Abstract:
A projection display apparatus generates image light by modulating, with an image signal, light emitted from a light source disposed in a lamp house, and projects the generated image light onto a screen. The projection display apparatus has an air inlet duct for introducing air, to cool the light source, into the lamp house and an air outlet duct for expelling the air discharged from the lamp house out of the projection display apparatus. The air outlet duct has an opening defined in a side wall thereof, and a lid pivotally mounted thereon for selectively opening and closing the opening. The lid is not opened under normal pressure in the air outlet duct when the light source operates normally, and is opened when an abnormal pressure buildup higher than the normal pressure is applied to the lid, thereby releasing the pressure buildup.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a light source device and a projection display apparatus, and more particularly to a technology for minimizing damage caused when a high-pressure discharge lamp as a light source is burst.  
         [0003]     2. Description of the Related Art  
         [0004]     Projection display apparatus such as liquid crystal projectors and DLP (Digital Light Processing) projectors have recently been in widespread use. Generally, a projection display apparatus has a lamp as a light source, an image forming device for modulating light emitted from the lamp with an image signal, and an image optics for projecting image light that is generated by the image forming device onto a screen at an enlarged scale.  
         [0005]     One conventional DLP projector having three digital micromirror devices (DMDS) is shown in  FIG. 1  of the accompanying drawings. As shown in  FIG. 1 , the DLP projector has a light source comprising high-pressure discharge lamp  50  placed in metal lamp house  51  that is disposed in a main housing. Light emitted from high-pressure discharge lamp  50  is collected and guided by a reflector to travel through a predetermined light path to prism unit  52 . The light applied to prism unit  52  is separated thereby into color lights in three primaries, i.e., red (R), green (G), and blue (B). Each of the separated color lights are then applied to the DMDs (not shown). The DMDs modulate the respective color lights and output the modulated color lights again to prism unit  52 , which combines the color lights into image light. The image light is then projected by projection lens  53  onto a screen (not shown) at an enlarged scale.  
         [0006]     The DLP projector also has a cooling fan  55  disposed in the main housing to-cool high-pressure discharge lamp  50 . Cooling fan  55  delivers cooling air (ambient air) through inlet duct  56  into lamp house  51 . After having cooled high-pressure discharge lamp  50 , the cooling air is discharged through outlet duct  57  out of the main housing. High-pressure discharge lamp  50  is burst on rare occasions due to shocks, abnormal temperature rises, or individual lamp defects inherent in high-pressure discharge lamp  50 . When high-pressure discharge lamp  50  is ruptured, the bulb thereof and the nearby reflector are broken up into pieces under the shock of the rupture, and the broken pieces tend to flow through outlet duct  57  and be ejected from the main housing. To avoid damage due to the ejected pieces, outlet duct  57  is designed to have a snake like shape with increased length and which incorporates therein three metal mesh filters  58  through  60  to prevent the broken pieces from being scattered out of the main housing. Details of the structure for preventing the broken pieces from being scattered out of the main housing are disclosed in Japanese laid-open patent publication No. 2003-202630 and Japanese laid-open patent publication No. 2004-294749.  
         [0007]     Xenon lamps have a high internal bulb pressure of about  20  atmospheric pressures and a large volume. When they are burst, they are liable to release energy large enough to deform the metal lamp house which houses the xenon lamp therein. If the light source of a projection display apparatus comprises a xenon lamp, therefore, it is necessary to combine the xenon lamp with a more reliable and stronger structure for preventing broken pieces of the lamp from being ejected rather than instead of using other lamps as the light source.  
         [0008]     The conventional proposal to use a longer outlet duct with metal mesh filters disposed therein is disadvantageous in that the cooling air cannot be discharged efficiently and has a reduced cooling effect, and the projector itself tends to become unduly large in size. In Particular, the longer outlet duct directly results in an increase in the size of the projector.  
       SUMMARY OF THE INVENTION  
       [0009]     It is an object of the present invention to provide a light source device and a projection display apparatus which have a structure for reliably preventing broken pieces of a lamp from being scattered out when the lamp is ruptured, without causing an increase in the size of the light source device and the projection display apparatus and without causing a reduction in the cooling effect.  
         [0010]     According to an aspect of the present invention, there is provided a projection display apparatus comprising a lamp house, a high-pressure discharge lamp disposed in the lamp house, an image forming device for modulating light emitted from the high-pressure discharge lamp with an image signal, and an image optics for projecting image light generated by the image forming device, the lamp house having an air inlet port for introducing cooling air therethrough, an air outlet port for discharging the cooling air that is introduced through the air inlet port, at least one opening other than the air inlet port and the air outlet port, and a lid for opening the opening only when a pressure higher than the pressure of the cooling air that is introduced through the air inlet port and discharged through the air outlet port is applied to the lid.  
         [0011]     According to another aspect of the present invention, there is provided a projection display apparatus comprising an air outlet duct that is connected to the air outlet port of the lamp house and has at least one opening and a lid for opening the opening only when a pressure higher than the pressure of the cooling air introduced that is through the air inlet port and discharged through the air outlet port is applied to the lid.  
         [0012]     According to still another aspect of the present invention, there is provided a light source device comprising a lamp house and a high-pressure discharge lamp disposed in the lamp house, the lamp house having an air inlet port for introducing cooling air therethrough, an air outlet port for discharging the cooling air that is introduced through the air inlet port, at least one opening other than the air inlet port and the air outlet port, and a lid for opening the opening only when a pressure higher than the pressure of the cooling air introduced through the air inlet port and discharged through the air outlet port is applied to the lid.  
         [0013]     According to yet another aspect of the present invention, there is provided a light source device comprising an air outlet duct that is connected to the air outlet port of the lamp house and has at least one opening and a lid for opening the opening only when a pressure higher than the pressure of the cooling air introduced through the air inlet port and discharged through the air outlet port is applied to the lid.  
         [0014]     The lid is not opened under a pressure lower than the pressure of the cooling air that is introduced through the air inlet port and discharged through the air outlet port, and is opened only when a pressure higher than the pressure of the cooling air that is introduced through the air inlet port and discharged through the air outlet port is applied to the lid.  
         [0015]     The above and other objects, features, and advantages of the present invention will become apparent from the following description with reference to the accompanying drawings which illustrate examples of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a schematic plan view of a conventional projection display apparatus;  
         [0017]      FIG. 2  is a schematic plan view of a projection display apparatus according to a first embodiment of the present invention;  
         [0018]      FIG. 3  is an enlarged cross-sectional view of a lamp house and nearby components of the projection display apparatus shown in  FIG. 2 ;  
         [0019]      FIG. 4  is an enlarged perspective view of a first duct member of the projection display apparatus shown in  FIG. 2 ;  
         [0020]      FIG. 5  is a schematic plan view of a projection display apparatus according to second embodiment of the present invention;  
         [0021]      FIG. 6  is a schematic plan view of a projection display apparatus according to a third embodiment of the present invention; and  
         [0022]      FIG. 7  is an enlarged perspective view of a lamp house of the projection display apparatus shown in  FIG. 5 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]     Like or corresponding parts are denoted by like or corresponding reference characters throughout views.  
       1st Embodiment  
       [0024]     A projection display apparatus according to a first embodiment of the present invention is a DLP projector having DMDs (Digital Micromirror Devices) as image forming devices (light valves).  FIG. 2  shows in schematic plan the projection display apparatus according to the first embodiment of the present invention.  FIG. 3  shows in enlarged cross section a lamp house and nearby components of the projection display apparatus shown in  FIG. 2 .  FIG. 4  shows in enlarged perspective a part of first duct member of the projection display apparatus shown in  FIG. 2 .  
         [0025]     As shown in  FIG. 2 , lamp house  2  is disposed in a main housing  3  of the DLP projector, and accommodates therein xenon lamp  1  as a light source. Lamp house  2  is in the form of a metal box. Lamp house  2  houses therein a reflector for collecting and guiding light emitted from xenon lamp  1 . Lamp house  2  has a window (not shown) though which the light that is guided by the reflector is projected from the lamp house  2 .  
         [0026]     As shown in  FIG. 3 , lamp house  2  has two air inlet ports  6  defined in side wall  5  thereof and two air outlet ports  8  defined in side wall  7  that is located opposite to side wall  5 . The main housing  3  accommodates therein cooling fan  10  in the form of a sirocco fan. Lamp house  2  communicates with cooling fan  10  through air inlet ports  6  and communicates with the exterior of the main housing  3  through air outlet ports  8 . Specifically, air inlet duct  11  has an end opening that is connected to an air delivery port (not shown) of cooling fan  10  and also has two air discharge ports  12  defined in a side wall thereof. Air discharge ports  12  are connected each of air inlet ports  6  of lamp house  2 . Air outlet duct  13  has an end opening that is connected to air exhaust port  15  (see  FIG. 2 ) defined in the main housing  3  and hence communicates with the exterior of the main housing  3 . Air outlet duct  13  has two air intake ports  16  defined in a side wall thereof and connected to each of air outlet ports  8  of lamp house  2 . Each of air inlet ports  6  of lamp house  2  have protruding flanges fitted in each of air discharge ports  12  of air inlet duct  11 . Similarly, each of air outlet ports  8  have protruding flanges fitted in each of air intake ports  16  of air outlet duct  13 . Air inlet duct  11  and air outlet duct  13  may have flanges held in close contact with side walls  5 ,  7 , respectively. Alternatively, lamp house  2 , air inlet duct  11 , and air outlet duct  13  may have no flanges at all.  
         [0027]     As shown in  FIG. 2 , air outlet duct  13  comprises first duct member  13   a , second duct member  13   b , third duct member  13   c , and fourth duct member  13   d . These duct members  13   a  through  13   d  are in the form of prismatic tubes made of synthetic resin or metal. As shown in  FIG. 3 , air intake ports  16  that are connected to each of air outlet ports  8  of lamp house  2  are defined in a side wall of first duct member  13   a . As shown in  FIG. 2 , fourth duct member  13   d  has an end that is connected to air exhaust port  15  defined in the main housing  3 . Second duct member  13   b  and third duct member  13   c  are positioned between and interconnect first duct member  13   a  and fourth duct member  13   d.    
         [0028]     First duct member  13   a  has opening  17  defined in an end wall thereof that is opposite the end wall thereof that is joined to second duct member  13   b . Plate-like lid  18  is swingably mounted on first duct member  13   a  for selectively opening and closing opening  17 . As shown in  FIG. 4 , lid  18  has a side edge pivotally mounted on a side edge of opening  17  by spring-biased hinge  20 . Lid  18  is normally urged by spring-biased hinge  20  to close opening  17  as indicated by the arrow “a”. Lid  18  can be opened as indicated by the arrow “b” only when xenon lamp  1  (see  FIG. 2 ) is burst. Specifically, when xenon lamp  1  is burst, the internal pressure in lamp house  2  increases, and hence the internal pressure in first duct member  13   a  that is connected to lamp house  2  also increases. The pressure buildup in first duct member  13   a  pushes lid  18  open against the bias of spring-biased hinge  20 , as indicated by the arrow “b”. Now, the pressure in first duct member  13   a  is released through opening  17 . Cooling fan  10  forcibly delivers ambient air as cooling air into lamp house  2 . After having cooled xenon lamp  1  in lamp house  2 , the cooling air is discharged to the exterior through air outlet duct  13 . The spring force of spring-biased hinge  20  is set to such a value that lid  18  is not opened under normal pressure (air pressure) P in air outlet duct  13 , and lid  18  is opened under a pressure buildup in lamp house  2  that is higher than the pressure P.  
         [0029]     When the pressure in lamp house  2  rises to an abnormally high level due to the rupture of xenon lamp  1 , lid  18  is automatically opened under the pressure buildup to release the excessive pressure through opening  17 . Therefore, broken pieces of xenon lamp  1  are prevented from being ejected from the main housing  3  through air outlet duct  13  even if the number of mesh filters that are disposed in air outlet duct  13  is smaller than in the conventional projection display apparatus. Consequently, the projection display apparatus according to the first-embodiment provides the same safety as or higher safety than the conventional projection display apparatus with a smaller number of mesh filters disposed in air outlet duct  13 .  
         [0030]     According to the first embodiment, mesh filters are interposed between first duct member  13   a  and second duct member  13   b  and between third duct member  13   c  and fourth duct member  13   d . Stated otherwise, no mesh filter is interposed between second duct member  13   b  and third duct member  13   c.    
         [0031]     When the pressure in lamp house  2  drops back to a normal level, opening  17  is automatically closed by lid  18  under the bias of spring-biased hinge  20 . When broken xenon lamp  1  is replaced with new xenon lamp  1 , the light source device can be used again. Lamp house  2  and air outlet duct  13  do not need to be replaced.  
         [0032]     The number of mesh filters used and the locations of those mesh filters are determined taking into consideration the length and volume of air outlet duct  13 . Therefore, the number of the mesh filters and the locations thereof are not limited to those described above. According to the present invention, however, the projection display apparatus provides the same safety as or higher safety than the conventional projection display apparatus with a smaller number of mesh filters disposed in air outlet duct  13  insofar as those projection display apparatus are used under the same conditions.  
         [0033]     According to the present invention, furthermore, the projection display apparatus provides the same safety as or higher safety than the conventional projection display apparatus even if air outlet duct  13  shown in  FIG. 2  is shorter.  FIG. 5  shows in schematic plan a projection display apparatus with a shorter air outlet duct according to a modification of the first embodiment. The projection display apparatus shown in  FIG. 5  is also a DLP projector. The DLP projector shown in  FIG. 5  has air outlet duct  13  comprising first duct member  13   a , second duct member  13   b , and third duct member  13   c , with fourth duct member  13   d  being dispensed with. Third duct member  13   c  communicates with the exterior of the main housing  3 . Air outlet duct  13  shown in  FIG. 5  allows housing  3  and hence the DLP projector to be reduced in size. Those parts shown in  FIG. 5  which are identical to those shown in  FIG. 2  are denoted by identical reference characters.  
         [0034]     Other details of the DLP projectors shown in  FIGS. 2 and 5  which have not been described above are identical to those of the conventional DLP projector. Specifically, light emitted from xenon lamp  1  is collected and guided by a reflector to travel through a predetermined light path to prism unit  21 . The light applied to prism unit  21  is separated thereby into color lights in three primaries, i.e., red (R), green (G), and blue (B). Each of the separated color lights are then applied respectively to the DMDs (not shown). The DMDs modulate the respective color lights and output the modulated color lights again to prism unit  21 , which combines the color lights into image light. The image light is then projected by projection lens  22  onto a screen (not shown) at an enlarged scale.  
         [0035]     The projection display apparatus according to the present invention is not limited to a 3-chip DLP projector. The present invention is applicable to all projection display apparatus which employ a high-pressure discharge lamp as a light source, including 1-chip DLP projectors and liquid crystal projectors.  
       2nd Embodiment  
       [0036]     A projection display apparatus according to a second embodiment of the present invention is shown in  FIGS. 6 and 7 . The projection display apparatus according to the second embodiment is a DLP projector having basic structural details identical to those of the DLP projectors shown in  FIGS. 2 and 5 . Those parts shown in  FIG. 6  and  7  which are identical to those shown in  FIGS. 2 and 5  are denoted by identical reference characters, and will not be described in detail below.  
         [0037]     The DLP projector according to the second embodiment differs from the DLP projector according to the first embodiment in that lamp house  2  has opening  30  and lid  31 . Specifically, as shown in  FIGS. 6 and 7 , opening  30  is defined in side wall  32  of lamp house  2  which lies perpendicularly to side wall  5  connected to air inlet duct  11  and side wall  7  connected to air outlet duct  13 . Opening  30  is omitted from illustration in  FIG. 6  for the sake of brevity. Plate-like lid  31  is swingably mounted on lamp house  2  for selectively opening and closing opening  30 . As shown in  FIG. 7 , lid  31  has a side edge pivotally mounted on a side edge of opening  30  by spring-biased hinge  33 . Lid  31  is normally urged by spring-biased hinge  33  to close opening  30  as indicated by the arrow “a”. Lid  31  can be opened as indicated by the arrow “b” only when xenon lamp  1  (see  FIG. 6 ) is burst. Specifically, when xenon lamp  1  is burst, the internal pressure in lamp house  2  increases. The pressure buildup in lamp house  2  pushes lid  31  open against the bias of spring-biased hinge  33 , as indicated by the arrow “b”. At this stage, the pressure in lamp house  2  is released through opening  30 . Cooling fan  10  forcibly delivers ambient air as cooling air into lamp house  2 . After having cooled xenon lamp  1  in lamp house  2 , the cooling air is discharged to the exterior though air outlet duct  13 . The spring force of spring-biased hinge  33  is set to such a value that lid  33  is not opened under normal pressure (air pressure) P in lamp house  2  and lid  33  is opened under pressure buildup in lamp house  2  that is higher than the pressure P.  
         [0038]     As shown in  FIG. 7 , mesh filters  35  are fitted in each of air outlet ports  8  that are defined in side wall  7  of lamp house  2 . Air outlet ports  8  have different sizes.  
         [0039]     When xenon lamp  1  is ruptured, lid  31  is automatically opened under the pressure buildup to release the excessive pressure through opening  30 . Therefore, as with the DLP projector according to the first embodiment, the projection display apparatus according to the second embodiment provides the same safety as or higher safety than the conventional projection display apparatus with a smaller number of mesh filters being used. The projection display apparatus according to the second embodiment provides the same safety as or higher safety than the conventional projection display apparatus even if air outlet duct  13  is shorter.  
         [0040]     The projection display apparatus according to the present invention include projection display apparatus having all the features described above. For example, the projection display apparatus may have openings which are defined in both the lamp house and the air outlet duct and which can be automatically opened under a pressure buildup developed when the light source is ruptured.  
         [0041]     According to the first embodiment, of the duct members of the air outlet duct, the duct member that is positioned most closely to the lamp house has an opening that can automatically be opened by a lid. However, another duct member may have such an opening. From the standpoint of quickly releasing the pressure buildup from the lamp house, it is preferable that an opening that can be automatically opened by a lid be positioned on the lamp house or as close as possible to the lamp house. Though the air outlet duct is constructed of a plurality of duct members according to the first and second embodiments, the air outlet duct may comprise a single duct member.  
         [0042]     While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.