Abstract:
A three-dimensional (3D) display apparatus is provided. The 3D display apparatus includes a display device, a twisted nematic (TN) liquid crystal panel, and a lens unit. The display device is configured to output first polarized lights of an image. The TN liquid crystal panel is coupled to the display device and containing a plurality of controllable pixel display areas to receive the polarized lights with a first polarization direction from the display device. Each pixel display area is capable of being in a first state in which the first polarization direction is transformed into a second polarization direction different from the first polarization direction and a second state in which the first polarization direction is maintained. Further, the lens unit is coupled to the TN liquid crystal panel and is configured to guide the polarized lights with the second polarization direction to pass through and to guide polarized lights with the first polarization direction into predetermined transmitting directions for 3D display.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of PCT patent application No. PCT/CN2010/070290 filed on Jan. 20, 2010, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to twisted nematic (TN) display technologies and, more particularly, to the methods and systems for three dimensional (3D) display based on TN liquid crystal panels. 
       BACKGROUND 
       [0003]    Nowadays, twisted nematic (TN) LC Panel (or TN LC cell) is being widely used in various fields, especially in display technologies.  FIG. 1  illustrates a conventional TN LC panel. Glass substrate  11  and glass substrate  12  are arranged in parallel with a predetermined distance therebetween. On the inner surfaces of substrate  11  and substrate  12 , transparent electrodes  13  and  14  are provided respectively. Further, on the outer surfaces of the electrodes  13  and  14 , alignment layers  15  and  16  are provided respectively, and the rubbing directions of alignment layers  15  and  16  are perpendicular to each other. TN liquid crystal is filled between alignment layers  15  and  16 . 
         [0004]    When there is no voltage applied between the transparent electrodes  13  and  14 , linearly polarized lights entering the TN LC panel via an alignment layer in a direction parallel to the rubbing direction of the alignment layer, the TN LC panel will change the polarization direction of the lights by 90 degrees coming out of the TN LC panel. However, when a voltage applied between the transparent electrodes  13  and  14  is greater than or equal to a threshold voltage, TN molecules re-align the long axis along the direction of the electric field between transparent electrodes  13  and  14 , and the TN LC panel does not change the polarization of the entering lights. 
         [0005]    Further, conventional 2D/3D switchable display systems, such as one disclosed in Chinese patent application no. CN101387758A, often position an above-mentioned TN LC panel in front of a regular display screen as the 2D/3D switching device. The 2D/3D display is switched by regulating polarization directions of lights passing the TN LC panel through controlling voltages applied to the TN LC panel. Thus, the 2D/3D display switching is often done for the entire display screen and not for different portions of the display screen. 
         [0006]    To solve the above problem, other conventional 2D/3D switchable display systems use a thin film transistor (TFT) TN LCD panel as the switching means. Because, in the TFT TN LCD panel, pixels can be individually addressed, 2D/3D switching can be realized on portions of the display screen. However, TFT TN LCD panels are complex and expensive, and often need to place non-transparent TFT circuit wires and grating wires, etc., on the substrates, which may need to be covered by a black matrix. Thus, an effective display area may be reduced, the aperture ratio may be reduced, and the existence of the black matrix may impact image display quality. However, if removing the black matrix, bright lines may appear along the electrodes, which may also impact image display quality. 
         [0007]    The disclosed methods and systems are directed to solve one or more problems set forth above and other problems. 
       BRIEF SUMMARY OF THE DISCLOSURE 
       [0008]    One aspect of the present disclosure includes a three-dimensional (3D) display apparatus. The 3D display apparatus includes a display device, a twisted nematic (TN) liquid crystal panel, and a lens unit. The display device is configured to output first polarized lights of an image. The TN liquid crystal panel is coupled to the display device and containing a plurality of controllable pixel display areas to receive the polarized lights with a first polarization direction from the display device. Each pixel display area is capable of being in a first state in which the first polarization direction is transformed into a second polarization direction different from the first polarization direction and a second state in which the first polarization direction is maintained. Further, the lens unit is coupled to the TN liquid crystal panel and is configured to guide the polarized lights with the second polarization direction to pass through and to guide polarized lights with the first polarization direction into predetermined transmitting directions for 3D display. 
         [0009]    Another aspect of the present disclosure includes a TN liquid crystal panel. The TN liquid crystal panel includes a first control layer, a second control layer, and a TN liquid crystal layer arranged between the first control layer and the second control layer. The first control layer includes a first substrate, a first electrode section, and a first alignment layer. The second control layer includes a second substrate, a second electrode section, and a second alignment layer. Further, the first electrode section includes a plurality of first electrodes arranged in a first direction and parallel to one another. The second electrode section includes a plurality of second electrodes arranged in a second direction different from the first direction and parallel to one another, and the second direction is perpendicular to the first direction. A plurality of controllable pixel display areas are formed by the plurality of first electrodes, the plurality of second electrodes, and the TN liquid crystal layer to transform a polarization direction of entering lights. 
         [0010]    Another aspect of the present disclosure includes a light polarization switching device. The light polarization switching device includes a first control layer having a plurality of first electrodes extending in a first direction, and a second control layer having a plurality of second electrodes extending in a second direction crossing the first direction. The light polarization switching device also includes a twisted nematic (TN) liquid crystal layer sandwiched between the first and second control layers. Further, at least one of the plurality of first electrodes and the plurality of second electrodes has a shape selected from a wave shape, a curve shape, and a zigzag shape. 
         [0011]    Other aspects of the present disclosure can be understood by those skilled in the art in light of the description, the claims, and the drawings of the present disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  illustrates a conventional TN cell; 
           [0013]      FIG. 2  illustrates a diagram of an exemplary TN panel consistent with the disclosed embodiments; 
           [0014]      FIG. 3  illustrates an exemplary electrode section consistent with the disclosed embodiments; 
           [0015]      FIG. 4  illustrates an exemplary electrode section consistent with the disclosed embodiments; 
           [0016]      FIG. 5  illustrates an exemplary configuration of a TN panel consistent with the disclosed embodiments; 
           [0017]      FIG. 6  illustrates an exemplary 3D display system consistent with the disclosed embodiments; and 
           [0018]      FIG. 7  illustrates a block diagram of an exemplary controller consistent with the disclosed embodiments. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Reference will now be made in detail to exemplary embodiments of the invention, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
         [0020]      FIG. 6  shows a structural diagram of an exemplary 3D display system  60 . As showed in  FIG. 6 , 3D display system  60  includes a display device  61 , a twisted nematic (TN) liquid crystal panel (TN panel)  62 , a first lens array  63 , a second lens array  64 , and a controller  65 . Other components may be added and certain devices may be removed without departing from the principles of the disclosed embodiments. Further, space between various components is shown for illustrative purposes, the disclosed embodiments may or may not have such space. 
         [0021]    3D display system  60  may be used to display three-dimensional (3D) images. Display device  61  may be provided with sets of images to be viewed by a viewer&#39;s left eye and right eye separately. Each set of images are from a different viewpoint. For example, a stereo (two viewpoints) 3D image may include an image set for a viewer&#39;s left eye (i.e., a left image) and a corresponding image set for the viewer&#39;s right eye (i.e., a right image), with a certain parallax between the left image and the right image. Various viewpoints may also be used. 
         [0022]    3D display system  60  may also display full-resolution two-dimensional (2D) images, and may switch between 2D display and 3D display dynamically. Further, 3D display system  60  may also have 2D display and 3D display on a same display screen at the same time. For example, when multiple display windows are opened on display device  61 , certain display window or windows may display 3D images, while certain display windows may display 2D images, and each display window may switch 2D display to 3D display or vice versa dynamically. 
         [0023]    Display device  61  may include any appropriate device for displaying images, such as a plasma display panel (PDP) display, a cathode ray tube (CRT) display, a liquid crystal display (LCD), an organic light emitting diode (OLED) display, and other types of displays. Display device  61  may be used in computers, consumer electronics, medical equipment, professional equipment, or other systems requiring information display. Optionally, a polarizer sheet may be positioned over display device  61  to make lights from display device  61  linearly polarized before entering TN panel  62 . 
         [0024]    Controller  65  may include any appropriate device for providing control and other functionalities to 3D display system  60 .  FIG. 7  shows an exemplary block diagram of controller  65 . As shown in  FIG. 7 , controller  65  may include a processor  6502 , a random access memory (RAM) unit  6504 , a read-only memory (ROM) unit  6506 , a communication interface  6508 , an input/output interface unit  6510 , and a driving unit  6512 . Other components may be added and certain devices may be removed without departing from the principles of the disclosed embodiments. 
         [0025]    Processor  6502  may include any appropriate type of graphic processing unit (GPU), general-purpose microprocessor, digital signal processor (DSP) or microcontroller, and application specific integrated circuit (ASIC), etc. Processor  6502  may execute sequences of computer program instructions to perform various processes associated with display system  60 . The computer program instructions may be loaded into RAM  6504  for execution by processor  6502  from read-only memory  6506 . 
         [0026]    Communication interface  6508  may provide communication connections such that display system  60  may be accessed remotely and/or communicate with other systems through computer networks or other communication networks via various communication protocols, such as transmission control protocol/internet protocol (TCP/IP), hyper text transfer protocol (HTTP), etc. 
         [0027]    Input/output interface  6510  may be provided for users to input information into display system  60  or for the users to receive information from display system  60 . For example, input/output interface  6510  may include any appropriate input device, such as a remote control, a keyboard, a mouse, an electronic tablet, voice communication devices, or any other optical or wireless input devices. Further, driving unit  6512  may include any appropriate driving circuitry to drive various devices, such as TN panel  62  and/or display device  61 . 
         [0028]    Returning to  FIG. 6 , TN panel  62  may include any appropriate device coupled with display device  61  to provide 3D display.  FIG. 2  illustrates a diagram of an exemplary TN panel  62 . As showed in  FIG. 2 , TN panel  62  includes a first substrate  21 , a first electrode  22 , a first alignment layer  23 , a second alignment layer  24 , a second electrode  25 , a second substrate  26 , and TN liquid crystal  20 . Other components may also be included. 
         [0029]    First substrate  21 , first electrode  22 , and first alignment layer  23  may form a first control layer, while second alignment layer  24 , second electrode  25 , and second substrate  26  may form a second control layer. TN liquid crystal  20  may be sealed in the space between the first control layer and the second control layer by sealing edges of the first control layer and the second control layer using, for example, special glues. As used here, an electrode may refer to an electrode section including a plurality of electrodes or an individual electrode according to the context of the disclosure. 
         [0030]    In the first control layer, first substrate  21 , first electrode  22 , and first alignment layer  23  may be made of any appropriate transparent materials. First electrode  22  may include a plurality of electrodes arranged in a certain pattern. The plurality of electrodes may also be in any appropriate shape such that a large area of substrate may be covered by the plurality of electrodes. For example, the plurality of electrodes of first electrode  22  may be in a sinusoid shape, a wave shape, a curve shape, and a zigzag shape, etc. In certain embodiments, the plurality of electrodes of first electrode  22  may be in one or more shape selected from a wave shape, a curve shape, and a zigzag shape. As shown in  FIG. 3 , a plurality of sinusoid-shaped electrodes of first electrode  22  may be used. Each of sinusoid-shaped strip electrodes may be arranged horizontally in parallel and separated by a certain predetermined distance. Other shapes or arrangements may also be used. 
         [0031]    The plurality of first electrodes  22  may be arranged or built on the surface of first substrate  21 . First alignment layer  23  is arranged on top of the plurality of first electrodes  22 . For example, first alignment layer  23  may be formed by applying an alignment agent on the top of first electrodes  22  and first substrate  21 . 
         [0032]    Further, in the second control layer, second alignment layer  24 , second electrode  25 , and second substrate  26  may also be made of any appropriate transparent materials. Similar to the first control layer, as shown in  FIG. 4 , second electrode  25  may also include a plurality of sinusoid-shaped strip electrodes. The plurality of electrodes of second electrode  25  may also be in a wave shape, a curve shape, and a zigzag shape, etc., or any appropriate shape such that a large area of substrate may be covered by the plurality of electrodes of second electrode  25 . For example, the plurality of electrodes of first electrode  22  may be in one or more shape selected from a wave shape, a curve shape, and a zigzag shape. Each of sinusoid-shaped strip electrodes may be arranged vertically in parallel and separated by a certain predetermined distance. That is, the plurality of second electrodes  25  may be arranged in a right angle or any appropriate angle with respect to the plurality of first electrodes  22 . Other shapes or arrangements may also be used. 
         [0033]    The plurality of second electrodes  25  may be arranged or built on the surface of second substrate  26 . Second alignment layer  24  is arranged on top of the plurality of second electrodes  25  with a flat surface. Further, TN liquid crystal layer  20  may be placed between first alignment layer  23  and second alignment layer  24 . 
         [0034]    Thus, the first control layer and the second control layer are arranged in parallel. Further, certain liner materials, e.g. a sealant, may be placed between first alignment layer  23  and second alignment layer  24  to keep the distance between the first control layer and the second control layer, or between first alignment layer  23  and second alignment layer  24 , being a predetermined distance.  FIG. 5  shows an exemplary configuration of TN panel  62 . Although only eight first electrodes a 1  to a 8  and eight second electrodes b 1  to b 8  are shown for illustrative purposes, any number of electrodes may be used. 
         [0035]    As shown in  FIG. 5 , the horizontally-arranged plurality of first electrodes  22  and vertically-arranged plurality of second electrodes  25  may overlap each other such that an 8×8 pixel display areas can be formed. That is, the pixel display areas are defined by a 1 , a 2 , a 3 , a 4 , a 5 , a 6 , a 7 , and a 8  in horizontal direction and b 1 , b 2 , b 3 , b 4 , b 5 , b 6 , b 7 , and b 8  in vertical direction. Each display area includes portions of various layers, such as the second control layer, the first control layer, and the TN liquid crystal layer  20  determined by a first electrode and a second electrode. For illustrative purposes, the 8×8 pixel display areas may be represented by an 8×8 two dimensional pixel matrix. 
         [0036]    A column of the pixel matrix represents first electrode  22  and a row of the pixel matrix represents second electrode  25 . Thus, a pixel display area a ij  may represent a pixel display area defined by i-th row and j-th column, wherein i is from 1, 2, 3, . . . , 8, and j is also from 1, 2, 3, . . . , 8. 
         [0037]    When no voltage is applied to electrodes of the pixel display area a ij , under the effects of first alignment layer  23  and second alignment layer  24 , TN liquid crystal  20  in a ij  is twisted by 90 degrees. When lights enter TN panel  62  with a polarization direction parallel to the rubbing direction of the entering alignment layer and pass through TN panel  62 , the polarization direction of the lights is rotated in 90 degrees when coming out TN panel  62 . This state of TN liquid crystal  20  may be referred as a first state. 
         [0038]    On the other hand, when a voltage applied between the electrodes of the pixel display area a ij , for example, by applying to the i-th electrode and the j-th electrode separate voltages U i  and U j , respectively, and the difference between U i  and U j  is greater than or equal to a threshold voltage, TN liquid crystal  20  may be in an electric field formed between the i-th electrode and the j-th electrode. TN liquid crystal molecules may re-align the long axis along the direction of the electric field between the i-th electrode and the j-th electrode, i.e., along a direction perpendicular to the direction from first substrate  21  to second substrate  26 . Thus, display area a ij  does not change the polarization direction of the entering lights. This state of TN liquid crystal  20  may be referred as a second state. Therefore, by applying different voltages to different columns and rows, different pixel display areas can be controlled separately in a different state. 
         [0039]    That is, certain pixel display areas may be controlled to be in one of the first state and the second state, while certain other pixel display areas may be controlled to be in the other one of the first state and the second state. In certain embodiments, a row (vertical) scanning mechanism or a column (horizontal) scanning mechanism may be used to control switching between the states of TN liquid crystal  20 . Further, the scanning frequency may be chosen such that the TN liquid crystal switches from the first state to the second state in a short time, while remaining in or around the second state for a time period equal to or greater than the period of the scanning frequency. Thus, when scanning the last row of TN panel  62 , the first row that is already switched from the first state to the second state can still remain in the second state and does not return to the first state. 
         [0040]    For example, in  FIG. 5 , at the beginning, a same voltage U 0  may be applied to electrodes a 1  to a 8  (i.e., first electrodes  22 ). To perform the row scanning process, starting with b 1 , each row from b 1  to b 8  is scanned and applied to a voltage U 1 . When scanning a particular row, for example, the 5 th  row (i.e., b 5 ), a pulse voltage U 2  may be applied to electrodes a 3 , a 4 , a 5 , a 6 , and a 7 , such that the voltage difference between these electrodes and electrode b 5 , U 2 -U 1 , is greater than or equal to U th , where U th  is the threshold voltage for TN liquid crystal  20  to change state, (U 1 -U 0 ) is less than U th  and (U 2 -U 0 ) is also less than U th . Thus, TN liquid crystal  20  in pixel display areas a 53 , a 54 , a 55 , a 56 , and a 57  change state from the first state to the second state at about the same time. 
         [0041]    Similarly, when scanning the 6 th  row, a pulse voltage U 2  may be applied to electrodes a 3 , a 4 , a 5 , a 6 , and a 7 , such that the voltage difference between these electrodes and electrode b 6 , i.e., (U 2 -U 1 ), is greater than or equal to U th , and TN liquid crystal  20  in pixel display areas a 63 , a 64 , a 65 , a 66 , and a 67  change state from the first state to the second state at about the same time. When scanning the 7 th  row, a pulse voltage U 2  may be applied to electrodes a 3 , a 4 , a 5 , a 6 , and a 7 , such that the voltage difference between these electrodes and electrode b 7 , i.e., U 2 -U 1 , is greater than or equal to U th , and TN liquid crystal  20  in pixel display areas a 73 , a 74 , a 75 , a 76 , and a 77  change state from the first state to the second state at about the same time. 
         [0042]    Further, when scanning the 8 th  row, a pulse voltage U 2  may be applied to electrodes a 3 , a 4 , a 5 , a 6 , and a 7 , such that the voltage difference between these electrodes and electrode b 8 , i.e., U 2 -U 1 , is greater than or equal to U th , and TN liquid crystal  20  in pixel display areas a 83 , a 84 , a 85 , a 86 , and a 87  change state from the first state to the second state at about the same time. In addition, because of a high scanning frequency, when scanning the 8 th  row, TN liquid crystal  20  in pixel display areas a 53 , a 54 , a 55 , a 56 , a 57 , a 63 , a 64 , a 65 , a 66 , a 67 , a 73 , a 74 , a 75 , a 76 , and a 77  are still in the second state, while TN liquid crystal  20  in other pixel display areas is in the first state. 
         [0043]    Thus, the above example illustrates that pixel display areas of rows  5 ,  6 ,  7 , and  8  and columns  3 ,  4 ,  5 ,  6 , and  7  are controlled in the second state while other pixel display areas are in the first state. That is, with the disclosed methods and systems, individual pixel display areas may be controlled separately. In addition, if there is a need to reverse the state of TN liquid crystal  20  in a pixel display area a ij , a pulse voltage may be applied to j-th column during scanning the i-th row such that TN liquid crystal  20  in a ij  can reverse its long axis and change back to the first state. A similar column scanning mechanism may also be used. 
         [0044]    Returning to  FIG. 6 , first lens array  63  may include any appropriate single refraction lens arranged in an array configuration, and second lens array  64  may include any appropriate double refraction lens arranged in an array configuration. Further, first lens array  63  may be coupled closely with second lens array  64  to act as certain convex lenses when directing linearly polarized light from display device  61  and TN panel  62 . 
         [0045]    For illustrative purpose, polarized lights outputted from display device  61  are referred as first polarized lights with a particular polarization direction. If the polarization direction is changed by TN panel  62 , the polarized lights outputted from TN panel  62  are referred as second polarized lights with a different polarization direction. Otherwise, TN panel  62  merely passes the first polarized lights. That is, if TN panel  62  does not change the polarization direction of the first polarized lights, no second polarized lights may exist. Further, first alignment layer  23  (i.e., the one close to display device  61 ) may have the same alignment direction as the first polarized lights, which may be realized by a sheet polarizer over display device  61 . 
         [0046]    As shown in  FIG. 6 , first lens array  63  may have a light incident surface which is plane, and a plurality of elongate semi-cylindrical convex surfaces. First lens array  63  may be made of optically isotropic materials with a single refractive index of n 1 . 
         [0047]    The second lens array  64  may have a light output surface which is plane and a plurality of elongate semi-cylindrical concave light incident surfaces. Each concave lens may be coupled to corresponding convex lens from first lens array  63 , which may make the two lens arrays a tight-fit, coupled, and double flat surface unit. Other configurations may also be used. Further, second lens array  64  may be made of optically anisotropic materials. 
         [0048]    Optically anisotropic material may be birefringent or double refraction, meaning the optically anisotropic material has two different refractive indices, an ordinary refractive index n o  and an extraordinary refractive index n e . Lights with a polarization direction perpendicular to the lens&#39; optical axis have the refractive index of n 0 ; while lights with a polarization direction parallel to the lens&#39; optical axis have a refractive index of n e . The optical axis of second lens array  64  is shown in  FIG. 6  as a double arrow, parallel to the polarization direction of the first polarized lights from display device  61 . Further, n 1 =n 0 , and n 0 &gt;n e . That is, when first lens array  63  is a convex lens array, the refractive index of the first lens array is equal to a larger one of an ordinary refractive index and an extraordinary refractive index of second lens array  64 . 
         [0049]    During operation, 3D display system  60  may have both 3D and 2D display on different portions of display screen. For example, as shown in  FIG. 6 , the upper two rays represent lights for 3D display, and the lower two rays represent lights for 2D display. 
         [0050]    For 3D display, controller  65  may control TN panel  62  such that pixel display areas corresponding to the lights for 3D display are in the second state. That is, the first polarized lights of pixels outputted from display device  61  pass through TN panel  62  without change in polarization direction. The first polarized lights then pass first lens array  63  and enter second lens array  64 . Because the optical axis of second lens array  64  is parallel to the polarization direction of the first polarized lights, second lens array  64  has a refractive index of n e , n 1 &gt;n e . Thus, this difference between the refractive indices, an optical step, makes lights at the interface between the convex surface of first lens array  63  and the concave surface of second lens array  64  converging. The coupled lens array thus acts as a convex lens and directs the first polarized lights (e.g., lights from a right image and a left image) to a viewer&#39;s right eye and left eye respectively to realize 3D display. 
         [0051]    On the other hand, for 2D display, controller  65  may control TN panel  62  such that pixel display areas corresponding to the lights for 2D display are in the first state. The first polarized lights may enter TN panel  62  and the polarization direction of the first polarized lights may be changed by TN panel  62  in, for example, 90 degrees. Thus, the second polarized lights are outputted from TN panel  62 . Because the polarization direction of the second polarized lights is now perpendicular to the optical axis of second lens array  64 , second lens array  64  has a refractive index of n 0 , and n 1 =n o . Thus, no optical step exists at the interface between convex surface of first lens array  63  and the concave surface of second lens array  64 . The second polarized lights therefore go straight through the coupled lens array to the viewer&#39;s both eyes without separation to realize 2D display. 
         [0052]    In addition, first lens array  63  and second lens array  64  can be designed differently from the ones shown in  FIG. 6 . For example, first lens array  63  can include concave lens of optically isotropic materials and second lens array  64  can include convex lens of optically anisotropic material with n 1 =min(n o ,n e ). That is, when first lens array  63  is a concave lens array, the refractive index of the first lens array is equal to a smaller one of an ordinary refractive index and an extraordinary refractive index of second lens array  64 . Other types of designs or configurations may also be used. 
         [0053]    By using the disclosed systems and methods, separate control over pixel or pixels of display devices may be realized in a simple and flexible way, and the 2D/3D image display quality may also be substantially improved. Further, by using sinusoid-shaped or other wave-shaped electrodes, voltages can be applied at a single end of the sinusoid-shaped electrode strip thus may reduce the amount of wires for individual pixels. Thus, no black matrix may be needed in the disclosed systems, and the effective display area and the aperture ratio may be both increased. Further, bright lines may be avoided or reduced by using sinusoid or wave shaped strip electrodes. In addition, the electrodes do not need to be arranged on a same surface. For example, some electrodes may be on one side of a substrate while other electrodes may be on the other side of the substrate, which may further reduce cost and complexity of the disclosed systems.