Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-257884, filed Sep. 3, 2002, the entire contents of which are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an illumination apparatus in which usage efficiency of light is high and variations in quantity of light are little, and to a display apparatus which projects and displays an image by using the illumination apparatus. 
   2. Description of the Related Art 
   Conventionally, as a high directivity illumination apparatus used for a projection display apparatus or the like, examples in which an LED emitting diffused light and a tapered rod are provided thereat are disclosed in U.S. Pat. Nos. 6,318,863 and 6,227,669 B1. Namely, an LED light source is disposed so as to be close to a small-diameter opening of the tapered rod. Light which is incident from the small-diameter opening of the tapered rod into the tapered rod is transmitted so as to be totally reflected at the internal surface of the tapered rod. The respective light rays are converted so as to have small angles, and are emitted from a large-diameter opening of the tapered rod toward a projection lens. Accordingly, an illumination apparatus which can be used for a projection display apparatus using an image display member in which an allowable angle of incident light is narrow can be obtained. 
   Incidentally, a method for holding an optical part which has a rod shape is disclosed in Japanese Patent Application KOKAI Publication (JP-A) No. 8-227034 and JP-A No. 10-253923. The object of the method in 8-227034 is ensuring a positioning accuracy over a long period, and radiating a thermal stress. In order to attain the objects, a structure in which a rod integrator side surface is biased by a supporting member having a mask function as well and springs is disclosed. Further, the object of 10-253923 is in ensuring a heat resistance of the supporting member of the rod integrator whose temperature becomes high, and ensuring a structural holding accuracy. In order to attain the objects, a structure is disclosed in which the rod integrator is biased onto a supporting member formed from a metal plate by using spring members from the side surface, and at the same time, the rod integrator is biased in the optical axis direction due to the spring members being hooked on one portion of an incident end plane. 
   BRIEF SUMMARY OF THE INVENTION 
   According to a first aspect of the present invention, there is provided an illumination apparatus comprising: 
   an illuminant which radiates diffused light from an outgoing plane and generates heat; 
   a light guiding member configured to guide the diffused light from the illuminant while reflecting the diffused light at the internal surface thereof, the light guiding member including: an incident end which is close to the outgoing plane of the illuminant, and into which the diffused light is incident and which is larger than the outgoing plane of the illuminant; and an outgoing end which is larger than the incident end; and 
   a holding member configured to integrally hold the illuminant and the light guiding member at a predetermined interval, the holding member including: a heat conducting portion configured to conduct the heat generated at the illuminant; and a heat radiating portion configured to radiate heat from the heat conducting portion. 
   According to a second aspect of the present invention, there is provided a display apparatus comprising: 
   an illumination apparatus including:
         an illuminant which radiates diffused light from an outgoing plane and generates heat;   a light guiding member configured to guide the diffused light from the illuminant while reflecting the diffused light at the internal surface thereof, the light guiding member having: an incident end which is close to the outgoing plane of the illuminant, and into which the diffused light is incident and which is larger than the outgoing plane of the illuminant; and an outgoing end which is larger than the incident end; and   a holding member configured to integrally hold the illuminant and the light guiding member at a predetermined interval, the holding member having: a heat conducting portion configured to conduct the heat generated at the illuminant; and a heat radiating portion configured to radiate heat from the heat conducting portion;       

   an illumination lens configured to condense the light from the outgoing end of the light guiding member of the illumination apparatus; and 
   an image display member disposed in the vicinity of the rear side focal point position of the illumination lens. 
   According to a third aspect of the present invention, there is provided a display apparatus comprising: 
   an illumination apparatus including:
         an illuminant which radiates diffused light from an outgoing plane and generates heat;   a light guiding member configured to guide the diffused light from the illuminant while reflecting the diffused light at the internal surface thereof, the light guiding member having: an incident end which is close to the outgoing plane of the illuminant, and into which the diffused light is incident and which is larger than the outgoing plane of the illuminant; and an outgoing end which is larger than the incident end; and   a holding member configured to integrally hold the illuminant and the light guiding member at a predetermined interval, the holding member having: a heat conducting portion configured to conduct the heat generated at the illuminant; and a heat radiating portion configured to radiate heat from the heat conducting portion;       

   an image display member disposed in the vicinity of the outgoing end of the light guiding member of the illumination apparatus; and 
   a projection optical system configured to image an image of the image display member on a projection plane. 
   According to a fourth aspect of the present invention, there is provided an illumination apparatus comprising: 
   an illuminant which radiates diffused light from an outgoing plane and generates heat; 
   light guiding means for guiding the diffused light from the illuminant while reflecting the diffused light at the internal surface thereof, the light guiding means including: an incident end which is close to the outgoing plane of the illuminant, and into which the diffused light is incident and which is larger than the outgoing plane of the illuminant; and an outgoing end which is larger than the incident end; and 
   holding means for integrally holding the illuminant and the light guiding means at a predetermined interval, the holding means including: a heat conducting portion which conducts the heat generated at the illuminant; and a heat radiating portion which radiates heat from the heat conducting portion. 
   According to a fifth aspect of the present invention, there is provided a display apparatus comprising: 
   an illumination apparatus including:
         an illuminant which radiates diffused light from an outgoing plane and generates heat;   light guiding means for guiding the diffused light from the illuminant while reflecting the diffused light at the internal surface thereof, the light guiding means having: an incident end which is close to the outgoing plane of the illuminant, and into which the diffused light is incident and which is larger than the outgoing plane of the illuminant; and an outgoing end which is larger than the incident end; and   holding means for integrally holding the illuminant and the light guiding means at a predetermined interval, the holding means having: a heat conducting portion which conducts the heat generated at the illuminant; and a heat radiating portion which radiates heat from the heat conducting portion;       

   an illumination lens which condenses the light from the outgoing end of the light guiding means of the illumination apparatus; and 
   image displaying means disposed in the vicinity of the rear side focal point position of the illumination lens. 
   According to a sixth aspect of the present invention, there is provided a display apparatus comprising: 
   an illumination apparatus including:
         an illuminant which radiates diffused light from an outgoing plane and generates heat;   light guiding means for guiding the diffused light from the illuminant while reflecting the diffused light at the internal surface thereof, the light guiding means having: an incident end which is close to the outgoing plane of the illuminant, and into which the diffused light is incident and which is larger than the outgoing plane of the illuminant; and an outgoing end which is larger than the incident end; and   holding means for integrally holding the illuminant and the light guiding means at a predetermined interval, the holding means having: a heat conducting portion which conducts the heat generated at the illuminant; and a heat radiating portion which radiates heat from the heat conducting portion;       

   image displaying means disposed in the vicinity of the outgoing end of the light guiding means of the illumination apparatus; and 
   projection optical means for imaging an image of the image displaying means on a projection plane. 
   Advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
       FIG. 1  is a cross sectional view showing a structure of a first embodiment of an illumination apparatus of the present invention; 
       FIG. 2  is an explanatory diagram showing angle conversion characteristics of a tapered rod; 
       FIG. 3  is a partial cross sectional view of a holding portion of the tapered rod of the illumination apparatus relating to the first embodiment; 
       FIG. 4  is a partial cross sectional view of another example of the holding portion of the tapered rod of the illumination apparatus relating to the first embodiment; 
       FIG. 5  is a partial cross sectional view of even another example of the holding portion of the tapered rod of the illumination apparatus relating to the first embodiment; 
       FIG. 6  is a cross sectional view showing a structure of a modified example of the illumination apparatus relating to the first embodiment of the invention; 
       FIG. 7  is a cross sectional view showing a structure of a second embodiment of an illumination apparatus of the invention; 
       FIG. 8  is a cross sectional view showing a structure of a third embodiment of an illumination apparatus of the invention; 
       FIG. 9  is a cross sectional view showing a structure of a fourth embodiment of an illumination apparatus of the invention; 
       FIG. 10  is a cross sectional view showing a structure of a fifth embodiment of an illumination apparatus of the invention; 
       FIG. 11  is a cross sectional view showing a structure of a sixth embodiment of an illumination apparatus of the invention; 
       FIG. 12  is a diagram showing a structure of a first embodiment of a display apparatus using, as an illumination unit, the illumination apparatus relating to one of the first to third embodiments as a seventh embodiment of the invention; 
       FIG. 13  is a diagram showing a structure of a second embodiment of an display apparatus using, as the illumination unit, the illumination apparatus relating to one of the first to third embodiments as an eighth embodiment of the invention; and 
       FIG. 14  is a diagram showing a structure of a third embodiment of an display apparatus using, as the illumination unit, the illumination apparatus relating to one of the first to third embodiments as a ninth embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
   [First Embodiment] 
   As shown in  FIG. 1 , in a first embodiment of an illumination apparatus of the invention, a high intensity light-emitting diode  10  (hereinafter an LED chip) is used as an illuminant, and a tapered rod  20  is used as a light guiding member. Here, the LED chip  10  and tapered rod  20  are integrally held such that the LED chip  10  and an incident end of the tapered rod  20  are disposed at predetermined positions which are closed to one another via a thin air layer by a holding member constituted of an LED base  30 , an LED substrate  31 , an LED holder  32 , collars  33 , spacers  34 , fixing screws  35 , and a rod holder  36 . Namely, the LED chip  10  serving as the illuminant is held by the LED holder  32  via the LED base  30  and the LED substrate  31 . These LED base  30 , LED substrate  31 , and LED holder  32  function as a heat conducting portion conducting heat which is generated at the LED chip  10 . 
   The LED holder  32  has radiating fins  32 A serving as a heat radiating portion for radiating heat which the LED chip  10  generates. The LED holder  32  is formed from a material having a high heat conductivity, for example, a metal such as an aluminum or the like, in order to efficiently transmit the heat from the above-describe LED chip  10  to the radiating fins  32 A. The LED holder  32  is combined with the rod holder  36  by the fixing screws  35  via the collars  33  and the spacers  34  which are formed from a material having low thermal conductivity, for example, ceramics or a plastics. Therefore, it is possible to reduce the transmission of the heat, which the LED chip  10  generates, from the LED holder  32  to the rod holder  36 . 
   The diffused light, which was radiated due to the LED chip  10  being energized, is incident from the incident end of the tapered rod  20  close to the LED chip  10  into the interior of the tapered rod  20 . The incident end of the tapered rod  20  is larger than the LED chip  10 , and the LED chip  10  and the incident end of the tapered rod  20  are disposed so as to be adjacent to one another via a thin air layer. Therefore, light rays having a broad angle range of the diffused light from the LED chip  10  are incident onto the incident end of the tapered rod  20 . 
   Among the diffused light radiated from the LED chip  10 , the light ray which was incident into the tapered rod  20  at a small angle directly reaches an outgoing end of the tapered rod  20  and is emitted while maintaining the original angle as is. Further, the light ray which was incident into the tapered rod  20  at a large angle is totally reflected once or more at the internal surface of the side surface of the tapered rod  20  and is converted into a small angle, and is emitted from the outgoing end of the tapered rod  20 . Accordingly, although the diffused light radiated from the LED chip  10  has a broad angle distribution which is called Lambertian, as an example is shown in  FIG. 2 , the diffused light is converted into a light whose angle distribution is narrow due to the angle conversion effect by the tapered rod  20 . In this way, the diffused light from the LED chip  10  can be efficiently fetched by the combination of the LED chip  10  and the tapered rod  20 , and at the same time, the radiation angle thereof can be efficiently converted into a narrow angle. Therefore, an illumination apparatus which is bright and has high directivity can be realized with a simple structure. 
   By the way, accompanying the radiation of the diffused light due to the LED chip  10  being energized, because the electric energy which was not converted into light energy as the diffused light is converted into thermal energy, the LED chip  10  generates heat. The majority of the heat generated at the LED chip  10  is transmitted by the LED base  30 , the LED substrate  31 , and the LED holder  32  having high heat conductivity, and is heat-radiated from the surface of the LED holder  32 , and at the same time, is more effectively radiated to the outside by the radiating fins  32 A provided at the LED holder  32 . Due to this effect, a temperature rise of the LED chip  10  itself is suppressed at a constant level, and deterioration of the light-emitting characteristic and shortening of the life are prevented. Note that, because these members relating to heat radiation are used as the holding member of the LED chip  10  as well, the heat can be efficiently radiated with a simple structure. 
   Further, because the air layer is provided between the LED chip  10  and the tapered rod  20 , there is no case in which the optical characteristic of the tapered rod  20  deteriorates due to heat being directly transmitted from the LED chip  10  to the tapered rod  20 . Further, the temperature of the air contacting the LED chip  10  rises due to the heat generation of the LED chip  10 . However, the air can be replaced by convection or forced draft through apertures of the rod holder  36  or air holes  36 A provided at the rod holder  36 . Therefore, there is no case in which the optical characteristic of the tapered rod  20  deteriorates due to the temperature rise of the air at the surroundings of the tapered rod  20 . Note that the invention is not limited to the case of using air, and it goes without saying that the same function and effect can be obtained if another gas or liquid which can carry heat is circulated. 
   Moreover, as described above, the LED holder  32  is fixed to the rod holder  36  by using the fixing screws  35  with the collars  33  and the spacers  34  which are formed from materials such as low heat conductivity resins or the like being interposed therebetween as a heat insulating portion, and transmission of heat from the LED holder  32  to the rod holder  36  is suppressed. Accordingly, there is no case in which the optical characteristic of the tapered rod  20  deteriorates due to the heat of the LED chip  10  being transmitted to the tapered rod  20  via the rod holder  36 . 
   Note that holding portion coatings  37  are applied onto the contact portions between the tapered rod  20  and the rod holder  36 . Concretely, it is configured as shown in partial enlarged views of the rod holding portion of  FIG. 3  to FIG.  5 . 
   In an example shown in  FIG. 3 , low refractive index layers  37 A whose refractive index are lower than that of the tapered rod  20  are provided as the holding portion coatings  37  at rod side surface  21  portions of the tapered rod  20  which the rod holder  36  contact. Here, the low refractive index layer  37 A may be a dielectric film, a resin, an adhesive, or the like, and the tapered rod  20  and the rod holder  36  are adhered and fixed to one another with the low refractive index layers  37 A being interposed therebetween. In accordance with such a structure, among the light incident from the incident end  22  of the tapered rod  20  into the interior of the tapered rod  20 , the light ray which is incident into the rod side surface  21  at a small angle is incident into the low refractive index layer  37 A, and is diffused at the rod holder  36 . Further, the light ray which is incident at a large angle is totally reflected at the interface of the low refractive index layer  37 A and the tapered rod  20 . Therefore, loss due to the tapered rod  20  being held can be reduced. 
   Further, in an example shown in  FIG. 4 , metal films  37 B having high reflectance such as Al, Ag, or the like are provided at the rod side surfaces  21  portion of the tapered rod  20  which the rod holder  36  contact. Namely, the tapered rod  20  and the rod holder  36  are adhered and fixed to one another by unillustrated adhesives with the metal films  37 B being interposed therebetween. In accordance with such a structure, the light which is incident into the tapered rod  20  goes toward the outgoing end while being totally reflected at the rod side surface  21 . In this case, because the light which was incident onto the portion contacting with the rod holder  36  is reflected due to the high reflectance of the metal film  37 B regardless of the angle of incidence, loss due to the tapered rod  20  being held can be suppressed so as to be lower. 
   Further, in an example shown in  FIG. 5 , a low refractive index film  37 C formed from a dielectric film whose refractive index is lower than that of the tapered rod  20  is provided at the rod side surface  21  portion of the tapered rod  20  which the rod holder  36  contacts, and furthermore, the metal film  37 B having a high reflectance such as Al, Ag, or the like is provided thereat. Namely, the tapered rod  20  and the rod holder  36  are adhered and fixed to one another by unillustrated adhesives with the low refractive index films  37 C and the metal films  37 B being interposed therebetween. In accordance with such a structure, the light which is incident into the tapered rod  20  goes toward the outgoing end while being totally reflected at the rod side surface  21 . In this case, when the light which was incident onto the portion contacting with the rod holder  36  is incident onto the rod side surface  21  at a large angle of incidence, the light is totally reflected at the interface between the tapered rod side surface  21  and the low refractive index film  37 C and goes toward the outgoing end without loss. Further, when the light is incident onto the rod side surface  21  at a small angle of incidence, the light is incident into the interior of the low refractive index film  37 C. However, because the light is reflected at the interface between the low refractive index film  37 C and the metal film  37 B, loss due to the tapered rod  20  being held can be suppressed so as to be lower. 
     FIG. 6  is a cross sectional view showing a structure of a modified example of the illumination apparatus relating to the first embodiment of the invention. Namely, in this modified example, the tapered rod  20  in the first embodiment is a hollow tapered pipe  23  whose reflective surface is directed to the internal surface. A reflective mirror  24  on which a high reflectance coating is applied is provided at the internal surface of the tapered pipe  23 , and the reflective mirror  24  reflects the incident light ray at a high reflectance, and guides the reflected light to the outgoing end. Accordingly, the effect of the tapered pipe  23  is the same as that of the tapered rod  20 . 
   When the tapered pipe  23  is used, in addition to the effect in the first embodiment as described above, the following characteristic effect is provided. Namely, differently from the case of the tapered rod  20 , because there is no problem of scattering or leakage of light by the holding portion, special coating is not required for the holding portion. Further, because the air fetched from the air holes  36 A of the holding portion can be flowed by using the hollow portion in the interior of the tapered pipe  23 , the effect of heat radiation can be further improved. 
   [Second Embodiment] 
   Next, a second embodiment of the present invention will be described. As shown in  FIG. 7 , in the second embodiment of an illumination apparatus of the invention as well, in the same way as in the first embodiment, the LED chip  10  is used as the illuminant, and the tapered rod  20  is used as the light guiding member. Further, as shown in the drawing, the LED chip  10  and tapered rod  20  are integrally held by the LED base  30 , the LED substrate  31 , the LED holder  32 , the fixing screws  35 , and the rod holder  36 . However, in the present embodiment, the LED chip  10  and the tapered rod  20  are held such that the LED chip  10  and the incident end  22  of the tapered rod  20  are disposed at predetermined positions adjacent to one another with, not an air layer such as that in the first embodiment, but a transparent resin  38  whose heat conductivity is low and which is a thin translucent heat insulating member being interposed therebetween. 
   Therefore, in the second embodiment, the diffused light, which was radiated due to the LED chip  10  being energized, permeates through the transparent resin  38 , and is incident from the incident end  22  of the adjacent tapered rod  20  to the interior of the tapered rod  20 . The incident end  22  of the tapered rod  20  is larger than the LED chip  10 , and the LED chip  10  and the incident end  22  of the tapered rod  20  are disposed so as to be adjacent to one another via the thin transparent resin  38 . Therefore, the diffused light from the LED chip  10  is efficiently incident from the incident end  22  of the tapered rod  20 . Further, the diffused light incident into the tapered rod  20  is converted into a light whose angle distribution is narrow in the same way as in the first embodiment. 
   In accordance with the illumination apparatus having such a structure, in the same way as in the illumination apparatus relating to the first embodiment, accompanying the radiation of the diffused light due to the LED chip  10  being energized, the majority of the heat generated at the LED chip  10  is transmitted by the LED base  30 , the LED substrate  31 , the LED holder  32 , and the rod holder  36  having high heat conductivity, and is radiated from the surfaces of the LED holder  32  and the rod holder  36 , and at the same time, is effectively radiated to the outside by the radiating fins  32 A and radiating fins  36 B provided at the LED holder  32  and the rod holder  36 . Due to this effect, temperature rise of the LED chip  10  itself is suppressed at a constant level, and deterioration of the light-emitting characteristic is prevented. 
   Further, in the present embodiment, the transparent resin  38  having a heat conductivity lower than the heat conductivity of the LED base  30 , LED substrate  31 , LED holder  32 , rod holder  36 , or the like is provided between the LED chip  10  and the tapered rod  20 , and heat conduction from the LED chip  10  to the tapered rod  20  is suppressed. Therefore, there is no case in which the optical characteristic deteriorates due to the temperature rise of the tapered rod  20  or arising of the internal temperature gradient. Further, the temperature of the air at the surroundings of the LED chip  10  rises due to the heat generation of the LED chip  10 . However, the air is replaced by convection or forced draft through the apertures of the rod holder  36  or the air holes provided at the rod holder  36 . Therefore, there is no case in which the optical characteristic of the tapered rod  20  deteriorates due to the temperature rise of the air at the surroundings of the tapered rod  20 . Note that, due to the transparent resin  38  being provided, not only the LED chip  10  and the incident end  22  of the tapered rod  20  can be accurately positioned, but also variations in the positions thereof can be made little with respect to external causes, and can be made stable. 
   Moreover, in the second embodiment, with respect to the rod holder  36 , the radiating fins  36 B are provided at one portion of the rod holder  36 , and narrow portions  36 C 1  whose cross sectional areas are small are provided along the rod supporting portions  36 C actually supporting the tapered rod  20 . Due to the heat resistance of the narrow portion  36 C 1  being made large, the transmission of the heat of the LED chip  10  from the rod holder  36  to the tapered rod  20  is suppressed, and there is no case in which the optical characteristic of the tapered rod  20  deteriorates. 
   [Third Embodiment] 
   Next, a third embodiment of the present invention will be described. As shown in  FIG. 8 , an illumination apparatus relating to the third embodiment of the invention uses the LED chip  10  serving as the illuminant and uses the tapered rod  20  serving as the light guiding member. Further, as illustrated, the LED chip  10  and the tapered rod  20  are integrally held such that the LED chip  10  and the incident end  22  of the tapered rod  20  are disposed at predetermined positions which are closed to one another via a thin air layer by a holding member constituted of the LED base  30 , the LED substrate  31 , the LED holder  32 , linear guides  39  integrally provided at the LED holder  32 , the collars  33 , the spacers  34 , the fixing screws  35 , and the rod holder  36 . 
   In the illuminant apparatus having such a structure, the LED chip  10  and the tapered rod  20  are held so as to be relatively (in the direction perpendicular to the paper plane) movable while maintaining a predetermined interval as is by the linear guides  39  integrally provided with the LED holder  32 . Accordingly, because the LED chip  10  can be shifted from the position facing the incident end  22  of the tapered rod  20  by driving means (not shown), transmission of heat to the tapered rod  20  can be suppressed, and the LED chip  10  can be effectively cooled. Further, because the LED chip  10  and the tapered rod  20  can be moved while maintaining the predetermined interval as is in this way, it is configured such that a plurality of LED chips  10  are arranged in the moving direction, and due to light-emitting control being carried out such that only the LED chip  10  which reached the position facing the incident end  22  of the tapered rod  20  is made to emit light, the LED chip  10  emitting light can be switched. Therefore, a life per one LED can be lengthened, and a color of illumination light can be changed by using the LED chip  10  whose luminescent color is different. 
   [Fourth Embodiment] 
   Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, an illumination apparatus illuminates an objective irradiating plane by using the illumination apparatus relating to one of the first to third embodiments described above as an illuminant unit. 
     FIG. 9  is a cross sectional view showing a structure of the fourth embodiment of the illumination apparatus of the invention. Namely, illumination is carried out by directly irradiating the illumination light from an illumination unit  40  which is the illumination apparatus relating to one of the first to third embodiments, for example, to the first embodiment of the invention as shown in  FIG. 1  onto the objective irradiating plane  50 . 
   In accordance with the fourth embodiment, the illumination apparatus can be realized with a simple structure. 
   Note that a plurality of illumination units  40  irradiating illumination light may be arranged and disposed with respect to the same objective irradiating plane  50 , and in this case, illumination which is brighter and has even less illumination non-uniformity is possible. 
   [Fifth Embodiment] 
   Next, a fifth embodiment of the present invention will be described. As shown in  FIG. 10 , in the fifth embodiment of an illumination apparatus of the invention, the illumination apparatus is an illumination apparatus which irradiates the illumination light from the illumination unit  40  which is the illumination apparatus relating to one of the first to third embodiments described above, for example, to the first embodiment of the invention shown in  FIG. 1  onto the objective irradiating plane  50  in the vicinity of the rear side focal point position of the illumination lens  60  via an illumination lens  60  disposed in the vicinity of the illumination unit  40 . 
   In accordance with the fifth embodiment, the illumination apparatus having little illumination non-uniformity is possible. Further, because the illumination lens  60  is disposed in the vicinity of the illumination unit  40 , the illumination apparatus formed from these illumination unit  40  and illumination lens  60  can be compactly configured. 
   Note that a plurality of illumination units  40  may be arranged and disposed with respect to the one illumination lens  60 , and in this case, illumination which is brighter and has even less illumination non-uniformity is possible. 
   [Sixth Embodiment] 
   Next, a sixth embodiment of the present invention will be described. As shown in  FIG. 11 , in the sixth embodiment of an illumination apparatus of the invention, illumination is carried out by irradiating the illumination light from the illumination unit  40  onto the objective irradiating plane  50  by using the illumination lens  60  imaging the outgoing end of the illumination unit  40  which is the illumination apparatus relating to one of the first to third embodiments described above, for example, to the first embodiment of the invention as shown in  FIG. 1  on the objective irradiating plane  50 . 
   In accordance with the sixth embodiment, illumination can be carried out in a shape corresponding to the shape of the outgoing end of the illumination unit  40 . 
   [Seventh Embodiment] 
   Next, a seventh embodiment of the present invention will be described.  FIG. 12  is a diagram showing a structure of a first embodiment of a display apparatus using, as the illumination unit, the illumination apparatus relating to one of the first to third embodiments as the seventh embodiment of the invention. Namely, for example, the illumination lens  60  condensing light from the outgoing end is provided at the outgoing end side of the illumination unit  40  which is the illumination apparatus relating to the first embodiment of the invention as shown in  FIG. 1 , and a slide film  70  serving as an image display member is disposed in the vicinity of the rear side focal point position of the illumination lens  60 . At this time, given that a rear side focal length of the illumination lens  60  is L, a width across dimension of the slide film  70  is 2W, and a maximum angle of the light ray radiated from the outgoing end of the illumination unit  40  is θmax (refer to FIG.  2 ), it is configured so as to satisfy:
 
tan −1 ( W/L )≦θmax.
 
   Moreover, a projection lens  80  formed from two lenses is disposed at the rear side of the slide film  70 , and an image of the slide film  70  is imaged and projected on a screen (not shown) or the like serving as an image projection plane  90 . 
   Due to the display apparatus being configured in this way, the light radiated from the outgoing end of the light guiding member can be condensed onto a given region at the rear side focal point position of the illumination lens  60  regardless of the outgoing position from the outgoing end. Therefore, the slide film  70  serving as the image display member can be efficiently illuminated, and a bright display image can be obtained. 
   Further, in general, an image height Y at the focal point position with respect to an angle of view θ of the light ray incident into the lens whose focal length is L can be expressed by Y=L×tan θ. Therefore, when the width across dimension of the image display member is 2W, given that the maximum angle of the light ray radiated from the outgoing end of the illumination unit  40  is θmax, due to the relationship of tan −1 (W/L)≦θmax being satisfied, the light radiated from the outgoing end of the light guiding member can be effectively irradiated with respect to the size of the image display member. Note that, from the standpoint of usage efficiency of light, it suffices that θmax is made as small as possible within a range in which it satisfies the relational expression. 
   Note that, in the present embodiment, the slide film  70  is used as the image display member. However, it goes without saying that the image display member may be an LCD panel or a display device such as a two dimensional micro mirror deflection array known as a digital micro mirror device (DMD: the registered trademark of Texas Instruments Incorporated, USA) as disclosed in U.S. Pat. No. 6,129,437, or the like. Further, a transmission type lens is used as the illumination lens  60 . However, the illumination lens  60  may be constituted of a reflective mirror having the same effect or a combination of a lens and a mirror. Moreover, it may be configured such that the projection lens  80  is not used and the image display member is directly seen, and an eyepiece for imaging an image on a retina may be used in place of the projection lens  80 . 
   [Eighth Embodiment] 
   Next, an eighth embodiment of the present invention will be described.  FIG. 13  is a diagram showing a structure of a second embodiment of the display apparatus using, as an illumination unit, the illumination apparatus relating to one of the first to third embodiments as the eighth embodiment of the invention. Namely, for example, the illumination lens  60  which condenses light from the outgoing end is disposed at the outgoing end side of the illumination unit  40  which is the illumination apparatus relating to the first embodiment of the invention as shown in  FIG. 1  such that the outgoing end of the illumination unit  40  is positioned at the front side focal point position of the illumination lens  60 . Furthermore, an LCD  71  serving as the image display member is disposed in the vicinity of the rear side focal point position of the illumination lens  60 . At this time, given that a rear side focal length of the illumination lens  60  is L, a width across dimension of the LCD  71  is 2W, and a maximum angle of the light ray radiated from the outgoing end of the illumination unit  40  is θmax (refer to FIG.  2 ), it is configured so as to satisfy:
 
tan −1 ( W/L )≦θmax.
 
   Moreover, the projection lens  80  formed from two lenses is disposed at the rear side of the LCD  71 , and an image of the LCD  71  is imaged and projected on a screen (not shown) or the like which is the image projection plane  90 . 
   Due to the display apparatus being configured in this way, in the same way as in the seventh embodiment, because the light radiated from the outgoing end of the light guiding member can be condensed onto a given region at the rear side focal point position of the illumination lens  60  regardless of the outgoing position from the outgoing end, the LCD  71  serving as the image display member can be efficiently illuminated, and a bright display image can be obtained. Further, in particular, in the present embodiment, the light radiated from the outgoing end of the light guiding member can be condensed onto a given region at the rear side focal point position of the illumination lens  60  regardless of the outgoing position, and at the same time, a distribution of the angle of incidence of the light which was condensed within the illuminated range can be made small. Therefore, in particular, the LCD  71  serving as the image display member in which a dependency on angle of incidence is large can be efficiently illuminated, and a bright display image without unevenness can be obtained. 
   Further, in general, an image height Y at the focal point position with respect to the angle of view θ of the light ray incident into the lens whose focal length is L can be expressed by Y=L×tan θ. Therefore, when the width across dimension of the image display member is 2W, given that the maximum angle of the light ray radiated from the outgoing end of the illumination unit  40  is θmax, due to the relationship of tan −1 (W/L)≦θmax being satisfied, the light radiated from the outgoing end of the light guiding member can be effectively irradiated with respect to the size of the image display member. Note that, from the standpoint of usage efficiency of light, it suffices that θmax is made as small as possible within a range in which it satisfies the relational expression. 
   Note that, in the present embodiment, the LCD  71  is used as the image display member. However, the image display member may be a slide film, a two-dimensional micro mirror deflection array, or the like. Further, a transmission type lens is used as the illumination lens  60 . However, the illumination lens  60  may be constituted of a reflective mirror having the same effect or a combination of a lens and a mirror. Moreover, it may be configured such that the projection lens  80  is not used and the image display member is directly seen, and an eyepiece for imaging an image on a retina may be used in place of the projection lens  80 . 
   [Ninth Embodiment] 
   Next, a ninth embodiment of the present invention will be described.  FIG. 14  is a diagram showing a structure of a third embodiment of the display apparatus using, as an illumination unit, the illumination apparatus relating to one of the first to third embodiments as the ninth embodiment of the invention. Namely, for example, the LCD  71  serving as the image display member is disposed in the vicinity of the outgoing end of the illumination unit  40  which is the illumination apparatus relating to the first embodiment of the invention as shown in  FIG. 1 , and the a projection lens  80  formed from two lenses serving as a projection optical system is disposed at the rear side of the LCD  71 . At this time, an image of the LCD  71  is imaged and projected on a screen (not shown) or the like which is the image projection plane  90  by the projection lens  80 . 
   In accordance with the present embodiment, a display apparatus which projects an image with a simple structure and in which an optical efficiency is high can be realized. 
   Note that the LCD  71  is used as the image display member. However, the image display member may be a display device such as a slide film, a two-dimensional micro mirror deflection array, or the like. Moreover, the transmission type lenses are used as the projection lens  80 . However, the projection lens  80  may be constituted of reflective mirrors having the same effect or a combination of a lens and a mirror. 
   The invention was described above on the basis of the embodiments. However, the invention is not limited to the embodiments described above, and it goes without saying that various modifications and applications are possible within a range which does not deviate from the gist of the invention. For example, the cross sectional shapes of the tapered rod  20  and the tapered pipe  23  may be rectangular, and may be circular or elliptical as well. Further, the material of the tapered rod  20  may be a glass, and may be a transparent resin. 
   Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, and representative devices shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

Technology Category: 3