JP2013218341A - Liquid crystal display device and method of driving liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device and a driving method for a liquid crystal panel that allows a common voltage value to be the optimum value even if the amount of light that enters the liquid crystal panel is varied.SOLUTION: A liquid crystal display device comprises: a common voltage generating section 15 for supplying common voltage to a common electrode where a plurality of liquid crystal cells constituting a liquid crystal panel 13 are commonly connected; a liquid crystal driving section 12 for supplying voltage according to an input video signal to the plurality of liquid crystal cells, and allowing an image based on the input video signal to be displayed on the liquid crystal panel 13; and a control section 10 for changing a value of the common voltage generated by the common voltage generating section 15 according to a signal representing the amount of light entering the liquid crystal panel 13.

Description

  The present invention relates to a liquid crystal display device, and more particularly to a technique for driving a liquid crystal panel.

  The liquid crystal panel is composed of a plurality of liquid crystal cells. Each liquid crystal cell has a structure in which liquid crystal is sandwiched between two electrodes. One electrode is a pixel electrode corresponding to a video display pixel, and is charged / discharged to a voltage corresponding to the video signal via a thin film transistor (TFT). The other electrode is a common electrode (common electrode) connected to each liquid crystal cell. A common voltage (DC voltage) is applied to the common electrode.

  In order to prevent characteristic deterioration of the liquid crystal panel, the pixel electrode is AC driven, and a common voltage value (fixed value) applied to the common electrode is set so that no DC voltage is applied to the liquid crystal. In Japanese Patent Application Laid-Open No. 2008-164852 (hereinafter referred to as Patent Document 1), the screen is divided into a plurality of areas, the feature amount of the video signal is calculated for each area, and the optimum feature amount is calculated based on the calculated feature amount. A method for setting the common voltage is described.

JP 2008-164852 A

  In the liquid crystal panel in which the voltage of the video signal is supplied to the pixel electrode via the thin film transistor, a leakage current of an amount corresponding to the amount of incident light (light energy or thermal energy) is generated. If the amount of light incident on the liquid crystal panel is changed to increase the contrast, the amount of leak current also changes. For example, when displaying bright images, high brightness is achieved by maximizing the amount of light, and when displaying dark images, the amount of light is limited to improve contrast. The amount of leakage current also changes. When the amount of leakage current changes, the set value of the common voltage deviates from the optimum value (a value at which no DC voltage is applied to the liquid crystal), and as a result, the characteristics of the liquid crystal panel deteriorate.

  Further, if the set value of the common voltage is deviated from the optimum value, the following problems such as occurrence of flicker, decrease in contrast, and color misregistration may occur.

  FIG. 8 shows an example of a video signal waveform of line inversion driving for switching the polarity of the video signal for each horizontal scanning period. The video signal waveform is such that the side having a positive potential with respect to the common potential is a positive video signal and the side having a negative potential is a negative video signal.

  The center voltage is a voltage applied to the liquid crystal panel as an intermediate potential between the positive polarity signal and the negative polarity signal of the input video signal. The positive video signal and the negative video signal are vertically symmetrical about the center potential. When the common voltage value deviates from the optimum value, there is a difference between the relationship between the voltage of the positive video signal and the common voltage and the relationship between the negative video signal voltage and the common voltage when displaying a certain gradation. Occurs and is recognized as flicker.

  In addition, when the common voltage value deviates from the optimum value, when displaying a black video, the potential of one polarity of the video signal is not sufficient to display black, and black is floating. Become. For this reason, contrast deteriorates.

  In addition, a change in the potential difference between the video signal and the common voltage causes a change in luminance of each color, resulting in a color shift.

  Even in the device described in Patent Document 1, when the amount of light incident on the liquid crystal panel is changed, the set value of the common voltage deviates from the optimum value, causing the above-described problems.

  An object of the present invention is to solve the above problems and provide a liquid crystal display device and a liquid crystal panel driving method capable of setting the common voltage value to an optimum value even when the amount of light incident on the liquid crystal panel is changed. There is to do.

In order to achieve the above object, a liquid crystal display device including a liquid crystal panel according to an aspect of the present invention is provided.
A common voltage generator for supplying a common voltage to a common electrode to which a plurality of liquid crystal cells constituting the liquid crystal panel are connected in common;
A liquid crystal driving unit that supplies a voltage according to an input video signal to the plurality of liquid crystal cells to display an image based on the input video signal on the liquid crystal panel;
It has a control part which changes the value of the common voltage generated by the common voltage generation part according to the signal which shows the amount of light which enters the liquid crystal panel.

According to another aspect of the present invention, a liquid crystal display device including a liquid crystal panel is provided.
A common voltage generator for supplying a common voltage to a common electrode to which a plurality of liquid crystal cells constituting the liquid crystal panel are connected in common;
A liquid crystal driving unit for supplying a voltage corresponding to an input video signal whose polarity is inverted every certain period to the plurality of liquid crystal cells and displaying an image based on the input video signal on the liquid crystal panel;
A value of a center voltage applied to the liquid crystal panel as an intermediate potential between a positive signal and a negative signal of the input video signal is changed according to a signal indicating the amount of light incident on the liquid crystal panel. It has a control part.

According to one embodiment of the present invention, a method for driving a liquid crystal panel including a plurality of liquid crystal cells includes:
A voltage corresponding to an input video signal is supplied to the plurality of liquid crystal cells to display an image based on the input video signal on the liquid crystal panel, and a common voltage is applied to a common electrode to which the plurality of liquid crystal cells are connected in common. Supply
A value of a common voltage supplied to the common electrode is changed according to a signal indicating the amount of light incident on the liquid crystal panel.

According to another aspect of the present invention, a method for driving a liquid crystal panel composed of a plurality of liquid crystal cells includes:
A voltage corresponding to an input video signal whose signal polarity is inverted every certain period is supplied to the plurality of liquid crystal cells to display an image based on the input video signal on the liquid crystal panel, and the plurality of liquid crystal cells Supply a common voltage to the common electrode connected in common,
A value of a center voltage applied to the liquid crystal panel as an intermediate potential between a positive signal and a negative signal of the input video signal is changed according to a signal indicating the amount of light incident on the liquid crystal panel. It is characterized by that.

1 is a block diagram illustrating a configuration of a liquid crystal display device according to a first embodiment of the present invention. It is a figure which shows an example of the look-up table (LUT) which shows the relationship between a light quantity and a common voltage value. 3 is a flowchart showing a procedure of common voltage control processing performed in the liquid crystal display device shown in FIG. 1. It is a figure which shows an example of the look-up table (LUT) which shows the relationship between a light quantity and a center voltage value. It is a flowchart which shows one procedure of the center voltage control process performed with the liquid crystal display device which is the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the liquid crystal display device which is the 3rd Embodiment of this invention. It is a block diagram which shows the structure of the liquid crystal display device which is the 4th Embodiment of this invention. It is a wave form diagram which shows an example of the video signal waveform of the line inversion drive which switches the polarity of a video signal for every horizontal scanning period.

  Next, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing the configuration of the liquid crystal display device according to the first embodiment of the present invention.

  Referring to FIG. 1, the liquid crystal display device includes a control unit 10, a video signal processing circuit 11, a liquid crystal drive unit 12, a liquid crystal panel 13, a storage unit 14, a common voltage generation unit 15, a buffer 16, a timer 17, and a light detection unit 18. Have

  The liquid crystal panel 13 is a liquid crystal panel in which AC driving is performed in which the polarity of the voltage applied to the pixel electrode of the liquid crystal is inverted at a predetermined cycle, and is composed of a plurality of liquid crystal cells. Each liquid crystal cell usually has a structure in which a liquid crystal is sandwiched between two electrodes. One electrode is a pixel electrode corresponding to a video display pixel, and a video signal voltage is supplied via a thin film transistor (TFT). Charging / discharging is performed by the on / off operation of the thin film transistor, and the voltage corresponding to the video signal is set. The other electrode is a common electrode (common electrode) connected to the plurality of liquid crystal cells, and a DC voltage is applied thereto.

  For AC driving, one or a combination of dot inversion driving, line inversion driving, and frame inversion driving can be applied. Here, it is assumed that line inversion driving is applied. In the line inversion drive, the polarities of the voltages supplied to each other are inverted between the odd lines and the even lines in the liquid crystal cell columns (horizontal lines) arranged in the horizontal direction of the liquid crystal panel 13. In this line inversion drive, for example, the odd line is fixed to positive polarity and the even line is fixed to negative polarity, and the polarity of the odd line and even line is inverted for each frame (or field). However, any method may be applied.

  The video signal processing circuit 11 performs processing necessary for displaying on the liquid crystal panel 13 video based on a video signal supplied from an external video signal source such as a personal computer. The video signal from the video processing circuit 11 is subjected to pixel conversion to an appropriate size and supplied to the liquid crystal drive unit 12.

  The liquid crystal driving unit 12 AC drives the liquid crystal panel 13 based on the video signal supplied from the video signal processing circuit 11. In the AC driving of the liquid crystal panel 13, the liquid crystal driving unit 12 inverts the polarity of the video signal every horizontal scanning period with reference to the center voltage from the control unit 10.

  The common voltage generator 15 generates a common voltage corresponding to the common voltage value set by the controller 10. The common voltage generated by the common voltage generator 15 is supplied via a buffer 16 to a common electrode to which liquid crystal cells constituting the liquid crystal panel 13 are connected in common.

  The light detection unit 18 detects the amount of light incident on the liquid crystal panel 13. The amount of light to be detected is not limited as long as the amount of light incident on the liquid crystal panel 13 can be relatively detected. The light detection unit 18 may be disposed in the vicinity of the light source that illuminates the liquid crystal panel 13. In this case, the light detection unit 18 detects the amount of white light from the light source. Further, the light detection unit 18 may be disposed in the vicinity of the liquid crystal panel 13.

  In the case of a three-plate liquid crystal display device, the light detection unit 18 is disposed in the vicinity of one of the liquid crystal panels. In this case, the light detection unit 18 detects the amount of monochromatic light incident on the liquid crystal panel. Further, the light detection unit 18 may extract and detect a part of white light from the light source or a part of monochromatic light incident on the liquid crystal panel using a reflector or the like. In the case where the wavelength distribution of light emitted by the light source is substantially constant and the light detection unit 18 is arranged in the vicinity of the liquid crystal panel, all other liquid crystals are based on the detection result of only monochromatic light (for example, green) You may control the common voltage of a panel.

  The storage unit 14 stores a table indicating the relationship between the light amount and the common voltage. Specifically, a lookup table (LUT) indicating the relationship between the light amount and the common voltage value as shown in FIG. The number of data in the LUT is determined by the relationship between the light amount and the common voltage, but more accurate control can be performed by linear interpolation between the set data. For example, in the case of the LUT shown in FIG. 2, the common voltage value is set for each of the light amounts of 25%, 50%, 75%, and 100%, and linear interpolation is performed between these values. In the LUT shown in FIG. 2, the common voltage decreases as the amount of light increases.

  The control unit 10 includes a CPU (Central Processor Unit), and controls operations of the video signal processing circuit 11, the liquid crystal driving unit 12, and the common voltage generation unit 15. The control unit 10 refers to the LUT stored in the storage unit 14, determines a common voltage value corresponding to the light amount detected by the light detection unit 18, and uses the determined common voltage value as the common voltage generation unit 15. Set for.

  The light amount detection interval by the light detection unit 18 depends on the shift amount of the common voltage, but if it is about several seconds, the characteristic deterioration of the liquid crystal panel does not become a problem, so the interval is set to several seconds. The light amount detection interval is measured by the timer 17. The control unit 10 determines the light amount detection interval by the light detection unit 18 based on the measurement time by the timer 17.

  Next, common voltage control processing performed in the liquid crystal display device of the present embodiment will be described.

  FIG. 3 is a flowchart showing one procedure of the common voltage control process.

  Referring to FIG. 3, first, the control unit 10 determines whether or not the count value of the timer 17 has reached a predetermined count value (step S10).

  When the count value reaches the predetermined count value, the control unit 10 causes the light detection unit 18 to detect the amount of light (step S11). Next, the control unit 10 refers to the LUT stored in the storage unit 14 and determines a common voltage value corresponding to the amount of light detected by the light detection unit 18 (step S12). Then, the control unit 10 sets the determined common voltage value for the common voltage generation unit 15, and the common voltage generation unit 15 supplies the liquid crystal panel 13 with the common voltage corresponding to the set common voltage value. Each liquid crystal cell to be configured is supplied to a common electrode connected in common.

  According to the liquid crystal display device of the present embodiment, the common voltage supplied to the common electrode of the liquid crystal panel 13 is changed to an optimal value according to the amount of light incident on the liquid crystal panel 13 at regular time intervals. Thereby, it is possible to prevent the characteristic deterioration of the liquid crystal panel 13 caused by the deviation of the optimum common voltage when the amount of incident light on the liquid crystal panel 13 is changed, and the flicker caused by the deviation of the optimum common voltage is deteriorated. It is possible to prevent deterioration of contrast and color misregistration.

  In the configuration shown in FIG. 1, means for changing the amount of light incident on the liquid crystal panel may be provided in order to increase the contrast. As this means, for example, power control and light shielding control means in the third and fourth embodiments described later can be used. By performing the light amount detection when controlling the light amount, the load on the control unit 10 can be reduced. At this time, the change in the light amount due to the deterioration of the light source over time generally occurs in units of several hours, so the light amount detection interval can be set in units of several hours.

(Second Embodiment)
The liquid crystal display device of the present embodiment has the same configuration as that shown in FIG. 1, but the center voltage is controlled according to the incident light quantity of the liquid crystal panel instead of the common voltage control. Different from that of form.

  The storage unit 14 stores a table indicating the relationship between the light amount and the center voltage of the video signal. Specifically, a lookup table (LUT) indicating the relationship between the light amount and the center voltage value as shown in FIG. The number of data in the LUT is determined by the relationship between the light amount and the center voltage, but more accurate control can be performed by linearly complementing the set data.

  For example, in the case of the LUT shown in FIG. 4, the center voltage value is set for each of the light amounts of 25%, 50%, 75%, and 100%, and linear interpolation is performed between these values. In the LUT shown in FIG. 4, the center voltage increases as the amount of light increases. The change in the center voltage in this LUT is just opposite to the change in the common voltage in the LUT shown in FIG.

  The common voltage generator 15 generates a common voltage corresponding to the common voltage value set by the controller 10. The common voltage value is a fixed value (a preset optimum value). The common voltage generated by the common voltage generator 15 is supplied via a buffer 16 to a common electrode to which liquid crystal cells constituting the liquid crystal panel 13 are connected in common.

  The control unit 10 refers to the LUT stored in the storage unit 14, determines a center voltage value corresponding to the amount of light detected by the light detection unit 18, and sends the determined center voltage value to the liquid crystal drive unit 12. Supply. The liquid crystal drive unit 12 inverts the polarity of the video signal for each horizontal scanning period with reference to the center voltage value from the control unit 10.

  Next, the center voltage control process performed in the liquid crystal display device of this embodiment will be described.

  FIG. 5 is a flowchart showing one procedure of the center voltage control process. Referring to FIG. 5, first, the control unit 10 determines whether or not the count value of the timer 17 has reached a predetermined count value (step S20).

  When the count value reaches the predetermined count value, the control unit 10 causes the light detection unit 18 to detect the amount of light (step S21). Next, the control unit 10 refers to the LUT stored in the storage unit 14 and determines a center voltage value corresponding to the amount of light detected by the light detection unit 18 (step S22). Then, the control unit 10 sets the determined center voltage value for the liquid crystal driving unit 12, and the liquid crystal driving unit 12 sets the polarity of the video signal for each horizontal scanning period with reference to the set center voltage value. Is reversed. At this time, control is performed so that the amplitude of the video signal does not change.

  According to the liquid crystal display device of the present embodiment, the center voltage of the liquid crystal panel 13 is changed to an optimal value according to the amount of incident light on the liquid crystal panel 13 at regular time intervals. Thereby, it is possible to prevent the characteristic deterioration of the liquid crystal panel 13 caused by the deviation of the optimum common voltage when the amount of incident light on the liquid crystal panel 13 is changed, and the flicker caused by the deviation of the optimum common voltage is deteriorated. It is possible to prevent deterioration of contrast and color misregistration.

(Third embodiment)
FIG. 6 is a block diagram showing a configuration of a liquid crystal display device according to the third embodiment of the present invention.

  The liquid crystal display device of the present embodiment has a configuration in which the timer 17 and the light detection unit 18 are deleted and a light source 20 and a power control unit 21 are added to the configuration shown in FIG.

  In the liquid crystal display device of the present embodiment, the amount of light is controlled by controlling the power consumption of the light source 20 by utilizing the correlation between the power consumption of the light source 20 and the amount of light incident on the liquid crystal panel 13. At the same time, the common voltage value is controlled according to the power consumption value. Except this point, it is basically the same as that of the first embodiment.

  Hereinafter, features of the liquid crystal display device of the present embodiment will be described in detail.

  The video signal processing circuit 11 detects an APL (Average Picture Level) or a histogram of the input video signal and supplies the detection result to the control unit 10. The storage unit 14 stores characteristic data indicating the relationship between the power consumption value of the light source 20 and the common voltage value as an LUT. With respect to the number of data in the LUT, more accurate control can be performed by performing linear interpolation between the set data.

  The control unit 10 determines the area ratio of white and black of the image displayed on the liquid crystal panel 13 based on the detection result from the video signal processing circuit 11, and sets the power consumption value of the power source 20 according to the area ratio. decide. Specifically, the control unit 10 increases the power consumption of the power source 20 to achieve high brightness when the video is bright, and decreases the power consumption of the power source 20 when the video is dark. Improve contrast.

  In addition, the control unit 10 supplies an instruction signal including a power consumption value determined according to the area ratio of white and black to the power control unit 21. At the same time, the control unit 10 refers to the characteristic data stored in the storage unit 14, determines a common voltage value according to the determined power consumption value, and sets the common voltage according to the common voltage value to the common voltage generation unit. 15 is generated. The power control unit 21 performs power control of the light source 30 based on the power consumption value determined by the control unit 10.

  Also in the liquid crystal display device of the present embodiment, the common voltage supplied to the common electrode of the liquid crystal panel 13 is changed to an optimum value corresponding to the amount of light incident on the liquid crystal panel 13 as in the first embodiment. The Accordingly, even when the amount of incident light on the liquid crystal panel 13 is changed by the power control by the power control unit 21, the common voltage is set to the optimum value. Therefore, the characteristic deterioration of the liquid crystal panel 13, flicker deterioration, contrast deterioration, color, etc. A shift or the like can be prevented.

  In the above-described liquid crystal display device of the present embodiment, the control unit 10 sets a power consumption value for the power control unit 21 in accordance with the level of the input video signal, and refers to the characteristic data stored in the storage unit 14. Then, the common voltage value corresponding to the power consumption value is determined. In this operation, the center voltage value can be determined instead of the common voltage value. Specific operations will be described below.

  The storage unit 14 stores characteristic data indicating the relationship between the power consumption value of the light source 20 and the center voltage value. The liquid crystal driving unit 12 supplies a voltage corresponding to an input video signal whose signal polarity is inverted every certain period to a plurality of liquid crystal cells to display an image based on the input video signal on the liquid crystal panel 13.

  The control unit 10 sets a power consumption value for the power control unit 21 in accordance with the level of the input video signal, refers to the characteristic data stored in the storage unit 14, and determines the center voltage corresponding to the power consumption value. Determine the value. Based on the determined center voltage value, the control unit 10 changes the value of the center voltage applied to the liquid crystal panel 13 as an intermediate potential between the positive signal and the negative signal of the input video signal.

  By controlling the center voltage in accordance with the above incident light amount, the common voltage can be set to an optimum value, so that it is possible to prevent deterioration of the characteristics of the liquid crystal panel 13, deterioration of flicker, deterioration of contrast, color shift, and the like. .

  In the present embodiment, the light amount of the light source 20 deteriorates (becomes dark) due to secular change. Characteristic data indicating the degree of deterioration due to secular change (characteristic data consisting of an average value of deterioration) is acquired in advance, and based on the characteristic data, power consumption is set so that the amount of light incident on the liquid crystal panel 13 is constant. You may add the process which controls.

(Fourth embodiment)
FIG. 7 is a block diagram showing a configuration of a liquid crystal display device according to the fourth embodiment of the present invention.

  The liquid crystal display device of the present embodiment has a configuration in which the timer 17 and the light detection unit 18 are deleted and a light shielding unit 30 and a light shielding control unit 31 are added to the configuration shown in FIG.

  In the liquid crystal display device according to the present embodiment, there is a correlation between the transmittance (light shielding ratio) represented by the ratio of the intensity of light passing through the light shielding means 30 to the intensity of incident light and the amount of light incident on the liquid crystal panel 13. Thus, the amount of light is controlled by controlling the transmittance of the light shielding means 30, and the common voltage value is controlled according to the transmittance. Except this point, it is basically the same as that of the first embodiment.

  Hereinafter, features of the liquid crystal display device of the present embodiment will be described in detail.

  The video signal processing circuit 11 detects the APL and histogram of the input video signal and supplies the detection result to the control unit 10. The storage unit 14 stores characteristic data indicating the relationship between the transmittance of the light shielding unit 30 and the common voltage value as an LUT. With respect to the number of data in the LUT, more accurate control can be performed by performing linear interpolation between the set data.

  The control unit 10 determines the area ratio of white and black of the image displayed on the liquid crystal panel 13 based on the detection result from the video signal processing circuit 11, and sets the transmittance of the light shielding means 30 according to the area ratio. decide. Specifically, the control unit 10 increases the transmittance of the light shielding unit 30 in order to achieve high brightness when the image is bright, and decreases the transmittance of the light shielding unit 30 when the image is dark. Improve contrast.

  Further, the control unit 10 supplies an instruction signal including the transmittance determined according to the area ratio of white and black to the light shielding control unit 31. At the same time, the control unit 10 refers to the characteristic data stored in the storage unit 14, determines a common voltage value corresponding to the determined transmittance, and sets the common voltage corresponding to the common voltage value to the common voltage generation unit 15. Is generated.

  The light blocking control unit 31 controls the amount of blocking incident light in the blocking unit 30 based on the transmittance determined by the control unit 10. The shielding means 30 is, for example, an aperture or a shutter that is used in a camera or the like. The light shielding control unit 31 controls the amount of the incident light that is blocked by the shielding unit 30 by controlling the size of the aperture of the diaphragm.

  Also in the liquid crystal display device of the present embodiment, the common voltage supplied to the common electrode of the liquid crystal panel 13 is changed to an optimum value corresponding to the amount of light incident on the liquid crystal panel 13 as in the first embodiment. The Accordingly, even when the amount of incident light on the liquid crystal panel 13 is changed by the light shielding control by the light shielding control unit 31, the common voltage is set to the optimum value. Therefore, the characteristic deterioration of the liquid crystal panel 13, the flicker deterioration, the contrast deterioration, the color A shift or the like can be prevented.

  In the above-described liquid crystal display device of the present embodiment, the control unit 10 sets the transmittance for the light shielding control unit 31 according to the level of the input video signal, and refers to the characteristic data stored in the storage unit 14. The common voltage value corresponding to the transmittance is determined. In this operation, the center voltage value can be determined instead of the common voltage value. Specific operations will be described below.

  The storage unit 14 stores characteristic data indicating the relationship between the light shielding rate of the light shielding means 30 and the center voltage value. The liquid crystal driving unit 12 supplies a voltage corresponding to an input video signal whose signal polarity is inverted every certain period to a plurality of liquid crystal cells to display an image based on the input video signal on the liquid crystal panel 13.

  The control unit 10 sets the transmittance with respect to the light shielding control unit 31 according to the level of the input video signal, and refers to the characteristic data stored in the storage unit 14 to determine the center voltage value according to the transmittance. decide. Based on the determined center voltage value, the control unit 10 changes the value of the center voltage applied to the liquid crystal panel 13 as an intermediate potential between the positive signal and the negative signal of the input video signal.

  By controlling the center voltage in accordance with the above incident light amount, the common voltage can be set to an optimum value, so that it is possible to prevent deterioration of the characteristics of the liquid crystal panel 13, deterioration of flicker, deterioration of contrast, color shift, and the like. .

  Also in this embodiment, the light quantity of the light source deteriorates (becomes dark) due to aging. Characteristic data indicating the degree of deterioration due to secular change (characteristic data consisting of an average value of deterioration) is acquired in advance, and based on the characteristic data, the light shielding rate so that the amount of light incident on the liquid crystal panel 13 is constant. You may add the process which controls.

  Each embodiment described above is an example of the present invention, and the configuration and operation thereof can be changed without departing from the spirit of the invention.

  The present invention can be applied to all liquid crystal display devices using a liquid crystal panel, including projectors and the like.

DESCRIPTION OF SYMBOLS 10 Control part 11 Video signal processing circuit 12 Liquid crystal drive part 13 Liquid crystal panel 14 Memory | storage part 15 Common voltage generation part 16 Buffer 17 Timer 18 Light detection part

In order to achieve the above object, a liquid crystal display device including a liquid crystal panel according to an aspect of the present invention is provided.
A common voltage generator for supplying a common voltage to a common electrode to which a plurality of liquid crystal cells constituting the liquid crystal panel are connected in common;
A positive video signal and a negative video signal are generated based on the input video signal for each predetermined period so that the center voltage becomes an intermediate potential, and the positive and negative video signals are generated according to the generated positive and negative video signals. a liquid crystal driving unit for supplying to the pixel electrodes respectively corresponding voltages to the plurality of liquid crystal cells,
The liquid crystal panel in accordance with a value corresponding to the light amount is the amount of light incident on, the value before xenon pointer voltage and having a control unit for supplying to the liquid crystal driving section.

According to one embodiment of the present invention, a method for driving a liquid crystal panel including a plurality of liquid crystal cells includes:
A positive video signal and a negative video signal are generated based on the input video signal for each predetermined period so that the center voltage becomes an intermediate potential, and the positive and negative video signals are generated according to the generated positive and negative video signals. Supplying a voltage to the pixel electrodes corresponding to the plurality of liquid crystal cells,
In response to said value corresponding to the light amount is the amount of light incident on the liquid crystal panel, prior to said changing the value of the xenon pointer voltage.

The control unit 10 determines the area ratio of white and black of the image displayed on the liquid crystal panel 13 based on the detection result from the video signal processing circuit 11, and sets the power consumption value of the light source 20 according to the area ratio. decide. Specifically, the control unit 10 increases the power consumption of the light source 20 in order to achieve high brightness when the image is bright, and decreases the power consumption of the light source 20 when the image is dark. Improve contrast.

In addition, the control unit 10 supplies an instruction signal including a power consumption value determined according to the area ratio of white and black to the power control unit 21. At the same time, the control unit 10 refers to the characteristic data stored in the storage unit 14, determines a common voltage value according to the determined power consumption value, and sets the common voltage according to the common voltage value to the common voltage generation unit. 15 is generated. The power control unit 21 performs power control of the light source 20 based on the power consumption value determined by the control unit 10.

Shielding control unit 31 controls the amount that blocks incident light on the light means 30 shielding based on the transmission rate determined by the control unit 10. Light means 30 shielding is a diaphragm or a shutter used in a camera or the like. Shielding control unit 31, by controlling the size of the opening of the diaphragm to control the amount that blocks incident light on the light means 30 shielding.

Claims (10)

A liquid crystal display device comprising a liquid crystal panel,
A common voltage generator for supplying a common voltage to a common electrode to which a plurality of liquid crystal cells constituting the liquid crystal panel are connected in common;
A liquid crystal driving unit that supplies a voltage according to an input video signal to the plurality of liquid crystal cells to display an image based on the input video signal on the liquid crystal panel;
A liquid crystal display device comprising: a control unit that changes a value of a common voltage generated by the common voltage generation unit in accordance with a signal indicating an amount of light incident on the liquid crystal panel. A light detection unit for detecting the amount of light incident on the liquid crystal panel;
A storage unit storing characteristic data indicating a relationship between the incident light amount and a common voltage value;
The control unit refers to the characteristic data stored in the storage unit, determines a common voltage value according to the amount of light detected by the light detection unit, and sets the common voltage according to the common voltage value to the common The liquid crystal display device according to claim 1, wherein the liquid crystal display device is generated by a voltage generator. A light source for illuminating the liquid crystal panel;
A power control unit that performs power control of the light source based on a set power consumption value;
A storage unit storing characteristic data indicating a relationship between a power consumption value of the light source and a common voltage value;
The control unit sets a power consumption value for the power control unit in accordance with the level of the input video signal, refers to characteristic data stored in the storage unit, and determines a common value corresponding to the power consumption value. The liquid crystal display device according to claim 1, wherein a voltage value is determined and a common voltage corresponding to the common voltage value is generated by the common voltage generation unit. A shielding means that is provided on the incident surface side of the liquid crystal panel and adjusts the amount of light incident on the liquid crystal panel by blocking a part of the incident light;
A storage unit storing characteristic data indicating a relationship between a transmittance and a common voltage value represented by a ratio of the intensity of light passing through the shielding unit to the intensity of light incident on the shielding unit;
A light shielding control unit for controlling an amount of shielding the incident light in the shielding means based on the set transmittance;
The control unit sets a transmittance for the light shielding control unit according to a level of the input video signal, and refers to characteristic data stored in the storage unit, and a common voltage value corresponding to the transmittance The liquid crystal display device according to claim 1, wherein a common voltage corresponding to the common voltage value is generated by the common voltage generator. A liquid crystal display device comprising a liquid crystal panel,
A common voltage generator for supplying a common voltage to a common electrode to which a plurality of liquid crystal cells constituting the liquid crystal panel are connected in common;
A liquid crystal driving unit for supplying a voltage corresponding to an input video signal whose polarity is inverted every certain period to the plurality of liquid crystal cells and displaying an image based on the input video signal on the liquid crystal panel;
A value of a center voltage applied to the liquid crystal panel as an intermediate potential between a positive signal and a negative signal of the input video signal is changed according to a signal indicating the amount of light incident on the liquid crystal panel. A liquid crystal display device having a control unit. A light detection unit for detecting the amount of light incident on the liquid crystal panel;
A storage unit storing characteristic data indicating a relationship between the incident light amount and the center voltage value;
The control unit refers to the characteristic data stored in the storage unit, determines a center voltage value corresponding to the amount of light detected by the light detection unit, and the liquid crystal panel based on the determined center voltage value The liquid crystal display device according to claim 5, wherein the value of the center voltage applied to the is changed. A light source for illuminating the liquid crystal panel;
A power control unit that performs power control of the light source based on a set power consumption value;
A storage unit storing characteristic data indicating a relationship between a power consumption value of the light source and a center voltage value;
The control unit sets a power consumption value for the power control unit in accordance with the level of the input video signal, and refers to characteristic data stored in the storage unit to determine a center corresponding to the power consumption value. The liquid crystal display device according to claim 5, wherein a voltage value is determined, and a value of the center voltage applied to the liquid crystal panel is changed based on the determined center voltage value. A shielding means that is provided on the incident surface side of the liquid crystal panel and adjusts the amount of light incident on the liquid crystal panel by blocking a part of the incident light;
A storage unit storing characteristic data indicating a relationship between a transmittance and a center voltage value expressed by a ratio of light intensity that has passed through the shielding unit to light intensity incident on the shielding unit;
A light shielding control unit for controlling an amount of shielding the incident light in the shielding means based on the set transmittance;
The control unit sets a transmittance for the light-shielding control unit according to the level of the input video signal, and refers to characteristic data stored in the storage unit, and a center voltage value corresponding to the transmittance The liquid crystal display device according to claim 5, wherein the value of the center voltage applied to the liquid crystal panel is changed based on the determined center voltage value. A method for driving a liquid crystal panel comprising a plurality of liquid crystal cells,
A voltage corresponding to an input video signal is supplied to the plurality of liquid crystal cells to display an image based on the input video signal on the liquid crystal panel, and a common voltage is applied to a common electrode to which the plurality of liquid crystal cells are connected in common. Supply
A method for driving a liquid crystal panel, wherein a value of a common voltage supplied to the common electrode is changed in accordance with a signal indicating the amount of light incident on the liquid crystal panel. A method for driving a liquid crystal panel comprising a plurality of liquid crystal cells,
A voltage corresponding to an input video signal whose signal polarity is inverted every certain period is supplied to the plurality of liquid crystal cells to display an image based on the input video signal on the liquid crystal panel, and the plurality of liquid crystal cells Supply a common voltage to the common electrode connected in common,
A value of a center voltage applied to the liquid crystal panel as an intermediate potential between a positive signal and a negative signal of the input video signal is changed according to a signal indicating the amount of light incident on the liquid crystal panel. , Liquid crystal panel driving method.

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