Among those conventional goggle-free 3D image displaying techniques capable of 2D/3D image switching and dual-directional displaying of 3D images, there are two that are similarly designed to achieve the above mentioned 3D functions basically by applying a vertical strip parallax barrier and a Liquid Crystal device, referring as LC device hereinafter, with double-layered ITO electrode layer upon a display screen having R, G, and B sub-pixels in a strip configuration, and one of which is a method disclosed in U.S. Pat. No. 7,453,529 B2 by Samsung Electronics Co., Ltd., referring as the Samsung Patent hereinafter, and the other is a method disclosed in U.S. Pub. No. 2008/0231767A1 by Masterimage 3D Inc., referring as the Masterimage Patent hereinafter. Generally, the 2D/3D image switching is achieved by transparentizing the LC device through the control of external driving voltage for enabling a 2D image displaying. In addition, the 3D image displaying in the Landscape and Portrait displaying mode of the display screen can also be performed by enabling the LC device to have different parallax barrier structures through the control of external driving voltage, and thereby, achieving the dual-directional displaying of 3D images. However, a wrong design of the electrode structure resulting a problem of light leakage in the shield elements of parallax barrier can generally cause severe cross-talk phenomenon, further, due to the design faults in parallax barrier, the 3D image displaying in Portrait mode can generally suffered by sever color distortion.
The following description relates to the construction of the aforesaid LC device as well as its functions and shortcomings Please refer to FIG. 1 and FIG. 2, which are schematic diagrams showing a display screen in a Landscape displaying mode and a Portrait displaying mode. As shown in FIG. 1 and FIG. 2, a Cartesian coordinate system of XYZ-axes is defined for a display screen in a manner that the long side of the display screen is arranged parallel to the X axis and the short side of the display screen is arranged parallel to the Y-axis, whereas such arrangement is fixed and will not change with the rotation of the display screen. Thereby, for a viewer watching the display screen, the Landscape displaying mode is that the long side of the display screen is arranged horizontally while the sort side thereof is arranged vertical to the viewer, and thus the RGD sub-pixels are vertically arranged for the viewer, and on the other hand, the Portrait displaying mode is that the long side of the display screen is arranged vertically while the sort side thereof is arranged horizontal to the viewer, and thus the RGD sub-pixels are horizontally arranged for the viewer. It is noted that for the display screen having the aforesaid RGB sub-pixel arrangement, it is generally referred as a display screen with strip configuration which is the mainstream product on the market. Other than that there are display screens of Delta configuration, Mosaic configuration, Pentile configuration, and so on.
Please refer to FIG. 3, which is a schematic diagram showing a parallax barrier used in the aforesaid Samsung Patent and Materimage Patent. It is noted that the LC devices used respectively in these two patents are structurally the same and using two ITO electrode layers to compose the structure of parallax barrier electrodes.
As shown in FIG. 3, the LC (Liquid Crystal) parallax barrier 10 used is about the same size as the display screen 1 and is orientated in the same way as the display screen 1. Moreover, such LC parallax barrier 10 is primarily composed of two linear polarizers 11, two transparent substrates 12, an upper electrode layer 13, a lower electrode layer 16, two alignment layers 14, a liquid crystal layer 15, in which the liquid crystal used in the liquid crystal layer 15 is a TN-type liquid crystal, the polarization directions of the two polarizers 11 are perpendicular to each other, and both the upper and the lower electrode layers 13, 16 are made of a transparent ITO conductive film with barrier electrodes of specially designed shapes. Thereby, when the external driving voltage V is zero, the LC parallax barrier 10 is transparentized for displaying 2D images.
Please refer to FIG. 4, which is a schematic diagram showing a barrier electrode disclosed in the Samsung Patent. As shown in FIG. 4, the parallax barrier by Samsung is primarily composed of an upper ITO layer 13 and a lower ITO layer 16, whereas each of the two ITO layers 13, 16 is formed with two comb-shaped electrodes 13a, 13b, 16a, 16b that are alternatively disposed with respect to one another, as each of the four comb-shaped electrodes 13a, 13b, 16a, 16b is composed of a plurality of strip electrodes which are electrically connected. In addition, the comb-shaped electrodes 13a, 13b of the upper ITO layer 13 are arranged parallel to the Y axis while the comb-shaped electrodes 16a, 16b of the lower ITO layer 16 are arranged parallel to the X axis. Thus, the disposing orientation of the upper and lower comb-shaped electrodes are perpendicular to each other. Comparing with those conventional vertical strip parallax barriers, slantwise strip parallax barriers and slant-and-step parallax barriers, the structure of parallax barriers composed of comb-shaped electrodes is exactly the same as the structure of vertical strip parallax barriers.
Please refer to FIG. 5, which is a schematic diagram showing the electrical characteristics of the comb-shaped electrode of Samsung Patent while being applied in Landscape displaying mode. In the Landscape displaying mode, a driving voltage V is applied to one of the comb-shaped electrode 13a on the upper ITO layer 13 while the two comb-shaped electrodes 16a, 16b on the lower ITO layer 16 are grounded simultaneously. Thereby, the two comb-shaped electrodes 16a, 16b are used to constructed a common ground electrode, while the comb-shaped electrode 13a is used as a vertical strip parallax barrier for blocking and shielding the transmission of light.
Please refer to FIG. 6, which is a schematic diagram showing the electrical characteristics of the comb-shaped electrode of Samsung Patent while being applied in Portrait displaying mode. In the Portrait displaying mode, a driving voltage V is applied to one of the comb-shaped electrode 16a on the lower ITO layer 16 while the two comb-shaped electrodes 13a, 13b on the upper ITO layer 13 are grounded simultaneously. Thereby, the two comb-shaped electrodes 13a, 13b are used to constructed a common ground electrode, while the comb-shaped electrode 16a is used as a vertical strip parallax barrier for blocking and shielding the transmission of light.
Nevertheless, the parallax barrier of the Samsung Patent can not avoid the problem of light leakage. Please refer to FIG. 7, which is a schematic diagram showing a light leakage phenomenon caused by the parallax barrier of the Samsung Patent while being applied in Landscape displaying mode. While being activated electrically in a way shown in FIG. 5, the gaps 17 in the common ground electrode that is composed of the two comb-shaped electrodes 16a, 16b are not grounded, thus there is no proper electrical field being exerted upon the liquid crystals at positions corresponding to those gaps 17 for enabling they to perform the function of light blocking and shielding, causing an undesirable light leakage phenomenon to happen. Thereby, a severe cross-talk effect is resulted for deteriorating 3D performance.
At the same time, the parallax barrier of the Samsung Patent also can not avoid the problem of light leakage while being applied in Portrait displaying mode. Please refer to FIG. 8, which is a schematic diagram showing a light leakage phenomenon caused by the parallax barrier of the Samsung Patent while being applied in Portrait displaying mode. While being activated electrically in a way shown in FIG. 6, the gaps 18 in the common ground electrode that is composed of the two comb-shaped electrodes 13a, 13b are not grounded, thus there is no proper electrical field being exerted upon the liquid crystals at positions corresponding to those gaps 18 for enabling they to perform the function of light blocking and shielding, causing an undesirable light leakage phenomenon to happen. Thereby, a severe cross-talk effect is resulted for deteriorating 3D performance.
Moreover, the parallax barrier of the Samsung Patent also can not avoid the problem of color distortion while being applied in Portrait displaying mode. Please refer to FIG. 9 and FIG. 10, which are schematic diagram showing the relative relationship between a 2-view combined image and a parallax barrier of the Samsung Patent in Portrait displaying mode. As shown in FIG. 9 and FIG. 10, when a display screen 1 is positioned in a portrait manner, its RGB arrangement will become a horizontal arrangement, while the structure design of parallax barrier adopted by the Samsung Patent allows the opening width for each opening element 16c in this parallax barrier to be corresponded to one view unit composed of three RGB sub-pixels in the left view L and also allows the shielding width for each shield element 16a, i.e. the comb-shaped electrodes 16a, to be corresponded to one view unit composed of three RGB sub-pixels in the right view R. Consequently, the phenomenon of color distortion occurs that deteriorates the 3D performance severely when changing of viewing position.
Please refer to FIG. 11 to FIG. 13, which are schematic diagrams showing the relationship between color distortion phenomenon and the changing of viewing positions. Hereinafter, 3D perception of left eye is exemplified to illustrate the mechanism of color distortion phenomenon. As shown in FIG. 11, while the left eye 2 of a viewer is located exactly at an optimum viewing point OVP(L), only a left image L can be viewed clearly by the left eye 2 through all the opening elements 16c of the parallax barrier. However, as shown in FIG. 12, when the left eye 2 of the viewer is moved slightly to the left away from the OVP(L), through the same opening elements 16c the left eye can perceive light from a R-sub-pixel of a right image R in addition to the left image L, resulting the perceived 3D image to become reddish. On the other hand, as shown in FIG. 13, when the left eye 2 of the viewer is moved slightly to the right away from the OVP(L), through the same opening elements 16c the left eye can perceive light from a B-sub-pixel of a right image R in addition to the left image L, resulting the perceived 3D image to become bluish.
Please refer to FIG. 14, which is a schematic diagram showing a barrier electrode disclosed in the Masterimage Patent. As shown in FIG. 14, the parallax barrier provided by Masterimage is primarily composed of an upper electrode layer 13, having a plurality of cell-type electrodes formed thereon; and a lower electrode layer 16, not being illustrated in FIG. 14, designed to be used as a common ground electrode. Thus, a strip parallax barrier can be achieved with respect to the X axis and the Y axis by the connection of a matrix circuit and a driving voltage.
Please refer to FIG. 15, which is a schematic diagram showing the electrical characteristics of the cell-type electrodes of Masterimage Patent while being applied in Landscape displaying mode. In Landscape displaying mode, a driving voltage V is applied to the upper electrode layer 13 where all the cell-type electrodes arranged on even-number columns, i.e. c0, c2, c4, and c6, are electrically connected, so as to construct a vertical strip parallax barrier for blocking and shielding the transmission of light.
Please refer to FIG. 16, which is a schematic diagram showing the electrical characteristics of the cell-type electrodes of Masterimage Patent while being applied in Portrait displaying mode. In Landscape displaying, a driving voltage V is applied to the upper electrode layer 13 where all the cell-type electrodes arranged on even-number rows, i.e. r0, r2, and r4, are electrically connected, so as to construct a horizontal strip parallax barrier for blocking and shielding the transmission of light.
Nevertheless, the parallax barrier of the Masterimage Patent can not avoid the problem of light leakage. Please refer to FIG. 17, which is a schematic diagram showing a light leakage phenomenon caused by the parallax bather of the Masterimage Patent. Although strip-like barriers c0, c2, c4, c6, r0, r2, and r4 can be achieved through electrical connection, there are still gaps existed between the cell-type electrodes since the strip-like barriers is achieved by a number of serially connected cell-type electrodes. That is, no matter it is displayed in 3D portrait mode or in 3D landscape mode, there are always gaps existed respectively between any two neighboring cells, referring as barrier electrode gap. Thus, liquid crystals that are disposed in those gaps can not be driven by applied voltage for performing the preferred shielding effect, causing an undesirable light leakage phenomenon to happen in a manner similar to the Samsung Patent. Thereby, a severe cross-talk caused by the light leakage phenomenon deteriorates 3D performance. Please refer to FIG. 17 where two pictures of an activated Materimage barrier are illustrated. In FIG. 17, there are a plurality of short white lines that are clearly visible in the pictures no matter the barrier is being applied in Landscape displaying mode or in Portrait displaying mode.
Moreover, the parallax barrier of the Masterimage Patent also can not avoid the problem of color distortion. While being applied in Portrait displaying mode, the parallax barrier of the Masterimage Patent can performed similarly to the parallax barrier of the Samsung Patent with respect to the relative relationship between its structure and the 3D combined image, as shown in FIG. 9. Therefore, no further description for the parallax barrier of the Masterimage Patent relating to color distortion is provided herein.
To sum up, both the parallax barriers in the Samsung and Masterimage Patents are constructed using two strip barriers that are arranged perpendicular to each other and respectively disposed on two ITO layers in a LC device, i.e. a LC device of double ITO electrode layer, while enabling a display screen to provide 2D/3D image switching and dual-directional 3D image displaying. However, due to the faulty design in its barrier electrode, the unavoidable light leakage through the designed shielding areas causes severe cross-talk effect. Further, for a display screen having R, G, and B sub-pixels in a strip configuration that is used in Portrait mode, the 3D image being displayed suffers severe color distortion also due to the faulty design in its barrier electrode.
There are already many studies being provided in response to the aforesaid problems of light leakage and color distortion. One of which is a multi-functional liquid crystal parallax barrier device disclosed in TW Pat. Publication No. 201124769, and is substantially a LC device mainly formed by two independently disposed common electrode layers, i.e. an upper common electrode layer and a lower electrode layer, and two independently disposed barrier electrode layers, i.e. an upper barrier electrode layer and a lower barrier electrode layer. Thereby, the aforesaid multi-functional liquid crystal parallax barrier device, being referred as an LC device with four-layered electrode structure hereinafter, is capable of resolving the light leakage problem. In addition, each of the upper and the lower barrier electrode layer can be a vertical strip parallax barrier, a slantwise strip parallax barrier, or a slant-and-step parallax barrier. However, it is noted that such aforesaid patent did not mention any effective solution for solving the color distortion issue.
Another such study is a dual-direction device for displaying three-dimensional images that is disclosed in TW Pat.—Publication No. 201133032, which is also an LC device with four-layered electrode structure designed to be applied in a display screen having R, G, and B sub-pixels in a strip configuration. Operationally, when the R, G, and B sub-pixels are vertically arranged for Landscape displaying mode, a structure of vertical strip parallax barrier is used for displaying 3D images, and on the other hand, when the R, G, and B sub-pixels are horizontally arranged for Portrait displaying mode, a structure of slant-and-step parallax barrier is used for displaying 3D images, so as to achieve the purpose of dual-directional 3D images displaying while solving the issue of color distortion at the same time. In addition, in this patent application, the abovementioned vertical strip parallax barrier and slant-and-step parallax barrier are optimized for working cooperatively with a corresponding multi-view 3D image combined formulas and also the optimization conditions for obtaining optimal viewing distance in each displaying mode are provided. That is, by enabling both the minimum horizontal display unit and the minimum vertical display unit of a view image to have the same width, the display screen can have the same optimal viewing distance in both the Landscape and Portrait displaying mode, so as to achieve the convenience of usage in 3D application.
Another such study is also a dual-direction device for displaying three-dimensional images that is disclosed in TW Pat. Publication No. 201209448, which is also an LC device with four-layered electrode structure, but is designed to be applied in a display screen having R, G, and B sub-pixels in a delta configuration and mosaic configuration. With the aforesaid device, the required vertical strip parallax barrier and slant-and-step parallax barrier are optimized for working cooperatively with a corresponding multi-view 3D image combined formulas so as to resolve the issues of light leakage and color distortion.
Furthermore, there is a dual-direction device for displaying three-dimensional images that is disclosed in TW Pat. Publication No.—201209450, which is also an LC device with four-layered electrode structure, but is designed to be applied in a display screen having R, G, and B sub-pixels in a delta configuration. With the aforesaid device, the required vertical strip parallax barrier and slantwise strip parallax barrier are optimized for working cooperatively with a corresponding multi-view 3D image combined formulas so as to resolve the issues of light leakage and color distortion.
Moreover, there is further a multi-view three-dimensional image displaying method disclosed in TW Pat. Publication No. 201243393. Although the aforesaid patent has no relation with the dual-directional displaying, it discloses a further 3D art for a display screen having R, G, and B sub-pixels in a strip configuration while the R, G, and B sub-pixels being arranged horizontally. In this patent application, the required slantwise strip parallax barrier is optimized and provided for working cooperatively with a corresponding multi-view 3D image combined formulas so as to be used for displaying 3D images without color distortion.
To sum up, in the aforesaid TW patents, the light leakage problem is solved by the design of an LC device with four-layered electrode structure, whereas the issue of color distortion is resolved by the optimization designs of a slantwise strip parallax barrier and a slant-and-step parallax barrier.
However, in the field of 3D display utilizing the principle of parallax barrier and having both 2D/3D image switching and dual-directional 3D image displaying abilities, those aforesaid patents are not able to provide a LC device with single-layered barrier electrode structure that can not only provide both 2D/3D image switching and dual-directional 3D image displaying functions, but also capable of solving the problems of light leakage and color distortion. Not to mention that there is no such LC devices existed today that is designed based upon the lenticular technology. Therefore, the goal of present invention is to use a single-layered electrode to equip the parallax barrier or the lenticular structure, so as not only to achieve the purpose of 2D/3D image switching and dual-directional 3D image displaying, but also solve the problems of light leakage and color distortion.
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