WO2012124592A1

WO2012124592A1 - Liquid crystal display device and three-dimensional image display system provided with same

Info

Publication number: WO2012124592A1
Application number: PCT/JP2012/055935
Authority: WO
Inventors: 亮山川
Original assignee: シャープ株式会社
Priority date: 2011-03-15
Filing date: 2012-03-08
Publication date: 2012-09-20

Abstract

A liquid crystal display device (1) is capable of displaying a three-dimensional image by switching an image for a right eye and an image for a left eye each frame for display, and is provided with: a sub-frame division unit (42a) that divides one frame into a plurality of sub-frames; a gradation determination unit (42b) that determines respective gradations of the plurality of sub-frames such that the average value of the gradations of the plurality of sub-frames in a pixel (34) is a prescribed gradation to be displayed by the pixel (34) in the one frame; and a polarity reversion/amplification unit (42c) that reverses the polarity of a voltage applied to the pixel (34) each frame in response to each of the gradations for the respective sub-frames determined by the gradation determination unit (42b). The gradation determination unit (42b) determines the respective gradations of the plurality of sub-frames such that the gradation in a fourth sub-frame period (d) that is the last among the plurality of sub-frames is the smallest. Thus, liquid crystal is driven on AC, multi-gradation display is performed with low power consumption, and crosstalk caused by delay response of liquid crystal molecules is prevented.

Description

Liquid crystal display device and stereoscopic image display system including the same

The present invention relates to a liquid crystal display device capable of displaying a stereoscopic video and a stereoscopic video display system including the same.

In recent years, a frame rate control method (hereinafter referred to as FRC method) has been developed as one of driving methods for liquid crystal panels.

In the FRC method, in a case where an intermediate gradation between the first gradation and the second gradation is displayed on a certain pixel, the first gradation is displayed on the pixel in a certain frame, and the second gradation is displayed on the next frame. It is a method of displaying.

By switching between the first gradation and the second gradation in a short time, an intermediate gradation between the first gradation and the second gradation is displayed on the pixel to the human eye. It is recognized. By the FRC method, an increase in power consumption due to an increase in the number of circuits accompanying an increase in the number of gradations can be prevented.

In addition, the liquid crystal panel is generally driven by an alternating current to prevent deterioration of liquid crystal characteristics.

Patent Document 1 discloses a driving method using the FRC method while AC driving a liquid crystal panel.

FIG. 7 is a diagram for explaining a gradation display method of a liquid crystal display device using the FRC method described in Patent Document 1. FIG. 7 shows the voltage applied to the liquid crystal of a certain pixel for each reference period.

In the first reference period, a positive voltage V2 corresponding to the second gradation is applied to the liquid crystal in the first frame. In the second reference period, a negative voltage V2 corresponding to the second gradation is applied to the liquid crystal in the second frame.

In the third reference period, a negative voltage −V2 corresponding to the second gradation is applied to the liquid crystal in the second frame. In the fourth reference period, a positive voltage + V2 corresponding to the second gradation is applied to the liquid crystal in the third frame.

In this way, the liquid crystal is AC driven while using the FRC method by canceling the positive polarity applied voltage and the negative polarity applied voltage in the first to fourth reference cycles.

JP 2003-66915 A (published on March 5, 2003)

Here, as a driving method of a liquid crystal panel capable of displaying a stereoscopic (3D) image, a frame sequential method is generally used.

FIG. 8 is a diagram showing luminance change of an ideal frame sequential pixel. FIG. 9 is a diagram illustrating a luminance change of an actual frame sequential pixel. 8 and 9, L represents the left-eye video display period, and R represents the right-eye video display period. The vertical axis represents the voltage applied to the pixel.

In the frame sequential method, the driving of the liquid crystal molecules is controlled so that the image for the right eye and the image for the left eye are alternately displayed on the liquid crystal display panel for each frame. Then, in accordance with the display image, a stereoscopic video is displayed by performing opening / closing control of the right-eye liquid crystal shutter and the left-eye liquid crystal shutter.

As shown in FIG. 8, it is ideal that the liquid crystal molecules change digitally when the voltage for the right eye image and the voltage for the left eye image are alternately applied to the pixels.

However, as shown in FIG. 9, since the response speed of liquid crystal molecules is actually limited, when the right-eye video voltage and the left-eye video voltage are alternately applied to the pixel, the voltage applied to the pixel is It changes gently. Along with this, the luminance change of the pixel also changes gently.

As a result, for example, as shown in the shaded portion of FIG. 9, the falling of the right-eye video voltage enters the left-eye video display period, or the rising of the left-eye video voltage enters the right-eye video display period.

9 indicates that a desired luminance is not obtained immediately after switching between the right-eye video voltage and the left-eye video voltage, and crosstalk occurs due to this luminance difference.

The present invention has been made to solve the above-described problems, and its object is to drive a liquid crystal by alternating current to perform multi-gradation display with low power consumption and to occur with a response delay of liquid crystal molecules. It is to prevent crosstalk.

In order to solve the above problems, the liquid crystal display device of the present invention is a liquid crystal display device capable of displaying a stereoscopic image by switching between a right-eye image and a left-eye image for each frame. Sub-frame dividing means for dividing one frame into a plurality of sub-frames, and an average value of gradations of the plurality of sub-frames in the pixel of interest is a prescribed gradation to be displayed by the pixel of interest in the one frame. The gradation determining means for determining each of the gradations of the plurality of subframes and the application to the target pixel corresponding to each of the gradations for each of the subframes determined by the gradation determining means. Polarity reversing means for reversing the polarity of the applied voltage for each frame, and the gradation determining means includes the plurality of sub-frames so that the gradation of the last sub-frame is minimized. It is characterized by determining the respective gradations of the sub-frame.

According to the above configuration, one frame is divided into a plurality of subframes by the subframe dividing means. Then, the gradation determining means is configured to output the plurality of sub-subpixels so that an average value of gradations of the plurality of sub-frames in the pixel of interest is a predetermined gradation to be displayed by the pixel of interest in the one frame. Each frame gradation is determined.

Thus, the specified gradation that the pixel of interest should display in one frame can be displayed by a combination of gradations of the plurality of subframes. For this reason, an increase in the number of circuits accompanying the increase in the number of gradations can be suppressed, and a multi-gradation display can be performed with low power consumption.

According to the above configuration, the polarity inversion means inverts the polarity of the voltage applied to the pixel of interest for each frame corresponding to each gradation for each subframe determined by the gradation determination means. Let As a result, each of the gradations for each of the subframes determined by the gradation determination unit can be displayed on the target pixel while the target pixel is AC driven. For this reason, characteristic deterioration of the liquid crystal can be prevented.

Furthermore, according to the above configuration, the gradation determination means determines the gradation of each of the plurality of subframes so that the gradation of the last subframe among the plurality of subframes becomes the smallest.

Therefore, among the absolute values of the voltages applied to the target pixel corresponding to the gradations of the plurality of subframes, the target pixel corresponding to the gradation of the last subframe adjacent to the next frame. The absolute value of the voltage applied to is the smallest.

As a result, even if the polarity of the voltage applied to the pixel of interest is inverted between the first frame and the next frame, the response amount of the liquid crystal molecules accompanying the application of the voltage can be reduced. It is possible to prevent crosstalk that occurs with the response delay.

The liquid crystal display device of the present invention is a liquid crystal display device capable of displaying a stereoscopic image by switching between a right-eye image and a left-eye image for each frame, and one frame is divided into a plurality of subframes. The subframe dividing means for dividing, and the average value of the gradations of the plurality of subframes in the pixel of interest is the prescribed gradation to be displayed by the pixel of interest in the one frame. Inversion of the polarity of the voltage applied to the pixel of interest for each frame corresponding to each of the gradations for each subframe determined by the gradation determination means and gradation determination means for determining each gradation Polarity reversing means for causing the gradation determining means to reduce the gradation of the last subframe among the plurality of subframes so that the gradation of the last subframe is minimized. To determine.

As a result, the liquid crystal is AC driven to perform multi-gradation display with low power consumption, and the effect of preventing crosstalk caused by the response delay of the liquid crystal molecules is exhibited.

It is a block diagram showing the structure of the three-dimensional video display system of 1st Embodiment. It is a figure showing the structure of the liquid crystal display panel with which the liquid crystal display device of 1st Embodiment is provided. It is a figure for demonstrating the applied voltage for every flame | frame to a pixel. It is a figure showing the gradation determination table for sub-frames stored in the table storage part. It is a block diagram showing the structure of the three-dimensional video display stem of 2nd Embodiment. It is a figure for demonstrating the applied voltage for every flame | frame to a pixel. It is a figure explaining the gradation display method of the liquid crystal display device using the conventional FRC method. It is a figure showing the luminance change of the pixel of an ideal frame sequential system. It is a figure showing the luminance change of the pixel of an actual frame sequential system.

Hereinafter, embodiments of the present invention will be described in detail.

[First Embodiment]
(Configuration of the liquid crystal display device 10)
The configuration of the liquid crystal display device 10 will be described with reference to FIGS.

FIG. 2 shows a configuration of the liquid crystal panel 30 constituting the liquid crystal display device 10.

The liquid crystal panel 30 is a liquid crystal panel arranged in the liquid crystal display device 10 so that a stereoscopic video can be displayed by switching and displaying a right-eye video and a left-eye video for each frame.

The liquid crystal panel 30 includes a source driver 31, a gate driver 32, and a pixel array 33.

The liquid crystal panel 30 includes a TFT substrate on which display pixel electrodes and TFT elements for applying a voltage to the pixel electrodes are arranged in a matrix, and a counter substrate on which common electrodes and color filters are arranged to face the pixel electrodes. Are arranged so as to face each other through the liquid crystal layer.

The pixel array 33 includes a plurality of pixels 34 arranged in a matrix. The pixel 34 includes the pixel electrode and the TFT element, a common electrode, and a liquid crystal layer disposed between the pixel electrode and the common electrode.

The source driver (horizontal drive circuit) 31 is disposed along the upper side of the pixel array 33, for example, and the gate driver (vertical drive circuit) 32 is disposed along the left side of the pixel array 33.

The source driver 31 performs D / A conversion on the display data latched in units of one line in the horizontal direction and applies the grayscale voltage to the pixel electrode of the pixel 34 from the upper side to the lower side (that is, in the vertical direction) in units of one horizontal line. Write sequentially.

The liquid crystal molecules in the pixel 34 are driven by the potential difference between the pixel electrode and the common electrode generated by the gradation voltage. By controlling the driving of the liquid crystal molecules for each pixel 34, the transmission of the pixel 34 is controlled. As a result, an image that the user can appreciate can be displayed on the pixel array 33.

FIG. 1 is a block diagram showing a configuration of a stereoscopic video display system 1 according to the present embodiment.

The stereoscopic image display system 1 is a liquid crystal display device capable of displaying a stereoscopic (3D) image by a frame sequential method.

As shown in FIG. 1, the stereoscopic video display system 1 includes a liquid crystal display device 10 and light-shielding glasses 20. The liquid crystal display device 10 includes a liquid crystal panel 30 and a liquid crystal drive circuit 40.

The liquid crystal driving circuit 40 sequentially outputs a right-eye video signal and a left-eye video signal having different polarities for each frame to the liquid crystal panel 30, thereby displaying a stereoscopic video on the pixel array 33 of the liquid crystal panel 30. Is.

The liquid crystal driving circuit 40 includes a video processing unit 41, a gradation control unit 42, a table storage unit 44, and a shutter control unit 45. The video processing unit 41 includes a gradation signal generation unit 41a and a left / right identification signal generation unit (left / right identification signal generation means) 41b. The gradation control unit 42 includes a subframe dividing unit (subframe dividing unit) 42a, a gradation determining unit (gradation determining unit) 42b, and a polarity inverting / amplifying unit (polarity inverting unit) 42c. Yes.

The video processing unit 41 obtains a video signal D including the right-eye video signal DR and the left-eye video signal DL from the outside.

The gradation signal generation unit 41a sequentially calculates the gradation for each frame of each pixel 34 of the right-eye video and the left-eye video from the video signal D acquired by the video processing unit 41. The gradation calculated by the gradation signal generation unit 41a is a prescribed gradation that a certain pixel 34 should display in one frame in order to display an image. This specified gradation is referred to as a specified gradation.

The gradation signal generation unit 41a sequentially outputs the right-eye video signal DR1 and the left-eye video signal DL1 that are signals indicating the specified gradation for each frame of each pixel 34 to the gradation control unit 42.

The left / right identification signal generation unit 41b generates a left / right identification signal RL indicating whether the signal output from the gradation signal generation unit 41a to the gradation control unit 42 is the right-eye video signal DR1 or the left-eye video signal DL1. To do. That is, the left / right identification signal RL is a signal including information indicating whether the stereoscopic video displayed on the liquid crystal display device 10 is a right-eye video or a left-eye video.

The left / right identification signal generation unit 41b outputs the generated left / right identification signal RL together with the output of the right-eye video signal DR1 or the left-eye video signal DL1 of the gradation signal generation unit 41a to the gradation control unit 42 and the shutter control. To the unit 45.

The subframe dividing unit 42a divides one frame into a plurality of subframes. In the present embodiment, the subframe dividing unit 42a divides one frame into four.

Note that the number of subframes into which one frame is divided is not limited to four, and may be three or more. Further, it may be divided so as to correspond to a sub-frame gradation determination table stored in a table storage unit 44 described later.

The gradation determining unit 42b determines the gradation of each subframe divided by the subframe dividing unit 42a.

The gradation determination unit 42b has a plurality of gradations so that an average value of gradations of a plurality of subframes in a certain pixel (target pixel) 34 becomes a gradation (specified gradation) to be displayed by the pixel 34 in one frame. Each gradation of the subframe is determined.

The polarity inversion / amplification unit 42c inverts the plus / minus polarity of the voltage applied to the pixel 34 in response to the left / right identification signal RL output from the left / right identification signal generation unit 41b, or the gradation determination unit 42b. The voltage value corresponding to the gradation for each subframe determined by is set.

In the present embodiment, the polarity inversion / amplification unit 42c sets the voltage for the right eye image to have a positive polarity and the voltage for the left eye image to have a negative polarity. The right eye video voltage and the left eye video voltage need only have different polarities, and the right eye video voltage may have a negative polarity and the left eye video voltage may have a positive polarity.

In the table storage unit 44, a gradation determination table for the gradation determination unit 42b to determine the gradation for each subframe is stored. The table storage unit 44 may store only one gradation determination table or a plurality of gradation determination tables. The gradation determination table will be described later.

When the shutter control unit 45 acquires the left / right identification signal RL output from the left / right identification signal generation unit 41b, the shutter control unit 45 generates a shutter control signal OC, which is a control signal for the light shielding glasses 20 including the acquired left / right identification signal RL. . Then, the shutter control unit 45 outputs the generated shutter control signal OC to the light shielding glasses 20. Accordingly, the shutter control unit 45 controls the driving of the left-eye light-shielding liquid crystal shutter 21 and the right-eye light-shielding liquid crystal shutter 22 of the light-shielding glasses 20 in the transmission state or the light-shielding state.

The light-shielding glasses 20 include a liquid crystal shutter 21 for shielding the left eye of the user and a liquid crystal shutter 22 for shielding the right eye. When the light-shielding glasses 20 obtain the shutter control signal OC output from the shutter control unit 45, the light-shielding glasses 20 transmit each of the left-eye light-shielding liquid crystal shutter 21 and the right-eye light-shielding liquid crystal shutter 22 based on the shutter control signal OC. Control the degree.

That is, when the left / right identification signal RL changes from low to high, the light-shielding glasses 20 bring the right-eye light-shielding liquid crystal shutter 22 into a transmissive state and the left-eye light-shielding liquid crystal shutter 21 into a light-shielded state. On the other hand, when the left / right identification signal RL changes from high to low, the light-shielding glasses 20 place the left-eye light-shielding liquid crystal shutter 21 in the transmission state and the right-eye light-shielding liquid crystal shutter 22 in the light-shielding state.

Thereby, according to the video displayed on the liquid crystal panel 30, the user can stereoscopically view the stereoscopic video by causing the video light to enter the right eye or the left eye of the user.

(Driving control of 3D image display system)
Next, drive control of the stereoscopic video display system will be described with reference to FIGS.

FIG. 3 is a diagram for explaining a voltage applied to a certain pixel 34 for each frame.

The liquid crystal display 10 sequentially displays a right-eye video display period (period R in FIG. 3) for displaying a right-eye video and a left-eye video display period (in FIG. 3) for displaying a left-eye video for each frame. This is a so-called frame-sequential video display device that displays a stereoscopic video by alternately repeating the period L).

Assuming that the consecutive frames are the first frame, the second frame, the third frame,..., In FIG. 3, the right-eye video display period, the left-eye video display period, the right-eye video display period,. It has become.

The left / right identification signal RL is high (High; information indicating that the stereoscopic image displayed on the liquid crystal display device 10 is a right-eye image) and is a right-eye signal, and low (Low; displayed on the liquid crystal display device 10). Information indicating that the stereoscopic video to be processed is a video for the left eye).

The left / right identification signal RL is high in the first frame and low in the second frame. Even after the third frame, the signal repeats high and low.

Signal Q represents the voltage applied to the pixel 34. That is, if the absolute value of the signal Q is large, it indicates that the luminance (transmittance) of the pixel 34 is high.

Then, in order to display the gradation for the right-eye image on the pixel 34, a positive polarity voltage is applied as the signal Q. On the other hand, in order to display the gray scale for the left-eye image on the pixel 34, a negative voltage is applied as the signal Q.

Thus, the liquid crystal display device 10 is AC driven by alternately applying + polarity and −polarity voltages to the pixels 34 for each frame. As a result, it is possible to prevent the DC voltage from being continuously applied and to prevent deterioration of the liquid crystal characteristics.

The plus / minus polarity of the signal Q is determined by the high / low of the left / right identification signal RL. That is, when the gradation control unit 42 acquires the left / right identification signal RL that is high from the left / right identification signal generation unit 41b, the polarity inversion / amplification unit 42c sends a voltage application signal indicating a positive polarity voltage to the liquid crystal panel 30. Output. When the liquid crystal panel 30 acquires the voltage application signal from the polarity inversion / amplification unit 42c, the liquid crystal panel 30 applies the positive voltage indicated by the acquired voltage application signal to the pixel 34 via the source driver 31 and the gate driver 32. Thereby, the gradation display of the right eye image is performed on the pixel 34.

On the other hand, when the gradation control unit 42 acquires the left / right identification signal RL that is low from the left / right identification signal generation unit 41b, the polarity inversion / amplification unit 42c sends a voltage application signal indicating a negative polarity voltage to the liquid crystal panel 30. Output. When the liquid crystal panel 30 acquires the voltage application signal from the polarity inversion / amplification unit 42c, the liquid crystal panel 30 applies a negative voltage indicated by the acquired voltage application signal to the pixel 34 via the source driver 31 and the gate driver 32. Thereby, the gradation display of the left-eye image is performed on the pixel 34.

Also, as shown in FIG. 3, in this embodiment, one frame is divided into four subframes.

The first frame is divided into four subframes of a first subframe period a, a second subframe period b, a third subframe period c, and a fourth subframe period d, which are successive periods.

The second frame is divided into four subframes of a first subframe period e, a second subframe period f, a third subframe period g, and a fourth subframe period h, which are successive periods.

A voltage applied to the pixel 34 (hereinafter referred to as a specified applied voltage) in order to display a specified gradation (specified gradation) to be displayed in the right-eye video display period of the first frame is (+ V ).

In addition, in order to display a specified gradation (specified gradation) to be displayed in the left-eye video display period of the second frame, a voltage (specified application voltage) applied to the pixel 34 is set to (−V). .

As an example, the specified gradations of the frame immediately before the first frame, the first frame, and the second frame are set to 0 gradation, 896 gradations (10 bits), and 896 gradations (10 bits) in order.

Then, a necessary applied voltage to the pixel 34 for displaying 0 gradation is set to 0V. Further, of the necessary applied voltages to the pixel 34 for displaying 896 gradations, the positive polarity voltage is (+ V) and the negative polarity voltage is (−V).

Note that it is assumed that a voltage (0 V) is applied to the pixel 34 in the last subframe period of the frame immediately before the first frame.

The left / right identification signal RL rises from low to high at the beginning of the first frame. Thus, the polarity inversion / amplification unit 42c recognizes that the first frame is the right-eye video display period.

Among the first frames, in the subframe period a which is the first subframe period, the gradation determination unit 42b maintains the voltage (0V) applied last in the frame before the first frame. The gradation of the pixel 34 is determined. For this reason, the voltage 0V is continuously applied to the pixel 34 in the first subframe period a.

The gradation determination unit 42b determines that the gradation of the first subframe period a is smaller than the maximum value of the gradations of the plurality of subframes. As a result, the change in the voltage accompanying the change in the polarity of the voltage applied to the pixel 34 between frames is suppressed, and the crosstalk caused by the response delay of the liquid crystal molecules is prevented.

Then, during the first subframe period a, that is, when the left / right identification signal RL is switched from low to high, the gradation determination unit 42b performs the following second subframe period b to fourth subframe period d. Each gradation is determined.

Here, the gradation determination unit 42b determines the gradation of the second subframe b and the third subframe c so that the value is larger than the specified gradation.

At this time, the gradation determination unit 42b refers to the table stored in the table storage unit 44 and determines the gradations of the second subframe b and the third subframe c.

FIG. 4 is a diagram showing a gradation determination table for subframes stored in the table storage unit 44. The gradation determination table represents the gradation of the current first subframe period a in the vertical direction, and the prescribed gradation to be displayed in the first frame in the horizontal direction.

In the first subframe period a, the table storage unit 44 refers to the table stored in the table storage unit 44. Here, since the gradation of the first subframe period a is 0 and the specified gradation to be displayed in the first frame is 896, the table storage unit 44 determines that the current gradation “0” and the next frame The gray level “976” at the intersection of the gray level “896” is determined to be the gray level of the second subframe period b and the third subframe period c.

Then, the polarity inversion / amplification unit 42c generates the voltage to be applied to the pixel 34 during the second subframe period b and the third subframe period c at a voltage corresponding to the gradation determined by the gradation determination unit 42b. A voltage application signal is output to the liquid crystal panel 30. Here, the + polarity voltage corresponding to the 976 gradation is set to + 2V.

In the liquid crystal panel 30, a voltage (+2 V) is applied to the target pixel 34 via the source driver 31 and the gate driver 32.

That is, in the second subframe period b and the third subframe period c, by applying a voltage (+ 2V) higher than the specified applied voltage (+ V) for displaying the specified gradation in the first frame, The driving speed of the liquid crystal molecules is improved, and the luminance higher than the prescribed luminance (luminance corresponding to the prescribed gradation) in the first frame is displayed on the pixel 34.

Further, the gradation determination unit 42b also determines the gradation of the fourth subframe d while determining the gradation of each of the second subframe b and the third subframe c. The gradation determination unit 42b determines the gradation of the fourth subframe d so that the value is smaller than the prescribed gradation in the first frame.

That is, the gradation determination unit 42b determines that the average of the total gradation of the first subframe period a, the second subframe period b, the third subframe period c, and the fourth subframe period d is the first frame. The gradation of the fourth subframe period d is determined so that the prescribed gradation is obtained.

Further, the gradation determining unit 42b determines that the gradation of the fourth subframe period d among the first subframe period a, the second subframe period b, the third subframe period c, and the fourth subframe period d is The gray levels of the first subframe period a, the second subframe period b, the third subframe period c, and the fourth subframe period d are determined so as to be minimized.

Here, the gradation determination unit 42b determines the gradation of the fourth subframe period d to be 0.

Then, the polarity inversion / amplification unit 42c generates a voltage application signal so as to apply a voltage to the pixel 34 during the fourth subframe period d at a voltage (0 V) corresponding to the gradation determined by the gradation determination unit 42b. Output to the liquid crystal panel 30.

In the liquid crystal panel 30, a voltage (0 V) is applied to the target pixel 34 via the source driver 31 and the gate driver 32.

Thus, in the first subframe period a and the fourth subframe period d, by applying a voltage (0 V) lower than the specified applied voltage (+ V) in the first frame, that is, a voltage having a small absolute value, A brightness lower than the target brightness is displayed.

As a result, the voltage applied to the pixel 34 in the second subframe period b and the third subframe c cancels the voltage applied to the pixel 34 in the first subframe period a and the fourth subframe period d. Thus, the first frame is visually recognized by the user as if the specified applied voltage (+ V) was applied. This is because the change in luminance of a minute pixel that is lit at high speed can be felt only by the average value to the human eye.

In addition, the absolute value of the voltage applied to the pixel 34 corresponding to each gradation of the first subframe period a, the second subframe period b, the third subframe period c, and the fourth subframe period d. Among them, the absolute value of the voltage applied to the pixel 34 corresponding to the gradation in the fourth subframe period d is the smallest. That is, the absolute value of the voltage applied to the pixel 34 corresponding to the gradation of the fourth subframe period d adjacent to the second frame (next frame) is the smallest.

Thereby, even if the polarity of the voltage applied to the pixel 34 is inverted between the first frame and the second frame, the response amount of the liquid crystal molecules accompanying the change in the polarity of the voltage can be reduced. It is possible to prevent crosstalk that occurs due to the response delay of the liquid crystal molecules.

Next, the left / right identification signal RL falls from high to low at the beginning of the second frame. Thereby, the polarity inversion / amplification unit 42c recognizes that the second frame is the left-eye video display period.

In the first subframe period e, which is the first subframe period of the second frame, the gradation determination unit 42b applies the voltage (0 V) applied in the last fourth subframe period d of the first frame. The gradation for the pixel 34 is determined so as to be maintained. For this reason, the voltage 0V is continuously applied to the pixel 34 in the first subframe period e.

Then, during the first subframe period e, that is, when the left / right identification signal RL is switched from high to low, the gradation determination unit 42b performs each of the next second subframe period f to the fourth subframe period h. To determine the gradation.

Here, the gradation determination unit 42b determines the gradation of the second subframe f and the third subframe g so that the value is larger than the specified gradation.

At this time, the gradation determination unit 42b refers to the table (see FIG. 4) stored in the table storage unit 44 to determine the gradations of the second subframe f and the third subframe g.

Here, since the gradation in the first subframe e is “0” and the specified gradation in the second frame is “896”, the current gradation “0” and the gradation “896” of the next frame are set. The gradation “976” at the intersection of the two is determined so as to be the gradation of the second subframe period f and the third subframe period g.

Then, the polarity inversion / amplification unit 42c generates the voltage to be applied to the pixel 34 during the second subframe period f and the third subframe period g at a voltage corresponding to the gradation determined by the gradation determination unit 42b. A voltage application signal is output to the liquid crystal panel 30. Here, a negative polarity voltage corresponding to 976 gradations is set to (−2V).

In the liquid crystal panel 30, a voltage (−2 V) is applied to the target pixel 34 via the source driver 31 and the gate driver 32.

That is, in the second subframe period f and the third subframe period g, a voltage (−2 V) lower than the specified applied voltage (−V) for displaying the specified gradation in the second frame is applied. Thus, the response speed of the liquid crystal molecules is improved, and the brightness higher than the specified brightness in the second frame is displayed.

Further, the gradation determination unit 42b also determines the gradation of the fourth subframe h while determining the gradation of each of the second subframe f and the third subframe g. The gradation determination unit 42b determines the gradation of the fourth subframe h so that the value is smaller than the prescribed gradation in the second frame.

That is, the gradation determination unit 42b determines that the total gradation value of the first subframe period e, the second subframe period f, the third subframe period g, and the fourth subframe period h is the second frame. The gradation of the fourth subframe period h is determined so that the specified display gradation is obtained. Here, the gradation determination unit 42b determines the gradation of the fourth subframe period h to be 0.

Then, the polarity inversion / amplification unit 42c transmits a voltage application signal to the pixel 34 so as to apply a voltage to the pixel 34 during the fourth subframe period d at a voltage (0V) corresponding to the gradation determined by the gradation determination unit 42b. Output to 30.

Thus, in the first subframe period e and the fourth subframe period h, a voltage (0V) higher than the specified applied voltage (−V) in the second frame, that is, a voltage having a small absolute value is applied. The brightness lower than the target brightness is displayed.

As a result, the applied voltage in the second subframe period f and the third subframe g and the applied voltage in the first subframe period e and the fourth subframe period h cancel each other, and the second frame is applied with the specified voltage. It is visually recognized by the user as the voltage (−V) is applied.

In this way, the gradation determination unit 42b determines the gradation of the first subframe period e, which is the subframe period adjacent to the first frame, in the second frame. It is determined to be the same as the subframe period d.

That is, the gradation determination unit 42b is adjacent to the second frame and is the last fourth subframe period d among the first frames divided into the plurality of first subframe periods a to the fourth subframe engine d. The gradation of the first first subframe period e of the second frame is determined so as to be the same as the gradation of.

Thus, the polarity inversion / amplification unit 42c applies a voltage to the pixel 34 so that the voltage in the first subframe period e is the same as the voltage in the fourth subframe period d. For this reason, even if the polarity of the voltage applied to the pixel 34 is inverted between the right-eye video display period and the left-eye video display period, the liquid crystal molecules hardly move.

As a result, the crosstalk (the image for the right eye enters the left eye) due to the slow response speed of the liquid crystal molecules hardly occurs. Then, compared to the case where the gradation in the fourth subframe period d is different from the gradation in the first subframe period e, crosstalk can be prevented more reliably.

In particular, in FIG. 3, since the voltage is (0V) in the adjacent subframe periods (the fourth subframe period d and the first subframe period e) in which the polarity of the voltage is inverted, the + polarity voltage is applied to the second frame. It is not applied. For this reason, crosstalk can be reliably prevented.

Note that the voltage does not necessarily have to be 0 in adjacent subframe periods (the fourth subframe period d and the first subframe period e) in which the polarity of the voltage is inverted. The gradation of each subframe may be determined so that the gradation does not change as much as possible immediately before and immediately after the switching between the right-eye video display period and the left-eye video display period.

That is, in the fourth subframe period d and the first subframe period e, the gradation setting is performed so that a voltage whose absolute value is smaller than the voltage applied in each of the first and second frames is applied. It only has to be done.

As a result, the movement of the liquid crystal molecules in the adjacent subframe periods (the fourth subframe period d and the first subframe period e) in which the polarity of the voltage is inverted is suppressed, and the response speed of the liquid crystal molecules is low. Crosstalk can be suppressed.

Further, although it has been described that the specified gradation of each of the first frame and the second frame is “896”, the gradation of each subframe is determined using the table shown in FIG. Is not to be done.

For example, the relationship between the specified display gradation in the frame and the gradation in each subframe in the frame is not limited to that described above. When the specified display gradation in the first frame is 700, the first subframe The gradation may be 600 gradations in a and the fourth subframe d, and 800 gradations in the second subframe period b and the third subframe period c.

Also, a plurality of tables as shown in FIG. 4 may be stored in the table storage unit 44, and the optimum table may be referred to according to the ambient temperature.

Thus, even if the ambient temperature changes, crosstalk can be suppressed regardless of the temperature dependence of the liquid crystal.

Further, the subframe dividing unit 42a divides one frame into four. Accordingly, among the four subframes, the third subframe period b and the fourth subframe period c are provided between the first first subframe period a and the last fourth subframe period d. become.

For this reason, it is possible to display a specified gradation while suppressing a change in gradation of each of a plurality of subframes, and to prevent crosstalk caused by a response delay of liquid crystal molecules.

However, the number by which the subframe dividing unit 42a divides one frame is not limited to four, and may be three or more. Thereby, the gradation determination unit 42b can display the specified gradation within one frame by determining the gradation of the subframe sandwiched between the first and last subframes to be the maximum.

In the above description, the switching from the right-eye video display period to the left-eye video display period has been described, but conversely, from the left-eye video display period (fourth subframe period h) to the right-eye video display period. The present invention can be similarly applied when switching to a video display period (first subframe period in the next frame).

Further, not only the drive control in one pixel 34 of a pixel of interest but also the drive of the pixel 34 and its surrounding pixels are controlled in consideration of the application timing of the drive voltage with the surrounding pixels of the pixel 34. Also good.

For example, like the dither method, it is perceived by the human eye with the total luminance with the surrounding pixels.

Therefore, in the sub-frame period (fourth sub-frame d and first sub-frame period e) corresponding to switching from the right-eye video display period to the left-eye video display period, the pixel of interest 34 and, for example, the four surrounding pixels (up / down / left / right pixels) ), The voltage applied to each pixel is controlled so that the total luminance does not change. By doing so, flicker can be reduced.

[Second Embodiment]
Next, a second embodiment will be described. For convenience of explanation, members having the same functions as those in the drawings described in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.

FIG. 5 is a block diagram showing the configuration of the stereoscopic video display stem 1 ′ according to the present embodiment.

FIG. 6 is a diagram for explaining a voltage applied to a certain pixel 34 for each frame according to the second embodiment.

In the first embodiment, the light shielding glasses 20 switch between the transmission state and the light shielding state of the left and right light shielding

liquid crystal shutters

21 and 22 for each frame.

On the other hand, in the present embodiment, the light-shielding glasses 20 puts both the left and right light-shielding

liquid crystal shutters

21 and 22 in a light-shielded state in the subframe period for switching between the right-eye video display period and the left-eye video display period. .

As shown in FIG. 5, when one frame is divided into a plurality of subframes, the subframe dividing unit 42a outputs information indicating the number of divided subframes to the shutter control unit 45.

The shutter control unit 45 acquires information indicating the left / right identification signal RL output from the left / right identification signal generation unit 41b and the number of subframes output from the subframe division unit 42a.

Then, when the left / right identification signal RL rises from low to high, the shutter control unit 45 causes the right-eye liquid crystal shutter 22 to be in a transmissive state after the first subframe period a elapses, and the left / right identification signal RL changes from high. When falling to low, after the elapse of the first subframe period e, a shutter control signal OC ′, which is a control signal for controlling the light-shielding glasses 20 so as to bring the liquid crystal shutter 21 for the left eye into a transmission state, is generated. To do.

Then, the shutter control unit 45 controls the driving of the light shielding glasses 20 by outputting the generated shutter control signal OC ′ to the light shielding glasses 20.

As shown in FIG. 6, when the light shielding glasses 20 obtains the shutter control signal OC ′ output from the shutter control unit 45, the left eye light shielding liquid crystal shutter 21 and the right eye light shielding are obtained based on the shutter control signal OC ′. The transmissivity of each liquid crystal shutter 22 is controlled.

That is, when the left / right identification signal RL changes from low to high, the light-shielding glasses 20 turn off both the

liquid crystal shutters

21 and 22 in the light-shielding state (OFF) in the first subframe period a, and after the first subframe period a has elapsed. Only the liquid crystal shutter 22 for the right eye is in a transmission state (ON). Then, after the elapse of the second subframe period b and the third subframe period c, in the fourth subframe period d, the right-eye liquid crystal shutter 22 is turned off (OFF). As a result, in the fourth subframe period d, both the

liquid crystal shutters

21 and 22 are in a light shielding state.

Then, when the left / right identification signal RL changes from high to low, the light-shielding glasses 20 continue the light-shielding state (OFF) of both the left and right

liquid crystal shutters

21 and 22 in the first subframe period e, and the first subframe period e After the elapse of time, only the liquid crystal shutter 21 for the left eye is set to the transmission state (ON). Then, after the elapse of the second subframe period f and the third subframe period g, in the fourth subframe period h, the liquid crystal shutter 21 for the left eye is turned off (OFF). Thereby, in the fourth subframe period h, both the

liquid crystal shutters

21 and 22 are in a light shielding state.

In this way, the light-shielding glasses 20 put both the left and right light-shielding

liquid crystal shutters

21 and 22 in the light-shielding state in the sub-frame period for switching between the right-eye video display period and the left-eye video display period. Thus, it is possible to prevent the user from viewing the stereoscopic video on the side opposite to the

liquid crystal shutters

21 and 22 in the transmissive state. Thereby, crosstalk can be reliably prevented.

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

Also, the gradation determining means determines the gradation of the first subframe among the plurality of subframes so as to be smaller than the maximum value of the gradations of the plurality of subframes. As a result, it is possible to suppress the change in the voltage accompanying the change in the polarity of the voltage applied to the pixel of interest between frames, so that it is possible to prevent the crosstalk caused by the response delay of the liquid crystal molecules. it can.

In addition, the gradation determination unit is arranged so that the first frame of the first frame is equal to the gradation of the last subframe among the previous frames adjacent to the one frame and divided into a plurality of subframes. It is preferable to determine the gradation of the subframe.

This makes it possible to more reliably suppress the occurrence of crosstalk associated with polarity reversal.

Further, the number of the one frame divided by the subframe dividing means is preferably 3 or more. With the above configuration, the gradation determining means determines that the gradation of the subframe between the first and last subframes among the three subframes is maximized, so The above specified gradation can be displayed.

Also, it is preferable that the number of the one frame divided by the subframe dividing means is four. According to the above configuration, the plurality of subframes have two subframes between the first subframe and the last subframe, so that the change in gradation of each of the plurality of subframes is suppressed and defined. Gradation can be displayed, and crosstalk that occurs with the response delay of liquid crystal molecules can be prevented.

The stereoscopic video display system of the present invention includes the liquid crystal display device, a light-shielding eyeglass including a liquid crystal shutter for the right eye and a liquid crystal shutter for the left eye, and the liquid crystal display device further includes the above-described liquid crystal display device. Left and right identification signal generating means for generating a left and right identification signal including information indicating whether the stereoscopic video to be displayed on the liquid crystal display device is the right-eye video or the left-eye video;
It is preferable to include a shutter control unit that controls driving of the right-eye liquid crystal shutter and the left-eye liquid crystal shutter based on the left-right identification signal.

With the above configuration, it is possible to cause the light-shielding glasses to control the driving of the right-eye liquid crystal shutter and the left-eye liquid crystal shutter according to the stereoscopic image displayed on the liquid crystal display device. Thereby, it is possible to obtain a stereoscopic video system that allows the user to stereoscopically view the stereoscopic video displayed on the liquid crystal display device.

Further, when the information indicating that the image is for the right eye is acquired, the shutter control unit causes the liquid crystal shutter for the right eye to be in a transmissive state and acquires information indicating the image for the left eye. It is preferable to make the liquid crystal shutter for transmission transparent.

According to the above configuration, when the right eye image is displayed on the liquid crystal display device, the light-shielding glasses make the right eye liquid crystal shutter in a transmissive state, and the left eye image is displayed on the liquid crystal display device. The left-eye liquid crystal shutter can be driven to be in a transmissive state. As a result, the stereoscopic video displayed on the liquid crystal display device can be stereoscopically viewed by the user.

Further, when the shutter control unit obtains information indicating that the video is for the right eye, when the first subframe period of the plurality of subframes has elapsed, the liquid crystal shutter for the right eye is brought into a transmission state, When the information indicating that the video is for the left eye is acquired, it is preferable that the liquid crystal shutter for the left eye is in a transmissive state when the first subframe period of the plurality of subframes has elapsed.

According to the above configuration, the light-shielding glasses set the right-eye or left-eye liquid crystal shutter in a transmissive state after the first subframe period has elapsed. It is possible to prevent the user from seeing the stereoscopic video on the opposite side to the above. Thereby, crosstalk can be reliably prevented.

The present invention can be used for a liquid crystal display device that is required to display a stereoscopic image and a stereoscopic image display system using the same.

DESCRIPTION OF SYMBOLS 1 3D image display system 1 '3D image display stem 10 Liquid crystal display device 20 Light-shielding glasses 21/22 Liquid crystal shutter 30 Liquid crystal panel 34 Pixel (pixel of interest)
40 Liquid crystal drive circuit 41a Gradation signal generation unit 41b Left / right identification signal generation unit (left / right identification signal generation means)
42 gradation control unit 42a subframe dividing unit (subframe dividing means)
42b Gradation determination unit (gradation determination means)
42c Polarity inversion / amplification unit (polarity inversion means)
44 Table storage unit 45 Shutter control unit

Claims

A liquid crystal display device capable of displaying a stereoscopic video by switching and displaying a right-eye video and a left-eye video for each frame,
Subframe dividing means for dividing one frame into a plurality of subframes;
The level at which each of the gradations of the plurality of subframes is determined so that the average value of the gradations of the plurality of subframes in the pixel of interest becomes the specified gradation that the pixel of interest should display in the one frame Key decision means,
Corresponding to each gradation for each subframe determined by the gradation determination means, the polarity inversion means for inverting the polarity of the voltage applied to the pixel of interest for each frame,
The liquid crystal display device, wherein the gradation determining means determines the gradation of each of the plurality of subframes so that the gradation of the last subframe among the plurality of subframes is minimized.
The gradation determination means determines the gradation of the first subframe of the plurality of subframes to be smaller than the maximum value of the gradations of the plurality of subframes. A liquid crystal display device according to 1.
The gradation determining means is arranged such that the first subframe of the one frame is the same as the gradation of the last subframe among the previous frames adjacent to the one frame and divided into a plurality of subframes. The liquid crystal display device according to claim 2, wherein the gradation is determined.
4. The liquid crystal display device according to claim 1, wherein the number of the one frame divided by the sub-frame dividing means is 3 or more.
4. The liquid crystal display device according to claim 1, wherein the number of the one frame divided by the sub-frame dividing means is four.
A liquid crystal display device according to any one of claims 1 to 5,
A stereoscopic video display system comprising a right-eye liquid crystal shutter and a left-eye liquid crystal shutter,
The liquid crystal display device further includes:
Left and right identification signal generating means for generating a left and right identification signal including information indicating whether the stereoscopic video to be displayed on the liquid crystal display device is the right-eye video or the left-eye video;
A stereoscopic video display system comprising: a liquid crystal shutter for the right eye and a shutter control unit that controls driving of the liquid crystal shutter for the left eye based on the left / right identification signal.
When acquiring the information indicating that the image is for the right eye, the shutter control unit causes the liquid crystal shutter for the right eye to be in a transmissive state and acquires the information indicating the image for the left eye. The stereoscopic image display system according to claim 6, wherein the liquid crystal shutter is set in a transmissive state.
When the shutter control unit obtains the information indicating that the video is for the right eye, when the first subframe period of the plurality of subframes has elapsed, the right eye liquid crystal shutter is set in a transmissive state, and the left eye 8. The liquid crystal shutter for the left eye is set in a transmissive state when the first subframe period of the plurality of subframes has elapsed when acquired as information indicating that the video is a video for use. 9. 3D image display system.