Abstract:
An image displaying projector is provided comprising a lamp for emitting the light for image projection, a light tunnel for receiving the light from the lamp at one end opening of a tubular portion thereof which has two openings provided at both ends, guiding the light as it reflects on an inner side of the tubular portion, and releasing the light from the other end opening of the tubular portion, and an imaging device for producing an optical image by means of the light released from the light tunnel. The light tunnel is made of a thin metal sheet folded to shape the tubular portion which has two openings provided at both ends. The image displaying projector can easily be manufactured with a less number of components and steps. The thin metal sheet of the light tunnel is high in the radiation of heat, preventing from being heated up and fractured by the heat of the light emitted from the lamp.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an image displaying projector for projecting an image onto a screen and a light tunnel structure in an image displaying projector.  
           [0003]    2. Description of the Related Art  
           [0004]    An image displaying projector is known for producing an optical image on its imaging device from its image data supplied by a personal computer or a video camera and projecting it on a screen for display. Such a conventional image displaying projector includes commonly an image projection system shown in FIG. 9 where a light tunnel  92  is provided for condensing and collimating the light received from a lamp  90 . In the image projection system, the light emitted from the lamp  90  (its optical axis denoted by the one-dot chain line with the arrow) is colored by a color wheel  91  and then condensed and collimated by the light tunnel  92  before compensated for waveform effects by a corrective lens  93 . The light from the lamp  90  is reflected by a mirror  94 , converged by a relay lens  95 , and directed to an imaging device  96 . As the light is reflected on an image forming plane of the imaging device  96 , an image produced on the image forming plane can be projected by a projection lens  97 .  
           [0005]    Those components in the conventional image displaying projector are commonly assembled together with a support base  98  and installed in a housing, as shown in FIG. 10. Meanwhile, the color wheel  91  is not illustrated for simplicity. The lamp  90  is separately provided as it has to be replaced with a new one. The light tunnel  92  comprises four glass members bonded together to a tubular shape and mounted to the support base  98  by a metal retainer spring (fitting)  99  pressing down. The retainer spring  99  has a set of elastic press-down tabs  99   a,    99   b,    99   c,  and  99   d  as best shown in FIG. 11. When the retainer spring  99  is joined by screws (not shown) to the support base  98 , its press-down tabs  99   a,    99   b,    99   c,  and  99   d  securely hold down the light tunnel  92 .  
           [0006]    It is however necessary for the light from the lamp  90  effectively reflecting on the imaging device  96  to adjust the angle at which the light tunnel  92  is mounted to the support base  98 . The angle adjustment for the light tunnel  92  is conducted with an angle adjusting spring (not shown) operated to lift up and hold the light tunnel  92  and then pressed down by a couple of angle adjusting screws (not shown).  
           [0007]    The corrective lens  93  has two lenses  93   a  and  93   b  held together to the inner wall of a metal tube  93   e  by retainer rings  93   c  and  93   d  respectively, as shown in FIG. 12. The corrective lens  93  of an assembly is mounted to the support base  98  at the output end of the light tunnel  92 , as shown in FIG. 13.  
           [0008]    Alternatively in a projection display using a space light modulator such as a liquid crystal light bulb, a light tunnel arranged in the cross section to match a geometrical shape of the space light modulator is provided between the light source lamp and the space light modulator for optimizing the intensity of light to be projected onto a screen (for example, as disclosed in Japanese Patent Laid-Open Publication HEI8-271854). Also, a liquid crystal projector is introduced in which a light tunnel arranged to match in the aspect ratio with an imaging device is provided between the light source and the imaging device (for example as disclosed in Japanese Patent Laid-Open Publication HEI8-286146). Moreover, an illuminating apparatus for a projector is equipped with a light tunnel of which the input end for receiving light from the light source is smaller in the cross section than the output end (for example, as disclosed in Japanese Patent Laid-Open Publication HEI10-48476).  
           [0009]    The light tunnel in the conventional image displaying projector however has the four glass members bonded by an adhesive to a tubular form thus increasing the steps of production and resulting in the cost up. Also, the light tunnel of the glass members is mounted to the support base by the retainer spring of an extra component. Furthermore, as the light tunnel is exposed to the light from the lamp, it is heated up and its glass members which are low in the radiation of heat may be deteriorated or fractured if worse. When the light emitted from the lamp is incident to one end plane of the light tunnel, it enters the glass members and its output from the other end may interrupt the image to be projected.  
           [0010]    The adjustment of the angle for the light tunnel is made by the angle adjusting spring lifting the light tunnel and the angle adjusting screws determining the angle. Accordingly, its arrangement becomes intricate while the action of the angle adjusting is not easy. The corrective lens has the two lenses held in the lens holding tube with the held of the retaining rings and its assembly is mounted to the support base. This will increase the number of the components as well as the number of the production steps and hardly reduce the cost. Also, the other prior arts disclosed in Japanese Patent Laid-Open Publications HEI8-271854, HEI8-286146, and HEI10-48476 fail to eliminate the foregoing drawbacks.  
         SUMMARY OF THE INVENTION  
         [0011]    The present invention has been developed for eliminating the foregoing drawbacks and its object is to provide an image displaying projector and a light tunnel structure in an image displaying projector where the light tunnel is made of a thin metal sheet bent to a tubular form acting as a holder for a corrective lens and can be mounted to a support base with no use of extra fittings while its angle for mounting is adjusted with ease.  
           [0012]    According to an aspect of the present invention, an image displaying projector for producing and projecting an optical image, comprises: a lamp for emitting a light for image projection; a light tunnel having a tubular portion and two openings provided at both ends, which receives the light from the lamp at one end opening of the tubular portion, and guides the light as it reflects on an inner side of the tubular portion, and releases it from the other end opening of the tubular portion; and an imaging device for producing an optical image by means of the light released from the light tunnel, wherein the light tunnel is made of a thin metal sheet folded to shape the tubular portion which has two openings provided at both ends.  
           [0013]    Since the light tunnel according to the present invention is made of the thin metal sheet bent to a tubular form, it requires no conventional step of bonding four glass sheets to a tubular form with the use of an adhesive and allows its structure to be fabricated with a less number of components and a less number of steps, hence significantly decreasing its production cost. Also, the light tunnel made of the thin metal sheet is improved in the radiation of heat and can thus be prevented from being heated up and fractured by the heat of the light emitted from the lamp. The light tunnel allows no portions of the light received from the lamp to pass through the tubular portion material itself and interrupt an image to be projected.  
           [0014]    According to another aspect of the present invention, a light tunnel structure in an image displaying projector for producing an optical image by means of the light guided therein through the tunnel from a lamp on an imaging device, wherein the light tunnel has a tubular portion and two openings provided at both ends, which receives the light from the lamp at one end opening thereof, and guides the light as it reflects on an inner side of the tubular portion, and releases it from the other end opening of the tubular portion, wherein the tubular portion is made of a thin metal sheet bend to a tubular form.  
           [0015]    The tubular portion of the light tunnel according to the present invention is made of the thin metal sheet bent to a tubular form and can thus be fabricated with a less number of components and a less number of steps, hence decreasing its production cost. Also, the tubular portion made of the thin metal sheet is improved in the radiation of heat and can thus be prevented from being heated up and fractured by the heat of received light. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 is a schematically perspective view of an image displaying projector which has a light tunnel showing one embodiment of the present invention;  
         [0017]    [0017]FIG. 2 is a perspective view of an interior arrangement of the image displaying projector;  
         [0018]    [0018]FIG. 3 is an exploded perspective view of an image projection engine in the image displaying projector;  
         [0019]    [0019]FIG. 4 is a perspective view of the light tunnel mounted to a body in the image displaying projector;  
         [0020]    [0020]FIG. 5 is a perspective view of a light tunnel showing another embodiment of the present invention;  
         [0021]    [0021]FIG. 6 is a perspective view of the light tunnel mounted to a body;  
         [0022]    [0022]FIG. 7 is a perspective view of a light tunnel showing a further embodiment of the present invention;  
         [0023]    [0023]FIGS. 8A and 8B are cross sectional views taken along the line A-A and the line B-B respectively of FIG. 7 with the light tunnel mounted to the body;  
         [0024]    [0024]FIG. 9 is a perspective view of a conventional optical image projection system;  
         [0025]    [0025]FIG. 10 is a perspective view of the conventional optical image projection system mounted to a support base;  
         [0026]    [0026]FIG. 11 is a perspective view of a conventional light tunnel with a fitting;  
         [0027]    [0027]FIG. 12 is a cross sectional view of a corrective lens in the conventional arrangement; and  
         [0028]    [0028]FIG. 13 is a perspective view of the corrective lens secured in the conventional arrangement. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]    Some embodiments of the present invention will be described referring to the relevant drawings. The description starts with a first embodiment of the present invention. As shown in FIGS. 1 and 2, an image displaying projector  100  is designed for producing an image on an imaging device from an image signal supplied by a personal computer or a video camera and projecting it onto a screen or a wall.  
         [0030]    The image displaying projector  100  has a projection lens  2  provided on the front side of a housing  1  thereof for projecting an optical image produced on the imaging device. Also, the image displaying projector  100  includes an image projection engine  5  for producing an image on the imaging device and projecting it through the projection lens  2  and a lamp unit  6  for illuminating the imaging screen of the image projection engine  5 , both accommodated in the housing  1 . The housing  1  comprises an upper cover  1   a  and a lower case  1   b.  The image projection engine  5  is anchored to the lower case  1   b  while the lamp unit  6  is detachably mounted to a lamp housing  7  in the lower case  1   b.    
         [0031]    The image projection engine  5  is not explained. As shown in FIG. 3, the image projection engine  5  comprises a light tunnel  30 , a tablet (corrective) lens  40 , a reflecting mirror  51 , a relay lens  52 , the imaging device  53 , and a projection lens unit  54  which includes the projection lens  2 . These components are assembled and mounted on a chassis  60  (an image projection engine body) acting as the support base.  
         [0032]    The light tunnel  30  is designed for condensing and collimating the light received from the lamp unit  6  and comprises a tubular portion  31  and a mounting portion  32  formed integral with the tubular portion  31 . The light tunnel  30  is made of a thin metal sheet processed on its surface with a reflecting mirror coating. More specifically, the thin metal sheet is bent at one end with its reflecting mirror coating inside to form the tubular portion  31 . The other end of the thin metal sheet represents the mounting portion  32 .  
         [0033]    As the tubular portion  31  is made by bending the thin metal sheet, its has four-sided openings provided at both ends thereof and its inner space acts as a light guiding path for condensing and collimating the input light. Also, the tubular portion  31  has an inner side thereof covered with a reflective mirror coating for inhibiting the absorption of light and guiding the light at a higher efficiency. The mounting portion  32  has a couple positioning apertures  33   a  and  33   b  and a couple of screw holes  34   a  and  34   b  provided therein for mounting the light tunnel  30  to the chassis  60 .  
         [0034]    The chassis  60  has a tunnel installing groove  61  of a V-shape in the cross section provided therein for installing the tubular portion  31  of the light tunnel  30 , a couple of projections  62   a  and  62   b  provided thereon for determining the position of the light tunnel  30 , and a couple of screw holes  63   a  and  63   b  provided therein for accepting retainer screws (not shown) to retain the light tunnel  30 .  
         [0035]    With the positioning apertures  33   a  and  33   b  of the mounting portion  32  engaging with the positioning projections  62   a  and  62   b,  the tubular portion  31  is set at its position in the tunnel installing groove  61 . Simultaneously, the screw holes  34   a  and  34   b  of the mounting portion  32  are aligned with their respective screw holes  63   a  and  63   b  of the chassis  60  when the positioning apertures  33   a  and  33   b  engage with the positioning projections  62   a  and  62   b.    
         [0036]    As shown in FIG. 4, the light tunnel  30  can correctly be positioned with its tubular portion  31  seated in the tunnel installing groove  61  through having the positioning apertures  33   a  and  33   b  engaged with their respective positioning projections  62   a  and  62   b  and the screw holes  34   a  and  34   b  aligned with their respective screw holes  63   a  and  63   b.  With the retainer screws being threaded in, the light tunnel  30  is fixedly mounted to the chassis  60  with its tubular portion  31  seated in the tunnel installing groove  61 .  
         [0037]    The light emitted from the lamp unit  6  (denoted by the one-dot chain line with the arrow along the optical axis) is colored by a color wheel (not shown) and received by one end opening  30   a  (input side) of the tubular portion  31  where it travels through its inner space (the light guiding path) and reflects on its inner wall thus to be condensed and collimated before released from the other end opening (output side).  
         [0038]    The tablet lens  40  has a couple of lenses (not shown) held by retainer rings to a tube thereof for compensating the effect of wavelengths of the output light released from the tubular portion  31  of the light tunnel  30 . The tablet lens  40  is securely fitted into a lens fitting groove  64  of a semi-circular shape in the cross section provided in the chassis  60  adjacent to the output end of the tubular portion  31 .  
         [0039]    The reflecting mirror  51  is mounted to a mirror mounting side  65  of the chassis  60  for reflecting the light released from the tablet lens  40 . The relay lens  52  is located between the reflecting mirror  51  and the imaging device  53  for converging the light reflected by the reflecting mirror  51  on the imaging device  53 .  
         [0040]    The imaging device  53  has a matrix of micro-mirrors arranged to form the imaging screen for reflecting the input light and producing its optical image. The imaging device  53  is mounted to an opening  66  of the chassis  60  and can reflect the light released from the relay lens  52  and produce its optical image with the micro-mirrors tilted at angles by a signal from a controller (not shown). The projection lens unit  54  is provided in an opening  67  of the chassis  60  for projecting onto a screen the image produced on the reflected light by the imaging device  53 .  
         [0041]    As described, the light tunnel  30  is made with ease by simply bending the thin metal sheet to form its tubular portion  31 . The light tunnel  30  made of a metallic material has a higher degree of heat radiation and can thus be protected from being deteriorated and fractured by the heat of the light emitted from the lamp unit  6 . Also, the light tunnel  30  inhibits the light received from the lamp unit  6  from traveling off its light guide path and interrupting the optical image to be projected. Moreover, the tubular portion  31  and the mounting portion  32  of the light tunnel  30  are formed integral with each other from a single sheet of the metallic material, hence allowing the light tunnel  30  to be mounted to the chassis  60  with no use of extra fittings. The projections  62   a  and  62   b  may be replaced by recesses in the chassis  60  which engage with corresponding projections provided on the mounting portion  32  as replacing the positioning apertures  33   a  and  33   b.    
         [0042]    A second embodiment of the present invention will now be described. As shown in FIGS. 5 and 6, a light tunnel  30  of this embodiment has a tubular portion  31 , a mounting portion  32 , and specifically a lens holder  35  for holding down a couple of lenses  40   a  and  40   b  of a tablet lens  40 . The light tunnel  30  is also made of a thin metal sheet and its tubular portion  31  and mounting portion  32  are identical in the configuration to those of the previous embodiment. The lens holder  35  extends continuously to the mounting portion  32  and the tubular portion  31  with elasticity and is shaped by pressing to have a couple of ring-like ends  35   a  and  35   b  for engagement with the upper halves of the two lenses  40   a  and  40   b  respectively.  
         [0043]    On the other hand, a chassis  60  has a couple of lens holding portions  64   a  and  64   b  for holding the lower halves of the two lenses  40   a  and  40   b  of the tablet lens  40 . The two lenses  40   a  and  40   b  are fitted directly at the lower half with their respective lens holding portions  64   a  and  64   b.  The other arrangements of this embodiment are identical to those of the previous embodiment.  
         [0044]    When the light tunnel  30  is mounted to the chassis  60 , its lens holder  35  holds down with from above its elasticity the two lenses  40   a  and  40   b  of the tablet lens  40  fitted with the lens holding portions  64   a  and  64   b  of the chassis  60 . At the time, the two lenses  40   a  and  40   b  can be engaged at the upper half with and securely retained by the corresponding ring-like ends  35   a  and  35   b  of the lens holder  35 .  
         [0045]    Accordingly, in addition of the advantage of the previous embodiment, this embodiment allows the two lenses  40   a  and  40   b  of the tablet lens  40  to be fitted to the chassis  60  with not use of extra lens holding components such as a tube and retainer rings.  
         [0046]    A third embodiment of the present invention will be described. Referring to FIG. 7, a light tunnel  30  of this embodiment has a tubular portion  31 , input end retainer springs  36   a  and  36   b,  output end flexible springs  38   a  and  38   b  acting as angle adjusters for mounting the tubular portion  31  to the chassis  60  and adjusting the angle of the tubular portion  31 .  
         [0047]    The light tunnel  30  is made of a thin metal sheet and its tubular portion  31  is shaped by the same manner as of the previous embodiment where the thin metal sheet is bent with its reflecting mirror coating inside to have a tubular form. The input end retainer springs  36   a  and  36   b  are shaped by folding outwardly an upper tab portion and a lower tab portion at the input opening  30   a  of the tubular portion  31 . In particular, the input end retainer spring  36   a  has a positioning projection  37   a  provided thereon and the input end retainer spring  36   b  also has a positioning projection  37   b  provided thereon. The output end flexible springs  38   a  and  38   b  are shaped by folding outwardly an upper tab portion and a left tab portion, seen from the input opening  30   a,  at the output opening  30   b  of the tubular portion  31 .  
         [0048]    The chassis  60  has a tunnel inserting portion  70  provided therein into which the light tunnel  30  is inserted and held in substantially a horizontal direction. The tunnel inserting portion  70  comprises an input end holder  71  for holding the light tunnel  30  adjacent to its input opening  30   a  and an output end holder  72  for holding the light tunnel  30  adjacent to its output opening  30   b.    
         [0049]    The input end holder  71  has two positioning apertures  73   a  and  73   b  provided in the upper and lower sides thereof respectively for determining the position of the light tunnel  30  at its input opening  30   a.  The output end holder  72  has two screw holes  74   a  and  74   b  provided in the lower side and the left side, seen from the input opening  30   a,  thereof for threading angle adjusting screws (not shown) for the light tunnel  30 . The other arrangements of this embodiment are also identical to those of the previous embodiment.  
         [0050]    When the light tunnel  30  is mounted to the tunnel inserting portion  70  of the chassis  60 , its tubular portion  31  can be adjusted to a desired angle on the chassis  60 .  
         [0051]    The mounting of the light tunnel  30  to the chassis  60  and the adjustment of its angle will now be described in more detail referring to FIGS. 8A and 8B. As the light tunnel  30  is inserted into the tunnel insertion portion  70 , its input end retainer springs  36   a  and  36   b  press against the inner wall of the input end holder  71 . The positioning projections  37   a  and  37   b  are engaged and joined with the corresponding positioning apertures  73   a  and  73   b  by the elastic action of the retainer springs  36   a  and  36   b.  This permits the light tunnel  30  to be stably secured at the input end with its positioning projections  37   a  and  37   b  accepted by the corresponding positioning apertures  73   a  and  73   b  due to the elastic effect of the input end retainer springs  36   a  and  38   b.    
         [0052]    With the light tunnel  30  remaining secured at the input end, angle adjusting screws  80   a  and  80   b  are threaded into the corresponding screw holes  74   a  and  74   b.  As the tubular portion  31  is urged at the lower side of the output end by the angle adjusting screw  80   a,  and at a right side of the input opening  30   a  by the angle adjusting screw  80   b,  its output end flexible springs  38   a  and  37   b  press against the inner wall of the output end holder  72 . This permits the output end of the light tunnel  30  to remain securely held by the pressing force of the two screws  80   a  and  80   b  and the elastic action of the output end flexible springs  38   a  and  38   b.    
         [0053]    When the angle adjusting screw  80   a  is further threaded in, its distal end presses against the lower side at the output end of the tubular portion  31  which is thus lifted upward with the input end acting as a filcrum and compresses the output end flexible spring  38   a.  Alternatively when the angle adjusting screw  80   a  is loosened, the output end of the tubular portion  31  is lifted down about the fulcrum of the input end by the elastic action of the output end flexible spring  38   a.  By adjusting the threading of the screw  80   a,  the angle of the tubular portion  31  along the upward and downward directions can favorably be controlled.  
         [0054]    When the angle adjusting screw  80   b  is further threaded in, its distal end presses against the right side at the output end of the tubular portion  31  which is thus shifted leftward with the input end acting as the fulcrum and compresses the output end flexible spring  38   b.  Alternatively when the angle adjusting screw  80   b  is loosened, the output end of the tubular portion  31  is shifted rightward about the fulcrum of the input end by the elastic action of the output end flexible spring  38   b.  By adjusting the threading of the screw  80   b,  the angle of the tubular portion  31  along the leftward and rightward directions can favorably be controlled.  
         [0055]    In addition to the advantages of the previous embodiments, the third embodiment allows the light tunnel  30  set in the tunnel inserting portion  70  of the chassis  60  to be tilted to desired angles along the two, horizontal and vertical, directions through simply threading the angle adjusting screws  80   a  and  80   b.    
         [0056]    This application is based on Japanese utility model application No. 2002-6041 filed in Japan dated Sep. 25, 2002, the contents of which are hereby incorporated by references.