Abstract:
A projective display apparatus having an illumination unit which includes a light source, an integrator lens and a collimator lens, a light splitter unit which splits light beams from the illumination unit into a plurality of color components, a plurality of light valves, a cooling fan, and a wind guiding unit. A respective one of the light valves corresponds to a respective one of the color components. The wind guiding unit guides the cooling wind from the cooling fan to the illumination unit and the light valves. The wind guiding unit splits and forms at least two branch wind guiding paths. One of the branch wind guiding paths guides cooling wind from the cooling fan to the illumination unit and another of the branch wind guiding paths guides the cooling wind to the light valves.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation of U.S. application Ser. No. 10/028,424, filed Dec. 28, 2001, now U.S. Pat. No. 6,595,645, which is a continuation of Ser. No. 09/392,563, filed Sep. 9, 1999, now U.S. Pat. No. 6,334,686, the subject matter of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a display-apparatus technology used for projecting a picture on a screen by using a light valve device such as a liquid-crystal display panel and adopted in equipment such as a liquid-crystal projector apparatus, a liquid-crystal television and a projective display apparatus. 
     There have been provided conventional display apparatuses such as a liquid-crystal projector for projecting a picture on a screen or the like in an enlarged size by conversion of a light emitted by a light source such as a lamp into concentrations of pixels and adjustment of the concentrations using a light valve device such as a liquid-crystal display panel. 
     The light valve device generally comprises a semiconductor driving device and an optically functioning material. In order to have the semiconductor driving device and the optically functioning material operate normally, it is necessary to keep them at a predetermined temperature, for example the temperature is about 60 degrees Celsius or lower. 
     On the other hand, all the light emitted by the light source except that eventually used for projection is absorbed by elements such as the light valve device and its peripheral optical devices, being converted thereby into heat energy. For this reason, it is necessary to cool the light valve device employed in the projective display apparatus so as to prevent the temperature of the light valve device from exceeding a range of the normal operation due to overheating. The need for such cooling is rising more and more as the intensity of the light source is increased in recent years to raise the luminance of the projected picture. This is because the amount of heat dissipated by the light valve device increases as the intensity of the light source is raised. 
     The performances and functions of some optically functioning components other than the light valve device and some of those made of a polymer material change at a high temperature. It is thus necessary to keep them at a predetermined temperature, for example the temperature is about 150 degrees Celsius or lower. That is, it is necessary to cool the optically functioning components other than the light valve device as the luminance of the projected picture is increased. 
     In addition, since the focus of an optical system employed in such a display apparatus is positioned on the picture surface of the light valve device, a foreign particle such as dust stuck to the light valve device or areas in close proximity thereto is projected on the screen as it is in an enlarged size as a shadow appearing on the screen. In consequence, there are raised serious problems of prevention of dust from being stuck to the light valve device or areas in close proximity thereto and maintainability including removal of stuck dust as a matter of course. 
     There is a typical conventional technology of cooling a light valve device which is disclosed in Japanese Patent Laid-open No. Hei 9-120046. According to this technology which is relevant to the present invention, a wind is blown to a side surface of a liquid-crystal light valve to cool the heated liquid-crystal light valve. In this way, an increase in temperature caused by heat dissipated by the liquid-crystal light valve device(liquid-crystal display panel)can be suppressed by the cooling. According to this relevant technology, since a wind is blown from one side only, however, the temperature on the entrance side of the cooling wind decreases while the temperature on the exit side increases, resulting in a difference in temperature which makes it impossible to obtain a sufficient performance particularly at a high luminance. In this respect, this conventional technology does not adequately address the problem. In addition, this conventional technology also does not address a lack of cooling power as evidenced by the fact that the total amount of heat dissipated by the light valve device is raised with an increase in luminance. Furthermore, this conventional technology also does not address the necessity to cool optically functioning components other than the light valve device as the luminance is increased. 
     There is another relevant technology of cooling a light valve device which is disclosed in Japanese Patent Laid-open No. Hei 5-53200. According to this relevant technology, a sirocco fan of a pressure centrifugal type is used for cooling a light valve means. By doing so, a sufficient wind blowing capacity can be assured by using even a duct with a relatively small diameter, allowing the cooling to be carried out with a high degree of efficiency. Nevertheless, this conventional technology also does not address the necessity to cool optically functioning components other than the light valve device as the luminance is increased. 
     There is also a relevant technology of preventing dust from being stuck in a picture display apparatus as is disclosed in Japanese Patent Laid-open No. Hei 7-152009. According to this relevant technology, a transmission light valve device serving as a liquid-crystal display panel is placed in a hermetically sealed space. An air is circulated in the hermetically sealed space to let the liquid-crystal display panel radiate heat dissipated thereby to the outside of the space. In this way, it is possible to prevent dust from being stuck to the liquid-crystal display panel. In some cases, however, the cooling power becomes insufficient as heat is dissipated as a result of increasing the luminance. In addition, dust introduced during a fabrication process may be inadvertently included in the hermetically sealed space. Thus, this relevant technology also does not address a problem of maintainability caused by, among other things, the difficulty to remove such dust. 
     With respect to the maintainability of a picture display apparatus, there is a relevant technology disclosed in Japanese Patent Laid-open No. Hei 7-311372. According to this relevant technology, the interior of the picture display apparatus comprises a combination of units which can be attached and detached individually. With such a configuration, each of the units can be maintained and replaced with ease. According to this relevant technology, however, a unit including a liquid-crystal light valve device and a projection lens requiring frequent maintenance checks has a configuration which allows this specific unit to be attached and detached only in the projection direction of the projection lens. It is thus necessary to disassemble units of the whole optical system in order to attach or detach the specific unit. 
     In the case of the technologies disclosed in Japanese Patent Laid-open Nos. Hei 9-120046 and Hei 5-53200, the cooling of the light valve device and the disposition of dust stuck to the light valve device and areas in close proximity thereto are required as the luminance is increased. Otherwise, problems such as an abnormal operation caused by overheating and a shadow appearing on the screen due to the stuck dust as described above will likely arise. However, the relevant technologies do not address these problems and, of course, do not take solutions to the problems into consideration. In addition, these relevant technologies do not address the necessity to cool optically functioning devices at the same time either. 
     In the case of the technology disclosed in Japanese Patent Laid-open No. Hei 7-152009, cooling is done by an air circulated in a hermetically sealed space. Thus, efficient cooling can not be much expected. As a result, it is quite within the bounds of possibility that the light valve device can not be cooled sufficiently in the event of an increased amount of dissipated heat due to an increased intensity of the light emitted by the light source. In this case, in spite of the fact that the picture display apparatus will no longer operate normally, the relevant technology does not address the problem and, of course, does not take a solution to the problem into consideration. The relevant technology also does not address a problem related to the maintenance of the picture display apparatus, and, of course, does not take a solution to the problem into consideration. 
     In the case of the technology disclosed in Japanese Patent Laid-open No. Hei 7-311372, workability during maintenance is not taken into consideration adequately as evidenced by, among other things, the fact that it is necessary to disassemble peripheral members of the light valve device during maintenance work of the device or components in close proximity thereto. 
     SUMMARY OF THE INVENTION 
     It is thus an object of the present invention addressing the problems described above to provide a display apparatus technology that is capable of cooling a light valve means and other optically functioning components with a high degree of efficiency and offers excellent maintainability of peripheral components surrounding the light valve device. 
     In order to achieve the object described above, the picture display apparatus provide by the present invention can have one of the following configurations: 
     1 In a display optical unit for a display apparatus for displaying a picture by splitting a light emitted by an illumination means into a plurality of color components using a splitting means, modulating each of said color components using a light valve means and guiding modulated color components to a projection means, an optical axis of said projection means is shifted from an optical axis of said illumination means and said splitting means, and said projection means can be attached and detached in a direction in which said optical axes are shifted from each other. 
     2 In a display optical unit for a display apparatus for displaying a picture by modulating a light emitted by an illumination means using a light valve means and guiding a modulated light to a projection means, said light valve means is cooled by cooling winds blown by a cooling means to said light valve means through a plurality of wind supply openings in directions within the range 45 degrees to 315 degrees. 
     3 In a display optical unit for a display apparatus for displaying a picture by modulating a light emanating from an illumination means and passing through a polarization means using a light valve means and guiding a modulated light to a projection means, said polarization means is cooled by cooling winds blown by a cooling means to said polarization means through a plurality of wind supply openings in directions within the range 45 degrees to 315 degrees. 
     4 In a display optical unit for a display apparatus for displaying a picture by modulating a light emitted by an illumination means using a light valve means and guiding a modulated light to a projection means, said light valve means is cooled by a cooling means including a wind generating means for blowing a cooling wind and a wind guiding path for splitting said cooling wind and for supplying a split cooling wind to a plurality of optical means including at least said light valve means. 
     5 In a display optical unit for a display apparatus for displaying a picture by modulating a light emitted by an illumination means using a light valve means and guiding a modulated light to a projection means, said light valve means is cooled by cooling winds blown by a cooling means to a light incidence surface and a light emission surface of said light valve means in directions within the range 45 degrees to 315 degrees. 
     6 In a display optical unit for a display apparatus for displaying a picture by modulating a light emanating from an illumination means and passing through a polarization means using a light valve means and guiding a modulated light to a projection means, said polarization means is cooled by cooling winds blown by a cooling means to a light incidence surface and a light emission surface of said polarization means in directions within the range 45 degrees to 315 degrees. 
     7 In a display apparatus for displaying a picture by splitting a light emitted by an illumination means into a plurality of color components using a splitting means, modulating each of said color components using a light valve means and guiding modulated color components to a projection means, an optical axis of said projection means is shifted from an optical axis of said illumination means and said splitting means, and said projection means can be attached and detached in a direction in which said optical axes are shifted from each other. 
     8 In a display apparatus for displaying a picture by modulating a light emitted by an illumination means using a light valve means and guiding a modulated light to a projection means, said light valve means is cooled by cooling winds blown by a cooling means to said light valve means through a plurality of wind supply openings in directions within the range 45 degrees to 315 degrees. 
     9 In a display apparatus for displaying a picture by modulating a light emanating from an illumination means and passing through a polarization means using a light valve means and guiding a modulated light to a projection means, said polarization means is cooled by cooling winds blown by a cooling means to said polarization means through a plurality of wind supply openings in directions within the range 45 degrees to 315 degrees. 
     10 In a display optical unit for a display apparatus for displaying a picture by modulating a light emitted by an illumination means using a light valve means and guiding a modulated light to a projection means, said light valve means is cooled by a cooling means including a wind generating means for blowing a cooling wind and a wind guiding path for splitting said cooling wind and for supplying a split cooling wind to a plurality of optical means including at least said light valve means. 
     11 In a display apparatus for displaying a picture by modulating a light emitted by an illumination means using a light valve means and guiding a modulated light to a projection means, said light valve means is cooled by cooling winds blown by a cooling means to a light incidence surface and a light emission surface of said light valve means in directions within the range 45 degrees to 315 degrees. 
     12 In a display apparatus for displaying a picture by modulating a light emanating from an illumination means and passing through a polarization means using a light valve means and guiding a modulated light to a projection means, said polarization means is cooled by cooling winds blown by a cooling means to a light incidence surface and a light emission surface of said polarization means in directions within the range 45 degrees to 315 degrees. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an explanatory diagram used for describing a detachment/attachment technology adopted in a display apparatus implemented by a first embodiment of the present invention; 
     FIG. 2 is a diagram showing an external appearance of the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 3 is a diagram showing a squint view of the bottom of the external appearance of the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 4 is a cross-sectional diagram showing the position of a picture projected by the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 5 is a diagram showing a squint view of the configuration of an optical unit employed in the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 6 is a diagram showing a squint view of the configuration of the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 7 is a diagram showing a squint view of the configuration of the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 8 is a diagram showing a squint view of the internal configuration of the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 9 is an explanatory diagram used for describing attachment and detachment of a projection means to and from the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 10 is a diagram showing a squint view of a cooling duct employed in the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 11 is a diagram showing a cross section of the configuration of a cooling system in the picture display apparatus implemented by the first embodiment of the present invention; 
     FIG. 12 is a diagram showing the configuration of a cooling system in the picture display apparatus implemented by a second embodiment of the present invention; 
     FIG. 13 is a diagram showing the configuration of a cooling system in the picture display apparatus implemented by a third embodiment of the present invention; 
     FIG. 14 is a diagram showing the configuration of a cooling system in the picture display apparatus implemented by a fourth embodiment of the present invention; and 
     FIG. 15 is an explanatory diagram used for describing attachment and detachment of a projection means to and from the picture display apparatus implemented by a fifth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Some preferred embodiments of the present invention are described by referring to accompanying diagrams as follows. 
     FIGS. 1 to  12  are explanatory diagrams referred to in an explanation of a first embodiment of the present invention. 
     In a picture display apparatus shown in FIG. 1, a projection unit  500  can be attached to and detached from a lower-side unit case  700  of an optical unit  10 . The projection unit  500  is attached or detached in an upward direction with respect to the projection direction of a projection lens employed in the picture display apparatus shown in FIG.  1 . 
     Before getting into a detailed description, the configuration of the picture display apparatus implemented by this embodiment is explained in a simple and plain manner by referring to FIGS. 2 to  8 . 
     FIG. 2 is a diagram showing an external appearance of the picture-display apparatus implemented by the embodiment of the present invention. An optical unit  10  is accommodated in the picture display apparatus  1 . In the picture display apparatus  1 , a projection-lens means, which is a portion of the projection unit  500 , is exposed to the outside of an external cabinet of the picture display apparatus  1 . The projection-lens means projects a picture on an external screen or the like. An inlet port  110  and an exhaust port  111  are provided on the front surface and on the rear side of a side surface of the picture display apparatus  1  respectively. An air is introduced from the atmosphere outside the picture display apparatus  1  through the inlet port  110  to cool the interior of the apparatus  1 . The air becoming warmed during the cooling is then exhausted to the outside of the picture display apparatus  1  through the exhaust port  111 . 
     The picture display apparatus  1  is operated by the user who operates an operation button  113 , or by an operation signal provided by an external source to the apparatus  1  through a first remote-operation receiving unit  117 . The picture display apparatus  1  is carried by the user by grabbing a handle  122 . 
     FIG. 3 is a diagram showing a squint view of the bottom of the external appearance of the picture display apparatus  1  shown in FIG.  2 . 
     On the bottom of the picture display apparatus  1 , there is provided a replacement cover  114  to be opened to allow a light source to be accessed for replacement by another. In addition, there are also provided a first adjustment foot  112  and a second adjustment foot  115  for adjusting the installation angle of the picture display apparatus  1  as a whole in order to adjust a projection angle of a projected picture. To put it in detail, the heights of the first and second adjustment feet  112  and  115  are adjusted in order to finely adjust the position and the gradient of the projected picture. 
     Picture signals generated by external sources are supplied to the picture display apparatus  1  through a first input terminal  118  and a second input terminal  120 . Power is supplied to the picture display apparatus  1  through a power supply connector  119 . A second remote-operation receiving unit  116  provided on the rear surface of the picture display apparatus  1  has the same function as the first remote-operation receiving unit  117  shown in FIG.  2 . 
     On the side surface opposite to the handle  122  shown in FIG. 2, there are provided foots  121  each having a height bigger than those of the input terminals  118  and  120  so that, when the user carrying the picture display apparatus  1  by grabbing the handle  122  puts the apparatus  1  on a floor, the terminals  118  and  120  and other components provided on the same surface are not injured. 
     FIGS. 4A and 4B are diagrams showing respectively a squint view and a side view of an operating state of the picture display apparatus  1  shown in FIG.  1 . As shown in the figures, beams radiated by the picture display apparatus  1  are projected on a screen as a picture  122 . As shown in FIG. 4B, the picture display apparatus  1  projects the picture  122  at such a position on the screen that an optical axis  124  of the projected beams is oriented upward with respect to an optical axis  123  of the projection unit, forming the so-called gate quantity(or gate angle)  126  on an optical axis  125  of the projection lens. The gate quantity  126  formed on the optical axis  125  of the projection lens avoids keystone distortion (or trapezoidal distortion) which is generated when a picture is projected on a higher screen with the picture display apparatus  1  placed on a flat base such as a desk. To put it in detail, by placing the projection lens at such a location that the optical axis  125  of the projection lens is set at a predetermined displacement from the optical axis  123 , a picture projected in a slanting direction will have a shape with no rectangular distortion or the like. The predetermined displacement is referred to hereafter as a gate quantity  126 . 
     To be more specific, a displacement of a predetermined optical axis set in advance is referred to as a gate and the magnitude of the gate is known as a gate quantity  126 . A gate quantity  126  is provided in the upward direction as shown in FIG.  4 B. 
     When the picture display apparatus  1  is suspended from a ceiling, the apparatus  1  is turned upside down when compared with the installation posture shown in FIG.  4 . In this case, a picture can be projected on a screen beneath the ceiling with the optical axis  124  of the projected beams oriented downward with respect to the ceiling. 
     FIG. 5 is a diagram showing an optical configuration inside the picture display apparatus shown in FIG.  1 . 
     As shown in the figure, a beam emitted by the light source  101  at a proper quantity of light first of all passes through a first integrator lens  202 , a second integration lens  203  and a first collimator lens  401  before being reflected by a first reflection mirror  407 . The reflected beam then passes through a second collimator lens  301 , being guided to a second dichroic mirror  408 . In the second dichroic mirror  408 , the beam is split into  2  components with different colors which are typically red and cyan. The red component passes through the second dichroic mirror  408 , traveling to a fourth reflection mirror  412  while the cyan component is reflected to a third dichroic mirror  409 . In the third dichroic mirror  409 , the incident cyan component is further split into 2 components with different colors which are typically green and blue. The blue component passes through the third dichroic mirror  409 , traveling to an first relay lens  402  while the green component is reflected to a G (green) condenser lens  405 . In this way, the beam is split into a plurality of color components required for expressing a color picture. 
     The beam components with different colors travel to light valve means dedicated to the different colors. To be more specific, the red beam component reflected by the fourth reflection mirror  412  travels to an R light valve device  413  by way of an R (red) condenser lens  404 . The green beam component incident to the G condenser lens  405  goes to a G light valve device  415 . The blue beam component incident to the first relay lens  402  goes to a B (blue) light valve device  414  by way of a filter  419 , a fourth reflection mirror  410 , a B relay lens  403 , an sixth reflection mirror  411  and a B condenser lens  406 . Driven by a driving circuit means not shown in the figure, each of the light valve means for the different color components displays an image so that the beams of the different color components incident to the light valve means are modulated in the means according to the images before traveling to the projection unit  500 . The projection unit  500  employs a prism serving as a synthesis means for synthesizing a plurality of color components. Eventually, the modulated beams are radiated to the outside of the picture display apparatus  1  by a projection lens  501 . 
     As a result, the images displayed on the light valve devices  413 ,  414  and  415  for the different colors are projected on a screen not shown in the figure as a picture with an enlarged size. 
     As explained earlier by referring to FIG. 4, a gate quantity is set by, among others, shifting the optical axis of the prism and the optical axis of the projection lens  501  employed in the projection unit  500 . Thus, a beam obtained as a result of a synthesis in the prism is projected in a direction shifted by an angle corresponding to the gate quantity set by the projection lens  501 . 
     FIG. 6 is a diagram showing the configuration of an optical system  10  inside the picture display apparatus shown in FIG.  1 . FIG. 5 shows a layout of optical components of the optical system  10  which are supported by a lower-side unit case  700  of the optical system  10 . 
     The light source  101  is installed on the optical unit  10 , being supported by a light-source unit  100 . The light-source unit  100  needs to be replaced when necessary in dependence on conditions of its usage. For this reason, the light-source unit  100  can be attached to and detached from the optical unit  10 . 
     A centrifugal cooling means  130  introduces an air from the atmosphere outside the picture display apparatus and blows a wind to members which are required to be cooled. Examples of the members that need to be cooled are the light valve means in the optical unit  10 . 
     The projection unit  500  is installed on the lower-side unit case  700  constituting a lower-side portion of the optical unit  10 . That is, the projection unit  500  is installed on the lower-side unit case  700  which supports the optical components as described above. 
     FIG. 7 is a diagram showing an upper-side unit case  701  installed on the lower-side unit case  700  in the configuration of the optical unit  10  explained earlier by referring to FIG.  6 . 
     On the upper-side unit case  701 , there are installed a first cover  160  and a second cover  161  above the light valve means. 
     A light-source housing  151  is installed above the light-source unit  100  and an axial fan  150  is further provided on the light-source housing  151 . The axial fan  150  is used mainly for cooling the light-source unit  100  and components in close proximity thereto. 
     FIG. 8 is a diagram showing a state in which the optical unit  10  is accommodated in an external cabinet. For explanation purposes, the figure shows the external cabinet with the upper portion thereof removed. 
     In the optical unit  10  accommodated in the external cabinet of the picture display apparatus  1 , an air introduced from the atmosphere outside the apparatus  1  by way of the inlet port  110  is supplied to a centrifugal cooling means  130  for cooling mainly components in the optical unit  10 . After cooling the components, the air is exhausted to the inside of the external cabinet. On the other hand, the axial fan  150  facing the exhaust port  111  exhausts the air warmed after being used for cooling the light-source unit  100  and the components in close proximity thereto to the outside of the picture display apparatus  1 . At that time, the air flowing to spaces in close proximity to the light-source unit  100  is the air inside the external cabinet which includes the air used for cooling the components in the optical unit  10  described above. In addition, the axial fan  150  also exhaust all the air used for cooling electrical circuit components such as a power supply and a signal processing circuit, which are not shown in the figure, to the outside of the picture display apparatus  1 . 
     The cooling temperature of the light source  101  employed in the light-source unit  100  is typically 600 degrees Celsius which is much higher than a typical cooling temperature of 50 degrees Celsius for the optical unit  10  and the power supply not shown in the figure. Thus, the air with a temperature thereof increased from an atmospheric temperature of typically 20 degrees Celsius to about 25 degrees Celsius after being used once for cooling the optical unit  10  and the power supply can be still used for cooling the light source  101  without causing a problem. 
     In this way, the whole picture display apparatus  1  is cooled. 
     The description is continued by referring back to FIG.  1 . 
     As described above, the projection unit  500  can be attached to and detached from the lower-side unit case  700 . The position of the projection unit  500  on the lower-side unit case  700  is fixed by putting a positioning hole  510 , a first positioning hole  511  and a second positioning hole  512  provided on the projection unit  500  in a state of being engaged respectively with 3 protrusions provided on the lower-side unit case  700 , namely, a first positioning protrusion  710 , a second positioning protrusion  711  and a third positioning protrusion  712 . To be more specific, first of all, the positioning hole  510  provided on the projection unit  500  is put in a state of being engaged with the first positioning protrusion  710  provided on the lower-side unit case  700 . Then, the first positioning hole  511  provided on the projection unit  500  is put in a state of being engaged with the second positioning protrusion  711  provided on the lower-side unit case  700 . Finally, the second positioning hole  512  provided on the projection unit  500  is put in a state of being engaged with the third positioning protrusion  712  provided on the lower-side unit case  700 . 
     After the projection unit  500  has been put in a state of being engaged with the lower-side unit case  700 , the projection unit  500  is then fixed on the lower-side unit case  700  by tightening a fix screw  713 . 
     FIG. 9 is a diagram showing a squint view of the attachment/detachment state of the projection unit  500  of FIG. 1 seen from a different angle. The projection unit  500  can be directly attached to and detached from the lower-side unit case  700 . That is, the projection unit  500  including the light valve means can be attached to and detached from the lower-side unit case  700  so that preventive maintenance work such as cleaning the light valve means can be done without removing other components such as the upper-side unit. 
     If a direction to remove the projection unit  500  indicated by an arrow  730  is oriented to match a setting direction of the gate quantity of the projection lens, the removal distance can be shortened so that the projection unit  500  can be removed with ease. 
     FIG. 10 is a diagram showing a squint view of details of a cooling system. FIG. 11 is a diagram showing details of connection of a duct employed in the cooling system shown in FIG.  10 . 
     A duct serving as a wind guiding unit  714  is provided on the lower-side unit case  700  employed in the optical unit  10 . As shown in FIG. 11, the wind guiding unit  714  serves as a wind guiding path in conjunction with a guide member  717  provided separately. A wind output by a centrifugal fan  140  blows to components including the light valve means through this wind guiding path. At the ends of the wind guiding path comprising the wind guiding unit  714  and the guide member  717 , there are branch portions at which the wind guiding unit  714  is split into a second wind guiding unit  715  and  2  other branch wind guiding paths going to the light valve means  414 . A first cooling wind  719  flows through a side supply opening  722  to cool the light valve means  413 ,  414  and  415 , and a second cooling wind  720  flows through a bottom supply opening  721  to cool the light valve means  413 ,  414  and  415 . A wind guiding plate  716  is provided for the second wind guiding unit  715 . The wind guiding plate  716  and the second wind guiding unit  715  are 2 members constituting another wind guiding path or a third branch wind path. At the end of the this third branch wind guiding path, there is a space  718  between the first collimator  301  and the second integrator lens  203 . The duct serving as the second guiding unit  715  is connected to the space  718 . In this configuration, when the centrifugal tan  140  is rotating, a wind blown by the centrifugal fan  140  is split at the branch portions of the wind guiding path comprising the wind guiding unit  714  and the guide member  717 , going to the 2 branch wind guiding paths toward the light valve means  414  and the B branching wind guiding unit  715  serving as the third branch wind guiding path. The wind going to the second branching wind guiding unit  715  serving as the third branch wind guiding path further blows forward to the space  718  between the first collimator  301  and the second integrator lens  203 , cooling the first collimator  301  and the second integrator lens  203  which serve as optically functioning parts. The wind then enters the outside of the optical unit  10 . 
     In this way, it is possible to cool not only the light valve means and its peripheral parts, but also the optically functioning parts. 
     FIG. 12 is an explanatory diagram showing directions of cooling winds around the light valve means. As shown in this figure, a wind blown by the centrifugal fan  140  is split at the branch portions to ducts (wind guiding paths), some of which end at a side supply opening  722  and a bottom supply opening  721  which both face the light valve means  414  and are oriented in directions almost perpendicular to each other as shown in FIG.  12 . The winds are thus blown through a plurality of supply openings in directions within the range 45 to 315 degrees. By blowing 2 winds in different directions in this way, at about the center of the light valve means  414 , the flows of winds form a turbulent flow, increasing the heat-transfer efficiency and making effective cooling possible. That is, a turbulent flow is formed forcibly to increase the cooling efficiency. In this way, the cooling power can be enhanced without increasing the wind blowing capacity in particular. 
     That is, a turbulent flow is formed forcibly to increase the cooling efficiency. In this way, the cooling power can be enhanced without increasing the wind blowing capacity in particular. 
     The flows of airs are explained with reference to FIG. 12 by taking a light valve means as an example. In actuality, however, polarization means are provided on the upstream and downstream sides of the light valve means in many cases. Much like a light valve means, a polarization means is also an optically functioning part that dissipates heat, hence, requiring cooling. It is needless to say that a polarization means provided at the location of the light valve means shown in FIG. 12 can be cooled in the same way. In addition, with polarization means provided on the upstream and downstream sides of the light valve means, the polarization means and the light valve means can also be cooled simultaneously in the same way as well. 
     In a word, the first embodiment of the present invention is capable of providing a solution to the problem of a rising amount of heat dissipated by optically functioning components accompanying an increase in luminance. The embodiment has an effect of effectively solving the problem by blowing cooling winds to the light valve means at a plurality of different angles to increase the heat-transfer efficiency and applying the same cooling means as the light valve means to optically functioning components other than the light valve means to cool those components. As for the maintainability of the light valve means and components in close proximity to the light valve means, the picture display apparatus is designed into a configuration wherein the projection unit can be attached to and detached from the optical unit. The embodiment also allows the projection unit to be attached and detached from the optical unit by attaching and detaching the projection unit to and from the optical unit in a direction coinciding the direction of the gate quantity of the projection lens, hence, exhibiting an effect of excellent maintainability. 
     FIG. 13 is a diagram showing a squint view of cooling by a second embodiment of the present invention. As shown in the figure, the light valve means  414  and components in close proximity to the light valve means  414  are cooled by blowing winds over the back surface or the surface of incidence and the front surface or the surface of emission of the light valve means  414  in directions opposite to each other. To put it in detail, a blowing direction  724  of a supply opening  722  on the surface of incidence is opposite to a blowing direction  723  of a supply opening  721  on the surface of emission. In this way, the temperature gradients of the light valve means can be averaged unlike the conventional technique of cooling the light valve means whereby a wind is blown in only one direction so that the temperature on the incidence side of the wind is low while the temperature on the emission side of the wind is relatively high. In addition, since the temperature gradients can be averaged, the highest temperature in the light valve means in question can be suppressed and, as a result, the cooling efficiency is increased. According to the second embodiment of the present invention, there is exhibited an effect of an improved cooling efficiency of the light valve means and components in close proximity to the light valve means. 
     FIG. 14 is a diagram showing branching of ducts in a third embodiment of the present invention. 
     As shown in FIG. 14, a wind blown by the centrifugal fan  0  is split at a wind guiding path  714  into a wind going to the light valve means  414  and a wind proceeding through a wind guiding path  715 . The wind proceeding through the wind guiding path  715  is further split at a branch portion into a wind going to a space  718  between the first collimator  301  and the second integrator lens  203 , and a wind proceeding to a space  780  between the light source  101  and the first integrator lens  401 . The wind that further blows forward to the space  718  between the first collimator  301  and the second integrator lens  203  cools the first collimator  301  and the second integrator lens  203  which serve as optically functioning parts. On the other hand, the wind proceeding to a space  780  between the light source  101  and the first integrator lens  401  cools the surface of emission of the light source  101  and the first integrator lens  401 . After the cooling, the winds are exhausted to the outside of the optical unit. According to the third embodiment of the present invention, there is exhibited an effect of a capability of efficiently cooling a plurality of optically-functioning-component pairs that need to be cooled. 
     FIG. 15 is a diagram showing a squint view of a fourth embodiment of the present invention. 
     In the configuration of the fourth embodiment, the light valve means  413 ,  414  and  415  and a prism unit  760  serving as a color synthesizing means are assembled to form a single body which can be attached to and detached from the optical unit. 
     With such the configuration according to the fourth embodiment of the present invention, there is exhibited an effect of easy maintenance such as cleaning to solve problems caused by, among other things, sticking of dust to the light valve means as described above. 
     The present invention has been exemplified by embodiments employing liquid crystals as light valve means. It should be noted that another light valve means of the transmission or reflection type such as a infinitesimal mirror array system or the laser address liquid-crystal system can also be used in the same way as long as the other light valve means is capable of modulating an incident light and projected the modulated light as a picture. In addition, the present invention has been exemplified by the so-called 3-plate system wherein 3 light valve means  413 ,  414  and  415  are employed. It is needless to say, however, that the same effects can be exhibited for a system employing only 1 or 2 light valve means. 
     In the system implemented by the embodiments described above, a picture is projected on a screen from a position in front of the screen. It is worth noting that the scope of the present invention is not limited to such embodiments. For example, the present invention can also be applied to a picture display apparatus of the so-called back-surface projection type wherein a picture is projected on a screen from a position behind the screen. 
     In addition, while the picture display apparatus has been exemplified by a portable compact apparatus, it is needless to say that the same effects can be obtained for an apparatus of any other type such as a fixed apparatus permanently installed at a place like a theater or an outdoor apparatus installed outside a building as part of the building. 
     In a word, the present invention provides a picture display apparatus for radiating a light emitted by a light source to a light valve means for modulating the light and projecting the modulated light on a screen as a picture, wherein the light valve means is cooled by blowing winds to the light valve means at a plurality of different angles to create a turbulent flow so as to increase the cooling efficiency. As for the cooling of optically functioning components other than the light valve means, a cooling wind is split at a branch portion of a duct to provide a configuration in which the optically functioning components other than the light valve means and the light valve means itself can be cooled at the same time. 
     In addition, the picture display apparatus is designed into a configuration wherein a projection means can be detached from the optical unit in the upward direction and an installation base common to the projection means and the optical unit is adopted to avoid a problem of a shift in optical position accompanying an attachment or a detachment of the projection unit to and from the optical unit. Furthermore, in an attachment or a detachment of the projection unit to and from the optical unit, the projection means alone can be attached to or detached from the optical unit with ease without the necessity to disassemble the optical unit. 
     As described above, the light valve means can be cooled with a high degree of efficiency by virtue of a turbulent flow of cooling winds. In addition, it is possible to use the cooling means for cooling the light valve means also for cooling other optically functioning components which need cooling as the luminance is increased. Moreover, since the projection means can be attached to or detached from the optical unit with ease, the maintenance work is made simple. 
     As described above, according to the present invention, it is possible to cool light valve means, components in close proximity thereto and other optically functioning components as well as to remove dust from the light valve means. 
     The present invention can be implemented by modified versions of the embodiments described above without deviating from the spirit and principal characteristics of the invention. Thus, the embodiments described above are no more than just preferred examples to implement the present invention in several aspects and, thus, are not intended to limit the scope of the invention. The scope of the present invention is defined by the range of claims appended at the end of this specification. It is therefore contemplated that the appended claims will cover any such modified versions of the embodiments as they fall within the true scope of the present invention.