Driving method of three-dimensional display device

A three-dimensional display device includes an image display portion for time-sharing a left eye image and a right eye image, and a parallax barrier for separating the left and right eye images provided from the image display portion into a direction of a left eye and a right eye of a user, respectively, by using a first and a second electrode set.A method includes applying a first driving voltage to the first electrode set during a first period, and applying a second driving voltage to the second electrode set during a second period. The second driving voltage has a level different from that of the first driving voltage.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2005-0127720, filed in the Korean Intellectual Property Office, on Dec. 22, 2005, the entire content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a driving method of a three-dimensional display device, and in particular, to a driving method of an autostereoscopic three-dimensional display device using a parallax barrier.

2. Description of the Related Art

A three-dimensional display device may be categorized as a stereoscopic display device where a user wears a viewing aid such as polarizing glasses, or an autostereoscopic display device where the user can see a desired three-dimensional image without wearing such a viewing aid.

A common autostereoscopic display device utilizes an optical separation element such as a lenticular lens, a parallax barrier, or a microlens array, to spatially separate or isolate the left-eye image part and the right-eye image part displayed at an image display unit in the directions of the left and right eyes of the user, respectively.

In particular, the parallax barrier may be formed with a liquid crystal shutter utilizing a transmission type liquid crystal display, and in this case, it may be converted between a two-dimensional mode and a three-dimensional mode. Thus the parallax barrier can be applied to laptop computers or cellular phones.

Generally, the parallax barrier includes stripe-shaped light interception portions and light transmission portions. It selectively separates left and right eye images displayed at the image display unit through the light transmission portions such that the left and right eye images are respectively provided to the left and right eyes of the user.

A common three-dimensional display device having a parallax barrier displays left and right eye images according to left and right image signals inputted to pixels of the image display portion, and it separates the left and right eye images spatially by using the parallax barrier.

However, since the left and right images are entered into the respective eyes of the user, the resolution of a three-dimensional image is no more than half as fine as that of a two-dimensional image.

To solve this problem, a time-sharing type of three-dimensional display device has been developed.

An image display portion of the time-sharing type of three-dimensional display device shows patterns of left and right eye images, and the patterns of the left and right eye images are changed alternately at regular time intervals. Patterns of the light interception portions and the light transmission portions of the parallax barrier are changed alternately at the regular time intervals.

Accordingly, the time-sharing type of three-dimensional display device provides left and right images having patterns that are opposite to each other at certain time intervals to the left and right eyes of the user, respectively.

Consequently, the time-sharing type of three-dimensional display device provides a three-dimensional image having a resolution that is equal (or substantially equal) to that of a two-dimensional image.

The parallax barrier of the time-sharing type of three-dimensional display device may be formed with a liquid crystal shutter utilizing a transmission type of liquid crystal display, and the liquid crystal display may include first electrodes and second electrodes formed in a striped pattern and arranged alternately and repeatedly relative to each other.

Light transmittance rates for portions of the parallax barrier corresponding to each of the electrodes should be substantially uniform to enable the user to see images having a regular (or uniform) brightness during operation of the time-sharing type of three-dimensional display device.

However, it is difficult for the time-sharing type of three-dimensional display device to maintain a uniform light transmittance rate due to differences in lengths of electrode paths along which applied voltages are conducted.

SUMMARY OF THE INVENTION

It is an aspect of the present invention to provide a driving method for a time-sharing type of three-dimensional display device that can maintain the same (or a uniform) light transmittance rate at portions of a parallax barrier of the display device corresponding to electrodes of the display device during operation of the device.

In exemplary embodiments according to the present invention, a driving method of a three-dimensional display device with one or more of the following features is provided.

A three-dimensional display device includes an image display portion adapted to time-share an image to display a left eye image and a right eye image, and a parallax barrier for receiving the left eye image and the right eye image from the image display portion and for directing the left eye image and the right eye image towards a left eye and a right eye of a user, respectively, by operating a first electrode set and a second electrode set of the parallax barrier.

A driving method includes applying a first driving voltage to the first electrode set during a first period, the first driving voltage having a first level, and applying a second driving voltage to the second electrode set during a second period, the second driving voltage having a second level, wherein the second level is different from the first level.

The parallax barrier may include a first substrate on which the first electrode set and the second electrode set are arranged, a second substrate facing the first substrate, a common electrode located on the second substrate, and a liquid crystal layer located between the first substrate and the second substrate.

The first electrode set may include a plurality of first electrodes, a first connection electrode for electrically connecting the first electrodes, a first terminal electrode connected at an end of the first connection electrode, and a first connection terminal connected to an end of the first terminal electrode and adapted to receive the first driving voltage.

The second electrode set may include a plurality of second electrodes, a second connection electrode for electrically connecting the second electrodes, and a second connection terminal connected to an end of the second connection electrode and adapted to receive the second driving voltage.

The applying the first driving voltage to the first electrode set may include applying the first driving voltage at the first connection terminal, and the applying the second driving voltage to the second electrode set may include applying the second driving voltage at the second connection terminal.

The first level may be set higher than the second level.

The first level may be set to have a range from about 1.5 to 2 times the second level.

The driving method may include displaying on the image display portion, during the first period, a first image including the left and right eye images formed in a first pattern, and displaying on the image display portion, during the second period, a second image including the left and right eye images formed in a second pattern, wherein the second pattern is opposite to the first pattern.

The driving method may include forming first pixel columns and second pixel columns respectively corresponding to the first electrodes and the second electrodes. The displaying the first image may include displaying the left eye image of the first image on the first pixel columns and displaying the right eye image of the first image on the second pixel columns. The displaying the second image may include displaying the right eye image of the second image on the first pixel columns and displaying the left eye image of the second image on the second pixel columns.

A three-dimensional display device may include an image display portion capable of being oriented in a first mode to provide a portrait-type view and in a second mode to provide a landscape-type view and is adapted to time-share an image to display a left eye image and a right eye image in a time-shared manner. The three-dimensional display device may also include a parallax barrier having a first electrode set and a second electrode set arranged to extend along a first direction and further having a third electrode set and a fourth electrode set arranged to extend along a second direction perpendicular to the first direction.

The parallax barrier may be adapted to receive the left eye image and the right eye image from the image display portion and to direct the left eye image and the right eye image towards a left eye and a right eye of a user, respectively.

A driving method may include, in the first mode, applying a first driving voltage to the first electrode set during a first period, the first driving voltage having a first level, and applying a second driving voltage to the second electrode set during a second period, the second driving voltage having a second level different from the first level. The driving method may also include, in the second mode, applying a third driving voltage to the third electrode set during the first period, the third driving voltage having a third level, and applying a fourth driving voltage to the fourth electrode set during the second period, the fourth driving voltage having a fourth level different from the third level.

The parallax barrier may include a first substrate on which the first electrode set and the second electrode set are arranged, a second substrate on which the third electrode set and the fourth electrode set are arranged, the second substrate facing the first substrate, and a liquid crystal layer located between the first substrate and the second substrate.

The first electrode set may include a plurality of first electrodes, a first connection electrode for electrically connecting the first electrodes, a first terminal electrode connected at an end of the first connection electrode, and a first connection terminal connected to an end of the first terminal electrode and adapted to receive the first driving voltage.

The second electrode set may include a plurality of second electrodes, a second connection electrode for electrically connecting the second electrodes, and a second connection terminal connected to an end of the second connection electrode and adapted to receive the second driving voltage.

The third electrode set may include a plurality of third electrodes, a third connection electrode for electrically connecting the third electrodes, and a third connection terminal connected to an end of the third connection electrode and adapted to receive the third driving voltage.

The fourth electrode set may include a plurality of fourth electrodes, a fourth connection electrode for electrically connecting the fourth electrodes, a fourth terminal electrode connected to an end of the fourth connection electrode, and a fourth connection terminal connected to an end of the fourth terminal electrode and adapted to receive the fourth driving voltage.

In the first mode, the applying the first driving voltage to the first electrode set during the first period may include applying the first driving voltage at the first connection terminal, and the applying the second driving voltage to the second electrode set may include applying the second driving voltage at the second connection terminal during the second period. In the second mode, the applying the third driving voltage to the third electrode set may include applying the third driving voltage at the third connection terminal, and the applying the fourth driving voltage to the fourth electrode set may include applying the fourth driving voltage at the fourth connection terminal.

In the first mode, the first level may be set higher than the second level, and, in the second mode, the fourth level may be set higher than the third level.

By way of example, the first level may be set to have a range from about 1.5 to 2 times the second level, and the fourth level may be set to have a range from about 1.5 to 2 times the third level.

The driving method may include, in the first mode, displaying on the image display portion, during the first period, a first image including the left and right eye images formed in a first pattern and displaying on the image display portion, during the second period, a second image including the left and right eye images formed in a second pattern, wherein the second pattern is opposite to the first pattern. The driving method may also include, in the second mode, displaying on the image display portion, during the first period, a third image including the left and right eye images formed in a third pattern and displaying on the image display portion, during the second period, a fourth image including the left and right eye images formed in a fourth pattern, wherein the fourth pattern is opposite to the third pattern.

The driving method may include, in the first mode, forming first pixel columns and second pixel columns respectively corresponding to the first electrodes and the second electrodes. The displaying the first image during the first period may include displaying the left eye image of the first image on the first pixel columns and displaying the right eye image of the first image on the second pixel columns. The displaying the second image during the second period may include displaying the right eye image of the second image on the first pixel columns and displaying the left eye image of the second image on the second pixel columns. The driving method may also include, in the second mode, forming first pixel rows and second pixel rows respectively corresponding to the third electrodes and the fourth electrodes. The displaying the third image during the first period may include displaying the left eye image of the third image on the first pixel rows and displaying the right eye image of the third image on the second pixel rows. The displaying the fourth image during the second period may include displaying the right eye image of the fourth image on the first pixel rows and displaying the left eye image of the fourth image on the second pixel rows.

According to the driving method of the present invention, degradation of the quality of a three-dimensional image due to differences in lengths of electrode paths along which applied voltages are conducted can be prevented in a time-sharing type of three-dimensional display device.

DETAILED DESCRIPTION

The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which certain exemplary embodiments of the present invention are shown.

FIG. 1is a sectional view of a three-dimensional display device operated by a driving method according to a first exemplary embodiment of the present invention.

As shown inFIG. 1, the three-dimensional display device includes an image display portion100and a parallax barrier200facing the image display portion100.

The image display portion100displays a left eye image and a right eye image that have certain or predetermined patterns. First and second images that have different patterns of the left and right eye images relative to each other are repeatedly displayed at a frequency, which may be predetermined.

Any suitable display device may be used as the image display portion100. For instance, the image display portion100may be formed with a cathode ray tube, a liquid crystal display, a plasma display panel, a field emission display device, an organic electroluminescence display device, or any other suitable display device.

The parallax barrier200may be formed with a liquid crystal shutter. The parallax barrier200includes a first substrate10and a second substrate12facing each other. Electrodes for driving a liquid crystal layer22disposed between the first and second substrates10and12are formed (or arranged) on or at respective inner surfaces of the first and second substrates.

The first and second substrates10and12may be formed of rectangular glass.

First electrodes14and second electrodes16are formed on the first substrate10, and a common electrode18is formed on the second substrate12. The common electrode18may be formed as a single-body electrode.

The electrodes14,16, and18may be formed with a transparent material, such as Indium Tin Oxide (ITO), and a pair of polarizing plates24aand24bare formed on (or at) respective outer surfaces of the first and second substrates10and12, respectively.

A pair of alignment layers20aand20b, covering the electrodes14,16, and18, are formed on the first and second substrates10and12, respectively.

Structures of the electrodes formed on the first substrate10will be described more fully hereinafter in more detail.

FIG. 2shows a structure of a first electrode set140and a second electrode set160formed on the first substrate10.

As shown inFIG. 2, the first electrode set140includes a plurality of the first electrodes14formed to extend along a direction corresponding to a longer side of the first substrate10(the direction of the Y-axis inFIG. 2), a first connection electrode14aelectrically connecting the first electrodes14, a first terminal electrode14bformed to extend along a direction parallel to the first electrodes14on an end of the first connection electrode14a, and a first connection terminal14cformed on an end of the first terminal electrode14b.

The first electrodes14are arranged in a striped pattern with certain or predetermined distances therebetween on the first substrate10.

The second electrode set160includes a plurality of the second electrodes16arranged to extend along a direction corresponding to the longer side of the first substrate10, a second connection electrode16aelectrically connecting the second electrodes16, and a second connection terminal16clocated on an end of the second connection electrode16a.

Each of the second electrodes16are arranged between the first electrodes14along the direction corresponding to the longer side of the first substrate10in a striped pattern.

Pixel arrays and an operation of the image display portion will be described hereinafter in more detail.FIGS. 3A and 3Bshow the pixel arrays of the image display portion in the first exemplary embodiment of the present invention during a first period t1and a second period t2, respectively.

First pixel columns30and second pixel columns32, including sub pixels arranged along a vertical direction of the image display portion100(the direction of the Y-axis inFIGS. 3A and 3B), are arranged alternately and repeatedly along a horizontal direction of the image display portion100(the direction of the X-axis inFIGS. 3A and 3B).

As shown inFIG. 3A, during the first period t1, the first pixel columns30display left eye images LR, LG, and LBcorresponding to a left eye image signal, and the second pixel columns32display right eye images RR, RG, and RBcorresponding to a right eye image signal.

In this way, a first image is displayed on the image display portion during the first period t1.

Referring back toFIG. 2, in the first period t1, a driving voltage is applied to the first electrodes14at the first connection terminal14cthrough the first terminal electrode14band the first connection electrode14a.

A reference voltage, which by way of example may be a ground voltage, is applied to the second electrodes16at the second connection terminal16cthrough the second connection electrode16a. The reference voltage is also applied to the common electrode18.

Accordingly, when the parallax barrier is a liquid crystal display of a normally white mode of transmission, portions of the barrier on which the first electrodes14are located become light interception portions, and portions of the barrier on which the second electrodes16are located become light transmission portions.

In contrast, when the parallax barrier is a liquid crystal display of a normally black mode of transmission, portions of the barrier on which the first electrodes14are located become light transmission portions, and portions of the barrier on which the second electrodes16are located become light interception portions.

As shown inFIG. 3B, during the second period t2, the first pixel columns30display right eye images RR, RG, and RBcorresponding to a right eye image signal, and the second pixel columns32display the left eye images LR, LG, and LBcorresponding to a left eye image signal.

In this way, a second image is displayed on the image display portion during the second period t2. As shown inFIGS. 3A and 3B, the pattern of the first image displayed during the first period t1is opposite to the pattern of the second image displayed during the second period t2.

Referring back toFIG. 2, in the second period t2, the reference voltage is applied to the first electrodes14at the first connection terminal14cthrough the first terminal electrode14band the first connection electrode14a.

The driving voltage is applied to the second electrodes16at the second connection terminal16cthrough the second connection electrode16a. The reference voltage is also applied to the common electrode18.

Accordingly, when the parallax barrier is a liquid crystal display of a normally white mode of transmission, portions of the barrier on which the second electrodes16are located become light interception portions, and portions of the barrier on which the first electrodes14are located become light transmission portions.

In contrast, when the parallax barrier is a liquid crystal display of a normally black mode of transmission, portions of the barrier on which the second electrodes16are located become light transmission portions, and portions of the barrier on which the first electrodes14are located become light interception portions.

According to the operation of the three-dimensional display device as described above, the left eye of a user sees the image displayed by the first pixel columns30during the first period t1and the image displayed by the second pixel columns32during the second period t2.

In contrast, the right eye of the user sees the image displayed by the second pixel columns32during the first period t1and sees the image displayed by the first pixel columns30during the second period t2.

Accordingly, the user can see a three-dimensional image having a resolution that is as fine as (or substantially as fine as) a resolution of a two-dimensional image.

The light interception portions formed during the first period t1and the light interception portions formed during the second period t2should be characterized by light transmittance rates that are equal (or substantially equal) to each other in order to provide three-dimensional images to the user that are natural in appearance.

Similarly, the light transmission portions formed during the first period t1and the light transmission portions formed during the second period t2should be characterized by light transmittance rates that are equal (or substantially equal) to each other.

Therefore, the level of a voltage effectively applied to the first electrodes14during the first period t1and the level of a voltage effectively applied to the second electrodes16during the second period t2should be substantially equal to each other.

However, as shown inFIG. 2, paths from the first and second connection terminals14cand16cto the first and second electrodes14and16, respectively, are different in length from each other.

That is, when voltages of a uniform (or equal) level are applied at the first and second connection terminals14cand16c, a voltage drop due to the electrical resistance of the first terminal electrode14bresults, and therefore the voltage effectively applied to the first electrodes14is substantially lower than that effectively applied to the second electrodes16.

Accordingly, in the first exemplary embodiment of the present invention, voltages having levels that are different from each other are applied at the first and second connection terminals14cand16c. This will be described hereinafter in more detail.

FIG. 4is a graph showing voltages applied to the first and second connection terminals during an operation of the parallax barrier.

In a manner substantially similar to that described above, during the first period t1, a first driving voltage V1is applied at the first connection terminal14c, and a reference voltage is applied at the second connection terminal16c.

Then, during the second period t2, the reference voltage is applied to the first connection terminal14c, and a second driving voltage V2is applied to the second connection terminal16c.

In this case, the first driving voltage V1is set to be higher than the second driving voltage V2to compensate for the resulting voltage drop.

However, when the first driving voltage V1is less than 1.5 times as high as the second driving voltage V2, it may be difficult to reduce a corresponding difference in brightness due to the resulting voltage drop.

Also, when the first driving voltage V1is more than twice as high as the second driving voltage V2, too large of a voltage may be effectively applied to the first electrodes14, and therefore a brightness corresponding to the first electrodes14may be stronger than a brightness corresponding to the second electrodes16even given the resulting voltage drop over the first terminal electrode14b.

Thus, to maintain a more consistent level of brightness, in one embodiment of the invention, the first driving voltage V1applied at the first connection terminal14cis set to have a range from about 1.5 to 2 times the second driving voltage V2applied at the second connection terminal16c.

However, the scope of the present invention is not limited to the range of voltage ratios specified in the first exemplary embodiment. Rather, the value of the voltage ratio can be changed according to a corresponding structure or structures of electrodes and/or corresponding driving conditions in a given embodiment.

According to the driving method of the first exemplary embodiment, since the difference between the voltages effectively applied to the first and second electrodes14and16resulting from the voltage drop over the electrical resistance of the first terminal electrode14bmay be reduced, the difference in transmission brightness levels produced by the parallax barrier can be reduced.

Table 1 andFIG. 5show results of experiments that indicate effectiveness of the driving method of the first exemplary embodiment.

A normally white mode liquid crystal display was made, and transmission brightness according to various voltages applied to each of the electrodes was measured.

Referring to Table 1 andFIG. 5, when voltages of uniform (or equal) levels were applied at the first and second connection terminals, a transmission brightness corresponding to the first electrode was higher than a transmission brightness corresponding to the second electrode.

That is, since a lower voltage was effectively applied to the first electrode than to the second electrode because of a resulting voltage drop, a light transmission rate corresponding to the first electrode was lower than that corresponding to the second electrode, and accordingly a transmission brightness corresponding to the first electrode was higher compared to that corresponding to the second electrode.

However, when a voltage of 5V was applied at the second connection terminal and a voltage of 8.5V was applied at the first connection terminal, levels of transmission brightness corresponding to the first electrode and the second electrode were substantially equal to each other.

FIG. 6is a sectional view showing a three-dimensional display device operated by a driving method according to a second exemplary embodiment of the present invention.

The three-dimensional display device of the second exemplary embodiment can be oriented in either of a first mode providing a portrait-type view and a second mode providing a landscape-type view according to a selection by the user to rotate the image display portion together with the parallax barrier.

As shown inFIG. 6, the three-dimensional display device includes an image display portion300and a parallax barrier400facing the image display portion300.

The parallax barrier400includes a first substrate40and a second substrate42facing each other.

In order to drive a liquid crystal layer52located between the first and second substrates40and42, first electrodes44and second electrodes46are formed (or arranged) on the first substrate10, and third electrodes48and fourth electrodes are formed on the second substrate42.

Since the elements of the three-dimensional display device of the second embodiment, except for the electrodes formed on the second substrate42, are substantially similar to corresponding elements of the first exemplary embodiment described above, only the structures of the electrodes formed on the second substrate42will be described more fully hereinafter.

FIGS. 7A and 7Bshow a third electrode set480and a fourth electrode set490formed on the second substrate42.FIG. 7Ashows the third and fourth electrode sets as operated in the first mode providing a portrait-type view, andFIG. 7Bshows the third and fourth electrode sets as operated in the second mode providing a landscape-type view.

The third electrode set480includes a plurality of the third electrodes48formed to extend along a direction corresponding to a shorter side of the second substrate42(the direction of the X-axis inFIG. 7A), a third connection electrode48aelectrically connecting the third electrodes48, and a third connection terminal48cformed on an end of the third connection electrode48a.

The third electrodes48are arranged in a striped pattern with predetermined distances therebetween.

The fourth electrode set490includes a plurality of the fourth electrodes49arranged to extend along a direction corresponding to the shorter side of the second substrate42, a fourth connection electrode49aelectrically connecting the fourth electrodes49, a fourth terminal electrode49bformed to extend along a direction parallel to the fourth electrodes49on an end of the fourth connection electrode49a, and a fourth connection terminal49clocated on an end of the fourth terminal electrode49b.

The fourth electrodes49are arranged between the third electrodes48in a striped pattern on the second substrate42.

Pixel arrays and an operation of the image display portion will be described hereinafter in more detail. As described above, the three-dimensional display device according to the second exemplary embodiment of the present invention can be operated in either of the first mode and the second mode.

Since the pixel arrays and the operation of the image display portion in the first mode are substantially similar to those described above with respect to the first exemplary embodiment, only the pixel arrays and the operation of the image display portion in the second mode will be described hereinafter in more detail.

FIG. 8AandFIG. 8Bshow the pixel arrays of the image display portion in the second mode during a first period t1and a second period t2, respectively.

First pixel rows60and second pixel rows62, including sub pixels arranged along a vertical direction of the image display portion300(the direction of the Y-axis inFIG. 8A), are arranged alternately and repeatedly along a horizontal direction of the image display portion300(the direction of the X-axis inFIGS. 8A and 8B).

As shown inFIG. 8A, during the first period t1, the first pixel rows60display left eye images LR, LG, and LBcorresponding to a left eye image signal, and the second pixel rows62display right eye images RR, RG, and RBcorresponding to a right eye image signal.

A third image is displayed on the image display portion during the first period t1in this way.

Referring back toFIG. 7B, in the first period t1, a driving voltage is applied to the third electrodes48at the third connection terminal48cthrough the third connection electrode48a.

A reference voltage is applied to the fourth electrodes49at the fourth connection terminal49cthrough the fourth terminal electrode49band the fourth connection electrode49a.

In the second mode, a reference voltage is applied to the first and second electrodes formed on the first substrate (seeFIG. 6, for example) such that the first and second electrodes serve as a common, single-body electrode substantially similar to the common electrode18in the first exemplary embodiment.

Accordingly, when the parallax barrier is a liquid crystal display of a normally white mode of transmission, portions of the barrier on which the third electrodes48are located become light interception portions, and portions of the barrier on which the fourth electrodes49are located become light transmission portions.

In contrast, when the parallax barrier is a liquid crystal display of a normally black mode of transmission, portions of the barrier on which the third electrodes48are located become light transmission portions, and portions of the barrier on which the fourth electrodes49are located become light interception portions.

As shown inFIG. 8B, during the second period t2, the first pixel rows60display right eye images RR, RG, and RBcorresponding to a right eye image signal, and the second pixel rows62display left eye images LR, LG, and LBcorresponding to a left eye image signal.

A fourth image is displayed on the image display portion during the second period t2in this way. The pattern of the third image displayed during the first period t1is opposite to the pattern of the fourth image displayed during the second period t2.

Referring back toFIG. 7B, in the first period t2, the reference voltage is applied to the third electrodes48at the third connection terminal48cthrough the third connection electrode48a.

The driving voltage is applied to the fourth electrodes49at the fourth connection terminal49cthrough the fourth terminal electrode49band the fourth connection electrode49a.

Similar to the situation of the first period t1, the reference voltage is applied to both the first and second electrodes formed on the first substrate such that the first and second electrodes serve as a common, single-body electrode.

Thus, when the parallax barrier is a liquid crystal display of a normally white mode of transmission, portions of the barrier on which the fourth electrodes49are located serve as light interception portions, and portions of the barrier on which the third electrodes48are located serve as light transmission portions.

In contrast, when the parallax barrier is a liquid crystal display of a normally black mode of transmission, portions of the barrier on which the fourth electrodes49are located serve as light transmission portions, and portions of the barrier on which the third electrodes48are located serve as light interception portions.

According to the described-above operation of the three-dimensional display device, the left eye of a user sees the image displayed by the first pixel rows60during the first period t1and sees the image displayed by the second pixel rows62during the second period t2.

The right eye of the user sees the image displayed by the second pixel rows62during the first period t1and sees the image displayed by the first pixel rows60during the second period t2.

Accordingly, the user can see a three-dimensional image having a resolution that is as fine as a resolution of a two-dimensional image.

The light interception portions formed during the first period t1and the light interception portions formed during the second period t2should be characterized by light transmittance rates that are substantially equal to each other in order to provide three-dimensional images to the user that are natural in appearance.

Similarly, the light transmission portions formed during the first period t1and the light transmission portions formed during the second period t2should be characterized by light transmittance rates that are substantially equal to each other.

Therefore, the level of a voltage effectively applied to the third electrodes48during the first period t1and the level of a voltage effectively applied to the fourth electrodes49during the second period t2should be substantially equal to each other.

However, as shown inFIGS. 7A and 7B, paths from the third and fourth connection terminals48cand49cto each of the third and fourth electrodes48and49, respectively, are different in length from each other.

That is, when voltages of a uniform level are applied at the third and fourth connection terminals48cand49c, a voltage drop due to the electrical resistance of the fourth terminal electrode49bresults, and therefore the voltage effectively applied to the fourth electrodes49is substantially lower than that effectively applied to the third electrodes48.

Accordingly, in the second exemplary embodiment of the present invention, voltages having levels that are different from each other are applied at the third and fourth connection terminals48cand49c. This will be described hereinafter in more detail.

FIG. 9is a graph showing voltages applied to the third and fourth connection terminals respectively during an operation of the parallax barrier.

As described above, during the first period t1, a third driving voltage V3is applied at the third connection terminal48c, and a reference voltage is applied at the fourth connection terminal49c.

Then, during the second period t2, the reference voltage is applied at the third connection terminal48c, and a fourth driving voltage V4is applied at the fourth connection terminal49c.

In this case, the fourth driving voltage V4is set to be higher than the third driving voltage V3to compensate for the resulting voltage drop.

However, when the fourth driving voltage V4is less than 1.5 times as high as the third driving voltage V3, it may be difficult to reduce the difference of brightness due to the resulting voltage drop.

When the fourth driving voltage V4is more than twice as high as the third driving voltage V3, too large of a voltage may be effectively applied to the fourth electrodes49, even given the resulting voltage drop over the fourth terminal electrode49b, and a brightness corresponding to the fourth electrodes49may be stronger than a brightness corresponding to the third electrodes48.

Thus, to maintain a more consistent level of brightness, the fourth driving voltage V4that is applied at the fourth connection terminal49cmay be set to have a range from about 1.5 to 2 times the third driving voltage V3that is applied at the third connection terminal48c.

However, the scope of the present invention is not limited to the range of voltage ratios specified above. Rather, the value of the voltage ratio can be changed according to a corresponding structure or structures of electrodes and/or corresponding driving conditions in a given embodiment.

According to the driving method of the second exemplary embodiment, since the difference between the voltages effectively applied to the third and fourth electrodes48and49resulting from the voltage drop over the electrical resistance of the fourth terminal electrode49bmay be reduced, the difference in transmission brightness levels produced by the parallax barrier can be reduced.