JP2003271111A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize an image display device which can reduce the power consumption of a light source, improving the ratio of the modulation of a light receiving optical modulation means with dielectric anisotropy, and securing luminance required. <P>SOLUTION: A detection circuit 102 outputs a level indicating the characteristics of an inputted image signal, a selecting circuit 103 selects the output of the detection circuit 102 in a first selection period, the inputted image signal is selected and outputted in a second selection period, and a writing circuit 104 outputs voltage corresponding to the output of the selecting circuit 103 to a liquid crystal panel 107. Meanwhile, a light source control circuit 106 controls the luminance of the light source 105 on the basis of the inputted image signal from an input terminal 101 and the signal of the level indicating the characteristics of the image signal from the detection circuit 102, and the light source 105 emits light to the liquid crystal panel 107. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device for displaying a video signal on a light receiving type light modulating means made of a material having a dielectric anisotropy, and more particularly, it relates to a light modulating element to emit light. The present invention relates to a technique for reducing power consumption of a lighting unit that emits light.

[0002]

2. Description of the Related Art Image display devices are widely used as screen display devices for television receivers and computer devices. These image display devices include a light receiving display device such as a liquid crystal display device and a light emitting display device such as a CRT display device. Of these, the light-receiving type display device displays an image on a light-receiving type light modulating unit (such as a liquid crystal panel). Therefore, a light source is usually provided and light is emitted from the back surface of the light-receiving type light modulating unit for display. The brightness of the display image is adjusted by generating brightness and adjusting the emission brightness of this light source.

As a method of adjusting the brightness of this light source,
For example, it is disclosed in JP-A-5-127608, "Liquid crystal display device". The method disclosed in this publication detects the average luminance level of an input video signal, lowers the luminance of a light source when the average luminance level is higher than a predetermined reference luminance level, and raises the luminance of the light source when the average luminance level is low. Therefore, it is intended to always obtain a constant average display brightness.

Further, as a method of adjusting the lighting of the light source, the light source is turned on only for a predetermined period of time immediately after writing about one frame of the input video signal into the display element, and the light source is turned off in other periods. In some systems, the power consumption is reduced by shortening the lighting period.

On the other hand, in an image display device including a liquid crystal panel using a liquid crystal material having a dielectric anisotropy, such as a liquid crystal display device, the liquid crystal is applied by an applied voltage written in the liquid crystal panel. It is known that as the alignment state of liquid crystal molecules in the panel changes, the dielectric constant (charge capacity) also changes. This dielectric anisotropy will be briefly described.

For example, the charge q written in the liquid crystal₀Is
Liquid determined by the alignment state of liquid crystal molecules just before writing
The charge capacity of the crystal is c₀, The applied voltage written is v₀To
When, q₀= C₀・ V₀ Becomes On the other hand, the liquid crystal molecules
Charge q after the response converges to the equilibrium state₁Is a liquid crystal molecule
Is determined by the orientation state after the response converges to the equilibrium state
The charge capacity of the liquid crystal is c₁, Response of liquid crystal molecules to equilibrium
The voltage after bundling is v₁Then, q₁= C₁・ V₁ Becomes By the law of conservation of charge, q₀= Q₁ Therefore, c₀・ V₀= C₁・ V₁ Is established. Where c₀And c₁Is due to the dielectric anisotropy,
Since the values are different, v ₀And v₁Have different values.

This means that the written voltage and the voltage after the liquid crystal has responded and converged to the equilibrium state with respect to the written voltage are different, and up to the state in the middle of reaching the desired equilibrium state with respect to the written voltage. It only means that the liquid crystal does not respond.

Regarding the charge capacity of this liquid crystal, in general,
The larger the applied voltage value, the larger the applied voltage. That is, in the case of a liquid crystal in which the applied voltage corresponding to the highest luminance level has a larger value than the applied voltage corresponding to the lowest luminance level, which is called normally black, the charge capacity of the liquid crystal has a higher luminance level. The larger the orientation, the larger the value.

On the contrary, in the case of a liquid crystal in which the applied voltage corresponding to the lowest luminance level has a larger value than the applied voltage corresponding to the highest luminance level, which is called normally white, the charge of the liquid crystal is increased. The capacitance has a larger value as the orientation state corresponds to a lower brightness level.

[0010]

However, in the conventional light source brightness adjusting method disclosed in the above publication, the average brightness of the display image can be kept constant, but there is an adjustment for increasing the brightness of the light source. Therefore, the consumed power tends to increase, and a sufficient improvement effect cannot be obtained in terms of power saving.

Further, although the above-mentioned conventional light source lighting adjustment method tends to reduce power consumption, the average brightness of the display image tends to decrease because of the adjustment for shortening the lighting period of the light source. It is not possible to obtain a sufficient improvement effect on the brightness of the image. That is, there is a trade-off relationship between power saving and brightness improvement.

Further, in the light receiving display device having the dielectric anisotropy, the display element does not converge to the desired equilibrium state in response to the voltage applied to the display element, so that the desired brightness can be obtained. There is a problem that there is no.

Therefore, an object of the present invention is to solve the above problems and to increase the power consumption of the light source by performing a writing process for improving the modulation rate of the light receiving type light modulating means and an adjustment for lowering the brightness of the light source. Another object of the present invention is to provide an image display device capable of maintaining visual display brightness.

[0014]

In order to solve the above problems, the present invention takes the following means. That is, in the image display device of interest, the light receiving type light modulating means is made of a material having dielectric constant anisotropy, and the input image signal is displayed on the light receiving type light modulating means. In such an image display device, the present invention includes a detection unit, a selection unit, a writing unit, an illumination unit, and an illumination control unit having the following contents.

The detecting means receives the video signal as an input,
The level indicating the characteristics of the video signal is output. Here, regarding the level that represents the characteristics of the video signal,
Various things are assumed. Although specifically described later, there are, for example, the highest luminance level, the lowest luminance level, the average luminance level of the video signal detected from the video signal. It may be the same signal as the video signal. Also, not the one detected,
It may be the highest brightness level as a predetermined video signal.

The selecting means receives the video signal and the output of the detecting means as input, and selects a first output period for outputting the output of the detecting means, and a second selecting period for selecting and outputting the video signal. It has a selection period. The writing means receives the output of the selecting means as an input and outputs the voltage corresponding to the signal level of the input to the light receiving type optical modulating means. The illumination means emits light to the light receiving type light modulating means. The illumination control means controls the brightness of the illumination means based on the input video signal and the detection output of the detection means.

The operation of the above configuration is as follows.
Prior to the writing means applying a voltage according to the signal level of the input video signal to the light receiving type light modulating means, the detecting means detects the level representing the characteristic of the input video signal,
A voltage corresponding to the characteristic level is preliminarily applied. First
Is a period in which a voltage according to the characteristic level is applied, and the second selection period is a period in which a voltage according to the level of the input video signal is applied. The first selection period is preliminary application, while the second selection period is full-scale application. In the prior art, only full-scale application was performed, whereas in the present invention, preliminary application and full-scale application are combined.

In the light modulating element of the light receiving type light modulating means with dielectric anisotropy, a difference occurs between the applied voltage written and the holding voltage after the response is converged. In order to reduce this difference, preliminary application is performed before full-scale application to bring the alignment state of the light modulation element immediately before full-scale application close to the desired alignment state in advance. By this preliminary application, the holding voltage of the light modulation element at the end of the first selection period approaches the desired holding voltage. The holding voltage at the end of the first selection period maintains the alignment state of the light modulation element immediately before the full-scale application. From the first selection period to the second selection period, the selection means applies the voltage corresponding to the signal level of the input video signal in full-scale application. At this time, the difference between the alignment state immediately before full-scale application and the desired alignment state is already reduced. Therefore, it is possible to converge the response of the light modulation element to a state closer to the desired equilibrium state, and it is possible to improve the modulation factor of the light receiving type light modulation means as compared with the conventional technique.

The degree of improvement of the modulation rate is the modulation rate (orientation state) as a result of preliminary application in the first selection period and the modulation result as a result of full-scale application in the second selection period after the preliminary application. It depends on the difference with the ratio (orientation state). It also
It depends on the difference between the balanced voltage level resulting from the preliminary application and the balanced voltage level resulting from the full-scale application after the preliminary application. The brightness of the illumination means may be controlled according to this difference. The light modulation element has a property of response speed, which means the time required to transit from one alignment state to another alignment state. This is determined by the constituent material of the light modulation element, the manufacturing method, and the like. The difference between the equilibrium voltage level as a result of the preliminary application and the equilibrium voltage level as a result of the full-scale application also affects the response speed, which is known. Therefore, the difference between the balanced voltage level as a result of the preliminary application and the balanced voltage level as a result of the full-scale application can be obtained from the level of the input video signal and the detection signal level by the detection means. The illumination control means controls the brightness of the illumination means based on the input video signal and the detection output of the detection means. That is, the brightness of the illumination means is adaptively controlled according to the degree of improvement of the modulation rate. As a result, in order to obtain the same display brightness as the conventional technology,
The brightness of the lighting unit can be further reduced, and the power consumed by the lighting unit can be reduced.

The preferred embodiments of the invention of the above constitution will be listed below.

In a preferred embodiment of the above invention,
The light modulating element in the light receiving type light modulating means may be composed of a liquid crystal element.

According to this, when a liquid crystal element having a high response speed is used, it is possible to shorten the time required for the light receiving type light modulating means to converge the response to a desired equilibrium state and to make the display brightness bright. it can.

In a preferred embodiment of the invention described above, the light receiving type light modulating means may be constructed as follows. That is, a plurality of scanning lines and a plurality of display signal lines arranged so as to intersect with each other, pixel electrodes arranged in a matrix corresponding to the intersections of the scanning lines and the display signal lines, and the pixel electrodes The optical modulator may be connected to the optical modulator.

As a result, it becomes possible to develop a general technique of displaying an image composed of pixels in a matrix.

In a preferred embodiment of the invention described above, the detecting means and the selecting means are configured as follows. That is, the detecting means is configured to output a level representing a characteristic of the video signal for approximately one frame period. Further, the selecting means is provided with the following first selecting period and second selecting period in a cycle for displaying an image of approximately one frame period of the video signal. That is, a first selection period in which the output of the detection means is selected and a signal for approximately one frame period is output, and the first selection period in the same period as a period in which an image in the approximately one frame period is displayed. Later, a second selection period in which the video signal is selected and a signal for approximately one frame period is output.

The keyword here is "approximately one frame period". That is, it is described that the period of the level representing the characteristic of the video signal detected by the detecting means is approximately one frame period. Further, in the first selection period in which the selection unit switches and the second selection period, in the first selection period in which the detection unit is output in the first half, the signal for approximately one frame period is time-width compressed and output. In the second selection period in which the input video signal is output in the latter half, it is described that a signal for approximately one frame period is time-width compressed and output.

According to this, it is possible to improve the modulation rate of the light receiving type light modulating means and reduce the power of the illuminating means by the control of the illuminating control means with respect to the inputted video signal in units of one frame. It is possible to improve the display image by the light receiving type light modulating means uniformly in the plane.

As another preferable mode, the detecting means and the selecting means are configured as follows. That is, the detection means is configured to output a level representing the characteristic of the video signal in about one scanning period. Further, the selection means is provided with the following first selection period and second selection period during a period for displaying an image of approximately one scanning period of the video signal. That is, the output of the detection means is selected to be approximately 1
After the first selection period in which a signal for a scanning period is output and the first selection period in the same period as the period for displaying an image in the approximately 1 scanning period, the video signal is selected to perform approximately 1 scanning. And a second selection period for outputting a signal for the period.

The keyword here is “approximately one scanning period”
Is. That is, it is described that the period of the level representing the characteristic of the video signal detected by the detecting means is approximately one scanning period. Further, regarding the first selection period and the second selection period in which the selection unit switches,
In the first selection period in which the output of the detection unit in the first half is performed, a signal for approximately one scanning period is time-width compressed and output, and in the second selection period in which the input video signal is output in the second half, the signal for approximately one scanning period is also output. It is described that the time width is compressed and output.

According to this, it is possible to improve the modulation rate of the light receiving type light modulating means and reduce the power of the illuminating means by the control of the illuminating control means with respect to the input video signal in units of one scanning period. The display image can be improved by the light-receiving type light modulating means every scanning period.

In the above invention, a preferred aspect is that the lighting control means is configured to alternately repeat a lighting period and a non-lighting period.

According to this, for example, by turning off the lighting means in the first selection period of the preliminary application, it is possible to reduce the power consumed by the lighting means.

Further, in the above invention, the following can be mentioned as a preferable embodiment from another angle. That is, the detection means, as a feature of the video signal,
That is, it is configured to output the same signal level as the input video signal.

The keyword here is "same signal level".
Is. According to this configuration, in order to realize the convergence of the response of the light-receiving optical modulation means corresponding to the brightness level of the input video signal at each time, the state closer to the desired equilibrium state than in the conventional case can be obtained. The response can be converged, and the modulation rate of the light receiving type light modulating means can be improved. As a result, in order to obtain the same display brightness as the conventional one, the brightness of the illuminating means can be made lower than the conventional brightness by the control of the illuminating control means, and the power consumed by the illuminating means can be reduced.

In another preferred aspect of the above-mentioned invention, the detecting means is characterized in that the video signal is
That is, the maximum luminance level of the input video signal is detected and output.

The keyword here is “maximum brightness level”
Is. According to this configuration, on the one hand, in order to realize the response convergence of the light receiving type optical modulation means corresponding to the highest luminance level of the input video signal, it is possible to achieve a state closer to the desired equilibrium state than the conventional one. The response can be converged, and the modulation rate of the light receiving type light modulating means can be improved. On the other hand, it is possible to improve the modulation rate of the light-receiving type optical modulation means corresponding to a level other than the maximum brightness level of the input video signal. as a result,
In order to obtain the same display brightness as the conventional one, the brightness of the lighting means can be made lower than the conventional brightness by the control of the lighting control means, and the power consumed by the lighting means can be reduced.

In another preferred aspect of the above invention, the detecting means is characterized in that the video signal is
That is, it is configured to detect and output the lowest luminance level of the input video signal.

The keyword here is “minimum brightness level”
Is. According to this configuration, on the one hand, in order to realize the response convergence of the light receiving type optical modulation means corresponding to the lowest luminance level of the input video signal, it is possible to achieve a state closer to the desired equilibrium state than the conventional one. The response can be converged, and the modulation rate of the light receiving type light modulating means can be improved. On the other hand, it is possible to improve the modulation rate of the light receiving type light modulating means corresponding to the level other than the minimum luminance level of the input video signal. as a result,
In order to obtain the same display brightness as the conventional one, the brightness of the lighting means can be made lower than the conventional brightness by the control of the lighting control means, and the power consumed by the lighting means can be reduced.

In another preferred aspect of the above-mentioned invention, the detecting means is characterized in that
That is, the average luminance level of the input video signal is detected and output.

The keyword here is “average brightness level”
Is. According to this configuration, on the other hand, in order to realize the response convergence of the light receiving type optical modulation means corresponding to the average luminance level of the input video signal, it is possible to achieve a state closer to the desired equilibrium state than the conventional one. The response can be converged, and the modulation rate of the light receiving type light modulating means can be improved. On the other hand, it is possible to improve the modulation rate of the light-receiving type optical modulation means corresponding to other than the average luminance level of the input video signal. as a result,
In order to obtain the same display brightness as the conventional one, the brightness of the lighting means can be made lower than the conventional brightness by the control of the lighting control means, and the power consumed by the lighting means can be reduced.

In another preferred aspect of the above-mentioned invention, the detecting means is characterized in that the video signal is characterized by:
That is, it is configured to output the highest luminance level as a video signal.

The keyword here is "maximum luminance level as a video signal". This is different from the detection of the maximum brightness level of the input video signal. It is the maximum luminance level of the video signal itself, which is predetermined in the specifications of the image display device. With this configuration, it is possible to improve the modulation rate of the light-receiving optical modulator that corresponds to each luminance level of the input video signal. As a result, in order to obtain a display brightness equivalent to that of the conventional one, the brightness of the illuminating means can be made lower than the conventional brightness by the control of the illuminating control means, and the power consumed by the illuminating means can be reduced. .

In summary, according to the present invention, it is possible to realize an image display device capable of displaying an image with high brightness without increasing the power consumption of the illumination means.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image display device according to the present invention will be described below in detail with reference to the drawings. Although the image display device of the present invention uses the light receiving type light modulating means, a case where a liquid crystal panel called a normally black composed of liquid crystal elements is used as the light receiving type light modulating means will be exemplified below. And explain.

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of an image display device according to Embodiment 1 of the present invention. In FIG. 1, 101 is an input terminal to which a video signal for image display is supplied. 102 is an input terminal 1
01 is a detection circuit as a detection means for detecting and outputting a level representing the characteristics of the video signal input. 103
Is a video signal input from the input terminal 101 and the detection circuit 1
02 is a selection circuit as a selection unit that selects and outputs any one of the detection levels input from 02. Reference numeral 104 is a writing circuit as a writing unit that outputs an applied voltage corresponding to the signal input from the selection circuit 103. Reference numeral 107 denotes a liquid crystal panel as a light receiving type light modulating means for displaying a video signal by changing the amount of incident light by changing the modulation rate corresponding to the applied voltage input from the writing circuit 104. Reference numeral 105 denotes a light source that is arranged around the liquid crystal panel 107 and serves as an illumination unit that emits light to the liquid crystal panel 107. Reference numeral 106 denotes a light source control circuit as an illumination control unit that controls the brightness of the light source 105 according to the video signal input from the input terminal 101 and the detection level input from the detection circuit 102.

A video signal for displaying an image is input from the input terminal 101. The video signal input from the input terminal 101 is input to the detection circuit 102, the selection circuit 103, and the light source control circuit 106. The detection circuit 102 is
The same signal level as that of the video signal is output to the selection circuit 103 and the light source control circuit 106 in the approximately one frame period of the video signal input from the input terminal 101. The selection circuit 103 provides a first selection period and a second selection period during a period for displaying an image of approximately one frame period of the video signal, and a signal for one frame period of the image is provided in each selection period. The detection level input from the detection circuit 102 is selected in the first selection period, and the video signal input from the input terminal 101 is selected in the second selection period to write them respectively. Output to the circuit 104.

The writing circuit 104 outputs the applied voltage corresponding to the signal input from the selection circuit 103 to the liquid crystal panel 107. The light source control circuit 106 controls the brightness of the light source 105 based on the video signal input from the input terminal 101 and the detection level input from the detection circuit 102. Under the control of the light source control circuit 106, the light source 105 emits light to the liquid crystal panel 107 by changing the brightness of lighting. The liquid crystal panel 107 has a plurality of scanning lines and a plurality of display signal lines arranged so as to intersect with each other, and pixel electrodes arranged in a matrix corresponding to the intersections of the scanning lines and the display signal lines. And a liquid crystal element connected to the pixel electrode. This liquid crystal panel 107
Is the light source 10 according to the transmittance obtained by the writing circuit 104.
5, the amount of light incident from the input terminal 101 is changed.
The video signal input from is displayed, and the image corresponding to the input signal is displayed.

Regarding the image display device of the first embodiment as described above, a part of the liquid crystal panel 107 corresponding to one pixel at the top of the screen is designated as L_TGT, and a detailed description will be given while paying attention to the liquid crystal part L_TGT. .

FIG. 2 is a timing chart showing an example of the response of the liquid crystal in the image display device of the first embodiment.

FIG. 2A shows a video signal input from the input terminal 101. This video signal has the content of the lowest luminance level as a video signal on one side of the image in the nth frame and the image in the (n + 1) th frame. It is assumed that the contents change from the highest luminance level as a video signal to the intermediate luminance level as a video signal from top to bottom.

FIG. 2B shows the output of the detection level of the detection circuit 102. As described above, the detection circuit 102 outputs the same signal level as the input video signal detected in one frame period, but in this example, like the video signal changing from P1 to Q1 in FIG. Output a changing signal.

FIG. 2C shows the selection output of the selection circuit 103. In the first selection period, a signal obtained by compressing one frame period of the detection signal changing from P1 to Q1 in FIG. 2B into a 1/2 time width is output, and in the second selection period, FIG.
Then, a signal obtained by compressing one frame period of the video signal of 1 to 1/2 time width is output.

FIG. 2D shows the output of the writing circuit 104. The signal of FIG. 2C is sampled and output at timing TW1 and timing TW2.

FIG. 2E shows a change in the holding voltage of the liquid crystal portion L_TGT with respect to the writing of the applied voltage from the writing circuit 104, and FIG. 2F shows a change in the alignment state of the liquid crystal portion L_TGT. The main part of FIG. 2 (e) is enlarged and transferred to FIG. 8 (a).

FIG. 2G shows the transmittance of incident light, which changes depending on the alignment state of the liquid crystal portion L_TGT.

First, as shown in FIG. 2B, the (n + 1) th
During the frame period, the detection circuit 102 operates the input terminal 10
For the video signal input from 1, the same signal as the input video signal is output. The selection circuit 103 is shown in FIG.
As shown in (c), in the first selection period in the (n + 1) th frame period, the contents of the output of the detection circuit 102 for one frame period are output to the writing circuit 104.

Within this first selection period, the write circuit 104
Let TW1 be the timing at which the applied voltage is written to the liquid crystal part L_TGT, at this timing TW1,
As shown in FIG. 2D, the writing circuit 104 writes an applied voltage corresponding to the highest brightness level as a video signal in the liquid crystal portion. Since this is at the same level as the input video signal, it means the same as writing the applied voltage to be displayed on the liquid crystal portion L_TGT.

At this time, the liquid crystal portion L_TGT responds to the video signal input from the input terminal 101 in the nth frame, and as a result, as shown in FIG. 2F, the alignment state corresponding to the lowest luminance level as the video signal. Has become. Therefore, at the above-mentioned timing TW1, the liquid crystal portion L_T in the alignment state corresponding to the lowest brightness level.
The applied voltage corresponding to the highest brightness level will be written to the GT.

Here, assuming that the charge capacity of the liquid crystal portion L_TGT immediately before writing the applied voltage at this timing TW1 is c_BK, the holding voltage is v_BK, and the applied voltage to be written is v_OBJ1, it is calculated by q_BO1 = c_BK · v_OBJ1. The amount of electric charge q_BO1 is accumulated in the liquid crystal portion L_TGT.

After this timing TW1, the liquid crystal portion L_
The TGT transits toward the alignment state corresponding to the written applied voltage. Since the charge capacity of the liquid crystal called normally black used in this description has a larger value as the alignment state corresponding to a high brightness level increases, the charge capacity of the liquid crystal portion L_TGT also changes with the change of the alignment state. It will gradually change to a larger value.

Since q_BO1 does not change according to the law of conservation of electric charge, the holding voltage of the liquid crystal part L_TGT gradually changes to a small value as the charge capacity of the liquid crystal part L_TGT changes to a large value. .

Therefore, this liquid crystal portion L_TGT is shown in FIG.
As shown in (e), FIG. 8 (a), and FIG. 2 (f), a response is generated until the alignment state corresponding to the voltage is matched while repeating the change of the charge capacity and the holding voltage accompanying the transition of the alignment state. Continue.

The liquid crystal portion L_TGT has the timing T
C_BO1 is the charge capacity and v_CNV1 is the holding voltage when the response converges completely to the writing of the applied voltage at W1.
Assuming 1, it is assumed that c_BO1> c_BK and v_CNV11 <v_OBJ1 because q_BO1 is constant. Hold voltage v_CNV when response is converged
It can be seen that 11 has a value smaller than the written applied voltage v_OBJ1.

This means that the liquid crystal portion L_TGT does not respond to the alignment state corresponding to the applied voltage v_OBJ1 written, and as shown in FIG. 2 (g), at the timing TW1 by the writing circuit 104. By writing the applied voltage once, the desired transmittance for light cannot be obtained.

Such a difference between the written applied voltage and the holding voltage after the response has converged is desired with respect to the alignment state of the liquid crystal portion immediately before the applied voltage is written and the written applied voltage. It is determined according to the difference between the alignment state of the liquid crystal portion and the alignment state.

That is, when the difference between the above two orientation states is small, the charge capacity of the liquid crystal portion immediately before the applied voltage is written, which is caused by the dielectric anisotropy, and the response after the response voltage converges to the applied voltage. The difference from the charge capacity of the liquid crystal part becomes small. Therefore, the difference between the written applied voltage and the holding voltage after the response convergence is also small, and the liquid crystal portion responds to the applied voltage in a state close to the desired alignment state.

Therefore, after the timing TW1, in the second selection period in the (n + 1) th frame period in which the liquid crystal portion does not completely respond and converge to the applied voltage written, the selection circuit 103 operates as shown in FIG. 2 (c), the n-th video signal input from the input terminal 101 is input.
The contents of one frame period of +1 frame are written into the writing circuit 10
Output to 4.

Within this second selection period, the write circuit 104
When the timing for writing the applied voltage to the liquid crystal portion L_TGT is TW2, at this timing TW2, as shown in FIG. 2D, the writing circuit 104 sets the applied voltage to be displayed on the liquid crystal portion L_TGT. The applied voltage corresponding to the highest brightness level as a video signal is written in the liquid crystal part.

Therefore, at this timing TW2, the same applied voltage as at the timing TW1 is applied to the liquid crystal portion L_T.
Since it is written in GT, it means that the applied voltage to be displayed is written twice in the liquid crystal portion L_TGT.

At the timing TW2, the charge capacity of the liquid crystal portion L_TGT immediately before the applied voltage is written is c_B.
Assuming G1, the charge quantity q_GO1 calculated by q_GO1 = c_BG1 · v_OBJ1 is obtained by writing the applied voltage at the timing TW2 to the liquid crystal portion L_TG.
It has been accumulated in T.

As described above, the charge capacity of the liquid crystal portion L_TGT becomes larger as the orientation state corresponding to the higher brightness level increases, and therefore c_BG1> c_BK. Therefore, q_GO1> q_BO1. That is, the charge capacity written at the timing TW2 is larger than the charge capacity written at the timing TW1.

After this timing TW2, the liquid crystal portion L_TGT is kept constant with q_GO1 according to the law of conservation of charge.
As shown in FIG. 2E, FIG. 8A, and FIG. 2F, a transition is made toward the alignment state corresponding to the applied voltage written again, and the charge accompanying the transition of the alignment state While repeatedly changing the capacitance and the holding voltage, the response is continued until the alignment state corresponding to the voltage is matched.

When the liquid crystal portion L_TGT converges in response to the writing of the applied voltage at the timing TW2, if the charge capacity is c_GO1 and the holding voltage is v_CNV12, then q_GO1> q_BO1 and therefore c_GO1> c_BO1. Is assumed.

Further, when the response of the liquid crystal is converged, the charge capacity and the holding voltage uniquely correspond to each other, and thus v_CNV12> v_CNV11.

That is, as shown in FIGS. 2E and 8A, the write circuit 104 for the liquid crystal portion L_TGT.
The applied voltage is written between the applied voltage and the holding voltage after the response converges more twice when the applied voltage is written once at timing TW1 than when the applied voltage is written twice at timing TW1. 2F, the liquid crystal portion L_TGT responds and converges to a state closer to the desired alignment state with respect to the applied voltage, as shown in FIG.

Therefore, as shown in FIG. 2 (g), the liquid crystal portion L_TGT has an improved transmittance, and a desired transmittance for light can be obtained. As the transmittance of the liquid crystal portion L_TGT is higher, the light incident from the light source 105 is transmitted more, so that the liquid crystal portion L_TGT is displayed brighter. When the response of the liquid crystal portion is converged, the transmittance of the liquid crystal portion is determined by the alignment state of the liquid crystal portion, and the alignment state of the liquid crystal portion uniquely corresponds to the holding voltage of the liquid crystal portion. . Therefore, the transmittance of the liquid crystal part can be determined by the holding voltage of the liquid crystal part,
The above-mentioned degree of improvement of the transmittance is v_CNV11 and v_CN.
It can be judged by the difference from V12. This v_CNV11 will be described.

The liquid crystal portion L_TGT has the property of response speed which means the time required to transit from one alignment state to another alignment state. This is determined by the constituent material of the liquid crystal, the manufacturing method, and the like. From this response speed, the time transition of the alignment state in the liquid crystal portion L_TGT, that is, the content of the time response can be known. Therefore, n +
At timing TW1 of one frame, the liquid crystal portion L_
The charge capacity c_TW1 of the TGT, the applied voltage v_TW1 to be written, the time t1 until the timing TW1 of the (n + 2) th frame which is the next frame, and the liquid crystal portion L_TG.
If the response speed of T is used, the response state of the liquid crystal portion L_TGT can be easily determined.

This charge capacity c_TW1 is the content in the state where the liquid crystal portion L_TGT has converged in response to the video signal of the nth frame, and therefore can be grasped by the video signal input from the input terminal 101. Also, the applied voltage v_T
W1 is the output itself of the detection circuit 102, and is the time t1.
Is determined by the video signal input from the input terminal 101. In addition, the response speed of the liquid crystal portion L_TGT is known depending on the constituent material.

Therefore, v_CNV11 can be calculated using the video signal input from the input terminal 101 and the detection level input from the detection circuit 102.

The v_CNV12 will be described.
In the calculation of v_CNV12, first, the timing T
The charge capacity c_TW of the liquid crystal portion L_TGT when responding from the timing TW1 to the timing TW2 in the same frame by writing the applied voltage in W1
It is necessary to calculate 2. This charge capacity c_TW2 is
At the timing TW1 of the (n + 1) th frame, the charge capacity c_TW1 of the liquid crystal portion L_TGT, the applied voltage v_TW1 to be written, and the timing TW of the (n + 1) th frame.
This can be easily determined by using the time t12 from 1 to the same timing TW2 of the (n + 1) th frame and the response speed of the liquid crystal portion L_TGT. This charge capacity c_TW1 is
Since the liquid crystal portion L_TGT has a response and convergence in response to the video signal of the nth frame, the input terminal 101
It can be grasped by the video signal input from. The applied voltage v_TW1 is the output itself of the detection circuit 102, and the time t12 is determined by the video signal input from the input terminal 101. In addition, the response speed of the liquid crystal portion L_TGT is known depending on the constituent material. Therefore, it can be calculated using the charge capacity c_TW2, the video signal input from the input terminal 101, and the detection level input from the detection circuit 102.

Therefore, the timing T of the (n + 1) th frame
In W2, the liquid crystal portion L_T that can be calculated in the same manner as above
Using the charge capacity of GT, the applied voltage to be written, the time until the timing TW1 of the n + 2th frame which is the next frame, and the response speed of the liquid crystal portion L_TGT,
The response state of the liquid crystal part L_TGT can be easily determined, and v_C
NV12 can be calculated.

As shown in FIGS. 2 (e) and 8 (a), the relationship between these two holding voltages is v_CNV12> v_CNV11. Therefore, the write circuit 10 for the liquid crystal portion L_TGT is set.
4. The transmittance of the liquid crystal portion L_TGT obtained when the writing of the applied voltage by 4 is performed only at the timing TW1 is r11, and the transmittance of the liquid crystal portion L_TGT obtained when the writing of the applied voltage is performed at the timing TW1 and the timing TW2 is r.
If it is 12, r12> r11.

Writing circuit 10 for the liquid crystal part L_TGT
4, the display brightness of the liquid crystal portion L_TGT obtained when the applied voltage is written only at the timing TW1 is Y11, and the above-mentioned timings TW1 and T
Assuming that the display brightness of the liquid crystal portion L_TGT obtained in the case of W2 is Y12, suppose that r11 is 70% and r1 is 70%.
When 2 is 90% and the brightness of the light source is the same, Y11: Y12 = 70: 90, which means that Y12 is brighter. Therefore, the brightness of the light source when the writing voltage is written to the liquid crystal portion L_TGT by the writing circuit 104 only at the timing TW1 is L11, and the above timing TW1.
And the brightness of the light source when the timing is TW2.
When set to 2, if L11: L12 = 90: 70, then Y12 can be made equal to Y11.
At this time, the brightness of the light source is reduced by about 22%, so that the power consumption of the light source can be reduced accordingly.

The light source control circuit 106, as described above,
Liquid crystal portion L_ obtained by writing the applied voltage
The degree of improvement in the TGT transmittance can be calculated using the video signal input from the input terminal 101 and the detection level input from the detection circuit 102, v_CNV11 and v_CNV.
The brightness of the light source 105 is controlled so as to be low based on the difference between the light source 105 and the light source.

Further, the light source control circuit 106 includes a liquid crystal portion L.
The light source 105 is turned off during the first selection period, which is a period in which the transmittance of _TGT is small, and is turned on during the second selection period, and the extinguishing period and the lighting period are alternately repeated.

As described above, the light source 105 is turned on only during the period when the transmittance of the liquid crystal portion L_TGT is good, so that the liquid crystal portion L is effectively turned on during the lighting period of the light source 105.
The brightness of _TGT is obtained, and the power consumption of the light source 105 can be further reduced.

The light source 105 emits light to the liquid crystal part L_TGT by changing the brightness of lighting by the control as described above from the light source control circuit 106. As a result, the liquid crystal portion L_TGT changes the amount of light incident from the light source 105 according to the transmittance improved by writing the applied voltage twice, and an image corresponding to the video signal input from the input terminal 101. Can be displayed.

Although the above description focuses on the liquid crystal part L_TGT, it is clear that the part of the liquid crystal panel 107 corresponding to any pixel can be similarly described.

Thus, as described above, according to the present embodiment, for the liquid crystal panel 107, the first selection period and the second selection period by the detection circuit 102, the selection circuit 103, and the writing circuit 104 are set. By writing the applied voltage twice in and, the transmittance of the liquid crystal panel 107 can be improved. Therefore, even if the brightness of the light source 105 is lowered, the liquid crystal panel 107 can display the image corresponding to the video signal input from the input terminal 101 with sufficient brightness. That is, it is possible to realize an image display device that can reduce the power consumption of the light source 105.

(Second Embodiment) Next, an image display device according to a second embodiment of the present invention will be described. As for the configuration of the image display device of the present embodiment, the configuration of FIG. 1 in the case of the first embodiment is applied. However, in the image display device according to the second embodiment, the detection circuit 102 includes the input terminal 1
The maximum luminance level of the video signal is detected in approximately one frame period of the video signal input from 01, and the detection result is output to the selection circuit 103. The feature is that the maximum brightness level of the video signal is detected.

Regarding the operation of the image display device according to the second embodiment, as in the case of the image display device according to the first embodiment, pay attention to a part L_TGT of the liquid crystal panel 107 corresponding to one pixel at the top of the screen. And explain.

FIG. 3 is a timing chart showing an example of the response of the liquid crystal in the image display device of the second embodiment.

FIG. 3A shows a video signal input from the input terminal 101, and this video signal is the same as that in FIG. 2A in the first embodiment.

FIG. 3B shows the output of the detection level of the detection circuit 102. As described above, the detection circuit 102 outputs the highest brightness level of the input video signal detected in one frame period. In this example, the highest brightness level indicated by P1 in FIG. 3A is the detection output. . The detection circuit 102 holds the highest brightness level P1 for one frame period.

FIG. 3C shows the selection output of the selection circuit 103. In the first selection period, the highest luminance level P1 in FIG. 3B is held and output, and in the second selection period, FIG.
Then, a signal obtained by compressing one frame period of the video signal of 1 to 1/2 time width is output.

FIG. 3D shows the output of the writing circuit 104. The signal of FIG. 3C is sampled and output at timing TW1 and timing TW2. As a result, it is similar to that of FIG.

FIG. 3E shows a change in the holding voltage of the liquid crystal portion L_TGT with respect to the writing of the applied voltage from the writing circuit 104, and FIG. 3F shows a change in the alignment state of the liquid crystal portion L_TGT. The essential part of FIG. 3 (e) is enlarged and transferred to FIG. 8 (b).

FIG. 3G shows the transmittance of incident light, which changes depending on the alignment state of the liquid crystal portion L_TGT.

As shown in FIG. 3B, in the (n + 1) th frame period, the detection circuit 102 detects and outputs the highest luminance level in the (n + 1) th frame of the video signal input from the input terminal 101. This detection at the highest brightness level is different from the detection of the same signal as the video signal in the first embodiment.

In the case of the above video signal, the liquid crystal portion L_
The output of the detection circuit 102 with respect to the TGT is the same as the contents of the topmost part of the screen of the input video signal, so that the liquid crystal portion L_TGT operates in the same manner as the image display device according to the first embodiment. Therefore, it will be briefly described below.

As shown in FIG. 3C, the selection circuit 103 outputs the output of the detection circuit 102 to the writing circuit 104 in the first selection period of the (n + 1) th frame period. At the timing TW1 when the writing circuit 104 writes the applied voltage to the liquid crystal portion L_TGT, as shown in FIG. 3D, the applied voltage corresponding to the highest brightness level as the video signal is written in the liquid crystal portion. However, since this is equivalent to the contents of the input video signal at the top of the screen, it is the same as writing the applied voltage to be displayed on the liquid crystal portion L_TGT. Therefore, as shown in FIG. 3 (f), at the timing TW1, the liquid crystal portion L_TG in the alignment state corresponding to the lowest luminance level.
For T, the applied voltage corresponding to the highest brightness level will be written.

At this timing TW1, the charge capacity of the liquid crystal portion L_TGT immediately before the applied voltage is written is c_B.
K, the applied voltage written is v_OBJ2, and
Assuming that the charge capacity is c_BO2 and the holding voltage is v_CNV21 when the liquid crystal part L_TGT completely responds to the writing of the applied voltage at the timing TW1, the charge amount q_BO2 calculated by q_BO2 = c_BK · v_OBJ2 is obtained. Since it has been accumulated in the liquid crystal portion L_TGT and c_BO2> c_BK, it is assumed from the law of conservation of charge that v_CNV21 <v_OBJ2.

As shown in FIG. 3C, the selection circuit 103 selects the n + 1th frame of the video signal input from the input terminal 101 in the second selection period after the timing TW1 in the n + 1th frame period. The contents for one frame period are output to the writing circuit 104.

At timing TW2 in the second selection period in which the writing circuit 104 writes the applied voltage to the liquid crystal portion L_TGT, as shown in FIG. 3D, the application corresponding to the highest luminance level as the video signal is performed. A voltage will be written to the liquid crystal part. This means that the applied voltage to be displayed on the liquid crystal portion L_TGT is written twice.

At this timing TW2, the charge capacity of the liquid crystal portion L_TGT immediately before the applied voltage is written is c_B.
G2, and the liquid crystal part L_TGT has the timing TW.
Assuming that the charge capacity is c_GO2 and the holding voltage is v_CNV22 when the response converges to the writing of the applied voltage at 2, the charge amount q_GO2 calculated by q_GO2 = c_BG2 · v_OBJ2 is accumulated in the liquid crystal portion L_TGT. Therefore, since c_BG2> c_BK q_GO2> q_BO2, it is assumed that c_GO2> c_BO2 v_CNV22> v_CNV21.

Here, the applied voltage written in the liquid crystal portion L_TGT at the timing TW2 in the image display device of the first embodiment and the applied voltage written in the liquid crystal portion L_TGT at the timing TW2 in the image display device of the second embodiment. Is the content at the top of the screen of the video signal input together, and therefore v_OBJ1 of the image display apparatus of the first embodiment and v_OBJ2 of the image display apparatus of the second embodiment have the same content.

Therefore, v_CNV11 = v_CNV21 Therefore, v_CNV22> v_CNV11 Will be.

That is, as shown in FIGS. 3E and 8B, the write circuit 104 for the liquid crystal portion L_TGT.
Compared with the case where the writing of the applied voltage by the above is performed only once at the timing TW1 in the image display apparatus of the first embodiment, the case where the writing of the applied voltage is performed twice at the timing TW1 and the timing TW2 in the image display apparatus of the second embodiment Better
The difference between the applied voltage that has been written and the holding voltage after the response has converged becomes smaller, and as shown in FIG. , The response converges to a state closer to the liquid crystal part L_TG, as shown in FIG.
The transmittance of T is improved.

Writing circuit 10 for liquid crystal part L_TGT
4, the applied voltage is written in the image display device of the first embodiment only at the timing TW1, the transmittance of the liquid crystal portion L_TGT is r11, the display brightness is Y11, and the image display of the second embodiment is performed. If the transmittance of the liquid crystal portion L_TGT obtained when the apparatus performs the timing TW1 and the timing TW2 is r22 and the display brightness is Y22, then r22> r11, and r11 is 70%, r22 is 90%, and the light source If the brightness is the same, it follows that Y11: Y22 = 70: 90, so Y22 is brighter. Therefore, the writing of the applied voltage to the liquid crystal portion L_TGT by the writing circuit 104 is performed by the image display device of the first embodiment only at the timing TW1, the brightness of the light source is L11, and in the image display device of the second embodiment. When the brightness of the light source at the timing TW1 and the timing TW2 is L22, if L11: L22 = 90: 70, then Y22 can be equal to Y11.

The light source control circuit 106 controls the liquid crystal portion L_TG.
The degree of improvement in the transmittance of T is v_CNV11 and v_CNV2.
Judging from the difference with 2, the brightness of the light source 105 is reduced and the power consumption is controlled according to the degree of improvement in the transmittance. This v_CNV11 and v_CNV22
As described above, as described in the description of the image display device according to the first embodiment, it can be easily calculated using the video signal input from the input terminal 101 and the detection level input from the detection circuit 102.

Further, the light source control circuit 106 includes a liquid crystal part L.
The light source 105 is turned off during the first selection period, which is a period in which the transmittance of _TGT is small, and is turned on during the second selection period, and the extinguishing period and the lighting period are alternately repeated. The light source 105 emits light to the liquid crystal portion L_TGT by changing the brightness of lighting by the above control from the light source control circuit 106. As a result, the liquid crystal part L_TGT changes the amount of light incident from the light source 105 by the improved transmissivity by writing the applied voltage twice, and the input terminal 1
An image corresponding to the video signal input from 01 can be displayed.

Although the above description focuses on the liquid crystal part L_TGT, it is clear that the part of the liquid crystal panel 107 corresponding to any pixel can be similarly described.

Therefore, as described above, according to the present embodiment, the same effect as in the case of the first embodiment can be obtained. That is, with respect to the liquid crystal panel 107, the first circuit including the detection circuit 102, the selection circuit 103, and the writing circuit 104.
By writing the applied voltage twice during the selection period of 2 and the selection period of 2, the transmittance of the liquid crystal panel 107 can be improved. Therefore, even if the brightness of the light source 105 is lowered, the liquid crystal panel 107 is still connected to the input terminal 101.
The image corresponding to the video signal input from can be displayed with sufficient brightness. That is, it is possible to realize an image display device that can reduce the power consumption of the light source 105.

(Third Embodiment) Next, an image display device according to a third embodiment of the present invention will be described. As for the configuration of the image display device of the present embodiment, the configuration of FIG. 1 in the case of the first embodiment is applied. However, in the image display device according to the third embodiment, the detection circuit 102 has the input terminal 1
The minimum luminance level of the video signal is detected in approximately one frame period of the video signal input from 01, and the detection result is output to the selection circuit 103. The feature is that the lowest luminance level of the video signal is detected.

Regarding the operation of the image display device of the third embodiment, as in the case of the image display device of the first embodiment, pay attention to a part L_TGT of the liquid crystal panel 107 corresponding to one pixel at the top of the screen. And explain.

FIG. 4 is a timing chart showing an example of liquid crystal response in the image display device of the third embodiment.

FIG. 4A shows a video signal input from the input terminal 101, and this video signal is the same as that in FIG. 2A in the first embodiment.

FIG. 4B shows the detection level output of the detection circuit 102. As described above, the detection circuit 102 outputs the lowest luminance level of the input video signal detected in one frame period. In this example, the lowest luminance level indicated by Q1 in FIG. 4A is the detection output. . The detection circuit 102 holds the minimum brightness level Q1 for one frame period.

FIG. 4C shows the selection output of the selection circuit 103. In the first selection period, the lowest luminance level Q1 in FIG. 4B is held and output, and in the second selection period, FIG.
Then, a signal obtained by compressing one frame period of the video signal of 1 to 1/2 time width is output.

FIG. 4D shows the output of the writing circuit 104. The signal of FIG. 4C is sampled and output at timing TW1 and timing TW2. The level of the first selection period is lower than in the first and second embodiments.

FIG. 4E shows changes in the holding voltage of the liquid crystal portion L_TGT with respect to the writing of the applied voltage from the writing circuit 104. According to FIG. 4D, the level of the first selection period is lower than in the first and second embodiments. Figure 4
The main part of (e) is enlarged and transcribed in FIG. 8 (c).

FIG. 4F shows a change in the alignment state of the liquid crystal portion L_TGT. According to FIG. 4E, the rising is slower than in the first and second embodiments in the first selection period.

FIG. 4G shows the transmittance of incident light, which changes depending on the alignment state of the liquid crystal portion L_TGT. According to FIG. 4 (f), the rising is slower in the first selection period than in the first and second embodiments.

As shown in FIG. 4B, in the (n + 1) th frame period, the detection circuit 102 detects and outputs the lowest luminance level in the (n + 1) th frame of the video signal input from the input terminal 101. The detection at the lowest brightness level is different from the detection at the highest brightness level in the second embodiment.

In the case of the above video signal, the liquid crystal portion L_
The output of the detection circuit 102 with respect to the TGT is the contents of the bottom of the screen of the input video signal (the top of the screen in the second embodiment), and the video signal has an intermediate luminance level.

As shown in FIG. 4C, the selection circuit 103 outputs the output of the detection circuit 102 to the writing circuit 104 in the first selection period of the (n + 1) th frame period. At the timing TW1 of writing the applied voltage to the liquid crystal portion L_TGT, the writing circuit 104 writes the applied voltage corresponding to the intermediate luminance level as the video signal, as shown in FIG. 4D. At this time, the liquid crystal portion L_TGT is in an alignment state corresponding to the lowest brightness level, as shown in FIG.

The charge capacity of the liquid crystal portion L_TGT immediately before the applied voltage is written at the timing TW1 is c_B.
K, the applied voltage to be written is v_OBJ3, and
Assuming that the charge capacity is c_BO3 and the holding voltage is v_CNV31 when the liquid crystal part L_TGT completely responds to the writing of the applied voltage at the timing TW1, the charge amount q_BO3 calculated by q_BO3 = c_BK · v_OBJ3 is obtained. Since it has been accumulated in the liquid crystal portion L_TGT and c_BO3> c_BK, it is assumed from the law of conservation of charge that v_CNV31 <v_OBJ3.

As shown in FIG. 4C, the selection circuit 103 operates in the (n + 1) th frame of the video signal input from the input terminal 101 in the second selection period after the timing TW1 in the (n + 1) th frame period. The contents for one frame period are output to the writing circuit 104.

At timing TW2 in the second selection period in which the writing circuit 104 writes the applied voltage to the liquid crystal portion L_TGT, as shown in FIG. 4D, the application corresponding to the highest luminance level as the video signal is applied. A voltage will be written to the liquid crystal part. This is v_OBJ1 in the description of the image display device according to the first embodiment.

Therefore, the charge capacity of the liquid crystal portion L_TGT immediately before writing the applied voltage at the timing TW2 is c_BG3, and the charge capacity when the liquid crystal portion L_TGT converges in response to the writing of the applied voltage at the timing TW2. And holding voltage are c_GO3 and v_C, respectively.
Assuming NV32, the charge amount q_GO3 calculated by q_GO3 = c_BG3 · v_OBJ1 is obtained by writing the applied voltage at the timing TW2 to the liquid crystal portion L_TG.
It has been accumulated in T.

As described above, the charge capacity of the liquid crystal portion L_TGT has a larger value as it becomes an alignment state corresponding to a higher brightness level, and therefore c_BG3> c_BK q_GO3> q_BO3. Therefore, c_GO3> c_BO3 v_CNV32> v_CNV31. Is supposed to be.

Here, the applied voltage v_OBJ corresponding to the video signal level to be displayed on the liquid crystal portion L_TGT.
1 is written only once at the timing TW1 in the image display device of the first embodiment, and is written at the timing TW2 after the first selection period in the image display device of the third embodiment. Think about.

The charge capacity c_BK at the timing TW1 in the image display device of the first embodiment and the third embodiment.
As described above, the charge capacity c_BG3 at the timing TW2 in the image display device has the relationship of c_BG3> c_BK.

In both cases, the same applied voltage v_O
Since BJ1 is written, the charge q_BO1 accumulated in the liquid crystal part L_TGT at the timing TW1 in the image display device of the first embodiment and the charge q_BO1 accumulated in the liquid crystal part L_TGT at the timing TW2 in the image display device of the third embodiment. The relation with q_BO3 is q_GO3> q_BO1. Therefore, it can be said that, regarding the charge capacity and the holding voltage after the respective responses converge, c_GO3> c_BO1 v_CNV32> v_CNV11.

That is, as shown in FIGS. 4E and 8C, the write circuit 104 for the liquid crystal portion L_TGT.
Compared with the case where the application of the applied voltage is written only once at the timing TW1 in the image display apparatus of the first embodiment, the case where the application of the applied voltage is performed twice at the timing TW1 and the timing TW2 in the image display apparatus of the third embodiment Better
The difference between the written applied voltage and the holding voltage after the response has converged becomes small, and as shown in FIG. 4 (f), the liquid crystal portion L_TGT has a desired alignment state with respect to the applied voltage. , The response converges to a closer state. As a result, as shown in FIG. 4G, the liquid crystal portion L_TGT has improved transmittance.

Writing circuit 10 for liquid crystal portion L_TGT
4, the applied voltage is written in the image display device of the first embodiment only at the timing TW1, the transmittance of the liquid crystal portion L_TGT is r11, the display brightness is Y11, and the image of the third embodiment is displayed. Assuming that the transmittance of the liquid crystal portion L_TGT obtained at the timing TW1 and the timing TW2 on the display device is r32 and the display brightness is Y32, r32> r11, and r11 is 70%, r32 is 80%, If the brightness of the light source is the same, Y11: Y32 = 70: 80, so it can be seen that Y32 is brighter. Therefore, in the image display device of the third embodiment, the brightness of the light source is L11 when the applied voltage is written to the liquid crystal portion L_TGT by the writing circuit 104 only at the timing TW1 in the image display device of the first embodiment. When the brightness of the light source at the timing TW1 and the timing TW2 is L32, if L11: L32 = 80: 70, Y32 can be equal to Y11.

The light source control circuit 106 controls the liquid crystal part L_TG.
The degree of improvement of the transmittance of T is v_CNV11 and v_CNV3.
The brightness of the light source 105 is lowered according to the degree of improvement in the transmittance determined by the difference between the two, and the power consumption is controlled to be reduced. The v_CNV 11 and v_CNV 32 can be easily calculated using the video signal input from the input terminal 101 and the detection level input from the detection circuit 102, as described in the description of the image display device according to the first embodiment. It is a thing.

Further, the light source control circuit 106 includes a liquid crystal portion L.
The light source 105 is turned off during the first selection period, which is a period in which the transmittance of _TGT is small, and is turned on during the second selection period, and the extinguishing period and the lighting period are alternately repeated. The light source 105 emits light to the liquid crystal portion L_TGT by changing the brightness of lighting by the above control from the light source control circuit 106. As a result, the liquid crystal part L_TGT changes the amount of light incident from the light source 105 by the improved transmissivity by writing the applied voltage twice, and the input terminal 1
An image corresponding to the video signal input from 01 can be displayed.

Although the above description focuses on the liquid crystal portion L_TGT, it is obvious that a part of the liquid crystal panel 107 corresponding to any pixel can be similarly described.

Therefore, as described above, according to the present embodiment, the same effect as in the case of the first embodiment can be obtained. That is, with respect to the liquid crystal panel 107, the first circuit including the detection circuit 102, the selection circuit 103, and the writing circuit 104.
By writing the applied voltage twice during the selection period of 2 and the selection period of 2, the transmittance of the liquid crystal panel 107 can be improved. Therefore, even if the brightness of the light source 105 is lowered, the liquid crystal panel 107 is still connected to the input terminal 101.
The image corresponding to the video signal input from can be displayed with sufficient brightness. That is, it is possible to realize an image display device that can reduce the power consumption of the light source 105.

(Fourth Embodiment) Next, an image display device according to a fourth embodiment of the present invention will be described. As for the configuration of the image display device of the present embodiment, the configuration of FIG. 1 in the case of the first embodiment is applied. However, in the image display device according to the fourth embodiment, the detection circuit 102 has the input terminal 1
The average luminance level of the video signal input from the video signal 01 is detected in approximately one frame period, and the detection result is output to the selection circuit 103. The feature is that the average luminance level of the video signal is detected.

Regarding the operation of the image display device of the fourth embodiment, as in the case of the image display device of the first embodiment, pay attention to a part L_TGT of the liquid crystal panel 107 corresponding to one pixel at the top of the screen. And explain.

FIG. 5 is a timing chart showing an example of response of liquid crystal in the image display device of the fourth embodiment.

FIG. 5A shows a video signal input from the input terminal 101, and this video signal is the same as that in FIG. 2A in the first embodiment.

FIG. 5B shows the output of the detection level of the detection circuit 102. As described above, the detection circuit 102 outputs the average luminance level of the input video signal detected in one frame period. In this example, the average of the highest luminance level P1 and the lowest luminance level Q1 in FIG. The average brightness level R1 represented by (P1 + Q1) / 2 of is the detection output. The detection circuit 102 holds the average luminance level R1 for one frame period.

FIG. 5C shows the selection output of the selection circuit 103. In the first selection period, the average luminance level R1 in FIG. 5B is held and output, and in the second selection period, FIG.
Then, a signal obtained by compressing one frame period of the video signal of 1 to 1/2 time width is output.

FIG. 5D shows the output of the writing circuit 104. The signal of FIG. 5C is sampled and output at timing TW1 and timing TW2. The level of the first selection period is lower than those in the first and second embodiments, and the third embodiment
Is higher.

FIG. 5E shows changes in the holding voltage of the liquid crystal portion L_TGT with respect to the writing of the applied voltage from the writing circuit 104. According to FIG. 5D, the level of the first selection period is lower than in the first and second embodiments. Figure 5
The main part of (e) is enlarged and transcribed in FIG. 8 (d).

FIG. 5 (f) shows changes in the alignment state of the liquid crystal portion L_TGT. According to FIGS. 5 (e) and 8 (d), the rising in the first selection period is the same as in the first and second embodiments.
It is slower and faster than the third embodiment.

FIG. 5G shows the transmittance of incident light, which changes depending on the alignment state of the liquid crystal portion L_TGT. It corresponds to FIG.

As shown in FIG. 5B, in the (n + 1) th frame period, the detection circuit 102 detects and outputs the average luminance level in the (n + 1) th frame of the video signal input from the input terminal 101. The point of detection at the average luminance level is different from the other embodiments.

In the case of the above video signal, the liquid crystal portion L_
The output of the detection circuit 102 to the TGT becomes the contents of the central portion of the screen of the input video signal (the uppermost part of the screen in the second embodiment, the lowermost part of the screen in the third embodiment), and the highest luminance level as the video signal. 3/4 level (below,
75% luminance level).

As shown in FIG. 5C, the selection circuit 103 outputs the output of the detection circuit 102 to the writing circuit 104 in the first selection period of the (n + 1) th frame period.

At the timing TW1 at which the applied voltage is written to the liquid crystal portion L_TGT, the writing circuit 104 operates as shown in FIG.
As shown in (d), the applied voltage corresponding to the 75% luminance level as the video signal is written. At this time, the liquid crystal portion L_TGT is in an alignment state corresponding to the lowest luminance level, as shown in FIG.

At the timing TW1, the charge capacity of the liquid crystal portion L_TGT immediately before the applied voltage is written is c_B.
K, the applied voltage to be written is v_OBJ4, and
Assuming that the charge capacity is c_BO4 and the holding voltage is v_CNV41 when the liquid crystal portion L_TGT completely responds to the writing of the applied voltage at the timing TW1, the charge amount q_BO4 calculated by q_BO4 = c_BK · v_OBJ4 is obtained. Since it has been accumulated in the liquid crystal portion L_TGT and c_BO4> c_BK, it is assumed that v_CNV41 <v_OBJ4 from the law of conservation of charge.

As shown in FIG. 5C, the selection circuit 103 selects the n + 1th frame of the video signal input from the input terminal 101 in the second selection period after the timing TW1 in the n + 1th frame period. The contents for one frame period are output to the writing circuit 104.

At timing TW2 in the second selection period in which the writing circuit 104 writes the applied voltage to the liquid crystal portion L_TGT, as shown in FIG. 5D, the application corresponding to the highest luminance level as the video signal is performed. A voltage is written in the liquid crystal portion, which is v_OBJ1 in the description of the image display device according to the first embodiment.

Therefore, the charge capacity of the liquid crystal portion L_TGT immediately before writing the applied voltage at the timing TW2 is c_BG4, and the charge capacity when the liquid crystal portion L_TGT converges in response to the writing of the applied voltage at the timing TW2. And holding voltage are c_GO4 and v_C, respectively.
Assuming NV42, the charge amount q_GO4 calculated by q_GO4 = c_BG4 · v_OBJ1 is obtained by writing the applied voltage at the timing TW2 to the liquid crystal portion L_TG.
It has been accumulated in T.

As described above, the charge capacity of the liquid crystal portion L_TGT has a larger value as it becomes an alignment state corresponding to a higher brightness level, and therefore c_BG4> c_BK q_GO4> q_BO4. Therefore, c_GO4> c_BO4 v_CNV42> v_CNV41. Is supposed to be.

Here, the applied voltage v_OBJ corresponding to the video signal level to be displayed on the liquid crystal portion L_TGT.
1 is written only once at the timing TW1 in the image display device of the first embodiment, and is written at the timing TW2 after the first selection period in the image display device of the fourth embodiment. Think about.

The charge capacity c_BK at the timing TW1 in the image display device of the first embodiment and the fourth embodiment.
As described above, the charge capacity c_BG4 at the timing TW2 in the image display device has the relationship of c_BG4> c_BK.

In both cases, the same applied voltage v_O
Since BJ1 is written, the charge q_BO1 accumulated in the liquid crystal part L_TGT at the timing TW1 in the image display device of the first embodiment and the charge q_BO1 accumulated in the liquid crystal part L_TGT at the timing TW2 in the image display device of the fourth embodiment. The relationship with q_BO4 is q_GO4> q_BO1. Therefore, it can be said that the charge capacities and the holding voltages after the respective responses converge are c_GO4> c_BO1 v_CNV42> v_CNV11.

That is, as shown in FIGS. 5E and 8D, the write circuit 104 for the liquid crystal portion L_TGT.
Compared with the case where the writing of the applied voltage is performed only once at the timing TW1 in the image display device of the first embodiment, the writing of the applied voltage is performed twice at the timing TW1 and the timing TW2 in the image display device of the fourth embodiment. Better
The difference between the written applied voltage and the holding voltage after the response has converged becomes small, and as shown in FIG. 5 (f), the liquid crystal portion L_TGT is aligned with the desired alignment state with respect to the applied voltage. , The response converges to a closer state. As a result, as shown in FIG. 5G, the liquid crystal portion L_TGT has improved transmittance.

Writing circuit 10 for liquid crystal portion L_TGT
4, the applied voltage is written in the image display device of the first embodiment only at the timing TW1, the transmittance of the liquid crystal portion L_TGT is r11, the display brightness is Y11, and the image of the fourth embodiment is displayed. Assuming that the transmittance of the liquid crystal portion L_TGT obtained at the timing TW1 and the timing TW2 on the display device is r42 and the display brightness is Y42, r42> r11, and r11 is 70%, r42 is 85%, If the brightness of the light source is the same, it follows that Y11: Y42 = 70: 85, and thus Y42 is brighter. Therefore, in the image display device of the fourth embodiment, the brightness of the light source is L11 when the applied voltage is written to the liquid crystal portion L_TGT by the writing circuit 104 only at the timing TW1 in the image display device of the first embodiment. When the brightness of the light source at the timing TW1 and the timing TW2 is L42, Y42 can be equal to Y11 if L11: L42 = 85: 70.

The light source control circuit 106 controls the liquid crystal part L_TG.
The degree of improvement in the transmittance of T is v_CNV11 and v_CNV4.
The brightness of the light source 105 is lowered according to the degree of improvement in the transmittance determined by the difference between the two, and the power consumption is controlled to be reduced. The v_CNV11 and v_CNV42 can be easily calculated using the video signal input from the input terminal 101 and the detection level input from the detection circuit 102, as described in the description of the image display device according to the first embodiment. It is a thing.

Further, the light source control circuit 106 includes a liquid crystal portion L.
The light source 105 is turned off during the first selection period, which is a period in which the transmittance of _TGT is small, and is turned on during the second selection period, and the extinguishing period and the lighting period are alternately repeated. The light source 105 emits light to the liquid crystal portion L_TGT by changing the brightness of lighting by the above control from the light source control circuit 106. As a result, the liquid crystal part L_TGT changes the amount of light incident from the light source 105 by the improved transmissivity by writing the applied voltage twice, and the input terminal 1
An image corresponding to the video signal input from 01 can be displayed.

Although the above description focuses on the liquid crystal portion L_TGT, it is obvious that a part of the liquid crystal panel 107 corresponding to any pixel can be similarly described.

Therefore, as described above, according to the present embodiment, the same effect as in the case of the first embodiment can be obtained. That is, with respect to the liquid crystal panel 107, the first circuit including the detection circuit 102, the selection circuit 103, and the writing circuit 104.
By writing the applied voltage twice during the selection period of 2 and the selection period of 2, the transmittance of the liquid crystal panel 107 can be improved. Therefore, even if the brightness of the light source 105 is lowered, the liquid crystal panel 107 is still connected to the input terminal 101.
The image corresponding to the video signal input from can be displayed with sufficient brightness. That is, it is possible to realize an image display device that can reduce the power consumption of the light source 105.

(Fifth Embodiment) Next, an image display device according to a fifth embodiment of the present invention will be described. As for the configuration of the image display device of the present embodiment, the configuration of FIG. 1 in the case of the first embodiment is applied. However, in the image display device of the fifth embodiment, the detection circuit 102 outputs the highest luminance level as a video signal to the selection circuit 103. The highest luminance level as the video signal here is different from the highest luminance level detected every moment of the input video signal. It is the maximum luminance level of the video signal itself, which is predetermined in the specifications of the image display device.

Regarding the operation of the image display device of the fifth embodiment, as in the case of the image display device of the first embodiment, pay attention to a part L_TGT of the liquid crystal panel 107 corresponding to one pixel at the top of the screen. And explain.

FIG. 6 is a timing chart showing an example of response of liquid crystal in the image display device of the fifth embodiment.

FIG. 6A shows a video signal input from the input terminal 101, and this video signal is the same as that in FIG. 2A in the first embodiment.

FIG. 6B shows the detection level output of the detection circuit 102, FIG. 6C shows the selection output of the selection circuit 103, and FIG. 6D shows the output of the writing circuit 104.

FIG. 6E shows a change in the holding voltage of the liquid crystal portion L_TGT with respect to the writing of the applied voltage from the writing circuit 104, and FIG. 6F shows a change in the alignment state of the liquid crystal portion L_TGT. The main part of FIG. 6 (e) is enlarged and transferred to FIG. 8 (e).

FIG. 6G shows the transmittance with respect to the incident light, which changes depending on the alignment state of the liquid crystal portion L_TGT.

As shown in FIG. 6B, in the (n + 1) th frame period, the detection circuit 102 outputs the highest luminance level as a video signal with respect to the video signal input from the input terminal 101. This is not the highest brightness level detected from the video signal in the (n + 1) th frame but the predetermined highest brightness level of the video signal itself.

In the case of the above video signal, the liquid crystal portion L_
The output of the detection circuit 102 with respect to the TGT is the same as the content of the input video signal at the top of the screen.

As shown in FIG. 6C, the selection circuit 103 outputs the output of the detection circuit 102 to the writing circuit 104 in the first selection period of the (n + 1) th frame period.

At the timing TW1 of writing the applied voltage to the liquid crystal portion L_TGT, the writing circuit 104 is set to the state shown in FIG.
As shown in (d), the applied voltage corresponding to the highest brightness level as the video signal is written. At this time, the liquid crystal portion L_TGT is in an alignment state corresponding to the lowest brightness level, as shown in FIG.

The charge capacity of the liquid crystal portion L_TGT immediately before the applied voltage is written at the timing TW1 is c_B.
K, the applied voltage to be written is v_OBJ5, and
Assuming that the charge capacity is c_BO5 and the holding voltage is v_CNV51 when the liquid crystal part L_TGT completely responds to the writing of the applied voltage at the timing TW1, the charge amount q_BO5 calculated by q_BO5 = c_BK · v_OBJ5 is obtained. Since it has been accumulated in the liquid crystal portion L_TGT and c_BO5> c_BK, it is assumed from the law of conservation of charge that v_CNV51 <v_OBJ5.

As shown in FIG. 6C, the selection circuit 103 selects the n + 1th frame of the video signal input from the input terminal 101 in the second selection period after the timing TW1 in the n + 1th frame period. The contents for one frame period are output to the writing circuit 104.

At timing TW2 in the second selection period in which the writing circuit 104 writes the applied voltage to the liquid crystal portion L_TGT, as shown in FIG. 6D, the application corresponding to the highest luminance level as the video signal is performed. A voltage is written in the liquid crystal portion, which is v_OBJ1 in the description of the image display device according to the first embodiment.

Therefore, the charge capacity of the liquid crystal portion L_TGT immediately before writing the applied voltage at this timing TW2 is c_BG5, and the charge capacity when the liquid crystal portion L_TGT converges in response to the writing of the applied voltage at the timing TW2. And holding voltage are c_GO5 and v_C, respectively.
Assuming NV52, the charge quantity q_GO5 calculated by q_GO5 = c_BG5 · v_OBJ1 is calculated by writing the applied voltage at the timing TW2 to the liquid crystal portion L_TG.
It has been accumulated in T.

As described above, the charge capacity of the liquid crystal portion L_TGT has a larger value as it becomes an alignment state corresponding to a higher brightness level, and therefore c_BG5> c_BK q_GO5> q_BO5. Therefore, c_GO5> c_BO5 v_CNV52> v_CNV51. Is supposed to be.

Here, the applied voltage v_OBJ corresponding to the video signal level to be displayed on the liquid crystal portion L_TGT.
1 is written only once at the timing TW1 in the image display device of the first embodiment, and is written at the timing TW2 after the first selection period in the image display device of the fifth embodiment. Think about.

The charge capacity c_BK at the timing TW1 in the image display device of the first embodiment and the fifth embodiment.
As described above, the charge capacity c_BG5 at the timing TW2 in the image display device has the relationship of c_BG5> c_BK.

In both cases, the same applied voltage v_O
Since BJ1 is written, the charge q_BO1 accumulated in the liquid crystal part L_TGT at the timing TW1 in the image display device of the first embodiment and the charge q_BO1 accumulated in the liquid crystal part L_TGT at the timing TW2 in the image display device of the fifth embodiment. The relationship with q_BO5 is q_GO5> q_BO1. Therefore, it can be said that the charge capacity and the holding voltage after the convergence of the respective responses are c_GO5> c_BO1 v_CNV52> v_CNV11.

That is, as shown in FIGS. 6E and 8E, the write circuit 104 for the liquid crystal portion L_TGT.
Compared with the case where the application of the applied voltage is performed only once at the timing TW1 in the image display apparatus of the first embodiment, the case where the application of the applied voltage is performed twice at the timing TW1 and the timing TW2 in the image display apparatus of the fifth embodiment Better
The difference between the applied voltage that has been written and the holding voltage after the response has converged becomes smaller, and as shown in FIG. , The response converges to a closer state. As a result, as shown in FIG. 6G, the liquid crystal portion L_TGT has improved transmittance.

Writing circuit 10 for liquid crystal portion L_TGT
4, the applied voltage is written in the image display device according to the first embodiment only at the timing TW1, the transmittance of the liquid crystal portion L_TGT is r11, the display brightness is Y11, and the image of the fifth embodiment is displayed. When the transmittance of the liquid crystal portion L_TGT obtained when the display device performs the timing TW1 and the timing TW2 is r52 and the display brightness is Y52, r52> r11, and r11 is 70% and r52 is 90%. If the brightness of the light source is the same, it follows that Y11: Y52 = 70: 90, and thus Y52 becomes brighter. Therefore, the writing of the applied voltage to the liquid crystal portion L_TGT by the writing circuit 104 is performed by the image display device of the first embodiment only at the timing TW1, the brightness of the light source is L11, and in the image display device of the fifth embodiment. When the brightness of the light source at the timing TW1 and the timing TW2 is L52, if Y11: L52 = 90: 70, then Y52 can be equal to Y11.

The light source control circuit 106 controls the liquid crystal portion L_TG.
The degree of improvement in the transmittance of T is v_CNV11 and v_CNV5.
The brightness of the light source 105 is lowered according to the degree of improvement in the transmittance determined by the difference between the two, and the power consumption is controlled to be reduced. The v_CNV 11 and v_CNV 52 can be easily calculated using the video signal input from the input terminal 101 and the detection level input from the detection circuit 102, as described in the description of the image display device according to the first embodiment. It is a thing.

Further, the light source control circuit 106 includes a liquid crystal portion L.
The light source 105 is turned off during the first selection period, which is a period in which the transmittance of _TGT is small, and is turned on during the second selection period, and the extinguishing period and the lighting period are alternately repeated. The light source 105 emits light to the liquid crystal portion L_TGT by changing the brightness of lighting by the above control from the light source control circuit 106. As a result, the liquid crystal part L_TGT changes the amount of light incident from the light source 105 by the improved transmissivity by writing the applied voltage twice, and the input terminal 1
An image corresponding to the video signal input from 01 can be displayed.

Although the above description focuses on the liquid crystal part L_TGT, it is clear that the part of the liquid crystal panel 107 corresponding to any pixel can be similarly described.

Therefore, as described above, according to the present embodiment, the same effect as that of the first embodiment can be obtained. That is, with respect to the liquid crystal panel 107, the first circuit including the detection circuit 102, the selection circuit 103, and the writing circuit 104.
By writing the applied voltage twice during the selection period of 2 and the selection period of 2, the transmittance of the liquid crystal panel 107 can be improved. Therefore, even if the brightness of the light source 105 is lowered, the liquid crystal panel 107 is still connected to the input terminal 101.
The image corresponding to the video signal input from can be displayed with sufficient brightness. That is, it is possible to realize an image display device that can reduce the power consumption of the light source 105.

(Sixth Embodiment) Next, an image display device according to a sixth embodiment of the present invention will be described. As for the configuration of the image display device of the present embodiment, the configuration of FIG. 1 in the case of the first embodiment is applied. However, in the image display device according to the sixth embodiment, the detection circuit 102 has the input terminal 1
01 in the approximately 1 scanning period of the video signal,
The same signal level as the video signal is output to the selection circuit 103. In addition, the selection circuit 103 is configured to display the first signal in the cycle for displaying an image in the approximately one scanning period of the video signal.
Of the detection level input from the detection circuit 102, the video signal input from the input terminal 101 is selected in the second selection period, and the selection result is output to the writing circuit 104. is there. Embodiments 1 to 5 above
In contrast to this, about 1 frame period is the reference, whereas in the present embodiment, about 1 scanning period is the reference.

A video signal for displaying an image is input from the input terminal 101. The video signal input from the input terminal 101 is input to the detection circuit 102, the selection circuit 103, and the light source control circuit 106. The detection circuit 102 is
The selection circuit 1 selects the same signal level as the video signal in approximately one scanning period of the video signal input from the input terminal 101.
03 and the light source control circuit 106. Selection circuit 1
Reference numeral 03 provides a first selection period and a second selection period in a period for displaying an image of approximately one scanning period of the video signal, and outputs a signal for one scanning period of the image in each selection period. In the first selection period, the detection level input from the detection circuit 102 is selected, and in the second selection period, the video signal input from the input terminal 101 is selected, and the writing circuit is selected. To 104.

The writing circuit 104 applies the applied voltage corresponding to the signal input from the selection circuit 103 to the liquid crystal panel 107.
Output to. The light source control circuit 106 controls the brightness of the light source 105 based on the video signal input from the input terminal 101 and the detection level input from the detection circuit 102.
Under the control of the light source control circuit 106, the light source 105 emits light to the liquid crystal panel 107 by changing the brightness of lighting. The liquid crystal panel 107 has a plurality of scanning lines and a plurality of display signal lines arranged so as to intersect with each other, and pixel electrodes arranged in a matrix corresponding to the intersections of the scanning lines and the display signal lines. And a liquid crystal element connected to the pixel electrode. The liquid crystal panel 107 changes the amount of light incident from the light source 105 according to the transmittance obtained by the writing circuit 104, displays a video signal input from the input terminal 101, and displays an image corresponding to the input signal. To do.

Regarding the operation of the image display device of the sixth embodiment, as in the case of the image display device of the first embodiment,
Liquid crystal panel 10 corresponding to the leftmost pixel of a certain screen
A description will be given by focusing on a part L_TGT of 7.

FIG. 7 is a timing chart showing an example of liquid crystal response in the image display device of the sixth embodiment.
While one frame period is the reference in FIGS. 2 to 6, one scanning period is the reference in FIG. 7. This becomes clear by describing "nth line, (n + 1) th line" at the top of the figure.

FIG. 7A shows a video signal input from the input terminal 101. In this video signal, the contents of the lowest luminance level as the video signal are uniformly applied to the nth line and the nth line.
In the +1 line, the content changes from the highest luminance level as a video signal to the intermediate luminance level as a video signal from the left to the right of the image.

FIG. 7B shows the output of the detection level of the detection circuit 102. As described above, the detection circuit 102 outputs the same signal level as the input video signal detected in one frame period, but in this example, like the video signal changing from P1 to Q1 in FIG. 7A. Output a changing signal.

FIG. 7C shows the selection output of the selection circuit 103. In the first selection period, a signal obtained by compressing one frame period of the detection signal changing from P1 to Q1 in FIG. 7B into a 1/2 time width is output, and in the second selection period, FIG.
Then, a signal obtained by compressing one frame period of the video signal of 1 to 1/2 time width is output.

FIG. 7D shows the output of the writing circuit 104. The signal of FIG. 7C is sampled and output at timing TW1 and timing TW2.

FIG. 7E shows a change in the holding voltage of the liquid crystal portion L_TGT with respect to the writing of the applied voltage from the writing circuit 104, and FIG. 7F shows a change in the alignment state of the liquid crystal portion L_TGT. The main part of FIG. 7 (e) is enlarged and transferred to FIG. 8 (f).

FIG. 7G shows the transmittance of incident light, which changes depending on the alignment state of the liquid crystal portion L_TGT.

First, as shown in FIG. 7B, the (n + 1) th
During the line period, the detection circuit 102 has the input terminal 101
The same signal as the input video signal is output with respect to the video signal input from. The selection circuit 103 is shown in FIG.
As shown in (1), in the first selection period in the (n + 1) th line period, the contents for one line period of the detection circuit 102 are output to the writing circuit 104.

At the timing TW1 in the first selection period for writing the applied voltage to the liquid crystal portion L_TGT, the writing circuit 104 corresponds to the highest luminance level as the video signal, as shown in FIG. 7 (d). The applied voltage is shown in Fig. 7 (f).
As shown in, the writing is performed on the liquid crystal portion L_TGT in the alignment state corresponding to the lowest brightness level.

At this timing TW1, the charge capacity of the liquid crystal portion L_TGT immediately before the applied voltage is written is c_B.
K, the applied voltage to be written is v_OBJ6, and
Assuming that the charge capacity is c_BO6 and the holding voltage is v_CNV61 when the liquid crystal part L_TGT completely responds to the writing of the applied voltage at the timing TW1, the charge amount q_BO6 calculated by q_BO6 = c_BK · v_OBJ6 is obtained. It is stored in the liquid crystal portion L_TGT. Further, since c_BO6> c_BK from the relationship between the alignment state and the charge capacity due to the response of the liquid crystal portion L_TGT described in the image display device of the first embodiment, it is assumed that v_CNV61 <v_OBJ6 from the law of conservation of charge. .

As shown in FIG. 7C, the selection circuit 103 selects the n + 1th line of the video signal input from the input terminal 101 in the second selection period after the timing TW1 in the n + 1th line period. The content for one line period is output to the writing circuit 104.

At timing TW2 in the second selection period in which the writing circuit 104 writes the applied voltage to the liquid crystal part L_TGT, as shown in FIG. 7D, the application corresponding to the highest luminance level as the video signal is performed. A voltage will be written to the liquid crystal portion, which is the same as v_OBJ6 above.

Therefore, the charge capacity of the liquid crystal portion L_TGT immediately before writing the applied voltage at the timing TW2 is c_BG6, and the charge capacity when the liquid crystal portion L_TGT converges in response to the writing of the applied voltage at the timing TW2. And holding voltage are c_GO6 and v_C, respectively.
Assuming NV62, the charge amount q_GO6 calculated by q_GO6 = c_BG6 · v_OBJ6 is obtained by writing the applied voltage at the timing TW2 to the liquid crystal part L_TG.
It has been accumulated in T.

As described above, the charge capacity of the liquid crystal portion L_TGT becomes larger as the orientation state corresponding to the higher brightness level increases, and therefore c_BG6> c_BK q_GO6> q_BO6. Therefore, c_GO6> c_BO6 v_CNV62> v_CNV61. Is supposed to be.

That is, as shown in FIGS. 7E and 8F, the write circuit 104 for the liquid crystal portion L_TGT.
The applied voltage is written between the applied voltage and the holding voltage after the response converges more twice when the applied voltage is written once at timing TW1 than when the applied voltage is written twice at timing TW1. 7F, the liquid crystal part L_TGT comes to have a response convergence to a state closer to the alignment state desired with respect to the applied voltage, as shown in FIG. As a result,
As shown in (g), the liquid crystal portion L_TGT has improved transmittance.

Writing circuit 10 for liquid crystal part L_TGT
4 is the liquid crystal portion L_TGT obtained when the applied voltage is written only at the timing TW1, the display brightness is Y61, and the liquid crystal portion L_T obtained when the timing TW1 and the timing TW2 are obtained.
If the GT transmittance is r62 and the display brightness is Y62, then r62> r61, and if r61 is 70%, r62 is 90%, and the brightness of the light source is the same, then Y61: Y62 = 70: 90 Therefore, it can be seen that Y62 becomes brighter. Therefore, the brightness of the light source when writing the applied voltage to the liquid crystal portion L_TGT by the writing circuit 104 only at the timing TW1 is L61, and the brightness of the light source when performing the writing at the timing TW1 and the timing TW2 is L62. At this time, if L61: L62 = 90: 70, Y62 can be made equal to Y61.

At this time, since the brightness of the light source can be reduced by about 22%, the power consumption of the light source can be reduced accordingly.

The light source control circuit 106 controls the liquid crystal part L_TG.
The degree of improvement in the transmittance of T is v_CNV61 and v_CNV6.
The brightness of the light source 105 is lowered according to the degree of improvement in the transmittance determined by the difference between the two, and the power consumption is controlled to be reduced. The v_CNV 61 and v_CNV 62 can be easily calculated using the video signal input from the input terminal 101 and the detection level input from the detection circuit 102, as described in the description of the image display device according to the first embodiment. It is a thing.

Further, the light source control circuit 106 includes a liquid crystal portion L.
The light source 105 is turned off during the first selection period, which is a period in which the transmittance of _TGT is small, and is turned on during the second selection period, and the extinguishing period and the lighting period are alternately repeated.

As described above, the light source 105 is turned on only during the period when the transmittance of the liquid crystal portion L_TGT is good, so that the liquid crystal portion L is effectively turned on during the lighting period of the light source 105.
The brightness of _TGT is obtained, and the power consumption of the light source 105 can be further reduced.

The light source 105 emits light to the liquid crystal portion L_TGT by changing the brightness of its lighting by the above control from the light source control circuit 106. As a result, the liquid crystal portion L_TGT changes the amount of light incident from the light source 105 according to the transmittance improved by writing the applied voltage twice, and an image corresponding to the video signal input from the input terminal 101. Can be displayed.

Although the above description focuses on the liquid crystal portion L_TGT, it is obvious that a part of the liquid crystal panel 107 corresponding to any pixel can be similarly described.

Therefore, as described above, according to the present embodiment, the same effect as in the case of the first embodiment can be obtained. That is, with respect to the liquid crystal panel 107, the first circuit including the detection circuit 102, the selection circuit 103, and the writing circuit 104.
By writing the applied voltage twice during the selection period of 2 and the selection period of 2, the transmittance of the liquid crystal panel 107 can be improved. Therefore, even if the brightness of the light source 105 is lowered, the liquid crystal panel 107 is still connected to the input terminal 101.
The image corresponding to the video signal input from can be displayed with sufficient brightness. That is, it is possible to realize an image display device that can reduce the power consumption of the light source 105.

In the image display device of the sixth embodiment based on the one scanning period, the operation of the detection circuit 102 is changed from the input terminal 101 described in the first embodiment based on the one frame period. The description has been given assuming that the same signal level as that of the input video signal is output. However, 1
As a development of the sixth embodiment based on the scanning period, the operation of the detection circuit 102 may be the detection content described in any of the second to fifth embodiments based on the one frame period, and any operation may be performed. Even in this case, it is obvious that an image display device that can reduce the power consumption of the light source 105 can be realized.

In the above description, the case of a normally black liquid crystal panel has been described, but the present invention can be similarly applied to a case of a normally white liquid crystal panel.

[0223]

According to the present invention, the following effects are exhibited. That is, in the present invention, the writing is performed on the light modulation element of the light receiving type light modulation means having the dielectric anisotropy, which has the property that the applied voltage written and the holding voltage after the response converges. When the plugging means applies the voltage, the first
Selection period and a second selection period are provided, a voltage according to the characteristic level of the input video signal is preliminarily applied during the first selection period, and a voltage according to the signal level of the input video signal is determined during the second selection period. Voltage is applied in earnest. That is,
Preliminary application is performed prior to full-scale application to bring the alignment state of the light modulation element immediately before full-scale application close to the desired alignment state in advance. As a result, it is possible to converge the response of the light modulation element to a state closer to the desired equilibrium state, and it is possible to improve the modulation rate of the light receiving type light modulation means. In addition, the illumination control means, based on the level of the input video signal and the detection signal level by the detection means, corresponding to the difference between the balanced voltage level of the result of preliminary application and the balanced voltage level of the result of full-scale application, That is, the brightness of the illumination means is adaptively controlled according to the degree of improvement of the modulation rate.
The brightness of the illumination means can be further lowered to obtain the required display brightness, and the power consumption can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image display device according to first to sixth embodiments of the present invention.

FIG. 2 is a timing chart illustrating the operation of the image display device according to the first embodiment of the present invention.

FIG. 3 is a timing chart illustrating the operation of the image display device according to the second embodiment of the present invention.

FIG. 4 is a timing chart illustrating the operation of the image display device according to the third embodiment of the present invention.

FIG. 5 is a timing chart explaining the operation of the image display device according to the fourth embodiment of the present invention.

FIG. 6 is a timing chart illustrating the operation of the image display device according to the fifth embodiment of the present invention.

FIG. 7 is a timing chart illustrating the operation of the image display device according to the sixth embodiment of the present invention.

FIG. 8 is a timing chart in which an essential part of (e) in each of FIGS. 2 to 7 is enlarged and transcribed.

[Explanation of symbols]

101 input terminal 102 detection circuit (detection means) 103 selection circuit (selection means) 104 writing circuit (writing means) 105 Light source (illumination means) 106 Light source control circuit (lighting control means) 107 Liquid crystal panel (light receiving type light modulating means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G09G 3/34 G09G 3/34 J (72) Inventor Takahiro Kobayashi 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial In-house F-term (reference) 2H093 NA06 NB29 NC42 NC52 ND09 ND39 5C006 AA01 AA16 AC11 AF42 AF44 AF45 AF46 AF51 AF52 AF53 AF64 AF69 AF71 BB16 BB29 BC03 BC11 BF02 BF14 BF24 BF44 EA01 FA14 FA16 FA20 FA47 DD08BB05 FA05 508080 EE19 EE29 FF11 GG08 GG12 JJ02 JJ04 KK02 KK04 KK43

Claims (11)

[Claims] 1. An image display device for displaying an input video signal on a light-receiving optical modulation means made of a material having a dielectric anisotropy, wherein a characteristic of the video signal is expressed with the video signal as an input. A detection means for outputting a level; a first selection period in which the video signal and the output of the detection means are input and the output of the detection means is selected and output; and a second selection period for selecting and outputting the video signal Selection means having a selection period of, a writing means for receiving the output of the selection means as an input and outputting a voltage corresponding to the signal level of the input to apply to the light-receiving optical modulator, the light-receiving optical An image display device comprising: an illumination unit that emits light to a modulation unit; and an illumination control unit that receives the video signal and the output of the detection unit as input and controls the brightness of the illumination unit. 2. The image display device according to claim 1, wherein the light-receiving-type light modulation means has a light modulation element formed of a liquid crystal element. 3. The light-receiving type light modulating means is arranged in a matrix corresponding to a plurality of scanning lines and a plurality of display signal lines arranged so as to intersect with each other, and an intersection of the scanning lines and the display signal line. The image display device according to claim 1, wherein the image display device is configured by a pixel electrode disposed in the pixel electrode and a light modulation element connected to the pixel electrode. 4. The detecting means outputs a level representing the characteristic of the video signal in the approximately 1 frame period, and the selecting means outputs the level in the cycle for displaying the image in the approximately 1 frame period of the video signal. A first selection period in which the output of the detection means is selected and a signal for approximately one frame period is output, and a period after the first selection period in the same period as the period for displaying an image in the approximately one frame period, The image display device according to claim 1, further comprising a second selection period for selecting the video signal and outputting a signal for approximately one frame period. 5. The detection means outputs a level representing a characteristic of the video signal in the approximately 1 scanning period, and the selection means in the cycle for displaying an image of the video signal in the approximately 1 scanning period. A first selection period for selecting an output of the detection means and outputting a signal for approximately one scanning period;
And a second selection period for selecting the video signal and outputting a signal for approximately one scanning period after the first selection period in the same period as the period for displaying an image in the approximately one scanning period. The image display device according to claim 1, wherein: 6. The image display device according to claim 1, wherein the illumination control unit alternately repeats a lighting period and a non-lighting period. 7. The image display device according to claim 1, wherein the detection unit outputs the same signal as the input video signal as a feature of the video signal. . 8. The detection means detects and outputs a maximum luminance level of an input video signal as a characteristic of the video signal, and outputs the detected maximum brightness level. Image display device. 9. The detecting means detects and outputs a minimum luminance level of an input video signal as a characteristic of the video signal, and outputs the detected minimum brightness level. Image display device. 10. The detection means detects and outputs an average luminance level of an input video signal as a feature of the video signal, and outputs the average brightness level. Image display device. 11. The image display device according to claim 1, wherein the detection unit outputs a maximum luminance level as a video signal as a characteristic of the video signal.