent emission light of the mixed illumination light 457 shown in part (c) of FIG. 16 is located at the center of the repetition time of the low pulse of the gate signal, and T1 and T2 are in the same relationship. Here, T1 is the time until the intermittent light emission component starts to emit light with reference to the rise of the gate signal shown in part (b) of FIG. It is assumed that the time when the start of the intermittent light emission component is delayed with respect to the rising edge of the gate signal is positive time, and the case where the phase of the start of intermittent light emission component is advanced is negative time. T2 is the time until the period T0 ends with reference to the time at which the intermittent light emission component ends light emission. Note that the light emission phase of the intermittent light emission component is controlled by the intermittent pulse signal 453 from the intermittent light emission drive circuit 407. By controlling the emission phase of the intermittent emission light of such a gate signal and mixed illumination light, the effects of reducing the tailing and flicker described in the first embodiment can be obtained.

  The gate signal shown in part (d) of FIG. 16 is a signal for operating the gate electrode (G3 or G4) in the central part of the screen, and is shifted by the time T3 with respect to the vertical synchronization signal 452. . Regarding the relationship between T3 and the frame period T0, approximately three times T3 is T0. FIG. 16E shows a light emission waveform of the mixed illumination light 458 that illuminates the pixels belonging to the gate electrodes G3 and G4, and T4 and T5 have the same relationship.

  The phase of the gate electrode shown in part (f) of FIG. 16 is shifted by the time T6 with respect to the vertical synchronization signal. Note that approximately 3/2 times T6 is T0. In the emission phase of the intermittent emission light of the mixed illumination light 459 in the part (g) of FIG. 16, T7 and T8 have the same relationship. As described above, the tail reduction described in the first embodiment is performed by matching the timing at which the pixel is driven and updated and the phase of the intermittent emission light of the mixed illumination light that illuminates the pixel to the center of the pixel update timing. Flicker reduction can be realized for the entire display screen.

  In the present embodiment, the light guide unit is divided into three parts, but the same effect can be obtained with four or more parts. In the present embodiment, the light source is described as being an LED, but is not limited to an LED. Further, in the present embodiment, the liquid crystal panel is described as a transmissive type, but the present embodiment can also be applied to a reflective type.

  In this embodiment, the light guide unit may be a light guide plate made of acrylic resin, the lamp unit may be disposed on the side surface of the light guide plate, and mixed illumination light may be input from the end surface of the light guide plate. Further, the intermittent light emission and the continuous light emission may be mixed in the light guide plate without being mixed in the lamp unit. Alternatively, the lamp unit may be disposed on the back surface of the liquid crystal panel, and a gap may be provided between the lamp unit and the liquid crystal panel, and intermittent light emission and continuous light emission may be mixed in the gap.

  In this embodiment, it has been described that the lamp units have partitions so that the illumination lights of the lamp units are not mixed. However, the illumination light may be controlled not to be mixed depending on the directivity of the light source without providing the partitions.

  As described above, the video display device according to the present embodiment divides the area for illuminating the liquid crystal panel by the combination of the lamp unit and the light guide unit. The illumination light is mixed illumination light in which intermittent emission light and continuous emission light are mixed. The light emission phase of the intermittent light emission component between the mixed illumination lights that illuminate each area is different between the areas. Depending on the selection of the gate electrode (addressing), the update timing of the pixel transmittance varies depending on the location of the display screen. Therefore, the effect of the difference in the update timing phase shifts the emission phase of the intermittent emission light of multiple lamp units. To solve.

  The effect obtained by illuminating the liquid crystal panel with the mixed illumination light is the same as that described in the first embodiment, and is an effect that it is possible to provide an optimal display image with clear moving image display and no flicker interference.

  In FIG. 16, it has been described that T1 = T2, T4 = T5, and T7 = T8. However, the phase of the intermittent emission light with respect to these gate electrode pulses is D / 2 ≦ P ≦ (100 described in the first embodiment. -It should be designed to satisfy the condition of D / 2). If the intermittent light emission phase P described in FIG. 1 is applied to FIG. 16, P = (T0 + T1-T2) / 2. Further, the intermittent light emission time ratio D is D = (T0−T1−T2).

  Therefore, from FIG. 16, a condition of 0 ≦ T1 is derived as a condition for obtaining the effect of the present invention. That is, if T1 is 0 or more, the intermittent light emission component is not divided into two in the unit of the repetition period T0, and a good tailing effect is obtained. That T1 is equal to or greater than 0 means that the phase of the light emission start of the intermittent light emission component is delayed from the rise of the gate signal. Similarly, a condition of 0 ≦ T2 is also derived. The fact that T2 is 0 or more means that the phase of the end of light emission of the intermittent light emission component is ahead of the time until the period T0 ends, in other words, the time of the next gate signal rise. The light emission waveform is a repetitive signal having a period T0, and when T1 has a negative value, T2 also has a negative value. For example, when T0 = 17 milliseconds and the light emission time of the intermittent light emission component is 7 milliseconds, light may be emitted at T1 = 1 millisecond and T2 = 9 milliseconds. Alternatively, light may be emitted at T1 = 5 milliseconds and T2 = 5 milliseconds. It is good also as T1 = 10 milliseconds and T2 = 0 milliseconds. In the setting of T1 = 13 milliseconds, T2 becomes negative. Therefore, such a light emission phase may not be selected. Even in the case of T2 = 12 milliseconds, since T1 is a negative value, the effect of this embodiment cannot be obtained. Therefore, it is sufficient that such a light emission phase is not selected. In many cases, the video display apparatus adjusts the image quality based on subjective judgment, but parameters such as the light emission time and light emission intensity of the intermittent light emission component may be determined under the condition of 0 ≦ T1 or 0 ≦ T2. .

[Embodiment 3]
A video display apparatus according to still another embodiment of the present invention will be described with reference to FIGS. The configuration of the video display apparatus of this embodiment is the same as that shown in FIG. The means for modulating the illumination light from the light source is a transmissive liquid crystal.

  In the present embodiment, unlike the first and second embodiments, a liquid crystal having general response characteristics is assumed. General response characteristics refer to those having a time constant of about 2 to 5 milliseconds. The time constant is defined as the time required to change to approximately 63% of the desired target transmittance state. The time to reach 90% of the target transmittance state is approximately 2.3 times the time constant. Liquid crystals with a slow response with a time constant of 10 milliseconds or more exist in the world, but are excluded here.

  Here, an object of the present invention is to improve the amount of tailing. As a premise for improving the tailing, it is known that it is necessary to combine both the improvement of the hold-type characteristics and the improvement of the liquid crystal response time. If the hold-type light emission is improved for a liquid crystal with a slow response, interference such as a broken edge of the image occurs. Therefore, here, the upper limit of the assumption of the time constant of the liquid crystal is 5 milliseconds.

  FIG. 17 is a timing chart for explaining the operation of the video display apparatus of this embodiment. FIG. 17A shows a gate signal supplied to a gate electrode to which a pixel belongs when attention is paid to a certain pixel. T0 shown in part (a) of FIG. 17 is the period of the vertical synchronization signal of the video signal 111, and is 16.7 milliseconds for the NTSC video signal. Part (b) of FIG. 17 shows a change in the transmittance of the pixel of interest when the time constant of the liquid crystal is 3.5 milliseconds. The time required for the liquid crystal to change to 90% of the target transmittance is about 8 milliseconds. The pixel changes to a transmittance corresponding to white in a certain frame, and changes to a transmittance corresponding to black in the next frame, that is, 0%. The vertical axis of the (c) part and (e) part of FIG.

  FIG. 17C shows a light emission waveform of mixed illumination light that illuminates the pixel. The conditions of the emission waveform are the same as those described in the third row of FIG. That is, the duty ratio D of the intermittent light emission component is 20%, and the ratio S1 of the intermittent light emission component to the total light emission intensity is 20%. T11 shown in part (c) of FIG. 17 is the rise time of the intermittent emission light from the low period of the gate signal. T1 shows the best timing for illuminating the liquid crystal in part (b) of FIG. 17, and T11 is 75% of T0.

  Further, part (d) of FIG. 17 shows a change in transmittance of liquid crystal different from that of part (b) of FIG. 17, that is, liquid crystal having a time constant of 2.2 milliseconds. The time required for the liquid crystal to change to 90% of the target transmittance is about 5 milliseconds. Part (e) of FIG. 17 shows the state of the best mixed illumination light for illuminating the liquid crystal of part (d) of FIG. 17, and T12 which is the phase of the intermittent light emission component is 65 of T0. %.

  FIG. 18A to FIG. 18D are diagrams for explaining the best light emission phase of the intermittent light emission component when the response time constant of the liquid crystal is 3.5 milliseconds. The light emission conditions of the light source are the same as in part (c) of FIG. 17, where the duty ratio D of the intermittent light emission component is 20% and the light emission intensity ratio S1 of the intermittent light emission component is 20%.

  FIG. 18A shows the response waveform of the liquid crystal. This is a response of transmittance when white for three frames is written. The transient response of the liquid crystal is approximated by an exponential function, and the time constant is 3.5 milliseconds as described above. FIG. 18B shows a light emission waveform of the light source. The intermittent light emission phase P is the best 75%. FIG. 18C shows the tailing in the case where the characteristics of FIG. 18A are set for the response of the liquid crystal and the characteristics of FIG. 18B are set for the light emission waveform of the light source in the tailing model shown in FIG. It shows the amount. The tail amount threshold is assumed to be 10% to 90%. The amount of tailing is approximately 0.2 pixels.

  In the case described with reference to FIG. 13, the tailing response is a straight line. However, in the tailing model including the transient response of the liquid crystal, the tailing response is a curve as shown in FIG. However, since the inclinations of the inclinations 1 and 3 shown in the part (e) of FIG. 5 are gentle with respect to the inclination 2 and the human eye does not respond, the effects described in the first embodiment can be obtained.

  FIG. 18D shows characteristics when the intermittent light emission phase P is changed in the tailing amount calculation performed in FIG. As is apparent from the figure, when P is 75% to 80%, the amount of tailing is minimized and high image quality is obtained. In the portion other than the range of P, the amount of tailing increases. This is because the portions with the slopes 1 and 3 shown in the portion (e) of FIG. 5 exceed the set threshold value of the trailing amount.

  FIG. 19A to FIG. 19D are diagrams for explaining the best light emission phase of the intermittent light emission component when the liquid crystal time constant is 2.2 milliseconds. The light emission conditions of the light source are the same as those in the portions (c) and (e) of FIG.

  FIG. 19A shows a response waveform of the liquid crystal. The transient response of the liquid crystal is approximated by an exponential function. FIG. 19B shows a light emission waveform of the light source. The intermittent light emission phase P is the best 65%. FIG. 19C shows the tailing when the characteristics of FIG. 19A are set for the response of the liquid crystal and the characteristics of FIG. 19B are set for the light emission waveform of the light source in the tailing model shown in FIG. Indicates the amount. The amount of tailing is approximately 0.19 pixels. FIG. 19D shows characteristics when the intermittent light emission phase P is changed in the tailing amount calculation performed in FIG. As is apparent from the figure, when P is 60% to 70%, the amount of tailing is minimized and high image quality is obtained. In the portion other than the range of P, the amount of tailing increases. This is because the portions with the slopes 1 and 3 shown in the portion (e) of FIG. 5 exceed the set threshold value of the trailing amount.

  As described above, the video display device according to the above-described embodiment illuminates the liquid crystal with the illumination light including the first light emission component and the second light emission component, or the intermittent light emission component and the continuous light emission component. As a result, it is possible to improve the tailing amount and the flicker amount, which cannot be obtained by the conventional impulse light emission. Here, a relatively slow response liquid crystal is used.

  In this case, the optimum value of the tailing amount is determined by the intermittent light emission phase P, and the phase changes according to the time constant τ of the liquid crystal. Therefore, if the best intermittent light emission phase P is PA, PA = F [τ]. Here, F [] means a function.

This function is not a simple linear function, but P tends to increase as τ increases. If the time constant τ is determined, PA becomes a certain constant. Furthermore, when it can be considered that τ = 0 in the high-speed response, PA = 50%, as described with reference to FIG. Therefore, in the case of a certain time constant τ, when the constant determined from the function F [] is K,
PA = 50 + K (where 0 ≦ K ≦ (50−D / 2)).

  The constant K may be determined by measuring the response of the liquid crystal of the video display device, or may be determined by an experiment such as subjective evaluation. In the conventional technology related to the impulse type light emission, it is assumed that the flashing pulse lighting phase is the best in the second half of the vertical synchronization of the video to which the liquid crystal responds sufficiently, or the second half of the gate signal to which the pixel belongs when attention is paid to a certain pixel. Yes. However, in the present embodiment, among the inclinations 1, 2, and 3 shown in part (e) of FIG. 5, the inclinations 1 and 3 are not recognized by utilizing the low dynamic contrast response of the observer's eyes. It is necessary to. The balance between the tilts 1 and 3 is determined by the time constant of the liquid crystal. Therefore, in order to prevent the observer from recognizing the slopes 1 and 3 in the portion (e) of FIG. 5 in a balanced manner, the phase of the intermittent light emission component with respect to the video signal rewrite repetitive operation is controlled.

[Embodiment 4]
A video display apparatus according to still another embodiment of the present invention will be described with reference to FIGS. The display panel in the video display device of the present embodiment is an EL (electroluminescence) panel that emits light by active matrix driving. Unlike the case of illuminating a transmissive display panel with illumination light from a light source, which is shown in Embodiment 1, the EL panel emits light by flowing a current corresponding to image information to an EL element arranged for each pixel. Light and dark are controlled and an image is generated.

  FIG. 20 is a diagram showing a configuration of a pixel of the EL panel of this embodiment. The EL pixel 601 includes a scan electrode 602, a signal electrode 603, a TFT 604, a capacitor 605, a TFT 606, a TFT 607, a TFT 608, an EL element 609, a power source 610, and a scan electrode 611.

  For example, in the case of an NTSC video signal, there are 525 scan electrodes 602 on the display panel. Further, since the NTSC video signal has a vertical frequency of 60 Hz, the scan electrode 602 is selected approximately every 31.75 microseconds (= 1/60/525). The scan electrode is common to other pixels arranged in the horizontal direction of the display panel.

  Image information to be displayed is supplied from the signal electrode 603. For example, in the case of an NTSC video signal, there are 640 or 720 signal electrodes 603 on the display panel. The signal electrode 603 is used in common among a plurality of pixels arranged in the vertical direction of the display panel. When the scan electrode 602 of the target pixel is selected and a pulse is supplied, the TFT 604 is turned on. Since image information is supplied to the signal electrode 603 in accordance with this timing, this information is held in the capacitor 605 in the form of voltage (or charge).

  When the target pixel enters the non-selection period, the TFT 604 is turned off and the voltage of the capacitor 605 is held. The EL element 609 emits light with a desired luminance by flowing a current determined by the voltage held in the capacitor 605 from the power source 610. Here, the EL pixel 601 of this embodiment has two systems for supplying current to the EL element 609. The two systems are a system via the TFT 606 and a system via the TFT 607. The TFT 607 is controlled to be turned on / off by the TFT 608 controlled by the scan electrode 611.

  FIG. 21 is a diagram for explaining the operation of the EL pixel 601. FIG. 21A shows the waveform of the pulse signal supplied to the scan electrode 602. The repetition period T is 16.7 milliseconds (= 1/60) in the NTSC video signal. FIG. 21B shows the waveform of the pulse signal of the scan electrode 611. A portion (c) of FIG. 21 shows a waveform of a current flowing through the drain of the TFT 606. This current is supplied from the power source 610 and flows through the source-drain of the TFT 606 to the EL element. Further, this current changes when the TFT 604 is turned on while the scan electrode 602 is High and the voltage between the terminals of the capacitor 605 is updated.

  It is assumed that the response of the EL element is faster than the response of a general liquid crystal, for example, and the scan electrode 602 changes to a desired current during the high period. Further, as shown in part (c) of FIG. 21, a relatively large current I1 is set in a certain period, and the pixel emits light brightly. A small current I2 flows in the next cycle, and the EL element 609 emits light darkly.

  FIG. 21D shows the waveform of the current supplied from the power supply 610 via the TFT 607. The amplitude of this current is determined by the voltage of the capacitor 605 as in the TFT 606 system. Therefore, I1 = I3 and I2 = I4 in the portions (c) and (d) of FIG.

  However, the TFT 607 is different from the TFT 606 in that it is controlled by the scan electrode 611. That is, the TFT 608 is turned on while the pulse of the scan electrode 611 is High. In this case, since the voltage between the gate and source of the TFT 607 is 0, the TFT 607 is off. While the scan electrode 611 is low, the TFT 608 is turned off. In this case, the TFT 607 is controlled by the voltage between the terminals of the capacitor 605, and a current flows as shown in part (d) of FIG.

  The waveform of the current flowing through the EL element 609 is as shown in part (e) of FIG. 21, which is the sum of the waveform of part (c) and the waveform of part (d) in FIG. That is, I5 = I1, I6 = I1 + I3, I7 = I2, and I8 = I2 + I4.

  The EL element 609 emits light in accordance with the current waveform in part (e) of FIG. The light emission waveform depends on the current-light emission characteristics of the EL element. If the characteristics are proportional to each other, the light emission waveform is equivalent to the portion (e) of FIG. By emitting light with this waveform, it is possible to obtain the effect of simultaneously improving the tailing amount and the flicker amount described in FIG. 8 of the first embodiment.

  As described above, the video display device of this embodiment uses, for example, an active matrix driven self-luminous EL panel. Then, there are two TFTs controlled by the capacitor 605 storing the video information, and currents are supplied to the respective TFTs at different timings to generate light emission waveforms corresponding to intermittent light emission and continuous light emission. That is, the light emission of the pixel is composed of the first light emission component and the second light emission component described in FIG. Or it is comprised from an intermittent light emission component and a continuous light emission component.

  Further, the intermittent light emission phase P is controlled by the phase management of the pulse of the scan electrode 611. Since the response of the EL element is generally faster than that of the liquid crystal, the best phase PA may be 50% as described with reference to FIG. 13, but even when the best phase changes due to other factors, the scan electrode What is necessary is just to control by the phase of 611.

  Also, the duty ratio D can be controlled by the low period of the scan electrode 611. In order to increase the light emission energy (that is, light emission intensity) of the intermittent light emission component or the first light emission component, the duty ratio D may be increased.

  Further, since the selection operation of the scan electrode 602 may be 1/60 second as in the conventional hold type light emitting EL device, it is necessary to speed up the scan electrode driver (not shown) and the signal electrode driver (not shown). Therefore, there is no need to perform clock rate conversion or the like using a frame memory or the like for storing a video signal externally. The number of capacitors may be one as in the conventional hold type light emitting EL device.

  FIG. 22 is a diagram for explaining another embodiment of the EL pixel. 22 that have the same functions as those in FIG. 20 are denoted by the same reference numerals. The EL pixel 701 in FIG. 22 includes a capacitor 702, a capacitor 703, a TFT 704, a TFT 705, a TFT 706, a scan electrode 707, and a scan electrode 708.

  When the pixel is selected, the TFT 604 is turned on, and a voltage corresponding to the video information is written to the capacitor. This voltage is written to the capacitor 702 and the capacitor 703 connected in series. Further, the TFT 705 and the TFT 706 are alternately turned on / off, and the source-gate voltage of the TFT 704 is switched.

  That is, the voltage of the capacitor 703 becomes the source-gate voltage of the TFT 704 when the TFT 705 is on and the sum of the voltages between the terminals of the capacitor 703 and the capacitor 702 is the TFT 706 is on.

  The current of the EL element 609 is switched by these two gate voltages. The TFT 706 is controlled by the scan electrode 707. The TFT 705 is controlled by the scan electrode 708. Note that a signal obtained by inverting the logic of the scan electrode 707 may be input to the gate of the TFT 705 by arranging an inverter in the pixel.

  FIG. 23 is a diagram for explaining the operation of the EL pixel 701. FIG. 23A shows the waveform of the pulse signal supplied to the scan electrode 602. 23B shows the waveform of the pulse signal of the scan electrode 708, and FIG. 23C shows the waveform of the pulse signal of the scan electrode 707. In FIG. FIG. 23D shows a current waveform of the EL element 609 controlled by the TFT 705.

While the scan electrode 708 is High, the TFT 705 is turned on, and the gate-source voltage of the TFT 704 is defined by the voltage across the capacitor 703. This voltage is obtained by dividing the voltage written at the time of pixel selection by the capacitors 703 and 702. If the write voltage at the time of selection is V and the capacitances of the capacitor 702 and the capacitor 703 are C1 and C2, respectively, the voltage V2 across the capacitor 703 is
V2 = V * (C1 * C2 / C1 + C2)
It becomes.

  A portion (e) of FIG. 23 shows a current waveform of the EL element 609 controlled by the TFT 706. The TFT 706 is turned on while the scan electrode 707 is High, and the gate-source voltage of the TFT 704 becomes the voltage V written at the time of pixel selection.

Here, V and V2 have a relationship of V2 <V, and assuming that the gate-source voltage of the TFT 704 and the drain current of the TFT 704 are proportional, the currents I11 and I12 shown in the part (d) of FIG. , Currents I13 and I14 shown in part (e) of FIG.
I11 = I13 * (C1 * C2 / C1 + C2)
I12 = I14 * (C1 * C2 / C1 + C2)
It becomes the relationship.

  The part (f) in FIG. 23 shows the waveform of the current that actually flows through the EL element 609, and is the sum of the waveform in the part (d) and the waveform in the part (e) in FIG. If the current-light emission luminance characteristic of the EL element 609 is linear, the light emission luminance waveform of the EL element 609 is the waveform shown in part (f) of FIG.

  That is, the light emission of the pixel is composed of the first light emission component and the second light emission component described in FIG. Or it is comprised from an intermittent light emission component and a continuous light emission component. With this waveform, it is possible to improve both the trailing amount and the flicker amount described in the first embodiment. The intermittent light emission phase P and the duty ratio D of the intermittent light emission component are controlled by the phase management of the pulses of the scan electrodes 707 and 708. When it is desired to increase the light emission energy (that is, luminance) of the intermittent light emission component or the first light emission component, it can be controlled by the capacitance ratio of the capacitors 702 and 703. Alternatively, the Low period of the scan electrode 707 may be increased and the High period of the scan electrode 708 may be decreased.

  As described above, as described with reference to FIGS. 22 and 23, the video display apparatus according to the present embodiment uses the video information stored in the capacitor in a divided state. Since the selection operation of the scan electrode 602 may be 1/60 second as in the conventional hold type light emitting EL device, it is not necessary to speed up the scan electrode driver (not shown) or the signal electrode driver (not shown). There is no need to perform clock rate conversion or the like using a frame memory or the like for storing a video signal externally.

  In the above description, the case where the display panel is an organic EL panel has been described. For example, in a non-light-emitting transmissive liquid crystal panel, data written to a pixel is controlled to modulate illumination light from a light source. The light emission waveform of the pixel described above may be realized. In the case of a liquid crystal panel, a pixel is composed of a pixel selection TFT and a capacitor. However, by inserting a luminance switching TFT in the same manner as described above, the charge of the capacitor is controlled to change the transmittance of the liquid crystal and to change the pixel luminance. May be set. Further, without adding a luminance switching TFT, data corresponding to different luminance may be written by accessing the pixel selection TFT twice or more in one frame (frame is a unit constituting a screen). .

[Embodiment 5]
A video display apparatus according to still another embodiment of the present invention will be described with reference to FIG. In the video display device of this embodiment, the display panel is an EL (electroluminescence) panel that emits light by active matrix driving, or a liquid crystal panel that does not emit light by active matrix driving. In this embodiment, by supplying a voltage corresponding to image information to an EL element or a liquid crystal element arranged for each pixel, the brightness of light emission is controlled and an image is generated.

  FIG. 24 is a diagram for explaining the operation timing of the video display apparatus according to the present embodiment. In order to simplify the description, it is assumed that the display panel has five scanning lines. A portion (a) of FIG. 24 shows the waveform of the vertical synchronizing signal, which is a reference for screen repetition. In the case of an NTSC video signal, the frequency of the vertical synchronization signal is 60 Hz. FIG. 24B shows the waveform of the horizontal synchronizing signal. The scanning lines are assumed to be 5 lines, and 5 pulses from H11 to H15 are generated in one vertical period. 24C shows the waveform of the data signal, which is a signal supplied to one of the plurality of data electrodes arranged in the horizontal direction of the display panel.

  Here, the video display device of the present embodiment has a frame memory that separately stores video signals in units of frames, and by accessing the image data stored in the frame memory, the data in the time axis direction of the data can be obtained. Sort. Here, the pixel located at the top of the screen is designated as pixel 1 and the pixel located below is designated as pixel 2, so that numbers 1 to 5 are assigned to the pixels located on the same data electrode in the order of arrangement in the vertical direction. shake. The video data displayed on the pixel 1 is D1, and the video data displayed on the pixel 2 is D2. D11, D12, and D13 mean video data obtained by dividing D1 into three and rearranging them in the time direction.

  As shown in part (c) of FIG. 24, for example, in the case of data for pixel 1, D11 is generated at the beginning of the H11 period, D12 is generated at the second of H13, and D13 is generated at the third of H14. Sort the data. It is assumed that 100% level of white (255 levels at 8 bits) is input to D1 in a certain frame, and 60% level of gray (150 levels at 8 bits) is input to the next frame after 1/60 seconds. The division of the image data is determined by the duty ratio D and the emission intensity ratio S. For example, it is assumed that the duty ratio D = 50% and the light emission intensity ratio S = 80%.

  Further, it is assumed that the instantaneous peak luminance that can be emitted by the pixels of the video display device is 1000 nits. If the white signal is D1 = 100%, the instantaneous light emission luminance (the height of the vertical axis of the first light emission) described in FIG. 1 is 100% and 1000 nits. The second light emission has a light emission intensity ratio S of 20%, and the instantaneous light emission luminance (the height of the vertical axis of the second light emission) in FIG. 1 is 250 nits, which is 25%. The calculation is performed at 250 nit = 1000 nit * 50% / 80% * 20%. Numerical values of 50%, 80%, and 20% correspond to D, S, and (100-S) in FIG. Thus, D11, D12, and D13 are determined from D1 by calculation determined by the duty ratio D and the emission intensity ratio S. The video data is divided and set so that a 100% white signal emits light at an instantaneous light emission luminance of D11 = 25%, D12 = 100%, and D13 = 25%. Assuming that the video data and the light emission luminance are proportional, in other words, with 8-bit video data, the division of the 255 level white signal is D11 = 64 level, D12 = 255 level, and D13 = 64 level. From the instantaneous light emission luminance and the duty ratio of 50%, the average screen luminance is 1000 * 0.5 + 250 * 0.5 = 625 nit.

  In the case of the gray gradation of D1 = 60%, the value is 60% of that described for the white signal. That is, if D1 = 60%, D11 = 15%, D12 = 60%, and D13 = 15%. Assuming that the brightness corresponding to each of D11, D12, and D13 is L11, L12, and L13, if the 100% instantaneous light emission brightness is 1000 nits, then L11 = 150 nits, L12 = 600 nits, and L13 = 150 nits.

  FIG. 24D shows the waveform of a pulse signal applied to the scan electrode that scans the pixel 1. It is assumed that the pixel 1 is located at the upper part of the screen. Note that it is assumed that there are five scanning lines, and five pixels exist on the same data electrode. It is assumed that the video signal D1 is video data displayed on the pixel 1.

  The scan signal generates a pulse three times in one vertical period. This pulse is about 1/3 of the horizontal period. Further, the pulse generated three times in one vertical cycle is shifted in phase with respect to the horizontal synchronizing signal. The phase of the video data D11, D12, and D13 divided and rearranged in the time direction corresponds to the phase of the high period of the scan signal of the pixel 1. That is, the image data of the pixels 1 rearranged in the time direction is taken into the pixel 1 by the scan signal, thereby defining the light emission of the pixel 1.

  In the waveform of part (d) of FIG. 24, the first pulse from the left is located in the first half of the horizontal synchronizing signal, the second pulse is located in the middle, and the third pulse is located in the second half. ing. A portion (e) in FIG. 24 is a light emission waveform of the pixel 1. The vertical axis represents luminance. Assume that D1 = 100% (255 level) white signal. During the first High period of the scan signal, the pixel 1 is set to L11 which is a light emission state (light emission luminance) determined by D11. The instantaneous light emission luminance at this time is 250 nits in the above example. Since the data of D11 is held when the scan signal falls to Low, the pixel 1 continues to emit light at 250 nits. Next, D12 is written as the pixel data of the pixel 1 in the second High period. In the above example, L12 = 1000 nit. Since the scan signal falls to Low again, D12 is held, and the pixel 1 continues to emit light at 1000 nits. Similarly, L13 = 250 nit corresponding to D13 is written and held in the third scan pulse. That is, in the present embodiment, the light emission luminance corresponding to the video data of the data signal of (c) part of FIG. 24 is set in accordance with the timing when the scan signal of (d) part of FIG. 24 is High.

For example, in the case of an EL element, video data is held as a capacitor voltage, and a current corresponding to the voltage is passed through the EL element to emit light. In the case of a liquid crystal element, video data is held as a charge, and the liquid crystal is modulated so as to have a transmittance corresponding to the charge.
L11, L12, and L13 in part (c) of FIG. 24 are, for example, L11 = L13 and L12> L11. By emitting light with this waveform, it is possible to obtain the effect of simultaneously improving the tailing amount and the flicker amount described in FIG. 8 of the first embodiment. The duty ratio D of the first light emission component described in FIG. 1 is determined by the rearrangement of the data signals and the pulse phase of the corresponding scan signal. The emission intensity ratio S is determined by the division method (ratio) of video data division of D11, D12, and D13. Parts (f) and (g) in FIG. 24 show a case where attention is paid to the pixel 3, which is another pixel. Video data obtained by dividing the video data D3 written and displayed in the pixel 3 is denoted as D31, D32, and D33. The emission brightness corresponding to each data is L31, L32, and L33.

  The pixel 3 exists in the center of the screen. The operation timing in this pixel is basically the same as that of pixel 1, and the phase is shifted by two lines. Therefore, the scan signal of each pixel does not become High at the same time.

  As described above, the video display device according to the present embodiment is processed so that data to be applied to the data electrodes is rearranged in advance and three data are arranged per one horizontal cycle. A scan signal for selecting in the vertical direction outputs a high signal three times per vertical synchronization signal. Furthermore, a plurality of scan signals do not become High at the same time.

  By writing data at such a timing, the light emission waveform as shown in part (e) of FIG. 24 is obtained from the video display device of the present embodiment. This waveform is composed of a first luminescent component and a second luminescent component as shown in FIG. Or it consists of an intermittent light emission component and a continuous light emission component. When the pixel emits light with this waveform, an ideal improvement in the amount of tailing and the amount of flicker is performed.

  In this embodiment, an external memory is provided to control the light emission waveform by rearranging data, so that the pixel structure of the display panel is updated once per vertical synchronization signal, for example, by adding scan electrodes. Therefore, it is not necessary to change from a general configuration such as this, and an existing display panel can be used.

  Further, the duty ratio D of the intermittent light emission component can be controlled by managing the rearrangement of data signals. Similarly, the light emission phase P of the intermittent light emission component can be controlled by managing the rearrangement of data signals.

[Embodiment 6]
Still another embodiment of the present invention will be described with reference to FIGS. In the present embodiment, the duty ratio D between the first light-emitting component and the second light-emitting component and the light emission intensity ratio S of the first light-emitting component described in the part (a) of FIG. The optimum condition will be described. Note that the amount of tailing described below is calculated based on the model described in FIG.

  Further, the threshold value of the luminance change for calculating the tailing amount is 15% and 85% of the tailing luminance change. This threshold value does not have an absolute numerical value, but changes depending on the screen brightness and screen size of the video display device. Here, it is assumed that even if the luminance change defined by the inclination 1 and the inclination 3 described in FIG. 5E increases to about 15% of the entire luminance change, it is not noticeable to human eyes. ing. The flicker amount is calculated from the Fourier transform of the light emission waveform, as described with reference to FIG.

  FIG. 25A to FIG. 25C show the relationship between the duty ratio D, the trailing amount, and the flicker amount when the emission intensity ratio S is fixed at 70% or 90%. Note that, when the duty ratio D is equal to the light emission intensity ratio S, the light emission waveform becomes a direct current, which is excluded from FIG. Further, when the duty ratio D is larger than the light emission intensity ratio S, the instantaneous light emission intensity of the first light emission component becomes smaller than the instantaneous light emission intensity of the second light emission component, and the effect of this embodiment is also described in this case. Excluded because it is not a place to do.

  As shown in FIG. 25A, the duty ratio D <light emission intensity ratio S and the light emission intensity ratio is fixed at 70% or 90%, and the possible duty ratio D is used, and the model shown in FIG. When the indicated tailing amount and the flicker amount shown in FIG. 6 are calculated, the characteristic shifts in the lower left direction from the characteristic of the prior art with respect to all the duty ratios D. By the video display device of the present embodiment, It can be seen that the effect of simultaneously reducing the amount of tailing and the amount of flicker is obtained.

  FIGS. 26A to 26C show the relationship between the emission intensity ratio S of the first emission component, the trailing amount, and the flicker amount when the duty ratio D is fixed at 10% or 70%. Is. As shown in FIG. 26A, when the duty ratio D <light emission intensity ratio S and the duty ratio D is fixed at 10% or 70%, the light emission intensity ratio (here 70%) is less than 100%. It can be seen that the effect of simultaneously reducing the trailing amount and the flicker amount is obtained with respect to the emission intensity ratio S.

  FIGS. 27A and 27B show the relationship between the duty ratio D, the amount of tailing, and the amount of flicker when the emission intensity ratio S is fixed at 40%. Under this condition, the effect of the video display device of this embodiment cannot be obtained. In the description of FIG. 26A, the light emission intensity ratio S is set to 70% when the combination of the light emission intensity ratio S and the duty ratio D eliminates the simultaneous reduction effect of the trailing amount and the flicker amount. Because there is.

  This is because the change in luminance defined by the slopes 1 and 3 among the slopes 1, 2 and 3 described in FIG. This is because the amount of tailing increases because it exceeds 85%. Therefore, in this embodiment, the case where the emission intensity ratio S = 40% is excluded.

  FIGS. 28A and 28B show the relationship among the duty ratio D, the amount of tailing, and the amount of flicker when the emission intensity ratio S is fixed at 60%. Under this condition, depending on the duty ratio D, there may or may not be a simultaneous reduction effect of the trailing amount and the flicker amount.

  When the characteristics of FIGS. 25 to 28 are summarized, the conditions of the duty ratio D and the emission intensity ratio S that are effective in this embodiment are shown in FIG. In FIG. 29, the horizontal axis represents the duty ratio D, and the vertical axis represents the emission intensity ratio S.

  The duty ratio D and the light emission intensity ratio S are 62 ≦ S <100 and 0 <D <100 and D <S, or 48 <S <62 and D ≦ (S−48) /0.23. A certain condition B is satisfied. In FIG. 29, a region indicated by halftone dots is a region satisfying condition A, and a region indicated by diagonal lines is a region satisfying condition B.

  Note that the condition of S = 100 means that intermittent light emission of the prior art is performed, and thus is not included in the conditions A and B. The condition S = D means that the instantaneous light emission intensity of the first light emission component is equal to the instantaneous light emission intensity of the second light emission component, and is not included in the conditions A and B.

  Furthermore, the condition that S = 0 or D = 0 means that the first light-emitting component is 0, and thus is not included in the conditions A and B. Further, the condition of D = 100 means that the second light emitting component is 0, and thus is not included in the conditions A and B.

  As described with reference to FIG. 25, the condition A provides the simultaneous reduction effect of the trailing amount and the flicker amount with respect to all the duty ratios D that can be taken with respect to a certain emission intensity ratio S. Further, as described with reference to FIG. 27, the values of D and S that are not included in the condition A and the condition B cannot obtain the simultaneous reduction effect of the trailing amount and the flicker amount. Further, as described with reference to FIG. 28A, the range of the emission intensity ratio S that satisfies the condition B can obtain the effect of simultaneously reducing the trailing amount and the flicker amount only in the case of a certain duty ratio D.

  FIG. 30A and FIG. 30B show the relationship between the amount of trailing and the amount of flicker when the emission intensity ratio S = 62%. In this case, it can be seen that there is an effect of simultaneously reducing the trailing amount and the flicker amount with respect to the possible duty ratio D. FIG. 31A and FIG. 31B show the relationship between the amount of tailing and the amount of flicker when the emission intensity ratio S = 48%. In this case, there is no duty ratio D at which the effect of the present embodiment can be obtained. From FIG. 28, FIG. 30, and FIG. 31, it can be seen that the emission intensity ratio S under condition B is 48 <S <62.

  32 (a) and 32 (b) show the upper limit of the duty ratio D for obtaining the simultaneous reduction effect of the tailing amount and the flicker amount in the range of 48 <S <62, the tailing model and the flicker analysis. It is calculated by. The characteristic of the emission intensity ratio S with respect to the duty ratio D can be approximated to a straight line of approximately S = 0.23D + 48. Since the above effect can be obtained if the duty ratio is smaller than the duty ratio D, D ≦ (S−48) /0.23 is set as the condition B.

  FIG. 33A to FIG. 33C are diagrams for explaining the degree of improvement in tailing and flicker when six representative points are extracted from the region satisfying the conditions A and B. FIG. That is, as shown in FIG. 33A, points P1 to P6 were extracted. The values of D and S at each point are shown in FIG.

  For each of these points P1 to P6, the tailing amount and the flicker amount are obtained based on the model shown in FIG. 5, and plotted in the tailing amount-flicker amount graph is FIG. 33 (c). As shown in FIG. 33 (c), the tailing amount and the flicker amount at each point are shifted in the lower left direction from the intermittent lighting (impulse type display) line of the prior art. Therefore, it can be said that both image quality interferences of tailing and flicker are improved at the same time.

  FIG. 34A and FIG. 34B are diagrams showing an example of the light emission waveform of the pixel. The horizontal axis represents time, and the vertical axis represents instantaneous light emission intensity, which shows the instantaneous light emission intensity for one cycle. FIG. 34A shows a dimming function of the video display device (a function for switching the brightness of the entire screen by the user) and a control method of the video display device, so that the frequency is approximately 2.4 KHz (16.7 milliseconds). 40 times) saw-tooth waves are superimposed on the light emission waveform.

  Even with such a light emission waveform, since the human eye does not follow the repetition frequency of 2.4 KHz, it is equivalent to the light emission waveform shown in FIG. 34B, and the tailing and flicker, which are the effects of this embodiment, are improved simultaneously. Effect is obtained.

  That is, the waveform of the first light-emitting component and the second light-emitting component are described by rectangular waves in FIG. However, the present invention is not limited to this rectangular wave. As described with reference to FIG. 5, in the hold type display device, there is a problem in that the human eye integrates the light emission of the pixel in a direction deviated from the original integration direction. The deviation in the integration direction and the integration path occurs to follow the moving object with the eyes. The conventional impulse type display device reduces tailing interference by partially suppressing light emission, but this embodiment simultaneously improves the flicker amount while reducing the amount of tailing. The light emission waveform of the present embodiment is achieved by concentrating the light emission intensity of the light emission intensity ratio S, that is, so-called light emission energy, at the time specified by the duty ratio D. Therefore, it goes without saying that the effect is not reduced even if it is not a pure rectangular wave.

  FIG. 35A shows a light emission waveform in the case where the second light emission component is composed of fine pulses. The horizontal axis represents time, and the vertical axis represents instantaneous light emission intensity, showing a light emission waveform for one cycle. Also in this case, as in FIG. 34, since the human eye does not follow a fine pulse, the light emission intensity of the second light emission component is equivalent to the light emission waveform indicated by the broken line, and both tailing and flicker can be improved. is there.

  When adjusting the light emission intensity ratio (100-S)% of the second light emitting component, the pulse lighting time T0 may be adjusted as shown in FIG. 35A, or FIG. As shown, the pulse intensity L0 may be changed.

  In addition, what is necessary is just to select the value which a human eye does not follow for the repetition frequency of a 2nd light emission component. For example, it may be several kiloHz like the frequency of the sawtooth wave of FIG. 17, or may be several times the video vertical frequency of about 150 Hz. Further, depending on the characteristics of the displayed video of the video display device and the viewing environment, a frequency of 80 Hz may be used, or 100 Hz may be used. For example, in a video display device with a screen brightness of about 250 nits, the human eye may recognize continuous light even at about 120 Hz, that is, twice the frequency of the NTSC video signal. For example, in a video display device with a screen brightness of 500 nit, flicker may be felt at 120 Hz, and it may not be recognized as continuous light unless the frequency is 300 Hz or higher. When the video displayed by the video display device has many still images, a slight change in the luminance of the screen may appear as an obstacle, and when there are many moving image displays, there may be a case where a certain amount of screen fluctuation does not matter. In short, a frequency suitable for the system configuration of the video display device may be selected as appropriate.

  FIG. 36 shows a case where the lighting response waveform of the pixel is a triangular wave. The horizontal axis represents time, and the vertical axis represents instantaneous light emission intensity, showing a light emission waveform for one cycle. Such a waveform can also be regarded as equivalent to a light emission response indicated by a broken line. When the light emission waveform of FIG. 36 is applied to the model described with reference to FIG. 5, the slopes 1 and 3 in FIG. 5E draw a curve instead of a straight line, but the slope 2 with respect to the slopes 1 and 3 is the first. Since it is determined by the duty ratio D and the light emission intensity ratio S between the light emitting component and the second light emitting component, it is possible to simultaneously improve both image quality interference of tailing and flicker.

  FIG. 37 shows a case where the response of light emission is an exponential function. In this case as well as FIG. 36, this is equivalent to the light emission characteristic indicated by the broken line, and the effect of this embodiment can be obtained.

  As described above, if the relationship between the duty ratio D and the light emission intensity ratio S between the first light emission component and the second light emission component satisfies either the above-described condition A or condition B, the emission waveform is as follows. It doesn't matter what it is.

  The instantaneous light emission intensity of the first light emission component is larger than the instantaneous light emission intensity of the second light emission component, but the instantaneous light emission intensity of the first light emission component is, for example, within a range that can be ignored with respect to the luminance of the entire pixel. It may be smaller than the instantaneous emission intensity of the second emission component. That is, when the light emission waveform vibrates (for example, in the case of the triangular wave shown in FIG. 34A), the instantaneous light emission intensity of the first light emission component is the instantaneous light emission intensity of the second light emission component at a part of the vibration peak. It can be smaller. 34 (a) is equivalent to FIG. 34 (b), the first emission component is obtained when the emission waveform of FIG. 34 (a) is replaced with the emission waveform of FIG. 34 (b). The instantaneous light emission intensity of the second light emission component may be larger than the instantaneous light emission intensity of the second light emission component.

  In the above description, tailing is defined as a range of luminance change from 15% to 85%. Here, for example, when the screen brightness of the video display device is bright, such as 600 nits, or when the viewing environment is dark, the duty ratio D and the slopes 1 and 3 described with reference to FIG. Under the condition of the emission intensity ratio S, the observer visually recognizes the slopes 1 and 3, and the tail improvement effect may be reduced. In such a case, the light emission response waveform may be set within a range that satisfies the conditions of the duty ratio D and the light emission intensity ratio S shown in FIG.

  FIG. 38 shows a duty ratio D that provides a simultaneous reduction effect of the tailing amount and the flicker amount when the tailing to which the human eye responds assumes that the luminance change is in the range of 10% to 90%. The emission intensity ratio S is shown.

  In this case, D and S are conditions A1 where 79 ≦ S <100 and 0 <D <100 and D <S, or conditions where 69 <S <79 and D ≦ (S−69) /0.127. Satisfy B1. In FIG. 38, the area indicated by halftone dots is the area that satisfies the condition A1, and the area indicated by diagonal lines is the area that satisfies the condition B1.

  FIG. 39A to FIG. 39C show the amount of tailing and flicker when S is fixed at 70 or 80 in the condition A1 or B1 shown in FIG. As shown in FIG. 39A, when S = 80, there is an effect of simultaneously reducing the trailing amount and the flicker amount regardless of the duty ratio D. In addition, when S = 70, the above effect is obtained only when D = 10.

  40 (a) and 40 (b) show the upper limit of the duty ratio D for obtaining the simultaneous reduction effect of the trailing amount and the flicker amount in the range of 69 <S <79 shown in the condition B1 of FIG. It is calculated by a tailing model and flicker analysis.

  The characteristic of the emission intensity ratio S with respect to the duty ratio D can be approximated to a straight line of approximately S = 0.127D + 69. If the duty ratio is smaller than D, the above-described effect can be obtained. Therefore, D ≦ (S−69) /0.127 is set as the condition B1.

  As described above, by setting the duty ratio D and the light emission intensity ratio S of the first light emission component to a certain condition, both the tailing amount and the flicker amount can be simultaneously achieved with respect to the conventional impulse light emission technology. Improvement effect is obtained. In addition, if the screen brightness in the video display device increases, flicker is easily perceived (Ferry-Porter's law). Therefore, when an image is displayed with high luminance by the conventional intermittent lighting method, flicker interference is likely to occur. In addition, since the human eye is more sensitive to blinking than the cone of photoreceptor cells, that is, the periphery of the visual field is more sensitive to flickering, flicker interference is easily recognized when the display panel in a video display device is enlarged. Become. Therefore, the display quality improvement method for a video display device according to the present invention is particularly effective for improving the display quality of a video display device with high brightness or a large screen.

  Further, the conditions of the duty ratio D and the emission intensity ratio S described in FIG. 29 are calculated by replacing the trailing amount and the flicker amount with a simple model. The image quality of the video display device is largely dependent on the subjectivity of the observer, and it is also difficult to accurately quantify because it depends on the viewing environment, but in the subjective evaluation experiment based on the conditions obtained by the present inventors, It is confirmed that there is no big difference between the condition obtained by the model and the evaluation result.

  Further, the conditions of the duty ratio D and the emission intensity ratio S described in FIG. 29 are calculated by replacing the trailing amount and the flicker amount with a simple model, and the model is obtained when a white object moves. The amount of tailing in this case and the amount of flicker when white is displayed are assumed. A normal viewing video has almost no white signal of 100%. Therefore, when the average luminance level of the video actually displayed is about 50% with respect to the video display device having a screen luminance of 500 nit, for example, the screen luminance of the video display device is equivalently replaced with 250 nit (= 500/2). Thus, the optimum values of the duty ratio D and the emission intensity ratio S may be obtained. In that case, the values of D and S may be determined from information such as a histogram (video data distribution) of the video to be displayed. Alternatively, a configuration may be adopted in which video feature quantities such as a luminance histogram and an average luminance level are automatically detected from the input video signal, and the light emission characteristics of the pixels can be automatically switched.

  Further, the flicker amount is determined by a 60 Hz component that is the first harmonic. In reality, a harmonic component that is an integer multiple of 60 Hz is generated, but the present inventors have confirmed through experiments that only the 60 Hz component should be focused and suppressed. For example, there may occur a case where a harmonic of 120 Hz is recognized as interference for reasons such as an increase in screen size or brightness, but in this case as well, as described above, the light emission waveform is Fourier-transformed and 60 Hz and 120 Hz. What is necessary is just to obtain | require the conditions of duty ratio D and light emission intensity ratio S, paying attention to the quantity of both components.

  In the present embodiment, the video signal is described in NTSC, but it is also suitable for displaying a video signal of a personal computer, for example. For example, when the vertical frequency of the video display device is 75 Hz or the like, the flicker amount perceived by the observer is smaller because the sensitivity of the human eye is lower than that of 60 Hz. Observed as an obstruction. Also in this case, paying attention to the 75 Hz component, the conditions of the duty ratio D and the emission intensity ratio S may be obtained as in the present embodiment.

  With respect to the relationship between the duty ratio D and the emission intensity ratio S of the present embodiment, the case where the tailing is defined by the threshold values of 15% and 85% of the luminance change has been described with reference to FIG. Moreover, the case where it defined with the threshold value of 10% and 90% was demonstrated using FIG. However, the absolute threshold value is never uniquely determined. This is because the image quality of the video display device depends on the subjectivity of the observer. Or it changes also in viewing environment, such as ambient illuminance and viewing distance. Furthermore, it changes also in the point whether the image to display is a still image or a moving image. The point is that, among various applications of video display devices, an optimum value is determined each time, and qualitative and quantitative evaluation is performed using the method described in this embodiment, and finally, subjective evaluation is performed. Just do it.

  Further, the average luminance level of the display image may be detected, and parameters such as the duty ratio D, the emission intensity ratio S, and the emission phase of the first emission may be controlled dynamically or adaptively. This control may be performed based on the histogram of the image. Motion information such as inter-frame differences may be used. Illuminance information may be obtained and controlled from an illuminance sensor that measures the illuminance around the video display device. Furthermore, you may use the information of those time fluctuations. The maximum value and the minimum value of luminance included in the video to be displayed may be used.

  The motion of the image may be detected as a vector, and control may be performed based on the information. In conjunction with the function of switching the screen brightness by the viewer, it may be controlled with a different parameter each time. The power consumption of the entire video display device may be detected, and parameters may be controlled to reduce power consumption. The parameter may be controlled so that the screen brightness is lowered when the continuous operation time from the power-on is detected and the lamp is lit for a long time.

  Furthermore, although the light emission waveform of the pixel in the present embodiment has been described with two types of light emission components, the first and second light emission components, it is not particularly limited to two types. Depending on the modulation means of the pixel, an optimum characteristic may be obtained by separately defining the third light emission component and controlling it separately. The fourth and fifth light emitting components may be defined. In that case, in the model described with reference to FIG. 5, a waveform by light emission divided into a plurality of parts is set in part (a) of FIG. 5, and video information to be displayed is set in part (b) of FIG. If the information on the luminance change in the vertical direction of the part (c) is calculated and the integration calculation is performed in the direction of the arrow 2, the corresponding luminance change waveform of the tail can be obtained. Even in the case of three or more types of light emission, it is possible to analyze using the model of this embodiment, and it is possible to derive the optimum operating condition from the analysis result.

  Further, if the element that emits light from the pixel has a finite response time in time, the information on the time response may be input to the part (a) or (b) of FIG. They can be analyzed from the items described in the above-described embodiment, and an optimum operating condition can be derived.

  In the present embodiment, the amount of flicker is defined as the ratio of DC to the first harmonic in the Fourier transform result. Here, an absolute value may be introduced, and the harmonic ratio may be weighted for each absolute value. The absolute value corresponds to, for example, the average screen brightness of the video display device. If the screen brightness is bright, the allowable flicker amount decreases (becomes strict conditions) and changes depending on the average screen brightness. Therefore, if the ratio of DC to first harmonic is handled as a function of screen brightness, the accuracy of the flicker amount is further improved. Also, the flicker amount may be defined including the second harmonic.

[Supplement]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The video display device according to the present invention includes video display means having a plurality of pixels, and light emitting means for illuminating the video display means. The video display means is illuminated by the light emitting means, and the video is displayed on the pixels. In a video display device that displays an image based on a video signal by modulating illumination light according to a signal, the light emitting means is configured to illuminate the video display means with light having an intermittent light emission component and a continuous light emission component. May be.

  In the above configuration, flickering is performed while displaying a clear outline by suppressing the tailing of the moving object by illuminating the display panel by mixing light emission with different characteristics, that is, continuous light emission component and intermittent light emission component. Interference can be suppressed.

  In the video display device according to the present invention, in the video display device, the light emission phase of the intermittent light emission component is an update time for updating the modulation rate of the pixel to a different value and a time response of a change in the modulation rate of the pixel. It may be determined depending on the characteristics.

  In the above configuration, the phase of the intermittent light emission component is controlled according to the characteristics of the pixel. Thereby, it is possible to more effectively suppress the tailing of the moving object and the flicker interference according to the characteristics of the pixel.

In the video display device according to the present invention, in the video display device, the plurality of pixels are arranged in a matrix, and the video display means includes a plurality of row electrodes arranged in a row. Is applied with a scanning signal for scanning the image display means in the vertical direction, the pixel is updated to a value with a different modulation rate at the timing of the scanning signal, and the light emission period of the intermittent light emitting component from the timing of the scanning signal When the time to the center of Ta is Ta, the period time from the timing of the scanning signal to the timing of the next scanning signal is T0, and the constant determined from the time response characteristics of the change in the modulation factor of the pixel is K,
Ta = (1/2 + K) × T0 (where 0 ≦ K ≦ 0.5)
You may come to satisfy the relationship.

  With the above configuration, the light emission phase of the intermittent light emission component can be determined by the update time and the time response characteristic.

  In the video display device according to the present invention, in the video display device, the light emitting means is divided into blocks, and each part of the light emitting means divided into the blocks is a partial area of the video display means. It is also possible to illuminate a pixel located in the area. In addition, the light emission phases of the intermittent light emission components may be different from each other in each part of the light emitting means divided into the blocks.

  When the pixel transmission update timing differs depending on the screen location of the video display means, the above configuration absorbs the influence of the phase difference of the update timing by shifting the emission phase of the intermittent emission component, and the emission phase Can be adjusted to a more appropriate state.

In the video display device according to the present invention, in the video display device in which the light emitting unit is divided into blocks, the plurality of pixels are arranged in a matrix, and the video display unit is arranged in a plurality of rows. A scanning signal for scanning the image display means in the vertical direction is applied to the row electrode, and the pixel is updated to a value having a different modulation rate at the timing of the scanning signal, so that the block electrode In each of the divided light emitting means, the time from the timing of the scanning signal to the center of the light emission period of the intermittent light emitting component is Ta, and the period of time from the timing of the scanning signal to the timing of the next scanning signal is T0, When the constant determined from the time response characteristic of the change in the modulation rate of the pixel is K,
Ta = (1/2 + K) × T0 (where 0 ≦ K ≦ 0.5)
You may come to satisfy the relationship.

  With the above configuration, the light emission phase of the intermittent light emission component can be determined by the update time and the time response characteristic, and the light emission phase can be adjusted to a more appropriate state.

  In the video display device according to the present invention, the light emitting means may include a first light source that emits light that forms the intermittent light emitting component, and a second light source that emits light that forms the continuous light emitting component. Further, at least one of the first light source and the second light source may be a semiconductor light emitting element. The semiconductor light emitting element may be a light emitting diode. The second light source may be a fluorescent lamp using discharge. The video display means may be a liquid crystal panel using a liquid crystal material.

  Alternatively, a video display device according to the present invention has a plurality of pixels, and in the video display device that displays an image by performing light emission based on a video signal in each pixel, in order to solve the above problems, Each pixel may be configured to display an image with light having an intermittent light emission component and a continuous light emission component.

  In the above configuration, flickering is performed while displaying a clear outline by suppressing the tailing of the moving object by illuminating the display panel by mixing light emission with different characteristics, that is, continuous light emission component and intermittent light emission component. Interference can be suppressed.

  In the video display device according to the present invention, in the video display device described above, the light emission phase of the intermittent light emission component is an update time for updating the light emission luminance of the pixel to a different value and a time response of a change in the light emission luminance of the pixel. It may be determined depending on the characteristics.

  In the above configuration, the phase of the intermittent light emission component is controlled according to the characteristics of the pixel. Thereby, it is possible to more effectively suppress the tailing of the moving object and the flicker interference according to the characteristics of the pixel.

In the video display device according to the present invention, in the video display device, the plurality of pixels are arranged in a matrix, and a scanning signal for scanning the plurality of pixels in the vertical direction is provided in each row of pixels. Applied, and the pixel is updated to a value with different emission luminance at the timing of the scanning signal, Ta is the time from the timing of the scanning signal to the center of the light emission period of the intermittent light emitting component, and the timing from the timing of the scanning signal to the next When the period time until the timing of the scanning signal is T0, and the constant determined from the time response characteristics of the light emission luminance change of the pixel is K,
Ta = (1/2 + K) × T0 (where 0 ≦ K ≦ 0.5)
You may come to satisfy the relationship.

  With the above configuration, the light emission phase of the intermittent light emission component can be determined by the update time and the time response characteristic.

  In the video display device according to the present invention, in the video display device, the plurality of pixels are divided into blocks each formed of a single row or a plurality of rows, and the light emission phase of the intermittent light emission component is between the blocks. May be different from each other.

  When the pixel transmission update timing differs depending on the screen location of the video display means, the above configuration absorbs the influence of the phase difference of the update timing by shifting the emission phase of the intermittent emission component, and the emission phase Can be adjusted to a more appropriate state.

In the video display device according to the present invention, in the video display device in which the light emitting means is divided into blocks, the plurality of pixels are arranged in a matrix, and the pixels in each row are vertically arranged. A scanning signal for scanning in the direction is applied, and the pixel is updated to a value with different emission luminance at the timing of the scanning signal. In each block, the center of the light emission period of the intermittent light emitting component from the timing of the scanning signal Time is Ta, the period time from the timing of the scanning signal to the timing of the next scanning signal is T0, and the constant determined from the time response characteristic of the change in the light emission luminance of the pixel is K,
Ta = (1/2 + K) × T0 (where 0 ≦ K ≦ 0.5)
You may come to satisfy the relationship.

  With the above configuration, the light emission phase of the intermittent light emission component can be determined by the update time and the time response characteristic, and the light emission phase can be adjusted to a more appropriate state.

  According to the present invention, it is possible to simultaneously improve moving image tailing and flicker. These effects are particularly prominent when the video display device is increased in brightness and size. Therefore, the present invention is particularly suitable for increasing the size and brightness of the LCD.

It is a figure which shows the light emission waveform of the video display apparatus which concerns on one Embodiment of this invention. It is a block diagram which shows the structure of the video display apparatus which concerns on one Embodiment of this invention. It is sectional drawing of the video display apparatus of FIG. 3 is a timing chart for explaining the operation of the video display device in FIG. 2. It is a figure for qualitatively explaining the operation of the tail improvement and flicker interference reduction of the video display device of FIG. FIG. 6A to FIG. 6I are diagrams for quantitatively explaining the effect of the video display device of FIG. It is a figure for demonstrating quantitatively the effect of the video display apparatus of FIG. It is a figure which shows quantitatively the effect of the video display apparatus of FIG. FIG. 9A to FIG. 9F are diagrams for explaining the relationship between the duty ratio D of the intermittent light emission component and the intermittent light emission phase P in FIG. FIGS. 10A to 10F are diagrams for explaining the relationship between the duty ratio D of the intermittent light emission component and the intermittent light emission phase P in FIG. FIG. 11A to FIG. 11F are diagrams for explaining the relationship between the duty ratio D of the intermittent light emission component and the intermittent light emission phase P in FIG. It is a figure which shows the suitable relationship between the duty ratio D of the intermittent light emission component in FIG. 1, and the intermittent light emission phase P. FIG. 13A to FIG. 13E are diagrams for explaining the phase of the light emission waveform according to the video display device of FIG. It is a figure for demonstrating the effect by the video display apparatus of FIG. 2 by subjective evaluation. It is a block diagram which shows the structure of the video display apparatus concerning other embodiment of this invention. FIG. 16 is a timing chart illustrating an operation of the video display device in FIG. 15. FIG. 12 is a timing chart illustrating an operation of a video display apparatus according to still another embodiment of the present invention. FIG. 18A to FIG. 18D are diagrams for explaining the best light emission phase of the intermittent light emission component when the response time constant of the liquid crystal is 3.5 milliseconds. FIG. 19A to FIG. 19D are diagrams for explaining the best light emission phase of the intermittent light emission component when the liquid crystal time constant is 2.2 milliseconds. It is a block diagram which shows the structure of the video display apparatus concerning other embodiment of this invention. FIG. 21 is a timing chart illustrating an operation of the EL pixel of FIG. 20. FIG. 22 is a diagram showing still another configuration example of the EL pixel in FIG. 20. It is a timing chart which shows operation | movement of the pixel of FIG. 12 is a timing chart illustrating an operation of a video display apparatus according to still another embodiment of the present invention. 25 (a) to 25 (c) are diagrams illustrating the relationship among the duty ratio D, the trailing amount, and the flicker amount when the emission intensity ratio S is fixed at 70% or 90%. FIGS. 26A to 26C show the relationship between the emission intensity ratio S of the first emission component, the trailing amount, and the flicker amount when the duty ratio D is fixed at 10% or 70%. FIG. FIGS. 27A and 27B are diagrams showing the relationship among the duty ratio D, the trailing amount, and the flicker amount when the emission intensity ratio S is fixed at 40%. FIGS. 28A and 28B are diagrams showing the relationship among the duty ratio D, the amount of tailing, and the amount of flicker when the emission intensity ratio S is fixed at 60%. It is a figure which shows the relationship between the duty ratio D and emission intensity ratio S suitable in this invention. FIG. 30A and FIG. 30B are diagrams showing the relationship between the amount of tailing and the amount of flicker when the emission intensity ratio S = 62%. FIG. 31A and FIG. 31B are diagrams showing the relationship between the amount of tailing and the amount of flicker when the emission intensity ratio S = 48%. 32 (a) and 32 (b) show the upper limit of the duty ratio D for obtaining the simultaneous reduction effect of the tailing amount and the flicker amount in the range of 48 <S <62, the tailing model and the flicker analysis. It is a figure which shows the result calculated by these. FIG. 33A to FIG. 33C are diagrams for explaining the degree of improvement in tailing and flicker when six representative points are extracted from the region satisfying the conditions A and B. FIG. 34 (a) and 34 (b) are diagrams showing examples of light emission waveforms applicable to the video display device of the present invention. FIGS. 35A and 35B are diagrams showing other examples of light emission waveforms applicable to the video display device of the present invention. It is a figure which shows the other example of the light emission waveform applicable to the video display apparatus of this invention. It is a figure which shows the other example of the light emission waveform applicable to the video display apparatus of this invention. When it is assumed that the tailing to which the human eye responds has a luminance change in the range of 10% to 90%, the duty ratio D and the emission intensity ratio S that can simultaneously reduce the tailing amount and the flicker amount are obtained. FIG. FIG. 39A to FIG. 39C are diagrams showing the amount of tailing and flicker when S is fixed at 69 or 79 in the condition A1 or the condition B1 shown in FIG. 40 (a) and 40 (b) show the upper limit of the duty ratio D for obtaining the simultaneous reduction effect of the trailing amount and the flicker amount in the range of 69 <S <79 shown in the condition B1 of FIG. It is a figure which shows the result calculated by the tailing model and the flicker analysis. It is a figure which shows the generation | occurrence | production principle of animation tailing qualitatively. It is a figure which shows the conventional moving image tailing improvement technique qualitatively. It is a figure which shows the subject of the conventional animation tailing improvement technology quantitatively. It is a figure which shows the subject of the conventional animation tailing improvement technology quantitatively.

Explanation of symbols

100 video display device 101 display panel (video display means)
102 Video controller 103 Data driver 104 Scan driver 105 Column electrode 106 Row electrode 107, 108 Lamp drive circuit 109, 110 Lamp (light emitting means)
111 Video signal 112 Data signal 113 Scan signal 114 Lamp control signal 115 Intermittent light emission (intermittent light emission component)
116 Sustained light (sustained light component)
201 light guide space 202 mixed illumination light 203 display image light 401 liquid crystal panel (image display means)
402 Liquid crystal controller 403 Source driver 404 Gate driver 405 Source electrode 406 Gate electrode 407 Intermittent light emission drive circuit 408 Continuous light emission drive circuits 409, 410, 411 Lamp unit (light emission means)
412, 413, 414 Light guide unit 451 Video signal 452 Vertical synchronization signal 453, 454, 455 Intermittent pulse signal 456 Continuous duration signal 457, 458, 459 Mixed illumination light 601 EL pixel 602, 611 Scan electrode 603 Signal electrode 604, 606, 607, 608 TFT
605 Capacitor 609 EL element 610 Power supply 701 EL pixel 702, 703 Capacitor 704, 705, 706 TFT
707, 708 Scan electrode

Claims (14)

In a video display device that displays video by modulating the luminance of pixels based on a video signal,
A first light-emitting component that occupies a time of D% of the vertical period of the video signal and has a light emission intensity of S% of the light emission intensity of a pixel displayed within the vertical period;
Emitting a second light-emitting component that occupies (100-D)% of the vertical period and has a light emission intensity of (100-S)% of the light emission intensity of the pixels displayed in the vertical period ;
The values of D and S are
Condition A: 62 ≦ S <100 and 0 <D <100 and D <S, or
Condition B: 48 <S <62 and D ≦ (S−48) /0.23
While satisfying
When the ratio of the time from the start of the vertical cycle to the center of the light emission period related to the first light emission component with respect to the vertical cycle of the video signal is P%,
D / 2 ≦ P ≦ (100−D / 2) and 0 <D <100
By controlling the first light emission component and the second light emission component so that the tailing amount and the flicker amount in the case of S = 100 are simultaneously reduced , a video display device characterized in that . The value of P is K, which is a constant determined from the response time constant of the video display means.
2. The video display device according to claim 1, wherein P = 50 + K (where 0 ≦ K ≦ (50−D / 2)). Video display means for setting pixel transmittance based on the video signal;
A light source body for illuminating the video display means,
The ratio of the time from the timing at which the vertical cycle starts to the center of the light emission period of the first light emission component to the vertical cycle is controlled by the light source body. 2. The video display device according to 2. The video display device according to claim 3, wherein the light source body is a semiconductor light emitting element. The video display device according to claim 4, wherein the semiconductor light emitting element is a light emitting diode. The video display device according to claim 3, wherein the light source body is a cold cathode fluorescent lamp. 7. The video display device according to claim 3, wherein the light source body varies the value of P for each area formed by dividing the video display screen. 8. Video display means for setting the luminance of the pixel based on the video signal,
2. The video display means controls the ratio P of the time from the timing at which the vertical cycle starts to the center of the light emission period related to the first light emission component to the vertical cycle. Or the video display apparatus of 2. 9. The video display device according to claim 8, wherein the video display means is an organic EL panel. 9. The video display device according to claim 8, wherein the video display means is a liquid crystal panel. The video display means has a memory for holding the video signal for each pixel,
By referring to the memory a plurality of times per vertical period of the video signal, the light emission waveform of each pixel is light emission composed of the first light emission component and the second light emission component. The video display device according to claim 8. The video display means has a light emitting element for each pixel,
The video display device according to claim 11, wherein the light emission amount of the light emitting element is controlled by information stored in the memory. The video display means is supplied with video data rearranged in advance with respect to the time axis,
By selecting the same pixel three times with respect to the vertical period of the video signal, the light emission waveform of each pixel is light emission composed of the first light emission component and the second light emission component. The video display device according to claim 8. Video display means for setting pixel transmittance based on the video signal;
A light source body for illuminating the video display means,
It is arranged between optical paths formed between the video display means and the light source body, controls the intensity of illumination light of the light source body, and relates to the first light emission component from the timing when the vertical period starts. The video display device according to claim 1, further comprising: a light control unit that controls a ratio P of the time to the center of the light emission period with respect to the vertical period.

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