Abstract:
An electro-optical modulator includes a substrate, a first electrode over the substrate, a second electrode over the first electrode, the first electrode and second electrode being capable of providing an electric field between the first electrode and the second electrode, and a modulating structure between the first electrode and the second electrode, the modulating structure containing at least one liquid crystal cell capable of operating in one of a reflective mode and a transmissive mode under the control of the electrical field.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to a display device and more particularly, to a liquid crystal electro-optical modulator and a method of optical modulation. 
         [0002]    As information technology continues to evolve, the demands for light modulation in commercial product applications such as c-signature, e-tag, e-booking and smart cards have been increasing in recent years. It is desirable to have an electro-optical modulator that is cost effective and satisfies the commercial product applications. 
       BRIEF SUMMARY OF THE INVENTION 
       [0003]    Examples of the invention may provide an electro-optical modulator and a method of optical modulation. 
         [0004]    Examples of the invention may provide an electro-optical modulator that comprises a substrate, a first electrode over the substrate, a second electrode over the first electrode, the first electrode and second electrode being capable of providing an electric field between the first electrode and the second electrode, and a modulating structure between the first electrode and the second electrode, the modulating structure containing at least one liquid crystal cell capable of operating in one of a reflective mode and a transmissive mode under the control of the electrical field. 
         [0005]    Examples of the invention may also provide an electro-optical modulator that comprises a first pair of electrodes capable of applying a first electric field, a first liquid crystal cell between two electrodes of the first pair of electrodes and capable of operating in one of a reflective mode and a transmissive mode under the control of the first electrical field, a second pair of electrodes over the first liquid crystal cell, the second pair of electrodes capable of applying a second electric field, and a second liquid crystal cell between two electrodes of the second pair of electrodes and capable of being controlled by the second electrical field. 
         [0006]    Some examples of the invention may also provide an electro-optical modulator that comprises a first pair of electrodes capable of applying a first electrical field, a first modulating structure between two electrodes of the first pair of electrodes, the first modulating structure including a first liquid crystal cell capable of operating in one of a reflective mode and a transmissive mode under the control of the first electrical field, a second pair of electrodes over the first liquid crystal cell, the second pair of electrodes capable of applying a second electrical field, and a second modulating structure between two electrodes the second pair of electrodes, the second modulating structure including a second liquid crystal cell capable of operating in one of an isotropic mode and an anisotropic mode under the control of the second electrical field. 
         [0007]    Examples of the invention may also provide a method of optical modulation that comprises providing a modulator comprising a pair of electrodes, a modulating structure formed between the pair of electrodes, and a liquid crystal cell formed in the modulating structure capable of operating in one of a first mode and a second mode, operating the liquid crystal cell in the first mode, applying an electrical field between the pair of electrodes, and switching the liquid crystal cell from the first mode to the second mode. 
         [0008]    Examples of the invention may also provide a method of optical modulation that comprises providing a modulator including a first pair of electrodes, a first liquid crystal cell formed between the first pair of electrodes capable of operating in one of a reflective mode and a transmissive mode, a second pair of electrodes formed over the first liquid crystal cell, and a second liquid crystal cell formed between the second pair of electrodes, operating the first liquid crystal cell in one of the reflective mode and the transmissive mode, and applying an electrical field between at least one of the first pair of electrodes or the second pair of electrodes. 
         [0009]    Some examples of the invention may also provide a method of optical modulation that comprises providing a modulator including a first pair of electrodes, a first liquid crystal cell formed between the first pair of electrodes capable of operating in one of a reflective mode and a transmissive mode, a second pair of electrodes formed over the first liquid crystal cell, and a second liquid crystal cell formed between the second pair of electrodes capable of operating in one of an isotropic mode and an anisotropic mode, operating the first liquid crystal cell in one of the reflective mode and the transmissive mode, operating the second liquid crystal cell in one of the isotropic mode and the anisotropic mode, and applying an electrical field between at least one of the first pair of electrodes or the second pair of electrodes. 
         [0010]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
     
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0011]    The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings examples consistent with the invention. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
           [0012]    In the drawings: 
           [0013]      FIGS. 1A to 1D  are cross-sectional diagrams of electro-optical modulators consistent with examples of the present invention; 
           [0014]      FIGS. 2A to 2C  are diagrams each illustrating a method for operating an electro-optical modulator consistent with an example of the present invention; 
           [0015]      FIG. 3A  is a cross-sectional diagram of an electro-optical modulator consistent with another example of the present invention; 
           [0016]      FIG. 3B  is a cross-sectional diagram of an electro-optical modulator consistent with still another example of the present invention; 
           [0017]      FIG. 4A  is a cross-sectional diagram of an electro-optical modulator consistent with an example of the present invention; 
           [0018]      FIG. 4B  is a cross-sectional diagram of an electro-optical modulator consistent with another example of the present invention; 
           [0019]      FIG. 5A  is a diagram illustrating a method for operating the electro-optical modulator illustrated in  FIG. 4A ; 
           [0020]      FIG. 5B  is a diagram illustrating another method for operating the electro-optical modulator illustrated in  FIG. 4A ; 
           [0021]      FIG. 5C  is a diagram illustrating a method for operating an electro-optical modulator consistent with an example of the present invention; 
           [0022]      FIG. 5D  is a diagram illustrating another method for operating the electro-optical modulator illustrated in  FIG. 5C ; 
           [0023]      FIG. 6A  is a cross-sectional diagram of an electro-optical modulator consistent with an example of the present invention; 
           [0024]      FIG. 6B  is a cross-sectional diagram of an electro-optical modulator consistent with another example of the present invention; 
           [0025]      FIG. 7A  is a diagram illustrating a method for operating the electro-optical modulator illustrated in  FIG. 6A ; and 
           [0026]      FIG. 7B  is a diagram illustrating another method for operating the electro-optical modulator illustrated in  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Reference will now be made in detail to the present embodiments of the invention, examples of 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 portions. 
         [0028]      FIGS. 1A to 1D  are cross-sectional diagrams of electro-optical modulators  10 - 1  to  10 - 4  consistent with examples of the present invention. Referring to  FIG. 1A , the electro-optical modulator  10 - 1  includes a substrate  11 , a first conductive layer  12 - 1 , a modulating structure  13 - 1 , a liquid crystal cell  14  and a second conductive layer  12 - 2 . The substrate  11  is optically transparent and may be made of polymer materials such as polyethylenterephthalate (PET), polycarbonate (PC) and polyethersulfone (PES). In one example, the thickness of the substrate  11  may be approximately  125  micrometers (μm), but this may vary for various applications. The first conductive layer  12 - 1 , formed over the substrate  11 , serves as a first electrode of the electro-optical modulator  10 - 1 . The first conductive layer  12 - 1  may be a transparent conductive layer, such as a layer of indium tin oxide (ITO) or indium zinc oxide (IZO) having a thickness of approximately 0.1 to 0.2 μm, or a conducting polymer having a thickness of approximately 1 μm in some examples. The modulating structure  13 - 1  includes a plurality of modulating units  130  and is made of a polymer material such as fish gel and photograph gel. The height of the modulating structure  13 - 1  may range from approximately 5 to 15 μm in one example. The liquid crystal cell  14  includes a plurality of cell units  14 - 1 , each of which may include a mixture of liquid crystal molecules  15  and fine particles  16 . The weight percentage of the fine particles  16  in a cell unit  14 - 1  ranges from approximately 0.1% to 20%. Each of the plurality of cell units  14 - 1  corresponds to one of the plurality of modulating units  130 . Specifically, each of the plurality of modulating units  130  functions to serves as a containment device that encapsulates or confines a corresponding one of the plurality of cell units  14 - 1 . The second conductive layer  12 - 2 , formed over the modulating structure  13 - 1 , serves as a second electrode of the electro-optical modulator  10 - 1 . The second conductive layer  12 - 2  includes a similar material to the first conductive layer  12 - 1 , and has substantially the same thickness as the first conductive layer  12 - 1 . 
         [0029]    In the present example, the modulating structure  13 - 1  is formed by a conventional microencapsulating process, which encapsulates droplets of liquid crystal molecules and fine particles in polymer walls. 
         [0030]    Referring to  FIG. 1B , the electro-optical modulator  10 - 2  includes a similar structure to the electro-optical modulator  10 - 1  illustrated in  FIG. 1A  except a modulating structure  13 - 2 . The modulating structure  13 - 2  includes a plurality of polymer banks  131  and a sealing layer  132  formed over the plurality of polymer banks  131 . Each of the plurality of polymer banks  131  and the sealing layer  132  defines a modulating unit (not numbered) corresponding to one of the plurality of cell units  14 - 1 . The modulating structure  13 - 2  may be formed by a conventional photolithography or molding process. 
         [0031]    Referring to  FIG. 1C , the electro-optical modulator  10 - 3  includes a similar structure to the electro-optical modulator  10 - 1  illustrated in  FIG. 1A  except a modulating structure  13 - 3 . The modulating structure  13 - 3  includes a plurality of polymer walls  133 . Each of the plurality of polymer walls  133  and the second conductive layer  12 - 2  defines a modulating unit (not numbered) corresponding to one of the plurality of cell units  14 - 1 . The modulating structure  13 - 3  may be formed by a conventional photo-induced phase separation process. 
         [0032]    Referring to  FIG. 1D , the electro-optical modulator  10 - 4  includes a similar structure to the electro-optical modulator  10 - 1  illustrated in  FIG. 1A  except a modulating structure  13 - 4 . The modulating structure  13 - 4  includes a plurality of modulating units  134 . Each of the plurality of modulating units  134  corresponds to one of the plurality of cell units  14 - 1 . The modulating structure  13 - 4  may be formed by a conventional interfacial polymerization process. 
         [0033]      FIGS. 2A to 2C  are diagrams each illustrating a method for operating an electro-optical modulator consistent with an example of the present invention. Referring to  FIG. 2A , as an example of the electro-optical modulator  10 - 1  illustrated in  FIG. 1A , the liquid crystal molecules  15  are oriented in a first pattern such that an incident light is reflected back. Specifically, an incident light at the substrate  11  from, for example, a backlight source is reflected by the liquid crystal cell  14 . Similarly, an incident light at the second conductive layer  12 - 2  from, for example, an ambient light source is reflected by the liquid crystal cell  14 . The electro-optical modulator  10 - 1  is said to operate in a reflective mode. The liquid crystal molecules  15  are not necessarily required to center around fine particles  16  as illustrated in  FIGS. 1A and 2A . Other patterns that enable the liquid crystal cell  14  to reflect an incident light are also possible. 
         [0034]    Referring to  FIG. 2B , an electro-optical modulator  20 - 1  includes a similar structure to the electro-optical modulator  10 - 1  illustrated in  FIG. 2A  except that the liquid crystal molecules  15  are oriented in a second pattern, which allows an incident light to pass the liquid crystal cell  14 . The electro-optical modulator  20 - 1  is said to operate in a transmissive mode. In operation, by applying a suitable electrical field between the first conductive layer  12 - 1  and the second conductive layer  12 - 2 , a reflective-mode modulator such as the modulator  10 - 1  illustrated in  FIG. 2A  is able to be switched to a transmissive-mode modulator such as the modulator  20 - 1  illustrated in  FIG. 2B , and vice versa. The electro-optical modulators  10 - 1  and  20 - 1  respectively illustrated in  FIGS. 1A and 2B  therefore exhibit bistable properties, which means that an electro-optical modulator may operate in either a first or a second stable state when an external source such as an electrical field is removed. In the present example, the first state refers to the reflective mode and the second state refers to the transmissive mode, and vice versa. In one example consistent with the present invention, the electrical field ranges from several volts per micrometer to several tens of volts per micrometer. The electrical field may be built by applying voltage signals of different amplitudes or applying voltage signals at different frequencies to the first conductive layer  12 - 1  and the second conductive layer  12 - 2 . 
         [0035]    Referring to  FIG. 2C , an electro-optical modulator  20 - 2  includes a similar structure to the electro-optical modulator  10 - 1  illustrated in  FIG. 2A  except a liquid crystal cell  24 , a second conductive layer  22 - 1  and a third conductive layer  22 - 2  separated from the second conductive layer  22 - 1 . The liquid crystal cell  24  includes reflective-mode cell units  24 - 1  and transmissive-mode cell units  24 - 2 . In operation, each of the reflective-mode cell units  24 - 1  is able to be switched to the transmissive mode by applying a first electrical field between the first conductive layer  12 - 1  and the second conductive layer  22 - 1 . Similarly, each of the transmissive-mode cell units  24 - 2  is able to be switched to the reflective mode by applying a second electrical field between the first conductive layer  12 - 1  and the third conductive layer  22 - 2 . Skilled persons in the art will understand that the first conductive layer  12 - 1  extends in a first direction, while the second conductive layer  22 - 1  and the third conductive layer  22 - 2  extend in a second direction substantially orthogonal to the first direction. Furthermore, skilled persons in the art will understand that one of the modulating structures  13 - 2 ,  13 - 3  and  13 - 4  respectively illustrated in  FIGS. 1B ,  1 C and  1 D may also be used in the electro-optical modulators  20 - 1  and  20 - 2  as well as the modulating structure  13 - 1 . 
         [0036]      FIG. 3A  is a cross-sectional diagram of an electro-optical modulator  30 - 1  consistent with another example of the present invention. Referring to  FIG. 3A , the electro-optical modulator  30 - 1  includes a similar structure to the electro-optical modulator  20 - 2  illustrated in  FIG. 2C  except a light absorbing layer  31 . The light absorbing layer  31 , disposed between the liquid crystal cell  24  and the second conductive layer  22 - 1  and the third conductive layer  22 - 2 , is capable of absorbing light transmitting through the liquid crystal cell  24  and in particular, the cell units  24 - 2 . In another example, the light absorbing layer  31  is disposed over the second conductive layer  22 - 1  and the third conductive layer  22 - 2  so that the conductive layers  22 - 1  and  22 - 2  are sandwiched between the liquid crystal cell  24  and the light absorbing layer  31 . 
         [0037]      FIG. 3B  is a cross-sectional diagram of an electro-optical modulator  30 - 2  consistent with still another example of the present invention. Referring to  FIG. 3B , the electro-optical modulator  30 - 2  includes a similar structure to the electro-optical modulator  20 - 2  illustrated in  FIG. 2C  except a liquid crystal cell  34 . The liquid crystal cell  34  includes a plurality of dichroic dyes  17  in cell units  34 - 1 . The cell units  34 - 1  are capable of absorbing light transmitting through the liquid crystal cell  34 , which otherwise would operate in the reflective mode in the absence of the dichroic dyes  17 . 
         [0038]    The electro-optical modulator  30 - 2  further includes a reflector  32  disposed over the first conductive layer  22 - 1  and the second conductive layer  22 - 2 . The reflector  32  is capable of reflecting light transmitting through the liquid crystal cell  34  and in particular, the cell units  24 - 2 . In another example, the reflector  32  is disposed between the conductive layers  22 - 1 ,  22 - 2 .and the liquid crystal cell  34 . 
         [0039]      FIG. 4A  is a cross-sectional diagram of an electro-optical modulator  40 - 1  consistent with an example of the present invention. Referring to  FIG. 4A , the electro-optical modulator  40 - 1  includes a first modulator similar to the electro-optical modulator  10 - 1  illustrated in  FIG. 1A  and a second modulator  45 . The first modulator  10 - 1  includes the first substrate  11 , the first electrode  12 - 1 , the modulating structure  13 - 1 , the first liquid crystal cell  14  and the second electrode  12 - 2 . The second modulator  45 , which functions to serve as a panel of the electro-optical modulator  40 - 1 , may be laminated to the first modulator  10 - 1 . The second modulator  45  includes a second substrate  41 - 1 , a first polarizer  47 - 1 , a third electrode  42 - 1 , spacers  43 , a fourth electrode  42 - 2 , a fifth electrode  42 - 3 , a second liquid crystal cell  44 , a second polarizer  47 - 2  and a third substrate  41 - 2 . 
         [0040]      FIG. 4B  is a cross-sectional diagram of an electro-optical modulator  40 - 2  consistent with another example of the present invention. Referring to  FIG. 4B , the electro-optical modulator  40 - 2  includes a first modulator  46  and a second modulator  48 . The first modulator  46  is similar to the electro-optical modulator  10 - 1  illustrated in  FIG. 1A  except a first polarizer  46 - 1 , which is disposed to sandwich the first substrate  11  with the first electrode  12 - 1 . The second modulator  48  includes the second electrode  12 - 2 , the spacers  43 , the fourth electrode  42 - 2 , the fifth electrode  42 - 3 , the second liquid crystal cell  44 , the second polarizer  47 - 2  and the third substrate  41 - 2 . 
         [0041]      FIG. 5A  is a diagram illustrating a method for operating the electro-optical modulator  40 - 1  illustrated in  FIG. 4A . Referring to  FIG. 5A , assuming that the second liquid crystal cell  44  is a vertically arranged (VA) mode panel and no electrical field is applied between the third electrode  42 - 1  and the fifth electrode  42 - 3 , an incident light at the third substrate  41 - 2  transmitting through the second polarizer  47 - 2  and the second liquid crystal cell  44  is blocked by the first polarizer  47 - 1 . As a comparison, if an electrical field is applied between the third electrode  42 - 1  and the fourth electrode  42 - 2 , changing the orientation of the liquid crystal molecules in the second liquid crystal cell  44 , an incident light at the third substrate  41 - 2  transmitting through the second liquid crystal cell  44  is reflected by the first liquid crystal cell  14  operating in the reflective mode. The reflected light transmits through the second liquid crystal cell  44  to a viewer  55  at the third substrate  41 - 2 . 
         [0042]      FIG. 5B  is a diagram illustrating another method for operating the electro-optical modulator  40 - 1  illustrated in  FIG. 4A . Referring to  FIG. 5B , a first electrical field is applied between the first electrode  12 - 1  and the second electrode  12 - 2  to switch the first modulator  10 - 1  to the transmissive mode. If no electrical field is applied between the third electrode  42 - 1  and the fifth electrode  42 - 3 , an incident light at the first substrate  11  transmitting through the first liquid crystal cell  14 , the first polarizer  47 - 1  and the second liquid crystal cell  44  is blocked by the second polarizer  47 - 2 . As a comparison, if a second electrical field is applied between the third electrode  42 - 1  and the fourth electrode  42 - 2 , changing the orientation of the liquid crystal molecules in the second liquid crystal cell  44 , an incident light at the first substrate  11  transmitting through the first liquid cell  14  and the second liquid crystal cell  44  to the viewer  55  at the third substrate  41 - 2 . 
         [0043]      FIG. 5C  is a diagram illustrating a method for operating an electro-optical modulator  50  consistent with an example of the present invention. Referring to  FIG. 5C , the electro-optical modulator  50  includes a similar structure to the electro-optical modulator  40 - 1  illustrated in  FIG. 5A  except a second modulator  56 , which is a twisted nematic (TN) mode panel. In operation, if no electrical field is applied between the third electrode  42 - 1  and the fifth electrode  42 - 3 , an incident light at the third substrate  41 - 2  transmitting through the second polarizer  47 - 2  and a second liquid crystal cell  54  is blocked by the first polarizer  47 - 1 . As a comparison, if an electrical field is applied between the third electrode  42 - 1  and the fourth electrode  42 - 2 , changing the orientation of the liquid crystal molecules in the second liquid crystal cell  54 , an incident light at the third substrate  41 - 2  transmitting through the second liquid crystal cell  54  is reflected by the first liquid crystal cell  14  operating in the reflective mode. The reflected light transmits through the second liquid crystal cell  54  to a viewer  55  at the third substrate  41 - 2 . 
         [0044]      FIG. 5D  is a diagram illustrating another method for operating the electro-optical modulator  50  illustrated in  FIG. 5C . Referring to  FIG. 5D , a first electrical field is applied between the first electrode  12 - 1  and the second electrode  12 - 2  to switch the first modulator  10 - 1  to the transmissive mode. If no electrical field is applied between the third electrode  42 - 1  and the fifth electrode  42 - 3 , an incident light at the first substrate  11  transmitting through the first liquid crystal cell  14 , the first polarizer  47 - 1  and the second liquid crystal cell  54  is blocked by the second polarizer  47 - 2 . As a comparison, if a second electrical field is applied between the third electrode  42 - 1  and the fourth electrode  42 - 2 , changing the orientation of the liquid crystal molecules in the second liquid crystal cell  54 , an incident light at the first substrate  11  transmitting through the first liquid cell  14  and the second liquid crystal cell  54  to the viewer  55  at the third substrate  41 - 2 . 
         [0045]      FIG. 6A  is a cross-sectional diagram of an electro-optical modulator  60 - 1  consistent with an example of the present invention. Referring to  FIG. 6A , the electro-optical modulator  60 - 1  includes a first modulator similar to the electro-optical modulator  10 - 1  illustrated in  FIG. 1A  and a second modulator  65 . The first modulator  10 - 1  includes the first substrate  11 , the first electrode  12 - 1 , the first modulating structure  13 - 1 , the first liquid crystal cell  14  and the second electrode  12 - 2 . The second modulator  65 , which functions to serve as a panel of the electro-optical modulator  60 - 1 , may be laminated to the first modulator  10 - 1 . The second modulator  65  includes a second substrate  61 - 1 , a first polarizer  67 - 1 , a third electrode  62 - 1 , a second modulating structure  63 , a fourth electrode  62 - 2 , a fifth electrode  62 - 3 , a second liquid crystal cell  64 , a second polarizer  67 - 2  and a third substrate  61 - 2 . 
         [0046]    The first liquid crystal cell  14  is operable in a reflective mode or a transmissive mode. In one aspect, the first liquid crystal cell  14  includes inorganic fine particles such as silica particles and positive liquid crystal molecules. In another aspect, the first liquid crystal cell  14  includes organic fine particles such as polystyrene or divinylbenzene (DVB) copolymer particles and positive liquid crystal molecules. The second liquid crystal cell  64  exhibits an isotropic optical feature (hereinafter “isotropic mode”) in the absence of an electrical field, or exhibits an anisotropic optical feature (hereinafter “anisotropic mode”) in the presence of an electrical field. In the isotropic mode, the optical property of liquid crystal molecules is independent of direction. In contrast, in the anisotropic mode, the optical property of liquid crystal molecules is dependent of direction. In one aspect, the second liquid crystal cell  64  includes carbon nanotube (CNT) particles and negative liquid crystal molecules. In another aspect, the second liquid crystal cell  64  includes carbon  60  Fullerene particles and negative liquid crystal molecules. 
         [0047]      FIG. 6B  is a cross-sectional diagram of an electro-optical modulator  60 - 2  consistent with another example of the present invention. Referring to  FIG. 6B , the electro-optical modulator  60 - 2  includes a first modulator  66  and a second modulator  68 . The first modulator  66  is similar to the electro-optical modulator  10 - 1  illustrated in  FIG. 1A  except a first polarizer  66 - 1 , which is disposed to sandwich the first substrate  11  with the first electrode  12 - 1 . The second modulator  68  includes the second electrode  12 - 2 , the second modulating structure  63 , the fourth electrode  62 - 2 , the fifth electrode  62 - 3 , the second liquid crystal cell  64 , the second polarizer  67 - 2  and the third substrate  61 - 2 . 
         [0048]      FIG. 7A  is a diagram illustrating a method for operating the electro-optical modulator  60 - 1  illustrated in  FIG. 6A . Referring to  FIG. 7A , if no electrical field is applied between the third electrode  62 - 1  and the fifth electrode  62 - 3 , an incident light at the third substrate  61 - 2  transmitting through the second polarizer  67 - 2  and the second liquid crystal cell  64  is blocked by the first polarizer  67 - 1 . As a comparison, if an electrical field is applied between the third electrode  62 - 1  and the fourth electrode  62 - 2  to switch the second liquid crystal cell  64  from the isotropic mode to the anisotropic mode, an incident light at the third substrate  61 - 2  transmitting through the second liquid crystal cell  64  is reflected by the first liquid crystal cell  14  operating in the reflective mode. The reflected light transmits through the second liquid crystal cell  64  to the viewer  55  at the third substrate  61 - 2 . 
         [0049]      FIG. 7B  is a diagram illustrating another method for operating the electro-optical modulator  60 - 1  illustrated in  FIG. 6A . Referring to  FIG. 7B , a first electrical field is applied between the first electrode  12 - 1  and the second electrode  12 - 2  to switch the first modulator  10 - 1  to the transmissive mode. If no electrical field is applied between the third electrode  62 - 1  and the fifth electrode  62 - 3 , an incident light at the first substrate  11  transmitting through the first liquid crystal cell  14 , the first polarizer  67 - 1  and the second liquid crystal cell  64  is blocked by the second polarizer  67 - 2 . As a comparison, if a second electrical field is applied between the third electrode  62 - 1  and the fourth electrode  62 - 2  to switch the second liquid crystal cell  64  from the isotropic mode to the anisotropic mode, an incident light at the first substrate  11  transmitting through the first liquid cell  14  and the second liquid crystal cell  64  to the viewer  55  at the third substrate  61 - 2 . 
         [0050]    It will be appreciated by those skilled in the art that changes could be made to one or more of the examples described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular examples disclosed, but it is intended to cover modifications within the scope of the present invention as defined by the appended claims. 
         [0051]    Further, in describing certain illustrative examples of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.