KR101882937B1 - Stereoscopic image display device and driving method thereof - Google Patents

Abstract

The present invention relates to an active retarder type stereoscopic image display apparatus and a driving method thereof. The stereoscopic image display apparatus of the present invention includes a display panel for displaying a left-eye image and a right-eye image in a time-division manner in a 3D mode; A backlight unit including light sources for illuminating the display panel; A first polarized light is emitted when the first driving voltage is applied to the scan electrodes by rotating the liquid crystal by a voltage difference between the scan electrodes and the reference electrode attached to the display panel, An active retarder for emitting light of a second polarized light when a second driving voltage is applied; A left eye filter for passing only light of the first polarized light and a right eye filter for passing only light of the second polarized light; And applying a reference voltage to the reference electrode and applying the first driving voltage or the second driving voltage to the scan electrodes so that the rotation of the liquid crystal of the active retarder occurs only during a period in which the light sources are turned off, And a further driving unit.

Description

TECHNICAL FIELD [0001] The present invention relates to a stereoscopic image display device and a method of driving the stereoscopic image display device.

The present invention relates to an active retarder type stereoscopic image display apparatus and a driving method thereof.

The stereoscopic display device displays a stereoscopic image using a stereoscopic technique or an autostereoscopic technique. The binocular parallax method uses parallax images of right and left eyes with large stereoscopic effect, and can be divided into a spectacular method and a non-spectacular method. In the spectacle method, there is a pattern retarder method in which a polarizing direction of a left-right parallax image is displayed on a direct-view type display device or a projector, and a stereoscopic image is implemented using polarizing glasses. In the eyeglass system, there is a shutter glass system in which right and left parallax images are displayed in a time-division manner on a direct view type display device or a projector, and a stereoscopic image is implemented using liquid crystal shutter glasses. In the non-eyeglass system, an optical plate such as a parallax barrier or a lenticular lens is generally used to separate the optical axes of the left and right parallax images to realize a stereoscopic image.

On the other hand, an active retarder method of time-sharing right-and-left parallax images on a direct viewing type display device or a projector in a spectacles system, changing the polarization direction and displaying stereoscopic images using polarized glasses is being developed. In the active retarder scheme, the display element displays a monocular image (e.g., a left eye image) during an odd frame period and another monocular image (e.g., a right eye image) during an even frame period, The polarization characteristic of the left eye image and the polarization characteristic of the right eye image are converted differently. The active retarder converts the polarization characteristics of the left eye image and the polarization characteristics of the right eye image differently using a liquid crystal. The response speed of the liquid crystal is slow due to inherent characteristics such as viscosity and elasticity, as shown in equations (1) and (2).

(gamma)는 액정분자의 회전점도(rotational viscosity)를 각각 의미한다.In Equation (1), τ _r denotes a rising time when a voltage is applied to the liquid crystal, V _a denotes an applied voltage, and V _F denotes a Freederick Transition Voltage ), D is the cell gap of the liquid crystal cell of the active retarder,

(gamma) means the rotational viscosity of the liquid crystal molecule, respectively.

In Equation (2), τ _f denotes a falling time at which the liquid crystal is restored to its original state due to the elastic restoring force after the voltage applied to the liquid crystal is turned off, and K denotes elastic modulus inherent to the liquid crystal.

Owing to the slow response speed of the liquid crystal of the active retarder, the active retarder can convert the left eye image with the polarization characteristic of the right eye image, not the polarization characteristic of the left eye image, even though the display element displays the left eye image. In addition, although the display device displays the right eye image, the active retarder can convert the right eye image with the polarization characteristic of the left eye image, not the polarization characteristic of the right eye image. In this case, a 3D crosstalk occurs in which the left eye image and the right eye image overlap each other. Because of this 3D crosstalk, not only the user may feel dizziness, but also the stereoscopic image quality may be deteriorated.

The present invention provides an active retarder type stereoscopic image display device capable of reducing 3D crosstalk and a driving method thereof.

The stereoscopic image display apparatus of the present invention includes a display panel for displaying a left-eye image and a right-eye image in a time-division manner in a 3D mode; A backlight unit including light sources for illuminating the display panel; A first polarized light is emitted when the first driving voltage is applied to the scan electrodes by rotating the liquid crystal by a voltage difference between the scan electrodes and the reference electrode attached to the display panel, An active retarder for emitting light of a second polarized light when a second driving voltage is applied; A left eye filter for passing only light of the first polarized light and a right eye filter for passing only light of the second polarized light; And applying a reference voltage to the reference electrode and applying the first driving voltage or the second driving voltage to the scan electrodes so that the rotation of the liquid crystal of the active retarder occurs only during a period in which the light sources are turned off, And a further driving unit.

A method of driving a stereoscopic image display apparatus includes a display panel for displaying a left-eye image and a right-eye image in a time-division manner in a 3D mode, a backlight unit including light sources for irradiating light on the display panel, An active retarder attached to switch polarization characteristics of light incident from the display panel; and polarized glasses that pass only light of the first polarized light through the left eye filter and pass only light of the second polarized light through the right eye filter A stereoscopic image display method comprising: applying a first driving voltage or a second driving voltage to scan electrodes of an active retarder and applying a reference voltage to a reference electrode; And a second driving voltage is applied to the scan electrodes when the first driving voltage is applied to the scan electrodes by rotating the liquid crystal by a voltage difference between the scan electrodes and the reference electrode, Wherein the step of applying the first driving voltage or the second driving voltage to the scan electrodes of the active retarder and the step of applying the reference voltage to the reference electrode comprises the steps of: And the first driving voltage or the second driving voltage is applied to the scan electrodes so that the rotation of the liquid crystal of the active retarder occurs only during a period in which the light sources are turned off.

The present invention controls the on / off timing of the active retarder according to the on / off timing of the light sources of the backlight unit.

And applies the first driving voltage and the second driving voltage to start and complete the transition of the liquid crystal of the active retarder during a period in which the light sources are turned off.

As a result, the present invention can reduce the 3D crosstalk due to the response delay of the liquid crystal of the active retarder.

1 is a block diagram schematically showing a stereoscopic image display apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating a method of implementing an active retarder type stereoscopic image according to an exemplary embodiment of the present invention. Referring to FIG.
3 is a flowchart illustrating a method of driving a stereoscopic image display apparatus according to a first embodiment of the present invention.
FIG. 4 is a diagram specifically illustrating the on-off timing of the active retarder according to the first embodiment of the present invention.
5 is a flowchart illustrating a method of driving a stereoscopic image display apparatus according to a second embodiment of the present invention.
FIG. 6 is a diagram specifically showing the on-off timing of the active retarder according to the second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The names of components used in the following description are selected in consideration of ease of specification, and may be different from actual product names.

1 is a block diagram schematically showing a stereoscopic image display apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a method of implementing an active retarder type stereoscopic image according to an exemplary embodiment of the present invention. Referring to FIG. 1 and 2, a stereoscopic image display apparatus according to the present invention includes a display panel 10, polarizing glasses 20, an active retarder 30, a gate driver 110, a data driver 120, A driving unit 130, a timing controller 140, a host system 150, and the like. The stereoscopic image display device of the present invention can be applied to a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an organic light emitting diode Diodes, and OLEDs). Although the present invention has been described with reference to liquid crystal display elements in the following embodiments, it should be noted that the present invention is not limited to liquid crystal display elements.

In the display panel 10, a liquid crystal layer is formed between two substrates. The substrate of the display panel 10 may be implemented as a glass, a plastic, or a film. On the upper substrate 10a of the display panel 10, a color filter array including a black matrix, a color filter, a common electrode, and the like is formed. The data lines D and the gate lines G are formed on the lower substrate 10b of the display panel 10 such that the data lines D and the gate lines G intersect each other. A TFT array in which pixels are arranged in a matrix form is formed in the cell regions defined by the TFT array. Each of the pixels of the display panel 10 is connected to the thin film transistor and driven by an electric field between the pixel electrode and the common electrode. The common electrode is formed on the upper substrate 10a in a vertical electric field driving method such as a TN (Twisted Nematic) mode and a VA (Vertical Alignment) mode. The common electrode is formed in the IPS (In Plane Switching) mode and the FFS And is formed on the lower substrate 10b together with the pixel electrode in the horizontal electric field driving system. The liquid crystal mode of the display panel 10 can be implemented in any liquid crystal mode as well as the TN mode, VA mode, IPS mode, and FFS mode described above.

The display panel 10 displays an image under the control of the timing controller 140. The display panel 10 displays a 2D image in the 2D mode and time-divisionally displays the left eye image and the right eye image in the 3D mode. The operation of the display panel 10 in the 3D mode according to the embodiment of the present invention will be described later with reference to FIGS. 3 to 6. FIG.

The display panel 10 is typically a transmissive liquid crystal display panel that modulates light from the backlight unit. The backlight unit includes a light source that is turned on in accordance with the driving current supplied from the backlight driver, a light guide plate (or diffusion plate), and a plurality of optical sheets. The backlight unit may be implemented as a direct type backlight unit or an edge type backlight unit. The light sources of the backlight unit may include any one of a light source of HCFL (Cold Cathode Fluorescent Lamp), CCFL (Cold Cathode Fluorescent Lamp), EEFL (External Electrode Fluorescent Lamp), LED .

The backlight driver generates a driving current for turning on the light sources of the backlight unit. The backlight driving unit turns on / off the driving current supplied to the light sources under the control of the backlight control unit. The backlight control unit supplies backlight control data that adjusts the backlight luminance and lighting timing in accordance with the global / local dimming signal (DIM) input from the host system 150 and the backlight control signal (C _BL ) input from the timing controller 140 to the SPI (Serial Pheripheral Interface) data format to the backlight driver.

Referring to FIG. 3, an upper polarizer 11a is attached to the upper substrate 10a of the display panel 10, and a lower polarizer 11b is attached to the lower substrate 10b. The light transmission axis r1 of the upper polarizer plate 11a and the light transmission axis r2 of the lower polarizer plate 11b are orthogonal. An alignment film for setting a pre-tilt angle of the liquid crystal is formed on the upper substrate 10a and the lower substrate 10b. A spacer for maintaining a cell gap of the liquid crystal layer is formed between the upper substrate 10a and the lower substrate 10b of the display panel 10. [ An active retarder 30 is attached on the upper polarizing plate 11a.

The active retarder 30 may be implemented as a liquid crystal panel that includes a reference electrode and a plurality of scan electrodes facing each other with a liquid crystal layer interposed therebetween and does not include a polarizer, a color filter, and a black matrix. The active retarder 30 may be implemented in a TN (Twisted Nematic) mode. When the first driving voltage Vd1 is applied to the scan electrodes, the active retarder 30 passes the light without changing the polarization characteristic of the light incident from the display panel 10. The active retarder 30 delays the phase value of the light incident from the display panel 10 by? / 2 (? Is the wavelength of light) when the second driving voltage Vd2 is applied to the scan electrodes. Therefore, the active retarder 30 emits the first polarized light P1 when the first driving voltage Vd1 is applied to the scan electrodes, and the second driving voltage Vd2 is applied to the scan electrodes The light of the second polarized light P2 is emitted. The polarizing glasses 20 include a left eye filter F _{L for} allowing only light of the first polarized light P1 to pass and a right eye filter F _{R for} passing only the light of the second polarized light P2.

The light passing through the upper polarizer 11a of the display panel 10 has a polarization characteristic of the first polarized light P1. The active retarder 30 allows light of the first polarized light P1 incident from the display panel 10 to pass therethrough when the first driving voltage Vd1 is applied to the scan electrodes. When the second driving voltage Vd2 is applied to the scan electrodes, the active retarder 30 delays the light of the first polarized light P1 incident from the display panel 10 by? / 2, And converts it into a polarized light P2. Accordingly, the user sees only the image of the first polarized light P1 incident on the left eye filter of the polarizing glasses 20 as the left eye, and the image of the second polarized light P2 incident on the right eye of the polarized glasses 20 as the right eye . As a result, the user can feel a stereoscopic effect due to the binocular parallax.

The active retarder driver 130 supplies the reference voltage and the first or second driving voltage Vd1 / Vd2 to the active retarder 30 under the control of the timing controller 140. [ The active retreader driving unit 130 may determine whether the mode is a 2D mode or a 3D mode according to a mode signal MODE input from the timing controller 140. [ The active retarder driver 130 supplies the reference voltage to the reference electrode of the active retarder 30 in the 2D mode and supplies the first driving voltage Vd1 to the scan electrodes. The active retarder driver 130 supplies a reference voltage to the reference electrode of the active retarder 30 in the 3D mode. The active retarder driving unit 130 applies a first driving voltage Vd1 or a second driving voltage Vd1 to the scan electrodes of the active retarder 30 according to the active retarder control signal C _AR input from the timing controller 140 in the 3D mode. 2 driving voltage Vd2. In the 3D mode, the active retarder driver 130 applies a first driving voltage (e.g., a first driving voltage) to the scan electrodes of the active retarder 30 so that the rotation of the liquid crystal of the active retarder 30 occurs only during the period when the light sources of the backlight unit are turned off. (Vd1) or the second driving voltage (Vd2). A detailed description of a method of driving the active retarder 30 that minimizes the 3D crosstalk according to the embodiment of the present invention in the 3D mode will be described later with reference to FIGS. 3 to 6. FIG.

The data driver 120 includes a plurality of source drive ICs. The source drive ICs convert the image data (RGB) input from the timing controller 140 into a positive / negative gamma compensation voltage to generate positive / negative analog data voltages. Positive / negative polarity analog data voltages output from the source drive ICs are supplied to the data lines D of the display panel 10.

The gate driver 110 sequentially supplies gate pulses synchronized with the data voltage to the gate lines G of the display panel 10 under the control of the timing controller 140. The gate driver 110 may be composed of a plurality of gate drive integrated circuits each including a shift register, a level shifter for converting an output signal of the shift register into a swing width suitable for TFT driving of the liquid crystal cell, have. Alternatively, the gate driver 110 may be formed directly on the lower substrate 10b of the display panel 10 using a GIP (gate drive IC in panel) method. In the case of the GIP method, the level shifter is mounted on a PCB (Printed Circuit Board), and the shift register can be formed on the lower substrate 10b of the display panel 10. [

The timing controller 140 supplies a gate driver control signal to the gate driver 110 (110) based on the image data (RGB) and the timing signals Vsync, Hsync, DE, and CLK output from the host system 150 and the mode signal MODE. And outputs the data driver control signal to the data driver 120. [ In particular, the timing controller 140 multiplies the frame frequency by L (L is a natural number equal to or greater than 2) times, preferably four times or more, of the input frame frequency, and outputs the gate driver control signal, Signal, a backlight control signal, and an active retarder control signal. The input frame frequency is 50 Hz in the PAL (Phase Alternate Line) method and 60 Hz in the National Television Standards Committee (NTSC) method.

The gate driver control signal includes a gate start pulse (GSP), a gate shift clock (GSC), and a gate output enable signal (GOE). The gate start pulse (GSP) controls the timing of the first gate pulse. The gate shift clock GSC is a clock signal for shifting the gate start pulse GSP. The gate output enable signal GOE controls the output timing of the gate driver 110. [

The data driver control signal includes a source start pulse (SSP), a source sampling clock (SSC), a source output enable (SOE) signal, a polarity control signal (POL) . The source start pulse SSP controls the data sampling start timing of the data driver 120. The source sampling clock is a clock signal that controls the sampling operation of the data driver 120 based on the rising or falling edge. The source start pulse SSP and the source sampling clock SSC may be omitted if the digital video data to be input to the data driver 120 is transmitted in accordance with the mini LVDS (Low Voltage Differential Signaling) interface standard. The polarity control signal POL inverts the polarity of the data voltage output from the data driver 120 to L (L is a natural number) horizontal period period. The source output enable signal SOE controls the output timing of the data driver 120.

The host system 150 supplies the image data RGB to the timing controller 140 through an interface such as a Low Voltage Differential Signaling (LVDS) interface or a Transition Minimized Differential Signaling (TMDS) interface. The host system 150 also supplies timing signals (Vsync, Hsync, DE, CLK), a mode signal (MODE), and the like to the timing controller 140.

Hereinafter, a driving method of the active retarder 30 capable of minimizing the 3D crosstalk according to the embodiment of the present invention in the 3D mode will be described in detail with reference to FIG. 3 to FIG. The driving method of the active retarder 30 capable of minimizing the 3D crosstalk according to the embodiment of the present invention is designed in consideration of the on and off timings of the light sources of the backlight unit and the liquid crystal response characteristics of the active retarder 30 .

3 is a flowchart illustrating a method of driving a stereoscopic image display apparatus according to a first embodiment of the present invention. FIG. 4 is a diagram specifically illustrating the on-off timing of the active retarder according to the first embodiment of the present invention.

Referring to FIG. 4, the display panel 10 is driven at a frame frequency of 240 Hz. The display panel 10 has been described mainly the left-eye image data (RGB _L), the black data (Black), right eye image data (RGB _R), and the black data (Black) are alternately addressed to, it is not limited to Should be noted. The active retarder 30 is driven at a frame frequency of 120 Hz whereas the display panel 10 is driven at a frame frequency of 240 Hz. That is, the first driving voltage Vd1 and the second driving voltage Vd2 are alternately applied to the active retarder 30 based on a frame frequency of 120 Hz.

In FIG. 4, Td1 denotes a first initial delay time, Ts1 denotes a first liquid crystal transition time, Td2 denotes a second initial delay time, and Ts2 denotes a second liquid crystal transition time. Only the first driving voltage Vd1 and the second driving voltage Vd2 are applied to the scan electrodes of the active retarder 30 and the liquid crystal is turned according to the voltage difference between the scan electrodes and the reference voltage. Accordingly, the first initial delay time Td1 is set to the first driving voltage Vd1 when the voltage applied to the scan electrodes is changed from the second driving voltage Vd2 to the first driving voltage Vdl And the time required for the transition of the liquid crystal to start. The first liquid crystal transition time Ts1 indicates the time taken for the liquid crystal to transition according to the voltage difference between the reference voltage and the first driving voltage Vd1. In addition, the second initial delay time Td2 may be determined based on a time point at which the voltage applied to the scan electrodes changes from the first drive voltage Vd1 to the second drive voltage Vd2, And the time required for the transition of the liquid crystal to start. The second liquid crystal transition time Ts2 means a time taken for the liquid crystal to transition according to the voltage difference between the reference voltage and the second driving voltage Vd2.

In FIG. 4, the light sources of the backlight unit are lit at the point in time corresponding to the Tb1 period at the beginning of the even frame (fourth n-2 and fourth n frames) ) Period from the start time point by the Tb2 period. At this time, Tb1 and Tb2 may vary according to the PWM duty ratio of the light sources of the backlight unit. It should be noted that the timing of turning on and off the light sources of the backlight unit of the present invention is not limited to the timing of turning on and off the light sources of the backlight unit illustrated in Fig. The light sources of the backlight unit may be turned on before the start time of the even frame (fourth n-2 and fourth n frame) periods, and off after the start time of the odd frame (fourth n-1 and fourth n + .

The first embodiment of the present invention is a method of driving the active retarder 30 capable of minimizing the 3D crosstalk by causing the transition of the liquid crystal of the active retarder 30 to start from the point of time when the light sources of the backlight unit are turned off . Hereinafter, a method of driving the stereoscopic image display apparatus according to the first embodiment of the present invention in the 3D mode will be described with reference to FIGS. 3 and 4. FIG.

First, the timing controller 140 addresses the left eye image data RGB _L to the display panel 10 during the 4n-3 (n is a natural number) frame period. Under the control of the timing controller 140, the data driver 120 converts the left eye image data RGB _L into the analog data voltage during the 4n-3 frame period and supplies it to the display panel 10. In addition, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be extinguished during the 4n-3 frame period. The backlight driver turns off the light sources of the backlight unit during the 4n-3 frame period in accordance with the backlight control signal. (S101, S102)

Second, black data (Black) is addressed to the display panel 10 during the 4n-2 frame period. Under the control of the timing controller 140, the data driver 120 converts the black data (Black) into analog data voltages during the 4n-2 frame period and supplies them to the display panel 10. (S103, S104)

Thirdly, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be turned on at a point of time Tb1 elapses from the start time of the (4n-2) -th frame period. The backlight driver turns on the light sources of the backlight unit at a point of time Tb1 elapses from the start time of the (4n-2) -th frame period according to the backlight control signal. (S105, S106)

Fourth, the timing controller 140 controls the active retarder 30 to apply the second driving voltage Vd2 to the active retarder 30 at a time point earlier by (Td2 + Tb2) than the start time of the (4n-1) And generates a control signal. When the second driving voltage Vd2 is applied to the active retarder 30, the liquid crystal of the active retarder 30 starts to transition according to the voltage difference between the scan electrodes and the reference electrode. At this time, the liquid crystal of the active retarder 30 reaches the saturation period after the second initial delay time Td2 and the second liquid crystal transition time Ts2 have elapsed. However, when the light sources of the backlight unit are turned on during the second liquid crystal transition time Ts2, since the image of the first polarized light and the image of the second polarized light both enter the polarized glasses 20, the user feels 3D crosstalk A problem arises.

In order to solve such a problem, the first embodiment of the present invention is characterized in that the active retarder 30 is driven in the second driving mode at a time point earlier by the time Tb2 than the starting point of the 4n-1 frame period at which the light sources of the backlight unit are extinguished The voltage Vd2 is applied. Particularly, since the liquid crystal does not transition at the second initial delay time Td2, the first embodiment of the present invention is characterized in that the active retarder 30 (Td2 + Tb2) The second driving voltage Vd2 is applied. (S107, S108)

Fifth, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be extinguished by a time Tb2 from the start time of the 4n-1 frame period. The backlight driving unit extinguishes the light sources of the backlight unit at a time point earlier than the starting time point of the (4n-1) frame period by the time period of Tb2 in accordance with the backlight control signal. (S109, S110)

Sixth, the timing controller 140 addresses the right eye image data RGB _R on the display panel 10 during the 4n-1 frame period. Under the control of the timing controller 140, the data driver 120 converts the right eye image data RGB _R into the analog data voltage during the 4n-1 frame period and supplies it to the display panel 10. In addition, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be extinguished during the 4n-1 frame period. The backlight driver turns off the light sources of the backlight unit during the (4n-1) -th frame period in accordance with the backlight control signal. (S111, S112)

Seventh, black data (Black) is addressed to the display panel 10 during the 4n frame period. Under the control of the timing controller 140, the data driver 120 converts the black data (Black) into analog data voltages during the 4 < n > frame period and supplies them to the display panel 10. (S113, S114)

Eighth, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be turned on at a point of time Tb1 elapses from the start time of the 4n frame period. The backlight driver turns on the light sources of the backlight unit at a point of time Tb1 elapses from the start time of the 4n frame period according to the backlight control signal. (S115, S116)

The timing controller 140 controls the active retarder 30 to apply the first driving voltage Vd1 to the active retarder 30 at a time point earlier by the period of (Td1 + Tb2) than the starting point of the (4 + 1) And generates a control signal. When the first driving voltage Vd1 is applied to the active retarder 30, the liquid crystal of the active retarder 30 starts to transition according to the voltage difference between the scan electrodes and the reference electrode. At this time, the liquid crystal of the active retarder 30 reaches the saturation period after the first initial delay time Td1 and the first liquid crystal transition time Ts1 have elapsed. However, when the light sources of the backlight unit are turned on during the first liquid crystal transition time Ts1, since the image of the first polarized light and the image of the second polarized light both enter the polarizing glasses 20, the user feels 3D crosstalk A problem arises.

In order to solve such a problem, the first embodiment of the present invention is characterized in that the active retarder 30 is driven in the first drive mode at a point earlier by the time Tb2 than the start point of the (4n + 1) -th frame period at which the light sources of the backlight unit are extinguished The voltage Vd1 is applied. In particular, since the liquid crystal does not transition to the first initial delay time Td1, the first embodiment of the present invention is characterized in that the active retarder 30 (Td1 + Tb2) The first driving voltage Vd1 is applied. (S117, S118)

In the tenth, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be extinguished at a time point earlier than the start time point of the (4n + 1) -th frame period by the time period Tb2. The backlight driving unit extinguishes the light sources of the backlight unit at a time point earlier than the starting time point of the (4n + 1) -th frame period by the time period of Tb2 in accordance with the backlight control signal. (S119, S120)

As described above, according to the first embodiment of the present invention, transition of the liquid crystal of the active retarder 30 starts from the point of time when the light sources of the backlight unit are turned off, and transition of the liquid crystal is completed before the light sources of the backlight unit are turned on . As a result, the first embodiment of the present invention can reduce the 3D crosstalk due to the response delay of the liquid crystal of the active retarder 30.

5 is a flowchart illustrating a method of driving a stereoscopic image display apparatus according to a second embodiment of the present invention. FIG. 6 is a diagram specifically showing the on-off timing of the active retarder according to the second embodiment of the present invention.

Referring to FIG. 6, the display panel 10 is driven at a frame frequency of 240 Hz. The display panel 10 has been described mainly the left-eye image data (RGB _L), the black data (Black), right eye image data (RGB _R), and the black data (Black) are alternately addressed to, it is not limited to Should be noted. The active retarder 30 is driven at a frame frequency of 120 Hz whereas the display panel 10 is driven at a frame frequency of 240 Hz. That is, the first driving voltage Vd1 and the second driving voltage Vd2 are alternately applied to the active retarder 30 based on a frame frequency of 120 Hz.

In FIG. 6, Td1 denotes a first initial delay time, Ts1 denotes a first liquid crystal transition time, Td2 denotes a second initial delay time, and Ts2 denotes a second liquid crystal transition time. Only the first driving voltage Vd1 and the second driving voltage Vd2 are applied to the scan electrodes of the active retarder 30 and the liquid crystal is turned according to the voltage difference between the scan electrodes and the reference voltage. Accordingly, the first initial delay time Td1 is set to the first driving voltage Vd1 when the voltage applied to the scan electrodes is changed from the second driving voltage Vd2 to the first driving voltage Vdl And the time required for the transition of the liquid crystal to start. The first liquid crystal transition time Ts1 indicates the time taken for the liquid crystal to transition according to the voltage difference between the reference voltage and the first driving voltage Vd1. In addition, the second initial delay time Td2 may be determined based on a time point at which the voltage applied to the scan electrodes changes from the first drive voltage Vd1 to the second drive voltage Vd2, And the time required for the transition of the liquid crystal to start. The second liquid crystal transition time Ts2 means a time taken for the liquid crystal to transition according to the voltage difference between the reference voltage and the second driving voltage Vd2.

In FIG. 6, the light sources of the backlight unit are lit at the point in time when the Tb1 period elapses from the start time of the even frame (4n-2 and 4n frame), and the odd- ) Period from the start time point by the Tb2 period. At this time, Tb1 and Tb2 may vary according to the PWM duty ratio of the light sources of the backlight unit. It should be noted that the on and off timings of the light sources of the backlight unit of the present invention are not limited to the on and off timings of the light sources of the backlight unit illustrated in Fig. The light sources of the backlight unit may be turned on before the start time of the even frame (fourth n-2 and fourth n frame) periods, and off after the start time of the odd frame (fourth n-1 and fourth n + .

The second embodiment of the present invention is a method of driving the active retarder 30 capable of minimizing the 3D crosstalk by allowing the transition of the liquid crystal of the active retarder 30 to be completed from the point in time when the light sources of the backlight unit are turned on . Hereinafter, a method of driving the stereoscopic image display apparatus according to the second embodiment of the present invention in the 3D mode will be described with reference to FIGS. 5 and 6. FIG.

First, the timing controller 140 addresses the left eye image data RGB _L to the display panel 10 during the 4n-3 (n is a natural number) frame period. Under the control of the timing controller 140, the data driver 120 converts the left eye image data RGB _L into the analog data voltage during the 4n-3 frame period and supplies it to the display panel 10. In addition, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be extinguished during the 4n-3 frame period. The backlight driver turns off the light sources of the backlight unit during the 4n-3 frame period in accordance with the backlight control signal. (S201, S202)

Second, the timing controller 140 supplies the active retarder 30 with the first driving voltage Vd1 (Td1 + Ts1) at a time point earlier than the time point Tb1 by the time Tb1 at the start of the 4n-2 frame period Quot;) < / RTI > When the first driving voltage Vd1 is applied to the active retarder 30, the liquid crystal of the active retarder 30 starts to transition according to the voltage difference between the scan electrodes and the reference electrode. At this time, the liquid crystal of the active retarder 30 reaches the saturation period after the first initial delay time Td1 and the first liquid crystal transition time Ts1 have elapsed. However, when the light sources of the backlight unit are turned on during the first liquid crystal transition time Ts1, since the image of the first polarized light and the image of the second polarized light both enter the polarizing glasses 20, the user feels 3D crosstalk A problem arises.

In order to solve this problem, the second embodiment of the present invention differs from the first embodiment in that the light source of the backlight unit is turned on at a time point (Td1 + Ts1) from the start point of the (4n-2) The first driving voltage Vd1 is applied to the active retarder 30. [ Therefore, since the transition of the liquid crystal of the active retarder 30 is completed at the time when the light sources of the backlight unit are turned on, the user can view the 3D crosstalk-free video. (S203, S204)

Third, black data (Black) is addressed to the display panel 10 during the 4n-2 frame period. Under the control of the timing controller 140, the data driver 120 converts the black data (Black) into analog data voltages during the 4n-2 frame period and supplies them to the display panel 10. (S205, S206)

Fourth, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be turned on at a point of time Tb1 elapses from the start time of the 4n-2 frame period. The backlight driver turns on the light sources of the backlight unit at a point of time Tb1 elapses from the start time of the (4n-2) -th frame period according to the backlight control signal. (S207, S208)

Fifth, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be extinguished by a time Tb2 from the start time of the 4n-1 frame period. The backlight driving unit extinguishes the light sources of the backlight unit at a time point earlier than the starting time point of the (4n-1) frame period by the time period of Tb2 in accordance with the backlight control signal. (S209, S210)

Sixth, the timing controller 140 addresses the right eye image data RGB _R on the display panel 10 during the 4n-1 frame period. Under the control of the timing controller 140, the data driver 120 converts the right eye image data RGB _R into the analog data voltage during the 4n-1 frame period and supplies it to the display panel 10. In addition, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be extinguished during the 4n-1 frame period. The backlight driver turns off the light sources of the backlight unit during the (4n-1) -th frame period in accordance with the backlight control signal. (S211, S212)

The timing controller 140 supplies the second driving voltage Vd2 to the active retarder 30 at a time point earlier than (Td2 + Ts2) after the elapse of the period Tb1 at the start of the 4n-th frame period To generate an active retarder control signal. When the second driving voltage Vd2 is applied to the active retarder 30, the liquid crystal of the active retarder 30 starts to transition according to the voltage difference between the scan electrodes and the reference electrode. At this time, the liquid crystal of the active retarder 30 reaches the saturation period after the second initial delay time Td2 and the second liquid crystal transition time Ts2 have elapsed. However, when the light sources of the backlight unit are turned on during the second liquid crystal transition time Ts2, since the image of the first polarized light and the image of the second polarized light both enter the polarized glasses 20, the user feels 3D crosstalk A problem arises.

In order to solve this problem, the second embodiment of the present invention is characterized in that the light source of the backlight unit is activated (Td2 + Ts2) at a time point earlier than the time point when the light source of the backlight unit is turned on by the period of Tb1 at the start of the 4n- And applies the second driving voltage Vd2 to the retarder 30. [ Therefore, since the transition of the liquid crystal of the active retarder 30 is completed at the time when the light sources of the backlight unit are turned on, the user can view the 3D crosstalk-free video. (S213, S214)

Eighth, black data (Black) is addressed to the display panel 10 during the 4n frame period. Under the control of the timing controller 140, the data driver 120 converts the black data (Black) into analog data voltages during the 4 < n > frame period and supplies them to the display panel 10. (S215, S216)

For the ninth time, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be turned on at the time when the Tb1 period elapses from the start time of the 4n frame period. The backlight driver turns on the light sources of the backlight unit at a point of time Tb1 elapses from the start time of the 4n frame period according to the backlight control signal. (S217, S218)

In the tenth, the timing controller 140 generates a backlight control signal for controlling the light sources of the backlight unit to be extinguished at a time point earlier than the start time point of the (4n + 1) -th frame period by the time period Tb2. The backlight driving unit extinguishes the light sources of the backlight unit at a time point earlier than the starting time point of the (4n + 1) -th frame period by the time period of Tb2 in accordance with the backlight control signal. (S219, S220)

As described above, according to the second embodiment of the present invention, since the transition of the liquid crystal of the active retarder 30 is completed from the point in time when the light sources of the backlight unit are turned on and after the light sources of the backlight unit are turned off, To be completed. As a result, the second embodiment of the present invention can reduce the 3D crosstalk due to the response delay of the liquid crystal of the active retarder 30.

On the other hand, from the first and second embodiments of the present invention, the application time point of the first driving voltage Vd1 and the second driving voltage Vd2 that can minimize the 3D crosstalk can be determined. That is, as in the first embodiment of the present invention, the transition of the liquid crystal of the active retarder 30 is started from the point of time when the light sources of the backlight unit are extinguished, and the light source of the backlight unit When the application time point of the first drive voltage Vd1 and the second drive voltage Vd2 is determined so that the transition of the liquid crystal of the active retarder 30 is completed from the time point of the active retarder 30, Crosstalk can be minimized.

More specifically, referring to FIG. 3 to FIG. 6, it is assumed that (Td1 + Tb2) is longer than the starting point of the (4n-3) The 3D crosstalk due to the liquid crystal response delay of the active retarder 30 can be minimized when the first driving voltage Vd1 is applied to the active retarder 30 during the period of + Ts1. In addition, an active retarder (Td2 + Tb2) is provided between the previous time point (Td2 + Tb2) and the (4n-1) th frame start time point, The third crosstalk caused by the liquid crystal response delay of the active retarder 30 can be minimized.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the present invention should not be limited to the details described in the detailed description, but should be defined by the claims.

10: display panel 10a: upper substrate
10b: lower substrate 11a: upper polarizer plate
11b: lower polarizer plate 20: polarizing glasses
30: active retarder 110: gate driver
120: Data driver 130: Active retarder driver
140: timing controller 150: host system

Claims (4)

A display panel for displaying the left eye image and the right eye image in a time-division manner in the 3D mode;
A backlight unit including light sources for illuminating the display panel;
A first polarized light is emitted when the first driving voltage is applied to the scan electrodes by rotating the liquid crystal by a voltage difference between the scan electrodes and the reference electrode attached to the display panel, An active retarder for emitting light of a second polarized light when a second driving voltage is applied;
A left eye filter for passing only light of the first polarized light and a right eye filter for passing only light of the second polarized light; And
A reference voltage is applied to the reference electrode and the turn-off timing of the light sources of the backlight unit is switched on and off based on the time taken for the liquid crystal to transition so that the rotation of the liquid crystal of the active retarder occurs only during a period in which the light sources are turned off. And an active retarder driving unit for applying the first driving voltage or the second driving voltage to the scan electrodes at a time point before the timing. The method according to claim 1,
The time required for the transition of the liquid crystal after the application of the first driving voltage to the start of the liquid crystal is defined as a first initial delay time based on a time point at which the voltage applied to the scan electrodes is changed from the second driving voltage to the first driving voltage, And a first liquid crystal transition time of a liquid crystal transition according to a voltage difference between a first driving voltage of the scan electrodes and a reference voltage of the reference electrode is referred to as a first liquid crystal transition time,
Wherein the first driving voltage is a first driving voltage,
And is applied between a time point that is earlier than the unlit timing of the light sources of the backlight unit by a first initial delay time and a time point that is earlier than the lighting timing of the light sources of the backlight unit by a first initial delay time and a first liquid crystal transition time Dimensional image display device. The method according to claim 1,
A time period from when the voltage applied to the scan electrodes is changed from the first drive voltage to the second drive voltage to the start of transition of the liquid crystal after the second drive voltage is applied is defined as a second initial delay And a second liquid crystal transition time of a liquid crystal transition according to a voltage difference between a second driving voltage of the scan electrodes and a reference voltage of the reference electrode is referred to as a second liquid crystal transition time,
The second driving voltage may be,
Is applied between a point in time that is earlier by a second initial delay time than an unlit timing of the light sources of the backlight unit and a point in time that is earlier by a second initial delay time than a lighting timing of the light sources of the backlight unit by a second liquid crystal transition time Dimensional image display device. A display panel for displaying the left eye image and the right eye image in a time-division manner in the 3D mode, a backlight unit including light sources for irradiating light to the display panel, and a polarizing plate attached to the display panel, And polarizing glasses that pass only light of the first polarized light through the left eye filter and pass only light of the second polarized light through the right eye filter. In the stereoscopic image display apparatus,
Applying a first driving voltage or a second driving voltage to the scan electrodes of the active retarder and applying a reference voltage to the reference electrode; And
And a second driving voltage is applied to the scan electrodes when the first driving voltage is applied to the scan electrodes by rotating the liquid crystal by the voltage difference between the scan electrodes and the reference electrode, And emits the light of the second polarized light,
Applying a first driving voltage or a second driving voltage to the scan electrodes of the active retarder and applying a reference voltage to the reference electrode,
The first driving voltage is applied to the backlight unit at a time point earlier than the turn-off timing and the lighting timing of the light sources of the backlight unit based on the time taken for the liquid crystal to shift so that the rotation of the liquid crystal of the active retarder occurs only during the period in which the light sources are turned off. Or a second driving voltage is applied to the scan electrodes.

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