Abstract:
A projector includes a plurality of light modulation elements adapted to modulate a plurality of colored light beams based on image data, a combining optical system adapted to combine the modulated colored light beams to emit image light, and a projection optical system adapted to project the image light emitted from the combining optical system on a projection screen. The light modulation elements are disposed with respect to the combining optical system so that long sides of the respective light modulation elements are adjacent to each other. Signal line cable boards adapted to provide the respective light modulation elements with signals, and coupled to short sides of the respective light modulation elements. A scanning direction of writing the image data to the light modulation elements is set to be parallel to a direction of the short side of an image display area in each of the light modulation elements.

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a projector. 
     2. Related Art 
     Projectors are capable of displaying large screen images, and therefore, draw attention not only as display devices for presentation, but also as image display devices for displaying images required to have high quality, such as movies. Therefore, in the projectors, growth of resolution of light modulation elements is in progress, and there is a tendency of ever-growing sizes of the light modulation elements. The growth of the light modulation element sizes causes growth of sizes of overall optical systems, which incurs growth of the sizes of the projectors, and at the same time, increase in cost. 
     The lower limit of the pitches of the pixels constituting the light modulation elements is generally believed to be in a range of 8 through 9 μm. Therefore, in order for obtaining the resolution of, for example, 4K2K (assumed to be 4096 pixels in the lateral direction×2160 pixels in the vertical direction), the size (the diagonal length) of the area (referred to as an image display area) available for image display in the light modulation elements needs to be equal to or greater than 1.6 inch. 
       FIGS. 6A and 6B  are diagrams showing a configuration of the light modulation element and the optical system in the periphery thereof in a typical projector in the related art. It should be noted that  FIG. 6A  is a perspective view, and  FIG. 6B  is a plan view corresponding to  FIG. 6A , namely a diagram of the configuration shown in  FIG. 6A  viewed from a direction along the arrow a. 
     As shown in  FIGS. 6A and 6B , in the typical projector, the light modulation elements  100 R,  100 G, and  100 B corresponding respectively to red (R), green (G), and blue (B) are each disposed so as to have the long side in the horizontal direction (the direction of the x-axis or the y-axis among the x, y, and z-axes shown in  FIG. 6A ) and the short side in the vertical direction (the vertical direction in  FIG. 6A , namely the direction of the z-axis among the x, y, and z axes). In other words, the light modulation elements  100 R,  100 G, and  100 B are arranged so that one of the short sides of the light modulation element  100 R and one of the short sides of the light modulation element  100 G are adjacent to each other, and further the other of the short sides of the light modulation element  100 G and one of the short sides of the light modulation element  100 B are adjacent to each other, in a similar manner. Further, in this case, in the positional relationship between the light modulation elements  100 R,  100 G, and  100 B, and a cross dichroic prism  110  as a combining optical system, each of the short sides of each of the light modulation elements  100 R,  100 G, and  100 B is disposed along a height direction (the z-axis direction) of four triangular prisms forming the cross dichroic prism  110 . 
     It should be noted that the light modulation elements  100 R,  100 G, and  100 B are arranged to modulate the R, G, and B colored light beams, respectively, based on image data, and the colored light beams modulated by the respective light modulation elements  100 R,  100 G, and  100 B are combined by the cross dichroic prism  110  to be output as image light. The image light emitted from the cross dichroic prism  110  is then projected by a projection optical system  120  on a projection screen, not shown, as a landscape image. 
     Further, to the light modulation elements  100 R,  100 G, and  100 B, there are respectively connected signal line cable substrates  130 R,  130 G, and  130 B each having various signal lines such as a data line for supplying the image data and a control line for supplying a control signal, printed thereon. It is general that these signal line cable substrates  130 R,  130 G, and  130 B are each formed of a flexible printed circuit board, and connected respectively to the long sides of the light modulation elements  100 R,  100 G, and  100 B. It should be noted that the signal line cable substrates  130 R,  130 G, and  130 B are hereinafter referred to as FPC boards  130 R,  130 G, and  130 B, respectively. 
     In the typical projector of the related art, the light modulation elements  100 R,  100 G, and  100 B, and the cross dichroic prism  110  have the configuration shown in  FIGS. 6A and 6B . Therefore, assuming that each of the light modulation elements  100 R,  100 G, and  100 B has a resolution of, for example, 4K2K, the diagonal size of the image display area in each of the light modulation elements  100 R,  100 G, and  100 B is about 1.6 inch as described above. The size of the cross dichroic prism  110  in the case of using such light modulation elements needs to be about 60 mm (one side L 1  of the square composed of end surfaces of the respective four triangular prisms)×60 mm (the other side L 2  of the square composed of end surfaces of the respective four triangular prisms)×35 mm (the height H of the triangular prisms), and further, the lens diameter of the projection optical system  120  needs to be equal to or greater than 70 mm. It should be noted that, assuming that the lens diameter of the projection optical system is 70 mm, the F-value of 2.5 can be achieved in the design giving priority to the brightness of the lens of the projection optical system. 
     As described above, in the typical projector of the related art, the higher the resolution of the light modulation element is, the further the growth of the sizes of the cross dichroicprism  110  and the projection optical system  120  proceeds, which forms a factor causing decrease in the productivity of these optical elements and increase in the cost thereof. 
     To cope with the above, it is possible to arrange the light modulation elements  100 R,  100 G, and  100 B so that the long sides of the respective light modulation elements  100 R,  100 G, and  100 B are adjacent to each other while keeping the direction of the long sides of the respective light modulation elements  100 R,  100 G, and  100 B to be the horizontal direction (the lateral direction in  FIG. 7A ) as shown in  FIG. 7A . In this case, the light modulation elements  100 R,  100 G, and  100 B have the arrangement in which each of the long sides of each of the light modulation is disposed along the height direction (the x-axis direction) of the four triangular prisms constituting the cross dichroic prism  110 . It should be noted that  FIG. 7A  is a perspective view of the light modulation elements  100 R,  100 G, and  100 B arranged so that the long sides thereof are adjacent to each other, and  FIG. 7B  is a side view corresponding to  FIG. 7A , namely the diagram of the light modulation elements viewed in a direction along the arrow b. 
     By arranging the light modulation elements  100 R,  100 G, and  100 B so that the long sides thereof are adjacent to each other as shown in  FIGS. 7A and 7B , the size of the cross dichroic prism  110  becomes about 35 mm (one side L 1  of the square composed of end surfaces of the respective four triangular prisms)×35 mm (the other side L 2  of the square composed of end surfaces of the respective four triangular prisms)×60 mm (the height H of the triangular prisms) even in the case with the light modulation elements having the same resolution as that of the light modulation elements  100 R,  100 G, and  100 B shown in  FIGS. 6A and 6B . Further, the lens diameter of the projection optical system becomes about 45 mm. Therefore, the volume of the cross dichroic prism  110  can be reduced to about 60% of that in the case shown in  FIGS. 6A and 6B . Further, in this case, it is possible to achieve the F-value of 2.0 by designing the lens diameter of the projection optical system to be 50 mm, and therefore, downsizing is thought to be possible while keeping the same performance as in the case shown in  FIGS. 6A and 6B . 
     However, if the light modulation elements  100 R,  100 G, and  100 B are arranged so that the long sides thereof are adjacent to each other, there arises a problem that at least one of the FPC boards  130 R,  130 G, and  130 B connected respectively to the light modulation elements  100 R,  100 G, and  100 B shields the light input from a light source to the respective light modulation elements  100 R,  100 G, and  100 B, thus the light from the light source is prevented from appropriately entering the light modulation elements  100 R,  100 G, and  100 B, respectively. 
       FIG. 8  is a diagram schematically showing a general configuration of the optical system of the projector in the case in which the light modulation elements  100 R,  100 G, and  100 B are arranged as shown in  FIGS. 7A and 7B . As shown in  FIG. 8 , the light from the light source  140  is separated by a first dichroic mirror  151  into the red light (R), the green light (G), and the blue light (B), and the blue light (B) thus separated is input by a mirror  161  to the light modulation element  100 B while the red light (R) and the green light (G) thus separated from the blue light (B) is separated by a second dichroic mirror  152  into the red light (R) and the green light (G). Further, the green light (G) separated by the second dichroic mirror  152  is input to the light modulation element  100 G while the red light (R) is input by mirrors  162 ,  163  to the light modulation element  100 R. 
     In the optical system shown in  FIG. 8 , when considering, for example, the light modulation element  100 G corresponding to the green light (G), the FPC board  130 G is coupled to the lower long side of the light modulation element  100 G as shown in the drawing in the light modulation element  100 G of the green light (G), and consequently, shields the blue light (B) separated by the dichroic mirror  151 . 
     It should be noted that although the FPC board can be curved or bent within an appropriate angle, if the FPC board is bent at an excessively acute angle or an excessive twist or the like is applied to the FPC board, a broken line or the like might be caused. Therefore, the FPC board needs to be connected to other devices in a manner not providing the FPC board with folding with an excessively acute angle or an excessive twist. Therefore, if the light modulation elements  100 R,  100 G, and  100 B are arranged so that the long sides thereof are adjacent to each other, at least one of the FPC boards  130 R,  130 G, and  130 B should exist on the light path as shown in  FIG. 8 . 
     As a method for coping with this problem, it is possible to connect the FPC boards  130 R,  130 G, and  130 B to the short sides of the respective light modulation elements  100 R,  100 G, and  100 B. For example, JP-A-11-249070 (Document 1) shows a technology (hereinafter referred to as a related art technology) of arranging the light modulation elements so as to have the long sides adjacent to each other, and at the same time connecting the FPC boards to the short sides of the respective light modulation elements. By thus arranging the light modulation elements so as to have the long sides of the respective light modulation elements adjacent to each other, downsizing of the cross dichroic prism becomes possible, and further, by connecting the FPC boards to the short sides of the respective light modulation elements, it becomes possible to remove the FPC boards connected to the respective light modulation elements from the light paths of the respective colored light beams, thus an advantage of preventing the FPC boards from shielding the colored light beams can be obtained. 
     However, if it is arranged to connect the FPC boards simply to the short sides, there arises the following problem. The scanning direction for image data writing in the typical projector is set to be parallel to a direction (referred to as a long side direction) along the long side. Therefore, in the case of the light modulation element having a resolution of 4K2K, 4096 signal lines disposed along the long side are necessary for providing each of the pixels of the light modulation element. Therefore, if the FPC board is connected simply to the short side thereof while keeping the scanning direction for image data writing to the long side direction, a wiring space for leading the 4096 signal lines to the FPC board provided on the short side is required. This causes growth in overall size of the light modulation element. 
       FIGS. 9A and 9B  are diagrams schematically showing the arrangement of the signal lines of the light modulation element. Although the light modulation element  100 G for the green light (G) is shown in  FIGS. 9A and 9B , the light modulation elements  100 R and  100 B for the red light (R) and the blue light (B) have substantially the same configurations. It should be noted that  FIG. 9A  shows the typical light modulation element having the FPC board  130  coupled to the long side thereof, and in this case, there is adopted a configuration in which the 4096 signal lines from the FPC board  130 G are connected to a data line driver  102  disposed along the long side (the long side of the image display area  101 ) of the light modulation element  100 G. It should be noted that in the configuration, a gate line driver  103  is disposed on the short side (the short side of the image display area  101 ) of the light modulation element  100 G, and a few signal lines for control from the FPC board  130 G are connected to the gate line driver  103 . 
       FIG. 9B  shows the case in which the FPC board  130 G is coupled to the short side of the light modulation element  100 G shown in  FIG. 9A . In the case in which the FPC board  130 G is coupled to the short side of the light modulation element  100 G, the wiring space (the area A surrounded by the dotted frame in the drawing) for leading the 4096 signal lines connected to the data line driver  102  disposed on the long side to the FPC board  130 G coupled to the short side is required as shown in  FIG. 9B . Since an area of at least 10 mm in size in the z-axis direction shown in the drawing is required as the wiring space, which causes the growth in the overall size of the light modulation element. 
     Therefore, if the FPC boards are simply coupled to the short side while keeping the long side direction of the light modulation elements  100 R,  100 G, and  100 B to the scanning direction for the image data writing, it is hardly possible to make the most use of the advantage obtained by disposing the light modulation elements  100 R,  100 G, and  100 B so as to have the long sides adjacent to each other, namely the advantage of making it possible to downsize the cross dichroic prism and the projection optical system. 
     SUMMARY 
     An advantage of some aspects of the invention is to provide a projector allowing downsizing of the combining optical system and the projection optical system even in the case of using a high resolution light modulation element. 
     A projector according to a first aspect of the invention includes a plurality of light modulation elements adapted to modulate a plurality of colored light beams with respective color components based on image data, a combining optical system adapted to combine the colored light beams, which are modulated by the respective light modulation elements, to emit the combined colored light beams as image light, and a projection optical system adapted to project the image light emitted from the combining optical system on a projection screen, and, the light modulation elements are disposed with respect to the combining optical system so that long sides of the respective light modulation elements are adjacent to each other, signal line cable boards adapted to provide the respective light modulation elements with signals, and coupled to short sides of the respective light modulation elements, and a scanning direction of writing the image data to the light modulation elements is set to be parallel to a direction of the short side of an image display area in each of the light modulation elements. 
     According to the projector of the first aspect of the invention, the light modulation elements are disposed with respect to the combining optical system so that the long sides of the respective light modulation elements are adjacent to each other. In this case, the relationship between the light modulation elements and the cross dichroicprism as the combining optical system corresponding to an arrangement in which the long sides of the light modulation elements are disposed along the height direction of the triangular prisms forming the cross dichroic prism. Thus, the volume of the combining optical system (the cross dichroic prism) can be reduced, thus achieving the downsizing of the combining optical system (the cross dichroic prism). Thus, the increase in productivity and the reduction in the cost of the optical elements such as the combining optical system (the cross dichroic prism) or the projection optical system can be achieved. Further, according to the present aspect of the invention, since the focal length of the projection optical system can be shortened, a higher luminance can easily be achieved using a bright lens with a rather large aperture. 
     Further, according to the projector in the first aspect of the invention, since the light modulation elements are disposed so that the long sides thereof are adjacent to each other, and the signal line cable boards (FPC boards) are coupled to the short sides of the respective light modulation elements, the problem that the FPC board shields the colored light beams input to the light modulation elements can be avoided. 
     Further, in the projector of the first aspect of the invention, the scanning direction of writing the image data to each of the light modulation elements is set to be parallel to the direction (referred to as a short side direction) along the short side of the image display area in each of the light modulation elements. Thus, in the case in which the FPC board is coupled to the short side of each of the light modulation elements, the wiring space for leading a number of data lines from the data line driver to the FPC board can be made smaller, thus the overall size of the light modulation element can be reduced to be a smaller size. Further, by setting the scanning direction for writing to be parallel to the short side direction, the number of data lines can also be reduced, thus the advantage of reducing the width of the FPC board can also be obtained. 
     Further, the projector according to the first aspect of the invention preferably includes an image data processing device including a first frame memory and a second frame memory each capable of holding the image data to be displayed corresponding to one frame, an address information generation section adapted to generate address information for executing writing and retrieving the image data on the first frame memory and the second frame memory, a frame memory control section adapted to control writing and retrieving of the image data on the first frame memory and the second frame memory based on the address information from the address information generation section, and alight modulation element drive section adapted to drive each of the light modulation elements based on the image data retrieved from either one of the first frame memory and the second frame memory, and the frame memory control section, while writing the image data corresponding to one frame in one of the first frame memory and the second frame memory, retrieves the image data corresponding to one frame previously written in the other of the first frame memory and the second frame memory, and converts the scanning direction of writing the image data into the direction of the short side of the image display area of each of the light modulation elements in one of writing and retrieving the image data. 
     By adopting the configuration of writing of the image data and retrieving of the image data are executed on the separate frame memories as described above, the scanning direction conversion process for setting the scanning direction for writing to be parallel to the short side direction can appropriately be executed. In other words, if it is attempted to execute the scanning direction conversion process with a single frame memory, when executing retrieving of the image data from the frame memory in order for setting the scanning direction for writing to be parallel to the short side direction, there might be caused a problem that, for example, the image data written as the image data for the subsequent frame exists in an area with the address for the data corresponding to a certain pixel on which the retrieving process is executed. In contrast, as in the case with the invention, by executing the writing and retrieving of the image data on the separate frame memories, such a problem can be solved, and the image data corresponding to the one frame can appropriately be retrieved with the scanning direction parallel to the short side direction. 
     Further, in the projector according to the first aspect of the invention, it is preferable that the frame memory control section controls executing writing and retrieving of the image data on the first frame memory and the second frame memory so that the writing of the image data corresponding to the one frame and the retrieving of the image data corresponding to one frame are executed in sync with each other. 
     As described above, by making the writing of the image data corresponding to one frame to one of the frame memories and the retrieving of the image data corresponding to one frame from the other of the frame memories are executed in sync with each other, the process of writing the image data corresponding to one frame and the process of retrieving the image data corresponding to one frame becomes possible continuously, and it becomes possible to output the retrieved image data to the light modulation element drive section as the image data with the continuous frames. 
     A projector according to a second aspect of the invention includes a plurality of light modulation elements adapted to modulate a plurality of colored light beams with respective color components based on image data, a combining optical system adapted to combine the colored light beams, which are modulated by the respective light modulation elements, to emit the combined colored light beams as image light, and a projection optical system adapted to project the image light emitted from the combining optical system on a projection screen, and a cooling device adapted to cool at least the light modulation elements, and, the light modulation elements are disposed with respect to the combining optical system so that long sides of the respective light modulation elements are adjacent to each other, and signal line cable boards adapted to provide the respective light modulation elements with signals are coupled to short sides of the respective light modulation elements, and the cooling device is disposed so as to flow the cooling air from the cooling device along a direction of the long side of each of the light modulation elements. 
     According to the projector of the second aspect of the invention, similarly to the projector of the first aspect of the invention, there can be obtained the advantage that the downsizing of the composing optical system (the cross dichroic prism) can be achieved, and the problem that the FPC board shields the colored light input to the light modulation element can be solved. Further, according to the projector in the second aspect of the invention, it is arranged that the cooling air from the cooling device is made to flow along the long side direction of the light modulation elements. This means that the cooling air is made to flow laterally, by flowing the cooling air in the lateral direction, there can be obtained an advantage of reducing the chances of stacking the dust on the light modulation elements and the cross dichroic prism. In other words, the dust generally falls in a direction of gravitational force, and by flowing the cooling air in a direction perpendicular to the gravitational direction, the chances of accumulating the dust on the light modulation elements or the cross dichroic prism and so on can be reduced. 
     It should be noted that also in the second projector according to this aspect, it is preferable to have the same feature as the projector of the first aspect of the invention. 
     Further, in the projector according to the second aspect of the invention, it is preferable that a scanning direction of writing the image data to the light modulation elements is set to be parallel to a direction of the short side of an image display area in each of the light modulation elements. 
     Thus, in the case in which the FPC board is coupled to the short side of each of the light modulation elements, the wiring space for leading a number of data lines from the data line driver to the FPC board can be made smaller, thus the overall size of the light modulation element can be reduced to be a smaller size in addition to the advantage that the chances of accumulating the dust on the light modulation elements and the cross dichroic prism can be reduced. Further, by setting the scanning direction for writing to be parallel to the short side direction, the number of data lines can also be reduced, thus the advantage of reducing the width of the FPC board can also be obtained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIGS. 1A and 1B  are diagrams showing a configuration of light modulation elements and an optical system in the periphery thereof in the projector according to a first embodiment. 
         FIG. 2  is a diagram schematically showing a general configuration of the optical system of the projector in the case in which the light modulation elements  100 R,  100 G, and  100 B are arranged as shown in  FIGS. 1A and 1B . 
         FIG. 3  is a diagram schematically showing an arrangement of signal lines of the light modulation element of the projector according to the first embodiment. 
         FIG. 4  is a diagram showing a configuration of an image data processing device in the projector according to the first embodiment. 
         FIG. 5  is a diagram showing a configuration of light modulation elements and an optical system and so on in the periphery thereof in the projector according to a second embodiment. 
         FIGS. 6A and 6B  are diagrams showing a configuration of the light modulation element and the optical system in the periphery thereof in a typical projector. 
         FIGS. 7A and 7B  are diagrams showing a configuration of light modulation elements and an optical system in the periphery thereof in the case of arranging the light modulation elements so that the long sides thereof are adjacent to each other while keeping the respective long sides of the light modulation elements in a lateral direction (a horizontal direction). 
         FIG. 8  is a diagram schematically showing a general configuration of the optical system of the projector in the case in which the light modulation elements are arranged as shown in  FIGS. 7A and 7B . 
         FIGS. 9A and 9B  are diagrams schematically showing an arrangement of signal lines of a light modulation element. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, some embodiments of the invention will be explained. 
     First Embodiment 
       FIGS. 1A and 1B  are diagrams showing a configuration of light modulation elements and an optical system in the periphery thereof in a projector according to a first embodiment, and in particular showing an image light forming optical system including a plurality of light modulation elements (assumed to be light modulation elements  100 R,  100 G, and  100 B corresponding respectively to R, G, and B) and a cross dichroic prism  110  as a combining optical system, and a projection optical system  120 . It should be noted that  FIG. 1A  is a perspective view, and  FIG. 1B  is a plan view corresponding to  FIG. 1A , namely a diagram of the configuration shown in  FIG. 1A  viewed from a direction along the arrow b. 
     As shown in  FIGS. 1A and 1B , in the projector according to the present embodiment of the invention, the light modulation elements  100 R,  100 G, and  100 B corresponding respectively to the red light (R), the green light (G), and the blue light (B) are arranged so that the long sides thereof are adjacent to each other. In other words, one of the long sides of the light modulation element  100 G and one of the long sides of the light modulation element  100 R are disposed adjacent to each other, and similarly, the other of the long sides of the light modulation element  100 G and one of the long sides of the light modulation element  100 B are disposed adjacent to each other. It should be noted that in  FIGS. 1A and 1B , -z direction in the z-axis corresponds to the direction of the gravitational force. Therefore, it is assumed that the projector according to the first embodiment has a bottom section (the side provided with legs of the projector) of the projector on the -z direction side of the image light forming optical system. Further, it is also assumed that each of the light modulation elements  100 R,  100 G, and  100 B has a resolution of 4K2K (assumed to be 4096 pixels in the lateral direction×2160 pixels in the vertical direction). 
     Further, in this case, in the positional relationship between the light modulation elements  100 R,  100 G, and  100 B, and a cross dichroic prism  110 , the light modulation elements  100 R,  100 G, and  100 B are disposed so that each of the long sides of each of the light modulation elements  100 R,  100 G, and  100 B is disposed along a height direction (the x-axis direction) of four triangular prisms forming the cross dichroic prism  110 . Further, in the projector according to the first embodiment, there is adopted a configuration of coupling the FPC boards  130 R,  130 G, and  130 B respectively to the short side of the light modulation elements  100 R,  100 G, and  100 B. 
       FIG. 2  is a diagram schematically showing a general configuration of the optical system of the projector in the case in which the light modulation elements  100 R,  100 G, and  100 B are arranged as shown in  FIGS. 1A and 1B . In the optical system shown in  FIG. 2 , the arrangement of the optical constituents is substantially the same as the configuration shown in  FIG. 8 , and the same sections are denoted with the same reference numerals. The configuration shown in  FIG. 2  is different from the configuration shown in  FIG. 8  in that the FPC boards  130 R,  130 G, and  130 B are coupled to the short sides of the respective light modulation elements  100 R,  100 G, and  100 B in the configuration shown in  FIG. 2 , while the FPC boards  130 R,  130 G, and  130 B are coupled to the long sides of the respective light modulation elements  100 R,  100 G, and  100 B in the configuration shown in  FIG. 8 . 
     As described above, in the configuration of the optical system of the projector according to the first embodiment, the light modulation elements  100 R,  100 G, and  100 B are disposed so that the long sides thereof are adjacent to each other, and at the same time, the FPC boards  130 R,  130 G, and  130 B are coupled to the short sides of the respective light modulation elements. Although the configuration described hereinabove is substantially the same as the related art (the technology disclosed in the Document 1) described above, in the projector according to the first embodiment, downsizing of the size of each of the light modulation elements  100 R,  100 G, and  100 B becomes possible by setting the scanning direction for the image data writing in each of the light modulation elements  100 R,  100 G, and  100 B to be parallel to the short side direction of the image display area in each of the light modulation elements. 
     It should be noted that in the present specification, “the scanning direction for writing” denotes the high-speed scanning out of the high-speed scanning (so-called “horizontal scanning”) and the low-speed scanning (so-called “vertical scanning”). In other words, in the embodiment of the invention, the real vertical direction (the z-axis direction in each of the drawings) and the high-speed scanning direction become substantially parallel to each other (the real vertical direction and the so-called horizontal scanning direction become substantially parallel to each other). Further, hereinafter, “the scanning direction for writing” is simply denoted as “the scanning direction.” 
       FIG. 3  is a diagram schematically showing an arrangement of signal lines of the light modulation element of the projector according to the first embodiment. Although the light modulation element  100 G for the green light (G) is shown in  FIG. 3 , the light modulation elements  100 R and  100 B for the red light (R) and the blue light (B) have substantially the same configurations. 
     In the projector according to the first embodiment, the scanning direction of each of the light modulation elements  100 R,  100 G, and  100 B is set to be parallel to the short side direction. Therefore, as shown in  FIG. 3 , in the configuration, the data line driver  102  is disposed on the short side of each of the light modulation elements ( FIG. 3  shows the light modulation element  100 G), and the data lines for supplying the image data from the FPC board  130 G are connected to the data line driver  102 . In this case, the light modulation element  100 G is a light modulation element of 4K2K, and therefore, has 2160 data lines corresponding to the number of pixels arranged in the short side direction. Meanwhile, on the long side of the light modulation element  100 G, there is disposed a gate line driver  103 . To the gate lined river  103 , there are connected a few signal lines such as a signal line for control. 
     By providing the structure shown in  FIG. 3  to each of the light modulation elements  100 R,  100 G, and  100 B, the wiring space (the area A surrounded by the dotted line frame shown in  FIG. 9B ) for leading the data lines to the short side as in the light modulation element shown in  FIG. 9B , for example, can be eliminated, therefore, it is possible to downsize the overall light modulation element while keeping the resolution. 
     In order for making the configuration of the light modulation element shown in  FIG. 3  possible, in the projector according to the first embodiment, the image data processing device shown in  FIG. 4  is provided. 
       FIG. 4  is a diagram showing a configuration of the image data processing device in the projector according to the first embodiment. As shown in  FIG. 4 , the image data processing device  500  has an image data input section  510  for inputting the image data to be displayed, a first frame memory  520  for storing the image data corresponding to one frame (one screen) of the image data input to the image data input section  510 , a second frame memory  530  similarly storing the image data corresponding to one frame (one screen) of the image data, a light modulation element drive section  540  for driving each of the light modulation elements  100 R,  100 G, and  100 B based on the image data retrieved from either one of the first frame memory  520  and the second frame memory  530 , an address information generation section  550  for generating the address information when executing writing and retrieving of the image data on the first frame memory  520  and the second frame memory  530 , and a frame memory control section  560  for controlling the writing and retrieving to and from the first and second frame memories  520 ,  530  based on the address information from the address information generation section  550 . 
     It should be noted that in the projector according to the first embodiment, it is assumed that writing of the image data with the scanning direction along the long side direction is executed when writing the image data to the first and second frame memories  520 ,  530 , and when retrieving the image data from the first and second frame memories  520 ,  530 , a process of retrieving the image data with the scanning direction along the short side direction, namely a scanning direction conversion process is executed. Such a scanning direction conversion process is executed by the frame memory control section  560  based on the address information from the address information generation section  550 . 
     In the configuration described above, the writing and retrieving control of the image data to and from the first and second frame memories  520 ,  530  by the frame memory control section  560  is executed in the following manner. 
     Now, it is assumed that the writing of the image data corresponding to a certain frame (assumed to be the nth frame) is completed in the first frame memory  520 , and subsequently the writing of the n+1th frame to the second frame memory  530  has been started. In sync with the writing of the n+1th frame to the second frame memory  530 , the image data corresponding to the nth frame, which has already been written, is retrieved from the first frame memory  520 , and subsequently, in sync with the writing of the image data corresponding to the n+2th frame to the first frame memory  520 , the image data corresponding to the n+1th frame, which has already been written, is retrieved from the second frame memory  530 . In other words, the writing process and the retrieving process of the image data corresponding to one frame are alternately executed on the first frame memory  520  and the second frame memory  530 . 
     The frame memory control section  560  executes the writing and retrieving control of the image data described above on the first and second frame memory  520 ,  530 . In such a writing and retrieving control of the image data, when retrieving the image data from the first and second frame memories  520 ,  530 , the scanning direction conversion process with the scanning direction parallel to the short side direction of the light modulation element. The scanning direction conversion process with the scanning direction parallel to the short side direction can be realized by obtaining the image data to each pixel based on the address information from the address information generation section  550 . 
     Since the writing and retrieving of the image data are executed in the separate frame memories in the image data processing device shown in  FIG. 4 , the scanning direction conversion process for setting the scanning direction to be parallel to the short side direction can appropriately be executed. In other words, if it is attempted to execute the scanning direction conversion process with a single frame memory, when executing retrieving of the image data from the frame memory in order for setting the scanning direction to be parallel to the short side direction, there might be caused a problem that, for example, the image data written as the image data for the subsequent one frame exists in an area with the address for the image data corresponding to a certain pixel on which the retrieving process is executed. In contrast, as shown in  FIG. 4 , by executing the writing and retrieving of the image data on the separate frame memories (the first and second frame memories  520 ,  530 ) alternately, such a problem can be solved, and the image data corresponding to the one frame can appropriately be retrieved with the scanning direction parallel to the short side direction. 
     Further, when executing the writing and retrieving control of the image data described above on the first and second frame memories  520 ,  530 , the frame memory control section  560  controls the writing and retrieving of the first frame memory  520  and the second frame memory  530  so that the writing of the image data corresponding to one frame and retrieving of the image data corresponding to one frame are in sync with each other. Thus, the writing and retrieving of the image data on the first frame memory  520  and the second frame memory  530  are finished simultaneously in each frame. 
     Since the frame memory control section  560  executes such writing and retrieving control, it becomes possible to continuously execute writing of the image data corresponding to one frame and retrieving of the image data corresponding to one frame, thus the image data thus retrieved can be output to the light modulation element drive section as the image data of the continuous frames. 
     As explained hereinabove, according to the projector related to the first embodiment, the light modulation elements  100 R,  100 G, and  100 B are disposed so that the long sides thereof are adjacent to each other with respect to the cross dichroic prism  110 . Thus, the volume of the cross dichroic prism  110  can be reduced, thus achieving the downsizing of the cross dichroic prism  110 . Thus, the increase in productivity and the reduction in the cost of the optical elements such as the cross dichroic prism or the projection optical system can be achieved. Further, according to the present embodiment of the invention, since the focal length of the projection optical system can be shortened, a higher luminance can easily be achieved using a bright lens with a rather large aperture. 
     Further, according to the projector related to the first embodiment, since the FPC boards  130 R,  130 G, and  130 B are coupled to the short sides of the respective light modulation elements  100 R,  100 G, and  100 B, the problem that the FPC board shields the colored light input from the light source to the light modulation elements can be avoided. Further, in the projector according to the first embodiment, the scanning direction of each of the light modulation elements  100 R,  100 G, and  100 B is set to be parallel to the short side direction of the light modulation elements. In this case, by executing the image data processing explained with reference to  FIG. 4 , the image data with the scanning direction parallel to the short side direction can appropriately be provided to the light modulation elements  100 R,  100 G, and  100 B. 
     By setting the scanning direction to be parallel to the short side direction of the light modulation elements  100 R,  100 G, and  100 B, the wiring space for leading a number of data lines from the data line driver  102  to the FPC boards  130 R,  130 G, and  130 B can be reduced to an extremely small space in the case of coupling the FPC boards  130 R,  130 G, and  130 B to the short sides of the respective light modulation elements  100 R,  100 G and  100 B, thus the size of the overall light modulation element can be reduced to be a small size. 
     Further, by setting the scanning direction to be parallel to the short side direction, the number of data lines can also be reduced, thus the advantage of making it possible to reduce the width of the FPC boards  130 R,  130 G, and  130 B can also be obtained. For example, in the case in which the each of the light modulation elements  100 R,  100 G and  100 B has a resolution of 4K2K, the number of data lines on the short side becomes 2160, and therefore, in simple comparison on the number of data lines with the case of setting the scanning direction to be parallel to the long side direction in the light modulation element with the same resolution of 4K2K, the data lines roughly a half as many as the latter case are enough. Thus, the width of each of the FPC boards  130 R,  130 G, and  130 B coupled to the respective light modulation elements  100 R,  100 G and  100 B can be reduced. 
     It should be noted that although in the embodiment described above the scanning direction conversion process for setting the scanning direction to be parallel to the short side is arranged to be executed when retrieving the data from the first and second frame memories  520 ,  530 , it is also possible to arrange that the scanning direction conversion process is executed when writing the data into the first and second frame memories  520 ,  530  instead of retrieving. 
     Second Embodiment 
       FIG. 5  is a diagram showing a configuration of light modulation elements and an optical system and so on in the periphery thereof in the projector according to a second embodiment. The configuration of the light modulation elements and the optical system in the periphery thereof shown in  FIG. 5  is substantially the same as that shown in  FIGS. 1A and 1B , and what is different from that shown in  FIGS. 1A and 1B  is a cooling device  600  capable of cooling at least the light modulation elements  100 R,  100 G, and  100 B provided thereto. It should be noted that the same constituents as those shown in  FIGS. 1A and 1B  are denoted with the same reference numerals. 
     As shown in  FIG. 5 , the projector according to the second embodiment has a structure in which the cooling air  610  from the cooling device  600  flows in a lateral direction, namely along the long side direction (the x-axis direction) of the light modulation elements  100 R,  100 G, and  100 B. By thus flowing the cooling air in the lateral direction, there can be obtained an advantage of reducing the chances of accumulating the dust on the light modulation elements  100 R,  100 G, and  100 B and the cross dichroic prism  110 . In other words, the dust generally falls in the direction of gravitational force (-z direction in the z-axis), and therefore, by flowing the cooling air along the direction (the x-axis direction) perpendicular to the direction of gravitational force, it becomes possible to reduce the chances of accumulating the dust on the light modulation elements  100 R,  100 G, and  100 B and the cross dichroic prism  110 . 
     Further, also in the projector according to the second embodiment, it is possible to set the scanning direction to be parallel to the short side direction similarly to the first embodiment by executing the image data processing explained with reference to  FIG. 4 , thus the advantages described regarding the projector according to the first embodiment in addition to the advantage of reducing the chances of accumulating the dust on the light modulation elements  100 R,  100 G, and  100 B, and the cross dichroic prism  110  are obtained. 
     It should be noted that the invention is not limited to the embodiments described above, but can be put into practice with various modifications within the scope or spirits of the invention. For example, although in the embodiments described above, the transmissive liquid crystal panels are explained, the invention can be put into practice with reflective liquid crystal panels. 
     Further, although in the embodiments, the explanations are presented assuming that the resolution of the light modulation elements  100 R,  100 G, and  100 B is 4K2K, this is nothing more than an example, it is obvious that the resolution is not limited to the 4K2K. 
     The entire disclosure of Japanese Patent Application No. 2008-034116, filed Feb. 15, 2008 is expressly incorporated by reference herein.