JP2015004909A - Electro-optic device, method for driving electro-optic device, and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase a degree of display uniformity in sub-field driving.SOLUTION: An electro-optic device 1 includes: a pixel Px including a liquid crystal element CL; and a display control unit 100 which generates a data signal VD designating an ON or OFF state of the pixel Px based on an image signal Din designating a gradation to be displayed by the pixel Px, which divides a display period T into a plurality of sub-field periods SF, of the display period T and a reset period R that are alternately arranged on a temporal axis, and which supplies the data signal VD to the pixel Px in each of the subfield periods SF. The display control unit 100 generates the data signal VD to be supplied to the pixel Px in one display period T in such a manner that whichever gradation is designated by the image signal Din as a gradation to be displayed by the pixel Px in the one display period T, the transmittance of the liquid crystal element CL at an end time of one reset period R subsequent to the one display period T is equal to or more than a first value Bmin that is larger than a minimum transmittance that can be achieved by the liquid crystal element CL.

Description

  The present invention relates to an electro-optical device, a driving method of the electro-optical device, and an electronic apparatus.

  In an electro-optical device including a liquid crystal element, a display period is divided into a plurality of subfield periods, and the liquid crystal element is driven in either an on state or an off state for each subfield period, so that pixels are displayed in the display period. A technique related to so-called subfield driving for controlling gradation to be displayed is known (for example, Patent Document 1).

JP 2003-114661 A

In sub-field driving, the gradation displayed by a pixel in the display period is determined by the integral value over the display period of the transmittance of the liquid crystal element included in the pixel. Therefore, in order to ensure the uniformity of display, the response speed of the liquid crystal element is made uniform so that variation in error between the gradation that the pixel should display and the gradation that the pixel actually displays is displayed. Is required to be small. Since the response speed of the liquid crystal element varies depending on the transmittance of the liquid crystal element, the uniformity of the liquid crystal element is uniformed by uniformizing the transmittance of the liquid crystal element at the start of the display period, and the degree of display uniformity Can be increased.
By the way, when two types of images are alternately displayed in a time-division manner, such as when the electro-optical device displays a stereoscopic image, a display period in which one image is displayed in order to suppress mixing of the two types of images. And a reset period is provided between the display period for displaying other images. Since the response speed of a liquid crystal element is slow, when a reset period is provided between display periods, the variation in the transmittance of the liquid crystal element at the end of the display period for displaying one image is different from the display period for displaying another image. It may appear as a variation in the transmittance of the liquid crystal element at the start. As a result, in the display period in which other images are displayed, the response speed of the liquid crystal element varies, which may cause a problem that the degree of display uniformity is reduced. When the transmittance of the liquid crystal element becomes the minimum value or the maximum value that can be taken, the response speed of the liquid crystal element is particularly slow. Therefore, for example, when a liquid crystal element having the minimum (or maximum) transmittance and a liquid crystal element having the minimum (or maximum) transmittance are mixed, the response speed of the liquid crystal elements varies greatly, and the display In many cases, the degree of uniformity is further reduced.

  The present invention has been made in view of the above-described circumstances, and one of its purposes is to provide a reset period between display periods in a technique for driving an electro-optical element in an on or off state for each subfield. Another object of the present invention is to provide a technique capable of increasing the degree of display uniformity.

  In order to solve the above problems, an electro-optical device according to an embodiment of the present invention is based on a video signal when a pixel including a liquid crystal element and a video signal designating a gradation to be displayed by the pixel are supplied. Generating a data signal designating ON or OFF of the pixel, and dividing the display period into a plurality of subfield periods among the display period and the reset period alternately arranged on the time axis, A display control unit that supplies the data signal to the pixel in each of the plurality of subfield periods, and the display control unit should display the video signal in a display period in which the pixel is one. Whatever gradation is specified as the gradation, the transmittance of the liquid crystal element at the end of one reset period subsequent to the one display period is determined by the liquid crystal element. The minimum transmittance such that the first value or more values greater than that, to generate a data signal supplied to the pixel in the one of the display period, characterized in that.

According to the present invention, the transmittance of the liquid crystal element at the end of the reset period, that is, at the start of the display period is set to a value larger than the minimum transmittance that the liquid crystal element can take. For this reason, at the start of the display period, it is possible to prevent a liquid crystal element having the minimum transmittance and a liquid crystal element having the minimum transmittance from being mixed, and variation in response speed of the liquid crystal elements increases. This can be prevented. As a result, it is possible to prevent the degree of display nonuniformity from being reduced due to variations in the response speed of the liquid crystal elements.
In the present invention, the value of the data signal designating that the pixel is turned on may be a variable value that differs for each subfield period.

  In the electro-optical device described above, the display control unit may be configured such that the video signal specifies any gradation as a gradation that the pixel should display in one display period. At the end of one display period, the pixel in the one display period is such that the transmittance of the liquid crystal element is equal to or less than a second value smaller than the maximum transmittance that the liquid crystal element can take. A data signal to be supplied may be generated.

  According to this aspect, compared to the case where the transmittance of the liquid crystal element can be the maximum transmittance at the end of one display period, the liquid crystal element at the end of one reset period following the one display period. Variations in transmittance can be reduced. For this reason, it is possible to increase the degree of display uniformity.

In the electro-optical device described above, the transmittance of the liquid crystal element included in the pixel when the pixel is turned on is larger than the transmittance when the pixel is turned off, and the display control unit However, when the minimum gradation is designated as the gradation that the pixel should display in the display period, the pixel of the pixel in at least one subfield period of the plurality of subfield periods included in the display period. The data signal designating ON may be supplied to the pixel.
According to this aspect, since the pixel is turned on in at least one subfield period of the display period, it becomes possible to prevent the transmittance of the liquid crystal element from reaching the minimum transmittance at the end of the display period. . For this reason, it is possible to prevent the transmittance of the liquid crystal element from becoming a minimum value at the start of the display period next to the display period, and as a result, it is possible to increase the degree of display uniformity. .

In the electro-optical device described above, the display control unit may include the plurality of pixels included in the display period when the video signal specifies a maximum gradation as a gradation to be displayed by the pixel in the display period. The data signal designating that the pixel is turned off may be supplied to the pixel in at least one of the subfield periods.
According to this aspect, it is possible to prevent the transmittance of the liquid crystal element from reaching the maximum transmittance at the end of the display period. For this reason, the dispersion | variation in the transmittance | permeability of a liquid crystal element can be restrained small at the time of the start of the display period following the said display period. As a result, the degree of display uniformity can be increased.

In the electro-optical device described above, the display control unit includes the plurality of gradations included in the display period in order to display the gradation specified by the video signal and the gradation specified by the video signal on the pixel. A subfield code, which is data for designating ON / OFF of the pixel for each subfield period, is stored in association with each other, and the subfield code is selected from the storage unit based on the video signal And a generation unit capable of generating the data signal based on the subfield code selected by the selection unit, wherein the generation unit includes the plurality of subfield codes selected by the selection unit. In the case of the data specifying the pixel off in all of the subfield periods, the subfield code selected by the selection unit is selected. Is corrected so as to designate ON of the pixel in at least one subfield period of the plurality of subfield periods, and the data signal is generated based on the corrected subfield code. There may be.
According to this aspect, it is possible to prevent the transmittance of the liquid crystal element from becoming the minimum transmittance at the end of the display period. For this reason, it is possible to prevent the transmittance of the liquid crystal element from becoming a minimum value at the start of the display period next to the display period, and as a result, it is possible to increase the degree of display uniformity. .

In the electro-optical device described above, when the subfield code selected by the selection unit is data specifying ON of the pixel in all of the plurality of subfield periods, the selection unit Is corrected so that the pixel is turned off in at least one subfield period of the plurality of subfield periods, and the data signal is corrected based on the corrected subfield code. It may be characterized by generating.
According to this aspect, it is possible to prevent the transmittance of the liquid crystal element from reaching the maximum transmittance at the end of the display period. For this reason, the dispersion | variation in the transmittance | permeability of a liquid crystal element can be restrained small at the time of the start of the display period following the said display period. As a result, the degree of display uniformity can be increased.

  In the electro-optical device described above, the one subfield period may be a last subfield period among the plurality of subfield periods included in the display period. Good.

  In addition, when an electro-optical device according to the present invention is supplied with a pixel having a liquid crystal element and a video signal designating a gradation to be displayed by the pixel, the pixel is turned on or off based on the video signal. A data signal for designating off is generated, and the display period is divided into a plurality of subfield periods among the display periods and the reset periods alternately arranged on the time axis, and the plurality of subfield periods A display control unit that supplies the data signal to the pixel, and the display control unit is configured so that the video signal has a gradation that the pixel should display in one display period. Even when a gray scale is designated, the transmittance of the liquid crystal element is higher than the maximum transmittance that the liquid crystal element can take at the end of one reset period following the one display period. So that again a third value following values, and generates a data signal supplied to the pixel in the one of the display period, characterized in that.

  Further, the above-described driving method of the electro-optical device is a driving method of the electro-optical device including a pixel including a liquid crystal element, and when the video signal specifying the gradation to be displayed by the pixel is supplied, Based on the video signal, a data signal that specifies whether the pixel is on or off is generated, and the display period is divided into a plurality of subfield periods among the display period and the reset period that are alternately arranged on the time axis. In each of the plurality of subfield periods, the data signal is supplied to the pixel, and the data signal supplied to the pixel in one display period is the video signal, the pixel is the one Regardless of which gradation is designated as the gradation to be displayed in the display period, the liquid crystal element is formed at the end of one reset period following the one display period. Transmittance, the is the minimum transmittance of the first value or more values to become the signal is greater than the possible of the liquid crystal element, characterized in that.

  In addition, an electronic apparatus according to the present invention includes the above-described electro-optical device. Examples of such electronic devices include a car navigation device, a personal computer, a television, a projection display device, and a mobile phone.

1 is a block diagram of an electro-optical device according to a first embodiment of the invention. FIG. It is a circuit diagram of a pixel circuit. It is explanatory drawing for demonstrating the operation | movement period of a pixel. 6 is a timing chart for explaining the operation of the electro-optical device. 6 is a timing chart for explaining the operation of the electro-optical device. It is explanatory drawing for demonstrating SF code. It is explanatory drawing for demonstrating the change of the transmittance | permeability of a liquid crystal element. It is explanatory drawing for demonstrating the change of the transmittance | permeability of the liquid crystal element which concerns on contrast. It is explanatory drawing for demonstrating the change of the transmittance | permeability of the liquid crystal element which concerns on contrast. It is explanatory drawing for demonstrating the change with time of the transmittance | permeability of a liquid crystal element. It is explanatory drawing for demonstrating the change with time of the transmittance | permeability of a liquid crystal element. It is explanatory drawing for demonstrating the change of the transmittance | permeability of the liquid crystal element which concerns on 1st Embodiment. It is explanatory drawing for demonstrating the change of the transmittance | permeability of the liquid crystal element which concerns on 1st Embodiment. 12 is an explanatory diagram for explaining a change in transmittance of a liquid crystal element according to Modification 2. FIG. It is explanatory drawing for demonstrating the change of the transmittance | permeability of the liquid crystal element which concerns on contrast. 14 is a timing chart for explaining the operation of an electro-optical device according to Modification 6. It is a perspective view of an electronic device (projection type display device). It is a perspective view of an electronic device (personal computer). It is a perspective view of an electronic device (cellular phone).

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, in each figure, the size and scale of each part are appropriately changed from the actual ones. Further, since the embodiments described below are preferable specific examples of the present invention, various technically preferable limitations are attached thereto. However, the scope of the present invention is particularly limited in the following description. Unless otherwise stated, the present invention is not limited to these forms.

<A. Embodiment>
FIG. 1 is a block diagram of an electro-optical device 1 according to the first embodiment of the present invention. The electro-optical device 1 displays a stereoscopic image by alternately displaying a right-eye image and a left-eye image to which parallax is given in a time-sharing manner. The electro-optical device 1 displays the right-eye image and the left-eye image by subfield driving.

  The electro-optical device 1 includes an electro-optical panel 10, a control unit 50, and stereoscopic glasses 60. The electro-optical panel 10 includes a display unit 30 in which a plurality of pixels Px are arranged, and a drive circuit 20 that drives each pixel Px. On the electro-optical panel 10, right-eye images and left-eye images are alternately displayed in a time division manner. Hereinafter, the drive circuit 20 and the control unit 50 may be collectively referred to as the display control unit 100.

  As shown in FIG. 1, the display unit 30 is formed with M scanning lines 32 extending in the x direction and N data lines 34 extending in the y direction intersecting the x direction ( M and N are natural numbers). A plurality of pixels Px are arranged in a matrix of vertical M rows × horizontal N columns corresponding to each intersection of the scanning lines 32 and the data lines 34 in the display unit 30. In the present embodiment, the pixels Px are arranged at all of the M × N intersections formed by the M scanning lines 32 and the N data lines 34, but some of these M × N intersections. It does not matter even if it is arranged.

The drive circuit 20 is a circuit that supplies a data signal VD [n] (n = 1 to N) designating a gradation to be displayed by each pixel Px to a pixel circuit 40 provided corresponding to each pixel Px. A scanning line driving circuit 22 and a data line driving circuit 24 are provided.
The scanning line driving circuit 22 sequentially selects the scanning lines 32 by supplying the scanning signals Y [1] to Y [M] corresponding to the scanning lines 32 to the scanning lines 32. Specifically, the scanning signal Y [m] (m = 1 to M) is set to a predetermined selection potential (that is, the scanning line 32 of the mth row is selected), so that the scanning line 32 of the mth row. Is selected.
The data line driving circuit 24 supplies data signals VD [1] to VD [N] to each of the N data lines 34 in synchronization with the selection of the scanning line 32 by the scanning line driving circuit 22. The data signal VD [n] (n = 1 to N) is variably set according to the gradation specified by the video signal Din described later for each pixel Px.

FIG. 2 is a circuit diagram of the pixel circuit 40 provided corresponding to each pixel Px. As shown in FIG. 2, each pixel circuit 40 includes a liquid crystal element CL, a selection switch Sw, a capacitor Co, and a light source (not shown).
The liquid crystal element CL is an electro-optical element including a pixel electrode 41, a common electrode 42, and a liquid crystal 43 provided between the pixel electrode 41 and the common electrode 42. When a voltage is applied to the liquid crystal element CL (that is, between the pixel electrode 41 and the common electrode 42), the relative transmittance of the liquid crystal element CL changes according to the magnitude of the applied voltage. The pixel Px displays a gradation corresponding to the relative transmittance of the liquid crystal element CL.
Here, the relative transmittance of the liquid crystal element CL is the amount of light transmitted through the liquid crystal element CL when no voltage is applied to the liquid crystal element CL and the liquid crystal 43 is most difficult to transmit light. The liquid crystal is set so that the amount of light transmitted through the liquid crystal element CL is 100% when the maximum voltage that can be applied to the liquid crystal element CL is applied and the liquid crystal 43 is most likely to transmit light. The amount of light transmitted through the element CL is scaled. Hereinafter, the relative transmittance of the liquid crystal element CL may be simply referred to as “transmittance”.
In the present embodiment, the liquid crystal 43 included in the liquid crystal element CL is a VA (Virtical Alignment) method, and the pixel Px displays black in a state where no voltage is applied between the pixel electrode 41 and the common electrode 42 (liquid crystal The case of the normally black mode in which the relative transmittance of the element CL is 0%) will be described as an example.

The common electrode 42 is set to a predetermined reference potential Vcom. The capacitor Co has one end electrically connected to the pixel electrode 41 and the other end electrically connected to a capacitor line 36 maintained at a constant voltage. The common electrode 42 is also electrically connected to the capacitor line 36.
The selection switch Sw is, for example, an N-channel transistor, and is provided between the pixel electrode 41 and the data line 34, and controls the electrical connection (conduction / insulation) between the two. Specifically, the gate of the selection switch Sw that is an N-channel transistor is electrically connected to the scanning line 32, and when the scanning signal Y [m] is set to the selection potential, the pixel circuit 40 in the m-th row. The selection switch Sw provided in is turned on. When the selection switch Sw is turned on, the data signal VD [n] is supplied from the data line 34 to the pixel circuit 40, and a voltage corresponding to the data signal VD [n] is applied to the liquid crystal element CL. The As a result, the liquid crystal element CL of the pixel circuit 40 is set to a transmittance corresponding to the data signal VD [n], and the pixel Px corresponding to the pixel circuit 40 has a gradation corresponding to the data signal VD [n]. Is displayed.
After the voltage corresponding to the data signal VD [n] is applied to the liquid crystal element CL of the pixel circuit 40, when the selection switch Sw is turned off, the data signal VD [n] is held by the capacitor Co. Therefore, each pixel Px displays a gradation corresponding to the data signal VD [n] in a period from when the selection switch Sw is turned on to when it is next turned on.

Returning to FIG. As shown in FIG. 1, the control unit 50 includes a signal generation unit 51, a glasses control circuit 52, a display information generation unit 53, and a storage unit 54.
The signal generator 51 is supplied with a synchronization signal from a host device (not shown). The synchronization signal is a signal including, for example, a vertical synchronization signal Vsnc, a horizontal synchronization signal, a dot clock signal, and the like. The signal generator 51 generates a control signal Ctr that is a signal for controlling the operation of the electro-optical device 1 based on the synchronization signal, and supplies the generated control signal Ctr to the drive circuit 20. The control signal Ctr is a signal including, for example, a vertical synchronization signal Vsnc, a Y input pulse signal Dyin, a reset signal Vrst, a Y clock signal Cly, an enable signal, a dot clock signal, and the like. Details of these various signals will be described later.

The spectacles control circuit 52 generates a spectacles control signal that is a signal for controlling the operation of the stereoscopic spectacles 60 based on the control signal Ctr generated by the signal generation unit 51, and supplies the spectacles control signal to the stereoscopic spectacles 60. To supply.
The stereoscopic glasses 60 are glasses-type instruments worn by an observer when viewing a stereoscopic image displayed on the electro-optical panel 10, and include a left-eye shutter 62 and a right eye positioned in front of the left eye of the observer. And a right-eye shutter 64 positioned in front of the camera. Each of the left-eye shutter 62 and the right-eye shutter 64 is based on the spectacles control signal supplied from the spectacles control circuit 52, and is in an open state (transmission state) that transmits the irradiation light and a closed state that blocks the irradiation light ( The light shielding state). For example, a liquid crystal shutter that changes from one of the open state and the closed state to the other by changing the alignment direction of the liquid crystal according to the applied voltage may be employed as the left-eye shutter 62 and the right-eye shutter 64.

When the video signal Din is supplied from a host device (not shown) in synchronization with the synchronization signal, the display information generation unit 53 generates an image based on the video signal Din and the SF code Cd stored in the storage unit 54. Data Dx is generated.
The video signal Din is data that specifies the gradation to be displayed in each pixel Px. In the present embodiment, the video signal Din is digital data that defines the gradation to be displayed in each pixel Px in 256 steps (ie, 8 bits) from “0” to “255”. In the present embodiment, the image data Dx is a digital signal, but may be an analog signal.
The storage unit 54 stores the gradation specified by the video signal Din for each pixel Px and the subfield code (SF code) Cd in association with each other. The SF code Cd will be described later.

The display information generation unit 53 includes a selection unit 531 and a generation unit 532.
The selection unit 531 selects the SF code Cd corresponding to the video signal Din from the storage unit 54 and supplies the selected SF code Cd to the generation unit 532.
The generation unit 532 generates the corrected SF code Cdx by correcting the SF code Cd selected by the selection unit 531. Then, the generation unit 532 generates image data Dx based on the generated corrected SF code Cdx, and supplies the generated image data Dx to the data line driving circuit 24. The data line drive circuit 24 generates the data signal VD [n] by D / A converting the image data Dx generated by the display information generation unit 53. Details of the correction SF code Cdx will be described later.

FIG. 3 is an explanatory diagram for explaining an operation period of each pixel Px (pixel circuit 40) included in the electro-optical device 1.
As shown in FIG. 3, the operation period of each pixel Px includes a plurality of frame periods F. The frame period F is a period determined for each pixel Px. More specifically, the frame period F refers to the case where each pixel Px displays the one stereoscopic image composed of one left-eye image and one right-eye image. This is a period necessary for displaying the gradation corresponding to the stereoscopic image (that is, the gradation corresponding to one left-eye image and the gradation corresponding to one right-eye image).
In the present embodiment, the electro-optical device 1 displays 60 stereoscopic images per second. Therefore, in this embodiment, the time length of the frame period F is about 16.67 milliseconds.

As shown in FIG. 3, each frame period F includes a reset period R1, a left-eye image display period T1 (hereinafter simply referred to as “display period T1”), a reset period R2, and a right-eye image display. It is divided into periods T2 (hereinafter simply referred to as “display period T2”). The reset period R1 is a period started simultaneously with the start of the frame period F, the display period T1 is a period following the reset period R1, the reset period R2 is a period following the display period T1, and the display period T2 is This is a period that follows the reset period R2 and ends at the same time as the frame period F. Hereinafter, the display period T1 and the display period T2 may be collectively referred to as “display period T”, and the reset period R1 and the reset period R2 may be collectively referred to as “reset period R”.
Each pixel Px displays a gradation corresponding to the image for the left eye displayed on the display unit 30 by the electro-optical device 1 in the display period T1, and the electro-optical device 1 displays on the display unit 30 in the display period T2. The gradation corresponding to the image for the right eye is displayed.

  As shown in FIG. 3, each display period T includes five unit periods U (unit periods U [1] to U [5]) having the same time length. Each reset period R is composed of two unit periods U (unit periods U [1] to U [2]) having the same time length. The unit period U means that after the scanning line driving circuit 22 starts to select the first scanning line 32, the M scanning lines 32 from the first to Mth rows are selected, and then the second scanning line 32 again. This is a period having a time length equal to the period until the selection of one scanning line 32 starts.

Each unit period U is divided into two subfield periods SF. That is, each display period T is divided into ten subfield periods SF [1] to SF [10]. Each reset period R is divided into four subfield periods SF [1] to SF [4].
In the present embodiment, each of the ten subfield periods SF included in the display period T and each of the four subfield periods SF included in the reset period R have the same time length. As described above, since the time length of the frame period F is about 16.67 milliseconds in the present embodiment, the time length of each subfield period SF in the present embodiment is about 0.60 milliseconds.

The data line driving circuit 24 supplies the data signal VD [n] to the pixel Px at the timing when each of the ten subfield periods SF included in the display period T of the pixel Px is started. In the present embodiment, the data signal VD [n] is a signal that designates ON or OFF of the pixel Px. That is, the data line driving circuit 24 supplies the data signal VD [n] to each pixel Px every subfield period SF, thereby designating each pixel Px on or off every subfield period SF.
When the data line drive circuit 24 designates ON for a pixel Px, the data signal VD [n] supplied to the pixel Px is supplied with a potential at which the pixel Px displays the maximum gradation (that is, the pixel Px). The potential is such that the relative transmittance of the liquid crystal element CL included in Px is maximized. Further, when the data line driving circuit 24 designates OFF for the pixel Px, the data signal VD [n] supplied to the pixel Px is supplied with a potential (that is, the pixel Px displays the minimum gradation) (that is, The potential is set such that the relative transmittance of the liquid crystal element CL included in the pixel Px is minimized.
Further, the data line driving circuit 24 has a positive data signal VD [that is higher than the reference potential Vcom in the subfield periods SF [1] to SF [5] in the display period T of the pixel Px. n] is supplied to the pixel Px, and in the subfield periods SF [6] to SF [10], a negative data signal VD [n] that is lower than the reference potential Vcom is supplied to the pixel Px.
In the present embodiment, the data signal VD [n] is set to a value that specifies the maximum gradation or the minimum gradation of the pixel Px. It may be set. In this case, the value of the data signal VD [n] may be a variable value that differs for each subfield period SF.

Further, the data line driving circuit 24 is a data signal that designates the pixel Px to be turned off at the timing when each of the four subfield periods SF included in the reset period R of the pixel Px is started. Supply VD [n].
In the present embodiment, the data line driving circuit 24 sets the data signal VD [n] supplied to the pixel Px in the reset period R to a potential at which the pixel Px displays the minimum gradation. It may be set to a predetermined reset potential. That is, since the electro-optical device 1 supplies a predetermined potential to the pixel Px in the reset period R and does not actively control the gradation of the pixel Px, the video signal Din or the image data Dx Can be suppressed to a small memory capacity.

Hereinafter, the entire operation period of the electro-optical device 1 defined separately from the operation period of the pixel Px described above will be described.
The operation period (frame period F, unit period U, display period T, etc.) of the pixels Px described above is a period that starts for each pixel Px in each row triggered by the selection of the scanning line 32 by the scanning line driving circuit 22. This is a period that starts at a different timing for each row where the pixel Px is located. On the other hand, the operation period of the electro-optical device 1 is a period uniquely defined as the entire electro-optical device 1.
Hereinafter, the relationship between the operation period of the electro-optical device 1 and the operation periods of the plurality of pixels Px included in the electro-optical device 1 will be described with reference to FIGS. 4 and 5.

FIG. 4 is a timing chart for explaining the operation of the electro-optical device 1. As shown in FIG. 4 (A), the operation period of the electro-optical device 1 is divided into a plurality of reference frame period ^{B F.}
Reference frame period ^{B F} is the vertical synchronizing signal Vsnc included in the synchronization signal is a period until a timing at which the next high level from the timing at which a high level, having a time length of the same frame period F of each pixel Px . The reference frame period ^{B F} The electro-optical device 1 is a period for displaying one stereoscopic image comprising a first left-eye image and one right-eye image.

As shown in FIG. 4A, each reference frame period ^B F includes a reference reset period ^B R1 that is started simultaneously with the start of the reference frame period ^B F, a reference display period ^B T1 that follows the reference reset period ^B R1, reference reset period ^B R2 following the reference display period ^B T1, and is divided into a reference display period ^B T2 following the reference reset period ^B R2. In the following, a reference reset period ^B R1 and ^B R2, collectively referred to as the reference reset period ^B R, a reference display period ^B T1 and ^B T2, may be collectively referred to as the reference display period ^B T.

As shown in FIG. 4 (A) and (B), the reference display period ^B T is divided into five reference unit period ^B U having equal time length from each other ^{(B U [1] ~ B} U [5]) Is done. Although not shown, a reference reset period ^{B R} is divided into two reference unit period ^{B U.} Each reference unit period ^{B U,} a reset signal Vrst included in the control signal Ctr is a period until the next high level from the timing at which the high level, the time length of the same and the unit period U of each pixel Px Have.
Further, as shown in FIGS. 4B and 4C, the Y input pulse signal Dyin included in the control signal Ctr rises to a high level in a period that is half the period in which the reset signal Vrst rises to a high level. Hereinafter, a waveform until the Y input pulse signal Dyin rises to a high level and then falls to a low level is referred to as an input pulse Dy. That, Y input pulse signal Dyin are 10 inputs the pulse Dy [1] ~Dy [10] , 4 pieces of input pulses inputted in each reference reset period ^B R input at each reference display period ^B T Dy [1] to Dy [4]. For convenience of explanation, when one input pulse Dy is represented among the 14 input pulses Dy, the natural number z satisfying 1 ≦ z ≦ 10 is used to represent the input pulse Dy [z]. .

As shown in FIG. 4C, the Y clock signal Cly is a signal with a duty ratio of 50% having a cycle twice that of the horizontal scanning period H.
The scanning line driving circuit 22 narrows the input pulse Dy [z] to a width corresponding to a half cycle of the Y clock signal Cly based on the Y clock signal Cly (width corresponding to the horizontal scanning period H) and the horizontal scanning period H. The selection pulse YS [z] is generated by delaying the input pulse by one step and narrowing the delayed input pulse to a width corresponding to half of the horizontal scanning period H based on an enable signal (not shown). The scanning signals Y [1] to Y [M] are output to each scanning line 32. FIG. 4 illustrates the case where M = 800.
In each display period T or reset period R, odd-numbered selection pulses YS [z] are output in the first half of each horizontal scanning period H, and even-numbered selection pulses YS [z] are in the second half of each horizontal scanning period H. Is output at.

As described above, the scanning line driving circuit 22 outputs the selection pulse YS [z] as the scanning signal Y [m], thereby setting the scanning signal Y [m] to a predetermined selection potential, and the first to second rows. The M scanning lines 32 are selected one by one for each horizontal scanning period H. Then, at the timing when the scanning line driving circuit 22 outputs the selection pulse YS [z] to the m-th scanning line 32, the subfield period SF [z] is started in the m-th pixel Px.
In addition, the data line driving circuit 24 outputs the selection pulse YS [z] to the m-th row scanning line 32 and selects the m-th row pixel Px, so that the pixel Px becomes a sub-line. A data signal VD [n] designating a gradation to be displayed in the field period SF [z] is supplied.
In the following, selecting the scanning line 32 by outputting the selection pulse YS [z] as the scanning signal Y [m] to the scanning line 32 is expressed as a selection line L [z]. .

Figure 5 shows the electro-optical device 1 of the reference display period ^{B T} and reference reset period ^{B R,} the display period T and the reset period R of the pixels Px, as well as the relationship of the opening and closing state of the shutter of the stereoscopic glasses 60.
As shown in FIG. 5, after the start of the reference display period ^{B T,} the display period T for the pixel Px in the first row is started, then, with a delay of the horizontal scanning period H in each row, the display of each line of pixels Px Periods T are started in sequence. In the display period T, the selection of the scanning lines 32 represented as the selection lines L [1] to L [10] is triggered by the horizontal scanning period H for each row, and the subfields of the pixels Px in each row. Periods SF [1] to SF [10] are started.
Similarly, after the start of the reference reset period ^{B R,} a reset period R for the pixel Px in the first row is started, then, with a delay of the horizontal scanning period H in each row, the reset period R of each row of the pixel Px the order To begin. Further, in the reset period R, the selection of the scanning line 32 represented as the selection lines L [1] to L [4] is triggered, and the subfield of the pixel Px of each row is delayed by the horizontal scanning period H for each row. Periods SF [1] to SF [4] are started.
In the present embodiment, from the start of the reference display period ^{B T,} after a lapse of two times the horizontal scanning period H, while the display period T of the pixel Px in the first row is started, this is an example , for example, start and may start the display period T of the first row of the pixel Px simultaneously the reference display period ^{B T,} may start a predetermined interval after the lapse. The same applies to the reset period R.

  As shown in FIG. 5, the eyeglass control circuit 52 controls the left-eye shutter 62 to the open state and the right-eye shutter 64 to the closed state during the display period T1 of the pixels Px in the first row. Further, the glasses control circuit 52 controls the right-eye shutter 64 to the open state and the left-eye shutter 62 to the closed state during the display period T2 of the pixels Px in the first row. Further, the glasses control circuit 52 controls both the left-eye shutter 62 and the right-eye shutter 64 to be closed during the reset period R (R1, R2) of the pixels Px in the first row.

The period during which the left-eye shutter 62 and the right-eye shutter 64 described above are controlled to be in an open state is merely an example. The eyeglass control circuit 52 controls the left-eye shutter 62 to be in an open state in a period including at least a part of the display period T1 of the m-th row of pixels Px, and in the display period T1 of the m-th row of pixels Px, The eye shutter 64 is controlled to be in a closed state, and the right eye shutter 64 is controlled to be in an open state in a period including at least a part of the display period T2 of the m-th row of pixels Px, thereby displaying the m-th row of pixels Px. What is necessary is just to control the shutter 62 for left eyes to a closed state in period T2.
For example, in addition to the display period T (T1, T2) of the pixel Px in the first row, in the unit period U [1] of the reset period R (R2, R1) of the pixel Px in the first row subsequent to the display period T. The shutters (the left-eye shutter 62 and the right-eye shutter 64) may be controlled to be in the open state. For example, the shutter (for the left eye) is displayed only in the unit periods U [2] to U [5] excluding the first unit period U [1] in the display period T (T1, T2) of the pixels Px in the first row. The shutter 62 and the right eye shutter 64) are controlled to be in the open state, and the left eye shutter 62 and the right eye shutter 64 are controlled to be closed in the unit period U [1] of the pixel Px in the first row. Good. Further, for example, the shutters (the left-eye shutter 62 and the right-eye shutter 64) may be controlled to be in the open state during the reference display period ( ^B T1, ^B T2).

As described above, in the electro-optical device 1 according to this embodiment, the pixel Px is turned on or off in each of the ten subfield periods SF included in the display period T, so that the pixel Px is displayed in the display period T. An image is displayed by subfield driving for controlling the gradation to be displayed.
More specifically, when the electro-optical device 1 displays the gradation specified by the video signal Din on the pixel Px in the display period T, in each of the ten subfield periods SF included in the display period T. The gradation to be displayed by the pixel Px is controlled by determining, based on the SF code Cd stored in the storage unit 54, whether to specify the on or off state for the pixel Px.
Hereinafter, the relationship between the SF code Cd and the gradation displayed by the pixel Px will be described.

FIG. 6 is a diagram illustrating an example of the contents stored in the storage unit 54. The storage unit 54 has 256 types of gradations “0” to “255” that can be designated for each pixel Px by the video signal Din, and 256 SF codes corresponding to these 256 types of gradations on a one-to-one basis. Cd (Cd [0] to Cd [255]) is stored in association with each other.
Each SF code Cd [k] (k is an integer satisfying 0 ≦ k ≦ 255) is a value “designating that the pixel Px is turned on for each of the ten subfield periods SF included in the display period T. This is 10-bit data in which either “1” or a value “0” that designates turning off the pixel Px is set. For example, the SF code Cd [2] shown in FIG. 6 specifies that the pixel Px is turned on in the subfield periods SF [1] and SB [6] in the display period T, and the SF code Cd [3] is The content is to designate that the pixel Px is turned on in the subfield periods SF [1] and SB [3].

FIG. 7 is an explanatory diagram showing a change in transmittance of the liquid crystal element CL included in the pixel Px when the pixel Px is turned on or off in the subfield periods SF [1] to SF [10] of the display period T. is there. Specifically, in the graph shown in this figure, the horizontal axis represents time, and the vertical axis represents the transmittance of the liquid crystal element CL included in the pixel Px.
FIG. 7A illustrates the case where the pixel Px is turned on or off based on the SF code Cd [2], and the pixel Px is turned on in the subfield periods SF [1] and SF [6]. This represents a change in transmittance of the liquid crystal element CL included in the pixel Px. Here, the total value of the area G1 and the area G2 represents an integral value in the display period T of the transmittance of the liquid crystal element CL included in the pixel Px.
FIG. 7B illustrates a case where the pixel Px is turned on or off based on the SF code Cd [3], and the pixel Px is designated on in the subfield periods SF [1] and SF [3]. , Represents a change in transmittance of the liquid crystal element CL included in the pixel Px. Here, the area G3 represents an integral value in the display period T of the transmittance of the liquid crystal element CL included in the pixel Px.

Both SF codes Cd [2] and Cd [3] designate ON for the pixel Px in two subfield periods SF in the display period T. Therefore, the gradation displayed by the pixel Px when the pixel Px is turned on or off based on the SF code Cd [2] is controlled when the pixel Px is turned on or off based on the SF code Cd [3]. It is also considered that it becomes equal to the gradation of.
However, the liquid crystal element CL has a slower response speed than an electro-optical element such as DML (Digital Micromirror Device). Therefore, as shown in FIGS. 7A and 7B, the area G3 is larger than the sum of the areas G1 and G2. The gradation that the pixel Px displays in the display period T is determined based on the integral value in the display period T of the transmittance of the liquid crystal element CL included in the pixel Px. Accordingly, when the pixel Px is turned on or off based on the SF code Cd [3], the pixel Px is displayed in the display period T as compared with the case where the pixel Px is controlled based on the SF code Cd [2]. The gradation level becomes high (that is, the pixel Px can be displayed brighter).

In this way, even when the total time length of the period in which the pixel Px is turned on in the display period T is the same, when the pixel Px is turned on in the plurality of discrete subfield periods SF, As the time interval between the plurality of subfield periods SF becomes shorter, the gradation level displayed by the pixel Px in the display period T becomes higher.
The SF code Cd in the present embodiment takes into account the response speed of the liquid crystal 43 included in the liquid crystal element CL, and the gradations designated by the 256 SF codes Cd with respect to the pixel Px are mutually different. Different gradations are set.

As described above, in the electro-optical device 1 according to the present embodiment, the generation unit 532 generates the corrected SF code Cdx [k] in which the SF code Cd [k] selected by the selection unit 531 is corrected, and the corrected SF code. Image data Dx is generated based on Cdx [k].
Specifically, the generation unit 532 first has the transmittance of the liquid crystal element CL at the end of the reset period R following the display period T, and the transmittance of the liquid crystal element CL at the end of the display period T. The corrected SF code Cdx [k] is generated by correcting the SF code Cd [k] so as to be equal to or greater than the value Amin and equal to or less than the value Amax (an example of “second value”).
Secondly, when the correction SF code Cdx [k] indicates a value “1” that designates ON for the pixel Px in the subfield period SF [z], the generation unit 532 sets the subfield period SF [ At z], the image data Dx corresponding to the data signal VD [n] designating the maximum gradation for the pixel Px is generated. On the other hand, when the corrected SF code Cdx [k] indicates a value “0” that specifies that the pixel Px is off in the subfield period SF [z], the generation unit 532 generates the subfield period SF [z]. The image data Dx corresponding to the data signal VD [n] designating the minimum gradation for the pixel Px is generated.
Details of correction of the SF code Cd executed by the generation unit 532 and details of the value Amin and the value Amax will be described later.

In the following, in order to explain the significance of generating the image data Dx and the data signal VD [n] based on the corrected SF code Cdx obtained by correcting the SF code Cd in the electro-optical device 1 according to the present embodiment, SF The case where the image data Dx and the data signal VD [n] are generated based on the code Cd (hereinafter referred to as “proportional”) will be described.
Note that the electro-optical device according to the comparative example does not generate the image data Dx based on the corrected SF code Cdx, but generates the image data Dx based on the SF code Cd. It is assumed that the configuration is the same as that of the optical device 1.

FIG. 8 shows the pixel Px in the case where ON is specified in all the subfield periods SF of the display period T2 based on the SF code Cd [255] with respect to the pixel Px included in the electro-optical device related to the proportionality. It is explanatory drawing showing the change of the transmittance | permeability of liquid crystal element CL with which is equipped.
Among these, FIG. 8A shows the display when the pixel Px is designated OFF in all the subfield periods SF of the display period T1 preceding the display period T2 based on the SF code Cd [0]. The change in the transmittance of the liquid crystal element CL in the period T2 is exemplified.
FIG. 8B shows a display period when the pixel Px is designated ON in all the subfield periods SF of the display period T1 preceding the display period T2 based on the SF code Cd [255]. The change in the transmittance of the liquid crystal element CL at T2 is exemplified.

As shown in FIG. 8A, when OFF is specified for all the subfield periods SF of the display period T1 for the pixel Px, the liquid crystal element CL transmittance at the end of the display period T1 is 0%. Or it becomes a value close to 0%. Therefore, the transmittance of the liquid crystal element CL at the end of the reset period R2 subsequent to the display period T1, that is, at the start of the display period T2, is also 0% or a value close to 0%.
On the other hand, as shown in FIG. 8B, when the pixel Px is turned on in all the subfield periods SF of the display period T1, the liquid crystal element CL transmittance at the end of the display period T1 is It becomes a value close to 100% or 100%. Therefore, the transmittance of the liquid crystal element CL at the start of the display period T2 is a value larger than 0%.

FIG. 10 is an explanatory diagram illustrating an example of a change over time of the transmittance of the liquid crystal element CL included in the pixel Px when the data signal VD [n] for turning on the pixel Px is supplied to the pixel Px. It is. In the graph shown in FIG. 10, the vertical axis represents the transmittance of the liquid crystal element CL, and the horizontal axis represents the elapsed time since the data signal VD [n] designating ON is supplied to the pixel Px.
In this figure, the transmittance of the liquid crystal element CL (hereinafter sometimes referred to as “initial transmittance”) at the timing when the data signal VD [n] is supplied is changed in the range of 0% to 80%. The change in transmittance of the liquid crystal element CL of the pixel Px corresponding to each initial transmittance is represented.

As shown in FIG. 10, the rising speed (response speed) of the transmittance of the liquid crystal element CL becomes slower as the initial transmittance of the liquid crystal element CL approaches 0%. In particular, when the initial transmittance of the liquid crystal element CL is smaller than 1%, the rising speed of the transmittance of the liquid crystal element CL is significantly slower than when the initial transmittance is 1% or more. This is because when the transmittance of the liquid crystal element CL is close to 0%, the alignment regulating force acting on the liquid crystal molecules included in the liquid crystal 43 of the liquid crystal element CL is strong, and therefore the data signal VD [n] is transmitted to the liquid crystal element CL. Even if it is supplied, it takes time until the liquid crystal molecules included in the liquid crystal element CL start to move.
Therefore, the liquid crystal molecules included in the liquid crystal 43 of the liquid crystal element CL are in a state where the liquid crystal element CL is slightly inclined from the alignment state in which the transmittance of the liquid crystal element CL is 0%, and the alignment regulation force on the liquid crystal molecules is weakened. The rising speed of transmittance can be increased. In other words, by increasing the initial transmittance of the liquid crystal element CL as much as 0% (for example, by setting it to 1% or more), the transmission of the liquid crystal element CL compared to the case where the initial transmittance is 0%. The rate of rate rise can be greatly increased.

For this reason, as shown in FIG. 8B, when the transmittance of the liquid crystal element CL at the start of the display period T2 is larger than 0%, the start of the display period T2 as shown in FIG. Compared with the case where the transmittance of the liquid crystal element CL at the time is 0%, the rising speed of the transmittance of the liquid crystal element CL is significantly increased.
As a result, in the case shown in FIG. 8B, the area _GW2X representing the integral value of the transmittance of the liquid crystal element CL in the display period T2 is the liquid crystal element CL in the display period T2 in the case shown in FIG. _And becomes larger _{than the} area _GW1X representing the integral value of the transmittance of the pixel, and the gradation level displayed by the pixel Px in the display period T2 is also increased. That is, even when the highest gradation is designated for the pixel Px in the display period T2, the gradation actually displayed by the pixel Px is displayed by the pixel Px in the display period T1 preceding the display period T2. Variations due to the difference in gradation that have been made will occur. That is, in the electro-optical device related to the proportionality, the gray level displayed by the pixel Px in one display period T affects the gray level displayed by the pixel Px in the display period T next to the one display period T. As a result, the display becomes uneven.

  FIG. 9 illustrates that the pixel Px included in the proportional electro-optical device is turned on based on the SF code Cd [255] in all the subfield periods SF of the display period T1, and the display period In all subfield periods SF of the display period T2, which is the display period T subsequent to T1, a change in transmittance of the liquid crystal element CL included in the pixel Px in the case where OFF is specified based on the SF code Cd [0]. It is explanatory drawing showing.

As shown in FIG. 9, when ON is designated for all the subfield periods SF in the display period T1 for the pixel Px, the liquid crystal element CL transmittance at the end of the display period T1 is 100% or 100%. A close value. Therefore, the transmittance of the liquid crystal element CL at the end of the reset period R2 subsequent to the display period T1, that is, at the start of the display period T2, becomes a value larger than 0%. In the case shown in FIG. 9, the area representing the integral value of the transmittance of the liquid crystal element CL in the display period T2 is represented by the symbol _GBX .
On the other hand, although illustration is omitted, for the pixel Px, off is designated in all the subfield periods SF of the display period T1, and off is designated in the display period T2, which is the display period T next to the display period T1. In this case, the transmittance of the liquid crystal element CL at the start of the display period T2 is 0% or a value close to 0%. Therefore, the integral value of the transmittance of the liquid crystal element CL in this case is 0 or a value close to 0. That is, even when the lowest gradation is designated for the pixel Px in the display period T2, the gradation actually displayed by the pixel Px varies (that is, the pixel Px cannot display black). Occurs).

In this manner, the electro-optical device according to the comparative example has the gray level displayed by the pixel Px in one display period T in the other display period T in which the display period T is the next display period T of the one display period T. Affects the gradation displayed. As a result, the pixel Px displays a gradation different from the designated gradation, or an error occurs between the designated gradation and the gradation actually displayed by the pixel Px.
Therefore, the electro-optical device 1 according to the present embodiment corrects the SF code Cd [k] by correcting the SF code Cd [k] so that the gradation displayed by the pixel Px can be accurately displayed. Based on the above, the image data Dx and the data signal VD [n] are generated.
Specifically, as described above, the electro-optical device 1 uses the SF code so that the transmittance of the liquid crystal element CL at the end of one display period T is not less than the value Amin and not more than the value Amax. A corrected SF code Cdx [k] is generated by correcting Cd [k], and a data signal VD [n] is generated based on the generated corrected SF code Cdx [k]. Thus, regardless of the gradation that the video signal Din designates as the gradation that the pixel Px should display in one display period T, the video signal Din is displayed in the next display period T of the one display period T. It becomes possible to keep the initial transmittance of the liquid crystal element CL at the start within a predetermined range. As a result, it is possible to prevent the gradation displayed by the pixel Px in one display period T from affecting the gradation displayed by the pixel Px in the display period T subsequent to the one display period T. Px can display an accurate gradation.

The value Amax and the value Amin that define the transmittance range of the liquid crystal element CL at the end of the display period T are the allowable range of the initial transmittance of the liquid crystal element CL at the start of the display period T next to the display period T. It is determined based on a minimum value Bmin (an example of “first value”) and a maximum value Bmax (an example of “third value”).
Specifically, when the data signal VD [n] for designating the pixel Px to be turned off is supplied in the reset period R, the value Amin indicates that the transmittance value of the liquid crystal element CL at the end of the reset period R is Bmin. The transmittance of the liquid crystal element CL at the start of the reset period R. The value Amax is the transmittance of the liquid crystal element CL at the start of the reset period R such that the value of the transmittance of the liquid crystal element CL at the end of the reset period R is Bmax.

FIG. 11 is an explanatory diagram illustrating an example of a change over time of the transmittance of the liquid crystal element CL included in the pixel Px when the data signal VD [n] for turning off the pixel Px is supplied to the pixel Px. It is. In the graph shown in this figure, the vertical axis represents the transmittance of the liquid crystal element CL, and the horizontal axis represents time. Further, the broken lines Ra and Rb shown in this figure are the liquid crystal elements CL when the data signal VD [n] for designating the pixel Px to be turned off is supplied to the pixel Px in the period corresponding to the reset period R. It represents the change in transmittance.
In the example shown in FIGS. 10 and 11, the value Bmin is set to 2%, and the value Bmax is set to 4%. Therefore, the value Amin is determined to be 10% as indicated by the broken line Ra in FIG. Further, the value Amin is determined to be 49% as indicated by the broken line Rb in FIG.

The value Bmin and the value Bmax may be determined so as to satisfy at least the condition that the value Bmin is greater than 0%, for example, 1% or more (first condition). In this case, the value Bmax may be any value (that is, the value Bmax may be larger than the value Bmin and not more than 100%). In this case, the value Amax may be any value (that is, the value Amax is larger than the value Amin and 100% or less).
By setting the value Bmin to be larger than 0% (for example, 1% or more), the case where the alignment regulating force acts strongly on the liquid crystal molecules as in the case where the transmittance of the liquid crystal element CL is 0% is excluded. As a result, the case where the rising rate of the transmittance of the liquid crystal element CL is extremely slow can be eliminated. Therefore, it is possible to reduce the variation in error between the gradation specified by the video signal Din and the gradation actually displayed by the pixel Px, and to accurately display the gradation specified by the video signal Din. Thereby, display uniformity can be ensured.

However, in this embodiment, in order to further increase the degree of display uniformity, the value Bmin and the value Bmax are determined so as to satisfy the following second condition in addition to the first condition.
That is, as shown in FIG. 10, in this embodiment, when the initial transmittance of the liquid crystal element CL in the display period T is the value Bmin, the transmittance of the liquid crystal element CL is a predetermined transmission value. When the initial time transmittance of the liquid crystal element CL in the display period T is the value Bmax, and the time length until the transmittance of the liquid crystal element CL reaches the predetermined transmittance. It is determined that the condition (second condition) that the difference from the length is equal to or less than a predetermined interval ΔTh (for example, 0.1 ms or less) is satisfied.
In the example shown in FIG. 10, the value Bmin is set to 2% and the value Bmax is set to 4% so that the first condition and the second condition are satisfied. Based on these values Bmin and Bmax, the value Amin is set to 10% and the value Amax is set to 49%.
In the present embodiment, the value Bmin and the value Bmax are determined so as to satisfy the second condition, but may be values determined in advance so as to ensure display uniformity. In this case, at least the value Bmin is preferably 0.1% or more, and the value Bmax is preferably 20% or less.

When the generation unit 532 of the electro-optical device 1 according to the present embodiment controls on / off of the pixel Px based on the SF code Cd [k], the transmittance of the liquid crystal element CL at the end of the display period T is the value Amin. When the value is smaller than or larger than the value Amax, the SF code Cd [k] is corrected to generate a corrected SF code Cdx [k].
Specifically, when on / off of the pixel Px is controlled based on the SF code Cd [k], when the transmittance of the liquid crystal element CL at the end of the display period T becomes larger than the value Amax, the generation unit 532 Then, by setting the value “0” to at least one of the values specified by the SF code Cd [k] for the subfield period SF [10] or SF [9], the liquid crystal element CL at the end of the display period T is set. The correction SF code Cdx [k] is generated so that the transmittance of the A becomes less than the value Amax.
Further, when the on / off of the pixel Px is controlled based on the SF code Cd [k], when the transmittance of the liquid crystal element CL at the end of the display period T becomes smaller than the value Amin, the generation unit 532 By setting the value “1” to at least one of the values specified by the code Cd [k] for the subfield period SF [10] or SF [9], the transmittance of the liquid crystal element CL at the end of the display period T is set. The correction SF code Cdx [k] is generated so that becomes equal to or greater than the value Amin.
On the other hand, even if the generation unit 532 controls on / off of the pixel Px based on the SF code Cd [k], the transmittance of the liquid crystal element CL at the end of one display period T is greater than or equal to the value Amin. When Amax or less, the SF code Cd [k] is directly used as the corrected SF code Cdx [k] without correcting the SF code Cd [k].
Note that the generation unit 532 may determine whether to correct the SF code Cd [k] based on the setting information stored in the storage unit 54 and the like. Here, the setting information may be information in which the SF code Cd [k] is associated with the transmittance of the liquid crystal element CL at the end of the display period T, or the SF code Cd [k] Information associated with a flag indicating the necessity of correction may be used.

FIG. 12 is an explanatory diagram illustrating a change in transmittance of the liquid crystal element CL of the pixel Px included in the electro-optical device 1 according to this embodiment. Specifically, FIG. 12 illustrates a case where ON is designated for the pixel Px in the subfield periods SF [1] to SF [9] of the display period T2 based on the corrected SF code Cdx [255]. This represents a change in transmittance of the liquid crystal element CL included in the pixel Px.
Among these, FIG. 12A shows that the pixel Px is turned off in the subfield periods SF [1] to SF [9] of the display period T1 preceding the display period T2 based on the corrected SF code Cdx [0]. A change in the transmittance of the liquid crystal element CL in the display period T2 when specified and ON is specified in the subfield period SF [10] will be exemplified.
FIG. 12B shows that the pixel Px is turned on in the subfield periods SF [1] to SF [9] of the display period T1 preceding the display period T2 based on the corrected SF code Cdx [255]. Then, a change in the transmittance of the liquid crystal element CL in the display period T2 when off is designated in the subfield period SF [10] is exemplified.

In both the case shown in FIG. 12A and the case shown in FIG. 12B, the liquid crystal element CL transmittance at the end of the display period T1 is not less than the value Amin and not more than the value Amax. Therefore, the transmittance of the liquid crystal element CL at the end of the reset period R2 subsequent to the display period T1, that is, at the start of the display period T2, is not less than the value Bmin and not more than the value Bmax. That is, the rising speed of the transmittance of the liquid crystal element CL in the case shown in FIG. 12A and the rising speed of the transmittance of the liquid crystal element CL in the case shown in FIG. Can be tricked.
As a result, in the case shown in FIG. 12A, the area _GW1 representing the integral value of the transmittance of the liquid crystal element CL in the display period T2 is equal to the liquid crystal element CL in the display period T2 in the case shown in FIG. It can be considered that it coincides with the area _GW2 representing the integral value of the transmittance. That is, the maximum value (area G _W2 ) and minimum value (area G _W1 ) of the integral value of the transmittance of the liquid crystal element CL in the display period T when the highest gradation is designated for the pixel Px according to the present embodiment. The difference between the maximum value (area G _W2X ) and the minimum value (area G _W1X ) of the integral value of the transmittance of the liquid crystal element CL when the highest gradation is designated for the pixel Px included in the electro-optical device related to the _{proportionality} ) Is smaller than the difference. That is, according to the present embodiment, in the display period T1, whether the highest gradation or the lowest gradation is designated for the pixel Px in the display period T1, the pixel Px in the display period T2. Makes it possible to accurately display the gradations to be displayed, and to ensure the uniformity of display.

  FIG. 13 shows that the pixel Px included in the electro-optical device 1 according to this embodiment is turned off in the subfield periods SF [1] to SF [9] of the display period T2 based on the correction SF code Cdx [0]. Represents the change in the transmittance of the liquid crystal element CL included in the pixel Px. Among these, FIG. 13A shows the display period T2 when the pixel Px is controlled to be turned on or off based on the correction SF code Cdx [0] in the display period T1 preceding the display period T2. The change in the transmittance of the liquid crystal element CL is exemplified. FIG. 13B shows the transmittance of the liquid crystal element CL in the display period T2 when the pixel Px is controlled to be turned on or off based on the corrected SF code Cdx [255] in the display period T1. Illustrate changes.

In both the case shown in FIG. 13A and the case shown in FIG. 13B, the liquid crystal element CL transmittance at the end of the display period T1 is not less than the value Amin and not more than the value Amax, and at the start of the display period T2. Both of the transmittances of the liquid crystal element CL are equal to or greater than the value Bmin and equal to or less than the value Bmax. As a result, in the case shown in FIG. 13A, the total value of the area G _B1-1 and the area G _B1-2 representing the integral value of the transmittance of the liquid crystal element CL in the display period T2 is shown in FIG. in the case shown, it can be the sum of the areas G _{B 2 - 1} and the area G _B2-2 representing an integral value of transmittance of the liquid crystal element CL in the display period T2, and a match considered. That is, in the case where the lowest gradation is designated for the pixel Px according to the present embodiment, the maximum integrated value of the transmittance of the liquid crystal element CL in the display period T (the area G _B2-1 and the area G _B2-2 are The difference between the total value) and the minimum value (the total value of the areas G _B1-1 and G _B1-2 ) is a liquid crystal element in the case where the lowest gradation is designated for the pixel Px provided in the electro-optical device related to the proportionality It is smaller than the difference between the maximum value (area G _BX ) and the minimum value “0” of the integrated value of the transmittance of CL. That is, in the present embodiment, in the display period T1, the pixel Px is displayed in the display period T2 regardless of whether the highest gradation is designated for the pixel Px or the lowest gradation is designated. It is possible to accurately display the gradation to be obtained, and to ensure display uniformity.

  As described above, in this embodiment, on / off of the pixel Px is controlled based on the corrected SF code Cdx obtained by correcting the SF code Cd. For this reason, the initial transmittance of the liquid crystal element CL at the start of the display period T can be kept within the range between the value Bmin and the value Bmax, and the gradation and the pixel Px designated by the video signal Din are actually displayed. In addition, the variation in error between the gradations to be performed can be reduced, and the gradation specified by the video signal Din can be accurately displayed by the pixel Px. Thereby, display uniformity can be ensured.

In order to ensure display uniformity, the reset period R is sufficiently long, and the initial transmittance of the liquid crystal element CL at the start of the display period T is set to 0% or a value close to 0%. It is also possible to assume an aspect of aligning.
However, when the initial transmittance of the liquid crystal element CL at the start of the display period T is set to 0% or a value close to 0%, the rising rate of the transmittance of the liquid crystal element CL in the display period T is slowed down. Further, when the time length of the reset period R is increased, the time length of the display period T is shortened. Therefore, in the aspect in which the length of the reset period R is increased, the image displayed by the electro-optical device 1 becomes dark as a whole.
On the other hand, in the present embodiment, the initial transmittance of the liquid crystal element CL at the start of the display period T is set to a value greater than “0” and a value Bmin or more. For this reason, the rising speed of the transmittance of the liquid crystal element CL in the display period T can be increased, and the image displayed by the electro-optical device 1 can be brightened as a whole.
In the present embodiment, the time length of the reset period R can be shortened as compared with the case where the initial transmittance of the liquid crystal element CL is set to 0%. For this reason, the time length of the display period T can be increased, and as a result, the operation speed of the electro-optical device 1 can be decreased.

<B. Modification>
Each of the above forms can be variously modified. Specific modifications are exemplified below. Two or more aspects arbitrarily selected from the following examples can be appropriately combined within a range that does not contradict each other.

<Modification 1>
In the embodiment described above, the generation unit 532 corrects the values corresponding to the subfield periods SF [9] and SF [10] among the values indicated by the SF code Cd [k], thereby correcting the corrected SF code Cdx [ k], but the present invention is not limited to such a mode, and a value corresponding to at least one subfield period SF among a plurality of subfield periods SF included in the display period T. The corrected SF code Cdx [k] may be generated by correcting.
For example, the generation unit 532 corrects a value corresponding to a predetermined number of subfield periods SF including the last subfield period SF among a plurality of subfield periods SF included in the display period T, thereby correcting the SF code Cdx. [K] may be generated. Further, for example, the generation unit 532 corrects only the value corresponding to the last subfield period SF in the plurality of subfield periods SF included in the display period T among the values indicated by the SF code Cd [k], The corrected SF code Cdx [k] may be generated.

<Modification 2>
In the above-described embodiment and modification, the allowable range (value Bmin and value Bmax) of the initial transmittance of the liquid crystal element CL at the start of the display period T is determined so as to satisfy at least the first condition. The invention is not limited to such an embodiment. In addition to the above-described first condition (or both the first condition and the second condition), the case where the pixel Px displays the maximum gradation and the minimum floor are displayed. It may be determined that the third condition, which is a condition for the contrast ratio when displaying a tone, is satisfied. Hereinafter, the third condition will be described with reference to FIGS. 14 and 15.

FIG. 14 is an explanatory diagram for explaining the contrast ratio when the pixel Px of the electro-optical device 1 according to the present invention displays the maximum gradation and the minimum gradation. FIG. 15 is an explanatory diagram for explaining the contrast ratio when the pixel Px of the electro-optical device according to the above-described comparative example displays the maximum gradation and the minimum gradation. 14 and 15, the horizontal axis represents time, and the vertical axis represents the absolute transmittance of the liquid crystal element CL in addition to the transmittance (relative transmittance) of the liquid crystal element CL.
Here, the absolute transmittance of the liquid crystal element CL is the light emitted from the light source, with the amount of light when the observer directly recognizes the light emitted from the light source (not via the liquid crystal element CL) as 100%. The amount of light when all of the above are blocked is scaled to 0%. The absolute transmittance La when the transmittance (relative transmittance) of the liquid crystal element CL is 100% is smaller than 100%, and the absolute transmittance when the transmittance (relative transmittance) of the liquid crystal element CL is 0%. Lb is greater than 0%.

As shown in FIG. 14, the integral value of the absolute transmittance of the liquid crystal element CL in the display period T when the pixel Px of the electro-optical device 1 according to the present invention displays the maximum gradation based on the corrected SF code Cdx. The area to be represented is ^A G _W1, and the area representing the integral value of the absolute transmittance of the liquid crystal element CL in the display period T when displaying the minimum gradation based on the corrected SF code Cdx is ^A G _B1 . Further, as shown in FIG. 15, the integral value of the absolute transmittance of the liquid crystal element CL in the display period T when the pixel Px of the electro-optical device according to the proportional display displays the maximum gradation based on the SF code Cd. The area to be represented is ^A G _W2, and the area representing the integral value of the absolute transmittance of the liquid crystal element CL in the display period T when displaying the minimum gradation based on the SF code Cd is ^A G _B2 .
In this case, in the electro-optical device 1 according to the present invention, the (relative) transmittance of the liquid crystal element CL at the start of the display period T is equal to or greater than Bmin (> 0), and thus the absolute transmittance at this time is greater than Lb. growing. On the other hand, in the electro-optical device according to the proportionality, the (relative) transmittance of the liquid crystal element CL at the start of the display period T can be set to “0”, and thus the absolute transmittance at this time is equal to Lb. Therefore, the area ^A G _B1 is smaller than the area ^A G _B2 , and the area ^A G _W1 is larger than the area ^A G _W2 .

The third condition is that the contrast ratio “ ^A G _W1 ÷ ^A G _B1 ” that can be displayed by the pixel Px of the electro-optical device 1 according to the present invention can be displayed by the pixel Px of the electro-optical device related to the comparison. contrast ratio of the gradation is larger than ^"a G _W2 ÷ ^a G _B2", a condition that.
The electro-optical device 1 according to this modification determines the value Bmin and the value Bmax representing the (relative) transmittance range of the liquid crystal element CL at the start of the display period T so that the third condition is satisfied. For this reason, the electro-optical device 1 according to the present modification can increase the contrast ratio compared to the electro-optical device according to the proportionality, and can display a clear image.

<Modification 3>
In the embodiment and the modification described above, when the generation unit 532 controls on / off of the pixel Px based on the SF code Cd [k], the transmittance of the liquid crystal element CL at the end of the display period T is greater than the value Amin. Is smaller (or larger than the value Amax), the SF code Cd [k] is corrected. However, the present invention is not limited to such a mode, and the value indicated by the SF code Cd. The necessity of correction may be determined based on the above.
Specifically, the value indicated by the SF code Cd [k] corresponds to a predetermined number of consecutive subfield periods SF including the last subfield period SF among the plurality of subfield periods SF included in the display period T. When all of the values are “1” or “0”, correction may be performed.
For example, when all the values indicated by the SF code Cd [k] are “0”, the value corresponding to the last subfield period SF may be corrected to “1”. When all the values indicated by the SF code Cd [k] are “1”, the value corresponding to the last subfield period SF may be corrected to “0”.

<Modification 4>
In the embodiment and the modification described above, the storage unit 54 stores the SF code Cd. However, the present invention is not limited to such an aspect, and the storage unit 54 is replaced with the SF code Cd (or The correction SF code Cdx may be stored together with the SF code Cd.
In this case, the selection unit 531 selects the correction SF code Cdx corresponding to the video signal Din from the storage unit 54, and the generation unit 532 generates image data Dx corresponding to the correction SF code Cdx selected by the selection unit 531. Anything is acceptable.

<Modification 5>
The correction SF code Cdx includes “1” and “0” included in values corresponding to the first half subfield period SF among the plurality of subfield periods SF constituting the display period T among the values indicated by the correction SF code Cdx. ”And the number of“ 1 ”and“ 0 ”values included in the value corresponding to the second subfield period SF are equal (hereinafter referred to as“ fourth condition ”). May be).
In this case, in each display period T, the time length in which the pixel Px holds the positive polarity data signal VD [n] and the time length in which the negative polarity data signal VD [n] is held are equalized. can do. As a result, application of a DC voltage to the liquid crystal element CL can be suppressed, so-called “burn-in” can be prevented, and deterioration of the liquid crystal element CL can be minimized.
In the above-described embodiment and Modifications 1 to 3, the generation unit 532 may generate the corrected SF code Cdx so as to satisfy the fourth condition in addition to the first condition to the third condition. Good.

<Modification 6>
In the embodiment and the modification described above, the scanning line driving circuit 22 outputs the two selection pulses YS [z] in a time division manner in each horizontal scanning period H, but the present invention is limited to such an aspect. Instead, one selection pulse YS [z] may be output for each horizontal scanning period H as shown in FIG. In this case, each unit period U [z] may correspond to each subfield period SF [z].
Further, the scanning line driving circuit 22 may output three or more selection pulses YS [z] for each horizontal scanning period H. In this case, each unit period U [z] may be divided into three or more subfield periods SF.

<Modification 7>
In the embodiment and the modification described above, the display period T is divided into five unit periods U, and the reset period R is divided into two unit periods U, but the present invention is limited to such a mode. Instead, the display period T and the reset period R only need to be composed of one or more unit periods U.

<Modification 8>
In the embodiment and the modification described above, the display period T is divided into a plurality of subfield periods SF having the same time length. However, the present invention is not limited to such a mode, and a plurality of subfield periods SF are included. Some subfield periods SF in the field period SF may be divided so as to have a different time length from other subfield periods SF.
For example, the display period T is divided into a plurality of first subfield periods having a first time length and a plurality of second subfield periods having a second time length different from the first time length. It may be a thing. For example, the display period T may be divided into a plurality of subfield periods SF having different time lengths.

<Modification 9>
In the embodiment and the modification described above, the liquid crystal 43 is a VA system, but may be a TN (Twisted Nematic) system. In other words, the electro-optical device 1 is in a normally white mode in which the pixel Px displays white (the relative transmittance of the liquid crystal element CL is 100%) when no voltage is applied between the pixel electrode 41 and the common electrode 42. It may operate.
In this case, the first condition is that the value Bmax (third value) is smaller than 100% instead of the content that the value Bmin (first value) is larger than 0%. Any content may be used as long as the content indicates (for example, a value of 99% or less).

<C. Application example>
The electro-optical device 1 exemplified in the above embodiments can be used in various electronic apparatuses. 17 to 19 exemplify specific forms of electronic devices that employ the electro-optical device 1.

  FIG. 17 is a schematic diagram of a projection display device (three-plate projector) 4000 to which the electro-optical device 1 is applied. The projection display device 4000 includes three electro-optical devices 1 (1R, 1G, 1B) corresponding to different display colors (red, green, blue). The illumination optical system 4001 supplies the red component r of the light emitted from the illumination device (light source) 4002 to the electro-optical device 1R, the green component g to the electro-optical device 1G, and the blue component b to the electro-optical device 1B. To supply. Each electro-optical device 1 functions as a light modulator (light valve) that modulates each monochromatic light supplied from the illumination optical system 4001 in accordance with a display image. The projection optical system 4003 synthesizes the emitted light from each electro-optical device 1 and projects it onto the projection surface 4004. The observer visually recognizes the image projected on the projection surface 4004 with the stereoscopic glasses 60 (not shown in FIG. 17).

  FIG. 18 is a perspective view of a portable personal computer that employs the electro-optical device 1. The personal computer 2000 includes an electro-optical device 1 that displays various images, and a main body 2010 on which a power switch 2001 and a keyboard 2002 are installed.

  FIG. 19 is a perspective view of a mobile phone to which the electro-optical device 1 is applied. The cellular phone 3000 includes a plurality of operation buttons 3001 and scroll buttons 3002, and the electro-optical device 1 that displays various images. By operating the scroll button 3002, the screen displayed on the electro-optical device 1 is scrolled.

  Note that electronic devices to which the electro-optical device according to the invention is applied include the devices exemplified in FIGS. 17 to 19, personal digital assistants (PDAs), digital still cameras, televisions, video cameras, Car navigation devices, in-vehicle displays (instrument panels), electronic notebooks, electronic paper, calculators, word processors, workstations, videophones, POS terminals, printers, scanners, copiers, video players, equipment with touch panels, etc. Can be mentioned.

DESCRIPTION OF SYMBOLS 1 ... Electro-optical device, 10 ... Electro-optical panel, 20 ... Drive circuit, 22 ... Scan line drive circuit, 24 ... Data line drive circuit, 30 ... Display part, 32 ... Scan line, 34 ... ... Data line, 40 ... Pixel circuit, 50 ... Control unit, 51 ... Signal generation unit, 52 ... Glasses control circuit, 53 ... Display information generation unit, 531 ... Selection unit, 532 ... Generation unit, 54 …… Storage unit, 60 …… Stereoscopic glasses, 62 …… Left eye shutter, 64 …… Right eye shutter, CL …… Liquid crystal element, Px …… Pixel.

Claims (10)

A pixel comprising a liquid crystal element;
When a video signal designating a gradation to be displayed by the pixel is supplied, a data signal designating on or off of the pixel is generated based on the video signal, and
Of the display period and the reset period alternately arranged on the time axis, the display period is divided into a plurality of subfield periods, and the data signal is supplied to the pixel in each of the plurality of subfield periods. A display control unit to supply;
With
The display control unit
Even if the video signal specifies any gradation as the gradation that the pixel should display in one display period,
At the end of one reset period following the one display period, the transmittance of the liquid crystal element is a value equal to or greater than a first value greater than the minimum transmittance that the liquid crystal element can take. Generating a data signal to be supplied to the pixel in the one display period;
An electro-optical device. The display control unit
Even if the video signal specifies any gradation as the gradation that the pixel should display in one display period,
At the end of the one display period, in the one display period, the transmittance of the liquid crystal element is equal to or less than a second value smaller than the maximum transmittance that the liquid crystal element can take. Generating a data signal to be supplied to the pixel;
The electro-optical device according to claim 1. When the pixel is turned on, the transmittance of the liquid crystal element included in the pixel is
Greater than the transmittance when the pixel is turned off,
The display control unit
When the video signal specifies a minimum gradation as a gradation that the pixel should display in the display period,
Supplying the data signal designating ON of the pixel to the pixel in at least one subfield period of the plurality of subfield periods included in the display period;
The electro-optical device according to claim 1, wherein the electro-optical device is provided. The display control unit
When the video signal specifies the maximum gradation as the gradation that the pixel should display in the display period,
Supplying the pixel with the data signal designating turning off of the pixel in at least one subfield period of the plurality of subfield periods included in the display period;
The electro-optical device according to claim 3. The display control unit
In order to display the gradation specified by the video signal and the gradation specified by the video signal on the pixel, the pixel is turned on or off for each of the plurality of subfield periods included in the display period. A storage unit that stores subfield codes that are data in association with each other;
A selection unit that selects the subfield code from the storage unit based on the video signal;
A generating unit capable of generating the data signal based on the subfield code selected by the selecting unit;
With
The generator is
When the subfield code selected by the selection unit is data designating the pixel off in all of the plurality of subfield periods,
The subfield code selected by the selection unit is corrected to designate ON of the pixel in at least one subfield period of the plurality of subfield periods, and based on the corrected subfield code, Generate data signals,
The electro-optical device according to claim 1, wherein the electro-optical device is any one of the above. The generator is
When the subfield code selected by the selection unit is data specifying ON of the pixel in all of the plurality of subfield periods,
The subfield code selected by the selection unit is corrected to specify that the pixel is turned off in at least one subfield period of the plurality of subfield periods, and based on the corrected subfield code, Generate data signals,
The electro-optical device according to claim 5. The one subfield period is:
Of the plurality of subfield periods included in the display period, the last subfield period.
The electro-optical device according to claim 3, wherein the electro-optical device is any one of the above. A pixel comprising a liquid crystal element;
When a video signal designating a gradation to be displayed by the pixel is supplied, a data signal designating on or off of the pixel is generated based on the video signal, and
Of the display period and the reset period alternately arranged on the time axis, the display period is divided into a plurality of subfield periods, and the data signal is supplied to the pixel in each of the plurality of subfield periods. A display control unit to supply;
With
The display control unit
Even if the video signal specifies any gradation as the gradation that the pixel should display in one display period,
At the end of one reset period following the one display period, the transmittance of the liquid crystal element is a value equal to or smaller than a third value smaller than the maximum transmittance that the liquid crystal element can take. Generating a data signal to be supplied to the pixel in the one display period;
An electro-optical device.   An electronic apparatus comprising the electro-optical device according to claim 1. A driving method of an electro-optical device including a pixel including a liquid crystal element,
When a video signal specifying the gradation to be displayed by the pixel is supplied,
Based on the video signal, a data signal that specifies whether the pixel is on or off is generated,
Of the display period and the reset period alternately arranged on the time axis, the display period is divided into a plurality of subfield periods, and the data signal is supplied to the pixel in each of the plurality of subfield periods. Supply
The data signal supplied to the pixel in one display period is:
Even if the video signal specifies any gradation as the gradation that the pixel should display in the one display period,
At the end of one reset period following the one display period, the transmittance of the liquid crystal element is a signal equal to or greater than a first value that is greater than the minimum transmittance that the liquid crystal element can take. ,
A driving method for an electro-optical device.

Images