JPWO2011064878A1 - Liquid crystal display device and control method thereof - Google Patents

Abstract

A driving voltage (panel driving voltage) for driving individual liquid crystal elements of the liquid crystal panel slightly changes due to leakage or the like. Provided are a liquid crystal display device and a control method therefor, which can solve the problem that the voltage change becomes a luminance change of a display image and may be visually recognized as flicker. The liquid crystal display device of the present invention includes a liquid crystal panel (13) having a plurality of liquid crystal elements, and an arbitrary waveform generating section (14) for generating a first signal based on a change in a panel driving voltage waveform for driving the liquid crystal elements. And a light source (18) for illuminating the display panel by changing the amount of light according to the first signal.

Description

  The present invention relates to a liquid crystal display device including a liquid crystal panel, a liquid crystal driving unit that drives the liquid crystal panel, and a light source that outputs light that illuminates the liquid crystal panel, and a control method thereof.

  A liquid crystal panel forms an image using a plurality of liquid crystal elements whose states change in accordance with the drive voltage, and the drive voltage (panel drive voltage) for driving each liquid crystal element is maintained while one image is formed. Is done. However, the panel drive voltage changes slightly due to leakage or the like. This voltage change becomes a luminance change of the display image, and may be visually recognized as flicker.

  As a driving method of the liquid crystal panel, there is a vertical inversion driving method for inverting the panel driving voltage polarity for each field as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-304385). In a liquid crystal display device using such a driving method, a change in the panel driving voltage held in the liquid crystal panel appears as a luminance change between fields. Therefore, the entire screen is visually recognized as flicker in the field period, and the display quality is remarkably improved. Reduce.

  In order to reduce flicker, for example, by setting the field frequency to twice the input video frequency, the time for changing the panel drive voltage is shortened, the amount of change in the panel drive voltage due to leakage is suppressed, and the field frequency is increased. Therefore, there is a countermeasure that makes it difficult to visually recognize because the sensitivity of human eyes falls.

JP 2007-304385 A

  However, in the above-described method, the flicker is not easily seen and is not fundamentally corrected. The amount of flicker tends to increase as the panel aperture ratio, which is particularly important in the characteristics of the liquid crystal panel, is improved.

  Further, when the field frequency of the video signal is 50 Hz, even if it is driven at double speed, it is 100 Hz, which is a frequency that can be sufficiently visually recognized by human eyes. If the frequency is tripled to 150 Hz, the frequency becomes difficult to see, but the response speed of the liquid crystal panel is slow, so there is a limit to the driving frequency, which is difficult to realize.

  The objective of this invention is providing the liquid crystal display device which can solve the subject mentioned above, and its control method.

In order to achieve the above object, the liquid crystal display device of the present invention comprises:
A liquid crystal panel comprising a plurality of liquid crystal elements;
An arbitrary waveform generating unit that generates a first signal based on a change in a panel driving voltage waveform for driving the liquid crystal element;
A light source that illuminates the display panel by changing the amount of light according to the first signal.

In order to achieve the above object, a method for controlling a liquid crystal display device of the present invention includes:
A method for controlling a liquid crystal display device having a liquid crystal panel comprising a plurality of liquid crystal elements,
An arbitrary waveform generating step for generating a first signal based on a change in a panel driving voltage waveform for driving the liquid crystal element;
An illumination step of illuminating the display panel by changing the amount of light according to the first signal.

  According to the present invention, a liquid crystal display device generates a first signal based on a change in a panel driving voltage waveform for driving a liquid crystal element, and changes a light amount according to the generated first signal to change a display panel. Illuminate.

  For this reason, it is possible to suppress the occurrence of flicker caused by a change in luminance due to the fluctuation of the panel drive voltage within one field period, and to prevent the display quality of the display image from being deteriorated.

It is a block diagram which shows the structure of the liquid crystal display device of the 1st Embodiment of this invention. It is a figure which shows an example of the fluctuation | variation of the panel drive voltage hold | maintained at a liquid crystal panel. It is a figure which shows an example of the fluctuation | variation of the optical response waveform of the liquid crystal element which arises with the fluctuation | variation of a panel drive voltage. It is a figure which shows an example of the VT characteristic of a liquid crystal panel. It is a block diagram which shows the structure of the liquid crystal display device of the 2nd Embodiment of this invention.

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated with reference to drawings.
(First embodiment)
FIG. 1 is a block diagram showing a configuration of a liquid crystal display device 10 according to a first embodiment of the present invention.

  A liquid crystal display device 10 shown in FIG. 1 includes a video signal processing unit 11, a liquid crystal drive unit 12, a liquid crystal panel 13, an arbitrary waveform generation unit 14, a histogram detection unit 15, a light output control unit 16, and a control amplitude. The adjusting unit 17 and the light source 18 are included.

  Since the liquid crystal panel 13 is a transmissive liquid crystal panel having a general configuration, detailed description thereof is omitted.

  The video signal given from the outside is supplied to the video signal processing unit 11, the histogram detection unit 15, and the light output control unit 16.

  The video signal processing unit 11 generates a signal for driving the liquid crystal panel 13 according to the video signal and outputs the signal to the liquid crystal driving unit 12.

  The liquid crystal driving unit 12 supplies the signal output from the video signal processing unit 11 to the liquid crystal panel 13 to drive the liquid crystal panel 13, and starts one field period based on the signal output from the video signal processing unit 11. The vertical synchronization timing indicating the timing is output to the arbitrary waveform generator 14.

  The arbitrary waveform generation unit 14 generates a waveform based on a change in the panel drive voltage waveform for driving the liquid crystal element in synchronization with the vertical synchronization timing output from the liquid crystal drive unit 12, and generates a waveform signal indicating the generated waveform. This is output to the control amplitude adjustment unit 17. This waveform is the basis of a light amount signal for changing the light amount of the light source 18, and is substantially equal to the change in the light amount.

  The histogram detection unit 15 detects the gradation of the video signal, generates a histogram of the detected gradation, and outputs it to the control amplitude adjustment unit 17.

  The light output control unit 16 is provided to statically or dynamically change the amount of light output from the light source 18. Here, “static” means that the light output level is changed by a user's operation, and “dynamic” means that the light output level is changed depending on the pattern of the video signal.

  By changing the light output level, the apparent dynamic range of the video display output can be expanded. This technology has been clarified as prior art.

  The light output control unit 16 outputs a light amount level signal indicating the changed light amount to the control amplitude adjusting unit 17.

  The control amplitude adjusting unit 17 adjusts the amplitude of the waveform indicated by the waveform signal output from the arbitrary waveform generating unit 14 based on the gradation histogram of the video signal output from the histogram detecting unit 15, and further performs optical output control. The light amount signal indicating the light amount, which is increased or decreased according to the amount of fluctuation of the light amount indicated by the waveform whose amplitude is adjusted, is output to the light source 18 from the light amount indicated by the light amount level signal output from the unit 16.

  The light source 18 outputs light that illuminates the liquid crystal panel 13 based on the light amount signal output from the control amplitude adjusting unit 17.

  Next, the operation of the liquid crystal display device 10 will be described.

  First, the change in the amount of light necessary for the light source will be described with reference to FIG. 2A. FIG. 2A is an explanatory diagram of the occurrence of flicker due to the leakage current of the liquid crystal panel 13.

  The panel drive voltage waveform shown in FIG. 2A indicates the panel drive voltage to one pixel electrode of the liquid crystal panel when a full screen solid image is displayed. In the liquid crystal panel 13, it is necessary to AC drive the pixel electrodes in order to prevent deterioration of liquid crystal characteristics. Here, an example of a driving method in which the polarity is inverted for each field is shown.

  The ideal panel drive voltage is a rectangular wave as indicated by the dotted line in the figure centering on the video center voltage VMID. A waveform such as a solid line is caused by a leakage current caused by light.

  The voltage shift of the TFT moves not in the center of VMID but in the ground potential (0V) direction. For this reason, the waveform is asymmetric with respect to VMID on the positive polarity side and the negative polarity side, and this appears as a luminance difference between the positive polarity side and the negative polarity side, resulting in flicker.

  For this reason, flicker is suppressed by setting VCOM so that the areas of the positive polarity side and the negative polarity side are the same. However, since the adjustment of VCOM only eliminates the average luminance difference between the positive polarity side and the negative polarity side, it cannot cope with the luminance change in the field due to leakage. For this reason, flicker remains.

  Therefore, in the present embodiment, the arbitrary waveform generation unit 14 is provided to change the light amount of the light source so as to cancel the fluctuation of the optical response waveform based on the fluctuation of the panel drive voltage shown in FIG. 2A. The arbitrary waveform generation unit 14 generates a predetermined waveform for controlling the amount of light that illuminates the liquid crystal panel 13 in synchronization with the vertical synchronization timing.

  FIG. 2B is a diagram illustrating an example of the fluctuation of the optical response waveform of the liquid crystal element caused by the fluctuation of the panel driving voltage. In FIG. 2B, the transmittance of the liquid crystal element is used as an example of the optical response waveform. In addition, although the waveform shown in FIG. 2B is simply drawn as a straight line, the actual characteristics differ depending on the type of the liquid crystal panel 13 and may be curved. Any look-up table method can be used as long as the waveform is stored in a ROM (Read Only Memory).

  Between time T1 and T2, since the positive panel drive voltage to be held decreases to the negative polarity side, the transmittance of the liquid crystal element decreases. In addition, the transmittance of the liquid crystal element decreases between the times T2 and T3 because the held negative panel drive voltage decreases to the positive polarity side.

  The arbitrary waveform generation unit 14 generates a waveform that is an inverse characteristic of the optical response waveform.

  The histogram detection unit 15 detects the gradation of the video signal, generates a histogram of the detected gradation, and the light output control unit 16 outputs the light amount level signal to the control amplitude adjustment unit 17. The control amplitude adjustment unit 17 controls the amplitude of the generated waveform based on the histogram generated by the histogram detection unit 15.

  FIG. 3 is a diagram illustrating an example of the VT characteristic (the relationship between the panel drive voltage and the transmittance) of the liquid crystal panel 13.

  As described above, gradation control is performed according to the applied panel drive voltage. When the panel drive voltage is low, the gray level region is on the black side, when the panel drive voltage is medium, it is a halftone region, and when the panel drive voltage is high, the gray level region is on the white side.

  As shown in FIG. 3, the amount of change in transmittance with respect to the change in panel drive voltage varies depending on the gradation. That is, the transmittance variation with respect to the panel drive voltage variation in the halftone gradation region is larger than the transmittance variation with respect to the panel drive voltage variation in the black or white gradation region.

  Therefore, the control amplitude adjusting unit 17 controls the amplitude of the waveform generated by the arbitrary waveform generating unit 14 based on the detected grayscale of the video signal with the highest number of detections.

  Specifically, when the gradation with the highest number of detections is included in the halftone gradation area, the waveform amplitude is increased, and when the gradation is included in the black or white gradation area, Reduce the amplitude.

  The control amplitude adjustment unit 17 increases or decreases the amount of fluctuation of the light amount indicated by the waveform whose amplitude is adjusted from the light amount indicated by the light amount level signal, and outputs the light amount signal to the light source 18. The light source 18 outputs light to the liquid crystal panel 13 based on the output light amount signal.

As described above, according to the present embodiment, the liquid crystal display device 10 generates a waveform based on fluctuations in the panel drive voltage, adjusts the amplitude of the generated waveform using the histogram of the gradation of the video signal, and the light amount level signal is Outputs the amount of light that has been increased or decreased from the amount of light indicated by the amount of fluctuation in the amount of light indicated by the amplitude of the adjusted waveform. It is possible to prevent deterioration in display quality of the displayed image.

  Note that the leak current is generated when light is applied to the pixel electrode, and the amount of the leak current also varies depending on the amount of light applied. Therefore, when the amount of light output from the light source 18 is changed by the light output control unit 16, the amount of leakage current also changes.

In this case, the amount of output light can be changed by changing the amount of adjustment of the waveform amplitude by the control amplitude adjusting unit 17. For example, when the light quantity is halved, the waveform amplitude may be halved.
(Second Embodiment)
FIG. 4 is a block diagram showing the configuration of the liquid crystal display device 20 according to the second embodiment of the present invention.

  In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted.

  The liquid crystal display device 20 shown in FIG. 4 differs from the liquid crystal display device 10 of the first embodiment in that a diaphragm unit 21 is provided.

  The aperture 21 is provided between the liquid crystal panel 13 and the light source 18 and adjusts the amount of light output from the light source 18.

  Next, the operation of the liquid crystal display device 20 will be described.

  The control amplitude adjustment unit 17 outputs a light amount signal to the diaphragm unit 21. The diaphragm unit 21 adjusts the amount of light output from the light source 18 based on the output light amount signal.

  As described above, according to the present embodiment, the liquid crystal display device 20 adjusts the light amount output from the light source 18 based on the light amount signal and outputs the adjusted light amount to the liquid crystal panel 13.

Therefore, similarly to the liquid crystal display device 10 of the first embodiment, it is possible to suppress the occurrence of flicker caused by the change in luminance due to the fluctuation of the panel drive voltage within one field period, and to reduce the display quality of the display video. Can be prevented.
The occurrence of flicker that occurs within one field period can be suppressed, and the display quality of the display image can be prevented from deteriorating.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

Claims (20)

A liquid crystal panel comprising a plurality of liquid crystal elements;
An arbitrary waveform generating unit that generates a first signal based on a change in a panel driving voltage waveform for driving the liquid crystal element;
And a light source that illuminates the display panel by changing a light amount in accordance with the first signal. The liquid crystal display device according to claim 1.
A histogram detector that detects the gradation of the video signal and generates a second signal indicating a gradation histogram;
A control amplitude adjustment unit that generates a third signal obtained by adjusting the first signal with the second signal;
The light source is a liquid crystal display device that illuminates the display panel by changing the amount of light according to the third signal. The liquid crystal display device according to claim 1.
A histogram detector that detects the gradation of the video signal and generates a second signal indicating a gradation histogram;
A light output control unit for determining a light amount according to the video signal and generating a third signal indicating the determined light amount;
A control amplitude adjusting unit that adjusts the first signal with the second signal, and generates a fourth signal that is increased or decreased according to the adjusted signal;
The light source is a liquid crystal display device that illuminates the display panel by changing an amount of light according to the fourth signal. The liquid crystal display device according to claim 2 or claim 3,
The control amplitude adjuster is
A liquid crystal display device that adjusts the first signal based on a gray scale that is detected most frequently in the video signal, as indicated by the second signal. The liquid crystal display device according to any one of claims 1 to 4,
The first signal is:
A liquid crystal display device, which is a signal indicating an inverse characteristic of the changed panel drive voltage waveform. A liquid crystal panel comprising a plurality of liquid crystal elements;
A light source for illuminating the display panel;
An arbitrary waveform generating unit that generates a first signal based on a change in a panel driving voltage waveform for driving the liquid crystal element;
And a diaphragm for adjusting the amount of light output from the light source in accordance with the first signal. The liquid crystal display device according to claim 6.
A histogram detector that detects the gradation of the video signal and generates a second signal indicating a gradation histogram;
A control amplitude adjustment unit that generates a third signal obtained by adjusting the first signal with the second signal;
The diaphragm unit is a liquid crystal display device that adjusts an amount of light output from the light source in accordance with the third signal. The liquid crystal display device according to claim 6.
A histogram detector that detects the gradation of the video signal and generates a second signal indicating a gradation histogram;
A light output control unit for determining a light amount according to the video signal and generating a third signal indicating the determined light amount;
A control amplitude adjusting unit that adjusts the first signal with the second signal and generates a fourth signal that is increased or decreased in accordance with the adjusted signal;
The diaphragm unit is a liquid crystal display device that adjusts an amount of light output from the light source in accordance with the fourth signal. The liquid crystal display device according to claim 7 or 8,
The control amplitude adjuster is
A liquid crystal display device that adjusts the first signal based on a gray scale that is detected most frequently in the video signal, as indicated by the second signal. The liquid crystal display device according to any one of claims 6 to 9,
The first signal is:
A liquid crystal display device, which is a signal indicating an inverse characteristic of the changed panel drive voltage waveform. A method for controlling a liquid crystal display device having a liquid crystal panel comprising a plurality of liquid crystal elements,
An arbitrary waveform generating step for generating a first signal based on a change in a panel driving voltage waveform for driving the liquid crystal element;
And a lighting step of illuminating the display panel by changing the amount of light according to the first signal. The control method according to claim 11, wherein
A histogram detection step of detecting a gradation of the video signal and generating a second signal indicating a gradation histogram;
A control amplitude adjusting step for generating a third signal obtained by adjusting the first signal by the second signal;
In the illumination step, a control method of illuminating the display panel by changing a light amount according to the third signal. The control method according to claim 11, wherein
A histogram detection step of detecting a gradation of the video signal and generating a second signal indicating a gradation histogram;
A light output control step of determining a light amount according to the video signal and generating a third signal indicating the determined light amount;
A control amplitude adjustment step of adjusting the first signal by the second signal and generating a fourth signal obtained by increasing or decreasing the third signal according to the adjusted signal,
In the illumination step, a control method of illuminating the display panel by changing a light amount according to the fourth signal. The control method according to claim 12 or 13,
In the control amplitude adjustment step,
A control method for adjusting the first signal based on a grayscale having the highest number of detection times in the video signal indicated by the second signal The control method according to any one of claims 11 to 14,
The first signal is:
A control method, which is a signal indicating an inverse characteristic of the changed panel drive voltage waveform. A method for controlling a liquid crystal display device having a liquid crystal panel comprising a plurality of liquid crystal elements,
An illumination step for illuminating the display panel;
An arbitrary waveform generating step for generating a first signal based on a change in a panel driving voltage waveform for driving the liquid crystal element;
And a diaphragm step for adjusting an amount of light output from the light source in accordance with the first signal. The control method according to claim 16, wherein
A histogram detection step of detecting a gradation of the video signal and generating a second signal indicating a gradation histogram;
A control amplitude adjusting step for generating a third signal obtained by adjusting the first signal by the second signal;
A control method of adjusting the amount of light output from the light source in accordance with the third signal in the aperture step. The control method according to claim 16, wherein
A histogram detection step of detecting a gradation of the video signal and generating a second signal indicating a gradation histogram;
A light output control step of determining a light amount according to the video signal and generating a third signal indicating the determined light amount;
A control amplitude adjustment step of adjusting the first signal by the second signal and generating a fourth signal obtained by increasing or decreasing the third signal according to the adjusted signal,
A control method of adjusting the amount of light output from the light source in accordance with the fourth signal in the aperture step. The control method according to claim 17 or claim 18,
In the control amplitude adjustment step,
A control method for adjusting the first signal based on a gradation indicated by the second signal and having the highest number of detections in the video signal. The control method according to any one of claims 16 to 19,
The first signal is:
A control method, which is a signal indicating an inverse characteristic of the changed panel drive voltage waveform.

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