JP2011197384A - Liquid crystal driving device, liquid crystal display device, and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal driving device in which deterioration of an image can be suppressed, a liquid crystal display device, and a projector.SOLUTION: The liquid crystal driving device 5A drives a liquid crystal panel 442 and adjusts at least one of the voltage level of counter electrode voltage applied to the counter electrode of the liquid crystal panel 442 and the duty ratio of pixel electrode voltage which is applied to the pixel electrode of the liquid crystal panel 442 and whose polarity is reversed within one period, in accordance with the use state of the liquid crystal panel 442. Accordingly, since quantity of electric charges held by liquid crystal materials of the pixel can be made nearly coincide with each other in a positive polarity side and a negative polarity side in the pixel electrode voltage, gradation of the pixels can be made nearly coincident with each other in the positive polarity side and the negative polarity side.

Description

  The present invention relates to a liquid crystal driving device that drives a liquid crystal panel, a liquid crystal display device including the liquid crystal driving device, and a projector.

2. Description of the Related Art Conventionally, an image display device including a liquid crystal panel (liquid crystal cell array) and a driving device (data line driving circuit and row driving circuit) that drives the liquid crystal panel based on an image signal and forms an image according to the image signal. Is known (see, for example, Patent Document 1).
Here, the liquid crystal panel has a configuration in which a liquid crystal material is sealed between a pair of translucent substrates via an alignment film, and a polarizing plate is provided outside the pair of translucent substrates. Of these pair of translucent substrates, one translucent substrate is a drive substrate (array substrate) for driving liquid crystal, and includes a plurality of scanning lines, a plurality of data lines (signal lines), and these It has a switching element such as a TFT (Thin Film Transistor) arranged according to the intersection of the scanning line and the data line, and a pixel electrode to which a pixel electrode voltage is applied from the data line through the switching element. The other translucent substrate is a counter substrate having a counter electrode, and a counter electrode voltage is applied to the counter electrode.

  In such a liquid crystal panel, when the switching element is turned on (conductive state) by a voltage (scanning signal) applied from the driving device via the scanning line, the pixel electrode is also transferred from the driving device to the pixel electrode via the data line. A voltage is applied. The liquid crystal material responds based on the potential difference between the pixel electrode voltage and the counter electrode voltage, and the alignment state of the liquid crystal material is changed. Such driving is performed for all pixels. The light beam incident through one polarizing plate is modulated by each pixel, and the modulated light beam is emitted from the liquid crystal panel through the other polarizing plate, so that an image corresponding to the image signal is output. The

JP 2006-106689 A

Here, the voltage level of the pixel electrode voltage varies depending on the input image signal. On the other hand, since the optimum value of the voltage level of the counter electrode voltage varies depending on individual differences of the liquid crystal panels, it is set at the shipping stage according to the characteristics of the liquid crystal panel.
However, depending on the usage state of the image display device, the voltage level of the counter electrode voltage set at the shipping stage may not be appropriate. For example, the optimum value (optimum level) of the counter electrode voltage may differ depending on the gradation of the pixel used for image formation. When a pixel electrode voltage and a counter electrode voltage having a voltage level that is not appropriate for the pixel electrode voltage are applied, a positive polarity side (a portion having a higher voltage level than the counter electrode voltage) of the pixel electrode voltage whose polarity is reversed The potential difference with respect to the counter electrode voltage differs on the negative polarity side (portion where the voltage level is lower than the counter electrode voltage). In such a case, the amount of charge held in the liquid crystal material is different between the positive polarity side and the negative polarity side, and the gradation (display) is different between the positive polarity side and the negative polarity side. Such a difference is recognized as flicker, and there is a problem that a visually recognized image deteriorates.

  An object of the present invention is to provide a liquid crystal driving device, a liquid crystal display device, and a projector that can suppress image deterioration.

  In order to achieve the above-described object, the liquid crystal driving device of the present invention is a liquid crystal driving device for driving a liquid crystal panel, and is opposed to the counter electrode of the liquid crystal panel according to the usage state of the liquid crystal panel. At least one of the voltage level of the electrode voltage and the duty ratio of the pixel electrode voltage that is applied to the pixel electrode of the liquid crystal panel and whose polarity is inverted within one period is adjusted.

  As a configuration of such a liquid crystal panel, a translucent drive substrate, a translucent counter substrate disposed opposite to the drive substrate, and a liquid crystal material sealed between the drive substrate and the counter substrate, The driving substrate includes a scanning line, a data line, a switching element connected to the scanning line and the data line, and a pixel connected to the switching element and applying a pixel electrode voltage to the liquid crystal material The structure which has an electrode and the said counter substrate has a counter electrode which applies a counter electrode voltage to the said liquid-crystal material can be illustrated.

  According to the present invention, at least one of the voltage level of the counter electrode voltage and the duty ratio of the pixel electrode voltage whose polarity is inverted within one cycle is adjusted according to the usage state of the liquid crystal panel. According to this, on the positive polarity side held in the liquid crystal material of the pixel based on the potential difference with respect to the counter electrode voltage on the positive polarity side in the pixel electrode voltage and the pulse width of the pixel electrode voltage on the positive polarity side. The amount of charge, the potential difference with respect to the counter electrode voltage on the negative polarity side, and the charge amount on the negative polarity side held in the liquid crystal material of the pixel based on the pulse width of the pixel electrode voltage on the negative polarity side are approximately Can be matched. Therefore, since the gradation of the pixel can be substantially matched between the positive polarity side and the negative polarity side, occurrence of flicker can be suppressed and deterioration of the displayed image can be suppressed.

  In the liquid crystal driving device of the present invention, the liquid crystal driving device drives the liquid crystal panel according to input image information, and the usage state is an average luminance level of an image generated based on the image information. It is preferable.

Here, when the average luminance level is high, the voltage level of the pixel electrode voltage applied to the liquid crystal panel is high, and when the average luminance level is low, the voltage level of the pixel electrode voltage is low.
On the other hand, in the present invention, the average luminance level of the image generated based on the image information, that is, the voltage level of the counter electrode voltage and the pixel electrode voltage according to the voltage level of the applied pixel electrode voltage. At least one of the duty ratios can be adjusted. Accordingly, an image corresponding to the input image information can be appropriately displayed.

  In the liquid crystal drive device of the present invention, when the average luminance level is high, the voltage level of the counter electrode voltage is set higher than a predetermined level, or the pulse width on the positive polarity side of the pixel electrode voltage is set on the negative polarity side. If the average luminance level is lower than the pulse width, the voltage level of the counter electrode voltage is set lower than a predetermined level, or the pulse width on the positive side of the pixel electrode voltage is set to the pulse on the negative side. It is preferable to make it longer than the width.

The predetermined level can be, for example, the voltage level of the counter electrode voltage suitable for the pixel electrode voltage when the gray level of the pixel is an intermediate gray level.
According to the present invention, when the average luminance level is high and the voltage level of the applied pixel electrode voltage is high, the voltage level of the counter electrode voltage is set higher than a predetermined level, or the duty ratio of the pixel electrode voltage is set. The pulse width on the positive polarity side is set to a duty ratio shorter than the pulse width on the negative polarity side. Thereby, it is possible to ensure that the amount of charge held in the liquid crystal material is substantially the same between the positive polarity side and the negative polarity side in the pixel electrode voltage.
Similarly, when the average luminance level is low and the voltage level of the applied pixel electrode voltage is low, the voltage level of the counter electrode voltage is set lower than a predetermined level, or the duty ratio of the pixel electrode voltage is set to the positive electrode The pulse width on the negative side is set to a duty ratio longer than the pulse width on the negative side. According to this, the amount of charges held in the liquid crystal material can be substantially matched with each other on the positive side and the negative side in the pixel electrode voltage.
Therefore, regardless of the level of the average luminance level, the gradation of the pixel can be substantially matched between the positive polarity side and the negative polarity side in the pixel electrode voltage, and the occurrence of flicker can be reliably suppressed.

  Alternatively, in the liquid crystal driving device of the present invention, the liquid crystal driving device drives the liquid crystal panel based on a gamma correction value corresponding to a set color mode among color modes having different use gradations, and uses the liquid crystal panel. The state is preferably the set color mode.

Examples of such color modes include “dynamic” with a high use gradation and “theater” with a low use gradation.
Here, the voltage level of the pixel electrode voltage applied to the liquid crystal panel rises and falls based on the gamma correction value in accordance with the level of use gradation in the set color mode.
On the other hand, in the present invention, according to the set color mode, that is, according to the voltage level of the applied pixel electrode voltage, at least one of the voltage level of the counter electrode voltage and the duty ratio of the pixel electrode voltage. To adjust. According to this, as described above, the amount of charge held in the liquid crystal material of the pixel can be substantially matched between the positive side and the negative side in the pixel electrode voltage. Therefore, the occurrence of flicker can be suppressed and image degradation can be suppressed.

  In the liquid crystal drive device of the present invention, when the use gradation of the set color mode is high, the voltage level of the counter electrode voltage is set higher than a predetermined level, or the positive polarity side pulse of the pixel electrode voltage When the width is made shorter than the pulse width on the negative polarity side and the use gradation of the set color mode is low, the voltage level of the counter electrode voltage is made lower than a predetermined level, or the pixel electrode voltage The pulse width on the positive polarity side is preferably longer than the pulse width on the negative polarity side.

As in the case described above, the predetermined level can be, for example, the voltage level of the counter electrode voltage suitable for the pixel electrode voltage when the pixel gradation is set to the intermediate gradation.
According to the present invention, as in the case described above, when the color mode with a high use gradation is set and the voltage level of the applied pixel electrode voltage is high, the voltage level of the counter electrode voltage is set higher than a predetermined level. Alternatively, the duty ratio of the pixel electrode voltage is set to a duty ratio in which the pulse width on the positive polarity side is shorter than the pulse width on the negative polarity side. According to this, the amount of charges held in the liquid crystal material can be substantially matched with each other on the positive side and the negative side in the pixel electrode voltage.

Similarly, when a color mode with a low use gradation is set and the voltage level of the applied pixel electrode voltage is low, the voltage level of the counter electrode voltage is set lower than a predetermined value, or the pixel electrode voltage The duty ratio is set to a duty ratio in which the pulse width on the positive polarity side is longer than the pulse width on the negative polarity side. According to this, the amount of charges held in the liquid crystal material can be substantially matched with each other on the positive side and the negative side in the pixel electrode voltage.
Therefore, the gray level of the pixel can be substantially matched between the positive polarity side and the negative polarity side of the pixel electrode voltage without depending on the level of the usage gray level according to the set color mode, and flicker is surely generated. Can be suppressed.

In addition, a liquid crystal display device of the present invention includes the above-described liquid crystal driving device and a liquid crystal panel driven by the liquid crystal driving device.
According to the present invention, it is possible to achieve the same effect as that of the above-described liquid crystal driving device, thereby displaying an image in which the deterioration of image quality is suppressed.

According to another aspect of the invention, there is provided a projector that modulates a light beam emitted from a light source and displays an image according to image information, and includes the above-described liquid crystal display device.
According to the present invention, the same effects as those of the above-described liquid crystal display device can be obtained.

FIG. 1 is a schematic diagram illustrating a configuration of a projector according to a first embodiment of the invention. The block diagram which shows the structure of the control apparatus in the said embodiment. The figure which shows the counter electrode voltage and pixel electrode voltage in the said embodiment. The block diagram which shows the structure of the control apparatus which the projector which concerns on 2nd Embodiment of this invention has. The block diagram which shows the structure of the control apparatus which the projector which concerns on 3rd Embodiment of this invention has. The figure which shows the counter electrode voltage and pixel electrode voltage in the said embodiment. The block diagram which shows the structure of the control apparatus which the projector which concerns on 4th Embodiment of this invention has. The figure which shows the counter electrode voltage and pixel electrode voltage which are applied to a liquid crystal panel by the control apparatus which the projector which is a modification of each said embodiment has.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described based on the drawings.
[Configuration of projector]
FIG. 1 is a schematic diagram illustrating a configuration of a projector 1 according to the present embodiment.
The projector 1 according to the present embodiment modulates a light beam emitted from a light source device 411 provided therein to form image light corresponding to image information, and the image light is projected onto a projection surface (not shown) such as a screen. ) Enlarging projection on top. As shown in FIG. 1, the projector 1 includes an exterior housing 2 having an overall substantially rectangular parallelepiped shape, a liquid crystal display device 3 </ b> A housed in the exterior housing 2, and an operation device 6 for operating the projector 1. (See FIG. 2). In addition to these, although not shown, the projector 1 includes a cooling device that cools the inside of the projector 1, a power supply device that supplies power to each component inside the projector 1, and the like.

  Among these, the operation device 6 is composed of a plurality of keys provided to be exposed on the outer surface of the exterior housing 2, and the operation device 6 provides an operation signal corresponding to the input key to the control device 5 </ b> A described later. Output to. As such keys, for example, a power key for turning on / off the power, a direction key for performing various settings, and a determination key, as well as switching color modes such as “dynamic”, “living room”, and “theater”. Examples include a switching key.

[Configuration of liquid crystal display device]
The liquid crystal display device 3A displays an image corresponding to image information (including an image signal) input from a connected external device or the like on the projection surface. The liquid crystal display device 3A includes an image forming device 4 and a control device 5A.

[Configuration of image forming apparatus]
The image forming device 4 is an optical device that forms and projects image light under the control of the control device 5A. The image forming apparatus 4 has a substantially L-shape in plan view that extends along the back surface of the exterior housing 2 and extends along the side surface of the exterior housing 2. Such an image forming apparatus 4 includes a uniform illumination device 41, a color separation device 42, a relay device 43, an electro-optical device 44, a projection optical device 45, and each of these devices 41 to 44 housed and arranged therein, and a projection. And an optical component housing 46 for supporting and fixing the optical device 45 at a predetermined position.

The uniform illumination device 41 illuminates an image forming area of a liquid crystal panel 442 described later substantially uniformly. The uniform illumination device 41 includes a light source device 411, a pair of lens arrays 412 and 413, a polarization conversion element 414, and a superimposing lens 415.
Among these, the light source device 411 reflects the light emitted from the light source 416, reflects the light emitted from the light source 416 and converges it at a predetermined position, and reflects and converges at the reflective mirror 417. A collimating lens 418 that collimates the light beam with respect to the illumination optical axis A is provided. As such a light source 416, a light source lamp such as an ultra-high pressure mercury lamp can be employed, and a solid light source such as an LED (Light Emitting Diode) can also be employed.

The color separation device 42 includes dichroic mirrors 421 and 422 and a reflection mirror 423, and the relay device 43 includes an incident side lens 431, a relay lens 433, and reflection mirrors 432 and 434.
The electro-optical device 44 includes three field lenses 441 and three liquid crystal panels 442 as three light modulation devices (the liquid crystal panels for red light, green light, and blue light are respectively 442R, 442G, and 442B). , Three incident-side polarizing plates 443, a viewing angle compensation plate 444 and an outgoing-side polarizing plate 445, and one cross dichroic prism 446 as a color composition device.
The projection optical device 45 enlarges and projects the image light synthesized by the cross dichroic prism 446 and forms an image on the projection surface. The projection optical device 45 is configured as a combined lens in which a plurality of lenses are housed in a cylindrical barrel.

  In such an image forming apparatus 4, a light beam emitted from the uniform illumination device 41 and having a uniform in-plane illuminance in the illumination area is R (red), G (green), B ( Blue) is separated into three color lights. Each separated color light is modulated by the corresponding liquid crystal panel 442 according to image information, and image light for each color light is formed. Each image light is combined by the cross dichroic prism 446 and projected by the projection optical device 45.

[Configuration of control device]
FIG. 2 is a block diagram showing the configuration of the control device 5A.
The control device 5A controls the operation of the entire projector 1 autonomously or according to a user operation. For example, the control device 5A drives the liquid crystal panel 442 based on the above-described image information, and causes the liquid crystal panel 442 to form an image corresponding to the image information. That is, the control device 5A corresponds to the liquid crystal driving device of the present invention.
As shown in FIG. 2, the control device 5A includes a video processing unit 51, a frame memory 52, an APL calculation unit 53, a counter electrode voltage setting unit 54, a flash memory 55, and a liquid crystal driver 56.

Among these, the frame memory 52 is a memory used for image formation by the video processing unit 51, and is configured to be capable of storing image data for at least one frame.
The flash memory 55 is a storage unit that stores various programs and data necessary for control by the control device 5A. As such data, for example, an LUT (Look-Up Table) in which an average value of APL (Average Picture Level) of an image and a voltage level of a counter electrode voltage applied to the liquid crystal panel 442 are associated with each other. Is remembered.

The video processing unit 51 processes the above-described image information and generates an image (frame) corresponding to the image information on the frame memory 52. Then, the video processing unit 51 outputs an image signal corresponding to the image to the liquid crystal driver 56.
The APL calculation unit 53 refers to the image (frame) generated on the frame memory 52 by the video processing unit 51, calculates the APL of the image, and calculates the average value of APL within a predetermined period. Note that the present invention is not limited to this, and frames generated at a predetermined interval among the generated frames may be acquired, and an average value of APLs of the acquired frames may be calculated.

The counter electrode voltage setting unit 54 sets the voltage level of the counter electrode voltage output to the liquid crystal panel 442 by the liquid crystal driver 56. That is, as will be described in detail later, the counter electrode voltage setting unit 54 has substantially the same potential difference between the counter electrode voltage on the positive polarity side of the pixel electrode voltage and the counter electrode voltage on the negative polarity side. Thus, the voltage level of the counter electrode voltage is set.
Such a counter electrode voltage setting unit 54 obtains a voltage level corresponding to the average value of the APL calculated by the APL calculation unit 53 from the LUT of the flash memory 55, and uses the counter electrode voltage of the voltage level as the liquid crystal driver 56. To output to the liquid crystal panel 442. Thereby, the counter electrode voltage is optimized based on the average value of APL.
Note that the voltage level of the counter electrode voltage is set to a voltage level (shipment level) suitable for the pixel electrode voltage when the gradation of each pixel of the liquid crystal panel 442 is set to an intermediate gradation at the shipment stage.

The liquid crystal driver 56 sends the data signal and the scanning signal to the liquid crystal panel 442 in accordance with the image signal (including the vertical / horizontal synchronization signal and the data enable signal in addition to the data signal and the scanning signal) input from the video processing unit 51. Are respectively output to the data line and the scanning line. At this time, the liquid crystal driver 56 applies a pixel electrode voltage Vs whose polarity is inverted in a half cycle as a data signal.
Further, the liquid crystal driver 56 applies a counter electrode voltage at a voltage level set by the counter electrode voltage setting unit 54 to the liquid crystal panel 442. As a result, the liquid crystal material of each pixel of the liquid crystal panel 442 holds a charge corresponding to the potential difference between the pixel electrode voltage applied to the pixel electrode via the data line and the counter electrode voltage applied to the counter electrode. Thus, the gradation (luminance level) of the pixel is determined.

  At this time, when the voltage level of the pixel electrode voltage is high, the amount of charge held in the liquid crystal material of the pixel increases. For this reason, the gradation of a pixel becomes high and the pixel is displayed brightly. On the other hand, when the voltage level of the pixel electrode voltage is low, the amount of charge held in the liquid crystal material of the pixel is small. For this reason, the gradation of the pixel is lowered and the pixel is darkly displayed.

[Voltage level of the counter electrode voltage applied to the liquid crystal panel]
FIG. 3 is a diagram showing the counter electrode voltage Vcom and the pixel electrode voltage Vs applied to the liquid crystal panel 442 by the liquid crystal driver 56.
Here, a state where the voltage level of the counter electrode voltage is not appropriate will be described.
When the pixel electrode voltage Vs having a voltage level suitable for the counter electrode voltage Vcom at the shipping level is applied, as shown in FIG. 3A, the positive polarity side of the pixel electrode voltage Vs (the voltage from the counter electrode voltage Vcom is higher). The potential difference from the counter electrode voltage Vcom at a high level) and the potential difference from the counter electrode voltage Vcom at the negative polarity side (portion where the voltage level is lower than the counter electrode voltage Vcom) are substantially the same. For this reason, the amount of charge held in the liquid crystal material of the pixel (the amount of charge corresponding to the area of the hatched portion in FIG. 3A) is approximately the same on the positive side and the negative side, and the gradation ( Is substantially the same between the positive polarity side and the negative polarity side.

  On the other hand, when the pixel electrode voltage Vs whose voltage level is lower than the voltage level shown in FIG. 3A is applied in a state where the counter electrode voltage Vcom having the same voltage level as that in FIG. As shown in (B), the potential difference on the positive polarity side and the potential difference on the negative polarity side in the pixel electrode voltage Vs are different. For this reason, the amount of charge held in the liquid crystal material of the pixel differs between the positive polarity side and the negative polarity side, and the gradation (display) of the pixel differs between the positive polarity side and the negative polarity side. Causes flicker.

On the other hand, in the present embodiment, the liquid crystal driver 56 outputs the voltage level corresponding to the APL calculated by the APL calculation unit 53 based on the image generated according to the input image information. The counter electrode voltage setting unit 54 sets the voltage level of the counter electrode voltage. Thereby, the voltage level of the counter electrode voltage Vcom is lowered from the above-described shipping level.
Therefore, even when the pixel electrode voltage Vs having a low APL and a low voltage level is applied, the potential difference between the pixel electrode voltage Vs and the counter electrode voltage Vcom on the positive polarity side as shown in FIG. The potential difference on the negative polarity side can be made substantially coincident. For this reason, the amount of charge held in the liquid crystal material can be substantially matched between the positive polarity side and the negative polarity side, and the gradation (display) of the pixels can be substantially matched between the positive polarity side and the negative polarity side. it can. Therefore, the occurrence of flicker can be suppressed.

When the APL is high, the counter electrode voltage setting unit 54 sets the voltage level of the counter electrode voltage to a high voltage level acquired based on the APL. As a result, the voltage level of the counter electrode voltage Vcom is raised from the aforementioned shipping level.
For this reason, as in the case described above, the amount of charge held in the liquid crystal material can be made substantially the same on the positive side and the negative side in the pixel electrode voltage Vs. Therefore, the gradation (display) of the pixels can be substantially matched on the positive polarity side and the negative polarity side, and the occurrence of flicker can be suppressed.

The projector 1 according to the present embodiment described above has the following effects.
The counter electrode voltage setting unit 54 adjusts and sets the level of the voltage level of the counter electrode voltage according to the average value of the APL of the input image. According to this, as described above, the amount of charge held in the liquid crystal material of the pixel can be substantially matched between the positive side and the negative side in the pixel electrode voltage. Accordingly, the gradation of the pixels can be substantially matched between the positive polarity side and the negative polarity side, so that the display image can be prevented from being deteriorated by flicker.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.
The projector according to this embodiment has the same configuration as that of the projector 1 described above. Here, in the projector 1, the counter electrode voltage setting unit 54 sets the voltage level of the counter electrode voltage based on the average value of the APL of the image corresponding to the input image signal. On the other hand, in the projector according to the present embodiment, the voltage level of the counter electrode voltage is set based on the gamma correction value corresponding to the color mode set by the user. In this respect, the projector according to the present embodiment is different from the projector 1. In the following description, parts that are the same as or substantially the same as those already described are assigned the same reference numerals and description thereof is omitted.

FIG. 4 is a block diagram illustrating a configuration of the control device 5B included in the projector according to the present embodiment.
The projector according to the present embodiment has the same configuration as the projector 1 described above except that the liquid crystal display device 3B is provided instead of the liquid crystal display device 3A. The liquid crystal display device 3B includes an image forming device 4 and a control device 5B.
As shown in FIG. 4, the control device 5B includes a gamma setting unit 57, a counter electrode voltage setting unit 54B, and a flash memory 55B in place of the APL calculation unit 53, the counter electrode voltage setting unit 54, and the flash memory 55. Has the same configuration as the control device 5A.

The gamma setting unit 57 determines the color mode set by the user based on the operation signal input from the operation device 6 in response to the user's input operation to the mode switching key, and according to the color mode. Set the gamma correction value.
Similarly to the flash memory 55, the flash memory 55B is a storage unit that stores various programs and data necessary for control by the control device 5B. Further, the flash memory 55B stores an LUT in which the gamma correction value set by the gamma setting unit 57 is associated with the voltage level of the counter electrode voltage.

Similar to the counter electrode voltage setting unit 54, the counter electrode voltage setting unit 54B adjusts the voltage level of the counter electrode voltage so that the potential difference with respect to the counter electrode voltage is substantially the same between the positive polarity side and the negative polarity side of the pixel electrode voltage. Set. The counter electrode voltage setting unit 54B refers to the LUT of the flash memory 55B, acquires a voltage level corresponding to the set gamma correction value, and sets the voltage level of the counter electrode voltage to the voltage level. As a result, the counter electrode voltage at the voltage level is applied from the liquid crystal driver 56 to the liquid crystal panel 442.
In the present embodiment, the voltage level of the counter electrode voltage is set to the above-described shipping level at the shipping stage, and the color mode is set to “living” which is a color mode using an intermediate gradation. ing.

Here, as described above, the gamma correction value is changed when the color mode is changed. The gamma correction value is referred to by the video processing unit 51, and the output of the data signal based on the generated image is corrected based on the gamma correction value. That is, the use gradation range of each pixel of the liquid crystal panel 442 is set by the gamma correction value.
For example, when “dynamic” using a high gradation range is set as the color mode, the gamma setting unit 57 sets a gamma correction value corresponding to “dynamic”. As a result, the voltage level of the data signal output from the video processing unit 51 is increased, and the gradation of each pixel is increased.
On the other hand, when “theater” using a low gradation range is set by the user as the color mode, the gamma setting unit 57 sets a gamma correction value corresponding to “theater”. Thereby, the voltage level of the data signal output from the video processing unit 51 is lowered, and the gradation of each pixel is lowered.

The counter electrode voltage setting unit 54B adjusts the voltage level of the counter electrode voltage applied to the liquid crystal panel 442 by the liquid crystal driver 56 in accordance with such a change in the color mode, that is, a change in the gamma correction value.
Specifically, when a pixel electrode voltage Vs having a high voltage level is applied as a data signal by correction based on a gamma correction value corresponding to a color mode using a high gradation range, the counter electrode voltage setting unit 54B The voltage level of the counter electrode voltage Vcom is set higher than the shipping level. As a result, as in the case shown in FIG. 3A, the charge amount held in the liquid crystal material can be substantially matched between the positive polarity side and the negative polarity side in the pixel electrode voltage Vs. The gray level of the pixel can be substantially matched between the negative side and the negative side, and the occurrence of flicker can be suppressed.

  When the pixel electrode voltage Vs having a low voltage level is applied as a data signal by correction based on a gamma correction value corresponding to a color mode using a low gradation range, the counter electrode voltage setting unit 54B The voltage level of the electrode voltage Vcom is set lower than the shipping level. As a result, as in the case shown in FIG. 3C, the amount of charge held in the liquid crystal material can be substantially matched between the positive polarity side and the negative polarity side in the pixel electrode voltage Vs. The gradation (display) of the pixels can be substantially matched between the negative side and the negative side, and the occurrence of flicker can be suppressed.

According to the projector according to the present embodiment described above, the same effects as those of the projector 1 described above can be obtained.
That is, the voltage level of the common electrode voltage Vcom is adjusted by the common electrode voltage setting unit 54B based on the set color mode gamma correction value. According to this, as described above, the charge amount held in the liquid crystal material of the pixel can be substantially matched between the positive polarity side and the negative polarity side in the pixel electrode voltage Vs. Therefore, since the gradation of the pixel can be substantially matched between the positive polarity side and the negative polarity side, display image deterioration due to flicker can be suppressed.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.
The projector according to the present embodiment has the same configuration as the projector 1 described above. Here, the projector 1 adjusts the voltage level of the counter electrode voltage to substantially match the amount of charge held in the liquid crystal material on the positive side and the negative side of the pixel electrode voltage, thereby flickering. Suppression of the occurrence of. On the other hand, the projector according to the present embodiment adjusts the ratio (duty ratio) between the pulse width on the positive polarity side and the pulse width on the negative polarity side of the pixel electrode voltage within one cycle, thereby adjusting the charge. The amount is substantially matched to suppress the occurrence of flicker. In this respect, the projector according to the present embodiment and the projector 1 are different. In the following description, parts that are the same as or substantially the same as those already described are assigned the same reference numerals and description thereof is omitted.

FIG. 5 is a block diagram illustrating a configuration of a control device 5C included in the projector according to the present embodiment.
The projector according to the present embodiment has the same configuration as that of the projector 1 described above except that it includes a liquid crystal display device 3C instead of the liquid crystal display device 3A. The liquid crystal display device 3C includes an image forming device 4 and a control device 5C.
As shown in FIG. 5, the control device 5C has the same configuration as the control device 5A except that it includes a duty ratio setting unit 58 and a flash memory 59 instead of the counter electrode voltage setting unit 54 and the flash memory 55. .

  Similarly to the flash memory 55, the flash memory 59 is a storage unit that stores various programs and data necessary for control by the control device 5C. The flash memory 59 is an LUT in which an average value of APL (Average Picture Level) of an image corresponding to input image information and a duty ratio of a pixel electrode voltage applied to the liquid crystal panel 442 are associated with each other. (Look-Up Table) is stored.

  In this LUT, the pulse width (period) on the positive polarity side of the pixel electrode voltage Vs is negative with respect to the average value of high APL, that is, when the pixel electrode voltage Vs having a high voltage level is applied. A shorter duty ratio is set than the pulse width on the active side. Further, the pulse width on the positive side of the pixel electrode voltage Vs has a negative polarity with respect to the average value of the low APL, that is, when the pixel electrode voltage Vs having a low voltage level is applied to the LUT. A duty ratio longer than the pulse width on the side is set.

The duty ratio setting unit 58 refers to the LUT of the flash memory 59 and acquires a duty ratio corresponding to the average value of APL calculated by the APL calculation unit 53. Then, the duty ratio setting unit 58 sets the duty ratio of the pixel electrode voltage Vs output from the liquid crystal driver 56 to the acquired duty ratio. Thereby, the duty ratio of the pixel electrode voltage Vs is optimized based on the average value of APL.
In the present embodiment, the voltage level of the counter electrode voltage Vcom output from the liquid crystal driver 56 is not adjusted. Therefore, the voltage level of the counter electrode voltage Vcom is constant regardless of the voltage level of the pixel electrode voltage Vs. In the shipping stage, the duty ratio of the pixel electrode voltage Vs is set to a duty ratio in which the pulse width on the positive polarity side and the pulse width on the negative polarity side are the same.

FIG. 6 is a diagram illustrating the counter electrode voltage Vcom and the pixel electrode voltage Vs applied to the liquid crystal panel 442.
When the average value of APL is high (when the pixel electrode voltage Vs having a high voltage level is applied) and the voltage level of the counter electrode voltage Vcom is not appropriate with respect to the voltage level of the pixel electrode voltage Vs, the pixel electrode The potential difference with respect to the counter electrode voltage Vcom on the positive polarity side at the voltage Vs is different from the potential difference on the negative polarity side. Here, as in the shipping stage, when the duty ratio of the pixel electrode voltage is set to a duty ratio in which the pulse width on the positive polarity side and the pulse width on the negative polarity side are the same, FIG. As shown, the amount of charge held in the liquid crystal material of the pixel differs between the positive polarity side and the negative polarity side. For this reason, a difference occurs in pixel gradation between the positive polarity side and the negative polarity side, and flicker occurs.

  On the other hand, the duty ratio setting unit 58 sets the duty ratio of the pixel electrode voltage Vs to a duty ratio that makes the pulse width on the positive polarity side shorter than the pulse width on the negative polarity side based on the average value of APL. To do. Thereby, as shown in FIG. 6B, although the potential difference on the positive polarity side in the pixel electrode voltage Vs is larger than the potential difference on the negative polarity side, the amount of charge held in the liquid crystal material of the pixel is changed to the positive polarity side. It can be made to substantially coincide with the negative polarity side. Therefore, the gradation of the pixels can be substantially matched between the positive polarity side and the negative polarity side, and the occurrence of flicker can be suppressed.

  On the other hand, when the average value of APL is low (when the pixel electrode voltage Vs having a low voltage level is applied) and the counter electrode voltage Vcom is not appropriate with respect to the pixel electrode voltage Vs, as in the case described above, the positive electrode The potential difference with respect to the counter electrode voltage Vcom on the negative side is different from the potential difference on the negative side. Here, when the pulse width on the positive polarity side and the pulse width on the negative polarity side in the pixel electrode voltage Vs are set to the same duty ratio, as shown in FIG. 6C, the liquid crystal material of the pixel The amount of charge held in the pixel is different between the positive polarity side and the negative polarity side, and the gradation of the pixel is different between the positive polarity side and the negative polarity side, and flicker occurs.

  In contrast, the duty ratio setting unit 58 sets the duty ratio of the pixel electrode voltage Vs to a duty ratio that makes the pulse width on the positive polarity side longer than the pulse width on the negative polarity side based on the average value of APL. To do. As a result, as shown in FIG. 6D, although the potential difference on the positive polarity side in the pixel electrode voltage Vs is smaller than the potential difference on the negative polarity side, the amount of charge held in the liquid crystal material of the pixel is changed to the positive polarity side. And the negative polarity side can be substantially matched. Thereby, the gradation of the pixel can be substantially matched between the positive polarity side and the negative polarity side, and the occurrence of flicker can be suppressed.

According to the projector according to the present embodiment described above, the same effects as the projector 1 described above can be obtained, and the following effects can be obtained.
That is, the duty ratio of the pixel electrode voltage Vs whose polarity is inverted within one cycle is adjusted by the duty ratio setting unit 58 according to the average value of APL of the input image. According to this, the amount of electric charge held in the liquid crystal material of the pixel can be made substantially equal on the positive side and the negative side on the pixel electrode voltage. Therefore, the gradation of the pixels can be substantially matched between the positive polarity side and the negative polarity side, and display image deterioration due to flicker can be suppressed.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described.
The projector according to the present embodiment has the same configuration as the projector shown in the third embodiment. Here, in the projector shown in the third embodiment, the duty ratio of the pixel electrode voltage Vs is set based on the average value of the APL of the formed image. In contrast, in the projector according to the present embodiment, the duty ratio is set based on the gamma correction value corresponding to the set color mode, similarly to the projector shown in the second embodiment. In this respect, the projector according to the present embodiment is different from the projector shown in the third embodiment. In the following description, parts that are the same as or substantially the same as those already described are assigned the same reference numerals and description thereof is omitted.

FIG. 7 is a block diagram illustrating a configuration of a control device 5D included in the projector according to the present embodiment.
The projector according to the present embodiment has the same configuration as that of the projector described in the third embodiment, except that the liquid crystal display device 3D is provided instead of the liquid crystal display device 3C. The liquid crystal display device 3D includes an image forming device 4 and a control device 5D.
As shown in FIG. 7, the control device 5D includes the above-described gamma setting unit 57, duty ratio setting unit 58D, and flash memory 59D instead of the APL calculation unit 53, the duty ratio setting unit 58, and the flash memory 59. Has the same configuration as the control device 5C.

  Among these, the flash memory 59D, like the flash memory 59, is a storage unit that stores various programs and data necessary for control by the control device 5D. The flash memory 59D stores an LUT in which the gamma correction value set by the gamma setting unit 57 and the duty ratio of the pixel electrode voltage Vs output by the liquid crystal driver 56 are associated with each other.

  The duty ratio setting unit 58D refers to the LUT of the flash memory 59D, acquires a duty ratio corresponding to the gamma correction value set by the gamma setting unit 57, and applies the pixel applied from the liquid crystal driver 56 to the duty ratio. The duty ratio of the electrode voltage Vs is set. As in the case described above, at the shipping stage, the duty ratio of the pixel electrode voltage Vs is set to a duty ratio in which the pulse width on the positive polarity side and the pulse width on the negative polarity side are the same.

Here, as described above, the output of the data signal (the voltage level of the pixel electrode voltage Vs) based on the image generated by the video processing unit 51 is corrected based on the gamma correction value changed when the color mode is changed. Then, the usable gradation range of each pixel of the liquid crystal panel 442 is set.
Then, according to the change of the gamma correction value, the duty ratio setting unit 58D sets the duty ratio of the pixel electrode voltage applied by the liquid crystal driver 56.

  Thereby, when the pixel electrode voltage Vs having a high voltage level is applied by the correction based on the gamma correction value corresponding to the color mode using the high gradation range, the duty ratio setting unit 58D includes the duty ratio setting unit. Similarly to 58, the duty ratio of the pixel electrode voltage Vs is set to a duty ratio in which the pulse width on the positive polarity side is shorter than the pulse width on the negative polarity side. As a result, similarly to the case shown in FIG. 6B, the amount of charge held in the liquid crystal material can be substantially matched between the positive polarity side and the negative polarity side in the pixel electrode voltage Vs. Therefore, the gradations of the pixels can be substantially matched on the positive polarity side and the negative polarity side, and the occurrence of flicker can be suppressed.

  When the pixel electrode voltage Vs having a low voltage level is applied by the correction based on the gamma correction value corresponding to the color mode using the low gradation range, the duty ratio setting unit 58D is set to the duty ratio setting unit 58. Similarly, the duty ratio of the pixel electrode voltage Vs is set such that the pulse width on the positive polarity side is longer than the pulse width on the negative polarity side. As a result, as in the case shown in FIG. 6D, the amount of charge held in the liquid crystal material can be substantially matched between the positive polarity side and the negative polarity side in the pixel electrode voltage Vs. Therefore, the gradations of the pixels can be substantially matched on the positive polarity side and the negative polarity side, and the occurrence of flicker can be suppressed.

According to the projector according to the present embodiment described above, the same effects as those of the projector described in the third embodiment can be obtained.
That is, the duty ratio of the pixel electrode voltage Vs whose polarity is inverted within one cycle is adjusted by the duty ratio setting unit 58D according to the set gamma correction value of the color mode. According to this, the amount of charge held in the liquid crystal material of the pixel can be substantially matched between the positive polarity side and the negative polarity side in the pixel electrode voltage Vs. Accordingly, the gradation of the pixels can be substantially matched between the positive polarity side and the negative polarity side, so that the display image can be prevented from being deteriorated by flicker.

[Modification of Embodiment]
The present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the scope that can achieve the object of the present invention are included in the present invention.
In the first and second embodiments, the voltage level of the counter electrode voltage Vcom is adjusted. In the third and fourth embodiments, the duty ratio of the pixel electrode voltage Vs is adjusted. The amount of charge held in the liquid crystal material of the pixel on the positive polarity side and the negative polarity side is substantially matched to suppress the occurrence of flicker. However, the present invention is not limited to this. That is, the adjustment of the voltage level of the counter electrode voltage and the adjustment of the duty ratio of the pixel electrode voltage may be linked.

FIG. 8 is a diagram showing the counter electrode voltage Vcom and the pixel electrode voltage Vs applied to the liquid crystal panel 442 from the control device, which is a modification of the above embodiments.
For example, when the average value of APL is low or when a color mode using a low gradation range is set, the pixel electrode voltage Vs having the voltage level shown in FIG. 8A is applied to the liquid crystal panel 442. The counter electrode voltage setting unit lowers the voltage level of the applied counter electrode voltage Vcom, and the duty ratio setting unit sets the duty ratio so that the pulse width on the positive polarity side is longer than the pulse width on the negative polarity side. Sets the duty ratio of the electrode voltage. Even in such a case, as shown in FIG. 8B, the amount of charge held in the liquid crystal material of the pixel can be substantially matched on the positive side and the negative side in the pixel electrode voltage Vs, and flicker Can be suppressed.

  In the first and third embodiments, based on the average value of APL calculated by the APL calculation unit 53, the counter electrode voltage setting unit 54 and the duty ratio setting unit 58 have the voltage level of the counter electrode voltage Vcom and the pixel Although the duty ratio of the electrode voltage Vs is set, the present invention is not limited to this. In other words, when the input image is a still image, the APL of the input image may be calculated once, and the counter electrode voltage setting unit 54 and the duty ratio setting unit 58 may calculate the counter electrode voltage Vcom based on the APL. The voltage level and the duty ratio of the pixel electrode voltage Vs may be set.

In each of the above embodiments, the projector 1 includes the three liquid crystal panels 442R, 442G, and 442B, but the present invention is not limited to this. That is, the present invention can also be applied to a projector using two or less or four or more liquid crystal panels.
In each of the above-described embodiments, the configuration in which the image forming apparatus 4 has a substantially L shape in plan view has been described. However, the configuration is not limited thereto, and for example, a configuration having a substantially U shape in plan view may be employed. .
In the above-described embodiment, the transmissive liquid crystal panel 442 having a different light beam incident surface and light beam emission surface is used. However, a reflective liquid crystal panel having the same light incident surface and light emission surface may be used.

  In each of the embodiments described above, the liquid crystal display devices 3A to 3D are employed in the front-type projector 1 that performs projection from the direction in which the screen is observed. However, the present invention is not limited to this, and the direction in which the screen is observed. Can also be used in rear-type projectors that project from the opposite side. Further, the present invention can be applied to a liquid crystal display including a liquid crystal panel and a liquid crystal driving device.

  The present invention can be used for a liquid crystal driving device for driving a liquid crystal panel, and can be suitably used for a liquid crystal display device such as a liquid crystal projector and a liquid crystal display.

  DESCRIPTION OF SYMBOLS 1 ... Projector, 3A-3D ... Liquid crystal display device, 5A-5D ... Control apparatus (liquid crystal drive device), 442 (442R, 442G, 442B) ... Liquid crystal panel, Vcom ... Counter electrode voltage, Vs ... Pixel electrode voltage.

Claims (7)

A liquid crystal driving device for driving a liquid crystal panel,
Depending on the usage state of the liquid crystal panel, the voltage level of the counter electrode voltage applied to the counter electrode of the liquid crystal panel and the pixel electrode voltage that is applied to the pixel electrode of the liquid crystal panel and whose polarity is inverted within one cycle. A liquid crystal driving device characterized by adjusting at least one of the duty ratio. The liquid crystal driving device according to claim 1,
The liquid crystal driving device drives the liquid crystal panel according to input image information,
The use state is an average luminance level of an image generated based on the image information. The liquid crystal driving device according to claim 2,
If the average brightness level is high,
Making the voltage level of the counter electrode voltage higher than a predetermined level, or making the pulse width on the positive side of the pixel electrode voltage shorter than the pulse width on the negative side,
If the average brightness level is low,
A liquid crystal driving device characterized in that the voltage level of the counter electrode voltage is made lower than a predetermined level, or the pulse width on the positive side of the pixel electrode voltage is made longer than the pulse width on the negative side. The liquid crystal driving device according to claim 1,
The liquid crystal driving device drives the liquid crystal panel based on a gamma correction value corresponding to a set color mode among color modes having different use gradations,
The use state is the set color mode. The liquid crystal driving device according to claim 1, wherein: The liquid crystal driving device according to claim 4,
When the use gradation of the set color mode is high,
Making the voltage level of the counter electrode voltage higher than a predetermined level, or making the pulse width on the positive side of the pixel electrode voltage shorter than the pulse width on the negative side,
When the use color tone of the set color mode is low,
A liquid crystal driving device characterized in that the voltage level of the counter electrode voltage is made lower than a predetermined level, or the pulse width on the positive polarity side of the pixel electrode voltage is made longer than the pulse width on the negative polarity side. A liquid crystal driving device according to any one of claims 1 to 5,
A liquid crystal display device comprising: a liquid crystal panel driven by the liquid crystal driving device. A projector that modulates a light beam emitted from a light source and displays an image according to image information,
A projector comprising the liquid crystal display device according to claim 6.

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