Patent Publication Number: US-2007097503-A1

Title: Light blocking device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2005-312262 and 2006-215658. The entire disclosures of Japanese Patent Application Nos. 2005-312262 and 2006-215658 are hereby incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a light blocking device configured and arranged to adjust the amount of incident light transmitted therethrough. The light blocking device is especially useful as a sun visor of a vehicle or a vehicle sunroof unit.  
      2. Background Information  
      Japanese Laid-Open Patent Publication No. S62-50222 discloses one example of conventional vehicle sun visors for adjusting the amount of sunlight allowed to pass into a vehicle passenger compartment. The conventional sun visor disclosed in this reference includes a movable plate and a stationary plate. Strips of two types of polarizing film are arranged alternately in prescribed intervals on each of the movable plate and the stationary plate. The polarizing directions of the two types of polarizing film are  90 ° out of phase. By moving the movable plate relative to the stationary plate, the width of the portions where the polarizing films (whose polarization directions are 90° out of phase) on the movable plate and the stationary plate overlap is changed, and thus, the amount of incident light allowed to pass into the passenger compartment is adjusted.  
      In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved light blocking device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.  
     SUMMARY OF THE INVENTION  
      With the conventional sun visor described in the above mentioned reference, since strips of polarizing film whose polarizing directions differ by 90° are arranged alternately in prescribed intervals, the amount of light allowed to pass through the sun visor can only be adjusted across the entire surface of the stationary plate by moving the movable plate with respect to the stationary plate. However, such conventional sun visors cannot select a specific section or area of the surface of the sun visor where the light is blocked. Also such conventional sun visors cannot adjust the size of the selected area where the light is blocked.  
      Accordingly, one object of the present invention is to provide a light blocking device, sun visor, and sunroof unit in which the area where light is blocked can be selected and the size of the selected area can be adjusted.  
      In order to achieve the above mentioned object, a light blocking device is provided that basically comprises a polarizing plate unit, a first movable polarizing plate and a second movable polarizing plate. The polarizing plate unit includes a first polarizing section with a first polarization direction and a second polarizing section with a second polarization direction that is different from the first polarization direction. The first and second polarizing sections are disposed laterally with respect to each other in an alignment direction. The first movable polarizing plate is movably disposed in the alignment direction to selectively overlap the first and second polarizing sections. The first movable polarizing plate has a polarization direction that is substantially identical to the first polarization direction. The second movable polarizing plate is movably disposed in the alignment direction to selectively overlap the first movable polarizing plate. The second movable polarizing plate has a polarization direction that is substantially identical to the second polarization direction.  
      These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Referring now to the attached drawings which form a part of this original disclosure:  
       FIG. 1  is a perspective view of a light blocking device in the form of a sun visor in accordance with a first embodiment of the present invention;  
       FIG. 2  is a cross sectional view of the sun visor in accordance with the first embodiment of the present invention taken along a section line  2 - 2  of  FIG. 1 ;  
       FIG. 3  is a cross sectional view of the sun visor showing a positional relationship between a main polarizing plate unit and first and second movable polarizing plates of the sun visor when an entire surface of the sun visor is arranged as a light transmissive area in accordance with the first embodiment of the present invention;  
       FIG. 4  includes a diagram (A) illustrating a schematic exploded view of the main polarizing plate unit and the first and second movable polarizing plates of the sun visor with the positional relationship as shown in  FIG. 3 , and a diagram (B) illustrating a schematic diagram for showing the light transmissive area of the sun visor corresponding to a state of the sun visor illustrated in the diagram (A) in accordance with the first embodiment of the present invention;  
       FIG. 5  is a cross sectional view of the sun visor showing a positional relationship between the main polarizing plate unit and the first and second movable polarizing plates of the sun visor when the entire surface of the sun visor is arranged as a light-blocking area in accordance with the first embodiment of the present invention;  
       FIG. 6  includes a diagram (A) illustrating a schematic exploded view of the main polarizing plate unit and the first and second movable polarizing plates of the sun visor with the positional relationship as shown in  FIG. 5 , and a diagram (B) illustrating a schematic diagram for showing the light transmissive state of the sun visor corresponding to a state of the sun visor illustrated in the diagram (A) in accordance with the first embodiment of the present invention;  
       FIG. 7  is a cross sectional view of the sun visor showing a positional relationship between the main polarizing plate unit and the first and second movable polarizing plates of the sun visor when a left half of the surface of the sun visor is arranged as a light-blocking area in accordance with the first embodiment of the present invention;  
       FIG. 8  includes a diagram (A) illustrating a schematic exploded view of the main polarizing plate unit and the first and second movable polarizing plates of the sun visor with the positional relationship as shown in  FIG. 7 , and a diagram (B) illustrating a schematic diagram for showing the light transmissive area of the sun visor corresponding to a state of the sun visor illustrated in the diagram (A) in accordance with the first embodiment of the present invention;  
       FIG. 9  is a cross sectional view of the sun visor showing a positional relationship between the main polarizing plate unit and the first and second movable polarizing plates of the sun visor that is adjusted from the positional relationship shown in  FIG. 7  to expand the light-blocking area in accordance with the first embodiment of the present invention;  
       FIG. 10  includes a diagram (A) illustrating a schematic exploded view of the main polarizing plate unit and the first and second movable polarizing plates of the sun visor with the positional relationship as shown in  FIG. 9 , and a diagram (B) illustrating a schematic diagram for showing the light transmissive area of the sun visor corresponding to a state of the sun visor illustrated in the diagram (A) in accordance with the first embodiment of the present invention;  
       FIG. 11  is a cross sectional view of the sun visor showing a positional relationship between the main polarizing plate unit and the first and second movable polarizing plates when a right half of the surface of the sun visor is arranged as a light-blocking area in accordance with the first embodiment of the present invention;  
       FIG. 12  includes a diagram (A) illustrating a schematic exploded view of the main polarizing plate unit and the first and second movable polarizing plates of the sun visor with the positional relationship as shown in  FIG. 11 , and a diagram (B) illustrating a schematic diagram for showing the light transmissive area of the sun visor corresponding to a state of the sun visor illustrated in the diagram (A) in accordance with the first embodiment of the present invention;  
       FIG. 13  is a cross sectional view of the sun visor showing a positional relationship between the main polarizing plate unit and the first and second movable polarizing plates that is adjusted from the positional relationship shown in  FIG. 11  to expand the light-blocking area in accordance with the first embodiment of the present invention;  
       FIG. 14  is a cross sectional view of the sun visor showing a positional relationship between the main polarizing plate unit and the first and second movable polarizing plates when a middle portion of the sun visor is arranged as a light-blocking area in accordance with the first embodiment of the present invention;  
       FIG. 15  includes a diagram (A) illustrating a schematic exploded view of the main polarizing plate unit and the first and second movable polarizing plates of the sun visor with the positional relationship as shown in  FIG. 14 , and a diagram (B) illustrating a schematic diagram for showing the light transmissive area of the sun visor corresponding to a state of the sun visor illustrated in the diagram (A) in accordance with the first embodiment of the present invention;  
       FIG. 16  is a cross sectional view of the sun visor showing a positional relationship between the main polarizing plate unit and the first and second movable polarizing plates that is adjusted from the positional relationship shown in  FIG. 14  to change the light-blocking area in accordance with the first embodiment of the present invention;  
       FIG. 17  is a cross sectional view of a sun visor in accordance with a modified structure of the first embodiment of the present invention;  
       FIG. 18  is a schematic exploded view of first and second movable polarizing plates, a main polarizing plate unit, and a plurality of reinforcing plates of the sun visor illustrated in  FIG. 17  in accordance with the modified structure of the first embodiment of the present invention;  
       FIG. 19  is a series of diagrams (A) to (D) wherein the diagram (A) is a diagrammatic view of an operating lever attached to the first movable polarizing plate, the diagram (B) is a diagrammatic view of the sun visor having the operating levers provided on the first and second movable polarizing plates, the diagram (C) is a schematic view of the first and second movable polarizing plates with the operating levers and the main polarizing plate unit, and the diagram (D) is a side view of the first and second movable polarizing plates with the operating levers and the main polarizing plate unit in accordance with the first embodiment of the present invention;  
       FIG. 20  is a schematic view of a sun visor illustrating an arrangement of the first and second movable polarizing plates in accordance with a comparison example that is problematic when operating levers are provided;  
       FIG. 21  is a schematic rear perspective view of a vehicle equipped with a light blocking device in the form of a sunroof unit in accordance with a second embodiment of the present invention;  
       FIG. 22  is a schematic front perspective view of a roof portion of a vehicle body shown in  FIG. 21  illustrating a main polarizing window plate unit and a portion of the vehicle body in accordance with the second embodiment of the present invention;  
       FIG. 23  is a cross sectional view of the roof portion of the vehicle taken along a section line  23 - 23  of  FIG. 21  in accordance with the second embodiment of the present invention;  
       FIG. 24  is a schematic front perspective view of the roof portion of the vehicle body shown in  FIGS. 21 and 22  in a state in which a roof panel and the main polarizing window plate unit are removed in accordance with the second embodiment of the present invention;  
       FIG. 25  is a schematic front perspective view of first and second rail frames and the first and second movable polarizing window plates of the sunroof unit in accordance with the second embodiment of the present invention;  
       FIG. 26  is a schematic front perspective view of the first movable polarizing window plate and the first (top) rail frame in accordance with the second embodiment of the present invention;  
       FIG. 27  is a schematic top plan view illustrating a relationship between a drive motor and the movable polarizing window plate in accordance with the second embodiment of the present invention;  
       FIG. 28  is a schematic diagram of the vehicle for illustrating forward and backward movements of the first and second movable polarizing window plates with respect to the polarizing window plate in accordance with the second embodiment of the present invention;  
       FIG. 29  includes a diagram (A) illustrating a schematic diagram of the vehicle with a positional relationship of the first and second movable polarizing window plates with respect to the main polarizing window plate unit when an entire area of the sunroof window opening is arranged as a light transmissive area, and a diagram (B) for showing the light transmissive area of the sunroof window opening corresponding to a state of the sunroof unit illustrated in the diagram (A) in accordance with the second embodiment of the present invention;  
       FIG. 30  includes a diagram (A) illustrating a schematic diagram of the vehicle with a positional relationship of the first and second movable polarizing window plates with respect to the main polarizing window plate unit when the entire area of the sunroof window opening is arranged as a light-blocking area, and a diagram (B) for showing the light transmissive area of the sunroof window opening corresponding to a state of the sunroof unit illustrated in the diagram (A) in accordance with the second embodiment of the present invention;  
       FIG. 31  includes a diagram (A) illustrating a schematic diagram of the vehicle with a positional relationship of the first and second movable polarizing window plates with respect to the main polarizing window plate unit when a frontward portion of the area of the sunroof window opening is arranged as a light-blocking area, and a diagram (B) for showing the light transmissive area of the sunroof window opening corresponding to a state of the sunroof unit illustrated in the diagram (A) in accordance with the second embodiment of the present invention;  
       FIG. 32  includes a diagram (A) illustrating a schematic diagram of the vehicle with a positional relationship of the first and second movable polarizing window plates with respect to the main polarizing window plate unit when a rearward portion of the area of the sunroof window opening is arranged as a light-blocking area, and a diagram (B) for showing the light transmissive area of the sunroof window opening corresponding to a state of the sunroof unit illustrated in the diagram (A) in accordance with the second embodiment of the present invention;  
       FIG. 33  includes a diagram (A) illustrating a schematic diagram of the vehicle with a positional relationship of the first and second movable polarizing window plates with respect to the main polarizing window plate unit that is adjusted from the positional relationship illustrated in  FIG. 32  to expand the light-blocking area, and a diagram (B) for showing the light transmissive area of the sunroof window opening corresponding to a state of the sunroof unit illustrated in the diagram (A) in accordance with the second embodiment of the present invention;  
       FIG. 34  includes a diagram (A) illustrating a schematic diagram of the vehicle with a positional relationship of the first and second movable polarizing window plates with respect to the main polarizing window plate unit when a middle portion of the sunroof window opening is arranged as a light-blocking area, and a diagram (B) for showing the light transmissive area of the sunroof window opening corresponding to a state of the sunroof unit illustrated in the diagram (A) in accordance with the second embodiment of the present invention; and  
       FIG. 35  is a schematic diagram of the vehicle illustrating a head clearance of the vehicle in accordance with the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Selected embodiments of the present invention will now be explained with reference to the drawings. It will be apparent to those skilled in the art from this disclosure that the following descriptions of the embodiments of the present invention are provided for illustration only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.  
      Referring initially to  FIGS. 1 and 2 , a sun visor  1  is illustrated as one type of a light blocking device in accordance with a first embodiment of the present invention. While in the first embodiment, the light blocking device is applied to the sun visor  1  that is preferably installed inside of a vehicle or the like, it will be apparent to those skilled in the art from this disclosure that light blocking device of the present invention can be applied to other devices as needed and/or desired. The sun visor  1  basically includes a frame  2 , a main polarizing plate unit  3 , a first movable polarizing plate  4  and a second movable polarizing plate  5 . The frame  2  has a generally rectangular opening  2 A as shown in  FIG. 1 . The main polarizing plate unit  3  is fixedly coupled to the frame  2  within the opening  2 A. The first movable polarizing plate  4  and the second movable polarizing plate  5  are arranged substantially parallel to the main polarizing plate unit  3 . Moreover, the first movable polarizing plate  4  and the second movable polarizing plate  5  are arranged in different positions along a direction perpendicular to the surface of the main polarizing plate unit  3  (i.e., the vertical direction in  FIG. 2 ) such that each of the first movable polarizing plate  4  and the second movable polarizing plate  5  can be moved independently with respect to the main polarizing plate unit  3  without interfering with each other. More specifically, in this first embodiment of the present invention, the first movable polarizing plate  4  is disposed within the opening  2 A on a first side of the main polarizing plate unit  3  and the second movable polarizing plate  5  is disposed within the opening  2 A on a second side of the main polarizing plate unit  3 .  
      The main polarizing plate unit  3 , the first movable polarizing plate  4 , and the second movable polarizing plate  5  preferably constitute the light blocking device of the present invention.  
      In this first embodiment, the main polarizing plate unit  3  includes a pair of first and second polarizing sections  3 A and  3 B. The first and second polarizing sections  3 A and  3 B are arranged such that the polarization direction of the first polarizing section  3 A differs from the polarization direction of the second polarizing section  3 B by 90°. The first and second polarizing sections  3 A and  3 B are aligned to the left and right of each other (i.e., an alignment direction is a horizontal direction of the sun visor  1 ) with respect to the frame  2  of the sun visor  1  as seen in  FIGS. 1 and 2 .  
      For example, the first polarizing section  3 A is arranged such that the polarization direction of the first polarizing section  3 A is the vertical direction with respect to the sun visor  1  in  FIG. 1 . Therefore, the first polarizing section  3 A passes light that oscillates in the vertical direction and blocks light that oscillates in the horizontal direction. In such case, the second polarizing section  3 B is arranged such that the polarization direction of the second polarizing section  3 B is the horizontal direction with respect to the sun visor  1  in  FIG. 1 . Therefore, the second polarizing section  3 B passes light that oscillates in the horizontal direction and blocks light that oscillates in the vertical direction. The border between the first polarizing section  3 A and the second polarizing section  3 B is positioned approximately at the midpoint along the horizontal length of the main polarizing plate unit  3  as shown in  FIGS. 1 and 2 . Thus, the first polarizing section  3 A and the second polarizing section  3 B of the main polarizing plate unit  3  are approximately the same size and have generally the same shape.  
      The first movable polarizing plate  4  is mounted in the opening  2 A of the frame  2  such that the first movable polarizing plate  4  can be moved horizontally (left and right direction in  FIGS. 1 and 2 ) with respect to the main polarizing plate unit  3  that is fixedly coupled to the frame  2 . The first movable polarizing plate  4  has approximately the same size and shape as the first polarizing section  3 A of the main polarizing plate unit  3 . The first movable polarizing plate  4  is configured and arranged such that the polarization direction of the first movable polarizing plate  4  is substantially the same as the polarization direction of the first polarizing section  3 A of the main polarizing plate unit  3  (i.e., the vertical direction of the sun visor  1  in this example). In this embodiment, the polarization direction of the first movable polarizing plate  4  is preferably identical to the polarization direction of the first polarizing section  3 A of the main polarizing plate unit  3 . Thus, the first movable polarizing plate  4  passes light that oscillates in the vertical direction and blocks light that oscillates in the horizontal direction.  
      The second movable polarizing plate  5  is mounted in the opening  2 A of the frame  2  such that the second movable polarizing plate  5  can be moved horizontally (left and right direction in  FIGS. 1 and 2 ) with respect to the main polarizing plate unit  3  that is fixedly coupled to the frame  2 . The second movable polarizing plate  5  has approximately the same size and shape as the second polarizing section  3 B of the main polarizing plate unit  3 . In other words, in the first embodiment, the first and second polarizing sections  3 A and  3 B of the main polarizing plate unit  3  and the first and second movable polarizing plates  4  and  5  have approximately the same size and shape. The second movable polarizing plate  5  is configured and arranged such that the polarization direction of the second movable polarizing plate  5  is substantially the same as the polarization direction of the second polarizing section  3 B of the main polarizing plate unit  3  (i.e., the horizontal direction of the sun visor  1  in this example). In this embodiment, the polarization direction of the second movable polarizing plate  5  is preferably identical to the polarization direction. Thus, the second movable polarizing plate  5  passes light that oscillates in the horizontal direction and blocks light that oscillates in the vertical direction.  
      Although in this embodiment the polarization direction of the first movable polarizing plate  4  is exactly the same as the polarization direction of the first polarizing section  3 A of the main polarizing plate unit  3 , it is acceptable for these polarizing directions to be slightly different (e.g., up to approximately 5°). Similarly, it is acceptable for the polarization direction of the second movable polarizing plate  5  to be slightly different (e.g., up to approximately 5°) from the polarization direction of the second polarizing section  3 B of the main polarizing plate unit  3 .  
      With the present invention, since the first movable polarizing plate  4  and the second movable polarizing plate  5  are provided which can move with respect to the main polarizing plate unit  3  having the first polarizing section  3 A and the second polarizing section  3 B, the area of the sun visor  1  where light is blocked can be selected by moving the first and second movable polarizing plates  4  and  5  so as to change portions in which the first and second movable polarizing plates  4  and  5  overlap with the first and second polarizing sections  3 A and  3 B. Moreover, the size of the area of the sun visor  1  where light is blocked can be adjusted by adjusting the length (width) of the overlapping portions between the first and second movable polarizing plates  4  and  5  and the first and second polarizing sections  3 A and  3 B.  
      Referring now to  FIGS. 3-16 , method of selecting the light-blocking area in the sun visor  1  described above will now be explained.  
     Full Transmissive Area  
       FIG. 3  is a cross sectional view of the sun visor  1  showing a positional relationship of the main polarizing plate unit  3  and the first and second movable polarizing plates  4  and  5  for obtaining a full transmissive area throughout the entire surface of the sun visor  1 . In order to achieve a state in which light is transmitted (allowed to pass through) across the entire surface of the sun visor  1 , the first movable polarizing plate  4  is moved to be aligned with the left half of the opening  2 A of the frame  2  and the second movable polarizing plate  5  is moved to be aligned with the right half of the opening  2 A of the frame  2 , as shown in  FIG. 3 . In other words, the entirety of the first movable polarizing plate  4  is overlapped with the first polarizing section  3 A of the main polarizing plate unit  3  and the entirety of the second movable polarizing plate  5  is overlapped with the second polarizing section  3 B of the main polarizing plate unit  3 .  
      As mentioned above, the polarization direction of the first movable polarizing plate  4  is the same as the polarization direction of the first polarizing section  3 A of the main polarizing plate unit  3  (e.g., the vertical direction of the sun visor  1 ) and the polarization direction of the second movable polarizing plate  5  is the same as the polarization direction of the second polarizing section  3 B of the main polarizing plate unit  3  (e.g., the horizontal direction of the sun visor  1 ). Therefore, as seen in the diagram (A) of  FIG. 4 , light P 1  incident on the first movable polarizing plate  4  and light P 2  incident on the second polarizing section  3 B of the main polarizing plate unit  3  are transmitted. (As used herein, “transmitted” means that the portion of the incident light P 1  oscillating in the polarization direction of the first movable polarizing plate  4  and the first polarizing section  3 A (e.g., the vertical direction of the sun visor  1 ) is transmitted and the portion of the incident light P 1  oscillating in a direction perpendicular to the polarization direction (e.g., the horizontal direction of the sun visor  1 ) is blocked. Likewise, the portion of the incident light P 2  oscillating in the polarization direction of the second movable polarizing plate  5  and the second polarizing section  3 B (e.g., the horizontal direction of the sun visor  1 ) is transmitted and the portion of the incident light P 2  oscillating in a direction perpendicular to the polarization direction (e.g., the vertical direction of the sun visor  1 ) is blocked. The same meaning of “transmitted” applies in the following explanations.)  
      Consequently, as shown in the diagram (B) of  FIG. 4 , the entire surface SI of the sun visor  1  becomes a light transmissive area.  
     Full Light-Blocking Area  
       FIG. 5  is a cross sectional view of the sun visor  1  showing a positional relationship of the main polarizing plate unit  3  and the first and second movable polarizing plates  4  and  5  for obtaining a full light-blocking area throughout the entire surface of the sun visor  1 . In order to achieve a state in which light is blocked across the entire surface of the sun visor  1 , the first movable polarizing plate  4  is moved to be aligned with the right half of the opening  2 A of the frame  2  and the second movable polarizing plate  5  is moved to be aligned with the left half of the opening  2 A of the frame  2 , as shown in  FIG. 5 . In other words, the entirety of the first movable polarizing plate  4  is overlapped with the second polarizing section  3 B of the main polarizing plate unit  3  and the entirety of the second movable polarizing plate  5  is overlapped with the first polarizing section  3 A of the main polarizing plate unit  3 .  
      As mentioned above, the polarization direction of the first movable polarizing plate  4  (e.g., the vertical direction of the sun visor  1 ) differs from the polarization direction of the second polarizing section  3 B of the main polarizing plate unit  3  (e.g., the horizontal direction of the sun visor  1 ) by 90° and the polarization direction of the second movable polarizing plate  5  (e.g., the horizontal direction of the sun visor  1 ) differs from the polarization direction of the first polarizing section  3 A of the main polarizing plate unit  3  (e.g., the vertical direction of the sun visor  1 ). Therefore, as shown in the diagram (A) of  FIG. 6 , light P 1  incident on the first polarizing section  3 A of the main polarizing plate unit  3  and light P 2  incident on the first movable polarizing plate  4  are blocked.  
      Consequently, as shown in the diagram (B) of  FIG. 6 , the entire surface SI of the sun visor  1  becomes a light-blocking area.  
     Light-Blocking Area on Left Side  
       FIG. 7  is a cross sectional view of the sun visor  1  showing a positional relationship of the main polarizing plate unit  3  and the first and second movable polarizing plates  4  and  5  for obtaining a light-blocking area on the left side (as seen in  FIG. 1 ) of the sun visor  1 . In order to achieve a state in which a light-blocking area is positioned on the left half of the sun visor  1 , the first and second movable polarizing plates  4  and  5  are both moved to be aligned with the left half of the opening  2 A of the frame  2 . In other words, the first and second movable polarizing plates  4  and  5  are moved to overlap with the first polarizing section  3 A of the main polarizing plate unit  3  as shown in  FIG. 7 .  
      As mentioned above, the polarization direction of the second movable polarizing plate  5  (e.g., the horizontal direction of the sun visor  1 ) differs from the polarization direction of the first polarizing section  3 A of the main polarizing plate unit  3  (e.g., the vertical direction of the sun visor  1 ) by 90°. Therefore, light P 1  incident on the first movable polarizing plate  4  is blocked as shown in the diagram (A) of  FIG. 8 . Meanwhile, light P 2  incident on the second polarizing section  3 B of the main polarizing plate unit  3  is transmitted. More specifically, as mentioned above, the portion of the incident light P 2  oscillating in the polarization direction of the second polarizing section  3 B (e.g., the horizontal direction of the sun visor  1 ) is transmitted and the portion of the incident light P 2  oscillating in a direction perpendicular to the polarization direction (e.g., the vertical direction of the sun visor  1 ) is blocked.  
      Consequently, as shown in the diagram (B) of  FIG. 8 , the left half S 1   a  of the surface S 1  of the sun visor  1  becomes a light-blocking area and the right half S 1   b  becomes a light transmissive area.  
      Moreover, from the state shown in  FIG. 7 , the light-blocking area can be expanded rightward by moving the position of the first movable polarizing plate  4  to the right as shown in  FIG. 9 .  FIG. 9  is a cross sectional view of the sun visor  1  showing a positional relationship of the main polarizing plate unit  3  and the first and second movable polarizing plates  4  and  5  that is adjusted from the positional relationship shown in  FIG. 7  to expand the light-blocking area. In this case, light P 1  incident on the first movable polarizing plate  4  and light P 1 ′ incident of the first polarizing section  3 A are blocked as shown in the diagram (A) of  FIG. 10 . Meanwhile, light P 2  incident on the second polarizing section  3 B of the main polarizing plate unit  3  is transmitted. The size of the light-blocking area in the sun visor  1  can be adjusted between a state with the light-blocking area on the left side as shown in  FIG. 7  and a state with full light-blocking area as shown in  FIG. 5  by moving the first movable polarizing plate  4 .  
      Consequently, as shown in the diagram (B) of  FIG. 10 , the light is blocked in the area S 1   a ′, which is bigger than the left half S I a as shown in the diagram (B) of  FIG. 8 .  
     Light-Blocking Area on Right Side  
       FIG. 11  is a cross sectional view of the sun visor  1  showing a positional relationship of the main polarizing plate unit  3  and the first and second movable polarizing plates  4  and  5  for obtaining a light-blocking area on the right side (as seen in  FIG. 1 ) of the sun visor  1 . In order to achieve a state in which a light-blocking area is positioned on the right half of the sun visor  1 , the first and second movable polarizing plates  4  and  5  are both moved to be aligned with the right half of the opening  2 A of the frame  2 . In other words, the first and second movable polarizing plates  4  and  5  are both moved to overlap with the second polarizing section  3 B of the main polarizing plate unit  3  as shown in  FIG. 11 .  
      As mentioned above, the polarization direction of the first movable polarizing plate  4  (e.g., the vertical direction of the sun visor  1 ) differs from the polarization direction of the second polarizing section  3 B of the main polarizing plate unit  3  (e.g., the horizontal direction of the sun visor I) by 90°. Therefore, light P 2  incident on the first movable polarizing plate  4  is blocked. On the other hand, light PI incident on the first polarizing section  3 A of the main polarizing plate unit  3  is transmitted as shown in the diagram (A) of  FIG. 12 . More specifically, as mentioned above, the portion of the incident light P 1  oscillating in the polarization direction of the first polarizing section  3 A is transmitted and the portion of the incident light oscillating in a direction perpendicular to the polarization direction of the first polarizing section  3 A is blocked.  
      Consequently, as shown in the diagram (B) of  FIG. 12 , the left half S 1   a  of the sun visor  1  becomes a light transmissive area and the right half S 1   b  becomes a light-blocking area.  
      Moreover, from the state shown in  FIG. 11 , the light-blocking area can be expanded leftward by moving the position of the second movable polarizing plate  5  to the left as shown in  FIG. 13 .  FIG. 13  is a cross sectional view of the sun visor  1  showing a positional relationship of the main polarizing plate unit  3  and the first and second movable polarizing plates  4  and  5  that is adjusted from the positional relationship shown in  FIG. 11  for expanding the light-blocking area. The size of the light-blocking area in the sun visor  1  can be adjusted between a state with the light-blocking area on the right side as shown in  FIG. 11  and a state with full light-blocking area as shown in  FIG. 5  by moving the second movable polarizing plate  5 .  
     Light-Blocking Area in Middle Portion  
       FIG. 14  is a cross sectional view of the sun visor  1  showing a positional relationship of the main polarizing plate unit  3  and the first and second movable polarizing plates  4  and  5  for obtaining a light-blocking area in the middle portion of the sun visor  1 . In order to achieve a state in which a light-blocking area is positioned in a middle portion of the sun visor  1 , the first and second movable polarizing plates  4  and  5  are moved to positions in a middle portion of the opening  2 A, as shown in  FIG. 14 .  
      As mentioned above, the polarization direction of the first movable polarizing plate  4  (e.g., the vertical direction of the sun visor  1 ) differs from the polarization direction of the second polarizing section  3 B of the main polarizing plate unit  3  (e.g., the horizontal direction of the sun visor  1 ) by 90° and the polarization direction of the second movable polarizing plate  5  (e.g., the horizontal direction of the sun visor  1 ) differs from the polarization direction of the first polarizing section  3 A of the main polarizing plate unit  3  (e.g., the vertical direction of the sun visor  1 ) by 90°. Therefore, as shown in  FIG. 14  and the diagram (A) of  FIG. 15 , light P 3  incident on an area corresponding to a rightward portion of the first polarizing section  3 A where it overlaps with the second movable polarizing plate  5  and light P 4  incident on an area corresponding to a leftward portion of the second polarizing section  3 B where it overlaps with the first movable polarizing plate  4  are blocked. Meanwhile, light P 5  incident on an area corresponding to a leftward portion of the first polarizing section  3 A of the main polarizing plate unit  3  and light P 6  incident on an area corresponding to a rightward portion of the second polarizing section  3 B of the main polarizing plate unit  3  are transmitted.  
      Consequently, as shown in the diagram (B) of  FIG. 15 , a middle portion S 1   c  of the sun visor  1  becomes a light-blocking area and side portions S 1   d  and S 1   e  on both sides of the middle portion S 1   c  become light transmissive areas.  
      Moreover, as shown in  FIG. 16 , the width W of the light-blocking area can be changed (expanded or shrunk) and the position of the light-blocking area can be moved by moving the first and second movable polarizing plates  4  and  5  in left and right direction.  
      With the sun visor  1  in accordance with the first embodiment of the present invention, the first and second movable polarizing plates  4  and  5  are arranged to sandwich the main polarizing plate unit  3  therebetween. The first movable polarizing plate  4  and the second movable polarizing plate  5  can be moved by extending one&#39;s hand to the front side or the back side of the aligned polarizing plate unit  3 . Thus, when one of the first and second movable polarizing plates  4  and  5  is being moved, the other one of the first and second movable polarizing plates  4  and  5  (i.e., the one not being moved) does not impede or interfere with the movement of the one of the first and second movable polarizing plates  4  and  5  that is being moved.  
      Alternatively, a pair of operating levers R 1  and R 2  can be provided on the first and second movable polarizing plates  4  and  5 , respectively, as shown in the diagrams (A) to (D) of FIGS.  19  in order to make it easier to operate the first and second movable polarizing plates  4  and  5 . In such case too, the first operating lever R 1  of the first movable polarizing plate  4  and the second operating lever R 2  of the second movable polarizing plate  5  do not interfere with (contact) each other when the first and second movable polarizing plates  4  and  5  are moved. If the first and second movable polarizing plates  4  and  5  are arranged on the same side of the main polarizing plate unit  3 , then the first movable polarizing plate  4  may contact the lever  2  as shown in  FIG. 20 .  
      As described previously, with the present invention, the light-blocking area can be selected and the width of the light-blocking area can be adjusted by moving (changing the positions of) the first and second movable polarizing plates  4  and  5 .  
      Moreover, the first movable polarizing plate  4  has substantially the same size and the same shape as the first polarizing section  3 A of the main polarizing plate unit  3 . Consequently, light that oscillates in the polarization direction of the first movable polarizing plate  4  and the first polarizing section  3 A can be transmitted across the entire surface of the first polarizing section  3 A and the first movable polarizing plate  4  when the first polarizing section  3 A and the first movable polarizing plate  4  are entirely overlapping each other.  
      Similarly, the second movable polarizing plate  5  has substantially the same size and the same shape as the second polarizing section  3 B of the main polarizing plate unit  3 . Consequently, light that oscillates in the polarization direction of the second movable polarizing plate  5  and the second polarizing section  3 B can be transmitted across the entire surface of the second polarizing section  3 B and the second movable polarizing plate  5  when the second polarizing section  3 B and the second movable polarizing plate  5  are entirely overlapping each other.  
      Additionally, the first polarizing section  3 A and the second polarizing section  3 B of the main polarizing plate unit  3  have substantially the same size and shape. Therefore, both the transmission and the blocking of light can be accomplished over the entire surface of the main polarizing plate unit  3 .  
      Referring now to  FIGS. 17 and 18 , a modified structure of the sun visor  10  in accordance with the first embodiment will be explained. In the sun visor  10  with the modified structure, transparent reinforcing plates  13 A,  13 B,  14  and  15  have been added. The transparent reinforcing plate  13 A (first transparent reinforcing plate) is adhesively attached to a rearward side (top side in  FIG. 17 ) of the first polarizing section  3 A of the main polarizing plate unit  3  that faces in the direction of the first movable polarizing plate  4 . The transparent reinforcing plate  13 B (second transparent reinforcing plate) is adhesively attached to the frontward side (bottom side in  FIG. 17 ) of the second polarizing section  3 B of the main polarizing plate unit  3  that faces in the direction of the second movable polarizing plate  5 . The transparent reinforcing plate  14  (third transparent reinforcing plate) is adhesively attached to an outward side (top side in  FIG. 17 ) of the first movable polarizing plate  4  that faces away from the main polarizing plate unit  3 . The transparent reinforcing plate  15  (fourth transparent reinforcing plate) is adhesively attached to an outward side bottom side in  FIG. 17 ) of the second movable polarizing plate  5  that faces away from the main polarizing plate unit  3 .  
      With the modified structure of the sun visor  10 , a reinforcing plate does not exist between the first movable polarizing plate  4  and the second polarizing section  3 B or between the second movable polarizing plate  5  and the first polarizing section  3 A when light is being blocked by the first movable polarizing plate  4  and the second polarizing section  3 B or by the second movable polarizing plate  5  and the second polarizing section  3 B. Consequently, the light can be blocked reliably.  
      If a reinforcing plate were disposed between the first movable polarizing plate  4  and the second polarizing section  3 B or between the second movable polarizing plate  5  and the first polarizing section  3 A, then, for example, the horizontally polarized light exiting the second movable polarizing plate  5  might be scattered by the reinforcing plate, thereby causing vertically oscillating light to strike the first polarizing section  3 A. Since vertically oscillating light passes through the first polarizing section  3 A, the sun visor would not be able to reliably block the light.  
     Second Embodiment  
      Referring now to FIGS.  21  to  35 , a light blocking device in accordance with a second embodiment will now be explained. In view of the similarity between the first and second embodiments, the parts of the second embodiment that are identical to the parts of the first embodiment will be given the same reference numerals as the parts of the first embodiment. Moreover, the descriptions of the parts of the second embodiment that are identical to the parts of the first embodiment may be omitted for the sake of brevity.  
      In the second embodiment, the light blocking device is applied to a sunroof unit  100  of a vehicle.  FIG. 21  shows a vehicle body  101  of the vehicle or automobile provided with the sunroof unit  100 . The vehicle body  101  has a passenger compartment  102  and a ceiling support frame  104  provided around the perimeter of the ceiling side of the passenger compartment  102 .  
      As shown in  FIGS. 21 and 22 , the ceiling support frame  104  comprises a pair of left and right roof side rails  105 , a front side rail  106  connected to the front ends (longitudinally frontward ends) of the left and right roof side rails  105 , and a rear side rail  107  connected to the rear ends (longitudinally rearward ends) of the left and right roof side rails  105 . A roof panel  108  is mounted to the ceiling support frame  104 . As shown in FIGS.  21  to  23 , a sunroof window opening  109  is provided in the roof panel  108 .  
       FIG. 23  is a cross sectional view of the roof portion of the vehicle taken along a section line  23 - 23  of  FIG. 21  illustrating a portion where a main polarizing window plate unit (main polarizing plate unit)  110  is secured (fixed) to the roof panel  108 . As shown in  FIG. 23 , the main polarizing window plate unit  110  is fixed into the sunroof window opening  109 . As shown in  FIGS. 21 and 22 , a first polarizing section  110   a  is provided on a frontward portion of the main polarizing window plate unit  110  and a second polarizing section  110   b  is provided on a rearward portion of the main polarizing window plate unit  110 .  
      The first polarizing section  110   a  is preferably positioned over the front seat (not shown) of the vehicle and the second polarizing section  110   b  is preferably positioned over the rear seat (not shown). The first and second polarizing sections  110   a  and  110   b  can be made by applying a coating (polarizing layer, i.e., polarizing film) for light polarization onto a sheet of transparent glass or transparent resin. The first and second polarizing sections  110   a  and  110   b  are arranged such that the polarization direction of the first polarizing section  110   a  differs from the polarization direction of the second polarizing section  110   b  by 90°. The first and second polarizing sections  110   a  and  110   b  are aligned to the front and rear of each other (i.e., an alignment direction is front to rear direction of the vehicle) with respect to the sunroof window opening  109  of the roof panel  108  as seen in  FIGS. 21 and 22 .  
      For example, the first polarizing section  110   a  is arranged such that the polarization direction of the first polarizing section  110   a  is the lengthwise direction with respect to the vehicle in  FIG. 21 . Therefore, the first polarizing section  110   a  passes light that oscillates in the longitudinal direction of the vehicle and blocks light that oscillates in the widthwise direction of the vehicle. In such case, the second polarizing section  110   b  is arranged such that the polarization direction of the second polarizing section  110   b  is the widthwise direction with respect to the vehicle in  FIG. 21 . Therefore, the second polarizing section  110   b  passes light that oscillates in the widthwise direction and blocks light that oscillates in the lengthwise direction. The border between the first polarizing section  110   a  and the second polarizing section  110   b  is positioned approximately at the midpoint along the longitudinal length of the main polarizing window plate unit  110  as shown in  FIGS. 21 and 22 . Thus, the first polarizing section  110   a  and the second polarizing section  110   b  of the main polarizing window plate unit  110  are approximately the same size and have generally the same shape.  
      As shown in  FIG. 23 , first and second rail frames  111  and  112  for supporting first and second movable polarizing window plates  113  and  114 , respectively, are mounted to the ceiling support frame  104  below the main polarizing window plate unit  110 . The first and second rail frames  111  and  112  are arranged above and below each other in an overlapping fashion as shown in FIGS.  23  to  25 . As shown in  FIG. 23 , left and right guide rails  111   a  are formed on both transversely facing sides (left and right sides in the widthwise direction of the vehicle) of the first rail frame  111  and left and right guide rails  112   a  are formed on both transversely facing sides (left and right sides in the widthwise direction of the vehicle) of the second rail frame  112 .  
      The first movable polarizing window plate (movable polarizing plate)  113  is supported at both transversely facing side portions thereof on the left and right guide rails  111   a  such that it can move freely in the longitudinal direction of the vehicle. The first movable polarizing window plate  113  has a polarization direction that is substantially the same as the polarization direction of the first polarizing section  110   a  of the main polarizing window plate unit  110 . More specifically, the first movable polarizing window plate  113  is configured to block the transmission of light that oscillates in the widthwise direction of the vehicle. The second movable polarizing window plate (movable polarizing plate)  114  is supported at both transversely facing side portions thereof on the left and right guide rails  112   a  such that it can move freely in the longitudinal direction of the vehicle. The second movable polarizing window plate  114  has a polarization direction that is substantially the same as the polarization direction of the second polarizing section  110   b  of the main polarizing window plate unit  110 . More specifically, the second movable polarizing window plate  114  is configured to block the transmission of light that oscillates in the lengthwise direction of the vehicle. The first movable polarizing window plate  113  and the second movable polarizing window plate  114  are arranged in different positions along the direction perpendicular to the planes thereof (i.e., the vertical direction of the vehicle) such that each can be moved independently with respect to the main polarizing window plate unit  110  without interfering with each other. In this embodiment, both of the first and second movable polarizing window plates  113  and  114  are arranged below (on the same side of) the main polarizing window plate unit  110  as seen in  FIG. 23 .  
      Although not shown in  FIG. 23 , guide rollers are preferably mounted to the transversely facing side portions of the first and second movable polarizing window plates  113  and  114 . The first and second movable polarizing window plates  113  and  114  are supported on the guide rails  111   a  and  112   a , respectively, with the guide rollers such that the first and second movable polarizing window plates  113  and  114  do not vibrate or otherwise move in the vertical direction.  
       FIG. 24  is a schematic front perspective view of the roof portion of the vehicle shown in  FIGS. 21 and 22  in a state in which the roof panel  108  and the main polarizing window plate unit  110  are removed for the illustration purpose.  
      As shown in  FIGS. 25 and 26 , a rear support part  111   b  is provided on the longitudinally rearward end of the first rail frame  111 . Similarly, a rear support part (not shown) is provided on the rearward end of the second rail frame  112 . As shown in  FIG. 25 , a drive motor  115  is mounted to the rear support part  111   b  of the first rail frame  111  and a drive motor  116  is mounted to the rear support part of the second rail frame  112 . As shown in  FIG. 27 , a drive gear  115   a  is arranged to be driven by the drive motor  115  and a drive gear  116   a  is arranged to be driven by the drive motor  116 . Each of the drive motors  115  and  116  can be driven by turning a switch (not shown) forward and backward.  
      As shown in  FIG. 27 , the drive gear  115   a  meshes with drive wires  115   b  and  115   c  that are coupled to both transverse sides of the first movable polarizing window plate  113 . More specifically, one end of each of the drive wires  115   b  and  115   c  is attached to one of two brackets  113   a  provided on opposite side portions of the first movable polarizing window plate  113  and the other end of each of the drive wires  115   b  and  115   c  is free. Additionally, guide parts (not shown) that extend along the guide rails  111   a  are provided such that the other ends of the drive wires  115   b  and  115   c  that are free can move back and forth in the longitudinal direction of the vehicle.  
      When the drive motor  115  rotates the drive gear  115   a  forward or backward, the drive wires  115   b  and  115   c  are moved forward or backward along the lengthwise direction and, as indicated with the arrows  17  and  18  in  FIG. 28 , the first movable polarizing window plate  113  is moved forward or backward along the longitudinal direction of the vehicle. Since a conventional technology can be used for moving the first movable polarizing window plate  113 , the details of the relationship between the drive gear  115   a  and the drive wires  115   b  and  115   c  are omitted in the drawings.  
      Similarly, as shown in  FIG. 27 , the drive gear  116   a  meshes with drive wires  116   b  and  116   c  that are coupled to both transverse sides of the second movable polarizing window plate  114 . One end of each of the drive wires  116   b  and  116   c  is attached to one of two brackets  114   a  provided on opposite side portions of the second movable polarizing window plate  114  and the other end of each of the drive wires  116   b  and  116   c  is free. Additionally, guide parts (not shown) that extend along the guide rails  112   a  are provided such that the other ends of the drive wires  116   b  and  116   c  can move back and forth in the longitudinal direction of the vehicle.  
      When the drive motor  116  rotates the drive gear  116   a  forward or backward, the drive wires  116   b  and  116   c  are moved forward or backward along the lengthwise direction and, as indicated with the arrows  19  and  20  in  FIG. 28 , the second movable polarizing window plate  114  is moved forward or backward along the longitudinal direction of the vehicle. Since a conventional technology can be used for moving the second movable polarizing window plate  114 , the details of the relationship between the drive gear  116   a  and the drive wires  116   b  and  116   c  are omitted in the drawings.  
      Together, the left and right roof side rails  105 , the front side rail  106 , the rear side rail  107 , the main polarizing window plate unit  110 , the first and second rail frames  111  and  112 , the first and second drive motors  115  and  116 , the drive gears  115   a  and  116   a , the drive wires  115   b  and  115   c  and  116   b  and  116   c , and the first and second movable polarizing window plates  113  and  114  preferably constitute the sunroof unit  100  of the present invention. Meanwhile, the main polarizing window plate unit  110  and the first and second movable polarizing window plates  113  and  114  preferably constitute the light blocking device.  
      Referring now to FIGS.  29  to  35 , the operation of the sunroof unit  100  described above will now be explained. First, an explanation will be given on making the entire area of the sunroof window opening  109  to be fully light transmitting. Then, an explanation will be given on making the entire area of the sunroof window opening  109  to be fully light blocking. Finally, explanations will be given on making a first part of the sunroof window opening  109  to be light blocking and a second part to be light transmitting; i.e., one of the front and rear portions of the sunroof window opening  109  being light transmitting and the other of the front and rear portions of the sunroof window opening  109  being light blocking, or light blocking a middle portion of the sunroof window opening  109 .  
     Full Transmissive Area  
       FIG. 29  includes a diagram (A) illustrating a schematic side view of the vehicle with a positional relationship of the first and second movable polarizing window plates  113  and  114  with respect to the main polarizing window plate unit  110  for allowing the light to transmit through the entire sunroof window opening  109 , and a diagram (B) for showing the light transmissive area of the sunroof window opening  109  corresponding to a state of the sunroof unit  100  illustrated in the diagram (A) in accordance with the second embodiment of the present invention.  
      In order to achieve a state in which light is transmitted (allowed to pass through) across the entire sunroof window opening  109 , the first movable polarizing window plate  113  is moved to the forward side of the sunroof window opening  109  and the second movable polarizing window plate  114  is moved to the rearward side of the sunroof window opening  109  as shown in the diagram (A) of  FIG. 29 . In other words, the first movable polarizing window plate  113  is positioned such that it overlaps with the first polarizing section  110   a  of the main polarizing window plate unit  110  and the second movable polarizing window plate  114  is positioned such that it overlaps with the second polarizing section  110   b  of the main polarizing window plate unit  110 .  
      Since the polarization direction of the first movable polarizing window plate  113  is the same as the polarization direction of the first polarizing section  110   a  (e.g., the longitudinal direction of the vehicle) and the polarization direction of the second movable polarizing window plate  114  is the same as the polarization direction of the second polarizing section  10   b  (e.g., the widthwise direction of vehicle), the light incident on both first and second polarizing sections  110   a  and  110   b  of the main polarizing window plate unit  110  is transmitted. (As used herein, “transmitted” means that the portion of the light incident on each of the first and second polarizing sections  110   a  and  110   b  that oscillates in the polarization direction of the respective one of the first and second polarizing section  110   a  and  110   b  is transmitted and the portion of the incident light oscillating in a direction perpendicular to the respective polarization direction is blocked. The same meaning of “transmitted” applies in the explanations that follow.)  
      Consequently, as shown in the diagram (B) of  FIG. 29 , the entire area T 1  of the sunroof window opening  109  becomes a light transmissive area.  
     Full Light-Blocking Area  
       FIG. 30  includes a diagram (A) illustrating a schematic side view of the vehicle with a positional relationship of the first and second movable polarizing window plates  113  and  114  with respect to the main polarizing window plate unit  110  for blocking the light in the entire sunroof window opening  109 , and a diagram (B) for showing the light transmissive area of the sunroof window opening  109  corresponding to a state of the sunroof unit  100  illustrated in the diagram (A) in accordance with the second embodiment of the present invention;  
      In order to achieve a state in which light is blocked (not allowed to pass through) across the entire sunroof window opening  109 , the second movable polarizing window plate  114  is moved to the forward side of the sunroof window opening  109  and the first movable polarizing window plate  113  is moved to the rearward side of the sunroof window opening  109 , as shown in the diagram (A) of  FIG. 30 . In other words, the first movable polarizing window plate  113  is positioned such that it overlaps with the second polarizing section  110   b  of the main polarizing window plate unit  110  and the second movable polarizing window plate  114  is positioned such that it overlaps with the first polarizing section  110   a  of the main polarizing window plate unit  110 .  
      Since the polarization direction of the first movable polarizing window plate  113  differs from the polarization direction of the second polarizing section  110   b  by 90° and the polarization direction of the second movable polarizing window plate  114  differs from the polarization direction of the first polarizing section  110   a  by 90°, the light incident on both first and second polarizing sections  110   a  and  110   b  of the main polarizing window plate unit  110  is blocked.  
      Consequently, as shown in the diagram (B) of  FIG. 30 , the entire area Ti of the sunroof window opening  109  becomes a light-blocking area.  
     Light-Blocking Area on Frontward Side  
       FIG. 31  includes a diagram (A) illustrating a schematic side view of the vehicle with a positional relationship of the movable polarizing window plates with respect to the polarizing window plate when the frontward side of the sunroof window opening  109  is made into the light-blocking area, and a diagram (B) for showing the light transmissive area of the sunroof window opening  109  corresponding to a state of the sunroof unit  100  illustrated in the diagram (A) in accordance with the second embodiment of the present invention.  
      In order to achieve a state in which a light-blocking area is positioned on the frontward half of the sunroof window opening  109 , both of the first and second movable polarizing window plates  113  and  114  are moved to the frontward side of the sunroof window opening  109  as shown in the diagram (A) of  FIG. 31 . In other words, the first movable polarizing window plate  113  and the second movable polarizing window plate  114  are both positioned such that they overlap with the first polarizing section  110   a  of the main polarizing window plate unit  110 .  
      Since the polarization direction of the first movable polarizing window plate  113  differs from the polarization direction of the second movable polarizing window plate  114  by 90°, the light incident on the first polarizing section  110   a  of the main polarizing window plate unit  110  is blocked.  
      Consequently, as shown in the diagram (B) of  FIG. 31 , the frontward half T 1   a  of the sunroof window opening  109  becomes a light-blocking area and the rearward half T 1   b  of the sunroof window opening  109  becomes a light transmissive area.  
      Since the polarization directions of the first movable polarizing window plate  113  and the second polarizing section  110   b  differ by 90° and the polarization directions of the second movable polarizing window plate  114  and the first polarizing section  110   a  differ by 90°, the light-blocking area can be expanded rearward by moving the first movable polarizing window plate  113  rearward from the position shown in the diagram (A) of  FIG. 31 .  
     Light-Blocking Area on Rearward Side  
       FIG. 32  includes a diagram (A) illustrating a schematic side view of the vehicle with a positional relationship of the first and second movable polarizing window plates  113  and  114  with respect to the main polarizing window plate unit  110  when the rearward side of the sunroof window opening  109  is made into the light-blocking area, and a diagram (B) for showing the light transmissive area of the sunroof window opening  109  corresponding to a state of the sunroof unit  100  illustrated in the diagram (A) in accordance with the second embodiment of the present invention;  
      In order to achieve a state in which a light-blocking area is positioned on the rearward half of the sunroof window opening  109 , both of the first and second movable polarizing window plates  113  and  114  are moved to the rearward side of the sunroof window opening  109  as shown in the diagram (A) of  FIG. 32 . In other words, the first movable polarizing window plate  113  and the second movable polarizing window plate  114  are both positioned such that they overlap with the second polarizing section  110   b  of the main polarizing window plate unit  110 .  
      Since the polarization direction of the first movable polarizing window plate  113  differs from the polarization direction of the second movable polarizing window plate  114  by 90°, the light incident on the second polarizing section  110   b  of the main polarizing window plate unit  110  is blocked.  
      Consequently, as shown in the diagram (B) of  FIG. 32 , the rearward half T 1   b  of the sunroof window opening  109  becomes a light-blocking area and the frontward half T 1   a  of the sunroof window opening  109  becomes a light transmissive area.  
      When the first and second movable polarizing window plates  113  and  114  are both moved rearward, the head clearance Hd can be increased as shown in  FIG. 35 .  
      Since the polarization directions of the first movable polarizing window plate  113  and the second polarizing section  110   b  differ by 90° and the polarization directions of the second movable polarizing window plate  114  and the first polarizing section  110   a  differ by 90°, the light-blocking area can be expanded frontward as shown in the diagram (B) of  FIG. 33  by moving the second movable polarizing window plate  114  frontward as shown in the diagram (A) of  FIG. 33 .  
     Light-Blocking Area in Middle Portion  
       FIG. 34  includes a diagram (A) illustrating a schematic side view of the vehicle with a positional relationship of the first and second movable polarizing window plates  113  and  114  with respect to the main polarizing window plate unit  110  when the middle portion of the sunroof window opening  109  is made into the light-blocking area, and a diagram (B) for showing the light transmissive area of the sunroof window opening  109  corresponding to a state of the sunroof unit  100  illustrated in the diagram (A) in accordance with the second embodiment of the present invention.  
      In order to achieve a state in which a light-blocking area is positioned in a middle portion of the sunroof window opening  109 , both of the first and second movable polarizing window plates  113  and  114  are moved to the middle portion of the sunroof window opening  109  as shown in the diagram (A) of  FIG. 34 .  
      Since the polarization direction of the first movable polarizing window plate  113  differs from the polarization direction of the second polarizing section  110   b  of the main polarizing window plate unit  110  by 90° and the polarization direction of the second movable polarizing window plate  114  differs from the polarization direction of the first polarizing section  10   a  of the main polarizing window plate unit  110  by 90°, light incident on a rearward portion of the first polarizing section  110   a  and light incident on a frontward portion of the second polarizing section  110   b  are blocked.  
      Consequently, as shown in the diagram (B) of  FIG. 34 , the middle portion T 1   c  of the sunroof window opening  109  becomes a light-blocking area.  
      Since the polarization directions of the first movable polarizing window plate  113  and the second polarizing section  110   b  differ by 90° and the polarization directions of the second movable polarizing window plate  114  and the first polarizing section  110   a  differ by 90°, the longitudinal dimension L of the light-blocking area in the middle portion T 1   c  of the sunroof window opening  109  can be adjusted by moving the first and second movable polarizing window plates  113  and  114  frontward and rearward.  
      By moving the first and second movable polarizing window plates  113  and  114  as described above, the light-blocking area can be selected and the size (the dimension L in the longitudinal direction of the vehicle) of the light-blocking area can be adjusted.  
      When the main polarizing window plate unit  110  and the first movable polarizing window plate  113  and  114  are made of a transparent glass sheet or transparent resin sheet having a polarizing film applied thereto, effects that are similar to those obtained with the second embodiment can be obtained by forming the respective polarizing film on the bottom surface of the main polarizing window plate unit  110  and on the top surfaces of the first and second movable polarizing window plates  113  and  114 .  
      Since both of the first and second movable polarizing window plates  113  and  114  are arranged on the same side of the main polarizing window plate unit  110 , it is easy to arranged the guide rails  111   a  and  112   a  of the first and second rail frames  111  and  112 , respectively, and the drive motors  115  and  116  even if the sunroof unit  1  is used as the boundary between the inside and the outside of the vehicle.  
     General Interpretation of Terms  
      In understanding the scope of the present invention, the term “comprising” and its derivatives, as used herein, are intended to be open ended terms that specify the presence of the stated features, elements, components, groups, integers, and/or steps, but do not exclude the presence of other unstated features, elements, components, groups, integers and/or steps. The foregoing also applies to words having similar meanings such as the terms, “including”, “having” and their derivatives. Also, the terms “part,” “section,” “portion,” “member” or “element” when used in the singular can have the dual meaning of a single part or a plurality of parts. Also as used herein to describe the above embodiments, the following directional terms “forward, rearward, above, downward, vertical, horizontal, below and transverse” as well as any other similar directional terms refer to those directions of a vehicle equipped with the present invention. Accordingly, these terms, as utilized to describe the present invention should be interpreted relative to a vehicle equipped with the present invention. The terms of degree such as “substantially”, “about” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed.  
      While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired. Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Every feature which is unique from the prior art, alone or in combination with other features, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.